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Sample records for active volcanic zone

  1. Active volcanism on Venus in the Ganiki Chasma rift zone

    NASA Astrophysics Data System (ADS)

    Shalygin, E. V.; Markiewicz, W. J.; Basilevsky, A. T.; Titov, D. V.; Ignatiev, N. I.; Head, J. W.

    2015-06-01

    Venus is known to have been volcanically resurfaced in the last third of solar system history and to have undergone a significant decrease in volcanic activity a few hundred million years ago. However, fundamental questions remain: Is Venus still volcanically active today, and if so, where and in what geological and geodynamic environment? Here we show evidence from the Venus Express Venus Monitoring Camera for transient bright spots that are consistent with the extrusion of lava flows that locally cause significantly elevated surface temperatures. The very strong spatial correlation of the transient bright spots with the extremely young Ganiki Chasma, their similarity to locations of rift-associated volcanism on Earth, provide strong evidence for their volcanic origin and suggests that Venus is currently geodynamically active.

  2. Analysis of radar images of the active volcanic zone at Krafla, Iceland: The effects of look azimuth biasing

    NASA Technical Reports Server (NTRS)

    Garvin, J. B.; Williams, R. S., Jr.

    1989-01-01

    The geomorphic expression of Mid-Ocean-Ridge (MOR) volcanism in a subaerial setting occurs uniquely on Earth in Iceland, and the most recent MOR eruptive activity has been concentrated in the Northeastern Volcanic Zone in an area known as Krafla. Within the Krafla region are many of the key morphologic elements of MOR-related basaltic volcanism, as well as volcanic explosion craters, subglacial lava shields, tectonic fissure swarms known as gjar, and basaltic-andesite flows with well developed ogives (pressure-ridges). The objective was to quantify the degree to which the basic volcanic and structural features can be mapped from directional SAR imagery as a function of the look azimuth. To accomplish this, the current expression of volcanic and tectonic constructs was independently mapped within the Krafla region on the E, W, and N-looking SAR images, as well as from SPOT Panchromatic imagery acquired in 1987. The initial observations of the E, W, and N images indicates that fresh a'a lava surfaces are extremely radar bright (rough at 3 cm to meter scales) independent of look direction; this suggests that these flows do not have strong flow direction related structures at meter and cm scales, which is consistent with typical Icelandic a'a lava surfaces in general. The basic impression from a preliminary analysis of the effects of look azimuth biasing on interpretation of the geology of an active MOR volcanic zone is that up to 30 percent of the diagnostic features can be missed at any given look direction, but that having two orthogonal look direction images is probably sufficient to prevent gross misinterpretation.

  3. Intraglacial volcanism in the Western Volcanic Zone, Iceland

    NASA Astrophysics Data System (ADS)

    Jakobsson, S. P.; Johnson, G. L.

    2012-07-01

    The Western Volcanic Zone in Iceland (64.19° to 65.22° N) has the morphological characteristics of a distinct Mid-Atlantic ridge segment. This volcanic zone was mapped at a scale of 1:36.000, and 258 intraglacial monogenetic volcanoes from the Late Pleistocene (0.01-0.78 Ma) were identified and investigated. The zone is characterized by infrequent comparatively large volcanic eruptions and the overall volcanic activity appears to have been low throughout the Late Pleistocene. Tholeiitic basaltic rocks dominate in the Western Volcanic Zone with about 0.5 vol. % of intermediate and silicic rocks. The basalts divide into picrites, olivine tholeiites, and tholeiites. Three main eruptive phases can be distinguished in the intraglacial volcanoes: an effusive deep-water lava phase producing basal pillow lavas, an explosive shallow-water phase producing hyaloclastites and an effusive subaerial capping lava phase. Three evolutionary stages therefore charcterize these volcanoes; late dykes and irregular minor intrusions could be added as the fourth main stage. These intrusions are potential heat sources for short-lived hydrothermal systems and may play an important role in the final shaping of the volcanoes. Substantial parts of the hyaloclastites of each unit are proximal sedimentary deposits. The intraglacial volcanoes divide into two main morphological groups, ridge-shaped volcanoes, i.e., tindars (including pillow lava ridges) and subrectangular volcanoes, i.e., tuyas and hyaloclastite or pillow lava mounds. The volume of the tuyas is generally much larger than that of the tindars. The largest tuya, Eiríksjökull, is about 48 km3 and therefore the largest known monogenetic volcano in Iceland. Many of the large volcanoes, both tuyas and tindars, show a similar, systematic range in geochemistry. The most primitive compositions were erupted first and the magmas then changed to more differentiated compositions. The ridge-shaped tindars clearly erupted from volcanic

  4. Fracturing and earthquake activity within the Prestahnúkur fissure swarm in the Western Volcanic Rift Zone of Iceland

    NASA Astrophysics Data System (ADS)

    Hjartardóttir, Ásta Rut; Hjaltadóttir, Sigurlaug; Einarsson, Páll; Vogfjörd, Kristín.; Muñoz-Cobo Belart, Joaquín.

    2015-12-01

    The Prestahnúkur fissure swarm is located within the ultraslowly spreading Western Volcanic Zone in Iceland. The fissure swarm is characterized by normal faults, open fractures, and evidence of subglacial fissure eruptions (tindars). In this study, fractures and faults within the Prestahnúkur fissure swarm were mapped in detail from aerial photographs to determine the extent and activity of the fissure swarm. Earthquakes during the last ~23 years were relocated to map the subsurface fault planes that they delineate. The Prestahnúkur fissure swarm is 40-80 km long and up to ~20 km wide. Most of the areas of the fissure swarm have been glacially eroded, although a part of it is covered by postglacial lava flows. The fissure swarm includes numerous faults with tens of meters vertical offset within the older glacially eroded part, whereas open fractures are found within postglacial lava flows. Comparison of relocated earthquakes and surface fractures indicates that some of the surface fractures have been activated at depth during the last ~23 years, although no dike intrusions have been ongoing. The existence of tindars nevertheless indicates that dike intrusions and rifting events do occur within the Prestahnúkur fissure swarm. The low-fracture density within postglacial lava flows and low density of postglacial eruptive fissures indicate that rifting episodes occur less often than in the faster spreading Northern Volcanic Zone.

  5. The geochemistry of lithium-bearing geothermal water, Taupo Volcanic Zone, and shallow fluid processes in a very active silicic volcanic arc

    NASA Astrophysics Data System (ADS)

    Dean, A. S.; Hoskin, P. W.; Rudnick, R. L.; Liu, X.; Boseley, C.

    2011-12-01

    The Li abundances and isotopic systematics of Taupo Volcanic Zone (TVZ) geothermal fluids preserves a record of processes occurring within shallow portions of geothermal reservoirs as well as deeper portions of the arc crust. Understanding Li cycling and isotopic fractionation in TVZ geothermal systems contributes to a more refined understanding of physicochemical processes affecting New Zealand's geothermal resources. A comprehensive dataset of 73 samples was compiled, with samples collected from geothermal surface features (springs, spouters, geysers, etc.) and electric-power industry production wells, collectively representing18 geothermal fields across the breadth and width the TVZ. No comparable dataset of fluid analyses exists. Ion chromatography, AAS, and quadrupole ICP-MS analyses were done for Li, Cl-, SiO2, SO42- K, Na, Ca, Mg, B, Sr and Pb concentrations. Lithium abundance in geothermal fluids from the TVZ have a dataset-wide average of 5.9 mg/L and range 4 μg/L to 29 mg/L. The Li abundance and Li/Cl ratios for geothermal water and steam condensates vary systematically as a result of boiling, mixing, and water/rock reaction. Lithium abundance and Li/Cl ratios are, therefore, indicators of shallow (above 2.5 km) and locally variable reservoir processes. δ7Li analysis of 63 samples was performed at the University of Maryland, College Park. Data quality was controlled by measurement of L-SVEC as a calibration standard and by multiple analysis of selected samples. The average δ7Li value for TVZ geothermal fluids is -0.8%. Most δ7Li values for geothermal water fall within a small range of about -3% to+2% indicating similar processes are causing similar isotopic fractionation throughout the region. Considered together, Li aundances and δ7Li values, in combination with numerical models, indicate possible evolution pathways and water/rock reactions in TVZ geothermal systems. Models based on rocks and surface water analysis indicate that Li cycles and

  6. 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

  7. Magma storage under Iceland's Eastern Volcanic Zone

    NASA Astrophysics Data System (ADS)

    Maclennan, J.; Neave, D.; Hartley, M. E.; Edmonds, M.; Thordarson, T.; Morgan, D. J.

    2014-12-01

    The Eastern Volcanic Zone (EVZ) of Iceland is defined by a number of volcanic systems and large basaltic eruptions occur both through central volcanoes (e.g. Grímsvötn) and on associated fissure rows (e.g. Laki, Eldgjá). We have collected a large quantity of micro-analytical data from a number of EVZ eruptions, with the aim of identifying common processes that occur in the premonitory stages of significant volcanic events. Here, we focus on the AD 1783 Laki event, the early postglacial Saksunarvatn tephra and the sub-glacially erupted Skuggafjöll tindar and for each of these eruptions we have >100 olivine-hosted or plagioclase-hosted melt inclusion analyses for major, trace and volatile elements. These large datasets are vital for understanding the history of melt evolution in the plumbing system of basaltic volcanoes. Diverse trace element compositions in melt inclusions hosted in primitive macrocrysts (i.e. Fo>84, An>84) indicate that the mantle melts supplied to the plumbing system of EVZ eruptions are highly variable in composition. Concurrent mixing and crystallisation of these melts occurs in crustal magma bodies. The levels of the deepest of these magma bodies are not well constrained by EVZ petrology, with only a handful of high-CO2 melt inclusions from Laki providing evidence for magma supply from >5 kbar. In contrast, the volatile contents of melt inclusions in evolved macrocrysts, which are close to equilibrium with the carrier liquids, indicate that final depths of inclusion entrapment are 0.5-2 kbar. The major element composition of the matrix glasses shows that the final pressure of equilibration between the melt and its macrocryst phases also occurred at 0.5-2 kbar. The relationship between these pressures and seismic/geodetic estimates of chamber depths needs to be carefully evaluated. The melt inclusion and macrocryst compositional record indicates that injection of porphyritic, gas-rich primitive melt into evolved/enriched and degassed shallow

  8. Io. [theories concerning volcanic activity

    NASA Technical Reports Server (NTRS)

    Johnson, T. V.; Soderblom, L. A.

    1983-01-01

    A report on the continuing investigation of Io is presented. Gravitational resonance is discussed as the cause of Io's volcanism, and the volcanic activity is explained in terms of sulfur chemistry. Theories concerning the reasons for the two main types of volcanic eruptions on Io are advanced and correlated with geographical features of the satellite. The sulfur and silicate models of the calderas are presented, citing the strengths and weaknesses of each. Problems of the gravitational resonance theory of Io's heat source are then described. Finally, observations of Io planned for the Galileo mission are summarized.

  9. Complex interaction between Strombolian and phreatomagmatic eruptions in the Quaternary monogenetic volcanism of the Catalan Volcanic Zone (NE of Spain)

    NASA Astrophysics Data System (ADS)

    Martí, Joan; Planagumà, Llorenç; Geyer, Adelina; Canal, Esther; Pedrazzi, Dario

    2011-04-01

    The Catalan Volcanic Zone (CVZ), at the NE of the Iberian peninsula, is one of the Quaternary alkaline volcanic provinces of the European rifts system. The CVZ has been active during the last 12 Ma. Despite the fact that this volcanism is significant in extension and volume, and that eruptions have also occurred in Holocene times, it is mostly unknown compared to the contemporaneous alkaline volcanism in other parts of Western and Central Europe. Volcanism younger than 0.5 Ma is mostly concentrated in an area of about 100 km 2 located between the main cities of Olot and Girona. This basaltic volcanic field comprises more than 50 monogenetic cones including scoria cones, lava flows, tuff rings, and maars. Magmatic eruptions range from Hawaiian to violent Strombolian. Phreatomagmatism is also common and has contributed to the construction of more than a half of these volcanic edifices, frequently associated with the Strombolian activity but also independently, giving rise to a large variety of eruptive sequences. We describe the main characteristics of this volcanism and analyse in particular the successions of deposits that form some of these volcanoes and discuss the potential causes of such a wide diversity of eruptive sequences. We find that the main cause of such complex eruptive behaviour resides in the stratigraphic, structural and hydrogeological characteristics of the substrate above which the volcanoes were emplaced, rather than on the compositional characteristics of the erupting magma, as they do not show significant variations among the different volcanoes studied.

  10. Amazonian volcanic activity at the Syrtis volcanic province, Mars

    NASA Astrophysics Data System (ADS)

    Platz, Thomas; Jodlowski, Piotr; Fawdon, Peter; Michael, Greg; Tanaka, Kenneth

    2014-05-01

    The Syrtis Major volcanic province, including the entire Syrtis Major Planum, is located near the Martian highland/lowland transitional zone west of Isidis Planitia. It covers ≡7.4×105 km2 and contains two low-shield volcanic edifices with N-S elongated calderas named Nili and Meroe Paterae. The estimated thickness of erupted material in the province ranges from approximately 0.5 km to 1.0 km with a total volume of about 1.6-3.2×105 km3 [1]. The timing of volcanic activity in the Syrtis Major volcanic province has been suggested to be restricted to the Hesperian Period [1-4]. In the geological map of Greeley and Guest [2], volcanic material of Syrtis Major was assigned an Hesperian age based on the density of observed craters larger than 5 km in diameter. Using the same crater density range, recent studies of Hiesinger et al. [1] and Tanaka et al. [3] and Tanaka et al. [4] assigned an Early Hesperian and Early to Late Hesperian age, respectively, for the entire province. In this study we mapped lava flows, lava channels, and major lava-flow margins and report model ages for lava-flow formation and caldera segments of Nili and Meroe Paterae. The objective of this ongoing survey is to better understand the eruption frequency of this volcanic province. In total, we mapped 67 lava flows, caldera segments, and intra-crater fillings of which 55 were dated. Crater size-frequency distributions (CSFD) were mapped on HRSC and CTX imagery using CraterTools [5]. CSFDs were analyzed and model ages determined in Craterstats [6] using the production and chronology functions of Ivanov [7] and Hartmann and Neukum [8], respectively. A detailed description of the utilization of the crater-counting technique and its limitations with respect to small-scale mapping is given in Platz et al. [9]. Model ages range between 838 Ma (Middle Amazonian) to 3.6 Ga (Late Hesperian). In our survey, a broad age peak occurs between 2 to 2.6 Ga, continuously declining thereafter. We note that

  11. Fracture systems of the Western Volcanic Zone, Iceland

    NASA Astrophysics Data System (ADS)

    Rut Hjartardóttir, Ásta; Einarsson, Páll; Björgvinsdóttir, Sigríður

    2015-04-01

    The Western Volcanic Zone in Iceland is an approximately 120 km long and 30-40 km wide branch of the Mid-Atlantic plate boundary, extending towards the north from its triple junction with the Reykjanes Oblique Rift and the South Iceland Seismic Zone. The Western Volcanic Zone is an ultra-slow spreading part of the plate boundary, since the spreading in southern central Iceland is split between the Western and the Eastern Volcanic Zones. These volcanic zones, as well as the South Iceland Seismic Zone and the Hofsjökull volcanic system, form the boundary of the Hreppar microplate. In this study, fractures, including tensional fractures and faults, as well as eruptive fissures, were mapped in detail from aerial photographs. Orientation of the fractures was also calculated. This was done to study the extent of the volcanic zone, as well as its characteristics. The Western Volcanic Zone can be divided into several different fracture zones; The Hengill, Prestahnúkur, Kjölur, Hrómundartindur and Krákur fissure swarms, as well as an east-west oriented fracture system of unknown origin west of the Western Volcanic Zone. The Hengill fissure swarm is located in the southern part of the Western Volcanic Zone. It extends at least 30 km north of the Hengill central volcano. The Þingvellir graben is a part of the Hengill fissure swarm. The Prestahnúkur fissure swarm extends about 20 km towards the north and likely about 35 km towards the south from the Prestahnúkur central volcano. This fissure swarm is characterized by large-offset normal faults in Pleistocene formations. The Kjölur fissure swarm is located between the Western Volcanic Zone, and the Hofsjökull central volcano. We suggest that this fissure swarm, which is about 25 km long, likely belongs to the Hofsjökull volcanic system since its northern part bends towards the Hofsjökull central volcano. The Hrómundartindur fissure swarm extends towards the north from Hrómundartindur, which is located next to

  12. Melt zones beneath five volcanic complexes in California: an assessment of shallow magma occurrences

    SciTech Connect

    Goldstein, N.E.; Flexser, S.

    1984-12-01

    Recent geological and geophysical data for five magma-hydrothermal systems were studied for the purpose of developing estimates for the depth, volume and location of magma beneath each area. The areas studied were: (1) Salton Trough, (2) The Geysers-Clear Lake, (3) Long Valley caldera, (4) Coso volcanic field, and (5) Medicine Lake volcano, all located in California and all selected on the basis of recent volcanic activity and published indications of crustal melt zones. 23 figs.

  13. Magma genesis of the acidic volcanism in the intra-arc rift zone of the Izu volcanic arc, Japan

    NASA Astrophysics Data System (ADS)

    Haraguchi, S.; Tokuyama, H.; Ishii, T.

    2010-12-01

    The Izu volcanic arc extends over 550 km from the Izu Peninsula, Japan, to the Nishinoshima Trough or Sofugan tectonic line. It is the northernmost segment of the Izu-Bonin-Mariana arc system, which is located at the eastern side of the Philippine Sea Plate. The recent magmatism of the Izu arc is bimodal and characterized by basalt and rhyolite (e.g. Tamura and Tatsumi 2002). In the southern Izu arc, volcanic front from the Aogashima to the Torishima islands is characterized by submarine calderas and acidic volcanisms. The intra-arc rifting, characterized by back-arc depressions, small volcanic knolls and ridges, is active in this region. Volcanic rocks were obtained in 1995 during a research cruise of the R/V MOANA WAVE (Hawaii University, cruise MW9507). Geochemical variation of volcanic rocks and magma genesis was studied by Hochstaedter et al. (2000, 2001), Machida et al (2008), etc. These studies focused magma and mantle dynamics of basaltic volcanism in the wedge mantle. Acidic volcanic rocks were also dredged during the curies MW9507. However, studies of these acidic volcanics were rare. Herein, we present petrographical and chemical analyses of these acidic rocks, and compare these results with those of other acidic rocks in the Izu arc and lab experiments, and propose a model of magma genesis in a context of acidic volcanism. Dredge sites by the cruise MW9507 are 120, and about 50 sites are in the rift zone. Recovered rocks are dominated by the bimodal assemblage of basalt-basaltic andesite and dacite-rhyolite. The most abundant phase is olivine basalt, less than 50 wt% SiO2. Andesites are minor in volume and compositional gap from 56 to 65 wt% SiO2 exists. The across-arc variation of the HFSE contents and ratios, such as Zr/Y and Nb/Zr of rhyolites exhibit depleted in the volcanic front side and enriched in reararc side. This characteristic is similar to basaltic volcanism pointed out by Hochstaedter et al (2000). The petrographical features of rhyolites

  14. Surface deformation in volcanic rift zones

    USGS Publications Warehouse

    Pollard, D.D.; Delaney, P.T.; Duffield, W.A.; Endo, E.T.; Okamura, A.T.

    1983-01-01

    The principal conduits for magma transport within rift zones of basaltic volcanoes are steeply dipping dikes, some of which feed fissure eruptions. Elastic displacements accompanying a single dike emplacement elevate the flanks of the rift relative to a central depression. Concomitant normal faulting may transform the depression into a graben thus accentuating the topographic features of the rift. If eruption occurs the characteristic ridge-trough-ridge displacement profile changes to a single ridge, centered at the fissure, and the erupted lava alters the local topography. A well-developed rift zone owes its structure and topography to the integrated effects of many magmatic rifting events. To investigate this process we compute the elastic displacements and stresses in a homogeneous, two-dimensional half-space driven by a pressurized crack that may breach the surface. A derivative graphical method permits one to estimate the three geometric parameters of the dike (height, inclination, and depth-to-center) and the mechanical parameter (driving pressure/rock stiffness) from a smoothly varying displacement profile. Direct comparison of measured and theoretical profiles may be used to estimate these parameters even if inelastic deformation, notably normal faulting, creates discontinuities in the profile. Geological structures (open cracks, normal faults, buckles, and thrust faults) form because of stresses induced by dike emplacement and fissure eruption. Theoretical stress states associated with dilation of a pressurized crack are used to interpret the distribution and orientation of these structures and their role in rift formation. ?? 1983.

  15. The Physics of a Volcanic System: What is the Actual Role Played by Tectonic Setting in Controlling Volcanic Activity?

    NASA Astrophysics Data System (ADS)

    Canon-Tapia, E.

    2005-12-01

    Modern text-books commonly explain volcanic activity as a direct consequence of plate tectonics, overlooking the different scales characteristic of both types of processes. By acknowledging such differences, however, it is possible to envisage a model of a volcanic system that is based in the same principles of hydrostatics established by Blaise Pascal over 300 yrs ago. Such principles allow us to estimate the local conditions required for the occurrence of volcanism at a given location highlighting the importance of the rock strength and the density difference between melt and its surroundings. This model shows that the minimum thickness of the zone of partial melting in the mantle (or seismically defined Low Velocity Zone) that is required to feed volcanic activity might range from 5 to over 100 km, but also that under certain circumstances a rock strength < 200 MPa may suffice to keep magma trapped at depth whereas in other cases a strength > 600 MPa will not suffice to stop magma ascent resulting in volcanic activity at the surface. Consequently, the model of volcanism developed here explains why is that a given LVZ may lead to volcanic activity in some places whereas a completely identical LVZ may not result in volcanic activity in a different location. Consequently, this model provides a general framework that allows us to better understand the actual role played by tectonic setting in controlling volcanism at a planetary scale.

  16. Effects of deglaciation on the petrology and eruptive history of the Western Volcanic Zone, Iceland

    NASA Astrophysics Data System (ADS)

    Eason, Deborah E.; Sinton, John M.; Grönvold, Karl; Kurz, Mark D.

    2015-06-01

    New observations and geochemical analyses of volcanic features in the 170-km-long Western Volcanic Zone (WVZ) of Iceland constrain spatial and temporal variations in volcanic production and composition associated with the last major deglaciation. Subglacial eruptions represent a significant portion of the late Quaternary volcanic budget in Iceland. Individual features can have volumes up to ˜48 km3 and appear to be monogenetic. Subaqueous to subaerial transition zones provide minimum estimates of ice sheet thickness at the time of eruption, although water-magma interactions and fluctuating lake levels during eruption can lead to complex lithological sequences. New major and trace element data for 36 glacial and postglacial eruptive units, combined with observations of lava surface quality, passage zone heights, and 3He exposure ages of some glacial units, indicate a maximum in volcanic production in the WVZ during the last major ice retreat. Anomalously high volcanic production rates continue into the early postglacial period and coincide with significant incompatible element depletions and slightly higher CaO and SiO2 and lower FeO content at a given MgO. Subglacial units with strong incompatible element depletions also have lava surfaces that lack evidence of subsequent glaciation. These units likely formed after the onset of deglaciation, when rapidly melting ice sheets increased decompression rates in the underlying mantle, leading to anomalously high melting rates in the depleted upper mantle. This process also can explain the eruption of extremely depleted picritic lavas during the early postglacial period. These new observations indicate that the increased volcanic activity associated with glacial unloading peaked earlier than previously thought, before Iceland was completely ice free.

  17. Active Volcanic Plumes on Io

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This color image, acquired during Galileo's ninth orbit around Jupiter, shows two volcanic plumes on Io. One plume was captured on the bright limb or edge of the moon (see inset at upper right), erupting over a caldera (volcanic depression) named Pillan Patera after a South American god of thunder, fire and volcanoes. The plume seen by Galileo is 140 kilometers (86 miles) high and was also detected by the Hubble Space Telescope. The Galileo spacecraft will pass almost directly over Pillan Patera in 1999 at a range of only 600 kilometers (373 miles).

    The second plume, seen near the terminator (boundary between day and night), is called Prometheus after the Greek fire god (see inset at lower right). The shadow of the 75-kilometer (45- mile) high airborne plume can be seen extending to the right of the eruption vent. The vent is near the center of the bright and dark rings. Plumes on Io have a blue color, so the plume shadow is reddish. The Prometheus plume can be seen in every Galileo image with the appropriate geometry, as well as every such Voyager image acquired in 1979. It is possible that this plume has been continuously active for more than 18 years. In contrast, a plume has never been seen at Pillan Patera prior to the recent Galileo and Hubble Space Telescope images.

    North is toward the top of the picture. The resolution is about 6 kilometers (3.7 miles) per picture element. This composite uses images taken with the green, violet and near infrared filters of the solid state imaging (CCD) system on NASA's Galileo spacecraft. The images were obtained on June 28, 1997, at a range of more than 600,000 kilometers (372,000 miles).

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page

  18. Tephrochronology of the southernmost Andean Southern Volcanic Zone, Chile

    NASA Astrophysics Data System (ADS)

    Weller, D. J.; Miranda, C. G.; Moreno, P. I.; Villa-Martínez, R.; Stern, C. R.

    2015-12-01

    Correlations among and identification of the source volcanoes for over 60 Late Glacial and Holocene tephras preserved in eight lacustrine sediment cores taken from small lakes near Coyhaique, Chile (46° S), were made based on the stratigraphic position of the tephra in the cores, lithostratigraphic data (tephra layer thickness and grain size), and tephra petrochemistry (glass color and morphology, phenocryst phases, and bulk-tephra trace element contents determined by ICP-MS). The cores preserve a record of explosive eruptions, since ˜17,800 calibrated years before present (cal years BP), of the volcanoes of the southernmost Andean Southern Volcanic Zone (SSVZ). The suggested source volcanoes for 55 of these tephras include Hudson (32 events), Mentolat (10 events), and either Macá or Cay or some of the many minor monogenetic eruptive centers (MECs; 13 events) in the area. Only four of these eruptions had been previously identified in tephra outcrops in the region, indicating the value of lake cores for identifying smaller eruptions in tephrochronologic studies. The tephra records preserved in these lake cores, combined with those in marine cores, which extend these records back to 20,000 cal years BP, prior to the Last Glacial Maximum, suggest that no significant temporal change in the frequency of explosive eruptions was associated with deglaciation. Over this time period, Hudson volcano, one of the largest and longest lived volcanoes in the Southern Andes, has had >55 eruptions (four of them were very large) and has produced >45 km3 of pyroclastic material, making it also one of the most active volcanoes in the SVZ in terms of both frequency and volume of explosive eruptions.

  19. Modeling Diverse Pathways to Age Progressive Volcanism in Subduction Zones.

    NASA Astrophysics Data System (ADS)

    Kincaid, C. R.; Szwaja, S.; Sylvia, R. T.; Druken, K. A.

    2015-12-01

    One of the best, and most challenging clues to unraveling mantle circulation patterns in subduction zones comes in the form of age progressive volcanic and geochemical trends. Hard fought geological data from many subduction zones, like Tonga-Lau, the Cascades and Costa-Rica/Nicaragua, reveal striking temporal patterns used in defining mantle flow directions and rates. We summarize results from laboratory subduction models showing a range in circulation and thermal-chemical transport processes. These interaction styles are capable of producing such trends, often reflecting apparent instead of actual mantle velocities. Lab experiments use a glucose working fluid to represent Earth's upper mantle and kinematically driven plates to produce a range in slab sinking and related wedge transport patterns. Kinematic forcing assumes most of the super-adiabatic temperature gradient available to drive major downwellings is in the tabular slabs. Moreover, sinking styles for fully dynamic subduction depend on many complicating factors that are only poorly understood and which can vary widely even for repeated parameter combinations. Kinematic models have the benefit of precise, repeatable control of slab motions and wedge flow responses. Results generated with these techniques show the evolution of near-surface thermal-chemical-rheological heterogeneities leads to age progressive surface expressions in a variety of ways. One set of experiments shows that rollback and back-arc extension combine to produce distinct modes of linear, age progressive melt delivery to the surface through a) erosion of the rheological boundary layer beneath the overriding plate, and deformation and redistribution of both b) mantle residuum produced from decompression melting and c) formerly active, buoyant plumes. Additional experiments consider buoyant diapirs rising in a wedge under the influence of rollback, back-arc spreading and slab-gaps. Strongly deflected diapirs, experiencing variable rise

  20. Geophysical Limitations on the Habitable Zone: Volcanism and Plate Tectonics

    NASA Astrophysics Data System (ADS)

    Noack, Lena; Rivoldini, Attilio; Van Hoolst, Tim

    2016-04-01

    Planets are typically classified as potentially life-bearing planets (i.e. habitable planets) if they are rocky planets and if a liquid (e.g. water) could exist at the surface. The latter depends on several factors, like for example the amount of available solar energy, greenhouse effects in the atmosphere and an efficient CO2-cycle. However, the definition of the habitable zone should be updated to include possible geophysical constraints, that could potentially influence the CO2-cycle. Planets like Mars without plate tectonics and no or only limited volcanic events can only be considered to be habitable at the inner boundary of the habitable zone, since the greenhouse effect needed to ensure liquid surface water farther away from the sun is strongly reduced. We investigate if the planet mass as well as the interior structure can set constraints on the occurrence of plate tectonics and outgassing, and therefore affect the habitable zone, using both parameterized evolution models [1] and mantle convection simulations [1,2]. We find that plate tectonics, if it occurs, always leads to sufficient volcanic outgassing and therefore greenhouse effect needed for the outer boundary of the habitable zone (several tens of bar CO2), see also [3]. One-plate planets, however, may suffer strong volcanic limitations. The existence of a dense-enough CO2 atmosphere allowing for the carbon-silicate cycle and release of carbon at the outer boundary of the habitable zone may be strongly limited for planets: 1) without plate tectonics, 2) with a large planet mass, and/or 3) a high iron content. Acknowledgements This work has been funded by the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office through the Planet Topers alliance, and results within the collaboration of the COST Action TD 1308. References Noack, L., Rivoldini, A., and Van Hoolst, T.: CHIC - Coupling Habitability, Interior and Crust, INFOCOMP 2015, ISSN 2308-3484, ISBN 978

  1. Prediction and monitoring of volcanic activities

    SciTech Connect

    Sudradjat, A.

    1986-07-01

    This paper summarizes the state of the art for predicting and monitoring volcanic activities, and it emphasizes the experience obtained by the Volcanological Survey Indonesia for active volcanoes. The limited available funds, the large number of active volcanoes to monitor, and the high population density of the volcanic area are the main problems encountered. Seven methods of volcano monitoring are applied to the active volcanoes of Indonesia: seismicity, ground deformation, gravity and magnetic studies, self-potential studies, petrochemistry, gas monitoring, and visual observation. Seismic monitoring augmented by gas monitoring has proven to be effective, particularly for predicting individual eruptions at the after-initial phase. However, the success of the prediction depends on the characteristics of each volcano. In general, the initial eruption phase is the most difficult phenomenon to predict. The preparation of hazard maps and the continuous awareness of the volcanic eruption are the most practical ways to mitigate volcanic danger.

  2. Active Volcanic Eruptions on Io

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Six views of the volcanic plume named Prometheus, as seen against Io's disk and near the bright limb (edge) of the satellite by the SSI camera on the Galileo spacecraft during its second (G2) orbit of Jupiter. North is to the top of each frame. To the south-southeast of Prometheus is another bright spot that appears to be an active plume erupting from a feature named Culann Patera. Prometheus was active 17 years ago during both Voyager flybys, but no activity was detected by Voyager at Culann. Both of these plumes were seen to glow in the dark in an eclipse image acquired by the imaging camera during Galileo's first (G1) orbit, and hot spots at these locations were detected by Galileo's Near-Infrared Mapping Spectrometer.

    The plumes are thought to be driven by heating sulfur dioxide in Io's subsurface into an expanding fluid or 'geyser'. The long-lived nature of these eruptions requires that a substantial supply of sulfur dioxide must be available in Io's subsurface, similar to groundwater. Sulfur dioxide gas condenses into small particles of 'snow' in the expanding plume, and the small particles scatter light and appear bright at short wavelengths. The images shown here were acquired through the shortest-wavelength filter (violet) of the Galileo camera. Prometheus is about 300 km wide and 75 km high and Culann is about 150 km wide and less than 50 km high. The images were acquired on September 4, 1996 at a range of 2,000,000 km (20 km/pixel resolution). Prometheus is named after the Greek fire god and Culann is named after the Celtic smith god.

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the

  3. 40Ar/39Ar dating of Quaternary feldspar: examples from the Taupo Volcanic Zone, New Zealand

    USGS Publications Warehouse

    Pringle, M.S.; McWilliams, M.; Houghton, B.F.; Lanphere, M.A.; Wilson, C.J.N.

    1992-01-01

    Using a continuous laser and resistance furnace, we have measured ages on Quaternary plagioclase with an absolute precision of about ??30 ka and on Quaternary sanidine with a relative precision of better than 1%. Such precision was achieved by using low-temperature heating steps to remove much of the nonradiogenic argon contamination. Plagioclase is one of the most common mineral phases in volcanic rocks; thus, these procedures will be widely applicable to many problems for which precise radiometric age control has not been available. We studied plagioclase and plagioclase-sanidine concentrates from the oldest and the three largest silicic ash-flow deposits of the Taupo Volcanic Zone, New Zealand, one of the world's largest and most active volcanic systems. The results are in close agreement with new magnetostratigraphic data, suggesting that existing fission-track age determinations significantly underestimate the age of older units, and shift the inception of Taupo Vaolcanic Zone volcanism back to at least 1600 ka. -from Authors

  4. Helium-3 emission related to volcanic activity

    SciTech Connect

    Sano, Y.; Nakamura, Y.; Wakita, H.; Urabe, A.; Tominaga, T.

    1984-04-13

    The helium-3/helium-4 ratio in bubbling gases from ten hot springs located around Mount Ontake, an active volcano in central Japan, ranges from 1.71 R/sub atm/ (1.71 times the atmospheric ratio of 1.40 x 10/sup -6/) to 6.15 R/sub atm/. The value of the ratio decreases with distance from the central cone of the volcano. Such a tendency may be a characteristic of helium-3 emission in volcanic areas and suggests more primitive helium-3 is carried with fluid flowing through a conduit during volcanic activity. 6 references, 1 figure, 1 table.

  5. Rapid uplift during 2007-2012 at Laguna del Maule volcanic field, Andean Southern Volcanic Zone, Chile

    NASA Astrophysics Data System (ADS)

    Le Mevel, H.; Feigl, K.; Ali, T.; Cordova V., M. L.; DeMets, C.; Singer, B. S.

    2012-12-01

    The Laguna del Maule (LdM) volcanic field includes an unusual concentration of post-glacial rhyolitic lava coulees and domes, dated between 24 to 2 thousand years old that cover more than 100 square kilometers and erupted from 24 vents that encircle a 20-km-diameter lake basin on the range crest. The recent concentration of rhyolite is unparalleled in the Southern Volcanic Zone of the Andes. Moreover, the western portion of the LdM volcanic field has experienced rapid uplift since 2007, leading to questions about the current configuration of the magmatic system and processes that drive the ongoing inflation. We aim to quantify the active deformation of the LdM volcanic field and its evolution with time. To do so, we use interferometric synthetic aperture radar (InSAR) data acquired by three satellite missions: Envisat in 2003 and 2004, ALOS between 2007 and 2010, and TerraSAR-X in 2012. An interferogram spanning March 2003 to February 2004 "shows no deformation" (Fournier et al., 2010). From 2007 through 2012, however, the shortening of the satellite-to-ground distance revealed a range change rate of greater than 200 mm/yr along the radar line of sight. The deformation includes a circular area 20 km in diameter centered on the western portion of the circle of young rhyolite domes. To analyze the InSAR results, we employ the General Inversion for Phase Technique (GIPhT; Feigl and Thurber, 2009; Ali and Feigl, 2012). We have considered several hypotheses to interpret this deformation. Artefacts such as orbital errors, atmospheric perturbations or topographic contribution cannot account for the observed signal. We also reject the hypothesis of uplift due to gravitational unloading of the crust based on our modeling of independently measured lake level variations over the observed time interval. We thus attribute the deformation to the intrusion of magma into the upper crust below the southwest region of the LdM volcanic field. The best fit to the InSAR data is

  6. Volcanic activity: a review for health professionals.

    PubMed Central

    Newhall, C G; Fruchter, J S

    1986-01-01

    Volcanoes erupt magma (molten rock containing variable amounts of solid crystals, dissolved volatiles, and gas bubbles) along with pulverized pre-existing rock (ripped from the walls of the vent and conduit). The resulting volcanic rocks vary in their physical and chemical characteristics, e.g., degree of fragmentation, sizes and shapes of fragments, minerals present, ratio of crystals to glass, and major and trace elements composition. Variability in the properties of magma, and in the relative roles of magmatic volatiles and groundwater in driving an eruption, determine to a great extent the type of an eruption; variability in the type of an eruption in turn influences the physical characteristics and distribution of the eruption products. The principal volcanic hazards are: ash and larger fragments that rain down from an explosion cloud (airfall tephra and ballistic fragments); flows of hot ash, blocks, and gases down the slopes of a volcano (pyroclastic flows); "mudflows" (debris flows); lava flows; and concentrations of volcanic gases in topographic depressions. Progress in volcanology is bringing improved long- and short-range forecasts of volcanic activity, and thus more options for mitigation of hazards. Collaboration between health professionals and volcanologists helps to mitigate health hazards of volcanic activity. Images FIGURE 1 FIGURE 2 FIGURE 6a-6e FIGURE 6a-6e FIGURE 8 FIGURE 9 FIGURE 10 FIGURE 11 PMID:3946726

  7. Volcanic activity: a review for health professionals

    SciTech Connect

    Newhall, C.G.; Fruchter, J.S.

    1986-03-01

    Volcanoes erupt magma (molten rock containing variable amounts of solid crystals, dissolved volatiles, and gas bubbles) along with pulverized pre-existing rock (ripped from the walls of the vent and conduit). The resulting volcanic rocks vary in their physical and chemical characteristics, e.g., degree of fragmentation, sizes and shapes of fragments, minerals present, ratio of crystals to glass, and major and trace element composition. Variability in the properties of magma, and in the relative roles of magmatic volatiles and groundwater in driving an eruption, determine to a great extent the type of an eruption; variability in the type of an eruption in turn influences the physical characteristics and distribution of the eruption products. The principal volcanic hazards are: ash and larger fragments that rain down from an explosion cloud (airfall tephra and ballistic fragments); flows of hot ash, blocks, and gases down the slopes of a volcano (pyroclastic flows); mudflows (debris flows); lava flows; and concentrations of volcanic gases in topographic depressions. Progress in volcanology is bringing improved long- and short-range forecasts of volcanic activity, and thus more options for mitigation of hazards. Collaboration between health professionals and volcanologists helps to mitigate health hazards of volcanic activity.

  8. Studying monogenetic volcanoes with Terrestrial Laser Scanner: Case study at Croscat volcano (Garrotxa Volcanic Zone, Spain)

    NASA Astrophysics Data System (ADS)

    Geyer Traver, A.; Garcia-Selles, D.; Peddrazzi, D.; Barde-Cabusson, S.; Marti, J.; Muñoz, J.

    2013-12-01

    Monogenetic basaltic zones are common in many volcanic environments and may develop under very different geodynamic conditions. Despite existing clear similarities between the eruptive activity of different monogenetic volcanic fields, important distinctions may arise when investigating in detail the individual eruptive sequences. Interpretation of the deposits and consequently, the reconstruction and characterization of these eruptive sequences is crucial to evaluate the potential hazard in case of active areas. In diverse occasions, erosional processes (natural and/or anthropogenic) may partly destroy these relatively small-sized volcanic edifices exposing their internal parts. Furthermore, despite human activity in volcanic areas is sometimes unimportant due to the remote location of the monogenetic cones, there are places where this form of erosion is significant, e.g. Croscat volcano (Catalan Volcanic Field, Spain). In any case, when studying monogenetic volcanism, it is usual to find outcrops where the internal structure of the edifices is, for one or other reason, well exposed. However, the access to these outcrops may be extremely difficult or even impossible. During the last years, it has been demonstrated that the study of outcrops with problematic or completely restricted access can be carried out by means of digital representations of the outcrop surface. Digital outcrops make possible the study of those areas with natural access limitations or safety issues and may facilitate visualization of the features of interest over the entire outcrop, as long as the digital outcrop can be analysed while navigated in real- time, with optional displays for perspective, scale distortions, and attribute filtering. In particular, Terrestrial Laser Scanning (TSL) instruments using Light Detection And Ranging technology (LIDAR) are capable of capturing topographic details and achieve modelling accuracy within a few centimetres. The data obtained enables the creation of

  9. Tellurium in active volcanic environments: Preliminary results

    NASA Astrophysics Data System (ADS)

    Milazzo, Silvia; Calabrese, Sergio; D'Alessandro, Walter; Brusca, Lorenzo; Bellomo, Sergio; Parello, Francesco

    2014-05-01

    Tellurium is a toxic metalloid and, according to the Goldschmidt classification, a chalcophile element. In the last years its commercial importance has considerably increased because of its wide use in solar cells, thermoelectric and electronic devices of the last generation. Despite such large use, scientific knowledge about volcanogenic tellurium is very poor. Few previous authors report result of tellurium concentrations in volcanic plume, among with other trace metals. They recognize this element as volatile, concluding that volcanic gases and sulfur deposits are usually enriched with tellurium. Here, we present some results on tellurium concentrations in volcanic emissions (plume, fumaroles, ash leachates) and in environmental matrices (soils and plants) affected by volcanic emissions and/or deposition. Samples were collected at Etna and Vulcano (Italy), Turrialba (Costa Rica), Miyakejima, Aso, Asama (Japan), Mutnovsky (Kamchatka) at the crater rims by using common filtration techniques for aerosols (polytetrafluoroethylene filters). Filters were both eluted with Millipore water and acid microwave digested, and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Volcanic ashes emitted during explosive events on Etna and Copahue (Argentina) were analyzed for tellurium bulk composition and after leaching experiments to evaluate the soluble fraction of tellurium. Soils and leaves of vegetation were also sampled close to active volcanic vents (Etna, Vulcano, Nisyros, Nyiragongo, Turrialba, Gorely and Masaya) and investigated for tellurium contents. Preliminary results showed very high enrichments of tellurium in volcanic emissions comparing with other volatile elements like mercury, arsenic, thallium and bismuth. This suggests a primary transport in the volatile phase, probably in gaseous form (as also suggested by recent studies) and/or as soluble salts (halides and/or sulfates) adsorbed on the surface of particulate particles and ashes. First

  10. Magnetic characteristics of fracture zones and constraints on the subsurface structure of the Colima Volcanic Complex, western Mexico

    NASA Astrophysics Data System (ADS)

    López-Loera, H.; Fucugauchi, J. U.; Alva-Valdivia, L. M.

    2013-05-01

    Detailed magnetic anomaly surveys over the central and southern sector of the Colima rift, western Mexico, are used to investigate the subsurface structure and faults and/or fractures in the volcanic terrains formed by activity in the Colima volcanic complex (CVC). The CVC is located within the large north-south Colima rift in western Mexico. The Colima rift is a major active tectonic structure, trending perpendicular to the Middle America Trench and related to subduction of the Rivera and Cocos plates. Volcanic activity in the CVC has migrated southward toward the trench. Analyses of faults and recent deformation in the CVC and Colima rift are of major interest in volcano-tectonic studies and for hazard assessment. Structural analyses and fault mapping, however, are diffi cult because young volcanic and pyroclastic rocks obscure structural features and stratigraphy. Most of the southern Colima rift is covered by volcanic avalanches and volcaniclastic units, which have resulted in resurfacing of the volcanic terrains. Here we show that magnetic anomalies permit identifi cation of faults and mapping of volcano- sedimentary and volcanic units. Total magnetic fi eld measurements spaced every 0.5 km along 8 profi les, with an overall length of 284.5 km and covering the CVC sector of the Colima rift, have been obtained. We recognize fractures and fault zones of local and regional character from their characteristic magnetic anomaly response. Large mapped structures include the north-south Montitlan, northeast-southwest La Lumbre, and east-west La Escondida faults, which can be traced across the area from the magnetic profiles. Fault magnetic anomalies are modeled by lateral contrasts in terms of step models assuming thin dipping elongated zones along the fault planes. The study shows that faults in the CVC volcanic terrain can be investigated by magnetic surveying.

  11. Bimodal volcanism in a tectonic transfer zone: Evidence for tectonically controlled magmatism in the southern Central Andes, NW Argentina

    NASA Astrophysics Data System (ADS)

    Petrinovic, I. A.; Riller, U.; Brod, J. A.; Alvarado, G.; Arnosio, M.

    2006-04-01

    This field-based and analytical laboratory study focuses on the genetic relationship between bimodal volcanic centres and fault types of an important tectonic transfer zone in the southern Central Andes, the NW-SE striking Calama-Olacapato-Toro (COT) volcanic belt. More specifically, tectono-magmatic relationships are examined for the 0.55 Ma Tocomar, the 0.78 Ma San Jerónimo and the 0.45 Ma Negro de Chorrillos volcanic centres in the Tocomar area (66°30 W-24°15 S). Structures of the COT volcanic belt, notably NW-SE striking strike-slip faults and NE-SW trending normal faults, accommodated differential shortening between major N-S striking thrust faults on the Puna Plateau. We present evidence that bimodal volcanism was contemporaneous with activity of these fault types in the COT volcanic belt, whereby eruption and composition of the volcanic rocks in the Tocomar and San Jerónimo-Negro de Chorrillos areas appear to have been controlled by the kinematics of individual faults. More specifically, rhyolitic centres such as the Tocomar are associated with normal faults, whereas shoshonitic-andesitic monogenetic volcanoes, e.g., the San Jerónimo and Negro de Chorrillos centres, formed at strike-slip dominated faults. Thus, the eruption of higher viscous rhyolite magmas appears to have been facilitated in tectonic settings characterized by horizontal dilation whereas ascent and effusive volcanic activity of less viscous and hot basaltic andesites to shoshonites were controlled by subvertical strike-slip faults. While the Tocomar rhyolites are interpreted to be derived from an anatectic crustal source, geochemical characteristics of the San Jerónimo and Negro de Chorrillos shoshonitic andesites are in agreement with a deeper source. This suggests that the composition of erupted volcanic rocks as well as their spatial distribution in the Tocomar area is controlled by the activity of specific fault types. Such volcano-tectonic relationships are also evident from older

  12. Timescales and conditions of crystallization in the Pokai and Chimpanzee Ignimbrites, Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Connor, M.; Gualda, G. A.; Gravley, D. M.

    2013-12-01

    Silicic magmas give rise to explosive eruptions that are both of scientific and societal interest. The central Taupo Volcanic Zone in New Zealand has been volcanically active for 2 Ma and represents the most active volcanic area in the world today. Particularly intense volcanic activity took place as part of a flare-up event that occurred from ~340 to ~240 ka, when 7 large ignimbrite eruptions took place, as well as many smaller eruptions, which erupted a total of at least 3000 km3 of magma. This project seeks to identify the conditions and timescales over which magma bodies that gave rise to these ignimbrite eruptions evolved. We aim to understand how much of the tens of thousands of years between successive eruptions were characterized by the presence of large bodies of silicic magma within the crust, as well the magma distribution within the crust during those times. We focus on the Chimpanzee and Pokai ignimbrites, which together erupted ~150 km3 of magma. The Pokai ignimbrite erupted at ~275 ka, while the Chimpanzee ignimbrite (undated) erupted between ~320 and 275 ka. Pumice clasts from the Chimpanzee and Pokai ignimbrite were collected in the field. Pumice bulk densities were measured using a submersion technique. Quartz and plagioclase crystals were extracted through a crushing, sieving, and winnowing procedure. Whole crystals were hand-picked under a conventional microscope, mounted on epoxy, and polished to expose grain interiors. Grain mounts were analyzed under an SEM using back-scattered electron, cathodoluminescence (CL), and energy-dispersive x-ray (EDX) imaging. Bulk-densities vary from 0.42 to 0.81 g/cm3 for Pokai and between 0.52 and 0.64 g/cm3 for Chimpanzee pumice clasts. Plagioclase is the dominant crystal phase in both units. Several plagioclase crystals have inclusions of orthopyroxene, ilmenite, magnetite, and zircon, which in some cases form clusters. Quartz is rare but is present in pumice from both deposits. Both plagioclase and quartz

  13. An assessment of the crustal remelting hypothesis for volcanism in the Freyja Montes deformation zone

    NASA Technical Reports Server (NTRS)

    Namiki, Noriyuki; Solomon, Sean C.

    1991-01-01

    The linear mountain belts of Ishtar Terra on Venus are notable for their topographic relief and slope and for the intensity of surface deformation. The mountains surround the highland plain Lakshmi Planum, the site of two major paterae and numerous other volcanic features and deposits, and evidence is widespread for volcanism within the mountains and in terrain immediately outward of the mountain belt units. While two hypotheses for magmatism can be distinguished on the basis of the chemistry of the melts, chemical data are presently lacking for the Ishtar region. The competing hypotheses for magmatism in Western Ishtar Terra can also be tested with thermal models, given a kinematic or dynamic model for the evolution of the region. The crustal remelting hypothesis is assessed, using the kinematic scenario of Head for the evolution of Freyja Montes. In that scenario, Freyja Montes formed by a sequence of large scale underthrusts of the lithosphere of the North Polar Plains beneath Ishtar Terra, with successive blocks of underthrust crust sutured in imbricate fashion onto the thickened crust of Lakshmi Planum and the mantle portion of underthrusting lithosphere episodically detached. The numerical experiments thus show that volcanic activity associated with the formation of the Frejya Montes deformation zone can be explained by crustal melting, due either to direct contact of crustal material with the hot asthenosphere or to heat generation in a thickened crustal layer.

  14. Active Volcanism on IO: Global Distribution and Variations in Activity

    NASA Technical Reports Server (NTRS)

    Lopes-Gautier, R.; McEwen, A.; Smythe, W.; Geissler, P.; Kamp, L.; Davies, A.; Spencer, J.; Keszthelyi, L.; Carlson, R.; Leader, F.; Mehlman, R.; Soderblom, L.

    1999-01-01

    Io's volcanic activity has been monitored by instruments aboard the Galileo spacecraft since June 28, 1996. We present results from observations by the Near-Infrared Mapping Spectrometer (NIM) for the first ten orbits of Galileo, correlate them with results from the Solid State Imaging System (SSI)and from ground-based observations, and compare them to what was known about Io's volcanic activity from observations made during the two Voyager fly-bys in 1979.

  15. The Magmatic-Hydrothermal Transition of The Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Chambefort, I. S.; Dilles, J. H.; Heinrich, C. A.; Wälle, M.

    2015-12-01

    The Taupo Volcanic Zone (TVZ), New Zealand is a rifting arc that produced over the last 2 My over 6000 km3 of caldera-associated volcanic products. About four times as much magma is estimated to be trapped at depth below the central TVZ than is erupted, feeding heat, volatiles and chemicals into 23 geothermal systems with a total of ca. 4.2 GW thermal energy release. We present here a combined study linking melt, hypersaline and dilute fluid inclusion chemistry, surface and reservoir fluid chemistry and whole rock lithochemistry and discuss the magmatic-hydrothermal chemical zoning in large silicic systems. New dataset of full lithogeochemistry in active geothermal systems of the TVZ refine the zoned chemical footprint left by both dilute meteoric-dominated and magmatic-hydrothermal fluids. Altered whole rock trace elements content (including precious metals and volatiles) shows major variation with depth, due to the influence of past hydrothermal activity, magmatic degassing, natural variability of the reservoir rocks, and current active fluid-rock interactions. The concentrations of Li, Cs, Tl, Bi, Sn, Ag, Se, Te, as well as Au, generally increase upward toward the paleosurface, where they are 10-100 times greater than near known or potentially 'active' intrusions. New direct in-situ analyses of trapped fluid inclusions in phenocrysts and hydrothermal veins associated with magmatic subsolidus crystallization are compared with liquid-dominated dilute fluid inclusions and geothermal fluids Li, Cs, B, Na, Cl, K content (and precious metals) providing a unique direct assessment of the role of each component (magma, rock, fluids) in New Zealand's world known geothermal systems.

  16. Volcanic Activities of Hakkoda Volcano after the 2011 Tohoku Earthquake

    NASA Astrophysics Data System (ADS)

    Yamamoto, M.; Miura, S.

    2014-12-01

    the direction connecting Odake summit crater and Jigoku-numa. These results suggest that the extensional field generated by the 2011 Tohoku Earthquake causes the upward movement of volcanic fluids and heat from the deep, and results in an activation of hydrothermal activities at the pre-existent fracture zone at the Hakkoda volcanic group.

  17. Tectonic lineaments in the cenozoic volcanics of southern Guatemala: Evidence for a broad continental plate boundary zone

    NASA Technical Reports Server (NTRS)

    Baltuck, M.; Dixon, T. H.

    1984-01-01

    The northern Caribbean plate boundary has been undergoing left lateral strike slip motion since middle Tertiary time. The western part of the boundary occurs in a complex tectonic zone in the continental crust of Guatemala and southernmost Mexico, along the Chixoy-Polochic, Motogua and possibly Jocotan-Chamelecon faults. Prominent lineaments visible in radar imagery in the Neogene volcanic belt of southern Guatemala and western El Salvador were mapped and interpreted to suggest southwest extensions of this already broad plate boundary zone. Because these extensions can be traced beneath Quaternary volcanic cover, it is thought that this newly mapped fault zone is active and is accommodating some of the strain related to motion between the North American and Caribbean plates. Onshore exposures of the Motoqua-Polochic fault systems are characterized by abundant, tectonically emplaced ultramafic rocks. A similar mode of emplacement for these off shore ultramafics, is suggested.

  18. Pre-eruption deformation and seismic anomalies in 2012 in Tolbachik volcanic zone, Kamchatka

    NASA Astrophysics Data System (ADS)

    Kugaenko, Yulia; Saltykov, Vadim; Titkov, Nikolay

    2014-05-01

    Tolbachik volcanic zone (active volcano Plosky Tolbachik, dormant volcano Ostry Tolbachik and Tolbachik zone of cinder cones) is situated in the south part of Klyuchevskaya group of volcanoes in Kamchatka. All historical fissure eruptions of Tolbachik volcanic zone (1740, 1941, 1975-76 and 2012-13) were connected with one or another activity of Plosky Tolbachik volcano. In 1941 the fissure vent was occurred during the completion of 1939-41 terminal eruption of Plosky Tolbachik. In 1975 the Large Tolbachik Fissure Eruption (LTFE) was forestalled by Plosky Tolbachik terminal activity of the Hawaiian type and then was accompanied by the catastrophic collapse in the crater of Plosky Tolbachik. What events took place in the vicinity of Plosky Tolbachik in 2012 before the 2012-13 fissure eruption? In contrast of the 1975-76 LTFE the eruption 2012-13 was not preceded by intensive seismic preparation. Nowadays Klyuchevskaya group of volcanoes is under monitoring by 12 seismic stations, so we can investigate seismicity in details on the lower energy level then forty years ago. We analyzed seismicity of Plosky Tolbachik using regional catalogue 1999-2012. Anomalies of low-energy (M≥1.5) seismicity parameters (increase of seismicity rate and seismic energy) were discovered. This is evidence of seismic activization covered the whole Plosky Tolbachik volcano. The significance of this anomaly was estimated by distribution function of emitted seismic energy. Statistically significant transition of seismicity from background level to high and extremely high levels was revealed. It corresponds to multiple growth of earthquake number and seismic energy in 2012, July-November (five months before the eruption). The seismicity transition from background level to high level was happen in August 2012. During last three weeks before fissure eruption seismicity of analyzed seismoactive volume was on extremely high level. Earthquakes from fissure site directly appeared only on November 27

  19. Active and Recent Volcanism and Hydrogeothermal Activity on Mars

    NASA Astrophysics Data System (ADS)

    Edgett, Kenneth S.; Cantor, B. A.; Harrison, T. N.; Kennedy, M. R.; Lipkaman, L. J.; Malin, M. C.; Posiolova, L. V.; Shean, D. E.

    2010-10-01

    There are no active volcanoes or geysers on Mars today, nor in the very recent past. Since 1997, we have sought evidence from targeted narrow angle camera images and daily, global wide angle images for active or very recent (decades to < 10 Ma) volcanism or hydrogeothermal events on Mars. Despite > 11 years of daily global imaging and coverage of > 60% of Mars at ≤ 6 m/pixel (with the remaining < 40% largely outside of volcanic regions), we have found no such evidence, although one lava field in Aeolis (5°N, 220°W) stands out as possibly the site of the most recent volcanism. Authors of impact crater size-frequency studies suggest some volcanic landforms on Mars are as young as tens to hundreds of Ma. This interpreted youth has implications for understanding the internal geophysical state of Mars and has encouraged those seeking sources for trace gases (methane) in the atmosphere and those seeking "warm havens for life” (Jakosky 1996, New Scientist 150, 38-42). We targeted thousands of Mars Global Surveyor (MGS) MOC and Mars Reconnaissance Orbiter (MRO) CTX (and HiRISE) images to examine volcanic regions; we also studied every MGS MOC and MRO MARCI wide angle image. For evidence of active volcanism, we sought eruption plumes, new vents, new tephra deposits, and new volcanogenic flows not observed in earlier images. For recent volcanism, we sought volcanogenic flows with zero or few superposed impact craters and minimal regolith development or superposed eolian sediment. Targets included all volcanic landforms identified in research papers as "recent” as well as areas speculated to have exhibited eruptive plumes. An independent search for endogenic heat sources, a key Mars Odyssey THEMIS objective, has also not produced a positive result (Christensen et al. 2005, P24A-01, Eos, Trans. Am. Geophys. Union 86/52).

  20. Active Volcanism on Io: Global Distribution and Variations in Activity

    USGS Publications Warehouse

    Lopes-Gautier, R.; McEwen, A.S.; Smythe, W.B.; Geissler, P.E.; Kamp, L.; Davies, A.G.; Spencer, J.R.; Keszthelyi, L.; Carlson, R.; Leader, F.E.; Mehlman, R.; Soderblom, L.

    1999-01-01

    Io's volcanic activity has been monitored by instruments aboard the Galileo spacecraft since June 28, 1996. We present results from observations by the near-infrared mapping spectrometer (NIMS) for the first 10 orbits of Galileo, correlate them with results from the Solid State Imaging System (SSI) and from groundbased observations, and compare them to what was known about Io's volcanic activity from observations made during the two Voyager flybys in 1979. A total of 61 active volcanic centers have been identified from Voyager, groundbased, and Galileo observations. Of these, 41 are hot spots detected by NIMS and/or SSI. Another 25 locations were identified as possible active volcanic centers, mostly on the basis of observed surface changes. Hot spots are correlated with surface colors, particularly dark and red deposits, and generally anti-correlated with white, SO2-rich areas. Surface features corresponding to the hot spots, mostly calderas or flows, were identified from Galileo and Voyager images. Hot spot temperatures obtained from both NIMS and SSI are consistent with silicate volcanism, which appears to be widespread on Io. Two types of hot spot activity are present: persistent-type activity, lasting from months to years, and sporadic events, which may represent either short-lived activity or low-level activity that occasionally flares up. Sporadic events are not often detected, but may make an important contribution to Io's heat flow and resurfacing. The distribution of active volcanic centers on the surface does not show any clear correlation with latitude, longitude, Voyager-derived global topography, or heat flow patterns predicted by the asthenosphere and deep mantle tidal dissipation models. However, persistent hot spots and active plumes are concentrated toward lower latitudes, and this distribution favors the asthenosphere rather than the deep mantle tidal dissipation model. ?? 1999 Academic Press.

  1. Volcanic Activity at Tvashtar Catena, Io

    NASA Technical Reports Server (NTRS)

    Milazzo, M. P.; Keszthelyi, L. P.; Radebaugh, J.; Davies, A. G.; McEwen, A. S.

    2004-01-01

    Tvashtar Catena (63 N, 120 W) is one of the most interesting features on Io. This chain of large paterae (caldera-like depressions) has exhibited highly variable volcanic activity in a series of observations. Tvashtar is the type example of a style of volcanism seen only at high latitudes, with short-lived Pele-type plumes and short-lived by intense thermal events. Evidence for a hot spot at Tvashtar was first detected in an eclipse observation in April 1997 (orbit G7) by the Solid State Imager (SSI) on the Galileo Spacecraft. Tvashtar was originally targeted for observation at higher resolution in the close flyby in November 1999 (I25) because of its interesting large-scale topography. There are relatively few but generally larger paterae at high latitudes on Io. I25 images revealed a 25 km long, 1-2 km high lava curtain via a pattern of saturation and bleeding in the CCD image, which requires very high temperatures.

  2. Volcanism, mantle exhumation and spreading at the axial zone of a fossil slow spreading ocean

    NASA Astrophysics Data System (ADS)

    Chalot-Prat, F.; Coco, E.

    2003-04-01

    Within an axial zone of a slow spreading ocean, the mechanisms checking together volcano emplacement, mantle exhumation and ocean enlargement are poorly known. In order to better assess how they could be linked , a detailed mapping of a fossil ocean-floor structure, preserved from alpine tectonic and metamorphism, was performed in the Chenaillet unit (Franco-Italian Alps)(Chalot-Prat &Coco, submit.). The detailed 3D geometry of the ophiolite evidences that from its dimensions, topography, morphology, and the architecture of the volcanic cover at different scales, the Chenaillet unit is a witness of an axial zone of Atlantic type. The basement (serpentinized peridotites and gabbros), below and in the prolongation of the volcanic cover (le50 m), is capped by a tectonic breccias horizon (Chalot-Prat and Manatschal, 2002), underlining detachment faults responsible for its exhumation at the seafloor. Clasts of dolerite, found within the fault zone, indicate that basement exhumation had to be active during and even after volcano emplacement. Stair- and comb-type volcanic systems check the distribution of individual volcanoes; the higher the edifice, the younger it is relative to the others. In the stair-type (up to 600 m of height difference between base and top), each step is formed with a pillow and tube tongue stacking fed from fissural conduits located at the root of each step. This system formed by uplift, step by step fracturation of an already exhumed basement, and magma injection along the fissures once formed. The comb-type (up to 200 m of height difference between base and top) consists in well-defined alignments of pillow and tube conic edifices. Their central feeder dykes are emplaced on the crossing of two types of fractures, oblique (tooth) and parallel (line) to the main branch of the comb. Along a same line, eruptions are coeval as proved by rhythmic variations of major and trace element contents of basalts from one line to another. The comb formation

  3. Tectonic controls on the genesis of ignimbrites from the Campanian Volcanic Zone, southern Italy

    USGS Publications Warehouse

    Rolandi, G.; Bellucci, F.; Heizler, M.T.; Belkin, H.E.; de Vivo, B.

    2003-01-01

    The Campanian Plain is an 80 x 30 km region of southern Italy, bordered by the Apennine Chain, that has experienced subsidence during the Quaternary. This region, volcanologically active in the last 600 ka, has been identified as the Campanian Volcanic Zone (CVZ). The products of three periods of trachytic ignimbrite volcanism (289-246 ka, 157 ka and 106 ka) have been identified in the Apennine area in the last 300 ka. These deposits probably represent distal ash flow units of ignimbrite eruptions which occurred throughout the CVZ. The resulting deposits are interstratified with marine sediments indicating that periods of repeated volcano-tectonic emergence and subsidence may have occurred in the past. The eruption, defined as the Campanian Ignimbrite (CI), with the largest volume (310 km3), occurred in the CVZ 39 ka ago. The products of the CI eruption consist of two units (unit-1 and unit-2) formed from a single compositionally zoned magma body. Slightly different in composition, three trachytic melts constitute the two units. Unit-1 type A is an acid trachyte, type B is a trachyte and type C of unit-2 is a mafic trachyte. The CI, vented from pre-existing neotectonic faults, formed during the Apennine uplift, Initially the venting of volatile-rich type A magma deposited the products to the N-NE of the CVZ. During the eruption, the Acerra graben already affected by a NE-SW fault system, was transected by E-W faults, forming a cross-graben that extended to the gulf of Naples. E-W faults were then further dislocated by NE-SW transcurrent movements. This additional collapse significantly influenced the deposition of the B-type magma of unit-1, and the C-type magma of unit-2 toward the E-SE and S, in the Bay of Naples. The pumice fall deposit underlying the CI deposits, until now thought to be associated with the CI eruption, is not a strict transition from plinian to CI-forming activity. It is derived instead from an independent source probably located near the

  4. Chronology and dynamics of a large silicic magmatic system. Central Taupo volcanic zone, New Zealand

    SciTech Connect

    Houghton, B.F.; Wilson, C.J.N. ); McWilliams, M.O. ); Lanphere, M.A.; Pringle, M.S. ); Weaver, S.D. ); Briggs, R.M. )

    1995-01-01

    The central Taupo Volcanic Zone in New Zealand is a region of intense Quaternary silicic volcanism accompanying rapid extension of continental crust. At least 34 caldera-forming ignimbrite eruptions have produced a complex sequence of relatively short-lived, nested, and/or overlapping volcanic centers over 1.6 m.y. Silicic volcanism at Taupo is similar to the Yellowstone system in size, longevity, thermal flux, and magma output rate. However, Taupo contrasts with Yellowstone in the exceptionally high frequency, but small size, of caldera-forming eruptions. This contrast reflects the thin, rifted nature of the crust, which precludes the development of long-term magmatic cycles at Taupo. 11 refs., 4 figs., 1 tab.

  5. Reef growth and volcanism on the submarine southwest rift zone of Mauna Loa, Hawaii

    USGS Publications Warehouse

    Moore, J.G.; Normark, W.R.; Szabo, B. J.

    1990-01-01

    A marine sampling program, utilizing the PISCES-5 submersible operated by the Hawaii Undersea Research Laboratory (NOAA), has confirmed the presence of a major submerged coral reef offshore from Ka Lae (South Point), Hawaii. The top of the reef is now 150-160 m below sea level. Radiocarbon and Useries dating indicates that it drowned about 13.9 ka by the combined effects of island subsidence (2.5 mm/year) and the rapid rise of sea level at the end of the last glaciation so that the relative submergence rate of more than 10 mm/year exceeded the upward growth rate of the reef. The submerged reef caps the offshore part of the southwest rift-zone ridge of Mauna Loa, which has apparently undergone little volcanic activity offshore since 170 ka, and possibly since 270 ka. This fact suggests that rift zone activity is becoming increasingly restricted toward the upper part of the volcano, a condition possibly heralding the end of the shield-building stage. ?? 1990 Springer-Verlag.

  6. The Online GVP/USGS Weekly Volcanic Activity Report: Providing Timely Information About Worldwide Volcanism

    NASA Astrophysics Data System (ADS)

    Mayberry, G. C.; Guffanti, M. C.; Luhr, J. F.; Venzke, E. A.; Wunderman, R. L.

    2001-12-01

    The awesome power and intricate inner workings of volcanoes have made them a popular subject with scientists and the general public alike. About 1500 known volcanoes have been active on Earth during the Holocene, approximately 50 of which erupt per year. With so much activity occurring around the world, often in remote locations, it can be difficult to find up-to-date information about current volcanism from a reliable source. To satisfy the desire for timely volcano-related information the Smithsonian Institution and US Geological Survey combined their strengths to create the Weekly Volcanic Activity Report. The Smithsonian's Global Volcanism Program (GVP) has developed a network of correspondents while reporting worldwide volcanism for over 30 years in their monthly Bulletin of the Global Volcanism Network. The US Geological Survey's Volcano Hazards Program studies and monitors volcanoes in the United States and responds (upon invitation) to selected volcanic crises in other countries. The Weekly Volcanic Activity Report is one of the most popular sites on both organization's websites. The core of the Weekly Volcanic Activity Report is the brief summaries of current volcanic activity around the world. In addition to discussing various types of volcanism, the summaries also describe precursory activity (e.g. volcanic seismicity, deformation, and gas emissions), secondary activity (e.g. debris flows, mass wasting, and rockfalls), volcanic ash hazards to aviation, and preventative measures. The summaries are supplemented by links to definitions of technical terms found in the USGS photoglossary of volcano terms, links to information sources, and background information about reported volcanoes. The site also includes maps that highlight the location of reported volcanoes, an archive of weekly reports sorted by volcano and date, and links to commonly used acronyms. Since the Weekly Volcanic Activity Report's inception in November 2000, activity has been reported at

  7. Integrating Multiple Space Ground Sensors to Track Volcanic Activity

    NASA Technical Reports Server (NTRS)

    Chien, Steve; Davies, Ashley; Doubleday, Joshua; Tran, Daniel; Jones, Samuel; Kjartansson, Einar; Thorsteinsson, Hrobjartur; Vogfjord, Kristin; Guomundsson, Magnus; Thordarson, Thor; Mandl, Daniel

    2011-01-01

    Volcanic activity can occur with little or no warning. Increasing numbers of space borne assets can enable coordinated measurements of volcanic events to enhance both scientific study and hazard response. We describe the use of space and ground measurements to target further measurements as part of a worldwide volcano monitoring system. We utilize a number of alert systems including the MODVOLC, GOESVOLC, US Air Force Weather Advisory, and Volcanic Ash Advisory Center (VAAC) alert systems. Additionally we use in-situ data from ground instrumentation at a number of volcanic sites, including Iceland.

  8. Geodetic Constraints From The Volcanic Arc Of The Andaman - Nicobar Subduction Zone

    NASA Astrophysics Data System (ADS)

    Earnest, A.; Krishnan, R.; Mayandi, S.; Sringeri, S. T.; Jade, S.

    2012-12-01

    We report first ever GPS derived surface deformation rates in the Barren and Narcondum volcanic islands east of Andaman-Nicobar archipelago which lies in the Bay of Bengal, a zone that generates frequent earthquakes, and coincides with the eastern plate boundary of India. The tectonics of this region is predominantly driven by the subduction of the Indian plate under the Burma plate. Andaman sea region hosts few volcanoes which lies on the inner arc extending between Sumatra and Myanmar with the sub-aerial expressions at Barren and Narcondum Islands. Barren Island, about 135 km ENE of Port Blair, is presently active with frequent eruptive histories whereas Narcondum is believed to be dormant. We initiated precise geodetic campaign mode measurements at Barren Island between 2007 to 2012 and one year (2011-2012) continuous measurements at Narcondum island. Preliminary results from this study forms a unique data set, being the first geodetic estimate from the volcanic arc of this subducting margin. Our analysis indicates horizontal convergence of the Barren benchmark to south-westward (SW) direction towards the Andaman accretionary fore-arc wedge where as the Narcondum benchmark recorded northeast (NE) motion. West of the Andaman fore-arc there is NE oriented subduction of the Indian plate which is moving at the rate of ~5 cm/yr. Convergence rates for the Indian plate from the Nuvel 1A model also show oblique convergence towards N23°E at 5.4 cm/yr. GPS derived inter seismic motion of Andaman islands prior to 2004 Sumatra earthquake is ~4.5 cm/yr NE. The marginal sea basin east of Barren Island at the Andaman spreading ridge has a NNW orienting opening of the sea-floor at 3.6 cm/yr. However the recent post seismic measurements of Andaman islands indicate rotation of displacement vectors from SW to NNE during 2005 to 2012. In this tectonic backdrop, the estimated rate of displacement of the volcanic islands probably represents a composite signal of tectonic as well as

  9. Off-axis magmatism along a subaerial back-arc rift: Observations from the Taupo Volcanic Zone, New Zealand.

    PubMed

    Hamling, Ian J; Hreinsdóttir, Sigrun; Bannister, Stephen; Palmer, Neville

    2016-06-01

    Continental rifting and seafloor spreading play a fundamental role in the generation of new crust. However, the distribution of magma and its relationship with tectonics and volcanism remain poorly understood, particularly in back-arc settings. We show evidence for a large, long-lived, off-axis magmatic intrusion located on the margin of the Taupo Volcanic Zone, New Zealand. Geodetic data acquired since the 1950s show evidence for uplift outside of the region of active extension, consistent with the inflation of a magmatic body at a depth of ~9.5 km. Satellite radar interferometry and Global Positioning System data suggest that there was an increase in the inflation rate from 2003 to 2011, which correlates with intense earthquake activity in the region. Our results suggest that the continued growth of a large magmatic body may represent the birth of a new magma chamber on the margins of a back-arc rift system. PMID:27386580

  10. Off-axis magmatism along a subaerial back-arc rift: Observations from the Taupo Volcanic Zone, New Zealand

    PubMed Central

    Hamling, Ian J.; Hreinsdóttir, Sigrun; Bannister, Stephen; Palmer, Neville

    2016-01-01

    Continental rifting and seafloor spreading play a fundamental role in the generation of new crust. However, the distribution of magma and its relationship with tectonics and volcanism remain poorly understood, particularly in back-arc settings. We show evidence for a large, long-lived, off-axis magmatic intrusion located on the margin of the Taupo Volcanic Zone, New Zealand. Geodetic data acquired since the 1950s show evidence for uplift outside of the region of active extension, consistent with the inflation of a magmatic body at a depth of ~9.5 km. Satellite radar interferometry and Global Positioning System data suggest that there was an increase in the inflation rate from 2003 to 2011, which correlates with intense earthquake activity in the region. Our results suggest that the continued growth of a large magmatic body may represent the birth of a new magma chamber on the margins of a back-arc rift system. PMID:27386580

  11. Off-axis magmatism along a subaerial back-arc rift: Observations from the Taupo Volcanic Zone, New Zealand.

    PubMed

    Hamling, Ian J; Hreinsdóttir, Sigrun; Bannister, Stephen; Palmer, Neville

    2016-06-01

    Continental rifting and seafloor spreading play a fundamental role in the generation of new crust. However, the distribution of magma and its relationship with tectonics and volcanism remain poorly understood, particularly in back-arc settings. We show evidence for a large, long-lived, off-axis magmatic intrusion located on the margin of the Taupo Volcanic Zone, New Zealand. Geodetic data acquired since the 1950s show evidence for uplift outside of the region of active extension, consistent with the inflation of a magmatic body at a depth of ~9.5 km. Satellite radar interferometry and Global Positioning System data suggest that there was an increase in the inflation rate from 2003 to 2011, which correlates with intense earthquake activity in the region. Our results suggest that the continued growth of a large magmatic body may represent the birth of a new magma chamber on the margins of a back-arc rift system.

  12. Hydrothermal reservoir beneath Taal Volcano (Philippines): Implications to volcanic activity

    NASA Astrophysics Data System (ADS)

    Nagao, T.; Alanis, P. B.; Yamaya, Y.; Takeuchi, A.; Bornas, M. V.; Cordon, J. M.; Puertollano, J.; Clarito, C. J.; Hashimoto, T.; Mogi, T.; Sasai, Y.

    2012-12-01

    Taal Volcano is one of the most active volcanoes in the Philippines. The first recorded eruption was in 1573. Since then it has erupted 33 times resulting in thousands of casualties and large damages to property. In 1995, it was declared as one of the 15 Decade Volcanoes. Beginning in the early 1990s it has experienced several phases of abnormal activity, including seismic swarms, episodes of ground deformation, ground fissuring and hydrothermal activities, which continues up to the present. However, it has been noted that past historical eruptions of Taal Volcano may be divided into 2 distinct cycles, depending on the location of the eruption center, either at Main Crater or at the flanks. Between 1572-1645, eruptions occurred at the Main Crater, in 1707 to 1731, they occurred at the flanks. In 1749, eruptions moved back to the Main Crater until 1911. During the 1965 and until the end of the 1977 eruptions, eruptive activity once again shifted to the flanks. As part of the PHIVOLCS-JICA-SATREPS Project magnetotelluric and audio-magnetotelluric surveys were conducted on Volcano Island in March 2011 and March 2012. Two-dimensional (2-D) inversion and 3-D forward modeling reveals a prominent and large zone of relatively high resistivity between 1 to 4 kilometers beneath the volcano almost directly beneath the Main Crater, surrounded by zones of relatively low resistivity. This anomalous zone of high resistivity is hypothesized to be a large hydrothermal reservoir filled with volcanic fluids. The presence of this large hydrothermal reservoir could be related to past activities of Taal Volcano. In particular we believe that the catastrophic explosion described during the 1911 eruption was the result of the hydrothermal reservoir collapsing. During the cycle of Main Crater eruptions, this hydrothermal reservoir is depleted, while during a cycle of flank eruptions this reservoir is replenished with hydrothermal fluids.

  13. Volcanic activity at Tvashtar Catena, Io

    USGS Publications Warehouse

    Milazzo, M.P.; Keszthelyi, L.P.; Radebaugh, J.; Davies, A.G.; Turtle, E.P.; Geissler, P.; Klaasen, K.P.; Rathbun, J.A.; McEwen, A.S.

    2005-01-01

    Galileo's Solid State Imager (SSI) observed Tvashtar Catena four times between November 1999 and October 2001, providing a unique look at a distinctive high latitude volcanic complex on Io. The first observation (orbit I25, November 1999) resolved, for the first time, an active extraterrestrial fissure eruption; the brightness temperature was at least 1300 K. The second observation (orbit I27, February 2000) showed a large (??? 500 km 2) region with many, small, hot, regions of active lava. The third observation was taken in conjunction with Cassini imaging in December 2000 and showed a Pele-like, annular plume deposit. The Cassini images revealed an ???400 km high Pele-type plume above Tvashtar Catena. The final Galileo SSI observation of Tvashtar (orbit I32, October 2001), revealed that obvious (to SSI) activity had ceased, although data from Galileo's Near Infrared Mapping Spectrometer (NIMS) indicated that there was still significant thermal emission from the Tvashtar region. In this paper, we primarily analyze the style of eruption during orbit I27 (February 2000). Comparison with a lava flow cooling model indicates that the behavior of the Tvashtar eruption during I27 does not match that of simple advancing lava flows. Instead, it may be an active lava lake or a complex set of lava flows with episodic, overlapping eruptions. The highest reliable color temperature is ???1300 K. Although higher temperatures cannot be ruled out, they do not need to be invoked to fit the observed data. The total power output from the active lavas in February 2000 was at least 1011 W. ?? 2005 Elsevier Inc. All rights reserved.

  14. Volcanic Gas

    MedlinePlus

    ... Hazards Tephra/Ash Lava Flows Lahars Volcanic Gas Climate Change Pyroclastic Flows Volcanic Landslides Preparedness Volcano Hazard Zones ... Please see our discussion of volcanic gases and climate change for additional information. Hydrogen sulfide (H 2 S) is ...

  15. A new view into the Cascadia subduction zone and volcanic arc: Implications for earthquake hazards along the Washington margin

    USGS Publications Warehouse

    Parsons, T.; Trehu, A.M.; Luetgert, J.H.; Miller, K.; Kilbride, F.; Wells, R.E.; Fisher, M.A.; Flueh, E.; ten Brink, U.S.; Christensen, N.I.

    1998-01-01

    In light of suggestions that the Cascadia subduction margin may pose a significant seismic hazard for the highly populated Pacific Northwest region of the United States, the U.S. Geological Survey (USGS), the Research Center for Marine Geosciences (GEOMAR), and university collaborators collected and interpreted a 530-km-long wide-angle onshore-offshore seismic transect across the subduction zone and volcanic arc to study the major structures that contribute to seismogenic deformation. We observed (1) an increase in the dip of the Juan de Fuca slab from 2??-7?? to 12?? where it encounters a 20-km-thick block of the Siletz terrane or other accreted oceanic crust, (2) a distinct transition from Siletz crust into Cascade arc crust that coincides with the Mount St. Helens seismic zone, supporting the idea that the mafic Siletz block focuses seismic deformation at its edges, and (3) a crustal root (35-45 km deep) beneath the Cascade Range, with thinner crust (30-35 km) east of the volcanic arc beneath the Columbia Plateau flood basalt province. From the measured crustal structure and subduction geometry, we identify two zones that may concentrate future seismic activity: (1) a broad (because of the shallow dip), possibly locked part of the interplate contact that extends from ???25 km depth beneath the coastline to perhaps as far west as the deformation front ???120 km offshore and (2) a crustal zone at the eastern boundary between the Siletz terrane and the Cascade Range.

  16. Diffuse CO2 emission from the NE volcanic rift-zone of Tenerife (Canary Islands, Spain): a 15 years geochemical monitoring

    NASA Astrophysics Data System (ADS)

    Padilla, Germán; Alonso, Mar; Shoemaker, Trevor; Loisel, Ariane; Padrón, Eleazar; Hernández, Pedro A.; Pérez, Nemesio M.

    2016-04-01

    The North East Rift (NER) volcanic zone of Tenerife Island is one of the three volcanic rift-zones of the island (210 km2). The most recent eruptive activity along the NER volcanic zone took place in the 1704-1705 period with the volcanic eruptions of Siete Fuentes, Fasnia and Arafo volcanoes. The aim of this study was to report the results of a soil CO2 efflux survey undertaken in June 2015, with approximately 580 measuring sites. In-situ measurements of CO2 efflux from the surface environment of NER volcanic zone were performed by means of a portable non-dispersive infrared spectrophotometer (NDIR) model LICOR Li800 following the accumulation chamber method. To quantify the total CO2 emission from NER volcanic zone, soil CO2 efflux contour maps were constructed using sequential Gaussian simulation (sGs) as interpolation method. The total diffuse CO2 emission rate was estimated in 1209 t d‑1, with CO2 efflux values ranging from non-detectable (˜0.5 g m‑2 d‑1) up to 123 g m‑2 d‑1, with an average value of 5.9 g m‑2 d‑1. If we compare these results with those obtained in previous surveys developed in a yearly basis, they reveal slightly variations from 2006 to 2015, with to pulses in the CO2 emission observed in 2007 and 2014. The main temporal variation in the total CO2 output does not seem to be masked by external variations. First peak precedes the anomalous seismicity registered in and around Tenerife Island between 2009 and 2011, suggesting stress-strain changes at depth as a possible cause for the observed changes in the total output of diffuse CO2 emission. Second peak could be related with futures changes in the seismicity. This study demonstrates the importance of performing soil CO2 efflux surveys as an effective surveillance volcanic tool.

  17. The Kohuamuri siliceous sinter as a vector for epithermal mineralisation, Coromandel Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Hamilton, Ayrton; Campbell, Kathleen; Rowland, Julie; Browne, Patrick

    2016-04-01

    The Kohuamuri siliceous sinter is the largest known fossil hot-spring system in the Hauraki Goldfield, a 200 × 40 km volcanic terrain with at least 50 adularia-illite epithermal deposits formed 16.3-5.6 Ma within the Coromandel Volcanic Zone, New Zealand. The sinter is associated with rhyolite and ignimbrite of the Whitianga Caldera (Miocene-Pliocene) and consists of two deposits, the Kohuamuri deposit itself, a large in situ outcrop (47,000 m2) and its associated sinter boulder field (4500 m2), and the Kaitoke deposit 900 m to the southwest, comprising boulders in a landslide situated on a normal fault. The well-preserved macroscopic and microscopic textures at Kohuamuri are similar to actively forming and ancient hot-spring deposits elsewhere, derived from deep circulating, magmatically heated, near-neutral pH alkali chloride fluids oversaturated in amorphous silica and that discharge at the Earth's surface at ≤100 °C. Lithofacies, petrography, mineralogy, as well as trace element concentrations of the Kohuamuri/Kaitoke deposits were used to locate likely palaeo-thermal conduits from the deep reservoir and to reconstruct the palaeoenvironmental setting of the siliceous sinter as an aid to assessing the economic potential of the ancient geothermal system. Both deposits contain the high-temperature (>75 °C) geyserite lithofacies, with the Kohuamuri deposit also exhibiting textures affiliated with cooler middle and distal sinter apron areas, as well as geothermally influenced marsh facies. Trace element analysis of sinter lithofacies revealed concentrations and zonations of Au, Ag, base metals (Pb, Cu, Zn) and pathfinder elements (As, Sb) associated with epithermal deposits, elevated in the proximal vent area, and providing evidence of possible Au and Ag ore mineralisation at depth. The methodology used in this study could be utilised globally to identify and assess as yet unidentified epithermal deposits.

  18. Electrical resistivity image of the upper crust within the Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Bibby, H. M.; Caldwell, T. G.; Risk, G. F.

    1998-05-01

    The Taupo Volcanic Zone (TVZ) forms a region of back-arc extension within the continental crust of New Zealand and is notable for its caldera volcanism, high rate of magmatic production, and high heat flow. On the eastern side of the TVZ, volcanism terminates abruptly along a linear margin. We present the interpretation of three multiple-source bipole-dipole resistivity surveys across this margin. The major features of the measured data can be reproduced by using two-dimensional models of the resistivity in the upper 10 km of the crust. Along the margin the high-resistivity graywacke basement (300 Ωm increasing to 1300 Ωm) is downfaulted to the west across a zone about 6 km wide, with a total vertical offset of approximately 2 km. The easternmost fault is overlain by an unbroken 0.24 Ma ignimbrite sheet, suggesting the fault has been inactive for this period. Further to the west, at depths greater than 2 km, a conductive zone about 15 km wide and of total conductance 180-280 S has been identified. This conductive zone can be modeled by using a range of resistivities (40-3 Ωm) and thicknesses (8-2 km). Models incorporating resistivities less than 15 Ωm require the low-resistivity zone to be wedge shaped, so that conductance increases to the west. The low resistivity is believed to be caused by the presence of clay alteration within volcanoclastic rocks. The large volume of volcanic rocks at depth can be linked to a series of caldera-forming eruptions that have taken place along the eastern side of the TVZ.

  19. Characteristics of Fault Zones in Volcanic Rocks Near Yucca Flat, Nevada Test Site, Nevada

    SciTech Connect

    Donald Sweetkind; Ronald M. Drake II

    2007-11-27

    During 2005 and 2006, the USGS conducted geological studies of fault zones at surface outcrops at the Nevada Test Site. The objectives of these studies were to characterize fault geometry, identify the presence of fault splays, and understand the width and internal architecture of fault zones. Geologic investigations were conducted at surface exposures in upland areas adjacent to Yucca Flat, a basin in the northeastern part of the Nevada Test Site; these data serve as control points for the interpretation of the subsurface data collected at Yucca Flat by other USGS scientists. Fault zones in volcanic rocks near Yucca Flat differ in character and width as a result of differences in the degree of welding and alteration of the protolith, and amount of fault offset. Fault-related damage zones tend to scale with fault offset; damage zones associated with large-offset faults (>100 m) are many tens of meters wide, whereas damage zones associated with smaller-offset faults are generally a only a meter or two wide. Zeolitically-altered tuff develops moderate-sized damage zones whereas vitric nonwelded, bedded and airfall tuff have very minor damage zones, often consisting of the fault zone itself as a deformation band, with minor fault effect to the surrounding rock mass. These differences in fault geometry and fault zone architecture in surface analog sites can serve as a guide toward interpretation of high-resolution subsurface geophysical results from Yucca Flat.

  20. Characteristics of Fault Zones in Volcanic Rocks Near Yucca Flat, Nevada Test Site, Nevada

    USGS Publications Warehouse

    Sweetkind, Donald S.; Drake II, Ronald M.

    2007-01-01

    During 2005 and 2006, the USGS conducted geological studies of fault zones at surface outcrops at the Nevada Test Site. The objectives of these studies were to characterize fault geometry, identify the presence of fault splays, and understand the width and internal architecture of fault zones. Geologic investigations were conducted at surface exposures in upland areas adjacent to Yucca Flat, a basin in the northeastern part of the Nevada Test Site; these data serve as control points for the interpretation of the subsurface data collected at Yucca Flat by other USGS scientists. Fault zones in volcanic rocks near Yucca Flat differ in character and width as a result of differences in the degree of welding and alteration of the protolith, and amount of fault offset. Fault-related damage zones tend to scale with fault offset; damage zones associated with large-offset faults (>100 m) are many tens of meters wide, whereas damage zones associated with smaller-offset faults are generally a only a meter or two wide. Zeolitically-altered tuff develops moderate-sized damage zones whereas vitric nonwelded, bedded and airfall tuff have very minor damage zones, often consisting of the fault zone itself as a deformation band, with minor fault effect to the surrounding rock mass. These differences in fault geometry and fault zone architecture in surface analog sites can serve as a guide toward interpretation of high-resolution subsurface geophysical results from Yucca Flat.

  1. Evolution of a dynamic paleo-hydrothermal system at Mangatete, Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Drake, Bryan D.; Campbell, Kathleen A.; Rowland, Julie V.; Guido, Diego M.; Browne, Patrick R. L.; Rae, Andrew

    2014-08-01

    Recent quarrying and active faulting at Mangatete, Taupo Volcanic Zone (TVZ), New Zealand, illuminate a rare spatial and temporal window on a dynamic Late Quaternary geothermal system. Detailed geological mapping, stratigraphic logging, AMS 14C dating, and textural and mineralogical analyses were used to construct a complex history of hydrothermal, volcanological and tectonic activity from ~ 36 to 2 ka. Extinct, surface hydrothermal manifestations occur over a ~ 2 km2 area, and include in situ siliceous sinters distributed on normal fault terraces, an inferred hydrothermal eruption breccia (HEB) containing acid-etched sinter blocks, another probable HEB that was bathed in silicifying thermal fluids, and sinter clasts that were entrained in a debris flow associated with a volcanic ash event. Preserved sinter textures typical of near-neutral pH, alkali chloride spring discharge channels, aprons, terraces and affiliated marshes comprise plant-rich, palisade, tufted bubble mat, and domal stromatolitic fabrics. In addition, a packed fragmental sinter facies is shown herein to constitute silicified microbial mats that were broken, transported and deposited as point bar deposits in thermal spring-fed streams. Moreover, four unusual siliceous sinter fabrics-vuggy, globular spongy, scalloped, and arcuate wavy layered-are interpreted to have formed from local acid-sulfate-chloride thermal springs, possibly associated with paleo-fumaroles. The reconstructed history of paleo-hydrothermal activity indicates that the oldest sinters (~ 36 ka) at Mangatete developed in alkali chloride hot springs, but then underwent post-depositional alterion/overprinting by acid-sulfate steam condensate and were dismembered, possibly by a hydrothermal eruption. Low pH hot-spring discharges forming the unusual, inferred acid sinter fabrics were localized in the same area. A shift in paleo-hydrology is evidenced by unaltered, alkali chloride sinters dated between ~ 22 and 3 ka. A cluster of sinter

  2. 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

  3. A geophysical survey of active volcanism in the Central and Southern Andes

    NASA Astrophysics Data System (ADS)

    Jay, Jennifer Ann

    The subduction of the Nazca plate beneath the South American plate results in great earthquakes and active volcanism along the Andean margin. The Central Volcanic Zone (CVZ) between 15°S and 28°S and the Southern Volcanic Zone (SVZ) between 33°S and 46°S are separated by a zone of flat slab subduction and differ significantly in the manifestation of current volcanic activity. The CVZ has been considered less hazardous due to the few number of historical volcanic eruptions compared to the SVZ, yet it contains the largest mid-crustal magma body on Earth and erupted at least 10,000 km 3 of ignimbrite in the Late Miocene (10-1 Ma). In this dissertation, I use InSAR (interferometric synthetic aperture radar), thermal remote sensing, and seismology to investigate active volcanism in the Central and Southern Andes. InSAR and thermal remote sensing provide synoptic coverage along the volcanic arc, and seismic experiments allow further examination of selected volcanoes. I establish the first catalog of seismicity at Uturuncu volcano in Bolivia, where InSAR has observed continuous uplift since 1992, and find an unusually high seismicity rate for a Pleistocene volcano as well as swarm activity and triggered earthquakes. I then conduct a survey using satellite thermal infrared data to detect thermal hotspots related to volcanic activity throughout the CVZ and SVZ. I find hotspots at many volcanoes that had not previously been documented, with the CVZ containing more volcanoes with hotspots than the SVZ. One of the most thermally active volcanoes in the SVZ, Cordon Caulle volcano, experienced a large rhyodacitic eruption from 2011-2012. I use InSAR and petrology to model the pre-eruptive conditions at depth and co-eruptive processes and find that a large, long-lived crustal magma reservoir must be present beneath Cordon Caulle. Finally, I carry out an InSAR survey of volcanoes in southern Peru, completing a regional study of volcano deformation in the CVZ and allowing for a

  4. Crustal deformation and volcanism at active plate boundaries

    NASA Astrophysics Data System (ADS)

    Geirsson, Halldor

    Most of Earth's volcanoes are located near active tectonic plate boundaries, where the tectonic plates move relative to each other resulting in deformation. Likewise, subsurface magma movement and pressure changes in magmatic systems can cause measurable deformation of the Earth's surface. The study of the shape of Earth and therefore studies of surface deformation is called geodesy. Modern geodetic techniques allow precise measurements (˜1 mm accuracy) of deformation of tectonic and magmatic systems. Because of the spatial correlation between tectonic boundaries and volcanism, the tectonic and volcanic deformation signals can become intertwined. Thus it is often important to study both tectonic and volcanic deformation processes simultaneously, when one is trying to study one of the systems individually. In this thesis, I present research on crustal deformation and magmatic processes at active plate boundaries. The study areas cover divergent and transform plate boundaries in south Iceland and convergent and transform plate boundaries in Central America, specifically Nicaragua and El Salvador. The study is composed of four main chapters: two of the chapters focus on the magma plumbing system of Hekla volcano, Iceland and the plate boundary in south Iceland; one chapter focuses on shallow controls of explosive volcanism at Telica volcano, Nicaragua; and the fourth chapter focuses on co- and post-seismic deformation from a Mw = 7.3 earthquake which occurred offshore El Salvador in 2012. Hekla volcano is located at the intersection of a transform zone and a rift zone in Iceland and thus is affected by a combination of shear and extensional strains, in addition to co-seismic and co-rifting deformation. The inter-eruptive deformation signal from Hekla is subtle, as observed by a decade (2000-2010) of GPS data in south Iceland. A simultaneous inversion of this data for parameters describing the geometry and source characteristics of the magma chamber at Hekla, and

  5. Rapid uplift in Laguna del Maule volcanic field of the Andean Southern Volcanic Zone (Chile) measured by satellite radar interferometry

    NASA Astrophysics Data System (ADS)

    Feigl, K.; Ali, T.; Singer, B. S.; Pesicek, J. D.; Thurber, C. H.; Jicha, B. R.; Lara, L. E.; Hildreth, E. W.; Fierstein, J.; Williams-Jones, G.; Unsworth, M. J.; Keranen, K. M.

    2011-12-01

    The Laguna del Maule (LdM) volcanic field of the Andean Southern Volcanic Zone extends over 500 square kilometers and comprises more than 130 individual vents. As described by Hildreth et al. (2010), the history has been defined from sixty-eight Ar/Ar and K-Ar dates. Silicic eruptions have occurred throughout the past 3.7 Ma, including welded ignimbrite associated with caldera formation at 950 ka, small rhyolitic eruptions between 336 and 38 ka, and a culminating ring of 36 post-glacial rhyodacite and rhyolite coulees and domes that encircle the lake. Dating of five post-glacial flows implies that these silicic eruptions occurred within the last 25 kyr. Field relations indicate that initial eruptions comprised modest volumes of mafic rhyodacite magma that were followed by larger volumes of high silica rhyolite. The post-glacial flare-up of silicic magmatism from vents distributed around the lake, is unprecedented in the history of this volcanic field. Using satellite radar interferometry (InSAR), Fournier et al. (2010) measured uplift at a rate of more than 180 mm/year between 2007 and 2008 in a round pattern centered on the west side of LdM. More recent InSAR observations suggest that rapid uplift has continued from 2008 through early 2011. In contrast, Fournier et al. found no measurable deformation in an interferogram spanning 2003 through 2004. In this study, we model the deformation field using the General Inversion of Phase Technique (GIPhT), as described by Feigl and Thurber (2009). Two different models fit the data. The first model assumes a sill at ~5 km depth has been inflating at a rate of more than 20 million cubic meters per year since 2007. The second model assumes that the water level in the lake dropped at a rate of 20 m/yr from January 2007 through February 2010, thus reducing the load on an elastic simulation of the crust. The rate of intrusion inferred from InSAR is an order of magnitude higher than the average rate derived from well-dated arc

  6. Recent volcanic activity on Venus - Evidence from radiothermal emissivity measurements

    NASA Astrophysics Data System (ADS)

    Robinson, C. A.; Wood, J. A.

    1993-03-01

    Radiothermal emissivity measurements are analyzed in order to study large volcanic constructs on Venus and to correlate details of the reflectivity/emissivity patterns with geological landforms and stratigraphy visible in corresponding SAR images. There appears to be a correlation between locations on Venus where high emissivity at high altitudes and low emissivity at low altitudes are observed. These phenomena are attributed here to relatively recent volcanic activity: the former to summit eruptions that have not had time to weather to the low-emissivity state, the latter to continuing emission of volcanic gases from neighboring small plains volcanoes. The pattern of reflectivity and emissivity on Maat Mons is examined in the light of these findings. It is concluded that Maat Mons has undergone the most recent episode of volcanic activity of all the volcanoes studied here.

  7. Recent volcanic activity on Venus - Evidence from radiothermal emissivity measurements

    NASA Technical Reports Server (NTRS)

    Robinson, Cordula A.; Wood, John A.

    1993-01-01

    Radiothermal emissivity measurements are analyzed in order to study large volcanic constructs on Venus and to correlate details of the reflectivity/emissivity patterns with geological landforms and stratigraphy visible in corresponding SAR images. There appears to be a correlation between locations on Venus where high emissivity at high altitudes and low emissivity at low altitudes are observed. These phenomena are attributed here to relatively recent volcanic activity: the former to summit eruptions that have not had time to weather to the low-emissivity state, the latter to continuing emission of volcanic gases from neighboring small plains volcanoes. The pattern of reflectivity and emissivity on Maat Mons is examined in the light of these findings. It is concluded that Maat Mons has undergone the most recent episode of volcanic activity of all the volcanoes studied here.

  8. Rapid uplift in Laguna del Maule volcanic field of the Andean Southern Volcanic zone (Chile) 2007-2012

    NASA Astrophysics Data System (ADS)

    Feigl, Kurt L.; Le Mével, Hélène; Tabrez Ali, S.; Córdova, Loreto; Andersen, Nathan L.; DeMets, Charles; Singer, Bradley S.

    2014-02-01

    The Laguna del Maule (LdM) volcanic field in Chile is an exceptional example of postglacial rhyolitic volcanism in the Southern Volcanic Zone of the Andes. By interferometric analysis of synthetic aperture radar (SAR) images acquired between 2007 and 2012, we measure exceptionally rapid deformation. The maximum vertical velocity exceeds 280 mm yr-1. Although the rate of deformation was negligible from 2003 January to 2004 February, it accelerated some time before 2007 January. Statistical testing rejects, with 95 per cent confidence, four hypotheses of artefacts caused by tropospheric gradients, ionospheric effects, orbital errors or topographic relief, respectively. The high rate of deformation is confirmed by daily estimates of position during several months in 2012, as measured by analysis of signals transmitted by the Global Positioning System (GPS) and received on the ground at three stations around the reservoir forming the LdM. The fastest-moving GPS station (MAU2) has a velocity vector of [-180 ± 4, 46 ± 2, 280 ± 4] mm yr-1 for the northward, eastward and upward components, respectively, with respect to the stable interior of the South America Plate. The observed deformation cannot be explained by changes in the gravitational load caused by variations in the water level in the reservoir. For the most recent observation time interval, spanning 44 d in early 2012, the model that best fits the InSAR observations involves an inflating sill at a depth of 5.2 ± 0.3 km, with length 9.0 ± 0.3 km, width 5.3 ± 0.4 km, dip 20 ± 3° from horizontal and strike 14 ± 5° clockwise from north, assuming a rectangular dislocation in a half-space with uniform elastic properties. During this time interval, the estimated rate of tensile opening is 1.1 ± 0.04 m yr-1, such that the rate of volume increase in the modelled sill is 51 ± 5 million m3 yr-1 or 1.6 ± 0.2 m3 s-1. From 2004 January to 2012 April the total increase in volume was at least 0.15 km3 over the 5.2-yr

  9. Style of Plate Spreading Derived from the 2008-2014 Velocity Field Across the Northern Volcanic Zone of Iceland

    NASA Astrophysics Data System (ADS)

    Drouin, V.; Sigmundsson, F.; Hreinsdottir, S.; Ofeigsson, B.; Sturkell, E.; Einarsson, P.

    2015-12-01

    The Northern Volcanic Zone (NVZ) of Iceland is a subaerial part of the divergent boundary between the North-American and Eurasian Plates. At this latitude, the full spreading between the plates is accommodated by the NVZ. We derived the plate boundary velocity field from GPS campaign and continuous measurements between 2008 and 2014, a time period free of any magma intrusion. Average velocities were estimated in the ITRF08 reference frame. The overall extension is consistent with 18 mm/yr in the 104°N direction spreading, in accordance with the MORVEL2010 plate motion model. We find that a 40km-wide band along the plate boundary accommodates about 75% of the full plate velocities. Within this zone, the average strain rate is approximately 0.35 μstrain/yr. The deformation field and the strain rate are, however, much affected by other sources of deformations in the NVZ. These include magmatic sources at the most active volcanic centers, glacial rebound near the ice-caps and geothermal power-plant water extraction. Magmatic sources include a shallow magma chamber deflation under Askja caldera, as well as under Þeistareykir and eventual deep magma inflation north of Krafla volcano. Vatnajökull ice cap melting causes large uplift and outward displacements in the southern part of the NVZ. The two geothermal power-plants near Krafla are inducing local deflations. Our GPS velocities show a 35° change in the direction of the plate boundary axis north of Askja volcano that we infer to be linked to the geometric arrangement of volcanic systems within the NVZ.We use a simple arctangent model to describe the plate spreading to provide constraints on the location and the locking depth of the spreading axis. For that purpose we divided the area in short overlapping segments having the same amount of GPS points along the plate spreading direction and inverted for the location of the center of the spreading axis and locking depth. With this simple model we can account for most

  10. Kinematically - controlled deep contact of the East European Platform and the Carpathian Orogen in the Vrancea Bending Zone and contact with the Neogene Volcanic Zone

    NASA Astrophysics Data System (ADS)

    Dragut, Dorina-Alina

    2016-04-01

    The complex zone between the Moesian and East European platforms to the south and east and the Southern Europe continental units were amalgamated in the last 20 million years in an intricate dynamics of what was thought to be the eastern component of the Alpine Tethys. By seismic tomography and attenuation studies, a high velocity body extended from the near surface to deeper levels than 300 km was pointed out as having a very complex geometry which suggests a very active three dimensional evolution. Most of the frequent, persistent and clustered seismic events from this contact area known as Vrancea Seismogenic Zone are located into this high velocity body. The origin of this seismicity is highly controversial. Among most of the accepted assumptions on its origins, two look like most robust: (a) the recent studies consider the subduction of the Tehys oceanic lithosphere, and (b) delamination of a portion of the East European / Moesian continental mantle after the oceanic lithosphere subduction ended sometimes in the mid-Miocene. The delamination zone was probably a near-horizontal mid-lithospheric interface dripping down into the mantle. Towards the internal part of the Bend Zone, the volcanic activity, dominant in the Neogene time, ceased some 400,000 years ago but there are evidences that the last stages of the alkali-basaltic volcanic activity has post-volcanic effects even at present. We integrate satellite geodesy results with various seismological studies in order to explain the very small values of the present-day horizontal component of the velocity field, almost at the edge of technological detectability. The vectors have a very peculiar distribution which we interpret as supporting the idea of the mantle flow around the high seismic velocity body detected via seismological investigations. We estimate an anti-clockwise deep rotation flow around the lithospheric "slab" which is seated adjacent to the astensosphere advancing towards the surface, having

  11. Monitoring the NW volcanic rift-zone of Tenerife, Canary Islands, Spain: sixteen years of diffuse CO_{2} degassing surveys

    NASA Astrophysics Data System (ADS)

    Rodríguez, Fátima; Halliwell, Simon; Butters, Damaris; Padilla, Germán; Padrón, Eleazar; Hernández, Pedro A.; Pérez, Nemesio M.

    2016-04-01

    Tenerife is the largest of the Canary Islands and, together with Gran Canaria, is the only one that has developed a central volcanic complex characterized by the eruption of differentiated magmas. At present, one of the most active volcanic structures in Tenerife is the North-West Rift-Zone (NWRZ), which has hosted two historical eruptions: Arenas Negras in 1706 and Chinyero in 1909. Since the year 2000, 47 soil CO2 efflux surveys have been undertaken at the NWRZ of Tenerife Island to evaluate the temporal and spatial variations of CO2 efflux and their relationships with the volcanic-seismic activity. We report herein the last results of diffuse CO2 efflux survey at the NWRZ carried out in July 2015 to constrain the total CO2 output from the studied area. Measurements were performed in accordance with the accumulation chamber method. Spatial distribution maps were constructed following the sequential Gaussian simulation (sGs) procedure. During 2015 survey, soil CO2 efflux values ranged from non-detectable up to 103 g m‑2 d‑1. The total diffuse CO2 output released to atmosphere was estimated at 403 ± 17 t d‑1, values higher than the background CO2 emission estimated on 143 t d‑1. For all campaigns, soil CO2 efflux values ranged from non-detectable up to 141 g m‑2 d‑1, with the highest values measured in May 2005. Total CO2 output from the studied area ranged between 52 and 867 t d‑1. Temporal variations in the total CO2 output showed a temporal correlation with the onsets of seismic activity, supporting unrest of the volcanic system, as is also suggested by anomalous seismic activity recorded in the area during April 22-29, 2004. Spatial distribution of soil CO2 efflux values also showed changes in magnitude and amplitude, with higher CO2 efflux values located along a trending WNW-ESE area. Subsurface magma movement is proposed as a cause for the observed changes in the total output of diffuse CO2 emission, as well as for the spatial distribution of

  12. The Reporoa Caldera, Taupo Volcanic Zone: source of the Kaingaroa Ignimbrites

    USGS Publications Warehouse

    Nairn, I.A.; Wood, C.P.; Bailey, R.A.

    1994-01-01

    The Reporoa Caldera occupies the northern end of the Reporoa Depression, previously described as a tectonic fault-angle depression. Earlier confirmation of the topographic basin as a caldera had been hindered by the lack of an associated young pyroclastic flow deposit of large enough volume to have caused caldera collapse. New exposures on the eastern margin of the Reporoa basin reveal thick lithic lag breccias (>30 m) interbedded within the 0.24 Ma Kaingaroa Ignimbrites. These ignimbrites were previously attributed to the adjacent Okataina Volcanic Centre. Lag breccia thicknesses and maximum clast sizes decrease rapidly outward from the caldera rim, and discrete breccias are absent from ignimbrite sections more than 3 km from the rim. The lithic lag breccias, together with structural and geophysical evidence, confirm Reporoa Caldera as the source of the c. 100 km3 Kaingaroa Ignimbrites, adding another major rhyolitic volcanic centre to the seven previously recognized in the Taupo Volcanic Zone. Other, older, calderas may also be present in the Reporoa Depression. ?? 1994 Springer-Verlag.

  13. Radon (222Rn) in groundwater studies in two volcanic zones of central Mexico

    NASA Astrophysics Data System (ADS)

    Cortés, A.; Cardona, A.; Pérez-Quezadas, J.; Inguaggiato, S.; Vázquez-López, C.; Golzarri, J. I.; Espinosa, G.

    2013-07-01

    The distribution of radon (222Rn) concentrations in groundwater from two basins of volcanic origin is presented. Regions have different physiographic characteristics with fractured mafic/intermediate and felsic rocks. Samples were taken from deep wells and springs. Concentrations were field measured by two methods: i) scintillator, coupled to a photomultiplier, and ii) passive method, using Nuclear Track Detectors. Qualitatively, results of 222Rn measured with both techniques are comparable only when concentrations have values less than 1 Bq/l. For the Basin of Mexico City the data shows an average difference of 0.13 Bq/l. Results of 222Rn concentrations in 46 groundwater samples indicate that the data are below 11.1 Bq/l, with both methodologies. Low concentrations of 222Rn in the Basin of Mexico City are related to the mafic intermediate composition rocks such as basalt. The anomalies with high values are correlated with the transition zone between volcanic units and clays from ancient lakes. In San Luis Potosí 10 samples show an average of 4.2 Bq/l. These concentrations compared with those of the Basin of Mexico City are related to the composition of the felsic (rhyolite) volcanic rocks.

  14. The recent seismo-volcanic activity at Deception Island volcano

    NASA Astrophysics Data System (ADS)

    Ibáñez, Jesús M.; Almendros, Javier; Carmona, Enrique; Martínez-Arévalo, Carmen; Abril, Miguel

    2003-06-01

    This paper reviews the recent seismic studies carried out at Deception Island, South Shetland Islands, Antarctica, which was monitored by the Argentinean and Spanish Antarctic Programs since 1986. Several types of seismic network have been deployed temporarily during each Antarctic summer. These networks have consisted of a variety of instruments, including radio-telemetered stations, autonomous digital seismic stations, broadband seismometers, and seismic arrays. We have identified two main types of seismic signals generated by the volcano, namely pure seismo-volcanic signals, such as volcanic tremor and long-period (LP) events, and volcano-tectonic (VT) earthquakes. Their temporal distributions are far from homogeneous. Volcanic tremors and LP events usually occur in seismic swarms lasting from a few hours to some days. The number of LP events in these swarms is highly variable, from a background level of less than 30/day to a peak activity of about 100 events/h. The occurrence of VT earthquakes is even more irregular. Most VT earthquakes at Deception Island have been recorded during two intense seismic crises, in 1992 and 1999, respectively. Some of these VT earthquakes were large enough to be felt by researchers working on the island. Analyses of both types of seismic events have allowed us to derive source locations, establish seismic source models, analyze seismic attenuation, calculate the energy and stress drop of the seismic sources, and relate the occurrence of seismicity to the volcanic activity. Pure seismo-volcanic signals are modelled as the consequence of hydrothermal interactions between a shallow aquifer and deeper hot materials, resulting in the resonance of fluid-filled fractures. VT earthquakes constitute the brittle response to changes in the distribution of stress in the volcanic edifice. The two VT seismic series are probably related to uplift episodes due to deep injections of magma that did not reach the surface. This evidence, however

  15. Ancient Tectonic and Volcanic Activity in the Tharsis Region

    NASA Astrophysics Data System (ADS)

    Werner, S. C.; Kronberg, P.; Hauber, E.; Grott, M.; Steinberger, B.; Torsvik, T. H.; Neukum, G.

    The two topographically dominating volcanic provinces on Mars are the Tharsis and the Elysium regions, situated close to the equator on the dichotomy boundary between the heavily cratered (older) highlands and the northern lowlands (about 100 degrees apart). The regions are characterized by volcanoes whose morphologies are analogous to volcanic landforms on Earth, and the huge volcanoes in the Tharsis region (Olympus Mons and Tharsis Montes) are prime examples resembling many characteristics of Hawaiian shield volcanoes. The main difference between the Martian and terrestrial volcanoes are their size and the length of the flows, possibly due to higher eruption rates, the "stationary" character of the source (no plate tectonics) and the lower gravity. The Tharsis plateau is the topographically most prominent region on Mars, and associated with an areoid high. On Earth, large geoid highs are related to longlived heterogeneities near the core-mantle boundary that are sources for large igneous provinces. The Tharsis' volcanic vent structures were active at least episodically over the past 4 billion years (based on crater count statistics), which indicates long-lived volcanic and magmatic activity. Two major groups of tectonic features are related to the Tharsis bulge: a concentric set of wrinkle ridges indicating compression radial to Tharsis,and several sets of extensional structures that radiate outward from different centers within Tharsis, indicating tension circumferential to Tharsis. No landforms imply ancient plate tectonics. Here, we present surface ages associated with volcanic and tectonic landforms with a special focus on the ancient magma-tectonic environment (see Grott et al. 2006, this volume). We will examine the long-lived volcanism and tectonic surface expressions and discuss whether Mars volcanism could represent deep mantle plumes.

  16. Impact of the Orozco Fracture Zone on the central Mexican Volcanic Belt

    NASA Astrophysics Data System (ADS)

    Hammersley, L. C.; Blatter, D. L.

    2009-12-01

    We present a compilation of available geochemical data and new XRF major and trace element analyses of laves erupted adjacent to the Tzitzio Gap (TG), a prominent indentation in the central Mexican Volcanic Belt (MVB). In this region, centered at 101oW, Quaternary volcanism is displaced approximately 100 km toward the back of the arc. This embayment in the volcanic front is roughly aligned with the projected position of the Orozco Fracture Zone (OFZ), which separates segments of the Cocos Plate that differ in age by approximately 5 million years. The fracturing of the oceanic lithosphere associated with the OFZ appears to have caused alteration and increased the buoyancy of this ~100 km wide linear feature. Several indicators of the buoyancy of the OFZ have been reported, including shallowing of the Middle America Trench (MAT), seaward advancement of the shoreline, and the uplift and exposure of deeply buried and deformed Jurassic to Oligocene rocks that comprise the TG region. Arc volcanism in the regions surrounding the TG provides constraints on the subduction of the OFZ. In the central MVB, enrichment in fluid mobile elements such as Ba, Sr, P2O5, Pb and K2O typically decreases with distance from the Middle America Trench, consistent with progressive dehydration of the downgoing slab. Numerous studies in the central MVB have demonstrated that this fluid-mobile element enriched signature results from flux-induced melting at the front of the arc, while decompression melting of asthenospheric mantle peridotite is dominant at the back of the arc. Our data show that volcanism behind the TG exhibits an anomalous fluid signature (high K2O, P2O5, Ba, and Pb), more commonly associated with the front of the MVB, superimposed on compositions similar to those from extensional regions in northern Mexico. We propose that these distinctive structural and geochemical characteristics arise from subduction of the OFZ. Increased buoyancy of the fracture zone may cause it to

  17. Regional Triggering of Volcanic Activity Following Large Magnitude Earthquakes

    NASA Astrophysics Data System (ADS)

    Hill-Butler, Charley; Blackett, Matthew; Wright, Robert

    2015-04-01

    There are numerous reports of a spatial and temporal link between volcanic activity and high magnitude seismic events. In fact, since 1950, all large magnitude earthquakes have been followed by volcanic eruptions in the following year - 1952 Kamchatka M9.2, 1960 Chile M9.5, 1964 Alaska M9.2, 2004 & 2005 Sumatra-Andaman M9.3 & M8.7 and 2011 Japan M9.0. While at a global scale, 56% of all large earthquakes (M≥8.0) in the 21st century were followed by increases in thermal activity. The most significant change in volcanic activity occurred between December 2004 and April 2005 following the M9.1 December 2004 earthquake after which new eruptions were detected at 10 volcanoes and global volcanic flux doubled over 52 days (Hill-Butler et al. 2014). The ability to determine a volcano's activity or 'response', however, has resulted in a number of disparities with <50% of all volcanoes being monitored by ground-based instruments. The advent of satellite remote sensing for volcanology has, therefore, provided researchers with an opportunity to quantify the timing, magnitude and character of volcanic events. Using data acquired from the MODVOLC algorithm, this research examines a globally comparable database of satellite-derived radiant flux alongside USGS NEIC data to identify changes in volcanic activity following an earthquake, February 2000 - December 2012. Using an estimate of background temperature obtained from the MODIS Land Surface Temperature (LST) product (Wright et al. 2014), thermal radiance was converted to radiant flux following the method of Kaufman et al. (1998). The resulting heat flux inventory was then compared to all seismic events (M≥6.0) within 1000 km of each volcano to evaluate if changes in volcanic heat flux correlate with regional earthquakes. This presentation will first identify relationships at the temporal and spatial scale, more complex relationships obtained by machine learning algorithms will then be examined to establish favourable

  18. The Extremes of Volcanic Activity: Earth and Jupiter's Moon Io

    NASA Astrophysics Data System (ADS)

    Lowes, L. L.; Lopes, R.

    2004-12-01

    Jupiter's moon Io is the solar system's most volcanically active body, and the only place that magmatic volcanic eruptions have been observed beyond Earth. One of the first images of Io obtained by NASA's Voyager 1 spacecraft in 1979 shows a plume above one of its volcanoes. The NASA Voyager and Galileo spacecraft imaged many explosive eruptions of plumes and deposits - which travel hundreds of kilometers (farther than on the Earth or the Moon). Very hot lavas that are erupting from volcanic vents on Io may be similar to lavas that erupted on Earth billions of years ago. Understanding the physical processes driving volcanic eruptions is important for the understanding of terrestrial volcanoes, not only because of their potential hazards, but also as geologic resources, biologic environments, and for their role in shaping the surface of Earth and other planets. Volcanic eruptions are perhaps the most dramatic events on Earth, and are of intrinsic interest to students, youth, and adults. Topics involving volcanoes are a part of the national science education benchmarks for understanding the Earth's composition and structure for grades 6-8 (the process of creating landforms) and grades 9-12 (the effects of movement of crustal plates). Natural events on Earth coupled with exciting discoveries in space can serve to heighten the awareness of these phenomena and provide learning opportunities for real world applications of science. Educational applications for youth to compare volcanic activity on Io and Earth have been done through NASA-sponsored field trip workshops to places such as Yellowstone National Park (allowing educators to experience environments similar to those on other worlds), targeted classroom and hands-on activities, special interest books, and other resources. A sampling of such activities will be presented, and discussion invited on other related developmentally appropriate resources and activities.

  19. Classifying Volcanic Activity Using an Empirical Decision Making Algorithm

    NASA Astrophysics Data System (ADS)

    Junek, W. N.; Jones, W. L.; Woods, M. T.

    2012-12-01

    Detection and classification of developing volcanic activity is vital to eruption forecasting. Timely information regarding an impending eruption would aid civil authorities in determining the proper response to a developing crisis. In this presentation, volcanic activity is characterized using an event tree classifier and a suite of empirical statistical models derived through logistic regression. Forecasts are reported in terms of the United States Geological Survey (USGS) volcano alert level system. The algorithm employs multidisciplinary data (e.g., seismic, GPS, InSAR) acquired by various volcano monitoring systems and source modeling information to forecast the likelihood that an eruption, with a volcanic explosivity index (VEI) > 1, will occur within a quantitatively constrained area. Logistic models are constructed from a sparse and geographically diverse dataset assembled from a collection of historic volcanic unrest episodes. Bootstrapping techniques are applied to the training data to allow for the estimation of robust logistic model coefficients. Cross validation produced a series of receiver operating characteristic (ROC) curves with areas ranging between 0.78-0.81, which indicates the algorithm has good predictive capabilities. The ROC curves also allowed for the determination of a false positive rate and optimum detection for each stage of the algorithm. Forecasts for historic volcanic unrest episodes in North America and Iceland were computed and are consistent with the actual outcome of the events.

  20. Explosive Volcanic Activity at Extreme Depths: Evidence from the Charles Darwin Volcanic Field, Cape Verdes

    NASA Astrophysics Data System (ADS)

    Kwasnitschka, T.; Devey, C. W.; Hansteen, T. H.; Freundt, A.; Kutterolf, S.

    2013-12-01

    Volcanic eruptions on the deep sea floor have traditionally been assumed to be non-explosive as the high-pressure environment should greatly inhibit steam-driven explosions. Nevertheless, occasional evidence both from (generally slow-) spreading axes and intraplate seamounts has hinted at explosive activity at large water depths. Here we present evidence from a submarine field of volcanic cones and pit craters called Charles Darwin Volcanic Field located at about 3600 m depth on the lower southwestern slope of the Cape Verdean Island of Santo Antão. We examined two of these submarine volcanic edifices (Tambor and Kolá), each featuring a pit crater of 1 km diameter, using photogrammetric reconstructions derived from ROV-based imaging followed by 3D quantification using a novel remote sensing workflow, aided by sampling. The measured and calculated parameters of physical volcanology derived from the 3D model allow us, for the first time, to make quantitative statements about volcanic processes on the deep seafloor similar to those generated from land-based field observations. Tambor cone, which is 2500 m wide and 250 m high, consists of dense, probably monogenetic medium to coarse-grained volcaniclastic and pyroclastic rocks that are highly fragmented, probably as a result of thermal and viscous granulation upon contact with seawater during several consecutive cycles of activity. Tangential joints in the outcrops indicate subsidence of the crater floor after primary emplacement. Kolá crater, which is 1000 m wide and 160 m deep, appears to have been excavated in the surrounding seafloor and shows stepwise sagging features interpreted as ring fractures on the inner flanks. Lithologically, it is made up of a complicated succession of highly fragmented deposits, including spheroidal juvenile lapilli, likely formed by spray granulation. It resembles a maar-type deposit found on land. The eruption apparently entrained blocks of MORB-type gabbroic country rocks with

  1. Crustal structure, heat flux and mass transfer within a continental back-arc basin: Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Stern, T. A.; Benson, A.; Greve, A.

    2012-12-01

    New seismic crustal structure data combined with gravity analysis provide constraints on mass and heat transfer processes in a continental back-arc basin. A recent high resolution seismic refraction, wide-angle experiment across the Taupo Volcanic Zone (TVZ), New Zealand, shows the lower crust is dominated by a ~ 10 km thick, lozenge-shaped body with seismic P-wave velocities of 6.8-7.1 km/s. Seismic reflections define the top and bottom surface of the body at depths of ~ 15 and 25 km, respectively. This "rift-pillow" we interpret as a mafic under-plate that will be in various stages of cooling. Heat fluxes from the TVZ at a rate of about 4GW, and the area is extending at a rate of 10-16 mm/y. To sustain 4GW in steady state for this extension rate requires the continuous intrusion, then cooling, of a molten -layer about 10-15 km thick. Thus the rift pillow is likely to be the main source of heat and rhyolite volcanism that dominates the surface processes within the TVZ. On the southeastern margin of the TVZ lies the active volcanic arc of andesite and dacitic volcanoes. Directly beneath the arc at a depth of ~ 32 km we detect a bright seismic reflection of limited lateral extent (~ 18 km wide). The relative amplitude and negative phase of this reflection suggests a melt body of unknown thickness. We relate this melt body to corner of an upwelling of the mantle asthenosphere, which feeds the primary melts into the active volcanic arc, and also may supply melt to rift pillow structure in the central TVZ. Gravity anomalies across the central North Island are dominated by a long wavelength signal related to subduction. We remove this regional effect with 2-way, third-order polynomial to leave a residual that is largely due to the rifting process in the back arc basin. The residual signal has a classical rift signature of a central low of -55 mgals and gravity highs of about +10 mgals over the flanks of the TVZ. Using the detailed seismic data as a constraint we account

  2. Evolution of a dynamic paleo-hydrothermal system at Mangatete, Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Drake, Bryan D.; Campbell, Kathleen A.; Rowland, Julie V.; Guido, Diego M.; Browne, Patrick R. L.; Rae, Andrew

    2014-08-01

    Recent quarrying and active faulting at Mangatete, Taupo Volcanic Zone (TVZ), New Zealand, illuminate a rare spatial and temporal window on a dynamic Late Quaternary geothermal system. Detailed geological mapping, stratigraphic logging, AMS 14C dating, and textural and mineralogical analyses were used to construct a complex history of hydrothermal, volcanological and tectonic activity from ~ 36 to 2 ka. Extinct, surface hydrothermal manifestations occur over a ~ 2 km2 area, and include in situ siliceous sinters distributed on normal fault terraces, an inferred hydrothermal eruption breccia (HEB) containing acid-etched sinter blocks, another probable HEB that was bathed in silicifying thermal fluids, and sinter clasts that were entrained in a debris flow associated with a volcanic ash event. Preserved sinter textures typical of near-neutral pH, alkali chloride spring discharge channels, aprons, terraces and affiliated marshes comprise plant-rich, palisade, tufted bubble mat, and domal stromatolitic fabrics. In addition, a packed fragmental sinter facies is shown herein to constitute silicified microbial mats that were broken, transported and deposited as point bar deposits in thermal spring-fed streams. Moreover, four unusual siliceous sinter fabrics-vuggy, globular spongy, scalloped, and arcuate wavy layered-are interpreted to have formed from local acid-sulfate-chloride thermal springs, possibly associated with paleo-fumaroles. The reconstructed history of paleo-hydrothermal activity indicates that the oldest sinters (~ 36 ka) at Mangatete developed in alkali chloride hot springs, but then underwent post-depositional alterion/overprinting by acid-sulfate steam condensate and were dismembered, possibly by a hydrothermal eruption. Low pH hot-spring discharges forming the unusual, inferred acid sinter fabrics were localized in the same area. A shift in paleo-hydrology is evidenced by unaltered, alkali chloride sinters dated between ~ 22 and 3 ka. A cluster of sinter

  3. Late Cenozoic calc-alkaline volcanism over the Payenia shallow subduction zone, South-Central Andean back-arc (34°30‧-37°S), Argentina

    NASA Astrophysics Data System (ADS)

    Litvak, Vanesa D.; Spagnuolo, Mauro G.; Folguera, Andrés; Poma, Stella; Jones, Rosemary E.; Ramos, Víctor A.

    2015-12-01

    A series of mesosilicic volcanic centers have been studied on the San Rafael Block (SRB), 300 km to the east of the present-day volcanic arc. K-Ar ages indicate that this magmatic activity was developed in at least two stages: the older volcanic centers (˜15-10 Ma) are located in the central and westernmost part of the SRB (around 36°S and 69°W) and the younger centers (8-3.5 Ma) are located in an eastern position (around 36°S and 69°30‧W) with respect to the older group. These volcanic rocks have andesitic to dacitic compositions and correspond to a high-K calc-alkaline sequence as shown by their SiO2, K2O and FeO/MgO contents. Elevated Ba/La, Ba/Ta and La/Ta ratios show an arc-like signature, and primitive mantle normalized trace element diagrams show typical depletions of high field strength elements (HFSE) relative to large ion lithophile elements (LILE). Rare earth element (REE) patterns suggest pyroxene and amphibole crystallization. Geochemical data obtained for SRB volcanic rocks support the proposal for a shallow subduction zone for the latest Miocene between 34°30″-37°S. Regionally, SRB volcanism is associated with a mid-Miocene to early Pliocene eastward arc migration caused by the shallowing of the subducting slab in the South-Central Andes at these latitudes, which represents the evolution of the Payenia shallow subduction segment. Overall, middle Miocene to early Pliocene volcanism located in the Payenia back-arc shows evidence for the influence of slab-related components. The younger (8-3.5 Ma) San Rafael volcanic rocks indicate the maximum slab shallowing and the easternmost extent of slab influence in the back-arc.

  4. Multidimensional analysis and probabilistic model of volcanic and seismic activities

    NASA Astrophysics Data System (ADS)

    Fedorov, V.

    2009-04-01

    A search for space and time regularities in volcanic and seismic events for the purpose of forecast method development seems to be of current concern, both scientifically and practically. The seismic and volcanic processes take place in the Earth's field of gravity which in turn is closely related to gravitational fields of the Moon, the Sun, and the planets of the Solar System. It is mostly gravity and tidal forces that exercise control over the Earth's configuration and relief. Dynamic gravitational interaction between the Earth and other celestial bodies makes itself evident in tidal phenomena and other effects in the geospheres (including the Earth's crust). Dynamics of the tidal and attractive forces is responsible for periodical changes in gravity force, both in value and direction [Darwin, 1965], in the rate of rotation and orbital speed; that implies related changes in the endogenic activity of the Earth. The Earth's rotation in the alternating gravitational field accounts to a considerable extent for regular pattern of crustal deformations and dislocations; it is among principal factors that control the Earth's form and structure, distribution of oceans and continents and, probably, continental drift [Peive, 1969; Khain, 1973; Kosygin, 1983]. The energy of gravitational interaction is transmitted through the tidal energy to planetary spheres and feeds various processes there, including volcanic and seismic ones. To determine degree, character and special features of tidal force contribution to the volcanic and seismic processes is of primary importance for understanding of genetic and dynamic aspects of volcanism and seismicity. Both volcanic and seismic processes are involved in evolution of celestial bodies; they are operative on the planets of the Earth group and many satellites [Essays…, 1981; Lukashov, 1996]. From this standpoint, studies of those processes are essential with a view to development of scenarios of the Earth's evolution as a celestial

  5. GPS-derived coupling estimates for the Central America subduction zone and volcanic arc faults: El Salvador, Honduras and Nicaragua

    NASA Astrophysics Data System (ADS)

    Correa-Mora, F.; DeMets, C.; Alvarado, D.; Turner, H. L.; Mattioli, G.; Hernandez, D.; Pullinger, C.; Rodriguez, M.; Tenorio, C.

    2009-12-01

    We invert GPS velocities from 32 sites in El Salvador, Honduras and Nicaragua to estimate the rate of long-term forearc motion and distributions of interseismic coupling across the Middle America subduction zone offshore from these countries and faults in the Salvadoran and Nicaraguan volcanic arcs. A 3-D finite element model is used to approximate the geometries of the subduction interface and strike-slip faults in the volcanic arc and determine the elastic response to coupling across these faults. The GPS velocities are best fit by a model in which the forearc moves 14-16 mmyr-1 and has coupling of 85-100 per cent across faults in the volcanic arc, in agreement with the high level of historic and recent earthquake activity in the volcanic arc. Our velocity inversion indicates that coupling across the potentially seismogenic areas of the subduction interface is remarkably weak, averaging no more than 3 per cent of the plate convergence rate and with only two poorly resolved patches where coupling might be higher along the 550-km-long segment we modelled. Our geodetic evidence for weak subduction coupling disagrees with a seismically derived coupling estimate of 60 +/- 10 per cent from a published analysis of earthquake damage back to 1690, but agrees with three other seismologic studies that infer weak subduction coupling from 20th century earthquakes. Most large historical earthquakes offshore from El Salvador and western Nicaragua may therefore have been intraslab normal faulting events similar to the Mw 7.3 1982 and Mw 7.7 2001 earthquakes offshore from El Salvador. Alternatively, the degree of coupling might vary with time. The evidence for weak coupling indirectly supports a recently published hypothesis that much of the Middle American forearc is escaping to the west or northwest away from the Cocos Ridge collision zone in Costa Rica. Such a hypothesis is particularly attractive for El Salvador, where there is little or no convergence obliquity to drive the

  6. Neogene extension and volcanism in the Kunlun fault zone Northern Tibet

    NASA Astrophysics Data System (ADS)

    Jolivet, M.; Brunel, M.; Seward, D.; Malavieille, J.; Roger, F.; Leyreloup, A.; Arnaud, N.

    2003-04-01

    Significant extensional features have been described in Tibet, especially in the southern part of the plateau. The data presented here have been gathered in the Jingyu basin and describe transtensional features affecting the Tibetan plateau on its northern margin. West of 91^o E, the lithospheric strike-slip Kunlun Fault is divided into several segments in a complex pattern involving large relay zones. Some of those segments join at the edge of small-scale, E-W elongated pull-apart basins filled with Quaternary sediments. Magmatic activity, shown by large basaltic lava flows and small basaltic volcanic cones is often associated with the basins. There are no clear relationships between the rifts described further to the south (Yin et al., 1999) and this new type of extensional structures. The Jingyu basin started to form during the Miocene when SW-NE compression and E-W strike-slip faulting were replaced by localised E-W extension and strike-slip faulting. We propose that this change in the deformation pattern corresponds in age with the onset of continental subduction underneath the Kunlun Ranges. We suggest that initiation of this subduction could be responsible for the relaxation of the SW-NE directed constraints in the Bayan Har -- Songpan Garze terrane, allowing localised extension along the Kunlun Fault. Thermochronologic, sedimentary and tectonic data imply that E-W strike-slip movements in the western Kunlun Ranges started at least in Late Eocene times. This in turn might indicate that the Kunlun Fault, which was though to be younger than 10 Ma, is much older (Kidd and Molnar, 1988; Yin et al., 1999). Finally we show for the first time the relation between faulting and extrusive magmatism in North Tibet. If the shoshonites found in North Tibet were associated with the intracontinental subduction underneath the Kunlun Range, then the age of initiation of this subduction would probably have to be revised to account for the 15 Ma old lava flows in the Jingyu

  7. Impact of the Orozco Fracture Zone on the central Mexican Volcanic Belt

    NASA Astrophysics Data System (ADS)

    Blatter, Dawnika L.; Hammersley, Lisa

    2010-11-01

    This study investigates a prominent indentation in the central Mexican Volcanic Belt (MVB), referred to as the Tzitzio Gap (TG). In this region, centered at 101° W, Quaternary volcanism is displaced approximately 100 km toward the back of the arc. This embayment is roughly aligned with the projected position of the Orozco Fracture Zone (OFZ), which separates segments of the Cocos Plate that differ in age by approximately 5 Ma. The fracturing of the oceanic lithosphere associated with the OFZ appears to have caused alteration and increased the buoyancy of this ~ 100 km-wide linear feature. Several indicators of the buoyancy of the OFZ have been reported, including shallowing of the Middle America Trench (MAT), seaward advancement of the shoreline, and the uplift and exposure of deeply buried and deformed Jurassic to Oligocene rocks that comprise the TG region. Arc volcanism in the regions surrounding the TG provides constraints on the subduction of the OFZ. In the central MVB, enrichment in fluid-mobile elements such as Ba, Sr, P 2O 5, Pb and K 2O typically decreases with distance from the Middle America Trench, consistent with progressive dehydration of the down-going slab. Numerous studies in the central MVB have demonstrated that this fluid-mobile element enriched signature results from flux-induced melting at the front of the arc, while decompression melting of asthenospheric mantle peridotite is dominant at the back of the arc. The data presented here (a compilation of available geochemical data and new XRF major and trace element analyses of lavas erupted adjacent to the TG) shows that the volcanism that occurs behind the TG exhibits an anomalous fluid signature (high K 2O, P 2O 5, Ba, and Pb) superimposed on compositions similar to those from the extensional regions in northern Mexico. We propose that these distinctive structural and geochemical characteristics arise from subduction of the OFZ. Increased buoyancy of the fracture zone may cause it to subduct

  8. Structural controls on the spatial distribution and geochemical composition of volcanism in a continental rift zone; an example from Owens Valley, eastern California

    NASA Astrophysics Data System (ADS)

    Haproff, P. J.; Yin, A.

    2014-12-01

    Bimodal volcanism is common in continental rift zones. Structural controls to the emplacement and compositions of magmas, however, are not well understood. To address this issue, we examine the location, age, and geochemistry of active volcanic centers, and geometry and kinematics of rift-related faults across the active transtensional Owens Valley rift zone. Building on existing studies, we postulate that the spatial distribution and geochemical composition of volcanism are controlled by motion along rift-bounding fault systems. Along-strike variation in fault geometry and characteristics of active volcanism allow us to divide Owens Valley into three segments: southern, northern, and central. The southern segment of Owens Valley is a simple shear, asymmetric rift bounded to the west by the east-dipping Sierra Nevada frontal fault (SNFF). Active vents of Coso volcanic field are distributed along the eastern rift shoulder and characterized by the eruption of bimodal lavas. The SNFF within this segment is low-angle and penetrates through the lithosphere and into the ductile asthenosphere, allowing for mantle-derived magma to migrate across the weakest part of the fault zone beneath the eastern rift shoulder. Magma thermally weakens wall rocks and eventually stalls in the crust where the melt develops a greater felsic component prior to eruption. The northern segment of Owens Valley displays similar structural geometry, as the west-dipping White Mountains fault (WMF) is listric at depth and offsets the crust and mantle lithosphere, allowing for vertical transport of magma and reservoir emplacement within the crust. Bimodal lavas periodically erupted in the Long Valley Caldera region along the western rift shoulder. The central segment of Owens Valley is a pure shear, symmetric graben generated by motion along the SNFF and WMF. The subvertical, right-slip Owens Valley fault (OVF) strikes along the axis of the valley and penetrates through the lithosphere into the

  9. Frequency Based Volcanic Activity Detection through Remotely Sensed Data

    NASA Astrophysics Data System (ADS)

    Worden, A. K.; Dehn, J.; Webley, P. W.

    2015-12-01

    Satellite remote sensing has proved to offer a useful and relatively inexpensive method for monitoring large areas where field work is logistically unrealistic, and potentially dangerous. Current sensors are able to detect the majority of explosive volcanic activity; those that tend to effect and represent larger scale changes in the volcanic systems, eventually relating to ash producing periods of extended eruptive activity, and effusive activity. As new spaceborne sensors are developed, the ability to detect activity improves so that a system to gauge the frequency of volcanic activity can be used as a useful monitoring tool. Four volcanoes were chosen for development and testing of a method to monitor explosive activity: Stromboli (Italy); Shishaldin and Cleveland (Alaska, USA); and Karymsky (Kamchatka, Russia). Each volcano studied had similar but unique signatures of pre-cursory and eruptive activity. This study has shown that this monitoring tool could be applied to a wide range of volcanoes and still produce useful and robust data. Our method deals specifically with the detection of small scale explosive activity. The method described here could be useful in an operational setting, especially at remote volcanoes that have the potential to impact populations, infrastructure, and the aviation community. A number of important factors will affect the validity of application of this method. They are: (1) the availability of a continuous and continually populated dataset; (2) appropriate and reasonable sensor resolutions; (3) a recorded history of the volcano's previous activity; and, if available, (4) some ground-based monitoring system. We aim to develop the method further to be able to capture and evaluate the frequency of other volcanic processes such as lava flows, phreatomagmatic eruptions and dome growth and collapse. The work shown here has served to illustrate the capability of this method and monitoring tool for use at remote, un-instrumented volcanoes.

  10. The Aeolian Volcanic Arc: New Insights From Subduction Zone Thermal Models and Mineral Solubility Scaling Relationships

    NASA Astrophysics Data System (ADS)

    Creamer, J.; van Keken, P.; Engdahl, E. R.; Spera, F. J.; Bohrson, W. A.

    2007-12-01

    The Calabrian subduction zone, situated southeast of the Italian 'boot' in the Ionian Sea, is the latest manifestation of African-Eurasian plate interaction. This plate interaction has been remarkably dynamic since the Mesozoic, hosting episodes of mountain belt and volcanic arc formation including, for example, the Alpine, Carpathian and Apennine orogenic belts and Hellanic and, most recently, Aeolian volcanic arcs. Subduction of cold oceanic lithosphere beneath Europe initiated around 80 Ma, and the last 30 Ma have been characterized by alternating episodes of rapid back-arc rifting and back-arc spreading (up to 6-8 cm/yr) mediated by dip-parallel and/or trench-parallel tears in the descending slab resulting from differential trench rollback (Wortel and Spakman 2000). Backarc extension effectively moved the plate boundary from the European continental margin in the north to the African continental margin in the south, creating the modern Western Mediterranean basins. The Tyrrhenian oceanic basin was opened during the latest episode of trench rollback, from 5-2 Ma, followed by initiation of the subduction-related Aeolian volcanism by 1.3 Ma (Beccaluva et al. 1982) and complete cessation of extension of the overriding plate around 0.8-0.5 Ma (Goes et al. 2004). The seven subaerial volcanoes of the Aeolian volcanic arc sit atop thin (16-30 km) continental crust, and collectively tap a heterogeneous mantle source. Slab geometry in the depth range of 150 to 500 km has been refined using the hypocenter relocation procedure of Engdahl et al 1998 for teleseismic events beneath the Tyrrhenian Sea, in conjunction with recent tomographic results. The thermal state of the Calabrian subduction zone at depths relevant to dehydration and magma genesis has been investigated using a 2-dimensional time-dependent thermal model of the descending slab and convecting mantle wedge based on seismic, geologic and geodetic observational data. Modeling methodology follows van Keken et al

  11. Detection from Space of Active Volcanism on Earth and, Potentially, on Venus and Rocky Exoplanets

    NASA Astrophysics Data System (ADS)

    Mouginis-Mark, P. J.

    2015-05-01

    Volcanic eruptions (lava flows, lava lakes, and explosive activity) on Earth have been monitored from space for >3 decades. Such observations are extrapolated to understand how volcanic activity on Venus and rocky exoplanets may be detected.

  12. Multiple episodes of hydrothermal activity and epithermal mineralization in the southwestern Nevada volcanic field and their relations to magmatic activity, volcanism and regional extension

    SciTech Connect

    Weiss, S.I.; Noble, D.C.; Jackson, M.C.

    1994-12-31

    Volcanic rocks of middle Miocene age and underlying pre-Mesozoic sedimentary rocks host widely distributed zones of hydrothermal alteration and epithermal precious metal, fluorite and mercury deposits within and peripheral to major volcanic and intrusive centers of the southwestern Nevada volcanic field (SWNVF) in southern Nevada, near the southwestern margin of the Great Basin of the western United States. Radiometric ages indicate that episodes of hydrothermal activity mainly coincided with and closely followed major magmatic pulses during the development of the field and together spanned more than 4.5 m.y. Rocks of the SWNVF consist largely of rhyolitic ash-flow sheets and intercalated silicic lava domes, flows and near-vent pyroclastic deposits erupted between 15.2 and 10 Ma from vent areas in the vicinity of the Timber Mountain calderas, and between about 9.5 and 7 Ma from the outlying Black Mountain and Stonewall Mountain centers. Three magmatic stages can be recognized: the main magmatic stage, Mountain magmatic stage (11.7 to 10.0 Ma), and the late magmatic stage (9.4 to 7.5 Ma).

  13. Glass shards, pumice fragments and volcanic aerosol particles - diagenesis a recorder of volcanic activity?

    NASA Astrophysics Data System (ADS)

    Obenholzner, J. H.; Schroettner, H.; Poelt, P.; Delgado, H.

    2003-04-01

    Detailed SEM/EDS studies of Triassic (Southern Alps, A, I, Sl) and Miocene (Mixteca Alta, Mexico) tuffs revealed that volcanic glass shards can be replaced by zeolites (analcite), chlorites and smectites preserving the shape of primary shards (1). The Triassic pyroclastic deposits have been incorporated in the pre-Alpine burial diagenesis, the Miocene pyroclastic deposits are bentonites. The volcanologist is impressed by the circumstances that million years old pyroclast relict textures can be sized. Shape parameters obtained by image analysis can be compared with much younger pyroclastic deposits (2). Both deposits have not been effected by shearing. The alteration of pumice fragments of Triassic age is not a simple replacement process. Intergrowth of different illites and chlorites and probably vesicle filling by SiO2 and subsequent overgrowth make a reconstruction sometimes difficult. These processes are accompanied by the formation of REE-, Y- and Zr-bearing minerals as well as with the alteration of zircons. Studies of recently erupted ash from Popocatepetl volcano reveal the presence of a variety of µm-sized contact-metamorphosed clasts being a part of the volcanic ash (3). Such clasts should be present in many older pyroclastic deposits, especially where volcanoes had been situated on massive sedimentary units providing contact metamorphism in the realm of a magma chamber or during magma ascent. Volcanic aerosol particles collected in 1997 from the passively degassing plume of Popocatepetl volcano revealed in FESEM/EDS analysis (H. Schroettner and P. Poelt) a wide spectrum of fluffy, spherical and coagulated spherical particles (µm-sized). Under pre-vacuum conditions they remained stable for ca. 3 years (3). In nature the fate of these particles in the atmosphere is unknown. Are there relicts in marine, lacustrine sediments and ice cores, which could be used as proxies of volcanic activity? (1) Obenholzner &Heiken,1999. Ann.Naturhist.Mus.Wien, 100 A, 13

  14. Measuring volcanic gases at Taal Volcano Main Crater for monitoring volcanic activity and possible gas hazard

    NASA Astrophysics Data System (ADS)

    Arpa, M.; Hernandez Perez, P. A.; Reniva, P.; Bariso, E.; Padilla, G.; Melian Rodriguez, G.; Barrancos, J.; Calvo, D.; Nolasco, D.; Padron, E.; Garduque, R.; Villacorte, E.; Fajiculay, E.; Perez, N.; Solidum, R.

    2012-12-01

    were made using a multigas sensor. In terms of volcanic gas hazard, CO2 in air near a fumarole vent can be as high as 25,000 ppm, while the highest H2S recorded was at 14 ppm (March, 2011). Without a multigas sensor, we measured the concentrations of only CO2 and H2S in air near the fumaroles using the Westsystem fluxmeter. During the latest survey last July 2012, the highest measured CO2 in air was 13,000 ppm and for H2S it was 28 ppm to above detection limit. The campaign-type CO2 efflux surveys in the MCL and measurements of the fumaroles are done at least once or twice a year with increased frequency of surveys when signs of unrest are detected. These measurements are important because Taal Volcano Island, although designated as a permanent danger zone, is permanently inhabited.

  15. Active Volcanism on Io as Seen by Galileo SSI

    USGS Publications Warehouse

    McEwen, A.S.; Keszthelyi, L.; Geissler, P.; Simonelli, D.P.; Carr, M.H.; Johnson, T.V.; Klaasen, K.P.; Breneman, H.H.; Jones, T.J.; Kaufman, J.M.; Magee, K.P.; Senske, D.A.; Belton, M.J.S.; Schubert, G.

    1998-01-01

    Active volcanism on Io has been monitored during the nominal Galileo satellite tour from mid 1996 through late 1997. The Solid State Imaging (SSI) experiment was able to observe many manifestations of this active volcanism, including (1) changes in the color and albedo of the surface, (2) active airborne plumes, and (3) glowing vents seen in eclipse. About 30 large-scale (tens of kilometers) surface changes are obvious from comparison of the SSI images to those acquired by Voyager in 1979. These include new pyroclastic deposits of several colors, bright and dark flows, and caldera-floor materials. There have also been significant surface changes on Io during the Galileo mission itself, such as a new 400-km-diameter dark pyroclastic deposit around Pillan Patera. While these surface changes are impressive, the number of large-scale changes observed in the four months between the Voyager 1 and Voyager 2 flybys in 1979 suggested that over 17 years the cumulative changes would have been much more impressive. There are two reasons why this was not actually the case. First, it appears that the most widespread plume deposits are ephemeral and seem to disappear within a few years. Second, it appears that a large fraction of the volcanic activity is confined to repeated resurfacing of dark calderas and flow fields that cover only a few percent of Io's surface. The plume monitoring has revealed 10 active plumes, comparable to the 9 plumes observed by Voyager. One of these plumes was visible only in the first orbit and three became active in the later orbits. Only the Prometheus plume has been consistently active and easy to detect. Observations of the Pele plume have been particularly intriguing since it was detected only once by SSI, despite repeated attempts, but has been detected several times by the Hubble Space Telescope at 255 nm. Pele's plume is much taller (460 km) than during Voyager 1 (300 km) and much fainter at visible wavelengths. Prometheus-type plumes (50

  16. Active Volcanism on Io as Seen by Galileo SSI

    NASA Astrophysics Data System (ADS)

    McEwen, Alfred S.; Keszthelyi, Laszlo; Geissler, Paul; Simonelli, Damon P.; Carr, Michael H.; Johnson, Torrence V.; Klaasen, Kenneth P.; Breneman, H. Herbert; Jones, Todd J.; Kaufman, James M.; Magee, Kari P.; Senske, David A.; Belton, Michael J. S.; Schubert, Gerald

    1998-09-01

    Active volcanism on Io has been monitored during the nominal Galileo satellite tour from mid 1996 through late 1997. The Solid State Imaging (SSI) experiment was able to observe many manifestations of this active volcanism, including (1) changes in the color and albedo of the surface, (2) active airborne plumes, and (3) glowing vents seen in eclipse. About 30 large-scale (tens of kilometers) surface changes are obvious from comparison of the SSI images to those acquired by Voyager in 1979. These include new pyroclastic deposits of several colors, bright and dark flows, and caldera-floor materials. There have also been significant surface changes on Io during the Galileo mission itself, such as a new 400-km-diameter dark pyroclastic deposit around Pillan Patera. While these surface changes are impressive, the number of large-scale changes observed in the four months between the Voyager 1 and Voyager 2 flybys in 1979 suggested that over 17 years the cumulative changes would have been much more impressive. There are two reasons why this was not actually the case. First, it appears that the most widespread plume deposits are ephemeral and seem to disappear within a few years. Second, it appears that a large fraction of the volcanic activity is confined to repeated resurfacing of dark calderas and flow fields that cover only a few percent of Io's surface. The plume monitoring has revealed 10 active plumes, comparable to the 9 plumes observed by Voyager. One of these plumes was visible only in the first orbit and three became active in the later orbits. Only the Prometheus plume has been consistently active and easy to detect. Observations of the Pele plume have been particularly intriguing since it was detected only once by SSI, despite repeated attempts, but has been detected several times by the Hubble Space Telescope at 255 nm. Pele's plume is much taller (460 km) than during Voyager 1 (300 km) and much fainter at visible wavelengths. Prometheus-type plumes (50

  17. 3D conductivity image of a young continental rift: Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Heise, W.; Caldwell, T. G.; Bibby, H. M.; Bennie, S. L.

    2009-04-01

    The Taupo Volcanic Zone (TVZ), in the North Island, New Zealand is a continental back arc rift associated with the subduction of the Pacific Plate under the Australian Plate and is characterised by the eruption of large volumes of rhyolitic magma during the last 1.6 Ma and an exceptionally high present-day heat flow. Data from 220 magnetotelluric soundings covering the central (rhyolitic) part of the TVZ were analysed using 3D inverse resistivity modelling and phase tensor visualisation techniques. Modelling results compare well with the thickness of conductive volcaniclastic material in filling the rift basin and calderas and expected from observed gravity anomalies. Phase tensor ellipticity correlates well with the resistivity gradient in the 3D inversion model showing how the phase data control the inversion and allowing identification of which structures are, or are not, resolved by the data. The inverse modelling results show a zone of high conductivity in the lower crust and upper-mantle along the central rift-axis that correlates with a zone of high phase observed at long periods. An unusual feature of the MT data at periods of 3-30s is the large phase tensor skew angle values that coincide with the margins of a localized gravity high in the centre of the survey area. This feature appears to be caused by the interaction of a thick near surface layer of high conductive volcaniclastic material with conductive structures at greater depth.

  18. Structure of the Pliocene Camp dels Ninots maar-diatreme (Catalan Volcanic Zone, NE Spain)

    NASA Astrophysics Data System (ADS)

    Oms, O.; Bolós, X.; Barde-Cabusson, S.; Martí, J.; Casas, A.; Lovera, R.; Himi, M.; Gómez de Soler, B.; Campeny Vall-Llosera, G.; Pedrazzi, D.; Agustí, J.

    2015-11-01

    Maar volcanoes expose shallower or deeper levels of their internal structure as a function of the degree of erosion. In El Camp dels Ninots maar-diatreme (Catalan Volcanic Zone, Spain), the tephra ring has been largely eroded, and the remaining volcanic deposits infilling the diatreme are hidden under a lacustrine sedimentary infill of the crater. The volcano shows hardly any exposure, so its study needs the application of direct (e.g., boreholes) and indirect (shallow geophysics) subsurface exploration techniques. Additionally, this maar-diatreme was built astride two different substrates (i.e., mixed setting) as a result of its location in a normal fault separating Neogene sediments from Paleozoic granites. In order to characterize the internal structure and post-eruption stratigraphy of the maar-diatreme, we did geological studies (mapping, continuous core logging, and description of the tephra ring outcrops) and near-surface geophysics, including nine transects of electric resistivity tomography and a gravity survey. Results show that the deeper part of the diatreme is excavated into granites and is relatively steep and symmetrical. The uppermost diatreme is asymmetrical because of mechanical contrast between granites and Pliocene sands. The maar crater contained a lake permanently isolated from the surrounding relief and was deep enough to host anoxic bottom waters while its margins had shallower waters. These lake conditions preserved the remarkable Pliocene fossil record found in the lacustrine sediments.

  19. Young volcanoes in the Chilean Southern Volcanic Zone: A statistical approach to eruption prediction based on time series

    NASA Astrophysics Data System (ADS)

    Dzierma, Y.; Wehrmann, H.

    2010-03-01

    Forecasting volcanic activity has long been an aim of applied volcanology with regard to mitigating consequences of volcanic eruptions. Effective disaster management requires both information on expected physical eruption behaviour such as types and magnitudes of eruptions as typical for the individual volcano, usually reconstructed from deposits of past eruptions, and the likelihood that a new eruption will occur within a given time. Here we apply a statistical procedure to provide a probability estimate for future eruptions based on eruption time series, and discuss the limitations of this approach. The statistical investigation encompasses a series of young volcanoes of the Chilean Southern Volcanic Zone. Most of the volcanoes considered have been active in historical times, in addition to several volcanoes with a longer eruption record from Late-Pleistocene to Holocene. Furthermore, eruption rates of neighbouring volcanoes are compared with the aim to reveal possible regional relations, potentially resulting from local to medium-scale tectonic dynamics. One special focus is directed to the two currently most active volcanoes of South America, Llaima and Villarrica, whose eruption records comprise about 50 historical eruptions over the past centuries. These two front volcanoes are considered together with Lanín Volcano, situated in the back-arc of Villarrica, for which the analysis is based on eight eruptions in the past 10 ka. For Llaima and Villarrica, affirmed tests for independence of the repose times between successive eruptions permit to assume Poisson processes; which is hampered for Lanín because of the more limited availability of documented eruptions. The assumption of stationarity reaches varying degrees of confidence depending on the time interval considered, ameliorating towards the more recent and hence probably more complete eruption record. With these pre-requisites of the time series, several distribution functions are fit and the goodness of

  20. Seismic Activity at tres Virgenes Volcanic and Geothermal Field

    NASA Astrophysics Data System (ADS)

    Antayhua, Y. T.; Lermo, J.; Quintanar, L.; Campos-Enriquez, J. O.

    2013-05-01

    The volcanic and geothermal field Tres Virgenes is in the NE portion of Baja California Sur State, Mexico, between -112°20'and -112°40' longitudes, and 27°25' to 27°36' latitudes. Since 2003 Power Federal Commission and the Engineering Institute of the National Autonomous University of Mexico (UNAM) initiated a seismic monitoring program. The seismograph network installed inside and around the geothermal field consisted, at the beginning, of Kinemetrics K2 accelerometers; since 2009 the network is composed by Guralp CMG-6TD broadband seismometers. The seismic data used in this study covered the period from September 2003 - November 2011. We relocated 118 earthquakes with epicenter in the zone of study recorded in most of the seismic stations. The events analysed have shallow depths (≤10 km), coda Magnitude Mc≤2.4, with epicentral and hypocentral location errors <2 km. These events concentrated mainly below Tres Virgenes volcanoes, and the geothermal explotation zone where there is a system NW-SE, N-S and W-E of extensional faults. Also we obtained focal mechanisms for 38 events using the Focmec, Hash, and FPFIT methods. The results show normal mechanisms which correlate with La Virgen, El Azufre, El Cimarron and Bonfil fault systems, whereas inverse and strike-slip solutions correlate with Las Viboras fault. Additionally, the Qc value was obtained for 118 events. This value was calculated using the Single Back Scattering model, taking the coda-waves train with window lengths of 5 sec. Seismograms were filtered at 4 frequency bands centered at 2, 4, 8 and 16 Hz respectively. The estimates of Qc vary from 62 at 2 Hz, up to 220 at 16 Hz. The frequency-Qc relationship obtained is Qc=40±2f(0.62±0.02), representing the average attenuation characteristics of seismic waves at Tres Virgenes volcanic and geothermal field. This value correlated with those observed at other geothermal and volcanic fields.

  1. Volcanic hazard management in dispersed volcanism areas

    NASA Astrophysics Data System (ADS)

    Marrero, Jose Manuel; Garcia, Alicia; Ortiz, Ramon

    2014-05-01

    Traditional volcanic hazard methodologies were developed mainly to deal with the big stratovolcanoes. In such type of volcanoes, the hazard map is an important tool for decision-makers not only during a volcanic crisis but also for territorial planning. According to the past and recent eruptions of a volcano, all possible volcanic hazards are modelled and included in the hazard map. Combining the hazard map with the Event Tree the impact area can be zoned and defining the likely eruptive scenarios that will be used during a real volcanic crisis. But in areas of disperse volcanism is very complex to apply the same volcanic hazard methodologies. The event tree do not take into account unknown vents, because the spatial concepts included in it are only related with the distance reached by volcanic hazards. The volcanic hazard simulation is also difficult because the vent scatter modifies the results. The volcanic susceptibility try to solve this problem, calculating the most likely areas to have an eruption, but the differences between low and large values obtained are often very small. In these conditions the traditional hazard map effectiveness could be questioned, making necessary a change in the concept of hazard map. Instead to delimit the potential impact areas, the hazard map should show the expected behaviour of the volcanic activity and how the differences in the landscape and internal geo-structures could condition such behaviour. This approach has been carried out in La Palma (Canary Islands), combining the concept of long-term hazard map with the short-term volcanic scenario to show the expected volcanic activity behaviour. The objective is the decision-makers understand how a volcanic crisis could be and what kind of mitigation measurement and strategy could be used.

  2. Sensor web enables rapid response to volcanic activity

    USGS Publications Warehouse

    Davies, Ashley G.; Chien, Steve; Wright, Robert; Miklius, Asta; Kyle, Philip R.; Welsh, Matt; Johnson, Jeffrey B.; Tran, Daniel; Schaffer, Steven R.; Sherwood, Robert

    2006-01-01

    Rapid response to the onset of volcanic activity allows for the early assessment of hazard and risk [Tilling, 1989]. Data from remote volcanoes and volcanoes in countries with poor communication infrastructure can only be obtained via remote sensing [Harris et al., 2000]. By linking notifications of activity from ground-based and spacebased systems, these volcanoes can be monitored when they erupt.Over the last 18 months, NASA's Jet Propulsion Laboratory (JPL) has implemented a Volcano Sensor Web (VSW) in which data from ground-based and space-based sensors that detect current volcanic activity are used to automatically trigger the NASA Earth Observing 1 (EO-1) spacecraft to make highspatial-resolution observations of these volcanoes.

  3. Multidimensional analysis and probabilistic model of volcanic and seismic activities

    NASA Astrophysics Data System (ADS)

    Fedorov, V.

    2009-04-01

    A search for space and time regularities in volcanic and seismic events for the purpose of forecast method development seems to be of current concern, both scientifically and practically. The seismic and volcanic processes take place in the Earth's field of gravity which in turn is closely related to gravitational fields of the Moon, the Sun, and the planets of the Solar System. It is mostly gravity and tidal forces that exercise control over the Earth's configuration and relief. Dynamic gravitational interaction between the Earth and other celestial bodies makes itself evident in tidal phenomena and other effects in the geospheres (including the Earth's crust). Dynamics of the tidal and attractive forces is responsible for periodical changes in gravity force, both in value and direction [Darwin, 1965], in the rate of rotation and orbital speed; that implies related changes in the endogenic activity of the Earth. The Earth's rotation in the alternating gravitational field accounts to a considerable extent for regular pattern of crustal deformations and dislocations; it is among principal factors that control the Earth's form and structure, distribution of oceans and continents and, probably, continental drift [Peive, 1969; Khain, 1973; Kosygin, 1983]. The energy of gravitational interaction is transmitted through the tidal energy to planetary spheres and feeds various processes there, including volcanic and seismic ones. To determine degree, character and special features of tidal force contribution to the volcanic and seismic processes is of primary importance for understanding of genetic and dynamic aspects of volcanism and seismicity. Both volcanic and seismic processes are involved in evolution of celestial bodies; they are operative on the planets of the Earth group and many satellites [Essays…, 1981; Lukashov, 1996]. From this standpoint, studies of those processes are essential with a view to development of scenarios of the Earth's evolution as a celestial

  4. Linking Plagioclase Zoning Patterns to Active Magma Processes

    NASA Astrophysics Data System (ADS)

    Izbekov, P. E.; Nicolaysen, K. P.; Neill, O. K.; Shcherbakov, V.; Plechov, P.; Eichelberger, J. C.

    2015-12-01

    Plagioclase, one of the most common and abundant mineral phases in volcanic products, will vary in composition in response to changes in temperature, pressure, composition of the ambient silicate melt, and melt H2O concentration. Changes in these parameters may cause dissolution or growth of plagioclase crystals, forming characteristic textural and compositional variations (zoning patterns), the complete core-to-rim sequence of which describes events experienced by an individual crystal from its nucleation to the last moments of its growth. Plagioclase crystals in a typical volcanic rock may look drastically dissimilar despite their spatial proximity and the fact that they have erupted together. Although they shared last moments of their growth during magma ascent and eruption, their prior experiences could be very different, as plagioclase crystals often come from different domains of the same magma system. Distinguishing similar zoning patterns, correlating them across the entire population of plagioclase crystals, and linking these patterns to specific perturbations in the magmatic system may provide additional perspective on the variety, extent, and timing of magma processes at active volcanic systems. Examples of magma processes, which may be distinguished based on plagioclase zoning patterns, include (1) cooling due to heat loss, (2) heating and/or pressure build up due to an input of new magmatic material, (3) pressure drop in response to magma system depressurization, and (4) crystal transfer between different magma domains/bodies. This review will include contrasting examples of zoning patters from recent eruptions of Karymsky, Bezymianny, and Tolbachik Volcanoes in Kamchatka, Augustine and Cleveland Volcanoes in Alaska, as well as from the drilling into an active magma body at Krafla, Iceland.

  5. Interactions between active faulting, volcanism, and sedimentary processes at an island arc: Insights from Les Saintes channel, Lesser Antilles arc

    NASA Astrophysics Data System (ADS)

    Leclerc, F.; Feuillet, N.; Deplus, C.

    2016-07-01

    New high-resolution marine geophysical data allow to characterize a large normal fault system in the Lesser Antilles arc, and to investigate the interactions between active faulting, volcanism, sedimentary, and mass-wasting processes. Les Saintes fault system is composed of several normal faults that form a 30 km wide half-graben accommodating NE-SW extension. It is bounded by the Roseau fault, responsible for the destructive Mw 6.3 21 November 2004 earthquake. The Roseau fault has been identified from the island of Basse-Terre to Dominica. It is thus 40 km long, and it could generate Mw 7 earthquakes in the future. Several submarine volcanoes are also recognized. We show that the fault system initiated after the main volcanic construction and subsequently controls the emission of volcanic products. The system propagates southward through damage zones. At the tip of the damage zones, several volcanic cones were recently emplaced probably due to fissures opening in an area of stress increase. A two-way interaction is observed between active faulting and sedimentary processes. The faults control the development of the main turbiditic system made of kilometer-wide canyons, as well as the location of sediment ponding. In turn, erosion and sedimentation prevent scarp growth at the seafloor. Faulting also enhances mass-wasting processes. Since its initiation, the fault system has consequently modified the morphologic evolution of the arc through perturbation of the sedimentary processes and localization of the more recent volcanic activity.

  6. Extensive and Diverse Submarine Volcanism and Hydrothermal Activity in the NE Lau Basin

    NASA Astrophysics Data System (ADS)

    Embley, R. W.; Merle, S. G.; Lupton, J. E.; Resing, J.; Baker, E. T.; Lilley, M. D.; Arculus, R. J.; Crowhurst, P. V.

    2009-12-01

    The northeast Lau basin, the NE “corner” of the Tonga subduction zone, has an unusual concentration of young submarine volcanism and hydrothermal activity. The area is bounded on the west by overlapping spreading centers opening at rates up to 120 mm/yr, on the north by the E-W trending Tonga trench and on the east by the Tofua arc front. From the south, the Fonualei rift spreading center (FRSC) overlaps with the southern rift of The Mangatolo triple junction spreading center (MTJSC). The northern arm of the MTJSC overlaps with the northeast Lau spreading center (NELSC). Surveys of the area with an EM300 sonar system in November 2008 show high backscatter over the 10-20 km wide neovolcanic zones of the FRSC, MTJSC and NELSC. High backscatter is also associated with: (1) a 10-km diameter, hydrothermally active, volcanic caldera/cone (Volcano “O”) lying between the NELSC and the northern Tofua arc front; (2) a rift zone extending north from volcano “O” and intersecting the NELSC near the Tonga trench; and (3) a series of volcanoes constructed along SW-NE trending crustal tears in the northernmost backarc near the east-west portion of the Tonga Trench. Two eruptions were detected in November 2008 during hydrothermal plume surveys of the area. Subsequent dives with the remotely operated vehicle Jason 2 in May 2009 revealed that the southern NELSC eruption was a short-lived, primarily effusive eruption. The second eruption was detected on the summit of the largest SW-NE trending volcano (West Mata) and was ongoing when Jason 2 arrived on site more than 6 months later. It was producing both pillow lavas and abundant volcaniclastic debris streams that have a characteristic appearance on the sonar backscatter map. There is also an unusual series of lava flows emanating from ridges and scarps between Volcano “O” and West Mata. These flows contain drained-out lava ponds up to 2 km in diameter. The apparent high level of volcanic activity in the NE Lau basin

  7. Results From NICLAKES Survey of Active Faulting Beneath Lake Nicaragua, Central American Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Funk, J.; Mann, P.; McIntosh, K.; Wulf, S.; Dull, R.; Perez, P.; Strauch, W.

    2006-12-01

    In May of 2006 we used a chartered ferry boat to collect 520 km of seismic data, 886 km of 3.5 kHz subbottom profiler data, and 35 cores from Lake Nicaragua. The lake covers an area of 7700 km2 within the active Central American volcanic arc, forms the largest lake in Central America, ranks as the twentieth largest freshwater lake in the world, and has never been previously surveyed or cored in a systematic manner. Two large stratovolcanoes occupy the central part of the lake: Concepcion is presently active, Maderas was last active less than 2000 years ago. Four zones of active faulting and doming of the lake floor were mapped with seismic and 3.5 kHz subbottom profiling. Two of the zones consist of 3-5-km-wide, 20-30-km-long asymmetric rift structures that trend towards the inactive cone of Maderas Volcano in a radial manner. The northeastern rift forms a 20-27-m deep depression on the lake bottom that is controlled by a north-dipping normal fault. The southwestern rift forms a 25-35-m deep depression controlled by a northeast-dipping normal fault. Both depressions contain mound-like features inferred to be hydrothermal deposits. Two zones of active faulting are associated with the active Concepcion stratovolcano. A 600-m-wide and 6-km-long fault bounded horst block extends westward beneath the lake from a promontory on the west side of the volcano. Like the two radial rift features of Maderas, the horst points roughly towards the active caldera of Concepcion. A second north-south zone of active faulting, which also forms a high, extends off the north coast of Concepcion and corresponds to a localized zone of folding and faulting mapped by previous workers and inferred by them to have formed by gravitational spreading of the flank of the volcano. The close spatial relation of these faults to the two volcanic cones in the lake suggests that the mechanism for faulting is a result of either crustal movements related to magma intrusion or gravitational sliding and is

  8. Cordon Caulle: an active volcanic-geothermal extensional system of Southern Andes of Chile

    NASA Astrophysics Data System (ADS)

    Sepulveda, F.

    2013-05-01

    Cordon Caulle (CC; 40.5° S) is an active volcanic-geothermal system of the Southern Volcanic Zone (SVZ; 37°-44°S). Morphologically, the CC system is a 6 km x 13 km volcanic plateau bordered by NW-trending structures, limited by Puyehue Volcano to the SE and by Caldera Nevada Caldera to the NW. While the SVZ is dominantly basaltic, CC is unique in that it has produced a wide compositional spectrum from basalt to rhyolite. The most recent volcanic activity of Puyehue-CC (last 70 ky) is dominantly silicic, including two historic fissure eruptions (1921-1922; 1960) and a recent central eruption from Puyehue Volcano (2011). Abnormally silicic volcanism was formerly attributed to a localized compression and long-term magma residence and differentiation, resulting from the NW orientation of underlying CC structures with respect to a NE-oriented σ1 (linked to regional strike-slip stress state). However, later studies, including examination of morpho-tectonic features; detailed structural analysis of the 1960 eruption (triggered by Mw 9.5 1960 Chilean Earthquake); InSAR deformation and gravity surveys, point to both historic and long-term extension at CC with σhmax oriented NNW to NW. The pre-2011 (i.e. Puyehue Volcano eruption) geothermal features of CC included boiling hot springs and geysers (Caldera Nevada) and fumaroles (CC and Puyehue Volcano). Both water and gas chemistry surveys were undertaken to assess the source fluid composition and equilibrium temperature. The combination of water and gas geothermometers led to a conceptual model of a stratified geothermal reservoir, with shallow, low-chloride, steam-heated aquifers equilibrated at temperatures between 150°-180°C, overlying a deeper, possibly dominated reservoir with temperatures in excess of 280°C. Gas chemistry also produced the highest He ratios of the SVZ, in agreement with a relatively pure, undiluted magmatic signature and heat source fueling the geothermal system. Other indicators such as N2/Ar

  9. Origin and accumulation mechanisms of petroleum in the Carboniferous volcanic rocks of the Kebai Fault zone, Western Junggar Basin, China

    NASA Astrophysics Data System (ADS)

    Chen, Zhonghong; Zha, Ming; Liu, Keyu; Zhang, Yueqian; Yang, Disheng; Tang, Yong; Wu, Kongyou; Chen, Yong

    2016-09-01

    The Kebai Fault zone of the West Junggar Basin in northwestern China is a unique region to gain insights on the formation of large-scale petroleum reservoirs in volcanic rocks of the western Central Asian Orogenic Belt. Carboniferous volcanic rocks are widespread in the Kebai Fault zone and consist of basalt, basaltic andesite, andesite, tuff, volcanic breccia, sandy conglomerate and metamorphic rocks. The volcanic oil reservoirs are characterized by multiple sources and multi-stage charge and filling history, characteristic of a complex petroleum system. Geochemical analysis of the reservoir oil, hydrocarbon inclusions and source rocks associated with these volcanic rocks was conducted to better constrain the oil source, the petroleum filling history, and the dominant mechanisms controlling the petroleum accumulation. Reservoir oil geochemistry indicates that the oil contained in the Carboniferous volcanic rocks of the Kebai Fault zone is a mixture. The oil is primarily derived from the source rock of the Permian Fengcheng Formation (P1f), and secondarily from the Permian Lower Wuerhe Formation (P2w). Compared with the P2w source rock, P1f exhibits lower values of C19 TT/C23 TT, C19+20TT/ΣTT, Ts/(Ts + Tm) and ααα-20R sterane C27/C28 ratios but higher values of TT C23/C21, HHI, gammacerane/αβ C30 hopane, hopane (20S) C34/C33, C29ββ/(ββ + αα), and C29 20S/(20S + 20R) ratios. Three major stages of oil charge occurred in the Carboniferous, in the Middle Triassic, Late Triassic to Early Jurassic, and in the Middle Jurassic to Late Jurassic periods, respectively. Most of the oil charged during the first stage was lost, while moderately and highly mature oils were generated and accumulated during the second and third stages. Oil migration and accumulation in the large-scale stratigraphic reservoir was primarily controlled by the top Carboniferous unconformity with better porosity and high oil enrichment developed near the unconformity. Secondary dissolution

  10. Comparative mass balance of volcanic edifices at the southern volcanic zone of the Andes between 33°S and 46°S

    NASA Astrophysics Data System (ADS)

    Völker, David; Kutterolf, Steffen; Wehrmann, Heidi

    2011-08-01

    Volcano edifice volume calculations are presented for 65 volcanoes of the 1400 km long Chilean Southern Volcanic Zone (SVZ) as a basic step in subduction zone mass budgets. Volume calculations are performed in a Geographical Information System that integrates Digital Elevation Models based on of Shuttle Radar Topography Mission as well as ASTER-GDEM topographic data, LANDSAT satellite images and geological maps. The method of volume calculation is straightforward for isolated, morphologically well-defined stratovolcanoes. Uncertainties increase for volcanic edifices that formed on pre-existing rugged terrain, for multi-phase eruptive centers, as well as for eroded edifices. A revised segmentation of the arc is used to describe the spatial volume distribution of extruded magma along the SVZ and to discuss controlling tectonic factors. Peak volumes between arc and back arc are offset by 400 km. The total volcanic extrusion is in the range of 10-13 km 3/km/Ma. Major differences between the SVZ and the Central American subduction system are notable with regard to volcano density and maximum volumes.

  11. Modelling the interaction between volcanic sources and fault zones at the Etna Mount

    NASA Astrophysics Data System (ADS)

    Aloisi, Marco; Mattia, Mario; Monaco, Carmelo; Pulvirenti, Fabio

    2010-05-01

    Analytical and numerical modeling techniques are jointly applied to simulate geophysical processes in the Earth's crust. The methods are of a complementary nature. Analytical models have been used traditionally due to the lightness of the request computational resources but they are strongly limited in the ability to quantify observables, to describe multiphysics processes and to use more complicated material rheologies and Earth's topography. All these properties can be achieved by using numerical models even though it requires long time of calculation and the deep knowledge of the studied geophysical system. The 2002-2003 Etna eruptive event involved two different sectors of the volcano providing a big amount of geophysical data. The eruption produced severe fires in the woods, destroyed many tourist infrastructures and interrupted one of the principal roads. It was heralded, accompanied and followed by an intense seismic activity that was culminated with the earthquake (M ~ 4.4) on October 29 that produced severe damages in the S. Venerina village. The eruption was deeply analyzed by analytical (e.g., Aloisi et al., 2003; Aloisi et al., 2006; Bonforte et al., 2007; Currenti et al., 2008a) and numerical modeling (Walter et al., 2005; Currenti et al., 2008b). The numerical models have proved that the medium heterogeneities and the area topography strongly affect the volcano deformation field. The Etna Mount, jointly with a motley lithological setting, is characterized by a complex tectonic scenery that influences the structural evolution of the volcanic edifice. Important fault zones intersect the volcano edifice, perturbing the deformation pattern produced by the volcanic sources. The displacement and stress of blocks are affected by the deformation of discontinuities to a degree (Liu and Zhongkui, 2007), therefore the fault zones can not be neglected in an overall study. In this work, we present a numerical model for the 2002-2003 Etna eruption that kept in

  12. Fissure swarms and fracture systems within the Western Volcanic Zone, Iceland - Effects of spreading rates

    NASA Astrophysics Data System (ADS)

    Hjartardóttir, Ásta Rut; Einarsson, Páll; Björgvinsdóttir, Sigríður G.

    2016-10-01

    The Western Volcanic Zone (WVZ) in Iceland is ∼120 km long and 40 km wide. It offers an opportunity to study rift zones in a local ultra-slow spreading area close to a hotspot. Fractures were mapped from aerial photographs and digital elevation models. Most surface fractures are located in the southern part of the WVZ. The majority of the fractures have a north-northeasterly orientation, some deviations occur from this, especially in the north part of the WVZ. Fracture orientations are therefore quite uniform in the southern, faster spreading part of the WVZ, but more irregular in the slower-spreading northern part. This suggests different stress fields in the north part, which could be due to the influence of the Hreppar microplate and possibly also due to stress fields induced by crustal deformation because of changes in glacial load in the area. Such glacially-induced stress fields may have similar or even more influence than crustal spreading in the slower spreading northern part of the WVZ. Lower fracture density towards the north within the WVZ suggests lower frequency of rifting events in the north part, in accordance with less spreading in the north as measured by GPS geodetic measurements.

  13. Active Volcanic and Hydrothermal Processes at NW Rota-1 Submarine Volcano: Mariana Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Embley, R. W.; Baker, E. T.; Butterfield, D. A.; Chadwick, W. W.; de Ronde, C.; Dower, J.; Evans, L.; Hein, J.; Juniper, K.; Lebon, G.; Lupton, J. E.; Merle, S.; Metaxas, A.; Nakamura, K.; Resing, J. E.; Roe, K.; Stern, R.; Tunnicliffe, V.

    2004-12-01

    Dives with the remotely operated vehicle ROPOS in March/April 2004 documented a volcanic eruption at NW Rota-1, a submarine volcano of basaltic composition located at 14\\deg 36.0'N, 144\\deg 46.5'E lying 65 km northwest of Rota Island in the Commonwealth of the Northern Mariana Islands. The site was chosen as a dive target because of the of the high concentrations of H2S and alunite in the hydrothermal plume overlying its summit in February 2003. The summit of the volcano is composed of curvilinear volcanic ridge oriented NW-SE bounded by NE-SW trending normal faults. Lavas collected on the upper part of the edifice are primitive to moderately fractionated basalts (Mg# = 51-66). The eruptive activity is occurring within a small crater (Brimstone Pit) located on the upper south flank of the volcano at 550 m, about 30 m below the summit. The crater is approximately 15 m wide and at least 20 meters deep. The ROPOS's cameras observed billowing clouds of sulfur-rich fluid rising out of the crater, punctuated by frequent bursts of several minutes duration that entrained glassy volcanic ejecta up to at least 2 cm in diameter. ROPOS recorded a temperature of 38\\degC within the plume. The volcanic activity had substantial temporal variability on the scale of minutes. ROPOS was sometimes completely enveloped by the plume while on the rim of the crater, and its surfaces were coated with large sulfur droplets. Black glassy fragments were entrained in the plume up to least 50 m above the crater and deposits of this material were on ledges and tops of outcrops up to several hundred meters from Brimstone Pit. The pit crater fluids have an extremely high content of particulate sulfur and extremely acidic, with pH around 2.0. This strongly implicates magmatic degassing of SO2 and disproportionation into elemental S and sulfuric acid. Diffuse venting of clear fluids was also present on the summit of the volcano, with temperatures exceeding 100\\degC in volcaniclastic sands

  14. Non-volcanic tremor in Cascadia: Segmented along strike, anti-correlated with earthquakes, and offset from the locked zone

    NASA Astrophysics Data System (ADS)

    Boyarko, D. C.; Brudzinski, M. R.; Allen, R. M.; Porritt, R. W.

    2009-12-01

    Episodic tremor and slip (ETS), the spatial and temporal correlation of slow slip events monitored by GPS observations and non-volcanic tremor (NVT) monitored by seismic signals, is a recently discovered type of deformation thought to occur immediately down-dip from the seismogenic zone along several subduction margins. Owing to the wealth of geodetic and seismic observatories in Washington and Vancouver Island, ETS in northern Cascadia has been the subject of numerous studies over the last half-decade, while the rest of the margin has received considerably less attention. We will present a comprehensive review of tremor activity along the southern Cascadia margin between 2005 and 2007 using both semi-automated and fully-automated source location routines. We will also utilize the fully-automated routine to expand the scope to include the entire Cascadia margin and episodes after 2007, including the great 2008 ETS episode which spans nearly the entire length of the margin. The along-strike length of activity of an individual episode varies between 30 to 900 km, evolving in a very complex manner with periods of steady and halting migration and frequent along-strike jumps (30-600 km). The initiation and termination points of laterally-continuous tremor activity appear to be repeatable features between NVT episodes which support the hypothesis of segmentation within the ETS zone. The distribution of tremor epicenters occur within a narrow band confined by the surface projections of the 30 and 40 km contours of the subducting plate interface. We find the tremor zone is spatially offset by as much as 50 km down-dip from the thermally- and geodetically-defined transition zone, which may decrease the efficiency of stress transmission and slip propagation during either transient or seismogenic deformation episodes. Intriguingly, NVT activity is spatially anti-correlated with local seismicity, suggesting the two processes occur mutually exclusive of one another. We propose

  15. Mafic monogenetic vents at the Descabezado Grande volcanic field (35.5°S-70.8°W): the northernmost evidence of regional primitive volcanism in the Southern Volcanic Zone of Chile

    NASA Astrophysics Data System (ADS)

    Salas, Pablo A.; Rabbia, Osvaldo M.; Hernández, Laura B.; Ruprecht, Philipp

    2016-06-01

    In the Andean Southern Volcanic Zone (SVZ), the broad distribution of mafic compositions along the recent volcanic arc occurs mainly south of 37°S, above a comparatively thin continental crust (≤~35 km) and mostly associated with the dextral strike-slip regime of the Liquiñe-Ofqui Fault Zone (LOFZ). North of 36°S, mafic compositions are scarce. This would be in part related to the effect resulting from protracted periods of trapping of less evolved ascending magmas beneath a thick Meso-Cenozoic volcano-sedimentary cover that lead to more evolved compositions in volcanic rocks erupted at the surface. Here, we present whole-rock and olivine mineral chemistry data for mafic rocks from four monogenetic vents developed above a SVZ segment of thick crust (~45 km) in the Descabezado Grande volcanic field (~35.5°S). Whole-rock chemistry (MgO > 8 wt%) and compositional variations in olivine (92 ≥ Fo ≥ 88 and Ni up to ~3650 ppm) indicate that some of the basaltic products erupted through these vents (e.g., Los Hornitos monogenetic cones) represent primitive arc magmas reaching high crustal levels. The combined use of satellite images, regional data analysis and field observations allow to recognize at least 38 mafic monogenetic volcanoes dispersed over an area of about 5000 km2 between 35.5° and 36.5°S. A link between ancient structures inherited from pre-Andean tectonics and the emplacement and distribution of this mafic volcanism is suggested as a first-order structural control that may explain the widespread occurrence of mafic volcanism in this Andean arc segment with thick crust.

  16. Lahar hazard zones for eruption-generated lahars in the Lassen Volcanic Center, California

    USGS Publications Warehouse

    Robinson, Joel E.; Clynne, Michael A.

    2012-01-01

    lahar generation, we assume that the maximum historical water equivalent, 3.90 m, covers the entire basin area inside the H/L cone. The product of planimetric area of each basin inside the H/L and the maximum historical water equivalent yields the maximum water volume available to generate a lahar. We then double the water volumes to approximate maximum lahar volumes. The maximum lahar volumes and an understanding of the statistical uncertainties inherent to the LAHARZ calculations guided our selection of six hypothetical volumes, 1, 3, 10, 30, 60, and 90x106 m3, to delineate concentric lahar inundation zones. The lahar inundation zones extend, in general, tens of kilometers away from Lassen Peak. The small, more-frequent lahar inundation zones (1 and 3x106 m3) are, on average, 10 km long. The exceptions are the zones in Warner Creek and Mill Creek, which extend much further. All but one of the small, more-frequent lahar inundation zones reach outside of the Lassen Volcanic National Park boundary, and the zone in Mill Creek extends well past the park boundary. All of the medium, moderately frequent lahar inundation zones (10 and 30x106 m3) extend past the park boundary and could potentially impact the communities of Viola and Old Station and State Highways 36 and 44, both north and west of Lassen Peak. The approximately 27-km-long on average, large, less-frequent lahar inundation zones (60 and 90x106 m3) represent worst-case lahar scenarios that are unlikely to occur. Flood hazards continue downstream from the toes of the lahars, potentially affecting communities in the Sacramento River Valley.

  17. Volcanic hazards of the Idaho National Engineering Laboratory and adjacent areas

    SciTech Connect

    Hackett, W.R.; Smith, R.P.

    1994-12-01

    Potential volcanic hazards are assessed, and hazard zone maps are developed for the Idaho National Engineering Laboratory (INEL) and adjacent areas. The basis of the hazards assessment and mapping is the past volcanic history of the INEL region, and the apparent similarity of INEL volcanism with equivalent, well-studied phenomena in other regions of active volcanism, particularly Hawaii and Iceland. The most significant hazards to INEL facilities are associated with basaltic volcanism, chiefly lava flows, which move slowly and mainly threaten property by inundation or burning. Related hazards are volcanic gases and tephra, and ground disturbance associated with the ascent of magma under the volcanic zones. Several volcanic zones are identified in the INEL area. These zones contain most of the volcanic vents and fissures of the region and are inferred to be the most probable sites of future INEL volcanism. Volcanic-recurrence estimates are given for each of the volcanic zones based on geochronology of the lavas, together with the results of field and petrographic investigations concerning the cogenetic relationships of INEL volcanic deposits and associated magma intrusion. Annual probabilities of basaltic volcanism within the INEL volcanic zones range from 6.2 {times} 10{sup {minus}5} per year (average 16,000-year interval between eruptions) for the axial volcanic zone near the southern INEL boundary and the Arco volcanic-rift zone near the western INEL boundary, to 1 {times} 10{sup {minus}5} per year (average 100,000-year interval between eruptions) for the Howe-East Butte volcanic rift zone, a geologically old and poorly defined feature of the central portion of INEL. Three volcanic hazard zone maps are developed for the INEL area: lava flow hazard zones, a tephra (volcanic ash) and gas hazard zone, and a ground-deformation hazard zone. The maps are useful in land-use planning, site selection, and safety analysis.

  18. Magma storage depths in the Eastern Volcanic Zone of Iceland: disentangling disequilibrium and tuning thermobarometers

    NASA Astrophysics Data System (ADS)

    Neave, D.; Maclennan, J.; Thordarson, T.; Hartley, M. E.; Buisman, I.; Namur, O.; Halldorsson, S. A.

    2015-12-01

    The Eastern Volcanic Zone (EVZ) is the most volcanically productive of Iceland's neovolcanic zones. In addition to being the source of numerous small but disruptive eruptions, such Eyjafjallajökull in 2010 and Grímsvötn in 2011, the EVZ is notable for generating very large eruptions such as the environmentally impacting Laki eruption in 1783-84 and the widely dispersed Saksunarvatn Ash. Thus, investigating the plumbing systems of volcanoes in the EVZ not only reveals information about magma reservoir behaviour and crustal structure, but also has important implications for hazard management. However, in order to obtain reliable estimates of pre-eruptive magma storage conditions and depths from minerals a number of conditions need to be met first. Firstly, all estimates of pre-eruptive conditions need to be placed into petrogenetic frameworks that consider the extensive disequilibrium that results not only from fractionation, but also from magma mixing and crystal mush entrainment. Secondly, it is important to verify that the mineral-melt equilibrium, i.e. thermobarometeric, models used are well calibrated at the expected conditions of magma storage. Using a range of techniques including QEMSCAN imaging, textural analysis and geochemical microanalysis of crystals, glasses and melt inclusions, we present internally consistent models of magma evolution and storage for a number of eruptions in the EVZ, including Laki and the 10ka Grímsvötn tephra series (i.e. Saksunarvatn Ash). All eruptions studied preserve evidence of mixing and crystallisation of primitive melts in the mid-crust (8-20 km) followed by crystallisation of evolved and, in general, more incompatible element-enriched melts in the shallow crust (0-8 km) shortly before eruption. Substantial uncertainties in storage depths nevertheless remain because of incomplete calibration of clinopyroxene-melt equilibria at mid-crustal pressures. As part of an ongoing experimental campaign on Icelandic magma

  19. Implications for Melt Differentiation Processes in the Central Mexican Volcanic Belt from 'Zoned' Monogenetic Volcanoes

    NASA Astrophysics Data System (ADS)

    Straub, S. M.; Gomez-Tuena, A.; Goldstein, S. L.; Cai, Y. M.; Martin-Del Pozzo, A.

    2007-05-01

    Across-arc mass balances require the knowledge of composition and the origins of the mass of melt. This "melt mass" may derive from slab, mantle, or crustal sources, whereby these possible sources will be reflected in magma chemistry. In order to identify the arc melt sources, we are studying a broad range of alkaline ('intraplate- type') to calc-alkaline ('arc type') Holocene volcanic rocks in the Central Mexican Volcanic Belt (CMVB) constructed on thick continental crust (~40-47 km). Sr-Nd-Pb isotope ratios similar to those from subarc mantle xenoliths in all erupted magmas, together with trace elements, point towards a dominant mantle origin of melts along with some slab-derived component, but negligible crustal additions. In order to understand how isotope and trace elements relate with major element diversity, we focus on monogenetic volcanoes with a significant zonation in major elements (e.g. Chichinautzin, Guespalapa, Suchiooc). Monogenetic volcanoes build in a single event and hence their magmas must derive from similar sources. Within zoned monogenetic centers, two different trends are recognized: (1) a 'source trend'; and (2) 'differentiation trends'. The 'source trend' describes the trend of decreasing FeO* and TiO2 with increasing Mg#, which precedes high-Mg# (>60-75) calc- alkaline and alkaline magmas. The 'source trend' parallels the tholeiitic trend of Fe-enrichment with decreasing Mg# observed in oceanic basalts, but culminates at lower overall maxima of FeO* (~9 wt%) and TiO2(~2 wt%) (FeO* ~16 wt% and TiO2 ~3.5 wt%). High-Ni olivines contained in alkaline and calc-alkaline 'source trend' magmas suggest that the 'source trend' is generated through repeated mantle melting induced by fluid addition from slab (Straub et al., G3, submitted). This supports models of mantle origin of primary high-Mg# andesite melts. However, the majority of CMVB magma have lower Mg#- numbers and plot on trajectories that emanate from any point of the 'source trend

  20. Overview of electromagnetic methods applied in active volcanic areas of western United States

    NASA Astrophysics Data System (ADS)

    Skokan, Catherine K.

    1993-06-01

    A better understanding of active volcanic areas in the United States through electromagnetic geophysical studies received foundation from the many surveys done for geothermal exploration in the 1970's. Investigations by governmental, industrial, and academic agencies include (but are not limited to) mapping of the Cascades. Long Valley/Mono area, the Jemez volcanic field, Yellowstone Park, and an area in Colorado. For one example — Mt. Konocti in the Mayacamas Mountains, California — gravity, magnetic, and seismic, as well as electromagnetic methods have all been used in an attempt to gain a better understanding of the subsurface structure. In each of these volcanic regions, anomalous zones were mapped. When conductive, these anomalies were interpreted to be correlated with hydrothermal activity and not to represent a magma chamber. Electrical and electromagnetic geophysical methods can offer valuable information in the understanding of volcanoes by being the method which is most sensitive to change in temperature and, therefore, can best map heat budget and hydrological character to aid in prediction of eruptions.

  1. Jovian dust streams: A monitor of Io's volcanic plume activity

    USGS Publications Warehouse

    Kruger, H.; Geissler, P.; Horanyi, M.; Graps, A.L.; Kempf, S.; Srama, R.; Moragas-Klostermeyer, G.; Moissl, R.; Johnson, T.V.; Grun, E.

    2003-01-01

    Streams of high speed dust particles originate from Jupiter's moon Io. After release from Io, the particles collect electric charges in the Io plasma torus, gain energy from the co-rotating electric field of Jupiter's magnetosphere, and leave the Jovian system into interplanetary space with escape speeds over 200 km s-1. The Galileo spacecraft has continuously monitored the dust streams during 34 revolutions about Jupiter between 1996 and 2002. The observed dust fluxes exhibit large orbit-to-orbit variability due to systematic and stochastic changes. After removal of the systematic variations, the total dust emission rate of Io has been calculated. It varies between 10-3 and 10 kg s-1, and is typically in the range of 0.1 to 1 kg s-1. We compare the dust emission rate with other markers of volcanic activity on Io like large-area surface changes caused by volcanic deposits and sightings of volcanic plumes. Copyright 2003 by the American Geophysical Union.

  2. Volcanic activity within the Vestmannaeyjar archipelago, south of Iceland

    NASA Astrophysics Data System (ADS)

    Hoskuldsson, A.; Kjartansson, E.; Hey, R.; Driscoll, N.

    2006-12-01

    Bathymetric research with multibeam techniques and chirp profiles reveal the volcanic topography of the Vestmannaeyjar archipelago just off the south coast of Iceland. Within the archipelago two historic eruptions have occurred, Surtsey 1963-1967 and the one of Heimaey in 1973. Five other eruptive vents have been identified as Holocene, Storhöfdi ~8000 BP, Sæfell ~6220 BP, Helgafell ~5900 BP and the islands Bjarnarey and Ellirey ~4500 BP. High precision multibeam data reveal several other eruptive vents and their geometry in the area. From the geometry it can be concluded that prehistoric volcanic activity in the area is dominated by phreatomagmatic activity. Tuff cones up to 2 km in diameter are observed in the area of Heimaey. Eustatic sea level changes can be inferred from these volcanic formations (Rofubodi vent) , indicating that a rise of up to 80 m has occurred since late Pleistocene times (~12000 years BP). Further our data show that sea level rise occurred in steps, as is manifested by the Alsey reef, now submerged and extending north of that island. The data also allow us to identify four major submarine lava flows in the area. One from the Eldfell eruption in 1973, one from the Helgafell eruption 5900 BP, one from the Storhofdi eruption ~8000BP and finally a lava flow that is extending from Faxasker towards the north west. The Vestmannaeyjar archipelago is forming a ridge extending NE to SW. The ridge is about 5 km wide and 30 km long. The ridge rises from a depth of some 72 m in the west but falls off to about 130 m in the east. The eastern border is more prominent than the western one. The Vestmannaeyjar ridge ends abruptly in the north, just prior to reaching the main outwash delta from the main island Iceland. A narrow trough has been formed in the area, Allinn, as the outwash delta propagates towards the ridge. Our data also allow for interpretation on relative timing of the volcanic formations. It has been shown that the LGM ice sheet extended to

  3. The search for active release of volcanic gases on Mars

    NASA Astrophysics Data System (ADS)

    Khayat, Alain; Villanueva, Geronimo; Mumma, Michael; Tokunaga, Alan

    2015-11-01

    The study of planetary atmospheres by means of spectroscopy is important for understanding their origin and evolution. The presence of short-lived trace gases in the martian atmosphere would imply recent production, for example, by ongoing geologic activity. On Earth, sulfur dioxide (SO2), sulfur monoxide (SO) and hydrogen sulfide (H2S) are the main sulfur-bearing gases released during volcanic outgassing. Carbonyl sulfide (OCS), also released from some volcanoes on Earth (e.g., Erebus and Nyiragongo), could be formed by reactions involving SO2 or H2S inside magma chambers. We carried out the first ground-based, semi-simultaneous, multi-band and multi-species search for such gases above the Tharsis and Syrtis volcanic regions on Mars. The submillimeter search extended between 23 November 2011 and 13 May 2012 which corresponded to Mars’ mid Northern Spring and early Northern Summer seasons (Ls = 34-110°). The strong submillimeter rotational transitions of SO2, SO and H2S were targeted using the high-resolution heterodyne receiver (aka Barney) on the Caltech Submillimeter Observatory. We reached sensitivities sufficient to detect a volcanic release on Mars that is 4% of the SO2 released continuously from Kilauea volcano in Hawaii, or 5% that of the Masaya volcano in Nicaragua. The infrared search covered OCS in its combination band (ν2+ν3) at 3.42 μm at two successive Mars years, during Mars’ late Northern Spring and mid Northern Summer seasons, spanning Ls= 43º and Ls= 147º. The targeted volcanic districts were observed during the two intervals, 14 Dec. 2011 to 6 Jan. 2012 in the first year, and 30 May 2014 to 16 June 2014 in the second year, using the high resolution infrared spectrometer (CSHELL) on NASA’s Infrared Telescope Facility (NASA/IRTF). We will present our results and discuss their implications for current volcanic outgassing activity on the red planet. We gratefully acknowledge support from the NASA Planetary Astronomy Program under NASA

  4. Alkalic (ocean-island basalt type) and calc-alkalic volcanism in the Mexican volcanic belt: A case for plume-related magmatism and propagating rifting at an active margin?

    NASA Astrophysics Data System (ADS)

    Márquez, Alvaro; Oyarzun, Roberto; Doblas, Miguel; Verma, Surendra P.

    1999-01-01

    The Mexican volcanic belt has been traditionally regarded as a classic case of subduction-related calc-alkalic volcanism. However, a series of geologic, geophysical, and petrological arguments makes this simple relationship doubtful. A seismic gap beneath the belt, a large-scale mantle anomaly, a graben triple-junction domain, and the presence of volumetrically important oceanic-island basalt (OIB) volcanism throughout the belt suggest a more complex tectonic scenario involving plume- and subduction-related processes. We here propose a model involving the development of a propagating rift opening from west to east in response to plume activity. The process started in Miocene time within the western sector of the belt (Guadalajara) and gave rise to a graben triple junction and OIB-type and calc-alkalic volcanism. Extension and volcanism proceeded to the east, giving rise to progressively younger ages for the initiation of OIB-type volcanism: (1) Miocene in the west (e.g., Guadalajara), (2) Pliocene in the central zone (e.g., Michoacán-Guanajuato), and (3) Quaternary farther east (e.g., Chichinautzin). Geochemical evidence suggests that part of the modern calc-alkalic volcanism (e.g., Chichinautzin) may be derived from magma mixing between the OIB mafic magmas and silicic, crust-derived magmas. However, we do not preclude some influence of the subducting slab in the generation of other (e.g., Jorullo) calc-alkalic volcanic rocks. Our model suggests a currently unrooted upper plume attached to the subcontinental lithosphere, which defines a hot zone beneath the Mexican volcanic belt.

  5. Using array MT data to image the crustal resistivity structure of the southeastern Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Bertrand, E. A.; Caldwell, T. G.; Bannister, S.; Soengkono, S.; Bennie, S. L.; Hill, G. J.; Heise, W.

    2015-10-01

    Magnetotelluric (MT) data from 169 locations covering a 700 km2 region in the southeastern part of the Taupo Volcanic Zone, New Zealand, are used to generate a 3-D resistivity inversion model to a depth of 10 km. Isolated zones of low-resistivity (< 30 Ωm) below 3 km are imaged in the basement that appear to be associated with the geothermal fields at Rotokawa, Ngatamariki and Ohaaki, but not with the geothermal fields at Orakei-Korako and Te Kopia. These low-resistivity zones are interpreted to be recent intrusions that feed heat and magmatic fluid to the overlying system of hydrothermal convection supplying the geothermal fields. At Rotokawa, hypocentres of thermally induced seismicity coincide with the top of the deep low-resistivity zone and suggest that temperatures sufficient for melting are reached at ~ 4.5 km depth. In most cases these deep low-resistivity zones are located at the margins of areas of low-gravity, which suggests that the intrusions lie at the margins of old caldera collapse structures. The 3-D resistivity model indicates that geological structure and magmatic intrusions play a more direct role than previously envisaged, and significantly influence the overarching system of convective heat and mass transport in the Taupo Volcanic Zone.

  6. Neotectonic development of the El Salvador Fault Zone and implications for deformation in the Central America Volcanic Arc: Insights from 4-D analog modeling experiments

    NASA Astrophysics Data System (ADS)

    Alonso-Henar, Jorge; Schreurs, Guido; Martinez-Díaz, José Jesús; Álvarez-Gómez, José Antonio; Villamor, Pilar

    2015-01-01

    The El Salvador Fault Zone (ESFZ) is an active, approximately 150 km long and 20 km wide, segmented, dextral strike-slip fault zone within the Central American Volcanic Arc striking N100°E. Although several studies have investigated the surface expression of the ESFZ, little is known about its structure at depth and its kinematic evolution. Structural field data and mapping suggest a phase of extension, at some stage during the evolution of the ESFZ. This phase would explain dip-slip movements on structures that are currently associated with the active, dominantly strike slip and that do not fit with the current tectonic regime. Field observations suggest trenchward migration of the arc. Such an extension and trenchward migration of the volcanic arc could be related to slab rollback of the Cocos plate beneath the Chortis Block during the Miocene/Pliocene. We carried out 4-D analog model experiments to test whether an early phase of extension is required to form the present-day fault pattern in the ESFZ. Our experiments suggest that a two-phase tectonic evolution best explains the ESFZ: an early pure extensional phase linked to a segmented volcanic arc is necessary to form the main structures. This extensional phase is followed by a strike-slip dominated regime, which results in intersegment areas with local transtension and segments with almost pure strike-slip motion. The results of our experiments combined with field data along the Central American Volcanic Arc indicate that the slab rollback intensity beneath the Chortis Block is greater in Nicaragua and decreases westward to Guatemala.

  7. Thyroid cancer incidence in relation to volcanic activity

    SciTech Connect

    Arnbjoernsson, E.A.; Arnbjoernsson, A.O.; Olafsson, A.

    1986-01-01

    Environmental or genetic factors are sought to explain the high incidence of thyroid cancer in Iceland. At present, it is impossible to cite any environmental factor, particularly one related to the volcanic activity in the country, which could explain the high incidence of thyroid cancer in Iceland. However, the thyroid gland in Icelanders is very small due to the high intake of iodine from seafood. It is, therefore, easier for physicians to find thyroid tumors. Furthermore, genetic factors are very likely to be of great importance in the small, isolated island of Iceland.

  8. Lake-floor sediment texture and composition of a hydrothermally-active, volcanic lake, Lake Rotomahana

    NASA Astrophysics Data System (ADS)

    Pittari, A.; Muir, S. L.; Hendy, C. H.

    2016-03-01

    Young volcanic lakes undergo a transition from rapid, post-eruptive accumulation of volcaniclastic sediment to slower pelagic settling under stable lake conditions, and may also be influenced by sublacustrine hydrothermal systems. Lake Rotomahana is a young (129 year-old), hydrothermally-active, volcanic lake formed after the 1886 Tarawera eruption, and provides a unique insight into the early evolution of volcanic lake systems. Lake-bottom sediment cores, 20-46 cm in length, were taken along a transect across the lake and characterised with respect to stratigraphy, facies characteristics (i.e., grain size, componentry) and pore water silica concentrations. The sediments generally comprise two widespread facies: (i) a lower facies of light grey to grey, very fine lacustrine silt derived from the unconsolidated pyroclastic deposits that mantled the catchment area immediately after the eruption, which were rapidly reworked and redeposited into the lake basin; and (ii) an upper facies of dark, fine-sandy diatomaceous silt, that settled from the pelagic zone of the physically stable lake. Adjacent to sublacustrine hydrothermal vents, the upper dark facies is absent, and the upper part of the light grey to grey silt is replaced by a third localised facies comprised of hydrothermally altered pale yellow to yellowish brown, laminated silt with surface iron-rich encrustations. Microspheres, which are thought to be composed of amorphous silica, although some may be halloysite, have precipitated from pore water onto sediment grains, and are associated with a decrease in pore water silicon concentration. Lake Rotomahana is an example of a recently-stabilised volcanic lake, with respect to sedimentation, that shows signs of early sediment silicification in the presence of hydrothermal activity.

  9. A plutonic view of explosive volcanism: the shatter zone of the Cadillac Mountain granite, Maine

    NASA Astrophysics Data System (ADS)

    Wiebe, R.

    2013-12-01

    of clast size distribution of CR fragments in SZA and SZB suggests an extremely high-energy environment consistent with a pyroclastic eruption from the CMG magma chamber (Roy et al. 2012). If such an eruption did occur, one expected effect would be episodic, sudden drops in pressure during degassing and eruptive events. Since the lower part of the chamber was apparently relatively dry (hypersolvus alkali feldspar with ternary feldspar occurs in CMG immediately above the GD), the drop in pressure would lower H2O activity so that the Ab-rich loop of the alkali feldspar phase diagram would shift to higher T, causing the melt to fall below the liquidus and shift the equilibrium solid feldspar to higher Or values. This matches the initial oscillatory zone to higher Or on the homogeneous cores. Because the SZ terminates at the top of the GD, it is likely that mafic input contributed to the eruption. The large inward increase in the crystallization T of the matrix from SZA to SZC probably records initial escape of a cooler felsic cap and upwelling of deep, hot hypersolvus magma along with partial collapse of the chamber roof.

  10. A multi-disciplinary investigation into the distribution of melt along the Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Hamling, I. J.; Hreinsdottir, S.; Kilgour, G.; Bertrand, E. A.

    2015-12-01

    The 300 km long Taupo Volcanic Zone (TVZ) formed as a result of back-arc rifting associated with subduction of the Pacific Plate beneath the Australian Plate. The TVZ is home to two of the most active rhyolitic calderas in the world, Taupo and Okataina, and is thought to have erupted more than 10,000 km3 of predominately rhyolitic magma, with ~640 km3 of material over the past 61 ka from Taupo and Okataina alone. Using GPS and interferometric synthetic aperture radar (InSAR) data, collected by the European (ESA) and Japanese (JAXA) space agencies, we present ground deformation observations from 2003 to 2011 and show widespread subsidence across the central TVZ at rates of up to 20 mm/yr. Using simple elastic dislocation models to represent the contraction of a sill like body, we predict an annual volume change of up to 0.016 km3 beneath the central TVZ and suggest that the majority of the observed subsidence is a result of the cooling and subsequent contraction of magma within the shallow crust. Furthermore, with New Zealand volcanoes now added to the GEO's Geohazard Supersites and Natural Laboratories initiative, we will detail our attempts at integrating geodetic, magnetotelluric and petrological datasets to image the plumbing system beneath the TVZ.

  11. Geochemical variability of hydrothermal emissions between three Pacific volcanic arc systems: Alaskan-Aleutian and Cascadian, North America and Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Blackstock, J. M.; Horton, T. W.; Gravley, D. M.; Deering, C. D.

    2013-12-01

    Knowledge of the source, transport, and fate of hydrothermal fluids in the upper crust informs our understanding and interpretation of ore-forming processes, volcanogenic hazards, geothermal resources, and volatile cycling. Co-variation between fluid inclusion CO2/CH4 and N2/Ar ratios is an established tracer of magmatic, meteoric, and crustal fluid end-members. Yet, this tracer has had limited application to macroscopic fluid reservoirs accessible via geothermal wells and hydrothermal features (e.g. pools). In this study, we compared the covariance CO2/CH4 and N2/Ar ratios of gases collected throughout the Taupo Volcanic Zone, New Zealand (TVZ), the Alaska-Aleutian Volcanic Arc, USA (AAVA), and the Cascadian Volcanic Arc, USA (CVA) with corresponding δ13C and 3He/4He values. Our findings show that there is good agreement between these proxies for different end-member contributions at coarse scales. However, some samples classified as meteoric water according to the CO2/CH4 and N2/Ar ratios also show more positive δ13C values (~ -7.0 per mil) and relatively higher 3He/4He ratios indicative of magmatic input from primarily mantle sources. This unexpected result may be related to magmatic fluids, CO2 in particular, mixing with predominantly meteoric derived waters. The potential to identify magmatic CO2 in groundwater samples overlying geothermal systems in differing volcanic arc settings using simple and cost-effective gas ratios is a promising step forward in the search for ';surface blind' but developable geothermal systems and volcanic monitoring. 3He/4He anomalies also support this inference and underscore the potential decoupling of thermal anomalies and magmatic-derived fluids in the Earth's crust. The general agreement between the co-variation of CO2/CH4 and N2/Ar ratios with other isotope and geochemical proxies for magmatic, meteoric, and crustal end-members is encouraging to employ expanded use of these ratios for both the exploration and monitoring of

  12. Spatial and temporal variations of diffuse CO_{2} degassing at the N-S volcanic rift-zone of Tenerife (Canary Islands, Spain) during 2002-2015 period

    NASA Astrophysics Data System (ADS)

    Alonso, Mar; Ingman, Dylan; Alexander, Scott; Barrancos, José; Rodríguez, Fátima; Melián, Gladys; Pérez, Nemesio M.

    2016-04-01

    Tenerife is the largest of the Canary Islands and, together with Gran Canaria Island, is the only one with a central volcanic complex that started to grow at about 3.5 Ma. Nowadays the central complex is formed by Las Cañadas caldera, a volcanic depression measuring 16×9 km that resulted from multiple vertical collapses and was partially filled by post-caldera volcanic products. Up to 297 mafic monogenetic cones have been recognized on Tenerife, and they represent the most common eruptive activity occurring on the island during the last 1 Ma (Dóniz et al., 2008). Most of the monogenetic cones are aligned following a triple junction-shaped rift system, as result of inflation produced by the concentration of emission vents and dykes in bands at 120o to one another as a result of minimum stress fracturing of the crust by a mantle upwelling. The main structural characteristic of the southern volcanic rift (N-S) of the island is an apparent absence of a distinct ridge, and a fan shaped distribution of monogenetic cones. Four main volcanic successions in the southern volcanic rift zone of Tenerife, temporally separated by longer periods (˜70 - 250 ka) without volcanic activity, have been identified (Kröchert and Buchner, 2008). Since there are currently no visible gas emissions at the N-S rift, diffuse degassing surveys have become an important geochemical tool for the surveillance of this volcanic system. We report here the last results of diffuse CO2 efflux survey at the N-S rift of Tenerife, performed using the accumulation chamber method in the summer period of 2015. The objectives of the surveys were: (i) to constrain the total CO2 output from the studied area and (ii) to evaluate occasional CO2 efflux surveys as a volcanic surveillance tool for the N-S rift of Tenerife. Soil CO2 efflux values ranged from non-detectable up to 31.7 g m-2 d-1. A spatial distribution map, constructed following the sequential Gaussian simulation (sGs) procedure, did not show an

  13. Spatial and temporal variations of diffuse CO_{2} degassing at the N-S volcanic rift-zone of Tenerife (Canary Islands, Spain) during 2002-2015 period

    NASA Astrophysics Data System (ADS)

    Alonso, Mar; Ingman, Dylan; Alexander, Scott; Barrancos, José; Rodríguez, Fátima; Melián, Gladys; Pérez, Nemesio M.

    2016-04-01

    Tenerife is the largest of the Canary Islands and, together with Gran Canaria Island, is the only one with a central volcanic complex that started to grow at about 3.5 Ma. Nowadays the central complex is formed by Las Cañadas caldera, a volcanic depression measuring 16×9 km that resulted from multiple vertical collapses and was partially filled by post-caldera volcanic products. Up to 297 mafic monogenetic cones have been recognized on Tenerife, and they represent the most common eruptive activity occurring on the island during the last 1 Ma (Dóniz et al., 2008). Most of the monogenetic cones are aligned following a triple junction-shaped rift system, as result of inflation produced by the concentration of emission vents and dykes in bands at 120o to one another as a result of minimum stress fracturing of the crust by a mantle upwelling. The main structural characteristic of the southern volcanic rift (N-S) of the island is an apparent absence of a distinct ridge, and a fan shaped distribution of monogenetic cones. Four main volcanic successions in the southern volcanic rift zone of Tenerife, temporally separated by longer periods (˜70 - 250 ka) without volcanic activity, have been identified (Kröchert and Buchner, 2008). Since there are currently no visible gas emissions at the N-S rift, diffuse degassing surveys have become an important geochemical tool for the surveillance of this volcanic system. We report here the last results of diffuse CO2 efflux survey at the N-S rift of Tenerife, performed using the accumulation chamber method in the summer period of 2015. The objectives of the surveys were: (i) to constrain the total CO2 output from the studied area and (ii) to evaluate occasional CO2 efflux surveys as a volcanic surveillance tool for the N-S rift of Tenerife. Soil CO2 efflux values ranged from non-detectable up to 31.7 g m‑2 d‑1. A spatial distribution map, constructed following the sequential Gaussian simulation (sGs) procedure, did not show an

  14. Galileo SSI Observations of Volcanic Activity at Tvashtar Catena, Io

    NASA Technical Reports Server (NTRS)

    Milazzo, M. P.; Keszthely, L. P.; Radebaugh, J.; Davies, A. G.; Turtle, E. P.; Geissler, P.; Klaasen, K. P.; McEwen, A. S.

    2005-01-01

    Introduction: We report on the analysis of the Galileo SSI's observations of the volcanic activity at Tvashtar Catena, Io as discussed by Milazzo et al. Galileo's Solid State Imager (SSI) observed Tvashtar Catena (63 deg N, 120 deg W) four times between November 1999 and October 2001, providing a unique look at the distinctive high latitude volcanism on Io. The November 1999 observation spatially resolved, for the first time, an active extraterrestrial fissure eruption. The brightness temperature of the lavas at the November 1999 fissure eruption was 1300 K. The second observation (orbit I27, February 2000) showed a large (approx. 500 sq km) region with many, small spots of hot, active lava. The third observation was taken in conjunction with a Cassini observation in December 2000 and showed a Pele-like plume deposition ring, while the Cassini images revealed a 400 km high Pele-type plume above the Catena. The final Galileo SSI observation of Tvashtar was acquired in October 2001, and all obvious (to SSI) activity had ceased, although data from Galileo's Near Infrared Mapping Spectrometer (NIMS) indicated that there was still significant thermal emission from the Tvashtar region. We have concentrated on analyzing the style of eruption during orbit I27 (February 2000). Comparison with a lava flow cooling model indicates that the behavior of the Tvashtar eruption during I27 does not match that of "simple" advancing lava flows. Instead, it may be an active lava lake or a complex set of lava flows with episodic, overlapping (in time and space) eruptions.

  15. Evolution of a Chemically Zoned Magma Body: Black Mountain Volcanic Center, southwestern Nevada

    NASA Astrophysics Data System (ADS)

    Vogel, Thomas A.; Noble, Donald C.; Younker, Leland W.

    1989-05-01

    Rocks of the Black Mountain volcanic center consist of four ash flow sheets and units of lava that underlie, interfinger with, and overlie the sheets. Rocks from the center represent three magma types. Magma type c was present through the history of the center, whereas types a and b were available after the eruption of the Rocket Wash Member, during the eruptions of the Pahute Mesa and Trail Ridge members. The magma types are defined by trace element ratios; for example, magma types a, b, and c have La/Th values of 1.0-3.5, >7.5, and 3.5-7.5. Silica contents in the magma types a, b, and c range from 71.5 to 74.1, from 65.8 to 69.2, and from 55.6 to 73.8 wt %, respectively. The stratigraphic distribution of chemically distinct pumice fragments within the ash flow sheets is used to show that magma type a was located in the uppermost part of the chamber and was underlain successively by magma types b and c. Because pumice fragments that belong to all three magma types occur in individual cooling units, a zoned magma body must have existed during this period. Magma mixing is indicated by the disequilibrium phenocrysts which are common in pumice fragments from all magma types; however, this mixing did not destroy the original zoning of the upper part of the magma body. Most of the chemical variation of magma type c is consistent with fractionation of feldspar, olivine, and pyroxene, but abundant disequilibrium, mafic phenocrysts indicate that magma replenishment and mixing were common. Magma type b had much higher La/Th and light rare earth element (LREE)/heavy rare earth element values and must have originated independently from magma type c. Most likely the two types were derived from different source material. The low La/Th values of magma type a can be explained by separation of a phenocryst assemblage containing both a LREE-bearing phase and zircon from either magma types b or c, or possibly by the partial melting of source material containing these phases.

  16. The Cenozoic volcanism in the Kivu rift: Assessment of the tectonic setting, geochemistry, and geochronology of the volcanic activity in the South-Kivu and Virunga regions

    NASA Astrophysics Data System (ADS)

    Pouclet, A.; Bellon, H.; Bram, K.

    2016-09-01

    The Kivu rift is part of the western branch of the East African Rift system. From Lake Tanganyika to Lake Albert, the Kivu rift is set in a succession of Precambrian zones of weakness trending NW-SE, NNE-SSW and NE-SW. At the NW to NNE turn of the rift direction in the Lake Kivu area, the inherited faults are crosscut by newly born N-S fractures which developed during the late Cenozoic rifting and controlled the volcanic activity. From Lake Kivu to Lake Edward, the N-S faults show a right-lateral en echelon pattern. Development of tension gashes in the Virunga area indicates a clockwise rotation of the constraint linked to dextral oblique motion of crustal blocks. The extensional direction was W-E in the Mio-Pliocene and ENE-WSW in the Pleistocene to present time. The volcanic rocks are assigned to three groups: (1) tholeiites and sodic alkali basalts in the South-Kivu, (2) sodic basalts and nephelinites in the northern Lake Kivu and western Virunga, and (3) potassic basanites and potassic nephelinites in the Virunga area. South-Kivu magmas were generated by melting of spinel + garnet lherzolite from two sources: an enriched lithospheric source and a less enriched mixed lithospheric and asthenospheric source. The latter source was implied in the genesis of the tholeiitic lavas at the beginning of the South-Kivu tectono-volcanic activity, in relationships with asthenosphere upwelling. The ensuing outpouring of alkaline basaltic lavas from the lithospheric source attests for the abortion of the asthenospheric contribution and a change of the rifting process. The sodic nephelinites of the northern Lake Kivu originated from low partial melting of garnet peridotite of the sub-continental mantle due to pressure release during swell initiation. The Virunga potassic magmas resulted from the melting of garnet peridotite with an increasing degree of melting from nephelinite to basanite. They originated from a lithospheric source enriched in both K and Rb, suggesting the

  17. Gold-silver mining districts, alteration zones, and paleolandforms in the Miocene Bodie Hills Volcanic Field, California and Nevada

    USGS Publications Warehouse

    Vikre, Peter G.; John, David A.; du Bray, Edward A.; Fleck, Robert J.

    2015-09-25

      Based on volcanic stratigraphy, geochronology, remnant paleosurfaces, and paleopotentiometric surfaces in mining districts and alteration zones, present landforms in the Bodie Hills volcanic field reflect incremental construction of stratovolcanoes and large- to small-volume flow-domes, magmatic inflation, and fault displacements. Landform evolution began with construction of the 15–13 Ma Masonic and 13–12 Ma Aurora volcanic centers in the northwestern and northeastern parts of the field, respectively. Smaller volcanoes erupted at ~11–10 Ma in, between, and south of these centers as erosional detritus accumulated north of the field in Fletcher Valley. Distally sourced, 9.7–9.3 Ma Eureka Valley Tuff filled drainages and depressions among older volcanoes and was partly covered by nearly synchronous eruptives during construction of four large 10–8 Ma volcanoes, in the southern part of the field. The lack of significant internal fault displacement, distribution of Eureka Valley Tuff, and elevation estimates derived from floras, suggest that the Bodie Hills volcanic field attained present elevations mostly through volcano construction and magmatic inflation, and that maximum paleoelevations (>8,500 ft) at the end of large volume eruptions at ~8 Ma are similar to present elevations.

  18. Gold-silver mining districts, alteration zones, and paleolandforms in the Miocene Bodie Hills Volcanic Field, California and Nevada

    USGS Publications Warehouse

    Vikre, Peter G.; John, David A.; du Bray, Edward A.; Fleck, Robert J.

    2015-01-01

      Based on volcanic stratigraphy, geochronology, remnant paleosurfaces, and paleopotentiometric surfaces in mining districts and alteration zones, present landforms in the Bodie Hills volcanic field reflect incremental construction of stratovolcanoes and large- to small-volume flow-domes, magmatic inflation, and fault displacements. Landform evolution began with construction of the 15–13 Ma Masonic and 13–12 Ma Aurora volcanic centers in the northwestern and northeastern parts of the field, respectively. Smaller volcanoes erupted at ~11–10 Ma in, between, and south of these centers as erosional detritus accumulated north of the field in Fletcher Valley. Distally sourced, 9.7–9.3 Ma Eureka Valley Tuff filled drainages and depressions among older volcanoes and was partly covered by nearly synchronous eruptives during construction of four large 10–8 Ma volcanoes, in the southern part of the field. The lack of significant internal fault displacement, distribution of Eureka Valley Tuff, and elevation estimates derived from floras, suggest that the Bodie Hills volcanic field attained present elevations mostly through volcano construction and magmatic inflation, and that maximum paleoelevations (>8,500 ft) at the end of large volume eruptions at ~8 Ma are similar to present elevations.

  19. The use of digital outcrops to study monogenetic volcanoes: Case study at Croscat volcano (Garrotxa Volcanic Zone, Spain)

    NASA Astrophysics Data System (ADS)

    Geyer, Adelina; García-Sellés, David; Pedrazzi, Dario; Barde-Cabusson, Stéphanie; Martí, Joan; Muñoz, Josep Anton

    2014-05-01

    During the last years, it has been demonstrated that the study of outcrops with difficult or completely restricted access can be carried out by means of digital representations of the outcrop surface. Furthermore, the study of digital outcrops may facilitate visualization of the features of interest over the entire outcrop, as long as the digital outcrop can be analysed while navigating in real-time, with optional displays for perspective, scale distortions, and attribute filtering. In particular, Terrestrial Laser Scanning (TSL) instruments using Light Detection And Ranging technology (LIDAR) are capable of capturing topographic details and achieve modelling accuracy within a few centimetres. The data obtained permits the creation of detailed 3-D terrain models of larger coverage and accuracy than conventional methods and with almost complete safety of the operators. Here we show digital outcrops may be useful to perform the description of the internal structure of exposed volcanic edifices. A further advantageous application is the estimate of erosion rates and patterns that may be helpful in terms of hazard assessment or preservation of volcanic landscapes. We use as an example of application the Croscat volcano, a monogenetic edifice of the La Garrotxa volcanic field (Spain), which quarrying jobs have exposed the internal part of the volcano leading to a perfect view of its interior but making difficult the access to the upper parts. The Croscat volcano is additionally one of the most emblematic symbols of the La Garrotxa Volcanic Zone Natural Park being its preservation a main target of the park administration.

  20. Phenomenology of non-volcanic deep tremor, slow slip and the third slow earthquake in southwest Japan subduction zone

    NASA Astrophysics Data System (ADS)

    Obara, K.; Ito, Y.; Sekine, S.; Hirose, H.; Shiomi, K.

    2006-12-01

    Coupling phenomena of the non-volcanic low-frequency tremor and short-term slow slip event reflect the subduction process at the transition zone of deeper plate interface. In southwest Japan, non-volcanic tremors are distributed in some clusters along the 30km depth contour line of the upper boundary of the subducting Philippine Sea plate [Obara, 2002]. Peak of tremor activity recurs with regular intervals accompanying to short- term slow slip event lasting for a several days [Obara, et al., 2004]. In western Shikoku, the episodic tremor and slow slip have been clearly detected every six months. On the other hand, in central and eastern Shikoku, the tremor occurs with a few months interval. This suggests that the periodic stick-slip behavior has a spatial variation along the same slab. The regularity of recurrence interval is sometimes distorted by other seismic phenomena. In western Shikoku, the episodic tremor and slip occurred in winter and summer during two years of 2001 and 2002. However, during and after the period of the long-term slow slip event on the latter half of 2003 in this area, the recurrence interval was shortened to three months. Then, the half-year interval returned again since 2005. Northern Kii and Tokai areas, located on both sides of the Ise Bay, central part of Japan, are active tremor and slip source areas with the recurrence interval of six months. In December 2004 and July 2005, the episodic tremor and slip occurred in both areas independently with time gap of a few weeks. On the other hand, in January 2006, the tremor and slow slip began from the central part of Kii peninsula and gradually migrated to northeast. The activity at last went across the Ise Bay and advanced through the Tokai area. This continuous activity extending for 200km is the first accident since the tremor monitoring has started from 2001. Beneath the Ise Bay area, the configuration of the subducting Philippine Sea plate has a small ridge structure estimated from the

  1. Middle Cambrian to Late Ordovician evolution of the Appalachian margin: Foundering of a passive margin to form a subduction zone and volcanic arc

    SciTech Connect

    Washington, P.A. , Southern Pines, NC )

    1994-03-01

    From late Middle Cambrian to early Late Ordovician time, the Appalachian passive margin experienced a series of orogenic events culminating in the Taconic orogeny. Most of these events are generally viewed as enigmatic and isolated, but they can be viewed as a coherent tectonic sequence of events. The early stages involved broad uplifts and localized extension, especially of internal shelf and adjacent continental interiors. Later stages involved increased subsidence rates of the outer shelf, resulting in retreat of the outer margin of the carbonate platform.The beginning of volcanic activity coincides with, or immediately follows, the rapid subsidence. Onset of compressional orogenesis is often temporally separated from the initial rapid subsidence. These events can be integrated into a tectonic model in which the passive margin is converted into an active Andean margin. Early uplift and extension events represented the surface expression of the beginning of deep-seated downward mantle convection. Subsequent rapid subsidence events represented the mechanical failure of the lithosphere as the convection reaches maturity. Failure of the lithosphere resulted in a subduction zone that quickly created arc volcanism. The compressive Taconic orogenesis occurred when the arc was thrust back onto the shelf margin as the subduction zone migrated continentward in response to progressively channeled convective flow.

  2. Seismic refraction studies of volcanic crust in Costa Rica and of critical zones in the southern Sierra Nevada, California and Laramie Range, Wyoming

    NASA Astrophysics Data System (ADS)

    Hayes, Jorden L.

    This work demonstrates the utility of seismic refraction surveys to understanding geologic processes at a range of scales. Each chapter presents subsurface maps of seismic p-wave velocities, which vary due to contrasts in elastic material properties. In the following chapters we examine seismic p-wave velocity variations that result from volcanic and tectonic processes within Earth's crust and chemical and physical weathering processes within Earth's near-surface environment. Chapter one presents results from an across-arc wide-angle seismic refraction survey of the Costa Rican volcanic front. These results support the hypothesis that juvenile continental crust may form along volcanic island arcs if built upon relatively thick substrates (i.e., large igneous provinces). Comparisons of velocity-depth functions show that velocities within the active arc of Costa Rica are lower than other modern island arcs (i.e., volcanic arcs built upon oceanic crust) and within the high-velocity extreme of bulk continental crust. Chapter two shows that physical processes can dominate over chemical processes in generating porosity in the deep critical zone and outlines a new framework for interpreting subsurface chemical and physical weathering at the landscape scale. Direct measurements of saprolite from boreholes at the Southern Sierra Nevada Critical Zone Observatory show that, contrary to convention, saprolite may experience high levels of volumetric strain (>35%) and uniform mass loss in the upper 11 m. By combining observations from boreholes and seismic refraction surveys we create a map of volumetric strain across the landscape. Variations in inferred volumetric strain are consistent with opening-mode fracture patterns predicted by topographic and tectonic stress models. Chapter three is a characterization of fracture distribution in the deep critical zone from geophysical and borehole observations in the Laramie Mountains, Wyoming. Data from core and down-hole acoustic

  3. A new model for the development of the active Afar volcanic margin

    NASA Astrophysics Data System (ADS)

    Pik, Raphaël; Stab, Martin; Bellahsen, Nicolas; Leroy, Sylvie

    2016-04-01

    response to the deformation of the lithosphere, through a petrological and geochemical study of the pre- to syn-rift lavas and concluded that the lithospheric mantle experienced the combined effect of post-plume cooling, but also thinning during the Miocene. This is accompanied by the early channelization of the plume head into narrower zones, which helped focus extension at the future volcanic margins location. The anomalous mantle potential temperature increased during the very last localization phase (< 1 Ma), which leads us to argue in favor of the focussed activity of a plume stem below the volcanic margin, instead of purely passive adiabatic decompression. Our new interpretation of the regional isotopic signatures of lavas depicts a clear framework of the Afar plume and lithospheric mantle relationships to on going extension and segmentation of these margins, and allow us to propose new contrasted models for their development.

  4. Temporal and geochemical constraints on active volcanism in southeastern Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Catalano, J. P.; Baldwin, S.; Fitzgerald, P. G.; Webb, L. E.; Hollocher, K.

    2010-12-01

    have negative Nb and positive Sr anomalies, but the LREE and incompatible elements are depleted with respect to the volcanics on SE Goodenough. While trace and REE geochemistry suggests that young volcanics are derived from a subduction zone source, lack of a well defined increase in P-wave velocities associated with a southward subducted slab [beneath the Papuan Peninsula], and lack of 10Be enrichment in samples collected from historic eruptive products on Mt. Lamington suggests that active subduction is not responsible for generation of young lavas. An alternative hypothesis is that the negative Nb anomaly in young Woodlark Rift lavas is an inherited component and modern volcanism in the D’Entrecasteaux Islands results from decompression melting of a previously ‘subduction modified mantle as the lithosphere is extended ahead of the westward propagating seafloor spreading rift tip.

  5. Igneous activity and related ore deposits in the western and southern Tushar Mountains, Marysvale volcanic field, west-central Utah

    USGS Publications Warehouse

    Steven, Thomas A.

    1984-01-01

    PART A: Igneous activity in the Marysvale volcanic field of western Utah can be separated into many episodes of extrusion, intrusion, and hydrothermal activity. The rocks of the western Tushar Mountains, near the western part of the volcanic field, include intermediate-composition, calc-alkalic volcanic rocks erupted from scattered volcanoes in Oligocene through earliest Miocene time and related monzonitic intrusions emplaced 24-23 m.y. ago. Beginning 22-21 m.y. ago and extending through much of the later Cenozoic, a bimodal basalt-rhyolite assemblage was erupted widely throughout the volcanic field. Only volcanic and intrusive rocks belonging to the rhyolitic end member of this bimodal assemblage are present in the western Tushar Mountains; most of these rocks either fill the Mount Belknap caldera (19 m.y. old) or are part of the rhyolite of Gillies Hill (9---8 m.y. old). Episodic hydrothermal activity altered and mineralized rocks at many places in the western Tushar Mountains during Miocene time. The earliest activity took place in and adjacent to monzonitic calcalkalic intrusions emplaced in the vicinity of Indian Creek and Cork Ridge. These rocks were widely propylitized, and gold-bearing quartz-pyrite-carbonate veins formed in local fractures. Hydrothermal activity associated with the Mount Belknap caldera mobilized and redeposited uranium contained in the caldera-fill rocks and formed primary concentrations of lithophile elements (including molybdenum and uranium) in the vicinity of intrusive bodies. Hydrothermal activity associated with the rhyolite of Gillies Hill altered and mineralized rocks at several places along the fault zone that marks the western margin of the Tushar Mountains; the zoned alunite and gold deposits at Sheep Rock, the gold deposit at the Sunday Mine, and an alunite deposit near Indian Creek were thus produced. Resetting of isotopic ages suggests that another center of hydrothermally altered rocks associated with a buried pluton about

  6. Tectonic Setting and Bimodal Magmatic Evolution of Eocene Volcanic Rocks of the Bijgerd-Kuh-e Kharchin area, Uromieh-Dokhtar Zone, Iran

    NASA Astrophysics Data System (ADS)

    Davarpanah, A.; Khalatbari-Jafari, M.; Babaie, H. A.; Krogstad, E. J.; Mobasher, K.; La Tour, T. E.; Deocampo, D. M.

    2008-12-01

    Geochemical composition and texture of the Middle and Late Eocene volcanic, volcaniclastic, and volcanic- sedimentary rocks in the Bijgerd-Kuh-e Kharchin area, northwest of Saveh, provide significant geochemical and geological clues for the tectonic and magmatic evolution of the Uromieh-Dokhtar volcanic-plutonic zone of Iran. The Middle Eocene volcanic rocks have an intermediate composition and include green tuff and tuffaceous sandstone with intercalated sandstone, sandy tuff, and shale. The shale has lenses of nummulite- bearing limestone with a Middle Eocene detrital age. The time between the Middle and Late Eocene volcanic activities in this area is marked by the presence of andesite and rhyolitic tuff. The Late Eocene succession is distinguished by the presence of four alternating levels (horizons) of intermediate lava and ignimbrite which we designate as Eig. The ignimbrites of the Eig sequence have a rhyolitic composition and include ignimbrite- breccia, ignimbrite-tuff, and ignimbrite-lava pairs. The volume of the felsic volcanic rocks in this sequence far exceeds that of the intermediate rocks, which makes it unlikely that they evolved through the magmatic differentiation of a basaltic magma. The presence of the nummulite-bearing limestone lenses, and sandstone and conglomerate interbeds between the ignimbrites, suggests a shallow marine environment for the pyroclastic deposition and probably the eruptions. The tuff and siltstone of the Est unit that sits above the first ignimbrite may represent deep water, Late Eocene deposit. Oligo-Miocene limestone of the Qom Formation unconformably overlies the uppermost Late Eocene ignimbrite. Washings from red marls give microfossils with Late Eocene age for the Eig sequence, which is synchronous with other paleontological evidence that puts the peak volcanic activity as Late Eocene in the Bijgerd-Kuh-e Kharchin area. Field and petrographic evidence for magma mixing/mingling is given by the presence of mafic

  7. Results from NICLAKES Survey of Active Faulting Beneath Lake Managua,Central American Volcanic arc

    NASA Astrophysics Data System (ADS)

    McIntosh, K.; Funk, J.; Mann, P.; Perez, P.; Strauch, W.

    2006-12-01

    Lake Managua covers an area of 1,035 km2 of the Central American volcanic arc and is enclosed by three major stratovolcanoes: Momotombo to the northwest was last active in AD 1905, Apoyeque in the center on the Chiltepe Peninsula was last active ca. 4600 years BP, and Masaya to the southeast was last active in AD 2003. A much smaller volcano in the lake (Momotombito) is thought to have been active <4500 yrs B.P. In May of 2006, we used a chartered barge to collect 330 km of 3.5 kHz profiler data along with coincident 274 km of sidescan sonar and 27 km of seismic reflection data. These data identify three zones of faulting on the lake floor: 1) A zone of north-northeast-striking faults in the shallow (2.5-7.5 m deep) eastern part of the lake that extends from the capital city of Managua, which was severely damaged by shallow, left-lateral strike-slip displacements on two of these faults in 1931 (M 5.6) and 1972 (M 6.2): these faults exhibit a horst and graben character and include possible offsets on drowned river valleys 2) a semicircular rift zone that is 1 km wide and can be traced over a distance of 30 km in the central part of the lake; the rift structure defines the deepest parts of the lake ranging from 12 to 18 m deep and is concentric about the Apoyeque stratocone/Chiltepe Peninsula; and 3) a zone of fault scarps defining the northwestern lake shore that may correlate to the northwestern extension of the Mateare fault zone, a major scarp-forming fault that separates the Managua lowlands from the highlands south and west of the city. Following previous workers, we interpret the northeast- trending group of faults in the eastern part of the lake as part of a 15-km-long discontinuity where the trend of the volcanic arc is offset in a right-lateral sense. The semi-circular pattern of the rift zone that is centered on Chiltepe Peninsula appears to have formed as a distal effect of either magma intrusion or withdrawal from beneath this volcanic complex. The

  8. Geochemical evidence of multiple isolated magma batches in the paired Mamaku and Ohakuri eruption, Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Bégué, F.; Deering, C. D.; Gravley, D.; kennedy, B.; Chambefort, I. S.

    2012-12-01

    The Central Taupo Volcanic Zone (TVZ) is a rifted-arc where dominantly rhyolitic volcanism is closely related with extensional tectonism. The 240ka paired Mamaku (>145km3) and Ohakuri (>100km3) eruption evacuated rhyolitic magma from the Rotorua and Ohakuri calderas, respectively, which are situated ~35km apart. Structural links between these two calderas have already been mapped, with collateral subsidence features having formed simultaneously as the calderas collapsed. The Mamaku and Ohakuri ignimbrites share pronounced geochemical similarities; they co-erupted three different pumice types each, from a rhyo-dacite (Type 3) to more evolved high-silica rhyolite compositions (Type 2 and 1), with the same mineral assemblage (plagioclase, quartz, orthopyroxene, Fe-Ti oxides), and nearly identical bulk pumice and matrix glass compositions for Type 1 and 2. New data on quartz-hosted melt inclusions, however, show that each type from the Mamaku and the Ohakuri has a distinct signature. The Mamaku melt is distinct from the Ohakuri based on its lower U content (Ma<1ppm, Oh.2-4ppm), higher Cs content (Ma.5-7ppm, Oh.2-5ppm), higher Li (Ma.60-90ppm, Oh.20-55ppm), and higher water by difference (WBD, Ma.~5.2wt%, Oh.~4.4wt%). Likewise, Type 1 and 2 data for the Mamaku and Ohakuri, plot along distinct trends for major and trace elements (e.g. CaO, Rb, Sr). These results rule out crystal fractionation as a potential mechanism for generation of a Type 1 rhyolite from a Type 2, as has been suggested by previous authors. The Ohakuri airfall, which was the first to erupt and is interbedded with the Mamaku ignimbrite, shows geochemical characteristics distinct from Type 1 and 2 melt inclusions from both Mamaku and Ohakuri ignimbrites. While matrix glass compositions are identical to the Type 1 pumice, melt inclusions differ, in recording higher Li and Cs contents. Furthermore no mixing or mingling is observed in the pumices (i.e. melt inclusion from a certain type only occur in the

  9. Mihi Breccia: A stack of lacustrine sediments and subaqueous pyroclastic flows within the Taupo Volcanic Zone, New Zealand

    USGS Publications Warehouse

    Downs, Drew

    2016-01-01

    The Taupo Volcanic Zone (TVZ), New Zealand, encompasses a wide variety of arc-related strata, although most of its small-volume (non-caldera-forming) eruptions are poorly-exposed and extensively hydrothermally altered. The Mihi Breccia is a stratigraphic sequence consisting of interbedded rhyolitic pyroclastic flows and lacustrine sediments with eruption ages of 281 ± 18 to at least 239 ± 6 ka (uncertainties at 2σ). In contrast to other small-volume rhyolitic eruptions within the TVZ, Mihi Breccia is relatively well-exposed within the Paeroa fault block, and contains minimal hydrothermal alteration. Pyroclastic flow characteristics and textures including: 1) breadcrusted juvenile clasts, 2) lack of welding, 3) abundant ash-rich matrix, 4) lack of fiamme and eutaxitic textures, 5) lack of thermal oxidation colors, 6) lack of cooling joints, 7) exclusive lacustrine sediment lithic clasts, and 8) interbedding with lacustrine sediments, all indicating that Mihi Breccia strata originated in a paleo-lake system. This ephemeral paleo-lake system is inferred to have lasted for > 50 kyr (based on Mihi Breccia age constraints), and referred to as Huka Lake. Mihi Breccia pyroclastic flow juvenile clast geochemistry and petrography correspond with similar-aged (264 ± 8, 263 ± 10, and 247 ± 4 ka) intra-caldera rhyolite domes filling the Reporoa caldera (source of the 281 ± 81 Kaingaroa Formation ignimbrite). These exposed intra-caldera rhyolite domes (as well as geophysically inferred subsurface domes) are proposed to be source vents for the Mihi Breccia pyroclastic flows. Soft-sediment deformation associated with Mihi Breccia strata indicate either seismic shock, rapid sediment loading during pyroclastic flow emplacement, or both. Thus, the Mihi Breccia reflects a prolonged series of subaqueous rhyolite dome building and associated pyroclastic flows, accompanied by seismic activity, emplaced into a large paleo-lake system within the TVZ.

  10. An Early Cretaceous volcanic arc/marginal basin transition zone, Peninsula hardy, southernmost Chile

    NASA Astrophysics Data System (ADS)

    Miller, Christopher A.; Barton, Michael; Hanson, Richard E.; Fleming, Thomas H.

    1994-10-01

    The Hardy Formation represents a latest Jurassic-Early Cretaceous volcanic arc that was located along the Pacific margin of southern South America. It was separated from the continent by a marginal basin floored by portions of an ophiolite sequence (the Rocas Verdes ophiolites). The transition between the arc and marginal basin occurs on Peninsula Hardy, southernmost Chile, where there is a lateral facies transition from arc deposits of the Hardy Formation into proximal marginal basin fill of the Yahgan Formation. Interfingering of arc and marginal basin sequences demonstrates that subduction-related arc magmatism was concurrent with marginal basin formation. The lateral facies transition is reflected in the geochemistry of volcanic rocks from the Hardy and Yahgan formations. Basalts, andesites and dacites of the arc sequence follow a calc-alkaline differentiation trend whereas basalts from the marginal basin follow a tholeiitic differentiation trend. Estimates of temperature and oxygen fugacity for crystallization of the arc andesites are similar to values reported for other calc-alkaline andesites. It is suggested that water activity influenced the early or late crystallization of Ti-magnetite and this controlled the style of differentiation of the magmas erupted on Peninsula Hardy. Magmas with high water contents evolved along the calc-alkaline differentiation trend whereas those with low water contents evolved along the tholeiitic differentiation trend. Some rhyolites are differentiated from the calc-alkaline andesites and dacites, but most appear to be the products of crustal anatexis on the basis of trace-element evidence. The arc basalts and some marginal basin basalts show relative enrichment in LILE, relative depletion in HFSE, and enrichment in LREE. Other marginal basin basalts are LREE depleted and show small relative depletions in HFSE. Basalts with both calc-alkaline and tholeiitic affinities can also be recognized in the Rocas Verdes ophiolites

  11. Gish Bar Patera, Io: Geology and Volcanic Activity, 1996-2001

    NASA Technical Reports Server (NTRS)

    Perry, Jason; Radebaugh, Jani; Lopes, Rosaly; McEwen, Alfred; Keszthelyi, Laszlo

    2003-01-01

    Since the two Voyagers passed by Jupiter in 1979, it has been known that volcanic activity is ubiquitous on the surface of Io. With over 400 volcanic centers, Io is even more volcanically active than the earth with massive flood basalt-style eruptions and komatitite lavas a common occurrence. Additionally, some volcanoes appear to be giant lava lakes, with violent activity churning the crust of the lake for periods of 20 years or more. Finally, sulfur is believed to play a large role in Io's volcanism, be it as a primary lava or as a secondary product of large, high-temperature eruptions. By studying one volcano in particular, Gish Bar Patera, one can observe many of these characteristics in one volcanic center.

  12. Evidence for late tertiary volcanic activity in the northern black hills, South dakota.

    PubMed

    Kirchner, J G

    1977-05-27

    Rhyolitic volcanic rock in the northern Black Hills has a potassium-argon isotopic age of 10.5 +/- 1.5 million years. This is considerably younger than any previously reported igneous activity in this or adjacent areas and indicates that the renewed uplift of the Black Hills, which occurred after the Oligocene epoch, was also accompanied by some volcanism. PMID:17778711

  13. 2011 volcanic activity in Alaska: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    McGimsey, Robert G.; Maharrey, J. Zebulon; Neal, Christina A.

    2014-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, and volcanic unrest at or near three separate volcanic centers in Alaska during 2011. The year was highlighted by the unrest and eruption of Cleveland Volcano in the central Aleutian Islands. AVO annual summaries no longer report on activity at Russian volcanoes.

  14. Io's Diverse Styles of Volcanic Activity: Results from Galileo NIMS

    NASA Technical Reports Server (NTRS)

    Lopes, R. M. C.; Smythe, W. D.; Kamp, L. W.; Doute, S.; Carlson, R.; McEwen, A.; Geissler, P.

    2001-01-01

    Observations by Galileo's Near-Infrared Mapping Spectrometer were used to map the thermal structure of several of Io's hot spots, revealing different styles of volcanism Additional information is contained in the original extended abstract..

  15. Presynaptic active zones in invertebrates and vertebrates.

    PubMed

    Ackermann, Frauke; Waites, Clarissa L; Garner, Craig C

    2015-08-01

    The regulated release of neurotransmitter occurs via the fusion of synaptic vesicles (SVs) at specialized regions of the presynaptic membrane called active zones (AZs). These regions are defined by a cytoskeletal matrix assembled at AZs (CAZ), which functions to direct SVs toward docking and fusion sites and supports their maturation into the readily releasable pool. In addition, CAZ proteins localize voltage-gated Ca(2+) channels at SV release sites, bringing the fusion machinery in close proximity to the calcium source. Proteins of the CAZ therefore ensure that vesicle fusion is temporally and spatially organized, allowing for the precise and reliable release of neurotransmitter. Importantly, AZs are highly dynamic structures, supporting presynaptic remodeling, changes in neurotransmitter release efficacy, and thus presynaptic forms of plasticity. In this review, we discuss recent advances in the study of active zones, highlighting how the CAZ molecularly defines sites of neurotransmitter release, endocytic zones, and the integrity of synapses.

  16. Presynaptic active zones in invertebrates and vertebrates

    PubMed Central

    Ackermann, Frauke; Waites, Clarissa L; Garner, Craig C

    2015-01-01

    The regulated release of neurotransmitter occurs via the fusion of synaptic vesicles (SVs) at specialized regions of the presynaptic membrane called active zones (AZs). These regions are defined by a cytoskeletal matrix assembled at AZs (CAZ), which functions to direct SVs toward docking and fusion sites and supports their maturation into the readily releasable pool. In addition, CAZ proteins localize voltage-gated Ca2+ channels at SV release sites, bringing the fusion machinery in close proximity to the calcium source. Proteins of the CAZ therefore ensure that vesicle fusion is temporally and spatially organized, allowing for the precise and reliable release of neurotransmitter. Importantly, AZs are highly dynamic structures, supporting presynaptic remodeling, changes in neurotransmitter release efficacy, and thus presynaptic forms of plasticity. In this review, we discuss recent advances in the study of active zones, highlighting how the CAZ molecularly defines sites of neurotransmitter release, endocytic zones, and the integrity of synapses. PMID:26160654

  17. Complex explosive volcanic activity on the Moon within Oppenheimer crater

    NASA Astrophysics Data System (ADS)

    Bennett, Kristen A.; Horgan, Briony H. N.; Gaddis, Lisa R.; Greenhagen, Benjamin T.; Allen, Carlton C.; Hayne, Paul O.; Bell, James F.; Paige, David A.

    2016-07-01

    Oppenheimer crater is a floor-fractured crater located within the South Pole-Aitken basin on the Moon, and exhibits more than a dozen localized pyroclastic deposits associated with the fractures. Localized pyroclastic volcanism on the Moon is thought to form as a result of intermittently explosive Vulcanian eruptions under low effusion rates, in contrast to the higher-effusion rate, Hawaiian-style fire fountaining inferred to form larger regional deposits. We use Lunar Reconnaissance Orbiter Camera images and Diviner Radiometer mid-infrared data, Chandrayaan-1 orbiter Moon Mineralogy Mapper near-infrared spectra, and Clementine orbiter Ultraviolet/visible camera images to test the hypothesis that the pyroclastic deposits in Oppenheimer crater were emplaced via Vulcanian activity by constraining their composition and mineralogy. Mineralogically, we find that the deposits are variable mixtures of orthopyroxene and minor clinopyroxene sourced from the crater floor, juvenile clinopyroxene, and juvenile iron-rich glass, and that the mineralogy of the pyroclastics varies both across the Oppenheimer deposits as a whole and within individual deposits. We observe similar variability in the inferred iron content of pyroclastic glasses, and note in particular that the northwest deposit, associated with Oppenheimer U crater, contains the most iron-rich volcanic glass thus far identified on the Moon, which could be a useful future resource. We propose that this variability in mineralogy indicates variability in eruption style, and that it cannot be explained by a simple Vulcanian eruption. A Vulcanian eruption should cause significant country rock to be incorporated into the pyroclastic deposit; however, large areas within many of the deposits exhibit spectra consistent with high abundances of juvenile phases and very little floor material. Thus, we propose that at least the most recent portion of these deposits must have erupted via a Strombolian or more continuous fire

  18. Diffuse CO2 degassing and volcanic activity at Cape Verde islands, West Africa

    NASA Astrophysics Data System (ADS)

    Dionis, Samara M.; Pérez, Nemesio M.; Hernández, Pedro A.; Melián, Gladys; Rodríguez, Fátima; Padrón, Eleazar; Sumino, Hirochika; Barrrancos, Jose; Padilla, Germán D.; Fernandes, Paulo; Bandomo, Zuleyka; Silva, Sónia; Pereira, Jose M.; Semedo, Hélio; Cabral, Jeremias

    2015-04-01

    Diffuse CO2 emission surveys were carried out at São Vicente, Brava, and Fogo islands, Cape Verde, archipelago to investigate the relationship between diffuse CO2 degassing and volcanic activity. Total amounts of diffuse CO2 discharged through the surface environment of the islands of São Vicente, Brava, and Fogo were estimated in 226, 50, and 828 t d-1, respectively. The highest CO2 efflux values of the three volcanic islands systems were observed at the summit crater of Pico do Fogo (up to 15.7 kg m-2 d-1). Statistical graphical analysis of the data suggests two geochemical populations for the diffuse CO2 emission surveys. The geometric mean of the peak population, expressed as a multiple of the geometric mean of the background population, seems to be the best diffuse CO2 emission geochemical parameter to correlate with the volcanic activity (age of the volcanism) for these three island volcanic systems at Cape Verde. This observation is also supported by helium isotopic signature observed in the Cape Verde's fluids, fumaroles, and ground waters. This study provides useful information about the relationship between diffuse CO2 degassing and volcanic activity at Cape Verde enhancing the use of diffuse CO2 emission as a good geochemical tool, for volcanic monitoring at Cape Verde as well as other similar volcanic systems.

  19. Catastrophic volcanism

    NASA Technical Reports Server (NTRS)

    Lipman, Peter W.

    1988-01-01

    Since primitive times, catastrophes due to volcanic activity have been vivid in the mind of man, who knew that his activities in many parts of the world were threatened by lava flows, mudflows, and ash falls. Within the present century, increasingly complex interactions between volcanism and the environment, on scales not previously experienced historically, have been detected or suspected from geologic observations. These include enormous hot pyroclastic flows associated with collapse at source calderas and fed by eruption columns that reached the stratosphere, relations between huge flood basalt eruptions at hotspots and the rifting of continents, devastating laterally-directed volcanic blasts and pyroclastic surges, great volcanic-generated tsunamis, climate modification from volcanic release of ash and sulfur aerosols into the upper atmosphere, modification of ocean circulation by volcanic constructs and attendent climatic implications, global pulsations in intensity of volcanic activity, and perhaps triggering of some intense terrestrial volcanism by planetary impacts. Complex feedback between volcanic activity and additional seemingly unrelated terrestrial processes likely remains unrecognized. Only recently has it become possible to begin to evaluate the degree to which such large-scale volcanic processes may have been important in triggering or modulating the tempo of faunal extinctions and other evolutionary events. In this overview, such processes are examined from the viewpoint of a field volcanologist, rather than as a previous participant in controversies concerning the interrelations between extinctions, impacts, and volcanism.

  20. Volcanic geology and eruption frequency, lower east rift zone of Kilauea volcano, Hawaii

    USGS Publications Warehouse

    Moore, R.B.

    1992-01-01

    Detailed geologic mapping and radiocarbon dating of tholeiitic basalts covering about 275 km2 on the lower east rift zone (LERZ) and adjoining flanks of Kilauea volcano, Hawaii, show that at least 112 separate eruptions have occurred during the past 2360 years. Eruptive products include spatter ramparts and cones, a shield, two extensive lithic-rich tuff deposits, aa and pahoehoe flows, and three littoral cones. Areal coverage, number of eruptions and average dormant interval estimates in years for the five age groups assigned are: (I) historic, i.e. A D 1790 and younger: 25%, 5, 42.75; (II) 200-400 years old: 50%, 15, 14.3: (III) 400-750 years old: 20%, 54, 6.6; (IV) 750-1500 years old: 5%, 37, 20.8; (V) 1500-3000 years old: <1%, 1, unknown. At least 4.5-6 km3 of tholeiitic basalt have been erupted from the LERZ during the past 1500 years. Estimated volumes of the exposed products of individual eruptions range from a few tens of cubic meters for older units in small kipukas to as much as 0.4 km3 for the heiheiahulu shield. The average dormant interval has been about 13.6 years during the past 1500 years. The most recent eruption occurred in 1961, and the area may be overdue for its next eruption. However, eruptive activity will not resume on the LERZ until either the dike feeding the current eruption on the middle east rift zone extends farther down rift, or a new dike, unrelated to the current eruption, extends into the LERZ. ?? 1992 Springer-Verlag.

  1. Early Detection of Volcanic Eruptions Using Lightning Activity in South America

    NASA Astrophysics Data System (ADS)

    Nicora, M. G.; Bürgesser, R. E.; Quel, E. J.; Avila, E.

    2013-05-01

    A study of the lightning activity produced by the eruption of the Cordón Caulle volcano during June 2011 was performed by using the World Wide Lightning Location Network data. The observed lightning activity corresponds to the electrical activity of the volcanic plume with a good correlation between the amount of lightning detected and the volcanic plume height. Although the detected lightning activity was low, the results agree with previous studies and show that lightning activity could be use as a proxy of the volcanic activity. This study also shows the feasibility on the use of the network for early detection of volcanic eruptions. The Global Volcanic Lightning Monitor is an experimental research project, based on the World Wide Lightning Location Network data, which sent an alert of the eruption of the Cordón Caulle volcanic complex before the report of the National Service of Geology and Mining (SERNAGEOMIN) of Chile. This demonstrate the relevance of the system as support of national warning systems (if any) and, where there are no continuous monitoring of eruptive systems, as early warning of volcanic eruptions.

  2. 1996 volcanic activity in Alaska and Kamchatka: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    Neal, Christina A.; McGimsey, Robert G.

    1997-01-01

    During 1996, the Alaska Volcano Observatory (AVO) responded to eruptive activity, anomalous seismicity, or suspected volcanic activity at 10 of the approximately 40 active volcanic centers in the state of Alaska. As part of a formal role in KVERT (the Kamchatkan Volcano Eruption Response Team), AVO staff also disseminated information about eruptions and other volcanic unrest at six volcanic centers on the Kamchatka Peninsula and in the Kurile Islands, Russia.

  3. SO2 on Venus: IUE, HST and ground-based measurements, and the active volcanism connection

    NASA Technical Reports Server (NTRS)

    Na, C. Y.; Barker, E. S.; Stern, S. A.; Esposito, L. W.

    1993-01-01

    Magellan images have shown that the volcanic features are widespread over the surface of Venus. The question of whether there is active volcanism is important for understanding both the atmospheric and the geological processes on Venus. The thick cloud cover of Venus precludes any direct observation of active volcanoes even if they exist. The only means of monitoring the active volcanism on Venus at present seems to be remote sensing from Earth. Continuous monitoring of SO2 is important to establish the long term trend of SO2 abundance and to understand the physical mechanism responsible for the change.

  4. Isotopic compositions of volcanic arc rocks in the Southern Volcanic Zone (33°-43°S), Chile: along- and across-arc variations

    NASA Astrophysics Data System (ADS)

    Jacques, Guillaume; Hoernle, Kaj; Gill, Jim; Wehrmann, Heidi

    2014-05-01

    We investigate young, olivine-bearing volcanic arc (VA) rocks from the Southern Volcanic Zone (33-43°S; SVZ) in Chile, and from the backarc (BA) in Argentina for their major and trace element, and Sr-Nd-Hf-Pb-O isotope geochemistry. The compositional data are processed to identify the source components contributing to the arc magmas and to estimate their proportions, with the aim to better understand the effects of the large-scale along-arc tectonic variations onto melt generation and erupted compositions. The Transitional (T) SVZ (34.5-38°S; Jacques et al., 2013) samples overlap the BA samples in Sr and Nd isotopes, whereas the Central (C) SVZ (38-43°S; Jacques et al., submitted, Chemical Geology) samples are shifted to slightly higher Sr and/or Nd isotope ratios. All samples form a tight correlation on the Pb isotope diagrams. The VA samples plot at the radiogenic end of the positive BA array and overlap trench sediment, indicating mixing between a South Atlantic MORB-type source and a slab component derived from subducted trench sediments and altered oceanic crust. On the Nd versus Hf isotope diagram, the VA and BA form two sub parallel linear trends, neither pointing to subducting sediment. The VA may display an asthenospheric mantle array, whereas enriched Proterozoic lithospheric mantle may be involved in the BA. The CSVZ samples have higher fluid-mobile to fluid-immobile element ratios and lower more- to less-incompatible fluid-immobile element ratios than the TSVZ samples, consistent with higher hydrous melt flux and higher degrees of melting resulting in higher magma production and eruption rates in the CSVZ. Low δ18O(melt) of CSVZ lavas suggests that the source of the enhanced water flux is likely to be hydrated lower crust and serpentinized upper mantle of the incoming plate, resulting from the multiple large fracture zones in this part of the SVZ. The δ18O(melt) values of the NSVZ, TSVZ and BA, on the other hand, largely overlap the MORB mantle

  5. Soil gas radon and volcanic activity at El Hierro (Canary Islands) before and after the 2011-2012 submarine eruption

    NASA Astrophysics Data System (ADS)

    Barrancos, J.; Padilla, G.; Hernandez Perez, P. A.; Padron, E.; Perez, N.; Melian Rodriguez, G.; Nolasco, D.; Dionis, S.; Rodriguez, F.; Calvo, D.; Hernandez, I.

    2012-12-01

    El Hierro is the youngest and southernmost island of the Canarian archipelago and represents the summit of a volcanic shield elevating from the surrounding seafloor at depth of 4000 m to up to 1501 m above sea level. The island is believed to be near the present hotspot location in the Canaries with the oldest subaerial rocks dated at 1.12 Ma. The subaerial parts of the El Hierro rift zones (NE, NW and S Ridges) are characterized by tightly aligned dyke complexes with clusters of cinder cones as their surface expressions. Since July 16, 2011, an anomalous seismicity at El Hierro Island was recorded by IGN seismic network. Volcanic tremor started at 05:15 hours on October 10, followed on the afternoon of October 12 by a green discolouration of seawater, strong bubbling and degassing indicating the initial stage of submarine volcanic eruption at approximately 2 km off the coast of La Restinga, El Hierro. Soil gas 222Rn and 220Rn activities were continuously measured during the period of the recent volcanic unrest occurred at El Hierro, at two different geochemical stations, HIE02 and HIE03. Significant increases in soil 222Rn activity and 222Rn/220Rn ratio from the soil were observed at both stations prior the submarine eruption off the coast of El Hierro, showing the highest increases before the eruption onset and the occurrence of the strongest seismic event (M=4.6). A statistical analysis showed that the long-term trend of the filtered data corresponded closely to the seismic energy released during the volcanic unrest. The observed increases of 222Rn are related to the rock fracturing processes (seismic activity) and the magmatic CO2 outflow increase, as observed in HIE03 station. Under these results, we find that continuous soil radon studies are important for evaluating the volcanic activity of El Hierro and they demonstrate the potential of applying continuous monitoring of soil radon to improve and optimize the detection of early warning signals of future

  6. Rapid response of a hydrologic system to volcanic activity: Masaya volcano, Nicaragua

    USGS Publications Warehouse

    Pearson, S.C.P.; Connor, C.B.; Sanford, W.E.

    2008-01-01

    Hydrologic systems change in response to volcanic activity, and in turn may be sensitive indicators of volcanic activity. Here we investigate the coupled nature of magmatic and hydrologic systems using continuous multichannel time series of soil temperature collected on the flanks of Masaya volcano, Nicaragua, one of the most active volcanoes in Central America. The soil temperatures were measured in a low-temperature fumarole field located 3.5 km down the flanks of the volcano. Analysis of these time series reveals that they respond extremely rapidly, on a time scale of minutes, to changes in volcanic activity also manifested at the summit vent. These rapid temperature changes are caused by increased flow of water vapor through flank fumaroles during volcanism. The soil temperature response, ~5 °C, is repetitive and complex, with as many as 13 pulses during a single volcanic episode. Analysis of the frequency spectrum of these temperature time series shows that these anomalies are characterized by broad frequency content during volcanic activity. They are thus easily distinguished from seasonal trends, diurnal variations, or individual rainfall events, which triggered rapid transient increases in temperature during 5% of events. We suggest that the mechanism responsible for the distinctive temperature signals is rapid change in pore pressure in response to magmatism, a response that can be enhanced by meteoric water infiltration. Monitoring of distal fumaroles can therefore provide insight into coupled volcanic-hydrologic-meteorologic systems, and has potential as an inexpensive monitoring tool.

  7. Crystal preferred orientations of minerals from mantle xenoliths in alkali basaltic rocks form the Catalan Volcanic Zone (NE Spain)

    NASA Astrophysics Data System (ADS)

    Fernández-Roig, Mercè; Galán, Gumer; Mariani, Elisabetta

    2015-04-01

    Mantle xenoliths in alkali basaltic rocks from the Catalan Volcanic Zone, associated with the Neogene-Quaternary rift system in NE Spain, are formed of anhydrous spinel lherzolites and harzburgites with minor olivine websterites. Both peridotites are considered residues of variable degrees of partial melting, later affected by metasomatism, especially the harzburgites. These and the websterites display protogranular microstructures, whereas lherzolites show continuous variation between protogranular, porphyroclastic and equigranular forms. Thermometric data of new xenoliths indicate that protogranular harzburgites, lherzolites and websterites were equilibrated at higher temperatures than porphyroclastic and equigranular lherzolites. Mineral chemistry also indicates lower equilibrium pressure for porphyroclastic and equigranular lherzolites than for the protogranular ones. Crystal preferred orientations (CPOs) of olivine and pyroxenes from these new xenoliths were determined with the EBSD-SEM technique to identify the deformation stages affecting the lithospheric mantle in this zone and to assess the relationships between the deformation fabrics, processes and microstructures. Olivine CPOs in protogranular harzburgites, lherzolites and a pyroxenite display [010]-fiber patterns characterized by a strong point concentration of the [010] axis normal to the foliation and girdle distribution of [100] and [001] axes within the foliation plane. Olivine CPO symmetry in porphyroclastic and equigranular lherzolites varies continuously from [010]-fiber to orthorhombic and [100]-fiber types. The orthorhombic patterns are characterized by scattered maxima of the three axes, which are normal between them. The rare [100]-fiber patterns display strong point concentration of [100] axis, with normal girdle distribution of the other two axes, which are aligned with each other. The patterns of pyroxene CPOs are more dispersed than those of olivine, especially for clinopyroxene, but

  8. 2010 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    Neal, Christina A.; Herrick, Julie; Girina, O.A.; Chibisova, Marina; Rybin, Alexander; McGimsey, Robert G.; Dixon, Jim

    2014-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, volcanic unrest or suspected unrest at 12 volcanic centers in Alaska during 2010. The most notable volcanic activity consisted of intermittent ash emissions from long-active Cleveland volcano in the Aleutian Islands. AVO staff also participated in hazard communication regarding eruptions or unrest at seven volcanoes in Russia as part of an ongoing collaborative role in the Kamchatka and Sakhalin Volcanic Eruption Response Teams.

  9. Hydrothermal Mineralization Along the Volcanically Active Mariana Arc

    NASA Astrophysics Data System (ADS)

    de Ronde, C. E.; Hein, J. R.; Embley, R. W.; Stern, R. J.

    2004-12-01

    In March and April, 2004, ROPOS ROV dives took place from the R/V T.G. Thompson along the volcanically active Mariana arc to ground truth CTD data collected a year earlier that indicated hydrothermal activity. Dives took place on seven volcanoes, six of which showed hydrothermal activity. We present data on samples collected from NW Rota-1 (14° , 36'N, 144° , 46'E), E. Diamante (15° , 56'N, 145° , 41'E), and NW Eifuku (21° , 29'N, 144° , 03'E), the three sites most studied. All the hydrothermal systems found are associated with volcano summits, or with resurgent domes inside a caldera. Brimstone vent at NW Rota-1 provided a dramatic display of thick, bellowing, yellow plumes that contained ash and molten sulfur. This site occurs at 500 m water depth and clearly shows closely associated magmatic-hydrothermal discharge. Sulfur was the dominant hydrothermal mineral deposited around the vent and occurs as spheres in the surrounding volcaniclastic sediment, fracture fill and veins, and massive deposits. The Black Forest vent field at E Diamante consists of a sulfide-sulfate chimney system developed at about 650 m water depth. This is the only mature system discovered and consists of numerous tall (up to 9 m) chimneys. The measured fluid temperature of 240° C produces boiling at the depth of the vents. The chimneys and mounds are composed of varying amounts of pyrite, sphalerite, chalcopyrite, barite, and anhydrite. Hydrothermal Mn oxides occur on the surface of inactive chimneys. This mineralogy contrasts with the other two systems, which deposit sulfur as the dominant hydrothermal product. The Cu-Zn-Fe-Ba mineralization is perhaps largely controlled by water/rock interaction. A unique hydrothermal field (Champagne field) was found at NW Eifuku where liquid CO2 is discharging from focused- and diffuse-flow vents at 1600 m water depth. The focused-flow vents consist of small chimneys and mounds up to a meter high that are composed of sulfur and yet to be

  10. Hot and Saline Spring Behaviour in the Taupo Volcanic Zone and the North-East German Basin

    NASA Astrophysics Data System (ADS)

    Cacace, M.; Kissling, W.

    2012-04-01

    Hot springs occur in geothermal regions worldwide, and often have important economic or cultural values which can be threatened by geothermal developments. In this paper we describe models of hot springs in the Taupo Volcanic Zone (TVZ) in New Zealand, and of saline springs in the Northeast German Basin (NEGB). In New Zealand, the operation of the Wairakei geothermal power station in the 1950's and early 1960's lead to the collapse of the thermal area known as 'Geyser Valley', and more recently, the spring and Geyser activity in Rotorua was threatened by the widespread and uncontrolled drawoff of geothermal water for domestic use. Similarly, in the NEGB, discharge of saline springs poses serious challenges for groundwater management for agricultural and domestic use, having additional implications for future geothermal energy projects. Despite their obviously very different nature the springs in NEGB and TVZ do have some common characteristics: they both feed fluid to the surface from deeper (geothermal) aquifers through embedded hydrogeological heterogeneities (e.g. fracture systems, erosional gaps and unconformities in the internal stratigraphic sequence), and data shows that they both exhibit irregular flowrates, temperatures and chemistries. Currently used models of hot/saline springs do not show these types of behaviour and offer no understanding of the mechanisms of variability in either setting, or indeed the nature of the connections to deeper aquifers. In this paper we present early results from a study aimed at identifying the most important physical mechanisms governing the dynamics of these systems. We use the simulation code NaCl-Tough2 (Kissling, 2005a,b) to accurately represent the thermodynamics of fluids in both systems. Though relatively simplistic in terms of the modelled geometry these models provide new important insights into the variability of the observed flow dynamics as well as in their causative processes at depths. The results obtained

  11. Magma-derived CO2 emissions in the Tengchong volcanic field, SE Tibet: Implications for deep carbon cycle at intra-continent subduction zone

    NASA Astrophysics Data System (ADS)

    Zhang, Maoliang; Guo, Zhengfu; Sano, Yuji; Zhang, Lihong; Sun, Yutao; Cheng, Zhihui; Yang, Tsanyao Frank

    2016-09-01

    Active volcanoes at oceanic subduction zone have long been regard as important pathways for deep carbon degassed from Earth's interior, whereas those at continental subduction zone remain poorly constrained. Large-scale active volcanoes, together with significant modern hydrothermal activities, are widely distributed in the Tengchong volcanic field (TVF) on convergent boundary between the Indian and Eurasian plates. They provide an important opportunity for studying deep carbon cycle at the ongoing intra-continent subduction zone. Soil microseepage survey based on accumulation chamber method reveals an average soil CO2 flux of ca. 280 g m-2 d-1 in wet season for the Rehai geothermal park (RGP). Combined with average soil CO2 flux in dry season (ca. 875 g m-2 d-1), total soil CO2 output of the RGP and adjacent region (ca. 3 km2) would be about 6.30 × 105 t a-1. Additionally, we conclude that total flux of outgassing CO2 from the TVF would range in (4.48-7.05) × 106 t a-1, if CO2 fluxes from hot springs and soil in literature are taken into account. Both hot spring and soil gases from the TVF exhibit enrichment in CO2 (>85%) and remarkable contribution from mantle components, as indicated by their elevated 3He/4He ratios (1.85-5.30 RA) and δ13C-CO2 values (-9.00‰ to -2.07‰). He-C isotope coupling model suggests involvement of recycled organic metasediments and limestones from subducted Indian continental lithosphere in formation of the enriched mantle wedge (EMW), which has been recognized as source region of the TVF parental magmas. Contamination by crustal limestone is the first-order control on variations in He-CO2 systematics of volatiles released by the EMW-derived melts. Depleted mantle and recycled crustal materials from subducted Indian continental lithosphere contribute about 45-85% of the total carbon inventory, while the rest carbon (about 15-55%) is accounted by limestones in continental crust. As indicated by origin and evolution of the TVF

  12. Castro ring zone: a 4,500-km2 fossil hydrothermal system in the Challis volcanic field, central Idaho.

    USGS Publications Warehouse

    Criss, R.E.; Ekren, E.B.; Hardyman, R.F.

    1984-01-01

    The largest fossil hydrothermal system occupying a 4500 km2 area in central Idaho is revealed by delta 18O studies. The remains of this meteoric-hydrothermal system are preserved within a sharply bounded, 15 km wide, 70-km-diameter annulus of low delta 18O rock (+2.0 to -8.8per mille) termed the Castro ring zone. The zone is centred on a less depleted (+4.5) core zone consisting of granitic rocks of the Castro pluton. This 700-km2 Eocene subvolcanic batholith has intruded, domed, and hydrothermally metamorphosed a thick sequence of Challis Volcanics, the stratigraphically low rocks in the 2000-km2 Van Horn Peak and the 1000-km2 Thunder Mountain cauldron complexes being most strongly altered. Less extreme 18O depletions occur in the youngest major ash-flow sheets of these complexes, indicating a vertical 18O gradient. Water/rock ratios of geothermal systems are surprisingly insensitive to the circulation scale.-L.-di H.

  13. G-EVER Activities and the Next-generation Volcanic Hazard Assessment System

    NASA Astrophysics Data System (ADS)

    Takarada, S.

    2013-12-01

    The Asia-Pacific Region Global Earthquake and Volcanic Eruption Risk Management (G-EVER) is a consortium of Asia-Pacific geohazard research institutes that was established in 2012. G-EVER aims to formulate strategies to reduce the risks of disasters worldwide caused by the occurrence of earthquakes, tsunamis and volcanic eruptions. G-EVER is working on enhancing collaboration, sharing of resources, and making information on the risks of earthquakes and volcanic eruptions freely available and understandable. The 1st G-EVER International Symposium was held in Tsukuba, Japan in March 11, 2013. The 2nd Symposium is scheduled in Sendai, Tohoku Japan, in Oct. 19-20, 2013. Currently, 4 working groups were proposed in the G-EVER Consortium. The next-generation volcano hazard assessment WG is developing a useful system for volcanic eruption prediction, risk assessment, and evacuation at various eruption stages. The assessment system is based on volcanic eruption history datasets, volcanic eruption database, and numerical simulations. Volcanic eruption histories including precursor phenomena leading to major eruptions of active volcanoes are very important for future prediction of volcanic eruptions. A high quality volcanic eruption database, which contains compilations of eruption dates, volumes, and types, is important for the next-generation volcano hazard assessment system. Proposing international standards on how to estimate the volume of volcanic products is important to make a high quality volcanic eruption database. Spatial distribution database of volcanic products (e.g. tephra and pyroclastic flow distributions), encoded into a GIS based database is necessary for more precise area and volume estimation and risk assessments. The volcanic eruption database is developed based on past eruption results, which only represents a subset of possible future scenarios. Therefore, numerical simulations with controlled parameters are needed for more precise volcanic eruption

  14. Synaptic Vesicle Proteins and Active Zone Plasticity.

    PubMed

    Kittel, Robert J; Heckmann, Manfred

    2016-01-01

    Neurotransmitter is released from synaptic vesicles at the highly specialized presynaptic active zone (AZ). The complex molecular architecture of AZs mediates the speed, precision and plasticity of synaptic transmission. Importantly, structural and functional properties of AZs vary significantly, even for a given connection. Thus, there appear to be distinct AZ states, which fundamentally influence neuronal communication by controlling the positioning and release of synaptic vesicles. Vice versa, recent evidence has revealed that synaptic vesicle components also modulate organizational states of the AZ. The protein-rich cytomatrix at the active zone (CAZ) provides a structural platform for molecular interactions guiding vesicle exocytosis. Studies in Drosophila have now demonstrated that the vesicle proteins Synaptotagmin-1 (Syt1) and Rab3 also regulate glutamate release by shaping differentiation of the CAZ ultrastructure. We review these unexpected findings and discuss mechanistic interpretations of the reciprocal relationship between synaptic vesicles and AZ states, which has heretofore received little attention.

  15. Synaptic Vesicle Proteins and Active Zone Plasticity

    PubMed Central

    Kittel, Robert J.; Heckmann, Manfred

    2016-01-01

    Neurotransmitter is released from synaptic vesicles at the highly specialized presynaptic active zone (AZ). The complex molecular architecture of AZs mediates the speed, precision and plasticity of synaptic transmission. Importantly, structural and functional properties of AZs vary significantly, even for a given connection. Thus, there appear to be distinct AZ states, which fundamentally influence neuronal communication by controlling the positioning and release of synaptic vesicles. Vice versa, recent evidence has revealed that synaptic vesicle components also modulate organizational states of the AZ. The protein-rich cytomatrix at the active zone (CAZ) provides a structural platform for molecular interactions guiding vesicle exocytosis. Studies in Drosophila have now demonstrated that the vesicle proteins Synaptotagmin-1 (Syt1) and Rab3 also regulate glutamate release by shaping differentiation of the CAZ ultrastructure. We review these unexpected findings and discuss mechanistic interpretations of the reciprocal relationship between synaptic vesicles and AZ states, which has heretofore received little attention. PMID:27148040

  16. Subduction zone mantle enrichment by fluids and Zr-Hf-depleted crustal melts as indicated by backarc basalts of the Southern Volcanic Zone, Argentina

    NASA Astrophysics Data System (ADS)

    Holm, Paul M.; Søager, Nina; Alfastsen, Mads; Bertotto, Gustavo W.

    2016-10-01

    We aim to identify the components metasomatizing the mantle above the subducting Nazca plate under part of the Andean Southern Volcanic Zone (SVZ). We present new major and ICP-MS trace element and Sr, Nd and high-precision Pb isotope analyses of primitive olivine-phyric alkali basalts from the Northern Segment Volcanic Field, part of the Payenia province in the backarc of the Transitional SVZ. One new 40Ar-39Ar age determination confirms the Late Pleistocene age of this most northerly part of the province. All analysed rocks have typical subduction zone type incompatible element enrichment, and the rocks of the Northern Segment, together with the neighbouring Nevado Volcanic Field, have isotopic compositions intermediate between adjacent Transitional SVZ arc rocks and southern Payenia OIB-type basaltic rocks. Modelling the Ba-Th-Sm variation we demonstrate that fluids as well as 1-2% melts of upper continental crust (UCC) enriched their mantle sources, and La-Nb-Sm variations additionally indicate that the pre-metasomatic sources ranged from strongly depleted to undepleted mantle. Low Eu/Eu* and Sr/Nd also show evidence for a UCC component in the source. The contribution of Chile Trench sediments to the magmas seems insignificant. The Zr/Sm and Hf/Sm ratios are relatively low in many of the Northern Segment rocks, ranging down to 17 and 0.45, respectively, which, together with relatively high Th/U, is argued to indicate that the metasomatizing crustal melts were derived by partial melting of subducted UCC that had residual zircon, in contrast to the UCC melts added to Transitional SVZ arc magmas. Mixing between depleted and undepleted mantle, enriched by UCC and fluids, is suggested by Sr, Nd and Pb isotopes of the Northern Segment and Nevado magmas. The metasomatized undepleted mantle south of the Northern Segment is suggested to be part of upwelling OIB-type mantle, whereas the pre-metasomatically depleted mantle also can be found as a component in some arc

  17. New Perspectives on the Volcano-Tectonic Evolution of the Wairakei-Tauhara Geothermal System, Taupo Volcanic Zone, New Zealand, from U-Pb Dating of Zircons

    NASA Astrophysics Data System (ADS)

    Rosenberg, M. D.; Wilson, C. J. N.; Bignall, G.; Sepulveda, F.; Ireland, T. R.

    2014-12-01

    Wairakei-Tauhara (WK-TH) is one of the largest geothermal systems in the actively rifting Taupo Volcanic Zone. SIMS U-Pb dating of magmatic zircons (using SHRIMP-RG) from hydrothermally altered rhyolitic lavas and ignimbrites has provided new ages which constrain the major episodes of locally sourced volcanism and basin subsidence that were major influences on structural evolution and hydrology of the system. The WK-TH system is located in the southern Taupo-Reporoa Basin (TRB) across a horst-graben structure defined by predominantly NE-SW striking faults of the Taupo Rift. The geothermal system is hosted in late Quaternary volcanic and sedimentary strata and underlying Jurassic-Cretaceous greywacke basement. When combined with a robust stratigraphic architecture refined using data from >200 geothermal wells up to 3 km deep, the dating reveals that the majority of all known WK-TH rhyolite lavas (each ~0.1 km3 to ~7 km3) were extruded in a relatively short time interval from ~ 310 ka to ~120 ka and occur in a spatial cluster in the uppermost ~1.5 km of strata beneath the north-western (Wairakei) area. Stratigraphy and dating revealed at least one local rhyolite extrusion occurred at ~ 940 ka, and also an apparent >500 ka lapse in volcanic activity or local deposition after that event. The ages of strata from the Tauhara (south-eastern) area make it clear that a substantial volume of ignimbrite was emplaced into then eroded from the southern TRB between ~0.35 and 0.31 Ma, and then after ~0.31 Ma, replaced with as much as 2.5 km thickness of tuffs and sediments. Correlation by age of the locally named Wairakei Ignimbrite with the regional ~349 ka Whakamaru group of ignimbrites reinforces the value of this unit as a key stratigraphic marker and constrains the timing of major fault formation/reactivation, potentially with implications for understanding the structure and subsidence of Whakamaru caldera and evolution of the Taupo-Reporoa Basin.

  18. [Molecular mechanism at the presynaptic active zone].

    PubMed

    Ohtsuka, Toshihisa

    2011-07-01

    Our higher brain functions such as learning and memory, emotion, and consciousness depend on the precise regulation of complicated neural networks in the brain. Neurons communicate with each other through the synapse, which comprise 3 regions: the presynapse, synaptic cleft, and postsynapse. The active zone (AZ) beneath the presynaptic membrane is the principal site for Ca2+ -dependent neurotransmitter release: AZ is involved in determining the site for docking and synaptic vesicle fusion. Presently, the full molecular composition of AZ is unclear, but it is known to contain several AZ-specific proteins, including cytomatrix of the active zone-associated protein (CAST)/ERC2, ELKS, RIM1, Munc13-1, Piccolo/Aczonin, and Bassoon. CAST and ELKS are novel active zone proteins that directly bind to Rab3-interacting molecules (RIMs), Bassoon, and Piccolo, and are thought to play a role in neurotransmitter release by binding these to AZ proteins. In this review, current advances in studies on AZ structure and function have been summarized, and the focus is mainly on protein-protein interactions among the AZ proteins.

  19. Inferno Chasm Rift Zone, Idaho: A Terrestrial Analog for Plains-style Volcanism in Southeastern Mare Serenitatis on the Moon

    NASA Astrophysics Data System (ADS)

    Garry, W. B.; Hughes, S. S.; Kobs-Nawotniak, S. E.

    2015-12-01

    Volcanic features aligned along a linear graben in southeastern Mare Serenitatis (19°N, 27.5°E) on the Moon resemble a series of effusive basaltic landforms erupted along the Inferno Chasm rift zone within Craters of the Moon National Monument and Preserve (COTM), Idaho (42°58'00"N, 113°11'25"W). This region in Idaho is the type-locale for terrestrial plains-style volcanism. Examples of lunar plains-style volcanism have previously been described within Orientale Basin at Lacus Veris and Lacus Autumni, but this eruption style has not been used to describe the site in Mare Serenitatis. The SSERVI FINESSE team (Field Investigations to Enable Solar System Science and Exploration) has documented the features along Inferno Chasm rift using a LiDAR, Differential Global Positioning Systems, and Unmanned Aerial Vehicles (UAV) to compare with Lunar Reconnaissance Orbiter Narrow-Angle Camera images and digital terrain models. The region in southeastern Mare Serenitatis provides one of the best concentrations of features representative of lunar plains-style volcanism. On the Moon, these features include a cone (Osiris), a flat-topped dome, a rille-like channel (Isis), a vent, and a possible perched lava pond. In Idaho, the analog features include a dome (Grand View Crater), a rille-like channel (Inferno Chasm), vents (Cottrells Blowout, Horse Butte), and a perched lava pond (Papadakis). Both the scale and morphology of the features on the Moon are similar to the features in Idaho. For example, the channel in Isis is ~3 km long, 283 m-wide, and 25 m deep compared to Inferno Chasm which is ~1.7 km long, 100 m wide, and 20 m deep. The slope of the channel in Isis is -1.2°, while the channel in Inferno Chasm has a slope of -0.33°. The alignment of landforms on the Moon and Idaho are both consistent with dike emplacement. Observations of the flow stratigraphy for features in Idaho will inform the potential eruption conditions of the individual features on the Moon.

  20. Volcanic passive margins

    NASA Astrophysics Data System (ADS)

    Geoffroy, Laurent

    2005-12-01

    Compared to non-volcanic ones, volcanic passive margins mark continental break-up over a hotter mantle, probably subject to small-scale convection. They present distinctive genetic and structural features. High-rate extension of the lithosphere is associated with catastrophic mantle melting responsible for the accretion of a thick igneous crust. Distinctive structural features of volcanic margins are syn-magmatic and continentward-dipping crustal faults accommodating the seaward flexure of the igneous crust. Volcanic margins present along-axis a magmatic and tectonic segmentation with wavelength similar to adjacent slow-spreading ridges. Their 3D organisation suggests a connection between loci of mantle melting at depths and zones of strain concentration within the lithosphere. Break-up would start and propagate from localized thermally-softened lithospheric zones. These 'soft points' could be localized over small-scale convection cells found at the bottom of the lithosphere, where adiabatic mantle melting would specifically occur. The particular structure of the brittle crust at volcanic passive margins could be interpreted by active and sudden oceanward flow of both the unstable hot mantle and the ductile part of the lithosphere during the break-up stage. To cite this article: L. Geoffroy, C. R. Geoscience 337 (2005).

  1. Characterization of volcanic activity using observations of infrasound, volcanic emissions, and thermal imagery at Karymsky Volcano, Kamchatka, Russia

    NASA Astrophysics Data System (ADS)

    Lopez, T.; Fee, D.; Prata, F.

    2012-04-01

    Karymsky Volcano is one of the most active and dynamic volcanoes in Kamchatka, with activity ranging from vigorous degassing, frequent ash emissions, and apparent vent sealing, all punctuated by daily to weekly explosive magmatic eruptions. Recent studies have highlighted the strengths in using complementary infrasound measurements and remote volcanic emission measurements to characterize volcanic activity, with the potential to discriminate emission-type, approximate ash-cloud height, and estimate SO2 emission mass. Here we use coincident measurements of infrasound, SO2, ash, and thermal radiation collected over a ten day period at Karymsky Volcano in August 2011 to characterize the observed activity and elucidate vent processes. The ultimate goal of this project is to enable different types of volcanic activity to be identified using only infrasound data, which would significantly improve our ability to continuously monitor remote volcanoes. Four types of activity were observed. Type 1 activity is characterized by discrete ash emissions occurring every 1 - 5 minutes that either jet or roil out of the vent, by plumes from 500 - 1500 m (above vent) altitudes, and by impulsive infrasonic onsets. Type 2 activity is characterized by periodic pulses of gas emission, little or no ash, low altitude (100 - 200 m) plumes, and strong audible jetting or roaring. Type 3 activity is characterized by sustained emissions of ash and gas, with multiple pulses lasting from ~1 - 3 minutes, and by plumes from 300 - 1500 m. Type 4 activity is characterized by periods of relatively long duration (~30 minutes to >1 hour) quiescence, no visible plume and weak SO2 emissions at or near the detection limit, followed by an explosive, magmatic eruption, producing ash-rich plumes to >2000 m, and centimeter to meter (or greater) sized pyroclastic bombs that roll down the flanks of the edifice. Eruption onset is accompanied by high-amplitude infrasound and occasionally visible shock

  2. Evidence of explosive seafloor volcanic activity from the Walvis Ridge, South Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Haxel, J. H.; Dziak, R. P.

    2005-07-01

    Hydrophones moored in the North Atlantic Ocean recorded a sequence of explosive, volcano-acoustic signals originated at the Walvis Ridge in the South Atlantic Ocean. 365 explosive signals were detected from the Walvis Ridge beginning 24 November 2001 continuing through March 2002. The largest swarm began on 19 December at 2329 GMT, and lasted 1.25 hrs producing 32 locatable events. Swarm locations are centered on the northern flank of an unnamed seamount (-32.96°S -5.22°W), northwest of Wüst Seamount. These signals are interpreted as volcanogenic explosions due to similarities with acoustic signals recorded from a confirmed submarine eruption in the Caribbean in 2001 (Kick'em Jenny volcano). The observations presented suggest recent magmatic activity along the Walvis Ridge may be unrelated to the Tristan da Cunha mantle plume. Furthermore, these events lend support for an extensional fracture-zone model resulting in the recurrence of volcanic activity along older segments of large-scale sea floor lineaments.

  3. Volcanic features of Io

    USGS Publications Warehouse

    Carr, M.H.; Masursky, H.; Strom, R.G.; Terrile, R.J.

    1979-01-01

    Volcanic activity is apparently higher on Io than on any other body in the Solar System. Its volcanic landforms can be compared with features on Earth to indicate the type of volcanism present on Io. ?? 1979 Nature Publishing Group.

  4. Volcanic eruption source parameters from active and passive microwave sensors

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    It is well known, in the volcanology community, that precise information of the source parameters characterising an eruption are of predominant interest for the initialization of the Volcanic Transport and Dispersion Models (VTDM). Source parameters of main interest would be the top altitude of the volcanic plume, the flux of the mass ejected at the emission source, which is strictly related to the cloud top altitude, the distribution of volcanic mass concentration along the vertical column as well as the duration of the eruption and the erupted volume. Usually, the combination of a-posteriori field and numerical studies allow constraining the eruption source parameters for a given volcanic event thus making possible the forecast of ash dispersion and deposition from future volcanic eruptions. So far, remote sensors working at visible and infrared channels (cameras and radiometers) have been mainly used to detect, track and provide estimates of the concentration content and the prevailing size of the particles propagating within the ash clouds up to several thousand of kilometres far from the source as well as track back, a-posteriori, the accuracy of the VATDM outputs thus testing the initial choice made for the source parameters. Acoustic wave (infrasound) and microwave fixed scan radar (voldorad) were also used to infer source parameters. In this work we want to put our attention on the role of sensors operating at microwave wavelengths as complementary tools for the real time estimations of source parameters. Microwaves can benefit of the operability during night and day and a relatively negligible sensitivity to the presence of clouds (non precipitating weather clouds) at the cost of a limited coverage and larger spatial resolution when compared with infrared sensors. Thanks to the aforementioned advantages, the products from microwaves sensors are expected to be sensible mostly to the whole path traversed along the tephra cloud making microwaves particularly

  5. Magma reservoirs and neutral buoyancy zones on Venus - Implications for the formation and evolution of volcanic landforms

    NASA Technical Reports Server (NTRS)

    Head, James W.; Wilson, Lionel

    1992-01-01

    The production of magma reservoirs and neutral buoyancy zones (NBZs) on Venus and the implications of their development for the formation and evolution of volcanic landforms are examined. The high atmospheric pressure on Venus reduces volatile exsolution and generally serves to inhibit the formation of NBZs and shallow magma reservoirs. For a range of common terrestrial magma-volatile contents, magma ascending and erupting near or below mean planetary radius (MPR) should not stall at shallow magma reservoirs; such eruptions are characterized by relatively high total volumes and effusion rates. For the same range of volatile contents at 2 km above MPR, about half of the cases result in the direct ascent of magma to the surface and half in the production of neutral buoyancy zones. NBZs and shallow magma reservoirs begin to appear as gas content increases and are nominally shallower on Venus than on earth. For a fixed volatile content, NBZs become deeper with increasing elevation: over the range of elevations treated in this study (-1 km to +4.4 km) depths differ by a factor of 2-4. Factors that may account for the low height of volcanoes on Venus are discussed.

  6. 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

  7. Geochronological and geochemical constraints on the petrogenesis of late Cretaceous volcanic rock series from the eastern Sakarya zone, NE Anatolia-Turkey

    NASA Astrophysics Data System (ADS)

    Aydin, Faruk; Oǧuz, Simge; Şen, Cüneyt; Uysal, İbrahim; Başer, Rasim

    2016-04-01

    New SHRIMP zircon U-Pb ages and whole-rock geochemical data as well as Sr-Nd-Pb and δ18O isotopes of late Cretaceous volcanic rock series from the Giresun and Artvin areas (NE Anatolia, Turkey) in the northern part of the eastern Sakarya zone (ESZ) provide important evidence for northward subduction of the Neo-Tethyan oceanic lithosphere along the southern border of the ESZ. In particular, tectonic setting and petrogenesis of these subduction-related volcanites play a critical role in determining the nature of the lower continental crust and mantle dynamics during late Mesozoic orogenic processes in this region. The late Cretaceous time in the ESZ is represented by intensive volcanic activities that occurred in two different periods, which generally consist of alternation of mafic-intermediate (basaltic to andesitic) and felsic rock series (dacitic to rhyolitic) within each period. Although there is no geochronological data for the lower mafic-intermediate rock series of the first volcanic period, U-Pb zircon dating from the first cycle of felsic rocks yielded ages ranging from 88.6±1.8 to 85.0±1.3 Ma (i.e. Coniacian-Early Santonian). The first volcanic period in the region is generally overlain by reddish biomicrite-rich sedimentary rocks of Santonian-Early Campanian. U-Pb zircon dating for the second cycle of mafic-intermediate and felsic rocks yielded ages varying from 84.9±1.7 to 80.8±1.5Ma (i.e. Early to Middle Campanian). The studied volcanic rocks have mostly transitional geochemical character changing from tholeiitic to calc-alkaline with typical arc signatures. N-MORB-normalised multi-element and chondrite-normalised rare earth element (REE) patterns show that all rocks are enriched in LILEs (e.g. Rb, Ba, Th) and LREEs (e.g. La, Ce) but depleted in Nb and Ti. In particular, the felsic samples are characterised by distinct negative Eu anomalies. The samples are characterized by a wide range of Sr-Nd-Pb isotopic compositions (initial ɛNd values from -7

  8. Geologic evolution of the Jemez Mountains and their potential for future volcanic activity

    SciTech Connect

    Burton, B.W.

    1982-01-01

    Geophysical and geochemical data and the geologic history of the Rio Grande rift and the vicinity of the Jemez Mountains are summarized to determine the probability of future volcanic activity in the Los Alamos, New Mexico area. The apparent cyclic nature of volcanism in the Jemez Mountains may be related to intermittent thermal inputs into the volcanic system beneath the region. The Jemez lineament, an alignment of late Cenozoic volcanic centers that crosses the rift near Los Alamos, has played an important role in the volcanic evolution of the Jemez Mountains. Geophysical data suggest that there is no active shallow magma body beneath the Valles caldera, though magma probably exists at about 15 km beneath this portion of the rift. The rate of volcanism in the Jemez Mountains during the last 10 million years has been 5 x 10/sup -9//km/sup 2//y. Lava or ash flows overriding Laboratory radioactive waste disposal sites would have little potential to release radionuclides to the environment. The probability of a new volcano intruding close enough to a radioactive waste disposal site to effect radionuclide release is 2 x 10/sup -7//y.

  9. Continental Collision Zones are Primary Sites of net Continental Crustal Growth: Evidence From the Linzizong Volcanic Succession in Southern Tibet

    NASA Astrophysics Data System (ADS)

    Niu, Y.; Mo, X.; Dong, G.; Zhao, Z.; Hou, Z.; Zhou, S.; Ke, S.

    2007-12-01

    The Linzizong volcanics (ca. 65-45Ma) and the coeval batholiths (ca. 60-40Ma) of andesitic-to-rhyolitic composition are magmatic response to the India-Asia continental collision that began at ca. 70-65Ma and ended at ca. 45-40Ma with convergence continuing to present [1,2]. These syncollisional magmatic rocks are widely distributed along much of the >1500km long Gangdese Belt immediately north of the India-Asia suture (Yarlung-Zangbo) in southern Tibet [2-6]. Our study of the Linzizong volcanics from the Linzhou Basin (near Lhasa) encourages the proposal that syncollisional granitoid magmatism may in fact account for much of the net contribution to continental crust growth. The Linzizong volcanics in the Linzhou Basin show a first-order temporal change from the lower andesitic formation (64.4-60.6Ma), to the middle dacitic formation (ca. 54Ma), and to the upper rhyolitic formation (48.7-43.9Ma). The three formations show no systematic but overlapping Nd-Sr isotope variations. The isotopically depleted samples with ɛNd(t)>0 (up to + 8) indicate that their primary sources are of mantle origin. The best source candidate in the broad context of Tethyan ocean closing and India- Asia collision is the remaining part of the Tethyan ocean crust [6]. This ocean crust melts when reaching its hydrous solidus during and soon after the collision in the amphibolite facies, producing andesitic melts parental to the Linzizong volcanics (also the coeval batholiths) with inherited mantle isotopic signatures [6]. Ilmenite is abundant in amphibolite [7], and partial melting of amphibolite with ilmenite as a residual phase accounts for the depletion of Nb, Ta and Ti in the melt. The effect of ocean crust alteration plus involvement of mature crustal materials (e.g., recycled terrigeneous sediments) enhances the elevated abundances of Ba, Rb, Th, U, K and Pb in the melt [8,9]. These give the syncolissional Linzizong volcanics characteristic "arc-like" geochemical signature. Residual

  10. A volcanic province near the western termination of the Charlie-Gibbs Fracture Zone at the rifted margin, offshore northeast Newfoundland

    NASA Astrophysics Data System (ADS)

    Keen, C. E.; Dafoe, L. T.; Dickie, K.

    2014-06-01

    A mid-Cretaceous to Late Cretaceous volcanic province, named here the Charlie-Gibbs Volcanic Province, is described near the western termination of the Charlie-Gibbs Fracture Zone, against the rifted continental margin northeast of Newfoundland. We used seismic data to map 14 volcanic seamounts, now buried below younger sediments. They rise 0.7 to 2 s two-way time (twt) above the surrounding basement level and are about 8-30 km wide. Some are conical while others are more flat-topped. Underlying igneous units resembling flows and sills are also observed. Based on magnetic modeling of the large positive magnetic anomalies associated with the seamounts, the total thickness of igneous rocks can locally reach about 8 km. This magmatism occurred in the vicinity of the Charlie-Gibbs Fracture Zone and extends about 150 km to the north along the rifted continental margin. The volcanic province also forms the northern boundary of the Jurassic-Early Cretaceous Orphan Basin, along a major transform margin there. Truncation of rift-related structures which extend to deep crustal levels is observed at the transform, along trends similar to those of prerift Appalachian terrane boundaries on the adjacent shelf. This suggests the existence of a preexisting weak zone in the continental lithosphere within which a complex strike-slip fault system developed and may have controlled the location of final continental breakup between the Rockall and North American plates in the Late Cretaceous.

  11. Sulfur dioxide - Episodic injection shows evidence for active Venus volcanism

    NASA Astrophysics Data System (ADS)

    Esposito, L. W.

    1984-03-01

    Pioneer Venus ultraviolet spectra from the first 5 years of operation show a decline (by more than a factor of 10) in sulfur dioxide abundance at the cloud tops and in the amount of submicron haze above the clouds. At the time of the Pioneer Venus encounter, the values for both parameters greatly exceeded earlier upper limits. However, Venus had a similar appearance in the late 1950's, implying the episodic injection of sulfur dioxide possibly caused by episodic volcanism. The amount of haze in the Venus middle atmosphere is about ten times that found in earth's stratosphere after the most recent major volcanic eruptions, and the thermal energy required for this injection on Venus is greater by about an order of magnitude than the largest of these recent earth eruptions and about as large as the Krakatoa eruption of 1883. The episodic behavior of sulfur dioxide implies that steady-state models of the chemistry and dynamics of cloud-top regions may be of limited use.

  12. Sulfur dioxide: episodic injection shows evidence for active venus volcanism.

    PubMed

    Esposito, L W

    1984-03-01

    Pioneer Venus ultraviolet spectra from the first 5 years of operation show a decline (by more than a factor of 10) in sulfur dioxide abundance at the cloud tops and in the amount of submicron haze above the clouds. At the time of the Pioneer Venus encounter, the values for both parameters greatly exceeded earlier upper limits. However, Venus had a similar appearance in the late 1950's, implying the episodic injection of sulfur dioxide possibly caused by episodic volcanism. The amount of haze in the Venus middle atmosphere is about ten times that found in Earth's stratosphere after the most recent major volcanic eruptions, and the thermal energy required for this injection on Venus is greater by about an order of magnitude than the largest of these recent Earth eruptions and about as large as the Krakatoa eruption of 1883. The episodic behavior of sulfur dioxide implies that steady-state models of the chemistry and dynamics of cloud-top regions may be of limited use.

  13. U.S. Geological Survey's Alert Notification System for Volcanic Activity

    USGS Publications Warehouse

    Gardner, Cynthia A.; Guffanti, Marianne C.

    2006-01-01

    The United States and its territories have about 170 volcanoes that have been active during the past 10,000 years, and most could erupt again in the future. In the past 500 years, 80 U.S. volcanoes have erupted one or more times. About 50 of these recently active volcanoes are monitored, although not all to the same degree. Through its five volcano observatories, the U.S. Geological Survey (USGS) issues information and warnings to the public about volcanic activity. For clarity of warnings during volcanic crises, the USGS has now standardized the alert-notification system used at its observatories.

  14. Volcanism and associated hazards: The Andean perspective

    USGS Publications Warehouse

    Tilling, R.I.

    2009-01-01

    Andean volcanism occurs within the Andean Volcanic Arc (AVA), which is the product of subduction of the Nazca Plate and Antarctica Plates beneath the South America Plate. The AVA is Earth's longest but discontinuous continental-margin volcanic arc, which consists of four distinct segments: Northern Volcanic Zone, Central Volcanic Zone, Southern Volcanic Zone, and Austral Volcanic Zone. These segments are separated by volcanically inactive gaps that are inferred to indicate regions where the dips of the subducting plates are too shallow to favor the magma generation needed to sustain volcanism. The Andes host more volcanoes that have been active during the Holocene (past 10 000 years) than any other volcanic region in the world, as well as giant caldera systems that have produced 6 of the 47 largest explosive eruptions (so-called "super eruptions") recognized worldwide that have occurred from the Ordovician to the Pleistocene.

    The Andean region's most powerful historical explosive eruption occurred in 1600 at Huaynaputina Volcano (Peru). The impacts of this event, whose eruptive volume exceeded 11 km3, were widespread, with distal ashfall reported at distances >1000 km away. Despite the huge size of the Huaynaputina eruption, human fatalities from hazardous processes (pyroclastic flows, ashfalls, volcanogenic earthquakes, and lahars) were comparatively small owing to the low population density at the time. In contrast, lahars generated by a much smaller eruption (<0.05 km 3) in 1985 of Nevado del Ruiz (Colombia) killed about 25 000 people - the worst volcanic disaster in the Andean region as well as the second worst in the world in the 20th century. The Ruiz tragedy has been attributed largely to ineffective communications of hazards information and indecisiveness by government officials, rather than any major deficiencies in scientific data. Ruiz's disastrous outcome, however, together with responses to subsequent hazardous eruptions in Chile, Colombia

  15. Pliocene-Quaternary syn-collision volcanism of the Javakheti Ridge, NW Armenia: impact on models of magma generation in the Arabia-Eurasia collision zone

    NASA Astrophysics Data System (ADS)

    Meliksetian, Kh.; Neill, I.; Allen, M. B.; Navarsardyan, G.; Karapetyan, S.

    2012-04-01

    The Armenian Highlands and Southern Caucasus formed during convergence and collision between the Arabian and Eurasian margins from the Late Mesozoic to the present. These events culminate in the growth of the present-day Turkish-Iranian high plateau. Pliocene-Quaternary magmatism followed plateau building, and is a key feature of the entire region. However, petrogenetic models are sparse, particularly for outcrops in the Armenia sector. Mantle-derived magmatism in Turkey has been linked to Tethyan slab break-off and/or lithospheric delamination following the Arabia-Eurasia collision. In this study we consider preliminary petrographic and geochemical results from the Javakheti ridge and surrounding areas, in NW Armenia, and their relationship to the orogenic plateau as a whole. The N-S trending Javakheti ridge is the southerly extension of the Samsari ridge in Georgia, and is one of several Pliocene-Quaternary volcanic uplands in Armenia and the Lesser Caucasus (e.g. Gegham, Vardenis and Syunik). The basement consists of the Sevan-Akera suture between the South Armenian Block, of Gondwanaland origin, and the Eurasian active margin and associated Mesozoic island arc of the Lesser Caucasus. Arc-continent collision and obduction occurred in the Late Cretaceous or Paleocene-Eocene. The first Pliocene-Quaternary magmatism in the area is represented by valley-filling fissure-fed basaltic flows, examples of which have been dated to ~2.7-2.0 Ma in Georgia and Armenia. The ridge itself consists of eroded intermediate to felsic flows forming a central volcanic complex. Recently published Ar-Ar dating of ash layers related to the complex reveal ages of ~1.8-1.9 Ma. The flows are cut by numerous Quaternary cinder cones. Volcanism on the ridge complex appears to young towards the north, and the ridge remains tectonically active, undergoing extension at 1.25 mm/yr, according to GPS data. Preliminary geochemical results indicate the valley-filling flows, the ridge, and cinder

  16. Volcanic and Hydrothermal Activity of the North Su Volcano: New Insights from Repeated Bathymetric Surveys and ROV Observations

    NASA Astrophysics Data System (ADS)

    Thal, J.; Bach, W.; Tivey, M.; Yoerger, D.

    2013-12-01

    Bathymetric data from cruises in 2002, 2006, and 2011 were combined and compared to determine the evolution of volcanic activity, seafloor structures, erosional features and to identify and document the distribution of hydrothermal vents on North Su volcano, SuSu Knolls, eastern Manus Basin (Papua New Guinea). Geologic mapping based on ROV observations from 2006 (WHOI Jason-2) and 2011 (MARUM Quest-4000) combined with repeated bathymetric surveys from 2002 and 2011 are used to identify morphologic features on the slopes of North Su and to track temporal changes. ROV MARUM Quest-4000 bathymetry was used to develop a 10 m grid of the top of North Su to precisely depict recent changes. In 2006, the south slope of North Su was steeply sloped and featured numerous white smoker vents discharging acid sulfate waters. These vents were covered by several tens of meters of sand- to gravel-sized volcanic material in 2011. The growth of this new cone changed the bathymetry of the south flank of North Su up to ~50 m and emplaced ~0.014 km3 of clastic volcanic material. This material is primarily comprised of fractured altered dacite and massive fresh dacite as well as crystals of opx, cpx, olivine and plagioclase. There is no evidence for pyroclastic fragmentation, so we hypothesize that the fragmentation is likely related to hydrothermal explosions. Hydrothermal activity varies over a short (~50 m) lateral distance from 'flashing' black smokers to acidic white smoker vents. Within 2 weeks of observation time in 2011, the white smoker vents varied markedly in activity suggesting a highly episodic hydrothermal system. Based on ROV video recordings, we identified steeply sloping (up to 30°) slopes exposing pillars and walls of hydrothermal cemented volcaniclastic material representing former fluid upflow zones. These features show that hydrothermal activity has increased slope stability as hydrothermal cementation has prevented slope collapse. Additionally, in some places

  17. Volcan de Fuego de Colima, review of the 2003 explosion activity and its morfological changes

    NASA Astrophysics Data System (ADS)

    Juan Jose, R. R.

    2003-12-01

    Volcan de Fuego de Colima, Mexico, (19§30'44 '' N and 103§37'02 '' W) is an stratovolcano located in the western front of the Trans Mexican volcanic belt. It shows 3 explosive events at least during the last 500 years (VEI=4), being the nearest those happened in 1818 and 1913. In the year 2002, after a stage of dome growth and later collapses of incandescent material on the volcanic edifice, its activity suffered changes during the first months of the year 2003. The volcanic activity during this period is characterized by the occurrence of lava collapses concentrated at west and south-west flanks of the edifice. During this period, a lava emission rate of 0.15 m3/s is taking place. The material collapses occurred from the summit reaches an average 250 per day. After this behavior the lava movement decrease and obstruct the lava conduct changing the volcanic activity during this period to an explosive scenario. During the months of May, June, July and August of 2003 several explosive events have been presented, being the most significant those happened the days July 17th (05:27) August 2 (15:41) and August 28th (11:52). These three events in particular, have been those that bigger changes have caused in the morphology of the summit. A description of the eruptive development of this stage is presented in the one that the main explosions and their reaches can be identified.

  18. Characterization of unsaturated zone hydrogeologic units using matrix properties and depositional history in a complex volcanic environment

    USGS Publications Warehouse

    Flint, L.E.; Buesch, D.C.; Flint, A.L.

    2006-01-01

    Characterization of the physical and unsaturated hydrologic properties of subsurface materials is necessary to calculate flow and transport for land use practices and to evaluate subsurface processes such as perched water or lateral diversion of water, which are influenced by features such as faults, fractures, and abrupt changes in lithology. Input for numerical flow models typically includes parameters that describe hydrologic properties and the initial and boundary conditions for all materials in the unsaturated zone, such as bulk density, porosity, and particle density, saturated hydraulic conductivity, moisture-retention characteristics, and field water content. We describe an approach for systematically evaluating the site features that contribute to water flow, using physical and hydraulic data collected at the laboratory scale, to provide a representative set of physical and hydraulic parameters for numerically calculating flow of water through the materials at a site. An example case study from analyses done for the heterogeneous, layered, volcanic rocks at Yucca Mountain is presented, but the general approach for parameterization could be applied at any site where depositional processes follow deterministic patterns. Hydrogeologic units at this site were defined using (i) a database developed from 5320 rock samples collected from the coring of 23 shallow (<100 m) and 10 deep (500-1000 m) boreholes, (ii) lithostratigraphic boundaries and corresponding relations to porosity, (iii) transition zones with pronounced changes in properties over short vertical distances, (iv) characterization of the influence of mineral alteration on hydrologic properties such as permeability and moisture-retention characteristics, and (v) a statistical analysis to evaluate where boundaries should be adjusted to minimize the variance within layers. Model parameters developed in this study, and the relation of flow properties to porosity, can be used to produce detailed and

  19. Diverse Eruptions at Approximately 2,200 Years B.P. on the Great Rift, Idaho: Inferences for Magma Dynamics Along Volcanic Rift Zones

    NASA Technical Reports Server (NTRS)

    Hughes, S. S.; Nawotniak, S. E. Kobs; Borg, C.; Mallonee, H. C.; Purcell, S.; Neish, C.; Garry, W. B.; Haberle, C. W.; Lim, D. S. S.; Heldmann, J. L.

    2016-01-01

    Compositionally and morphologically diverse lava flows erupted on the Great Rift of Idaho approximately 2.2 ka (kilo-annum, 1000 years ago) during a volcanic "flare-up" of activity following an approximately 2 ky (kiloyear, 1000 years) hiatus in eruptions. Volcanism at Craters of the Moon (COTM), Wapi and Kings Bowl lava fields around this time included primitive and evolved compositions, separated over 75 kilometers along the approximately 85 kilometers-long rift, with striking variability in lava flow emplacement mechanisms and surface morphologies. Although the temporal associations may be coincidental, the system provides a planetary analog to better understand magma dynamics along rift systems, including that associated with lunar floor-fractured craters. This study aims to help bridge the knowledge gap between ancient rift volcanism evident on the Moon and other terrestrial planets, and active rift volcanism, e.g., at Hawai'i and Iceland.

  20. Living in the heart of a volcanic hazard zone and the issues that affect community vulnerability and resilience

    NASA Astrophysics Data System (ADS)

    Bird, Deanne; Gísladóttir, Guőrún; Dominey-Howes, Dale

    2010-05-01

    Volcanic risk mitigation strategies were revised for residents living in the eastern jökulhlaup hazard zone of Mýrdalsjökull, southern Iceland. These plans were trialled during a full-scale evacuation exercise on 25 March 2006. In order to assess residents' perception of and response to the exercise and proposed mitigation strategies a mixed methods survey was applied. This investigation consisted of field observations during the exercise and semi-structured interviews with emergency management officials and residents of a small rural community after the exercise. This community was the focus of this survey because these residents did not consider the previous plan appropriate to their beliefs and needs. The results of the survey revealed that residents are reluctant to evacuate and do not agree with the proposed strategies. Residents believe that the newly devised plans do not address the contextual issues of their community. Factors influencing the residents' perception are inherited knowledge, attachment to place and livelihood connections (i.e. concern for livestock). Residents' requests for alternative plans, in case adverse environmental conditions prevent evacuation, were ignored. Consequently, emergency managers failed to resolve residents' risk mitigation concerns prior to the evacuation exercise. We recommend that emergency managers should incorporate local knowledge and perceptions to ensure reduced vulnerability and enhanced community resilience.

  1. Melt extraction in mush zones: The case of crystal-rich enclaves at the Sabatini Volcanic District (central Italy)

    NASA Astrophysics Data System (ADS)

    Masotta, M.; Mollo, S.; Gaeta, M.; Freda, C.

    2016-04-01

    A peculiar feature of the Sabatini Volcanic District (SVD, central Italy) is the occurrence of crystal-poor pumices and crystal-rich enclaves within the same eruptive host-deposit. The stratigraphic sequence of pumices and enclaves indicates the tapping of a stratified magma chamber, where a crystal-poor phonolitic magma lay on top of a more primitive crystal-rich magma. The crystal-rich enclaves are genetically related to the pumices and record the evolution of a solidification front, in which a more differentiated melt was produced, extracted and eventually erupted. We collected and analyzed crystal-rich enclaves from one of the largest phonolitic eruptions at the SVD and used their petrological and geochemical features to reconstruct magma differentiation and crystal-melt separation in the solidification front. On this basis, three groups of enclaves have been identified: porphyritic enclaves, holocrystalline enclaves and sanidinites. The mineralogical variability faithfully reproduces the spatial and temporal evolution expected of a solidification front, from early-to-intermediate crystallization conditions (porphyritic and holocrystalline type) to the late stage of solidification (sanidinites), in which the percolation of a more differentiated melt through the crystal mush triggered the instability of the solidification front. Results from numerical models indicate that gravitational instability is the most efficient mechanism to explain melt extraction in mush zones of medium-sized (~ 10 km3), short-lived (~ 104 years) magma chambers.

  2. Volcanology and volcanic activity with a primary focus on potential hazard impacts for the Hawaii geothermal project

    SciTech Connect

    Moore, R.B.; Delaney, P.T.; Kauahikaua, J.P.

    1993-10-01

    This annotated bibliography reviews published references about potential volcanic hazards on the Island of Hawaii that are pertinent to drilling and operating geothermal wells. The first two sections of this annotated bibliography list the most important publications that describe eruptions of Kilauea volcano, with special emphasis on activity in and near the designated geothermal subzones. References about historic eruptions from Mauna Loa`s northeast rift zone, as well as the most recent activity on the southern flank of dormant Mauna Kea, adjacent to the Humu`ula Saddle are described. The last section of this annotated bibliography lists the most important publications that describe and analyze deformations of the surface of Kilauea and Mauna Loa volcanoes.

  3. Location of Non-volcanic Tremors along the Cascadia Subduction Zone Using the Source- Scanning Algorithm

    NASA Astrophysics Data System (ADS)

    Farahbod, A.; Calvert, A.

    2009-05-01

    Due to the nature of Episodic Tremor and Slip (ETS) events, a long-term study and continuous seismic and geodetic data are required for a detailed study. Here we focus on tremors that occur along the Cascadia subduction zone between southern Vancouver Island and Northern California during slow slip events in two full-life cycles starting February 2003. The origin times and hypocenters of all tremors are estimated using the Source-Scanning Algorithm (SSA) of Kao (2004). We processed more than 200 days of continuously recorded seismic data from the US roughly the same amount of information extracted from the Canadian seismograms by compiling tremor catalogs provided by the Geological Survey of Canada (GSC) or by direct analysis of the waveforms. The majority of the well-located tremors in southern Vancouver Island, the Canada-US border region and northern Washington occur at a depth which ranges from 20 km to 40 km. In central and southern Washington, the depth of the well-located events gradually decreases with a westward shift of the epicenters towards the coast. Also both temporally and spatially it seems that tremors occur in locations with absent or sparse seismicity. In this study we will examine the geographical variability of ETS events as well as hypocentral migration rates and segmentation.

  4. Recurring Swarms of Deep Long Period Earthquakes in the Denali Volcanic Gap Suggest a Continuation of Volcanic Processes in the Absence of Active Volcanism

    NASA Astrophysics Data System (ADS)

    Holtkamp, S. G.; Ruppert, N. A.; Silwal, V.; Christensen, D. H.; Nye, C. J.

    2014-12-01

    Seismicity in the northern segment of the Denali Volcanic Gap clusters bimodally with depth, with dense clusters of earthquakes occurring in the subducting slab at >100 km depth beneath Denali, and within the crust north of the Denali fault at <20 km depth. On January 22, 2014, the Alaska Earthquake Center recorded a Deep Long Period earthquake (DLP), magnitude 1.7, at 40 km depth north of the Denali Fault. The epicenter for this event was <5 km of broadband station TRF, so the depth is well constrained. The DLP event is almost devoid of energy above 5 Hz. Receiver functions for stations TRF and SBL, both <10 km of the epicenter, show Moho depths of 36-40 km.We used waveforms of this DLP as a template event for network matched filtering, which identifies similar signals in continuous time series. We processed this template event from June 1999 to July 2014. We use several matches produced by this template as additional templates, iterating the process. Using this methodology, we identify over 300 DLP's. Events typically come in swarms lasting hours to days with no events exceeding magnitude 2. Swarms are separated by months to years of little detectable activity. A swarm of events on June 30, 2001 coincides with the Broadband Experiment Across the Alaska Range (BEAAR) seismic deployment, and was recorded by 15 broadband seismometers within 100 km of the epicenter. A preliminary waveform inversion for the focal mechanism of this event results in isotropic (implosive) and double couple components.We argue that these DLP's are evidence of magmatic or volatile movement through the sub-arc mantle wedge, even though there is no active volcanism at the surface. Relative relocations, utilizing cross correlated p- and s- waveforms, highlight a nest of seismicity with no structures such as planes or conduits. Lack of planar features, as well as the isotopic component and lack of strike slip to the focal mechanism, may argue against a deep extension of the Hines Creek or

  5. 2013 volcanic activity in Alaska: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    Dixon, James P.; Cameron, Cheryl; McGimsey, Robert G.; Neal, Christina A.; Waythomas, Chris

    2015-08-14

    The Alaska Volcano Observatory (AVO) responded to eruptions, volcanic unrest or suspected unrest, and seismic events at 18 volcanic centers in Alaska during 2013. Beginning with the 2013 AVO Summary of Events, the annual description of the AVO seismograph network and activity, once a stand-alone publication, is now part of this report. Because of this change, the annual summary now contains an expanded description of seismic activity at Alaskan volcanoes. Eruptions occurred at three volcanic centers in 2013: Pavlof Volcano in May and June, Mount Veniaminof Volcano in June through December, and Cleveland Volcano throughout the year. None of these three eruptive events resulted in 24-hour staffing at AVO facilities in Anchorage or Fairbanks.

  6. 2013 volcanic activity in Alaska: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    Dixon, James P.; Cameron, Cheryl; McGimsey, Robert G.; Neal, Christina A.; Waythomas, Chris

    2015-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptions, volcanic unrest or suspected unrest, and seismic events at 18 volcanic centers in Alaska during 2013. Beginning with the 2013 AVO Summary of Events, the annual description of the AVO seismograph network and activity, once a stand-alone publication, is now part of this report. Because of this change, the annual summary now contains an expanded description of seismic activity at Alaskan volcanoes. Eruptions occurred at three volcanic centers in 2013: Pavlof Volcano in May and June, Mount Veniaminof Volcano in June through December, and Cleveland Volcano throughout the year. None of these three eruptive events resulted in 24-hour staffing at AVO facilities in Anchorage or Fairbanks.

  7. Presynaptic Active Zone Density during Development and Synaptic Plasticity.

    PubMed

    Clarke, Gwenaëlle L; Chen, Jie; Nishimune, Hiroshi

    2012-01-01

    Neural circuits transmit information through synapses, and the efficiency of synaptic transmission is closely related to the density of presynaptic active zones, where synaptic vesicles are released. The goal of this review is to highlight recent insights into the molecular mechanisms that control the number of active zones per presynaptic terminal (active zone density) during developmental and stimulus-dependent changes in synaptic efficacy. At the neuromuscular junctions (NMJs), the active zone density is preserved across species, remains constant during development, and is the same between synapses with different activities. However, the NMJ active zones are not always stable, as exemplified by the change in active zone density during acute experimental manipulation or as a result of aging. Therefore, a mechanism must exist to maintain its density. In the central nervous system (CNS), active zones have restricted maximal size, exist in multiple numbers in larger presynaptic terminals, and maintain a constant density during development. These findings suggest that active zone density in the CNS is also controlled. However, in contrast to the NMJ, active zone density in the CNS can also be increased, as observed in hippocampal synapses in response to synaptic plasticity. Although the numbers of known active zone proteins and protein interactions have increased, less is known about the mechanism that controls the number or spacing of active zones. The following molecules are known to control active zone density and will be discussed herein: extracellular matrix laminins and voltage-dependent calcium channels, amyloid precursor proteins, the small GTPase Rab3, an endocytosis mechanism including synaptojanin, cytoskeleton protein spectrins and β-adducin, and a presynaptic web including spectrins. The molecular mechanisms that organize the active zone density are just beginning to be elucidated.

  8. Monitoring of slip at the transition zone on the plate interface estimated from non-volcanic deep low-frequency tremors in southwestern Japan

    NASA Astrophysics Data System (ADS)

    Ishida, R.; Hiramatsu, Y.; Obara, K.; Matsuzawa, T.

    2011-12-01

    In southwestern Japan, non-volcanic deep low-frequency (DLF) tremors (e.g., Obara, 2002) and short-term slow slip events (S-SSEs; e.g., Obara et al., 2004) occur in temporal and spatial coincidence with the active stages of DLF tremors (Obara et al., 2004). Based on this feature, Hiramatsu et al. (2008) proposed a method to monitor slip at the transition zone between the locked and aseismic slip zones on the plate interface using DLF tremors. In this study, we applied the method as the same way of previous studies (Hiramatsu et al., 2008; Hirose et al., 2010) and estimated the long-term average slip rate at the transition zone from DLF tremors in southwestern Japan. We also estimated the slip distributions of S-SSEs from DLF tremors using the modified envelope correlation method (ECM) tremor catalog (Maeda and Obara, 2009) and the hourly centroid tremor catalog (Obara et al., 2010) along with the ECM tremor catalog (Obara, 2002) in southwestern Japan. The modified ECM applied both the differential travel time and the spatial distribution of mean square amplitudes to estimate a tremor's spatial location and radiation energy. The hourly centroid tremor catalog is constructed using a clustering process to estimate centroid locations, revealing clear depth-dependent behavior of the tremor activity. The cumulative seismic moment from 2001 to 2009 increases at a constant rate, indicating a constant moment release rate in the long-term average. We estimated slip rate at the transition zone using the formula ˙ {M0} = μ S_˙ {U}, where ˙ {M0} is the moment release rate, μ the rigidity, S the fault area that is related to the slip of S-SSEs in each region, and ˙ {U} the slip rate. We obtained the slip rates of 4.1 ± 0.5 cm/yr, 3.7 ± 0.6 cm/yr, and 2.6 ± 0.2 cm/yr in the western Shikoku, northern Kii peninsula, and Tokai regions, respectively, at the transition zone through the analyzed period. The slip deficit rate at the transition zone in each region is 2.6cm/yr, 2

  9. Rare-earth element geochemistry and the origin of andesites and basalts of the Taupo Volcanic Zone, New Zealand

    USGS Publications Warehouse

    Cole, J.W.; Cashman, K.V.; Rankin, P.C.

    1983-01-01

    Two types of basalt (a high-Al basalt associated with the rhyolitic centres north of Taupo and a "low-Al" basalt erupted from Red Crater, Tongariro Volcanic Centre) and five types of andesite (labradorite andesite, labradorite-pyroxene andesite, hornblende andesite, pyroxene low-Si andesite and olivine andesite/low-Si andesite) occur in the Taupo Volcanic Zone (TVZ), North Island, New Zealand. Rare-earth abundances for both basalts and andesites are particularly enriched in light rare-earth elements. High-Al basalts are more enriched than the "low-Al" basalt and have values comparable to the andesites. Labradorite and labradorite-pyroxene andesites all have negative Eu anomalies and hornblende andesites all have negative Ce anomalies. The former is probably due to changing plagioclase composition during fractionation and the latter to late-stage hydration of the magma. Least-squares mixing models indicate that neither high-Al nor "low-Al" basalts are likely sources for labradorite/labradorite-pyroxene andesites. High-Al basalts are considered to result from fractionation of olivine and clinopyroxene from a garnet-free peridotite at the top of the mantle wedge. Labradorite/labradorite-pyroxene andesites are mainly associated with an older NW-trending arc. The source is likely to be garnet-free but it is not certain whether the andesites result from partial melting of the top of the subducting plate or a hydrated lower portion of the mantle wedge. Pyroxene low-Si andesites probably result from cumulation of pyroxene and calcic plagioclase within labradorite-pyroxene andesites, and hornblende andesites by late-stage hydration of labradorite-pyroxene andesite magma. Olivine andesites, low-Si andesites and "low-Al" basalts are related to the NNE-trending Taupo-Hikurangi arc structure. Although the initial source material is different for these lavas they have probably undergone a similar history to the labradorite/labradorite-pyroxene andesites. All lavas show evidence

  10. Soil radon measurements as a potential tracer of tectonic and volcanic activity.

    PubMed

    Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

    2016-04-15

    In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009-2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.

  11. Soil radon measurements as a potential tracer of tectonic and volcanic activity

    PubMed Central

    Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

    2016-01-01

    In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009–2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes. PMID:27079264

  12. Soil radon measurements as a potential tracer of tectonic and volcanic activity

    NASA Astrophysics Data System (ADS)

    Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

    2016-04-01

    In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009–2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes.

  13. Soil radon measurements as a potential tracer of tectonic and volcanic activity.

    PubMed

    Neri, Marco; Ferrera, Elisabetta; Giammanco, Salvatore; Currenti, Gilda; Cirrincione, Rosolino; Patanè, Giuseppe; Zanon, Vittorio

    2016-01-01

    In Earth Sciences there is a growing interest in studies concerning soil-radon activity, due to its potential as a tracer of numerous natural phenomena. Our work marks an advance in the comprehension of the interplay between tectonic activity, volcanic eruptions and gas release through faults. Soil-radon measurements, acquired on Mt. Etna volcano in 2009-2011, were analyzed. Our radon probe is sensitive to changes in both volcanic and seismic activity. Radon data were reviewed in light of the meteorological parameters. Soil samples were analyzed to characterize their uranium content. All data have been summarized in a physical model which identifies the radon sources, highlights the mechanism of radon transport and envisages how such a mechanism may change as a consequence of seismicity and volcanic events. In the NE of Etna, radon is released mainly from a depth of <1400 m, with an ascent speed of >50 m/day. Three periods of anomalous gas release were found (February 2010, January and February 2011). The trigger of the first anomaly was tectonic, while the second and third had a volcanic origin. These results mark a significant step towards a better understanding of the endogenous mechanisms that cause changes in soil-radon emission at active volcanoes. PMID:27079264

  14. Significance of an Active Volcanic Front in the Far Western Aleutian Arc

    NASA Astrophysics Data System (ADS)

    Yogodzinski, G. M.; Kelemen, P. B.; Hoernle, K.

    2015-12-01

    Discovery of a volcanic front west of Buldir Volcano, the western-most emergent Aleutian volcano, demonstrates that the surface expression of Aleutian volcanism falls below sea level just west of 175.9° E longitude, but is otherwise continuous from mainland Alaska to Kamchatka. The newly discovered sites of western Aleutian seafloor volcanism are the Ingenstrem Depression, a 60 km-long structural depression just west of Buldir, and an unnamed area 300 km further west, referred to as the Western Cones. These locations fall along a volcanic front that stretches from Buldir to Piip Seamount near the Komandorsky Islands. Western Aleutian seafloor volcanic rocks include large quantities of high-silica andesite and dacite, which define a highly calc-alkaline igneous series and carry trace element signatures that are unmistakably subduction-related. This indicates that subducting oceanic lithosphere is present beneath the westernmost Aleutian arc. The rarity of earthquakes below depths of 200 km indicates that the subducting plate is unusually hot. Some seafloor volcanoes are 6-8 km wide at the base, and so are as large as many emergent Aleutian volcanoes. The seafloor volcanoes are submerged in water depths >3000 m because they sit on oceanic lithosphere of the Bering Sea. The volcanic front is thus displaced to the north of the ridge of arc crust that underlies the western Aleutian Islands. This displacement, which developed since approximately 6 Ma when volcanism was last active on the islands, must be a consequence of oblique convergence in a system where the subducting plate and large blocks of arc crust are both moving primarily in an arc-parallel sense. The result is a hot-slab system where low subduction rates probably limit advection of hot mantle to the subarc, and produce a relatively cool and perhaps stagnant mantle wedge. The oceanic setting and highly oblique subduction geometry also severely limit rates of sediment subduction, so the volcanic rocks, which

  15. Characterization of the Etna volcanic emissions through an active biomonitoring technique (moss-bags): part 2--morphological and mineralogical features.

    PubMed

    Calabrese, S; D'Alessandro, W

    2015-01-01

    Volcanic emissions were studied at Mount Etna (Italy) by using moss-bags technique. Mosses were exposed around the volcano at different distances from the active vents to evaluate the impact of volcanic emissions in the atmosphere. Morphology and mineralogy of volcanic particulate intercepted by mosses were investigated using scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS). Particles emitted during passive degassing activity from the two active vents, Bocca Nuova and North East Crater (BNC and NEC), were identified as silicates, sulfates and halide compounds. In addition to volcanic particles, we found evidences also of geogenic, anthropogenic and marine spray input. The study has shown the robustness of this active biomonitoring technique to collect particles, very useful in active volcanic areas characterized by continuous degassing and often not easily accessible to apply conventional sampling techniques.

  16. Characterization of the Etna volcanic emissions through an active biomonitoring technique (moss-bags): part 2--morphological and mineralogical features.

    PubMed

    Calabrese, S; D'Alessandro, W

    2015-01-01

    Volcanic emissions were studied at Mount Etna (Italy) by using moss-bags technique. Mosses were exposed around the volcano at different distances from the active vents to evaluate the impact of volcanic emissions in the atmosphere. Morphology and mineralogy of volcanic particulate intercepted by mosses were investigated using scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS). Particles emitted during passive degassing activity from the two active vents, Bocca Nuova and North East Crater (BNC and NEC), were identified as silicates, sulfates and halide compounds. In addition to volcanic particles, we found evidences also of geogenic, anthropogenic and marine spray input. The study has shown the robustness of this active biomonitoring technique to collect particles, very useful in active volcanic areas characterized by continuous degassing and often not easily accessible to apply conventional sampling techniques. PMID:25311770

  17. Regeneration of the active zone at the frog neuromuscular junction

    PubMed Central

    1984-01-01

    The active zone is a unique specialization of the presynaptic membrane and is believed to be the site of transmitter release. The formation of the active zone and the relationship of this process to transmitter release were studied at reinnervated neuromuscular junctions in the frog. At different times after a nerve crush, the cutaneous pectoris muscles were examined with intracellular recording recording and freeze- fracture electron microscopy. The P face of a normal active zone typically consists of two double rows of particles lined up in a continuous segment located opposite a junctional fold. In the initial stage of reinnervation, clusters of large intramembrane particles surrounding membrane elevations appeared on the P face of nerve terminals. Like normal active zones, these clusters were aligned with junctional folds. Vesicle openings, which indicate transmitter release, were seen at these primitive active zones, even though intramembrane particles were not yet organized into the normal pattern of two double rows. The length of active zones at this stage was only approximately 15% of normal. During the secondary stage, every junction was reinnervated and most active zones had begun to organize into the normal pattern with normal orientation. Unlike normal, there were often two or more discontinuous short segments of active zone aligned with the same junctional fold. The total length of active zone per junctional fold increased to one-third of normal, mainly because of the greater number of segments. In the third stage, the number of active zone segments per junctional fold showed almost no change when compared with the secondary stage. However, individual segments elongated and increased the total length of all active zone segments per junctional fold to about two-thirds of the normal length. The dynamic process culminated in the final stage, during which elongating active zones appeared to join together and the number of active zone segments per

  18. Exploratory Data Analysis Using a Dedicated Visualization App: Looking for Patterns in Volcanic Activity

    NASA Astrophysics Data System (ADS)

    van Manen, S. M.; Chen, S.

    2015-12-01

    Here we present an App designed to visualize and identify patterns in volcanic activity during the last ten years. It visualizes VEI (volcanic explosivity index) levels, population size, frequency of activity, and geographic region, and is designed to address the issue of oversampling of data. Often times, it is difficult to access a large set of data that can be scattered at first glance and hard to digest without visual aid. This App serves as a model that solves this issue and can be applied to other data. To enable users to quickly assess the large data set it breaks down the apparently chaotic abundance of information into categories and graphic indicators: color is used to indicate the VEI level, size for population size within 5 km of a volcano, line thickness for frequency of activity, and a grid to pinpoint a volcano's latitude. The categories and layers within them can be turned on and off by the user, enabling them to scroll through and compare different layers of data. By visualising the data this way, patterns began to emerge. For example, certain geographic regions had more explosive eruptions than others. Another good example was that low frequency larger impact volcanic eruptions occurred more irregularly than smaller impact volcanic eruptions, which had a more stable frequencies. Although these findings are not unexpected, the easy to navigate App does showcase the potential of data visualization for the rapid appraisal of complex and abundant multi-dimensional geoscience data.

  19. Chemistry of ash-leachates: a reliable monitoring tool for volcanic activity

    NASA Astrophysics Data System (ADS)

    Armienta, M. A.; De la Cruz-Reyna, S.; Soler, A.; Ceniceros, N.; Cruz, O.; Aguayo, A.

    2012-04-01

    Real-time volcanic hazard assessment requires the integrated interpretation of data obtained with different monitoring methods, particularly when people may be at risk. One of the methods rendering earliest precursory variations reflecting the internal state of a volcano is the geochemical analysis of gases, ground or lake waters related to volcanic systems, and volcanic ash. At Popocatépetl volcano, Central México, chemical fluctuations of the soluble cover of volcanic ash particles has proved to reflect diverse characteristics of the eruption types. Chloride, sulfate and fluoride concentrations of ash leachates have been consistently measured within the current eruptive episode beginning in December 1994. Particularly, main anions presented diverse relative concentrations in periods of dome extrusions, contrasting with hydrothermal activity or quiescence. Multivariate statistical analysis revealed that higher proportions of fluoride in the leachates corresponded to new dome emplacements and relatively higher sulfate concentrations to hydrothermal ashes, although these results may be ambiguous at times. However, different sulfur isotopic ratios were measured in sulfate from ashes erupted during periods dominated by hydrothermal activity to those emitted during dome emplacement. Additionally, ascent of fresh magma was reflected on high fluoride concentrations jointly with low 34S-SO4 isotopic values. It is thus recommended to maintain persistent analyses of ash-leachates from on-going eruptions as a monitoring tool at active volcanoes.

  20. The Volcanic Ash Strategic Initiative Team (VAST) - operational testing activities and exercises

    NASA Astrophysics Data System (ADS)

    Wotawa, Gerhard; Arnold, Delia; Eckhardt, Sabine; Kristiansen, Nina; Maurer, Christian; Prata, Fred; Stohl, Andreas; Zehner, Claus

    2013-04-01

    The project VAST performs its activities within an ESA (European Space Agency) initiative to enhance the use of Earth Observation (EO) data in volcanic ash monitoring and forecasting. The VAST project aims at further exploring the suitability of EO data for such activities and to improve volcanic ash atmospheric transport forecasting services through exercises and demonstration activities in operational environments. Previous to the in-house deployment of the demonstration service, several exercises on operations and communication exchange are needed and first results are presented here. These exercises include technical in-house settings and conceptual planning of the operations with procedure development, volcanic eruptions drills that trigger the acquiring of data and dispersion/forecasting calculations with preliminary estimates of source terms and finally, an international exercise that provides a test case volcanic event to evaluate response times and the usefulness of the different products obtained. Products also include ensemble dispersion forecasts, on one hand multi-input ensembles utilizing the ECMWF EPS system, and on the other hand multi-model ensembles based on different dispersion models driven with different input data. As part of the work, socio-economic aspects need to be taken into account as well. This includes also the identification of best practices on how results can be presented to the stakeholders, including national authorities and policy makers, and the general public.

  1. The STRATegy COLUMN for Precollege Science Teachers: Volcanic Activity.

    ERIC Educational Resources Information Center

    Metzger, Ellen Pletcher

    1995-01-01

    Describes resources for information and activities involving volcanoes. Includes an activity that helps students become familiar with the principal types of volcanoes and explores how the viscosity of magma affects the way a volcano erupts. (MKR)

  2. Planetary Volcanism

    NASA Technical Reports Server (NTRS)

    Antonenko, I.; Head, J. W.; Pieters, C. W.

    1998-01-01

    The final report consists of 10 journal articles concerning Planetary Volcanism. The articles discuss the following topics: (1) lunar stratigraphy; (2) cryptomare thickness measurements; (3) spherical harmonic spectra; (4) late stage activity of volcanoes on Venus; (5) stresses and calderas on Mars; (6) magma reservoir failure; (7) lunar mare basalt volcanism; (8) impact and volcanic glasses in the 79001/2 Core; (9) geology of the lunar regional dark mantle deposits; and (10) factors controlling the depths and sizes of magma reservoirs in Martian volcanoes.

  3. Observing Active Volcanism on Earth and Beyond With an Autonomous Science Investigation Capability

    NASA Astrophysics Data System (ADS)

    Davies, A. G.; Mjolsness, E. D.; Fink, W.; Castano, R.; Park, H. G.; Zak, M.; Burl, M. C.

    2001-12-01

    Operational constraints imposed by restricted downlink and long communication delays make autonomous systems a necessity for exploring dynamic processes in the Solar System and beyond. Our objective is to develop an onboard, modular, automated science analysis tool that will autonomously detect unexpected events, identify rare events at predicted sites, quantify the processes under study, and prioritize the science data and analyses as they are collected. A primary target for this capability is terrestrial active volcanism. Our integrated, science-driven command and control package represents the next stage of the automatic monitoring of volcanic activity pioneered by GOES. The resulting system will maximize science return from day-to-day instrument use and provide immediate reaction to capture the fullest information from infrequent events. For example, a sensor suite consisting of a Galileo-like multi-filter visible wavelength camera and an infrared spectrometer, can acquire high-spatial resolution data of eruptions of lava and volcanic plumes and identify large concentrations of volcanic SO2. After image/spectrum formation, software is applied to the data which is capable of change detection (in the visible and infrared), feature identification (both in imagery and spectra), and novelty detection. In this particular case, the latter module detects change in the parameter space of an advanced multi-component black-body volcanic thermal emission model by means of a novel technique called the "Grey-Box" method which analyzes time series data through a combination of deterministic and stochastic models. This approach can be demonstrated using data obtained by the Galileo spacecraft of ionian volcanism. The system autonomously identifies the most scientifically important targets and prioritizes data and analyses for return. All of these techniques have been successfully demonstrated in laboratory experiments, and are ready to be tested in an operational environment

  4. Surface heat flow and CO2 emissions within the Ohaaki hydrothermal field, Taupo Volcanic Zone, New Zealand

    USGS Publications Warehouse

    Rissmann, C.; Christenson, B.; Werner, C.; Leybourne, M.; Cole, J.; Gravley, D.

    2012-01-01

    Carbon dioxide emissions and heat flow have been determined from the Ohaaki hydrothermal field, Taupo Volcanic Zone (TVZ), New Zealand following 20a of production (116MW e). Soil CO2 degassing was quantified with 2663 CO2 flux measurements using the accumulation chamber method, and 2563 soil temperatures were measured and converted to equivalent heat flow (Wm -2) using published soil temperature heat flow functions. Both CO2 flux and heat flow were analysed statistically and then modelled using 500 sequential Gaussian simulations. Forty subsoil CO 2 gas samples were also analysed for stable C isotopes. Following 20a of production, current CO2 emissions equated to 111??6.7T/d. Observed heat flow was 70??6.4MW, compared with a pre-production value of 122MW. This 52MW reduction in surface heat flow is due to production-induced drying up of all alkali-Cl outflows (61.5MW) and steam-heated pools (8.6MW) within the Ohaaki West thermal area (OHW). The drying up of all alkali-Cl outflows at Ohaaki means that the soil zone is now the major natural pathway of heat release from the high-temperature reservoir. On the other hand, a net gain in thermal ground heat flow of 18MW (from 25MW to 43.3??5MW) at OHW is associated with permeability increases resulting from surface unit fracturing by production-induced ground subsidence. The Ohaaki East (OHE) thermal area showed no change in distribution of shallow and deep soil temperature contours despite 20a of production, with an observed heat flow of 26.7??3MW and a CO 2 emission rate of 39??3T/d. The negligible change in the thermal status of the OHE thermal area is attributed to the low permeability of the reservoir beneath this area, which has limited production (mass extraction) and sheltered the area from the pressure decline within the main reservoir. Chemistry suggests that although alkali-Cl outflows once contributed significantly to the natural surface heat flow (~50%) they contributed little (<1%) to pre-production CO 2

  5. Geosphere-biosphere interactions in bio-activity volcanic lakes: evidences from Hule and Rìo Cuarto (Costa Rica).

    PubMed

    Cabassi, Jacopo; Tassi, Franco; Mapelli, Francesca; Borin, Sara; Calabrese, Sergio; Rouwet, Dmitri; Chiodini, Giovanni; Marasco, Ramona; Chouaia, Bessem; Avino, Rosario; Vaselli, Orlando; Pecoraino, Giovannella; Capecchiacci, Francesco; Bicocchi, Gabriele; Caliro, Stefano; Ramirez, Carlos; Mora-Amador, Raul

    2014-01-01

    Hule and Río Cuarto are maar lakes located 11 and 18 km N of Poás volcano along a 27 km long fracture zone, in the Central Volcanic Range of Costa Rica. Both lakes are characterized by a stable thermic and chemical stratification and recently they were affected by fish killing events likely related to the uprising of deep anoxic waters to the surface caused by rollover phenomena. The vertical profiles of temperature, pH, redox potential, chemical and isotopic compositions of water and dissolved gases, as well as prokaryotic diversity estimated by DNA fingerprinting and massive 16S rRNA pyrosequencing along the water column of the two lakes, have highlighted that different bio-geochemical processes occur in these meromictic lakes. Although the two lakes host different bacterial and archaeal phylogenetic groups, water and gas chemistry in both lakes is controlled by the same prokaryotic functions, especially regarding the CO2-CH4 cycle. Addition of hydrothermal CO2 through the bottom of the lakes plays a fundamental priming role in developing a stable water stratification and fuelling anoxic bacterial and archaeal populations. Methanogens and methane oxidizers as well as autotrophic and heterotrophic aerobic bacteria responsible of organic carbon recycling resulted to be stratified with depth and strictly related to the chemical-physical conditions and availability of free oxygen, affecting both the CO2 and CH4 chemical concentrations and their isotopic compositions along the water column. Hule and Río Cuarto lakes were demonstrated to contain a CO2 (CH4, N2)-rich gas reservoir mainly controlled by the interactions occurring between geosphere and biosphere. Thus, we introduced the term of bio-activity volcanic lakes to distinguish these lakes, which have analogues worldwide (e.g. Kivu: D.R.C.-Rwanda; Albano, Monticchio and Averno: Italy; Pavin: France) from volcanic lakes only characterized by geogenic CO2 reservoir such as Nyos and Monoun (Cameroon). PMID

  6. Geosphere-biosphere interactions in bio-activity volcanic lakes: evidences from Hule and Rìo Cuarto (Costa Rica).

    PubMed

    Cabassi, Jacopo; Tassi, Franco; Mapelli, Francesca; Borin, Sara; Calabrese, Sergio; Rouwet, Dmitri; Chiodini, Giovanni; Marasco, Ramona; Chouaia, Bessem; Avino, Rosario; Vaselli, Orlando; Pecoraino, Giovannella; Capecchiacci, Francesco; Bicocchi, Gabriele; Caliro, Stefano; Ramirez, Carlos; Mora-Amador, Raul

    2014-01-01

    Hule and Río Cuarto are maar lakes located 11 and 18 km N of Poás volcano along a 27 km long fracture zone, in the Central Volcanic Range of Costa Rica. Both lakes are characterized by a stable thermic and chemical stratification and recently they were affected by fish killing events likely related to the uprising of deep anoxic waters to the surface caused by rollover phenomena. The vertical profiles of temperature, pH, redox potential, chemical and isotopic compositions of water and dissolved gases, as well as prokaryotic diversity estimated by DNA fingerprinting and massive 16S rRNA pyrosequencing along the water column of the two lakes, have highlighted that different bio-geochemical processes occur in these meromictic lakes. Although the two lakes host different bacterial and archaeal phylogenetic groups, water and gas chemistry in both lakes is controlled by the same prokaryotic functions, especially regarding the CO2-CH4 cycle. Addition of hydrothermal CO2 through the bottom of the lakes plays a fundamental priming role in developing a stable water stratification and fuelling anoxic bacterial and archaeal populations. Methanogens and methane oxidizers as well as autotrophic and heterotrophic aerobic bacteria responsible of organic carbon recycling resulted to be stratified with depth and strictly related to the chemical-physical conditions and availability of free oxygen, affecting both the CO2 and CH4 chemical concentrations and their isotopic compositions along the water column. Hule and Río Cuarto lakes were demonstrated to contain a CO2 (CH4, N2)-rich gas reservoir mainly controlled by the interactions occurring between geosphere and biosphere. Thus, we introduced the term of bio-activity volcanic lakes to distinguish these lakes, which have analogues worldwide (e.g. Kivu: D.R.C.-Rwanda; Albano, Monticchio and Averno: Italy; Pavin: France) from volcanic lakes only characterized by geogenic CO2 reservoir such as Nyos and Monoun (Cameroon).

  7. Geosphere-Biosphere Interactions in Bio-Activity Volcanic Lakes: Evidences from Hule and Rìo Cuarto (Costa Rica)

    PubMed Central

    Cabassi, Jacopo; Tassi, Franco; Mapelli, Francesca; Borin, Sara; Calabrese, Sergio; Rouwet, Dmitri; Chiodini, Giovanni; Marasco, Ramona; Chouaia, Bessem; Avino, Rosario; Vaselli, Orlando; Pecoraino, Giovannella; Capecchiacci, Francesco; Bicocchi, Gabriele; Caliro, Stefano; Ramirez, Carlos; Mora-Amador, Raul

    2014-01-01

    Hule and Río Cuarto are maar lakes located 11 and 18 km N of Poás volcano along a 27 km long fracture zone, in the Central Volcanic Range of Costa Rica. Both lakes are characterized by a stable thermic and chemical stratification and recently they were affected by fish killing events likely related to the uprising of deep anoxic waters to the surface caused by rollover phenomena. The vertical profiles of temperature, pH, redox potential, chemical and isotopic compositions of water and dissolved gases, as well as prokaryotic diversity estimated by DNA fingerprinting and massive 16S rRNA pyrosequencing along the water column of the two lakes, have highlighted that different bio-geochemical processes occur in these meromictic lakes. Although the two lakes host different bacterial and archaeal phylogenetic groups, water and gas chemistry in both lakes is controlled by the same prokaryotic functions, especially regarding the CO2-CH4 cycle. Addition of hydrothermal CO2 through the bottom of the lakes plays a fundamental priming role in developing a stable water stratification and fuelling anoxic bacterial and archaeal populations. Methanogens and methane oxidizers as well as autotrophic and heterotrophic aerobic bacteria responsible of organic carbon recycling resulted to be stratified with depth and strictly related to the chemical-physical conditions and availability of free oxygen, affecting both the CO2 and CH4 chemical concentrations and their isotopic compositions along the water column. Hule and Río Cuarto lakes were demonstrated to contain a CO2 (CH4, N2)-rich gas reservoir mainly controlled by the interactions occurring between geosphere and biosphere. Thus, we introduced the term of bio-activity volcanic lakes to distinguish these lakes, which have analogues worldwide (e.g. Kivu: D.R.C.-Rwanda; Albano, Monticchio and Averno: Italy; Pavin: France) from volcanic lakes only characterized by geogenic CO2 reservoir such as Nyos and Monoun (Cameroon). PMID

  8. High resolution DEM from Tandem-X interferometry: an accurate tool to characterize volcanic activity

    NASA Astrophysics Data System (ADS)

    Albino, Fabien; Kervyn, Francois

    2013-04-01

    Tandem-X mission was launched by the German agency (DLR) in June 2010. It is a new generation high resolution SAR sensor mainly dedicated to topographic applications. For the purpose of our researches focused on the study of the volcano-tectonic activity in the Kivu Rift area, a set of Tandem-X bistatic radar images were used to produce a high resolution InSAR DEM of the Virunga Volcanic Province (VVP). The VVP is part of the Western branch of the African rift, situated at the boundary between D.R. Congo, Rwanda and Uganda. It has two highly active volcanoes, Nyiragongo and Nyamulagira. A first task concerns the quantitative assessment of the vertical accuracy that can be achieved with these new data. The new DEMs are compared to other space borne datasets (SRTM, ASTER) but also to field measurements given by differential GPS. Multi-temporal radar acquisitions allow us to produce several DEM of the same area. This appeared to be very useful in the context of an active volcanic context where new geomorphological features (faults, fissures, volcanic cones and lava flows) appear continuously through time. For example, since the year 2000, time of the SRTM acquisition, we had one eruption at Nyiragongo (2002) and six eruptions at Nyamulagira (2001, 2002, 2004, 2006, 2010 and 2011) which all induce large changes in the landscape with the emplacement of new lava fields and scoria cones. From our repetitive Tandem-X DEM production, we have a tool to identify and also quantify in term of size and volume all the topographic changes relative to this past volcanic activity. These parameters are high value information to improve the understanding of the Virunga volcanoes; the accurate estimation of erupted volume and knowledge of structural features associated to past eruptions are key parameters to understand the volcanic system, to ameliorate the hazard assessment, and finally contribute to risk mitigation in a densely populated area.

  9. Evidence of recent deep magmatic activity at Cerro Bravo-Cerro Machín volcanic complex, central Colombia. Implications for future volcanic activity at Nevado del Ruiz, Cerro Machín and other volcanoes

    NASA Astrophysics Data System (ADS)

    Londono, John Makario

    2016-09-01

    In the last nine years (2007-2015), the Cerro Bravo-Cerro Machín volcanic complex (CBCMVC), located in central Colombia, has experienced many changes in volcanic activity. In particular at Nevado del Ruiz volcano (NRV), Cerro Machin volcano (CMV) and Cerro Bravo (CBV) volcano. The recent activity of NRV, as well as increasing seismic activity at other volcanic centers of the CBCMVC, were preceded by notable changes in various geophysical and geochemical parameters, that suggests renewed magmatic activity is occurring at the volcanic complex. The onset of this activity started with seismicity located west of the volcanic complex, followed by seismicity at CBV and CMV. Later in 2010, strong seismicity was observed at NRV, with two small eruptions in 2012. After that, seismicity has been observed intermittently at other volcanic centers such as Santa Isabel, Cerro España, Paramillo de Santa Rosa, Quindío and Tolima volcanoes, which persists until today. Local deformation was observed from 2007 at NRV, followed by possible regional deformation at various volcanic centers between 2011 and 2013. In 2008, an increase in CO2 and Radon in soil was observed at CBV, followed by a change in helium isotopes at CMV between 2009 and 2011. Moreover, SO2 showed an increase from 2010 at NRV, with values remaining high until the present. These observations suggest that renewed magmatic activity is currently occurring at CBCMVC. NRV shows changes in its activity that may be related to this new magmatic activity. NRV is currently exhibiting the most activity of any volcano in the CBCMVC, which may be due to it being the only open volcanic system at this time. This suggests that over the coming years, there is a high probability of new unrest or an increase in volcanic activity of other volcanoes of the CBCMVC.

  10. International Collaboration on Building Local Technical Capacities for Monitoring Volcanic Activity at Pacaya Volcano, Guatemala.

    NASA Astrophysics Data System (ADS)

    Escobar-Wolf, R. P.; Chigna, G.; Morales, H.; Waite, G. P.; Oommen, T.; Lechner, H. N.

    2015-12-01

    Pacaya volcano is a frequently active and potentially dangerous volcano situated in the Guatemalan volcanic arc. It is also a National Park and a major touristic attraction, constituting an important economic resource for local municipality and the nearby communities. Recent eruptions have caused fatalities and extensive damage to nearby communities, highlighting the need for risk management and loss reduction from the volcanic activity. Volcanic monitoring at Pacaya is done by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (INSIVUMEH), instrumentally through one short period seismic station, and visually by the Parque Nacional Volcan de Pacaya y Laguna de Calderas (PNVPLC) personnel. We carry out a project to increase the local technical capacities for monitoring volcanic activity at Pacaya. Funding for the project comes from the Society of Exploration Geophysicists through the Geoscientists Without Borders program. Three seismic and continuous GPS stations will be installed at locations within 5 km from the main vent at Pacaya, and one webcam will aid in the visual monitoring tasks. Local educational and outreach components of the project include technical workshops on data monitoring use, and short thesis projects with the San Carlos University in Guatemala. A small permanent exhibit at the PNVPLC museum or visitor center, focusing on the volcano's history, hazards and resources, will also be established as part of the project. The strategy to involve a diverse group of local collaborators in Guatemala aims to increase the chances for long term sustainability of the project, and relies not only on transferring technology but also the "know-how" to make that technology useful. Although not a primary research project, it builds on a relationship of years of joint research projects at Pacaya between the participants, and could be a model of how to increase the broader impacts of such long term collaboration partnerships.

  11. The calc-alkaline and adakitic volcanism of the Sabzevar structural zone (NE Iran): Implications for the Eocene magmatic flare-up in Central Iran

    NASA Astrophysics Data System (ADS)

    Moghadam, Hadi Shafaii; Rossetti, Federico; Lucci, Federico; Chiaradia, Massimo; Gerdes, Axel; Martinez, Margarita Lopez; Ghorbani, Ghasem; Nasrabady, Mohsen

    2016-04-01

    A major magmatic flare-up is documented along the Bitlis-Zagros suture zone in Eocene-Oligocene times. The Cenozoic magmatism of intraplate Central Iran is an integrant part of this tectono-magmatic scenario. The Cenozoic magmatism of the Sabzevar structural zone consists of mostly intermediate to felsic intrusions and volcanic products. These igneous rocks have calc-alkaline and adakitic geochemical signatures, with nearly coincident zircon U-Pb and mica Ar-Ar ages of ca. 45 Ma. Adakitic rocks have quite low HREE and high Sr/Y ratio, but share most of their geochemical features with the calc-alkaline rocks. The Sabzevar volcanic rocks have similar initial Sr, Nd and Pb isotope ratios, showing their cogenetic nature. Nd model ages cluster tightly around ~ 0.2-0.3 Ga. The geochemistry of the Sabzevar volcanic rocks, along with their isotopic signatures, might strangle that an upper mantle source, metasomatized by slab-derived melts was involved in generating the Sabzevar calc-alkaline rocks. A bulk rock trace element modeling suggests that amphibole-plagioclase-titanite-dominated replenishment-fractional crystallization (RFC) is further responsible for the formation of the middle Eocene Sabzevar adakitic rocks. Extensional tectonics accompanied by lithospheric delamination, possibly assisted by slab break-off and melting at depth was responsible for the Eocene formation of the Sabzevar magmatic rocks and, more in general, for the magmatic "flare-up" in Iran.

  12. Factors limiting microbial activity in volcanic tuff at Yucca Mountain

    SciTech Connect

    Kieft, T.L.; Kovacik, W.P.; Taylor, J.

    1996-09-01

    Samples of tuff aseptically collected from 10 locations in the Exploratory Shaft Facility at the site of the proposed high-level nuclear waste repository at Yucca Mountain, Nevada Test Site were analyzed for microbiological populations, activities, and factors limiting microbial activity. Radiotracer assays ({sup 14}C-labeled organic substrate mineralization), direct microscopic counts, and plate counts were used. Radiolabeled substrates were glucose, acetate, and glutamate. Radiotracer experiments were carried out with and without moisture and inorganic nutrient amendments to determine factors limiting to microbial activities. Nearly all samples showed the presence of microorganisms with the potential to mineralize organic substrates. Addition of inorganic nutrients stimulated activities in a small number of samples. The presence of viable microbial communities within the tuff has implications for transport of contaminants.

  13. Search for ongoing volcanic activity on Venus: Case study of Maat Mons, Sapas Mons and Ozza Mons

    NASA Astrophysics Data System (ADS)

    Basilevsky, A. T.; Shalygin, E. V.; Markiewicz, W. J.; Titov, D. V.; Roatsch, Th.; Kreslavsky, M. A.

    2012-04-01

    Maat Mons volcano and its vicinities show evidence of geologically very recent volcanism. We consider Venus Monitoring Camera (VMC) night-side images of this area. Analysis of VMC images taken in 12 observation sessions during the time period from 31 Oct 2007 to 15 Jun 2009 did not reveal any suspicious high-emission spots which could be signatures of the presently ongoing volcanic eruptions. If Maat Mons volcano had the eruption history similar to that of Mauna Loa, Hawaii, in the 20th century, the probability to observe an eruption in this VMC observation sequence would be about 8%, meaning that the absence of detection does not mean that Maat is not active in the present epoch. Blurring of the thermal radiation coming from Venus surface by the planet atmosphere decreases detectability of thermal signature of fresh lavas. We simulated near-infrared images of the study area with artificially added lava flows having surface temperature 1000 K and various areas. These simulations showed that 1 km2 lava flows should be marginally seen by VMC. An increase of the lava surface area to 2 - 3 km2 makes them visible on the plains and increase of the area to 4 - 5 km2 makes them visible even in deep rift zones. Typical individual lava flows on Mauna Loa are a few km2, however, they often have been formed during weeks to months and the instantaneous size of the hot flow surface was usually much smaller. Thus the detection probability is significantly lower than 8%, but it is far from negligible. Our consideration suggests that further search of Maat Mons area and other areas including young rift zones makes sense and should be continued. More effective search could be done if observations simultaneously cover most part of the night side of Venus for relatively long (years) time of continuous observations.

  14. Search for ongoing volcanic activity on Venus: Case study of Maat Mons, Sapas Mons and Ozza Mons volcanoes

    NASA Astrophysics Data System (ADS)

    Shalygin, E. V.; Basilevsky, A. T.; Markiewicz, W. J.; Titov, D. V.; Kreslavsky, M. A.; Roatsch, Th.

    2012-12-01

    We report on attempts to find the ongoing volcanic activity from near-infrared night-time observations with the Venus Monitoring Camera (VMC) onboard of Venus Express. Here we consider VMC images of the areas of Maat Mons volcano and its vicinities, which, as it follows from analysis of the Magellan data, show evidence of geologically very recent volcanism. Analysis of VMC images taken in 12 observation sessions during the time period from 31 October 2007 to 15 June 2009 did not reveal any suspicious high-emission spots which could be signatures of the presently ongoing volcanic eruptions. We compare this time sequence of observations with the history of eruptions of volcano Mauna Loa, Hawaii, in the 20th century. This comparison shows that if Maat Mons volcano had the eruption history similar to that of Mauna Loa, the probability to observe an eruption in this VMC observation sequence would be about 8%, meaning that the absence of detection does not mean that Maat is not active in the present epoch. These estimates do not consider the effect of absorption and blurring of the thermal radiation coming from Venus surface by the planet atmosphere and clouds, which decreases detectability of thermal signature of fresh lavas. To assess the role of this effect we simulated near-infrared images of the study area with artificially added circular and rectangular (with different aspect ratios) lava flows having surface temperature 1000 K and various areas. These simulations showed that 1 km2 lava flows should be marginally seen by VMC. An increase of the lava surface area to 2-3 km2 makes them visible on the plains and increase of the area to 4-5 km2 makes them visible even in deep rift zones. Typical individual lava flows on Mauna Loa are a few km2, however, they often have been formed during weeks to months and the instantaneous size of the hot flow surface was usually much smaller. Thus the detection probability is significantly lower than 8%, but it is far from

  15. Spatial distribution of intrinsic and scattering seismic attenuation in active volcanic islands - I: model and the case of Tenerife Island

    NASA Astrophysics Data System (ADS)

    Prudencio, Janire; Del Pezzo, Edoardo; García-Yeguas, Araceli; Ibáñez, Jesús M.

    2013-12-01

    The complex volcanic system of Tenerife Island is known to have a highly heterogeneous character, as recently confirmed by velocity tomography. We present new information derived from intrinsic quality factor inverse maps (Qi-1), scattering quality factor inverse maps (Qs-1) and total quality factor inverse maps (Qt-1) obtained for the same region. The data set used in this work is the result of the analysis of an active seismic experiment carried out, using offshore shots (air guns) recorded at over 85 onshore seismic stations. The estimates of the attenuation parameters are based on the assumption that the seismogram energy envelopes are determined by seismic energy diffusion processes occurring inside the island. Diffusion model parameters, proportional to Qi-1 and to Qs-1, are estimated from the inversion of the energy envelopes for any source-receiver couple. They are then weighted with a new graphical approach based on a Gaussian space probability function, which allowed us to create `2-D probabilistic maps' representing the space distribution of the attenuation parameters. The 2-D images obtained reveal the existence of a zone in the centre of the island characterized by the lowest attenuation effects. This effect is interpreted as highly rigid and cooled rocks. This low-attenuation region is bordered by zones of high attenuation, associated with the recent historical volcanic activity. We calculate the transport mean free path obtaining a value of around 4 km for the frequency range 6-12 Hz. This result is two orders of magnitude smaller than values calculated for the crust of the Earth. An absorption length between 10 and 14 km is associated with the average intrinsic attenuation parameter. These values, while small in the context of tectonic regions, are greater than those obtained in volcanic regions such as Vesuvius or Merapi. Such differences may be explained by the magnitude of the region of study, over three times larger than the aforementioned study

  16. Compilation of Disruptions to Airports by Volcanic Activity (Version 1.0, 1944-2006)

    USGS Publications Warehouse

    Guffanti, Marianne; Mayberry, Gari C.; Casadevall, Thomas J.; Wunderman, Richard

    2008-01-01

    Volcanic activity has caused significant hazards to numerous airports worldwide, with local to far-ranging effects on travelers and commerce. To more fully characterize the nature and scope of volcanic hazards to airports, we collected data on incidents of airports throughout the world that have been affected by volcanic activity, beginning in 1944 with the first documented instance of damage to modern aircraft and facilities in Naples, Italy, and extending through 2006. Information was gleaned from various sources, including news outlets, volcanological reports (particularly the Smithsonian Institution's Bulletin of the Global Volcanism Network), and previous publications on the topic. This report presents the full compilation of the data collected. For each incident, information about the affected airport and the volcanic source has been compiled as a record in a Microsoft Access database. The database is incomplete in so far as incidents may not have not been reported or documented, but it does present a good sample from diverse parts of the world. Not included are en-route diversions to avoid airborne ash clouds at cruise altitudes. The database has been converted to a Microsoft Excel spreadsheet. To make the PDF version of table 1 in this open-file report resemble the spreadsheet, order the PDF pages as 12, 17, 22; 13, 18, 23; 14, 19, 24; 15, 20, 25; and 16, 21, 26. Analysis of the database reveals that, at a minimum, 101 airports in 28 countries were impacted on 171 occasions from 1944 through 2006 by eruptions at 46 volcanoes. The number of affected airports (101) probably is better constrained than the number of incidents (171) because recurring disruptions at a given airport may have been lumped together or not reported by news agencies, whereas the initial disruption likely is noticed and reported and thus the airport correctly counted.

  17. Major changes in the post-glacial evolution of magmatic compositions and pre-eruptive conditions of Llaima Volcano, Andean Southern Volcanic Zone, Chile

    NASA Astrophysics Data System (ADS)

    Schindlbeck, J. C.; Freundt, A.; Kutterolf, S.

    2014-06-01

    Llaima is one of the most active volcanoes of the Chilean volcanic front with recent explosive eruptions in 2008 and 2009. Understanding how the volcano evolved to its present state is essential for predictions of its future behavior. The post-glacial succession of explosive volcanic eruptions of Llaima stratovolcano started with two caldera-forming eruptions at ˜16 and ˜15 ka, that emplaced two large-volume basaltic-andesitic ignimbrites (unit I). These are overlain by a series of fall deposits (unit II) changing from basaltic-andesitic to dacitic compositions with time. The prominent compositionally zoned, dacitic to andesitic Llaima pumice (unit III) was formed by a large Plinian eruption at ˜10 ka that produced andesitic surge deposits (unit IV) in its terminal phase. The following unit V represents a time interval of ˜8,000 years during which at least 30 basaltic to andesitic ash and lapilli fall deposits with intercalated volcaniclastic sediments and paleosols were emplaced. Bulk rock, mineral, and glass chemical data constrain stratigraphic changes in magma compositions and pre-eruptive conditions that we interpret in terms of four distinct evolutionary phases. Phase 1 (=unit I) magmas have lower large ion lithophile (LIL)/high field strength (HFS) element ratios compared to younger magmas and thus originated from a mantle source less affected by slab-derived fluids. They differentiated in a reservoir at mid-crustal level. During the post-caldera phase 2 (=units II-IV), relatively long residence times between eruptions allowed for increasingly differentiated magmas to form in a reservoir in the middle crust. Fractional crystallization led to volatile enrichment and oversaturation and is the driving force for the large Plinian eruption of the most evolved (unit III) dacite at Llaima, although replenishment by hot andesite probably triggered the eruption. During the subsequent phase 3 (=unit V >3 ka), frequent mafic replenishments at mid-crustal storage

  18. Electrical activity during the 2006 Mount St. Augustine volcanic eruptions

    USGS Publications Warehouse

    Thomas, Ronald J.; Krehbiel, Paul R.; Rison, William; Edens, H. E.; Aulich, G. D.; McNutt, S.R.; Tytgat, Guy; Clark, E.

    2007-01-01

    By using a combination of radio frequency time-of-arrival and interferometer measurements, we observed a sequence of lightning and electrical activity during one of Mount St. Augustine's eruptions. The observations indicate that the electrical activity had two modes or phases. First, there was an explosive phase in which the ejecta from the explosion appeared to be highly charged upon exiting the volcano, resulting in numerous apparently disorganized discharges and some simple lightning. The net charge exiting the volcano appears to have been positive. The second phase, which followed the most energetic explosion, produced conventional-type discharges that occurred within plume. Although the plume cloud was undoubtedly charged as a result of the explosion itself, the fact that the lightning onset was delayed and continued after and well downwind of the eruption indicates that in situ charging of some kind was occurring, presumably similar in some respects to that which occurs in normal thunderstorms.

  19. Electrical activity during the 2006 Mount St. Augustine volcanic eruptions.

    PubMed

    Thomas, R J; Krehbiel, P R; Rison, W; Edens, H E; Aulich, G D; Winn, W P; McNutt, S R; Tytgat, G; Clark, E

    2007-02-23

    By using a combination of radio frequency time-of-arrival and interferometer measurements, we observed a sequence of lightning and electrical activity during one of Mount St. Augustine's eruptions. The observations indicate that the electrical activity had two modes or phases. First, there was an explosive phase in which the ejecta from the explosion appeared to be highly charged upon exiting the volcano, resulting in numerous apparently disorganized discharges and some simple lightning. The net charge exiting the volcano appears to have been positive. The second phase, which followed the most energetic explosion, produced conventional-type discharges that occurred within plume. Although the plume cloud was undoubtedly charged as a result of the explosion itself, the fact that the lightning onset was delayed and continued after and well downwind of the eruption indicates that in situ charging of some kind was occurring, presumably similar in some respects to that which occurs in normal thunderstorms. PMID:17322054

  20. Thermo-physical rock properties of greywacke basement rock and intrusive lavas from the Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Mielke, P.; Weinert, S.; Bignall, G.; Sass, I.

    2016-09-01

    Greywacke of the Waipapa and Torlesse (Composite) Terrane form the basement of the Taupo Volcanic Zone (TVZ), New Zealand. Together with inferred buried lavas, domes and igneous complexes they are likely to be the dominant rock type prevailing at depths > 4 km beneath the TVZ. A fundamental understanding of the rock properties of the deep formations is of utmost importance for the exploration of deep unconventional geothermal resources. An outcrop analogue study was conducted to improve the understanding of the thermo-physical rock properties of likely deep buried rock formations beneath the TVZ. A total of 145 core samples were taken at 10 locations inside and outside the TVZ and their grain and bulk density, porosity, matrix permeability, bulk thermal conductivity and specific heat capacity, and the compressional and shear wave velocities measured on oven-dry samples. Additional tests of the unconfined compressive strength were conducted for selected greywacke samples to quantify their mechanical rock strength. The obtained data indicates that the thermo-physical rock properties are mainly controlled by porosity, and minor by mineralogy, texture and grain size. Samples from Waipapa-type and Torlesse-type greywacke exhibit minor rheological differences, with Waipapa-type greywacke having lowest porosity (about 1% vs. 3%) and highest bulk thermal conductivity (2.5 W m- 1 K- 1 vs. 1.7 W m- 1 K- 1) and specific heat capacity (0.8 kJ kg- 1 K- 1 vs. 0.7 kJ kg- 1 K- 1). Matrix permeability is < 1E-16 m2 for all greywacke samples. Tested lavas exhibit heterogeneous rock properties due to their wide range of porosity (< 1% up to 32%). The thermo-physical rock properties were tested at laboratory conditions (ambient temperature and pressure), which do not reflect the in situ conditions at greater depth. With depth, thermal conductivity and acoustic wave velocity are likely to decrease caused by micro fractures resulting from thermal cracking of the rock, while specific

  1. Explosive activity associated with the growth of volcanic domes

    USGS Publications Warehouse

    Newhall, C.G.; Melson, W.G.

    1983-01-01

    Domes offer unique opportunities to measure or infer the characteristics of magmas that, at domes and elsewhere, control explosive activity. A review of explosive activity associated with historical dome growth shows that: 1. (1) explosive activity has occurred in close association with nearly all historical dome growth; 2. (2) whole-rock SiO2 content, a crude but widely reported indicator of magma viscosity, shows no systematic relationship to the timing and character of explosions; 3. (3) the average rate of dome growth, a crude indicator of the rate of supply of magma and volatiles to the near-surface enviornment, shows no systematic relationship to the timing or character of explosions; and 4. (4) new studies at Arenal and Mount St. Helens suggest that water content is the dominant control on explosions from water-rich magmas, whereas the crystal content and composition of the interstitial melt (and hence magma viscosity) are equally or more important controls on explosions from water-poor magmas. New efforts should be made to improve current, rather limited techniques for monitoring pre-eruption volatile content and magma viscosity, and thus the explosive potential of magmas. ?? 1983.

  2. Quantifying unsteadiness and dynamics of pulsatory volcanic activity

    NASA Astrophysics Data System (ADS)

    Dominguez, L.; Pioli, L.; Bonadonna, C.; Connor, C. B.; Andronico, D.; Harris, A. J. L.; Ripepe, M.

    2016-06-01

    Pulsatory eruptions are marked by a sequence of explosions which can be separated by time intervals ranging from a few seconds to several hours. The quantification of the periodicities associated with these eruptions is essential not only for the comprehension of the mechanisms controlling explosivity, but also for classification purposes. We focus on the dynamics of pulsatory activity and quantify unsteadiness based on the distribution of the repose time intervals between single explosive events in relation to magma properties and eruptive styles. A broad range of pulsatory eruption styles are considered, including Strombolian, violent Strombolian and Vulcanian explosions. We find a general relationship between the median of the observed repose times in eruptive sequences and the viscosity of magma given by η ≈ 100 ṡtmedian. This relationship applies to the complete range of magma viscosities considered in our study (102 to 109 Pa s) regardless of the eruption length, eruptive style and associated plume heights, suggesting that viscosity is the main magma property controlling eruption periodicity. Furthermore, the analysis of the explosive sequences in terms of failure time through statistical survival analysis provides further information: dynamics of pulsatory activity can be successfully described in terms of frequency and regularity of the explosions, quantified based on the log-logistic distribution. A linear relationship is identified between the log-logistic parameters, μ and s. This relationship is useful for quantifying differences among eruptive styles from very frequent and regular mafic events (Strombolian activity) to more sporadic and irregular Vulcanian explosions in silicic systems. The time scale controlled by the parameter μ, as a function of the median of the distribution, can be therefore correlated with the viscosity of magmas; while the complexity of the erupting system, including magma rise rate, degassing and fragmentation efficiency

  3. Hawaiian oral tradition describes 400 years of volcanic activity at Kīlauea

    USGS Publications Warehouse

    Swanson, Donald A.

    2008-01-01

    Culturally significant oral tradition involving Pele, the Hawaiian volcano deity, and her youngest sister Hi'iaka may involve the two largest volcanic events to have taken place in Hawai'i since human settlement: the roughly 60-year-long ‘Ailā’au eruption during the 15th century and the following development of Kīlauea's caldera. In 1823, Rev. William Ellis and three others became the first Europeans to visit Kīlauea's summit and were told stories about Kīlauea's activity that are consistent with the Pele–Hi'iaka account and extend the oral tradition through the 18th century. Recent geologic studies confirm the essence of the oral traditions and illustrate the potential value of examining other Hawaiian chants and stories for more information about past volcanic activity in Hawai‘i.

  4. First volcanic CO2 budget estimate for three actively degassing volcanoes in the Central American Volcanic Arc

    NASA Astrophysics Data System (ADS)

    Robidoux, Philippe; Aiuppa, Alessandro; Conde, Vladimir; Galle, Bo; Giudice, Gaetano; Avard, Geoffroy; Muñoz, Angélica

    2014-05-01

    CO2 is a key chemical tracer for exploring volcanic degassing mechanisms of basaltic magmatic systems (1). The rate of CO2 release from sub-aerial volcanism is monitored via studies on volcanic plumes and fumaroles, but information is still sparse and incomplete for many regions of the globe, including the majority of the volcanoes in the Central American Volcanic Arc (2). Here, we use a combination of remote sensing techniques and in-situ measurements of volcanic gas plumes to provide a first estimate of the CO2 output from three degassing volcanoes in Central America: Turrialba, in Costa Rica, and Telica and San Cristobal, in Nicaragua. During a field campaign in March-April 2013, we obtained (for the three volcanoes) a simultaneous record of SO2 fluxes (from the NOVAC network (3)) and CO2 vs. SO2 concentrations in the near-vent plumes (obtained via a temporary installed fully-automated Multi-GAS instrument (4)). The Multi-GAS time-series allowed to calculate the plume CO2/SO2 ratios for different intervals of time, showing relatively stable gas compositions. Distinct CO2 - SO2 - H2O proportions were observed at the three volcanoes, but still within the range of volcanic arc gas (5). The CO2/SO2 ratios were then multiplied by the SO2 flux in order to derive the CO2 output. At Turrialba, CO2/SO2 ratios fluctuated, between March 12 and 19, between 1.1 and 5.7, and the CO2flux was evaluated at ~1000-1350 t/d (6). At Telica, between March 23 and April 8, a somewhat higher CO2/SO2 ratio was observed (3.3 ± 1.0), although the CO2 flux was evaluated at only ~100-500 t/d (6). At San Cristobal, where observations were taken between April 11 and 15, the CO2/SO2 ratio ranged between 1.8 and 7.4, with a mean CO2 flux of 753 t/d. These measurements contribute refining the current estimates of the total CO2 output from the Central American Volcanic Arc (7). Symonds, R.B. et al., (2001). J. Volcanol. Geotherm. Res., 108, 303-341 Burton, M. R. et al. (2013). Reviews in

  5. Geochemistry and Magmagenesis of the Early May 2008 Rhyolitic Magma Erupted by Chaiten Volcano, Southern Andes Volcanic Zone

    NASA Astrophysics Data System (ADS)

    Munoz, J. O.; Basualto, D.; Moreno, H.; Peña, P.; Mella, M.

    2008-12-01

    Chaiten volcano, located in the southern portion of the Southern Andes Volcanic Zone, is a 2 km diameter Holocene obsidian rhyolitic dome inside a 3 km wide caldera formed by an Upper Pleistocene basaltic to andesitic sequence. Chaiten volcano started a plinian eruption on May 1 evolving to subplinian and weak strombolian with time. Eruption has produced a significant evolution of craters geometry, volume of pyroclastic materials, gas and water emissions, large amount of fall out ash, new rhyolitic dome that is still growing, minor pyroclastic flows to the north, lateral blast to the east, and several lahars and mud flows mainly to the south along the river partially burying the Chaiten city. Six glassy, fibrous and banded, highly porous, crystal poor (zoned and twinned plagioclase, hornblende, orthopyroxene and magnetite) rhyolitic pumice and obsidian (including explosion breccias with andesitic to basaltic country rock fragments)fragments and three ash samples (also crystal poor including cristoballite, quartz, feldspars and biotite) representative of the early stage of the explosive eruption have major, trace and REE whole rock geochemical composition indicating an important crustal input in the magmagenesis (high SiO2=73-75, low Al2O3=12.75-14.80, MgO=0.1-0.6, CaO=1.4-1.9, TiO2=0.15-0.28, S=0.01-0.13, moderated K2O=2,7-3.0, Na2O=3.9-4.8 and Rb=95-121ppm, high Ba= 619-665 and Cs=5.71-7.75 and low Sr =142-161, Nb=8.00- 8.75, Y=13-14, Zr=106-121 and La/Yb=20-23 ratios, depleted HREE and HREE patterns and Eu moderate negative anomaly), as also does the previously documented <9,370 yBP rhyolitic pumice and obsidian dome, the last also showing crustal Sr, Nd and Pb isotopic signature (Lopez et al., 1993, Stern et al., 2002, Naranjo and Stern, 2004). Early May samples are depleted in MHEE and HREE and have higher La/Yb (20- 23), Rb/Ba (0.15-0.18), Ba/Sr (3.8-4.7) and Rb/Sr (0.65-0.85) ratios compare to basaltic to andesitic lavas from the Michinmahuida volcano

  6. Satellite measurements of recent volcanic activity at Oldoinyo Lengai, Tanzania

    NASA Astrophysics Data System (ADS)

    Vaughan, R. Greg; Kervyn, Matthieu; Realmuto, Vince; Abrams, Michael; Hook, Simon J.

    2008-06-01

    Oldoinyo Lengai (OL) is the only active volcano in the world that produces natrocarbonatite lava. These carbonate-rich lavas are unique in that they have relatively low temperatures (495-590 °C) and very low viscosity. OL has been erupting intermittently since 1983, mostly with small lava flows, pools and spatter cones (hornitos) confined to the summit crater. Explosive, ash-producing eruptions are rare, however, on September 4, 2007 the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) captured the first satellite image of an ash plume erupting from OL, which may be indicative of a new phase of more silica-rich products and explosive activity that has not occurred since 1966-1967. In the months prior to the eruption, thermal infrared (TIR) satellite monitoring detected an increasing number of thermal anomalies around OL. Data from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor analyzed with the MODLEN algorithm detected more than 30 hot spots in the last week of August and first week of September 2007, some of which were from bush fires ignited by lava flows or spatter around the volcano. Higher-resolution ASTER data confirmed the location of these burn scars associated with lava flows. ASTER also detected the appearance of an anomalous hot spot at the summit of OL in mid-June with temperatures ~ 440 °C, the presence of several new lava flows in the crater in July and August, and on September 4 measured higher temperatures (~ 550 °C) possibly suggesting a more silicate-rich eruption. ASTER spectral emissivity data were interpreted to indicate a mixture of carbonate and silicate ash in the eruption plume from September 4. Based on the analysis of both ASTER and MODIS data combined with occasional field observations, there appear to have been 2 distinct eruptive events so far in 2007: a typical natrocarbonatite eruption confined to the summit crater in June-July, and a more intense eruption in August-September consisting of

  7. Middle Miocene hiatus in volcanic activity in the Great Basin area of the Western United States

    USGS Publications Warehouse

    McKee, E.H.; Noble, D.C.; Silberman, M.L.

    1970-01-01

    A summary of potassium-argon dates shows that a high level of igneous activity in the Great Basin and adjacent regions during middle Tertiary time (40 to 20 my ago) was followed by a period of relative quiescence in middle Miocene time that lasted for several million years (from 20 to 17 my ago). Volcanism resumed 16 my ago mainly at the margins of the region and has continued to the present. ?? 1970.

  8. Evidence of volcanic and glacial activity in Chryse and Acidalia Planitiae, Mars

    USGS Publications Warehouse

    Martinez-Alonso, Sara; Mellon, Michael T.; Banks, Maria E.; Keszthelyi, Laszlo P.; McEwen, Alfred S.

    2011-01-01

    Chryse and Acidalia Planitiae show numerous examples of enigmatic landforms previously interpreted to have been influenced by a water/ice-rich geologic history. These landforms include giant polygons bounded by kilometer-scale arcuate troughs, bright pitted mounds, and mesa-like features. To investigate the significance of the last we have analyzed in detail the region between 60°N, 290°E and 10°N, 360°E utilizing HiRISE (High Resolution Imaging Science Experiment) images as well as regional-scale data for context. The mesas may be analogous to terrestrial tuyas (emergent sub-ice volcanoes), although definitive proof has not been identified. We also report on a blocky unit and associated landforms (drumlins, eskers, inverted valleys, kettle holes) consistent with ice-emplaced volcanic or volcano-sedimentary flows. The spatial association between tuya-like mesas, ice-emplaced flows, and further possible evidence of volcanism (deflated flow fronts, volcanic vents, columnar jointing, rootless cones), and an extensive fluid-rich substratum (giant polygons, bright mounds, rampart craters), allows for the possibility of glaciovolcanic activity in the region.Landforms indicative of glacial activity on Chryse/Acidalia suggest a paleoclimatic environment remarkably different from today's. Climate changes on Mars (driven by orbital/obliquity changes) or giant outflow channel activity could have resulted in ice-sheet-related landforms far from the current polar caps.

  9. Can vesicle size distributions predict eruption intensity during volcanic activity?

    NASA Astrophysics Data System (ADS)

    LaRue, A.; Baker, D. R.; Polacci, M.; Allard, P.; Sodini, N.

    2013-06-01

    We studied three-dimensional (3-D) vesicle size distributions by X-ray microtomography in scoria collected during the relatively quiescent Phase II of the 2010 eruption at Eyjafjallajökull volcano, Iceland. Our goal was to compare the vesicle size distributions (VSDs) measured in these samples with those found in Stromboli volcano, Italy. Stromboli was chosen because its VSDs are well-characterized and show a correlation with eruption intensity: typical Strombolian activity produces VSDs with power-law exponents near 1, whereas larger and more energetic Vulcanian-type explosions and Plinian eruptions produce VSDs with power-law exponents near 1.5. The hypothesis to be tested was whether or not the samples studied in this work would contain VSDs similar to normal Strombolian products, display higher power-law exponents, or be described by exponential functions. Before making this comparison we tested the hypothesis that the phreatomagmatic nature of the Eyjafjallajökull eruption might have a significant effect on the VSDs. We performed 1 atm bubble-growth experiments in which the samples were inundated with water and compared them to similar, control, experiments without water inundation. No significant differences between the VSDs of the two sets of experiments were found, and the hypothesis is not supported by the experimental evidence; therefore, VSDs of magmatic and phreatomagmatic eruptions can be directly compared. The Phase II Eyjafjallajökull VSDs are described by power law exponents of ~ 0.8, typical of normal Strombolian eruptions. The comparable VSDs and behavior of Phase II of the Eyjafjallajökull 2010 eruption to Stromboli are interpreted to be a reflection of similar conduit systems in both volcanoes that are being constantly fed by the ascent of deep magma that mixes with resident magma at shallow depths. Such behavior implies that continued activity during Phase II of the Eyjafjallajökull eruption could be expected and would have been predicted

  10. The Southern Part of the Southern Volcanic Zone (SSVZ; 42-46S) of the Andes: History of Medium and Large Explosive Holocene Eruptions

    NASA Astrophysics Data System (ADS)

    Stern, C. R.; Naranjo, J. A.

    2008-12-01

    Chaitén volcano is one of 13 large volcanic centers, and numerous small cones, comprising the southern part of the Andean Southern Volcanic Zone (SVZ), that results from the subduction of the Nazca plate (at 7.8 cm/yr) between the landward extension of the Chiloé FZ at 42S and the Chile Rise - Trench triple junction at 46S. Chaitén is a rhyolite dome inside a 3 km diameter caldera located 15 km west of the larger Michinmahuida stratovolcano. Other stratovolcanoes in the SSVZ include Yate, Hornopirén, Corcovado, Yanteles, Melimoyu, Mentolat, Cay and Macá. Hudson volcano, the southernmost in the Southern SVZ, is a large 10 km caldera, while Huequi and Hualaihué - Cordón Cabrera are a group of small aligned cinder cones possibly related to a larger eroded volcanic complex. Prior to the May 2008 eruption of Chaitén, the only well documented historic eruptions in this segment of the Andean arc were the explosive eruption of Hudson in August 1991 (Naranjo et al. 1993), and two eruptions of Michinmahuida in 1742 and 1834-35. Tephra deposits provide evidence of 11 prehistoric explosive Holocene eruptions of the southernmost SSVZ Hudson volcano, including two large eruptions near <6700 and <3600 BP (Naranjo and Stern 1998). The 6700 BP eruption produced greater than 18 km3 of andesitic tephra, possibly the largest Holocene eruption in all the southern Andes. Although Hudson is clearly the most active of the Southern SVZ volcanoes in terms of both volume and frequency of explosive eruptions, tephra deposits indicate that seven of the other SSVZ volcanoes, including Chaitén, also have had medium to large Holocene explosive eruptions (Naranjo and Stern 2004). Three of these eruptions were from Corcovado at approximately <9190, <7980 and <6870 BP, one from Yanteles at <9180 BP, two from Melimoyu at <2740 and <1750 BP, one from Mentolat at <6960 and one from Macá at <1540 BP. Two other eruptions, at <6350 and <3820 BP, we interpret as having been produced by

  11. Relationship between the latest activity of mare volcanism and topographic features of the Moon

    NASA Astrophysics Data System (ADS)

    Kato, Shinsuke; Morota, Tomokatsu; Yamaguchi, Yasushi; Watanabe, Sei-ichiro; Otake, Hisashi; Ohtake, Makiko

    2016-04-01

    Lunar mare basalts provide insights into compositions and thermal history of lunar mantle. According to crater counting analysis with remote sensing data, the model ages of mare basalt units indicate a second peak of magma activity at the end of mare volcanism (~2 Ga), and the latest eruptions were limited in the Procellarum KREEP Terrane (PKT), which has high abundances of heat-producing elements. In order to understand the mechanism for causing the second peak and its magma source, we examined the correlation between the titanium contents and eruption ages of mare basalt units using compositional and chronological data updated by SELENE/Kaguya. Although no systematic relationship is observed globally, a rapid increase in mean titanium (Ti) content occurred at 2.3 Ga in the PKT, suggesting that the magma source of mare basalts changed at that time. The high-Ti basaltic eruption, which occurred at the late stage of mare volcanism, can be correlated with the second peak of volcanic activity at ~2 Ga. The latest volcanic activity can be explained by a high-Ti hot plume originated from the core-mantle boundary. If the hot plume was occurred, the topographic features formed by the hot plume may be remained. We calculated the difference between topography and selenoid and found the circular feature like a plateau in the center of the PKT, which scale is ~1000 km horizontal and ~500 m vertical. We investigated the timing of ridge formation in the PKT by using stratigraphic relationship between mare basalts and ridges. The ridges were formed before and after the high-Ti basaltic eruptions and seem to be along with the plateau. These results suggest that the plateau formation is connected with the high-Ti basaltic eruptions.

  12. 2009 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    McGimsey, Robert G.; Neal, Christina A.; Girina, Olga A.; Chibisova, Marina; Rybin, Alexander

    2014-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, volcanic unrest, and reports of unusual activity at or near eight separate volcanic centers in Alaska during 2009. The year was highlighted by the eruption of Redoubt Volcano, one of three active volcanoes on the western side of Cook Inlet and near south-central Alaska's population and commerce centers, which comprise about 62 percent of the State's population of 710,213 (2010 census). AVO staff also participated in hazard communication and monitoring of multiple eruptions at ten volcanoes in Russia as part of its collaborative role in the Kamchatka and Sakhalin Volcanic Eruption Response Teams.

  13. 1995 volcanic activity in Alaska and Kamchatka: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    McGimsey, Robert G.; Neal, Christina A.

    1996-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptive activity or suspected volcanic activity (SVA) at 6 volcanic centers in 1995: Mount Martin (Katmai Group), Mount Veniaminof, Shishaldin, Makushin, Kliuchef/Korovin, and Kanaga. In addition to responding to eruptive activity at Alaska volcanoes, AVO also disseminated information for the Kamchatkan Volcanic Eruption Response Team (KVERT) on the 1995 eruptions of 2 Russian volcanoes: Bezymianny and Karymsky. This report summarizes volcanic activity in Alaska during 1995 and the AVO response, as well as information on the 2 Kamchatkan eruptions. Only those reports or inquiries that resulted in a "significant" investment of staff time and energy (here defined as several hours or more for reaction, tracking, and follow-up) are included. AVO typically receives dozens of phone calls throughout the year reporting steaming, unusual cloud sightings, or eruption rumors. Most of these are resolved quickly and are not tabulated here as part of the 1995 response record.

  14. Multi-Source Autonomous Response for Targeting and Monitoring of Volcanic Activity

    NASA Technical Reports Server (NTRS)

    Davies, Ashley G.; Doubleday, Joshua R.; Tran, Daniel Q.

    2014-01-01

    The study of volcanoes is important for both purely scientific and human survival reasons. From a scientific standpoint, volcanic gas and ash emissions contribute significantly to the terrestrial atmosphere. Ash depositions and lava flows can also greatly affect local environments. From a human survival standpoint, many people live within the reach of active volcanoes, and therefore can be endangered by both atmospheric (ash, debris) toxicity and lava flow. There are many potential information sources that can be used to determine how to best monitor volcanic activity worldwide. These are of varying temporal frequency, spatial regard, method of access, and reliability. The problem is how to incorporate all of these inputs in a general framework to assign/task/reconfigure assets to monitor events in a timely fashion. In situ sensing can provide a valuable range of complementary information such as seismographic, discharge, acoustic, and other data. However, many volcanoes are not instrumented with in situ sensors, and those that have sensor networks are restricted to a relatively small numbers of point sensors. Consequently, ideal volcanic study synergistically combines space and in situ measurements. This work demonstrates an effort to integrate spaceborne sensing from MODIS (Terra and Aqua), ALI (EO-1), Worldview-2, and in situ sensing in an automated scheme to improve global volcano monitoring. Specifically, it is a "sensor web" concept in which a number of volcano monitoring systems are linked together to monitor volcanic activity more accurately, and this activity measurement automatically tasks space assets to acquire further satellite imagery of ongoing volcanic activity. A general framework was developed for evidence combination that accounts for multiple information sources in a scientist-directed fashion to weigh inputs and allocate observations based on the confidence of an events occurrence, rarity of the event at that location, and other scientists

  15. Acoustic waves in the atmosphere and ground generated by volcanic activity

    SciTech Connect

    Ichihara, Mie; Lyons, John; Oikawa, Jun; Takeo, Minoru

    2012-09-04

    This paper reports an interesting sequence of harmonic tremor observed in the 2011 eruption of Shinmoe-dake volcano, southern Japan. The main eruptive activity started with ashcloud forming explosive eruptions, followed by lava effusion. Harmonic tremor was transmitted into the ground and observed as seismic waves at the last stage of the effusive eruption. The tremor observed at this stage had unclear and fluctuating harmonic modes. In the atmosphere, on the other hand, many impulsive acoustic waves indicating small surface explosions were observed. When the effusion stopped and the erupted lava began explosive degassing, harmonic tremor started to be transmitted also to the atmosphere and observed as acoustic waves. Then the harmonic modes became clearer and more stable. This sequence of harmonic tremor is interpreted as a process in which volcanic degassing generates an open connection between the volcanic conduit and the atmosphere. In order to test this hypothesis, a laboratory experiment was performed and the essential features were successfully reproduced.

  16. Volcanic activity in Alaska: summary of events and response of the Alaska Volcano Observatory 1993

    USGS Publications Warehouse

    Neal, Christina A.; McGimsey, Robert G.; Doukas, Michael P.

    1996-01-01

    During 1993, the Alaska Volcano Observatory (AVO) responded to episodes of eruptive activity or false alarms at nine volcanic centers in the state of Alaska. Additionally, as part of a formal role in KVERT (the Kamchatkan Volcano Eruption Response Team), AVO staff also responded to eruptions on the Kamchatka Peninsula, details of which are summarized in Miller and Kurianov (1993). In 1993, AVO maintained seismic instrumentation networks on four volcanoes of the Cook Inlet region--Spurr, Redoubt, Iliamna, and Augustine--and two stations at Dutton Volcano near King Cove on the Alaska Peninsula. Other routine elements of AVO's volcano monitoring program in Alaska include periodic airborne measurement of volcanic SO2 and CO2 at Cook Inlet volcanoes (Doukas, 1995) and maintenance of a lightning detection system in Cook Inlet (Paskievitch and others, 1995).

  17. Explosive volcanic activity on Venus: The roles of volatile contribution, degassing, and external environment

    NASA Astrophysics Data System (ADS)

    Airey, M. W.; Mather, T. A.; Pyle, D. M.; Glaze, L. S.; Ghail, R. C.; Wilson, C. F.

    2015-08-01

    We investigate the conditions that will promote explosive volcanic activity on Venus. Conduit processes were simulated using a steady-state, isothermal, homogeneous flow model in tandem with a degassing model. The response of exit pressure, exit velocity, and degree of volatile exsolution was explored over a range of volatile concentrations (H2O and CO2), magma temperatures, vent altitudes, and conduit geometries relevant to the Venusian environment. We find that the addition of CO2 to an H2O-driven eruption increases the final pressure, velocity, and volume fraction gas. Increasing vent elevation leads to a greater degree of magma fragmentation, due to the decrease in the final pressure at the vent, resulting in a greater likelihood of explosive activity. Increasing the magmatic temperature generates higher final pressures, greater velocities, and lower final volume fraction gas values with a correspondingly lower chance of explosive volcanism. Cross-sectionally smaller, and/or deeper, conduits were more conducive to explosive activity. Model runs show that for an explosive eruption to occur at Scathach Fluctus, at Venus' mean planetary radius (MPR), 4.5% H2O or 3% H2O with 3% CO2 (from a 25 m radius conduit) would be required to initiate fragmentation; at Ma'at Mons (~9 km above MPR) only ~2% H2O is required. A buoyant plume model was used to investigate plume behaviour. It was found that it was not possible to achieve a buoyant column from a 25 m radius conduit at Scathach Fluctus, but a buoyant column reaching up to ~20 km above the vent could be generated at Ma'at Mons with an H2O concentration of 4.7% (at 1300 K) or a mixed volatile concentration of 3% H2O with 3% CO2 (at 1200 K). We also estimate the flux of volcanic gases to the lower atmosphere of Venus, should explosive volcanism occur. Model results suggest explosive activity at Scathach Fluctus would result in an H2O flux of ~107 kg s-1. Were Scathach Fluctus emplaced in a single event, our model

  18. Petrological Features of The Post-Collisional Volcanics on the Izmir-Ankara-Erzincan Suture Zone at Around Almus and Yıldızeli Regions, NE Turkey.

    NASA Astrophysics Data System (ADS)

    Göçmengil, G.; Karacik, Z.; Genç, Ş. C.

    2014-12-01

    Following the closure of the northern Neo-Tethyan ocean, post-collisional magmatism developed both on the Izmir-Ankara-Erzincan suture zone (IAESZ) and the northern (Pontides) and southern (Kırşehir block) continents. Cenozoic volcanics (particularly Middle to Upper Eocene) from the Almus and Yıldızeli regions (NE, Turkey) have poorly known and exposed along the northern and southern part of the IAESZ respectively. In this presentation; we present geological, geochemical and isotopic data of these volcanic rocks to characterize the petrological evolution and petrogenesis on the different tectonic blocks. Almus region, have a composite basement of Mesozoic metamorphic and ophiolitic rocks. Volcanic and sedimentary units of the Middle Eocene covering the basement units have a stratigraphic sequence of: a basal conglomerate; fossiliferous sandstone/shale; epiclastic rocks; auto-brecciated lavas with basalt/basaltic andesite lava flows. All these units are cut by trachyte stocks. Besides, basement of Yıldızeli region consisting of Cretaceous Kırşehir block metamorphics with IAESZ melangé and flysch units. Volcanic and sedimentary units covers the basement are trachyte-trachyandesite lavas; fossiliferous limestone; basalt/basaltic andesite lava flows; pyroclastic units with dacitic lavas. Basalt/basaltic andesites from Almus region are sub-alkaline/mildly alkaline and display middle to high-K character. REE data display relative enrichments in LILE (Sr, K, Rb, Ba, Th) together with negative anomalies of Nb, Ta and P. Trachyte stocks are shoshonitic and display LILE enrichment together with negative patters of Nb, Ta, P and Eu. Besides, trachyte-trachyandesite and basalt/basaltic andesite from Yıldızeli region are sub-alkaline/mildly alkaline with middle-K to shoshonitic character. REE patterns show enrichments in LILE and depletion of Nb, Ta, P and Ti for both rock suites. The 87Sr/86Sr and 143Nd/144Nd ratios of volcanic rocks from both regions, range from 0

  19. The geochemistry and petrogenesis of basalts from the Taupo Volcanic Zone and Kermadec Island Arc, S.W. Pacific

    NASA Astrophysics Data System (ADS)

    Gamble, J. A.; Smith, I. E. M.; McCulloch, M. T.; Graham, I. J.; Kokelaar, B. P.

    1993-01-01

    Basalts from the Taupo Volcanic Zone (TVZ), New Zealand, the Kermadec Island Arc (KA) and its back-arc basin, the Havre Trough show systematic variations in trace-element and isotope geochemistry which are attributed to differences in tectonic setting and source heterogeneity along a more or less continuous plate boundary. Basalts from the Kermadec Arc are characterised by low abundances of high field strength elements (HFSE) such as Ti, Zr, Nb, Ta and Hf and have high ratios of Ti/Zr and low ratios of Ti/Sc and Ti/V relative to typical MORB. Basalts from TVZ also show low abundances of the HFS elements relative to MORB but show lower Ti/Zr, higher Ti/V and Ti/Sc ratios and generally higher Zr abundances than KA most basalts. The Havre Trough basalt is mildly alkaline (< 1% normative nepheline) like many back-arc basin basalts from the Pacific rim, contrasting with the hypersthene normative TVZ and KA rocks. It has higher Zr than most TVZ basalts and all KA basalts. Ratios such as Ti/V, Ti/Sc and Ti/Zr are within the range of TVZ and MORB basalts but distinct from KA basalts. The depleted (relative to MORB) HFSE characteristics of the KA and TVZ basalts are complemented by high abundances of large ion lithophile elements (LIL), such as Ba, Rb and K, when compared to MORB, yielding the distinctive LIL-enriched pattern of subduction related rocks on a normalised multi-element plot. In contrast, the Havre Trough basalt is MORB-like. Chondrite-normalised Rare Earth Element (REE) patterns for the TVZ basalts show a field overlapping with that defined by the southern KA (Rumble Sea Mounts), with light REE enriched patterns (Ce/Yb n = ˜ 1.8-3) and flat heavy REE (Tb-Lu). Basalts from the northern KA are typically light REE depleted (Ce/Yb n = 0.5) or slightly enriched (Ce/Yb n = 1.5). The REE pattern of the Havre Trough basalt is distinctive from both the KA and TVZ fields, being richer in the heavy REE, yet similar to many basalts from back-arc basins. Sr and Nd

  20. Elastic flexure explains the offset of primary volcanic activity upstream of the Réunion and Hawaii plume axis

    NASA Astrophysics Data System (ADS)

    Gerbault, Muriel; Fontaine, Fabrice; Rabinowicz, Michel; Bystricky, Micha

    2016-04-01

    Recent tomography reveals that surface volcanism at la Réunion and Hawaii develops offset by 150-180 km upstream to the plume axis with respect to plate motion. We use elasto-visco-plastic 2D numerical models to describe the development of compressional stresses at the base of the lithosphere, resulting from elastic plate bending above the upward load exerted by the plume head. This horizontal compression is ~20 km thick, has a ~ 150 km radius and lays around ~50-70 km depth where temperature varies from ~600°C to ~750°C. It is suggested that the buoyant melts percolating in the plume head pond below this zone of compression and eventually spread laterally to the extent where compression vanishes. There, melts resume their ascension and propagate through dikes up to ~35 km depth where the field stress rotates again due to plate curvature change. Flexural compression is a transient phenomenon that depends: (i) on the relaxation time of elasto-plastic stresses between ~600° and ~750°C, (ii) on the thermal erosion of the lithosphere induced by the plume, and (iii) on the ratio of the normal versus tangential stress exerted by the plume on the lithosphere. We find that for a plate 70 My old, this horizontal compression lasts for about 5 Myrs. This time span exceeds the time during which both the Indian and Pacific plates drift over the Reunion and Hawaii plumes, respectively. Accordingly, our model explains i) the ~150 km shift between the surface volcanism and the axis of the plume, ii) the ~5 Myrs synchronous activity of the volcanoes of la Réunion and Mauritius, and (iii) the present pounding of melts at 35 km depth detected below the Reunion and Mauritius Islands. Plume-lithosphere interaction is one of the numerous subjects that Genia Burov studied and modeled; the present study uses a similar code to the one he used, and is inspired by several of his assumptions. In support of his own goals and worries, we show here the importance of thermo

  1. Is uplift of volcano clusters in the Tohoku Volcanic Arc, Japan, driven by magma accumulation in hot zones? A geodynamic modeling study

    NASA Astrophysics Data System (ADS)

    George, Ophelia A.; Malservisi, Rocco; Govers, Rob; Connor, Charles B.; Connor, Laura J.

    2016-06-01

    In many volcanic arcs, the rate of tectonic uplift cannot be explained by lithospheric plate motion alone but may be associated with dynamic uplift. Buoyant forces associated with underplated magma bodies lift the upper crust and leads to relatively high rates of topographic change. One such region is northern Honshu, Japan, where Quaternary volcano clusters are spatially associated with uplifted crust and isostatic gravity anomalies. Axisymmetric inversion of Bouguer gravity data for the Sengan volcano cluster shows that these gravity anomalies can be modeled by 30 km radius bodies emplaced at ˜15 km depth. Axisymmetric, finite element models, generated using GTECTON, of a layered Earth representative of the Tohoku crust indicate that the deformation of these midcrustal intrusions produces elevated topography on the surface directly above the intrusion that is bounded by a shallow peripheral trough. The wavelengths of vertical deformation produced by these bodies are sensitive to the thickness of the models' elastic layer and relatively insensitive to the models' rheology. This suggests that the amplitude of the vertical deformation represents a trade-off between the size of the intrusion and the thickness of the elastic layer and is less strongly influenced by the rheology of the lithosphere into which the bodies are emplaced. Our results are consistent with hot zone and hot finger models for the arc and indicate that Tohoku Volcanic Arc features such as gravity anomalies and uplifted basement are related to crustal magma intrusions and hot zones rather than directly related to mantle processes.

  2. Using U-series and beryllium isotopes to reveal the occurrence and relative timing of crustal and mantle processes in the Southern Volcanic Zone of Chile

    NASA Astrophysics Data System (ADS)

    Cooper, L. B.; Reubi, O.; Dungan, M. A.; Bourdon, B.; Langmuir, C. H.; Turner, S. J.; Schaefer, J. M.

    2012-12-01

    Magmas erupted from subduction zone volcanoes represent the end products of multiple magmatic processes occurring in the asthenospheric mantle wedge and overlying lithosphere (i.e., fluid addition, melting, assimilation, and crystal fractionation). To resolve the contributions of diverse processes and components, and the relative timing of these events, we have determined U-series activities (U-Th-Ra-Pa) for 60 and 10Be compositions for 20 historic or very young lavas carefully chosen on the basis of major and trace element analyses of 625 samples from six volcanoes in the Andean Southern Volcanic Zone of Chile (37.6-41.1°S: Nevados de Chillán, Antuco, Llaima, Lonquimay, Villarrica, and Osorno). Our dataset demonstrates that each of these volcanoes reflects a unique combination and sequence of magmatic processes that are only revealed through analysis of multiple samples spanning the extent of intra-volcano and intra-eruption chemical variation. Sigmarsson et al. (1990; 2002) identified a regional trend using U-series and Be from mostly single samples, which they interpreted to represent along-strike variations in the flux of slab-derived fluids into the wedge [from 230Th-excess plus 226Ra-deficit plus low 10Be/9Be at Chillán towards progressively higher 238U- and Ra-excesses and 10Be/9Be at Villarrica and Osorno]. These data fall within the much broader array defined by our results, but we infer the operation of assimilation (e.g., Llaima; Reubi et al., 2011) and aging of subduction zone components of variable compositions and proportions in the mantle prior to partial melting as important factors in generating the highly individualized and complex U-series systematics observed at each of these six volcanoes. All of the volcanoes exhibit evidence of assimilation, with the exception of Lonquimay which has undergone mostly closed-system fractional crystallization. At Llaima and Chillán the assimilant is crustal. At Villarica, flux-related melts that dominate in

  3. 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.

  4. Infrasound Monitoring of the Volcanic Activities of Japanese Volcanoes in Korea

    NASA Astrophysics Data System (ADS)

    Lee, H. I.; Che, I. Y.; Shin, J. S.

    2015-12-01

    Since 1999 when our first infrasound array station(CHNAR) has been installed at Cheolwon, Korea Institute of Geoscience and Mineral Resources(KIGAM) is continuously observing infrasound signals with an infrasound array network, named KIN(Korean Infrasound Network). This network is comprised of eight seismo-acoustic array stations(BRDAR, YPDAR, KMPAR, CHNAR, YAGAR, KSGAR, ULDAR, TJIAR). The aperture size of the smallest array is 300m and the largest is about 1.4km. The number of infrasound sensors are between 4(TJIAR) and 18(YAGAR), and 1~5 seismometers are collocated with infrasound sensors. Many interesting infrasound signals associated with different type of sources, such as blasting, large earthquake, bolide, volcanic explosion are detected by KIN in the past 15 years. We have analyzed the infrasound signals possibly associated with the japanese volcanic explosions with reference to volcanic activity report published by Japanese Meteorological Agency. Analysis results of many events, for example, Asama volcano explosion in 2004 and Shinmoe volcano in 2011, are well matched with the official report. In some cases, however, corresponding infrasound signals are not identified. By comparison of the infrasound signals from different volcanoes, we also found that the characteristics of signals are distinguishing. It may imply that the specific volcano has its own unique fingerprint in terms of infrasound signal. It might be investigated by long-term infrasound monitoring for a specific volcano as a ground truth generating repetitive infrasound signal.

  5. Active zones of mammalian neuromuscular junctions: formation, density, and aging

    PubMed Central

    Nishimune, Hiroshi

    2012-01-01

    Presynaptic active zones are synaptic vesicle release sites that playessential roles in the function and pathology of mammalian neuromuscular junctions (NMJs). The molecular mechanisms of active zone organization utilize presynaptic voltage-dependent calcium channels (VDCCs) in NMJs as scaffolding proteins. VDCCs interact extracellularly with the muscle-derived synapse organizer, laminin β2, and interact intracellularly with active zone-specific proteins, such as Bassoon, CAST/Erc2/ELKS2alpha, ELKS, Piccolo, and RIMs. These molecular mechanisms are supported by studies in P/Q- and N-type VDCCs double-knockout mice, and they are consistent with the pathological conditions of Lambert-Eaton myasthenic syndrome and Pierson syndrome, which are caused by autoantibodies against VDCCs or by a laminin β2 mutation. During normal postnatal maturation, NMJs maintain the density of active zones, while NMJs triple their size. However, active zones become impaired during aging. Propitiously, muscle exercise ameliorates the active zone impairment in aged NMJs, which suggests the potential for therapeutic strategies. PMID:23252894

  6. Trace elements in scalp hair of children chronically exposed to volcanic activity (Mt. Etna, Italy).

    PubMed

    Varrica, D; Tamburo, E; Dongarrà, G; Sposito, F

    2014-02-01

    The aim of this survey was to use scalp hair as a biomonitor to evaluate the environmental exposure to metals and metalloids of schoolchildren living around the Mt. Etna area, and to verify whether the degree of human exposure to trace elements is subject to changes in local environmental factors. Twenty trace elements were determined in 376 samples of scalp hair from schoolboys (11-13 years old) of both genders, living in ten towns located around the volcanic area of Mt. Etna (Sicily). The results were compared with those (215 samples) from children living in areas of Sicily characterized by a different geological setting (reference site). As, U and V showed much higher concentrations at the volcanic site whereas Sr was particularly more abundant at the reference site. Linear Discriminant Analysis (LDA) indicated an Etna factor, made up of V, U and Mn, and a second factor, concerning the reference site, characterized by Ni and Sr, and to a lesser extent by Mo and Cd. Significant differences in element concentrations were also observed among three different sectors of Mt. Etna area. Young people living in the Mt. Etna area are naturally exposed to enhanced intakes of some metals (V, U, Mn) and non-metals (e.g., As) than individuals of the same age residing in other areas of Sicily, characterized by different lithologies and not influenced by volcanic activity. The petrographic nature of local rocks and the dispersion of the volcanic plume explain the differences, with ingestion of water and local food as the most probable exposure pathways.

  7. Assessing microbial activities in metal contaminated agricultural volcanic soils--An integrative approach.

    PubMed

    Parelho, C; Rodrigues, A S; Barreto, M C; Ferreira, N G C; Garcia, P

    2016-07-01

    Volcanic soils are unique naturally fertile resources, extensively used for agricultural purposes and with particular physicochemical properties that may result in accumulation of toxic substances, such as trace metals. Trace metal contaminated soils have significant effects on soil microbial activities and hence on soil quality. The aim of this study is to determine the soil microbial responses to metal contamination in volcanic soils under different agricultural land use practices (conventional, traditional and organic), based on a three-tier approach: Tier 1 - assess soil microbial activities, Tier 2 - link the microbial activity to soil trace metal contamination and, Tier 3 - integrate the microbial activity in an effect-based soil index (Integrative Biological Response) to score soil health status in metal contaminated agricultural soils. Our results showed that microbial biomass C levels and soil enzymes activities were decreased in all agricultural soils. Dehydrogenase and β-glucosidase activities, soil basal respiration and microbial biomass C were the most sensitive responses to trace metal soil contamination. The Integrative Biological Response value indicated that soil health was ranked as: organic>traditional>conventional, highlighting the importance of integrative biomarker-based strategies for the development of the trace metal "footprint" in Andosols. PMID:27057992

  8. 2005 Volcanic Activity in Alaska, Kamchatka, and the Kurile Islands: Summary of Events and Response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    McGimsey, R.G.; Neal, C.A.; Dixon, J.P.; Ushakov, Sergey

    2008-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptive activity or suspected volcanic activity at or near 16 volcanoes in Alaska during 2005, including the high profile precursory activity associated with the 2005?06 eruption of Augustine Volcano. AVO continues to participate in distributing information about eruptive activity on the Kamchatka Peninsula, Russia, and in the Kurile Islands of the Russian Far East, in conjunction with the Kamchatkan Volcanic Eruption Response Team (KVERT) and the Sakhalin Volcanic Eruption Response Team (SVERT), respectively. In 2005, AVO helped broadcast alerts about activity at 8 Russian volcanoes. The most serious hazard posed from volcanic eruptions in Alaska, Kamchatka, or the Kurile Islands is the placement of ash into the atmosphere at altitudes traversed by jet aircraft along the North Pacific and Russian Trans East air routes. AVO, KVERT, and SVERT work collaboratively with the National Weather Service, Federal Aviation Administration, and the Volcanic Ash Advisory Centers to provide timely warnings of volcanic eruptions and the production and movement of ash clouds.

  9. Volcanic activity in the Acambay Graben: a < 25 Ka subplinian eruption from the Temascalcingo volcano and implications for volcanic hazard.

    NASA Astrophysics Data System (ADS)

    Pedrazzi, Dario; Aguirre Díaz, Gerardo; Sunyé Puchol, Ivan; Bartolini, Stefania; Geyer, Adelina

    2016-04-01

    The Trans-Mexican Volcanic Belt (TMVB) contains a large number of stratovolcanoes, some well-known, as Popocatepetl, Iztaccihuatl, Nevado de Toluca, or Colima and many others of more modest dimensions that are not well known but constitute the majority in the TMVB. Such volcanoes are, for example, Tequila, San Juan, Sangangüey, Cerro Culiacán, Cerro Grande, El Zamorano, La Joya, Palo Huerfano, Jocotitlán, Altamirano and Temascalcingo, among many others. The Temascalcingo volcano (TV) is an andesitic-dacitic stratovolcano located in the Trans-Mexican Volcanic Belt (TMVB) at the eastern part of the Acambay Graben (northwest portion of Estado de México). The TV is composed mainly by dacitic, porphyritic lavas, block and ash deposits and subordinate pumice fall deposits and ignimbrites (Roldán-Quintana et al., 2011). The volcanic structure includes a summit caldera that has a rectangular shape, 2.5×3.5 km, with the largest side oriented E-W, parallel to major normal faults affecting the edifice. The San Mateo Pumice eruption is one of the greatest paroxysmal episodes of this volcano with pumice deposits mainly exposed at the scarp of the Acambay-Tixmadeje fault and at the northern and northeastern flanks of TV. It overlies a paleosol dated at 25 Ka. A NE-trending dispersion was obtained from field data covering an area of at least 80 km2. These deposits overlie older lava flows and mud flows and are discontinuously covered and eroded by younger reworked deposits of Temascalcingo volcano. This event represents a highly explosive phase that generated a relatively thick and widespread pumice fallout deposit that may occur again in future eruptions. A similar eruption today would have a significantly impact in the region, overall due to the fact that there has been no systematic assessment of the volcanic hazard in any of the studies that have been conducted so far in the area. So, this is a pending and urgent subject that must be tackled without delay. Financed by

  10. Geochemical Interpretation of Collision Volcanism

    NASA Astrophysics Data System (ADS)

    Pearce, Julian

    2014-05-01

    Collision volcanism can be defined as volcanism that takes place during an orogeny from the moment that continental subduction starts to the end of orogenic collapse. Its importance in the Geological Record is greatly underestimated as collision volcanics are easily misinterpreted as being of volcanic arc, extensional or mantle plume origin. There are many types of collision volcanic province: continent-island arc collision (e.g. Banda arc); continent-active margin collision (e.g. Tibet, Turkey-Iran); continent-rear-arc collision (e.g. Bolivia); continent-continent collision (e.g. Tuscany); and island arc-island arc collision (e.g. Taiwan). Superimposed on this variability is the fact that every orogeny is different in detail. Nonetheless, there is a general theme of cyclicity on different time scales. This starts with syn-collision volcanism resulting from the subduction of an ocean-continent transition and continental lithosphere, and continues through post-collision volcanism. The latter can be subdivided into orogenic volcanism, which is related to thickened crust, and post-orogenic, which is related to orogenic collapse. Typically, but not always, collision volcanism is preceded by normal arc volcanism and followed by normal intraplate volcanism. Identification and interpretation of collision volcanism in the Geologic Record is greatly facilitated if a dated stratigraphic sequence is present so that the petrogenic evolution can be traced. In any case, the basis of fingerprinting collision terranes is to use geochemical proxies for mantle and subduction fluxes, slab temperatures, and depths and degrees of melting. For example, syn-collision volcanism is characterized by a high subduction flux relative to mantle flux because of the high input flux of fusible sediment and crust coupled with limited mantle flow, and because of high slab temperatures resulting from the decrease in subduction rate. The resulting geochemical patterns are similar regardless of

  11. ASI-Volcanic Risk System (SRV): a pilot project to develop EO data processing modules and products for volcanic activity monitoring, first results.

    NASA Astrophysics Data System (ADS)

    Silvestri, M.; Musacchio, M.; Buongiorno, M. F.; Dini, L.

    2009-04-01

    The Project called Sistema Rischio Vulcanico (SRV) is funded by the Italian Space Agency (ASI) in the frame of the National Space Plan 2003-2005 under the Earth Observations section for natural risks management. The SRV Project is coordinated by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) which is responsible at national level for the volcanic monitoring. The project philosophy is to implement, by incremental versions, specific modules which allow to process, store and visualize through Web GIS tools geophysical parameters suitable for volcanic risk management. The ASI-SRV is devoted to the development of an integrated system based on Earth Observation (EO) data to respond to specific needs of the Italian Civil Protection Department (DPC) and improve the monitoring of Italian active volcanoes during all the risk phases (Pre Crisis, Crisis and Post Crisis). The ASI-SRV system provides support to risk managers during the different volcanic activity phases and its results are addressed to the Italian Civil Protection Department (DPC). SRV provides the capability to manage the import many different EO data into the system, it maintains a repository where the acquired data have to be stored and generates selected volcanic products. The processing modules for EO Optical sensors data are based on procedures jointly developed by INGV and University of Modena. This procedures allow to estimate a number of parameters such as: surface thermal proprieties, gas, aerosol and ash emissions and to characterize the volcanic products in terms of composition and geometry. For the analysis of the surface thermal characteristics, the available algorithms allow to extract information during the prevention phase and during the Warning and Crisis phase. In the prevention phase the thermal analysis is directed to the identification of temperature variation on volcanic structure which may indicate a change in the volcanic activity state. At the moment the only sensor that

  12. Silicate volcanism on Io

    NASA Astrophysics Data System (ADS)

    Carr, M. H.

    1986-03-01

    This paper is mainly concerned with the nature of volcanic eruptions on Io, taking into account questions regarding the presence of silicates or sulfur as principal component. Attention is given to the generation of silicate magma, the viscous dissipation in the melt zone, thermal anomalies at eruption sites, and Ionian volcanism. According to the information available about Io, it appears that its volcanism and hence its surface materials are dominantly silicic. Several percent of volatile materials such as sulfur, but also including sodium- and potassium-rich materials, may also be present. The volatile materials at the surface are continually vaporized and melted as a result of the high rates of silicate volcanism.

  13. Petrology and Geochemistry of Quaternary Mafic Volcanism in the Northern of Lake Van, Eastern Anatolia Collision Zone, Turkey

    NASA Astrophysics Data System (ADS)

    Oyan, Vural; Keskin, Mehmet; Ünal, Esin; Sharkov, Evgenii V.

    2013-04-01

    Quaternary mafic lavas in the north of Lake Van erupted not only from eruption center like Girekol miniature shield volcano but also from N-S (Yüksektepe volcanic field) and E-W (Ormuktepe volcanic field) extending extensional fractures. Literature K/Ar dates (Lebedev et al., 2010) indicate that the basaltic and hawaiitic lavas erupted in a period between 1.08 and 0.36 Ma. These lavas are composed of olivine, plagioclase, augite and titanoaugite crystals and display porphyritic to aphyric textures. Major oxide, trace element and isotopic characteristics of the Quaternary lavas indicate that hawaiitic lavas are the fractionated derivates of a primitive alkali basaltic magma via fractional crystallization combined with assimilation process. Results of our AFC and EC-AFC models imply that alkali basaltic lavas assimilated negligible crustal material (~2%) in contrast to the hawaiitic lavas that experienced crustal contamination between 3% and 10%. LIL and LRE elements of the most primitive lavas display enrichments relative to HFS elements on N- MORB-normalized spidergrams while their lead isotopic ratios exhibit trends heading towards the EM2 type mantle, implying the importance of a distinct subduction component in the source. To evaluate partial melting processes in mantle source region of the Quaternary mafic volcanism, we conducted partial melting models. Results of our models suggest the presence of both garnet and spinel peridotite as the sources material with a partial melting degree ~5 % and mixing of the derivative melts from them in the genesis of the mafic alkaline lavas.

  14. A spaceborne inventory of volcanic activity in Antarctica and southern oceans, 2000-10

    USGS Publications Warehouse

    Patrick, Matthew R.; Smellie, John L.

    2015-01-01

    Of the more than twenty historically active volcanoes in Antarctica and the sub-Antarctic region only two, to our knowledge, host any ground-based monitoring instruments. Moreover, because of their remoteness, most of the volcanoes are seldom visited, thus relegating the monitoring of volcanism in this region almost entirely to satellites. In this study, high temporal resolution satellite data from the Hawaii Institute of Geophysics and Planetology's MODVOLC system using MODIS (Moderate Resolution Imaging Spectroradiometer) are complemented with high spatial resolution data (ASTER, or Advanced Spaceborne Thermal Emission and Reflection Radiometer, and similar sensors) to document volcanic activity throughout the region during the period 2000–10. Five volcanoes were observed in eruption (Mount Erebus, Mount Belinda, Mount Michael, Heard Island and McDonald Island), which were predominantly low-level and effusive in nature. Mount Belinda produced tephra, building a cinder cone in addition to an extensive lava field. Five volcanoes exhibited detectable thermal, and presumed fumarolic, activity (Deception, Zavodovski, Candlemas, Bristol, and Bellingshausen islands). A minor eruption reported at Marion Island was not detected in our survey due to its small size. This study also discovered a new active vent on Mount Michael, tracked dramatic vent enlargement on Heard Island, and provides an improved picture of the morphology of some of the volcanoes.

  15. Activity-related redistribution of presynaptic proteins at the active zone.

    PubMed

    Tao-Cheng, J-H

    2006-09-01

    Immunogold labeling distributions of seven presynaptic proteins were quantitatively analyzed under control conditions and after high K+ depolarization in excitatory synapses from dissociated rat hippocampal cultures. Three parallel zones in presynaptic terminals were sampled: zones I and II, each about one synaptic vesicle wide extending from the active zone; and zone III, containing a distal pool of vesicles up to 200 nm from the presynaptic membrane. The distributions of SV2 and synaptophysin, two synaptic vesicle integral membrane proteins, generally followed the distribution of synaptic vesicles, which were typically evenly distributed under control conditions and had a notable depletion in zone III after stimulation. Labels of synapsin I and synuclein, two synaptic vesicle-associated proteins, were similar to each other; both were particularly sparse in zone I under control conditions but showed a prominent enrichment toward the active zone, after stimulation. Labels of Bassoon, Piccolo and RIM 1, three active zone proteins, had very different distribution profiles from one another under control conditions. Bassoon was enriched in zone II, Piccolo and RIM 1 in zone I. After stimulation, Bassoon and Piccolo remained relatively unchanged, but RIM 1 redistributed with a significant decrease in zone I, and increases in zones II and III. These results demonstrate that Bassoon and Piccolo are stable components of the active zone while RIM 1, synapsin I and synuclein undergo dynamic redistribution with synaptic activity.

  16. Hydrological Modeling of Groundwater Disturbance to Gravity Signal for High-accuracy Monitoring of Volcanic Activity

    NASA Astrophysics Data System (ADS)

    Kazama, T.; Okubo, S.

    2007-12-01

    Gravity observation is one of the effective methods to detect magma movements in volcanic eruptions [e.g., Furuya et al., J. Geoph. Res., 2003]. Groundwater-derived disturbances have to be corrected from gravity variations for highly accurate monitoring of volcanic activities. They have been corrected with empirical methods, such as tank models and regression curves [e.g., Imanishi et al., J. Geodyn., 2006]. These methods, however, are not based on hydrological background, and are very likely to eliminate volcanic signals excessively. The correction method of groundwater disturbance has to be developed with hydrological and quantitative approach. We thus estimate the gravity disturbance arising from groundwater as follows. (1) Groundwater distributions are simulated on a hydrological model, utilizing groundwater flow equations. (2) Groundwater-derived gravity value is estimated for each instant of time, by integrating groundwater distributions spatially. (3) The groundwater-derived gravity, as the correction value, is subtracted from observed gravity data. In this study, we simulated groundwater flow and groundwater-derived gravity value on the east part of the Asama volcano, central Japan. A simple hydrological model was supposed, consisting of homogeneous soil, lying on a flat impermeable basement. Hydraulic conductivity, which defines groundwater velocity, was set as 2.0×10-6[m/s], which is consistent with typical volcanic soils. We also observed time variations of watertable height, soil moisture and gravity simultaneously during the summer of 2006 at Asama volcano, and compared the observations with the theoretical values. Both simulated groundwater distributions and gravity changes agree fairly well with observed values. On variations of water level and moisture content, rapid increase at the time of rainfalls and exponential decrease after rainfalls were illustrated. Theoretical gravity changes explained 90% of the observed gravity increase (+20μgals) for

  17. Crystal Zoning Constrains on the Processes and Time Scales Involved in Monogenetic Mafic Volcanism (Tenerife, Canary Islands)

    NASA Astrophysics Data System (ADS)

    Albert, H.; Costa Rodriguez, F.; Marti, J.

    2014-12-01

    Most of the historical eruptive activity in Tenerife has been relatively mafic and mildly-explosive monogenetic eruptions, and thus it seems that this activity is the most likely in the near future. Here we investigate the processes and time scales that lead to such eruptions with the aim to better interpret and plan for any possible unrest in the island. We focus on three historical eruptions: Siete Fuentes (December 31 1704-January 1705), Fasnia (January 5-January 13 1705) and Arafo (February 2-February 26 1705) issued from a 10 km long basaltic fissure eruption oriented N45E and covering an area of 10.4 km2. The erupted volume increases by 5-fold from the first to the last eruption. All magmas are tephritic, although the bulk-rock becomes more mafic with time due to accumulation of olivine with Cr-spinel inclusions, and clinopyroxene rather than to the appearance of a truly more primitive melt. Olivine core compositions of the three eruptions range between Fo79 and Fo87. Frequency histograms show three main populations: at Fo79-80, Fo80-82 and Fo84-87 displaying normal and reverse zoning. Thermodynamic calculations show that only cores with Fo80-82 are in equilibrium with the whole rock. Clinopyroxene phenocrysts can have large pools of matrix glass and show rims of different composition. Only the rims, with Mg#84-86, are in equilibrium with the whole-rock. Considering olivine cores and clinopyroxene rims in equilibrium we obtained a temperature range of 1150-1165°C, and MELTS calculations suggest pressures of 1 to 5 kbar. The variety of olivine core populations reflects mixing and mingling between three different magmas, and their proportions have changed with time from Siete Fuentes to Arafo. Most crystals have complex zoning profiles that record two events: (1) one of magma mixing/mingling at depth, (2) another of magma transport and ascent to the surface. Magma mixing at depth ranges from about 3 months to two years and is similar for the three eruptions

  18. Evidence of lightning and volcanic activity on Venus - Pro and con

    NASA Astrophysics Data System (ADS)

    Scarf, F. L.; Russell, C. T.

    1988-04-01

    It is argued that the impulsive 100-Hz noise bursts detected with the use of the electric field antenna on the Pioneer Venus Orbiter (PVO) have plasma wave charcteristics that can only be explained if they are whistler mode signals of a type that can be produced by atmospheric discharges. It is further argued that these data are evidence for lightning and volcanic activity on Venus. A reply contends that the PVO electric field measurements are unrelated to either the lower atmosphere or the surface of Venus.

  19. Evidence of lightning and volcanic activity on Venus - Pro and con

    NASA Technical Reports Server (NTRS)

    Scarf, Frederick L.; Russell, Christopher T.

    1988-01-01

    It is argued that the impulsive 100-Hz noise bursts detected with the use of the electric field antenna on the Pioneer Venus Orbiter (PVO) have plasma wave charcteristics that can only be explained if they are whistler mode signals of a type that can be produced by atmospheric discharges. It is further argued that these data are evidence for lightning and volcanic activity on Venus. A reply contends that the PVO electric field measurements are unrelated to either the lower atmosphere or the surface of Venus.

  20. Temporal monitoring of Bardarbunga volcanic activity with TanDEM-X

    NASA Astrophysics Data System (ADS)

    Rossi, C.; Minet, C.; Fritz, T.; Eineder, M.; Erten, E.

    2015-12-01

    On August 29, 2014, a volcanic activity started in the lava field of Holuhraun, at the north east of the Bardarbunga caldera in Iceland. The activity was declared finished on February 27, 2015, thus lasting for about 6 months. During these months the magma chamber below the caldera slowly emptied, causing the rare event of caldera collapse. In this scenario, TanDEM-X remote sensing data is of particular interest. By producing high-resolution and accurate elevation models of the caldera, it is possible to evaluate volume losses and topographical changes useful to increase the knowledge about the volcanic activity dynamics. 5 TanDEM-X InSAR acquisitions have been commanded between August 01, 2014 and November 08, 2014. 2 acquisitions have been commanded before the eruption and 3 acquisitions afterwards. To fully cover the volcanic activity, also the lava flow area at the north-west of the caldera has been monitored and a couple of acquisitions have been employed to reveal the subglacial graben structure and the lava path. In this context, the expected elevation accuracy is studied on two levels. Absolute height accuracy is analyzed by inspecting the signal propagation at X-band in the imaged medium. Relative height accuracy is analyzed by investigating the InSAR system parameters and the local geomorphology. It is shown how the system is very well accurate with mean height errors below the meter. Moreover, neither InSAR processing issues, e.g. phase unwrapping errors, nor complex DEM calibration aspects are problems to tackle. Caldera is imaged in its entirety and new cauldron formations and, in general, the complete restructuring of the glacial volcanic system is well represented. An impressive caldera volume loss of about 1 billion cubic meters is measured in about two months. The dyke propagation from the Bardarbunga cauldron to the Holuhraun lava field is also revealed and a graben structure with a width of up to 1 km and a sinking of a few meters is derived

  1. Probabilistic constraints from existing and future radar imaging on volcanic activity on Venus

    NASA Astrophysics Data System (ADS)

    Lorenz, Ralph D.

    2015-11-01

    We explore the quantitative limits that may be placed on Venus' present-day volcanic activity by radar imaging of surface landforms. The apparent nondetection of new lava flows in the areas observed twice by Magellan suggests that there is a ~60% chance that the eruption rate is ~1 km3/yr or less, using the eruption history and area/volume flow geometry of terrestrial volcanoes (Etna, Mauna Loa and Merapi) as a guide. However, if the detection probability of an individual flow is low (e.g. ~10%) due to poor resolution or quality and unmodeled viewing geometry effects, the constraint (<10 km3/yr) is not useful. Imaging at Magellan resolution or better of only ~10% of the surface area of Venus on a new mission (30 years after Magellan) would yield better than 99% chance of detecting a new lava flow, even if the volcanic activity is at the low end of predictions (~0.01 km3/yr) and is expressed through a single volcano with a stochastic eruption history. Closer re-examination of Magellan data may be worthwhile, both to search for new features, and to establish formal (location-dependent) limits on activity against which data from future missions can be tested. While Magellan-future and future-future comparisons should offer much lower detection thresholds for erupted volumes, a probabilistic approach will be required to properly understand the implications.

  2. A preliminary comparison of RST and MODVOLC techniques for satellite monitoring of thermal volcanic activity

    NASA Astrophysics Data System (ADS)

    Lacava, Teodosio; Coviello, Irina; Marchese, Francesco; Mazzeo, Giuseppe; Pergola, Nicola; Tramutoli, Valerio

    2010-05-01

    The potential of satellite sensors working in middle infrared (MIR) region of the electromagnetic spectrum for the detection of hotspots related to active lava flows has been largely demonstrated. Among current available sensors useful for such an application, MODIS (Moderate Resolution Imaging Spectroradiometer), on board NASA-EOS satellites, offers a good compromise between spatial resolution and temporal coverage together with a high dynamic range in MIR region. Based on such satellite data, the MODVOLC algorithm has shown good performances in detecting thermal volcanic features at a global scale. This method has been implemented in an automatic processing chain for near real time monitoring of active volcanoes, with hotspot products continuously posted on the web. On the other hand, the RST (Robust Satellite Techniques) approach has already been successfully used to monitor volcanoes at different geographic locations, under different environmental and observational conditions. An advanced version of RST has recently been proposed, in order to further improve detection and monitoring of thermal volcanic features both in terms of reliability and sensitivity. In this paper, results of a preliminary comparison between RST, implemented on MODIS data, and MODVOLC techniques will be presented. Results of this study, carried out on Mount Etna area during recent lava effusion episodes, will be analyzed and discussed also by validating satellite products with independent and detailed bulletins of eruptive activity.

  3. Hydrothermal Activity and Volcanism on the Southern Mid-Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Haase, K. M.; Scientific Party, M.

    2005-12-01

    In April 2005 four recently discovered different hydrothermal fields on the slow-spreading Mid-Atlantic Ridge (MAR) south of the Equator were studied and sampled using a remotely operated vehicle (ROV) during cruise METEOR 64/1. Three of these hydrothermally active fields (called Turtle Pits, Red Lion, and Wideawake) occur at about 3000 m water depth in the centre of a MAR segment at 4° 48'S which appears to be volcanically very active. The youngest lava flow partly covers the low-temperature, diffuse flow Wideawake mussel field and is thus probably only a few years old. The high-temperature Turtle Pits hydrothermal field with four active vent structures lies some 300 m west of the diffuse vent field and is characterized by boiling fluids with temperatures close to 400° C. The mineral assemblage recovered from inactive hydrothermal mounds includes massive magnetite+hematite+sulfate and differs from that of the presently active vents and indicates more oxidizing conditions during the earlier activity. The vent fluids at Turtle Pits contain relatively high contents of hydrogen which may have formed during iron oxidation processes when basaltic magmas crystallized. The high fluid temperatures, the change to more reducing conditions, and the relatively high hydrogen contents in the fluids are most likely due to the ascent of magmas from the mantle that fed the very recent eruption. The high-temperature Red Lion hydrothermal field lies some 2 km north of the Turtle Pits field and consists of at least four active black smokers surrounded by several inactive sulfide mounds. The composition of the Red Lion fluids differs significantly from the Turtle Pits fluids, possibly owing largely to a difference in the temperature of the two systems. The fourth hydrothermally active field on the southern MAR, the Liliput field, was discovered near 9° 33'S in a water depth of 1500 m and consists of several low-temperature vents. A shallow hydrothermal plume in the water column

  4. 2007 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: Summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    McGimsey, Robert G.; Neal, Christina A.; Dixon, James P.; Malik, Nataliya; Chibisova, Marina

    2011-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, and volcanic unrest at or near nine separate volcanic centers in Alaska during 2007. The year was highlighted by the eruption of Pavlof, one of Alaska's most frequently active volcanoes. Glaciated Fourpeaked Mountain, a volcano thought to have been inactive in the Holocene, produced a phreatic eruption in the autumn of 2006 and continued to emit copious amounts of steam and volcanic gas into 2007. Redoubt Volcano showed the first signs of the unrest that would unfold in 2008-09. AVO staff also participated in hazard communication and monitoring of multiple eruptions at seven volcanoes in Russia as part of its collaborative role in the Kamchatka and Sakhalin Volcanic Eruption Response Teams.

  5. 2008 Volcanic activity in Alaska, Kamchatka, and the Kurile Islands: Summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    Neal, Christina A.; McGimsey, Robert G.; Dixon, James P.; Cameron, Cheryl E.; Nuzhdaev, Anton A.; Chibisova, Marina

    2011-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, and volcanic unrest or suspected unrest at seven separate volcanic centers in Alaska during 2008. Significant explosive eruptions at Okmok and Kasatochi Volcanoes in July and August dominated Observatory operations in the summer and autumn. AVO maintained 24-hour staffing at the Anchorage facility from July 12 through August 28. Minor eruptive activity continued at Veniaminof and Cleveland Volcanoes. Observed volcanic unrest at Cook Inlet's Redoubt Volcano presaged a significant eruption in the spring of 2009. AVO staff also participated in hazard communication regarding eruptions or unrest at nine volcanoes in Russia as part of a collaborative role in the Kamchatka and Sakhalin Volcanic Eruption Response Teams.

  6. Investigating Geothermal Activity, Volcanic Systems, and Deep Tectonic Tremor on Akutan Island, Alaska, with Array Seismology

    NASA Astrophysics Data System (ADS)

    Haney, M. M.; Prejean, S. G.; Ghosh, A.; Power, J. A.; Thurber, C. H.

    2012-12-01

    In addition to hosting one of the most active volcanoes in the Aleutian Arc, Akutan Island, Alaska, is the site of a significant geothermal resource within Hot Springs Bay Valley (HSBV). We deployed 15 broadband (30 s to 50 Hz) seismometers in and around HSBV during July 2012 as part of an effort to establish a baseline for background seismic activity in HSBV prior to geothermal production on the island. The stations recorded data on-site and were retrieved in early September 2012. Additional targets for the array include the tracking of deep tectonic tremor known to occur within the Aleutian subduction zone and the characterization of volcano-tectonic (VT) and deep long period (DLP) earthquakes from Akutan Volcano. Because 13 of the stations in the array sit within an area roughly 1.5 km by 1.5 km, we plan to apply methods based on stacking and beamforming to analyze the waveforms of extended signals lacking clear phase arrivals (e.g., tremor). The average spacing of the seismometers, roughly 350 m, provides sensitivity to frequencies between 2-8 Hz. The stacking process also increases the signal-to-noise ratio of small amplitude signals propagating across the array (e.g., naturally occurring geothermal seismicity). As of August 2012, several episodes of tectonic tremor have been detected in the vicinity of Akutan Island during the array deployment based on recordings from nearby permanent stations operated by the Alaska Volcano Observatory (AVO). This is the first small-aperture array deployed in the Aleutian Islands and the results should serve as a guide for future array deployments along the Aleutian Arc as part of the upcoming EarthScope and GeoPRISMS push into Alaska. We demonstrate the power of array methods based on stacking at Akutan Volcano using a sequence of DLP earthquakes from June 11, 2012 that were recorded on the permanent AVO stations. We locate and characterize the lowest frequency portion of the signals at 0.5 Hz. At these low frequencies, the

  7. Oblique Subduction and Strain Partitioning: Tectonic Role of Margin-Parallel and Margin-Transverse Structures at the Southern Volcanic Zone of the Andes

    NASA Astrophysics Data System (ADS)

    Stanton-Yonge, A.; Cembrano, J. M.; Griffith, W. A.; St Julien, R. C.; Iturrieta, P. C.

    2015-12-01

    Convergent margins undergoing oblique subduction develop margin-parallel structural domains, which are responsible for the accommodation of long-term crustal deformation within the overriding plate. Although the Andes are no exception, evidence of transverse-to-the-orogen regional structures has been documented along its entire length. The relevance of these structures is widely recognized; however, whether and how they participate in the accommodation of crustal deformation is not yet fully understood. The Southern Volcanic Zone of the Andes (SVZ) is an excellent area to address this problem because it displays regional transverse-to-the-arc structures which play a strong structural control on the spatial distribution and genesis of volcanoes and geothermal springs, which proves the existence of a strong interplay between tectonics and magmatic/hydrothermal fluid flow. This work aims to determine the nature and kinematics of selected case studies of transverse structures along the SVZ during the different phases of the subduction seismic cycle and their structural interaction with margin-parallel fault systems, particularly the strike-slip, intra-arc Liquiñe-Ofqui Fault System (LOFS). By the implementation of an elastic, regional-scale, numerical model of the subduction at the Chilean margin using the boundary elements method (BEM), fault slip rates and associated displacement, strain and stress fields in the surrounding continental lithosphere are calculated for the case study sites. Preliminary results show that the LOFS behaves as a dextral-reverse structure during the interseismic period of the subduction seismic cycle, with increasing fault slip rates towards its southern end, where the western block moves at a rate of 7 mm/yr to the north, suggesting that the LOFS accounts for strain partitioning. It is expected that transverse structures, particularly those misorientated with respect to the prevailing stress field, will display considerably lower slip rate

  8. Volcanism in southern Guinevere Planitia, Venus: Regional volcanic history and morphology of volcanic domes

    NASA Technical Reports Server (NTRS)

    Crown, David A.; Stofan, Ellen R.; Plaut, Jeffrey J.

    1993-01-01

    Guinevere Planitia is a low-lying region located between the highlands of Beta Regio and Eistla Regio. Analyses of Pioneer Venus, Goldstone, and Arecibo radar data suggested that the surface of Guinevere Planitia is dominated by volcanism, primarily in the form of bright, dark, and mottled plains units. Also identified in this region was the Beta-Eistla Deformation Zone, composed of ovoids and discontinuous segments of lineament belts that have been embayed by the surrounding plains. The resolution of Magellan SAR images allows detailed investigations of the volcanic deposits found in the area in order to determine the types of eruptive activity which have occurred and to constrain the regional volcanic history. Analyses of an area of southern Guinevere Planitia between 0-25 deg N and 300-330 deg indicate the presence of a wide variety of volcanic land forms, including large shield volcanoes, widespread plains, lava flow fields, and small domes, cones, and shields as well as coronae and other circular structures that have associated volcanic deposits.

  9. Active fault systems and tectono-topographic configuration of the central Trans-Mexican Volcanic Belt

    NASA Astrophysics Data System (ADS)

    Szynkaruk, Ewa; Graduño-Monroy, Víctor Hugo; Bocco, Gerardo

    2004-07-01

    The central Trans-Mexican Volcanic Belt (TMVB) reflects the interplay between three regional fault systems: the NNW-SSE to NW-SE striking Taxco-Querétaro fault system, the NE-SW striking system, and the E-W striking Morelia-Acambay fault system. The latter is the youngest and consists of fault scarps up to 500 m high, whose formation caused structural and morphological reorganization of the region. In this paper, we investigate possible activity of the three systems within the central TMVB, and assess the role that they play in controlling the tectono-topographic configuration of the area. Our study is based on DEM-derived morphometric maps, longitudinal river profiles, geomorphologic mapping, and structural field data concerning recent faulting. We find that all three regional fault systems are active within the central TMVB, possibly with different displacement rates and/or type of motion; and that NNW-SSE and NE-SW striking faults control the major tectono-topographic elements that build up the region, which are being re-shaped by E-W striking faults. We also find that tectonic information can be deciphered from the topography of the youthful volcanic arc in question, regardless its complexity.

  10. Ultra-long-range hydroacoustic observations of submarine volcanic activity at Monowai, Kermadec Arc

    NASA Astrophysics Data System (ADS)

    Metz, D.; Watts, A. B.; Grevemeyer, I.; Rodgers, M.; Paulatto, M.

    2016-02-01

    Monowai is an active submarine volcanic center in the Kermadec Arc, Southwest Pacific Ocean. During May 2011, it erupted over a period of 5 days, with explosive activity directly linked to the generation of seismoacoustic T phases. We show, using cross-correlation and time-difference-of-arrival techniques, that the eruption is detected as far as Ascension Island, equatorial South Atlantic Ocean, where a bottom moored hydrophone array is operated as part of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organization. Hydroacoustic phases from the volcanic center must therefore have propagated through the Sound Fixing and Ranging channel in the South Pacific and South Atlantic Oceans, a source-receiver distance of ~15,800 km. We believe this to be the furthest documented range of a naturally occurring underwater signal above 1 Hz. Our findings, which are consistent with observations at regional broadband stations and long-range, acoustic parabolic equation modeling, have implications for submarine volcano monitoring.

  11. Autonomous Volcanic Activity Detection with ASE on EO-1 Hyperion: Applications for Planetary Missions

    NASA Astrophysics Data System (ADS)

    Davies, A. G.; Baker, V.; Castano, R.; Chien, S.; Cichy, B.; Doggett, T.; Dohm, J.; Greeley, R.; Rabideau, G.; Sherwood, R.; Williams, K.; ASE Project Team

    2003-05-01

    The New Millennium Program (NMP) Space Technology 6 (ST-6) Autonomous Sciencecraft Experiment (ASE) will fly two scene classifiers on the Earth Orbiting 1 (EO-1) spacecraft in the fall of 2003, and will demonstrate autonomous, onboard processing of Hyperion imager 0.4-2.4 micron hyperspectral data, and autonomous, science-driven planning and acquisition of subsequent observations. ASE is an experiment to meet NASA's call for systems with reduced downlink and onboard data processing to enable autonomous missions. ASE software is divided into three classes: (1) spacecraft command and control; (2) an onboard planner (CASPER); and (3) modular science algorithms, which are used to process raw data to search out specific features and spectral signatures. The ASE Science Team has developed scene classifiers to detect thermal emission in both day and nighttime Hyperion data, and are continuing to develop other scene classifiers for ice, snow, water and land for future release and flight on EO-1. Once uploaded, the thermal scene classifier effectively turns the EO-1 spacecraft into an autonomously operating and reacting volcanic activity detector. It is possible to envision such a capability on spacecraft observing volcanism on Io and Triton, autonomously identifying and classifying activity, identifying sites deserving of closer scrutiny, and retasking the spacecraft to observe them, thus fulfilling NASA's goal of fully-autonomous, science-driven spacecraft. This work was carried out at the Jet Propulsion Laboratory-California Institute of Technology, under contract to NASA.

  12. 1997 volcanic activity in Alaska and Kamchatka: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    McGimsey, Robert G.; Wallace, Kristi L.

    1999-01-01

    The Alaska Volcano Observatory (AVO) monitors over 40 historically active volcanoes along the Aleutian Arc. Twenty are seismically monitored and for the rest, the AVO monitoring program relies mainly on pilot reports, observations of local residents and ship crews, and daily analysis of satellite images. In 1997, AVO responded to eruptive activity or suspect volcanic activity at 11 volcanic centers: Wrangell, Sanford, Shrub mud volcano, Iliamna, the Katmai group (Martin, Mageik, Snowy, and Kukak volcanoes), Chiginagak, Pavlof, Shishaldin, Okmok, Cleveland, and Amukta. Of these, AVO has real-time, continuously recording seismic networks at Iliamna, the Katmai group, and Pavlof. The phrase “suspect volcanic activity” (SVA), used to characterize several responses, is an eruption report or report of unusual activity that is subsequently determined to be normal or enhanced fumarolic activity, weather-related phenomena, or a non-volcanic event. In addition to responding to eruptive activity at Alaska volcanoes, AVO also disseminated information for the Kamchatkan Volcanic Eruption Response Team (KVERT) about the 1997 activity of 5 Russian volcanoes--Sheveluch, Klyuchevskoy, Bezymianny, Karymsky, and Alaid (SVA). This report summarizes volcanic activity and SVA in Alaska during 1997 and the AVO response, as well as information on the reported activity at the Russian volcanoes. Only those reports or inquiries that resulted in a “significant” investment of staff time and energy (here defined as several hours or more for reaction, tracking, and follow-up) are included. AVO typically receives dozens of reports throughout the year of steaming, unusual cloud sightings, or eruption rumors. Most of these are resolved quickly and are not tabulated here as part of the 1997 response record.

  13. Conditions for oceans on Earth-like planets orbiting within the habitable zone: importance of volcanic CO{sub 2} degassing

    SciTech Connect

    Kadoya, S.; Tajika, E. E-mail: tajika@astrobio.k.u-tokyo.ac.jp

    2014-08-01

    Earth-like planets in the habitable zone (HZ) have been considered to have warm climates and liquid water on their surfaces if the carbonate-silicate geochemical cycle is working as on Earth. However, it is known that even the present Earth may be globally ice-covered when the rate of CO{sub 2} degassing via volcanism becomes low. Here we discuss the climates of Earth-like planets in which the carbonate-silicate geochemical cycle is working, with focusing particularly on insolation and the CO{sub 2} degassing rate. The climate of Earth-like planets within the HZ can be classified into three climate modes (hot, warm, and snowball climate modes). We found that the conditions for the existence of liquid water should be largely restricted even when the planet is orbiting within the HZ and the carbonate-silicate geochemical cycle is working. We show that these conditions should depend strongly on the rate of CO{sub 2} degassing via volcanism. It is, therefore, suggested that thermal evolution of the planetary interiors will be a controlling factor for Earth-like planets to have liquid water on their surface.

  14. Spatial distribution of intrinsic and scattering seismic attenuation in active volcanic islands - II: Deception Island images

    NASA Astrophysics Data System (ADS)

    Prudencio, Janire; Ibáñez, Jesús M.; García-Yeguas, Araceli; Del Pezzo, Edoardo; Posadas, Antonio M.

    2013-12-01

    In this work, we present regional maps of the inverse intrinsic quality factor (Qi-1), the inverse scattering quality factor (Qs-1) and total inverse quality factor (Qt-1) for the volcanic environment of Deception Island (Antarctica). Our attenuation study is based on diffusion approximation, which permits us to obtain the attenuation coefficients for every single couple source-receiver separately. The data set used in this research is derived from an active seismic experiment using more than 5200 offshore shots (air guns) recorded at 32 onshore seismic stations and four ocean bottom seismometers. To arrive at a regional distribution of these values, we used a new mapping technique based on a Gaussian space probability function. This approach led us to create `2-D probabilistic maps' of values of intrinsic and scattering seismic attenuation. The 2-D tomographic images confirm the existence of a high attenuation body below an inner bay of Deception Island. This structure, previously observed in 2-D and 3-D velocity tomography of the region, is associated with a massive magma reservoir. Magnetotelluric studies reach a similar interpretation of this strong anomaly. Additionally, we observed areas with lower attenuation effects that bear correlation with consolidated structures described in other studies and associated with the crystalline basement of the area. Our calculations of the transport mean-free path and absorption length for intrinsic attenuation gave respective values of ≈ 950 m and 5 km, which are lower than the values obtained in tectonic regions or volcanic areas such as Tenerife Island. However, as observed in other volcanic regions, our results indicate that scattering effects dominate strongly over the intrinsic attenuation.

  15. Evidence for Subglacial Volcanic Activity Beneath the area of the Divide of the West Antarctic Ice Sheet

    NASA Astrophysics Data System (ADS)

    Behrendt, J. C.

    2013-12-01

    There is an increasing body of aeromagnetic, radar ice-sounding, heat flow, subglacial volcanic earthquakes, several exposed active and subglacial volcanoes and other lines of evidence for volcanic activity associated with the West Antarctic Rift System (WR) since the origin (~25 Ma) of the West Antarctic Ice Sheet (WAIS), which flows through it. Exposed late Cenozoic, alkaline volcanic rocks, 34 Ma to present concentrated in Marie Byrd Land (LeMasurier and Thomson, 1990), but also exposed along the rift shoulder on the Transantarctic Mountains flank of the WR, and >1 million cubic kilometers, of mostly subglacially erupted 'volcanic centers' beneath the WAIS inferred from aeromagnetic data, have been interpreted as evidence of a magmatic plume. About 18 high relief, (~600-2000 m) 'volcanic centers' presently beneath the WAIS surface, probably were erupted subaerially when the WAIS was absent, based on the 5-km orthogonally line spaced Central West Antarctica aerogeophysical survey. All would be above sea level after ice removal and isostatic adjustment. Nine of these high relief peaks are in the general area beneath the divide of the WAIS. This high bed relief topography was first interpreted in the 1980s as the volcanic 'Sinuous Ridge ' based on a widely spaced aeromagnetic -radar ice sounding survey (Jankowski et al,. 1983). A 70-km wide, circular ring of interpreted subglacial volcanic rocks was cited as evidence of a volcanic caldera underlying the ice sheet divide based on the CWA survey (Behrendt et al., 1998). A broad magnetic 'low' surrounding the caldera area possibly is evidence of a shallow Curie isotherm. High heat flow reported from temperature logging (Clow et al., 2012) in the WAISCORE and a thick volcanic ash layer in the core (Dunbar et al., 2012) are consistent with this interpretation. A 2 km-high subaerially erupted volcano (subglacial Mt Thiel, ~78.5 degrees S, 111 degrees W) ~ 100 km north from the WAISCORE could be the source of the ash

  16. Connecting Io's volcanic activity to the Io plasma torus: comparison of Galileo/NIMS volcanic and ground-based torus observations

    NASA Astrophysics Data System (ADS)

    Magalhaes, F. P.; Lopes, R. M. C.; Rathbun, J. A.; Gonzalez, W. D.; Morgenthaler, J. P.; Echer, E.; Echer, M. P. D. S.

    2015-12-01

    Io, the innermost of the Jupiter's four Galilean moons, is a remarkable object in the Solar System, due to its intense and energetic volcanic activity. The volcanic sulfur and oxygen in Io's tenuous atmosphere escapes forming an extended neutral cloud around Io and Jupiter. Subsequently, by ionization and pickup ions, a ring of charged particles encircling Jupiter is created, forming the Io plasma torus. Considering this scenario, it is reasonable to expect that the Io plasma torus should be affected by changes in Io's volcanism. Interactions between Io and the Jovian environment is unique and yet not very well understood. Here we present two sets of observations. One from the Galileo Near-Infrared Imaging Spectrograph (NIMS) instrument, which obtained spectral image cubes between 0.7 and 5.2 microns. The other dataset is from ground-based observations of the [SII] 6731 Å emission lines from the Io plasma torus, obtained at McMath-Pierce Solar Telescope, at Kitt Peak. Our dataset from the [SII] 6731 Å emission lines cover more years than the one from the NIMS data. The years presented in this work for a comparative study are from 1998 through 2001. Using the NIMS instrument we were able to identify which volcanoes were active and measure their level of activity. From the [SII] 6731 Å emission lines we were able to trace the densest part of the torus and also the brightness of both ansa. By comparing the results from the Galileo instrument and the ground-based observations, we are exploring how the Io plasma torus responds to large eruptions from Io. We aim with this study to help improve our understanding of this complex coupled system, Jupiter-Io.

  17. Subsurface biological activity zone detection using genetic search algorithms

    SciTech Connect

    Mahinthakumar, G.; Gwo, J.P.; Moline, G.R.; Webb, O.F.

    1999-12-01

    Use of generic search algorithms for detection of subsurface biological activity zones (BAZ) is investigated through a series of hypothetical numerical biostimulation experiments. Continuous injection of dissolved oxygen and methane with periodically varying concentration stimulates the cometabolism of indigenous methanotropic bacteria. The observed breakthroughs of methane are used to deduce possible BAZ in the subsurface. The numerical experiments are implemented in a parallel computing environment to make possible the large number of simultaneous transport simulations required by the algorithm. The results show that genetic algorithms are very efficient in locating multiple activity zones, provided the observed signals adequately sample the BAZ.

  18. Terrestrial Laser Scanning of Lava Flows to Constrain Fracture Models in Geothermal Reservoirs; a Case Study from the Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Massiot, C.; Garcia-Sélles, D.; Nicol, A., , Prof; Mcnamara, D. D.; Townend, J.; Archibald, G.; Siratovich, P. A.; Villeneuve, M.

    2015-12-01

    Geothermal reservoirs hosted in volcanic rocks, like the Rotokawa Geothermal Field in the Taupo Volcanic Zone (TVZ), New Zealand, typically contain fracture networks that control fluid flow. Realistic discrete fracture network (DFN) models have the potential to improve geothermal resource management. However, the spatial distribution and geometries of fracture networks are often poorly understood due to limited data and complex deformation histories including lava emplacement, subsequent burial and faulting.To understand better the distribution of fractures formed during lava emplacement, we study andesitic flow exposures from Mt Ruapehu, at the southern end of the TVZ. Terrestrial Laser Scanner (TLS) acquisition on three 50-200 m2 outcrops provided large 3D point clouds of the shape of the outcrop. Delineation of thousands of individual fractures has been semi-automated using local geometrical constraints and a shape detection algorithm detecting planar and curved surfaces. Fracture orientation, length, area, linear (P10) and areal (P20) densities from the TLS data provide input parameters for the DFN models. Fracture detection is validated using high-resolution panoramic photographs (GigaPan) and manual scanline measurements. Cooling joints are highly connected via sub-horizontal joints that are aligned with vesicular layers. UCS tests show a mechanical anisotropy between vertical and horizontal samples. Most of the cooling joints terminate within or at the brecciated margins of individual flows which contrast mechanically with the massive flow interior. Thus, highly connected and curved fractures are mostly confined to lava flows.This study provides a framework for developing DFNs for geothermal reservoirs hosted in andesitic flows based on empirical observations of intrinsic fracturing and mechanical anisotropies of the host lithology. Fractures in individual lava flows may be interconnected in the reservoir by a combination of cooling joints, subsequent

  19. Influence of seismic processes and volcanic activity on the formation of disastrous floods

    NASA Astrophysics Data System (ADS)

    Trifonov, Dmitriy

    2014-05-01

    models of hydraulic systems, but ultimately due to difference of pressures in their respective segments and areas of the transport network. At the exit of the groundwater on the surface such change in pressure is connected both with the state of the actual water flow in underground cavities, or violations of the structure (topology) of 3D-network. As one of the major and sudden reasons of change of pressure in the underground system can serve seismic processes, including volcanic eruptions (as magmatic and ash). During these processes enormous underground space can be freed from the dense rock. This leads to rapid changes in pressure and that, in principle, a new topology of 3D network and water flows in it. It is important that such dynamic processes occur over huge distances in underground basins of thousands of kilometers [3], of course, with a certain time delay. In the result of the analysis of large-scale flooding in Russia in 2001-2002, as well as the catastrophic floods in Western Europe, in the Amur region of Russia and in the state of Colorado USA in 2013, a correlation between seismic and volcanic activities and floods, expressed by specific numerical correlation coefficients, has been revealed. For example, knowing the date, location and magnitude of an earthquake, we can identify potentially dangerous territories in the aspect of the probability of occurrence of floods, because the stresses in the crust, spreading from the hypocenter of earthquakes, and their subsequent relaxation are one of the most important factors of floods. Mechanisms of distribution of these stresses are well-studied today [2] unlike their influence on the groundwater. The defined boundaries of potentially dangerous sites are broad enough; with regard to the direction of distribution of stress, it is about the sectors in 40 degrees (from the line of the movement of the crustal plate) in the direction from the boundaries of lithospheric plates. Distribution of this impact occurs, as a

  20. The influence of Ryukyu subduction on magma genesis in the Northern Taiwan Volcanic Zone and Middle Okinawa Trough - Evidence from boron isotopes

    NASA Astrophysics Data System (ADS)

    Pi, Ju-Lien; You, Chen-Feng; Wang, Kuo-Lung

    2016-09-01

    Boron (B) is an excellent geochemical tracer for investigating crustal recycling processes at convergent margins, due to its high fluid mobility under high P-T conditions, distinct elemental abundances and isotopic compositions in the mantle wedge and subducting slabs. The Northern Taiwan Volcanic Zone (NTVZ), wherein the nature of magma genesis has long been a topic of debate, is located at the rear side of the Okinawa Trough (OT), an atypical back-arc rift in the Ryukyu subduction system. In this study, B and B isotopes (δ11B) were measured in 19 volcanic rocks collected from the NTVZ and the middle Okinawa Trough (MOT) to assess the influence of the Ryukyu subduction system on magma genesis. The B concentrations in the MOT and NTVZ volcanic rocks are 5.8 to 13.6 mg/L and 2.2 to 48.6 mg/L, respectively. The large B abundances variation in the NTVZ was caused mainly by variable degrees of partial melting. The Nb/B and δ11B in the MOT have small ranges of 0.5 to 0.6 and - 2.7‰ to 0.2‰, respectively, whereas they range widely from 0.4 to 2.5 and from - 8.6‰ to 2.4‰, respectively in the NTVZ. These Nb/B values suggest that the magma contains a smaller subduction component than that normally observed in arcs, although this component is still more substantial than in a typical back-arc setting. The δ11B results indicate insignificant influence of the subducting Philippine Sea Plate at 2.6 Ma, but it becomes more substantial later in the NTVZ. The mixing proportions of sediment derived fluids in onshore volcanoes in the NTVZ imply a rather heterogeneous mantle wedge near the plate boundary, most likely due to either a heterogeneous source of slab derived fluids or more complicated mantle flow. A substantial B flux from the subducting slab in the incipient back-arc rifting in the MOT and NTVZ may reflect characteristics of a cold, steep and fast subducting slab, which may be capable of carrying volatiles efficiently into greater depth in subduction zones. The

  1. Long term validation of Robust Satellite Techniques (RST) for thermal volcanic activity monitoring

    NASA Astrophysics Data System (ADS)

    Marchese, Francesco; Filizzola, Carolina; Genzano, Nicola; Mazzeo, Giuseppe; Paciello, Rossana; Pergola, Nicola; Tramutoli, Valerio

    2010-05-01

    A multi-temporal scheme of satellite data analysis, named RST (Robust Satellite Techniques), already successfully used to study and monitor several active volcanoes, has recently been tested on a long time series of NOAA-AVHRR records acquired over Mount Etna area for a full assessment of its performances. Satellite records acquired at different time of pass (e.g. day/night, winter/summer), from 1995 to 2008 (14 years of satellite records analyzed), processed following RST prescriptions, have been strictly validated using ground based information reported in the volcano bulletins freely available on the web. In this work results of this detailed validation analysis will be presented, discussing performances of such an approach for an automatic satellite monitoring of thermal volcanic features. Moreover, RST capabilities in detecting even abrupt changes in thermal signal related to the beginning of new eruptive events, by using data provided by geostationary satellite like MSG-SEVIRI, will be investigated, for a possible implementation of such an approach within an integrated Early Warning System devoted to volcanic hazard mitigation.

  2. Patterns of late Cenozoic volcanic and tectonic activity in the West Antarctic rift system revealed by aeromagnetic surveys

    USGS Publications Warehouse

    Behrendt, John C.; Saltus, R.; Damaske, D.; McCafferty, A.; Finn, C.A.; Blankenship, D.; Bell, R.E.

    1996-01-01

    Aeromagnetic surveys, spaced ???5 km, over widely separated areas of the largely ice- and sea-covered West Antarctic rift system, reveal similar patterns of 100- to 1700-nT, shallow-source magnetic anomalies interpreted as evidence of extensive late Cenozoic volcanism. We use the aeromagnetic data to extend the volcanic rift interpretation over West Antarctica starting with anomalies over (1) exposures of highly magnetic, late Cenozoic volcanic rocks several kilometers thick in the McMurdo-Ross Island area and elsewhere; continuing through (2) volcanoes and subvolcanic intrusions directly beneath the Ross Sea continental shelf defined by marine magnetic and seismic reflection data and aeromagnetic data and (3) volcanic structures interpreted beneath the Ross Ice Shelf partly controlled by seismic reflection determinations of seafloor depth to (4) an area of similar magnetic pattern over the West Antarctic Ice Sheet (400 km from the nearest exposed volcanic rock), where interpretations of late Cenozoic volcanic rocks at the base of the ice are controlled in part by radar ice sounding. North trending magnetic rift fabric in the Ross Sea-Ross Ice Shelf and Corridor Aerogeophysics of the Southeast Ross Transect Zone (CASERTZ) areas, revealed by the aeromagnetic surveys, is probably a reactivation of older rift trends (late Mesozoic?) and is superimposed on still older crosscutting structural trends revealed by magnetic terrace maps calculated from horizontal gradient of pseudogravity. Longwavelength (???100-km wide) magnetic terraces from sources within the subvolcanic basement cross the detailed survey areas. One of these extends across the Ross Sea survey from the front of the Transantarctic Mountains with an east-southeast trend crossing the north trending rift fabric. The Ross Sea-Ross Ice Shelf survey area is characterized by highly magnetic northern and southern zones which are separated by magnetically defined faults from a more moderately magnetic central zone

  3. Drastic shift in lava geochemistry in the volcanic-front to rear-arc region of the Southern Kamchatkan subduction zone: Evidence for the transition from slab surface dehydration to sediment melting

    NASA Astrophysics Data System (ADS)

    Duggen, Svend; Portnyagin, Maxim; Baker, Joel; Ulfbeck, David; Hoernle, Kaj; Garbe-Schönberg, Dieter; Grassineau, Nathalie

    2007-01-01

    The shift of lava geochemistry between volcanic front to rear-arc volcanoes in active subduction zones is a widespread phenomenon. It is somehow linked to an increase of the slab surface depth of the subducting oceanic lithosphere and increasing thickness of the mantle wedge and new constraints for its causes may improve our understanding of magma generation and element recycling in subduction zones in general. As a case study, this paper focuses on the geochemical composition of lavas from two adjacent volcanic centres from the volcanic front (VF) to rear-arc (RA) transition of the Southern Kamchatkan subduction zone, with the aim to examine whether the shift in lava geochemistry is associated with processes in the mantle wedge or in the subducted oceanic lithosphere or both. The trace element and O-Sr-Nd-Hf-Pb (double-spike)-isotopic composition of the mafic Mutnovsky (VF) and Gorely (RA) lavas in conjunction with geochemical modelling provides constraints for the degree of partial melting in the mantle wedge and the nature of their slab components. Degrees of partial melting are inferred to be significantly higher beneath Mutnovsky (˜18%) than Gorely (˜10%). The Mutnovsky (VF) slab component is dominated by hydrous fluids, derived from subducted sediments and altered oceanic crust, eventually containing minor but variable amounts of sediment melts. The composition of the Gorely slab component strongly points to a hydrous silicate melt, most likely mainly stemming from subducted sediments, although additional fluid-contribution from the underlying altered oceanic crust (AOC) is likely. Moreover, the Hf-Nd-isotope data combined with geochemical modelling suggest progressive break-down of accessory zircon in the melting metasediments. Therefore, the drastic VF to RA shift in basalt chemistry mainly arises from the transition of the nature of the slab component (from hydrous fluid to melt) in conjunction with decreasing degrees of partial melting within ˜15 km

  4. Major Regional Earthquake as a Trigger for Enhanced Volcanic Activity: Evidence from Satellite Thermal Data

    NASA Astrophysics Data System (ADS)

    Harris, A.; Ripepe, M.; Wright, R.; Dell Donne, D.

    2006-12-01

    Data output by the Moderate Resolution Imaging Spectroradiometer (MODIS) Volcanic hot spot detection algorithm (MODVOLC), as given on http://hotspot.higp.hawaii.edu, allow construction of heat and volume flux time-series for on-going effusive volcanic eruptions. Using MODVOLC-derived time-series we were able to track an immediate eruptive response at two Javanese volcanic systems, Merapi and Semeru, to the magnitude 6.3 earthquake that occurred just off-shore of Java on 26 May 2006. Both volcanoes were active at the time of the earthquake, with the two volcanoes being ~50 km north and ~280 km east of the earthquake epicenter, respectively. Between 10 May and 14 June hot spot activity at Merapi and Semeru was detected by MODVOLC on twenty occasions. From these MODIS data we were able to identify three phases of activity. The first phase spanned 17-29 May and was characterized by relatively low volume fluxes of 5±2 and 4±2 x 104 m3/d at Merapi and Semeru, respectively. The second phase began on 30 May, lasted until 7 June, and was characterized by increased volume fluxes (11±5 and 11±8 x 104 m3/d). The final phase was underway by 8 June and was characterized by a return to lower volume fluxes (8±4 and 7±5 x 104 m3/d). At both systems, we thus recorded a coupled response to the earthquake, beginning 3 days after the event, lasting 9 days and involving a doubling in the rate of volumetric output. The response felt in eruptive activity appears to have lagged ~72 hours behind the trigger event. This no doubt relects the time it takes the change in stress field felt by the deep chamber at the two active systems to be transmitted to the surface. The effect, however, was short-lived, with the volume fluxes returning to values typical of those prior to the earthquake after ~9 days, indicating that the effect (change in the pressure differential) and symptom (increase in erupted volume flux) was transient and short-lived. Previous work has focused on attempting to draw

  5. Characterizing active volcanic processes at Kilauea volcano using LiDAR scanning

    NASA Astrophysics Data System (ADS)

    LeWinter, A. L.; Finnegan, D. C.; Patrick, M. R.; Anderson, S. W.; Orr, T. R.

    2012-12-01

    Active craters and lava lakes evolve in response to a variety of volcanic processes. Quantifying those changes can be difficult or even impossible, for safety reasons, due to the technical limitations of sensors that require a minimum standoff distance. In recent years, advancements in ground-based Light Detection and Ranging (LiDAR) scanners and accessibility to these systems have enhanced our ability to capture data in a diversity of volcanic settings at the highest spatial and temporal resolutions yet seen. Moreover, advancements in full-waveform digitization have significantly improved the ability to acquire data in environments where ash, steam, and sulfur dioxide emissions have historically hampered efforts. Kilauea's ongoing summit eruption, which began in March 2008, has been characterized in part by the evolution of its vent into a 160-meter diameter collapse crater holding an active lava lake. This process has been documented in detail by field and webcam observations, but has not been accurately quantified. Our research focuses on acquiring repeat, high-resolution full-waveform LiDAR data throughout 2012 to monitor changes in the geometry of Kilauea's active lava lake and the crater to which it is confined. We collected LiDAR data in February and July 2012, with plans for an additional survey in October 2012. Our results show changes in the shape of the vent walls and the shape and level of the confined lava lake. Specifically, the LiDAR data has revealed 1) changes in the lava lake level, corresponding to tiltmeter observations of pressure fluctuations in the summit magma reservoir, 2) enlargement of the vent cavity, due to frequent rock falls, and 3) modifications to the lake size and surrounding lava ledges due to competing processes of accretion and collapse. The rapid acquisition of repeat, high-resolution topographic data enables researchers to more accurately characterize shape and volume changes involved in a range of eruptive systems, while

  6. Discovery of Active Hydrothermal Sites Along the Mariana Volcanic Arc, Western Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Baker, E. T.; Embley, R. W.; Resing, J. A.; Lupton, J. E.; Massoth, G. J.; de Ronde, C. E.; Nakamura, K.; Walker, S. L.

    2003-12-01

    Some 20,000 km of volcanic arcs, roughly one-third the total length of the global midocean ridge (MOR) system, rim the western Pacific Ocean. But compared to 25 years of hydrothermal investigations along MORs, exploration of similar activity on the estimated 600 submarine arc volcanoes is only beginning. In February 2003, as part of the Submarine Ring of Fire project funded by NOAA's Ocean Exploration Program, we made the first systematic survey of hydrothermal activity along the 1270-km-long Mariana intraoceanic volcanic arc, which lies almost entirely within the US EEZ. Prior fieldwork had documented active (but low-temperature) hydrothermal discharge on only three volcanoes: Kasuga 2, Kasuga 3, and Esmeralda Bank. During the cruise, we conducted 70 CTD operations over more than 50 individual volcanoes from 13° N to 23° N, plus a continuous CTD survey along 75 km of the back-arc spreading center (13° 15'N to 13° 41'N) adjacent to the southern end of the arc. We found evidence for active hydrothermal venting at 11 submarine volcanoes with summit (or caldera floor) depths ranging from 50 to 1550 m. Two additional sites were identified on the back-arc spreading center. Ongoing analyses of collected water samples could increase these totals. Our results confirmed continuing hydrothermal activity at Kasuga 2 (but not Kasuga 3) and Esmeralda Bank, in addition to newly discovered sites on nine other volcanoes. Many of these sites produce intense and widely dispersed plumes indicative of vigorous, high-temperature discharge. The volcanoes with active hydrothermal systems are about equally divided between those with and without summit calderas. The addition of the Marianas data greatly improves our view of hydrothermal sources along arcs. The 20,000 km of Pacific arcs can be divided between 6380 km of intraoceanic (i.e., mostly submarine) arcs and 13,880 km of island (i.e., mostly subaerial) arcs. At present, ˜15% of the total length of Pacific arcs has been surveyed

  7. Lithospheric failure and intra-plate volcanism in response to intense yielding: An example from the Greenland Fracture Zone, North Atlantic

    NASA Astrophysics Data System (ADS)

    Døssing, A.; Watts, A. B.

    2012-04-01

    The Greenland Fracture Zone (GFZ) in the northern NE Atlantic outlines a 200 km long boundary between oceanic crust in the Greenland Basin and highly thinned, continental crust beneath the East Greenland Ridge (EGR). Seismic reflection, refraction and Bouguer anomaly data show evidence of significant crustal flexure across the GFZ. We argue that the flexure is caused by mechanical loading/unloading on a normal fault that dips towards the Greenland Basin. Simple 2D flexure modeling show that the best fit elastic thickness for 50 Ma crust in the Greenland Basin is only 10 km. We interpret the low elastic thickness as the result of intense yielding and a possible break in the oceanic lithosphere. This interpretation is supported by indications of a buried volcano of possible middle Miocene age, which is located above the point of greatest crustal curvature and at a site of abrupt changes in geometry of post-middle Miocene sedimentary seismic sequences. We associate the failure and associated intra-plate volcanism with multiple vertical tectonic events at the GFZ throughout the Cenozoic. Finally, seismic evidence is shown of pervasive bending-related faulting along the entire fracture-zone trench slope, some of which penetrate several kilometers into the upper mantle.

  8. California's potential volcanic hazards

    SciTech Connect

    Jorgenson, P. )

    1989-01-01

    Although volcanic eruptions have occurred infrequently in California during the last few thousand years, the potential danger to life and property from volcanoes in the state is great enough to be of concern, according to a recent U.S. Geological Survey (USGS) publication. The 17-page bulletin, Potential Hazards from Future Volcanic Eruptions in California, gives a brief history of volcanic activity in California during the past 100,000 years, descriptions of the types of volcanoes in the state, the types of potentially hazardous volcanic events that could occur, and hazard-zonation maps and tables depicting six areas of the state where volcanic eruptions might occur. The six areas and brief descriptions of their past volcanic history and potential for future volcanic hazards are briefly summarized here.

  9. Assessment of volcanic hazards, vulnerability, risk and uncertainty (Invited)

    NASA Astrophysics Data System (ADS)

    Sparks, R. S.

    2009-12-01

    A volcanic hazard is any phenomenon that threatens communities . These hazards include volcanic events like pyroclastic flows, explosions, ash fall and lavas, and secondary effects such as lahars and landslides. Volcanic hazards are described by the physical characteristics of the phenomena, by the assessment of the areas that they are likely to affect and by the magnitude-dependent return period of events. Volcanic hazard maps are generated by mapping past volcanic events and by modelling the hazardous processes. Both these methods have their strengths and limitations and a robust map should use both approaches in combination. Past records, studied through stratigraphy, the distribution of deposits and age dating, are typically incomplete and may be biased. Very significant volcanic hazards, such as surge clouds and volcanic blasts, are not well-preserved in the geological record for example. Models of volcanic processes are very useful to help identify hazardous areas that do not have any geological evidence. They are, however, limited by simplifications and incomplete understanding of the physics. Many practical volcanic hazards mapping tools are also very empirical. Hazards maps are typically abstracted into hazards zones maps, which are some times called threat or risk maps. Their aim is to identify areas at high levels of threat and the boundaries between zones may take account of other factors such as roads, escape routes during evacuation, infrastructure. These boundaries may change with time due to new knowledge on the hazards or changes in volcanic activity levels. Alternatively they may remain static but implications of the zones may change as volcanic activity changes. Zone maps are used for planning purposes and for management of volcanic crises. Volcanic hazards maps are depictions of the likelihood of future volcanic phenomena affecting places and people. Volcanic phenomena are naturally variable, often complex and not fully understood. There are

  10. Aspects of historical eruptive activity and volcanic unrest at Mt. Tongariro, New Zealand: 1846-2013

    NASA Astrophysics Data System (ADS)

    Scott, Bradley J.; Potter, Sally H.

    2014-10-01

    The 6 August and 21 November 2012 eruptions from Upper Te Maari crater have heightened interest in past activity at Mt. Tongariro, New Zealand. Risks caused by volcanic hazards are increasingly being quantified by using probability estimates through expert elicitation, partly based on the frequency of past eruptions. To maximise the accuracy of these risk values at Mt. Tongariro, a historical eruption catalogue is required. This paper presents the findings of a detailed historical chronology of unrest and eruptions at Mt. Tongariro between 1846 AD and 2013 AD. It builds on the findings of previous researchers, highlighting that volcanic eruptions and unrest have occurred frequently from this volcano. Eruptions are now thought to have occurred at Mt. Tongariro in 1869, 1892, 1896-97, 1899, 1926, 1927, 1934 and 2012. Eruptions also potentially occurred in 1846, 1855, 1886, and 1928, in addition to frequent eruptions from neighbouring Mt. Ngauruhoe. The number of recognised eruptions during the 1896-97 episode has increased to 18, and the Red Crater area has been found to be more active than previously appreciated. Multiple episodes of unrest not resulting in eruptions have also been identified. New eruption recurrence rates are derived from this catalogue, with the baseline probability of the onset of an eruption episode calculated to be 0.07 per year (if 1896-97 and 2012 are considered as one episode each, and all others separately), and the maximum eruption rate within an eruption episode is 18 per year. These new data contribute towards risk assessments for future eruptions at Mt. Tongariro.

  11. Geothermal systems in volcanic arcs: Volcanic characteristics and surface manifestations as indicators of geothermal potential and favorability worldwide

    NASA Astrophysics Data System (ADS)

    Stelling, P.; Shevenell, L.; Hinz, N.; Coolbaugh, M.; Melosh, G.; Cumming, W.

    2016-09-01

    This paper brings a global perspective to volcanic arc geothermal assessments by evaluating trends and correlations of volcanic characteristic and surface manifestation data from world power production sites in subduction zone volcanic settings. The focus of the work was to evaluate volcanic centers individually and as a group in these arcs by correlating various geologic characteristics with known potential to host electricity grade geothermal systems at the volcanic centers. A database was developed that describes key geologic factors expected to be indicative of productive geothermal systems in a global training set, which includes all 74 subduction zone volcanic centers world-wide with current or proven power production capability. Importantly, this data set only contains data from subduction zone volcanoes and contains no negative cases, limiting the populations of any statistical groups. Regardless, this is the most robust geothermal benchmark training set for magmatic-heated systems to date that has been made public. The work reported here is part of a larger project that included data collection, evaluation, correlations and weightings, fairway and favorability modeling and mapping, prediction of blind systems, and uncertainty analysis to estimate errors associated with model predictions. This first paper describes volcano characteristics, compositions and eruption ages and trends along with surface manifestation observations and temperatures as they relate to known power producing systems. Our findings show a strong correlation between the presence and size of active flank fumarole areas and installed power production. Additionally, the majority of volcanic characteristics, including long-held anecdotal correlations related to magmatic composition or size, have limited to no correlation with power production potential. Notable exceptions are correlations between greater power yield from geothermal systems associated with older (Pleistocene) caldera systems

  12. U-series disequilibrium in rear-arc volcanoes from the Northern Volcanic Zone in Ecuador; along-arc variation and implications for petrogenetic processes

    NASA Astrophysics Data System (ADS)

    Garrison, J. M.; Matthews, T. P.; Sims, K. W.; Escobar, R. D.; Yogodzinski, G. M.; Waters, C. L.

    2012-12-01

    Ecuador has been the focus of several studies that document the across-arc geochemical variation in the Northern Volcanic Zone (NVZ), and these studies have been useful in illustrating that from west to east, the lavas are higher in alkali and the fluid mobile elements. Of less focus has been the north to south along-arc variation that is illustrated by volcanoes including Sumaco, Pan de Azucar and El Reventador. Reventador is the northernmost volcano in the rear-arc of the NVZ and has been active since a renewed cycle of activity began in November 2002. Sumaco is located 30 km to the south and has been inactive since at least 1933, although no historic eruptions have been recorded for this volcano. Located between these two volcanoes is the inactive Pan de Azucar volcano, for which there exists no data on the eruptive history. The goal of this research is to document changes in geochemical variation from north to south in the rear-arc of Ecuador and to link this to a petrogenetic process or processes. During a 2010 expedition we collected samples from Sumaco and Reventador Volcanoes, and obtained samples from Pan de Azucar volcano from our colleagues at the IGEPN in Quito. Samples were analyzed for U-series isotopes in addition to major and trace elements. In terms of major and trace elements, El Reventador lavas are weakly alkaline and contain plagioclase, pyroxene and olivine as the major phases, whereas the Sumaco lavas are strongly alkaline and contain titanian augite and hauyne as major phases. The Pan de Azucar samples are compositionally intermediate between the two. Generally speaking, from north to south Ba/Nb decreases from a maximum of 150 at Reventador to 50 at Sumaco, whereas the La/Yb increases from 30 to 50. Other systematic N-S changes include decreasing Ba/Th, which is negatively correlated with Sr concentrations that range from 1000 (Reventador) to 4000 (Sumaco). This is consistent with lower fluid input from N-S that generates smaller degrees of

  13. Recent and episodic volcanic and glacial activity on Mars revealed by the High Resolution Stereo Camera.

    PubMed

    Neukum, G; Jaumann, R; Hoffmann, H; Hauber, E; Head, J W; Basilevsky, A T; Ivanov, B A; Werner, S C; van Gasselt, S; Murray, J B; McCord, T

    2004-12-23

    The large-area coverage at a resolution of 10-20 metres per pixel in colour and three dimensions with the High Resolution Stereo Camera Experiment on the European Space Agency Mars Express Mission has made it possible to study the time-stratigraphic relationships of volcanic and glacial structures in unprecedented detail and give insight into the geological evolution of Mars. Here we show that calderas on five major volcanoes on Mars have undergone repeated activation and resurfacing during the last 20 per cent of martian history, with phases of activity as young as two million years, suggesting that the volcanoes are potentially still active today. Glacial deposits at the base of the Olympus Mons escarpment show evidence for repeated phases of activity as recently as about four million years ago. Morphological evidence is found that snow and ice deposition on the Olympus construct at elevations of more than 7,000 metres led to episodes of glacial activity at this height. Even now, water ice protected by an insulating layer of dust may be present at high altitudes on Olympus Mons.

  14. Chemical evolution at the coasts of active volcanic islands in a primordial salty ocean

    NASA Astrophysics Data System (ADS)

    Strasdeit, H.; Fox, S.

    2008-09-01

    The Prebiotic Hot-Volcanic-Coast Scenario It has been suggested that in the Hadean eon (4.5-3.8 Ga before present) no permanent continents but volcanic islands and short-lived protocontinents protruded from the first ocean [1, 2]. As the geothermal heat production was considerably higher than today, it is reasonable to assume that hot volcanic coasts were much more abundant. The salinity of the ocean was probably up to two times higher than the modern value [3]. Under these conditions, the evaporation of seawater at active volcanic coasts must have produced sea salt crusts - a process that can still be observed today [4]. On the hot lava rock, the salt crusts can subsequently experience temperatures up to some hundred degrees Celsius. The seawater probably contained abiotically formed organic molecules such as amino acids, which were inevitably embedded into the sea salt crusts. Different prebiotic sources of amino acids have been discussed: (i) comets and meteorites [5], electrical discharges in the atmosphere [6, 7], and deep-sea hydrothermal vents [8]. We undertook a systematic study of solid salt-amino acid mixtures, especially of their formation and thermal behavior under simulated conditions of the hotvolcanic- coast scenario. Laboratory Experiments Amino acids@salts Artificial Hadean seawater was prepared by dissolving NaCl (705 mmol), MgCl2 (80 mmol), KCl (15 mmol), CaCl2 (15 mmol), and an α-amino acid (5-10 mmol) or a mixture of α-amino acids. In order to model the first step of the hot-volcanic-coast scenario, the solutions were evaporated to dryness. Vibrational spectroscopy (IR, Raman) and X-ray powder diffraction showed that the resulting solid residues were not heterogeneous mixtures of salt and amino acid crystals. Instead the amino acid molecules were coordinated in calcium or magnesium complexes. We have studied the rac-alanine ( + H3NCH(CH3)COO -, Hala) system in more detail and found that the complex that is present in the mixture has the

  15. Mixing and mingling in the evolution of andesite dacite magmas; evidence from co-magmatic plutonic enclaves, Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Cole, J. W.; Gamble, J. A.; Burt, R. M.; Carroll, L. D.; Shelley, D.

    2001-10-01

    The southeastern side of the Taupo Volcanic Zone, New Zealand is marked by a line of andesite/dacite/low-silica rhyolite complexes. Co-magmatic plutonic enclaves occur within the lavas of the four youngest complexes: White Island, Motuhora (Whale Island), Edgecumbe and Tauhara. The enclaves range from coarse-grained gabbros, diorites, granodiorites and a syenite to finer-grained dolerites and microdiorites. The more mafic types are generally porphyritic with large phenocrysts of plagioclase, usually with extensive sieve textures in the cores and corroded margins. Most of these enclaves, including the coarser-grained plutonic examples, contain glass and many are miarolitic. Diorites and microdiorites/dolerites predominate at White Island, Motuhora and Edgecumbe; many are porphyritic. Enclaves at Tauhara are more variable; those collected from Hipaua Dome include a range from microdiorites to quartz microdiorites and those from Rubbish Tip Dome include microdiorites, a granodiorite, and a syenite. Most enclaves show textural evidence for disequilibrium with multiple populations of plagioclase and pyroxene. They also show considerable textural variation, even within a thin section, with coarse-grained gabbros/diorites intimately mixed with finer-grained dolerites/microdiorites. Geochemically and isotopically, most enclaves have a similar composition with their host lavas, although some have lower silica contents. Enclaves at Motuhora and Tauhara are isotopically more variable, indicating multiple sources and a more complex petrogenesis. Most diorite/microdiorite enclaves are interpreted to represent parts of a crystal mush formed during fractionation of andesite/dacite magma, and entrained during later rise of magma to the surface. The granodiorite from Rubbish Tip Dome, Tauhara, probably represents part of a silicic magma chamber within the crust that fed the host low-silica rhyolite lava dome. Variability within the enclaves indicates the complexity likely to occur

  16. Characterising volcanic activity of Piton de la Fournaise volcano by the spatial distribution of seismic velocity changes

    NASA Astrophysics Data System (ADS)

    Sens-Schoenfelder, C.; Pomponi, E.

    2013-12-01

    We apply Passive Image Interferometry to investigate the seismic noise recorded from October 2009 until December 2011 by 21 stations of the IPGP/OVPF seismic network installed on Piton de la Fournaise volcano within the UnderVolc project. The analyzed period contains three eruptions in 2009 and January 2010, two eruptions plus one dyke intrusion in late 2010, and a seismic crises in 2011. Seismic noise of vertical and horizontal components is cross-correlated to measure velocity changes as apparent stretching of the coda. For some station pairs the apparent velocity changes exceed 1% and a decorrelation of waveforms is observed at the time of volcanic activity. This distorts monitoring results if changes are measured with respect to a global reference. To overcome this we present a method to estimate changes using multiple references that stabilizes the quality of estimated velocity changes. We observe abrupt changes that occur coincident with volcanic events as well as long term transient signals. Using a simple assumption about the spatial sensitivity of our measurements we can map the spatial distribution of velocity changes for selected periods. Comparing these signals with volcanic activity and GPS derived surface deformation we can identify patterns of the velocity changes that appear characteristic for the type of volcanic activity. We can differentiate intrusive processes associated with inflation and increased seismic activity, periods of relaxation without seismicity and eruptions solely based on the velocity signal. This information can help to assess the processes acting in the volcano.

  17. Autonomous Sensorweb Operations for Integrated Space, In-Situ Monitoring of Volcanic Activity

    NASA Technical Reports Server (NTRS)

    Chien, Steve A.; Doubleday, Joshua; Kedar, Sharon; Davies, Ashley G.; Lahusen, Richard; Song, Wenzhan; Shirazi, Behrooz; Mandl, Daniel; Frye, Stuart

    2010-01-01

    We have deployed and demonstrated operations of an integrated space in-situ sensorweb for monitoring volcanic activity. This sensorweb includes a network of ground sensors deployed to the Mount Saint Helens volcano as well as the Earth Observing One spacecraft. The ground operations and space operations are interlinked in that ground-based intelligent event detections can cause the space segment to acquire additional data via observation requests and space-based data acquisitions (thermal imagery) can trigger reconfigurations of the ground network to allocate increased bandwidth to areas of the network best situated to observe the activity. The space-based operations are enabled by an automated mission planning and tasking capability which utilizes several Opengeospatial Consortium (OGC) Sensorweb Enablement (SWE) standards which enable acquiring data, alerts, and tasking using web services. The ground-based segment also supports similar protocols to enable seamless tasking and data delivery. The space-based segment also supports onboard development of data products (thermal summary images indicating areas of activity, quicklook context images, and thermal activity alerts). These onboard developed products have reduced data volume (compared to the complete images) which enables them to be transmitted to the ground more rapidly in engineering channels.

  18. Unraveling the lipolytic activity of thermophilic bacteria isolated from a volcanic environment.

    PubMed

    Stathopoulou, Panagiota M; Savvides, Alexander L; Karagouni, Amalia D; Hatzinikolaou, Dimitris G

    2013-01-01

    In a bioprospecting effort towards novel thermostable lipases, we assessed the lipolytic profile of 101 bacterial strains isolated from the volcanic area of Santorini, Aegean Sea, Greece. Screening of lipase activity was performed both in agar plates and liquid cultures using olive oil as carbon source. Significant differences were observed between the two screening methods with no clear correlation between them. While the percentage of lipase producing strains identified in agar plates was only 17%, lipolytic activity in liquid culture supernatants was detected for 74% of them. Nine strains exhibiting elevated extracellular lipase activities were selected for lipase production and biochemical characterization. The majority of lipase producers revealed high phylogenetic similarity with Geobacillus species and related genera, whilst one of them was identified as Aneurinibacillus sp. Lipase biosynthesis strongly depended on the carbon source that supplemented the culture medium. Olive oil induced lipase production in all strains, but maximum enzyme yields for some of the strains were also obtained with Tween-80, mineral oil, and glycerol. Partially purified lipases revealed optimal activity at 70-80°C and pH 8-9. Extensive thermal stability studies revealed marked thermostability for the majority of the lipases as well as a two-step thermal deactivation pattern.

  19. Unraveling the lipolytic activity of thermophilic bacteria isolated from a volcanic environment.

    PubMed

    Stathopoulou, Panagiota M; Savvides, Alexander L; Karagouni, Amalia D; Hatzinikolaou, Dimitris G

    2013-01-01

    In a bioprospecting effort towards novel thermostable lipases, we assessed the lipolytic profile of 101 bacterial strains isolated from the volcanic area of Santorini, Aegean Sea, Greece. Screening of lipase activity was performed both in agar plates and liquid cultures using olive oil as carbon source. Significant differences were observed between the two screening methods with no clear correlation between them. While the percentage of lipase producing strains identified in agar plates was only 17%, lipolytic activity in liquid culture supernatants was detected for 74% of them. Nine strains exhibiting elevated extracellular lipase activities were selected for lipase production and biochemical characterization. The majority of lipase producers revealed high phylogenetic similarity with Geobacillus species and related genera, whilst one of them was identified as Aneurinibacillus sp. Lipase biosynthesis strongly depended on the carbon source that supplemented the culture medium. Olive oil induced lipase production in all strains, but maximum enzyme yields for some of the strains were also obtained with Tween-80, mineral oil, and glycerol. Partially purified lipases revealed optimal activity at 70-80°C and pH 8-9. Extensive thermal stability studies revealed marked thermostability for the majority of the lipases as well as a two-step thermal deactivation pattern. PMID:23738330

  20. Quantitative Modeling of Volcanic SO2: Integrated Monitoring of Precursory Activity

    NASA Astrophysics Data System (ADS)

    Reath, K. A.; Watson, M.; Ramsey, M. S.

    2015-12-01

    Many volcanoes produce some level of precursory activity prior to a large eruption. However, this activity may only be detected depending on the available monitoring system in place. In certain cases, precursors can be interpreted to make forecasts about the timing and magnitude of the impending eruption. Furthermore, changes in this activity are used to determine the style of the eruption provided the mechanics producing these precursory signals are properly understood. One important precursory measurement is the rate of volcanic gas exsolution. In particular CO2 and SO2 are measured to predict changes in the magma depth as well as its composition. Another important precursory measurement is the thermal flux discharged from summit vents. For example, three precursory periods at Kliuchevskoi volcano in 2005, 2007, and 2009 were studied using thermal infrared (TIR) satellite data obtained from both the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Advanced Very High Resolution Radiometer (AVHRR) sensors. TIR data is also sensitive to the spectral absorbance of volcanogenic SO2. Software to detect and model SO2 flux has now been applied to previously-acquired ASTER data of these three eruptions at Kliuchevskoi. By directly comparing the measured thermal flux and the modelled SO2 flux during the precursory period, the mechanisms leading to the larger eruption are better resolved. Applying these same techniques to future precursory activity would allow the type and duration until onset of the impending eruption to be better predicted in the precursory phase.

  1. Volcanic Risk Perception and Preparedness in Communities within the Mount Baker and Glacier Peak Lahar Hazard Zones

    NASA Astrophysics Data System (ADS)

    Corwin, K.; Brand, B. D.

    2014-12-01

    A community's ability to effectively respond to and recover from natural hazards depends on both the physical characteristics of the hazard and the community's inherent resilience. Resilience is shaped by a number of factors including the residents' perception of and preparedness for a natural hazard as well as the level of institutional preparedness. This study examines perception of and preparedness for lahar hazards from Mount Baker and Glacier Peak in Washington's Skagit Valley. Through an online survey, this study isolates the influence of specific variables (e.g., knowledge, past experience, scientific background, trust in various information sources, occupation, self-efficacy, sense of community) on risk perception and explores reasons behind the frequent disconnect between perception and preparedness. We anticipate that individuals with more extensive education in the sciences, especially geology or earth science, foster greater trust in scientists and a more accurate knowledge, understanding, and perception of the volcanic hazards in their community. Additionally, little research exists examining the extent to which first responders and leaders in response-related institutions prepare on a personal level. Since these individuals work toward community preparedness professionally, we hypothesize that they will be more prepared at home than members of the general public. Finally, the Skagit Valley has a significant history of flooding. We expect that the need to respond to and recover from frequent flooding creates a community with an inherently higher level of preparedness for other hazards such as lahars. The results of this study will contribute to the understanding of what controls risk perception and the interplay between perception and preparedness. At a broader level, this study provides local and state-level emergency managers information to evaluate and improve response capabilities and communication with the public and key institutions in order to

  2. Water-quality effects on Baker Lake of recent volcanic activity at Mount Baker, Washington

    USGS Publications Warehouse

    Bortleson, Gilbert Carl; Wilson, Reed T.; Foxworthy, B.L.

    1976-01-01

    Increased volcanic activity on Mount Baker, which began in March 1975, represents the greatest known activity of a Cascade Range volcano since eruptions at Lassen Peak, Calif. during 1914-17. Emissions of dust and increased emanations of steam, other gases, and heat from the Sherman Crater area of the mountain focused attention on the possibility of hazardous events, including lava flows, pyroclastic eruptions, avalanches, and mudflows. However, the greatest undesirable natural results that have been observed after one year of the increased activity are an increase in local atmospheric pollution and a decrease in the quality of some local water resources, including Baker Lake. Baker Lake, a hydropower reservoir behind Upper Baker Dam, supports a valuable fishery resource and also is used for recreation. The lake's feedwater is from Baker River and many smaller streams, some of which, like Boulder Creek, drain parts of Mount Baker. Boulder Creek receives water from Sherman Crater, and its channel is a likely route for avalanches or mudflows that might originate in the crater area. Boulder Creek drains only about 5 percent of the total drainage area of Baker Lake, but during 1975 carried sizeable but variable loads of acid and dissolved minerals into the lake. Sulfurous gases and the fumarole dust from Sherman Crater are the main sources for these materials, which are brought into upper Boulder Creek by meltwater from the crater. In September 1973, before the increased volcanic activity, Boulder Creek near the lake had a pH of 6.0-6.6; after the increase the pH ranged as low as about 3.5. Most nearby streams had pH values near 7. On April 29, in Boulder Creek the dissolved sulfate concentration was 6 to 29 times greater than in nearby creeks or in Baker River; total iron was 18-53 times greater than in nearby creeks; and other major dissolved constituents generally 2 to 7 times greater than in the other streams. The short-term effects on Baker Lake of the acidic

  3. The petrology of Paleogene volcanism in the Central Sakarya, Nallıhan Region: Implications for the initiation and evolution of post-collisional, slab break-off-related magmatic activity

    NASA Astrophysics Data System (ADS)

    Kasapoğlu, Bülent; Ersoy, Yalçın E.; Uysal, İbrahim; Palmer, Martin R.; Zack, Thomas; Koralay, Ersin O.; Karlsson, Andreas

    2016-03-01

    Zircon ages, mineral chemistry, whole-rock major and trace element compositions, as well as Sr-Nd isotopic ratios of basaltic (basanite, basalt, and hawaiite with MgO = 3.90-10.06 and SiO2 = 43.18-48.16) to andesitic (SiO2 = 50.86-61.27) and rhyolitic (SiO2 = 71.11-71.13) volcanic rocks (E-W emplaced Nallıhan volcanics) in the Lower Eocene terrestrial sedimentary units in the Central Sakarya Zone were studied and compared with those of the northerly located E-W-trending Eocene volcanic rocks (the Kızderbent Volcanics with 52.7-38.1 Ma radiometric ages) that are thought to be related to slab break-off process following the continental collision in the NW Anatolia. Zircon U-Pb ages of the Nallıhan volcanics vary from 51.7 ± 4.7 to 47.8 ± 2.4 Ma. Clinopyroxene from the basaltic and andesitic rocks record crystallization conditions from ~ 7-8 kbars (~ 23 km) and ~ 1210 °C, to 4.5-1.5 kbars (~ 14-1.5 km) and 1110-1010 °C crystallization conditions, respectively. The olivine-bearing, high-MgO (up to 10 wt%) basaltic rocks of the Nallıhan volcanics have nepheline-normative and Na-alkaline compositions, while the andesitic to rhyolitic rocks show calc-alkaline affinity with mainly sodic character. This is the first time this type of volcanic rock has been described in this region. The initial Sr isotopic ratios of both basaltic and andesitic-rhyolitic samples from the Nallıhan volcanics are similar (~ 0.7040-0.7045), indicating that fractional crystallization processes were not accompanied by crustal contamination and that the magma chambers were likely stored within ophiolitic units. Trace element ratios suggest that the Nallıhan volcanics were derived from E-MORB- or OIB-like enriched mantle sources, while the Kızderbent volcanics had N-MORB-like depleted mantle sources. Both volcanic units were produced by partial melting of spinel-bearing (shallow) mantle sources that had undergone subduction-related enrichment processes, with the degree of enrichment having

  4. The Volcanic History of Mars and Influences on Carbon Outgassing

    NASA Astrophysics Data System (ADS)

    Bleacher, J. E.; Whelley, P.

    2015-12-01

    Exploration of Mars has revealed some of the most impressive volcanic landforms found throughout the solar system. Volatiles outgassed from volcanoes were likely to have strongly influenced atmospheric chemistry and affected the martian climate. On Earth the role of carbon involved in volcanic outgassing is strongly influenced by tectonic setting, with the greatest weight percent contributions coming from partial mantle melts associated with hot spot volcanism. Most martian volcanic centers appear to represent this style of volcanism. Thus, one important factor in understanding the martian carbon cycle through time is understanding this volatile's link to the planet's volcanic history. The identified volcanic constructs on Mars are not unlike those of the Earth suggesting similar magmatic and eruptive processes. However, the dimensions of many martian volcanic features are significantly larger. The distribution of volcanoes and volcanic deposits on Mars are not spatially or temporally uniform. Large volcanoes (> 100 km diameter) are spatially concentrated in volcanic provinces that likely represent focused upwellings or zones of crustal weakness that enabled magma ascension. Smaller (10s km diameters) volcanoes such as cones, low shields and fissures are often grouped into fields and their lava flows coalesce to produce low slope plains. In some cases plains lava fields are quite extensive with little to no evidence for the volcanic constructs. Although martian volcanism appears to have been dominated by effusive eruptions with likely contributions from passive degassing from the interior, explosive volcanic centers and deposits are known to exist. After the development of a martian crust the planet's volcanic style appears to have evolved from early explosive activity to effusive activity centered at major volcanoes to effusive distributed activity in fields. However, questions remain as to whether or not these styles significantly overlapped in time and if so

  5. Volcanic gas

    USGS Publications Warehouse

    McGee, Kenneth A.; Gerlach, Terrance M.

    1995-01-01

    In Roman mythology, Vulcan, the god of fire, was said to have made tools and weapons for the other gods in his workshop at Olympus. Throughout history, volcanoes have frequently been identified with Vulcan and other mythological figures. Scientists now know that the “smoke" from volcanoes, once attributed by poets to be from Vulcan’s forge, is actually volcanic gas naturally released from both active and many inactive volcanoes. The molten rock, or magma, that lies beneath volcanoes and fuels eruptions, contains abundant gases that are released to the surface before, during, and after eruptions. These gases range from relatively benign low-temperature steam to thick hot clouds of choking sulfurous fume jetting from the earth. Water vapor is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide. Other volcanic gases are hydrogen sulfide, hydrochloric acid, hydrogen, carbon monoxide, hydrofluoric acid, and other trace gases and volatile metals. The concentrations of these gas species can vary considerably from one volcano to the next.

  6. Recent Fluvial, Volcanic, and Tectonic Activity on the Cerberus Plains of Mars

    NASA Astrophysics Data System (ADS)

    Berman, Daniel C.; Hartmann, William K.

    2002-09-01

    Athabasca and Marte Valles lie on the Cerberus plains, between the young, lava-covered plains of Elysium Planitia and Amazonis Planitia. To test pre- MGS ( Mars Global Surveyor) suggestions of extremely young volcanic and fluvial activity, we present the first crater counts from MGS imagery, at resolutions (˜2-20 m/pixel) much higher than previously available. The most striking result, based on morphologic relations as well as crater counts from different stratigraphic units, is to confirm quantitatively that these channel systems are much younger than most other major outflow channels. The general region has an average model age for lava and fluvial surfaces of ≤200 Myr, and has possibly seen localized water releases, interspersed with lava flows, within the past 20 Myr. The youngest lavas may be no more than a few megayears old. Access of lava and liquid brines to the surface may be favored by openings of the Cerberus Fossae fracture system, but, as shown in the new images, the fractures appear to have continued developing more recently than the most recent lavas or fluvial activity. The Cerberus Fossae system may be an analog to an early stage of Valles Marineris, and its youthful activity raises questions about regional tectonic history. Large-volume water delivery to the surface of young lava flows in recent martian history puts significant boundary conditions on the storage and history of water on Mars.

  7. Terrestrial volcanism in space and time

    NASA Technical Reports Server (NTRS)

    Simkin, Tom

    1993-01-01

    A survey is presented of current volcanic activity around the world and of dated volcanism over the past 10,000 yrs. The patterns in the data are described. The hazard presented by volcanism is briefly examined.

  8. Methanotrophic activity and bacterial diversity in volcanic-geothermal soils at Pantelleria island (Italy)

    NASA Astrophysics Data System (ADS)

    Gagliano, A. L.; D'Alessandro, W.; Tagliavia, M.; Parello, F.; Quatrini, P.

    2014-04-01

    Volcanic and geothermal systems emit endogenous gases by widespread degassing from soils, including CH4, a greenhouse gas twenty-five times as potent as CO2. Recently, it has been demonstrated that volcanic/geothermal soils are source of methane, but also sites of methanotrophic activity. Methanotrophs are able to consume 10-40 Tg of CH4 a-1 and to trap more than 50% of the methane degassing through the soils. We report on methane microbial oxidation in the geothermally most active site of Pantelleria island (Italy), Favara Grande, whose total methane emission was previously estimated in about 2.5 t a-1. Laboratory incubation experiments with three top-soil samples from Favara Grande indicated methane consumption values up to 950 ng g-1 dry soil h-1. One of the three sites, FAV2, where the highest oxidation rate was detected, was further analysed on a vertical soil profile and the maximum methane consumption was measured in the top-soil layer but values > 100 ng g-1 h-1 were maintained up to a depth of 15 cm. The highest consumption rate was measured at 37 °C, but a still recognizable consumption at 80 °C (> 20 ng g-1 h-1) was recorded. In order to estimate the bacterial diversity, total soil DNA was extracted from Favara Grande and analysed using a Temporal Temperature Gradient gel Electrophoresis (TTGE) analysis of the amplified bacterial 16S rRNA gene. The three soil samples were probed by PCR using standard proteobacterial primers and newly designed verrucomicrobial primers targeting the unique methane monooxygenase gene pmoA; the presence of methanotrophs was detected in sites FAV2 and FAV3, but not in FAV1, where harsher chemical-physical conditions and negligible methane oxidation were detected. The pmoA gene libraries from the most active site FAV2 pointed out a high diversity of gammaproteobacterial methanotrophs distantly related to Methylococcus/Methylothermus genera and the presence of the newly discovered acido-thermophilic methanotrophs

  9. Methanotrophic activity and diversity of methanotrophs in volcanic geothermal soils at Pantelleria (Italy)

    NASA Astrophysics Data System (ADS)

    Gagliano, A. L.; D'Alessandro, W.; Tagliavia, M.; Parello, F.; Quatrini, P.

    2014-10-01

    Volcanic and geothermal systems emit endogenous gases by widespread degassing from soils, including CH4, a greenhouse gas twenty-five times as potent as CO2. Recently, it has been demonstrated that volcanic or geothermal soils are not only a source of methane, but are also sites of methanotrophic activity. Methanotrophs are able to consume 10-40 Tg of CH4 a-1 and to trap more than 50% of the methane degassing through the soils. We report on methane microbial oxidation in the geothermally most active site of Pantelleria (Italy), Favara Grande, whose total methane emission was previously estimated at about 2.5 Mg a-1 (t a-1). Laboratory incubation experiments with three top-soil samples from Favara Grande indicated methane consumption values of up to 59.2 nmol g-1 soil d.w. h-1. One of the three sites, FAV2, where the highest oxidation rate was detected, was further analysed on a vertical soil profile, the maximum methane consumption was measured in the top-soil layer, and values greater than 6.23 nmol g-1 h-1 were still detected up to a depth of 13 cm. The highest consumption rate was measured at 37 °C, but a still detectable consumption at 80 °C (> 1.25 nmol g-1 h-1) was recorded. The soil total DNA extracted from the three samples was probed by Polymerase Chain Reaction (PCR) using standard proteobacterial primers and newly designed verrucomicrobial primers, targeting the unique methane monooxygenase gene pmoA; the presence of methanotrophs was detected at sites FAV2 and FAV3, but not at FAV1, where harsher chemical-physical conditions and negligible methane oxidation were detected. The pmoA gene libraries from the most active site (FAV2) pointed to a high diversity of gammaproteobacterial methanotrophs, distantly related to Methylocaldum-Metylococcus genera, and the presence of the newly discovered acido-thermophilic Verrucomicrobia methanotrophs. Alphaproteobacteria of the genus Methylocystis were isolated from enrichment cultures under a methane

  10. Late Cenozoic volcanism, subduction, and extension in the Lassen region of California, southern Cascade Range

    USGS Publications Warehouse

    Guffanti, M.; Clynne, M.A.; Smith, James G.; Muffler, L.J.P.; Bullen, T.D.

    1990-01-01

    Some 537 volcanic vents younger than 7 Ma are identified and these are classified into five age intervals and five compositional categories based on SiO2 content. Maps of vents by age and composition illustrate regionally representative volcanic trends. By 2 Ma, the eastern limit of volcanism had contracted westward toward the late Quaternary arc. Late Quaternary volcanism is concentrated around and north of the silicic Lassen volcanic center. The belt of most recent volcanism (25-0 ka) has been active since at least 2 Ma. Most mafic volcanism is calcalkaline basalt and basaltic andesite. Normal faults and linear groups of vents are evidence of widespread crustal extension throughout most of the Lassen region. NNW orientation of maximum horizontal stress is indicated. The Lassen volcanic region is thought to occur above the subducting Gorda North plate but also within a broad zone of distributed extension that occurs in the North American lithosphere east and southeast of the present Cascadia subduction zone. The scarcity of volcanic rocks older than 7 Ma suggests that a more compressive lithospheric stress regime prior to the late Miocene extensional episode may have suppressed volcanism. -from Authors

  11. Influence of explosive volcanic events on the activation versus de-activation of a modern turbidite system: the example of the Dohrn canyon-fan in the continental slope of the Campania volcanic district (Naples Bay, Italy - Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Roca, M.; Budillon, F.; Pappone, G.; Insinga, D.

    2015-12-01

    The interplay between volcanic activity, volcano-clastic yield and activation/deactivation of a turbidite system can be evaluated along the continental margin of Campania region (Tyrrhenian Sea - Italy), an active volcanic area, where three wide canyon-fans occur at short distances one to another. Actually, the Dohrn, Magnaghi and Cuma canyons cut the continental slope and shelf off Ischia and Procida volcanic islands and off the Campania Plain where Phlegraean Field and Mt. Vesuvius active vents are located. This research, partly supported by the Italian Flagship Project Ritmare, is based on single-channel, high-resolution seismic profiles (Sparker-One 16 kJ, 0.5 s twtt), swath-bathymetry and litho- and tephra-stratigraphy of gravity cores. We focused on the stratigraphic constraint of paleo-thalweg features and channel/levees deposits in seismics, debris flow, turbidites and hemipelagites in cores, to learn more on the activation/deactivation stages of the canyon Dohrn, in the frame of relative eustatic sea level variations over the Middle Pleistocene-Holocene time span.Preliminary outcomes suggest that even major volcanic events occurred in the last 300 ky, such as ignimbrite eruptions or large fallouts, have caused the infilling of the canyon head and the cover of pre-existing seabed morphology. As a consequence, the temporary deactivation of the turbidite system has occurred, despite the volcano-clastic overload in the coastal environment. Phases of renewed activities of the thalweg are observed to be in step with falling stages of sea level, which have driven the re-incision of canyon valleys through continuous volcano-clastic debris and turbidites down-flows. Since Holocene, the quiescence of the Dohrn Canyon has been documented, despite the intense volcano-tectonic activity in the area.

  12. Acute health effects associated with exposure to volcanic air pollution (vog) from increased activity at Kilauea Volcano in 2008.

    PubMed

    Longo, Bernadette M; Yang, Wei; Green, Joshua B; Crosby, Frederick L; Crosby, Vickie L

    2010-01-01

    In 2008, the Kilauea Volcano on the island of Hawai'i increased eruption activity and emissions of sulfurous volcanic air pollution called vog. The purpose of this study was to promptly assess for a relative increase in cases of medically diagnosed acute illnesses in an exposed Hawaiian community. Using a within-clinic retrospective cohort design, comparisons were made for visits of acute illnesses during the 14 wk prior to the increased volcanic emissions (low exposure) to 14 wk of high vog exposure when ambient sulfur dioxide was threefold higher and averaged 75 parts per billion volume per day. Logistic regression analysis estimated effect measures between the low- and high-exposure cohorts for age, gender, race, and smoking status. There were statistically significant positive associations between high vog exposure and visits for medically diagnosed cough, headache, acute pharyngitis, and acute airway problems. More than a sixfold increase in odds was estimated for visits with acute airway problems, primarily experienced by young Pacific Islanders. These findings suggest that the elevated volcanic emissions in 2008 were associated with increased morbidity of acute illnesses in age and racial subgroups of the general Hawaiian population. Continued investigation is crucial to fully assess the health impact of this natural source of sulfurous air pollution. Culturally appropriate primary- and secondary-level health prevention initiatives are recommended for populations in Hawai'i and volcanically active areas worldwide. PMID:20818536

  13. California's Vulnerability to Volcanic Hazards: What's at Risk?

    NASA Astrophysics Data System (ADS)

    Mangan, M.; Wood, N. J.; Dinitz, L.

    2015-12-01

    California is a leader in comprehensive planning for devastating earthquakes, landslides, floods, and tsunamis. Far less attention, however, has focused on the potentially devastating impact of volcanic eruptions, despite the fact that they occur in the State about as frequently as the largest earthquakes on the San Andreas Fault Zone. At least 10 eruptions have occurred in the past 1,000 years—most recently in northern California (Lassen Peak 1914 to 1917)—and future volcanic eruptions are inevitable. The likelihood of renewed volcanism in California is about one in a few hundred to one in a few thousand annually. Eight young volcanoes, ranked as Moderate to Very High Threat [1] are dispersed throughout the State. Partially molten rock (magma) resides beneath at least seven of these—Medicine Lake Volcano, Mount Shasta, Lassen Volcanic Center, Clear Lake Volcanic Field, Long Valley Volcanic Region, Coso Volcanic Field, and Salton Buttes— causing earthquakes, toxic gas emissions, hydrothermal activity, and (or) ground deformation. Understanding the hazards and identifying what is at risk are the first steps in building community resilience to volcanic disasters. This study, prepared in collaboration with the State of California Governor's Office of Emergency Management and the California Geological Survey, provides a broad perspective on the State's exposure to volcano hazards by integrating mapped volcano hazard zones with geospatial data on at-risk populations, infrastructure, and resources. The study reveals that ~ 16 million acres fall within California's volcano hazard zones, along with ~ 190 thousand permanent and 22 million transitory populations. Additionally, far-field disruption to key water delivery systems, agriculture, utilities, and air traffic is likely. Further site- and sector-specific analyses will lead to improved hazard mitigation efforts and more effective disaster response and recovery. [1] "Volcanic Threat and Monitoring Capabilities

  14. Active volcanism beneath the West Antarctic ice sheet and implications for ice-sheet stability

    USGS Publications Warehouse

    Blankenship, D.D.; Bell, R.E.; Hodge, S.M.; Brozena, J.M.; Behrendt, John C.; Finn, C.A.

    1993-01-01

    IT is widely understood that the collapse of the West Antarctic ice sheet (WAIS) would cause a global sea level rise of 6 m, yet there continues to be considerable debate about the detailed response of this ice sheet to climate change1-3. Because its bed is grounded well below sea level, the stability of the WAIS may depend on geologically controlled conditions at the base which are independent of climate. In particular, heat supplied to the base of the ice sheet could increase basal melting and thereby trigger ice streaming, by providing the water for a lubricating basal layer of till on which ice streams are thought to slide4,5. Ice streams act to protect the reservoir of slowly moving inland ice from exposure to oceanic degradation, thus enhancing ice-sheet stability. Here we present aerogeophysical evidence for active volcanism and associated elevated heat flow beneath the WAIS near the critical region where ice streaming begins. If this heat flow is indeed controlling ice-stream formation, then penetration of ocean waters inland of the thin hot crust of the active portion of the West Antarctic rift system could lead to the disappearance of ice streams, and possibly trigger a collapse of the inland ice reservoir.

  15. Development of an automatic volcanic ash sampling apparatus for active volcanoes

    NASA Astrophysics Data System (ADS)

    Shimano, Taketo; Nishimura, Takeshi; Chiga, Nobuyuki; Shibasaki, Yoshinobu; Iguchi, Masato; Miki, Daisuke; Yokoo, Akihiko

    2013-12-01

    We develop an automatic system for the sampling of ash fall particles, to be used for continuous monitoring of magma ascent and eruptive dynamics at active volcanoes. The system consists of a sampling apparatus and cameras to monitor surface phenomena during eruptions. The Sampling Apparatus for Time Series Unmanned Monitoring of Ash (SATSUMA-I and SATSUMA-II) is less than 10 kg in weight and works automatically for more than a month with a 10-kg lead battery to obtain a total of 30 to 36 samples in one cycle of operation. The time range covered in one cycle varies from less than an hour to several months, depending on the aims of observation, allowing researchers to target minute-scale fluctuations in a single eruptive event, as well as daily to weekly trends in persistent volcanic activity. The latest version, SATSUMA-II, also enables control of sampling parameters remotely by e-mail commands. Durability of the apparatus is high: our prototypes worked for several months, in rainy and typhoon seasons, at windy and humid locations, and under strong sunlight. We have been successful in collecting ash samples emitted from Showa crater almost everyday for more than 4 years (2008-2012) at Sakurajima volcano in southwest Japan.

  16. Aerogeophysical evidence for active volcanism beneath the West Antarctic Ice Sheet

    NASA Technical Reports Server (NTRS)

    Blankenship, Donald D.; Bell, Robin E.; Hodge, Steven M.; Brozena, John M.; Behrendt, John C.

    1993-01-01

    Although it is widely understood that the collapse of the West Antarctic Ice Sheet (WAIS) would cause a global sea-level rise of 6 m, there continues to be considerable debate about the response of this ice sheet to climate change. The stability of the WAIS, which is characterized by a bed grounded well below sea level, may depend on geologically controlled conditions at the base, which are independent of climate. Ice streams moving up to 750 m/yr disperse material from the interior through to the oceans. As these ice streams tend to buffer the reservoir of slow-moving inland ice from exposure to oceanic degradation, understanding the ice-streaming process is important for evaluating WAIS stability. There is strong evidence that ice streams slide on a lubricating layer of water-saturated till. Development of this basal layer requires both water and easily eroded sediments. Active lithospheric extension may elevate regional heat flux, increase basal melting, and trigger ice streaming. If a geologically defined boundary with a sharp contrast in geothermal flux exists beneath the WAIS, ice streams may only be capable of operating as a buffer over a restricted region. Should ocean waters penetrate beyond this boundary, the ice-stream buffer would disappear, possibly triggering a collapse of the inland ice reservoir. Aerogeophysical evidence for active volcanism and elevated heat flux beneath the WAIS near the critical region where ice streaming begins is presented.

  17. Volcanic activity and satellite-detected thermal anomalies at Central American volcanoes

    NASA Technical Reports Server (NTRS)

    Stoiber, R. E. (Principal Investigator); Rose, W. I., Jr.

    1973-01-01

    The author has identified the following significant results. A large nuee ardente eruption occurred at Santiaguito volcano, within the test area on 16 September 1973. Through a system of local observers, the eruption has been described, reported to the international scientific community, extent of affected area mapped, and the new ash sampled. A more extensive report on this event will be prepared. The eruption is an excellent example of the kind of volcanic situation in which satellite thermal imagery might be useful. The Santiaguito dome is a complex mass with a whole series of historically active vents. It's location makes access difficult, yet its activity is of great concern to large agricultural populations who live downslope. Santiaguito has produced a number of large eruptions with little apparent warning. In the earlier ground survey large thermal anomalies were identified at Santiaguito. There is no way of knowing whether satellite monitoring could have detected changes in thermal anomaly patterns related to this recent event, but the position of thermal anomalies on Santiaguito and any changes in their character would be relevant information.

  18. Stress fields of the overriding plate at convergent margins and beneath active volcanic arcs.

    PubMed

    Apperson, K D

    1991-11-01

    Tectonic stress fields in the overriding plate at convergent plate margins are complex and vary on local to regional scales. Volcanic arcs are a common element of overriding plates. Stress fields in the volcanic arc region are related to deformation generated by subduction and to magma generation and ascent processes. Analysis of moment tensors of shallow and intermediate depth earthquakes in volcanic arcs indicates that the seismic strain field in the arc region of many convergent margins is subhorizontal extension oriented nearly perpendicular to the arc. A process capable of generating such a globally consistent strain field is induced asthenospheric corner flow below the arc region. PMID:17774792

  19. Hydrogeology of the Valles Marineris-Chaotic Terrain Transition Zone, Mars

    NASA Astrophysics Data System (ADS)

    Komatsu, G.; Rossi, A. P.; di Lorenzo, S.

    2004-03-01

    The Valles Marineris-chaotic terrain transition zone on Mars is rich in landforms indicative of past water and volcanic activities. Complex interactions of such activities are represented by features at Gangis Chasma and its surroundings.

  20. Temperature and pH control on lipid composition of silica sinters from diverse hot springs in the Taupo Volcanic Zone, New Zealand.

    PubMed

    Kaur, Gurpreet; Mountain, Bruce W; Stott, Matthew B; Hopmans, Ellen C; Pancost, Richard D

    2015-03-01

    Microbial adaptations to environmental extremes, including high temperature and low pH conditions typical of geothermal settings, are of interest in astrobiology and origin of life investigations. The lipid biomarkers preserved in silica deposits associated with six geothermal areas in the Taupo Volcanic Zone were investigated and variations in lipid composition as a function of temperature and pH were assessed. Lipid analyses reveal highly variable abundances and distributions, reflecting community composition as well as adaptations to extremes of pH and temperature. Biomarker profiles reveal three distinct microbial assemblages across the sites: the first in Champagne Pool and Loop Road, the second in Orakei Korako, Opaheke and Ngatamariki, and the third in Rotokawa. Similar lipid distributions are observed in sinters from physicochemically similar springs. Furthermore, correlation between lipid distributions and geothermal conditions is observed. The ratio of archaeol to bacterial diether abundance, bacterial diether average chain length, degree of GDGT cyclisation and C31 and C32 hopanoic acid indices typically increase with temperature. At lower pH, the ratio of archaeol to bacterial diethers, degree of GDGT cyclisation and C31 and C32 hopanoic acid indices are typically higher. No trends in fatty acid distributions with temperature or pH are evident, likely reflecting overprinting due to population influences.

  1. Depth to Curie temperature or bottom of the magnetic sources in the volcanic zone of la Réunion hot spot

    NASA Astrophysics Data System (ADS)

    Gailler, Lydie-Sarah; Lénat, Jean-François; Blakely, Richard J.

    2016-09-01

    We present an innovative study to generalize Curie Point Depth (CPD) determinations at the scale of oceanic volcanic islands, an approach which has previously focused largely on continental areas. In order to determine the validity of this technique in oceanic environments, we first tested the approach on sets of sea-floor-spreading anomalies. Assuming that magnetic anomalies are concentrated within the oceanic crust and uppermost mantle, the Curie depth should deepen as oceanic lithosphere increases in age and thickness away from spreading centers. The calculated depths to the magnetic bottom are in agreement with this general pattern. On the basis of this test, we then applied the method to La Réunion Island and surrounding oceanic lithosphere. The calculated extent of magnetic sources lies at depths between 10 and 30 km and exhibits a complex topography, presumably caused by a combination of various magmatic and tectonic lithospheric structures. These calculations indicate that magnetic sources extend well below the crust-mantle interface at this location. To the first order, the bottom of the magnetic surface shallows beneath Réunion and Mauritius Islands due to the thermal effect of the hot spot, and deepens away from La Réunion edifice. On the scale of the Mascarene Basin, several discontinuities in the CPD correlate well with major fracture zones.

  2. Altiplano-Puna volcanic complex of the central Andes

    NASA Technical Reports Server (NTRS)

    De Silva, S. L.

    1989-01-01

    A model is presented accounting for many features of the Altiplano-Puna volcanic complex situated in the Central Volcanic Zone of the Andes which contains 50 recently active volcanoes. The dominant elements of the complex are several large nested caldera complexes which are the source structures for the major regionally distributed ignimbrite sheets that characterize the complex. The study of the complex reveals the importance of the intersection of subsidiary axis-oblique tectonic trends related to regional stress fields peculiar to individual oceanic ridge sections with the axis-parallel trends predominant at all spreading centers in localizing hydrothermal discharge zones.

  3. Lateral Dispersion of Volcanic Ash From the Flanks of an Actively Erupting Submarine Volcano

    NASA Astrophysics Data System (ADS)

    Walker, S. L.; Baker, E. T.; Resing, J. A.; Lebon, G. T.; Lupton, J. E.; Greene, R. R.

    2006-12-01

    NW Rota-1 is an actively erupting submarine volcano along the Mariana Arc, rising some 2500 m from the local seafloor. Eruptions at Brimstone Pit, located about 30 m below the summit on the south side of the volcano at 550 m water depth, have been directly observed since 2004. Water column surveys (using CTD-O vertical cast and tow methods) in 2003, 2004 and 2006 mapped the distribution of both persistent and variable particle plumes over the summit and down the flanks. In all years, there was a non-buoyant laterally dispersing plume over the summit that was optically intense and very thin (25-30 m plume maximum), measurable up to 2-3 km from the summit. The plume was most intense in 2003 and 2004 with dNTU values reaching 5 (the upper limit of the optical backscatter sensor). High concentrations of particulate sulfur in the plume contribute to these unusually intense optical signals, as sulfur particles are efficient optical backscatters. The plume maxima depth has steadily declined over 3 years: 460 m in 2003, 485 m in 2004, and 505-530 m in 2006. In 2003, both hydrothermal and volcanic components were detected in the plume, so it is not certain that the 2003 data represent pre-eruption conditions. Deeper layers of turbidity were absent in 2003, but were observed in multiple layers surrounding the volcano in 2004 and 2006 from depths of about 700 m extending to >2500 m, and were detectable at distances up to 18 km from the summit. Microscopy and chemical analysis indicates that the particles in these layers are overwhelmingly glass fragments rather than hydrothermal precipitates. Over the scale of 3-6 days, repeat tows showed significant decreases in particle concentrations, implying some of the particles settled rapidly from these plumes. The most likely source of these layers is gravity flow of volcanic ash down the flanks, fed by violent eruptions at the summit. Detachment from the seafloor may be controlled by turbulence from current flow or internal waves

  4. Subduction and volcanism in the Iberia-North Africa collision zone from tomographic images of the upper mantle

    NASA Astrophysics Data System (ADS)

    Villaseñor, Antonio; Chevrot, Sébastien; Harnafi, Mimoun; Gallart, Josep; Pazos, Antonio; Serrano, Inmaculada; Córdoba, Diego; Pulgar, Javier A.; Ibarra, Pedro

    2015-11-01

    New tomographic images of the upper mantle beneath the westernmost Mediterranean suggest that the evolution of the region experienced two subduction-related episodes. First subduction of oceanic and/or extended continental lithosphere, now located mainly beneath the Betics at depths greater than 400 km, took place on a NW-SE oriented subduction zone. This was followed by a slab-tear process that initiated in the east and propagated to the west, leading to westward slab rollback and possibly lower crustal delamination. The current position of the slab tear is located approximately at 4°W, and to the west of this location the subducted lithosphere is still attached to the surface along the Gibraltar Arc. Our new P-wave velocity model is able to image the attached subducted lithosphere as a narrow high-velocity body extending to shallow depths, coinciding with the region of maximum curvature of the Gibraltar Arc, the occurrence of intermediate-depth earthquakes, and anomalously thick crust. This thick crust has a large influence in the measured teleseismic travel time residuals and therefore in the obtained P-wave tomographic model. We show that removing the effects of the thick crust significantly improves the shallow images of the slab and therefore the interpretations based on the seismic structure.

  5. 2012 volcanic activity in Alaska: summary of events and response of the Alaska Volcano Observatory

    USGS Publications Warehouse

    Herrick, Julie A.; Neal, Christina A.; Cameron, Cheryl E.; Dixon, James P.; McGimsey, Robert G.

    2014-01-01

    The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, volcanic unrest, or suspected unrest at 11 volcanic centers in Alaska during 2012. Of the two verified eruptions, one (Cleveland) was clearly magmatic and the other (Kanaga) was most likely a single phreatic explosion. Two other volcanoes had notable seismic swarms that probably were caused by magmatic intrusions (Iliamna and Little Sitkin). For each period of clear volcanic unrest, AVO staff increased monitoring vigilance as needed, reviewed eruptive histories of the volcanoes in question to help evaluate likely outcomes, and shared observations and interpretations with the public. 2012 also was the 100th anniversary of Alaska’s Katmai-Novarupta eruption of 1912, the largest eruption on Earth in the 20th century and one of the most important volcanic eruptions in modern times. AVO marked this occasion with several public events.

  6. Experimental petrology applied to volcanic processes

    NASA Astrophysics Data System (ADS)

    Rutherford, Malcolm J.

    Interest in volcanism has been stimulated by recent eruptions at Mount St. Helens, Kilauea, Pinatubo, and in the Aleutians, and by intrusive activity in Long Valley, Calif. The improved scientific understanding of magma systems and volcanic processes that has developed from theoretical modeling and field and analytical studies of these and other volcanic centers has been complemented by recent results from experimental petrology. The experiments make it possible to determine the conditions (for example, pressure [P], temperature [T], oxidation state [fO2], and the volatile content [fH2O, fCO2]) of the pre-eruption magma. This information provides an estimate of the magma storage region depth, the potential role of volatiles in the eruption process, and compositional zoning in the subvolcanic magma.

  7. Soft-sediment deformation in New Zealand: Structures resulting from the 2010/11 Christchurch earthquakes and comparison with Pleistocene sediments of the Taupo Volcanic Zone (TVZ)

    NASA Astrophysics Data System (ADS)

    Scholz, C.; Downs, D. T.; Gravley, D.; Quigley, M.; Rowland, J. V.

    2011-12-01

    The distinction between seismites and other event-related soft-sediment deformation is a challenging problem. Recognition and interpretation is aided by comparison of recent examples produced during known seismic events and those generated experimentally. Seismites are important features, once recognized in a rock, for interpretations of paleotectonic environment, tectonic relationships of sediments in basins, sedimentary facies analysis, evaluation of earthquake frequency and hazard and consequent land managment. Two examples of soft-sediment deformation, potentially generated through ground shaking and associated liquefaction, are described from within the TVZ: 1) Near Matata on the western margin of the Whakatane Graben. This location has a complicated en-echelon fault history and large earthquakes occur from time to time (e.g., 1987 ML6.3 Edgecumbe event). The structures occur in ~550 ka volcanic sediments, and represent soft-sediment deformation within stratigraphically-bounded layers. Based on paleoenvironment, appearance, and diagnostic criteria described by other authors (Sims 1975; Hempton and Dewey 1983), we interpret these features to have formed by ground shaking related to an earthquake and/or possibly accompanying large volcanic eruptions, rather than by slope failure. 2) Near Taupo, 3 km from the active Kaiapo fault. Lakeward dipping, nearly horizontal lacustrine sediments overlay Taupo Ignimbrite (1.8 ka). At one outcrop the lake beds have subsided into the underlying substrate resulting in kidney-shaped features. These structures formed as a result of liquefaction of the underlying substrate, which may have been caused by ground shaking related to either seismic or volcanic activity. However, inferred time relationships are more consistent with seismic-induced ground shaking. We compare and contrast the form and geometry of the above structures with seismites generated during the recent Christchurch earthquakes (Sep. 2010 and Feb. 2011). Hempton, M

  8. The South Tibetan Tadpole Zone: Ongoing density sorting at the Moho beneath the Indus-Tsangpo suture zone (and beneath volcanic arcs?)

    NASA Astrophysics Data System (ADS)

    Kelemen, Peter; Hacker, Bradley

    2016-04-01

    at less than 700°C (e.g. Jackson 02). We build on earlier studies (LePichon et al 92, 97; Schulte-Pelkum et al 05; Monsalve et al 08) to develop the hypothesis that there is rapid growth of garnet at 80 km and 1000°C within subducting Indian crust, causing increased rock densities. Dense eclogites founder into the mantle, while relatively buoyant lithologies accumulate in thickening lower crust. Mantle return flow plus radioactive heating in thick, felsic crust maintains high temperature, facilitating formation of hybrid magmas and pyroxenites. The crustal volume grows at 760 cubic m/yr/m of strike length. Moho-depth earthquakes may be due to localized deformation and thermal runaway in weak layers and along the margins of dense, foundering diapirs (e.g., Larsen & Yuen 97; Braeck & Podladchikov 07; Kelemen & Hirth 07; Lister et al 08; Kufner et al 16). A similar process may take place at some convergent margins, where forearc crust is thrust beneath hot, magmatic arc crust, leading to extensive, Moho-depth density sorting and hybrid crust-mantle magmatism in Arc Tadpole Zones.

  9. The interplay between deformation and volcanic activity: new data from the central sector of the Campi Flegrei caldera

    NASA Astrophysics Data System (ADS)

    Isaia, Roberto; Sabatino, Ciarcia; Enrico, Iannuzzi; Ernesto, Prinzi; D'Assisi, Tramparulo Francesco; Stefano, Vitale

    2016-04-01

    The new excavation of a tunnel in the central sector of the Campi Flegrei caldera allowed us to collect new stratigraphic and structural data shedding light on the volcano-tectonic evolution of the last 10 ka. The analyzed sequences are composed by an alternation of volcanic, lacustrine, fluvial and marine sediments hosting several deformation structures such as faults, sedimentary dykes and fractures. A review of available well log togheter with the new data were used to perform a 3D reconstruction of paleo-surfaces resulted after the main volcanic and deformation episodes. Results show as the paleo-morphology was strictly controlled by faults and fractures that formed meso-scale channels and depressions subsequently filled by tephra and volcanoclastic sediments. The measured structures indicate an extensional deformation accompanying the ground uplift occurred in various stages of the caldera evolution. Stratigraphic relationships between structures and volcanic deposits further constrain the timing of the deformation phases. Presently an unrest phase of the Campi Flegrei caldera is marked by variations of different parameters such as ground deformation activities well recorded by GPS data, topographic leveling and satellite surveys. The results of this study provide further insight into the long term deformation pattern of the caldera and provide a key to interpret the ground deformation scenarios accompanying a possible resumption of volcanism.

  10. Complex explosive volcanic activity on the Moon within Oppenheimer crater, Icarus

    USGS Publications Warehouse

    Bennett, Kristen A; Horgan, Briony H N; Gaddis, Lisa R.; Greenhagen, Benjamin T; Allen, Carlton C.; Hayne, Paul O; Bell, James F III; Paige, David A.

    2016-01-01

    Oppenheimer Crater is a floor-fractured crater located within the South Pole-Aitken basin on the Moon, and exhibits more than a dozen localized pyroclastic deposits associated with the fractures. Localized pyroclastic volcanism on the Moon is thought to form as a result of intermittently explosive Vulcanian eruptions under low effusion rates, in contrast to the higher-effusion rate, Hawaiian-style fire fountaining inferred to form larger regional deposits. We use Lunar Reconnaissance Orbiter Camera images and Diviner Radiometer mid-infrared data, Chandrayaan-1 orbiter Moon Mineralogy Mapper near-infrared spectra, and Clementine orbiter Ultraviolet/Visible camera images to test the hypothesis that the pyroclastic deposits in Oppenheimer crater were emplaced via Vulcanian activity by constraining their composition and mineralogy. Mineralogically, we find that the deposits are variable mixtures of orthopyroxene and minor clinopyroxene sourced from the crater floor, juvenile clinopyroxene, and juvenile iron-rich glass, and that the mineralogy of the pyroclastics varies both across the Oppenheimer deposits as a whole and within individual deposits. We observe similar variability in the inferred iron content of pyroclastic glasses, and note in particular that the northwest deposit, associated with Oppenheimer U crater, contains the most iron-rich volcanic glass thus far identified on the Moon, which could be a useful future resource. We propose that this variability in mineralogy indicates variability in eruption style, and that it cannot be explained by a simple Vulcanian eruption. A Vulcanian eruption should cause significant country rock to be incorporated into the pyroclastic deposit; however, large areas within many of the deposits exhibit spectra consistent with high abundances of juvenile phases and very little floor material. Thus, we propose that at least the most recent portion of these deposits must have erupted via a Strombolian or more continuous fire

  11. Integrating science and education during an international, multi-parametric investigation of volcanic activity at Santiaguito volcano, Guatemala

    NASA Astrophysics Data System (ADS)

    Lavallée, Yan; Johnson, Jeffrey; Andrews, Benjamin; Wolf, Rudiger; Rose, William; Chigna, Gustavo; Pineda, Armand

    2016-04-01

    In January 2016, we held the first scientific/educational Workshops on Volcanoes (WoV). The workshop took place at Santiaguito volcano - the most active volcano in Guatemala. 69 international scientists of all ages participated in this intensive, multi-parametric investigation of the volcanic activity, which included the deployment of seismometers, tiltmeters, infrasound microphones and mini-DOAS as well as optical, thermographic, UV and FTIR cameras around the active vent. These instruments recorded volcanic activity in concert over a period of 3 to 9 days. Here we review the research activities and present some of the spectacular observations made through this interdisciplinary efforts. Observations range from high-resolution drone and IR footage of explosions, monitoring of rock falls and quantification of the erupted mass of different gases and ash, as well as morphological changes in the dome caused by recurring explosions (amongst many other volcanic processes). We will discuss the success of such integrative ventures in furthering science frontiers and developing the next generation of geoscientists.

  12. Multiple late Triassic carbon cycle perturbations preceding intensified volcanic activity in the Central Atlantic Magmatic Province

    NASA Astrophysics Data System (ADS)

    Ruhl, Micha; Kürschner, Wolfram M.

    2010-05-01

    The end-Triassic mass extinction (~201.5 Ma), marked by terrestrial ecosystem changes and a 50% loss in marine biodiversity, coincides with a major disruption of the global carbon cycle. These events closely coincide with the onset of Central Atlantic Magmatic Province emplacement (Deenen et al., 2010) and the subsequent release of isotopically depleted carbon as gaseous CO2 and from the methane hydrate reservoir. Here we show that the end-Triassic C-cycle perturbation is preceded by two successive 2-3‰ Rhaetian negative excursions in marine and continental δ13CTOC records from the western Tethys and north-west European sections. A coinciding, albeit slightly smaller, negative excursion in a δ13C leaf-record (Lepidopteris ottonis) further suggests successive 13C depletion of the late Triassic global atmosphere. Extensive dyke and sill systems that allowed major flood basalt emplacement in the Central Atlantic Magmatic Province, already intruded sedimentary basins over large parts of Pangea during the late Triassic. Subsurface thermal metamorphism of organic rich strata potentially led to oxidation of organic carbon and the transfer of isotopically depleted carbon to the exogenic carbon pool. In this way causing changes in the global C-cycle already before the onset of major volcanic activity.

  13. Paterae on Io: Volcanic Activity Observed by Galileo's NIMS and SSI

    NASA Technical Reports Server (NTRS)

    Lopes, Rosaly; Kamp, Lucas; Smythe, W. D.; Carlson, R.; Radebaugh, Jani; Gregg, Tracy K.

    2003-01-01

    Paterae are the most ubiquitous volcanic construct on Io s surface. Paterae are irregular craters, or complex craters with scalloped edges, interpreted as calderas or pit craters. Data from Galileo has shown that the activity of Ionian paterae is often confined to its interior and that generally lava flows are not seen spilling out over the edges. We use observations from Galileo s Near-Infrared Mapping Spectrometer (NIMS) to study the thermal emission from several Ionian paterae and compare them with images in visible wavelengths obtained by Galileo s Solid State Imaging System (SSI). Galileo s close fly-bys of Io from 1999 to 2001 have allowed NIMS to image the paterae at high spatial resolution (1-30 km pixel). At these scales, several of these features reveal greater thermal emission around the edges, which can be explained as the crust of a lava lake breaking up against the paterae walls. Comparisons with imaging data show that lower albedo areas (which are indicative of young lavas) coincide with higher thermal emission areas on NIMS data. Other paterae, however, show thermal emission and features in the visible that are more consistent with lava flows over a solid patera floor. Identifying eruption styles on Io is important for constraining eruption and interior models on Io.

  14. Intumescence and pore structure of alkali-activated volcanic glasses upon exposure to high temperatures

    NASA Astrophysics Data System (ADS)

    Erdogan, S. T.

    2015-12-01

    Structures formed with ground perlite, a natural volcanic glass, activated with NaOH solutions, are shown to possess the ability to expand up to ~225 % of their original volumes upon exposure to temperatures in the 200-600 °C range. Porous solid with 3-7 MPa compressive strength and ˜450 kg/m3 or higher density are obtained. The observed expansion is believed to occur due to a loss of silanol condensation water, as vapor and is accompanied by an up to ~20 % loss in mass. A drop in pH to near-neutral values supports this idea. The size and total amount of pores in the final solid are controlled by concentration of the NaOH solution and thermal processing conditions. The pores formed are observed to be ~1-10 μm to mm-sized. The ability of perlite-based solids to intumesce over specific temperature ranges could be beneficial in applications where absorption of thermal energy is necessary, such as passive fire protection.

  15. Can we detect, monitor, and characterize volcanic activity using 'off the shelf' webcams and low-light cameras?

    NASA Astrophysics Data System (ADS)

    Harrild, M.; Webley, P. W.; Dehn, J.

    2015-12-01

    The ability to detect and monitor precursory events, thermal signatures, and ongoing volcanic activity in near-realtime is an invaluable tool. Volcanic hazards often range from low level lava effusion to large explosive eruptions, easily capable of ejecting ash to aircraft cruise altitudes. Using ground based remote sensing to detect and monitor this activity is essential, but the required equipment is often expensive and difficult to maintain, which increases the risk to public safety and the likelihood of financial impact. Our investigation explores the use of 'off the shelf' cameras, ranging from computer webcams to low-light security cameras, to monitor volcanic incandescent activity in near-realtime. These cameras are ideal as they operate in the visible and near-infrared (NIR) portions of the electromagnetic spectrum, are relatively cheap to purchase, consume little power, are easily replaced, and can provide telemetered, near-realtime data. We focus on the early detection of volcanic activity, using automated scripts that capture streaming online webcam imagery and evaluate each image according to pixel brightness, in order to automatically detect and identify increases in potentially hazardous activity. The cameras used here range in price from 0 to 1,000 and the script is written in Python, an open source programming language, to reduce the overall cost to potential users and increase the accessibility of these tools, particularly in developing nations. In addition, by performing laboratory tests to determine the spectral response of these cameras, a direct comparison of collocated low-light and thermal infrared cameras has allowed approximate eruption temperatures to be correlated to pixel brightness. Data collected from several volcanoes; (1) Stromboli, Italy (2) Shiveluch, Russia (3) Fuego, Guatemala (4) Popcatépetl, México, along with campaign data from Stromboli (June, 2013), and laboratory tests are presented here.

  16. Volcanism on Io

    NASA Astrophysics Data System (ADS)

    Davies, Ashley Gerard

    2014-03-01

    Preface; Introduction; Part I. Io, 1610 to 1995: Galileo to Galileo: 1. Io, 1610-1979; 2. Between Voyager and Galileo: 1979-95; 3. Galileo at Io; Part II. Planetary Volcanism: Evolution and Composition: 4. Io and Earth: formation, evolution, and interior structure; 5. Magmas and volatiles; Part III. Observing and Modeling Volcanic Activity: 6. Observations: thermal remote sensing of volcanic activity; 7. Models of effusive eruption processes; 8. Thermal evolution of volcanic eruptions; Part IV. Galileo at Io: the Volcanic Bestiary: 9. The view from Galileo; 10. The lava lake at Pele; 11. Pillan and Tvashtar: lava fountains and flows; 12. Prometheus and Amirani: Effusive activity and insulated flows; 13. Loki Patera: Io's powerhouse; 14. Other volcanoes and eruptions; Part V. Volcanism on Io: The Global View: 15. Geomorphology: paterae, shields, flows and mountains; 16. Volcanic plumes; 17. Hot spots; Part VI. Io after Galileo: 18. Volcanism on Io: a post-Galileo view; 19. The future of Io observations; Appendix 1; Appendix 2; References; Index.

  17. Basaltic rocks from the Andean Southern Volcanic Zone: Insights from the comparison of along-strike and small-scale geochemical variations and their sources

    NASA Astrophysics Data System (ADS)

    Hickey-Vargas, Rosemary; Holbik, Sven; Tormey, Daniel; Frey, Frederick A.; Moreno Roa, Hugo

    2016-08-01

    The origin of spatial variations in the geochemical characteristics of volcanic rocks erupted in the Andean Southern Volcanic Zone (SVZ) has been studied by numerous researchers over the past 40 years. Diverse interpretations for along-strike, across-strike, and small-scale variations have been proposed. In this paper, we review geochemical data showing along-strike geochemical variations and address the processes causing such trends. We compare large- and small-scale changes of the same geochemical parameters in basaltic rocks in order to use spatial scale as a tool for isolating processes that may have the same result. Along-strike geochemical variations in the SVZ are expected, due to 1) greater thickness or age of the sub-arc continental crust and mantle lithosphere in the Northern SVZ (NSVZ; 33°S-34°30‧S) and Transitional SVZ (TSVZ; 34°30‧S-37°S) compared with the Central SVZ (CSVZ; 37°S-41.5°S) and Southern SVZ (SSVZ: 41.5°S-46°S); and 2) along-strike changes of the subducting Nazca plate and overlying asthenosphere. Basalts and basaltic andesites erupted at volcanic front stratovolcanoes define several along-strike geochemical trends: 1) higher 87Sr/86Sr and lower 143Nd/144Nd at volcanoes in the NSVZ compared with the TSVZ, CSVZ, and SSVZ; 2) higher and more variable La/Yb at volcanoes in the NSVZ and TSVZ compared with the CSVZ and SSVZ; 3) lower 87Sr/86Sr for a given 143Nd/144Nd at volcanoes in the TSVZ compared with the CSVZ and SSVZ; and 4) large values for time-sensitive subduction tracers such as 10Be/9Be and (238U/230Th) at some volcanoes in the CSVZ, but not in the NSVZ and TSVZ. Geochemical parameters that distinguish the TSVZ from the CSVZ and SSVZ are also found within the CSVZ at small basaltic eruptive centers (SEC) aligned with the Liquiñe-Ofqui Fault System (LOFS), which extends from 38°S to the southernmost SVZ. Our interpretation is that CSVZ magmas with strong time-sensitive subduction tracers represent the ambient subduction

  18. Fractal dimension analysis of the magnetic time series associated with the volcanic activity of Popocatépetl

    NASA Astrophysics Data System (ADS)

    Flores-Marquez, E. L.; Galvez-Coyt, G.; Cifuentes-Nava, G.

    2012-12-01

    Fractal analysis of the total magnetic field (TMF) time series from 1997 to 2003 at Popocatépetl Volcano is performed and compared with the TMF-series of the Teoloyucan Magnetic Observatory, 100 km away. Using Higuchi's fractal dimension method (D). The D changes over time for both series were computed. It was observed, when the time windows used to compute D increase in length, both series show nearly the same behavior. Some criteria of comparison were employed to discriminate the local effects inherent to volcano-magnetism. The simultaneous maximum in D (1.8) of the TMF series at Popocatépetl Volcano and the recovered volcanic activity indicates a scaling relation of the TMF at Popocatépetl Volcano and demonstrates a link between the magnetic field and volcanic activity.

  19. Intracaldera volcanic activity, Toledo caldera and embayment, Jemez Mountains, New Mexico

    SciTech Connect

    Heiken, G.; Goff, F.; Stix, J.; Shafiqullah, M.; Garcia, S.; Hagan, R.

    1986-02-10

    The Toledo caldera was formed at 1.47 +- 0.06 Ma during the catastrophic eruption of the lower member, Bandelier Tuff. The caldera was obscured at 1.12 +- 0.03 Ma during eruption of the equally voluminous upper member of the Bandelier Tuff that led to formation of the Valles caldera. Earlier workers interpreted a 9-km-diameter embayment, located NE of the Valles caldera (Toledo embayment), to be a remnant of the Toledo caldera. Drill hole data and new K-Ar dates of Toledo intracaldera domes redefine the position of Toledo caldera, nearly coincident with and of the same dimensions as the younger Valles caldera. the Toledo embayment may be of tectonic origin or a small Tschicoma volcanic center caldera. This interpretation is consistent with distribution of the lower member of the Bandelier Tuff and with several other field and drilling-related observations. Explosive activity associated with Cerro Toledo Rhyolite domes is recorded in tuff deposits located between the lower and upper members of the Bandelier Tuff on the northeast flank of the Jemez Mountains. Recorded in the tuff deposits are seven cycles of explosive activity. Most cycles consists of phreatomagmatic tuffs that grade upward into Plinian pumice beds. A separate deposit, of the same age and consisting of pyroclastic surges and flows, is associated with Rabbit Mountain, located on the southeast rim of the Valles-Toledo caldera complex. These are the surface expression of what may be a thicker, more voluminous intracaldera tuff sequence. The combined deposits of the lower and upper members of the Bandelier Tuff, Toledo and Valles intracaldera sediments, tuffs, and dome lavas form what we interpret to be a wedge-shaped caldera fill. This sequence is confirmed by deep drill holes and gravity surveys.

  20. Active submarine volcanism on the Society hotspot swell (west Pacific): A geochemical study

    SciTech Connect

    Devey, C.W.; Albarede, F.; Michard, A. ); Cheminee, J.L. ); Muehe, R.; Stoffers, P. )

    1990-04-10

    The present work deals with the petrography and geochemistry of lavas dredged from five active submarine volcanoes (named Mehetia, Moua Pihaa, Rocard, Teahitia, and Cyana) from the southeast end of the Society Islands hotspot trace. Most samples are basic and alkaline. Fractionation modelling based on major and minor compatible element variations suggests that olivine and minor clinopyroxene were the major fractionating phases. Rocard and Cyana have yielded more evolved, trachy-phonolitic, glassy samples. Both basaltic and phonolitic samples are incompatible-element enriched. The trachy-phonolite patterns show middle (REE) depletion and negative Eu anomalies. The Moua Pihaa basalts have flatter patterns than the other basalts. All smaples, with the exception of a sample from Moua Pihaa which has elevated {sup 206}Pb/{sup 204}Pb, fall on linear Sr-Nd-Pb isotopic arrays, suggesting two end-member mixing. The Sr isotopic variations in the samples excluding Moua Pihaa correlate positively with Rb/Nb, Pb/Ce, and SiO{sub 2} variations, idicating a component of mantle enriched by injection of material from a subducted oceanic slab. Correlation of {sup 207}Pb/{sup 204}Pb with {sup 87}Sr/{sup 86}Sr suggests that the subducted material is geochemically old. The absence of a MORB component in the Society magmatism, the small volumes of the Polynesian hotspot volcanoes, and the lack of more intense volcanic activity near the center of the Pacific Superswell, all lead to the conclusion that the latter is unlikely to be caused by a large convective plume.

  1. Microbial abundance and activities in relation to water potential in the vadose zones of arid and semiarid sites.

    PubMed

    Kieft, T L; Amy, P S; Brockman, F J; Fredrickson, J K; Bjornstad, B N; Rosacker, L L

    1993-07-01

    Numbers and activities of microorganisms were measured in the vadose zones of three arid and semiarid areas of the western United States, and the influence of water availability was determined. These low-moisture environments have vadose zones that are commonly hundreds of meters thick. The specific sampling locations chosen were on or near U.S. Department of Energy facilities: the Nevada Test Site (NTS), the Idaho National Engineering Laboratory (INEL), and the Hanford Site (HS) in southcentral Washington State. Most of the sampling locations were uncontaminated, but geologically representative of nearby locations with storage and/or leakage of waste compounds in the vadose zone. Lithologies of samples included volcanic tuff, basalt, glaciofluvial and fluvial sediments, and paleosols (buried soils). Samples were collected aseptically, either by drilling bore-holes (INEL and HS), or by excavation within tunnels (NTS) and outcrop faces (paleosols near the HS). Total numbers of microorganisms were counted using direct microscopy, and numbers of culturable microorganisms were determined using plate-count methods. Desiccation-tolerant microorganisms were quantified by plate counts performed after 24 h desiccation of the samples. Mineralization of (14)C-labeled glucose and acetate was quantified in samples at their ambient moisture contents, in dried samples, and in moistened samples, to test the hypothesis that water limits microbial activities in vadose zones. Total numbers of microorganisms ranged from log 4.5 to 7.1 cells g(-1) dry wt. Culturable counts ranged from log <2 to 6.7 CFU g(-1) dry wt, with the highest densities occurring in paleosol (buried soil) samples. Culturable cells appeared to be desiccation-tolerant in nearly all samples that had detectable viable heterotrophs. Water limited mineralization in some, but not all samples, suggesting that an inorganic nutrient or other factor may limit microbial activities in some vadose zone environments.

  2. The Martian hydrologic system: Multiple recharge centers at large volcanic provinces and the contribution of snowmelt to outflow channel activity

    NASA Astrophysics Data System (ADS)

    Russell, Patrick S.; Head, James W.

    2007-02-01

    Global recharge of the martian hydrologic system has traditionally been viewed as occurring through basal melting of the south polar cap. We conclude that regional recharge of a groundwater system at the large volcanic provinces, Elysium and Tharsis, is also very plausible and has several advantages over a south polar recharge source in providing a more direct, efficient supply of water to the outflow channel source regions surrounding these areas. This recharge scenario is proposed to have operated concurrently with and within the context of a global cryosphere-hydrosphere system of the subsurface characteristic of post-Noachian periods. To complement existing groundwater flow modeling studies, we examine geologic evidence and possible mechanisms for accumulation of water at high elevations on the volcanic rises, such as melting snow, infiltration, and increased effective permeability of the subsurface between the recharge zone and outflow source. Evidence for the presence of large Amazonian-aged cold-based piedmont glaciers on the Tharsis Montes has been well documented. Climate modeling predicts snow accumulation on high volcanic rises at obliquities thought to be typical over much of martian history. Thermal gradients causing basal melting of snowpack over 1 km thick could provide several kg m -2 yr -1 of water, charging a volume equivalent to the pore space in a square meter column of subsurface in less than 1.5×10 5 yr. In order to account for estimated outflow channel volumes, the subsurface volume above the elevation of the outflow channels must be charged several times over the area of Tharsis. Complete aquifer recharge can be accomplished in ˜0.3-2 My through the snowpack melting mechanism at Tharsis and in ˜5×10 4 years for channel requirements at Elysium. Abundant radial dikes emanating from large martian volcanic rises can crack and/or melt the cryosphere, initiating water outflow and creating anisotropies that can channel subsurface water from a

  3. Evolution of Popocatépetl volcano's glaciers in Mexico with and without volcanic activity: diagnosis from a minimal mass balance model

    NASA Astrophysics Data System (ADS)

    Ontiveros-Gonzalez, G.; Cortes Ramos, J.; Delgado Granados, H.

    2013-05-01

    This work describes the influence of eruptive activity on the evolution of the glacial cover on Popocatepetl volcano. Here, we try to answer a simple question: what had happened if this glacier had not been affected by the volcanic activity? In order to answer this question we modeled the mass balance evolution of this glacier using meteorological data and a minimal mass balance model developed for glaciers elsewhere. For this model we assumed no volcanic activity. These results were compared with measurements available for the actual situation at Popocatépetl Volcano. It was possible to separate the influence of the volcanic activity on the evolution of this glacier system considering two scenarios: one was modeled with a simulation of the mass balance where volcanic activity does not affect, and a second scenario is based on the documented studies developed around the glacial disappearance of the glaciers.

  4. Formation of Golgi-derived active zone precursor vesicles.

    PubMed

    Maas, Christoph; Torres, Viviana I; Altrock, Wilko D; Leal-Ortiz, Sergio; Wagh, Dhananjay; Terry-Lorenzo, Ryan T; Fejtova, Anna; Gundelfinger, Eckart D; Ziv, Noam E; Garner, Craig C

    2012-08-01

    Vesicular trafficking of presynaptic and postsynaptic components is emerging as a general cellular mechanism for the delivery of scaffold proteins, ion channels, and receptors to nascent and mature synapses. However, the molecular mechanisms leading to the selection of cargos and their differential transport to subneuronal compartments are not well understood, in part because of the mixing of cargos at the plasma membrane and/or within endosomal compartments. In the present study, we have explored the cellular mechanisms of active zone precursor vesicle assembly at the Golgi in dissociated hippocampal neurons of Rattus norvegicus. Our studies show that Piccolo, Bassoon, and ELKS2/CAST exit the trans-Golgi network on a common vesicle that requires Piccolo and Bassoon for its proper assembly. In contrast, Munc13 and synaptic vesicle proteins use distinct sets of Golgi-derived transport vesicles, while RIM1α associates with vesicular membranes in a post-Golgi compartment. Furthermore, Piccolo and Bassoon are necessary for ELKS2/CAST to leave the Golgi in association with vesicles, and a core domain of Bassoon is sufficient to facilitate formation of these vesicles. While these findings support emerging principles regarding active zone differentiation, the cellular and molecular analyses reported here also indicate that the Piccolo-Bassoon transport vesicles leaving the Golgi may undergo further changes in protein composition before arriving at synaptic sites.

  5. Molecular Remodeling of the Presynaptic Active Zone of Drosophila Photoreceptors via Activity-Dependent Feedback.

    PubMed

    Sugie, Atsushi; Hakeda-Suzuki, Satoko; Suzuki, Emiko; Silies, Marion; Shimozono, Mai; Möhl, Christoph; Suzuki, Takashi; Tavosanis, Gaia

    2015-05-01

    Neural activity contributes to the regulation of the properties of synapses in sensory systems, allowing for adjustment to a changing environment. Little is known about how synaptic molecular components are regulated to achieve activity-dependent plasticity at central synapses. Here, we found that after prolonged exposure to natural ambient light the presynaptic active zone in Drosophila photoreceptors undergoes reversible remodeling, including loss of Bruchpilot, DLiprin-α, and DRBP, but not of DSyd-1 or Cacophony. The level of depolarization of the postsynaptic neurons is critical for the light-induced changes in active zone composition in the photoreceptors, indicating the existence of a feedback signal. In search of this signal, we have identified a crucial role of microtubule meshwork organization downstream of the divergent canonical Wnt pathway, potentially via Kinesin-3 Imac. These data reveal that active zone composition can be regulated in vivo and identify the underlying molecular machinery.

  6. Monitoring and analyses of volcanic activity using remote sensing data at the Alaska Volcano Observatory: Case study for Kamchatka, Russia, December 1997

    NASA Astrophysics Data System (ADS)

    Schneider, D. J.; Dean, K., G.; Dehn, J.; Miller, T., P.; Kirianov, V. Yu.

    There are about 100 potentially active volcanoes in the North Pacific Ocean region that includes Alaska, the Kamchatka Peninsula, and the Kurile Islands, but fewer than 25% are monitored seismically. The region averages about five volcanic eruptions per year, and more than 20,000 passengers and millions of dollars of cargo fly the air routes in this region each day. One of the primary public safety objectives of the Alaska Volcano Observatory (AVO) is to mitigate the hazard posed by volcanic ash clouds drifting into these busy air traffic routes. The AVO uses real-time remote sensing data (AVHRR, GOES, and GMS) in conjunction with other methods (primarily seismic) to monitor and analyze volcanic activity in the region. Remote sensing data can be used to detect volcanic thermal anomalies and to provide unique information on the location, movement, and composition of volcanic eruption clouds. Satellite images are routinely analyzed twice each day at AVO and many times per day during crisis situations. As part of its formal working relationship with the Kamchatka Volcanic Eruption Response Team (KVERT), the AVO provides satellite observations of volcanic activity in Kamchatka and distributes notices of volcanic eruptions from KVERT to non-Russian users in the international aviation community. This paper outlines the current remote sensing capabilities and operations of the AVO and describes the responsibilities and procedures of federal agencies and international aviation organizations for volcanic eruptions in the North Pacific region. A case study of the December 4, 1997, eruption of Bezymianny volcano, Russia, is used to illustrate how real-time remote sensing and hazard communication are used to mitigate the threat of volcanic ash to aircraft.

  7. Volcanic Catastrophes

    NASA Astrophysics Data System (ADS)

    Eichelberger, J. C.

    2003-12-01

    volcanism on humankind in the North Pacific, where Holocene time saw many caldera-forming eruptions in an area of comparatively intense human activity.

  8. Sr and O Isotope Geochemistry of Volcán Uturuncu, Andean Central Volcanic Zone, Bolivia: Resolving Crustal and Mantle Contributions to Continental Arc Magmatism

    NASA Astrophysics Data System (ADS)

    Michelfelder, G.; Feeley, T.

    2015-12-01

    This study reports oxygen isotope ratios determined by laser fluorination of mineral separates and in situ Sr isotope ratios (mainly plagioclase) from andesitic to dacitic composition lava flows erupted from Volcán Uturuncu in the Andean Central Volcanic Zone (CVZ). Variation in δ18O values (6.6-11.8‰ relative to SMOW) for the lava suite is large and the data as a whole exhibit no simple correlation with any parameter of compositional evolution. Plagioclase separates from nearly all rocks have δ18O values (6.6-11.8‰) higher than expected for production of the magmas by partial melting of little evolved basaltic lavas erupted in the back arc regions of the CVZ. Most Uturuncu magmas must therefore contain high 18O crustal material. This hypothesis is further supported by textures and isotopic variation (87Sr/86Sr= 0.7098-0.7165) within single plagioclase phenocrysts suggesting repeated mixing followed by crustal contamination events occurring in the shallow crustal reservoir. The dacite composition rocks show more variable and extend to higher δ18O ratios than andesite composition rocks. These features are interpreted to reflect assimilation of heterogeneous upper continental crust by low 18O andesitic magmas followed by mixing or mingling with similar composition hybrid magmas with high 18O. Conversely, the δ18O values of the andesites suggest contamination of the magmas by continental crust modified by intrusion of mantle derived basaltic magmas. These results demonstrate on a relatively small scale the strong influence that intrusion of mantle-derived mafic magmas can have on modifying the composition of pre-existing continental crust in regions of melt production. Given this result, similar, but larger-scale, regional trends in magma compositions may reflect an analogous but more extensive process wherein the continental crust becomes progressively hybridized beneath frontal arc localities as a result of protracted intrusion of subduction

  9. Friction in volcanic environments

    NASA Astrophysics Data System (ADS)

    Kendrick, Jackie E.; Lavallée, Yan

    2016-04-01

    to eruption behaviour and during ascent magma behaves in an increasingly rock-like manner as it degasses and crystallises. This character aids the development of shear zones in the conduit, producing fault surfaces that host gouge, cataclasite and pseudotachylyte and which control the last hundreds of meters of ascent by frictional slip. Recent work has shown that the occurrence of vesiculation of gas bubbles modifies the rheology of frictional melt and in extreme cases can trigger eruption style to switch from effusive to explosive activity. Hence it is of vital importance to recognise the frictional behaviour of volcanic rocks and magmas to understand the continuation of an eruption and associated hazards.

  10. Contrasting estimates on the depth of magma storage zones in volcanic systems from mineral barometry and phase equilibrium experiments: a case study from Mount Merapi, Indonesia

    NASA Astrophysics Data System (ADS)

    Erdmann, Saskia; Martel, Caroline

    2015-04-01

    Mount Merapi, located in central Java, erupts on average every 5-10 years by discharging block-and-ash flows that pose local, but spatially restricted hazards. In 2010, however, the volcano erupted with a force that has been unprecedented in over 100 years. Its proximity to the metropolis of Yogyakarta with a population of >4 million makes short- and long-term eruption forecasting a task of vital importance. Critical to the appraisal of the volcano's hazard potential are tight constraints on its upper-crustal magma plumbing system and particularly on the location of its pre-eruptive reservoir. Previous petrological studies have estimated on the basis of amphibole and clinopyroxene barometry that the main magma storage zone below Merapi is located at depths of >10-15 km, while geophysical surveys have inferred significant magma storage zones at depths of ~5.5-9 km. We have carried out phase equilibrium experiments on basaltic andesite erupted in 2010, which indicate that the main pre-eruptive reservoir is located at a depth of ~7-8 km (~200 MPa). Our results thus corroborate the findings of earlier geophysical surveys and highlight the extreme uncertainty of mineral-based pressure estimates for volcanic magma systems. We point out that the commonly employed amphibole barometric calibrations of Ridolfi et al. (2010) and Ridolfi & Renzulli (2012) calculate low crystallization pressure for amphibole crystallized from felsic melt and high crystallization pressure for amphibole crystallized from mafic melt, and that the calculated pressure is thus largely unrelated to true values. Commonly employed clinopyroxene barometers (e.g., those of Nimis 1999; Putirka 2008) are also of limited use for estimating the location of crustal magma reservoirs, because the methods have large standard errors and are extremely temperature-sensitive. As a result, the calculated crystallization pressures inevitably indicate crystallization over a large range of depths, often from deep- to

  11. Time variability of Io's volcanic activity from near-IR adaptive optics observations on 100 nights in 2013-2015

    NASA Astrophysics Data System (ADS)

    de Kleer, Katherine; de Pater, Imke

    2016-12-01

    Jupiter's moon Io is a dynamic target, exhibiting extreme and time-variable volcanic activity powered by tidal forcing from Jupiter. We have conducted a campaign of high-cadence observations of Io with the goal of characterizing its volcanic activity. Between Aug 2013 and the end of 2015, we imaged Io on 100 nights in the near-infrared with adaptive optics on the Keck and Gemini N telescopes, which resolve emission from individual volcanic hot spots. During our program, we made over 400 detections of 48 distinct hot spots, some of which were detected 30+ times. We use these observations to derive a timeline of global volcanic activity on Io, which exhibits wide variability from month to month. The timelines of thermal activity at individual volcanic centers have geophysical implications, and will permit future characterization by others. We evaluate hot spot detection limits and give a simple parameterization of the minimum detectable intensity as a function of emission angle, which can be applied to other analyses. We detected three outburst eruptions in August 2013, but no other outburst-scale events were observed in the subsequent ∼90 observations. Either the cluster of events in August 2013 was a rare occurrence, or there is a mechanism causing large events to occur closely-spaced in time. We also detected large eruptions (though not of outburst scale) within days of one another at Kurdalagon Patera and Sethlaus/Gabija Paterae in 2015. As was also seen in the Galileo dataset, the hot spots we detected can be separated into two categories based on their thermal emission: those that are persistently active for 1 year or more at moderate intensity, and those that are only briefly active, are time-variable, and often reach large intensities. A small number of hot spots in the latter category appear and subside in a matter of days, reaching particularly high intensities; although these are not bright enough to qualify as outbursts, their thermal signatures follow

  12. Using IMS hydrophone data for detecting submarine volcanic activity: Insights from Monowai, 26°S Kermadec Arc

    NASA Astrophysics Data System (ADS)

    Metz, Dirk; Watts, Anthony B.; Grevemeyer, Ingo; Rodgers, Mel; Paulatto, Michele

    2016-04-01

    Only little is known on active volcanism in the ocean. As eruptions are attenuated by seawater and fallout does not regularly reach the sea surface, eruption rates and mechanisms are poorly understood. Estimations on the number of active volcanoes across the modern seas range from hundreds to thousands, but only very few active sites are known. Monowai is a submarine volcanic centre in the northern Kermadec Arc, Southwest Pacific Ocean. During May 2011, it erupted over a period of five days, with explosive activity directly linked to the generation of seismoacoustic tertiary waves ('T-phases'), recorded at three broadband seismic stations in the region. We show, using windowed cross-correlation and time-difference-of-arrival techniques, that T-phases associated with this eruption are detected as far as Ascension Island, South Atlantic Ocean, where two bottom-moored hydrophone arrays are operated as part of the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). We observe a high incidence of T-phase arrivals during the time of the eruption, with the angle of arrival stabilizing at the geodesic azimuth between the IMS arrays and Monowai. T-phases from the volcanic centre must therefore have propagated through the Sound Fixing And Ranging (SOFAR) channel in the South Pacific and South Atlantic Oceans and over a total geodesic range of approximately 15,800 km, one of the longest source-receiver distances of any naturally occurring underwater signal ever observed. Our findings, which are consistent with observations at regional broadband stations and two dimensional, long-range, parabolic equation modelling, highlight the exceptional capabilities of the hydroacoustic waveform component of the IMS for remotely detecting episodes of submarine volcanic activity. Using Monowai and the hydrophone arrays at Ascension Island as a natural laboratory, we investigate the long-term eruptive record of a submarine volcano from

  13. Morpho-structural evolution of a volcanic island developed inside an active oceanic rift: S. Miguel Island (Terceira Rift, Azores)

    NASA Astrophysics Data System (ADS)

    Sibrant, A. L. R.; Hildenbrand, A.; Marques, F. O.; Weiss, B.; Boulesteix, T.; Hübscher, C.; Lüdmann, T.; Costa, A. C. G.; Catalão, J. C.

    2015-08-01

    The evolution of volcanic islands is generally marked by fast construction phases alternating with destruction by a variety of mass-wasting processes. More specifically, volcanic islands located in areas of intense regional deformation can be particularly prone to gravitational destabilisation. The island of S. Miguel (Azores) has developed during the last 1 Myr inside the active Terceira Rift, a major tectonic structure materializing the present boundary between the Eurasian and Nubian lithospheric plates. In this work, we depict the evolution of the island, based on high-resolution DEM data, stratigraphic and structural analyses, high-precision K-Ar dating on separated mineral phases, and offshore data (bathymetry and seismic profiles). The new results indicate that: (1) the oldest volcanic complex (Nordeste), composing the easternmost part of the island, was dominantly active between ca. 850 and 750 ka, and was subsequently affected by a major south-directed flank collapse. (2) Between at least 500 ka and 250 ka, the landslide depression was massively filled by a thick lava succession erupted from volcanic cones and domes distributed along the main E-W collapse scar. (3) Since 250 kyr, the western part of this succession (Furnas area) was affected by multiple vertical collapses; associated plinian eruptions produced large pyroclastic deposits, here dated at ca. 60 ka and less than 25 ka. (4) During the same period, the eastern part of the landslide scar was enlarged by retrogressive erosion, producing the large Povoação valley, which was gradually filled by sediments and young volcanic products. (5) The Fogo volcano, in the middle of S. Miguel, is here dated between ca. 270 and 17 ka, and was affected by, at least, one southwards flank collapse. (6) The Sete Cidades volcano, in the western end of the island, is here dated between ca. 91 and 13 ka, and experienced mutliple caldera collapses; a landslide to the North is also suspected from the presence of a

  14. Off-axis volcanism in the Gregory rift, east Africa: implications for models of continental rifting

    SciTech Connect

    Bosworth, W.

    1987-05-01

    The largest volcanic centers of the Gregory rift occur in two belts located 100 to 150 km east and west of the axis of the rift valley. These off-axis volcanic belts include the highest peaks on the continent of Africa and are interpreted to lie above the intersection of low-angle detachment systems with the base of a regionally thinned lithosphere. These detachment systems are manifested at the surface as a series of breakaway zones and regional bounding faults that produce subbasins with half-graben form. The asymmetry of subbasins alternates along the rift axis, indicating that the polarity of the underlying active detachment systems also reverses. The detachments are separated laterally by regional oblique-slip accommodation zones typified by wrench-style tectonism. Off-axis from the rift, the detachments are inferred to merge along strike as they cut to the base of the lithosphere. This results in irregular but persistent paired zones of volcanism and lithospheric thinning off-axis from the rift proper. The development of major volcanic cones such as Mount Kilimanjaro may be controlled by the interaction of leaky accommodation zones with the regions of structurally thinned lithosphere. The central Kenya hot spot has produced the anomalous quantities of volcanic material that fills the Gregory rift and probably enhances the off-axis volcanism but does not directly control its location. The model proposed here for tectonic controls of volcanism in the Gregory rift may be applicable to Phanerozoic continental rifts in general.

  15. Review of magnetic field monitoring near active faults and volcanic calderas in California: 1974-1995

    USGS Publications Warehouse

    Mueller, R.J.; Johnston, M.J.S.

    1998-01-01

    Differential magnetic fields have been monitored along the San Andreas fault and the Long Valley caldera since 1974. At each monitoring location, proton precession magnetometers sample total magnetic field intensity at a resolution of 0.1 nT or 0.25 nT. Every 10 min, data samples are transmitted via satellite telemetry to Menlo Park, CA for processing and analysis. The number of active magnetometer sites has varied during the past 21 years from 6 to 25, with 12 sites currently operational. We use this network to identify magnetic field changes generated by earthquake and volcanic processes. During the two decades of monitoring, five moderate earthquakes (M5.9 to M7.3) have occurred within 20 km of magnetometer sites located along the San Andreas fault and only one preseismic signal of 1.5 nT has been observed. During moderate earthquakes, coseismic magnetic signals, with amplitudes from 0.7 nT to 1.3 nT, have been identified for 3 of the 5 events. These observations are generally consistent with those calculated from simple seismomagnetic models of these earthquakes and near-fault coseismic magnetic field disturbances rarely exceed one nanotesla. These data are consistent with the concept of low shear stress and relatively uniform displacement of the San Andreas fault system as expected due to high pore fluid pressure on the fault. A systematic decrease of 0.8-1 nT/year in magnetic field has occurred in the Long Valley caldera since 1989. These magnetic field data are similar in form to observed geodetically measured displacements from inflation of the resurgent dome. A simple volcanomagnetic model involving pressure increase of 50 MPa/a at a depth of 7 km under the resurgent dome can replicate these magnetic field observations. This model is derived from the intrusion model that best fits the surface deformation data. ?? 1998 Elsevier Science B.V.

  16. Mesozooplankton distribution near an active volcanic island in the Andaman Sea (Barren Island).

    PubMed

    Pillai, Honey U K; Jayaraj, K A; Rafeeq, M; Jayalakshmi, K J; Revichandran, C

    2011-05-01

    The study addresses the distribution and diversity of mesozooplankton near the active volcano-Barren Island (Andaman Sea) in the context of persistent volcanic signature and warm air pool existing for the last few months. Sampling was done from the stations along the west and east side of the volcano up to a depth of 1,000 m during the inter monsoon (April) of 2006. Existence of feeble warm air pool was noticed around the Island (Atm. Temp. 29°C). Sea surface temperature recorded as 29.9°C on the west and 29.6°C on the east side stations. High mesozooplankton biomass was observed in the study area than the earlier reports. High density and biomass observed in the surface layer decreased significantly to the deeper depths. Lack of correlation was observed between mesozooplankton biomass and density with chl. a. Twenty-three mesozooplankton taxa were observed with copepoda as the dominant taxa followed by chaetognatha. The relative abundance of chaetognatha considerably affected the copepod population density in the surface layer. A noticeable feature was the presence of cumaceans, a hyperbenthic fauna in the surface, mixed layer and thermocline layer on the western side station where the volcano discharges in to the sea. The dominant order of copepoda, the calanoida was represented by 52 species belonging to 17 families. The order poecilostomatoida also had a significant contribution. Copepods exhibited a clear difference in their distribution pattern in different depth layers. The families Calanidae and Pontellidae showed a clear dominance in the surface whereas small-sized copepods belonging to the families Clausocalanidae and Paracalanidae were observed as the predominant community in the mixed layer and thermocline layer depth. Families Metridinidae, Augaptilidae and Aetideidae were observed as dominant in deeper layers.

  17. Maximizing Mission Science Return Through use of Spacecraft Autonomy: Active Volcanism and the Autonomous Sciencecraft Experiment

    NASA Astrophysics Data System (ADS)

    Chien, S.; Davies, A. G.; Sherwood, R.; ASE Science Team

    2005-08-01

    Deep-space missions have been unable to react to dynamic events as encounter observation sequences are planned well in advance. In the case of planet, asteroid and comet fly-bys, the limited resources available are allocated to individual instruments long beforehand. However, for monitoring or mapping mission phases, alternative strategies and technologies are now available. Now, onboard data processing allows greater spacecraft and instrument flexibility, affording the ability to react rapidly to dynamic events, and increasing the science content of returned data. Such new technology has already been successfully demonstrated in the form of the New Millennium Program Autonomous Sciencecraft Experiment (ASE). In 2004 ASE successfully demonstrated advanced autonomous science data acquisition, processing, and product downlink prioritization, as well as autonomous fault detection and spacecraft command and control. ASE is software onboard the EO-1 spacecraft, in Earth-orbit. ASE controlled the Hyperion instrument, a hyperspectral imager with 220 wavelengths from 0.4 to 2.5 μm and 30 m/pixel spatial resolution. ASE demonstrated that spacecraft autonomy will be advantageous to future missions by making the best use of limited downlink, e.g., by increasing science content per byte of returned data, and by avoiding the return of null (no-change/no feature) datasets. and by overcoming communication delays through decision-making onboard enabling fast reaction to dynamic events. We envision this flight-proven science-driven spacecraft command-and-control technology being used on a wide range of missions to search for and monitor dynamic events, such as active, high-temperature volcanism on Earth and Io, and cryovolcanism on Triton and possibly other icy satellites. Acknowledgements: Part of this work was carried out at the Jet Propulsion Laboratory-California Institute of Technology, under contract to NASA. We thank the EO-1 Flight Management Team and Chris Stevens and Art

  18. Groundwater flow processes and mixing in active volcanic systems: the case of Guadalajara (Mexico)

    NASA Astrophysics Data System (ADS)

    Hernández-Antonio, A.; Mahlknecht, J.; Tamez-Meléndez, C.; Ramos-Leal, J.; Ramírez-Orozco, A.; Parra, R.; Ornelas-Soto, N.; Eastoe, C. J.

    2015-09-01

    other active volcanic systems on Earth.

  19. Volcanic Activity on lo at the Time of the Ulysses Encounter.

    PubMed

    Spencer, J R; Howell, R R; Clark, B E; Klassen, D R; O'connor, D

    1992-09-11

    The population of heavy ions in lo's torus is ultimately derived from lo volcanism. Groundbased infrared observations of lo between October 1991 and March 1992, contemporaneous with the 8 February 1992 Ulysses observations of the lo torus, show that volcanic thermal emission was at the low end of the normal range at all lo longitudes during this period. In particular, the dominant hot spot Loki was quiescent. Resolved images show that there were at least four hot spots on lo's Jupiter-facing hemisphere, including Loki and a long-lived spot on the leading hemisphere (Kanehekili), of comparable 3.5-micrometer brightness but higher temperature.

  20. How to Make an Active Zone: Unexpected Universal Functional Redundancy between RIMs and RIM-BPs.

    PubMed

    Acuna, Claudio; Liu, Xinran; Südhof, Thomas C

    2016-08-17

    RIMs and RIM-binding proteins (RBPs) are evolutionary conserved multidomain proteins of presynaptic active zones that are known to recruit Ca(2+) channels; in addition, RIMs perform well-recognized functions in tethering and priming synaptic vesicles for exocytosis. However, deletions of RIMs or RBPs in mice cause only partial impairments in various active zone functions and have no effect on active zone structure, as visualized by electron micrographs, suggesting that their contribution to active zone functions is limited. Here, we show in synapses of the calyx of Held in vivo and hippocampal neurons in culture that combined, but not individual, deletions of RIMs and RBPs eliminate tethering and priming of synaptic vesicles, deplete presynaptic Ca(2+) channels, and ablate active zone complexes, as analyzed by electron microscopy of chemically fixed synapses. Thus, RBPs perform unexpectedly broad roles at the active zone that together with those of RIMs are essential for all active zone functions. PMID:27537484

  1. How to Make an Active Zone: Unexpected Universal Functional Redundancy between RIMs and RIM-BPs.

    PubMed

    Acuna, Claudio; Liu, Xinran; Südhof, Thomas C

    2016-08-17

    RIMs and RIM-binding proteins (RBPs) are evolutionary conserved multidomain proteins of presynaptic active zones that are known to recruit Ca(2+) channels; in addition, RIMs perform well-recognized functions in tethering and priming synaptic vesicles for exocytosis. However, deletions of RIMs or RBPs in mice cause only partial impairments in various active zone functions and have no effect on active zone structure, as visualized by electron micrographs, suggesting that their contribution to active zone functions is limited. Here, we show in synapses of the calyx of Held in vivo and hippocampal neurons in culture that combined, but not individual, deletions of RIMs and RBPs eliminate tethering and priming of synaptic vesicles, deplete presynaptic Ca(2+) channels, and ablate active zone complexes, as analyzed by electron microscopy of chemically fixed synapses. Thus, RBPs perform unexpectedly broad roles at the active zone that together with those of RIMs are essential for all active zone functions.

  2. Monitoring Io volcanic activity using the Keck AO system: 2-5μm sunlit and eclipse observations

    NASA Astrophysics Data System (ADS)

    Marchis, F.; de Pater, I.; Le Mignant, D.; Roe, H. G.; Fusco, T.; Graham, J. R.; Prange, R.; Macintosh, B.

    2002-12-01

    Galileo provided us with spectacular images of the volcanically active Io moon over the last 7 years, but we understand little about the physical processes occurring on this moon. Groundbased monitoring programs help characterize the long time evolution of Io's volcanic activity, such as the frequency, spatial distribution and temperature of hot spots and outbursts. Our group started a monitoring program of Io's volcanic activity using the Keck II Adaptive Optics (AO) system and its recently installed near-infrared camera NIRC2. Here we report groundbased observations of Io conducted in December 2001 (UT), at 0.05" resolution (120-140 km on Io) in K', i.e., ~4 times better than HST and than global Galileo NIMS images. Our 1-5 micron data enable us to determine the temperature of individual hot spots, a key parameter for geophysical/volcanic flow models. We will present: i) Io in reflected sunlight in K', L', and M bands. We used Io itself as reference source for the wavefront sensor of the AO system. Our L and M-band images show both reflected sunlight and thermal emission from volcanic hot spots. The contrast of images is enhanced using the MISTRAL deconvolution algorithme. The 12 images taken on 10 days provides a complete survey of Io surface during one full rotation. 26 active hot spots were detected on the entire surface in L band (3.8μm), approximatively three times more in M band (4.7μm). One active hot spot is seen in K band (2.2μm) in the Pele area. A study of individual hot spot (temperature, emission area, nature) will be presented. ii) Io in eclipse. While Io is in Jupiter's shadow, it is invisible to the wavefront sensor, but its hot spots are easily visible in the near-infrared. We imaged Io during the 18 Dec. 2001 eclipse using Ganymede (30" from Io, moving relative to Io at ~0.5"/min) as a reference source. A dozen of faint hot spots are detected at both K' and L', allowing temperature estimates for each of them. Keck Science team is composed of

  3. Metal Concentrations in Two Commercial Tuna Species from an Active Volcanic Region in the Mid-Atlantic Ocean.

    PubMed

    Torres, Paulo; Rodrigues, Armindo; Soares, Lília; Garcia, Patrícia

    2016-02-01

    Concentrations of cadmium (Cd), mercury (Hg), and lead [Pb (µg g(-1) wet weight)] were determined in liver and muscle samples of 15 bigeye (Thunnus obesus) and 15 skipjack tunas (Katsuwonus pelamis) caught over an active volcanic region in the Mid-Atlantic Ocean (Azores, Portugal) and evaluated regarding consumption safety. None of the muscle samples (edible part) exceeded the European Union (EU) maximum limits (MLs) for Hg and Pb. Cd concentrations in muscle were much greater than EU MLs with 53 and 26 % of the bigeye tuna and skipjack tuna, respectively, in exceedance of the limits. Results obtained in this work, together with other studies in the same region, support the existence of an important volcanic source of Cd in waters of the Mid-Atlantic region, which should be carefully monitored given the importance of many commercial marine species for human consumption, mainly in Europe. PMID:26681184

  4. Metal Concentrations in Two Commercial Tuna Species from an Active Volcanic Region in the Mid-Atlantic Ocean.

    PubMed

    Torres, Paulo; Rodrigues, Armindo; Soares, Lília; Garcia, Patrícia

    2016-02-01

    Concentrations of cadmium (Cd), mercury (Hg), and lead [Pb (µg g(-1) wet weight)] were determined in liver and muscle samples of 15 bigeye (Thunnus obesus) and 15 skipjack tunas (Katsuwonus pelamis) caught over an active volcanic region in the Mid-Atlantic Ocean (Azores, Portugal) and evaluated regarding consumption safety. None of the muscle samples (edible part) exceeded the European Union (EU) maximum limits (MLs) for Hg and Pb. Cd concentrations in muscle were much greater than EU MLs with 53 and 26 % of the bigeye tuna and skipjack tuna, respectively, in exceedance of the limits. Results obtained in this work, together with other studies in the same region, support the existence of an important volcanic source of Cd in waters of the Mid-Atlantic region, which should be carefully monitored given the importance of many commercial marine species for human consumption, mainly in Europe.

  5. On the statistics of El Nino occurrences and the relationship of El Nino to volcanic and solar/geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    1989-01-01

    El Nino is conventionally defined as an anomalous and persistent warming of the waters off the coasts of Ecuador and Peru in the eastern equatorial Pacific, having onset usually in Southern Hemispheric summer/fall. Some of the statistical aspects of El Nino occurrences are examined, especially as they relate to the normal distribution and to possible associations with volcanic, solar, and geomagnetic activity. With regard to the very strong El Nino of 1982 to 1983, it is noted that, although it may very well be related to the 1982 eruptions of El Chichon, the event occurred essentially on time (with respect to the past behavior of elapsed times between successive El Nino events; a moderate-to-stronger El Nino was expected during the interval 1978 to 1982, assuming that El Nino occurrences are normally distributed, having a mean elapsed time between successive onsets of 4 years and a standard deviation of 2 years and a last known occurrence in 1976). Also, although not widely recognized, the whole of 1982 was a record year for geomagnetic activity (based on the aa geomagnetic index, with the aa index registering an all time high in February 1982), perhaps, important for determining a possible trigger for this and other El Nino events. A major feature is an extensive bibliography (325 entries) on El Nino and volcanic-solar-geomagnetic effects on climate. Also, included is a tabular listing of the 94 major volcanic eruptions of 1835 to 1986.

  6. Postcaldera volcanism and hydrothermal activity revealed by autonomous underwater vehicle surveys in Myojin Knoll caldera, Izu-Ogasawara arc

    NASA Astrophysics Data System (ADS)

    Honsho, Chie; Ura, Tamaki; Kim, Kangsoo; Asada, Akira

    2016-06-01

    Myojin Knoll caldera, one of the submarine silicic calderas lying on the volcanic front of the northern Izu-Ogasawara arc, has attracted increasing attention since the discovery of a large hydrothermal field called the Sunrise deposit. Although numerous submersible surveys have been conducted in Myojin Knoll caldera, they have not sufficiently explored areas to produce a complete picture of the caldera and understand the origin of the Sunrise deposit. We conducted comprehensive deep-sea surveys using an autonomous underwater vehicle and obtained high-resolution bathymetric and magnetic data and sonar images from ~70% of the caldera. The detailed bathymetric map revealed that faulting and magma eruptions, possibly associated with an inflation-deflation cycle of the magma reservoir during postcaldera volcanism, had generally occurred in the caldera wall. The main dome of the central cone was covered with lava flows and exhibits exogenous growth, which is unusual for rhyolitic domes. The magnetization distribution in the central cone indicates preferential magma intrusion along a NW-SE direction. It is presumed that magma migrated along this direction and formed a rhyolite dome at the foot of the southeastern caldera wall, where the Sunrise deposit occurs. The Sunrise deposit is composed mainly of three ridges extending in slope directions and covers ~400 × ~400 m. Magnetization reduction in the deposit area is small, indicating that the alteration zone beneath the Sunrise deposit is slanting rather than vertical. It is presumed that several slanting and near-vertical volcanic vents serve as pathways of hydrothermal fluid in Myojin Knoll caldera.

  7. 78 FR 14963 - Foreign-Trade Zone 163-Ponce, Puerto Rico; Authorization of Production Activity; Zimmer...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-08

    ... Foreign-Trade Zones Board Foreign-Trade Zone 163--Ponce, Puerto Rico; Authorization of Production Activity; Zimmer Manufacturing BV (Medical Devices); Ponce, Puerto Rico On November 1, 2012, CODEZOL, C.D., grantee of FTZ 163, submitted a notification of proposed production activity to the Foreign-Trade Zones...

  8. 78 FR 52759 - Foreign-Trade Zone 265-Conroe, Texas: Authorization of Production Activity; Bauer Manufacturing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-26

    ... Foreign-Trade Zones Board Foreign-Trade Zone 265--Conroe, Texas: Authorization of Production Activity; Bauer Manufacturing Inc. (Foundation Casings and Tools/Accessories for Pile Drivers and Boring Machinery... of proposed production activity to the Foreign-Trade Zones (FTZ) Board on behalf of...

  9. Active crustal deformation of the El Salvador Fault Zone (ESFZ) using GPS data: Implications in seismic hazard assessment

    NASA Astrophysics Data System (ADS)

    Staller, Alejandra; Benito, Belen; Jesús Martínez-Díaz, José; Hernández, Douglas; Hernández-Rey, Román; Alonso-Henar, Jorge

    2014-05-01

    El Salvador, Central America, is part of the Chortis block in the northwestern boundary of the Caribbean plate. This block is interacting with a diffuse triple junction point with the Cocos and North American plates. Among the structures that cut the Miocene to Pleistocene volcanic deposits stands out the El Salvador Fault Zone (ESFZ): It is oriented in N90º-100ºE direction, and it is composed of several structural segments that deform Quaternary deposits with right-lateral and oblique slip motions. The ESFZ is seismically active and capable of producing earthquakes such as the February 13, 2001 with Mw 6.6 (Martínez-Díaz et al., 2004), that seriously affected the population, leaving many casualties. This structure plays an important role in the tectonics of the Chortis block, since its motion is directly related to the drift of the Caribbean plate to the east and not with the partitioning of the deformation of the Cocos subduction (here not coupled) (Álvarez-Gómez et al., 2008). Together with the volcanic arc of El Salvador, this zone constitutes a weakness area that allows the motion of forearc block toward the NW. The geometry and the degree of activity of the ESFZ are not studied enough. However their knowledge is essential to understand the seismic hazard associated to this important seismogenic structure. For this reason, since 2007 a GPS dense network was established along the ESFZ (ZFESNet) in order to obtain GPS velocity measurements which are later used to explain the nature of strain accumulation on major faults along the ESFZ. The current work aims at understanding active crustal deformation of the ESFZ through kinematic model. The results provide significant information to be included in a new estimation of seismic hazard taking into account the major structures in ESFZ.

  10. Development of a portable active long-path differential optical absorption spectroscopy system for volcanic gas measurements

    USGS Publications Warehouse

    Vita, Fabio; Kern, Christoph; Inguaggiato, Salvatore

    2014-01-01

    Active long-path differential optical absorption spectroscopy (LP-DOAS) has been an effective tool for measuring atmospheric trace gases for several decades. However, instruments were large, heavy and power-inefficient, making their application to remote environments extremely challenging. Recent developments in fibre-coupling telescope technology and the availability of ultraviolet light emitting diodes (UV-LEDS) have now allowed us to design and construct a lightweight, portable, low-power LP-DOAS instrument for use at remote locations and specifically for measuring degassing from active volcanic systems. The LP-DOAS was used to measure sulfur dioxide (SO2) emissions from La Fossa crater, Vulcano, Italy, where column densities of up to 1.2 × 1018 molec cm−2 (~ 500 ppmm) were detected along open paths of up to 400 m in total length. The instrument's SO2 detection limit was determined to be 2 × 1016 molec cm−2 (~ 8 ppmm), thereby making quantitative detection of even trace amounts of SO2 possible. The instrument is capable of measuring other volcanic volatile species as well. Though the spectral evaluation of the recorded data showed that chlorine monoxide (ClO) and carbon disulfide (CS2) were both below the instrument's detection limits during the experiment, the upper limits for the X / SO2 ratio (X = ClO, CS2) could be derived, and yielded 2 × 10−3 and 0.1, respectively. The robust design and versatility of the instrument make it a promising tool for monitoring of volcanic degassing and understanding processes in a range of volcanic systems.

  11. Similarities and contrasts in tectonic and volcanic style and history along the Colorado plateaus-to-basin and range transition zone in Western Arizona: Geologic framework for tertiary extensional tectonics

    NASA Technical Reports Server (NTRS)

    Young, R. A.; Mckee, E. H.; Hartman, J. H.; Simmons, A. M.

    1985-01-01

    The overall temporal and spatial relations between middle Tertiary volcanism and tectonism from the Basin and Range province onto the edge of the Colorado Plateaus province suggest that a single magnetic-tectonic episode affected the entire region more or less simultaneously during this period. The episode followed a post-Laramide (late Eocene through Oligocene) period of 25 million years of relative stability. Middle Tertiary volcanism did not migrate gradually eastward in a simple fashion onto the Colorado Plateau. In fact, late Oligocene volcanism appears to be more voluminous near the Aquarius Mountains than throughout the adjacent Basin and Range province westward to the Colorado River. Any model proposed to explain the cause of extension and detachment faulting in the eastern part of the Basin and Range province must consider that the onset of volcanism appears to have been approximately synchronous from the Colorado River region of the Basin and Range across the transition zone and onto the edge of the Colorado Plateaus.

  12. Assessing the state of our knowledge of continental arc volcanism: The Tatara-San Pedro Complex, 36°S, Andean Southern Volcanic Zone: Talca and Tatara-San Pedro, Chile 4-12 February 2007

    USGS Publications Warehouse

    Jaupart, Claude; Sisson, Thomas W.; Blundy, Jon; Arculus, Richard

    2007-01-01

    Tatara-San Pedro Volcanic Complex in Chile is one of the best studied continental arc volcanic centers in the world. In connection to this, a field forum was conducted to discuss the processes involved in the construction of such volcanoes and the origins of its magmas. With 40 international participants from diverse scientific backgrounds, the forum opened in the Talca municipal library with two days of presentation, fieldworks and a hike to the trailhead. The key issues that were tackled include information on the compositions, ages, and distributions of preserved eruptive products.

  13. 77 FR 26737 - Foreign-Trade Zone 235-Lakewood, NJ: Notification of Proposed Production Activity; Cosmetic...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-07

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE Foreign-Trade Zones Board Foreign-Trade Zone 235--Lakewood, NJ: Notification of Proposed Production Activity; Cosmetic Essence Innovations, LLC (Fragrance Bottling); Holmdel, NJ Cosmetic Essence...

  14. Geophysical signature of hydration-dehydration processes in active subduction zones

    NASA Astrophysics Data System (ADS)

    Reynard, Bruno

    2013-04-01

    Seismological and magneto-telluric tomographies are potential tools for imaging fluid circulation when combined with petrophysical models. Recent measurements of the physical properties of serpentine allow refining hydration of the mantle and fluid circulation in the mantle wedge from geophysical data. In the slab lithospheric mantle, serpentinization caused by bending at the trench is limited to a few kilometers below the oceanic crust (<5 km). Double Wadati-Benioff zones, 20-30 km below the crust, are explained by deformation of dry peridotites, not by serpentine dehydration. It reduces the required amount of water stored in solid phases in the slab (Reynard et al., 2010). In the cold (<700°C) fore-arc mantle wedge above the subducting slab, serpentinization is caused by the release of large amounts of hydrous fluids in the cold mantle above the dehydrating subducted plate. Low seismic velocities in the wedge give a time-integrated estimate of hydration and serpentinization. Serpentinization reaches 50-100% in hot subduction, while it is below 10% in cold subduction (Bezacier et al., 2010; Reynard, 2012). Electromagnetic profiles of the mantle wedge reveal high electrical-conductivity bodies. In hot areas of the mantle wedge (> 700°C), water released by dehydration of the slab induces melting of the mantle under volcanic arcs, explaining the observed high conductivities. In the cold melt-free wedge (< 700°C), high conductivities in electromagnetic profiles provide "instantaneous" images of fluid circulation because the measured electrical conductivity of serpentine is below 0.1 mS/m (Reynard et al., 2011). A small fraction (ca. 1% in volume) of connective high-salinity fluids accounts for the highest observed conductivities. Low-salinity fluids (≤ 0.1 m) released by slab dehydration evolve towards high-salinity (≥ 1 m) fluids during progressive serpentinization in the wedge. These fluids can mix with arc magmas at depths and account for high-chlorine melt

  15. Super-resolution microscopy of the synaptic active zone.

    PubMed

    Ehmann, Nadine; Sauer, Markus; Kittel, Robert J

    2015-01-01

    Brain function relies on accurate information transfer at chemical synapses. At the presynaptic active zone (AZ) a variety of specialized proteins are assembled to complex architectures, which set the basis for speed, precision and plasticity of synaptic transmission. Calcium channels are pivotal for the initiation of excitation-secretion coupling and, correspondingly, capture a central position at the AZ. Combining quantitative functional studies with modeling approaches has provided predictions of channel properties, numbers and even positions on the nanometer scale. However, elucidating the nanoscopic organization of the surrounding protein network requires direct ultrastructural access. Without this information, knowledge of molecular synaptic structure-function relationships remains incomplete. Recently, super-resolution microscopy (SRM) techniques have begun to enter the neurosciences. These approaches combine high spatial resolution with the molecular specificity of fluorescence microscopy. Here, we discuss how SRM can be used to obtain information on the organization of AZ proteins.

  16. Super-resolution microscopy of the synaptic active zone

    PubMed Central

    Ehmann, Nadine; Sauer, Markus; Kittel, Robert J.

    2015-01-01

    Brain function relies on accurate information transfer at chemical synapses. At the presynaptic active zone (AZ) a variety of specialized proteins are assembled to complex architectures, which set the basis for speed, precision and plasticity of synaptic transmission. Calcium channels are pivotal for the initiation of excitation-secretion coupling and, correspondingly, capture a central position at the AZ. Combining quantitative functional studies with modeling approaches has provided predictions of channel properties, numbers and even positions on the nanometer scale. However, elucidating the nanoscopic organization of the surrounding protein network requires direct ultrastructural access. Without this information, knowledge of molecular synaptic structure-function relationships remains incomplete. Recently, super-resolution microscopy (SRM) techniques have begun to enter the neurosciences. These approaches combine high spatial resolution with the molecular specificity of fluorescence microscopy. Here, we discuss how SRM can be used to obtain information on the organization of AZ proteins. PMID:25688186

  17. Magnetic fields over active tectonic zones in ocean

    USGS Publications Warehouse

    Kopytenko, Yu. A.; Serebrianaya, P.M.; Nikitina, L.V.; Green, A.W.

    2002-01-01

    The aim of our work is to estimate the electromagnetic effects that can be detected in the submarine zones with hydrothermal activity. It is known that meso-scale flows appear in the regions over underwater volcanoes or hot rocks. Their origin is connected with heat flux and hot jets released from underwater volcanoes or faults in a sea bottom. Values of mean velocities and turbulent velocities in plumes were estimated. Quasiconstant magnetic fields induced by a hot jet and a vortex over a plume top are about 1-40 nT. Variable magnetic fields are about 0.1-1 nT. These magnetic disturbances in the sea medium create an additional natural electromagnetic background that must be considered when making detailed magnetic surveys. ?? 2002 Elsevier Science Ltd. All rights reserved.

  18. Volcanology 2020: How will thermal remote sensing of volcanic surface activity evolve over the next decade?

    NASA Astrophysics Data System (ADS)

    Ramsey, Michael S.; Harris, Andrew J. L.

    2013-01-01

    Volcanological remote sensing spans numerous techniques, wavelength regions, data collection strategies, targets, and applications. Attempting to foresee and predict the growth vectors in this broad and rapidly developing field is therefore exceedingly difficult. However, we attempted to make such predictions at both the American Geophysical Union (AGU) meeting session entitled Volcanology 2010: How will the science and practice of volcanology change in the coming decade? held in December 2000 and the follow-up session 10 years later, Looking backward and forward: Volcanology in 2010 and 2020. In this summary paper, we assess how well we did with our predictions for specific facets of volcano remote sensing in 2000 the advances made over the most recent decade, and attempt a new look ahead to the next decade. In completing this review, we only consider the subset of the field focused on thermal infrared remote sensing of surface activity using ground-based and space-based technology and the subsequent research results. This review keeps to the original scope of both AGU presentations, and therefore does not address the entire field of volcanological remote sensing, which uses technologies in other wavelength regions (e.g., ultraviolet, radar, etc.) or the study of volcanic processes other than the those associated with surface (mostly effusive) activity. Therefore we do not consider remote sensing of ash/gas plumes, for example. In 2000, we had looked forward to a "golden age" in volcanological remote sensing, with a variety of new orbital missions both planned and recently launched. In addition, exciting field-based sensors such as hand-held thermal cameras were also becoming available and being quickly adopted by volcanologists for both monitoring and research applications. All of our predictions in 2000 came true, but at a pace far quicker than we predicted. Relative to the 2000-2010 timeframe, the coming decade will see far fewer new orbital instruments with

  19. Chemical evolution of thermal springs at Arenal Volcano, Costa Rica: Effect of volcanic activity, precipitation, seismic activity, and Earth tides

    NASA Astrophysics Data System (ADS)

    López, D. L.; Bundschuh, J.; Soto, G. J.; Fernández, J. F.; Alvarado, G. E.

    2006-09-01

    Arenal Volcano in NW Costa Rica, Central America has been active during the last 37 years. However, only relatively low temperature springs have been identified on its slopes with temperatures less than around 60 °C. The springs are clustered on the NE and NW slopes of the volcano, close to contacts between the recent and older volcanic products or at faults that intercept the volcano. This volcano is located in a rain forest region with annual rainfall averaging around 5 m. During the last 15 years, the temperature and chemical composition of 4 hot springs and 2 cold springs have been monitored approximately every 3 months. In addition, two more thermal sites were identified recently and sampled, as well as two boreholes located on a fault NE of the volcano. Scatter plots of chemical species such as Cl and B suggest that the waters in these discharges belong to the same aquifer with a saline end member similar to Río Tabacón at the beginning of the study period (1990) and the deeper borehole (B-2) in 2004. The waters of Quebrada Bambú and Quebrada Fría represent a more dilute end member. Both long-term (over the 15 years) and short-term or seasonal decreases in concentration and steady or decreasing temperature are noted in NW springs. Springs located at the NE show increasing temperatures and ion concentrations, except for bicarbonate that has decreased in concentration for all the springs. This behavior is likely associated with a shallow source for the solutes and heat for this aquifer. To the NW the early lavas and pyroclastic flows have been cooling down, decreasing the contribution of leaching products to the infiltrating waters. To the NE, pyroclastic flows to the N during the last decade are contributing increasing concentrations of solutes and heat throughout water infiltration and circulation within the faults and the surficial drainage that has a NE regional trend. For the short-term or seasonal variations, concentrations of chemical constituents

  20. Long-term risk in a recently active volcanic system: Evaluation of doses and indoor radiological risk in the quaternary Vulsini Volcanic District (Central Italy)

    NASA Astrophysics Data System (ADS)

    Capaccioni, B.; Cinelli, G.; Mostacci, D.; Tositti, L.

    2012-12-01

    Volcanic rocks in the Vulsini Volcanic District (Central Italy) contain high concentrations of 238U, 232Th and 40K due to subduction-related metasomatic enrichment of incompatible elements in the mantle source coupled with magma differentiation within the upper crust. Due to their favorable mechanical properties they have been extensively used for construction since the Etruscan age. In the old buildings of the Bolsena village, one of the most populated ancient village in the area, the major source of indoor radioactivity is 222Rn, a radioactive noble gas descendant of 238U. Direct 222Rn indoor measurements have detected extremely high values in the old center due to the combined effect of building materials, radon fluxes from the volcanic basement and low air exchange rates. In these cases the evaluated risk of developing lung cancer within a 75 year lifetime reaches up to 40% for ever smokers. Simulations of "standard rooms" built with different tuffs and lavas collected from the Vulsini Volcanic District have also provided estimations of the effective doses and lifetime risk for radiogenic cancer. Other than by the method adopted for calculation, the total evaluated risk for each volcanic rock depends on different parameters, such as: radionuclide content, radon emanation power, occupancy factor and air exchange rate. Occupancy factor and air exchange rate appear as the only controlling parameters able to mitigate the indoor radiological risk.

  1. Aerosol disturbances of the stratosphere over Tomsk according to data of lidar observations in volcanic activity period 2006-2011

    NASA Astrophysics Data System (ADS)

    Makeev, Andrey P.; Burlakov, Vladimir D.; Dolgii, Sergey I.; Nevzorov, Aleksey V.; Trifonov, Dimitar A.

    2012-11-01

    We summarize and analyze the lidar measurements (Tomsk: 56.5°N; 85.0°E) of the optical characteristics of the stratospheric aerosol layer (SAL) in the volcanic activity period 2006-2011. The background SAL state with minimal aerosol content, which was observed since 1997 under the conditions of long-term volcanically quiescent period, was interrupted in October 2006 by a series of explosive eruptions of volcanoes of the Pacific Ring of Fire: Rabaul (October 2006, New Guinea); Okmok and Kasatochi (July-August 2008, Aleutian Islands); Redoubt (March-April 2009, Alaska); Sarychev Peak (June 2009, Kuril Islands), and Grimsvötn (May 2011, Iceland). A short-term and minor disturbance of the lower stratosphere was also observed in April 2010 after eruption of the Icelandic volcano Eyjafjallajokull. The developed regional empirical model of the vertical distribution of background SAL optical characteristics was used to identify the periods of elevated stratospheric aerosol content after each of the volcanic eruptions.

  2. Early Jurassic Volcanism in the South Lhasa Terrane, Southern Tibet: Record of Back-arc Extension in the Active Continental Margin

    NASA Astrophysics Data System (ADS)

    Wei, Y.; Zhao, Z.; Zhu, D. C.; Wang, Z.; Liu, D.; Mo, X.

    2015-12-01

    Indus-Yarlung Zangbo Suture Zone (IYZSZ) represents the Mesozoic remnants of the Neo-Tethyan Ocean lithosphere after its northward subduction beneath the Lhasa Terrane. The evolution of the Neo-Tethyan Ocean prior to India-Asia collision remains unclear. To explore this period of history, we investigate zircon U-Pb geochronology, geochemistry and Nd-Hf isotopes of the Early Jurassic bimodal-like volcanic sequence around Dagze area, south Tibet. The volcanic sequence comprises calc-alkaline basalts to rhyolites whereas intermediate components are volumetrically restricted. Zircons from a basaltic andesite yielded crystallization age of 178Ma whereas those from 5 silicic rocks were dated at 183-174Ma, which suggest that both the basaltic and the silicic rocks are coeval. The basaltic rocks are enriched in LREE and LILE, and depleted in HFSE, with Epsilon Nd(t) of 1.6-4.0 and zircon Epsilon Hf(t) of 0.7-11.8, which implies that they were derived from a heterogenetic mantle source metasomatized by subduction components. Trace element geochemistry shows that the basaltic rocks are compositionally transitional from normal mid-ocean ridge basalts (N-MORB) to island arc basalts (IAB, e.g. Zedong arc basalts of ~160-155Ma in the south margin of Lhasa Terrane), with the signature of immature back-arc basin basalts. The silicic rocks display similar Nd-Hf isotopic features of the Gangdese batholith with Epsilon Nd(t) of 0.9-3.4 and zircon Epsilon Hf(t) of 2.4-17.7, indicating that they were possibly generated by anatexis of basaltic juvenile lower crust, instead of derived from the basaltic magma. These results support an Early to Middle Jurassic (183-155Ma) model that the back-arc extension tectonic setting were existing in the active continental margin in the south Lhasa Terrane.

  3. Long-Term Uplift in the Altiplano-Puna Neovolcanic Zone: Evidence of an Active Magmatic Diapir?

    NASA Astrophysics Data System (ADS)

    Fialko, Y.; Pearse, J.

    2012-12-01

    We present InSAR observations of a long-term uplift in the Altiplano-Puna neovolcanic zone (central Andes, South America). Previous observations revealed a a massive Ultra Low Velocity Zone (ULVZ) at depth of 17-19 km (Zandt et al., 2003), and surface deformation that was attributed to Uturuncu, a dormant volcano in the middle of the Altiplano-Puna neovolcanic zone (Pritchard and Simons, 2002). Our time series analysis of combined data from different sensors (ERS-1/2 and ENVISAT), satellite tracks, and observation modes (fine beam and ScanSAR) reveals that the central uplift has persisted at a nearly constant rate of ~1 cm/yr over the last two decades, and is surrounded by a broad zone of subsidence. We use the satellite line-of-sight velocities from different look directions to constrain the depth and geometry of the inferred sources of magmatic unrest. Inversions based on elastic half-space models indicate that the inflation source is located well below the brittle-ductile transition, and likely resides at the depth of the seismically imaged ULVZ. We investigated the effects of inelastic deformation in the ambient crust using finite element models. The models incorporated laboratory-derived rheologies of the ambient crust, and geotherms appropriate for an active neo-volcanic zone such as the one in the Altiplano-Puna province. Based on a large number of numerical simulations constrained by the observed surface velocities, we conclude that the ongoing uplift and peripheral subsidence result from a large mid-crustal diapir fed by a partially molten source region in the middle crust. The observed pattern of surface deformation due to the Altiplano-Puna ULVZ is remarkably similar to that due to the Socorro Magma Body (SMB) in central New Mexico, USA (Pearse and Fialko, 2010), suggesting a common process. mosaic of the mean LOS velocity showing uplift and peripheral subsidence due to the inferred mid-crustal diapir.

  4. Volcanism Assocciated Bentonite Formation (KURŞUNLU Area) in the Southern Margin of Galatean Volcanic Province , NW of Central Anatolia Turkey

    NASA Astrophysics Data System (ADS)

    Sözeri, Koray; Karakas, Zehra; Varol, Baki

    2010-05-01

    The studied area is located in the southern margin of Galatean Volcanic Province which was developed on the Upper Cretaceous accretionary complex and bounded on the north by an intercontinental shear zone - North Anatolian Fault Zone. The volcanic province shows post-collisional tectonic setting from a previously subduction-modified mantle sources , in which main volcanic activity took place through the Miocene period ( between 25-10 Ma) and the latest cycle was completed between 11-8.5 Ma represented by local alkali basaltic flows resting. on the older volcanic units that directly related rift volcanism induced by regional extensional tectonic. The volcanics assocciated with bentonite beds (Kurşunlu -Çankırı) dated as late Miocene, consist of basaltic and andesitic lavas and their pyroclastic rocks such as agglomera , volcanic breccia and tuffs which are capped by volcanic sandstones with conglomeratic interlayers. Bentonites make the outcrops in the shape of lens and heads exposed in the Kurşunlu and Şabanozu volcanics. XRD analyses have revealed that smectite is dominant clay mineral of the bentonite beds in the volcanic realms. The smectite generally is rich in Na. So it has been determined as Na-Ca smectite responding to end member. SEM study indicates that smectite was originated from alteration of feldspars, supported by revers relationship between feldspars and smectites which are gradually increased with the loose of feldispars. On the other hand some smectites were precipitated as void- or fracture fills. All findings suggest that smectites studied were formed very closed the volcanic rocks, in which feldspar alterations or dissolution under humid conditions of shallow lake or local swamps created the suitable conditions leading to formation of the bentonite beds.

  5. Geophysical expression of caldera related volcanism, structures and mineralization in the McDermitt volcanic field

    NASA Astrophysics Data System (ADS)

    Rytuba, J. J.; Blakely, R. J.; Moring, B.; Miller, R.

    2013-12-01

    30 km trend that then arcs NE into the caldera. These anomalies reflect near surface rhyolite intrusions that underlie the caldera-fill sediments that have been altered to K-feldpar and clay minerals. K gamma ray anomalies also delineate this zone of alteration. The last phase of volcanism occurs in the central part of the caldera and is associated with a broad aeromagnetic high with individual high-amplitude aeromagnetic highs coincident with three large volcanic vents. No hydrothermal alteration is associated with this last phase of volcanism. On the SW side of the McDermitt volcanic field a 10 km wide, 60 km long, NNW-trending zone of late Miocene normal faults developed after cessation of volcanism and prior to Basin and Range faulting. We propose that this extensional fault zone is the eastern continuation of the NW trending Brothers Fault Zone, but changes to a NNW trend where it is deflected by the plutons that underlies the McDermitt volcanic field. Plutons that underlie all three of these Mid Miocene volcanic fields have minimized post-caldera extensional faulting. Thus only caldera ring fracture faults were available for the development of hydrothermal systems in areas where post caldera intrusive activity was localized.

  6. Cenozoic volcanic rocks of Saudi Arabia

    USGS Publications Warehouse

    Coleman, R.G.; Gregory, R.T.; Brown, G.F.

    2016-01-01

    The historical record of volcanic activity in Saudi Arabia suggests that volcanism is dormant. The harrats should be evaluated for their potential as volcanic hazards and as sources of geothermal energy. The volcanic rocks are natural traps for groundwater; thus water resources for agriculture may be significant and should be investigated.

  7. 33 CFR 3.70-20 - Activities Far East Marine Inspection Zone.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... this part. (b) Only for this part, the boundary between Activities Far East and Activities Europe... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Activities Far East Marine... ZONES Fourteenth Coast Guard District § 3.70-20 Activities Far East Marine Inspection Zone....

  8. 33 CFR 3.70-20 - Activities Far East Marine Inspection Zone.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... this part. (b) Only for this part, the boundary between Activities Far East and Activities Europe... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Activities Far East Marine... ZONES Fourteenth Coast Guard District § 3.70-20 Activities Far East Marine Inspection Zone....

  9. 33 CFR 3.70-20 - Activities Far East Marine Inspection Zone.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... this part. (b) Only for this part, the boundary between Activities Far East and Activities Europe... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Activities Far East Marine... ZONES Fourteenth Coast Guard District § 3.70-20 Activities Far East Marine Inspection Zone....

  10. 33 CFR 3.70-20 - Activities Far East Marine Inspection Zone.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... this part. (b) Only for this part, the boundary between Activities Far East and Activities Europe... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Activities Far East Marine... ZONES Fourteenth Coast Guard District § 3.70-20 Activities Far East Marine Inspection Zone....

  11. 33 CFR 3.70-20 - Activities Far East Marine Inspection Zone.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... this part. (b) Only for this part, the boundary between Activities Far East and Activities Europe... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Activities Far East Marine... ZONES Fourteenth Coast Guard District § 3.70-20 Activities Far East Marine Inspection Zone....

  12. The Chthonomonas calidirosea Genome Is Highly Conserved across Geographic Locations and Distinct Chemical and Microbial Environments in New Zealand's Taupō Volcanic Zone

    PubMed Central

    Lee, Kevin C.; Stott, Matthew B.; Dunfield, Peter F.; Huttenhower, Curtis; McDonald, Ian R.

    2016-01-01

    ABSTRACT Chthonomonas calidirosea T49T is a low-abundance, carbohydrate-scavenging, and thermophilic soil bacterium with a seemingly disorganized genome. We hypothesized that the C. calidirosea genome would be highly responsive to local selection pressure, resulting in the divergence of its genomic content, genome organization, and carbohydrate utilization phenotype across environments. We tested this hypothesis by sequencing the genomes of four C. calidirosea isolates obtained from four separate geothermal fields in the Taupō Volcanic Zone, New Zealand. For each isolation site, we measured physicochemical attributes and defined the associated microbial community by 16S rRNA gene sequencing. Despite their ecological and geographical isolation, the genome sequences showed low divergence (maximum, 1.17%). Isolate-specific variations included single-nucleotide polymorphisms (SNPs), restriction-modification systems, and mobile elements but few major deletions and no major rearrangements. The 50-fold variation in C. calidirosea relative abundance among the four sites correlated with site environmental characteristics but not with differences in genomic content. Conversely, the carbohydrate utilization profiles of the C. calidirosea isolates corresponded to the inferred isolate phylogenies, which only partially paralleled the geographical relationships among the sample sites. Genomic sequence conservation does not entirely parallel geographic distance, suggesting that stochastic dispersal and localized extinction, which allow for rapid population homogenization with little restriction by geographical barriers, are possible mechanisms of C. calidirosea distribution. This dispersal and extinction mechanism is likely not limited to C. calidirosea but may shape the populations and genomes of many other low-abundance free-living taxa. IMPORTANCE This study compares the genomic sequence variations and metabolisms of four strains of Chthonomonas calidirosea, a rare

  13. Crystallisation ages in coeval silicic magma bodies: 238U-230Th disequilibrium evidence from the Rotoiti and earthquake flat eruption deposits, Taupo volcanic zone, New Zealand

    USGS Publications Warehouse

    Charlier, B.L.A.; Peate, D.W.; Wilson, C.J.N.; Lowenstern, J. B.; Storey, M.; Brown, S.J.A.

    2003-01-01

    The timescales over which moderate to large bodies of silicic magma are generated and stored are addressed here by studies of two geographically adjacent, successive eruption deposits in the Taupo Volcanic Zone, New Zealand. The earlier, caldera-forming Rotoiti eruption (>100 km3 magma) at Okataina volcano was followed, within months at most, by the Earthquake Flat eruption (??? 10 km3 magma) from nearby Kapenga volcano; both generated nonwelded ignimbrite and coeval widespread fall deposits. The Rotoiti and Earthquake Flat deposits are both crystal-rich high-silica rhyolites, with sparse glass-bearing granitoid fragments also occurring in Rotoiti lag breccias generated during caldera collapse. Here we report 238U-230Th disequilibrium data on whole rocks and mineral separates from representative Rotoiti and Earthquake Flat pumices and the co-eruptive Rotoiti granitoid fragments using TIMS and in situ zircon analyses by SIMS. Multiple-grain zircon-controlled crystallisation ages measured by TIMS from the Rotoiti pumice range from 69??3 ka ( 350 ka, with a pronounced peak at 70-90 ka. The weighted mean of isochrons is 83??14 ka, in accord with the TIMS data. One glass-bearing Rotoiti granitoid clast yielded an age of 57??8 ka by TIMS (controlled by Th-rich phases that, however, are not apparently present in the juvenile pumices). Another glass-bearing Rotoiti granitoid yielded SIMS zircon model ages peaking at 60-90 ka, having a similar age distribution to the pumice. Age data from pumices are consistent with a published 64??4 ka eruptive age (now modified to 62??2 ka), but chemical and/or mineralogical data imply that the granitoid lithics are not largely crystalline Rotoiti rhyolite, but instead represent contemporaneous partly molten intrusions reflecting different sources in their chemistries and mineralogies. Similarly, although the Earthquake Flat eruption immediately followed (and probably was triggered by) the Rotoiti event, age data from juvenile material

  14. Subsidence in the geothermal fields of the Taupo Volcanic Zone, New Zealand from 1996 to 2005 measured by InSAR

    NASA Astrophysics Data System (ADS)

    Hole, J. K.; Bromley, C. J.; Stevens, N. F.; Wadge, G.

    2007-10-01

    A number of the geothermal systems in the Taupo Volcanic Zone (TVZ), New Zealand, have been utilised on a large scale to provide heat and to generate electricity, in some cases causing areas of localised subsidence. Subsidence monitoring using field-based surveys is practically constrained by limits to available resources so we have investigated the use of satellite differential radar interferometry (InSAR) for this purpose. Using ERS and Envisat radar data spanning 1996 to 2005, we have mapped the deformation at five of the heavily utilised geothermal fields of the TVZ. Subsidence signals were identified at the Ohaaki geothermal field from 1999-2004, and at Wairakei-Tauhara from 1996-2005, where our measurements compare well with coeval levelling data across the wider deformation field. Subsidence was also measured at Rotorua from 1996-2000. In favourable conditions, the InSAR measurements provide a relatively dense spatial coverage of the deformation field that extends well beyond the boundaries of the geothermal systems and beyond the scope of the networks of levelling benchmarks. In the case of the Wairakei-Tauhara geothermal field, using InSAR it is now possible to improve the spatial resolution near the field margins and to interpret the subsidence signals in the context of the wider, more regional, deformation. Our data also provide new insights into possible fault motion at the Mokai geothermal field occurring around the time of the commissioning of its first power station. We note, however, that the InSAR technique is not without limitations. High gradient subsidence features are poorly represented, although this can be resolved to some extent via a trade-off in data processing. Temporal decorrelation, a well known problem for this technique, is also an issue for TVZ geothermal fields. Therefore, we find that it is possible to provide fortuitous snapshots of the deformation at the TVZ geothermal fields, but operational monitoring using InSAR would be

  15. Lake-level rise in the late Pleistocene and active subaquatic volcanism since the Holocene in Lake Kivu, East African Rift

    NASA Astrophysics Data System (ADS)

    Ross, Kelly Ann; Smets, Benoît; De Batist, Marc; Hilbe, Michael; Schmid, Martin; Anselmetti, Flavio S.

    2014-09-01

    The history of Lake Kivu is strongly linked to the activity of the Virunga volcanoes. Subaerial and subaquatic volcanoes, in addition to lake-level changes, shape the subaquatic morphologic and structural features in Lake Kivu's Main Basin. Previous studies revealed that volcanic eruptions blocked the former outlet of the lake to the north in the late Pleistocene, leading to a substantial rise in the lake level and subsequently the present-day thermohaline stratification. Additional studies have speculated that volcanic and seismic activities threaten to trigger a catastrophic release of the large amount of gases dissolved in the lake. The current study presents a bathymetric mapping and seismic profiling survey that covers the volcanically active area of the Main Basin at a resolution that is unprecedented for Lake Kivu. New geomorphologic features identified on the lake floor can accurately describe related lake-floor processes for the first time. The late Pleistocene lowstand is observed at 425 m depth, and volcanic cones, tuff rings, and lava flows observed above this level indicate both subaerial and subaquatic volcanic activities during the Holocene. The geomorphologic analysis yields new implications on the geologic processes that have shaped Lake Kivu's basin, and the presence of young volcanic features can be linked to the possibility of a lake overturn.

  16. Magmatic activity beneath the quiescent Three Sisters volcanic center, central Oregon Cascade Range, USA

    USGS Publications Warehouse

    Wicks, Charles W.; Dzurisin, Daniel; Ingebritsen, Steven E.; Thatcher, Wayne R.; Lu, Zhong; Iverson, Justin

    2002-01-01

    Images from satellite interferometric synthetic aperture radar (InSAR) reveal uplift of a broad ???10 km by 20 km area in the Three Sisters volcanic center of the central Oregon Cascade Range, ???130 km south of Mt. St. Helens. The last eruption in the volcanic center occurred ???1500 years ago. Multiple satellite images from 1992 through 2000 indicate that most if not all of ???100 mm of observed uplift occurred between September 1998 and October 2000. Geochemical (water chemistry) anomalies, first noted during 1990, coincide with the area of uplift and suggest the existence of a crustal magma reservoir prior to the uplift. We interpret the uplift as inflation caused by an ongoing episode of magma intrusion at a depth of ???6.5 km.

  17. Localization of Volcanic Activity: Topographic Effects on Dike Propagation, Eruption and COnduit Formation

    SciTech Connect

    E.S. Gaffney; B. Damjanac

    2006-05-12

    Magma flow in a dike rising in a crack whose strike runs from a highland or a ridge to an adjacent lowland has been modeled to determine the effect of topography on the flow. It is found that there is a distinct tendency for the flow to be diverted away from the highland end of the strike toward the lowland. Separation of the geometric effect of the topography from its effect on lateral confining stresses on the crack indicates that both contribute to the effect but that the effect of stress is less important. Although this analysis explains a tendency for volcanic eruptions to occur in low lands, it does not preclude eruptions on highlands. The particular configuration modeled mimics topography around the proposed nuclear waste repository at Yucca Mountain, Nevada, so that the results may indicate some reduction in the volcanic hazard to the site.

  18. Evidence of recent volcanic activity on the ultraslow-spreading Gakkel ridge.

    PubMed

    Edwards, M H; Kurras, G J; Tolstoy, M; Bohnenstiehl, D R; Coakley, B J; Cochran, J R

    2001-02-15

    Seafloor spreading is accommodated by volcanic and tectonic processes along the global mid-ocean ridge system. As spreading rate decreases the influence of volcanism also decreases, and it is unknown whether significant volcanism occurs at all at ultraslow spreading rates (<1.5 cm yr(-1)). Here we present three-dimensional sonar maps of the Gakkel ridge, Earth's slowest-spreading mid-ocean ridge, located in the Arctic basin under the Arctic Ocean ice canopy. We acquired this data using hull-mounted sonars attached to a nuclear-powered submarine, the USS Hawkbill. Sidescan data for the ultraslow-spreading (approximately 1.0 cm yr(-1)) eastern Gakkel ridge depict two young volcanoes covering approximately 720 km2 of an otherwise heavily sedimented axial valley. The western volcano coincides with the average location of epicentres for more than 250 teleseismic events detected in 1999, suggesting that an axial eruption was imaged shortly after its occurrence. These findings demonstrate that eruptions along the ultraslow-spreading Gakkel ridge are focused at discrete locations and appear to be more voluminous and occur more frequently than was previously thought.

  19. Evidence of recent volcanic activity on the ultraslow-spreading Gakkel ridge.

    PubMed

    Edwards, M H; Kurras, G J; Tolstoy, M; Bohnenstiehl, D R; Coakley, B J; Cochran, J R

    2001-02-15

    Seafloor spreading is accommodated by volcanic and tectonic processes along the global mid-ocean ridge system. As spreading rate decreases the influence of volcanism also decreases, and it is unknown whether significant volcanism occurs at all at ultraslow spreading rates (<1.5 cm yr(-1)). Here we present three-dimensional sonar maps of the Gakkel ridge, Earth's slowest-spreading mid-ocean ridge, located in the Arctic basin under the Arctic Ocean ice canopy. We acquired this data using hull-mounted sonars attached to a nuclear-powered submarine, the USS Hawkbill. Sidescan data for the ultraslow-spreading (approximately 1.0 cm yr(-1)) eastern Gakkel ridge depict two young volcanoes covering approximately 720 km2 of an otherwise heavily sedimented axial valley. The western volcano coincides with the average location of epicentres for more than 250 teleseismic events detected in 1999, suggesting that an axial eruption was imaged shortly after its occurrence. These findings demonstrate that eruptions along the ultraslow-spreading Gakkel ridge are focused at discrete locations and appear to be more voluminous and occur more frequently than was previously thought. PMID:11236991

  20. Ten years of soil CO2 continuous monitoring on Mt. Etna: Exploring the relationship between processes of soil degassing and volcanic activity

    NASA Astrophysics Data System (ADS)

    Liuzzo, Marco; Gurrieri, Sergio; Giudice, Gaetano; Giuffrida, Giovanni

    2013-08-01

    The measurement of soil CO2 flux variations is a well-established practice in many volcanic areas around the world. Until recently, however, most of these were made using direct sampling methods. These days, a variety of automatic devices providing real-time data now make the continuous monitoring of volcanic areas possible. A network of automatic geochemical monitoring stations (EtnaGas network) was developed by INGV Palermo and installed at various sites on the flanks of Mt. Etna. Here, we present a large set of soil CO2 flux data recorded by the network, dating back 10 years, a period in which several noteworthy eruptive phenomena occurred. Our statistical analysis strongly suggests that anomalous measurements of soil CO2 flux are attributable to volcanic origin and in almost all cases precede volcanic activity. Here, we present the actual data series recorded by EtnaGAS and an interpretative model of the expected behavior of soil CO2 flux (in terms of increase-decrease cycles), which corresponded well with the volcanic activity during this period. Through the use of a comparative approach, incorporating both volcanological and geochemical data, the global soil CO2 flux trends are put into a coherent framework, highlighting close links between the time flux variations and volcanic activities. These insights, made possible from 10 years of uninterrupted data, confirm the importance of continuous monitoring of volcanic soil degassing, and may contribute in the forecasting of imminent eruptive activity or the temporal evolution of an in-progress eruption, therefore facilitating Civil Defense planning in volcanic areas under high-hazard conditions.

  1. 78 FR 20091 - Foreign-Trade Zone 26-Atlanta, Georgia, Authorization of Production Activity, Perkins Shibaura...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-03

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE Foreign-Trade Zones Board Foreign-Trade Zone 26--Atlanta, Georgia, Authorization of Production Activity, Perkins Shibaura Engines, LLC (Diesel Engines), Griffin, Georgia On November 29, 2012, Georgia Foreign-Trade Zone, Inc., grantee of FTZ 26,...

  2. 78 FR 28801 - Foreign-Trade Zone 117-Orange, TX, Authorization of Production Activity, Signal International...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-16

    ... notice in the Federal Register inviting public comment (78 FR 4383, 1-22-2013). The FTZ Board has... Foreign-Trade Zones Board Foreign-Trade Zone 117--Orange, TX, Authorization of Production Activity, Signal International Texas GP, LLC (Shipbuilding), Orange, TX On January 10, 2013, the Foreign Trade Zone of...

  3. Eighteen years of geochemical monitoring at the oceanic active volcanic island of El Hierro (Canary Islands, Spain)

    NASA Astrophysics Data System (ADS)

    Asensio-Ramos, María; Alonso, Mar; Sharp, Emerson; Woods, Hannah; Barrancos, José; Pérez, Nemesio M.

    2016-04-01

    We report herein the latest results of a diffuse CO2 efflux survey at El Hierro volcanic system carried out during the summer period of 2015 to constrain the total CO2 output from the studied area a during post-eruptive period. El Hierro Island (278 km2) is the youngest and the SW-most of the Canary Islands. On July 16, 2011, a seismic-volcanic crisis started with the occurrence of more than 11,900 seismic events and significant deformation along the island. On October 10, 2011, the dominant character of seismicity changed dramatically from discrete earthquakes to continuous tremor, a clear indication that magma was rapidly approaching the surface immediately before the onset of the eruption, October 12. Eruption was declared over on 5 March, 2012. In order to monitor the volcanic activity of El Hierro Island, from 1998 to 2015 diffuse CO2 emission studies have been performed at El Hierro volcanic system in a yearly basis (˜600 observation sites) according to the accumulation chamber method. Spatial distribution maps were constructed following the sequential Gaussian simulation (sGs) procedure. To quantify the total CO2 emission from the studied area, 100 simulations for each survey have been performed. During the eruption period, soil CO2 efflux values range from non-detectable (˜0.5 g m-2 d-1) up to 457 g m-2 d-1, reaching in November 27, 2011, the maximum CO2 output estimated value of all time series, 2,398 t d-1, just before the episodes of maximum degassing observed as vigorous bubbling at the sea surface and an increment in the amplitude of the tremor signal. During the 2015 survey, soil CO2 efflux values ranged from non-detectable up to 41 g m-2 d-1. The spatial distribution of diffuse CO2 emission values seemed to be controlled by the main volcano structural features of the island. The total diffuse CO2 output released to atmosphere was estimated at 575 ± 24 t d-1, value slightly higher that the background CO2 emission estimated at 422 t d-1 (Melián et

  4. Eighteen years of geochemical monitoring at the oceanic active volcanic island of El Hierro (Canary Islands, Spain)

    NASA Astrophysics Data System (ADS)

    Asensio-Ramos, María; Alonso, Mar; Sharp, Emerson; Woods, Hannah; Barrancos, José; Pérez, Nemesio M.

    2016-04-01

    We report herein the latest results of a diffuse CO2 efflux survey at El Hierro volcanic system carried out during the summer period of 2015 to constrain the total CO2 output from the studied area a during post-eruptive period. El Hierro Island (278 km2) is the youngest and the SW-most of the Canary Islands. On July 16, 2011, a seismic-volcanic crisis started with the occurrence of more than 11,900 seismic events and significant deformation along the island. On October 10, 2011, the dominant character of seismicity changed dramatically from discrete earthquakes to continuous tremor, a clear indication that magma was rapidly approaching the surface immediately before the onset of the eruption, October 12. Eruption was declared over on 5 March, 2012. In order to monitor the volcanic activity of El Hierro Island, from 1998 to 2015 diffuse CO2 emission studies have been performed at El Hierro volcanic system in a yearly basis (˜600 observation sites) according to the accumulation chamber method. Spatial distribution maps were constructed following the sequential Gaussian simulation (sGs) procedure. To quantify the total CO2 emission from the studied area, 100 simulations for each survey have been performed. During the eruption period, soil CO2 efflux values range from non-detectable (˜0.5 g m‑2 d‑1) up to 457 g m‑2 d‑1, reaching in November 27, 2011, the maximum CO2 output estimated value of all time series, 2,398 t d‑1, just before the episodes of maximum degassing observed as vigorous bubbling at the sea surface and an increment in the amplitude of the tremor signal. During the 2015 survey, soil CO2 efflux values ranged from non-detectable up to 41 g m‑2 d‑1. The spatial distribution of diffuse CO2 emission values seemed to be controlled by the main volcano structural features of the island. The total diffuse CO2 output released to atmosphere was estimated at 575 ± 24 t d‑1, value slightly higher that the background CO2 emission estimated at 422 t

  5. Volcanism Studies: Final Report for the Yucca Mountain Project

    SciTech Connect

    Bruce M. Crowe; Frank V. Perry; Greg A. Valentine; Lynn M. Bowker

    1998-12-01

    This report synthesizes the results of volcanism studies conducted by scientists at the Los Alamos National Laboratory and collaborating institutions on behalf of the Department of Energy's Yucca Mountain Project. An assessment of the risk of future volcanic activity is one of many site characterization studies that must be completed to evaluate the Yucca Mountain site for potential long-term storage of high-level radioactive waste. The presence of several basaltic volcanic centers in the Yucca Mountain region of Pliocene and Quaternary age indicates that there is a finite risk of a future volcanic event occurring during the 10,000-year isolation period of a potential repository. Chapter 1 introduces the volcanism issue for the Yucca Mountain site and provides the reader with an overview of the organization, content, and significant conclusions of this report. The risk of future basaltic volcanism is the primary topic of concern including both events that intersect a potential repository and events that occur near or within the waste isolation system of a repository. Future volcanic events cannot be predicted with certainty but instead are estimated using formal methods of probabilistic volcanic hazard assessment (PVHA). Chapter 2 describes the volcanic history of the Yucca Mountain region (YMR) and emphasizes the Pliocene and Quaternary volcanic record, the interval of primary concern for volcanic risk assessment. The distribution, eruptive history, and geochronology of Plio-Quaternary basalt centers are described by individual center emphasizing the younger postcaldera basalt (<5 Ma). The Lathrop Wells volcanic center is described in detail because it is the youngest basalt center in the YMR. The age of the Lathrop Wells center is now confidently determined to be about 75 thousand years old. Chapter 3 describes the tectonic setting of the YMR and presents and assesses the significance of multiple alternative tectonic models. The Crater Flat volcanic zone is

  6. DYNAMICS OF NASCENT AND ACTIVE ZONE ULTRASTRUCTURE AS SYNAPSES ENLARGE DURING LTP IN MATURE HIPPOCAMPUS

    PubMed Central

    Bell, Maria Elizabeth; Bourne, Jennifer N.; Chirillo, Michael A.; Mendenhall, John M.; Kuwajima, Masaaki; Harris, Kristen M.

    2014-01-01

    Nascent zones and active zones are adjacent synaptic regions that share a postsynaptic density, but nascent zones lack the presynaptic vesicles found at active zones. Here dendritic spine synapses were reconstructed through serial section electron microscopy (3DEM) and EM tomography to investigate nascent zone dynamics during long-term potentiation (LTP) in mature rat hippocampus. LTP was induced with theta-burst stimulation and comparisons were made to control stimulation in the same hippocampal slices at 5 minutes, 30 minutes, and 2 hours post-induction and to perfusion-fixed hippocampus in vivo. Nascent zones were present at the edges of ~35% of synapses in perfusion-fixed hippocampus and as many as ~50% of synapses in some hippocampal slice conditions. By 5 minutes, small dense core vesicles known to transport active zone proteins moved into more presynaptic boutons. By 30 minutes, nascent zone area decreased without significant change in synapse area, suggesting that presynaptic vesicles were recruited to pre-existing nascent zones. By 2 hours, both nascent and active zones were enlarged. Immunogold labeling revealed that glutamate receptors can be found in nascent zones; however, average distances from nascent zones to docked presynaptic vesicles ranged from 170±5 nm in perfusion-fixed hippocampus to 251±4 nm at enlarged synapses by 2 hours during LTP. Prior stochastic modeling suggests that falloff in glutamate concentration reduces the probability of glutamate receptor activation from 0.4 at the center of release to 0.1 just 200 nm away. Thus, conversion of nascent zones to functional active zones likely requires the recruitment of presynaptic vesicles during LTP. PMID:25043676

  7. Maturation of active zone assembly by Drosophila Bruchpilot

    PubMed Central

    Fouquet, Wernher; Owald, David; Wichmann, Carolin; Mertel, Sara; Depner, Harald; Dyba, Marcus; Hallermann, Stefan; Kittel, Robert J.; Eimer, Stefan

    2009-01-01

    Synaptic vesicles fuse at active zone (AZ) membranes where Ca2+ channels are clustered and that are typically decorated by electron-dense projections. Recently, mutants of the Drosophila melanogaster ERC/CAST family protein Bruchpilot (BRP) were shown to lack dense projections (T-bars) and to suffer from Ca2+ channel–clustering defects. In this study, we used high resolution light microscopy, electron microscopy, and intravital imaging to analyze the function of BRP in AZ assembly. Consistent with truncated BRP variants forming shortened T-bars, we identify BRP as a direct T-bar component at the AZ center with its N terminus closer to the AZ membrane than its C terminus. In contrast, Drosophila Liprin-α, another AZ-organizing protein, precedes BRP during the assembly of newly forming AZs by several hours and surrounds the AZ center in few discrete punctae. BRP seems responsible for effectively clustering Ca2+ channels beneath the T-bar density late in a protracted AZ formation process, potentially through a direct molecular interaction with intracellular Ca2+ channel domains. PMID:19596851

  8. Volcanic mesocyclones.

    PubMed

    Chakraborty, Pinaki; Gioia, Gustavo; Kieffer, Susan W

    2009-03-26

    A strong volcanic plume consists of a vertical column of hot gases and dust topped with a horizontal 'umbrella'. The column rises, buoyed by entrained and heated ambient air, reaches the neutral-buoyancy level, then spreads radially to form the umbrella. In classical models of strong volcanic plumes, the plume is assumed to remain always axisymmetric and non-rotating. Here we show that the updraught of the rising column induces a hydrodynamic effect not addressed to date-a 'volcanic mesocyclone'. This volcanic mesocyclone sets the entire plume rotating about its axis, as confirmed by an unprecedented analysis of satellite images from the 1991 eruption of Mount Pinatubo. Destabilized by the rotation, the umbrella loses axial symmetry and becomes lobate in plan view, in accord with satellite records of recent eruptions on Mounts Pinatubo, Manam, Reventador, Okmok, Chaiten and Ruang. The volcanic mesocyclone spawns waterspouts or dust devils, as seen in numerous eruptions, and groups the electric charges about the plume to form the 'lightning sheath' that was so prominent in the recent eruption of Mount Chaiten. The concept of a volcanic mesocyclone provides a unified explanation for a disparate set of poorly understood phenomena in strong volcanic plumes. PMID:19325632

  9. The Eldivan ophiolite and volcanic rocks in the İzmir-Ankara-Erzincan suture zone, Northern Turkey: Geochronology, whole-rock geochemical and Nd-Sr-Pb isotope characteristics

    NASA Astrophysics Data System (ADS)

    Çelik, Ömer Faruk; Chiaradia, Massimo; Marzoli, Andrea; Billor, Zeki; Marschik, Robert

    2013-07-01

    Gabbros and dolerite dikes of the Eldivan ophiolite and basaltic volcanic rocks of the ophiolitic mélange in the central part of the İzmir-Ankara-Erzincan (IAE) suture zone were investigated for their 40Ar/39Ar age and whole-rock-major-trace element and Sr-Nd-Pb isotope compositions. Based on geological and geochemical characteristics basaltic volcanic rocks in the ophiolitic mélange are subdivided into two groups (Groups I and II) with ocean island basalts or enriched mid-ocean ridge basalt characteristics, respectively. Gabbros and dolerite dikes of the Eldivan ophiolite (Groups III and IV) have instead geochemical compositions indicative of a subduction-related environment. The volcanic rocks of Group I have 87Sr/86Sr(i) between 0.7037 and 0.7044, ƐNd(i)-DM of - 4.5 to - 5.6, and 206Pb/204Pb(i) ranging between 18.35 and 18.75. Group II volcanic rocks have higher 87Sr/86Sr(i) values (0.7049-0.7055), ƐNd(i)-DM ranging between - 5.4 and - 6.0, and 206Pb/204Pb(i) between 18.14 and 18.62. The Nd isotopic signatures and 207Pb/204Pb(i) values of the volcanic rocks of both groups point to a different source with respect to those of the Eldivan ophiolite. The low 206Pb/204Pb(i) values relative to the ophiolitic rocks seem to exclude a significant contribution from a HIMU reservoir, whereas the 207Pb/204Pb(i) values slightly above the NHRL might indicate some contribution from an EM2-type reservoir. Gabbros (Group III) of the Eldivan ophiolite and dolerite dikes (Group IV) cross-cutting the ultramafic part of the ophiolite show 87Sr/86Sr(i) between 0.7038 and 0.7053, ƐNd(i)-DM from - 2 to - 3.6 and 206Pb/204Pb(i) between 18.10 and 18.80. The gabbros yield ca. 150 Ma 40Ar/39Ar amphibole-plateau ages, which, together with the geochemical data, indicate that they were produced above subducted oceanic lithosphere in the IAE ocean domain in Late Jurassic times. Therefore, the Eldivan ophiolite in the IAE suture zone constitutes a link between the Hellenide

  10. Factors controlling the final depth of active and failed continental rift zones

    NASA Astrophysics Data System (ADS)

    Thybo, H.; Elesin, Y.; Artemieva, I. M.

    2012-12-01

    Rift zones are elongated, narrow tectonic depressions in the Earth's surface which with time become filled with sediments and volcanics. Rifting processes may lead to break-up of continental plates to form new oceanic lithosphere. Subsidence of rift basins is caused by thinning of the crust and lithospheric mantle, together with thermal relaxation and isostatic compensation for the extra load of sediments. It is generally believed that the final depth of rift basins is primarily controlled by the amount of stretching. However, we show that the relative rheological strength of faults inside and outside rift zones exerts substantial control on the volume of the final rift basin (by more than a factor of 3) even for the same amount of extension (total or inside the rift zone). This surprising result is mainly caused by irreversible deepening of the rift graben during stretching due to lower crustal flow when the faults in the rift zone are weak, whereas the effect is negligible for strong faults. Relatively strong faults inside the rift zone lead to substantial stretching of adjacent crust, and we find that long term stretching outside the main rift zone may explain the formation of wide continental margins, which are now below sea level. We also demonstrate that fast syn-rift erosion/sedimentation rates can increase the final volume of rift basins by up to a factor of 1.7 for weak crustal faults, whereas this effect is insignificant for strong faults inside the rift zone. These findings have significant implications for estimation of stretching factors, tectonic forces, and geodynamic evolution of sedimentary basins around failed rift zones.