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Sample records for active volcanic zone

  1. Okataina Volcanic Centre, Taupo Volcanic Zone, New Zealand: A review of volcanism and synchronous pluton development in an active, dominantly silicic caldera system

    NASA Astrophysics Data System (ADS)

    Cole, J. W.; Deering, C. D.; Burt, R. M.; Sewell, S.; Shane, P. A. R.; Matthews, N. E.

    2014-01-01

    The Okataina Volcanic Centre (OVC) is one of eight caldera systems, which form the central part of the Taupo Volcanic Zone, New Zealand. During its ~ 625 kyr volcanic history, which perhaps equates to ~ 750 kyr of magmatic history, the OVC has experienced two definite periods of caldera collapse (Matahina, ~ 322 ka, and Rotoiti, for which dates of 61 and 45 ka have recently been published), one probable collapse (Utu, ~ 557 ka) and one possible collapse (Kawerau, ~ 33 ka). Each collapse accompanied voluminous ignimbrite eruptions. Rhyolite dome extrusion and explosive tephra eruptions have occurred throughout the history of OVC.

  2. Rates of volcanic activity along the southwest rift zone of Mauna Loa volcano, Hawaii.

    USGS Publications Warehouse

    Lipman, P.W.

    1981-01-01

    Flow-by-flow mapping of the 65 km long subaerial part of the southwest rift zone and adjacent flanks of Mauna Loa Volcano, Hawaii, and about 50 new 14C dates on charcoal from beneath these flows permit estimates of rates of lava accumulation and volcanic growth over the past 10 000 years. The sequence of historic eruptions along the southwest rift zone, beginning in 1868, shows a general pattern of uprift migration and increasing eruptive volume, culminating in the great 1950 eruption. No event comparable to 1950, in terms of volume or vent length, is evident for at least the previous 1000 years. Rates of lava accumulation along the zone have been subequal to those of Kilauea Volcano during the historic period but they were much lower in late prehistoric time (unpubl. Kilauea data by R. T. Holcomb). Rates of surface covering and volcanic growth have been markedly asymmetric along Mauna Loa's southwest rift zone. Accumulation rates have been about half again as great on the northwest side of the rift zone in comparison with the southeast side. The difference apparently reflects a westward lateral shift of the rift zone of Mauna Loa away from Kilauea Volcano, which may have acted as a barrier to symmetrical growth of the rift zone. -Author

  3. 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.

  4. Volcanism and aseismic slip in subduction zones

    SciTech Connect

    Acharya, H.

    1981-01-10

    The spatial and temporal relationship of volcanism to the occurrence of large earthquakes and convergent plate motion is examined. The number of volcanic eruptions per year in a convergent zone is found to be linearly related to the aseismic slip component of plate motion. If the aseismic slip rate is low (coupling between converging plates is strong), then the primary manifestation of tectonic activity is the occurrence of large earthquakes with only infrequent volcanic activity. If, however, the aseismic slip rate is high (coupling is weak), then there are few large earthquakes, and volcanism is the principal manifestation of tectonic activity. This model is consistent with the spatial distribution of large earthquakes and active volcanoes in the circum-Pacific area. It is tested by examining the extent of volcanic activity in the rupture zones of the 1952--1973 sequence of earthquakes in the Japan--Kurile Islands area. The number of volcanic euptions along these zones during the interval between large earthquakes is used to compute the aseismic slip rates for these segments, based on the relationship developed in this study. The aseismic slip rates so computed agree with those determined from the earthquake history of the area and rates of plate motion. The agreement suggests that in the interval between large earthquakes, the aseismic plate motion is manifested in a specific number of volcanic eruptions. Therefore in areas with adequate historial data it should be possible to use the model developed in this study to monitor volcanic eruptions for long-term prediction of large earthquakes.

  5. 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

  6. 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.

  7. Three-dimensional electrical resistivity image of magma beneath an active continental rift, Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Heise, Wiebke; Caldwell, T. Grant; Bibby, Hugh M.; Bennie, Stewart L.

    2010-05-01

    Magmatic activity in regions of continental extension may result in huge (>400 km3) explosive eruptions of viscous, gas-rich silicic-magma. Geochemical and geological data suggest that the large volumes of magma erupted are produced by extracting interstitial liquid from a long-lived ‘mush zone’ (a mixture of solid crystals and liquid melt) that accumulates in liquid-dominated lenses at the top of a much thicker region of lower melt-fraction mush. Such lenses will be highly electrically conductive compared with normal mid-crustal rocks. Here we use results of 220 magnetotelluric (MT) soundings to construct a 3-D electrical resistivity image of the northern (silicic) part of New Zealand's Taupo Volcanic Zone, a young continental rift associated with very high heat flow and intense silicic volcanism. The electrical resistivity image shows a plume-like structure of high conductivity, interpreted to be a zone of interconnected melt, rising from depths >35 km beneath the axis of extension.

  8. Earthquake swarm activity highlights crustal faulting associated with the Waimangu-Rotomahana-Mt Tarawera geothermal field, Taupo Volcanic Zone

    NASA Astrophysics Data System (ADS)

    Bannister, Stephen; Sherburn, Steven; Bourguignon, Sandra

    2016-03-01

    The Waimangu-Rotomahana-Mt.Tarawera geothermal field (WRTGF) in the Taupo Volcanic Zone, New Zealand, experiences frequent but sporadic earthquake swarms with durations of less than 1 day. Here we examine detailed locations of the seismic activity using precise double-difference relative location techniques. We utilize a combination of cross-correlation-derived arrival times and catalogue-based arrival times from 582 earthquakes recorded in the area between 2004 and 2015 for the relocation analysis. The new earthquake locations highlight a ~ 6 km long NE-SW lineation, which we infer to represent a sub-surface fault that extends along the northern side of Waimangu geothermal system and the north-western end of Lake Rotomahana. We suggest that this structural feature acts as a permeable pathway for aqueous fluid and CO2 release up to the surface geothermal field and Lake Rotomahana, from a deeper magmatic source.

  9. A multidisciplinary study in the geodynamic active western Eger rift (Central Europe): The Quaternary volcanic complex Mytina and the recent CO2-degassing zone Hartousov

    NASA Astrophysics Data System (ADS)

    Flechsig, C.; Heinicke, J.; Kaempf, H. W.; Nickschick, T.; Mrlina, J.

    2013-12-01

    The Eger rift (Central Europe) belongs to the European Cenozoic rift system and represents an approximately 50 km wide and 300 km long ENE-WSW striking continental rift that formed during the Upper Cretaceous-Tertiary transition. This rift zone is one of the most active seismic regions in Central Europe. Especially, the western part of the Eger rift area is dominated by ongoing hidden magmatic processes in the intra-continental lithospheric mantle. Besides of known quaternary volcanoes, these processes take place in absence of any presently active volcanism at the surface. However, they are expressed by a series of phenomena distributed over a relatively large area, like occurrence of repeated earthquake swarms, surface exhalation of mantle-derived and CO2-enriched fluids at mofettes and mineral springs, and enhanced heat flow. At present this is the only known intra-continental region where such deep-seated, active lithospheric processes currently occur. The aim of the project is to investigate the tectonic/geologic near surface structure and the degassing processes of the mofette field of Hartousov, where soil gas measurements (concentration and flux rate) in an area of appr. 3x2 km traced a permeable NS extended segment of a fault zone and revealed highly permeable Diffuse Degassing Structures (DDS). The second target is volcanic environment of the Quaternary volcanic complex Mytina maar and the cinder cone Zelezna hurka/Eisenbühl. The investigations are intended to clarify: a) the spatio-temporal reconstruction of the maar complex, and the palaeo volcanic scenario (geological model, tectonic settings, distribution of pyroclastica, b) the geological structure and the tectonic control of the recent degassing zone, and c) the comperative interpretation of both regions in the consideration of potential future volcanic risk assessment in sub-regions of the western Eger Rift. To investigate both regions the following methods are used: geoelectrics, geomagnetics

  10. 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

  11. 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

  12. Venus - Limited extension and volcanism along zones of lithospheric weakness

    NASA Technical Reports Server (NTRS)

    Schaber, G. G.

    1982-01-01

    Three global-scale zones of possible tectonic origin are described as occurring along broad, low rises within the Equatorial Highlands on Venus (lat 50 deg N to 50 deg S, long 60 deg to 310 deg). The two longest of these tectonic zones, the Aphrodite-Beta and Themis-Atla zones, extend for 21,000 and 14,000 km, respectively. Several lines of evidence indicate that Beta and Atla Regiones, located at the only two intersections of the three major tectonic zones, are dynamically supported volcanic terranes associated with currently active volcanism. Rift valleys south of Aphrodite Terra and between Beta and Phoebe Regiones are characterized by 75- to 100-km widths, raised rims, and extensions of only a few tens of kilometers, about the same magnitudes as in continental rifts on the earth. Horizontal extension on Venus was probably restricted by an early choking-off of plate motion by high crustal and upper-mantle temperatures, and the subsequent loss of water and an asthenosphere.

  13. Resistivity structure of the central Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

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

    1999-06-01

    The Taupo Fault Belt (TFB) is a 15-km-wide zone of active normal faulting, which is located in the central portion of the Taupo Volcanic Zone (TVZ), New Zealand, and is aligned sub-parallel to the strike of this zone. A large-scale multiple-source bipole-dipole resistivity survey has shown that the TFB is characterised by high resistivity (ca. 250 Ωm) to depths of ca. 7 km, in contrast to the adjacent regions in the east and west of the TVZ where resistivities are much lower (<50 Ωm). The eastern edge of the TFB is marked by the Paeroa fault. East of the fault, the Taupo-Reporoa depression is filled with volcaniclastic rocks that have low resistivities believed to be caused by the presence of clay alteration. At the Paeroa fault, the conductive volcaniclastics are downthrown to the west by about 1 km but they can be traced no more than 2.5 km west into the TFB. To the west of the TFB, a low-resistivity layer about 500 m deep has been identified as a sequence of older (>1 Ma) ignimbrites that have undergone slow diagenetic alteration that has produced clay minerals. The volcaniclastics in the TFB have high resistivities which suggests that they have not undergone significant alteration and are thus younger than the volcaniclastics in the regions to both east and west. These high resistivities are also consistent with the absence of surface geothermal activity and low heat flow. The TFB also exhibits high seismicity and active faulting in contrast with its surrounding. It was not possible to determine the depth to basement rocks in the TFB because of the lack of resistivity contrast between the basement and the overlying volcanics, but gravity data indicate that the young volcanics are no more than 3 km thick.

  14. 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.

  15. 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

  16. 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.

  17. 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

  18. Surface deformation in volcanic rift zones

    NASA Astrophysics Data System (ADS)

    Pollard, David D.; Delaney, Paul T.; Duffield, Wendell A.; Endo, Elliot T.; Okamura, Arnold T.

    1983-05-01

    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.

  19. 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.

  20. Planetary volcanism - A study of volcanic activity in the solar system

    NASA Technical Reports Server (NTRS)

    Cattermole, Peter

    1989-01-01

    The nature of volcanic activity, theoretical models of its role in planetary evolution, and the evidence for volcanism on the planets and planetary satellites are examined in an introductory overview for advanced undergraduate and graduate students. Chapters are devoted to volcanism as a planetary process, the generation and evolution of magmas, magma ascent and eruption, the properties and behavior of volcanic flows, volcanic landforms, the distribution of volcanic rocks in the solar system, and volcanic plains and their development. Consideration is given to lunar volcanism, shield volcanoes and paterae, volcanism on Io, volcanism on icy satellites, and the rheological analysis of volcanic flows.

  1. Volcanically Active Regions on Io

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Shown here is a portion of one of the highest-resolution images of Io (Latitude: +10 to +60 degrees, Longitude: 180 to 225 degrees) acquired by the Galileo spacecraft, revealing immense lava flows and other volcanic landforms. Several high-temperature volcanic hot spots have been detected in this region by both the Near Infrared Mapping Spectrometer and the imaging system of Galileo. The temperatures are consistent with active silicate volcanism in lava flows or lava lakes (which reside inside irregular depressions called calderas). The large dark lava flow in the upper left region of the image is more than 400 km long, similar to ancient flood basalts on Earth and mare lavas on the Moon.

    North is to the top of the picture and the sun illuminates the surface from the left. The image covers an area 1230 kilometers wide and the smallest features that can be discerned are 2.5 kilometers in size. This image was taken on November 6th, 1996, at a range of 245,719 kilometers by the Solid State Imaging (CCD) system on the Galileo Spacecraft.

    Launched in October 1989, Galileo entered orbit around Jupiter on December 7, 1995. The spacecraft's mission is to conduct detailed studies of the giant planet, its largest moons and the Jovian magnetic environment. The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

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

  2. 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.

  3. 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

  4. 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.

  5. 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

  6. 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

  7. Volcanic eruptions and solar activity

    NASA Technical Reports Server (NTRS)

    Stothers, Richard B.

    1989-01-01

    The historical record of large volcanic eruptions from 1500 to 1980 is subjected to detailed time series analysis. In two weak but probably statistically significant periodicities of about 11 and 80 yr, the frequency of volcanic eruptions increases (decreases) slightly around the times of solar minimum (maximum). Time series analysis of the volcanogenic acidities in a deep ice core from Greenland reveals several very long periods ranging from about 80 to about 350 yr which are similar to the very slow solar cycles previously detected in auroral and C-14 records. Solar flares may cause changes in atmospheric circulation patterns that abruptly alter the earth's spin. The resulting jolt probably triggers small earthquakes which affect volcanism.

  8. 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.

  9. 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

  10. Mount St. Helens' volcanic ash: hemolytic activity.

    PubMed

    Vallyathan, V; Mentnech, M S; Stettler, L E; Dollberg, D D; Green, F H

    1983-04-01

    Volcanic ash samples from four Mount St. Helens' volcanic eruptions were subjected to mineralogical, analytical, and hemolytic studies in order to evaluate their potential for cytotoxicity and fibrogenicity. Plagioclase minerals constituted the major component of the ash with free crystalline silica concentrations ranging from 1.5 to 7.2%. The in vitro hemolytic activity of the volcanic ash was compared to similar concentrations of cytotoxic and inert minerals. The ash was markedly hemolytic, exhibiting an activity similar to chrysotile asbestos, a known fibrogenic agent. The hemolysis of the different ash samples varied with particle size but not with crystalline silica concentration. The results of these studies taken in conjunction with the results of our animal studies indicate a fibrogenic potential of volcanic ash in heavily exposed humans. PMID:6832120

  11. 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

  12. Imaging the deep source of the Rotorua and Waimangu geothermal fields, Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    Magnetotelluric data were recorded in a 45 × 10 km band crossing the Rotorua and Waimangu geothermal fields in the northern part of the Taupo Volcanic Zone in the central North Island of New Zealand. 3-D inverse modelling of these data show that beneath the low resistivity areas marking the near surface geothermal fields, localised electrically conductive zones are present in the crust below about 2.5 and 3.5 km depth at Rotorua and Waimangu, respectively. At increasing depth these conductive zones broaden and appear to merge with a larger conductive zone at 8 km depth situated between the geothermal systems. At Rotorua the top of the conductive zone is situated directly beneath the area of greatest surface heat and gas discharge. At Waimangu the uppermost part of the deeper conductive zone is situated beneath the western part of Lake Rotomahana, also an area of intense surface thermal activity and high heat flux. The localised conductive zones are interpreted to be high temperature (quasi-magmatic) fluids rising from a broader zone of partial melt at deeper levels.

  13. 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.

  14. 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

  15. Volcanic and Structural History of the NE Rift Zone of Tenerife, Canary Islands, Spain

    NASA Astrophysics Data System (ADS)

    Carracedo, J.; Guillou, H.; Badiola, E. R.; Torrado, F. P.; Troll, V.; Delcamp, A.; Paris, R.; Gonzalez, A. R.

    2008-12-01

    The NE Rift of Tenerife is an excellent example of a persistent, recurrent rift, providing important evidence on the origin and dynamics of these major volcanic features. The rift developed in three successive, intense and relatively short eruptive stages (a few hundred ka), separated by longer periods of quiescence or reduced activity: A Miocene stage (7203+/-155ka), apparently extending the central Miocene shield of Tenerife towards the Anaga massif; an Upper Pliocene stage (2710+/-58ka) and the latest stage, with the main eruptive phase, in the Pleistocene. Detailed geological (GIS) mapping, geomagnetic reversal mapping and stratigraphic correlation, and radioisotopic (K/Ar) dating of volcanic formations allowed the reconstruction of the latest period of rift activity. In the early phases of this stage the majority of the eruptions grouped tightly along the axis of the rift and show reverse polarity (corresponding to the Matuyama). Dykes are of normal and reverse polarities. In the final phase of activity, eruptions are more disperse and lavas and dykes are consistently of normal polarity (Brunhes). Volcanic units of normal polarity crossed by dykes of normal and reverse polarities yield ages apparently compatible with normal events (M-B Precursor and Jaramillo) in the Upper Matuyama epoch. Three lateral collapses successively mass-wasted the rift: The Micheque collapse, completely concealed by subsequent nested volcanism, and the Güímar and La Orotava collapses, that are only partially filled. Pre- collapse and nested volcanism is predominantly basaltic, except in the Micheque collapse, where magmas evolved towards intermediate and felsic (trachytic) compositions. Rifts in the Canary Islands are long-lasting, recurrent features, probably related to primordial, plume-related fractures acting throughout the entire growth of the islands. Basaltic volcanism forms the bulk of the islands and rift zones. However, collapses of the flanks of the rifts disrupt their

  16. 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.

  17. 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

  18. Kawah Ijen volcanic activity: a review

    NASA Astrophysics Data System (ADS)

    Caudron, Corentin; Syahbana, Devy Kamil; Lecocq, Thomas; Van Hinsberg, Vincent; McCausland, Wendy; Triantafyllou, Antoine; Camelbeeck, Thierry; Bernard, Alain; Surono

    2015-03-01

    Kawah Ijen is a composite volcano located at the easternmost part of Java island in Indonesia and hosts the largest natural acidic lake in the world. We have gathered all available historical reports on Kawah Ijen's activity since 1770 with the purpose of reviewing the temporal evolution of its activity. Most of these observations and studies have been conducted from a geochemical perspective and in punctuated scientific campaigns. Starting in 1991, the seismic activity and a set of volcanic lake parameters began to be weekly available. We present a database of those measurements that, combined with historical reports, allow us to review each eruption/unrest that occurred during the last two centuries. As of 2010, the volcanic activity is monitored by a new multi-disciplinary network, including digital seismic stations, and lake level and temperature measurements. This detailed monitoring provides an opportunity for better classifying seismic events and forecasting volcanic unrest at Kawah Ijen, but only with the understanding of the characteristics of this volcanic system gained from the historical review presented here.

  19. 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

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. Magmatic zoning of Late Cenozoic volcanism in Central Mongolia: Relation with the mantle plume

    NASA Astrophysics Data System (ADS)

    Kudryashova, E. A.; Yarmolyuk, V. V.; Kozlovsky, A. M.; Savatenkov, V. M.

    2010-05-01

    The concentric zonal structure of the Late Cenozoic volcanism areal in Central Mongolia which is situated on the territory of the Khangai vault has been educed. The central part of the structure conforms to the axial part of the vault and is presented with volcanic fields of the Watershed graben and newest valley flows. The peripheral zone is presented with volcanic fields located along the vault frame (Taryat graben, Lake Valley graben, and grabens of the Orkhon-Selenga interfluve). The structural zoning of the areal comports with the substantial zoning of volcanism products. The rocks of the central part have isotopic (Sr, Nd, Pb) and geochemical characteristics conforming to the most primitive (like PREMA) compositions of mantle sources of magmatism. Magmatism sources in the peripheral zone of the volcanic areal, besides the PREMA mantle, contained a substance of enriched mantle like EMI. The character of substantial and structural zoning of volcanism is caused by the influence of the mantle plume on the Central Asia lithosphere. According to geophysical and isotopic-geochemical data, this plume had a lower mantle nature.

  7. 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.

  8. A decade's overview of Io's volcanic activity

    NASA Technical Reports Server (NTRS)

    Matson, D. L.; Veeder, G. J.; Johnson, T. V.; Blaney, D. L.; Goguen, J. D.

    1993-01-01

    Over the past decade some aspects of Io's volcanic activity have changed greatly, while others have essentially remained constant. This contrast has emerged from our study of multi-wavelength, infrared, observations of Io's thermal emission. From 1983 to 1992 we observed the disk integrated flux density of Io from the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. Our spectral coverage allows us to separate out the emission components due to volcanic thermal anomalies which are warmer than the background emission caused by solar heating. Our temporal coverage allows us to resolve individual eruptions and also to obtain the disk-integrated flux density as a function of longitude (or, equivalently, orbital phase angle). Characteristics that persisted over the decade involve Loki's location and intensity of emission, the leading hemisphere emission, and the average heat flow. The variable aspects of Io over the decade include Loki's hotter area(s) and the outbursts in the leading hemisphere.

  9. Triggering of volcanic activity by large earthquakes

    NASA Astrophysics Data System (ADS)

    Avouris, D.; Carn, S. A.; Waite, G. P.

    2011-12-01

    Statistical analysis of temporal relationships between large earthquakes and volcanic eruptions suggests seismic waves may trigger eruptions even over great distances, although the causative mechanism is not well constrained. In this study the relationship between large earthquakes and subtle changes in volcanic activity was investigated in order to gain greater insight into the relationship between dynamic stress and volcanic response. Daily measurements from the Ozone Monitoring Instrument (OMI), onboard the Aura satellite, provide constraints on volcanic sulfur dioxide (SO2) emission rates as a measure of subtle changes in activity. An SO2 timeseries was produced from OMI data for thirteen persistently active volcanoes. Seismic surface-wave amplitudes were modeled from the source mechanisms of moment magnitude (Mw) ≥7 earthquakes, and peak dynamic stress (PDS) was calculated. The SO2 timeseries for each volcano was used to calculate a baseline threshold for comparison with post-earthquake emission. Delay times for an SO2 response following each earthquake at each volcano were analyzed and compared to a random catalog. The delay time analysis was inconclusive. However, an analysis based on the occurrence of large earthquakes showed a response at most volcanoes. Using the PDS calculations as a filtering criterion for the earthquake catalog, the SO2 mass for each volcano was analyzed in 28-day windows centered on the earthquake origin time. If the average SO2 mass after the earthquake was greater than an arbitrary percentage of pre-earthquake mass, we identified the volcano as having a response to the event. This window analysis provided insight on what type of volcanic activity is more susceptible to triggering by dynamic stress. The volcanoes with lava lakes included in this study, Ambrym, Gaua, Villarrica, and Erta Ale, showed a clear response to dynamic stress while the volcanoes with lava domes, Merapi, Semeru, and Bagana showed no response at all. Perhaps

  10. 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.

  11. Spatial and temporal variations in magma-assisted rifting, Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Rowland, Julie V.; Wilson, Colin J. N.; Gravley, Darren M.

    2010-02-01

    Taupo Volcanic Zone (TVZ), New Zealand, is a NNE-trending rifting arc, active for ~ 2 Myr, with a 125-km-long central segment characterized by exceptionally voluminous rhyolite volcanism. The volcanic segmentation reflects along-axis variations in magmatism with implications for the thermal state of the crust and consequent rifting dynamics. Along the zone to the north and south of Central TVZ, the limbs of broad monoclines, disrupted to various degrees by normal faults, dip SE against major NW-facing fault zones. In these northern and southern segments, the loci of magmatism (shown by the position of volcanoes) and rifting (manifested by the distribution of seismicity and modern (< 61 ka) faulting in the Taupo Fault Belt (TFB)) coincide. Mantle-derived magmas are localized within the crust in a plexus of small bodies, dikes and sills, and dike-assisted rifting operates at times (but not always) as shown by the historic record. In contrast, throughout most of Central TVZ the loci of magmatism and tectonism (shown by the distribution of high-temperature geothermal systems and inferred from geophysical models and surface fault studies) are offset laterally and extensional strain appears to be partitioned accordingly. Geological, geophysical and geodetic studies indicate the following magma-assisted mechanisms of extension in Central TVZ: 1) mafic dike intrusion of length scale > 20 km and width > 1 m oriented perpendicular to the extension direction; 2) fault slips of < 2 m on structures along-strike from and coeval with silicic eruptions, some of which were triggered by mafic dike intrusion; 3) rifting episodes associated with regional-scale uplift, multi-fault rupture (slips < 2 m) and transient subsidence, arguably driven by changes in state at shallow depths. Volcanic studies of < 340 ka deposits demonstrate that an additional, but less frequent, mechanism involves temporally higher rates of fault slip with regional-scale collapse of rift basins in association

  12. 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

  13. 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.

  14. Crustal heat transfer in the Taupo Volcanic Zone (New Zealand): comparison with other volcanic arcs and explanatory heat source models

    NASA Astrophysics Data System (ADS)

    Hochstein, M. P.

    1995-10-01

    The Taupo Volcanic Zone (TVZ) is a 200-km-long volcanic arc segment which developed ≤2 Ma ago within the continental crust of the North Island of New Zealand and lies at the southern end of the much larger Tonga-Kermadec arc system. The total crustal heat transfer of the TVZ is at present c. 2600 MW/100 km, most of the heat being transferred by convective geothermal systems. The rate of transfer is anomalously high in comparison to that of other active arcs, and arguably the highest world wide for such a setting. Heat transfer of other active arcs appear to vary almost linearly with subduction speed (about 150 MW/100 km for 10 mm/yr). The mass rate of common type arc extrusions (basalts, andesites, dacites) also increases almost linearly with subduction speed. This allows separation of the TVZ heat transfer into a "normal" component, associated with extrusions and intrusions of andesites and dacites (about 600 MW/100 km), and an "anomalous" component of about 2000 MW/100 km, related to extrusions and intrusions of rhyolitic melts whose generation is not directly controlled by subduction processes. Rhyolitic melts in the TVZ are partial melts of dominantly crustal origin. Comparison with other arcs indicates that the long-term extrusion rate of TVZ rhyolites (about 400 kg/s per 100 km) is also the highest world wide for this setting. The occurrence of voluminous Quaternary rhyolitic pyroclastics is a rare phenomenon and appears to be associated with a few arc segments (TVZ, Sumatra, Kyushu) that undergo significant crustal deformation. Various models have been proposed to explain the phenomenon of the anomalously high heat transfer within the TVZ. Models which require only heat transfer from plumes and subcrustal melts, either ponded at the crust/mantle boundary or intruding a spreading crust, are not suitable because the associated heat transfer at the contact is too low by a factor 2 to explain the required transfer rate of about 0.8 W/m 2 representing the

  15. 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

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. 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

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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 ...

  8. Cenozoic volcanic rocks of North Kamchatka: In search of subduction zones

    NASA Astrophysics Data System (ADS)

    Shapiro, M. N.; Solov'ev, A. V.

    2011-05-01

    Two belts of subaerial volcanic rocks—the Eocene Kinkil belt and the Neogene belt of the Sredinny Range—extend along the Kamchatka Isthmus. It is suggested that their formation is related to subduction of the oceanic lithosphere beneath the continental margin of North Kamchatka. The oceanic lithosphere consumed in the subduction zones could have been formed as a result of active spreading in the Komandorsky Basin. In the simplest case, both spreading and subduction reflect the northwestward motion of the lithosphere of the Komandorsky Plate relative to Kamchatka, the Shirshov Ridge, and the Aleutian Basin combined into one relatively immobile plate conventionally called the North American Plate. The authors perform a simulation of conjugate spreading and subduction. The most important parameter determining the regional geodynamics—the velocity of the Komandorsky Plate moving relative to the North American Plate—is taken as 2.5, 5.0, and 7.5 cm/yr. The calculated ages of the onset and end of volcanic activity in the aforementioned belts are compared with the dates obtained with the isotopic and paleontological methods. For the Eocene Kinkil belt, where volcanism started 44 Ma ago, the model age of the onset of subduction depends on the accepted velocity of the motion of the Komandorsky Plate and varies from 54 Ma at the velocity of 2.5 cm/yr to 47.5 Ma at the velocity of 7.5 cm/yr. It can be assumed that the model of fast subduction in this age interval is most consistent with the geological data. For the Miocene-Pliocene belt of the Sredinny Range, assuming the velocity of the motion of the Komandorsky Plate at 5.0 and 7.5 cm/yr, multiple rifting at the boundary with the Shirshov Ridge should be assumed. Therefore, for the end of the Neogene, a model with low velocity (2.5-5.0 cm/yr, i.e., about 4.0 cm/yr) is preferable.

  9. 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.

  10. 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.

  11. Possible Non-volcanic Tremor Discovered in the Reelfoot Fault Zone, Northern Tennessee

    NASA Astrophysics Data System (ADS)

    Langston, C. A.; Williams, R. A.; Magnani, M.; Rieger, D. M.

    2007-12-01

    A swarm of ~80 microearthquakes was fortuitously detected in 20, 14 second-duration long-offset vibroseis shotgathers collected for a seismic reflection experiment near Mooring, TN, directly over the Reelfoot fault zone on the afternoon of 16 November 2006. These natural events show up in the shotgathers as near-vertically incident P waves with a dominant frequency of 10-15 Hz. The reflection line was 715m in length consisting of 144 channels with a sensor spacing of 5m, 8Hz vertical geophones, and recording using a Geometrics 24bit Geode seismograph. Small variations in event moveout across the linear array indicate that the seismicity was not confined to the same hypocenter and probably occurred at depths of approximately 10 km. The largest events in the series are estimated to have local magnitudes of ~-1 if at 10 km distance from the array. This is about 2.5 magnitude units lower than the threshold for local events detected and located by the CERI cooperative network in the area. The seismicity rate was ~1000 events per hour based on the total time duration of the shotgathers. The expected number of earthquakes of ML greater than or equal to -1 for the entire central United States is only 1 per hour. This detection of microseismic swarms in the Reelfoot fault zone indicates active physical processes that may be similar to non-volcanic tremor seen in the Cascadia and San Andreas fault zones and merits long-term monitoring to understand its source.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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

  18. 40Ar/39Ar Geochronology of the Pleistocene to Historic Puyehue-Cordon Caulle Volcanic Complex, Andean Southern Volcanic Zone, Chile

    NASA Astrophysics Data System (ADS)

    Harper, M. A.; Singer, B. S.; Moreno Roa, H. A.

    2003-12-01

    Linking magma reservoir processes beneath arc volcanoes to their surficial expression as eruptive events is hampered, in part, by an incomplete knowledge of long-term eruptive flux. To address this problem, we have begun to quantify the eruptive history of the 105 km3 Puyehue-Cordon Caulle Volcanic Complex at 40.5° S in the Andean Southern Volcanic Zone (SVZ) using a combination of 40Ar/39Ar dating and geologic mapping. Puyehue-Cordon Caulle has erupted low-medium K basaltic to rhyolitic magma that spans the largest range of major element compositions in the southern SVZ. Low radiogenic argon contents necessitate the incremental heating of multiple aliquots (200-800 mg) of groundmass from each lava using a low-blank resistance furnace. New 40Ar/39Ar plateau ages from 26 lavas suggest that volcanism began ca. 250 ka. Numerous Mid- to Late Pleistocene vents were active between 250 and 33 ka and produced at least 85 km3 of basaltic to andesitic lava, tephra, and ignimbrites. More recently, the large Puyehue stratovolcano, built between 45 and 2.7 ka, erupted 18-21 km3 of basaltic to rhyolitic lava and tephra. Puyehue began to grow after 45 ka with the eruption of 8-10 km3 of dacitic and rhyodacitic lava followed by several km3 of basalt and basaltic andesite that erupted between 15.1 +/- 2.6 ka and 10.0 +/- 1.1 ka. The final stage of cone growth, comprising 1-2 km3 of rhyolitic and rhyodacitic lava and tephra, began by 10 ka and culminated at 2.66 +/- 0.19 ka (14C date) with the plinian eruption of several km3 of airfall deposits zoned from dacite to basaltic andesite. The average eruptive rate for Puyehue volcano is 0.4-0.5 km3/k.y., twice that of Tatara-San Pedro volcano located ˜ 500 km to the north. Glaciers eroded extensive parts of the complex between 200 and 15 ka, making our growth rate a minimum estimate. The Cordon Caulle fissural zone, which extends for 15 km to the NW of the modern Puyehue edifice, has erupted 2 km3 of rhyodacitic to rhyolitic lavas

  19. 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.

  20. Fracturing and Seismicity at the Prestahnúkur Fissure Swarm in the Ultra-Slowly Spreading Western Volcanic Zone, Iceland

    NASA Astrophysics Data System (ADS)

    Hjartardottir, A. R.; Hjaltadottir, S.; Einarsson, P.; Vogfjord, K. S.

    2014-12-01

    Extension across the mid-Atlantic plate boundary in south Iceland is taken up by two parallel zones, the Western and the Eastern Volcanic Zones. Spreading across the western zone is of the order of 1-7 mm/year, qualifying it as an ultra-slow rift. The Prestahnúkur fissure swarm in the Western Volcanic Zone offers an opportunity to study magma-tectonic interaction in an ultra-slow spreading setting. In this study, fractures and faults were mapped in detail from aerial photographs to determine the extent of the fissure swarm. The fissure swarm is about 60 km long and 10 km wide, although its extent to the south is uncertain due to its linkage with the adjacent Hengill fissure swarm. The fissure swarm has both open fractures, indicating postglacial activation, and normal faults with up to 45 m vertical offset. Hyaloclastite ridges („tindars"), produced by subglacial fissure eruptions during the Pleistocene, are found within the fissure swarm, as well as postglacial lava flows. Intermittent seismicity occurs in the area. Earthquakes during the last ~24 years were relocated to study their relation with the surface fractures. Relocation of these events indicate that some of the fractures seen on surface have been activated during these years. The small cumulative seismic moment and slow spreading measured by geodetic methods nevertheless show that no dike intrusions have occurred during this period. Pleistocene tindars and Holocene lavas are clear indications of magmatism, however. We therefore suggest that the Prestahnúkur fissure swarm is mainly formed by diking and rifting during rifting episodes, whereas small scale fracture movements can occur during inter-rifting periods. The present small-scale fracture movements may indicate lack of magma to drive dike intrusions.

  1. Shear wave velocity variation across the Taupo Volcanic Zone, New Zealand, from receiver function inversion

    USGS Publications Warehouse

    Bannister, S.; Bryan, C.J.; Bibby, H.M.

    2004-01-01

    The Taupo Volcanic Zone (TVZ), New Zealand is a region characterized by very high magma eruption rates and extremely high heat flow, which is manifest in high-temperature geothermal waters. The shear wave velocity structure across the region is inferred using non-linear inversion of receiver functions, which were derived from teleseismic earthquake data. Results from the non-linear inversion, and from forward synthetic modelling, indicate low S velocities at ???6- 16 km depth near the Rotorua and Reporoa calderas. We infer these low-velocity layers to represent the presence of high-level bodies of partial melt associated with the volcanism. Receiver functions at other stations are complicated by reverberations associated with near-surface sedimentary layers. The receiver function data also indicate that the Moho lies between 25 and 30 km, deeper than the 15 ?? 2 km depth previously inferred for the crust-mantle boundary beneath the TVZ. ?? 2004 RAS.

  2. 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

  3. 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

  4. Triggered tremors beneath the seismogenic zone of an active fault zone, Kyushu, Japan

    NASA Astrophysics Data System (ADS)

    Miyazaki, Masahiro; Matsumoto, Satoshi; Shimizu, Hiroshi

    2015-11-01

    Non-volcanic tremors were induced by the surface waves of the 2012 Sumatra earthquake around the Hinagu fault zone in Kyushu, Japan. We inferred from dense seismic observation data that the hypocenters of these tremors were located beneath the seismogenic zone of the Hinagu fault. Focal mechanisms of the tremors were estimated using S-wave polarization angles. The estimated focal mechanisms show similarities to those of shallow earthquakes in this region. In addition, one of the nodal planes of the focal mechanisms is almost parallel to the strike direction of the Hinagu fault. These observations suggest that the tremors were triggered at the deeper extension of the active fault zone under stress conditions similar to those in the shallower seismogenic region. A low-velocity anomaly beneath the hypocentral area of the tremors might be related to the tremor activity.

  5. 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.

  6. 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.

  7. Seismic velocity structure of the central Taupo Volcanic Zone, New Zealand, from local earthquake tomography

    NASA Astrophysics Data System (ADS)

    Sherburn, Steven; Bannister, Stephen; Bibby, Hugh

    2003-03-01

    The 3-D distribution of P-wave velocity (Vp) and the P-wave/S-wave velocity ratio (Vp/Vs) are derived for the crust in the central Taupo Volcanic Zone (TVZ), New Zealand, by tomographic inversion of P- and S-wave arrival time data from local earthquakes. Resolution in the seismogenic mid-crust (4-6 km) is good, but poorer above and below these depths. The 3-D velocity model has several Vp anomalies as large as ±5% in the mid-lower crust (4-10 km) and more than ±10% in the upper crust (0-4 km). The model achieves a 55% reduction in data variance from an initial 1-D model. Young caldera structures, Okataina, Rotorua, and Reporoa, are characterised by low Vp anomalies at a depth of about 4 km and these coincide with large negative residual gravity anomalies. We attribute these anomalies to large volumes of low Vp, low-density, volcaniclastic sediments that have filled these caldera collapse structures. Although there are no Vp anomalies which suggest the presence of molten or semi-molten magma beneath the TVZ, a large, high Vp anomaly of more than +15% and a high Vp/Vs anomaly are observed coincident with a diorite pluton beneath the Ngatamariki geothermal field. However, Vp anomalies cannot be seen beneath the largest geothermal fields, Waimangu, Waiotapu, and Reporoa, and, consequently, if such anomalies exist, they must be below the resolution of our data. A prominent Vp contrast of 5-10% occurs at a depth of about 6 km beneath the boundary between the Taupo-Reporoa Depression and the Taupo Fault Belt (TFB), coincident with the eastern limit of the seismic activity beneath the TFB. We interpret this velocity contrast as being caused by the presence of extensive, non-molten, intrusives beneath the Taupo-Reporoa Depression. We suggest that the high-velocity material beneath the Taupo-Reporoa Depression is isolated from regional extension in the TVZ, and from the resulting faulting and seismicity, which occurs preferentially within the weaker material of the TFB. We

  8. 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

  9. Automated, reproducible delineation of zones at risk from inundation by large volcanic debris flows

    USGS Publications Warehouse

    Schilling, Steve P.; Iverson, Richard M.

    1997-01-01

    Large debris flows can pose hazards to people and property downstream from volcanoes. We have developed a rapid, reproducible, objective, and inexpensive method to delineate distal debris-flow hazard zones. Our method employs the results of scaling and statistical analyses of the geometry of volcanic debris flows (lahars) to predict inundated valley cross-sectional areas (A) and planimetric areas (B) as functions of lahar volume. We use a range of specified lahar volumes to evaluate A and B. In a Geographic Information System (GIS) we employ the resulting range of predicted A and B to delineate gradations in inundation hazard, which is highest near the volcano and along valley thalwegs and diminishes as distances from the volcano and elevations above valley floors increase. Comparison of our computer-generated hazard maps with those constructed using traditional, field-based methods indicates that our method can provide an accurate means of delineating lahar hazard zones.

  10. 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.

  11. 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

  12. The influence of volcanic activity on suspended sediment yield of rivers (Kamchatka, Russia)

    NASA Astrophysics Data System (ADS)

    Kuksina, Ludmila

    2014-05-01

    Kamchatka is specific region of suspended sediment yield formation. This fact is particularly connected with active volcanism in the territory. The influence of volcanism on suspended sediment yield characteristics was studied in various time scales - into-diurnal, seasonal and long-term ones. The study of spatial variability of these characteristics reveals the maximum values characterize river basins in zones of strong impact of volcanic eruptions, especially, rivers draining slopes and flanks of active volcanoes. Into-diurnal fluctuations were studied for rivers in volcanic areas. They are characterized by synchronous changes of water flow and turbidity. It's determined by weak erosion-preventive capacity of friable volcanic deposits and big slopes of channels (2.5 - 6.0 %). The maximum of water flow and turbidity is observed at the period between 12 and 6 pm. The air temperature reaches its maximum by that time, and consequently, the intensity of snow melting is also maximum one. The maximum of turbidity advances diurnal maximum of water flow a little, and it's connected with the features of flood wave moving and consecutive maximums of slopes, turbidity, velocity, water flow, and capacity of stream during flush. Into-diurnal fluctuations are determined by complicated and little-studied processes of mass transfer between stream and channel deposits. These processes are connected with into-diurnal changes of stream capacity and water transfer between channel and underflow. As the result water regime is pulsating. Rivers under the influence of volcanic eruptions transport the main amount of sediments during floods which usually occur in summer-autumn period (in the absence of extreme floods in winter-spring period during volcanic eruptions). Combination of maximum snow supply, significant precipitation in warm part of the year and weak erosion-preventive capacity of friable volcanic deposits on volcanoes slopes is the reason of the most intense erosion in this

  13. 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.

  14. 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

  15. Active Submarine Hotspot Volcanism on the Kerguelen Plateau

    NASA Astrophysics Data System (ADS)

    Coffin, M. F.; Leser, T. E.

    2012-12-01

    Heard and McDonald Islands on the Kerguelen Plateau, southern Indian Ocean, are active intraplate hotspot volcanoes. Heard Island is approximately 43 km long, and encompasses an area of approximately 368 square km. It is dominated by Big Ben, a roughly circular volcano with a base diameter of 18-20 km, and a maximum elevation of 2745 m. The McDonald Islands have an area of approximately 2.5 square km. Due to a lack of human habitation and no geoscientific monitoring, and cloud cover precluding satellite remote sensing for geoscientific purposes, the level of volcanic activity of the islands is unknown, but observers on passing ships frequently report eruptions, including molten lava, volcanic plumes, and tephra, and active fumaroles. Bathymetric, seismic reflection, magnetic, and gravity data acquired around Heard and McDonald Islands suggest that submarine magmatism affects a broad region of surrounding Kerguelen Plateau seafloor. In this region, we have identified six distinct fields of sea knolls that we interpret to be volcanic in origin. Individual fields contain from approximately 14 to approximately 140 sea knolls, and are not uniformly distributed around Heard and McDonald Islands. Given that Heard and McDonald Islands are volcanically active, it is likely that at least some of the interpreted submarine volcanoes are active and drive hydrothermal circulation.

  16. 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

  17. 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

  18. Oxygen Isotopes in Intra-Back Arc Basalts from the Andean Southern Volcanic Zone

    NASA Astrophysics Data System (ADS)

    Parks, B. H.; Wang, Z.; Saal, A. E.; Frey, F. A.; Blusztajn, J.

    2013-12-01

    The chemical compositions of volcanic rocks from the Andean Southern Volcanic Zone (SVZ) reflect complex and dynamic interactions among the subducting oceanic lithosphere, the mantle wedge, and the overlying continental crust. Oxygen isotope ratios of olivine phenocrysts can be a useful means to identifying their relative contributions to the arc magmatism. In this study, we report high-precision oxygen-isotope ratios of olivine phenocrysts in a set of intra-back arc basalts from the SVZ. The samples were collected from monogenetic cinder cones east of the volcanic front (35-39 degrees S), and have been geochemically well-characterized with major and trace element contents, and Sr-Nd-Pb isotope compositions. Compared to lavas from the volcanic front, these intra-back arc lavas have similar radiogenic isotope, and a more alkalic and primitive (higher MgO content) chemical composition. We determined the oxygen-isotope ratios using the CO2-laser-fluorination method set up at the Department of Geology and Geophysics, Yale University following the techniques reported in Wang et al (2011). The samples were analyzed with standards of Gore Mountain Garnet (5.77×0.12‰ 1σ; Valley et al., 1995) and Kilbourne Hole Olivine (5.23×0.07‰ 1σ; Sharp, 1990) in order to account for minor changes in the vacuum line during analyses. The obtained δ18OSMOW values of olivine phenocrysts from the intra-back arc basalts vary from 4.98×0.01 to 5.34×0.01‰. This range, surprisingly, is similar to the δ18O values of olivines from mantle peridotites (5.2×0.2‰). Preliminary results indicate significant correlations of 87Sr/86Sr, 143Nd/144Nd and trace element ratios of the basaltic matrix with the δ18O values of olivine phenocrysts, indicating at least three components involved in the formation of the arc volcanism. By comparing the δ18O with the variations of major and trace element contents (e.g., MgO, TiO2 and Ni), and trace element ratios (e.g. Ba/Nb), we evaluate the effects

  19. From feeder dykes to scoria cones: the tectonically controlled plumbing system of the Rauðhólar volcanic chain, Northern Volcanic Zone, Iceland

    NASA Astrophysics Data System (ADS)

    Friese, Nadine; Bense, Frithjof A.; Tanner, David C.; Gústafsson, Lúðvík E.; Siegesmund, Siegfried

    2013-06-01

    The Rauðhólar volcanic chain, located in the Northern Volcanic Zone of Iceland, has been variably eroded such that, in the northern part, the original scoria cones are preserved, while the central and southern parts expose their shallow feeders. The chain thus offers insight into the inner workings of the near-surface feeder system of scoria cones. The volcanic chain was mapped in 3D using GPS. The en echelon-arranged volcanic chain can be divided into three parts: The southernmost part contains only plugs and necks with a thin pyroclastic cover as well as multi-tiered lava flows. The central part combines partially eroded scoria cones, (feeder) dyke intersections, and welded scoria interbedded within rootless and clastogenic lava flows; the welded scoria is composed of different kinds of lithics and bombs. The northern part preserves almost intact, overlapping scoria cones with voluminous lapilli-sized scoriaceous deposits. The overall dyke trend is orthogonal but shows radial patterns in individual cone complexes. Feeder dykes observed to depths of about 200 m below the volcanic chain are up to 8 m thick and flare in to conduits in the uppermost 20-50 m. The exposed shallow plumbing system shows that magma pathways through the volcanic edifice are very complex with incremental, repeated intrusions. We interpret the arcuate shape to be the result of a local change in the orientation of the stress field because the Rauðhólar volcanic chain is located within a major relay structure between volcanoes on the eastern Fremrinámur rift arm and a rift extension with grabens on the western periphery.

  20. 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

  1. Serpentine in active subduction zones

    NASA Astrophysics Data System (ADS)

    Reynard, Bruno

    2013-09-01

    Serpentinization is a key phenomenon for understanding the geodynamics of subduction zones in the 10-200 km depth range. Serpentines are a major water carrier, and their rheological properties have a strong influence on deformation partitioning and seismicity at depths. I review experimental investigations that have been conducted on serpentines, with emphasis on the large body of data acquired over the past decade. Determinations of physical properties at the pressure and temperature conditions of subductions allow interpreting geophysical data in active subduction in terms of mineralogy and petrology, and to link the presence of serpentinites with deformation and fluid circulation. The fluid budget can be partially constrained from geophysical data. Elasticity data provide a quantitative basis for mapping serpentinization in the mantle wedge and slab from seismic tomography. Anisotropy suggests the existence of thin serpentinite channels above the plate interface, that account for mechanical decoupling inferred from down-dip limit of the seismogenic zone and heat flow. Strain-rate dependent rheology of antigorite serpentine is consistent with stable deformation of this thin layer or channel over timescales ranging from those of the seismic cycle to those of thermal equilibration and exhumation of high-pressure rocks, and with the geological record of subduction-related deformation. Circulation of serpentinizing fluids depends on the permeability structure, and is imaged by electrical conductivity tomography. It could be controlled by fracturing in the undeformed cold nose of the mantle wedge, and by plastic deformation along the plate interface. Fluid migration mechanisms are similar to those inferred from petrological and geochemical data on exhumed serpentinites. Estimation of the fluid budget associated with serpentine formation will rely on numerical simulations for which coupling of kinetics of hydration and dehydration at scales ranging from grain size up

  2. Variations of water, sulphur, and chlorine in mafic to intermediate tephras along the Chilean Southern Volcanic Zone

    NASA Astrophysics Data System (ADS)

    Wehrmann, Heidi; Hoernle, Kaj; Jacques, Guillaume; Garbe-Schönberg, Dieter; Trumbull, Robert; Wiedenbeck, Michael

    2014-05-01

    Relating along-arc variations in melt volatile concentrations to differences in the tectonic parameters of a subduction system can help to identify processes influencing the volatile inventories of arc magmas. Here we present pre-eruptive water, sulphur, and chlorine concentrations in olivine-hosted melt inclusions in mafic to intermediate tephras along the volcanic front of the Chilean Southern Volcanic Zone (SVZ) between 33°S and 43°S, determined by SIMS and electron microprobe. Additionally, melt water abundances were estimated by plagioclase-melt hygrometry. We observe systematic along-arc variations in water content, H2O/K2O, and ratios of highly fluid-mobile to less fluid-mobile trace elements (e.g. Ba/Nb, Pb/Ce), with a peak observed in the Central (C)SVZ (38°S to 42°S). This suggests a strong involvement of slab fluids in these melts. Ratios of more incompatible to less incompatible trace elements, such as La/Yb, La/Sm, or Sm/Lu, are lower in the CSVZ, reflecting higher degrees of mantle melting. The higher-degree, hydrous flux melting beneath the CSVZ, as revealed from volatile and trace element geochemistry, coincides with peak volumes of extruded material in this arc segment, which is indicative of large magma production rates (Völker et al., 2011). Furthermore, a low-velocity seismic anomaly and high Vp/Vs ratios in this region have been interpreted by Dzierma et al. (2012) as the result of elevated fluid infiltration into the mantle wedge, originating from the subducting Valdivia Fracture Zone. Integration of the geophysical, morphological, and geochemical data suggests that the increased transport of water into the system through hydration of the incoming plate at fracture zones and bend faults leads to a generation of large amounts of water-rich, higher-degree melts, and subsequently to intense volcanic activity with respect to volcano volumes and eruption frequency. An inverse along-arc trend is displayed by the melts' S and Cl concentrations

  3. 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.

  4. 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).

  5. 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

  6. 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

  7. 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

  8. 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.

  9. 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.

  10. 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

  11. Modelling Gravimetric Fluctuations due to Hydrological Processes in Active Volcanic Settings

    NASA Astrophysics Data System (ADS)

    Hemmings, B.; Gottsmann, J.; Whitaker, F.

    2014-12-01

    Both static and dynamic gravimetric surveys are widely used to monitor magmatic processes in active volcanic settings. However, attributing residual gravimetric signals solely to magma movement can result in misdiagnosis of a volcano's pre-eruptive state and incorrect assessment of hazard. The relative contribution of magmatic and aqueous fluids to integrated gravimetric and geodetic data has become an important topic for debate, particularly in restless caldera systems. Groundwater migration driven by volcanically-induced pressure changes, and groundwater mass fluctuations associated with seasonal and inter-annual variations in recharge may also contribute to measured gravity changes. Here we use numerical models to explore potential gravimetric signals associated with fundamental hydrological processes, focusing on variations in recharge and hydrogeological properties. TOUGH2 simulations demonstrate the significance of groundwater storage within a thick unsaturated zone (up to 100 m). Changes are dominantly in response to inter-annual recharge variations and can produce measurable absolute gravity variations of several 10s of μgal. Vadose zone storage and the rate of response to recharge changes depend on the hydrological properties. Porosity, relative and absolute permeability and capillary pressure conditions all affect the amplitude and frequency of modelled gravity time series. Spatial variations in hydrologic properties and importantly, hydrological recharge, can significantly affect the phase and amplitude of recorded gravity signals. Our models demonstrate the potential for an appreciable hydrological component within gravimetric measurements on volcanic islands. Characterisation of hydrological processes within a survey area may be necessary to robustly interpret gravity signals in settings with significant recharge fluctuations, a thick vadose zone and spatially variable hydrological properties. Such modelling enables further exploration of feedbacks

  12. 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.

  13. 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.

  14. 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

  15. 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

  16. 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

  17. 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

  18. Episodes of fluvial and volcanic activity in Mangala Valles, Mars

    NASA Astrophysics Data System (ADS)

    Keske, Amber L.; Hamilton, Christopher W.; McEwen, Alfred S.; Daubar, Ingrid J.

    2015-01-01

    A new mapping-based study of the 900-km-long Mangala Valles outflow system was motivated by the availability of new high-resolution images and continued debates about the roles of water and lava in outflow channels on Mars. This study uses photogeologic analysis, geomorphic surface mapping, cratering statistics, and relative stratigraphy. Results show that Mangala Valles underwent at least two episodes of fluvial activity and at least three episodes of volcanic activity during the Late Amazonian. The occurrence of scoured bedrock at the base of the mapped stratigraphy, in addition to evidence provided by crater retention ages, suggests that fluvial activity preceded the deposition of two of the volcanic units. Crater counts performed at 30 locations throughout the area have allowed us to construct the following timeline: (1) formation of Noachian Highlands and possible initial flooding event(s) before ∼1 Ga, (2) emplacement of Tharsis lava flows in the valley from ∼700 to 1000 Ma, (3) a megaflooding event at ∼700-800 Ma sourced from Mangala Fossa, (4) valley fill by a sequence of lava flows sourced from Mangala Fossa ∼400-500 Ma, (5) another megaflooding event from ∼400 Ma, (6) a final phase of volcanism sourced from Mangala Fossa ∼300-350 Ma, and (7) emplacement of eolian sedimentary deposits in the northern portion of the valley ∼300 Ma. These results are consistent with alternating episodes of aqueous flooding and volcanism in the valles. This pattern of geologic activity is similar to that of other outflow systems, such as Kasei Valles, suggesting that there is a recurring, and perhaps coupled, nature of these processes on Mars.

  19. 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

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. Extensional faulting in the Taupo Volcanic Zone, New Zealand: stress/strain cycling and deformation partitioning from numerical models

    NASA Astrophysics Data System (ADS)

    Dempsey, D. E.; Ellis, S. M.; Archer, R.; Rowland, J. V.

    2010-12-01

    The Taupo Volcanic Zone of New Zealand’s Central North Island is characterized by widespread normal faulting that accommodates a high proportion of the region’s 7-15 mm yr-1 tectonic extension. Abundant volcanism and geothermal activity are accompanied by seismicity to depths of ~6-8 km. This suggests a shallow brittle-ductile transition (BDT) consistent with the high heat flow (700-800 mW m-1) observed in the region. Fault structures vary from arrays of short strands with lengths of 0.1-1 km to extensive, solitary strands several 10’s of km in length. Fault dip at the surface is estimated to be 55-70o but may shallow near seismogenic depths. Using the finite element software package Abaqus a model is developed to describe movements on a single normal fault under extensional boundary conditions. A visco-elasto-plastic rheology describes crustal deformation and accounts for a transition from brittle to ductile behavior at ~7 km depth. Faults are modeled as internal contact surfaces extending from the surface to depth and whose slip behavior is prescribed by varying the surface coefficient of friction. Fault rupture is cyclical and occurs every 300-1000 years. Over several cycles dip-slip fault displacement is observed to partition into three zones. In the upper crust (~0-7 km) slip is predominantly rigid body and corresponds to minimal elastic straining. Below this, within a ~3 km deep mid-crustal region corresponding to the BDT, dip-slip gradually reduces to zero, accommodated by the development of elastic strain. In the lower crust dip-slip and elastic strain are nearly zero and thus fault behavior is absent. During the period of quiescence following a seismic episode a region of increased visco-elastic creep develops in the lower crust, driven in part by the stress stored elastically in the accommodation zone directly above. Localization of elastic strain in the mid-crust may have implications for hydrothermal fluid flow hosted therein. Pore fluid pressure

  6. 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

  7. 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.

  8. Relationship between Jovian Hectometric Attenuation Lanes And Io Volcanic Activity

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Gurnett, D. A.; Spencer, J. R.; Stansberry, J. A.

    2001-01-01

    Within the Galileo plasma wave instrument data a narrow (in frequency) attenuation band is seen in the hectometric (HOM) emission that varies in frequency with system III longitude. This attenuation lane is believed to be the result of near-grazing incidence or coherent scattering of radio emission near the outer edge of the Io torus, i.e., when the ray path is nearly tangent to an L shell containing the Io flux tube. Such a process should, therefore, be enhanced when the Io volcanic activity is increased and the Io flux tube has enhanced density. We have performed a systematic study of the existing Galileo radio emission data in an effort to determine the phenomenology and frequency of occurrence of the attenuation lanes and the association, if any, with published volcanic activity of Io. Our results indicate that the attenuation lanes are present almost all of the time but are enhanced on occasion. The best examples of attenuation lanes occur when Galileo is within approximately 65 R(sub J) of Jupiter and thus are probably more apparent because of the increased signal-to-noise ratio of the radio receivers. The lack of continuous monitoring of Io activity and the lack of known activity on the anti-Earthward side of Io are problematic and make detailed correlation with radio emission very difficult at this time. Nevertheless, if the data are displayed for periods when the spacecraft is within 65 R(sub J) (i.e., for each perijove pass), then the highest-contrast lanes occur on most passes when the Io volcanic activity is also high for that pass. These results support our current understanding of attenuation lane formation and suggest that future efforts can be made to better understand the interaction of HOM emission with the Io flux tube.

  9. Is There any Relationship Between Active Tabriz Fault Zone and Bozkush Fault Zones, NW Iran?

    NASA Astrophysics Data System (ADS)

    ISIK, V.; Saber, R.; Caglayan, A.

    2012-12-01

    Tectonic plate motions and consequent earthquakes can be actively observed along the northwestern Iran. The Tabriz fault zone (TFZ), also called the North Tabriz fault, active right-lateral strike-slip fault zone with slip rates estimated as ~8 mm/yr, has been vigorously deforming much of northwestern Iran for over the past several million years. Historical earthquakes on the TFZ consist of large magnitude, complimentary rupture length and changed the landscape of regions surrounding the fault zone. The TFZ in the city of Bostanabad is more segmented with several strands and joined by a series of WNW-ESE trending faults, called the Bozkush fault zones. The Bozkush fault zones (BFZ's) (south and north), bounding arch-shaped Bozkush mountains, generates not only hundreds of small earthquakes each year but also has provided significant earthquakes that have been historically documented. The rock units deformed within the BFZ's include Eocene-Oligocene volcanic rocks with intercalation limestone, Oligo-Miocene clastic rocks with intercalation gypsiferous marl and Plio-Quaternary volcano-sedimentary rocks, travertine and alluvium. The North and South Bozkush fault zones are characterized by development of structures typically associated with transpression. These include right-lateral strike-slip faults, thrust faults and foldings. Our field studies indicate that these zones include step to sub-vertical fault surfaces trending NW and NE with slickenlines. Slickensides preserve brittle kinematic indicators (e.g., Riedel shear patterns, slickenside marks) suggesting both dextral displacements and top-to-the-NE/NW and-SE/SW sense of shearing. Besides, mesoscopic and microscopic ductile kinematic indicators (e.g., asymmetric porphyroclasts, C/S fabrics) within Miocene gypsum marl show dextral displacements. Fault rocks along most of these faults consist of incohesive fault breccia and gauge. Adjacent to the fault contact evidence of bedding in Oligo-Miocene and Plio

  10. 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

  11. Bookshelf faulting and transform motion between rift segments of the Northern Volcanic Zone, Iceland

    NASA Astrophysics Data System (ADS)

    Green, R. G.; White, R. S.; Greenfield, T. S.

    2013-12-01

    Plate spreading is segmented on length scales from 10 - 1,000 kilometres. Where spreading segments are offset, extensional motion has to transfer from one segment to another. In classical plate tectonics, mid-ocean ridge spreading centres are offset by transform faults, but smaller 'non-transform' offsets exist between slightly overlapping spreading centres which accommodate shear by a variety of geometries. In Iceland the mid-Atlantic Ridge is raised above sea level by the Iceland mantle plume, and is divided into a series of segments 20-150 km long. Using microseismicity recorded by a temporary array of 26 three-component seismometers during 2009-2012 we map bookshelf faulting between the offset Askja and Kverkfjöll rift segments in north Iceland. The micro-earthquakes delineate a series of sub-parallel strike-slip faults. Well constrained fault plane solutions show consistent left-lateral motion on fault planes aligned closely with epicentral trends. The shear couple across the transform zone causes left-lateral slip on the series of strike-slip faults sub-parallel to the rift fabric, causing clockwise rotations about a vertical axis of the intervening rigid crustal blocks. This accommodates the overall right-lateral transform motion in the relay zone between the two overlapping volcanic rift segments. The faults probably reactivated crustal weaknesses along the dyke intrusion fabric (parallel to the rift axis) and have since rotated ˜15° clockwise into their present orientation. The reactivation of pre-existing rift-parallel weaknesses is in contrast with mid-ocean ridge transform faults, and is an important illustration of a 'non-transform' offset accommodating shear between overlapping spreading segments.

  12. 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.

  13. Holocene tephrostratigraphy of southern Chiloé Continental (Andean southern volcanic zone; ~43°S), Chile

    NASA Astrophysics Data System (ADS)

    Lachowycz, S.; Smith, V. C.; Pyle, D. M.; Mather, T. A.

    2012-12-01

    The eruptive history of the volcanoes in the southern part of the Andean Southern Volcanic Zone (42.5-45°S) is very poorly constrained: only several late Quaternary eruptions have been identified, mostly from study of sparse roadcuts [1]. In this study, we further constrain the Holocene explosive eruption history around 43°S by identifying and analysing tephra layers preserved in a ~3.25m long peat core from Cuesta Moraga [2], ~35km east of Yanteles volcano. Cryptotephra was extracted following the method of [3], in addition to macrotephra; owing to the vicinity of the sampling site to the tephra sources, cryptotephra was found throughout the core stratigraphy, but was sufficiently variable in concentration that discrete layers were identifiable and attributed to specific eruptions. Chemical analysis of the glass by electron microprobe shows that the tephra layers originate from a number of volcanoes in the region. This new tephrostratigraphy improves our knowledge of the important history of explosive volcanism in this area, potentially tying the tephrostratigraphies of surrounding areas (e.g., [4]) and allowing improved evaluation of regional volcanic risk. [1] Naranjo, J.A.., and C. R. Stern, 2004. Holocene tephrochronology of the southernmost part (42°30'-45°S) of the Andean Southern Volcanic Zone. Revista geológica de Chile, 31, pp. 225-240. [2] Heusser, C.J., et al., 1992. Paleoecology of late Quaterary deposits in Chiloé Continental, Chile. Revista Chilena de Historia Natural, 65, pp. 235-245. [3] Blockley, S.P.E., et al., 2005. A new and less destructive laboratory procedure for the physical separation of distal glass tephra shards from sediments. Quaternary Science Reviews, 24, pp. 1952-1960. [4] Watt, S.F.L., et al., 2011. Holocene tephrochronology of the Hualaihue region (Andean southern volcanic zone, ~42°S), southern Chile. Quaternary International, 246, pp. 324-343.

  14. Fluid flow and mud volcanism in the Eastern Mediterranean incipient collision zones

    NASA Astrophysics Data System (ADS)

    Zitter, T. A. C.; Woodside, J. M.; Mascle, J.

    2003-04-01

    Fluid venting activity, either coupled with mud volcanism or along deep active faults or both, has been investigated in the Eastern Mediterranean Sea, mainly in two areas associated with the incipient collision process between Africa and Eurasia. Mud volcanoes are abundant on the crestal part of the Mediterranean Ridge accretionary prism, in association with thrusts, back-thrusts and transcurrent features. They are also found in the Anaximander Mountains/Florence Rise area, to the west of Cyprus, where a wrench system accommodates the pre-collisional deformation. Combined swath multibeam bathymetry and imagery, seismic profiling (ANAXIPROBE survey, 1995 and PRISMED II survey, 1998) and O.R.E.Tech sidescan sonar data (MEDINETH survey, 1999) indicate the genetic relationship between mud volcanoes and tectonics, particularly potential influence of strike-slip faulting. The in situ observations of mud volcanoes (MEDINAUT survey, 1998) have revealed common characteristics at cold seeps, such as carbonate crust constructions and specific chemosynthetic-based fauna. Ground-truth of the sonar data shows that the geophysical signature of mud volcanoes may be related to spatial and temporal evolution of mud volcanism activity, because the seafloor characteristics (surface of the mud flows, distribution and nature of the crusts) and the degree of colonization by benthic fauna vary with the intensity and age of the fluid seepage. Moreover, clay mineralogy studies on the mud matrix samples give insights into the depositional environment, age, and depth of the lithological unit from which the mud breccia is extruded. The shallow signature of the mud reservoir tends to indicate that the overpressured fluids originate from deeper strata than the solid phase of the expelled material.

  15. 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.

  16. 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.

  17. Paleomagnetism of Harutagawa formation in the Hohi Volcanic Zone in northeastern part of Kyushu Island, Japan

    NASA Astrophysics Data System (ADS)

    Kudou, T.; Shibuya, H.

    2008-12-01

    The Beppu-Shimabara graben in the Hohi Volcanic Zone (HVZ) in northeastern part of Kyushu Island, Japan is thought to be a volcano-tectonic depression. Volcanic stratigraphy and age studies of the area have unraveled the late Pliocene structural formation history of HVZ (e.g. Kamata, 1994, Kido, 2007). The age and sedimentation rate of lacustrine deposits in HVZ is one of the keys for interpreting the temporal relation between the formation of Beppu-Shimabara graben and the huge pyroclastic flows appeared in the area. We study the magnetostratigraphy of the Harutagawa formation, which is one of those lacustrine deposits. The formation is dominated by conglomerates and mad stones to siltstones, in the lower and upper parts, respectively, but bares many tuff layers all over the formation. Fission track ages of two tuff layers, one is from lower part and the other is from upper part of Harutagawa formation, are determined as 3.86 ± 0.77Ma and 3.6 ± 0.2Ma, respectively (Kido, 2007). Samples for paleomagnetic analyses have been collected at 28 sites in several continuous outcrop of the Harutagawa formation. The sites are set to be spaced equally in the stratigraphy. Samples were collected by a portable electric motor drill. A few pilot specimens from each site are subjected to progressive thermal and alternating field (AF) demagnetization. However, AF demagnetization is not effective. All remaining specimens are, therefore, submitted to the progressive thermal demagnetization. The samples have mean magnetic intensity of 1.7 × 10- 4A/m and 7.7 × 10-5A/m before and after demagnetization, respectively. Samples from 6 sites have no stable component or are thought to be completely remagnetized by the present magnetic field. As the result, 22 sites are determined their polarities; 8 were reversed and 14 were normal. The normal polarity sites were correlative to Sidufjall, Nunivak and Cochiti subchrons in the Gilbert reversed polarity chron. This correlation indicates that

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. Nondestructive neutron activation analysis of volcanic samples: Hawaii

    SciTech Connect

    Zoller, W.H.; Finnegan, D.L.; Crowe, B.

    1986-01-01

    Samples of volcanic emissions have been collected between and during eruptions of both Kilauea and Mauna Loa volcanoes during the last three years. Airborne particles have been collected on Teflon filters and acidic gases on base-impregnated cellulose filters. Chemically neutral gas-phase species are collected on charcoal-coated cellulose filters. The primary analytical technique used is nondestructive neutron activation analysis, which has been used to determine the quantities of up to 35 elements on the different filters. The use of neutron activation analysis makes it possible to analyze for a wide range of elements in the different matrices used for the collection and to learn about the distribution between particles and gas phases for each of the elements.

  5. Mapping Weak, Altered Zones and Perched Water With Aerogeophysical Measurements at Mount Adams, Washington: Implications for Volcanic Instability

    NASA Astrophysics Data System (ADS)

    Finn, C. A.; Deszcz-Pan, M.; Anderson, E. D.; Horton, R.

    2006-12-01

    Hydrothermally altered rocks, particularly if water saturated, can weaken stratovolcanoes. This increases the potential for catastrophic sector collapses that can lead to destructive debris flows. Evaluating the hazards associated with such alteration is difficult, because alteration has been mapped on few active volcanoes and the distribution and intensity of subsurface alteration and location of perched water tables are largely unknown on any active volcano. At Mount Adams, some Holocene debris flows contain abundant hydrothermal minerals derived from collapse of an altered edifice. Intense hydrothermal alteration can significantly reduce the resistivity (from hundreds to tens ohm-m) and magnetization of volcanic rocks. These changes can be identified with helicopter electromagnetic and magnetic measurements and visualized in 3D. 100 m is the greatest depth that the lowest frequency electromagnetic data could penetrate into the low resistivity, altered zones; outside the altered zones, the depth of penetration was up to 300 m. Total-field magnetic data can detect magnetization variations to several thousand meters depth. Electromagnetic and magnetic data, combined with geological mapping and rock property measurements, indicate the presence of appreciable thicknesses of hydrothermally altered rock in the central core of Mount Adams north of the summit. We identify steep cliffs at the western edge of this zone as the likely source for future large debris flows. Water, and perhaps melted ice, is needed as a lubricant to transform debris avalanches into lahars. Therefore, knowing the distribution of both is important for hazard assessments. Over the low resistivity summit, the electromagnetic data detected ice with a thickness of 0 to about 80 m and an estimated volume of up to 0.1 km3. Over resistive ridges ice thicknesses could not be determined. The electromagnetic data also identified perched water tables in the brecciated core of the upper 300 m of the volcano

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. GRID based Thermal Images Processing for volcanic activity monitoring

    NASA Astrophysics Data System (ADS)

    Mangiagli, S.; Coco, S.; Drago, L.; Laudani, A.,; Lodato, L.; Pollicino, G.; Torrisi, O.

    2009-04-01

    Since 2001, the Catania Section of the National Institute of Geophysics and Volcanology (INGV) has been running the video stations recording the volcanic activity of Mount Etna, Stromboli and the Fossa Crater of Vulcano island. The video signals of 11 video cameras (seven operating in the visible band and four in infrared) are sent in real time to INGV Control Centre where they are visualized on monitors and archived on a dedicated NAS storage. The video surveillance of the Sicilian volcanoes, situated near to densely populated areas, helps the volcanologists providing the Civil Protection authorities with updates in real time on the on-going volcanic activity. In particular, five video cameras are operating on Mt. Etna and they record the volcano from the south and east sides 24 hours a day. During emergencies, mobile video stations may also be used to better film the most important phases of the activity. Single shots are published on the Catania Section intranet and internet websites. On June 2006 a A 40 thermal camera was installed in Vulcano La Fossa Crater. The location was in the internal and opposite crater flank (S1), 400 m distant from the fumarole field. The first two-year of data on temperature distribution frequency were recorded with this new methodology of acquisition, and automatically elaborated by software at INGV Catania Section. In fact a dedicated software developed in IDL, denominated Volcano Thermo Analysis (VTA), was appositely developed in order to extract a set of important features, able to characterize with a good approssimation the volcanic activity. In particular the program first load and opportunely convert the thermal images, then according to the Region Of Interest (ROI) and the temperature ranges defined by the user provide to automatic spatial and statistic analysis. In addition the VTA is able to analysis all the temporal series of images available in order to achieve the time-event analysis and the dynamic of the volcanic

  11. 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.

  12. Geochemistry and petrogenetic history of lavas from Sumaco Volcano, Northern Volcanic Zone, Ecuador

    NASA Astrophysics Data System (ADS)

    Escobar, R. D.; Garrison, J. M.; Sims, K. W.; Matthews, T. P.; Yogodzinski, G. M.

    2012-12-01

    Sumaco Volcano is located in the rear arc of the Northern Volcanic Zone (NVZ) of Ecuador, 105 km from the capital city of Quito. It is one of several volcanoes in the rear arc of the NVZ and is located south of El Reventador volcano. On the basis of summit morphology, Sumaco is believed to have erupted most recently in 1933, however there are few constraints on the timing of past eruptions and it is currently inactive. Lava flows on the steep, jungle-covered flanks are largely inaccessible and therefore few studies have been published for this volcano, and most representative samples are from the volcano summit. The goals of this research are 1) to use major and trace element data to obtain a better understanding of the petrogenetic history of Sumaco Volcano and 2) to use U-series isotopes to constrain the eruption ages and, if possible get information about magma storage times. We collected and sent 23 rock samples to Washington State University for analysis of major and trace elements using XRF and ICP, including six lavas from the summit and 17 from the southern flanks, including bread-crust bombs. A subgroup of samples was chosen for U-series disequilibrium measurements on whole rocks and minerals. Based on hand-sample observations and electron microprobe analyses, the primary mineral phases found in the Sumaco lavas include titanaugite, hauyne, olivine and plagioclase, with accessory apatite and hercynite. The plagioclase and apatite have seive textures consistent with magma mixing or recharge, and the titanaugite crystals are euhedral with oscillatory zoning that records repeated recharge events. On the basis of major and trace element data, the lavas are alkaline and range in composition from picro-basalt to tephri-phonolite; the picro basalt has MgO of 10 wt % and the summit samples are the most evolved with MgO of 2 wt %. The summit lavas (also presumed to be the youngest lavas) have the highest concentration of alkali elements with K2O content (> 4 wt

  13. 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

  14. Ohaaki reservoir chemistry: characteristics of an arc-type hydrothermal system in the Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Christenson, B. W.; Mroczek, E. K.; Kennedy, B. M.; van Soest, M. C.; Stewart, M. K.; Lyon, G.

    2002-06-01

    Situated along the eastern margin of the Taupo Volcanic Zone (TVZ), the high-gas and high-enthalpy production fluids from the Ohaaki geothermal field are chemically similar to other arc-type volcanic systems found along this part of the TVZ. Two thermal upwellings can be distinguished within the field, each apparently emanating from fault structures in the Mesozoic basement greywackes. Although both plumes have similar salinities and appear to be fully equilibrated with the reservoir rocks containing them, fluids associated with the eastern upflow zone are enriched in B and F compared to those in the western upflow zone. δ 2H and δ 18O signatures for water suggest that up to 20% of the water in the discharges may derive from a magmatic source, and a δ 2H-Cl trend established by the East-Bank fluids indicate end-member mixing between a high-Cl fluid and Cl-deficient steam containing as much as 40% arc-type vapour. Gas signatures in fluids from the two production fields show compositional differences that cannot be explained by physical reservoir processes. The eastern fluids have higher N 2/Ar and CO 2/He ratios, and consistently higher CH 4-CO 213C fractionation temperatures than those in the western upflow zone. In addition, stark differences in 3He/ 4He and 40Ar/ 36Ar ratios for the two production fields suggest two-component mixing for the respective source components, with the eastern fluids having a significantly larger radiogenic gas content than those to the west. Collectively, these signatures suggest the presence of a relatively young and shallowly seated degassing intrusive beneath the eastern upflow zone, perhaps as shallow as 4 km beneath the surface.

  15. 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.

  16. Relationship between normal faulting and volcanic activity in the Taranaki backarc basin, New Zealand

    NASA Astrophysics Data System (ADS)

    Giba, M.; Walsh, J. J.; Nicol, A.

    2009-04-01

    Volcanoes and normal faults are, by definition, both present within volcanic rifts. Despite this association the causal relationships between volcanism and normal faulting can be unclear and are poorly understood. One of the principal challenges for investigations of the links between faulting and volcanic activity, is the definition of the detailed temporal relationships between these two processes. The northern Taranaki Basin, which benefits from excellent seismic (2D and 3D) and drillhole coverage, provides the basis for a detailed study of volcanism and faulting over the last ca 15 Myr. Most of the basin is characterised by sedimentation rates which exceed fault displacement rates, a condition which permits displacement backstripping of these syn-sedimentary growth faults. The timing of a suite of mostly andesitic submarine volcanoes has been constrained by interdigitation of the volcanic cones with basinal sedimentary rocks. Eleven dated horizons within the ca 15 Myr and younger stratigraphy together with mapping provide a means of examining the temporal and spatial links between fault and volcanic activity within the basin. The northern Taranaki Basin has a multiphase deformation history, with extension during the Late Cretaceous to Mid Eocene (ca 80-45 Ma), followed by contraction in the Late Eocene to Early Miocene (ca 40-18 Ma) and then by Mid Miocene to recent back arc extension (ca 15-0 Ma). The youngest phase of extensional faulting initiated in the north and west of the basin and migrated to the southeast where present activity is focused. Volcanic activity also commenced in the north during the Mid Miocene and migrated towards the south and east. Volcanism and backarc extension are driven by subduction of the Pacific plate along the Hikurangi margin. The southward and eastward migration of both faulting and volcanic activity is attributed to the steepening and rotation of the subducting slab beneath the Taranaki Basin. Despite the common origin of

  17. 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

  18. 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.

  19. 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.

  20. 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

  1. Role of cryptic amphibole crystallization in magma differentiation at Hudson volcano, Southern Volcanic Zone, Chile

    NASA Astrophysics Data System (ADS)

    Kratzmann, David J.; Carey, Steven; Scasso, Roberto A.; Naranjo, Jose-Antonio

    2010-02-01

    Hudson volcano (Chile) is the southern most stratovolcano of the Andean Southern Volcanic Zone and has produced some of the largest Holocene eruptions in South America. There have been at least 12 recorded Holocene explosive events at Hudson, with the 6700 years BP, 3600 years BP, and 1991 eruptions the largest of these. Hudson volcano has consistently discharged magmas of similar trachyandesitic and trachydacitic composition, with comparable anhydrous phenocryst assemblages, and pre-eruptive temperatures and oxygen fugacities. Pre-eruptive storage conditions for the three largest Holocene events have been estimated using mineral geothermometry, melt inclusion volatile contents, and comparisons to analogous high pressure experiments. Throughout the Holocene, storage of the trachyandesitic magmas occurred at depths between 0.2 and 2.7 km at approximately ~972°C (±25) and log fO2 -10.33-10.24 (±0.2) (one log unit above the NNO buffer), with between 1 and 3 wt% H2O in the melt. Pre-eruptive storage of the trachydacitic magma occurred between 1.1 and 2.0 km, at ~942°C (±26) and log fO2 -10.68 (±0.2), with ~2.5 wt% H2O in the melt. The evolved trachyandesitic and trachydacitic magmas can be derived from a basaltic parent primarily via fractional crystallization. Entrapment pressures estimated from plagioclase-hosted melt inclusions suggest relatively shallow levels of crystallization. However, trace element data (e.g., Dy/Yb ratio trends) suggests amphibole played an important role in the differentiation of the Hudson magmas, and this fractionation is likely to have occurred at depths >6 km. The absence of a garnet signal in the Hudson trace element data, the potential staging point for differentiation of parental mafic magmas [i.e., ~20 km (e.g., Annen et al. in J Petrol 47(3):505-539, 2006)], and the inferred amphibolite facies [~24 km (e.g., Rudnick and Fountain in Rev Geophys 33:267-309, 1995)] combine to place some constraint on the lower limit of depth of

  2. 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..

  3. The dynamic history of the Trans-Mexican Volcanic Belt and the Mexico subduction zone

    NASA Astrophysics Data System (ADS)

    Ferrari, Luca; Orozco-Esquivel, Teresa; Manea, Vlad; Manea, Marina

    2012-02-01

    The Trans-Mexican Volcanic Belt (TMVB) is a 1000 km long Neogene continental arc showing a large variation in composition and volcanic style, and an intra-arc extensional tectonics. It overlies the Rivera and Cocos slabs, which display marked changes in geometry. Geophysical studies indicate that lithospheric mantle is very thin or absent beneath the forearc and arc, the fluids from the slab are released in a 40 to 100 km wide belt beneath the frontal part of the arc, and the lower crust beneath the arc is partially molten. East of 101°W the TMVB is built on a Precambrian to Paleozoic crust with thickness of 50-55 km. West of 101°W the TMVB is underlain by Jurassic to Cenozoic marine and continental arcs with a 35-40 km thick crust. The evolution of the TMVB occurred in four stages: 1) from ~ 20 to 10 Ma the initial andesitic arc moved inland showing progressively drier melting and, eventually, slab melting, suggesting flattening of the subducted slab; 2) since ~ 11 Ma a pulse of mafic volcanism migrated from west to east reaching the Gulf of Mexico by 7 Ma. This mafic lavas marks the lateral propagation of a slab tear, triggered by cessation of subduction beneath Baja California; 3) thereafter, the volcanic front started moving trenchward, with a marked phase of silicic volcanism between 7.5 and 3 Ma, local emplacement of small volume intraplate-like basalts since 5 Ma, and development of extensional faulting. These features are related to slab rollback, enhancing asthenophere flux into the mantle wedge and promoting partial melting of the crust; 4) the modern arc consists of a frontal belt dominated by flux and slab melting, and a rear belt characterized by more differentiated rocks or by mafic lavas with little or no evidence of subduction fluids but higher asthenosphere fingerprint.

  4. Characterization and interpretation of volcanic activity at Redoubt, Bezymianny and Karymsky volcanoes through direct and remote measurements of volcanic emissions

    NASA Astrophysics Data System (ADS)

    Lopez, Taryn M.

    Surface measurements of volcanic emissions can provide critical insight into subsurface processes at active volcanoes such as the influx or ascent of magma, changes in conduit permeability, and relative eruption size. In this dissertation I employ direct and remote measurements of volcanic emissions to characterize activity and elucidate subsurface processes at three active volcanoes around the North Pacific. The 2009 eruption of Redoubt Volcano, Alaska, produced elevated SO2 emissions that were detected by the Ozone Monitoring Instrument (OMI) satellite sensor for over three months. This provided a rare opportunity to characterize Redoubt's daily SO2 emissions and to validate the OMI measurements. Order of magnitude variations in daily SO2 mass were observed, with over half of the cumulative SO2 emissions released during the explosive phase of the eruption. Correlations among OMI daily SO2 mass, tephra mass and acoustic energies during the explosive phase suggest that OMI data may be used to infer eruption size and explosivity. From 2007 through 2010 direct and remote measurements of volcanic gas composition and flux were measured at Bezymianny Volcano, Kamchatka, Russia. During this period Bezymianny underwent five explosive eruptions. Estimates of passive and eruptive SO2 emissions suggest that the majority of SO2 is released passively. Order of magnitude variations in total volatile flux observed throughout the study period were attributed to changes in the depth of gas exsolution and separation from the melt at the time of sample collection. These findings suggest that exsolved gas composition may be used to detect magma ascent prior to eruption at Bezymianny Volcano. Karymsky Volcano, Kamchatka, Russia, is a dynamic volcano which exhibited four end-member activity types during field campaigns in 2011 and 2012, including: discrete ash explosions, pulsatory degassing, gas jetting, and explosive eruption. These activity types were characterized quantitatively

  5. 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

  6. Estimation of age of Dali-Ganis rifting and associated volcanic activity, Venus

    NASA Technical Reports Server (NTRS)

    Basilevsky, A. T.

    1993-01-01

    This paper deals with the estimation of age for the Dali and Ganis Chasma rift zones and their associated volcanism based on photogeologic analysis of stratigraphic relations of rift-associated features with impact craters which have associated features indicative of their age. The features are radar-dark and parabolic, and they are believed to be mantles of debris derived from fallout of the craters' ejecta. They are thought to be among the youngest features on the Venusian surface, so their 'parent' craters must also be very young, evidently among the youngest 10 percent of Venus' crater population. Dali Chasma and Ganis Chasma are a part of a system of rift zones contained within eastern Aphrodite and Atla Regio which is a significant component of Venus tectonics. The rifts of this system are fracture belts which dissect typical Venusian plains with rare islands of tessera terrain. The rift zone system consists of several segments following each other (Diane, Dali, Ganis) and forming the major rift zone line, about 10,000 km long, which has junctions with several other rift zones, including Parga Chasma Rift. The junctions are usually locations of rift-associated volcanism in the form of volcanic edifices (Maat and Ozza Montes) or plain-forming flows flooding some areas within the rift zones and the adjacent plains.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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

  14. 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

  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. Observed multivariable signals of late 20th and early 21st century volcanic activity

    NASA Astrophysics Data System (ADS)

    Santer, Benjamin D.; Solomon, Susan; Bonfils, Céline; Zelinka, Mark D.; Painter, Jeffrey F.; Beltran, Francisco; Fyfe, John C.; Johannesson, Gardar; Mears, Carl; Ridley, David A.; Vernier, Jean-Paul; Wentz, Frank J.

    2015-01-01

    The relatively muted warming of the surface and lower troposphere since 1998 has attracted considerable attention. One contributory factor to this "warming hiatus" is an increase in volcanically induced cooling over the early 21st century. Here we identify the signals of late 20th and early 21st century volcanic activity in multiple observed climate variables. Volcanic signals are statistically discernible in spatial averages of tropical and near-global SST, tropospheric temperature, net clear-sky short-wave radiation, and atmospheric water vapor. Signals of late 20th and early 21st century volcanic eruptions are also detectable in near-global averages of rainfall. In tropical average rainfall, however, only a Pinatubo-caused drying signal is identifiable. Successful volcanic signal detection is critically dependent on removal of variability induced by the El Niño-Southern Oscillation.

  17. Basaltic Diatreme To Root Zone Volcanic Processes In Tuzo Kimberlite Pipe (Gahcho Kué Kimberlite Field, NWT, Canada)

    NASA Astrophysics Data System (ADS)

    Seghedi, I.; Kurszlaukis, S.; Maicher, D.

    2009-05-01

    Tuzo pipe is infilled by a series of coherent and fragmental kimberlite facies types typical for a diatreme to root zone transition level. Coherent or transitional coherent kimberlite facies dominate at depth, but also occur at shallow levels, either as dikes or as individual or agglutinated coherent kimberlite clasts (CKC). Several fragmental kimberlite varieties fill the central and shallow portions of the pipe. The definition, geometry and extent of the geological units are complex and are controlled by vertical elements. Specific for Tuzo is: (1) high abundance of locally derived xenoliths (granitoids and minor diabase) between and within the kimberlite phases, varying in size from sub-millimeter to several tens of meters, frequent in a belt-like domain between 120-200 m depth in the pipe; (2) the general presence of CKC, represented by round-subround, irregular to amoeboid-shaped clasts with a macrocrystic or aphanitic texture, mainly derived from fragmentation of erupting magma and less commonly from previously solidified kimberlite, as well as recycled pyroclasts. In addition, some CKC are interpreted to be intersections of a complex dike network. This diversity attests formation by various volcanic processes, extending from intrusive to explosive; (3) the presence of bedded polymict wall- rock and kimberlite breccia occurring mostly in deep levels of the pipe below 345 m depth. The gradational contact relationships of these deposits with the surrounding kimberlite rocks and their location suggest that they formed in situ. The emplacement of Tuzo pipe involved repetitive volcanic explosions alternating with periods of relative quiescence causing at least partial consolidation of some facies. The volume deficit in the diatreme-root zone after each eruption was compensated by gravitational collapse of overlying diatreme tephra and pre-fragmented wall-rock xenoliths. Highly explosive phases were alternating with weak explosions or intrusive phases, suggesting

  18. 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.

  19. Use of High Temporal Resolution Thermal Imagery of Karymsky's Volcanic Plume to Constrain Volcanic Activity and Elucidate Vent Processes

    NASA Astrophysics Data System (ADS)

    Lopez, T. M.; Dehn, J.; Belousov, A.; Fee, D.; Buurman, H.; Grapenthin, R.; Ushakov, S.

    2011-12-01

    Analysis of high temporal resolution thermal imagery of the volcanic plume from Karymsky volcano, Kamchatka, Russia, was performed to characterize the activity and elucidate vent processes observed during a field campaign from 21 through 26 July 2008. Observed emission styles ranged from explosive eruptions, gas jetting, gas puffing, passive degassing, to absent degassing. These styles can be broadly categorized according to the thermal data. Specifically, we interpret: (1) apparent temperatures in excess of 120°C to indicate eruption of juvenile material; (2) exponential trends between maximum apparent temperature and radiation above background values to indicate degassing or explosive eruptions; (3) flat and/or flat-exponential hybrid trends between maximum apparent temperature and radiation to indicate absent degassing and/or gas puffing, or a transition between degassing and absent degassing; and (4) strong periodicity identified by inspection or through power spectral density analysis of timeseries data to indicate gas puffing. Based on our thermal observations we propose that these styles of volcanic emissions are primarily controlled by shallow vent processes, with the range of emission styles reflecting a continuum between open and closed vent activity. Specifically, we propose that (1) periods of absent degassing indicate vent sealing; (2) periods of gas puffing indicate cyclic behavior between partial vent sealing and vent fracturing; and (3) passive degassing, gas jetting, and continuous eruption all indicate open vent conditions. We suggest that secondary influences by magma recharge and gas exsolution processes may contribute to variations in degassing style under open vent conditions. These results suggest that trends in thermal timeseries data, such as maximum apparent temperature and radiation, can be used to quantitatively characterize volcanic activity and may help constrain vent processes at active volcanoes.

  20. 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

  1. 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

  2. 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.

  3. 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

  4. Regimes of Volcanic Activity at Mt. Etna in 2007-2009 inferred from Unsupervised Pattern Recognition on Volcanic Tremor Data

    NASA Astrophysics Data System (ADS)

    Falsaperla, S. M.; Behncke, B.; Langer, H. K.; Messina, A.; Spampinato, S.

    2009-12-01

    Mt Etna is a well monitored basaltic volcano for which high-quality, multidisciplinary data set are continuously available for around-the-clock surveillance. Particularly, volcano-seismic data sets cover decades long local recordings, temporally encompassing different styles of eruptive activity, from Strombolian eruptions to lava fountains and lava flows. Intense earthquakes swarms have often heralded effusive activity. However, from the seismic point of view, volcanic tremor has proved to be one of the most reliable indicators of impending eruptive activity. Indeed, changes in the volcano feeder show up in the signature of tremor, its spectral characteristics and source location. Some of us (Langer and Messina) have recently developed a new software for the classification of volcanic tremor data, combining Self Organizing Maps (also known as Kohonen Maps) along with Cluster and Fuzzy Analysis. This software allows us to analyse the background seismic radiation at permanent broadband stations located at various distance from the summit craters to identify transitions from pre-eruptive to eruptive activity. Throughout the analysis of the data flow, the software provides an unsupervised classification of the spectral characteristics (i.e., amplitude and frequency content) of the signal. The information embedded in the spectrum is interpreted to assign a specific state of the volcano. An application of this new software is proposed here on the eruptive events at Etna of 2007-2009, which consisted of 7 episodes of lava fountaining, periodic Strombolian activity at the summit craters, followed by lava emissions on the upper east flank of the volcano, with start on 13 May 2008 and end on 6 July 2009. In the study period the source of volcanic tremor was always shallow (less than 3 km) and within the volcano edifice. The upraise of magma to the surface was fast and associated with changes of volcanic tremor features, which covered time windows of variable duration from

  5. The ups and downs of the TVZ: Geodetic observations of deformation around the Taupo Volcanic Zone, New Zealand

    NASA Astrophysics Data System (ADS)

    Hamling, I. J.; Hreinsdóttir, S.; Fournier, N.

    2015-06-01

    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, with current extension rates of 8-15 mm yr-1. 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. Both InSAR and vertical GPS data show widespread subsidence across the central TVZ at rates of up to 20 mm yr-1. Using simple elastic dislocation models to represent the contraction of a sill like body at 6 km depth, we predict an annual volume change of 0.011-0.016 km3 beneath the central TVZ. We suggest that the majority of the observed subsidence is a result of the cooling and subsequent contraction of magma within the shallow crust.

  6. Mud volcanism as an indicator of late to neopleistocene-holocene activity of the Chilik-Kemin fault, Yli depression, Northern Tien Shan

    NASA Astrophysics Data System (ADS)

    Deev, E. V.; Kokh, S. N.; Sokol, E. V.; Zol'nikov, I. D.; Panov, V. S.

    2014-11-01

    It is revealed that the Altyn-Emel mud volcanic field (43°52'56″ N, 79°06'31″ E) in the Yli depression (Dzharkent trough) is structurally linked to the northeastern end of the Chilik-Kemin deep fault. The mud volcano is related to hydrocarbon-rich gases (including methane) and pressure artesian mineralized thermal waters, which uplifted to the surface along the fault zone. It is suggested that the earthquakes with M≤ 5 related both to the Chilik-Kemin fault and other seismic generating structures intensified the mud volcanic activity. In some cases, the eruptions were accompanied by the short-lived ignition of hydrocarbon gases and formation of the Na-rich paralavas. The mud volcanism of the Altyn-Emel field has been manifested during the last 15-20 k.a., and, consequently, the northeastern part of the Chilik-Kemin fault is an active structure.

  7. 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.

  8. Characterizing Magmatic Sources in the Central Andes Volcanic Zone with a Regional InSAR Time Series Survey

    NASA Astrophysics Data System (ADS)

    Henderson, S. T.; Pritchard, M. E.

    2011-12-01

    The Central Andes Volcanic Zone (CVZ) contains many intriguing areas of ongoing crustal deformation detectable with InSAR. Foremost among these are the 1-2cm/yr radar line-of-sight (LOS) inflations near Uturuncu Volcano in Bolivia and the Lazufre volcanic area spanning the border of Chile and Argentina (Pritchard and Simons 2002). These two deformation sources are intriguing in that they are long-lived (>10yrs), have large diameters (>50km), and have modeled sources at mid-crustal depths (10-20km). For Uturuncu, the best-fitting source depths coincide with the seismically imaged Altiplano-Puna Magma Body (eg. Chimielowsi et al. 1999, Zandt et al. 2003). Regional InSAR time series analysis enables the spatial and temporal comparison of the Uturuncu and Lazufre signals with other deformations in a sub-region of the CVZ from 1992 to the present. Our study focuses on volcanic deformation, but we also resolve non-magmatic deformation signals including landslides and salars. The study region benefits from a large InSAR dataset of 631 ERS and ENVISAT interferograms, distributed between two descending tracks and two ascending tracks, covering up to 870 kilometers along the volcanic arc. We employ an inversion method based on the SBAS algorithm (Berardino 2002), but modified to avoid interpolation across dates with incoherent values. This modification effectively deals with the heterogeneous spatial extents and data gaps present in individual interferograms for long tracks. With our time series results we investigate the timing of possible magma migrations and we explore the parameters of forward models that match observations. Results indicate continuing monotonic inflation styles at Uturuncu and Lazufre with maximum LOS uplift at 1.0cm/yr and 2.5cm/yr respectively (Pritchard and Simons 2004, Froger et al. 2007, Ruch et al. 2009). We discuss evidence for 2mm/yr broad LOS deflation collocated with the Uturuncu inflation signal and comment on possible models for its origin

  9. Distributed Anelastic Strain and its Relationship to Compliant Zones Surrounding Active Faults of the Eastern California Shear Zone

    NASA Astrophysics Data System (ADS)

    Shelef, E.; Oskin, M.; Fialko, Y.

    2006-12-01

    Geologic measurements of distributed anelastic strain (DAS) adjacent to active strike slip faults of the Mojave Desert portion of the Eastern California shear zone quantify the magnitude, mechanism, temporal evolution, and relationship of DAS to fault compliant zones imaged via InSAR. Prefaulting markers (mylonitic lineation, dikes, and faults assumed linear prior to dextral faulting) in crystalline rocks next to the Harper Lake fault and Calico fault indicate that DAS accounts for 6 to 23 percent of total displacement and that this displacement scales with fault slip. We conclude that DAS is a significant, active process that is not restricted to the initial fault propagation stage. We find that the width of the zone of DAS is 400-700 m on each side of the faults studied, irrespective of total fault slip. 60 percent of the displacement due to DAS occurs within 100 m of the Calico fault. A similar zone of more intense deformation occurs adjacent to the Harper Lake fault. These 100m- wide-zones are of the same extent but much less intensely deformed compared to the damage zones surrounding the San Andreas fault. Based on these relationships, we hypothesize that damage feedback progressively focuses DAS into a stable, approximately 100-m-wide-zone where its intensity can increase proportionally to fault slip. Disruption of linear markers supports that DAS in crystalline rocks occurs via slip along secondary faults and small-scale block rotation with block sizes decreasing with proximity to faults. The widths of the geologically documented zones of DAS in the Eastern California shear zone are similar to the approximately 1 km width of compliant zones modeled from InSAR observations of surface deformation due to stress changes caused by nearby earthquakes. This correlation suggests a relationship between damage- reduction of shear modulus and displacement via DAS. Paleomagnetic measurements of prefaulting and syntectonically emplaced volcanic rocks in sedimentary

  10. Crustal movements at a divergent plate boundary: interplay between volcano deformation, geothermal processes, and plate spreading in the Northern Volcanic Zone, Iceland since 2008.

    NASA Astrophysics Data System (ADS)

    Drouin, Vincent; Sigmundsson, Freysteinn; Hreinsdóttir, Sigrún; Ofeigsson, Benedikt G.; Sturkell, Erik; Islam, Tariqul

    2014-05-01

    Iceland is a subaerial part of the Mid-Atlantic Ridge, where the divergent plate boundary between the North-American and Eurasian Plates can be studied. The Northern Volcanic Zone (NVZ) of Iceland, comprised of several volcanic systems, is particularly well suited to study interplay between volcanoes, geothermal areas and plate spreading, as the zone is relatively simple and accommodates the full spreading of the plates (18.6 mm/yr in a direction of 105 degrees according to NUVEL-1A predictions). The most recent volcanic activity in the area was the Krafla rifting episode (1975-1984). In 2007-2008 two intrusive events were detected: one in Upptypingar and the other in Þeistareykir. Extensive crustal deformation studies have been carried out in the NVZ; we report the results of recent GPS and Interferometric Synthetic Aperture Radar (InSAR) studies focusing on Krafla, Þeistareykir and Askja volcanic systems in the NVZ. An extensive GPS survey was undertaken in 2013, with over 135 stations occupied. This data was evaluated in conjunction with data acquired since 2008, to generate a velocity field spanning this entire time period. In addition to an existing continuous GPS (cGPS) station, three cGPS stations were installed in the area in 2011-2012. The 2008-2013 GPS velocities were compared to earlier GPS results, and complementary analysis of InSAR images was undertaken. Earlier studies have shown that the Krafla caldera underwent uplift during 1984-1989, followed by subsidence. Since 1995, the maximum subsidence in Krafla has shifted from directly above the shallow magma chamber towards an array of boreholes (geothermal exploitation) in Leirbotnar. Similar subsidence has been observed around another array of boreholes in Bjarnaflag, 7 km further south. The most significant signal on the velocities calculated from campaign GPS data over the 5 year period, is plate spreading with an E-W velocity of about 12 mm/yr over a 30 km wide area. However it also shows an

  11. 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).

  12. 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

  13. Across-arc geochemical variations in the Southern Volcanic Zone, Chile (34.5-38.0°S): Constraints on mantle wedge and slab input compositions

    NASA Astrophysics Data System (ADS)

    Jacques, G.; Hoernle, K.; Gill, J.; Hauff, F.; Wehrmann, H.; Garbe-Schönberg, D.; van den Bogaard, P.; Bindeman, I.; Lara, L. E.

    2013-12-01

    Crustal assimilation (e.g. Hildreth and Moorbath, 1988) and/or subduction erosion (e.g. Stern, 1991; Kay et al., 2005) are believed to control the geochemical variations along the northern portion of the Chilean Southern Volcanic Zone. In order to evaluate these hypotheses, we present a comprehensive geochemical data set (major and trace elements and O-Sr-Nd-Hf-Pb isotopes) from Holocene primarily olivine-bearing volcanic rocks across the arc between 34.5°S and 38.0°S, including volcanic front centers from Tinguiririca to Callaqui, the rear arc centers of Infernillo Volcanic Field, Laguna del Maule and Copahue, and extending 300 km into the backarc. We also present an equivalent data set for Chile trench sediments outboard of this profile. The volcanic arc (including volcanic front and rear arc) samples primarily range from basalt to andesite/trachyandesite, whereas the backarc rocks are low-silica alkali basalts and trachybasalts. All samples show some characteristic subduction zone trace element enrichments and depletions, but the backarc samples show the least. Backarc basalts have higher Ce/Pb, Nb/U, Nb/Zr, and Ta/Hf, and lower Ba/Nb and Ba/La, consistent with less of a slab-derived component in the backarc and, consequently, lower degrees of mantle melting. The mantle-like δ18O in olivine and plagioclase phenocrysts (volcanic arc = 4.9-5.6‰ and backarc = 5.0-5.4‰) and lack of correlation between δ18O and indices of differentiation and other isotope ratios, argue against significant crustal assimilation. Volcanic arc and backarc samples almost completely overlap in Sr and Nd isotopic composition. High precision (double-spike) Pb isotope ratios are tightly correlated, precluding significant assimilation of older sialic crust but indicating mixing between a South Atlantic Mid Ocean-Ridge Basalt (MORB) source and a slab component derived from subducted sediments and altered oceanic crust. Hf-Nd isotope ratios define separate linear arrays for the volcanic

  14. 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

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

    NASA Astrophysics Data System (ADS)

    Head, James W.; Wilson, Lionel

    1992-03-01

    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.

  16. 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.

  17. 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

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. 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.

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

    NASA Technical Reports Server (NTRS)

    Esposito, L. W.

    1984-01-01

    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.

  4. 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.

  5. Volcanism and associated hazards: the Andean perspective

    NASA Astrophysics Data System (ADS)

    Tilling, R. I.

    2009-12-01

    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 km3) 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, Ecuador, and

  6. 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

  7. Fracturing of doleritic intrusions and associated contact zones: Implications for fluid flow in volcanic basins

    NASA Astrophysics Data System (ADS)

    Senger, Kim; Buckley, Simon J.; Chevallier, Luc; Fagereng, Åke; Galland, Olivier; Kurz, Tobias H.; Ogata, Kei; Planke, Sverre; Tveranger, Jan

    2015-02-01

    Igneous intrusions act as both carriers and barriers to subsurface fluid flow and are therefore expected to significantly influence the distribution and migration of groundwater and hydrocarbons in volcanic basins. Given the low matrix permeability of igneous rocks, the effective permeability in- and around intrusions is intimately linked to the characteristics of their associated fracture networks. Natural fracturing is caused by numerous processes including magma cooling, thermal contraction, magma emplacement and mechanical disturbance of the host rock. Fracturing may be locally enhanced along intrusion-host rock interfaces, at dyke-sill junctions, or at the base of curving sills, thereby potentially enhancing permeability associated with these features. In order to improve our understanding of fractures associated with intrusive bodies emplaced in sedimentary host rocks, we have investigated a series of outcrops from the Karoo Basin of the Eastern Cape province of South Africa, where the siliciclastic Burgersdorp Formation has been intruded by various intrusions (thin dykes, mid-sized sheet intrusions and thick sills) belonging to the Karoo dolerite. We present a quantified analysis of fracturing in- and around these igneous intrusions based on five outcrops at three individual study sites, utilizing a combination of field data, high-resolution lidar virtual outcrop models and image processing. Our results show a significant difference between the three sites in terms of fracture orientation. The observed differences can be attributed to contrasting intrusion geometries, outcrop geometry (for lidar data) and tectonic setting. Two main fracture sets were identified in the dolerite at two of the sites, oriented parallel and perpendicular to the contact respectively. Fracture spacing was consistent between the three sites, and exhibits a higher degree of variation in the dolerites compared to the host rock. At one of the study sites, fracture frequency in the

  8. Twenty-five million years of silicic volcanism in the southern central volcanic zone of the Andes: Geochemistry and magma genesis of ignimbrites from 25 to 27 °S, 67 to 72 °W

    NASA Astrophysics Data System (ADS)

    Schnurr, W. B. W.; Trumbull, R. B.; Clavero, J.; Hahne, K.; Siebel, W.; Gardeweg, M.

    2007-09-01

    Silicic volcanism in the Andean Central Volcanic Zone (CVZ) produced one of the world's largest Neogene ignimbrite provinces. The largest and best-known CVZ ignimbrites are located on the Altiplano-Puna plateau north of 24 °S. Their compositions and huge erupted volumes suggest an origin by large-scale crustal melting, and present-day geophysical anomalies in this region suggest still active zones of partial melting in the middle crust. Farther south in the CVZ, the Cerro Galán complex erupted ignimbrites in the late Miocene and Pliocene that are quite similar in volume and composition to those from north of 24 °S and they have a similar origin. However, there are a great many other, smaller ignimbrites in the southern CVZ whose compositions and geodynamic significance are poorly known. These are the subject of this paper. We present a geochemical study of 28 ignimbrite units from the southern CVZ at 25 °S to 27 °S, whose ages cover the full span of arc activity in this area, from about 25 Ma to 1 Ma. The small to medium volume ignimbrites (< 10 km 3) form valley-fill or sheet-like deposits, many of which are chemically zoned. Notwithstanding individual differences, there are several common characteristic features within the group of southern CVZ ignimbrites. By far the dominant composition is metaluminous, crystal-poor rhyolite (mean values from 236 samples: SiO 2 = 73.5 wt.%, A/CNK = 1.02, K 2O/Na 2O = 1.4). Regular major and trace element differentiation trends suggest fractionation from intermediate arc magmas and this is supported by radiogenic isotopic ratios of Sr, Nd and Pb, which show complete overlap between the silicic ignimbrites and andesite-dacites from contemporary stratovolcanoes. There are no major changes in composition of the silicic ignimbrites over the 25 Ma span of activity. We attribute minor but significant differences in isotopic composition and Nb-Ta concentration according to location in the West Cordillera (Chile) or the southern

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 40Ar/39Ar geochronology of the Neogene-Quaternary Harrat Al-Madinah intercontinental volcanic field, Saudi Arabia: Implications for duration and migration of volcanic activity

    NASA Astrophysics Data System (ADS)

    Moufti, M. R.; Moghazi, A. M.; Ali, K. A.

    2013-01-01

    New 40Ar/39Ar ages, based on incremental heating techniques for groundmass separates of 25 samples, are presented for the Harrat Al-Madinah volcanic field, part of Harrat Rahat in the north western part of the Arabian plate. This area is an active volcanic field characterized by the occurrence of two historical eruptions approximately in 641 and 1256 AD. Field investigations of the main volcanic landforms indicate dominantly monogenetic strombolian eruptions, in addition to local more explosive eruptions. The lavas consist mainly of olivine basalt and hawaiite flows with minor evolved rocks of mugearite, benmoreite, and trachyte that occur mainly as domes, tuff cones and occasionally as lava flows. Previous K/Ar dating shows that the Harrat Al-Madinah lava flows and associated domes comprise seven units spanning an age range of ca. 1.7 Ma-Recent. The new 40Ar/39Ar age determinations confirm, to a great extent, the previously obtained K/Ar ages in the sense that no major systematic biases were found in the general stratigraphy of the different flow units. However, the 40Ar/39Ar plateau ages show that volcanism in this area began in the Neogene (˜10 Ma) and continued to Recent, with the most voluminous eruptions occurring in the Quaternary. Neogene volcanism occurred in at least three pulses around 10, 5 and 2 Ma, whereas Quaternary volcanism produced at least seven units reflecting lava flow emplacement in the time period of 1.90 Ma-Recent. Thus, the whole duration of volcanic activity in the Harrat Al-Madinah (10 Ma-Recent) appears much longer than that previously identified. The longevity of volcanism in the same part of the moving Arabian plate and absence of evidence for uni-directional migration of volcanic activity indicate that there is no fixed plume beneath this region. The NNW-trending distribution of the volcanic vents is parallel to the Red Sea, and suggests their origin is related to periodic extensional episodes along the reactivated Red Sea fault

  17. 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

  18. Polarization analysis of non-volcanic tremor at Guerrero subduction zone (Mexico)

    NASA Astrophysics Data System (ADS)

    Palo, M.; Capuano, P.

    2012-04-01

    Since its first observation occurred about ten years ago in Japan, non-volcanis tremor (NVT) has been observed in many areas worldwide. NVT is generally associated with fluid movements in the lithosphere and, together with the slow-slip events, are considered a key factor to understand the stress state and stress transfer in tectonic frameworks, especially in subduction zones. Here, we analyze the polarization properties of the NVTs recorded at Guerrero subduction segment of the Cocos plate (Mexico). The Guerrero subduction segment represents a very important case study for its seismic gap. Indeed, there is an absence of large earthquakes in this part of the subducting plate for the last hundred years, and this segment is expected to be able to originate an earthquake of magnitude 8. NVT at Guerrero is a long-duration, low-amplitude, nonimpulsive seismic radiation with most energy concentrated in the frequency range 1-8 Hz. These events have been located at a depth of 20-50 km mainly in correspondence of the tip of the mantle wedge [Payero et al., 2008; Kostoglodov et al., 2010]. Data-set is composed of one year (2006) long continuous seismic recordings of five three-component broad-band stations belonging to the seismic network installed during MASE experiment (available on IRIS website). We apply the Kanasewich algorithm to the continuous seismic recordings. This algorithm performs the diagonalization of the covariance matrix constructed using the three ground motion components and provides three parameters describing the polarization properties: the azimuth and dip angles constrain the direction of oscillation in a Cartesian reference frame, whereas the rectilinearity indicates if the oscillation is circular, elliptical or linear. We find that the NVT events can be detected looking at the time pattern of the polarization parameters. In detail, during NVT the dispersion of all the parameters decreases, the dip angle focuses on high values (indicating shallow

  19. 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.

  20. 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

  1. 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

  2. Unravelling the deep fluid composition in the Taupo Volcanic Zone: insight into the magmatic-hydrothermal transition

    NASA Astrophysics Data System (ADS)

    Chambefort, I. S.; Lewis, B.; Boseley, C.; Begue, F.; Rae, A.

    2012-12-01

    The Ngatamariki Geothermal Field represents the only location in the Taupo Volcanic Zone where geothermal well drilling has intercepted intrusive rocks with a high temperature alteration halo. Thus it presents the perfect opportunity to study the magmatic-hydrothermal transition in the TVZ by characterising the nature of the deep magmatic fluids inferred to be linked to the geothermal heat source. In addition to the calc-alkaline Ngatamariki diorite (encountered in a 1985 drillhole; Wood, 1986), recent (2012) geothermal drilling encountered a quartz-phyric tonalite. After emplacement, these intrusions cooled, degassed, and produced a high temperature alteration halo, associated with intense quartz-illite/muscovite-pyrite alteration and pervasive quartz replacement of the overlying tuff-breccia. This alteration zone contains abundant high temperature quartz veins, similar to quartz veining stockwork characteristic of Porphyry Cu (±Au-Mo) systems. The recently encountered quartz-phyric tonalite contains common phenocrysts of quartz and pseudomorphs of plagioclase and minor ferromagnesian minerals (predominantly amphiboles) in a medium-grained, magnetite-bearing felsic groundmass. Quartz phenocrysts are generally rounded and embayed quartz eyes (≤1 cm diam.), or skeletal crystals. SEM-CL imaging was used to map the crystallisation history of the phenocrystic quartz in the tonalite and the quartz veins cross-cutting the diorite and overlying pyroclastic rocks. The quartz eyes show a complex growth history with zones of dissolution and recrystallisation. Skeletal quartz crystals also have complex zoning and are outlined by myrmekitic textures and/or dendritic overgrowths with the groundmass (granophyric textures). These features form in granites due to undercooling during shallow magmatic emplacement and are often associated with the exsolution of a volatile phase. Cathodoluminescence indicates that the edges of the quartz veins are lined by euhedral crystals

  3. Applicability of statistical eruption analysis to the geological record of Villarrica and Lanín volcanoes, Southern Volcanic Zone, Chile

    NASA Astrophysics Data System (ADS)

    Wehrmann, Heidi; Dzierma, Yvonne

    2011-03-01

    Standard stochastic failure-analysis techniques are applied to the geological eruption records of Villarrica and Lanín volcanoes in the Chilean Southern Volcanic Zone. These statistical methods are used to estimate the probabilities of eruptions large enough to leave a trace in the geological record. For Villarrica, the standard lifetime distributions predict a near 100% probability that such an eruption should have occurred between 489 AD and today. If the VEI = 3 eruptions observed in the historical record are large enough to be preserved in the geological record, the probability of such a future eruption of Villarrica is about 20% in the next 100 years. In the case of Lanín, the applicability of the exponential, Weibull and log-logistic distributions to the geological record is doubtful, since the volcano appears to have experienced alternating high- and low-activity regimes. Only the mixture-of-exponentials distribution can take into account the possible dormancy descending to final extinction, resulting in a probability of about 16% that Lanín will ever erupt again in the future. The contrasting behaviour of the eruption records of these two neighbouring volcanoes in terms of the number of eruptions and the length of the repose-time intervals serves to examine to what extent the method can be applied to geological eruption records. This study contributes to directing statistical eruption analysis towards time scales long enough to investigate large-magnitude eruptions, and it includes the possibility of dormancy/extinction.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS. Part 2: application to Taupo Volcanic Zone rhyolites

    NASA Astrophysics Data System (ADS)

    Bégué, Florence; Gualda, Guilherme A. R.; Ghiorso, Mark S.; Pamukcu, Ayla S.; Kennedy, Ben M.; Gravley, Darren M.; Deering, Chad D.; Chambefort, Isabelle

    2014-11-01

    Constraining the pressure of crystallisation of large silicic magma bodies gives important insight into the depth and vertical extent of magmatic plumbing systems; however, it is notably difficult to constrain pressure at the level of detail necessary to understand shallow magmatic systems. In this study, we use the recently developed rhyolite-MELTS geobarometer to constrain the crystallisation pressures of rhyolites from the Taupo Volcanic Zone (TVZ). As sanidine is absent from the studied deposits, we calculate the pressures at which quartz and feldspar are found to be in equilibrium with melt now preserved as glass (the quartz +1 feldspar constraint of Gualda and Ghiorso, Contrib Mineral Petrol 168:1033. doi:10.1007/s00410-014-1033-3. 2014). We use glass compositions (matrix glass and melt inclusions) from seven eruptive deposits dated between ~320 and 0.7 ka from four distinct calderas in the central TVZ, and we discuss advantages and limitations of the rhyolite-MELTS geobarometer in comparison with other geobarometers applied to the same eruptive deposits. Overall, there is good agreement with other pressure estimates from the literature (amphibole geobarometry and H2O-CO2 solubility models). One of the main advantages of this new geobarometer is that it can be applied to both matrix glass and melt inclusions—regardless of volatile saturation. The examples presented also emphasise the utility of this method to filter out spurious glass compositions. Pressure estimates obtained with the new rhyolite-MELTS geobarometer range between ~250 to ~50 MPa, with a large majority at ~100 MPa. These results confirm that the TVZ hosts some of the shallowest rhyolitic magma bodies on the planet, resulting from the extensional tectonic regime and thinning of the crust. Distinct populations with different equilibration pressures are also recognised, which is consistent with the idea that multiple batches of eruptible magma can be present in the crust at the same time and

  10. 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)

  11. 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

  12. 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

  13. Molecular Mechanism of Active Zone Organization at Vertebrate Neuromuscular Junctions

    PubMed Central

    Nishimune, Hiroshi

    2013-01-01

    Organization of presynaptic active zones is essential for development, plasticity, and pathology of the nervous system. Recent studies indicate a trans-synaptic molecular mechanism that organizes the active zones by connecting the pre- and the postsynaptic specialization. The presynaptic component of this trans-synaptic mechanism is comprised of cytosolic active zone proteins bound to the cytosolic domains of voltage-dependent calcium channels (P/Q-, N-, and L-type) on the presynaptic membrane. The postsynaptic component of this mechanism is the synapse organizer (laminin β2) that is expressed by the postsynaptic cell and accumulates specifically on top of the postsynaptic specialization. The pre- and the postsynaptic components interact directly between the extracellular domains of calcium channels and laminin β2 to anchor the presynaptic protein complex in front of the postsynaptic specialization. Hence, the presynaptic calcium channel functions as a scaffolding protein for active zone organization and as an ion-conducting channel for synaptic transmission. In contrast to the requirement of calcium influx for synaptic transmission, the formation of the active zone does not require the calcium influx through the calcium channels. Importantly, the active zones of adult synapses are not stable structures and require maintenance for their integrity. Furthermore, aging or diseases of the central and peripheral nervous system impair the active zones. This review will focus on the molecular mechanisms that organize the presynaptic active zones and summarize recent findings at the neuromuscular junctions and other synapses. PMID:22135013

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. The impact of relict organic materials on the denitrification capacity in the unsaturated-saturated zone continuum of three volcanic profiles.

    PubMed

    Clague, J C; Stenger, R; Clough, T J

    2013-01-01

    The denitrification capacity of wetlands, riparian zones, and aquifers in glacial outwash areas is well documented, but little or no information exists for volcanic profiles, particularly those containing relict organic matter contained in or on top of paleosols (old soils buried by volcanic deposits) below the groundwater table. Relict carbon contained in these layers could provide the necessary electrons to fuel heterotrophic denitrification. To the best of our knowledge, this is the first study investigating the denitrification capacity in both the unsaturated and saturated zone of volcanic profiles. Samples from three profile types with differing organic matter distribution were amended with N-enriched nitrate (NO-) and incubated in the laboratory under anaerobic conditions. Dinitrogen (N) dominated the N gas fluxes; averaged across all samples, it accounted for 96% of the total N (nitrous oxide [NO] and N) gas fluxes. Dinitrogen fluxes were generally highest in the A horizon samples (4.1-6.2 nmol N g h), but substantial fluxes were also observed in some paleosol layers (up to 0.72 nmol N g h). A significant correlation ( < 0.001) was found between the concentration of extractable dissolved organic carbon and the total N gas flux produced in samples from below the A horizon, suggesting that heterotrophic denitrification was the dominant NO attenuation process in this study. Extrapolation of lab-derived denitrification capacities to field conditions suggests that the denitrification capacity of profiles containing relict soil organic matter in the saturated zone exceeds the estimated N leaching from the root zone. PMID:23673749

  1. 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.

  2. 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

  3. 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.

  4. Volcanism in Kamchatka, Russia

    NASA Astrophysics Data System (ADS)

    Eichelberger, J. C.; Eichelberger, L. G.

    2008-12-01

    The diverse and robust volcanism of Kamchatka challenges our understanding of subduction zone volcanism on both local volcanic and regional tectonic scales (e.g., AGU Geophysics Monograph 172). One might expect the two North Pacific peninsula/ island arc pairs, Kamchatka Peninsula/ Kuriles and Alaska Peninsula/ Aleutians, to be twins, but there are some important differences as well as similarities. In both cases, the continental margin largely controls the position of the volcanic front on the peninsulas and the associated island arcs are pinned to the peninsula tips. The unusually acute Aleutian-Kamchatka subduction cusp may have formed by jamming and outboard (southeastward) jumping of Bering subduction at about 50 Ma to form the Aleutians, with capture of the Bering microplate by the North American plate. Perhaps the acuteness was augmented by convergence of the Emperor Seamount Chain with the junction. Another outboard (eastward) jump may explain the two lines of volcanoes in Kamchatka, which are partially separated by the rift-like Central Kamchatka Depression. This is thought to have occurred at 7 - 10 Ma when 3 seamounts were accreted as capes to the eastern edge of Kamchatka. But other workers, pointing to east-west chemical trends and persistence of volcanism in the inboard Sredinny Range, prefer to postulate two depths of volatile release from the same intact slab. On the Alaska Peninsula, Quaternary volcanic deposits are discontinuous and even famous Mount Katmai is a volumetric dwarf. The opposite is the case in Kamchatka, where pre-volcanic basement under the young eastern volcanic front is sparsely exposed and Holocene stratovolcanoes rise as high as 4,835 m. Calderas are so numerous they sometimes overlap. Some exhibit repeated andesitic stratovolcano - silicic caldera cycles over remarkably short time frames. Remoteness, international politics, and challenging weather have conspired to make Kamchatka's volcanoes less appreciated by non

  5. 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.

  6. 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

  7. 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

  8. The Oruanui and Taupo Magma Bodies (central Taupo Volcanic Zone, NZ): Evolution and Longevity as recorded in Pumice Textures

    NASA Astrophysics Data System (ADS)

    Wright, K. A.; Pamukcu, A. S.; Gualda, G. A. R.

    2014-12-01

    The central Taupo Volcanic Zone (TVZ: New Zealand) has produced numerous large-volume high-silica rhyolite eruptions in the past 1.6 Ma. In this study, we focus on two such eruptions, derived from the same area: the 26.5 ka Oruanui- the most recent supereruption in earth's history- and the 1.8 ka Taupo- the most recent large, rhyolitic eruption from the TVZ. In order to understand the evolution of these crystal-poor magma bodies and constrain their pre-eruptive residence times in the crust, we use x-ray tomography and energy dispersive spectroscopy (EDS) to qualitatively and quantitatively characterize pumice textures in both Oruanui and Taupo. We obtain crystal size distributions (CSDs) using x-ray tomography for three groups of phases: quartz+feldspar, magnetite+ilmenite, and zircon. Quartz+feldspar size distributions from both eruptions show a shallow-sloped log-linear section describing large crystals (>~200 µm), which we interpret as a pre-eruptive crystal population that grew over time under low supersaturation. Magnetite+ilmenite and zircon size distributions are also log-linear, but have fewer crystals and a smaller maximum crystal size (<200 μm). Taupo quartz+feldspar size distributions are kinked at ~200 μm and show a steep-sloped section describing small crystals (<200 μm), which we interpret to represent a crystal population that nucleated and grew during eruptive decompression. In contrast, Oruanui distributions are not kinked. This difference is supported by EDS compositional maps that show a small (20-50 μm) crystal population in Taupo samples, but not in Oruanui samples. This is consistent with rhyolite-MELTS geobarometry results, which indicate the Taupo magma resided at higher pressures (i.e. greater depth) than did the Oruanui magma. As such, Taupo magma had a longer path to eruption and thus more time for crystal nucleation and growth during decompression. Timescales calculated from CSD slopes of the pre-eruptive crystal populations of

  9. 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.

  10. Chemical composition of soils in the areas of volcanic ashfalls around active volcanoes in Kamchatka

    NASA Astrophysics Data System (ADS)

    Zakharikhina, L. V.; Litvinenko, Yu. S.

    2016-03-01

    The geochemical features of volcanic soils (Andosols) in the northern soil province of Kamchatka are identified. The background regional concentrations ( Cb r ) of most of chemical elements in the studied soils are lower than their average concentrations in soils of the world and in the European volcanic soils. Only Na, Ca, and Mg are present in elevated concentrations in all the studied soils in the north of Kamchatka. Regional background concentrations of elements are exceeded by 1.6 times in the area of active ashfalls of the Tolbachik volcano and by 1.3 times in the area of active ashfalls of the Shiveluch volcano. The concentrations of mobile forms of elements in these areas exceed their regional background concentrations by 2.1 and 2.6 times, respectively.

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. 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

  16. The systematics of chlorine, fluorine, and water in Izu arc front volcanic rocks: Implications for volatile recycling in subduction zones

    NASA Astrophysics Data System (ADS)

    Straub, Susanne M.; Layne, Graham D.

    2003-11-01

    We studied the systematics of Cl, F and H 2O in Izu arc front volcanic rocks using basaltic through rhyolitic glass shards and melt inclusions (Izu glasses) from Oligocene to Quaternary distal fallout tephra. These glasses are low-K basalts to rhyolites that are equivalent to the Quaternary lavas of the Izu arc front (Izu VF). Most of the Izu glasses have Cl ˜400-4000 ppm and F ˜70-400 ppm (normal-group glasses). Rare andesitic melt inclusions (halogen-rich andesites; HRA) have very high abundances of Cl (˜6600-8600 ppm) and F (˜780-910 ppm), but their contents of incompatible large ion lithophile elements (LILE) are similar to the normal-group glasses. The preeruptive H 2O of basalt to andesite melt inclusions in plagioclase is estimated to range from ˜2 to ˜10 wt% H 2O. The Izu magmas should be undersaturated in H 2O and the halogens at their preferred levels of crystallization in the middle to lower crust (˜3 to ˜11 kbar, ˜820° to ˜1200°C). A substantial portion of the original H 2O is lost due to degassing during the final ascent to surface. By contrast, halogen loss is minor, except for loss of Cl from siliceous dacitic and rhyolitic compositions. The behavior of Cl, F and H 2O in undegassed melts resembles the fluid mobile LILE (e.g.; K, Rb, Cs, Ba, U, Pb, Li). Most of the Cl (>99%), H 2O (>95%) and F (>53%) in the Izu VF melts appear to originate from the subducting slab. At arc front depths, the slab fluid contains Cl = 0.94 ± 0.25 wt%, F = 990 ± 270 ppm and H 2O = 25 ± 7 wt%. If the subducting sediment and the altered basaltic crust were the only slab sources, then the subducted Cl appears to be almost entirely recycled at the Izu arc (˜77-129%). Conversely, H 2O (˜13-22% recycled at arc) and F (˜4-6% recycled) must be either lost during shallow subduction or retained in the slab to greater depths. If a seawater-impregnated serpentinite layer below the basaltic crust were an additional source of Cl and H 2O, the calculated percentage of

  17. 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

  18. Neotectonic deformation in the Eurasia-Arabia collision zone, the East Anatolian Plateau, E Turkey: evidence from palaeomagnetic study of Neogene-Quaternary volcanic rocks

    NASA Astrophysics Data System (ADS)

    Hisarlı, Z. Mümtaz; Çinku, Mualla Cengiz; Ustaömer, Timur; Keskin, Mehmet; Orbay, Naci

    2016-01-01

    Palaeomagnetic studies of the Neogene-Quaternary rocks of Anatolia have been mostly interpreted in the light of its westward escape as a result of the collision between the Arabian and Eurasian plates along the Bitlis-Zağros suture during the Neotectonic period. However, within the collision zone, in East Anatolia, palaeomagnetic data are not available. In order to help understand the deformational history of Eastern Anatolia during the Neotectonic period, we have carried out a palaeomagnetic study of Miocene-Quaternary volcanic rocks from 100 sites, selected on the basis of their geographical position and known age. The results indicate that the study area can be divided into five principal tectonic blocks, based on earthquake activity and the rotation that the blocks underwent. These blocks are the Van Block (VB), the Kars Block (KB), the Anatolian Block (AB), the Pontide Block (PB), and the Arabian Block (ARB). The largest counterclockwise (CCW) tectonic rotations were encountered in the AB and PB, whereas the largest clockwise (CW) rotations were recorded in the VB. The sinistral East Anatolian Fault and the Erzurum Fault Zone form the present boundary of these two contrasting, CW and CCW-rotating domains. Both the AB and the PB exhibit similar amount of rotation until the Quaternary, during which the AB rotated 13° CCW while the PB remained stable. The Quaternary rotation of the AB is attributed to the activity of the North Anatolian Fault. The KB shows the smallest amount of CW rotation during all of the time intervals studied. All of the blocks studied indicate an acceleration in the amount of rotations during the Quaternary, which was preceded by a period of relative tectonic stability during the Late Pliocene. Following the collision of the Arabian Plate with the Eurasian Plate during the Mid-Miocene, the crust was initially thickened by thrusting and folding. This was followed by lateral extrusion and differential rotation of the crustal blocks during

  19. Polymagmatic activity and complex magma evolution at the monogenetic Mt Gambier Volcanic Complex in the Newer Volcanics Province, SE Australia

    NASA Astrophysics Data System (ADS)

    van Otterloo, Jozua; Raveggi, Massimo; Cas, Ray; Maas, Roland

    2015-04-01

    Monogenetic volcanism can produce eruptive suites showing considerable complexity in compositional features and pre-eruptive magma evolution. The ~5 ka Mt Gambier Volcanic Complex (MGVC), a monogenetic volcanic centre in the Newer Volcanics Province (NVP), SE Australia, is a good example. It displays a complex stratigraphy of interbedded deposits related to different eruption styles from a multi-vent system. Formation of the MGVC proceeded through simultaneous eruption of two alkali basaltic magma batches: a more alkaline and light rare earth element enriched basanite batch (Mg# 58-62) in the west and a trachybasalt batch (Mg# 58-64) enriched in SiO2 and CaO in the east. Trace element modelling suggests an origin of both magma batches from a single parental melt formed by 4-5% partial melting of a metasomatised lherzolite source in the asthenospheric mantle (2.2 GPa; ~80 km). At the base of the lithosphere, part of this parental melt interacted with a deep-seated pyroxenite contaminant to form the trachybasaltic suite. Further modification of either magma batch at crustal levels appears to have been negligible. Isotope and trace element signatures are consistent with the inferred asthenospheric magma source; Pb isotopes in particular suggest a source with mixed Indian mid-ocean ridge basalt (MORB)-Enriched Mantle 2 (EM2) affinities, the latter perhaps related to metasomatic overprinting. It is argued that Cainozoic NVP volcanism in SE Australia is not necessarily related to a mantle plume but can be explained by other models involving asthenospheric upwelling. Fast magma ascent rates in the lithosphere evidenced by the presence of mantle xenoliths may reflect reactivation of lithospheric structures that provide magma pathways to the surface.

  20. 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.

  1. 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

  2. Can vesicle size distributions assess eruption intensity during volcanic activity?

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    We studied three-dimensional (3-D) vesicle size distributions by X-ray microtomography in scoria collected during the relatively quiescent Phase II of the April-May 2010 eruption at Eyjafjallajökull volcano, Iceland. Our goal was to compare cumulative 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 first 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 a second hypothesis, which was that the magma-water interactions in the Eyjafjallajökull eruption might have a significant effect on the VSDs. We performed 1 bar 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 second hypothesis is not supported by the experimental evidence. The Phase II Eyjafjallajökull VSDs are described by power-law exponents of ~0.8, typical of normal Strombolian eruptions, and support the first hypothesis. 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 mingled/mixed magma from depth. Such behavior implies that continued activity during Phase II of the Eyjafjallajökull eruption could be expected and would have been predicted, had our VSDs been measured in

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. Submarine volcanic activity, ocean-acoustic waves and internal ocean tides

    NASA Astrophysics Data System (ADS)

    Sugioka, Hiroko; Fukao, Yoshio; Hibiya, Toshiyuki

    2005-12-01

    Submarine volcanic event often generates acoustic waves (T-waves) traveling over long distances through the low velocity channel (SOFAR) of the ocean. By a method of coherent stacking of T-waves from a submarine volcanic activity in northern Mariana, we found a significant semidiurnal variation of T-wave travel times. The amplitude of variation is an order of larger than those reported in the previous ocean sound transmission experiments. Ray-theoretical consideration for the numerically simulated ocean tides indicates that such large T-phase travel time variation is a consequence of large up-and-down movement of seawater around the axis of the SOFAR channel due to the M2 internal tide effectively converted from external tidal forcing. T-phases, a ubiquitous feature of the ocean acoustic noise field, can be used to infer internal tidal motion and the associated ocean mixing.

  8. 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.

  9. Characterization of a deep geothermal reservoir in an active volcanic area

    NASA Astrophysics Data System (ADS)

    Brehme, M.; Kamah, Y.; Koestono, H.; Zimmermann, G.; Regenspurg, S.; Erbaş, K.; Wiegand, B.; Sauter, M.

    2012-04-01

    In this study an integrated methodological approach to characterize a complex deep geothermal reservoir located in an active volcanic setting in Indonesia is presented. The methods applied include hydraulic and hydrogeochemical (incl. isotope tracer) techniques to model groundwater flow, heat transport, and hydro-geochemical properties of the reservoir. 3D geological and hydraulic models of the area were constructed based on deep drill profiles, collected fluid and rock samples, and mapping of geological structures. First results show that the geothermal reservoir is composed of major geological units such as altered andesite, basalt, breccia, and tuff layers. Several tectonic faults crosscut the geological units into individual blocks and reservoirs and influence hydraulic pathways in multiple ways. Hot water and steam are produced by nine wells. Fluids are reinjected into the reservoir through one injection well. Currently, a geothermal plant produces 60 MWe from steam withdrawn. Temperatures of the geothermal system range between 250 and 350 °C (Koestono et al. 2010). Based on the chemical composition of fluids from the production wells (concentration of major ions and physicochemical parameters) at least two different hydro-geochemical reservoirs could be identified. The deep reservoir with a moderate pH of 5 is marked by total silica concentrations up to 350 mg/L and high chloride concentrations of 430 mg/L. For the shallow reservoir, highly acidic conditions with pH values of 2.9 are analysed for water, while steam shows pH values around 4. Furthermore, high chloride (1550 mg/L), total silica (460 mg/L), and sulphate concentrations (1600 mg/L) are characteristic for the shallow reservoir. According to Giggenbach (1988) and Nicholson (1993) the water can be classified into sulphate-rich waters and neutral chloride-waters. Sulphate-rich water is expected to occur near to the heat source while chloride-rich waters discharge near the outflow zone. Surface

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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.

  17. Final closure of the Paleo-Asian Ocean along the Solonker Suture Zone: Constraints from geochronological and geochemical data of Permian volcanic and sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Eizenhöfer, Paul R.; Zhao, Guochun; Zhang, Jian; Sun, Min

    2014-04-01

    There is a broad consensus that the Solonker Suture Zone marks the final closure of the Paleo-Asian Ocean, which led to the formation of the eastern segment of the Central Asian Orogenic Belt. However, when and how the final closure occurred still remains controversial. To address this issue, provenance analysis of Permian sedimentary rocks of arc basins along the Xar Moron River was carried out. Geochemical analysis revealed a close relationship between the sedimentary and volcanic rock suite in the study region suggesting short transport distances and a complex convergent arc setting. Detrital zircon U-Pb analysis identified two major age provenances: (1) the Precambrian basement of the North China Craton (~2497 Ma and ~1844 Ma) and (2) the Paleozoic Southern Accretionary Orogen along the northern margin of North China (~436 Ma and ~269 Ma). The present locations of identified age provenances indicate southward subduction beneath the northern margin of North China. A comparison of the youngest age population in the sedimentary rocks with U-Pb ages obtained for subduction-related volcanic rocks implies that the Solonker Suture Zone formed from the Late Permian to Early Triassic. The results of our study advocate a complex Permian arc system which was probably similar to present-day Southeast Asia.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. Geodynamic interpretations of plate subduction in the northernmost part of the Central Volcanic Zone from the geochemical evolution and quantification of the crustal contamination of the Nevado Solimana volcano, southern Peru

    NASA Astrophysics Data System (ADS)

    Vatin-Pérignon, Nicole; Oliver, Richard A.; Goemans, Pierre; Keller, Francine; Briqueu, Louis; Guido Salas, A.

    1992-04-01

    The northernmost volcanoes of the Central Volcanic Zone (CVZ, southern Peru) form three isolated composite centres along the western side of the active arc segment. This particular situation is comparable to the Chilean volcanic region at the southernmost end of the CVZ; in both cases, volcanoes lie close to the discontinuity where the Benioff zone becomes less steeply inclined and where crustal thickness decreases. The Solimana volcano (15°25'S), the oldest of the northerly eruptive centres, is built upon a Late Precambrian/Palaeozoic basement intruded by an Upper Cretaceous granite and unconformably overlain by Cenozoic volcanics. After a mid-Miocene andesitic activity along N10° regional faults, the Solimana volcanic history ranged from 4 Ma to Recent and built a composite andesite/dacite centre which consists of two units, preand post-caldera collapses and a youngest intra-caldera basaltic andesite phreatomagmatic activity. Fumaroles with thermal hot springs and precipitates indicate continuing activity of this volcano. North of 16°S, other adjacent volcanoes show the same evolution. Mineral chemistry and geochemical variations of the Solimana series are similar to those obtained from most high-K CVZ lavas and are largely consistent with fractionation processes. A restricted range of compositions of phenocryst assemblages, together with trace element data showing prominent LIL element enrichments relative to HFS element depletions, are typical of subduction-related continental arc magmas. However, this localized volcanism in the vicinity of the Nazca ridge-continent collision shows specific signatures: a weakly positive correlation between 87Sr/ 86Sr and Rb/Sr ratios, a high Ba and Sr content of basaltic andesites and both low ɛ Nd (- 2 to - 4) and high ɛSr (+16 to +21) values show differences north of 16°S from those to the south and suggest that distinct processes have controlled this environment. High Ba values for the most primitive lavas may be

  3. Monitoring volcanic activities using correlation patterns between infrasound and ground motion

    NASA Astrophysics Data System (ADS)

    Ichihara, M.; Takeo, M.; Yokoo, A.

    2012-04-01

    This paper presents a simple method to distinguish infrasonic signals from wind noise using a cross-correlation function of signals from a microphone and a co-located seismometer. The method makes use of a particular feature of the cross-correlation function of vertical ground motion generated by infrasound, and the infrasound itself. Contribution of wind noise to the correlation function is effectively suppressed by separating the microphone and the seismometer by several meters because the correlation length of wind noise is much shorter than wavelengths of infrasound. The method is tested with data from volcanoes, and demonstrates that the method effectively detects not only the main eruptions, but also minor activity generating weak infrasound hardly visible in the wave traces. In addition, the correlation function gives more information about volcanic activity than infrasound alone. The correlation pattern changes when the spectral feature of the infrasound and/or the seismic wave changes and the relative strength of infrasound and seismic wave changes, both of which are expected to be accompanied by change in eruptive activity. Therefore, a graphical presentation of temporal variation in the cross-correlation function enables to see qualitative changes of eruptive activities at a glance. This method is particularly useful when available sensors are limited, and will extend the utility of a single microphone and seismometer in monitoring and understanding volcanic activity. The method is used to analyze sequences of two recent eruptions of Asama and Shinmoe-dake volcanoes, Japan.

  4. 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

  5. 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

  6. From Source to Surface: Towards a Better Understanding of Heat and Mass Transfer in the Geothermal Systems at the Taupo Volcanic Zone, New Zealand (Invited)

    NASA Astrophysics Data System (ADS)

    Deering, C. D.; Gravley, D. M.; Blackstock, J. M.; Begue, F.

    2013-12-01

    The central portion of the Taupo Volcanic Zone (TVZ) is the most active silicic volcanic region on Earth and boasts an anomalous heat flow of ~4500 MW emanating from more than 20 active geothermal systems. Several studies have argued that hydrothermal fluids are derived from two spatially discrete sources: an arc-type fluid in the east and a back-arc-type fluid in the west. This variability has been interpreted to be related to specific magma types at depth: 1) low-gas (i.e. CO2), high Cl, low B and Li/Cs ratio systems related to rhyolitic magmas, and 2) high-gas, low Cl, high B and Li/Cs ratio systems related to andesitic magmas. Here we report the results of two studies that suggest alternative origin(s) for the chemical variability measured at the surface, one from the source and one from fluid-rock interaction. First, we have evaluated a large, new geochemical database of fluid chemistry and, similar to previous studies we find that two distinct B/Cl ratios are present in TVZ fluids. However, contrary to earlier work, our results do not exhibit an east-west spatial distribution of fluid chemistry. Rather, higher B/Cl ratios occur on both the eastern and western margins. We also observe that fluids in local fields can switch between the different B/Cl ratio types through time. This discrepancy possibly indicates that B is not behaving conservatively and B/Cl ratios of hydrothermal fluids are not directly linked to the current tectonomagmatic setting. Unlike the B/Cl ratios, the Li/Cs ratios of the same fluids are similar, irrespective of their geographical location, implying a similar parent-fluid across the TVZ. We suggest that ascending fluids originate from a geochemically similar parent-fluid at depth as indicated by Li/Cs ratios and through varying contributions of B from water-rock interaction, two B/Cl groups arise. Previous water-rock interaction studies of geologic formations in the TVZ and recent geophysical imaging of hydrothermal plumes in the TVZ

  7. Tertiary volcanic activity at Sonora Pass, CA: arc and non-arc magmatism in the central Sierra Nevada

    NASA Astrophysics Data System (ADS)

    Roelofs, A.; Glazner, A. F.; Farmer, G. L.

    2004-12-01

    The volume and composition of Tertiary volcanic rocks in the Sierra Nevada of California changes dramatically near Sonora Pass (latitude 38° N). North of Sonora Pass is a large volume of volcanic rocks petrographically and chemically linked to subduction in the Cascade arc. South of Sonora Pass these calc-alkaline rocks are lacking and the only preserved volcanic rocks are small-volume mafic to intermediate potassic lavas that may have been generated by Pliocene lithospheric delamination (e.g. Farmer et al 2002). We have undertaken geologic mapping and geochemical and isotopic analysis of rocks near Sonora Pass at the boundary between these two magmatic provinces. At Sonora Pass, the 16-10 m.y.-old Relief Peak Formation and its hypabyssal equivalents are dominated by hornblende-phyric andesite lava flows and mudflow breccias (a stratovolcano assemblage) with marked high field-strength element (HFSE) depletions relative to large-ion lithophile elements (LILE), high Sri ( ˜ 0.7056), and low ɛ Nd (-1.4 > ɛ Nd > -2.5). The overlying Stanislaus Group ( ˜10-8 my old) has elevated HFSE and LILE relative to the Relief Peak Formation, anhydrous mineralogy, and similar isotope ratios (Sri ˜ 0.7056, -1.9 > ɛ Nd > -3.4). The overlying Disaster Peak Formation is petrographically similar to the Relief Peak Formation. Lavas of the Relief Peak Formation may have been derived from the hydrated, LILE-rich and HFSE-poor mantle wedge above the subducting Juan de Fuca plate as part of the ancestral Cascade arc. The eruption of the dry, HFSE- and LILE-richer Stanislaus Group from vents near those of the Relief Peak Formation and to the east during an apparent pause in Relief Peak-type activity may represent a temporary shift to a dry, more fertile, isotopically enriched source in the mantle. The shift coincides with the arrival of the subducted Mendocino Fracture Zone (MFZ) beneath Sonora Pass, and the change in plate stress as the MFZ traversed the region may have influenced

  8. Sustaining volcanism in Central Kamchatka

    NASA Astrophysics Data System (ADS)

    Nikulin, Alex

    Flux-induced melting in the mantle wedge acts as the driving mechanism of arc volcanism in subduction zone environments. The primary control on the geographical position of arc volcanic centers is the depth of the subducting plate beneath the overriding plate. Globally, the average depth to the subducting plate beneath volcanic arcs is estimated at ˜100km. Volcanoes of the Central Kamchatka Depression in Eastern Russia comprise the most active volcanic arc system in the world with the depth of the subducting Pacific plate beneath the arc estimated at 180-200km, greatly in excess of the global average. In my research I attempt to describe the special tectonic circumstances that explain the deviation of the subduction depth constraint on arc volcanism in Central Kamchatka. In my study I rely on geophysical and geochemical data and petrological modeling to propose a new geodynamic model to explain voluminous volcanic activity in Central Kamchatka. In the initial stage of the study I conducted a geophysical investigation using receiver function methodology to map and describe the contact of the subducting Juan de Fuca Plate in the well-instrumented Cascadia subduction zone. I calculated and compiled a database of receiver function profiles from stations along the extent of the Cascadia forearc and mapped a low velocity anisotropic zone proposed to be serpentinized material along the forearc axis. In the second stage of my study I applied a similar methodology to describe the sub-crustal structure of Central Kamchatka. Results of this effort suggested presence of a low-velocity zone in the upper mantle separate from the subducting Pacific plate. I proceeded to investigate the tectonic origin of this feature in the final stage of my dissertation work with the use of receiver function migration, geochemical analysis and petrological modeling. I was able to further constrain the position of the low velocity anomaly and derive geochemical and petrological evidence linking

  9. 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.

  10. Monitoring volcanic activity using correlation patterns between infrasound and ground motion

    NASA Astrophysics Data System (ADS)

    Ichihara, M.; Takeo, M.; Yokoo, A.; Oikawa, J.; Ohminato, T.

    2012-02-01

    This paper presents a simple method to distinguish infrasonic signals from wind noise using a cross-correlation function of signals from a microphone and a collocated seismometer. The method makes use of a particular feature of the cross-correlation function of vertical ground motion generated by infrasound, and the infrasound itself. Contribution of wind noise to the correlation function is effectively suppressed by separating the microphone and the seismometer by several meters because the correlation length of wind noise is much shorter than wavelengths of infrasound. The method is applied to data from two recent eruptions of Asama and Shinmoe-dake volcanoes, Japan, and demonstrates that the method effectively detects not only the main eruptions, but also minor activity generating weak infrasound hardly visible in the wave traces. In addition, the correlation function gives more information about volcanic activity than infrasound alone, because it reflects both features of incident infrasonic and seismic waves. Therefore, a graphical presentation of temporal variation in the cross-correlation function enables one to see qualitative changes of eruptive activity at a glance. This method is particularly useful when available sensors are limited, and will extend the utility of a single microphone and seismometer in monitoring volcanic activity.

  11. 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.

  12. Active Volcanism Late in Martian History - Evidence from Crater Counts in the Tharsis Region

    NASA Astrophysics Data System (ADS)

    Grier, J. A.; Berman, D. C.; Hartmann, W. K.; Bottke, W. F.; Kesthelyi, L. P.

    2001-11-01

    The current hypothesis of young Martian volcanism is based on several lines of evidence including analyses of Martian meteorites, photogeologic examination of the planet's surface and detailed crater count studies of high resolution images from MGS/MOC. In addition, some possible signs of recent liquid water on Mars may be evidence of active volcanism as a heat source. Early crater count studies were questioned on the basis of two major uncertainties: very small sampling of counts on young flows, and poor absolute surface age estimates on Mars. Our attack on these uncertainties includes both improving the detailed crater count statistics on the large Martian shield volcanoes and their surrounding lava plains, and refining the absolute ages of counted units using new estimates of the crater production rate on Mars. We have obtained counts on Olympus Mons, Pavonis Mons and Arsia Mons. We have targeted areas both on the slopes and inter-volcanic plains, and have begun examining the caldera regions. Our initial examination of the counts of caldera floors indicates terrains with statistically significant age differences, suggesting for some volcanoes sustained episodes of caldera collapse or resurfacing. Our slope and inter-volcanic plains data when plotted with the latest calibrated isochrons yield some very young ages, 10 My or younger for some small flows. The estimated uncertainty in the age data is about a factor of two. Our preliminary conclusions therefore appear to support the hypothesis of very recent volcanism on Mars. However, it is clear that a critical issue regarding crater counting on high resolution MOC images is the necessity of avoiding the ubiquitous dust on the Martian surface. TES data have shown that dust mantles exist over much of the Tharsis region, and it is critical that the ages of the terrains counted do not appear artificially young due to dust cover of some of the craters. We have begun a systematic review of counted MOC images and

  13. 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

  14. NAUDUR explorers discover recent volcanic activity along the East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Auzende, Jean-Marie; Sinton, John

    Surveying an ultra-fast spreading ridge along the East Pacific Rise (EPR), explorers aboard the submersible Nautile examined features such as lava pillows and tubes, sulfide chimneys, black smokers, hot shimmering waters, and colonies of animals living in hydrothermal vents to learn more about the processes of accretion and tectonics on the ocean floor. Taken together, the observations of the EPR between 17°S and 19°S from the 1993 NAUDUR cruise (a French acronym for Nautile on Ultra-fast Ridge) indicate recent volcanic eruptions occurring as frequently as every few years.The NAUDUR cruise was designed to study the interaction between magmatic, tectonic, and hydrothermal processes at an ultra-fast spreading axis of the EPR. Researchers performing twenty three dives in five regions (Figure 1) along the axis of the Garrett fracture zone collected more than 150 rock samples and made 52 gravity measurements [Auzende et al., 1994]. The Garrett fracture zone (13°S) and the Easter Microplate limit a large segment of the East Pacific Rise where the accretion rate is near the upper limit for present-day spreading values (141 to 162mm/yr) [Perram et al., 1993]. The five dive regions with distinct morphological characteristics represent different stages in the accretion process.

  15. 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

  16. Origin of the ca. 90 Ma magnesia-rich volcanic rocks in SE Nyima, central Tibet: Products of lithospheric delamination beneath the Lhasa-Qiangtang collision zone

    NASA Astrophysics Data System (ADS)

    Wang, Qing; Zhu, Di-Cheng; Zhao, Zhi-Dan; Liu, Sheng-Ao; Chung, Sun-Lin; Li, Shi-Min; Liu, Dong; Dai, Jin-Gen; Wang, Li-Quan; Mo, Xuan-Xue

    2014-06-01

    Bulk-rock major and trace element, Sr-Nd-Hf isotope, zircon U-Pb age, and zircon Hf isotopic data of the Late Cretaceous Zhuogapu volcanic rocks in the northern Lhasa subterrane provide a new insight into tectonic processes following the collision of the terrane with the Qiangtang zone. SHRIMP zircon U-Pb dating reveals that the Zhuogapu volcanic rocks crystallized at ca. 91 Ma, postdating the development of a regional angular unconformity between the Upper Cretaceous and the underlying strata in the Lhasa-Qiangtang collision zone. Compared to the Andean arc-type andesites and dacites, the Zhuogapu volcanic rocks are characterized by higher MgO of 2.78-5.86 wt.% and Mg# of 54-64 for andesites and MgO of 2.30-2.61 wt.% and Mg# of 55-58 for dacites. Eight andesite samples have whole-rock (87Sr/86Sr)i of 0.7054-0.7065, εNd(t) of - 3.2 to - 1.7, and εHf(t) of + 3.8-+ 6.4, similar to those of the three dacite samples with (87Sr/86Sr)i = 0.7056-0.7060, εNd(t) of - 2.7 to - 2.2, and εHf(t) of + 5.6-+ 7.0. Thirteen analyses from a dacite sample give positive zircon εHf(t) of + 5.6 to + 8.7. These signatures indicate that the Zhuogapu Mg-rich andesites were most likely derived from partial melting of a delaminated mafic lower crust (including the lowermost crust straddling the northern and central Lhasa subterranes) that led to the generation of the Zhuogapu primary melts with adakitic signatures and small negative εNd(t). Such melts subsequently experienced interaction of melt-asthenospheric mantle peridotite followed by the modification of highly fractionated magmas in shallow crustal magma chamber. Hornblende-controlled fractionation results in the change of geochemical composition from Mg-rich andesitic to Mg-rich dacitic magmas. Field observations, together with geochronological and geochemical data, indicate that the Zhuogapu Mg-rich volcanic rocks and coeval magmatism in the northern Lhasa subterrane may be the result of thickened lithospheric delamination

  17. 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

  18. Correlation of volcanic activity with sulfur oxyanion speciation in a crater lake

    SciTech Connect

    Takano, B.

    1987-03-27

    The Yugama crater lake at Kusatsu-Shirane volcano, Japan, contains nearly 2200 tons (2800 parts per million) of polythionate ions (S/sub n/O/sub 6//sup 2 -/, where n = 4 to 9). Analytical data on lake water sampled before and during eruptions in 1982 showed that the concentrations of polythionates decreased and sulfate increased in response to the preeruption activities of the subaqueous fumaroles. These changes were observed 2 months before the first phreatic explosion on 26 October 1982. The monitoring of polythionates and sulfate in crater lake water is a promising means of anticipating potential volcanic eruption hazards.

  19. Silicate volcanism on Io

    NASA Technical Reports Server (NTRS)

    Carr, M. H.

    1986-01-01

    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.

  20. Collaborative studies target volcanic hazards in Central America

    NASA Astrophysics Data System (ADS)

    Bluth, Gregg J. S.; Rose, William I.

    Central America is the second-most consistently active volcanic zone on Earth, after Indonesia. Centuries of volcanic activity have produced a spectacular landscape of collapsed calderas, debris flows, and thick blankets of pyroclastic materials. Volcanic activity dominates the history, culture, and daily life of Central American countries.January 2002 marked the third consecutive year in which a diverse group of volcanologists and geophysicists conducted focused field studies in Central America. This type of multi-institutional collaboration reflects the growing involvement of a number of U.S. and non-U.S. universities, and of other organizations, in Guatemala and El Salvador (Table 1).

  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. The Effect of Recent Volcanic Activity on the Seismic Structure of Madagascar

    NASA Astrophysics Data System (ADS)

    Wysession, M. E.; Aleqabi, G. I.; Pratt, M. J.; Shore, P.; Wiens, D. A.; Nyblade, A.; Rambolamanana, G.; Andriampenomanana Ny Ony, F. S. T.; Tsiriandrimanana, R.

    2014-12-01

    The seismic structure of Madagascar is determined using ambient-noise and two-plane-wave earthquake surface waves analyses. A deep low-velocity anomaly is seen in regions of recent volcanic activity in the central and northern regions of the island. The primary data used are from the 2011-2013 MACOMO (Madagascar, the Comoros, and Mozambique) broadband seismic array from the PASSCAL program of IRIS (Incorporated Research Institutions for Seismology), funded by the NSF. Additional data came from the RHUM-RUM project (led by G. Barruol and K. Sigloch), the Madagascar Seismic Profile (led by F. Tilmann), and the GSN. For the ambient-noise study, Rayleigh wave green's functions for all interstation paths are extracted from the broadband seismic data recorded from August 2011 until October 2013. Rayleigh wave group and phase velocity dispersion curves are extracted in the 8 - 50 s period range, identifying shallow crustal structure. For deeper structure, the two-plane-wave method is used on teleseismic earthquake data to obtain surface wave phase velocities in the 20 - 182 s period range. In the inversion, a finite-frequency kernel is used for each period, and a 1-D shear velocity structure is determined at each location. A three-dimensional S-wave velocity model of the crust and upper mantle is obtained from assembling the 1-D models. Preliminary results show a good correlation between the Rayleigh wave velocities and the geology of Madagascar, which includes areas of ancient Archaean craton. The slowest seismic velocities are associated with known volcanic regions in both the central and northern regions, which have experienced volcanic activity within the past million years.

  3. Monitoring Io's Volcanic Activity in the Visible and Infrared from JUICE - It's All About (Eruption) Style

    NASA Astrophysics Data System (ADS)

    Davies, A. G.; Matson, D.; McEwen, A. S.; Keszthelyi, L. P.

    2012-12-01

    The European Space Agency's Jupiter Icy Moons Explorer (JUICE) will provide many opportunities for long-range monitoring of Io's extraordinary silicate, high-temperature volcanic activity [1, 2]. A considerable amount of valuable work can be performed even with relatively low-spatial-resolution observations [2]. Techniques developed from the examination and analysis of Galileo Near Infrared Mapping Spectrometer (NIMS) data, as well as observations of terrestrial silicate volcanic activity, allows the identification of likely eruption style [2] at many locations where the entire eruption is sub-pixel. Good temporal coverage, especially for episodic eruptions (including high-energy "outburst" eruptions), is important for modelling purposes. With opportunities to observe Io on a regular basis (hours-days) during cruise/orbital reduction phases, a visible-to-near-infrared mapping spectrometer (covering ~0.4-5.5 μm) is the best instrument to chart the magnitude and variability of Io's volcanic activity, allowing comparison with an existing and constantly expanding set of Io observations [e.g. 1, 3]. The eruption temperature of Io's dominant silicate lava, a constraint on interior composition and conditions, is a major unanswered question in the wake of the Galileo mission [1]. A careful approach to instrument design is needed to ensure that observations by both imager and IR spectrometer on JUICE are capable of determining lava eruption temperature [e.g., 4] in low spatial resolution data. With an ideal thermal target (e.g., an outburst eruption, or the proposed lava lake at Pele) the imager should obtain multi-spectral data in a rapid sequence to allow stability of the thermal source to be quantified. Observations by imager and spectrometer have to be contemporaneous and unsaturated. References: [1] Davies, A. (2007) "Volcanism on Io", Cam. Univ. Press. [2] Davies, A. et al. (2010) JVGR, 194, 75-99. [3] Veeder, G. et al. (2012) Icarus, 219, 701-722. [4] Davies, A. et

  4. 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.

  5. 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.

  6. Volcanic activity and its link to glaciation cycles: Single-grain age and geochemistry of Early to Middle Miocene volcanic glass from ANDRILL AND-2A core, Antarctica

    NASA Astrophysics Data System (ADS)

    Nyland, R. E.; Panter, K. S.; Rocchi, S.; Di Vincenzo, G.; Del Carlo, P.; Tiepolo, M.; Field, B.; Gorsevski, P.

    2013-01-01

    In the frame of the ANtarctic DRILLing Program, volcanic glass fragments were collected from the AND-2A core between ~ 354 and 765 m below sea floor (mbsf) as accumulations (5-70 vol.%) within sediments. Here, we present the physical characteristics, age and geochemistry of the glass, which enable us to reconstruct Early to Middle Miocene volcanic activity in southern McMurdo Sound and, for the first time, document the response of volcanism to climate change in Antarctica. Glass-rich sediments include muddy-to-fine sandstone and stratified diamictite. Glass varies in color, size, vesicularity, crystal content, angularity, and degree of alteration. The mostly fresh glass exhibits delicate cuspate forms indicating deposition as primary ash fall. 40Ar-39Ar age determinations on individual glass grains are in good agreement with the depositional age model of the sediments (ca. 15.6 to 18.6 Ma), supporting for most of them a primary origin, however, some samples do contain older fragments that indicate glass recycling during times of enhanced glacial erosion. Most glasses are mafic (MgO = 3 to 9 wt.%) and vary from hypersthene to nepheline normative with a restricted range in SiO2 (45.2 ± 0.8 wt.%, 1σ) and trace element concentrations typical of the rift-related alkaline rocks in the Erebus Volcanic Province. The glass extends known composition of early phase Mount Morning activity (ca. 11-19 Ma), the only known Early to Middle Miocene source, to a more mafic end, revealing a previously unknown explosive, strongly alkaline, basaltic phase and the most primitive forms of both strongly alkaline (basanite to phonolite) and moderately alkaline (alkali basalt to trachyte) magma associations. The glass-rich sediments occur in glacimarine sequences that record 56 cycles of glacial advance and retreat. Volcanic response to glacial cyclicity is observed both physically and geochemically in AND-2A glass. Higher glass volumes in sediments correlate with ice minimum conditions

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. The search for active volcanism on Venus with Venus Express/VIRTIS data

    NASA Astrophysics Data System (ADS)

    Tsang, C. C. C.; Virtis Team

    The composition of the lower atmosphere of Venus is of primary importance in understanding the past and indeed current evolution of climatology on this most enigmatic of planets In discovering the near infrared windows centered at 2 3 1 7 and 1 18 microns Allen and Crawford 1 in 1983 paved the way for the lower 40km of the atmosphere to be probed remotely from space This has led Venus Express to carry imaging spectrometers such as VIRTIS to make full use of this phenomenon Some fundamental questions concerning the exact makeup of the atmosphere will be answered by analyzing VIRTIS data Data collected from past observations indicate the possibility of current volcanic activity on the surface of Venus The monitoring of SO 2 at the cloud tops indicate a steady drop in concentration suggesting a possible source of SO 2 is due to volcanism 2 whilst deep atmospheric values below the clouds suggest a uniform mixing ratio 3 The analysis VIRTIS data at 2 48 micron window will no doubt shed light on this matter Analysis of the micro-window complex at 1 18 microns shows that we can image the surface of the planet in the infrared whilst negating most of the effects of the atmosphere 4 We can monitor the surface brightness temperatures to look for hot spots indicative of volcanic plumes another key goal of Venus Express and VIRTIS We have developed a radiative transfer model to analyse Venus Express VIRTIS data in the near infrared windows The retrieval model uses the correlated-k distribution method which incorporates the use

  14. Time series analysis of thermal variation on Italian volcanic active areas by using IR satellite data

    NASA Astrophysics Data System (ADS)

    Silvestri, M.; Buongiorno, M. F.; Pieri, D. C.

    2014-12-01

    To monitoring of active volcanoes the systematic acquisition of medium/high resolution thermal data and the subsequent analysis of time series may improve the capability to detect small surface temperature variation related to changes in volcanic activity level and contribute to the early warning systems. Examples on the processing of long time series based EO data of Mt Etna activity and Phlegraean Fields observation by using remote sensing techniques and at different spatial resolution data (ASTER - 90mt, AVHRR -1km, MODIS-1km, MSG SEVIRI-3km) are showed. The use of TIR sensors with high spatial resolution offers the possibility to obtain detailed information on the areas where there are significant changes, detecting variation in fumaroles fields and summit craters before eruptions. Thanks to ASTER thermal infrared (TIR, 5 bands) regions of the electromagnetic spectrum we have obtained the surface temperature map on the volcano area. For this study we have considered the ASTER's night observations that show well defined episodes of increasing thermal emission of crater thanks to a more uniform background temperature. Two different procedures are shown, both using the TIR high spatial resolution data: for Phlegraean Fields (active but quiescent volcano) the analysis of time series of surface temperature which may improve the capability to detect small surface temperature variation related to changes in volcanic activity level; for Mt. Etna (active volcano) a semi-automatic procedure which extract the summit area radiance values with the goal of detecting variation related to eruptive events. The advantage of direct download of EO data by means INGV antennas even though low spatial resolution offers the possibility of a systematic data processing having a daily updating of information for prompt response and hazard mitigation. At the same time the comparison of surface temperature retrievals at different scale is an important issue for future satellite sensors.

  15. The past 5,000 years of volcanic activity at Mt. Pelee martinique (F.W.I.): Implications for assessment of volcanic hazards

    NASA Astrophysics Data System (ADS)

    Westercamp, D.; Traineau, H.

    1983-09-01

    The history of Mt. Pelée, Martinique, was subdivided into three stages based on field geology and 14C data. The two first stages constructed an ancient Mt. Pelée and an intermediate cone between 0.4 m.y and 19,500 y.b.p. The third (or present) stage started 13,500 years ago, after a repose of 6,000 years. This paper focuses on the activity of Mt. Pelée during the past 5,000 years as a means to assess and zone volcanic hazards of the 23 magmatic eruptions during the past 5,000 years. The ages of 21 eruptions of this period are based on 75 new 14C dates. The types of phenomena and distribution of pyroclasts relate to four main types of activity: — The first type consists of pumice-and-ash flows that are not preceded by a Plinian fall. Two eruptions (named P6 and P4) illustrate this type, for which the mixture of gas, ash, and pumice simply overflow the vent and flood several valleys. — The second type differs from the first by the occurrence of a preliminary moderate Plinian-fall stage. Four eruptions (P5, P31, P2 and P1) illustrate this type. Two eruptions (P3 2 and P3 3) experienced cataclysmic Plinian explosions and pumiceous surges. — The third type is related to dome growth with the rise of viscous spines and the production of related block-and-ash flows. Five eruptions (1929, Sept. 1902-1904, NPM, NAB 2 and NMP) illustrate this type. — The fourth type is characterized by violent ejection of more-or-less heterogeneous nuées ardentes. The direction of the blast, dictated by the morphology of the crater, has been towards the south several times at Mt. Pelee. Four eruptions (May 1902, NAB1, NRP2 and NRP3) belong to this type. Future magmatic eruptions at Mt. Pelée will very likely belong to one of these four types. Assessment of hazards at Mt. Pelée is based upon the behavior of the volcano during the past 5,000 years because: (1) recognition of past magmatic eruptions is quite complete and well-dated, and (2) no structural change has occurred in the

  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. 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

  18. Structural Analysis of Active North Bozgush Fault Zone (NW Iran)

    NASA Astrophysics Data System (ADS)

    Saber, R.; Isik, V.; Caglayan, A.

    2013-12-01

    NW Iran is one of the seismically active regions between Zagros Thrust Belt at the south and Caucasus at the north. Not only large magnitude historical earthquakes (Ms>7), but also 1987 Bozgush, 1997 Ardebil (Mw 6.1) and 2012 Ahar-Varzagan (Mw 6.4) earthquakes reveal that the region is seismically active. The North Bozgush Fault Zone (NBFZ) in this region has tens of kilometers in length and hundreds of meters in width. The zone has produced some large and destructive earthquakes (1593 M:6.1 and 1883 M:6.2). The NBFZ affects the Cenozoic units and along this zone Eocene units thrusted over Miocene and/or Plio-Quaternary sedimentary units. Together with morphologic features (stream offsets and alluvial fan movements) affecting the young unites reveal that the zone is active. The zone is mainly characterized by strike-slip faults with reverse component and reverse faults. Reverse faults striking N55°-85°E and dip of 40°-50° to the SW while strike-slip faults show right lateral slip with N60°-85°W and N60°-80°E directions. Our structural data analysis in NBFZ indicates that the axis direction of σ2 principal stress is vertical and the stress ratio (R) is 0.12. These results suggest that the tectonic regime along the North Bozgush Fault Zone is transpressive. Obtained other principal stresses (σ1, σ3) results are compatible with stress directions and GPS velocity suggested for NW Iran.

  19. 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

  20. Observations on the Origin of Across-Strike Geochemical Variations in Quaternary Silicic Lava Flows from the Andean Central Volcanic Zone: Comparision of Data from Individual Eruptive Centers

    NASA Astrophysics Data System (ADS)

    Michelfelder, G.; Feeley, T.; Klemetti, E. W.; Wilder, A. D.

    2011-12-01

    In an effort to better understand the origin of across-strike K2O enrichments in silicic volcanic rocks (60-68 wt.% SiO2) from the Andean Central Volcanic Zone, we compare geochemical and isotopic compositions of Quaternary (<1.0 Ma) lava flows erupted at three well-characterized composite volcanoes situated along a narrow southeast striking transect between 21oS and 22oS. From northwest to southeast these are volcáns Aucanqilcha, Ollagüe, and Uturuncu. Aucanqilcha is located on the arc front entirely within Chile; Ollagüe is ~25 km east of the arc front in the transition zone between the arc front and Bolivian Altiplano; Uturuncu is ~75 km east of the arc front on the Altiplano. Trends observed include the following. At a given SiO2 content lavas erupted with increasing distance from the arc front display systematically higher K2O, P2O5, TiO2, Rb, Th, Y, REE and HFSE contents; Rb/Sr elemental ratios; and Sr isotopic ratios (0.7055 - 0.7165). In contrast, the lavas display systematically lower Al2O3, Na2O, Sr, and Ba contents; Ba/Nb, Ba/Zr, K/Rb, and Sr/Y elemental ratios; and Nd isotopic ratios (0.51239 - 0.51214). In addition, Eu anomalies become progressively more negative toward the SE. It is unlikely that these trends solely reflect regular across-strike variations in mantle source compositions or degrees of melting for parental magmas given the highly modified isotopic ratios relative to primitive intra-oceanic arc magmas, which requires extensive contamination by or derivation within the continental crust. Instead, these data favor a model in which lower crustal source rocks for the lavas become progressively older and more feldspar-rich with increasing distance from the arc front. In this regard, our preliminary interpretation is that silicic magmas erupted along the arc front reflect melting of relatively young, mafic composition amphibolitic source rocks with a garnet- (but not feldspar-) rich residual mineralogy and that the lower crust becomes

  1. Electrification of volcanic plumes

    NASA Astrophysics Data System (ADS)

    Mather, T. A.; Harrison, R. G.

    planets. The direct hazard of volcanic lightning to communities on Earth is generally low compared to other aspects of volcanic activity.

  2. 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

  3. Electrification of volcanic plumes

    NASA Astrophysics Data System (ADS)

    Mather, T. A.; Harrison, R. G.

    2006-07-01

    Volcanic lightning, perhaps the most spectacular consequence of the electrification of volcanic plumes, has been implicated in the origin of life on Earth, and may also exist in other planetary atmospheres. Recent years have seen volcanic lightning detection used as part of a portfolio of developing techniques to monitor volcanic eruptions. Remote sensing measurement techniques have been used to monitor volcanic lightning, but surface observations of the atmospheric electric Potential Gradient (PG) and the charge carried on volcanic ash also show that many volcanic plumes, whilst not sufficiently electrified to produce lightning, have detectable electrification exceeding that of their surrounding environment. Electrification has only been observed associated with ash-rich explosive plumes, but there is little evidence that the composition of the ash is critical to its occurrence. Different conceptual theories for charge generation and separation in volcanic plumes have been developed to explain the disparate observations obtained, but the ash fragmentation mechanism appears to be a key parameter. It is unclear which mechanisms or combinations of electrification mechanisms dominate in different circumstances. Electrostatic forces play an important role in modulating the dry fall-out of ash from a volcanic plume. Beyond the local electrification of plumes, the higher stratospheric particle concentrations following a large explosive eruption may affect the global atmospheric electrical circuit. It is possible that this might present another, if minor, way by which large volcanic eruptions affect global climate. The direct hazard of volcanic lightning to communities is generally low compared to other aspects of volcanic activity.

  4. Assembly of a zoned volcanic magma chamber from multiple magma batches: The Cerberean Cauldron, Marysville Igneous Complex, Australia

    NASA Astrophysics Data System (ADS)

    Clemens, J. D.; Birch, W. D.

    2012-12-01

    The Late Devonian (374 Ma) Cerberean Cauldron forms the northern part of the Marysville Igneous Complex, in Central Victoria, Australia, filled with around 900 km3 of intra-caldera ignimbrites. The basal volcanic formation is the rhyolitic high-Al Rubicon Ignimbrite, overlain by a larger volume of crystal-rich rhyolitic low-Al Rubicon Ignimbrite, which grades upward into the voluminous, rhyodacitic Lake Mountain Ignimbrite. The rocks are S-type in character, with initial 87Sr/86Sr around 0.709 to 0.710 and ɛNdt varying from - 4.7 to - 6.0, suggesting metagreywacke protoliths. The chemistry of the volcanic rocks is incompatible with formation by a differentiation mechanism. Experimentally determined phase relations of a low-Al Rubicon Ignimbrite and a Lake Mountain Ignimbrite show that early crystallisation of the Lake Mountain magma began at > 450 MPa and at > 875 °C (possibly up to 940 °C), with an initial magma H2O content of 4.1 to 5.3 wt.%. In the pre-eruption magma chamber, the Rubicon Ignimbrite magma had a temperature of ≥ 780 °C and contained ≥ 4 wt.% H2O. Each formation, and indeed smaller volumes of rock, appears to have been produced by partial melting of slightly contrasting greywackes in a protolith with spatial variations in its chemistry and mineralogy, with the magma delivered in batches to a high-level chamber. The Rubicon Ignimbrite magmas underwent some internal differentiation, probably by crystal settling, prior to eruption, and variations in the Lake Mountain Ignimbrite are most probably due to small but variable degrees of peritectic phase entrainment. The limited gradation between the Rubicon Ignimbrite and Lake Mountain Ignimbrite is due to minor, pre-eruption mixing across the magma interface. Such limited mixing between individual magma batches appears typical of anatectic granitic magmas.

  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. 78 FR 4155 - Agency Information Collection Activities: Application for Foreign Trade Zone and/or Status...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-01-18

    ... Foreign Trade Zone and/or Status Designation, and Application for Foreign Trade Zone Activity Permit... Application for Foreign Trade Zone Admission and/or Status Designation, and Application for Foreign Trade Zone... Foreign Trade Zone Admission and/or Status Designation, and Application for Foreign Trade......

  7. 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

  8. GEOFIM: A WebGIS application for integrated geophysical modeling in active volcanic regions

    NASA Astrophysics Data System (ADS)

    Currenti, Gilda; Napoli, Rosalba; Sicali, Antonino; Greco, Filippo; Negro, Ciro Del

    2014-09-01

    We present GEOFIM (GEOphysical Forward/Inverse Modeling), a WebGIS application for integrated interpretation of multiparametric geophysical observations. It has been developed to jointly interpret scalar and vector magnetic data, gravity data, as well as geodetic data, from GPS, tiltmeter, strainmeter and InSAR observations, recorded in active volcanic areas. GEOFIM gathers a library of analytical solutions, which provides an estimate of the geophysical signals due to perturbations in the thermal and stress state of the volcano. The integrated geophysical modeling can be performed by a simple trial and errors forward modeling or by an inversion procedure based on NSGA-II algorithm. The software capability was tested on the multiparametric data set recorded during the 2008-2009 Etna flank eruption onset. The results encourage to exploit this approach to develop a near-real-time warning system for a quantitative model-based assessment of geophysical observations in areas where different parameters are routinely monitored.

  9. 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.

  10. 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

  11. 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

  12. Neurotransmitters couple brain activity to subventricular zone neurogenesis

    PubMed Central

    Young, Stephanie Z.; Taylor, M. Morgan; Bordey, Angélique

    2011-01-01

    Adult neurogenesis occurs in two privileged microenvironments, the hippocampal subgranular zone of the dentate gyrus and the subventricular zone (SVZ) along the lateral ventricle. This review focuses on accumulating evidence suggesting that the activity of specific brain regions or bodily states influences SVZ cell proliferation and neurogenesis. Neuromodulators such as dopamine and serotonin have been shown to have long-range effects through neuronal projections into the SVZ. Local GABA and glutamate signaling have demonstrated effects on SVZ proliferation and neurogenesis, but an extra-niche source of these neurotransmitters remains to be explored and options will be discussed. There is also accumulating evidence that diseases and bodily states such as Alzheimer's disease, seizures, sleep, and pregnancy influence SVZ cell proliferation. With such complex behavior and environmentally-driven factors that control subregion-specific activity, it will become necessary to account for overlapping roles of multiple neurotransmitter systems on neurogenesis when developing cell therapies or drug treatments. PMID:21395856

  13. 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

  14. Possible Recent Volcanic Activity on the East Pacific Rise at 9° 32'N

    NASA Astrophysics Data System (ADS)

    Kurokawa, T.; Edwards, M. H.; Johnson, P.; Fornari, D. J.; Perfit, M.; Schouten, H.; Tivey, M. A.

    2002-12-01

    In 2001, the DSL-120A near-bottom mapping system was used to survey a 31.4 km by 6.8 km corridor of the East Pacific Rise crest between 9° 25'N and 9° 57'N. The mapping system included a 120 kHz sidescan and interferometric bathymetry sonar that was used to produce 2 meter-resolution sidescan images of the corridor. The sidescan data depict three scarps located approximately 3 km west of the ridge axis that are interpreted to have been volcanically overprinted between 9° 31'N and 9° 32'N on the basis of sharply lineated features that are interrupted along-strike. In transcripts, video, and 35 mm film footage of the same region collected during Alvin Dive 2490 in 1992, these same scarps are documented as two inward-facing and one outward-facing vertical walls that are 17-18 m high. Co-registration of the DSL-120A and Alvin 2490 datasets shows a strong correlation between other features that are depicted in both the acoustic and photographic data, but the appearance of the scarps changes markedly between 1992 and 2001. In the DSL-120A sidescan data, amorphous-shaped regions of relatively high backscatter characterize the area where the scarps are thought to be volcanically overprinted. In some cases, these reflective patches appear to pond at the base of faults or to spill over the faults. To verify whether the morphology changes between 1992 and 2001 reflect recent volcanic activity on the flank of the ridge axis, we have located SeaMARC-II data for the same region collected in 1987. A cursory examination of the much lower-resolution SeaMARC-II sidescan images vaguely shows the presence of similarly-shaped reflective scarps in the approximate location of the new flow. We are presently reprocessing the SeaMARC-II data to improve the data resolution, making a map from the DSL-120A bathymetry data, and searching for additional datasets that may confirm the existence of a new off-axis flow. The results of our efforts will be reported in December.

  15. The Interfacial Transition Zone in Alkali-Activated Slag Mortars

    NASA Astrophysics Data System (ADS)

    San Nicolas, Rackel; Provis, John

    2015-12-01

    The interfacial transition zone (ITZ) is known to strongly influence the mechanical and transport properties of mortars and concretes. This paper studies the ITZ between siliceous (quartz) aggregates and alkali activated slag binders in the context of mortar specimens. Backscattered electron images (BSE) generated in an environmental scanning electron microscope (ESEM) are used to identify unreacted binder components, reaction products and porosity in the zone surrounding aggregate particles, by composition and density contrast. X-ray mapping is used to exclude the regions corresponding to the aggregates from the BSE image of the ITZ, thus enabling analysis of only the binder phases, which are segmented into binary images by grey level discrimination. A distinct yet dense ITZ region is present in the alkali-activated slag mortars, containing a reduced content of unreacted slag particles compared to the bulk binder. The elemental analysis of this region shows that it contains a (C,N)-A-S-H gel which seems to have a higher content of Na (potentially deposited through desiccation of the pore solution) and a lower content of Ca than the bulk inner and outer products forming in the main binding region. These differences are potentially important in terms of long-term concrete performance, as the absence of a highly porous interfacial transition zone region is expected to provide a positive influence on the mechanical and transport properties of alkali-activated slag concretes.

  16. Ambient noise tomography in the Naruko/Onikobe volcanic area, NE Japan: implications for geofluids and seismic activity

    NASA Astrophysics Data System (ADS)

    Tamura, Jun; Okada, Tomomi

    2016-01-01

    To understand the earthquake generation in volcanic areas, it is important to investigate the presence of geofluids in the uppermost crust. We applied ambient noise tomography to the Naruko/Onikobe volcanic area and constructed a detailed 3-D S-wave velocity ( V s) model using continuous records from a dense seismic network and surrounding stations. The low-velocity zones were found beneath Naruko Volcano, Onikobe Caldera, and Mt. Kurikoma. The low-velocity zone beneath Onikobe Caldera may correspond to a magma reservoir, which is also characterized by surrounding S-wave reflectors. The molten magma originates from the upwelling flows in the mantle wedge. We also conducted the relocation of aftershocks of the 2008 Iwate-Miyagi Nairiku earthquake by double-difference tomography based on the obtained velocity model. Beneath Mt. Kurikoma, aftershock distribution delineates one of the unfavorably oriented fault planes of the main shock, which implies that the low-velocity zone around the fault plane is related to the presence of overpressurized fluid.

  17. Receiver function images of the mantle transition zone beneath NE China: New constraints on intraplate volcanism, deep subduction and their potential link

    NASA Astrophysics Data System (ADS)

    Liu, Zheng; Niu, Fenglin; Chen, Yongshun John; Grand, Steve; Kawakatsu, Hitoshi; Ning, Jieyuan; Tanaka, Satoru; Obayashi, Masayuki; Ni, James

    2015-02-01

    In order to better understand the deep subduction geometry of the Pacific plate and genesis of intraplate volcanism in northeast China (NE China), we computed a total of 45,505 receiver functions from 788 teleseismic events recorded by 255 stations (NECESSArray temporal and permanent stations) in NE China. We used a common-conversion-point stacking (CCP) method to generate a 3D reflectivity volume beneath the study area. To position the P-to-S conversions to the correct depths, we employed 3D crustal and mantle models as references to make time to depth conversion. The 3D reflectivity volume was generated in an area between 115°-135°E and 40°-49°N, in the depth range of 300 to 800 km. We found significant topographic relief on the 660-km discontinuity across the study area. In particular, in a westward Pacific plate subduction section between 40°N and ∼45.5°N, the 660-km discontinuity is depressed by as much as ∼30-40 km along the western extension of the deep seismicity. The depression is elongated along the strike of the deep seismicity and is confined to a 200-300 km region in the E-W direction of subduction. To the west of this depression the 660-km discontinuity is uplifted by 5-10 km in a rectangular area of ∼100 km by 200 km centered at about 125°E and 43°N. In the north, the 660-km discontinuity is moderately depressed (∼20 km) in a broad area that extends further west. The high and low regions in the 660-km topographic map correlate, respectively, with low- and high-velocity anomalies in the P- and S-wave tomographic velocity images at the same depth. Our results suggest that slab stagnation might not be occurring in the southern part of the NE China, where the Changbaishan volcanic complex is located, thus the magmatism is unlikely caused by dehydration of the flat-lying Pacific slab in the transition zone. The low velocity mantle upwelling arising from a gap of stagnant slabs is a likely source that feeds the volcanic complex in NE China.

  18. 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.

  19. 78 FR 16701 - Agency Information Collection Activities: Application for Foreign Trade Zone and/or Status...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-18

    ... Foreign Trade Zone and/or Status Designation, and Application for Foreign Trade Zone Activity Permit... approval in accordance with the Paperwork Reduction Act: Application for Foreign Trade Zone Admission and/or Status Designation, and Application for Foreign Trade Zone Activity Permit (CBP Forms 214,...

  20. Recent seismicity detection increase in the Santorini volcanic island complex

    NASA Astrophysics Data System (ADS)

    Chouliaras, G.; Drakatos, G.; Makropoulos, K.; Melis, N. S.

    2012-04-01

    Santorini is the most active volcanic complex in the South Aegean Volcanic Arc. To improve the seismological network detectability of the seismicity in this region, the Institute of Geodynamics of the National Observatory of Athens (NOA) recently installed 4 portable seismological stations supplementary to the 3 permanent stations operating in the region. The addition of these stations has significantly improved the detectability and reporting of the local seismic activity in the NOA instrumental seismicity catalogue. In this study we analyze quantitatively the seismicity of the Santorini volcanic complex. The results indicate a recent significant reporting increase mainly for events of small magnitude and an increase in the seismicity rate by more than 100%. The mapping of the statistical significance of the rate change with the z-value method reveals that the rate increase exists primarily in the active fault zone perpendicular to the extensional tectonic stress regime that characterizes this region. The spatial distribution of the b-value around the volcanic complex indicates a low b-value distribution parallel to the extensional stress field, while the b-value cross section of the volcanic complex indicates relatively high b-values under the caldera and a significant b-value decrease with depth. These results are found to be in general agreement with the results from other volcanic regions and they encourage further investigations concerning the seismic and volcanic hazard and risk estimates for the Santorini volcanic complex using the NOA earthquake catalogue.

  1. 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

  2. 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.

  3. Sacks-Evertson Borehole Strainmeters: New Designs, Volcanic Activity and Slow Earthquakes

    NASA Astrophysics Data System (ADS)

    Linde, A. T.; Sacks, S.

    2008-12-01

    The quality of borehole strain data depends on a variety of factors, perhaps the most important being the character of rock in the immediate vicinity of the instrument. In tectonically active areas it is often difficult to find sites that provide suitable geometry for studying the activity and also have strong competent rock with few or no fractures. We have tested new designs, for both dilatometers and 3 component Sacks-Evertson hydraulic strainmeters, and have found that, in sites we would previously have rejected because of rock quality, we now obtain reliable data. The approach depends on two factors: the sensing components of the instruments have always been ~3m in length so that they integrate over that vertical interval of rock and additionally we can now have a weak inclusion so that we minimize the mechanical impedance contrast between rock and cement plus instrument. Our current three component design is radically different from the modified Sakata-type used previously. Numerical modeling of the design shows that the response to strain change is essentially perfect; compared with earlier designs this gives better shear response and avoids strain concentrations in the rock wall. This design also provides good data from a site with very low rock quality. Data recorded in Taiwan from the 'weak' single component system have been critically important in allowing us to identify and model slow earthquakes triggered by typhoons. During a 5 year interval we have observed 20 slow earthquakes (durations of hours to days), 11 of which are coincident with typhoons (30 during that time span). This part of Taiwan (south east) experiences extremely high deformation rates but has a paucity of large earthquakes. Our data and modeling indicate that the stressed region is segmented by slow relief of stress, reducing the likelihood of seismic failure over extended fault lengths. Borehole strain recordings of volcanic activity in Montserrat and in Iceland have been critical in

  4. 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

  5. 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

  6. 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

  7. Identification of a volcaniclastic tsunami deposit at a volcanically active region in southeastern Kyushu, Japan

    NASA Astrophysics Data System (ADS)

    Yamada, M.; Nakamura, Y.; Moriwaki, H.; Chiba, T.; Fujino, S.

    2014-12-01

    A total of two pumiceous layers bounded by sharp upper and lower contacts with surrounding mud were evident in almost all of the 19 sediment cores in southeastern Kyushu, Japan. The upper orange-tinged pumiceous layer A with approx. 5 cm thickness was present at around 2.0-3.5 m deep, while the lower white-tinged pumiceous layer B with a few millimeters to 1.5 cm thickness was found beneath the layer A. The major element composition and refraction index of volcanic glass shards in layers A and B were consistent with those of standard sample of Kr-M and Sz-7, respectively. The Kr-M tephra, sourced from the Mt. Kirishima in southern part of Kyushu, was deposited approx. 4600 years ago, while the Sz-7 tephra, sourced from the Sakurajima in southern part of Kyushu, was deposited approx. 5000 years ago. Selected seeds, leaves, and plant debris obtained from mud samples immediately beneath the layers A and B provided their limiting-maximum ages of approx. 4500 cal. yr BP and 4500-4600 cal. yr BP. The results of the tephra analyses and radiocarbon age indicate that the layer A is the Kr-M fall tephra. However, the limiting-maximum age of the layer B is 400 years younger than the fall age of Sz-7. Given the higher percentage of marine and brackish diatoms than the background mud, deposition of the layer B is thought to be due to a seawater inundation event such as tsunami. It is quite likely that volcaniclastic tsunami deposits exist not only in Kyushu, but also at any site in the subduction zones all over the world. The same approach as this study contributes to the discovery of overlooked tsunami deposits in other areas.

  8. 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.

  9. A frictional law for volcanic ash gouge

    NASA Astrophysics Data System (ADS)

    Lavallée, Y.; Hirose, T.; Kendrick, J. E.; De Angelis, S.; Petrakova, L.; Hornby, A. J.; Dingwell, D. B.

    2014-08-01

    Volcanic provinces are structurally active regions - undergoing continual deformation along faults. Within such fault structures, volcanic ash gouge, containing both crystalline and glassy material, may act as a potential fault plane lubricant. Here, we investigate the frictional properties of volcanic ash gouges with varying glass fractions using a rotary shear apparatus at a range of slip rates (1.3-1300 mm/s) and axial stresses (0.5-2.5 MPa). We show that the frictional behaviour of volcanic ash is in agreement with Byerlee's friction law at low slip velocities, irrespective of glass content. The results reveal a common non-linear reduction of the friction coefficient with slip velocity and yield a frictional law for fault zones containing volcanic ash gouge. Textural analysis reveals that strain localisation and the development of shear bands are more prominent at higher slip velocities (>10 mm/s). The textures observed here are similar to those recorded in ash gouge at the surface of extrusive spines at Mount St. Helens (USA). We use the rate-weakening component of the frictional law to estimate shear-stress-resistance reductions associated with episodic seismogenic slip events that accompany magma ascent pulses. We conclude that the internal structure of volcanic ash gouge may act as a kinematic marker of exogenic dome growth.

  10. Exploring for geothermal resource in a dormant volcanic system: The Haleakala Southwest Rift Zone, Maui, Hawai'i

    NASA Astrophysics Data System (ADS)

    Martini, B. A.; Lewicki, J. L.; Kennedy, B. M.; Lide, C.; Oppliger, G.; Drakos, P. S.

    2011-12-01

    Suites of new geophysical and geochemical surveys provide compelling evidence for geothermal resource at the Haleakala Southwest Rift Zone (HSWRZ) on Maui Island, Hawai'i. Ground-based gravity (~400 stations) coupled with heli-borne magnetics (~1500 line kilometers) define both deep and shallow fractures/faults while also delineating potentially widespread subsurface hydrothermal alteration on the lower flanks (below approximately 1800 feet a.s.l.). Multi-level, upward continuation calculations and 2-D gravity and magnetic modeling provide information on source depths, but lack of lithologic information leaves ambiguity in the estimates. Lithology and physical property data from future drilling will improve these interpretations. Additionally, several well-defined gravity lows (possibly vent zones) lie coincident with magnetic highs suggesting the presence of dike intrusions at depth; a potentially young source of heat for a modern geothermal system. Soil CO2 fluxes were measured along transects across geophysically-defined faults and fractures as well as young cinder cones along the HSWRZ; a weak anomalous flux signal was observed at one young cinder cone location. Dissolved inorganic carbon concentrations and δ13C compositions and 3He/4He values measured in several shallow groundwater samples indicate addition of magmatic CO2 and He to the groundwater system. The general lack of observed magmatic surface CO2 signals on the HSWRZ is therefore likely due to a combination of groundwater 'scrubbing' of CO2 and relatively high biogenic surface CO2 fluxes that mask magmatic CO2. Similar surveys at the Puna geothermal field on the Kilauea Lower East Rift Zone (KLERZ) also showed a lack of surface CO2 flux signals attributed to a magmatic source, while aqueous geochemistry indicated contribution of magmatic CO2 and He to shallow groundwaters at both Maui and Puna. As magma has been intercepted in geothermal drilling at the Puna field, the lack of measured surface CO2

  11. Intermediate products of sulfur disproportional reaction and their physical role in effusive to explosive submarine volcanic activity

    NASA Astrophysics Data System (ADS)

    Nakamura, K.; Takano, B.; Butterfield, D. A.; Resing, J.; Chadwick, W. W.; Embley, R. W.

    2009-12-01

    Recent direct observations of submarine volcanic activity in the Mariana Arc are giving us a chance to examine the role of volcanic gas in submarine volcanic conduits. Unlike subaerial volcanoes, where hydrogeologic conditions have different character from place to place, the overlying water mass above submarine volcanoes gives a uniform hydrographic setting. Currently, the places where we can directly observe submarine volcanic activity are located deeper than 400 m, which raises the boiling point of seawater to over 240 deg C. This situation allows us to examine the interaction of volcanic gases with ambient seawater at a shorter distance from the magma source than at subaerial volcanic settings. Arc volcano settings give us longer and more frequent opportunities to make observations and provide a more diverse range of submarine volcanism than ridge settings. Among the three major components of volcanic gases (i.e., H2O, CO2 and SO2), water follows a two phase boundary below the critical temperature after volatile components leave from the magmatic source. Milky sulfur sol bearing hydrothermal fluid is commonly observed throughout Mariana active sites. Most of the sulfur sol (colloidal elemental sulfur and polysulfides) might be formed by disproportional reaction of sulfur dioxide with seawater when water vapor shrinks to liquid water. The reaction creates not only sulfur sol but also various types of sulfite, which affects the pH of seawater. We detected short-lived sulfite species in the water column above several active Mariana volcanoes such as NW Rota-1, Daikoku and Nikko by on-board HPLC. Because most observations are made on the liquid phase side of H2O boundary, it is very hard to get data to investigate the physical and chemical sulfur sol forming process occurring on the vapor phase side or at the critical state (i.e., near the magma source process). Carbon dioxide behaves as a gas at a wide range of pressures and temperatures and carries heat and

  12. 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.

  13. 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

  14. 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

  15. Volcanic Hazards Survey in the Trans Mexican Volcanic Belt

    NASA Technical Reports Server (NTRS)

    Abrams, Michael; Siebe, Claus; Macias, Jose Luis

    1996-01-01

    We have assembled a digital mosaic of 11 Landsat Thematic images to serve as a mapping base for reconnaissance activities within the Trans Mexican Volcanic Belt. This will aid us in interpretation and in the evaluation of potential activity of all the volcanic centers there. One result is a volcanic hazards map of the area.

  16. 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.

  17. 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

  18. 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

  19. Exploring for Volcanic and Hydrothermal Activity Above Off-axis Melt Lenses near the East Pacific Rise

    NASA Astrophysics Data System (ADS)

    West, A. J.; Torres, M. A.; Nealson, K. H.

    2014-12-01

    Two Alvin dives (AL 4771 and 4774) transected the seafloor directly above the two largest Off-Axis Melt Lenses (O-AML) east of the East Pacific Rise (EPR) axis at 9 39'N and 9 54'N. In 2008, a 3D high-resolution seismic reflection survey (MGL-0812) discovered O-AMLs 3-7 km from the EPR at 2-3 km below the seafloor. Several other O-AML in the crust have been subsequently detected in several locations up to 20 km from the spreading axis at fast and intermediate spreading ridges; understanding their impacts is increasingly important. During the dives, no currently active hydrothermal venting or fresh lava was seen, suggesting that these features do not constantly power off-axis geological activity. However, the seafloor appears much younger at small volcanic seamounts in the 9 39'N than at the 9 54'N site. At 9 39'N, we used Alvin to explore the off-axis volcanic mound complex, reaching the summit of the three largest mounds. Although no evidence for on-going hydrothermal or volcanic activity was detected, the seafloor wore a thin sediment layer of ~10cm and thin Mn-coatings on 9 rock samples, suggesting volcanism more recently than would be expected based on the spreading-rate age of the crust. At 9 54'N, the Alvin trackline started south of a prominent abyssal hill, which has an unusual D-shape over 1 km wide in the center, crossed the abyssal hill, visited two local hummocks on top, and then attempted to find volcanic activity on the near slope of EPR axis by going as far west was possible during the dive. Heavy sediment everywhere on the abyssal hill, to the depth of push cores (~30 cm) and probably much deeper in many areas and 4 rock samples from the abyssal hill were quite weathered with little glass intact, suggest that this site is unaffected by the underlying O-AML. Upslope toward the EPR west of the abyssal hill, 4 rocks collected appear somewhat younger, and sediment became thinner. In addition, 3 CTD tow-yos over each O-AML found no evidence of active

  20. Exploring for Volcanic and Hydrothermal Activity Above Off-axis Melt Lenses near the East Pacific Rise

    NASA Astrophysics Data System (ADS)

    White, S. M.; Lee, A. J.; Rubin, K. H.

    2015-12-01

    Two Alvin dives (AL 4771 and 4774) transected the seafloor directly above the two largest Off-Axis Melt Lenses (O-AML) east of the East Pacific Rise (EPR) axis at 9 39'N and 9 54'N. In 2008, a 3D high-resolution seismic reflection survey (MGL-0812) discovered O-AMLs 3-7 km from the EPR at 2-3 km below the seafloor. Several other O-AML in the crust have been subsequently detected in several locations up to 20 km from the spreading axis at fast and intermediate spreading ridges; understanding their impacts is increasingly important. During the dives, no currently active hydrothermal venting or fresh lava was seen, suggesting that these features do not constantly power off-axis geological activity. However, the seafloor appears much younger at small volcanic seamounts in the 9 39'N than at the 9 54'N site. At 9 39'N, we used Alvin to explore the off-axis volcanic mound complex, reaching the summit of the three largest mounds. Although no evidence for on-going hydrothermal or volcanic activity was detected, the seafloor wore a thin sediment layer of ~10cm and thin Mn-coatings on 9 rock samples, suggesting volcanism more recently than would be expected based on the spreading-rate age of the crust. At 9 54'N, the Alvin trackline started south of a prominent abyssal hill, which has an unusual D-shape over 1 km wide in the center, crossed the abyssal hill, visited two local hummocks on top, and then attempted to find volcanic activity on the near slope of EPR axis by going as far west was possible during the dive. Heavy sediment everywhere on the abyssal hill, to the depth of push cores (~30 cm) and probably much deeper in many areas and 4 rock samples from the abyssal hill were quite weathered with little glass intact, suggest that this site is unaffected by the underlying O-AML. Upslope toward the EPR west of the abyssal hill, 4 rocks collected appear somewhat younger, and sediment became thinner. In addition, 3 CTD tow-yos over each O-AML found no evidence of active

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. Active Extensional Structures Discovered by the Airborne LiDAR Mapping in the Tatun Volcanic Region, Taiwan

    NASA Astrophysics Data System (ADS)

    Chan, Y.; Chang, K.; Chen, R.; Lee, J.; Hsieh, Y.

    2006-12-01

    Complex tectonic deformation is present in northern Taiwan where the Philippine Sea plate is subducting under the Eurasian plate and the Okinawa trough is opening to the east. The Tatun volcanic region and the Taipei metropolitan basin are considered the products resulted from such complex tectonic environment. Furthermore, contractional deformation was prevailed in the earlier stage, as evidenced by several major thrust faults truncating the Tertiary strata. However, the expected nowadays extensional deformation is not fully characterized, for example, the Shanchiao fault bounding the western Taipei basin and its northern extension into the Tatun volcanic region. Based on industrial seismic profiles, it appeared that several well developed normal faults reactivated pre-existing thrust faults offshore northern Taiwan. These normal faults likely extend into the land where the Tatun volcanics erupted through and covered on the Tertiary strata. It is our intentions to better inspect the deformational pattern existing within the Tatun volcanic region where forests dominate on the surface making field investigation difficult. In this study we apply high-resolution airborne LiDAR-derived digital terrain model to characterize possible joints, fractures, and faults in the Tatun volcanic region. The LiDAR-derived DTM was processed so that bare ground is revealed using virtual removal of forests. The derived 2-m DTM was then examined to map out topographic features possibly resulted from the linear geologic structures. We discovered clear distribution and pattern of the joints and fractures in the Tatun volcanic region for the first time. The mapped structural patterns reveal strong evidence for regional extensional deformation in northern Taiwan, especially within the Tatun volcanic region. We also uncovered branches of normal faults extending possibly from the Shanchiao fault into the Tatun volcanic region. The discovered normal fault, perhaps active, cut across flat

  8. 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.

  9. 50 CFR Table 8 to Part 679 - Harvest Zone Codes for Use With Vessel Activity Reports

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Harvest Zone Codes for Use With Vessel... ECONOMIC ZONE OFF ALASKA Pt. 679, Table 8 Table 8 to Part 679—Harvest Zone Codes for Use With Vessel Activity Reports Harvest Zone Description A1 BSAI EEZ off Alaska A2 GOA EEZ off Alaska B State waters...

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. Identification of activity regimes by unsupervised pattern classification of volcanic tremor data. Case studies from Mt. Etna.

    NASA Astrophysics Data System (ADS)

    Langer, H.; Behncke, B.; Falsaperla, S.; Messina, A.; Spampinato, S.

    2009-04-01

    The monitoring of the seismic background signal - commonly referred to as volcanic tremor - has become a key tool for volcanic surveillance, particularly when field surveys are unsafe and/or visual observations are hampered by bad weather conditions. Indeed, it could be demonstrated that changes in the state of activity of the volcano show up in the volcanic tremor signature, such as amplitude and frequency content. Hence, the analysis of the characteristics of volcanic tremor leads us to pass from a mere monoparametric vision of the data to a multivariate one, which can be tackled with modern concepts of multivariate statistics. For this aim we present a recently developed software package which combines various concepts of unsupervised classification, in particular cluster analysis and Kohonen maps. Unsupervised classification is based on a suitable definition of similarity between patterns rather than on a-priori knowledge of their class membership. It aims at the identification of heterogeneities within a multivariate data set, thus permitting to focalize critical periods where significant changes in signal characteristics are encountered. The application of the software is demonstrated on sample sets derived from Mt. Etna during eruptions in 2001, 2006 and 2007-8.

  15. 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.

  16. Anomalous geomagnetic variations associated with the volcanic activity of the Mayon volcano, Philippines during 2009-2010

    NASA Astrophysics Data System (ADS)

    Takla, E. M.; Yoshikawa, A.; Kawano, H.; Uozumi, T.; Abe, S.

    2014-12-01

    Local anomalous geomagnetic variations preceding and accompanying the volcanic eruptions had been reported by several researchers. This paper uses continuous high-resolution geomagnetic data to examine the occurrence of any anomalous geomagnetic field variations that possibly linked with the volcanic eruption of the Mayon volcano, Philippines during 2009-2010. The nearest geomagnetic observing point from the Mayon volcano is the Legazpi (LGZ) station, Philippines; which is located about 13 km South of the Mayon volcano. The amplitude range of daily variations and the amplitude of Ultra Low Frequency emissions in the Pc3 range (Pc3; 10-45 s) were examined at the LGZ station and also were compared with those from the Davao (DAV) station, Philippines as a remote reference station. Both the LGZ and DAV stations belong to the MAGDAS Network. The result of data analysis reveals significant anomalous changes in the amplitude range of daily variations and the Pc3 amplitude at the LGZ station before and during the volcanic eruption of the Mayon volcano. From the obtained results, it appears that the observed anomalous variations are dependent on the change in the underground conductivity connected with variation in the physical properties of the Earth's crust due to the activity of the Mayon volcano. Therefore, these anomalous geomagnetic variations are considered to be of a local volcanic origin.

  17. 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

  18. Volcanic activity observed from continuous seismic records in the region of the Klyuchevskoy group of volcanoes

    NASA Astrophysics Data System (ADS)

    Shapiro, N.; Droznin, D.; Droznina, S.; Senyukov, S.; Chebrov, V.; Gordeev, E.; Frank, W.

    2015-12-01

    We analyze continuous seismic records from 18 permanent stations operated in vicinity of the Klyuchevskoy group of volcanos (Kamchatka, Russia) during the period between 2009 and 2014. We explore the stability of the inter-station cross-correlation to detect different periods of sustained emission from seismic energy. The main idea of this approach is that cross-correlation waveforms computed from a wavefield emitted by a seismic source from a fixed position remain stable during the period when this source is acting. The detected periods of seismic emission correspond to different episodes of activity of volcanoes: Klyuchevskoy, Tolbachik, Shiveluch, and Kizimen. For Klyuchevskoy and Tolbachik whose recent eruptions are mostly effusive, the detected seismic signals correspond to typical volcanic tremor, likely caused by degassing processes. For Shiveluch and Kizimen producing more silicic lavas, the observed seismic emission often consists of many repetitive long period (LP) seismic events that might be related to the extrusion of viscous magmas. We develop an approach for automatic detection of these individual LP events in order to characterize variations of their size and recurrence in time.

  19. Monitoring active volcanoes and mitigating volcanic hazards: the case for including simple approaches

    NASA Astrophysics Data System (ADS)

    Stoiber, Richard E.; Williams, Stanley N.

    1990-07-01

    Simple approaches to problems brought about eruptions and their ensuing hazardous effects should be advocated and used by volcanologists while awaiting more sophisticated remedies. The expedients we advocate have all or many of the following attributes: only locally available materials are required; no extensive training of operators or installation is necessary; they are affordable and do not require foreign aid or exports; they are often labor intensive and are sustainable without outside assistance. Where appropriate, the involvement of local residents is advocated. Examples of simple expedients which can be used in forecasting or mitigating the effects of crises emphasize the relative ease and the less elaborate requirements with which simple approaches can be activated. Emphasis is on visual observations often by untrained observers, simple meteorogical measurements, observations of water level in lakes, temperature and chemistry of springs and fumaroles, new springs and collapse areas and observations of volcanic plumes. Simple methods are suggested which can be applied to mitigating damage from mudflows, nuées ardentes, tephra falls and gas discharge. A review in hindsight at Ruiz includes the use of both chemical indicators and simple mudflow alarms. Simple expedients are sufficiently effective that any expert volcanologist called to aid in a crisis must include them in the package of advice offered. Simple approaches are a critical and logical complement to highly technical solutions to hazardous situations.

  20. 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.

  1. 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.

  2. Volcanic and seismic activity at Stromboli preceding the 2002-2003 flank eruption

    NASA Astrophysics Data System (ADS)

    Burton, M.; Calvari, S.; Spampinato, L.; Lodato, L.; Pino, N. A.; Marchetti, E.; Murè, F.

    Regular surveys with a thermal camera from both ground- and helicopter-based surveys have been carried out on Stromboli since October 2001. This data set allowed us to detect morphological changes in Stromboli's summit craters produced by major explosions and to track an increase in volcanic activity associated with a heightened magma level within the main conduit that preceded the 2002-2003 effusive eruption. Together with thermal measurements, geophysical surveys performed in May and September/October 2002 highlighted clear increases in the amplitude of very long period (VLP) events, consistent with the ascent of the magma column above the VLP source region. The increased magma level was probably induced by elevated pressure in the deep feeding system, controlled by regional tectonic stress. This, in turn, pressurized the uppermost part of the crater terrace, producing greater soil permeability and soil degassing. Eventually, the magma loading caused the NW flank of the summit craters to fracture, allowing lava to flood out at high effusion rates on 28 December 2002, starting an approximately 6-month-long effusive eruption.

  3. Lung clearance of neutron-activated Mount St. Helens volcanic ash in the rat.

    PubMed

    Wehner, A P; Wilerson, C L; Stevens, D L

    1984-10-01

    To determine pulmonary deposition and clearance of inhaled volcanic ash, rats received a single 60-min, nose-only exposure to neutron-activated ash. Over a period of 128 days after exposure, the rats were sacrificed in groups of five animals. Lungs were analyzed for the radionuclide tracers 46Sc, 59Fe, and 60Co by gamma-ray spectrometry. The alveolar ash burdens, determined by the radionuclides 46Sc and 59Fe, are in good agreement for the majority of samples analyzed, indicating ash particulate levels in the lungs, rather than leached radionuclides. The ash deposition estimates based on 60Co were appreciably lower for the lungs, indicating that 60Co leached from the ash. Approximately 110 micrograms ash, or 6% of the inhaled ash, was initially retained in the deep lung. The biological half-time of the alveolar ash burden was 39 days. After 90 days, the mean lung burden had decreased to about 20% of its initial value; 128 days after exposure, about 10% remained. PMID:6489290

  4. 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. PMID

  5. The nature of the volcanic activity at Loki: Insights from Galileo NIMS and PPR data

    NASA Astrophysics Data System (ADS)

    Howell, Robert R.; Lopes, Rosaly M. C.

    2007-02-01

    Loki is the largest patera and the most energetic hotspot on Jupiter's moon Io, in turn the most volcanically active body in the Solar System, but the nature of the activity remains enigmatic. We present detailed analysis of Galileo Near-Infrared Mapping Spectrometer (NIMS) and PhotoPolarimeter/Radiometer (PPR) observations covering the 1.5-100 μm wavelength range during the I24, I27, and I32 flybys. The general pattern of activity during these flybys is consistent with previously proposed models of a resurfacing wave periodically crossing a silicate lava lake. In particular our analysis of the I32 NIMS observations shows, over much of the observed patera, surface temperatures and implied ages closely matching those expected for a wave advancing counterclockwise at 0.94-1.38 km/day. The age pattern is different than other published analyses which do not show as clearly this azimuthal pattern. Our analysis also shows two additional distinctly different patera surfaces. The first is located along the inner and outer margins where components with a 3.00-4.70-μm color temperature of 425 K exist. The second is located at the southwestern margin where components with a 550-K color temperature exist. Although the high temperatures could be caused by disruption of a lava lake crust, some additional mechanism is required to explain why the southwest margin is different from the inner or outer ones. Finally, analysis of the temperature profiles across the patera reveal a smoothness that is difficult to explain by simple lava cooling models. Paradoxically, at a subpixel level, wide temperature distributions exist which may be difficult to explain by just the presence of hot cracks in the lava crust. The resurfacing wave and lava cooling models explain well the overall characteristics of the observations. However, additional physical processes, perhaps involving heat transport by volatiles, are needed to explain the more subtle features.

  6. Insights into shallow magma storage and crystallization at Volcán Llaima (Andean Southern Volcanic Zone, Chile)

    NASA Astrophysics Data System (ADS)

    Bouvet de Maisonneuve, C.; Dungan, M. A.; Bachmann, O.; Burgisser, A.

    2012-01-01

    Scoriae produced by four mafic historic eruptions of Volcán Llaima are used to elucidate magma differentiation, recharge, mixing, and eruption triggering. Whole-rock, mineral, and olivine-hosted melt inclusion chemistry suggest that basaltic andesites (~ 52-53.5 wt.% SiO 2) stall at immediately sub-edifice depths (≤ 4 km beneath the base of the volcano), where they crystallize to large extents and form mush bodies. Melt inclusion trends overlap with the whole-rock data trends defined by the entire volcano up to 53-55% SiO 2, but more evolved compositions define divergent trends for some elements, with up to 2.2 wt.% TiO 2 (increasing Zr) and Al 2O 3 as low as 12.5 wt.% (decreasing Sr) at 57-58 wt.% SiO 2. These more evolved melt compositions are inferred to be the result of shallow evolution of interstitial melt during the formation of crystal mush bodies, as a consequence of degassing and crystallization with a reduced participation of Fe-Ti-oxides. The inferred suppression of Fe-Ti-oxide stability and the modal dominance of plagioclase crystallization are consistent with low fluid-saturation pressures of ~ 40-70 MPa inferred from average H 2O contents for mafic arc magmas (dominantly 1-4 wt.%) but low CO 2 contents (dominantly 0-300 ppm) in melt inclusions. The broad range in olivine core compositions (Fo 69-83) and the absence of correlated degassing and magma evolution trends in historic Llaima magmas suggest that they are stored as multiple dike-like bodies created by a high frequency of magma replenishment relative to the frequency of large eruptions. This temporal-spatial disconnection leads to isolated evolution and degassing of discrete magma batches, followed by remobilization and assembly just prior to eruption. Eruptions are probably triggered by recharge of relatively hot, mafic, and much less degassed magma, in accord with dominantly reversely-zoned olivine crystals, and higher olivine-melt temperatures recorded by the relatively primitive matrix

  7. Post-collisional adakitic volcanism in the eastern part of the Sakarya Zone, Turkey: evidence for slab and crustal melting

    NASA Astrophysics Data System (ADS)

    Dokuz, Abdurrahman; Uysal, İbrahim; Siebel, Wolfgang; Turan, Mehmet; Duncan, Robert; Akçay, Miğraç

    2013-11-01

    New geochemical and isotopic data for post-collisional Early Eocene and Late Miocene adakitic rocks from the eastern part of the Sakarya Zone, Turkey, indicate that slab and lower crustal melting, respectively, played key roles in the petrogenesis of these rocks. The Early Eocene Yoncalık dacite (54.4 Ma) exhibits high Sr/Y and La/Yb ratios, low Y and HREE concentrations, moderate Mg# (44-65), and relatively high ɛNd and low ISr values, similar to adakites formed by slab melting associated with subduction. Geochemical composition of the Yoncalık dacite cannot be explained by simple crystal fractionation and/or crustal contamination of andesitic parent magma, but is consistent with the participation of different proportions of melts derived from subducted basalt and sediments. Sr/Y correlates horizontally with Rb/Y, and Pb/Nd correlates vertically with Nd isotopic composition, indicating that Sr and Pb budgets are strongly controlled by melt addition from the subducting slab, whereas positive correlations between Th/Nd and Pb/Nd, and Rb/Y and Nb/Y point to some contribution of sediment melt. In addition to low concentrations of heavy rare earth elements (~2-3 times chondrite), a systematic decrease in their concentrations and Nb/Ta ratios with increasing SiO2 contents suggests that slab partial melting occurred in the garnet stability field and that these elements were mobilized by fluid flux. These geochemical and isotopic signatures are best explained by slab breakoff and fusion shortly after the initiation of collision. Although the Late Micone Tavdağı rhyolite (8.75 Ma) has some geochemical features identical to adakites, such as high Sr/Y and La/Yb ratios, low Y and HREE concentrations, other requirements, such as sodic andesite and/or dacite with relatively high MgO and Mg# (>50), relatively high Ni and Cr, low K2O/Na2O (<0.4), high Sr (>400 ppm), for slab-derived adakites are not provided. It is sodic in composition and shows no traces of fractionation

  8. 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.

  9. Detection of aeromagnetic anomaly change associated with volcanic activity: An application of the generalized mis-tie control method

    NASA Astrophysics Data System (ADS)

    Nakatsuka, Tadashi; Utsugi, Mitsuru; Okuma, Shigeo; Tanaka, Yoshikazu; Hashimoto, Takeshi

    2009-12-01

    Repeat aeromagnetic surveys may assist in mapping and monitoring long-term changes associated with volcanic activity. However, when dealing with repeat aeromagnetic survey data, the problem of how to extract the real change of magnetic anomalies from a limited set of observations arises, i.e. the problem of spatial aliasing. Recent development of the generalized mis-tie control method for aeromagnetic surveys flown at variable elevations enables us to statistically extract the errors from ambiguous noise sources. This technique can be applied to overcome the spatial alias effect when detecting magnetic anomaly changes between aeromagnetic surveys flown at different times. We successfully apply this technique to Asama Volcano, one of the active volcanoes in Japan, which erupted in 2004. Following the volcanic activity in 2005, we conducted a helicopter-borne aeromagnetic survey, which we compare here to the result from a previous survey flown in 1992. To discuss small changes in magnetic anomalies induced by volcanic activity, it is essential to estimate the accuracy of the reference and the repeat aeromagnetic measurements and the probable errors induced by data processing. In our case, the positioning inaccuracy of the 1992 reference survey was the most serious factor affecting the estimation of the magnetic anomaly change because GPS was still in an early stage at that time. However, our analysis revealed that the magnetic anomaly change over the Asama Volcano area from 1992 to 2005 exceeded the estimated error at three locations, one of which is interpreted as a loss of magnetization induced by volcanic activity. In this study, we suffered from the problem of positioning inaccuracy in the 1992 survey data, and it was important to evaluate its effect when deriving the magnetic anomaly change.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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...

  18. 33 CFR 3.70-20 - Activities Far East Marine Inspection Zone.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Activities Far East Marine... SECURITY GENERAL COAST GUARD AREAS, DISTRICTS, SECTORS, MARINE INSPECTION ZONES, AND CAPTAIN OF THE PORT ZONES Fourteenth Coast Guard District § 3.70-20 Activities Far East Marine Inspection Zone....

  19. 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.

  20. New inferences from spectral seismic energy measurement of a link between regional seismicity and volcanic activity at Mt. Etna, Italy

    NASA Astrophysics Data System (ADS)

    Ortiz, R.; Falsaperla, S.; Marrero, J. M.; Messina, A.

    2009-04-01

    The existence of a relationship between regional seismicity and changes in volcanic activity has been the subject of several studies in the last years. Generally, activity in basaltic volcanoes such as Villarica (Chile) and Tungurahua (Ecuador) shows very little changes after the occurrence of regional earthquakes. In a few cases volcanic activity has changed before the occurrence of regional earthquakes, such as observed at Teide, Tenerife, in 2004 and 2005 (Tárraga et al., 2006). In this paper we explore the possible link between regional seismicity and changes in volcanic activity at Mt. Etna in 2006 and 2007. On 24 November, 2006 at 4:37:40 GMT an earthquake of magnitude 4.7 stroke the eastern coast of Sicily. The epicenter was localized 50 km SE of the south coast of the island, and at about 160 km from the summit craters of Mt. Etna. The SSEM (Spectral Seismic Energy Measurement) of the seismic signal at stations at 1 km and 6 km from the craters highlights that four hours before this earthquake the energy associated with volcanic tremor increased, reached a maximum, and finally became steady when the earthquake occurred. Conversely, neither before nor after the earthquake, the SSEM of stations located between 80 km and 120 km from the epicentre and outside the volcano edifice showed changes. On 5 September, 2007 at 21:24:13 GMT an earthquake of magnitude 3.2 and 7.9 km depth stroke the Lipari Island, at the north of Sicily. About 38 hours before the earthquake occurrence, there was an episode of lava fountain lasting 20 hours at Etna volcano. The SSEM of the seismic signal recorded during the lava fountain at a station located at 6 km from the craters highlights changes heralding this earthquake ten hours before its occurrence using the FFM method (e.g., Voight, 1988; Ortiz et al., 2003). A change in volcanic activity - with the onset of ash emission and Strombolian explosions - was observed a couple of hours before the occurrence of the regional

  1. 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

  2. Spatial distribution of microfractures in damage zone along active faults

    NASA Astrophysics Data System (ADS)

    Mizoguchi, K.; Ueta, K.

    2011-12-01

    For basement faults without overlying quaternary sediments, there are few methods to determine whether the fault is active or not. Recently, we focus on microfracture characteristics of damage zone along active faults as used for the assessment of seismic activity of basement faults. In this study, we examined a newly-found active fault (Sasaki et al., 2011) located to the east of the epicentral area of 1943 Tottori earthquake, southwest Japan. The fault zone consists of the 75 cm thick fault core of the purple-colored clayey fault gouge and the fault breccia with cataclastic foliation, and the surrounding damage zone developed in Cretaceous Kyushozan granite. A subsidiary fault accompanying a fault core of white clayey fault gouge that ranges from 3 to 5 mm thickness is located at about 110 m from the main fault. We collected ten orientated samples 9 m to 180 m from the main fault. The samples were coated with epoxy and then thin sections were cut perpendicular to the fault plane and parallel to a horizontal plane because the slip direction is unknown. Microfracture density data were collected from 40 quartz grains per thin section (per sample). A thin section is marked with a square grid at 3 mm intervals and we picked one grain up in each square of the grid marked on the thin section to reduce operator sampling bias resulting from the selection of quartz grains. Quartz is suitable to estimate the damage that the rock sample has sustained because quartz without cleavage acts as an isotropic medium for fracturing and it is physically and chemically resistant to weathering than other minerals constituting the granite. We counted the number of microfractures that intersected a line which was drawn from the edge of each quartz grain, through the center point, to the other edge of the grain. The linear microfracture density for each sample is calculated to be the total number of microfractures intersecting the lines divided by the total counting line length. Under the

  3. Temporal changes in thermal waters related to volcanic activity of Tokachidake Volcano, Japan: implications for forecasting future eruptions

    NASA Astrophysics Data System (ADS)

    Takahashi, Ryo; Shibata, Tomo; Murayama, Yasuji; Ogino, Tagiru; Okazaki, Noritoshi

    2015-01-01

    In order to detect changes in volcanic activity of Tokachidake Volcano, Japan, we have continuously monitored thermal waters discharging at the western to southwestern flank of the volcano since 1986. The steam-heated waters in the Nukkakushi crater discharged with boiling temperature until 2002. Thermal waters at the Tokachidake spa area have similar compositions to fumarolic gas emitted from the summit craters, indicating that the waters formed by absorption of volcanic gas into shallow aquifers. Thermal waters at the Fukiage spa area were derived from the same aquifer as the Tokachidake spa area until early 1986. However, after that time, NaCl-type thermal water entered the Fukiage spa area during the increase in volcanic activity associated with the 1988-1989 eruption, thus leading to a clear increase in Cl concentrations and temperature. After the eruption, the supply of the NaCl-type thermal water was halted, and the Cl concentrations of the thermal waters decreased. In contrast, SO4 concentrations gradually increased in the Fukiage spa area after 1989, and the temperature has been maintained. These observations indicate that SO4-rich thermal water with a relatively high temperature entered the system instead of the NaCl-type thermal water. As was the case for the 1988-1989 eruption, the Cl concentrations at the Fukiage spa area increased in 2012 during an increase in volcanic activity, implying that the supply of the NaCl-type thermal water had resumed. However, the chemical changes in the thermal waters since 2012 are small compared with those before the 1988-1989 eruption, with oxygen and hydrogen isotopic compositions remaining nearly the same as those of meteoric waters.

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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.

  9. 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. PMID:20717718

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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

  16. 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.

  17. 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

  18. 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.

  19. Conceptual model of volcanism and volcanic hazards of the region of Ararat valley, Armenia

    NASA Astrophysics Data System (ADS)

    Meliksetian, Khachatur; Connor, Charles; Savov, Ivan; Connor, Laura; Navasardyan, Gevorg; Manucharyan, Davit; Ghukasyan, Yura; Gevorgyan, Hripsime

    2015-04-01

    Armenia and the adjacent volcanically active regions in Iran, Turkey and Georgia are located in the collision zone between the Arabian and Eurasian lithospheric plates. The majority of studies of regional collision related volcanism use the model proposed by Keskin, (2003) where volcanism is driven by Neo-Tethyan slab break-off. In Armenia, >500 Quaternary-Holocene volcanoes from the Gegham, Vardenis and Syunik volcanic fields are hosted within pull-apart structures formed by active faults and their segments (Karakhanyan et al., 2002), while tectonic position of the large in volume basalt-dacite Aragats volcano and periphery volcanic plateaus is different and its position away from major fault lines necessitates more complex volcano-tectonic setup. Our detailed volcanological, petrological and geochemical studies provide insight into the nature of such volcanic activity in the region of Ararat Valley. Most magmas, such as those erupted in Armenia are volatile-poor and erupt fairly hot. Here we report newly discovered tephra sequences in Ararat valley, that were erupted from historically active Ararat stratovolcano and provide evidence for explosive eruption of young, mid K2O calc-alkaline and volatile-rich (>4.6 wt% H2O; amph-bearing) magmas. Such young eruptions, in addition to the ignimbrite and lava flow hazards from Gegham and Aragats, present a threat to the >1.4 million people (~ ½ of the population of Armenia). We will report numerical simulations of potential volcanic hazards for the region of Ararat valley near Yerevan that will include including tephra fallout, lava flows and opening of new vents. Connor et al. (2012) J. Applied Volcanology 1:3, 1-19; Karakhanian et al. (2002), JVGR, 113, 319-344; Keskin, M. (2003) Geophys. Res. Lett. 30, 24, 8046.

  20. The Variation of Volcanic Tremor During Active Stage in the 1986 Izu-Oshima Eruption

    NASA Astrophysics Data System (ADS)

    Kurokawa, Aika; Kurita, Kei

    2014-05-01

    Izu-Oshima is one of the most active volcanoes in Japan. The latest eruption of Nov. 1986 exhibited a curious eruption sequence; the strombolian type eruption started on 15 Nov. at the central vent and it had continued for 4 days. Then after it ceased, subplinian type fissure eruptions occurred inside and outside the caldera where several hundreds meters to few kilometers away from the central vent. Lava flows were associated with these two eruption episodes. Petrologically compositions of these two kinds of lava are completely dissimilar; magma from the central vent is basaltic with narrow range of chemical composition, which is almost same as that of the previous stages while magma from the fissures is evolved one with wider variations of composition [Aramaki and Fujii, 1988]. This means that two distinct magma sources, which were chemically separated but mechanically coupled, should have existed prior to the eruption. The most important issue concerning this eruption is how the mechanical interaction between two magma sources took place and evolved. Throughout the eruption sequence, remarkable activities of seismic tremor have been observed. In this presentation we report evolution of tremor sources to characterize the interaction based on the recently recovered seismic records and we propose a reinterpretation of the eruption sequence. We analyzed volcanic tremor in Nov. 1986 on digitized seismic records of 7 stations in the Island. The aim of this analysis is to estimate the movement of two kinds of magma associated with the change of the eruption styles. Firstly root mean square amplitudes of the filtered seismic signals and their spectrum were calculated. The tremor style changed from continuous mode to intermittent, sporadic mode at the period between the summit eruption and the fissure eruptions. The dominant frequency also changed around the same time. Secondly to derive the location of tremor source, Amplitude Inversion Method [Battaglia and Aki, 2003

  1. 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.

  2. Similarities and contrasts in tecto