Serreta 1998-2001 submarine volcanic eruption, offshore Terceira (Azores): Characterization of the vent and inferences about the eruptive dynamics

NASA Astrophysics Data System (ADS)

Casas, David; Pimentel, Adriano; Pacheco, José; Martorelli, Eleonora; Sposato, Andrea; Ercilla, Gemma; Alonso, Belen; Chiocci, Francesco

2018-05-01

High-resolution bathymetric data and seafloor sampling were used to characterize the most recent volcanic eruption in the Azores region, the 1998-2001 Serreta submarine eruption. The vent of the eruption is proposed to be an asymmetric topographic high, composed of two coalescing volcanic cones, underlying the location where lava balloons had been observed at the sea surface during the eruption. The volcanic products related to the 1998-2001 eruption are constrained to an area of 0.5 km2 around the proposed vent position. A submarine Strombolian-style eruption producing basaltic lava balloons, ash and coarse scoriaceous materials with limited lateral dispersion led to the buildup of the cones. The 1998-2001 Serreta eruption shares many similarities with other intermediate-depth lava balloon-forming eruptions (e.g., the 1891 eruption offshore Pantelleria and the 2011-2012 eruption south of El Hierro), revealing the particular conditions needed for the production of this unusual and scarcely documented volcanic product.

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.

History of the magmatic feeding system of the Campi Flegrei caldera (Italy)

NASA Astrophysics Data System (ADS)

Civetta, L.; Arienzo, I.; D'Antonio, M.; di Renzo, V.; di Vito, M. A.; Orsi, G.

2007-05-01

The definition of the magmatic feeding system of active volcanoes in terms of architecture, composition, crystallization time-scale, relationships between composition of the erupted magmas and structural position of the vents, and magma processes, is of paramount importance for volcanic hazards evaluation. Investigations aimed at defining the Campi Flegeri magmatic system, include detailed mineralogical, geochemical and isotopic analyses (Sr, Nd, Pb, Th,U). The magmatic feeding system of the Campi Flegrei caldera is characterized by deep and shallow magma reservoirs. In the deep reservoirs (20-10 km depth) mantle- derived magmas differentiated and were contaminated by continental crust. In the shallow reservoirs isotopically distinct magmas, further differentiated, contaminated, and mixed and mingled before eruptions. These processes generated isotopically distinct components, variably interacting with the different structural elements of the Campi Flegrei caldera through time. The relationships between the structural position of the eruption vents, during the last 15 ka of activity, and the isotopic composition of the magmas erupted at the Campi Flegrei caldera allow us to reconstruct the architecture of the magmatic feeding system and to infer the chemical and isotopic composition of the magma feeding a future eruption, according to vent position.

A decade of volcanic construction and destruction at the summit of NW Rota-1 seamount: 2004-2014

NASA Astrophysics Data System (ADS)

Schnur, Susan R.; Chadwick, William W.; Embley, Robert W.; Ferrini, Vicki L.; de Ronde, Cornel E. J.; Cashman, Katharine V.; Deardorff, Nicholas D.; Merle, Susan G.; Dziak, Robert P.; Haxel, Joe H.; Matsumoto, Haru

2017-03-01

Arc volcanoes are important to our understanding of submarine volcanism because at some sites frequent eruptions cause them to grow and collapse on human timescales. This makes it possible to document volcanic processes. Active submarine eruptions have been observed at the summit of NW Rota-1 in the Mariana Arc. We use remotely operated vehicle videography and repeat high-resolution bathymetric surveys to construct geologic maps of the summit of NW Rota-1 in 2009 and 2010 and relate them to the geologic evolution of the summit area over a 10 year period (2004-2014). We find that 2009 and 2010 were characterized by different eruptive styles, which affected the type and distribution of eruptive deposits at the summit. Year 2009 was characterized by ultraslow extrusion and autobrecciation of lava at a single eruptive vent, producing a large cone of blocky lava debris. In 2010, higher-energy explosive eruptions occurred at multiple closely spaced vents, producing a thin blanket of pebble-sized tephra overlying lava flow outcrops. A landslide that occurred between 2009 and 2010 had a major effect on lithofacies distribution by removing the debris cone and other unconsolidated deposits, revealing steep massive flow cliffs. This relatively rapid alternation between construction and destruction forms one end of a seamount growth and mass wasting spectrum. Intraplate seamounts, which tend to grow larger than arc volcanoes, experience collapse events that are orders of magnitude larger and much less frequent than those occurring at subduction zone settings. Our results highlight the interrelated cyclicity of eruptive activity and mass wasting at submarine arc volcanoes.

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.

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.

Dynamics within geyser conduits, and sensitivity to environmental perturbations: insights from a periodic geyser in the El Tatio Geyser Field, Atacama Desert, Chile

USGS Publications Warehouse

Munoz-Saez, Carolina; Manga, Michael; Hurwitz, Shaul; Rudolph, Maxwell L.; Namiki, Atsuko; Wang, Chi-Yuen

2015-01-01

Despite more than 200 years of scientific study, the internal dynamics of geyser systems remain poorly characterized. As a consequence, there remain fundamental questions about what processes initiate and terminate eruptions, and where eruptions begin. Over a one-week period in October 2012, we collected down-hole measurements of pressure and temperature in the conduit of an exceptionally regular geyser (132 s/cycle) located in the Chilean desert. We identified four stages in the geyser cycle: (1) recharge of water into the conduit after an eruption, driven by the pressure difference between water in the conduit and in a deeper reservoir; (2) a pre-eruptive stage that follows the recharge and is dominated by addition of steam from below; (3) the eruption, which occurs by rapid boiling of a large mass of water at the top of the water column, and decompression that propagates boiling conditions downward; (4) a relaxation stage during which pressure and temperature decrease until conditions preceding the recharge stage are restored. Eruptions are triggered by the episodic addition of steam coming from depth, suggesting that the dynamics of the eruptions are dominated by geometrical and thermodynamic complexities in the conduit and reservoir. Further evidence favoring the dominance of internal processes in controlling periodicity is also provided by the absence of responses of the geyser to environmental perturbations (air pressure, temperature and probably also Earth tides).

History of the Magmatic Feeding System of the Campi Flegrei Caldera

NASA Astrophysics Data System (ADS)

Orsi, G.; Civetta, L.; Arienzo, I.; D'Antonio, M.; di Renzo, V.; di Vito, M. A.

2007-12-01

The definition of the magmatic feeding system of active volcanoes, in terms of composition, time-scale of crystallization, relation between composition of the erupted magma and structural position of vents, magma chamber processes and architecture, is of extreme importance for the hazard evaluation. The studies that are carried out for the definition of the magmatic systems include detailed mineralogical, geochemical and isotopic analyses (Sr, Nd, Pb). The Campi Flegrei caldera magmatic structure is characterized by deep and shallow magma chambers. In the deep reservoir (20-10 km depth) mantle derived magmas differentiate and are contaminated with continental crust. In the shallow reservoirs isotopically distinct magmas further differentiate, mix and mingle before the eruptions. These processes generated isotopically distinct components that were variably involved along different structures of the Campi Flegrei caldera during time. At Campi Flegrei caldera the relation between the structural position of the eruptive vent, for the last 14 ka of activity, and the isotopic composition of the emitted magma allow us to reconstruct the architecture of the magmatic feeding system and to infer the chemical and isotopic composition, and the magma chamber location and processes, of the future eruption, according to the position of the vent

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.

Eruption dynamics of Hawaiian-style fountains: The case study of episode 1 of the Kilauea Iki 1959 eruption

USGS Publications Warehouse

Stovall, W.K.; Houghton, Bruce F.; Gonnermann, H.; Fagents, S.A.; Swanson, D.A.

2011-01-01

Hawaiian eruptions are characterized by fountains of gas and ejecta, sustained for hours to days that reach tens to hundreds of meters in height. Quantitative analysis of the pyroclastic products from the 1959 eruption of K??lauea Iki, K??lauea volcano, Hawai'i, provides insights into the processes occurring during typical Hawaiian fountaining activity. This short-lived but powerful eruption contained 17 fountaining episodes and produced a cone and tephra blanket as well as a lava lake that interacted with the vent and fountain during all but the first episode of the eruption, the focus of this paper. Microtextural analysis of Hawaiian fountaining products from this opening episode is used to infer vesiculation processes within the fountain and shallow conduit. Vesicle number densities for all clasts are high (106-107 cm-3). Post-fragmentation expansion of bubbles within the thermally-insulated fountain overprints the pre-fragmentation bubble populations, leading to a reduction in vesicle number density and increase in mean vesicle size. However, early quenched rims of some clasts, with vesicle number densities approaching 107 cm-3, are probably a valid approximation to magma conditions near fragmentation. The extent of clast evolution from low vesicle-to-melt ratio and corresponding high vesicle number density to higher vesicle-to-melt ratio and lower vesicle-number density corresponds to the length of residence time within the fountain. ?? 2010 Springer-Verlag.

The 2014 eruptions of Pavlof Volcano, Alaska

USGS Publications Warehouse

Waythomas, Christopher F.; Haney, Matthew M.; Wallace, Kristi; Cameron, Cheryl E.; Schneider, David J.

2017-12-22

Pavlof Volcano is one of the most frequently active volcanoes in the Aleutian Island arc, having erupted more than 40 times since observations were first recorded in the early 1800s . The volcano is located on the Alaska Peninsula (lat 55.4173° N, long 161.8937° W), near Izembek National Wildlife Refuge. The towns and villages closest to the volcano are Cold Bay, Nelson Lagoon, Sand Point, and King Cove, which are all within 90 kilometers (km) of the volcano (fig. 1). Pavlof is a symmetrically shaped stratocone that is 2,518 meters (m) high, and has about 2,300 m of relief. The volcano supports a cover of glacial ice and perennial snow roughly 2 to 4 cubic kilometers (km3) in volume, which is mantled by variable amounts of tephra fall, rockfall debris, and pyroclastic-flow deposits produced during historical eruptions. Typical Pavlof eruptions are characterized by moderate amounts of ash emission, lava fountaining, spatter-fed lava flows, explosions, and the accumulation of unstable mounds of spatter on the upper flanks of the volcano. The accumulation and subsequent collapse of spatter piles on the upper flanks of the volcano creates hot granular avalanches, which erode and melt snow and ice, and thereby generate watery debris-flow and hyperconcentrated-flow lahars. Seismic instruments were first installed on Pavlof Volcano in the early 1970s, and since then eruptive episodes have been better characterized and specific processes have been documented with greater certainty. The application of remote sensing techniques, including the use of infrasound data, has also aided the study of more recent eruptions. Although Pavlof Volcano is located in a remote part of Alaska, it is visible from Cold Bay, Sand Point, and Nelson Lagoon, making distal observations of eruptive activity possible, weather permitting. A busy air-travel corridor that is utilized by a numerous transcontinental and regional air carriers passes near Pavlof Volcano. The frequency of air travel across the region results in a relatively large number of airborne observations of eruptive activity. During the 2014 Pavlof eruptions, the Alaska Volcano Observatory received observations and photographs from pilots and local observers, which aided evaluation of the eruptive activity and the areas affected by eruptive products.This report outlines the chronology of events associated with the 2014 eruptive activity at Pavlof Volcano, provides documentation of the style and character of the eruptive episodes, and reports briefly on the eruptive products and impacts. The principal observations are described and portrayed on maps and photographs, and the 2014 eruptive activity is compared to historical eruptions.

An approach to source characterization of tremor signals associated with eruptions and lahars

NASA Astrophysics Data System (ADS)

Kumagai, Hiroyuki; Mothes, Patricia; Ruiz, Mario; Maeda, Yuta

2015-11-01

Tremor signals are observed in association with eruption activity and lahar descents. Reduced displacement ( D R) derived from tremor signals has been used to quantify tremor sources. However, tremor duration is not considered in D R, which makes it difficult to compare D R values estimated for different tremor episodes. We propose application of the amplitude source location (ASL) method to characterize the sources of tremor signals. We used this method to estimate the tremor source location and source amplitude from high-frequency (5-10 Hz) seismic amplitudes under the assumption of isotropic S-wave radiation. We considered the source amplitude to be the maximum value during tremor. We estimated the cumulative source amplitude ( I s) as the offset value of the time-integrated envelope of the vertical seismogram of tremor corrected for geometrical spreading and medium attenuation in the 5-10-Hz band. For eruption tremor signals, we also estimated the cumulative source pressure ( I p) from an infrasonic envelope waveform corrected for geometrical spreading. We studied these parameters of tremor signals associated with eruptions and lahars and explosion events at Tungurahua volcano, Ecuador. We identified two types of eruption tremor at Tungurahua: noise-like inharmonic waveforms and harmonic oscillatory signals. We found that I s increased linearly with increasing source amplitude for lahar tremor signals and explosion events, but I s increased exponentially with increasing source amplitude for inharmonic eruption tremor signals. The source characteristics of harmonic eruption tremor signals differed from those of inharmonic tremor signals. We found a linear relation between I s and I p for both explosion events and eruption tremor. Because I p may be proportional to the total mass involved during an eruption episode, this linear relation suggests that I s may be useful to quantify eruption size. The I s values we estimated for inharmonic eruption tremor were consistent with previous estimates of volumes of tephra fallout. The scaling relations among source parameters that we identified will contribute to our understanding of the dynamic processes associated with eruptions and lahars. This new approach is applicable in analyzing tremor sources in real time and may contribute to early assessment of the size of eruptions and lahars.

Multifractal characterization of Vesuvio lava-flow margins and its implications

NASA Astrophysics Data System (ADS)

Luongo, G.; Mazzarella, A.; Di Donna, G.

2000-09-01

The digitized lava-flow margins of well-defined extended eruptions occurring at Vesuvio in 1760, 1794, 1861, 1906, 1929 and 1944 are found to follow fractal behaviours inside a scaling region enclosed between 50 and 400 m. Although the invariance region is well respected, the fractal dimension D varies from one lava flow to another: the more irregular the lava-flow margin, the larger the value of D. The ascertained dependence of D on the duration of premonitory activity, preceding the emission of lavas, might provide some insight into the inner volcanic processes before the eruption and into the dynamical processes operating during flow emplacement.

Using Digital Cameras to Detect Warning Signs of Volcanic Eruptions

NASA Astrophysics Data System (ADS)

Girona, T.; Huber, C.; Trinh, K. T.; Protti, M.; Pacheco, J. F.

2017-12-01

Monitoring volcanic outgassing is fundamental to improve the forecasting of volcanic eruptions. Recent efforts have led to the advent of new methods to measure the concentration and flux of volcanic gases with unprecedented temporal resolution, thus allowing us to obtain reliable high-frequency (up to 1 Hz) time series of outgassing activity. These high-frequency methods have shown that volcanic outgassing can be periodic sometimes (with periodicities ranging from 101 s to 103 s), although it remains unknown whether the spectral features of outgassing reflect the processes that ultimately trigger volcanic unrest and eruptions. In this study, we explore the evolution of the spectral content of the outgassing activity of Turrialba volcano (Costa Rica) using digital images (with digital brightness as a proxy for the emissions of water vapor [Girona et al., 2015]). Images were taken at 1 km distance with 1 Hz sampling rate, and the time period analyzed (from April 2016 to April 2017) is characterized by episodes of quiescent outgassing, ash explosions, and sporadic eruptions of ballistics. Our preliminary results show that: 1) quiescent states of Turrialba volcano are characterized by outgassing frequency spectra with fractal distribution; 2) superimposed onto the fractal frequency spectra, well-defined pulses with period around 100 s emerge hours to days before some of the eruptions of ballistics. An important conclusion of this study is that digital cameras can be potentially used in real-time volcano monitoring to detect warning signs of eruptions, as well as to better understand subsurface processes and track the changing conditions below volcanic craters. Our ongoing study also explores the correlation between the evolution of the spectral content of outgassing, infrasound data, and shallow seismicity. Girona, T., F. Costa, B. Taisne, B. Aggangan, and S. Ildefonso (2015), Fractal degassing from Erebus and Mayon volcanoes revealed by a new method to monitor H2O emission cycles, J. Geophys. Res. 120, 2988-3002, doi:10.1002/2014JB011797.

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.

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.

An atlas of volcanic ash

NASA Technical Reports Server (NTRS)

Heiken, G.

1974-01-01

Volcanic ash samples collected from a variety of recent eruptions were studied, using petrography, chemical analyses, and scanning electron microscopy to characterize each ash type and to relate ash morphology to magma composition and eruption type. The ashes are best placed into two broad genetic categories: magnetic and hydrovolcanic (phreatomagmatic). Ashes from magmatic eruptions are formed when expanding gases in the magma form a froth that loses its coherence as it approaches the ground surface. During hydrovolcanic eruptions, the magma is chilled on contact with ground or surface waters, resulting in violent steam eruptions. Within these two genetic categories, ashes from different magma types can be characterized. The pigeon hole classification used here is for convenience; there are eruptions which are driven by both phreatic and magmatic gases.

Seismic time-frequency analysis of the recent 2015 eruptive activity of Volcán de Colima, Mexico

NASA Astrophysics Data System (ADS)

Vargas-Bracamontes, D. M.; Nava Pichardo, F. A.; Reyes Dávila, G. A.; Arámbula-Mendoza, R.; Martínez Fierros, A.; Ramírez Vázquez, A.; González Amezcua, M.

2015-12-01

Volcán de Colima is an andesitic stratovolcano located in western Mexico. It is considered the most active volcano in Mexico, with activity characterized mainly by intermittent effusive and explosive episodes. On July 10th-12th 2015, Volcán de Colima underwent its most intense eruptive phase since its Plinian eruption in 1913. A partial collapse of the dome and of the crater wall generated several pyroclastic flows, the largest of which reached almost 10 km to the south of the volcano. Lava flows along with incandescent rockfalls descended through various flanks of the volcanic edifice. Ashfall affected people up to 40 km from the volcano's summit. Inhabitants from the small villages closest to the volcano were evacuated and authorities sealed off a 12 km area. We present an overview of the seismic activity that preceded and accompanied this eruptive phase, with data from the closest broadband and short period seismic stations of the Volcán de Colima monitoring network. We focus on the search of temporal information within the spectral content of the seismic signals. We first employ common time-frequency representations such as Fourier and wavelet transforms, but we also apply more recent techniques proposed for the analysis of non-stationary signals, such as empirical mode decomposition and the synchrosqueezing transform. We present and discuss the performances of these various methods characterizing and quantifying spectral changes which could be used to forecast future eruptive events and to evaluate the course of volcanic processes during ongoing eruptions.

Tephra Sedimentation from a Short-term Wind-affected Volcanic Plume of the 8 October 2016 Aso Nakadake Eruption, Japan

NASA Astrophysics Data System (ADS)

Tsuji, T.; Nishizaka, N.; Onishi, K.

2017-12-01

Sedimentation processes during explosive volcanic eruptions can be constrained based on detailed analysis of grain-size variation of tephra deposits. Especially, an accurate description of the amount of fine particles has also significant implications for the assessment of specific tephra hazards. Grain size studies for single short-term eruption has advantage to contribute understanding the sedimentation processes because it is simple compared to long-lasting eruption. The 2016 Aso Nakadake eruption, Japan represents an ideal for the study of short-term eruptions thanks to an accurate investigation. Then, we investigate the grain size variation with distance from the vent and sedimentological features of the deposit to discuss the sedimentation processes of the tephra fragments. The eruption provided pyroclastic flow deposit and fallout tephra which distributed NE to ENE direction from the vent. The deposits between 4 and 20 km from vent consist of fine-coated lapilli to coarse ash, ash pellet and mud droplet in ascending degree. The samples are lapilli-bearing within 20 km from vent and those outside of 20 km mainly consist of ash particles. Detailed analyses of individual samples highlight a rapid decay of maximum and mean grain size for the deposit from proximal to distal. The decay trend of maximum grain-size is approximated by three segments of exponential curves with two breaks-in-slope at 10 and 40 km from vent. Most of the sampled deposits are characterized by bimodal grain-size distributions, with the modes of the coarse subpopulation decreasing with distance from vent and those of the fine subpopulation being mostly stable. The fine subpopulation has been interpreted as being mostly associated with size-selective sedimentation processes (e.g., particle aggregation) confirmed by the existence of fine-coated particles, ash pellet and mud droplet. As the fine-coated particles generally have a higher terminal velocity than the individual constituent particles, those could be related with the rapid decrease of maximum grain-size with distance from vent at proximal area. Further detail grain-size analyses and theoretical studies can be contributed to understand the effect of fine ash aggregation on sedimentation processes quantitatively.

Pre-eruptive volatile and erupted gas phase characterization of the 2014 basalt of Bárðarbunga volcanic system, Iceland.

NASA Astrophysics Data System (ADS)

Haddadi, Baptiste; Moune, Séverine; Sigmarsson, Olgeir; Gauthier, Pierre-Jean; Gouhier, Mathieu

2015-04-01

The 2014 Holuhraun eruption on the Bárðarbunga Volcanic System is the largest fissure eruption in Iceland since the 1783 Laki eruption. The eruption started end of August 2014 and has been characterized by large emission of SO2 into the atmosphere. It provides a rare opportunity to study in details magmatic and degassing processes during a large-volume fissure eruption. In order to characterize the pre-eruptive magmatic composition and to assess the plume chemistry at the eruption site, lava and tephra were sampled together with the eruption plume. The basalt composition is olivine tholeiite with MgO close to 7 wt%. It is phenocryst-poor with plagioclase as the dominant mineral phase but olivine and clinopyroxene are also present together with sulphide globules composed principally of pyrite and chalcopyrite. The volatile (S, Cl and F) and major element concentrations were measured by the electron microprobe in melt inclusions (MIs) trapped in plagioclase and clinopyroxene and groundmass glass. The MIs composition ranges from fairly primitive basaltic compositions (MgO: 9.03 wt%) down to evolved qz-tholeiites (MgO: 5.57 wt%), with estimated pre-eruptive S concentrations of 1500 ppm. Tephra groundmass glass contains 400 ppm S, whereas Cl and F concentrations are respectively slightly lower and indistinguishable from those in the MIs. This implies limited exsolution of halogens but 75% of the initial sulphur content. Relatively to their total iron content, MIs are sulphur saturated, and their oxygen fugacity close to the FMQ buffer. The difference between the estimated initial volatile concentrations measured in the MIs and in the tephra groundmass (i.e. the so-called petrological method) yields 7.2 Mt SO2, limited HCl and no HF atmospheric mass loading from the Holuhraun 2014 eruption. The SO2/HCl molar ratio of the gas phase, calculated from the MIs, is 13 and 14, respectively, using average and estimated pre-eruptive S and Cl concentrations in the MIs. Filter-pack sampling of the gas plume was performed 2 October 2014 few hundred meters to the W of the active crater row. Filter packs were composed of three filters in series: one PTFE filter to collect particulate phases, followed by two impregnated filters to trap major gaseous species (SO2, HF and HCl). Sulphate (SO4) and halide (Cl- and F-) ion concentrations were determined by ion chromatography. The SO2/HCl molar ratio in the erupted gas phase at the eruption site is 29-46, only slightly higher than that estimated from the MIs. Trace element volatility and fluxes are discussed elsewhere (Gauthier et al., 2015) but the average SO2 flux calculated from lava volume estimate end of November as 1.2 km3 (Gouhier et al., 2015) is close to 1100 kg/sec. This is the highest SO2 flux ever estimated from gas plume measurements. References: Gauthier et al. (2015) Trace element degassing patterns and volcanic fluxes to the atmosphere during the 2014 Holuhraun eruption, Iceland. EGU General Assembly 2015. Gouhier et al. (2015) Retrieval of lava and SO2 long-lived emissions using MSG-SEVIRI data during the 2014 Holuhraun eruption. EGU General Assembly 2015.

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).

Characterization of freshwater changes in lakes of Nahuel Huapi National Park produced by the 2011 Puyehue-Cordón Caulle eruption.

PubMed

Catán, Soledad Perez; Juarez, Natalia A; Bubach, Débora F

2016-10-01

This work supplies a characterization of the chemical properties, including data of dissolved major and minor components in surface and pore water collected in Argentinean lakes surrounding the impacted area of Puyehue-Cordón Caulle volcanic complex, in the 2011 eruption. The principal component analysis and Pollution Load Index were used for the identification of water changes by volcanic ashes deposited throughout 1 year of eruption. The element content between water column and pore water provided a direct evidence of the potential dissolution of the element. Many chemical transformations, after the pyroclastic material contacted with the freshwater, were observed such as large pH changes from 3.2 to 8.1, electrical conductivity of 28.9 to 457 μs/cm, and redox potential of 171 to 591 mV. The maximum concentrations measured of F, Al, and Hg were 600, 40, and 0.0382 μg/L respectively. These concentrations in water column were lower than the limit of aquatic life protection for chronic toxicity. The Pollution Load Index indicated very low pollution for sites far away from the volcano and moderated pollution in closely sites. The processes were stabilized at the end of the monitoring, 1 year after the eruption.

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.

Microbiological characterization of post-eruption “snowblower” vents at Axial Seamount, Juan de Fuca Ridge

PubMed Central

Meyer, Julie L.; Akerman, Nancy H.; Proskurowski, Giora; Huber, Julie A.

2013-01-01

Microbial processes within the subseafloor can be examined during the ephemeral and uncommonly observed phenomena known as snowblower venting. Snowblowers are characterized by the large quantity of white floc that is expelled from the seafloor following mid-ocean ridge eruptions. During these eruptions, rapidly cooling lava entrains seawater and hydrothermal fluids enriched in geochemical reactants, creating a natural bioreactor that supports a subseafloor microbial “bloom.” Previous studies hypothesized that the eruption-associated floc was made by sulfide-oxidizing bacteria; however, the microbes involved were never identified. Here we present the first molecular analysis combined with microscopy of microbial communities in snowblower vents from samples collected shortly after the 2011 eruption at Axial Seamount, an active volcano on the Juan de Fuca Ridge. We obtained fluid samples and white flocculent material from active snowblower vents as well as orange flocculent material found on top of newly formed lava flows. Both flocculent types revealed diverse cell types and particulates when examined by phase contrast and scanning electron microscopy (SEM). Distinct archaeal and bacterial communities were detected in each sample type through Illumina tag sequencing of 16S rRNA genes and through sequencing of the sulfide oxidation gene, soxB. In fluids and white floc, the dominant bacteria were sulfur-oxidizing Epsilonproteobacteria and the dominant archaea were thermophilic Methanococcales. In contrast, the dominant organisms in the orange floc were Gammaproteobacteria and Thaumarchaeota Marine Group I. In all samples, bacteria greatly outnumbered archaea. The presence of anaerobic methanogens and microaerobic Epsilonproteobacteria in snowblower communities provides evidence that these blooms are seeded by subseafloor microbes, rather than from microbes in bottom seawater. These eruptive events thus provide a unique opportunity to observe subseafloor microbial communities. PMID:23785361

The ten-year eruption of Kilauea Volcano

USGS Publications Warehouse

Clague, D.A.; Heliker, C.

1992-01-01

About 1 km3 of lava erupted during the first 0 years of the eruption. Lava flows have destroyed 181 houses and severed the coastal highway along the volcano's south flank, severely restricting transportation on this part of the island of Hawaii. the eruption consisted of many distinct episodes characterized by activity at different vents and by different eruptive styles. the following summarizes the first 10 years of the eruption, starting with the initial outbreak in 1983.

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

Chemistry and chronology of magmatic processes, Central Kenya Peralkaline province, East African Rift

NASA Astrophysics Data System (ADS)

Anthony, E.; Deino, A. L.; White, J. C.; Omenda, P. A.

2014-12-01

We report here a synthesis of the geochemistry of magma evolution correlated with 40Ar/39Ar, 14 C, and U-series chronology for volcanoes in the Central Kenya Peralkaline Province (CKPP). The volcanic centers - Menengai, Eburru, Olkaria, Longonot, and Suswa - are at the apex of the Kenya Dome, and consist of trachyte, phonolite, comendite, and pantellerite. These volcanic centers are within the graben of the EARS and are characterized by a shield-building phase followed by caldera collapse and subsequent post-caldera eruptions. Geochemical modeling demonstrates that the magmas are the result of fractional crystallization of alkali basaltic magmas and magma mixing. Longonot and Suswa have the most chronologic data -14 C, Ar/Ar and U-series - and they show that the youngest eruptions have 230 Th/232Th of 0.8, which was inherited from the magma system prior to eruption. Subsequent changes in 230 Th/232 Th are due to post-eruptive decay of 230 Th and correlate well with 14 C and Ar/Ar.

The 2005 eruption of Kliuchevskoi volcano: Chronology and processes derived from ASTER spaceborne and field-based data

NASA Astrophysics Data System (ADS)

Rose, Shellie; Ramsey, Michael

2009-07-01

Kliuchevskoi volcano, located on the Kamchatka peninsula of eastern Russia, is one of the largest and most active volcanoes in the world. Its location and diversity of eruption styles make satellite-based monitoring and characterization of its eruptive activity essential. In 2005, the Kamchatka Volcano Emergency Response Team (KVERT) first reported that seismic activity of Kliuchevskoi increased above background levels on 12 January (Kamchatka Volcanic Eruption Response Team (KVERT) Report, 2005. Kliuchevskoi Volcano, 14 January through 13 May 2005. ( http://www.avo.alaska.edu/activity/avoreport.php?view=kam info&id=&month=January&year=2005). Cited January 2007). By 15 January Kliuchevskoi entered an explosive-effusive phase, which lasted for five months and produced basaltic lava flows, lahar deposits, and phreatic explosions along its northwestern flank. We present a comparison between field observations and multispectral satellite image data acquired by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument in order to characterize the eruptive behavior. The ASTER instrument was targeted in an automated urgent request mode throughout the eruption timeline in order to collect data at the highest observation frequency possible. Brightness temperatures were calculated in all three ASTER wavelength regions during lava flow emplacement. The maximum lava flow brightness temperatures, calculated from the 15 m/pixel visible near infrared (VNIR) data, were in excess of 800 °C. The shortwave infrared (SWIR) data were radiometrically and geometrically corrected, normalized to the same gain settings, and used to estimate an eruptive volume of 2.35 × 10 - 2 km 3 at the summit. These data were also used to better constrain errors arising in the thermal infrared (TIR) data due to sub-pixel thermal heterogeneities. Based on all the ASTER data, the eruption was separated into three phases: an initial explosive phase (20 January-31 January), an explosive-effusive phase (1 February-8 March), and a subsequent cooling phase. Decorrelation stretch (DCS) images of the TIR data also suggested the presence of silicate ash, SO 2, and water vapor plumes that extended up to 300 km from the summit. The ASTER rapid-response program provided important multispectral, moderate spatial resolution information that was used to detect and monitor the eruptive activity of this remote volcano which can be applied to other eruptions worldwide.

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.

Eifel maars: Quantitative shape characterization of juvenile ash particles (Eifel Volcanic Field, Germany)

NASA Astrophysics Data System (ADS)

Rausch, Juanita; Grobéty, Bernard; Vonlanthen, Pierre

2015-01-01

The Eifel region in western central Germany is the type locality for maar volcanism, which is classically interpreted to be the result of explosive eruptions due to shallow interaction between magma and external water (i.e. phreatomagmatic eruptions). Sedimentary structures, deposit features and particle morphology found in many maar deposits of the West Eifel Volcanic Field (WEVF), in contrast to deposits in the East Eifel Volcanic Field (EEVF), lack the diagnostic criteria of typical phreatomagmatic deposits. The aim of this study was to determine quantitatively the shape of WEVF and EEVF maar ash particles in order to infer the governing eruption style in Eifel maar volcanoes. The quantitative shape characterization was done by analyzing fractal dimensions of particle contours (125-250 μm sieve fraction) obtained from Scanning electron microscopy (SEM) and SEM micro-computed tomography (SEM micro-CT) images. The fractal analysis (dilation method) and the fractal spectrum technique confirmed that the WEVF and EEVF maar particles have contrasting multifractal shapes. Whereas the low small-scale dimensions of EEVF particles (Eppelsberg Green Unit) coincide with previously published values for phreatomagmatic particles, the WEVF particles (Meerfelder Maar, Pulvermaar and Ulmener Maar) have larger values indicating more complex small-scale features, which are characteristic for magmatic particles. These quantitative results are strengthening the qualitative microscopic observations, that the studied WEVF maar eruptions are rather dominated by magmatic processes. The different eruption styles in the two volcanic fields can be explained by the different geological and hydrological settings found in both regions and the different chemical compositions of the magmas.

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.

Resistivity variations related to the large March 9, 1998 eruption at La Fournaise volcano inferred by continuous MT monitoring

NASA Astrophysics Data System (ADS)

Wawrzyniak, Pierre; Zlotnicki, Jacques; Sailhac, Pascal; Marquis, Guy

2017-11-01

The 2645 m-high La Fournaise volcano, located in the Southwest of Réunion Island (Indian Ocean), is a shield basaltic volcano where effusive eruptions generally occur along long fissures starting from the summit, alongside major fractures that characterize the eruptions' dynamism and effusivity. Between 1992 and 1998, the volcano underwent a quiet period during which few earthquakes were recorded. Minor seismic activity returned after 1997 and picked up in March 1998 during the 35 h preceding the March 9 eruption. From 1996, two autonomous stations (CSV and BAV) were installed on the volcano. CSV was located inside the Enclos Fouqué caldera while BAV was positioned 8.2 km NW of the volcano summit. Horizontal components of the electric and magnetic fields were sampled every 20 s. Continuous time-series were available from 1996 to 1999 at CSV, and from 1997 to March 1998 at BAV. Data have been processed using both single-station and remote-reference processing. Both results show apparent resistivity variations synchronous to the eruption. Time-lapse impedance estimates are computed on overlapping time windows of about two days at both stations. The only major decrease of the observed impedance coincides with the March 1998 eruption. At CSV, the resistivity started to drop about five days before the eruption, reached several local minima until April, and then slowly increased as the volcanic crisis reduced in activity. After the end of the crisis in September 1998, the apparent resistivity recovered its pre-crisis value. The time-lapse results also show variability in directionality: sharp and elongated phase tensor ellipse residuals appear during the eruption with a N105° orientation, suggesting the emergence of an almost NS-striking dyke. A 1D background model built from MT soundings performed during the quiet period (1996 to February 1998) on which a 3D NS-striking dyke was added shows a good agreement with phase tensor residuals and spatial distribution of the resistivity variations observed during the eruption.

Seismological evidence for long-term and rapidly accelerating magma pressurization preceding the 2009 eruption of Redoubt Volcano, Alaska

NASA Astrophysics Data System (ADS)

Roman, Diana C.; Gardine, Matthew D.

2013-06-01

Successful eruption forecasts are heavily dependent on the recognition of well-established patterns in volcano monitoring data. Therefore, it is critical to develop, in retrospect, an understanding of the physical basis for cases of abnormal precursory behavior, as the basis for (a) a complete understanding of the range of precursory signals that may be expected at a particular volcano and (b) development of new monitoring approaches to detect more subtle signals of the underlying processes responsible for common patterns of seismic unrest. Here, using a hybrid analysis of shear-wave splitting (SWS) and double-couple fault-plane solutions (FPS), we document the timing and nature of local stress field changes in the months to days preceding the 2009 eruption of Redoubt Volcano, Alaska, which was characterized by an abnormally long period of precursory low-frequency seismicity reflected in multiple escalations of alert levels prior to the eruption. We find that an approximately ~90° change in the polarization of fast S-wavelets (Φ) accompanied the earliest signs of seismic unrest in 2008 and continued through the eruption before diminishing in 2009. A similar change in the orientation of VT FPS occurred 18-48 h prior to the eruption onset on March 23, 2009, but almost two months after a strong increase in the rate of shallow VT earthquakes. Combined, our SWS and FPS results show the earliest-, and latest-known changes in seismic monitoring data, respectively, and are suggestive of a protracted period of slow magma ascent followed by a short period of rapidly increasing magma pressurization beneath the volcano. These results demonstrate the power of a combined stress-field analysis for clarifying the processes driving ambiguous seismic unrest at active volcanoes.

A Reappraisal of Seismicity and Eruptions of Pantelleria Island and the Sicily Channel (Italy)

NASA Astrophysics Data System (ADS)

Spampinato, Salvatore; Ursino, Andrea; Barbano, Maria Serafina; Pirrotta, Claudia; Rapisarda, Salvatore; Larocca, Graziano; Platania, Pier Raffaele

2017-07-01

Three main tectonic depressions (the Pantelleria, Linosa and Malta troughs), the expression of a continental rift, characterize the Sicily Channel, a region with recent volcanic activity attested by the Pantelleria and Linosa volcanic islands, as well as numerous seamounts. To understand the seismic and eruptive behaviour of this area, we compare historical and instrumental seismicity retrieved from catalogues with recordings from both a mobile seismic network and a permanent station deployed at Pantelleria. A review of historical eruptions affecting the Sicily Channel is also presented. Recent instrumental seismicity shows that the Sicily Channel is characterized by a low level of seismicity, with earthquakes mainly occurring as isolated events, rather than swarms as observed during the few documented eruptive periods. The results of a seismic survey in 2006-2007, as well as the signals recorded by a permanent station in 2010-2014, enable stating that also Pantelleria is characterized by a very low rate of seismicity. The available, though scant, historical information suggests a recurrence time of about a century for the volcanic activity and that eruptions are usually preceded by seismic swarms. In the only historical known eruption of Pantelleria, in addition to shocks, uplifting and increasing fumarole activity, were observed. Notwithstanding the lack of eruptions over the past century, and despite the low recent seismic rate, we believe that the geophysical monitoring of the Sicily Channel needs improving since it is an area of potentially high seismic and volcanic hazard given the presence of several active submarine eruptive centres.

New observations from Surtsey, the definitive surtseyan volcano

NASA Astrophysics Data System (ADS)

White, J. D.; Jakobsson, S. P.

2013-12-01

The eruption that formed Surtsey lasted from 1963 into 1967, and provides the name used for emergent eruptions from the seafloor, and sometimes even more generally for any eruption involving explosive interaction of magma with water. New work on Surtsey's eruption is allowing us to extend our understanding of many aspects of its evolution and the processes that took place both prior to emergence and after, when it was so well observed by Sigurdur Thorarinsson and others. In 1979, drilling through Surtsey was accomplished, and a core acquired that extends almost to the pre-eruption seafloor. Near the base of the hole, unlithified pyroclastic deposits were encountered, and sampled as drill cuttings. These are highly vesicular, and many show large populations of small, spherical to sub-spherical vesicles. Examination of the core and dozens of thin sections reveals strong palagonite rims on pyroclasts at many intervals in the core, developed particularly well on highly vesicular and originally glassy pyroclasts. In the uppermost several meters armoured lapilli are present, along with "vesiculated tuff". We see no evidence for deep subsidence of surficial deposits at the site cored, and our working hypothesis is that an eruption stratigraphy can be established from the drillsite. On the emergent cone, a notable feature not previously emphasized is an abundance of blocks from the pre-eruption seafloor. These blocks have been identified as lithified volcaniclastic material deposited as turbidites largely from the Vestmann Islands. It will be important to quantify the abundance of this seafloor sedimentary rock as clasts in Surtsey's deposits, because these lithic clasts imply excavation, perhaps substantial, of the pre-eruption seafloor. No fragments of pillow lava have been identified in Surtsey's ejecta, but there are abundant fragments of dikes characterized by parallel bands of vesicles and, on some fragments, paired chilled margins. Many of these exhibit strong cracking and a cauliflower-like appearance on one side, but they are not true cauliflower bombs. Juvenile bombs are also abundant, and display ubiquitous composite textures. Typical juvenile bombs have glassy weakly fractured surfaces and a contorted internal structure in which pyroclasts are entwined with stretched and bubbled coherent basalt. These textures are interpreted to have developed through strong 'recycling' processes that allowed capture of older pyroclasts within new ones through in-vent welding and agglutination, or in some cases by capture of particles within magma that was subsequently disrupted. Taken as a whole, these new observations challenge existing models for Surtsey's eruption. A new assessment of eruptive processes will take into account evidence for both ubiquitous hot-state particle recycling, and excavation and ejection of subvolcanic sedimentary strata at times in the eruption, including during the last explosive phase.

Catalog of Tephra Samples from Kilauea's Summit Eruption, March-December 2008

USGS Publications Warehouse

Wooten, Kelly M.; Thornber, Carl R.; Orr, Tim R.; Ellis, Jennifer F.; Trusdell, Frank A.

2009-01-01

The opening of a new vent within Halema'uma'u Crater in March 2008 ended a 26-year period of no eruptive activity at the summit of Kilauea Volcano. It also heralded the first explosive activity at Kilauea's summit since 1924 and the first of eight discrete explosive events in 2008. At the onset of the eruption, the Hawaiian Volcano Observatory (HVO) initiated a rigorous program of sample collection to provide a temporally constrained suite of tephra samples for petrographic, geochemical, and isotopic studies. Petrologic studies help us understand conditions of magma generation at depth; processes related to transport, storage, and mixing of magma within the shallow summit region; and specific circumstances leading to explosive eruptions. This report provides a catalog of tephra samples erupted at Kilauea's summit from March 19, 2008, through the end of 2008. The Kilauea 2008 Summit Sample Catalog is tabulated in the accompanying Microsoft Excel file, of2009-1134.xls (four file types linked on right). The worksheet in this file provides sampling information and sample descriptions. Contextual information for this catalog is provided below and includes (1) a narrative of 2008 summit eruptive activity, (2) a description of sample collection methods, (3) a scheme for characterizing a diverse range in tephra lithology, and (4) an explanation of each category of sample information (column headers) in the Microsoft Excel worksheet.

Disintegration of an eruptive filament via interactions with quasi-separatrix layers

NASA Astrophysics Data System (ADS)

Liu, Rui; Chen, Jun; Wang, YuMing

2018-06-01

The disintegration of solar filaments via mass drainage is a frequently observed phenomenon during a variety of filament activities. It is generally considered that the draining of dense filament material is directed by both gravity and magnetic field, yet the detailed process remains elusive. Here we report on a partial filament eruption during which filament material drains downward to the surface not only along the filament's legs, but to a remote flare ribbon through a fan-out curtain-like structure. It is found that the magnetic configuration is characterized by two conjoining dome-like quasi-sepratrix layers (QSLs). The filament is located underneath one QSL dome, whose footprint apparently bounds the major flare ribbons resulting from the filament eruption, whereas the remote flare ribbon matches well with the other QSL dome's far-side footprint. We suggest that the interaction of the filament with the overlying QSLs results in the splitting and disintegration of the filament.

The July - August 2014 Mt. Etna eruptions: insights on the magmatic feeding system from geochemical and geophysical data

NASA Astrophysics Data System (ADS)

Zuccarello, Francesco; Cannata, Andrea; Gresta, Stefano; Palano, Mimmo; Viccaro, Marco

2016-04-01

The 2014 volcanic activity of Mt. Etna has been characterized by a marked change in the eruptive behavior with respect to the one that occurred during the 2011-2013 time interval. During the 2011-2013 period, the volcanic activity was characterized by the occurrence of more than 40 vigorous lava fountain episodes at the summit New South-East Crater (hereinafter NSEC). Conversely, from the end of 2013 to the end of 2014, although intense Strombolian and effusive activity took place at NSEC, the volcanic activity never culminated in sustained lava fountaining and voluminous tephra emission. The July - August 2014 eruption can be framed within such a low level of volcanic activity. This eruption started on July 5 2014, when a fissure opened on the lower eastern flank of the summit North-East Crater (hereinafter NEC), close to the fracture field of the 2008-2009 eruption. These fissures fed weak Strombolian activity and minor lava emission from two new vents located at about 3000 m elevation. On July 25, more intense Strombolian activity took place at a further vent opened close to these two vents, at 3090 m elevation. The eruption from the vents on the lower eastern flank of NEC continued until August 9. Before the end of this eruption, on 8 August a new eruptive episode started at NSEC. This last eruption, culminating during August 11-14 with vigorous Strombolian activity and lava effusion, ended on August 16. Moreover, such a contemporaneous activity at both NSEC and NEC lends credit to the existence of a shallow link between the two craters. Taking advantage from the availability of an extensive dataset of geochemical, seismic and geodetic data we have here analyzed the volcanic activity characterizing this eruptive event. This integrated, multidisciplinary study is aimed at improving the knowledge of the deeper and shallower portions of the magmatic feeding system along with the magma transfer mechanisms toward the surface.

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.

The role of magma mixing/mingling and cumulate melting in the Neapolitan Yellow Tuff caldera-forming eruption (Campi Flegrei, Southern Italy)

NASA Astrophysics Data System (ADS)

Forni, Francesca; Petricca, Eleonora; Bachmann, Olivier; Mollo, Silvio; De Astis, Gianfilippo; Piochi, Monica

2018-06-01

Understanding the mechanisms responsible for the generation of chemical gradients in high-volume ignimbrites is key to retrieve information on the processes that control the maturation and eruption of large silicic magmatic reservoirs. Over the last 60 ky, two large ignimbrites showing remarkable zoning were emplaced during caldera-forming eruptions at Campi Flegrei (i.e., Campanian Ignimbrite, CI, 39 ka and Neapolitan Yellow Tuff, NYT, 15 ka). While the CI displays linear compositional, thermal and crystallinity gradients, the NYT is a more complex ignimbrite characterized by crystal-poor magmas ranging in composition from trachy-andesites to phonolites. By combining major and trace element compositions of matrix glasses and mineral phases from juvenile clasts located at different stratigraphic heights along the NYT pyroclastic sequence, we interpret such compositional gradients as the result of mixing/mingling between three different magmas: (1) a resident evolved magma showing geochemical characteristics of a melt extracted from a cumulate mush dominated by clinopyroxene, plagioclase and oxides with minor sanidine and biotite; (2) a hotter and more mafic magma from recharge providing high-An plagioclase and high-Mg clinopyroxene crystals and (3) a compositionally intermediate magma derived from remelting of low temperature mineral phases (i.e., sanidine and biotite) within the cumulate crystal mush. We suggest that the presence of a refractory crystal mush, as documented by the occurrence of abundant crystal clots containing clinopyroxene, plagioclase and oxides, is the main reason for the lack of erupted crystal-rich material in the NYT. A comparison between the NYT and the CI, characterized by both crystal-poor extracted melts and crystal-rich magmas representing remobilized portions of a "mature" (i.e., sanidine dominated) cumulate residue, allows evaluation of the capability of crystal mushes of becoming eruptible upon recharge.

Time-series analysis of fissure-fed multi-vent activity: a snapshot from the July 2014 eruption of Etna volcano (Italy)

NASA Astrophysics Data System (ADS)

Spina, L.; Taddeucci, J.; Cannata, A.; Sciotto, M.; Del Bello, E.; Scarlato, P.; Kueppers, U.; Andronico, D.; Privitera, E.; Ricci, T.; Pena-Fernandez, J.; Sesterhenn, J.; Dingwell, D. B.

2017-07-01

On 5 July 2014, an eruptive fissure opened on the eastern flank of Etna volcano (Italy) at 3.000 m a.s.l. Strombolian activity and lava effusion occurred simultaneously at two neighbouring vents. In the following weeks, eruptive activity led to the build-up of two cones, tens of meters high, here named Crater N and Crater S. To characterize the short-term (days) dynamics of this multi-vent system, we performed a multi-parametric investigation by means of a dense instrumental network. The experimental setup, deployed on July 15-16th at ca. 300 m from the eruption site, comprised two broadband seismometers and three microphones as well as high speed video and thermal cameras. Thermal analyses enabled us to characterize the style of eruptive activity at each vent. In particular, explosive activity at Crater N featured higher thermal amplitudes and a lower explosion frequency than at Crater S. Several episodes of switching between puffing and Strombolian activity were noted at Crater S through both visual observation and thermal data; oppositely, Crater N exhibited a quasi-periodic activity. The quantification of the eruptive style of each vent enabled us to infer the geometry of the eruptive system: a branched conduit, prone to rapid changes of gas flux accommodated at the most inclined conduit (i.e. Crater S). Accordingly, we were able to correctly interpret acoustic data and thereby extend the characterization of this two-vent system.

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.

2014 Mount Ontake eruption: characteristics of the phreatic eruption as inferred from aerial observations

NASA Astrophysics Data System (ADS)

Kaneko, Takayuki; Maeno, Fukashi; Nakada, Setsuya

2016-05-01

The sudden eruption of Mount Ontake on September 27, 2014, led to a tragedy that caused more than 60 fatalities including missing persons. In order to mitigate the potential risks posed by similar volcano-related disasters, it is vital to have a clear understanding of the activity status and progression of eruptions. Because the erupted material was largely disturbed while access was strictly prohibited for a month, we analyzed the aerial photographs taken on September 28. The results showed that there were three large vents in the bottom of the Jigokudani valley on September 28. The vent in the center was considered to have been the main vent involved in the eruption, and the vents on either side were considered to have been formed by non-explosive processes. The pyroclastic flows extended approximately 2.5 km along the valley at an average speed of 32 km/h. The absence of burned or fallen trees in this area indicated that the temperatures and destructive forces associated with the pyroclastic flow were both low. The distribution of ballistics was categorized into four zones based on the number of impact craters per unit area, and the furthest impact crater was located 950 m from the vents. Based on ballistic models, the maximum initial velocity of the ejecta was estimated to be 111 m/s. Just after the beginning of the eruption, very few ballistic ejecta had arrived at the summit, even though the eruption plume had risen above the summit, which suggested that a large amount of ballistic ejecta was expelled from the volcano several tens-of-seconds after the beginning of the eruption. This initial period was characterized by the escape of a vapor phase from the vents, which then caused the explosive eruption phase that generated large amounts of ballistic ejecta via sudden decompression of a hydrothermal reservoir.

Catastrophic eruptions of the directed-blast type at Mount St. Helens, bezymianny and Shiveluch volcanoes

USGS Publications Warehouse

Bogoyavlenskaya, G.E.; Braitseva, O.A.; Melekestsev, I.V.; Kiriyanov, V. Yu; Dan, Miller C.

1985-01-01

This paper describes catastrophic eruptions of Mount St. Helens (1980), Bezymianny (1955-1956), and Shiveluch (1964) volcanoes. A detailed description of eruption stages and their products, as well as the quantitative characteristics of the eruptive process are given. The eruptions under study belong to the directed-blast type. This type is characterized by the catastrophic character of the climatic stage during which a directed blast, accompanied by edifice destruction, the profound ejection of juvenile pyroclastics and the formation of pyroclastic flows, occur. The climatic stage of all three eruptions has similar characteristics, such as duration, kinetic energy of blast (1017-1018 J), the initial velocity of debris ejection, morphology and size of newly-formed craters. But there are also certain differences. At Mount St. Helens the directed blast was preceeded by failure of the edifice and these events produced separable deposits, namely debris avalanche and directed blast deposits which are composed of different materials and have different volumes, thickness and distribution. At Bezymianny, failure did not precede the blast and the whole mass of debris of the old edifice was outburst only by blast. The resulting deposits, represented by the directed blast agglomerate and sand facies, have characteristics of both the debris avalanche and the blast deposit at Mount St. Helens. At Shiveluch directed-blast deposits are represented only by the directed-blast agglomerate; the directed-blast sand facies, or blast proper, seen at Mount St. Helens is absent. During the period of Plinian activity, the total volumes of juvenile material erupted at Mount St. Helens and at Besymianny were roughly comparable and exceeded the volume of juvenile material erupted at Shiveluch, However, the volume of pyroclastic-flow deposits erupted at Mount St. Helens was much less. The heat energy of all three eruptions is comparable: 1.3 ?? 1018, 3.8-4.8 ?? 1018 and 1 ?? 1017 J for Shiveluch, Bezymianny, and Mount St. Helens, respectively. ?? 1985.

Earthquake Tidal Triggering Associated with the 2015 Eruption of Axial Seamount

NASA Astrophysics Data System (ADS)

Wilcock, W. S. D.; Tolstoy, M.; Waldhauser, F.; Tan, Y. J.; Garcia, C.; Arnulf, A. F.; Crone, T. J.

2016-12-01

The Ocean Observatories Initiative's real time cabled observatory at Axial Seamount includes a seven station seismic network that spans the southern half of the summit caldera. The network has been in operation since late 2014 and, in conjunction with geodetic sensors on the observatory, has recorded an exceptional data set to characterize the dynamics of the caldera through the April 2015 eruption. Prior to the eruption, earthquake rates were high and double-difference locations show that the inflation of the volcano was accommodated by deformation on an outward dipping caldera ring fault. The onset of the eruption was marked by a seismic crisis on April 24 and rapid deflation of the volcano; the caldera ring fault accommodated deflation and guided a dike beneath the east rim of the caldera. The seismic crisis was followed by a steady decline in the rates of earthquakes and deflation. Numerous seafloor explosions document the timing and location of lava flows in the caldera and on the north rift of the seamount. They ceased after about a month when the volcano started to reinflate. Efforts are presently underway to improve the resolution of hypocenters both through the use of cross-correlation-based double-difference hypocenter locations (Tan et al., this meeting) and by the incorporation of three-dimensional velocity models that account for the heterogeneous structure of the volcano. One particularly interesting aspect of the seismicity is the tidal triggering. Prior to the eruption, when the volcano is critically stressed, the earthquakes show a strong tidal triggering signal with higher rates of seismicity near low tides when faults are unclamped. Earthquake rates at the lowest tides are about six times those at the highest tides. There are also noticeable temporo-spatial patterns in the earthquake swarms that occur at each low tide suggesting that the characteristics of tidal triggering may be spatial dependent. Following the eruption, only a weak tidal triggering signal remains. We will present the results of ongoing efforts to characterize the patterns of tidal triggering, relate them to prior observations on mid-ocean ridges, and understand the implications for earthquake nucleation, eruption forecasting, and hydrological processes.

Eruptions at Lone Star Geyser, Yellowstone National Park, USA, part 1: energetics and eruption dynamics

USGS Publications Warehouse

Karlstrom, Leif; Hurwitz, Shaul; Sohn, Robert; Vandemeulebrouck, Jean; Murphy, Fred; Rudolph, Maxwell L.; Johnston, Malcolm J.S.; Manga, Michael; McCleskey, R. Blaine

2013-01-01

Geysers provide a natural laboratory to study multiphase eruptive processes. We present results from a four–day experiment at Lone Star Geyser in Yellowstone National Park, USA. We simultaneously measured water discharge, acoustic emissions, infraredintensity, and visible and infrared video to quantify the energetics and dynamics of eruptions, occurring approximately every three hours. We define four phases in the eruption cycle: 1) a 28 ± 3 minute phase with liquid and steam fountaining, with maximum jet velocities of 16–28 m s− 1, steam mass fraction of less than ∼ 0.01. Intermittently choked flow and flow oscillations with periods increasing from 20 to 40 s are coincident with a decrease in jet velocity and an increase of steam fraction; 2) a 26 ± 8 minute post–eruption relaxation phase with no discharge from the vent, infrared (IR) and acoustic power oscillations gliding between 30 and 40 s; 3) a 59 ± 13 minute recharge period during which the geyser is quiescent and progressively refills, and 4) a 69 ± 14 minute pre–play period characterized by a series of 5–10 minute–long pulses of steam, small volumes of liquid water discharge and 50–70 s flow oscillations. The erupted waters ascend froma 160 − 170° C reservoir and the volume discharged during the entire eruptive cycle is 20.8 ± 4.1 m3. Assuming isentropic expansion, we calculate a heat output from the geyser of 1.4–1.5 MW, which is < 0.1% of the total heat output from Yellowstone Caldera.

The Baia-Fondi di Baia eruption at Campi Flegrei: stratigraphy and dynamics of a multi-stage caldera reactivation event

NASA Astrophysics Data System (ADS)

Pistolesi, Marco; Bertagnini, Antonella; Di Roberto, Alessio; Isaia, Roberto; Vona, Alessandro; Cioni, Raffaello; Giordano, Guido

2017-09-01

The Baia-Fondi di Baia eruption is one of the sporadic events that have occurred in the western sector of the Campi Flegrei caldera. It dates back to 9525-9696 bp and opened Epoch 2 of the caldera activity after a 1000-year-long period of quiescence. Although relatively small in terms of erupted volume with respect to most of the events of the past 15 ka, the Baia-Fondi di Baia eruption was characterized by a complex series of events, which have led to different interpretations in the literature. We present a detailed stratigraphic study of 40 outcrops in a sector of about 90 km2, coupled with sedimentological (grain size, componentry), physical (density, vesicularity), textural, and compositional analyses of the erupted deposits. Based on these data, we interpret the stratigraphic succession as being related to two distinct eruptive episodes (Baia and Fondi di Baia). These were separated by a short time interval, and each was characterized by different eruptive phases. The Baia eruptive episode started in a shallow-water environment with an explosive vent-opening phase that formed a breccia deposit (Unit I), rapidly followed by alternating fallout activity and dense, pyroclastic density current deposits generation (Unit II). Sedimentological features and pumice textural analyses suggest that deposition of Unit II coincided with the intensity peak of the eruption, with the fallout deposit being characterized by a volume of 0.06 ± 0.008 km3 (corresponding to a total erupted mass of 4.06 ± 0.5 × 1010 kg), a column height of 17 km, and a corresponding mass flow rate of 1.8 × 107 kg s-1. The associated tephra also shows the highest vesicularity (up to 81 vol.%) the highest vesicle number density (1.01 × 108 cm-3) and decompression rate (0.69 MPa s-1). This peak phase waned to turbulent, surge-like activity possibly associated with Vulcanian explosions and characterized by progressively lower intensity, as shown by density/vesicularity and textural properties of the erupted juvenile material (Unit III). This first eruptive episode was followed by a short quiescence, interrupted by the onset of a second eruptive episode (Fondi di Baia) whose vent opening deposited a breccia bed (Unit IV) which at some key outcrops directly overlies the fallout deposit of Unit II. The final phase of the Fondi di Baia episode strongly resembles Unit II, although sedimentological (presence of obsidian clasts which are absent in the Baia deposits) and textural (lower vesicularity, vesicle number density, and decompression rate values) features, together with a more limited dispersal, suggest that this phase of the eruption had a lower intensity. The large range of groundmass glass compositions, associated with variable proportions of highly (phonolitic-trachytic) and mildly (tephriphonolitic-latitic) evolved end-members in the erupted products, also suggests that these eruptive episodes were fed by at least two different magma batches that interacted during the different phases, with an increase of tephriphonolitic-latitic magma occurring during the Fondi di Baia stage.

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.

Mount St. Helens eruptive behavior during the past 1500 yr.

USGS Publications Warehouse

Hoblitt, R.P.; Crandell, D.R.; Mullineaux, D.R.

1980-01-01

During the past 1500 yr Mount St. Helens, Washington, has repeatedly erupted dacite domes, tephra, and pyroclastic flows as well as andesite lava flows and tephra. Two periods of activity prior to 1980, each many decades long, were both initiated by eruptions of volatile-rich dacite which were followed by andesite, then by dacite. A third eruptive period was characterized by the eruption of volatile-poor dacite that formed a dome and minor pyroclastic flows. The prolonged duration of some previous eruptive periods suggests that the current activity could continue for many years. The volatile-rich dacite that has been erupted to date probably will be followed by gas-poor magma, but it cannot yet be predicted whether a more mafic magma will be extruded during the current eruptive period.-Authors

The 2012-2014 eruptive cycle of Copahue Volcano, Southern Andes. Magmatic-Hydrothermal system interaction and manifestations.

NASA Astrophysics Data System (ADS)

Morales, Sergio; Alarcón, Alex; Basualto, Daniel; Bengoa, Cintia; Bertín, Daniel; Cardona, Carlos; Córdova, Maria; Franco, Luis; Gil, Fernando; Hernandez, Erasmo; Lara, Luis; Lazo, Jonathan; Mardones, Cristian; Medina, Roxana; Peña, Paola; Quijada, Jonathan; San Martín, Juan; Valderrama, Oscar

2015-04-01

Copahue Volcano (COPV), in Southern Andes of Chile, is an andesitic-basaltic stratovolcano, which is located on the western margin of Caviahue Caldera. The COPV have a NE-trending fissure with 9 aligned vents, being El Agrio the main currently active vent, with ca. 400 m in diameter. The COPV is placed into an extensive hydrothermal system which has modulated its recent 2012-2014 eruptive activity, with small phreatic to phreatomagmatic eruptions and isolated weak strombolian episodes and formation of crater lakes inside the main crater. Since 2012, the Southern Andes Volcano Observatory (OVDAS) carried out the real-time monitoring with seismic broadband stations, GPS, infrasound sensors and webcams. In this work, we report pre, sin, and post-eruptive seismic activity of the last two main eruptions (Dec, 2012 and Oct, 2014) both with different seismic precursors and superficial activity, showing the second one a particularly appearance of seismic quiescence episodes preceding explosive activity, as an indicator of interaction between magmatic-hydrothermal systems. The first episode, in late 2012, was characterized by a low frequency (0.3-0.4 Hz and 1.0-1.5 Hz) continuous tremor which increased gradually from background noise level amplitude to values of reduced displacement (DR), close to 50 cm2 at the peak of the eruption, reaching an eruptive column of ~1.5 km height. After few months of recording low energy seismicity, a sequence of low frequency, repetitive and low energy seismic events arose, with a frequency of occurrence up to 300 events/hour. Also, the VLP earthquakes were added to the record probably associated with magma intrusion into a deep magmatic chamber during all stages of eruptive process, joined to the record of VT seismicity during the same period, which is located throughout the Caviahue Caldera area. Both kind of seismic patterns were again recorded in October 2014, being the precursor of the new eruptive cycle at this time as well as the deformation of the volcanic edifice detected by GPS network. In this new eruptive process, the record of tremor was followed by particular seismic quiescence, as precursors of explosive activity which evolved from low acoustic energy signals toward more energetic signals with impulsive first arrivals and strong attenuation, joined to night incandescence in the main vent without evident juvenile material ejected, which could be associated to the temporal depression of the hydrothermal system located in the volcano system. The recent eruptive episode at Copahue Volcano is a good example of the complex temporal evolution of the interaction between magmatic and hydrothermal systems.

The Ongoing 2011 Eruption of Cordón Caulle (Southern Andes) and its Related Hazards

NASA Astrophysics Data System (ADS)

Amigo, A.; Lara, L. E.; Silva, C.; Orozco, G.; Bertin, D.

2011-12-01

On June 4, 2011, at 18:45 UTC, Cordón Caulle volcano (Southern Andes, 40.52S, 72.14W) erupted explosively after 51 years of quiescence. The last eruption occurred in 1960 and was triggered by the great Mw 9.5 Chile earthquake. The ongoing eruption started after 2 months of increased shallow seismicity as recorded by OVDAS (the volcano observatory at Sernageomin). This close monitoring effort allowed a timely eruption forecast with at least 3 hours of warning, which facilitated the crisis response. In addition to this successful performance, for the first time in Chile volcanic hazards were assessed in advance supporting the emergency management. In particular, tephra dispersal was daily forecasted using the ASHFALL advection-diffusion model and potential lahars and PDC impact zones were delineated according to numerical approaches. The first eruptive stage lasted 27 hours. It was characterized by ca. 15-km strong Plinian-like column, associated with the emission of 0.2 - 0.4 km3 of magma (DRE). Tephra fallout mostly occurred in Chile and Argentina, although fine particles and aerosols circumnavigated the globe twice, causing disruptions on air navigation across the Southern Hemisphere. The second ongoing eruptive stage has been characterized by persistent weak plumes and lava emission at effusion rates in the range of 20 and 60 m3/s, which total volume is estimated <0.20 km3 (at the end of July 2011). Eruptive products have virtually the same bulk composition as those of the historical 1921 and 1960 eruptions, corresponding to phenocryst-poor rhyodacites (67 - 70% SiO2) for what a pre-eruptive temperature of ca. 920C could be inferred. In contrast to the previous eruptive cycles, the ongoing eruption has not evolved (at the time of writing) as a fissure eruption although the vent is atop of fault scarp that borders the Pleistocene-Holocene extensional graben of the Cordón Caulle. This episode is a good case of successful eruption forecast and hazards assessment but it is also an important case-study of silicic eruptions in an arc segment where mostly mafic magmas have been erupted during the Holocene.

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).

Primary failure of eruption: further characterization of a rare eruption disorder.

PubMed

Frazier-Bowers, Sylvia A; Koehler, Karen E; Ackerman, James L; Proffit, William R

2007-05-01

Posterior open bite has several possible causes, including primary failure of eruption (PFE) that affects all teeth distal to the most mesial involved tooth, mechanical failure of eruption (MFE) (primarily ankylosis) that affects only the involved tooth or teeth, and soft-tissue interferences with eruption (other). Radiographs and other clinical records for 97 cases of failure of posterior eruption submitted for consultation were analyzed to further characterize PFE and distinguish it from MFE. Of the 97 cases, 38 were judged to be clear-cut PFE; 19 were diagnosed as MFE; 32 were classified as indeterminate failure because they were too young to be certain of the distinction between PFE and MFE; and 8 were placed in the "other" category. Two subtypes of PFE were observed. In type 1, eruption failure occurred at or near the same time for all teeth in an affected quadrant. In type 2, a gradient of the time of failure was present, so that some further development of the teeth posterior to the most mesial affected tooth was observed before eruption failure. A family history of eruption problems was noted in 10 of the 38 PFE subjects (26%), and a pedigree analysis was done for 4 families. This was consistent with autosomal dominant transmission. The distinction between PFE and MFE is clinically important because it determines whether all posterior teeth, or only individual affected teeth, will not respond to orthodontic force. Certain diagnosis often requires progress radiographs so that the pattern of eruption of teeth distal to the most mesial affected tooth can be observed.

Magnetic Flux Rope Identification and Characterization from Observationally Driven Solar Coronal Models

NASA Astrophysics Data System (ADS)

Lowder, Chris; Yeates, Anthony

2017-09-01

Formed through magnetic field shearing and reconnection in the solar corona, magnetic flux ropes are structures of twisted magnetic field, threaded along an axis. Their evolution and potential eruption are of great importance for space weather. Here we describe a new methodology for the automated detection of flux ropes in simulated magnetic fields, utilizing field-line helicity. Our Flux Rope Detection and Organization (FRoDO) code, which measures the magnetic flux and helicity content of pre-erupting flux ropes over time, as well as detecting eruptions, is publicly available. As a first demonstration, the code is applied to the output from a time-dependent magnetofrictional model, spanning 1996 June 15-2014 February 10. Over this period, 1561 erupting and 2099 non-erupting magnetic flux ropes are detected, tracked, and characterized. For this particular model data, erupting flux ropes have a mean net helicity magnitude of 2.66× {10}43 Mx2, while non-erupting flux ropes have a significantly lower mean of 4.04× {10}42 Mx2, although there is overlap between the two distributions. Similarly, the mean unsigned magnetic flux for erupting flux ropes is 4.04× {10}21 Mx, significantly higher than the mean value of 7.05× {10}20 Mx for non-erupting ropes. These values for erupting flux ropes are within the broad range expected from observational and theoretical estimates, although the eruption rate in this particular model is lower than that of observed coronal mass ejections. In the future, the FRoDO code will prove to be a valuable tool for assessing the performance of different non-potential coronal simulations and comparing them with observations.

Shallow system rejuvenation and magma discharge trends at Piton de la Fournaise volcano (La Réunion Island)

NASA Astrophysics Data System (ADS)

Coppola, Diego; Di Muro, Andrea; Peltier, Aline; Villeneuve, Nicolas; Ferrazzini, Valerie; Favalli, Massimiliano; Bachèlery, Patrick; Gurioli, Lucia; Harris, Andrew; Moune, Séverine; Vlastélic, Ivan; Galle, Bo; Arellano, Santiago; Aiuppa, Alessandro

2017-04-01

During April 2007, the largest historical eruption of Piton de la Fournaise (Île de La Réunion, France) drained the shallow plumbing system and resulted in collapse of the summit crater. Following the 2007 eruption, Piton de la Fournaise entered a seven-year long period of near-continuous deflation interrupted, in June 2014, by a new phase of significant inflation. By integrating multiple datasets (lava discharge rates, deformation, seismicity, gas flux, gas composition, and lava chemistry), we here show that the progressive migration of magma from a deeper (below sea level) storage zone gradually rejuvenated and pressurized the above-sea-level portion of the magmatic system to provoke four small (<5 × 10 6 m3) eruptions from vents located close to the summit cone. Progressive increase in output rate between each eruption culminated, with the fifth, longest-lasting (August-October 2015) and largest-volume (45 ± 15 × 10 6 m3) eruption of the cycle. Activity observed in 2014 and 2015 points to a phase of shallow system rejuvenation and discharge, whereby continuous magma supply provoked eruptions from increasingly deeper and larger magma storage zones. Downward depressurization continued until unloading of the deepest, least differentiated magma triggered an "effusive paroxysm" that emptied the main shallow reservoir and terminated the cycle. Such an unloading process may characterize the evolution of shallow magmatic systems at other persistently active effusive centers.

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.

Reconstruction of a phreatic eruption on 27 September 2014 at Ontake volcano, central Japan, based on proximal pyroclastic density current and fallout deposits

NASA Astrophysics Data System (ADS)

Maeno, Fukashi; Nakada, Setsuya; Oikawa, Teruki; Yoshimoto, Mitsuhiro; Komori, Jiro; Ishizuka, Yoshihiro; Takeshita, Yoshihiro; Shimano, Taketo; Kaneko, Takayuki; Nagai, Masashi

2016-05-01

The phreatic eruption at Ontake volcano on 27 September 2014, which caused the worst volcanic disaster in the past half-century in Japan, was reconstructed based on observations of the proximal pyroclastic density current (PDC) and fallout deposits. Witness observations were also used to clarify the eruption process. The deposits are divided into three major depositional units (Units A, B, and C) which are characterized by massive, extremely poorly sorted, and multimodal grain-size distribution with 30-50 wt% of fine ash (silt-clay component). The depositional condition was initially dry but eventually changed to wet. Unit A originated from gravity-driven turbulent PDCs in the relatively dry, vent-opening phase. Unit B was then produced mainly by fallout from a vigorous moist plume during vent development. Unit C was derived from wet ash fall in the declining stage. Ballistic ejecta continuously occurred during vent opening and development. As observed in the finest population of the grain-size distribution, aggregate particles were formed throughout the eruption, and the effect of water in the plume on the aggregation increased with time and distance. Based on the deposit thickness, duration, and grain-size data, and by applying a scaling analysis using a depth-averaged model of turbulent gravity currents, the particle concentration and initial flow speed of the PDC at the summit area were estimated as 2 × 10-4-2 × 10-3 and 24-28 m/s, respectively. The tephra thinning trend in the proximal area shows a steeper slope than in similar-sized magmatic eruptions, indicating a large tephra volume deposited over a short distance owing to the wet dispersal conditions. The Ontake eruption provided an opportunity to examine the deposits from a phreatic eruption with a complex eruption sequence that reflects the effect of external water on the eruption dynamics.

Social and environmental impact of volcaniclastic flows related to 472 AD eruption at Vesuvius from stratigraphic and geoarcheological data

NASA Astrophysics Data System (ADS)

Di Vito, Mauro A.; de Vita, Sandro; Rucco, Ilaria; Bini, Monica; Zanchetta, Giovanni; Aurino, Paola; Cesarano, Mario; Ebanista, Carlo; Rosi, Mauro; Ricciardi, Giovanni

2017-04-01

There is a growing number of evidences in the surrounding plain of Somma-Vesuvius volcano which indicate that along with primary volcanic processes (i.e. fallout, pyroclastic density currents) the syn-eruptive and post-eruptive volcaniclastic remobilization has severely impacted the ancient civilizations, which flourished in the area. This represents an important starting point for understanding the future hazard related to a potential (and not remote) renewal of volcanic activity of the Campaniana volcanoes. We present geoarcheological and stratigraphic data obtained from the analysis of more than 160 sections in the Campanian plain showing the widespread impact of volcaniclastic debris flows and floods originated from the rapid remobilization of the products of the AD 472 eruption of Somma-Vesuvius, both on the environment and on the human landscape. This eruption was one of the two sub-Plinian historical events of Somma Vesuvius. This event largely impacted the northern and eastern territory surrounding the volcano with deposition of a complex sequence of pyroclastic-fallout and -current deposits. These sequences were variably affected by syn- and post-eruptive mobilization both along the Somma-Vesuvius slopes and the Apennine valleys with the emplacement of thick mud- and debris-flows which strongly modified the preexisting paleogeography of the Plain with irretrievable damages to the agricultural and urban landscape. The multidisciplinary approach to the study of the sequences permitted to reconstruct the palaeoenvironment before the eruption and the timing of the emplacement of both pyroclastic and volcanoclastic deposits. The preexisting landscape was characterized by intense human occupation, although showing strong evidences of degradation and abandonment due to the progressive decline of the Roman Empire. The impact of volcaniclastic flows continued for decades after the eruption as highlighted in the studied sequences by stratigraphic and archaeologic data. In fact the volcanoclastic flows emplacement continued at least until the following AD 512 eruption of Somma-Vesuvius, and likely contributed to the final decline of the Roman civilization in the area.

Cause and risk of catastrophic eruptions in the Japanese Archipelago.

PubMed

Tatsumi, Yoshiyuki; Suzuki-Kamata, Keiko

2014-01-01

The Japanese Archipelago is characterized by active volcanism with variable eruption styles. The magnitude (M)-frequency relationships of catastrophic caldera-forming eruptions (M ≥ 7) are statistically different from those of smaller eruptions (M ≤ 5.7), suggesting that different mechanisms control these eruptions. We also find that volcanoes prone to catastrophic eruptions are located in regions of low crustal strain rate (<0.5 × 10(8)/y) and propose, as one possible mechanism, that the viscous silicic melts that cause such eruptions can be readily segregated from the partially molten lower crust and form a large magma reservoir in such a tectonic regime. Finally we show that there is a ∼1% probability of a catastrophic eruption in the next 100 years based on the eruption records for the last 120 ky. More than 110 million people live in an area at risk of being covered by tephra >20 cm thick, which would severely disrupt every day life, from such an eruption on Kyushu Island, SW Japan.

Cause and risk of catastrophic eruptions in the Japanese Archipelago

PubMed Central

TATSUMI, Yoshiyuki; SUZUKI-KAMATA, Keiko

2014-01-01

The Japanese Archipelago is characterized by active volcanism with variable eruption styles. The magnitude (M)-frequency relationships of catastrophic caldera-forming eruptions (M ≥ 7) are statistically different from those of smaller eruptions (M ≤ 5.7), suggesting that different mechanisms control these eruptions. We also find that volcanoes prone to catastrophic eruptions are located in regions of low crustal strain rate (<0.5 × 108/y) and propose, as one possible mechanism, that the viscous silicic melts that cause such eruptions can be readily segregated from the partially molten lower crust and form a large magma reservoir in such a tectonic regime. Finally we show that there is a ∼1% probability of a catastrophic eruption in the next 100 years based on the eruption records for the last 120 ky. More than 110 million people live in an area at risk of being covered by tephra >20 cm thick, which would severely disrupt every day life, from such an eruption on Kyushu Island, SW Japan. PMID:25391319

Imaging of volcanic activity on Jupiter's moon Io by Galileo during the Galileo Europa Mission and the Galileo Millennium Mission

USGS Publications Warehouse

Keszthelyi, L.; McEwen, A.S.; Phillips, C.B.; Milazzo, M.; Geissler, P.; Turtle, E.P.; Radebaugh, J.; Williams, D.A.; Simonelli, D.P.; Breneman, H.H.; Klaasen, K.P.; Levanas, G.; Denk, T.; Alexander, D.D.A.; Capraro, K.; Chang, S.-H.; Chen, A.C.; Clark, J.; Conner, D.L.; Culver, A.; Handley, T.H.; Jensen, D.N.; Knight, D.D.; LaVoie, S.K.; McAuley, M.; Mego, V.; Montoya, O.; Mortensen, H.B.; Noland, S.J.; Patel, R.R.; Pauro, T.M.; Stanley, C.L.; Steinwand, D.J.; Thaller, T.F.; Woncik, P.J.; Yagi, G.M.; Yoshimizu, J.R.; Alvarez, Del; Castillo, E.M.; Belton, M.J.S.; Beyer, R.; Branston, D.; Fishburn, M.B.; Mueller, B.; Ragan, R.; Samarasinha, N.; Anger, C.D.; Cunningham, C.; Little, B.; Arriola, S.; Carr, M.H.; Asphaug, E.; Moore, J.; Morrison, D.; Rages, K.; Banfield, D.; Bell, M.; Burns, J.A.; Carcich, B.; Clark, B.; Currier, N.; Dauber, I.; Gierasch, P.J.; Helfenstein, P.; Mann, M.; Othman, O.; Rossier, L.; Solomon, N.; Sullivan, R.; Thomas, P.C.; Veverka, J.; Becker, T.; Edwards, K.; Gaddis, L.; Kirk, R.; Lee, E.; Rosanova, T.; Sucharski, R.M.; Beebe, R.F.; Simon, A.; Bender, K.; Chuang, F.; Fagents, S.; Figueredo, P.; Greeley, R.; Homan, K.; Kadel, S.; Kerr, J.; Klemaszewski, J.; Lo, E.; Schwarz, W.; Williams, K.; Bierhaus, E.; Brooks, S.; Chapman, C.R.; Merline, B.; Keller, J.; Schenk, P.; Tamblyn, P.; Bouchez, A.; Dyundian, U.; Ingersoll, A.P.; Showman, A.; Spitale, J.; Stewart, S.; Vasavada, A.; Cunningham, W.F.; Johnson, T.V.; Jones, T.J.; Kaufman, J.M.; Magee, K.P.; Meredith, M.K.; Orton, G.S.; Senske, D.A.; West, A.; Winther, D.; Collins, G.; Fripp, W.J.; Head, J. W.; Pappalardo, R.; Pratt, S.; Procter, L.; Spaun, N.; Colvin, T.; Davies, M.; DeJong, E.M.; Hall, J.; Suzuki, S.; Gorjian, Z.; Giese, B.; Koehler, U.; Neukum, G.; Oberst, J.; Roatsch, T.; Tost, W.; Schuster, P.; Wagner, R.; Dieter, N.; Durda, D.; Greenberg, R.J.; Hoppa, G.; Jaeger, W.; Plassman, J.; Tufts, R.; Fanale, F.P.; Gran,

2001-01-01

The Solid-State Imaging (SSI) instrument provided the first high- and medium-resolution views of Io as the Galileo spacecraft closed in on the volcanic body in late 1999 and early 2000. While each volcanic center has many unique features, the majority can be placed into one of two broad categories. The "Promethean" eruptions, typified by the volcanic center Prometheus, are characterized by long-lived steady eruptions producing a compound flow field emplaced in an insulating manner over a period of years to decades. In contrast, "Pillanian" eruptions are characterized by large pyroclastic deposits and short-lived but high effusion rate eruptions from fissures feeding open-channel or open-sheet flows. Both types of eruptions commonly have ???100-km-tall, bright, SO2-rich plumes forming near the flow fronts and smaller deposits of red material that mark the vent for the silicate lavas. Copyright 2001 by the American Geophysical Union.

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.

Studying the Formation and Evolution of Eruptive Solar Magnetic Flux Ropes

NASA Astrophysics Data System (ADS)

Linton, M.

2017-12-01

Solar magnetic eruptions are dramatic sources of solar activity, and dangerous sources of space weather hazards. Many of these eruptions take the form of magnetic flux ropes, i.e., magnetic fieldlines wrapping around a core magnetic flux tube. Investigating the processes which form these flux ropes both prior to and during eruption, and investigating their evolution after eruption, can give us a critical window into understanding the sources of and processes involved in these eruptions. This presentation will discuss modeling and observational investigations into these various phases of flux rope formation, eruption, and evolution, and will discuss how these different explorations can be used to develop a more complete picture of erupting flux rope dynamics. This work is funded by the NASA Living with a Star program.

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.

Textural constraints on the dynamics of the 2000 Miyakejima eruption

NASA Astrophysics Data System (ADS)

Garozzo, Ileana; Romano, Claudia; Giordano, Guido; Geshi, Nobuo; Vona, Alessandro

2016-04-01

Miyakejima Volcano is a basaltic-andesite stratovolcano active from ~10.000 years, located on the north of the Izu-Bonin arc. During the last 600 years the volcano has been characterized mainly by flank fissure activity, with explosive phreatomagmatic eruptions on the coastal areas. In the last century, the activity became more frequent and regular with intervals of 20 to 70 years (1940, 1962, 1983 and 2000). The last activity started on 27 June 2000, with a minor submarine eruption on the west coast of the volcano, and proceeded with six major summit eruptions from July 8 to August 29. The eruptions led to the formation of a collapse caldera ~1.6 km across. The total erupted tephra represents only 1.7% in volume of the caldera, the high fragmentation of magma produced mainly fine-grained volcanic ash. In order to improve the understanding on the triggering and dynamics of this explosive eruption, we carried out a detailed investigation of the erupted materials with particular attention to the textural features of juvenile pyroclasts (Vesicle and Crystal Size Distributions). The stratigraphic record can be divided into six fall units, corresponding to the six summit eruptions, although juvenile materials were identified only in 4 units (unit 2, 4, 5, 6). We selected about 100 juvenile grains sampled from the bottom to the top of each level, to be analyzed by scanning electron microscopy. The study of juvenile morphological features allowed us to recognize the existence of three characteristic morphotypes, showing marked differences in their external morphologies and internal textures (from poorly to highly crystallized and vesiculated clasts). The distribution of these morphotypes is non-homogeneous along the eruptive sequence indicating changes of dynamics during magma ascent. Juveniles do not show features inherited from the interaction with external water. Vesicle Volume Distributions of the selected ash grains show that the three types of pyroclasts experienced different nucleation and growth processes. Also the Vesicles Number Densities (VNDs) vary of about one order of magnitude in the different populations (from 107 to 108 cm-3), with values comparable with those commonly related to sub-Plinian and Plinian eruptions. Data from the CSD analysis show perfect agreement with the measured VNDs (crystal population densities increasing with VNDs), suggesting a link between the degassing history and the syn-eruptive crystallization. The results of the textural analysis are used to produce a conduit model for the 2000 Miyakejima eruption. Textural analysis and modeling data are presented to reconstruct the eruptive dynamics leading to this high - energetic eruption.

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.

Reconstruction of total grain size distribution of the climactic phase of a long-lasting eruption: the example of the 2008-2013 Chaitén eruption

NASA Astrophysics Data System (ADS)

Alfano, Fabrizio; Bonadonna, Costanza; Watt, Sebastian; Connor, Chuck; Volentik, Alain; Pyle, David M.

2016-07-01

The 2008-2013 eruption of Chaitén Volcano (Chile) was a long-lasting eruption whose climactic phase (May 6, 2008) produced a sub-Plinian plume, with height ranging between 14 and 20 km that dispersed to the NE, reaching the Atlantic coast of Argentina. The erupted material was mainly of lithic origin (˜77 wt%), resulting in a unimodal total grain size distribution (TGSD) dominated by coarse ash (77 wt%), with Mdϕ of 2.7 and σϕ of 2.4. Lapilli clasts (>2 mm) dominate the proximal deposit within ~20 km of the vent, while coarse (63 μm-2 mm) and fine ash (<63 μm) sedimented as far as 800 km from vent, generating mostly poly-modal grain size distributions across the entire deposit. Given that most of the mass is sedimented in proximal areas, results show that possible contributions of later explosive events to the thickness of the distal deposit where layers are less distinguishable (>400 km) do not significantly affect the determination of the TGSD. In contrast, gaps in data sampling in the medial deposit (in particular the gap between 50 and 350 km from vent that coincides with shifts in sedimentation regimes) have large impacts on estimates of TGSD. Particle number distribution for this deposit is characterized by a high power-law exponent (3.0) following a trend very similar to the vesicle size distribution in the juvenile pyroclasts. Although this could be taken to indicate a bubble-driven fragmentation process, we suggest that fragmentation was more likely the result of a shear-driven process because of the predominance of non-vesicular products (lithics and obsidians) and the large fraction of coarse ash in the TGSD.

Contrasting patterns of vesiculation in low, intermediate, and high Hawaiian fountains: A case study of the 1969 Mauna Ulu eruption

USGS Publications Warehouse

Parcheta, Carolyn E.; Houghton, Bruce F.; Swanson, Donald A.

2013-01-01

Hawaiian-style eruptions, or Hawaiian fountains, typically occur at basaltic volcanoes and are sustained, weakly explosive jets of gas and dominantly coarse, juvenile ejecta (dense spatter to delicate reticulite). Almost the entire range of styles and mass eruption rates within Hawaiian fountaining occurred during twelve fountaining episodes recorded at Mauna Ulu, Kīlauea between May and December 1969. Such diversity in intensity and style is controlled during magma ascent by many processes that can be constrained by the size and shape of vesicles in the 1969 pyroclasts. This paper describes pyroclast vesicularity from high, intermediate, and low fountaining episodes with eruption rates from 0.05 to 1.3 × 106 m3 h− 1. As each eruptive episode progressed, magma ascent slowed in and around the vent system, offering extended time for bubbles to grow and coalesce. Late ejected pyroclasts are thus characterized by populations of fewer and larger vesicles with relaxed shapes. This progression continued in the intervals between episodes after termination of fountain activity. The time scale for this process of shallow growth, coalescence and relaxation of bubbles is typically tens of hours. Rims and cores of pumiceous pyroclasts from moderate to high fountaining episodes record a second post-fragmentation form of vesicle maturation. Partially thermally insulated pyroclasts can have internal bubble populations evolve more dynamically with continued growth and coalescence, on a time scale of only minutes, during transport in the fountains. Reticulite, which formed in a short-lived fountain 540 m in height, underwent late, short-lived bubble nucleation followed by rapid growth of a uniform bubble population in a thermally insulated fountain, and quenched at the onset of permeability before significant coalescence. These contrasting patterns of shallow degassing and outgassing were the dominant controls in determining both the form and duration of fountaining episodes at Mauna Ulu, and probably for many other Hawaiian-style eruptions.

Eruption and emplacement dynamics of a thick trachytic lava flow of the Sancy volcano (France)

NASA Astrophysics Data System (ADS)

Latutrie, Benjamin; Harris, Andrew; Médard, Etienne; Gurioli, Lucia

2017-01-01

A 70-m-thick, 2200-m-long (51 × 106 m3) trachytic lava flow unit underlies the Puy de Cliergue (Mt. Dore, France). Excellent exposure along a 400-m-long and 60- to 85-m-high section allows the flow interior to be accessed on two sides of a glacial valley that cuts through the unit. We completed an integrated morphological, structural, textural, and chemical analysis of the unit to gain insights into eruption and flow processes during emplacement of this thick silicic lava flow, so as to elucidate the chamber and flow dynamic processed that operate during the emplacement of such systems. The unit is characterized by an inverse chemical stratification, where there is primitive lava beneath the evolved lava. The interior is plug dominated with a thin basal shear zone overlying a thick basal breccia, with ramping affecting the entire flow thickness. To understand these characteristics, we propose an eruption model that first involves processes operating in the magma chamber whereby a primitive melt is injected into an evolved magma to create a mixed zone at the chamber base. The eruption triggered by this event first emplaced a trachytic dome, into which banded lava from the chamber base was injected. Subsequent endogenous dome growth led to flow down the shallow slope to the east on which the highly viscous (1012 Pa s) coulée was emplaced. The flow likely moved extremely slowly, being emplaced over a period of 4-10 years in a glacial manner, where a thick (>60-m) plug slid over a thin (5-m-thick) basal shear zone. Excellent exposure means that the Puy de Cliergue complex can be viewed as a case type location for understanding and defining the eruption and emplacement of thick, high-viscosity, silicic lava flow systems.

Maps showing the development of the Pu'u 'O'o-Kupaianaha flow field, June 1984-February 1987, Kilauea Volcano, Hawaii

USGS Publications Warehouse

Heliker, Christina; Ulrich, George E.; Margriter, Sandy C.; Hoffmann, John P.

2001-01-01

The Pu'u 'O'o - Kupaianaha eruption on the middle east rift zone of Kilauea began in January 1983 with intermittent activity along several fissures. By June 1983, the eruption had localized at the Pu'u 'O'o vent, and the activity settled into an increasingly regular pattern of brief eruptive episodes characterized by high lava fountains. The first 18 months of this eruption are chronicled in Wolfe and others (1988), which includes maps of the flows erupted in episodes 1-20. The maps presented here extend this series through the beginning of episode 48.

Morphology and petrography of volcanic ashes.

NASA Technical Reports Server (NTRS)

Heiken, G.

1972-01-01

Study of volcanic ash samples collected from a variety of recent eruptions using petrography, chemical analyses, and scanning electron microscopy to characterize each type and to relate ash morphology to magma composition and the type of eruption. The ashes are placed in the broad genetic categories of magmatic and phreatomagmatic. The morphology of ash particles from magmatic eruptions of high viscosity magma is governed primarily by vesicle density and shape. Ash particles from eruptions of low viscosity magmas are mostly droplets. The morphology of ash particles from phreatomagmatic eruptions is controlled by stresses within the chilled magma which result in fragmentation of the glass to form small blocky or pyramidal glass ash particles.

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).

Analyses of Etna Eruptive Activity From 18th Century and Characterization of Flank Eruptions

NASA Astrophysics Data System (ADS)

del Carlo, P.; Branca, S.; Coltelli, M.

2003-12-01

Etna explosive activity has usually been considered subordinate with respect to the effusive eruptions. Nevertheless, in the last decade and overall after the 2001 and 2002 flank eruptions, explosive activity has drawn the attention of the scientific and politic communities owing to the damages that the long-lasting ash fall caused to Sicily's economy. We analyzed the eruptions from the 18th century to find some analogous behavior of Etna in the past. A study of the Etna historical record (Branca and Del Carlo, 2003) evidenced that after the 1727 eruption, there are no more errors in the attribution of the year of the eruption. Furthermore from this time on, the scientific quality of the chronicles allowed us to obtain volcanological information and to estimate the magnitude of the major explosive events. The main goal of this work was to characterize the different typologies of Etna eruptions in the last three centuries. Meanwhile, we have tried to find the possible relationship between the two kinds of activity (explosive and effusive) in order to understand the complexity of the eruptive phenomena and define the short-term behavior of Etna. On the base of the predominance of the eruptive typology (effusive or explosive) we have classified the flank eruptions in three classes: i) Type 1: almost purely effusive; ii) Type 2: the intensity of explosive activity comparable with the effusive; iii) Type 3: almost purely explosive with minor lava effusion (only the 1763 La Montagnola and 2002 eruptions belong to this class). Long-lasting explosive activity is produced by flank eruptions with continuous ash emission and prolonged fallout on the flanks (e.g. 1763, 1811, 1852-53, 1886, 1892, 2001 and 2002 eruptions). At summit craters continuous activity is weaker, whereas the strongest explosive eruptions are short-lived events. Furthermore, from the 18th to 20th century there were several years of intense and discontinuous summit explosive activity, from high strombolian to fire fountain. This activity produced abundant ash fall in the whole volcano area reaching the Calabria region and Malta Island. Generally, some of these periods preceded important flank eruptions. Concerning the occurrence of the higher magnitude explosive events, we observe that at least one subplinian eruption occurred both in the 18th and 19th centuries. In the 20th century the increased quality of the scientific reports has allowed to recognize 6 subplinian eruptions from summit craters.

Shallow system rejuvenation and magma discharge trends at Piton de la Fournaise volcano (La Réunion Island)

NASA Astrophysics Data System (ADS)

Coppola, D.; Di Muro, A.; Peltier, A.; Villeneuve, N.; Ferrazzini, V.; Favalli, M.; Bachèlery, P.; Gurioli, L.; Harris, A. J. L.; Moune, S.; Vlastélic, I.; Galle, B.; Arellano, S.; Aiuppa, A.

2017-04-01

Basaltic magma chambers are often characterized by emptying and refilling cycles that influence their evolution in space and time, and the associated eruptive activity. During April 2007, the largest historical eruption of Piton de la Fournaise (Île de La Réunion, France) drained the shallow plumbing system (> 240 ×106 m3) and resulted in collapse of the 1-km-wide summit crater. Following these major events, Piton de la Fournaise entered a seven-year long period of near-continuous deflation interrupted, in June 2014, by a new phase of significant inflation. By integrating multiple datasets (lava discharge rates, deformation, seismicity, gas flux, gas composition, and lava chemistry), we here show that the progressive migration of magma from a deeper (below sea level) storage zone gradually rejuvenated and pressurized the above-sea-level portion of the magmatic system consisting of a vertically-zoned network of relatively small-volume magma pockets. Continuous inflation provoked four small (< 5 ×106 m3) eruptions from vents located close to the summit cone and culminated, during August-October 2015, with a chemically zoned eruption that erupted 45 ± 15 ×106 m3 of lava. This two-month-long eruption evolved through (i) an initial phase of waning discharge, associated to the withdrawal of differentiated magma from the shallow system, into (ii) a month-long phase of increasing lava and SO2 fluxes at the effusive vent, coupled with CO2 enrichment of summit fumaroles, and involving emission of less differentiated lavas, to end with, (iii) three short-lived (∼2 day-long) pulses in lava and gas flux, coupled with arrival of cumulative olivine at the surface and deflation. The activity observed at Piton de la Fournaise in 2014 and 2015 points to a new model of shallow system rejuvenation and discharge, whereby continuous magma supply causes eruptions from increasingly deeper and larger magma storage zones. Downward depressurization continues until unloading of the deepest, least differentiated magma triggers pulses in lava and gas flux, accompanied by rapid contraction of the volcano edifice, that empties the main shallow reservoir and terminates the cycle. Such an unloading process may characterize the evolution of shallow magmatic systems at other persistently active effusive centers.

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.

Comparison of Galunggung1982-83 and Eyjafjalla-2010 Eruptions: definition of eruption dynamics from 3D Ash Surface Morphology

NASA Astrophysics Data System (ADS)

Aydar, E.; Höskuldsson, A.; Ersoy, O.; Gourgaud, A.

2012-04-01

We consider that all works, concepts on aviation safety, security codes, establishment of warning systems etc begin in 1982, when two commercial jumbo jets en route to Australia across Indonesia suffered loss of engine thrust from ingesting volcanic ash from the erupting Galunggung Volcano, Java, and descended more than 20,000 ft before the engines could be restarted (Casadevall, 1991). It is not the only incident of this kind but this Galunggung eruption had a pionner character attracting attention on aviation safety against volcanic eruptions in international community. As the needs for precautions on aviation safety against volcanic ash encounters began with Galunggung 1982 eruption and as we all concerned by the measures taken by ICAO due to Eyjafjallajökull-2010 eruption, we aimed to investigate this last huge airspace perturbing eruption and compare the volcanic ashes produced by those two eruptions. Volcanic ash characterization should be most important parameter to understand how the eruption concerned unrolled. Galunggung 1982-83 eruption was exceptionally long, lasting about nine months between 5 April 1982-8 January 1983). During this well known eruption, the composition of the erupted magma evolved from andesite (58% SiO2) to Mg-rich basalt (47% SiO2), while the style of the eruption changed drastically through time (Katili and Sudrdajat, 1984; Sudrajat and Tilling, 1984; Gourgaud et al., 1989 gourgaud etal 2000). Paralel to chemical changes and water consumption, eruption dynamic was also changed and occured in three eruption phases with different eruptive styles as an initial Vulcanian phase (5 April-13 May), a phreatomagmatic phase (17 May-28 October) and a Strombolian phase (3 November-8 January), have been recognized (Katili and Sudradjat,1984). We examined the surficial morphological features of proximal tephra collected from Galunggung and Eyjafjalla volcanoes. Surface texture and morphology of volcanic ash particles change according to various fragmentation mechanisms. Several common types of ashes produced during phreatomagmatic fragmentation process bear blocky-equant, mosslike, plate-like and drop or spherical shapes, besides, magmatic fragmentation leads to the formation of vesiculated fragments. We applied some quantitative statistical parameters for surface descriptors of volcanic ashes such as "Average roughness of profile (Ra), Maximum valley height of roughness profile (Rv), profile irregularities of roughness profile, Surface Area (SA), Volume (V), Fractal Dimension of Roughness (DAS)". We compared quantitative morphological data acquired from both eruptions. The grain size distribution of Eyjafjalla-2010 eruption, ash surface morphology, tephras types and textural parameters exhibit that magma input was important during the first phase (14-16 April) than following days. First phase ashes have either tubular vesicles as classically known for plinian deposits or curviplanar cut vesicles and some brittle fracturations, characteristics of phreatomagmatism. Interestingly, coarse fragmentation happened after the first phase. There is great similarities between two eruptions, but in reverse sens that in Galunggung, the eruption started with vulcanian style then phreatomatism and lasted with strombolian activity. Besides in Eyjafjalla-2010, eruptive phase started with basaltic activities at the North, then phreatomagmatism and toward the end a slight vulcanian style happened.

Geological Evidences for a Large Tsunami Generated by the 7.3 ka Kikai Caldera Eruption, Southern Japan

NASA Astrophysics Data System (ADS)

Yamada, M.; Fujino, S.; Satake, K.

2017-12-01

The 7.3 ka eruption of Kikai volcano, southern Kyushu, Japan, is one of the largest caldera-forming eruption in the world. Given that a huge caldera was formed in shallow sea area during the eruption, a tsunami must have been generated by a sea-level change associated. Pyroclastic flow and tsunami deposits by the eruption have been studied around the caldera, but they are not enough to evaluate the tsunami size. The goal of this study is to unravel sizes of tsunami and triggering caldera collapse by numerical simulations based on a widely-distributed tsunami deposit associated with the eruption. In this presentation, we will provide an initial data on distribution of the 7.3 ka tsunami deposit contained in sediment cores taken at three coastal lowlands in Wakayama, Tokushima, and Oita prefectures (560 km, 520 km, and 310 km north-east from the caldera, respectively). A volcanic ash from the eruption (Kikai Akahoya tephra: K-Ah) is evident in organic-rich muddy sedimentary sequence in all sediment cores. Up to 6-cm-thick sand layer, characterized by a grading structure and sharp bed boundary with lower mud, is observed immediately beneath the K-Ah tephra in all study sites. These sedimentary characteristics and broad distribution indicate that the sand layer was most likely deposited by a tsunami which can propagate to a wide area, but not by a local storm surge. Furthermore, the stratigraphic relationship implies that the study sites must have been inundated by the tsunami prior to the ash fall. A sand layer is also evident within the K-Ah tephra layer, suggesting that the sand layer was probably formed by a subsequent tsunami wave during the ash fall. These geological evidences for the 7.3 ka tsunami inundation will contribute to a better understanding of the caldera collapse and the resultant tsunami, but also of the tsunami generating system in the eruptive process.

East Pacific rise at 21°N: the volcanic, tectonic, and hydrothermal processes of the central axis

USGS Publications Warehouse

Ballard, Richard D.; Francheteau, Jean; Juteau, Tierre; Rangan, Claude; Normark, William

1981-01-01

Photographs obtained by the ANGUS survey system at 21°N reveal many similarities to the geological processes delineated at other spreading centers and in particular those observed in the Galapagos Rift at 86°W. The region of recent volcanism is restricted to a narrow zone (Zone 1) approximately 1 km wide. This suggests that the width of the magma chamber feeding these flows is also narrow at the top. Variations in sediment cover are used to subdivide the flows within Zone 1 into three sheet-flow/pillow-flow pairs. The youngest pair appears to have erupted form a linear fissure 8 km long running parallel to the valley axis. This fissure is part of a larger en echelon pattern of eruptive fissures. Active hydrothermal vents associated with the youngest flows are situated directly above the apparent eruptive fissure. The high (350°C) temperature for some of the fluids exiting from the vents suggests a highly restricted circulation system involving, at times, little to no mixing with cold seawater. The lava terrain in the remainder of Zone 1 and bordering regions is characterized by extensive fracturing, further suggesting a narrow upper dimension to the magma chamber and also that subsurface hydrothermal deposition of massive sulfides may lead to a reduction in the mixing processes.

East Pacific Rise at 21 °N: The volcanic, tectonic, and hydrothermal processes of the central axis

USGS Publications Warehouse

Ballard, Richard D.; Francheteau, Jean; Juteau, Tierre; Rangan, Claude; Normark, William R.

1981-01-01

Photographs obtained by the ANGUS survey system at 21°N reveal many similarities to the geological processes delineated at other spreading centers and in particular those observed in the Galapagos Rift at 86°W. The region of recent volcanism is restricted to a narrow zone (Zone l) approximately l km wide. This suggests that the width of the magma chamber feeding these flows is also narrow at the top. Variations in sediment cover are used to subdivide the flows within Zone 1 into three sheet-flow/pillow-flow pairs. The youngest pair appears to have erupted form a linear fissure 8 km long running parallel to the valley axis. This fissure is part of a larger en echelon pattern of eruptive fissures. Active hydrothermal vents associated with the youngest flows are situated directly above the apparent eruptive fissure. The high (350°C) temperature for some of the fluids exiting from the vents suggests a highly restricted circulation system involving, at times, little to no mixing with cold seawater. The lava terrain in the remainder of Zone l and bordering regions is characterized by extensive fracturing, further suggesting a narrow upper dimension to the magma chamber and also that subsurface hydrothermal deposition of massive sulfides may lead to a reduction in the mixing processes.

East Pacific rise at 21°N: The volcanic, tectonic, and hydrothermal processes of the central axis

NASA Astrophysics Data System (ADS)

Ballard, Robert D.; Francheteau, Jean; Juteau, Tierre; Rangan, Claude; Normark, William

1981-09-01

Photographs obtained by the ANGUS survey system at 21°N reveal many similarities to the geological processes delineated at other spreading centers and in particular those observed in the Galapagos Rift at 86°W. The region of recent volcanism is restricted to a narrow zone (Zone 1) approximately 1 km wide. This suggests that the width of the magma chamber feeding these flows is also narrow at the top. Variations in sediment cover are used to subdivide the flows within Zone 1 into three sheet-flow/pillow-flow pairs. The youngest pair appears to have erupted form a linear fissure 8 km long running parallel to the valley axis. This fissure is part of a larger en echelon pattern of eruptive fissures. Active hydrothermal vents associated with the youngest flows are situated directly above the apparent eruptive fissure. The high (350°C) temperature for some of the fluids exiting from the vents suggests a highly restricted circulation system involving, at times, little to no mixing with cold seawater. The lava terrain in the remainder of Zone 1 and bordering regions is characterized by extensive fracturing, further suggesting a narrow upper dimension to the magma chamber and also that subsurface hydrothermal deposition of massive sulfides may lead to a reduction in the mixing processes.

Magma replenishment and volcanic unrest inferred from the analysis of VT micro-seismicity and seismic velocity changes at Piton de la Fournaise Volcano

NASA Astrophysics Data System (ADS)

Brenguier, F.; Rivemale, E.; Clarke, D. S.; Schmid, A.; Got, J.; Battaglia, J.; Taisne, B.; Staudacher, T.; Peltier, A.; Shapiro, N. M.; Tait, S.; Ferrazzini, V.; Di Muro, A.

2011-12-01

Piton de la Fournaise volcano (PdF) is among the most active basaltic volcanoes worldwide with more than one eruption per year on average. Also, PdF is densely instrumented with short-period and broad-band seismometers as well as with GPS receivers. Continuous seismic waveforms are available from 1999. Piton de la Fournaise volcano has a moderate inter-eruptive seismic activity with an average of five detected Volcano-Tectonic (VT) earthquakes per day with magnitudes ranging from 0.5 to 3.5. These earthquakes are shallow and located about 2.5 kilometers beneath the edifice surface. Volcanic unrest is captured on average a few weeks before eruptions by measurements of increased VT seismicity rate, inflation of the edifice summit, and decreased seismic velocities from correlations of seismic noise. Eruptions are usually preceded by seismic swarms of VT earthquakes. Recently, almost 50 % of seismic swarms were not followed by eruptions. Within this work, we aim to gather results from different groups of the UnderVolc research project in order to better understand the processes of deep magma transfer, volcanic unrest, and pre-eruptive magma transport initiation. Among our results, we show that the period 1999-2003 was characterized by a long-term increase of VT seismicity rate coupled with a long-term decrease of seismic velocities. These observations could indicate a long-term replenishment of the magma storage area. The relocation of ten years of inter-eruptive micro-seismicity shows a narrow (~300 m long) sub-vertical fault zone thus indicating a conduit rather than an extended magma reservoir as the shallow magma feeder system. Also, we focus on the processes of short-term volcanic unrest and prove that magma intrusions within the edifice leading to eruptions activate specific VT earthquakes that are distinct from magma intrusions that do not lead to eruptions. We thus propose that, among the different pathways of magma transport within the edifice, only one will allow magma to reach the edifice summit. Moreover, we have identified transient seismic velocity changes lasting a few weeks that could be associated with unreported lateral magma intrusions not leading to eruptions. The clustering of pre-eruptive micro-seismicity between mid 1999-2003 shows that seismic events repeat over successive seismic swarms and suggests that the magma pathway is spatially separated from the seismic faults. Also, the inversion for focal mechanisms shows dominant sub-horizontal P-axes indicating that part of the pre-eruptive micro-seismicity is due to the horizontal compressive stress induced by magma injection. Finally, the analysis of long-term GPS data recorded on the edifice flank shows a constant lateral displacement rate of 3.5 cm/year. More work will be needed in order to infer the possible mutual interactions between magma unrest and transport and the large-scale deformation of the edifice flank.

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

Ascent velocity and dynamics of the Fiumicino mud eruption, Rome, Italy

NASA Astrophysics Data System (ADS)

Vona, A.; Giordano, G.; De Benedetti, A. A.; D'Ambrosio, R.; Romano, C.; Manga, M.

2015-08-01

In August 2013 drilling triggered the eruption of mud near the international airport of Fiumicino (Rome, Italy). We monitored the evolution of the eruption and collected samples for laboratory characterization of physicochemical and rheological properties. Over time, muds show a progressive dilution with water; the rheology is typical of pseudoplastic fluids, with a small yield stress that decreases as mud density decreases. The eruption, while not naturally triggered, shares several similarities with natural mud volcanoes, including mud componentry, grain-size distribution, gas discharge, and mud rheology. We use the size of large ballistic fragments ejected from the vent along with mud rheology to compute a minimum ascent velocity of the mud. Computed values are consistent with in situ measurements of gas phase velocities, confirming that the stratigraphic record of mud eruptions can be quantitatively used to infer eruption history and ascent rates and hence to assess (or reassess) mud eruption hazards.

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.

Familial polymorphous cold eruption.

PubMed

Martin, S; Eastern, J; Knox, J M

1981-02-01

An erythematous, burning papular eruption, constitutional symptoms, fever, and arthropathy developed in a 65-year-old patient after cold exposure. Involvement of other family members occurred in an autosomal dominant pattern. Histopathologic examination of a biopsy specimen revealed telangiectasia and primarily neutrophilic perivascular inflammation, consistent with earlier biopsy reports of this syndrome. Although previously called "familial cold urticaria," this disease is not characterized by urticaria and may be best descriptively termed, "familial polymorphous cold eruption."

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.

Plinian vs. phreatomagmatic eruptions at Grímsvötn volcano, Iceland

NASA Astrophysics Data System (ADS)

Haddadi, Baptiste; Sigmarsson, Olgeir; Larsen, Guðrún

2016-04-01

Grímsvötn is a subglacial central volcano located under the Vatnajökull ice cap, above the assumed centre of the Iceland mantle plume. Historical explosive eruptions are mostly of phreatomagmatic character whereas pure magmatic behaviour may characterize the largest eruptions. What causes this different eruption behaviour is uncertain. Here, we report petrological estimates of crystallization depth and volatile degassing as recorded by sulfur concentrations in melt inclusions (MI) hosted by ferromagnesian minerals and the groundmass glass. Tephra from four eruptions, AD 1823, 1873, 2004 and 2011, were selected. The 2011 and 1873 are the largest known historical eruptions, whereas the 2004 eruption is probably amongst the smallest. The repose time preceding those eruptions is surprisingly similar, or 6 to 7 years, and the major-element compositions are uniform. Plagioclase, clinopyroxene (cpx) and olivine are the three coexisting phases at the liquidus in the quartz-tholeiites of Grímsvötn. The cpx-melt geothermobarometer (Putirka 2008) applied to the 2011 tephra reveals that cpx crystallized over a large range of P from 60 to 640 MPa (depth range: 1.7-18km) and T between 1060 and 1175°C before the Plinian eruption, therefore mobilizing the entire crustal magma system. In contrast, the phreatomagmatic tephra do not record the shallowest crystallization but interestingly all four tephra have identical median entrapment pressure of approximately 400 MPa. Therefore, the depth from which the magma bodies are derived, does not explain the difference in explosivity between those eruptions nor the variable magma volume (V) produced. Sulfur concentrations in MI are only slightly higher in the Plinian products, the difference (10%) being insufficient to explain the different eruption regimes. The ΔS, the difference between the maximum S concentrations in MI and the mean of the groundmass glass for a given eruption, is higher in the Plinian tephra. Based on literature data for the VDRE of 2004, 2011 and Laki eruptions, a semi-log correlation with R2 = 0.92 was obtained. From ΔS = 1094 + 262 log V, we calculate DRE volumes of 0.02 and 0.3 km3 for the 1823 and 1873 eruptions, respectively. The latter volume is similar to estimates from Thorarinsson (1974), whereas little is known about the relatively small 1823 eruption. This simple method allows volume assessments of older historical eruptions and, thus, the magma flux of Grímsvötn volcano over the centuries. Here, we apply the volume estimates for the five eruptions in question to evaluate the degassing efficiency of these explosive basaltic eruptions. An excellent correlation between residual S concentrations in the groundmass glass and the logarithm of the magma volume emitted (R2 = 0.98) reveals that tephra from the small phreatomagmatic eruptions in 2004 and 1823 are only partially outgassed whereas those of the Plinian 1873 and 2011 are largely outgassed, with the subaerial Laki products being almost completely outgassed. The efficiency of volatile degassing is thus correlated with the eruption size that in turn is most likely controlled by deeper-seated processes.

Tephra architecture, pyroclast texture and magma rheology of mafic, ash-dominated eruptions: the Violent Strombolian phase of the Pleistocene Croscat (NE Spain) eruption.

NASA Astrophysics Data System (ADS)

Cimarelli, C.; Di Traglia, F.; Vona, A.,; Taddeucci, J.

2012-04-01

A broad range of low- to mid-intensity explosive activity is dominated by the emission of ash-sized pyroclasts. Among this activity, Violent Strombolian phases characterize the climax of many mafic explosive eruptions. Such phases last months to years, and produce ash-charged plumes several kilometers in height, posing severe threats to inhabited areas. To tackle the dominant processes leading to ash formation during Violent Strombolian eruptions, we investigated the magma rheology and the field and textural features of products from the 11 ka Croscat basaltic complex scoria cone in the Quaternary Garrotxa Volcanic Field (GVF). Field, grain-size, chemical (XRF, FE-SEM and electron microprobe) and textural analyses of the Croscat pyroclastic succession outlined the following eruption evolution: activity at Croscat began with fissural, Hawaiian-type fountaining that rapidly shifted towards Strombolian style from a central vent. Later, a Violent Strombolian explosion included several stages, with different emitted volumes and deposit features indicative of differences within the same eruptive style: at first, quasi-sustained fire-fountaining with ash jet and plume produced a massive, reverse to normal graded, scoria deposit; later, a long lasting series of ash-explosions produced a laminated scoria deposit. The eruption ended with a lava flow breaching the western-side of the volcano. Scoria clasts from the Croscat succession ubiquitously show micrometer- to centimeter-sized, microlite-rich domains (MRD) intermingled with volumetrically dominant, microlite-poor domains (MPD). MRD magmas resided longer in a relatively cooler, degassed zone lining the conduit walls, while MPD ones travelled faster along the central, hotter streamline, the two interminging along the interface between the two velocity zones. The preservation of two distinct domains in the short time-scale of the eruption was favoured by their rheological contrast related to the different microlite abundances. The proportion of MPD and MRD, in agreement with bubble-number density (BND), in different tephra layers reflects the extent of the fast- and slow-flowing zones, thus reflecting the ascent velocity profile of magma during the different phases. Recent works (Kueppers et al. 2006, "Explosive energy" during volcanic eruptions from fractal analysis of pyroclasts) indicate that fractal fragmentation theory may allow for quantifying fragmentation processes during explosive volcanic eruptions by calculating the fractal dimension (D) of the size distribution of pyroclasts. At Croscat, BND and MPD/MRD volume ratio decreased during the violent Strombolian activity while D increased, suggesting that the decrease in the magma flow rate was accompanied by the increase in fragmentation efficiency, i.e. by the increase in the ash production capability. This trend may be tentatively attributed to an increased rheological stiffness of the magma progressively enhancing its brittle, more efficient fragmentation.

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.

Rare earth element contents of the Lusi mud: An attempt to identify the environmental origin of the hot mudflow in East Java - Indonesia

NASA Astrophysics Data System (ADS)

Agustawijaya, Didi Supriadi; Karyadi, Karyadi; Krisnayanti, Baiq Dewi; Sutanto, Sutanto

2017-12-01

The Sidoarjo mudflow in East Java, Indonesia, has been erupting since May 29th, 2006. The eruption has been known as the Lusi (lumpur Sidoarjo), which was previously considered as a remote seismic event consequence, but current geyser-like activities show an association with a geothermal phenomenon. A method of characterizing rare earth elements (REE) is commonly an effective tool for recognizing a geothermal system, and here it is adapted to particularly indicate the environmental origin of the Lusi mud. Results show that the Lusi hot mud is made of a porous smectite structure of a shale rock type, which becomes an ideal tank for trapping the REE, especially the light REE. Volcanic activities seem to be an important influence in the eruption; however, since there is a lack of significant isotopic evidences in the mobilization of the REE during the eruption, the chloride neutral pH water of the Lusi may hardly contain the REE. The moderate Ce and Eu anomalies found in the REE patterns of the mud strongly indicate a sea-floor basin as the most probable environment for the REE fractionation during the sedimentary rock formation, in which the weathering processes of volcanic rock origin enriched the Lusi shale with the REE.

Pyroclastic deposits as a guide for reconstructing the multi-stage evolution of the Somma-Vesuvius Caldera

NASA Astrophysics Data System (ADS)

Cioni, Raffaello; Santacroce, Roberto; Sbrana, Alessandro

The evolution of the Somma-Vesuvius caldera has been reconstructed based on geomorphic observations, detailed stratigraphic studies, and the distribution and facies variations of pyroclastic and epiclastic deposits produced by the past 20,000years of volcanic activity. The present caldera is a multicyclic, nested structure related to the emptying of large, shallow reservoirs during Plinian eruptions. The caldera cuts a stratovolcano whose original summit was at 1600-1900m elevation, approximately 500m north of the present crater. Four caldera-forming events have been recognized, each occurring during major Plinian eruptions (18,300 BP "Pomici di Base", 8000 BP "Mercato Pumice", 3400 BP "Avellino Pumice" and AD 79 "Pompeii Pumice"). The timing of each caldera collapse is defined by peculiar "collapse-marking" deposits, characterized by large amounts of lithic clasts from the outer margins of the magma chamber and its apophysis as well as from the shallow volcanic and sedimentary units. In proximal sites the deposits consist of coarse breccias resulting from emplacement of either dense pyroclastic flows (Pomici di Base and Pompeii eruptions) or fall layers (Avellino eruption). During each caldera collapse, the destabilization of the shallow magmatic system induced decompression of hydrothermal-magmatic and hydrothermal fluids hosted in the wall rocks. This process, and the magma-ground water interaction triggered by the fracturing of the thick Mesozoic carbonate basement hosting the aquifer system, strongly enhanced the explosivity of the eruptions.

The palaeogeographic setting and the local environmental impact of the 130 ka Falconiera tuff-cone eruption (Ustica island, Italy)

NASA Astrophysics Data System (ADS)

de Vita, Sandro; Foresta Martin, Franco

2017-04-01

This research focuses on the effects of the last eruption at Ustica (Suthern Tyrrhenian Sea, Italy), which formed the Falconiera tuff-cone at around 130 ka BP in the north-eastern tip of the island. This eruption was mainly explosive and phreatomagmatic, and emplaced a series of pyroclastic surge beds that formed an asymmetric tuff cone. This is the most easily recognizable volcanic edifice on Ustica, although its north-eastern sector has been partially eroded. A section of the feeding conduit is exposed northward, and is composed of lavas that fed the last stages of the eruption characterized by an intracrateric lava lake and a Strombolian scoria-fallout deposit. The eruption occurred during Upper Pleistocene Marine Isotopic Substage 5.5, a warm period characterized by a high sea-level stand (6±3 m above the present sea level in stable areas) and the diffusion of subtropical flora and fauna across the Mediterranean sea. This eruption slightly modified the morphology of Ustica, but impacted both marine and terrestrial environments, burying beach deposits rich in mollusk shells (i.e. Strombus bubonius, Conus testudinarius, Brachidontes puniceus), colonies of corals (Cladocora caespitosa) and subaerial plants (Chamaerops humilis). These organisms, found in some cases in their life position, along with other lines of evidence, provide information on the palaeogeography of this sector of the island at the time of the eruption, and on the local impact of this event on the environment.

Mammalian enamel maturation: Crystallographic changes prior to tooth eruption

PubMed Central

Kallistová, Anna; Horáček, Ivan; Šlouf, Miroslav; Skála, Roman; Fridrichová, Michaela

2017-01-01

Using the distal molar of a minipig as a model, we studied changes in the microstructural characteristics of apatite crystallites during enamel maturation (16-23 months of postnatal age), and their effects upon the mechanical properties of the enamel coat. The slow rate of tooth development in a pig model enabled us to reveal essential heterochronies in particular components of the maturation process. The maturation changes began along the enamel-dentine junction (EDJ) of the trigonid, spreading subsequently to the outer layers of the enamel coat to appear at the surface zone with a 2-month delay. Correspondingly, at the distal part of the tooth the timing of maturation processes is delayed by 3-5 month compared to the mesial part of the tooth. The early stage of enamel maturation (16-20 months), when the enamel coat is composed almost exclusively of radial prismatic enamel, is characterized by a gradual increase in crystallite thickness (by a mean monthly increment of 3.8 nm); and an increase in the prism width and thickness of crystals composed of elementary crystallites. The late stage of maturation (the last two months prior to tooth eruption), marked with the rapid appearance of the interprismatic matrix (IPM) during which the crystals densely infill spaces between prisms, is characterized by an abrupt decrease in microstrain and abrupt changes in the micromechanical properties of the enamel: a rapid increase in its ability to resist long-term load and its considerable hardening. The results suggest that in terms of crystallization dynamics the processes characterizing the early and late stage of mammalian enamel maturation represent distinct entities. In regards to common features with enamel formation in the tribosphenic molar we argue that the separation of these processes could be a common apomorphy of mammalian amelogenetic dynamics in general. PMID:28196135

Mammalian enamel maturation: Crystallographic changes prior to tooth eruption.

PubMed

Kallistová, Anna; Horáček, Ivan; Šlouf, Miroslav; Skála, Roman; Fridrichová, Michaela

2017-01-01

Using the distal molar of a minipig as a model, we studied changes in the microstructural characteristics of apatite crystallites during enamel maturation (16-23 months of postnatal age), and their effects upon the mechanical properties of the enamel coat. The slow rate of tooth development in a pig model enabled us to reveal essential heterochronies in particular components of the maturation process. The maturation changes began along the enamel-dentine junction (EDJ) of the trigonid, spreading subsequently to the outer layers of the enamel coat to appear at the surface zone with a 2-month delay. Correspondingly, at the distal part of the tooth the timing of maturation processes is delayed by 3-5 month compared to the mesial part of the tooth. The early stage of enamel maturation (16-20 months), when the enamel coat is composed almost exclusively of radial prismatic enamel, is characterized by a gradual increase in crystallite thickness (by a mean monthly increment of 3.8 nm); and an increase in the prism width and thickness of crystals composed of elementary crystallites. The late stage of maturation (the last two months prior to tooth eruption), marked with the rapid appearance of the interprismatic matrix (IPM) during which the crystals densely infill spaces between prisms, is characterized by an abrupt decrease in microstrain and abrupt changes in the micromechanical properties of the enamel: a rapid increase in its ability to resist long-term load and its considerable hardening. The results suggest that in terms of crystallization dynamics the processes characterizing the early and late stage of mammalian enamel maturation represent distinct entities. In regards to common features with enamel formation in the tribosphenic molar we argue that the separation of these processes could be a common apomorphy of mammalian amelogenetic dynamics in general.

Building and Characterizing Volcanic Landscapes with a Numerical Landscape Evolution Model and Spectral Techniques

NASA Astrophysics Data System (ADS)

Richardson, P. W.; Karlstrom, L.

2016-12-01

The competition between constructional volcanic processes such as lava flows, cinder cones, and tumuli compete with physical and chemical erosional processes to control the morphology of mafic volcanic landscapes. If volcanic effusion rates are high, these landscapes are primarily constructional, but over the timescales associated with hot spot volcanism (1-10 Myr) and arcs (10-50 Myr), chemical and physical erosional processes are important. For fluvial incision to occur, initially high infiltration rates must be overcome by chemical weathering or input of fine-grained sediment. We investigate lava flow resurfacing, using a new lava flow algorithm that can be calibrated for specific flows and eruption magnitude/frequency relationships, into a landscape evolution model to complete two modeling experiments to investigate the interplay between volcanic resurfacing and fluvial incision. We use a stochastic spatial vent distribution calibrated from the Hawaiian eruption record to resurface a synthetically produced ocean island. In one experiment, we investigate the consequences of including time-dependent channel incision efficiency. This effectively mimics the behavior of transient hydrological development of lava flows. In the second experiment, we explore the competition between channel incision and lava flow resurfacing. The relative magnitudes of channel incision versus lava flow resurfacing are captured in landscape topography. For example, during the shield building period for ocean islands, effusion rates are high and the signature of lava flow resurfacing dominates. In contrast, after the shield building phase, channel incision begins and eventually dominates the topographic signature. We develop a dimensionless ratio of resurfacing rate to erosion rate to characterize the transition between these processes. We use spectral techniques to characterize volcanic features and to pinpoint the transition between constructional and erosional morphology on modeled landscapes and on the Big Island of Hawaii.

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.

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

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.

Characterization of stem and progenitor cells in the dental pulp of erupted and unerupted murine molars

PubMed Central

Balic, Anamaria; Aguila, H. Leonardo; Caimano, Melissa J.; Francone, Victor P.; Mina, Mina

2010-01-01

In the past few years there have been significant advances in the identification of putative stem cells also referred to as “mesenchymal stem cells” (MSC) in dental tissues including the dental pulp. It is thought that MSC in dental pulp share certain similarities with MSC isolated from other tissues. However, cells in dental pulp are still poorly characterized. This study focused on the characterization of progenitor and stem cells in dental pulps of erupted and unerupted mice molars. Our study showed that dental pulps from unerupted molars contain a significant number of cells expressing CD90+/CD45-, CD117+/CD45-, Sca-1+/CD45- and little if any CD45+ cells. Our in vitro functional studies showed that dental pulp cells from unerupted molars displayed extensive osteo-dentinogenic potential but were unable to differentiate into chondrocytes and adipocytes. Dental pulp from erupted molars displayed a reduced number of cells, contained higher percentage of CD45+ and lower percentage of cells expressing CD90+/CD45-, CD117+/CD45- as compared to unerupted molars. In vitro functional assays demonstrated the ability of a small fraction of cells to differentiate into odontoblasts, osteoblasts, adipocytes and chondrocytes. There was a significant reduction in the osteo-dentinogenic potential of the pulp cells derived from erupted molars compared to unerupted molars. Furthermore, the adipogenic and chondrogenic differentiation of pulp cells from erupted molars was dependent on a long induction period and infrequent. Based on these findings we propose that the dental pulp of the erupted molars contain a small population of multipotent cells, whereas the dental pulp of the unerupted molars does not contain multipotent cells but is enriched in osteo-dentinogenic progenitors engaged in the formation of coronal and radicular odontoblasts. PMID:20193787

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.

Numerical modeling of magma-tectonic interactions at Pacaya Volcano, Guatemala

NASA Astrophysics Data System (ADS)

Wauthier, C.

2017-12-01

Pacaya Volcano is composed of several volcanic cones located along the southern rim of the Amatitlan caldera, approximately 25 km south of Guatemala City. It is a basaltic volcano located in the Central American Volcanic Arc. The shallow magma plumbing system at Pacaya likely includes at least three magma reservoirs: a very shallow ( 0.2-0.4 km depth) reservoir located below and possibly within the MacKenney cone, a 4 km deep reservoir located northwest of the summit, and a shallow dike-like conduit below the summit which fed the recent flank eruptions. Pacaya's western flank is slipping in a stick-slip fashion, and the instability seems associated with larger volume eruptions. Flank instability phases indeed occurred in 2010 and 2014 in coincidence with major intrusive and eruptive phases, suggesting a positive feedback between the flank motion and major intrusions. Simple analytical models are insufficient to fit the geodetic observations and model the flank processes and their mechanical interactions with the magmatic system. Here, numerical modeling approaches are used to characterize the 2014 flank deformation episode and magma-tectonic interactions.

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.

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.

Petrology of the 1877 eruption of Cotopaxi Volcano, Ecuador: Insight on magma evolution and storage

NASA Astrophysics Data System (ADS)

Saalfeld, M. A.; Panter, K. S.; Kelley, D.

2017-12-01

Cotopaxi is a stratovolcano in the Northern Andes Volcanic Zone, and has a history of bimodal volcanism, alternating between rhyolite and andesite. With Cotopaxi reawakening in 2015 after 100 years of quiescence, the question of what is occurring beneath the surface becomes especially poignant. To answer this question, we must look to the volcano's past. This work characterizes the mineralogy and geochemistry of the recent eruptive products of Cotopaxi, with emphasis on the two pulses of the 1877 eruption. Additionally, pressure and temperature are estimated for magmas prior to eruption. This will allow a better understanding of the magma plumbing system and its evolution over time. Over the past 500 years Cotopaxi has had five major eruptive events (VEI 3-4), which occurred in 1532, 1742, 1744, 1768, and 1877, and included pyroclastic surges, scoria flows, and lahars. After the initial pulse of the 1877 eruption and the subsequent lahars, a second pulse of magma produced a pyroclastic density current containing scoria clasts up to 1 meter in diameter. All samples are basaltic andesite to andesite (56-59 wt. % SiO2), and a mineral assemblage of pl + opx + cpx + mag ± ol. Plagioclase range from An47 to An78 and show both normal and reverse zoning. Normally zoned crystals exhibit greater compositional variation between cores and rims than reversely zoned crystals (median Ancore-Anrim 8% vs 4%, respectively), indicating that crystal fractionation is a dominant process but that mixing also played a role in magma genesis. Pyroxenes occur as augite and enstatite and do not exhibit significant zoning. The similar petrology of these eruptions suggests that they were part of a relatively long-lived system that underwent differentiation and replenishment between eruptions. Thermobarometric data indicate that magma storage occurred at temperatures of 1100-1150°C and pressures ranging from 2 kbar (during the 1877 eruption) to 4 kbar (during the 1742 eruption), which is equivalent to depths of 7 and 14 km, respectively. Geodetic and seismic data from Hickey et al. (2015) indicate that magma is currently being stored at a depth of 4-5 km. While thermobarometry is poorly constrained, it suggests magma storage has become progressively shallower over time. Hickey et al. (2015), J. Geophys. Res. Solid Earth 120, 1473-1486.

Will Mount Etna erupt before EGU General Assembly 2017?

NASA Astrophysics Data System (ADS)

Aloisi, Marco; Cannavo', Flavio; Palano, Mimmo

2017-04-01

Mount Etna has historically recorded a long and very various series of eruptions. The eruptions have mostly shown an episodic character, despite a near continuous supply of magma. In the last years, activity at Mount Etna seems to follow a recurrent pattern characterized by very similar "inflation/paroxysmal events/deflation" dynamic. The paroxysms occurred in December 2015 and May 2016, which involved the "Voragine" crater, can be considered among the most violent observed during the last two decades. These events showed high lava fountains, in the order of hundreds of meters in height, and eruption columns, several kilometres high. A new cycle, characterized by a clear similar inflation of the whole volcano edifice is currently underway. Here, we analyse these recent volcanic cycles and discuss about a) a possible upper bound for the inflation dynamic, above which a paroxysmal event occurs, b) the comparison of the models generating the considered lava fountains and c) a possible time-predictable model of the expected paroxysmal event.

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

MHD Modeling of the Sympathetic Eruptions Observed on August 1, 2010

NASA Astrophysics Data System (ADS)

Mikic, Z.; Torok, T.; Titov, V. S.; Downs, C.; Linker, J.; Lionello, R.; Riley, P.

2013-12-01

The multiple solar eruptions observed by SDO on August 1, 2010 present a special challenge to theoretical models of CME initiation. SDO captured in detail a remarkable chain of sympathetic eruptions that involved the entire visible hemisphere of the Sun (Schrijver et al. 2011). It consisted of several flares and six filament eruptions/CMEs, and triggered a geomagnetic storm on August 3 (de Toma et al. 2010). This series of eruptions was also observed by the two STEREO spacecraft. This collection of observations presents a unique opportunity to understand sympathetic eruptions theoretically. We have previously simulated the three principal filament eruptions (and their associated CMEs) that characterized this event. We have had some success in reproducing their observed synchronicity. We will present further simulations that attempt to get a better match with observations. Such simulations will help us to understand the possible mechanisms by which the various filament eruptions/CMEs may be linked. The modeling of such events is very useful for incorporation into future space weather prediction models. Research supported by NASA's Heliophysics Theory and Living With a Star Programs, and NSF/FESD.

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.

Clonal expansion of Epstein-Barr virus (EBV)-infected γδ T cells in patients with chronic active EBV disease and hydroa vacciniforme-like eruptions.

PubMed

Wada, Taizo; Toga, Akiko; Sakakibara, Yasuhisa; Toma, Tomoko; Hasegawa, Minoru; Takehara, Kazuhiko; Shigemura, Tomonari; Agematsu, Kazunaga; Yachie, Akihiro

2012-10-01

Chronic active Epstein-Barr virus (EBV) disease (CAEBV) is a systemic EBV-positive lymphoproliferative disorder characterized by fever, lymphadenopathy, and splenomegaly. Patients with CAEBV may present with cutaneous symptoms, including hypersensitivity to mosquito bites and hydroa vacciniforme (HV)-like eruptions. HV is a rare photodermatosis characterized by vesicles and crust formation after exposure to sunlight, with onset in childhood, and is associated with latent EBV infection. While γδ T cells have recently been demonstrated to be the major EBV-infected cell population in HV, the immunophenotypic features of EBV-infected γδ T cells in CAEBV with HV-like eruptions or HV remain largely undetermined. We describe three patients with CAEBV whose γδ T cells were found to be the major cellular target of EBV. HV-like eruptions were observed in two of these patients. A clonally expanded subpopulation of γδ T cells that were highly activated and T cell receptor Vγ9- and Vδ2-positive cells was demonstrated in all patients. We also show that the clonally expanded γδ T cells infiltrated into the HV-like eruptions in one patient from whom skin biopsy specimens were available. These results suggest the pathogenic roles of clonally expanded γδ T cells infected by EBV in patients with CAEBV and HV-like eruptions.

Volcanic Eruption Observations from an Elevated Point of the Stromboli Using Thermal Infrared Hyperspectral Imaging

NASA Astrophysics Data System (ADS)

Morton, V.; Gagnon, M. A.; Marcotte, F.; Gouhier, M.; Smekens, J. F.

2017-12-01

Many urban areas are located near active volcanoes around the world. Therefore, scientific research on different indicators of imminent eruptions is carried out on an ongoing basis. Due to the hazardous and unpredictable behavior of volcanoes, remote sensing technologies are normally preferred for investigations. Over the years, the Telops Hyper-Cam, a high-performance infrared hyperspectral camera, has established itself as a reference tool for investigating gas clouds over large distances. In order to illustrate the benefits of standoff infrared hyperspectral imaging for characterizing volcanic processes, many different measurements were carried out from an elevated point ( 800 m) of the Stromboli volcano (Italy) by researchers from the Université Blaise-Pascal (Clermont-Ferrand, France). The Stromboli volcano is well known for its periodic eruptions of small magnitude containing various proportions of ash, lava and gases. Imaging was carried out at a relatively high spectral and spatial resolution before and during eruptions from the North-East (NE) craters. Both sulfur dioxide (SO2) and sulfur tetrafluoride (SiF4) could be successfully identified within the volcano's plume from their distinct spectral features. During the passive degassing phase, a total amount of 3.3 kg of SO2 and 0.8 g of SiF4 were estimated. A violent eruption from NE1 crater was then observed and a total of 45 g and and 7 g of SO2 and SiF4 were estimated respectively. These results are in good agreement with previous work using a UV-SO2 camera. Finally, a smaller eruption from NE2 crater was observed. Total amounts of 3 kg and 17 g of SO2 and SiF4 were estimated respectively. Quantitative chemical maps for both gases will be presented. The results show that standoff thermal infrared hyperspectral imaging provides unique insights for a better understanding of volcanic eruptions.

An Analysis of Eruptions Detected by the LMSAL Eruption Patrol

NASA Astrophysics Data System (ADS)

Hurlburt, N. E.; Higgins, P. A.; Jaffey, S.

2014-12-01

Observations of the solar atmosphere reveals a wide range of real and apparent motions, from small scale jets and spicules to global-scale coronal mass ejections. Identifying and characterizing these motions are essential to advance our understanding the drivers of space weather. Automated and visual identifications are used in identifying CMEs. To date, the precursors to these — eruptions near the solar surface — have been identified primarily by visual inspection. Here we report on an analysis of the eruptions detected by the Eruption Patrol, a data mining module designed to automatically identify eruptions from data collected by Solar Dynamics Observatory's Atmospheric Imaging Assembly (SDO/AIA). We describe the module and use it both to explore relations with other solar events recorded in the Heliophysics Event Knowledgebase and to identify and access data collected by the Interface Region Imaging Spectrograph (IRIS) and Solar Optical Telescope (SOT) on Hinode for further analysis.

Reticulite, Scoria and Lava: Foam Formation in Hawaiian Fire Fountain Eruptions

NASA Astrophysics Data System (ADS)

Rust, A. C.; Cashman, K. V.

2006-12-01

Hawaiian fire fountain eruptions can generate three types of foams: 1) scoria pyroclasts characterized by spherical bubbles and typical vesicularities of 70-85%, 2) reticulite pyroclasts consisting of a polygonal network of trigonal glass struts and vesicularities of 95-99% and 3) lava flows with bubble contents as high as 70-80%. We use bubble textures to explore the origins of these three distinct foams. With these data and the observation that all three foam types can erupt simultaneously, we discuss the dynamics of Hawaiian eruptions. Our main focus is reticulite, which is a minor but ubiquitous product of relatively high Hawaiian fountains. Compared to scoria, reticulite is more vesicular and has a larger mean bubble size and a much more uniform bubble size distribution. It was previously suggested that reticulite results from further expansion of hot scoria foam. However, to form reticulite from scoria requires not only that gas expand faster than it can percolate through bubble networks in scoria, but also requires processes such as Ostwald ripening that will reduce the range of bubble sizes. Such processes commonly occur in the formation of polygonal soap foams for instance. However, we suggest that a better analogue for reticulite formation is popcorn. In particular we propose that reticulite did not evolve from scoria but from magma that experienced (1) near-instantaneous bubble nucleation followed by (2) rapid and uniform expansion to generate (3) a polyhedral 'dry' foam that then (4) experienced near-instantaneous film rupture and quenching throughout the foam. In contrast, it seems that there are other parts of the system where bubble nucleation is not instantaneous and yields a broader size distribution of bubbles that expand more slowly, maintain spherical shapes, and become permeable through coalescence of small melt films between spherical bubble walls. We suggest that reticulite only forms in relatively high fire fountains, not because of longer time for expansion but because of higher ascent rates in these eruptions.

Open-path FTIR spectroscopy of magma degassing processes during eight lava fountains on Mount Etna

NASA Astrophysics Data System (ADS)

La Spina, Alessandro; Burton, Mike; Allard, Patrick; Alparone, Salvatore; Murè, Filippo

2016-04-01

In June-July 2001 a series of 16 discrete lava fountain paroxysms occurred at the Southeast summit crater (SEC) of Mount Etna, preceding a 28-day long violent flank eruption. Each paroxysm was preceded by lava effusion, growing seismic tremor and a crescendo of Strombolian explosive activity culminating into powerful lava fountaining up to 500m in height. During 8 of these 16 events we could measure the chemical composition of the magmatic gas phase (H2O, CO2, SO2, HCl, HF and CO), using open-path Fourier transform infrared (OP-FTIR) spectrometry at ˜1-2km distance from SEC and absorption spectra of the radiation emitted by hot lava fragments. We show that each fountaining episode was characterized by increasingly CO2-rich gas release, with CO2/SO2and CO2/HCl ratios peaking in coincidence with maxima in seismic tremor and fountain height, whilst the SO2/HCl ratio showed a weak inverse relationship with respect to eruption intensity. Moreover, peak values in both CO2/SO2ratio and seismic tremor amplitude for each paroxysm were found to increase linearly in proportion with the repose interval (2-6 days) between lava fountains. These observations, together with a model of volatile degassing at Etna, support the following driving process. Prior to and during the June-July 2001 lava fountain sequence, the shallow (˜2km) magma reservoir feeding SEC received an increasing influx of deeply derived carbon dioxide, likely promoted by the deep ascent of volatile-rich primitive basalt that produced the subsequent flank eruption. This CO2-rich gas supply led to gas accumulation and overpressure in SEC reservoir, generating a bubble foam layer whose periodical collapse powered the successive fountaining events. The anti-correlation between SO2/HCl and eruption intensity is best explained by enhanced syn-eruptive degassing of chlorine from finer particles produced during more intense magma fragmentation.

Complex dynamics of small-moderate volcanic events: the example of the 2011 rhyolitic Cordón Caulle eruption, Chile

NASA Astrophysics Data System (ADS)

Pistolesi, Marco; Cioni, Raffaello; Bonadonna, Costanza; Elissondo, Manuela; Baumann, Valerie; Bertagnini, Antonella; Chiari, Laura; Gonzales, Rafael; Rosi, Mauro; Francalanci, Lorella

2015-01-01

After decades of repose, Puyehue-Cordón Caulle Volcano (Chile) erupted in June 2011 following a month of continuously increasing seismic activity. The eruption dispersed a large volume of rhyolitic tephra over a wide area and was characterized by complex dynamics. During the initial climactic phase of the eruption (24-30 h on 4-5 June), 11-14-km-high plumes dispersed most of the erupted tephra eastward towards Argentina, reaching as far as the Atlantic Ocean. This first eruptive phase was followed by activity of lower intensity, leading to the development of a complex stratigraphic sequence, mainly due to rapid shifts in wind direction and eruptive style. The resulting tephra deposits consist of 13 main layers grouped into four units. Each layer was characterized based on its dispersal direction, sedimentological features, and on the main characteristics of the juvenile fraction (texture, density, petrography, chemistry). The lowest part of the eruptive sequence (Unit I), corresponding to the tephra emitted between 4 and 5 June, is composed of alternating lapilli layers with a total estimated volume of ca. 0.75 km3; these layers record the highest intensity phase, during which a bent-over plume dispersed tephra towards the southeast-east, with negligible up-wind sedimentation. Products emitted during 5-6 June (Unit II) signaled an abrupt shift in wind direction towards the north, leading to the deposition of a coarse ash deposit in the northern sector (ca. 0.21 km3 in volume), followed by a resumption of easterly directed winds. A third phase (Unit III) began on 7 June and resulted in tephra deposits in the eastern sector and ballistic bombs around the vent area. A final phase (Unit IV) started after 15 June and was characterized by the emission of fine-grained white tephra from ash-charged plumes during low-level activity and the extrusion of a viscous lava flow. Timing and duration of the first eruptive phases were constrained based on comparison of the dispersal of the main tephra layers with satellite images, showing that most of the tephra was emitted during the first 72 h of the event. The analyzed juvenile material tightly clusters within the rhyolitic field, with negligible chemical variations through the eruptive sequence. Textural observations reveal that changes in eruption intensity (and consequently in magma ascent velocity within the conduit) and complex interactions between gas-rich and gas-depleted magma portions during ascent resulted in vesicular clasts with variable degrees of shear localization, and possibly in the large heterogeneity of the juvenile material.

The Initial Development of Transient Volcanic Plumes as a Function of Source Conditions

NASA Astrophysics Data System (ADS)

Tournigand, Pierre-Yves; Taddeucci, Jacopo; Gaudin, Damien; Peña Fernández, Juan José; Del Bello, Elisabetta; Scarlato, Piergiorgio; Kueppers, Ulrich; Sesterhenn, Jörn; Yokoo, Akihiko

2017-12-01

Transient volcanic plumes, having similar eruption duration and rise timescales, characterize many unsteady Strombolian to Vulcanian eruptions. Despite being more common, such plumes are less studied than their steady state counterpart from stronger eruptions. Here we investigate the initial dynamics of transient volcanic plumes using high-speed (visible light and thermal) and high-resolution (visible light) videos from Strombolian to Vulcanian eruptions of Stromboli (Italy), Fuego (Guatemala), and Sakurajima (Japan) volcanoes. Physical parameterization of the plumes has been performed by defining their front velocity, velocity field, volume, and apparent surface temperature. We also characterized the ejection of the gas-pyroclast mixture at the vent, in terms of number, location, duration, and frequency of individual ejection pulses and of time-resolved mass eruption rate of the ejecta's ash fraction. Front velocity evolves along two distinct trends related to the initial gas-thrust phase and later buoyant phase. Plumes' velocity field, obtained via optical flow analysis, highlights different features, including initial jets and the formation and/or merging of ring vortexes at different scales. Plume volume increases over time following a power law trend common to all volcanoes and affected by discharge history at the vent. Time-resolved ash eruption rates range between 102 and 107 kg/s and may vary up to 2 orders of magnitude within the first seconds of eruption. Our results help detailing how the number, location, angle, duration, velocity, and time interval between ejection pulses at the vents crucially control the initial (first tens of second), and possibly later, evolution of transient volcanic plumes.

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.

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).

Thermal remote sensing as a part of Exupéry volcano fast response system

NASA Astrophysics Data System (ADS)

Zakšek, Klemen; Hort, Matthias

2010-05-01

In order to understand the eruptive potential of a volcanic system one has to characterize the actual state of stress of a volcanic system that involves proper monitoring strategies. As several volcanoes in highly populated areas especially in south east Asia are still nearly unmonitored a mobile volcano monitoring system is currently being developed in Germany. One of the major novelties of this mobile volcano fast response system called Exupéry is the direct inclusion of satellite based observations. Remote sensing data are introduced together with ground based field measurements into the GIS database, where the statistical properties of all recorded data are estimated. Using physical modelling and statistical methods we hope to constrain the probability of future eruptions. The emphasis of this contribution is on using thermal remote sensing as tool for monitoring active volcanoes. One can detect thermal anomalies originating from a volcano by comparing signals in mid and thermal infrared spectra. A reliable and effective thermal anomalies detection algorithm was developed by Wright (2002) for MODIS sensor; it is based on the threshold of the so called normalized thermal index (NTI). This is the method we use in Exupéry, where we characterize each detected thermal anomaly by temperature, area, heat flux and effusion rate. The recent work has shown that radiant flux is the most robust parameter for this characterization. Its derivation depends on atmosphere, satellite viewing angle and sensor characteristics. Some of these influences are easy to correct using standard remote sensing pre-processing techniques, however, some noise still remains in data. In addition, satellites in polar orbits have long revisit times and thus they might fail to follow a fast evolving volcanic crisis due to long revisit times. Thus we are currently testing Kalman filter on simultaneous use of MODIS and AVHRR data to improve the thermal anomaly characterization. The advantage of this technique is that it increases the temporal resolution through using images from different satellites having different resolution and sensitivity. This algorithm has been tested for an eruption at Mt. Etna (2002) and successfully captures more details of the eruption evolution than would be seen by using only one satellite source. At the moment for Exupéry, merely MODIS (a sensor aboard NASA's Terra and Aqua satellite) data are used for the operational use. As MODIS is a meteorological sensor, it is suitable also for producing general overview images of the crisis area. Therefore, for each processed MODIS image we also produce RGB image where some basic meteorological features are classified: e.g. clouds, volcanic ash plumes, ocean, etc. In the case of detected hotspot an additional image is created; it contains the original measured radiances of the selected channels for the crisis area. All anomaly and processing parameters are additionally written into an XML file. The results are available in web GIS in the worst case two hours after NASA provides level 1b data online.

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.

Evidence of a complex shallow reservoir network from micro-textural observations of the scoria products of the 1085 AD Sunset Crater eruption

NASA Astrophysics Data System (ADS)

Alfano, F.; Pioli, L.; Clarke, A. B.; Ort, M. H.; Roggensack, K.; Self, S.

2014-12-01

Sunset Crater volcano is the youngest scoria cone of the San Francisco Volcanic Field (SFVF). The >300-m-high Sunset Crater, located ~25 km northeast of Flagstaff, erupted about 1085 AD and is a remarkable example of a highly explosive basaltic eruption. The explosive activity produced a tephra sequence of at least eight main fall units associated with major explosive phases. The total cumulative volume is ~0.3 km3 DRE. The volume of individual fall units varies between 0.02 and 0.08 km3 DRE, and an associated column height was up to 20 km high. The products have uniform chemical composition (~47 wt.% SiO2), with phenocrysts of plagioclase, olivine and pyroxene that represent about the 6 vol% of the samples. Despite the uniform chemical and crystal-phase characteristics of the products, the textures are very heterogeneous. Two textural endmembers, intimately intermingled at the mm-scale within a single clast, were identified: one endmember (sideromelane) is characterized by higher vesicularity (~66%), with large regular sub-spherical vesicles (modal diameter 0.6 mm), a glass-rich groundmass (> 95 vol%) and evidence of post-fragmentation vesicle expansion; the second endmember texture (tachylite) is characterized by lower vesicularity (~32%), with small highly irregular vesicles (modal diameter 0.3 mm) that result in a higher vesicle number density than the sideromelane, and a groundmass rich in microcrysts (> 95 vol%), mainly Fe-oxides. Textural characteristics suggest interaction between magmas stored at different depths. The tachylitic texture is present in different proportions in the products of the different eruptive phases, while some small-scale variability seems to suggest variation in the crystallization conditions. However, given the uniform phenocryst composition, these small-scale variations are probably due to differences in the residence time rather than to different storage depths. As a result, our observations suggest the temporary storage of portions of the erupted magma in a complex fracture network or conduit system located at very shallow levels (and possibly within the cone) where the magma could degas and crystallize, producing the observed tachylitic texture. These processes also caused an increase in magma viscosity, likely enhancing eruption explosivity.

Timing, tempo and paleoenvironmental influence of Deccan volcanism relative to the KT extinction

NASA Astrophysics Data System (ADS)

Adatte, Thierry; Keller, Gerta; Schoene, Blair; Khadri, Syed

2015-04-01

Deccan Traps erupted in three main phases with 6% total Deccan volume in phase-1 (base C30n), 80% in phase-2 (C29r) and 14% in phase-3 (C29n). Recent studies indicate that the bulk (80%) of Deccan trap eruptions (Phase-2) occurred over a relatively short time interval in magnetic polarity C29r (Chenet et al., 2008). Moreover, U-Pb zircon geochronology shows that the main Phase 2 began 250 ka before the Cretaceous-Tertiary (KT) mass extinction, suggesting a cause-and-effect relationship (Blair et al., 2015). In India a strong floral response is observed as a direct consequence of volcanic phase-2. In Lameta (infratrappean) sediments preceding the volcanic eruptions, palynoflora are dominated by gymnosperms and angiosperms (Samant and Mohabey, 2005). Shortly after the onset of Deccan phase-2, this floral association was decimated as indicated by a sharp decrease in pollen and spores coupled with the appearance of fungi, which mark increasing stress conditions apparently as a direct result of volcanic activity. The inter-trappean sediments corresponding to the Phases 2 and 3 are characterized by the highest alteration CIA index values suggesting increased acid rains due to SO2 emissions. Closer to the eruption center, the lava flows are generally separated by red weathered horizons known as red boles, marking a quiescent period between two basalt flows. Red boles consist mainly of red silty clays characterized by concentrations of immobile elements such as Al and Fe3+ ions, which provide indirect evidence of a primitive form of paleo-laterite that probably developed during the short periods of weathering between eruptions. There are at least 15 thick red bole layers in C29r below the KT boundary, and all were deposited in phase-2 volcanic eruptions that occurred over a time span of about 250 ky. These short duration exposures are reflected in the mineralogical and geochemical data that indicate rapid weathering (high CIA) but arid conditions. The arid conditions can be explained by acid rain, which accelerated the weathering process. These observations indicate that Deccan volcanism played a key role in increasing atmospheric CO2 and SO2 levels that resulted in global warming and acidified oceans, thus increasing biotic stress that predisposed faunas to eventual extinction at the KTB.

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

A stratospheric aerosol increase

NASA Technical Reports Server (NTRS)

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

1980-01-01

Large disturbances were noted in the stratospheric aerosol content in the midlatitude Northern Hemisphere commencing about 7 months after the eruption of La Soufriere and less than 1 month after the eruption of Sierra Negra. The aerosol was characterized by a very steep size distribution in the 0.15 to 0.25 micron radius range and contained a volatile component. Measurements near the equator and at the South Pole indicate that the disturbance was widespread. These observations were made before the May 18 eruption of Mt. St. Helens.

Pseudoephedrine may cause "pigmenting" fixed drug eruption.

PubMed

Ozkaya, Esen; Elinç-Aslan, Meryem Sevinç

2011-05-01

Fixed drug eruption (FDE) is a distinctive drug eruption characterized by recurrent well-defined lesions in the same location each time the responsible drug is taken. Two different clinical forms have been described: the common classic pigmenting form and the rare nonpigmenting form. Nonpigmenting FDE is mainly characterized by symmetrical large erythematous plaques and the dermal histopathologic reaction pattern. Pseudoephedrine is known as the major inducer of nonpigmenting FDE. Pigmenting FDE from pseudoephedrine has not been reported previously. Here, the first case of pseudoephedrine-induced pigmenting FDE is reported, showing the characteristic features of classic pigmenting FDE such as asymmetry, normal-sized lesions, and the epidermodermal histopathologic reaction pattern. Moreover, a positive occlusive patch-test reaction to pseudoephedrine could be demonstrated on postlesional FDE skin for the first time.

Developing a NASA strategy for sampling a major Pinatubo-like volcanic eruption

NASA Astrophysics Data System (ADS)

Newman, P. A.; Jucks, K. W.; Maring, H. B.

2016-12-01

Based on history, it is reasonable to expect a major volcanic eruption in the foreseeable future. By "major volcanic eruption", we mean an eruption that injects a substantial amount of material, gases and particles, into the stratosphere as a result of one eruption event. Such a volcanic eruption can impact weather, climate, and atmospheric chemistry on regional, hemispheric and global scales over significant time periods. Further, such an eruption can be an unintended analog for a number of geo-engineering schemes for mitigating greenhouse warming of the Earth. In order to understand and project the consequences of a major eruption, it is necessary to make a number of observations from a variety of perspectives. Such an eruption will occur, in the immediate sense, unexpectedly. Therefore, it is wise to have a thoughtfully developed plan for executing a rapid response that makes useful observations. A workshop was held on 17-18 May 2016 at NASA GSFC to develop a NASA observation strategy that could be quickly implemented in response to a major volcanic eruption, and would characterize the changes to atmospheric (especially stratospheric) composition following a large volcanic eruption. In this presentation we will provide an overview of the elements of this strategy with respect to satellite, balloon, ground, and aircraft observations. In addition, models simulations and forecasts will play a key role in any response strategy. Results will also be shown from a spectrum of simulations of volcanic eruptions that support this NASA strategy.

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.

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.

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

Volcanic Eruption Forecasts From Accelerating Rates of Drumbeat Long-Period Earthquakes

NASA Astrophysics Data System (ADS)

Bell, Andrew F.; Naylor, Mark; Hernandez, Stephen; Main, Ian G.; Gaunt, H. Elizabeth; Mothes, Patricia; Ruiz, Mario

2018-02-01

Accelerating rates of quasiperiodic "drumbeat" long-period earthquakes (LPs) are commonly reported before eruptions at andesite and dacite volcanoes, and promise insights into the nature of fundamental preeruptive processes and improved eruption forecasts. Here we apply a new Bayesian Markov chain Monte Carlo gamma point process methodology to investigate an exceptionally well-developed sequence of drumbeat LPs preceding a recent large vulcanian explosion at Tungurahua volcano, Ecuador. For more than 24 hr, LP rates increased according to the inverse power law trend predicted by material failure theory, and with a retrospectively forecast failure time that agrees with the eruption onset within error. LPs resulted from repeated activation of a single characteristic source driven by accelerating loading, rather than a distributed failure process, showing that similar precursory trends can emerge from quite different underlying physics. Nevertheless, such sequences have clear potential for improving forecasts of eruptions at Tungurahua and analogous volcanoes.

ATMOSPHERIC DISPERSAL AND DEPOSITION OF TEPHRA FROM A POTENTIAL VOLCANIC ERUPTION AT YUCCA MOUNTAIN, NEVADA

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

C. Harrington

2004-10-25

The purpose of this model report is to provide documentation of the conceptual and mathematical model (Ashplume) for atmospheric dispersal and subsequent deposition of ash on the land surface from a potential volcanic eruption at Yucca Mountain, Nevada. This report also documents the ash (tephra) redistribution conceptual model. These aspects of volcanism-related dose calculation are described in the context of the entire igneous disruptive events conceptual model in ''Characterize Framework for Igneous Activity'' (BSC 2004 [DIRS 169989], Section 6.1.1). The Ashplume conceptual model accounts for incorporation and entrainment of waste fuel particles associated with a hypothetical volcanic eruption through themore » Yucca Mountain repository and downwind transport of contaminated tephra. The Ashplume mathematical model describes the conceptual model in mathematical terms to allow for prediction of radioactive waste/ash deposition on the ground surface given that the hypothetical eruptive event occurs. This model report also describes the conceptual model for tephra redistribution from a basaltic cinder cone. Sensitivity analyses and model validation activities for the ash dispersal and redistribution models are also presented. Analyses documented in this model report update the previous documentation of the Ashplume mathematical model and its application to the Total System Performance Assessment (TSPA) for the License Application (TSPA-LA) igneous scenarios. This model report also documents the redistribution model product outputs based on analyses to support the conceptual model. In this report, ''Ashplume'' is used when referring to the atmospheric dispersal model and ''ASHPLUME'' is used when referencing the code of that model. Two analysis and model reports provide direct inputs to this model report, namely ''Characterize Eruptive Processes at Yucca Mountain, Nevada and Number of Waste Packages Hit by Igneous Intrusion''. This model report provides direct inputs to the TSPA, which uses the ASHPLUME software described and used in this model report. Thus, ASHPLUME software inputs are inputs to this model report for ASHPLUME runs in this model report. However, ASHPLUME software inputs are outputs of this model report for ASHPLUME runs by TSPA.« less

The evolution of Yellowstone's magmatic system over the past 630 kyr: Insights from the crystal record

NASA Astrophysics Data System (ADS)

Stelten, M. E.

2017-12-01

The Yellowstone Plateau volcanic field in northwestern Wyoming is one of the world's largest, active silicic volcanic centers, and has produced three caldera-forming "super eruptions" over the past 2.1 Myr. As a result, the petrologic evolution of Yellowstone's magmatic system has been the focus of numerous studies over the past 60 years. Early studies at Yellowstone focused on characterizing whole-rock chemical and isotopic variations observed in magmas erupted over Yellowstone's lifetime. While these have provided important insights into the source of Yellowstone magmas and the processes controlling their compositional evolution though time, whole-rock studies are limited in their ability to identify the mechanisms and timescales of rhyolite generation. In contrast, much of the recent work at Yellowstone has focused on applying micro-analytical techniques to characterize the age and composition of phenocrysts hosted in Yellowstone rhyolites. These studies have greatly advanced our understanding of the magmatic system at Yellowstone and have provided crucial new insights into the mechanisms and timescales of rhyolite generation. In particular, recent work has focused on applying micro-analytical techniques to study the age and origin of the [1] three caldera-forming eruptions that produced the Huckleberry Ridge, Mesa Falls, Lava Creek tuffs and [2] post-Lava Creek tuff intracaldera rhyolites that compose the Plateau Rhyolite. As a result, a wealth of crystal-chemical data now exists for rhyolites erupted throughout Yellowstone's 2.1 Myr history. These data provide a unique opportunity to create a detailed reconstruction of Yellowstone's magmatic system through time. In this contribution, I integrate available age, chemical, and isotopic data for phenocrysts hosted in Yellowstone rhyolites to construct a model for the evolution of Yellowstone's magmatic system from the caldera-forming eruption of the Lava Creek tuff at ca. 0.63 Ma to the present day. In particular, I highlight new insights into [1] the physical nature of Yellowstone's magmatic system, [2] the ways in which the mechanisms and timescales of rhyolite generation have changed though time, and [3] implications for the current state of the Yellowstone's magmatic system.

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.

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.

Late Holocene volcanism at Medicine Lake Volcano, northern California Cascades

USGS Publications Warehouse

Donnelly-Nolan, Julie M.; Champion, Duane E.; Grove, Timothy L.

2016-05-23

Late Holocene volcanism at Medicine Lake volcano in the southern Cascades arc exhibited widespread and compositionally diverse magmatism ranging from basalt to rhyolite. Nine well-characterized eruptions have taken place at this very large rear-arc volcano since 5,200 years ago, an eruptive frequency greater than nearly all other Cascade volcanoes. The lavas are widely distributed, scattered over an area of ~300 km2 across the >2,000-km2 volcano. The eruptions are radiocarbon dated and the ages are also constrained by paleomagnetic data that provide strong evidence that the volcanic activity occurred in three distinct episodes at ~1 ka, ~3 ka, and ~5 ka. The ~1-ka final episode produced a variety of compositions including west- and north-flank mafic flows interspersed in time with fissure rhyolites erupted tangential to the volcano’s central caldera, including the youngest and most spectacular lava flow at the volcano, the ~950-yr-old compositionally zoned Glass Mountain flow. At ~3 ka, a north-flank basalt eruption was followed by an andesite eruption 27 km farther south that contains quenched basalt inclusions. The ~5-ka episode produced two caldera-focused dacitic eruptions. Quenched magmatic inclusions record evidence of intrusions that did not independently reach the surface. The inclusions are present in five andesitic, dacitic, and rhyolitic host lavas, and were erupted in each of the three episodes. Compositional and mineralogic evidence from mafic lavas and inclusions indicate that both tholeiitic (dry) and calcalkaline (wet) parental magmas were present. Petrologic evidence records the operation of complex, multi-stage processes including fractional crystallization, crustal assimilation, and magma mixing. Experimental evidence suggests that magmas were stored at 3 to 6 km depth prior to eruption, and that both wet and dry parental magmas were involved in generating the more silicic magmas. The broad distribution of eruptive events and the relative accessibility and good exposure of lavas, combined with physical and petrologic evidence for multiple and varied mafic inputs, has created an unusual opportunity to understand the workings of this large magmatic system. A combined total of more than 25 intrusive and extrusive events are indicated for late Holocene time. Plutonic inclusions, some with ages as young as Holocene, were also brought to the surface in five of the eruptions. All eruptions took place along northwest- to northeast-trending alignments of vents, reflecting the overall east-west extensional tectonic environment. The interaction of tectonism and volcanism is a dominant influence at this subduction-related volcano, located where the west edge of the extensional Basin and Range Province impinges on the Cascades arc. Ongoing subsidence focused at the central caldera has been documented along with geophysical evidence for a small magma body. This evidence, combined with the frequency of eruptive and intrusive activity in late Holocene time, an active geothermal system, and intermittent long-period seismic events indicate that the volcano is likely to erupt again.

Episode 49 of the Pu'u 'Ō'ō-Kūpaianaha eruption of Kilauea volcano-breakdown of a steady-state eruptive era

USGS Publications Warehouse

Mangan, M.T.; Heliker, C.C.; Mattox, T.N.; Kauahikaua, J.P.; Helz, R.T.

1995-01-01

The Pu'u 'O'o-Kupaianaha eruption (1983-present) is the longest lived rift eruption of either Kilauea or neighboring Mauna Loa in recorded history. The initial fissure opening in January 1983 was followed by three years of episodic fire fountaining at the Pu'u 'O'o vent on Kilauea's east rift zone ∼19km from the summit (episodes 4–47). These spectacular events gave way in July 1986 to five and a half years of near-continuous, low-level effusion from the Kupaianaha vent, ∼ 3km to the cast (episode 48). A 49th episode began in November 1991 with the opening of a new fissure between Pu'u 'O'o and Kupaianaha. This three week long outburst heralded an era of more erratic eruptive behavior characterized by the shut down of Kupaianaha in February 1992 and subsequent intermittent eruption from vents on the west flank of Pu'u 'O'o (episodes 50 and 51). The events occurring over this period are due to progressive shrinkage of the rift-zone reservoir beneath the eruption site, and had limited impact on eruption temperatures and lava composition.

Construction of the North Head (Maungauika) tuff cone: a product of Surtseyan volcanism, rare in the Auckland Volcanic Field, New Zealand

NASA Astrophysics Data System (ADS)

Agustín-Flores, Javier; Németh, Károly; Cronin, Shane J.; Lindsay, Jan M.; Kereszturi, Gábor

2015-02-01

The Auckland Volcanic Field (AVF) comprises at least 52 monogenetic eruption centres dispersed over ˜360 km2. Eruptions have occurred sporadically since 250 ka, predominantly when glacio-eustatic sea levels were lower than today. Now that around 35 % of the field is covered by shallow water (up to 30 m depth), any eruption occurring in the present or near future within this area may display Surtseyan dynamics. The North Head tuff cone evidences eruptive dynamics caused by magma interaction with seawater. The first stages of the eruption comprise a phreatomagmatic phase that built a 48-m-high tuff cone. North Head tuff deposits contain few lithic fragments (<10 vol%) and are characterized by deposits from collapsing tephra jets and fall from relatively wet tephra columns. The conditions needed for this eruption existed between 128 and 116 ka, when the sea level in the Auckland area was at least 10-12 m above the pre-eruptive surface. The hazards associated with this type of eruption pose a risk to the densely populated coastal residential zones and the activities of one of the busiest harbours in New Zealand.

Episode 49 of the Pu'u 'O'o-Kupaianaha eruption of Kilauea volcano - breakdown of a steady-state eruptive era

NASA Astrophysics Data System (ADS)

Mangan, M. T.; Heliker, C. C.; Mattox, T. N.; Kauahikaua, J. P.; Helz, R. T.

1995-04-01

The Pu'u 'O'o-Kupaianaha eruption (1983-present) is the longest lived rift eruption of either Kilauea or neighboring Mauna Loa in recorded history. The initial fissure opening in January 1983 was followed by three years of episodic fire fountaining at the Pu'u 'O'o vent on Kilauea's east rift zone ˜19km from the summit (episodes 4 47). These spectacular events gave way in July 1986 to five and a half years of nearcontinuous, low-level effusion from the Kupaianaha vent, ˜ 3km to the cast (episode 48). A 49th episode began in November 1991 with the opening of a new fissure between Pu'u 'O'o and Kupaianaha. this three week long outburst heralded an era of more erratic eruptive behavior characterized by the shut down of Kupaianaha in February 1992 and subsequent intermittent eruption from vents on the west flank of Pu'u 'O'o (episodes 50 and 51). The events occurring over this period are due to progressive shrinkage of the rift-zone reservoir beneath the eruption site, and had limited impact on eruption temperatures and lava composition.

Pyroclast acceleration and energy partitioning in fake explosive eruptions

NASA Astrophysics Data System (ADS)

Gaudin, Damien; Taddeucci, Jacopo; Scheu, Bettina; Valentine, Greg; Capponi, Antonio; Kueppers, Ulrich; Graettiger, Allison; Sonder, Ingo

2014-05-01

Explosive eruptions are characterized by the fast release of energy, with gas expansion playing a lead role. An excess of pressure may be generated either by the exsolution and accumulation of volatiles (e.g., vulcanian and strombolian explosions) or by in situ vaporization of water (e.g., phreato-magmatic explosions). The release of pressurized gas ejects magma and country rock pyroclasts at velocities that can reach several hundred of meters per second. The amount and velocity of pyroclasts is determined not only by the total released energy, but also by the system-specific dynamics of the energy transfer from gas to pyroclasts. In this context, analogue experiments are crucial, since the amount of available energy is determined. Here, we analyze three different experiments, designed to reproduce different aspects of explosive volcanism, focusing on the acceleration phase of the pyroclasts, in order to compare how the potential energy is transferred to the pyroclasts in different systems. In the first, shock-tube-type experiment, salt crystals resting in a pressurized Plexiglas cylinder are accelerated when a diaphragm set is suddenly opened, releasing the gas. In the second experiment, a pressurized air bubble is released in a water-filled Plexiglas pipe; diaphragm opening causes sudden expansion and bursting of the bubble and ejection of water droplets. In the last experiment, specifically focusing on phreatomagmatic eruptions, buried explosive charges accelerate the overlying loose material. All experiments were monitored by multiple high speed cameras and a variety of sensors. Despite the largely differing settings and processes, particle ejection velocity above the vent from the three experiments share a non-linear decay over time. Fitting this decay allows to estimate a characteristic depth that is related to the specific acceleration processes. Given that the initial available energy is experimentally controlled a priori, the information on the acceleration processes (and related kinetic energy) can be used to brings new constraints on the energy partition and general pyroclasts ejection mechanisms during eruptions.

Characterization of open and closed volcanic systems in Indonesia and Mexico using InSAR time series

NASA Astrophysics Data System (ADS)

Chaussard, E.; Amelung, F.; Aoki, Y.

2013-08-01

use 2007-2011 Advanced Land Observing Satellite (ALOS) data to perform an arc-wide interferometric synthetic aperture radar (InSAR) time series survey of the Trans-Mexican Volcanic Belt (TMVB) and to study time-dependent ground deformation of four Indonesian volcanoes selected following the 2007-2009 study of Chaussard and Amelung (2012). Our objectives are to examine whether arc volcanoes exhibit long-term edifice-wide cyclic deformation patterns that can be used to characterize open and closed volcanic systems and to better constrain in which cases precursory inflation is expected. We reveal deformation cycles at both regularly active and previously inactive Indonesian volcanoes, but we do not detect deformation in the TMVB, reflecting a lower activity level. We identify three types of relationships between deformation and activity: inflation prior to eruption and associated with or followed by deflation (Kerinci and Sinabung), inflation without eruption and followed by slow deflation (Agung), and eruption without precursory deformation (Merapi, Colima, and Popocatépetl; at Merapi, no significant deformation is detected even during eruption). The first two cases correspond to closed volcanic systems and suggest that the traditional model of magmatic systems and eruptive cycles do apply to andesitic volcanoes (i.e., inflation and deflation episodes associated with magma accumulation or volatile exsolution in a crustal reservoir followed by eruptions or in situ cooling). In contrast, the last case corresponds to open volcanic systems where no significant pressurization of the magmatic reservoirs is taking place prior to eruptions and thus no long-term edifice-wide ground deformation can be detected. We discuss these results in terms of InSAR's potential for forecasting volcanic unrest.

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.

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.

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.

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.

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

Potential impacts of tephra fallout from a large-scale explosive eruption at Sakurajima volcano, Japan

NASA Astrophysics Data System (ADS)

Biass, S.; Todde, A.; Cioni, R.; Pistolesi, M.; Geshi, N.; Bonadonna, C.

2017-10-01

We present an exposure analysis of infrastructure and lifeline to tephra fallout for a future large-scale explosive eruption of Sakurajima volcano. An eruption scenario is identified based on the field characterization of the last subplinian eruption at Sakurajima and a review of reports of the eruptions that occurred in the past six centuries. A scenario-based probabilistic hazard assessment is performed using the Tephra2 model, considering various eruption durations to reflect complex eruptive sequences of all considered reference eruptions. A quantitative exposure analysis of infrastructures and lifelines is presented primarily using open-access data. The post-event impact assessment of Magill et al. (Earth Planets Space 65:677-698, 2013) after the 2011 VEI 2 eruption of Shinmoedake is used to discuss the vulnerability and the resilience of infrastructures during a future large eruption of Sakurajima. Results indicate a main eastward dispersal, with longer eruption durations increasing the probability of tephra accumulation in proximal areas and reducing it in distal areas. The exposure analysis reveals that 2300 km of road network, 18 km2 of urban area, and 306 km2 of agricultural land have a 50% probability of being affected by an accumulation of tephra of 1 kg/m2. A simple qualitative exposure analysis suggests that the municipalities of Kagoshima, Kanoya, and Tarumizu are the most likely to suffer impacts. Finally, the 2011 VEI 2 eruption of Shinmoedake demonstrated that the already implemented mitigation strategies have increased resilience and improved recovery of affected infrastructures. Nevertheless, the extent to which these mitigation actions will perform during the VEI 4 eruption presented here is unclear and our hazard assessment points to possible damages on the Sakurajima peninsula and the neighboring municipality of Tarumizu.

Advances in the Quantitative Characterization of the Shape of Ash-Sized Pyroclast Populations: Fractal Analyses Coupled to Micro- and Nano-Computed Tomography Techniques

NASA Astrophysics Data System (ADS)

Rausch, J.; Vonlanthen, P.; Grobety, B. H.

2014-12-01

The quantification of shape parameters in pyroclasts is fundamental to infer the dominant type of magma fragmentation (magmatic vs. phreatomagmatic), as well as the behavior of volcanic plumes and clouds in the atmosphere. In a case study aiming at reconstructing the fragmentation mechanisms triggering maar eruptions in two geologically and compositionally distinctive volcanic fields (West and East Eifel, Germany), the shapes of a large number of ash particle contours obtained from SEM images were analyzed by a dilation-based fractal method. Volcanic particle contours are pseudo-fractals showing mostly two distinct slopes in Richardson plots related to the fractal dimensions D1 (small-scale "textural" dimension) and D2 (large-scale "morphological" dimension). The validity of the data obtained from 2D sections was tested by analysing SEM micro-CT slices of one particle cut in different orientations and positions. Results for West Eifel maar particles yield large D1 values (> 1.023), resembling typical values of magmatic particles, which are characterized by a complex shape, especially at small scales. In contrast, the D1 values of ash particles from one East Eifel maar deposit are much smaller, coinciding with the fractal dimensions obtained from phreatomagmatic end-member particles. These quantitative morphological analyses suggest that the studied maar eruptions were triggered by two different fragmentation processes: phreatomagmatic in the East Eifel and magmatic in the West Eifel. The application of fractal analysis to quantitatively characterize the shape of pyroclasts and the linking of fractal dimensions to specific fragmentation processes has turned out to be a very promising tool for studying the fragmentation history of any volcanic eruption. The next step is to extend morphological analysis of volcanic particles to 3 dimensions. SEM micro-CT, already applied in this study, offers the required resolution, but is not suitable for the analysis of a large number of particles. Newly released nano CT-scanners, however, allows the simultaneous analysis of a statistically relevant number of particles (in the hundreds range). Preliminary results of a first trial will be presented.

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.

Video monitoring of the persistent strombolian activity of Stromboli volcano represents a window on its plumbing system and an opportunity for understanding the eruptive processes

NASA Astrophysics Data System (ADS)

Coltelli, Mauro; Biale, Emilio; Ciancitto, Francesco; Pecora, Emilio; Prestifilippo, Michele

2014-05-01

Since 1994 a video-surveillance camera located on a peak just above the active volcanic vents of Stromboli island records the explosive activity of one of the few volcanoes on the world performing a persistent eruptive activity. From 2003, after one of the larger lava flow eruption of the last century, the video-surveillance system was enhanced with more stations having both thermal and visual cameras. The video-surveillance helps volcanologists to characterize the mild explosive activity of Stromboli named Strombolian and to distinguish between the frequent "ordinary" Strombolian explosions and the occasional "extraordinary" strong Strombolian explosions that periodically occur. A new class of extraordinary explosions was discovered filling the gap between the ordinary activity and the strong explosions named major explosions when the tephra fallout covers large areas on the volcano summit and paroxysmal ones when the bombs fall down to the inhabited area along the coast of the island. In order to quantify the trend of the ordinary Strombolian explosions and to understand the occurring of the extraordinary strong Strombolian explosions a computer assisted image analysis was developed to process the huge amount of thermal and visual images recorded in several years. The results of this complex analysis allow us to clarify the processes occurring in the upper plumbing system where the pockets/trains of bubbles coalesce and move into the active vent conduits producing the ordinary Strombolian activity, and to infer the process into the deeper part of the plumbing system where new magma supply and its evolution lead to the formation of the extraordinary strong Strombolian explosions.

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.

The morphology and evolution of the Stromboli 2002-2003 lava flow field--An example of a basaltic flow field emplaced on a steep slope

USGS Publications Warehouse

Lodato, Luigi; Harris, A.; Spampinato, L.; Calvari, Sonia; Dehn, J.; Patrick, M.

2007-01-01

The use of a hand-held thermal camera during the 2002–2003 Stromboli effusive eruption proved essential in tracking the development of flow field structures and in measuring related eruption parameters, such as the number of active vents and flow lengths. The steep underlying slope on which the flow field was emplaced resulted in a characteristic flow field morphology. This comprised a proximal shield, where flow stacking and inflation caused piling up of lava on the relatively flat ground of the vent zone, that fed a medial–distal lava flow field. This zone was characterized by the formation of lava tubes and tumuli forming a complex network of tumuli and flows linked by tubes. Most of the flow field was emplaced on extremely steep slopes and this had two effects. It caused flows to slide, as well as flow, and flow fronts to fail frequently, persistent flow front crumbling resulted in the production of an extensive debris field. Channel-fed flows were also characterized by development of excavated debris levees in this zone (Calvari et al. 2005). Collapse of lava flow fronts and inflation of the upper proximal lava shield made volume calculation very difficult. Comparison of the final field volume with that expecta by integrating the lava effusion rates through time suggests a loss of ~70% erupted lava by flow front crumbling and accumulation as debris flows below sea level. Derived relationships between effusion rate, flow length, and number of active vents showed systematic and correlated variations with time where spreading of volume between numerous flows caused an otherwise good correlation between effusion rate, flow length to break down. Observations collected during this eruption are useful in helping to understand lava flow processes on steep slopes, as well as in interpreting old lava–debris sequences found in other steep-sided volcanoes subject to effusive activity.

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.

Precursory signals of the 2014-15 Fogo eruption (Cape Verde) detected by surface CO2 emission and heat flow observations

NASA Astrophysics Data System (ADS)

Pérez, Nemesio M.; Dionis, Samara; Fernandes, Paulo; Barrancos, José; Rodríguez, Fátima; Bandomo, Zuleyka; Hernández, Pedro A.; Melián, Gladys V.; Silva, Sónia; Padilla, Germán; Padrón, Eleazar; Cabral, Jeremias; Calvo, David; Asensio-Ramos, María; Pereira, José Manuel; Gonçalves, António A.; Barros, Inocencio; Semedo, Helio

2015-04-01

On November 23, 2014 a new eruption occurred at Fogo volcano (Cape Verde) after 19 years of the last eruptive event in 1995. In the case of the 1995 Fogo eruption, a volcano monitoring program for the volcanic surveillance of Fogo did not exist. On the contrary, a simple and multidisciplinary volcano monitoring program was initiated since 2007 to detect early warning signals of a new volcanic unrest such as the 2014-15 Fogo eruption. Diffuse CO2 emission surveys at the summit crater of Pico do Fogo volcano were periodically carried out from May 2007 to October 2014 to provide this multidisciplinary approach and to monitor potential volcanic activity changes. During this 7 year period, CO2 efflux ranged from non detectable (< 1.5 g m-2 d-1) up to relatively high (61.9 kg m-2 d-1) values. The observed average δ13C- CO2 values related to these diffuse CO2 emission surveys ranged from -22.1 to 1.6 ‰, and surface heat flux measurements, following the method of Dawson (1964), showed also a wide range of values from 0.1 to 460 W m-2. Areas with the highest observed CO2 efflux values were also characterized by a relatively high soil temperature and an intense surface hydrothermal alteration, which supports that degassing process is primary controlled by an advective mechanism generated by geothermal gradients (convection). Two periods of anomalous diffuse CO2 emission were observed between February 2009 to February 2010 and March to August 2014, respectively. Rest of surveys showed the lowest variability on diffuse CO2 emission, ranging from 23 to 186 t d-1 (average = 86 t d-1). The first anomalous period was characterized by a sharp increase on diffuse CO2 emission, suggesting the first magma intrusion beneath Pico do Fogo volcano. This observation is also supported by a significant change on the δ13C- CO2 signature from May 2009 (-10.2 ‰) to February 2010 (-6.1‰) of the diffuse CO2 degassing, indicating an enrichment on the magmatic CO2 component. On February 2010, the diffuse CO2 emission rate was 219 ± 36 t d-1 (Dionis et al., 2015). The second anomalous period started on March 2014, eight months before the 2014-15 Fogo eruption onset, and reached a relatively high value of 337 ± 119 t d-1 on August 30, 2014. It was likely caused by rising of magmatic gases from a second magma intrusion which ended on an eruption. Heat flow temporal evolution during the observation period also shows a quasi-continuous increase before the eruption onset, with the maximum observed heat flow (16.4 ± 3.4 MW) on March 2014. These geochemical and geophysical evidences are clearly precursory signals of the 2014-15 Fogo eruption. Dawson, G.B. (1964), N Z J Geol Geophys 7:155-171; Dionis S. et al. (2015), Bull. Volcanol., in press

Investigating Degassing in Felsic and Mafic Magmas by 3-D Imaging of Vesicle Pathways

NASA Astrophysics Data System (ADS)

Polacci, M.; Baker, D. R.; Piochi, M.; Mancini, L.

2009-12-01

Volatiles are the motor of volcanic eruptions. Studies of vesiculation in erupted products can provide information on how volatiles exsolve, grow and are lost from magmas as lava and tephra fragments bear the fingerprints of such processes in vesicle and crystal textures. We summarize here the results of a series of X-ray computed microtomographic experiments that were performed on about 70 volcanic specimens of mainly basaltic and trachytic compositions. A first sample suite comprises samples collected from explosive activity at persistently degassing basaltic volcanoes, namely Stromboli (Aeolian Islands), Etna (Eastern Sicily) and Ambrym (Vanuatu Islands); a second suite consists of pumice and scoria clasts from Plinian to Subplinian to Vulcanian eruptions that occurred in the Campi Flegrei caldera (Southern Italy). The tomographic images provide us with a complete 3-D view of our sampled material through which it is possible to reconstruct the geometry of the vesicle network and explore how gas was transported in the investigated magmas. We find that basaltic scoriae exhibit two types of vesicles: large (~ mm^3), coalescing vesicles with complex, convoluted shapes and small-to-intermediate sized (<~1x10^-3 mm^3), spherical to sub-spherical, poorly connected or isolated vesicles. The former vesicles were interpreted as percolation pathways for gas to flow non-explosively to the volcano crater and thought to sustain the persistent passive gas release that characterizes these volcanoes. The fact that such vesicles were found in products erupted from active basaltic volcanoes located in different tectonic settings and characterized by different explosivity strongly suggests that basaltic systems appear to follow a common degassing pathway. However, not all explosive basaltic rocks contain large, coalescing vesicles. Pumice clasts from the much more violent, dangerous and less frequent paroxysmal explosions at Stromboli do not have this type of vesicles, demonstrating that basaltic volcanoes develop different vesicle textures and therefore degassing dynamics with increasing explosive activity. Trachytic pumices from highly explosive eruptions display a much finer structure in comparison to scoriae having sub-spherical to slightly deformed large vesicles and a large population of small spherical vesicles (1x10^-3 - <1x10^-5 mm^3). These two vesicle textures were mainly ascribed to the rapid ascent of a supersaturated magma under closed-system degassing, in comparison to the open-system conditions of basaltic magmas. Large interconnected vesicles that form micro-cracks are, however, found in some denser pyroclasts from Campi Flegrei. This suggests that gas was percolating in the conduit system before the eruption and that open-system degassing may be an effective way through which gas is lost in a moderately violent manner at the crater surface in some explosive felsic eruptions. Ultimately this study reveals that 3-D imaging of volcanic rocks is an essential tool for investigating degassing conditions in erupted magmas.

The Grizzly Lake complex (Yellowstone Volcano, USA): Mixing between basalt and rhyolite unraveled by microanalysis and X-ray microtomography

NASA Astrophysics Data System (ADS)

Morgavi, Daniele; Arzilli, Fabio; Pritchard, Chad; Perugini, Diego; Mancini, Lucia; Larson, Peter; Dingwell, Donald B.

2016-09-01

Magma mixing is a widespread petrogenetic process. It has long been suspected to operate in concert with fractional crystallization and assimilation to produce chemical and temperature gradients in magmas. In particular, the injection of mafic magmas into felsic magma chambers is widely regarded as a key driver in the sudden triggering of what often become highly explosive volcanic eruptions. Understanding the mechanistic event chain leading to such hazardous events is a scientific goal of high priority. Here we investigate a mingling event via the evidence preserved in mingled lavas using a combination of X-ray computed microtomographic and electron microprobe analyses, to unravel the complex textures and attendant chemical heterogeneities of the mixed basaltic and rhyolitic eruption of Grizzly Lake in the Norris-Mammoth corridor of the Yellowstone Plateau volcanic field (YVF). We observe evidence that both magmatic viscous inter-fingering of magmas and disequilibrium crystallization/dissolution processes occur. Furthermore, these processes constrain the timescale of interaction between the two magmatic components prior to their eruption. X-ray microtomography images show variegated textural features, involving vesicle and crystal distributions, filament morphology, the distribution of enclaves, and further textural features otherwise obscured in conventional 2D observations and analyses. Although our central effort was applied to the determination of mixing end members, analysis of the hybrid portion has led to the discovery that mixing in the Grizzly Lake system was also characterized by the disintegration and dissolution of mafic crystals in the rhyolitic magma. The presence of mineral phases in both end member, for example, forsteritic olivine, sanidine, and quartz and their transport throughout the magmatic mass, by a combination of both mixing dynamics and flow imposed by ascent of the magmatic mass and its eruption, might have acted as a "geometric perturbation" of flow fields further fuelling mass exchange between magmas in terms of both chemical diffusion and crystal transfer. These results illuminate the complexity of mixing in natural magmatic systems, identifying several reaction-related textural factors that must be understood more deeply in order to advance our understanding of this igneous process.

Repeat terrestrial lidar mapping of the new volcanic vent at Holuhraun, Iceland

NASA Astrophysics Data System (ADS)

Richardson, J. A.; Whelley, P.; Sutton, S.; Needham, D. H.; Byrne, S.; Hamilton, C.

2016-12-01

The locations and morphologies of volcanic vents are essential observations that inform models of volcanic processes on Earth and other planets. Post-eruption morphologic changes at vents are important to characterize in order to more confidently use data gathered from mapping volcanic terrains. We present two terrestrial lidar surveys of the recently formed volcanic vent that fed the Holuhraun lava flow in the Northeastern Region of Iceland. While many studies have measured erosion rate at older volcanic vents, these surveys were performed 6 and 18 months after the end of the eruption and present an opportunity to measure morphologic changes at a brand-new vent. The Holuhraun eruption began in August 2014 by effusing lava through a fissure and continued until February 2015, emplacing approximately 1.4 km³ of lava over nearly 85 km². During the eruption the predominant activity at the northern end of the fissure produced a large (50 m high, 500 m long) cinder-canyon with scoria covered flanks. Lava ponded within this vent and drained to form a primary channel to the northeast. As lava drained through the channel, high stands of lava were preserved as "bathtub rings" on the walls of the vent. Following the cessation of activity at Holuhraun, two lidar surveys were carried out inside the vent, in August 2015 and August 2016. A Riegl VZ-400 scanner was used to collect the point cloud data, which give a precise 3D model of the vent with relative accuracy of 15 cm between scan positions. Differences between the two 3D point clouds are used to distinguish between flow emplacement and post-flow modifications to the surface, and to quantify the surface erosion rate experienced by the young vent. Near-infrared (1550 nm wavelength) reflectance values can also be correlated to lava textures and materials within the vent, providing additional information about how the vent was built syn-eruption and how it degrades post-eruption.

White and gray pumice in pyroclastic deposits. (Invited)

NASA Astrophysics Data System (ADS)

Wright, H. M.; Cashman, K. V.

2013-12-01

Many primary pyroclastic deposits contain at least two different colors of pumice, including volumetrically dominant white and subordinate gray. White pumice is vesicular, microlite-free, and in most cases represents direct samples of the principal magma reservoir. In contrast, subordinate gray pumice with lower vesicularity and/or more abundant microlites may sample either deep recharge OR shallow vanguard magma, where both may record information on eruption triggers. Pumice may appear gray for several reasons: 1. Gray pumice has a less-evolved bulk composition than white pumice. Presence of less-evolved (generally deep-derived) magma provides information about possible recharge magma and/or pre-eruptive compositional variation in the magma storage region. A well-known example of this difference is the 1912 eruption of Novarupta [Hildreth & Fierstein, 2012], which includes white (rhyolite) and gray (andesite and dacite) pumice. 2. Gray pumice contains elevated microlite number densities and/or microlite crystallinities and is compositionally similar to white pumice. a. Gray pumice contains abundant broken crystal fragments and lithic fragments. Broken crystals and incorporated white pumice indicate passage through the primary magma reservoir. Incorporated lithic fragments indicate breakage of wall rock and creation of new transport pathways. Microlites and breadcrusted surfaces indicate slow and/or episodic ascent at shallow levels. This textural association indicates that proto-gray pumice magma played an active role in creating a conduit to the surface. In some cases, small differences in chemistry may further indicate differences in magma batches (recharge pulses). This textural variation is found in the products of high-crystallinity large-volume (Plinian or boil-over style) eruptions, as in the Cerro Galan Ignimbrite, Argentina [Wright et al., 2011]. b. Gray pumice contains abundant microlites due to differences in decompression and/or cooling history. In this case, microlites indicate shallow degassing-induced crystallization, where proto-gray pumice forms vanguard magma or a shallow conduit plug. Gray pumice originating in a shallow conduit plug is common in Vulcanian and subPlinian silicic eruptions and is seen in the 1980 Plinian and subPlinian eruptions of Mount St. Helens [Klug & Cashman, 1994; Cashman & McConnell, 2005]. c. Gray pumice may record syn-eruptive changes in the magmatic system, often manifested as crystallization caused by either decompression or cooling [cf., Gurioli et al., 2005; Andrews & Gardner, 2010]. In summary, the compositional and textural complexities of gray pumice provide detail on pre- and syn-eruptive magmatic processes that may be impossible to obtain from (dominant) white pumice alone. Subtle compositional variations may characterize melts available to recharge and destabilize the upper magma reservoir, whereas crystal textures and compositions can be compared with experimental data to infer shallow magma ascent associated with conduit formation prior to climatic activity. Thus, analysis of gray pumice in pyroclastic deposits can yield new insight into the dynamics of eruptive processes.

Large historical eruptions at subaerial mud volcanoes, Italy

NASA Astrophysics Data System (ADS)

Manga, M.; Bonini, M.

2012-11-01

Active mud volcanoes in the northern Apennines, Italy, currently have gentle eruptions. There are, however, historical accounts of violent eruptions and outbursts. Evidence for large past eruptions is also recorded by large decimeter rock clasts preserved in erupted mud. We measured the rheological properties of mud currently being erupted in order to evaluate the conditions needed to transport such large clasts to the surface. The mud is well-characterized by the Herschel-Bulkley model, with yield stresses between 4 and 8 Pa. Yield stresses of this magnitude can support the weight of particles with diameters up to several mm. At present, particles larger than this size are not being carried to the surface. The transport of larger clasts to the surface requires ascent speeds greater than their settling speed in the mud. We use a model for the settling of particles and rheological parameters from laboratory measurements to show that the eruption of large clasts requires ascent velocities > 1 m s-1, at least three orders of magnitude greater than during the present, comparatively quiescent, activity. After regional earthquakes on 20 May and 29 May 2012, discharge also increased at locations where the stress changes produced by the earthquakes would have unclamped feeder dikes below the mud volcanoes. The magnitude of increased discharge, however, is less than that inferred from the large clasts. Both historical accounts and erupted deposits are consistent in recording episodic large eruptions.

The Ottaviano eruption of Somma-Vesuvio (8000 y B.P.): a magmatic alternating fall and flow-forming eruption

NASA Astrophysics Data System (ADS)

Rolandi, G.; Maraffi, S.; Petrosino, P.; Lirer, L.

1993-11-01

The Ottaviano eruption occurred in the late neolithic (8000 y B.P.). 2.40 km 3 of phonolitic pyroclastic material (0.61 km 3 DRE) were emplaced as pyroclastic flow, surge and fall deposits. The eruption began with a fall phase, with a model column height of 14 km, producing a pumice fall deposit (LA). This phase ended with short-lived weak explosive activity, giving rise to a fine-grained deposit (L1), passing to pumice fall deposits as the result of an increasing column height and mass discharge rate. The subsequent two fall phases (producing LB and LC deposits), had model column heights of 20 and 22 km with eruption rates of 2.5 × 10 7 and 2.81 × 10 7 kg/s, respectively. These phases ended with the deposition of ash layers (L2 and L3), related to a decreasing, pulsing explosive activity. The values of dynamic parameters calculated for the eruption classify it as a sub-plinian event. Each fall phase was characterized by variations in the eruptive intensity, and several pyroclastic flows were emplaced (F1 to F3). Alternating pumice and ash fall beds record the waning of the eruption. Finally, owing to the collapse of a eruptive column of low gas content, the last pyroclastic flow (F4) was emplaced.

The Impact of Continental Configuration on Global Response to Large Igneous Province Eruptions

NASA Astrophysics Data System (ADS)

Stellmann, J.; West, A. J.; Ridgwell, A.; Becker, T. W.

2017-12-01

The impact of Large Igneous Province eruptions as recorded in the geologic record varies widely; some eruptions cause global warming, large scale ocean acidification and anoxia and mass extinctions while others cause some or none of these phenomena. There are several potential factors which may determine the global response to a Large Igneous Province eruption; here we consider continental configuration. The arrangement of continents controls the extent of shallow seas, ocean circulation and planetary albedo; all factors which impact global climate and its response to sudden changes in greenhouse gas concentrations. To assess the potential impact of continental configuration, a suite of simulated eruptions was carried out using the cGENIE Earth system model in two end-member continental configurations: the end-Permian supercontinent and the modern. Eruptions simulated are comparable to an individual pulse of a Large Igneous Province eruption with total CO2 emissions of 1,000 or 10,000 GtC erupted over 1,000 or 10,000 years, spanning eruptions rates of .1-10 GtC/yr. Global response is characterized by measuring the magnitude and duration of changes to atmospheric concentration of CO2, saturation state of calcite and ocean oxygen levels. Preliminary model results show that end-Permian continental configuration and conditions (radiative balance, ocean chemistry) lead to smaller magnitude and shorter duration changes in atmospheric pCO2 and ocean saturation state of calcite following the simulated eruption than the modern configuration.

Generalized benign cutaneous reaction to cytarabine.

PubMed

Ruben, Beth S; Yu, Wesley Y; Liu, Fan; Truong, Sam V; Wang, Kevin C; Fox, Lindy P

2015-11-01

Cytarabine-induced toxicity manifests as various cutaneous morphologies. A generalized papular purpuric eruption has not been well described. We aimed to characterize a distinct cytarabine-related eruption. We reviewed all cases of cytarabine-related toxicity with papular purpuric eruptions or violaceous erythema at the University of California, San Francisco between 2006 and 2011. Sixteen cases were identified. The eruption began as erythematous papules that evolved into coalescing purpuric papules and plaques. It had affinity for intertriginous areas, neck, ears, and scalp. Pruritus was common, but no systemic complications were documented. Thirteen patients (81.3%) developed the eruption after completion of chemotherapy. Differential diagnosis often included viral exanthem (62.5%), drug eruption (50%), and vasculitis (37.5%). Histopathology was nonspecific but commonly demonstrated sparse lymphocytic infiltrates, spongiosis, and/or red cell extravasation. Importantly, the eruption was neither predicted by past cytarabine exposure nor predictive of future recurrence. This is a review of cases from a single institution. Observation was limited to acute hospitalization, however, charts were reviewed for subsequent reactions on rechallenge. The eruption described herein represents a specific skin-limited reaction to cytarabine. Awareness of its characteristic morphology, distribution, and timeline will aid in clinical diagnosis. Reassurance concerning its benign nature will prevent unnecessary intervention or cessation of chemotherapy. Copyright © 2015 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.

Remote sensing and petrological observations on the 2012-2013 fissure eruption at Tolbachik volcano, Kamchatka: Implications for reconstruction of the eruption chronology

NASA Astrophysics Data System (ADS)

Melnikov, Dmitry; Volynets, Anna O.

2015-12-01

We present a reconstruction of the chronological sequence of events that took place during the first days of the 2012-2013 Tolbachik fissure eruption using petrological data and remote sensing methods. We were forced to use this approach because bad weather conditions did not allow direct observations during the first two days of the eruption. We interpreted infrared images from the scanning radiometer VIIRS Suomi NPP and correlated the output with the results of the geochemical study, including comparison of the ash, deposited at the period from 27 to 29 November, with the samples of lava and bombs erupted from the Menyailov and Naboko vents. We argue that the compositional change observed in the eruption products (the decrease of SiO2 concentration and K2O/MgO ratio, increase of MgO concentration and Mg#) started approximately 24 h after the eruption began. At this time the center of activity moved to the southern part of the fissure, where the Naboko group of vents was formed; therefore, this timeframe also characterizes the timing of the Naboko vent opening. The Naboko group of vents remained active until the end of eruption in September 2013.

Implications of historical eruptive-vent migration on the northeast rift zone of Mauna Loa Volcano, Hawaii

NASA Astrophysics Data System (ADS)

Lockwood, John P.

1990-07-01

Five times within the past 138 yr (1852, 1855-1856, 1880-1881, 1942, and 1984), lava flows from vents on the northeast rift zone of Mauna Loa Volcano have reached within a few kilometres of Hilo (the largest city on the Island of Hawaii). Most lavas erupted on this rift zone in historical time have traveled northeastward (toward Hilo), because their eruptive vents have been concentrated north of the rift zone's broad topographic axis. However, with few exceptions each successive historical eruption on the northeast rift zone has occurred farther southeast than the preceding one. Had the 1984 eruptive vents (the most southeasterly yet) opened less than 200 m farther southeast, the bulk of the 1984 lavas would have flowed away from Hilo. If this historical vent-migration pattern continues, the next eruption on the northeast rift zone could send lavas to the southeast, toward less populated areas. The historical Mauna Loa vent-migration patterns mimic the southeastern "younging" of the Hawaiian-Emperor volcanic chain and may be cryptically related to northwestward movement of the Pacific plate. Systematic temporal-spatial vent-migration patterns may characterize eruptive activity at other volcanoes with flank activity and should be considered as an aid to long-term prediction of eruption sites.

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.

A new model for the growth of basaltic shields based on deformation of Fernandina volcano, Galápagos Islands

USGS Publications Warehouse

Bagnardi, Marco; Amelung, Falk; Poland, Michael P.

2013-01-01

Space-geodetic measurements of surface deformation produced by the most recent eruptions at Fernandina – the most frequently erupting volcano in the Galápagos Archipelago – reveal that all have initiated with the intrusion of subhorizontal sills from a shallow magma reservoir. This includes eruptions from fissures that are oriented both radially and circumferentially with respect to the summit caldera. A Synthetic Aperture Radar (SAR) image acquired 1–2 h before the start of a radial fissure eruption in 2009 captures one of these sills in the midst of its propagation toward the surface. Galápagos eruptive fissures of all orientations have previously been presumed to be fed by vertical dikes, and this assumption has guided models of the origin of the eruptive fissure geometry and overall development of the volcanoes. Our findings allow us to reinterpret the internal structure and evolution of Galápagos volcanoes and of similar basaltic shields. Furthermore, we note that stress changes generated by the emplacement of subhorizontal sills feeding one type of eruption may control the geometry of subsequent eruptive fissures. Specifically, circumferential fissures tend to open within areas uplifted by sill intrusions that initiated previous radial fissure eruptions. This mechanism provides a possible explanation for the pattern of eruptive fissures that characterizes all the western Galápagos volcanoes, as well as the alternation between radial and circumferential fissure eruptions at Fernandina. The same model suggests that the next eruption of Fernandina will be from a circumferential fissure in the area uplifted by the 2009 sill intrusion, just southwest of the caldera rim.

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.

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.

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.

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.

Preliminary Volcano-Hazard Assessment for Redoubt Volcano, Alaska

USGS Publications Warehouse

Waythomas, Christopher F.; Dorava, Joseph M.; Miller, Thomas P.; Neal, Christina A.; McGimsey, Robert G.

1997-01-01

Redoubt Volcano is a stratovolcano located within a few hundred kilometers of more than half of the population of Alaska. This volcano has erupted explosively at least six times since historical observations began in 1778. The most recent eruption occurred in 1989-90 and similar eruptions can be expected in the future. The early part of the 1989-90 eruption was characterized by explosive emission of substantial volumes of volcanic ash to altitudes greater than 12 kilometers above sea level and widespread flooding of the Drift River valley. Later, the eruption became less violent, as developing lava domes collapsed, forming short-lived pyroclastic flows associated with low-level ash emission. Clouds of volcanic ash had significant effects on air travel as they drifted across Alaska, over Canada, and over parts of the conterminous United States causing damage to jet aircraft. Economic hardships were encountered by the people of south-central Alaska as a result of ash fallout. Based on new information gained from studies of the 1989-90 eruption, an updated assessment of the principal volcanic hazards is now possible. Volcanic hazards from a future eruption of Redoubt Volcano require public awareness and planning so that risks to life and property are reduced as much as possible.

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.

The 2005 and 2006 eruptions of Ol Doinyo Lengai: assessing deep and shallow processes at an active carbonatite volcano using volatile chemistry and fluxes

NASA Astrophysics Data System (ADS)

Fischer, T.; Burnard, P.; Marty, B.; Palhol, F.; Mangasini, F.; Shaw, A. M.

2006-12-01

The African Rift valleys are sites of classical carbonatite volcano complexes. Ol Doinyo Lengai, the spectacular cone that rises to nearly 3000 m above Tanzania's Eastern Rift Valley, is the world's only active carbonatite volcano. High-alkali carbonatite lavas from this volcano were first recognized in the 1960's and the oldest natrocarbonatite tuffs have been dated to 1250 years B.P.. Earlier eruptions produced phonolitic and nephelinitc lavas [1]. Since the 1960's the volcano has erupted frequently producing carbonatite lava flows. Explosive eruptions are much less frequent but have occurred in 1966, 1983 [1] and 1993 [3] producing ash, cones and natrocarbonatite tephra. In July 2005, we launched an expedition to the crater to collect gas and rock samples. On July 4, the volcano began erupting low viscosity, low T (540C) high velocity (2 m/sec) lava flows at a rate of about 0.3 m3/sec. By afternoon, the lava was flowing over the eastern crater rim. During the eruption we sampled gases from nearby hornitos at 120 and 168C, yielding pristine magmatic gases characterized by 75 mol% H2O, 22% CO2, < 1% SO2, H2S, HCl and traces of H2, He, Ar, N2, CH4 and CO. CO2-CH4-CO gas equilibrium temperatures are 580C consistent with lava flow temperatures. N2-He-Ar abundances indicate an upper mantle origin of volatiles, confirmed by isotopes [4]. SO2 flux measured by mini DOAS was low (10 t/day). CO2 fluxes calculated using CO2/SO2 are 3000 to 4000 t/day. Volatiles measured in the carbonatite lavas by SIMS show low H2O (< 0.7 wt%), high S (0.2 to 1 wt%) and Cl (0.6 to 1.4 wt%) and variable F (0.06 to 0.7 wt%). CO2 contents are 30 wt% with major and trace elements typical of natrocarbonatite lavas previously reported in [1]. The release of all CO2 (30 wt% or 20 t/day) from eruption lavas would only produce a small fraction of the measured CO2. In March 2006 eyewitnesses [3] reported the occurrence of an explosive eruption and some of us returned to the volcano on May 12. The morphology of the crater had changed and was now filled with lava 2 m deep. The central cone area had collapsed. We sampled a deposit of carbonatite ash containing accretionary lapilli suggesting water-magma or water-ash interaction. The measured SO2 flux was low (approx. 10 t/day). Our data and observations imply that 1) Ol Doinyo Lengai gases originate from the upper mantle and have equilibrium temperatures consistent with carbonatite magmas, 2) the CO2 flux measured during the eruption cannot be produced by the eruption of carbonatite lavas and additional CO2 is released from the mantle, 3) explosive eruptions (such as in 2006) may be triggered by hydromagmatic processes. Alternatively the fountain material interacted with rain at the surface. 1 Dawson, J.B. (1962) nature 195, 1075-76; 2 Dawson, J.B. (1989) Carbonatites ;3 http://www.mtsu.edu/; 4 Burnard et al., AGU Fall 06

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.

The Diversity of Martian Volcanic Features as Seen in MOC Images and MOLA Topographic Data

NASA Technical Reports Server (NTRS)

Mouginis-Mark, Peter J.

2004-01-01

This project focused on the evolution of the summit areas of Martian volcanoes. By using data collected from the Mars Orbiter Camera (MOC) and Mars Laser Altimeter (MOLA) instruments, we tried to better understand the diversity of constructional volcanism on Mars, and hence further understand eruption processes. We investigated the styles of volcanism on the major volcanic constructs (Olympus, Arsia, Pavonis, and Ascraeus Montes), and also studied the role of magma-volatile interactions within the shallow subsurface of these volcanoes and the surrounding areas. Theoretical models for internal processes within volcanoes, including the thermal influences of dike intrusions on pre-existing volatiles, were developed based on our identification of landform distributions. Our work provided new insights into the diversity of volcanism on Mars, and the distribution of Martian volatiles in space and time. Highlights of our results include: 1) The identification of large ash deposits at the summit of Arsia Mons; 2) The study of a large flank eruption on Elysium Mons and the estimation of the effusion rate needed to produce the observed lava channel; 3) The quantitative description of dike intrusion into volatile-rich terrain to explain the origin of Hrad Vallis; 4) The identification of constructional ridges on top of very young lava flows from Olympus Mons, with the interpretation that these ridges were formed by very recent phreatomagmatic eruptions; and 5) The characterization of the dimensions and slope distributions on 18 volcanic edifices on Mars.

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.

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.

Automated detection of solar eruptions

NASA Astrophysics Data System (ADS)

Hurlburt, N.

2015-12-01

Observation of the solar atmosphere reveals a wide range of motions, from small scale jets and spicules to global-scale coronal mass ejections (CMEs). Identifying and characterizing these motions are essential to advancing our understanding of the drivers of space weather. Both automated and visual identifications are currently used in identifying Coronal Mass Ejections. To date, eruptions near the solar surface, which may be precursors to CMEs, have been identified primarily by visual inspection. Here we report on Eruption Patrol (EP): a software module that is designed to automatically identify eruptions from data collected by the Atmospheric Imaging Assembly on the Solar Dynamics Observatory (SDO/AIA). We describe the method underlying the module and compare its results to previous identifications found in the Heliophysics Event Knowledgebase. EP identifies eruptions events that are consistent with those found by human annotations, but in a significantly more consistent and quantitative manner. Eruptions are found to be distributed within 15 Mm of the solar surface. They possess peak speeds ranging from 4 to 100 km/s and display a power-law probability distribution over that range. These characteristics are consistent with previous observations of prominences.

Distinguishing and correlating deposits from large ignimbrite eruptions using paleomagnetism: The Cougar Point Tuffs (mid-Miocene), southern Snake River Plain, Idaho, USA

NASA Astrophysics Data System (ADS)

Finn, David R.; Coe, Robert S.; Brown, Ethan; Branney, Michael; Reichow, Marc; Knott, Thomas; Storey, Michael; Bonnichsen, Bill

2016-09-01

In this paper, we present paleomagnetic, geochemical, mineralogical, and geochronologic evidence for correlation of the mid-Miocene Cougar Point Tuff (CPT) in southwest Snake River Plain (SRP) of Idaho. The new stratigraphy presented here significantly reduces the frequency and increases the scale of known SRP ignimbrite eruptions. The CPT section exposed at the Black Rock Escarpment along the Bruneau River has been correlated eastward to the Brown's Bench escarpment (six common eruption units) and Cassia Mountains (three common eruption units) regions of southern Idaho. The CPT records an unusual pattern of geomagnetic field directions that provides the basis for robust stratigraphic correlations. Paleomagnetic characterization of eruption units based on geomagnetic field variation has a resolution on the order of a few centuries, providing a strong test of whether two deposits could have been emplaced from the same eruption or from temporally separate events. To obtain reliable paleomagnetic directions, the anisotropy of anhysteretic remanence was measured to correct for magnetic anisotropy, and an efficient new method was used to remove gyroremanence acquired during alternating field demagnetization.

Oxidation of shallow conduit magma: Insight from μ-XANES analysis on volcanic ash particle

NASA Astrophysics Data System (ADS)

Miwa, T.; Ishibashi, H.; Iguchi, M.

2014-12-01

Redox state of magma is important to understand dynamics of volcanic eruptions because magma properties such as composition of degassed volatiles, stability field of minerals, and rheology of magma depend on redox state. To evaluate redox state of magma, Fe3+/ΣFe ratio [= Fe3+/( Fe3++ Fe2+)] of volcanic glass has been measured non-destructively by Fe-K edge μ-XANES (micro X-ray Absorption Near Edge Structure) spectroscopy (e.g., Cottrell and Kelly, 2011). We performed textural, compositional, and Fe-K edge μ-XANES analyses on volcanic ash to infer oxidation process of magma at shallow conduit during eruption at Bromo Volcano, Indonesia. The volcanic ash particles were collected in 24th March 2011 by real-time sampling from ongoing activity. The activity was characterized by strombolian eruption showing magma head ascended to near the ground surface. The ash sample contains two type of volcanic glasses named as Brown and Black glasses (BrG and BlG), based on their color. Textual analysis shows microlite crystallinities are same in the two type of glasses, ranging from 0 to 3 vol.%. EPMA analyses show that all of the glasses have almost identical andesitic composition with SiO2 = 60 wt.%. In contrast, Fe-K edge μ-XANES spectra with the analytical method by Ishibashi et al. (in prep) demonstrate that BrG (Fe3+/ΣFe = 0.20-0.26) is more oxidized than BlG (Fe3+/ΣFe = 0.32-0.60). From combination of the glass composition, the measured Fe3+/ΣFe ratio and 1060 degree C of temperature (Kress and Carmichael, 1991), the oxygen fugacities are estimated to be NNO and NNO+4 for BrG and BlG, respectively. The volcanic glasses preserve syn-eruptive physicochemical conditions by rapid quenching due to their small size ranging from 125 to 250 μm. Our results demonstrate that BrG and BlG magmas are textually and chemically identical but their redox conditions are different at the eruption. The oxidation of magma can be caused by following two processes; 1) diffusive transport of oxygen, and 2) dissociation reaction of hydrogen from magma head. The two processes should be easy to occur in shallower region of the conduit. Therefore we suggest BlG magma existed in shallower part of the conduit than BrG magma. The K-edge μ-XANES analysis can be strong tool for understanding on degassing and ascent process of magma at shallow conduit.

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.

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.

Infrasonic component of volcano-seismic eruption tremor

NASA Astrophysics Data System (ADS)

Matoza, Robin S.; Fee, David

2014-03-01

Air-ground and ground-air elastic wave coupling are key processes in the rapidly developing field of seismoacoustics and are particularly relevant for volcanoes. During a sustained explosive volcanic eruption, it is typical to record a sustained broadband signal on seismometers, termed eruption tremor. Eruption tremor is usually attributed to a subsurface seismic source process, such as the upward migration of magma and gases through the shallow conduit and vent. However, it is now known that sustained explosive volcanic eruptions also generate powerful tremor signals in the atmosphere, termed infrasonic tremor. We investigate infrasonic tremor coupling down into the ground and its contribution to the observed seismic tremor. Our methodology builds on that proposed by Ichihara et al. (2012) and involves cross-correlation, coherence, and cross-phase spectra between waveforms from nearly collocated seismic and infrasonic sensors; we apply it to datasets from Mount St. Helens, Tungurahua, and Redoubt Volcanoes.

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.

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.

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.

From the Slab to the Surface: Origin, Storage, Ascent, and Eruption of Volatile-Bearing Magmas in the Aleutian arc

NASA Astrophysics Data System (ADS)

Roman, D.; Plank, T. A.; Hauri, E. H.; Rasmussen, D. J.; Power, J. A.; Lyons, J. J.; Haney, M. M.; Werner, C. A.; Kern, C.; Lopez, T. M.; Izbekov, P. E.; Stelling, P. L.

2016-12-01

We present initial results from an integrated geochemical-geophysical study of the Unimak-Cleveland corridor of the Aleutian volcanic arc, which encompasses six volcanoes spanning 450 km of the arc that have erupted in the past 25 years with a wide range of magmatic water contents. This relatively small corridor also exhibits a range of deep and upper-crustal seismicity, apparent magma storage depths, and depths to the subducting tectonic plate. The ultimate goal of this study is to link two normally disconnected big-picture problems: 1) the deep origin of magmas and volatiles, and 2) the formation and eruption of crustal magma reservoirs, which we will do by establishing the depth(s) of crustal magma reservoirs and pre-eruptive volatile contents throughout the corridor. Our preliminary work focuses on the geographic end members Shishaldin Volcano, which last erupted in 2014-2015, and Cleveland Volcano, which last erupted in April-May of this year (2016). Both systems are persistently degassing, open-vent volcanoes whose frequent eruptions are typically characterized by minimal precursory seismicity, making eruption forecasting challenging. At Cleveland, we analyze data from a 12-station broadband seismic network deployed from August 2015-July 2016, which is complemented by two permanent seismo-acoustic stations operated by the Alaska Volcano Observatory (AVO). We also analyze tephras from recent eruptions (including 2016) and conducted ground- and helicopter-based gas emission surveys. At Shishaldin, we analyze data from the permanent AVO network, which is comprised of mainly short-period, single-component seismic stations. We also present preliminary analyses of samples of recent eruptive deposits and gas emission data. Through integration of these various datasets we present preliminary interpretations related to the origin, storage, ascent and eruption of volatile-bearing magmas at Cleveland and Shishaldin volcanoes.

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.

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.

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.

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.

Low sulfur content in submarine lavas: an unreliable indicator of subaerial eruption

USGS Publications Warehouse

Davis, A.S.; Clague, D.A.; Schulz, M.S.; Hein, J.R.

1991-01-01

Low S content (<250 ppm) has been used to identify subaerially erupted Hawaiian and Icelandic lavas. Large differences in S content of submarine-erupted lavas from different tectonic settings indicate that the behavior of S is complex. Variations in S abundance in undegassed, submarine-erupted lavas can result from different source compositions, different percentages of partial melting, and crystal fractionation. Low S concentrations in highly vesicular submarine lavas suggest that partial degassing can occur despite great hydrostatic pressure. These processes need to be evaluated before using S content as an indicator of eruption depth. -Authors

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.

The ash deposits of the 4200 BP Cerro Blanco eruption: the largest Holocene eruption of the Central Andes

NASA Astrophysics Data System (ADS)

Fernandez-Turiel, Jose-Luis; Saavedra, Julio; Perez-Torrado, Francisco-Jose; Rodriguez-Gonzalez, Alejandro; Carracedo, Juan-Carlos; Lobo, Agustin; Rejas, Marta; Gallardo, Juan-Fernando; Osterrieth, Margarita; Carrizo, Julieta; Esteban, Graciela; Martinez, Luis-Dante; Gil, Raul-Andres; Ratto, Norma; Baez, Walter

2015-04-01

We present new data about a major eruption -spreading approx. 110 km3 ashes over 440.000 km2- long thought to have occurred around 4200 years ago in the Cerro Blanco Volcanic Complex (CBVC) in the Central Andes of NW Argentina (Southern Puna, 26°45' S, 67°45' W). This eruption may be the biggest during the past five millennia in the Central Volcanic Zone of the Andes, and possibly one of the largest Holocene eruptions in the world. Discrimination and correlation of pyroclastic deposits of this eruption of Cerro Blanco was conducted comparing samples of proximal (domes, pyroclastic flow and fall deposits) with distal ash fall deposits (up to 400 km from de vent). They have been characterized using optical and electron microscopy (SEM), X-ray diffraction, particle-size distribution by laser diffraction and electron microprobe and HR-ICP-MS with laser ablation for major and trace element composition of glass, feldspars and biotite. New and published 14C ages were calibrated using Bayesian statistics. An one-at-a-time inversion method was used to reconstruct the eruption conditions using the Tephra2 code (Bonadonna et al. 2010, https://vhub.org/resources/tephra2). This method allowed setting the main features of the eruption that explains the field observations in terms of thickness and grain size distributions of the ash fall deposit. The main arguments that justify the correlation are four: 1) Compositional coincidence for glass, feldspars, and biotite in proximal and distal materials; 2) Stratigraphic and geomorphological relationships, including structure and thickness variation of the distal deposits; 3) Geochronological consistency, matching proximal and distal ages; and 4) Geographical distribution of correlated outcrops in relation to the eruption centre at the coordinates of Cerro Blanco. With a magnitude of 7.0 and a volcanic explosivity index or VEI 7, this eruption of ~4200 BP at Cerro Blanco is the largest in the last five millennia known in the Central Volcanic Zone of the Andes. The implications of these results go far beyond having an excellent chronostratigraphic marker to reconstruct the Holocene geologic history of a large area of South America. Besides the effects directly associated with eruptive process, a deposit of tephra is very ephemeral and rapidly is reworked and redeposited. The interaction of the huge amount of ashes of this eruption with the wind and water in the large watersheds of the region must mobilize enormous amounts of both particulate and chemical elements to the large Chacopampean Plain. How impacted this eruption on the environmental, pollen, faunal and archaeological mid-Holocene records are features currently under study. On the other hand, the occurrence of Holocene volcanism in the southern Puna leads to consider new scenarios of volcanic hazard over large and densely populated areas in South America. Financial support was provided by the QUECA Project (MINECO, CGL2011-23307). Part of the analytical work was carried out in the Geochemistry Facility of labGEOTOP in the ICTJA-CSIC, infrastructure co-funded by ERDF-EU (Ref. CSIC08-4E-001).

Constraining the Spatial and Temporal Variability of Atmospheric Conditions to Explore the Infrasound Detection of Volcanic Eruptions in Alaska

NASA Astrophysics Data System (ADS)

Iezzi, A. M.; Schwaiger, H. F.; Fee, D.; Haney, M. M.

2015-12-01

Alaska's over 50 historically active volcanoes span 2,500 kilometers, and their eruptions pose great threats to the aviation industry. This makes both prompt observations of explosion onsets and changes in intensity a necessity. Due to their expansive range and remoteness, these volcanoes are predominantly monitored by local seismic networks, remote observations including satellite imagery and infrasound sensors. Infrasound is an especially crucial tool in this area because infrasound data collection is not obstructed by frequent cloud cover (as in satellite imagery) and infrasound waves can travel hundreds to thousands of kilometers. However, infrasound station coverage is relatively sparse and strong wind and temperature gradients in the atmosphere create multiple waveguides and shadow zones where the propagation of infrasound is enhanced and diminished, respectively. To accurately constrain volcanic source information and the long-range propagation of infrasound waves, a detailed characterization of the spatial and temporal variability of the atmosphere is vital. These properties can be constrained using a ground-to-space model similar to that of Drob et al. (2003) based upon varied meteorological observations and applied to infrasound waves to model the propagation of infrasound. Here we present the first results of a re-analysis system constructed by the Alaska Volcano Observatory to accurately characterize and model long-range infrasound propagation from volcanic eruptions. We select a number of case studies to examine infrasound detections (or lack thereof) from recent eruptions of Alaskan volcanoes, including the November 2014 eruption of Pavlof Volcano and July 2015 eruption of Cleveland Volcano. Detailed examination of the acoustic propagation conditions will provide additional insight into detection capability and eruption dynamics with future work aiming to implement real-time long-range infrasound propagation modeling.Drob, Douglas P., J. M. Picone, and M. Garcés. "Global morphology of infrasound propagation." Journal of Geophysical Research: Atmospheres (1984-2012) 108.D21 (2003).

Evolution of Effluent Chemistry at Crystal Geyser, Green River, Utah

NASA Astrophysics Data System (ADS)

Han, W. S.; Park, E.; Choung, S.; Kim, C. Y.; Piao, J.; Han, G.

2016-12-01

Several cold-water geysers and springs are located adjacent to the Green River in Utah where two major east-west faults, the Little Grand Wash and the Salt Wash Graben faults, trend roughly parallel to each other. Among these springs and geysers is Crystal Geyser, located immediately north of the Little Grand Wash fault and approximately 6 km south of the town of Green River. In this study, the fluid mechanics of the regularly erupting Crystal Geyser was investigated by instrumenting its conduit with pressure, temperature, pH, EC, and dissolved oxygen sensors, measuring every 1 minute during and between eruptions. The single eruption cycle at Crystal geyser lasted over four days and was composed of four parts: Minor Eruption (mEP), Major Eruption (MEP), Aftershock Eruption (Ae) and Recharge (R). Current eruption patterns exhibit a bimodal distribution although previous measurements and anecdotal evidence suggests that this pattern was different prior to recent seismic activity. Based on chemical characteristics, the primary sourcing aquifers characterized to be both Entrada and Navajo Sandstones with minor contribution from Paradox Formation brine. Contemporaneously, dissolved ionic species vary 0-44% while transition from mEP, MEP and R even if the degree of changes was different from individual ion. Generally, Na+, K+, Cl- and SO42- regularly decrease at the onset and throughout the MEP. These species then increase in concentration during the mEP. Conversely, Ca2+, Mg2+, Fe2+ and Sr2+ decrease and increase in concentration during the MEP and mEP, respectively. Inverse geochemical modeling was conducted to characterize the contribution of Crystal geyser effluents from endmembers of Entrada Sandstone, Navajo Sandstone and Paradox Formations. Results of inverse modeling show that, during the mEP, the Navajo, Entrada and brine supply 62-65%, 33-36% and 1%, respectively. During the MEP, the contribution shifts to 53-56%, 42-45% and 1% for the Navajo, Entrada and Brine, respectively.

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.

Unearthing The Eruptive Personality Of El Salvador's Santa Ana (Ilamatepec) Volcano Though In-depth Stratigraphic Analysis Of Pre-1904 Deposits

NASA Astrophysics Data System (ADS)

Gallant, E.; Martinez-Hackert, B.

2011-12-01

The Santa Ana (Ilamatepec) volcano (2384 m) in densely populated El Salvador Central America presents serious volcanic hazard potential. The volcano is a prevalent part of every day life in El Salvador; the sugarcane and coffee belt of the country are to its Southern and Western flanks, recreational areas lies to its East, and second and third largest cities of El Salvador exist within its 25 km radius. Understanding the eruptive characteristics and history is imperative due to the volcano's relative size (the highest in the country) and it's explosive, composite nature. Historical records indicate at least 9 potential VEI 3 eruptions since 1521 AD. The volcano's relative inaccessibility and potential hazards do not promote a vast reservoir of research activity, as can be seen in the scarcity of published papers on topics prior to the 1904 eruption. This research represents the first steps towards creating a comprehensive stratigraphic record of the crater and characterizing its eruptive history, with an eventual goal of recreating the volcanic structure prior to its collapse. Samples of pre-1904 eruptive material were taken from the southern wall of an E-W oriented fluvial gully located within the SSW of the tertiary crater. These were analyzed using thin sections and optical microscopy, grain size distribution techniques, and scanning electron microscopy. The 15-layer sequence indicates an explosive history characterized by intense phreatomagmatic phases, plinian, sub-plinian and basaltic/andesitic composition strombolian activity. Another poster within the session will discuss an older sequence within the walls of the secondary crater. Further detailed studies will be required to gain a better understanding of the characteristics of Santa Ana Volcano.

Separated two-phase flow and basaltic eruptions

NASA Astrophysics Data System (ADS)

Vergniolle, Sylvie; Jaupart, Claude

1986-11-01

Fluid dynamical models of volcanic eruptions are usually made in the homogeneous approximation where gas and liquid are constrained to move at the same velocity. Basaltic eruptions exhibit the characteristics of separated flows, including transitions in their flow regime, from bubbly to slug flow in Strombolian eruptions and from bubbly to annular flow in Hawaiian ones. These regimes can be characterized by a parameter called the melt superficial velocity, or volume flux per unit cross section, which takes values between 10-3 and 10-2 m/s for bubbly and slug flow, and about 1 m/s for annular flow. We use two-phase flow equations to determine under which conditions the homogeneous approximation is not valid. In the bubbly regime, in which many bubbles rise through the moving liquid, there are large differences between the two-phase and homogeneous models, especially in the predictions of gas content and pressure. The homogeneous model is valid for viscous lavas such as dacites because viscosity impedes bubble motion. It is not valid for basaltic lavas if bubble sizes are greater than 1 cm, which is the case. Accordingly, basaltic eruptions should be characterized by lower gas contents and lower values of the exit pressure, and they rarely erupt in the mist and froth regimes, which are a feature of more viscous lavas. The two-phase flow framework allows for the treatment of different bubble populations, including vesicles due to exsolution by pressure release in the volcanic conduit and bubbles from the magma chamber. This yields information on poorly constrained parameters including the effective friction coefficient for the conduit, gas content, and bubble size in the chamber. We suggest that the observed flow transitions record changes in the amount and size of gas bubbles in the magma chamber at the conduit entry.

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.

A complex magma mixing origin for rocks erupted in 1915, Lassen Peak, California

USGS Publications Warehouse

Clynne, M.A.

1999-01-01

The eruption of Lassen Peak in May 1915 produced four volcanic rock types within 3 days, and in the following order: (1) hybrid black dacite lava containing (2) undercooled andesitic inclusions, (3) compositionally banded pumice with dark andesite and light dacite bands, and (4) unbanded light dacite. All types represent stages of a complex mixing process between basaltic andesite and dacite that was interrupted by the eruption. They contain disequilibrium phenocryst assemblages characterized by the co-existence of magnesian olivine and quartz and by reacted and unreacted phenocrysts derived from the dacite. The petrography and crystal chemistry of the phenocrysts and the variation in rock compositions indicate that basaltic andesite intruded dacite magma and partially hybridized with it. Phenocrysts from the dacite magma were reacted. Cooling, cyrstallization, and vesiculation of the hybrid andesite magma converted it to a layer of mafic foam. The decreased density of the andesite magma destabilized and disrupted the foam. Blobs of foam rose into and were further cooled by the overlying dacite magma, forming the andesitic inclusions. Disaggregation of andesitic inclusions in the host dacite produced the black dacite and light dacite magmas. Formation of foam was a dynamic process. Removal of foam propagated the foam layer downward into the hybrid andesite magma. Eventually the thermal and compositional contrasts between the hybrid andesite and black dacite magmas were reduced. Then, they mixed directly, forming the dark andesite magma. About 40-50% andesitic inclusions were disaggregated into the host dacite to produce the hybrid black dacite. Thus, disaggregation of inclusions into small fragments and individual crystals can be an efficient magma-mixing process. Disaggregation of undercooled inclusions carrying reacted host-magma phenocrysts produces co-existing reacted and unreacted phenocrysts populations.

Volcanic plume and bomb field masses from thermal infrared camera imagery

NASA Astrophysics Data System (ADS)

Harris, A. J. L.; Delle Donne, D.; Dehn, J.; Ripepe, M.; Worden, A. K.

2013-03-01

Masses erupted during normal explosions at Stromboli volcano (Italy) are notoriously difficult to measure. We present a method that uses thermal infrared video for cooling bomb fields to obtain the total power emitted by all hot particles emitted during an explosion. A given mass of magma (M) will emit a finite amount of thermal power, defined by M cp(Te-T0), cp and Te being magma specific heat capacity and temperature, and T0 being ambient temperature. We use this relation to convert the total power emitted by the bomb field to the mass required to generate that power. To do this we extract power flux curves for the field and integrate this through time to obtain total power (E). This is used to estimate mass (Q) in Q=E/cp(Te-T0). When applied to individual bombs we obtain masses of between 1 and 9 kg per bomb, or a volume of 970 and 6500 cm3. These volumes equate to spheres with diameters 12 and 27 cm. For the entire bomb field we obtain volumes of 7-28 m3. We calculate masses for 32 eruptions and obtain typical bomb masses of between 103 and 104 kg per eruption. In addition, we estimate that between 102 and 103 kg of gas and ash are emitted as part of a mixed plume of bombs, gas and ash. We identify two types of eruption on the basis of the erupted bomb masses and the ratio of the plume's gas-and-ash component to the bomb component. The first type is bomb-dominated, is characterized by bomb masses of 104 kg and has ash-gas/ bomb ratios of ˜0.02. The second type is ash-and-gas dominated, is characterized by erupted bomb masses of 103 kg and has ash-gas/bomb ratios of around one, and as high as two. There is no correlation between the quantity of bombs and quantity of gas-ash erupted. In addition, while source pressure for each explosion correlates with the quantity of gas and ash erupted, the mass of bombs emitted varies independently of pressure.

Locating the depth of magma supply for volcanic eruptions, insights from Mt. Cameroon

PubMed Central

Geiger, Harri; Barker, Abigail K.; Troll, Valentin R.

2016-01-01

Mt. Cameroon is one of the most active volcanoes in Africa and poses a possible threat to about half a million people in the area, yet knowledge of the volcano’s underlying magma supply system is sparse. To characterize Mt. Cameroon’s magma plumbing system, we employed mineral-melt equilibrium thermobarometry on the products of the volcano’s two most recent eruptions of 1999 and 2000. Our results suggest pre-eruptive magma storage between 20 and 39 km beneath Mt. Cameroon, which corresponds to the Moho level and below. Additionally, the 1999 eruption products reveal several shallow magma pockets between 3 and 12 km depth, which are not detected in the 2000 lavas. This implies that small-volume magma batches actively migrate through the plumbing system during repose intervals. Evolving and migrating magma parcels potentially cause temporary unrest and short-lived explosive outbursts, and may be remobilized during major eruptions that are fed from sub-Moho magma reservoirs. PMID:27713494

Characterization of moderate ash-and-gas explosions at Santiaguito volcano, Guatemala, from infrasound waveform inversion and thermal infrared measurements

NASA Astrophysics Data System (ADS)

Angelis, S. De; Lamb, O. D.; Lamur, A.; Hornby, A. J.; von Aulock, F. W.; Chigna, G.; Lavallée, Y.; Rietbrock, A.

2016-06-01

The rapid discharge of gas and rock fragments during volcanic eruptions generates acoustic infrasound. Here we present results from the inversion of infrasound signals associated with small and moderate gas-and-ash explosions at Santiaguito volcano, Guatemala, to retrieve the time history of mass eruption rate at the vent. Acoustic waveform inversion is complemented by analyses of thermal infrared imagery to constrain the volume and rise dynamics of the eruption plume. Finally, we combine results from the two methods in order to assess the bulk density of the erupted mixture, constrain the timing of the transition from a momentum-driven jet to a buoyant plume, and to evaluate the relative volume fractions of ash and gas during the initial thrust phase. Our results demonstrate that eruptive plumes associated with small-to-moderate size explosions at Santiaguito only carry minor fractions of ash, suggesting that these events may not involve extensive magma fragmentation in the conduit.

Locating the depth of magma supply for volcanic eruptions, insights from Mt. Cameroon.

PubMed

Geiger, Harri; Barker, Abigail K; Troll, Valentin R

2016-10-07

Mt. Cameroon is one of the most active volcanoes in Africa and poses a possible threat to about half a million people in the area, yet knowledge of the volcano's underlying magma supply system is sparse. To characterize Mt. Cameroon's magma plumbing system, we employed mineral-melt equilibrium thermobarometry on the products of the volcano's two most recent eruptions of 1999 and 2000. Our results suggest pre-eruptive magma storage between 20 and 39 km beneath Mt. Cameroon, which corresponds to the Moho level and below. Additionally, the 1999 eruption products reveal several shallow magma pockets between 3 and 12 km depth, which are not detected in the 2000 lavas. This implies that small-volume magma batches actively migrate through the plumbing system during repose intervals. Evolving and migrating magma parcels potentially cause temporary unrest and short-lived explosive outbursts, and may be remobilized during major eruptions that are fed from sub-Moho magma reservoirs.

Characterization of moderate ash-and-gas explosions at Santiaguito volcano, Guatemala, from infrasound waveform inversion and thermal infrared measurements.

PubMed

Angelis, S De; Lamb, O D; Lamur, A; Hornby, A J; von Aulock, F W; Chigna, G; Lavallée, Y; Rietbrock, A

2016-06-28

The rapid discharge of gas and rock fragments during volcanic eruptions generates acoustic infrasound. Here we present results from the inversion of infrasound signals associated with small and moderate gas-and-ash explosions at Santiaguito volcano, Guatemala, to retrieve the time history of mass eruption rate at the vent. Acoustic waveform inversion is complemented by analyses of thermal infrared imagery to constrain the volume and rise dynamics of the eruption plume. Finally, we combine results from the two methods in order to assess the bulk density of the erupted mixture, constrain the timing of the transition from a momentum-driven jet to a buoyant plume, and to evaluate the relative volume fractions of ash and gas during the initial thrust phase. Our results demonstrate that eruptive plumes associated with small-to-moderate size explosions at Santiaguito only carry minor fractions of ash, suggesting that these events may not involve extensive magma fragmentation in the conduit.

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

Eruptive vellus hair cysts: report of a pediatric case with partial response to calcipotriene therapy.

PubMed

Erkek, Emel; Kurtipek, Gülcan Saylam; Duman, Deniz; Sanli, Cihat; Erdoğan, Sibel

2009-12-01

Eruptive vellus hair cysts (EVHCs) are characterized by asymptomatic, follicular, comedonelike papules usually located on the anterior chest and abdomen. We present a pediatric case of EVHC associated with attention deficit hyperactivity disorder that partially responded to calcipotriene cream within 2 months. Our aim is to refamiliarize clinicians with a common albeit frequently unrecognized disorder of vellus hair follicles.

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.

Lava-flow characterization at Pisgah Volcanic Field, California, with multiparameter imaging radar

USGS Publications Warehouse

Gaddis, L.R.

1992-01-01

Multi-incidence-angle (in the 25?? to 55?? range) radar data aquired by the NASA/JPL Airborne Synthetic Aperture Radar (AIRSAR) at three wavelengths simultaneously and displayed at three polarizations are examined for their utility in characterizing lava flows at Pisgah volcanic field, California. Pisgah lava flows were erupted in three phases; flow textures consist of hummocky pahoehoe, smooth pahoehoe, and aa (with and without thin sedimentary cover). Backscatter data shown as a function of relative age of Pisgah flows indicate that dating of lava flows on the basis of average radar backscatter may yield ambiguous results if primary flow textures and modification processes are not well understood. -from Author

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.

Earthquake induced variations in extrusion rate: A numerical modeling approach to the 2006 eruption of Merapi Volcano (Indonesia)

NASA Astrophysics Data System (ADS)

Carr, Brett B.; Clarke, Amanda B.; de'Michieli Vitturi, Mattia

2018-01-01

Extrusion rates during lava dome-building eruptions are variable and eruption sequences at these volcanoes generally have multiple phases. Merapi Volcano, Java, Indonesia, exemplifies this common style of activity. Merapi is one of Indonesia's most active volcanoes and during the 20th and early 21st centuries effusive activity has been characterized by long periods of very slow (<0.1 m3 s-1) extrusion rate interrupted every few years by short episodes of elevated extrusion rates (1-4 m3 s-1) lasting weeks to months. One such event occurred in May-July 2006, and previous research has identified multiple phases with different extrusion rates and styles of activity. Using input values established in the literature, we apply a 1D, isothermal, steady-state numerical model of magma ascent in a volcanic conduit to explain the variations and gain insight into corresponding conduit processes. The peak phase of the 2006 eruption occurred in the two weeks following the May 27 Mw 6.4 earthquake 50 km to the south. Previous work has suggested that the peak extrusion rates observed in early June were triggered by the earthquake through either dynamic stress-induced overpressure or the addition of CO2 due to decarbonation and gas escape from new fractures in the bedrock. We use the numerical model to test the feasibility of these proposed hypotheses and show that, in order to explain the observed change in extrusion rate, an increase of approximately 5-7 MPa in magma storage zone overpressure is required. We also find that the addition of ∼1000 ppm CO2 to some portion of the magma in the storage zone following the earthquake reduces water solubility such that gas exsolution is sufficient to generate the required overpressure. Thus, the proposed mechanism of CO2 addition is a viable explanation for the peak phase of the Merapi 2006 eruption. A time-series of extrusion rate shows a sudden increase three days following the earthquake. We explain this three-day delay by the combined time required for the effects of the earthquake and corresponding CO2 increase to develop in the magma storage system (1-2 days), and the time we calculate for the affected magma to ascend from storage zone to surface (40 h). The increased extrusion rate was sustained for 2-7 days before dissipating and returning to pre-earthquake levels. During this phase, we estimate that 3.5 million m3 DRE of magma was erupted along with 11 ktons of CO2. The final phase of the 2006 eruption was characterized by highly variable extrusion rates. We demonstrate that those changes were likely controlled by failure of the edifice that had been confining the dome to Merapi's crater and subsequent large dome collapses. The corresponding reductions in confining pressure caused increased extrusion rates that rapidly rebuilt the dome and led to further collapses, a feedback cycle that prolonged the eruption. In a more general sense, this study demonstrates that both internal changes, such as magma volatile content and overpressure, and external forces, such as edifice collapse and regional earthquakes, can affect variations in eruption intensity. Further, we also demonstrate how these external forces can initiate internal changes and how these parameters may interact with one another in a feedback scenario.

Large-scale and Long-duration Simulation of a Multi-stage Eruptive Solar Event

NASA Astrophysics Data System (ADS)

Jiang, chaowei; Hu, Qiang; Wu, S. T.

2015-04-01

We employ a data-driven 3D MHD active region evolution model by using the Conservation Element and Solution Element (CESE) numerical method. This newly developed model retains the full MHD effects, allowing time-dependent boundary conditions and time evolution studies. The time-dependent simulation is driven by measured vector magnetograms and the method of MHD characteristics on the bottom boundary. We have applied the model to investigate the coronal magnetic field evolution of AR11283 which was characterized by a pre-existing sigmoid structure in the core region and multiple eruptions, both in relatively small and large scales. We have succeeded in producing the core magnetic field structure and the subsequent eruptions of flux-rope structures (see https://dl.dropboxusercontent.com/u/96898685/large.mp4 for an animation) as the measured vector magnetograms on the bottom boundary evolve in time with constant flux emergence. The whole process, lasting for about an hour in real time, compares well with the corresponding SDO/AIA and coronagraph imaging observations. From these results, we show the capability of the model, largely data-driven, that is able to simulate complex, topological, and highly dynamic active region evolutions. (We acknowledge partial support of NSF grants AGS 1153323 and AGS 1062050, and data support from SDO/HMI and AIA teams).

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.

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.

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.

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.

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.

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.

Monitoring and Modeling: The Future of Volcanic Eruption Forecasting

NASA Astrophysics Data System (ADS)

Poland, M. P.; Pritchard, M. E.; Anderson, K. R.; Furtney, M.; Carn, S. A.

2016-12-01

Eruption forecasting typically uses monitoring data from geology, gas geochemistry, geodesy, and seismology, to assess the likelihood of future eruptive activity. Occasionally, months to years of warning are possible from specific indicators (e.g., deep LP earthquakes, elevated CO2 emissions, and aseismic deformation) or a buildup in one or more monitoring parameters. More often, observable changes in unrest occur immediately before eruption, as magma is rising toward the surface. In some cases, little or no detectable unrest precedes eruptive activity. Eruption forecasts are usually based on the experience of volcanologists studying the activity, but two developing fields offer a potential leap beyond this practice. First, remote sensing data, which can track thermal, gas, and ash emissions, as well as surface deformation, are increasingly available, allowing statistically significant research into the characteristics of unrest. For example, analysis of hundreds of volcanoes indicates that deformation is a more common pre-eruptive phenomenon than thermal anomalies, and that most episodes of satellite-detected unrest are not immediately followed by eruption. Such robust datasets inform the second development—probabilistic models of eruption potential, especially those that are based on physical-chemical models of the dynamics of magma accumulation and ascent. Both developments are essential for refining forecasts and reducing false positives. For example, many caldera systems have not erupted but are characterized by unrest that, in another context, would elicit strong concern from volcanologists. More observations of this behavior and better understanding of the underlying physics of unrest will improve forecasts of such activity. While still many years from implementation as a forecasting tool, probabilistic physio-chemical models incorporating satellite data offer a complement to expert assessments that, together, can form a powerful forecasting approach.

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.

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

Earth Observations taken by the Expedition 18 Crew

NASA Image and Video Library

2009-02-24

ISS018-E-035716 (24 Feb. 2009) --- Minchinmavida and Chaiten Volcanoes in Chile are featured in this image photographed by an Expedition 18 crewmember on the International Space Station. The Andes mountain chain along the western coastline of South America includes numerous active stratovolcanoes. The majority of these volcanoes are formed, and fed, by magma generated as the oceanic Nazca tectonic plate moves northeastward and plunges beneath the less dense South American continental tectonic plate (a process known as subduction). The line of Andean volcanoes marks the approximate location of the subduction zone. This astronaut photograph highlights two volcanoes located near the southern boundary of the Nazca ? South America subduction zone in southern Chile. Dominating the scene is the massive Minchinmavida stratovolcano at center. An eruption of this glaciated volcano was observed by Charles Darwin during his Galapagos Island voyage in 1834; the last recorded eruption took place the following year. The white, snow covered summit of Minchinmavida is blanketed by gray ash erupted from its much smaller but now active neighbor to the west, Volcan (volcano) Chaiten. The historically inactive Chaiten volcano, characterized by a large lava dome within a caldera (an emptied and collapsed magma chamber beneath a volcano) roared back to life unexpectedly on May 2, 2008, generating dense ash plumes and forcing the evacuation of the nearby town of Chaiten. Volcanic activity continues at Chaiten, including partial collapse of a new lava dome and generation of a pyroclastic flow several days before this photograph was taken. A steam and ash plume is visible extending to the northeast from the eruptive center of the volcano.

Reduction of randomness in seismic noise as a short-term precursor to a volcanic eruption.

PubMed

Glynn, C C; Konstantinou, K I

2016-11-24

Ambient seismic noise is characterized by randomness incurred by the random position and strength of the noise sources as well as the heterogeneous properties of the medium through which it propagates. Here we use ambient noise data recorded prior to the 1996 Gjálp eruption in Iceland in order to show that a reduction of noise randomness can be a clear short-term precursor to volcanic activity. The eruption was preceded on 29 September 1996 by a Mw ~5.6 earthquake that occurred in the caldera rim of the Bárdarbunga volcano. A significant reduction of randomness started occurring 8 days before the earthquake and 10 days before the onset of the eruption. This reduction was observed even at stations more than 100 km away from the eruption site. Randomness increased to its previous levels 160 minutes after the Bárdarbunga earthquake, during which time aftershocks migrated from the Bárdarbunga caldera to a site near the Gjálp eruption fissure. We attribute this precursory reduction of randomness to the lack of higher frequencies (>1 Hz) in the noise wavefield caused by high absorption losses as hot magma ascended in the upper crust.

Curtain eruptions from Enceladus' south-polar terrain.

PubMed

Spitale, Joseph N; Hurford, Terry A; Rhoden, Alyssa R; Berkson, Emily E; Platts, Symeon S

2015-05-07

Observations of the south pole of the Saturnian moon Enceladus revealed large rifts in the south-polar terrain, informally called 'tiger stripes', named Alexandria, Baghdad, Cairo and Damascus Sulci. These fractures have been shown to be the sources of the observed jets of water vapour and icy particles and to exhibit higher temperatures than the surrounding terrain. Subsequent observations have focused on obtaining close-up imaging of this region to better characterize these emissions. Recent work examined those newer data sets and used triangulation of discrete jets to produce maps of jetting activity at various times. Here we show that much of the eruptive activity can be explained by broad, curtain-like eruptions. Optical illusions in the curtain eruptions resulting from a combination of viewing direction and local fracture geometry produce image features that were probably misinterpreted previously as discrete jets. We present maps of the total emission along the fractures, rather than just the jet-like component, for five times during an approximately one-year period in 2009 and 2010. An accurate picture of the style, timing and spatial distribution of the south-polar eruptions is crucial to evaluating theories for the mechanism controlling the eruptions.

Curtain eruptions from Enceladus' south-polar terrain

NASA Astrophysics Data System (ADS)

Spitale, Joseph N.; Hurford, Terry A.; Rhoden, Alyssa R.; Berkson, Emily E.; Platts, Symeon S.

2015-05-01

Observations of the south pole of the Saturnian moon Enceladus revealed large rifts in the south-polar terrain, informally called `tiger stripes', named Alexandria, Baghdad, Cairo and Damascus Sulci. These fractures have been shown to be the sources of the observed jets of water vapour and icy particles and to exhibit higher temperatures than the surrounding terrain. Subsequent observations have focused on obtaining close-up imaging of this region to better characterize these emissions. Recent work examined those newer data sets and used triangulation of discrete jets to produce maps of jetting activity at various times. Here we show that much of the eruptive activity can be explained by broad, curtain-like eruptions. Optical illusions in the curtain eruptions resulting from a combination of viewing direction and local fracture geometry produce image features that were probably misinterpreted previously as discrete jets. We present maps of the total emission along the fractures, rather than just the jet-like component, for five times during an approximately one-year period in 2009 and 2010. An accurate picture of the style, timing and spatial distribution of the south-polar eruptions is crucial to evaluating theories for the mechanism controlling the eruptions.

Reduction of randomness in seismic noise as a short-term precursor to a volcanic eruption

PubMed Central

Glynn, C. C.; Konstantinou, K. I.

2016-01-01

Ambient seismic noise is characterized by randomness incurred by the random position and strength of the noise sources as well as the heterogeneous properties of the medium through which it propagates. Here we use ambient noise data recorded prior to the 1996 Gjálp eruption in Iceland in order to show that a reduction of noise randomness can be a clear short-term precursor to volcanic activity. The eruption was preceded on 29 September 1996 by a Mw ~5.6 earthquake that occurred in the caldera rim of the Bárdarbunga volcano. A significant reduction of randomness started occurring 8 days before the earthquake and 10 days before the onset of the eruption. This reduction was observed even at stations more than 100 km away from the eruption site. Randomness increased to its previous levels 160 minutes after the Bárdarbunga earthquake, during which time aftershocks migrated from the Bárdarbunga caldera to a site near the Gjálp eruption fissure. We attribute this precursory reduction of randomness to the lack of higher frequencies (>1 Hz) in the noise wavefield caused by high absorption losses as hot magma ascended in the upper crust. PMID:27883050

Ozone depletion following future volcanic eruptions

NASA Astrophysics Data System (ADS)

Eric Klobas, J.; Wilmouth, David M.; Weisenstein, Debra K.; Anderson, James G.; Salawitch, Ross J.

2017-07-01

While explosive volcanic eruptions cause ozone loss in the current atmosphere due to an enhancement in the availability of reactive chlorine following the stratospheric injection of sulfur, future eruptions are expected to increase total column ozone as halogen loading approaches preindustrial levels. The timing of this shift in the impact of major volcanic eruptions on the thickness of the ozone layer is poorly known. Modeling four possible climate futures, we show that scenarios with the smallest increase in greenhouse gas concentrations lead to the greatest risk to ozone from heterogeneous chemical processing following future eruptions. We also show that the presence in the stratosphere of bromine from natural, very short-lived biogenic compounds is critically important for determining whether future eruptions will lead to ozone depletion. If volcanic eruptions inject hydrogen halides into the stratosphere, an effect not considered in current ozone assessments, potentially profound reductions in column ozone would result.

Combined Hinode, STEREO, and TRACE Observations of a Solar Filament Eruption: Evidence for Destabilization by Flux-Cancelation Tether Cutting

NASA Technical Reports Server (NTRS)

Sterling, Alphonse C.; Moore, R. L.

2007-01-01

We present observations from Hinode, STEREO, and TRACE of a solar filament eruption and flare that occurred on 2007 March 2. Data from the two new satellites, combined with the TRACE observations, give us fresh insights into the eruption onset process. HINODE/XRT shows soft X-ray (SXR) activity beginning approximately 30 minutes prior to ignition of bright flare loops. STEREO andTRACE images show that the filament underwent relatively slow motions coinciding with the pre-eruption SXR brightenings, and it underwent rapid eruptive motions beginning near the time of flare onset. Concurrent HINODE/SOT magnetograms showed substantial flux cancelation under the filament at the site of the pre-eruption SXR activity. From these observations we infer that progressive tether-cutting reconnection driven by photospheric convection caused the slow rise of the filament and led to its eruption. NASA supported this work through a NASA Heliosphysics GI grant.

Volcanic crystals as time capsules of eruption history.

PubMed

Ubide, Teresa; Kamber, Balz S

2018-01-23

Crystals formed prior to a volcanic event can provide evidence of processes leading to and timing of eruptions. Clinopyroxene is common in basaltic to intermediate volcanoes, however, its ability as a recorder of pre-eruptive histories has remained comparatively underexplored. Here we show that novel high-resolution trace element images of clinopyroxene track eruption triggers and timescales at Mount Etna (Sicily, Italy). Chromium (Cr) distribution in clinopyroxene from 1974 to 2014 eruptions reveals punctuated episodes of intrusion of primitive magma at depth. Magma mixing efficiently triggered volcanism (success rate up to 90%), within only 2 weeks of arrival of mafic intrusions. Clinopyroxene zonations distinguish between injections of mafic magma and regular recharges with more evolved magma, which often fail to tip the system to erupt. High Cr zonations can therefore be used to reconstruct past eruptions and inform responses to geophysical signals of volcano unrest, potentially offering an additional approach to volcano hazard monitoring.

Eruption rate, area, and length relationships for some Hawaiian lava flows

NASA Technical Reports Server (NTRS)

Pieri, David C.; Baloga, Stephen M.

1986-01-01

The relationships between the morphological parameters of lava flows and the process parameters of lava composition, eruption rate, and eruption temperature were investigated using literature data on Hawaiian lava flows. Two simple models for lava flow heat loss by Stefan-Boltzmann radiation were employed to derive eruption rate versus planimetric area relationship. For the Hawaiian basaltic flows, the eruption rate is highly correlated with the planimetric area. Moreover, this observed correlation is superior to those from other obvious combinations of eruption rate and flow dimensions. The correlations obtained on the basis of the two theoretical models, suggest that the surface of the Hawaiian flows radiates at an effective temperature much less than the inner parts of the flowing lava, which is in agreement with field observations. The data also indicate that the eruption rate versus planimetric area correlations can be markedly degraded when data from different vents, volcanoes, and epochs are combined.

Using submarine lava pillars to record mid-ocean ridge eruption dynamics

USGS Publications Warehouse

Gregg, Tracy K.P.; Fornari, Daniel J.; Perfit, Michael R.; Ridley, W. Ian; Kurz, Mark D.

2000-01-01

Submarine lava pillars are hollow, glass-lined, basaltic cylinders that occur at the axis of the mid-ocean ridge, and within the summit calderas of some seamounts. Typically, pillars are ~1-20 m tall and 0.25-2.0 m in diameter, with subhorizontal to horizontal glassy selvages on their exterior walls. Lava pillars form gradually during a single eruption, and are composed of lava emplaced at the eruption onset as well as the last lava remaining after the lava pond has drained. On the deep sea floor, the surface of a basaltic lava flow quenches to glass within 1 s, thereby preserving information about eruption dynamics, as well as chemical and physical properties of lava within a single eruption. Investigation of different lava pillars collected from a single eruption allows us to distinguish surficial lava-pond or lava-lake geochemical processes from those operating in the magma chamber. Morphologic, major-element, petrographic and helium analyses were performed on portions of three lava pillars formed during the April 1991 eruption near 9°50'N at the axis of the East Pacific Rise. Modeling results indicate that the collected portions of pillars formed in ~2-5 h, suggesting a total eruption duration of ~8-20 h. These values are consistent with observed homogeneity in the glass helium concentrations and helium diffusion rates. Major-element compositions of most pillar glasses are homogeneous and identical to the 1991 flow, but slight chemical variations measured in the outermost portions of some pillars may reflect post-eruptive processes rather than those occurring in subaxial magma bodies. Because lava pillars are common at mid-ocean ridges (MORs), the concepts and techniques we present here may have important application to the study of MOR eruptions, thereby providing a basis for quantitative comparisons of volcanic eruptions in geographically and tectonically diverse settings. More research is needed to thoroughly test the hypotheses presented here. (C) 2000 Published by Elsevier Science B.V. All rights reserved.

Incorporating the eruptive history in a stochastic model for volcanic eruptions

NASA Astrophysics Data System (ADS)

Bebbington, Mark

2008-08-01

We show how a stochastic version of a general load-and-discharge model for volcanic eruptions can be implemented. The model tracks the history of the volcano through a quantity proportional to stored magma volume. Thus large eruptions can influence the activity rate for a considerable time following, rather than only the next repose as in the time-predictable model. The model can be fitted to data using point-process methods. Applied to flank eruptions of Mount Etna, it exhibits possible long-term quasi-cyclic behavior, and to Mauna Loa, a long-term decrease in activity. An extension to multiple interacting sources is outlined, which may be different eruption styles or locations, or different volcanoes. This can be used to identify an 'average interaction' between the sources. We find significant evidence that summit eruptions of Mount Etna are dependent on preceding flank eruptions, with both flank and summit eruptions being triggered by the other type. Fitted to Mauna Loa and Kilauea, the model had a marginally significant relationship between eruptions of Mauna Loa and Kilauea, consistent with the invasion of the latter's plumbing system by magma from the former.

Textural evolution of magma during the 9.4-ka trachytic explosive eruption at Kilian Volcano, Chaîne des Puys, France

NASA Astrophysics Data System (ADS)

Colombier, M.; Gurioli, L.; Druitt, T. H.; Shea, T.; Boivin, P.; Miallier, D.; Cluzel, N.

2017-02-01

Textural parameters such as density, porosity, pore connectivity, permeability, and vesicle size distributions of vesiculated and dense pyroclasts from the 9.4-ka eruption of Kilian Volcano, were quantified to constrain conduit and eruptive processes. The eruption generated a sequence of five vertical explosions of decreasing intensity, producing pyroclastic density currents and tephra fallout. The initial and final phases of the eruption correspond to the fragmentation of a degassed plug, as suggested by the increase of dense juvenile clasts (bimodal density distributions) as well as non-juvenile clasts, resulting from the reaming of a crater. In contrast, the intermediate eruptive phases were the results of more open-conduit conditions (unimodal density distributions, decreases in dense juvenile pyroclasts, and non-juvenile clasts). Vesicles within the pyroclasts are almost fully connected; however, there are a wide range of permeabilities, especially for the dense juvenile clasts. Textural analysis of the juvenile clasts reveals two vesiculation events: (1) an early nucleation event at low decompression rates during slow magma ascent producing a population of large bubbles (>1 mm) and (2) a syn-explosive nucleation event, followed by growth and coalescence of small bubbles controlled by high decompression rates immediately prior to or during explosive fragmentation. The similarities in pyroclast textures between the Kilian explosions and those at Soufrière Hills Volcano on Montserrat, in 1997, imply that eruptive processes in the two systems were rather similar and probably common to vulcanian eruptions in general.

A Study of the Initiation Process of Coronal Mass Ejections and the Tool for Their Auto-Detection

NASA Astrophysics Data System (ADS)

Olmedo, Oscar

Coronal mass ejections (CMEs) are the most energetic and important solar activity. They are often associated with other solar phenomena such as flares and filament/prominence eruptions. Despite the significant improvement of CME study in the past decade, our understanding of the initiation process of CMEs remains elusive. In order to solve this issue, an approach that combines theoretical modelling and empirical analysis is needed. This thesis is a combination of three studies, two of which investigate the initiation process of CMEs, and the other is the development of a tool to automatically detect CMEs. First, I investigate the stability of the well-known eruptive flux rope model in the context of the torus instability. In the flux rope model, the pre-eruptive CME structure is a helical flux rope with two footpoints anchored to the solar surface. The torus instability is dependent on the balance between two opposing magnetic forces, the outward Lorentz self-force (also called curvature hoop force) and the restoring Lorentz force of the ambient magnetic fields. Previously, the condition of stability derived for the torus instability assumed that the pre-eruptive structure was a semicircular loop above the photosphere without anchored footpoints. I extend these results to partial torus flux ropes of any circularity with anchored footpoints and discovered that there is a dependence of the critical index on the fractional number of the partial torus, defined by the ratio between the arc length of the partial torus above the photosphere and the circumference of a circular torus of equal radius. I coin this result the partial torus instability (PTI). The result is more general than has been previously derived and extends to loops of any arc above the photosphere. It will be demonstrated that these results can help us understand the confinement, growth, and eventual eruption of a flux rope CME. Second, I use observations of eruptive prominences associated with CMEs to examine the behaviour of their initiation and compare these observations to theoretical models. Since theoretical models specify the pre-existence of a flux rope, the observational challenge is the interpretation of the flux rope in solar images. A good proxy for flux ropes is prominences, because of its obvious elongated helical structure above the magnetic polarity line. I compare the prominence kinematics and the associated extrapolated magnetic fields. This observational study yields two key conclusions. The first is that there is a dependence of the ejecta's kinematics on how the ambient magnetic field decay's. The second is that the critical decay index, theorized to be where the flux rope transitions from a stable to unstable configuration, is dependent on the geometry of the loop. This second result is in qualitative agreement with the theorized PTI. Finally, I develop a tool to automatically detect CME events in coronagraph images. Because of the large amount of data collected over the years, searching for candidate events to study can be daunting. In order to facilitate the search of CME event candidates, an algorithm was developed to automatically detect and characterize CMEs seen in coronagraph images. With this tool, one need not scroll through the large number of images, and only focus on particular subsets. The auto-detection reduces human bias of CME characterization. Such automated detection algorithms can have other applications, such as space weather alerts in near-real time. In summary, this thesis has improved our understanding of the initiation process of CMEs by taking both theoretical and observational studies. Future work includes investigating a larger number of events to give a better statistical characterization of the results found in the observational study. Furthermore, modification to the theoretical model of the PTI, for example by ncluding a repulsive force due to induced photospheric currents, can improve the quantitative agreement with observations. The complete knowledge of the initiation of CMEs is important because it can help us to predict when such an event may occur. Such a prediction can aid in mitigating severe space weather effects at the Earth.

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.

Thermomechanical controls on magma supply and volcanic deformation: application to Aira caldera, Japan.

PubMed

Hickey, James; Gottsmann, Joachim; Nakamichi, Haruhisa; Iguchi, Masato

2016-09-13

Ground deformation often precedes volcanic eruptions, and results from complex interactions between source processes and the thermomechanical behaviour of surrounding rocks. Previous models aiming to constrain source processes were unable to include realistic mechanical and thermal rock properties, and the role of thermomechanical heterogeneity in magma accumulation was unclear. Here we show how spatio-temporal deformation and magma reservoir evolution are fundamentally controlled by three-dimensional thermomechanical heterogeneity. Using the example of continued inflation at Aira caldera, Japan, we demonstrate that magma is accumulating faster than it can be erupted, and the current uplift is approaching the level inferred prior to the violent 1914 Plinian eruption. Magma storage conditions coincide with estimates for the caldera-forming reservoir ~29,000 years ago, and the inferred magma supply rate indicates a ~130-year timeframe to amass enough magma to feed a future 1914-sized eruption. These new inferences are important for eruption forecasting and risk mitigation, and have significant implications for the interpretations of volcanic deformation worldwide.

Thermomechanical controls on magma supply and volcanic deformation: application to Aira caldera, Japan

PubMed Central

Hickey, James; Gottsmann, Joachim; Nakamichi, Haruhisa; Iguchi, Masato

2016-01-01

Ground deformation often precedes volcanic eruptions, and results from complex interactions between source processes and the thermomechanical behaviour of surrounding rocks. Previous models aiming to constrain source processes were unable to include realistic mechanical and thermal rock properties, and the role of thermomechanical heterogeneity in magma accumulation was unclear. Here we show how spatio-temporal deformation and magma reservoir evolution are fundamentally controlled by three-dimensional thermomechanical heterogeneity. Using the example of continued inflation at Aira caldera, Japan, we demonstrate that magma is accumulating faster than it can be erupted, and the current uplift is approaching the level inferred prior to the violent 1914 Plinian eruption. Magma storage conditions coincide with estimates for the caldera-forming reservoir ~29,000 years ago, and the inferred magma supply rate indicates a ~130-year timeframe to amass enough magma to feed a future 1914-sized eruption. These new inferences are important for eruption forecasting and risk mitigation, and have significant implications for the interpretations of volcanic deformation worldwide. PMID:27619897

Drift pumice in the Central Indian Ocean Basin: Geochemical evidence

NASA Astrophysics Data System (ADS)

Pattan, J. N.; Mudholkar, A. V.; Jai Sankar, S.; Ilangovan, D.

2008-03-01

Abundant white to light grey-coloured pumice without ferromanganese oxide coating occurs within the Quaternary sediments of the Central Indian Ocean Basin (CIOB). Two distinct groups of pumice are identified from their geochemical composition, which allow one to define two different origins linked to two separate eruptions. One group of pumice is a dacitic type characterized by high Fe, Ti, Mg, Al and Ca with comparatively low contents of Si, rare-earth elements (∑REE, 69 ppm), Rb, Sr, U, Th, Ba, V, Nb, Sc, Mo and Co, which strongly suggest an origin from the 1883 Krakatau eruption. The other group is rhyolitic and is characterized by low contents of Fe, Ti, Mg and Ca and high Si, ∑REE content (121 ppm), Rb, Sr, U, Th, Ba, V, Nb, Mo, Co, and Sc and correlates well with the composition of the Youngest Toba Tuff (YTT) eruption of ˜74 ka from Northern Sumatra and is being reported for the first time. Therefore, correlation of the pumice to the 1883 Krakatau and YTT eruptions indicates that the pumice drifted to the CIOB and eventually sank when it became waterlogged. However, physical properties such as density, specific gravity, porosity and degree of saturation required for sinking of pumice for both 1883 Krakatau and YTT are almost similar.

Abstract volume for the 2016 biennial meeting of the Yellowstone Volcano Observatory

USGS Publications Warehouse

Lowenstern, Jacob B.

2016-10-20

IntroductionEvery two years, scientists, natural resource managers, outreach specialists, and a variety of other interested parties get together for the biennial meeting of the Yellowstone Volcano Observatory (YVO). Each time, the theme varies. In past years, we have focused the meeting around topics including monitoring plans, emergency response, geodesy, and outreach. This year, we spent the first half-day devoted to recent research results, plans for upcoming studies, and geothermal monitoring. On the second day, our focus switched to eruption precursors, particularly as they apply to large caldera systems.Very few large explosive eruptions from caldera systems have taken place in recorded history. Therefore, there are few empirical data with which to characterize the nature of volcanic unrest that might precede eruptions with volcano explosivity index (VEI) of six or greater. For this reason, we set up a series of talks that explore what we know and don’t know about large eruptions. We performed an informal expert elicitation (a frequently used method to characterize expert opinion) with a small number of our colleagues, which served as the basis for a productive discussion session.This short volume of abstracts and extended abstracts provides a summary of the presentations made at the YVO meeting held in Mammoth Hot Springs, Wyoming, on May 10–11, 2016.

The Novarupta-Katmai eruption of 1912 - largest eruption of the twentieth century; centennial perspectives

USGS Publications Warehouse

Hildreth, Wes; Fierstein, Judy

2012-01-01

The explosive outburst at Novarupta (Alaska) in June 1912 was the 20th century's most voluminous volcanic eruption. Marking its centennial, we illustrate and document the complex eruptive sequence, which was long misattributed to nearby Mount Katmai, and how its deposits have provided key insights about volcanic and magmatic processes. It was one of the few historical eruptions to produce a collapsed caldera, voluminous high-silica rhyolite, wide compositional zonation (51-78 percent SiO2), banded pumice, welded tuff, and an aerosol/dust veil that depressed global temperature measurably. It emplaced a series of ash flows that filled what became the Valley of Ten Thousand Smokes, sustaining high-temperature metal-transporting fumaroles for a decade. Three explosive episodes spanned ~60 hours, depositing ~17 km3 of fallout and 11±2 km3 of ignimbrite, together representing ~13.5 km3 of zoned magma. No observers were nearby and no aircraft were in Alaska, and so the eruption narrative was assembled from scattered villages and ship reports. Because volcanology was in its infancy and the early investigations (1915-23) were conducted under arduous expeditionary conditions, many provocative misapprehensions attended reports based on those studies. Fieldwork at Katmai was not resumed until 1953, but, since then, global advances in physical volcanology and chemical petrology have gone hand in hand with studies of the 1912 deposits, clarifying the sequence of events and processes and turning the eruption into one of the best studied in the world. To provide perspective on this century-long evolution, we describe the geologic and geographic setting of the eruption - in a remote, sparsely inhabited wilderness; we review the cultural and scientific contexts at the time of the eruption and early expeditions; and we compile a chronology of the many Katmai investigations since 1912. Products of the eruption are described in detail, including eight layers of regionwide fallout, nine packages of ash flows, and three lava domes that followed the explosive pyroclastic episodes. Changes in the proportions of coerupting rhyolite, dacite, and andesite pumice documented for the fallout and ash-flow successions, which are locally interbedded, permit close correlation of those synchronously emplaced sequences and their varied facies. Petrological correlation of the sequence of deposits near Novarupta with ash layers at Kodiak village, 170 km downwind, where three episodes of ashfall were recorded (to the hour), provides key constraints on timing of the eruptive events. Syneruptive collapse of a kilometer-deep caldera took place atop Mount Katmai, a stratovolcano centered 10 km east of the eruption site at Novarupta, owing to drainage of magma from beneath the Katmai edifice. Correlation of ~50 earthquakes recorded at distant seismic stations (including 14 shocks of magnitude 6.0 to 7.0) to fitful caldera collapse provides further constraints on eruption timing, because layers of nonjuvenile breccia and mud ejected from Mount Katmai during collapse pulses are intercalated with the pumice-fall layers from Novarupta. Structure of the Novarupta vent, a 2-km-wide depression backfilled by welded tuff and inferred to be funnel-shaped at depth, is described in detail, as is the 4-km-wide caldera at Mount Katmai. Discussions are also provided concerning: (1) the impact on global climate of the great mass of sulfur-poor but halogen-rich aerosol ejected into the atmosphere by the rhyolite-dominated eruption; (2) chemical and mineralogical effects of the fumarolic acid gases; and (3) the timing of several syneruptive landslide deposits sandwiched within the pumice-fall sequence. Secondary posteruption phenomena characterized include impounded lakes, ash-rich debris flows, phreatic craters on the ignimbrite sheet, responses of glaciers to the fallout blanket and to beheading by caldera collapse, growth of new glaciers inside the caldera, and gradual filling of the caldera lake. Structure, composition, and ages of the several andesite-dacite stratovolcanoes, closely clustered near Novarupta, all of which remain fumarolically and seismically active, are summarized. But among them only Mount Katmai extends compositionally to include basalt and rhyolite. The petrological affinities of 1912 magmas erupted at Novarupta with pre-1912 Katmai lavas are outlined, and various chemical, mineralogical, isotopic, and experimental data are assembled to construct a model of preeruptive magma storage beneath Mount Katmai. The monograph concludes by comparing the 1912 eruption with several other well-studied large explosive eruptions, 14 of them historical and 9 prehistoric. Finally, we retrospectively review the historical difficulties in understanding what had actually taken place at Katmai in 1912 and the century of progress in volcano science that has allowed most of it to be figured out.

The Physical and Petrologic Evolution of a Multi-vent Volcanic Field Associated With Yellowstone-Newberry Volcanism

NASA Astrophysics Data System (ADS)

Brueseke, M. E.; Hart, W. K.

2004-12-01

The Santa Rosa-Calico volcanic field (SC) of northern Nevada is perhaps the most chemically and physically diverse of all volcanic fields associated with mid-Miocene northwestern USA volcanism. SC volcanism occurred from 16.5 to 14 Ma and was characterized by the eruption of a complete compositional spectrum from basalt through high-Si rhyolite. Locally derived tholeiitic lava flows and shallow intrusive bodies are chemically and isotopically identical to the Steens Basalt (87/86Sri=<0.7040), the Oregon Plateau-wide mid-Miocene flood basalt. Andesite-dacite lava flows are exposed as at least four geographically and chemically distinct packages representing products of multiple, discrete magmatic systems. The most voluminous of these is calc-alkaline and characterized by abundant granitoid and mafic xenoliths/xenocrysts and radiogenic Sr isotopic ratios. Subalkaline silicic lava flows, domes, and shallow intrusive bodies define three diffuse north-south trending zones. Textural, chemical, and isotopic variability within the silicic units is linked to their spatial and temporal distribution, again necessitating the existence of multiple magmatic systems. The youngest locally derived silicic units are ash flows exposed in the central portion of the SC that erupted in actively forming sedimentary basins at ˜15.4 Ma. Underlying the 400-1500m thick package of SC volcanic rocks are temporally ( ˜103 and ˜85 Ma), chemically, and isotopically (87/86Sr at 16 Ma= 0.7045 to 0.7058 and 0.7061 to >0.7070) heterogeneous granitoid plutons and a package of ˜20-23 Ma calc-alkaline, arc-related intermediate lava flows. The observed disequilibrium textures, xenoliths, and chemical/isotopic diversity suggests that upwelling Steens magma interacted with local crust, siliceous crustal melts, and the mafic plutonic roots of early Miocene arc volcanism in multiple magmatic systems characterized by heterogeneous open system processes. The formation of these systems is tectonically controlled as evidenced by magma eruption/ascent along active zones of lithospheric extension. Thus, the observed physical and chemical diversity in this volcanic field is attributed to a combination of factors; tectonic setting, availability of upwelling mafic magma(s), nature of pre-Miocene crustal addition and lithospheric modification, and the resulting array of magma sources and petrogenetic processes.

New insights into Holocene eruption episodes from proximal deposit sequences at Mt. Taranaki (Egmont), New Zealand

NASA Astrophysics Data System (ADS)

Torres-Orozco, Rafael; Cronin, Shane J.; Pardo, Natalia; Palmer, Alan S.

2017-01-01

Upper stratovolcano flanks contain the most nuanced depositional record of long eruption episodes, but steep, irregular terrain makes these sequences difficult to correlate and interpret. This necessitates development of a detailed and systematic approach to describing localized depositional facies and relating these to eruptive processes. In this work, the late-Holocene eruption history of Mt. Taranaki/Egmont, New Zealand, was re-assessed based on a study of proximal deposits spanning the 14C-dated age range of 5.0-0.3 cal ka B.P. Mt. Taranaki is a textbook-example stratovolcano, with geological evidence pointing to sudden switches in scale, type and frequency of eruptions over its 130 ka history. The proximal stratigraphy presented here almost doubles the number of eruptions recognized from previous soil-stratigraphy studies. A total of 53 lithostratigraphic bed-sets record eruptions of the summit crater and parasitic vents like Fanthams Peak (the latter between 3.0 and 1.5 cal ka B.P.). At least 12 of the eruptions represented by these bed-sets comprise deposits comparable with or thicker than those of the latest sub-Plinian eruption of AD 1655. The largest eruption episode represented is the 4.6-4.7-cal ka B.P. Kokowai. Contrasting eruption styles were identified, from stable basaltic-andesite eruption columns at Fanthams Peak, to andesitic lava-dome extrusion, blasts and partial collapse of unstable eruption columns at Mt. Taranaki's summit. The centemetre-scale proximal deposit descriptions were used to identify several previously unknown, smaller eruption events. These details are indispensable for building a comprehensive probabilistic event record and in the development of realistic eruptive scenarios for complex eruption episodes prior to re-awakening of a volcano.

Explosive processes during the 2015 eruption of Axial Seamount, as recorded by seafloor hydrophones

NASA Astrophysics Data System (ADS)

Caplan-Auerbach, J.; Dziak, R. P.; Haxel, J.; Bohnenstiehl, D. R.; Garcia, C.

2017-04-01

Following the installation of the Ocean Observatories Initiative cabled array, the 2015 eruption of Axial Seamount, Juan de Fuca ridge, became the first submarine eruption to be captured in real time by seafloor seismic and acoustic instruments. This eruption also marked the first instance where the entire eruption cycle of a submarine volcano, from the previous eruption in 2011 to the end of the month-long 2015 event, was monitored continuously using autonomous ocean bottom hydrophones. Impulsive sounds associated with explosive lava-water interactions are identified within hydrophone records during both eruptions. Explosions within the caldera are acoustically distinguishable from those occurring in association with north rift lava flows erupting in 2015. Acoustic data also record a series of broadband diffuse events, occurring in the waning phase of the eruption, and are interpreted as submarine Hawaiian explosions. This transition from gas-poor to gas-rich eruptive activity coincides with an increase in water temperature within the caldera and with a decrease in the rate of deflation. The last recorded diffuse events coincide with the end of the eruption, represented by the onset of inflation. All the observed explosion signals couple strongly into the water column, and only weakly into the solid Earth, demonstrating the importance of hydroacoustic observations as a complement to seismic and geodetic studies of submarine eruptions.

SYMPATHETIC FILAMENT ERUPTIONS CONNECTED BY CORONAL DIMMINGS

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

Jiang Yunchun; Yang Jiayan; Hong Junchao

2011-09-10

We present for the first time detailed observations of three successive, interdependent filament eruptions that occurred one by one within 5 hr from different locations beyond the range of a single active region. The first eruption was observed from an active region and was associated with a coronal mass ejection (CME), during which diffuse and complex coronal dimmings formed, largely extending to the two other filaments located in quiet-Sun regions. Then, both quiescent filaments consecutively underwent the second and third eruptions, while the nearby dimmings were persistent. Comparing the result of a derived coronal magnetic configuration, the magnetic connectivity betweenmore » the dimmings suggested that they were caused by the joint effect of simple expansion of overlying loop systems forced by the first eruption, as well as by its erupting field interacting or reconnecting with the surrounding magnetic structures. Note that the dimming process in the first eruption indicated a weakening and partial removal of an overlying magnetic field constraint on the two other filaments, and thus one can physically connect these eruptions as sympathetic. It appears that the peculiar magnetic field configuration in our event was largely favorable to the occurrence of sympathetic filament eruptions. Because coronal dimmings are frequent and common phenomena in solar eruptions, especially in CME events, it is very likely that they represent a universal agent that can link consecutive eruptions nearby with sympathetic eruptions.« less

Physical Parameters of Vulcanian Eruptions at Pichincha Volcano, Ecuador: Bomb Morphologies and Textures

NASA Astrophysics Data System (ADS)

Wright, H. M.; Cashman, K.; Rosi, M.; Cioni, R.

2003-12-01

Vulcanian eruptions are common at many volcanoes around the world. These eruptions occur in energetic pulses and eject relatively small amounts of material. Each blast event (vulcanian eruption) has been inferred to represent a "throat-clearing" process that ejects a conduit plug. As such, we can examine the ejected material to reconstruct the conduit stratigraphy. The recent sequence of vulcanian eruptions at Guagua Pichincha volcano provides an opportunity to learn more about the dynamics of and pressurization conditions preceding vulcanian eruptions. From late 1999 - mid 2000, Pichincha experienced a series of vulcanian eruptions that ejected ballistic bombs, which now cover the surface of the crater. Bomb types range from dense to highly vesicular, with many exhibiting the breadcrusting that is ubiquitous in vulcanian deposits. Clast morphology varies with clast density, with slightly vesicular bombs having thick, glassy crusts and widely spaced cracks, whereas more vesicular bombs have thinner crusts and more closely spaced, regular crack patterns. The wide range of clast types appears to represent the stratigraphy of the conduit prior to each eruptive event, with denser blocks formed from more degassed magma near the top of the pre-eruptive conduit plug and more vesicular blocks representing deeper, less degassed levels in the conduit. This study uses the ballistic bombs, including the abundant breadcrust bombs, to learn more about conduit processes during a typical vulcanian eruption. In particular, we use the rapidly quenched crusts of breadcrust bombs, which preserve pre-eruptive conduit material, to determine gradients in volatile and crystal content in the conduit. The volatile content (both H2O and CO2) of the pre-eruptive melt was determined from FTIR spectroscopic analysis of bomb rind matrix glass. These values reach up to 1.2 wt% water and 10 ppm CO2, equivalent to 15 MPa maximum recorded presusure, or approximately 600 meters maximum depth. Coincident with the volatile gradient, microlite populations in bombs with dense, glassy crusts have uniform tabular shapes, whereas microlites in bombs with vesicular rinds have more variable crystal shapes. Insight into these degassing and crystallization conditions may help us understand pressurization mechanisms for the eruptions. The differences between the ballistic bombs will provide a picture of the conduit prior to eruption.

The 2011 unrest at Katla volcano: Characterization and interpretation of the tremor sources

NASA Astrophysics Data System (ADS)

Sgattoni, Giulia; Gudmundsson, Ólafur; Einarsson, Páll; Lucchi, Federico; Li, Ka Lok; Sadeghisorkhani, Hamzeh; Roberts, Roland; Tryggvason, Ari

2017-05-01

A 23-hour tremor burst was recorded on July 8-9th 2011 at the Katla subglacial volcano, one of the most active and hazardous volcanoes in Iceland. This was associated with deepening of cauldrons on the ice cap and a glacial flood that caused damage to infrastructure. Increased earthquake activity within the caldera started a few days before and lasted for months afterwards and new seismic activity started on the southern flank. No visible eruption broke the ice and the question arose as to whether this episode relates to a minor subglacial eruption with the tremor being generated by volcanic processes, or by the flood. The tremor signal consisted of bursts with varying amplitude and duration. We have identified and described three different tremor phases, based on amplitude and frequency features. A tremor phase associated with the flood was recorded only at stations closest to the river that flooded, correlating in time with rising water level observed at gauging stations. Using back-projection of double cross-correlations, two other phases have been located near the active ice cauldrons and are interpreted to be caused by volcanic or hydrothermal processes. The greatly increased seismicity and evidence of rapid melting of the glacier may be explained by a minor sub-glacial eruption. A less plausible interpretation is that the tremor was generated by hydrothermal boiling and/or explosions with no magma involved. This may have been induced by pressure drop triggered by the release of water when the glacial flood started. All interpretations require an increase of heat released by the volcano.

Interactions between mafic eruptions and glacial ice or snow: implications of the 2010 Eyjafjallajökull, Iceland, eruption for hazard assessments in the central Oregon Cascades

NASA Astrophysics Data System (ADS)

McKay, D.; Cashman, K. V.

2010-12-01

The 2010 eruption of Eyjafjallajökull, Iceland, demonstrated the importance of addressing hazards specific to mafic eruptions in regions where interactions with glacial ice or snow are likely. One such region is the central Oregon Cascades, where there are hundreds of mafic vents, many of which are Holocene in age. Here we present field observations and quantitative analyses of tephra deposits from recent eruptions at Sand Mountain, Yapoah Cone, and Collier Cone (all <4 ka). These deposits differ from typical Cascade cinder cone deposits in several ways. Most significantly, the Sand Mountain eruption produced a relatively large tephra blanket (~1 km3) that is unusually fine-grained: average clast size is 0.063 - 0.5 mm, in contrast to tephra from typical Cascade cinder cones, which are dominated by small lapilli-sized clasts rather than ash. The eruption of Eyjafjallajökull earlier this year prompted us to investigate the role that ice or snow may have played in the production of unusually fine-grained tephra during the Sand Mountain eruption. The eruption date of Sand Mountain is not well constrained, but it likely occurred during the Neoglacial phase of ice advance, which lasted from ~2 to 8 ka in the central Oregon Cascades (Marcott et al., 2009). During the Neoglacial, winter snowfall was likely ~23% greater and summer temperatures ~1.4°C cooler than present (Marcott, 2009). Although ice did not advance to the elevation of the Sand Mountain vents during this time, the eruption could have occurred through several meters of snow. We have also seen very fine-grained tephra at Yapoah Cone, which is located at a higher elevation and may have interacted with glacial ice. In addition to being characterized by unusually fine grainsize, the Yapoah tephra blanket is deposited directly on top of hyaloclastite in several locations. Tephra from Collier Cone is not characterized by unusually fine grainsize, but several sections of the deposit exhibit features that suggest deposition on top of, or interbedding with, snow that later melted away. Identification of features in mafic tephra that suggest interactions with glacial ice or snow has significant implications for regional volcanic hazard assessments. Specifically, the unique hazards posed by Eyjafjallajökull, especially hazards to air travel caused by unusually fine-grained tephra, could be repeated in the Cascades. Although glacial ice is presently limited to elevations above ~2300 m in the central Oregon Cascades, winter snowpack can exceed 5 m at elevations of ~1800 m and above. If a cinder cone eruption were to occur during winter months, interaction with snow could generate phreatomagmatic activity and outburst flooding similar to the 2010 eruption of Eyjafjallajökull, along with similar hazards to regional air travel and nearby infrastructure. For this reason, we suggest that seasonality should be an important consideration in volcanic hazard assessments for the central Oregon Cascades.

Post-eruptive Submarine Terrace Development of Capelinhos, Azores

NASA Astrophysics Data System (ADS)

Zhongwei Zhao, Will; Mitchell, Neil; Quartau, Rui; Tempera, Fernando; Bricheno, Lucy

2017-04-01

Erosion of the coasts of volcanic islands by waves creates shallow banks, but how erosion proceeds with time to create them and how it relates to wave climate is unclear. In this study, historical and recent marine geophysical data collected around the Capelinhos promontory (western Faial Island, Azores) offer an unusual opportunity to characterize how a submarine terrace developed after the eruption. The promontory was formed in 1957/58 during a Surtseyan eruption that terminated with extensive lava forming new rocky coastal cliffs. Historical measurements of coastline position are supplemented here with coastlines measured from 2004 and 2014 Google Earth images in order to characterize coastline retreat rate and distance for lava- and tephra-dominated cliffs. Swath mapping sonars were used to characterize the submarine geometry of the resulting terrace (terrace edge position, gradient and morphology). Limited photographs are available from a SCUBA dive and drop-down camera deployments to ground truth the submarine geomorphology. The results reveal that coastal retreat rates have decreased rapidly with the time after the eruption, possibly explained by the evolving resistance to erosion of cliff base materials. Surprisingly, coastline retreat rate decreases with terrace width in a simple inverse power law with terrace width. We suspect this is only a fortuitous result as wave attenuation over the terrace will not obviously produce the variation, but nevertheless it shows how rapidly the retreat rate declines. Understanding the relationship between terrace widening shelf and coastal cliff retreat rate may be more widely interesting if they can be used to understand how islands evolve over time into abrasional banks and guyots.

Building the oceanic crust: Insights on volcanic emplacement processes at the hotspot-influenced Galápagos Spreading Center, 92°W

NASA Astrophysics Data System (ADS)

McClinton, J. T.; White, S. M.; Colman, A.; Sinton, J. M.

2011-12-01

The Galápagos Spreading Center (GSC) displays a range of axial morphology due to increased magma supply from the adjacent Galápagos mantle plume. Over 30 years of scientific exploration has also documented the associated variations in volcanic terrain, crustal thickness, and geochemistry of erupted basalts, but until recently the fine-scale ("lava flow scale") volcanic features of the GSC had not been investigated. Using the Alvin submersible and aided by near-bottom photographic surveys by TowCam and sub-meter-scale sonar surveys by AUV Sentry, we mapped and sampled 12 individual eruptive units covering ~16km2 of seafloor on the ridge axis of the GSC at 92°W. Variations in AUV Sentry bathymetry and DSL-120A backscatter enabled us to characterize the fine-scale surface morphology within each eruptive unit. Lava flow morphologies within each unit were identified using a neuro-fuzzy classifier which assigns pixels as pillows, lobates, sheets, or fissures by using attributes derived from high-resolution sonar bathymetry and backscatter (McClinton et al., submitted PE&RS). An accuracy assessment indicates approximately 90% agreement between the lava morphology map and an independent set of visual observations. The result of this classification effort is that we are able to quantitatively examine the spatial distribution of lava flow morphology as it relates to the emplacement of lava flows within each eruptive unit at a mid-ocean ridge. Preliminary analyses show that a large, segment-centered volcanic cone which straddles the axial summit graben (the "Empanada") is constructed mostly of pillow lavas, while volcanism in the rifted center of the cone consists of lobate and sheet flows. Conversely, along the rest of the segment, on-axis eruptions consist mainly of pillow lava with most sheet and lobate flows found outside of a small axial summit graben. At least some of these sheet flows are fed by lava channels, suggesting emplacement over distances up to 1km, while pillow lava within the summit graben form low mounds; we speculate that eruption effusion rates decreased over the eruptive episode, producing changes in lava morphology within the larger eruptive units. Many axial mounds are also cut by the graben faults. The relatively young appearance of the lava surfaces at 92°W argues for a close relationship between volcanism and graben faulting on this part of the ridge.

Ash production and dispersal from sustained low-intensity Mono-Inyo eruptions

NASA Astrophysics Data System (ADS)

Black, Benjamin A.; Manga, Michael; Andrews, Benjamin

2016-08-01

Recent rhyolitic volcanism has demonstrated that prolonged low-intensity ash venting may accompany effusive dome formation. We examine the possibility and some consequences of episodes of extended, weak ash venting at the rhyolitic Mono-Inyo chain in Eastern California. We describe ash-filled cracks within one of the youngest domes, Panum Crater, which provide a textural record of ash venting during dome effusion. We use synchrotron-based X-ray computed tomography to characterize the particles in these tuffisites. Particle sizes in well-sorted tuffisite layers agree well with grain size distributions observed during weak ash venting at Soufrière Hills Volcano, Montserrat, and yield approximate upper and lower bounds on gas velocity and mass flux during the formation of those layers. We simulate ash dispersal with Ash3d to assess the consequences of long-lived Mono-Inyo ash venting for ash deposition and the accompanying volcanic hazards. Our results highlight the sensitivity of large-scale outcomes of volcanic eruptions to small-scale processes.

Physical mechanisms leading to two-dimensional gas content evolution within a volcanic conduit

NASA Astrophysics Data System (ADS)

Collombet, M.; Burgisser, A.; Chevalier, L. A. C.

2017-12-01

The eruption of viscous magma at the Earth's surface often gives rise to abrupt regime changes. The transition from the gentle effusion of a lava dome to brief but powerful explosions is a common regime change. This transition is often preceded by the sealing of the shallow part of the volcanic conduit and the accumulation of volatile-rich magma underneath, a situation that collects the energy to be brutally released during the subsequent explosion. While conduit sealing is well-documented, volatile accumulation has proven harder to characterize. In this study, we use a 2D conduit flow numerical model including gas loss within the magma and into the wallrock to follow the evolution of gas content during a regime transition. Using various initial porosity distributions, permeability laws and boundary conditions, we track the physical parameters that prevent or enhance gas escape from the magma. Our approach aims to identify the physical processes controlling eruptive transitions and to highlight the importance of using field data observations to constrain numerical models.

The Eggøyan eruption in 1732, Jan Mayen; an emerging ankaramitic surtseyjan type eruption

NASA Astrophysics Data System (ADS)

Gjerlxw, E.; Hoskuldsson, A.; Pedersen, R. B.; Thorseth, I. H.

2011-12-01

Jan Mayen is a volcanic island situated at 71°N and 8°W. The Island is build up of two main edifices, Sør Jan and Nord Jan (Beerenberg). Volcanic activity on the island is little known, and however at least 4 eruptions are documented at the island since early 18th century. An expedition to the island in summer 2011 reveals that first of these eruptions formed the tuffcone Eggøyan in 1732 AD. The Eggøyan tuffcone is situated at the north east foot of Beerenberg volcano, about 2.5 km from the coastline marked by Valberget. The tuffcone is about 1.5 km in diameter and emerges from about 35 m depth to reach the altitude of at least 217 m above sea level. Pre Eggøyan Lava flows on the sandy coast west of the edifice are covered by up to 1.6 m of ash some 3 km from the vent. These lava flows have been suggested to be formed in the 1732 eruption and the 1818 eruption of Jan Mayen. However, they are covered with the Eggøyan tephra and thus considerable older. Volcanic tephra from the Eggøyan eruption forms the uppermost tephra layer on the Eastern flanks of Beerenberg. Contemporary description of the 1732 eruption, tell of violent explosive eruption at the east side of Beerenberg observed by German whalers for 28 hours, while sailing past the island in May that year. A Dutch wailer group arriving to the island in June that year, report fine ash covering the island in such a way they sink up to mid leg into it. Our study this summer shows that the only eruption these descriptions can report to are the Eggøyan eruption, dating it precisely to the spring 1732. The eruptive products are made up of frothy glass and ol, cpx and opx crystals, which characterize the flank eruptions of Beerenberg. In this presentation we shall present first results of intense fragmentation of deep gas rich ankaramitic magma from the Jan Mayen are and its interaction with seawater in shallow coastal settings.

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.

Central San Juan caldera cluster: Regional volcanic framework

USGS Publications Warehouse

Lipman, Peter W.

2000-01-01

Eruption of at least 8800 km3 of dacitic-rhyolitic magma as 9 major ash-slow sheets (individually 150-5000 km3) was accompanied by recurrent caldera subsidence between 28.3 and about 26.5 Ma in the central San Juan Mountains, Colorado. Voluminous andesitic-decitic lavas and breccias were 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 explosive volcanism, making the central San Juan caldera cluster an exceptional site for study of caldera-related volcanic processes. Exposed calderas vary in size from 10 to 75 km in maximum diameter, the largest calderas being associated with the most voluminous eruptions. After collapse of the giant La Garita caldera during eruption if the Fish Canyon Tuff at 17.6 Ma, seven additional explosive eruptions and calderas formed inside the La Garita depression within about 1 m.y. Because of the nested geometry, maximum loci of recurrently overlapping collapse events are inferred to have subsided as much as 10-17 km, far deeper than the roof of the composite subvolcanic batholith defined by gravity data, which represents solidified caldera-related magma bodies. Erosional dissection to depths of as much as 1.5 km, although insufficient to reach the subvolcanic batholith, has exposed diverse features of intracaldera ash-flow tuff and interleaved caldera-collapse landslide deposits that accumulated to multikilometer thickness within concurrently subsiding caldera structures. The calderas display a variety of postcollapse resurgent uplift structures, and caldera-forming events produced complex fault geometries that localized late mineralization, including the epithermal base- and precious-metal veins of the well-known Creede mining district. Most of the central San Juan calderas have been deeply eroded, and their identification is dependent on detailed geologic mapping. In contrast, the primary volcanic morphology of the symmetrically resurgent Creede caldera, the volcanic framework for Lake Creede, has been exceptionally preserved because of rapid infilling by moat sediments of the Creede Formation, which were preferentially eroded during the past few million years. The ash-flow tuffs and caldera of the central San Juan region have been widely recognized as exceptional sites for study of explosive volcanic processes, and the results reported here provide new insights into processes of pyroclastic eruption and emplacement, geometric interrelations between caldera subsidence and resurgence, the petrologic diversity of sequential ash-flow eruptions, recurrent eruption of intermediate-composition lavas after each caldera-forming event, associated regional fault development, volume relations between ash-flow eruptions and associated calderas, the emplacement of subvolcanic batholiths, and involvement of mantle-derived mafic phases in magma-generation processes.

Unraveling the diversity in arc volcanic eruption styles: Examples from the Aleutian volcanic arc, Alaska

NASA Astrophysics Data System (ADS)

Larsen, Jessica F.

2016-11-01

The magmatic systems feeding arc volcanoes are complex, leading to a rich diversity in eruptive products and eruption styles. This review focuses on examples from the Aleutian subduction zone, encompassed within the state of Alaska, USA because it exhibits a rich diversity in arc structure and tectonics, sediment and volatile influx feeding primary magma generation, crustal magma differentiation processes, with the resulting outcome the production of a complete range in eruption styles from its diverse volcanic centers. Recent and ongoing investigations along the arc reveal controls on magma production that result in diversity of eruptive products, from crystal-rich intermediate andesites to phenocryst-poor, melt-rich silicic and mafic magmas and a spectrum in between. Thus, deep to shallow crustal "processing" of arc magmas likely greatly influences the physical and chemical character of the magmas as they accumulate in the shallow crust, the flow physics of the magmas as they rise in the conduit, and eruption style through differences in degassing kinetics of the bubbly magmas. The broad spectrum of resulting eruption styles thus depends on the bulk magma composition, melt phase composition, and the bubble and crystal content (phenocrysts and/or microlites) of the magma. Those fundamental magma characteristics are in turn largely determined by the crustal differentiation pathway traversed by the magma as a function of tectonic location in the arc, and/or the water content and composition of the primary magmas. The physical and chemical character of the magma, set by the arc differentiation pathway, as it ascends towards eruption determines the kinetic efficiency of degassing versus the increasing internal gas bubble overpressure. The balance between degassing rate and the rate at which gas bubble overpressure builds then determines the conditions of fragmentation, and ultimately eruption intensity.

Volcaniclastic stratigraphy of Gede Volcano, West Java, Indonesia: How it erupted and when

NASA Astrophysics Data System (ADS)

Belousov, A.; Belousova, M.; Krimer, D.; Costa, F.; Prambada, O.; Zaennudin, A.

2015-08-01

Gede Volcano, West Java (Indonesia), is located 60 km south of Jakarta within one of the regions with highest population density in the world. Therefore, knowledge of its eruption history is necessary for hazard evaluation, because even a small eruption would have major societal and economic consequences. Here we report the results of the investigation of the stratigraphy of Gede (with the focus on its volcaniclastic deposits of Holocene age) and include 23 new radiocarbon dates. We have found that a major part of the volcanic edifice was formed in the Pleistocene when effusions of lavas of high-silica basalt dominated. During this period the volcano experienced large-scale lateral gravitational failure followed by complete reconstruction of the edifice, formation of the summit subsidence caldera and its partial refilling. After a repose period of > 30,000 years the volcanic activity resumed at the Pleistocene/Holocene boundary. In the Holocene the eruptions were dominantly explosive with magma compositions ranging from basaltic andesite to rhyodacite; many deposits show heterogeneity at the macroscopic hand specimen scale and also in the minerals, which indicates interactions between mafic (basaltic andesite) and silicic (rhyodacite) magmas. Significant eruptions of the volcano were relatively rare and of moderate violence (the highest VEI was 3-4; the largest volume of erupted pyroclasts 0.15 km3). There were 4 major Holocene eruptive episodes ca. 10,000, 4000, 1200, and 1000 yr BP. The volcanic plumes of these eruptions were not buoyant and most of the erupted products were transported in the form of highly concentrated valley-channelized pyroclastic flows. Voluminous lahars were common in the periods between the eruptions. The recent eruptive period of the volcano started approximately 800 years ago. It is characterized by frequent and weak VEI 1-2 explosive eruptions of Vulcanian type and rare small-volume extrusions of viscous lava. We estimate that during last 10,000 years, Gede erupted less than 0.3 km3 DRE (Dense Rock Equivalent) of magma. Such small productivity suggests that the likelihood of future large-volume (VEI ≥ 5) eruptions of the volcano is low, although moderately strong (VEI 3-4) explosive eruptions capable of depositing pyroclastic flows and lahars onto the NE foot of the volcano are more likely.

The 2011-2012 paroxysmal eruptions at Mt. Etna volcano: Insights on the vertically zoned plumbing system

NASA Astrophysics Data System (ADS)

Giacomoni, P. P.; Coltorti, M.; Mollo, S.; Ferlito, C.; Braiato, M.; Scarlato, P.

2018-01-01

The activity of Mt. Etna volcano from January 2011 to April 2012 was characterized by 24 paroxysmal, short-duration (from a few to several hours) eruptions at the New South-East summit crater. Despite the violence of the activity, no appreciable geophysical signals were recorded during this period, except for an increase in seismic tremors just minutes/hours before the occurrence of the paroxysm. This type of activity represents a significant shift from the mainly effusive eruptions of 2004, 2006, and 2008/2009, as well as from the lateral rift-related events of 2001 and 2002/2003. The 2011-2012 paroxysmal activity thus represents an important opportunity to better understand the effects of different magmatic parameters (i.e., P-T-fO2) and magmatic H2O content on the crystallization and fractionation processes. To this aim the petrographic and geochemical features of lava and scoria clasts from 10 paroxysmal events have been investigated. Fractional crystallization modelling indicates that most of the eruptions are related to magmas rising along the vertically-developed feeding system of the volcano, accompanied by one main recharge of a more primitive, deep-seated magma feeding the 4/3/2012 event. Olivine-, clinopyroxene-, and plagioclase-melt equilibria and thermobarometric calculations were performed in order to estimate the crystallization conditions of magmas. These calculations reveal that the erupted products contain different phenocryst populations in equilibrium with a spectrum of primitive to more evolved magma compositions. On the basis of crystal composition, crystal-melt equilibrium conditions and thermobarometric estimations, four main magmatic facies have been recognized: F1, 1600 MPa at 1270 °C (Ol Fo88); F2, 800 MPa to 600 MPa at 1178 °C to 1151 °C (Ol Fo84-78); F3, 450 MPa to 250 MPa at 1139 °C to 1118 °C (Ol Fo79-74); F4, < 250 MPa at < 1120 °C (Ol Fo75-70). The overall geochemistry and thermobarometric data allow us to characterize the central feeding system as continuous and vertically zoned. During the 2011-2012 activity the studied 30/7/11, 29/8/11, 8/9/11, 18/3/11 and 24/4/12 events were fed by magma residing at F3 and F4 facies. Mafic magma influx from deeper F2 facies occurred 18/2/11 and 20/8/11, with a major recharge event before the 4/3/12 eruption. The primitive magma is testified by rare olivine crystals equilibrated at the F1 facies, located at crust-mantle boundary depth and close to liquidus temperature.

Seismic array observations for monitoring phreatic eruptions in Iwojima Island, Japan

NASA Astrophysics Data System (ADS)

Ueda, H.; Kawaguchi, R.; Chiba, K.; Fujita, E.; Tanada, T.

2015-12-01

Iwojima is an active volcanic island located within a 10 km wide submarine caldera about 1250 km to the south of Tokyo, Japan. The volcanic activity is characterized by intensive earthquake activity associated with an island-wide uplift with high uplift rate (30~40 cm/year) and hydrothermal activity. In the last 10 years, phreatic eruptions took place in and near the island in 2012, 2013, and 2015. In such restless volcano, predictions and detections of occurrence points of phreatic eruptions are important for ensuring safety of residents. In the previous studies, we found that the earthquake activity of Iwojima highly correlates with the island wide large uplift, but the precursory activity of the phreatic eruption in 2012 was deviated from the correlation (Ueda et al. 2013 AGU Fall Meeting). For prediction of occurrence points of phreatic eruptions and investigation of the eruption mechanism, we began observation by seismic arrays at two areas in December 2014. The seismic arrays enable to locate epicenters of volcanic tremors, which are not well located by existing seismic stations. In May and June 2015, Japan Maritime Self-Defense Force stayed in Iwojima and a live camera of Japan Meteorological Agency found very small phreatic eruptions occurred at the northern beach. Existing seismic stations could not detect seismic signals related with the eruptions. The seismic array could detect weak seismic signals related with the eruptions. Although the seismic arrays could not detect precursory signals because of too small eruption, we expect the seismic arrays can detect precursory seismic signals suggesting occurrence points of small or medium-sized phreatic eruptions. The seismic arrays also detected epicenters of harmonic and monotonic tremors took place at an active fumarolic field in the north earthen part of Iwojima. The apparent velocity of seismic waves (~1km/s) strongly suggests that the tremors relate with hydrothermal activity near ground surface.

Hybrid Pyroclastic Deposits Accumulated From The Eruptive Transitional Regime of Plinian Eruptions.

NASA Astrophysics Data System (ADS)

di Muro, Andrea; Rosi, Mauro

In the past 15 years sedimentological studies (Valentine and Giannetti, 1995; Wilson and Hildreth, 1997; Rosi et al., 2001), physical models (Neri et al., 1988; Veitch and Woods, 2000; Kaminski and Jaupart, 2001) and laboratory experiments (Carey et al., 1988) converge at defining a new eruptive regime transitional between the fully convective and the fully collapsing end -members. Buoyant columns and density currents are contemporaneously fed in the transitional dynamic regime and fall beds are intercalated with the density current deposits in the area invested by them. The sedimentological analysis of the well exposed 800yr B.P. plinian eruption of the volcano Quilotoa (Ecuador) enabled us to i) recognize a gradual evolution of the eruptive regime, ii) characterize the fall and density current deposits emplaced during the transitional regime. The eruptive activity began with at least two phreatic explosions and the effusion of a small volume lava dome. Eruptive behaviour then switched to explosive and fed a purely convective column that accumulated a reverse graded pumice fall while rising up to an height of 30 km. A small volume, diluted and slow density current (S1 current) was emplaced in the proximal SW sector just before the column reached its maximum height. Two group s of more voluminous and faster intra-plinian density currents (S2 and S3 currents) were subsequently emplaced contemporaneously with the accumulation of the lower and upper part respectively of a normal graded pumice fall bed. S2 and S3 currents were radially distributed around the crater and deposited bedded layers with facies of decreasing energy when moving away from the crater. Massive beds of small volume were emplaced only i) inside the proximal valley channel near the topography break in slope, ii) outside the valley channel in medial area where the currents impinged against relieves. A thick sequence of pyroclastic flow deposits (S4 currents) accumulated in the valley channels around the crater only in a post-plinian phase. During this phase, the convective plume was purely coignimbritic. The runout (from 4 to 11 km) and the degree of valley -confinement progressively increased from S1 to S4 currents. The eruption ended with the collapse of a 2.6 km summit caldera. During this last eruptive phase, coarse lithic-rich flow units with runout shorter than previously were emplaced. The parallel evolution of column height (grain-size), fountain height (size of ballistics) and flow properties (surges vs. flows) compares well with the numerical simulations of pyroclastic dispersion performed by Neri et al. (2002). In the whole dispersion area, the fall bed has a polymodal grain-size. The coarse modes of the fall appear related to the plinian column, while the fines ones have a co-ignimbrite fall origin. Sub-pop ulation analysis shows that the fine modes are related to ash aggregation that in transitional eruptions plays a significant role in the deposition of very fine sizzes also in very proximal areas. The fall deposit is totally eroded and reworked by the syn-plinian currents in the proximal areas and partially eroded in the medial areas. Grain-size and maximum clast analysis indicate that a significant fraction of the intraplinian beds is of primary fall origin. Strong similarities are found between the Quilot oa deposits and that accumulated during the transitional phase of the 1991 Pinatubo eruption (Rosi et al., 2001). These evidences should be carefully taken in account for risk assessment when analysing deposits accumulated in the transitional eruptive regi me with the aim at calculating the physical parameters characterizing the density currents ( Brissette and Lajoie, 1990). References : Brissette FP and Lajoie J (1990) Depositional mechanics of turbulent nuées ardentes (surges) from their grain-sizes. Bull Volcanol 53:60-66. Carey S, Sigurdsson H, Sparks RSJ (1988) Experimental studies of particle-laden plumes. J Geophys Res 93:15314-15328 Kaminski E and Jaupart C (2001) Marginal stability of atmospheric eruption columns and pyroclastic flow generation J Geophys Res 106: 21785-21798 Neri A, Papale P and Macedonio G (1998) The role of magma composition and water content in explosive eruptions: 2. Pyroclastic dispersion dynamics. J Volcanol Geotherm Res 87: 95-115 Neri A, Di Muro A, Rosi M (2002) Mass partition during collapsing and transitional columns by using numerical simulations. In press on J Volcanol Geotherm Res Rosi M., Paladio-Melosantos M.L., Di Muro A., Leoni R., Bacolcol T. (2001) Fall vs Flow Activity During the 1991 Climactic Eruption of Mt. Pinatubo (Philippines). Bull Volcanol 62: 549-566 Valentine G.A., Giannetti B. (1995) Single Pyroclastic beds deposited by simultaneous fallout and surge processes: Roccamonfina volcano, Italy. J Volcanol Geotherm Res 64:129-137. Veitch G and Woods A (2002) Particle recycling and oscillations of volcanic eruption columns. J of Geophys Res, 105: 2829-2842. Wilson C.J.N., Hildreth W. (1997) The Bishop Tuff: new insights from eruptive stratigraphy J of Geol. 105:407-439.

Dynamics of seismogenic volcanic extrusion at Mount St Helens in 2004-05

USGS Publications Warehouse

Iverson, R.M.; Dzurisin, D.; Gardner, C.A.; Gerlach, T.M.; LaHusen, R.G.; Lisowski, M.; Major, J.J.; Malone, S.D.; Messerich, J.A.; Moran, S.C.; Pallister, J.S.; Qamar, A.I.; Schilling, S.P.; Vallance, J.W.

2006-01-01

The 2004-05 eruption of Mount St Helens exhibited sustained, near-equilibrium behaviour characterized by relatively steady extrusion of a solid dacite plug and nearly periodic shallow earthquakes. Here we present a diverse data set to support our hypothesis that these earthquakes resulted from stick-slip motion along the margins of the plug as it was forced incrementally upwards by ascending, solidifying, gas-poor magma. We formalize this hypothesis with a dynamical model that reveals a strong analogy between behaviour of the magma-plug system and that of a variably damped oscillator. Modelled stick-slip oscillations have properties that help constrain the balance of forces governing the earthquakes and eruption, and they imply that magma pressure never deviated much from the steady equilibrium pressure. We infer that the volcano was probably poised in a near-eruptive equilibrium state long before the onset of the 2004-05 eruption. ??2006 Nature Publishing Group.

Diltiazem-induced acute generalised exanthematous pustulosis.

PubMed

Wakelin, S H; James, M P

1995-07-01

Pustulation is a major feature in several different dermatoses, and it may also occur as a manifestation of drug hypersensitivity. Acute generalized exanthematous pustulosis (AGEP) is an uncommon eruption characterized by acute, extensive formation of sterile pustules, fever and peripheral blood leucocytosis. It shares several clinical and histological features in common with pustular psoriasis. Most reported cases have been triggered by ingestion of broad spectrum antibiotics, particularly betalactams and macrolides. There is usually rapid resolution of the eruption on drug withdrawal. We report the case of a 58 year-old woman who developed AGEP shortly after commencing treatment with the calcium channel blocker diltiazem hydrochloride. The eruption followed a biphasic course, and improved following treatment with systemic corticosteroids and methotrexate. AGEP appears to be a rare adverse cutaneous reaction to diltiazem, whereas a wide range of other skin eruptions have been reported more commonly with this drug.

CrystalMoM: a tool for modeling the evolution of Crystals Size Distributions in magmas with the Method of Moments

NASA Astrophysics Data System (ADS)

Colucci, Simone; de'Michieli Vitturi, Mattia; Landi, Patrizia

2016-04-01

It is well known that nucleation and growth of crystals play a fundamental role in controlling magma ascent dynamics and eruptive behavior. Size- and shape-distribution of crystal populations can affect mixture viscosity, causing, potentially, transitions between effusive and explosive eruptions. Furthermore, volcanic samples are usually characterized in terms of Crystal Size Distribution (CSD), which provide a valuable insight into the physical processes that led to the observed distributions. For example, a large average size can be representative of a slow magma ascent, and a bimodal CSD may indicate two events of nucleation, determined by two degassing events within the conduit. The Method of Moments (MoM), well established in the field of chemical engineering, represents a mesoscopic modeling approach that rigorously tracks the polydispersity by considering the evolution in time and space of integral parameters characterizing the distribution, the moments, by solving their transport differential-integral equations. One important advantage of this approach is that the moments of the distribution correspond to quantities that have meaningful physical interpretations and are directly measurable in natural eruptive products, as well as in experimental samples. For example, when the CSD is defined by the number of particles of size D per unit volume of the magmatic mixture, the zeroth moment gives the total number of crystals, the third moment gives the crystal volume fraction in the magmatic mixture and ratios between successive moments provide different ways to evaluate average crystal length. Tracking these quantities, instead of volume fraction only, will allow using, for example, more accurate viscosity models in numerical code for magma ascent. Here we adopted, for the first time, a quadrature based method of moments to track the temporal evolution of CSD in a magmatic mixture and we verified and calibrated the model again experimental data. We also show how the equations and the tool developed can be integrated in a magma ascent numerical model, with application to eruptive events occurred at Stromboli volcano (Italy).

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 .

Probabilistic evaluation of the physical impact of future tephra fallout events for the Island of Vulcano, Italy

NASA Astrophysics Data System (ADS)

Biass, Sebastien; Bonadonna, Costanza; di Traglia, Federico; Pistolesi, Marco; Rosi, Mauro; Lestuzzi, Pierino

2016-05-01

A first probabilistic scenario-based hazard assessment for tephra fallout is presented for La Fossa volcano (Vulcano Island, Italy) and subsequently used to assess the impact on the built environment. Eruption scenarios are based upon the stratigraphy produced by the last 1000 years of activity at Vulcano and include long-lasting Vulcanian and sub-Plinian eruptions. A new method is proposed to quantify the evolution through time of the hazard associated with pulsatory Vulcanian eruptions lasting from weeks to years, and the increase in hazard related to typical rainfall events around Sicily is also accounted for. The impact assessment on the roofs is performed by combining a field characterization of the buildings with the composite European vulnerability curves for typical roofing stocks. Results show that a sub-Plinian eruption of VEI 2 is not likely to affect buildings, whereas a sub-Plinian eruption of VEI 3 results in 90 % of the building stock having a ≥12 % probability of collapse. The hazard related to long-lasting Vulcanian eruptions evolves through time, and our analysis shows that the town of Il Piano, located downwind of the preferential wind patterns, is likely to reach critical tephra accumulations for roof collapse 5-9 months after the onset of the eruption. If no cleaning measures are taken, half of the building stock has a probability >20 % of suffering roof collapse.

Correlating the electrification of volcanic plumes with ashfall textures at Sakurajima Volcano, Japan

NASA Astrophysics Data System (ADS)

Smith, Cassandra M.; Van Eaton, Alexa R.; Charbonnier, Sylvain; McNutt, Stephen R.; Behnke, Sonja A.; Thomas, Ronald J.; Edens, Harald E.; Thompson, Glenn

2018-06-01

Volcanic lightning detection has become a useful resource for monitoring remote, under-instrumented volcanoes. Previous studies have shown that the behavior of volcanic plume electrification responds to changes in the eruptive processes and products. However, there has not yet been a study to quantify the links between ash textures and plume electrification during an actively monitored eruption. In this study, we examine a sequence of vulcanian eruptions from Sakurajima Volcano in Japan to compare ash textural properties (grain size, shape, componentry, and groundmass crystallinity) to plume electrification using a lightning mapping array and other monitoring data. We show that the presence of the continual radio frequency (CRF) signal is more likely to occur during eruptions that produce large seismic amplitudes (>7 μm) and glass-rich volcanic ash with more equant particle shapes. We show that CRF is generated during energetic, impulsive eruptions, where charge buildup is enhanced by secondary fragmentation (milling) as particles travel out of the conduit and into the gas-thrust region of the plume. We show that the CRF signal is influenced by a different electrification process than later volcanic lightning. By using volcanic CRF and lightning to better understand the eruptive event and its products these key observations will help the monitoring community better utilize volcanic electrification as a method for monitoring and understanding ongoing explosive eruptions.

Active Submarine Volcanoes and Electro-Optical Sensor Networks: The Potential of Capturing and Quantifying an Entire Eruptive Sequence at Axial Seamount, Juan de Fuca Ridge

NASA Astrophysics Data System (ADS)

Delaney, J. R.; Kelley, D. S.; Proskurowski, G.; Fundis, A. T.; Kawka, O.

2011-12-01

The NE Pacific Regional Scale Nodes (RSN) component of the NSF Ocean Observatories Initiative is designed to provide unprecedented electrical power and bandwidth to the base and summit of Axial Seamount. The scientific community is engaged in identifying a host of existing and innovative observation and measurement techniques that utilize the high-power and bandwidth infrastructure and its real-time transmission capabilities. The cable, mooring, and sensor arrays will enable the first quantitative documentation of myriad processes leading up to, during, and following a submarine volcanic event. Currently planned RSN instrument arrays will provide important and concurrent spatial and temporal constraints on earthquake activity, melt migration, hydrothermal venting behavior and chemistry, ambient currents, microbial community structure, high-definition (HD) still images and HD video streaming from the vents, and water-column chemistry in the overlying ocean. Anticipated, but not yet funded, additions will include AUVs and gliders that continually document the spatial-temporal variations in the water column above the volcano and the distal zones. When an eruption appears imminent the frequency of sampling will be increased remotely, and the potential of repurposing the tracking capabilities of the mobile sensing platforms will be adapted to the spatial indicators of likely eruption activity. As the eruption begins mobile platforms will fully define the geometry, temperature, and chemical-microbial character of the volcanic plume as it rises into the thoroughly documented control volume above the volcano. Via the Internet the scientific community will be able to witness and direct adaptive sampling in response to changing conditions of plume formation. A major goal will be to document the eruptive volume and link the eruption duration to the volume of erupted magma. For the first time, it will be possible to begin to quantify the time-integrated output of an underwater volcanic eruption linked to the heat, chemical, and biological fluxes. In the late stages of the event, the dissipation of the "event plume" into the surrounding water column and the plume's migration patterns in the ambient regional flow will be tracked using specifically designed mobile sensor-platforms. The presence of these assets opens the potential for more immediate, coordinated, and thorough event responses than the community has previously been able to mount. Given the relative abundance of information on many variables in a verifiable and archived spatial and temporal context, and the rapidly evolving ability to conduct real-time genomic analyses, our community may be able to secure entirely novel organisms that are released into the overlying ocean only under well-characterized eruptive conditions.

Surface morphology of caldera-forming eruption deposits revealed by lidar mapping of Crater Lake National Park, Oregon- Implications for emplacement and surface modification

USGS Publications Warehouse

Robinson, Joel E.; Bacon, Charles R.; Major, Jon J.; Wright, Heather M.; Vallance, James W.

2017-01-01

Large explosive eruptions of silicic magma can produce widespread pumice fall, extensive ignimbrite sheets, and collapse calderas. The surfaces of voluminous ignimbrites are rarely preserved or documented because most terrestrial examples are heavily vegetated, or severely modified by post-depositional processes. Much research addresses the internal sedimentary characteristics, flow processes, and depositional mechanisms of ignimbrites, however, surface features of ignimbrites are less well documented and understood, except for comparatively small-volume deposits of historical eruptions. The ~7,700 calendar year B.P. climactic eruption of Mount Mazama, USA vented ~50 km3 of magma, deposited first as rhyodacite pumice fall and then as a zoned rhyodacite-to-andesite ignimbrite as Crater Lake caldera collapsed. Lidar collected during summer 2010 reveals the remarkably well-preserved surface of the Mazama ignimbrite and related deposits surrounding Crater Lake caldera in unprecedented detail despite forest cover. The ±1 m lateral and ±4 cm vertical resolution lidar allows surface morphologies to be classified. Surface morphologies are created by internal depositional processes and can point to the processes at work when pyroclastic flows come to rest. We describe nine surface features including furrow-ridge sets and wedge-shaped mounds in pumice fall eroded by high-energy pyroclastic surges, flow- parallel ridges that record the passage of multiple pyroclastic flows, perched benches of marginal deposits stranded by more-mobile pyroclastic-flow cores, hummocks of dense clasts interpreted as lag deposit, transverse ridges that mark the compression and imbrication of flows as they came to rest, scarps indicating ignimbrite remobilization, fields of pit craters caused by phreatic explosions, fractures and cracks caused by extensional processes resulting from ignimbrite volume loss, and stream channels eroded in the newly formed surface. The nine morphologies presented here illustrate a dynamic depositional environment that varied spatially and with time during the eruption, and show that multiple processes modified the ignimbrite after deposition, both during and after the eruption.

Surface morphology of caldera-forming eruption deposits revealed by lidar mapping of Crater Lake National Park, Oregon - Implications for deposition and surface modification

NASA Astrophysics Data System (ADS)

Robinson, Joel E.; Bacon, Charles R.; Major, Jon J.; Wright, Heather M.; Vallance, James W.

2017-08-01

Large explosive eruptions of silicic magma can produce widespread pumice fall, extensive ignimbrite sheets, and collapse calderas. The surfaces of voluminous ignimbrites are rarely preserved or documented because most terrestrial examples are heavily vegetated, or severely modified by post-depositional processes. Much research addresses the internal sedimentary characteristics, flow processes, and depositional mechanisms of ignimbrites, however, surface features of ignimbrites are less well documented and understood, except for comparatively small-volume deposits of historical eruptions. The 7700 calendar year B.P. climactic eruption of Mount Manama, USA, vented 50 km3 of magma, deposited first as rhyodacite pumice fall and then as a zoned rhyodacite-to-andesite ignimbrite as Crater Lake caldera collapsed. Lidar collected during summer 2010 reveals the remarkably well-preserved surface of the Manama ignimbrite and related deposits surrounding Crater Lake caldera in unprecedented detail despite forest cover. The ± 1 m lateral and ± 4 cm vertical resolution lidar allows surface morphologies to be classified. Surface morphologies are created by internal depositional processes and can point to the processes at work when pyroclastic flows come to rest. We describe nine surface features including furrow-ridge sets and wedge-shaped mounds in pumice fall eroded by high-energy pyroclastic surges, flow-parallel ridges that record the passage of multiple pyroclastic flows, perched benches of marginal deposits stranded by more-mobile pyroclastic-flow cores, hummocks of dense clasts interpreted as lag deposit, transverse ridges that mark the compression and imbrication of flows as they came to rest, scarps indicating ignimbrite remobilization, fields of closely spaced pits caused by phreatic explosions, fractures and cracks due to extensional processes resulting from ignimbrite volume loss, and stream channels eroded in the newly formed surface. The nine morphologies presented here illustrate a dynamic depositional environment that varied spatially and with time during the eruption, and show that multiple processes modified the ignimbrite after deposition, both during and after the eruption.

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.

Spatial vent opening probability map of El Hierro Island (Canary Islands, Spain)

NASA Astrophysics Data System (ADS)

Becerril, Laura; Cappello, Annalisa; Galindo, Inés; Neri, Marco; Del Negro, Ciro

2013-04-01

The assessment of the probable spatial distribution of new eruptions is useful to manage and reduce the volcanic risk. It can be achieved in different ways, but it becomes especially hard when dealing with volcanic areas less studied, poorly monitored and characterized by a low frequent activity, as El Hierro. Even though it is the youngest of the Canary Islands, before the 2011 eruption in the "Las Calmas Sea", El Hierro had been the least studied volcanic Island of the Canaries, with more historically devoted attention to La Palma, Tenerife and Lanzarote. We propose a probabilistic method to build the susceptibility map of El Hierro, i.e. the spatial distribution of vent opening for future eruptions, based on the mathematical analysis of the volcano-structural data collected mostly on the Island and, secondly, on the submerged part of the volcano, up to a distance of ~10-20 km from the coast. The volcano-structural data were collected through new fieldwork measurements, bathymetric information, and analysis of geological maps, orthophotos and aerial photographs. They have been divided in different datasets and converted into separate and weighted probability density functions, which were then included in a non-homogeneous Poisson process to produce the volcanic susceptibility map. Future eruptive events on El Hierro is mainly concentrated on the rifts zones, extending also beyond the shoreline. The major probabilities to host new eruptions are located on the distal parts of the South and West rifts, with the highest probability reached in the south-western area of the West rift. High probabilities are also observed in the Northeast and South rifts, and the submarine parts of the rifts. This map represents the first effort to deal with the volcanic hazard at El Hierro and can be a support tool for decision makers in land planning, emergency plans and civil defence actions.

Quantification of the Intrusion Process at Kïlauea Volcano, Hawai'I

NASA Astrophysics Data System (ADS)

Wright, T. L.; Marsh, B. D.

2014-12-01

Knowing the time between initial intrusion and later eruption of a given volume of differentiated magma is key to evaluating the connections among magma transport and emplacement, solidification and differentiation, and melt extraction and eruption. Cooling rates for two Kïlauea lava lakes as well as known parent composition and residence times for intrusions that resulted in fractionated lavas later erupted on the East Rift Zone in 1955 (34 years) and 1977 (22 years) allow intrusion dimensions to be calculated. We model intrusions beneath Kïlauea's East Rift Zone near their point of separation from the magma transport path at ~ 5 km depth using Jaeger's (1957) method calibrated against Alae and Makaopuhi lava lakes with wallrock temperatures above the curie point at 450-550°C. Minimum thicknesses of 50-70 meters are found for intrusions that fed the two fractionated lavas, as well as for long-lived magma bodies identified from geodetic monitoring during many East Rift eruptions. These intrusions began as dikes, but probably became sills or laccolithic bodies that remained near the transport path. Short-lived intrusions also arrested near the magma transport path, but that retain a dike geometry, are hypothesized to serve as a trigger for the small but discrete increments of seaward movement on Kïlauea's south flank that characterize slow-slip earthquakes. Two additional thoughts arise from the quantitative modeling of magma cooling. First, long-term heating of the wallrock surrounding the horizontal East Rift Zone transport path slows the rate of cooling within the conduit, possibly contributing to the longevity of the East Rift eruption that began in 1983. Second, the combined effects of heating of the wall rock and ever-increasing magma supply rate from the mantle may have forced breakdown and widening of the vertical transport conduit, which could explain the 5-15-km deep long-period earthquake swarms beneath Kīlauea's summit between 1987 and 1992.

The Campi Flegrei Deep Drilling Project: using borehole measurements to discriminate magmatic and geothermal effects in caldera unrest

NASA Astrophysics Data System (ADS)

De Natale, Giuseppe; Troise, Claudia; Carlino, Stefano; Troiano, Antonio; Giulia Di Giuseppe, Maria; Piochi, Monica; Somma, Renato; Tramelli, Anna; Kilburn, Christopher

2015-04-01

Large calderas are potentially the most risky volcanic areas in the world since they are capable of producing huge eruptions whose major effects can involve human life and activities from regional to global scale. Calderas worldwide are characterized by frequent episodes of unrest which, only in few cases, culminate with eruptions. This ambiguous behavior is generally explained in terms of magma intrusion or disturbance of geothermal fluids in the shallow crust, which are both source of ground deformations and seismicity. A major goal is to determine the relative contribution of each process, because the potential for eruptions significantly enhanced if magma movements emerge as the primary component. A very important case study is the active Campi Flegrei caldera, hosting part of the large city of Naples (Southern Italy). In the framework of the Campi Flegrei Deep Drilling Project new filed data from pilot borehole have been recorded (permeability and in situ stress) by using a novel procedure of Leak Off Test. These new data, particularly the actual permeability, are fundamental to calibrate the caldera unrest models at Campi Flegrei and, , to put constrains to forecast the maximum future eruptive scenario. We show here that these new data, integrated by fluid-dynamical modeling, allow to assess that only about a third of the maximum uplift recorded in 1982-1984 may be due to shallow aquifer perturbation, so that the remaining part should be due to magma inflow, corresponding to about 0.05 Km3 of new magma if we assume a sill-like reservoir located at 4 km of depth. Considering an almost equivalent magma inflow for the 1969-1972 unrest, which showed a similar uplift, we got a total magma inflow of 0.1 Km3. It is then very important to assess the times for cooling of such accumulated magma, in order to assess the eruption hazard.

Using rocks to reveal the inner workings of magma chambers below volcanoes in Alaska’s National Parks

USGS Publications Warehouse

Coombs, Michelle L.; Bacon, Charles R.

2012-01-01

Alaska is one of the most vigorously volcanic regions on the planet, and Alaska’s national parks are home to many of the state’s most active volcanoes. These pose both local and more distant hazards in the form of lava and pyroclastic flows, lahars (mudflows), ash clouds, and ash fall. Alaska’s volcanoes lie along the arc of the Aleutian-Alaskan subduction zone, caused as the oceanic Pacific plate moves northward and dips below the North American plate. These volcanoes form as water-rich fluid from the down-going Pacific plate is released, lowering the melting temperature of rock in the overlying mantle and enabling it to partially melt. The melted rock (magma) migrates upward, collecting at the base of the approximately 25 mile (40 km) thick crust, occasionally ascending into the shallow crust, and sometimes erupting at the earth’s surface.During volcanic unrest, scientists use geophysical signals to remotely visualize volcanic processes, such as movement of magma in the upper crust. In addition, erupted volcanic rocks, which are quenched samples of magmas, can tell us about subsurface magma characteris-tics, history, and the processes that drive eruptions. The chemical compositions of and the minerals present in the erupted magmas can reveal conditions under which these magmas were stored in crustal “chambers”. Studies of the products of recent eruptions of Novarupta (1912), Aniakchak (1931), Trident (1953-74), and Redoubt (2009) volcanoes reveal the depths and temperatures of magma storage, and tell of complex interactions between magmas of different compositions. One goal of volcanology is to determine the processes that drive or trigger eruptions. Information recorded in the rocks tells us about these processes. Here, we demonstrate how geologists gain these insights through case studies from four recent eruptions of volcanoes in Alaska national parks.

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.

Seismic envelope-based detection and location of ground-coupled airwaves from volcanoes in Alaska

USGS Publications Warehouse

Fee, David; Haney, Matt; Matoza, Robin S.; Szuberla, Curt A.L.; Lyons, John; Waythomas, Christopher F.

2016-01-01

Volcanic explosions and other infrasonic sources frequently produce acoustic waves that are recorded by seismometers. Here we explore multiple techniques to detect, locate, and characterize ground‐coupled airwaves (GCA) on volcano seismic networks in Alaska. GCA waveforms are typically incoherent between stations, thus we use envelope‐based techniques in our analyses. For distant sources and planar waves, we use f‐k beamforming to estimate back azimuth and trace velocity parameters. For spherical waves originating within the network, we use two related time difference of arrival (TDOA) methods to detect and localize the source. We investigate a modified envelope function to enhance the signal‐to‐noise ratio and emphasize both high energies and energy contrasts within a spectrogram. We apply these methods to recent eruptions from Cleveland, Veniaminof, and Pavlof Volcanoes, Alaska. Array processing of GCA from Cleveland Volcano on 4 May 2013 produces robust detection and wave characterization. Our modified envelopes substantially improve the short‐term average/long‐term average ratios, enhancing explosion detection. We detect GCA within both the Veniaminof and Pavlof networks from the 2007 and 2013–2014 activity, indicating repeated volcanic explosions. Event clustering and forward modeling suggests that high‐resolution localization is possible for GCA on typical volcano seismic networks. These results indicate that GCA can be used to help detect, locate, characterize, and monitor volcanic eruptions, particularly in difficult‐to‐monitor regions. We have implemented these GCA detection algorithms into our operational volcano‐monitoring algorithms at the Alaska Volcano Observatory.

Variations in eruptive style and depositional processes of Neoproterozoic terrestrial volcano-sedimentary successions in the Hamid area, North Eastern Desert, Egypt

NASA Astrophysics Data System (ADS)

Khalaf, Ezz El Din Abdel Hakim

2013-07-01

Two contrasting Neoproterozoic volcano-sedimentary successions of ca. 600 m thickness were recognized in the Hamid area, Northeastern Desert, Egypt. A lower Hamid succession consists of alluvial sediments, coherent lava flows, pyroclastic fall and flow deposits. An upper Hamid succession includes deposits from pyroclastic density currents, sills, and dykes. Sedimentological studies at different scales in the Hamid area show a very complex interaction of fluvial, eruptive, and gravitational processes in time and space and thus provided meaningful insights into the evolution of the rift sedimentary environments and the identification of different stages of effusive activity, explosive activity, and relative quiescence, determining syn-eruptive and inter-eruptive rock units. The volcano-sedimentary deposits of the study area can be ascribed to 14 facies and 7 facies associations: (1) basin-border alluvial fan, (2) mixed sandy fluvial braid plain, (3) bed-load-dominated ephemeral lake, (4) lava flows and volcaniclastics, (5) pyroclastic fall deposits, (6) phreatomagmatic volcanic deposits, and (7) pyroclastic density current deposits. These systems are in part coeval and in part succeed each other, forming five phases of basin evolution: (i) an opening phase including alluvial fan and valley flooding together with a lacustrine period, (ii) a phase of effusive and explosive volcanism (pulsatory phase), (iii) a phase of predominant explosive and deposition from base surges (collapsing phase), and (iv) a phase of caldera eruption and ignimbrite-forming processes (climactic phase). The facies architectures record a change in volcanic activity from mainly phreatomagmatic eruptions, producing large volumes of lava flows and pyroclastics (pulsatory and collapsing phase), to highly explosive, pumice-rich plinian-type pyroclastic density current deposits (climactic phase). Hamid area is a small-volume volcano, however, its magma compositions, eruption styles, and inter-eruptive breaks suggest, that it closely resembles a volcanic architecture commonly associated with large, composite volcanoes.

Detection of plumes at Redoubt and Etna volcanoes using the GPS SNR method

NASA Astrophysics Data System (ADS)

Larson, Kristine M.; Palo, Scott; Roesler, Carolyn; Mattia, Mario; Bruno, Valentina; Coltelli, Mauro; Fee, David

2017-09-01

Detection and characterization of volcanic eruptions is important both for public health and aircraft safety. A variety of ground sensors are used to monitor volcanic eruptions. Data from these ground sensors are subsequently incorporated into models that predict the movement of ash. Here a method to detect volcanic plumes using GPS signals is described. Rather than carrier phase data used by geodesists, the method takes advantage of attenuations in signal to noise ratio (SNR) data. Two datasets are evaluated: the 2009 Redoubt Volcano eruptions and the 2013/2015 eruptions at Mt. Etna. SNR-based eruption durations are compared with previously published seismic, infrasonic, and radar studies at Redoubt Volcano. SNR-based plume detections from Mt. Etna are compared with L-band radar and tremor observations. To place these SNR observations from Redoubt and Etna in context, a model of the propagation of GPS signals through both water/water vapor and tephra is developed. Neither water nor fine ash particles will produce the observed attenuation of GPS signals, while scattering caused by particles > 1 cm in diameter potentially could.

The eruptive history and magmatic evolution of Aluto volcano: new insights into silicic peralkaline volcanism in the Ethiopian rift

NASA Astrophysics Data System (ADS)

Hutchison, William; Pyle, David M.; Mather, Tamsin A.; Yirgu, Gezahegn; Biggs, Juliet; Cohen, Benjamin E.; Barfod, Dan N.; Lewi, Elias

2016-12-01

The silicic peralkaline volcanoes of the East African Rift are some of the least studied volcanoes on Earth. Here we bring together new constraints from fieldwork, remote sensing, geochronology and geochemistry to present the first detailed account of the eruptive history of Aluto, a restless silicic volcano located in a densely populated section of the Main Ethiopian Rift. Prior to the growth of the Aluto volcanic complex (before 500 ka) the region was characterized by a significant period of fault development and mafic fissure eruptions. The earliest volcanism at Aluto built up a trachytic complex over 8 km in diameter. Aluto then underwent large-volume ignimbrite eruptions at 316 ± 19 ka and 306 ± 12 ka developing a 42 km2 collapse structure. After a hiatus of 250 ka, a phase of post-caldera volcanism initiated at 55 ± 19 ka and the most recent eruption of Aluto has a radiocarbon age of 0.40 ± 0.05 cal. ka BP. During this post-caldera phase highly-evolved peralkaline rhyolite lavas, ignimbrites and pumice fall deposits have erupted from vents across the complex. Geochemical modelling is consistent with rhyolite genesis from protracted fractionation (> 80%) of basalt that is compositionally similar to rift-related basalts found east of the complex. Based on the style and volume of recent eruptions we suggest that silicic eruptions occur at an average rate of 1 per 1000 years, and that future eruptions of Aluto will involve explosive emplacement of localised pumice cones and effusive obsidian coulees of volumes in the range 1-100 × 106 m3.

Assessing future vent opening locations at the Somma-Vesuvio volcanic complex: 1. A new information geodatabase with uncertainty characterizations

NASA Astrophysics Data System (ADS)

Tadini, A.; Bisson, M.; Neri, A.; Cioni, R.; Bevilacqua, A.; Aspinall, W. P.

2017-06-01

This study presents new and revised data sets about the spatial distribution of past volcanic vents, eruptive fissures, and regional/local structures of the Somma-Vesuvio volcanic system (Italy). The innovative features of the study are the identification and quantification of important sources of uncertainty affecting interpretations of the data sets. In this regard, the spatial uncertainty of each feature is modeled by an uncertainty area, i.e., a geometric element typically represented by a polygon drawn around points or lines. The new data sets have been assembled as an updatable geodatabase that integrates and complements existing databases for Somma-Vesuvio. The data are organized into 4 data sets and stored as 11 feature classes (points and lines for feature locations and polygons for the associated uncertainty areas), totaling more than 1700 elements. More specifically, volcanic vent and eruptive fissure elements are subdivided into feature classes according to their associated eruptive styles: (i) Plinian and sub-Plinian eruptions (i.e., large- or medium-scale explosive activity); (ii) violent Strombolian and continuous ash emission eruptions (i.e., small-scale explosive activity); and (iii) effusive eruptions (including eruptions from both parasitic vents and eruptive fissures). Regional and local structures (i.e., deep faults) are represented as linear feature classes. To support interpretation of the eruption data, additional data sets are provided for Somma-Vesuvio geological units and caldera morphological features. In the companion paper, the data presented here, and the associated uncertainties, are used to develop a first vent opening probability map for the Somma-Vesuvio caldera, with specific attention focused on large or medium explosive events.

Forecasting volcanic ash dispersal and coeval resuspension during the April-May 2015 Calbuco eruption

NASA Astrophysics Data System (ADS)

Reckziegel, F.; Bustos, E.; Mingari, L.; Báez, W.; Villarosa, G.; Folch, A.; Collini, E.; Viramonte, J.; Romero, J.; Osores, S.

2016-07-01

Atmospheric dispersion of volcanic ash from explosive eruptions or from subsequent fallout deposit resuspension causes a range of impacts and disruptions on human activities and ecosystems. The April-May 2015 Calbuco eruption in Chile involved eruption and resuspension activities. We overview the chronology, effects, and products resulting from these events, in order to validate an operational forecast strategy for tephra dispersal. The modelling strategy builds on coupling the meteorological Weather Research and Forecasting (WRF/ARW) model with the FALL3D dispersal model for eruptive and resuspension processes. The eruption modelling considers two distinct particle granulometries, a preliminary first guess distribution used operationally when no field data was available yet, and a refined distribution based on field measurements. Volcanological inputs were inferred from eruption reports and results from an Argentina-Chilean ash sample data network, which performed in-situ sampling during the eruption. In order to validate the modelling strategy, results were compared with satellite retrievals and ground deposit measurements. Results indicate that the WRF-FALL3D modelling system can provide reasonable forecasts in both eruption and resuspension modes, particularly when the adjusted granulometry is considered. The study also highlights the importance of having dedicated datasets of active volcanoes furnishing first-guess model inputs during the early stages of an eruption.

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

NASA Astrophysics Data System (ADS)

Caudron, Corentin; Taisne, Benoit; Kugaenko, Yulia; Saltykov, Vadim

2015-12-01

In contrast of the 1975-76 Tolbachik eruption, the 2012-13 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 movement prior to this important eruption. A clear seismic migration within the seismic swarm, started 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 flows, was recorded (at 11:00 UTC, 27 November 2012). In order to get a first order approximation of the magma location, we compare the calculated seismic intensity ratios with the theoretical ones. As expected, the observations suggest that the seismicity migrated toward the eruption location. However, we explain the pre-eruptive observed ratios by a vertical migration under the northern slope of Plosky Tolbachik volcano followed by a 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.

Crystallization Conditions at Cascade and Other Arc Volcanoes: The Role of Recharge, and Ultimate, Proximal and Immediate Causes of Eruption

NASA Astrophysics Data System (ADS)

Putirka, K. D.

2016-12-01

A number of hypotheses have been offered to explain why volcanoes erupt. These include magma mixing, mafic recharge, or partial crystallization, any of which can drive parts or all of a system to vapor saturation, and so add to a magma's buoyancy. Age dates indicate long pre-eruption storage times for felsic magmas erupted at arcs, indicating that mafic recharge magmas, which can reinvigorate such systems, is a possible eruption trigger. However, plutonic systems reveal numerous recharge events that have no obvious ties to eruption (Coint et al. 2013; Putirka et al. 2014). And crystallization conditions at some arc systems support the implicit view, that recharge might be a necessary, but not a sufficient condition for eruption. At several Cascade volcanoes, Cpx and Amp crystals record coolings of 100-300oC. The Cpx grains derive exclusively from mafic enclaves, while Amp grains derive from both host and enclave materials. These considerable coolings call for a time lag following recharge, and indicate that vapor saturation is a proximal, although not necessarily an immediate cause of eruption. But we cannot discount recharge altogether. At the Cascades and at other arcs, Cpx crystalizes throughout the middle and upper crust, mostly from the surface down to 15 km. And high Fo olivine grains provide evidence for very hot magmas that intrude the upper mantle and lower crust, and possibly the middle crust, if hydrous. Volcanic pathways thus clearly extend into the middle crust, and at times, well below the Moho. It is unclear to what extent these deep pathways are hydraulically connected to the surface, or the role of deep-seated processes in initiating or sustaining eruptions. Progress in understanding these pathways, and triggering mechanisms, requires our differentiating "ultimate", "proximal" and "immediate" causes, and determining which of various magmatic processes provide necessary or sufficient conditions for eruption.

Petrologic constraints on rift-zone processes - Results from episode 1 of the Puu Oo eruption of Kilauea volcano, Hawaii

USGS Publications Warehouse

Garcia, M.O.; Ho, R.A.; Rhodes, J.M.; Wolfe, E.W.

1989-01-01

The Puu Oo eruption in the middle of Kilauea volcano's east rift zone provides an excellent opportunity to utilize petrologic constraints to interpret rift-zone processes. Emplacement of a dike began 24 hours before the start of the eruption on 3 January 1983. Seismic and geodetic evidence indicates that the dike collided with a magma body in the rift zone. Most of the lava produced during the initial episode of the Puu Oo eruption is of hybrid composition, with petrographic and geochemical evidence of mixing magmas of highly evllved and more mafic compositions. Some olivine and plagioclase grains in the hybrid lavas show reverse zoning. Whole-rock compositional variations are linear even for normally compatible elements like Ni and Cr. Leastsquares mixing calculations yield good residuals for major and trace element analyses for magma mixing. Crystal fractionation calculations yield unsatisfactory residuals. The highly evolved magma is similar in composition to the lava from the 1977 eruption and, at one point, vents for these two eruptions are only 200 m apart. Possibly both the 1977 lava and the highly evolved component of the episode 1 Puu Oo lava were derived from a common body of rift-zone-stored magma. The more mafic mixing component may be represented by the most mafic lava from the January 1983 eruption; it shows no evidence of magma mixing. The dike that was intruded just prior to the start of the Puu Oo eruption may have acted as a hydraulic plunger causing mixing of the two rift-zone-stored magmas. ?? 1989 Springer-Verlag.

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.

The 2008 phreatomagmatic eruption of Okmok volcano, Aleutian Islands, Alaska: Chronology, deposits, and landform changes

USGS Publications Warehouse

Jessica Larsen,; Neal, Christina; Schaefer, Janet R.; Kaufman, Max; Lu, Zhong

2015-01-01

Okmok volcano, Aleutian Islands, Alaska, explosively erupted over a five-week period between July 12 and August 23, 2008. The eruption was predominantly phreatomagmatic, producing fine-grained tephra that covered most of northeastern Umnak Island. The eruption had a maximum Volcanic Explosivity Index (VEI) of 4, with eruption column heights up to 16 km during the opening phase. Several craters and a master tuff cone formed in the caldera as a result of phreatomagmatic explosions and accumulated tephra-fall and surge deposits. Ascending magma continuously interacted with an extensive shallow groundwater table in the caldera, resulting in the phreatomagmatic character of the eruption. Syneruptive explosion and collapse processes enlarged a pre-existing lake, created a second, entirely new lake, and formed new, deep craters. A field of ephemeral collapse pits and collapse escarpments formed where rapid groundwater withdrawal removed material from beneath capping lava flows. This was the first significant phreatomagmatic event in the U.S. since the Ukinrek Maars eruption in 1977.

Reduced cooling following future volcanic eruptions

NASA Astrophysics Data System (ADS)

Hopcroft, Peter O.; Kandlbauer, Jessy; Valdes, Paul J.; Sparks, R. Stephen J.

2017-11-01

Volcanic eruptions are an important influence on decadal to centennial climate variability. Large eruptions lead to the formation of a stratospheric sulphate aerosol layer which can cause short-term global cooling. This response is modulated by feedback processes in the earth system, but the influence from future warming has not been assessed before. Using earth system model simulations we find that the eruption-induced cooling is significantly weaker in the future state. This is predominantly due to an increase in planetary albedo caused by increased tropospheric aerosol loading with a contribution from associated changes in cloud properties. The increased albedo of the troposphere reduces the effective volcanic aerosol radiative forcing. Reduced sea-ice coverage and hence feedbacks also contribute over high-latitudes, and an enhanced winter warming signal emerges in the future eruption ensemble. These findings show that the eruption response is a complex function of the environmental conditions, which has implications for the role of eruptions in climate variability in the future and potentially in the past.

Understanding the plume dynamics of explosive super-eruptions.

PubMed

Costa, Antonio; J Suzuki, Yujiro; Koyaguchi, Takehiro

2018-02-13

Explosive super-eruptions can erupt up to thousands of km 3 of magma with extremely high mass flow rates (MFR). The plume dynamics of these super-eruptions are still poorly understood. To understand the processes operating in these plumes we used a fluid-dynamical model to simulate what happens at a range of MFR, from values generating intense Plinian columns, as did the 1991 Pinatubo eruption, to upper end-members resulting in co-ignimbrite plumes like Toba super-eruption. Here, we show that simple extrapolations of integral models for Plinian columns to those of super-eruption plumes are not valid and their dynamics diverge from current ideas of how volcanic plumes operate. The different regimes of air entrainment lead to different shaped plumes. For the upper end-members can generate local up-lifts above the main plume (over-plumes). These over-plumes can extend up to the mesosphere. Injecting volatiles into such heights would amplify their impact on Earth climate and ecosystems.

A novel approach to estimate the eruptive potential and probability in open conduit volcanoes

PubMed Central

De Gregorio, Sofia; Camarda, Marco

2016-01-01

In open conduit volcanoes, volatile-rich magma continuously enters into the feeding system nevertheless the eruptive activity occurs intermittently. From a practical perspective, the continuous steady input of magma in the feeding system is not able to produce eruptive events alone, but rather surplus of magma inputs are required to trigger the eruptive activity. The greater the amount of surplus of magma within the feeding system, the higher is the eruptive probability.Despite this observation, eruptive potential evaluations are commonly based on the regular magma supply, and in eruptive probability evaluations, generally any magma input has the same weight. Conversely, herein we present a novel approach based on the quantification of surplus of magma progressively intruded in the feeding system. To quantify the surplus of magma, we suggest to process temporal series of measurable parameters linked to the magma supply. We successfully performed a practical application on Mt Etna using the soil CO2 flux recorded over ten years. PMID:27456812

A novel approach to estimate the eruptive potential and probability in open conduit volcanoes.

PubMed

De Gregorio, Sofia; Camarda, Marco

2016-07-26

In open conduit volcanoes, volatile-rich magma continuously enters into the feeding system nevertheless the eruptive activity occurs intermittently. From a practical perspective, the continuous steady input of magma in the feeding system is not able to produce eruptive events alone, but rather surplus of magma inputs are required to trigger the eruptive activity. The greater the amount of surplus of magma within the feeding system, the higher is the eruptive probability.Despite this observation, eruptive potential evaluations are commonly based on the regular magma supply, and in eruptive probability evaluations, generally any magma input has the same weight. Conversely, herein we present a novel approach based on the quantification of surplus of magma progressively intruded in the feeding system. To quantify the surplus of magma, we suggest to process temporal series of measurable parameters linked to the magma supply. We successfully performed a practical application on Mt Etna using the soil CO2 flux recorded over ten years.

A multi-source probabilistic hazard assessment of tephra dispersal in the Neapolitan area

NASA Astrophysics Data System (ADS)

Sandri, Laura; Costa, Antonio; Selva, Jacopo; Folch, Arnau; Macedonio, Giovanni; Tonini, Roberto

2015-04-01

In this study we present the results obtained from a long-term Probabilistic Hazard Assessment (PHA) of tephra dispersal in the Neapolitan area. Usual PHA for tephra dispersal needs the definition of eruptive scenarios (usually by grouping eruption sizes and possible vent positions in a limited number of classes) with associated probabilities, a meteorological dataset covering a representative time period, and a tephra dispersal model. PHA then results from combining simulations considering different volcanological and meteorological conditions through weights associated to their specific probability of occurrence. However, volcanological parameters (i.e., erupted mass, eruption column height, eruption duration, bulk granulometry, fraction of aggregates) typically encompass a wide range of values. Because of such a natural variability, single representative scenarios or size classes cannot be adequately defined using single values for the volcanological inputs. In the present study, we use a method that accounts for this within-size-class variability in the framework of Event Trees. The variability of each parameter is modeled with specific Probability Density Functions, and meteorological and volcanological input values are chosen by using a stratified sampling method. This procedure allows for quantifying hazard without relying on the definition of scenarios, thus avoiding potential biases introduced by selecting single representative scenarios. Embedding this procedure into the Bayesian Event Tree scheme enables the tephra fall PHA and its epistemic uncertainties. We have appied this scheme to analyze long-term tephra fall PHA from Vesuvius and Campi Flegrei, in a multi-source paradigm. We integrate two tephra dispersal models (the analytical HAZMAP and the numerical FALL3D) into BET_VH. The ECMWF reanalysis dataset are used for exploring different meteorological conditions. The results obtained show that PHA accounting for the whole natural variability are consistent with previous probabilities maps elaborated for Vesuvius and Campi Flegrei on the basis of single representative scenarios, but show significant differences. In particular, the area characterized by a 300 kg/m2-load exceedance probability larger than 5%, accounting for the whole range of variability (that is, from small violent strombolian to plinian eruptions), is similar to that displayed in the maps based on the medium magnitude reference eruption, but it is of a smaller extent. This is due to the relatively higher weight of the small magnitude eruptions considered in this study, but neglected in the reference scenario maps. On the other hand, in our new maps the area characterized by a 300 kg/m2-load exceedance probability larger than 1% is much larger than that of the medium magnitude reference eruption, due to the contribution of plinian eruptions at lower probabilities, again neglected in the reference scenario maps.

Hydrovolcanic ash emission between August 14 and 24, 2015 at Cotopaxi volcano (Ecuador): Characterization and eruption mechanisms

NASA Astrophysics Data System (ADS)

Troncoso, Liliana; Bustillos, Jorge; Romero, Jorge E.; Guevara, Alicia; Carrillo, Janina; Montalvo, Estefano; Izquierdo, Tatiana

2017-07-01

Cotopaxi is an active, hazardous and ice-covered stratovolcano 60 km southeast of Quito, (Ecuador) whose last major eruption occurred in 1877. During 2001-2002, volcanic unrest characterized by volcanic seismicity and deformation ended without eruptive activity. On April 2015, a new increase of seismicity, SO2 emissions, thermal anomalies and edifice deformation, evolved into the onset of a new eruptive cycle, beginning August 14. We sampled and measured the ash fall deposits to the west of Cotopaxi between August 14 and 24, 2015. The ash collected was analyzed using grain size, X-Ray fluorescence, X-Ray diffraction and scanning electron microscope (SEM-EDS), revealing the eruptive products to be compound of dense fragments (mostly lithics), diverse types of scoria, pumice, free fractured crystals, glassy particles and aggregates. Most of hydrothermal alteration is observed during the initial stage of the eruption (14-15 August; including Cu oxides and Fe minerals in the lithics). The glassy particles were blocky morphology, and textural changes were recognized over 10 days of eruption, varying from null or low vesicularity to low-to-moderate vesicularity, occasionally exhibiting molten or subrounded textures. The bulk ash has a basaltic-andesitic composition ( 55.67 wt% of SiO2), while clusters of selected particles (likely juvenile) analyzed through SEM + EDS reveal dacitic composition (65.67 and 65.8 wt% SiO2). Plagioclase, clinopyroxene and orthopyroxene are the main minerals present, with accessory anhydrite, melanterite and pyrite (these typically observed during the initial stage of eruption). These variations in addition to the geophysical background, led us to interpret this eruption as the result of the volcano's hydrothermal system disruption due to a shallow, low-volume magma input, which initially evolved into phreatic activity at surface level. Further activity up to 24 August was triggered by the indirect interaction between magma and the depleted hydrothermal system, generating a magmatic-hydrothermal eruption. The issue is important for evaluating unrest periods at active stratovolcanoes, and the impact of their initial, low-volume ash falls in neighboring communities. b. N° 3. Actualización de la actividad (11 de Junio de 2015). c. N° 5. Incremento en la actividad (14 de Agosto de 2015). d. N° 6. Incremento en la actividad (14 de Agosto de 2015). e. N° 9. Análisis de la actividad del volcán Cotopaxi y propuesta de escenarios (21 de Agosto de 2015). f. N° 14 Observaciones visuales y térmicas del volcán, disminución de la energía sísmica y características de las cenizas analizadas (05 de Septiembre de 2015)

Magma decompression rates during explosive eruptions of Kīlauea volcano, Hawaii, recorded by melt embayments

USGS Publications Warehouse

Ferguson, David J.; Gonnermann, Helge M.; Ruprecht, Philipp; Plank, Terry; Hauri, Erik H.; Houghton, Bruce F.; Swanson, Donald A.

2016-01-01

The decompression rate of magma as it ascends during volcanic eruptions is an important but poorly constrained parameter that controls many of the processes that influence eruptive behavior. In this study, we quantify decompression rates for basaltic magmas using volatile diffusion in olivine-hosted melt tubes (embayments) for three contrasting eruptions of Kīlauea volcano, Hawaii. Incomplete exsolution of H2O, CO2, and S from the embayment melts during eruptive ascent creates diffusion profiles that can be measured using microanalytical techniques, and then modeled to infer the average decompression rate. We obtain average rates of ~0.05–0.45 MPa s−1 for eruptions ranging from Hawaiian style fountains to basaltic subplinian, with the more intense eruptions having higher rates. The ascent timescales for these magmas vary from around ~5 to ~36 min from depths of ~2 to ~4 km, respectively. Decompression-exsolution models based on the embayment data also allow for an estimate of the mass fraction of pre-existing exsolved volatiles within the magma body. In the eruptions studied, this varies from 0.1 to 3.2 wt% but does not appear to be the key control on eruptive intensity. Our results do not support a direct link between the concentration of pre-eruptive volatiles and eruptive intensity; rather, they suggest that for these eruptions, decompression rates are proportional to independent estimates of mass discharge rate. Although the intensity of eruptions is defined by the discharge rate, based on the currently available dataset of embayment analyses, it does not appear to scale linearly with average decompression rate. This study demonstrates the utility of the embayment method for providing quantitative constraints on magma ascent during explosive basaltic eruptions.

Magma decompression rates during explosive eruptions of Kīlauea volcano, Hawaii, recorded by melt embayments

NASA Astrophysics Data System (ADS)

Ferguson, David J.; Gonnermann, Helge M.; Ruprecht, Philipp; Plank, Terry; Hauri, Erik H.; Houghton, Bruce F.; Swanson, Donald A.

2016-10-01

The decompression rate of magma as it ascends during volcanic eruptions is an important but poorly constrained parameter that controls many of the processes that influence eruptive behavior. In this study, we quantify decompression rates for basaltic magmas using volatile diffusion in olivine-hosted melt tubes (embayments) for three contrasting eruptions of Kīlauea volcano, Hawaii. Incomplete exsolution of H2O, CO2, and S from the embayment melts during eruptive ascent creates diffusion profiles that can be measured using microanalytical techniques, and then modeled to infer the average decompression rate. We obtain average rates of ~0.05-0.45 MPa s-1 for eruptions ranging from Hawaiian style fountains to basaltic subplinian, with the more intense eruptions having higher rates. The ascent timescales for these magmas vary from around ~5 to ~36 min from depths of ~2 to ~4 km, respectively. Decompression-exsolution models based on the embayment data also allow for an estimate of the mass fraction of pre-existing exsolved volatiles within the magma body. In the eruptions studied, this varies from 0.1 to 3.2 wt% but does not appear to be the key control on eruptive intensity. Our results do not support a direct link between the concentration of pre-eruptive volatiles and eruptive intensity; rather, they suggest that for these eruptions, decompression rates are proportional to independent estimates of mass discharge rate. Although the intensity of eruptions is defined by the discharge rate, based on the currently available dataset of embayment analyses, it does not appear to scale linearly with average decompression rate. This study demonstrates the utility of the embayment method for providing quantitative constraints on magma ascent during explosive basaltic eruptions.

Volcanic forcing for climate modeling: a new microphysics-based data set covering years 1600-present

NASA Astrophysics Data System (ADS)

Arfeuille, F.; Weisenstein, D.; Mack, H.; Rozanov, E.; Peter, T.; Brönnimann, S.

2014-02-01

As the understanding and representation of the impacts of volcanic eruptions on climate have improved in the last decades, uncertainties in the stratospheric aerosol forcing from large eruptions are now linked not only to visible optical depth estimates on a global scale but also to details on the size, latitude and altitude distributions of the stratospheric aerosols. Based on our understanding of these uncertainties, we propose a new model-based approach to generating a volcanic forcing for general circulation model (GCM) and chemistry-climate model (CCM) simulations. This new volcanic forcing, covering the 1600-present period, uses an aerosol microphysical model to provide a realistic, physically consistent treatment of the stratospheric sulfate aerosols. Twenty-six eruptions were modeled individually using the latest available ice cores aerosol mass estimates and historical data on the latitude and date of eruptions. The evolution of aerosol spatial and size distribution after the sulfur dioxide discharge are hence characterized for each volcanic eruption. Large variations are seen in hemispheric partitioning and size distributions in relation to location/date of eruptions and injected SO2 masses. Results for recent eruptions show reasonable agreement with observations. By providing these new estimates of spatial distributions of shortwave and long-wave radiative perturbations, this volcanic forcing may help to better constrain the climate model responses to volcanic eruptions in the 1600-present period. The final data set consists of 3-D values (with constant longitude) of spectrally resolved extinction coefficients, single scattering albedos and asymmetry factors calculated for different wavelength bands upon request. Surface area densities for heterogeneous chemistry are also provided.

Volcanic forcing for climate modeling: a new microphysics-based dataset covering years 1600-present

NASA Astrophysics Data System (ADS)

Arfeuille, F.; Weisenstein, D.; Mack, H.; Rozanov, E.; Peter, T.; Brönnimann, S.

2013-02-01

As the understanding and representation of the impacts of volcanic eruptions on climate have improved in the last decades, uncertainties in the stratospheric aerosol forcing from large eruptions are now not only linked to visible optical depth estimates on a global scale but also to details on the size, latitude and altitude distributions of the stratospheric aerosols. Based on our understanding of these uncertainties, we propose a new model-based approach to generating a volcanic forcing for General-Circulation-Model (GCM) and Chemistry-Climate-Model (CCM) simulations. This new volcanic forcing, covering the 1600-present period, uses an aerosol microphysical model to provide a realistic, physically consistent treatment of the stratospheric sulfate aerosols. Twenty-six eruptions were modeled individually using the latest available ice cores aerosol mass estimates and historical data on the latitude and date of eruptions. The evolution of aerosol spatial and size distribution after the sulfur dioxide discharge are hence characterized for each volcanic eruption. Large variations are seen in hemispheric partitioning and size distributions in relation to location/date of eruptions and injected SO2 masses. Results for recent eruptions are in good agreement with observations. By providing accurate amplitude and spatial distributions of shortwave and longwave radiative perturbations by volcanic sulfate aerosols, we argue that this volcanic forcing may help refine the climate model responses to the large volcanic eruptions since 1600. The final dataset consists of 3-D values (with constant longitude) of spectrally resolved extinction coefficients, single scattering albedos and asymmetry factors calculated for different wavelength bands upon request. Surface area densities for heterogeneous chemistry are also provided.

Externally triggered renewed bubble nucleation in basaltic magma: the 12 October 2008 eruption at Halema‘uma‘u Overlook vent, Kīlauea, Hawai‘i, USA

USGS Publications Warehouse

Carey, Rebecca J.; Manga, Michael; Degruyter, Wim; Swanson, Donald; Houghton, Bruce F.; Orr, Tim R.; Patrick, Matthew R.

2012-01-01

From October 2008 until present, dozens of small impulsive explosive eruptions occurred from the Overlook vent on the southeast side of Halema‘uma‘u Crater, at Kīlauea volcano, USA. These eruptions were triggered by rockfalls from the walls of the volcanic vent and conduit onto the top of the lava column. Here we use microtextural observations and data from clasts erupted during the well-characterized 12 October 2008 explosive eruption at Halema‘uma‘u to extend existing models of eruption triggering. We present a potential mechanism for this eruption by combining microtextural observations with existing geophysical and visual data sets. We measure the size and number density of bubbles preserved in juvenile ejecta using 2D images and X-ray microtomography. Our data suggest that accumulations of large bubbles with diameters of >50μm to at least millimeters existed at shallow levels within the conduit prior to the 12 October 2008 explosion. Furthermore, a high number density of small bubbles <50 μm is measured in the clasts, implying very rapid nucleation of bubbles. Visual observations, combined with preexisting geophysical data, suggest that the impact of rockfalls onto the magma free surface induces pressure changes over short timescales that (1) nucleated new additional bubbles in the shallow conduit leading to high number densities of small bubbles and (2) expanded the preexisting bubbles driving upward acceleration. The trigger of eruption and bubble nucleation is thus external to the degassing system.

Satellite thermal and tilt measurements of the 2007 - 2008 eruptive period at Kilauea volcano: Implications for down rift magma transport

NASA Astrophysics Data System (ADS)

Steffke, A. M.; Harris, A. J.

2010-12-01

The 2007-2008 eruptive period at Kilauea volcano, Hawai‘i, was characterized by frequent changes in style, location and intensity of effusive activity. We use thermal data from the GOES-Imager and MODIS to investigate three particularly interesting eruptive periods: (1) June 17 - July 4, 2007 (the Father’s Day eruption), (2) July 21 - August 5, 2007, and (3) August 6 - 11, 2008. Each of these eruptive periods were accompanied by deflation-inflation events (DI events) at the summit of Kilauea, with a delayed increase in activity at Pu `u `O`o, indicating the arrival of new magma at the eruption sites, some 20 km distant from the summit, following each DI event. Arrival of new magma, and the associated increase in effusive activity, is apparent in the satellite data as an increase in the thermal intensity of the recorded hot spot. This allows us to time the arrival of new magma (or its pressure pulse) down the rift zone that connects the summit and the eruption site over a time scale of hours, or in the case of GOES data - 15 minutes. We can compare the satellite-derived thermal intensity time series with the deflation and inflation events occurring at the summit to determine transit times for the response down rift. Using both the satellite and tilt measurements, the volumes of magma entering and exiting the system can also be compared, with the satellite data giving the volume subsequently erupted down rift at Pu`u `O`o and across the active lava flow field.

Preliminary impact assessment of effusive eruptions at Etna volcano

NASA Astrophysics Data System (ADS)

Cappello, Annalisa; Michaud-Dubuy, Audrey; Branca, Stefano; De Beni, Emanuela; Del Negro, Ciro

2016-04-01

Lava flows are a recurring and widespread form of volcanic activity that threaten people and property around the world. The growing demographic congestion around volcanic structures increases the potential risks and costs that lava flows represent, and leads to a pressing need for faster and more accurate assessment of lava flow impact. To fully evaluate potential effects and losses that an effusive eruption may cause to society, property and environment, it is necessary to consider the hazard, the distribution of the exposed elements at stake and the associated vulnerability. Lava flow hazard assessment is at an advanced state, whereas comprehensive vulnerability assessment is lacking. Cataloguing and analyzing volcanic impacts provide insight on likely societal and physical vulnerabilities during future eruptions. Here we quantify the lava flow impact of two past main effusive eruptions of Etna volcano: the 1669, which is the biggest and destructive flank eruption to have occurred on Etna in historical time, and the 1981, lasting only 6 days, but characterized by an intense eruptive dynamics. Different elements at stake are considered, including population, hospitals, critical facilities, buildings of historic value, industrial infrastructures, gas and electricity networks, railways, roads, footways and finally land use. All these elements were combined with the 1669 and 1981 lava flow fields to quantify the social damage and economic loss.

Bottom Characterization with High Resolution Sonar Data and Geochemical Analyses of an Uninvestigated Cone in Lagoa das Furnas on São Miguel Island, Azores Archipelago

NASA Astrophysics Data System (ADS)

Andersson, T.

2015-12-01

Lagoa das Furnas is a crater lake located in an area exposed to geohazards from earthquakes and volcanic activity on the island São Miguel in the Azores Archipelago. The Furnas volcanic center has a long history of earthquakes and volcanic activity. The area is relatively well studied except for the lake floor. Therefore, a high resolution geophysical and geological mapping survey was conducted at Lagoa das Furnas. Sidescan sonar was used to map the surface of the lake floor and single beam sonar was used to acquire sub-bottom profiles. In addition to the geophysical mapping, sediment surface sampling and core drilling were carried out followed by geochemical analyses of the retrieved material. The mapped data permitted a characterization of the floor of Lagoa das Furnas and revealed several volcanic features including fumarolic activity and a previously uninvestigated volcanic cone in the southern part of the lake. In order to unravel the origin of this cone several methods were applied, including analyses of tephra and minerals collected from the cone itself and from nearby deposits of two known eruptions, Furnas I and Furnas 1630. Sedimentological, petrological, geochemical and geochronological studies of pyroclastic deposits from the cone suggest a subaqueous eruption linked to the Furnas 1630 eruption. The chemistry of glass and crystal fragments sampled from the cone suggests that it is composed of more evolved magma than that of the main Furnas 1630, implying that the lake cone is likely a product of the last eruptional phase. According to historical records, two of three lakes were lost due the Furnas 1630 eruption. The results of this study show that the remaining lake is most likely Lagoa das Furnas, which consequently must have existed before the 1630 eruption.

Identifying open and closed system behaviors at Tungurahua volcano (Ecuador) using SO2 and seismo-acoustic measurements

NASA Astrophysics Data System (ADS)

Hidalgo, Silvana; Battaglia, Jean; Bernard, Benjamin; Steele, Alexander; Arellano, Santiago; Galle, Bo

2014-05-01

Tungurahua is one of the most active volcanoes in Ecuador. It is located in Central Ecuador, 160 km South of Quito and 8 km South of the touristic town of Baños. Tungurahua had one eruption every century since 1500, with an activity characterized by ash fallouts and pyroclastic and lava flows. The current eruptive period of Tungurahua began in 1999 with multiple episodes of explosive activity that have threatened the local population. The monitoring network is constituted by 5 short period and 5 broadband seismic stations, 4 DOAS permanent instruments, 4 tiltmeters, 2 permanent high resolution GPS, 4 digital cameras and 10 acoustic flow monitors. The correct interpretation of the different data acquired by this network allows a better understanding of the eruptive behavior of Tungurahua in order to provide early warning to the local population. Tungurahua changed its behavior from a continuously erupting volcano, as it was until 2008, to a sporadically erupting one, showing clear quiescence phases lasting from 40 to 184 days, and intense activity phases lasting from 15 to 70 days. Activity phases are characterized by Strombolian and Vulcanian eruptive styles, producing ash fallouts and in a few occasions pyroclastic flows. In terms of hazard to the local population, one of the goals of monitoring Tungurahura is to forecast the onset and evolution of eruptive phases. In particular the occurrence of large Vulcanian explosions which occur when the conduit is closed is a major issue. Since 2010 we focused our study on the relation between SO2 gas emissions, the seismic and acoustic energies of explosions and the tremor amplitudes. The first observation of comparing these different datasets is that the correlation between seismic and SO2 degassing is not straightforward, and actually the relation reflects the conditions at the vent: open or closed. The onset of eruptive phases in open conduit conditions can be identified which leads to an effective eruption forecasting. An example of this behavior is the eruptive phase between December 2009 and March 2010 when SO2 measurements increased 4 days before the amplitude of tremor and 9 days before the occurrence of the first explosions. Conversely, if the vent is closed at the beginning of a phase and no evident seismic precursors are observed forecasting is hardly possible. During an ongoing eruptive phase, the relation between these parameters allows to identify periods when the conduit is totally open as degassing may occur almost without generating any seismicity. Therefore the forecasting of escalating open conduit activity or a partial closing of the system is possible. Such a case was observed and forecasted on December 2011. In this work, we present observational evidence of these mechanisms which are used to identify possible patterns of evolution of the activity, contributing to a more effective volcanic hazard assessment.

The Puu Oo eruption of Kilauea Volcano, Hawaii

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

Wolfe, E.W.

1988-01-01

The Puu Oo eruption is the most voluminous and longest-lived historical flank eruption of Kilauea volcano. A pattern of episodic lava discharge developed in which relatively brief periods of vigorous fountaining and high-volume flow production alternated with longer repose periods. The activity was intensely monitored, and results of the first 11/2 yrs of observation and measurement are reported, including geologic observations, lava sampling, temperature measurements, compositional analyses, petrologic study, studies of gas composition and the role of gases in the eruptive process, geodetic measurements during emplacement of the feeder dike, and seismic and electrical studies.

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

Jiang, Yunchun; Yang, Jiayan; Liu, Yu

In this paper, we report the interaction and subsequent merging of two sinistral filaments (F1 and F2) occurring at the boundary of AR 9720 on 2001 December 6. The two filaments were close and nearly perpendicular to each other. The interaction occurred after F1 was erupted and the eruption was impeded by a more extended filament channel (FC) standing in the way, in which F2 was embedded. The erupted material ran into FC along its axis, causing F1 and F2 to merge into a single structure that subsequently underwent a large-amplitude to-and-fro motion. A significant plasma heating process was observedmore » in the merging process, making the mixed material largely disappear from the Hα passband, but appear in Extreme Ultraviolet Telescope 195 Å images for a while. These observations can serve as strong evidence of merging reconnection between the two colliding magnetic structures. A new sinistral filament was formed along FC after the cooling of the merged and heated material. No coronal mass ejection was observed to be associated with the event; though, the eruption was accompanied by a two-ribbon flare with a separation motion, indicating that the eruption had failed. This event shows that, in addition to overlying magnetic fields, such an interaction is an effective restraint to make a filament eruption fail in this way.« less

Comparing eruptions of varying intensity at Kilauea via melt inclusion analysis

NASA Astrophysics Data System (ADS)

Ferguson, D. J.; Plank, T. A.; Hauri, E. H.; Houghton, B. F.; Gonnermann, H. M.; Swanson, D. A.; Blaser, A. P.

2013-12-01

Over the past 500 years explosive summit eruptions from Kilauea volcano, Hawaii, have exhibited a range of eruption magnitudes, from large basaltic sub-plinian events to Hawaiian lava fountains of various intensity. Knowledge of the factors controlling such dramatic changes in explosivity and mass discharge rate is vital for understanding the dynamics of explosive basaltic magma systems, but these remain poorly constrained. At Kilauea this information also has important implications for hazard assessment, as future eruptions may be far larger than those observed historically. To investigate the processes associated with eruptions of varying magnitudes we have analyzed the composition and dissolved volatile contents (H2O-CO2-S-Cl-F) of olivine-hosted melt inclusions, sampled from tephra deposits associated with three eruptions of different sizes: a moderate lava-fountain (1959 Episode of Kilauea Iki); an exceptionally high lava-fountain (1500 CE Keanakāko'i reticulite) and a basaltic sub-plinian eruption (1650 CE Keanakāko'i layer 6 scoria). Over this time period (~500 years) we find no major shifts in the major element composition of primary melts feeding the Kilauea magmatic system, and melt inclusions from all eruptions record similar maximum water (~0.7 wt% H2O) and CO2 (~300 ppm) contents, regardless of eruption magnitude. Co-variations between other volatile species, such as CO2 and S, do not support a role for excess volatiles (i.e. CO2) in the larger eruptions via ';gas-fluxing'. Our data therefore suggests that major shifts in eruptive magnitude are unlikely to be linked to either changes in the primary volatile content of the melts or excess gas supplied by open-system degassing of deeper melts. Rather we find evidence for significant variations in the shallow degassing behavior of magmas associated with the larger Keanakāko'i eruptions (sub-plinian and strong lava-fountaining events) compared to that from less vigorous moderate Kilauea Iki lava-fountaining events. On plots of CO2 versus H2O, Kilauea Iki MI's record volatile contents consistent with equilibrium degassing of magma rising from a depth of ~3 km. In contrast, the volatile contents of melts from the more explosive eruptions appear to be strongly affected by degassing processes at shallow depths (< 300 m), indicating variations in the ascent and storage of melts over this time-period. These changes in storage conditions may be linked to variations in the depth of the summit caldera, which was significantly greater during the older more explosive eruptive phases.

Volcanic Thunder From Explosive Eruptions at Bogoslof Volcano, Alaska

NASA Astrophysics Data System (ADS)

Haney, Matthew M.; Van Eaton, Alexa R.; Lyons, John J.; Kramer, Rebecca L.; Fee, David; Iezzi, Alexandra M.

2018-04-01

Lightning often occurs during ash-producing eruptive activity, and its detection is now being used in volcano monitoring for rapid alerts. We report on infrasonic and sonic recordings of the related, but previously undocumented, phenomenon of volcanic thunder. We observe volcanic thunder during the waning stages of two explosive eruptions at Bogoslof volcano, Alaska, on a microphone array located 60 km away. Thunder signals arrive from a different direction than coeruptive infrasound generated at the vent following an eruption on 10 June 2017, consistent with locations from lightning networks. For the 8 March 2017 eruption, arrival times and amplitudes of high-frequency thunder signals correlate well with the timing and strength of lightning detections. In both cases, the thunder is associated with lightning that continues after significant eruptive activity has ended. Infrasonic and sonic observations of volcanic thunder offer a new avenue for studying electrification processes in volcanic plumes.

Gas analyses from the Pu'u O'o eruption in 1985, Kilauea volcano, Hawaii

USGS Publications Warehouse

Greenland, L.P.

1986-01-01

Volcanic gas samples were collected from July to November 1985 from a lava pond in the main eruptive conduit of Pu'u O'o from a 2-week-long fissure eruption and from a minor flank eruption of Pu'u O'o. The molecular composition of these gases is consistent with thermodynamic equilibrium at a temperature slightly less than measured lava temperatures. Comparison of these samples with previous gas samples shows that the composition of volatiles in the magma has remained constant over the 3-year course of this episodic east rift eruption of Kilauea volcano. The uniformly carbon depleted nature of these gases is consistent with previous suggestions that all east rift eruptive magmas degas during prior storage in the shallow summit reservoir of Kilauea. Minor compositional variations within these gas collections are attributed to the kinetics of the magma degassing process. ?? 1986 Springer-Verlag.

Voluminous eruption from a zoned magma body after an increase in supply rate at Axial Seamount

NASA Astrophysics Data System (ADS)

Chadwick, W. W.; Paduan, J. B.; Clague, D. A.; Dreyer, B. M.; Merle, S. G.; Bobbitt, A. M.; Caress, D. W.; Philip, B. T.; Kelley, D. S.; Nooner, S. L.

2016-12-01

Axial Seamount is the best monitored submarine volcano in the world, providing an exceptional window into the dynamic interactions between magma storage, transport, and eruption processes in a mid-ocean ridge setting. An eruption in April 2015 produced the largest volume of erupted lava since monitoring and mapping began in the mid-1980s after the shortest repose time, due to a recent increase in magma supply. The higher rate of magma replenishment since 2011 resulted in the eruption of the most mafic lava in the last 500-600 years. Eruptive fissures at the volcano summit produced pyroclastic ash that was deposited over an area of at least 8 km2. A systematic spatial distribution of compositions is consistent with a single dike tapping different parts of a thermally and chemically zoned magma reservoir that can be directly related to previous multichannel seismic-imaging results.

Initiation of Solar Eruptions

NASA Technical Reports Server (NTRS)

Sterling, Alphonse C.; Moore, Ronald L.

2007-01-01

We consider processes occurring just prior to and at the start of the onset of flare- and CME-producing solar eruptions. Our recent work uses observations of filament motions around the time of eruption onset as a proxy for the evolution of the fields involved in the eruption. Frequently the filaments show a slow rise prior to fast eruption, indicative of a slow expansion of the field that is about co explode. Work by us and others suggests that reconnection involving emerging or canceling flux results in a lengthening of fields restraining the filament-carrying field, and the consequent upward expansion of the field in and around the filament produces the filament's slow rise: that is, the reconnection weakens the magnetic "tethers" ("tether-weakening" reconnection), and results in the slow rise of the filament. It is still inconclusive, however, what mechanism is responsible for the switch from the slow rise to the fast eruption.

Active Eruptions in the NE Lau Basin

NASA Astrophysics Data System (ADS)

Resing, J. A.; Embley, R. W.

2009-12-01

NE Lau Response Team: K Rubin, E Baker, J Lupton, M Lilley, T Shank, S Merle, R Dziak, T Collasius (Jason 2 Expedition Leader), N Buck, T Baumberger, D Butterfield, D Clague, D Conlin, J Cowen, R Davis, L Evans, J Huber, M Keith, N Keller, P Michael, E Podowski, A-L Reysenbach, K Roe, H Thomas, S Walker. During a May 2009 cruise to W Mata volcano in the NE Lau Basin, we made the first observations of an active eruption on the deep-sea floor. The cruise was organized after volcanic activity was detected at two sites (W Mata volcano and NE Lau Spreading Center, NELSC) during a Nov. 2008 NOAA-PMEL expedition. At that time, both sites had elevated H2 concentrations and volcaniclastic shards in the hydrothermal plumes. Moored hydrophone data since Jan 2009 indicate that the activity at W Mata has been continuous between these expeditions. Results of our cruise and other work suggest that the NE Lau Basin hosts an unusually high level of magmatic activity, making it an ideal location to study the effects of magmatic processes on hydrothermal activity and associated ecosystems. W Mata was visited with 5 ROV Jason 2 dives and 2 dives with the MBARI autonomous mapping vehicle in May 2009. It was actively erupting at the 1200 m deep summit during each, so a hydrophone was deployed locally to collect acoustic data. Ship and shore-based analysis of HD video, molten lava, rocks, sediments, hot spring waters, and micro- and macro biological specimens collected by Jason 2 have provided a wealth of data. The eruption itself was characterized by extrusion of red, molten lava, extensive degassing, formation of large magma bubbles, explosive pyroclast ejection, and the active extrusion of pillow lavas. The erupting magmas are boninite, a relatively rare magma type found only at convergent margins. The hydrothermal fluids are generally acidic and all diffuse fluids collected were microbially active, even those at pH <3. W Mata was host to shrimp similar to those found at several other submarine volcanoes including actively erupting NW Rota. Two dives were also conducted on the NELSC, which was no longer erupting and showed no signs of extensive eruption-related hydrothermal activity. A new lava flow was found beneath the Nov. 2008 zone of near-bottom water column temperature anomalies. Preliminary radiometric dating of lavas is consistent with a Nov. 2008 eruption. For >20 yrs the PMEL-Vents and NSF RIDGE programs have sought to observe active eruptions to understand their impacts and modes of occurrence, yet these dynamic events have been difficult to capture. This response cruise produced new insights on submarine volcanism, including the first documented back-arc spreading center eruption, the first boninitic eruption, and the first observation of pillow lava formation in the deep sea, arguably one of Earth’s most common surface rock forms. The “rapidity” with which we were able to return to these sites aided in this success. The cruise on the R/V TG Thompson was funded by NSF through the R2K, MARGINS, and MGG programs, and by NOAA Ocean Exploration and PMEL. Over 37 letters of interest were submitted from the scientific community to join the cruise and/or to receive samples, from which a multidisciplinary team of petrologists, fluid chemists, oceanographers, geophysicists, and macro- and micro- biologists was assembled.

Investigating the Magnetic Imprints of Major Solar Eruptions with SDO /HMI High-cadence Vector Magnetograms

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

Sun Xudong; Hoeksema, J. Todd; Liu Yang

The solar active region photospheric magnetic field evolves rapidly during major eruptive events, suggesting appreciable feedback from the corona. Previous studies of these “magnetic imprints” are mostly based on line of sight only or lower-cadence vector observations; a temporally resolved depiction of the vector field evolution is hitherto lacking. Here, we introduce the high-cadence (90 s or 135 s) vector magnetogram data set from the Helioseismic and Magnetic Imager, which is well suited for investigating the phenomenon. These observations allow quantitative characterization of the permanent, step-like changes that are most pronounced in the horizontal field component (B {sub h}). Amore » highly structured pattern emerges from analysis of an archetypical event, SOL2011-02-15T01:56, where B {sub h} near the main polarity inversion line increases significantly during the earlier phase of the associated flare with a timescale of several minutes, while B {sub h} in the periphery decreases at later times with smaller magnitudes and a slightly longer timescale. The data set also allows effective identification of the “magnetic transient” artifact, where enhanced flare emission alters the Stokes profiles and the inferred magnetic field becomes unreliable. Our results provide insights on the momentum processes in solar eruptions. The data set may also be useful to the study of sunquakes and data-driven modeling of the corona.« less

Occurrence of inter-eruption debris flow and hyperconcentrated flood-flow deposits on Vesuvio volcano, Italy

NASA Astrophysics Data System (ADS)

Lirer, L.; Vinci, A.; Alberico, I.; Gifuni, T.; Bellucci, F.; Petrosino, P.; Tinterri, R.

2001-02-01

In the period between AD 79 and AD 472 eruptions, inter-eruption debris flow and hyperconcentrated-flood-flow deposits were deposited in the Somma-Vesuvio areas. These deposits, forming cliffs at the Torre Bassano and Torre Annunziata, were generated by highly erosive floods, whose erosive capacity was enhanced by acceleration due to the steepness of the volcano slopes. In this type of deposits were distinguished five depositional facies (from A to E) outcropping well at Torre Bassano where they are stacked in three fining-upward (FU) sequences, probably representing three forestepping — backstepping episodes in the emplacement area of gravity flows. These five facies from coarse to fine are interpreted to represent the downcurrent evolution of particular composite sediment gravity flows characterized by horizontal segregation of the main grain-size population. The blocking of these highly concentrated composite parent flows would first produce the deposition of the coarse front part to form facies A and then the overriding of this deposit by the bipartite flow, which constitutes the body of the flow. This flow is composed of a highly concentrated basal inertia carpet responsible for the deposition of facies B, C and D and an upper hyperconcentrated flood flow that forms facies E, through traction plus fallout processes, respectively. Finally, the occurrence of "lahar" type events at Somma-Vesuvio region even at present times is discussed.

Field-based high-speed imaging of explosive eruptions

NASA Astrophysics Data System (ADS)

Taddeucci, J.; Scarlato, P.; Freda, C.; Moroni, M.

2012-12-01

Explosive eruptions involve, by definition, physical processes that are highly dynamic over short time scales. Capturing and parameterizing such processes is a major task in eruption understanding and forecasting, and a task that necessarily requires observational systems capable of high sampling rates. Seismic and acoustic networks are a prime tool for high-frequency observation of eruption, recently joined by Doppler radar and electric sensors. In comparison with the above monitoring systems, imaging techniques provide more complete and direct information of surface processes, but usually at a lower sampling rate. However, recent developments in high-speed imaging systems now allow such information to be obtained with a spatial and temporal resolution suitable for the analysis of several key eruption processes. Our most recent set up for high-speed imaging of explosive eruptions (FAMoUS - FAst, MUltiparametric Set-up,) includes: 1) a monochrome high speed camera, capable of 500 frames per second (fps) at high-definition (1280x1024 pixel) resolution and up to 200000 fps at reduced resolution; 2) a thermal camera capable of 50-200 fps at 480-120x640 pixel resolution; and 3) two acoustic to infrasonic sensors. All instruments are time-synchronized via a data logging system, a hand- or software-operated trigger, and via GPS, allowing signals from other instruments or networks to be directly recorded by the same logging unit or to be readily synchronized for comparison. FAMoUS weights less than 20 kg, easily fits into four, hand-luggage-sized backpacks, and can be deployed in less than 20' (and removed in less than 2', if needed). So far, explosive eruptions have been recorded in high-speed at several active volcanoes, including Fuego and Santiaguito (Guatemala), Stromboli (Italy), Yasur (Vanuatu), and Eyjafiallajokull (Iceland). Image processing and analysis from these eruptions helped illuminate several eruptive processes, including: 1) Pyroclasts ejection. High-speed videos reveal multiple, discrete ejection pulses within a single Strombolian explosion, with ejection velocities twice as high as previously recorded. Video-derived information on ejection velocity and ejecta mass can be combined with analytical and experimental models to constrain the physical parameters of the gas driving individual pulses. 2) Jet development. The ejection trajectory of pyroclasts can also be used to outline the spatial and temporal development of the eruptive jet and the dynamics of gas-pyroclast coupling within the jet, while high-speed thermal images add information on the temperature evolution in the jet itself as a function of the pyroclast size and content. 2) Pyroclasts settling. High-speed videos can be used to investigate the aerodynamic settling behavior of pyroclasts from bomb to ash in size and including ash aggregates, providing key parameters such as drag coefficient as a function of Re, and particle density. 3) The generation and propagation of acoustic and shock waves. Phase condensation in volcanic and atmospheric aerosol is triggered by the transit of pressure waves and can be recorded in high-speed videos, allowing the speed and wavelength of the waves to be measured and compared with the corresponding infrasonic signals and theoretical predictions.

Mapping the ductile-brittle transition of magma

NASA Astrophysics Data System (ADS)

Kendrick, J. E.; Lavallee, Y.; Dingwell, D. B.

2010-12-01

During volcanic unrest, eruptive activity can switch rapidly from effusive to explosive. Explosive eruptions require the fragmentation of magma, in which, if deformation rate is too fast to be relaxed, magma undergoes a transition in deformation mechanism from viscous and/or ductile to brittle. Our knowledge of the deformation mechanisms of magma ascent and eruption remains, to date, poor. Many studies have constrained the glass transition (Tg) of the interstitial melt phase; yet the effect of crystals and bubbles are unresolved. During ascent, magma undergoes P-T changes which induce crystallization, thereby inducing a transition from viscous to ductile and, in some cases, to brittle deformation. Here, we explore the deformation mechanisms of magma involved in the dome-building eruptions and explosions that occurred at Volcán de Colima (Mexico) since 1998. For this purpose, we investigated the rheology of dome lavas, containing 10-45 vol.% rhyolitic interstitial melt, 55-90 vol.% crystals and 5-20 vol.% bubbles. The interstitial glass is characterized by electron microprobe and Tg is characterized using a differential scanning calorimeter and a dilatometer. The population of crystals (fraction, shape and size distribution) is described optically and quantified using ImageJ and AMOCADO. The rheological effects of crystals on the deformation of magmas are constrained via acoustic emission (AE) and uniaxial deformation experiments at temperature above Tg (900-980 °C) and at varied applied stresses (and strain rates: 10-6 to 10-2 s-1). The ratio of ductile to brittle deformation across the ductile-brittle transition is quantified using the output AE energy and optical and SEM analysis. We find that individual dome lava sample types have different mechanical responses, yielding a significant range of measured strain rates under a given temperature and applied stress. Optical analysis suggests that at low strain rates, ductile deformation is mainly controlled by the groundmass, whereas fractures initiate sporadically in phenocrysts. At high strain rates continuous fracture initiate in the phenocrysts and propagate through the groundmass. AE analysis suggests the ductile-brittle transition to approximate two orders of magnitude of strain rate and that it is temperature dependent. Within the transition, the different ratio of ductile to brittle deformation processes controls the strain to failure. This study shows that the presence of crystals widens the range of strain rates of the ductile-brittle transition and the failure of magma becomes dependent on total strain. Our findings will be discussed in the context of different eruptive scenarios.

Earth Observations taken by the Expedition 20 crew

NASA Image and Video Library

2009-08-05

ISS020-E-028123 (5 Aug. 2009) --- Mount Hood, Oregon is featured in this image photographed by an Expedition 20 crew member on the International Space Station. Mount Hood is located within the Cascade Range of the western United States, and is the highest peak (3,426 m) in Oregon. The Cascade Range is characterized by a line of volcanoes associated with a slab of oceanic crust that is subducting, or descending underneath, the westward moving continental crust of North America. Magma generated by the subduction process rises upward through the crust and feeds a line of active volcanoes that extends from northern California in the United States to southern British Columbia in Canada. While hot springs and steam vents are still active on Mount Hood, the last eruption from the volcano occurred in 1866. The volcano is considered dormant, but still actively monitored. Separate phases of eruptive activity produced pyroclastic flows and lahars ? mudflows ? that carried erupted materials down all of the major rivers draining the volcano. Gray volcanic deposits extend southwards along the banks of the White River (upper right), and form several prominent ridges along the southeast to southwest flanks of the volcano. The deposits contrast sharply with the green vegetated lower flanks of the volcano. The Mount Hood stratovolcano ? a typically cone-shaped volcanic structure formed by interlayered lava flows and explosive eruption deposits ? hosts twelve mapped glaciers along its upper flanks (center). Like other glaciers in the Pacific Northwest, the Hood glaciers have been receding due to global warming, and have lost an estimated 61 percent of their volume over the past century. The predicted loss of glacial meltwater under future warming scenarios will have significant effects on regional hydrology and water supplies.

Pre-eruptive ground deformation of Azerbaijan mud volcanoes detected through satellite radar interferometry (DInSAR)

NASA Astrophysics Data System (ADS)

Antonielli, Benedetta; Monserrat, Oriol; Bonini, Marco; Righini, Gaia; Sani, Federico; Luzi, Guido; Feyzullayev, Akper A.; Aliyev, Chingiz S.

2014-12-01

Mud volcanism is a process that leads to the extrusion of subsurface mud, fragments of country rocks, saline waters and gases. This mechanism is typically linked to hydrocarbon traps, and the extrusion of this material builds up a variety of conical edifices with a similar morphology to those of magmatic volcanoes, though smaller in size. The Differential Interferometry Synthetic Aperture Radar (DInSAR) technique has been used to investigate the ground deformation related to the activity of the mud volcanoes of Azerbaijan. The analysis of a set of wrapped and unwrapped interferograms, selected according to their coherence, allowed the detection of significant superficial deformation related to the activity of four mud volcanoes. The ground displacement patterns observed during the period spanning from October 2003 to November 2005 are dominated by uplift, which reach a cumulative value of up to 20 and 10 cm at the Ayaz-Akhtarma and Khara-Zira Island mud volcanoes, respectively. However, some sectors of the mud volcano edifices are affected by subsidence, which might correspond to deflation zones that coexist with the inflation zones characterized by the dominant uplift. Important deformation events, caused by fluid pressure and volume variations, have been observed both (1) in connection with main eruptive events in the form of pre-eruptive uplift, and (2) in the form of short-lived deformation pulses that interrupt a period of quiescence. Both deformation patterns show important similarities to those identified in some magmatic systems. The pre-eruptive uplift has been observed in many magmatic volcanoes as a consequence of magma intrusion or hydrothermal fluid injection. Moreover, discrete short-duration pulses of deformation are also experienced by magmatic volcanoes and are repeated over time as multiple inflation and deflation events.

Eruption History of Cone D: Implications for Current and Future Activity at Okmok Caldera

NASA Astrophysics Data System (ADS)

Beget, J.; Almberg, L.; Faust-Larsen, J.; Neal, C.

2008-12-01

Cone B at Okmok Caldera erupted in 1817, and since then activity has beeen centered in and around Cone A in the SW part of Okmok Caldera. However, prior to 1817 at least a half dozen other eruptive centers were active at various times within the caldera. Cone D was active between ca. 2000-1500 yr BP., and underwent at least two separate intervals characterized by violent hydromagmatic explosions and surge production followed by the construction of extensive lava deltas in a 150-m-deep intra-caldera lake. Reconstructions of cone morphology indicate the hydromagmatic explosions occurred when lake levels were shallow or when the eruptive cones had grown to reach the surface of the intra-caldera lake. The effusion rate over this interval averaged several million cubic meters of lava per year, implying even higher outputs during the actual eruptive episodes. At least two dozen tephra deposits on the volcano flanks date to this interval, and record frequent explosive eruptions. The pyroclastic flows and surges from Cone D and nearby cones extend as far as 14 kilometers from the caldera rim, where dozens of such deposits are preserved in a section as much as 6 m thick at a distance of 8 km beyond the rim. A hydromagmatic explosive eruption at ca. 1500 yr BP generated very large floods and resulted in the draining of the caldera lake. The 2008 hydromagmatic explosive eruptions in the Cone D area caused by interactions with lake water resulted in the generation of surges, floods and lahars that are smaller but quite similar in style to the prehistoric eruptions at Cone E ca. 2000-1500 yr BP. The style and magnitude of future eruptions at vents around Cone D will depend strongly on the evolution of the intra-caldera lake system.

Tephrostratigraphy of Changbaishan volcano, northeast China, since the mid-Holocene

NASA Astrophysics Data System (ADS)

Sun, Chunqing; Liu, Jiaqi; You, Haitao; Nemeth, Karoly

2017-12-01

A detailed tephrostratigraphy of an active volcano is essential for evaluating its eruptive history, forecasting future eruptions and correlation with distal tephra records. Changbaishan volcano is known for its Millennium eruption (ME, AD 940s; VEI 7) and the ME tephra has been detected in Greenland ice cores ∼9000 km from the vent. However, the pre-Millennium (pre-ME) and post-Millennium (post-ME) eruptions are still poorly characterized. In this study, we present a detailed late Holocene eruptive sequence of Changbaishan volcano based on single glass shard compositions from tephra samples collected from around the caldera rim and flanks. Tephra ages are constrained by optically stimulated luminescence (OSL) and AMS 14C dates. Tephra from the mid-Holocene pre-ME eruption can be divided into two pyroclastic fall subunits, and it cannot be correlated with any known Changbaishan-sourced tephra recorded in the Japan Sea based on major element composition of glass shards, such as the B-J (Baegdusan-Japan Basin) and B-V (Baegdusan-Vladivostok-oki) tephras. ME pyroclastic fall deposits from the caldera rims and volcanic flanks can be correlated to the juvenile pumice lapilli or blocks within the pyroclastic density current (PDC) deposits deposited in the valleys around the volcano based on glass shard compositions. Our results indicate that the glass shard compositions of proximal ME tephra are more varied than previously thought and can be correlated with distal ME tephra. In addition, widely-dispersed mafic scoria was ejected by the ME Plinian column and deposited on the western and southern summits and the eastern flank of the volcano. Data for glass from post-ME eruptions, such as the historically-documented AD 1403, AD 1668 and AD 1702 eruptions, are reported here for the first time. Except for the ME, other Holocene eruptions, including pre-ME and post-ME eruptions, had the potential to form widely-distributed tephra layers around northeast Asia, and our dataset provides a proximal reference for tephra and cryptotephra studies in surrounding areas.

Probabilistic tephra hazard maps for the Neapolitan area: Quantitative volcanological study of Campi Flegrei eruptions

NASA Astrophysics Data System (ADS)

Mastrolorenzo, G.; Pappalardo, L.; Troise, C.; Panizza, A.; de Natale, G.

2008-07-01

Tephra fall is a relevant hazard of Campi Flegrei caldera (Southern Italy), due to the high vulnerability of Naples metropolitan area to such an event. Here, tephra derive from magmatic as well as phreatomagmatic activity. On the basis of both new and literature data on known, past eruptions (Volcanic Explosivity Index (VEI), grain size parameters, velocity at the vent, column heights and erupted mass), and factors controlling tephra dispersion (wind velocity and direction), 2D numerical simulations of fallout dispersion and deposition have been performed for a large number of case events. A bayesian inversion has been applied to retrieve the best values of critical parameters (e.g., vertical mass distribution, diffusion coefficients, velocity at the vent), not directly inferable by volcanological study. Simulations are run in parallel on multiple processors to allow a fully probabilistic analysis, on a very large catalogue preserving the statistical proprieties of past eruptive history. Using simulation results, hazard maps have been computed for different scenarios: upper limit scenario (worst-expected scenario), eruption-range scenario, and whole-eruption scenario. Results indicate that although high hazard characterizes the Campi Flegrei caldera, the territory to the east of the caldera center, including the whole district of Naples, is exposed to high hazard values due to the dominant westerly winds. Consistently with the stratigraphic evidence of nature of past eruptions, our numerical simulations reveal that even in the case of a subplinian eruption (VEI = 3), Naples is exposed to tephra fall thicknesses of some decimeters, thereby exceeding the critical limit for roof collapse. Because of the total number of people living in Campi Flegrei and the city of Naples (ca. two million of inhabitants), the tephra fallout risk related to a plinian eruption of Campi Flegrei largely matches or exceeds the risk related to a similar eruption at Vesuvius.

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.

Characterization of the Dynamic Pressure Response of Fuels in Microchannels

NASA Astrophysics Data System (ADS)

Haendler, Brenda; Pisano, Albert; Liepmann, Dorian

2004-11-01

In order to create a self-pumping fuel vaporization and delivery systems for a MEMS rotary engine power system, the dynamic pressure response due to phase eruption of fuels in micro channels must be characterized. Testing is done using micro channels with diameters the same order of magnitude as the critical bubble radius, a constant mass flow rate syringe pump, and a steady heat source. Pressure changes in the micro channel due to the periodic movement of the phase change meniscus are measured for a variety of flow conditions. A discrete Fourier transform is performed on the data to determine the dominant frequencies in the signal. Critical trends are discussed comparing both the frequency and the amplitude of the pressure spikes for a variety of temperatures and flow rates. The results presented on the trends in the pressure signature due to phase eruption for fuels are then related back to the fuel delivery system, which is using a nozzle-diffuser design to accomplish positive flow rectification given the periodic pressure condition at the phase eruption interface.

Relationship between formation/eruption of maxillary teeth and skeletal pattern of maxilla.

PubMed

Suda, Naoto; Hiyama, Shigetoshi; Kuroda, Takayuki

2002-01-01

Previous reports have indicated that formation and eruption of the maxillary teeth, especially the molars, are delayed in skeletal Class III patients compared with Class I and Class II patients. However, the relationship between the formation/eruption of maxillary teeth and the skeletal pattern of the maxilla is not yet clear. To examine this relationship, we studied 81 skeletal Class III Japanese patients (mean age, 8.8 years). The sample was divided into 2 groups: a maxillary retrusion (MR) group, characterized by a small SNA angle and a short palatal length, and a control group in which those values were in the normal range for patients of Japanese descent. There was no significant difference in the rate of formation for the maxillary and mandibular teeth between the 2 groups. The eruption of the maxillary second molars was delayed in the MR group compared with the control group. There were no significant differences between the 2 groups for any other teeth. A multiple-regression analysis was carried out to examine whether the skeletal pattern of the maxilla is a useful indicator for predicting the eruption of the maxillary teeth. The results showed that palatal length and chronologic age were significant independent (explanatory) variables for predicting eruption of the maxillary second molars. These findings indicated that the skeletal pattern of the maxilla is a useful indicator for predicting the timing of maxillary molar eruption when considering treatment of skeletal Class III malocclusions.

Monitoring El Hierro submarine volcanic eruption events with a submarine seismic array

NASA Astrophysics Data System (ADS)

Jurado, Maria Jose; Molino, Erik; Lopez, Carmen

2013-04-01

A submarine volcanic eruption took place near the southernmost emerged land of the El Hierro Island (Canary Islands, Spain), from October 2011 to February 2012. The Instituto Geografico Nacional (IGN) seismic stations network evidenced seismic unrest since July 2012 and was a reference also to follow the evolution of the seismic activity associated with the volcanic eruption. From the beginning of the eruption a geophone string was installed less than 2 km away from the new volcano, next to La Restinga village shore, to record seismic activity related to the volcanic activity, continuously and with special interest on high frequency events. The seismic array was endowed with 8, high frequency, 3 component, 250 Hz, geophone cable string with a separation of 6 m between them. The analysis of the dataset using spectral techniques allows the characterization of the different phases of the eruption and the study of its dynamics. The correlation of the data analysis results with the observed sea surface activity (ash and lava emission and degassing) and also with the seismic activity recorded by the IGN field seismic monitoring system, allows the identification of different stages suggesting the existence of different signal sources during the volcanic eruption and also the posteruptive record of the degassing activity. The study shows that the high frequency capability of the geophone array allow the study of important features that cannot be registered by the standard seismic stations. The accumulative spectral amplitude show features related to eruptive changes.

Latest Pleistocene crustal cannibalization at Baekdusan (Changbaishan) as traced by oxygen isotopes of zircon from the Millennium Eruption

NASA Astrophysics Data System (ADS)

Cheong, Albert Chang-sik; Sohn, Young Kwan; Jeong, Youn-Joong; Jo, Hui Je; Park, Kye-Hun; Lee, Youn Soo; Li, Xian-Hua

2017-07-01

The silicic volcanism of Baekdusan (Changbaishan), which is on the border between North Korea and China, was initiated in the Late Pleistocene and culminated in the 10th century with a powerful (volcanic explosivity index = 7) commendite-trachyte eruption commonly referred to as the "Millennium Eruption." This study presents oxygen isotope data of zircon in trachydacitic pumices ejected during the Millennium Eruption, together with whole-rock geochemical and Sr-Nd-Pb isotopic data that manifest once again the A-type and EM1 affinities of the Millennium Eruption magma. The zircon crystals, dated by previous studies at ca. 12-9 ka, show a moderate inter-grain variation in δ18O from 3.69‰ to 5.03‰. These values are consistently lower than the normal mantle range, and interpreted to have resulted from the digestion of meteoric-hydrothermally altered intracaldera rocks in the shallow magma chamber beneath Baekdusan just prior to the crystallization of the zircons, rather than from derivation from low-δ18O sources deep in the mantle. The whole-rock geochemical/isotopic considerations suggest that the magma mainly self-cannibalized the earlier erupted volcanic carapace around the magma chamber. This study highlights the usefulness of zircon oxygen isotopes for characterizing past volcanic activity that has now been commonly eroded away and implies that the generation of Yellowstone-type low-δ18O magma is not a rare phenomenon in large-volume silicic 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.

Assessing the likelihood of volcanic eruption through analysis of volcanotectonic earthquake fault plane solutions

NASA Astrophysics Data System (ADS)

Roman, D. C.; Neuberg, J.; Luckett, R. R.

2006-08-01

Episodes of volcanic unrest do not always lead to an eruption. Many of the commonly monitored signals of volcanic unrest, including surface deformation and increased degassing, can reflect perturbations to a deeper magma storage system, and may persist for years without accompanying eruptive activity. Signals of volcanic unrest can also persist following the end of an eruption. Furthermore, the most reliable eruption precursor, the occurrence of low-frequency seismicity, appears to reflect very shallow processes and typically precedes eruptions by only hours to days. Thus, the identification of measurable and unambiguous indicators that are sensitive to changes in the mid-level conduit system during an intermediate stage of magma ascent is of critical importance to the field of volcano monitoring. Here, using data from the ongoing eruption of the Soufrière Hills Volcano, Montserrat, we show that ˜90° changes in the orientation of double-couple fault-plane solutions for high-frequency 'volcanotectonic' (VT) earthquakes reflect pressurization of the mid-level conduit system prior to eruption and may precede the onset of eruptive episodes by weeks to months. Our results demonstrate that, once the characteristic stress field response to magma ascent at a given volcano is established, a relatively simple analysis of VT fault-plane solutions may be used to make intermediate-term assessments of the likelihood of future eruptive activity.

Multiple coincident eruptive seismic tremor sources during the 2014-2015 eruption at Holuhraun, Iceland

NASA Astrophysics Data System (ADS)

Eibl, Eva P. S.; Bean, Christopher J.; Jónsdóttir, Ingibjörg; Höskuldsson, Armann; Thordarson, Thorvaldur; Coppola, Diego; Witt, Tanja; Walter, Thomas R.

2017-04-01

We analyze eruptive tremor during one of the largest effusive eruptions in historical times in Iceland (2014/2015 Holuhraun eruption). Seismic array recordings are compared with effusion rates deduced from Moderate Resolution Imaging Spectroradiometer recordings and ground video monitoring data and lead to the identification of three coexisting eruptive tremor sources. This contrasts other tremor studies that generally link eruptive tremor to only one source usually associated with the vent. The three sources are (i) a source that is stable in back azimuth and shows bursts with ramp-like decrease in amplitude at the beginning of the eruption: we link it to a process below the open vents where the bursts correlate with the opening of new vents and temporary increases in the lava fountaining height; (ii) a source moving by a few degrees per month while the tremor amplitude suddenly increases and decreases: back azimuth and slowness correlate with the growing margins of the lava flow field, whilst new contact with a river led to fast increases of the tremor amplitude; and (iii) a source moving by up to 25° southward in 4 days that cannot be related to any observed surface activity and might be linked to intrusions. We therefore suggest that eruptive tremor amplitudes/energies are used with caution when estimating eruptive volumes, effusion rates, or the eruption explosivity as multiple sources can coexist during the eruption phase. Our results suggest that arrays can monitor both the growth of a lava flow field and the activity in the vents.

Kilauea's Ongoing Eruption: 25th Year Brings Major Changes

NASA Astrophysics Data System (ADS)

Orr, T. R.

2007-12-01

2007 marks the 25th year of nearly continuous eruption on Kilauea's east rift zone. Episodic high lava fountains, which built the Pu`u `O`o cone during the first three years of the eruption, ended in 1986. Activity then migrated downrift and the Kupaianaha shield was formed by passive effusion of lava. The change in eruptive style resulted in a switch at Pu`u `O`o from cone construction to cone collapse that has been ongoing for the last two decades. Activity at Kupaianaha ceased in 1992, and the eruption resumed at Pu`u `O`o. The eruptive style established at Kupaianaha continued, however, with continuous effusion from vents on the southwest flank of the Pu`u `O`o cone. The last 15 years have been characterized by the formation of relatively stable tube systems---broken only by a brief fissure eruption uprift of Pu`u `O`o in 1997---that have carried lava from the flank vents to the ocean about 9 km away. The Prince Kuhio Kalanianaole (PKK) tube, the most recent of these tube systems to develop, was active from March 2004 to June 2007. The PKK flow was emplaced almost entirely on older flows of this eruption and entered the ocean in several locations over a span of 6 km. The "Father's Day" intrusion of June 17--19, 2007, robbed the supply of magma to Pu`u `O`o and, thus, the active flow field. The floor of the Pu`u `O`o crater dropped 80--100 m, the PKK tube system drained, and the active flows and ocean entry quickly stagnated. On June 19, a short-lived fissure eruption broke out low on the east flank of Kane Nui o Hamo, about 6 km uprift of Pu`u `O`o, burying only 0.22 hectares. The eruption at Kilauea paused from June 20 through July 1 or 2, when lava returned to Pu`u `O`o and began refilling the collapsed crater. Near midnight on July 20--21, after at least 19 days of lava lake growth, the lava pond within the Pu`u `O`o crater drained suddenly when a series of fissures opened on the east flank of the cone and propagated ~2 km downrift. The new activity, dubbed the July 21 eruption, initially fed `a`a and pahoehoe flows but, within a few days, developed into a system of perched lava ponds. By the end of July, the perched pond over the easternmost fissure evolved into an open channel feeding a series of `a`a flows heading downrift around the north side of the Kupaianaha shield. The lava supply from other fissure segments declined and stagnated within a few days of the lava channel's formation. As of September 4, 2007, `a`a flows have extended up to ~6 km from the fissure and have covered more than 600 hectares. Unless the eruption supply rate increases, `a`a flows fed by the open channel will likely travel no more than a few kilometers from the vent and pose no threat to those living downslope. If the eruptive style changes, however, to one characterized by tube-fed pahoehoe, then downslope communities could be directly impacted.

Towards forecasting volcanic eruptions on a global scale

NASA Astrophysics Data System (ADS)

Hooper, A. J.; Heimisson, E. R.; Gaddes, M.; Bagnardi, M.; Sigmundsson, F.; Spaans, K.; Parks, M.; Gudmundsson, M. T.; Ebmeier, S. K.; Holohan, E. P.; Wright, T. J.; Jonsdottir, K.; Hreinsdottir, S.; Dumont, S.; Ofeigsson, B.; Vogfjord, K. S.

2016-12-01

Volcanic eruptions can cause loss of life, damage health, and have huge economic impacts, providing strong societal motivation for predicting eruptive behavior prior to and during eruptions. I will present here recent progress we have made in mechanical modelling with a predictive capacity, and how we are expanding volcano monitoring to a global scale. The eruption of Bardarbunga volcano, Iceland, in 2014-2015 was the largest eruption there for more than 200 years, producing 1.6 km3of lava. Prior to eruption, magma propagated almost 50 km beneath the surface, over a period of two weeks. Key questions to answer in advance of such eruptions are: will it erupt, where, how much and for how long? We developed a model based on magma taking a path that maximizes energy release, which aligns well with the actual direction taken. Our model also predicts eruption in a topographic low, as actually occurred. As magma was withdrawn, the volcano surface sagged downwards. A coupled model of magma flow and piston-like collapse predicts a declining magma flow rate and ground subsidence rate, in accordance with that observed. With such a model, observations can be used to predict the timescale and rates of eruption, even before one starts. The primary data needed to constrain these predictive models are measurements of surface deformation. In Iceland, this is achieved using high accuracy GPS, however, most volcanoes have no ground instrumentation. A recent ESA mission, Sentinel-1, can potentially image deformation at almost all subaerial volcanoes every 6 days, using a technique called interferometric synthetic aperture radar (InSAR). This will allow us to detect early stages of magma migration at any volcano, then task other satellites to acquire data at a higher rate. We are working on a system to process all Sentinel-1 data in near-real time, which is a big data challenge. We have also developed new algorithms that maximize signal extraction from each new acquisition and recognize when the deformation pattern at any volcano has changed significantly. There are still challenges to overcome to incude processes occurring within the magma as it moves, cools, crystallizes and exsolves gases. But with this combined approach of global data collection and innovative modelling, we hope to better mitigate the effects of volcanic eruptions going forward.

Transient numerical model of magma ascent dynamics: application to the explosive eruptions at the Soufrière Hills Volcano

NASA Astrophysics Data System (ADS)

La Spina, G.; de'Michieli Vitturi, M.; Clarke, A. B.

2017-04-01

Volcanic activity exhibits a wide range of eruption styles, from relatively slow effusive eruptions that produce lava flows and lava domes, to explosive eruptions that can inject large volumes of fragmented magma and volcanic gases high into the atmosphere. Although controls on eruption style and scale are not fully understood, previous research suggests that the dynamics of magma ascent in the shallow subsurface (< 10 km depth) may in part control the transition from effusive to explosive eruption and variations in eruption style and scale. Here we investigate the initial stages of explosive eruptions using a 1D transient model for magma ascent through a conduit based on the theory of the thermodynamically compatible systems. The model is novel in that it implements finite rates of volatile exsolution and velocity and pressure relaxation between the phases. We validate the model against a simple two-phase Riemann problem, the Air-Water Shock Tube problem, which contains strong shock and rarefaction waves. We then use the model to explore the role of the aforementioned finite rates in controlling eruption style and duration, within the context of two types of eruptions at the Soufrière Hills Volcano, Montserrat: Vulcanian and sub-Plinian eruptions. Exsolution, pressure, and velocity relaxation rates all appear to exert important controls on eruption duration. More significantly, however, a single finite exsolution rate characteristic of the Soufrière Hills magma composition is able to produce both end-member eruption durations observed in nature. The duration therefore appears to be largely controlled by the timescales available for exsolution, which depend on dynamic processes such as ascent rate and fragmentation wave speed.

Introduction to section 2. Climax-stage magmatism: Growth history Of Kilauea Volcano and its instability

NASA Astrophysics Data System (ADS)

Lipman, Peter W.

On the south flank of Hawai'i Island, frequent eruptions, abundant earthquakes, and rapid ground deformation mark the current locus of volcanism along the Hawaiian Ridge. Kïlauea and Mauna Loa volcanoes are in a tholeiitic shield-building stage, erupting mainly on land. South of Kïlauea, Lö'ihi Seamount has erupted alkalic and transitional basalts that mark the growth of Hawai`i's youngest volcano. Kïlauea is the most active volcano on Earth, and its summit caldera and two rift zones characterize the typical shield stage of Hawaiian volcanoes. Kïlauea's south flank, between the rift zones, is subject to sustained and episodic seaward displacements associated with frequent earthquakes and expressed on land by the Hilina fault system.

Uranium-Series Isotopic Constraints on Recent Changes in the Eruptive Behaviour of Merapi Volcano, Java, Indonesia

NASA Astrophysics Data System (ADS)

Gertisser, R.; Handley, H. K.; Reagan, M. K.; Berlo, K.; Barclay, J.; Preece, K.; Herd, R.

2011-12-01

Merapi volcano (Central Java) is one of the most active and deadly volcanoes in Indonesia. The 2010 eruption was the volcano's largest eruption since 1872 and erupted much more violently than expected. Prior to 2010, volcanic activity at Merapi was characterised by several months of slow dome growth punctuated by gravitational dome failures, generating small-volume pyroclastic density currents (Merapi-type nuées ardentes). The unforeseen, large-magnitude events in 2010 were different in many respects: pyroclastic density currents travelled > 15 km beyond the summit causing widespread devastation in proximal areas on Merapi's south flank and ash emissions from sustained eruption columns resulted in ash fall tens of kilometres away from the volcano. The 2010 events have proved that Merapi's relatively small dome-forming activity can be interrupted at relatively short notice by larger explosive eruptions, which appear more common in the geological record. We present new geochemical and Uranium-series isotope data for the volcanic products of both the 2006 and 2010 eruptions at Merapi to investigate the driving forces behind this unusual explosive behaviour and their timescales. An improved knowledge of these processes and of changes in the pre-eruptive magma system has important implications for the assessment of hazards and risks from future eruptive activity at Merapi.

Periodic changes in effluent chemistry at cold-water geyser: Crystal geyser in Utah

NASA Astrophysics Data System (ADS)

Han, Weon Shik; Watson, Z. T.; Kampman, Niko; Grundl, Tim; Graham, Jack P.; Keating, Elizabeth H.

2017-07-01

Crystal geyser is a CO2-driven cold-water geyser which was originally drilled in the late 1930's in Green River, Utah. Utilizing a suite of temporal groundwater sample datasets, in situ monitoring of temperature, pressure, pH and electrical conductivity from multiple field trips to Crystal geyser from 2007 to 2014, periodic trends in groundwater chemistry from the geyser effluent were identified. Based on chemical characteristics, the primary sourcing aquifers are characterized to be both the Entrada and Navajo Sandstones with a minor contribution from Paradox Formation brine. The single eruption cycle at Crystal geyser lasted over four days and was composed of four parts: Minor Eruption (mEP), Major Eruption (MEP), Aftershock Eruption (Ae) and Recharge (R). During the single eruption cycle, dissolved ionic species vary 0-44% even though the degree of changes for individual ions are different. Generally, Na+, K+, Cl- and SO42- regularly decrease at the onset and throughout the MEP. These species then increase in concentration during the mEP. Conversely, Ca2+, Mg2+, Fe2+ and Sr2+ increase and decrease in concentration during the MEP and mEP, respectively. The geochemical inverse modeling with PHREEQC was conducted to characterize the contribution from three end-members (Entrada Sandstone, Navajo Sandstone and Paradox Formation brine) to the resulting Crystal geyser effluent. Results of the inverse modeling showed that, during the mEP, the Navajo, Entrada and brine supplied 62-65%, 36-33% and 1-2%, respectively. During the MEP, the contribution shifted to 53-56%, 45-42% and 1-2% for the Navajo, Entrada and Paradox Formation brine, respectively. The changes in effluent characteristics further support the hypothesis by Watson et al. (2014) that the mEP and MEP are driven by different sources and mechanisms.

Local infrasound observations of large ash explosions at Augustine Volcano, Alaska, during January 11–28, 2006

USGS Publications Warehouse

Petersen, Tanja; De Angelis, Silvio; Tytgat, Guy; McNutt, Stephen R.

2006-01-01

We present and interpret acoustic waveforms associated with a sequence of large explosion events that occurred during the initial stages of the 2006 eruption of Augustine Volcano, Alaska. During January 11–28, 2006, 13 large explosion events created ash-rich plumes that reached up to 14 km a.s.l., and generated atmospheric pressure waves that were recorded on scale by a microphone located at a distance of 3.2 km from the active vent. The variety of recorded waveforms included sharp N-shaped waves with durations of a few seconds, impulsive signals followed by complex codas, and extended signals with emergent character and durations up to minutes. Peak amplitudes varied between 14 and 105 Pa; inferred acoustic energies ranged between 2×108 and 4×109 J. A simple N-shaped short-duration signal recorded on January 11, 2006 was associated with the vent-opening blast that marked the beginning of the explosive eruption sequence. During the following days, waveforms with impulsive onsets and extended codas accompanied the eruptive activity, which was characterized by explosion events that generated large ash clouds and pyroclastic flows along the flanks of the volcano. Continuous acoustic waveforms that lacked a clear onset were more common during this period. On January 28, 2006, the occurrence of four large explosion events marked the end of this explosive eruption phase at Augustine Volcano. After a transitional period of about two days, characterized by many small discrete bursts, the eruption changed into a stage of more sustained and less explosive activity accompanied by the renewed growth of a summit lava dome.

Formation of cordierite-bearing lavas during anatexis in the lower crust beneath Lipari Island (Aeolian arc, Italy)

USGS Publications Warehouse

Di, Martino C.; Forni, F.; Frezzotti, M.L.; Palmeri, R.; Webster, J.D.; Ayuso, R.A.; Lucchi, F.; Tranne, C.A.

2011-01-01

Cordierite-bearing lavas (CBL;~105 ka) erupted from the Mt. S. Angelo volcano at Lipari (Aeolian arc, Italy) are high-K andesites, displaying a range in the geochemical and isotopic compositions that reflect heterogeneity in the source and/or processes. CBL consist of megacrysts of Ca-plagioclase and clinopyroxene, euhedral crystals of cordierite and garnet, microphenocrysts of orthopyroxene and plagioclase, set in a heterogeneous rhyodacitic-rhyolitic groundmass containing abundant metamorphic and gabbroic xenoliths. New petrographic, chemical and isotopic data indicate formation of CBL by mixing of basaltic-andesitic magmas and high-K peraluminous rhyolitic magmas of anatectic origin and characterize partial melting processes in the lower continental crust of Lipari. Crustal anatectic melts generated through two main dehydration-melting peritectic reactions of metasedimentary rocks: (1) Biotite + Aluminosilicate + Quartz + Albite = Garnet + Cordierite + K-feldspar + Melt; (2) Biotite + Garnet + Quartz = Orthopyroxene + Cordierite + K-feldspar + Melt. Their position into the petrogenetic grid suggests that heating and consequent melting of metasedimentary rocks occurred at temperatures of 725 < T < 900??C and pressures of 0.4-0.45 GPa. Anatexis in the lower crust of Lipari was induced by protracted emplacement of basic magmas in the lower crust (~130 Ky). Crustal melting of the lower crust at 105 ka affected the volcano evolution, impeding frequent maficmagma eruptions, and promoting magma stagnation and fractional crystallization processes. ?? 2011 Springer-Verlag.

Numerical modeling perspectives on zircon crystallization and magma reservoir growth at the Laguna del Maule volcanic field, central Chile

NASA Astrophysics Data System (ADS)

Andersen, N. L.; Dufek, J.; Singer, B. S.

2017-12-01

Magma reservoirs in the middle to upper crust are though to accumulate incrementally over 104 -105 years. Coupled crystallization ages and compositions of zircon are a potentially powerful tracer of reservoir growth and magma evolution. However, complex age distributions and disequilibrium trace element partitioning complicate the interpretation of the zircon record in terms of magmatic processes. In order to make quantitative predictions of the effects of magmatic processes that contribute reservoir growth and evolution—such as cooling and crystallization, magma recharge and mixing, and rejuvenation and remelting of cumulate-rich reservoir margins—we develop a model of zircon saturation and growth within a numerical framework of coupled thermal transfer, phase equilibrium, and magma dynamics. We apply this model to the Laguna del Maule volcanic field (LdM), located in central Chile. LdM has erupted at least 40 km3 of rhyolite from 36 vents distributed within a 250 km2 lake basin. Ongoing unrest demonstrates the large, silicic magma system beneath LdM remains active to this day. Zircon from rhyolite erupted between c. 23 and 1.8 ka produce a continuous distribution of 230Th-238U ages ranging from eruption to 40 ka, as well as less common crystal domains up to 165 ka and rare xenocrysts. Zircon trace element compositions fingerprint compositionally distinct reservoirs that grew within the larger magma system. Despite the dominantly continuous distributions of ages, many crystals are characterized by volumetrically substantial, trace element enriched domains consistent with rapid crystal growth. We utilize numerical simulations to assess the magmatic conditions required to catalyze these "blooms" of crystallization and the magma dynamics that contributed to the assembly of the LdM magma system.

The Magmatic Plumbing System of the Campi Flegrei Caldera.

NASA Astrophysics Data System (ADS)

Lucia, C.; Ilenia, A.; Massimo, D.; Valeria, D.; Mauro, D.; Giovanni, O.

2006-12-01

The Campi Flegrei caldera is a nested and resurgent structure generated by at least two major collapses. Large sectors of the structural boundary of both calderas resulted from partial reactivation of pre-existing faults generated by regional tectonism. Its magmatic system is still active with the last eruption occurring in 1538 A.D. (Monte Nuovo), widespread fumaroles and hot springs activity, and the unrest episodes in the last 35 years, with a maximum net uplift of about 3.5 m in the Pozzuoli area. The definition of the history of the magmatic feeding system of this caldera, in terms of composition, time- scale and depth of crystallization, relation between composition of the erupted magma and structural position of the vent, and magma chamber processes, is of extreme importance for a better understanding of the dynamic conditions of the present day magma chamber and for evaluating of the extent to which the behavior of the magmatic system can be predicted. The Campi Flegrei caldera magmatic plumbing system is characterized by deep and shallow reservoirs. Campi Flegrei magmas originated in a subduction modified mantle source, stagnate at mid crustal level (20- 10 km depth), where they differentiated and are contaminated with the continental crust. From the "deep reservoir" shoshonitic to latitic magmas rise towards the surface along the NE aligned regional fault reactivated during the caldera collapse, whereas trachytic magmas rise mostly along faults and fractures bordering the resurgent block and the southern part of the Campi Flegrei caldera. Repeated arrival of trachytic to phonolitic magmas form shallow reservoirs at 4-3 km depth, in which differentiation and mixing processes occur before and during the eruption.

Automated detection and characterization of harmonic tremor in continuous seismic data

NASA Astrophysics Data System (ADS)

Roman, Diana C.

2017-06-01

Harmonic tremor is a common feature of volcanic, hydrothermal, and ice sheet seismicity and is thus an important proxy for monitoring changes in these systems. However, no automated methods for detecting harmonic tremor currently exist. Because harmonic tremor shares characteristics with speech and music, digital signal processing techniques for analyzing these signals can be adapted. I develop a novel pitch-detection-based algorithm to automatically identify occurrences of harmonic tremor and characterize their frequency content. The algorithm is applied to seismic data from Popocatepetl Volcano, Mexico, and benchmarked against a monthlong manually detected catalog of harmonic tremor events. During a period of heightened eruptive activity from December 2014 to May 2015, the algorithm detects 1465 min of harmonic tremor, which generally precede periods of heightened explosive activity. These results demonstrate the algorithm's ability to accurately characterize harmonic tremor while highlighting the need for additional work to understand its causes and implications at restless volcanoes.

Characterizing a decade of behavior at Volcán de Colima, Mexico using long term InSAR and thermal remote sensing data

NASA Astrophysics Data System (ADS)

Sorge, J.; Williams-Jones, G.; Wright, R.; Varley, N. R.

2010-12-01

Satellite imagery is playing an increasingly prominent role in volcanology as it allows for consistent monitoring of remote, dangerous, and/or under-monitored volcanoes. One such system is Volcán de Colima (Mexico), a persistently active andesitic stratovolcano. Its characteristic and hazardous activity includes lava dome growth, pyroclastic flows, explosions, and Plinian to Subplinian eruptions, which have historically occurred at the end of Volcán de Colima’s eruptive cycle. Despite the availability of large amounts of historical satellite imagery, methods to process and interpret these images over long time periods are limited. Furthermore, while time-series InSAR data from a previous study (December 2002 to August 2006) detected an overall subsidence between 1 and 3 km from the summit, there is insufficient temporal resolution to unambiguously constrain the source processes. To address this issue, a semi-automated process for time-based characterization of persistent volcanic activity at Volcán de Colima has been developed using a combination of MODIS and GOES satellite imagery to identify thermal anomalies on the volcano edifice. This satellite time-series data is then combined with available geodetic data, a detailed eruption history, and other geophysical time-series data (e.g., seismicity, explosions/day, effusion rate, environmental data, etc.) and examined for possible correlations and recurring patterns in the multiple data sets to investigate potential trigger mechanisms responsible for the changes in volcanic activity. GOES and MODIS images are available from 2000 to present at a temporal resolution of one image every 30 minutes and up to four images per day, respectively, creating a data set of approximately 180,000 images. Thermal anomalies over Volcán de Colima are identified in both night- and day-time images by applying a time-series approach to the analysis of MODIS data. Detection of false anomalies, caused by non-volcanic heat sources such as fires or solar heating (in the daytime images), is mitigated by adjusting the MODIS detection thresholds, through comparison of daytime versus nighttime results, and by observing the spatial distribution of the anomalies on the edifice. Conversely, anomalies may not be detected due to cloud cover; clouds absorb thermal radiation limiting or preventing the ability of the satellite to measure thermal events; therefore, the anomaly data is supplemented with a cloud cover time-series data set. Fast Fourier and Wavelet transforms are then applied to the continuous, uninterrupted intervals of satellite observation to compare and correlate with the multiple time-series data sets. The result is the characterization of the behavior of an individual volcano, based on an extended time period. This volcano specific, comprehensive characterization can then be used as a predictive tool in the real-time monitoring of volcanic activity.

The Physical Processes of CME/ICME Evolution

NASA Astrophysics Data System (ADS)

Manchester, Ward; Kilpua, Emilia K. J.; Liu, Ying D.; Lugaz, Noé; Riley, Pete; Török, Tibor; Vršnak, Bojan

2017-11-01

As observed in Thomson-scattered white light, coronal mass ejections (CMEs) are manifest as large-scale expulsions of plasma magnetically driven from the corona in the most energetic eruptions from the Sun. It remains a tantalizing mystery as to how these erupting magnetic fields evolve to form the complex structures we observe in the solar wind at Earth. Here, we strive to provide a fresh perspective on the post-eruption and interplanetary evolution of CMEs, focusing on the physical processes that define the many complex interactions of the ejected plasma with its surroundings as it departs the corona and propagates through the heliosphere. We summarize the ways CMEs and their interplanetary CMEs (ICMEs) are rotated, reconfigured, deformed, deflected, decelerated and disguised during their journey through the solar wind. This study then leads to consideration of how structures originating in coronal eruptions can be connected to their far removed interplanetary counterparts. Given that ICMEs are the drivers of most geomagnetic storms (and the sole driver of extreme storms), this work provides a guide to the processes that must be considered in making space weather forecasts from remote observations of the corona.

Petrology of lavas from episodes 2-47 of the Puu Oo eruption of Kilauea Volcano, Hawaii: Evaluation of magmatic processes

USGS Publications Warehouse

Garcia, M.O.; Rhodes, J.M.; Wolfe, E.W.; Ulrich, G.E.; Ho, R.A.

1992-01-01

The Puu Oo eruption of Kilauea Volcano in Hawaii is one of its largest and most compositionally varied historical eruptions. The mineral and whole-rock compositions of the Puu Oo lavas indicate that there were three compositionally distinct magmas involved in the eruption. Two of these magmas were differentiated (<6.8 wt% MgO) and were apparently stored in the rift zone prior to the eruption. A third, more mafic magma (9-10 wt% MgO) was probably intruded as a dike from Kilauea's summit reservoir just before the start of the eruption. Its intrusion forced the other two magmas to mix, forming a hybrid that erupted during the first three eruptive episodes from a fissure system of vents. A new hybrid was erupted during episode 3 from the vent where Puu Oo later formed. The composition of the lava erupted from this vent became progressively more mafic over the next 21 months, although significant compositional variation occurred within some eruptive episodes. The intra-episode compositional variation was probably due to crystal fractionation in the shallow (0.0-2.9 km), dike-shaped (i.e. high surface area/volume ratio) and open-topped Puu Oo magma reservoir. The long-term compositional variation was controlled largely by mixing the early hybrid with the later, more mafic magma. The percentage of mafic magma in the erupted lava increased progressively to 100% by episode 30 (about two years after the eruption started). Three separate magma reservoirs were involved in the Puu Oo eruption. The two deeper reservoirs (3-4 km) recharged the shallow (0.4-2.9 km) Puu Oo reservoir. Recharge of the shallow reservoir occurred rapidly during an eruption indicating that these reservoirs were well connected. The connection with the early hybrid magma body was cut off before episode 30. Subsequently, only mafic magma from the summit reservoir has recharged the Puu Oo reservoir. ?? 1992 Springer-Verlag.

A multidisciplinary effort to assign realistic source parameters to models of volcanic ash-cloud transport and dispersion during eruptions

USGS Publications Warehouse

Mastin, Larry G.; Guffanti, Marianne C.; Servranckx, R.; Webley, P.; Barsotti, S.; Dean, K.; Durant, A.; Ewert, John W.; Neri, A.; Rose, W.I.; Schneider, David J.; Siebert, L.; Stunder, B.; Swanson, G.; Tupper, A.; Volentik, A.; Waythomas, Christopher F.

2009-01-01

During volcanic eruptions, volcanic ash transport and dispersion models (VATDs) are used to forecast the location and movement of ash clouds over hours to days in order to define hazards to aircraft and to communities downwind. Those models use input parameters, called “eruption source parameters”, such as plume height H, mass eruption rate Ṁ, duration D, and the mass fraction m63 of erupted debris finer than about 4ϕ or 63 μm, which can remain in the cloud for many hours or days. Observational constraints on the value of such parameters are frequently unavailable in the first minutes or hours after an eruption is detected. Moreover, observed plume height may change during an eruption, requiring rapid assignment of new parameters. This paper reports on a group effort to improve the accuracy of source parameters used by VATDs in the early hours of an eruption. We do so by first compiling a list of eruptions for which these parameters are well constrained, and then using these data to review and update previously studied parameter relationships. We find that the existing scatter in plots of H versus Ṁ yields an uncertainty within the 50% confidence interval of plus or minus a factor of four in eruption rate for a given plume height. This scatter is not clearly attributable to biases in measurement techniques or to well-recognized processes such as elutriation from pyroclastic flows. Sparse data on total grain-size distribution suggest that the mass fraction of fine debris m63 could vary by nearly two orders of magnitude between small basaltic eruptions (∼ 0.01) and large silicic ones (> 0.5). We classify eleven eruption types; four types each for different sizes of silicic and mafic eruptions; submarine eruptions; “brief” or Vulcanian eruptions; and eruptions that generate co-ignimbrite or co-pyroclastic flow plumes. For each eruption type we assign source parameters. We then assign a characteristic eruption type to each of the world's ∼ 1500 Holocene volcanoes. These eruption types and associated parameters can be used for ash-cloud modeling in the event of an eruption, when no observational constraints on these parameters are available.

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

First detection of precursory ground inflation of a small phreatic eruption by InSAR

NASA Astrophysics Data System (ADS)

Kobayashi, Tomokazu; Morishita, Yu; Munekane, Hiroshi

2018-06-01

Phreatic eruptions are caused by pressurization of geothermal fluid sources at shallow levels. They are relatively small compared to typical magmatic eruptions, but can be very hazardous. However, owing to their small magnitudes, their occurrences are difficult to predict. Here we show the detection of locally distributed ground inflation preceding a small phreatic eruption at the Hakone volcano, Japan, through the application of interferometric synthetic aperture radar analysis. The ground inflation proceeded the eruption at slow speed of ∼5 mm/month with a spatial size of ∼200 m in the early stage, and then it accelerated 2 months before the eruption that occurred for the first time in 800-900 yrs. The ground uplift reached ∼30 cm, and the eruption occurred nearby the most deformed part. The deformation speed correlated well with inflation of spherical source located at 4.8 km below sea level, thus suggesting that heat and/or volcanic fluid supply from the spherical source, maybe magma reservoir, directly drove the subsurface hydrothermal activity. Our results demonstrate that high-spatial-resolution deformation data can be a good indicator of subsurface pressure conditions with pinpoint spatial accuracy during the preparatory process of phreatic eruptions.

A multidisciplinary approach for high-resolution reconstruction of the eruptive past of La Soufrière (Guadeloupe) over the last 12 000 years: Implications for hazards assessment.

NASA Astrophysics Data System (ADS)

Legendre, Yoann; Komorowski, Jean-Christophe; Boudon, Georges

2010-05-01

La Soufrière de Guadeloupe is a dangerous andesitic composite volcano characterized over the last 12 000 years by numerous phreatic eruptions that alternate with few magmatic eruptions, including the last magmatic and best-studied "Soufrière" subplinian eruption in 1530 AD, and unusually numerous flank-collapse events. Field analysis of the deposits provide constraints for values of the physical input parameters for simple models which provide with first-order simulation of eruptive phenomena, and from which quantitative probabilistic hazard maps can be elaborated in which epistemic and aleatory uncertainty can be incorporated and quantified. The study of yesterday's eruptions provide key insights for elaborating realistic simulations and describing potential eruptive scenarios for tomorrow's eruptions. However hazard assessment is biased towards eruptions of significant magnitude that produce extensive, and relatively thick deposits. Nevertheless, eruptions of moderate magnitude which are often more frequent, can significantly affect vulnerable island communities living at short distances from the vent. However, their deposits are ephemeral in the geologic record on account of intense erosion from tropical rainfall, important soil development and erosion by the emplacement of recurrent pyroclastic density currents, debris avalanches, and mudflows. We have developed a novel approach by using a manual sediment corer to obtain undisturbed sedimentary eruptive archives in sheltered zones on the volcano where a longer eruption record has been preserved. We describe two such cores (6.32 and 6.64 m long) that extend over at least 8700 years and that contain several thin tephra layers missing at the outcrop scale. We combine these new data with the analysis of more than 120 stratigraphic sections on outcrops studied over the last decade to provide a new eruptive chronology for La Soufriere volcano over the last 12 000 years. This chronology is robustly constrained by 105 new 14C age dates of wood, charcoal, and paleosoil samples that complete the existing 14C database (total of about 261 dates). A multidisciplinary analysis (sedimentology, lithology, microtextures, magnetic susceptibility) of the sediment cores and field data has allowed us to identify hidden, and missing eruptions, and to re-interpret mis-identified eruptions. For the last 12 000 years we have identified at least 5 distinct new pumice fallout deposits, some of which are associated with pumice pyroclastic flow deposits. We also identified several deposits formed by magmatic turbulent pyroclastic density currents (blasts) mostly associated with flank-collapse events. Thus, the number of Holocene magmatic eruptions has significantly increased compared to previous knowledge. More over we have identified eruptive sequences that consist of a diverse range of phenomena including edifice-collapse, associated laterally directed explosions (blasts), pumice fallout with column-collapse and dome growth similar to the AD1530 most recent magmatic eruption. The magmatic eruptive rate could be twice as important with 11-13 magmatic eruptions in 12 000 years, a rate of about 0.92-1.08 magmatic eruption by 1000 years. This new data will allow a better determination of the recurrence, magnitude, intensity, and the spatio-temporal evolution of deposit types that define different eruptive scenarios. Hence, this high-resolution reconstruction of the eruptive past will provide the basis for an improved probabilistic hazard and risk assessment for La Soufrière of Guadeloupe, a dangerous volcano, currently experiencing prolongued unrest since 1992.

Data evaluation, analysis, and scientific study

NASA Technical Reports Server (NTRS)

Wu, S. T.

1991-01-01

Extensive work was performed in data analysis and modeling of solar active phenomena. The work consisted in the study of UV data from the Ultraviolet Spectrometer and Polarimeter (UVSP) instrument on board the Solar Maximum Mission satellite. These data were studied in conjunction with X-rays from the Hard X-ray Imaging Spectrometer (HXIS) instrument, and with H-alpha and magnetographic data from ground-based observatories. The processes we studied are the active phenomena which result from the interaction of the solar magnetic fields with the plasma in the outer regions of the solar atmosphere. These processes include some very dynamic processes such as the prominence eruptions and the 'microflares'. Our research aimed at characterizing the following: the observed phenomena, the possible physical models, and the relevance to the chromospheric and coronal heating.

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.

Basaltic scoria fallout deposits from Ambrym volcano (Vanuatu archipelago): Textural and geochemical evidence of plinian eruptive styles

NASA Astrophysics Data System (ADS)

Balcone-Boissard, H.; Boudon, G.; Poulain, P.

2017-12-01

Plinian eruptions are among the most threatening volcanic hazard responsible of gas and solid particles release into atmosphere leading to potential damages at various spatial and time scales. Such explosive activity generally involves differentiated magmas, silica-rich enough to behave as viscous media and volatile-rich enough to generate significant overpressure in ascending magma. In some rare cases, Plinian eruptions can occur with more basic magmas as basalts. Few eruptions are now recognized on Earth, on Etna (122 BC), Masaya (Fontana) or Tarawera (1886). On Ambrym volcano (Vanuatu), the caldera formation was the result of several large eruptions including some Plinian events dated around 2000 yr. BP. By applying joint textural and geochemical investigations of a representative stratigraphic section of one of these eruptions we present new arguments to discuss the origin of such explosivity for basic magma. To achieve this goal we establish a degassing budget (H2O, CO2, SO2, F, Cl) through the petrological investigation by comparing melt inclusion and residual glass. We compare these results to those of quantitative textural description of pumice clasts through SEM images treated using Image J software, thus linking textural and geochemical arguments. We thus highlight that a low volatile content is not responsible of the overpressure leading to explosivity. Textural characteristics evidence vesicle organisation and low microlite content close that described for Plinian eruption involving differentiated melt. Degassing processes occur following a closed-system degassing evolution well correlated with textural parameters. By comparison to deposits of other basaltic Plinian eruptions, we show that for 122 BC eruption of Mt Etna, textural signature is diverse although we also evidence closed-system degassing processes. This study also permits to confirm that Ambrym is a valuable contributor to halogen release into the atmosphere at a time of reflexion on volcanic halogen contribution to atmosphere budget.

Quantify ash aggregation associated to the 26 April 1979 Saint Vincent de la Soufrière eruption

NASA Astrophysics Data System (ADS)

Poret, Matthieu; Costa, Antonio; Folch, Arnau

2016-04-01

The 26 April 1979 an eruption occurred at Saint Vincent de la Soufrière volcano, West Indies, generating an extended tephra fallout deposit from the slope of the volcano toward the South of the island. This event was observed and studied by Brazier et al. (1982). This study provided a few tens of field observations that allowed an estimation of the tephra loading map and other observations on volcanological parameters such as eruptive column height, duration and erupted volume. They also provided information related to aggregation that was significant during the eruption. Here, the field observations and the meteorological fields are used in order to reconstruct the tephra dispersal by using the Fall3D model. The main goal is to better quantify the total mass of fine ash that aggregated during the eruption providing important information and constraints on aggregation processes. The preliminary results show that field observations are well captured using the simplified aggregation parameterization proposed by Cornell et al. (1983) whereas accretionary lapilli can be described adding a second aggregate class (with a diameter of 2 mm, a density of 2000 kg/m3 and a sphericity of 1) representing only a few percentage of the total amount of tephra. Such percentage was estimated by an empirical approach best fitting field observation. The simulation that best fit the field observations gives an estimation of the column height of about 12.5 km above the vent, a mass eruption rate of 6.0d+6 kg/s and a total mass of 2.2d+9 kg erupted. To go further we will use these results within the 1-D cross-section averaged eruption column model named FPLUME-1.0 based on the Buoyant Plume Theory (BPT) that considers aggregation processes within the plume.

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.

Study New Pregress on Volcanic Phreatomagmatic Eruption

NASA Astrophysics Data System (ADS)

Sun, Q.; Fan, Q.; Li, N.

2007-12-01

As an essential and important type of volcanic eruption on earth, phreatomagmatic eruption is characterized by groundwater-related explosive eruption and subsequent base surge deposit and maar lakes. Base surge deposit and maar lakes are widely distributed all over the world, and also in the Northeast China and the southern China. Study of phreatomagmatic eruption maybe dated back to 1921, and in the following over 80 years, many works have been done on phreatomagmatic eruption, using various of methods of volcanic geology, petrology, sedimentology, physical volcanology and digital modeling, to discuss its origin and mechanism. In this paper, we focus on the geological feature of the base surge deposit and dynamic mechanism of the phreatomagmatic eruption. When ascending basaltic magma meets with ground ( surface ) water, violent explosion would occur, this action was called phreatomagmatic eruption. The main product of this kind of eruption are maars and base surge. As to the base surge, it has long been treated as sedimentary tuff by mistake. Usually, base surge is distributed around maar, different from the distribution of sedimentary tuff. Typical phenomena of base surge caused by phreatomagmatic eruption can be observed through the detail field work, such as large-scale and low-angle cross-bedding, slaty-bedding, current-bedding and distal facies accretionary lapilli. In order to explain the dynamic mechanism of phreatomagmatic eruption thoroughly, we propose a simple model in this paper in light of the elasticity theory. Some conclusions can be drawn as follows: the larger the radius of maar, the larger the explosive wallop needed for the formation of maar is; provided that the radius of maar and depth of explosive point are limited, then the larger the area of contact surface between magma and groundwater, the stronger the explosive energy will be; if the explosive energy and area of explosive point are restricted, the larger the radius of maar, the greater the depth of explosive point can be inferred; when the explosive energy and radius of maar are qualified, the depth of explosive point decreases with increasing of the area of contact surface between magma and groundwater. As for the maximum stress, undoubtedly it should occur on the surface of the overlying formation.

Developing Regional Tephrostratigraphic Frameworks: Applications and Challenges.

NASA Astrophysics Data System (ADS)

Fontijn, K.; Pyle, D. M.; Smith, V.; Mather, T. A.

2017-12-01

Detailed stratigraphic studies of pyroclastic deposits form arguably the best tool to estimate the frequency and magnitude of explosive eruptions at volcanoes where limited or no historical records exist. As such tephrostratigraphy forms a first-order assessment of potential future eruptive behavior at poorly known volcanoes. Alternations of soils and pyroclastic deposits at proximal to medial distances of the volcano however typically only allow reconstructing eruptive behavior within the Holocene. Moreover, they only tend to preserve relatively large explosive eruptions, of magnitude 3-4 and above, and therefore almost invariably form a biased view of the frequency-magnitude relationships at a particular volcano. Long lacustrine records in medial to distal regions offer significant potential to obtain a more complete view of the explosive eruptive record as they often preserve thin fine-grained tephra deposits representing either small-scale explosive eruptions not preserved on land, or distal ash deposits from large explosive eruptions. Furthermore, these sedimentary records often contain material that can be dated to establish a detailed age-depth model that can be used to date the eruptions and estimate the tempo of activity. In settings where volcanoes and lakes closely co-exist, integrating terrestrial and lacustrine data therefore allows the development of regional-scale tephrostratigraphic frameworks. Such frameworks provide a view of temporal trends in volcanic activity and mid/long-term eruptive rates on a regional scale rather than at the level of an individual volcano, i.e. in interaction with regional tectonic stress regimes. They also highlight the spatial distribution of deposits from large explosive eruptions, allowing improved estimates of magnitudes of individual eruptions as well as of frequency of impact by volcanic ash in specific regions. Provided such tephra horizons are well characterized and dated they can be used as age marker horizons and help fine-tune age models for palaeoenvironmental studies. In this presentation we will highlight a few key examples of both local and regional-scale tephrostratigraphic frameworks in East Africa, Chile and South-East Asia, and discuss the multidisciplinary applications as well as challenges posed by data acquisition.

Degassing and microlite crystallization during pre-climactic events of the 1991 eruption of Mt. Pinatubo, Philippines

USGS Publications Warehouse

Hammer, J.E.; Cashman, K.V.; Hoblitt, R.P.; Newman, S.

1999-01-01

Dacite tephras produced by the 1991 pre-climactic eruptive sequence at Mt. Pinatubo display extreme heterogeneity in vesicularity, ranging in clast density from 700 to 2580 kg m-3. Observations of the 13 surge-producing blasts that preceded the climactic plinian event include radar-defined estimates of column heights and seismically defined eruptive and intra-eruptive durations. A comparison of the characteristics of erupted material, including microlite textures, chemical compositions, and H2O contents, with eruptive parameters suggests that devolatilization-induced crystallization of the magma occurred to a varying extent prior to at least nine of the explosive events. Although volatile loss progressed to the same approximate level in all of the clasts analyzed (weight percent H2O=1.26-1.73), microlite crystallization was extremely variable (0-22%). We infer that syn-eruptive volatile exsolution from magma in the conduit and intra-eruptive separation of the gas phase was facilitated by the development of permeability within magma residing in the conduit. Correlation of maximum microlite crystallinity with repose interval duration (28-262 min) suggests that crystallization occurred primarily intra-eruptively, in response to the reduction in dissolved H2O content that occurred during the preceding event. Detailed textural characterization, including determination of three-dimensional shapes and crystal size distributions (CSD), was conducted on a subset of clasts in order to determine rates of crystal nucleation and growth using repose interval as the time available for crystallization. Shape and size analysis suggests that crystallization proceeded in response to lessening degrees of feldspar supersaturation as repose interval durations increased. We thus propose that during repose intervals, a plug of highly viscous magma formed due to the collapse of vesicular magma that had exsolved volatiles during the previous explosive event. If plug thickness grew proportionally to the square root of time, and if magma pressurization increased during the eruptive sequence, the frequency of eruptive pulses may have been modulated by degassing of magma within the conduit. Dense clasts in surge deposits probably represent plug material entrained by each subsequent explosive event.

Pyroclastic Deposits in Floor-Fractured Craters: A Unique Style or Lunar Basaltic Volcanism?

NASA Technical Reports Server (NTRS)

Allen, Carlton C.; DonaldsonHanna, Kerri L.; Pieters, Carle M.; Moriarty, Daniel P.; Greenhagen, Benjamin T.; Bennett, Kristen A.; Kramer, Georgiana Y.; Paige, David A.

2013-01-01

The lunar maria were formed by effusive fissure flows of low-viscosity basalt. Regional pyroclastic deposits were formed by deep-sourced fire-fountain eruptions dominated by basaltic glass. Basaltic material is also erupted from small vents within floor-fractured impact craters. These craters are characterized by shallow, flat floors cut by radial, concentric and/or polygonal fractures. Schultz [1] identified and classified over 200 examples. Low albedo pyroclastic deposits originate from depressions along the fractures in many of these craters.

Importance of Geodetically Controlled Topography to Constrain Rates of Volcanism and Internal Magma Plumbing Systems

NASA Technical Reports Server (NTRS)

Glaze, Lori S.; Baloga, S. M.; Garvin, James B.; Quick, Lynnae C.

2014-01-01

Investigation of lava flow deposits is a key component of Investigation II.A.1 in the VEXAG Goals, Objectives and Investigations. Because much of the Venus surface is covered in lava flows, characterization of lava flow emplacement conditions(eruption rate and eruption duration) is critical for understanding the mechanisms through which magma is stored and released onto the surface as well as for placing constraints on rates of volcanic resurfacing throughout the geologic record preserved at the surface.

The 2004–2008 dome-building eruption at Mount St. Helens, Washington: Epilogue

USGS Publications Warehouse

Dzurisin, Daniel; Moran, Seth C.; Lisowski, Michael; Schilling, Steve P.; Anderson, Kyle R.; Werner, Cynthia A.

2015-01-01

The 2004–2008 dome-building eruption at Mount St. Helens ended during winter 2007–2008 at a time when field observations were hampered by persistent bad weather. As a result, recognizing the end of the eruption was challenging—but important for scientists trying to understand how and why long-lived eruptions end and for public officials and land managers responsible for hazards mitigation and access restrictions. In hindsight, the end of the eruption was presaged by a slight increase in seismicity in December 2007 that culminated on January 12–13, 2008, with a burst of more than 500 events, most of which occurred in association with several tremor-like signals and a spasmodic burst of long-period earthquakes. At about the same time, a series of regular, localized, small-amplitude tilt events—thousands of which had been recorded during earlier phases of the eruption—came to an end. Thereafter, seismicity declined to 10–20 events per day until January 27–28, when a spasmodic burst of about 50 volcano-tectonic earthquakes occurred over a span of 3 h. This was followed by a brief return of repetitive “drumbeat” earthquakes that characterized much of the eruption. By January 31, however, seismicity had declined to 1–2 earthquakes per day, a rate similar to pre-eruption levels. We attribute the tilt and seismic observations to convulsive stagnation of a semisolid magma plug in the upper part of the conduit. The upward movement of the plug ceased when the excess driving pressure, which had gradually decreased throughout the eruption as a result of reservoir deflation and increasing overburden from the growing dome, was overcome by increasing friction as a result of cooling and crystallization of the plug.

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.

Eruptive Facial Postinflammatory Lentigo: Clinical and Dermatoscopic Features.

PubMed

Cabrera, Raul; Puig, Susana; Larrondo, Jorge; Castro, Alex; Valenzuela, Karen; Sabatini, Natalia

2016-11-01

The face has not been considered a common site of fixed drug eruption, and the authors lack dermatoscopic studies of this condition on the subject. The authors sought to characterize clinical and dermatoscopic features of 8 cases of an eruptive facial postinflammatory lentigo. The authors conducted a retrospective review of 8 cases with similar clinical and dermatoscopic findings seen from 2 medical centers in 2 countries during 2010-2014. A total of 8 patients (2 males and 6 females) with ages that ranged from 34 to 62 years (mean: 48) presented an abrupt onset of a single facial brown-pink macule, generally asymmetrical, with an average size of 1.9 cm. after ingestion of a nonsteroidal antiinflammatory drugs that lasted for several months. Dermatoscopy mainly showed a pseudonetwork or uniform areas of brown pigmentation, brown or blue-gray dots, red dots and/or telangiectatic vessels. In the epidermis, histopathology showed a mild hydropic degeneration and focal melanin hyperpigmentation. Melanin can be found freely in the dermis or laden in macrophages along with a mild perivascular mononuclear infiltrate. The authors describe eruptive facial postinflammatory lentigo as a new variant of a fixed drug eruption on the face.

Numerical simulations of block-and-ash flows using the Titan2D flow model: examples from the 2006 eruption of Merapi Volcano, Java, Indonesia

NASA Astrophysics Data System (ADS)

Charbonnier, S. J.; Gertisser, R.

2009-10-01

We present Titan2D simulations of two well-characterized block-and-ash flow (BAF) events of the 2006 eruption of Merapi (Java, Indonesia) that affected the Gendol valley on the volcano’s southern flank and adjacent, densely populated interfluve (non-valley) areas: (1) a single dome-collapse event to the south that generated one of the smaller, post-June 14 flows and (2) a sustained, multiple dome-collapse event, also directed to the south, that produced the largest flows of the 2006 eruption emplaced in the afternoon of June 14. Using spatially varying bed friction angles, Titan2D is capable of reproducing the paths, velocities, runout distance, areas covered and deposited volumes of these flows over highly complex topography. The model results provide the basis for estimating the areas and levels of hazards associated with BAFs generated during relatively short as well as prolonged dome-collapse periods and guidance during future eruptive crises at Merapi.

Ground penetrating radar documents short-term near-surface hydrological changes around Old Faithful Geyser, Yellowstone National Park, USA

NASA Astrophysics Data System (ADS)

Lynne, Bridget Y.; Heasler, Henry; Jaworowski, Cheryl; Smith, Gary J.; Smith, Isaac J.; Foley, Duncan

2018-04-01

In April 2015, Ground Penetrating Radar (GPR) was used to characterize the shallow subsurface (< 5 m depth) of the western sinter slope immediately adjacent to Old Faithful Geyser and near the north side of an inferred geyser cavity. A series of time-sequence images were collected between two eruptions of Old Faithful Geyser. Each set of time-sequence GPR recordings consisted of four transects aligned to provide coverage near the potential location of the inferred 15 m deep geyser chamber. However, the deepest penetration we could achieve with a 200 MHz GPR antennae was 5 m. Seven time-sequence events were collected over a 48-minute interval to image changes in the near-surface, during pre- and post-eruptive cycles. Time-sequence GPR images revealed a series of possible micro-fractures in a highly porous siliceous sinter in the near-surface that fill and drain repetitively, immediately after an eruption and during the recharge period prior to the next main eruptive event.

InSAR observations of deformation associated with new episodes of volcanism at Kilauea Volcano, Hawai'i, 2007

USGS Publications Warehouse

Poland, Michael P.

2008-01-01

In June 2007, the Pu'u 'Ō'ō-Kūpaianaha eruption of Kīlauea Volcano was interrupted when magma intruded the east rift zone (ERZ), resulting in a small extrusion of lava near Makaopuhi Crater. Deformation associated with the activity was exceptionally well-documented by ASAR interferometry, which indicates deflation of the summit and uplift and extension of the ERZ. Models of co-intrusion interferograms suggest that the dike was emplaced in two distinct segments. The modeled volume of the dike greatly exceeds that of the deflation source, raising the possibility that magma from the downrift Pu'u 'Ō'ō vent (dominant extrusion site at Kīlauea since 1983) contributed to the eruption near Makaopuhi, or that the magma that fed the eruption from the summit was compressible. A month following the Makaopuhi eruption, an eruptive fissure opened on the east flank of Pu'u 'Ō'ō. Interferograms, processed within 48 hours of the event, were critical in demonstrating that the magma source feeding the eruption was shallow. The eruption probably resulted from overpressure in Pu'u 'Ō'ō's magmatic system.

Eruptive and Geomorphic Processes at the Lathrop Wells Scoria Cone

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

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

2006-08-03

The {approx}80 ka Lathrop Wells volcano (southern Nevada, U.S.A.) preserves evidence for a range of explosive processes and emplacement mechanisms of pyroclastic deposits and lava fields in a small-volume basaltic center. Early cone building by Strombolian bursts was accompanied by development of a fan-like lava field reaching {approx}800 m distance from the cone, built upon a gently sloping surface. Lava flows carried rafts of cone deposits, which provide indirect evidence for cone facies in lieu of direct exposures in the active quarry. Subsequent activity was of a violent Strombolian nature, with many episodes of sustained eruption columns up to amore » few km in height. These deposited layers of scoria lapilli and ash in different directions depending upon wind direction at the time of a given episode, reaching up to {approx}20 km from the vent, and also produced the bulk of the scoria cone. Lava effusion migrated from south to north around the eastern base of the cone as accumulation of lavas successively reversed the topography at the base of the cone. Late lavas were emplaced during violent Strombolian activity and continued for some time after explosive eruptions had waned. Volumes of the eruptive products are: fallout--0.07 km{sup 3}, scoria cone--0.02 km{sup 3}, and lavas--0.03 km{sup 3}. Shallow-derived xenolith concentrations suggest an upper bound on average conduit diameter of {approx}21 m in the uppermost 335 m beneath the volcano. The volcano was constructed over a period of at least seven months with cone building occurring only during part of that time, based upon analogy with historical eruptions. Post-eruptive geomorphic evolution varied for the three main surface types that were produced by volcanic activity: (1) scoria cone, (2) low relief surfaces (including lavas) with abundant pyroclastic material, and (3) lavas with little pyroclastic material. The role of these different initial textures must be accounted for in estimating relative ages of volcanic surfaces, and failure to account for this resulted in previous erroneous interpretation that the volcano is polycyclic (eruptions separated by 1,000s-10,000s of years). Lathrop Wells volcano provides an example of the wide range of eruptive processes that can occur with little change in major element composition; the variation in explosive and effusive processes, including their simultaneous occurrence, must result entirely from fluid dynamic, crystallization, and degassing processes in the ascending multiphase magma. The volcano also provides key analog information regarding processes that are important for volcanic risk assessment at the proposed Yucca Mountain radioactive waste repository, {approx}18 km north of the volcano.« less

The Geothermal Systems along the Watukosek fault system (East Java, Indonesia):The Arjuno-Welirang Volcanic Complex and the Lusi Mud-Eruption

NASA Astrophysics Data System (ADS)

Inguaggiato, Salvatore; Mazzini, Adriano; Vita, Fabio; Sciarra, Alessandra

2016-04-01

The Java Island is characterized by an intense volcanic activity with more then 100 active volcanoes. Moreover, this island is also known by the presence of many mud volcanoes and hydrothermal springs. In particular, in the 2006 several sudden hot mud eruptions, with fluids around 100° C, occurred in the NE side of the island resulting in a prominent eruption named Lusi (contraction of Lumpur Sidoarjo) located along the major Watukosek strike-slip fault zone. The Watukosek fault system, strikes from the Arjuno-Welirang volcanic complex, intersects Lusi and extends towards the NE of the Java island. Conversely of the normal mud eruptions (cold fluids emitted in a short time period of few days), the Lusi eruption was characterized by a persistent effusive hot fluids emissions for a long-time period of, so far, nearly a decade. Moreover, the isotopic composition of emitted gases like Helium showed a clear magmatic origin. For this reasons we decided to investigate the near Arjuno-Welirang complex located on the same strike-slip fault. Arjuno-Welirang is a twin strato-volcano system located in the East of Java along the Watukosek fault, at about 25 km SW respect to the Lusi volcano system. It features two main peaks: Arjuno (3339 masl) and Welirang (3156 masl). The last recorded eruptive activity took place in August 1950 from the flanks of Kawah Plupuh and in October 1950 from the NW part of the Gunung Welirang. This strato-volcano is characterized by a S-rich area, with high T-vent fumarole at least up to 220° C (and likely higher), located mainly in the Welirang crater. In addition, several hot springs vent from the flanks of the volcano, indicate the presence of a large hydrothermal system. During July 2015, in the framework of the Lusi Lab project (ERC grant n° 308126), we carried out a geochemical field campaign on the Arjuno-Welirang volcano hydrothermal system area, sampling water and dissolved gases from the thermal and cold springs located on the flanks of the volcano and from two high-T fumaroles located on the summit area of Welirang. Hydrothermal springs reveal temperatures up to 53° C and pH between 6.2 and 8.2. The hydrothermal springs show a volatile content (mainly CO2 and He) that is several order of magnitude higher than the Air Saturated Waters values (ASW) indicating a strong gas/water interaction processes between waters of meteoric origin and deep volatiles of volcanic origin. The hydrothermal springs have dissolved helium isotopic values with clear magmatic signature (R/Ra around 7) that is remarkably close to the helium isotope values from the fumaroles (R/Ra= 7.30). The isotopic composition of helium measured in the fluids emitted from the Lusi mud-volcano around 6.5R/Ra is very similar to the Welirang volcanic fluids indicating the presence of magmatic gases in the Lusi emitted fluids. While the isotopic composition of waters in the Welirang and Lusi fluids are markedly different suggesting a different origin and/or recharge areas for these two hydrothermal systems. These data support the hypothesis that the presence of volcanic gases could have triggered and conveyed the hot and persistent mud fluids emissions of Lusi volcano.

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.

Determining the physical and chemical processes behind four caldera-forming eruptions in rapid succession in the San Juan caldera cluster, Colorado, USA

NASA Astrophysics Data System (ADS)

Curry, A. C.; Caricchi, L.; Lipman, P. W.

2017-12-01

A primary goal of volcanology is to understand the frequency and magnitude of large, explosive volcanic eruptions to mitigate their impact on society. Recent studies show that the average magma flux and the time between magma injections into a given magmatic-volcanic system fundamentally control the frequency and magnitude of volcanic eruptions, yet these parameters are unknown for many volcanic regions on Earth. We focus on major and trace element chemistry of individual phases and whole-rock samples, initial zircon ID-TIMS analyses, and zircon SIMS oxygen isotope analyses of four caldera-forming ignimbrites from the San Juan caldera cluster in the Southern Rocky Mountain volcanic field, Colorado, to determine the physical and chemical processes leading to large eruptions. We collected outflow samples along stratigraphy of the three caldera-forming ignimbrites of the San Luis caldera complex: the Rat Creek Tuff ( 150 km3), Cebolla Creek Tuff ( 250 km3), and Nelson Mountain Tuff (>500 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 large eruptions occurred in rapid succession between 26.91 ± 0.02 Ma (Rat Creek Tuff) and 26.87 ± 0.02 Ma (Snowshoe Mountain Tuff), providing an opportunity to investigate the temporal evolution of magmatic systems feeding large, explosive volcanic eruptions. Major and trace element analyses show that the first and last eruption of the San Luis caldera complex (Rat Creek Tuff and Nelson Mountain Tuff) are rhyolitic to dacitic ignimbrites, whereas the Cebolla Creek Tuff and Snowshoe Mountain Tuff are crystal-rich, dacitic ignimbrites. Trace elements show enrichment in light rare-earth elements (LREEs) over heavy rare-earth elements (HREEs), and whereas the trace element patterns are similar for each caldera cycle, trace element values for each ignimbrite show variability in HREE concentrations. This variability indicates that these large eruptions sampled a magmatic system with some degree of internal heterogeneity. These results have implications for the chemical and physical processes, such as magmatic flux and injection periodicity, leading to the formation of large magmatic systems prior to large, explosive eruptions.

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.

Eruptive dynamics during magma decompression: a laboratory approach

NASA Astrophysics Data System (ADS)

Spina, L.; Cimarelli, C.; Scheu, B.; Wadsworth, F.; Dingwell, D. B.

2013-12-01

A variety of eruptive styles characterizes the activity of a given volcano. Indeed, eruptive styles can range from effusive phenomena to explosive eruptions, with related implications for hazard management. Rapid changes in eruptive style can occur during an ongoing eruption. These changes are, amongst other, related to variations in the magma ascent rate, a key parameter affecting the eruptive style. Ascent rate is in turn dependent on several factors such as the pressure in the magma chamber, the physical properties of the magma and the rate at which these properties change. According to the high number of involved parameters, laboratory decompression experiments are the best way to achieve quantitative information on the interplay of each of those factors and the related impact on the eruption style, i.e. by analyzing the flow and deformation behavior of the transparent volatile-bearing analogue fluid. We carried out decompression experiments following different decompression paths and using silicone oil as an analogue for the melt, with which we can simulate a range of melt viscosity values. For a set of experiments we added rigid particles to simulate the presence of crystals in the magma. The pure liquid or suspension was mounted into a transparent autoclave and pressurized to different final pressures. Then the sample was saturated with argon for a fixed amount of time. The decompression path consists of a slow decompression from the initial pressure to the atmospheric condition. Alternatively, samples were decompressed almost instantaneously, after established steps of slow decompression. The decompression path was monitored with pressure transducers and a high-speed video camera. Image analysis of the videos gives quantitative information on the bubble distribution with respect to depth in the liquid, pressure and time of nucleation and on their characteristics and behavior during the ongoing magma ascent. Furthermore, we also monitored the evolution of the expanding height of the silicone oil column with time after the decompression, due to the exsolution of the volatile argon and subsequent bubble growth. Contrastingly, autoclave-wall resolved shear strain of bubbles promotes rapid coalescence until a critical point when permeable outgassing is more efficient than continuing exsolution and bubble growth. At this point the column destabilizes and partially collapses. Collapse progresses until the top of the column is again impermeable and outgassing-driven column expansion resumes. This process repeats in cycles of growth, deformation, destabilization and densification until the melt is at equilibrium saturation with argon and the column collapses completely. We propose that direct observation of the timescales of growth and collapse of a decompressing, shearing column has important implications for decompression-driven rapid conduit ascent of low-viscosity, low-crystallinity magmas. Therefore, even at high exsolution rates, permeable outgassing can transiently retard magma ascent.

Monogenetic Arc Volcanism in the Central Andes: The "Hidden" Mafic Component in the Land of Andesite and Ignimbrite

NASA Astrophysics Data System (ADS)

van Alderwerelt, B. M.; Ukstins Peate, I.; Ramos, F. C.

2016-12-01

Faulting in the upper crust of the Central Andes has provided passage for small volumes of mafic magma to reach the surface, providing a window into petrogenetic processes in the region's deep crust and upper mantle. Mafic lavas are rare in the Central Andean region dominated by intermediate-composition arc volcanism and massive sheets of silicic ignimbrite, and provide key data on magmatic origin, evolution, and transport. This work characterizes fault-controlled, within-arc monogenetic eruptive centers representative of the most mafic volcanism in the Altiplano-Puna region of the Andes since (at least) the Mesozoic. Olivine-phyric basaltic andesite (54 wt% SiO2, 7.3 wt% MgO) at Cerro Overo maar and associated dome, La Albóndiga Grande, and an olivine-clinopyroxene flow (53 wt% SiO2, 6.7 wt% MgO) from Cordón de Puntas Negras have been erupted at the intersection of regional structural features and the modern volcanic arc. Bulk magma chemistry, radiogenic isotopes, and microanalyses of mineral and melt inclusion composition provide insight on the composition(s) of mafic magmas being delivered to the lowermost crust and the deep crustal processes which shape central Andean magma. Bulk major and trace elements follow regional arc differentiation trends and are clearly modified by crustal magmatic processes. In contrast, microanalyses reveal a much richer history with olivine-hosted melt inclusions recording multiple distinct magmas, including potential primary melts. Single crystal olivine 87Sr/86Sr from Cerro Overo (0.7041-0.7071) define a broader range than whole rock (0.7062-0.7065), indicating preservation of juvenile melt in olivine-hosted inclusions lost at the whole rock scale. Mineral chemistry (via EMPA) P-T calculations define a petrogenetic history for these endmember lavas. Field mapping, bulk chemistry, and microanalyses outline the generation, storage, transportation, and eventual eruption of the "hidden" mafic component of the Andean arc.

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.

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.

Illuminating the Voluminous Subsurface Structures of Old Faithful Geyser, Yellowstone National Park

NASA Astrophysics Data System (ADS)

Hurwitz, Shaul; Shelly, David R.

2017-10-01

Old Faithful geyser in Yellowstone National Park has attracted scientific research for almost a century and a half. Temperature and pressure measurements and video recordings in the geyser's conduit led to proposals of many quantitative eruption models. Nevertheless, information on the processes that initiate the geyser's eruption in the subsurface remained limited. Two new studies, specifically Wu et al. (2017) and Ward and Lin (2017), take advantage of recent developments in seismic data acquisition technology and processing methods to illuminate subsurface structures. Using a dense array of three-component nodal geophones, these studies delineate subsurface structures on a scale larger than previously realized, which exert control on the spectacular eruptions of Old Faithful geyser.

Syn-eruptive CO2 Degassing of Submarine Lavas Flows: Constraints on Eruption Dynamics

NASA Astrophysics Data System (ADS)

Soule, S. A.; Boulahanis, B.; Fundis, A.; Clague, D. A.; Chadwick, B.

2013-12-01

At fast- and intermediate-spreading rate mid-ocean ridges, quenched lava samples are commonly supersaturated in CO2 with concentrations similar to the pressure/depth of shallow crustal melt lenses. This supersaturation is attributed to rapid ascent and decompression rates that exceed the kinetic rates of bubble nucleation and growth. During emplacement, CO2 supersaturated lavas experience nearly isothermal and isobaric conditions over a period of hours. A recent study has demonstrated systematic decreases in CO2 with increasing transport distance (i.e. time) along a single flow pathway within the 2005-06 eruption at the East Pacific Rise (~2500 m.b.s.l.). Based on analysis of vesicle population characteristics and complementary noble gas measurements, it is proposed that diffusion of CO2 into bubbles can be used as a basis to model the gas loss from the melt and thus place constraints on the dynamics of the eruption. We suggest that submarine lava flows represent a natural experiment in degassing that isolates conditions of low to moderate supersaturation and highlights timescales of diffusion and vesiculation processes that are relevant to shallow crustal and conduit processes in subaerial basaltic volcanic systems. Here we report a new suite of volatile concentration analyses and vesicle size distributions from the 2011 eruption of Axial Volcano along the Juan de Fuca Ridge (~1500 m.b.s.l.). The lava flows from this eruption are mapped by differencing of repeat high-resolution bathymetric surveys, so that the geologic context of the samples is known. In addition, in-situ instrument records record the onset of the eruption and place constraints on timing that can be used to verify estimates of eruption dynamics derived from degassing. This sample suite provides a comprehensive view of the variability in volatile concentrations within a submarine eruption and new constraints for evaluating models of degassing and vesiculation. Initial results show systematic variability in CO2 supersaturation along eruptive fissures as well as with increasing distance along flows pathways providing constraints on threshold decompression rates required to nucleate and grow bubbles in a basaltic melt, timescales of degassing in natural systems, and the properties of consequent vesicle populations.

MHD Forces in Quasi-Static Evolution, Catastrophe, and ``Failed'' Eruption of Solar Flux Ropes

NASA Astrophysics Data System (ADS)

Chen, James

2017-08-01

This paper presents the first unified theoretical model of flux rope dynamics---a single set of flux-rope equations in ideal MHD---to describe as one dynamical process the quasi-static evolution, catastrophic transition to eruption, cessation (``failure'') of eruption, and the post-eruption quasi-equilibria. The model is defined by the major radial {\\it and} minor radial equations of motion including pressure. The initial equilibrium is a flux rope in a background plasma with pressure $p_c(Z)$ and an overlying magnetic field $B_c(Z)$. The flux rope is initially force-free, but theevolution is not required to be force- free. A single quasi-static control parameter, the rate of increase in poloidal flux, is used for the entire process. As this parameter is slowly increased, the flux rope rises, following a sequence of quasi-static equilibria. As the apex of the flux rope rises past a critical height $Z_{crt}$, it expands on a dynamical (Alfvénic) timescale. The eruption rapidly ceases, as the stored magnetic energy of eruption is exhausted, and a new equilibrium is established at height $Z_1 > Z_{crt}$. The calculated velocity profile resembles the observed velocity profiles in ``failed'' eruptions including a damped oscillation. In the post-eruption equilibria, the outward hoop force is balanced by the tension of the toroidal self magnetic field and pressure gradient force. Thus, the flux rope does not evolve in a force-free manner. The flux rope may also expand without reaching a new equilibrium, provided a sufficient amount of poloidal flux is injected on the timescale of eruption. This scenario results in a full CME eruption. It is shown that the minor radial expansion critically couples the evolution of the toroidal self-field and pressure gradient force. No parameter regime is found in which the commonly used simplifications---near-equilibrium minor radial expansion, force-free expansion, and constant aspect ratio $R/a$ (e.g., the torus instability equation)---are valid.Work supported by the Naval Research Laboratory Base Research Program

Numerical investigation of permeability models for low viscosity magmas: Application to the 2007 Stromboli effusive eruption

NASA Astrophysics Data System (ADS)

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

2017-09-01

Magma permeability is the most important factor controlling the transition between effusive and explosive styles during magma ascent at active volcanoes. When magma permeability is low, gas bubbles in the melt expand as the pressure decreases; above a critical gas volume fraction threshold, magma fragments, generating an explosive eruption. On the contrary, if magma is sufficiently permeable, gas ascends through the conduit towards the surface faster than the magma ascent speed, producing decoupling of gas and magma and reducing the maximum vesicularity. This decoupled flow inhibits fragmentation and leads to either an effusive eruption or quiescent degassing. Accurate modelling of permeability behaviour is therefore fundamental when simulating magma ascent processes. In this work, we compare different permeability models for low viscosity magmas using a 1D steady-state model. We use, as a test case, the 2007 effusive eruption at Stromboli volcano, Italy. We compare the numerical solutions computed using the linear Darcy's law with those obtained using the non-linear Forchheimer relation. Our numerical results show that, using Darcy's law and appropriate permeability models, it is possible to obtain an effusive eruption in agreement with observations. However, we found that, in the shallow conduit, the limit of applicability of Darcy's law (that is the modified Reynolds number Rem < 10) is exceeded due to high gas flow rates. Furthermore, we show that using Forchheimer's law and some parametric expressions for viscous and inertial permeabilities, results can be compatible with an effusive eruption, once appropriate values are chosen. However, one of the parameters required to obtain an effusive eruption, the friction coefficient between gas and melt, is several orders of magnitude lower than that determined from measurements of solid erupted samples. This result requires further experimental verification. We propose that our novel permeability modelling regime is suitable for basaltic volcanism. We highlight that permeabilities derived from studying solid samples are not representative of the actual permeability of a molten magma, at least in the case of low viscosity basaltic magmas. These findings have fundamental implications for the quantification of permeability, modelling of volcanic processes and volcanic eruption dynamics, and the forecasting of volcanic eruptions.

Video monitoring reveals pulsating vents and propagation path of fissure eruption during the March 2011 Pu'u 'Ō'ō eruption, Kilauea volcano

NASA Astrophysics Data System (ADS)

Witt, Tanja; Walter, Thomas R.

2017-01-01

Lava fountains are a common eruptive feature of basaltic volcanoes. Many lava fountains result from fissure eruptions and are associated with the alignment of active vents and rising gas bubbles in the conduit. Visual reports suggest that lava fountain pulses may occur in chorus at adjacent vents. The mechanisms behind such a chorus of lava fountains and the underlying processes are, however, not fully understood. The March 2011 eruption at Pu'u 'Ō'ō (Kilauea volcano) was an exceptional fissure eruption that was well monitored and could be closely approached by field geologists. The fissure eruption occurred along groups of individual vents aligned above the feeding dyke. We investigate video data acquired during the early stages of the eruption to measure the height, width and velocity of the ejecta leaving eight vents. Using a Sobel edge-detection algorithm, the activity level of the lava fountains at the vents was determined, revealing a similarity in the eruption height and frequency. Based on this lava fountain time series, we estimate the direction and degree of correlation between the different vents. We find that the height and velocity of the eruptions display a small but systematic shift in time along the vents, indicating a lateral migration of lava fountaining at a rate of 11 m/s from W to E. This finding is in agreement with a propagation model of a pressure wave originating at the Kilauea volcano and propagating through the dyke at 10 m/s from W to E. Based on this approach from videos only 30 s long, we are able to obtain indirect constraints on the physical dyke parameters, with important implications for lateral magma flow processes at depth. This work shows that the recording and analysis of video data provide important constraints on the mechanisms of lava fountain pulses. Even though the video sequence is short, it allows for the confirmation of the magma propagation direction and a first-order estimation of the dyke dimensions.

Pattern recognition in volcano seismology - Reducing spectral dimensionality

NASA Astrophysics Data System (ADS)

Unglert, K.; Radic, V.; Jellinek, M.

2015-12-01

Variations in the spectral content of volcano seismicity can relate to changes in volcanic activity. Low-frequency seismic signals often precede or accompany volcanic eruptions. However, they are commonly manually identified in spectra or spectrograms, and their definition in spectral space differs from one volcanic setting to the next. Increasingly long time series of monitoring data at volcano observatories require automated tools to facilitate rapid processing and aid with pattern identification related to impending eruptions. Furthermore, knowledge transfer between volcanic settings is difficult if the methods to identify and analyze the characteristics of seismic signals differ. To address these challenges we evaluate whether a machine learning technique called Self-Organizing Maps (SOMs) can be used to characterize the dominant spectral components of volcano seismicity without the need for any a priori knowledge of different signal classes. This could reduce the dimensions of the spectral space typically analyzed by orders of magnitude, and enable rapid processing and visualization. Preliminary results suggest that the temporal evolution of volcano seismicity at Kilauea Volcano, Hawai`i, can be reduced to as few as 2 spectral components by using a combination of SOMs and cluster analysis. We will further refine our methodology with several datasets from Hawai`i and Alaska, among others, and compare it to other techniques.

Tephra-fall deposits from the 1992 eruption of Crater Peak, Alaska: implications of clast textures for eruptive processes

USGS Publications Warehouse

Gardner, C.A.; Cashman, K.V.; Neal, C.A.

1998-01-01

The 1992 eruption of Crater Peak, Mount Spurr, Alaska, involved three subplinian tephra-producing events of similar volume and duration. The tephra consists of two dense juvenile clast types that are identified by color, one tan and one gray, of similar chemistry, mineral assemblage, and glass composition. In two of the eruptive events, the clast types are strongly stratified with tan clasts dominating the basal two thirds of the deposits and gray clasts the upper one third. Tan clasts have average densities between 1.5 and 1.7 g/cc and vesicularities (phenocryst free) of approximately 42%. Gray clasts have average densities between 2.1 and 2.3 g/cc, and vesicularities of approximately 20%; both contain abundant microlites. Average maximum plagioclase microlite lengths (13-15 ??m) in gray clasts in the upper layer are similar regardless of eruptive event (and therefore the repose time between them) and are larger than average maximum plagioclase microlite lengths (9-11 ???m) in the tan clasts in the lower layer. This suggests that microlite growth is a response to eruptive processes and not to magma reservoir heterogeneity or dynamics. Furthermore, we suggest that the low vesicularities of the clasts are due to syneruptive magmatic degassing resulting in microlitic growth prior to fragmentation and not to quenching of clasts by external groundwater.

The 2011 eruption of Nabro volcano, Eritrea: perspectives on magmatic processes from melt inclusions

NASA Astrophysics Data System (ADS)

Donovan, Amy; Blundy, Jon; Oppenheimer, Clive; Buisman, Iris

2018-01-01

The 2011 eruption of Nabro volcano, Eritrea, produced one of the largest volcanic sulphur inputs to the atmosphere since the 1991 eruption of Mt. Pinatubo, yet has received comparatively little scientific attention. Nabro forms part of an off-axis alignment, broadly perpendicular to the Afar Rift, and has a history of large-magnitude explosive silicic eruptions, as well as smaller more mafic ones. Here, we present and analyse extensive petrological data obtained from samples of trachybasaltic tephra erupted during the 2011 eruption to assess the pre-eruptive magma storage system and explain the large sulphur emission. We show that the eruption involved two texturally distinct batches of magma, one of which was more primitive and richer in sulphur than the other, which was higher in water (up to 2.5 wt%). Modelling of the degassing and crystallisation histories demonstrates that the more primitive magma rose rapidly from depth and experienced degassing crystallisation, while the other experienced isobaric cooling in the crust at around 5 km depth. Interaction between the two batches occurred shortly before the eruption. The eruption itself was likely triggered by recharge-induced destabilisation of vertically extensive mush zone under the volcano. This could potentially account for the large volume of sulphur released. Some of the melt inclusions are volatile undersaturated, and suggest that the original water content of the magma was around 1.3 wt%, which is relatively high for an intraplate setting, but consistent with seismic studies of the Afar plume. This eruption was smaller than some geological eruptions at Nabro, but provides important insights into the plumbing systems and dynamics of off-axis volcanoes in Afar.

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

The longevity of lava dome eruptions

NASA Astrophysics Data System (ADS)

Wolpert, Robert L.; Ogburn, Sarah E.; Calder, Eliza S.

2016-02-01

Understanding the duration of past, ongoing, and future volcanic eruptions is an important scientific goal and a key societal need. We present a new methodology for forecasting the duration of ongoing and future lava dome eruptions based on a database (DomeHaz) recently compiled by the authors. The database includes duration and composition for 177 such eruptions, with "eruption" defined as the period encompassing individual episodes of dome growth along with associated quiescent periods during which extrusion pauses but unrest continues. In a key finding, we show that probability distributions for dome eruption durations are both heavy tailed and composition dependent. We construct objective Bayesian statistical models featuring heavy-tailed Generalized Pareto distributions with composition-specific parameters to make forecasts about the durations of new and ongoing eruptions that depend on both eruption duration to date and composition. Our Bayesian predictive distributions reflect both uncertainty about model parameter values (epistemic uncertainty) and the natural variability of the geologic processes (aleatoric uncertainty). The results are illustrated by presenting likely trajectories for 14 dome-building eruptions ongoing in 2015. Full representation of the uncertainty is presented for two key eruptions, Soufriére Hills Volcano in Montserrat (10-139 years, median 35 years) and Sinabung, Indonesia (1-17 years, median 4 years). Uncertainties are high but, importantly, quantifiable. This work provides for the first time a quantitative and transferable method and rationale on which to base long-term planning decisions for lava dome-forming volcanoes, with wide potential use and transferability to forecasts of other types of eruptions and other adverse events across the geohazard spectrum.

Dynamics of gas-driven eruptions: Experimental simulations using CO2-H2O-polymer system

NASA Astrophysics Data System (ADS)

Zhang, Youxue; Sturtevant, B.; Stolper, E. M.

1997-02-01

We report exploratory experiments simulating gas-driven eruptions using the CO2-H2O system at room temperature as an analog of natural eruptive systems. The experimental apparatus consists of a test cell and a large tank. Initially, up to 1.0 wt% of CO2 is dissolved in liquid water under a pressure of up to 735 kPa in the test cell. The experiment is initiated by suddenly reducing the pressure of the test cell to a typical tank pressure of 10 kPa. The following are the main results: (1) The style of the process depends on the decompression ratio. There is a threshold decompression ratio above which rapid eruption occurs. (2) During rapid eruption, there is always fragmentation at the liquid-vapor interface. Fragmentation may also occur in the flow interior. (3) Initially, the top of the erupting column ascends at a constant acceleration (instead of constant velocity). (4) Average bubble radius grows as t2/3. (5) When viscosity is 20 times that of pure water or greater, a static foam may be stable after expansion to 97% vesicularity. The experiments provide several insights into natural gas-driven eruptions, including (1) the interplay between bubble growth and ascent of the erupting column must be considered for realistic modeling of bubble growth during gas-driven eruptions, (2) buoyant rise of the bubbly magma is not necessary during an explosive volcanic eruption, and (3) CO2-driven limnic eruptions can be explosive. The violence increases with the initial CO2 content dissolved in water.

Eruption Forecasting in Alaska: A Retrospective and Test of the Distal VT Model

NASA Astrophysics Data System (ADS)

Prejean, S. G.; Pesicek, J. D.; Wellik, J.; Cameron, C.; White, R. A.; McCausland, W. A.; Buurman, H.

2015-12-01

United States volcano observatories have successfully forecast most significant US eruptions in the past decade. However, eruptions of some volcanoes remain stubbornly difficult to forecast effectively using seismic data alone. The Alaska Volcano Observatory (AVO) has responded to 28 eruptions from 10 volcanoes since 2005. Eruptions that were not forecast include those of frequently active volcanoes with basaltic-andesite magmas, like Pavlof, Veniaminof, and Okmok volcanoes. In this study we quantify the success rate of eruption forecasting in Alaska and explore common characteristics of eruptions not forecast. In an effort to improve future forecasts, we re-examine seismic data from eruptions and known intrusive episodes in Alaska to test the effectiveness of the distal VT model commonly employed by the USGS-USAID Volcano Disaster Assistance Program (VDAP). In the distal VT model, anomalous brittle failure or volcano-tectonic (VT) earthquake swarms in the shallow crust surrounding the volcano occur as a secondary response to crustal strain induced by magma intrusion. Because the Aleutian volcanic arc is among the most seismically active regions on Earth, distinguishing distal VT earthquake swarms for eruption forecasting purposes from tectonic seismicity unrelated to volcanic processes poses a distinct challenge. In this study, we use a modified beta-statistic to identify pre-eruptive distal VT swarms and establish their statistical significance with respect to long-term background seismicity. This analysis allows us to explore the general applicability of the distal VT model and quantify the likelihood of encountering false positives in eruption forecasting using this model alone.

Early Detection of Eruptive Dykes Revealed by Normalized Difference Vegetation Index (NDVI) on Nyiragongo and Etna Volcanoes: Implications for Dyke Wedge Emplacement, Monitoring, and Risk Assessment.

NASA Astrophysics Data System (ADS)

Komorowski, J.; Houlié, N.; Kasereka, C. M.; Ciraba, H.

2006-12-01

Flank-fissure eruptions involve lateral injection and propagation of magma in a volcanic edifice along pre- existing fractures in the direction of a volcanic rift zone (VRZ) where magma intrusion and lava flow production are concentrated over time. Gradual dyke wedge emplacement on volcano flanks and in VRZ's does not necessarily trigger large amplitude deformation signals susceptible to be recorded months or even years before the actual eruption. We show that active and potentially eruptive areas in a VRZ can be detected up to 2 years before the arrival to the surface of the final eruptive dyke and venting of lava flows by processing satellite images applying a Normalized Difference Vegetation Index (NDVI) algorithm. A positive NDVI anomaly is indicative of excessive photosynthetic plant activity. A posteriori analysis of satellite images reveal that a high- NDVI linear anomaly was apparent in vegetated areas of VRZ's on Etna from 2000 to 2002 and on Nyiragongo in June 2001, several months to years before eruptive fractures formed directly above the NDVI anomaly. We propose that the observed NDVI linear anomalies are the signature of the integrated physico-chemical effects (increased heat and CO2 flux, H2O condensation) caused by the structurally-controlled progressive injection and propagation, in a VRZ and a few months to years before the eruption, of a series of dykes (dyke wedge) that did not reach the surface. We focus of Nyiragongo volcano where historical flank-fissure eruptions from lava lake drainage in 1977 and 2002 show a link with tectonics of the Kivu rift (western branch of the East African Rift System). In 2002, dykes were injected in the southern VRZ bounded by Kivu rift normal faults and propagated over 14 km producing lava flows that caused widespread destruction in the city of Goma. Data from Nyiragongo suggest that as a dyke wedge is formed and repeatedly reactivated, final eruptive dykes can be injected easily and can propagate rapidly further along the VRZ impacting populated areas far from the magmatic conduit. This has important implications for understanding the current process of magma convection feeding the active Nyiragongo lava lake as well as potential small-volume lateral magma injections into the reactivated southern VRZ. The NDVI processing methodology has potentially important implications for monitoring networks on deeply vegetated restless volcanoes with limited or difficult access. More importantly, on volcanoes where eruptive style changes from crater-centered to eccentric flank activity or for which new inactive VRZ's could be reactivated towards populated areas, our methodology constitutes a new tool for early detection of potential flank eruptive vents. By improving the understanding of the link between edifice structure and eruptive activity of effusive volcanoes it can significantly improve integrated risk analysis and the effectiveness of early-detection warning systems for populations at risk.

Magnetic Evolution Linked to the Interrelated Activity Complexes Involving Transequatorial Coronal Holes

NASA Astrophysics Data System (ADS)

Gutiérrez, Heidy; Taliashvili, Lela; Lazarian, Alexandre

2018-06-01

We studied a magnetic evolution linked to a cadence of interrelated activities developed in a large solar region during Carrington rotations, CRs 2119 - 2121, based on multi-wavelength and multi-spacecraft observations. Three coronal holes (CHs), two transequatorial and one isolated, eight filaments and some active regions were distributed closely in the region. Every of these filaments partial and/or complete eruption was linked to a Coronal Mass Ejection (CME) or coronal jet. We found different types of interrelated activities: eruptions of three pairs of interrelated filaments close to a CH and eruptions of two filaments close to the active region and CH. Some indicators of the magnetic reconnection were observed frequently during the pre- as well as post-filament eruptions. Additionally, post-filament eruption and/or post-CME processes show their implication in the evolution of nearby CHs and newly formed transient CHs or dimming regions, including a new CH formation. We discussed the small- and large-scale magnetic reconfigurations associated with these interrelated activity complexes, the ones involving long-lived transequatorial CHs, and their possible implication in the evolution of the global solar magnetic field, especially with the starting processes of quadruple configuration and polarity reversal of the solar cycle 24.

A cascade of magmatic events during the assembly and eruption of a super-sized magma body

NASA Astrophysics Data System (ADS)

Allan, Aidan. S. R.; Barker, Simon J.; Millet, Marc-Alban; Morgan, Daniel J.; Rooyakkers, Shane M.; Schipper, C. Ian; Wilson, Colin J. N.

2017-07-01

We use comprehensive geochemical and petrological records from whole-rock samples, crystals, matrix glasses and melt inclusions to derive an integrated picture of the generation, accumulation and evacuation of 530 km3 of crystal-poor rhyolite in the 25.4 ka Oruanui supereruption (New Zealand). New data from plagioclase, orthopyroxene, amphibole, quartz, Fe-Ti oxides, matrix glasses, and plagioclase- and quartz-hosted melt inclusions, in samples spanning different phases of the eruption, are integrated with existing data to build a history of the magma system prior to and during eruption. A thermally and compositionally zoned, parental crystal-rich (mush) body was developed during two periods of intensive crystallisation, 70 and 10-15 kyr before the eruption. The mush top was quartz-bearing and as shallow as 3.5 km deep, and the roots quartz-free and extending to >10 km depth. Less than 600 year prior to the eruption, extraction of large volumes of 840 °C low-silica rhyolite melt with some crystal cargo (between 1 and 10%), began from this mush to form a melt-dominant (eruptible) body that eventually extended from 3.5 to 6 km depth. Crystals from all levels of the mush were entrained into the eruptible magma, as seen in mineral zonation and amphibole model pressures. Rapid translation of crystals from the mush to the eruptible magma is reflected in textural and compositional diversity in crystal cores and melt inclusion compositions, versus uniformity in the outermost rims. Prior to eruption the assembled eruptible magma body was not thermally or compositionally zoned and at temperatures of 790 °C, reflecting rapid cooling from the 840 °C low-silica rhyolite feedstock magma. A subordinate but significant volume (3-5 km3) of contrasting tholeiitic and calc-alkaline mafic material was co-erupted with the dominant rhyolite. These mafic clasts host crystals with compositions which demonstrate that there was some limited pre-eruptive physical interaction of mafic magmas with the mush and melt-dominant body. However, the mafic magmas do not appear to have triggered the eruption or controlled magmatic temperatures in the erupted rhyolite. Integration of textural and compositional data from all available crystal types, across all dominant and subordinate magmatic components, allow the history of the Oruanui magma body to be reconstructed over a wide range of temporal scales using multiple techniques. This history spans the tens of millennia required to grow the parental magma system (U-Th disequilibrium dating in zircon), through the centuries and decades required to assemble the eruptible magma body (textural and diffusion modelling in orthopyroxene), to the months, days, hours and minutes over which individual phases of the eruption occurred, identified through field observations tied to diffusion modelling in magnetite, olivine, quartz and feldspar. Tectonic processes, rather than any inherent characteristics of the magmatic system, were a principal factor acting to drive the rapid accumulation of magma and control its release episodically during the eruption. This work highlights the richness of information that can be gained by integrating multiple lines of petrologic evidence into a holistic timeline of field-verifiable processes.

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.

How Pore-Fluid Pressure due to Heavy Rainfall Influences Volcanic Eruptions, Example of 1998 and 2008 Eruptions of Cerro Azul (Galapagos)

NASA Astrophysics Data System (ADS)

Albino, F.; Amelung, F.; Gregg, P. M.

2016-12-01

About 30 worldwide seismic studies have shown a strong correlation between rainfall and earthquakes in the past 22 years (e.g. Costain and Bollinger, 2010). Such correlation has been explained by the phenomenon of hydro-seismicity via pore pressure diffusion: an increase of pore-fluid in the upper crust reduces the normal stress on faults, which can trigger shear failure. Although this pore pressure effect is widely known for earthquakes, this phenomenon and more broadly poro-elasticity process are not widely studied on volcanoes. However, we know from our previous works that tensile failures that open to propagate magma through the surface are also pore pressure dependent. We have demonstrated that an increase of pore pressure largely reduces the overpressure required to rupture the magma reservoir. We have shown that the pore pressure has more influence on reservoir stability than other parameters such as the reservoir depth or the edifice loading. Here, we investigate how small pore-fluid changes due to hydrothermal or aquifer refill during heavy rainfall may perturb the conditions of failure around magma reservoirs and, what is more, if these perturbations are enough to trigger magma intrusions. We quantify the pore pressure effect on magmatic system by combining 1) 1D pore pressure diffusion model to quantify how pore pressure changes from surface to depth after heavy rainfall events and 2) 2D poro-elastic numerical model to provide the evolution of failure conditions of the reservoir as a consequence of these pore pressure changes. Sensitivity analysis is also performed to characterize the influence on our results of the poro-elastic parameters (hydraulic diffusivity, permeability and porosity) and the geometry of the magma reservoir and the aquifer (depth, size, shape). Finally, we apply our methodology to Cerro Azul volcano (Galapagos) where both last eruptions (1998 and 2008) occurred just after heavy rainfall events, without any pre-eruptive inflation. In the event eruptions can be triggered by pore pressure changes in the crust, meteorological records and water table measurements are required to improve eruption's forecast, especially in regions where heavy rainfall events (typhoons, monsoons or hurricanes) frequently occur, such as in Indonesia, Philippines or Central America.

Consequences of magma eruption dynamics: Intraflow variations in petrography and mineral chemistry within a single eruptive unit from Whitewater Canyon, Oregon

NASA Astrophysics Data System (ADS)

Ustunisik, G. K.; Nielsen, R. L.

2012-12-01

Individual lava flows are sometimes characterized by progressive changes in petrography and mineral chemistry which have been attributed to progressive magma chamber evacuation. In the case of Whitewater Canyon flow, a glacially quenched andesite unit on the NW flank of Mt. Jefferson, significant changes have been observed in phenocryst content and mineral chemistry within a transect from the early erupted components (inferred by flow morphology to be quenched against glacial ice ~10000 ybp), to the top of the 30 m thick flow unit. With the increasing distance from the quenched interface, the matrix changes from glassy to microcrystalline. The matrix material is generally similar in composition to the glassy melt inclusions rhyolitic in composition yet relatively degassed (lower Cl, S). Based on their morphology, we have identified at least 4 populations of plagioclase phenocrysts within the single flow: (1) Relatively unzoned high An cores (>An80) with oscillatory overgrowth, (2) Lower An cores (An50-60), associated with dacitic melt inclusions, (3) Cellular low An cores (An50-60) with higher An overgrowths (~An65-75), and (4) Lath shaped, sometimes oscillatory zoned moderately high An phenocrysts (An65-75) -often associated with olivine:cpx:plagioclase glomerocrysts. Melt inclusions are present in orthopyroxene and plagioclase, but only in the earliest erupted samples (within 5-10 meters of the quenched interface). This mafic component, characterized by olivine, intermediate plagioclase (An60-75), clinopyroxene, orthopyroxene, and oxides, was present at a range of scales from glomerocrysts to 10 cm+ enclaves. Amphibole and quartz are present only in samples from the interior of the flow unit. The width of reaction rims on amphibole increase as one progress upwards towards the flow interior. Our initial conclusions are this eruptive unit represents the progressive evacuation of a shallow magma chamber where the upper parts of the chamber had already been partially degassed. This is supported by the absence of amphibole phenocrysts in the first erupted, quenched samples. However, the presence of volatiles in glassy melt inclusions and phenocrysts suggests that the system had not completely degassed prior to the eruption. Also, the petrographic heterogeneity of the unit demonstrates that complete overturn and mixing did not happen at Mt. Jefferson. Therefore, eruption may have been triggered by the injection of mafic material; however, the petrographic and field evidence suggests that overturn is not required as part of that triggering event.

Ionospheric "Volcanology": Ionospheric Detection of Volcano Eruptions

NASA Astrophysics Data System (ADS)

Astafyeva, E.; Shults, K.; Lognonne, P. H.; Rakoto, V.

2016-12-01

It is known that volcano eruptions and explosions can generate acoustic and gravity waves. These neutral waves further propagate into the atmosphere and ionosphere, where they are detectable by atmospheric and ionospheric sounding tools. So far, the features of co-volcanic ionospheric perturbations are not well understood yet. The development of the global and regional networks of ground-based GPS/GNSS receivers has opened a new era in the ionospheric detection of natural hazard events, including volcano eruptions. It is now known that eruptions with the volcanic explosivity index (VEI) of more than 2 can be detected in the ionosphere, especially in regions with dense GPS/GNSS-receiver coverage. The co-volcanic ionospheric disturbances are usually characterized as quasi-periodic oscillations. The Calbuco volcano, located in southern Chile, awoke in April 2015 after 43 years of inactivity. The first eruption began at 21:04UT on 22 April 2015, preceded by only an hour-long period of volcano-tectonic activity. This first eruption lasted 90 minutes and generated a sub-Plinian (i.e. medium to large explosive event), gray ash plume that rose 15 km above the main crater. A larger second event on 23 April began at 04:00UT (01:00LT), it lasted six hours, and also generated a sub-Plinian ash plume that rose higher than 15 km. The VEI was estimated to be 4 to 5 for these two events. In this work, we first study ionospheric TEC response to the Calbuco volcano eruptions of April 2015 by using ground-based GNSS-receivers located around the volcano. We analyze the spectral characteristics of the observed TEC variations and we estimate the propagation speed of the co-volcanic ionospheric perturbations. We further proceed with the normal mode summation technique based modeling of the ionospheric TEC variations due to the Calbuco volcano eruptions. Finally, we attempt to localize the position of the volcano from the ionospheric measurements, and we also estimate the time of the beginning of the eruption.

Composite Calderas: The Long and Short of it

NASA Astrophysics Data System (ADS)

Gravley, D. M.; Hasegawa, T.; Nakagawa, M.; Wilson, C. J.

2006-12-01

Calderas formed in supereruptions are normally linked to a single magma body. However, caldera formation, regional tectonics, and multiple magma bodies may interact to form composite structures with complex geometries. The term composite caldera is often used without reference as to whether the `composite' is in time or space. Three examples of composite caldera styles from New Zealand and Japan show field, geophysical, geochemical and isotopic evidence to suggest that current models for the size, shape and evolution of calderas may be too simplistic. In our examples, multiple separate magma bodies distributed in either space or time, or both, may play a significant role in composite caldera formation. Multiple, clustered collapse events incremental in time: Akan caldera in Hokkaido appears to be a single, rectangular shaped caldera. However, the identification of 17 eruptive units spanning >1 Myr suggests that the caldera evolved incrementally over time and space. New gravity data shows that the caldera is actually a daisy-chain of 3 distinct collapse structures that can be correlated, using lithic componentry, to 3 major geochemical groups in the eruptive products. Multiple, clustered collapse events in a single eruption sequence: Shikotsu caldera in Hokkaido was originally thought to have formed following the eruption of a single large zoned magma chamber. However, the caldera-related deposits are characterized by several geochemically distinct pumice types that can not have been accommodated in a single magma system. Our studies suggest that the variations in pumice compositions are consistent with multiple distinct magma bodies feeding coeval eruptions from several vent sources within an area that collapsed to form a single caldera. Paired calderas with linking eruption-related regional faulting: Rotorua and Ohakuri calderas in New Zealand are 30 km apart and formed in close succession during a complex but virtually continuous eruption sequence at ca. 240 ka. The distinct calderas are joined in dumb-bell fashion by an intervening zone of eruption-related and immediately post-eruptive faulting and collapse.

From Vulcanian explosions to sustained explosive eruptions: The role of diffusive mass transfer in conduit flow dynamics

NASA Astrophysics Data System (ADS)

Mason, R. M.; Starostin, A. B.; Melnik, O. E.; Sparks, R. S. J.

2006-05-01

Magmatic explosive eruptions are influenced by mass transfer processes of gas diffusion into bubbles caused by decompression. Melnik and Sparks [Melnik, O.E., Sparks, R.S.J. 2002, Modelling of conduit flow dynamic during explosive activity at Soufriere Hills Volcano, Montserrat. In: Druitt, T.H., Kokelaar, B.P. (eds). The Eruption of Soufriere Hills Volcano, Montserrat, from 1995 to 1999. Geological Society, London, Memoirs, 21, 307-317] proposed two end member cases corresponding to complete equilibrium and complete disequilibrium. In the first case, diffusion is fast enough to maintain the system near equilibrium and a long-lived explosive eruption develops. In the latter case, pre-existing bubbles expand under conditions of explosive eruption and decompression, but diffusive gas transfer is negligible. This leads to a much shorter eruption. Here we develop this model to consider the role of mass transfer by investigating transient flows at the start of an explosive eruption triggered by a sudden decompression. The simulations reveal a spectrum of behaviours from sustained to short-lived highly non-equilibrium Vulcanian-style explosions lasting a few tens of seconds, through longer lasting eruptions that can be sustained for tens of minutes and finally to eruptions that can last hours or even days. Behaviour is controlled by a mass-transfer parameter, ω, which equals n*2/3D, where n* is the bubble number density and D is the diffusivity. The parameter ω is expected to vary between 10 - 5 and 1 s - 1 in nature and reflects a time-scale for efficient diffusion. The spectrum of model behaviours is consistent with variations in styles of explosive eruptions of silicic volcanoes. In the initial stages peak discharges occur over 10-20 s and then decline to low discharges. If a critical bubble overpressure is assumed to be the criterion for fragmentation then fragmentation may stop and start several times in the declining period causing several pulses of high-intensity discharge. For the cases of strong disequilibria, the fluxes can decrease to negligible values where other processes, such as gas escape through permeable magma, prevents explosive conditions becoming re-established so that explosive activity stops and dome growth can start. For cases closer to the equilibrium the eruption can evolve towards a quasi-steady sustained flow, never declining sufficiently for gas escape to become dominant.

The submarine volcano eruption at the island of El Hierro: physical-chemical perturbation and biological response

PubMed Central

Fraile-Nuez, E.; González-Dávila, M.; Santana-Casiano, J. M.; Arístegui, J.; Alonso-González, I. J.; Hernández-León, S.; Blanco, M. J.; Rodríguez-Santana, A.; Hernández-Guerra, A.; Gelado-Caballero, M. D.; Eugenio, F.; Marcello, J.; de Armas, D.; Domínguez-Yanes, J. F.; Montero, M. F.; Laetsch, D. R.; Vélez-Belchí, P.; Ramos, A.; Ariza, A. V.; Comas-Rodríguez, I.; Benítez-Barrios, V. M.

2012-01-01

On October 10 2011 an underwater eruption gave rise to a novel shallow submarine volcano south of the island of El Hierro, Canary Islands, Spain. During the eruption large quantities of mantle-derived gases, solutes and heat were released into the surrounding waters. In order to monitor the impact of the eruption on the marine ecosystem, periodic multidisciplinary cruises were carried out. Here, we present an initial report of the extreme physical-chemical perturbations caused by this event, comprising thermal changes, water acidification, deoxygenation and metal-enrichment, which resulted in significant alterations to the activity and composition of local plankton communities. Our findings highlight the potential role of this eruptive process as a natural ecosystem-scale experiment for the study of extreme effects of global change stressors on marine environments. PMID:22768379

Early extraction of the mandibular third molar in case of eruption disturbances of the second molar.

PubMed

Kavadia, S; Antoniades, K; Kaklamanos, E; Antoniades, V; Markovitsi, E; Zafiriadis, L

2003-01-01

General consensus has been reached on extracting mandibular third molars when they are involved in pathologic processes. However, early extraction is advisable in cases of eruption disturbances of the mandibular second molar, before or during orthodontic treatment. Thirty-two patients with early extraction of the mandibular third molar before or during orthodontic treatment were examined. In these cases either the presence of the third molar presented an obstacle in the eruption path of the second, or third molar germ removal was considered beneficial to the course of orthodontic treatment. Early extraction of the mandibular third molar facilitates the eruption of the second molar, especially in cases where evidence of crowding and lack of space in the posterior mandibular region exist. Orthodontic treatment may, in some cases, aggravate eruption disturbances of the second molar.

Numerical modeling of a sub Plinian eruption at La Soufrière de Guadeloupe: implications for pyroclastic density currents hazard assessment.

NASA Astrophysics Data System (ADS)

Esposti Ongaro, Tomaso; Neri, Augusto; Komorowski, Jean-Christophe

2013-04-01

We present three-dimensional numerical simulations of a sub-Plinian eruptive scenario at La Soufrière de Guadeloupe, aimed at assessing the capability of pyroclastic density currents to reach the inhabited regions on the volcano slopes, in case of the future resumption of the explosive activity. The selected eruptive scenario is similar to that hypothesized for the 1530 a.D. eruption, but several eruptive conditions have been analyzed to account for different behaviours of the eruptive column and percentages of collapse. Numerical results describe, in 3D and in time, the formation, instability and partial collapse of the eruptive column, and the simultaneous formation of a convective plume and several branched pyroclastic density currents. The proximal volcano morphology, characterized by the presence of ancient caldera rims and the remnants of the old edifice, controls the areal distribution of the collapsed material and the paths of channelized flows along the incised topography. The analysis of the 3D runs suggests that partial collapse scenarios produce steeply stratified pyroclastic density currents, which are strongly controlled by the topography and whose propagation is likely driven by the dynamics of the dense, basal layer. Although vertical grid size still does not allow the resolution of the dynamics of such concentrated flows, preliminary georeferenced maps of pyroclastic density currents' hazardous actions (temperature and dynamic pressure) provide interesting and useful information which can serve as a basis for elaborating a quantitative framework for the assessment of their impact on vulnerable infrastructures, networks, and population.

Volcanic plume height measured by seismic waves based on a mechanical model

USGS Publications Warehouse

Prejean, Stephanie G.; Brodsky, Emily E.

2011-01-01

In August 2008 an unmonitored, largely unstudied Aleutian volcano, Kasatochi, erupted catastrophically. Here we use seismic data to infer the height of large eruptive columns such as those of Kasatochi based on a combination of existing fluid and solid mechanical models. In so doing, we propose a connection between a common, observable, short-period seismic wave amplitude to the physics of an eruptive column. To construct a combined model, we estimate the mass ejection rate of material from the vent on the basis of the plume height, assuming that the height is controlled by thermal buoyancy for a continuous plume. Using the estimated mass ejection rate, we then derive the equivalent vertical force on the Earth through a momentum balance. Finally, we calculate the far-field surface waves resulting from the vertical force. The model performs well for recent eruptions of Kasatochi and Augustine volcanoes if v, the velocity of material exiting the vent, is 120-230 m s-1. The consistency between the seismically inferred and measured plume heights indicates that in these cases the far-field ~1 s seismic energy radiated by fluctuating flow in the volcanic jet during the eruption is a useful indicator of overall mass ejection rates. Thus, use of the model holds promise for characterizing eruptions and evaluating ash hazards to aircraft in real time on the basis of far-field short-period seismic data. This study emphasizes the need for better measurements of eruptive plume heights and a more detailed understanding of the full spectrum of seismic energy radiated coeruptively.

Floating basaltic lava balloons - constrains on the eruptive process based on morphologic parameters

NASA Astrophysics Data System (ADS)

Pacheco, J. M.; Zanon, V.; Kueppers, U.

2011-12-01

The 1998-2001 submarine Serreta eruption brought to science a new challenge. This eruption took place offshore of Terceira Island (Azores), on the so-called Serreta Submarine Ridge, corresponding to a basaltic fissure zone with alkaline volcanism, within a tectonic setting controlled by an hyper-slow spreading rift (the Terceira Rift). The inferred eruptive centers are alignment along a NE-SW direction over an area with depths ranging from 300 to more than 1000 meters. The most remarkable products of this eruption, were large basaltic balloons observed floating at the sea surface. Those balloons, designated as Lava Balloons, are spherical to ellipsoidal structures, ranging from 0.4 up to about 3 m in length, consisting of a thin lava shell enveloping a closed hollow interior, normally formed by a single large vesicle, or a few large convoluted vesicles, that grants an overall density below water density. The cross section of the lava shell usually ranges between 3 and 8 cm and has a distinct layered structure, with different layers defined by different vesicularity, bubble number density and crystal content. The outermost layer is characterized by very small vesicles and high bubble number density whereas the innermost layer has larger vesicles, lower bubble number density and higher crystal content. These observations indicate that the rapidly quenched outer layer preserved the original small vesicles present on the magma at the time of the balloon's formation while the inner layer continued to evolve, producing higher crystal content and allowing time for the expansion of vesicles inward and their efficient coalescence. The outer surface of the balloons exhibits patches of very smooth glassy surface and areas with striation and grooves resulting from small scale fluidal deformation. These surface textures are interpreted as the result of the extrusion process and were produced in a similar manner to the striation found on subaerial toothpaste lavas. Such characteristics are indicative that the outer surface of the balloon quenched as it was being extruded and preserved the scars of a squeeze-up process. On this outer surface, several superficial expansion cracks reveal that after its generation the balloon endured some expansion before reaching the sea surface, most likely due to hydrostatic decompression during its rise. The entire shell of the balloons shows bends and folds resulting from large ductile deformations, also suggesting an origin as an effusive process of squeezing-up a large vesicle through a fissure in a thin lava crust, similarly to the extrusion of a gas filled lava toe. Actually, the volume of the lava shell is not enough to produce all the gas in the balloons interior. More likely, at an earlier stage, degassing of magma as an open system allowed gas to segregate and accumulate to form large vesicles. The development of very large vesicles would be favored by a ponding system such as a lava lake.

Abrupt transition from fractional crystallization to magma mixing at Gorely volcano (Kamchatka) after caldera collapse

NASA Astrophysics Data System (ADS)

Gavrilenko, Maxim; Ozerov, Alexey; Kyle, Philip R.; Carr, Michael J.; Nikulin, Alex; Vidito, Christopher; Danyushevsky, Leonid

2016-07-01

A series of large caldera-forming eruptions (361-38 ka) transformed Gorely volcano, southern Kamchatka Peninsula, from a shield-type system dominated by fractional crystallization processes to a composite volcanic center, exhibiting geochemical evidence of magma mixing. Old Gorely, an early shield volcano (700-361 ka), was followed by Young Gorely eruptions. Calc-alkaline high magnesium basalt to rhyolite lavas have been erupted from Gorely volcano since the Pleistocene. Fractional crystallization dominated evolution of the Old Gorely magmas, whereas magma mixing is more prominent in the Young Gorely eruptive products. The role of recharge-evacuation processes in Gorely magma evolution is negligible (a closed magmatic system); however, crustal rock assimilation plays a significant role for the evolved magmas. Most Gorely magmas differentiate in a shallow magmatic system at pressures up to 300 MPa, ˜3 wt% H2O, and oxygen fugacity of ˜QFM + 1.5 log units. Magma temperatures of 1123-1218 °C were measured using aluminum distribution between olivine and spinel in Old and Young Gorely basalts. The crystallization sequence of major minerals for Old Gorely was as follows: olivine and spinel (Ol + Sp) for mafic compositions (more than 5 wt% of MgO); clinopyroxene and plagioclase crystallized at ˜5 wt% of MgO (Ol + Cpx + Plag) and magnetite at ˜3.5 wt% of MgO (Ol + Cpx + Plag + Mt). We show that the shallow magma chamber evolution of Old Gorely occurs under conditions of decompression and degassing. We find that the caldera-forming eruption(s) modified the magma plumbing geometry. This led to a change in the dominant magma evolution process from fractional crystallization to magma mixing. We further suggest that disruption of the magma chamber and accompanying change in differentiation process have the potential to transform a shield volcanic system to that of composite cone on a global scale.

Using Satellite Data to Characterize the Temporal Thermal Behavior of an Active Volcano: Mount St. Helens, WA

NASA Technical Reports Server (NTRS)

Vaughan, R. Greg; Hook, Simon J.

2006-01-01

ASTER thermal infrared data over Mt. St Helens were used to characterize its thermal behavior from Jun 2000 to Feb 2006. Prior to the Oct 2004 eruption, the average crater temperature varied seasonally between -12 and 6 C. After the eruption, maximum single-pixel temperature increased from 10 C (Oct 2004) to 96 C (Aug 2005), then showed a decrease to Feb 2006. The initial increase in temperature was correlated with dome morphology and growth rate and the subsequent decrease was interpreted to relate to both seasonal trends and a decreased growth rate/increased cooling rate, possibly suggesting a significant change in the volcanic system. A single-pixel ASTER thermal anomaly first appeared on Oct 1, 2004, eleven hours after the first eruption - 10 days before new lava was exposed at the surface. By contrast, an automated algorithm for detecting thermal anomalies in MODIS data did not trigger an alert until Dec 18. However, a single-pixel thermal anomaly first appeared in MODIS channel 23 (4 um) on Oct 13, 12 days after the first eruption - 2 days after lava was exposed. The earlier thermal anomaly detected with ASTER data is attributed to the higher spatial resolution (90 m) compared with MODIS (1 m) and the earlier visual observation of anomalous pixels compared to the automated detection method suggests that local spatial statistics and background radiance data could improve automated detection methods.

Recent and Hazardous Volcanic Activity Along the NW Rift Zone of Piton De La Fournaise Volcano, La Réunion Island

NASA Astrophysics Data System (ADS)

Walther, G.; Frese, I.; Di Muro, A.; Kueppers, U.; Michon, L.; Metrich, N.

2014-12-01

Shield volcanoes are a common feature of basaltic volcanism. Their volcanic activity is often confined to a summit crater area and rift systems, both characterized by constructive (scoria and cinder cones; lava flows) and destructive (pit craters; caldera collapse) phenomena. Piton de la Fournaise (PdF) shield volcano (La Réunion Island, Indian Ocean) is an ideal place to study these differences in eruptive behaviour. Besides the frequent eruptions in the central Enclos Fouqué caldera, hundreds of eruptive vents opened along three main rift zones cutting the edifice during the last 50 kyrs. Two short rift zones are characterized by weak seismicity and lateral magma transport at shallow depth (above sea level). Here we focus on the third and largest rift zone (15km wide, 20 km long), which extends in a north-westerly direction between PdF and nearby Piton des Neiges volcanic complex. It is typified by deep seismicity (up to 30 km), emitting mostly primitive magmas, testifying of high fluid pressures (up to 5 kbar) and large-volume eruptions. We present new field data (including stratigraphic logs, a geological map of the area, C-14 dating and geochemical analyses of the eruption products) on one of the youngest (~6kyrs) and largest lava field (Trous Blancs eruption). It extends for 24km from a height of 1800 m asl, passing Le Tampon and Saint Pierre cities, until reaching the coast. The source area of this huge lava flow has been identified in an alignment of four previously unidentified pit craters. The eruption initiated with intense fountaining activity, producing a m-thick bed of loose black scoria, which becomes densely welded in its upper part; followed by an alternation of volume rich lava effusions and strombolian activity, resulting in the emplacement 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-thick bed of glassy, dense scoria and a stratified lithic breccia, marking the pit crater foundering. Interestingly, this final stage compares well with the formation of pit craters on Kilauea volcano, Hawaii. Reoccurring of 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).

Anhydrite in the 1989 1990 lavas and xenoliths from Redoubt Volcano, Alaska

NASA Astrophysics Data System (ADS)

Swanson, S. E.; Kearney, C. S.

2008-08-01

The eruption of Redoubt Volcano in Alaska produced a moderate sulfur emission (estimated at 1 × 10 tons SO 2), but relatively small volume of lava (0.11 km ) with pre-eruption estimates of 840-950 °C and fO 21.5 to 2.0 log units above NNO (Swanson, S.E., Nye, C.J., Miller, T.P., Avery, V.F., 1994. Magma mixing in the 1989-1990 eruption of Redoubt Volcano: Part II. Evidence from mineral and glass chemistry. Journal of Volcanology and Geothermal Research 62, 453-468). Petrologic estimates of sulfur production (Sigurdsson, H., Devine, J.D.,Davis, A.N., 1985. The petrologic estimation of volcanic degassing. Jokull 35, 1-8) from this eruption (Gerlach, T., Westrich, H.R., Casadevall, T.J., Finnegan, D.L., 1994. Vapor Saturation and accumulation in magmas of the 1989-1990 eruption of Redoubt Volcano, Alaska. Journal of Volcanology and Geothermal Research 62, 317-337) are considerably less than the measured sulfur emission, leading workers to propose the existence of a pre-eruption vapor phase to explain the "excess" sulfur. Initial examination of the 1989-1990 Redoubt eruptive products reported anhydrite (Nye, C.J., Swanson, S.E., Avery, V.F., Miller, T.P., 1994. Geochemistry of the 1989-1990 eruption of Redoubt Volcano: Part I, whole-rock, major- and trace-element chemistry. Journal of Volcanology and Geothermal Research 62, 429-452.) in interstitial glass from some cognate gabbroic xenoliths, but anhydrite was not noted in any of the andesites. A Boeing 747 encountered the ash plume from the initial eruptive phase on December 15, 1989 and provided ash samples that reportedly contained gypsum (Bayhurst, G.K., Wohletz, K.H., Mason, A.S., 1994. A method for characterizing volcanic ash from the December 15, 1989, eruption of Redoubt Volcano, Alaska. U.S. Geological Survey Bulletin 2047, 13-17). However, the identification was based on EDS analyses on a SEM and the mineral could have been anhydrite. Reexamination of the 1989-1990 Redoubt lavas and xenoliths revealed the presence of rare, fine-grained (10s of microns) anhydrite crystals in the lavas and larger (10s to 100s of microns) crystals in the xenoliths. The anhydrite forms elongate crystals with sharp contacts against the groundmass glass. Grains show rounded terminations suggesting breakdown of the anhydrite, perhaps during eruption. The anhydrite is a sparse phase in the lavas, but occurs in lavas and cognate xenoliths erupted throughout the eruption. The presence and breakdown of anhydrite may explain the "excess" sulfur associated with the Redoubt eruption. A careful search of other freshly erupted andesitic lavas solidified from hydrous, oxidizing magmas should reveal other examples of anhydrite and cause a rethinking of the source of sulfur in volcanic emissions.

Thermal Evolution of a Failed Flux Rope Eruption Revealed by Temperature Maps

NASA Astrophysics Data System (ADS)

Song, H.; Zhang, J.; CHEN, Y.

2013-12-01

Flux rope is generally considered to be the fundamental magnetic configuration of a coronal mass ejection (CME). Recent observations suggest that hot channel or blob structures during the eruptions be the direct observational manifestation of flux ropes. In this study, we report our analysis of thermal evolution of a failed solar eruption with an apparent flux rope embedded. The thermal structure of the eruption is revealed through differential emission measure (DEM) analysis technique, which shows detailed temperature maps in both high spatial resolution and high temperature resolution based on SDO/AIA observations. Our results show that the flux rope exists in the corona before the eruption, and its temperature can quickly rise to over 10 MK within one minute of the eruption. The correlation study between the flux rope temperature and the soft x-ray flux suggests that the flux rope should be heated through the direct thermal energy release of magnetic reconnection. Further, we study the kinematic evolution process of the flux rope, in an effort to find the physical mechanism that prevents the magnetic rope eruption to become a full coronal mass ejection. This kind of study using temperature maps might reveal where and when magnetic reconnection takes place during solar eruptions.

Modeling Explosive Eruptions at Kīlauea, Hawai'i

NASA Astrophysics Data System (ADS)

Gonnermann, H. M.; Ferguson, D. J.; Blaser, A. P.; Houghton, B. F.; Plank, T. A.; Hauri, E. H.; Swanson, D. A.

2014-12-01

We have modeled eruptive magma ascent during two explosive eruptions of Kīlauea volcano, Hawai'i. They are the Hawaiian style Kīlauea Iki eruption, 1959, and the subplinian Keanakāko'i eruption, 1650 CE. We have modeled combined magma ascent in the volcanic conduit and exsolution of H2O and CO2 from the erupting magma. To better assess the relative roles of conduit processes and magma chamber, we also coupled conduit flow and magma chamber through mass balance and pressure. We predict magma discharge rates, superficial gas velocities, H2O and CO2 concentrations of the melt, magma chamber pressure, surface deformation, and height of the volcanic jet. Models are in part constrained by H2O and CO2 measured in olivine-hosted melt inclusions and by decompression rates recorded in melt embayment diffusion profiles. We present a parametric analysis, indicating that the pressure within the chamber that fed the subplinian Keanakāko'i eruption was significantly higher than lithostatic pressure. In contrast, chamber pressure for the Hawaiian Kīlauea Iki eruption was close to lithostatic. In both cases the superficial gas velocity, which affects the geometrical distribution of gas-liquid mixtures during upward flow in conduits, may have exceeded values at which bubble coalescence did not affect the flow.

Formation and Eruption Process of a Filament in Active Region NOAA 12241

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

Wang, Jincheng; Yan, Xiaoli; Qu, ZhongQuan

In order to better understand active-region filaments, we present an intensive study on the formation and eruption of a filament in active region NOAA 12241 during the period from 2014 December 18 to 19. Using observations from the Helioseismic and Magnetic Imager (HMI) vector magnetograms, we investigate the helicity injection rate, Lorentz force, and vertical electric current in the entire region associated with the filament. The helicity injection rate before eruption is found to be larger than that after eruption, while the vertical electric current undergoes an increase at first and then a gradual decrease, similar to what the magneticmore » flux undergoes. Meanwhile, we find that the right part of the filament is formed by magnetic reconnection between two bundles of magnetic field lines while the left part originated from shearing motion. The interaction of the two parts causes the eruption of this filament. The mean horizontal magnetic fields in the vicinity of the magnetic polarity inversion line (PIL) enhance rapidly during the eruption. Another striking phenomenon, where the vertical electric currents close to the magnetic PIL suddenly expand toward two sides during the eruption, is found. We propose that this fascinating feature is associated with the release of energy during the eruption.« less

Calderas produced by hydromagmatic eruptions through permafrost in northwest Alaska

NASA Technical Reports Server (NTRS)

Beget, J. E.

1993-01-01

Most hydromagmatic eruptions on Earth are generated by interactions of lava and ground or surface water. This eruptive process typically produces craters 0.1-1 km in diameter, although a few as large as 1-2 km were described. In contrast, a series of Pleistocene hydromagmatic eruptions through 80-100-m-thick permafrost on the Seward Peninsula of Alaska produced four craters 3-8 km in diameter. These craters, called the Espenberg maars, are the four largest maars known on Earth. The thermodynamic properties of ground ice influence the rate and amount of water melted during the course of the eruption. Large quantities of water are present, but only small amounts can be melted at any time to interact with magma. This would tend to produce sustained and highly explosive low water/magma (fuel-coolant) ratios during the eruptions. An area of 400 km(sub 2) around the Alaskan maars shows strong reductions in the density of thaw lakes, ground ice, and other surface manifestations of permafrost because of deep burial by coeval tephra falls. The unusually large Espenberg maars are the first examples of calderas produced by hydromagmatic eruptions. These distinctive landforms can apparently be used as an indicator of the presence of permafrost at the time of eruption.

Remotely Sensed Density Measurements of Volcanic Sulfur Dioxide Plumes Using a Spectral Long Wave Infrared Imager

DTIC Science & Technology

2002-09-01

USGS). (Tilling, R., Heliker, C., and Wright, T., “ Eruptions of Hawaiian Volcanoes ”) The mission of HVO is to monitor Hawaii’s Mauna Loa and Kilauea ...Hendley, J., “Living on Active Volcanoes ”) Hawaii’s Kilauea Volcano is unique in its long-term (1983 – present), nearly continuous eruptive ...monitoring the gas emission process of Kilauea Volcano . During periods of sustained eruption , Kilauea emits about 2,000 tons of sulfur dioxide gas (SO2

Sub-glacial volcanic eruptions

USGS Publications Warehouse

White, Donald Edward

1956-01-01

The literature on sub-glacial volcanic eruptions and the related flood phenomena has been reviewed as a minor part of the larger problem of convective and conductive heat transfer from intrusive magma. (See Lovering, 1955, for a review of the extensive literature on this subject.) This summary of data on sub-glacial eruptions is part of a program that the U.S. Geological Survey is conducting in connection with its Investigations of Geologic Processes project on behalf of the Division of Research, U.S. Atomic Energy Commission.

Explosive eruptions triggered by rockfalls at Kīlauea volcano, Hawaii

USGS Publications Warehouse

Orr, Tim R.; Thelen, Weston A.; Patrick, Matthew R.; Swanson, Donald A.; Wilson, David C.

2012-01-01

Ongoing eruptive activity at Kīlauea volcano’s (Hawai‘i) summit has been controlled in part by the evolution of its vent from a 35-m-diameter opening into a collapse crater 150 m across. Geologic observations, in particular from a network of webcams, have provided an unprecedented look at collapse crater development, lava lake dynamics, and shallow outgassing processes. These observations show unequivocally that the hundreds of transient outgassing bursts and weak explosive eruptions that have punctuated the vent’s otherwise nearly steady-state behavior, and that are associated with composite seismic events, were triggered by rockfalls from the vent walls onto the top of the lava column. While the process by which rockfalls drive the explosive bursts is not fully understood, we believe that it is initiated by the generation of a rebound splash, or Worthington jet, which then undergoes fragmentation. The external triggering of low-energy outgassing events by rockfalls represents a new class of small transient explosive eruptions.

Enhancement of eruption explosivity by heterogeneous bubble nucleation triggered by magma mingling.

PubMed

Paredes-Mariño, Joali; Dobson, Katherine J; Ortenzi, Gianluigi; Kueppers, Ulrich; Morgavi, Daniele; Petrelli, Maurizio; Hess, Kai-Uwe; Laeger, Kathrin; Porreca, Massimiliano; Pimentel, Adriano; Perugini, Diego

2017-12-04

We present new evidence that shows magma mingling can be a key process during highly explosive eruptions. Using fractal analysis of the size distribution of trachybasaltic fragments found on the inner walls of bubbles in trachytic pumices, we show that the more mafic component underwent fracturing during quenching against the trachyte. We propose a new mechanism for how this magmatic interaction at depth triggered rapid heterogeneous bubble nucleation and growth and could have enhanced eruption explosivity. We argue that the data support a further, and hitherto unreported contribution of magma mingling to highly explosive eruptions. This has implications for hazard assessment for those volcanoes in which evidence of magma mingling exists.

Black swans, power laws, and dragon-kings: Earthquakes, volcanic eruptions, landslides, wildfires, floods, and SOC models

NASA Astrophysics Data System (ADS)

Sachs, M. K.; Yoder, M. R.; Turcotte, D. L.; Rundle, J. B.; Malamud, B. D.

2012-05-01

Extreme events that change global society have been characterized as black swans. The frequency-size distributions of many natural phenomena are often well approximated by power-law (fractal) distributions. An important question is whether the probability of extreme events can be estimated by extrapolating the power-law distributions. Events that exceed these extrapolations have been characterized as dragon-kings. In this paper we consider extreme events for earthquakes, volcanic eruptions, wildfires, landslides and floods. We also consider the extreme event behavior of three models that exhibit self-organized criticality (SOC): the slider-block, forest-fire, and sand-pile models. Since extrapolations using power-laws are widely used in probabilistic hazard assessment, the occurrence of dragon-king events have important practical implications.

Observations of volcanic tremor during January-February 2005 eruption of Mt. Veniaminof, Alaska

USGS Publications Warehouse

De Angelis, Slivio; McNutt, Stephen R.

2007-01-01

Mt. Veniaminof, Alaska Peninsula, is a stratovolcano with a summit ice-filled caldera containing a small intracaldera cone and active vent. From January 2 to February 21, 2005, Mt. Veniaminof erupted. The eruption was characterized by numerous small ash emissions (VEI 0 to 1) and accompanied by low-frequency earthquake activity and volcanic tremor. We have performed spectral analyses of the seismic signals in order to characterize them and to constrain their source. Continuous tremor has durations of minutes to hours with dominant energy in the band 0.5– 4.0 Hz, and spectra characterized by narrow peaks either irregularly (non-harmonic tremor) or regularly spaced (harmonic tremor). The spectra of non-harmonic tremor resemble those of low-frequency events recorded simultaneously with surface ash explosions, suggesting that the source mechanisms might be similar or related. We propose that non-harmonic tremor at Mt. Veniaminof results from the coalescence of gas bubbles while low-frequency events are related to the disruption of large gas pockets within the conduit. Harmonic tremor, characterized by regular and quasisinusoidal waveforms, has duration of hours. Spectra containing up to five harmonics suggest the presence of a resonating source volume that vibrates in a longitudinal acoustic mode. An interesting feature of harmonic tremor is that frequency is observed to change over time; spectral lines move towards higher or lower values while the harmonic nature of the spectra is maintained. Factors controlling the variable characteristics of harmonic tremor include changes in acoustic velocity at the source and variations of the effective size of the resonator.

Relationship between eruption plume heights and seismic source amplitudes of eruption tremors and explosion events

NASA Astrophysics Data System (ADS)

Mori, A.; Kumagai, H.

2016-12-01

It is crucial to analyze and interpret eruption tremors and explosion events for estimating eruption size and understanding eruption phenomena. Kumagai et al. (EPS, 2015) estimated the seismic source amplitudes (As) and cumulative source amplitudes (Is) for eruption tremors and explosion events at Tungurahua, Ecuador, by the amplitude source location (ASL) method based on the assumption of isotropic S-wave radiation in a high-frequency band (5-10 Hz). They found scaling relations between As and Is for eruption tremors and explosion events. However, the universality of these relations is yet to be verified, and the physical meanings of As and Is are not clear. In this study, we analyzed the relations between As and Is for eruption tremors and explosion events at active volcanoes in Japan, and estimated As and Is by the ASL method. We obtained power-law relations between As and Is, in which the powers were different between eruption tremors and explosion events. These relations were consistent with the scaling relations at Tungurahua volcano. Then, we compared As with maximum eruption plume heights (H) during eruption tremors analyzed in this study, and found that H was proportional to 0.21 power of As. This relation is similar to the plume height model based on the physical process of plume rise, which indicates that H is proportional to 0.25 power of volumetric flow rate for plinian eruptions. This suggests that As may correspond to volumetric flow rate. If we assume a seismic source with volume changes and far-field S-wave, As is proportional to the source volume rate. This proportional relation and the plume height model give rise to the relation that H is proportional to 0.25 power of As. These results suggest that we may be able to estimate plume heights in realtime by estimating As during eruptions from seismic observations.

Water-magma interaction and plume processes in the 2008 Okmok eruption, Alaska

USGS Publications Warehouse

Unema, Joel; Ort, Michael H.; Larsen, Jessica D; Neal, Christina; Schaefer, Janet R.

2016-01-01

Eruptions of similar explosivity can have divergent effects on the surroundings due to differences in the behavior of the tephra in the eruption column and atmosphere. Okmok volcano, located on Umnak Island in the eastern Aleutian Islands, erupted explosively between 12 July and 19 August 2008. The basaltic andesitic eruption ejected ∼0.24 km3dense rock equivalent (DRE) of tephra, primarily directed to the northeast of the vent area. The first 4 h of the eruption produced dominantly coarse-grained tephra, but the following 5 wk of the eruption deposited almost exclusively ash, much of it very fine and deposited as ash pellets and ashy rain and mist. Meteorological storms combined with abundant plume water to efficiently scrub ash from the eruption column, with a rapid decrease in deposit thickness with distance from the vent. Grain-size analysis shows that the modes (although not their relative proportions) are very constant throughout the deposit, implying that the fragmentation mechanisms did not vary much. Grain-shape features consistent with molten fuel-coolant interaction are common. Surface and groundwater drainage into the vents provided the water for phreatomagmatic fragmentation. The available water (water that could reach the vent area during the eruption) was ∼2.8 × 1010 kg, and the erupted magma totaled ∼7 × 1011 kg, which yield an overall water:magma mass ratio of ∼0.04, but much of the water was not interactive. Although magma flux dropped from 1 × 107 kg/s during the initial 4 h to 1.8 × 105 kg/s for the remainder of the eruption, most of the erupted material was ejected during the lower-mass-flux period due to its much greater length, and this tephra was dominantly deposited within 10 km downwind of the vent. This highlights the importance of ash scrubbing in the evaluation of hazards from explosive eruptions.

Surficial Geologic Map of Mount Veniaminof Volcano, Alaska

NASA Astrophysics Data System (ADS)

Waythomas, C. F.; Miller, T. P.; Wallace, K.

2015-12-01

Mount Veniaminof volcano is a >300 km3 andesite to dacite stratovolcano, characterized by an 8 x 11 km diameter ice-filled summit caldera. Veniaminof is one of the most active volcanoes in the Aleutian arc and has erupted at least 15 times in the past 200 years. The volcano is located on the Alaska Peninsula (56.1979° N, 159.3931° W) about 780 km SW of Anchorage. Our geologic investigations have documented two large (>VEI 5) caldera-forming or -modifying eruptions (V1, V2) of Holocene age whose eruptive products make up most of the surficial deposits around the volcano. These deposits and other unconsolidated glacial, fluvial, and colluvial deposits are depicted on the accompanying map. The the V2 eruption occurred 4.1-4.4 ka (cal 2-sigma age range) and produced an extensive landscape-mantling sequence of pyroclastic deposits >50 km3 in volume that cover or partly obscure older unconsolidated eruptive products. The V1 eruption occurred 8-9 ka and its deposits lie stratigraphically below the pyroclastic deposits associated with the V2 eruption and a prominent, widespread tephra fall deposit erupted from nearby Black Peak volcano 4.4-4.6 ka. The V2 pyroclastic-flow deposits range from densely welded, columnar jointed units exposed along the main valley floors, to loose, unconsolidated, blanketing accumulations of scoriaceous (55-57% SiO2) and lithic material found as far as 75 km from the edifice. Large lahars also formed during the V2 eruption and flowed as far as 50 km from the volcano. The resulting deposits are present in all glacial valleys that head on the volcano and are 10-15 m thick in several locations. Lahar deposits cover an area of about 800-1000 km2, have an approximate volume of 1-2 km3, and record substantial inundation of the major valleys on all flanks of the edifice. Significant amounts of water are required to form lahars of this size, which suggests that an ice-filled summit caldera probably existed when the V2 eruption occurred.

Calderas and magma reservoirs

NASA Astrophysics Data System (ADS)

Cashman, Katharine V.; Giordano, Guido

2014-11-01

Large caldera-forming eruptions have long been a focus of both petrological and volcanological studies; petrologists have used the eruptive products to probe conditions of magma storage (and thus processes that drive magma evolution), while volcanologists have used them to study the conditions under which large volumes of magma are transported to, and emplaced on, the Earth's surface. Traditionally, both groups have worked on the assumption that eruptible magma is stored within a single long-lived melt body. Over the past decade, however, advances in analytical techniques have provided new views of magma storage regions, many of which provide evidence of multiple melt lenses feeding a single eruption, and/or rapid pre-eruptive assembly of large volumes of melt. These new petrological views of magmatic systems have not yet been fully integrated into volcanological perspectives of caldera-forming eruptions. Here we explore the implications of complex magma reservoir configurations for eruption dynamics and caldera formation. We first examine mafic systems, where stacked-sill models have long been invoked but which rarely produce explosive eruptions. An exception is the 2010 eruption of Eyjafjallajökull volcano, Iceland, where seismic and petrologic data show that multiple sills at different depths fed a multi-phase (explosive and effusive) eruption. Extension of this concept to larger mafic caldera-forming systems suggests a mechanism to explain many of their unusual features, including their protracted explosivity, spatially variable compositions and pronounced intra-eruptive pauses. We then review studies of more common intermediate and silicic caldera-forming systems to examine inferred conditions of magma storage, time scales of melt accumulation, eruption triggers, eruption dynamics and caldera collapse. By compiling data from large and small, and crystal-rich and crystal-poor, events, we compare eruptions that are well explained by simple evacuation of a zoned magma chamber (termed the Standard Model by Gualda and Ghiorso, 2013) to eruptions that are better explained by tapping multiple, rather than single, melt lenses stored within a largely crystalline mush (which we term complex magma reservoirs). We then discuss the implications of magma storage within complex, rather than simple, reservoirs for identifying magmatic systems with the potential to produce large eruptions, and for monitoring eruption progress under conditions where successive melt lenses may be tapped. We conclude that emerging views of complex magma reservoir configurations provide exciting opportunities for re-examining volcanological concepts of caldera-forming systems.

Measuring the speed of magma ascent during explosive eruptions of Kilauea, Hawaii

NASA Astrophysics Data System (ADS)

Ferguson, D. J.; Ruprecht, P.; Plank, T. A.; Hauri, E. H.; Gonnermann, H. M.; Houghton, B. F.; Swanson, D. A.

2014-12-01

The size and intensity of volcanic eruptions is controlled by a combination of the physical properties of magmas and the conditions of magma ascent. At basaltic volcanoes, where relatively fluid magmas are erupted, sustained explosive eruptions vary widely in style, from Hawaiian fountains erupted 10s to 100s of meter high to large Plinian type events, involving >20 km high eruption plumes. Decompression of magmas leads to volatile saturation and bubble growth, however it remains disputed how the dynamics of shallow ascent and degassing might control this disparate eruptive behaviour, or whether factors such as the initial volatile content exert the primary control on eruption style. A key issue is that the physical conditions of magma ascent, which may significantly impact eruptive dynamics, remain largely unconstrained by observational data. Here we quantify two primary variables - decompression rates and volatile contents - for magmas from three contrasting eruptions of Kīlauea volcano, Hawaii, using microanalysis and modelling of volatile diffusion along small melt tubes or embayments found in olivine crystals carried by the ascending magmas. During ascent decreasing solubility causes dissolved volatiles to diffuse along the embayment towards growing bubbles at the crystal edge. By modelling the diffusion of H2O, CO2 and S we obtain decompression rates, and indirectly ascent velocities, for the rising magma. For Hawaiian style fountaining events we obtain ascent rates of 0.05-0.07 MPa s-1 (~1 m s-1), whereas for a more intense subplinian eruption we obtain a notably faster rate of 0.29 MPa s-1 (>10m s-1). The timescales of melt transport from the storage region during these eruptions varied from around 3 to 40 minutes. We find no link between pre-eruptive volatile contents and eruption intensity, rather our results suggest that the eventual size of sustained explosive basaltic eruptions is likely governed by factors affecting the ascent velocity of melts in the volcanic conduit. The observed decompression rates are consistent with measured discharge rates, and with models predicting greater magma chamber overpressure for larger eruptions. Ascent rates may also further modulate dynamic processes in the volcanic conduit, such as the flow regime and bubble expansion, and consequently eruptive intensity.

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.

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.

Observational evidence of torus instability as trigger mechanism for coronal mass ejections: The 2011 August 4 filament eruption

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

Zuccarello, F. P.; Poedts, S.; Seaton, D. B.

Solar filaments are magnetic structures often observed in the solar atmosphere and consist of plasma that is cooler and denser than their surroundings. They are visible for days—even weeks—which suggests that they are often in equilibrium with their environment before disappearing or erupting. Several eruption models have been proposed that aim to reveal what mechanism causes (or triggers) these solar eruptions. Validating these models through observations represents a fundamental step in our understanding of solar eruptions. We present an analysis of the observation of a filament eruption that agrees with the torus instability model. This model predicts that a magneticmore » flux rope embedded in an ambient field undergoes an eruption when the axis of the flux rope reaches a critical height that depends on the topology of the ambient field. We use the two vantage points of the Solar Dynamics Observatory (SDO) and the Solar TErrestrial RElations Observatory to reconstruct the three-dimensional shape of the filament, to follow its morphological evolution, and to determine its height just before eruption. The magnetograms acquired by SDO/Helioseismic and Magnetic Imager are used to infer the topology of the ambient field and to derive the critical height for the onset of the torus instability. Our analysis shows that the torus instability is the trigger of the eruption. We also find that some pre-eruptive processes, such as magnetic reconnection during the observed flares and flux cancellation at the neutral line, facilitated the eruption by bringing the filament to a region where the magnetic field was more vulnerable to the torus instability.« less

Lava emplacements at Shiveluch volcano (Kamchatka) from June 2011 to September 2014 observed by TanDEM-X SAR-Interferometry

NASA Astrophysics Data System (ADS)

Heck, Alexandra; Kubanek, Julia; Westerhaus, Malte; Gottschämmer, Ellen; Heck, Bernhard; Wenzel, Friedemann

2016-04-01

As part of the Ring of Fire, Shiveluch volcano is one of the largest and most active volcanoes on Kamchatka Peninsula. During the Holocene, only the southern part of the Shiveluch massive was active. Since the last Plinian eruption in 1964, the activity of Shiveluch is characterized by periods of dome growth and explosive eruptions. The recent active phase began in 1999 and continues until today. Due to the special conditions at active volcanoes, such as smoke development, danger of explosions or lava flows, as well as poor weather conditions and inaccessible area, it is difficult to observe the interaction between dome growth, dome destruction, and explosive eruptions in regular intervals. Consequently, a reconstruction of the eruption processes is hardly possible, though important for a better understanding of the eruption mechanism as well as for hazard forecast and risk assessment. A new approach is provided by the bistatic radar data acquired by the TanDEM-X satellite mission. This mission is composed of two nearly identical satellites, TerraSAR-X and TanDEM-X, flying in a close helix formation. On one hand, the radar signals penetrate clouds and partially vegetation and snow considering the average wavelength of about 3.1 cm. On the other hand, in comparison with conventional InSAR methods, the bistatic radar mode has the advantage that there are no difficulties due to temporal decorrelation. By interferometric evaluation of the simultaneously recorded SAR images, it is possible to calculate high-resolution digital elevation models (DEMs) of Shiveluch volcano and its surroundings. Furthermore, the short recurrence interval of 11 days allows to generate time series of DEMs, with which finally volumetric changes of the dome and of lava flows can be determined, as well as lava effusion rates. Here, this method is used at Shiveluch volcano based on data acquired between June 2011 and September 2014. Although Shiveluch has a fissured topography with steep slopes, DEMs with a resolution of about 6 m can be calculated and the changes caused by volcanic activity can successfully be derived and quantified.

On the longevity of silicic magma based on multi-isotope investigation of zircons and modeling their survivals destinies

NASA Astrophysics Data System (ADS)

Bindeman, I. N.; Wotzlaw, J. F.; Melnik, O. E.

2015-12-01

Large volumes of crystal poor, near-liquidus rhyolites are erupted worldwide as tuffs and lavas in rift and hot spots more common previously on early earth, creating temporally very high magma production rates. In this contribution we combine results of IDTIMS dating of zircons with numerical modeling of zircon crystallization. New investigation of zircons in major Yellowstone tuffs: Huckleberry Ridge (Members A,B,C), Mesa Falls, and Lava Creek (A,B) tuffs was done by a combination of in situ measurements of oxygen isotopes followed by ID-TIMS U-Pb dating, Hf isotopes and trace elemental investigation of single crystals. We discover that nearly all zircons are of eruption age, but display significant isotope (O,Hf) diversity and often show decoupled O and Hf isotope systematics. This record rapid (~103yrs) double or triple remelting and sequestration from diverse Archean crust and hydrothermally altered shallow-crustal rocks from previous eruptive cycles, followed by effective mixing of co-existing magma reservoirs with diverse zircons prior to eruptions. Similar results characterize other studied Snake River Plain rhyolites in pre-Yellowstone Heise complex. These results collectively suggest that zircons crystallize after reheating above saturation rejuvenation in isotopically-diverse areas of the crust in the magma plumbing system. Modeling of zircon and quartz dissolution and crystallization trajectories outline conditions of survival (inheritance) vs complete dissolution on conductive timescales, and when combined with a phase diagram, magma T-t paths can be computed. Zircon rejuvenation requires hot, >770-800°C peak temperatures lasting 10-102yrs. We speculate that near liquidus hot and dry Yellowstone rhyolites are kept alive in a multi-batch state by a series of interconnected pods and sills that can rapidly get thermomechanically assembled into large, shallow and eruptable supervolcanoic magma bodies. We suggest that overpressure and roof dynamics and rheology plays a more important role than magma buyoncy. The runaway batch assembly process creates temporally very high magma production rates, orders of magnitude higher than for arc volcanoes. Such views have implication for the state of the magma chamber under Yellowstone and similar supervolcanoes elsewhere.

Setting of the Father's Day Eruption at Kilauea

NASA Astrophysics Data System (ADS)

Swanson, D. A.

2007-12-01

The Father's Day eruption and associated intrusion took place within a 10-km segment of Kilauea's east rift zone between Hi`iaka and Napau Craters--a segment that has had more numerous eruptions and intrusions than any other of comparable length during the past 200, probably the past 1000, years. Fifteen known eruptions started in this area in the past 200 years: 1840, 1922, 1923, 1962, August and October 1963, March and December 1965, August and October 1968, February and May 1969, May and November 1973, and March 1980 (only 3 cubic meters!). Three others, not previously designated as distinct eruptions despite having all the appropriate characteristics, took place during on-going eruptions: two in `Alo`i Crater in 1970 and 1972, and one in Napau Crater in 1997. Two of the largest shields on the east rift zone formed during long-lasting eruptions within this area--Kane Nui o Hamo at an unknown date, perhaps the 11-12th century, and Mauna Ulu (1969-1974). In addition, many small intrusions without eruptions are known. Seven short eruptions punctuated a prolonged eruption: four within the segment during the Mauna Ulu eruption, two at the summit and southwest rift zone during that same eruption, and one in Napau Crater in 1997 during the Pu`u `O`o eruption. Thus the Father's Day eruption is not unique by virtue of taking place during an ongoing eruption elsewhere along the rift zone. The increased frequency of activity in the segment during the 20th century is obvious, particularly after 1962. For most of the past 1,000 years, eruptions were centered at Kilauea's summit, with significant but lesser activity along the rift zones. A large summit deflation in 1924 ended the nearly continuous lava lake in Halemaumau, eventually leading to the past 5 decades of dominantly east rift zone activity. This segment of the rift zone contains most of the pit craters on Kilauea and gradually changes from a SE trend near the caldera to an ENE trend that characterizes the rest of the zone. The Koa`e fault system joins the east rift zone at the curve. The complex structural setting likely affects the frequency of magmatic activity in the segment. All of the eruptive and intrusive activity results in storage of isolated magma bodies. Not surprisingly, petrologists find evidence that summit magma mixes with stored, fractionated magma. The area near Makaopuhi Crater and Kane Nui o Hamo is a particular focus, inferred since the mid-1960s to harbor a shallow magma reservoir. All of the eruptions and intrusions are accompanied by sharp deflation and shallow seismicity at the summit and shallow seismicity and uplift along the intrusion or eruptive fissures. Most often, no seismicity occurs between the summit and the area of intrusion or eruption. Within that area, seismicity commonly migrates downrift but occasionally uprift. Similarly, crack opening generally progresses downrift, with a few exceptions. Cracks generally trend about 65 degrees and can be either left- or right-stepping. Cracks open along azimuths of 155-175, with local exceptions. There is no structural difference between eruptive cracks (fissures) and non- eruptive cracks. Single eruptive fissures rarely exceed 200 m in length, instead stepping within en echelon zones above a presumably linear dike. Since the late 1960s, widening has been measured across the active area during eruptions and intrusions, first by EDM and then by satellite-based systems. The opening is nearly symmetrical within the rift zone, but farther out the north flank barely responds whereas the south flank moves seaward. Available leveling data show uplift on either side of the dike and subsidence along the crest. Examples of deformation in the 1960s and 1970s will be presented, and bibliographic references to past activity will be available.

Monitoring Italian volcanoes by NOAA-AVHRR satellite data

NASA Astrophysics Data System (ADS)

Spinetti, C.; Buongiorno, M. F.; Amici, S.; Silvestri, M.; Lombardo, V.; Musacchio, M.; Doumaz, F.; Corradini, C.

2009-04-01

The INGV Remote Sensing unit is equipped with a NOAA-AVHRR receiving station that provides 4 to 10 images per day of the central Mediterranean area in the visible to thermal infrared bands. These data were acquired and processed in real time using automatic and semi-automatic procedures which outputs information collated in daily and weekly observation reports and outputs overview images in the DPC dedicated web page. Satellite information included the presence of hot spots as well as their temporal evolution in terms of temperature. An automatic procedure that calculate lava flow effusion rate has been developed. The procedure automatically sent alert via e-mail when an hot spot is present in the AVHRR data. Volcanic ash information AVHRR-derived has been also included in a separate system. These information concerned the presence of volcanic ash in air, an assessment of the area affected, as well as the plume dispersal direction, the ash plume altitude and the concentration of ash in air. The eruptions occurred both at Etna and Stromboli volcanoes in Sicily (Italy) has been surveyed by satellite. The different eruptions were characterized both by lava flow emissions and eruption of ash plumes with different impact to the surrounding villages and cities, causing problems to local communications and air traffic. Information provided by satellite sensors are communicate in observation reports integrating ground-based surveillance operated by INGV Catania Volcanology Observatory in agreement with the Italian Department of Civil Protection (DPC) responsible for volcanic risk and airports closure during the explosive phases.

Spatial distribution of volcanic ash deposits of 2011 Puyehue-Cordón Caulle eruption in Patagonia as measured by a perturbation in NDVI temporal dynamics

NASA Astrophysics Data System (ADS)

Easdale, M. H.; Bruzzone, O.

2018-03-01

Volcanic ash fallout is a recurrent environmental disturbance in forests, arid and semi-arid rangelands of Patagonia, South America. The ash deposits over large areas are responsible for several impacts on ecological processes, agricultural production and health of local communities. Public policy decision making needs monitoring information of the affected areas by ash fallout, in order to better orient social, economic and productive aids. The aim of this study was to analyze the spatial distribution of volcanic ash deposits from the eruption of Puyehue-Cordón Caulle in 2011, by identifying a sudden change in the Normalized Difference Vegetation Index (NDVI) temporal dynamics, defined as a perturbation located in the time series. We applied a sparse-wavelet transform using the Basis Pursuit algorithm to NDVI time series obtained from the Moderate Resolution Image Spectroradiometer (MODIS) sensor, to identify perturbations at a pixel level. The spatial distribution of the perturbation promoted by ash deposits in Patagonia was successfully identified and characterized by means of a perturbation in NDVI temporal dynamics. Results are encouraging for the future development of a new platform, in combination with data from forecasting models and tracking of ash cloud trajectories and dispersion, to inform stakeholders to mitigate impact of volcanic ash on agricultural production and to orient public intervention strategies after a volcanic eruption followed by ash fallout over a wide region.

Mount Cameroon Eruptions, Related Hazards and Effects on the Ecosystem

NASA Astrophysics Data System (ADS)

Aloatem Tazifor, A. N.

2016-02-01

Mount Cameroon (MC) is the highest peak in West and Central Africa. It is the only active volcano along the 1600km, Cameroon volcanic line with NE-SW orientation. It has a height of about 4100m above sea level, is a typical example of a hazardous volcano in a densely populated area, often causing damage by lava flows. It shows layered mafic volcanic sequence thought to be related to near-continuous eruptions within the last century during which period it has erupted 8 times in 1909, 1922, 1925, 1954, 1959, 1982, 1999 and 2000. These volcanic activities are suggested to be contributing factor to the many small-scale shallow landslides within the last 20 years which have resulted in the loss of about 30 lives and significant damage to farmland and property. The relatively high carbon dioxide (CO2) content in MC Glass inclusions support the interpretation that the CO2 gas responsible for the 1984 Lakes Monoun and 1986 Nyos disasters is magmatic in origin, which killed 37 and over 1800 people respectively. Months before the latest 2000 eruption, MC was characterized by a seismic swarm recorded in 03/2000 by analogue seismic stations. The co-eruptive period from May 28th to June 19th, 2000 was characterized by sequences of earth quakes, swarms and volcanic tremor. The main shock had a magnitude 3.2 event and a modified Mercalli intensity of 3 to 4. The largest seismic event recorded had a magnitude of 4. An explosion on 5th June, 2000, injured many members of a surveillance team, and a helicopter crash on 10th June, 2000 killed both pilots. It also led to lava flow across the Limbe-Idenau highway, damage of forest and palm plantations in Bakingili, and the evacuation of the 600 inhabitants of Bakingili. Never the less MC has positive impacts on the environment such as increased soil fertility where agro-industrial plantations have taken advantage, and more touristic sites have developed. After the last eruption of 2000, a number of seismographs have been placed along the MC site network with one at the Ekona Station, Esuke and Banga-Bakundu.

Geochemistry of the July 2015 pyroclastic flow at Volcán de Colima

NASA Astrophysics Data System (ADS)

Atlas, Z. D.; Long, E.; Macorps, E.; Garcia Hernandez, M.; Charbonnier, S. J.; Varley, N. R.

2016-12-01

We investigated the geochemical variation of the July 2015 pyroclastic density current (PDC) from Volcán de Colima, Mexico. This important eruption produced a highly mobile PDC, with the largest run-out since 1913 (10.7 km). The eruptive mechanism is still unclear and geochemical characterization is critical to determine its origin. Normalized major element concentrations define differentiation trends and concentrations similar to 1998-2000 lava, consistent with earlier volcanic products. SiO2 ranges from 59.9 to 61.0 wt.% with low Mg# (0.48-0.51), moderate K2O (1.35-1.42 wt.%) and higher total alkalis (6.95-7.66 wt.%). The PDC is characterized by high Sr, Ba, Nb and U, low Ba/Nb and Sc/Y ratios. Higher Sr can be attributed to abundant plagioclase, however high Ba, Nb and U must be attributed to other minerals. U is compatible in apatite or ilmenite but due to the incompatible behavior P2O5 with SiO2 apatite contribution is unlikely. Nb is partitioned into ilmenite but also biotite, while Ba strongly partitions to biotite/phlogopite, known from scoria cone lamprophyre magma erupted next to Volcán de Colima. Our data suggest that U along with some Nb is partitioned to Ti-Fe oxide or to ilmentie. Covariation of U and Nb with Ba suggests that biotite +/- ilmenite may be involved in the generation of the 2015 PDC magma. The lack of an Eu anomaly and overall REE patterns suggest that excess plagioclase likely comes from fragments of previously emplaced lava and that the source and overall generation of the PDC is similar to recent eruptive products. LILE along with high Nb is unlike 1913 but are more similar to 1869 and 1880 rocks, lower K melt inclusions of Reubi & Blundy (2008) and unit N from Crummy et al. (2014) erupted 7000 Ybp and represent a sharp departure from the pre-1999 eruptive products. Our results indicate that the PDC chemistry must have some influence from the addition of a biotite bearing gabbrotic endmember in accord with previous studies.

Infrasound as a Long Standing Tool for Monitoring Continental Ecuadorean Volcanoes

NASA Astrophysics Data System (ADS)

Ruiz, M. C.; Ortiz, H. D.; Hernandez, S.; Palacios, P.; Anzieta, J. C.

2017-12-01

In the last 10 years, infrasound and seismic methods have been successfully used in the continuous monitoring of eruptive activity at Tunguruhua, Reventador, Sangay and Cotopaxi volcanoes. After a dormant period of 81 years, Tungurahua woke up in 1999 and has since been characterized by vulcanian and strombolian eruptions. Beginning in July 2006, a permanent seismo-infrasonic network with 5 collocated seismic and infrasound sensors was installed through a cooperation with Japan International Cooperation Agency (JICA). It recorded more than 6,000 explosions at Tungurahua with reduced amplitudes larger than 270 Pa at 1 km from the active crater, including 3 explosions greater than 6000 Pa associated with short-lived explosions. Major and long sustained eruptions (July 14-15, 2006; August 16-17, 2006; February 6-8, 2008, May 28, 2010; December 4, 2010; December 3-4, 2011; August 18, 2012) generated seismic and infrasound tremors with complex waveforms. In 2002, Reventador volcano produced the largest eruption in Ecuador in the last century (VEI-4). Since September 2012, alternating periods of strombolian activity and short-lived vulcanian explosions are monitored by seismic and microbarometer sensors located on the south-east border of the caldera rim. Non-steady activity with fluctuations between quiescence and frequent explosions, tremor, and chugging events is recorded. Infrasound of explosions ranges from 75 to 6350 Pa in reduced peak-to-peak amplitudes. Sangay, a remote and very active volcano, is monitored by a broadband seismometer and microbarometer collocated at 8 km from the summit. Active periods during the last few months are characterized by explosion events followed by lava flows and small ash emissions. In March 2016, more than 100 explosions were recorded in a single day. Finally, in 2015 Cotopaxi volcano began its recent eruptive period after 138 years of quiescence. One month after the initiation of its eruptive activity, 76 harmonic infrasound signals with a characteristic 5 sec. period were recorded between September and December 2015 that have been related to outgassing or explosive bubble bursts that excite resonance modes in unfilled craters.

PTH intermittent administration may be a useful therapeutic agent to avoid premature eruption of the tooth.

PubMed

Vasconcelos, Daniel Fernando Pereira; Vasconcelos, Any Carolina Cardoso Guimarães

2016-03-01

Parathyroid hormone (PTH) acts as a controller of bone remodeling and has influence on periodontal tissues. In addition to the well-established catabolic effects (activation of bone resorption) of PTH, it is recognized that the PTH intermittent administration has anabolic effects (promotion of bone formation). However, there is no information regarding the effects of the PTH intermittent administration on the eruption tooth rate. Studies have shown that tooth eruption depends on the presence of osteoclasts to create an eruption pathway through the alveolar bone. It may also be controlled by osteoblast, precursor of osteoclast, and cells of periodontal ligament. Our hypothesis is based on previous studies showing that the PTH intermittent administration can promote bone formation, particularly in the areas around which the tooth erupts. Furthermore, the PTH intermittent administration influenced periodontal ligament fiber, what may be seen as greater organization, and isomerization, as well as higher birefringence of the periodontal ligament fiber, which then offers increased resistance to the process, delaying tooth eruption. Thus, this article opens new perspectives for the treatment and maintenance of teeth that can erupt early. Published by Elsevier Ltd.

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.

Widespread uplift and 'trapdoor' faulting on Galápagos volcanoes observed with radar interferometry.

PubMed

Amelung, F; Jónsson, S; Zebker, H; Segall, P

2000-10-26

Volcanic uplift, caused by the accumulation of magma in subsurface reservoirs, is a common precursor to eruptions. But, for some volcanoes, uplift of metres or more has not yet led to an eruption. Here we present displacement maps of volcanoes in the Galápagos Islands, constructed using satellite radar interferometry, that might help explain this dichotomy. We show that all but one of the seven volcanoes on the islands of Isabela and Fernandina deformed during 1992-99. Cerro Azul and Fernandina erupted during the observation period and show evidence of inflation, co-eruptive deflation and shallow dyke intrusion. In contrast, the largest volcano, Sierra Negra, has not erupted, yet exhibits spatially and temporally variable deformation, with a maximum uplift of 2.7 m between 1992 and 1999, which can be modelled by a shallow inflating sill. Inflation during 1997-98, however, was accompanied by 'trapdoor' faulting on a steeply dipping fracture system within the caldera. Repeated trapdoor faulting over geological time has formed an arcuate intra-caldera ridge within Sierra Negra and may have acted to relax stresses above the magma chamber, inhibiting summit eruptions. Similar processes may help explain large uplift unaccompanied by eruptive activity at other volcanoes.

Crustal contamination and crystal entrapment during polybaric magma evolution at Mt. Somma-Vesuvius volcano, Italy: Geochemical and Sr isotope evidence

USGS Publications Warehouse

Piochi, M.; Ayuso, R.A.; de Vivo, B.; Somma, R.

2006-01-01

New major and trace element analyses and Sr-isotope determinations of rocks from Mt. Somma-Vesuvius volcano produced from 25 ky BP to 1944 AD are part of an extensive database documenting the geochemical evolution of this classic region. Volcanic rocks include silica undersaturated, potassic and ultrapotassic lavas and tephras characterized by variable mineralogy and different crystal abundance, as well as by wide ranges of trace element contents and a wide span of initial Sr-isotopic compositions. Both the degree of undersaturation in silica and the crystal content increase through time, being higher in rocks produced after the eruption at 472 AD (Pollena eruption). Compositional variations have been generally thought to reflect contributions from diverse types of mantle and crust. Magma mixing is commonly invoked as a fundamental process affecting the magmas, in addition to crystal fractionation. Our assessment of geochemical and Sr-isotopic data indicates that compositional variability also reflects the influence of crustal contamination during magma evolution during upward migration to shallow crustal levels and/or by entrapment of crystal mush generated during previous magma storage in the crust. Using a variant of the assimilation fractional crystallization model (Energy Conservation-Assimilation Fractional Crystallization; [Spera and Bohrson, 2001. Energy-constrained open-system magmatic processes I: General model and energy-constrained assimilation and fractional crystallization (EC-AFC) formulation. J. Petrol. 999-1018]; [Bohrson, W.A. and Spera, F.J., 2001. Energy-constrained open-system magmatic process II: application of energy-constrained assimilation-fractional crystallization (EC-AFC) model to magmatic systems. J. Petrol. 1019-1041]) we estimated the contributions from the crust and suggest that contamination by carbonate rocks that underlie the volcano (2 km down to 9-10 km) is a fundamental process controlling magma compositions at Mt. Somma-Vesuvius in the last 8 ky BP. Contamination in the mid- to upper crust occurred repeatedly, after the magma chamber waxed with influx of new mantle- and crustal-derived magmas and fluids, and waned as a result of magma withdrawal and production of large and energetic plinian and subplinian eruptions. ?? 2005 Elsevier B.V. All rights reserved.

Patterns in Seismicity at Mt St Helens and Mt Unzen

NASA Astrophysics Data System (ADS)

Lamb, Oliver; De Angelis, Silvio; Lavallee, Yan

2014-05-01

Cyclic behaviour on a range of timescales is a well-documented feature of many dome-forming volcanoes. Previous work on Soufrière Hills volcano (Montserrat) and Volcán de Colima (Mexico) revealed broad-scale similarities in behaviour implying the potential to develop general physical models of sub-surface processes [1]. Using volcano-seismic data from Mt St Helens (USA) and Mt Unzen (Japan) this study explores parallels in long-term behaviour of seismicity at two dome-forming systems. Within the last twenty years both systems underwent extended dome-forming episodes accompanied by large Vulcanian explosions or dome collapses. This study uses a suite of quantitative and analytical techniques which can highlight differences or similarities in volcano seismic behaviour, and compare the behaviour to changes in activity during the eruptive episodes. Seismic events were automatically detected and characterized on a single short-period seismometer station located 1.5km from the 2004-2008 vent at Mt St Helens. A total of 714 826 individual events were identified from continuous recording of seismic data from 22 October 2004 to 28 February 2006 (average 60.2 events per hour) using a short-term/long-term average algorithm. An equivalent count will be produced from seismometer recordings over the later stages of the 1991-1995 eruption at MT Unzen. The event count time-series from Mt St Helens is then analysed using Multi-taper Method and the Short-Term Fourier Transform to explore temporal variations in activity. Preliminary analysis of seismicity from Mt St Helens suggests cyclic behaviour of subannual timescale, similar to that described at Volcán de Colima and Soufrière Hills volcano [1]. Frequency Index and waveform correlation tools will be implemented to analyse changes in the frequency content of the seismicity and to explore their relations to different phases of activity at the volcano. A single station approach is used to gain a fine-scale view of variations in seismic behaviour at both volcanoes with a focus on comparisons with changes in activity with the hope of gaining a greater understanding of sub-surface processes occurring within the volcanic systems. This approach and the techniques above were successfully implemented at Redoubt Volcano (USA) [2] which also concluded that these techniques may serve an important role in future real-time eruption monitoring efforts. [1] Lamb O., Varley N., Mather T. et al., in prep Similar Cyclic Behaviour at two lava domes, Volcán de Colima (Mexico) and Soufrière Hills volcano (Montserrat), with implications for monitoring. [2] Ketner, D. & Power, J., 2013. Characterization of seismic events during the 2009 eruption of Redoubt Volcano, Alaska. Journal of Volcanology and Geothermal Research, 259, pp.45-62

A contribution to the hazards assessment at Copahue volcano (Argentina-Chile) by facies analysis of a recent pyroclastic density current deposit

NASA Astrophysics Data System (ADS)

Balbis, C.; Petrinovic, I. A.; Guzmán, S.

2016-11-01

We recognised and interpreted a recent pyroclastic density current (PDC) deposit at the Copahue volcano (Southern Andes), through a field survey and a sedimentological study. The relationships between the behaviour of the PDCs, the morphology of the Río Agrio valley and the eruptive dynamics were interpreted. We identified two lithofacies in the deposit that indicate variations in the eruptive dynamics: i) the opening of the conduit and the formation of a highly explosive eruption that formed a diluted PDC through the immediate collapse of the eruptive column; ii) a continued eruption which followed immediately and records the widening of the conduit, producing a dense PDC. The eruption occurred in 2000 CE, was phreatomagmatic (VEI ≤ 2), with a vesiculation level above 4000 m depth and fragmentation driven by the interaction of magma with an hydrothermal system at ca. 1500 m depth. As deduced from the comparison between the accessory lithics of this deposit and those of the 2012 CE eruption, the depth of onset of vesiculation and fragmentation level in this volcano is constant in depth. In order to reproduce the distribution pattern of this PDC's deposit and to simulate potential PDC's forming-processes, we made several computational modelling from "denser" to "more diluted" conditions. The latter fairly reproduces the distribution of the studied deposit and represents perhaps one of the most dangerous possible scenarios of the Copahue volcanic activity. PDCs occurrence has been considered in the last volcanic hazards map as a low probability process; evidences found in this contribution suggest instead to include them as more probable and thus very important for the hazards assessment of the Copahue volcano.

Onset of the Magnetic Explosion in Solar Polar Coronal X-Ray Jets

NASA Astrophysics Data System (ADS)

Moore, Ronald L.; Sterling, Alphonse C.; Panesar, Navdeep

2017-08-01

We examine the onset of the driving magnetic explosion in 15 random polar coronal X-ray jets. Each eruption is observed in a coronal X-ray movie from Hinode and in a coronal EUV movie from Solar Dynamics Observatory. Contrary to the Sterling et al (2015, Nature, 523, 437) scenario for minifilament eruptions that drive polar coronal jets, these observations indicate: (1) in most polar coronal jets (a) the runaway internal tether-cutting reconnection under the erupting minifilament flux rope starts after the spire-producing breakout reconnection starts, not before it, and (b) aleady at eruption onset, there is a current sheet between the explosive closed magnetic field and ambient open field; and (2) the minifilament-eruption magnetic explosion often starts with the breakout reconnection of the outside of the magnetic arcade that carries the minifilament in its core. On the other hand, the diversity of the observed sequences of occurrence of events in the jet eruptions gives further credence to the Sterlling et al (2015, Nature, 523, 437) idea that the magnetic explosions that make a polar X-ray jet work the same way as the much larger magnetic explosions that make and flare and CME. We point out that this idea, and recent observations indicating that magnetic flux cancelation is the fundamental process that builds the field in and around pre-jet minifilaments and triggers the jet-driving magnetic explosion, together imply that usually flux cancelation inside the arcade that explodes in a flare/CME eruption is the fundamental process that builds the explosive field and triggers the explosion.This work was funded by the Heliophysics Division of NASA's Science Mission Directorate through its Living With a Star Targeted Research and Technology Program, its Heliophsyics Guest Investigators Program, and the Hinode Project.

Rapid cooling and cold storage in a silicic magma reservoir recorded in individual crystals.

PubMed

Rubin, Allison E; Cooper, Kari M; Till, Christy B; Kent, Adam J R; Costa, Fidel; Bose, Maitrayee; Gravley, Darren; Deering, Chad; Cole, Jim

2017-06-16

Silicic volcanic eruptions pose considerable hazards, yet the processes leading to these eruptions remain poorly known. A missing link is knowledge of the thermal history of magma feeding such eruptions, which largely controls crystallinity and therefore eruptability. We have determined the thermal history of individual zircon crystals from an eruption of the Taupo Volcanic Zone, New Zealand. Results show that although zircons resided in the magmatic system for 10 3 to 10 5 years, they experienced temperatures >650° to 750°C for only years to centuries. This implies near-solidus long-term crystal storage, punctuated by rapid heating and cooling. Reconciling these data with existing models of magma storage requires considering multiple small intrusions and multiple spatial scales, and our approach can help to quantify heat input to and output from magma reservoirs. Copyright © 2017, American Association for the Advancement of Science.

Voyager 2 Jupiter Eruption Movie

NASA Technical Reports Server (NTRS)

2000-01-01

This movie records an eruptive event in the southern hemisphere of Jupiter over a period of 8 Jupiter days. Prior to the event, an undistinguished oval cloud mass cruised through the turbulent atmosphere. The eruption occurs over avery short time at the very center of the cloud. The white eruptive material is swirled about by the internal wind patterns of the cloud. As a result of the eruption, the cloud then becomes a type of feature seen elsewhere on Jupiter known as 'spaghetti bowls'.

As Voyager 2 approached Jupiter in 1979, it took images of the planet at regular intervals. This sequence is made from 8 images taken once every Jupiter rotation period (about 10 hours). These images were acquired in the Violet filter around May 6, 1979. The spacecraft was about 50 million kilometers from Jupiter at that time.

This time-lapse movie was produced at JPL by the Image Processing Laboratory in 1979.

Deep intrusions, lateral magma transport and related uplift at ocean island volcanoes

NASA Astrophysics Data System (ADS)

Klügel, Andreas; Longpré, Marc-Antoine; García-Cañada, Laura; Stix, John

2015-12-01

Oceanic intraplate volcanoes grow by accumulation of erupted material as well as by coeval or discrete magmatic intrusions. Dykes and other intrusive bodies within volcanic edifices are comparatively well studied, but intrusive processes deep beneath the volcanoes remain elusive. Although there is geological evidence for deep magmatic intrusions contributing to volcano growth through uplift, this has rarely been demonstrated by real-time monitoring. Here we use geophysical and petrological data from El Hierro, Canary Islands, to show that intrusions from the mantle and subhorizontal transport of magma within the oceanic crust result in rapid endogenous island growth. Seismicity and ground deformation associated with a submarine eruption in 2011-2012 reveal deep subhorizontal intrusive sheets (sills), which have caused island-scale uplift of tens of centimetres. The pre-eruptive intrusions migrated 15-20 km laterally within the lower oceanic crust, opening pathways that were subsequently used by the erupted magmas to ascend from the mantle to the surface. During six post-eruptive episodes between 2012 and 2014, further sill intrusions into the lower crust and upper mantle have caused magma to migrate up to 20 km laterally, resulting in magma accumulation exceeding that of the pre-eruptive phase. A comparison of geobarometric data for the 2011-2012 El Hierro eruption with data for other Atlantic intraplate volcanoes shows similar bimodal pressure distributions, suggesting that eruptive phases are commonly accompanied by deep intrusions of sills and lateral magma transport. These processes add significant material to the oceanic crust, cause uplift, and are thus fundamentally important for the growth and evolution of volcanic islands. We suggest that the development of such a magma accumulation zone in the lower oceanic crust begins early during volcano evolution, and is a consequence of increasing size and complexity of the mantle reservoir system, and potentially the lithospheric stresses imposed by increasing edifice load.

Eruptive and environmental processes recorded by diatoms in volcanically-dispersed lake sediments from the Taupo Volcanic Zone, New Zealand

USGS Publications Warehouse

Harper, Margaret A.; Pledger, Shirley A.; Smith, Euan G. C.; Van Eaton, Alexa; Wilson, Colin J. N.

2015-01-01

Late Pleistocene diatomaceous sediment was widely dispersed along with volcanic ash (tephra) across and beyond New Zealand by the 25.4 ka Oruanui supereruption from Taupo volcano. We present a detailed analysis of the diatom populations in the Oruanui tephra and the newly discovered floras in two other eruptions from the same volcano: the 28.6 ka Okaia and 1.8 ka Taupo eruptions. For comparison, the diatoms were also examined in Late Pleistocene and Holocene lake sediments from the Taupo Volcanic Zone (TVZ). Our study demonstrates how these microfossils provide insights into the lake history of the TVZ since the Last Glacial Maximum. Morphometric analysis of Aulacoseira valve dimensions provides a useful quantitative tool to distinguish environmental and eruptive processes within and between individual tephras. The Oruanui and Okaia diatom species and valve dimensions are highly consistent with a shared volcanic source, paleolake and eruption style (involving large-scale magma-water interaction). They are distinct from lacustrine sediments sourced elsewhere in the TVZ. Correspondence analysis shows that small, intact samples of erupted lake sediment (i.e., lithic clasts in ignimbrite) contain heterogeneous diatom populations, reflecting local variability in species composition of the paleolake and its shallowly-buried sediments. Our analysis also shows a dramatic post-Oruanui supereruption decline in Cyclostephanos novaezelandiae, which likely reflects a combination of (1) reorganisation of the watershed in the aftermath of the eruption, and (2) overall climate warming following the Last Glacial Maximum. This decline is reflected in substantially lower proportions of C. novaezelandiae in the 1.8 ka Taupo eruption deposits, and even fewer in post-1.8 ka sediments from modern (Holocene) Lake Taupo. Our analysis highlights how the excellent preservation of siliceous microfossils in volcanic tephra may fingerprint the volcanic source region and retain a valuable record of volcanically-influenced environmental change.

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.

Understanding the eruption mechanisms of the explosive Bellecombe Eruptions on Piton de la Fournaise, La Réunion

NASA Astrophysics Data System (ADS)

Morgan, K.; Ort, M. H.; Di Muro, A.; Parnell, R. A.; Huff, W. D.

2017-12-01

Piton de la Fournaise (PdF) is an active basaltic volcano on La Réunion island. The Bellecombe Tephra was deposited from at least three unusually explosive eruptions between 3000-5000 ka. The Bellecombe eruptions were interpreted recently to have been due to rapid depressurization of the hydrothermal system when a deep fracture opened after lateral, seaward-directed sliding of the eastern flank, late in a large effusive eruption. This project tests this hypothesis by physically, mineralogically, and chemically characterizing the Bellecombe Tephra to look for evidence of the involvement of the PdF hydrothermal system in the eruptions and understand where the eruptions initiated. The Bellecombe tephra consists of three units separated by incipient soils. Both the Upper and Lower Bellecombe deposits are mostly medium to very fine ash. Lower Bellecombe deposits, from the first two eruptions, are mostly beds of glassy ash containing minor lithic grains and olivine crystals. Hydrothermal minerals, mostly smectite, are present in a few Lower Bellecombe beds. Since these minerals are only present in some beds, the smectite formed before deposition rather than as a product of surficial alteration. The Upper Bellecombe deposits record a third eruption and vary between clast-supported crystal- and lithic-rich lapilli beds and ash beds with abundant ash pellets. The crystals are mostly olivine, with lesser pyroxene and plagioclase and sparse hydrothermal quartz. Gabbro and oceanite clasts are abundant and trachytic pumice rare in these deposits. Hydrothermal minerals are common in most Upper Bellecombe beds. The presence of smectite in some of the Lower Bellecombe beds suggests these deposits came from a system below 200 ºC. Clays in the Upper Bellecombe beds - smectite and mixed layer R0 illite/smectite - imply a system at 40-140 ºC. The hydrothermal system was involved, but might not have been the primary impetus for these eruptions, since hydrothermal minerals are not present in all of the beds, but we find no evidence of high temperatures. The lower Bellecombe vent was near the active summit whereas the Upper Bellecombe vent was from a previously more active area, and this may be reflected in the temperatures of the hydrothermal system. The abundant olivine crystals confirm a relation to a large effusive oceanite eruption.

The exceptional activity and growth of the Southeast Crater, Mount Etna (Italy), between 1996 and 2001

NASA Astrophysics Data System (ADS)

Behncke, Boris; Neri, Marco; Pecora, Emilio; Zanon, Vittorio

2006-09-01

Between 1971 and 2001, the Southeast Crater was the most productive of the four summit craters of Mount Etna, with activity that can be compared, on a global scale, to the opening phases of the Pu‘u ‘Ō‘ō-Kūpaianaha eruption of Kīlauea volcano, Hawai‘i. The period of highest eruptive rate was between 1996 and 2001, when near-continuous activity occurred in five phases. These were characterized by a wide range of eruptive styles and intensities from quiet, non-explosive lava emission to brief, violent lava-fountaining episodes. Much of the cone growth occurred during these fountaining episodes, totaling 105 events. Many showed complex dynamics such as different eruptive styles at multiple vents, and resulted in the growth of minor edifices on the flanks of the Southeast Crater cone. Small pyroclastic flows were produced during some of the eruptive episodes, when oblique tephra jets showered the steep flanks of the cone with hot bombs and scoriae. Fluctuations in the eruptive style and eruption rates were controlled by a complex interplay between changes in the conduit geometry (including the growth of a shallow magma reservoir under the Southeast Crater), magma supply rates, and flank instability. During this period, volume calculations were made with the aid of GIS and image analysis of video footage obtained by a monitoring telecamera. Between 1996 and 2001, the bulk volume of the cone increased by ~36×106 m3, giving a total (1971 2001) volume of ~72×106 m3. At the same time, the cone gained ~105 m in height, reaching an elevation of about 3,300 m. The total DRE volume of the 1996 2001 products was ~90×106m3. This mostly comprised lava flows (72×106 m3) erupted at the summit and onto the flanks of the cone. These values indicate that the productivity of the Southeast Crater increased fourfold during 1996 2001 with respect to the previous 25 years, coinciding with a general increase in the eruptive output rates and eruption intensity at Etna. This phase of intense summit activity has been followed, since the summer of 2001, by a period of increased structural instability of the volcano, marked by a series of important flank eruptions.

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

Volcano-earthquake interaction at Mauna Loa volcano, Hawaii

NASA Astrophysics Data System (ADS)

Walter, Thomas R.; Amelung, Falk

2006-05-01

The activity at Mauna Loa volcano, Hawaii, is characterized by eruptive fissures that propagate into the Southwest Rift Zone (SWRZ) or into the Northeast Rift Zone (NERZ) and by large earthquakes at the basal decollement fault. In this paper we examine the historic eruption and earthquake catalogues, and we test the hypothesis that the events are interconnected in time and space. Earthquakes in the Kaoiki area occur in sequence with eruptions from the NERZ, and earthquakes in the Kona and Hilea areas occur in sequence with eruptions from the SWRZ. Using three-dimensional numerical models, we demonstrate that elastic stress transfer can explain the observed volcano-earthquake interaction. We examine stress changes due to typical intrusions and earthquakes. We find that intrusions change the Coulomb failure stress along the decollement fault so that NERZ intrusions encourage Kaoiki earthquakes and SWRZ intrusions encourage Kona and Hilea earthquakes. On the other hand, earthquakes decompress the magma chamber and unclamp part of the Mauna Loa rift zone, i.e., Kaoiki earthquakes encourage NERZ intrusions, whereas Kona and Hilea earthquakes encourage SWRZ intrusions. We discuss how changes of the static stress field affect the occurrence of earthquakes as well as the occurrence, location, and volume of dikes and of associated eruptions and also the lava composition and fumarolic activity.

Hinode Observations of the Onset Stage of a Solar Filament Eruption

NASA Technical Reports Server (NTRS)

Sterling, Alphonse C.; Moore, Ronald L.; Berger, Thomas E.; Bobra, Monica; Davis, John M.; Jibben, Patricia; Kano, R.; Lundquist, Loraine; Myers, D.; Narukage, N.;

Diatreme evolution during the phreatomagmatic eruption of the Songaksan tuff ring, Jeju Island, Korea

NASA Astrophysics Data System (ADS)

Go, S. Y.; Kim, G. B.; Jeong, J. O.; Sohn, Y. K.

2017-03-01

The Songaksan tuff ring, Jeju Island, Korea, which erupted ca. 3.7 ka BP in a coastal setting, provides an unusual opportunity to study the processes of phreatomagmatic eruption and the formation of a diatreme because of the exceptionally well-preserved ejecta beds and well-known subsurface geology. The tuff sequence can be divided into four units (A to D), which have distinctly different accidental componentry (quartz-rich vs. quartz-poor), grain surface features (abraded and ash-coated vs. unabraded and uncoated), and chemical compositions of juvenile particles. The basal tephra bed of unit A, which probably erupted after the removal of the relatively hard shallow-level (<120 m deep) substrate by initial cratering, comprises only unabraded and uncoated grains and contains abundant relatively deep-derived (>120 m deep) accidental grains, suggesting that the early erupted tephra had not yet experienced recycling and pre-eruption mixing in the diatreme. On the other hand, the overlying tephra beds of units A, B, and D contain an abundance of abraded and ash-coated juvenile/accidental grains, suggesting that the tephra comprised significant proportions of "recycled" or "premixed" materials from previous eruptions or subsurface explosions, which participated in the explosion-driven mixing in the diatreme before eventual ejection from the diatreme. Unit C is unusual in that it comprises extremely rare accidental grains and ash-coated juvenile/accidental grains. We interpret that the supply of solid materials, either accidental or juvenile, to the diatreme was greatly reduced because of temporary stabilization of the diatreme and the reduction in magma flux to the diatreme. The diatreme is therefore envisaged to have been filled with a water-saturated slurry, in which particle abrasion and adhesion were inhibited. We also infer that the diatreme fill was temporarily removed by a powerful explosion before eruption of unit C on the basis of the near absence of the tephra grains from earlier eruptions throughout the tephra beds of unit C. The ratio of tachylite to sideromelane grains generally increases up-section of the tuff sequence with two abrupt drops across the tuff unit boundaries. These variations are coincident with the changes in the chemical composition of juvenile particles, suggesting an overall decrease in magma flux punctuated by brief increases in magma flux associated with the arrival of new magma batches. The textural and compositional variations of the Songaksan tuff ring suggest that there can be significant variability in diatreme processes even during a purely phreatomagmatic eruption of a tuff ring, including removal and renewal of the diatreme fill, and that there is still much room for further investigation of the diatreme processes from the ejecta beds in order to make the current diatreme model more robust.

Identification of Volcanic Landforms and Processes on Earth and Mars using Geospatial Analysis (Invited)

NASA Astrophysics Data System (ADS)

Fagents, S. A.; Hamilton, C. W.

2009-12-01

Nearest neighbor (NN) analysis enables the identification of landforms using non-morphological parameters and can be useful for constraining the geological processes contributing to observed patterns of spatial distribution. Explosive interactions between lava and water can generate volcanic rootless cone (VRC) groups that are well suited to geospatial analyses because they consist of a large number of landforms that share a common formation mechanism. We have applied NN analysis tools to quantitatively compare the spatial distribution of VRCs in the Laki lava flow in Iceland to analogous landforms in the Tartarus Colles Region of eastern Elysium Planitia, Mars. Our results show that rootless eruption sites on both Earth and Mars exhibit systematic variations in spatial organization that are related to variations in the distribution of resources (lava and water) at different scales. Field observations in Iceland reveal that VRC groups are composite structures formed by the emplacement of chronologically and spatially distinct domains. Regionally, rootless cones cluster into groups and domains, but within domains NN distances exhibit random to repelled distributions. This suggests that on regional scales VRCs cluster in locations that contain sufficient resources, whereas on local scales rootless eruption sites tend to self-organize into distributions that maximize the utilization of limited resources (typically groundwater). Within the Laki lava flow, near-surface water is abundant and pre-eruption topography appears to exert the greatest control on both lava inundation regions and clustering of rootless eruption sites. In contrast, lava thickness appears to be the controlling factor in the formation of rootless eruption sites in the Tartarus Colles Region. A critical lava thickness may be required to initiate rootless eruptions on Mars because the lava flows must contain sufficient heat for transferred thermal energy to reach the underlying cryosphere and volatilize buried ground ice. In both environments, the spatial distribution of rootless eruption sites on local scales may either be random, which indicates that rootless eruption sites form independently of one another, or repelled, which implies resource limitation. Where competition for limited groundwater causes rootless eruption sites to develop greater than random NN separation, rootless eruption sites can be modeled as a system of pumping wells that extract water from a shared aquifer, thereby generating repelled distributions due to non-initiation or early cessation of rootless explosive activity at sites with insufficient access to groundwater. Thus statistical NN analyses can be combined with field observations and remote sensing to obtain information about self-organization processes within geological systems and the effects of environmental resource limitation on the spatial distribution of volcanic landforms. NN analyses may also be used to quantitatively compare the spatial distribution of landforms in different planetary environments and for supplying non-morphological evidence to discriminate between feature identities and geological formation mechanisms.

Monitoring and Characterizing the Geysering and Seismic Activity at the Lusi Mud Eruption Site, East Java, Indonesia

NASA Astrophysics Data System (ADS)

Karyono, Karyono; Obermann, Anne; Mazzini, Adriano; Lupi, Matteo; Syafri, Ildrem; Abdurrokhim, Abdurrokhim; Masturyono, Masturyono; Hadi, Soffian

2016-04-01

The Lusi eruption began on May 29, 2006 in the northeast of Java Island, Indonesia, and to date is still active. Lusi is a newborn sedimentary-hosted hydrothermal system characterized by continuous expulsion of liquefied mud and breccias and geysering activity. Lusi is located upon the Watukosek fault system, a left lateral wrench system connecting the volcanic arc and the bakarc basin. This fault system is still periodically reactivated as shown by field data. In the framework of the Lusi Lab project (ERC grant n° 308126) we conducted several types of monitoring. Based on camera observations, we characterized the Lusi erupting activity by four main behaviors occurring cyclically: (1) Regular activity, which consists in the constant emission of water and mud breccias (i.e. viscous mud containing clay, silt, sand and clasts) associated with the constant expulsion of gas (mainly aqueous vapor with minor amounts of CO2 and CH4) (2) Geysering phase with intense bubbling, consisting in reduced vapor emission and more powerful bursting events that do not seem to have a regular pattern. (3) Geysering phase with intense vapor and degassing discharge and a typically dense plume that propagates up to 100 m height. (4) Quiescent phase marking the end of the geysering activity (and the observed cycle) with no gas emissions or bursts observed. To investigate the possible seismic activity beneath Lusi and the mechanisms controlling the Lusi pulsating behaviour, we deployed a network of 5 seismic stations and a HD camera around the Lusi crater. We characterize the observed types of seismic activity as tremor and volcano-tectonic events. Lusi tremor events occur in 5-10 Hz frequency band, while volcano tectonic events are abundant in the high frequencies range from 5 Hz until 25 Hz. We coupled the seismic monitoring with the images collected with the HD camera to study the correlation between the seismic tremor and the different phases of the geysering activity. Key words: Lusi mud eruption, geysering activity, seismic activity

Volcanic Hazard Education through Virtual Field studies of Vesuvius and Laki Volcanoes

NASA Astrophysics Data System (ADS)

Carey, S.; Sigurdsson, H.

2011-12-01

Volcanic eruptions pose significant hazards to human populations and have the potential to cause significant economic impacts as shown by the recent ash-producing eruptions in Iceland. Demonstrating both the local and global impact of eruptions is important for developing an appreciation of the scale of hazards associated with volcanic activity. In order to address this need, Web-based virtual field exercises at Vesuvius volcano in Italy and Laki volcano in Iceland have been developed as curriculum enhancements for undergraduate geology classes. The exercises are built upon previous research by the authors dealing with the 79 AD explosive eruption of Vesuvius and the 1783 lava flow eruption of Laki. Quicktime virtual reality images (QTVR), video clips, user-controlled Flash animations and interactive measurement tools are used to allow students to explore archeological and geological sites, collect field data in an electronic field notebook, and construct hypotheses about the impacts of the eruptions on the local and global environment. The QTVR images provide 360o views of key sites where students can observe volcanic deposits and formations in the context of a defined field area. Video sequences from recent explosive and effusive eruptions of Carribean and Hawaiian volcanoes are used to illustrate specific styles of eruptive activity, such as ash fallout, pyroclastic flows and surges, lava flows and their effects on the surrounding environment. The exercises use an inquiry-based approach to build critical relationships between volcanic processes and the deposits that they produce in the geologic record. A primary objective of the exercises is to simulate the role of a field volcanologist who collects information from the field and reconstructs the sequence of eruptive processes based on specific features of the deposits. Testing of the Vesuvius and Laki exercises in undergraduate classes from a broad spectrum of educational institutions shows a preference for the web-based interactive tools compared with traditional paper-based laboratory exercises. The exercises are freely accessible for undergraduate classes such as introductory geology, geologic hazards, or volcanology. Accompany materials, such as lecture-based Powerpoint presentations about Vesuvius and Laki, are also being developed for instructors to better integrate the web-based exercises into their existing curriculum.

Source models for the March 5-9, 2011 Kamoamoa fissure eruption, Kilauea Volcano, Hawai`i, constrained by InSAR and in-situ observations

NASA Astrophysics Data System (ADS)

Lundgren, P.; Poland, M. P.; Miklius, A.; Yun, S.; Fielding, E. J.; Liu, Z.; Tanaka, A.; Szeliga, W. M.; Hensley, S.

2011-12-01

On March 5, 2011, the Kamoamoa fissure eruption began along the east rift zone (ERZ) of Kilauea Volcano. It followed several months of pronounced inflation at Kilauea's summit and was the first dike intrusion into the ERZ since June 2007. The eruption began in the late afternoon of March 5, 2011 (Hawaii Standard Time; UTC-10:00 hrs) with rapid deflation beginning at Pu'u 'O'o crater along the ERZ and followed about 30 minutes later at the summit. Magma from both locations fed the intrusion and an eruption that included lava fountaining along a set of discontinuous eruptive fissures ~2 km in length located between Napau and Pu'u 'O'o craters. Eruptive activity jumped between fissure segments until it ended on the night of March 9. A rich InSAR data set exists for this eruption from the COSMO-SkyMed (CSK), TerraSAR-X (TSX), ALOS PALSAR, and UAVSAR sensors. CSK data acquired on March 7 and processed that same day provided the earliest, quasi-real-time SAR data for this event. By March 10, after the eruption had ended, we had three CSK acquisitions and one ALOS scene acquired and processed. At present we have the following satellite data (UTC dates): ALOS March 6, 9, 11; CSK March 7, 10, 11; TSX March 11; from a mixture of ascending and descending tracks. UAVSAR airborne SAR data were acquired in early May 2011. Preliminary UAVSAR results are encouraging and complete processing should provide high-resolution data from four viewing directions. SAR data were acquired on all days of the eruption but March 8, allowing us to examine the progression of the dike opening beneath the surface with excellent spatial and temporal resolution. We use a combination of unwrapped interferograms, azimuthal pixel offsets, and in-situ data from GPS and electronic tiltmeters to model dike opening and summit deflation. GPS data are from the Hawaiian Volcano Observatory (HVO) continuous GPS network augmented by campaign occupations closer to the eruption area. Continuous tilt measurements are concentrated near Kilauea's summit and Pu'u 'O'o crater, with one site in between to help constrain dike propagation. To model the sources we use a Markov Chain Monte Carlo (MCMC) optimization to solve for Kilauea caldera source(s) and for the Kamoamoa dike dip, where we fixed the surface location of the dike based on field observations and solved for the opening distribution using Laplacian smoothing for a multi-patch dike. Preliminary models of the dike show 1-2 meters of dike opening at the beginning of the eruption, reaching 2-3 meters of opening by the end of the eruption. Preliminary results for the caldera favor a shallow source centered at roughly 1.5 km depth and extending in a SW-NE direction. Initial estimates of the volume changes show less than a 2 MCM (million cubic meters) decrease at the summit compared to a roughly 10 MCM increase for the dike. This difference suggests that much of the magma came from sources other than the shallow Kilauea summit source.

What factors control the superficial lava dome explosivity?

NASA Astrophysics Data System (ADS)

Boudon, Georges; Balcone-Boissard, Hélène; Villemant, Benoit; Morgan, Daniel J.

2015-04-01

Dome-forming eruption is a frequent eruptive style; lava domes result from intermittent, slow extrusion of viscous lava. Most dome-forming eruptions produce highly microcrystallized and highly- to almost totally-degassed magmas which have a low explosive potential. During lava dome growth, recurrent collapses of unstable parts are the main destructive process of the lava dome, generating concentrated pyroclastic density currents (C-PDC) channelized in valleys. These C-PDC have a high, but localized, damage potential that largely depends on the collapsed volume. Sometimes, a dilute ash cloud surge develops at the top of the concentrated flow with an increased destructive effect because it may overflow ridges and affect larger areas. In some cases, large lava dome collapses can induce a depressurization of the magma within the conduit, leading to vulcanian explosions. By contrast, violent, laterally directed, explosions may occur at the base of a growing lava dome: this activity generates dilute and turbulent, highly-destructive, pyroclastic density currents (D-PDC), with a high velocity and propagation poorly dependent on the topography. Numerous studies on lava dome behaviors exist, but the triggering of lava dome explosions is poorly understood. Here, seven dome-forming eruptions are investigated: in the Lesser Antilles arc: Montagne Pelée, Martinique (1902-1905, 1929-1932 and 650 y. BP eruptions), Soufrière Hills, Montserrat; in Guatemala, Santiaguito (1929 eruption); in La Chaîne des Puys, France (Puy de Dome and Puy Chopine eruptions). We propose a new model of superficial lava-dome explosivity based upon a textural and geochemical study (vesicularity, microcrystallinity, cristobalite distribution, residual water contents, crystal transit times) of clasts produced by these key eruptions. Superficial explosion of a growing lava dome may be promoted through porosity reduction caused by both vesicle flattening due to gas escape and syn-eruptive cristobalite precipitation. Both processes generate an impermeable and rigid carapace allowing overpressurisation of the inner parts of the lava dome by the rapid input of vesiculated magma batches. The thickness of the cristobalite-rich carapace is an inverse function of the external lava dome surface area. Thus the probability of a superficial lava dome explosion inversely depends on its size; explosive activity more likely occurs at the onset of the lava dome extrusion in agreement with observations. We evidence a two-step process in magma ascent with edification of the lava dome that may be accompanied by a rapid ascent of an undegassed batch of magma some days prior the explosive activity. This new result is of interest for the whole volcanological community and for risk management.

Chemical Evidence for Vertical Transport from Magma Chambers to the Surface During Mid-Ocean Ridge Volcanic Eruptions

NASA Astrophysics Data System (ADS)

Sinton, J. M.; Rubin, K. H.

2009-12-01

Many mid-ocean ridge eruptions show significant internal chemical heterogeneity; in general, the amount of chemical heterogeneity within eruptions scales with erupted volume. These variations reflect magmatic processes occurring in magma reservoirs prior to or possibly during eruption. For example, systematic variations in Mg# with along-axis distance in the early 90’s Aldo-Kihi (S. EPR near 17.5°S), 1996 N. Gorda, 1993 Co-Axial (Juan de Fuca Ridge), and 1991-2 and 2005-6 9°50’N EPR eruptions is unlikely to be related to fractionation during emplacement, and rather reflects variations in sub-axial magma reservoirs prior to eruption. Such variations are inconsistent with well-mixed sub-axial reservoirs and, in some cases, require relatively long-lived, systematic variations in reservoir temperatures along axis. Chemical heterogeneity within the Aldo-Kihi eruption preserves spatial variations in mantle-derived isotopic and trace element ratios with implications for the temporal and spatial scales of magma injections to the crust and along-axis mixing within shallow reservoirs. These spatial variations are difficult to reconcile with significant (> ~1 km) along-axis magma transport, as are striking correlations of chemical compositions with surface geological discontinuities or seismically imaged sub-axial magma chamber reflectors in the S. Hump (S. EPR), 9°50’N EPR, N. Gorda and 1975-1984 Krafla (N. Iceland) eruptive units. Rather, spatial correlations between surface lava compositions and sub-axial magma chamber properties or long-lived axial morphology suggest that most of the erupted magma was transported nearly vertically from the underlying reservoirs to the surface during these eruptions. In the case of the Krafla eruption, coincident deformation suggests a component of lateral melt migration at depth, despite chemical evidence for vertical transport of erupted lava from more than one chemical reservoir. In addition, along-ridge movement of earthquake epicenters during the 1992 Co-Axial and 1996 Gorda eruptions implies migration of stress release during these eruptions, even though vertical transport better explains chemical patterns. The nature of transport for most eruptions is unclear because of lack of systematic chemical patterns; this presentation emphasizes those cases where vertical transport appears to be required.

Estimating the magma supply rate at Kilauea volcano, Hawaii

NASA Astrophysics Data System (ADS)

Wright, T. L.; Klein, F. W.

2006-12-01

A frequent question is whether the magma supply rate to Kilauea is constant. Before seaward spreading of the south flank of Kilauea was demonstrated by the slip on a basal decollement that accompanied the M7.2 1975 south flank earthquake, the magma supply rate was equated to the identical eruption rates for three long-lived eruptions (3). Later, a continuous tilt record at Kilauea's summit was used to derive the volume of magma transported during deflations associated with rift eruptions (2), concluding that over a 30-year period about 38% of Kilauea's magma supply was left underground, but agreeing with the equivalency of overall magma supply and sustained eruption rates. Recent modeling of geodetic data gathered during Kilauea's current eruption (1) estimated a supply rate to accommodate spreading at 1.5 times the eruption rate. We approach the problem of magma supply, making two assumptions: 1. Eruption rates are controlled by the capacity of the underground transport paths to deliver magma to the surface. 2. Spreading of Kilauea's south flank is magma-driven and all space created during spreading is filled with new magma. On these premises, and in consideration of the physical properties of magma, eruption rates would have to be less than the supply rate; equivalence would imply a rigid edifice in which an open channel could deliver magma as if it were water. We are working to establish a third indicator of magma supply, the occurrence of seismic swarms in the stressed south flank. Many such swarms have been previously identified in association with documented eruptions and intrusions, but other swarms occur independently and may be associated with passive intrusion filling the room created during spreading. We contrast the seismic and geodetic data gathered during Kilauea's two longest monitored eruptions, Mauna Ulu (1969-1974) and Pu'u `O'o-Kupaianaha (1983-ongoing). For episodic high-fountaining episodes we calculate eruption efficiency as the ratio of erupted lava corrected for 20% vesicularity to the volume of magma calculated from summit deflation (2). Eruption rates (km3/yr) during these periods are .1068 and .1267, respectively, with eruption efficiencies of .7 and >1. Individual episodes vary in south flank seismic activity, suggesting short-term variability of the magma supply. Mauna Ulu was characterized by overall inflation of Kilauea's summit, including during continuous eruption, and by the occurrence of intrusions and eruptions elsewhere on the volcano. We interpret this as indicating a supply rate that exceeded the capacity of the plumbing to deliver magma to the surface. In contrast, the current eruption had nearly twenty years of summit deflation and almost no intrusions or eruptions elsewhere, indicating that magma was being mined from overall storage. With continuously recording GPS, a major component of magma supply can be equated to a modeled dilation associated with spreading, augmented by erupted volumes and summit inflation to ascertain the variability of supply rate. Correlation with south flank seismicity may allow even better discrimination of rates. 1. Cayol, V., et al., 2000, Science, v. 288, p. 2343-2346. 3. Dvorak, J.J., and Dzurisin, D., 1993, Jour. Geophys. Res., v. 98, no. B12, p. 22,255-22,268. 3. Swanson, D.A., 1972, Science, v. 175, no. 4018, p. 169-170.

Inferring the effects of compositional boundary layers on crystal nucleation, growth textures, and mineral chemistry in natural volcanic tephras through submicron-resolution imaging

NASA Astrophysics Data System (ADS)

Zellmer, Georg; Sakamoto, Naoya; Hwang, Shyh-Lung; Matsuda, Nozomi; Iizuka, Yoshiyuki; Moebis, Anja; Yurimoto, Hisayoshi

2016-09-01

Crystal nucleation and growth are first order processes captured in volcanic rocks and record important information about the rates of magmatic processes and chemical evolution of magmas during their ascent and eruption. We have studied glass-rich andesitic tephras from the Central Plateau of the Southern Taupo Volcanic Zone by electron- and ion-microbeam imaging techniques to investigate down to sub-micrometre scale the potential effects of compositional boundary layers (CBLs) of melt around crystals on the nucleation and growth of mineral phases and the chemistry of crystal growth zones. We find that CBLs may influence the types of mineral phases nucleating and growing, and growth textures such as the development of swallowtails. The chemistry of the CBLs also has the capacity to trigger intermittent overgrowths of nanometre-scale bands of different phases in rapidly growing crystals, resulting in what we refer to as cryptic phase zoning. The existence of cryptic phase zoning has implications for the interpretation of microprobe compositional data, and the resulting inferences made on the conditions of magmatic evolution. Identification of cryptic phase zoning may in future lead to more accurate thermobarometric estimates and thus geospeedometric constraints. In future, a more quantitative characterization of CBL formation and its effects on crystal nucleation and growth may contribute to a better understanding of melt rheology and magma ascent processes at the onset of explosive volcanic eruptions, and will likely be of benefit to hazard mitigation efforts.

Expanding and Contracting Coronal Loops as Evidence of Vortex Flows Induced by Solar Eruptions

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

Dudík, J.; Zuccarello, F. P.; Aulanier, G.

Eruptive solar flares were predicted to generate large-scale vortex flows at both sides of the erupting magnetic flux rope. This process is analogous to a well-known hydrodynamic process creating vortex rings. The vortices lead to advection of closed coronal loops located at the peripheries of the flaring active region. Outward flows are expected in the upper part and returning flows in the lower part of the vortex. Here, we examine two eruptive solar flares, the X1.1-class flare SOL2012-03-05T03:20 and the C3.5-class SOL2013-06-19T07:29. In both flares, we find that the coronal loops observed by the Atmospheric Imaging Assembly in its 171more » Å, 193 Å, or 211 Å passbands show coexistence of expanding and contracting motions, in accordance with the model prediction. In the X-class flare, multiple expanding and contracting loops coexist for more than 35 minutes, while in the C-class flare, an expanding loop in 193 Å appears to be close by and cotemporal with an apparently imploding loop arcade seen in 171 Å. Later, the 193 Å loop also switches to contraction. These observations are naturally explained by vortex flows present in a model of eruptive solar flares.« less

One hundred volatile years of volcanic gas studies at the Hawaiian Volcano Observatory: Chapter 7 in Characteristics of Hawaiian volcanoes

USGS Publications Warehouse

Sutton, A.J.; Elias, Tamar; Poland, Michael P.; Takahashi, T. Jane; Landowski, Claire M.

2014-01-01

The first volcanic gas studies in Hawai‘i, beginning in 1912, established that volatile emissions from Kīlauea Volcano contained mostly water vapor, in addition to carbon dioxide and sulfur dioxide. This straightforward discovery overturned a popular volatile theory of the day and, in the same action, helped affirm Thomas A. Jaggar, Jr.’s, vision of the Hawaiian Volcano Observatory (HVO) as a preeminent place to study volcanic processes. Decades later, the environmental movement produced a watershed of quantitative analytical tools that, after being tested at Kīlauea, became part of the regular monitoring effort at HVO. The resulting volatile emission and fumarole chemistry datasets are some of the most extensive on the planet. These data indicate that magma from the mantle enters the shallow magmatic system of Kīlauea sufficiently oversaturated in CO2 to produce turbulent flow. Passive degassing at Kīlauea’s summit that occurred from 1983 through 2007 yielded CO2-depleted, but SO2- and H2O-rich, rift eruptive gases. Beginning with the 2008 summit eruption, magma reaching the East Rift Zone eruption site became depleted of much of its volatile content at the summit eruptive vent before transport to Pu‘u ‘Ō‘ō. The volatile emissions of Hawaiian volcanoes are halogen-poor, relative to those of other basaltic systems. Information gained regarding intrinsic gas solubilities at Kīlauea and Mauna Loa, as well as the pressure-controlled nature of gas release, have provided useful tools for tracking eruptive activity. Regular CO2-emission-rate measurements at Kīlauea’s summit, together with surface-deformation and other data, detected an increase in deep magma supply more than a year before a corresponding surge in effusive activity. Correspondingly, HVO routinely uses SO2 emissions to study shallow eruptive processes and effusion rates. HVO gas studies and Kīlauea’s long-running East Rift Zone eruption also demonstrate that volatile emissions can be a substantial volcanic hazard in Hawai‘i. From its humble beginning, trying to determine the chemical composition of volcanic gases over a century ago, HVO has evolved to routinely use real-time gas chemistry to track eruptive processes, as well as hazards.

Volcanism on Mars

NASA Astrophysics Data System (ADS)

Head, J. W.

1981-11-01

Characterization of volcanic activity on Mars is reviewed and comparisons are made with knowledge of terrestrial volcanic history. The high frequency of calderas on earth and low abundance on Mars is taken to indicate a lack of plate tectonic subduction zones and silicic volcanism on Mars. Further characterization is noted to depend on remote sensing from Viking orbital and earth-based spectral and albedo data. Theoretical models of causative mechanisms of terrestrial morphology will be used to establish models of similar processes on Mars, including deposits identification, eruptive conditions, and theories of magma ascent, as well as the role of volatiles from both deep and shallow sources. The importance of returning to Mars with appropriately instrumented spacecraft to test the new theories is stressed. The topics were discussed in papers presented at the Mars colloquium at the California Institute of Technology in August, 1981.

Petrological evidence for non-linear increase of magmatic intrusion rates before eruption at open vent mafic volcanoe

NASA Astrophysics Data System (ADS)

Ruth, D. C. S.; Costa Rodriguez, F.

2015-12-01

The most active volcanoes on earth erupt in a yearly to decadal time scales, typically erupt mafic magmas and are open-vent systems with prominent degassing plumes (e.g. Mayon, Arenal, Llaima, Etna). Here we investigate the plumbing systems, dynamics, and processes that drive eruptions at these systems. These are key questions for improving hazard evaluation, and better understanding the unrest associated with these types of volcanoes. The petrology and geochemistry from six historical eruptions (1947-2006) of Mayon volcano (Philippines) shows that all lavas are basaltic andesite with phenocrysts of plagioclase + orthopyroxene (Opx) + clinopyroxene. Opx crystals show a variety of compositions and zoning patterns (reverse, normal or complex) with Mg# (= 100 *Mg/[Mg+Fe]) varying from 67 to 81. The simplest interpretation is that the low Mg# parts of the crystals resided on an upper crustal and crystal rich reservoir that was intruded by more primitive magmas from which the high Mg# parts of the crystals grew. Modelling Mg-Fe diffusion in Opx shows that times since magma injection and eruption range from a few days up to 3.5 years in all of the investigated eruptions. The longest diffusion times are shorter than the repose times between the eruptions, which implies that crystal recycling between eruptive events is negligible. This is a surprising result that shows that for each eruption a different part of the evolved crystal-rich plumbing system is activated. This can be due to random intrusion location or an irreversibility of the plumbing system that prevents multiple eruptions from the same crystal-rich part. Moreover, we find that the number of intrusions markedly increases before each eruption in a non-linear manner. Such an increased rate of intrusions with time might reflect non-linear rheological properties of the crystal-rich system, of the enclosing rocks, or the non-linear evolution of crystal-melt reaction-dissolution fronts during magma intrusions.

The Run-up to Volcanic Eruption Unveiled by Forensic Petrology and Geophysical Observations

NASA Astrophysics Data System (ADS)

Rasmussen, D. J.; Plank, T. A.; Roman, D. C.

2017-12-01

Volcanoes often warn of impending eruptions. However, one of the greatest challenges in volcano research is translating precursory geophysical signals into physical magmatic processes. Petrology offers powerful tools to study eruption run-up that benefit from direct response to magmatic forcings. Developing these tools, and tying them to geophysical observations, will help us identify eruption triggers (e.g., magmatic recharge, gas build-up, tectonic events) and understand the significance of monitored signals of unrest. We present an overview of petrologic tools used for studying eruption run-up, highlighting results from our study of the 1999 eruption of Shishaldin volcano. Olivine crystals contain chemical gradients, the consequence of diffusion following magma mixing events, which is modeled to determine mixing timescales. Modeled timescales provide strong evidence for at least three mixing events, which were triggered by magmatic recharge. Petrologic barometers indicate these events occurred at very shallow depths (within the volcanic edifice). The first mixing event occurred nine months before eruption, which was signaled by a swarm of deep-long period earthquake. Minor recharge events followed over two months, which are indicated by a second deep-long period earthquake swarm and a change in the local stress orientation measured by shear-wave splitting. Following these events, the system was relatively quiet until a large mixing event occurred 45 days prior to eruption, which was heralded by a large earthquake (M5.2). Following this event, geophysical signals of unrest intensified and became continuous. The final mixing event, beginning roughly a week before eruption, represents the final perturbation to the system before eruption. Our findings point to a relatively long run-up, which was subtle at first and intensified several weeks before eruption. This study highlights the strong link between geophysical signals of volcanic unrest and magmatic events, and helps open the door for the application of forensic petrology to unmonitored eruptions.

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.

Volcanic rocks and subglacial volcanism beneath the West Antarctic Ice Sheet in the West Antarctic Rift System, (WAIS) from aeromagnetic and radar ice sounding - Thiel Subglacial Volcano as possible source of the ash layer in the WAISCORE

NASA Astrophysics Data System (ADS)

Behrendt, J. C.

2012-12-01

Radar ice sounding and aeromagnetic surveys reported over the West Antarctic Ice Sheet (WAIS) have been interpreted as evidence of subglacial volcanic eruptions over a very extensive area (>500,000 km2 ) of the volcanically active West Antarctic rift system interpreted as caused by subglacial volcanic rocks. Several active volcanoes have shown evidence of eruption through the WAIS and several other active volcanoes are present beneath the WAIS reported from radar and aeromagnetic data. Five-kilometer spaced coincident aeromagnetic and radar ice sounding surveys since 1990 provide three dimensional characterization of the magnetic field and bed topography beneath the ice sheet. These 5-50-km-width, semicircular magnetic anomalies range from 100->1000 nT as observed ~1 km over the 2-3 km thick ice have been interpreted as evidence of subglacial eruptions. Comparison of a carefully selected subset of ~400 of the >1000 high-amplitude anomalies in the CWA survey having topographic expression at the glacier bed, showed >80% had less than 200-m relief. About 18 high-amplitude subglacial magnetic sources also have high topography and bed relief (>600 m) interpreted as subaerially erupted volcanic peaks when the WAIS was absent, whose competent lava flows protected their edifices from erosion. All of these would have high elevation above sea-level, were the ice removed and glacial rebound to have occurred. Nine of these subaerially erupted volcanoes are concentrated in the WAIS divide area. Behrendt et al., 1998 interpreted a circular ring of positive magnetic anomalies overlying the WAIS divide as caused by a volcanic caldera. The area is characterized by high elevation bed topography. The negative regional magnetic anomaly surrounding the caldera anomalies was interpreted as the result of a shallow Curie isotherm. High heat flow inferred from temperature logging in the WAISCORE (G. Clow 2012, personal communication; Conway, 2011) and a prominent volcanic ash layer in the core (Dunbar, 2011) are consistent with the magnetic data. A prominent subaerially-erupted subglacial volcano, here named Mt Thiel, about 100 km distant to the NE, at approximately 78o 25' S, 111o 20' W, may be the source of the ash layer. This peak is characterized by a ~400-nT positive magnetic anomaly which Behrendt el, 2004, modeled as having apparent susceptibility contrasts of .034 and .15 SI. From its appearance (and the moat surrounding it), Mt. Thiel has subsided somewhat since initial eruption as is the case for Mt. Erebus and the Hawaiian Island chain. I suggest that Mt Thiel, about 100 km distance from the WAISCORE, may be the source of the ash layer. The present rapid changes in the WAIS resulting from global warming, could be accelerated by subglacial volcanism