Generation, ascent and eruption of magma on the Moon: New insights into source depths, magma supply, intrusions and effusive/explosive eruptions (Part 2: Predicted emplacement processes and observations)

NASA Astrophysics Data System (ADS)

Head, James W.; Wilson, Lionel

2017-02-01

We utilize a theoretical analysis of the generation, ascent, intrusion and eruption of basaltic magma on the Moon to develop new insights into magma source depths, supply processes, transport and emplacement mechanisms via dike intrusions, and effusive and explosive eruptions. We make predictions about the intrusion and eruption processes and compare these with the range of observed styles of mare volcanism, and related features and deposits. Density contrasts between the bulk mantle and regions with a greater abundance of heat sources will cause larger heated regions to rise as buoyant melt-rich diapirs that generate partial melts that can undergo collection into magma source regions; diapirs rise to the base of the anorthositic crustal density trap (when the crust is thicker than the elastic lithosphere) or, later in history, to the base of the lithospheric rheological trap (when the thickening lithosphere exceeds the thickness of the crust). Residual diapiric buoyancy, and continued production and arrival of diapiric material, enhances melt volume and overpressurizes the source regions, producing sufficient stress to cause brittle deformation of the elastic part of the overlying lithosphere; a magma-filled crack initiates and propagates toward the surface as a convex upward, blade-shaped dike. The volume of magma released in a single event is likely to lie in the range 102 km3 to 103 km3, corresponding to dikes with widths of 40-100 m and both vertical and horizontal extents of 60-100 km, favoring eruption on the lunar nearside. Shallower magma sources produce dikes that are continuous from the source region to the surface, but deeper sources will propagate dikes that detach from the source region and ascend as discrete penny-shaped structures. As the Moon cools with time, the lithosphere thickens, source regions become less abundant, and rheological traps become increasingly deep; the state of stress in the lithosphere becomes increasingly contractional, inhibiting dike emplacement and surface eruptions. In contrast to small dike volumes and low propagation velocities in terrestrial environments, lunar dike propagation velocities are typically sufficiently high that shallow sill formation is not favored; local low-density breccia zones beneath impact crater floors, however, may cause lateral magma migration to form laccoliths (e.g., Vitello Crater) and sills (e.g., Humboldt Crater) in floor-fractured craters. Dikes emplaced into the shallow crust may stall and produce crater chains due to active and passive gas venting (e.g., Mendeleev Crater Chain) or, if sufficiently shallow, may create a near-surface stress field that forms linear and arcuate graben, often with pyroclastic and small-scale effusive eruptions (e.g., Rima Parry V). Effusive eruptions are modulated by effusion rates, eruption durations, cooling and supply limitations to flow length, and pre-existing topography. Relatively low effusion rate, cooling-limited flows lead to small shield volcanoes (e.g., Tobias Mayer, Milicius); higher effusion rate, cooling-limited flows lead to compound flow fields (e.g., most mare basins) and even higher effusion rate, long-duration flows lead to thermal erosion of the vent, effusion rate enhancement, and thermal erosion of the substrate to produce sinuous rilles (e.g., Rimae Prinz). Extremely high effusion rate flows on slopes lead to volume-limited flow with lengths of many hundreds of kilometers (e.g., the young Imbrium basin flows). Explosive, pyroclastic eruptions are common on the Moon. The low pressure environment in propagating dike crack-tips can cause gas formation at great depths and throughout dike ascent; at shallow crustal depths both the smelting reaction and the recently documented abundant magmatic volatiles in mare basalt magmas contribute to significant shallow degassing and pyroclastic activity associated with the dike as it erupts at the surface. Dikes penetrating to the surface produce a wide range of explosive eruption types whose manifestations are modulated by lunar environmental conditions: (1) terrestrial strombolian-style eruptions map to cinder/spatter cone-like constructs (e.g., Isis and Osiris); (2) Hawaiian-style eruptions map to broad flat pyroclastic blankets (e.g., Taurus-Littrow Apollo 17 dark mantle deposits); (3) gas-rich ultraplinian-like venting can cause Moon-wide dispersal of gas and foam droplets (e.g., many isolated glass beads in lunar soils); (4) vulcanian-like eruptions caused by solidification of magma in the dike tip, buildup of gas pressure and explosive disruption, can form dark-halo craters with mixed country rock (e.g., Alphonsus Crater floor); (5) ionian-like eruptions can be caused by artificial gas buildup in wide dikes, energetic explosive eruption and formation of a dark pyroclastic ring (e.g., Orientale dark ring); (6) multiple eruptions from many gas-rich fissures can form regional dark mantle deposits (e.g., Rima Bode, Sinus Aestuum); and (7) long duration, relatively high effusion rate eruptions accompanied by continuing pyroclastic activity cause a central thermally eroded lava pond and channel, a broader pyroclastic 'spatter' edifice, an even broader pyroclastic glass deposit and, if the eruption lasts sufficiently long, an associated inner thermally eroded vent and sinuous rille channel (e.g., Cobra Head and Aristarchus Plateau dark mantle). The asymmetric nearside-farside distribution of mare basalt deposits is most plausibly explained by crustal thickness differences; intrusion is favored on the thicker farside crust and extrusion is favored on the thinner nearside crust. Second-order effects include regional and global thermal structure (areal variations in lithospheric thickness as a function of time) and broad geochemical anomalies (the Procellarum-KREEP Terrain). Differences in mare basalt titanium content as a function of space and time are testimony to a laterally and vertically heterogeneous mantle source region. The rapidly decreasing integrated flux of mare basalts is a result of the thermal evolution of the Moon; continued cooling decreased diapiric rise and mantle melting, thickened the lithosphere, and caused the global state of stress to be increasingly contractional, all factors progressively inhibiting the generation, ascent and eruption of basaltic magma. Late-stage volcanic eruptions are typically widely separated in time and characterized by high-volume, high-effusion rate eruptions producing extensive volume-limited flows, a predictable characteristic of deep source regions below a thick lithosphere late in lunar history. This improved paradigm for the generation, ascent, intrusion and eruption of basaltic magma provides the basis for the broader interpretation of the lunar volcanic record in terms of variations in eruption conditions in space and time, and their relation to mantle heterogeneity and a more detailed understanding of lunar thermal evolution.

Preliminary investigation of the effects of eruption source parameters on volcanic ash transport and dispersion modeling using HYSPLIT

NASA Astrophysics Data System (ADS)

Stunder, B.

2009-12-01

Atmospheric transport and dispersion (ATD) models are used in real-time at Volcanic Ash Advisory Centers to predict the location of airborne volcanic ash at a future time because of the hazardous nature of volcanic ash. Transport and dispersion models usually do not include eruption column physics, but start with an idealized eruption column. Eruption source parameters (ESP) input to the models typically include column top, eruption start time and duration, volcano latitude and longitude, ash particle size distribution, and total mass emission. An example based on the Okmok, Alaska, eruption of July 12-14, 2008, was used to qualitatively estimate the effect of various model inputs on transport and dispersion simulations using the NOAA HYSPLIT model. Variations included changing the ash column top and bottom, eruption start time and duration, particle size specifications, simulations with and without gravitational settling, and the effect of different meteorological model data. Graphical ATD model output of ash concentration from the various runs was qualitatively compared. Some parameters such as eruption duration and ash column depth had a large effect, while simulations using only small particles or changing the particle shape factor had much less of an effect. Some other variations such as using only large particles had a small effect for the first day or so after the eruption, then a larger effect on subsequent days. Example probabilistic output will be shown for an ensemble of dispersion model runs with various model inputs. Model output such as this may be useful as a means to account for some of the uncertainties in the model input. To improve volcanic ash ATD models, a reference database for volcanic eruptions is needed, covering many volcanoes. The database should include three major components: (1) eruption source, (2) ash observations, and (3) analyses meteorology. In addition, information on aggregation or other ash particle transformation processes would be useful.

Identification of Low Coronal Sources of “Stealth” Coronal Mass Ejections Using New Image Processing Techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alzate, Nathalia; Morgan, Huw, E-mail: naa19@aber.ac.uk

Coronal mass ejections (CMEs) are generally associated with low coronal signatures (LCSs), such as flares, filament eruptions, extreme ultraviolet (EUV) waves, or jets. A number of recent studies have reported the existence of stealth CMEs as events without LCSs, possibly due to observational limitations. Our study focuses on a set of 40 stealth CMEs identified from a study by D’Huys et al. New image processing techniques are applied to high-cadence, multi-instrument sets of images spanning the onset and propagation time of each of these CMEs to search for possible LCSs. Twenty-three of these events are identified as small, low-mass, unstructuredmore » blobs or puffs, often occurring in the aftermath of a large CME, but associated with LCSs such as small flares, jets, or filament eruptions. Of the larger CMEs, seven are associated with jets and eight with filament eruptions. Several of these filament eruptions are different from the standard model of an erupting filament/flux tube in that they are eruptions of large, faint flux tubes that seem to exist at large heights for a long time prior to their slow eruption. For two of these events, we see an eruption in Large Angle Spectrometric Coronagraph C2 images and the consequent changes at the bottom edge of the eruption in EUV images. All 40 events in our study are associated with some form of LCS. We conclude that stealth CMEs arise from observational and processing limitations.« less

Crustal CO2 liberation during the 2006 eruption and earthquake events at Merapi volcano, Indonesia

NASA Astrophysics Data System (ADS)

Troll, Valentin R.; Hilton, David R.; Jolis, Ester M.; Chadwick, Jane P.; Blythe, Lara S.; Deegan, Frances M.; Schwarzkopf, Lothar M.; Zimmer, Martin

2012-06-01

High-temperature volcanic gas is widely considered to originate from ascending, mantle-derived magma. In volcanic arc systems, crustal inputs to magmatic gases mainly occur via subducted sediments in the mantle source region. Our data from Merapi volcano, Indonesia imply, however, that during the April-October 2006 eruption significant quantities of CO2 were added from shallow crustal sources. We show that prior to the 2006 events, summit fumarole gas δ13C(CO2) is virtually constant (δ13C1994-2005 = -4.1 ± 0.3‰), but during the 2006 eruption and after the shallow Yogyakarta earthquake of late May, 2006 (M6.4; hypocentres at 10-15 km depth), carbon isotope ratios increased to -2.4 ± 0.2‰. This rise in δ13C is consistent with considerable addition of crustal CO2 and coincided with an increase in eruptive intensity by a factor of ˜3 to 5. We postulate that this shallow crustal volatile input supplemented the mantle-derived volatile flux at Merapi, intensifying and sustaining the 2006 eruption. Late-stage volatile additions from crustal contamination may thus provide a trigger for explosive eruptions independently of conventional magmatic processes.

The 3D Distribution of Magma Bodies that Fed the Paraná Silicic Volcanics, Brazil: A Combination of Field Evidence, Textural Analysis, and Geothermobarometry

NASA Astrophysics Data System (ADS)

Harmon, L.; Gualda, G. A. R.; Gravley, D. M.

2016-12-01

The Paraná Silicic Volcanics include some of the largest eruptive deposits known in the geological record. However, we know very little about the magma bodies that fed these eruptions. Combining physical volcanology, geochemistry, and geothermobarometry techniques, we aim to find the sources of extinct magma bodies to build a 3D view of the magma structure at the time by discovering storage conditions, eruption styles, and post-eruption alteration. The approach elucidates temporal and spatial eruption styles and sequences of the silicic units that make up the Palmas unit of the Serra Geral formation, Brazil. We use field investigations to determine the history of volcanic deposits, domes, and changes in eruptive style; we map and characterize volcanic deposits based on thickness (thicker is proximal to source) and distribution of effusive (proximal to source) and explosive deposits. We focus on several exposed canyons that exhibit either exclusively explosive or effusive, or a clear progression from explosive to effusive deposits. The progression from explosive to effusive indicates a system change from explosively energetic to effusively waning. Additionally, observation of pervasive flow banding in both effusive and explosive deposits indicates rheomorphic flow through many portions of the field area, an indicator of hot emplacement. Geochemical work focuses on the pre-eruptive magma conditions to determine the depth of magma bodies. We utilize glass bearing samples of both the explosively deposited juvenile blob-like structures and obsidian samples to determine crystallization depth. The glass is variably altered, via silicification and devitrification processes, with the blobs more greatly silicified than the obsidian. We use rhyolite-MELTS geothermobarometry when pristine glass can be found. Initial results indicate shallow ( 80 MPa) storage conditions for the explosively erupted blobs. The combination of techniques builds a 3D understanding of extinct super-eruptive systems, and has the potential to unravel both the pre-eruptive and deposition dynamics of the Paraná Silicic Volcanics.

Backprojection of volcanic tremor

USGS Publications Warehouse

Haney, Matthew M.

2014-01-01

Backprojection has become a powerful tool for imaging the rupture process of global earthquakes. We demonstrate the ability of backprojection to illuminate and track volcanic sources as well. We apply the method to the seismic network from Okmok Volcano, Alaska, at the time of an escalation in tremor during the 2008 eruption. Although we are able to focus the wavefield close to the location of the active cone, the network array response lacks sufficient resolution to reveal kilometer-scale changes in tremor location. By deconvolving the response in successive backprojection images, we enhance resolution and find that the tremor source moved toward an intracaldera lake prior to its escalation. The increased tremor therefore resulted from magma-water interaction, in agreement with the overall phreatomagmatic character of the eruption. Imaging of eruption tremor shows that time reversal methods, such as backprojection, can provide new insights into the temporal evolution of volcanic sources.

Mass transfer processes in a post eruption hydrothermal system: Parameterisation of microgravity changes at Te Maari craters, New Zealand

NASA Astrophysics Data System (ADS)

Miller, Craig A.; Currenti, Gilda; Hamling, Ian; Williams-Jones, Glyn

2018-05-01

Fluid transfer and ground deformation at hydrothermal systems occur both as a precursor to, or as a result of, an eruption. Typically studies focus on pre-eruption changes to understand the likelihood of unrest leading to eruption; however, monitoring post-eruption changes is important for tracking the return of the system towards background activity. Here we describe processes occurring in a hydrothermal system following the 2012 eruption of Upper Te Maari crater on Mt Tongariro, New Zealand, from observations of microgravity change and deformation. Our aim is to assess the post-eruption recovery of the system, to provide a baseline for long-term monitoring. Residual microgravity anomalies of up to 92 ± 11 μGal per year are accompanied by up to 0.037 ± 0.01 m subsidence. We model microgravity changes using analytic solutions to determine the most likely geometry and source location. A multiobjective inversion tests whether the gravity change models are consistent with the observed deformation. We conclude that the source of subsidence is separate from the location of mass addition. From this unusual combination of observations, we develop a conceptual model of fluid transfer within a condensate layer, occurring in response to eruption-driven pressure changes. We find that depressurisation drives the evacuation of pore fluid, either exiting the system completely as vapour through newly created vents and fumaroles, or migrating to shallower levels where it accumulates in empty pore space, resulting in positive gravity changes. Evacuated pores then collapse, causing subsidence. In addition we find that significant mass addition occurs from influx of meteoric fluids through the fractured hydrothermal seal. Long-term combined microgravity and deformation monitoring will allow us to track the resealing and re-pressurisation of the hydrothermal system and assess what hazard it presents to thousands of hikers who annually traverse the volcano, within 2 km of the eruption site.

DOE Office of Scientific and Technical Information (OSTI.GOV)

G.A. Valentine; F.V. Perry; D. Krier

Five Pleistocene basaltic volcanoes in Crater Flat (southern Nevada) demonstrate the complexity of eruption processes associated with small-volume basalts and the effects of initial emplacement characteristics on post-eruptive geomorphic evolution of the volcanic surfaces. The volcanoes record eruptive processes in their pyroclastic facies ranging from ''classical'' Strombolian mechanisms to, potentially, violent Strombolian mechanisms. Cone growth was accompanied, and sometimes disrupted, by effusion of lavas from the bases of cones. Pyroclastic cones were built upon a gently southward-sloping surface and were prone to failure of their down-slope (southern) flanks. Early lavas flowed primarily southward and, at Red and Black Cone volcanoes,more » carried abundant rafts of cone material on the tops of the flows. These resulting early lava fields eventually built platforms such that later flows erupted from the eastern (at Red Cone) and northern (at Black Cone) bases of the cones. Three major surface features--scoria cones, lava fields with abundant rafts of pyroclastic material, and lava fields with little or no pyroclastic material--experienced different post-eruptive surficial processes. Contrary to previous interpretations, we argue that the Pleistocene Crater Flat volcanoes are monogenetic, each having formed in a single eruptive episode lasting months to a few years, and with all eruptive products having emanated from the area of the volcanoes main cones rather than from scattered vents. Geochemical variations within the volcanoes must be interpreted within a monogenetic framework, which implies preservation of magma source heterogeneities through ascent and eruption of the magmas.« less

Seismic equivalents of volcanic jet scaling laws and multipoles in acoustics

NASA Astrophysics Data System (ADS)

Haney, Matthew M.; Matoza, Robin S.; Fee, David; Aldridge, David F.

2018-04-01

We establish analogies between equivalent source theory in seismology (moment-tensor and single-force sources) and acoustics (monopoles, dipoles and quadrupoles) in the context of volcanic eruption signals. Although infrasound (acoustic waves < 20 Hz) from volcanic eruptions may be more complex than a simple monopole, dipole or quadrupole assumption, these elementary acoustic sources are a logical place to begin exploring relations with seismic sources. By considering the radiated power of a harmonic force source at the surface of an elastic half-space, we show that a volcanic jet or plume modelled as a seismic force has similar scaling with respect to eruption parameters (e.g. exit velocity and vent area) as an acoustic dipole. We support this by demonstrating, from first principles, a fundamental relationship that ties together explosion, torque and force sources in seismology and highlights the underlying dipole nature of seismic forces. This forges a connection between the multipole expansion of equivalent sources in acoustics and the use of forces and moments as equivalent sources in seismology. We further show that volcanic infrasound monopole and quadrupole sources exhibit scalings similar to seismicity radiated by volume injection and moment sources, respectively. We describe a scaling theory for seismic tremor during volcanic eruptions that agrees with observations showing a linear relation between radiated power of tremor and eruption rate. Volcanic tremor over the first 17 hr of the 2016 eruption at Pavlof Volcano, Alaska, obeyed the linear relation. Subsequent tremor during the main phase of the eruption did not obey the linear relation and demonstrates that volcanic eruption tremor can exhibit other scalings even during the same eruption.

ERUPTING FILAMENTS WITH LARGE ENCLOSING FLUX TUBES AS SOURCES OF HIGH-MASS THREE-PART CMEs, AND ERUPTING FILAMENTS IN THE ABSENCE OF ENCLOSING FLUX TUBES AS SOURCES OF LOW-MASS UNSTRUCTURED CMEs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hutton, Joe; Morgan, Huw, E-mail: joh9@aber.ac.uk

2015-11-01

The 3-part appearance of many coronal mass ejections (CMEs) arising from erupting filaments emerges from a large magnetic flux tube structure, consistent with the form of the erupting filament system. Other CMEs arising from erupting filaments lack a clear 3-part structure and reasons for this have not been researched in detail. This paper aims to further establish the link between CME structure and the structure of the erupting filament system and to investigate whether CMEs which lack a 3-part structure have different eruption characteristics. A survey is made of 221 near-limb filament eruptions observed from 2013 May 03 to 2014more » June 30 by Extreme UltraViolet (EUV) imagers and coronagraphs. Ninety-two filament eruptions are associated with 3-part structured CMEs, 41 eruptions are associated with unstructured CMEs. The remaining 88 are categorized as failed eruptions. For 34% of the 3-part CMEs, processing applied to EUV images reveals the erupting front edge is a pre-existing loop structure surrounding the filament, which subsequently erupts with the filament to form the leading bright front edge of the CME. This connection is confirmed by a flux-rope density model. Furthermore, the unstructured CMEs have a narrower distribution of mass compared to structured CMEs, with total mass comparable to the mass of 3-part CME cores. This study supports the interpretation of 3-part CME leading fronts as the outer boundaries of a large pre-existing flux tube. Unstructured (non 3-part) CMEs are a different family to structured CMEs, arising from the eruption of filaments which are compact flux tubes in the absence of a large system of enclosing closed field.« less

Magma transfer at Campi Flegrei caldera (Italy) before the 1538 AD eruption

NASA Astrophysics Data System (ADS)

Di Vito, Mauro A.; Acocella, Valerio; Aiello, Giuseppe; Barra, Diana; Battaglia, Maurizio; Carandente, Antonio; Del Gaudio, Carlo; de Vita, Sandro; Ricciardi, Giovanni; Rico, Ciro; Scandone, Roberto; Terrasi, Filippo

2017-04-01

Defining and understanding the shallow transfer of magma at volcanoes is crucial to forecast eruptions, possibly the ultimate goal of volcanology. This is particularly challenging at felsic calderas experiencing unrest, which typically includes significant changes in seismicity, deformation and degassing rates. Caldera unrest is particularly frequent, affects wide areas and often does not culminate in an eruption. Moreover its evidence is usually complicated by the presence of a hydrothermal system. As a result, forecasting any eruption and vent-opening sites within a caldera is very difficult. The Campi Flegrei caldera (CFc), in the densely inhabited area of Naples (Italy), is commonly considered one of the most dangerous active volcanic systems. CFc is a 12 km wide depression hosting two nested calderas formed during the eruptions of the Campanian Ignimbrite ( 39 ka) and the Neapolitan Yellow Tuff ( 15 ka). In the last 5 ka, resurgence, with uplift >60 m close to the central part of the caldera, was accompanied by volcanism between 4.8 and 3.8 ka. After 3 ka of quiescence, increasing seismicity and uplift preceded the last eruption at Monte Nuovo in 1538 for several decades. The most recent activity culminated in four unrest episodes between 1950-1952, 1969-1972, 1982-1984 and 2005-Present, with a cumulative uplift at Pozzuoli of 4.5 m; the present unrest episode has been interpreted as being magma-driven. These unrest episodes are considered the most evident expression of a longer-term (centuries or more) restless activity. The post-1980 deformation largely results from a magmatic oblate or sill-like source at 4 km depth below Pozzuoli. Despite the restless activity of CFc, the recent unrest episodes did not culminate in eruption, so that any possibility to define the pre-eruptive shallow transfer of magma remains elusive. Indeed, this definition is a crucial step in order to identify and understand pre-eruptive processes, and thus to make any forecast. To fill this gap, we focused on the last eruption of 1538, reconstructing its pre-eruptive deformation pattern. For this, we exploited the unique historical, archaeological, geological and long-term geodetic record of the caldera to carefully determine the height variations (and related errors) of 20 selected sites along its coastline. The integration of this large dataset permitted the first reconstruction of pre-eruptive short- and long-term ground deformation of the CFc and to model the magma transfer before the eruption. Our data suggest a progressive magma accumulation from 1251 to 1536 in a 4.6±0.9 km deep source below the caldera centre, and its transfer, between 1536 and 1538, to a 3.8±0.6 km deep magmatic source 4 km NW of the caldera centre, below Monte Nuovo; this peripheral source fed the eruption through a shallower source, 0.4±0.3 km deep. This reconstruction corroborates the existence of a stationary oblate source, below the caldera centre, that was feeding lateral eruptions for the last 5 ka, and suggests: repeated emplacement of magma through intrusions below the caldera centre; occasional lateral transfer of magma feeding non-central eruptions within the caldera. Comparison with historical unrest at calderas worldwide suggests that this behavior is common.

The 1998-2001 submarine lava balloon eruption at the Serreta ridge (Azores archipelago): Constraints from volcanic facies architecture, isotope geochemistry and magnetic data

NASA Astrophysics Data System (ADS)

Madureira, Pedro; Rosa, Carlos; Marques, Ana Filipa; Silva, Pedro; Moreira, Manuel; Hamelin, Cédric; Relvas, Jorge; Lourenço, Nuno; Conceição, Patrícia; Pinto de Abreu, Manuel; Barriga, Fernando J. A. S.

2017-01-01

The most recent submarine eruption observed offshore the Azores archipelago occurred between 1998 and 2001 along the submarine Serreta ridge (SSR), 4-5 nautical miles WNW of Terceira Island. This submarine eruption delivered abundant basaltic lava balloons floating at the sea surface and significantly changed the bathymetry around the eruption area. Our work combines bathymetry, volcanic facies cartography, petrography, rock magnetism and geochemistry in order to (1) track the possible vent source at seabed, (2) better constrain the Azores magma source(s) sampled through the Serreta submarine volcanic event, and (3) interpret the data within the small-scale mantle source heterogeneity framework that has been demonstrated for the Azores archipelago. Lava balloons sampled at sea surface display a radiogenic signature, which is also correlated with relatively primitive (low) 4He/3He isotopic ratios. Conversely, SSR lavas are characterized by significantly lower radiogenic 87Sr/86Sr, 206Pb/204Pb and 208Pb/204Pb ratios than the lava balloons and the onshore lavas from the Terceira Island. SSR lavas are primitive, but incompatible trace-enriched. Apparent decoupling between the enriched incompatible trace element abundances and depleted radiogenic isotope ratios is best explained by binary mixing of a depleted MORB source and a HIMU­type component into magma batches that evolved by similar shallower processes in their travel to the surface. The collected data suggest that the freshest samples collected in the SSR may correspond to volcanic products of an unnoticed and more recent eruption than the 1998-2001 episode.

Back-Projection Imaging of extended, high-frequency pre-, co-, and post-eruptive seismicity at El Jefe Geyser, El Tatio Geyser Field, Chile

NASA Astrophysics Data System (ADS)

Kelly, C. L.; Lawrence, J. F.; Beroza, G. C.

2017-12-01

El Tatio Geyser Field in northern Chile is the third largest geyser field in the world. It is comprised of 3 basins that span 10 km x 10 km at an average elevation of 4250 m and contains at least 80 active geysers. Heavy tourist traffic and previous geothermal exploration make the field relatively non-pristine and ideal for performing minimally invasive geophysical experiments. We deployed a dense array of 51 L-28 3-component geophones (1-10 m spacing, corner frequency 4.5 Hz, 1000 Hz sample rate), and 6 Trillium 120 broadband seismometers (2-20 m spacing, long period corner 120 s, 500 Hz sample rate) in a 50 m x 50 m grid in the central Upper Geyser Basin (the largest basin in area at 5 km x 5 km) during October 2012 as part of a collaborative study of hydrothermal systems between Stanford University; U.C. Berkeley; U. of Chile, Santiago; U. of Tokyo; and the USGS. The seismic array was designed to target at El Jefe Geyser (EJG), a columnar geyser (eruption height 1-1.5 m) with a consistent periodic eruption cycle of 132 +/- 3 s. Seismicity at EJG was recorded continuously for 9 days during which 6000 total eruptions occurred. Excluding periods of high anthropogenic noise (i.e. tourist visits, field work), the array recorded 2000 eruptions that we use to create 4D time-lapse images of the evolution of seismic source locations before, during and after EJG eruptions. We use a new back-projection processing technique to locate geyser signals, which tend to be harmonic and diffuse in nature, during characteristic phases of the EJG eruption cycle. We obtain Vp and Vs from ambient-field tomography and estimates of P and S propagation from a hammer source recorded by the array. We use these velocities to back-project and correlate seismic signals from all available receiver-pairs to all potential source locations in a subsurface model assuming straight-line raypaths. We analyze results for individual and concurrent geyser sources throughout an entire EJG eruption cycle and over multiple eruption cycles. We target specific seismic observations by restricting the frequency band of analysis (i.e., high or low frequency bands), and use our results to evaluate changes in source distributions before, during and after eruptions and compare them to synchronous surface observations (downhole pressure/temperature, discharge rate, thermal video).

The 2014-15 eruption and the short-term geochemical evolution of the Fogo volcano (Cape Verde): Evidence for small-scale mantle heterogeneity

NASA Astrophysics Data System (ADS)

Mata, J.; Martins, S.; Mattielli, N.; Madeira, J.; Faria, B.; Ramalho, R. S.; Silva, P.; Moreira, M.; Caldeira, R.; Moreira, M.; Rodrigues, J.; Martins, L.

2017-09-01

Recurrent eruptions at very active ocean island volcanoes provide the ideal means to gain insight on the scale of spatial variations at the mantle source and on temporal changes of magma genesis and evolution processes. In 2014, after 19 years of quiescence, Fogo volcano (Cape Verde Archipelago) experienced a new eruption, with the vents located 200 m from those of the 1995 eruption, and less than 2000 m from those of the 1951 event. This offered a unique opportunity to investigate the existence of small-scale mantle heterogeneities and the short-term compositional evolution of magmas erupted by a very active oceanic volcano like Fogo. Here we present petrological and geochemical data from the early stages of the Fogo's most recent eruption - started on November 23, 2014 - and compare them with the signature of previous eruptions (particularly those of 1995 and 1951). The magmas erupted in 2014 are alkaline (up to 23.4% and 0.94% of normative ne and lc, respectively) with somewhat evolved compositions (Mg # < 56), ranging from tephrites to phonotephrites. The eruption of phonotephritic lavas preceded the effusion of tephritic ones. Lavas carried to the surface clinopyroxene and kaersutite phenocrysts and cognate megacrysts, which indicate that the main stages of magma evolution occurred in magma chambers most probably located at mantle depths (25.6 ± 5.5 km below sea level). This was followed by a shallower (< 1.5 km below sea level) and shorter (≈ 50 days) magma stagnation before the eruption. 2014 magmas have more unradiogenic Sr and more radiogenic Nd compositions than those of the previous 1951 and 1995 eruptions, which generally have less radiogenic Pb ratios. These isotopic differences - coming from quasi-coeval materials erupted almost in the same place - are remarkable and reflect the small-scale heterogeneity of the underlying mantle source. Moreover, they reflect the limited isotopic averaging of the source composition during partial melting events as well as the inefficient homogenization within the plumbing system when on route to the surface. The lid effect of an old and thick lithosphere is considered of utmost importance to the preservation of a significant part of source heterogeneity by erupted magmas. The decrease in the contribution of an enriched component to the Fogo magmas in the 2014 eruption marks a change on the volcano short-term evolution that was characterized by a progressive increase of the importance of such a component. Nb/U ratios of the 2014 lavas are similar, within 2σ, to the mean value of OIB, but significantly lower than those reported for the 1995 and 1951 eruptions. This is considered to reflect the lack of significant mixing of the 2014 magmas with lithospheric melts, as opposed to what is here hypothesised for the two previous eruptions.

Infrasonic observations of the June 2009 Sarychev Peak eruption, Kuril Islands: Implications for infrasonic monitoring of remote explosive volcanism

NASA Astrophysics Data System (ADS)

Matoza, Robin S.; Le Pichon, Alexis; Vergoz, Julien; Herry, Pascal; Lalande, Jean-Marie; Lee, Hee-il; Che, Il-Young; Rybin, Alexander

2011-02-01

Sarychev Peak (SP), located on Ostrov Matua, Kurils, erupted explosively during 11-16 June 2009. Whereas remote seismic stations did not record the eruption, we report atmospheric infrasound (acoustic wave ~ 0.01-20 Hz) observations of the eruption at seven infrasound arrays located at ranges of ~ 640-6400 km from SP. The infrasound arrays consist of stations of the International Monitoring System global infrasound network and additional stations operated by the Korea Institute of Geoscience and Mineral Resources. Signals at the three closest recording stations IS44 (643 km, Petropavlovsk-Kamchatskiy, Kamchatka Krai, Russia), IS45 (1690 km, Ussuriysk, Russia), and IS30 (1774 km, Isumi, Japan) represent a detailed record of the explosion chronology that correlates well with an eruption chronology based on satellite data (TERRA, NOAA, MTSAT). The eruption chronology inferred from infrasound data has a higher temporal resolution than that obtained with satellite data. Atmosphere-corrected infrasonic source locations determined from backazimuth cross-bearings of first-arrivals have a mean centroid ~ 15 km from the true location of SP. Scatter in source locations of up to ~ 100 km result from currently unresolved details of atmospheric propagation and source complexity. We observe systematic time-variations in trace-velocity, backazimuth deviation, and signal frequency content at IS44. Preliminary investigation of atmospheric propagation from SP to IS44 indicates that these variations can be attributed to solar tide variability in the thermosphere. It is well known that additional information about active volcanic processes can be learned by deploying infrasonic sensors with seismometers at erupting volcanoes. This study further highlights the significant potential of infrasound arrays for monitoring volcanic regions such as the Kurils that have only sparse seismic network coverage.

Eruptive Source Parameters from Near-Source Gravity Waves Induced by Large Vulcanian eruptions

NASA Astrophysics Data System (ADS)

Barfucci, Giulia; Ripepe, Maurizio; De Angelis, Silvio; Lacanna, Giorgio; Marchetti, Emanuele

2016-04-01

The sudden ejection of hot material from volcanic vent perturbs the atmosphere generating a broad spectrum of pressure oscillations from acoustic infrasound (<10 Hz) to gravity waves (<0.03 Hz). However observations of gravity waves excited by volcanic eruptions are still rare, mostly limited to large sub-plinian eruptions and frequently at large distance from the source (>100 km). Atmospheric Gravity waves are induced by perturbations of the hydrostatic equilibrium of the atmosphere and propagate within a medium with internal density stratification. They are initiated by mechanisms that cause the atmosphere to be displaced as for the injection of volcanic ash plume during an eruption. We use gravity waves to infer eruptive source parameters, such as mass eruption rate (MER) and duration of the eruption, which may be used as inputs in the volcanic ash transport and dispersion models. We present the analysis of near-field observations (<7 km) of atmospheric gravity waves, with frequencies of 0.97 and 1.15 mHz, recorded by a pressure sensors network during two explosions in July and December 2008 at Soufrière Hills Volcano, Montserrat. We show that gravity waves at Soufrière Hills Volcano originate above the volcanic dome and propagate with an apparent horizontal velocities of 8-10 m/s. Assuming a single mass injection point source model, we constrain the source location at ~3.5 km a.s.l., above the vent, duration of the gas thrust < 140 s and MERs of 2.6 and 5.4 x10E7 kg/s, for the two eruptive events. Source duration and MER derived by modeling Gravity Waves are fully compatible with others independent estimates from field observations. Our work strongly supports the use of gravity waves to model eruption source parameters and can have a strong impact on our ability to monitor volcanic eruption at a large distance and may have future application in assessing the relative magnitude of volcanic explosions.

Using volcanic tremor for eruption forecasting at White Island volcano (Whakaari), New Zealand

NASA Astrophysics Data System (ADS)

Chardot, Lauriane; Jolly, Arthur D.; Kennedy, Ben M.; Fournier, Nicolas; Sherburn, Steven

2015-09-01

Eruption forecasting is a challenging task because of the inherent complexity of volcanic systems. Despite remarkable efforts to develop complex models in order to explain volcanic processes prior to eruptions, the material Failure Forecast Method (FFM) is one of the very few techniques that can provide a forecast time for an eruption. However, the method requires testing and automation before being used as a real-time eruption forecasting tool at a volcano. We developed an automatic algorithm to issue forecasts from volcanic tremor increase episodes recorded by Real-time Seismic Amplitude Measurement (RSAM) at one station and optimised this algorithm for the period August 2011-January 2014 which comprises the recent unrest period at White Island volcano (Whakaari), New Zealand. A detailed residual analysis was paramount to select the most appropriate model explaining the RSAM time evolutions. In a hindsight simulation, four out of the five small eruptions reported during this period occurred within a failure window forecast by our optimised algorithm and the probability of an eruption on a day within a failure window was 0.21, which is 37 times higher than the probability of having an eruption on any day during the same period (0.0057). Moreover, the forecasts were issued prior to the eruptions by a few hours which is important from an emergency management point of view. Whereas the RSAM time evolutions preceding these four eruptions have a similar goodness-of-fit with the FFM, their spectral characteristics are different. The duration-amplitude distributions of the precursory tremor episodes support the hypothesis that several processes were likely occurring prior to these eruptions. We propose that slow rock failure and fluid flow processes are plausible candidates for the tremor source of these episodes. This hindsight exercise can be useful for future real-time implementation of the FFM at White Island. A similar methodology could also be tested at other volcanoes even if only a limited network is available.

Volcanic deformation sources associated with Fogo 2011-2012 unrest, Azores - The first modelling result

NASA Astrophysics Data System (ADS)

Okada, Jun; Araújo, João; Bonforte, Alessandro; Guglielmino, Francesco; Lorenzo, Maria; Ferreira, Teresa

2016-04-01

Volcanic deformation is often observed at many active volcanoes in the world by using space geodesy techniques, namely GNSS and InSAR. More difficulties in judgement if eruptions are imminent or not arise when such phenomenon occurs at dormant volcanoes due to the lack of eruption experiences with monitoring data. The eruption triggering mechanism is still controversial at many cases, but many attempts to image deformation sources beneath volcanoes have been made using geophysical inversion techniques. In this study, we show the case study of Fogo (Água de Pau) volcano, S. Miguel Island, Azores which represents over 450 years of eruption dormancy since 1563-1564. In the recent decades Fogo has exhibited three prominent unrest episodes (1989, 2003-2006, and 2011-2012). The lack of geochemical and hydrothermal evidences for a magmatic intrusion during those episodes does not encourage discussions on resuming volcanic activity of Fogo. However, the inflation/uplift are evident on the edifices at least for the last two unrest episodes based on GPS data by Trota et al. (2009) and Okada et al. (2015), respectively. The preliminary deformation modelling based on repeated GPS campaign data suggested a shallow expanding spheroid (Trota et al. 2009) or a single Mogi sources beneath the summit caldera. We performed a more integrated inversion for the 2011-2012 episode using a genetic algorithm optimizing the source parameters. The best fit model agrees well with the regional/local tectonic lineament suggesting the close relation between the volcanic sources and the regional/local tectonics. The regional extensional stress (between Eurasia and Nubia plates) may play important roles for the ascent of volcanic fluids at Fogo volcano. We do not discard the possibility that Fogo may have been preparing for eruptions by intermittent ascents of magma at shallow crust (i.e. experiencing "failed eruptions") during the apparent dormant period. As a local monitoring agency, CIVISA (Center for Information and Seismovolcanic Surveillance of the Azores) continues to monitor Fogo's deformation in order to track changes in the source processes (source position and geometry, volume, pressure, etc.) as well as Fogo's seismicity and geochemistry.

El Cobreloa: A geyser with two distinct eruption styles

NASA Astrophysics Data System (ADS)

Namiki, A.; Munoz, C.; Manga, M.; Hurwitz, S.; King, E.; Negri, A.; Ortega, P.; Patel, A.; Rudolph, M.

2013-12-01

El Cobreloa geyser has two distinct eruption styles: vigorous major eruptions, and less energetic minor eruptions. Minor eruptions splash hot water intermittently over an approximately 4 minute time period. Major eruptions begin with an eruption style similar to minor eruptions, but then transition to a voluminous and water-dominated eruption, and finally end with energetic steam discharge. The steam discharge continues for approximately 1 hour. We calculated the eruption intervals by visual observations, acoustic measurements, and ground temperature measurements. All of measurements consistently show that each eruption style has a regular interval: 4 hours and 40 minutes for major eruptions, and ~13 minutes for minor eruptions. From these observations, we infer that there are two boiling loci that source each type of eruption, one at the bottom and the other at the top of the conduit. If the bottom of the conduit is hot enough, boiling begins at the bottom of the conduit to make a steam slug. As this slug ascends in the conduit, it heats the surrounding water. If the slug rises fast enough it splashes water when it reaches the surface, creating minor eruptions. Each successive steam slug continues to heat water in the conduit until it eventually reaches the boiling temperature everywhere. Once the top of the conduit begins boiling, the energetic steam discharge begins and the boiling propagates downward. Such a process causes major eruption. Geysers are often studied as an analogue to magmatic volcanoes because it is easier to document how mass and energy transfer lead to eruptions. El Cobreloa provides insight into how the system becomes primed for large eruptions.

A new approach to investigate an eruptive paroxysmal sequence using camera and strainmeter networks: Lessons from the 3-5 December 2015 activity at Etna volcano

NASA Astrophysics Data System (ADS)

Bonaccorso, A.; Calvari, S.

2017-10-01

Explosive sequences are quite common at basaltic and andesitic volcanoes worldwide. Studies aimed at short-term forecasting are usually based on seismic and ground deformation measurements, which can be used to constrain the source region and quantify the magma volume involved in the eruptive process. However, during single episodes of explosive sequences, integration of camera remote sensing and geophysical data are scant in literature, and the total volume of pyroclastic products is not determined. In this study, we calculate eruption parameters for four powerful lava fountains occurring at the main and oldest Mt. Etna summit crater, Voragine, between 3 and 5 December 2015. These episodes produced impressive eruptive columns and plume clouds, causing lapilli and ash fallout to more than 100 km away. We analyse these paroxysmal events by integrating the images recorded by a network of monitoring cameras and the signals from three high-precision borehole strainmeters. From the camera images we calculated the total erupted volume of fluids (gas plus pyroclastics), inferring amounts from 1.9 ×109 m3 (first event) to 0.86 ×109 m3 (third event). Strain changes recorded during the first and most powerful event were used to constrain the depth of the source. The ratios of strain changes recorded at two stations during the four lava fountains were used to constrain the pyroclastic fraction for each eruptive event. The results revealed that the explosive sequence was characterized by a decreasing trend of erupted pyroclastics with time, going from 41% (first event) to 13% (fourth event) of the total erupted pyroclastic volume. Moreover, the volume ratio fluid/pyroclastic decreased markedly in the fourth and last event. To the best of our knowledge, this is the first time ever that erupted volumes of both fluid and pyroclastics have been estimated for an explosive sequence from a monitoring system using permanent cameras and high precision strainmeters. During future explosive paroxysmal sequences this new approach might help in monitoring their evolution also to understand when/if they are going to finish. Knowledge of the total gas and pyroclastic fractions erupted during each lava fountain episode would improve our understanding of their processes and eruptive behaviour.

Modeling Volcanic Eruption Parameters by Near-Source Internal Gravity Waves.

PubMed

Ripepe, M; Barfucci, G; De Angelis, S; Delle Donne, D; Lacanna, G; Marchetti, E

2016-11-10

Volcanic explosions release large amounts of hot gas and ash into the atmosphere to form plumes rising several kilometers above eruptive vents, which can pose serious risk on human health and aviation also at several thousands of kilometers from the volcanic source. However the most sophisticate atmospheric models and eruptive plume dynamics require input parameters such as duration of the ejection phase and total mass erupted to constrain the quantity of ash dispersed in the atmosphere and to efficiently evaluate the related hazard. The sudden ejection of this large quantity of ash can perturb the equilibrium of the whole atmosphere triggering oscillations well below the frequencies of acoustic waves, down to much longer periods typical of gravity waves. We show that atmospheric gravity oscillations induced by volcanic eruptions and recorded by pressure sensors can be modeled as a compact source representing the rate of erupted volcanic mass. We demonstrate the feasibility of using gravity waves to derive eruption source parameters such as duration of the injection and total erupted mass with direct application in constraining plume and ash dispersal models.

Modeling Volcanic Eruption Parameters by Near-Source Internal Gravity Waves

PubMed Central

Ripepe, M.; Barfucci, G.; De Angelis, S.; Delle Donne, D.; Lacanna, G.; Marchetti, E.

2016-01-01

Volcanic explosions release large amounts of hot gas and ash into the atmosphere to form plumes rising several kilometers above eruptive vents, which can pose serious risk on human health and aviation also at several thousands of kilometers from the volcanic source. However the most sophisticate atmospheric models and eruptive plume dynamics require input parameters such as duration of the ejection phase and total mass erupted to constrain the quantity of ash dispersed in the atmosphere and to efficiently evaluate the related hazard. The sudden ejection of this large quantity of ash can perturb the equilibrium of the whole atmosphere triggering oscillations well below the frequencies of acoustic waves, down to much longer periods typical of gravity waves. We show that atmospheric gravity oscillations induced by volcanic eruptions and recorded by pressure sensors can be modeled as a compact source representing the rate of erupted volcanic mass. We demonstrate the feasibility of using gravity waves to derive eruption source parameters such as duration of the injection and total erupted mass with direct application in constraining plume and ash dispersal models. PMID:27830768

Seismic processes and migration of magma during the Great Tolbachik Fissure Eruption of 1975-1976 and Tolbachik Fissure Eruption of 2012-2013, Kamchatka Peninsula

NASA Astrophysics Data System (ADS)

Fedotov, S. A.; Slavina, L. B.; Senyukov, S. L.; Kuchay, M. S.

2015-12-01

Seismic and volcanic processes in the area of the northern group of volcanoes (NGV) in Kamchatka Peninsula that accompanied the Great Tolbachik Fissure Eruption (GTFE) of 1975-1976 and the Tolbachik Fissure Eruption (TFE, or "50 let IViS" due to anniversary of the Institute of Volcanology and Seismology, Far East Branch, Russian Academy of Sciences) of 2012-2013 and the seismic activity between these events are considered. The features of evolution of seismic processes of the major NGV volcanoes (Ploskii Tolbachik, Klyuchevskoy, Bezymannyi, and Shiveluch) are revealed. The distribution of earthquakes along depth, their spatial and temporal migration, and the relation of seismic and volcanic activity are discussed. The major features of seismic activity during the GTFE preparation and evolution and a development of earthquake series preceding the origin of the northern and southern breaks are described. The character of seismic activity between the GTFE and TFE is shown. The major peculiarities of evolution of seismic activity preceding and accompanying the TFE are described. The major magma sources and conduits of the NGV volcanoes are identified, as is the existence of a main conduit in the mantle and a common intermediate source for the entire NGV, the depth of which is 25-35 km according to seismic data. The depth of a neutral buoyancy layer below the NGV is 15-20 km and the source of areal volcanism of magnesian basalts northeast of the Klyuchevskoy volcano is located at depth of ~20 km. These data support the major properties of a 2010 geophysical model of magmatic feeding system of the Klyuchevskoy group of volcanoes. The present paper covers a wider NGV area and is based on the real experimental observations.

Rapid Mantle Source Variations During the Latest Episode of Kilauea's Prolonged Pu'u O'o Eruption, Hawaii

NASA Astrophysics Data System (ADS)

Marske, J. P.; Garcia, M. O.; Pietruszka, A. J.; Norman, M. D.; Rhodes, J. M.

2006-12-01

Nearly 24 years of continuous geochemical monitoring of lavas from the current Pu'u O'o eruption allow us to probe the mantle processes beneath Kilauea Volcano in unparalleled detail. Here we present new measurements Pb, Sr, and Nd isotope ratios and major- and trace-element abundances for lavas from episode 55 (1997-2006), which marks the longest and most voluminous interval of this eruption. Pu'u O'o lavas erupted since 1985 display systematic decreases in their TiO2, K2O, P2O5 and CaO abundances (normalized to 10 wt. % MgO to correct for olivine control) due to changes in the parental magma composition. Incompatible element ratios (e.g., Ba/Nb and La/Y) also show overall temporal decreases. Earlier erupted Pu'u O'o lavas displayed the most significant decrease in incompatible element ratios with near constant SiO2 contents, and a gradual increase in 87Sr/86Sr ratios. However, episode 55 lavas record significant increases in MgO- normalized SiO2 contents and 87Sr/86Sr with nearly constant (e.g. Ba/Nb) or a slightly reversed (e.g., TiO2 and K2O) trends in incompatible element ratios and abundances. There is little variation of 206Pb/204Pb ratios in lavas (18.38-18.43) erupted since 1985. Neither a single mantle source composition nor a change in partial melting conditions alone can explain these observations. Based on the isotopic and chemical variability, we conclude that early Pu'u O'o lavas originated from two distinct mantle source components: (1) a long-term depleted component (with relatively low 87Sr/86Sr ratios) that originated within the deep source of the Hawaiian plume that characterizes the earlier part of the eruption (1985-1992), and (2) a recently depleted component (i.e. a component that was recently depleted by prior melting) with low abundances of incompatible elements became increasingly important from 1992-1997. More recently, Pu'u O'o has tapped greater proportions of a new (3) long-term less depleted component (with higher 87Sr/86Sr ratios than observed from 1985-1992) that originated within the deep source region of the plume. This third component lies within typical Pb, Sr and Nd isotopic space for Kilauea, but represents a new source composition for the Pu'u O'o eruption. The systematic geochemical evolution of Pu'u O'o lavas reflects changes in the proportions of the mantle source components tapped throughout the eruption. The rapid isotope variations (on a time scale of years) in the most recent lavas suggest the mantle source components are heterogeneous on an extremely small scale, relative to the size of Kilauea's melting region.

Postglacial eruptive history of the Western Volcanic Zone, Iceland

NASA Astrophysics Data System (ADS)

Sinton, John; GröNvold, Karl; SæMundsson, KristjáN.

2005-12-01

New field observations, age constraints, and extensive chemical analyses define the complete postglacial eruptive history of the 170-km-long Western Volcanic Zone (WVZ) of Iceland, the ultraslow-spreading western boundary of the south Iceland microplate. We have identified 44 separate eruptive units, 10 of which are small-volume eruptions associated with the flanking Grímsnes system. Overall chemical variations are consistent with very simplified models of melting of a source approximating primitive mantle composition. The 17 eruptions in the first 3000 years of postglacial time account for about 64% of the total postglacial production and are incompatible-element depleted compared to younger units, consistent with enhanced melting as a consequence of rebound immediately following deglaciation. Steadily declining eruption rates for the last 9000 years also correlate with changes in average incompatible element ratios that appear to reflect continued decline in melting extents to the present day. This result is not restricted to the WVZ, however, and may herald a decline in melting throughout all of western Iceland during later postglacial time. Lavas from the northern part of the WVZ are depleted in incompatible elements relative to those farther south at all times, indicating either a long-wavelength gradient in mantle source composition or variations in the melting process along axis. We find no evidence in the postglacial volcanic record for current failure of the WVZ, despite evidence for continued propagation of the eastern margin of the microplate. The dominance of lava shields in the eruptive history of the WVZ contrasts with the higher number of fissure eruptions in other Icelandic volcanic zones. WVZ shields represent long-duration, low-effusion rate eruptions fed by recharge magma arising out of the mantle. Average effusion rate is the key variable distinguishing shield and fissure eruptions, both within the WVZ and between different volcanic zones. High effusion rate, large-volume eruptions require the presence of large crustal magma reservoirs, which have been rare or absent in the WVZ throughout postglacial time.

Magmatic and Volcanic Processes Interpreted from Recent Ash Emissions from Nevado del Ruiz, Colombia

NASA Astrophysics Data System (ADS)

Wall, K. T.; Harpel, C. J.; Martinez, L. M.; Ceballos, J. A.; Cortés, G. P.

2017-12-01

Nevado del Ruiz is a composite volcano located in the Colombian Central Cordillera. It is the modern edifice of the Nevado del Ruiz Volcanic Complex that has been active since 1.8 Ma. Through historic times, Ruiz has exhibited decades-long eruptive stages that include minor explosions and fumarolic activity bracketing one major magmatic event. Modern eruptive activity began with seismic unrest in 1984, a small explosive eruption on September 11, 1985, and the catastrophic lahar-generating eruption of November 13, 1985. Since then, Ruiz has periodically erupted plumes up to a few kilometers above the crater, including a phreatomagmatic eruption on September 1, 1989, eruptions on May 29 (1 km plume) and June 30 (8 km plume) 2012, and frequent minor ash emissions from 2015 through the present. We have examined a suite of samples from the 1985, 1989, 2012, and 2015 eruptions to assess the origin of erupted materials (juvenile vs. non-juvenile) and nature of eruptive and subvolcanic processes (e.g. fresh intrusion, phreatic explosion). The November 1985 ash is dominated by beige to light gray pumice and free crystals, while samples from September 1985 and the 1989 through 2015 eruptions contain other fresh looking angular to subangular particles, including dense glassy to microcrystalline chips and vesicular glass shards. If juvenile, as we suspect, these components indicate phreatomagmatic to magmatic eruptive processes. Vesicular glass ranges from colorless to brown, often within the same sample, suggesting that bimodal magmatic sources, as recorded by mingled pumices of November 1985, have continued to play a role in eruptions at Ruiz. In particular, ash from 1989 contains vesicular glass that is 65% colorless to beige and 35% brown. Sparse, very dark brown vesicular glass appears in ash from June 2012—a larger eruption than that of May 2012—and is also observed in some 2015 samples, suggesting a more prominent mafic component. In addition to our observations from binocular microscopy, we will present results from SEM and electron microprobe analyses that further clarify the magmatic conditions that produced these dense and vesicular glassy components, and that test our hypothesis that these particles represent juvenile material from continued phreatomagmatic to magmatic eruptions at Ruiz.

Infrasound and SO2 Observations of the 2011 Explosive Eruption of Nabro Volcano, Eritrea

NASA Astrophysics Data System (ADS)

Fee, D.; Carn, S. A.; Prata, F.

2011-12-01

Nabro volcano, Eritrea erupted explosively on 12 June 2011 and produced near continuous emissions and infrasound until mid-July. The eruption disrupted air traffic and severely affected communities in the region. Although the eruption was relatively ash-poor, it produced significant SO2 emissions, including: 1) the highest SO2 column ever retrieved from space (3700 DU), 2) >1.3 Tg SO2 mass on 13 June, and 3) >2 Tg of SO2 for the entire eruption, one of the largest eruptive SO2 masses produced since the 1991 eruption of Mt. Pinatubo. Peak emissions reached well into the stratosphere (~19 km). Although the 12 June eruption was preceded by significant seismicity and clearly detected by satellite sensors, Nabro volcano is an understudied volcano that lies in a remote region with little ground-based monitoring. The Nabro eruption also produced significant infrasound signals that were recorded by two infrasound arrays: I19DJ (Djibouti, 264 km) and I32KE (Kenya, 1708 km). The I19DJ infrasound array detected the eruption with high signal-noise and provides the most detailed eruption chronology available, including eruption onset, duration, changes in intensity, etc. As seen in numerous other studies, sustained low frequency infrasound from Nabro is coincident with high-altitude emissions. Unexpectedly, the eruption also produced hundreds of short-duration, impulsive explosion signals, in addition to the sustained infrasonic jetting signals more typical of subplinian-plinian eruptions. These explosions are variable in amplitude, duration, and often cluster in groups. Here we present: 1) additional analyses, classification, and source estimation of the explosions, 2) infrasound propagation modeling to determine acoustic travel times and propagation paths, 3) detection and characterization of the SO2 emissions using the Ozone Monitoring Instrument (OMI) and Spin Enhanced Visible and Infra-Red Instrument (SEVIRI), and 4) a comparison between the relative infrasound energy and SO2 measurements to investigate the relationship between degassing and infrasound, and to speculate on possible eruption source mechanisms. This example, in addition to other recent work, demonstrates the utility of using regional and global infrasound arrays to characterize explosive volcanic eruptions, particularly in remote and poorly monitored regions. Further, comparison of SO2 emissions and infrasound lends insight into degassing processes and shows the potential to use infrasound as a real-time, remote means to detect hazardous emissions.

Preliminary Spreadsheet of Eruption Source Parameters for Volcanoes of the World

USGS Publications Warehouse

Mastin, Larry G.; Guffanti, Marianne; Ewert, John W.; Spiegel, Jessica

2009-01-01

Volcanic eruptions that spew tephra into the atmosphere pose a hazard to jet aircraft. For this reason, the International Civil Aviation Organization (ICAO) has designated nine Volcanic Ash and Aviation Centers (VAACs) around the world whose purpose is to track ash clouds from eruptions and notify aircraft so that they may avoid these ash clouds. During eruptions, VAACs and their collaborators run volcanic-ashtransport- and-dispersion (VATD) models that forecast the location and movement of ash clouds. These models require as input parameters the plume height H, the mass-eruption rate , duration D, erupted volume V (in cubic kilometers of bubble-free or 'dense rock equivalent' [DRE] magma), and the mass fraction of erupted tephra with a particle size smaller than 63 um (m63). Some parameters, such as mass-eruption rate and mass fraction of fine debris, are not obtainable by direct observation; others, such as plume height or duration, are obtainable from observations but may be unavailable in the early hours of an eruption when VATD models are being initiated. For this reason, ash-cloud modelers need to have at their disposal source parameters for a particular volcano that are based on its recent eruptive history and represent the most likely anticipated eruption. They also need source parameters that encompass the range of uncertainty in eruption size or characteristics. In spring of 2007, a workshop was held at the U.S. Geological Survey (USGS) Cascades Volcano Observatory to derive a protocol for assigning eruption source parameters to ash-cloud models during eruptions. The protocol derived from this effort was published by Mastin and others (in press), along with a world map displaying the assigned eruption type for each of the world's volcanoes. Their report, however, did not include the assigned eruption types in tabular form. Therefore, this Open-File Report presents that table in the form of an Excel spreadsheet. These assignments are preliminary and will be modified to follow upcoming recommendations by the volcanological and aviation communities.

SYMPATHETIC SOLAR FILAMENT ERUPTIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Rui; Liu, Ying D.; Zimovets, Ivan

2016-08-10

The 2015 March 15 coronal mass ejection as one of the two that together drove the largest geomagnetic storm of solar cycle 24 so far was associated with sympathetic filament eruptions. We investigate the relations between the different filaments involved in the eruption. A surge-like small-scale filament motion is confirmed as the trigger that initiated the erupting filament with multi-wavelength observations and using a forced magnetic field extrapolation method. When the erupting filament moved to an open magnetic field region, it experienced an obvious acceleration process and was accompanied by a C-class flare and the rise of another larger filamentmore » that eventually failed to erupt. We measure the decay index of the background magnetic field, which presents a critical height of 118 Mm. Combining with a potential field source surface extrapolation method, we analyze the distributions of the large-scale magnetic field, which indicates that the open magnetic field region may provide a favorable condition for F2 rapid acceleration and have some relation with the largest solar storm. The comparison between the successful and failed filament eruptions suggests that the confining magnetic field plays an important role in the preconditions for an eruption.« less

Volcano warning systems: Chapter 67

USGS Publications Warehouse

Gregg, Chris E.; Houghton, Bruce F.; Ewert, John W.

2015-01-01

Messages conveying volcano alert level such as Watches and Warnings are designed to provide people with risk information before, during, and after eruptions. Information is communicated to people from volcano observatories and emergency management agencies and from informal sources and social and environmental cues. Any individual or agency can be both a message sender and a recipient and multiple messages received from multiple sources is the norm in a volcanic crisis. Significant challenges to developing effective warning systems for volcanic hazards stem from the great diversity in unrest, eruption, and post-eruption processes and the rapidly advancing digital technologies that people use to seek real-time risk information. Challenges also involve the need to invest resources before unrest to help people develop shared mental models of important risk factors. Two populations of people are the target of volcano notifications–ground- and aviation-based populations, and volcano warning systems must address both distinctly different populations.

Production, pathways and budgets of melts in mid-ocean ridges: An enthalpy based thermo-mechanical model

NASA Astrophysics Data System (ADS)

Mandal, Nibir; Sarkar, Shamik; Baruah, Amiya; Dutta, Urmi

2018-04-01

Using an enthalpy based thermo-mechanical model we provide a theoretical evaluation of melt production beneath mid-ocean ridges (MORs), and demonstrate how the melts subsequently develop their pathways to sustain the major ridge processes. Our model employs a Darcy idealization of the two-phase (solid-melt) system, accounting enthalpy (ΔH) as a function of temperature dependent liquid fraction (ϕ). Random thermal perturbations imposed in this model set in local convection that drive melts to flow through porosity controlled pathways with a typical mushroom-like 3D structure. We present across- and along-MOR axis model profiles to show the mode of occurrence of melt-rich zones within mushy regions, connected to deeper sources by single or multiple feeders. The upwelling of melts experiences two synchronous processes: 1) solidification-accretion, and 2) eruption, retaining a large melt fraction in the framework of mantle dynamics. Using a bifurcation analysis we determine the threshold condition for melt eruption, and estimate the potential volumes of eruptible melts (∼3.7 × 106 m3/yr) and sub-crustal solidified masses (∼1-8.8 × 106 m3/yr) on an axis length of 500 km. The solidification process far dominates over the eruption process in the initial phase, but declines rapidly on a time scale (t) of 1 Myr. Consequently, the eruption rate takes over the solidification rate, but attains nearly a steady value as t > 1.5 Myr. We finally present a melt budget, where a maximum of ∼5% of the total upwelling melt volume is available for eruption, whereas ∼19% for deeper level solidification; the rest continue to participate in the sub-crustal processes.

Depth of origin of magma in eruptions.

PubMed

Becerril, Laura; Galindo, Ines; Gudmundsson, Agust; Morales, Jose Maria

2013-09-26

Many volcanic hazard factors--such as the likelihood and duration of an eruption, the eruption style, and the probability of its triggering large landslides or caldera collapses--relate to the depth of the magma source. Yet, the magma source depths are commonly poorly known, even in frequently erupting volcanoes such as Hekla in Iceland and Etna in Italy. Here we show how the length-thickness ratios of feeder dykes can be used to estimate the depth to the source magma chamber. Using this method, accurately measured volcanic fissures/feeder-dykes in El Hierro (Canary Islands) indicate a source depth of 11-15 km, which coincides with the main cloud of earthquake foci surrounding the magma chamber associated with the 2011-2012 eruption of El Hierro. The method can be used on widely available GPS and InSAR data to calculate the depths to the source magma chambers of active volcanoes worldwide.

Depth of origin of magma in eruptions

PubMed Central

Becerril, Laura; Galindo, Ines; Gudmundsson, Agust; Morales, Jose Maria

2013-01-01

Many volcanic hazard factors - such as the likelihood and duration of an eruption, the eruption style, and the probability of its triggering large landslides or caldera collapses - relate to the depth of the magma source. Yet, the magma source depths are commonly poorly known, even in frequently erupting volcanoes such as Hekla in Iceland and Etna in Italy. Here we show how the length-thickness ratios of feeder dykes can be used to estimate the depth to the source magma chamber. Using this method, accurately measured volcanic fissures/feeder-dykes in El Hierro (Canary Islands) indicate a source depth of 11–15 km, which coincides with the main cloud of earthquake foci surrounding the magma chamber associated with the 2011–2012 eruption of El Hierro. The method can be used on widely available GPS and InSAR data to calculate the depths to the source magma chambers of active volcanoes worldwide. PMID:24067336

Eruption-induced modifications to volcanic seismicity at Ruapehu, New Zealand, and its implications for eruption forecasting

USGS Publications Warehouse

Bryan, C.J.; Sherburn, S.

2003-01-01

Broadband seismic data collected on Ruapehu volcano, New Zealand, in 1994 and 1998 show that the 1995-1996 eruptions of Ruapehu resulted in a significant change in the frequency content of tremor and volcanic earthquakes at the volcano. The pre-eruption volcanic seismicity was characterized by several independent dominant frequencies, with a 2 Hz spectral peak dominating the strongest tremor and volcanic earthquakes and higher frequencies forming the background signal. The post-eruption volcanic seismicity was dominated by a 0.8-1.4 Hz spectral peak not seen before the eruptions. The 2 Hz and higher frequency signals remained, but were subordinate to the 0.8-1.4 Hz energy. That the dominant frequencies of volcanic tremor and volcanic earthquakes were identical during the individual time periods prior to and following the 1995-1996 eruptions suggests that during each of these time periods the volcanic tremor and earthquakes were generated by the same source process. The overall change in the frequency content, which occurred during the 1995-1996 eruptions and remains as of the time of the writing of this paper, most likely resulted from changes in the volcanic plumbing system and has significant implications for forecasting and real-time assessment of future eruptive activity at Ruapehu.

Relative Source Locations of Continuous Tremor Before and After the Subplinian Events at Shinmoe-dake, in 2011

NASA Astrophysics Data System (ADS)

Ichihara, M.; Matsumoto, S.

2017-11-01

Volcano monitoring systems are not always ready to resolve signals at the onset of eruptive activity. This study makes use of stations installed later to calibrate the performance of the stations that had been operated before the eruption. Seven stations recorded continuous volcanic tremor before and during the subplinian eruptions of Shinmoe-dake, Japan, in 2011. We estimated the source locations of the tremor using the amplitude distribution. The stability of the analysis was obtained by careful selection of time windows in which signals from a single source are dominated. The site effects and the regional attenuation factor were evaluated using tremor recorded after the major eruptions by a dense seismic array and a good number of stations. A tremor source changed its depth beneath the crater for 1 week before the major eruption, rising from a depth of a few kilometer to the water layer 3 times, each of which occurred following shallow inflation and minor eruptions. It is interpreted as migration of gas probably with magma, which further transported heat to the water layer and triggered the subplinian eruptions.

Temporal Evolution of Surface Deformation and Magma Sources at Pacaya Volcano, Guatemala Revealed by InSAR

NASA Astrophysics Data System (ADS)

Wnuk, K.; Wauthier, C.

2016-12-01

Pacaya Volcano, Guatemala is a persistently active volcano whose western flank is unstable. Despite continuous activity since 1961, a lack of high temporal resolution geodetic surveying has prevented detailed modeling of Pacaya's underlying magmatic plumbing system. A new, temporally dense dataset of Interferometric Synthetic Aperture Radar (InSAR) RADARSAT-2 images, spanning December 2012 to March 2014, shows magmatic deformation before and during major eruptions in January and March 2014. Inverse modeling of InSAR surface displacements suggest that three magma bodies are responsible for observed deformation: (1) a 3.7 km deep spherical reservoir located northwest of the summit, (2) a 0.4 km deep spherical source located directly west of the summit, and (3) a shallow dike below the summit that provides the primary transport pathway for erupted materials. Periods of heightened activity are brought on by magma pulses at depth, which result in rapid inflation of the edifice. We observe an intrusion cycle at Pacaya that consists of deflation of one or both magma reservoirs followed by dike intrusion. Intrusion volumes are proportional to reservoir volume loss, and do not always result in an eruption. Periods of increased activity culminate with larger dike fed eruptions. Large eruptions are followed by inter eruptive periods marked by a decrease in crater explosions and a lack of deformation. A full understanding of magmatic processes at Pacaya is required to assess potential impacts on other aspects of the volcano such as the unstable western flank. Co-eruptive flank motion appears to have initiated a new stage of volcanic rifting at Pacaya defined by repeated NW-SE dike intrusions. This creates a positive feedback relationship whereby magmatic forcing from eruptive dike intrusions induces flank motion

Magma transfer at Campi Flegrei caldera (Italy) before the 1538 AD eruption

USGS Publications Warehouse

Di Vito, Mauro A.; Acocella, Valerio; Aiello, Giuseppe; Barra, Diana; Battaglia, Maurizio; Carandente, Antonio; Del Gaudio, Carlo; de Vita, Sandro; Ricciardi, Giovanni P.; Ricco, Ciro; Scandone, Roberto; Terrasi, Filippo

2016-01-01

Calderas are collapse structures related to the emptying of magmatic reservoirs, often associated with large eruptions from long-lived magmatic systems. Understanding how magma is transferred from a magma reservoir to the surface before eruptions is a major challenge. Here we exploit the historical, archaeological and geological record of Campi Flegrei caldera to estimate the surface deformation preceding the Monte Nuovo eruption and investigate the shallow magma transfer. Our data suggest a progressive magma accumulation from ~1251 to 1536 in a 4.6 ± 0.9 km deep source below the caldera centre, and its transfer, between 1536 and 1538, to a 3.8 ± 0.6 km deep magmatic source ~4 km NW of the caldera centre, below Monte Nuovo; this peripheral source fed the eruption through a shallower source, 0.4 ± 0.3 km deep. This is the first reconstruction of pre-eruptive magma transfer at Campi Flegrei and corroborates the existence of a stationary oblate source, below the caldera centre, that has been feeding lateral eruptions for the last ~5 ka. Our results suggest: 1) repeated emplacement of magma through intrusions below the caldera centre; 2) occasional lateral transfer of magma feeding non-central eruptions within the caldera. Comparison with historical unrest at calderas worldwide suggests that this behavior is common.

Magma transfer at Campi Flegrei caldera (Italy) before the 1538 AD eruption

PubMed Central

Di Vito, Mauro A.; Acocella, Valerio; Aiello, Giuseppe; Barra, Diana; Battaglia, Maurizio; Carandente, Antonio; Del Gaudio, Carlo; de Vita, Sandro; Ricciardi, Giovanni P.; Ricco, Ciro; Scandone, Roberto; Terrasi, Filippo

2016-01-01

Calderas are collapse structures related to the emptying of magmatic reservoirs, often associated with large eruptions from long-lived magmatic systems. Understanding how magma is transferred from a magma reservoir to the surface before eruptions is a major challenge. Here we exploit the historical, archaeological and geological record of Campi Flegrei caldera to estimate the surface deformation preceding the Monte Nuovo eruption and investigate the shallow magma transfer. Our data suggest a progressive magma accumulation from ~1251 to 1536 in a 4.6 ± 0.9 km deep source below the caldera centre, and its transfer, between 1536 and 1538, to a 3.8 ± 0.6 km deep magmatic source ~4 km NW of the caldera centre, below Monte Nuovo; this peripheral source fed the eruption through a shallower source, 0.4 ± 0.3 km deep. This is the first reconstruction of pre-eruptive magma transfer at Campi Flegrei and corroborates the existence of a stationary oblate source, below the caldera centre, that has been feeding lateral eruptions for the last ~5 ka. Our results suggest: 1) repeated emplacement of magma through intrusions below the caldera centre; 2) occasional lateral transfer of magma feeding non-central eruptions within the caldera. Comparison with historical unrest at calderas worldwide suggests that this behavior is common. PMID:27558276

Magma transfer at Campi Flegrei caldera (Italy) before the 1538 AD eruption.

PubMed

Di Vito, Mauro A; Acocella, Valerio; Aiello, Giuseppe; Barra, Diana; Battaglia, Maurizio; Carandente, Antonio; Del Gaudio, Carlo; de Vita, Sandro; Ricciardi, Giovanni P; Ricco, Ciro; Scandone, Roberto; Terrasi, Filippo

2016-08-25

Calderas are collapse structures related to the emptying of magmatic reservoirs, often associated with large eruptions from long-lived magmatic systems. Understanding how magma is transferred from a magma reservoir to the surface before eruptions is a major challenge. Here we exploit the historical, archaeological and geological record of Campi Flegrei caldera to estimate the surface deformation preceding the Monte Nuovo eruption and investigate the shallow magma transfer. Our data suggest a progressive magma accumulation from ~1251 to 1536 in a 4.6 ± 0.9 km deep source below the caldera centre, and its transfer, between 1536 and 1538, to a 3.8 ± 0.6 km deep magmatic source ~4 km NW of the caldera centre, below Monte Nuovo; this peripheral source fed the eruption through a shallower source, 0.4 ± 0.3 km deep. This is the first reconstruction of pre-eruptive magma transfer at Campi Flegrei and corroborates the existence of a stationary oblate source, below the caldera centre, that has been feeding lateral eruptions for the last ~5 ka. Our results suggest: 1) repeated emplacement of magma through intrusions below the caldera centre; 2) occasional lateral transfer of magma feeding non-central eruptions within the caldera. Comparison with historical unrest at calderas worldwide suggests that this behavior is common.

Studies of volcanoes of Alaska by satellite radar interferometry

USGS Publications Warehouse

Lu, Z.; Wicks, C.; Dzurisin, D.; Thatcher, W.; Power, J.; ,

2000-01-01

Interferometric synthetic aperture radar (InSAR) has provided a new imaging geodesy technique to measure the deformation of volcanoes at tens-of-meter horizontal resolution with centimeter to subcentimeter vertical precision. The two-dimensional surface deformation data enables the construction of detailed numerical models allowing the study of magmatic and tectonic processes beneath volcanoes. This paper summarizes our recent: InSAR studies over the Alaska-Aleutian volcanoes, which include New Trident, Okmok, Akutan, Augustine, Shishaldin, and Westdahl volcanoes. The first InSAR surface deformation over the Alaska volcanoes was applied to New Trident. Preliminary InSAR study suggested that New Trident volcano experienced several centimeters inflation from 1993 to 1995. Using the InSAR technique, we studied the 1997 eruption of Okmok. We have measured ???1.4 m deflation during the eruption, ???20 cm pre-eruptive inflation during 1992 to 1995, and >10 cm post-eruptive inflation within a year after the eruption, and modeled the deformations using Mogi sources. We imaged the ground surface deformation associated with the 1996 seismic crisis over Akutan volcano. Although seismic swarm did not result in an eruption, we found that the western part of the volcano uplifted ???60 cm while the eastern part of the island subsided. The majority of the complex deformation field at the Akutan volcano was modeled by dike intrusion and Mogi inflation sources. Our InSAR results also indicate that the pyroclastic flows from last the last eruption have been undergoing contraction/subsidence at a rate of about 3 cm per year since 1992. InSAR measured no surface deformation before and during the 1999 eruption of Shishaldin and suggested the eruption may be a type of open system. Finally, we applied satellite radar interferometry to Westdahl volcano which erupted 1991 and has been quiet since. We discovered this volcano had inflated about 15 cm from 1993 to 1998. In summary, satellite radar interferometry can not only be used to study a volcanic eruption, but also to detect aseismic deformation at quiescent volcanoes preceding a seismic swarm; it is a useful technique to study volcanic eruptions as well as to guide scientists to better focus their monitoring efforts.

Seismic evolution of the 1989-1990 eruption sequence of Redoubt Volcano, Alaska

USGS Publications Warehouse

Power, J.A.; Lahr, J.C.; Page, R.A.; Chouet, B.A.; Stephens, C.D.; Harlow, D.H.; Murray, T.L.; Davies, J.N.

1994-01-01

Redoubt Volcano in south-central Alaska erupted between December 1989 and June 1990 in a sequence of events characterized by large tephra eruptions, pyroclastic flows, lahars and debris flows, and episodes of dome growth. The eruption was monitored by a network of five to nine seismic stations located 1 to 22 km from the summit crater. Notable features of the eruption seismicity include : (1) small long-period events beginning in September 1989 which increased slowly in number during November and early December; (2) an intense swarm of long-period events which preceded the initial eruptions on December 14 by 23 hours; (3) shallow swarms (0 to 3 km) of volcano-tectonic events following each eruption on December 15; (4) a persistent cluster of deep (6 to 10 km) volcano-tectonic earthquakes initiated by the eruptions on December 15, which continued throughout and beyond the eruption; (5) an intense swarm of long-period events which preceded the eruptions on January 2; and (6) nine additional intervals of increased long-period seismicity each of which preceded a tephra eruption. Hypocenters of volcano-tectonic earthquakes suggest the presence of a magma source region at 6-10 km depth. Earthquakes at these depths were initiated by the tephra eruptions on December 15 and likely represent the readjustment of stresses in the country rock associated with the removal of magma from these depths. The locations and time-history of these earthquakes coupled with the eruptive behavior of the volcano suggest this region was the source of most of the erupted material during the 1989-1990 eruption. This source region appears to be connected to the surface by a narrow pipe-like conduit as inferred from the hypocenters of volcano-tectonic earthquakes. Concentrations of shallow volcano-tectonic earthquakes followed each of the tephra eruptions on December 15; these shocks may represent stress readjustment in the wall rock related to the removal of magma and volatiles at these depths. This shallow zone was the source area of the majority of long-period seismicity through the remainder of the eruption. The long-period seismicity likely reflects the pressurization of the shallow portions of the magmatic system. ?? 1994.

Extremely High Magma Emplacement Rates Recorded in the Golden Horn Batholith, WA

NASA Astrophysics Data System (ADS)

Eddy, M. P.; Bowring, S. A.; Tepper, J. H.; Miller, R. B.

2015-12-01

High SiO2 rhyolites emplaced during 'super-eruptions' demonstrate that large volumes of eruptible magma can exist in the upper crust. However, the timescale over which the magma reservoirs that source these eruptions are built remains controversial. Thermal models suggest that magma emplacement rates need to be > 0.005-0.01 km3/yr in order to accumulate enough eruptible magma to source a 'super-eruption'. Yet, these rates are higher than the time-averaged rates (< 0.001 km3/yr) for nearly all well-studied granitoid plutonic complexes. This disparity contradicts geologic evidence suggesting that the high SiO2 rhyolites emplaced during 'super-eruptions' are extracted from crystal rich magma chambers that should be preserved in the geologic record as granodioritic and granitic plutons. We quantify time-averaged magma emplacement rates for the upper crustal Golden Horn batholith, WA based on new geologic mapping and U-Pb zircon CA-IDTIMS geochronology. The batholith is exposed over 310 km3 and can be separated in the field into five intrusive units. High topography allows the 3D geometry of each phase to be constrained and their volumes range from < 100 km3 to > 400 km3. U-Pb zircon geochronology reveals that four of the five phases were assembled incrementally and distinct zircon populations from samples within these phases suggest that individual magmatic pulses had fully crystallized before the next arrived. However, six nearly identical U-Pb zircon dates from a > 400 km3 rapakivi granite show that this phase was built in ca. 50 kyr and that large portions may have been emplaced nearly simultaneously. The implied emplacement rate for this phase (≥ 0.008 km3/yr) is in agreement with those predicted for assembly of the upper crustal magma chambers that source 'super-eruptions', and it may provide a rare and unprecedented opportunity to study the processes that occur in such chambers.

Atmospheric processes affecting the separation of volcanic ash and SO2 in volcanic eruptions: inferences from the May 2011 Grímsvötn eruption

NASA Astrophysics Data System (ADS)

Prata, Fred; Woodhouse, Mark; Huppert, Herbert E.; Prata, Andrew; Thordarson, Thor; Carn, Simon

2017-09-01

The separation of volcanic ash and sulfur dioxide (SO2) gas is sometimes observed during volcanic eruptions. The exact conditions under which separation occurs are not fully understood but the phenomenon is of importance because of the effects volcanic emissions have on aviation, on the environment, and on the earth's radiation balance. The eruption of Grímsvötn, a subglacial volcano under the Vatnajökull glacier in Iceland during 21-28 May 2011 produced one of the most spectacular examples of ash and SO2 separation, which led to errors in the forecasting of ash in the atmosphere over northern Europe. Satellite data from several sources coupled with meteorological wind data and photographic evidence suggest that the eruption column was unable to sustain itself, resulting in a large deposition of ash, which left a low-level ash-rich atmospheric plume moving southwards and then eastwards towards the southern Scandinavian coast and a high-level predominantly SO2 plume travelling northwards and then spreading eastwards and westwards. Here we provide observational and modelling perspectives on the separation of ash and SO2 and present quantitative estimates of the masses of ash and SO2 that erupted, the directions of transport, and the likely impacts. We hypothesise that a partial column collapse or sloughing fed with ash from pyroclastic density currents (PDCs) occurred during the early stage of the eruption, leading to an ash-laden gravity intrusion that was swept southwards, separated from the main column. Our model suggests that water-mediated aggregation caused enhanced ash removal because of the plentiful supply of source water from melted glacial ice and from entrained atmospheric water. The analysis also suggests that ash and SO2 should be treated with separate source terms, leading to improvements in forecasting the movement of both types of emissions.

Stability of volcanic conduits: insights from magma ascent modelling and possible consequences on eruptive dynamics

NASA Astrophysics Data System (ADS)

Aravena, Alvaro; de'Michieli Vitturi, Mattia; Cioni, Raffaello; Neri, Augusto

2017-04-01

Geological evidences of changes in volcanic conduit geometry (i.e. erosive processes) are common in the volcanic record, as revealed by the occurrence of lithic fragments in most pyroclastic deposits. However, the controlling factors of conduit enlargement mechanisms are still partially unclear, as well as the influence of conduit geometry in the eruptive dynamics. Despite physical models have been systematically used for studying volcanic conduits, their mechanical stability has been poorly addressed. In order to study the mechanical stability of volcanic conduits during explosive eruptions, we present a 1D steady-state model which considers the main processes experimented by ascending magmas, such as crystallization, drag forces, fragmentation, outgassing and degassing; and the application of the Mogi-Coulomb collapse criterion, using a set of constitutive equations for studying typical cases of rhyolitic and trachytic explosive volcanism. From our results emerge that conduit stability is mainly controlled by magma rheology and conduit dimensions. Indeed, in order to be stable, feeding conduits of rhyolitic eruptions need larger radii respect to their trachytic counterparts, which is manifested in the higher eruption rates usually observed in rhyolitic explosive eruptions, as confirmed by a small compilation of global data. Additionally, for both magma compositions, we estimated a minimum magma flux for developing stable conduits (˜3ṡ106 kg/s for trachytic magmas and ˜8ṡ107 kg/s for rhyolitic magmas), which is consistent with the unsteady character commonly observed in low-mass flux events (e.g. sub-Plinian eruptions), which would be produced by episodic collapse events of the volcanic conduit, opposite to the mainly stationary high-mass flux events (e.g. Plinian eruptions), characterized by stable conduits. For a given magma composition, a minimum radius for reaching stable conditions can be computed, as a function of inlet overpressure and water content. Under the assumption that magma chamber conditions during a typical volcanic eruption follow a depressurizing trend, a continuous conduit widening process is expected. This process could explain the pervasive and continuous presence of lithic fragments in most pyroclastic deposits, even with stationary properties and conditions of the magma source (e.g. water content, temperature, composition).

Volcanic tremor and plume height hysteresis from Pavlof Volcano, Alaska

NASA Astrophysics Data System (ADS)

Fee, David; Haney, Matthew M.; Matoza, Robin S.; Van Eaton, Alexa R.; Cervelli, Peter; Schneider, David J.; Iezzi, Alexandra M.

2017-01-01

The March 2016 eruption of Pavlof Volcano, Alaska, produced an ash plume that caused the cancellation of more than 100 flights in North America. The eruption generated strong tremor that was recorded by seismic and remote low-frequency acoustic (infrasound) stations, including the EarthScope Transportable Array. The relationship between the tremor amplitudes and plume height changes considerably between the waxing and waning portions of the eruption. Similar hysteresis has been observed between seismic river noise and discharge during storms, suggesting that flow and erosional processes in both rivers and volcanoes can produce irreversible structural changes that are detectable in geophysical data. We propose that the time-varying relationship at Pavlof arose from changes in the tremor source related to volcanic vent erosion. This relationship may improve estimates of volcanic emissions and characterization of eruption size and intensity.

Multidirectional seismo-acoustic wavefield of strombolian explosions at Yasur, Vanuatu using a broadband seismo-acoustic network, infrasound arrays, and infrasonic sensors on tethered balloons

NASA Astrophysics Data System (ADS)

Matoza, R. S.; Jolly, A. D.; Fee, D.; Johnson, R.; Kilgour, G.; Christenson, B. W.; Garaebiti, E.; Iezzi, A. M.; Austin, A.; Kennedy, B.; Fitzgerald, R.; Key, N.

2016-12-01

Seismo-acoustic wavefields at volcanoes contain rich information on shallow magma transport and subaerial eruption processes. Acoustic wavefields from eruptions are predicted to be directional, but sampling this wavefield directivity is challenging because infrasound sensors are usually deployed on the ground surface. We attempt to overcome this observational limitation using a novel deployment of infrasound sensors on tethered balloons in tandem with a suite of dense ground-based seismo-acoustic, geochemical, and eruption imaging instrumentation. We present preliminary results from a field experiment at Yasur Volcano, Vanuatu from July 26th to August 4th 2016. Our observations include data from a temporary network of 11 broadband seismometers, 6 single infrasonic microphones, 7 small-aperture 3-element infrasound arrays, 2 infrasound sensor packages on tethered balloons, an FTIR, a FLIR, 2 scanning Flyspecs, and various visual imaging data. An introduction to the dataset and preliminary analysis of the 3D seismo-acoustic wavefield and source process will be presented. This unprecedented dataset should provide a unique window into processes operating in the shallow magma plumbing system and their relation to subaerial eruption dynamics.

Applying Fractal Dimensions and Energy-Budget Analysis to Characterize Fracturing Processes During Magma Migration and Eruption: 2011-2012 El Hierro (Canary Islands) Submarine Eruption

NASA Astrophysics Data System (ADS)

López, Carmen; Martí, Joan; Abella, Rafael; Tarraga, Marta

2014-07-01

The impossibility of observing magma migration inside the crust obliges us to rely on geophysical data and mathematical modelling to interpret precursors and to forecast volcanic eruptions. Of the geophysical signals that may be recorded before and during an eruption, deformation and seismicity are two of the most relevant as they are directly related to its dynamic. The final phase of the unrest episode that preceded the 2011-2012 eruption on El Hierro (Canary Islands) was characterized by local and accelerated deformation and seismic energy release indicating an increasing fracturing and a migration of the magma. Application of time varying fractal analysis to the seismic data and the characterization of the seismicity pattern and the strain and the stress rates allow us to identify different stages in the source mechanism and to infer the geometry of the path used by the magma and associated fluids to reach the Earth's surface. The results obtained illustrate the relevance of such studies to understanding volcanic unrest and the causes that govern the initiation of volcanic eruptions.

Magma migration at the onset of the 2012-13 Tolbachik eruption revealed by Seismic Amplitude Ratio Analyses

NASA Astrophysics Data System (ADS)

Taisne, B.; Caudron, C.; Kugaenko, Y.; Saltykov, V.

2015-12-01

In contrast of the 1975-76 Tolbachik eruption, the 2012-2013 Tolbachik eruption was not preceded by any striking change in seismic activity. By processing the Klyuchevskoy volcano group seismic data with the Seismic Amplitude Ratio Analysis (SARA) method, we gain insights into the dynamics of magma transfer prior to this important eruption. We highlighted a clear migration of the source of the microseismicity within the seismic swarm, starting 20 hours before the reported eruption onset (05:15 UTC, 26 November 2012). This migration proceeded in different phases and ended when eruptive tremor, corresponding to lava extrusion, was recorded (at ~11:00 UTC, 27 November 2012). In order to get a first order approximation of the location of the magma, we compare the calculated seismic intensity ratios with the theoretical ones. As expected, the observations suggest a migration toward the eruptive vent. However, we explain the pre-eruptive observed ratios by a vertical migration under the northern slope of Plosky Tolbachik volcano that would interact at shallower depth with an intermediate storage region and initiate the lateral migration toward the eruptive vents. Another migration is also captured by this technique and coincides with a seismic swarm that started 16-20 km to the south of Plosky Tolbachik at 20:31 UTC on November 28 and lasted for more than 2 days. This seismic swarm is very similar to the seismicity preceding the 1975-76 Tolbachik eruption and can be considered as a possible aborted eruption.

A Study of a Compound Solar Eruption with Two Consecutive Erupting Magnetic Structures

NASA Astrophysics Data System (ADS)

Dhakal, Suman K.; Chintzoglou, Georgios; Zhang, Jie

2018-06-01

We report a study of a compound solar eruption that was associated with two consecutively erupting magnetic structures and correspondingly two distinct peaks, during impulsive phase, of an M-class flare (M8.5). Simultaneous multi-viewpoint observations from SDO, GOES and STEREO-A show that this compound eruption originated from two pre-existing sigmoidal magnetic structures lying along the same polarity inversion line. Observations of the associated pre-existing filaments further show that these magnetic structures are lying one on top of the other, separated by 12 Mm in height, in a so-called “double-decker” configuration. The high-lying magnetic structure became unstable and erupted first, appearing as an expanding hot channel seen at extreme ultraviolet wavelengths. About 12 minutes later, the low-lying structure also started to erupt and moved at an even faster speed compared to the high-lying one. As a result, the two erupting structures interacted and merged with each other, appearing as a single coronal mass ejection in the outer corona. We find that the double-decker configuration is likely caused by the persistent shearing motion and flux cancellation along the source active region’s strong-gradient polarity inversion line. The successive destabilization of these two separate but closely spaced magnetic structures, possibly in the form of magnetic flux ropes, led to a compound solar eruption. The study of the compound eruption provides a unique opportunity to reveal the formation process, initiation, and evolution of complex eruptive structures in solar active regions.

Solar Activity and Solar Eruptions

NASA Technical Reports Server (NTRS)

Sterling, Alphonse C.

2006-01-01

Our Sun is a dynamic, ever-changing star. In general, its atmosphere displays major variation on an 11-year cycle. Throughout the cycle, the atmosphere occasionally exhibits large, sudden outbursts of energy. These "solar eruptions" manifest themselves in the form of solar flares, filament eruptions, coronal mass ejections (CMEs), and energetic particle releases. They are of high interest to scientists both because they represent fundamental processes that occur in various astrophysical context, and because, if directed toward Earth, they can disrupt Earth-based systems and satellites. Research over the last few decades has shown that the source of the eruptions is localized regions of energy-storing magnetic field on the Sun that become destabilized, leading to a release of the stored energy. Solar scientists have (probably) unraveled the basic outline of what happens in these eruptions, but many details are still not understood. In recent years we have been studying what triggers these magnetic eruptions, using ground-based and satellite-based solar observations in combination with predictions from various theoretical models. We will present an overview of solar activity and solar eruptions, give results from some of our own research, and discuss questions that remain to be explored.

Using Satellite Observations to Evaluate the AeroCOM Volcanic Emissions Inventory and the Dispersal of Volcanic SO2 Clouds in MERRA

NASA Technical Reports Server (NTRS)

Hughes, Eric J.; Krotkov, Nickolay; da Silva, Arlindo; Colarco, Peter

2015-01-01

Simulation of volcanic emissions in climate models requires information that describes the eruption of the emissions into the atmosphere. While the total amount of gases and aerosols released from a volcanic eruption can be readily estimated from satellite observations, information about the source parameters, like injection altitude, eruption time and duration, is often not directly known. The AeroCOM volcanic emissions inventory provides estimates of eruption source parameters and has been used to initialize volcanic emissions in reanalysis projects, like MERRA. The AeroCOM volcanic emission inventory provides an eruptions daily SO2 flux and plume top altitude, yet an eruption can be very short lived, lasting only a few hours, and emit clouds at multiple altitudes. Case studies comparing the satellite observed dispersal of volcanic SO2 clouds to simulations in MERRA have shown mixed results. Some cases show good agreement with observations Okmok (2008), while for other eruptions the observed initial SO2 mass is half of that in the simulations, Sierra Negra (2005). In other cases, the initial SO2 amount agrees with the observations but shows very different dispersal rates, Soufriere Hills (2006). In the aviation hazards community, deriving accurate source terms is crucial for monitoring and short-term forecasting (24-h) of volcanic clouds. Back trajectory methods have been developed which use satellite observations and transport models to estimate the injection altitude, eruption time, and eruption duration of observed volcanic clouds. These methods can provide eruption timing estimates on a 2-hour temporal resolution and estimate the altitude and depth of a volcanic cloud. To better understand the differences between MERRA simulations and volcanic SO2 observations, back trajectory methods are used to estimate the source term parameters for a few volcanic eruptions and compared to their corresponding entry in the AeroCOM volcanic emission inventory. The nature of these mixed results is discussed with respect to the source term estimates.

Magmatic vapor source for sulfur dioxide released during volcanic eruptions: Evidence from Mount Pinatubo

USGS Publications Warehouse

Wallace, P.J.; Gerlach, T.M.

1994-01-01

Sulfur dioxide (SO2) released by the explosive eruption of Mount Pinatubo on 15 June 1991 had an impact on climate and stratospheric ozone. The total mass of SO2 released was much greater than the amount dissolved in the magma before the eruption, and thus an additional source for the excess SO2 is required. Infrared spectroscopic analyses of dissolved water and carbon dioxide in glass inclusions from quartz phenocrysts demonstrate that before eruption the magma contained a separate, SO2-bearing vapor phase. Data for gas emissions from other volcanoes in subduction-related arcs suggest that preeruptive magmatic vapor is a major source of the SO2 that is released during many volcanic eruptions.

Hail formation triggers rapid ash aggregation in volcanic plumes

USGS Publications Warehouse

Van Eaton, Alexa R.; Mastin, Larry G.; Herzog, M.; Schwaiger, Hans F.; Schneider, David J.; Wallace, Kristi; Clarke, Amanda B

2015-01-01

During explosive eruptions, airborne particles collide and stick together, accelerating the fallout of volcanic ash and climate-forcing aerosols. This aggregation process remains a major source of uncertainty both in ash dispersal forecasting and interpretation of eruptions from the geological record. Here we illuminate the mechanisms and timescales of particle aggregation from a well-characterized ‘wet’ eruption. The 2009 eruption of Redoubt Volcano in Alaska incorporated water from the surface (in this case, a glacier), which is a common occurrence during explosive volcanism worldwide. Observations from C-band weather radar, fall deposits, and numerical modeling demonstrate that volcanic hail formed rapidly in the eruption plume, leading to mixed-phase aggregation of ~95% of the fine ash and stripping much of the cloud out of the atmosphere within 30 minutes. Based on these findings, we propose a mechanism of hail-like aggregation that contributes to the anomalously rapid fallout of fine ash and the occurrence of concentrically-layered aggregates in volcanic deposits.

Analytical volcano deformation source models

USGS Publications Warehouse

Lisowski, Michael; Dzurisin, Daniel

2007-01-01

Primary volcanic landforms are created by the ascent and eruption of magma. The ascending magma displaces and interacts with surrounding rock and fluids as it creates new pathways, flows through cracks or conduits, vesiculates, and accumulates in underground reservoirs. The formation of new pathways and pressure changes within existing conduits and reservoirs stress and deform the surrounding rock. Eruption products load the crust. The pattern and rate of surface deformation around volcanoes reflect the tectonic and volcanic processes transmitted to the surface through the mechanical properties of the crust.

Infrasonic wave accompanying a crack opening during the 2015 Hakone eruption

NASA Astrophysics Data System (ADS)

Yukutake, Yohei; Ichihara, Mie; Honda, Ryou

2018-03-01

To understand the initial process of the phreatic eruption of the Hakone volcano from June 29 to July 01, 2015, we analyzed infrasound data using the cross-correlation between infrasound and vertical ground velocity and compared the results of our analysis to the crustal deformation detected by tiltmeters and broadband seismometers. An infrasound signal and vertical ground motion due to an infrasound wave coupled to the ground were detected simultaneously with the opening of a crack source beneath the Owakudani geothermal region during the 2-min time period after 07:32 JST on June 29, 2015 (JST = UTC + 8 h). Given that the upper end of the open crack was approximately 150 m beneath the surface, the time for the direct emission of highly pressurized fluid from the upper end of the open crack to the surface should have exceeded the duration of the inflation owing to the hydraulic diffusivity in the porous media. Therefore, the infrasound signal coincident with the opening of the crack may reflect a sudden emission of volcanic gas resulting from the rapid vaporization of pre-existing groundwater beneath Owakudani because of the transfer of the volumetric strain change from the deformation source. We also noticed a correlation pattern corresponding to discrete impulsive infrasound signals during vent formation, which occurred several hours to 2 days after the opening of the crack. In particular, we noted that the sudden emission of vapor coincided with the inflation of the shallow pressure source, whereas the eruptive burst events accompanied by the largest vent formation were delayed by approximately 2 days. Furthermore, we demonstrated that the correlation method is a useful tool in detecting small infrasound signals and provides important information regarding the initial processes of the eruption.[Figure not available: see fulltext.

Constraints on magma processes, subsurface conditions, and total volatile flux at Bezymianny Volcano in 2007–2010 from direct and remote volcanic gas measurements

USGS Publications Warehouse

Lopez, Taryn; Ushakov, Sergey; Izbekov, Pavel; Tassi, Franco; Cahill, Cathy; Neill, Owen; Werner, Cynthia A.

2013-01-01

Direct and remote measurements of volcanic gas composition, SO2 flux, and eruptive SO2 mass from Bezymianny Volcano were acquired between July 2007 and July 2010. Chemical composition of fumarolic gases, plume SO2 flux from ground and air-based ultraviolet remote sensing (FLYSPEC), and eruptive SO2 mass from Ozone Monitoring Instrument (OMI) satellite observations were used along with eruption timing to elucidate magma processes and subsurface conditions, and to constrain total volatile flux. Bezymianny Volcano had five explosive magmatic eruptions between May 2007 and June 2010. The most complete volcanic gas datasets were acquired for the October 2007, December 2009, and May 2010 eruptions. Gas measurements collected prior to the October 2007 eruption have a relatively high ratio of H2O/CO2 (81.2), a moderate ratio of CO2/S (5.47), and a low ratio of S/HCl (0.338), along with moderate SO2 and CO2 fluxes of 280 and 980 t/d, respectively, and high H2O and HCl fluxes of ~ 45,000 and ~ 440 t/d, respectively. These results suggest degassing of shallow magma (consistent with observations of lava extrusion) along with potential minor degassing of a deeper magma source. Gas measurements collected prior to the December 2009 eruption are characterized by relatively low H2O/CO2 (4.13), moderate CO2/S (6.84), and high S/HCl (18.7) ratios, along with moderate SO2 and CO2 fluxes of ~ 220 and ~ 1000 t/d, respectively, and low H2O and HCl fluxes of ~ 1700 and ~ 7 t/d, respectively. These trends are consistent with degassing of a deeper magma source. Fumarole samples collected ~ 1.5 months following the May 2010 eruption are characterized by high H2O/CO2 (63.0), low CO2/S (0.986), and moderate S/HCl (6.09) ratios. These data are consistent with degassing of a shallow, volatile-rich magma source, likely related to the May eruption. Passive and eruptive SO2 measurements are used to calculate a total annual SO2 mass of 109 kt emitted in 2007, with passive emissions comprising ~ 87–95% of the total. Total annual volatile masses for the study period are estimated to range from 1.1 × 106 to 18 × 106 t/year. Annual CO2 masses are ~ 8 to 40 times larger than can be explained by degassing of dissolved CO2 within eruptive magma, suggesting that the eruptive magma contained a significant quantity of exsolved volatiles sourced either from the eruptive melt or unerupted magma at depth. Variable total volatile fluxes ranging from ~ 3000 t/d in 2009 to ~ 49,000 t/d in 2007 are attributed to variations in the depth of gas exsolution and separation from the melt under open-system degassing conditions. We propose that exsolved volatiles are quickly transported to the surface from ascending magma via permeable flow through a bubble and/or fracture network within the conduit and thus retain their equilibrium composition at the time of segregation from melt. The composition of surface CO2 and H2O emissions from 2007 to 2009 are compared with modeled exsolved fluid compositions for a magma body ascending from entrapment depths to estimate depth of fluid exsolution and separation from the melt. We find that at the time of sample collection magma had already begun ascent from the mid-crustal storage region and was located at maximum depths of ~ 3.7 km in August 2007, approximately 2 months prior to the next magmatic eruption, and ~ 4.6 km in July of 2009 approximately five months prior to the next magmatic eruption. These findings suggest that the exsolved gas composition at Bezymianny Volcano may be used to detect magma ascent prior to eruption.

Bombs, flyin' high. In-flight dynamics of volcanic bombs from Strombolian to Vulcanian eruptions.

NASA Astrophysics Data System (ADS)

Taddeucci, Jacopo; Alatorre, Miguel; Cruz Vázquez, Omar; Del Bello, Elisabetta; Ricci, Tullio; Scarlato, Piergiorgio; Palladino, Danilo

2016-04-01

Bomb-sized (larger than 64 mm) pyroclasts are a common product of explosive eruptions and a considerable source of hazard, both from directly impacting on people and properties and from wildfires associated with their landing in vegetated areas. The dispersal of bombs is mostly modeled as purely ballistic trajectories controlled by gravity and drag forces associated with still air, and only recently other effects, such as the influence of eruption dynamics, the gas expansion, and in-flight collisions, are starting to be quantified both numerically and observationally. By using high-speed imaging of explosive volcanic eruptions here we attempt to calculate the drag coefficient of free-flying volcanic bombs during an eruption and at the same time we document a wide range of in-flight processes affecting bomb trajectories and introducing deviations from purely ballistic emplacement. High-speed (500 frames per second) videos of explosions at Stromboli and Etna (Italy), Fuego (Gatemala), Sakurajima (Japan), Yasur (Vanuatu), and Batu Tara (Indonesia) volcanoes provide a large assortment of free-flying bombs spanning Strombolian to Vulcanian source eruptions, basaltic to andesitic composition, centimeters to meters in size, and 10 to 300 m/s in fly velocity. By tracking the bombs during their flying trajectories we were able to: 1) measure their size, shape, and vertical component of velocity and related changes over time; and 2) measure the different interactions with the atmosphere and with other bombs. Quantitatively, these data allow us to provide the first direct measurement of the aerodynamic behavior and drag coefficient of volcanic bombs while settling, also including the effect of bomb rotation and changes in bomb shape and frontal section. We also show how our observations have the potential to parameterize a number of previously hypothesized and /or described but yet unquantified processes, including in-flight rotation, deformation, fragmentation, agglutination, and bouncing of volcanic bombs.

Evaluation of Kilauea Eruptions By Using Stable Isotope Analysis

NASA Astrophysics Data System (ADS)

Rahimi, K. E.; Bursik, M. I.

2016-12-01

Kilauea, on the island of Hawaii, is a large volcanic edifice with numerous named vents scattered across its surface. Halema`uma`u crater sits with Kilauea caldera, above the magma reservoir, which is the main source of lava feeding most vents on Kilauea volcano. Halema`uma`u crater produces basaltic explosive activity ranging from weak emission to sub-Plinian. Changes in the eruption style are thought to be due to the interplay between external water and magma (phreatomagmatic/ phreatic), or to segregation of gas from magma (magmatic) at shallow depths. Since there are three different eruption mechanisms (phreatomagmatic, phreatic, and magmatic), each eruption has its own isotope ratios. The aim of this study is to evaluate the eruption mechanism by using stable isotope analysis. Studying isotope ratios of D/H and δ18O within fluid inclusion and volcanic glass will provide an evidence of what driven the eruption. The results would be determined the source of water that drove an eruption by correlating the values with water sources (groundwater, rainwater, and magmatic water) since each water source has a diagnostic value of D/H and δ18O. These results will provide the roles of volatiles in eruptions. The broader application of this research is that these methods could help volcanologists forecasting and predicting the current volcanic activity by mentoring change in volatiles concentration within deposits.

Understanding Volcanic Conduit Dynamics: from Experimental Fragmentation to Volcanic Eruptions

NASA Astrophysics Data System (ADS)

Arciniega-Ceballos, A.; Alatorre-Ibarguengoitia, M. A.; Scheu, B.; Dingwell, D. B.

2011-12-01

The investigation of conduit dynamics at high pressure, under controlled laboratory conditions is a powerful tool to understand the physics behind volcanic processes before an eruption. In this work, we analyze the characteristics of the seismic response of an "experimental volcano" focusing on the dynamics of the conduit behavior during the fragmentation process of volcanic rocks. The "experimental volcano" is represented by a shock tube apparatus, which consists of a low-pressure voluminous tank (3 x 0.40 m), for sample recovery; and a high-pressure pipe-like conduit (16.5 x 2,5 cm), which represents the volcanic source mechanism, where rock samples are pressurized and fragmented. These two serial steel pipes are connected and sealed by a set of diaphragms that bear pressures in a range of 4 to 20 MPa. The history of the overall process of an explosion consists of four steps: 1) the slow pressurization of the pipe-like conduit filled with solid pumice and gas, 2) the sudden removal of the diaphragms, 3) the rapid decompression of the system and 4) the ejection of the gas-particle mixture. Each step imprints distinctive features on the microseismic records, reflecting the conduit dynamics during the explosion. In this work we show how features such as waveform characteristics, the three components of the force system acting on the conduit, the independent components of the moment tensor, the volumetric change of the source mechanism, the arrival time of the shock wave and its velocity, are quantified from the experimental microseismic data. Knowing these features, each step of the eruptive process, the conduit conditions and the source mechanism characteristics can be determined. The procedure applied in this experimental approach allows the use of seismic field data to estimate volcanic conduit conditions before an eruption takes place. We state on the hypothesis that the physics behind the pressurization and depressurization process of any conduit is the same and the effects of such process on the conduit dynamics are independent of size. We first described the very-long period (VLP) and long-period (LP) signals, observed in many active volcanoes around the world, and from comparison of waveform characteristics with their experimental analogues (eLP and eVLP signals) we found remarkable similarities and equivalent physical meaning. Based on our experimental investigations and analysis of field data recorded during volcanic eruptions we may conclude that VLP signals are caused by the inflation-deflation behavior of the volcanic conduit due to the decompression process, and that LP signals are manly associated with cracking and fragmentation of the magmatic material (ash, magma and gas) filling the conduit and ascending to the surface. In addition, we accounted for the repetitive character of LP and VLP signals, as a consequence of contraction and dilatation of a steady non-destructive source mechanism, which systematically responds to pressure changes of the volcanic system.

Volcanic tremor and plume height hysteresis from Pavlof Volcano, Alaska.

PubMed

Fee, David; Haney, Matthew M; Matoza, Robin S; Van Eaton, Alexa R; Cervelli, Peter; Schneider, David J; Iezzi, Alexandra M

2017-01-06

The March 2016 eruption of Pavlof Volcano, Alaska, produced an ash plume that caused the cancellation of more than 100 flights in North America. The eruption generated strong tremor that was recorded by seismic and remote low-frequency acoustic (infrasound) stations, including the EarthScope Transportable Array. The relationship between the tremor amplitudes and plume height changes considerably between the waxing and waning portions of the eruption. Similar hysteresis has been observed between seismic river noise and discharge during storms, suggesting that flow and erosional processes in both rivers and volcanoes can produce irreversible structural changes that are detectable in geophysical data. We propose that the time-varying relationship at Pavlof arose from changes in the tremor source related to volcanic vent erosion. This relationship may improve estimates of volcanic emissions and characterization of eruption size and intensity. Copyright © 2017, American Association for the Advancement of Science.

From Rock to Magmatic Timescales in 25 Hours: Near-Real Time Petrological Volcanic Eruption Monitoring Tested with Basaltic Icelandic Tephras

NASA Astrophysics Data System (ADS)

Couperthwaite, F.; Morgan, D. J.; Thordarson, T.; Shea, T.; Harvey, J.

2016-12-01

Diffusion modeling of erupted crystals is routine for investigating pre-eruptive timescales within magma storage bodies and magma transport systems. The technique typically produces results some time after a volcanic eruption has commenced. This contribution employs a user-friendly, easy-to-use method for deployment in near-real time during an eruption, enabling rapid timescale assessment whilst retaining reliability. A `stress test' was undertaken to simulate analysis during an evolving eruption involving multiple tephra layers, to test method performance and assess the rapidity with which timescale data could be retrieved. The first tephra cycle was completely processed in 25 working hours, significantly faster than current traditional methods. Traditional limitations include slow data processing rates, the measurement of crystal orientations and sectioning angles, crystal shape uncertainties, and the possibilities of crystal growth and/or changing boundary conditions. These constraints have been considered for the new methodology with corrections applied at a crystal population level. Tephra samples from Vatnaöldur, Iceland were the study material for the stress test. 39 magmatic timescales from Mg-Fe interdiffusion across 25 olivine crystals were retrieved from the basal tephra layer representing eruption onset. Timescales range from 400 days to 160 days with olivine cores giving Forsterite (Fo) values of 82-84 and rim values 79 indicating a single olivine population showing normal zoning (Mg-rich core). The distribution of timescales is consistent with a single pulse of magma migrating from depth into a shallow system 1year before eruption onset. Magma arrival slows, then ceases by 5 months before eruption with no new magma entering the system in the days and weeks immediately before eruption. At the time of abstract submission, work is ongoing regarding the signals from later tephra units, but preliminary results indicate tapping of a source with longer crustal residence. Being able to retrieve this information within a day or so of the start of an eruption has exciting implications for eruption monitoring and hazard mitigation.

Seismic observations of Redoubt Volcano, Alaska - 1989-2010 and a conceptual model of the Redoubt magmatic system

USGS Publications Warehouse

Power, John A.; Stihler, Scott D.; Chouet, Bernard A.; Haney, Matthew M.; Ketner, D.M.

2013-01-01

Seismic activity at Redoubt Volcano, Alaska, has been closely monitored since 1989 by a network of five to ten seismometers within 22 km of the volcano's summit. Major eruptions occurred in 1989-1990 and 2009 and were characterized by large volcanic explosions, episodes of lava dome growth and failure, pyroclastic flows, and lahars. Seismic features of the 1989-1990 eruption were 1) weak precursory tremor and a short, 23-hour-long, intense swarm of repetitive shallow long-period (LP) events centered 1.4 km below the crater floor, 2) shallow volcano-tectonic (VT) and hybrid earthquakes that separated early episodes of dome growth, 3) 13 additional swarms of LP events at shallow depths precursory to many of the 25 explosions that occurred over the more than 128 day duration of eruptive activity, and 4) a persistent cluster of VT earthquakes at 6 to 9 km depth. In contrast the 2009 eruption was preceded by a pronounced increase in deep-LP (DLP) events at lower crustal depths (25 to 38 km) that began in mid-December 2008, two months of discontinuous shallow volcanic tremor that started on January 23, 2009, a strong phreatic explosion on March 15, and a 58-hour-long swarm of repetitive shallow LP events. The 2009 eruption consisted of at least 23 major explosions between March 23 and April 5, again accompanied by shallow VT earthquakes, several episodes of shallow repetitive LP events and dome growth continuing until mid July. Increased VT earthquakes at 4 to 9 km depth began slowly in early April, possibly defining a mid-crustal magma source zone. Magmatic processes associated with the 2009 eruption seismically activated the same portions of the Redoubt magmatic system as the 1989-1990 eruption, although the time scales and intensity vary considerably among the two eruptions. The occurrence of precursory DLP events suggests that the 2009 eruption may have involved the rise of magma from lower crustal depths. Based on the evolution of seismicity during the 1989-1990 and 2009 eruptions the Redoubt magmatic system is envisioned to consist of a shallow system of cracks extending 1 to 2 km below the crater floor, a magma storage or source region at roughly 3 to 9 km depth, and a diffuse magma source region at 25 to 38 km depth. Close tracking of seismic activity allowed the Alaska Volcano Observatory to successfully issue warnings prior to many of the hazardous explosive events that occurred in 2009.

Using an intelligent system to aid in tephra layer correlation of the tephra beds of the Mono-Inyo Craters, California

NASA Astrophysics Data System (ADS)

Hanson-Hedgecock, S.; Bursik, M.; Rogova, G.

2008-12-01

We are developing an intelligent system to correlate tephra layers by using the lithologic and geochemical characteristics of field samples, to aid geologists in interpreting eruption patterns in volcanic fields. Understanding the eruption history of a volcanic field from stratigraphic studies is important for forecasting future eruptive behavior and hazards. The intelligent system is used to define groups of tephra source vents and to correlate tephra layers based on a combination of geochemical data and lithostratigraphic characteristics. The tephra beds of the Mono-Inyo Craters, California, are used to test the ability of the intelligent system for tephra layer correlation. The data processing is performed by a suite of both unsupervised and supervised classifiers, built and combined within the framework of the Dempster-Shafer theory of evidence. We have developed algorithms to calculate isopleth maps of thickness, lithic and pumice size that are used in the processing of the lithostratigraphic data. This spatial information is important in the determination of eruption patterns and is used by an evidential nearest neighbor classifier to correlate tephra layers. Integrating a better isopleth approximation function and expert knowledge about stratigraphic order of the tephra layers into the classifier improves the lithostratigraphic correlation from 56% to 87% of layers correctly identified. Geochemical data for defining groups of tephra sources are processed by a suit of fuzzy k-means classifiers. Improved clustering results of geochemical data are achieved by the fusion of individual clustering results with an evidential combination method. The intelligent system aids correlation by showing matches and disparities between data patterns from different outcrops that may have been overlooked. The intelligent system produces a useful recognition result, while dealing with the uncertainty from sparse data and the imprecise description of layer characteristics.

National-level long-term eruption forecasts by expert elicitation

NASA Astrophysics Data System (ADS)

Bebbington, Mark S.; Stirling, Mark W.; Cronin, Shane; Wang, Ting; Jolly, Gill

2018-06-01

Volcanic hazard estimation is becoming increasingly quantitative, creating the potential for land-use decisions and engineering design to use volcanic information in an analogous manner to seismic codes. The initial requirement is to characterize the possible hazard sources, quantifying the likely timing, magnitude and location of the next eruption in each case. This is complicated by the extremely different driving processes at individual volcanoes, and incomplete and uneven records of past activity at various volcanoes. To address these issues, we carried out an expert elicitation approach to estimate future eruption potential for 12 volcanoes of interest in New Zealand. A total of 28 New Zealand experts provided estimates that were combined using Cooke's classical method to arrive at a hazard estimate. In 11 of the 12 cases, the elicited eruption duration increased with VEI, and was correlated with expected repose, differing little between volcanoes. Most of the andesitic volcanoes had very similar elicited distributions for the VEI of a future eruption, except that Taranaki was expected to produce a larger eruption, due to the current long repose. Elicited future vent locations for Tongariro and Okataina reflect strongly the most recent eruptions. In the poorly studied Bay of Islands volcanic field, the estimated vent location distribution was centred on the centroid of the previous vent locations, while in the Auckland field, it was focused on regions within the field without past eruptions. The elicited median dates for the next eruptions ranged from AD2022 (Whakaari/White Island) to AD4390 (Tuhua/Mayor Island).

Crustal Deformation Associated With the 2000 Eruption and Degassing Process of Miyakejima, Izu Islands, Japan

NASA Astrophysics Data System (ADS)

Nishimura, T.; Ozawa, S.; Murakami, M.; Sagiya, T.; Yarai, H.; Tada, T.; Kaidzu, M.

2001-12-01

Miyakejima is located in the northern part of the Izu Islands lying along the boundary between the Pacific plate and the Philippine Sea plate. Miyakejima volcano erupted on Miyakejima is located in the northern part of the Izu Islands which are a chain of volcanoes lying along the boundary between the Pacific plate and the Philippine Sea plate. Miyakejima volcano erupted on June 27, 2000 after the quiescence of 17 years. First eruption is a small submarine eruption 1.5km off the western coast of Miyakejima. Subsequently, several summit eruptions as tephra ejecta occurred in July and August 2000. The summit collapsed just after the first summit eruption and a caldera was formed for 40 days. Collapsed volume and erupted volume are estimated to be 0.6km3 and 0.02km3, respectively. In September 2000, the collapse caldera started emitting a large amount of volcanic gasses. A peak amount of degassing SO2 is ~70000 ton/day in the period from October to December 2000. Amount of volcanic gas is decreasing gradually and is 15000 ton/day (SO2 ) now. However, it is still larger than other active volcanoes. Permanent GPS data reveals the spatial pattern and time evolution of ground deformation. Inflation of Miyakejima was observed by continuous GPS and leveling before the 2000 eruption. The observed displacements associated with the 2000 eruption show radial pattern suggesting shrinking of the island and subsidence. This pattern continues for 14 months from July 2000. Though the rate of crustal deformation is almost constant from July to August 2000, it is decreasing exponentially with a time constant of ~150days from September 2000. We assumed a point deflation source and inverted the observed displacement to estimate parameters of the point source. Volume decrease and depth of the deflation source is 0.12km3 and 4.2km from July to August 2000. We interpret that it is the squeezing of magma from a magma chamber of Miyakejima volcano. The displacement observed in neighbor islands suggests that the squeezed magma and collapsed material of Miyakejima migrated northwestward by as much as 30km in the form of a dike intrusion. Volume decrease and depth of the deflation source is 2.9km and 0.016km3 from September 2000 to May 2001. Decreasing rate of the deflation source is an order of magnitude smaller than that of the previous period. We considered that degassing from magma mainly causes the deflation of magma chamber after September 2000. The decreasing rate estimated from crustal deformation was quantitatively consistent with that estimated from the rate of the emitting volcanic gasses (Kazahaya, personal communication). This consideration suggests that the magma does not migrate any more and that the magma chamber is in closed system. However, recent rate of the deformation is much smaller than that calculated from the degassing rate. This implies that new magma is supplied to the magma chamber from deeper region or that the depth of magma head becomes deeper in a conduit from the magma chamber to the caldera.

Cryovolcanic Conduit Evolution and Eruption on Icy Satellites

NASA Astrophysics Data System (ADS)

Mitchell, K. L.

2014-12-01

In silicate volcanism, such as on Earth or Io, eruptions typically result from fracture formation caused by interaction of tectonic stresses with inflating, pressurized magma sources, leading to transport of melt through an evolving conduit. On icy satellites the paradigm may be similar, resulting from some combination of tidal stresses and expansion of freezing water within, or near the base of, an ice shell. Such a fracture will result in eruption if mass continuity can be established, with buoyancy aided by exsolution and expansion of dissolved volatiles. After onset, conduit shape evolves due to: (1) shear-stresses or frictional erosional; (2) wallrock "bursting" due to massive wall stresses; (3) wall melting or condensation of particles due to heat transfer; or (4) changes in applied stresses. Preliminary thermodynamic and fluid mechanical analysis suggests some initial cooling during ascent resulting from exsolution and expansion of volatiles, thermally buffered by freezing, Conduit contraction may occur, and so evolution towards a deep, gas-filled plume chamber is difficult to accommodate without evoking a co-incidental process. Conduit flaring occurs near the surface where velocities are greatest, enhancing erosion. Here, viscous dissipative heating exceeds adiabatic cooling, and so some boiling (a few wt%) may occur. In contrast with silicate volcanism, decompression to below the triple point will occur within conduit, vent or jet, resulting in rapid freezing and boiling of the remaining water at a 6.8:1 ratio. Subsequent isentropic or adiabatic expansion within erupting jets may result in a few percent net of condensation or sublimation. These effects combined lead to ~4:1-7:1 solid:vapor ratios in the jet for most eruption conditions. These figures are consistent with the ~6:1 inferred in Enceladus' jets, supporting the hypothesis that the Enceladus plume draws from a subsurface body of liquids through a conduit. Similar results are anticipated if cryovolcanic plumes are confirmed on Europa. However, eruption from an ocean is more challenging there, as far greater volatile contents would be required to facilitate mass continuity from an initial fracture, and hence eruption, from the higher pressure source. Shallower sources, such as proposed under chaos, are less challenging.

Understanding Sulfur Systematics in Large Igneous Provinces Using Sulfur Isotopes

NASA Astrophysics Data System (ADS)

Novikova, S.; Edmonds, M.; Turchyn, A. V.; Maclennan, J.; Svensen, H.; Frost, D. J.; Yallup, C.

2013-12-01

The eruption of the Siberian Traps coincided with perhaps the greatest environmental catastrophe in Earth's history, at the Permo-Triassic boundary. The source and magnitude of the volatile emissions, including sulfur, associated with the eruption remain poorly understood yet were critical in forcing environmental change. Two of the primary questions are how much sulfur gases were emitted during the eruptions and from where they were sourced. Primary melts carry dissolved sulfur from the mantle. Magmas ponding in sills and ascending through dykes may also assimilate sulfur from country rocks, as well as heat the country rocks and generate fluids through contact metamorphism. If the magmas interacted thermally, for prolonged periods, with sulfur-rich country rocks then it is probable that the sulfur budget of these eruptions might have been augmented considerably. This is exactly what we have shown recently for a basaltic sill emplaced in oil shale that fed eruptions of the British Tertiary Province, where surrounding sediments showed extensive desulfurization (Yallup et al. Geoch. Cosmochim. Acta, online, 2013). In the current study sulfur isotopes and trace element abundances are used to discriminate sulfur sources and to model magmatic processes for a suite of Siberian Traps sill and lava samples. Our bulk rock and pyrite geochemical analyses illustrate clearly their high abundance of 34S over 32S. The high 34S/32S has been noted previously and linked to assimilation of sulfur from sediments but may alternatively be inherited from the mantle plume source. With the aim of investigating the sulfur isotopic signature in the melt prior to devolatilization, we use secondary ion mass spectrometry (SIMS), for which a specific set of glass standards was synthesised. In order to understand how sulfur isotopes fractionate during degassing we have also conducted a parallel study of well-characterized tephras from Kilauea Volcano, where sulfur degassing behavior is well known.

Using cGPS to estimate the magma budget for Soufrière Hills volcano, Montserrat, West Indies

NASA Astrophysics Data System (ADS)

Collinson, Amy; Neuberg, Jurgen; Pascal, Karen

2017-04-01

For over 20 years, Soufrière Hills Volcano, Montserrat has been in a state of volcanic unrest. Intermittent periods of dome building have been punctuated by explosive eruptions and dome collapse events, endangering the lives of the inhabitants of the island. The last episode of active magma extrusion was in February 2010, and the last explosive event (ash venting) in March 2012. Despite a lack of recent eruptive activity, the volcano continues to emit significant volumes of SO2 and shows an ongoing trend of island inflation as indicated by cGPS. Through the aid of three-dimensional numerical modelling, using a finite element method, we model the cGPS data to explore the potential sources of the ongoing island deformation. We consider both magmatic (dykes and chambers) and tectonic sources which result in entirely different interpretations: Whilst a magmatic source suggests the possibility for further eruption, a tectonic source may indicate cessation of volcanic activity. We investigate the effects that different sources (shapes, characters and depths) have on the surface displacement. We demonstrate that whilst a tectonic contribution cannot be completely discounted, the dominant source is magmatic. Consequently, we define a best-fit model which we use to assess the source volume change, and therefore, the potential current magma budget. Based on the similarity in the relative displacement between the cGPS stations at every episode of the eruption, we assume that the displacement for all Phases and Pauses can be explained by the same basic source. Therefore, we interpret the cGPS data with our source model for all the preceding Pauses and Phases to estimate the magma budget feeding the entire eruption. Subsequently, we derive important insights into the potential future eruptive behaviour of the volcano.

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high-frequency gas monitoring.

PubMed

de Moor, J Maarten; Aiuppa, A; Avard, G; Wehrmann, H; Dunbar, N; Muller, C; Tamburello, G; Giudice, G; Liuzzo, M; Moretti, R; Conde, V; Galle, B

2016-08-01

Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high-frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO 2 -rich gas (CO 2 /S total  > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur-rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is ~8-10 km deep, whereas the shallow magmatic gas source is at ~3-5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H 2 S/SO 2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO 2 and H 2 S/SO 2  > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H 2 S/SO 2  < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high-temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity.

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high‐frequency gas monitoring

PubMed Central

Aiuppa, A.; Avard, G.; Wehrmann, H.; Dunbar, N.; Muller, C.; Tamburello, G.; Giudice, G.; Liuzzo, M.; Moretti, R.; Conde, V.; Galle, B.

2016-01-01

Abstract Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high‐frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2‐rich gas (CO2/Stotal > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur‐rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is ~8–10 km deep, whereas the shallow magmatic gas source is at ~3–5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H2S/SO2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO2 and H2S/SO2 > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H2S/SO2 < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high‐temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity. PMID:27774371

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high-frequency gas monitoring

NASA Astrophysics Data System (ADS)

de Moor, J. Maarten; Aiuppa, A.; Avard, G.; Wehrmann, H.; Dunbar, N.; Muller, C.; Tamburello, G.; Giudice, G.; Liuzzo, M.; Moretti, R.; Conde, V.; Galle, B.

2016-08-01

Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high-frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2-rich gas (CO2/Stotal > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are accompanied by shallowly derived sulfur-rich magmatic gas emissions. Degassing modeling suggests that the deep magmatic reservoir is 8-10 km deep, whereas the shallow magmatic gas source is at 3-5 km. Two cycles of degassing and eruption are observed, each attributed to pulses of magma ascending through the deep reservoir to shallow crustal levels. The magmatic degassing signals were overprinted by a fluid contribution from the shallow hydrothermal system, modifying the gas compositions, contributing volatiles to the emissions, and reflecting complex processes of scrubbing, displacement, and volatilization. H2S/SO2 varies over 2 orders of magnitude through the monitoring period and demonstrates that the first eruptive episode involved hydrothermal gases, whereas the second did not. Massive degassing (>3000 T/d SO2 and H2S/SO2 > 1) followed, suggesting boiling off of the hydrothermal system. The gas emissions show a remarkable shift to purely magmatic composition (H2S/SO2 < 0.05) during the second eruptive period, reflecting the depletion of the hydrothermal system or the establishment of high-temperature conduits bypassing remnant hydrothermal reservoirs, and the transition from phreatic to phreatomagmatic eruptive activity.

Current State of an Intelligent System to Aid in Tephra Layer Correlation

NASA Astrophysics Data System (ADS)

Hanson-Hedgecock, S.; Bursik, M.; Rogova, G.

2007-12-01

We are developing a computer based intelligent system to correlate tephra layers by using the lithologic, mineralogic, and geochemical characteristics of field samples, to aid geologists in interpreting eruption patterns of volcanic chains and fields. The intelligent system is used to define groups of tephra source vents by utilizing geochemical data, and to correlate tephra layers based on lithostratigraphic characteristics. Understanding the eruption history of a volcano from stratigraphic studies is important for forecasting future eruptive behavior and hazards. In volcanic chains and fields with a complex eruptive history and no central vent, determining the spatio- temporal eruption patterns is difficult. Sedimentologic and chemical variability, and sparse sampling often result in relatively large variances and imprecision in the dataset. Lithostratigraphic and geochemical interpretation also depends on ones' level of expertise and can be subjective. The processing of lithostratigraphic features is conducted by a hybrid classifier, composed of supervised artificial neural networks (ANNs) combined within the framework of the Dempster-Shafer theory of evidence. Since lithostratigraphic features vary with distance from source, hypothetical vent locations are determined by using expert domain knowledge and geostatistical methods. Geochemical data are processed by a suit of fuzzy k- means classifiers. Each fuzzy k-means classifier assigns observations to multiple clusters with various degrees, called membership coefficients. The assignment minimizes a function of the total distance between the centers of clusters and the individual geochemical data patterns weighed by the membership coefficients. Improved clustering results of geochemical data are achieved by the fusion of individual clustering results with an evidential combination method. Lithostratigraphic data from individual tephra beds of the North Mono eruption sequence are used to test the effectiveness of the intelligent system for tephra layer correlation. Geochemical data from tephra bedsets of the Mono and Inyo Craters, CA, are used to test the effectiveness of the intelligent system for eruption sequence correlation. The intelligent system aids correlation by showing matches and disparities between data patterns from different outcrops that may have been overlooked in initial interpretations. Initial results show that the lithostratigraphic classifier is able to accurately differentiate known layers 76% of the time. Output from the lithostratigraphic classifier can furthermore be plotted directly as isopleth maps that can aid in rapid recognition of tephra layers as well as determination of eruption characteristics, e.g. eruption volume, plume height, etc. The intelligent system produces a useful recognition result, while dealing with the uncertainty from sparse data and the imprecise description of layer characteristics.

Magmatic Processes at Kilauea Volcano Revealed by the Puu Oo Eruption

NASA Astrophysics Data System (ADS)

Garcia, M. O.; Marske, J. P.; Pietruszka, A. P.; Rhodes, J. M.; Norman, M. D.; Eiler, J.

2008-12-01

The ongoing Puu Oo eruption (1983 to present) provides an unprecedented opportunity to probe the crustal and mantle magmatic processes beneath Kilauea volcano. Here we present Pb, Sr, Nd and O isotope ratios, major- and trace-element abundances, olivine compositions, and petrography data for Puu Oo lavas an compare them to the Kilauea historical record. Crustal processes are dominated by olivine fractionation and accumulation with minor clinopyroxene fractionation, and to a lesser extent and only periodically when eruption rates decrease, by crustal contamination. Systematic variations in Sr isotope ratios, incompatible trace element ratios, and MgO-normalized major elements document remarkable changes in parental magma compositions delivered to Puu Oo. Inflections in some trends correlate broadly with increasing intermediate depth earthquakes under the Kilauea's summit and to changes in eruption rate. Thus, volcanic events are influenced by melting and transport processes. One surprising feature is the systematic trend of Puu Oo rock compositions away from and beyond typical historical Kilauea compositions towards those of lavas from neighboring Mauna Loa volcano. The source for this component in Puu Oo lavas is a hybrid with about equal mixtures of historical Kilauea and Mauna Loa end members. The Puu Oo lava trend continues the cyclic pattern of compositional variation that extends back over 1000 years. Similar trends are also recorded on a coarser scale in HSDP lavas. These patterns of cyclic compositional variation are important for understanding melting processes in Hawaiian and other volcanoes.

Satellite radar interferometry measures deformation at Okmok Volcano

USGS Publications Warehouse

Lu, Zhong; Mann, Dorte; Freymueller, Jeff

1998-01-01

The center of the Okmok caldera in Alaska subsided 140 cm as a result of its February– April 1997 eruption, according to satellite data from ERS-1 and ERS-2 synthetic aperture radar (SAR) interferometry. The inferred deflationary source was located 2.7 km beneath the approximate center of the caldera using a point source deflation model. Researchers believe this source is a magma chamber about 5 km from the eruptive source vent. During the 3 years before the eruption, the center of the caldera uplifted by about 23 cm, which researchers believe was a pre-emptive inflation of the magma chamber. Scientists say such measurements demonstrate that radar interferometry is a promising spaceborne technique for monitoring remote volcanoes. Frequent, routine acquisition of images with SAR interferometry could make near realtime monitoring at such volcanoes the rule, aiding in eruption forecasting.

Stability of volcanic ash aggregates and break-up processes.

PubMed

Mueller, Sebastian B; Kueppers, Ulrich; Ametsbichler, Jonathan; Cimarelli, Corrado; Merrison, Jonathan P; Poret, Matthieu; Wadsworth, Fabian B; Dingwell, Donald B

2017-08-07

Numerical modeling of ash plume dispersal is an important tool for forecasting and mitigating potential hazards from volcanic ash erupted during explosive volcanism. Recent tephra dispersal models have been expanded to account for dynamic ash aggregation processes. However, there are very few studies on rates of disaggregation during transport. It follows that current models regard ash aggregation as irrevocable and may therefore overestimate aggregation-enhanced sedimentation. In this experimental study, we use industrial granulation techniques to artificially produce aggregates. We subject these to impact tests and evaluate their resistance to break-up processes. We find a dependence of aggregate stability on primary particle size distribution and solid particle binder concentration. We posit that our findings could be combined with eruption source parameters and implemented in future tephra dispersal models.

Mechanism of Human Tooth Eruption: Review Article Including a New Theory for Future Studies on the Eruption Process

PubMed Central

Kjær, Inger

2014-01-01

Human eruption is a unique developmental process in the organism. The aetiology or the mechanism behind eruption has never been fully understood and the scientific literature in the field is extremely sparse. Human and animal tissues provide different possibilities for eruption analyses, briefly discussed in the introduction. Human studies, mainly clinical and radiological, have focused on normal eruption and gender differences. Why a tooth begins eruption and what enables it to move eruptively and later to end these eruptive movements is not known. Pathological eruption courses contribute to insight into the aetiology behind eruption. A new theory on the eruption mechanism is presented. Accordingly, the mechanism of eruption depends on the correlation between space in the eruption course, created by the crown follicle, eruption pressure triggered by innervation in the apical root membrane, and the ability of the periodontal ligament to adapt to eruptive movements. Animal studies and studies on normal and pathological eruption in humans can support and explain different aspects in the new theory. The eruption mechanism still needs elucidation and the paper recommends that future research on eruption keeps this new theory in mind. Understanding the aetiology of the eruption process is necessary for treating deviant eruption courses. PMID:24688798

Simulations of Tsunami Triggered by the 1883 Krakatau Volcanic Eruption: Implications for Tsunami Hazard in the South China Sea

NASA Astrophysics Data System (ADS)

Tan, Y.; Lin, J.

2013-12-01

The 1883 Krakatau eruption in Indonesia is one of the largest recorded volcanic eruptions in recent history. The associated tsunami claimed about 36,000 lives and recorded run-up heights up to 30 m along the coastal regions in the Sunda Straits between the Indian Ocean and the South China Sea. Our study aims to better understand the generation and propagation mechanisms of this volcano-induced tsunami through modeling quantitatively the tsunami triggering processes at the source region. Comparison of non-linear simulations using the Cornell Multi-grid Coupled Tsunami Model (COMCOT) with observations reveals that a donut-shape 'hole and ring' initial condition for the tsunami source is able to explain the key characteristics of the observed tsunami: A 'hole' of about 6 km in diameter and 270 m in depth corresponds to the collapse of the Krakatau volcano on August 27, 1883, while a 'ring' of uplift corresponds to the deposition of the erupted volcanic materials. We found that the shallowness and narrowness of the entrance pathway of the Sunda Straits limited the northward transfer of the tsunami energy from the source region into the South China Sea. Instead, the topographic and bathymetric characteristics favored the southward transfer of the energy into the Indian Ocean. This might explain why Sri Lanka and India suffered casualties from this event, while areas inside the South China Sea, such as Singapore, did not record significant tsunami signals. Modeling results further suggest that the shallow topography of the surrounding islands around the Krakatau source region might have contributed to a reduction in maximum run-up heights in the coastal regions of the Sunda Straits.

Rapid Inflation Caused by Shallow Magmatic Activities at Okmok Volcano, Alaska, Detected by GPS Campaigns 2000-2003

NASA Astrophysics Data System (ADS)

Miyagi, Y.; Freymueller, J.; Kimata, F.; Sato, T.; Mann, D.

2006-12-01

Okmok volcano is located on Umnak Island in the Aleutian Arc, Alaska. This volcano consists of a large caldera, and there are several post-caldera cones within the caldera. It has erupted more than 10 times during the last century, with the latest eruption occurring in February 1997. Annual GPS campaigns during 2000-2003 have revealed a rapid inflation at Okmok volcano. Surface deformation indicates that Okmok volcano has been inflating during 2000-2003 at a variable inflation rate. Total displacements over three years are as large as 15 cm of maximum radial displacement and more than 35 cm of maximum uplift. Simple inflation pattern after 2001, showing radial outward displacements from the caldera center and significant uplifts, are modeled by a Mogi inflation source, which is located at the depth of about 3.1 km beneath the geometric center of the caldera, and we interpreted the source as a shallow magma chamber. The results from our GPS measurements correspond approximately to the results from InSAR measurement for almost same periods, except for an underestimate of the volume change rate of the source deduced by InSAR data for the period 2002-2003. Taking into consideration the results from InSAR measurements, the amount of volume increase in the source is estimated to be about 0.028 km3 during 1997-2003. This means that 20-54 percent of the volume erupted in the 1997 eruption has been already replenished in the shallow magma chamber. An eruption recurrence time is estimated from the volume change rate of the source to be about 15-30 years for 1997-sized eruptions, which is consistent with about 25 years average time interval between major eruptions at Okmok volcano. An additional modeling using a rectangular tensile source combined to the main spherical source suggests a possibility of other magma storage located between the main source and the active vent, which is associated with lateral magma transportation between them. The combined model improved residuals compared to those from single-source model, and provided significantly better fitting to the deformation data inside the caldera.

Seismological aspects of the 1989-1990 eruptions at redoubt volcano, Alaska: the SSAM perspective

USGS Publications Warehouse

Stephens, C.D.; Chouet, B.A.; Page, R.A.; Lahr, J.C.; Power, J.A.

1994-01-01

SSAM is a simple and inexpensive tool for continuous monitoring of average seismic amplitudes within selected frequency bands in near real-time on a PC-based data acquisition system. During the 1989-1990 eruption sequence at Redoubt Volcano, the potential of SSAM to aid in rapid identification of precursory Long-Period (LP) event swarms was realized, and since this time SSAM has been incorporated in routine monitoring efforts of the Alaska Volcano Observatory. In particular, an eruption that occurred on April 6 was successfully forecast primarily on the basis of recognizing the precursory LP activity on SSAM. Of twenty-two significant eruptions that occurred between December 14 and April 21, eleven had precursory swarms longer than one hour in duration that could be detected on SSAM. For individual swarms, the patterns of relative spectral amplitudes are distinct at each station and remain largely stationary through time, thus indicating that one source may have been preferentially and repeatedly activated throughout the swarm. Typically, a single spectral band dominates the signal at each seismic station: for the vigorous one-day swarm that preceded the first eruption on December 14, signals were sharply peaked in the 1.9-2.7 Hz band at the closest station, located 4 km from the vent, but were dominated by 1.3-1.9 Hz energy at three more distant stations located 7.5-22 km from the vent. The tendency for the signals from different swarms recorded at the same station to be peaked in the same frequency band suggests that all of the sources are characterized by a predominant length scale. Signals from the precursory LP swarms became weaker as the eruption sequence progressed, and swarms that occurred in March and April could only be detected at seismographs on the volcanic edifice. Onset times of precursory LP swarms prior to eruptions ranged from a few hours to about one week, but after the initial vent-clearing phase that ended December 19 these intervals tended to become progressively shorter for successive swarms. These trends in the relative onset times and intensities of successive precursory LP swarms are consistent with an overall depressurization of the magmatic system through time. In general, each of the swarms had an emergent onset, but the intensities did not always increase steadily until the eruptions. Instead, as the time of an eruption approached the intensity usually increased more rapidly before peaking and then declining prior to the eruption; for three of the swarms, two distinct peaks in intensity were apparent. The time intervals between final peaks in swarm intensity and ensuing eruptions ranged from about 2 hours to almost 2 days, but the peaks always occurred closer to the eruptions than to the swarm onsets. Both the onset of LP swarm activity and a decline in intensity prior to an eruption may represent critical points in the process of pressurization that drives the flow of fluids and gas in a sealed magmatic system. A notable exception to this pattern is the eruption of March 9 which lacked a detectable precursory LP swarm, but was followed by an unusually long period of strong LP seismicity that may have been stimulated by a depressurization of the magmatic system resulting from dome failure. On both December 14 and January 2, the spectra of early syn-eruptive signals have peaked signatures much like those of the spectra of precursory LP activity from shortly before the eruptions; these similarities may indicate that the source of precursory seismicity continued to be active during at least the early part of each eruption. In syn-eruptive signals from March and April recorded at stations on the volcanic edifice, the dominant spectral energy progressively shifts with time during the eruption to lower frequencies; at least part of the energy in these signals may have been generated by the debris flows associated with dome failures. ?? 1994.

Modeling post-eruptive deformation at Okmok volcano from GPS and InSAR using unscented Kalman filter

NASA Astrophysics Data System (ADS)

Xue, X.; Freymueller, J. T.

2017-12-01

Okmok, occupies most of northeastern Umnak Island in the Aleutian arc, started inflating soon after the 2008 eruption. Seven GPS sites have been operated after the eruption. Two of them are located within the caldera, three are around the rim of the caldera and two are out of the caldera. The InSAR timeseries have been generated using data from the C-band Envisat and X-band TerraSAR-X satellites (Qu et al., 2015). Both GPS and InSAR indicate more than 0.6 m uplift within the caldera and subtle subsidence outside the caldera. Based on single Mogi source, an unscented Kalman filter was successfully used to model the deformation at Okmok detected by GPS during 2000-2007. We have expanded it to be able to model multiple Mogi sources at different depths and integrate the InSAR observations. Before applying the Kalman filter, We remove a time-independent Mogi source and phase ramp from each InSAR image and obtain its variance-covariance information from the residual. We also determine the relative weight between GPS and InSAR data using variance component estimation. The GPS and InSAR timeseries can then be combined for the Kalman filter. Preliminary results show that two Mogi sources are more likely beneath Okmok volcano. The deep source is located at 8.5 km depth which deflated 0.016 km3 during the first 3 years after the eruption then reached a stable state. The deflating source explains the subsidence outside the caldera which can not be modeled with only one inflating source in any way. The shallow source, migrating 0.5 km from north to south, is located at 2 km depth within the caldera where is close to the source position before the eruption (Freymueller et al., 2010). The magma volume accumulation of the shallow source in the following 7 years from the 2008 eruption is 0.035 km3.

A comprehensive approach to monitoring volcano deformation as a window on the eruption cycle

USGS Publications Warehouse

Dzurisin, D.

2003-01-01

Since the 1980 eruption of Mount St. Helens, volcanologists have made considerable progress toward predicting eruptions on the basis of precursors that typically start a few days to several months in advance. Although accurate eruption prediction is by no means routine, it may now be possible in some cases to extend the effective warning period by anticipating the onset of short-term precursors. Three promising indicators of deep magmatic processes are (1) deep, long-period earthquakes and tremor that indicate the ascent of magma through the crust, (2) magmatic CO2 emission rate as a proxy for magma supply rate, and (3) relatively broad, generally aseismic surface uplift caused by magmatic intrusions. In the latter case it is essential to sample the deformation field thoroughly in both time and space to adequately constrain source models. Until recently, this has been nearly impossible because high-precision sensors could not be deployed in sufficient numbers, nor could extensive geodetic surveys be conducted often enough. Advances in instrumentation, interferometric synthetic aperture radar (InSAR), and telecommunications are helping to overcome these limitations. As a result, comprehensive geodetic monitoring of selected volcanoes is now feasible. A combination of InSAR, large-aperture GPS surveys, microgravity surveys, and dense arrays of continuous GPS stations, strain meters, and tiltmeters can reveal both spatial and temporal patterns of ground deformation throughout the eruption cycle. Improved geodetic monitoring of many of the world's volcanoes would be a major stride toward better understanding of magmatic processes and longer-term eruption forecasts.

Understanding and forecasting phreatic eruptions driven by magmatic degassing

NASA Astrophysics Data System (ADS)

Stix, John; de Moor, J. Maarten

2018-05-01

This paper examines phreatic eruptions which are driven by inputs of magma and magmatic gas. We synthesize data from several significant phreatic systems, including two in Costa Rica (Turrialba and Poás) which are currently highly active and hazardous. We define two endmember types of phreatic eruptions, the first (type 1) in which a deeper hydrothermal system fed by magmatic gases is sealed and produces overpressure sufficient to drive explosive eruptions, and the second (type 2) where magmatic gases are supplied via open-vent degassing to a near-surface hydrothermal system, vaporizing liquid water which drives the phreatic eruptions. The surficial source of type 2 eruptions is characteristic, while the source depth of type 1 eruptions is commonly greater. Hence, type 1 eruptions tend to be more energetic than type 2 eruptions. The first type of eruption we term "phreato-vulcanian", and the second we term "phreato-surtseyan". Some systems (e.g., Ruapehu, Poás) can produce both type 1 and type 2 eruptions, and all systems can undergo sealing at various timescales. We examine a number of precursory signals which appear to be important in understanding and forecasting phreatic eruptions; these include very long period events, banded tremor, and gas ratios, in particular H2S/SO2 and CO2/SO2. We propose that if these datasets are carefully integrated during a monitoring program, it may be possible to accurately forecast phreatic eruptions.[Figure not available: see fulltext.

Integrating field, textural, and geochemical monitoring to track eruption triggers and dynamics: a case study from Piton de la Fournaise

NASA Astrophysics Data System (ADS)

Gurioli, Lucia; Di Muro, Andrea; Vlastélic, Ivan; Moune, Séverine; Thivet, Simon; Valer, Marina; Villeneuve, Nicolas; Boudoire, Guillaume; Peltier, Aline; Bachèlery, Patrick; Ferrazzini, Valérie; Métrich, Nicole; Benbakkar, Mhammed; Cluzel, Nicolas; Constantin, Christophe; Devidal, Jean-Luc; Fonquernie, Claire; Hénot, Jean-Marc

2018-04-01

The 2014 eruption at Piton de la Fournaise (PdF), La Réunion, which occurred after 41 months of quiescence, began with surprisingly little precursory activity and was one of the smallest so far observed at PdF in terms of duration (less than 2 days) and volume (less than 0.4 × 106 m3). The pyroclastic material was composed of golden basaltic pumice along with fluidal, spiny iridescent and spiny opaque basaltic scoria. Density analyses performed on 200 lapilli reveal that while the spiny opaque clasts are the densest (1600 kg m-3) and most crystalline (55 vol. %), the golden pumices are the least dense (400 kg m-3) and crystalline (8 vol. %). The connectivity data indicate that the fluidal and golden (Hawaiian-like) clasts have more isolated vesicles (up to 40 vol. %) than the spiny (Strombolian-like) clasts (0-5 vol. %). These textural variations are linked to primary pre-eruptive magma storage conditions. The golden and fluidal fragments track the hotter portion of the melt, in contrast to the spiny fragments and lava that mirror the cooler portion of the shallow reservoir. Exponential decay of the magma ascent and output rates through time revealed depressurization of the source during which a stratified storage system was progressively tapped. Increasing syn-eruptive degassing and melt-gas decoupling led to a decrease in the explosive intensity from early fountaining to Strombolian activity. The geochemical results confirm the absence of new input of hot magma into the 2014 reservoir and confirm the emission of a single shallow, differentiated magma source, possibly related to residual magma from the November 2009 eruption. Fast volatile exsolution and crystal-melt separation (second boiling) were triggered by deep pre-eruptive magma transfer and stress field change. Our study highlights the possibility that shallow magma pockets can be quickly reactivated by deep processes without mass or energy (heat) transfer and produce hazardous eruptions with only short-term elusive precursors.

Tephrostratigraphy and Provenance From IODP Expedition 352, Izu-Bonin Arc: Tracing Tephra Sources and Volumes From the Oligocene to Recent

NASA Astrophysics Data System (ADS)

Kutterolf, S.; Schindlbeck, J. C.; Robertson, A. H. F.; Avery, A.; Baxter, A. T.; Petronotis, K.; Wang, K.-L.

2018-01-01

Provenance studies of widely distributed tephras, integrated within a well-defined temporal framework, are important to deduce systematic changes in the source, scale, distribution, and changes in regional explosive volcanism. Here, we establish a robust tephrochronostratigraphy for a total of 157 marine tephra layers collected during IODP Expedition 352. We infer at least three major phases of highly explosive volcanism during Oligocene to Pleistocene time. Provenance analysis based on glass composition assigns 56 of the tephras to a Japan source, including correlations with 12 major and widespread tephra layers resulting from individual eruptions in Kyushu, Central Japan, and North Japan between 115 ka and 3.5 Ma. The remaining 101 tephras are assigned to four source regions along the Izu-Bonin arc. One, exclusively assigned to the Oligocene age, is proximal to the Bonin Ridge islands; two reflect eruptions within the volcanic front and back-arc of the central Izu-Bonin arc, and a fourth region corresponds to the Northern Izu-Bonin arc source. First-order volume estimates imply eruptive magnitudes ranging from 6.3 to 7.6 for Japan-related eruptions and between 5.5 and 6.5 for IBM eruptions. Our results suggest tephras between 30 and 22 Ma reflect a subtly different Izu-Bonin chemical signature compared to the recent arc. After a ˜9 Ma gap in eruption, tephra supply from the Izu-Bonin arc predominated from 15 to 5 Ma, and finally a subequal mixture of tephra sources from the (palaeo)Honshu and Izu-Bonin arcs occured within the last ˜5 Ma.

Magmatic differentiation processes at Merapi Volcano: inclusion petrology and oxygen isotopes

NASA Astrophysics Data System (ADS)

Troll, Valentin R.; Deegan, Frances M.; Jolis, Ester M.; Harris, Chris; Chadwick, Jane P.; Gertisser, Ralf; Schwarzkopf, Lothar M.; Borisova, Anastassia Y.; Bindeman, Ilya N.; Sumarti, Sri; Preece, Katie

2013-07-01

Indonesian volcano Merapi is one of the most hazardous volcanoes on the planet and is characterised by periods of active dome growth and intermittent explosive events. Merapi currently degasses continuously through high temperature fumaroles and erupts basaltic-andesite dome lavas and associated block-and-ash-flows that carry a large range of magmatic, coarsely crystalline plutonic, and meta-sedimentary inclusions. These inclusions are useful in order to evaluate magmatic processes that act within Merapi's plumbing system, and to help an assessment of which phenomena could trigger explosive eruptions. With the aid of petrological, textural, and oxygen isotope analysis we record a range of processes during crustal magma storage and transport, including mafic recharge, magma mixing, crystal fractionation, and country rock assimilation. Notably, abundant calc-silicate inclusions (true xenoliths) and elevated δ18O values in feldspar phenocrysts from 1994, 1998, 2006, and 2010 Merapi lavas suggest addition of limestone and calc-silicate materials to the Merapi magmas. Together with high δ13C values in fumarole gas, crustal additions to mantle and slab-derived magma and volatile sources are likely a steady state process at Merapi. This late crustal input could well represent an eruption trigger due to sudden over-pressurisation of the shallowest parts of the magma storage system independently of magmatic recharge and crystal fractionation. Limited seismic precursors may be associated with this type of eruption trigger, offering a potential explanation for the sometimes erratic behaviour of Merapi during volcanic crises.

Relationships Between Subsurface Processes and Eruptive Products at Maar-diatreme Volcanoes Using Numerical Modeling and Tephra Ring Componentry

NASA Astrophysics Data System (ADS)

Sweeney, M. R.; Valentine, G.; Grosso, Z.

2016-12-01

Diatremes represent a unique example of a volcanic plumbing system in which the physical characteristics of the system control eruption dynamics, but in turn, the eruption dynamics greatly dictate how the diatreme evolves. As a result, interpreting surface deposits such as tephra rings is difficult in the context of the whole volcano system. Here we present a novel application of multiphase numerical modeling to simulate intra-diatreme explosions and their effects on transport and mixing length scales. This and previous work have shown that whether an explosion erupts material out of the diatreme depends on several variables, but especially the depth and energy of the explosion. Explosions deeper than 250 m are unlikely to erupt unless extremely large amounts of magma and water are involved. Erupted material at maar-diatreme volcanoes is therefore mostly sourced from the upper-most part of the diatreme. Our modeling shows that following an explosion, the material immediately surrounding and overlying the explosion site is propelled toward the surface via debris jets, which are imperfectly coupled gas-solid mixtures. As the debris jet ascends, material elsewhere in the diatreme undergoes substantial subsidence. This subsidence can be responsible for long residence times of clasts in the diatreme, which together with other factors such as "non-erupting" explosions, can bias a simple interpretation of tephra ring deposits (i.e. the presence of a certain lithology is indicative of the depth at which the eruption originated from). In light of these findings, tephra ring componentry from Dotsero Volcano (Colorado, USA) is compared to volume estimates of the well-constrained subsurface geology to estimate the proportions of different country rock units that might preside in the diatreme. These data in conjunction with different modeling scenarios elucidate intra-diatreme processes such as debris jet activity and their role in forming surface deposits.

Sulphur-rich volcanic eruptions and stratospheric aerosols

NASA Technical Reports Server (NTRS)

Rampino, M. R.; Self, S.

1984-01-01

Data from direct measurements of stratospheric optical depth, Greenland ice-core acidity, and volcanological studies are compared, and it is shown that relatively small but sulfur-rich volcanic eruptions can have atmospheric effects equal to or even greater than much larger sulfur-poor eruptions. These small eruptions are probably the most frequent cause of increased stratospheric aerosols. The possible sources of the excess sulfur released in these eruptions are discussed.

Combination of a pressure source and block movement for ground deformation analysis at Merapi volcano prior to the eruptions in 2006 and 2010

NASA Astrophysics Data System (ADS)

Aisyah, Nurnaning; Iguchi, Masato; Subandriyo; Budisantoso, Agus; Hotta, Kohei; Sumarti, Sri

2018-05-01

We analyzed ground deformation prior to the eruptions in 2006 and 2010 at Merapi volcano, Central Java, Indonesia. Ground deformation was monitored by electronic distance measurement (EDM) by measuring the slope distance toward 12 reflectors installed near the summit from five benchmarks on flanks every day. A large change of slope distance (CSD) was detected on the southeast and south baselines and a minor CSD was detected on the north and northwest baselines during the pre-eruptive stages of both the 2006 and 2010 eruptions. We applied a block movement model to the south and southeast baselines and a spherical pressure source model to the CSDs on the north and northwest baselines using the finite element method (FEM). The rates of block movement southward and the volume change of the pressure source increased on April 7, 2006 and continued at constant rates until the appearance of a new lava dome on April 26. Prior to the eruption in 2010, the block movement southeastward and the volume increase of the pressure source accelerated in the middle of October, and acceleration continued until the first outburst on October 26, 2010. Temporal patterns of the block movement and the increase in the volume of the pressure source correlate well with the increase in seismicity of VT and MP earthquakes. The pressure sources were obtained at a depth of 2 ± 0.5 km below the summit, and this position corresponds to the aseismic zone of VT earthquakes. Magma injection at the shallow part of this region causes an increase in the volume of the pressure source, and inflation of the ground of the summit triggered gravitational slip southeastward or southward of the ground surface. The volumes increases of the pressure sources were 9.7 ± 1 M m3 and 17.6 ± 0.8 M m3 in 2006 and 2010, respectively. The volume increase is related to the scale and type of the eruption. The effusive eruption in 2006 had a volcanic explosivity index (VEI) of 2 and the explosive eruption in 2010 had a VEI of 4. The directions and amounts of the block movement are strongly related to topography, hydrothermally weak zone and underground gap near the summit between West and East Domes.

Very slow lava extrusion continued for more than five years after the 2011 Shinmoedake eruption observed from SAR interferometry

NASA Astrophysics Data System (ADS)

Ozawa, T.; Miyagi, Y.

2017-12-01

Shinmoe-dake located to SW Japan erupted in January 2011 and lava accumulated in the crater (e.g., Ozawa and Kozono, EPS, 2013). Last Vulcanian eruption occurred in September 2011, and after that, no eruption has occurred until now. Miyagi et al. (GRL, 2014) analyzed TerraSAR-X and Radarsat-2 SAR data acquired after the last eruption and found continuous inflation in the crater. Its inflation decayed with time, but had not terminated in May 2013. Since the time-series of inflation volume change rate fitted well to the exponential function with the constant term, we suggested that lava extrusion had continued in long-term due to deflation of shallow magma source and to magma supply from deeper source. To investigate its deformation after that, we applied InSAR to Sentinel-1 and ALOS-2 SAR data. Inflation decayed further, and almost terminated in the end of 2016. It means that this deformation has continued more than five years from the last eruption. We have found that the time series of inflation volume change rate fits better to the double-exponential function than single-exponential function with the constant term. The exponential component with the short time constant has almost settled in one year from the last eruption. Although InSAR result from TerraSAR-X data of November 2011 and May 2013 indicated deflation of shallow source under the crater, such deformation has not been obtained from recent SAR data. It suggests that this component has been due to deflation of shallow magma source with excess pressure. In this study, we found the possibility that long-term component also decayed exponentially. Then this factor may be deflation of deep source or delayed vesiculation.

Infrasonic crackle and supersonic jet noise from the eruption of Nabro Volcano, Eritrea

NASA Astrophysics Data System (ADS)

Fee, David; Matoza, Robin S.; Gee, Kent L.; Neilsen, Tracianne B.; Ogden, Darcy E.

2013-08-01

The lowermost portion of an explosive volcanic eruption column is considered a momentum-driven jet. Understanding volcanic jets is critical for determining eruption column dynamics and mitigating volcanic hazards; however, volcanic jets are inherently difficult to observe due to their violence and opacity. Infrasound from the 2011 eruption of Nabro Volcano, Eritrea has waveform features highly similar to the "crackle" phenomenon uniquely produced by man-made supersonic jet engines and rockets and is characterized by repeated asymmetric compressions followed by weaker, gradual rarefactions. This infrasonic crackle indicates that infrasound source mechanisms in sustained volcanic eruptions are strikingly similar to jet noise sources from heated, supersonic jet engines and rockets, suggesting that volcanologists can utilize the modeling and physical understandings of man-made jets to understand volcanic jets. The unique, distinctive infrasonic crackle from Nabro highlights the use of infrasound to remotely detect and characterize hazardous eruptions and its potential to determine volcanic jet parameters.

Continuous monitoring of volcanoes with borehole strainmeters

NASA Astrophysics Data System (ADS)

Linde, Alan T.; Sacks, Selwyn

Monitoring of volcanoes using various physical techniques has the potential to provide important information about the shape, size and location of the underlying magma bodies. Volcanoes erupt when the pressure in a magma chamber some kilometers below the surface overcomes the strength of the intervening rock, resulting in detectable deformations of the surrounding crust. Seismic activity may accompany and precede eruptions and, from the patterns of earthquake locations, inferences may be made about the location of magma and its movement. Ground deformation near volcanoes provides more direct evidence on these, but continuous monitoring of such deformation is necessary for all the important aspects of an eruption to be recorded. Sacks-Evertson borehole strainmeters have recorded strain changes associated with eruptions of Hekla, Iceland and Izu-Oshima, Japan. Those data have made possible well-constrained models of the geometry of the magma reservoirs and of the changes in their geometry during the eruption. The Hekla eruption produced clear changes in strain at the nearest instrument (15 km from the volcano) starting about 30 minutes before the surface breakout. The borehole instrument on Oshima showed an unequivocal increase in the amplitude of the solid earth tides beginning some years before the eruption. Deformational changes, detected by a borehole strainmeter and a very long baseline tiltmeter, and corresponding to the remote triggered seismicity at Long Valley, California in the several days immediately following the Landers earthquake are indicative of pressure changes in the magma body under Long Valley, raising the question of whether such transients are of more general importance in the eruption process. We extrapolate the experience with borehole strainmeters to estimate what could be learned from an installation of a small network of such instruments on Mauna Loa. Since the process of conduit formation from the magma sources in Mauna Loa and other volcanic regions should be observable, continuous high sensitivity strain monitoring of volcanoes provides the potential to give short time warnings of impending eruptions. Current technology allows transmission and processing of rapidly sampled borehole strain data in real-time. Such monitoring of potentially dangerous volcanoes on a global scale would provide not only a wealth of scientific information but also significant social benefit, including the capability of diverting nearby in-flight aircraft.

Constraints on the Rates of Replenishment, Magma Mixing, and Crystal Recycling at Santorini Volcano, Greece

NASA Astrophysics Data System (ADS)

Martin, V. M.; Davidson, J. P.; Morgan, D. J.; Jerram, D. A.

2007-12-01

Santorini is a young, active volcano, which preserves abundant evidence for open-system processes such as magma replenishment and crystal recycling, and thus represents an ideal system in which to study magma chamber dynamics. Santorini is the largest volcanic centre in the Aegean arc, with an eruptive history spanning more than 250,000 years over two eruptive cycles. The cycles are dominated by extended periods of effusive shield-building activity with occasional large-magnitude explosive eruptions, the Minoan eruption of ~3600 years ago being the most recent. Current activity consists of a phase of post-caldera reconstruction, focused recently on the intra-caldera Kameni islands. Microsampling to measure 87Sr/86Sr ratios of plagioclase cores indicates the presence of a complex plumbing system beneath Santorini. Large rhyodacitic deposits typically contain a mafic component, interpreted as the eruption trigger. In some cases, the mafic magma groundmass and phenocrysts are isotopically similar to their rhyodacite host; other deposits show the opposite, implying the coexistence of isotopically distinct magma batches. To add further complexity, plagioclase phenocrysts are in some cases in equilibrium with their groundmass while others show the reverse, implying modification due to crystal recycling or shallow mixing processes prior to eruption. Mafic enclaves in the recent Kameni lavas, again interpreted as the probable eruption trigger, provide some constraints on the rates of these recycling, mixing, and triggering processes. Glomerocrysts and xenocrysts of recycled gabbroic cumulate material are present in a number of Kameni enclaves. Isotopic and chemical disequilibrium between the cumulate crystals and the host indicate that these fragments are derived from pre- existing crystal mush piles pervaded by the replenishing melts as they migrated to shallow levels, creating disequilibrium between the cumulate mineral cores and the replenishing melts. 87Sr/86Sr isotope ratios of plagioclase xenocryst cores suggest crystal recycling from a pre-Minoan source is probable. Olivine xenocrysts in the enclaves possess narrow (10-30 μm) Fe-Mg diffusion profiles, due to interaction with enclave magma groundmass, which can be used to estimate the interval between entrainment and eruption. Initial modelling of diffusion profiles from more than 60 crystals suggests short timescales, from 15 to 45 days, for the combined migration-replenishment-eruption cycle at Kameni.

Magma accumulation or second boiling - Investigating the ongoing deformation field at Montserrat, West Indies

NASA Astrophysics Data System (ADS)

Collinson, Amy; Neuberg, Jurgen; Pascal, Karen

2016-04-01

For over 20 years, Soufriere Hills Volcano, Montserrat has been in a state of volcanic unrest. Intermittent periods of dome building have been punctuated by explosive eruptions and dome collapse events, endangering the lives of the inhabitants of the island. The last episode of active magma extrusion was in February 2010, and the last explosive event (ash venting) in March 2012. Despite a lack of eruptive activity recently, the volcano continues to emit significant volumes of SO2 and shows an ongoing trend of island inflation. Through the aid of three-dimensional numerical modelling, using a finite element method, we explore the potential sources of the ongoing island inflation. We consider both magmatic (dykes and chamber) and tectonic sources. Whilst a magmatic source suggests the possibility for further eruption, a tectonic source may indicate cessation of volcanic activity. We show that a magmatic source is the most likely scenario, and illustrate the effect of different sources (shapes, characters and depths) on the surface displacement. Furthermore, through the inclusion of topographic data, we investigate how the topography may affect the displacement pattern at the surface. We investigate the conflicting scenarios of magma chamber resupply versus second boiling - crystallisation-induced degassing. Based on numerical modelling results, we suggest the required pressurisation is too high for crystallisation-induced degassing to be the dominant process - thereby suggesting magma accumulation may be ongoing. However, we show that second boiling may be a contributing factor, particularly when taking into account the local tectonics and regional stretching.

The flow structure of jets from transient sources and implications for modeling short-duration explosive volcanic eruptions

NASA Astrophysics Data System (ADS)

Chojnicki, K. N.; Clarke, A. B.; Adrian, R. J.; Phillips, J. C.

2014-12-01

We used laboratory experiments to examine the rise process in neutrally buoyant jets that resulted from an unsteady supply of momentum, a condition that defines plumes from discrete Vulcanian and Strombolian-style eruptions. We simultaneously measured the analog-jet discharge rate (the supply rate of momentum) and the analog-jet internal velocity distribution (a consequence of momentum transport and dilution). Then, we examined the changes in the analog-jet velocity distribution over time to assess the impact of the supply-rate variations on the momentum-driven rise dynamics. We found that the analog-jet velocity distribution changes significantly and quickly as the supply rate varied, such that the whole-field distribution at any instant differed considerably from the time average. We also found that entrainment varied in space and over time with instantaneous entrainment coefficient values ranging from 0 to 0.93 in an individual unsteady jet. Consequently, we conclude that supply-rate variations exert first-order control over jet dynamics, and therefore cannot be neglected in models without compromising their capability to predict large-scale eruption behavior. These findings emphasize the fundamental differences between unsteady and steady jet dynamics, and show clearly that: (i) variations in source momentum flux directly control the dynamics of the resulting flow; (ii) impulsive flows driven by sources of varying flux cannot reasonably be approximated by quasi-steady flow models. New modeling approaches capable of describing the time-dependent properties of transient volcanic eruption plumes are needed before their trajectory, dilution, and stability can be reliably computed for hazards management.

Chronology of the 2015 eruption of Hakone volcano, Japan: geological background, mechanism of volcanic unrest and disaster mitigation measures during the crisis

NASA Astrophysics Data System (ADS)

Mannen, Kazutaka; Yukutake, Yohei; Kikugawa, George; Harada, Masatake; Itadera, Kazuhiro; Takenaka, Jun

2018-04-01

The 2015 eruption of Hakone volcano was a very small phreatic eruption, with total erupted ash estimated to be in the order of only 102 m3 and ballistic blocks reaching less than 30 m from the vent. Precursors, however, had been recognized at least 2 months before the eruption and mitigation measures were taken by the local governments well in advance. In this paper, the course of precursors, the eruption and the post-eruptive volcanic activity are reviewed, and a preliminary model for the magma-hydrothermal process that caused the unrest and eruption is proposed. Also, mitigation measures taken during the unrest and eruption are summarized and discussed. The first precursors observed were an inflation of the deep source and deep low-frequency earthquakes in early April 2015; an earthquake swarm then started in late April. On May 3, steam wells in Owakudani, the largest fumarolic area on the volcano, started to blowout. Seismicity reached its maximum in mid-May and gradually decreased; however, at 7:32 local time on June 29, a shallow open crack was formed just beneath Owakudani as inferred from sudden tilt change and InSAR analysis. The same day mud flows and/or debris flows likely started before 11:00 and ash emission began at about 12:30. The volcanic unrest and the eruption of 2015 can be interpreted as a pressure increase in the hydrothermal system, which was triggered by magma replenishment to a deep magma chamber. Such a pressure increase was also inferred from the 2001 unrest and other minor unrests of Hakone volcano during the twenty-first century. In fact, monitoring of repeated periods of unrest enabled alerting prior to the 2015 eruption. However, since open crack formation seems to occur haphazardly, eruption prediction remains impossible and evacuation in the early phase of volcanic unrest is the only way to mitigate volcanic hazard.[Figure not available: see fulltext.

Tiny crystals give away the where and when of magma ascent

NASA Astrophysics Data System (ADS)

Ruth, D. C. S.; Costa Rodriguez, F.; Bouvet de Maisonneuve, C.; Franco, L.; Cortes, J. A.; Calder, E.

2016-12-01

Open vent volcanoes exhibit passive degassing and can transition to explosive behavior, with limited or no warning. Melt inclusion chemistry and volatile contents have been used to infer the inner dynamics of magma storage, recharge, degassing, and eruption triggering mechanisms. However, the interpretation of melt inclusion chemistry is ambiguous because it cannot constrain the residence times of the host crystals, which could have various sources and growth histories. To resolve this issue we combine diffusion chronometry and melt inclusion entrapment pressures from olivine crystals sourced from the 2008 eruption of Llaima volcano (Chile). Olivine crystals (core Fo70-84, rim Fo77-84) are dominantly reverse zoned, although normal zoned and complex zoned crystals are observed. These data reflect mixing between the mafic injecting magma and the crystal-rich resident magma. Fe/Mg diffusion timescales range between 16 and 1375 days. The diffusion data show a non-uniform distribution with no discernible peaks, indicating that magma injection is likely progressive, rather than punctuated. Entrapment pressures range between 8 and 151 MPa, overlapping with an inferred crystal-rich region. Longer timescales correspond to higher pressures, strongly suggesting a link between magma residence time and ascent from depth. To our knowledge, this relationship has not been previously demonstrated. We infer that mafic magma intruded at depths of 5 km below the edifice and mingled with a pre-existing crystal-mush 3 yr before the eruption. Magma migration and mingling continued and stalled at 2.5 km depth about a year prior to the eruption. Precursory activity such as volcano-tectonic and long period seismicity, and a series of minor explosions overlap with the diffusion times 6 months before the eruption. Similar diffusion timescales have been reported for eruptions at other open vent volcanoes. Our study provides the first temporal and spatial constraints on magma storage and ascent before an eruption. Furthermore at Llaima, and potentially open vent systems, the progressive nature of magma injection suggests that additional processes (e.g. variable ascent rates, changing viscosity, etc.) are needed to trigger an eruption.

Recurrent eruption and subsidence at the Platoro caldera complex, southeastern San Juan volcanic field, Colorado: New tales from old tuffs

USGS Publications Warehouse

Lipman, P.W.; Dungan, M.A.; Brown, L.L.; Deino, A.

1996-01-01

Reinterpretation of a voluminous regional ash-flow sheet (Masonic Park Tuff) as two separate tuff sheets of similar phenocryst-rich dacite erupted from separate source calderas has important implications for evolution of the multicyclic Platoro caldera complex and for caldera-forming processes generally. Masonic Park Tuff in central parts of the San Juan field, including the type area, was erupted from a concealed source at 28.6 Ma, but widespread tuff previously mapped as Masonic Park Tuff in the southeastern San Juan Mountains is the product of the youngest large-volume eruption of the Platoro caldera complex at 28.4 Ma. This large unit, newly named the "Chiquito Peak Tuff," is the last-erupted tuff of the Treasure Mountain Group, which consists of at least 20 separate ash-flow sheets of dacite to low-silica rhyolite erupted from the Platoro complex during a 1 m.y. interval (29.5-28.4 Ma). Two Treasure Mountain tuff sheets have volumes in excess of 1000 km3 each, and five more have volumes of 50-150 km3. The total volume of ash-flow tuff exceeds 2500 km3, and caldera-related lavas of dominantly andesitic composition make up 250-500 km3 more. A much greater volume of intermediate-composition magma must have solidified in subcaldera magma chambers. Most preserved features of the Platoro complex - including postcollapse asymmetrical trap-door resurgent uplift of the ponded intracaldera tuff and concurrent infilling by andesitic lava flows - postdate eruption of the Chiquito Peak Tuff. The numerous large-volume pre-Chiquito Peak ash-flow tuffs document multiple eruptions accompanied by recurrent subsidence; early-formed caldera walls nearly coincide with margins of the later Chiquito Peak collapse. Repeated syneruptive collapse at the Platoro complex requires cumulative subsidence of at least 10 km. The rapid regeneration of silicic magmas requires the sustained presence of an andesitic subcaldera magma reservoir, or its rapid replenishment, during the 1 m.y. life span of the Platoro complex. Either case implies large-scale stoping and assimilative recycling of the Tertiary section, including intracaldera tuffs.

Constraining the presence and abundance of an excess gas phase prior to the June 1991 eruption of Mt Pinatubo (Philippines) using S-isotopes

NASA Astrophysics Data System (ADS)

Bouvet de Maisonneuve, C.; Fiege, A.; Fabbro, G.; Kubo, A. I.

2016-12-01

Large explosive eruptions typically release orders of magnitude more S to the atmosphere than expected based on degassing of the erupted magma. To explain this, an excess, accumulated vapor phase is often proposed. Resolving the presence, composition, and source of such an exsolved volatile phase is essential, as it will drive eruptions towards increased explosivity. Integration of melt inclusion (MI) volatile contents (H, C, S, Cl, F) with S isotope data on melt inclusions, and sulfur-bearing minerals (anhydrite) can provide information on pre- and syn-eruptive degassing. The June 1991 eruption of Mt Pinatubo is an ideal candidate for such a study as it injected a >17 Mt of SO2 into the stratosphere, corresponding to a S excess release of a factor close to 100. The erupted magma was oxidized (QFM+3) and should therefore yield a clear isotopic trend. Volatile contents in glassy but vesicular quartz-hosted MIs were measured by SIMS and yield <3 wt% H2O and <100 ppm S but up to 1500 ppm CO2, in agreement with previous measurements. The MIs with few but large vapor bubbles (avoided during analysis) have lower H2O and CO2 contents and smaller standard deviations. The MIs with many small bubbles have higher volatile contents and standard deviations because the gas phase was not avoided during analysis. We observed scattered S contents and highly variable S isotope compositions for all MIs, which could be due to the presence of submicron S phases. Thus, we homogenized a batch of MIs under P-T-fO2 conditions that best correspond to pre-eruptive conditions. The δ34S for quartz-hosted MIs ranges from -1 to +14 ‰ and δ34S vs. S-H-C content trends are used to infer open or closed system degassing processes. In the near future, anhydrites and melt inclusions in other mineral hosts (amphibole and plagioclase) will be investigated in order to reconstruct the degassing history of the 1991 Pinatubo magma and to trace the S source.

Well-observed dynamics of flaring and peripheral coronal magnetic loops during an M-class limb flare

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Jinhua; Zhou, Tuanhui; Ji, Haisheng

2014-08-20

In this paper, we present a variety of well-observed dynamic behaviors for the flaring and peripheral magnetic loops of the M6.6 class extreme limb flare that occurred on 2011 February 24 (SOL2011-02-24T07:20) from EUV observations by the Atmospheric Imaging Assembly on the Solar Dynamics Observatory and X-ray observations by RHESSI. The flaring loop motion confirms the earlier contraction-expansion picture. We find that the U-shaped trajectory delineated by the X-ray corona source of the flare roughly follows the direction of a filament eruption associated with the flare. Different temperature structures of the coronal source during the contraction and expansion phases stronglymore » suggest different kinds of magnetic reconnection processes. For some peripheral loops, we discover that their dynamics are closely correlated with the filament eruption. During the slow rising to abrupt, fast rising of the filament, overlying peripheral magnetic loops display different responses. Two magnetic loops on the elbow of the active region had a slow descending motion followed by an abrupt successive fast contraction, while magnetic loops on the top of the filament were pushed outward, slowly being inflated for a while and then erupting as a moving front. We show that the filament activation and eruption play a dominant role in determining the dynamics of the overlying peripheral coronal magnetic loops.« less

Composition and origin of basaltic magma of the Hawaiian Islands

USGS Publications Warehouse

Powers, H.A.

1955-01-01

Silica-saturated basaltic magma is the source of the voluminous lava flows, erupted frequently and rapidly in the primitive shield-building stage of activity, that form the bulk of each Hawaiian volcano. This magma may be available in batches that differ slightly in free silica content from batch to batch both at the same and at different volcanoes; differentiation by fractionation of olivine does not occur within this primitive magma. Silica-deficient basaltic magma, enriched in alkali, is the source of commonly porphyritic lava flows erupted less frequently and in relatively negligible volume during a declining and decadent stage of activity at some Hawaiian volcanoes. Differentiation by fractionation of olivine, plagioclase and augite is evident among these lavas, but does not account for the silica deficiency or the alkali enrichment. Most of the data of Hawaiian volcanism and petrology can be explained by a hypothesis that batches of magma are melted from crystalline paridotite by a recurrent process (distortion of the equatorial bulge by forced and free nutational stresses) that accomplishes the melting only of the plagioclase and pyroxene component but not the excess olivine and more refractory components within a zone of fixed and limited depth. Eruption exhausts the supply of meltable magma under a given locality and, in the absence of more violent melting processes, leaves a stratum of crystalline refractory components. ?? 1955.

Integration of video and infrasound to understand source locations and vent geometry at Erebus Volcano, Antarctica

NASA Astrophysics Data System (ADS)

Jones, K. R.; Aster, R. C.; Johnson, J. B.; Kyle, P. R.; McIntosh, W. C.

2007-05-01

Infrasound monitoring at Erebus volcano has enabled us to quantify eruption energetics and precisely determine the source location of Strombolian eruptions. Since January 2006 we have operated a three-element network of identical infrasound pressure transducers, to track explosive eruptions, triangulate source locations of the eruptions, and distinguish activity from several vents with diverse activities. In December 2006 the network was expanded to six identical pressure transducers with improved azimuthal distribution sited ~300 m to 700 m from the erupting vents. These sensors have a dynamic range of +/-125 Pa and are able to record non-distorted waveforms for almost all eruptive events. Since January 2006, eruptions have been identified from locations within the ~40 m diameter phonolitic lava lake, an adjacent smaller "active vent", and a vent ~80 m distant from the lava lake known as "Werner's". Since late 2005 until the end of 2006, activity was considerably elevated at the "lava lake", from which frequent (up to six per day) explosions were noted. These events entailed gas bubble bursts, some of which were capable of ejecting bombs more than 1 km distant and producing infrasonic transients in excess of 100 Pa at a distance of 700 m. Activity from "Werner's" vent was much more subdued in terms of eruptive frequency and the radiated acoustic energy, with all signals less than about 5 Pa at 700 m. Activity from the "active vent" was also observed, though notably, these acoustic transients were extended in duration in terms of time (> 5 s to more than 30 s), which reflects extended duration ash-venting source mechanisms, corroborated by video records. The updated infrasound network has operated through a relative lull in eruptive intensity (November - December 2006 - January 2007). Since January 2007 more frequent and larger explosions from the lava lake have been observed and recorded with infrasound and video. We quantify this recent upsurge in lava lake activity and present speculative mechanisms to account for the variable eruptive behavior of Erebus lava lake.

Pigeonholing pyroclasts: Insights from the 19 March 2008 explosive eruption of Kīlauea volcano

USGS Publications Warehouse

Houghton, Bruce F.; Swanson, D.A.; Carey, R.J.; Rausch, J.; Sutton, A.J.

2011-01-01

We think, conventionally, of volcanic explosive eruptions as being triggered in one of two ways: by release and expansion of volatiles dissolved in the ejected magma (magmatic explosions) or by transfer of heat from magma into an external source of water (phreatic or phreatomagmatic explosions). We document here an event where neither magma nor an external water source was involved in explosive activity at K??lauea. Instead, the eruption was powered by the expansion of decoupled magmatic volatiles released from deeper magma, which was not ejected by the eruption, and the trigger was a collapse of near-surface wall rocks that then momentarily blocked that volatile flux. Mapping of the advected fall deposit a day after this eruption has highlighted the difficulty of constraining deposit edges from unobserved or prehistoric eruptions of all magnitudes. Our results suggest that the dispersal area of advected fall deposits could be miscalculated by up to 30% of the total, raising issues for accurate hazard zoning and assessment. Eruptions of this type challenge existing classification schemes for pyroclastic deposits and explosive eruptions and, in the past, have probably been interpreted as phreatic explosions, where the eruptive mechanism has been assumed to involve flashing of groundwater to steam. ?? 2011 Geological Society of America.

Towards quantifying the arc-scale and global magmatic response to deglaciation

NASA Astrophysics Data System (ADS)

Watt, S. F.; Pyle, D. M.; Mather, T. A.

2012-12-01

There is a growing body of evidence that the retreat of ice sheets after the last glacial maximum resulted in temporarily enhanced levels of volcanism. This has been postulated on the scale of individual edifices, and on regional scales in intraplate and rift settings. It has been proposed that this pattern was of global significance in contributing to rising atmospheric CO2 concentrations, and thereby formed a feedback process for global warming. However, the impact of deglaciation on volcanic arcs has been incompletely explored. Volcanic arcs account for 90% of present-day subaerial volcanic eruptions, and for volcanically-sourced volatiles they are therefore of first-order significance. Without a proper understanding of fluctuations in arc volcanic output, an assessment of global changes in volcanic activity cannot be made. Here, we present the first systematic assessment of the response of glaciated volcanic arcs to deglaciation. By using comprehensive compilations of eruption records from southern Chile, augmented by records from the Cascade and Kamchatka arcs, we show that the post-glacial increase in volcanism was relatively small in comparison to non-arc volcano-tectonic settings. Where ice unloading was at its greatest, eruption frequency approximately doubled for ~5 kyr, but this pattern is at the limit of statistical significance. The same period coincides with a few notably large explosive eruptions. In less heavily glaciated regions, no pattern can be deduced at the resolution of available data. While eruption patterns are commonly episodic, the timing of increases in activity does not always show a clear link to deglaciation. In light of the above, we critically examine available eruption records in an effort to constrain global-scale changes in volcanic output. We show that great caution must be exercised when attempting to quantify variation in volcanism from such data. Due to extremely sparse sampling (i.e. highly incomplete records), both temporal and spatial sampling biases must be corrected. Spatial variation in sampling rates is particularly significant. In some highly active volcanic regions, such as Indonesia, as few as 1 in 20,000 VEI ≥2 eruptions have been identified during the 5-20 ka time period. Globally, >99% of all eruptions of VEI ≥2 have not been identified. Because of this, variations in eruption rate between glaciated and non-glaciated regions cannot be precisely quantified. We attempt to account for such uncertainties, and suggest that, at most, global eruption rates may have doubled after the last glaciation, from 13-7 ka. This suggests that, although volcanism may have been an important source of CO2 in the early Holocene, it cannot have been a dominant control on changes in atmospheric CO2 after the last glacial maximum. To improve our ability to constrain global-scale patterns in magmatic processes, there is a need for improved records of past volcanic activity, particularly from several low-latitude regions, where data are extremely sparse.

Ilchulbong tuff cone, Jeju Island, Korea, revisited: A compound monogenetic volcano involving multiple magma batches, shifting vents, and discrete eruptive phases

NASA Astrophysics Data System (ADS)

Sohn, Y.; Brenna, M.; Smith, I. E.; Nemeth, K.; White, J. D.; Murtagh, R.; Jeon, Y.; Kwon, C.; Cronin, S. J.

2010-12-01

Ilchulbong (Sunrise Peak) tuff cone is a UNESCO World Heritage site that owes its scientific importance to the outstanding coastal exposures that surround it. It is also one of the classic sites that provided the sedimentary evidence for the primary pyroclastic processes that occur during phreatomagmatic basaltic eruptions. It has been long considered, based on the cone morphology, that this classic cone was produced via eruption from a single vent site. Reanalysis of the detailed sedimentary sequence has now revealed that two subtle paraconformities occur in this deposition sequence, one representing a significant time break of perhaps days to weeks or months, during which erosion and compaction of the lower cone occurred, the conduit cooled and solidified and a subsequent resumption of eruption took place in a new vent location. Detailed geochemical study of the juvenile clasts through this cone reveals that three separate alkali basaltic magma batches were erupted, the first and third erupted may be genetically related, with the latter showing evidence for longer periods of shallow-level fractionation. The second magma batch erupted was generated in a different mantle source area. Reconstructing the eruption sequence, the lower Ilchulbong cone was formed by eruption of magma 1. Cessation of eruption was accompanied by erosion to generate a volcano-wide unconformity, associated with reworked deposits in the lower cone flanks. The eruption resumed with magma 2 that, due to the cooled earlier conduit, was forced to erupt in a new site to the west of the initial vent. This formed the middle cone sequence over the initially formed structure. The third magma batch erupted with little or no interval after magma 2 from the same vent location, associated with cone instability and slumping, and making up the deposits of the upper cone. These results demonstrate how critical the examination for sedimentary evidence for time breaks in such eruption sequences is for detecting potential shifts in eruption chemistry and vent location. It appears that if eruption breaks are short, successive magma batches follow the same path, whereas if pauses are greater than a critical period, conduit solidification will force vent migration for subsequent magma batches. This has important implications for examining the controls of vent migration at other monogenetic volcanoes and for emergency management planning during future similar types of eruptions.

Magma supply dynamics at Westdahl volcano, Alaska, modeled from satellite radar interferometry

USGS Publications Warehouse

Lu, Z.; Masterlark, Timothy; Dzurisin, D.; Rykhus, Russ; Wicks, C.

2003-01-01

A group of satellite radar interferograms that span the time period from 1991 to 2000 shows that Westdahl volcano, Alaska, deflated during its 1991-1992 eruption and is reinflating at a rate that could produce another eruption within the next several years. The rates of inflation and deflation are approximated by exponential decay functions having time constants of about 6 years and a few days, respectively. This behavior is consistent with a deep, constant-pressure magma source connected to a shallow reservoir by a magma-filled conduit. An elastic deformation model indicates that the reservoir is located about 6 km below sea level and beneath Westdahl Peak. We propose that the magma flow rate through the conduit is governed by the pressure gradient between the deep source and the reservoir. The pressure gradient, and hence the flow rate, are greatest immediately after eruptions. Pressurization of the reservoir decreases both the pressure gradient and the flow rate, but eventually the reservoir ruptures and an eruption or intrusion ensues. The eruption rate is controlled partly by the pressure gradient between the reservoir and surface, and therefore it, too, decreases with time. When the supply of eruptible magma is exhausted, the eruption stops, the reservoir begins to repressurize at a high rate, and the cycle repeats. This model might also be appropriate for other frequently active volcanoes with stable magma sources and relatively simple magma storage systems.

Sustained long-period seismicity at Shishaldin Volcano, Alaska

USGS Publications Warehouse

Petersen, Tanja; Caplan-Auerbach, Jacqueline; McNutt, Stephen R.

2006-01-01

From September 1999 through April 2004, Shishaldin Volcano, Aleutian Islands, Alaska, exhibited a continuous and extremely high level of background seismicity. This activity consisted of many hundreds to thousands of long-period (LP; 1–2 Hz) earthquakes per day, recorded by a 6-station monitoring network around Shishaldin. The LP events originate beneath the summit at shallow depths (0–3 km). Volcano tectonic events and tremor have rarely been observed in the summit region. Such a high rate of LP events with no eruption suggests that a steady state process has been occurring ever since Shishaldin last erupted in April–May 1999. Following the eruption, the only other signs of volcanic unrest have been occasional weak thermal anomalies and an omnipresent puffing volcanic plume. The LP waveforms are nearly identical for time spans of days to months, but vary over longer time scales. The observations imply that the spatially close source processes are repeating, stable and non-destructive. Event sizes vary, but the rate of occurrence remains roughly constant. The events range from magnitude ∼0.1 to 1.8, with most events having magnitudes <1.0. The observations suggest that the conduit system is open and capable of releasing a large amount of energy, approximately equivalent to at least one magnitude 1.8–2.6 earthquake per day. The rate of observed puffs (1 per minute) in the steam plume is similar to the typical seismic rates, suggesting that the LP events are directly related to degassing processes. However, the source mechanism, capable of producing one LP event about every 0.5–5 min, is still poorly understood. Shishaldin's seismicity is unusual in its sustained high rate of LP events without accompanying eruptive activity. Every indication is that the high rate of seismicity will continue without reflecting a hazardous state. Sealing of the conduit and/or change in gas flux, however, would be expected to change Shishaldin's behavior.

Volcanic Forcing of Global Warming during the Pleistocene?

NASA Astrophysics Data System (ADS)

Ericson, J. E.

2002-12-01

The volcanic forcing hypothesis is a new model of global climatic change that may have significance for the history of the Earth and palaeoclimate. The rapid injection of CO2 into the atmosphere during volcanic eruption through underlying massive carbonate appears to trigger global warming through the emission of this greenhouse gas. The record of eruptions (10-20 Kya) of 6 volcanoes overlying 900-10,000 meters of carbonate of the Cordillerian geosyncline in the American Southwest is synchronous with the Late Pleistocene marine transgression record. The record of volcanic eruptions through massive carbonates (20-71 Kya) in Italy, Indonesia and the American Southwest appears to be synchronous with the Wisconsin interstadial events. The extension of the volcanic eruption and climatic records to 71 Kya and inclusion of other volcanic regions represents additional supporting of evidence of the volcanic forcing hypothesis. As an example of these processes, the thermal dissociation of carbonate by magma forming a volcanic conduit (0.4 km high, 0.5 km radius) and subsequent release of carbon dioxide would increase the atmospheric carbon dioxide by 25%. The emitted CO2 would trigger a series of other processes, ocean-atmospheric CO2 exchange, increased photosynthesis and changes with terrestrial biome and global warming. [Recent field reconnaissance of Sunset Crater (erupted 1064-65 AD) indicates the evidence for thermal dissolution of limestone during basaltic extrusion.] Carbon dioxide emitted from volcanic-carbonate sources meets several observed conditions: a rapid increase (<20 years) in atmospheric carbon dioxide, abrupt increases of marine (isotopic) carbon, dilution of atmospheric radiocarbon activity independent of fluctuations of the geomagnetic field and cosmic ray fluxes, temporal covariation of sulfate, Ca+2, and CO2 in ice core records and random, interstadial events during glaciation. Volcanic forcing hypothesis represents a new model and synthesis of natural processes involving recycling of marine carbonate through volcanic eruption leading to global warming.

Explosive eruption records from Eastern Africa: filling in the gaps with tephra records from stratified lake sequences

NASA Astrophysics Data System (ADS)

Lane, Christine; Asrat, Asfawossen; Cohen, Andy; Cullen, Victoria; Johnson, Thomas; Lamb, Henry; Martin-Jones, Catherine; Poppe, Sam; Schaebitz, Frank; Scholz, Christopher

2017-04-01

On-going research into the preservation of volcanic ash fall in stratified Holocene lake sediments in Eastern Africa reveals the level of incompleteness of our explosive eruption record. Only nine eruptions with VEI >4 are recorded in the LaMEVE database (Crosweller et al., 2012) and of the 188 Holocene eruptions listed for East African volcanoes in the Global Volcanism Programme database, only 24 are dated to > 2000 years ago (GVP, 2013). Tephrostratigraphic investigation of Holocene sediments from a number of lakes, including Lake Kivu (south of the Virunga volcanic field), Lake Victoria (west of the Kenyan Rift volcanism) and palaeolake Chew Bahir (southern Ethiopia), all reveal multiple tephra layers, which indicate vastly underestimated eruption histories. Whereas the tephra layers in Lake Kivu were all located macroscopically, no visible tephra layers were observed in the sediments from Lake Victoria and Chew Bahir. Instead, tephra are preserved as non-visible horizons (cryptotephra), revealed only after laboratory processing. These results indicate that even where we do have stratified visible tephra records, the number of past eruptions may still be a minimum. Cryptotephra studies therefore play a fundamental role in building comprehensive records of past volcanism. Challenges remain, in this understudied region, to identify the volcanic source of each of the tephra layers, which requires geochemical correlation to proximal volcanic deposits. Where correlations to source can be achieved, explosive eruption frequencies and recurrence rates may be assessed for individual volcanoes. Furthermore, if a tephra layer can be traced into multiple sedimentary sequences, the potential exists to evaluate eruption magnitude, providing a more useful criterion for risk assessment. Filling in the gaps in our understanding of East African Rift volcanism and the associated hazards is therefore critically dependent upon bringing together this important data from distal tephrostratigraphic records with the work of volcanologists studying more proximal deposits, and hazard modellers. Crosweller et al (2012) "Global database on large magnitude explosive volcanic eruptions (LaMEVE)" Journal of Applied Volcanology 1:4, doi:10.1186/2191-5040-1-4 Global Volcanism Program, 2013. Volcanoes of the World, v. 4.5.3. Venzke, E (ed.). Smithsonian Institution. Downloaded 06 Jan 2017. http://dx.doi.org/10.5479/si.GVP.VOTW4-2013

Transient deformation associated with explosive eruption measured at Masaya volcano (Nicaragua) using Interferometric Synthetic Aperture Radar

NASA Astrophysics Data System (ADS)

Stephens, K. J.; Ebmeier, S. K.; Young, N. K.; Biggs, J.

2017-09-01

Deformation caused by processes within a volcanic conduit are localised, transient, and therefore challenging to measure. However, observations of such deformation are important because they provide insight into conditions preceding explosive activity, and are important for hazard assessment. Here, we present measurements of low magnitude, transient deformation covering an area of ∼4 km2 at Masaya volcano spanning a period of explosive eruptions (30th April-17th May 2012). Radial uplift of duration 24 days and peak displacements of a few millimeters occurred in the month before the eruption, but switched to subsidence ∼27 days before the onset of the explosive eruption on 30th of April. Uplift resumed during, and continued for ∼16 days after the end of the explosive eruption period. We use a finite element modelling approach to investigate a range of possible source geometries for this deformation, and find that the changes in pressurisation of a conduit 450 m below the surface vent (radius 160 m and length 700 m), surrounded by a halo of brecciated material with a Young's modulus of 15 GPa, gave a good fit to the InSAR displacements. We propose that the pre-eruptive deformation sequence at Masaya is likely to have been caused by the movement of magma through a constriction within the shallow conduit system. Although measuring displacements associated with conduit processes remains challenging, new high resolution InSAR datasets will increasingly allow the measurement of transient and lower magnitude deformation signals, improving the method's applicability for observing transitions between volcanic activity characterised by an open and a closed conduit system.

Deformation associated with the 1997 eruption of Okmok volcano, Alaska

USGS Publications Warehouse

Mann, Dorte; Freymueller, Jeffrey T.; Lu, Z.

2002-01-01

Okmok volcano, located on Umnak Island in the Aleutian chain, Alaska, is the most eruptive caldera system in North America in historic time. Its most recent eruption occurred in 1997. Synthetic aperture radar interferometry shows deflation of the caldera center of up to 140 cm during this time, preceded and followed by inflation of smaller magnitude. The main part of the observed deformation can be modeled using a pressure point source model. The inferred source is located between 2.5 and 5.0 km beneath the approximate center of the caldera and ???5 km from the eruptive vent. We interpret it as a central magma reservoir. The preeruptive period features inflation accompanied by shallow localized subsidence between the caldera center and the vent. We hypothesize that this is caused by hydrothermal activity or that magma moved away from the central chamber and toward the later vent. Since all historic eruptions at Okmok have originated from the same cone, this feature may be a precursor that indicates an upcoming eruption. The erupted magma volume is ???9 times the volume that can be accounted for by the observed preeruptive inflation. This indicates a much longer inflation interval than we were able to observe. The observation that reinflation started shortly after the eruption suggests that inflation spans the whole time interval between eruptions. Extrapolation of the average subsurface volume change rate is in good agreement with the long-term eruption frequency and eruption volumes of Okmok.

Source of the great A.D. 1257 mystery eruption unveiled, Samalas volcano, Rinjani Volcanic Complex, Indonesia

PubMed Central

Lavigne, Franck; Degeai, Jean-Philippe; Komorowski, Jean-Christophe; Guillet, Sébastien; Robert, Vincent; Lahitte, Pierre; Oppenheimer, Clive; Stoffel, Markus; Vidal, Céline M.; Surono; Pratomo, Indyo; Wassmer, Patrick; Hajdas, Irka; Hadmoko, Danang Sri; de Belizal, Edouard

2013-01-01

Polar ice core records attest to a colossal volcanic eruption that took place ca. A.D. 1257 or 1258, most probably in the tropics. Estimates based on sulfate deposition in these records suggest that it yielded the largest volcanic sulfur release to the stratosphere of the past 7,000 y. Tree rings, medieval chronicles, and computational models corroborate the expected worldwide atmospheric and climatic effects of this eruption. However, until now there has been no convincing candidate for the mid-13th century “mystery eruption.” Drawing upon compelling evidence from stratigraphic and geomorphic data, physical volcanology, radiocarbon dating, tephra geochemistry, and chronicles, we argue the source of this long-sought eruption is the Samalas volcano, adjacent to Mount Rinjani on Lombok Island, Indonesia. At least 40 km3 (dense-rock equivalent) of tephra were deposited and the eruption column reached an altitude of up to 43 km. Three principal pumice fallout deposits mantle the region and thick pyroclastic flow deposits are found at the coast, 25 km from source. With an estimated magnitude of 7, this event ranks among the largest Holocene explosive eruptions. Radiocarbon dates on charcoal are consistent with a mid-13th century eruption. In addition, glass geochemistry of the associated pumice deposits matches that of shards found in both Arctic and Antarctic ice cores, providing compelling evidence to link the prominent A.D. 1258/1259 ice core sulfate spike to Samalas. We further constrain the timing of the mystery eruption based on tephra dispersal and historical records, suggesting it occurred between May and October A.D. 1257. PMID:24082132

The relevance of the 1198 eruption of Solfatara in the Phlegraean Fields (Campi Flegrei) as revealed by medieval manuscripts and historical sources

NASA Astrophysics Data System (ADS)

Scandone, R.; D'Amato, J.; Giacomelli, L.

2010-01-01

The Phlegraean Fields (Campi Flegrei) caldera in Italy had one well-documented eruption during the historical period (1538). Another eruption at Solfatara in 1198 is reported by sixteenth and seventeenth-century scholars, and has been commonly regarded as uncertain. In this paper we first discuss the circumstantial evidence and report of this eruption, then discuss the relevance of drawings made in the thirteenth through the fifteenth century illustrating the Solfatara and the primary literary and historical sources describing the site. We infer that the eruption was at most a minor phreatic explosion and we explore the conditions that may have led to the occurrence of this event and the establishment of a small crater pool subsequently used as a thermal bath from the later Middle Ages onward.

Fluid and Melt Inclusions as a tool to understand two high risk volcanic systems: Vesuvius and Campi Flegrei

NASA Astrophysics Data System (ADS)

De Vivo, B.

2017-12-01

In the Campania region (Southern Italy) major active volcanic systems occur in the greater metropolitan area of Naples: Mt. Somma-Vesuvius (SV) and the Campi Flegrei (CF). These volcanic systems have been studied for centuries, yet significant differences of opinions exist about their origins and behaviors. Here, I present some alternative views on issues based on more than 25 years of research, focusing the attention on role played by fluids and magmas based on fluid inclusions (FI) and melt inclusions (MI). In particular, FI and MI data from the Neapolitan volcanoes provide valuable information on the nature of fluid and melt phases trapped during the late evolutionary stages of the alkaline magmatic rocks; such data from past eruptions might be applied to predict the imminence of volcanic eruptions and help protect the population from such hazards. In my and my collaborator studies, FI and MI data have been also used to address the problem of bradyseism in the CF. Using FI and MI, to explain the bradyseism phenomena at CF, my collaborators and I described a new model that involves only hydrothermal fluids of magmatic or meteoric/marine origin with no direct involvement of the magma, other than as a heat source to explain the ground deformation. My collaborators and I explain the bradyseism as a purely hydrothermal model, using processes in porphyry systems as an analogue to those of the CF. SV activity is characterized by cyclic events, and in terms of volcanic risk assessment, a crucial aspect to understand is when a potential next explosive eruption might occur. Evaluating volcanic hazards requires knowledge of the processes that trigger eruptions and the nature and timing of geophysical/geochemical signals related to these processes. One approach to addressing this need is to link observable signals to pre-eruptive magmatic events deduced from studies of erupted magmas. I believe that a way to work in this direction is to determine the residence time, through MI diffusion profiles, of crystals in the magma chamber before an explosive event. I think that working on the crystals residence time of the many plinian eruptions we know to have occurred in SV history, could help us to understand better the relationships between tectonic, regional, event and explosive eruptions.

Hydrogeomorphic responses to explosive volcanic eruptions-what have we learned?

NASA Astrophysics Data System (ADS)

Major, J. J.

2011-12-01

Explosive eruptions can greatly alter landscape hydrology and geomorphology. Analyses of hydrogeomorphic responses to four major eruptions, spanning two orders of magnitude in eruption volume, reveal patterns in the timing, pace, and style of landscape response to explosive eruptions. Tephra fall can blanket broad swaths of landscape with sediment having a low-permeability surface, and can cause significant tree damage. Volcanic blasts can also deposit many tens of cm of fines-capped sediment across the landscape, and can raze or completely remove vast tracts of forest. Debris avalanches, pyroclastic flows, and lahars can fill channels and valley floors with meters to tens of meters of gravelly sand for tens of kilometers from source; straighten, smooth or obliterate channel planforms; and remove, bury, or smother riparian vegetation. Such disturbances can radically alter runoff regimes and the manner in which water is routed along channels. Surface-infiltration capacities of landscapes denuded by volcanic blast and pyroclastic flows following eruptions of Mount St. Helens (MSH) and Unzen were reduced 1-2 orders of magnitude (from >100 mm/hr to as little as 2-5 mm/hr). Altered hydrologic processes promoted substantial overland flow in basins normally dominated by subsurface flow; measurements at Unzen showed overland flow 3-5 times greater from barren, tephra-covered ground compared to vegetated ground. Hydrological analysis at MSH showed that post-eruption wet-season peakflow discharges increased by a few to tens of percent in eruption-affected basins. Changes in hydrological processes alter sediment erosion and transport; extensive hillslope and channel erosion can lead to sediment yields that exceed preeruption yields by orders of magnitude. Indeed, sediment yields from volcanically disturbed watersheds rival those of great sediment-producing rivers worldwide. Short-term landscape-denudation rates following explosive eruptions are typically 10-104 times greater than estimated long-term denudation rates, reflecting great mobility of highly erodible sediment delivered by eruptions. Despite sometimes cataclysmic eruption-induced disturbance, landscapes are resilient. Owing to erosional, biogenic, and cryogenic modifications of tephra surfaces, eruption-induced changes in runoff and river discharge commonly relax substantially within a decade. Elevated sediment transport, however, can persist for decades. Observations following eruption of MSH show that magnitude and duration of enhanced sediment transport varied chiefly with the nature of disturbance-high yields from basins bearing significant channel disturbance persist far longer than those from basins bearing only hillslope disturbance. Observations from MSH and Mount Pinatubo show that excessive sediment yields from severely disturbed landscapes decay considerably within a decade of eruption, but appear to plateau at levels that can exceed preeruption yields by tens of percent for at least a few decades. Studies at Mount Hood show that distal aggraded channels can take up to a century to return to preeruption base level. Prolonged excessive sediment transport following eruptions can cause environmental and socioeconomic harm that equals or exceeds that caused directly by eruptions.

Zircon oxygen isotopes reveal Ivrea-Verbano Zone source characteristics of the Sesia Valley Caldera

NASA Astrophysics Data System (ADS)

Economos, R. C.; Quick, J. E.; Sinigoi, S.; de Silva, S. L.

2013-12-01

The Sesia Valley, in the Italian Alpine foothills, contains >14 km diameter caldera adjacent to and structurally shallower than the famous Ivrea-Verbano Zone deep crustal section. The caldera and its associated eruptive sequence presents opportunity to explore volcanic magmatism in light of exposed and well characterized source candidates, namely lower crustal gabbros and the mid-crustal metasedimentary Kinzigite formation. Original geochemical characteristics of volcanic units have been obscured by the effects of subsequent hydrothermal alteration. The resistance of the mineral zircon to fluid alteration makes it a prime candidate for the preservation and exploration of these geochemical signals, such as O isotopes. Lower crustal gabbros in the Ivrea-Verbano Zone have broadly monotonic whole-rock δ18O values between +8 and +9‰VSMOW (Sinigoi et al., 1994). Kinzigites preserve a much higher and more heterogeneous δ18O values, typically ranging from +10‰ up to +15‰ (Baker, 1990). Zircons from the caldera-forming rhyolitic eruption units and a pre-caldera rhyodacitic unit were analyzed by ion microprobe at UCLA for in-situ oxygen isotope ratios. External reproducibility of within-mount standard R33 grains range from 0.27 to 0.36‰. Rhyolites from the caldera-forming eruption yield a range of δ18O(zircon) values from 6.3‰ to 8.3‰. This range displays rough correlation with CL activity - CL active grains have lower δ18O(zircon) values while CL dark grains have higher δ18O(zircon) values. This variation may correlate with U contents, which are notoriously low in zircons from Ivrea-Verbano Zone gabbros. We argue that the range in O isotope values suggests zircons are a good fit for magmas influenced by gabbro and Kinzigite sources. However, these zircons do not appear to be inherited directly from either the gabbro or Kinzigite sources as their O isotope signatures are typically intermediate between the two. The pre-caldera rhyodacite sample displays a much broader range of δ18O(zircon) values, from +6 to +10‰. These values, when corrected for melt-zircon isotopic fractionation, are an excellent match for mafic and felsic sources in the Ivrea-Verbano Zone. Thus, volcanic rocks of the Sesia Valley share spatial, temporal, and geochemical affinities for Ivrea-Verbano Zone sources, strengthening the body of evidence that the Sesia Valley Caldera represents the upper crustal portions of a complete crustal section contiguous with these mid- and lower-crustal Alpine exposures. These data demonstrate a difference in extent of hybridization of source signals in the rhyodacite (little homogenization) compared to the caldera-forming eruption (more homogenization). This suggests a record of variation in magmatic processes for precursor and climactic eruptions that is potentially related to the thermal maturation of the volcanic system and warrants additional study. Additional work on trace element concentrations, including Ti thermometry, on these grains will further elucidate these processes and their relationship to known zircon-bearing sources in the mid- to deep-crust of the Ivrea-Verbano Zone.

Ash-plume dynamics and eruption source parameters by infrasound and thermal imagery: The 2010 Eyjafjallajökull eruption

NASA Astrophysics Data System (ADS)

Ripepe, M.; Bonadonna, C.; Folch, A.; Delle Donne, D.; Lacanna, G.; Marchetti, E.; Höskuldsson, A.

2013-03-01

During operational ash-cloud forecasting, prediction of ash concentration and total erupted mass directly depends on the determination of mass eruption rate (MER), which is typically inferred from plume height. Uncertainties for plume heights are large, especially for bent-over plumes in which the ascent dynamics are strongly affected by the surrounding wind field. Here we show how uncertainties can be reduced if MER is derived directly from geophysical observations of source dynamics. The combination of infrasound measurements and thermal camera imagery allows for the infrasonic type of source to be constrained (a dipole in this case) and for the plume exit velocity to be calculated (54-142 m/s) based on the acoustic signal recorded during the 2010 Eyjafjallajökull eruption from 4 to 21 May. Exit velocities are converted into MER using additional information on vent diameter (50±10 m) and mixture density (5.4±1.1 kg/m3), resulting in an average ∼9×105 kg/s MER during the considered period of the eruption. We validate our acoustic-derived MER by using independent measurements of plume heights (Icelandic Meteorological Office radar observations). Acoustically derived MER are converted into plume heights using field-based relationships and a 1D radially averaged buoyant plume theory model using a reconstructed total grain size distribution. We conclude that the use of infrasonic monitoring may lead to important understanding of the plume dynamics and allows for real-time determination of eruption source parameters. This could improve substantially the forecasting of volcano-related hazards, with important implications for civil aviation safety.

MeMoVolc report on classification and dynamics of volcanic explosive eruptions

NASA Astrophysics Data System (ADS)

Bonadonna, C.; Cioni, R.; Costa, A.; Druitt, T.; Phillips, J.; Pioli, L.; Andronico, D.; Harris, A.; Scollo, S.; Bachmann, O.; Bagheri, G.; Biass, S.; Brogi, F.; Cashman, K.; Dominguez, L.; Dürig, T.; Galland, O.; Giordano, G.; Gudmundsson, M.; Hort, M.; Höskuldsson, A.; Houghton, B.; Komorowski, J. C.; Küppers, U.; Lacanna, G.; Le Pennec, J. L.; Macedonio, G.; Manga, M.; Manzella, I.; Vitturi, M. de'Michieli; Neri, A.; Pistolesi, M.; Polacci, M.; Ripepe, M.; Rossi, E.; Scheu, B.; Sulpizio, R.; Tripoli, B.; Valade, S.; Valentine, G.; Vidal, C.; Wallenstein, N.

2016-11-01

Classifications of volcanic eruptions were first introduced in the early twentieth century mostly based on qualitative observations of eruptive activity, and over time, they have gradually been developed to incorporate more quantitative descriptions of the eruptive products from both deposits and observations of active volcanoes. Progress in physical volcanology, and increased capability in monitoring, measuring and modelling of explosive eruptions, has highlighted shortcomings in the way we classify eruptions and triggered a debate around the need for eruption classification and the advantages and disadvantages of existing classification schemes. Here, we (i) review and assess existing classification schemes, focussing on subaerial eruptions; (ii) summarize the fundamental processes that drive and parameters that characterize explosive volcanism; (iii) identify and prioritize the main research that will improve the understanding, characterization and classification of volcanic eruptions and (iv) provide a roadmap for producing a rational and comprehensive classification scheme. In particular, classification schemes need to be objective-driven and simple enough to permit scientific exchange and promote transfer of knowledge beyond the scientific community. Schemes should be comprehensive and encompass a variety of products, eruptive styles and processes, including for example, lava flows, pyroclastic density currents, gas emissions and cinder cone or caldera formation. Open questions, processes and parameters that need to be addressed and better characterized in order to develop more comprehensive classification schemes and to advance our understanding of volcanic eruptions include conduit processes and dynamics, abrupt transitions in eruption regime, unsteadiness, eruption energy and energy balance.

Gas Eruptions Taper Off in Northwestern Oklahoma.

ERIC Educational Resources Information Center

Preston, Don

1980-01-01

Describes the eruption of inflammable natural gas from the ground surface in the Edith area near Camp Houston. Determining the source of the gas, the results established the Chester-Oswago interval as the most likely source. The surface venting has declined steadily; the likelihood of finding its cause is also described. (SK)

Mechanical coupling between earthquakes and volcanoes inferred from stress transfer models: evidence from Vesuvio, Etna and Alban Hills (Italy)

NASA Astrophysics Data System (ADS)

Cocco, M.; Feuillet, N.; Nostro, C.; Musumeci, C.

2003-04-01

We investigate the mechanical interactions between tectonic faults and volcanic sources through elastic stress transfer and discuss the results of several applications to Italian active volcanoes. We first present the stress modeling results that point out a two-way coupling between Vesuvius eruptions and historical earthquakes in Southern Apennines, which allow us to provide a physical interpretation of their statistical correlation. Therefore, we explore the elastic stress interaction between historical eruptions at the Etna volcano and the largest earthquakes in Eastern Sicily and Calabria. We show that the large 1693 seismic event caused an increase of compressive stress along the rift zone, which can be associated to the lack of flank eruptions of the Etna volcano for about 70 years after the earthquake. Moreover, the largest Etna eruptions preceded by few decades the large 1693 seismic event. Our modeling results clearly suggest that all these catastrophic events are tectonically coupled. We also investigate the effect of elastic stress perturbations on the instrumental seismicity caused by magma inflation at depth both at the Etna and at the Alban Hills volcanoes. In particular, we model the seismicity pattern at the Alban Hills volcano (central Italy) during a seismic swarm occurred in 1989-90 and we interpret it in terms of Coulomb stress changes caused by magmatic processes in an extensional tectonic stress field. We verify that the earthquakes occur in areas of Coulomb stress increase and that their faulting mechanisms are consistent with the stress perturbation induced by the volcanic source. Our results suggest a link between faults and volcanic sources, which we interpret as a tectonic coupling explaining the seismicity in a large area surrounding the volcanoes.

LARGE-SCALE CONTRACTION AND SUBSEQUENT DISRUPTION OF CORONAL LOOPS DURING VARIOUS PHASES OF THE M6.2 FLARE ASSOCIATED WITH THE CONFINED FLUX ROPE ERUPTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kushwaha, Upendra; Joshi, Bhuwan; Moon, Yong-Jae

We investigate evolutionary phases of an M6.2 flare and the associated confined eruption of a prominence. The pre-flare phase exhibits spectacular large-scale contraction of overlying extreme ultraviolet (EUV) coronal loops during which the loop system was subjected to an altitude decrease of ∼20 Mm (40% of the initial height) for an extended span of ∼30 minutes. This contraction phase is accompanied by sequential EUV brightenings associated with hard X-ray (HXR; up to 25 keV) and microwave (MW) sources from low-lying loops in the core region which together with X-ray spectra indicate strong localized heating in the source region before themore » filament activation. With the onset of the flare’s impulsive phase, we detect HXR and MW sources that exhibit intricate temporal and spatial evolution in relation to the fast rise of the prominence. Following the flare maximum, the filament eruption slowed down and subsequently became confined within the large overlying active region loops. During the confinement process of the erupting prominence, we detect MW emission from the extended coronal region with multiple emission centroids, which likely represent emission from hot blobs of plasma formed after the collapse of the expanding flux rope and entailing prominence material. RHESSI spectroscopy reveals high plasma temperature (∼30 MK) and substantial non-thermal characteristics (δ ∼ 5) during the impulsive phase of the flare. The time evolution of thermal energy exhibits a good correspondence with the variations in cumulative non-thermal energy, which suggests that the energy of accelerated particles is efficiently converted to hot flare plasma, implying an effective validation of the Neupert effect.« less

Multi-criteria correlation of tephra deposits to source centres applied in the Auckland Volcanic Field, New Zealand

NASA Astrophysics Data System (ADS)

Hopkins, Jenni L.; Wilson, Colin J. N.; Millet, Marc-Alban; Leonard, Graham S.; Timm, Christian; McGee, Lucy E.; Smith, Ian E. M.; Smith, Euan G. C.

2017-07-01

Linking tephras back to their source centre(s) in volcanic fields is crucial not only to reconstruct the eruptive history of the volcanic field but also to understand tephra dispersal patterns and thus the potential hazards posed by a future eruption. Here we present a multi-disciplinary approach to correlate distal basaltic tephra deposits from the Auckland Volcanic Field (AVF) to their source centres using proximal whole-rock geochemical signatures. In order to achieve these correlations, major and trace element tephra-derived glass compositions are compared with published and newly obtained whole-rock geochemical data for the entire field. The results show that incompatible trace element ratios (e.g. (Gd/Yb)N, (La/Yb)N, (Zr/Yb)N) vary widely across the AVF (e.g. (La/Yb)N = 5 to 40) but show a more restricted range within samples from a single volcanic centre (e.g. (La/Yb)N = 5 to 10). These ratios are also the least affected by fractional crystallisation and are therefore the most appropriate geochemical tools for correlation between tephra and whole-rock samples. However, findings for the AVF suggest that each volcanic centre does not have a unique geochemical signature in the field as a whole, thus preventing unambiguous correlation of tephras to source centre using geochemistry alone. A number of additional criteria are therefore combined to further constrain the source centres of the distal tephras including age, eruption scale, and location (of centres, and sites where tephra were sampled). The combination of tephrostratigraphy, 40Ar/39Ar dating and morphostratigraphic constraints allow, for the first time, the relative and absolute ordering of 48 of 53 volcanic centres of the Auckland Volcanic Field to be resolved. Eruption frequencies are shown to vary between 0.13 and 1.5 eruptions/kyr and repose periods between individual eruptions vary from <0.1 to 13 kyr, with 23 of the 48 centres shown to have pre-eruptive repose periods of <1000 years. No spatial evolutionary trends are noted, although a relationship between short repose periods and closely spaced eruption locations is identified for a number of centres. In addition, no temporal-geochemical trends are noted, but a relationship between geochemical signature and eruption volume is highlighted.

Vent Processes and Deposits of a Hiatus in a Violent Eruption: Quilotoa Volcano, Ecuador

NASA Astrophysics Data System (ADS)

Best, J. A.; Bustillos, J.; Ort, M. H.; Cashman, K. V.; Mothes, P. A.; di Muro, A.; Rosi, M.

2009-12-01

The 800 BP eruption of Quilotoa volcano, Ecuador, produced two plinian eruptions separated by a short (days-weeks) hiatus. We examine the tephra produced both during this hiatus and erupted at the onset of the second Plinian eruption. Units 1 and 3 (U1 and U3) of the eruption correspond to the first and second Plinian eruptions, respectively, and produced fallout and pyroclastic density currents. Unit 2 (U2) records processes during the hiatus and consists of two subunits: U2a, a vitric ashfall, and U2b, a crystal and lithic-rich fallout. 130 individual tephra samples of U1, U2, and U3 were collected from 24 sites along three radial transects from the volcano in January 2009. Thickness and grain-size features were described, with particular attention paid to U2. Grain-size and componentry analysis of a subset of these samples reveals a number of trends. The upper part of U1 is massive and normally graded at its top. This part of U1 is dominantly vitric ash smaller than 3.0 φ and likely represents the clearing of the air at the end of the first plinian eruption. U2a has a polymodal distribution with a large fraction of 4.0 φ and finer vitric material. Dune forms occur in this unit, which is interpreted to be the product of surges. U2b is coarser overall with alternating fine- (2-3φ) and coarse- (1-2φ) grained layers. The beds have a unimodal grain-size distribution and normal grading. U2b is interpreted as a fall deposit. The U2a/U2b contact is gradational in that 0-2 beds of U2b material occur within the uppermost U2a beds, indicating vent conditions for both briefly coexisted. U2c is a <2-cm-thick vitric ash with sparse crystal-rich lava lapilli. These lapilli also occur in the overlying basal U3 fallout, which has a polymodal grain-size distribution. Some U2b pumice fragments and crystals are stained orange, which gives U2b its characteristic color. Stained grains are also present but rare in other units and may have been sourced from the conduit walls. The high proportion of stained fragments in U2b requires a different, possibly hydrothermal, source. We interpret the lava lapilli of U2c and U3 as being from a single explosion, perhaps the opening of a new vent, and thus they indicate that the eruption was continuous from U2b through U3. Our current hypothesis is that, as the U1 eruption ended, acidic gas streamed through the material clogging the vent. This elutriated vitric material that eventually formed a cap on the system. As the U3 magma began its ascent, gas flux increased, leading to explosions that gradually removed the vitric cap and depositing the vitric U2a. Then, more continuous gas streaming led to the development of an pulsatory eruption column that carried the hot stained crystals and lithic fragments into a convecting column and eventual deposition as fallout of U2b, which was then followed by the establishment of the U3 eruption column.

Intrusion triggering of the 2010 Eyjafjallajökull explosive eruption.

PubMed

Sigmundsson, Freysteinn; Hreinsdóttir, Sigrún; Hooper, Andrew; Arnadóttir, Thóra; Pedersen, Rikke; Roberts, Matthew J; Oskarsson, Níels; Auriac, Amandine; Decriem, Judicael; Einarsson, Páll; Geirsson, Halldór; Hensch, Martin; Ofeigsson, Benedikt G; Sturkell, Erik; Sveinbjörnsson, Hjörleifur; Feigl, Kurt L

2010-11-18

Gradual inflation of magma chambers often precedes eruptions at highly active volcanoes. During such eruptions, rapid deflation occurs as magma flows out and pressure is reduced. Less is known about the deformation style at moderately active volcanoes, such as Eyjafjallajökull, Iceland, where an explosive summit eruption of trachyandesite beginning on 14 April 2010 caused exceptional disruption to air traffic, closing airspace over much of Europe for days. This eruption was preceded by an effusive flank eruption of basalt from 20 March to 12 April 2010. The 2010 eruptions are the culmination of 18 years of intermittent volcanic unrest. Here we show that deformation associated with the eruptions was unusual because it did not relate to pressure changes within a single magma chamber. Deformation was rapid before the first eruption (>5 mm per day after 4 March), but negligible during it. Lack of distinct co-eruptive deflation indicates that the net volume of magma drained from shallow depth during this eruption was small; rather, magma flowed from considerable depth. Before the eruption, a ∼0.05 km(3) magmatic intrusion grew over a period of three months, in a temporally and spatially complex manner, as revealed by GPS (Global Positioning System) geodetic measurements and interferometric analysis of satellite radar images. The second eruption occurred within the ice-capped caldera of the volcano, with explosivity amplified by magma-ice interaction. Gradual contraction of a source, distinct from the pre-eruptive inflation sources, is evident from geodetic data. Eyjafjallajökull's behaviour can be attributed to its off-rift setting with a 'cold' subsurface structure and limited magma at shallow depth, as may be typical for moderately active volcanoes. Clear signs of volcanic unrest signals over years to weeks may indicate reawakening of such volcanoes, whereas immediate short-term eruption precursors may be subtle and difficult to detect.

Geochemical and textural constraints on degassing processes in sub-Plinian eruptions: case-study of the Greenish Pumice eruption of Mount Somma-Vesuvius

NASA Astrophysics Data System (ADS)

Zdanowicz, G.; Boudon, G.; Balcone-Boissard, H.; Cioni, R.; Mundula, F.; Orsi, G.; Civetta, L.; Agrinier, P.

2018-04-01

Plinian eruptions are characterized by high intensity and an overall steady character, and result in a stable convective column. The main processes controlling the dynamics of such steady and stable plume systems have been extensively investigated. Conversely, sub-Plinian eruptions are unsteady, as recorded by the large variability of the products and deposits. Our knowledge of the processes creating this unsteadiness on various timescales remains limited, and still requires more observations as well as theoretical and experimental investigation. Here, we focus on the sub-Plinian eruption of the Greenish Pumice (GP, 19,265 ± 105 BP), Mt. Somma-Vesuvius (Italy). On the basis of coupled geochemical and textural analyses of samples from the well-established stratigraphy of the GP deposits, we investigate volatiles (H2O, CO2, F, Cl) to better constrain the unsteady sub-Plinian eruptive style. This allows us to carry out a detailed study of the degassing processes in relation to the eruption dynamics. We find that degassing by open-system processes generally dominates throughout the entire eruption, but alternates with episodes of closed-system degassing. The fluctuating degassing regimes, responsible for the variable magma ascent rate within the conduit, are also responsible for the eruptive column instability. Volatile behavior is well correlated with textural heterogeneities of the eruptive products. Both reflect higher conduit heterogeneity than for Plinian eruptions, where we find a higher horizontal gradient in magma ascent velocity due to a smaller conduit diameter.

The role of unsteady buoyancy flux on transient eruption plume velocity structure and evolution

NASA Astrophysics Data System (ADS)

Chojnicki, K. N.; Clarke, A. B.; Phillips, J. C.

2010-12-01

Volcanic vent exit velocities, eruption column velocity profiles, and atmospheric entrainment are important parameters that control the evolution of explosive volcanic eruption plumes. New data sets tracking short-term variability in such parameters are becoming more abundant in volcanology and are being used to indirectly estimate eruption source conditions such vent flux, material properties of the plume, and source mechanisms. However, inadequate theory describing the relationships between time-varying source fluxes and evolution of unsteady turbulent flows such as eruption plumes, limits the interpretation potential of these data sets. In particular, the relative roles of gas-thrust and buoyancy in volcanic explosions is known to generate distinct differences in the ascent dynamics. Here we investigate the role of initial buoyancy in unsteady, short-duration eruption dynamics through scaled laboratory experiments and provide an empirical description of the relationship between unsteady source flux and plume evolution. The experiments involved source fluids of various densities (960-1000 kg/m3) injected, with a range of initial momentum and buoyancy, into a tank of fresh water through a range of vent diameters (3-15 mm). A scaled analysis was used to determine the fundamental parameters governing the evolution of the laboratory plumes as a function of unsteady source conditions. The subsequent model can be applied to predict flow front propagation speeds, and maximum flow height and width of transient volcanic eruption plumes which can not be adequately described by existing steady approximations. In addition, the model describes the relative roles of momentum or gas-thrust and buoyancy in plume motion which is suspected to be a key parameter in quantitatively defining explosive eruption style. The velocity structure of the resulting flows was measured using the Particle Image Velocimetry (PIV) technique in which velocity vector fields were generated from displacements in time-resolved video images of particles in the flow interior. Cross-sectional profiles of vertical velocity and entrainment of ambient fluid were characterized using the resulting velocity vector maps. These data elucidate the relationship between flow front velocity and internal velocity structure which may improve interpretations of field measurements of volcanic explosions. The velocity maps also demonstrate the role of buoyancy in enhancing ambient entrainment and converting vertical velocity to horizontal velocity, which may explain why buoyancy at the vent leads to faster deceleration of the flow.

Magma genesis, storage and eruption processes at Aluto volcano, Ethiopia: lessons from remote sensing, gas emissions and geochemistry

NASA Astrophysics Data System (ADS)

Hutchison, William; Biggs, Juliet; Mather, Tamsin; Pyle, David; Gleeson, Matthew; Lewi, Elias; Yirgu, Gezahgen; Caliro, Stefano; Chiodini, Giovanni; Fischer, Tobias

2016-04-01

One of the most intriguing aspects of magmatism during the transition from continental rifting to sea-floor spreading is that large silicic magmatic systems develop within the rift zone. In the Main Ethiopian Rift (MER) these silicic volcanoes not only pose a significant hazard to local populations but they also sustain major geothermal resources. Understanding the journey magma takes from source to surface beneath these volcanoes is vital for determining its eruption style and for better evaluating the geothermal resources that these complexes host. We investigate Aluto, a restless silicic volcano in the MER, and combine a wide range of geochemical and geophysical techniques to constrain magma genesis, storage and eruption processes and shed light on magmatic-hydrothermal-tectonic interactions. Magma genesis and storage processes at Aluto were evaluated using new whole-rock geochemical data from recent eruptive products. Geochemical modelling confirms that Aluto's peralkaline rhyolites, that constitute the bulk of recent erupted products, are generated from protracted fractionation (>80 %) of basalt that is compositionally similar to rift-related basalts found on the margins of the complex. Crustal melting did not play a significant role in rhyolite genesis and melt storage depths of ~5 km can reproduce almost all aspects of their geochemistry. InSAR methods were then used to investigate magma storage and fluid movement at Aluto during an episode of ground deformation that took place between 2008 and 2010. Combining new SAR imagery from different viewing geometries we identified an accelerating uplift pulse and found that source models support depths of magmatic and/or fluid intrusion at ~5 km for the uplift and shallower depths of ~4 km for the subsidence. Finally, gas samples collected on Aluto in 2014 were used to evaluate magma and fluid transport processes. Our results show that gases are predominantly emanating from major fault zones on Aluto and that they display a clear magmatic carbon signature of -4.2 to -4.5 ‰. This provides compelling evidence that the magmatic and hydrothermal reservoirs of Aluto are physically connected. Bringing the new data sets together provides an integrated picture of the plumbing system of this restless rift volcano. Aluto's silicic magmas are generated and stored at depths of ~5 km. Magmatic intrusion and/or fluid injection in the cap of this magmatic reservoir drives edifice wide inflation while subsequent deflation is related to magmatic degassing and/or cooling of the geothermal reservoir at shallower depths. Tectonic faults that dissect the complex are a key component of this plumbing system and by connecting the deep reservoirs to the surface they not only provide important degassing pathways but will almost certainly be exploited during future eruptive events.

Magma Reservoir Processes Revealed by Geochemistry of the Ongoing East Rift Zone Eruption, Kilauea Volcano, Hawaii

NASA Astrophysics Data System (ADS)

Thornber, C. R.

2002-12-01

Geochemical data were examined for a suite of 1,000 near-vent lava samples from the Pu`u `O`o-Kupaianaha eruption of Kilauea, collected from January 1983 through October 2001. Bulk lava and glass compositions reveal short- and long-term changes in pre-eruptive magma conditions that can be correlated with changes in edifice deformation, shallow magma transfer and eruptive behavior. Two decades of eruption on Kilauea's east rift zone has yielded ~2 km3 of lava, 97% of which is sparsely olivine-phyric with an MgO range of 6.8 to 9.6 wt%. During separate brief intervals of low-volume, fissure eruption (episodes 1 to 3 and 54), isolated rift-zone reservoirs with lower-MgO and olv-cpx-plg-phryic magma were incorporated by more mafic magma immediately prior to eruption. During prolonged, near-continuous eruption(e.g.,episodes 48-53 and most of 55), steady-state effusion is marked by cyclic variations in olivine-saturated magma chemistry. Bulk lava MgO and eruption temperature vary in cycles of monthly to bi-annual frequency, while olivine-incompatible elements vary inversely to these cycles. However, MgO-normalized values and ratios of highly to moderately incompatible elements (HINCE/MINCE), which nullify olivine fractionation effects, reveal cycles in magma chemistry that occur prior to olivine crystallization over the magmatic temperature range that is tapped by this eruption (1205-1155°C). These short-term cycles are superimposed on a long-term decrease of HINCE/MINCE, which is widely thought to reflect a 20-year change in mantle-source conditions. While HINCE/MINCE variation in primitive recharge magma cannot be ruled out, the short-term fluctuations of this signature may require unreasonably complex mantle variations. Alternatively, the correspondence of HINCE/MINCE cycles with edifice deformation and eruptive behavior suggests that the long-term evolving magmatic condition is a result of prolonged succession of short-term shallow magmatic events. The consistent limits of repeated MgO and temperature variation imply end-member magma conditions that are regulated by open-system recharge of the shallow magmatic plumbing system. The low-end of MgO variation (7 wt%) approaches the low-pressure multiphase cotectic, which is maintained by open-system replenishment of a persistent magma reservoir. The high-temperature end-member (10 wt% MgO) is probably regulated by olivine fractionation in a zone of turbulent mixing between primitive recharge magma (15 wt% MgO) and resident cotectic magma. The highest temperature magmas are associated with eruption pulses that occur in response to intrusive events at the summit and initiate short-term increases of HINCE/MINCE. Subsequent changes toward lower magmatic temperatures are associated with periods of overall summit deflation, relatively low-level effusion, and frequent eruptive pauses. The long-term trends can be explained by episodic mixing of chemically uniform recharge melt with diminishing proportions of pre-1983 summit magma (maintained at cotectic conditions). Decreasing HINCE/MINCE may signify that a greater proportion of recharge magma is being diverted directly to Pu`u `O`o with minimal summit interaction or that the mass ratio of those mixing end-members has changed due to a depleted summit chamber (or both). The coincidence of long-term summit deflation since the 1982 summit eruption suggests that shallow processes related to summit reservoir depletion may be responsible for decreasing HINCE/MINCE and Pb isotopes in post-1982 steady-state eruption products. Magma derived from a uniform mantle-source, after having flushed out older resident magma, may now completely occupy the shallow magmatic plumbing system.

2010 AUGUST 1-2 SYMPATHETIC ERUPTIONS. I. MAGNETIC TOPOLOGY OF THE SOURCE-SURFACE BACKGROUND FIELD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Titov, V. S.; Mikic, Z.; Toeroek, T.

2012-11-01

A sequence of apparently coupled eruptions was observed on 2010 August 1-2 by Solar Dynamics Observatory and STEREO. The eruptions were closely synchronized with one another, even though some of them occurred at widely separated locations. In an attempt to identify a plausible reason for such synchronization, we study the large-scale structure of the background magnetic configuration. The coronal field was computed from the photospheric magnetic field observed at the appropriate time period by using the potential field source-surface model. We investigate the resulting field structure by analyzing the so-called squashing factor calculated at the photospheric and source-surface boundaries, asmore » well as at different coronal cross-sections. Using this information as a guide, we determine the underlying structural skeleton of the configuration, including separatrix and quasi-separatrix surfaces. Our analysis reveals, in particular, several pseudo-streamers in the regions where the eruptions occurred. Of special interest to us are the magnetic null points and separators associated with the pseudo-streamers. We propose that magnetic reconnection triggered along these separators by the first eruption likely played a key role in establishing the assumed link between the sequential eruptions. The present work substantiates our recent simplified magnetohydrodynamic model of sympathetic eruptions and provides a guide for further deeper study of these phenomena. Several important implications of our results for the S-web model of the slow solar wind are also addressed.« less

Modelling tephra dispersal and ash aggregation: The 26th April 1979 eruption, La Soufrière St. Vincent

NASA Astrophysics Data System (ADS)

Poret, M.; Costa, A.; Folch, A.; Martí, A.

2017-11-01

On the 26th April 1979, La Soufrière St. Vincent volcano (West Indies) erupted producing a tephra fallout that blanketed the main island and the neighboring Bequia Island, located southwards. Using deposit measurements and the available observations reported in Brazier et al. (1982), we estimated the optimal Eruption Source Parameters, such as the Mass Eruption Rate (MER), the Total Erupted Mass (TEM) and the Total Grain-Size Distribution (TGSD) by means of a computational inversion method. Tephra transport and deposition were simulated using the 3D Eulerian model FALL3D. The field-based TGSD reconstructed by Brazier et al. (1982) shows a bi-modal pattern having a coarse and a fine population with modes around 0.5 and 0.06 mm, respectively. A significant amount of aggregates was observed during the eruption. To quantify the relevance of aggregation processes on the bulk tephra deposit, we performed a comparative study in which we accounted for aggregation using three different schemes, computing ash aggregation within the plume under wet conditions, i.e. considering both the effects of air moisture and magmatic water, consistently with the eruptive phreatomagmatic eruption features. The sensitivity to the driving meteorological model (WRF/ARW) was also investigated by considering two different spatial resolutions (5 and 1 km) and model output frequencies. Results show that, for such short-lived explosive eruptions, high-resolution meteorological data are critical. Optimal results best-fitting all available observations indicate a column height of 12 km above the vent, a MER of 7.8 × 106 kg/s which, for an eruption duration of 370 s, gives a TEM of 2.8 × 109 kg. The optimal aggregate mean diameter obtained is 1.5Φ with a density of 350 kg/m3, contributing to 22% of the deposit mass.

Relating stress models of magma emplacement to volcano-tectonic earthquakes

NASA Astrophysics Data System (ADS)

Vargas-Bracamontes, D.; Neuberg, J.

2007-12-01

Among the various types of seismic signals linked to volcanic processes, volcano-tectonic earthquakes are probably the earliest precursors of volcanic eruptions. Understanding their relationship with magma emplacement can provide insight into the mechanisms of magma transport at depth and assist in the ultimate goal of forecasting eruptions. Volcano-tectonic events have been observed to occur on faults that experience increases in Coulomb stress changes as the result of magma intrusions. To simulate stress changes associated with magmatic injections, we test different models of volcanic sources in an elastic half-space. For each source model, we look at several aspects that influence the stress conditions of the magmatic system such as the regional tectonic setting, the effect of varying the elastic parameters of the media, the evolution of the magma with time, as well as the volume and rheology of the ascending magma.

The implications of gas slug ascent in a stratified magma for acoustic and ground deformation source mechanisms in Strombolian eruptions

NASA Astrophysics Data System (ADS)

Capponi, Antonio; Lane, Stephen J.; James, Mike R.

2017-06-01

The interpretation of geophysical measurements at active volcanoes is vital for hazard assessment and for understanding fundamental processes such as magma degassing. For Strombolian activity, interpretations are currently underpinned by first-order fluid dynamic models which give relatively straightforward relationships between geophysical signals and gas and magma flow. However, recent petrological and high-speed video evidence has indicated the importance of rheological stratification within the conduit and, here, we show that under these conditions, the straightforward relationships break down. Using laboratory analogue experiments to represent a rheologically-stratified conduit we characterise the distinct variations in the shear stress exerted on the upper sections of the flow tube and in the gas pressures measured above the liquid surface, during different degassing flow configurations. These signals, generated by varying styles of gas ascent, expansion and burst, can reflect field infrasonic measurements and ground motion proximal to a vent. The shear stress signals exhibit timescales and trends in qualitative agreement with the near-vent inflation-deflation cycles identified at Stromboli. Therefore, shear stress along the uppermost conduit may represent a plausible source of near-vent tilt, and conduit shear contributions should be considered in the interpretation of ground deformation, which is usually attributed to pressure sources only. The same range of flow processes can produce different experimental infrasonic waveforms, even for similar masses of gas escape. The experimental data resembled infrasonic waveforms acquired from different vents at Stromboli associated with different eruptive styles. Accurate interpretation of near-vent ground deformation, infrasonic signal and eruptive style therefore requires detailed understanding of: a) spatiotemporal magma rheology in the shallow conduit, and b) shallow conduit geometry, as well as bubble overpressure and volume.

Eruptive stratigraphy of the Tatara-San Pedro complex, 36°S, sourthern volcanic zone, Chilean Andes: reconstruction method and implications for magma evolution at long-lived arc volcanic centers

USGS Publications Warehouse

Dungan, M.A.; Wulff, A.; Thompson, R.

2001-01-01

The Quaternary Tatara-San Pedro volcanic complex (36°S, Chilean Andes) comprises eight or more unconformity-bound volcanic sequences, representing variably preserved erosional remnants of volcanic centers generated during 930 ky of activity. The internal eruptive histories of several dominantly mafic to intermediate sequences have been reconstructed, on the basis of correlations of whole-rock major and trace element chemistry of flows between multiple sampled sections, but with critical contributions from photogrammetric, geochronologic, and paleomagnetic data. Many groups of flows representing discrete eruptive events define internal variation trends that reflect extrusion of heterogeneous or rapidly evolving magna batches from conduit-reservoir systems in which open-system processes typically played a large role. Long-term progressive evolution trends are extremely rare and the magma compositions of successive eruptive events rarely lie on precisely the same differentiation trend, even where they have evolved from similar parent magmas by similar processes. These observations are not consistent with magma differentiation in large long-lived reservoirs, but they may be accommodated by diverse interactions between newly arrived magma inputs and multiple resident pockets of evolved magma and / or crystal mush residing in conduit-dominated subvolcanic reservoirs. Without constraints provided by the reconstructed stratigraphic relations, the framework for petrologic modeling would be far different. A well-established eruptive stratigraphy may provide independent constraints on the petrologic processes involved in magma evolution-simply on the basis of the specific order in which diverse, broadly cogenetic magmas have been erupted. The Tatara-San Pedro complex includes lavas ranging from primitive basalt to high-SiO2 rhyolite, and although the dominant erupted magma type was basaltic andesite ( 52-55 wt % SiO2) each sequence is characterized by unique proportions of mafic, intermediate, and silicic eruptive products. Intermediate lava compositions also record different evolution paths, both within and between sequences. No systematic long-term pattern is evident from comparisons at the level of sequences. The considerable diversity of mafic and evolved magmas of the Tatara-San Pedro complex bears on interpretations of regional geochemical trends. The variable role of open-system processes in shaping the compositions of evolved Tatara-San Pedro complex magmas, and even some basaltic magmas, leads to the conclusion that addressing problems such as are magma genesis and elemental fluxes through subduction zones on the basis of averaged or regressed reconnaissance geochemical datasets is a tenuous exercise. Such compositional indices are highly instructive for identifying broad regional trends and first-order problems, but they should be used with extreme caution in attempts to quantify processes and magma sources, including crustal components, implicated in these trends.

Soil gas geochemistry in relation to eruptive fissures on Timanfaya volcano, Lanzarote Island (Canary Islands, Spain)

NASA Astrophysics Data System (ADS)

Padrón, Eleazar; Padilla, Germán; Hernández, Pedro A.; Pérez, Nemesio M.; Calvo, David; Nolasco, Dácil; Barrancos, José; Melián, Gladys V.; Dionis, Samara; Rodríguez, Fátima

2013-01-01

We report herein the first results of an extensive soil gas survey performed on Timanfaya volcano on May 2011. Soil gas composition at Timanfaya volcano indicates a main atmospheric source, slightly enriched in CO2 and He. Soil CO2 concentration showed a very slight deep contribution of the Timanfaya volcanic system, with no clear relation to the main eruptive fissures of the studied area. The existence of soil helium enrichments in Timanfaya indicates a shallow degassing of crustal helium and other possible deeper sources probably form cooling magma bodies at depth. The main soil helium enrichments were observed in good agreement with the main eruptive fissures of the 1730-36 eruption, with the highest values located at those areas with a higher density of recent eruptive centers, indicating an important structural control for the leakage of helium at Timanfaya volcano. Atmospheric air slightly polluted by deep-seated helium emissions, CO2 degassed from a cooling magma body, and biogenic CO2, might be the most plausible explanation for the existence of soil gas. Helium is a deep-seated gas, exhibiting important emission rates along the main eruptive fissure of the 1730-36 eruption of Timanfaya volcano.

Evidence for an abrupt transition in the mantle-derived source to the Long Valley Caldera rhyolites after the climactic eruption: from subduction-modified lithosphere to asthenosphere

NASA Astrophysics Data System (ADS)

Waters, L.; Lange, R. A.

2014-12-01

Shortly after the climactic eruption of ~600 km3 of Bishop Tuff zoned rhyolitic magma, ~100 km3 of crystal-poor Early Rhyolite erupted inside Long Valley Caldera between ~750-650 ka as domes, glassy lavas, and tuffs (Hildreth, 2004). Despite similarities in bulk composition (e.g., 73-75 wt% SiO2; ~100 ppm Sr), there are marked differences between the Late (≥ 790°C) Bishop Tuff and postcaldera Early Rhyolites. Although crystal-poor (<5%), the Early Rhyolites are often saturated with 7-8 mineral phases (plag + opx + ilm + tmte + biotite + apatite + zircon ± pyrrhotite), but without the quartz, sanidine, and cpx additionally found in the more crystal-rich (12-24%) Late Bishop Tuff. Pre-eruptive temperatures, on the basis of two Fe-Ti oxides, range from 720-860°C, and ΔNNO values range from-0.4 to -0.9 (consistent with abundant ilmenite). Thus the Early Rhyolites record fO2 values that are nearly two orders of magnitude lower than those in the Late Bishop Tuff (ΔNNO = +1; Hildreth and Wilson, 2007). Application of the plagioclase-liquid hygrometer to Early Rhyolites gives pre-eruptive water contents ≤ 4.4 wt% H2O. The phenocrysts in Early Rhyolite obsidians often display euhedral and/or diffusion-limited growth textures, suggesting degassing-induced crystallization during rapid ascent. Isotopic data from the literature (e.g., Simon et al., 2014 and references therein) show that Long Valley rhyolites were derived from both crustal and mantle sources. We hypothesize that the drop in fO2 between the Late Bishop Tuff and Early Rhyolites may reflect a transition in their respective mantle source, from subduction-modified lithosphere to asthenosphere. Such a time-progressive transition in the mantle source of erupted basalts is seen throughout the Great Basin, occurring earliest in its central region and more recently toward its western margin (e.g. Cousens et al., 2012). Although the geochemistry of Quaternary basalts erupted around Long Valley indicate a subduction-modified lithosphere source (Cousens, 1996), the Early Rhyolites may be recording the crustal emplacement of basalts from the asthenosphere before any have yet erupted. If so, the Early Rhyolites may be derived from a greater proportion of crustal sources than calculated from isotopic data on the assumption of a lithospheric mantle source.

Thermomechanical milling of accessory lithics in volcanic conduits

NASA Astrophysics Data System (ADS)

Campbell, Michelle E.; Russell, James K.; Porritt, Lucy A.

2013-09-01

Accessory lithic clasts recovered from pyroclastic deposits commonly result from the failure of conduit wall rocks, and represent an underutilized resource for constraining conduit processes during explosive volcanic eruptions. The morphological features of lithic clasts provide distinctive 'textural fingerprints' of processes that have reshaped them during transport in the conduit. Here, we present the first study focused on accessory lithic clast morphology and show how the shapes and surfaces of these accessory pyroclasts can inform on conduit processes. We use two main types of accessory lithic clasts from pyroclastic fallout deposits of the 2360 B.P. subplinian eruption of Mount Meager, British Columbia, as a case study: (i) rough and subangular dacite clasts, and (ii) variably rounded and smoothed monzogranite clasts. The quantitative morphological data collected on these lithics include: mass, volume, density, 2-D image analysis of convexity (C), and 3-D laser scans for sphericity (Ψ) and smoothness (S). Shaping and comminution (i.e. milling) of clasts within the conduit are ascribed to three processes: (1) disruptive fragmentation due to high-energy impacts between clasts or between clasts and conduit walls, (2) ash-blasting of clasts suspended within the volcanic flux, and (3) thermal effects. We use a simplified conduit eruption model to predict ash-blasting velocities and lithic residence times as a function of clast size and source depth, thereby constraining the lithic milling processes. The extent of shape and surface modification (i.e. rounding and honing) is directly proportional to clast residence times within the conduit prior to evacuation. We postulate that the shallow-seated dacite clasts remain subangular and rough due to short (<2 min) residence times, whereas monzogranite clasts are much more rounded and smoothed due to deeper source depths and consequently longer residence times (up to ˜1 h). Larger monzogranite clasts are smoother than smaller clasts due to longer residence times and to greater differential velocities within the ash-laden jet. Lastly, our model residence times and mass loss estimates for rounded clasts are used to estimate minimum attrition rates due to volcanic ash-blasting within the conduit (e.g., 12 cm3 s-1 for 25 cm clasts, sourced at 2500 m depth).

The heartbeat of the volcano: The discovery of episodic activity at Prometheus on Io

USGS Publications Warehouse

Davies, A.G.; Wilson, L.; Matson, D.; Leone, G.; Keszthelyi, L.; Jaeger, W.

2006-01-01

The temporal signature of thermal emission from a volcano is a valuable clue to the processes taking place both at and beneath the surface. The Galileo Near Infrared Mapping Spectrometer (NIMS) observed the volcano Prometheus, on the jovian moon Io, on multiple occasions between 1996 and 2002. The 5 micron (??m) brightness of this volcano shows considerable variation from orbit to orbit. Prometheus exhibits increases in thermal emission that indicate episodic (though non-periodic) effusive activity in a manner akin to the current Pu'u 'O'o-Kupaianaha (afterwards referred to as the Pu'u 'O'o) eruption of Kilauea, Hawai'i. The volume of material erupted during one Prometheus eruption episode (defined as the interval from minimum thermal emission to peak and back to minimum) from 6 November 1996 to 7 May 1997 is estimated to be ???0.8 km3, with a peak instantaneous volumetric flux (effusion rate) of ???140 m3 s-1, and an averaged volumetric flux (eruption rate) of ???49 m3 s-1. These quantities are used to model subsurface structure, magma storage and magma supply mechanisms, and likely magma chamber depth. Prometheus appears to be supplied by magma from a relatively shallow magma chamber, with a roof at a minimum depth of ???2-3 km and a maximum depth of ???14 km. This is a much shallower depth range than sources of supply proposed for explosive, possibly ultramafic, eruptions at Pillan and Tvashtar. As Prometheus-type effusive activity is widespread on Io, shallow magma chambers containing magma of basaltic or near-basaltic composition and density may be common. This analysis strengthens the analogy between Prometheus and Pu'u 'O'o, at least in terms of eruption style. Even though the style of eruption appears to be similar (effusive emplacement of thin, insulated, compound pahoehoe flows) the scale of activity at Prometheus greatly exceeds current activity at Pu'u 'O'o in terms of volume erupted, area covered, and magma flux. Whereas the estimated magma chamber at Prometheus dwarfs the Pu'u 'O'o magma chamber, it fits within expectations if the Pu'u 'O'o chamber were scaled for the greater volumetric flux and lower gravity of Io. Recent volumetric eruption rates derived from Galileo data for Prometheus were considerably smaller than the rate that produced the extensive flows formed in the ???17 years between the Voyager and Galileo missions. These smaller eruption rates, coupled with the fact that flows are not expanding laterally, may mean that the immediate heat source that generates the Prometheus plume is simultaneously running out of available volatiles and the thermal energy that drives mobilization of volatiles. This raises the question of whether the current Prometheus eruption is in its last throes. ?? 2006 Elsevier Inc.

Surface deformation induced by magmatic processes at Pacaya Volcano, Guatemala revealed by InSAR

NASA Astrophysics Data System (ADS)

Wnuk, K.; Wauthier, C.

2017-09-01

Pacaya Volcano, Guatemala is a continuously active, basaltic volcano with an unstable western flank. Despite continuous activity since 1961, a lack of high temporal resolution geodetic surveying has prevented detailed modeling of Pacaya's underlying magmatic plumbing system. A new, temporally dense dataset of Interferometric Synthetic Aperture Radar (InSAR) RADARSAT-2 images, spanning December 2012 to March 2014, show magmatic deformation before and during major eruptions in January and March 2014. Inversion of InSAR surface displacements using simple analytical forward models suggest that three magma bodies are responsible for the observed deformation: (1) a 4 km deep spherical reservoir located northwest of the summit, (2) a 0.4 km deep spherical source located directly west of the summit, and (3) a shallow dike below the summit. Periods of heightened volcanic activity are instigated by magma pulses at depth, resulting in rapid inflation of the edifice. We observe an intrusion cycle at Pacaya that consists of deflation of one or both magma reservoirs followed by dike intrusion. Intrusion volumes are proportional to reservoir volume loss and do not always result in an eruption. Periods of increased activity culminate with larger dike-fed eruptions. Large eruptions are followed by inter-eruptive periods marked by a decrease in crater explosions and a lack of detected deformation. Co-eruptive flank motion appears to have initiated a new stage of volcanic rifting at Pacaya defined by repeated NW-SE oriented dike intrusions. This creates a positive feedback relationship whereby magmatic forcing from eruptive dike intrusions induce flank motion.

Using multiple data sets to populate probabilistic volcanic event trees

USGS Publications Warehouse

Newhall, C.G.; Pallister, John S.

2014-01-01

The key parameters one needs to forecast outcomes of volcanic unrest are hidden kilometers beneath the Earth’s surface, and volcanic systems are so complex that there will invariably be stochastic elements in the evolution of any unrest. Fortunately, there is sufficient regularity in behaviour that some, perhaps many, eruptions can be forecast with enough certainty for populations to be evacuated and kept safe. Volcanologists charged with forecasting eruptions must try to understand each volcanic system well enough that unrest can be interpreted in terms of pre-eruptive process, but must simultaneously recognize and convey uncertainties in their assessment. We have found that use of event trees helps to focus discussion, integrate data from multiple sources, reach consensus among scientists about both pre-eruptive process and uncertainties and, in some cases, to explain all of this to officials. Figure 1 shows a generic volcanic event tree from Newhall and Hoblitt (2002) that can be modified as needed for each specific volcano. This paper reviews how we and our colleagues have used such trees during a number of volcanic crises worldwide, for rapid hazard assessments in situations in which more formal expert elicitations could not be conducted. We describe how Multiple Data Sets can be used to estimate probabilities at each node and branch. We also present case histories of probability estimation during crises, how the estimates were used by public officials, and some suggestions for future improvements.

A SOLAR CORONAL JET EVENT TRIGGERS A CORONAL MASS EJECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jiajia; Wang, Yuming; Shen, Chenglong

2015-11-10

In this paper, we present multi-point, multi-wavelength observations and analysis of a solar coronal jet and coronal mass ejection (CME) event. Employing the GCS model, we obtained the real (three-dimensional) heliocentric distance and direction of the CME and found it to propagate at a high speed of over 1000 km s{sup −1}. The jet erupted before the CME and shared the same source region. The temporal and spacial relationship between these two events lead us to the possibility that the jet triggered the CME and became its core. This scenario hold the promise of enriching our understanding of the triggeringmore » mechanism of CMEs and their relations to coronal large-scale jets. On the other hand, the magnetic field configuration of the source region observed by the Solar Dynamics Observatory (SDO)/HMI instrument along with the off-limb inverse Y-shaped configuration observed by SDO/AIA in the 171 Å passband provide the first detailed observation of the three-dimensional reconnection process of a large-scale jet as simulated in Pariat et al. The eruption process of the jet highlights the importance of filament-like material during the eruption of not only small-scale X-ray jets, but likely also of large-scale EUV jets. Based on our observations and analysis, we propose the most probable mechanism for the whole event, with a blob structure overlaying the three-dimensional structure of the jet, to describe the interaction between the jet and the CME.« less

Role of Social Media and Networking in Volcanic Crises and Communication

NASA Astrophysics Data System (ADS)

Sennert, S.; Klemetti, E. W.; Bird, D. K.

2016-12-01

The growth of social media as a primary and often preferred news source has led to the rapid dissemination of information about volcanic eruptions and potential volcanic crises as they begin, evolve, and end. This information comes from a variety of sources: news organisations, emergency management personnel, individuals (both members of the public and official representatives), and volcano monitoring agencies. Once posted, this information is easily shared, increasing the reach to a much broader population than more traditional forms of media, such as radio and newspapers. The onset and popularity of social media as a vehicle for dissemination of eruption information points toward the need to systematically incorporate social media into the official channels that volcano observatories use to distribute activity statements, forecasts, and images. We explore two examples of projects that collect/disseminate information regarding volcanic crises and eruptive activity via social media sources; the Smithsonian/USGS Weekly Volcanic Activity Report (WVAR), which summarizes new and on-going volcanic activity globally and on a weekly basis, and Eruptions, a blog that discusses eruptions as well as other volcanic topics. Based on these experiences, recommendations are made to volcanic observatories in relation to the use of social media as a communication tool. These recommendations include: using social media as a two-way dialogue to communicate and receive information directly from the public and other sources; stating that the social media account is from an official source; and posting types of information that users want to see such as images, videos, and figures.

Volcanic eruptions on Io

NASA Technical Reports Server (NTRS)

Strom, R. G.; Schneider, N. M.; Terrile, R. J.; Hansen, C.; Cook, A. F.

1981-01-01

Nine eruption plumes which were observed during the Voyager 1 encounter with Io are discussed. During the Voyager 2 encounter, four months later, eight of the eruptions were still active although the largest became inactive sometime between the two encounters. Plumes range in height from 60 to over 300 km with corresponding ejection velocities of 0.5 to 1.0 km/s and plume sources are located on several plains and consist of fissures or calderas. The shape and brightness distribution together with the pattern of the surface deposition on a plume 3 is simulated by a ballistic model with a constant ejection velocity of 0.5 km/s and ejection angles which vary from 0-55 deg. The distribution of active and recent eruptions is concentrated in the equatorial regions and indicates that volcanic activity is more frequent and intense in the equatorial regions than in the polar regions. Due to the geologic setting of certain plume sources and large reservoirs of volatiles required for the active eruptions, it is concluded that sulfur volcanism rather than silicate volcanism is the most likely driving mechanism for the eruption plumes.

Analyzing the continuous volcanic tremors detected during the 2015 phreatic eruption of the Hakone volcano

NASA Astrophysics Data System (ADS)

Yukutake, Yohei; Honda, Ryou; Harada, Masatake; Doke, Ryosuke; Saito, Tatsuhiko; Ueno, Tomotake; Sakai, Shin'ichi; Morita, Yuichi

2017-12-01

In the present study, we analyze the seismic signals from a continuous volcanic tremor that occurred during a small phreatic eruption of the Hakone volcano, in the Owakudani geothermal region of central Japan, on June 29, 2015. The signals were detected for 2 days, from June 29 to July 1, at stations near the vents. The frequency component of the volcanic tremors showed a broad peak within 1-6 Hz. The characteristics of the frequency component did not vary with time and were independent of the amplitude of the tremor. The largest amplitude was observed at the end of the tremor activity, 2 days after the onset of the eruption. We estimated the location of the source using a cross-correlation analysis of waveform envelopes. The locations of volcanic tremors are determined near the vents of eruption and the surface, with the area of the upper extent of an open crack estimated using changes in the tilt. The duration-amplitude distribution of the volcanic tremor was consistent with the exponential scaling law rather than the power law, suggesting a scale-bound source process. This result suggests that the volcanic tremor originated from a similar physical process occurring practically in the same place. The increment of the tremor amplitude was coincident with the occurrence of impulsive infrasonic waves and vent formations. High-amplitude seismic phases were observed prior to the infrasonic onsets. The time difference between the seismic and infrasonic onsets can be explained assuming a common source located at the vent. This result suggests that both seismic and infrasonic waves are generated when a gas slug bursts at that location. The frequency components of the seismic phases observed just before the infrasonic onset were generally consistent with those of the tremor signals without infrasonic waves. The burst of a gas slug at the surface vent may be a reasonable model for the generation mechanism of the volcanic tremor and the occurrence of impulsive infrasonic signals.[Figure not available: see fulltext.

238U–230Th–226Ra–210Pb–210Po disequilibria constraints on magma generation, ascent, and degassing during the ongoing eruption of Kīlauea

USGS Publications Warehouse

Girard, Guillaume; Reagan, Mark K.; Sims, Kenneth W. W.; Thornber, Carl; Waters, Christopher L.; Phillips, Erin H.

2017-01-01

The timescales of magma genesis, ascent, storage and degassing at Kīlauea volcano, Hawai‘i are addressed by measuring 238U-series radionuclide abundances in lava and tephra erupted between 1982 and 2008. Most analyzed samples represent lavas erupted by steady effusion from Pu‘u ‘Ō‘ō and Kūpahianaha from 1983 to 2008. Also included are samples erupted at the summit in April 1982 and March 2008, along the East Rift Zone at the onset of the ongoing eruption in January 1983, and during vent shifting episodes 54 and 56, at Nāpau crater in January 1997, and Kane Nui O Hamo in June 2007. In general, samples have small (∼4%) excesses of (230Th) over (238U) and ∼3 to ∼17% excesses of (226Ra) over (230Th), consistent with melting of a garnet peridotite source at melting rates between 1 × 10–3 and 5 × 10–3 kg m–3 a–1, and melting region porosity between ∼2 and ∼10%, in agreement with previous studies of the ongoing eruption and historical eruptions. A small subset of samples has near-equilibrium (230Th/238U) values, and thus were generated at higher melting rates. Based on U–Th–Ra disequilibria and Th isotopic data from this and earlier studies, melting processes and sources have been relatively stable over at least the past two centuries or more, including during the ongoing unusually long (>30 years) and voluminous (4 km3) eruption. Lavas recently erupted from the East Rift Zone have average initial (210Pb/226Ra) values of 0·80 ± 0·11 (1σ), which we interpret to be the result of partitioning of 222Rn into a persistently generated CO2-rich gas phase over a minimum of 8 years. This (210Pb) deficit implies an average magma ascent rate of ≤3·7 km a–1 from ∼30 km depth to the surface. Spatter and lava associated with vent-opening episodes erupt with variable (210Pb) deficits ranging from 0·7 to near-equilibrium values in some samples. The samples with near-equilibrium (210Pb/226Ra) are typically more differentiated, suggesting decadal timescales of magma storage in shallow conduits or reservoirs that were not degassing. Lava and spatter samples erupted in the East Rift Zone and at the summit had (210Po) ∼0 at the time of eruption, which results from efficient partitioning of Po into the CO2- and SO2-rich gas phases during and prior to eruption. Summit ash and Pele’s hair samples from 2008 differ from lava and lapilli samples in that they have elevated initial (210Po), (210Pb/226Ra), and Pb concentrations because of Po condensation on tephra particles, and incorporation of fumarolic Po and Pb into erupted tephra fragments during quenching.

Multi-wavelength Observation of Filament Eruption associated with M-class Flare

NASA Astrophysics Data System (ADS)

Kim, S.; Yurchyshyn, V.; Jiang, C.

2017-12-01

We have investigated a M-class flare associated with filament eruption which developed into a Halo CME. The M-class flare occurred in 2011 August 4. For this study, we used the Nobryama Radioheliograph (NoRH) 17 and 34 GHz, RHESSI Hard X-ray satellite, and Atmo- spheric Imaging Assembly (AIA) and the Heliospheric Magentic Imager(HMI) onboard the Solar Dynamic Observatory (SDO). During the pre-eruption phase, clear nonthermal emission was detected in microwaves of NoRH and hard-X-ray of RHESSI. At the moment that the nonthermal emission start, the nonthermal sources appeared at the one edge of the filament structure on a polarity inversion line, and the slowing rising filament structure in AIA 94A underwent a sudden acceleration on its ascendance. Magnetograms showed converging motion of magnetic elements at the source position of HXR and MW. Based on the results, we conjecture that the plausible trigger of the filament eruption is magnetic reconnections at the HXR source position by converging motion of magnetic elements. In addition, we will discuss on the magnetic flux variation before and after the eruption based on the result of Nonlinear force-free field model.

Interchange Reconnection Associated with a Confined Filament Eruption: Implications for the Source of Transient Cold-dense Plasma in Solar Winds

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Ruisheng; Chen, Yao; Wang, Bing

The cold-dense plasma is occasionally detected in the solar wind with in situ data, but the source of the cold-dense plasma remains illusive. Interchange reconnections (IRs) between closed fields and nearby open fields are known to contribute to the formation of solar winds. We present a confined filament eruption associated with a puff-like coronal mass ejection (CME) on 2014 December 24. The filament underwent successive activations and finally erupted, due to continuous magnetic flux cancelations and emergences. The confined erupting filament showed a clear untwist motion, and most of the filament material fell back. During the eruption, some tiny blobsmore » escaped from the confined filament body, along newly formed open field lines rooted around the south end of the filament, and some bright plasma flowed from the north end of the filament to remote sites at nearby open fields. The newly formed open field lines shifted southward with multiple branches. The puff-like CME also showed multiple bright fronts and a clear southward shift. All the results indicate an intermittent IR existed between closed fields of the confined erupting filament and nearby open fields, which released a portion of filament material (blobs) to form the puff-like CME. We suggest that the IR provides a possible source of cold-dense plasma in the solar wind.« less

Carbon isotope systematics of Turrialba volcano, Costa Rica, using a portable cavity ring-down spectrometer

NASA Astrophysics Data System (ADS)

Malowany, K. S.; Stix, J.; de Moor, J. M.; Chu, K.; Lacrampe-Couloume, G.; Sherwood Lollar, B.

2017-07-01

Over the past two decades, activity at Turrialba volcano, Costa Rica, has shifted from hydrothermal to increasingly magmatic in character, with enhanced degassing and eruption potential. We have conducted a survey of the δ13C signatures of gases at Turrialba using a portable field-based CRDS with comparison to standard IRMS techniques. Our δ13C results of the volcanic plume, high-temperature vents, and soil gases reveal isotopic heterogeneity in the CO2 gas composition at Turrialba prior to its recent phase of eruptive activity. The isotopic value of the regional fault system, Falla Ariete (-3.4 ± 0.1‰), is in distinct contrast with the Central crater gases (-3.9 ± 0.1‰) and the 2012 high-temperature vent (-4.4 ± 0.2‰), an indication that spatial variability in δ13C may be linked to hydrothermal transport of volcanic gases, heterogeneities in the source composition, or magmatic degassing. Isotopic values of CO2 samples collected in the plume vary from δ13C of -5.2 to -10.0‰, indicative of mixing between atmospheric CO2 (-9.2 ± 0.1‰), and a volcanic source. We compare the Keeling method to a traditional mixing model (hyperbolic mixing curve) to estimate the volcanic source composition at Turrialba from the plume measurements. The predicted source compositions from the Keeling and hyperbolic methods (-3.0 ± 0.5‰ and -3.9 ± 0.4‰, respectively) illustrate two potential interpretations of the volcanic source at Turrialba. As of the 29 October 2014, Turrialba has entered a new eruptive period, and continued monitoring of the summit gases for δ13C should be conducted to better understand the dominant processes controlling δ13C fractionation at Turrialba.

A simple semi-empirical approach to model thickness of ash-deposits for different eruption scenarios

NASA Astrophysics Data System (ADS)

González-Mellado, A. O.; de La Cruz-Reyna, S.

2010-11-01

The impact of ash-fall on people, buildings, crops, water resources, and infrastructure depends on several factors such as the thickness of the deposits, grain size distribution and others. Preparedness against tephra falls over large regions around an active volcano requires an understanding of all processes controlling those factors, and a working model capable of predicting at least some of them. However, the complexity of tephra dispersion and sedimentation makes the search of an integral solution an almost unapproachable problem in the absence of highly efficient computing facilities due to the large number of equations and unknown parameters that control the process. An alternative attempt is made here to address the problem of modeling the thickness of ash deposits as a primary impact factor that can be easily communicated to the public and decision-makers. We develop a semi-empirical inversion model to estimate the thickness of non-compacted deposits produced by an explosive eruption around a volcano in the distance range 4-150 km from the eruptive source. The model was elaborated from the analysis of the geometric distribution of deposit thickness of 14 world-wide well-documented eruptions. The model was initially developed to depict deposits of potential eruptions of Popocatépetl and Colima volcanoes in México, but it can be applied to any volcano. It has been designed to provide planners and Civil Protection authorities of an accurate perception of the ash-fall deposit thickness that may be expected for different eruption scenarios. The model needs to be fed with a few easy-to-obtain parameters, namely, height of the eruptive column, duration of the explosive phase, and wind speed and direction, and its simplicity allows it to run in any platform, including a personal computers and even a notebook. The results may be represented as tables, two dimensional thickness-distance plots, or isopach maps using any available graphic interface. The model has been tested, with available data from some recent eruptions in México, and permits to generate ash-fall deposit scenarios from new situations, or to recreate past situations, or to superimpose scenarios from eruptions of other volcanoes. The results may be displayed as thickness vs. distance plots, or as deposit-thickness scenarios superimposed on a regional map by means of a visual computer simulator based on a user-friendly built-in computer graphic interface.

Origin of temporal compositional trends in monogenetic vent eruptions: Insights from the crystal cargo in the Papoose Canyon sequence, Big Pine Volcanic Field, CA

NASA Astrophysics Data System (ADS)

Gao, Ruohan; Lassiter, John C.; Ramirez, Gabrielle

2017-01-01

Many monogenetic vents display systematic temporal-compositional variations over the course of eruption. Previous studies have proposed that these trends may reflect variable degrees of crustal assimilation, or melting and mixing of heterogeneous mantle source(s). Discrimination between these two endmember hypotheses is critical for understanding the plumbing systems of monogenetic volcanoes, which pose a significant volcanic hazard in many areas. In this study, we examine the Papoose Canyon (PC) monogenetic vent in the Big Pine Volcanic Field (BPVF), which had been well characterized for temporal-compositional variations in erupted basalts. We present new major and trace element and Sr-Nd-Pb-O isotopic data from the PC "crystal cargo" (phenocrysts and xenoliths). Comparison of "crystal cargo" and host basalt provides new constraints on the history of magma storage, fractionation, and crustal contamination that are obscured in the bulk basalts due to pre- and syn-eruptive magma mixing processes. The abundances of phenocrysts and ultramafic xenoliths in the PC sequence decrease up-section. Olivine and clinopyroxene phenocrysts span a wide range of Mg# (77-89). The majority of phenocrysts are more evolved than olivine or clinopyroxene in equilibrium with their host basalts (Mg# = 68- 71, equilibrium Fo ≈ 85- 89). In addition, the ultramafic xenoliths display cumulate textures. Olivine and clinopyroxene from ultramafic xenoliths have Mg# (73-87) similar to the phenocrysts, and lower than typical mantle peridotites. Sr-Nd-Pb isotope compositions of the xenoliths are similar to early PC basalts. Finally, many clinopyroxene phenocrysts and clinopyroxene in xenoliths have trace element abundances in equilibrium with melts that are more enriched than the erupted basalts. These features suggest that the phenocrysts and xenoliths derive from melt that is more fractionated and enriched than erupted PC basalts. Pressure constraints suggest phenocrysts and ultramafic xenoliths crystallized at ∼5-7 kbar, corresponding to mid-crust depths. Correlations between HFSE depletion and Sr-Nd-Pb isotopic compositions, high δ18 O values in olivines, and radiogenic Os isotopic compositions in whole rocks also suggest incorporation of a crustally contaminated component. We propose that the phenocrysts and ultramafic xenoliths derive from melts that ponded and fractionated and assimilated continental crust, possibly in mid-crustal sills. These melts were drained and mixed with more primitive melts as the eruption began, and the temporal-compositional trends and decreasing crystal phase abundances reflect gradual deflation and exhaustion of these sills as the eruption progressed. The isotopic variations in the PC sequence span much of the compositional range observed in the BPVF. Evidence for variable crustal contamination of PC basalts suggests that much of the isotopic variation observed in the BPVF may also reflect crustal contamination rather than mantle source heterogeneity as previously proposed. In addition, evidence of pre-eruptive magma ponding and fractionation, if applicable to other monogenetic vents, may have significant implications for monitoring and hazard assessment of monogenetic volcano fields.

Characterization of fine volcanic ash from explosive eruption from Sakurajima volcano, South Japan

NASA Astrophysics Data System (ADS)

Nanayama, F.; Furukawa, R.; Ishizuka, Y.; Yamamoto, T.; Geshi, N.; Oishi, M.

2013-12-01

Explosive volcanic eruptions can affect infrastructure and ecosystem by their dispersion of the volcanic particle. Characterization of volcanic particle expelled by explosive eruption is crucial for evaluating for quantitative hazard assessment by future volcanic eruption. Especially for fine volcanic ash less than 64 micron in diameter, it can disperse vast area from the source volcano and be easily remobilized by surface wind and precipitation after the deposition. As fine volcanic ash is not preserved well at the earth surface and in strata except for enormously large scale volcanic eruption. In order to quantify quantitative characteristics of fine volcanic ash particle, we sampled volcanic ash directly falling from the eruption cloud from Showa crater, the most active vent of Sakurajima volcano, just before landing on ground. We newly adopted high precision digital microscope and particle grain size analyzer to develop hazard evaluation method of fine volcanic ash particle. Field survey was performed 5 sequential days in January, 2013 to take tamper-proof volcanic ash samples directly obtained from the eruption cloud of the Sakurajima volcano using disposable paper dishes and plastic pails. Samples were taken twice a day with time-stamp in 40 localities from 2.5 km to 43 km distant from the volcano. Japan Meteorological Agency reported 16 explosive eruptions of vulcanian style occurred during our survey and we took 140 samples of volcanic ash. Grain size distribution of volcanic ash was measured by particle grain size analyzer (Mophologi G3S) detecting each grain with parameters of particle diameter (0.3 micron - 1 mm), perimeter, length, area, circularity, convexity, solidity, and intensity. Component of volcanic ash was analyzed by CCD optical microscope (VHX-2000) which can take high resolution optical image with magnifying power of 100-2500. We discriminated each volcanic ash particle by color, texture of surface, and internal structure. Grain size distributions of volcanic ash from Sakurajima volcano have basically characteristics of unimodal and gaussian. Mode of distributions are 150 - 200 micron at 5 km and 70-80 micron at 20 km respectively from the Showa crater. Mode and deviation of the grain size distribution are function of distance from the source. Fine volcanic ash less than 1 micron in diameter is few and exists in every samples. Component of volcanic ash samples are dark-colored dense glass shard (ca. 50%), light-colored dense glass shard (10%), variously colored and vesiculated glass shard (10%), free crystal (20%), lithic fragment (10%), and altered fragment (less than 5%) which are mostly having similar ratio in every location suggesting single source process of the eruption. We also found fine volcanic ash samples less than 10 micron are frequently aggregated. The present study includes the result of "Research and Development of Margin Assessment Methodology of Decay Heat Removal Function against External Hazards" entrusted to Japan Atomic Energy Agency by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT).

Petrological and geochemical constraints on the recent increase in explosive activity at Santiaguito volcano, Guatemala

NASA Astrophysics Data System (ADS)

Wallace, Paul A.; Henton De Angelis, Sarah; De Angelis, Silvio; Kendrick, Jackie E.; Hornby, Adrian J.; Lamb, Oliver; von Aulock, Felix W.; Lamur, Anthony; Chigna, Gustavo; Rietbrock, Andreas; Dingwell, Donald B.; Lavallée, Yan

2017-04-01

The ability to forecast rapid changes in eruption style at highly active and dynamic volcanic systems is a fundamental aim for many geoscientists. Over the past century, Santiaguito's eruptive longevity of regular, small-to-moderate explosions (typical of dome-building episodes) have made it the ideal laboratory for the study of eruption dynamics. In 2015 this activity shifted to more violent, less regular explosive activity, potentially marking the onset of a renewed and recharged magmatic source. This study presents a unique, high resolution petrological and geochemical dataset using ash samples collected across this transition period, revealing detailed insights into the cause behind this rapid change in activity. Ash and bombs erupted between December 2015 and June 2016 are two-pyroxene andesites with whole-rock chemistry that is consistent with a long term trend towards more mafic material (Harris et al., 2003). Furthermore, although bulk chemistry is becoming more mafic, matrix glass compositions are the most evolved in all of Santiaguito's history. Despite this historical trend, the activity in early 2016 showed a rapid increase in bulk SiO2 (˜2 wt.%). The presence of xenocrystic olivine (Fo68-77) mantled by orthopyroxene (En69), a combination of normal and reverse zoned plagioclase phenocrysts (up to An91) and the majority of amphibole phenocrysts completely broken down to pseudomorphs provide strong evidence for a system in an advanced state of disequilibrium. Magma source conditions from amphibole suggest depths of ˜17-24.5 km and temperatures of ˜960-1010˚ C. Although depths are consistent with previous work (Scott et al., 2012), the data suggests elevated temperatures in the source region, a possible consequence of magmatic recharge. Through studying amphibole reaction rims, experiments suggest decompression alone would not be feasible to generate the textures recorded, thus providing evidence for a complex thermal and chemical history of the magma during pre-eruptive storage and ascent. Textural and micro-petrological variations have also been investigated to constrain pre-eruptive conduit conditions, focusing on microlite characteristics that facilitate assessment of crystallisation processes in the shallow conduit and magma ascent rates prior to eruption. Our data is complemented by geophysical observations recorded over the same period, providing further insights into eruption dynamics. This collaborative work not only captures unique observations of the on-going dynamic activity at Santiaguito, but aids in deciphering the complexities associated with transitions in eruptive behaviour for many active silicic volcanoes worldwide. Harris, A.J.L., Rose, W.I., Flynn, L.P., 2003. Temporal trends in lava dome extrusion at Santiaguito 1922 - 2000. Bull. Volcanol. 65, 77-89. Scott, J.A.J., Mather, T.A., Pyle, D.M., Rose, W.I., Chigna, G., 2012. The magmatic plumbing system beneath Santiaguito Volcano, Guatemala. Journal of Volcanology and Geothermal Research 237-238, 54-68.

Characterization of pyroclastic deposits and pre-eruptive soils following the 2008 eruption of Kasatochi Island Volcano, Alaska

USGS Publications Warehouse

Wang, B.; Michaelson, G.; Ping, C.-L.; Plumlee, G.; Hageman, P.

2010-01-01

The 78 August 2008 eruption of Kasatochi Island volcano blanketed the island in newly generated pyroclastic deposits and deposited ash into the ocean and onto nearby islands. Concentrations of water soluble Fe, Cu, and Zn determined from a 1:20 deionized water leachate of the ash were sufficient to provide short-term fertilization of the surface ocean. The 2008 pyroclastic deposits were thicker in concavities at bases of steeper slopes and thinner on steep slopes and ridge crests. By summer 2009, secondary erosion had exposed the pre-eruption soils along gulley walls and in gully bottoms on the southern and eastern slopes, respectively. Topographic and microtopographic position altered the depositional patterns of the pyroclastic flows and resulted in pre-eruption soils being buried by as little as 1 m of ash. The different erosion patterns gave rise to three surfaces on which future ecosystems will likely develop: largely pre-eruptive soils; fresh pyroclastic deposits influenced by shallowly buried, pre-eruptive soil; and thick (>1 m) pyroclastic deposits. As expected, the chemical composition differed between the pyroclastic deposits and the pre-eruptive soils. Pre-eruptive soils hold stocks of C and N important for establishing biota that are lacking in the fresh pyroclastic deposits. The pyroclastic deposits are a source for P and K but have negligible nutrient holding capacity, making these elements vulnerable to leaching loss. Consequently, the pre-eruption soils may also represent an important long-term P and K source. ?? 2010 Regents of the University of Colorado.

Contemporaneous eruption of calc-alkaline and alkaline lavas in a continental arc (Eastern Mexican Volcanic Belt): chemically heterogeneous but isotopically homogeneous source

NASA Astrophysics Data System (ADS)

Carrasco-Núñez, Gerardo; Righter, Kevin; Chesley, John; Siebert, Lee; Aranda-Gómez, José Jorge

2005-11-01

Nearly contemporaneous eruption of alkaline and calc-alkaline lavas occurred about 900 years BP from El Volcancillo paired vent, located behind the volcanic front in the Mexican Volcanic Belt (MVB). Emission of hawaiite (Toxtlacuaya) was immediately followed by calc-alkaline basalt (Río Naolinco). Hawaiites contain olivine microphenocrysts (Fo67-72), plagioclase (An56-60) phenocrysts, have 4-5 wt% MgO and 49.6-50.9 wt% SiO2. In contrast, calc-alkaline lavas contain plagioclase (An64-72) and olivine phenocrysts (Fo81-84) with spinel inclusions, and have 8-9 wt% MgO and 48.4-49.4 wt% SiO2. The most primitive lavas in the region (Río Naolinco and Cerro Colorado) are not as primitive as parental melts in other arcs, and could represent either (a) variable degrees of melting of a subduction modified, garnet-bearing depleted mantle source, followed by AFC process, or (b) melting of two distinct mantle sources followed by AFC processes. These two hypotheses are evaluated using REE, HFSE, and Sr, Os and Pb isotopic data. The Toxtlacuaya flow and the Y & I lavas can be generated by combined fractional crystallization and assimilation of gabbroic granulite, starting with a parental liquid similar to the Cerro Colorado basalt. Although calc-alkaline and alkaline magmas commonly occur together in other areas of the MVB, evidence for subduction component in El Volcancillo magmas is minimal and limited to <1%, which is a unique feature in this region further from the trench. El Volcancillo lavas were produced from two different magma batches: we surmise that the injection of calc-alkaline magma into an alkaline magma chamber triggered the eruption of hawaiites. Our results suggest that the subalkaline and hawaiitic lavas were formed by different degrees of partial melting of a similar, largely depleted mantle source, followed by later AFC processes. This model is unusual for arcs, where such diversity is usually explained by melting of heterogeneous (enriched and depleted) and subduction-modified mantle.

Magmatic Ascent and Eruption Processes on Mercury

NASA Astrophysics Data System (ADS)

Head, J. W.; Wilson, L.

2018-05-01

MESSENGER volcanic landform data and information on crustal composition allow us to model the generation, ascent, and eruption of magma; Mercury explosive and effusive eruption processes differ significantly from other terrestrial planetary bodies.

Imaging the complex geometry of a magma reservoir using FEM-based linear inverse modeling of InSAR data: application to Rabaul Caldera, Papua New Guinea

NASA Astrophysics Data System (ADS)

Ronchin, Erika; Masterlark, Timothy; Dawson, John; Saunders, Steve; Martì Molist, Joan

2017-06-01

We test an innovative inversion scheme using Green's functions from an array of pressure sources embedded in finite-element method (FEM) models to image, without assuming an a-priori geometry, the composite and complex shape of a volcano deformation source. We invert interferometric synthetic aperture radar (InSAR) data to estimate the pressurization and shape of the magma reservoir of Rabaul caldera, Papua New Guinea. The results image the extended shallow magmatic system responsible for a broad and long-term subsidence of the caldera between 2007 February and 2010 December. Elastic FEM solutions are integrated into the regularized linear inversion of InSAR data of volcano surface displacements in order to obtain a 3-D image of the source of deformation. The Green's function matrix is constructed from a library of forward line-of-sight displacement solutions for a grid of cubic elementary deformation sources. Each source is sequentially generated by removing the corresponding cubic elements from a common meshed domain and simulating the injection of a fluid mass flux into the cavity, which results in a pressurization and volumetric change of the fluid-filled cavity. The use of a single mesh for the generation of all FEM models avoids the computationally expensive process of non-linear inversion and remeshing a variable geometry domain. Without assuming an a-priori source geometry other than the configuration of the 3-D grid that generates the library of Green's functions, the geodetic data dictate the geometry of the magma reservoir as a 3-D distribution of pressure (or flux of magma) within the source array. The inversion of InSAR data of Rabaul caldera shows a distribution of interconnected sources forming an amorphous, shallow magmatic system elongated under two opposite sides of the caldera. The marginal areas at the sides of the imaged magmatic system are the possible feeding reservoirs of the ongoing Tavurvur volcano eruption of andesitic products on the east side and of the past Vulcan volcano eruptions of more evolved materials on the west side. The interconnection and spatial distributions of sources correspond to the petrography of the volcanic products described in the literature and to the dynamics of the single and twin eruptions that characterize the caldera. The ability to image the complex geometry of deformation sources in both space and time can improve our ability to monitor active volcanoes, widen our understanding of the dynamics of active volcanic systems and improve the predictions of eruptions.

An experimental study of the role of subsurface plumbing on geothermal discharge

USGS Publications Warehouse

Namiki, Atsuko; Ueno, Yoshinori; Hurwitz, Shaul; Manga, Michael; Munoz-Saez, Carolina; Murphy, Fred

2016-01-01

In order to better understand the diverse discharge styles and eruption intervals observed at geothermal features, we performed three series of laboratory experiments with differing plumbing geometries. A single, straight conduit that connects a hot water bath (flask) to a vent (funnel) can originate geyser-like periodic eruptions, continuous discharge like a boiling spring, and fumarole-like steam discharge, depending on the conduit length and radius. The balance between the heat loss from the conduit walls and the heat supplied from the bottom determines whether and where water can condense which in turn controls discharge style. Next, we connected the conduit to a cold water reservoir through a branch, simulating the inflow from an external water source. Colder water located at a higher elevation than a branching point can flow into the conduit to stop the boiling in the flask, controlling the periodicity of the eruption. When an additional branch is connected to a second cold water reservoir, the two cold reservoirs can interact. Our experiments show that branching allows new processes to occur, such as recharge of colder water and escape of steam from side channels, leading to greater variation in discharge styles and eruption intervals. This model is consistent with the fact that eruption duration is not controlled by emptying reservoirs. We show how differences in plumbing geometries can explain various discharge styles and eruption intervals observed in El Tatio, Chile, and Yellowstone, USA.

The Grainsize Characteristics of Coignimbrite Deposits

NASA Astrophysics Data System (ADS)

Engwell, Samantha; Eychenne, Julia

2015-04-01

Due to their long atmospheric residence time, identifying the source and understanding the dispersion processes of fine-grained ash is of great importance when considering volcanic hazard and risk. An exceptionally efficient mechanism to supply large volumes of fine-grained ash to the stratosphere is the formation of co-ignimbrite plumes. Such plumes form as air is entrained at the top of propagating pyroclastic density currents, allowing a neutrally buoyant package of gas and ash to loft to high altitudes, consequently dispersing over large areas. The study of ash deposits on land and in deep sea cores has demonstrated that such events have played a major role during ignimbrite-forming eruptions, including the Tambora 1815, the Minoan (Santorini), the Campanian Ignimbrite, and the Younger Toba Tuff eruptions, as well as during more recent, pyroclastic flow-forming, intermediate sized eruptions (Vulcanian to Plinian in style), e.g. Mount St. Helens 1980, Fugen-dake (Unzen) 1991, Pinatubo 1991, Montserrat 1997 and Tungurahua 2006 eruptions. Published, as well as new results from the study of co-ignimbrite deposits, show that co-ignimbrite plumes can rise to high altitudes into the atmosphere (the co-ignimbrite plumes from the May 18, 1980 Mount St Helens blast and the Campanian Ignimbrite eruptions reached 30 - 35 km a.s.l,), potentially distribute enormous volumes of ash (the 75 ka Toba eruption and the Minoan eruption of Santorini settled >800 km3 and >25 km3 of co-ignimbrite ash, respectively), and contribute much of the ash to very large (60±6 vol% of the Campanian fallout deposit 130 to 900 km from vent), as well as intermediate size (up to 58 wt% and 52 wt% in the 2006 Tungurahua and May 18, 1980 Mount St. Helens fallout deposits, respectively) explosive eruptions. Comparison of new data with those from the published record shows that co-ignimbrite deposits are strikingly similar, regardless of eruption conditions, and have distinct grain size characteristics. The deposits are very fine grained (< 100 microns), have unimodal grain size distributions skewed towards the fines, and are more poorly sorted in medial to distal areas than tephra fall deposits from vent-derived plumes at the same distance. Deposits from a single eruption show constant grain size over hundreds to thousands of kilometres, except for a slight coarsening close to source in some cases. In intermediate size eruptions, co-ignimbrite ash often settles synchronously to vent-derived tephra, leading to bimodal grain size fallout deposits. These observations highlight the propensity of the ash to remain in the atmosphere for extended periods of time, and pose important questions regarding how the ash is deposited, and especially the role of aggregation. The uniformity of co-ignimbrite ash means that, with regards to real-time dispersion modelling during an eruption, few assumptions are required for the initial grain size, however depositional assumptions utilised when modelling vent-derived plume dispersion, may not be able to accurately reproduce co-ignimbrite depositional patterns.

Challenging dyke ascent models using novel laboratory experiments: Implications for reinterpreting evidence of magma ascent and volcanism

NASA Astrophysics Data System (ADS)

Kavanagh, Janine L.; Burns, Alec J.; Hilmi Hazim, Suraya; Wood, Elliot P.; Martin, Simon A.; Hignett, Sam; Dennis, David J. C.

2018-04-01

Volcanic eruptions are fed by plumbing systems that transport magma from its source to the surface, mostly fed by dykes. Here we present laboratory experiments that model dyke ascent to eruption using a tank filled with a crust analogue (gelatine, which is transparent and elastic) that is injected from below by a magma analogue (dyed water). This novel experimental setup allows, for the first time, the simultaneous measurement of fluid flow, sub-surface and surface deformation during dyke ascent. During injection, a penny-shaped fluid-filled crack is formed, intrudes, and traverses the gelatine slab vertically to then erupt at the surface. Polarised light shows the internal stress evolution as the dyke ascends, and an overhead laser scanner measures the surface elevation change in the lead-up to dyke eruption. Fluorescent passive-tracer particles that are illuminated by a laser sheet are monitored, and the intruding fluid's flow dynamics and gelatine's sub-surface strain evolution is measured using particle image velocimetry and digital image correlation, respectively. We identify 4 previously undescribed stages of dyke ascent. Stage 1, early dyke growth: the initial dyke grows from the source, and two fluid jets circulate as the penny-shaped crack is formed. Stage 2, pseudo-steady dyke growth: characterised by the development of a rapidly uprising, central, single pseudo-steady fluid jet, as the dyke grows equally in length and width, and the fluid down-wells at the dyke margin. Sub-surface host strain is localised at the head region and the tail of the dyke is largely static. Stage 3, pre-eruption unsteady dyke growth: an instability in the fluid flow appears as the central fluid jet meanders, the dyke tip accelerates towards the surface and the tail thins. Surface deformation is only detected in the immediate lead-up to eruption and is characterised by an overall topographic increase, with axis-symmetric topographic highs developed above the dyke tip. Stage 4 is the onset of eruption, when fluid flow is projected outwards and focused towards the erupting fissure as the dyke closes. A simultaneous and abrupt decrease in sub-surface strain occurs as the fluid pressure is released. Our results provide a comprehensive physical framework upon which to interpret evidence of dyke ascent in nature, and suggest dyke ascent models need to be re-evaluated to account for coupled intrusive and extrusive processes and improve the recognition of monitoring signals that lead to volcanic eruptions in nature.

Photogrammetric Analysis of Changes in Crater Morphology at Telica Volcano, Nicaragua from 1994 to 2016

NASA Astrophysics Data System (ADS)

Hanagan, C.; La Femina, P.

2017-12-01

Understanding processes that lead to volcanic eruptions is paramount for predicting future volcanic activity. Telica volcano, Nicaragua is a persistently active volcano with hundreds of daily, low magnitude and low frequency seismic events, high-temperature degassing, and sub-decadal VEI 1-3 eruptions. The phreatic vulcanian eruptions of 1999, 2011, and 2013, and phreatic to phreatomagmatic vulcanian eruption of 2015 are thought to have resulted by sealing of the hydrothermal system prior to the eruptions. Two mechanisms have been proposed for sealing of the volcanic system, hydrothermal mineralization and landslides covering the vent. These eruptions affect the crater morphology of Telica volcano, and therefore the exact mechanisms of change to the crater's form are of interest to provide data that may support or refute the proposed sealing mechanisms, improving our understanding of eruption mechanisms. We use a collection of photographs between February 1994 and May 2016 and a combination of qualitative and quantitative photogrammetry to detect the extent and type of changes in crater morphology associated with 2011, 2013, and 2015 eruptive activity. We produced dense point cloud models using Agisoft PhotoScan Professional for times with sufficient photographic coverage, including August 2011, March 2013, December 2015, March 2016, and May 2016. Our May 2016 model is georeferenced, and each other point cloud was differenced using the C2C tool in CloudCompare and the M3C2 method (CloudCompare plugin) Lague et al. (2013). Results of the qualitative observations and quantitative differencing reveal a general trend of material subtraction from the inner crater walls associated with eruptive activity and accumulation of material on the crater floor, often visibly sourced from the walls of the crater. Both daily activity and VEI 1-3 explosive events changed the crater morphology, and correlation between a landslide-covered vent and the 2011 and 2015 eruptive sequences exists. Though further study and integration with other date sets is required, a positive feedback mechanism between accumulation of material blocking the vent, eruption, and subsequent accumulation of material to re-block the vent remains possible.

The variation of magma discharge during basaltic eruptions

NASA Technical Reports Server (NTRS)

Wadge, G.

1981-01-01

The different types of magmatic flow in basaltic eruptions are discussed, and processes explaining the eruptive history of specific volcanoes are investigated. The effusion rate curve is divided into waxing and waning flow parts, and the ideal, elastic response of the reservoir in the waning phase is analytically shown. Historical eruption rates of Mauna Loa, Kilauea, and Etna are presented, demonstrating that for each volcano there is a trend of decreasing rate with increasing duration of eruption, a relationship not predicted by a simple elastic model of magma release. The eruptive histories of these volcanoes is explained by the processes of modification of the eruptive conduits and the continued supply of magma from depth during eruption. Discharge variations from Paricutin, Hekla, and Kilauea Iki are discussed in detail.

Toward an integrative spatiotemporal architecture of the magma plumbing system leading to systematic Plinian eruption at Montagne Pelée Martinique (Lesser Antilles)

NASA Astrophysics Data System (ADS)

Boudon, G.; Balcone-Boissard, H.; Lyonnet, E.; Morgan, D. J.

2017-12-01

The dynamic of crustal magma reservoir may be at the origin of pressure/temperature variations that may trigger magma ascent and eruption. These changes can be registered during crystal growth and can probably produce at the surface geophysical or/and geochemical signals that could be registered by monitoring network, constituting precursory signals. For volcanoes where the plumbing system is well established in terms of volume and depth for a given cycle, repetitive eruptions of the same order of magnitude and involving similar magma composition may occur. It was the case for Montagne Pelée (Martinique, Lesser Antilles), sadly known for the 1902 lava dome-forming eruption that killed 30 000 inhabitants, and that produce repetitive Plinian eruptions in the last 15 ky. Are the perturbations in the dynamic of the magma storage identical for all these eruptions and is the timescale between these perturbations and the eruptions in the same order of magnitude? In the last decade, intracristalline diffusion modelling has been increasingly used to constrain timescale of magmatic processes. Recently this kind of investigations has been coupled to a petrological model of the magma storage region to better wholly describe its behaviour through a Crystal System Analysis (CSA) approach. Here we aim at constraining the pre-eruptive dynamic of the reservoir giving birth to the Plinian eruptions at Montagne Pelée. Precisely we attempt to identify the processes at the origin of the eruptions and the timescale between this process and the eruption. By studying the last five Plinian eruptions of this volcano the question of the systematic occurrence of one process at the same time prior eruption will be discussed. To achieve this goal we performed a detailed petrological description of the eruptive products of the first Plinian phase of these eruptions to build a CSA tree through EPMA and SEM analyses, coupled to Fe-Mg diffusion modelling in orthopyroxenes to retrieve timescale between the perturbation identified in the reservoir and the eruption. We thus highlight that: i) the perturbation event is not systematically the same through all eruptions; ii) the timescale that separate this event from the eruptions is in the order of 4-6 months, significantly shorter that what was up to now estimated for large silicic eruptions.

Linking Surface Activity to the Deep Volcanic Plumbing System: the CALIPSO Borehole Observatory Project on Montserrat

NASA Astrophysics Data System (ADS)

Young, S. R.; Voight, B.; Mattioli, G. S.; Linde, A. T.; Sacks, I. S.; Malin, P. E.; Shalev, E.; Hidayat, D.; Elsworth, D.; Sparks, R. S.; Neuberg, J.; Dunkley, P. N.; Norton, G. E.; Herd, R. A.; Edmonds, M.; Thompson, G.; Jolly, A.; Bass, V.

2003-12-01

The prolonged and ongoing volcanic activity at SoufriŠre Hills Volcano (SHV), Montserrat, provides a rare chance for collecting multi-stream monitoring data in support of volcano research. Conventional surface geophysical instrumentation and detailed observational and geochemical data have enabled the development of a good understanding of surface and near-surface physical processes controlling eruptive style and intensity at SHV. However, the geophysical character and behavior of the deeper plumbing system, including magma storage area(s) and deep recharge processes, are not well understood. Developing better models for the deep system will assist in providing timely warning of large events or changes in eruptive style, and may also provide some clues as to the likely duration of the eruption. Installation of seismic and deformational monitoring instrumentation at depth enables a significant increase in signal to noise ratio so that smaller signals can be recorded and more distant sites (and thus deeper investigation depth) utilized. A variety of cycle-lengths have been noted during the eruption of SHV, and we hope that the new CALIPSO data stream will enable development of models in which cycles from a few hours to a few decades can be linked together in an integrated physical model. Cycle lengths of 7 to 14 weeks (depending on eruption rate and equating to the eruption of about 35 million cubic meters of magma) are likely to source from the shallower of the two upper crustal reservoirs indicated by geochemical evidence. The 30 to 35 year cycles (the fourth one of which marked the start of the current eruption) may relate to processes concerning input of basaltic magma to the deeper plumbing system. We also hope to document geophysical changes in the plumbing system induced by regional seismicity; many eastern Caribbean volcanoes (including SHV between 1933 and 1935 and in 1985) have demonstrated characteristics of unrest triggered or invigorated by regional tectonic earthquakes of Richter magnitude 5 and above. Events within the historical triggering threshold occur every few years; two such events have so far occurred since CALIPSO instrument installation (a Mw6.6 about 400km NE of Montserrat and a Mw5.7 about 150km NE of Montserrat). Both are at the lower end of historical triggering threshold parameters for magnitude and distance and neither produced measurable changes in macro-seismicity or ground deformation beneath SHV.

Detection, Source Location, and Analysis of Volcano Infrasound

NASA Astrophysics Data System (ADS)

McKee, Kathleen F.

The study of volcano infrasound focuses on low frequency sound from volcanoes, how volcanic processes produce it, and the path it travels from the source to our receivers. In this dissertation we focus on detecting, locating, and analyzing infrasound from a number of different volcanoes using a variety of analysis techniques. These works will help inform future volcano monitoring using infrasound with respect to infrasonic source location, signal characterization, volatile flux estimation, and back-azimuth to source determination. Source location is an important component of the study of volcano infrasound and in its application to volcano monitoring. Semblance is a forward grid search technique and common source location method in infrasound studies as well as seismology. We evaluated the effectiveness of semblance in the presence of significant topographic features for explosions of Sakurajima Volcano, Japan, while taking into account temperature and wind variations. We show that topographic obstacles at Sakurajima cause a semblance source location offset of 360-420 m to the northeast of the actual source location. In addition, we found despite the consistent offset in source location semblance can still be a useful tool for determining periods of volcanic activity. Infrasonic signal characterization follows signal detection and source location in volcano monitoring in that it informs us of the type of volcanic activity detected. In large volcanic eruptions the lowermost portion of the eruption column is momentum-driven and termed the volcanic jet or gas-thrust zone. This turbulent fluid-flow perturbs the atmosphere and produces a sound similar to that of jet and rocket engines, known as jet noise. We deployed an array of infrasound sensors near an accessible, less hazardous, fumarolic jet at Aso Volcano, Japan as an analogue to large, violent volcanic eruption jets. We recorded volcanic jet noise at 57.6° from vertical, a recording angle not normally feasible in volcanic environments. The fumarolic jet noise was found to have a sustained, low amplitude signal with a spectral peak between 7-10 Hz. From thermal imagery we measure the jet temperature ( 260 °C) and estimate the jet diameter ( 2.5 m). From the estimated jet diameter, an assumed Strouhal number of 0.19, and the jet noise peak frequency, we estimated the jet velocity to be 79 - 132 m/s. We used published gas data to then estimate the volatile flux at 160 - 270 kg/s (14,000 - 23,000 t/d). These estimates are typically difficult to obtain in volcanic environments, but provide valuable information on the eruption. At regional and global length scales we use infrasound arrays to detect signals and determine their source back-azimuths. A ground coupled airwave (GCA) occurs when an incident acoustic pressure wave encounters the Earth's surface and part of the energy of the wave is transferred to the ground. GCAs are commonly observed from sources such as volcanic eruptions, bolides, meteors, and explosions. They have been observed to have retrograde particle motion. When recorded on collocated seismo-acoustic sensors, the phase between the infrasound and seismic signals is 90°. If the sensors are separated wind noise is usually incoherent and an additional phase is added due to the sensor separation. We utilized the additional phase and the characteristic particle motion to determine a unique back-azimuth solution to an acoustic source. The additional phase will be different depending on the direction from which a wave arrives. Our technique was tested using synthetic seismo-acoustic data from a coupled Earth-atmosphere 3D finite difference code and then applied to two well-constrained datasets: Mount St. Helens, USA, and Mount Pagan, Commonwealth of the Northern Mariana Islands Volcanoes. The results from our method are within <1° - 5° of the actual and traditional infrasound array processing determined back-azimuths. Ours is a new method to detect and determine the back-azimuth to infrasonic signals, which will be useful when financial and spatial resources are limited.

Sentinel-1 interferometry and modelling of the 2014 Fogo volcano crisis

NASA Astrophysics Data System (ADS)

Nikkhoo, Mehdi; Walter, Thomas R.; Prats-Iraola, Pau

2015-04-01

The Sentinel-1 mission is a European Space Agency's mission with the aim of earth surface monitoring on land and sea. Through the ESA project INSARAP, we aim at studying the Sentinel-1 InSAR performance for different study areas, and developing new routines for TOPS data analysis. Here we describe results achieved from Sentinel-1 acquisitions over Fogo Island, Cape Verdes. A new volcanic eruption occurred on Fogo volcano in November 2014, leading to a request for assistance communicated by the European ERCC (Emergency Response Coordination Centre). The eruption occurred after a 20 yr period of quiescence inside the Cha das Caldeiras, the embayment of a pre-historic giant landslide. The eruption affected populated areas and has lead to significant loss and destruction, forcing thousands of inhabitants to leave their homes. The timely acquisitions of Sentinel-1 data allows us the comparison of the amplitude and phase differences before and after the eruption. This is one of the first applications of Sentinel-1 data, allowing testing the system and accurate measurements of the deformation processes associated with the volcano eruption. Sentinel-1 InSAR results processed by us in ascending and descending geometry, allows developing numerical models to explain the deformation. To this aim we make use of a novel boundary element code that is based on the artifact free analytical solution of triangular dislocation elements (see Nikkhoo and Walter, 2015, Geophys. J. Int., doi:10.1093/gji/ggv035). The models consider topography and complex source geometries. We find that the magma dike is largely emplaced within the subaerial part of the volcano edifice, where the steep topography has large effects on InSAR results, the surface displacement, and the parameters of the models. Embedded in an inversion scheme, we could reproduce most of the deformation signals as determined in the Sentinel-1 InSAR data, although residuals remain in localized areas that might be associated to processes different than the considered dike. This work hence shows one of the first use of Sentinel-1 data in a volcanic crisis and helps assessing the magma path at depth and associated deformation complexities, relevant for preparation and designing monitoring networks for future eruptions.

Seismicity associated with quiescent-explosive transitions at dome forming eruptions: The July 2008 Vulcanian Explosion of Soufrière Hills Volcano, Montserrat

NASA Astrophysics Data System (ADS)

Rodgers, Mel; Smith, Patrick; Mather, Tamsin A.; Pyle, David M.

2017-04-01

During long-lived dome-forming eruptions volcanoes often transition between quiescent, effusive, and explosive behaviour. Soufrière Hills Volcano (SHV), Montserrat, has been erupting since 1995 and has repeatedly transitioned between these different phases of activity. At SHV many of the largest explosions have occurred either during periods of dome growth, or as major dome collapse events at the end of extrusion phases. However, on the 29th July 2008 a vulcanian explosion marked the transition from a quiescent phase (Pause 3) to explosion and then extrusion. This was one of the largest explosions by volume and the largest to occur outside a period of lava extrusion. The eruption was preceded by one of the most intense seismic swarms ever recorded at SHV. In this study we analysed precursory seismic data to investigate the subsurface volcanic processes that culminated in this eruption. We used spectral and multiplet analysis techniques, and applied a simple parameterization approach to relate monitoring observations (seismic, SO2, visual) to subsurface interpretations. These techniques would be available to most volcano observatories. Our study suggests that an initial VT swarm, coincident with ash-venting events, can be triggered by ascent of decoupled gas ahead of rising magma. A subsequent large LF swarm shows a coincident decrease in spectral content that we interpret as magma ascent through the upper conduit system. An ash-venting event on 27 July (a few hours before peak event rate) may have triggered rapid microlite growth. We observe an increase in the spectral content of the LF swarm that is concurrent with a decrease in event rates, suggesting pressurization of the magmatic system due to inhibited magmatic outgassing. Our results suggest that pressurization of the magmatic system may have occurred in the final 24 h before the vulcanian explosion. We also observe LP and Hybrid events within the same multiplet, suggesting that these events have very similar source processes and should be considered part of the same classification at SHV. Our study demonstrates the potential for using spectral and multiplet analysis to understand subsurface magmatic processes and for investigating the transition between quiescence and eruption.

Mitigation of volcanic hazards to aviation: The need for real-time integration of multiple data sources (Invited)

NASA Astrophysics Data System (ADS)

Schneider, D. J.

2009-12-01

The successful mitigation of volcanic hazards to aviation requires rapid interpretation and coordination of data from multiple sources, and communication of information products to a variety of end users. This community of information providers and information users include volcano observatories, volcanic ash advisory centers, meteorological watch offices, air traffic control centers, airline dispatch and military flight operations centers, and pilots. Each of these entities has capabilities and needs that are unique to their situations that evolve over a range of time spans. Prior to an eruption, information about probable eruption scenarios are needed in order to allow for contingency planning. Once a hazardous eruption begins, the immediate questions are where, when, how high, and how long will the eruption last? Following the initial detection of an eruption, the need for information changes to forecasting the movement of the volcanic cloud, determining whether ground operations will be affected by ash fall, and estimating how long the drifting volcanic cloud will remain hazardous. A variety of tools have been developed and/or improved over the past several years that provide additional data sources about volcanic hazards that is pertinent to the aviation sector. These include seismic and pressure sensors, ground-based radar and lidar, web cameras, ash dispersion models, and more sensitive satellite sensors that are capable of better detecting volcanic ash, gases and aerosols. Along with these improved capabilities come increased challenges in rapidly assimilating the available data sources, which come from a variety of data providers. In this presentation, examples from the recent large eruptions of Okmok, Kasatochi, and Sarychev Peak volcanoes will be used to demonstrate the challenges faced by hazard response agencies. These eruptions produced volcanic clouds that were dispersed over large regions of the Northern Hemisphere and were observed by pilots and detected by various satellite sensors for several weeks. The disruption to aviation caused by these eruptions further emphasizes the need to improve the real-time characterization of volcanic clouds (altitude, composition, particle size, and concentration) and to better understand the impacts of volcanic ash, gases and aerosols on aircraft, flight crews, and passengers.

Frictional-faulting model for harmonic tremor before Redoubt Volcano eruptions

NASA Astrophysics Data System (ADS)

Dmitrieva, Ksenia; Hotovec-Ellis, Alicia J.; Prejean, Stephanie; Dunham, Eric M.

2013-08-01

Seismic unrest, indicative of subsurface magma transport and pressure changes within fluid-filled cracks and conduits, often precedes volcanic eruptions. An intriguing form of volcano seismicity is harmonic tremor, that is, sustained vibrations in the range of 0.5-5Hz. Many source processes can generate harmonic tremor. Harmonic tremor in the 2009 eruption of Redoubt Volcano, Alaska, has been linked to repeating earthquakes of magnitudes around 0.5-1.5 that occur a few kilometres beneath the vent. Before many explosions in that eruption, these small earthquakes occurred in such rapid succession--up to 30 events per second--that distinct seismic wave arrivals blurred into continuous, high-frequency tremor. Tremor abruptly ceased about 30 s before the explosions. Here we introduce a frictional-faulting model to evaluate the credibility and implications of this tremor mechanism. We find that the fault stressing rates rise to values ten orders of magnitude higher than in typical tectonic settings. At that point, inertial effects stabilize fault sliding and the earthquakes cease. Our model of the Redoubt Volcano observations implies that the onset of volcanic explosions is preceded by active deformation and extreme stressing within a localized region of the volcano conduit, at a depth of several kilometres.

El Cobreloa: A geyser with two distinct eruption styles

NASA Astrophysics Data System (ADS)

Namiki, Atsuko; Muñoz-Saez, Carolina; Manga, Michael

2014-08-01

We performed field measurements at a geyser nicknamed "El Cobreloa," located in the El Tatio Geyser Field, Northern Andes, Chile. The El Cobreloa geyser has two distinct eruption styles: minor eruptions and more energetic and long-lived major eruptions. Minor eruptions splash hot water intermittently over an approximately 4 min time period. Major eruptions begin with an eruption style similar to minor eruptions, but then transition to a voluminous liquid water-dominated eruption, and finally end with energetic steam discharge that continues for approximately 1 h. We calculated eruption intervals by visual observations, acoustic measurements, and ground temperature measurements and found that each eruption style has a regular interval: 4 h and 40 min for major eruptions and ˜14 min for minor eruptions. Eruptions of El Cobreloa and geochemical measurements suggest interaction of three water sources. The geyser reservoir, connected to the surface by a conduit, is recharged by a deep, hot aquifer. More deeply derived magmatic fluids heat the reservoir. Boiling in the reservoir releases steam and hot liquid water to the overlying conduit, causing minor eruptions, and heating the water in the conduit. Eventually the water in the conduit becomes warm enough to boil, leading to a steam-dominated eruption that empties the conduit. The conduit is then recharged by a shallow, colder aquifer, and the eruption cycle begins anew. We develop a model for minor eruptions which heat the water in the conduit. El Cobreloa provides insight into how small eruptions prepare the geyser system for large eruptions.

Mantle-derived trace element variability in olivines and their melt inclusions

NASA Astrophysics Data System (ADS)

Neave, David A.; Shorttle, Oliver; Oeser, Martin; Weyer, Stefan; Kobayashi, Katsura

2018-02-01

Trace element variability in oceanic basalts is commonly used to constrain the physics of mantle melting and the chemistry of Earth's deep interior. However, the geochemical properties of mantle melts are often overprinted by mixing and crystallisation processes during ascent and storage. Studying primitive melt inclusions offers one solution to this problem, but the fidelity of the melt-inclusion archive to bulk magma chemistry has been repeatedly questioned. To provide a novel check of the melt inclusion record, we present new major and trace element analyses from olivine macrocrysts in the products of two geographically proximal, yet compositionally distinct, primitive eruptions from the Reykjanes Peninsula of Iceland. By combining these macrocryst analyses with new and published melt inclusion analyses we demonstrate that olivines have similar patterns of incompatible trace element (ITE) variability to the inclusions they host, capturing chemical systematics on intra- and inter-eruption scales. ITE variability (element concentrations, ratios, variances and variance ratios) in olivines from the ITE-enriched Stapafell eruption is best accounted for by olivine-dominated fractional crystallisation. In contrast, ITE variability in olivines and inclusions from the ITE-depleted Háleyjabunga eruption cannot be explained by crystallisation alone, and must have originated in the mantle. Compatible trace element (CTE) variability is best described by crystallisation processes in both eruptions. Modest correlations between host and inclusion ITE contents in samples from Háleyjabunga suggest that melt inclusions can be faithful archives of melting and magmatic processes. It also indicates that degrees of ITE enrichment can be estimated from olivines directly when melt inclusion and matrix glass records of geochemical variability are poor or absent. Inter-eruption differences in olivine ITE systematics between Stapafell and Háleyjabunga mirror differences in melt inclusion suites, and confirm that the Stapafell eruption was fed by lower degree melts from greater depths within the melting region than the Háleyjabunga eruption. Although olivine macrocrysts from Stapafell are slightly richer in Ni than those from Háleyjabunga, their overall CTE systematics (e.g., Ni/(Mg/Fe), Fe/Mn and Zn/Fe) are inconsistent with being derived from olivine-free pyroxenites. However, the major element systematics of Icelandic basalts require lithological heterogeneity in their mantle source in the form of Fe-rich and hence fusible domains. We thus conclude that enriched heterogeneities in the Icelandic mantle are composed of modally enriched, yet nonetheless olivine-bearing, lithologies and that olivine CTE contents provide an incomplete record of lithological heterogeneity in the mantle. Modally enriched peridotites may therefore play a more important role in oceanic magma genesis than previously inferred.

A new Mantle Source Tapped During Episode 55 of the Pu'u O'o Eruption From Kilauea Volcano

NASA Astrophysics Data System (ADS)

Marske, J. P.; Pietruszka, A. J.; Garcia, M. O.; Rhodes, J. M.

2005-12-01

Over 22 years of continuous geochemical monitoring of lavas from the current Pu'u O'o eruption allows us to probe the mantle and crustal processes beneath Kilauea Volcano in unparalleled detail. Episode 55 (1997-present) marks the longest and most voluminous Pu'u O'o eruptive interval. Here we present new Pb, Sr, and Nd isotopic ratios and major- and trace-element abundances for the most recent lavas (1999-2005). MgO variation diagrams show that most of the major-element variations are related to olivine fractionation. However, Pu'u O'o lavas display longer-term systematic decreases in their TiO2, K2O, P2O5 and CaO abundances (at a given MgO) due to changes in the parental magma composition. Incompatible element ratios (K2O/TiO2, Nb/Y, Nb/Zr) and MgO-normalized abundances (Sr, Rb, K) in episode 55 lavas delimit the lowest values observed during the Pu'u O'o eruption. Earlier Pu'u O'o lavas displayed a temporal decrease in highly over moderately incompatible trace-element ratios, near constant SiO2 contents, and a gradual increase in 87Sr/86Sr. However, episode 55 lavas (between days 5500-6500) record an increase in MgO-normalized SiO2 contents and even higher 87Sr/86Sr with near constant incompatible trace-element ratios. Neither a single mantle source composition nor a change in partial melting conditions can explain these observations. Based on 226Ra-230Th-238U disequilibria and partial melting modeling of trace elements, we conclude that Pu'u O'o lavas originate from at least two distinct mantle source components: (1) a recently depleted component that was subsequently remelted to explain the overall decreases of incompatible major- and trace-element ratios and abundances, and (2) a compositionally and isotopically distinct mantle component that was not previously melted within the Hawaiian plume to explain the temporal increase in 87Sr/86Sr and SiO2 abundances and the flattening trend of incompatible trace-element ratios. This second component lies within typical Pb, Sr and Nd isotopic space for Kilauea, but represents a new source composition for the Pu'u O'o eruption. These results can be explained by a recent (1999) change in the size or location of Pu'u O'o's melting region, which allowed this new source to be tapped.

Determining the physical processes behind four large eruptions in rapid sequence in the San Juan caldera cluster (Colorado, USA)

NASA Astrophysics Data System (ADS)

Curry, Adam; Caricchi, Luca; Lipman, Peter

2017-04-01

Large, explosive volcanic eruptions can have both immediate and long-term negative effects on human societies. Statistical analyses of volcanic eruptions show that the frequency of the largest eruptions on Earth (> ˜450 km3) differs from that observed for smaller eruptions, suggesting different physical processes leading to eruption. This project will characterize the petrography, whole-rock geochemistry, mineral chemistry, and zircon geochronology of four caldera-forming ignimbrites from the San Juan caldera cluster, Colorado, to determine the physical processes leading to eruption. We collected outflow samples along stratigraphy of the three caldera-forming ignimbrites of the San Luis caldera complex: the Nelson Mountain Tuff (>500 km3), Cebolla Creek Tuff (˜250 km3), and Rat Creek Tuff (˜150 km3); and we collected samples of both outflow and intracaldera facies of the Snowshoe Mountain Tuff (>500 km3), which formed the Creede caldera. Single-crystal sanidine 40Ar/39Ar ages show that these eruptions occurred in rapid succession between 26.91 ± 0.02 Ma (Rat Creek) and 26.87 ± 0.02 Ma (Snowshoe Mountain), providing a unique opportunity to investigate the physical processes leading to a rapid sequence of large, explosive volcanic eruptions. Recent studies show that the average flux of magma is an important parameter in determining the frequency and magnitude of volcanic eruptions. High-precision isotope-dilution thermal ionization mass spectrometry (ID-TIMS) zircon geochronology will be performed to determine magma fluxes, and cross-correlation of chemical profiles in minerals will be performed to determine the periodicity of magma recharge that preceded these eruptions. Our project intends to combine these findings with similar data from other volcanic regions around the world to identify physical processes controlling the regional and global frequency-magnitude relationships of volcanic eruptions.

Development and relationship of monogenetic and polygenetic volcanic fields in time and space.

NASA Astrophysics Data System (ADS)

Germa, Aurelie; Connor, Chuck; Connor, Laura; Malservisi, Rocco

2013-04-01

The classification of volcanic systems, developed by G. P. L. Walker and colleagues, relates volcano morphology to magma transport and eruption processes. In general, distributed monogenetic volcanic fields are characterized by infrequent eruptions, low average output rate, and a low spatial intensity of the eruptive vents. In contrast, central-vent-dominated systems, such as stratovolcanoes, central volcanoes and lava shields are characterized by frequent eruptions, higher average flux rates, and higher spatial intensity of eruptive vents. However, it has been observed that a stratovolcano is often associated to parasitic monogenetic vents on its flanks, related to the central silicic systems, and surrounded by an apron of monogenetic edifices that are part of the volcanic field but independent from the principal central system. It appears from spatial distribution and time-volume relationships that surface area of monogenetic fields reflects the lateral extent of the magma source region and the lack of magma focusing mechanisms. In contrast, magma is focused through a unique conduit system for polygenetic volcanoes, provided by a thermally and mechanically favorable pathway toward the surface that is maintained by frequent and favorable stress conditions. We plan to relate surface observations of spatio-temporal location of eruptive vents and evolution of the field area through time to processes that control magma focusing during ascent and storage in the crust. We choose to study fields that range from dispersed to central-vent dominated, through transitional fields (central felsic system with peripheral field of monogenetic vents independent from the rhyolitic system). We investigate different well-studied volcanic fields in the Western US and Western Europe in order to assess influence of the geodynamic setting and tectonic stress on the spatial distribution of magmatism. In summary, incremental spatial intensity maps should reveal how fast a central conduit is created during the development of a volcanic field, and how this could influence the outbreak of dispersed monogenetic volcanoes that are not geochemically linked to the central system.

Lattice Boltzmann modeling to explain volcano acoustic source.

PubMed

Brogi, Federico; Ripepe, Maurizio; Bonadonna, Costanza

2018-06-22

Acoustic pressure is largely used to monitor explosive activity at volcanoes and has become one of the most promising technique to monitor volcanoes also at large scale. However, no clear relation between the fluid dynamics of explosive eruptions and the associated acoustic signals has yet been defined. Linear acoustic has been applied to derive source parameters in the case of strong explosive eruptions which are well-known to be driven by large overpressure of the magmatic fluids. Asymmetric acoustic waveforms are generally considered as the evidence for supersonic explosive dynamics also for small explosive regimes. We have used Lattice-Boltzmann modeling of the eruptive fluid dynamics to analyse the acoustic wavefield produced by different flow regimes. We demonstrate that acoustic waveform well reproduces the flow dynamics of a subsonic fluid injection related to discrete explosive events. Different volumetric flow rate, at low-Mach regimes, can explain both the observed symmetric and asymmetric waveform. Hence, asymmetric waveforms are not necessarily related to the shock/supersonic fluid dynamics of the source. As a result, we highlight an ambiguity in the general interpretation of volcano acoustic signals for the retrieval of key eruption source parameters, necessary for a reliable volcanic hazard assessment.

The anatomy of a (potential) disaster: Volcanoes, behavior, and population viability of the short-tailed albatross (Phoebastria albatrus)

USGS Publications Warehouse

Finkelstein, M.E.; Wolf, S.; Goldman, M.; Doak, D.F.; Sievert, P.R.; Balogh, G.; Hasegawa, H.

2010-01-01

Catastrophic events, either from natural (e.g., hurricane) or human-induced (e.g., forest clear-cut) processes, are a well-known threat to wild populations. However, our lack of knowledge about population-level effects of catastrophic events has inhibited the careful examination of how catastrophes affect population growth and persistence. For the critically endangered short-tailed albatross (Phoebastria albatrus), episodic volcanic eruptions are considered a serious catastrophic threat since approximately 80% of the global population of ???2500 birds (in 2006) currently breeds on an active volcano, Torishima Island. We evaluated how short-tailed albatross population persistence is affected by the catastrophic threat of a volcanic eruption relative to chronic threats. We also provide an example for overcoming the seemingly overwhelming problems created by modelling the population dynamics of a species with limited demographic data by incorporating uncertainty in our analysis. As such, we constructed a stochastic age-based matrix model that incorporated both catastrophic mortality due to volcanic eruptions and chronic mortality from several potential sources (e.g., contaminant exposure, fisheries bycatch) to determine the relative effects of these two types of threats on short-tailed albatross population growth and persistence. Modest increases (1%) in chronic (annual) mortality had a 2.5-fold greater effect on predicted short-tailed albatross stochastic population growth rate (lambda) than did the occurrence of periodic volcanic eruptions that follow historic eruption frequencies (annual probability of eruption 2.2%). Our work demonstrates that periodic catastrophic volcanic eruptions, despite their dramatic nature, are less likely to affect the population viability and recovery of short-tailed albatross than low-level chronic mortality. ?? 2009 Elsevier Ltd.

Evolution of the 2015 Cotopaxi eruption revealed by combined geochemical & seismic observations

USGS Publications Warehouse

Hidalgo, Silvana; Battaglia, Jean; Arellano, Santiago; Sierra, Daniel; Bernard, Benjamin; Parra, Rene; Kelly, Peter; Dinger, Florian; Barrington, Charlotte; Samaniego, Pablo

2018-01-01

Through integration of multiple data streams to monitor volcanic unrest scientists are able to make more robust eruption forecast and to obtain a more holistic interpretation of volcanic systems. We examined gas emission and gas geochemistry, seismic and petrologic data recorded during the 2015 unrest of Cotopaxi (Ecuador) in order to decipher the origin and temporal evolution of this eruption. Identification of families of similar seismic events and the use of seismic amplitude ratios reveals temporal changes in volcanic processes. SO2 (300 to 24000 t/d), BrO/SO2 (5-10 x10-5), SO2/HCl (5.8 ± 4.8 and 6.6 ± 3.0) and CO2/SO2 (0.6 to 2.1) measured throughout the eruption indicate a shallow magmatic source. Bulk ash and glass chemistry indicate a homogenous andesitic (SiO2 wt%=56.94 ± 0.25) magma having undergone extensive S-exsolution and degassing during ascent. These data lead us to interpret this eruption as a magma intrusion and ascend to shallow levels. The intrusion progressively interacted with the hydrothermal system, boiled off water, and produced hydromagmatic explosions. A small volume of this intrusion continued to fragment and produced episodic ash emissions until it was sufficiently degassed and rheologically stiff. Based on the 470 kt of measured SO2 we estimate that ~ 65.3 x106 m3 of magma were required to supply the emitted gases. This volume exceeds the volume of erupted juvenile material by a factor of 50. This result emphasizes the importance of careful monitoring of Cotopaxi to identify the intrusion of a new batch of magma, which could rejuvenate the non-erupted material.

Numerical simulation of plagioclase rim growth during magma ascent at Bezymianny Volcano, Kamchatka

NASA Astrophysics Data System (ADS)

Gorokhova, N. V.; Melnik, O. E.; Plechov, P. Yu.; Shcherbakov, V. D.

2013-08-01

Slow CaAl-NaSi interdiffusion in plagioclase crystals preserves chemical zoning of plagioclase in detail, which, along with strong dependence of anorthite content in plagioclase on melt composition, pressure, and temperature, make this mineral an important source of information on magma processes. A numerical model of zoned crystal growth is developed in the paper. The model is based on equations of multicomponent diffusion with diagonal cross-component diffusion terms and accounts for mass conservation on the melt-crystal interface and growth rate controlled by undercooling. The model is applied to the data of plagioclase rim zoning from several recent Bezymianny Volcano (Kamchatka) eruptions. We show that an equilibrium growth model cannot explain crystallization of naturally observed plagioclase during magma ascent. The developed non-equilibrium model reproduced natural plagioclase zoning and allowed magma ascent rates to be constrained. Matching of natural and simulated zoning suggests ascent from 100 to 50 MPa during 15-20 days. Magma ascent rate from 50 MPa to the surface varies from eruption to eruption: plagioclase zoning from the December 2006 eruption suggests ascent to the surface in less than 1 day, whereas plagioclase zoning from March 2000 and May 2007 eruptions are better explained by magma ascent over periods of more than 30 days). Based on comparison of diffusion coefficients for individual elements a mechanism of atomic diffusion during plagioclase crystallization is proposed.

Waveform Template Matching and Analysis of Hydroacoustic Events from the April-May 2015 Eruption of Axial Volcano

NASA Astrophysics Data System (ADS)

Mann, M. E.; Bohnenstiehl, D. R.; Weis, J.

2016-12-01

The submarine emplacement of new lava flows during the 2015 eruption of Axial Volcano generated a series of impulsive acoustic signals that were captured by seismic and hydrophone sensors deployed as part of the Ocean Observatories Initiative cabled array network. A catalog of >37,000 explosions was created using a four-channel waveform matching routine using 800 template arrivals. Most of the explosions are sourced from a set of lava mounds erupted along the volcano's northern rift; however, a subset of 400 explosions are located within the caldera and track the flow of lava from a vent near its eastern rim. The earliest explosion occurs at 08:00 UTC on April 24, approximately four hours after the seismicity rate began to increase and two hours after bottom pressure recorders indicate the caldera floor began to subside. Between April 24 and 28 event rates are sustained at 1000/day. The rate then decreases gradually with explosive activity ending on 21 May, coincident with the initial re-inflation of the caldera. The windowed coefficient of variation of the inter-event time is approximately 1 throughout the eruption, consistent with a random process. The size-frequency distribution shows a bimodal pattern, with the loudest explosions, having received levels up to 157 dB re 1 micro-Pa, being produced during the first few hours of the eruption.

Variations in magma supply rate at Kilauea Volcano, Hawaii

USGS Publications Warehouse

Dvorak, John J.; Dzurisin, Daniel

1993-01-01

When an eruption of Kilauea lasts more than 4 months, so that a well-defined conduit has time to develop, magma moves freely through the volcano from a deep source to the eruptive site at a constant rate of 0.09 km3/yr. At other times, the magma supply rate to Kilauea, estimated from geodetic measurements of surface displacements, may be different. For example, after a large withdrawal of magma from the summit reservoir, such as during a rift zone eruption, the magma supply rate is high initially but then lessens and exponentially decays as the reservoir refills. Different episodes of refilling may have different average rates of magma supply. During four year-long episodes in the 1960s, the annual rate of refilling varied from 0.02 to 0.18 km3/yr, bracketing the sustained eruptive rate of 0.09 km3/yr. For decade-long or longer periods, our estimate of magma supply rate is based on long-term changes in eruptive rate. We use eruptive rate because after a few dozen eruptions the volume of magma that passes through the summit reservoir is much larger than the net change of volume of magma stored within Kilauea. The low eruptive rate of 0.009 km3/yr between 1840 and 1950, compared to an average eruptive rate of 0.05 km3/yr since 1950, suggests that the magma supply rate was lower between 1840 and 1950 than it has been since 1950. An obvious difference in activity before and since 1950 was the frequency of rift zone eruptions: eight rift zone eruptions occurred between 1840 and 1950, but more than 20 rift zone eruptions have occurred since 1950. The frequency of rift zone eruptions influences magma supply rate by suddenly lowering pressure of the summit magma reservoir, which feeds magma to rift zone eruptions. A temporary drop of reservoir pressure means a larger-than-normal pressure difference between the reservoir and a deeper source, so magma is forced to move upward into Kilauea at a faster rate.

Ground surface deformation patterns, magma supply, and magma storage at Okmok volcano, Alaska, from InSAR analysis: 2. Coeruptive deflation, July-August 2008

USGS Publications Warehouse

Lu, Zhong; Dzurisin, Daniel

2010-01-01

A hydrovolcanic eruption near Cone D on the floor of Okmok caldera, Alaska, began on 12 July 2008 and continued until late August 2008. The eruption was preceded by inflation of a magma reservoir located beneath the center of the caldera and ∼3 km below sea level (bsl), which began immediately after Okmok's previous eruption in 1997. In this paper we use data from several radar satellites and advanced interferometric synthetic aperture radar (InSAR) techniques to produce a suite of 2008 coeruption deformation maps. Most of the surface deformation that occurred during the eruption is explained by deflation of a Mogi-type source located beneath the center of the caldera and 2–3 km bsl, i.e., essentially the same source that inflated prior to the eruption. During the eruption the reservoir deflated at a rate that decreased exponentially with time with a 1/e time constant of ∼13 days. We envision a sponge-like network of interconnected fractures and melt bodies that in aggregate constitute a complex magma storage zone beneath Okmok caldera. The rate at which the reservoir deflates during an eruption may be controlled by the diminishing pressure difference between the reservoir and surface. A similar mechanism might explain the tendency for reservoir inflation to slow as an eruption approaches until the pressure difference between a deep magma production zone and the reservoir is great enough to drive an intrusion or eruption along the caldera ring-fracture system.

Ground surface deformation patterns, magma supply, and magma storage at Okmok volcano, Alaska, from InSAR analysis: 1. Intereruption deformation, 1997–2008

USGS Publications Warehouse

Lu, Zhong; Dzurisin, Daniel; Biggs, Juliet; Wicks, Charles; McNutt, Steve

2010-01-01

Starting soon after the 1997 eruption at Okmok volcano and continuing until the start of the 2008 eruption, magma accumulated in a storage zone centered ~3.5 km beneath the caldera floor at a rate that varied with time. A Mogi-type point pressure source or finite sphere with a radius of 1 km provides an adequate fit to the deformation field portrayed in time-sequential interferometric synthetic aperture radar images. From the end of the 1997 eruption through summer 2004, magma storage increased by 3.2–4.5 × 107 m3, which corresponds to 75–85% of the magma volume erupted in 1997. Thereafter, the average magma supply rate decreased such that by 10 July 2008, 2 days before the start of the 2008 eruption, magma storage had increased by 3.7–5.2 × 107 m3 or 85–100% of the 1997 eruption volume. We propose that the supply rate decreased in response to the diminishing pressure gradient between the shallow storage zone and a deeper magma source region. Eventually the effects of continuing magma supply and vesiculation of stored magma caused a critical pressure threshold to be exceeded, triggering the 2008 eruption. A similar pattern of initially rapid inflation followed by oscillatory but generally slowing inflation was observed prior to the 1997 eruption. In both cases, withdrawal of magma during the eruptions depressurized the shallow storage zone, causing significant volcano-wide subsidence and initiating a new intereruption deformation cycle.

Wideband acoustic records of explosive volcanic eruptions at Stromboli: New insights on the explosive process and the acoustic source

NASA Astrophysics Data System (ADS)

Goto, A.; Ripepe, M.; Lacanna, G.

2014-06-01

Wideband acoustic waves, both inaudible infrasound (<20 Hz) and audible component (>20 Hz), generated by strombolian eruptions were recorded at 5 kHz and correlated with video images. The high sample rate revealed that in addition to the known initial infrasound, the acoustic signal includes an energetic high-frequency (typically >100 Hz) coda. This audible signal starts before the positive infrasound onset goes negative. We suggest that the infrasonic onset is due to magma doming at the free surface, whereas the immediate high-frequency signal reflects the following explosive discharge flow. During strong gas-rich eruptions, positively skewed shockwave-like components with sharp compression and gradual depression appeared. We suggest that successive bursting of overpressurized small bubbles and the resultant volcanic jets sustain the highly gas-rich explosions and emit the audible sound. When the jet is supersonic, microexplosions of ambient air entrained in the hot jet emit the skewed waveforms.

Electrification processes and lightning generation in volcanic plumes—observations from recent eruptions

NASA Astrophysics Data System (ADS)

Van Eaton, A. R.; Smith, C. M.; Schneider, D. J.

2017-12-01

Lightning in volcanic plumes provides a promising way to monitor ash-producing eruptions and investigate their dynamics. Among the many methods of lightning detection are global networks of sensors that detect electromagnetic radiation in the very low frequency band (3-30 kHz), including the World Wide Lightning Location Network. These radio waves propagate thousands of kilometers at the speed of light, providing an opportunity for rapid detection of explosive volcanism anywhere in the world. Lightning is particularly valuable as a near real-time indicator of ash-rich plumes that are hazardous to aviation. Yet many fundamental questions remain. Under what conditions does electrical activity in volcanic plumes become powerful, detectable lightning? And conversely, can we use lightning to illuminate eruption processes and hazards? This study highlights recent observations from the eruptions of Redoubt (Alaska, 2009), Kelud (Indonesia, 2014), Calbuco (Chile, 2015), and Bogoslof (Alaska, 2017) to examine volcanic lighting from a range of eruption styles (Surtseyan to Plinian) and mass eruption rates from 10^5 to 10^8 kg/s. It is clear that lightning stroke-rates do not scale in a simple way with mass eruption rate or plume height across different eruptions. However, relative changes in electrical activity through individual eruptions relate to changes in eruptive intensity, ice content, and volcanic plume processes (fall vs. flow).

Magma Dynamics at Axial Seamount, Juan de Fuca Ridge, from Seafloor Deformation Data

NASA Astrophysics Data System (ADS)

Baumgardt, E.; Nooner, S. L.; Chadwick, W.

2014-12-01

Axial Seamount is located about 480 km west of the Oregon coast at the intersection of the Cobb hotspot and the Juan de Fuca Ridge. Two eruptions have been observed since routine observations began in the 1990's, one in January 1998 and the other in April 2011. Precise bottom pressure measurements have documented an inflation/deflation cycle within Axial's summit caldera. The slow inflation observed at the center of the caldera was punctuated by sudden rapid deflation of 3.2 m during the 1998 eruption and 2.4 m during the 2011 eruption. Pressure data collected in September 2013 from continuously recording bottom pressure recorders and campaign-style measurements with an ROV indicates that Axial Seamount inflated 1.57 m from April 2011 to September 2013 at an average inflation rate of 61 cm/yr, meaning it had already recovered more than 65% of the deflation from the 2011 eruption within just 2.4 years. The geometry and location of the deformation source is not well constrained by the spatially-sparse pressure data, particularly for the most recent co-eruption deflation and post-eruption inflation signals. Here, we use geodetic data collected in September 2013 to test the fit of multiple numerical models of increasing complexity. We show that for this time period (since April 2011) neither a simple point deformation source (Mogi model) nor an oblate spheroid (penny-shaped crack) provide a good fit to the data. We then use finite element models to build more complex inflation geometries, guided by recent seismically imaged magma reservoirs, in an attempt to understand the source(s) of the observed deformation pattern. The recent seismic data provide good constraints on magma reservoir geometry and show the most robust melt occurs under the southeast part of the caldera at Axial. However, previous geodetic measurements at Axial have consistently shown a deformation source near the caldera center. We use numerical modeling to attempt to reconcile these differences.

Source and dynamics of a volcanic caldera unrest: Campi Flegrei, 1983-84.

PubMed

De Siena, Luca; Chiodini, Giovanni; Vilardo, Giuseppe; Del Pezzo, Edoardo; Castellano, Mario; Colombelli, Simona; Tisato, Nicola; Ventura, Guido

2017-08-14

Despite their importance for eruption forecasting the causes of seismic rupture processes during caldera unrest are still poorly reconstructed from seismic images. Seismic source locations and waveform attenuation analyses of earthquakes in the Campi Flegrei area (Southern Italy) during the 1983-1984 unrest have revealed a 4-4.5 km deep NW-SE striking aseismic zone of high attenuation offshore Pozzuoli. The lateral features and the principal axis of the attenuation anomaly correspond to the main source of ground uplift during the unrest. Seismic swarms correlate in space and time with fluid injections from a deep hot source, inferred to represent geochemical and temperature variations at Solfatara. These swarms struck a high-attenuation 3-4 km deep reservoir of supercritical fluids under Pozzuoli and migrated towards a shallower aseismic deformation source under Solfatara. The reservoir became aseismic for two months just after the main seismic swarm (April 1, 1984) due to a SE-to-NW directed input from the high-attenuation domain, possibly a dyke emplacement. The unrest ended after fluids migrated from Pozzuoli to the location of the last caldera eruption (Mt. Nuovo, 1538 AD). The results show that the high attenuation domain controls the largest monitored seismic, deformation, and geochemical unrest at the caldera.

Using Geological Implications of a Physical Libration to Constrain Enceladus' Libration State

NASA Technical Reports Server (NTRS)

Hurford, T. A.; Bills, B. G.; Helfenstein, P.; Greenberg, R.; Hoppa, G. V.; Hamilton, D. P.

2009-01-01

Observations of Enceladus' south pole revealed large rifts in the crust, called "tiger stripes", which exhibit higher temperatures than the surrounding terrain and are likely sources of observed eruptions. Tidal stress may periodically open the tiger stripe rifts, controlling the timing and location of eruptions. Moreover, shear motion along rifts may produce the heat to drive eruptions.

Discriminating assimilants and decoupling deep- vs. shallow-level crystal records at Mount Adams using 238U-230Th disequilibria and Os isotopes

USGS Publications Warehouse

Jicha, B.R.; Johnson, C.M.; Hildreth, W.; Beard, B.L.; Hart, G.L.; Shirey, S.B.; Singer, B.S.

2009-01-01

A suite of 23 basaltic to dacitic lavas erupted over the last 350??kyr from the Mount Adams volcanic field has been analyzed for U-Th isotope compositions to evaluate the roles of mantle versus crustal components during magma genesis. All of the lavas have (230Th/238U) > 1 and span a large range in (230Th/232Th) ratios, and most basalts have higher (230Th/232Th) ratios than andesites and dacites. Several of the lavas contain antecrysts (crystals of pre-existing material), yet internal U-Th mineral isochrons from six of seven lavas are indistinguishable from their eruption ages. This indicates a relatively brief period of time between crystal growth and eruption for most of the phenocrysts (olivine, clinopyroxene, plagioclase, magnetite) prior to eruption. One isochron gave a crystallization age that is ~ 20-25??ka older than its corresponding eruptive age, and is interpreted to reflect mixing of older and juvenile crystals or a protracted period of magma storage in the crust. Much of the eruptive volume since 350??ka consists of lavas that have small to moderate 230Th excesses (2-16%), which are likely inherited from melting of a garnet-bearing intraplate ("OIB-like") mantle source. Following melt generation and subsequent migration through the upper mantle, most Mt. Adams magmas interacted with young, mafic lower crust, as indicated by 187Os/188Os ratios that are substantially more radiogenic than the mantle or those expected via mixing of subducted material and the mantle wedge. Moreover, Os-Th isotope variations suggest that unusually large 230Th excesses (25-48%) and high 187Os/188Os ratios in some peripheral lavas reflect assimilation of small degree partial melts of pre-Quaternary basement that had residual garnet or Al-rich clinopyroxene. Despite the isotopic evidence for lower crustal assimilation, these processes are not generally recorded in the erupted phenocrysts, indicating that the crystal record of the deep-level 'cryptic' processes has been decoupled from shallow-level crystallization. ?? 2008 Elsevier B.V.

AN ERUPTIVE HOT-CHANNEL STRUCTURE OBSERVED AT METRIC WAVELENGTH AS A MOVING TYPE-IV SOLAR RADIO BURST

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vasanth, V.; Chen, Yao; Feng, Shiwei

2016-10-10

Hot-channel (HC) structure, observed in the high-temperature passbands of the Atmospheric Imaging Assembly/ Solar Dynamic Observatory , is regarded as one candidate of coronal flux rope that is an essential element of solar eruptions. Here, we present the first radio imaging study of an HC structure in the metric wavelength. The associated radio emission manifests as a moving type-IV (t-IVm) burst. We show that the radio sources co-move outward with the HC, indicating that the t-IV emitting energetic electrons are efficiently trapped within the structure. The t-IV sources at different frequencies present no considerable spatial dispersion during the early stagemore » of the event, while the sources spread gradually along the eruptive HC structure at later stage with significant spatial dispersion. The t-IV bursts are characterized by a relatively high brightness temperature (∼10{sup 7}–10{sup 9} K), a moderate polarization, and a spectral shape that evolves considerably with time. This study demonstrates the possibility of imaging the eruptive HC structure at the metric wavelength and provides strong constraints on the t-IV emission mechanism, which, if understood, can be used to diagnose the essential parameters of the eruptive structure.« less

Application of Microbeam Techniques to Identifying and Assessing Comagmatic Mixing Between Summit and Rift Eruptions at Kilauea Volcano (Invited)

NASA Astrophysics Data System (ADS)

Thornber, C. R.; Rowe, M. C.; Adams, D. T.; Orr, T. R.

2010-12-01

Near-continuous eruption of Kilauea Volcano since 1983 has yielded an extensive record of glass, phenocryst and melt-inclusion chemistry from well-quenched lava that can be correlated with geophysical and geological monitoring data. Eruption temperatures are determined using glass thermometry. Microbeam evaluation of phenocryst mineralogy, morphology, texture, zoning and melt inclusions helps to constrain magma storage and transport within the edifice and to track the evolution of shallow magmatic plumbing during this prolonged eruptive era. For most of this eruption up to April 2001, east rift lava was olivine-phyric and olivine-liquid relations indicated equilibrium crystallization during summit-to-rift magma transport. From 2001 to present, most lava erupted from vents near Pu`u O`o has been a relatively low-temperature “hybrid”, characterized by a disequilibrium low-pressure phenocryst assemblage. Olivine (Fo81.5-80.5) coexists with phenocrysts of lower temperature clinopyroxene (±plagioclase, ±Fe-rich olivine). Mixing between hotter and cooler magma is texturally documented by complex pyroxene zoning and resorption and olivine overgrowths on resorbed pyroxene. The co-magmatic mixing is not apparent in bulk lava analyses, since both components are fractionates of parent magmas with indistinguishable trace-element signatures. Post-2001 rift-zone lava indicates perpetual flushing of stored magma by hotter recharge magma rising from the mantle source. Geophysical and gas monitoring data confirm an increase in magma supply to Kilauea Volcano between 2001 and 2008, which we have interpreted as increasing the efficiency of the flushing process. Since March 2008, the petrology of the new summit lava lake and contemporaneously erupted rift zone lava provides new perspective on complexities of magma degassing, crystallization and mixing prior to rift eruption. Bulk lava chemistry, SIMS and LA-ICPMS analyses of matrix glasses and olivine melt-inclusions in both rift zone lava and summit tephra reveal identical trace-element concentrations, thus confirming that both eruption sites share a common magma source. Because Kilauea magma degasses all of its primary sulfur (~1200 to 1500 ppm) at pressures less than 100 bars, shallow summit-to-rift magma mixing and crystallization is quantified by study of relative sulfur concentrations in melt inclusions. For higher temperature magma at the summit, olivine (Fo82.0-83.5) contains melt inclusions with 600-1400 ppm S. A small population of rift zone phenocrysts have similar sulfur contents, while typical rift zone olivine inclusions contain 300-700 ppm S. Complex zoned pyroxene phenocrysts with multiple inclusions have trapped melts of low to high sulfur concentrations ranging from100 to 1000 ppm. Collectively, these microbeam observations provide evidence for dynamic pre-eruptive comingling between hotter, sulfur-rich magma rising beneath the summit with a denser, cooler and degassed pyroxene-bearing magma mush, prior to eruption on the east rift.

Sequential assimilation of volcanic monitoring data to quantify eruption potential: Application to Kerinci volcano

NASA Astrophysics Data System (ADS)

Zhan, Yan; Gregg, Patricia M.; Chaussard, Estelle; Aoki, Yosuke

2017-12-01

Quantifying the eruption potential of a restless volcano requires the ability to model parameters such as overpressure and calculate the host rock stress state as the system evolves. A critical challenge is developing a model-data fusion framework to take advantage of observational data and provide updates of the volcanic system through time. The Ensemble Kalman Filter (EnKF) uses a Monte Carlo approach to assimilate volcanic monitoring data and update models of volcanic unrest, providing time-varying estimates of overpressure and stress. Although the EnKF has been proven effective to forecast volcanic deformation using synthetic InSAR and GPS data, until now, it has not been applied to assimilate data from an active volcanic system. In this investigation, the EnKF is used to provide a “hindcast” of the 2009 explosive eruption of Kerinci volcano, Indonesia. A two-sources analytical model is used to simulate the surface deformation of Kerinci volcano observed by InSAR time-series data and to predict the system evolution. A deep, deflating dike-like source reproduces the subsiding signal on the flanks of the volcano, and a shallow spherical McTigue source reproduces the central uplift. EnKF predicted parameters are used in finite element models to calculate the host-rock stress state prior to the 2009 eruption. Mohr-Coulomb failure models reveal that the shallow magma reservoir is trending towards tensile failure prior to 2009, which may be the catalyst for the 2009 eruption. Our results illustrate that the EnKF shows significant promise for future applications to forecasting the eruption potential of restless volcanoes and hind-cast the triggering mechanisms of observed eruptions.

Solar Eruptive Flares: from Physical Understanding to Probabilistic Forecasting

NASA Astrophysics Data System (ADS)

Georgoulis, M. K.

2013-12-01

We describe a new, emerging physical picture of the triggering of major solar eruptions. First, we discuss and aim to interpret the single distinguishing feature of tight, shear-ridden magnetic polarity inversion lines (PILs) in solar active regions, where most of these eruptions occur. Then we analyze the repercussions of this feature, that acts to form increasingly helical pre-eruption structures. Eruptions, with the CME progenitor preceding the flare, tend to release parts of the accumulated magnetic free energy and helicity that are always much smaller than the respective budgets of the source active region. These eruption-related decreases, however, are not optimal for eruption forecasting - this role is claimed by physically intuitive proxy parameters that could show increased pre-eruption sensitivity at time scales practical for prediction. Concluding, we show how reconciling this new information - jointly enabled by the exceptional resolution and quality of Hinode and cadence of SDO data - can lead to advances in understanding that outline the current state-of-the-art of our eruption-forecasting capability.

Numerical models of volcanic eruption plumes: inter-comparison and sensitivity

NASA Astrophysics Data System (ADS)

Costa, Antonio; Suzuki, Yujiro; Folch, Arnau; Cioni, Raffaello

2016-10-01

The accurate description of the dynamics of convective plumes developed during explosive volcanic eruptions represents one of the most crucial and intriguing challenges in volcanology. Eruptive plume dynamics are significantly affected by complex interactions with the surrounding atmosphere, in the case of both strong eruption columns, rising vertically above the tropopause, and weak volcanic plumes, developing within the troposphere and often following bended trajectories. The understanding of eruptive plume dynamics is pivotal for estimating mass flow rates of volcanic sources, a crucial aspect for tephra dispersion models used to assess aviation safety and tephra fallout hazard. For these reasons, several eruption column models have been developed in the past decades, including the more recent sophisticated computational fluid dynamic models.

Minifilament Eruption as the Source of a Blowout Jet, C-class Flare, and Type-III Radio Burst

NASA Astrophysics Data System (ADS)

Hong, Junchao; Jiang, Yunchun; Yang, Jiayan; Li, Haidong; Xu, Zhe

2017-01-01

We report a strong minifilament eruption associated with Geostationary Operational Environmental Satellite C1.6 flare and WIND type-III radio burst. The minifilament, which lies at the periphery of active region 12259, is detected by Hα images from the New Vacuum Solar Telescope. The minifilament undergoes a partial and then a full eruption. Simultaneously, two co-spatial jets are successively observed in extreme ultraviolet images from the Solar Dynamic Observatory. The first jet exhibits a typical fan-spine geometry, suggesting that the co-spatial minifilament is possibly embedded in magnetic fields with a fan-spine structure. However, the second jet displays blowout morphology when the entire minifilament erupts upward, leaving behind a hard X-ray emission source in the base. Differential emission measure analyses show that the eruptive region is heated up to about 4 MK during the fan-spine jet, while up to about 7 MK during the blowout jet. In particular, the blowout jet is accompanied by an interplanetary type-III radio burst observed by WIND/WAVES in the frequency range from above 10 to 0.1 MHz. Hence, the minifilament eruption is correlated with the interplanetary type-III radio burst for the first time. These results not only suggest that coronal jets can result from magnetic reconnection initiated by erupting minifilaments with open fields, but also shed light on the potential influence of minifilament eruption on interplanetary space.

MINIFILAMENT ERUPTION AS THE SOURCE OF A BLOWOUT JET, C-CLASS FLARE, AND TYPE-III RADIO BURST

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Junchao; Jiang, Yunchun; Yang, Jiayan

We report a strong minifilament eruption associated with Geostationary Operational Environmental Satellite C1.6 flare and WIND type-III radio burst. The minifilament, which lies at the periphery of active region 12259, is detected by H α images from the New Vacuum Solar Telescope. The minifilament undergoes a partial and then a full eruption. Simultaneously, two co-spatial jets are successively observed in extreme ultraviolet images from the Solar Dynamic Observatory . The first jet exhibits a typical fan-spine geometry, suggesting that the co-spatial minifilament is possibly embedded in magnetic fields with a fan-spine structure. However, the second jet displays blowout morphology whenmore » the entire minifilament erupts upward, leaving behind a hard X-ray emission source in the base. Differential emission measure analyses show that the eruptive region is heated up to about 4 MK during the fan-spine jet, while up to about 7 MK during the blowout jet. In particular, the blowout jet is accompanied by an interplanetary type-III radio burst observed by WIND /WAVES in the frequency range from above 10 to 0.1 MHz. Hence, the minifilament eruption is correlated with the interplanetary type-III radio burst for the first time. These results not only suggest that coronal jets can result from magnetic reconnection initiated by erupting minifilaments with open fields, but also shed light on the potential influence of minifilament eruption on interplanetary space.« less

Seismicity at Old Faithful Geyser: an isolated source of geothermal noise and possible analogue of volcanic seismicity

NASA Astrophysics Data System (ADS)

Kieffer, Susan Werner

1984-09-01

Old Faithful Geyser in Yellowstone National Park, U.S.A., is a relatively isolated source of seismic noise and exhibits seismic behavior similar to that observed at many volcanoes, including "bubblequakes" that resemble B-type "earthquakes", harmonic tremor before and during eruptions, and periods of seismic quiet prior to eruptions. Although Old Faithful differs from volcanoes in that the conduit is continuously open, that rock-fracturing is not a process responsible for seismicity, and that the erupting fluid is inviscid H 2O rather than viscous magma, there are also remarkable similarities in the problems of heat and mass recharge to the system, in the eruption dynamics, and in the seismicity. Water rises irregularly into the immediate reservoir of Old Faithful as recharge occurs, a fact that suggests that there are two enlarged storage regions: one between 18 and 22 m (the base of the immediate reservoir) and one between about 10 and 12 m depth. Transport of heat from hot water or steam entering at the base of the recharging water column into cooler overlying water occurs by migration of steam bubbles upward and their collapse in the cooler water, and by episodes of convective overturn. An eruption occurs when the temperature of the near-surface water exceeds the boiling point if the entire water column is sufficiently close to the boiling curve that the propagation of pressure-release waves (rarefactions) down the column can bring the liquid water onto the boiling curve. The process of conversion of the liquid water in the conduit at the onset of an eruption into a two-phase liquid-vapor mixture takes on the order of 30 s. The seismicity is directly related to the sequence of filling and heating during the recharge cycle, and to the fluid mechanics of the eruption. Short (0.2-0.3 s), monochromatic, high-frequency events (20-60 Hz) resembling unsustained harmonic tremor and, in some instances, B-type volcanic earthquakes, occur when exploding or imploding bubbles of steam cause transient vibrations of the fluid column. The frequency of the events is determined by the length of the water column and the speed of sound of the fluid in the conduit when these events occur; damping is controlled by the characteristic and hydraulic impedances, which depend on the above parameters, as well as on the recharge rate of the fluid. Two periods of reduced seismicity (of a few tens of seconds to nearly a minute in duration) occur during the recharge cycle, apparently when the water rises rapidly through the narrow regions of the conduit, causing a sudden pressure increase that temporarily suppresses steam bubble formation. A period of decreased seismicity also precedes preplay or an eruption; this appears to be the time when rising steam bubbles move into a zone of boiling that is acoustically decoupled from the wall of the conduit because of the acoustic impedance mismatch between boiling water ( ρ c ˜ 10 3g cm -2 s -1) and rock ( ρ c ˜ 3 × 10 5g cm 2 s -1). Sustained harmonic tremor occurs during the first one to one-and-a-half minutes of an eruption of Old Faithful, but is not detectable in the succeeding minutes of the eruption. The eruption tremor is caused by hydraulic transients propagating within a sublayer of unvesiculated water that underlies the erupting two-phase liquid—vapor mixture. The resonant frequencies of the fluid column decrease to about 1 Hz when all of the water in the conduit has been converted to a water—steam mixture. Surges are observed in the flow at this frequency, but the resonance has not been detected seismically, possibly because the two-phase erupting fluid is seismically decoupled from the rock on which seismometers are placed. If Old Faithful is an analogue for volcanic seismicity, this study shows that because the frequency of tremor depends on the acoustic properties of the fluid and on conduit dimensions, both properties must be considered in analysis of tremor in volcanic regions. Because magma sound speed can vary over nearly two orders of magnitude as it changes from an undersaturated liquid into a saturated two-phase mixture, tremor frequency might vary by this magnitude and very broad-band seismographs may be required if tremor is to be monitored as magma goes from an undersaturated liquid to a vesiculated froth. Cessation of fluid-induced seismicity may indicate that the processes that drive the transients cease, but it is also possible that the processes that drive the transients continue but the fluid properties change so that the fluid becomes acoustically decoupled from the rock on which seismometers are placed.

Equatorward dispersion of the Sarychev volcanic plume and the relation to the Asian summer monsoon

NASA Astrophysics Data System (ADS)

Wu, Xue; Griessbach, Sabine; Hoffmann, Lars

2017-04-01

Sulfur dioxide emissions and subsequent sulfate aerosols from strong volcanic eruptions have large impact on global climate. Although most of previous studies attribute the global influence to volcanic eruptions in the tropics, high-latitude volcanic eruptions are also an important cause for global climate variations. In fact, the potential climate impact of volcanic also largely depends on the season when eruptions occur, the erupted plume height and the surrounding meteorological conditions. This work focuses on the eruption of a high-latitude volcano Sarychev, and the role of Asian summer monsoon (ASM) during the transport and dispersion of the erupted plumes. First, the sulfur dioxide emission rate and height of emission of the Sarychev eruption in June 2009 are modelled using a Lagrangian particle dispersion model named Massive-Parallel Trajectory Calculations (MPTRAC), together with sulfur dioxide observations of the Atmospheric Infrared Sounder (AIRS/Aqua) and a backward trajectory approach. Then, the transport and dispersion of the plumes are modelled with MPTRAC and validated with sulfur dioxide observations from AIRS and aerosol observations from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The modelled trajectories and the MIPAS data both show the plumes are transported towards the tropics from the southeast edge of the ASM (in the vertical range of 340-400K) controlled by the clockwise winds of ASM, and from above the ASM (above 400K) in form of in-mixing process. Especially, in the vertical range around 340-400K, a transport barrier based on potential vorticity (PV) gradients separates the 'aerosol hole' inside of the ASM circulation and the aerosol-rich surrounding area, which shows the PV gradients based barrier may be more practical than the barrier based on the geopotential height. With help of ASM circulation, the aerosol transported to the tropics and stayed in the tropical lower stratosphere for about eight months, which were the main aerosol sources during that time. This enables the Sarychev eruption to have potential impact on global radiative budget similar to a tropical volcanic eruption.

Kilauea volcano: the degassing of a hot spot

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerlach, T.M.

1986-03-01

Hot spots such as Kilauea volcano can degas by a one-stage eruptive process or a two-stage process involving eruptive and noneruptive degassing. One stage degassing occurs during sustained summit eruptions and causes a direct environmental impact. Although generally less efficient than the one-stage degassing process, two stage degassing can cause 1 to 2 orders of magnitude greater impact in just a few hours during flank eruptions. Hot spot volcanos with resupplied crustal magma chambers may be capable of maintaining an equivalent impact from CO/sub 2/ and S outgassing during both eruptive and noneruptive periods. On average, a hot spot volcanomore » such as Kilauea is a minor polluter compared to man.« less

Textural and geochemical constraints on eruptive style of the 79AD eruption at Vesuvius

NASA Astrophysics Data System (ADS)

Balcone-Boissard, Hélène; Boudon, Georges; Villemant, Benoît.

2010-05-01

The 79AD eruption of Vesuvius, also known as the "Pompeii eruption", is the reference for one of the explosive eruptive styles, the plinian-type eruption. The eruption involved H2O-rich phonolitic magmas and is commonly divided into three phases: an initial phreatomagmatic phase, followed by a plinian event which produced a thick pumice fallout deposit and a final phase that was dominated by numerous column-collapse events. During the plinian phase, a first white pumice fallout was produced from a high steady eruptive column, followed by a grey pumice fallout originated by an oscillatory eruptive column with several partial column collapse events. This study focuses on the pumice fallout deposits, sampled in a proximal thick section, at the Terzigno quarry, 6 km southeast of the present crater. In order to constrain the degassing processes and the eruptive dynamics, major element compositions, residual volatile contents (H2O, Cl) and textural characteristics (vesicularity and microcrystallinity) were studied. A previous study that we performed on the pre-eruptive Cl content has shown that Cl may be used as an indicator of magma saturation with Cl-rich fluids and of pre-eruptive pressures. Cl contents measured in melt inclusions show that only the white pumice and the upper part of the grey pumice magma were H2O saturated prior eruption. Large variations in residual volatile contents exist between the different eruptive units and textural features strongly differ between white and grey pumice clasts but also within the grey pumice clasts. The degassing processes were thus highly heterogeneous: the white pumice eruptive units represent a typical closed-system degassing evolution whereas the first grey pumice one, stored in the same pre-eruptive saturation conditions, follows a particular open-system degassing evolution. Here we propose a new model of the 79AD eruption where pre-eruptive conditions (H2O saturation, magma temperature and viscosity) are the critical parameters which determine the diversity of the syn-eruptive degassing processes and hence the eruptive dynamics. We suggest that the oscillatory regime that dominates the grey pumice eruptive phase is linked to the pre-eruptive water undersaturation of most part of the grey magma and to the time delays necessary for H2O exsolution.

On the absence of InSAR-detected volcano deformation spanning the 1995-1996 and 1999 eruptions of Shishaldin Volcano, Alaska

USGS Publications Warehouse

Moran, S.C.; Kwoun, O.; Masterlark, Timothy; Lu, Z.

2006-01-01

Shishaldin Volcano, a large, frequently active basaltic-andesite volcano located on Unimak Island in the Aleutian Arc of Alaska, had a minor eruption in 1995–1996 and a VEI 3 sub-Plinian basaltic eruption in 1999. We used 21 synthetic aperture radar images acquired by ERS-1, ERS-2, JERS-1, and RADARSAT-1 satellites to construct 12 coherent interferograms that span most of the 1993–2003 time interval. All interferograms lack coherence within ∼5 km of the summit, primarily due to persistent snow and ice cover on the edifice. Remarkably, in the 5–15 km distance range where interferograms are coherent, the InSAR images show no intrusion- or withdrawal-related deformation at Shishaldin during this entire time period. However, several InSAR images do show deformation associated with a shallow ML 5.2 earthquake located ∼14 km west of Shishaldin that occurred 6 weeks before the 1999 eruption. We use a theoretical model to predict deformation magnitudes due to a volumetric expansion source having a volume equivalent to the 1999 erupted volume, and find that deformation magnitudes for sources shallower than 10 km are within the expected detection capabilities for interferograms generated from C-band ERS 1/2 and RADARSAT-1 synthetic aperture radar images. We also find that InSAR images cannot resolve relatively shallow deformation sources (1–2 km below sea level) due to spatial gaps in the InSAR images caused by lost coherence. The lack of any deformation, particularly for the 1999 eruption, leads us to speculate that magma feeding eruptions at the summit moves rapidly (at least 80m/day) from > 10 km depth, and that the intrusion–eruption cycle at Shishaldin does not produce significant permanent deformation at the surface.

Total grain-size distribution of four subplinian-Plinian tephras from Hekla volcano, Iceland: Implications for sedimentation dynamics and eruption source parameters

NASA Astrophysics Data System (ADS)

Janebo, Maria H.; Houghton, Bruce F.; Thordarson, Thorvaldur; Bonadonna, Costanza; Carey, Rebecca J.

2018-05-01

The size distribution of the population of particles injected into the atmosphere during a volcanic explosive eruption, i.e., the total grain-size distribution (TGSD), can provide important insights into fragmentation efficiency and is a fundamental source parameter for models of tephra dispersal and sedimentation. Recent volcanic crisis (e.g. Eyjafjallajökull 2010, Iceland and Córdon Caulle 2011, Chile) and the ensuing economic losses, highlighted the need for a better constraint of eruption source parameters to be used in real-time forecasting of ash dispersal (e.g., mass eruption rate, plume height, particle features), with a special focus on the scarcity of published TGSD in the scientific literature. Here we present TGSD data associated with Hekla volcano, which has been very active in the last few thousands of years and is located on critical aviation routes. In particular, we have reconstructed the TGSD of the initial subplinian-Plinian phases of four historical eruptions, covering a range of magma composition (andesite to rhyolite), eruption intensity (VEI 4 to 5), and erupted volume (0.2 to 1 km3). All four eruptions have bimodal TGSDs with mass fraction of fine ash (<63 μm; m63) from 0.11 to 0.25. The two Plinian dacitic-rhyolitic Hekla deposits have higher abundances of fine ash, and hence larger m63 values, than their andesitic subplinian equivalents, probably a function of more intense and efficient primary fragmentation. Due to differences in plume height, this contrast is not seen in samples from individual sites, especially in the near field, where lapilli have a wider spatial coverage in the Plinian deposits. The distribution of pyroclast sizes in Plinian versus subplinian falls reflects competing influences of more efficient fragmentation (e.g., producing larger amounts of fine ash) versus more efficient particle transport related to higher and more vigorous plumes, displacing relatively coarse lapilli farther down the dispersal axis.

Reconstruction of 23 November 2013 Etna Eruption Source Parameters through a multidisciplinary approach

NASA Astrophysics Data System (ADS)

Poret, Matthieu; Costa, Antonio; Corradini, Stefano; Merucci, Luca; Andronico, Daniele; Vulpiani, Gianfranco; Cristaldi, Antonio

2017-04-01

On 23 November 2013, Mt. Etna erupted producing the 17th paroxysmal episode of 2013. The eruption generated a buoyant plume that reached more than 10 km a.s.l. The volcanic cloud was dispersed by a wind oriented north-eastwards which drove the erupted tephra over an extending area starting from the slopes of the volcano (scoria and lapilli) to the Calabria and up to Puglia region (ash particles). The field samples were collected in proximal area but also in Calabria ( 160 km) and tephra sedimentation was reported in Salento, in Puglia region ( 400 km). Another source of information is the transmission of a pilot who reported the presence of volcanic ash over the Adriatic sea ( 30 km southwards the Albanian coasts) between 10.9 and 11.5 km a.s.l. on 23 November 2013 at 13:50 which likely corresponds to the top of the volcanic cloud made of aerosol and gas. This study aims at reconstructing the Eruption Source Parameters (ESP) of the paroxysm phase such as, the eruptive column height, the eruption duration, the Mass Eruption Rate (MER), the Total Erupted Mass (TEM), and the Total Grain-Size Distribution (TGSD) making use of a multidisciplinary approach. Tephra dispersal simulations were performed using the model Fall3D constraining the results against field deposits, ground-based Radar measurements, and the satellite (MSG-Seviri) retrievals. The three sets of observations are complementary covering the full range of the erupted particle sizes from centimetre to micrometre particles, allowing for a robust assessment of the ESP. Indeed, among the multidisciplinary procedure, the field observations helped to approximate the erupted mass and the coarse fraction of the TGSD, whereas the radar measurements provided an estimation of eruptive column height and MER, and the satellite was crucial to quantify the fine ash fraction (i.e. PM10) by tracking the evolution of the plume and its mass. The best-fit results are in agreement with previous estimations recently published the literature and return a column height of 11.3 km a.s.l., a MER of 2.9×106 kg/s, a TEM of 8.2×109 kg, and a PM10 content of 2.0% with respect to the TEM. Results were also compared with the AERONET aerosol network to investigate the ultra-fine ash (i.e. few microns). Keywords: Etna, Tephra dispersal modelling, Bulk granulometry, Aviation hazard, PM10

Intrusion Triggering of Explosive Eruptions: Lessons Learned from EYJAFJALLAJÖKULL 2010 Eruptions and Crustal Deformation Studies

NASA Astrophysics Data System (ADS)

Sigmundsson, F.; Hreinsdottir, S.; Hooper, A. J.; Arnadottir, T.; Pedersen, R.; Roberts, M. J.; Oskarsson, N.; Auriac, A.; Decriem, J.; Einarsson, P.; Geirsson, H.; Hensch, M.; Ofeigsson, B. G.; Sturkell, E. C.; Sveinbjornsson, H.; Feigl, K.

2010-12-01

Gradual inflation of magma chambers often precedes eruptions at highly active volcanoes. During eruptions, rapid deflation occurs as magma flows out and pressure is reduced. Less is known about the deformation style at moderately active volcanoes, such as Eyjafjallajökull, Iceland, where an explosive summit eruption of trachyandesite beginning on 14 April 2010 caused exceptional disruption to air traffic. This eruption was preceded by an effusive flank eruption of olivine basalt from 20 March - 12 April 2010. Geodetic and seismic observations revealed the growth of an intrusive complex in the roots of the volcano during three months prior to eruptions. After initial horizontal growth, modelling indicates both horizontal and sub-vertical growth in three weeks prior the first eruption. The behaviour is attributed to subsurface variations in crustal stress and strength originating from complicated volcano foundations. A low-density layer may capture magma allowing pressure to build before an intrusion can ascend towards higher levels. The intrusive complex was formed by olivine basalt as erupted on the volcano flank 20 March - 12 April; the intrusive growth halted at the onset of this eruption. Deformation associated with the eruption onset was minor as the dike had reached close to the surface in the days before. Isolated eruptive vents opening on long-dormant volcanoes may represent magma leaking upwards from extensive pre-eruptive intrusions formed at depth. A deflation source activated during the summit eruption of trachyandesite is distinct from, and adjacent to, all documented sources of inflation in the volcano roots. Olivine basalt magma which recharged the volcano appears to have triggered the summit eruption, although the exact mode of triggering is uncertain. Scenarios include stress triggering or propagation of olivine basalt into more evolved magma. The trachyandesite includes crystals that can be remnants of minor recent intrusion of olivine basalt. Alternatively, mixing of larger portion of olivine basalt with more evolved magma may have occurred. Intrusions may lead to eruptions not only when they find their way to the surface; at Eyjafjallajökull our observation show how primitive melts in an intrusive complex active since 1992 catalyzed an explosive eruption of trachyandesite. Eyjafjallajökull’s behaviour can be attributed to its off-rift setting with a relatively cold subsurface structure and limited magma at shallow depth, as may be typical for moderately active volcanoes. Clear signs of volcanic unrest signals over years to weeks may indicate reawakening of such volcanoes whereas immediate short-term precursors may be subtle and difficult to detect.

Down and Out at Pacaya Volcano: A Glimpse of Magma Storage and Diking as Interpreted From GPS Geodesy

NASA Astrophysics Data System (ADS)

Lechner, H. N.; Waite, G. P.; Wauthier, D. C.; Escobar-Wolf, R. P.; Lopez-Hetland, B.

2017-12-01

Geodetic data from an eight-station GPS network at Pacaya volcano Guatemala allows us to produce a simple analytical model of deformation sources associated with the 2010 eruption and the eruptive period in 2013-2014. Deformation signals for both eruptive time-periods indicate downward vertical and outward horizontal motion at several stations surrounding the volcano. The objective of this research was to better understand the magmatic plumbing system and sources of this deformation. Because this down-and-out displacement is difficult to explain with a single source, we chose a model that includes a combination of a dike and spherical source. Our modelling suggests that deformation is dominated the inflation of a shallow dike seated high within the volcanic edifice and deflation of a deeper, spherical source below the SW flank of the volcano. The source parameters for the dike feature are in good agreement with the observed orientation of recent vent emplacements on the edifice as well the horizontal displacement, while the parameters for a deeper spherical source accommodate the downward vertical motion. This study presents GPS observations at Pacaya dating back to 2009 and provides a glimpse of simple models of possible deformation sources.

Upward migration of the explosion sources at Sakurajima volcano, Japan, revield by a seismic network in the close vocinity of the summit crater

NASA Astrophysics Data System (ADS)

Ohminato, T.; Kaneko, T.; Koyama, T.; Watanabe, A.; Takeo, M.; Iguchi, M.

2011-12-01

Observations in the vicinity of summit area of active volcanoes are important not only for understanding physical processes in the volcanic conduit but also for eruption prediction and volcanic hazards mitigation. It is, however, challenging to install observation sensors near active vents because of the danger of sudden eruptions. We have been developing a volcano observation system based on an unmanned aerial vehicle (UAV) for safe observations near active volcanic vents. We deployed an unmanned autonomous helicopter which can aviate autonomously along a previously programmed path within a meter accuracy using real-time kinematics differential GPS equipment. The maximum flight time, flight distance, and payload are 90 minutes, 5km, and 10kg, respectively. By using the UAV, we installed seismic stations at the summit area of Sakurajima volcano, Japan. Since 2006, explosive eruptions have been continuing at the reopened Showa crater at the eastern flank near the summit of Sakurajima. Entering the area within 2 km from the active craters is prohibited, and thus there were no observation station in the summit area. From November 2nd to 12th, 2009, and from November 2nd to 12th, 2010, we conducted seismic station installation in Sakurajima summit area using UAV and successfully installed four seismic stations within 2km from the active craters. Since the installation of the seismic stations, we have succeeded in acquiring waveform data accompanying more than 500 moderate eruptions at Showa-crater. Except for the mechanical resonance contamination at 35Hz, the recorded waveforms are as good as that recorded at permanent stations in Sakurajima. Since the beginning of the observation in the vicinity of the summit crater, the normalized amplitudes of the signals accompanying eruptions at Showa crater had been almost steady. However, after early April 2011, gradual increase of the normalized amplitude started, and this increasing trend is continuing at the time of the abstract submission. This increasing trend of the normalized amplitude strongly suggests upward migration of the source of the explosive eruptions at Showa-crater. The upward migration may suggest further intensification of the activity of Sakurajima in the near future.

Identification and evolution of the juvenile component in 2004-2005 Mount St. Helens ash: Chapter 29 in A volcano rekindled: the renewed eruption of Mount St. Helens, 2004-2006

USGS Publications Warehouse

Rowe, Michael C.; Thornber, Carl R.; Kent, Adam J.R.; Sherrod, David R.; Scott, William E.; Stauffer, Peter H.

2008-01-01

Petrologic studies of volcanic ash are commonly used to identify juvenile volcanic material and observe changes in the composition and style of volcanic eruptions. During the 2004-5 eruption of Mount St. Helens, recognition of the juvenile component in ash produced by early phreatic explosions was complicated by the presence of a substantial proportion of 1980-86 lava-dome fragments and glassy tephra, in addition to older volcanic fragments possibly derived from crater debris. In this report, we correlate groundmass textures and compositions of glass, mafic phases, and feldspar from 2004-5 ash in an attempt to identify juvenile material in early phreatic explosions and to distinguish among the various processes that generate and distribute ash. We conclude that clean glass in the ash is derived mostly from nonjuvenile sources and is not particularly useful for identifying the proportion of juvenile material in ash samples. High Li contents (>30 μg/g) in feldspars provide a useful tracer for juvenile material and suggest an increase in the proportion of the juvenile component between October 1 and October 4, 2004, before the emergence of hot dacite on the surface of the crater on October 11, 2004. The presence of Li-rich feldspar out of equilibrium (based on Liplagioclase/melt partitioning) with groundmass and bulk dacite early in the eruption also suggests vapor enrichment in the initially erupted dacite. If an excess vapor phase was, indeed, present, it may have provided a catalyst to initiate the eruption. Textural and compositional comparisons between dome fault gouge and the ash produced by rockfalls, rock avalanches, and vent explosions indicate that the fault gouge is a likely source of ash particles for both types of events. Comparison of the ash from vent explosions and rockfalls suggests that the fault gouge and new dome were initially heterogeneous, containing a mixture of conduit and crater debris and juvenile material, but became increasingly homogeneous, dominated by juvenile material, by early January 2005.

Field-trip guide to subaqueous volcaniclastic facies in the Ancestral Cascades arc in southern Washington State—The Ohanapecosh Formation and Wildcat Creek beds

USGS Publications Warehouse

Jutzeler, Martin; McPhie, Jocelyn

2017-06-27

Partly situated in the idyllic Mount Rainier National Park, this field trip visits exceptional examples of Oligocene subaqueous volcaniclastic successions in continental basins adjacent to the Ancestral Cascades arc. The >800-m-thick Ohanapecosh Formation (32–26 Ma) and the >300-m-thick Wildcat Creek (27 Ma) beds record similar sedimentation processes from various volcanic sources. Both show evidence of below-wave-base deposition, and voluminous accumulation of volcaniclastic facies from subaqueous density currents and suspension settling. Eruption-fed facies include deposits from pyroclastic flows that crossed the shoreline, from tephra fallout over water, and from probable Surtseyan eruptions, whereas re-sedimented facies comprise subaqueous density currents and debris flow deposits.

Origins of cryptic variation in the Ediacaran-Fortunian rhyolitic ignimbrites of the Saldanha Bay Volcanic Complex, Western Cape, South Africa

NASA Astrophysics Data System (ADS)

Clemens, J. D.; Stevens, G.; Frei, D.; Joseph, C. S. A.

2017-12-01

The Saldanha eruption centre, on the West Coast of South Africa, consists of 542 Ma, intracaldera, S-type, rhyolite ignimbrites divided into the basal Saldanha Ignimbrite and the partly overlying Jacob's Bay Ignimbrite. Depleted-mantle Nd model ages suggest magma sources younger than the Early Mesoproterozoic, and located within the Neoproterozoic Malmesbury Group and Swartland complex metasedimentary and metavolcanic rocks that form the regional basement. The Sr isotope systematics suggest that the dominant source rocks were metavolcaniclastic rocks and metagreywackes, and that the magmas formed from separate batches extracted from the same heterogeneous source. No apparent magma mixing trends relate the Saldanha to the Jacob's Bay Ignimbrites, or either of these to the magmas that formed the Plankiesbaai or Tsaarsbank Ignimbrites in the neighbouring Postberg eruption centre. The magmas were extracted from their source rocks carrying small but significant proportions of peritectic and restitic accessory minerals. Variations in the content of this entrained crystal cargo were responsible for most of the chemical variations in the magmas. Although we cannot construct a cogent crystal fractionation model to relate these groups of magmas, at least some crystal fractionation occurred, as an overlay on the primary signal due to peritectic assemblage entrainment (PAE). Thus, the causes of the cryptic chemical variation among the ignimbrite magmas of the Saldanha centre are variable, but dominated by the compositions of the parent melts and PAE. The preservation of clear, source-inherited chemical signatures, in individual samples, calls into question the common interpretation of silicic calderas as having been formed in large magma reservoirs, with magma compositions shaped by magma mingling, mixing, and fractional crystallization. The Saldanha rocks suggest a more intimate connection between source and erupted magma, and perhaps indicate that silicic magmas are too viscous to be significantly modified by magma-chamber processes.

Geodetic Measurements and Numerical Modeling of the Deformation Cycle for Okmok Volcano, Alaska: 1993-2008

NASA Astrophysics Data System (ADS)

Ohlendorf, S. J.; Feigl, K.; Thurber, C. H.; Lu, Z.; Masterlark, T.

2011-12-01

Okmok Volcano is an active caldera located on Umnak Island in the Aleutian Island arc. Okmok, having recently erupted in 1997 and 2008, is well suited for multidisciplinary studies of magma migration and storage because it hosts a good seismic network and has been the subject of synthetic aperture radar (SAR) images that span the recent eruption cycle. Interferometric SAR can characterize surface deformation in space and time, while data from the seismic network provides important information about the interior processes and structure of the volcano. We conduct a complete time series analysis of deformation of Okmok with images collected by the ERS and Envisat satellites on more than 100 distinct epochs between 1993 and 2008. We look for changes in inter-eruption inflation rates, which may indicate inelastic rheologic effects. For the time series analysis, we analyze the gradient of phase directly, without unwrapping, using the General Inversion of Phase Technique (GIPhT) [Feigl and Thurber, 2009]. This approach accounts for orbital and atmospheric effects and provides realistic estimates of the uncertainties of the model parameters. We consider several models for the source, including the prolate spheroid model and the Mogi model, to explain the observed deformation. Using a medium that is a homogeneous half space, we estimate the source depth to be centered at about 4 km below sea level, consistent with the findings of Masterlark et al. [2010]. As in several other geodetic studies, we find the source to be approximately centered beneath the caldera. To account for rheologic complexity, we next apply the Finite Element Method to simulate a pressurized cavity embedded in a medium with material properties derived from body wave seismic tomography. This approach allows us to address the problem of unreasonably large pressure values implied by a Mogi source with a radius of about 1 km by experimenting with larger sources. We also compare the time dependence of the source to published results that used GPS data.

Geologic Map of Mount Mazama and Crater Lake Caldera, Oregon

USGS Publications Warehouse

Bacon, Charles R.

2008-01-01

Crater Lake partly fills one of the most spectacular calderas of the world, an 8-by-10-km basin more than 1 km deep formed by collapse of the volcano known as Mount Mazama (fig. 1) during a rapid series of explosive eruptions about 7,700 years ago. Having a maximum depth of 594 m, Crater Lake is the deepest lake in the United States. Crater Lake National Park, dedicated in 1902, encompasses 645 km2 of pristine forested and alpine terrain, including the lake itself, virtually all of Mount Mazama, and most of the area of the geologic map. The geology of the area was first described in detail by Diller and Patton (1902) and later by Williams (1942), whose vivid account led to international recognition of Crater Lake as the classic collapse caldera. Because of excellent preservation and access, Mount Mazama, Crater Lake caldera, and the deposits formed by the climactic eruption constitute a natural laboratory for study of volcanic and magmatic processes. For example, the climactic ejecta are renowned among volcanologists as evidence for systematic compositional zonation within a subterranean magma chamber. Mount Mazama's climactic eruption also is important as the source of the widespread Mazama ash, a useful Holocene stratigraphic marker throughout the Pacific Northwest, adjacent Canada, and offshore. A detailed bathymetric survey of the floor of Crater Lake in 2000 (Bacon and others, 2002) provides a unique record of postcaldera eruptions, the interplay between volcanism and filling of the lake, and sediment transport within this closed basin. Knowledge of the geology and eruptive history of the Mount Mazama edifice, greatly enhanced by the caldera wall exposures, gives exceptional insight into how large volcanoes of magmatic arcs grow and evolve. Lastly, the many smaller volcanoes of the High Cascades beyond the limits of Mount Mazama are a source of information on the flux of mantle-derived magma through the region. General principles of magmatic and eruptive processes revealed by the present study have been incorporated not only in scientific investigations elsewhere, but in the practical evaluation of hazards (Bacon and others, 1997b) and geothermal resources (Bacon and Nathenson, 1996) in the Crater Lake region. In addition to papers in scientific journals, field trip guides, and the hazard and geothermal reports, the major product of this long-term study of Mount Mazama is the geologic map. The map is unusual because it portrays bedrock (outcrop), surficial, and lake floor geology. Caldera wall geology is depicted in detail on the accompanying geologic panoramas.

Evidence for Cyclical Fractional Crystallization, Recharge, and Assimilation in Basalts of the Kimama Core, Central Snake River Plain, Idaho: A 5.5-million-year Highlight Reel of Petrogenetic processes in a Mid-Crustal Sill Complex

NASA Astrophysics Data System (ADS)

Potter, Katherine E.; Shervais, John W.; Christiansen, Eric H.; Vetter, Scott K.

2018-02-01

Basalts erupted in the Snake River Plain of central Idaho and sampled in the Kimama drill core link eruptive processes to the construction of mafic intrusions over 5.5 Ma. Cyclic variations in basalt composition reveal temporal chemical heterogeneity related to fractional crystallization and the assimilation of previously-intruded mafic sills. A range of compositional types are identified within 1912 m of continuous drill core: Snake River olivine tholeiite (SROT), low K SROT, high Fe-Ti, and evolved and high K-Fe lavas similar to those erupted at Craters of the Moon National Monument. Detailed lithologic and geophysical logs document 432 flow units comprising 183 distinct lava flows and 78 flow groups. Each lava flow represents a single eruptive episode, while flow groups document chemically and temporally related flows that formed over extended periods of time. Temporal chemical variation demonstrates the importance of source heterogeneity and magma processing in basalt petrogenesis. Low-K SROT and high Fe-Ti basalts are genetically related to SROT as, respectively, hydrothermally-altered and fractionated daughters. Cyclic variations in the chemical composition of Kimama flow groups are apparent as 21 upward fractionation cycles, six recharge cycles, eight recharge-fractionation cycles, and five fractionation-recharge cycles. We propose that most Kimama basalt flows represent typical fractionation and recharge patterns, consistent with the repeated influx of primitive SROT parental magmas and extensive fractional crystallization coupled with varying degrees of assimilation of gabbroic to ferrodioritic sills at shallow to intermediate depths over short durations. Trace element models show that parental SROT basalts were generated by 5-10% partial melting of enriched mantle at shallow depths above the garnet-spinel lherzolite transition. The distinctive evolved and high K-Fe lavas are rare. Found at four depths, 319 m, 1045 m, 1078 m, and 1189 m, evolved and high K-Fe flows are compositionally unrelated to SROT magmas and represent highly fractionated basalt, probably accompanied by crustal assimilation. These evolved lavas may be sourced from the Craters of the Moon/Great Rift system to the northeast. The Kimama drill core is the longest record of geochemical variation in the central Snake River Plain and reinforces the concept of magma processing in a layered complex.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eichelberger, J.C.

Magmatic activity, and particularly silicic magmatic activity, is the fundamental process by which continental crust forms and evolves. The transport of magma from deep crustal reservoirs to the surface is a neglected but important aspect of magmatic phenomena. It encompasses problems of eruptive behavior, hydrothermal circulation, and ore deposition, and must be understood in order to properly interpret deeper processes. Drilling provides a means for determining the relationship of shallow intrusive processes to eruption processes at young volcanoes where eruptions are best understood. Drilling also provides a means for directly observing the processes of heat and mass transfer by whichmore » recently emplaced intrusions approach equilibrium with their new environment. Drilling in the Inyo Chain, a 600-year-old chain of volcanic vents in California, has shown the close relationship of silicic eruption to shallow dike emplacement, the control of eruptive style by shallow porous-flow degassing, the origin of obsidian by welding, the development of igneous zonation by viscosity segregation, and the character and size of conduits in relation to well-understood magmatic and phreatic eruptions. 36 refs., 9 figs.« less

Mechanisms and timescales of generating eruptible rhyolitic magmas at Yellowstone caldera from zircon and sanidine geochronology and geochemistry

USGS Publications Warehouse

Stelten, Mark; Cooper, Kari M.; Vazquez, Jorge A.; Calvert, Andrew T.; Glessner, Justin G

2015-01-01

We constrain the physical nature of the magma reservoir and the mechanisms of rhyolite generation at Yellowstone caldera via detailed characterization of zircon and sanidine crystals hosted in three rhyolites erupted during the (ca. 170 – 70 ka) Central Plateau Member eruptive episode – the most recent post-caldera magmatism at Yellowstone. We present 238U-230Th crystallization ages and trace-element compositions of the interiors and surfaces (i.e., unpolished rims) of individual zircon crystals from each rhyolite. We compare these zircon data to 238U- 230Th crystallization ages of bulk sanidine separates coupled with chemical and isotopic data from single sanidine crystals. Zircon age and trace-element data demonstrate that the magma reservoir that sourced the Central Plateau Member rhyolites was long-lived (150 – 250 kyr) and genetically related to the preceding episode of magmatism, which occurred ca. 256 ka. The interiors of most zircons in each rhyolite were inherited from unerupted material related to older stages of Central Plateau Member magmatism or the preceding late Upper Basin Member magmatism (i.e., are antecrysts). Conversely, most zircon surfaces crystallized near the time of eruption from their host liquids (i.e., are autocrystic). The repeated recycling of zircon interiors from older stages of magmatism demonstrates that sequentially erupted Central Plateau Member rhyolites are genetically related. Sanidine separates from each rhyolite yield 238U-230Th crystallization ages at or near the eruption age of their host magmas, coeval with the coexisting zircon surfaces, but are younger than the coexisting zircon interiors. Chemical and isotopic data from single sanidine crystals demonstrate that the sanidines in each rhyolite are in equilibrium with their host melts, which considered along with their near-eruption crystallization ages suggests that nearly all CPM sanidines are autocrystic. The paucity of antecrystic sanidine crystals relative to antecrystic zircons require a model where eruptible rhyolites are generated by extracting melt and zircons from a long-lived mush of immobile crystal-rich magma. In this process the larger sanidine crystals remain trapped in the locked crystal network. The extracted melts (plus antecrystic zircon) amalgamate into a liquid dominated (i.e., eruptible) magma body that is maintained as a physically distinct entity relative to the bulk of the long-lived crystal mush. Zircon surfaces and sanidines in each rhyolite crystallize after melt extraction/amalgamation and their ages constrain the residence time of eruptible magmas at Yellowstone. Residence times of the large volume rhyolites (~40 – 70 km3) are ≤ 1 kyr (conservatively < 6 kyr), which suggests that large volumes of rhyolite can be generated rapidly by extracting melt from a crystal mush. Because the lifespan of the crystal mush that sourced the Central Plateau Member rhyolites is two orders of magnitude longer than the residence time of eruptible magma bodies within the reservoir, it is apparent that the Yellowstone magma reservoir spends most of its time in a largely-crystalline (i.e., uneruptible) state, similar to the present-day magma reservoir, and that eruptible magma bodies are ephemeral features.

Impacts of a volcanic eruption on the forest birdcommunity of Montserrat, Lesser Antilles.

Treesearch

B. DALSGAARD; G. M. HILTON; G. A. L. GRAY; L. AYMER; J. BOATSWAIN; J. FENTON DALEY; J. MARTIN; L. MARTIN; P. MURRAIN; W. J. ARENDT; W. OLESEN GIBBONSD

2007-01-01

Volcanic eruptions are an important and natural source of catastrophic disturbance to ecological communities. However, opportunities to study them are relatively rare. Here we report on the effects of the eruption of the Soufrière Hills volcano on the forest bird community of the Lesser Antillean island of Montserrat. The island’s species-poor avifauna includes 11...

Geodesy - the key for constraining rates of magma supply, storage, and eruption

NASA Astrophysics Data System (ADS)

Poland, Michael; Anderson, Kyle

2016-04-01

Volcanology is an inherently interdisciplinary science that requires joint analysis of diverse physical and chemical datasets to infer subsurface processes from surface observations. Among the diversity of data that can be collected, however, geodetic data are critical for elucidating the main elements of a magmatic plumbing system because of their sensitivity to subsurface changes in volume and mass. In particular, geodesy plays a key role in determining rates of magma supply, storage, and eruption. For example, surface displacements are critical for estimating the volume changes and locations of subsurface magma storage zones, and remotely sensed radar data make it possible to place significant bounds on eruptive volumes. Combining these measurements with geochemical indicators of magma composition and volatile content enables modeling of magma fluxes throughout a volcano's plumbing system, from source to surface. We combined geodetic data (particularly InSAR) with prior geochemical constraints and measured gas emissions from Kīlauea Volcano, Hawai`i, to develop a probabilistic model that relates magma supply, storage, and eruption over time. We found that the magma supply rate to Kīlauea during 2006 was 35-100% greater than during 2000-2001, with coincident increased rates of subsurface magma storage and eruption at the surface. By 2012, this surge in supply had ended, and supply rates were below those of 2000-2001; magma storage and eruption rates were similarly reduced. These results demonstrate the connection between magma supply, storage, and eruption, and the overall importance of magma supply with respect to volcanic hazards at Kīlauea and similar volcanoes. Our model also confirms the importance of geodetic data in modeling these parameters - rates of storage and eruption are, in some cases, almost uniquely constrained by geodesy. Future modeling efforts along these lines should also seek to incorporate gravity data, to better determine magma compressibility and subsurface mass change.

Magma Intrusion at Mount St. Helens, Washington, from Temporal Gravity Variations

NASA Astrophysics Data System (ADS)

Battaglia, Maurizio; Lisowski, Mike; Dzursin, Dan; Poland, Mike; Schilling, Steve; Diefenbach, Angie; Wynn, Jeff

2017-04-01

Mount St. Helens is a stratovolcano in the Pacific Northwest region of the United States, best known for its explosive eruption in May 1980 - deadliest and most economically destructive volcanic event in US history. Volcanic activity renewed in September 2004 with a dome forming eruption that lasted until 2008. This eruption was surprising because the preceding four years had seen the fewest earthquakes and no significant deformation since the 1980-86 eruption ended. After the dome forming eruption ended in July 2008, the volcano seismic activity and deformation went back to background values. Time-dependent gravimetric measurements can detect subsurface processes long before magma flow leads to earthquakes or other eruption precursors. A high-precision gravity monitoring network (referenced to a base station 36 km NW of the volcano) was set up at Mount St Helens in 2010. Measurements were made at 12 sites on the volcano (at altitudes between 1200 and 2350 m a.s.l.) and 4 sites far afield during the summers of 2010, 2012, and 2014. The repeated gravity measurements revealed an increase in gravity between 2010 and 2014. Positive residual gravity anomalies remained after accounting for changes in surface height, in the Crater Glacier, and in the shallow hydrothermal aquifer. The pattern of residual gravity changes, with a maximum of 57±12 μGal from 2010 to 2014, is radially symmetric and centered on the 2004-08 lava dome. Inversion of the residual gravity signal points to a source 2.5-4 km beneath the crater floor (i.e., in the magma conduit that fed eruptions in 1980-86 and 2004-08). We attribute the gravity increase to re-inflation of the magma plumbing system following the 2004-8 eruption. Recent seismic activity (e.g., the seismic swarm of March 2016) has been interpreted as a response to the slow recharging of the volcano magma chamber.

PRE-FLARE CORONAL JET AND EVOLUTIONARY PHASES OF A SOLAR ERUPTIVE PROMINENCE ASSOCIATED WITH THE M1.8 FLARE: SDO AND RHESSI OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joshi, Bhuwan; Kushwaha, Upendra; Veronig, Astrid M.

We investigate the triggering, activation, and ejection of a solar eruptive prominence that occurred in a multi-polar flux system of active region NOAA 11548 on 2012 August 18 by analyzing data from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory , the Reuven Ramaty High Energy Solar Spectroscopic Imager , and the Extreme Ultraviolet Imager/Sun Earth Connection Coronal and Heliospheric Investigation on board the Solar Terrestrial Relation Observatory . Prior to the prominence activation, we observed striking coronal activities in the form of a blowout jet, which is associated with the rapid eruption of a cool flux rope. Furthermore, themore » jet-associated flux rope eruption underwent splitting and rotation during its outward expansion. These coronal activities are followed by the prominence activation during which it slowly rises with a speed of ∼12 km s{sup −1} while the region below the prominence emits gradually varying EUV and thermal X-ray emissions. From these observations, we propose that the prominence eruption is a complex, multi-step phenomenon in which a combination of internal (tether-cutting reconnection) and external (i.e., pre-eruption coronal activities) processes are involved. The prominence underwent catastrophic loss of equilibrium with the onset of the impulsive phase of an M1.8 flare, suggesting large-scale energy release by coronal magnetic reconnection. We obtained signatures of particle acceleration in the form of power-law spectra with hard electron spectral index ( δ  ∼ 3) and strong HXR footpoint sources. During the impulsive phase, a hot EUV plasmoid was observed below the apex of the erupting prominence that ejected in the direction of the prominence with a speed of ∼177 km s{sup −1}. The temporal, spatial, and kinematic correlations between the erupting prominence and the plasmoid imply that the magnetic reconnection supported the fast ejection of prominence in the lower corona.« less

Rainfall-runoff properties of tephra: Simulated effects of grain-size and antecedent rainfall

NASA Astrophysics Data System (ADS)

Jones, Robbie; Thomas, Robert E.; Peakall, Jeff; Manville, Vern

2017-04-01

Rain-triggered lahars (RTLs) are a significant and often persistent secondary volcanic hazard at many volcanoes around the world. Rainfall on unconsolidated volcaniclastic material is the primary initiation mechanism of RTLs: the resultant flows have the potential for large runout distances (> 100 km) and present a substantial hazard to downstream infrastructure and communities. RTLs are frequently anticipated in the aftermath of eruptions, but the pattern, timing and scale of lahars varies on an eruption-by-eruption and even catchment-by-catchment basis. This variability is driven by a set of local factors including the grain size distribution, thickness, stratigraphy and spatial distribution of source material in addition to topography, vegetation coverage and rainfall conditions. These factors are often qualitatively discussed in RTL studies based on post-eruption lahar observations or instrumental detections. Conversely, this study aims to move towards a quantitative assessment of RTL hazard in order to facilitate RTL predictions and forecasts based on constrained rainfall, grain size distribution and isopach data. Calibrated simulated rainfall and laboratory-constructed tephra beds are used within a repeatable experimental set-up to isolate the effects of individual parameters and to examine runoff and infiltration processes from analogous RTL source conditions. Laboratory experiments show that increased antecedent rainfall and finer-grained surface tephra individually increase runoff rates and decrease runoff lag times, while a combination of these factors produces a compound effect. These impacts are driven by increased residual moisture content and decreased permeability due to surface sealing, and have previously been inferred from downstream observations of lahars but not identified at source. Water and sediment transport mechanisms differ based on surface grain size distribution: a fine-grained surface layer displayed airborne remobilisation, accretionary pellet formation, rapid surface sealing and infiltration-excess overland flow generation whilst a coarse surface layer demonstrated exclusively rainsplash-driven particle detachment throughout the rainfall simulations. This experimental protocol has the potential to quantitatively examine the effects of a variety of individual parameters in RTL initiation under controlled conditions.

Flux Cancelation: The Key to Solar Eruptions

NASA Technical Reports Server (NTRS)

Panesar, Navdeep K.; Sterling, Alphonse; Moore, Ronald; Chakrapani, Prithi; Innes, Davina; Schmit, Don; Tiwari, Sanjiv

2017-01-01

Solar coronal jets are magnetically channeled eruptions that occur in all types of solar environments (e.g. active regions, quiet-Sun regions and coronal holes). Recent studies show that coronal jets are driven by the eruption of small-scare filaments (minifilaments). Once the eruption is underway magnetic reconnection evidently makes the jet spire and the bright emission in the jet base. However, the triggering mechanism of these eruptions and the formation mechanism of the pre-jet minifilaments are still open questions. In this talk, mainly using SDOAIA and SDOHIM data, first I will address the question: what triggers the jet-driving minifilament eruptions in different solar environments (coronal holes, quiet regions, active regions)? Then I will talk about the magnetic field evolution that produces the pre-jet minifilaments. By examining pre-jet evolutionary changes in line-of-sight HMI magnetograms while examining concurrent EUV images of coronal and transition-region emission, we find clear evidence that flux cancelation is the main process that builds pre-jet minifilaments, and is also the main process that triggers the eruptions. I will also present results from our ongoing work indicating that jet-driving minifilament eruptions are analogous to larger-scare filament eruptions that make flares and CMEs. We find that persistent flux cancellation at the neutral line of large-scale filaments often triggers their eruptions. From our observations we infer that flux cancelation is the fundamental process from the buildup and triggering of solar eruptions of all sizes.

Flux Cancelation: The Key to Solar Eruptions

NASA Technical Reports Server (NTRS)

Panesar, Navdeep K.; Sterling, Alphonse; Moore, Ronald; Chakrapani, Prithi; Innes, Davina; Schmit, Don; Tiwari, Sanjiv

2017-01-01

Solar coronal jets are magnetically channeled eruptions that occur in all types of solar environments (e.g. active regions, quiet-Sun regions and coronal holes). Recent studies show that coronal jets are driven by the eruption of small-scale filaments (minifilaments). Once the eruption is underway magnetic reconnection evidently makes the jet spire and the bright emission in the jet base. However, the triggering mechanism of these eruptions and the formation mechanism of the pre-jet minifilaments are still open questions. In this talk, mainly using SDO/AIA and SDO/HMI data, first I will address the question: what triggers the jet-driving minifilament eruptions in different solar environments (coronal holes, quiet regions, active regions)? Then I will talk about the magnetic field evolution that produces the pre-jet minifilaments. By examining pre-jet evolutionary changes in line-of-sight HMI magnetograms while examining concurrent EUV images of coronal and transition-region emission, we find clear evidence that flux cancellation is the main process that builds pre-jet minifilaments, and is also the main process that triggers the eruptions. I will also present results from our ongoing work indicating that jet-driving minifilament eruptions are analogous to larger-scale filament eruptions that make flares and CMEs. We find that persistent flux cancellation at the neutral line of large-scale filaments often triggers their eruptions. From our observations we infer that flux cancellation is the fundamental process for the buildup and triggering of solar eruptions of all sizes.

The reawakening of Alaska's Augustine volcano

USGS Publications Warehouse

Power, John A.; Nye, Christopher J.; Coombs, Michelle L.; Wessels, Rick L.; Cervelli, Peter F.; Dehn, Jon; Wallace, Kristi L.; Freymueller, Jeffrey T.; Doukas, Michael P.

2006-01-01

The eruption was heralded by eight months of increasing seismicity, deformation, gas emission, and small phreatic eruptions, the latter consisting of explosions of steam and debris caused by heating and expansion of groundwater due to an underlying heat source.

Investigating the value of passive microwave observations for monitoring volcanic eruption source parameters

NASA Astrophysics Data System (ADS)

Montopoli, Mario; Cimini, Domenico; Marzano, Frank

2016-04-01

Volcanic eruptions inject both gas and solid particles into the Atmosphere. Solid particles are made by mineral fragments of different sizes (from few microns to meters), generally referred as tephra. Tephra from volcanic eruptions has enormous impacts on social and economical activities through the effects on the environment, climate, public health, and air traffic. The size, density and shape of a particle determine its fall velocity and thus residence time in the Atmosphere. Larger particles tend to fall quickly in the proximity of the volcano, while smaller particles may remain suspended for several days and thus may be transported by winds for thousands of km. Thus, the impact of such hazards involves local as well as large scales effects. Local effects involve mostly the large sized particles, while large scale effects are caused by the transport of the finest ejected tephra (ash) through the atmosphere. Forecasts of ash paths in the atmosphere are routinely run after eruptions using dispersion models. These models make use of meteorological and volcanic source parameters. The former are usually available as output of numerical weather prediction models or large scale reanalysis. Source parameters characterize the volcanic eruption near the vent; these are mainly the ash mass concentration along the vertical column and the top altitude of the volcanic plume, which is strictly related to the flux of the mass ejected at the emission source. These parameters should be known accurately and continuously; otherwise, strong hypothesis are usually needed, leading to large uncertainty in the dispersion forecasts. However, direct observations during an eruption are typically dangerous and impractical. Thus, satellite remote sensing is often exploited to monitor volcanic emissions, using visible (VIS) and infrared (IR) channels available on both Low Earth Orbit (LEO) and Geostationary Earth Orbit (GEO) satellites. VIS and IR satellite imagery are very useful to monitor the dispersal fine-ash cloud, but tend to saturate near the source due to the strong optical extinction of ash cloud top layers. Conversely, observations at microwave (MW) channels from LEO satellites have demonstrated to carry additional information near the volcano source due to the relative lower opacity. This feature makes satellite MW complementary to IR radiometry for estimating source parameters close to the volcano emission, at the cost of coarser spatial resolution. The presentation shows the value of passive MW observations for the detection and quantitative retrieval of volcanic emission source parameters through the investigation of notable case studies, such as the eruptions of Grímsvötn (Iceland, May 2011) and Calbuco (Cile, April 2015), observed by the Special Sensor Microwave Imager/Sounder and the Advanced Technology Microwave Sounder.

Role of social media and networking in volcanic crises and communication

USGS Publications Warehouse

Sennert, Sally K.; Klemetti, Erik W.; Bird, Deanne

2017-01-01

The growth of social media as a primary and often preferred news source has contributed to the rapid dissemination of information about volcanic eruptions and potential volcanic crises as an eruption begins. Information about volcanic activity comes from a variety of sources: news organisations, emergency management personnel, individuals (both public and official) and volcano monitoring agencies. Once posted, this information is easily shared, increasing the reach to a much broader population than the original audience. The onset and popularity of social media as a vehicle for eruption information dissemination has presented many benefits as well as challenges, and points towards a need for a more unified system for information. This includes volcano observatories using social media as an official channels to distribute activity statements, forecasts and predictions on social media, in addition to the archiving of images and data activity. This chapter looks at two examples of projects that collect / disseminate information regarding volcanic crises and eruptive activity utilizing social media sources. Based on those examples, recommendations are made to volcanic observatories in relation to the use of social media as a two-way communication tool. These recommendations include: using social media as a two-way dialogue to communicate and receive information directly from the public and other sources; stating that the social media account is from an official source; and, posting types of information that the public are seeking such as images, videos and figures.

Total sulfur dioxide emissions and pre-eruption vapor-saturated magma at Mount St. Helens, 1980-88

NASA Astrophysics Data System (ADS)

Gerlach, T. M.; McGee, K. A.

1994-12-01

SO2 from explosive volcanism can cause significant climatic and atmospheric impacts, but the source of the sulfur is controversial. Total ozone mapping spectrometer (TOMS), correlation spectrometer (COSPEC), and ash leachate data for Mount St. Helens from the time of the climactic eruption on 18 May 1980 to the final stages of non-explosive degassing in 1988 give a total SO2 emission of 2 Mt. COSPEC data show a sharp drop in emission rate that was apparently controlled by a decreasing rate of magma supply. A total SO2 emission of only 0.08 Mt is estimated from melt inclusion data and the conventional assumption that the main sulfur source was pre-eruption melt; commonly invoked sources of 'excess sulfur' (anhydrite decomposition, basaltic magma, and degassing of non-erupted magma) are unlikely in this case. Thus melt inclusions may significantly underestimate SO2 emissions and impacts of explosive volcanism on climate and the atmosphere. Measured CO2 emissions, together with the H2O content of melt inclusions and experimental solubility data, indicate the Mount St. Helens dacite was vapor-saturated at depth prior to ascent and suggest that a vapor phase was the main source of sulfur for the 2-Mt of SO2. A vapor source is consistent with experimental studies on the Mount St. Helens dacite and removes the need for a much debated shallow magma body.

Volcanic eruption source parameters from active and passive microwave sensors

NASA Astrophysics Data System (ADS)

Montopoli, Mario; Marzano, Frank S.; Cimini, Domenico; Mereu, Luigi

2016-04-01

It is well known, in the volcanology community, that precise information of the source parameters characterising an eruption are of predominant interest for the initialization of the Volcanic Transport and Dispersion Models (VTDM). Source parameters of main interest would be the top altitude of the volcanic plume, the flux of the mass ejected at the emission source, which is strictly related to the cloud top altitude, the distribution of volcanic mass concentration along the vertical column as well as the duration of the eruption and the erupted volume. Usually, the combination of a-posteriori field and numerical studies allow constraining the eruption source parameters for a given volcanic event thus making possible the forecast of ash dispersion and deposition from future volcanic eruptions. So far, remote sensors working at visible and infrared channels (cameras and radiometers) have been mainly used to detect, track and provide estimates of the concentration content and the prevailing size of the particles propagating within the ash clouds up to several thousand of kilometres far from the source as well as track back, a-posteriori, the accuracy of the VATDM outputs thus testing the initial choice made for the source parameters. Acoustic wave (infrasound) and microwave fixed scan radar (voldorad) were also used to infer source parameters. In this work we want to put our attention on the role of sensors operating at microwave wavelengths as complementary tools for the real time estimations of source parameters. Microwaves can benefit of the operability during night and day and a relatively negligible sensitivity to the presence of clouds (non precipitating weather clouds) at the cost of a limited coverage and larger spatial resolution when compared with infrared sensors. Thanks to the aforementioned advantages, the products from microwaves sensors are expected to be sensible mostly to the whole path traversed along the tephra cloud making microwaves particularly appealing for estimates close to the volcano emission source. Near the source the cloud optical thickness is expected to be large enough to induce saturation effects at the infrared sensor receiver thus vanishing the brightness temperature difference methods for the ash cloud identification. In the light of the introduction above, some case studies at Eyjafjallajökull 2010 (Iceland), Etna (Italy) and Calbuco (Cile), on 5-10 May 2010, 23rd Nov., 2013 and 23 Apr., 2015, respectively, are analysed in terms of source parameter estimates (manly the cloud top and mass flax rate) from ground based microwave weather radar (9.6 GHz) and satellite Low Earth Orbit microwave radiometers (50 - 183 GH). A special highlight will be given to the advantages and limitations of microwave-related products with respect to more conventional tools.

Chemical, mineralogical, and isotopic characteristics of mud from the LUSI mud volcano, Sidoarjo, East Java, Indonesia: implications for the environment, public health, and eruption processes

NASA Astrophysics Data System (ADS)

Plumlee, G. S.; Casadevall, T. J.; Wibowo, H. T.; Rosenbauer, R. J.; Johnson, C. A.; Breit, G. N.; Hageman, P. L.; Wolf, R. E.; Morman, S. A.

2009-12-01

On May 29, 2006, mud and gases began erupting from a vent 150 meters away from a gas exploration well near Sidoarjo, East Java, Indonesia. The eruption, called the LUSI mud volcano, has continued at rates as high as 160,000 m3 per day. At the request of the United States Department of State, the U.S. Geological Survey (USGS) has been providing technical assistance to the Indonesian Government on the geological and geochemical aspects of the mud eruption. This paper will present analytical results of mud samples collected in Sept. 2007 and Nov. 2008, and interpretive findings based on the analytical results. The 2007 mud sample contains high proportions of particles that could be ingestible by hand-mouth transmission (~98 vol % <250 microns,), inhalable into the upper respiratory tract (~80 vol % <10 microns), and respirable into the lung alveoli (~ 40 vol % <2.5 microns), so the mud and dust from the dried mud could be readily taken up by exposed individuals. Our results confirm those of a previous study that the levels of potentially toxic heavy metals or metalloids in the mud are low. A complex mixture of organic compounds in the mud is likely derived from petroleum source rocks. Although the 2007 mud sample contains several percent iron sulfides, net acid production tests indicate that enough carbonate material is also present to prevent the mud from becoming acid-generating due to weathering and sulfide oxidation in the near-surface environment. Water derived from settling mud deposits may have the potential to adversely affect the quality of surface- or groundwater sources for drinking water, due to high levels of fluoride, nitrate, iron, manganese, aluminum, sulfate, chloride, and total dissolved solids. The very high nitrate levels in the waters contained within the mud may present a source of nutrients that could enhance algal blooms and resulting adverse impacts such as hypoxia in fresh-water and marine ecosystems into which some of the mud is being discharged. In agreement with previous studies, water separated from the 2007 mud sample is compositionally and isotopically compatible with an origin as sedimentary formation water. The iron disulfide fraction of the mud sample is isotopically light, and likely formed by bacterial sulfate reduction during diagenesis of clay-rich rocks from which the mud was derived. A smaller, isotopically heavy monosulfide fraction likely formed later by thermogenic reduction of formation-water sulfate to sulfide and reaction of the resulting sulfide with reactive iron in the mud. Additional linked earth science and public health studies are needed to more fully understand eruption processes, and the potential environmental and health consequences of the erupting mud, waters, and gases, and of the accumulating mud deposits.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cadle, R.D.

A previously published 2-D numerical model of the global dispersion of an eruption cloud in the stratosphere as a function of time assumed an instantaneous injection of the eruption cloud (the source function). New calculations show that the dispersion rate is quite insensitive to the manner of introducing the source function into the model, including spreading the eruption time over 10 days. Results obtained by flying through the eruption clouds from explosive volcanoes in Guatemala indicated that most of the sulfur in such clouds is SO/sub 2/. If, as is generally believed, SO/sub 2/ reacts with OH in the stratosphere,more » leading to the production of H/sub 2/SO/sub 4/ droplets, high explosive eruptions can deplete the stratosphere of OH for long time periods. The OH is thus controlled by the rate of O(/sup 1/D) formation from ozone. By using the results from the 2-D dispersion model referred to above applied to the eruption cloud from the 1953 Agung eruption, and chemical kinetic rate constants, the 'e folding' residence time for sulfur dioxide conversion to sulfuric acid was estimated to be about 300 days. The Guatemala studies showed that the eruption clouds from explosive volcanoes contain large amounts of HCl. Unless much of this HCl is removed by rain accompanying the eruption, this HCl might be expected to have a marked influence on stratospheric chemistry as a result of the reaction OH+HCl..-->..H/sub 2/O+Cl. The volcanic HCl will probably remove OH much less rapidly than will SO/sub 2/, and if the OH concentration is greatly decreased by the SO/sub 2/, the above reaction may be too slow to be important.« less

Evolution of dike opening during the March 2011 Kamoamoa fissure eruption, Kīlauea Volcano, Hawai`i

USGS Publications Warehouse

Lundgren, Paul; Poland, Michael; Miklius, Asta; Orr, Tim R.; Yun, Sang-Ho; Fielding, Eric; Liu, Zhen; Tanaka, Akiko; Szeliga, Walter; Hensley, Scott; Owen, Susan

2013-01-01

The 5–9 March 2011 Kamoamoa fissure eruption along the east rift zone of Kīlauea Volcano, Hawai`i, followed months of pronounced inflation at Kīlauea summit. We examine dike opening during and after the eruption using a comprehensive interferometric synthetic aperture radar (InSAR) data set in combination with continuous GPS data. We solve for distributed dike displacements using a whole Kīlauea model with dilating rift zones and possibly a deep décollement. Modeled surface dike opening increased from nearly 1.5 m to over 2.8 m from the first day to the end of the eruption, in agreement with field observations of surface fracturing. Surface dike opening ceased following the eruption, but subsurface opening in the dike continued into May 2011. Dike volumes increased from 15, to 16, to 21 million cubic meters (MCM) after the first day, eruption end, and 2 months following, respectively. Dike shape is distinctive, with a main limb plunging from the surface to 2–3 km depth in the up-rift direction toward Kīlauea's summit, and a lesser projection extending in the down-rift direction toward Pu`u `Ō`ō at 2 km depth. Volume losses beneath Kīlauea summit (1.7 MCM) and Pu`u `Ō`ō (5.6 MCM) crater, relative to dike plus erupted volume (18.3 MCM), yield a dike to source volume ratio of 2.5 that is in the range expected for compressible magma without requiring additional sources. Inflation of Kīlauea's summit in the months before the March 2011 eruption suggests that the Kamoamoa eruption resulted from overpressure of the volcano's magmatic system.

Evolution of dike opening during the March 2011 Kamoamoa fissure eruption, Kīlauea Volcano, Hawai`i

NASA Astrophysics Data System (ADS)

Lundgren, Paul; Poland, Michael; Miklius, Asta; Orr, Tim; Yun, Sang-Ho; Fielding, Eric; Liu, Zhen; Tanaka, Akiko; Szeliga, Walter; Hensley, Scott; Owen, Susan

2013-03-01

5-9 March 2011 Kamoamoa fissure eruption along the east rift zone of Kīlauea Volcano, Hawai`i, followed months of pronounced inflation at Kīlauea summit. We examine dike opening during and after the eruption using a comprehensive interferometric synthetic aperture radar (InSAR) data set in combination with continuous GPS data. We solve for distributed dike displacements using a whole Kīlauea model with dilating rift zones and possibly a deep décollement. Modeled surface dike opening increased from nearly 1.5 m to over 2.8 m from the first day to the end of the eruption, in agreement with field observations of surface fracturing. Surface dike opening ceased following the eruption, but subsurface opening in the dike continued into May 2011. Dike volumes increased from 15, to 16, to 21 million cubic meters (MCM) after the first day, eruption end, and 2 months following, respectively. Dike shape is distinctive, with a main limb plunging from the surface to 2-3 km depth in the up-rift direction toward Kīlauea's summit, and a lesser projection extending in the down-rift direction toward Pu`u `Ō`ō at 2 km depth. Volume losses beneath Kīlauea summit (1.7 MCM) and Pu`u `Ō`ō (5.6 MCM) crater, relative to dike plus erupted volume (18.3 MCM), yield a dike to source volume ratio of 2.5 that is in the range expected for compressible magma without requiring additional sources. Inflation of Kīlauea's summit in the months before the March 2011 eruption suggests that the Kamoamoa eruption resulted from overpressure of the volcano's magmatic system.

Holocene volcanism of the upper McKenzie River catchment, central Oregon Cascades, USA

USGS Publications Warehouse

Deligne, Natalia I.; Conrey, Richard M.; Cashman, Katharine V.; Champion, Duane E.; Amidon, William H.

2016-01-01

To assess the complexity of eruptive activity within mafic volcanic fields, we present a detailed geologic investigation of Holocene volcanism in the upper McKenzie River catchment in the central Oregon Cascades, United States. We focus on the Sand Mountain volcanic field, which covers 76 km2 and consists of 23 vents, associated tephra deposits, and lava fields. We find that the Sand Mountain volcanic field was active for a few decades around 3 ka and involved at least 13 eruptive units. Despite the small total volume erupted (∼1 km3 dense rock equivalent [DRE]), Sand Mountain volcanic field lava geochemistry indicates that erupted magmas were derived from at least two, and likely three, different magma sources. Single units erupted from one or more vents, and field data provide evidence of both vent migration and reoccupation. Overall, our study shows that mafic volcanism was clustered in space and time, involved both explosive and effusive behavior, and tapped several magma sources. These observations provide important insights on possible future hazards from mafic volcanism in the central Oregon Cascades.

The influence of conduit processes on changes in style of basaltic Plinian eruptions: Tarawera 1886 and Etna 122 BC

NASA Astrophysics Data System (ADS)

Houghton, B. F.; Wilson, C. J. N.; Del Carlo, P.; Coltelli, M.; Sable, J. E.; Carey, R.

2004-09-01

Basaltic volcanism is most typically thought to produce effusion of lava, with the most explosive manifestations ranging from mild Strombolian activity to more energetic fire fountain eruptions. However, some basaltic eruptions are now recognized as extremely violent, i.e., generating widespread phreatomagmatic, subplinian and Plinian fall deposits. We focus here on the influence of conduit processes, especially partial open-system degassing, in triggering abrupt changes in style and intensity that occurred during two examples of basaltic Plinian volcanism. We use the 1886 eruption of Tarawera, New Zealand, the youngest known basaltic Plinian eruption and the only one for which there are detailed written eyewitness accounts, and the well-documented 122 BC eruption of Mount Etna, Italy, and present new grain size and vesicularity data from the proximal deposits. These data show that even during extremely powerful basaltic eruptions, conduit processes play a critical role in modifying the form of the eruptions. Even with very high discharge, and presumably ascent, rates, partial open-system behaviour of basaltic melts becomes a critical factor that leads to development of domains of largely stagnant and outgassed melt that restricts the effective radius of the conduit. The exact path taken in the waning stages of the eruptions varied, in response to factors which included conduit geometry, efficiency and extent of outgassing and availability of ground water, but a relatively abrupt cessation to sustained high-intensity discharge was an inevitable consequence of the degassing processes.

Volcanic hazard assessment for the Canary Islands (Spain) using extreme value theory

NASA Astrophysics Data System (ADS)

Sobradelo, R.; Martí, J.; Mendoza-Rosas, A. T.; Gómez, G.

2011-10-01

The Canary Islands are an active volcanic region densely populated and visited by several millions of tourists every year. Nearly twenty eruptions have been reported through written chronicles in the last 600 yr, suggesting that the probability of a new eruption in the near future is far from zero. This shows the importance of assessing and monitoring the volcanic hazard of the region in order to reduce and manage its potential volcanic risk, and ultimately contribute to the design of appropriate preparedness plans. Hence, the probabilistic analysis of the volcanic eruption time series for the Canary Islands is an essential step for the assessment of volcanic hazard and risk in the area. Such a series describes complex processes involving different types of eruptions over different time scales. Here we propose a statistical method for calculating the probabilities of future eruptions which is most appropriate given the nature of the documented historical eruptive data. We first characterize the eruptions by their magnitudes, and then carry out a preliminary analysis of the data to establish the requirements for the statistical method. Past studies in eruptive time series used conventional statistics and treated the series as an homogeneous process. In this paper, we will use a method that accounts for the time-dependence of the series and includes rare or extreme events, in the form of few data of large eruptions, since these data require special methods of analysis. Hence, we will use a statistical method from extreme value theory. In particular, we will apply a non-homogeneous Poisson process to the historical eruptive data of the Canary Islands to estimate the probability of having at least one volcanic event of a magnitude greater than one in the upcoming years. This is done in three steps: First, we analyze the historical eruptive series to assess independence and homogeneity of the process. Second, we perform a Weibull analysis of the distribution of repose time between successive eruptions. Third, we analyze the non-homogeneous Poisson process with a generalized Pareto distribution as the intensity function.

The timing and origin of pre- and post-caldera volcanism associated with the Mesa Falls Tuff, Yellowstone Plateau volcanic field

NASA Astrophysics Data System (ADS)

Stelten, Mark E.; Champion, Duane E.; Kuntz, Mel A.

2018-01-01

We present new sanidine 40Ar/39Ar ages and paleomagnetic data for pre- and post-caldera rhyolites from the second volcanic cycle of the Yellowstone Plateau volcanic field, which culminated in the caldera-forming eruption of the Mesa Falls Tuff at ca. 1.3 Ma. These data allow for a detailed reconstruction of the eruptive history of the second volcanic cycle and provide new insights into the petrogenesis of rhyolite domes and flows erupted during this time period. 40Ar/39Ar age data for the biotite-bearing Bishop Mountain flow demonstrate that it erupted approximately 150 kyr prior to the Mesa Falls Tuff. Integrating 40Ar/39Ar ages and paleomagnetic data for the post-caldera Island Park rhyolite domes suggests that these five crystal-rich rhyolites erupted over a centuries-long time interval at 1.2905 ± 0.0020 Ma (2σ). The biotite-bearing Moonshine Mountain rhyolite dome was originally thought to be the downfaulted vent dome for the pre-caldera Bishop Mountain flow due to their similar petrographic and oxygen isotope characteristics, but new 40Ar/39Ar dating suggest that it erupted near contemporaneously with the Island Park rhyolite domes at 1.2931 ± 0.0018 Ma (2σ) and is a post-caldera eruption. Despite their similar eruption ages, the Island Park rhyolite domes and the Moonshine Mountain dome are chemically and petrographically distinct and are not derived from the same source. Integrating these new data with field relations and existing geochemical data, we present a petrogenetic model for the formation of the post-Mesa Falls Tuff rhyolites. Renewed influx of basaltic and/or silicic recharge magma into the crust at 1.2905 ± 0.0020 Ma led to [1] the formation of the Island Park rhyolite domes from the source region that earlier produced the Mesa Falls Tuff and [2] the formation of Moonshine Mountain dome from the source region that earlier produced the biotite-bearing Bishop Mountain flow. These magmas were stored in the crust for less than a few thousand years before being erupted contemporaneously along a 30 km long, structurally controlled vent zone related to extracaldera Basin and Range faults. These data highlight the rapidity with which magma can be generated and erupted over large distances at Yellowstone.

Melt inclusion study of the most recent basanites from El Hierro and Lanzarote, Canary Islands

NASA Astrophysics Data System (ADS)

Gomez-Ulla, Alejandra; Sigmarsson, Olgeir; Huertas, Maria Jose; Ancochea, Eumenio

2015-04-01

The latest eruptions of both Lanzarote (one of the oldest and easternmost of the Canary Island archipelago) and El Hierro (the youngest and westernmost) produced basanite lavas. Major, volatile and trace element concentrations of melt inclusion (MI) hosted in olivine for both eruptions have been analysed. The basanites display primitive mantle normalized trace element spectra suggesting a magma source largely composed of recycled oceanic crust. In addition, beneath Lanzarote an interaction with a carbonatitic fluid phase or metasome would explain eccentric Ba/U and other trace element ratios. Contribution of carbonatitic component would readily account for extremely volatile-rich (Cl, F, S) MI from Lanzarote (Cl=1577-2500 ppm) whereas the maximum for El Hierro is 1080 ppm. The submarine character of the 2011-12 eruption off El Hierro appears to have affected the degassing behavior, whereas estimated sulfur emission to the atmosphere during the historical Lanzarote eruptions are amongst the highest observed so far. An estimated magma volume (VDRE) of 0.02 km3 yields atmospheric mass loading of 0.2 Mt SO2 from the 1824 Lanzarote eruption. Scaling the volume of the 1824 Lanzarote eruption to that of the previous Timanfaya eruption (1730-6; 5 km3) results in estimated 12 Mt SO2, an atmospheric mass loading only outnumbered by the historical Laki and Eldgjá eruptions in Iceland. The significantly greater volatile budget of basanites from Lanzarote compared to El Hierro is thus controlled by more fertile source composition closer to the African continent.

The plumbing of Old Faithful Geyser revealed by hydrothermal tremor

NASA Astrophysics Data System (ADS)

Vandemeulebrouck, J.; Roux, P.; Cros, E.

2013-05-01

Faithful Geyser in Yellowstone National Park (USA) has attracted numerous scientific investigations for over two centuries to better understand its geological structure, the physics of its eruptions, and the controls of its intermittency. Using data acquired with a seismic array in 1992, we track the sources of hydrothermal tremor produced by boiling and cavitation inside the geyser. The location of seismic sources identifies a previously unknown lateral cavity at 15 m below the surface, on the SW side of the vent, and connected to the conduit. This reservoir is activated at the beginning of each geyser eruption cycle and plays a major role in the oscillatory behavior of the water level in the conduit before each eruption.

On the prolonged lifetime of the El Chichon sulfuric acid aerosol cloud

NASA Technical Reports Server (NTRS)

Hofmann, D. J.; Rosen, J. M.

1987-01-01

The observed decay of the aerosol mixing ratio following the eruption of El Chichon appears to have been 20-30 percent slower than that following the eruption of Fuego in 1974, even though the sulfuric acid droplets were observed to grow to considerably larger sizes after El Chichon. This suggests the possible presence of a condensation nuclei and sulfuric acid vapor source and continued growth phenomena occurring well after the El Chichon eruption. It is proposed that the source of these nuclei and the associated vapor may be derived from annual evaporation and condensation of aerosol in the high polar regions during stratospheric warming events, with subsequent spreading to lower latitudes.

Stratigraphic architecture of hydromagmatic volcanoes that have undergone vent migration: a review of Korean case studies

NASA Astrophysics Data System (ADS)

Sohn, Y.

2011-12-01

Recent studies show that the architecture of hydromagmatic volcanoes is far more complex than formerly expected. A number of external factors, such as paleohydrology and tectonics, in addition to magmatic processes are thought to play a role in controlling the overall characteristics and architecture of these volcanoes. One of the main consequences of these controls is the migration of the active vent during eruption. Case studies of hydromagmatic volcanoes in Korea show that those volcanoes that have undergone vent migration are characterized by superposition or juxtaposition of multiple rim deposits of partial tuff rings and/or tuff cones that have contrasting lithofacies characteristics, bed attitudes, and paleoflow directions. Various causes of vent migration are inferred from these volcanoes. Large-scale collapse of fragile substrate is interpreted to have caused vent migration in the Early Pleistocene volcanoes of Jeju Island, which were built upon still unconsolidated continental shelf sediments. Late Pleistocene to Holocene volcanoes, which were built upon a stack of rigid, shield-forming lava flows, lack features due to large-scale substrate collapse and have generally simple and circular morphologies either of a tuff ring or of a tuff cone. However, ~600 m shift of the eruptive center is inferred from one of these volcanoes (Ilchulbong tuff cone). The vent migration in this volcano is interpreted to have occurred because the eruption was sourced by multiple magma batches with significant eruptive pauses in between. The Yangpori diatreme in a Miocene terrestrial half-graben basin in SE Korea is interpreted to be a subsurface equivalent of a hydromagmatic volcano that has undergone vent migration. The vent migration here is inferred to have had both vertical and lateral components and have been caused by an abrupt tectonic activity near the basin margin. In all these cases, rimbeds or diatreme fills derived from different source vents are bounded by either prominent or subtle, commonly laterally extensive truncation surfaces or stratigraphic discontinuities. Careful documentation of these surfaces and discontinuities thus appears vital to proper interpretation of eruption history, morphologic evolution, and even deep-seated magmatic processes of a hydromagmatic volcano. In this respect, the technique known as 'allostratigraphy' appears useful in mapping, correlation, and interpretation of many hydrovolcanic edifices and sequences.

Deep magma accumulation at Nyamulagira volcano in 2011 detected by GNSS observations

NASA Astrophysics Data System (ADS)

Ji, Kang Hyeun; Stamps, D. Sarah; Geirsson, Halldor; Mashagiro, Niche; Syauswa, Muhindo; Kafudu, Benjamin; Subira, Josué; d'Oreye, Nicolas

2017-10-01

People in the area of the Virunga Mountains, along the borders of the Democratic Republic of Congo, Rwanda, and Uganda, are at very high natural risk due to active volcanism. A Global Navigation Satellite System (GNSS) network, KivuGNet (Kivu Geodetic Network), has operated since 2009 for monitoring and research of the deformation of Nyamulagira and Nyiragongo volcanoes as well as tectonic deformation in the region. We detected an inflationary signal from the position time-series observed in the network using our detection method, which is a combination of Kalman filtering and principal component analysis. The inflation event began in October 2010 and lasted for about 6 months prior to the 2011-2012 eruption at Nyamulagira volcano. The pre-eruptive inflationary signal is much weaker than the co-eruptive signal, but our method successfully detected the signal. The maximum horizontal and vertical displacements observed are ∼9 mm and ∼5 mm, respectively. A Mogi point source at a depth >10 km can explain the displacement field. This suggests that a relatively deep source for the magma chamber generated the inflationary signal. The deep reservoir that is the focus of this study may feed a shallower magma chamber, which is the likely source of the 2011-2012 eruption. Continuous monitoring of the volcanic activity is essential for understanding the eruption cycle and assessing potential volcanic hazards.

Petrography of the Paleogene Volcanic Rocks of the Sierra Maestra, Southeastern Cuba

NASA Astrophysics Data System (ADS)

Bemis, V. L.

2006-12-01

This study is a petrographic analysis of over 200 specimens of the Paleogene volcanic rocks of the Sierra Maestra (Southerneastern Cuba), a key structure in the framework of the northern Caribbean plate boundary evolution. The purpose of this study is to understand the eruptive processes and the depositional environments. The volcanic sequence in the lower part of the Sierra Maestra begins with highly porphyritic pillow lavas, topped by massive tuffs and autoclastic flows. The presence of broken phenocrystals, palagonitic glass and hyaloclastites in this section of the sequence suggests that the prevalent mode of eruption was explosive. The absence of welding in the tuffs suggests that the rocks were emplaced in a deep submarine environment. Coherent flows, much less common than the massive tuffs, show evidence of autoclastic fracturing, also indicating low temperature-submarine environments. These observations support the hypothesis that the Sierra Maestra sequence may be neither part of the Great Antilles Arc of the Mesozoic nor any other fully developed volcanic arc, rather a 250 km long, submarine eruptive system of dikes, flows and sills, most likely a back-arc structure. The volcanic rocks of the upper sequence are all very fine grained, reworked volcaniclastic materials, often with the structures of distal turbidities, in mode and texture similar to those drilled on the Cayman Rise. This study suggests that the Sierra Maestra most likely records volcanism of diverse sources: a local older submarine source, and one or more distal younger sources, identifiable with the pan-Caribbean volcanic events of the Tertiary.

Triggering of Solar Magnetic Eruptions on Various Size Scales Alphonse Sterling

NASA Technical Reports Server (NTRS)

Sterling, A.C.

2010-01-01

A solar eruption that produces a coronal mass ejection (CME) together with a flare is driven by the eruption of a closed-loop magnetic arcade that has a sheared-field core. Before eruption, the sheared core envelops a polarity inversion line along which cool filament material may reside. The sheared-core arcade erupts when there is a breakdown in the balance between the confining downward-directed magnetic tension of the overall arcade field and the upward-directed force of the pent-up magnetic pressure of the sheared field in the core of the arcade. What triggers the breakdown in this balance in favor of the upward-directed force is still an unsettled question. We consider several eruption examples, using imaging data from the SoHO, TRACE and Hinode satellites, and other sources, along with information about the magnetic field of the erupting regions. In several cases, observations of large-scale eruptions, where the magnetic neutral line spans few x 10,000 km, are consistent with magnetic flux cancellation being the trigger to the eruption's onset, even though the amount of flux canceled is only few percent of the total magnetic flux of the erupting region. In several other cases, an initial compact (small size-scale) eruption occurs embedded inside of a larger closed magnetic loop system, so that the smaller eruption destabilizes and causes the eruption of the much larger system. In this way, small-scale eruptive events can result in eruption of much larger-scale systems.

1993-2011 Time dependent deformation of Eyjafjallajokull volcano, Iceland

NASA Astrophysics Data System (ADS)

Ali, T.; Feigl, K.; Pedersen, R.; Sigmundsson, F.

2011-12-01

We analyze synthetic aperture radar data acquired by ERS-1, ERS-2, Envisat, TerraSAR-X and ALOS satellites between 1993 and 2011 to characterize the deformation associated with activity at Eyjafjallajokull. The volcano had shown intermittent unrest for 18 years before erupting in 2010. An effusive lava eruption occurred from 20th March to 12th April and was followed by an explosive summit eruption from 14th April to 22nd May, disrupting air traffic. Satellite radar interferometry (InSAR) captured intrusive events in 1994 and 1999 when several decimeters of deformation occurred on the volcanic edifice. By inverting the geodetic data, Pedersen et al. [2004; 2006] inferred that sills between depths of 5-7 km had increased in volume by approximately 10-17 and 21-31 million cubic meters during each of two intrusive events in 1994 and 1999, respectively. In this study, we extend the time series analysis to the pre-eruptive, co-eruptive, and post-eruptive deformation associated with the 2010 eruptions. To describe the pre-eruptive deformation over several months, Sigmundsson et al. [2010] estimate the total volume increase in two sills and a dike to be 49-71 million cubic meters. During the effusive eruption, no significant deformation was observed in the interferograms. During the explosive eruption, deflation was observed, that continued at a low rate after the eruption ceased. To estimate source parameters, we use the General Inversion of Phase Technique [GIPhT; Feigl and Thurber, 2009] that analyzes the gradient of phase without the need for unwrapping. To quantify the misfit between the observed and modeled values of the phase gradient, the objective function calculates the cost as the absolute value of their difference, averaged over all sampled pixels. To minimize the objective function we use a simulated annealing algorithm. For computational efficiency, we approximate the fitting function using Taylor series. Calculation of derivatives requires evaluating the exact version of the fitting function, which for our particular problem involves solving the elasticity equations using the finite element method. The minimization procedure is performed several times before reaching convergence, typically in 5 to 15 iterations. GIPhT is suitable for monitoring volcanoes because it can be run quickly and automatically, as soon as the interferograms are formed. Preliminary results suggest several sources located between 3 and 8 km depth, consistent with seismic observations. The best-fitting models for the inflationary episodes of 1994, 1999 and 2010 are horizontal sills that increase in volume. The deflationary episode is best described by another horizontal sill that decreased in volume after 14th April 2010. The different location of the sources suggests significant movement of magma. Fitting a piece-wise linear polynomial to the time series of source strength estimated from the InSAR data, we find general agreement with independent data sets, including GPS measurements and earthquake locations.

Rapid assembly and rejuvenation of a large silicic magmatic system: Insights from mineral diffusive profiles in the Kidnappers and Rocky Hill deposits, New Zealand

NASA Astrophysics Data System (ADS)

Cooper, George F.; Morgan, Daniel J.; Wilson, Colin J. N.

2017-09-01

The timescales over which magmas in large silicic systems are reactivated, assembled and stored remains a fundamental question in volcanology. To address this question, we study timescales from Fe-Mg interdiffusion in orthopyroxenes and Ti diffusion in quartz from the caldera-forming 1200 km3 Kidnappers and 200 km3 Rocky Hill eruptions from the Mangakino volcanic centre (Taupo Volcanic Zone, New Zealand). The two eruptions came from the same source area, have indistinguishable 40Ar/39Ar ages (∼1.0 Ma) and zircon U-Pb age spectra, but their respective deposits are separated by a short period of erosion. Compositions of pumice, glass and mineral species in the collective eruption deposits define multiple melt dominant bodies but indicate that these shared a common magmatic mush zone. Diffusion timescales from both eruptions are used to build on chemical and textural crystal signatures and interpret both the crystal growth histories and the timing of magma accumulation. Fe-Mg interdiffusion profiles in orthopyroxenes imply that the three melt-dominant bodies, established through extraction of melt and crystals from the common source, were generated within 600 years and with peak accumulation rates within 100 years of each eruption. In addition, a less-evolved melt interacted with the Kidnappers magma, beginning ∼30 years prior to and peaking within 3 years of the eruption. This interaction did not directly trigger the eruption, but may have primed the magmatic system. Orthopyroxene crystals with the same zoning patterns from the Kidnappers and Rocky Hill pumices yield consistently different diffusion timescales, suggesting a time break between the eruptions of ∼20 years (from core-rim zones) to ∼10 years (outer rim zones). Diffusion of Ti in quartz reveals similarly short timescales and magmatic residence times of <30 years, suggesting quartz is only recording the last period of crystallization within the final eruptible melt. Accumulation of the eruptible magma for these two, closely successive eruptions was accomplished over centuries to decades, in contrast to the gestation time of the magmatic system of ∼200 kyr, as indicated by zircon age patterns. The magmatic system was able to recover after the Kidnappers eruption in only ∼10-20 years to accumulate enough eruptible melt and crystals for a second ∼ 200 km3 eruption. Our data support concepts of large silicic systems being stored as long-lived crystal mushes, with eruptible melts generated over extraordinarily short timescales prior to eruption.

Relationship between volcanic activity and shallow hydrothermal system at Meakandake volcano, Japan, inferred from geomagnetic and audio-frequency magnetotelluric measurements

NASA Astrophysics Data System (ADS)

Takahashi, Kosuke; Takakura, Shinichi; Matsushima, Nobuo; Fujii, Ikuko

2018-01-01

Hydrothermal activity at Meakandake volcano, Japan, from 2004 to 2014 was investigated by using long-term geomagnetic field observations and audio-frequency magnetotelluric (AMT) surveys. The total intensity of the geomagnetic field has been measured around the summit crater Ponmachineshiri since 1992 by Kakioka Magnetic Observatory. We reanalyzed an 11-year dataset of the geomagnetic total intensity distribution and used it to estimate the thermomagnetic source models responsible for the surface geomagnetic changes during four time periods (2004-2006, 2006-2008, 2008-2009 and 2013-2014). The modeled sources suggest that the first two periods correspond to a cooling phase after a phreatic eruption in 1998, the third one to a heating phase associated with a phreatic eruption in 2008, and the last one to a heating phase accompanying minor internal activity in 2013. All of the thermomagnetic sources were beneath a location on the south side of Ponmachineshiri crater. In addition, we conducted AMT surveys in 2013 and 2014 at Meakandake and constructed a two-dimensional model of the electrical resistivity structure across the volcano. Combined, the resistivity information and thermomagnetic models revealed that the demagnetization source associated with the 2008 eruptive activity, causing a change in magnetic moment about 30 to 50 times greater than the other sources, was located about 1000 m beneath Ponmachineshiri crater, within or below a zone of high conductivity (a few ohm meters), whereas the other three sources were near each other and above this zone. We interpret the conductive zone as either a hydrothermal reservoir or an impermeable clay-rich layer acting as a seal above the hydrothermal reservoir. Along with other geophysical observations, our models suggest that the 2008 phreatic eruption was triggered by a rapid influx of heat into the hydrothermal reservoir through fluid-rich fractures developed during recent seismic swarms. The hydrothermal reservoir remained hot after the 2008 eruption, and heat was sporadically transported upward through its low permeability ceiling.

Flux Cancelation: The Key to Solar Eruptions

NASA Technical Reports Server (NTRS)

Panesar, Navdeep K.; Sterling, Alphonse; Moore, Ronald; Chakrapani, Prithi; Innes, Davina; Schmit, Don; Tiwari, Sanjiv

2017-01-01

Solar coronal jets are magnetically channeled eruptions that occur in all types of solar environments (e.g. active regions, quiet-Sun regions and coronal holes). Recent studies show that coronal jets are driven by the eruption of small-scare filaments (minifilaments). Once the eruption is underway magnetic reconnection evidently makes the jet spire and the bright emission in the jet base. However, the triggering mechanism of these eruptions and the formation mechanism of the pre-jet minifilaments are still open questions. In this talk, mainly using SDO/AIA (Solar Dynamics Observatory / Atmospheric Imaging Assembly) and SDO/HIM (Solar Dynamics Observatory / Helioseismic and Magnetic Imager) data, first I will address the question: what triggers the jet-driving minifilament eruptions in different solar environments (coronal holes, quiet regions, active regions)? Then I will talk about the magnetic field evolution that produces the pre-jet minifilaments. By examining pre-jet evolutionary changes in line-of-sight HMI magnetograms while examining concurrent EUV (Extreme Ultra-Violet) images of coronal and transition-region emission, we find clear evidence that flux cancelation is the main process that builds pre-jet minifilaments, and is also the main process that triggers the eruptions. I will also present results from our ongoing work indicating that jet-driving minifilament eruptions are analogous to larger-scare filament eruptions that make flares and CMEs (Coronal Mass Ejections). We find that persistent flux cancellation at the neutral line of large-scale filaments often triggers their eruptions. From our observations we infer that flux cancelation is the fundamental process from the buildup and triggering of solar eruptions of all sizes.

The ELSA tephra stack: Volcanic activity in the Eifel during the last 500,000 years

NASA Astrophysics Data System (ADS)

Förster, Michael W.; Sirocko, Frank

2016-07-01

Tephra layers of individual volcanic eruptions are traced in several cores from Eifel maar lakes, drilled between 1998 and 2014 by the Eifel Laminated Sediment Archive (ELSA). All sediment cores are dated by 14C and tuned to the Greenland interstadial succession. Tephra layers were characterized by the petrographic composition of basement rock fragments, glass shards and characteristic volcanic minerals. 10 marker tephra, including the well-established Laacher See Tephra and Dümpelmaar Tephra can be identified in the cores spanning the last glacial cycle. Older cores down to the beginning of the Elsterian, show numerous tephra sourced from Strombolian and phreatomagmatic eruptions, including the 40Ar/39Ar dated differentiated tephra from Glees and Hüttenberg. In total, at least 91 individual tephra can be identified since the onset of the Eifel volcanic activity at about 500,000 b2k, which marks the end of the ELSA tephra stack with 35 Strombolian, 48 phreatomagmatic and 8 tephra layers of evolved magma composition. Many eruptions cluster near timings of the global climate transitions at 140,000, 110,000 and 60,000 b2k. In total, the eruptions show a pattern, which resembles timing of phases of global sea level and continental ice sheet changes, indicating a relation between endogenic and exogenic processes.

Identifying open magnetic field regions of the Sun and their heliospheric counterparts

NASA Astrophysics Data System (ADS)

Krista, L. D.; Reinard, A.

2017-12-01

Open magnetic regions on the Sun are either long-lived (coronal holes) or transient (dimmings) in nature. Both phenomena are fundamental to our understanding of the solar behavior as a whole. Coronal holes are the sources of high-speed solar wind streams that cause recurrent geomagnetic storms. Furthermore, the variation of coronal hole properties (area, location, magnetic field strength) over the solar activity cycle is an important marker of the global evolution of the solar magnetic field. Dimming regions, on the other hand, are short-lived coronal holes that often emerge in the wake of solar eruptions. By analyzing their physical properties and their temporal evolution, we aim to understand their connection with their eruptive counterparts (flares and coronal mass ejections) and predict the possibility of a geomagnetic storm. The author developed the Coronal Hole Automated Recognition and Monitoring (CHARM) and the Coronal Dimming Tracker (CoDiT) algorithms. These tools not only identify but track the evolution of open magnetic field regions. CHARM also provides daily coronal hole maps, that are used for forecasts at the NOAA Space Weather Prediction Center. Our goal is to better understand the processes that give rise to eruptive and non-eruptive open field regions and investigate how these regions evolve over time and influence space weather.

“Points requiring elucidation” about Hawaiian volcanism: Chapter 24

USGS Publications Warehouse

Poland, Michael P.; Carey, Rebecca; Cayol, Valérie; Poland, Michael P.; Weis, Dominique

2015-01-01

Hawaiian volcanoes, which are easily accessed and observed at close range, are among the most studied on the planet and have spurred great advances in the geosciences, from understanding deep Earth processes to forecasting volcanic eruptions. More than a century of continuous observation and study of Hawai‘i's volcanoes has also sharpened focus on those questions that remain unanswered. Although there is good evidence that volcanism in Hawai‘i is the result of a high-temperature upwelling plume from the mantle, the source composition and dynamics of the plume are controversial. Eruptions at the surface build the volcanoes of Hawai‘i, but important topics, including how the volcanoes grow and collapse and how magma is stored and transported, continue to be subjects of intense research. Forecasting volcanic activity is based mostly on pattern recognition, but determining and predicting the nature of eruptions, especially in serving the critical needs of hazards mitigation, require more realistic models and a greater understanding of what drives eruptive activity. These needs may be addressed by better integration among disciplines as well as by developing dynamic physics- and chemistry-based models that more thoroughly relate the physiochemical behavior of Hawaiian volcanism, from the deep Earth to the surface, to geological, geochemical, and geophysical data.

Frictional-faulting model for harmonic tremor before Redoubt Volcano eruptions

USGS Publications Warehouse

Dmitrieva, Ksenia; Hotovec-Ellis, Alicia J.; Prejean, Stephanie G.; Dunham, Eric M.

2013-01-01

Seismic unrest, indicative of subsurface magma transport and pressure changes within fluid-filled cracks and conduits, often precedes volcanic eruptions. An intriguing form of volcano seismicity is harmonic tremor, that is, sustained vibrations in the range of 0.5–5 Hz. Many source processes can generate harmonic tremor. Harmonic tremor in the 2009 eruption of Redoubt Volcano, Alaska, has been linked to repeating earthquakes of magnitudes around 0.5–1.5 that occur a few kilometres beneath the vent. Before many explosions in that eruption, these small earthquakes occurred in such rapid succession—up to 30 events per second—that distinct seismic wave arrivals blurred into continuous, high-frequency tremor. Tremor abruptly ceased about 30 s before the explosions. Here we introduce a frictional-faulting model to evaluate the credibility and implications of this tremor mechanism. We find that the fault stressing rates rise to values ten orders of magnitude higher than in typical tectonic settings. At that point, inertial effects stabilize fault sliding and the earthquakes cease. Our model of the Redoubt Volcano observations implies that the onset of volcanic explosions is preceded by active deformation and extreme stressing within a localized region of the volcano conduit, at a depth of several kilometres.

A kilohertz approach to Strombolian-style eruptions

NASA Astrophysics Data System (ADS)

Taddeucci, Jacopo; Scarlato, Piergiorgio; Del Bello, Elisabetta; Gaudin, Damien

2015-04-01

Accessible volcanoes characterized by persistent, relatively mild Strombolian-style explosive activity have historically hosted multidisciplinary studies of eruptions. These studies, focused on geophysical signals preceding, accompanying, and following the eruptions, have provided key insights on the physical processes driving the eruptions. However, the dynamic development of the single explosions that characterize this style of activity remained somewhat elusive, due to the timescales involved (order of 0.001 seconds). Recent technological advances now allow recording and synchronizing different data sources on time scales relevant to the short timescales involved in the explosions. In the last several years we developed and implemented a field setup that integrates visual and thermal imaging with acoustic and seismic recordings, all synchronized and acquired at timescales of 100-10000 Hz. This setup has been developed at several active volcanoes. On the one hand, the combination of these different techniques provides unique information on the dynamics and energetics of the explosions, including the parameterization of individual ejection pulses within the explosions, the ejection and emplacement of pyroclasts and their coupling-decoupling with the gas phases, the different stages of development of the eruption jets, and their reflection in the associated acoustic and seismic signals. On the other hand, the gained information provides foundation for better understanding and interpreting the signals acquired, at lower sampling rates but routinely, from volcano monitoring networks. Perhaps even more important, our approach allows parameterizing differences and commonalities in the explosions from different volcanoes and settings.

Role for syn-eruptive plagioclase disequilibrium crystallisation in basaltic magma ascent dynamics

NASA Astrophysics Data System (ADS)

La Spina, Giuseppe; Burton, Mike; de'Michieli Vitturi, Mattia; Arzilli, Fabio

2017-04-01

Magma ascent dynamics in volcanic conduits play a key role in determining the eruptive style of a volcano. The lack of direct observations inside the conduit means that numerical conduit models, constrained with observational data, provide invaluable tools for quantitative insights into complex magma ascent dynamics. The highly nonlinear, interdependent processes involved in magma ascent dynamics require several simplifications when modelling their ascent. For example, timescales of magma ascent in conduit models are typically assumed to be much longer than crystallisation and gas exsolution for basaltic eruptions. However, it is now recognized that basaltic magmas may rise fast enough for disequilibrium processes to play a key role on the ascent dynamics. The quantification of the characteristic times for crystallisation and exsolution processes are fundamental to our understanding of such disequilibria and ascent dynamics. Using observations from Mount Etna's 2001 eruption and a magma ascent model we are able to constrain timescales for crystallisation and exsolution processes. Our results show that plagioclase reaches equilibrium in 1-2 h, whereas ascent times were 1 h. Furthermore, we have related the amount of plagioclase in erupted products with the ascent dynamics of basaltic eruptions. We find that relatively high plagioclase content requires crystallisation in a shallow reservoir, whilst a low plagioclase content reflects a disequilibrium crystallisation occurring during a fast ascent from depth to the surface. Using these new constraints on disequilibrium plagioclase crystallisation we also reproduce observed crystal abundances for different basaltic eruptions: Etna 2002/2003, Stromboli 2007 (effusive eruption) and 1930 (paroxysm) and different Pu'u' O'o eruptions at Kilauea (episodes 49-53). Therefore, our results show that disequilibrium processes play a key role on the ascent dynamics of basaltic magmas and cannot be neglected when describing basaltic eruptions. Quantifying the characteristic times for crystallisation and exsolution represents a major step towards a more complete, realistic and general model of basaltic volcanism

Grain size and shape analysis of the AD 1226 tephra layer, Reykjanes volcanic system

NASA Astrophysics Data System (ADS)

Ösp Magnúsdóttir, Agnes; Höskuldsson, Ármann; Larsen, Guðrún; Tumi Guðmunsson, Magnús; Sigurgeirsson, Magnús Á.

2014-05-01

Recent explosive eruptions in Iceland have drawn attention to long range tephra transport in the atmosphere. In Iceland tephra forming explosion eruptions are frequent, due to abundance of water. However, the volcanism on the island is principally basaltic. Volcanism along the Reykjanes Peninsula is divided into five distinct volcanic systems. Volcano-tectonic activity within these systems is periodic, with recurrence intervals in the range of 1 ka. Last volcano-tectonic sequence began around AD 940, shortly after settlement of Iceland, and lasted through AD 1340. During this period activity was characterized by basaltic fissure eruptions. Furthermore, this activity period on the Reykjanes peninsula began within the eastern most volcanic system and gradually moved towards the west across the peninsula. The 1226 eruption was a basaltic fissure eruption with in the Reykjanes volcanic system. The eruption began on land and gradually progressed towards the SW until the volcanic fissure extended into the sea. Water-magma interaction changed the eruption from effusive into explosive forming the largest tephra layer on the peninsula. Due to its close proximity to the Keflavik international airport and that of the capital of Iceland it is important to get an insight into, the characteristics, generation and distribution of such tephra deposits. In this eruption the tephra produced had an approximate volume of 0.1 km3 and covered an area of some 3500 km2 within the 0.5 cm isopach. Total grain size distribution of this tephra layer will be presented along with analysis of principal grain shapes of the finer portion of the tephra layer as a function of distance from the source. The tephra grain size is dominated by particles finer than 1 millimeter with an almost complete absence of large grains independent of distance from the source. Comprehensive understanding of the characteristics of tephra generated in this eruption can help us to understand hazards posed by future eruptions of similar nature in the area.

The May 2005 eruption of Fernandina volcano, Galápagos: The first circumferential dike intrusion observed by GPS and InSAR

USGS Publications Warehouse

Chadwick, W.W.; Jonsson, Sigurjon; Geist, Dennis J.; Poland, M.; Johnson, Daniel J.; Batt, S.; Harpp, Karen S.; Ruiz, A.

2011-01-01

The May 2005 eruption of Fernandina volcano, Galápagos, occurred along circumferential fissures parallel to the caldera rim and fed lava flows down the steep southwestern slope of the volcano for several weeks. This was the first circumferential dike intrusion ever observed by both InSAR and GPS measurements and thus provides an opportunity to determine the subsurface geometry of these enigmatic structures that are common on Galápagos volcanoes but are rare elsewhere. Pre- and post- eruption ground deformation between 2002 and 2006 can be modeled by the inflation of two separate magma reservoirs beneath the caldera: a shallow sill at ~1 km depth and a deeper point-source at ~5 km depth, and we infer that this system also existed at the time of the 2005 eruption. The co-eruption deformation is dominated by uplift near the 2005 eruptive fissures, superimposed on a broad subsidence centered on the caldera. Modeling of the co-eruption deformation was performed by including various combinations of planar dislocations to simulate the 2005 circumferential dike intrusion. We found that a single planar dike could not match both the InSAR and GPS data. Our best-fit model includes three planar dikes connected along hinge lines to simulate a curved concave shell that is steeply dipping (~45–60°) toward the caldera at the surface and more gently dipping (~12–14°) at depth where it connects to the horizontal sub-caldera sill. The shallow sill is underlain by the deep point source. The geometry of this modeled magmatic system is consistent with the petrology of Fernandina lavas, which suggest that circumferential eruptions tap the shallowest parts of the system, whereas radial eruptions are fed from deeper levels. The recent history of eruptions at Fernandina is also consistent with the idea that circumferential and radial intrusions are sometimes in a stress-feedback relationship and alternate in time with one another.

Reconstruction of caldera collapse and resurgence processes in the offshore sector of the Campi Flegrei caldera (Italy)

NASA Astrophysics Data System (ADS)

Steinmann, Lena; Spiess, Volkhard; Sacchi, Marco

2015-04-01

Large collapse calderas are associated with exceptionally explosive volcanic eruptions, which are capable of triggering a global catastrophe second only to that from a giant meteorite impact. Therefore, active calderas have attracted significant attention in both scientific communities and governmental institutions worldwide. One prime example of a large collapse caldera can be found in southern Italy, more precisely in the northern Bay of Naples within the Campi Flegrei Volcanic Area. The Campi Flegrei caldera covers an area of approximately 200 km² defined by a quasi-circular depression, half onland, half offshore. It is still under debate whether the caldera formation was related to only one ignimbritic eruption namely the Neapolitan Yellow Tuff (NYT) eruption at 15 ka or if it is a nested-caldera system related to the NYT and the Campanian Ignimbrite eruption at 39 ka. During the last 40 years, the Campi Flegrei caldera has experienced episodes of unrest involving significant ground deformation and seismicity, which have nevertheless not yet led to an eruption. Besides these short-term episodes of unrest, long-term ground deformation with rates of several tens of meters within a few thousand years can be observed in the central part of the caldera. The source of both short-term and long-term deformation is still under debate and possibly related to a shallow hydrothermal system and caldera resurgence attributed to a deeper magma chamber, respectively. Understanding the mechanisms for unrest and eruptions is of paramount importance as a future eruption of the Campi Flegrei caldera would expose more than 500,000 people to the risk of pyroclastic flows. This study is based on a dense grid (semi-3D) of high-resolution multi-channel seismic profiles acquired in the offshore sector of the Campi Flegrei caldera. The seismic lines show evidence for the escape of fluids and/or gases along weak zones such as faults, thereby supporting the existence of a hydrothermal system. Moreover, a dome-like structure associated with a cluster of normal faults and an apical depression was identified in the center of the caldera, which corresponds very well with the on land observed location of the long-term uplift. Based on the seismic dataset, a conceptual reconstruction of the caldera deformation and depositional processes was developed. Furthermore, the seismic data show indications for a shallow ring-fault system associated with the collapse of the NYT caldera. In addition, major stratigraphic units such as the CI and NYT could be traced on a regional scale, thereby providing information about the eruptive processes and vent locations. Besides the volcano-tectonic aspects, a system tract analysis was carried out in order to reveal the interplay between eustatic sea-level variations and tectonically induced uplift and subsidence.

Ghost Remains After Black Hole Eruption

NASA Astrophysics Data System (ADS)

2009-05-01

NASA's Chandra X-ray Observatory has found a cosmic "ghost" lurking around a distant supermassive black hole. This is the first detection of such a high-energy apparition, and scientists think it is evidence of a huge eruption produced by the black hole. This discovery presents astronomers with a valuable opportunity to observe phenomena that occurred when the Universe was very young. The X-ray ghost, so-called because a diffuse X-ray source has remained after other radiation from the outburst has died away, is in the Chandra Deep Field-North, one of the deepest X-ray images ever taken. The source, a.k.a. HDF 130, is over 10 billion light years away and existed at a time 3 billion years after the Big Bang, when galaxies and black holes were forming at a high rate. "We'd seen this fuzzy object a few years ago, but didn't realize until now that we were seeing a ghost", said Andy Fabian of the Cambridge University in the United Kingdom. "It's not out there to haunt us, rather it's telling us something - in this case what was happening in this galaxy billions of year ago." Fabian and colleagues think the X-ray glow from HDF 130 is evidence for a powerful outburst from its central black hole in the form of jets of energetic particles traveling at almost the speed of light. When the eruption was ongoing, it produced prodigious amounts of radio and X-radiation, but after several million years, the radio signal faded from view as the electrons radiated away their energy. HDF 130 Chandra X-ray Image of HDF 130 However, less energetic electrons can still produce X-rays by interacting with the pervasive sea of photons remaining from the Big Bang - the cosmic background radiation. Collisions between these electrons and the background photons can impart enough energy to the photons to boost them into the X-ray energy band. This process produces an extended X-ray source that lasts for another 30 million years or so. "This ghost tells us about the black hole's eruption long after it has died," said co-author Scott Chapman, also of Cambridge University. "This means we don't have to catch the black holes in the act to witness the big impact they have." This is the first X-ray ghost ever seen after the demise of radio-bright jets. Astronomers have observed extensive X-ray emission with a similar origin, but only from galaxies with radio emission on large scales, signifying continued eruptions. In HDF 130, only a point source is detected in radio images, coinciding with the massive elliptical galaxy seen in its optical image. This radio source indicates the presence of a growing supermassive black hole. People Who Read This Also Read... Milky Way's Super-efficient Particle Accelerators Caught in The Act NASA Joins "Around the World in 80 Telescopes" Celebrate the International Year of Astronomy Galaxies Coming of Age in Cosmic Blobs "This result hints that the X-ray sky should be littered with such ghosts," said co-author Caitlin Casey, also of Cambridge, "especially if black hole eruptions are as common as we think they are in the early Universe." The power contained in the black hole eruption was likely to be considerable, equivalent to about a billion supernovas. The energy is dumped into the surroundings and transports and heats the gas. "Even after the ghost disappears, most of the energy from the black hole's eruption remains", said Fabian. "Because they're so powerful, these eruptions can have profound effects lasting for billions of years." The details of Chandra's data of HDF 130 helped secure its true nature. For example, in X-rays, HDF 130 has a cigar-like shape that extends for some 2.2 million light years. The linear shape of the X-ray source is consistent with the shape of radio jets and not with that of a galaxy cluster, which is expected to be circular. The energy distribution of the X-rays is also consistent with the interpretation of an X-ray ghost. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

Stratigraphic relationships and timing of the 2012 Havre submarine silicic volcanic eruption revealed by high resolution bathymetric mapping and observations by underwater vehicles.

NASA Astrophysics Data System (ADS)

Carey, R.; Soule, S. A.; Houghton, B. F.; White, J. D. L.; Manga, M.; Wysoczanski, R. J.; Tani, K.; McPhie, J.; Fornari, D. J.; Jutzeler, M.; Caratori Tontini, F.; Ikegami, F.; Jones, M.; Murch, A.; Fauria, K.; Mitchell, S. J.; Cahalan, R. C.; Conway, C.; McKenzie, W.

2015-12-01

The 2012 deep rhyolitic caldera eruption of Havre volcano in the Kermadec arc is the first historic observed submarine eruption that produced a pumice raft observed at the ocean's surface. Ship-based bathymetric surveys before and after the eruption permit the intricacies of eruption styles, products and timescales to be quantified. In 2015 we mapped this submarine volcano in unprecedented detail with two submergence vehicles in tandem, facilitating a wide and comprehensive geological survey and sampling mission. These efforts and observations show highly complex and often simultaneous eruptive behavior from more than 14 vents along two 3 km-long fissures that represent massive ruptures of the caldera walls. This survey also revealed an important role for pre- and inter-eruptive periods of mass wasting processes derived from the intrusion of magma and destablisation of caldera walls. The detailed characterization of the eruption products, and quantification of timescales provides the scientific community with the first glimpse of the nature of submarine, intermediate magnitude, deep silicic caldera eruptions and permits unanswered yet first order fundamental questions of submarine eruption and transport processes to be addressed in the decades to come.

Pre-eruptive magmatic processes re-timed using a non-isothermal approach to magma chamber dynamics.

PubMed

Petrone, Chiara Maria; Bugatti, Giuseppe; Braschi, Eleonora; Tommasini, Simone

2016-10-05

Constraining the timescales of pre-eruptive magmatic processes in active volcanic systems is paramount to understand magma chamber dynamics and the triggers for volcanic eruptions. Temporal information of magmatic processes is locked within the chemical zoning profiles of crystals but can be accessed by means of elemental diffusion chronometry. Mineral compositional zoning testifies to the occurrence of substantial temperature differences within magma chambers, which often bias the estimated timescales in the case of multi-stage zoned minerals. Here we propose a new Non-Isothermal Diffusion Incremental Step model to take into account the non-isothermal nature of pre-eruptive processes, deconstructing the main core-rim diffusion profiles of multi-zoned crystals into different isothermal steps. The Non-Isothermal Diffusion Incremental Step model represents a significant improvement in the reconstruction of crystal lifetime histories. Unravelling stepwise timescales at contrasting temperatures provides a novel approach to constraining pre-eruptive magmatic processes and greatly increases our understanding of magma chamber dynamics.

Pre-eruptive magmatic processes re-timed using a non-isothermal approach to magma chamber dynamics

PubMed Central

Petrone, Chiara Maria; Bugatti, Giuseppe; Braschi, Eleonora; Tommasini, Simone

2016-01-01

Constraining the timescales of pre-eruptive magmatic processes in active volcanic systems is paramount to understand magma chamber dynamics and the triggers for volcanic eruptions. Temporal information of magmatic processes is locked within the chemical zoning profiles of crystals but can be accessed by means of elemental diffusion chronometry. Mineral compositional zoning testifies to the occurrence of substantial temperature differences within magma chambers, which often bias the estimated timescales in the case of multi-stage zoned minerals. Here we propose a new Non-Isothermal Diffusion Incremental Step model to take into account the non-isothermal nature of pre-eruptive processes, deconstructing the main core-rim diffusion profiles of multi-zoned crystals into different isothermal steps. The Non-Isothermal Diffusion Incremental Step model represents a significant improvement in the reconstruction of crystal lifetime histories. Unravelling stepwise timescales at contrasting temperatures provides a novel approach to constraining pre-eruptive magmatic processes and greatly increases our understanding of magma chamber dynamics. PMID:27703141

Large explosive basaltic eruptions at Katla volcano, Iceland: Fragmentation, grain size and eruption dynamics

NASA Astrophysics Data System (ADS)

Schmith, Johanne; Höskuldsson, Ármann; Holm, Paul Martin; Larsen, Guðrún

2018-04-01

Katla volcano in Iceland produces hazardous large explosive basaltic eruptions on a regular basis, but very little quantitative data for future hazard assessments exist. Here details on fragmentation mechanism and eruption dynamics are derived from a study of deposit stratigraphy with detailed granulometry and grain morphology analysis, granulometric modeling, componentry and the new quantitative regularity index model of fragmentation mechanism. We show that magma/water interaction is important in the ash generation process, but to a variable extent. By investigating the large explosive basaltic eruptions from 1755 and 1625, we document that eruptions of similar size and magma geochemistry can have very different fragmentation dynamics. Our models show that fragmentation in the 1755 eruption was a combination of magmatic degassing and magma/water-interaction with the most magma/water-interaction at the beginning of the eruption. The fragmentation of the 1625 eruption was initially also a combination of both magmatic and phreatomagmatic processes, but magma/water-interaction diminished progressively during the later stages of the eruption. However, intense magma/water interaction was reintroduced during the final stages of the eruption dominating the fine fragmentation at the end. This detailed study of fragmentation changes documents that subglacial eruptions have highly variable interaction with the melt water showing that the amount and access to melt water changes significantly during eruptions. While it is often difficult to reconstruct the progression of eruptions that have no quantitative observational record, this study shows that integrating field observations and granulometry with the new regularity index can form a coherent model of eruption evolution.

Source mechanisms of persistent shallow earthquakes during eruptive and non-eruptive periods between 1981 and 2011 at Mount St. Helens, Washington

USGS Publications Warehouse

Lehto, Heather L.; Roman, Diana C.; Moran, Seth C.

2013-01-01

Shallow seismicity between 0 and 3-km depth has persisted at Mount St. Helens, Washington (MSH) during both eruptive and non-eruptive periods for at least the past thirty years. In this study we investigate the source mechanisms of shallow volcano-tectonic (VT) earthquakes at MSH by calculating high-quality hypocenter locations and fault plane solutions (FPS) for all VT events recorded during two eruptive periods (1981–1986 and 2004–2008) and two non-eruptive periods (1987–2004 and 2008–2011). FPS show a mixture of normal, reverse, and strike-slip faulting during all periods, with a sharp increase in strike-slip faulting observed in 1987–1997 and an increase in normal faulting in 1998–2004. FPS P-axis orientations show a ~ 90° rotation with respect to regional σ1 (N23°E) during 1981–1986 and 2004–2008, bimodal orientations (~ N-S and ~ E-W) during 1987–2004, and bimodal orientations at ~ N-E and ~ S-W from 2008–2011. We interpret these orientations to likely be due to pressurization accompanying the shallow intrusion and subsequent eruption of magma as domes during 1981–1986 and 2004–2008 and the buildup of pore pressure beneath a seismogenic volume (located at 0–1 km) with a smaller component due to the buildup of tectonic forces during 1987–2004 and 2008–2011.

Trace Element Geochemistry of Basaltic Tephra in Maar Cores; Implications for Centre Correlation, Field Evolution, and Mantle Source Characteristics of the Auckland Volcanic Field, New Zealand

NASA Astrophysics Data System (ADS)

Hopkins, J. L.; Leonard, G.; Timm, C.; Wilson, C. J. N.; Neil, H.; Millet, M. A.

2014-12-01

Establishing volcanic hazard and risk management strategies hinges on a detailed understanding of the type, timing and tephra dispersal of past eruptions. In order to unravel the pyroclastic eruption history of a volcanic field, genetic links between the deposits and eruption source centre need to be established. The Auckland Volcanic Field (AVF; New Zealand) has been active for ca. 200 kyr and comprises ca. 53 individual centres covering an area of ca. 360km2. These centres show a range of sizes and eruptive styles from maar craters and tuff rings, to scoria cones and lava flows consistent with both phreatomagmatic and magmatic eruptions. Superimposition of the metropolitan area of Auckland (ca. 1.4 million inhabitants) on the volcanic field makes it critically important to assess the characteristics of the volcanic activity, on which to base assessment and management of the consequent hazards. Here we present a geochemical approach for correlating tephra deposits to their source centres. To acquire the most complete stratigraphic record of pyroclastic events, maar crater cores from different locations, covering various depths and thus ages across the field were selected. Magnetic susceptibility and x-ray density scanning of the cores was used to identify the basaltic tephra horizons, which were sampled and in-situ analysis of individual shards undertaken for major and trace elements using EPMA and LA-ICP-MS techniques, respectively. Our results show that tephra shard trace element ratios are comparable and complementary to the AVF whole rock database. The use of specific trace element ratios (e.g. Gd/Yb vs. Zr/Yb) allows us to fingerprint and cross correlate tephra horizons between cores and, when coupled with newly acquired 40Ar-39Ar age dating and eruption size estimates, correlate horizons to their source centres. This integrated style of study can provide valuable information to help volcanic hazard management and forecasting, and mitigation of related risks.

Volcanic eruption volume flux estimations from very long period infrasound signals

NASA Astrophysics Data System (ADS)

Yamada, Taishi; Aoyama, Hiroshi; Nishimura, Takeshi; Iguchi, Masato; Hendrasto, Muhamad

2017-01-01

We examine very long period infrasonic signals accompanying volcanic eruptions near active vents at Lokon-Empung volcano in Indonesia, Aso, Kuchinoerabujima, and Kirishima volcanoes in Japan. The excitation of the very long period pulse is associated with an explosion, the emerging of an eruption column, and a pyroclastic density current. We model the excitation of the infrasound pulse, assuming a monopole source, to quantify the volume flux and cumulative volume of erupting material. The infrasound-derived volume flux and cumulative volume can be less than half of the video-derived results. A largely positive correlation can be seen between the infrasound-derived volume flux and the maximum eruption column height. Therefore, our result suggests that the analysis of very long period volcanic infrasound pulses can be helpful in estimating the maximum eruption column height.

Outstanding challenges in the seismological study of volcanic processes: Results from recent U.S. and European community-wide discussion workshops

NASA Astrophysics Data System (ADS)

Roman, D. C.; Rodgers, M.; Mather, T. A.; Power, J. A.; Pyle, D. M.

2014-12-01

Observations of volcanically induced seismicity are essential for eruption forecasting and for real-time and near-real-time warnings of hazardous volcanic activity. Studies of volcanic seismicity and of seismic wave propagation also provide critical understanding of subsurface magmatic systems and the physical processes associated with magma genesis, transport, and eruption. However, desipite significant advances in recent years, our ability to successfully forecast volcanic eruptions and fully understand subsurface volcanic processes is limited by our current understanding of the source processes of volcano-seismic events, the effects on seismic wave propagation within volcanic structures, limited data, and even the non-standardized terminology used to describe seismic waveforms. Progress in volcano seismology is further hampered by inconsistent data formats and standards, lack of state-of-the-art hardware and professional technical staff, as well as a lack of widely adopted analysis techniques and software. Addressing these challenges will not only advance scientific understanding of volcanoes, but also will lead to more accurate forecasts and warnings of hazardous volcanic eruptions that would ultimately save lives and property world-wide. Two recent workshops held in Anchorage, Alaska, and Oxford, UK, represent important steps towards developing a relationship among members of the academic community and government agencies, focused around a shared, long-term vision for volcano seismology. Recommendations arising from the two workshops fall into six categories: 1) Ongoing and enhanced community-wide discussions, 2) data and code curation and dissemination, 3) code development, 4) development of resources for more comprehensive data mining, 5) enhanced strategic seismic data collection, and 6) enhanced integration of multiple datasets (including seismicity) to understand all states of volcano activity through space and time. As presented sequentially above, these steps can be regarded as a road map for galvanizing and strengthening the volcano seismological community to drive new scientific and technical progress over the next 5-10 years.

Conduit stability effects on intensity and steadiness of explosive eruptions.

PubMed

Aravena, Álvaro; Cioni, Raffaello; de'Michieli Vitturi, Mattia; Neri, Augusto

2018-03-07

Conduit geometry affects magma ascent dynamics and, consequently, the style and evolution of volcanic eruptions. However, despite geological evidences support the occurrence of conduit widening during most volcanic eruptions, the factors controlling conduit enlargement are still unclear, and the effects of syn-eruptive variations of conduit geometry have not been investigated in depth yet. Based on numerical modeling and the application of appropriate stability criteria, we found out a strong relationship between magma rheology and conduit stability, with significant effects on eruptive dynamics. Indeed, in order to be stable, conduits feeding dacitic/rhyolitic eruptions need larger diameters respect to their phonolitic/trachytic counterparts, resulting in the higher eruption rates commonly observed in dacitic/rhyolitic explosive events. Thus, in addition to magma source conditions and viscosity-dependent efficiency for outgassing, we suggest that typical eruption rates for different magma types are also controlled by conduit stability. Results are consistent with a compilation of volcanological data and selected case studies. As stability conditions are not uniform along the conduit, widening is expected to vary in depth, and three axisymmetric geometries with depth-dependent radii were investigated. They are able to produce major modifications in eruptive parameters, suggesting that eruptive dynamics is influenced by syn-eruptive changes in conduit geometry.

Locating hydrothermal acoustic sources at Old Faithful Geyser using Matched Field Processing

NASA Astrophysics Data System (ADS)

Cros, E.; Roux, P.; Vandemeulebrouck, J.; Kedar, S.

2011-10-01

In 1992, a large and dense array of geophones was placed around the geyser vent of Old Faithful, in the Yellowstone National Park, to determine the origin of the seismic hydrothermal noise recorded at the surface of the geyser and to understand its dynamics. Old Faithful Geyser (OFG) is a small-scale hydrothermal system where a two-phase flow mixture erupts every 40 to 100 min in a high continuous vertical jet. Using Matched Field Processing (MFP) techniques on 10-min-long signal, we localize the source of the seismic pulses recorded at the surface of the geyser. Several MFP approaches are compared in this study, the frequency-incoherent and frequency-coherent approach, as well as the linear Bartlett processing and the non-linear Minimum Variance Distorsionless Response (MVDR) processing. The different MFP techniques used give the same source position with better focalization in the case of the MVDR processing. The retrieved source position corresponds to the geyser conduit at a depth of 12 m and the localization is in good agreement with in situ measurements made at Old Faithful in past studies.

Modelling the dynamics and hazards of explosive eruptions: Where we are now, and confronting the next challenges (Sergey Soloviev Medal Lecture)

NASA Astrophysics Data System (ADS)

Neri, Augusto

2017-04-01

Understanding of explosive eruption dynamics and assessment of their hazards continue to represent challenging issues to the present-day volcanology community. This is largely due to the complex and diverse nature of the phenomena, and the variability and unpredictability of volcanic processes. Nevertheless, important and continuing progress has been made in the last few decades in understanding fundamental processes and in forecasting the occurrences of these phenomena, thanks to significant advances in field, experimental and theoretical modeling investigations. For over four decades, for example, volcanologists have made major progress in the description of the nature of explosive eruptions, considerably aided by the development, improvement, and application of physical-mathematical models. Integral steady-state homogeneous flow models were first used to investigate the different controlling mechanisms and to infer the genesis and evolution of the phenomena. Through continuous improvements and quantum-leap developments, a variety of transient, 3D, multiphase flow models of volcanic phenomena now can implement state-of-the-art formulations of the underlying physics, new-generation analytical and experimental data, as well as high-performance computational techniques. These numerical models have proved to be able to provide key insights in the understanding of the dynamics of explosive eruptions (e.g. convective plumes, collapsing columns, pyroclastic density currents, short-lived explosions, etc.), as well as to represent a valuable tool in the quantification of potential eruptive scenarios and associated hazards. Simplified models based on a reduction of the system complexity have been also proved useful, combined with Monte Carlo and statistical methods, to generate quantitative probabilistic hazard maps at different space and time scales, some including the quantification of important sources of uncertainty. Nevertheless, the development of physical models able to accurately replicate, within acceptable statistical uncertainty, the evolution of explosive eruptions remains a challenging goal still to be achieved. Testing of the developed models versus large-scale experimental data and well-measured real events, real-time assimilation of observational data to forecast the process nature and evolution, as well as the quantification of the uncertainties affecting our system and modelling representations appear key next steps to further progress volcanological research and its essential contribution to the mitigation of volcanic risk.

Dating Kimberlite Eruption and Erosion Phases Using Perovskite, Zircon, and Apatite (U-Th)/He Geochronology to Link Cratonic Lithosphere Evolution and Surface Processes

NASA Astrophysics Data System (ADS)

Stanley, J. R.; Flowers, R. M.

2015-12-01

In many cases it is difficult to evaluate the synchronicity and thus potential connections between disparate geologic events, such as the links between processes in the mantle lithosphere and at the surface. Developing new geochronologic tools and strategies for integrating existing chronologic data with other information is essential for addressing these problems. Here we use (U-Th)/He dating of multiple kimberlitic minerals to date kimberlite eruption and cratonic erosion phases. This approach permits us to more directly assess the link between unroofing and thermomodification of the lithosphere by tying our results to information obtained from mantle-derived clasts in the same pipes. Kimberlites are rich sources of information about the composition of the cratonic lithosphere and its evolution over time. Their xenoliths and xenocrysts can preserve a snapshot of the entire lithosphere and its sedimentary cover at the time of eruption. Accurate geochronology of these eruptions is crucial for interpreting spatiotemporal trends, but kimberlites can be difficult to date using standard techniques. Here we show that the mid-temperature thermochonometers of the zircon and perovskite (U-Th)/He (ZHe, PHe) systems can be viable tools for dating kimberlite eruption. When combined with the low temperature sensitivity of (U-Th)/He in apatite (AHe), the (U-Th)/He system can be used to date both the emplacement and the erosional cooling history of kimberlites. The southern African shield is an ideal location to test the utility of this approach because the region was repeatedly intruded by kimberlites in the Cretaceous, with two major pulses at ~200-110 Ma and ~100-80 Ma. These kimberlites contain a well-studied suite of mantle xenoliths and xenocrysts that document lithospheric heating and metasomatism over this interval. Our ZHe and PHe dates overlap with published eruption ages and add new ages for undated pipes. Our AHe dates constrain the spatial patterns of Cretaceous erosion across the craton, with a phase of erosion that overlaps with when the lithosphere was thermochemically modified, especially in the more heavily altered off-craton regions. These results highlight the value of the (U-Th)/He system for dating a range of geologic events and evaluating elusive links between surface and deeper-earth processes.

Using infrasound waves to monitor tropospheric weather and crater morphology changes at Volcán Tungurahua, Ecuador

NASA Astrophysics Data System (ADS)

Ortiz, Hugo D.; Johnson, Jeffrey B.; Ramón, Patricio G.; Ruiz, Mario C.

2018-01-01

We use infrasound waves generated during eruptions of Volcán Tungurahua (Ecuador) to study both, changing atmospheric conditions and volcanic source characteristics. Analyzed infrasound data were recorded for a 32-month period by a five-station network located within 6.5 km from the vent. We use cross-network correlation to quantify the recurrent eruptive behavior of Tungurahua and results are corroborated by reports from the Ecuadorian monitoring agency. Cross-network lag times vary over short time periods (minutes to days) when vent location is stable and attribute these variations to changes in atmospheric structure. Assuming a fixed source location, we invert for average air temperatures and winds in Tungurahua's vicinity (< 6.5 km) and find evidence for diurnal and semidiurnal tropospheric tides. We also use cross-network correlation lag times to compute infrasound source positions with resolutions of 11.6 m, taking into account coarse NOAA atmospheric models for local winds and temperatures. Variable infrasound-derived source locations suggest source migration during the 32 months of analyzed data. Such source position variability is expected following energetic eruptions that destructively altered the crater/vent morphology as confirmed by imagery obtained during regular overflights.

Assessing Magmatic Processes and Hazards at two Basaltic Monogenetic Centers: Volcan Jorullo, Mexico, and Blue Lake Maar, Oregon

NASA Astrophysics Data System (ADS)

Johnson, E. R.; Cashman, K.; Wallace, P.; Delgado Granados, H.

2007-05-01

Although monogenetic basaltic volcanoes exhibit a wide variety of eruption styles, the origin of this diversity is poorly understood and often ignored when assessing volcanic hazards. To better understand magmatic processes and hazards associated with these eruptions, we have studied two monogenetic centers with differing behavior: Volcan Jorullo, a cinder cone in Mexico, and Blue Lake, a maar in the Oregon High Cascades. Although compositionally similar (medium-K basalt to basaltic andesite), their eruptive styles and products are quite different. Jorullo had violent strombolian eruptions that deposited alternating beds of ash and tephra, as well as lava flows. In contrast, Blue Lake exhibited initial phreatomagmatism that formed a 100m deep crater and produced surge deposits. This activity was followed by magmatic eruptions that produced deposits of tephra and bombs, but no lava flows. The diversity in eruptive style at these two centers reflects different magma ascent and crystallization processes, deduced using olivine-hosted melt inclusions. Jorullo melt inclusions trap variably degassed melts (0.5-5 wt% H2O; 0-1000 ppm CO2), with associated crystallization pressures that decrease from early (<4 kbars) to late (<100 bars) in the eruption. These data support the formation of a shallow storage region beneath the volcano that facilitated both crystallization and magma degassing, which is consistent with effusion of degassed lavas from the base of the cone throughout the eruption. In contrast, Blue Lake inclusions trap melts with a restricted range of volatiles (2.6-4 wt% H2O; 677-870 ppm CO2) corresponding to crystallization pressures of 2.2-3.2 kbars. This suggests that the magma feeding Blue Lake stalled in the upper crust and crystallized before ascending rapidly to the surface, without further crystallization of olivine or shallow storage. This is consistent with both the observed unstratified tephra deposits (indicating single rather than pulsatory eruptions) and the absence of lava flows. Our data suggest that in spite of similar compositions and volatile contents, these two volcanoes produced distinctive eruption styles. Although external water clearly played an important role in the eruption at Blue Lake, both volcanoes had explosive, magmatic volatile-driven eruptions. These eruptions clearly show that monogenetic centers are capable of a wide variety of eruptive styles and hazards, which may depend in large part on processes of magma ascent, degassing, and crystallization.

The onset of an eruption: selective assimilation of hydrothermal minerals during pre-eruptive magma ascent of the 2010 summit eruption of Eyjafjallajökull volcano, Iceland

NASA Astrophysics Data System (ADS)

Pistolesi, M.; Cioni, R.; Francalanci, L.; Bertagnini, A.; D'Oriano, C.; Braschi, E.; Höskuldsson, A.

2016-11-01

The complex processes occurring in the initial phases of an eruption are often recorded in the products of its opening stage, which are usually characterized by small volume and limited dispersal, and thus generally poorly studied. The 2010 eruption of Eyjafjallajökull (Iceland) represents a unique opportunity for these investigations thanks to the good preservation of tephra deposits within the ice/snow pack. A detailed geochemical investigation on the glassy groundmass of single ash clasts disclosed a population of fragments with unusual high 87Sr/86Sr (up to 0.70668) for Icelandic magmatism, and anomalous elemental composition with respect to most of the juvenile material of the eruption. This suggests that during its rise, before intruding into the ice cover, magma at a dyke tip selectively assimilated hydrothermal minerals with seawater-related, high-Sr isotopic ratios (zeolites, silica phases, anhydrite) hosted in altered volcanic/epiclastic rocks. According to the observed precursory seismicity, only restricted to few hours before the onset of the eruption, this process could have accompanied subcritical aseismic fracture opening during the days before the eruption, possibly related to stress corrosion-cracking processes, which enhanced the partial dissolution/melting and subsequent selective assimilation of the host rocks.

Mechanisms of Tooth Eruption and Orthodontic Tooth Movement

PubMed Central

Wise, G.E.; King, G.J.

2008-01-01

Teeth move through alveolar bone, whether through the normal process of tooth eruption or by strains generated by orthodontic appliances. Both eruption and orthodontics accomplish this feat through similar fundamental biological processes, osteoclastogenesis and osteogenesis, but there are differences that make their mechanisms unique. A better appreciation of the molecular and cellular events that regulate osteoclastogenesis and osteogenesis in eruption and orthodontics is not only central to our understanding of how these processes occur, but also is needed for ultimate development of the means to control them. Possible future studies in these areas are also discussed, with particular emphasis on translation of fundamental knowledge to improve dental treatments. PMID:18434571

Constraints on dike propagation from continuous GPS measurements

USGS Publications Warehouse

Segall, P.; Cervelli, Peter; Owen, S.; Lisowski, M.; Miklius, Asta

2001-01-01

The January 1997 East Rift Zone eruption on Kilauea volcano, Hawaii, occurred within a network of continuous Global Positioning System (GPS) receivers. The GPS measurements reveal the temporal history of deformation during dike intrusion, beginning ??? 8 hours prior to the onset of the eruption. The dike volume as a function of time, estimated from the GPS data using elastic Green's functions for a homogeneous half-space, shows that only two thirds of the final dike volume accumulated prior to the eruption and the rate of volume change decreased with time. These observations are inconsistent with simple models of dike propagation, which predict accelerating dike volume up to the time of the eruption and little or no change thereafter. Deflationary tilt changes at Kilauea summit mirror the inferred dike volume history, suggesting that the rate of dike propagation is limited by flow of magma into the dike. A simple, lumped parameter model of a coupled dike magma chamber system shows that the tendency for a dike to end in an eruption (rather than intrusion) is favored by high initial dike pressures, compressional stress states, large, compressible magma reservoirs, and highly conductive conduits linking the dike and source reservoirs. Comparison of model predictions to the observed dike volume history, the ratio of erupted to intruded magma, and the deflationary history of the summit magma chamber suggest that most of the magma supplied to the growing dike came from sources near to the eruption through highly conductive conduits. Interpretation is complicated by the presence of multiple source reservoirs, magma vesiculation and cooling, as well as spatial variations in dike-normal stress. Reinflation of the summit magma chamber following the eruption was measured by GPS and accompanied a rise in the level of the Pu'u O'o lava lake. For a spheroidal chamber these data imply a summit magma chamber volume of ??? 20 km3, consistent with recent estimates from seismic tomography. Continuous deformation measurements can be used to image the spatiotemporal evolution of propagating dikes and to reveal quantitative information about the volcanic plumbing systems. Copyright 2001 by the American Geophysical Union.

Constraints on dike propagation from continuous GPS measurements

NASA Astrophysics Data System (ADS)

Segall, Paul; Cervelli, Peter; Owen, Susan; Lisowski, Mike; Miklius, Asta

2001-09-01

The January 1997 East Rift Zone eruption on Kilauea volcano, Hawaii, occurred within a network of continuous Global Positioning System (GPS) receivers. The GPS measurements reveal the temporal history of deformation during dike intrusion, beginning ˜8 hours prior to the onset of the eruption. The dike volume as a function of time, estimated from the GPS data using elastic Green's functions for a homogeneous half-space, shows that only two thirds of the final dike volume accumulated prior to the eruption and the rate of volume change decreased with time. These observations are inconsistent with simple models of dike propagation, which predict accelerating dike volume up to the time of the eruption and little or no change thereafter. Deflationary tilt changes at Kilauea summit mirror the inferred dike volume history, suggesting that the rate of dike propagation is limited by flow of magma into the dike. A simple, lumped parameter model of a coupled dike magma chamber system shows that the tendency for a dike to end in an eruption (rather than intrusion) is favored by high initial dike pressures, compressional stress states, large, compressible magma reservoirs, and highly conductive conduits linking the dike and source reservoirs. Comparison of model predictions to the observed dike volume history, the ratio of erupted to intruded magma, and the deflationary history of the summit magma chamber suggest that most of the magma supplied to the growing dike came from sources near to the eruption through highly conductive conduits. Interpretation is complicated by the presence of multiple source reservoirs, magma vesiculation and cooling, as well as spatial variations in dike-normal stress. Reinflation of the summit magma chamber following the eruption was measured by GPS and accompanied a rise in the level of the Pu'u O'o lava lake. For a spheroidal chamber these data imply a summit magma chamber volume of ˜20 km3, consistent with recent estimates from seismic tomography. Continuous deformation measurements can be used to image the spatiotemporal evolution of propagating dikes and to reveal quantitative information about the volcanic plumbing systems.

Vent Processes and Deposits of a Hiatus in a Violent Eruption: Quilotoa Volcano, Ecuador

NASA Astrophysics Data System (ADS)

Best, J. A.; Bustillos, J.; Ort, M. H.; Cashman, K. V.; Mothes, P. A.; di Muro, A.; Rosi, M.

2010-12-01

The 800 BP eruption of Quilotoa volcano, Ecuador, produced two plinian eruptions separated by a short (days-weeks) hiatus. Units 1 and 3 (U1 and U3) of the eruption correspond to the first and second Plinian eruptions, respectively, and produced fallout and pyroclastic density currents. Unit 2 (U2) records processes during the hiatus and consists of three subunits: U2a, U2b, and U2c. 147 tephra samples of U1, U2, and U3 were collected from 25 sites from around the volcano. Thickness and grain-size features were described, with particular attention paid to U2, in order to characterize the processes that occurred during the eruptive hiatus. Grain-size and componentry analysis of a subset of these samples reveals a number of trends. The upper part of U1 is massive and normally graded at its top, 32-45 % dominantly vitric ash ≤ 3.0 φ, and likely represents the clearing of the air at the end of the first plinian eruption. U2a, present out to a maximum of 7 km from the vent, has a polymodal distribution with a large fraction of 4.0 φ and finer vitric material. Dune forms occur in this unit, which are interpreted to be the product of surges. The areal distribution of U2a is constrained by topography, whereas U2b is not. U2b is coarser overall with alternating fine- (2-3φ) and coarse- (1-2φ) grained layers. The beds, both coarse and fine, have a near-bimodal grain-size distribution and normal grading. U2b is interpreted as a fall deposit. The U2a/U2b contact is gradational in that 0-2 beds of U2b material occur within the uppermost U2a beds at proximal localities, indicating vent conditions for both briefly coexisted. U2c is a <2-cm-thick vitric ash bed with sparse dense juvenile vitric lapilli. These lapilli also occur in the overlying basal U3 fallout, which has a polymodal grain-size distribution. U2b is characteristically orange in color due to the dust that loosely covers the grains. Hydrothermal activity within the vent is likely the source of this staining, with the simultaneous milling of the weakened material producing the orange dust. We interpret the dense vitric lapilli ≥ -2.0 φ of U2c as being from an explosion through a lava dome, and thus they indicate that the eruption was continuous from U2c through U3. Our current hypothesis is that, as the U1 eruption ended, magma stalled deep in the conduit and degassed hot acidic gas that streamed through the material clogging the vent. This elutriated vitric material that eventually formed a cap on the system. As the U3 magma began its ascent, gas flux increased, leading to explosions that gradually removed the vitric cap and deposited the vitric U2a. Then, more continuous gas streaming led to the development of a pulsatory eruption column that carried hot crystals and vitric grains from the vent clog into a convecting column and eventual deposition as U2b fallout, which was then followed by the establishment of the U3 eruption column.

The significance of volcanic ash in Greenland ice cores during the Common Era

NASA Astrophysics Data System (ADS)

Plunkett, G.; Pilcher, J. R.; McConnell, J. R.; Sigl, M.; Chellman, N.

2017-12-01

Volcanic forcing is now widely regarded as a leading natural factor in short-term climate variability. Polar ice cores provide an unrivalled and continuous record of past volcanism through their chemical and particulate content. With an almost annual precision for the Common Era, the ice core volcanic record can be combined with historical data to investigate the climate and social impacts of the eruptions. The sulfate signature in ice cores is critical for determining the possible climate effectiveness of an eruption, but the presence and characterization of volcanic ash (tephra) in the ice is requisite for establishing the source eruption so that location and eruptive style can be better factored in to climate models. Here, we review the Greenland tephra record for the Common Era, and present the results of targeted sampling for tephra of volcanic events that are of interest either because of their suspected climate and societal impacts or because of their potential as isochrons in paleoenvironmental (including ice core) archives. The majority of identifiable tephras derive from Northern Hemisphere mid- to high latitude eruptions, demonstrating the significance of northern extra-tropical volcanic regions as a source of sulfates in Greenland. A number of targets are represented by sparse or no tephra, or shards that cannot be firmly correlated with a source. We consider the challenges faced in isolating and characterizing tephra from low latitude eruptions, and the implications for accurately modelling climate response to large, tropical events. Finally, we compare the ice core tephra record with terrestrial tephrostratigraphies in the circum-North Atlantic area to evaluate the potential for intercontinental tephra linkages and the refinement of volcanic histories.

Time dependence of volcano inflation: mass influx or viscoelastic relaxation? Insights from Grímsvötn volcano, Iceland

NASA Astrophysics Data System (ADS)

Segall, P.

2017-12-01

Distinguishing magma chamber pressurization from relaxation of a viscoelastic aureole surrounding the chamber based on geodetic measurements has remained challenging. Elastic models with mass inflow proportional to the pressure difference between the chamber and a deep reservoir predict exponentially decaying flux. For a spherical chamber surrounded by a Maxwell viscoelastic shell with pressure dependent recharge, the surface deformation is the sum of two exponentials (Segall, 2016). GPS displacements following eruptions of Grímsvötn, Iceland in 2004 and 2011 exhibit rapid post-eruptive inflation (time scale of 0.1 yr), followed by inflation with a much longer time constant. Markov Chain Monte Carlo inversion with the viscoelastic model shows the GPS time series can be fit with viscosity of 2e16 Pa-s, and a relatively incompressible magma, B = beta_c/ (beta_m + beta_c) > 0.6, where beta_m and beta_c are chamber and magma compressibility. The latter appears to conflict with the ratio of erupted volume to geodetically inferred source volume change, rv 10, obtained for the best fitting spherical (Mogi ) source (Hreinsdóttir, 2014). Since rv = 1/B, this implies a relatively compressible melt, B 0.1. Reexamination of the co-eruptive GPS and tilt data with the more general ellipsoidal model of Cervelli (2013), reveals that the best fitting sources are oblate (b/a 3), deeper, and with larger volume changes, rv 3, relative to spherical models. Oblate magma chambers are consistent with seismic tomography. FEM calculations including free surface effects lead to even larger co-eruptive volume changes, smaller rv and hence larger B. I conclude that the data are consistent with rapid post-eruptive inflation driven by viscoelastic relaxation with a relatively incompressible magma, although other interpretations will be discussed.

Thermal precursors in satellite images of the 1999 eruption of Shishaldin Volcano

NASA Astrophysics Data System (ADS)

Dehn, Jonathan; Dean, Kenneson; Engle, Kevin; Izbekov, Pavel

2002-07-01

Shishaldin Volcano, Unimak Island Alaska, began showing signs of thermal unrest in satellite images on 9 February 1999. A thermal anomaly and small steam plume were detected at the summit of the volcano in short-wave thermal infrared AVHRR (advanced very high resolution radiometer) satellite data. This was followed by over 2 months of changes in the observed thermal character of the volcano. Initially, the thermal anomaly was only visible when the satellite passed nearly directly over the volcano, suggesting a hot source deep in the central crater obscured from more oblique satellite passes. The "zenith angle" needed to see the anomaly increased with time, presumably as the thermal source rose within the conduit. Based on this change, an ascent rate of ca. 14 m per day for the thermal source was estimated, until it reached the summit on around 21 March. It is thought that Strombolian activity began around this time. The precursory activity culminated in a sub-Plinian eruption on 19 April, ejecting ash to over 45,000 ft. (13,700 m). The thermal energy output through the precursory period was calculated based on geometric constraints unique to Shishaldin. These calculations show fluctuations that can be tied to changes in the eruptive character inferred from seismic records and later geologic studies. The remote location of this volcano made satellite images a necessary observation tool for this eruption. To date, this is the longest thermal precursory activity preceding a sub-Plinian eruption recorded by satellite images in the region. This type of thermal monitoring of remote volcanoes is central in the efforts of the Alaska Volcano Observatory to provide timely warnings of volcanic eruption, and mitigate their associated hazards to air-traffic and local residents.

Volcanic Tremor at Mt. Etna, Italy, Preceding and Accompanying the Eruption of July August, 2001

NASA Astrophysics Data System (ADS)

Falsaperla, S.; Alparone, S.; D'Amico, S.; Grazia, G.; Ferrari, F.; Langer, H.; Sgroi, T.; Spampinato, S.

2005-11-01

The July 17 August 9, 2001 flank eruption of Mt. Etna was preceded and accompanied by remarkable changes in volcanic tremor. Based on the records of stations belonging to the permanent seismic network deployed on the volcano, we analyze amplitude and frequency content of the seismic signal. We find considerable changes in the volcanic tremor which mark the transition to different styles of eruptive activity, e.g., lava fountains, phreatomagmatic activity, Strombolian explosions. In particular, the frequency content of the signal decreases from 5 Hz to 3 Hz at our reference station ETF during episodes of lava fountains, and further decreases at about 2 Hz throughout phases of intense lava emission. The frequency content and the ratios of the signal amplitude allow us to distinguish three seismic sources, i.e., the peripheral dike which fed the eruption, the reservoir which fed the lava fountains, and the central conduit. Based on the analysis of the amplitude decay of the signal, we highlight the migration of the dike from a depth of ca. 5 km to about 1 km between July 10 and 12. After the onset of the effusive phase, the distribution of the amplitude decay at our stations can be interpreted as the overall result of sources located within the first half kilometer from the surface. Although on a qualitative basis, our findings shed some light on the complex feeding system of Mt. Etna, and integrate other volcanological and geophysical studies which tackle the problem of magma replenishment for the July August, 2001 flank eruption. We conclude that volcanic tremor is fundamental in monitoring Mt. Etna, not only as a marker of the different sources which act within the volcano edifice, but also of the diverse styles of eruptive activity.

Classifying the Sizes of Explosive Eruptions using Tephra Deposits: The Advantages of a Numerical Inversion Approach

NASA Astrophysics Data System (ADS)

Connor, C.; Connor, L.; White, J.

2015-12-01

Explosive volcanic eruptions are often classified by deposit mass and eruption column height. How well are these eruption parameters determined in older deposits, and how well can we reduce uncertainty using robust numerical and statistical methods? We describe an efficient and effective inversion and uncertainty quantification approach for estimating eruption parameters given a dataset of tephra deposit thickness and granulometry. The inversion and uncertainty quantification is implemented using the open-source PEST++ code. Inversion with PEST++ can be used with a variety of forward models and here is applied using Tephra2, a code that simulates advective and dispersive tephra transport and deposition. The Levenburg-Marquardt algorithm is combined with formal Tikhonov and subspace regularization to invert eruption parameters; a linear equation for conditional uncertainty propagation is used to estimate posterior parameter uncertainty. Both the inversion and uncertainty analysis support simultaneous analysis of the full eruption and wind-field parameterization. The combined inversion/uncertainty-quantification approach is applied to the 1992 eruption of Cerro Negro (Nicaragua), the 2011 Kirishima-Shinmoedake (Japan), and the 1913 Colima (Mexico) eruptions. These examples show that although eruption mass uncertainty is reduced by inversion against tephra isomass data, considerable uncertainty remains for many eruption and wind-field parameters, such as eruption column height. Supplementing the inversion dataset with tephra granulometry data is shown to further reduce the uncertainty of most eruption and wind-field parameters. We think the use of such robust models provides a better understanding of uncertainty in eruption parameters, and hence eruption classification, than is possible with more qualitative methods that are widely used.

The 2003 phreatomagmatic eruptions of Anatahan volcano - Textural and petrologic features of deposits at an emergent island volcano

USGS Publications Warehouse

Pallister, J.S.; Trusdell, F.A.; Brownfield, I.K.; Siems, D.F.; Budahn, J.R.; Sutley, S.F.

2005-01-01

Stratigraphic and field data are used in conjunction with textural and chemical evidence (including data from scanning electron microscope, electron microprobe, X-ray fluorescence, X-ray diffraction, and instrumental neutron activation analysis) to establish that the 2003 eruption of Anatahan volcano was mainly phreatomagmatic, dominated by explosive interaction of homogeneous composition low-viscosity crystal-poor andesite magma with water. The hydromagmatic mode of eruption contributed to the significant height of initial eruptive columns and to the excavation and eruption of altered rock debris from the sub-volcanic hydrothermal system. Volatile contents of glass inclusions in equilibrium phenocrysts less abundances of these constituents in matrix glass times the estimated mass of juvenile magma indicate minimum emissions of 19 kt SO2 and 13 kt Cl. This petrologic estimate of SO2 emission is an order-of-magnitude less than an estimate from TOMS. Similarly, inferred magma volumes from the petrologic data are an order of magnitude greater than those modeled from deformation data. Both discrepancies indicate additional sources of volatiles, likely derived from a separate fluid phase in the magma. The paucity of near-source volcanic-tectonic earthquakes preceding the eruption, and the dominance of sustained long-period tremor are attributed to the ease of ascent of the hot low-viscosity andesite, followed by a shallow phreatomagmatic mode of eruption. Phreatomagmatic eruptions are probably more common at emergent tropical island volcanoes, where shallow fresh-water lenses occur at near-sea-level vents. These relations suggest that phreatomagmatic explosions contributed to the formation of many of the near-sea-level craters and possibly even to the small calderas at the other Mariana islands.

Experimental estimates of the energy budget of hydrothermal eruptions; application to 2012 Upper Te Maari eruption, New Zealand

NASA Astrophysics Data System (ADS)

Montanaro, Cristian; Scheu, Bettina; Cronin, Shane J.; Breard, Eric C. P.; Lube, Gert; Dingwell, Donald B.

2016-10-01

Sudden hydrothermal eruptions occur in many volcanic settings and may include high-energy explosive phases. Ballistics launched by such events, together with ash plumes and pyroclastic density currents, generate deadly proximal hazards. The violence of hydrothermal eruptions (or explosive power) depends on the energy available within the driving-fluids (gas or liquid), which also influences the explosive mechanisms, volumes, durations, and products of these eruptions. Experimental studies in addition to analytical modeling were used here to elucidate the fragmentation mechanism and aspects of energy balance within hydrothermal eruptions. We present results from a detailed study of recent event that occurred on the 6th of August 2012 at Upper Te Maari within the Tongariro volcanic complex (New Zealand). The eruption was triggered by a landslide from this area, which set off a rapid stepwise decompression of the hydrothermal system. Explosive blasts were directed both westward and eastward of the collapsed area, with a vertical ash plume sourced from an adjacent existing crater. All explosions ejected blocks on ballistic trajectories, hundreds of which impacted New Zealand's most popular hiking trail and a mountain lodge, 1.4 km from the explosion locus. We have employed rocks representative of the eruption source area to perform rapid decompression experiments under controlled laboratory conditions that mimic hydrothermal explosions under controlled laboratory conditions. An experimental apparatus for 34 by 70 mm cylindrical samples was built to reduce the influence of large lithic enclaves (up to 30 mm in diameter) within the rock. The experiments were conducted in a temperature range of 250 °C-300 °C and applied pressure between 4 MPa and 6.5 MPa, which span the range of expected conditions below the Te Maari crater. Within this range we tested rapid decompression of pre-saturated samples from both liquid-dominated conditions and the vapor-dominated field. Further, we tested dry samples at the same pressure and temperature conditions. Results showed that host rock lithology and state of the interstitial fluid was a major influence on the fragmentation and ejection processes, as well as the energy partitioning. Clasts were ejected with velocities of up to 160 m/s as recorded by high-speed camera. In addition to rare large clasts (analogous to ballistics), a large amount of fine and very fine (<63 μm) ash was produced in all experiments. The efficiency of transformation of the total explosive energy into fragmentation energy was estimated between 10 to 15%, depending on the host rock lithology, while less than 0.1% of this was converted into kinetic energy. Our results suggest that liquid-to-vapor (flashing) expansion provides an order of magnitude higher energy release than steam expansion, which best explains the dynamics of the westward (and most energetic) directed blast at Te Maari. Considering the steam flashing as the primary energy source, the experiments suggested that a minimum explosive energy of 7 ×1010 to 2 ×1012 J was involved in the Te Maari blast. Experimental studies under controlled conditions, compared closely to a field example are thus highly useful in providing new insights into the energy release and hazards associated with eruptions in hydrothermal areas.

The Chaitén rhyolite lava dome: Eruption sequence, lava dome volumes, rapid effusion rates and source of the rhyolite magma

USGS Publications Warehouse

Pallister, John S.; Diefenbach, Angela K.; Burton, William C.; Munoz, Jorge; Griswold, Julia P.; Lara, Luis E.; Lowenstern, Jacob B.; Valenzuela, Carolina E.

2013-01-01

We use geologic field mapping and sampling, photogrammetric analysis of oblique aerial photographs, and digital elevation models to document the 2008-2009 eruptive sequence at Chaitén Volcano and to estimate volumes and effusion rates for the lava dome. We also present geochemical and petrologic data that contribute to understanding the source of the rhyolite and its unusually rapid effusion rates. The eruption consisted of five major phases: 1. An explosive phase (1-11 May 2008); 2. A transitional phase (11-31 May 2008) in which low-altitude tephra columns and simultaneous lava extrusion took place; 3. An exogenous lava flow phase (June-September 2008); 4. A spine extrusion and endogenous growth phase (October 2008-February 2009); and 5. A mainly endogenous growth phase that began after the collapse of a prominent Peléean spine on 19 February 2009 and continued until the end of the eruption (late 2009 or possibly earliest 2010). The 2008-2009 rhyolite lava dome has a total volume of approximately 0.8 km3. The effusion rate averaged 66 m3s-1 during the first two weeks and averaged 45 m3s-1 for the first four months of the eruption, during which 0.5 km3 of rhyolite lava was erupted. These are among the highest rates measured world-wide for historical eruptions of silicic lava. Chaitén’s 2008-2009 lava is phenocryst-poor obsidian and microcrystalline rhyolite with 75.3±0.3% SiO2. The lava was erupted at relatively high temperature and is remarkably similar in composition and petrography to Chaitén’s pre-historic rhyolite. The rhyolite’s normative composition plots close to that of low pressure (100-200 MPa) minimum melts in the granite system, consistent with estimates of approximately 5 to 10 km source depths based on phase equilibria and geodetic studies. Calcic plagioclase, magnesian orthopyroxene and aluminous amphibole among the sparse phenocrysts suggest derivation of the rhyolite by melt extraction from a more mafic magmatic mush. High temperature and relatively low viscosity enabled rapid magma ascent and high effusion rates during the dome-forming phases of the 2008-2009 eruption.

Magmatic processes revealed by anorthoclase textures and trace element modeling: The case of the Lajes Ignimbrite eruption (Terceira Island, Azores)

NASA Astrophysics Data System (ADS)

D'Oriano, Claudia; Landi, Patrizia; Pimentel, Adriano; Zanon, Vittorio

2017-11-01

The Lajes Ignimbrite on Terceira Island (Azores) records the last major pyroclastic density current-forming eruption of Pico Alto Volcano that occurred ca. 21 kyrs ago. This comenditic trachyte ignimbrite contains up to 30 vol% of crystals, mostly anorthoclase. Geochemical investigation of the products collected throughout two key outcrops reveals that major element compositions are poorly variable, whereas trace elements show significant variability, pointing to the presence of a zoned magma reservoir. Thermometry and oxygen fugacity estimations yielded pre-eruptive temperatures of 850-900 °C and ΔNNO from - 2.4 to - 1.8. Melt-alkali-feldspar hygrometer indicates magmatic H2O contents ranging from 5.8 wt% in the upper part of the reservoir to 3.6 wt% at the bottom, indicating that the magma reservoir (confined at 4 km depth) was mainly water-undersaturated before the eruption, except for the topmost portion. Two types of anorthoclase crystals were identified. Type 1 crystals show reverse to oscillatory zoning with An contents of 0.4-2.1 mol% and Ba of 200-2000 ppm. They formed in the middle/upper portion of the reservoir, where fractional crystallization processes dominated. Type 2 crystals, mainly present in the less evolved products, are characterized by patchy-zoned cores with large dissolution pockets surrounded by thick oscillatory-zoned rims and show a wide compositional range (An of 0.5-4.7 mol% and Ba of 142-4824 ppm). Their zoning patterns, together with whole-rock and glass compositions of the juvenile clasts, are consistent with the involvement of an anorthoclase-bearing cumulate from the bottom of the reservoir that underwent partial melting. Crystal dissolution was likely induced by the presence of a heat source at depth, without any mass transfer to the eruptible magma, as suggested by the lack of petrographic and chemical evidences of mixing between the resident comenditic trachyte and a mafic/intermediate magma. Thermal instability generated convective plumes that were responsible for the admittance of crystals from the cumulate level into the intermediate portions of the magma reservoir and possibly acted as trigger of the explosive eruption.

Post-eruptive flooding of Santorini caldera and implications for tsunami generation.

PubMed

Nomikou, P; Druitt, T H; Hübscher, C; Mather, T A; Paulatto, M; Kalnins, L M; Kelfoun, K; Papanikolaou, D; Bejelou, K; Lampridou, D; Pyle, D M; Carey, S; Watts, A B; Weiß, B; Parks, M M

2016-11-08

Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The caldera-forming eruption of Santorini in the Late Bronze Age is known to have been tsunamigenic, and caldera collapse has been proposed as a mechanism. Here, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Inflow of water and associated landsliding cut a deep, 2.0-2.5 km 3 , submarine channel, thus filling the caldera in less than a couple of days. If, as at most such volcanoes, caldera collapse occurred syn-eruptively, then it cannot have generated tsunamis. Entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations, were the main mechanisms of tsunami production.

Post-eruptive flooding of Santorini caldera and implications for tsunami generation

NASA Astrophysics Data System (ADS)

Nomikou, P.; Druitt, T. H.; Hübscher, C.; Mather, T. A.; Paulatto, M.; Kalnins, L. M.; Kelfoun, K.; Papanikolaou, D.; Bejelou, K.; Lampridou, D.; Pyle, D. M.; Carey, S.; Watts, A. B.; Weiß, B.; Parks, M. M.

2016-11-01

Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The caldera-forming eruption of Santorini in the Late Bronze Age is known to have been tsunamigenic, and caldera collapse has been proposed as a mechanism. Here, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Inflow of water and associated landsliding cut a deep, 2.0-2.5 km3, submarine channel, thus filling the caldera in less than a couple of days. If, as at most such volcanoes, caldera collapse occurred syn-eruptively, then it cannot have generated tsunamis. Entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations, were the main mechanisms of tsunami production.

Geologic map of the central San Juan caldera cluster, southwestern Colorado

USGS Publications Warehouse

Lipman, Peter W.

2006-01-01

The San Juan Mountains are the largest erosional remnant of a composite volcanic field that covered much of the southern Rocky Mountains in middle Tertiary time. The San Juan field consists mainly of intermediate-composition lavas and breccias, erupted about 35-30 Ma from scattered central volcanoes (Conejos Formation) and overlain by voluminous ash-flow sheets erupted from caldera sources. In the central San Juan Mountains, eruption of at least 8,800 km3 of dacitic-rhyolitic magma as nine major ash flow sheets (individually 150-5,000 km3) was accompanied by recurrent caldera subsidence between 28.3 Ma and about 26.5 Ma. Voluminous andesitic-dacitic lavas and breccias erupted from central volcanoes prior to the ash-flow eruptions, and similar lava eruptions continued within and adjacent to the calderas during the period of more silicic explosive volcanism. Exposed calderas vary in size from 10 to 75 km in maximum dimension; the largest calderas are associated with the most voluminous eruptions.

Post-eruptive flooding of Santorini caldera and implications for tsunami generation

PubMed Central

Nomikou, P.; Druitt, T. H.; Hübscher, C.; Mather, T. A.; Paulatto, M.; Kalnins, L. M.; Kelfoun, K.; Papanikolaou, D.; Bejelou, K.; Lampridou, D.; Pyle, D. M.; Carey, S.; Watts, A. B.; Weiß, B.; Parks, M. M.

2016-01-01

Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The caldera-forming eruption of Santorini in the Late Bronze Age is known to have been tsunamigenic, and caldera collapse has been proposed as a mechanism. Here, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Inflow of water and associated landsliding cut a deep, 2.0–2.5 km3, submarine channel, thus filling the caldera in less than a couple of days. If, as at most such volcanoes, caldera collapse occurred syn-eruptively, then it cannot have generated tsunamis. Entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations, were the main mechanisms of tsunami production. PMID:27824353

Characteristics of EIT Dimmings in Solar Eruptions

NASA Technical Reports Server (NTRS)

Adams, Mitzi; Sterling, A. C.

2006-01-01

Intensity "dimmings" in coronal images are a key feature of solar eruptions. Such dimmings are likely the source locations for much of the material expelled in coronal mass ejections (CMEs). Characteristics such as the timing of the dimmings with respect to the onset of other eruption signatures, and the location of the dimmings in the context of the magnetic field environment of the erupting region, are indicative of the mechanism leading to the eruption. We examine dimmings of six eruptions in images from the EUV Imaging Telescope (EIT) on SOHO, along with supplementary soft X-ray (SXR) data from GOES and the SXR Telescope (SXT) on Yohkoh. We examine the timing of the dimming onset and compare with the time of EUV and SXR brightening and determine the timescale for the recovery from dimming for each event. With line-of-sight photospheric magnetograms from the MDI instrument on SOHO, we determine the magnetic structure of the erupting regions and the locations of the dimmings in those regions. From our analysis we consider which mechanism likely triggered each eruption: internal tether cutting, external tether cutting ("breakout"), loss of equilibrium, or some other mechanism.

Magmatic plumbing system of Kilauea Volcano: Insights from Petrologic and Geochemical Monitoring

NASA Astrophysics Data System (ADS)

Garcia, M. O.; Pietruszka, A. J.; Marske, J.; Greene, A.; Lynn, K. J.

2016-12-01

Monitoring the petrology and geochemistry of lavas from active volcanoes in near realtime affords the opportunity to formulate and evaluate models for magma transport, mixing, and storage to help predict eruption scenarios with greater confidence and better understand magmatic plumbing systems (e.g., Poland et al. 2012, Nat. Geosci. 5, 295-300). Continous petrologic and geochemical monitoring of two ongoing eruptions at the summit and east rift zone of Kilauea Volcano on the Island of Hawaii have revealed much about the dynamics of magmatic processes. When the composition of lava shifted to a more MgO-rich composition in April 1983, we predicted that the Puu Oo eruption would not be short-lived. We had no idea it would continue for over 33 years. Subsequent changes in lava composition have highlighted the interplay between mixing pockets of rift-zone stored magma with new mantle-derived magma and the cooling-induced crystal fractionation during brief (usually days) eruption hiatuses. Surprisingly, the mantle derived magma has continued to change in composition including several 10-year cycles in Pb isotope ratios superimposed on a progressive depletion in highly incompatible elements (Greene et al. 2013, G3, doi: 10.1002/ggge.20285). These compositional trends are contrary to those observed for sustained basaltic eruptions on continents and argue for melt extraction from a multi-component source with 1-3 km wide heterogeneities. Compositional zoning within olivine phenocrysts, created by diffusive re-equilibration, also provide insights into magma mixing, storage, and transport at Kilauea. Timescales modeling of Fe-Mg and Ni concentration gradients within Puu Oo olivine indicate that crystals can be stored at magmatic temperatures for months to a few years before eruption (Shea et al. 2015, Geology 43, 935-938). Kilauea's ongoing eruptions continue to provide a dynamic laboratory for positing and testing models for the generation and evolution of basaltic magma.

Quartz phenocrysts preserve volcanic stresses at Long Valley and Yellowstone calderas

NASA Astrophysics Data System (ADS)

Befus, K. S.; Leonhardi, T. C.; Manga, M.; Tamura, N.; Stan, C. V.

2016-12-01

Magmatic processes and eruptions are the consequence of stresses active in volcanic environments. Few techniques are presently available to quantify those stresses because they operate in subsurface and/or hazardous environments, and thus new techniques are needed to advance our understanding of key processes. Here, we provide a dataset of volcanic stresses that were imparted to quartz crystals that traveled through, and were hosted within, pyroclastic and effusive eruptions from Long Valley and Yellowstone calderas. We measured crystal lattice deformation with submicron spatial resolution using the synchrotron X-ray microdiffraction beamline (12.3.2) at the Advanced Light Source, Lawrence Berkeley National Laboratory. Quartz from all units produces diffraction patterns with residual strains locked in the crystal lattice. We used Hooke's Law and the stiffness constants of quartz to calculate the stresses that caused the preserved residual strains. At Long Valley caldera, quartz preserves stresses of 187±80 MPa within pumice clasts in the F1 fall unit of the Bishop Tuff, and preserves stresses of 120±45 MPa from the Bishop Tuff welded ignimbrite. At Yellowstone caldera quartz preserves stresses of 115±30 and 140±60 MPa within pumices from the basal fall units of the Mesa Falls Tuff and the Tuff of Bluff Point, respectively. Quartz from near-vent and flow-front samples from Summit Lake lava flow preserves stresses up to 130 MPa, and show no variation with distance travelled. We believe that subsurface processes cause the measured residual stresses, but it remains unclear if they are relicts of fragmentation or from the magma chamber. The residual stresses from both Long Valley and Yellowstone samples roughly correlate to lithostatic pressures estimated for the respective pre-eruption magma storage depths. It is possible that residual stress in quartz provides a new geobarometer for crystallization pressure. Moving forward, we will continue to perform analyses and experiments on natural and synthetic crystals to better determine the source of residual stresses.

Strong S-wave attenuation and actively degassing magma beneath Taal volcano, Philippines, inferred from source location analysis using high-frequency seismic amplitudes

NASA Astrophysics Data System (ADS)

Kumagai, H.; Lacson, R. _Jr., Jr.; Maeda, Y.; Figueroa, M. S., II; Yamashina, T.

2014-12-01

Taal volcano, Philippines, is one of the world's most dangerous volcanoes given its history of explosive eruptions and its close proximity to populated areas. A key feature of these eruptions is that the eruption vents were not limited to Main Crater but occurred on the flanks of Volcano Island. This complex eruption history and the fact that thousands of people inhabit the island, which has been declared a permanent danger zone, together imply an enormous potential for disasters. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) constantly monitors Taal, and international collaborations have conducted seismic, geodetic, electromagnetic, and geochemical studies to investigate the volcano's magma system. Realtime broadband seismic, GPS, and magnetic networks were deployed in 2010 to improve monitoring capabilities and to better understand the volcano. The seismic network has recorded volcano-tectonic (VT) events beneath Volcano Island. We located these VT events based on high-frequency seismic amplitudes, and found that some events showed considerable discrepancies between the amplitude source locations and hypocenters determined by using onset arrival times. Our analysis of the source location discrepancies points to the existence of a region of strong S-wave attenuation near the ground surface beneath the east flank of Volcano Island. This region is beneath the active fumarolic area and above sources of pressure contributing inflation and deflation, and it coincides with a region of high electrical conductivity. The high-attenuation region matches that inferred from an active-seismic survey conducted at Taal in 1993. Our results, synthesized with previous results, suggest that this region represents actively degassing magma near the surface, and imply a high risk of future eruptions on the east flank of Volcano Island.

Seismicity at Old Faithful Geyser: an isolated source of geothermal noise and possible analogue of volcanic seismicity

USGS Publications Warehouse

Kieffer, S.W.

1984-01-01

Old Faithful Geyser in Yellowstone National Park, U.S.A., is a relatively isolated source of seismic noise and exhibits seismic behavior similar to that observed at many volcanoes, including "bubblequakes" that resemble B-type "earthquakes", harmonic tremor before and during eruptions, and periods of seismic quiet prior to eruptions. Although Old Faithful differs from volcanoes in that the conduit is continuously open, that rock-fracturing is not a process responsible for seismicity, and that the erupting fluid is inviscid H2O rather than viscous magma, there are also remarkable similarities in the problems of heat and mass recharge to the system, in the eruption dynamics, and in the seismicity. Water rises irregularly into the immediate reservoir of Old Faithful as recharge occurs, a fact that suggests that there are two enlarged storage regions: one between 18 and 22 m (the base of the immediate reservoir) and one between about 10 and 12 m depth. Transport of heat from hot water or steam entering at the base of the recharging water column into cooler overlying water occurs by migration of steam bubbles upward and their collapse in the cooler water, and by episodes of convective overturn. An eruption occurs when the temperature of the near-surface water exceeds the boiling point if the entire water column is sufficiently close to the boiling curve that the propagation of pressure-release waves (rarefactions) down the column can bring the liquid water onto the boiling curve. The process of conversion of the liquid water in the conduit at the onset of an eruption into a two-phase liquid-vapor mixture takes on the order of 30 s. The seismicity is directly related to the sequence of filling and heating during the recharge cycle, and to the fluid mechanics of the eruption. Short (0.2-0.3 s), monochromatic, high-frequency events (20-60 Hz) resembling unsustained harmonic tremor and, in some instances, B-type volcanic earthquakes, occur when exploding or imploding bubbles of steam cause transient vibrations of the fluid column. The frequency of the events is determined by the length of the water column and the speed of sound of the fluid in the conduit when these events occur; damping is controlled by the characteristic and hydraulic impedances, which depend on the above parameters, as well as on the recharge rate of the fluid. Two periods of reduced seismicity (of a few tens of seconds to nearly a minute in duration) occur during the recharge cycle, apparently when the water rises rapidly through the narrow regions of the conduit, causing a sudden pressure increase that temporarily suppresses steam bubble formation. A period of decreased seismicity also precedes preplay or an eruption; this appears to be the time when rising steam bubbles move into a zone of boiling that is acoustically decoupled from the wall of the conduit because of the acoustic impedance mismatch between boiling water (??c ??? 103 g cm-2 s-1) and rock (??c ??? 3 ?? 105 g cm2 s-1). Sustained harmonic tremor occurs during the first one to one-and-a-half minutes of an eruption of Old Faithful, but is not detectable in the succeeding minutes of the eruption. The eruption tremor is caused by hydraulic transients propagating within a sublayer of unvesiculated water that underlies the erupting two-phase liquid-vapor mixture. The resonant frequencies of the fluid column decrease to about 1 Hz when all of the water in the conduit has been converted to a water-steam mixture. Surges are observed in the flow at this frequency, but the resonance has not been detected seismically, possibly because the two-phase erupting fluid is seismically decoupled from the rock on which seismometers are placed. If Old Faithful is an analogue for volcanic seismicity, this study shows that because the frequency of tremor depends on the acoustic properties of the fluid and on conduit dimensions, both properties must be considered in analysis of tremor in volcanic regions. Because magma sound

A sensitivity analysis of volcanic aerosol dispersion in the stratosphere. [Mt. Fuego, Guatemala eruptions

NASA Technical Reports Server (NTRS)

Butler, C. F.

1979-01-01

A computer sensitivity analysis was performed to determine the uncertainties involved in the calculation of volcanic aerosol dispersion in the stratosphere using a 2 dimensional model. The Fuego volcanic event of 1974 was used. Aerosol dispersion processes that were included are: transport, sedimentation, gas phase sulfur chemistry, and aerosol growth. Calculated uncertainties are established from variations in the stratospheric aerosol layer decay times at 37 latitude for each dispersion process. Model profiles are also compared with lidar measurements. Results of the computer study are quite sensitive (factor of 2) to the assumed volcanic aerosol source function and the large variations in the parameterized transport between 15 and 20 km at subtropical latitudes. Sedimentation effects are uncertain by up to a factor of 1.5 because of the lack of aerosol size distribution data. The aerosol chemistry and growth, assuming that the stated mechanisms are correct, are essentially complete in several months after the eruption and cannot explain the differences between measured and modeled results.

Using Websites to Convey Scientific Uncertainties for Volcanic Processes and Potential Hazards

NASA Astrophysics Data System (ADS)

Venezky, D. Y.; Lowenstern, J. B.; Hill, D. P.

2005-12-01

The Yellowstone Volcano Observatory (YVO) and Long Valley Observatory (LVO) websites have greatly increased the public's awareness and access to information about scientific uncertainties for volcanic processes by communicating at multiple levels of understanding and varied levels of detail. Our websites serve a broad audience ranging from visitors unaware of the calderas, to lay volcano enthusiasts, to scientists, federal agencies, and emergency managers. Both Yellowstone and Long Valley are highly visited tourist attractions with histories of caldera-forming eruptions large enough to alter global climate temporarily. Although it is much more likely that future activity would be on a small scale at either volcano, we are constantly posed questions about low-probability, high-impact events such as the caldera-forming eruption depicted in the recent BBC/Discovery movie, "Supervolcano". YVO and LVO website objectives include: providing monitoring data, explaining the likelihood of future events, summarizing research results, helping media provide reliable information, and expanding on information presented by the media. Providing detailed current information is a crucial website component as the public often searches online to augment information gained from often cryptic pronouncements by the media. In May 2005, for example, YVO saw an order of magnitude increase in page requests on the day MSNBC ran the misleading headline, "Yellowstone eruption threat high." The headline referred not to current events but a general rating of Yellowstone as one of 37 "high threat" volcanoes in the USGS National Volcano Early Warning System report. As websites become a more dominant source of information, we continuously revise our communication plans to make the most of this evolving medium. Because the internet gives equal access to all information providers, we find ourselves competing with various "doomsday" websites that sensationalize and distort the current understanding of natural systems. For example, many sites highlight a miscalculated repose period for caldera-forming eruptions at Yellowstone and conclude that a catastrophic eruption is overdue. Recent revisions on the YVO website have discussed how intervals are calculated and why the commonly quoted values are incorrect. Our aim is to reduce confusion by providing clear, simple explanations that highlight the process by which scientists reach conclusions and calculate associated uncertainties.

Multi-proxy dating the 'Millennium Eruption' of Changbaishan to late 946 CE

NASA Astrophysics Data System (ADS)

Oppenheimer, Clive; Wacker, Lukas; Xu, Jiandong; Galván, Juan Diego; Stoffel, Markus; Guillet, Sébastien; Corona, Christophe; Sigl, Michael; Di Cosmo, Nicola; Hajdas, Irka; Pan, Bo; Breuker, Remco; Schneider, Lea; Esper, Jan; Fei, Jie; Hammond, James O. S.; Büntgen, Ulf

2017-02-01

Ranking among the largest volcanic eruptions of the Common Era (CE), the 'Millennium Eruption' of Changbaishan produced a widely-dispersed tephra layer (known as the B-Tm ash), which represents an important tie point for palaeoenvironmental studies in East Asia. Hitherto, there has been no consensus on its age, with estimates spanning at least the tenth century CE. Here, we identify the cosmogenic radiocarbon signal of 775 CE in a subfossil larch engulfed and killed by pyroclastic currents emplaced during the initial rhyolitic phase of the explosive eruption. Combined with glaciochemical evidence from Greenland, this enables us to date the eruption to late 946 CE. This secure date rules out the possibility that the Millennium Eruption contributed to the collapse of the Bohai Kingdom (Manchuria/Korea) in 926 CE, as has previously been hypothesised. Further, despite the magnitude of the eruption, we do not see a consequent cooling signal in tree-ring-based reconstructions of Northern Hemisphere summer temperatures. A tightly-constrained date for the Millennium Eruption improves the prospect for further investigations of historical sources that may shed light on the eruption's impacts, and enhances the value of the B-Tm ash as a chronostratigraphic marker.

Kink-induced full and failed eruptions of two coupled flux tubes of the same filament

NASA Astrophysics Data System (ADS)

Dechev, M.; Koleva, K.; Duchlev, P.

2018-02-01

In this work, we report results from the study of a filament/prominence eruption on 2014 May 4. This eruption belongs to the class of rarely reported causally linked eruptions of two coupled flux tubes (FTs) of a quiet region filament. We made a comparative analysis based on multiwave observations from Solar Dynamics Observatory (SDO) and Solar Terrestrial Relations Observatory (STEREO) A and B combining the high temporal and spatial data taken from three different viewpoints. The main results of the study are as follows: (1) The source of the eruptive prominence consists of two coupled FTs located near the eastern limb: top-located one (FT1) and bottom-located one (FT2). (2) FT1 and FT2 had the same helicity, i.e. left-handed twist and writhe. Their untwisting motion during eruption suggests that kink instability seems to act. (3) The kinematic evolution of the FT1 suggests a slow successful eruption that was associated with a slow CME. (4) The FT2 exhibited failed kinked eruption with a non-radial propagation followed by its reformation. This eruption was accompanied of apparent mass draining in the legs, flare-ribbons and post-flare EUV arcade.

A novel technology for measuring the eruption temperature of silicate lavas with remote sensing: Application to Io and other planets

NASA Astrophysics Data System (ADS)

Davies, Ashley Gerard; Gunapala, Sarath; Soibel, Alexander; Ting, David; Rafol, Sir; Blackwell, Megan; Hayne, Paul O.; Kelly, Michael

2017-09-01

The highly variable and unpredictable magnitude of thermal emission from evolving volcanic eruptions creates saturation problems for remote sensing instruments observing eruptions on Earth and on Io, the highly volcanic moon of Jupiter. For Io, it is desirable to determine the temperature of the erupting lavas as this measurement constrains lava composition. One method of determining lava eruption temperature is by measuring radiant flux at two or more wavelengths and fitting a blackbody thermal emission function. Only certain styles of volcanic activity are suitable, those where detectable thermal emission is from a restricted range of surface temperatures close to the eruption temperature. Volcanic processes where this occurs include large lava fountains; smaller lava fountains common in active lava lakes; and lava tube skylights. Problems that must be overcome to obtain usable data are: (1) the rapid cooling of the lava between data acquisitions at different wavelengths, (2) the unknown magnitude of thermal emission, which has often led to detector saturation, and (3) thermal emission changing on a shorter timescale than the observation integration time. We can overcome these problems by using the HOT-BIRD detector and a novel, advanced digital readout circuit (D-ROIC) to achieve a wide dynamic range sufficient to image lava on Io without saturating. We have created an instrument model that allows various instrument parameters (including mirror diameter, number of signal splits, exposure duration, filter band pass, and optics transmissivity) to be tested to determine the detectability of thermal sources on Io's surface. We find that a short-wavelength infrared instrument on an Io flyby mission can achieve simultaneity of observations by splitting the incoming signal for all relevant eruption processes and still obtain data fast enough to remove uncertainties in accurate determination of the highest lava surface temperatures. Observations at 1 and 1.5 μm are sufficient for this purpose. Even with a ten-way beam split, instrument throughput generates acceptable signal-to-noise values. Accurate constraints on lava eruption temperature are also possible with a visible wavelength detector so long as data at different wavelengths are obtained simultaneously and integration time is very short. Fast integration times are important for examining the thermal emission from lava tube skylights due to rapidly changing viewing geometry during close flybys. The technology described here is applicable to instruments observing terrestrial volcanism and for investigating proposed volcanic activity on Venus, where lava composition is not known.

The largest deep-ocean silicic volcanic eruption of the past century.

PubMed

Carey, Rebecca; Soule, S Adam; Manga, Michael; White, James; McPhie, Jocelyn; Wysoczanski, Richard; Jutzeler, Martin; Tani, Kenichiro; Yoerger, Dana; Fornari, Daniel; Caratori-Tontini, Fabio; Houghton, Bruce; Mitchell, Samuel; Ikegami, Fumihiko; Conway, Chris; Murch, Arran; Fauria, Kristen; Jones, Meghan; Cahalan, Ryan; McKenzie, Warren

2018-01-01

The 2012 submarine eruption of Havre volcano in the Kermadec arc, New Zealand, is the largest deep-ocean eruption in history and one of very few recorded submarine eruptions involving rhyolite magma. It was recognized from a gigantic 400-km 2 pumice raft seen in satellite imagery, but the complexity of this event was concealed beneath the sea surface. Mapping, observations, and sampling by submersibles have provided an exceptionally high fidelity record of the seafloor products, which included lava sourced from 14 vents at water depths of 900 to 1220 m, and fragmental deposits including giant pumice clasts up to 9 m in diameter. Most (>75%) of the total erupted volume was partitioned into the pumice raft and transported far from the volcano. The geological record on submarine volcanic edifices in volcanic arcs does not faithfully archive eruption size or magma production.

The largest deep-ocean silicic volcanic eruption of the past century

PubMed Central

Carey, Rebecca; Soule, S. Adam; Manga, Michael; White, James D. L.; McPhie, Jocelyn; Wysoczanski, Richard; Jutzeler, Martin; Tani, Kenichiro; Yoerger, Dana; Fornari, Daniel; Caratori-Tontini, Fabio; Houghton, Bruce; Mitchell, Samuel; Ikegami, Fumihiko; Conway, Chris; Murch, Arran; Fauria, Kristen; Jones, Meghan; Cahalan, Ryan; McKenzie, Warren

2018-01-01

The 2012 submarine eruption of Havre volcano in the Kermadec arc, New Zealand, is the largest deep-ocean eruption in history and one of very few recorded submarine eruptions involving rhyolite magma. It was recognized from a gigantic 400-km2 pumice raft seen in satellite imagery, but the complexity of this event was concealed beneath the sea surface. Mapping, observations, and sampling by submersibles have provided an exceptionally high fidelity record of the seafloor products, which included lava sourced from 14 vents at water depths of 900 to 1220 m, and fragmental deposits including giant pumice clasts up to 9 m in diameter. Most (>75%) of the total erupted volume was partitioned into the pumice raft and transported far from the volcano. The geological record on submarine volcanic edifices in volcanic arcs does not faithfully archive eruption size or magma production. PMID:29326974

Spatio-Temporal Modelling of the Pre-Eruptive Strain Localization in a Volcanic Edifice Using a Maxwell-Elasto-Brittle Rheology

NASA Astrophysics Data System (ADS)

Dansereau, V.; Got, J. L.

2017-12-01

Before a volcanic eruption, the pressurization of the volcanic edifice by a magma reservoir induces earthquakes and damage in the edifice; damage lowers the strength of the edifice and decreases its elastic properties. Anelastic deformations cumulate and lead to rupture and eruption. These deformations translate into surface displacements, measurable via GPS or InSAR (e.g., Kilauea, southern flank, or Piton de la Fournaise, eastern flank).Attempts to represent these processes are usually based on a linear-elastic rheology. More recently, linear elastic-perfectly plastic or elastic-brittle damage approaches were used to explain the time evolution of the surface displacements in basaltic volcanoes before an eruption. However these models are non-linear elastic, and can not account for the anelastic deformation that occurs during the pre-eruptive process. Therefore, they can not be used to represent the complete eruptive cycle, comprising loading and unloading phases. Here we present a new rheological approach for modelling the eruptive cycle called Maxwell-Elasto-Brittle, which incorporates a viscous-like relaxation of the stresses in an elastic-brittle damage framework. This mechanism allows accounting for the anelastic deformations that cumulate and lead to rupture and eruption. The inclusion of healing processes in this model is another step towards a complete spatio-temporal representation of the eruptive cycle. Plane-strain Maxwell-EB modelling of the deformation of a magma reservoir and volcanic edifice will be presented. The model represents the propagation of damage towards the surface and the progressive localization of the deformation along faults under the pressurization of the magma reservoir. This model allows a complete spatio-temporal representation of the rupture process. We will also discuss how available seismicity records and time series of surface displacements could be used jointly to constrain the model.

Timescales of magmatic processes prior to the ˜4.7 ka Agnano-Monte Spina eruption (Campi Flegrei caldera, Southern Italy) based on diffusion chronometry from sanidine phenocrysts

NASA Astrophysics Data System (ADS)

Iovine, Raffaella Silvia; Fedele, Lorenzo; Mazzeo, Fabio Carmine; Arienzo, Ilenia; Cavallo, Andrea; Wörner, Gerhard; Orsi, Giovanni; Civetta, Lucia; D'Antonio, Massimo

2017-02-01

Barium diffusion chronometry applied to sanidine phenocrysts from the trachytic Agnano-Monte Spina eruption (˜4.7 ka) constrains the time between reactivation and eruption of magma batches in the Campi Flegrei caldera. Backscattered electron imaging and quantitative electron microprobe measurements on 50 sanidine phenocrysts from representative pumice samples document core-to-rim compositional zoning. We focus on compositional breaks near the crystal rims that record magma mixing processes just prior to eruption. Diffusion times were modeled at a magmatic temperature of 930 °C using profiles based on quantitative BaO point analyses, X-ray scans, and grayscale swath profiles, yielding times ≤60 years between mixing and eruption. Such short timescales are consistent with volcanological and geochronological data that indicate that at least six eruptions occurred in the Agnano-San Vito area during few centuries before the Agnano-Monte Spina eruption. Thus, the short diffusion timescales are similar to time intervals between eruptions. Therefore, the rejuvenation time of magma residing in a shallow reservoir after influx of a new magma batch that triggered the eruption, and thus pre-eruption warning times, may be as short as years to a few decades at Campi Flegrei caldera.

Modulation of magmatic processes by CO2 flushing

NASA Astrophysics Data System (ADS)

Caricchi, Luca; Sheldrake, Tom E.; Blundy, Jon

2018-06-01

Magmatic systems are the engines driving volcanic eruptions and the source of fluids responsible for the formation of porphyry-type ore deposits. Sudden variations of pressure, temperature and volume in magmatic systems can produce unrest, which may culminate in a volcanic eruption and/or the abrupt release of ore-forming fluids. Such variations of the conditions within magmatic systems are commonly ascribed to the injection of new magma from depth. However, as magmas fractionating at depth or rising to the upper crust release CO2-rich fluids, the interaction between carbonic fluids and H2O-rich magmas stored in the upper crust (CO2 flushing), must also be a common process affecting the evolution of subvolcanic magma reservoirs. Here, we investigate the effect of gas injection on the stability and chemical evolution of magmatic systems. We calculate the chemical and physical evolution of magmas subjected to CO2-flushing using rhyolite-MELTS. We compare the calculations with a set of melt inclusion data for Mt. St. Helens, Merapi, Etna, and Stromboli volcanoes. We provide an approach that can be used to distinguish between melt inclusions trapped during CO2 flushing, magma ascent and decompression, or those affected by post-entrapment H2O-loss. Our results show that CO2 flushing is a widespread process in both felsic and mafic magmatic systems. Depending upon initial magma crystallinity and duration of CO2 input, flushing can either lead to volcanic eruption or fluid release. We suggest that CO2 flushing is a fundamental process modulating the behaviour and chemical evolution of crustal magmatic systems.

A Fracture-Mechanical Model of Crack Growth and Interaction: Application to Pre-eruptive Seismicity

NASA Astrophysics Data System (ADS)

Matthews, C.; Sammonds, P.; Kilburn, C.

2007-12-01

A greater understanding of the physical processes occurring within a volcano is a key aspect in the success of eruption forecasting. By considering the role of fracture growth, interaction and coalescence in the formation of dykes and conduits as well as the source mechanism for observed seismicity we can create a more general, more applicable model for precursory seismicity. The frequency of volcano-tectonic earthquakes, created by fracturing of volcanic rock, often shows a short-term increase prior to eruption. Using fracture mechanics, the model presented here aims to determine the conditions necessary for the acceleration in fracture events which produces the observed pre-eruptive seismicity. By focusing on the cause of seismic events rather than simply the acceleration patterns observed, the model also highlights the distinction between an accelerating seismic sequence ending with an eruption and a short-term increase which returns to background levels with no activity occurring, an event also observed in the field and an important capability if false alarms are to be avoided. This 1-D model explores the effects of a surrounding stress field and the distribution of multi-scale cracks on the interaction and coalescence of these cracks to form an open pathway for magma ascent. Similarly to seismic observations in the field, and acoustic emissions data from the laboratory, exponential and hyperbolic accelerations in fracturing events are recorded. Crack distribution and inter-crack distance appears to be a significant controlling factor on the evolution of the fracture network, dominating over the effects of a remote stress field. The generality of the model and its basis on fundamental fracture mechanics results makes it applicable to studies of fracture networks in numerous situations. For example looking at the differences between high temperature fracture processes and purely brittle failure the model can be similarly applied to fracture dynamics in the edifice of a long repose volcano and a lava dome.

Dating kimberlite emplacement with zircon and perovskite (U-Th)/He geochronology

NASA Astrophysics Data System (ADS)

Stanley, Jessica; Flowers, Rebecca

2017-04-01

Kimberlites provide rich information about the composition and evolution of cratonic lithosphere. They can entrain xenoliths and xenocrysts from the entire lithospheric column as they transit rapidly to the surface, providing information on the state of the deep lithosphere as well as any sedimentary units covering the craton at the time of eruption. Accurate geochronology of these eruptions is key for interpreting this information and discerning spatiotemporal trends in lithospheric evolution, but kimberlites can sometimes be difficult to date with available methods. Here we explore whether (U-Th)/He dating of zircon and perovskite can serve as reliable techniques for determining kimberlite emplacement ages by dating a suite of sixteen southern African kimberlites by zircon and/or perovskite (U-Th)/He (ZHe, PHe). Most samples with abundant zircon yielded ZHe dates reproducible to ≤15% dispersion that are in good agreement with published eruption ages, though there were several samples that were more scattered. Since the majority of dated zircon were xenocrystic, zircon with reproducible dates were fully reset during eruption or resided at temperatures above the ZHe closure temperature ( 180 °C) prior to entrainment in the kimberlite magma. We attribute scattered ZHe dates to shallowly sourced zircon that underwent incomplete damage annealing and/or partial He loss during the eruptive process. All seven kimberlites dated with PHe yielded dates reproducible to ≤15% dispersion and reasonable results. As perovskite has not previously been used as a (U-Th)/He chronometer, we conducted two preliminary perovskite 4He diffusion experiments to obtain initial estimates of its temperature sensitivity. These experiments suggest a PHe closure temperature of >300 °C. Perovskite in kimberlites is unlikely to be xenocrystic and its relatively high temperature sensitivity suggests that PHe dates will typically record emplacement rather than post-emplacement processes. ZHe and PHe geochronology can effectively date kimberlite emplacement and provide useful complements to existing techniques.

Temporal geochemical variations in lavas from Kīlauea's Pu`u `Ō`ō eruption (1983-2010): Cyclic variations from melting of source heterogeneities

NASA Astrophysics Data System (ADS)

Greene, Andrew R.; Garcia, Michael O.; Pietruszka, Aaron J.; Weis, Dominique; Marske, Jared P.; Vollinger, Michael J.; Eiler, John

2013-11-01

Geochemical time series analysis of lavas from Kīlauea's ongoing Pu`u `Ō`ō eruption chronicle mantle and crustal processes during a single, prolonged (1983 to present) magmatic event, which has shown nearly two-fold variation in lava effusion rates. Here we present an update of our ongoing monitoring of the geochemical variations of Pu`u `Ō`ō lavas for the entire eruption through 2010. Oxygen isotope measurements on Pu`u `Ō`ō lavas show a remarkable range (δ18O values of 4.6-5.6‰), which are interpreted to reflect moderate levels of oxygen isotope exchange with or crustal contamination by hydrothermally altered Kīlauea lavas, probably in the shallow reservoir under the Pu`u `Ō`ō vent. This process has not measurably affected ratios of radiogenic isotope or incompatible trace elements, which are thought to vary due to mantle-derived changes in the composition of the parental magma delivered to the volcano. High-precision Pb and Sr isotopic measurements were performed on lavas erupted at ˜6 month intervals since 1983 to provide insights about melting dynamics and the compositional structure of the Hawaiian plume. The new results show systematic variations of Pb and Sr isotope ratios that continued the long-term compositional trend for Kīlauea until ˜1990. Afterward, Pb isotope ratios show two cycles with ˜10 year periods, whereas the Sr isotope ratios continued to increase until ˜2003 and then shifted toward slightly less radiogenic values. The short-term periodicity of Pb isotope ratios may reflect melt extraction from mantle with a fine-scale pattern of repeating source heterogeneities or strands, which are about 1-3 km in diameter. Over the last 30 years, Pu`u `Ō`ō lavas show 15% and 25% of the known isotopic variation for Kīlauea and Mauna Kea, respectively. This observation illustrates that the dominant time scale of mantle-derived compositional variation for Hawaiian lavas is years to decades.

Volcanoes of the World: Reconfiguring a scientific database to meet new goals and expectations

NASA Astrophysics Data System (ADS)

Venzke, Edward; Andrews, Ben; Cottrell, Elizabeth

2015-04-01

The Smithsonian Global Volcanism Program's (GVP) database of Holocene volcanoes and eruptions, Volcanoes of the World (VOTW), originated in 1971, and was largely populated with content from the IAVCEI Catalog of Volcanoes of Active Volcanoes and some independent datasets. Volcanic activity reported by Smithsonian's Bulletin of the Global Volcanism Network and USGS/SI Weekly Activity Reports (and their predecessors), published research, and other varied sources has expanded the database significantly over the years. Three editions of the VOTW were published in book form, creating a catalog with new ways to display data that included regional directories, a gazetteer, and a 10,000-year chronology of eruptions. The widespread dissemination of the data in electronic media since the first GVP website in 1995 has created new challenges and opportunities for this unique collection of information. To better meet current and future goals and expectations, we have recently transitioned VOTW into a SQL Server database. This process included significant schema changes to the previous relational database, data auditing, and content review. We replaced a disparate, confusing, and changeable volcano numbering system with unique and permanent volcano numbers. We reconfigured structures for recording eruption data to allow greater flexibility in describing the complexity of observed activity, adding in the ability to distinguish episodes within eruptions (in time and space) and events (including dates) rather than characteristics that take place during an episode. We have added a reference link field in multiple tables to enable attribution of sources at finer levels of detail. We now store and connect synonyms and feature names in a more consistent manner, which will allow for morphological features to be given unique numbers and linked to specific eruptions or samples; if the designated overall volcano name is also a morphological feature, it is then also listed and described as that feature. One especially significant audit involved re-evaluating the categories of evidence used to include a volcano in the Holocene list, and reviewing in detail the entries in low-certainty categories. Concurrently, we developed a new data entry system that may in the future allow trusted users outside of Smithsonian to input data into VOTW. A redesigned website now provides new search tools and data download options. We are collaborating with organizations that manage volcano and eruption databases, physical sample databases, and geochemical databases to allow real-time connections and complex queries. VOTW serves the volcanological community by providing a clear and consistent core database of distinctly identified volcanoes and eruptions to advance goals in research, civil defense, and public outreach.

Insights Into the Workings of Rhyolitic Explosive Eruptions and Their Magmatic Sources

NASA Astrophysics Data System (ADS)

Wilson, C. J.

2011-12-01

The nature, role and significance of rhyolitic volcanism and its associated crustal magmatism have been widely recognised and documented over the past ~50 years. The products of such volcanism include the largest Quaternary eruptions on Earth, and these 'supereruptions' represent the largest terrestrial long-term hazard to humanity as well as reflecting resource-rich magmatic systems. Only three rhyolitic eruptions of any size have occurred over the last 100 years (Novarupta, Tuluman, Chaiten) and so patterns of rhyolitic volcanism have been inferred almost entirely from the products of past events. Numerous models for the dynamics of explosive activity have been generated from the resulting deposits, but many questions remain about the eruptions and their parental magma bodies. Central to understanding how rhyolitic systems operate is two suites of questions. First, what are the timescales of large explosive eruptions? Are they short-lived catastrophic events ('hours or days') or can they be prolonged over years to decades? How and why do large eruptions stop and start? Prehistoric large eruptions seem to show a great variety of timings, varying from days (e.g. Bishop Tuff) through months (e.g. Oruanui) to a decade or more (e.g. Huckleberry Ridge Tuff), with periods of high output alternating with hiatuses of minutes to years. Eruption rates, where they can be assessed, do not necessarily scale with the volume of the deposit. Large eruptions may be internally modulated by external (tectonic) forces, implying that eruption styles and products may be influenced by something that leaves no geological presence. Tectonic processes may control whether the evacuation of more than one magma body occurs, or trigger pairings of independent eruptions. The second suite of questions centres on the time periods over which the bodies of erupted magma accumulate and how they are assembled. Do tens to hundreds to thousands of cubic kilometres of eruptible magma collect over a time period proportional to the size of the body, or do other factors play a role? How completely are chambers emptied during eruptions? The value of zircon crystallization ages in measuring the timescales of silicic magma generation and accumulation is not in doubt. There are many ambiguities, however, in how such data are treated and interpreted, in part depending on the detail of the geological record and in part related to the uncertainties associated with individual age estimates. Magma bodies can have very short accumulation times which are different from the timescales implied by crystallization ages. Large bodies of melt-dominant magma may be thoroughly mixed, have floors rigid enough to permit flow of mafic influxes across them, and then be effectively totally evacuated during eruption. I will present an overview of ideas and information from combined field and laboratory case studies which contribute towards addressing the nature and dynamics of large silicic systems.

A Foamy Lava Lake at Kilauea Volcano, Hawai`i

NASA Astrophysics Data System (ADS)

Poland, M. P.; Carbone, D.

2012-12-01

Kilauea Volcano, in Hawai`i, is currently erupting from two locations simultaneously: along the east rift zone and at the summit. The east rift zone eruption began in 1983 and is characterized by lava effusion from the Pu`u `O`o and nearby vents, while the summit eruptive vent, which opened in 2008, persistently emits gas and small amounts of ash while hosting a lava lake. On March 5, 2011, a dike initiated from the east rift zone magma conduit and reached the surface, resulting in the 4.5-day-long Kamoamoa fissure eruption just uprift of Pu`u `O`o. The eruption was accompanied by summit deflation as magma withdrew from subsurface reservoirs to feed the fissure eruption. The level of the summit lava lake dropped as the summit deflated. A continuously recording gravimeter located at Kilauea's summit (about 150 m east of the center of the summit eruptive vent, 80 m above the vent rim, and about 140 m above the highest level reached by the lava lake) measured a gravity decrease of about 150 μGal during the lava level drop, after taking into account corrections for the solid Earth tide. The gravity signal is caused by a combination of three processes. First, subsidence of 15 cm due to summit deflation moved the gravimeter closer to the center of the Earth, resulting in a gravity increase. Second, mass removal from the subsurface magma reservoir at a depth of 1.4 km (based on a model from GPS and InSAR data) caused a gravity decrease. Third, the drop in the level of the lava lake, which reached a maximum of about 150 m, led to a gravity decrease. Assuming a simple point source of pressure change and a typical density for basaltic magma (2.3-2.7 g/cm3), the first two processes can only explain a small percent of the observed gravity decrease, which must therefore be mainly due to the drop in the level of the lava lake. We developed a numerical model of the summit eruptive vent that takes into account its complex geometry (as deduced from geological observations). Using the change in lava level over time (data courtesy of Matt Patrick), we estimated that a lava density of about 0.8 g/cm3 is required to fit the gravity time series. Gravity results, therefore, argue that the upper part of the vent is occupied by a low-density lava foam (in agreement with models of Kilauea's summit eruption from seismic, gas, and geologic data by Tim Orr and Matt Patrick) and provide the only means of quantifying the lava lake density.

Tilt recorded by a portable broadband seismograph: The 2003 eruption of Anatahan Volcano, Mariana Islands

USGS Publications Warehouse

Wiens, D.A.; Pozgay, S.H.; Shore, P.J.; Sauter, A.W.; White, R.A.

2005-01-01

The horizontal components of broadband seismographs are highly sensitive to tilt, suggesting that commonly deployed portable broadband seismic sensors may record important tilt information associated with volcanic eruptions. We report on a tilt episode that coincides with the first historical eruption of Anatahan volcano on May 10, 2003. The tilt was recorded by a Strekheisen STS-2 seismograph deployed in an underground insulated chamber 7 km west of the active vent. An ultra-long period signal with a dominant period of several hours was recorded on the E-W component beginning at 06:20 GMT on May 10, which coincides with the onset of continuous volcano-tectonic (VT) seismicity and is one hour prior to the eruption time estimated by the Volcanic Ash Advisory Center. The signal is much smaller on the N-S component and absent on the vertical component, suggesting it results from tilt that is approximately radial with respect to the active vent. An estimate of tilt as a function of time is recovered by deconvolving the record to acceleration and dividing by the acceleration of gravity. The record indicates an initial episode of tilt downward away from the volcanic center from 06:20-09:30 GMT, which we interpret as inflation of the shallow volcanic source. The tilt reverses, recording deflation, from 09:30 until 17:50, after which the tilt signal becomes insignificant. The inflation corresponds to a period of numerous VT events, whereas fewer events were recorded during the deflation episode, and the VT events subsequently resumed after the end of the deflationary tilt. The maximum tilt of 2 microradians can be used to estimate the volume of the source inflation (???2 million in m3), assuming a simple Mogi source model. These calculations are consistent with other estimates of source volume if reasonable source depths are assumed. Examination of broadband records of other eruptions may disclose further previously unrecognized tilt signals. Copyright 2005 by the American Geophysical Union.

Volcanic hazard assessment for the Canary Islands (Spain) using extreme value theory, and the recent volcanic eruption of El Hierro

NASA Astrophysics Data System (ADS)

Sobradelo, R.; Martí, J.; Mendoza-Rosas, A. T.; Gómez, G.

2012-04-01

The Canary Islands are an active volcanic region densely populated and visited by several millions of tourists every year. Nearly twenty eruptions have been reported through written chronicles in the last 600 years, suggesting that the probability of a new eruption in the near future is far from zero. This shows the importance of assessing and monitoring the volcanic hazard of the region in order to reduce and manage its potential volcanic risk, and ultimately contribute to the design of appropriate preparedness plans. Hence, the probabilistic analysis of the volcanic eruption time series for the Canary Islands is an essential step for the assessment of volcanic hazard and risk in the area. Such a series describes complex processes involving different types of eruptions over different time scales. Here we propose a statistical method for calculating the probabilities of future eruptions which is most appropriate given the nature of the documented historical eruptive data. We first characterise the eruptions by their magnitudes, and then carry out a preliminary analysis of the data to establish the requirements for the statistical method. Past studies in eruptive time series used conventional statistics and treated the series as an homogeneous process. In this paper, we will use a method that accounts for the time-dependence of the series and includes rare or extreme events, in the form of few data of large eruptions, since these data require special methods of analysis. Hence, we will use a statistical method from extreme value theory. In particular, we will apply a non-homogeneous Poisson process to the historical eruptive data of the Canary Islands to estimate the probability of having at least one volcanic event of a magnitude greater than one in the upcoming years. Shortly after the publication of this method an eruption in the island of El Hierro took place for the first time in historical times, supporting our method and contributing towards the validation of our results.

Identifying recycled ash in basaltic eruptions

PubMed Central

D'Oriano, Claudia; Bertagnini, Antonella; Cioni, Raffaello; Pompilio, Massimo

2014-01-01

Deposits of mid-intensity basaltic explosive eruptions are characterized by the coexistence of different types of juvenile clasts, which show a large variability of external properties and texture, reflecting alternatively the effects of primary processes related to magma storage or ascent, or of syn-eruptive modifications occurred during or immediately after their ejection. If fragments fall back within the crater area before being re-ejected during the ensuing activity, they are subject to thermally- and chemically-induced alterations. These ‘recycled' clasts can be considered as cognate lithic for the eruption/explosion they derive. Their exact identification has consequences for a correct interpretation of eruption dynamics, with important implications for hazard assessment. On ash erupted during selected basaltic eruptions (at Stromboli, Etna, Vesuvius, Gaua-Vanuatu), we have identified a set of characteristics that can be associated with the occurrence of intra-crater recycling processes, based also on the comparison with results of reheating experiments performed on primary juvenile material, at variable temperature and under different redox conditions. PMID:25069064

Grain size distribution and characteristics of the tephra from the Vatnaöldur AD 871±2 eruption, Iceland.

NASA Astrophysics Data System (ADS)

Jónsdóttir, Tinna; Larsen, Guðrún; Guðmundsson, Magnús

2014-05-01

Basaltic explosive eruptions in Iceland are frequent and often occur from vents in regions of surface lakes, large groundwater reservoirs or within glaciers. The recent Eyjafjallajökull eruption in 2010 and Grímsvötn eruption 2011 highlighted the vulnerability of passenger jet aircraft to ash in the atmosphere. Iceland's volcanoes are the most potent producers of tephra in Europe, and the frequent occurrence of basaltic explosive eruptions is a major factor in causing this. As a step in increasing the knowledge on the tephra erupted in basaltic explosive eruptions, we study the grain size distribution of a large (~5 km3) explosive basaltic eruption that occurred in AD 871±2. The source is the 25 km long Vatnaöldur crater row in south-central Iceland. The crater row lies within the Bárðarbunga-Veiðivötn volcanic system, one of the most productive volcanic systems in Iceland in recent times. Samples for grain size analysis were collected at six different locations along the broad northwest-trending dispersal axis. Sampling sites ranged in 1.5 km to 120 km distance from the largest vent Skyggnir, near the southern end of the crater row. The Vatnaöldur eruption has been classified as phreatomagmatic, erupting through fractured bedrock composed of recent lavas, hyaloclastites and pillow lava in an area characterized by a high groundwater level and surface lakes. Explosive activity dominanted the ~ 25 km long discontinuous fissure, as tuff cones were formed and conduits reached under groundwater table. During the eruption the tephra layer was dispersed in all directions. The area within the 0.5 cm isopach is 50,000 km2 and this tephra has also been identified in Greenland ice cores. The grain size analysis indicates that one dominant characteristic of the tephra is the scarcity of pyroclasts over 1 mm in diameter. In the ash sampled more than 4 km from source larger grain sizes are absent. The dispersion in the more distal parts, at distances of 60 - 120 km is dominated by peaks between 0.250 and 0.063 mm, with the deposit showing slight tendency for progressively higher proportion of fines with distance.In the more proximal sections different phases in the eruption have been identified.

Observation and modeling of source effects in coda wave interferometry at Pavlof volcano

USGS Publications Warehouse

Haney, M.M.; van, Wijik K.; Preston, L.A.; Aldridge, D.F.

2009-01-01

Sorting out source and path effects for seismic waves at volcanoes is critical for the proper interpretation of underlying volcanic processes. Source or path effects imply that seismic waves interact strongly with the volcanic subsurface, either through partial resonance in a conduit (Garces et al., 2000; Sturton and Neuberg, 2006) or by random scattering in the heterogeneous volcanic edifice (Wegler and Luhr, 2001). As a result, both source and path effects can cause seismic waves to repeatedly sample parts of the volcano, leading to enhanced sensitivity to small changes in material properties at those locations. The challenge for volcano seismologists is to detect and reliably interpret these subtle changes for the purpose of monitoring eruptions. ?? 2009 Society of Exploration Geophysicists.

Role of syn-eruptive plagioclase disequilibrium crystallization in basaltic magma ascent dynamics.

PubMed

La Spina, G; Burton, M; De' Michieli Vitturi, M; Arzilli, F

2016-12-12

Timescales of magma ascent in conduit models are typically assumed to be much longer than crystallization and gas exsolution for basaltic eruptions. However, it is now recognized that basaltic magmas may rise fast enough for disequilibrium processes to play a key role on the ascent dynamics. The quantification of the characteristic times for crystallization and exsolution processes are fundamental to our understanding of such disequilibria and ascent dynamics. Here we use observations from Mount Etna's 2001 eruption and a magma ascent model to constrain timescales for crystallization and exsolution processes. Our results show that plagioclase reaches equilibrium in 1-2 h, whereas ascent times were <1 h. Using these new constraints on disequilibrium plagioclase crystallization we also reproduce observed crystal abundances for different basaltic eruptions. The strong relation between magma ascent rate and disequilibrium crystallization and exsolution plays a key role in controlling eruption dynamics in basaltic volcanism.

Role of syn-eruptive plagioclase disequilibrium crystallization in basaltic magma ascent dynamics

PubMed Central

La Spina, G.; Burton, M.; de' Michieli Vitturi, M.; Arzilli, F.

2016-01-01

Timescales of magma ascent in conduit models are typically assumed to be much longer than crystallization and gas exsolution for basaltic eruptions. However, it is now recognized that basaltic magmas may rise fast enough for disequilibrium processes to play a key role on the ascent dynamics. The quantification of the characteristic times for crystallization and exsolution processes are fundamental to our understanding of such disequilibria and ascent dynamics. Here we use observations from Mount Etna's 2001 eruption and a magma ascent model to constrain timescales for crystallization and exsolution processes. Our results show that plagioclase reaches equilibrium in 1–2 h, whereas ascent times were <1 h. Using these new constraints on disequilibrium plagioclase crystallization we also reproduce observed crystal abundances for different basaltic eruptions. The strong relation between magma ascent rate and disequilibrium crystallization and exsolution plays a key role in controlling eruption dynamics in basaltic volcanism. PMID:27941750

Real Time Tracking of Magmatic Intrusions by means of Ground Deformation Modeling during Volcanic Crises.

PubMed

Cannavò, Flavio; Camacho, Antonio G; González, Pablo J; Mattia, Mario; Puglisi, Giuseppe; Fernández, José

2015-06-09

Volcano observatories provide near real-time information and, ultimately, forecasts about volcano activity. For this reason, multiple physical and chemical parameters are continuously monitored. Here, we present a new method to efficiently estimate the location and evolution of magmatic sources based on a stream of real-time surface deformation data, such as High-Rate GPS, and a free-geometry magmatic source model. The tool allows tracking inflation and deflation sources in time, providing estimates of where a volcano might erupt, which is important in understanding an on-going crisis. We show a successful simulated application to the pre-eruptive period of May 2008, at Mount Etna (Italy). The proposed methodology is able to track the fast dynamics of the magma migration by inverting the real-time data within seconds. This general method is suitable for integration in any volcano observatory. The method provides first order unsupervised and realistic estimates of the locations of magmatic sources and of potential eruption sites, information that is especially important for civil protection purposes.

Real Time Tracking of Magmatic Intrusions by means of Ground Deformation Modeling during Volcanic Crises

PubMed Central

Cannavò, Flavio; Camacho, Antonio G.; González, Pablo J.; Mattia, Mario; Puglisi, Giuseppe; Fernández, José

2015-01-01

Volcano observatories provide near real-time information and, ultimately, forecasts about volcano activity. For this reason, multiple physical and chemical parameters are continuously monitored. Here, we present a new method to efficiently estimate the location and evolution of magmatic sources based on a stream of real-time surface deformation data, such as High-Rate GPS, and a free-geometry magmatic source model. The tool allows tracking inflation and deflation sources in time, providing estimates of where a volcano might erupt, which is important in understanding an on-going crisis. We show a successful simulated application to the pre-eruptive period of May 2008, at Mount Etna (Italy). The proposed methodology is able to track the fast dynamics of the magma migration by inverting the real-time data within seconds. This general method is suitable for integration in any volcano observatory. The method provides first order unsupervised and realistic estimates of the locations of magmatic sources and of potential eruption sites, information that is especially important for civil protection purposes. PMID:26055494

Triggering of solar magnetic eruptions on various size scales

NASA Astrophysics Data System (ADS)

Sterling, Alphonse

A solar eruption that produces a coronal mass ejection (CME) together with a flare is driven by the eruption of a closed-loop magnetic arcade that has a sheared-field core. Before eruption, the sheared core envelops a polarity inversion line along which cool filament material may reside. The sheared-core arcade erupts when there is a breakdown in the balance between the confining downward-directed magnetic tension of the overall arcade field and the upward-directed force of the pent-up magnetic pressure of the sheared field in the core of the arcade. What triggers the breakdown in this balance in favor of the upward-directed force is still an unsettled question. We consider several eruption examples, using imaging data from the SoHO, TRACE and Hinode satellites, and other sources, along with information about the magnetic field of the erupting regions. In several cases, observations of large-scale eruptions, where the magnetic neutral line spans ˜ few ×10,000 km, are consistent with magnetic flux cancelation being the trigger to the eruption's onset, even though the amount of flux canceled is only ˜ few percent of the total magnetic flux of the erupting region. In several other cases, an initial compact (small size-scale) eruption occurs embedded inside of a larger closed magnetic loop system, so that the smaller eruption destabilizes and causes the eruption of the much larger system. In this way, small-scale eruptive events can result in eruption of much larger-scale systems. This work was funded by NASA's Science Mission Directorate thought the Living With a Star Targeted Research and Technology Program, the Supporting Research and Program, and the Hinode project.

Characteristics of Helicopter-Generated and Volcano-Related Seismic Tremor Signals

NASA Astrophysics Data System (ADS)

Eibl, Eva P. S.; Lokmer, Ivan; Bean, Christopher J.; Akerlie, Eggert; Vogfjörd, Kristin S.

2017-04-01

In volcanic environments it is crucial to distinguish between man-made seismic signals and signals created by the volcano. We compare volcanic, seismic signals with helicopter generated, seismic signals recorded in the last 2.5 years in Iceland. In both cases a long-lasting, emergent seismic signal, that can be referred to as seismic tremor, was generated. In the case of a helicopter, the rotating blades generate pressure pulses that travel through the air and excite Rayleigh waves at up to 40 km distance depending on wind speed, wind direction and topographic features. The longest helicopter related seismic signal we recorded was at the order of 40 minutes long. The tremor usually has a fundamental frequency of more than 10 Hz and overtones at integers of the fundamental frequency. Changes in distance lead to either increases or decreases of the frequency due to the Doppler Effect and are strongest for small source-receiver distances. The volcanic tremor signal was recorded during the Bardarbunga eruption at Holuhraun in 2014/15. For volcano-related seismic signals it is usually more difficult to determine the source process that generated the tremor. The pre-eruptive tremor persists for 2 weeks, while the co-eruptive tremor lasted for 6 months. We observed no frequency changes, most energy between 1 and 2 Hz and no or very little energy above 5 Hz. We compare the different characteristics of helicopter-related and volcano-related seismic signals and discuss how they can be distinguished. In addition we discuss how we can determine if a frequency change is related to a moving source or change in repeat time or a change in the geometry of the resonating body.

The evolution of periodic seismicity, waveform similarity, and conduit processes during unrest episodes at Tungurahua volcano, Ecuador, in 2015

NASA Astrophysics Data System (ADS)

Bell, Andrew; Hernandez, Stephen; Gaunt, Elizabeth; Mothes, Patricia; Hidalgo, Silvana; Ruiz, Mario

2016-04-01

Tungurahua is a large andesitic stratovolcano located in the Andes of Ecuador. The current eruptive phase at Tungurahua began in 1999, and has been characterised by episodes of vulcanian and strombolian activity, interspersed by periods of relative quiescence. Despite showing only modest eruptive activity in 2015, seismic data revealed a pronounced change in the behaviour of the magma-conduit system compared to the preceding 15 years of activity. The change is most notable in the periodicity of interevent-times of volcanic earthquakes. Previous seismicity at Tungurahua is characterised by interevent-time periodicities typical of a Poisson process, or modestly clustered, with slightly elevated (anti-clustered) periodicities observed only rarely during vulcanian episodes. However, activity in 2015 saw a series of unrest episodes characterised by highly-periodic interevent-times, and including several notable episodes of 'drumbeat' earthquakes. Here we report seismic and associated geophysical signals recorded at Tungurahua in 2015 by the monitoring network of the Instituto Geofisico of Ecuador, their relation to conduit processes, and implications for the origins of unrest and likely future activity. Although the nature of the low-frequency seismic signals change both within and between unrest episodes, the underlying periodicity is more consistent and gradually evolving. Waveform similarity is high within phases, resulting from the repeated activation of persistent sources, but low between different episodes, suggesting the emergence of new sources and locations. The strength of periodicity is correlated with the average waveform similarity for all unrest episodes, with the relatively low waveform similarities observed for the highly periodic drumbeat earthquakes in April due to contamination from coexisting continuous tremor. Eruptive activity consisted of a few minor explosions and ash emission events. Notably, a short-lived episode of Strombolian activity in November with juvenile magma was quickly followed by a resumption of periodic low-frequency seismicity. The changes in the seismicity of Tungurahua in 2015 suggest a significant change in the magma-conduit system. Elevated periodicity may indicate the presence of a slowly upward moving plug at a depth of 1-2km below the summit crater, likely associated with the unusually long repose period since the last major vulcanian episode in October 2014. Evolution in the periodicity and type of seismic signals within and between unrest episodes will be controlled by a combination of the gas flux and permeability, and a balance between thermo-mechanical plug degradation and time-dependent healing processes. These factors are also likely to determine the nature of future eruptive activity.

Carbon isotope constraints on degassing of carbon dioxide from Kilauea Volcano

USGS Publications Warehouse

Gerlach, T.M.; Taylor, B.E.

1990-01-01

We examine models for batch-equilibrium and fractional-equilibrium degassing of CO2 from magma at Kilauea Volcano. The models are based on 1. (1) the concept of two-stage degassing of CO2 from magma supplied to the summit chamber, 2. (2) C isotope data for CO2 in eruptive and noneruptive (quiescent) gases from Kilauea and 3. (3) data for the isotopic fractionation of C between CO2 and C dissolved in tholeiitic basalt melt. The results of our study indicate that 1. (1) both eruptive and noneruptive degassing of CO2 most closely approach a batch equilibrium process, 2. (2) the ??13C of parental magma supplied to the summit chamber is in the range -4.1 to-3.4??? and 3. (3) the ??13C of melt after summit chamber degassing is in the range -7 to -8???, depending upon the depth of equilibration. We also present ??13C data for CO2 in eruptive gases from the current East Rift Zone eruption. These are the first C isotope data for CO2 in high-temperature (>900??C) eruptive gases from Kilauea; they have a mean ??13C value of -7.82 ?? 0.24??? and are similar to those predicted for the melt after summit chamber degassing. The minor role played by fractional degassing of ascending magma at Kilauea means that exsolved CO2 tends to remain entrained in and coherent with its host melt during ascent from both mantle source regions and crustal magma reservoirs. This has important implications for magma dynamics at Kilauea. ?? 1990.

Recent progress in understanding the eruptions of classical novae

NASA Technical Reports Server (NTRS)

Shara, Michael M.

1988-01-01

Dramatic progress has occurred in the last two decades in understanding the physical processes and events leading up to, and transpiring during the eruption of a classical nova. The mechanism whereby a white dwarf accreting hydrogen-rich matter from a low-mass main-sequence companion produces a nova eruption has been understood since 1970. The mass-transferring binary stellar configuration leads inexorably to thermonuclear runaways detected at distances of megaparsecs. Summarized here are the efforts of many researchers in understanding the physical processes which generate nova eruptions; the effects upon nova eruptions of different binary-system parameters (e.g., chemical composition or mass of the white dwarf, different mass accretion rates); the possible metamorphosis from dwarf to classical novae and back again; and observational diagnostics of novae, including x ray and gamma ray emission, and the characteristics and distributions of novae in globular clusters and in extragalactic systems. While the thermonuclear-runaway model remains the successful cornerstone of nova simulation, it is now clear that a wide variety of physical processes, and three-dimensional hydrodynamic simulations, will be needed to explain the rich spectrum of behavior observed in erupting novae.

Tree-ring width reveals the preparation of the 1974 Mt. Etna eruption

PubMed Central

Seiler, Ruedi; Houlié, Nicolas; Cherubini, Paolo

2017-01-01

Reduced near-infrared reflectance observed in September 1973 in Skylab images of the western flank of Mt. Etna has been interpreted as an eruption precursor of the January 1974 eruption. Until now, it has been unclear when this signal started, whether it was sustained and which process(es) could have caused it. By analyzing tree-ring width time-series, we show that the reduced near-infrared precursory signal cannot be linked to a reduction in annual tree growth in the area. However, comparing the tree-ring width time-series with both remote sensing observations and volcano-seismic activity enables us to discuss the starting date of the pre-eruptive period of the 1974 eruption. PMID:28266610

ASTER Images Merapi Continuing Eruption

NASA Image and Video Library

2010-11-18

This thermal infrared image from NASA Terra spacecraft of Merapi continuing eruption has been processed to reveal the dominant presence of volcanic ash in the eruption plume and clouds, displayed in dark red. The warm volcanic flow appears bright.

Magma degassing and eruption dynamics of the Avellino pumice Plinian eruption of Somma-Vesuvius (Italy). Comparison with the Pompeii eruption

NASA Astrophysics Data System (ADS)

Balcone-Boissard, H.; Boudon, G.; Ucciani, G.; Villemant, B.; Cioni, R.; Civetta, L.; Orsi, G.

2012-05-01

The eruptive history of Mt. Somma-Vesuvius is characterised by large explosive events: Pomici di Base eruption (22,030 ± 175 yr cal BP), Mercato (8890 ± 90 yr cal BP), Avellino (3945 ± 10 yr cal BP) and Pompeii (79 AD). Pre-eruptive conditions and sin-eruptive degassing processes of the Avellino eruption, the highest-magnitude Plinian event, have been investigated, using volatile contents (F, Cl, H2O) in melt inclusions and residual glass, and textural characteristics of pumice clasts of the 9 fallout layers sampled in detail in a representative sequence. The sequence displays an up-section sharp colour change from white to grey, corresponding to variations in both magma composition and textural characteristics. The pre-eruptive conditions have been constrained by systematic measurements of Cl content in both melt inclusions and matrix glass of pumice clasts. The pumice glass composition varies from Na-rich phonolite (white pumice) to K-rich phonolite (grey pumice). The measured Cl values constantly cluster at 5200 ± 400 ppm (buffer value), whatever the composition of the melt, suggesting that the entire magma body was saturated with sub-critical fluids. This Cl saturation constrains the pre-eruptive pressures and maximum H2O contents at 200 ± 10 MPa and 6.3 ± 0.2 wt.% H2O for the white pumice melt and 195 ± 15 MPa and 5.2 ± 0.2 wt.% H2O for the grey pumice melt. The fluid phase, mainly composed of a H2O-rich vapour phase and brine, probably accumulated at the top of the reservoir and generated an overpressure able to trigger the onset of the eruption. Magma degassing was rather homogeneous for the white and grey eruptive units, mostly occurring through closed-system processes, leading to a typical Plinian eruptive style. A steady-state withdrawal of an H2O-saturated magma may explain the establishment of a sustained Plinian column. Variation from white to grey pumice is accompanied by decrease of mean vesicularity and increase of mean microcrystallinity and permeability related to significant vesicle coalescence. Despite this, the ascending magma column still evolves under closed-system degassing, without significant gas loss through conduit walls. The Avellino eruption shows numerous similarities with the 79 AD Pompeii eruption in pre-eruptive conditions, degassing processes and eruptive style which are discussed here.

The 1928 eruption of Mount Etna (Italy): Reconstructing lava flow evolution and the destruction and recovery of the town of Mascali

NASA Astrophysics Data System (ADS)

Branca, Stefano; De Beni, Emanuela; Chester, David; Duncan, Angus; Lotteri, Alessandra

2017-04-01

Mount Etna in Sicily (Italy) shows > 2500 years of interactions between volcanic eruptions and human activity, and these are well documented in historical sources. During the last 400 years, flank eruptions have had major impacts on the urban fabric of the Etna region, especially in 1651-54, 1669, 1923 and 1928, and it is the last of these which is the focus of this paper. A detailed field and historical reconstruction of the 1928 eruption is presented which allows three themes to be discussed: the evolution of the flow field, lava volume and average magma discharge rate trend; the eruption's human impact, particularly the destruction of the town of Mascali; and the recovery of the region with re-construction of Mascali in a new location. Detailed mapping of lava flows allowed the following dimensions to be calculated: total area, 4.38 × 106 m2; maximum length, 9.4 km; volume, 52.91 ± 5.21 × 106 m3 and an average effusion rate of 38.5 m3 s-1. Time-averaged discharged rates are calculated allowing the reconstruction of their temporal variations during the course of the eruption evidencing a high maximum effusion rate of 374 m3 s- 1. These trends, in particular with regard to the Lower Fissure main phase of the eruption, are in accordance with the 'idealized discharge model' of Wadge (1981), proposed for basaltic eruptions driven by de-pressurization of magma sources, mainly through reservoir relaxation (i.e. elastic contraction of a magma body). The eruption took place when Italy was governed by Mussolini and the fascist party. The State response both, during and in the immediate aftermath of the eruption and in the years that followed during which Mascali was reconstructed, was impressive. This masked a less benign legacy, however, that can be traced for several subsequent decades of using responses to natural catastrophes to manufacture State prestige by reacting to, rather than planning for, disasters.

Mass ejections. [during solar flares

NASA Technical Reports Server (NTRS)

Rust, D. M.; Hildner, E.; Hansen, R. T.; Dryer, M.; Mcclymont, A. N.; Mckenna-Lawlor, S. M. P.; Mclean, D. J.; Schmahl, E. J.; Steinolfson, R. S.; Tandberg-Hanssen, E.

1980-01-01

Observations and model simulations of solar mass ejection phenomena are examined in an investigation of flare processes. Consideration is given to Skylab and other observations of flare-associated sprays, eruptive prominences, surges and coronal transients, and to MHD, gas dynamic and magnetic loop models developed to account for them. Magnetic forces are found to confine spray material, which originates in preexisting active-region filaments, within steadily expanding loops, while surges follow unmoving, preexisting magnetic field lines. Simulations of effects of a sudden pressure pulse at the bottom of the corona are found to exhibit many characteristics of coronal transients associated with flares, and impulsive heating low in the chromosphere is found to be able to account for surges. The importance of the magnetic field as the ultimate source of energy which drives eruptive phenomena as well as flares is pointed out.

A closer look at the pyroclastic density current deposits of the May 18, 1980 eruption of Mt St Helens

NASA Astrophysics Data System (ADS)

Mackaman-Lofland, C. A.; Brand, B. D.; Dufek, J.

2010-12-01

Pyroclastic Density Currents (PDCs) are the most dangerous hazard associated with explosive volcanic eruptions. Due to the danger associated with observing these ground-hugging currents of searing hot gas, ash, and rock in real time, their processes are poorly understood. In order to understand flow dynamics, including what controls how far PDCs travel and how they interact with topography, it is necessary to study their deposits. The May 18th, 1980 eruption of Mt. St. Helens produced multiple PDCs, burying the area north of the volcano under 10s of meters of PDC deposits. Because the eruption is one of the best observed on record, individual flow units can be correlated to changes in eruptive intensity throughout the day (e.g., Criswell, 1987). Deep drainage erosion over the past 30 years has exposed the three-dimensional structure of the PDC deposits, making this intensive study possible. Up to six flow units have been identified along the large western drainage of the pumice plain. Each flow unit has intricate vertical and lateral facies changes and complex cross-cutting relationships away from source. The most proximal PDC deposits associated with the afternoon flows on May 18 are exposed 4 km from source in tributaries of the large drainage on the western side of the pumice plain. Hummocks from the debris avalanche are also exposed above and within these proximal drainages. It is apparent that the PDCs were often erosional, entraining large blocks from the hummocks and depositing them in close proximity downstream. The currents were also depositional, as thick sequences of PDC deposits are found in areas between hummocks, which thin to veneers above them. This indicates that the currents were interacting with complex topography early in their propagation, and is reflected by spatially variable bed conditions including rapid changes in bedding and granulometry characteristics within individual flow units. For example, within 20 lateral meters of a given flow unit, depositional features can vary from massive, diffusely-stratified to stratified, and cross stratified. We interpret this variability as a result of interaction with nearby topography, rapid sedimentation of large blocks, or a combination of the two; this implies rapid spatial and temporal instabilities in the current. For each flow unit we measure deposit thickness, bedding style, clast size, density and sorting, and degree of pumice rounding with distance from source. We use this data to better understand and interpret flow dynamics from depositional characteristics. The data we collect will be used to refine and validate numerical models of PDCs, ultimately providing a more accurate hazard assessment for explosive eruptions.

A phase coherence approach to identifying co-located earthquakes and tremor

NASA Astrophysics Data System (ADS)

Hawthorne, J. C.; Ampuero, J.-P.

2018-05-01

We present and use a phase coherence approach to identify seismic signals that have similar path effects but different source time functions: co-located earthquakes and tremor. The method used is a phase coherence-based implementation of empirical matched field processing, modified to suit tremor analysis. It works by comparing the frequency-domain phases of waveforms generated by two sources recorded at multiple stations. We first cross-correlate the records of the two sources at a single station. If the sources are co-located, this cross-correlation eliminates the phases of the Green's function. It leaves the relative phases of the source time functions, which should be the same across all stations so long as the spatial extent of the sources are small compared with the seismic wavelength. We therefore search for cross-correlation phases that are consistent across stations as an indication of co-located sources. We also introduce a method to obtain relative locations between the two sources, based on back-projection of interstation phase coherence. We apply this technique to analyse two tremor-like signals that are thought to be composed of a number of earthquakes. First, we analyse a 20 s long seismic precursor to a M 3.9 earthquake in central Alaska. The analysis locates the precursor to within 2 km of the mainshock, and it identifies several bursts of energy—potentially foreshocks or groups of foreshocks—within the precursor. Second, we examine several minutes of volcanic tremor prior to an eruption at Redoubt Volcano. We confirm that the tremor source is located close to repeating earthquakes identified earlier in the tremor sequence. The amplitude of the tremor diminishes about 30 s before the eruption, but the phase coherence results suggest that the tremor may persist at some level through this final interval.

Plumbing of continental basaltic volcanoes from the mantle to the surface, 1: Insights from field relationships at the Lunar Crater Volcanic Field (Nevada, USA)

NASA Astrophysics Data System (ADS)

Valentine, G. A.; Cortes, J. A.; Widom, E.; Smith, E. I.

2011-12-01

Monogenetic intraplate volcanoes offer unique insights into the linkages between magma sources, crustal ascent, and eruption processes. We focus here on the northernmost part of the Lunar Crater Volcanic Field (LCVF), Nevada, with ~45 monogenetic volcanoes in a 10 km long, 5 km wide band. Within that band, many volcanoes occur in localized clusters with up to 5 volcanoes (of different ages) per square kilometer. Most of the clusters are elongated in a direction that parallels the trend of the LCVF as a whole. Currently it is uncertain whether such clusters are related to faults in the underlying rocks because of the thick, young cover of basaltic volcanic products. However, in other areas, especially along the periphery of the volcanic field, vents often correspond with pre-existing normal faults, and it seems likely that elongated clusters represent areas of repeated (over time scales of ~1-2 Ma) injection of feeder dikes into faults in the shallow crust. The edges of the volcanic field in the northernmost part are defined by sharp boundaries, where there is a sharp transition from high volcano concentration on one side, to no volcanoes on the other. A fundamental question is whether this transition reflects a similar spatial distribution in the mantle source area, or whether it is due entirely to shallow structural controls on magma ascent. The northernmost part of the LCVF provides an ideal case study for testing relationships between physical parameters (volume, fissure length, eruptive style) and geochemistry. We focus on three volcanoes, two of which are closely spaced (~500 m) but occurred at times separated by 100s ka (based upon surface morphology). The older of these two, informally called the OPB volcano (older, phenocryst bearing) is likely mid-Pleistocene in age; the younger is referred to as YMB (younger, megacrysts bearing). The third volcano, previously named Marcath/Black Rock, is the youngest in the volcanic field, located ~4 km southwest of OPB and YMB, with a surface exposure age of 38±10 ka (Shepard et al., 1995, Geology 23, 21-24). OPB has a volume of ~2.4x107 m3 (volumes include lavas and cones), with eruptions apparently from a small cone (~300 m basal diameter) with Strombolian facies recorded in the cone and a lava field averaging ~15 m thick and 2.8 km long. YMB has a volume of ~1.7x107 m3 and erupted from a 700 m long fissure, producing a spatter rampart and thin, ~5 km long, aa flow field. Marcath volcano produced ~1.4x108 m3 in extensive aa lavas (extending 3.3 km) from its ~500 m long fissure vent system, plus tephra fall deposit that has been traced, to date, to ~8 km from the cone, which suggests violent Strombolian processes. This information, combined with geochemical and petrologic data reported in a separate abstract (Cortés et al., this volume), enable us test the potential relationships of source heterogeneities, composition, and magma batch volume to eruptive processes.

Assessing Causes and Consequences of Columbia River Basalt Volcanism with Zircon Geochronology

NASA Astrophysics Data System (ADS)

Kasbohm, J.; Schoene, B.

2017-12-01

The Columbia River Basalt (CRB) is the youngest and best-preserved continental flood basalt province, but its mechanism of origin remains disputed. While some workers favor a mantle plume source to generate the large volume of flood basalts, others prefer subduction-related processes such as slab breakoff. Additionally, based on current geochronological (K-Ar and 40Ar/39Ar) estimates for the age of the CRB, there appears to be a very broad temporal coincidence between the main eruptive phase of the CRB and the Mid-Miocene Climate Optimum (MMCO), a period of elevated global temperatures and atmospheric CO2. Currently, large analytical uncertainties preclude the detailed calculation of volumetric eruption rates, which will be essential to test models of origin and to pinpoint correlation to climate records. To develop a complete record of eruption rates through the CRB, we use CA-ID-TIMS U-Pb zircon geochronology, which is capable of yielding 2σ uncertainties on single analyses of ca. 10 kyr. While basalt does not typically saturate zircon, interflow sediments, paleosols, and volcaniclastic layers in the CRB stratigraphy contain felsic zircon-bearing ash, likely sourced from both the Cascades arc and incipient Snake River plain volcanism. We use U-Pb zircon dates from these horizons to bracket the age of basalt flows. Preliminary results show that 88% of the total volume of the CRB (the Imnaha, Grande Ronde, and Wanapum Basalts) erupted in 700 kyr, beginning 16.6 Ma, with an average effusion rate of 0.26 km3/yr and with occurrence of lava flows propagating from south to north at a minimum rate of 0.3 m/yr. Thus far, these results do not preclude a mantle plume origin, but do place quantitative constraints on geodynamic numerical models hoping to constrain flood basalt origins. Although models based on prior geochronology have suggested that degassing from the CRB was insufficient to cause the MMCO, our calculated reduction in the duration of the main phase of CRB eruptions suggest that the flood basalt had a more concentrated environmental forcing effect than previously realized.

NEW ASPECTS OF A LID-REMOVAL MECHANISM IN THE ONSET OF AN ERUPTION SEQUENCE THAT PRODUCED A LARGE SOLAR ENERGETIC PARTICLE (SEP) EVENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David A.

We examine a sequence of two ejective eruptions from a single active region on 2012 January 23, using magnetograms and EUV images from the Solar Dynamics Observatory's (SDO) Helioseismic and Magnetic Imager (HMI) and Atmospheric and Imaging Assembly (AIA), and EUV images from STEREO/EUVI. This sequence produced two coronal mass ejections (CMEs) and a strong solar energetic particle event (SEP); here we focus on the magnetic onset of this important space weather episode. Cheng et al. showed that the first eruption's ({sup E}ruption 1{sup )} flux rope was apparent only in ''hotter'' AIA channels, and that it removed overlying field thatmore » allowed the second eruption ({sup E}ruption 2{sup )} to begin via ideal MHD instability; here we say that Eruption 2 began via a ''lid removal'' mechanism. We show that during Eruption 1's onset, its flux rope underwent a ''tether weakening'' (TW) reconnection with field that arched from the eruption-source active region to an adjacent active region. Standard flare loops from Eruption 1 developed over Eruption 2's flux rope and enclosed filament, but these overarching new loops were unable to confine that flux rope/filament. Eruption 1's flare loops, from both TW reconnection and standard-flare-model internal reconnection, were much cooler than Eruption 2's flare loops (GOES thermal temperatures of ∼7.5 MK and 9 MK, compared to ∼14 MK). The corresponding three sequential GOES flares were, respectively, due to TW reconnection plus earlier phase Eruption 1 tether-cutting reconnection, Eruption 1 later-phase tether-cutting reconnection, and Eruption 2 tether-cutting reconnection.« less

Focal mechanism of the seismic series prior to the 2011 El Hierro eruption

NASA Astrophysics Data System (ADS)

del Fresno, C.; Buforn, E.; Cesca, S.; Domínguez Cerdeña, I.

2015-12-01

The onset of the submarine eruption of El Hierro (10-Oct-2011) was preceded by three months of low-magnitude seismicity (Mw<4.0) characterized by a well documented hypocenter migration from the center to the south of the island. Seismic sources of this series have been studied in order to understand the physical process of magma migration. Different methodologies were used to obtain focal mechanisms of largest shocks. Firstly, we have estimated the joint fault plane solutions for 727 shocks using first motion P polarities to infer the stress pattern of the sequence and to determine the time evolution of principle axes orientation. Results show almost vertical T-axes during the first two months of the series and horizontal P-axes on N-S direction coinciding with the migration. Secondly, a point source MT inversion was performed with data of the largest 21 earthquakes of the series (M>3.5). Amplitude spectra was fitted at local distances (<20km). Reliability and stability of the results were evaluated with synthetic data. Results show a change in the focal mechanism pattern within the first days of October, varying from complex sources of higher non-double-couple components before that date to a simpler strike-slip mechanism with horizontal tension axes on E-W direction the week prior to the eruption onset. A detailed study was carried out for the 8 October 2011 earthquake (Mw=4.0). Focal mechanism was retrieved using a MT inversion at regional and local distances. Results indicate an important component of strike-slip fault and null isotropic component. The stress pattern obtained corresponds to horizontal compression in a NNW-SSE direction, parallel to the southern ridge of the island, and a quasi-horizontal extension in an EW direction. Finally, a simple source time function of 0.3s has been estimated for this shock using the Empirical Green function methodology.

Characterization of seismicity at Volcan Baru, Panama: May 2013 through April 2014

NASA Astrophysics Data System (ADS)

Hopp, Chet J.

Volcan Baru, in the western province of Chiriqui, is Panama's youngest and most active volcano. Although Baru has experienced no historic eruptions there have been four eruptive episodes in the last 1600 years, the most recent occurring 400-500 years ago (Sherrod et al., 2007). In addition, there have been four reported earthquake swarms in the last 100 years. The most recent swarm occurred in May of 2006, prompting a USGS hazard assessment (Sherrod et al., 2007). In order to characterize local seismicity and provide a reference for future monitoring efforts, we established a seismic network that operated from May 2013 through April 2014. The network consisted of eight temporary single-component, short-period sensors loaned by OSOP Panama, and three permanent stations distributed over a 35 by 15 km area. During operation of the network a catalog of 91 local events were detected, located and then used to calculate a minimum 1-D velocity model for Baru. Of particular interest were a cluster of events west of the town of Boquete. A template matching detection technique was used to identify another 47 smaller magnitude events in the area of this cluster. Spectrograms for the largest events in the cluster show a broad band of frequencies up to ˜20 Hz suggesting a predominantly tectonic source while eight focal mechanisms were calculated which suggest strike-slip and reverse faulting may be the predominant source processes. Further study is encouraged to better constrain the source processes and investigate how volcanic processes might affect local tectonics. 1. 1The material contained in this thesis is intended for submission to the Journal of Volcanology and Geothermal Research .

Are Avellino (4365 cal BP) and Pompeii twin plinian eruptions? Pre-eruptive constraints and degassing history

NASA Astrophysics Data System (ADS)

Boudon, Georges; Balcone-Boissard, Hélène; Villemant, Benoît.; Ucciani, Guillaume; Cioni, Raffaello

2010-05-01

Somma-Vesuvius activity started 35 ky ago and is characterized by numerous eruptions of variable composition and eruptive style, sometimes interrupted by long periods of unrest. The main explosive eruptions are represented by four plinian eruptions: Pomici di Base eruption (22 cal ky), Mercato (~8900 cal BP), Avellino (4365 cal BP) and Pompeii (79 AD). The 79 AD eruption embodies the most famous eruption since it's responsible of the destruction of Pompeii and Herculanum and it's the first described eruption. The Avellino eruption represents the last plinian event that preceded the Pompeii eruption. The eruptive sequence is similar to the 79 AD plinian eruption, with an opening phase preceding a main plinian fallout activity which ended by a phreatomagmatic phase. The fallout deposit displays a sharp colour contrast from white to grey pumice, corresponding to a magma composition evolution. We focus our study on the main fallout deposit that we sampled in detail in the Traianello quarry, 9 km North-North East of the crater, to investigate the degassing processes during the eruption, using volatile content and textural observations. Density and vesicularity measurements were obtained on a minimum of 100 pumice clasts sampled in 10 stratigraphic levels in the fallout deposit. On the basis of the density distribution, bulk geochemical data, point analytical measurements on glasses (melt inclusions and residual glass) and textural observations were obtained simultaneously on a minimum of 5 pumice clasts per eruptive unit. The glass composition, in particular the Na/K ratio, evolves from Na-rich phonolite for white pumices to a more K-rich phonolite for grey pumices. The pre-eruptive conditions are constrained by systematic Cl measurements in melt inclusions and matrix glass of pumice clasts. The entire magma was saturated relative to sub-critical fluids (a Cl-rich H2O vapour phase and a brine), with a Cl melt content buffered at ~6000 ppm, and a mean pre-eruptive H2O content depending of the magma composition. Most of the pumices of the different eruptive units show that H2O degassing during the eruption followed a typical closed-system evolution as expected for plinian eruption. Contrary to H2O, Cl was not efficiently degassed during the plinian phase of the eruption: the matrix glass composition remains close to the pre-eruptive content. Compared to the 79AD eruption the degassing processes showed by the whole Avellino plinian phase is more homogeneous and similar to the white pumice phase of the Pompeii eruption whereas the open-system degassing mode identified from the grey pumices of the 79AD eruption is not represented during the Avellino eruption.

Lava Eruption and Emplacement: Using Clues from Hawaii and Iceland to Probe the Lunar Past

NASA Technical Reports Server (NTRS)

Needham, Debra Hurwitz; Hamilton, C. W.; Bleacher, J. E.; Whelley, P. L.; Young, K. E.; Scheidt, S. P.; Richardson, J. A.; Sutton, S. S.

2017-01-01

Investigating recent eruptions on Earth is crucial to improving understanding of relationships between eruption dynamics and final lava flow morphologies. In this study, we investigated eruptions in Holuhraun, Iceland, and Kilauea, Hawaii to gain insight into the lava dynamics near the source vent, the initiation of lava channels, and the origin of down-channel features. Insights are applied to Rima Bode on the lunar nearside to deduce the sequence of events that formed this lunar sinuous rille system. These insights are crucial to correctly interpreting whether the volcanic features associated with Rima Bode directly relate to eruption conditions at the vent and, thus, can help us understand those eruption dynamics, or, alternatively, whether the features formed as a result of more localized influences on lava flow dynamics. For example, if the lava channel developed early in the eruption and was linked to pulses in vent activity, its morphology can be analyzed to interpret the flux and duration of the eruption. Conversely, if the lava channel initiated late in the eruption as the result of a catastrophic breaching of lava that had previously pooled within the vent [e.g., 1], then the final channel morphology will not indicate eruption dynamics but rather local dynamics associated with that breach event. Distinguishing between these two scenarios is crucial for correctly interpreting the intensity and duration of volcanic history on the Moon.

Lava Eruption and Emplacement: Using Clues from Hawaii and Iceland to Probe the Lunar Past

NASA Technical Reports Server (NTRS)

Needham, D. H.; Hamilton, C. W.; Bleacher, J. E.; Whelley, P. L.; Young, K. E.; Scheidt, S. P.; Richardson, J. A.; Sutton, S. S.

2017-01-01

Investigating recent eruptions on Earth is crucial to improving understanding of relationships between eruption dynamics and final lava flow morphologies. In this study, we investigated eruptions in Holuhraun, Iceland, and Kilauea, Hawaii to gain insight into the lava dynamics near the source vent, the initiation of lava channels, and the origin of down-channel features. Insights are applied to Rima Bode on the lunar nearside to deduce the sequence of events that formed this lunar sinuous rille system.These insights are crucial to correctly interpreting whether the volcanic features associated with Rima Bode directly relate to eruption conditions at the vent and, thus, can help us understand those eruption dynamics, or, alternatively, whether the features formed as a result of more localized influences on lava flow dynamics. For example, if the lava channel developed early in the eruption and was linked to pulses in vent activity, its morphology can be analyzed to interpret the flux and duration of the eruption. Conversely, if the lava channel initiated late in the eruption as the result of a catastrophic breaching of lava that had previously pooled within the vent [e.g., 1], then the final channel morphology will not indicate eruption dynamics but rather local dynamics associated with that breach event. Distinguishing between these two scenarios is crucial for correctly interpreting the intensity and duration of volcanic history on the Moon.

Estimating different eruptive style volcanic areas of Mars from NASA Martian Meteorites Compendium data

NASA Astrophysics Data System (ADS)

Mari, Nicola; Verrino, Miriam

2016-04-01

The geomorphological characteristics of the Martian surface suggest that both effusive and explosive eruptive behaviour occurred. We investigated whether data about magma viscosity could be extrapolated from Mars SNCs (Shergotty, Nakhla, and Chassigny classes) meteorites, by using available geochemical and petrographic data from the NASA Martian Meteorites Compendium. Viscosity was used to characterize how eruptive style could change in different volcanic regions of planet Mars. Data about composition and crystallinity of 41 SNCs meteorites were used and classified, avoiding meteorites with poor/incomplete database. We assumed Mars as a one-plate planet, fO2 = QFM, and H2O wt% = 0 for each sample. Collected data from the Mars Global Surveyor Thermal Emission Spectrometer (MGS TES) identified the source regions for almost all the studied SNCs meteorites. As input for thermodynamic simulations we first needed to find the depth and pressure of the magmatic source for each meteorite sample through available Thermal Emission Imaging System (THEMIS). Data about average surface temperatures was used to establish whether a magmatic source is shallow or deep. Successively, we found the magma source depth (and pressure) by using the relationship with the heights of the volcanic edifice. The subsolidus equilibration temperatures found through petrologic softwares were used to calculate viscosity. Results indicate a crystallization temperature in a range from 1,120°C to 843°C, follow by a variation in viscosity from 101,43 to 105,97 Pa s. Viscosity seems to be higher in Tharsis, Elysium, Amazonis, and Syrtis Major regions than the remnant areas. According to past experimental studies about magma viscosity, we classified the eruptive style into effusive (101-103,5 Pa s), intermediate (103,5-104,5 Pa s), and explosive (104,5-106 Pa s). The Hellas Basin, Argyre Basin, Ganges Chasma, Eos Chasma, and Nili Fossae regions show an eruptive behaviour between effusive and intermediate, while the Tharsis, Elysium, Amazonis, Syrtis Major, and Terra Tyrrhena regions have a more explosive eruptive style, even if effusive/intermediate activity also occur. Our results seems to be in accord with the Martian geomorphology of the cited areas.

Underestimated risks of recurrent long-range ash dispersal from northern Pacific Arc volcanoes

PubMed Central

Bourne, A. J.; Abbott, P. M.; Albert, P. G.; Cook, E.; Pearce, N. J. G.; Ponomareva, V.; Svensson, A.; Davies, S. M.

2016-01-01

Widespread ash dispersal poses a significant natural hazard to society, particularly in relation to disruption to aviation. Assessing the extent of the threat of far-travelled ash clouds on flight paths is substantially hindered by an incomplete volcanic history and an underestimation of the potential reach of distant eruptive centres. The risk of extensive ash clouds to aviation is thus poorly quantified. New evidence is presented of explosive Late Pleistocene eruptions in the Pacific Arc, currently undocumented in the proximal geological record, which dispersed ash up to 8000 km from source. Twelve microscopic ash deposits or cryptotephra, invisible to the naked eye, discovered within Greenland ice-cores, and ranging in age between 11.1 and 83.7 ka b2k, are compositionally matched to northern Pacific Arc sources including Japan, Kamchatka, Cascades and Alaska. Only two cryptotephra deposits are correlated to known high-magnitude eruptions (Towada-H, Japan, ca 15 ka BP and Mount St Helens Set M, ca 28 ka BP). For the remaining 10 deposits, there is no evidence of age- and compositionally-equivalent eruptive events in regional volcanic stratigraphies. This highlights the inherent problem of under-reporting eruptions and the dangers of underestimating the long-term risk of widespread ash dispersal for trans-Pacific and trans-Atlantic flight routes. PMID:27445233

Shifts in the eruptive styles at Stromboli in 2010–2014 revealed by ground-based InSAR data

USGS Publications Warehouse

Di Traglia, Federico; Battaglia, Maurizio; Nolesini, Teresa; Lagomarsino, Daniela; Casaglia, Nicola

2015-01-01

Ground-Based Interferometric Synthetic Aperture Radar (GBInSAR) is an efficient technique for capturing short, subtle episodes of conduit pressurization in open vent volcanoes like Stromboli (Italy), because it can detect very shallow magma storage, which is difficult to identify using other methods. This technique allows the user to choose the optimal radar location for measuring the most significant deformation signal, provides an exceptional geometrical resolution, and allows for continuous monitoring of the deformation. Here, we present and model ground displacements collected at Stromboli by GBInSAR from January 2010 to August 2014. During this period, the volcano experienced several episodes of intense volcanic activity, culminated in the effusive flank eruption of August 2014. Modelling of the deformation allowed us to estimate a source depth of 482 ± 46 m a.s.l. The cumulative volume change was 4.7 ± 2.6 × 105 m3. The strain energy of the source was evaluated 3–5 times higher than the surface energy needed to open the 6–7 August eruptive fissure. The analysis proposed here can help forecast shifts in the eruptive style and especially the onset of flank eruptions at Stromboli and at similar volcanic systems (e.g. Etna, Piton de La Fournaise, Kilauea).

Shifts in the eruptive styles at Stromboli in 2010-2014 revealed by ground-based InSAR data.

PubMed

Di Traglia, Federico; Battaglia, Maurizio; Nolesini, Teresa; Lagomarsino, Daniela; Casagli, Nicola

2015-09-01

Ground-Based Interferometric Synthetic Aperture Radar (GBInSAR) is an efficient technique for capturing short, subtle episodes of conduit pressurization in open vent volcanoes like Stromboli (Italy), because it can detect very shallow magma storage, which is difficult to identify using other methods. This technique allows the user to choose the optimal radar location for measuring the most significant deformation signal, provides an exceptional geometrical resolution, and allows for continuous monitoring of the deformation. Here, we present and model ground displacements collected at Stromboli by GBInSAR from January 2010 to August 2014. During this period, the volcano experienced several episodes of intense volcanic activity, culminated in the effusive flank eruption of August 2014. Modelling of the deformation allowed us to estimate a source depth of 482 ± 46 m a.s.l. The cumulative volume change was 4.7 ± 2.6 × 10(5) m(3). The strain energy of the source was evaluated 3-5 times higher than the surface energy needed to open the 6-7 August eruptive fissure. The analysis proposed here can help forecast shifts in the eruptive style and especially the onset of flank eruptions at Stromboli and at similar volcanic systems (e.g. Etna, Piton de La Fournaise, Kilauea).

Underestimated risks of recurrent long-range ash dispersal from northern Pacific Arc volcanoes.

PubMed

Bourne, A J; Abbott, P M; Albert, P G; Cook, E; Pearce, N J G; Ponomareva, V; Svensson, A; Davies, S M

2016-07-21

Widespread ash dispersal poses a significant natural hazard to society, particularly in relation to disruption to aviation. Assessing the extent of the threat of far-travelled ash clouds on flight paths is substantially hindered by an incomplete volcanic history and an underestimation of the potential reach of distant eruptive centres. The risk of extensive ash clouds to aviation is thus poorly quantified. New evidence is presented of explosive Late Pleistocene eruptions in the Pacific Arc, currently undocumented in the proximal geological record, which dispersed ash up to 8000 km from source. Twelve microscopic ash deposits or cryptotephra, invisible to the naked eye, discovered within Greenland ice-cores, and ranging in age between 11.1 and 83.7 ka b2k, are compositionally matched to northern Pacific Arc sources including Japan, Kamchatka, Cascades and Alaska. Only two cryptotephra deposits are correlated to known high-magnitude eruptions (Towada-H, Japan, ca 15 ka BP and Mount St Helens Set M, ca 28 ka BP). For the remaining 10 deposits, there is no evidence of age- and compositionally-equivalent eruptive events in regional volcanic stratigraphies. This highlights the inherent problem of under-reporting eruptions and the dangers of underestimating the long-term risk of widespread ash dispersal for trans-Pacific and trans-Atlantic flight routes.

On a Possible Unified Scaling Law for Volcanic Eruption Durations

PubMed Central

Cannavò, Flavio; Nunnari, Giuseppe

2016-01-01

Volcanoes constitute dissipative systems with many degrees of freedom. Their eruptions are the result of complex processes that involve interacting chemical-physical systems. At present, due to the complexity of involved phenomena and to the lack of precise measurements, both analytical and numerical models are unable to simultaneously include the main processes involved in eruptions thus making forecasts of volcanic dynamics rather unreliable. On the other hand, accurate forecasts of some eruption parameters, such as the duration, could be a key factor in natural hazard estimation and mitigation. Analyzing a large database with most of all the known volcanic eruptions, we have determined that the duration of eruptions seems to be described by a universal distribution which characterizes eruption duration dynamics. In particular, this paper presents a plausible global power-law distribution of durations of volcanic eruptions that holds worldwide for different volcanic environments. We also introduce a new, simple and realistic pipe model that can follow the same found empirical distribution. Since the proposed model belongs to the family of the self-organized systems it may support the hypothesis that simple mechanisms can lead naturally to the emergent complexity in volcanic behaviour. PMID:26926425

On a Possible Unified Scaling Law for Volcanic Eruption Durations.

PubMed

Cannavò, Flavio; Nunnari, Giuseppe

2016-03-01

Volcanoes constitute dissipative systems with many degrees of freedom. Their eruptions are the result of complex processes that involve interacting chemical-physical systems. At present, due to the complexity of involved phenomena and to the lack of precise measurements, both analytical and numerical models are unable to simultaneously include the main processes involved in eruptions thus making forecasts of volcanic dynamics rather unreliable. On the other hand, accurate forecasts of some eruption parameters, such as the duration, could be a key factor in natural hazard estimation and mitigation. Analyzing a large database with most of all the known volcanic eruptions, we have determined that the duration of eruptions seems to be described by a universal distribution which characterizes eruption duration dynamics. In particular, this paper presents a plausible global power-law distribution of durations of volcanic eruptions that holds worldwide for different volcanic environments. We also introduce a new, simple and realistic pipe model that can follow the same found empirical distribution. Since the proposed model belongs to the family of the self-organized systems it may support the hypothesis that simple mechanisms can lead naturally to the emergent complexity in volcanic behaviour.

The variation of magma discharge during basaltic eruptions

NASA Technical Reports Server (NTRS)

Wadge, G.

1981-01-01

The rate at which basaltic magma is discharged during many eruptions varies substantially. An individual eruption has an eruption rate, which is the volumetric rate of discharge averaged over the whole or a major part of an eruption, and an effusion rate, which is the volumetric flux rate at any given time. In many cases, the effusion rate soon reaches a maximum after a short period of waxing flow (partly because of magmatic expansion); it then falls more slowly in the later parts of the eruption. The release of elastic strain energy from stored magma and the subvolcanic reservoir during eruption can give a waning flow of this type an exponential form. A comparison of the eruption rates of eruptions of Mauna Loa, Kilauea and Etna shows that for each volcano there is a trend of decreasing effusion rate with increasing duration of eruption. It is noted that this relationship is not predicted by a simple elastic model of magma release. Two other processes are invoked to explain the eruptive histories of these volcanoes: modification of the eruptive conduits and the continued supply of magma from depth during eruption.

The Influence of Conduit Processes During Basaltic Plinian Eruptions.

NASA Astrophysics Data System (ADS)

Houghton, B. F.; Sable, J. E.; Wilson, C. J.; Coltelli, M.; Del Carlo, P.

2001-12-01

Basaltic volcanism is most typically thought to produce effusion of lava, with the most explosive manifestations ranging from mild Strombolian activity to more energetic fire fountain eruptions. However, some basaltic eruptions are now recognized as extremely violent, i.e. generating widespread phreatomagmatic, subplinian and Plinian fall deposits. These eruptions are particularly dangerous because the ascent rate of basaltic magma prior to eruption can be very rapid (giving warning times as little as a few hours) and because their precursors may be ignored or misunderstood. The main question addressed in this talk is: what conditions in the conduit cause basaltic magma to adopt an eruption style more typical of chemically evolved, highly viscous magmas? Possible mechanisms (acting singly, or in concert) are: (1) interaction between magma and water, (ii) very rapid ascent producing a delayed onset of degassing then exceptionally rapid "runaway" vesiculation at shallow levels in the conduit, (iii) microlite crystallization and degassing of the magma during ascent leading to increased viscosity. We focus here on two examples of basaltic Plinian volcanism: the 1886 eruption of Tarawera, New Zealand, which is the youngest known basaltic Plinian eruption and the only one for which there are detailed written eyewitness accounts, and the well documented 122 BC eruption of Mount Etna, Italy. Field and laboratory evidence suggests that the Plinian phase of the 1886 eruption was a consequence of two processes. Firstly rheologic changes during magma ascent accompanied early (pre-fragmentation) interaction between the basaltic melt and water-bearing rhyolitic units forming the conduit walls and, secondly, late-stage magma:water interaction. In contrast, during the 122 BC eruption tectonic processes, such as slope failure or permanent displacement of a mobile flank of the volcano, appear to have triggered exceptionally rapid ascent, delayed onset of degassing and exceptionally rapid vesiculation at shallow levels in the conduit.

Quantifying distal dispersal and impact of volcanic ash from super-eruptions: an application to Campanian Ignimbrite

NASA Astrophysics Data System (ADS)

Costa, A.; Folch, A.; Macedonio, G.; Giaccio, B.; Isaia, R.; Smith, V. C.

2012-04-01

Distal and ultra-distal volcanic ash dispersal during a super-eruption was reconstructed for the first time, providing insights into eruption dynamics and the impact of these gigantic events. A novel computational methodology was applied to the ash fallout of the Campanian Ignimbrite (CI), the most powerful volcanic eruption in Europe in the last 200 kyrs. The method uses a 3D time-dependent computational ash dispersion model, an ensemble of wind fields, and hundreds of thickness observations of the CI tephra deposit. Results reveal that 250-300 km3 of fallout material was produced during the eruption, blanketing a region of ~3.7 million km2 with more than 5 mm of fine ash. The model also indicates that the column height was ~37-40 km, and the eruption lasted 2-4 days. The eruption would have caused a volcanic winter within the coldest and driest Heinrich event. Fluorine-bearing leachate from the volcanic ash and acid rain would have further affected food sources and severely impacted Late Middle Paleolithic groups in Southern and Eastern Europe.

An ignimbrite caldera from the bottom up: Exhumed floor and fill of the resurgent Bonanza caldera, Southern Rocky Mountain volcanic field, Colorado

USGS Publications Warehouse

Lipman, Peter W.; Zimmerer, Matthew J.; McIntosh, William C.

2015-01-01

Among large ignimbrites, the Bonanza Tuff and its source caldera in the Southern Rocky Mountain volcanic field display diverse depositional and structural features that provide special insights concerning eruptive processes and caldera development. In contrast to the nested loci for successive ignimbrite eruptions at many large multicyclic calderas elsewhere, Bonanza caldera is an areally isolated structure that formed in response to a single ignimbrite eruption. The adjacent Marshall caldera, the nonresurgent lava-filled source for the 33.9-Ma Thorn Ranch Tuff, is the immediate precursor for Bonanza, but projected structural boundaries of two calderas are largely or entirely separate even though the western topographic rim of Bonanza impinges on the older caldera. Bonanza, source of a compositionally complex regional ignimbrite sheet erupted at 33.12 ± 0.03 Ma, is a much larger caldera system than previously recognized. It is a subequant structure ∼20 km in diameter that subsided at least 3.5 km during explosive eruption of ∼1000 km3 of magma, then resurgently domed its floor a similar distance vertically. Among its features: (1) varied exposure levels of an intact caldera due to rugged present-day topography—from Paleozoic and Precambrian basement rocks that are intruded by resurgent plutons, upward through precaldera volcanic floor, to a single thickly ponded intracaldera ignimbrite (Bonanza Tuff), interleaved landslide breccia, and overlying postcollapse lavas; (2) large compositional gradients in the Bonanza ignimbrite (silicic andesite to rhyolite ignimbrite; 60%–76% SiO2); (3) multiple alternations of mafic and silicic zones within a single ignimbrite, rather than simple upward gradation to more mafic compositions; (4) compositional contrasts between outflow sectors of the ignimbrite (mainly crystal-poor rhyolite to east, crystal-rich dacite to west); (5) similarly large compositional diversity among postcollapse caldera-fill lavas and resurgent intrusions; (6) brief time span for the entire caldera cycle (33.12 to ca. 33.03 Ma); (7) an exceptionally steep-sided resurgent dome, with dips of 40°–50° on west and 70°–80° on northeast flanks. Some near-original caldera morphology has been erosionally exhumed and remains defined by present-day landforms (western topographic rim, resurgent core, and ring-fault valley), while tilting and deep erosion provide three-dimensional exposures of intracaldera fill, floor, and resurgent structures. The absence of Plinian-fall deposits beneath proximal ignimbrites at Bonanza and other calderas in the region is interpreted as evidence for early initiation of pyroclastic flows, rather than lack of a high eruption column. Although the absence of a Plinian deposit beneath some ignimbrites elsewhere has been interpreted to indicate that abrupt rapid foundering of the magma-body roof initiated the eruption, initial caldera collapse began at Bonanza only after several hundred kilometers of rhyolitic tuff had erupted, as indicated by the minor volume of this composition in the basal intracaldera ignimbrite. Caldera-filling ignimbrite has been largely stripped from the southern and eastern flank of the Bonanza dome, exposing large areas of caldera-floor as a structurally coherent domed plate, bounded by ring faults with locations that are geometrically closely constrained even though largely concealed beneath valley alluvium. The structurally coherent floor at Bonanza contrasts with fault-disrupted floors at some well-exposed multicyclic calderas where successive ignimbrite eruptions caused recurrent subsidence. Floor rocks at Bonanza are intensely brecciated within ∼100 m inboard of ring faults, probably due to compression and crushing of the subsiding floor in proximity to steep inward-dipping faults. Upper levels of the floor are locally penetrated by dike-like crack fills of intracaldera ignimbrite, interpreted as dilatant fracture fills rather than ignimbrite vents. The resurgence geometry at Bonanza has implications for intracaldera-ignimbrite volume; this parameter may have been overestimated at some young calderas elsewhere, with bearing on outflow-intracaldera ratios and times of initial caldera collapse. Such features at Bonanza provide insights for interpreting calderas universally, with respect to processes of caldera collapse and resurgence, inception of subsidence in relation to progression of the ignimbrite eruption, complications with characterizing structural versus topographic margins of calderas, contrasts between intra- versus extracaldera ignimbrite, and limitations in assessing volumes of large caldera-forming eruptions. Bonanza provides a rare site where intact caldera margins and floor are exhumed and exposed, providing valuable perspectives for understanding younger similar calderas in some of the world’s most active and dangerous silicic provinces.

The 1984 Mauna Loa eruption and planetary geolgoy

NASA Technical Reports Server (NTRS)

Moore, Henry J.

1987-01-01

In planetary geology, lava flows on the Moon and Mars are commonly treated as relatively simple systems. Some of the complexities of actual lava flows are illustrated using the main flow system of the 1984 Mauna Loa eruption. The outline, brief narrative, and results given are based on a number of sources. The implications of the results to planetary geology are clear. Volume flow rates during an eruption depend, in part, on the volatile content of the lava. These differ from the volume flow rates calculated from post eruption flow dimensions and the duration of the eruption and from those using models that assume a constant density. Mass flow rates might be more appropriate because the masses of volatiles in lavas are usually small, but variable and sometimes unknown densities impose severe restrictions on mass estimates.

Phreatic eruptions and deformation of Ioto Island (Iwo-jima), Japan, triggered by deep magma injection

NASA Astrophysics Data System (ADS)

Ueda, Hideki; Nagai, Masashi; Tanada, Toshikazu

2018-03-01

On Ioto Island (Iwo-jima), 44 phreatic eruptions have been recorded since 1889, when people began to settle there. Four of these eruptions, after the beginning of continuous observation by seismometers in 1976, were accompanied by intense seismic activity and rapid crustal deformation beforehand. Other eruptions on Ioto were without obvious crustal activities. In this paper, we discuss the mechanisms of phreatic eruptions on Ioto. Regular geodetic surveys and continuous GNSS observations show that Ioto intermittently uplifts at an abnormally high rate. All of the four eruptions accompanied by the precursors took place during intermittent uplifts. The crustal deformation before and after one of these eruptions revealed that a sill-like deformation source in the shallow part of Motoyama rapidly inflated before and deflated after the beginning of the eruption. From the results of a seismic array and a borehole survey, it is estimated that there is a layer of lava at a depth of about 100-200 m, and there is a tuff layer about 200-500 m beneath it. The eruptions accompanied by the precursors probably occurred due to abrupt boiling of hot water in hydrothermal reservoirs in the tuff layer, sealed by the lava layer and triggered by intermittent uplift. For the eruptions without precursors, the hydrothermal systems are weakly sealed by clay or probably occurred on the same principle as a geyser because phreatic eruptions had occurred beforehand and hydrostatic pressure is applied to the hydrothermal reservoirs.

Improvements on the relationship between plume height and mass eruption rate: Implications for volcanic ash cloud forecasting

NASA Astrophysics Data System (ADS)

Webley, P. W.; Dehn, J.; Mastin, L. G.; Steensen, T. S.

2011-12-01

Volcanic ash plumes and the dispersing clouds into the atmosphere are a hazard for local populations as well as for the aviation industry. Volcanic ash transport and dispersion (VATD) models, used to forecast the movement of these hazardous ash emissions, require eruption source parameters (ESP) such as plume height, eruption rate and duration. To estimate mass eruption rate, empirical relationships with observed plume height have been applied. Theoretical relationships defined by Morton et al. (1956) and Wilson et al. (1976) use default values for the environmental lapse rate (ELR), thermal efficiency, density of ash, specific heat capacity, initial temperature of the erupted material and final temperature of the material. Each volcano, based on its magma type, has a different density, specific heat capacity and initial eruptive temperature compared to these default parameters, and local atmospheric conditions can produce a very different ELR. Our research shows that a relationship between plume height and mass eruption rate can be defined for each eruptive event for each volcano. Additionally, using the one-dimensional modeling program, Plumeria, our analysis assesses the importance of factors such as vent diameter and eruption velocity on the relationship between the eruption rate and measured plume height. Coupling such a tool with a VATD model should improve pre-eruptive forecasts of ash emissions downwind and lead to improvements in ESP data that VATD models use for operational volcanic ash cloud forecasting.

Eruptive history and magmatic stability of Erebus volcano, Antarctica: Insights from englacial tephra

NASA Astrophysics Data System (ADS)

Iverson, Nels A.; Kyle, Philip R.; Dunbar, Nelia W.; McIntosh, William C.; Pearce, Nicholas J. G.

2014-11-01

A tephrostratigraphy of the active Antarctic Erebus volcano was determined from englacial tephra on the ice-covered flanks of Erebus and an adjacent volcano. The tephra are used to reconstruct the eruptive history and magmatic evolution of Erebus. More fine-grained and blocky particles define tephra formed in phreatomagmatic eruptions and larger fluidal shards are characteristic of magmatic eruptions and in some cases both eruptive types are identified in a single mixed tephra. The eruptions forming the mixed tephra likely started as phreatomagmatic eruptions which transitioned into Strombolian eruptions as the nonmagmatic water source was exhausted. We reconstructed the eruptive history of Erebus using the tephra layers stratigraphic position, 40Ar/39Ar ages, shard morphology, and grain size. Major and trace element analyses of individual glass shards were measured by electron probe microanalysis and LA-ICP-MS. Trachybasalt, trachyte, and phonolite tephra were identified. All phonolitic tephra are Erebus-derived with compositions similar to volcanic bombs erupted from Erebus over the past 40 years. The tephra show that Erebus magma has not significantly changed for 40 ka. The uniformity of the glass chemical composition implies that the phonolite magma has crystallized in the same manner without change throughout the late Quaternary, suggesting long-term stability of the Erebus magmatic system. Trachyte and trachybasalt tephra were likely erupted from Marie Byrd Land and the McMurdo Sound area, respectively. The trachytic tephra can be regionally correlated and could provide an important time-stratigraphic marker in Antarctic ice cores.

Long-period seismicity at Redoubt Volcano, Alaska, 1989-1990 related to magma degassing

USGS Publications Warehouse

Morrissey, M.M.

1997-01-01

The mass of exsolved magmatic H2O is estimated and compared to the mass of superheated steam (25-50 Mtons) released through the resonating crack producing the December 13-14, 1989 swarm of long-period seismic events at Redoubt Volcano. Results indicate degassing of a H2O-CO2-SO2-saturated magma upon ascending from at least 12 km to 3-4 km beneath the crater as the source of the superheated steam. The mass of exsolved H2O (3.2-250 Mtons) is estimated from solubility diagrams of H2O-CO2-saturated silicate melts for the ascent history of the Redoubt magmas. Crystal size distribution, seismological, petrological, and geochemical data are used to constrain the ascent history of the two andesitic magmas prior to the eruption. Two stages of crystallization are inferred from crystal size distributions of plagioclase crystals in andesites erupted in December 1989. The first stage occurred 30-150 years before the eruption in both magmas and the second stage occurred at least 8 years and 15 years before the eruption in the dacitic andesite and rhyolitic andesite, respectively. The depths of crystallization are constrained from the spatial and temporal variations of volcano-tectonic earthquakes locations (Lahr et al., 1994) and from the P-wave and S-wave velocity structures (Benz et al., 1996). These data suggest that the rhyolitic andesite magma ascended to a depth of 7-8 km within at least 15 years of the eruption. Within at least 8 years of the eruption, the dacitic andesite magma migrated to a depth just below the other magma body where it resided until hours to days of the eruption. At this time, the dacitic andesite magma mixed with the rhyolitic andesite magma and established the reservoir for the eruption. Near the top of the reservoir, some of the mixed magma was displaced into fractures which extended 4-5 km toward the surface. This displaced magma created the eruption conduit and released the fluids related to the resonating crack. This scenario is consistent with the trends in major-and trace-element chemistry, and the stability of hornblende in the pre-eruption Redoubt magmas. It also provides a source for the SO2 and CO2 emissions measured during the eruption.

Rootless eruption of a mandibular permanent canine.

PubMed

Shapira, Yehoshua; Kuftinec, Mladen M

2011-04-01

The purpose of this article was to describe the rootless eruption of a mandibular permanent canine in a 10-year-old boy; his mandible had been fractured in a car accident. The fracture was at the region of the developing canine, resulting in arrested root formation and causing abnormal, rootless eruption. Current theories on tooth eruption and the important role of the dental follicle in the process of eruption are discussed. Copyright © 2011 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Characterize Eruptive Processes at Yucca Mountain, Nevada

DOE Office of Scientific and Technical Information (OSTI.GOV)

G. Valentine

2001-12-20

This Analysis/Model Report (AMR), ''Characterize Eruptive Processes at Yucca Mountain, Nevada'', presents information about natural volcanic systems and the parameters that can be used to model their behavior. This information is used to develop parameter-value distributions appropriate for analysis of the consequences of volcanic eruptions through a potential repository at Yucca Mountain. Many aspects of this work are aimed at resolution of the Igneous Activity Key Technical Issue (KTI) as identified by the Nuclear Regulatory Commission (NRC 1998, p. 3), Subissues 1 and 2, which address the probability and consequence of igneous activity at the proposed repository site, respectively. Withinmore » the framework of the Disruptive Events Process Model Report (PMR), this AMR provides information for the calculations in two other AMRs ; parameters described herein are directly used in calculations in these reports and will be used in Total System Performance Assessment (TSPA). Compilation of this AMR was conducted as defined in the Development Plan, except as noted. The report begins with considerations of the geometry of volcanic feeder systems, which are of primary importance in predicting how much of a potential repository would be affected by an eruption. This discussion is followed by one of the physical and chemical properties of the magmas, which influences both eruptive styles and mechanisms for interaction with radioactive waste packages. Eruptive processes including the ascent velocity of magma at depth, the onset of bubble nucleation and growth in the rising magmas, magma fragmentation, and velocity of the resulting gas-particle mixture are then discussed. The duration of eruptions, their power output, and mass discharge rates are also described. The next section summarizes geologic constraints regarding the interaction between magma and waste packages. Finally, they discuss bulk grain size produced by relevant explosive eruptions and grain shapes.« less

Eruptive history of the youngest Mexican Shield and Mexico's most voluminous Holocene eruption: Cerro El Metate

NASA Astrophysics Data System (ADS)

Oryaëlle Chevrel, Magdalena; Guilbaud, Marie-Noelle; Siebe, Claus

2016-04-01

Small to medium-sized shield volcanoes are an important component of many volcanic fields on Earth. The Trans-Mexican Volcanic Belt, one of the most complex and active continental arcs worldwide, displays a large number of such medium-sized volcanoes. In particular the Michoacán-Guanajuato Volcanic Field (MGVF) situated in central Mexico, is the largest monogenetic volcanic field in the world and includes more than 1000 scoria cones and about four hundred medium-sized volcanoes, also known as Mexican shields. The Mexican shields nevertheless represent nearly 70% of the total volume erupted since 1 Ma and hence played a considerable role in the formation of the MGVF. However, the source, storage, and transport as well as the physical properties (density, viscosity, volatile content, etc.) of the magmas involved in these eruptions remain poorly constrained. Here, we focus on Cerro El Metate, the youngest monogenetic andesite shield volcano of the field. New C14 dates for the eruption yield a young age (~AD 1250), which briefly precedes the initial rise of the Tarascan Empire (AD 1350-1521) in this region. This volcano has a minimum volume of ~9.2 km3 DRE, and its viscous lava flows were emplaced during a single eruption over a period of ~35 years covering an area of 103 km2. By volume, this is certainly the largest eruption during the Holocene in Mexico, and it is the largest andesitic effusive eruption known worldwide for this period. Such a large volume of lava erupted in a relatively short time had a significant impact on the environment (modification of the hydrological network, forest fires, etc.), and hence, nearby human populations probably had to migrate. Its eruptive history was reconstructed through detailed mapping, and geochemical and rheological analyses of its thick hornblende-bearing andesitic flows. Early and late flows have distinct morphologies, chemical and mineralogical compositions, and isotopic signatures which show that these lavas were fed by two separate magma batches that followed distinct differentiation paths during their ascent. The source for both batches was a subduction-modified heterogeneous lithospheric upper mantle. Mineral thermometry and barometry reveal that after initial ascent through the crust, the first batch became temporarily stalled at a depth of ~7-10 km, allowing for crystallization and fractionation. Then, the second hotter batch ascended, bypassed the first batch without significant mingling or mixing of the two magmas and erupted. Stratigraphic relations between the distinct lava units indicate that this first eruptive episode was followed directly by the eruption of the first batch. The entire eruption was then purely effusive and continuous. The explosive eruption of such a large magma volume was avoided due to efficient and constant passive open-degassing of the magma as it ascended through the uppermost crust and erupted at the surface.

The source and longevity of sulfur in an Icelandic flood basalt eruption plume

NASA Astrophysics Data System (ADS)

Ilyinskaya, Evgenia; Edmonds, Marie; Mather, Tamsin; Schmidt, Anja; Hartley, Margaret; Oppenheimer, Clive; Pope, Francis; Donovan, Amy; Sigmarsson, Olgeir; Maclennan, John; Shorttle, Oliver; Francis, Peter; Bergsson, Baldur; Barsotti, Sara; Thordarson, Thorvaldur; Bali, Eniko; Keller, Nicole; Stefansson, Andri

2015-04-01

The Holuhraun fissure eruption (Bárðarbunga volcanic system, central Iceland) has been ongoing since 31 August 2014 and is now the largest in Europe since the 1783-84 Laki event. For the first time in the modern age we have the opportunity to study at first hand the environmental impact of a flood basalt fissure eruption (>1 km3 lava). Flood basalt eruptions are one of the most hazardous volcanic scenarios in Iceland and have had enormous societal and economic consequences across the northern hemisphere in the past. The Laki eruption caused the deaths of >20% of the Icelandic population by environmental pollution and famine and potentially also increased European levels of mortality through air pollution by sulphur-bearing gas and aerosol. A flood basalt eruption was included in the UK National Risk Register in 2012 as one of the highest priority risks. The gas emissions from Holuhraun have been sustained since its beginning, repeatedly causing severe air pollution in populated areas in Iceland. During 18-22 September, SO2 fluxes reached 45 kt/day, a rate of outgassing rarely observed during sustained eruptions, suggesting that the sulfur loading per kg of erupted magma exceeds both that of other recent eruptions in Iceland and perhaps also other historic basaltic eruptions globally. This raises key questions regarding the origin of these prodigious quantities of sulphur. A lack of understanding of the source of this sulfur, the conversion rates of SO2 gas into aerosol, the residence times of aerosol in the plume and the dependence of these on meteorological factors is limiting our confidence in the ability of atmospheric models to forecast gas and aerosol concentrations in the near- and far-field from Icelandic flood basalt eruptions. In 2015 our group is undertaking a project funded by UK NERC urgency scheme to investigate several aspects of the sulfur budget at Holuhraun using a novel and powerful approach involving simultaneous tracking of sulfur and chalcophile metals through the melt and the volcanic plume. By combining petrological analysis, in-plume sampling of gases and aerosol, and plume dispersion modelling, we will address two principal research objectives related to understanding the sulfur systematics of the eruption: (1) To examine the sulfur budget as recorded in the erupted rocks in the form of dissolved sulfur and sulfide minerals, which break down on eruption and (2) To investigate the SO2 lifetime in the atmosphere, by measurements in the both young and ageing eruption plume and plume dispersion modelling In addition we will analyse the characteristics of the aerosol mass necessary for health impact assessment. We will carry out two field campaigns, in January 2015 (short daylight) and, if the eruption is still ongoing, in April 2015 (long daylight). Here we present the first results of our project following the winter campaign.

Tephrochronology of the southernmost Andean Southern Volcanic Zone, Chile

NASA Astrophysics Data System (ADS)

Weller, D. J.; Miranda, C. G.; Moreno, P. I.; Villa-Martínez, R.; Stern, C. R.

2015-12-01

Correlations among and identification of the source volcanoes for over 60 Late Glacial and Holocene tephras preserved in eight lacustrine sediment cores taken from small lakes near Coyhaique, Chile (46° S), were made based on the stratigraphic position of the tephra in the cores, lithostratigraphic data (tephra layer thickness and grain size), and tephra petrochemistry (glass color and morphology, phenocryst phases, and bulk-tephra trace element contents determined by ICP-MS). The cores preserve a record of explosive eruptions, since ˜17,800 calibrated years before present (cal years BP), of the volcanoes of the southernmost Andean Southern Volcanic Zone (SSVZ). The suggested source volcanoes for 55 of these tephras include Hudson (32 events), Mentolat (10 events), and either Macá or Cay or some of the many minor monogenetic eruptive centers (MECs; 13 events) in the area. Only four of these eruptions had been previously identified in tephra outcrops in the region, indicating the value of lake cores for identifying smaller eruptions in tephrochronologic studies. The tephra records preserved in these lake cores, combined with those in marine cores, which extend these records back to 20,000 cal years BP, prior to the Last Glacial Maximum, suggest that no significant temporal change in the frequency of explosive eruptions was associated with deglaciation. Over this time period, Hudson volcano, one of the largest and longest lived volcanoes in the Southern Andes, has had >55 eruptions (four of them were very large) and has produced >45 km3 of pyroclastic material, making it also one of the most active volcanoes in the SVZ in terms of both frequency and volume of explosive eruptions.

Infrasound's capability to detect and characterise volcanic events, from local to regional scale.

NASA Astrophysics Data System (ADS)

Taisne, Benoit; Perttu, Anna

2017-04-01

Local infrasound and seismic networks have been successfully used for identification and quantification of explosions at single volcanoes. However the February, 2014 eruption of Kelud volcano, Indonesia, destroyed most of the local monitoring network. The use of remote seismic and infrasound sensors proved to be essential in the reconstruction of the eruptive sequence. The first recorded explosive event, with relatively weak seismic and infrasonic signature, was followed by a 2 hour sustained signal detected as far away as 11,000 km by infrasound sensors and up to 2,300 km away by seismometers. The volcanic intensity derived from these observations places the 2014 Kelud eruption between the intensity of the 1980 Mount St. Helens and the 1991 Pinatubo eruptions. The use of remote seismic stations and infrasound arrays in deriving valuable information about the onset, evolution, and intensity of volcanic eruptions is clear from the Kelud example. After this eruption the Singapore Infrasound Array became operational. This array, along with the other regional infrasound arrays which are part of the International Monitoring System, have recorded events from fireballs and regional volcanoes. The detection capability of this network for any specific volcanic event is not only dependent on the amplitude of the source, but also the propagation effects, noise level at each station, and characteristics of the regional persistent noise sources (like the microbarum). Combining the spatial and seasonal characteristics of this noise, within the same frequency band as significant eruptive events, with the probability of such events to occur, gives us a comprehensive understanding of detection capability for any of the 750 active or potentially active volcanoes in Southeast Asia.

Seismic and infrasonic source processes in volcanic fluid systems

NASA Astrophysics Data System (ADS)

Matoza, Robin S.

Volcanoes exhibit a spectacular diversity in fluid oscillation processes, which lead to distinct seismic and acoustic signals in the solid earth and atmosphere. Volcano seismic waveforms contain rich information on the geometry of fluid migration, resonance effects, and transient and sustained pressure oscillations resulting from unsteady flow through subsurface cracks, fissures and conduits. Volcanic sounds contain information on shallow fluid flow, resonance in near-surface cavities, and degassing dynamics into the atmosphere. Since volcanoes have large spatial scales, the vast majority of their radiated atmospheric acoustic energy is infrasonic (<20 Hz). This dissertation presents observations from joint broadband seismic and infrasound array deployments at Mount St. Helens (MSH, Washington State, USA), Tungurahua (Ecuador), and Kilauea Volcano (Hawaii, USA), each providing data for several years. These volcanoes represent a broad spectrum of eruption styles ranging from hawaiian to plinian in nature. The catalogue of recorded infrasonic signals includes continuous broadband and harmonic tremor from persistent degassing at basaltic lava vents and tubes at Pu'u O'o (Kilauea), thousands of repetitive impulsive signals associated with seismic longperiod (0.5-5 Hz) events and the dynamics of the shallow hydrothermal system at MSH, rockfall signals from the unstable dacite dome at MSH, energetic explosion blast waves and gliding infrasonic harmonic tremor at Tungurahua volcano, and large-amplitude and long-duration broadband signals associated with jetting during vulcanian, subplinian and plinian eruptions at MSH and Tungurahua. We develop models for a selection of these infrasonic signals. For infrasonic long-period (LP) events at MSH, we investigate seismic-acoustic coupling from various buried source configurations as a means to excite infrasound waves in the atmosphere. We find that linear elastic seismic-acoustic transmission from the ground to atmosphere is inadequate to explain the observations, and propose that the signals may result from sudden containment failure of a pressurized hydrothermal crack. For the broadband eruption tremor signals, we propose that the infrasonic signals represent a low-frequency form of jet noise, analogous to the noise from man-made jet engines, but operating with larger spatial scales and consequently longer time-scales. For the persistent hawaiian tremor signals, we propose that bubble cloud oscillation in the upper section of a roiling magma conduit and vortex dynamics in the shallow degassing region act as broadband and harmonic tremor sources. We also consider infrasound propagation effects in a dynamic atmosphere and discuss their effects on recorded signals. This dissertation demonstrates that combined seismic and infrasonic data provide complementary perspectives on eruptive activity.

Variable magma reservoir depths for Tongariro Volcanic Complex eruptive deposits from 10,000 years to present

NASA Astrophysics Data System (ADS)

Arpa, Maria Carmencita; Zellmer, Georg F.; Christenson, Bruce; Lube, Gert; Shellnutt, Gregory

2017-07-01

Mineral, groundmass and bulk rock chemical analyses of samples from the Tongariro Volcanic Complex were made to estimate depths of magma reservoirs for selected eruptive deposits. The sample set consists of two units from the 11,000 cal. years bp Mangamate Formation (Te Rato and Wharepu) and more recent deposits from near 1717 cal. years bp (Ngauruhoe and Red Crater) to 1975 (Ngauruhoe). The depths of crystallization were determined by established thermobarometers. Results show that the Mangamate eruptions of Te Rato and Wharepu originated from a deeper magma reservoir of about 28-35 km and likely ascended rapidly, whereas explosive eruption deposits from Ngauruhoe have depths of crystallization in the lower to mid-crust or about 7 to 22 km depth. A Red Crater lava flow had a possible magma reservoir depth from 4 to 9 km. The different eruptions sampled for this study tapped different reservoir levels, and the oldest and largest eruptions were sourced from the deepest reservoir.

Analysis of dynamics of vulcanian activity of Ubinas volcano, using multicomponent seismic antennas

NASA Astrophysics Data System (ADS)

Inza, L. A.; Métaxian, J. P.; Mars, J. I.; Bean, C. J.; O'Brien, G. S.; Macedo, O.; Zandomeneghi, D.

2014-01-01

A series of 16 vulcanian explosions occurred at Ubinas volcano between May 24 and June 14, 2009. The intervals between explosions were from 2.1 h to more than 6 days (mean interval, 33 h). Considering only the first nine explosions, the average time interval was 7.8 h. Most of the explosions occurred after a short time interval (< 8 h) and had low energy, which suggests that the refilling time was not sufficient for large accumulation of gas. A tremor episode followed 75% of the explosions, which coincided with pulses of ash emission. The durations of the tremors following the explosions were longer for the two highest energy explosions. To better understand the physical processes associated with these eruptive events, we localized the sources of explosions using two seismic antennas that were composed of three-component 10 and 12 sensors. We used the high-resolution MUSIC-3C algorithm to estimate the slowness vector for the first waves that composed the explosion signals recorded by the two antennas assuming propagation in a homogeneous medium. The initial part of the explosions was dominated by two frequencies, at 1.1 Hz and 1.5 Hz, for which we identified two separated sources located at 4810 m and 3890 m +/- 390 altitude, respectively. The position of these two sources was the same for the full 16 explosions. This implies the reproduction of similar mechanisms in the conduit. Based on the eruptive mechanisms proposed for other volcanoes of the same type, we interpret the position of these two sources as the limits of the conduit portion that was involved in the fragmentation process. Seismic data and ground deformation recorded simultaneously less than 2 km from the crater showed a decompression movement 2 s prior to each explosion. This movement can be interpreted as gas leakage at the level of the cap before its destruction. The pressure drop generated in the conduit could be the cause of the fragmentation process that propagated deeper. Based on these observations, we interpret the position of the highest source as the part of the conduit under the cap, and the deeper source as the limit of the fragmentation zone.

Hydrogeomorphic effects of explosive volcanic eruptions on drainage basins

USGS Publications Warehouse

Pierson, Thomas C.; Major, Jon J.

2014-01-01

Explosive eruptions can severely disturb landscapes downwind or downstream of volcanoes by damaging vegetation and depositing large volumes of erodible fragmental material. As a result, fluxes of water and sediment in affected drainage basins can increase dramatically. System-disturbing processes associated with explosive eruptions include tephra fall, pyroclastic density currents, debris avalanches, and lahars—processes that have greater impacts on water and sediment discharges than lava-flow emplacement. Geo-morphic responses to such disturbances can extend far downstream, persist for decades, and be hazardous. The severity of disturbances to a drainage basin is a function of the specific volcanic process acting, as well as distance from the volcano and magnitude of the eruption. Postdisturbance unit-area sediment yields are among the world's highest; such yields commonly result in abundant redeposition of sand and gravel in distal river reaches, which causes severe channel aggradation and instability. Response to volcanic disturbance can result in socioeconomic consequences more damaging than the direct impacts of the eruption itself.

Decadal to monthly timescales of magma transfer and reservoir growth at a caldera volcano.

PubMed

Druitt, T H; Costa, F; Deloule, E; Dungan, M; Scaillet, B

2012-02-01

Caldera-forming volcanic eruptions are low-frequency, high-impact events capable of discharging tens to thousands of cubic kilometres of magma explosively on timescales of hours to days, with devastating effects on local and global scales. Because no such eruption has been monitored during its long build-up phase, the precursor phenomena are not well understood. Geophysical signals obtained during recent episodes of unrest at calderas such as Yellowstone, USA, and Campi Flegrei, Italy, are difficult to interpret, and the conditions necessary for large eruptions are poorly constrained. Here we present a study of pre-eruptive magmatic processes and their timescales using chemically zoned crystals from the 'Minoan' caldera-forming eruption of Santorini volcano, Greece, which occurred in the late 1600s BC. The results provide insights into how rapidly large silicic systems may pass from a quiescent state to one on the edge of eruption. Despite the large volume of erupted magma (40-60 cubic kilometres), and the 18,000-year gestation period between the Minoan eruption and the previous major eruption, most crystals in the Minoan magma record processes that occurred less than about 100 years before the eruption. Recharge of the magma reservoir by large volumes of silicic magma (and some mafic magma) occurred during the century before eruption, and mixing between different silicic magma batches was still taking place during the final months. Final assembly of large silicic magma reservoirs may occur on timescales that are geologically very short by comparison with the preceding repose period, with major growth phases immediately before eruption. These observations have implications for the monitoring of long-dormant, but potentially active, caldera systems.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orange, N. Brice; Chesny, David L.; Oluseyi, Hakeem M.

Increasing evidence for coronal heating contributions from cooler solar atmospheric layers, notably quiet Sun (QS) conditions, challenges standard solar atmospheric descriptions of bright transition region (TR) emission. As such, questions about the role of dynamic QS transients in contributing to the total coronal energy budget are raised. Using observations from the Atmospheric Imaging Assembly and Heliosemic Magnetic Imager on board the Solar Dynamics Observatory, and numerical model extrapolations of coronal magnetic fields, we investigate a dynamic QS transient that is energetically isolated to the TR and extrudes from a common footpoint shared with two heated loop arcades. A non-causal relationshipmore » is established between episodic heating of the QS transient and widespread magnetic field re-organization events, while evidence is found favoring a magnetic topology that is typical of eruptive processes. Quasi-steady interchange reconnection events are implicated as a source of the transient’s visibly bright radiative signature. We consider the QS transient’s temporally stable (≈35 minutes) radiative nature to occur as a result of the large-scale magnetic field geometries of the QS and/or relatively quiet nature of the magnetic photosphere, which possibly act to inhibit energetic build-up processes that are required to initiate a catastrophic eruption phase. This work provides insight into the QS’s thermodynamic and magnetic relation to eruptive processes that quasi-steadily heat a small-scale dynamic and TR transient. This work explores arguments of non-negligible coronal heating contributions from cool atmospheric layers in QS conditions and contributes evidence to the notion that  solar wind mass feeds off of dynamic transients therein.« less

Volcano seismology

USGS Publications Warehouse

Chouet, B.

2003-01-01

A fundamental goal of volcano seismology is to understand active magmatic systems, to characterize the configuration of such systems, and to determine the extent and evolution of source regions of magmatic energy. Such understanding is critical to our assessment of eruptive behavior and its hazardous impacts. With the emergence of portable broadband seismic instrumentation, availability of digital networks with wide dynamic range, and development of new powerful analysis techniques, rapid progress is being made toward a synthesis of high-quality seismic data to develop a coherent model of eruption mechanics. Examples of recent advances are: (1) high-resolution tomography to image subsurface volcanic structures at scales of a few hundred meters; (2) use of small-aperture seismic antennas to map the spatio-temporal properties of long-period (LP) seismicity; (3) moment tensor inversions of very-long-period (VLP) data to derive the source geometry and mass-transport budget of magmatic fluids; (4) spectral analyses of LP events to determine the acoustic properties of magmatic and associated hydrothermal fluids; and (5) experimental modeling of the source dynamics of volcanic tremor. These promising advances provide new insights into the mechanical properties of volcanic fluids and subvolcanic mass-transport dynamics. As new seismic methods refine our understanding of seismic sources, and geochemical methods better constrain mass balance and magma behavior, we face new challenges in elucidating the physico-chemical processes that cause volcanic unrest and its seismic and gas-discharge manifestations. Much work remains to be done toward a synthesis of seismological, geochemical, and petrological observations into an integrated model of volcanic behavior. Future important goals must include: (1) interpreting the key types of magma movement, degassing and boiling events that produce characteristic seismic phenomena; (2) characterizing multiphase fluids in subvolcanic regimes and determining their physical and chemical properties; and (3) quantitatively understanding multiphase fluid flow behavior under dynamic volcanic conditions. To realize these goals, not only must we learn how to translate seismic observations into quantitative information about fluid dynamics, but we also must determine the underlying physics that governs vesiculation, fragmentation, and the collapse of bubble-rich suspensions to form separate melt and vapor. Refined understanding of such processes-essential for quantitative short-term eruption forecasts-will require multidisciplinary research involving detailed field measurements, laboratory experiments, and numerical modeling.

Geochemical and petrological indicators of volcanic behavior: Merapi volcano, Java, Indonesia

NASA Astrophysics Data System (ADS)

Troll, V. R.; Deegan, F. M.; Jolis, E. M.; Chadwick, J.; Blythe, L. S.; Freda, C.; Hilton, D. R.; Schwarzkopf, L. M.; Gertisser, R.; Zimmer, M.

2011-12-01

Gunung Merapi, one of Indonesia's most active volcanoes, is characterized by long periods of dome growth and intermittent explosive pyroclastic events. Merapi currently degasses continuously through high-T fumaroles (>200°C), and erupts crystal-rich basaltic-andesite that contains a large range of igneous and calc-silicate crustal inclusions. To evaluate mechanisms that trigger explosive eruptions, we sampled lavas, inclusions (xenoliths), and gas from active fumaroles. Additionally, we established a time-integrated experiment reaction series mimicking crustal assimilation at Merapi under magmatic conditions. Merapi lava contains abundant plagioclase crystals which show complex zoning and vary in anorthite (An) content between 40 and 95 mol% across resorption surfaces. A negative correlation between An mol% and other indicators of magmatic fractionation, such as MgO and FeO, has been observed. Moreover, Sr isotope analyses of discrete zones in plagioclase yields 87Sr/86Sr values that notably exceed those of the host lavas. Zones with the highest An content also tend to show the highest radiogenic Sr values, consistent with a Ca-rich, high-87Sr/86Sr crustal contaminant. Abundant metamorphosed limestone xenoliths contain compositionally identical feldspar to the high-An population in the lavas, demonstrating that magma-crust interaction is a significant process at Merapi. Carbon isotope ratios of fumarole CO2 sampled during quiescent degassing periods form a baseline of δ13C2001-2008 = -4.1%. The notable exceptions are the 2006 values, obtained immediately after the eruption and the 6.4 magnitude Yogyakarta earthquake, which show elevated δ13C values up to -2.4%. Notably, the rise in δ13C values coincided with an increase in eruptive intensity and volcano seismicity by a factor of 3 to 5 for several weeks after the earthquake. This is consistent with addition of a late-stage, crustal volatile component added to purely mantle and slab-derived volatile sources. This observation argues for extensive and ongoing magma-crust interaction beneath the volcano, especially during eruptive and/or seismic events. Our high P-T experiments show that interaction between Merapi magma and limestone can rapidly liberate crustal CO2 on a timescale of only seconds to minutes. We therefore expect vigorous CO2 bubble nucleation and growth on a scale of perhaps hours to days in nature. Late volatile input could therefore accelerate or trigger explosive eruptions independently of magmatic recharge and fractionation by sudden over-pressurization of the upper parts of the magma system. Such an event would provide shallow seismic warning signals immediately prior to an erratic, CO2-driven, eruption crisis. Thus we conclude that crust-mantle interaction processes have serious implications for eruptive behavior, volatile emission, and hazard management at Merapi and similar systems elsewhere.

Sources of ground movement at Vesuvius before the AD 79 eruption: Evidence from contemporary accounts and archaeological studies

NASA Astrophysics Data System (ADS)

Marturano, Aldo

2008-11-01

Historical sources have recorded earthquake shocks, their effects and difficulties that local inhabitants experienced before the AD 79 Pompeii eruption. Archaeological studies pointed out the effects of such seismicity, and have also evidenced that several water crises were occurring at Pompeii in that period. Indeed numerous sources show that, at the time of eruption, and probably some time before, the civic aqueduct, having ceased to be supplied by the regional one, was out of order and that a new one was being built. Since Roman aqueducts were usually built with a recommended minimum mean slope of 20 cm/km and Pompeii's aqueduct sloped from the nearby Apennines toward the town, this slope could have been easily cancelled by uplift that occurred in the area even if this was only moderate. For the crustal deformations a volcanic origin is proposed and a point source model is used to explain the observations. Simple analysis of the available data suggests that the ground deformations were caused by a < 2 km 3 volumetric change at a depth of ˜ 8 km that happened over the course of several decades.

Chronology, morphology and stratigraphy of pumiceous pyroclastic-flow (ignimbrite) deposits from the eruption of Mount St. Helens on 18 May 1983

NASA Technical Reports Server (NTRS)

Criswell, C. W.; Elston, W. E.

1984-01-01

Between 1217 and 1620 hours (PDT), on May 18, 1980, the magmatic eruption column of Mount St. Helens formed an ash fountain and pyroclastic flows dominated the eruption process over tephra ejection. Eurption-rate pulsations generally increased to a maximum at 1600 to 1700 hrs. After 1620 hrs, the eruption assumed an open-vent discharge with strong, vertical ejection of tephra. Relative eruption rates (relative mass flux rates) of the pyroclastic flows were determined by correlating sequential photographs and SLAR images, obtained during the eruption, with stratigraphy and surface morphology of the deposits.

Large, Moderate or Small? The Challenge of Measuring Mass Eruption Rates in Volcanic Eruptions

NASA Astrophysics Data System (ADS)

Gudmundsson, M. T.; Dürig, T.; Hognadottir, T.; Hoskuldsson, A.; Bjornsson, H.; Barsotti, S.; Petersen, G. N.; Thordarson, T.; Pedersen, G. B.; Riishuus, M. S.

2015-12-01

The potential impact of a volcanic eruption is highly dependent on its eruption rate. In explosive eruptions ash may pose an aviation hazard that can extend several thousand kilometers away from the volcano. Models of ash dispersion depend on estimates of the volcanic source, but such estimates are prone to high error margins. Recent explosive eruptions, including the 2010 eruption of Eyjafjallajökull in Iceland, have provided a wealth of data that can help in narrowing these error margins. Within the EU-funded FUTUREVOLC project, a multi-parameter system is currently under development, based on an array of ground and satellite-based sensors and models to estimate mass eruption rates in explosive eruptions in near-real time. Effusive eruptions are usually considered less of a hazard as lava flows travel slower than eruption clouds and affect smaller areas. However, major effusive eruptions can release large amounts of SO2 into the atmosphere, causing regional pollution. In very large effusive eruptions, hemispheric cooling and continent-scale pollution can occur, as happened in the Laki eruption in 1783 AD. The Bárdarbunga-Holuhraun eruption in 2014-15 was the largest effusive event in Iceland since Laki and at times caused high concentrations of SO2. As a result civil protection authorities had to issue warnings to the public. Harmful gas concentrations repeatedly persisted for many hours at a time in towns and villages at distances out to 100-150 km from the vents. As gas fluxes scale with lava fluxes, monitoring of eruption rates is therefore of major importance to constrain not only lava but also volcanic gas emissions. This requires repeated measurements of lava area and thickness. However, most mapping methods are problematic once lava flows become very large. Satellite data on thermal emissions from eruptions have been used with success to estimate eruption rate. SAR satellite data holds potential in delivering lava volume and eruption rate estimates, although availability and repeat times of radar platforms is still low compared to e.g. the thermal satellites. In the 2014-15 eruption, lava volume was estimated repeatedly from an aircraft-based system that combines radar altimeter with an on-board DGPS, yielding a several estimates of lava volume and time-averaged mass eruption rate.

Analysis of surface deformation during the eruptive process of El Hierro Island (Canary Islands, Spain): Detection, Evolution and Forecasting.

NASA Astrophysics Data System (ADS)

Berrocoso, M.; Fernandez-Ros, A.; Prates, G.; Martin, M.; Hurtado, R.; Pereda, J.; Garcia, M. J.; Garcia-Cañada, L.; Ortiz, R.; Garcia, A.

2012-04-01

The surface deformation has been an essential parameter for the onset and evolution of the eruptive process of the island of El Hierro (October 2011) as well as for forecasting changes in seismic and volcanic activity during the crisis period. From GNSS-GPS observations the reactivation is early detected by analizing the change in the deformation of the El Hierro Island regional geodynamics. It is found that the surface deformation changes are detected before the occurrence of seismic activity using the station FRON (GRAFCAN). The evolution of the process has been studied by the analysis of time series of topocentric coordinates and the variation of the distance between stations on the island of El Hierro (GRAFCAN station;IGN network; and UCA-CSIC points) and LPAL-IGS station on the island of La Palma. In this work the main methodologies and their results are shown: •The location (and its changes) of the litospheric pressure source obtained by applying the Mogi model. •Kalman filtering technique for high frequency time series, used to make the forecasts issued for volcanic emergency management. •Correlations between deformation of the different GPS stations and their relationship with seismovolcanic settings.

Syneruptive deep magma transfer and shallow magma remobilization during the 2011 eruption of Shinmoe-dake, Japan—Constraints from melt inclusions and phase equilibria experiments

NASA Astrophysics Data System (ADS)

Suzuki, Yuki; Yasuda, Atsushi; Hokanishi, Natsumi; Kaneko, Takayuki; Nakada, Setsuya; Fujii, Toshitsugu

2013-05-01

The 2011 Shinmoe-dake eruption started with a phreatomagmatic eruption (Jan 19), followed by climax sub-Plinian events and subsequent explosions (Jan 26-28), lava accumulation in the crater (end of January), and vulcanian eruptions (February-April). We have studied a suite of ejecta to investigate the magmatic system beneath the volcano and remobilization processes in the silicic magma mush. Most of the ejecta, including brown and gray colored pumice clasts (Jan 26-28), ballistically ejected dense lava (Feb 1), and juvenile particles in ash from the phreatomagmatic and vulcanian events are magma mixing products (SiO2 = 57-58 wt.%; 960-980 °C). Mixing occurred between silicic andesite (SA) and basaltic andesite (BA) magmas at a fixed ratio (40%-30% SA and 60%-70% BA). The SA magma had SiO2 = 62-63 wt.% and a temperature of 870 °C, and contains 43 vol.% phenocrysts of pyroxene, plagioclase, and Fe-Ti oxide. The BA magma had SiO2 = 55 wt.% and a temperature of 1030 °C, and contains 9 vol.% phenocrysts of olivine and plagioclase. The SA magma partly erupted without mixing as white parts of pumices and juvenile particles. The two magmatic end-members crystallized at different depths, requiring the presence of two separate magma reservoirs; shallower SA reservoir and deeper BA reservoir. An experimental study reveals that the SA magma had been stored at a pressure of 125 MPa, corresponding to a depth of 5 km. The textures and forms of phenocrysts from the BA magma indicate rapid crystallization directly related to the 2011 eruptive activity. The wide range of H2O contents of olivine melt inclusions (5.5-1.6 wt.%) indicates that rapid crystallization was induced by decompression, with olivine crystallization first (≤ 250 MPa), followed by plagioclase addition. The limited occurrence of olivine melt inclusions trapped at depths of < 5 km is consistent with the proposed magma system model, because olivine crystallization ceased after magma mixing. Our petrological model is consistent with a geophysical model that explains whole crustal deformation as being due to a single source located 7-8 km northwest of the Shinmoe-dake summit. However, even the shallowest estimated source of this deformation (7.5-6.2 km) is deeper than the SA reservoir, which thus requires a contribution of deeper BA magmas to the observed deformation. Remobilization of mush-like SA magma occurred in two stages before the early sub-Plinian event. Firstly, precursor mixing with BA magma and associated heating occurred (925-871 °C; stage-1 of ≥ 350 h), followed by final mixing with BA magma (stage-2). MgO profiles of magnetite phenocrysts define timescales of 0.7-15.2 h from this final mixing to eruption. The mixed and heated magmas, and stagnant mush that existed in the SA reservoir in the precursor stage, were finally erupted together. Magnetite phenocrysts in the Feb 18 ash reveal the occurrence of continuous erosion of the stagnant mush during the course of the 2011 eruptive activity.

Interferometric synthetic aperture radar study of Okmok volcano, Alaska, 1992-2003: Magma supply dynamics and postemplacement lava flow deformation

USGS Publications Warehouse

Lu, Z.; Masterlark, Timothy; Dzurisin, Daniel

2005-01-01

Okmok volcano, located in the central Aleutian arc, Alaska, is a dominantly basaltic complex topped with a 10-km-wide caldera that formed circa 2.05 ka. Okmok erupted several times during the 20th century, most recently in 1997; eruptions in 1945, 1958, and 1997 produced lava flows within the caldera. We used 80 interferometric synthetic aperture radar (InSAR) images (interferograms) to study transient deformation of the volcano before, during, and after the 1997 eruption. Point source models suggest that a magma reservoir at a depth of 3.2 km below sea level, located beneath the center of the caldera and about 5 km northeast of the 1997 vent, is responsible for observed volcano-wide deformation. The preeruption uplift rate decreased from about 10 cm yr−1 during 1992–1993 to 2 ∼ 3 cm yr−1 during 1993–1995 and then to about −1 ∼ −2 cm yr−1 during 1995–1996. The posteruption inflation rate generally decreased with time during 1997–2001, but increased significantly during 2001–2003. By the summer of 2003, 30 ∼ 60% of the magma volume lost from the reservoir in the 1997 eruption had been replenished. Interferograms for periods before the 1997 eruption indicate consistent subsidence of the surface of the 1958 lava flows, most likely due to thermal contraction. Interferograms for periods after the eruption suggest at least four distinct deformation processes: (1) volcano-wide inflation due to replenishment of the shallow magma reservoir, (2) subsidence of the 1997 lava flows, most likely due to thermal contraction, (3) deformation of the 1958 lava flows due to loading by the 1997 flows, and (4) continuing subsidence of 1958 lava flows buried beneath 1997 flows. Our results provide insights into the postemplacement behavior of lava flows and have cautionary implications for the interpretation of inflation patterns at active volcanoes.

Geomorphic Consequences of Volcanic Eruptions in Alaska: A Review

USGS Publications Warehouse

Waythomas, Christopher F.

2015-01-01

Eruptions of Alaska volcanoes have significant and sometimes profound geomorphic consequences on surrounding landscapes and ecosystems. The effects of eruptions on the landscape can range from complete burial of surface vegetation and preexisting topography to subtle, short-term perturbations of geomorphic and ecological systems. In some cases, an eruption will allow for new landscapes to form in response to the accumulation and erosion of recently deposited volcaniclastic material. In other cases, the geomorphic response to a major eruptive event may set in motion a series of landscape changes that could take centuries to millennia to be realized. The effects of volcanic eruptions on the landscape and how these effects influence surface processes has not been a specific focus of most studies concerned with the physical volcanology of Alaska volcanoes. Thus, what is needed is a review of eruptive activity in Alaska in the context of how this activity influences the geomorphology of affected areas. To illustrate the relationship between geomorphology and volcanic activity in Alaska, several eruptions and their geomorphic impacts will be reviewed. These eruptions include the 1912 Novarupta–Katmai eruption, the 1989–1990 and 2009 eruptions of Redoubt volcano, the 2008 eruption of Kasatochi volcano, and the recent historical eruptions of Pavlof volcano. The geomorphic consequences of eruptive activity associated with these eruptions are described, and where possible, information about surface processes, rates of landscape change, and the temporal and spatial scale of impacts are discussed.A common feature of volcanoes in Alaska is their extensive cover of glacier ice, seasonal snow, or both. As a result, the generation of meltwater and a variety of sediment–water mass flows, including debris-flow lahars, hyperconcentrated-flow lahars, and sediment-laden water floods, are typical outcomes of most types of eruptive activity. Occasionally, such flows can be quite large, with flow volumes in the range of 107–109 m3. A review of the lahars generated during the 2009 eruption of Redoubt volcano will illustrate the geomorphic impacts of lahars on stream channels and riparian habitat. Although much work is needed to develop a comprehensive understanding of the geomorphic consequences of volcanic activity in Alaska, this review provides a synthesis of some of the best-studied eruptions and perhaps will serve as a starting point for future work on this topic.

Geomorphic consequences of volcanic eruptions in Alaska: A review

USGS Publications Warehouse

Waythomas, Christopher F.

2015-01-01

Eruptions of Alaska volcanoes have significant and sometimes profound geomorphic consequences on surrounding landscapes and ecosystems. The effects of eruptions on the landscape can range from complete burial of surface vegetation and preexisting topography to subtle, short-term perturbations of geomorphic and ecological systems. In some cases, an eruption will allow for new landscapes to form in response to the accumulation and erosion of recently deposited volcaniclastic material. In other cases, the geomorphic response to a major eruptive event may set in motion a series of landscape changes that could take centuries to millennia to be realized. The effects of volcanic eruptions on the landscape and how these effects influence surface processes has not been a specific focus of most studies concerned with the physical volcanology of Alaska volcanoes. Thus, what is needed is a review of eruptive activity in Alaska in the context of how this activity influences the geomorphology of affected areas. To illustrate the relationship between geomorphology and volcanic activity in Alaska, several eruptions and their geomorphic impacts will be reviewed. These eruptions include the 1912 Novarupta–Katmai eruption, the 1989–1990 and 2009 eruptions of Redoubt volcano, the 2008 eruption of Kasatochi volcano, and the recent historical eruptions of Pavlof volcano. The geomorphic consequences of eruptive activity associated with these eruptions are described, and where possible, information about surface processes, rates of landscape change, and the temporal and spatial scale of impacts are discussed.A common feature of volcanoes in Alaska is their extensive cover of glacier ice, seasonal snow, or both. As a result, the generation of meltwater and a variety of sediment–water mass flows, including debris-flow lahars, hyperconcentrated-flow lahars, and sediment-laden water floods, are typical outcomes of most types of eruptive activity. Occasionally, such flows can be quite large, with flow volumes in the range of 107–109 m3. A review of the lahars generated during the 2009 eruption of Redoubt volcano will illustrate the geomorphic impacts of lahars on stream channels and riparian habitat. Although much work is needed to develop a comprehensive understanding of the geomorphic consequences of volcanic activity in Alaska, this review provides a synthesis of some of the best-studied eruptions and perhaps will serve as a starting point for future work on this topic.

USGS GNSS Applications to Volcano Disaster Response and Hazard Mitigation

NASA Astrophysics Data System (ADS)

Lisowski, M.; McCaffrey, R.

2015-12-01

Volcanic unrest is often identified by increased rates of seismicity, deformation, or the release of volcanic gases. Deformation results when ascending magma accumulates in crustal reservoirs, creates new pathways to the surface, or drains from magma reservoirs to feed an eruption. This volcanic deformation is overprinted by deformation from tectonic processes. GNSS monitoring of volcanoes captures transient volcanic deformation and steady and transient tectonic deformation, and we use the TDEFNODE software to unravel these effects. We apply the technique on portions of the Cascades Volcanic arc in central Oregon and in southern Washington that include a deforming volcano. In central Oregon, the regional TDEFNODE model consists of several blocks that rotate and deform internally and a decaying inflationary volcanic pressure source to reproduce the crustal bulge centered ~5 km west of South Sister. We jointly invert 47 interferograms that cover the interval from 1992 to 2010, as well as 2001 to 2015 continuous GNSS (cGNSS) and survey-mode (sGNSS) time series from stations in and around the Three Sisters, Newberry, and Crater Lake areas. A single, smoothly-decaying ~5 km deep spherical or prolate spheroid volcanic pressure source activated around 1998 provides the best fit to the combined geodetic data. In southern Washington, GNSS displacement time-series track decaying deflation of a ~8 km deep magma reservoir that fed the 2004 to 2008 eruption of Mount St. Helens. That deformation reversed when it began to recharge after the eruption ended. Offsets from slow slip events on the Cascadia subduction zone punctuate the GNSS displacement time series, and we remove them by estimating source parameters for these events. This regional TDEFNODE model extends from Mount Rainier south to Mount Hood, and additional volcanic sources could be added if these volcanoes start deforming. Other TDEFNODE regional models are planned for northern Washington (Mount Baker and Glacier Peak), northern California (Mount Shasta, Medicine Lake, Lassen Peak), and Long Valley. These models take advantage of the data from dense GNSS networks, they provide source parameters for volcanic and tectonic transients, and can be used to discriminate possible short- and long-term volcano- tectonic interactions.

SOLAR ERUPTION AND LOCAL MAGNETIC PARAMETERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jeongwoo; Chae, Jongchul; Liu, Chang

It is now a common practice to use local magnetic parameters such as magnetic decay index for explaining solar eruptions from active regions, but there can be an alternative view that the global properties of the source region should be counted as a more important factor. We discuss this issue based on Solar Dynamics Observatory observations of the three successive eruptions within 1.5 hr from the NOAA active region 11444 and the magnetic parameters calculated using the nonlinear force-free field model. Two violent eruptions occurred in the regions with relatively high magnetic twist number (0.5–1.5) and high decay index (0.9–1.1)more » at the nominal height of the filament (12″) and otherwise a mild eruption occurred, which supports the local-parameter paradigm. Our main point is that the time sequence of the eruptions did not go with these parameters. It is argued that an additional factor, in the form of stabilizing force, should operate to determine the onset of the first eruption and temporal behaviors of subsequent eruptions. As supporting evidence, we report that the heating and fast plasma flow continuing for a timescale of an hour was the direct cause for the first eruption and that the unidirectional propagation of the disturbance determined the timing of subsequent eruptions. Both of these factors are associated with the overall magnetic structure rather than local magnetic properties of the active region.« less

Low-frequency seismic events in a wider volcanological context

NASA Astrophysics Data System (ADS)

Neuberg, J. W.; Collombet, M.

2006-12-01

Low-frequency seismic events have been in the centre of attention for several years, particularly on volcanoes with highly viscous magmas. The ultimate aim is to detect changes in volcanic activity by identifying changes in the seismic behaviour in order to forecast an eruption, or in case of an ongoing eruption, forecast the short and longterm behaviour of the volcanic system. A major boost in recent years arose through several attempts of multi-parameter volcanic monitoring and modelling programs, which allowed multi-disciplinary groups of volcanologists to interpret seismic signals together with, e.g. ground deformation, stress field analysis and petrological information. This talk will give several examples of such multi-disciplinary projects, focussing on the joint modelling of seismic source processes for low-frequency events together with advanced magma flow models, and the signs of magma movement in the deformation and stress field at the surface.

Ultrafast syn-eruptive degassing and ascent trigger high-energy basic eruptions.

PubMed

Giuffrida, Marisa; Viccaro, Marco; Ottolini, Luisa

2018-01-09

Lithium gradients in plagioclase are capable of recording extremely short-lived processes associated with gas loss from magmas prior to extrusion at the surface. We present SIMS profiles of the 7 Li/ 30 Si ion ratio in plagioclase crystals from products of the paroxysmal sequence that occurred in the period 2011-2013 at Mt. Etna (Italy) in an attempt to constrain the final ascent and degassing processes leading to these powerful eruptions involving basic magma. The observed Li concentrations reflect cycles of Li addition to the melt through gas flushing, and a syn-eruptive stage of magma degassing driven by decompression that finally produce significant Li depletion from the melt. Modeling the decreases in Li concentration in plagioclase by diffusion allowed determination of magma ascent timescales that are on the order of minutes or less. Knowledge of the storage depth beneath the volcano has led to the quantification of a mean magma ascent velocity of ~43 m/s for paroxysmal eruptions at Etna. The importance of these results relies on the application of methods, recently used exclusively for closed-system volcanoes producing violent eruptions, to open-conduit systems that have generally quiet eruptive periods of activity sometimes interrupted by sudden re-awakening and the production of anomalously energetic eruptions.

Himawari-8 infrared observations of the June-August 2015 Mt Raung eruption, Indonesia

NASA Astrophysics Data System (ADS)

Kaneko, Takayuki; Takasaki, Kenji; Maeno, Fukashi; Wooster, Martin J.; Yasuda, Atsushi

2018-05-01

Volcanic activity involves processes that can change over short periods of time, which are sometimes closely related to the eruptive mode or the timing of its transitions. Eruptions bring high-temperature magma or gas to the surface; thermal observations of these eruptions can be used to determine the timeline of eruptive sequences or eruptive processes. In 2014, a new-generation meteorological satellite, Himawari-8, which carried a new sensor, the Advanced Himawari Imager (AHI), was launched. The AHI makes high-frequency infrared observations at a spatial resolution of 2 km during 10-min observation cycles. We analyzed an effusive eruption that occurred in 2015 at Mt Raung in Indonesia using these AHI images, which was the first attempt applying them to volcanological study. Based on the detailed analysis of the time-series variations in its thermal anomalies, this eruptive sequence was segmented into a Precursory Stage, Pulse 1, Pulse 2 and a Terminal Stage. Pulses 1 and 2 are effusive stages that exhibited a consecutive two-pulse pattern in their variations, reflecting changes in the lava effusion rate; the other stages are non-effusive. We were also able to determine the exact times of the onset and reactivation of lava flow effusion, as well as the precursory signals that preceded these events.

Post-eruptive sediment transport and surface processes on unvegetated volcanic hillslopes - A case study of Black Tank scoria cone, Cima Volcanic Field, California

NASA Astrophysics Data System (ADS)

Kereszturi, Gábor; Németh, Károly

2016-08-01

Conical volcanic edifices that are made up from lapilli to block/bomb pyroclastic successions, such as scoria cones, are widespread in terrestrial and extraterrestrial settings. Eruptive processes responsible for establishing the final facies architecture of a scoria cone are not well linked to numerical simulations of their post-eruptive sediment transport. Using sedimentological, geomorphic and 2D fragment morphology data from a 15-ky-old scoria cone from the Cima Volcanic Field, California, this study provides field evidence of the various post-eruptive sediment transport and degradation processes of scoria cones located in arid to semi-arid environments. This study has revealed that pyroclast morphologies vary downslope due to syn-eruptive granular flows, along with post-eruptive modification by rolling, bouncing and sliding of individual particles down a slope, and overland flow processes. The variability of sediment transport rates on hillslopes are not directly controlled by local slope angle variability and the flank length but rather by grain size, and morphological characteristics of particles, such as shape irregularity of pyroclast fragments and block/lapilli ratio. Due to the abundance of hillslopes degrading in unvegetated regions, such as those found in the Southwestern USA, granulometric influences should be accounted for in the formulation of sediment transport laws for geomorphic modification of volcanic terrains over long geologic time.

Cassini finds molecular hydrogen in the Enceladus plume: Evidence for hydrothermal processes

NASA Astrophysics Data System (ADS)

Waite, J. Hunter; Glein, Christopher R.; Perryman, Rebecca S.; Teolis, Ben D.; Magee, Brian A.; Miller, Greg; Grimes, Jacob; Perry, Mark E.; Miller, Kelly E.; Bouquet, Alexis; Lunine, Jonathan I.; Brockwell, Tim; Bolton, Scott J.

2017-04-01

Saturn’s moon Enceladus has an ice-covered ocean; a plume of material erupts from cracks in the ice. The plume contains chemical signatures of water-rock interaction between the ocean and a rocky core. We used the Ion Neutral Mass Spectrometer onboard the Cassini spacecraft to detect molecular hydrogen in the plume. By using the instrument’s open-source mode, background processes of hydrogen production in the instrument were minimized and quantified, enabling the identification of a statistically significant signal of hydrogen native to Enceladus. We find that the most plausible source of this hydrogen is ongoing hydrothermal reactions of rock containing reduced minerals and organic materials. The relatively high hydrogen abundance in the plume signals thermodynamic disequilibrium that favors the formation of methane from CO2 in Enceladus’ ocean.

Volcano infrasonic signals and magma degassing: First-order experimental insights and application to Stromboli

NASA Astrophysics Data System (ADS)

Lane, Stephen J.; James, Mike R.; Corder, Steven B.

2013-09-01

We demonstrate the rise and expansion of a gas slug as a fluid dynamic source mechanism for infrasonic signals generated by gas puffing and impulsive explosions at Stromboli. The fluid dynamics behind the rise, expansion and burst of gas slugs in the confines of an experimental tube can be characterised into different regimes. Passive expansion occurs for small gas masses, where negligible dynamic gas over-pressure develops during bubble ascent and, prior to burst, meniscus oscillation forms an important infrasonic source. With increasing gas mass, a transition regime emerges where dynamic gas over-pressure is significant. For larger gas masses, this regime transforms to fully explosive behaviour, where gas over-pressure dominates as an infrasonic source and bubble bursting is not a critical factor. The rate of change of excess pressure in the experimental tube was used to generate synthetic infrasonic waveforms. Qualitatively, the waveforms compare well to infrasonic waveforms measured from a range of eruptions at Stromboli. Assuming pressure continuity during flow through the vent, and applying dimensionless arguments from the first-order experiments, allows estimation of eruption metrics from infrasonic signals measured at Stromboli. Values of bubble length, gas mass and over-pressure calculated from infrasonic signals are in excellent agreement with those derived by independent means for eruptions at Stromboli, therefore providing a method of estimating eruption metrics from infrasonic measurement.

Hazard Assessment for POPOCATÉPETL Volcano Using Hasset: a Probability Event Tree Tool to Evaluate Future Eruptive Scenarios

NASA Astrophysics Data System (ADS)

Ferrés, D.; Reyes Pimentel, T. A.; Espinasa-Pereña, R.; Nieto, A.; Sobradelo, R.; Flores, X.; González Huesca, A. E.; Ramirez, A.

2013-05-01

Popocatépetl volcano is one of the most active in Latin America. During its last cycle of activity, beginning at the end of 1994, more than 40 episodes of dome construction and destruction have occurred inside the summit crater. Most of these episodes finished with eruptions of VEI 1-2. Eruptions of higher intensity were also registered in 1997, 2001 and 2009, of VEI≥3, which produced eruptive columns up to 8 km high and abundant and frequent ash falls on the villages at the eastern sector of the volcano. The January 22nd 2001 eruption also produced pyroclastic flows that followed several streams on the volcanic cone, reaching 4 to 6 km, and transforming to mudflows with ranges up to 15 km. The capital, Mexico City, is within the radius of 80 km from Popocatépetl volcano and can be affected by ash fall during the first months of the rainy season (May to July). Other important cities, such as Puebla and Atlixco, are located 15 to 30 km from the crater. Several villages of the states of México, Puebla and Morelos, which have a total population of 40,000 people, are inside the radius of 12 to 15 km, where the impacts of any of the products of an eruption, including pyroclastic flows, are possible. This high exposure of people and infrastructure around Popocatépetl volcano emphasizes the need of tools for early warning and the development of preventive actions to protect the population from volcanic phenomena. The diagnosis of the volcanic activity, based on the information provided by the monitoring systems, and the prognosis of the evolution of the volcano in the short-term is made by the Scientific Advisory Committee, formed by volcanologists of the National Autonomous University of Mexico, and by CENAPRED staff. From this prognosis, the alert level for the people is determined and it is spread by the code of the traffic light of volcanic alert. A volcanic event tree was constructed with the advisory of the scientific committee in the recent seismic-eruptive crisis of April-May 2012, in order to identify the most probable processes in which this unrest could have developed and to contribute to the diagnosis task. In this research, we propose a comparison between the processes identified in this preliminary volcanic event tree and another elaborated using a Hazard Assessment Event Tree probability tool (HASSET), built on a bayesian event tree structure, using mainly the information of the known eruptive history of Popocatépetl. The HASSET method is based on Bayesian Inference and is used to assess volcanic hazard of future eruptive scenarios, by evaluating the most relevant sources of uncertainty that play a role in estimating the future probability of occurrence of a specific volcanic event. The final goal is to find the most useful tools to make the diagnosis and prognosis of the Popocatépetl volcanic activity, integrating the known eruptive history of the volcano, the experience of the scientific committee and the information provided by the monitoring systems, in an interactive and user-friendly way.

Magma supply rate at kilauea volcano, 1952-1971.

PubMed

Swanson, D A

1972-01-14

The three longest Kilauea eruptions since 1952 produced lava at an overall constant rate of about 9 x 10(6) cubic meters per month (vesicle-free). This is considered to represent the rate of magma supply from a deep source, probably the mantle, because little or no summit deformation indicating high-level storage accompanied any of the three eruptions.

Geologic Mapping of Ascraeus Mons, Mars

NASA Astrophysics Data System (ADS)

Mohr, Kyle James

Ascraeus Mons (AM) is the northeastern most large shield volcano residing in the Tharsis province on Mars. AM has a diameter of 350 km and reaches a height of 16 km above Mars datum, making AM the third largest volcano on Mars. Previous mapping of a limited area of these volcanoes using HRSC images (13-25 m/pixel) revealed a diverse distribution of volcanic landforms within the calderas, along the flanks, rift aprons, and surrounding plains. The general scientific objective for which mapping was based was to show the different lava flow morphologies across AM to better understand the evolution and geologic history. A 1: 1,000,000 scale geologic map of Ascraeus Mons was produced using ArcGIS and will be submitted to the USGS for review and publication. Mapping revealed 26 units total, broken into three separate categories: Flank units, Apron and Scarp units, and Plains units. Units were defined by geomorphological characteristics such as: surface texture, albedo, size, location, and source. Defining units in this manner allowed for contact relationships to be observed, creating a relative age date for each unit to understand the evolution and history of this large shield volcano. Ascraeus Mons began with effusive, less viscous style of eruptions and transitioned to less effusive, more viscous eruptions building up the main shield. This was followed by eruptions onto the plains from the two main rift aprons on AM. Apron eruptions continued, while flank eruptions ceased, surrounding and embaying the flanks of AM. Eruptions from the rifts wane and build up the large aprons and low shield fields. Glaciers modified the base of the west flank and deposited the Aureole material. Followed by localized recent eruptions on the flanks, in the calderas, and small vent fields. Currently AM is modified by aeolian and tectonic processes. While the overall story of Ascraeus Mons does not change significantly, higher resolution imagery allowed for a better understanding of magma evolution and lava characteristics across the main shield. This study helps identify martian magma production rates and how not only Ascraeus Mons evolved, but also the Tharsis province and other volcanic regions of Mars.

Geologic Map of Ascraeus Mons, Mars

NASA Astrophysics Data System (ADS)

Mohr, K. J.; Williams, D. A.

2017-12-01

Ascraeus Mons (AM) is the northeastern most large shield volcano residing in the Tharsis province on Mars. AM has a diameter of 350 km and reaches a height of 16 km above Mars datum, making AM the third largest volcano on Mars. Previous mapping of a limited area of these volcanoes using HRSC images (13-25 m/pixel) revealed a diverse distribution of volcanic landforms within the calderas, along the flanks, rift aprons, and surrounding plains. The general scientific objective for which mapping was based was to show the different lava flow morphologies across AM to better understand the evolution and geologic history. A 1: 1,000,000 scale geologic map of Ascraeus Mons was produced using ArcGIS and will be submitted to the USGS for review and publication. Mapping revealed 26 units total, broken into three separate categories: Flank units, Apron and Scarp units, and Plains units. Units were defined by geomorphological characteristics such as: surface texture, albedo, size, location, and source. Defining units in this manner allowed for contact relationships to be observed, creating a relative age date for each unit to understand the evolution and history of this large shield volcano. Ascraeus Mons began with effusive, less viscous style of eruptions and transitioned to less effusive, more viscous eruptions building up the main shield. This was followed by eruptions onto the plains from the two main rift aprons on AM. Apron eruptions continued, while flank eruptions ceased, surrounding and embaying the flanks of AM. Eruptions from the rifts wane and build up the large aprons and low shield fields. Glaciers modified the base of the west flank and deposited the Aureole material. Followed by localized recent eruptions on the flanks, in the calderas, and small vent fields. Currently AM is modified by aeolian and tectonic processes. While the overall story of Ascraeus Mons does not change significantly, higher resolution imagery allowed for a better understanding of magma evolution and lava characteristics across the main shield. This study helps identify martian magma production rates and how not only Ascraeus Mons evolved, but also the Tharsis province and other volcanic regions of Mars.

The relationship between plutonism and volcanism: zircon ages from granitoid clasts in recent pyroclastic deposits from Tarawera volcano

NASA Astrophysics Data System (ADS)

Shane, P. A.; Storm, S.; Schmitt, A. K.; Lindsay, J.

2011-12-01

In Quaternary magmatic systems that have not undergone extensive uplift that would expose their intrusive roots, co-magmatic (and xenolithic) plutonic clasts entrained in eruptive deposits are an important source of information on the temporal relationship between plutonism and volcanism. Granitoid clasts in pyroclastic deposits of the 0.7 ka (Kaharoa) eruption from the Tarawera volcano of the Okataina Volcanic Centre (OVC), New Zealand, provide a rare insight to the plutonic processes beneath one of the most productive Quaternary rhyolite centers on Earth. SIMS U-Th and U-Pb data on 79 granitoid zircon crystals from six clasts reveal a unimodal age spectrum yielding a weighted average model age of 211 ± 4 ka (MSWD = 1.1). This crystallization event coincides with relative quiescence in OVC volcanism. A few outlier antecrysts date back to ~700 ka, a period significantly longer than the known volcanic record at OVC (probably ~330 ka). In contrast, zircon crystallization in co-erupted pumice and lava of the 0.7 ka Kaharoa event, and that of the three preceding rhyolite eruptions, occurred mostly during 0-50 ka. Thus, the granitoid clasts represent part of the system immediately beneath the volcano that survived assimilation and/or destruction in subsequent eruption and caldera collapse episodes. Brittle deformation features, incipient alteration and low-d18O whole-rock compositions (+3%) are consistent with a shallow solid carapace that has interacted with hydrothermal fluids. However, d18O SIMS analyses of zircons (+5.4 ± 0.2 %; n = 11) are consistent with magmatic compositions, and thus meteoric interaction occurred post-emplacement. The Kaharoa granitoids contrast with those ejected in the ~60 ka caldera-forming Rotoiti event, that were partly molten and display zircon age spectra indistinguishable from that in co-erupted pumices, suggesting the latter were derived from contemporaneous crystal mush. The 0.7 ka Kaharoa case shows that, over time, eruptible parts of a magmatic reservoir can become armored by a solidified intrusive carapace that minimizes interaction with other parts of the magmatic system and the surrounding wall-rocks. Thus, plutonic and volcanic evolution can diverge even in close proximity of the same magmatic system.

Coupling Eruptive Dynamics Models to Multi-fluid Plasma Dynamic Simulations at Enceladus

NASA Astrophysics Data System (ADS)

Paty, C. S.; Dufek, J.; Waite, J. H.; Tokar, R. L.

2011-12-01

The interaction of Saturn's magnetosphere with Enceladus provides an exciting natural laboratory for expanding our understanding of charge-neutral-dust interactions and their impact on mass and momentum loading of the system and the associated magnetic perturbations. However, one of the more challenging questions regarding the Enceladus plume relates to the subsurface eruptive mechanism responsible for generating the observed jets of material that compose the plume, and the three-dimensional distribution of neutral gas and dust in the plume. In this work we implement a multiphase eruptive dynamics model [cf. Dufek & Bergantz, 2007; Dufek and Bergantz, 2005] to examine the evolution of the plume morphology for a given eruption. We model the eruptive mechanism in a two-part, coupled domain including a fissure model and a plume model. A high resolution, multiphase, fissure model examines eruptive processes in a fissure from fragmentation to the surface. The fissure model is two-dimensional and provides spatial and temporal information about the dust/ice grains and gas. The depth to the fragmentation surface is currently treated as a free parameter and we examine a range of fissure morphologies. We do not explicitly force choked conditions at the vent, but rather due to the geometry, the velocities of the particle and gas mixture approach the sound speed for a 'dusty' gas mixture. The fissure model provides a source for the 3D plume model which examines the morphology of the plume resulting from different fissure configurations and provides a self-consistent physical basis to link concentrations in different regions of the plume to an eruptive mechanism. These initial models describing the resulting gas and dust grain distribution will be presented in the context of existing observations. We will also demonstrate the first stages of integration of these results into the existing multi-fluid plasma dynamic simulations of Enceladus' interaction with Saturn's magnetosphere. These more sophisticated plume morphologies and their effects on the plasma dynamic interaction will be assessed in the context of existing modeling efforts for this system.

Characteristics of Young Rhyolites at Taupo, New Zealand: Implications for the Sub-Surface Plutonic System

NASA Astrophysics Data System (ADS)

Wilson, C. J.; Charlier, B. L.

2007-12-01

The young history of Taupo volcano captures the growth and destruction in the 26.5 ka ca. 530 km3 Oruanui eruption of a large rhyolitic magma body, together with the subsequent rejuvenation of magma sources below the volcano. Integration of field information with petrological and isotopic studies at the whole-pumice and single- crystal scales provide a picture of this history. Several important contrasts are inferred to exist between Taupo and comparably-sized, long-lived silicic foci such at Long Valley and in the Bishop Tuff. At Taupo the following are demonstrable. 1. Even in crystal-poor rhyolites like the Oruanui, many grains are inherited antecrysts or xenocrysts. The Oruanui crystal-poor rhyolite body was an open system, with influxes of crystals (plus melt) from remobilised older crystal mush, melted metasedimentary country rocks and plutonics, and crystal-poor basaltic to andesitic magmas. 2. All the Taupo rhyolites were well mixed prior to eruption, and there are no gradients in the eruption products to suggest that the holding chamber(s) were stratified to any extent. 3. Mafic magmas rose into, interacted with, and ponded on the floors of crystal-poor rhyolite in the Oruanui and Waimihia (3.5 ka) examples, again implying that the chamber floor was sharply defined, not a gradual progression down into a more crystal- rich root zone. 4. Pre-Oruanui activity involved contrasting magma types being generated simultaneously, but erupting from geographically separated vents. Post-Oruanui activity has seen (subtly) contrasting magma groups being erupted from vents in the same geographic area, but separated in time. The Oruanui and post-Oruanui magmas are different and do not appear to be related by consanguinity or by mixing - the Oruanui eruption effectively destroyed its magma body. These features are consistent with rhyolite magma generation at Taupo that is exceptionally fast, driven by high fluxes of mafic magmas into a highly heterogeneous crustal melange of metasedimentary and igneous lithologies. There is no voluminous crystal mush body to act as a buffer for the rhyolite generation processes; the eruption frequency at Taupo gives no chance for such a body to develop.

Investigating the Source Mechanisms of Deflation-Inflation Events at Kilauea Volcano, Hawai`i

NASA Astrophysics Data System (ADS)

Johnson, J. H.; Anderson, K. R.; Poland, M. P.; Miklius, A.

2012-12-01

At Kilauea Volcano, Hawai`i, cyclic deflation-inflation ("DI") events have been observed on tiltmeters since 1988. Most DI events begin with deflation at the summit that generally lasts 12-72 hours and accumulate ~1-5 microradians of tilt as measured on the rim of Kilauea Caldera, followed by inflation that is initially rapid but wanes over the course of 12-48 hours as the net deformation approaches pre-event levels. This gives the tilt events a V- or U-shaped appearance in the tilt time series, depending on the onset deflation rates. DI events are also manifested at the Pu`u `O`o eruptive vent on Kilauea's east rift zone, about 20 km along the rift from the summit, and lag summit deformation by approximately 30-90 minutes (except during 2005-2007, when summit DI events were not detected at Pu`u `O`o). The temporal correlation of tilt at the caldera and east rift zone indicates that these events affect much of Kilauea's magma plumbing system, from the summit magma reservoir to the eruption site. Large-magnitude DI events are visible in data from continuously-recording GPS stations both at Kilauea's summit and at Pu`u `O`o, and some DI events have been imaged using InSAR. Tilt events with long-lived (several days) deflation phases are usually associated with decreases in lava effusion or even eruptive pauses on the east rift zone, while large inflationary phases are often accompanied by surges in lava effusion, new breakouts, and thus increased lava flow hazard. The lava level within the summit eruptive vent, which has been continuously visible since early 2010, correlates with tilt deformation associated with DI events. Seismic tremor levels measured at Kilauea summit at times also display a relation with DI events, sometimes correlated and sometimes anti-correlated. Tilt events have become more common since the onset of Kilauea's summit eruption in March 2008, increasing from about 5-10 per year before 2008 to more than 80 in the 8 months of 2012. Two possibly inter-related mechanisms have been suggested to explain the DI events: (1) blockage and subsequent clearing of the transport pathway that feeds the shallow summit magma system and conduit to Pu`u `O`o, and (2) convective overturns caused by replacement of degassed magma with gas-rich magma. Using a simple kinematic forward model, we invert deformation data from more than 400 DI events to estimate the location and volume change of the shallow summit source generating the ground tilt, and look for changes associated with the evolution of eruptive behaviour at Kilauea. More insight into the DI events can be gained by developing a physics-based model capable of linking magmatic processes with the temporal evolution of individual DI events. We will construct multiphysics finite element models (FEMs) to simulate deformation caused by the two proposed mechanisms to link the observations to the physical processes that drive DI events. The FEMs allow us to investigate complicated model configurations that account for 3D geometric configurations, distributions of rheologic properties, and multiple deformation sources. Crucially, the models also allow for temporal variation of fluid flow and subsurface pressurization, which will provide insights into the unique patterns of tilt observed at Kilauea.

Distinct Aqueous and Hydrocarbon Cryovolcanism on Titan and Other Icy Satellites (Invited)

NASA Astrophysics Data System (ADS)

Kargel, J. S.; Furfaro, R.; Candelaria, P.

2010-12-01

Almost as soon as low-temperature solar nebula condensation sequences were first computed, it was realized that icy satellites have an internal heat source in long-lived radioactivities and could undergo differentiation; furthermore, freezing-point depressants, such as ammonia, and apolar gases, such as methane, could enable icy satellites to undergo aqueous cryovolcanism. The subsequent recognition of tidal and gravitational potential energy sources increased expectations for cryovolcanism. Voyager imaging and discovery of apparent cryovolcanic landforms—best exhibited by Triton, more ambiguous elsewhere-- motivated studies of the phase relations, phase densities and other thermodynamic properties, solid- and liquid-state rheologies, and possible cryovolcanic eruptive behaviors and landform characteristics. Ironically, the closer we examined Jovian icy moons with Galileo, the rarer cryovolcanic landforms appeared to be, with only a few compelling and very well characterized cases found mainly on Europa. Compelling examples of effusive cryovolcanism mainly occupied local topographic lows, whereas cases not in low spots tended to exhibit signs of explosive emplacement. Spectacular evidence of explosive cryovolcanism or geyser-like behavior was found by Cassini on Enceladus, but most other icy Saturnian moons did not reveal any compelling indicators of eruptions. Titan has so far been a mixed case, where some indicators of cryovolcanism have been reported, but there is scant compelling evidence for the process. We think that the sparseness of compelling effusive cryovolcanic features on icy satellites is because free, unreacted ammonia is less common than previously thought, and the main aqueous liquids are salt-water solutions denser than ice I; hence, they tend not to erupt, or they erupt only if driven by gas exsolution; even then, a thin ice shell and high heat flow is needed to allow aqueous liquids near enough to the surface to erupt. On satellites with thick icy shells, stable aqueous liquids are mainly confined to deep levels and cryovolcanism does not occur unless ammonia is abundant, as it may be on Triton. On Titan, we think the icy shell is thick, ammonia might not be abundant, and aqueous cryovolcanism might occur rarely, if at all. However, many hydrocarbons are abundant on Titan—both photolytic and endogenic—and may melt in the icy crust and form low-temperature, buoyant liquids. Hydrocarbon cryovolcanism is likely. Hydrocarbon lavas may range from exceeding low viscosity unimolecular types to highly viscous and possibly asphalt-, wax-, or plastic-like solid-liquid mixtures of complex and highly polymerized compositions. Some hydrocarbons may melt just hundreds of meters to a few kilometers beneath Titan’s surface. Shallow hydrocarbon deposits may melt or crystallize when insulating surface hydrocarbon deposits are emplaced or removed by sublimation, fluvial, or eolian processes. Deep interior endogenic hydrocarbons may erupt if they evade a gauntlet of physical and chemical barriers during ascent. Hydrocarbon cryovolcanic landforms may resemble skating ponds, silicate lava flows, salt extrusions, asphalt flows, or glaciers.

Miocene calc-alkaline heritage in the pliocene postcollisional volcanism of monte arci (Sardinia, Italy)

NASA Astrophysics Data System (ADS)

Cioni, Roberto; Clocchiatti, Robert; Di Paola, Giovanni M.; Santacroce, Roberto; Tonarini, Sonia

1982-10-01

At Monte Arci alkaline (hawaiites to trachytes), subalkaline with a marked calc-alkaline character (basalts to dacites) and rhyolitic lavas were erupted almost simultaneously in Late Pliocene time. Major- and trace-element chemistry, microprobe mineralogy and isotopic data suggest a partial melting origin for both rhyolites and subalkaline rocks. Different sources are however inferred for two rock series: homogeneous, calc-alkaline in nature for subalkaline rocks; unhomogeneous, richer in 87Sr, for rhyolitic ones. Crystal fractionation differentiation from subcrustal alkali-basalts should have been the main process in the genesis of alkaline rocks. Large-scale contaminations with rhyolitic and/or alkaline rocks are evident in many of these lavas. Such a complicated magmatic association characterizes an area where volcanism related to post-collisional tensional movements in Pliocene time superimposes to Middle Miocene calc-alkaline basic volcanism related to previous subduction processes. The Pliocene volcanic history of Monte Arci emphasizes the influence of the paleogeodynamic environment on the nature of magmas erupted in post-continental collision areas, that are frequently difficult to arrange in the usual schemas connecting magma composition with tectonic setting.

Detecting and Cataloging Global Explosive Volcanism Using the IMS Infrasound Network

NASA Astrophysics Data System (ADS)

Matoza, R. S.; Green, D. N.; LE Pichon, A.; Fee, D.; Shearer, P. M.; Mialle, P.; Ceranna, L.

2015-12-01

Explosive volcanic eruptions are among the most powerful sources of infrasound observed on earth, with recordings routinely made at ranges of hundreds to thousands of kilometers. These eruptions can also inject large volumes of ash into heavily travelled aviation corridors, thus posing a significant societal and economic hazard. Detecting and counting the global occurrence of explosive volcanism helps with progress toward several goals in earth sciences and has direct applications in volcanic hazard mitigation. This project aims to build a quantitative catalog of global explosive volcanic activity using the International Monitoring System (IMS) infrasound network. We are developing methodologies to search systematically through IMS infrasound array detection bulletins to identify signals of volcanic origin. We combine infrasound signal association and source location using a brute-force, grid-search, cross-bearings approach. The algorithm corrects for a background prior rate of coherent infrasound signals in a global grid. When volcanic signals are identified, we extract metrics such as location, origin time, acoustic intensity, signal duration, and frequency content, compiling the results into a catalog. We are testing and validating our method on several well-known case studies, including the 2009 eruption of Sarychev Peak, Kuriles, the 2010 eruption of Eyjafjallajökull, Iceland, and the 2015 eruption of Calbuco, Chile. This work represents a step toward the goal of integrating IMS data products into global volcanic eruption early warning and notification systems. Additionally, a better characterization of volcanic signal detection helps improve understanding of operational event detection, discrimination, and association capabilities of the IMS network.

The isotopic and chemical evolution of Mount St. Helens

USGS Publications Warehouse

Halliday, A.N.; Fallick, A.E.; Dickin, A.P.; Mackenzie, A.B.; Stephens, W.E.; Hildreth, W.

1983-01-01

Isotopic and major and trace element analysis of nine samples of eruptive products spanning the history of the Mt. St. Helens volcano suggest three different episodes; (1) 40,000-2500 years ago: eruptions of dacite with ??{lunate}Nd = +5, ??{lunate}Sr = -10, variable ??18O, 206Pb/204Pb ??? 18.76, Ca/Sr ??? 60, Rb/Ba ??? 0.1, La/Yb ??? 18, (2) 2500-1000 years ago: eruptions of basalt, andesite and dacite with ??{lunate}Nd = +4 to +8, ??{lunate}Sr = -7 to -22, variable ??18O (thought to represent melting of differing mantle-crust reservoirs), 206Pb/204Pb = 18.81-18.87, variable Ca/Sr, Rb/Ba, La/Yb and high Zr, (3) 1000 years ago to present day: eruptions of andesite and dacite with ??{lunate}Nd = +6, ??{lunate}Sr = -13, ??18O ???6???, variable 206Pb/204Pb, Ca/Sr ??? 77, Rb/Ba = 0.1, La/Yb ??? 11. None of the products exhibit Eu anomalies and all are LREE enriched. There is a strong correlation between 87Sr/86Sr and differentiation indices. These data are interpreted in terms of a mantle heat source melting young crust bearing zircon and garnet, but not feldspar, followed by intrusion of this crustal reservoir by mantle-derived magma which caused further crustal melting and contaminated the crustal magma system with mafic components. Since 1000 years ago all the eruptions have been from the same reservoir which has displayed a much more gradual re-equilibration of Pb isotopic compositions than other components suggesting that Pb is being transported via a fluid phase. The Nd and Sr isotopic compositions lie along the mantle array and suggest that the mantle underneath Mt. St. Helens is not as depleted as MORB sources. There is no indication of seawater involvement in the source region. ?? 1983.

The volcanic-plutonic connection unveiled

NASA Astrophysics Data System (ADS)

Hartung, E.; Caricchi, L.; Floess, D.; Wallis, S.; Harayama, S.

2017-12-01

Are upper crustal plutons solidified magma bodies or residues from extracted and erupted liquids? This remains one of the key questions to address to understand the construction and eruption of upper crustal magmatic systems. We have investigated the Takidani Pluton and contemporaneous volcanic deposits (Nyukawa PFD, Chayano Tuff and Ebisutoge PD) distributed around this crustal intrusion to understand whether they were sourced from this pluton. The Takidani Pluton is a good candidate because it contains petrographic and geochemical evidences for residual melt extraction, and pressure quenching associated with eruptive activity (Hartung et al., 2017). We analysed major and trace element concentrations of 18 plagioclase phenocrysts (core to rim) from the Takidani Pluton and Nyukawa-Chayano-Ebisutoge eruptions. Major elements were first analysed using an electron microprobe and trace elements were subsequently determined by laser ablation inductively coupled mass spectrometry in the same spot. Plagioclase chemistry shows that the Chayano and Ebisutoge rhyolitic deposits are not petrogenetically related to either the Takidani Pluton or the Nyukawa PFD. However, plagioclase of the Nyukawa PDF and the Takidani Pluton show indistinguishable REE patterns suggesting a common source domain for plagioclase from the two units. Ebisutoge plagioclase grains commonly contain xenocrystic cores that have major and trace element compositions comparable to the plagioclase grains observed in the Takidani Pluton and Nyukawa PFD. Our data show that the Nyukawa and Takidani plagioclase are geochemically indistinguishable, suggesting that the Takidani pluton was the magma reservoir that fed this large eruptive unit (400 km3, Oikawa, 2003). The Ebisutoge magma was not extracted directly from the pluton, but interacted with Takidani-Nyukawa when it was still molten. We have no evidence to suggest that the Takidani Pluton was the source of either the Chayano Tuff or the Ebisutoge PD.

Volcanic Eruptions of the EPR and Ridge Axis Segmentation: An Interdisciplinary View

NASA Astrophysics Data System (ADS)

White, S.; Soule, S. A.; Tolstoy, M.; Waldhauser, F.; Rubin, K.

2008-12-01

The eruption of the EPR in 2005-06 provides an ideal window into the relationship between fine-scale segmentation of the ridge axis and individual eruptive episodes. Lava flow mapping of the eruption by visual and acoustic images, precise dates on multiple eruptive units, stress information from seismicity, long-term records of hydrothermal activity, and well known segment boundaries illustrate the relationships between eruptions and segmentation of mid-ocean ridges. Lava flows emerged from several sections of the axial summit trough (AST) during the eruption, presumably from en echelon fissures between 9 45'N and 9 57'N. Each en echelon fissure is a 4th order segment, and the overall area matches the 3rd Order segment between ~9 45'N and ~9 58'N. Within the eruption, the primary eruptive fissure jumped east by 600 m at 9 53'N, and ran along an inward facing fault scarp, although limited lava effusion also extended northward along the axial fissure. A zone of high seismicity connects the normal fault bounding the eastern fissure eruption with the main locus of eruption on the ridge axis to the south, suggesting that the offset eruption may have occurred in response to stress buildup on this fault. Radiometric ages indicate that the entire along-axis extent of the eruptive fissures activated initially, but that volcanic activity focused to a single fourth-order segment within 1-3 months. Previously indentified breaks in the AST and its overall outline were largely unchanged by the eruption. These observations support the hypothesis that fourth-order segments are offsets controlled by the mechanics of dike emplacement, whereas third-order segments represent discrete volcanic systems. Dike segmentation may be controlled by variations in underlying ridge structure or the magma reservoir. Hydrothermal systems disrupted as far south as 9 37'N may be responding to cracking due to stress interaction or share a common deeper magmatic source. Comparisons between the 1991 EPR eruption at the same site, and several mapped southern EPR eruptions, the 10 45'N EPR eruption in ca. 2003 all show similar relationships to segmentation

Cyclic flank-vent and central-vent eruption patterns

NASA Astrophysics Data System (ADS)

Takada, Akira

Many basaltic and andesitic polygenetic volcanoes have cyclic eruptive activity that alternates between a phase dominated by flank eruptions and a phase dominated by eruptions from a central vent. This paper proposes the use of time-series diagrams of eruption sites on each polygenetic volcano and intrusion distances of dikes to evaluate volcano growth, to qualitatively reconstruct the stress history within the volcano, and to predict the next eruption site. In these diagrams the position of an eruption site is represented by the distance from the center of the volcano and the clockwise azimuth from north. Time-series diagrams of Mauna Loa, Kilauea, Kliuchevskoi, Etna, Sakurajima, Fuji, Izu-Oshima, and Hekla volcanoes indicate that fissure eruption sites of these volcanoes migrated toward the center of the volcano linearly, radially, or spirally with damped oscillation, occasionally forming a hierarchy in convergence-related features. At Krafla, terminations of dikes also migrated toward the center of the volcano with time. Eruption sites of Piton de la Fournaise did not converge but oscillated around the center. After the convergence of eruption sites with time, the central eruption phase is started. The intrusion sequence of dikes is modeled, applying crack interaction theory. Variation in convergence patterns is governed by the regional stress and the magma supply. Under the condition that a balance between regional extension and magma supply is maintained, the central vent convergence time during the flank eruption phase is 1-10 years, whereas the flank vent recurrence time during the central eruption phase is greater than 100 years owing to an inferred decrease in magma supply. Under the condition that magma supply prevails over regional extension, the central vent convergence time increases, whereas the flank vent recurrence time decreases owing to inferred stress relaxation. Earthquakes of M>=6 near a volcano during the flank eruption phase extend the central vent convergence time. Earthquakes during the central eruption phase promote recurrence of flank eruptions. Asymmetric distribution of eruption sites around the flanks of a volcano can be caused by local stress sources such as an adjacent volcano.

Using Volcanic Lightning Measurements to Discern Variations in Explosive Volcanic Activity

NASA Astrophysics Data System (ADS)

Behnke, S. A.; Thomas, R. J.; McNutt, S. R.; Edens, H. E.; Krehbiel, P. R.; Rison, W.

2013-12-01

VHF observations of volcanic lightning have been made during the recent eruptions of Augustine Volcano (2006, Alaska, USA), Redoubt Volcano (2009, Alaska, USA), and Eyjafjallajökull (2010, Iceland). These show that electrical activity occurs both on small scales at the vent of the volcano, concurrent with an eruptive event and on large scales throughout the eruption column during and subsequent to an eruptive event. The small-scale discharges at the vent of the volcano are often referred to as 'vent discharges' and are on the order of 10-100 meters in length and occur at rates on the order of 1000 per second. The high rate of vent discharges produces a distinct VHF signature that is sometimes referred to as 'continuous RF' radiation. VHF radiation from vent discharges has been observed at sensors placed as far as 100 km from the volcano. VHF and infrasound measurements have shown that vent discharges occur simultaneously with the onset of eruption, making their detection an unambiguous indicator of explosive volcanic activity. The fact that vent discharges are observed concurrent with explosive volcanic activity indicates that volcanic ejecta are charged upon eruption. VHF observations have shown that the intensity of vent discharges varies between eruptive events, suggesting that fluctuations in eruptive processes affect the electrification processes giving rise to vent discharges. These fluctuations may be variations in eruptive vigor or variations in the type of eruption; however, the data obtained so far do not show a clear relationship between eruption parameters and the intensity or occurrence of vent discharges. Further study is needed to clarify the link between vent discharges and eruptive behavior, such as more detailed lightning observations concurrent with tephra measurements and other measures of eruptive strength. Observations of vent discharges, and volcanic lightning observations in general, are a valuable tool for volcano monitoring, providing a method for rapid detection of volcanic activity in real-time.

The Sr, Nd and O isotopic studies of the 1991 1995 eruption at Unzen, Japan

NASA Astrophysics Data System (ADS)

Chen, Chang-Hwa; Nakada, Setsuya; Shieh, Yuch-Ning; DePaolo, Donald J.

1999-04-01

The magma generation at Unzen volcano may be considered as the product of crustal material mixed with mantle magma accompanied by fractional crystallization (AFC). The magma in the Unzen volcano is estimated to consist of about 50-80% of residual magma ( F) and about 30-70% assimilated crustal material ( A) relative to the original magma. Concerning the 1991-1995 eruption, it is estimated that the magma formed as the result of mixing of about 50-60% crustal material and about 55-65% of residual magma. An alternative magma eruption model for the 1991-1995 eruption is proposed here. In the early stage, the isotopic characteristics of 1991 eruption are defined by AFC process in the deeper magma chamber. Later, the magma ascended through the conduit and quiescently stayed for a long time in a shallow reservoir before eruption. The minerals continuously crystallized as phenocrysts especially at the chilled top and outer margin in the shallow chamber. The crystallized phenocryst mush was reworked into the central part of the magma chamber by means of magma convection and rapid magma ascent. Therefore, the reaction between phenocrysts and melt occurs only in internal chemical disequilibrium in the magma chamber. In contrast, the isotopic compositions of the original magma shall be little influenced by the above processes throughout its eruptive history. The 1991-1995 eruptive rocks of the Unzen volcano show their characteristics in Sr and Nd isotopic values independent of their two previous eruptions. However, the isotopic values of early eruptive product could represent the original magma value. This result also supports the previous work of Chen et al. (1993) [Chen, C.H., DePaolo, D.J., Nakada, S., Shieh, Y.N., 1993. Relationship between eruption volume and neodymium isotopic composition at Unzen volcano. Nature 362, 831-834], that suggested the ɛNd of early or precursory eruptive products could be a qualitative indicator of the maximum size of a continuing or impending eruption.

Eruption precursors: Manifestations and strategies for detection

NASA Astrophysics Data System (ADS)

Poland, Michael; Pritchard, Matthew

2017-04-01

The past several decades have seen a rapid increase in volcano monitoring and modeling capabilities. Diverse arrays of instrument networks can detect a variety of pre-, co-, and post-eruptive phenomena, and remote sensing observations are available across a range of spatial, temporal, and spectral resolutions. A growing class of models, based on the physics of magmatic systems, are making use of these expanding datastreams, providing probabilistic assessments of such parameters as magma supply, volatile content, and eruption duration. To what extent, however, do these developments heighten our ability to identify eruption precursors? The advent of better data and new models provides an opportunity to reexamine our understanding of pre-eruption unrest, as well as our ability to detect and recognize it as such. An idealized model of the buildup to a volcanic eruption might include magma ascent from a deep source region and accumulation in the mid- to upper crust in the preceding months to years. The process might be manifested by surface inflation and deep long-period earthquakes, and accompanied by an increase in CO2 emissions. As magma continues to accumulate, distal volcano-tectonic earthquakes may result as stress builds on nearby faults, H2S emissions may increase as sulfur in a shallow reservoir is hydrolyzed by groundwater, and fumarole and spring temperatures may increase and show changes in chemistry. In the days to hours before an eruption, sudden changes in the rate and style of earthquakes (including repeating earthquakes and tremor) and deformation may occur as the magma reservoir ruptures and magma moves laterally or vertically. Phreatic eruptions might result as ascending magma comes into contact with groundwater, and SO2 emissions might increase as the path between the magma and surface dries out. How often does such a sequence actually occur? Relatively few volcanoes are comprehensively monitored prior to obvious expressions of unrest, so this is not an easy question to answer. From the limited record, it appears that at least a few volcanoes follow the model. For example, deep inflation, long-period earthquakes, and CO2 emissions were detected months before the 2009 eruption of Redoubt (Alaska). In the weeks to days before the eruption onset, fumarole temperatures and SO2 emissions increased, tremor was noted, and phreatic explosions presaged the extrusion of magma at the surface. Other volcanoes buck this idealized trend. Calbuco (Chile), for instance, showed no indication of inflation or seismicity in the days to years prior to the sudden onset of a magmatic eruption in 2015, despite InSAR and seismic monitoring that should have detected such unrest. Most volcanoes seem to fall between these two extremes, providing some indication of their eruptive potential via gas, thermal, seismic, or geodetic anomalies over timescales ranging from hours to years. Given limited resources and the challenges in terrestrial monitoring of all potential long- and intermediate-term eruption precursors, strategies for exploiting the wealth of remote sensing data and integrating derived insights into models of volcanic unrest are an important investment. Short-term eruption precursors, however, are best detected by ground-based monitoring—especially seismic and geodetic instruments.

Air Pollution Emissions Overview | Air Quality Planning & ...

EPA Pesticide Factsheets

2016-06-08

Air pollution comes from many different sources: stationary sources such as factories, power plants, and smelters and smaller sources such as dry cleaners and degreasing operations; mobile sources such as cars, buses, planes, trucks, and trains; and naturally occurring sources such as windblown dust, and volcanic eruptions, all contribute to air pollution.

Compositional Zoning in Kilauea Olivine: A Geochemical Tool for Investigating Magmatic Processes at Hawaiian Volcanoes

NASA Astrophysics Data System (ADS)

Lynn, Kendra J.

Olivine compositions and zoning patterns have been widely used to investigate the evolution of magmas from their source to the Earthfs surface. Modeling the formation of compositional zoning in olivine crystals has been used to retrieve timescales of magma residence, mixing, and transit. This dissertation is composed of three projects that apply diffusion chronometry principles to investigate how zoned olivine phenocrysts record magmatic processes at Hawaiian volcanoes. Olivine phenocrysts from K.lauea, the most active and thoroughly studied volcano in Hawaiei, are used to develop a better understanding of how Hawaiian olivine crystals record magmatic histories. This work begins by examining how crustal processes such as magma mixing and diffusive reequilibration can modify olivine compositions inherited from growth in parental magmas (Chapter 2). Diffusive re-equilibration of Fe-Mg, Mn, and Ni in olivine crystals overprints the chemical relationships inherited during growth, which strongly impacts interpretations about mantle processes and source components. These issues are further complicated by sectioning effects, where small (400 ƒEm along the c-axis) olivine crystals are more susceptible to overprinting compared to large (800 ƒEm) crystals. Olivine compositions and zoning patterns are then used to show that magmas during K.laueafs explosive Keanak.koei Tephra period (1500-1823 C.E.) were mixed and stored in crustal reservoirs for weeks to months prior to eruption (Chapter 3). Fe-Mg disequilibrium between olivine rims and their surrounding glasses show that a late-stage mixing event likely occurred hours to days prior to eruption, but the exact timescale is difficult to quantify using Fe-Mg and Ni diffusion. Lithium, a rapidly diffusing trace element in olivine, is modeled for the first time in a natural volcanic system to quantify this late-stage, short-duration mixing event (Chapter 4). Lithium zoning in olivine records both growth and diffusion processes that are affected by charge balancing requirements with growth zoning of P. Timescales from modeling diffuse Li zoning range from a few hours to three weeks, but most record short storage durations of four days or less. These timescales correspond to short storage periods after mixing. Thus, Li probably records the final perturbation of a magmatic system prior to eruption.

Source characterization for an explosion during the 2009 eruption of Redoubt Volcano from very-long-period seismic waves

USGS Publications Warehouse

Haney, Matthew M.; Chouet, Bernard A.; Dawson, Phillip B.; Power, John A.

2013-01-01

The 2009 eruption of Redoubt produced several very-long-period (VLP) signals associated with explosions. We invert for the source location and mechanism of an explosion at Redoubt volcano using waveform methods applied to broadband recordings. Such characterization of the source carries information on the geometry of the conduit and the physics of the explosion process. Inversions are carried out assuming the volcanic source can be modeled as a point source, with mechanisms described by a) a set of 3 orthogonal forces, b) a moment tensor consisting of force couples, and c) both forces and moment tensor components. We find that the source of the VLP seismic waves during the explosion is well-described by either a combined moment/force source located northeast of the crater and at an elevation of 1.6 km ASL or a moment source at an elevation of 800 m to the southwest of the crater. The moment tensors for the solutions with moment and force and moment-only share similar characteristics. The source time functions for both moment tensors begin with inflation (pressurization) and execute two cycles of deflation-reinflation (depressurization–repressurization). Although the moment/force source provides a better fit to the data, we find that owing to the limited coverage of the broadband stations at Redoubt the moment-only source is the more robust and reliable solution. Based on the moment-only solution, we estimate a volume change of 19,000 m3 and a pressure change of 7 MPa in a dominant sill and an out-of-phase volume change of 5000 m3 and pressure change of 1.8 MPa in a subdominant dike at the source location. These results shed new light on the magmatic plumbing system beneath Redoubt and complement previous studies on Vulcanian explosions at other volcanoes.

Large volume submarine ignimbrites in the Shikoku Basin: An example for explosive volcanism in the Western Pacific during the Late Miocene

NASA Astrophysics Data System (ADS)

Kutterolf, Steffen; Schindlbeck, Julie C.; Scudder, Rachel P.; Murray, Richard W.; Pickering, Kevin T.; Freundt, Armin; Labanieh, Shasa; Heydolph, Ken; Saito, Sanny; Naruse, Hajime; Underwood, Michael B.; Wu, Huaichun

2014-05-01

IODP Expedition 322, an interval of Late Miocene (7.6 to ˜9.1 Ma) tuffaceous and volcaniclastic sandstones was discovered in the Shikoku Basin (Site C0011B), Nankai region. This interval consists of bioturbated silty claystone including four 1-7 m thick interbeds of tuffaceous sandstones (TST) containing 57-82% (by volume) pyroclasts. We use major and trace element glass compositions, as well as radiogenic isotope compositions, to show that the tuffaceous sandstones beds derived from single eruptive events, and that the majority (TST 1, 2, 3a) came from different eruptions from a similar source region, which we have identified to be the Japanese mainland, 350 km away. In particular, diagnostic trace element ratios (e.g., Th/La, Sm/La, Rb/Hf, Th/Nb, and U/Th) and isotopic data indicate a marked contribution from a mantle source beneath continental crust, which is most consistent with a Japanese mainland source and likely excludes the Izu-Bonin island arc and back arc as a source region for the younger TST beds. Nevertheless, some of the chemical data measured on the oldest sandstone bed (TST 3b, Unit IIb) show affinity to or can clearly be attributed to an Izu-Bonin composition. While we cannot completely exclude the possibility that all TST beds derived from unknown and exotic Izu-Bonin source(s), the collected lines of evidence are most consistent with an origin from the paleo-Honshu arc for TST 1 through 3a. We therefore suggest the former collision zone between the Izu-Bonin arc and Honshu paleo-arc as the most likely region where the eruptive products entered the ocean, also concurrent with nearby (˜200 km) possible Miocene source areas for the tuffaceous sandstones at the paleo-NE-Honshu arc. Estimating the distribution area of the tuffaceous sandstones in the Miocene between this source region and the ˜350 km distant Expedition 322, using bathymetric constraints, we calculate that the sandstone beds represent minimum erupted magma volumes between ˜1 and 17 km3 (Dense Rock Equivalent (DRE)). We conclude that several large volume eruptions occurred during the Late Miocene time next to the collision zone of paleo-Honshu and Izu-Bonin arc and covered the entire Philippine Sea plate with meter thick, sheet-like pyroclastic deposits that are now subducted in the Nankai subduction zone.

Pre-eruption recharge of the Bishop magma system

USGS Publications Warehouse

Wark, D.A.; Hildreth, W.; Spear, F.S.; Cherniak, D.J.; Watson, E.B.

2007-01-01

The 650 km3 rhyolitic Bishop Tuff (eastern California, USA), which is stratigraphically zoned with respect to temperatures of mineral equilibration, reflects a corresponding thermal gradient in the source magma chamber. Consistent with previous work, application of the new TitaniQ (Ti-in-quartz) thermometer to quartz phenocryst rims documents an ???100 ??C temperature increase with chamber depth at the time of eruption. Application of TitaniQ to quartz phenocryst cores, however, reveals lower temperatures and an earlier gradient that was less steep, with temperature increasing with depth by only ???30 ??C. In many late-erupted crystals, sharp boundaries that separate low-temperature cores from high-temperature rims cut internal cathodoluminescent growth zoning, indicating partial phenocryst dissolution prior to crystallization of the high-temperature rims. Rimward jumps in Ti concentration across these boundaries are too abrupt (e.g., 40 ppm across a distance of <10 ??m) to have survived magmatic temperatures for more than ???100 yr. We interpret these observations to indicate heating-induced partial dissolution of quartz, followed by growth of high-temperature rims (made possible by lowering of water activity due to addition of CO2) within 100 yr of the climactic 760 ka eruption. Hot mafic melts injected into deeper parts of the magma system were the likely source of heat and CO2, raising the possibility that eruption and caldera collapse owe their origin to a recharge event. ?? 2007 Geological Society of America.

Shifts in the eruptive styles at Stromboli in 2010–2014 revealed by ground-based InSAR data

PubMed Central

Di Traglia, Federico; Battaglia, Maurizio; Nolesini, Teresa; Lagomarsino, Daniela; Casagli, Nicola

2015-01-01

Ground-Based Interferometric Synthetic Aperture Radar (GBInSAR) is an efficient technique for capturing short, subtle episodes of conduit pressurization in open vent volcanoes like Stromboli (Italy), because it can detect very shallow magma storage, which is difficult to identify using other methods. This technique allows the user to choose the optimal radar location for measuring the most significant deformation signal, provides an exceptional geometrical resolution, and allows for continuous monitoring of the deformation. Here, we present and model ground displacements collected at Stromboli by GBInSAR from January 2010 to August 2014. During this period, the volcano experienced several episodes of intense volcanic activity, culminated in the effusive flank eruption of August 2014. Modelling of the deformation allowed us to estimate a source depth of 482 ± 46 m a.s.l. The cumulative volume change was 4.7 ± 2.6 × 105 m3. The strain energy of the source was evaluated 3–5 times higher than the surface energy needed to open the 6–7 August eruptive fissure. The analysis proposed here can help forecast shifts in the eruptive style and especially the onset of flank eruptions at Stromboli and at similar volcanic systems (e.g. Etna, Piton de La Fournaise, Kilauea). PMID:26323251

The eruptive history of the Trous Blancs pit craters, La Réunion Island: The origin of a 24 km long lava flow

NASA Astrophysics Data System (ADS)

Walther, Georg; Frese, Ingmar; Di Muro, Andrea; Kueppers, Ulrich; Michon, Laurent; Métrich, Nicole

2015-04-01

The assessment of volcanic hazards is strongly based on the past eruptive behaviour of volcanoes and its morphological parameters. Since past eruption characteristics and their frequency provide the best probabilities of such eruptions for the future, understanding the complete eruptive history of a volcano is one of the most powerful tools in assessing the potential hazards or eruptions. At Piton de la Fournaise (PdF) volcano (La Réunion, Indian Ocean), the most frequent style of activity is the effusion of lava flows, which pose the greatest hazard by invasion of inhabited areas and destruction of human property. Here we examined the eruptive history of a previously uninvestigated area, believed to be the origin of a 24 km long lava flow. The eruptions recurrence time of PdF is about one eruption every 9 months in the central caldera. Besides this central activity, eruptive vents have been built along three main rift zones cutting the edifice during the last 50 kyrs. In this study we focused on the largest rift zone of about 15 km width and 20 km length, which extends in a north westerly direction between PdF and the nearby Piton des Neiges volcanic complex. This rift zone is typified by deep seismicity (up to 30 km), emitting mostly primitive magmas, indicative of high fluid pressures (up to 5 kbar) and large volume eruptions. Our area of investigation focused on four consecutively aligned pit craters called the Trous Blancs. These have been identified [1] as the source area of one of the youngest (ca. 6 kyrs) and largest lava field, which extends for 24 km from a height of 1800m asl, passing Le Tampon and Saint Pierre city, until it reaches the coast. To gain insight into the development of this eruption and possible future similar activity, we collected new field data (including stratigraphic logs, a geological map of the area, C-14 dating and geochemical analyses of the eruptive products). Fieldwork revealed that the eruption initiated with intense fountaining activity, producing a m-thick bed of loose black scoria, which becomes densely welded in its upper part. It was followed by an alternation of volume rich lava effusions and strombolian activity and deposition of meter-thick massive units of olivine basalt, alternating with coarse scoria beds in the proximal area. Activity ended with the emplacement of a dm sized bed of glassy, dense scoria and a stratified lithic breccia, marking the pit crater formation. Preliminary dating suggested that this type of eruption could have a millennial recurrence time at PdF. Reoccurring similar activity on the NW rift represents a major source of risk for this now densely populated region (more than 150,000 people living in the affected area). [1] Villeneuve, N., and P. Bachélery (2006),Revue de la typologie des eruptions au Piton de La Fournaise, processus et risqué volcaniques associés, Cybergeo: European Journal of Geography, 330,1-26

Hierarchy of facies of pyroclastic flow deposits generated by Laacher See type eruptions

NASA Astrophysics Data System (ADS)

Freundt, A.; Schmincke, H.-U.

1985-04-01

The upper Quaternary pyroclastic flow deposits of Laacher See volcano show compositional and structural facies variations on four different scales: (1) eruptive units of pyroclastic flows, composed of many flow units; (2) depositional cycles of as many as five flow units; flow units containing (3) regional intraflow-unit facies; and (4) local intraflow-unit subfacies. These facies can be explained by successively overlapping processes beginning in the magma column and ending with final deposition. The pyroclastic flow deposits thus reflect major aspects of the eruptive history of Laacher See volcano: (a) drastic changes in eruptive mechanism due to increasing access of water to the magma chamber and (b) change in chemical composition and crystal and gas content as evacuation of a compositionally zoned magma column progressed. The four scales of facies result from four successive sets of processes: (1) differentiation in the magma column and external factors governing the mechanism of eruption; (2) temporal variations of factors inducing eruption column collapse; (3) physical conditions in the eruption column and the way in which its collapse proceeds; and (4) interplay of flow-inherent and morphology-induced transport mechanics.

Integrating volcanic gas monitoring with other geophysical networks in Iceland

NASA Astrophysics Data System (ADS)

Pfeffer, Melissa A.

2017-04-01

The Icelandic Meteorological Office/Icelandic Volcano Observatory is rapidly developing and improving the use of gas measurements as a tool for pre- and syn-eruptive monitoring within Iceland. Observations of deformation, seismicity, hydrological properties, and gas emissions, united within an integrated approach, can provide improved understanding of subsurface magma movements. This is critical to evaluate signals prior to and during volcanic eruptions, issue timely eruption warnings, forecast eruption behavior, and assess volcanic hazards. Gas measurements in Iceland need to be processed to account for the high degree of gas composition alteration due to interaction with external water and rocks. Deeply-sourced magmatic gases undergo reactions and modifications as they move to the surface that exercise a strong control on the composition of surface emissions. These modifications are particularly strong at ice-capped volcanoes where most surface gases are dissolved in glacial meltwater. Models are used to project backwards from surface gas measurements to what the magmatic gas composition was prior to upward migration. After the pristine magma gas composition has been determined, it is used together with fluid compositions measured in mineral hosted melt inclusions to calculate magmatic properties to understand magma storage and migration and to discern if there have been changes in the volcanic system. The properties derived from surface gas measurements can be used as input to models interpreting deformation and seismic observations, and can be used as an additional, independent observation when interpreting hydrological and seismic changes. An integrated approach aids with determining whether observed hydro/geological changes can be due to the presence of shallow magma. Constraints on parameters such as magma gas content, viscosity and compressibility can be provided by the approach described above, which can be utilized syn-eruptively to help explain differences between erupted volumes and the inferred volume change of magma chambers. We will describe two recent examples of integrated monitoring in Iceland 1) syn-eruptive gas and deformation measurements used to simulate the subsurface properties of the magma from the 2014-2015 eruption of Bárðarbunga and 2) hydrological, seismic, and gas measurements made during the 2014 Sólheimajökull jökulhlaup used to discriminate between magmatic and hydrothermal origin of the flood and to perform a frequency analysis of past minor hydrothermal jökulhlaups.

Palaeomagnetic Emplacement Temperature Determinations of Pyroclastic and Volcaniclastic Deposits in Southern African Kimberlite Pipes

NASA Astrophysics Data System (ADS)

Fontana, G.; Mac Niocaill, C.; Brown, R.; Sparks, R. S.; Matthew, F.; Gernon, T. M.

2009-12-01

Kimberlites are complex, ultramafic and diamond-bearing volcanic rocks preserved in volcanic pipes, dykes and craters. The formation of kimberlite pipes is a strongly debated issue and two principal theories have been proposed to explain pipe formation: (1) the explosive degassing of magma, and (2) the interaction of rising magma with groundwater (phreatomagmatism). Progressive thermal demagnetization studies are a powerful tool for determining the emplacement temperatures of ancient volcanic deposits and we present the first application of such techniques to kimberlite deposits. Lithic clasts were sampled from a variety of lithofacies, from three pipes for which the internal geology is well constrained (A/K1 pipe, Orapa Mine, Botswana and the K1 and K2 pipes, Venetia Mine, South Africa). The sampled deposits included massive and layered vent-filling breccias with varying abundances of lithic inclusions and layered crater-filling pyroclastic deposits, talus breccias and volcaniclastic breccias. Lithic clasts sampled from layered and massive vent-filling pyroclastic deposits in A/K1 were emplaced at >590° C. Results from K1 and K2 provide a maximum emplacement temperature limit for vent-filling breccias of 420-460° C; and constrain equilibrium deposit temperatures at 300-340° C. Crater-filling volcaniclastic kimberlite breccias and talus deposits from A/K1 were emplaced at ambient temperatures, consistent with infilling of the pipe by post-eruption epiclastic processes. Identified within the epiclastic crater-fill succession is a laterally extensive 15-20 metre thick kimberlite pyroclastic flow deposit emplaced at temperatures of 220-440° C. It overlies the post-eruption epiclastic units and is considered an extraneous pyroclastic kimberlite deposit erupted from another kimberlite vent. The results provide important constraints on kimberlite emplacement mechanisms and eruption dynamics. Emplacement temperatures of >590°C for pipe-filling pyroclastic deposits are consistent with volatile-driven eruptions, and suggest phreatomagmatism did not play a major role in the generation of the deposits. The discovery of an extraneous pyroclastic flow deposit within the Orapa A/K1 epiclastic crater, which was erupted from another vent, suggests kimberlite eruptions are capable of producing sustained eruption columns and thick pyroclastic deposits involving significant transport away from source.

Character, mass, distribution, and origin of tephra-fall deposits of the 1989-1990 eruption of redoubt volcano, south-central Alaska

USGS Publications Warehouse

Scott, W.E.; McGimsey, R.G.

1994-01-01

The 1989-1990 eruption of Redoubt Volcano spawned about 20 areally significant tephra-fall deposits between December 14, 1989 and April 26, 1990. Tephra plumes rose to altitudes of 7 to more than 10 km and were carried mainly northward and eastward by prevailing winds, where they substantially impacted air travel, commerce, and other activities. In comparison to notable eruptions of the recent past, the Redoubt events produced a modest amount of tephra-fall deposits - 6 ?? 107 to 5 ?? 1010 kg for individual events and a total volume (dense-rock equivalent) of about 3-5 ?? 107 m3 of andesite and dacite. Two contrasting tephra types were generated by these events. Pumiceous tephra-fall deposits of December 14 and 15 were followed on December 16 and all later events by fine-grained lithic-crystal tephra deposits, much of which fell as particle aggregates. The change in the character of the tephra-fall deposits reflects their fundamentally different modes of origin. The pumiceous deposits were produced by magmatically driven explosions. The finegrained lithic-crystal deposits were generated by two processes. Hydrovolcanic vent explosions generated tephrafall deposits of December 16 and 19. Such explosions continued as a tephra source, but apparently with diminishing importance, during events of January and February. Ash clouds of lithic pyroclastic flows generated by collapse of actively growing lava domes probably contributed to tephra-fall deposits of all events from January 2 to April 26, and were the sole source of tephra fall for at least the last 4 deposits. ?? 1994.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lugaz, N.; Shibata, K.; Downs, C.

We present a numerical investigation of the coronal evolution of a coronal mass ejection (CME) on 2005 August 22 using a three-dimensional thermodynamic magnetohydrodynamic model, the space weather modeling framework. The source region of the eruption was anemone active region (AR) 10798, which emerged inside a coronal hole. We validate our modeled corona by producing synthetic extreme-ultraviolet (EUV) images, which we compare to EIT images. We initiate the CME with an out-of-equilibrium flux rope with an orientation and chirality chosen in agreement with observations of an H{alpha} filament. During the eruption, one footpoint of the flux rope reconnects with streamermore » magnetic field lines and with open field lines from the adjacent coronal hole. It yields an eruption which has a mix of closed and open twisted field lines due to interchange reconnection and only one footpoint line-tied to the source region. Even with the large-scale reconnection, we find no evidence of strong rotation of the CME as it propagates. We study the CME deflection and find that the effect of the Lorentz force is a deflection of the CME by about 3{sup 0} R{sup -1}{sub sun} toward the east during the first 30 minutes of the propagation. We also produce coronagraphic and EUV images of the CME, which we compare with real images, identifying a dimming region associated with the reconnection process. We discuss the implication of our results for the arrival at Earth of CMEs originating from the limb and for models to explain the presence of open field lines in magnetic clouds.« less

Modeling Potential Tephra Dispersal at Yucca Mountain, Nevada

NASA Astrophysics Data System (ADS)

Hooper, D.; Franklin, N.; Adams, N.; Basu, D.

2006-12-01

Quaternary basaltic volcanoes exist within 20 km [12 mi] of the potential radioactive waste repository at Yucca Mountain, Nevada, and future basaltic volcanism at the repository is considered a low-probability, potentially high-consequence event. If radioactive waste was entrained in the conduit of a future volcanic event, tephra and waste could be transported in the resulting eruption plume. During an eruption, basaltic tephra would be dispersed primarily according to the height of the eruption column, particle-size distribution, and structure of the winds aloft. Following an eruption, contaminated tephra-fall deposits would be affected by surface redistribution processes. The Center for Nuclear Waste Regulatory Analyses developed the computer code TEPHRA to calculate atmospheric dispersion and subsequent deposition of tephra and spent nuclear fuel from a potential eruption at Yucca Mountain and to help prepare the U.S. Nuclear Regulatory Commission to review a potential U.S. Department of Energy license application. The TEPHRA transport code uses the Suzuki model to simulate the thermo-fluid dynamics of atmospheric tephra dispersion. TEPHRA models the transport of airborne pyroclasts based on particle diffusion from an eruption column, horizontal diffusion of particles by atmospheric and plume turbulence, horizontal advection by atmospheric circulation, and particle settling by gravity. More recently, TEPHRA was modified to calculate potential tephra deposit distributions using stratified wind fields based on upper atmosphere data from the Nevada Test Site. Wind data are binned into 1-km [0.62-mi]-high intervals with coupled distributions of wind speed and direction produced for each interval. Using this stratified wind field and discretization with respect to height, TEPHRA calculates particle fall and lateral displacement for each interval. This implementation permits modeling of split wind fields. We use a parallel version of the code to calculate expected tephra and high-level waste accumulation at specified points on a two-dimensional spatial grid, thereby simulating a three- dimensional initial deposit. To assess subsequent tephra and high-level waste redistribution and resuspension, modeling grids were devised to measure deposition in eolian and fluvial source regions. The eolian grid covers an area of 2,600 km2 [1,000 mi2] and the fluvial grid encompasses 318 km2 [123 mi2] of the southernmost portion of the Fortymile Wash catchment basin. Because each realization is independent, distributions of tephra and high-level waste reflect anticipated variations in source-term and transport characteristics. This abstract is an independent product of the Center for Nuclear Waste Regulatory Analyses and does not necessarily reflect the view or regulatory position of the U.S. Nuclear Regulatory Commission.

Two-step solar filament eruptions

NASA Astrophysics Data System (ADS)

Filippov, B.

2018-04-01

Coronal mass ejections (CMEs) are closely related to eruptive filaments and usually are the continuation of the same eruptive process into the upper corona. There are failed filament eruptions when a filament decelerates and stops at some greater height in the corona. Sometimes the filament after several hours starts to rise again and develops into the successful eruption with a CME formation. We propose a simple model for the interpretation of such two-step eruptions in terms of equilibrium of a flux rope in a two-scale ambient magnetic field. The eruption is caused by a slow decrease of the holding magnetic field. The presence of two critical heights for the initiation of the flux-rope vertical instability allows the flux rope to stay after the first jump some time in a metastable equilibrium near the second critical height. If the decrease of the ambient field continues, the next eruption step follows.

Diverse Eruptive Activity Revealed by Acoustic and Electromagnetic Observations of the 14 July 2013 Intense Vulcanian Eruption of Tungurahua Volcano, Ecuador

NASA Astrophysics Data System (ADS)

Anderson, J. F.; Johnson, J. B.; Steele, A. L.; Ruiz, M. C.; Brand, B. D.

2018-04-01

During the powerful July 2013 eruption of Tungurahua volcano, Ecuador, we recorded exceptionally high amplitude, long-period infrasound (1,600-Pa peak-to-peak amplitude, 5.5-s period) on sensors within 2 km of the vent alongside electromagnetic signals from volcanic lightning serendipitously captured as interference. This explosion was one of Tungurahua's most powerful vulcanian eruptions since recent activity began in 1999, and its acoustic wave is among the most powerful volcanic infrasound ever recorded anywhere. We use these data to quantify erupted volume from the main explosion and to classify postexplosive degassing into distinct emission styles. Additionally, we demonstrate a highly effective method of recording lightning-related electromagnetic signals alongside infrasound. Detailed chronologies of powerful vulcanian eruptions are rare; this study demonstrates that diverse eruptive processes can occur in such eruptions and that near-vent infrasound and electromagnetic data can elucidate them.

Eruptions at Lone Star geyser, Yellowstone National Park, USA: 2. Constraints on subsurface dynamics

USGS Publications Warehouse

Vandemeulebrouck, Jean; Sohn, Robert A.; Rudolph, Maxwell L.; Hurwitz, Shaul; Manga, Michael; Johnston, Malcolm J.S.; Soule, S. Adam; McPhee, Darcy K.; Glen, Jonathan M.G.; Karlstrom, Leif; Murphy, Fred

2014-01-01

We use seismic, tilt, lidar, thermal, and gravity data from 32 consecutive eruption cycles of Lone Star geyser in Yellowstone National Park to identify key subsurface processes throughout the geyser's eruption cycle. Previously, we described measurements and analyses associated with the geyser's erupting jet dynamics. Here we show that seismicity is dominated by hydrothermal tremor (~5–40 Hz) attributed to the nucleation and/or collapse of vapor bubbles. Water discharge during eruption preplay triggers high-amplitude tremor pulses from a back azimuth aligned with the geyser cone, but during the rest of the eruption cycle it is shifted to the east-northeast. Moreover, ~4 min period ground surface displacements recur every 26 ± 8 min and are uncorrelated with the eruption cycle. Based on these observations, we conclude that (1) the dynamical behavior of the geyser is controlled by the thermo-mechanical coupling between the geyser conduit and a laterally offset reservoir periodically filled with a highly compressible two-phase mixture, (2) liquid and steam slugs periodically ascend into the shallow crust near the geyser system inducing detectable deformation, (3) eruptions occur when the pressure decrease associated with overflow from geyser conduit during preplay triggers an unstable feedback between vapor generation (cavitation) and mass discharge, and (4) flow choking at a constriction in the conduit arrests the runaway process and increases the saturated vapor pressure in the reservoir by a factor of ~10 during eruptions.

Towards a Numerical Description of Volcano Aeroacoustic Source Processes using Lattice Boltzmann Strategies

NASA Astrophysics Data System (ADS)

Brogi, F.; Malaspinas, O.; Bonadonna, C.; Chopard, B.; Ripepe, M.

2015-12-01

Low frequency (< 20Hz) acoustic measurements have a great potential for the real time characterization of volcanic plume source parameters. Using the classical source theory, acoustic data can be related to the exit velocity of the volcanic jet and to mass eruption rate, based on the geometric constrain of the vent and the mixture density. However, the application of the classical acoustic source models to volcanic explosive eruptions has shown to be challenging and a better knowledge of the link between the acoustic radiation and actual volcanic fluid dynamics processes is required. New insights into this subject could be given by the study of realistic aeroacoustic numerical simulations of a volcanic jet. Lattice Boltzmann strategies (LBS) provide the opportunity to develop an accurate, computationally fast, 3D physical model for a volcanic jet. In the field of aeroacoustic applications, dedicated LBS has been proven to have the low dissipative properties needed for capturing the weak acoustic pressure fluctuations. However, due to the big disparity in magnitude between the flow and the acoustic disturbances, even weak spurious noise sources in simulations can ruin the accuracy of the acoustic predictions. Reflected waves from artificial boundaries defined around the flow region can have significant influence on the flow field and overwhelm the acoustic field of interest. In addition, for highly multiscale turbulent flows, such as volcanic plumes, the number of grid points needed to represent the smallest scales might become intractable and the most complicated physics happen only in small portions of the computational domain. The implementation of the grid refinement, in our model allow us to insert local finer grids only where is actually needed and to increase the size of the computational domain for running more realistic simulations. 3D LBS model simulations for turbulent jet aeroacoustics have been accurately validated. Both mean flow and acoustic results are in good agreement with theory and experimental data available in the literature.

Nonlinear inversion of tilt-affected very long period records of explosive eruptions at Fuego volcano

NASA Astrophysics Data System (ADS)

Waite, Gregory P.; Lanza, Federica

2016-10-01

Magmatic processes produce a rich variety of volcano seismic signals, ranging over several orders of magnitude in frequency and over a wide range of mechanism types. We examined signals from 400 to 10 s period associated with explosive eruptions at Fuego volcano, Guatemala, that were recorded over 19 days in 2009 on broadband stations with 30 s and 60 s corner periods. The raw data from the closest stations include tilt effects on the horizontal components but also have significant signal at periods below the instrument corners on the vertical components, where tilt effects should be negligible. We address the problems of tilt-affected horizontal waveforms through a joint waveform inversion of translation and rotation, which allows for an investigation of the varying influence of tilt with period. Using a phase-weighted stack of six similar events, we invert for source moment tensor using multiple bands. We use a grid search for source type and constrained inversions, which provides a quantitative measure of source mechanism reliability. The 30-10 s band-pass results are consistent with previous work that modeled data with a combined two crack or crack and pipe model. At the longest-period band examined, 400-60 s, the source mechanism is like a pipe that could represent the shallowest portion of the conduit. On the other hand, source mechanisms in some bands are unconstrained, presumably due to the combined tilt-dominated and translation-dominated signals, which are not coincident in space and have different time spans.

Explosive volcanism may not be an inevitable consequence of magma fragmentation.

PubMed

Gonnermann, Helge M; Manga, Michael

2003-11-27

The fragmentation of magma, containing abundant gas bubbles, is thought to be the defining characteristic of explosive eruptions. When viscous stresses associated with the growth of bubbles and the flow of the ascending magma exceed the strength of the melt, the magma breaks into disconnected fragments suspended within an expanding gas phase. Although repeated effusive and explosive eruptions for individual volcanoes are common, the dynamics governing the transition between explosive and effusive eruptions remain unclear. Magmas for both types of eruptions originate from sources with similar volatile content, yet effusive lavas erupt considerably more degassed than their explosive counterparts. One mechanism for degassing during magma ascent, consistent with observations, is the generation of intermittent permeable fracture networks generated by non-explosive fragmentation near the conduit walls. Here we show that such fragmentation can occur by viscous shear in both effusive and explosive eruptions. Moreover, we suggest that such fragmentation may be important for magma degassing and the inhibition of explosive behaviour. This implies that, contrary to conventional views, explosive volcanism is not an inevitable consequence of magma fragmentation.

Magma-ice-sediment interactions and the origin of lava/hyaloclastite sequences in the Síða formation, South Iceland

USGS Publications Warehouse

Banik, Tenley J.; Wallace, Paul J.; Höskuldsson, Ármann; Miller, Calvin F.; Bacon, Charles R.; Furbish, David J.

2013-01-01

Products of subglacial volcanism can illuminate reconstructions of paleo-environmental conditions on both local and regional scales. Competing interpretations of Pleistocene conditions in south Iceland have been proposed based on an extensive sequence of repeating lava-and-hyaloclastite deposits in the Síða district. We propose here a new eruptive model and refine the glacial environment during eruption based on field research and analytical data for the Síða district lava/hyaloclastite units. Field observations from this and previous studies reveal a repeating sequence of cogenetic lava and hyaloclastite deposits extending many kilometers from their presumed eruptive source. Glasses from lava selvages and unaltered hyaloclastites have very low H2O, S, and CO2 concentrations, indicating significant degassing at or close to atmospheric pressure prior to quenching. We also present a scenario that demonstrates virtual co-emplacement of the two eruptive products. Our data and model results suggest repeated eruptions under thin ice or partially subaerial conditions, rather than eruption under a thick ice sheet or subglacial conditions as previously proposed.

Characterizing Volcanic Processes using Near-bottom, High Resolution Magnetic Mapping of the Caldera and Inner Crater of the Kick'em Jenny Submarine Volcano

NASA Astrophysics Data System (ADS)

Ruchala, T. L.; Chen, M.; Tominaga, M.; Carey, S.

2016-12-01

Kick'em Jenny (KEJ) is an active submarine volcano located in the Lesser Antilles subduction zone, 7.5 km north of the Caribbean island Grenada. KEJ, known as one of the most explosive volcanoes in Caribbean, erupted 12 times since 1939 with recent eruptions in 2001 and possibly in 2015. Multiple generations of submarine landslides and canyons have been observed in which some of them can be attributed to past eruptions. The structure of KEJ can be characterized as a 1300 m high conical profile with its summit crater located around 180 m in depth. Active hydrothermal venting and dominantly CO2 composition gas seepage take place inside this 250m diameter crater, with the most activity occurring primarily within a small ( 70 x 110 m) depression zone (inner crater). In order to characterize the subsurface structure and decipher the processes of this volcanic system, the Nautilus NA054 expedition in 2014 deployed the underwater Remotely Operated Vehicle (ROV) Hercules to conduct near-bottom geological observations and magnetometry surveys transecting KEJ's caldera. Raw magnetic data was corrected for vehicle induced magnetic noise, then merged with ROV to ship navigation at 1 HZ. To extract crustal magnetic signatures, the reduced magnetic data was further corrected for external variations such as the International Geomagnetic Reference Field and diurnal variations using data from the nearby San Juan Observatory. We produced a preliminary magnetic anomaly map of KEJ's caldera for subsequent inversion and forward modeling to delineate in situ magnetic source distribution in understanding volcanic processes. We integrated the magnetic characterization of the KEJ craters with shipboard multibeam, ROV visual descriptions, and photomosaics. Initial observations show the distribution of short wavelength scale highly magnetized source centered at the north western part of the inner crater. Although locations of gas seeps are ubiquitous over the inner crater area along ROV survey lines, some of their provinces coincide with distinctive magnetic characters, suggesting possible in situ structural or alteration boundaries (i.e. subsurface faults and hydrothermal destruction zones).

Characterization of organic contaminants in environmental samples associated with mount St. Helens 1980 volcanic eruption

USGS Publications Warehouse

Pereira, W.E.

1982-01-01

Volcanic ash, surface-water, and bottom-material samples obtained in the vicinity of Mount St. Helens after the May 18, 1980, eruption were analyzed for organic contaminants by using capillary gas chromatography-mass spectrometry-computer techniques. Classes of compounds identified include n-alkanes, fatty acids, dicarboxylic acids, aromatic acids and aldehydes, phenols, resin acids, terpenes, and insect juvenile hormones. The most probable source of these compounds is from pyrolysis of plant and soil organic matter during and after the eruption. The toxicity of selected compounds and their environmental significance are discussed.

Impacts of Volcanic Eruptions and Disturbances on Mid-Ocean Ridge Biological Communities

NASA Astrophysics Data System (ADS)

Shank, T. M.

2009-12-01

Understanding ecological processes in mid-ocean ridge benthic environments requires a knowledge of the temporal and spatial scales over which those processes take place. Over the past 17 years, the detection and now “direct observation” of more than nine seafloor eruptions and even more numerous and diverse geologic disturbances (e.g., dyking and cracking events) have provided a broad spectrum of perturbating seafloor phenomena that serve as key agents for creating new vent habitat, providing bursts of nutrients, supporting blooms of microbial and macrobiological communities, imparting magmatic/hydrothermal fluxes, controlling fluid geochemical composition, altering the successional stage of faunal communities, guiding the temporal and spatial scales of local extinction and recolonization, and for directing the evolution of physiological adaptations. Eruptions have now been documented on the East Pacific Rise, Southern Mid-Atlantic Ridge, Gakkel Ridge, Galapagos Rift, CoAxial, Northwest Rota, West Mata, and Loihi Seamounts, representing diverse emergent eruptive styles, from explosive pyroclastic deposits to thin lava flows, these processes are occurring in different biogeographic regions hosting different regional species pools. As such, not only do these eruptions provide a method of establishing a “time-zero” with which to construct manipulative temporal experiments, but also provide a contextual framework with which to interpret the affect eruptions and disturbance have on ecological interactions in different biogeographic regions of the world, and the timescales over which they vary. The temporal and spatial impact of these different eruptive styles in relation to the alteration of biological community structure will be discussed.

Spatial analysis of the impacts of the Chaitén volcano eruption (Chile) in three fluvial systems

NASA Astrophysics Data System (ADS)

Ulloa, H.; Iroumé, A.; Picco, L.; Mohr, C. H.; Mazzorana, B.; Lenzi, M. A.; Mao, L.

2016-08-01

The eruption of the Chaitén volcano in May 2008 generated morphological and ecological disturbances in adjacent river basins, and the magnitude of these disturbances depended on the type of dominant volcanic process affecting each of them. The aim of this study is to analyse the morphological changes in different periods in river segments of the Blanco, El Amarillo and Rayas river basins located near the Chaitén volcano. These basins suffered disturbances of different intensity and spatial distribution caused by tephra fall, dome collapses and pyroclastic density currents that damaged hillslope forests, widened channels and destroyed island and floodplain vegetation. Changes continued to occur in the fluvial systems in the years following the eruption, as a consequence of the geomorphic processes indirectly induced by the eruption. Channel changes were analyzed by comparing remote images of pre and post-eruption conditions. Two periods were considered: the first from 2008 to 2009-2010 associated with the explosive and effusive phases of the eruption and the second that correspond to the post-eruption stage from 2009-2010 to 2013. Following the first phases channel segments widened 91% (38 m/yr), 6% (7 m/yr) and 7% (22 m/yr) for Blanco, Rayas and El Amarillo Rivers, respectively, compared to pre-eruption condition. In the second period, channel segments additionally widened 42% (8 m/yr), 2% (2 m/yr) and 5% (4 m/yr) for Blanco, Rayas and El Amarillo Rivers, respectively. In the Blanco River 62 and 82% of the islands disappeared in the first and second period, respectively, which is 6-8 times higher than in the El Amarillo approximately twice the Rayas. Sinuosity increased after the eruption only in the Blanco River but the three study channels showed a high braiding intensity mainly during the first post-eruption period. The major disturbances occurred during the eruptive and effusive phases of Chaitén volcano, and the intensity of these disturbances reflects the magnitude of the dominant volcanic processes affecting each basin. Inputs of sediment from dome collapses and pyroclastic density currents and not ash fall seem to explain morphologic channel change magnitudes in the study segments. The resulting knowledge can facilitate land use planning and design of river restoration projects in areas affected by volcanic eruptions disturbances.

Ignimbrites of Armenia - Paleomagnetic constraints on flow direction and stratigraphy of pyroclastic activity of Mount Aragats

NASA Astrophysics Data System (ADS)

Kirscher, Uwe; Meliksetian, Khachatur; Gevorgyan, Hripsime; Navasardyan, Gevorg; Bachtadse, Valerian

2017-04-01

The Aragats volcano is one of the largest stratovolcanoes within the Turkish-Armenian-Iranian orogenic plateau. It is located close to the Armenian capital Yerevan, and only 30 km from the only nuclear power plant within the country. Additional to numerous lava flows, Mount Aragats is thought to be the source of at least two large pyroclastic eruptions leading to a huge number of ignimbrite outcrops, which are located surrounding Mount Aragats with an evaluated eruption radius of 50 km. The age of several ignimbrite outcrops has recently been determined to be 0.65 Ma (Meliksetian et al., 2014). The different ignimbrite flows are characterized by huge diversity of colors, degree of welding and textures. Due to that reason some disagreement exist on how these outcrops can be linked and how the eruption process actually happened in terms of different eruption phases and mixing mechanism of magmas during the eruption. To add constraints to this debate we carried out an intensive paleomagnetic investigation on most of the ignimbrite outcrops (32 sites) in terms of directional and anisotropy measurements. Paleomagnetic directional measurements yield basically two polarities: (1) a well grouped normal polarity is present in the majority of the studied sites including 3 sites which have supposedly originated from a different vent located on Turkish territory in the west; (2) a reversed polarity of the remaining sites with a somewhat increased scatter. Based on secular variation arguments and considering the high quality of the data we suggest that at least all young outcrops represent a single eruption phase in the area at 0.65 Ma, which is in agreement with an occurrence during the Brunhes geomagnetic chron. Additional to that, at least one earlier phase of pyroclastic activity took place prior to the Brunhes-Matuyama boundary (0.781 Ma). Anisotropy of magnetic susceptibility (AMS) suggests initial radial flow directions, which shortly after the eruption become topographically controlled. Such explosive eruptions with VEI≥5 are usually considered among most hazardous volcanic phenomena, therefore detailed multidisciplinary studies of such events occurred in the past are significantly important to estimate recurrence rates of such eruptions, their magnitudes to probabilistically access potential volcanic hazards to populated places and critical infrastructure. Melisketian, K., Savov, I., Connor, C., Halama, R., Jrbashyan, R., Navasardyan, G., Ghukasyan, Y., Gevorgyan, H., Manucharyan, D., Ishizuka, O., Quidelleur, X., Germa, A., 2014. Aragats stratovolcano in Armenia - volcano-stratigraphy and petrology. EGU General Assembly Conference Abstracts 16, 567.

Eruption patterns of the chilean volcanoes Villarrica, Llaima, and Tupungatito

NASA Astrophysics Data System (ADS)

Muñoz, Miguel

1983-09-01

The historical eruption records of three Chilean volcanoes have been subjected to many statistical tests, and none have been found to differ significantly from random, or Poissonian, behaviour. The statistical analysis shows rough conformity with the descriptions determined from the eruption rate functions. It is possible that a constant eruption rate describes the activity of Villarrica; Llaima and Tupungatito present complex eruption rate patterns that appear, however, to have no statistical significance. Questions related to loading and extinction processes and to the existence of shallow secondary magma chambers to which magma is supplied from a deeper system are also addressed. The analysis and the computation of the serial correlation coefficients indicate that the three series may be regarded as stationary renewal processes. None of the test statistics indicates rejection of the Poisson hypothesis at a level less than 5%, but the coefficient of variation for the eruption series at Llaima is significantly different from the value expected for a Poisson process. Also, the estimates of the normalized spectrum of the counting process for the three series suggest a departure from the random model, but the deviations are not found to be significant at the 5% level. Kolmogorov-Smirnov and chi-squared test statistics, applied directly to ascertaining to which probability P the random Poisson model fits the data, indicate that there is significant agreement in the case of Villarrica ( P=0.59) and Tupungatito ( P=0.3). Even though the P-value for Llaima is a marginally significant 0.1 (which is equivalent to rejecting the Poisson model at the 90% confidence level), the series suggests that nonrandom features are possibly present in the eruptive activity of this volcano.

Recurrent nova M31N 2008-12a: The 2017-eruption X-ray turn-off seen by Swift/XRT

NASA Astrophysics Data System (ADS)

Henze, M.; Darnley, M. J.; Shafter, A. W.; Kafka, S.; Kato, M.; Williams, S. C.; et al.

2018-01-01

The detection of supersoft X-ray source (SSS) emission from the 2017 eruption (ATel #11116) of the rapidly recurring nova M31N 2008-12a (Henze et al. 2014, 2015a, 2015b; Darnley et al. 2014, 2015, 2016) with the Neil Gehrels Swift observatory was announced in ATel #11130.

Risk assessment for tephra dispersal and sedimentation: the example of four Icelandic volcanoes

NASA Astrophysics Data System (ADS)

Biass, Sebastien; Scaini, Chiara; Bonadonna, Costanza; Smith, Kate; Folch, Arnau; Höskuldsson, Armann; Galderisi, Adriana

2014-05-01

In order to assist the elaboration of proactive measures for the management of future Icelandic volcanic eruptions, we developed a new approach to assess the impact associated with tephra dispersal and sedimentation at various scales and for multiple sources. Target volcanoes are Hekla, Katla, Eyjafjallajökull and Askja, selected for their high probabilities of eruption and/or their high potential impact. We combined stratigraphic studies, probabilistic strategies and numerical modelling to develop comprehensive eruption scenarios and compile hazard maps for local ground deposition and regional atmospheric concentration using both TEPHRA2 and FALL3D models. New algorithms for the identification of comprehensive probability density functions of eruptive source parameters were developed for both short and long-lasting activity scenarios. A vulnerability assessment of socioeconomic and territorial aspects was also performed at both national and continental scales. The identification of relevant vulnerability indicators allowed for the identification of the most critical areas and territorial nodes. At a national scale, the vulnerability of economic activities and the accessibility to critical infrastructures was assessed. At a continental scale, we assessed the vulnerability of the main airline routes and airports. Resulting impact and risk were finally assessed by combining hazard and vulnerability analysis.

Detecting and Characterizing Repeating Earthquake Sequences During Volcanic Eruptions

NASA Astrophysics Data System (ADS)

Tepp, G.; Haney, M. M.; Wech, A.

2017-12-01

A major challenge in volcano seismology is forecasting eruptions. Repeating earthquake sequences often precede volcanic eruptions or lava dome activity, providing an opportunity for short-term eruption forecasting. Automatic detection of these sequences can lead to timely eruption notification and aid in continuous monitoring of volcanic systems. However, repeating earthquake sequences may also occur after eruptions or along with magma intrusions that do not immediately lead to an eruption. This additional challenge requires a better understanding of the processes involved in producing these sequences to distinguish those that are precursory. Calculation of the inverse moment rate and concepts from the material failure forecast method can lead to such insights. The temporal evolution of the inverse moment rate is observed to differ for precursory and non-precursory sequences, and multiple earthquake sequences may occur concurrently. These observations suggest that sequences may occur in different locations or through different processes. We developed an automated repeating earthquake sequence detector and near real-time alarm to send alerts when an in-progress sequence is identified. Near real-time inverse moment rate measurements can further improve our ability to forecast eruptions by allowing for characterization of sequences. We apply the detector to eruptions of two Alaskan volcanoes: Bogoslof in 2016-2017 and Redoubt Volcano in 2009. The Bogoslof eruption produced almost 40 repeating earthquake sequences between its start in mid-December 2016 and early June 2017, 21 of which preceded an explosive eruption, and 2 sequences in the months before eruptive activity. Three of the sequences occurred after the implementation of the alarm in late March 2017 and successfully triggered alerts. The nearest seismometers to Bogoslof are over 45 km away, requiring a detector that can work with few stations and a relatively low signal-to-noise ratio. During the Redoubt eruption, earthquake sequences were observed in the months leading up to the eruptive activity beginning in March 2009 as well as immediately preceding 7 of the 19 explosive events. In contrast to Bogoslof, Redoubt has a local monitoring network which allows for better detection and more detailed analysis of the repeating earthquake sequences.

Magma ascent and lava flow emplacement rates during the 2011 Axial Seamount eruption based on CO2 degassing

NASA Astrophysics Data System (ADS)

Jones, M. R.; Soule, S. A.; Gonnermann, H. M.; Le Roux, V.; Clague, D. A.

2018-07-01

Quantitative metrics for eruption rates at mid-ocean ridges (MORs) would improve our understanding of the structure and formation of the uppermost oceanic crust and would provide a means to link volcanic processes with the conditions of the underlying magmatic system. However, these metrics remain elusive because no MOR eruptions have been directly observed. The possibility of disequilibrium degassing in mid-ocean ridge basalts (MORB), due to high eruptive depressurization rates, makes the analysis of volatile concentrations in MORB glass a promising method for evaluating eruption rates. In this study, we estimate magma ascent and lava flow emplacement rates during the 2011 eruption of Axial Seamount based on numerical modeling of diffusion-controlled bubble growth and new measurements of dissolved volatiles, vesicularity, and vesicle size distributions in erupted basalts. This dataset provides a unique view of the variability in magma ascent (∼0.02-1.2 m/s) and lava flow rates (∼0.1-0.7 m/s) during a submarine MOR eruption based on 50 samples collected from a >10 km long fissure system and three individual lava flow lobes. Samples from the 2011 eruption display an unprecedented range in dissolved CO2 concentrations, nearly spanning the full range observed on the global MOR system. The variable vesicularity and dissolved CO2 concentrations in these samples can be explained by differences in the extent of degassing, dictated by flow lengths and velocities during both vertical ascent and horizontal flow along the seafloor. Our results document, for the first time, the variability in magma ascent rates during a submarine eruption (∼0.02-1.2 m/s), which spans the global range previously proposed based on CO2 degassing. The slowest ascent rates are associated with hummocky flows while faster ascent rates produce channelized sheet flows. This study corroborates degassing-based models for eruption rates using comparisons with independent methods and documents the relationship between eruption dynamics, magma ascent rates, and the morphology of eruptive products. Globally, this approach allows interrogation of the processes that govern mid-ocean ridge eruptions and influence the formation of the oceanic crust.

Temporal variations in volumetric magma eruption rates of Quaternary volcanoes in Japan

NASA Astrophysics Data System (ADS)

Yamamoto, Takahiro; Kudo, Takashi; Isizuka, Osamu

2018-04-01

Long-term evaluations of hazard and risk related to volcanoes rely on extrapolations from volcano histories, including the uniformity of their eruption rates. We calculated volumetric magma eruption rates, compiled from quantitative eruption histories of 29 Japanese Quaternary volcanoes, and analyzed them with respect to durations spanning 101-105 years. Calculated eruption rates vary greatly (101-10-4 km3 dense-rock equivalent/1000 years) between individual volcanoes. Although large basaltic stratovolcanoes tend to have high eruption rates and relatively constant repose intervals, these cases are not representative of the various types of volcanoes in Japan. At many Japanese volcanoes, eruption rates are not constant through time, but increase, decrease, or fluctuate. Therefore, it is important to predict whether eruption rates will increase or decrease for long-term risk assessment. Several temporal co-variations of eruption rate and magmatic evolution suggest that there are connections between them. In some cases, magma supply rates increased in response to changing magma-generation processes. On the other hand, stable plumbing systems without marked changes in magma composition show decreasing eruption rates through time.[Figure not available: see fulltext.

The Driving Magnetic Field and Reconnection in CME/Flare Eruptions and Coronal Jets

NASA Technical Reports Server (NTRS)

Moore, Ronald L.

2010-01-01

Signatures of reconnection in major CME (coronal mass ejection)/flare eruptions and in coronal X-ray jets are illustrated and interpreted. The signatures are magnetic field lines and their feet that brighten in flare emission. CME/flare eruptions are magnetic explosions in which: 1. The field that erupts is initially a closed arcade. 2. At eruption onset, most of the free magnetic energy to be released is not stored in field bracketing a current sheet, but in sheared field in the core of the arcade. 3. The sheared core field erupts by a process that from its start or soon after involves fast "tether-cutting" reconnection at an initially small current sheet low in the sheared core field. If the arcade has oppositely-directed field over it, the eruption process from its start or soon after also involves fast "breakout" reconnection at an initially small current sheet between the arcade and the overarching field. These aspects are shown by the small area of the bright field lines and foot-point flare ribbons in the onset of the eruption. 4. At either small current sheet, the fast reconnection progressively unleashes the erupting core field to erupt with progressively greater force. In turn, the erupting core field drives the current sheet to become progressively larger and to undergo progressively greater fast reconnection in the explosive phase of the eruption, and the flare arcade and ribbons grow to become comparable to the pre-eruption arcade in lateral extent. In coronal X-ray jets: 1. The magnetic energy released in the jet is built up by the emergence of a magnetic arcade into surrounding unipolar "open" field. 2. A simple jet is produced when a burst of reconnection occurs at the current sheet between the arcade and the open field. This produces a bright reconnection jet and a bright reconnection arcade that are both much smaller in diameter that the driving arcade. 3. A more complex jet is produced when the arcade has a sheared core field and undergoes an ejective eruption in the manner of a miniature CME/flare eruption. The jet is then a combination of a miniature CME and the products of more widely distributed reconnection of the erupting arcade with the open field than in simple jets.

Determining the seismic source mechanism and location for an explosive eruption with limited observational data: Augustine Volcano, Alaska

NASA Astrophysics Data System (ADS)

Dawson, Phillip B.; Chouet, Bernard A.; Power, John

2011-02-01

Waveform inversions of the very-long-period components of the seismic wavefield produced by an explosive eruption that occurred on 11 January, 2006 at Augustine Volcano, Alaska constrain the seismic source location to near sea level beneath the summit of the volcano. The calculated moment tensors indicate the presence of a volumetric source mechanism. Systematic reconstruction of the source mechanism shows the source consists of a sill intersected by either a sub-vertical east-west trending dike or a sub-vertical pipe and a weak single force. The trend of the dike may be controlled by the east-west trending Augustine-Seldovia arch. The data from the network of broadband sensors is limited to fourteen seismic traces, and synthetic modeling confirms the ability of the network to recover the source mechanism. The synthetic modeling also provides a guide to the expected capability of a broadband network to resolve very-long-period source mechanisms, particularly when confronted with limited observational data.

Inversion of Coeval Shear and Normal Stress of Piton de la Fournaise Flank Displacement

NASA Astrophysics Data System (ADS)

Cayol, V.; Tridon, M.; Froger, J. L.; Augier, A.; Bachelery, P.

2016-12-01

The April 2007 eruption of Piton de la Fournaise was the biggest volcano eruptive crisis of the 20th and 21st centuries. InSAR captured a large (1.4 m) co-eruptive seaward slip of the volcano's eastern flank, which continued for more than a year at a decreasing rate. Co-eruptive uplift and post-eruptive subsidence were also observed. While it is generally agreed that flank displacement is induced by fault slip, we investigate wether this flank displacement might have been induced by a sheared sill, as suggested by observations of sheared sills at Piton des Neiges. To test this hypothesis, we develop a new method to invert a quadrangular curved source submitted to co-eval pressure and shear stress changes. This method, based on boundary elements, is applied to co-eruptive and post-eruptive InSAR data. We find that co-eruptive displacement is explained by a 2 km by 2 km detachment fault, parallel to the flank and probably coincident with a lithological discontinuity. The fracture is shallow enough to induce the co-eval uplift characteristic of a detachment fold. We determine the co-eruptive overpressure is zero, which indicates that the fracture is not a sheared sill. This finding confirms a previous determination obtained using a decision tree based on ratios of maximum displacements. The determined shear stress change of 2 MPa is conistent with the eastern flank loaded by previously intruded rift dikes. Post-eruptive displacement is well explained by slip and closure of the same fracture but over a larger (5 km by 8 km). This displacements is consistent with relaxation and the co-eruptive flank displacement and causal link between both displacement is investigated.

Characterizing the first historic eruption of Nabro, Eritrea: Insights from thermal and UV remote sensing

NASA Astrophysics Data System (ADS)

Sealing, Christine R.

June 2011 saw the first historic eruption of Nabro volcano, one of an ongoing sequence of eruptions in the Afar-Red Sea region since 2005. It halted air travel in northern Africa, contaminated food and water sources, and displaced thousands from their homes. Due to its remote location, little was known about this event in terms of the quantity of erupted products and the timing and mechanisms of their emplacement. Geographic isolation, previous quiescence and regional civil unrest meant that this volcano was effectively unmonitored at the time of eruption, and opportunities for field study are limited. Using free, publicly available satellite data, I examined rates of lava effusion and SO2 emission in order to quantify the amount of erupted products and understand the temporal evolution of the eruption, as well as explore what information can be gleaned about eruption mechanisms using remote sensing data. These data revealed a bimodal eruption, beginning with explosive activity marked by high SO2 emission totalling 1824 - 2299 KT, and extensive ash fall of 270 - 440 km2. This gave way to a period of rapid effusion, producing a ˜17 km long lava flow, and a volume of ˜22.1 x 106 m3. Mass balance between the SO2 and lava flows reveals no sulfur 'excess', suggesting that nearly all of the degassed magma was extruded. The 2011 eruption of Nabro lasted nearly 6 weeks, and may be considered the second largest historic eruption in Africa. Work such as this highlights the importance of satellite remote sensing for studying and monitoring volcanoes, particularly those in remote regions that may be otherwise inaccessible.

Post-eruptive flooding of Santorini caldera and implications for tsunami generation

NASA Astrophysics Data System (ADS)

Nomikou, Paraskevi; Druitt, Tim; Hübscher, Christian; Mather, Tamsin; Paulatto, Michele; Kalnins, Lara; Kelfoun, Karim; Papanikolaou, Dimitris; Bejelou, Konstantina; Lampridou, Danai; Pyle, David; Carey, Steven; Watts, Anthony; Weiß, Benedikt; Parks, Michelle

2017-04-01

Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The eruption of Santorini 3600 years ago was one of the largest of eruptions known worldwide from the past 10,000 years - and was at least 3 times larger than the catastrophic eruption of Krakatoa. This huge eruption evacuated large volumes of magma, causing collapse of the large caldera, which is now filled with seawater. Tsunamis from this eruption have been proposed to have played a role in the demise of the Minoan culture across the southern Aegean, through damage to coastal towns, harbors, shipping and maritime trade. Before the eruption, there was an older caldera in the northern part of Santorini, partly filled with a shallow lagoon. In our study, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Following subsidence of the caldera floor, rapid inflow of seawater and landslides cut a deep 2.0-2.5 km3 submarine channel into the northern flank of the caldera wall. Hydrodynamic modelling indicates that the caldera was flooded through this breach in less than a couple of days. It was previously proposed that collapse of the caldera could have led to the formation of a major tsunami; but this is ruled out by our new evidence. Any tsunami's generated were most likely caused by entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations. This idea is consistent with previous assertions that pyroclastic flows were the main cause of tsunamis at Krakatau.

Rapid transport of ash and sulfate from the 2011 Puyehue-Córdon Caulle (Chile) eruption to West Antarctica

NASA Astrophysics Data System (ADS)

Dowd, E.; Koffman, B. G.; Osterberg, E. C.; Ferris, D. G.; Hartman, L.; Wheatley, S.; Kurbatov, A.; Wong, G. J.; Markle, B. R.; Dunbar, N. W.; Kreutz, K. J.; Yates, M. G.

2017-12-01

The VEI 5 eruption of the Puyehue-Cordón Caulle volcanic complex (PCC) in central Chile, which began 4 June 2011, provides a rare opportunity to assess the rapid transport and deposition of sulfate and ash from a mid-latitude volcano to the Antarctic ice sheet. We present sulfate, microparticle concentrations of fine-grained ( 5 μm diameter) tephra, and geochemistry, which document the depositional sequence of volcanic products from the PCC eruption in West Antarctic snow and shallow firn. From the depositional phasing and duration of ash and sulfate peaks, we infer that transport occurred primarily through the troposphere but that ash and sulfate transport were decoupled. We use Hysplit back-trajectory modeling to assess circulation conditions in the weeks following the eruption, and find that atmospheric conditions favored mid-to-high latitude air parcel transport during 6-14 June and 4-18 July, 2011. We suggest that two discrete pulses of cryptotephra deposition relate to these intervals, and as such, constrain the sulfate transport and deposition lifespan to the 2-3 weeks following the eruption. Finally, we compare PCC depositional patterns to those of prominent low- and high-latitude eruptions in order to improve multiparameter-based efforts to identify "unknown source" eruptions in the ice core record. Our observations suggest that mid-latitude eruptions such as PCC can be distinguished from explosive tropical eruptions by differences in ash/sulfate phasing and in the duration of sulfate deposition, and from high-latitude eruptions by differences in particle size distribution and in cryptotephra geochemical composition.

Rapid transport of ash and sulfate from the 2011 Puyehue-Cordón Caulle (Chile) eruption to West Antarctica

NASA Astrophysics Data System (ADS)

Koffman, Bess G.; Dowd, Eleanor G.; Osterberg, Erich C.; Ferris, David G.; Hartman, Laura H.; Wheatley, Sarah D.; Kurbatov, Andrei V.; Wong, Gifford J.; Markle, Bradley R.; Dunbar, Nelia W.; Kreutz, Karl J.; Yates, Martin

2017-08-01

The Volcanic Explosivity Index 5 eruption of the Puyehue-Cordón Caulle volcanic complex (PCC) in central Chile, which began 4 June 2011, provides a rare opportunity to assess the rapid transport and deposition of sulfate and ash from a midlatitude volcano to the Antarctic ice sheet. We present sulfate, microparticle concentrations of fine-grained ( 5 μm diameter) tephra, and major oxide geochemistry, which document the depositional sequence of volcanic products from the PCC eruption in West Antarctic snow and shallow firn. From the depositional phasing and duration of ash and sulfate peaks, we infer that transport occurred primarily through the troposphere but that ash and sulfate transport were decoupled. We use Hybrid Single-Particle Lagrangian Integrated Trajectory back trajectory modeling to assess atmospheric circulation conditions in the weeks following the eruption and find that conditions favored southward air parcel transport during 6-14 June and 4-18 July 2011. We suggest that two discrete pulses of cryptotephra deposition relate to these intervals, and as such, constrain the sulfate transport and deposition lifespan to the 2-3 weeks following the eruption. Finally, we compare PCC depositional patterns to those of prominent low- and high-latitude eruptions in order to improve multiparameter-based efforts to identify "unknown source" eruptions in the ice core record. Our observations suggest that midlatitude eruptions such as PCC can be distinguished from explosive tropical eruptions by differences in ash/sulfate phasing and in the duration of sulfate deposition, and from high-latitude eruptions by differences in particle size distribution and in cryptotephra geochemical composition.

Degassing behavior of Mt. Etna volcano (Italy) before and during the 2008-2009 eruption, inferred from crater plume and soil gas measurements

NASA Astrophysics Data System (ADS)

Salerno, Giuseppe; La Spina, Alessandro; Giammanco, Salvatore; Burton, Michael; Caltabiano, Tommaso; Murè, Filippo; Randazzo, Daniele; Lopez, Manuela; Bruno, Nicola; Longo, Vincenza

2010-05-01

The evolution of magmatic degassing that preceded and accompanied the 2008-2009 Mt. Etna eruption was monitored by using a combination of: i) near-daily SO2 flux measurements; ii) calculated HCl and HF fluxes, obtained combining the daily SO2 flux values with discrete FTIR measurements of SO2/HCl and SO2/HF molar ratios; iii) periodic soil CO2 flux measurements. Thanks to the differential release of magmatic gas species from an ascending magma body we were able to track the magma transfer process in the volcano plumbing system from depth (< 5 km) to the surface. Our data suggest that the intermittent paroxysmal activity that mainly affected the South-East Crater (SEC) during 2007, displayed the efficient but complex nature of Mt. Etna's plumbing system, with gas-rich magma ascending and degassing via the central conduit system prior to eruption at the peripheral SEC. Conversely, the 15 month long 2008-09 eruption event was characterized by quasi steady state magma supply. The calculated volume of magma required to produce the observed SO2 flux during the 2008-2009 eruption closely matches the volume of erupted magma. This "eruptive" steady-state would indicate an almost perfect process of magma migration and eruption at the surface, without substantial storage within the volcano plumbing system.

Deformation of volcanic materials by pore pressurization: analog experiments with simplified geometry

NASA Astrophysics Data System (ADS)

Hyman, David; Bursik, Marcus

2018-03-01

The pressurization of pore fluids plays a significant role in deforming volcanic materials; however, understanding of this process remains incomplete, especially scenarios accompanying phreatic eruptions. Analog experiments presented here use a simple geometry to study the mechanics of this type of deformation. Syrup was injected into the base of a sand medium, simulating the permeable flow of fluids through shallow volcanic systems. The experiments examined surface deformation over many source depths and pressures. Surface deformation was recorded using a Microsoft® Kinect™ sensor, generating high-spatiotemporal resolution lab-scale digital elevation models (DEMs). The behavior of the system is controlled by the ratio of pore pressure to lithostatic loading (λ =p/ρ g D). For λ <10, deformation was accommodated by high-angle, reversed-mechanism shearing along which fluid preferentially flowed, leading to a continuous feedback between deformation and pressurization wherein higher pressure ratios yielded larger deformations. For λ >10, fluid expulsion from the layer was much faster, vertically fracturing to the surface with larger pressure ratios yielding less deformation. The temporal behavior of deformation followed a characteristic evolution that produced an approximately exponential increase in deformation with time until complete layer penetration. This process is distinguished from magmatic sources in continuous geodetic data by its rapidity and characteristic time evolution. The time evolution of the experiments compares well with tilt records from Mt. Ontake, Japan, in the lead-up to the deadly 2014 phreatic eruption. Improved understanding of this process may guide the evolution of magmatic intrusions such as dikes, cone sheets, and cryptodomes and contribute to caldera resurgence or deformation that destabilizes volcanic flanks.

Generation, ascent and eruption of magma on the Moon: New insights into source depths, magma supply, intrusions and effusive/explosive eruptions (Part 1: Theory)

NASA Astrophysics Data System (ADS)

Wilson, Lionel; Head, James W.

2017-02-01

We model the ascent and eruption of lunar mare basalt magmas with new data on crustal thickness and density (GRAIL), magma properties, and surface topography, morphology and structure (Lunar Reconnaissance Orbiter). GRAIL recently measured the broad spatial variation of the bulk density structure of the crust of the Moon. Comparing this with the densities of lunar basaltic and picritic magmas shows that essentially all lunar magmas were negatively buoyant everywhere within the lunar crust. Thus positive excess pressures must have been present in melts at or below the crust-mantle interface to enable them to erupt. The source of such excess pressures is clear: melt in any region experiencing partial melting or containing accumulated melt, behaves as though an excess pressure is present at the top of the melt column if the melt is positively buoyant relative to the host rocks and forms a continuously interconnected network. The latter means that, in partial melt regions, probably at least a few percent melting must have taken place. Petrologic evidence suggests that both mare basalts and picritic glasses may have been derived from polybaric melting of source rocks in regions extending vertically for at least a few tens of km. This is not surprising: the vertical extent of a region containing inter-connected partial melt produced by pressure-release melting is approximately inversely proportional to the acceleration due to gravity. Translating the ∼25 km vertical extent of melting in a rising mantle diapir on Earth to the Moon then implies that melting could have taken place over a vertical extent of up to 150 km. If convection were absent, melting could have occurred throughout any region in which heat from radioisotope decay was accumulating; in the extreme this could have been most of the mantle. The maximum excess pressure that can be reached in a magma body depends on its environment. If melt percolates upward from a partial melt zone and accumulates as a magma reservoir, either at the density trap at the base of the crust or at the rheological trap at the base of the elastic lithosphere, the excess pressure at the top of the magma body will exert an elastic stress on the overlying rocks. This will eventually cause them to fail in tension when the excess pressure has risen to close to twice the tensile strength of the host rocks, perhaps up to ∼10 MPa, allowing a dike to propagate upward from this point. If partial melting occurs in a large region deep in the mantle, however, connections between melt pockets and veins may not occur until a finite amount, probably a few percent, of melting has occurred. When interconnection does occur, the excess pressure at the top of the partial melt zone will rise abruptly to a high value, again initiating a brittle fracture, i.e. a dike. That sudden excess pressure is proportional to the vertical extent of the melt zone, the difference in density between the host rocks and the melt, and the acceleration due to gravity, and could readily be ∼100 MPa, vastly greater than the value needed to initiate a dike. We therefore explored excess pressures in the range ∼10 to ∼100 MPa. If eruptions take place through dikes extending upward from the base of the crust, the mantle magma pressure at the point where the dike is initiated must exceed the pressure due to the weight of the magmatic liquid column. This means that on the nearside the excess pressure must be at least ∼19 ± 9 MPa and on the farside must be ∼29 ± 15 MPa. If the top of the magma body feeding an erupting dike is a little way below the base of the crust, slightly smaller excess pressures are needed because the magma is positively buoyant in the part of the dike within the upper mantle. Even the smallest of these excess pressures is greater than the ∼10 MPa likely maximum value in a magma reservoir at the base of the crust or elastic lithosphere, but the values are easily met by the excess pressures in extensive partial melt zones deeper within the mantle. Thus magma accumulations at the base of the crust would have been able to intrude dikes part-way through the crust, but not able to feed eruptions to the surface; in order to be erupted, magma must have been extracted from deeper mantle sources, consistent with petrologic evidence. Buoyant dikes growing upward from deep mantle sources of partial melt can disconnect from their source regions and travel through the mantle as isolated bodies of melt that encounter and penetrate the crust-mantle density boundary. They adjust their lengths and internal pressure excesses so that the stress intensity at the lower tip is zero. The potential total vertical extent of the resulting melt body depends on the vertical extent of the source region from which it grew. For small source extents, the upper tip of the resulting dike crossing the crust-mantle boundary cannot reach the surface anywhere on the Moon and therefore can only form a dike intrusion; for larger source extents, the dike can reach the surface and erupt on the nearside but still cannot reach the surface on the farside; for even larger source extents, eruptions could occur on both the nearside and the farside. The paucity of farside eruptions therefore implies a restricted range of vertical extents of partial melt source region sizes, between ∼16 and ∼36 km. When eruptions can occur, the available pressure in excess of what is needed to support a static magma column to the surface gives the pressure gradient driving magma flow. The resulting typical turbulent magma rise speeds are ∼10 to a few tens of m s-1, dike widths are of order 100 m, and eruption rates from 1 to 10 km long fissure vents are of order 105 to 106 m3 s-1. Volume fluxes in lunar eruptions derived from lava flow thicknesses and surface slopes or rille lengths and depths are found to be of order 105 to 106 m3 s-1 for volume-limited lava flows and >104 to 105 m3 s-1 for sinuous rilles, with dikes widths of ∼50 m. The lower end of the volume flux range for sinuous rilles corresponds to magma rise speeds approaching the limit set by the fact that excessive cooling would occur during flow up a 30 km long dike kept open by a very low excess pressure. These eruptions were thus probably fed by partial melt zones deep in the mantle. Longer eruption durations, rather than any subtle topographic slope effects, appear to be the key to the ability of these flows to erode sinuous rille channels. We conclude that: (1) essentially all lunar magmas were negatively buoyant everywhere within the crust; (2) positive excess pressures of at least 20-30 MPa must have been present in mantle melts at or below the crust-mantle interface to drive magmas to the surface; (3) such pressures are easily produced in zones of partial melting by pressure-release during mantle convection or simple heat accumulation from radioisotopes; (4) magma volume fluxes available from dikes forming at the tops of partial melt zones are consistent with the 105 to 106 m3 s-1 volume fluxes implied by earlier analyses of surface flows; (5) eruptions producing thermally-eroded sinuous rille channels involved somewhat smaller volume fluxes of magma where the supply rate may be limited by the rate of extraction of melt percolating through partial melt zones.

Air Quality Planning & Standards | Air & Radiation | US EPA

EPA Pesticide Factsheets

2016-10-18

Air pollution comes from many different sources: stationary sources such as factories, power plants, and smelters and smaller sources such as dry cleaners and degreasing operations; mobile sources such as cars, buses, planes, trucks, and trains; and naturally occurring sources such as windblown dust, and volcanic eruptions, all contribute to air pollution.

Air Quality | Air Quality Planning & Standards | US EPA

EPA Pesticide Factsheets

2016-06-08

Air pollution comes from many different sources: stationary sources such as factories, power plants, and smelters and smaller sources such as dry cleaners and degreasing operations; mobile sources such as cars, buses, planes, trucks, and trains; and naturally occurring sources such as windblown dust, and volcanic eruptions, all contribute to air pollution.

Eruption mass estimation using infrasound waveform inversion and ash and gas measurements: Evaluation at Sakurajima Volcano, Japan

NASA Astrophysics Data System (ADS)

Fee, David; Izbekov, Pavel; Kim, Keehoon; Yokoo, Akihiko; Lopez, Taryn; Prata, Fred; Kazahaya, Ryunosuke; Nakamichi, Haruhisa; Iguchi, Masato

2017-12-01

Eruption mass and mass flow rate are critical parameters for determining the aerial extent and hazard of volcanic emissions. Infrasound waveform inversion is a promising technique to quantify volcanic emissions. Although topography may substantially alter the infrasound waveform as it propagates, advances in wave propagation modeling and station coverage permit robust inversion of infrasound data from volcanic explosions. The inversion can estimate eruption mass flow rate and total eruption mass if the flow density is known. However, infrasound-based eruption flow rates and mass estimates have yet to be validated against independent measurements, and numerical modeling has only recently been applied to the inversion technique. Here we present a robust full-waveform acoustic inversion method, and use it to calculate eruption flow rates and masses from 49 explosions from Sakurajima Volcano, Japan. Six infrasound stations deployed from 12-20 February 2015 recorded the explosions. We compute numerical Green's functions using 3-D Finite Difference Time Domain modeling and a high-resolution digital elevation model. The inversion, assuming a simple acoustic monopole source, provides realistic eruption masses and excellent fit to the data for the majority of the explosions. The inversion results are compared to independent eruption masses derived from ground-based ash collection and volcanic gas measurements. Assuming realistic flow densities, our infrasound-derived eruption masses for ash-rich eruptions compare favorably to the ground-based estimates, with agreement ranging from within a factor of two to one order of magnitude. Uncertainties in the time-dependent flow density and acoustic propagation likely contribute to the mismatch between the methods. Our results suggest that realistic and accurate infrasound-based eruption mass and mass flow rate estimates can be computed using the method employed here. If accurate volcanic flow parameters are known, application of this technique could be broadly applied to enable near real-time calculation of eruption mass flow rates and total masses. These critical input parameters for volcanic eruption modeling and monitoring are not currently available.

Compositional Variation in Magmas Supplied to the Southern East Pacific Rise, 17°-19° S: Implications for Magma Reservoir Dynamics

NASA Astrophysics Data System (ADS)

Bergmanis, E. C.; Sinton, J. M.; Rubin, K. H.; Gregg, T. K.; Cormier, M.

2002-12-01

Fine-scale observation and sampling of lavas from the southern EPR 17°-19° S reveal both short- and long-term compositional heterogeneity of flows produced in single eruptive episodes. Located between 17° 24' and 17° 36'S, the 140 x 106 m2 Aldo-Kihi flow reaches a maximum width of 2.2 km between 17° 26' and 17° 28'S; the presence of sheet flows, lava channels, and summit collapse troughs imply that the eruption was centered in this area of broad axial morphology. Some lava channels and collapsed lava tubes extend beyond the margins of the recently erupted Aldo-Kihi flow, indicating that lava distribution systems can persist over at least several hundreds of years and multiple separate eruptions were apparently centered in this region. Extensive glass analyses of the Aldo-Kihi flow show that MgO contents range from 7.7-8.4 wt %; all the samples with greater than 8.0 wt % MgO occur south of 17° 30'S. This result is hard to reconcile with along-axis propagation of a single dike, and suggests vertical eruption from a magma chamber that is compositionally zoned along-axis. Twenty-three other samples older than Aldo-Kihi contain > 8.0 wt % MgO; all but two occur south of 17° 28.4'S suggesting that the displacement of eruptive centers from the location of hottest subaxial magma is a long-lived feature of this region. Lack of compositional variation across some contacts indicates that this length of ridge has erupted compositionally similar lavas in separate volcanic episodes. Elsewhere distinctly different lava compositions include the several-hundred-year-old Rehu-Marka Fe-Ti basalt, and local occurrences of incompatible element-enriched T-MORB. The distribution of rock types in this area requires a complex history of mantle melting, recharge, cooling, and eruption that has been spatially systematic over time scales encompassing several eruptive episodes. Between 18° 31.5' and 18° 34.5'S the South Hump lava is distinctly bimodal with highly evolved ferrobasalts (MgO < 6.2 wt %, Na2O < 3.1 wt %) in the south, and basalts (~7.2 wt % MgO, Na2O > 3.1 wt %) in the north. Major and trace element data for these lavas indicate that they cannot be related by low-pressure fractional crystallization and that variations in mantle source composition appears to be required to explain the observed compositional variation. Existing geological evidence indicates that either the axial graben here was resurfaced by a single, chemically bimodal eruption, or by two adjacent eruptions that must be close in age. The boundary between the two chemical types corresponds to discontinuities in the axial magma chamber imaged by seismic reflection, as well as to significant differences in the thickness of seismic layer 2A. This result indicates that magma arising from vastly different melting processes can reside in adjacent crustal magma reservoirs and be tapped, either during a single eruption or during closely spaced eruptions in adjacent regions.

An abrupt change in the magmatic source of rhyolite volcanism in Long Valley, CA recorded by pre-eruptive oxygen fugacities of the Early Rhyolites (Obsidians): evidence of transition from subduction-modified lithosphere to asthenosphere

NASA Astrophysics Data System (ADS)

Waters, L.; Lange, R. A.

2016-12-01

Detailed mapping of the Long Valley (CA) region (Hildreth, 2004) reveals that the eruption of the Late Bishop Tuff (LBT) is followed by eruption of the Early Rhyolites (ER), which are obsidian lavas. The obsidians are paradoxical, as they erupted effusively, contain multiple phases (some of which vary in composition), and yet, they are crystal-poor. The obsidians are saturated in ≥7 phases (plagioclase + orthopyroxene + ilmenite + titanomagnetite + biotite + apatite + zircon ± pyrrhotite). Plagioclase and orthopyroxene crystals have rounded edges accompanying euhedral margins, and large (>200µm) ilmenites have swallow-tail growth. Plagioclase and orthopyroxene span a compositional range between An20-45 and En43-58, respectively, and phase equilibrium experiments confirm that these are phenocrysts, despite their complex textures. Pre-eruptive temperatures and fO2 values are calculated applying Fe-Ti oxide thermometry to all possible oxide pairs and range from 724-861°C and ΔNNO -0.3 to -0.9, respectively. Application of the plagioclase hygrometer to crystals in ER obsidians reveals pre-eruptive H2O contents of 3-5wt%. We propose that mineral compositions and textures within the ER obsidians record rapid growth due to degassing-induced crystallization of a superheated melt. Superheating is required to explain the origin of the ER lavas as it eliminates nucleation sites, requiring crystallization to occur on nuclei that form during degassing enabling effusive eruption of crystal-poor lavas. The ER obsidians differ from the LBT in their crystallinities (<5% vs. >12%), phenocryst phases (e.g., sanidine is absent in ER obsidians), plagioclase compositions (An20-45 vs. An20-29), and fO2 values (ΔNNO < -0.3 vs. +0.5), which suggests that the ER lavas may not be derived from the LBT reservoir. Rather, we hypothesize that the ER phenocryst assemblage, reduced fO2 values, and requirement for superheating can be explained if the obsidians formed as partial melts of a mixed lithology, consisting of pre-existing crust and an additional component with low fO2. We propose that the reduced component in the ER source is aesthenospheric basalt, which suggests that a transition in mantle source, from subduction-modified lithosphere to asthenosphere, has occurred beneath Long Valley.

Tooth Eruption without Roots

PubMed Central

2013-01-01

Root development and tooth eruption are very important topics in dentistry. However, they remain among the less-studied and -understood subjects. Root development accompanies rapid tooth eruption, but roots are required for the movement of teeth into the oral cavity. It has been shown that the dental follicle and bone remodeling are essential for tooth eruption. So far, only limited genes have been associated with root formation and tooth eruption. This may be due to the difficulties in studying late stages of tooth development and tooth movement and the lack of good model systems. Transgenic mice with eruption problems and short or no roots can be used as a powerful model for further deciphering of the cellular, molecular, and genetic mechanisms underlying root formation and tooth eruption. Better understanding of these processes can provide hints on delivering more efficient dental therapies in the future. PMID:23345536

Temporal and Spatial Variability in the Geochemistry of Axial and CoAxial Segment Lavas and their Mantle Sources

NASA Astrophysics Data System (ADS)

Smith, M. C.; Perfit, M. R.; Davis, C.; Kamenov, G. D.

2011-12-01

Three spatially related volcanic eruptions along the CoAxial Segment of the Juan de Fuca Ridge (JdFR) have documented emplacements between 1981 and 1993. Two of the historic flows outcrop at the "Flow Site" and were emplaced within less than 12 years and 500 m from one another. The third was emplaced at the "Floc Site" to the south in the 1980s. Previous studies have documented that CoAxial lavas are among the most incompatible element and isotopically depleted lavas along the entire JdFR, whereas the Axial Seamount segment immediately south of CoAxial has erupted the most chemically enriched lavas south of the Endeavor Segment. Geochemical studies have shown little temporal change in the chemistry of recent Axial Seamount eruptives, whereas CoAxial lavas exhibit distinct chemical differences over short time periods. Significant chemical differences observed among depleted CoAxial lavas emplaced close to one another in space and time are in marked contrast to the relatively constant chemical characteristics of enriched lavas erupted at the magmatically more robust Axial segment only 10's of kilometers to the south and west. New trace element and isotopic (Sr, Nd, Pb) geochemical analyses of historic and older CoAxial lavas have resulted in better documentation of interflow and intraflow chemical variation providing an improved understanding of spatial/temporal chemical variability in lavas, and further insight into JdFR magmatic processes. Modeling of major and trace element abundances suggest that the observed intraflow chemical variation within CoAxial lavas is largely due to shallow-level fractional crystallization but that a single fractional crystallization model cannot account for all interflow chemical variation. In fact, elemental and isotopic data require different parental magmas for each of the three recent CoAxial Segment lava flows suggesting very short-term differences or changes in the chemical character of the mantle source region. In particular, the 1980's Flow Site parental magma may have formed at higher pressures and due to smaller extents of melting than those magmas that erupted just over a decade later. A comparative analysis of the chemistry of CoAxial segment lavas with that of lavas from nearby seamounts, including Axial Seamount, and ridge segments show that much (though not all) of the data conforms well to binary mixing arrays, suggesting that many of the parental lavas from this region of the JdFR can be formed from variable amounts of mixing of two or more distinct mantle end-member sources. In addition to one or more depleted mantle (DM) sources, regional isotopic data also likely suggest a high U/Pb (HIMU) source component within the region of mantle melt generation. For most lavas strong correlations exist between long-lived radiogenic isotopes and ratios of the abundances of highly incompatible elements, suggesting that mantle heterogeneities sampled are ancient, however, in some cases elemental data is decoupled from the radiogenic isotope data indicating more recent depletion events.

Temporal and spectral characteristics of seismicity observed at Popocatepetl volcano, central Mexico

USGS Publications Warehouse

Arciniega-Ceballos, A.; Valdes-Gonzalez, C.; Dawson, P.

2000-01-01

Popocatepetl volcano entered an eruptive phase from December 21, 1994 to March 30, 1995, which was characterized by ash and fumarolic emissions. During this eruptive episode, the observed seismicity consisted of volcano-tectonic (VT) events, long-period (LP) events and sustained tremor. Before the initial eruption on December 21, VT seismicity exhibited no increase in number until a swarm of VT earthquakes was observed at 01:31 hours local time. Visual observations of the eruption occurred at dawn the next morning. LP activity increased from an average of 7 events a day in October 1994 to 22 events per day in December 1994. At the onset of the eruption, LP activity peaked at 49 events per day. LP activity declined until mid-January 1995 when no events were observed. Tremor was first observed about one day after the initial eruption and averaged 10 h per episode. By late February 1995, tremor episodes became more intermittent, lasting less than 5 min, and the number of LP events returned to pre-eruption levels (7 events per day). Using a spectral ratio technique, low-frequency oceanic microseismic noise with a predominant peak around 7 s was removed from the broadband seismic signal of tremor and LP events. Stacks of corrected tremor episodes and LP events show that both tremor and LP events contain similar frequency features with major peaks around 1.4 Hz. Frequency analyses of LP events and tremor suggest a shallow extended source with similar radiation pattern characteristics. The distribution of VT events (between 2.5 and 10 km) also points to a shallow source of the tremor and LP events located in the first 2500 m beneath the crater. Under the assumption that the frequency characteristics of the signals are representative of an oscillator we used a fluid-filled-crack model to infer the length of the resonator.

Multiwavelength observations of nova SMCN 2016-10a - one of the brightest novae ever observed

NASA Astrophysics Data System (ADS)

Aydi, E.; Page, K. L.; Kuin, N. P. M.; Darnley, M. J.; Walter, F. M.; Mróz, P.; Buckley, D. A. H.; Mohamed, S.; Whitelock, P.; Woudt, P.; Williams, S. C.; Orio, M.; Williams, R. E.; Beardmore, A. P.; Osborne, J. P.; Kniazev, A.; Ribeiro, V. A. R. M.; Udalski, A.; Strader, J.; Chomiuk, L.

2018-02-01

We report on multiwavelength observations of nova Small Magellanic Cloud Nova 2016-10a. The present observational set is one of the most comprehensive for any nova in the Small Magellanic Cloud, including low-, medium-, and high-resolution optical spectroscopy and spectropolarimetry from Southern African Large Telescope, Folded Low-Order Yte-Pupil Double-Dispersed Spectrograph, and Southern Astrophysical Research; long-term Optical Gravitational Lensing Experiment V- and I-bands photometry dating back to 6 yr before eruption; Small and Moderate Aperture Research Telescope System optical and near-IR photometry from ˜11 d until over 280 d post-eruption; Swift satellite X-ray and ultraviolet observations from ˜6 d until 319 d post-eruption. The progenitor system contains a bright disc and a main sequence or a sub-giant secondary. The nova is very fast with t2 ≃ 4.0 ± 1.0 d and t3 ≃ 7.8 ± 2.0 d in the V band. If the nova is in the SMC, at a distance of ˜61 ± 10 kpc, we derive MV, max ≃ -10.5 ± 0.5, making it the brightest nova ever discovered in the SMC and one of the brightest on record. At day 5 post-eruption the spectral lines show a He/N spectroscopic class and an Full Width at Half Maximum of ˜3500 km s-1, indicating moderately high ejection velocities. The nova entered the nebular phase ˜20 d post-eruption, predicting the imminent super-soft source turn-on in the X-rays, which started ˜28 d post-eruption. The super-soft source properties indicate a white dwarf mass between 1.2 and 1.3 M⊙ in good agreement with the optical conclusions.

Science in Support of Aviation-Risk Management since the April 2010 Eruption of Eyjafjallajökull, Iceland

NASA Astrophysics Data System (ADS)

Guffanti, M.; Mastin, L. G.; Schneider, D. J.; Tupper, A.

2010-12-01

The nearly week-long airspace closure over large parts of Europe and the North Atlantic in April 2010 that resulted from dispersion of ash from the eruption of Eyjafjallajökull prompted a shift from the accepted global policy of strict avoidance by aircraft of ash-contaminated airspace to one of allowing flight through zones of dilute ash under some circumstances. This shift was made in a crisis environment of rapidly mounting economic losses and social disruptions extending well beyond the European region. To get the global air transportation system moving again, European aviation authorities and associated meteorological offices created a new type of advisory product depicting forecasted zones of low ash concentrations in Eyjafjallajökull’s clouds that could be transited with expectation of no or minimal risk of aircraft damage, under the condition of more frequent aircraft inspections and enhanced risk management by airlines. Preliminary data of the European Aviation Safety Agency indicate that transit through Eyjafjallajökull’s dilute ash clouds caused some wear (primarily abrasion) to a few aircraft, but not to the severity of degraded engine performance in flight; after inspections the aircraft were returned to service and continued to operate without problems. Following the crisis, recognizing that such a fundamental shift in risk management requires sound scientific and engineering bases, the International Civil Aviation Organization (ICAO) formed an International Volcanic Ash Task Force that, in conjunction with the World Meteorological Organization (WMO), will incorporate advice and recommendations from scientific, aviation, and engineering experts worldwide about ways to improve (1) situational awareness to aviation users of impending volcanic eruptions, (2) characterization of critical eruption source parameters for incorporation in forecast modeling, (3) detection and characterization of volcanic clouds, (4) accuracy of volcanic ash transport and dispersion models, and (5) airworthiness of engine, avionics, and airframes by manufacturers and airlines. Ground-based, airborne, and space-based methods are being evaluated in terms of the above items, and results of pertinent scientific investigations of the eruption and volcanic cloud are being compiled. Key topical issues being addressed include the need to depict uncertainty in quantitative modeling of ash concentration and capabilities to visualize and compare geospatial data from different sources. The timeline for this work extends over the next 3 years. More information about the ICAO and WMO scientific advisory process for volcanic ash hazards is at http://www2.icao.int/en/anb/met-aim/met/ivatf/Lists/Meetings/AllItems.aspx/. This process is still being refined, but participation from the broader scientific community within the IVATF framework is crucial to its success.

Ignimbrites to batholiths: integrating perspectives from geological, geophysical, and geochronological data

USGS Publications Warehouse

Lipman, Peter W.; Bachmann, Olivier

2015-01-01

Multistage histories of incremental accumulation, fractionation, and solidification during construction of large subvolcanic magma bodies that remained sufficiently liquid to erupt are recorded by Tertiary ignimbrites, source calderas, and granitoid intrusions associated with large gravity lows at the Southern Rocky Mountain volcanic field (SRMVF). Geophysical data combined with geological constraints and comparisons with tilted plutons and magmatic-arc sections elsewhere are consistent with the presence of vertically extensive (>20 km) intermediate to silicic batholiths (with intrusive:extrusive ratios of 10:1 or greater) beneath the major SRMVF volcanic loci (Sawatch, San Juan, Questa-Latir). Isotopic data require involvement of voluminous mantle-derived mafic magmas on a scale equal to or greater than that of the intermediate to silicic volcanic and plutonic rocks. Early waxing-stage intrusions (35–30 Ma) that fed intermediate-composition central volcanoes of the San Juan locus are more widespread than the geophysically defined batholith; these likely heated and processed the crust, preparatory for ignimbrite volcanism (32–27 Ma) and large-scale upper-crustal batholith growth. Age and compositional similarities indicate that SRMVF ignimbrites and granitic intrusions are closely related, but the extent to which the plutons record remnants of former magma reservoirs that lost melt to volcanic eruptions has been controversial. Published Ar/Ar-feldspar and U-Pb-zircon ages for plutons spatially associated with ignimbrite calderas document final crystallization of granitoid intrusions at times indistinguishable from the tuff to ages several million years younger. These ages also show that SRMVF caldera-related intrusions cooled and solidified soon after zircon crystallization, as magma supply waned. Some researchers interpret these results as recording pluton assembly in small increments that crystallized rapidly, leading to temporal disconnects between ignimbrite eruption and intrusion growth. Alternatively, crystallization ages of the granitic rocks are here inferred to record late solidification, after protracted open-system evolution involving voluminous mantle input, lengthy residence (105–106yr) as near-solidus crystal mush, and intermittent separation of liquid to supply volcanic eruptions. The compositions of the least-evolved ignimbrite magmas tend to merge with those of caldera-related plutons, suggesting that the plutons record nonerupted parts of long-lived cogenetic magmatic systems, variably modified prior to final solidification. Precambrian-source zircons are scarce in caldera plutons, in contrast to their abundance in some peripheral waning-stage intrusions of the SRMVF, implying dissolution of inherited crustal zircon during lengthy magma assembly for the ignimbrite eruptions and construction of a subvolcanic batholith. Broad age spans of zircons (to several million years) from individual samples of some ignimbrites and intrusions, commonly averaged and interpreted as “intrusion-emplacement age,” alternatively provide an incomplete record of intermittent crystallization during protracted incremental magma-body assembly, with final solidification only when the system began to wane. Analyses of whole zircons cannot resolve late stages of crystal growth, and early growth in a long-lived magmatic system may be poorly recorded due to periods of zircon dissolution. Overall, construction of a batholith can take longer than recorded by zircon-crystallization ages, while the time interval for separation and shallow assembly of eruptible magma may be much shorter. Magma-supply estimates (from ages and volcano-plutonic volumes) yield focused intrusion-assembly rates sufficient to generate ignimbrite-scale volumes of eruptible magma, based on published thermal models. Mid-Tertiary processes of batholith assembly associated with the SRMVF caused drastic chemical and physical reconstruction of the entire lithosphere, probably accompanied by asthenospheric input.

Infrasound array observation at Sakurajima volcano

NASA Astrophysics Data System (ADS)

Yokoo, A.; Suzuki, Y. J.; Iguchi, M.

2012-12-01

Showa crater at the southeastern flank of the Sakurajima volcano has erupted since 2006, accompanying intermittent Vulcanian eruptions with small scale ash emissions. We conducted an array observation in the last half of 2011 in order to locate infrasound source generated by the eruptions. The array located 3.5 km apart from the crater was composed of 5 microphones (1kHz sampling) aligned in the radial direction from the crater with 100-m-intervals, and additional 4 microphones (200Hz sampling) in tangential direction to the first line in December 2011. Two peaks, around 2Hz and 0.5Hz, in power spectrum of the infrasound were identified; the former peak would be related to the eigen frequency of the vent of Showa crater, but the latter would be related to ejection of eruption clouds. They should be checked by experimental studies. The first 10 s infrasound signal was made by explosion directly and the following small amplitude infrasound tremors for about 2 min were mostly composed of diffraction and reflection waves from the topography around the volcano, mainly the wall of the Aira Caldera. It shows propagation direction of infrasound tremor after the explosion signals should be carefully examined. Clear change in the height of the infrasound source was not identified while volcanic cloud grew up. Strong eddies of the growing volcanic cloud would not be main sources of such weak infrasound signals, thus, infrasound waves are emitted mainly from (or through) the vent itself.

Searching for structural medium changes during the 2011 El Hierro (Spain) submarine eruption

NASA Astrophysics Data System (ADS)

Sánchez-Pastor, Pilar S.; Schimmel, Martin; López, Carmen

2017-04-01

Submarine volcanic eruptions are often difficult to study due to their restricted access that usually inhibits direct observations. That happened with the 2011 El Hierro eruption, which is the first eruption that has been tracked in real time in Canary Islands. For instance, despite the real-time tracking it was not possible to determine the exact end of the eruption. Besides, volcanic eruptions involve many dynamic (physical and chemical) processes, which cause structural changes in the surrounding medium that we expect to observe and monitor through passive seismic approaches. The purpose of this study is to detect and analyse these changes as well as to search for precursory signals to the eruption itself using ambient noise auto and cross-correlations. We employ different correlation strategies (classical and phase cross-correlation) and apply them to field data recorded by the IGN network during 2011 and 2012. The different preprocessing and processing steps are tested and compared to better understand the data, to find the robust signatures, and to define a routine work procedure. One of the problems we face is the presence of volcanic tremors, which cause a varying seismic response that we can not attribute to structural changes. So far, structural changes could not be detected unambiguously and we present our ongoing research in this field.

Current Sheet Properties and Dynamics During Sympathetic Breakout Eruptions

NASA Astrophysics Data System (ADS)

Lynch, B. J.; Edmondson, J. K.

2013-12-01

We present the continued analysis of the high-resolution 2.5D MHD simulations of sympathetic magnetic breakout eruptions from a pseudostreamer source region. We examine the generation of X- and O-type null points during the current sheet tearing and track the magnetic island formation and evolution during periods of reconnection. The magnetic breakout eruption scenario forms an overlying 'breakout' current sheet that evolves slowly and removes restraining flux from above the sheared field core that will eventually become the center of the erupting flux rope-like structure. The runaway expansion from the expansion-breakout reconnection positive feedback enables the formation of the second, vertical/radial current sheet underneath the rising sheared field core as in the standard CHSKP eruptive flare scenario. We will examine the flux transfer rates through the breakout and flare current sheets and compare the properties of the field and plasma inflows into the current sheets and the reconnection jet outflows into the flare loops and flux rope ejecta.

Initiation of Solar Eruptions: Recent Observations and Implications for Theories

NASA Technical Reports Server (NTRS)

Sterling, A. C.

2006-01-01

Solar eruptions involve the violent disruption of a system of magnetic field. Just how the field is destabilized and explodes to produce flares and coronal mass ejections (CMEs) is still being debated in the solar community. Here I discuss recent observational work into these questions by ourselves (me and my colleagues) and others. Our work has concentrated mainly on eruptions that include filaments. We use the filament motion early in the event as a tracer of the motion of the general erupting coronal field in and around the filament, since that field itself is hard to distinguish otherwise. Our main data sources are EUV images from SOHO/EIT and TRACE, soft Xray images from Yohkoh, and magnetograms from SOHO/MDI, supplemented with coronagraph images from SOHO/LASCO, hard X-ray data, and ground-based observations. We consider the observational findings in terms of three proposed eruption-initiation mechanisms: (i) runaway internal tether-cutting reconnection, (ii) slow external tether-cutting reconnection ("breakout"), and (iii) ideal MHD instability.

Magnetic Topology of the Global MHD Configuration on 2010 August 1-2

NASA Astrophysics Data System (ADS)

Titov, V. S.; Mikic, Z.; Torok, T.; Linker, J.; Panasenco, O.

2014-12-01

It appears that the global magnetic topology of the solar corona predetermines to a large extent the magnetic flux transfer during solar eruptions. We have recently analyzed the global topology for a source-surface model of the background magnetic field at the time of the 2010 August 1-2 sympathetic CMEs (Titov et al. 2012). Now we extend this analysis to a more accurate thermodynamic MHD model of the solar corona. As for the source-surface model, we find a similar triplet of pseudo-streamers in the source regions of the eruptions. The new study confirms that all these pseudo-streamers contain separatrix curtains that fan out from a basic magnetic null point, individual for each of the pseudo-streamers. In combination with the associated separatrix domes, these separatrix curtains fully isolate adjacent coronal holes of the like polarity from each other. However, the size and shape of the coronal holes, as well as their open magnetic fluxes and the fluxes in the lobes of the separatrix domes, are very different for the two models. The definition of the open separator field lines, where the (interchange) reconnection between open and closed magnetic flux takes place, is also modified, since the structurally unstable source-surface null lines do not exist anymore in the MHD model. In spite of all these differences, we reassert our earlier hypothesis that magnetic reconnection at these nulls and the associated separators likely plays a key role in coupling the successive eruptions observed by SDO and STEREO. The results obtained provide further validation of our recent simplified MHD model of sympathetic eruptions (Török et al. 2011). Research supported by NASA's Heliophysics Theory and LWS Programs, and NSF/SHINE and NSF/FESD.

Volcanic-ash hazard to aviation during the 2003-2004 eruptive activity of Anatahan volcano, Commonwealth of the Northern Mariana Islands

USGS Publications Warehouse

Guffanti, M.; Ewert, J.W.; Gallina, G.M.; Bluth, G.J.S.; Swanson, G.L.

2005-01-01

Within the Commonwealth of the Northern Mariana Islands (CNMI), Anatahan is one of nine active subaerial volcanoes that pose hazards to major air-traffic routes from airborne volcanic ash. The 2003-2004 eruptive activity of Anatahan volcano affected the region's aviation operations for 3 days in May 2003. On the first day of the eruption (10 May 2003), two international flights from Saipan to Japan were cancelled, and several flights implemented ash-avoidance procedures. On 13 May 2003, a high-altitude flight through volcanic gas was reported, with no perceptible damage to the aircraft. TOMS and MODIS analysis of satellite data strongly suggests that no significant ash and only minor amounts of SO2 were involved in the incident, consistent with crew observations. On 23 May 2003, airport operations were disrupted when tropical-cyclone winds dispersed ash to the south, dusting Saipan with light ashfall and causing flight cancellations there and at Guam 320 km south of the volcano. Operational (near-real-time) monitoring of ash clouds produced by Anatahan has been conducted since the first day of the eruption on 10 May 2003 by the Washington Volcanic Ash Advisory Center (VAAC). The VAAC was among the first groups outside of the immediate area of the volcano to detect and report on the unexpected eruption of Anatahan. After being contacted about an unusual cloud by National Weather Service forecasters in Guam at 1235 UTC on 10 May 2003, the VAAC analyzed GOES 9 images, confirming Anatahan as the likely source of an ash cloud and estimating that the eruption began at about 0730 UTC. The VAAC issued its first Volcanic Ash Advisory for Anatahan at 1300 UTC on 10 May 2003 more than 5 h after the start of the eruption, the delay reflecting the difficulty of detecting and confirming a surprise eruption at a remote volcano with no in situ real-time geophysical monitoring. The initial eruption plume reached 10.7-13.4 km (35,000-44,000 ft), well into jet cruise altitudes; thereafter, the maximum plume height decreased and during the rest of the eruption usually did not exceed ???5 km (???17,000 ft), which lessened the potential hazard to aircraft at higher cruise altitudes. Drifting ash clouds commonly extended hundreds of kilometers from the volcano, occasionally as far west as the Philippines. Over the course of the eruptive activity in 2003-2004, the VAAC issued 323 advisories (168 with graphical depictions of ash clouds) for Anatahan, serving as a reliable source of ash-cloud information for aviation-related meteorological offices and air carriers. With a record of frequent eruptions in the CNMI, continued satellite and in situ real-time geophysical monitoring is needed at Anatahan and other Marianas volcanoes so that potential hazards to aviation from any future eruptive activity can be quickly and correctly assessed. ?? 2005 Elsevier B.V. All rights reserved.

Volcanic-ash hazard to aviation during the 2003 2004 eruptive activity of Anatahan volcano, Commonwealth of the Northern Mariana Islands

NASA Astrophysics Data System (ADS)

Guffanti, Marianne; Ewert, John W.; Gallina, Gregory M.; Bluth, Gregg J. S.; Swanson, Grace L.

2005-08-01

Within the Commonwealth of the Northern Mariana Islands (CNMI), Anatahan is one of nine active subaerial volcanoes that pose hazards to major air-traffic routes from airborne volcanic ash. The 2003-2004 eruptive activity of Anatahan volcano affected the region's aviation operations for 3 days in May 2003. On the first day of the eruption (10 May 2003), two international flights from Saipan to Japan were cancelled, and several flights implemented ash-avoidance procedures. On 13 May 2003, a high-altitude flight through volcanic gas was reported, with no perceptible damage to the aircraft. TOMS and MODIS analysis of satellite data strongly suggests that no significant ash and only minor amounts of SO 2 were involved in the incident, consistent with crew observations. On 23 May 2003, airport operations were disrupted when tropical-cyclone winds dispersed ash to the south, dusting Saipan with light ashfall and causing flight cancellations there and at Guam 320 km south of the volcano. Operational (near-real-time) monitoring of ash clouds produced by Anatahan has been conducted since the first day of the eruption on 10 May 2003 by the Washington Volcanic Ash Advisory Center (VAAC). The VAAC was among the first groups outside of the immediate area of the volcano to detect and report on the unexpected eruption of Anatahan. After being contacted about an unusual cloud by National Weather Service forecasters in Guam at 1235 UTC on 10 May 2003, the VAAC analyzed GOES 9 images, confirming Anatahan as the likely source of an ash cloud and estimating that the eruption began at about 0730 UTC. The VAAC issued its first Volcanic Ash Advisory for Anatahan at 1300 UTC on 10 May 2003 more than 5 h after the start of the eruption, the delay reflecting the difficulty of detecting and confirming a surprise eruption at a remote volcano with no in situ real-time geophysical monitoring. The initial eruption plume reached 10.7-13.4 km (35,000-44,000 ft), well into jet cruise altitudes; thereafter, the maximum plume height decreased and during the rest of the eruption usually did not exceed ˜5 km (˜17,000 ft), which lessened the potential hazard to aircraft at higher cruise altitudes. Drifting ash clouds commonly extended hundreds of kilometers from the volcano, occasionally as far west as the Philippines. Over the course of the eruptive activity in 2003-2004, the VAAC issued 323 advisories (168 with graphical depictions of ash clouds) for Anatahan, serving as a reliable source of ash-cloud information for aviation-related meteorological offices and air carriers. With a record of frequent eruptions in the CNMI, continued satellite and in situ real-time geophysical monitoring is needed at Anatahan and other Marianas volcanoes so that potential hazards to aviation from any future eruptive activity can be quickly and correctly assessed.

Cassini finds molecular hydrogen in the Enceladus plume: Evidence for hydrothermal processes.

PubMed

Waite, J Hunter; Glein, Christopher R; Perryman, Rebecca S; Teolis, Ben D; Magee, Brian A; Miller, Greg; Grimes, Jacob; Perry, Mark E; Miller, Kelly E; Bouquet, Alexis; Lunine, Jonathan I; Brockwell, Tim; Bolton, Scott J

2017-04-14

Saturn's moon Enceladus has an ice-covered ocean; a plume of material erupts from cracks in the ice. The plume contains chemical signatures of water-rock interaction between the ocean and a rocky core. We used the Ion Neutral Mass Spectrometer onboard the Cassini spacecraft to detect molecular hydrogen in the plume. By using the instrument's open-source mode, background processes of hydrogen production in the instrument were minimized and quantified, enabling the identification of a statistically significant signal of hydrogen native to Enceladus. We find that the most plausible source of this hydrogen is ongoing hydrothermal reactions of rock containing reduced minerals and organic materials. The relatively high hydrogen abundance in the plume signals thermodynamic disequilibrium that favors the formation of methane from CO 2 in Enceladus' ocean. Copyright © 2017, American Association for the Advancement of Science.

Preliminary insights into a model for mafic magma fragmentation

NASA Astrophysics Data System (ADS)

Edwards, Matt; Pioli, Laura; Andronico, Daniele; Cristaldi, Antonio; Scollo, Simona

2017-04-01

Fragmentation of mafic magmas remains a poorly understood process despite the common occurrence of low viscosity explosive eruptions. In fact, it has been commonly overlooked based on the assumption that low viscosity magmas have very limited explosivity and low potential to undergo brittle fragmentation. However, it is now known that highly explosive, ash forming eruptions can be relatively frequent at several mafic volcanoes. Three questions arise due to this - What is the specific fragmentation mechanism occuring in these eruptions? What are the primary factors controlling fragmentation efficiency? Can a link between eruption style and fragmentation efficiency be quantified? We addressed these questions by coupling theoretical observations and field analysis of the recent May 2016 eruption at Mount Etna volcano. Within this complex 10-day event three paroxysmal episodes of pulsating basaltic lava jets alternating with small lava flows were recorded from a vent within the Voragine crater. The associated plumes which were produced deposited tephra along narrow axes to the east and south east. Sampling was done on the deposits associated with the first two plumes and the third one. We briefly characterise the May 2016 eruption by assessing plume height, eruption phases, total erupted masses and fallout boundaries and comparing them to previous eruptions. We also analyse the total grainsize distribution (TGSD) of the scoria particles formed in the jets. Conventional methods for obtaining grainsize and total distributions of an eruption are based on mass and provide limited information on fragmentation though. For this reason, the TGSD was assessed by coupling particle analyser data and conventional sieving data to assess both particle size and number of particle distributions with better precision. This allowed for more accurate testing of several existing models describing the shape of the TGSD. Coupled further with observations on eruption dynamics and eruption phase durations obtained from the network of fixed INGV cameras, early insight into possible links between fragmentation and eruption conditions are identified. A link between fragmentation and magma properties is also examined. We discuss the relationship between the conventional and new analytical methods and their potential in unraveling key information on the fragmentation process and analyse how the dataset on the May eruption can be modelled with the current fragmentation theories. Finally, we suggest the systematic use of a comprehensive TGSD dataset to develop a fragmentation model for mafic eruptions.

The 2006-2009 activity of the Ubinas volcano (Peru): Petrology of the 2006 eruptive products and insights into genesis of andesite magmas, magma recharge and plumbing system

NASA Astrophysics Data System (ADS)

Rivera, Marco; Thouret, Jean-Claude; Samaniego, Pablo; Le Pennec, Jean-Luc

2014-01-01

Following a fumarolic episode that started six months earlier, the most recent eruptive activity of the Ubinas volcano (south Peru) began on 27 March 2006, intensified between April and October 2006 and slowly declined until December 2009. The chronology of the explosive episode and the extent and composition of the erupted material are documented with an emphasis on ballistic ejecta. A petrological study of the juvenile products allows us to infer the magmatic processes related to the 2006-2009 eruptions of the andesitic Ubinas volcano. The juvenile magma erupted during the 2006 activity shows a homogeneous bulk-rock andesitic composition (56.7-57.6 wt.% SiO2), which belongs to a medium- to high-K calc-alkaline series. The mineral assemblage of the ballistic blocks and tephra consists of plagioclase > two-pyroxenes > Fe-Ti oxide and rare olivine and amphibole set in a groundmass of the same minerals with a dacitic composition (66-67 wt.% SiO2). Thermo-barometric data, based on two-pyroxene and amphibole stability, records a magma temperature of 998 ± 14 °C and a pressure of 476 ± 36 MPa. Widespread mineralogical and textural features point to a disequilibrium process in the erupted andesite magma. These features include inversely zoned "sieve textures" in plagioclase, inversely zoned clinopyroxene, and olivine crystals with reaction and thin overgrowth rims. They indicate that the pre-eruptive magmatic processes were dominated by recharge of a hotter mafic magma into a shallow reservoir, where magma mingling occurred and triggered the eruption. Prior to 2006, a probable recharge of a mafic magma produced strong convection and partial homogenization in the reservoir, as well as a pressure increase and higher magma ascent rate after four years of fumarolic activity. Mafic magmas do not prevail in the Ubinas pre-historical lavas and tephras. However, mafic andesites have been erupted during historical times (e.g. AD 1667 and 2006-2009 vulcanian eruptions). Hence, the most recent episode indicates that a resupply of mafic magmas has probably occurred at depth under Ubinas.

Direct Observations of Magnetic Flux Rope Formation during a Solar Coronal Mass Ejection

NASA Astrophysics Data System (ADS)

Song, H. Q.; Zhang, J.; Chen, Y.; Cheng, X.

2014-09-01

Coronal mass ejections (CMEs) are the most spectacular eruptive phenomena in the solar atmosphere. It is generally accepted that CMEs are the results of eruptions of magnetic flux ropes (MFRs). However, there is heated debate on whether MFRs exist prior to the eruptions or if they are formed during the eruptions. Several coronal signatures, e.g., filaments, coronal cavities, sigmoid structures, and hot channels (or hot blobs), are proposed as MFRs and observed before the eruption, which support the pre-existing MFR scenario. There is almost no reported observation of MFR formation during the eruption. In this Letter, we present an intriguing observation of a solar eruptive event that occurred on 2013 November 21 with the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory, which shows the formation process of the MFR during the eruption in detail. The process began with the expansion of a low-lying coronal arcade, possibly caused by the flare magnetic reconnection underneath. The newly formed ascending loops from below further pushed the arcade upward, stretching the surrounding magnetic field. The arcade and stretched magnetic field lines then curved in just below the arcade vertex, forming an X-point. The field lines near the X-point continued to approach each other and a second magnetic reconnection was induced. It is this high-lying magnetic reconnection that led to the formation and eruption of a hot blob (~10 MK), presumably an MFR, producing a CME. We suggest that two spatially separated magnetic reconnections occurred in this event, which were responsible for producing the flare and the hot blob (CME).

Direct Observations of Magnetic Flux Rope Formation during a Solar Coronal Mass Ejection

NASA Astrophysics Data System (ADS)

Song, H.; Zhang, J.; Chen, Y.; Cheng, X.

2014-12-01

Coronal mass ejections (CMEs) are the most spectacular eruptive phenomena in the solar atmosphere. It is generally accepted that CMEs are results of eruptions of magnetic flux ropes (MFRs). However, a heated debate is on whether MFRs pre-exist before the eruptions or they are formed during the eruptions. Several coronal signatures, e.g., filaments, coronal cavities, sigmoid structures and hot channels (or hot blobs), are proposed as MFRs and observed before the eruption, which support the pre existing MFR scenario. There is almost no reported observation about MFR formation during the eruption. In this presentation, we present an intriguing observation of a solar eruptive event with the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory, which shows a detailed formation process of the MFR during the eruption. The process started with the expansion of a low lying coronal arcade, possibly caused by the flare magnetic reconnection underneath. The newly-formed ascending loops from below further pushed the arcade upward, stretching the surrounding magnetic field. The arcade and stretched magnetic field lines then curved-in just below the arcade vertex, forming an X-point. The field lines near the X-point continued to approach each other and a second magnetic reconnection was induced. It is this high-lying magnetic reconnection that led to the formation and eruption of a hot blob (~ 10 MK), presumably a MFR, producing a CME. We suggest that two spatially-separated magnetic reconnections occurred in this event, responsible for producing the flare and the hot blob (CME), respectively.

Rapid heterogeneous assembly of multiple magma reservoirs prior to Yellowstone supereruptions.

PubMed

Wotzlaw, Jörn-Frederik; Bindeman, Ilya N; Stern, Richard A; D'Abzac, Francois-Xavier; Schaltegger, Urs

2015-09-10

Large-volume caldera-forming eruptions of silicic magmas are an important feature of continental volcanism. The timescales and mechanisms of assembly of the magma reservoirs that feed such eruptions as well as the durations and physical conditions of upper-crustal storage remain highly debated topics in volcanology. Here we explore a comprehensive data set of isotopic (O, Hf) and chemical proxies in precisely U-Pb dated zircon crystals from all caldera-forming eruptions of Yellowstone supervolcano. Analysed zircons record rapid assembly of multiple magma reservoirs by repeated injections of isotopically heterogeneous magma batches and short pre-eruption storage times of 10(3) to 10(4) years. Decoupled oxygen-hafnium isotope systematics suggest a complex source for these magmas involving variable amounts of differentiated mantle-derived melt, Archean crust and hydrothermally altered shallow-crustal rocks. These data demonstrate that complex magma reservoirs with multiple sub-chambers are a common feature of rift- and hotspot related supervolcanoes. The short duration of reservoir assembly documents rapid crustal remelting and two to three orders of magnitude higher magma production rates beneath Yellowstone compared to continental arc volcanoes. The short pre-eruption storage times further suggest that the detection of voluminous reservoirs of eruptible magma beneath active supervolcanoes may only be possible prior to an impending eruption.

Post-eruptive inflation of Okmok Volcano, Alaska, from InSAR, 2008–2014

USGS Publications Warehouse

Qu, Feifei; Lu, Zhong; Poland, Michael; Freymueller, Jeffrey T.; Zhang, Qin; Jung, Hyung-Sup

2016-01-01

Okmok, a ~10-km wide caldera that occupies most of the northeastern end of Umnak Island, is one of the most active volcanoes in the Aleutian arc. The most recent eruption at Okmok during July-August 2008 was by far its largest and most explosive since at least the early 19th century. We investigate post-eruptive magma supply and storage at the volcano during 2008–2014 by analyzing all available synthetic aperture radar (SAR) images of Okmok acquired during that time period using the multi-temporal InSAR technique. Data from the C-band Envisat and X-band TerraSAR-X satellites indicate that Okmok started inflating very soon after the end of 2008 eruption at a time-variable rate of 48-130 mm/y, consistent with GPS measurements. The “model-assisted” phase unwrapping method is applied to improve the phase unwrapping operation for long temporal baseline pairs. The InSAR time-series is used as input for deformation source modeling, which suggests magma accumulating at variable rates in a shallow storage zone at ~3.9 km below sea level beneath the summit caldera, consistent with previous studies. The modeled volume accumulation in the 6 years following the 2008 eruption is ~75% of the 1997 eruption volume and ~25% of the 2008 eruption volume.

Rapid heterogeneous assembly of multiple magma reservoirs prior to Yellowstone supereruptions

PubMed Central

Wotzlaw, Jörn-Frederik; Bindeman, Ilya N.; Stern, Richard A.; D’Abzac, Francois-Xavier; Schaltegger, Urs

2015-01-01

Large-volume caldera-forming eruptions of silicic magmas are an important feature of continental volcanism. The timescales and mechanisms of assembly of the magma reservoirs that feed such eruptions as well as the durations and physical conditions of upper-crustal storage remain highly debated topics in volcanology. Here we explore a comprehensive data set of isotopic (O, Hf) and chemical proxies in precisely U-Pb dated zircon crystals from all caldera-forming eruptions of Yellowstone supervolcano. Analysed zircons record rapid assembly of multiple magma reservoirs by repeated injections of isotopically heterogeneous magma batches and short pre-eruption storage times of 103 to 104 years. Decoupled oxygen-hafnium isotope systematics suggest a complex source for these magmas involving variable amounts of differentiated mantle-derived melt, Archean crust and hydrothermally altered shallow-crustal rocks. These data demonstrate that complex magma reservoirs with multiple sub-chambers are a common feature of rift- and hotspot related supervolcanoes. The short duration of reservoir assembly documents rapid crustal remelting and two to three orders of magnitude higher magma production rates beneath Yellowstone compared to continental arc volcanoes. The short pre-eruption storage times further suggest that the detection of voluminous reservoirs of eruptible magma beneath active supervolcanoes may only be possible prior to an impending eruption. PMID:26356304

Eruption style at Kīlauea Volcano in Hawai‘i linked to primary melt composition

USGS Publications Warehouse

Sides. I.R.,; Edmonds, M.; Maclennan, J.; Swanson, Don; Houghton, Bruce F.

2014-01-01

Explosive eruptions at basaltic volcanoes have been linked to gas segregation from magmas at shallow depths in the crust. The composition of primary melts formed at greater depths was thought to have little influence on eruptive style. Ocean island basaltic volcanoes are the product of melting of a geochemically heterogeneous mantle plume and are expected to give rise to heterogeneous primary melts. This range in primary melt composition, particularly with respect to the volatile components, will profoundly influence magma buoyancy, storage and eruption style. Here we analyse the geochemistry of a suite of melt inclusions from 25 historical eruptions at the ocean island volcano of Kīlauea, Hawai‘i, over the past 600 years. We find that more explosive styles of eruption at Kīlauea Volcano are associated statistically with more geochemically enriched primary melts that have higher volatile concentrations. These enriched melts ascend faster and retain their primary nature, undergoing little interaction with the magma reservoir at the volcano’s summit. We conclude that the eruption style and magma-supply rate at Kīlauea are fundamentally linked to the geochemistry of the primary melts formed deep below the volcano. Magmas might therefore be predisposed towards explosivity right at the point of formation in their mantle source region.

Reconstructing the plinian and co-ignimbrite sources of large volcanic eruptions: A novel approach for the Campanian Ignimbrite

PubMed Central

Marti, Alejandro; Folch, Arnau; Costa, Antonio; Engwell, Samantha

2016-01-01

The 39 ka Campanian Ignimbrite (CI) super-eruption was the largest volcanic eruption of the past 200 ka in Europe. Tephra deposits indicate two distinct plume forming phases, Plinian and co-ignimbrite, characteristic of many caldera-forming eruptions. Previous numerical studies have characterized the eruption as a single-phase event, potentially leading to inaccurate assessment of eruption dynamics. To reconstruct the volume, intensity, and duration of the tephra dispersal, we applied a computational inversion method that explicitly accounts for the Plinian and co-ignimbrite phases and for gravitational spreading of the umbrella cloud. To verify the consistency of our results, we performed an additional single-phase inversion using an independent thickness dataset. Our better-fitting two-phase model suggests a higher mass eruption rate than previous studies, and estimates that 3/4 of the total fallout volume is co-ignimbrite in origin. Gravitational spreading of the umbrella cloud dominates tephra transport only within the first hundred kilometres due to strong stratospheric winds in our best-fit wind model. Finally, tephra fallout impacts would have interrupted the westward migration of modern hominid groups in Europe, possibly supporting the hypothesis of prolonged Neanderthal survival in South-Western Europe during the Middle to Upper Palaeolithic transition. PMID:26883449

Reconstructing the plinian and co-ignimbrite sources of large volcanic eruptions: A novel approach for the Campanian Ignimbrite.

PubMed

Marti, Alejandro; Folch, Arnau; Costa, Antonio; Engwell, Samantha

2016-02-17

The 39 ka Campanian Ignimbrite (CI) super-eruption was the largest volcanic eruption of the past 200 ka in Europe. Tephra deposits indicate two distinct plume forming phases, Plinian and co-ignimbrite, characteristic of many caldera-forming eruptions. Previous numerical studies have characterized the eruption as a single-phase event, potentially leading to inaccurate assessment of eruption dynamics. To reconstruct the volume, intensity, and duration of the tephra dispersal, we applied a computational inversion method that explicitly accounts for the Plinian and co-ignimbrite phases and for gravitational spreading of the umbrella cloud. To verify the consistency of our results, we performed an additional single-phase inversion using an independent thickness dataset. Our better-fitting two-phase model suggests a higher mass eruption rate than previous studies, and estimates that 3/4 of the total fallout volume is co-ignimbrite in origin. Gravitational spreading of the umbrella cloud dominates tephra transport only within the first hundred kilometres due to strong stratospheric winds in our best-fit wind model. Finally, tephra fallout impacts would have interrupted the westward migration of modern hominid groups in Europe, possibly supporting the hypothesis of prolonged Neanderthal survival in South-Western Europe during the Middle to Upper Palaeolithic transition.

Nyamulagira’s magma plumbing system inferred from 15 years of InSAR

USGS Publications Warehouse

Wauthier, Christelle; Cayol, Valérie; Poland, Michael; Kervyn, François; D'Oreye, Nicolas; Hooper, Andrew; Samsonov, Sergei; Tiampo, Kristy; Smets, Benoit; Pyle, D. M.; Mather, T.A.; Biggs, J.

2013-01-01

Nyamulagira, located in the east of the Democratic Republic of Congo on the western branch of the East African rift, is Africa’s most active volcano, with an average of one eruption every 3 years since 1938. Owing to the socio-economical context of that region, the volcano lacks ground-based geodetic measurements but has been monitored by interferometric synthetic aperture radar (InSAR) since 1996. A combination of 3D Mixed Boundary Element Method and inverse modelling, taking into account topography and source interactions, is used to interpret InSAR ground displacements associated with eruptive activity in 1996, 2002, 2004, 2006 and 2010. These eruptions can be fitted by models incorporating dyke intrusions, and some (namely the 2006 and 2010 eruptions) require a magma reservoir beneath the summit caldera. We investigate inter-eruptive deformation with a multi-temporal InSAR approach. We propose the following magma plumbing system at Nyamulagira by integrating numerical deformation models with other available data: a deep reservoir (c. 25 km depth) feeds a shallower reservoir (c. 4 km depth); proximal eruptions are fed from the shallow reservoir through dykes while distal eruptions can be fed directly from the deep reservoir. A dyke-like conduit is also present beneath the upper southeastern flank of Nyamulagira.

Processes Influencing the Timing and Volume of Eruptions From the Youngest Supervolcano on Earth

NASA Astrophysics Data System (ADS)

Wilson, C. J. N.; Barker, S. J.; Morgan, D. J.; Rowland, J. V.; Schipper, I.

2015-12-01

In their stratigraphic records, silicic caldera volcanoes display wide ranges of eruptive styles and volumes. However, relationships between frequency and magnitude are often complex, and the forecasting of future activity is inherently problematic. Taupo volcano, New Zealand, provides a unique opportunity to investigate eruptive histories from a hyperactive, large silicic magmatic system with eruptive volumes that span 3-4 orders of magnitude, and show no clear relationships with the repose period. Taupo hosted the world's most recent supereruption at 25.4 ka, which discharged 530 km3 of magma in the episodic 10-phase Oruanui event. Only 5 kyr later, Taupo revived, with 3 dacitic eruptions from 21.5-17 ka and 25 rhyolite eruptions from 12-1.7 ka. Here we use trends in whole rock, glass and mineral chemistry to show how the magma system reestablished following the Oruanui event, and to consider what processes influence the state of the modern volcano. The post-Oruanui dacites reflect the first products of the rebuilding silicic magma system, as most of the Oruanui mush was reconfigured or significantly modified in composition following thermal fluxing accompanying post-caldera collapse readjustment. Compositional variations within the younger rhyolites at <12 ka reflect fine-scale temporal changes in mineral phase stability, closely linked to the development, stabilization and maturation of a new silicic mush system. For the most recent eruptions, the system underwent destabilization, resulting in increased volumes of melt extraction from the silicic mush. Orthopyroxene Fe-Mg diffusion timescales indicate that the onset of rapid heating and priming of the silicic mush occurred <100 years prior to the <2.15 ka eruptions, with subsequent melt accumulation occurring in only decades. The largest post-Oruanui eruption at 232 AD culminated from elevated mafic magma supply to the silicic mush pile, rapid melt accumulation and high differential tectonic stress build up, leading to one of the largest and most violent Holocene eruptions globally. The latest eruptions of Taupo highlight the multiple controls on the timing of eruptions, and demonstrate how the magmatic system can rapidly change behavior to generate large eruptible melt bodies on timescales of direct relevance to humans and monitoring initiatives.

Observing the 2010 Eyjafjallajökull, Iceland, Eruptions with NASA's Earth Observing-1 Spacecraft - Improving Data Flow In a Volcanic Crisis Through Use of Autonomy

NASA Astrophysics Data System (ADS)

Chien, S.; Davies, A. G.; Doubleday, J.; Tran, D. Q.; Gudmundsson, M. T.; Jónsdóttir, I.; Hoskuldsson, A.; Thordarson, T.; Jakobsdottir, S.; Wright, R.

2010-12-01

Eyjafjallajökull volcano, Iceland, erupted from 20 March to 12 April 2010 (a flank eruption) and again from 14 April to 23 May 2010. The latter eruption heavily impacted air travel across much of northern Europe, and highlighted the need to monitor and quickly react to new eruptions. The NASA Earth Observing 1 spacecraft (EO-1), which is managed by the NASA Goddard Space Flight Center, obtained over 50 observation pairs with the Hyperion hyperspectral imager and ALI (Advanced Land Imager) multispectral camera. EO-1 is the remote-sensing asset of a globe-spanning Volcano Sensor Web [1], where low spatial resolution data (e.g., MODIS) or alerts of ongoing or possible volcanic activity are used to trigger requests for high resolution EO-1 data. Advanced resource management software, developed in part for flight onboard EO-1 as part of the Autonomous Sciencecraft [2, 3] is now used to task EO-1. This system allowed rapid re-tasking of EO-1 to obtain both day and night data at high temporal resolution (on average every 2 days), unusual for such high spatial resolution imagers (Hyperion and ALI at 30 m/pixel, with an ALI panchromatic band at 10 m/pixel). About 50% of the data were impacted by cloud. Advances in data handling and communications during the last two years means that Hyperion and ALI data are typically on the ground and ready for analysis within a few hours of data acquisition. Automatic data processing systems at the NASA’s Jet Propulsion Laboratory process Hyperion data to (1) correct for atmospheric adsorption; (2) remove the sunlight component in daytime data; (3) identify hot pixels; (4) fit unsaturated data to determine temperature and area of sub-pixel thermal sources; (5) calculate total thermal emission and, from this, an effusion rate; (6) generate geo-located data products. The entire process is autonomous. Data products, as well as images generated, were sent to volcanologists in the field to aid in eruption assessment. The JPL group is now working with Icelandic scientists to develop a mechanism for triggering EO-1 observations from Icelandic Meteorological Office and University of Iceland in situ instruments. References: [1] Davies, A. G., et al., 2006, Eos, 87 (1), 1&5. [2] Chien, S. et al., 2005, J. Aerospace Computing, Information, & Communication, 2005, AIAA, 2, 196-216. [3] Davies, A. G. et al., 2006, Rem. Sens. Environ., 101, no. 4, 427-446. This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA.

Olivine-hosted melt inclusions as an archive of redox heterogeneity in magmatic systems

NASA Astrophysics Data System (ADS)

Hartley, Margaret E.; Shorttle, Oliver; Maclennan, John; Moussallam, Yves; Edmonds, Marie

2017-12-01

The redox state of volcanic products determines their leverage on the oxidation of Earth's oceans and atmosphere, providing a long-term feedback on oxygen accumulation at the planet's surface. An archive of redox conditions in volcanic plumbing systems from a magma's mantle source, through crustal storage, to eruption, is carried in pockets of melt trapped within crystals. While melt inclusions have long been exploited for their capacity to retain information on a magma's history, their permeability to fast-diffusing elements such as hydrogen is now well documented and their retention of initial oxygen fugacities (fO2) could be similarly diffusion-limited. To test this, we have measured Fe3+/ΣFe by micro-XANES spectroscopy in a suite of 65 olivine-hosted melt inclusions and 9 matrix glasses from the AD 1783 Laki eruption, Iceland. This eruption experienced pre-eruptive mixing of chemically diverse magmas, syn-eruptive degassing at the vent, and post-eruptive degassing during lava flow up to 60 km over land, providing an ideal test of whether changes in the fO2 of a magma may be communicated through to its cargo of crystal-hosted melt inclusions. Melt inclusions from rapidly quenched tephra samples have Fe3+/ΣFe of 0.206 ± 0.008 (ΔQFM of +0.7 ± 0.1), with no correlation between their fO2 and degree of trace element enrichment or differentiation. These inclusions preserve the redox conditions of the mixed pre-eruptive Laki magma. When corrected for fractional crystallisation to 10 wt.% MgO, these inclusions record a parental magma [Fe3+/ΣFe](10) of 0.18 (ΔQFM of +0.4), significantly more oxidised than the Fe3+/ΣFe of 0.10 that is often assumed for Icelandic basalt magmas. Melt inclusions from quenched lava selvages are more reduced than those from the tephra, having Fe3+/ΣFe between 0.133 and 0.177 (ΔQFM from -0.4 to +0.4). These inclusions have approached equilibrium with their carrier lava, which has been reduced by sulfur degassing. The progressive re-equilibration of fO2 between inclusions and carrier melts occurs on timescales of hours to days, causing a drop in the sulfur content at sulfide saturation (SCSS) and driving the exsolution of immiscible sulfide globules in the inclusions. Our data demonstrate the roles of magma mixing, progressive re-equilibration, and degassing in redox evolution within magmatic systems, and the open-system nature of melt inclusions to fO2 during these processes. Redox heterogeneity present at the time of inclusion trapping may be overprinted by rapid re-equilibration of melt inclusion fO2 with the external environment, both in the magma chamber and during slow cooling in lava at the surface. This can decouple the melt inclusion archives of fO2, major and trace element chemistry, and mask associations between fO2, magmatic differentiation and mantle source heterogeneity unless the assembly of diverse magmas is rapidly followed by eruption. Our tools for understanding the redox conditions of magmas are thus limited; however, careful reconstruction of pre- and post-eruptive magmatic history has enabled us to confirm the relatively oxidised nature of ocean island-type mantle compared to that of mid-ocean ridge mantle.

NSV 11749, an Elder Sibling of the Born-again Stars V605 Aql and V4334 Sgr?

NASA Astrophysics Data System (ADS)

Miller Bertolami, M. M.; Rohrmann, R. D.; Granada, A.; Althaus, L. G.

2011-12-01

We argue that NSV 11749, an eruption observed in the early twentieth century, was a rare event known as "very late thermal pulse" (VLTP). To support our argument we compare the light curve of NSV 11749 with those of the two bona fide VLTP objects known to date, V4334 Sgr and V605 Aql, and with those predicted by state-of-the-art stellar evolution models. Next, we explore the INT Photometric H-Alpha Survey (IPHAS) and Two Micron All Sky Survey (2MASS) catalogs for possible counterparts of the eruption. Our analysis shows that the VLTP scenario outperforms all other proposed scenarios as an explanation of NSV 11749. We identify an IPHAS/2MASS source at the eruption location of NSV 11749. The derived colors suggest that the object is not enshrouded in a thick dust shell as V605 Aql and V4334 Sgr. Also, the absence of an apparent planetary nebula at the eruption location suggests differences with known VLTP objects which might be linked to the intensity of the eruption and the mass of the object. Further exploration of this source and scenario seems desirable. If NSV 11749 was a born-again star, it would be the third event of its kind to have been observed and will strongly help us to increase our understanding of the later stages of stellar evolution and violent reactive convective burning.

Repeated magmatic intrusions at El Hierro Island following the 2011-2012 submarine eruption

NASA Astrophysics Data System (ADS)

Benito-Saz, Maria A.; Parks, Michelle M.; Sigmundsson, Freysteinn; Hooper, Andrew; García-Cañada, Laura

2017-09-01

After more than 200 years of quiescence, in July 2011 an intense seismic swarm was detected beneath the center of El Hierro Island (Canary Islands), culminating on 10 October 2011 in a submarine eruption, 2 km off the southern coast. Although the eruption officially ended on 5 March 2012, magmatic activity continued in the area. From June 2012 to March 2014, six earthquake swarms, indicative of magmatic intrusions, were detected underneath the island. We have studied these post-eruption intrusive events using GPS and InSAR techniques to characterize the ground surface deformation produced by each of these intrusions, and to determine the optimal source parameters (geometry, location, depth, volume change). Source inversions provide insight into the depth of the intrusions ( 11-16 km) and the volume change associated with each of them (between 0.02 and 0.13 km3). During this period, > 20 cm of uplift was detected in the central-western part of the island, corresponding to approximately 0.32-0.38 km3 of magma intruded beneath the volcano. We suggest that these intrusions result from deep magma migrating from the mantle, trapped at the mantle/lower crust discontinuity in the form of sill-like bodies. This study, using joint inversion of GPS and InSAR data in a post-eruption period, provides important insight into the characteristics of the magmatic plumbing system of El Hierro, an oceanic intraplate volcanic island.

The effect of wind and eruption source parameter variations on tephra fallout hazard assessment: an example from Vesuvio (Italy)

NASA Astrophysics Data System (ADS)

Macedonio, Giovanni; Costa, Antonio; Scollo, Simona; Neri, Augusto

2015-04-01

Uncertainty in the tephra fallout hazard assessment may depend on different meteorological datasets and eruptive source parameters used in the modelling. We present a statistical study to analyze this uncertainty in the case of a sub-Plinian eruption of Vesuvius of VEI = 4, column height of 18 km and total erupted mass of 5 × 1011 kg. The hazard assessment for tephra fallout is performed using the advection-diffusion model Hazmap. Firstly, we analyze statistically different meteorological datasets: i) from the daily atmospheric soundings of the stations located in Brindisi (Italy) between 1962 and 1976 and between 1996 and 2012, and in Pratica di Mare (Rome, Italy) between 1996 and 2012; ii) from numerical weather prediction models of the National Oceanic and Atmospheric Administration and of the European Centre for Medium-Range Weather Forecasts. Furthermore, we modify the total mass, the total grain-size distribution, the eruption column height, and the diffusion coefficient. Then, we quantify the impact that different datasets and model input parameters have on the probability maps. Results shows that the parameter that mostly affects the tephra fallout probability maps, keeping constant the total mass, is the particle terminal settling velocity, which is a function of the total grain-size distribution, particle density and shape. Differently, the evaluation of the hazard assessment weakly depends on the use of different meteorological datasets, column height and diffusion coefficient.

The Pucará Caldera: Evidences For A Miocene Caldera-Forming Eruption

NASA Astrophysics Data System (ADS)

Mulas, M.; Aviles Moran, H. S.; Flor Jimenez, M. A.; Sanclemente Ordoñez, E. R.; Le Pennec, J. L.; Larreta Torres, E. W.

2017-12-01

The southern sector of Ecuador (between 2°S and 6°S) has been characterized by intense magmatic activity in the period comprised between Oligocene and Miocene. The volcanic sequence in the Pucará-Santa Isabel sector is composed by the Saraguro Fm. (26-21 Ma) followed by the St. Isabel Fm. (18 - 7.6 Ma) and closed by the Tarqui Fm. (6.3 Ma). These volcanic formations, made principally of welded ignimbrites, show large lithofacies variability (boulder size to lapilli size lithics, crystal rich to fiamme-rich ignimbrites) that reflects different PDC run-out and principally different sources. The geomorphology shows a tectonic tilting, regionally affected by the Calacali - Pallatanga Fault (NE -SW trend) and locally by the Jubones (W-E trend) and Giròn (NE-SW trend) faults. The aim of this work is to obtain a detailed characterization of the stratigraphy and of the lithofacies of these ignimbrites, to understand the eruptive sequences and to identify source locations. The Saraguro Fm. consists of lava flows followed by an outflow crystal rich ignimbrite (Jubones Fm.). This ignimbrite is related to a caldera-forming eruption where the source, in accord with cinematic indicators and lateral lithofacies variations, is sited in the northern sector of Pucará city. A new eruptive cycle recorded by the St. Isabel Fm., appears after a pause of 2 Ma evidenced by the lacustrine sediments of the Jacapa Fm. In the SW sector from Pucará is present an elliptical depression boarded by a breccia ignimbrite. These ignimbrites are characterized by a coarse-grained ash matrix with m-sized boulder and heterogeneity of the nature of the lithic fragments. The stratigraphical, lithological, structural, and petrological features show evidence for previously undescribed caldera near Pucará. The stratigraphical evidences permit to assert that the 13-km X 7-km-wide Pucará caldera formed during the eruption is associated to the St. Isabel eruption. This research contributes to improve the volcanological history of this area that still remains unclear.

Petrological insights on the effusive-explosive transitions of the Nisyros-Yali Volcanic Center, South Aegean Sea

NASA Astrophysics Data System (ADS)

Popa, Razvan-Gabriel; Bachmann, Olivier; Ellis, Ben; Degruyter, Wim; Kyriakopoulos, Konstantinos

2017-04-01

Volcanoes erupting silicic, volatile-rich magmas can exhibit both effusive and explosive eruptions, even during closely spaced eruptive episodes. Understanding the effusive-explosive transition is fundamental in order to assess the hazards involved. Magma properties strongly influence the processes during magma ascent that determine the eruptive style. Here, we investigate the link between changing conditions in the magma reservoir and the eruptive style. The Quaternary Nisyros-Yali volcanic center, from the South Aegean Sea, provides an excellent natural laboratory to study this process. Over the last 60-100 kyrs, it produced a series of dacitic to rhyolitic eruptions that emplaced alternating effusive and explosive deposits (with explosive eruptions likely shortly following effusive ones). For this study, nine fresh and well-preserved units (five effusive and four explosive) were sampled and analyzed for whole-rock, groundmass glass and mineral compositions, in order to draw insights into the magma chamber processes and thermodynamic conditions that preceded both types of eruptions. Silicic magmas in Nisyros-Yali record a complex, open-system evolution, dominated by fractionation in mushy reservoirs at mid to upper crustal depths, frequently recharged by warmer input from below. Storage temperatures recorded by the amphibole-plagioclase thermometer span a wide range, and they are always cooler than the pre-eruptive temperatures yielded by Fe-Ti oxide thermometry for the same unit, whether it is effusive or explosive. However, magmas feeding effusive eruptions typically reached cooler conditions (expressed by the presence of low-Al, low-Ti amphiboles) than in the explosive cases. The difference between the pre-eruptive and the lowest storing temperatures in the Nisyros series are in the order of 10-30°C for explosive units, while the difference is of about 40-110°C for the effusive units. The Yali series does not perfectly fit this pattern, where explosive units have also been heated for 50-100°C. During crystallization and storage in subvolcanic magma reservoirs, relatively cold conditions and higher H2O contents would favor volatile saturation, allowing reservoirs to become more compressible. Hence, a higher fraction of magma recharge would be needed to reach the necessary chamber overpressure to trigger an eruption. In turn, this higher fraction of recharge would allow more mixing and heating of the resident silicic magma, lowering melt viscosity. This facilitates the formation of a permeable foam by growth and expansion of the already nucleated gas bubbles, inducing early syn-eruptive degassing in the conduit and favoring effusive outpouring of magma. In contrast, slightly warmer conditions (and/or slightly lower H2O concentrations) in the mush would lead to reservoirs with less exsolved volatiles, hence less compressible. Thus, eruptions would be triggered faster and pre-eruptive warming would be more limited, reducing magma viscosity less than in the previous case. Bubble nucleation would mostly be confined to the conduit with syn-eruptive degassing starting at shallower depths and being less efficient, thus favoring an explosive eruption.

Simulations and parameterisation of shallow volcanic plumes of Piton de la Fournaise, Reunion Island, using Meso-NH version 4-9-3

NASA Astrophysics Data System (ADS)

Sivia, S. G.; Gheusi, F.; Mari, C.; Di Muro, A.

2015-05-01

In mesoscale models (resolution ~ 1 km) used for regional dispersion of pollution plumes the volcanic heat sources and emissions of gases and aerosols, as well as the induced atmospheric convective motions, are all sub-grid-scale processes (mostly true for weak effusive eruptions) which need to be parameterised. We propose a modified formulation of the EDMF scheme (eddy diffusivity/mass flux) proposed by Pergaud et al. (2009) which is based on a single sub-grid updraft model. It is used to represent volcano induced updrafts tested for a case study of the January 2010 summit eruption of Piton de la Fournaise (PdF) volcano. The validation of this modified formulation using a reference large eddy simulation (LES) focuses on the ability of the model to transport tracer concentrations up to 1-2 km above the ground in the lower troposphere as is the case of majority of PdF eruptions. The modelled volcanic plume agrees reasonably with the profiles of SO2 (sulfur dioxide) tracer concentrations and specific humidity found from the reference LES. Sensitivity tests performed for the modified formulation of the EDMF scheme emphasise the sensitivity of the parameterisation to ambient fresh air entrainment at the plume base.

The Eruption of a Small-scale Emerging Flux Rope as the Driver of an M-class Flare and of a Coronal Mass Ejection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, X. L.; Xue, Z. K.; Wang, J. C.

Solar flares and coronal mass ejections are the most powerful explosions in the Sun. They are major sources of potentially destructive space weather conditions. However, the possible causes of their initiation remain controversial. Using high-resolution data observed by the New Solar Telescope of Big Bear Solar Observatory, supplemented by Solar Dynamics Observatory observations, we present unusual observations of a small-scale emerging flux rope near a large sunspot, whose eruption produced an M-class flare and a coronal mass ejection. The presence of the small-scale flux rope was indicated by static nonlinear force-free field extrapolation as well as data-driven magnetohydrodynamics modeling ofmore » the dynamic evolution of the coronal three-dimensional magnetic field. During the emergence of the flux rope, rotation of satellite sunspots at the footpoints of the flux rope was observed. Meanwhile, the Lorentz force, magnetic energy, vertical current, and transverse fields were increasing during this phase. The free energy from the magnetic flux emergence and twisting magnetic fields is sufficient to power the M-class flare. These observations present, for the first time, the complete process, from the emergence of the small-scale flux rope, to the production of solar eruptions.« less

Automated detection and cataloging of global explosive volcanism using the International Monitoring System infrasound network

NASA Astrophysics Data System (ADS)

Matoza, Robin S.; Green, David N.; Le Pichon, Alexis; Shearer, Peter M.; Fee, David; Mialle, Pierrick; Ceranna, Lars

2017-04-01

We experiment with a new method to search systematically through multiyear data from the International Monitoring System (IMS) infrasound network to identify explosive volcanic eruption signals originating anywhere on Earth. Detecting, quantifying, and cataloging the global occurrence of explosive volcanism helps toward several goals in Earth sciences and has direct applications in volcanic hazard mitigation. We combine infrasound signal association across multiple stations with source location using a brute-force, grid-search, cross-bearings approach. The algorithm corrects for a background prior rate of coherent unwanted infrasound signals (clutter) in a global grid, without needing to screen array processing detection lists from individual stations prior to association. We develop the algorithm using case studies of explosive eruptions: 2008 Kasatochi, Alaska; 2009 Sarychev Peak, Kurile Islands; and 2010 Eyjafjallajökull, Iceland. We apply the method to global IMS infrasound data from 2005-2010 to construct a preliminary acoustic catalog that emphasizes sustained explosive volcanic activity (long-duration signals or sequences of impulsive transients lasting hours to days). This work represents a step toward the goal of integrating IMS infrasound data products into global volcanic eruption early warning and notification systems. Additionally, a better understanding of volcanic signal detection and location with the IMS helps improve operational event detection, discrimination, and association capabilities.

Data-driven magnetohydrodynamic modelling of a flux-emerging active region leading to solar eruption

PubMed Central

Jiang, Chaowei; Wu, S. T.; Feng, Xuesheng; Hu, Qiang

2016-01-01

Solar eruptions are well-recognized as major drivers of space weather but what causes them remains an open question. Here we show how an eruption is initiated in a non-potential magnetic flux-emerging region using magnetohydrodynamic modelling driven directly by solar magnetograms. Our model simulates the coronal magnetic field following a long-duration quasi-static evolution to its fast eruption. The field morphology resembles a set of extreme ultraviolet images for the whole process. Study of the magnetic field suggests that in this event, the key transition from the pre-eruptive to eruptive state is due to the establishment of a positive feedback between the upward expansion of internal stressed magnetic arcades of new emergence and an external magnetic reconnection which triggers the eruption. Such a nearly realistic simulation of a solar eruption from origin to onset can provide important insight into its cause, and also has the potential for improving space weather modelling. PMID:27181846