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1

August 2008 eruption of Kasatochi volcano, Aleutian Islands, Alaska-resetting an Island Landscape  

USGS Publications Warehouse

Kasatochi Island, the subaerial portion of a small volcano in the western Aleutian volcanic arc, erupted on 7-8 August 2008. Pyroclastic flows and surges swept the island repeatedly and buried most of it and the near-shore zone in decimeters to tens of meters of deposits. Several key seabird rookeries in taluses were rendered useless. The eruption lasted for about 24 hours and included two initial explosive pulses and pauses over a 6-hr period that produced ash-poor eruption clouds, a 10-hr period of continuous ash-rich emissions initiated by an explosive pulse and punctuated by two others, and a final 8-hr period of waning ash emissions. The deposits of the eruption include a basal muddy tephra that probably reflects initial eruptions through the shallow crater lake, a sequence of pumiceous and lithic-rich pyroclastic deposits produced by flow, surge, and fall processes during a period of energetic explosive eruption, and a fine-grained upper mantle of pyroclastic-fall and -surge deposits that probably reflects the waning eruptive stage as lake and ground water again gained access to the erupting magma. An eruption with similar impact on the island's environment had not occurred for at least several centuries. Since the 2008 eruption, the volcano has remained quiet other than emission of volcanic gases. Erosion and deposition are rapidly altering slopes and beaches. ?? 2010 Regents of the University of Colorado.

Scott, W.E.; Nye, C.J.; Waythomas, C.F.; Neal, C.A.

2010-01-01

2

Geology and 40Ar/39Ar Geochronology of Akutan Volcano, Eastern Aleutian Islands  

NASA Astrophysics Data System (ADS)

40Ar/39Ar dating and new whole-rock geochemical analyses are used to establish an eruptive chronology for Akutan volcano, Akutan Island, in the eastern Aleutian island arc. Akutan Island (166° W, 54.1° N) is the site of long-lived volcanism and the entire island comprises volcanic rocks as old as 3.3 Ma (Richter et al., 1998, USGS Open-File 98-135). Our current focus is on the 225 km2 western half of the island, which is home to the Holocene active cone, Holocene to latest Pleistocene satellite vents, and underlying middle Pleistocene volcanic basement rocks. Eruptive products span the tholeiitic-calc-alkaline boundary, are medium-K, and range from basalt to dacite. Furnace incremental heating experiments on groundmass separates of 38 samples resulted in 29 40Ar/39Ar ages. The remainder did not yield radiogenic 40Ar contents and are likely Holocene in age. The oldest ages (1251×10 and 1385×12 ka) are from a wedge of flat-lying dissected lavas north of the Holocene cone; these likely represent the upper part of the volcanic basement that underlies the entire island. Above a major unconformity lie basaltic andesite to dacite lavas that range from 765× 4 to 522×8 ka. The eroded remnants of the source volcano for these flows appears to crop out as a series of variably hydrothermally altered breccias and domes 5 km east-northeast of the current summit. A 625 m-tall eroded basaltic center, Lava Peak, sits 6 km northwest of the summit; its deeply incised western flank exposes lava flows and a plug. Two flows are dated at 598×16 and 602×15 ka. A high ridge 1.5 km south of the summit is made of oxidized, mostly andesitic lavas 284-249 ka old; these are presumably the remnants of an eruptive center located near the current cone. Flat Top Peak, 3.5 km southwest of the summit, produced almost exclusively basalts and six dated lavas range from 155×8 to 98×18 ka. Lavas from Flat Top (1065 m asl) are deeply eroded suggesting extensive ice cover during marine isotope stages 4-2. Cascade Bight, an eruptive center 4.5 km southeast of the caldera, has apparently been active in the Holocene as two experiments on basaltic andesite lavas yielded no radiogenic argon. Holocene lavas are also exposed along the upper walls of the ~1,600 yr old summit caldera (Waythomas, 1999, Bull Volc, v. 61, p. 141-161), including dissected 1296 m-tall Akutan Peak (the current summit), as well as low on the north and west flanks of the Akutan edifice. Holocene lavas, including those from Cascade Bight as well as Lava Point satellite vent on the NW coast, all fall along a single tholeiitic, basalt-to-dacite evolutionary trend that has lower K than Pleistocene lavas. Our results show that the focus of volcanism has shifted within the western half of Akutan Island over the last ~600 ka, and that on occasion multiple volcanic centers have been active over the same time period, including within the Holocene.

Coombs, M. L.; Jicha, B. R.

2013-12-01

3

SAR-based Estimation of Glacial Extent and Velocity Fields on Isanotski Volcano, Aleutian Islands, Alaska  

NASA Astrophysics Data System (ADS)

Global studies show that Earth's glaciers are losing mass at increasing rates, creating a challenge for communities that rely on them as natural resources. Field observation of glacial environments is limited by cost and inaccessibility. Optical remote sensing is often precluded by cloud cover and seasonal darkness. Synthetic aperture radar (SAR) overcomes these obstacles by using microwave-frequency electromagnetic radiation to provide high resolution information on large spatial scales and in remote, atmospherically obscured environments. SAR is capable of penetrating clouds, operating in darkness, and discriminating between targets with ambiguous spectral signatures. This study evaluated the efficacy of two SAR Earth observation methods on small (< 7 km2) glaciers in rugged topography. The glaciers chosen for this study lie on Isanotski Volcano in Unimak Island, Aleutian Archipelago, USA. The local community on the island, the City of False Pass, relies on glacial melt for drinking water and hydropower. Two methods were used: (1) velocity field estimation based on Repeat Image Feature Tracking (RIFT) and (2) glacial boundary delineation based on interferometric coherence mapping. NASA Uninhabited Aerial Vehicle SAR (UAVSAR) single-polarized power images and JAXA Advanced Land Observing Satellite Phased Array type L-band SAR (ALOS PALSAR) single-look complex images were analyzed over the period 2008-2011. UAVSAR image pairs were coregistered to sub-pixel accuracy and processed with the Coregistration of Optically Sensed Images and Correlation (COSI-Corr) feature tracking module to derive glacial velocity field estimates. Maximum glacier velocities ranged from 28.9 meters/year to 58.3 meters/year. Glacial boundaries were determined from interferometric coherence of ALOS PALSAR data and subsequently refined with masking operations based on terrain slope and segment size. Accuracy was assessed against hand-digitized outlines from high resolution UAVSAR power images, yielding 83.0% producer's accuracy (errors of omission) and 86.1% user's accuracy (errors of commission). These results represent a refinement of a decades-old entry from the USGS National Hydrography Dataset (NHD). The information gained from this study could strengthen management practices by helping decision makers understand the ecological and economic consequences of glacial change. This procedure could be repeated in similar locations worldwide to provide communities with accurate, quantitative information about their changing glacial resources.

Sousa, D.; Lee, A.; Parker, O. P.; Pressler, Y.; Guo, S.; Osmanoglu, B.; Schmidt, C.

2012-12-01

4

Hazard communication by the Alaska Volcano Observatory Concerning the 2008 Eruptions of Okmok and Kasatochi Volcanoes, Aleutian Islands, Alaska  

NASA Astrophysics Data System (ADS)

The significant explosive eruptions of Okmok and Kasatochi volcanoes in 2008 tested the hazard communication systems at the Alaska Volcano Observatory (AVO) including a rigorous test of the new format for written notices of volcanic activity. AVO's Anchorage-based Operations facility (Ops) at the USGS Alaska Science Center serves as the hub of AVO's eruption response. From July 12 through August 28, 2008 Ops was staffed around the clock (24/7). Among other duties, Ops staff engaged in communicating with the public, media, and other responding federal and state agencies and issued Volcanic Activity Notices (VAN) and Volcano Observatory Notifications for Aviation (VONA), recently established and standardized products to announce eruptions, significant activity, and alert level and color code changes. In addition to routine phone communications with local, national and international media, on July 22, AVO held a local press conference in Ops to share observations and distribute video footage collected by AVO staff on board a U.S. Coast Guard flight over Okmok. On July 27, AVO staff gave a public presentation on the Okmok eruption in Unalaska, AK, 65 miles northeast of Okmok volcano and also spoke with local public safety and industry officials, observers and volunteer ash collectors. AVO's activity statements, photographs, and selected data streams were posted in near real time on the AVO public website. Over the six-week 24/7 period, AVO staff logged and answered approximately 300 phone calls in Ops and approximately 120 emails to the webmaster. Roughly half the logged calls were received from interagency cooperators including NOAA National Weather Service's Alaska Aviation Weather Unit and the Center Weather Service Unit, both in Anchorage. A significant number of the public contacts were from mariners reporting near real-time observations and photos of both eruptions, as well as the eruption of nearby Cleveland Volcano on July 21. As during the 2006 eruption of Augustine volcano in Cook Inlet, Alaska, the number of calls to Ops, emails to the webmaster, and the amount of data served via the AVO website greatly increased during elevated volcanic activity designated by the USGS aviation color code and volcano alert level. Lessons learned include, Ops staffing requirements during periods of high call volume, the need for ash fall hazard information in multiple languages, and the value of real-time observations of remote Aleutian eruptions made by local mariners. An important theme of public inquiries concerned the amount and potential climate impacts of the significant sulfur dioxide gas and ash plumes emitted by Okmok and Kasatochi, including specific questions on the amount of sulfur dioxide discharged during each eruption. The significant plumes produced at the onset of the Okmok and Kasatochi eruptions also had lengthy national and international aviation impacts and yet-to-be resolved hemispherical or possible global, climactic effects.

Adleman, J. N.; Cameron, C. E.; Neal, T. A.; Shipman, J. S.

2008-12-01

5

Diverse deformation patterns of Aleutian volcanoes from InSAR  

USGS Publications Warehouse

Interferometric synthetic aperture radar (InSAR) is capable of measuring ground-surface deformation with centimeter-to-subcentimeter precision at a spatial resolution of tens of meters over an area of hundreds to thousands of square kilometers. With its global coverage and all-weather imaging capability, InSAR has become an increasingly important measurement technique for constraining magma dynamics of volcanoes over remote regions such as the Aleutian Islands. The spatial pattern of surface deformation data derived from InSAR images enables the construction of detailed mechanical models to enhance the study of magmatic processes. This paper summarizes the diverse deformation patterns of the Aleutian volcanoes observed with InSAR and demonstrates that deformation patterns and associated magma supply mechanisms in the Aleutians are diverse and vary between volcanoes. These findings provide a basis for improved models and better understanding of magmatic plumbing systems.

Lu, Z.; Dzurisin, D.; Wicks, C., Jr.; Power, J.

2008-01-01

6

Hazard communication by the Alaska Volcano Observatory Concerning the 2008 Eruptions of Okmok and Kasatochi Volcanoes, Aleutian Islands, Alaska  

Microsoft Academic Search

The significant explosive eruptions of Okmok and Kasatochi volcanoes in 2008 tested the hazard communication systems at the Alaska Volcano Observatory (AVO) including a rigorous test of the new format for written notices of volcanic activity. AVO's Anchorage-based Operations facility (Ops) at the USGS Alaska Science Center serves as the hub of AVO's eruption response. From July 12 through August

J. N. Adleman; C. E. Cameron; T. A. Neal; J. S. Shipman

2008-01-01

7

Water in Aleutian Arc Volcanoes  

NASA Astrophysics Data System (ADS)

In the past decade, baseline data have been obtained on pre-eruptive water contents for several volcanic arcs worldwide. One surprising observation is that parental magmas contain ~ 4 wt% H2O on average at each arc worldwide [1]. Within each arc, the variation from volcano to volcano is from 2 to 6 w% H2O, with few exceptions. The similar averages at different arcs are unexpected given the order of magnitude variations in the concentration of other slab tracers. H2O is clearly different from other tracers, however, being both a major driver of melting in the mantle and a major control of buoyancy and viscosity in the crust. Some process, such as mantle melting or crustal storage, apparently modulates the water content of mafic magmas at arcs. Mantle melting may deliver a fairly uniform product to the Moho, if the wet melt process includes a negative feedback. On the other hand, magmas with variable water content may be generated in the mantle, but a crustal filter may lead to magma degassing up to a common mid-to-upper crustal storage region. Testing between these two end-member scenarios is critical to our understanding of subduction dehydration, global water budgets, magmatic plumbing systems, melt generation and eruptive potential. The Alaska-Aleutian arc is a prime location to explore this fundamental problem in the subduction water cycle, because active volcanoes vary more than elsewhere in the world in parental H2O contents (based on least-degassed, mafic melt inclusions hosted primarily in olivine). For example, Shishaldin volcano taps magma with among the lowest H2O contents globally (~ 2 wt%) and records low pressure crystal fractionation [2], consistent with a shallow magma system (< 1 km bsl). At the other extreme, Augustine volcano is fed by a mafic parent that contains among the highest H2O globally (~ 7 wt%), and has evolved by deep crystal fractionation [2], consistent with a deep magma system (~ 14 km bsl). Do these magmas stall at different depths because of different crustal regimes or because of different primary magma compositions? Do magmas degas until they physically stall, or do they stall when they start to degas? One test of this is whether H2O contents correlate with tracers from the subduction zone that are not fractionated easily during crystal fractionation or degassing. We find a strong negative correlation between H2O/Ce (based on the maximum H2O measured in a given inclusion population) and Nb/Ce in eight Aleutian volcanoes, which is well explained by variable amounts of a slab fluid, but would be fortuitous, or strongly disturbed, if major degassing took place in the crust during magma ascent. Thus, geochemical data point to a strong slab-mantle control on H2O, that may set the future course of magma ascent, storage and eruption. Integrated studies are needed to test this prediction, including seismic imaging and geodetic response of the volcanic system, from the slab to the surface. [1] Plank, et al. (2011) Min. Mag. 75: 1648. [2] Zimmer, et al. (2010) J. Pet. 51: 2411-2444.

Plank, T.; Zimmer, M. M.; Hauri, E. H.

2011-12-01

8

Magma mixing revealed by bulk-rock, phenocryst and microlite compositions in basaltic andesite samples from the 2008 eruption of Kasatochi Island volcano, central Aleutian Islands, Alaska  

NASA Astrophysics Data System (ADS)

The 7-8 August, 2008 eruption of Kasatochi Volcano, located in the central Aleutians Islands, Alaska, produced compositionally heterogeneous basaltic andesite (52-55 wt% SiO2). Bulk compositions of basaltic andesite samples lie along linear trends in element-element variation diagrams, while plagioclase, titanomagnetite and amphibole phenocrysts from the basaltic andesite are compositionally bimodal. Titanomagnetite phenocrysts are divided compositionally into low-Ti (~5 wt. % TiO2) and high-Ti (~8-10 wt. % TiO2) groups, while amphibole phenocrysts are divided into low-Al (~10-12 wt. % Al2O3) and high-Al (~14-16 wt. % Al2O3) populations. The first plagioclase population (Group 1), which is volumetrically dominant, consists of oscillatory-zoned phenocrysts that trend towards comparatively low-Ca rims (An55-65). These phenocrysts are normally zoned, with discrete spikes up to ~An90. The second population (Group 2) is more calcic with most rims up to ~An90, yet a subpopulation exists where rims sharply decrease in calcium content, reaching as low as ~An60, but are otherwise texturally and compositionally homogeneous (~An90). In addition to phenocryst compositions, plagioclase microlites are normally zoned, > 50% have rim compositions > An80, and they are typically more calcic than Group 1 rims. The most likely explanation for the compositional diversity in the bulk and phenocrysts is mixing between mafic and silicic end members, leading to linear mixing trends in the basaltic andesite bulk compositions. Group 1 plagioclase phenocrysts, low-Al amphibole and high-Ti titanomagnetite likely derived from the silicic mixing end member, while the mafic mixing end member contributed the Group 2 plagioclase phenocrysts, high-Al amphibole and low-Ti titanomagnetite. Plagioclase-liquid thermometry indicates that the mafic end member was likely hotter (900-1050 °C) than the silicic end member (800-950 °C). Microlites are frequently assumed to form due to decompression and magmatic degassing during ascent and eruption. However, in the case of Kasatochi, the mixing of these two magmas prior to eruption, and the temperature difference between them, led to undercooling of the mafic end member, and the nucleation of the anomalously high-An microlites in the mafic end member's more calcic liquids.

Neill, O. K.; Larsen, J. F.; Izbekov, P. E.; Nye, C. J.

2013-12-01

9

Aleutian Island prehistory: Living in insular extremes  

Microsoft Academic Search

Peoples of the Aleutian Islands lived under a number of stressful environmental constraints, including extreme isolation, volcanic eruptions, seismic activity (including tsunamis), frequent storms, rough seas, gale?force winds, frequent fog and precipitation, and an exclusive marine diet. Nevertheless, the Aleutian Islands supported a large maritime population during late prehistoric times. Cultural adaptations to these conditions included the use of relatively

Allen P. McCartney; Douglas W. Veltre

1999-01-01

10

Holocene Tephra Layers on Adak Island in the West-Central Aleutian Islands, Alaska  

NASA Astrophysics Data System (ADS)

Adak Island, Aleutian Islands, Alaska is covered with Holocene sequences of soil-tephra complexes. Tephra layers are useful for establishing a chronographic framework on the island. Black (1976) thought that the three conspicuous tephra deposits (Main, Intermediate and Sandwich) erupted from Kanaga volcano. Waythomas et al. (2001), however, inferred that a possible source volcano of the tephras was Mount Moffett, Adak Island. We conducted a tephrostratigraphic study on the island to re-evaluate the chronological framework and to determine the sources of the tephras. Chemical compositions of volcanic glass were determined by electron probe micro-analysis (EPMA). Radiocarbon dates were determined using accelerator mass spectrometry (AMS). The three tephra layers increase in thickness from south to north. Among them, Intermediate and Sandwich tephras contain fresh lithic fragments. Thickness and maximum diameter of lithic fragments (ML) suggests that their source was Adagdak volcano or a now submerged volcano nearby. The presence of a lava dome and crater rim in the northern part of Adagdak volcano makes it a likely candidate for the source of the tephras. Eruptions of the Intermediate, Sandwich, YBO and Forty Year tephra deposits were dated to approximately 7.2, 4.7, 3.6 and 0.4 cal ka BP, respectively.

Okuno, M.; Wada, K.; Gualtieri, L. M.; Nakamura, T.; Sarata, B.; Torii, M.

2011-12-01

11

Bimodal geochemical evolution at Sheveluch stratovolcano, Kamchatka, Russia: Consequence of a complex subduction at the junction of the Kuril Kamchatka and Aleutian island arcs  

Microsoft Academic Search

Adak-type andesites erupted as domes at Sheveluch volcano (Kamchatka Russia) have been associated with partial melting of the Pacific plate subducting under Kamchatka. The heat for melting at the plate edge has been proposed to be provided by an asthenosphere upwelling north of the junction of Kuril Kamchatka and Aleutian island arcs. However, Sheveluch volcano is composed of two volcano-stratigraphic

Carmelo Ferlito

2011-01-01

12

Reunion Island Volcano Erupts  

NASA Technical Reports Server (NTRS)

On January 16, 2002, lava that had begun flowing on January 5 from the Piton de la Fournaise volcano on the French island of Reunion abruptly decreased, marking the end of the volcano's most recent eruption. These false color MODIS images of Reunion, located off the southeastern coast of Madagascar in the Indian Ocean, were captured on the last day of the eruption (top) and two days later (bottom). The volcano itself is located on the southeast side of the island and is dark brown compared to the surrounding green vegetation. Beneath clouds (light blue) and smoke, MODIS detected the hot lava pouring down the volcano's flanks into the Indian Ocean. The heat, detected by MODIS at 2.1 um, has been colored red in the January 16 image, and is absent from the lower image, taken two days later on January 18, suggesting the lava had cooled considerably even in that short time. Earthquake activity on the northeast flank continued even after the eruption had stopped, but by January 21 had dropped to a sufficiently low enough level that the 24-hour surveillance by the local observatory was suspended. Reunion is essentially all volcano, with the northwest portion of the island built on the remains of an extinct volcano, and the southeast half built on the basaltic shield of 8,630-foot Piton de la Fournaise. A basaltic shield volcano is one with a broad, gentle slope built by the eruption of fluid basalt lava. Basalt lava flows easily across the ground remaining hot and fluid for long distances, and so they often result in enormous, low-angle cones. The Piton de la Fournaise is one of Earth's most active volcanoes, erupting over 150 times in the last few hundred years, and it has been the subject of NASA research because of its likeness to the volcanoes of Mars. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

2002-01-01

13

Criconematina (nematoda: tylenchida) from the Aleutian Islands  

SciTech Connect

A new genus (Cerchnotocriconema) and three new species (C. psephinum, Hemicycliophora anchitkaensis, and Paratylenchus amundseni) are described from Adak and Amchitka Islands in the Aleutian chain. The new genus differs from all other criconematid genera in having irregular, convex sculpturing consisting of small, oval plates on the anterior and posterior regions of each annule, with the mid-annular region minutely punctate or dentate. H. amchitkaensis n. sp. resembles H. sinilis Thorne and H. zuckermani Brzeski, but has only one head annule, instead of two. P. amundseni n. sp., which has a stylet 17 to 19 ..mu..m long, is similar to P. tatea Wu and Townsend and P. labiosus Anderson and Kimpinski, but differs by the presence of males and the possession of conoid-truncate lip region, functional spermatheca, and long male tail (c = 8.5 to 9.5). Seriespinula seymouri Wu (Mehta and Raski), Nothocriconema longulum (Gunhold) De Grisse and Loof, and Macroposthonia xenoplax (Raski) De Grisse and Loof are also reported from the islands.

Bernard, E.C.

1982-01-01

14

Geothermal Drilling In The Aleutians Reveals New Insights On Volcanic History Of Akutan Volcano  

NASA Astrophysics Data System (ADS)

In 2010, two thermal gradient wells were drilled in the Hot Springs Bay Valley geothermal resource area on Akutan Island, Alaska. Well TG-2 was drilled in the region of hot springs occurrence near the mouth of the valley and reached a depth of 253 m (833'). Well TG-4 was drilled near the head of the valley, closer to the current volcano, and reached a depth of 457 m (1500'). The core recovered from these wells represent the only drill core extracted from an Aleutian volcano to date and reveals an important missing piece of the surficial eruptive and erosional history of the volcano that cannot be determined from surface evaluation of recent eruptive deposits laid down on 500 ka bedrock outcrops. No intrusive rocks were encountered, indicating a rich history of surficial activity. The core is dominated (46% of recovered core) by basaltic lava flow deposits (49-52 wt% SiO2), consistent with other observed deposits on the island. These flows are interspersed with andesite lava flows (20% of core, ranging from 53-58 wt% SiO2), abundant mass wasting deposits (27% of core) and a series of ash and ash tuff layers that are some of the most silicic deposits identified at Akutan (up to 66 wt% SiO2). Ash deposits are restricted to the upper 125 m in both wells, are significantly thicker in TG-4, and are difficult to correlate between the two wells. Mass wasting deposits are diverse, including a subset characterized by matrix-supported heterolithologic breccias enclosed in a crystalline basaltic lava host. A shell-rich zone at 273 meters depth indicates that the transition between sub-marine and sub-aerial activity may be recorded in the core.

Stelling, P. L.

2013-12-01

15

AVIAN MORTALITY ASSOCIATED WITH A VOLCANIC GAS SEEP AT KISKA ISLAND, ALEUTIAN ISLANDS, ALASKA  

E-print Network

AVIAN MORTALITY ASSOCIATED WITH A VOLCANIC GAS SEEP AT KISKA ISLAND, ALEUTIAN ISLANDS, ALASKA gases such as carbon monoxide (CO), and carbon dioxide (CO2) from steam vents, fumaroles, and gas seeps-Petrels (Oceanodroma furcata) were found near a CO2 seep one year following the eruption (J. C. Williams, pers. comm

Jones, Ian L.

16

76 FR 35781 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Western Aleutian Islands golden king crab (WAG) fishery...1)(i) of this section. All information fields...Western Aleutian Islands golden king crab West regional...2)(i) of this section. (ii) The Regional...Western Aleutian Islands golden king crab West...

2011-06-20

17

76 FR 8700 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Western Aleutian Islands golden king crab (WAG) fishery...1)(i) of this section. All information fields...Western Aleutian Islands golden king crab West regional...2)(i) of this section. (ii) The Regional...Western Aleutian Islands golden king crab West...

2011-02-15

18

50 CFR Figure 8 to Part 679 - Aleutian Islands Chinook Salmon Savings Area  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Aleutian Islands Chinook Salmon Savings Area 8 Figure 8 to Part 679 Wildlife and Fisheries...Fig. 8 Figure 8 to Part 679—Aleutian Islands Chinook Salmon Savings Area ER30AU10.000 [75 FR 53069, Aug. 30,...

2012-10-01

19

50 CFR Figure 8 to Part 679 - Aleutian Islands Chinook Salmon Savings Area  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Aleutian Islands Chinook Salmon Savings Area 8 Figure 8 to Part 679 Wildlife and Fisheries...Fig. 8 Figure 8 to Part 679—Aleutian Islands Chinook Salmon Savings Area ER30AU10.000 [75 FR 53069, Aug. 30,...

2014-10-01

20

50 CFR Figure 8 to Part 679 - Aleutian Islands Chinook Salmon Savings Area  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Aleutian Islands Chinook Salmon Savings Area 8 Figure 8 to Part 679 Wildlife and Fisheries...Fig. 8 Figure 8 to Part 679—Aleutian Islands Chinook Salmon Savings Area ER30AU10.000 [75 FR 53069, Aug. 30,...

2013-10-01

21

50 CFR Figure 8 to Part 679 - Aleutian Islands Chinook Salmon Savings Area  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Aleutian Islands Chinook Salmon Savings Area 8 Figure 8 to Part 679 Wildlife and Fisheries...Fig. 8 Figure 8 to Part 679—Aleutian Islands Chinook Salmon Savings Area ER30AU10.000 [75 FR 53069, Aug. 30,...

2010-10-01

22

50 CFR Figure 8 to Part 679 - Aleutian Islands Chinook Salmon Savings Area  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Aleutian Islands Chinook Salmon Savings Area 8 Figure 8 to Part 679 Wildlife and Fisheries...Fig. 8 Figure 8 to Part 679—Aleutian Islands Chinook Salmon Savings Area ER30AU10.000 [75 FR 53069, Aug. 30,...

2011-10-01

23

50 CFR Table 23 to Part 679 - Aleutian Islands Coral Habitat Protection Areas  

Code of Federal Regulations, 2014 CFR

... 2014-10-01 2014-10-01 false Aleutian Islands Coral Habitat Protection Areas 23 Table 23 to Part 679 Wildlife...Pt. 679, Table 23 Table 23 to Part 679—Aleutian Islands Coral Habitat Protection Areas Area No. Name Latitude...

2014-10-01

24

50 CFR Table 23 to Part 679 - Aleutian Islands Coral Habitat Protection Areas  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Aleutian Islands Coral Habitat Protection Areas 23 Table 23 to Part 679 Wildlife and...Table 23 Table 23 to Part 679—Aleutian Islands Coral Habitat Protection Areas Area No. Name Latitude...

2010-10-01

25

50 CFR Table 23 to Part 679 - Aleutian Islands Coral Habitat Protection Areas  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Aleutian Islands Coral Habitat Protection Areas 23 Table 23 to Part 679 Wildlife and...Table 23 Table 23 to Part 679—Aleutian Islands Coral Habitat Protection Areas Area No. Name Latitude...

2013-10-01

26

50 CFR Table 23 to Part 679 - Aleutian Islands Coral Habitat Protection Areas  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Aleutian Islands Coral Habitat Protection Areas 23 Table 23 to Part 679 Wildlife and...Table 23 Table 23 to Part 679—Aleutian Islands Coral Habitat Protection Areas Area No. Name Latitude...

2011-10-01

27

50 CFR Table 23 to Part 679 - Aleutian Islands Coral Habitat Protection Areas  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Aleutian Islands Coral Habitat Protection Areas 23 Table 23 to Part 679 Wildlife and...Table 23 Table 23 to Part 679—Aleutian Islands Coral Habitat Protection Areas Area No. Name Latitude...

2012-10-01

28

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

USGS Publications Warehouse

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.

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

2014-01-01

29

A burial cave in the western Aleutian Islands, Alaska.  

PubMed

During the 1998 field season, the Western Aleutians Archaeological and Paleobiological Project (WAAPP) team located a cave in the Near Islands, Alaska. Near the entrance of the cave, the team identified work areas and sleeping/sitting areas surrounded by cultural debris and animal bones. Human burials were found in the cave interior. In 2000, with permission from The Aleut Corporation, archaeologists revisited the site. Current research suggests three distinct occupations or uses for this cave. Aleuts buried their dead in shallow graves at the rear of the cave circa 1,200 to 800 years ago. Aleuts used the front of the cave as a temporary hunting camp as early as 390 years ago. Finally, Japanese and American military debris and graffiti reveal that the cave was visited during and after World War II. Russian trappers may have also taken shelter there 150 to 200 years ago. This is the first report of Aleut cave burials west of the Delarof Islands in the central Aleutians. PMID:21755641

West, Dixie; Lefèvre, Christine; Corbett, Debra; Crockford, Susan

2003-01-01

30

A photographic guide to some vascular plants of Kiska Island, Aleutian Islands, Alaska  

E-print Network

Islands, Alaska, USA. Kiska supports a variety of habitats for vegetation, including seacoasts and beaches. With respect to plant biogeography, Kiska lies in the central Aleutian zone of depressed diversity, lacking. Stanford University Press, Stanford, California, 1008 pp. #12;Habitats for plants at Kiska Sea beaches

Jones, Ian L.

31

Marine Ornithology 37: 9395 (2009) Birds of the Aleutian Islands, Alaska is a monumental work on the  

E-print Network

93 Marine Ornithology 37: 93­95 (2009) Birds of the Aleutian Islands, Alaska is a monumental work, exhaustively researched, rigorously produced and edited ornithological monograph on all Aleutian birds, a data

Jones, Ian L.

32

Non-volcanic tremor in the Aleutian Islands captured by a mini-seismic array  

NASA Astrophysics Data System (ADS)

The Aleutian Islands are an interesting place to study because of the presence of abundant seismicity, both subduction and volcano related. In addition to regular earthquakes, the Islands host both volcanic and non-volcanic tremor. To capture this rich variety of seismicity, we designed and installed a mini-seismic array on Akutan Island in 2012. Akutan is located in the eastern Aleutians just off the tip of the Alaska Peninsula, near the eastern edge of the 1957 Mw8.6 earthquake rupture zone. A mini-seismic array is particularly useful in this logistically challenging environment where land cover is limited. We recorded and analyzed about 2 months of data, and found both volcanic and non-volcanic events. Here we focus on non-volcanic tremor and its characteristics as captured by the Akutan array. Akutan Island and the surrounding area turn out to be prolific producers of tremor. An automatic beam-backprojection algorithm [Ghosh et al., 2009] detects almost daily tremor activity with durations ranging from several minutes to more than 3.5 hours. On average, beam-backprojection detects 1.3 hours of tremor activity per day and in total, it detects about 5 times more duration of tremor activity compared to a visual check for tremor signal using the existing seismic network. We observe tremor sources both west and east of the Akutan array. Western sources are the most active ones and their slowness parameters are consistent with the locations of low-frequency earthquakes detected by Brown et al., 2013. The eastern source area has not been identified previously and appears to be active for only a few times during this study, but shows continuous activity for several hours. In addition, we observe temporal evolution of slowness parameters consistent with steady tremor migration. Moreover, low frequency earthquakes with impulsive body wave phases are identified within the tremor signal. They show S-minus-P times consistent with their being located at the model plate interface [Hayes et al., 2012]. The mini-seismic array combined with a beam-backprojection algorithm is providing an enhanced image of tremor activity in the Aleutian Islands, by greatly improving the level of detection and resolution of locations. This would enable us to perform more intricate analyses of tectonic behavior of slow earthquake and tremor, their possible interaction with regular earthquakes and therefore help better understand the subduction dynamics of the study area. Comparison between tremor duration detected by the beam-backprojection and existing seismic network. On average, beam-backprojection detected ~5 times more duration of tremor activity compared to the detection using existing network.

Ghosh, A.; Prejean, S. G.

2013-12-01

33

75 FR 59687 - Proposed Information Collection; Comment Request; Alaska Region Bering Sea & Aleutian Islands...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Aleutian Islands (BSAI) Crab Economic Data Reports AGENCY: National Oceanic...communities and monitors the ``economic stability for harvesters...CR Program's mandatory economic data collection report (EDR) used to assess...

2010-09-28

34

Volcanoes in the Infrared  

NSDL National Science Digital Library

In this video adapted from KUAC-TV and the Geophysical Institute at the University of Alaska, Fairbanks, satellite imagery and infrared cameras are used to study and predict eruptions of volcanoes in the Aleutian Islands, Alaska.

2008-11-04

35

Modeling potential tsunami sources for deposits near Unalaska Island, Aleutian Islands  

NASA Astrophysics Data System (ADS)

In regions with little seismic data and short historical records of earthquakes, we can use preserved tsunami deposits and tsunami modeling to infer if, when and where tsunamigenic earthquakes have occurred. The Aleutian-Alaska subduction zone in the region offshore of Unalaska Island is one such region where the historical and paleo-seismicity is poorly understood. This section of the subduction zone is not thought to have ruptured historically in a large earthquake, leading some to designate the region as a seismic gap. By modeling various historical and synthetic earthquake sources, we investigate whether or not tsunamis that left deposits near Unalaska Island were generated by earthquakes rupturing through Unalaska Gap. Preliminary field investigations near the eastern end of Unalaska Island have identified paleotsunami deposits well above sea level, suggesting that multiple tsunamis in the last 5,000 years have flooded low-lying areas over 1 km inland. Other indicators of tsunami inundation, such as a breached cobble beach berm and driftwood logs stranded far inland, were tentatively attributed to the March 9, 1957 tsunami, which had reported runup of 13 to 22 meters on Umnak and Unimak Islands, to the west and east of Unalaska. In order to determine if tsunami inundation could have reached the runup markers observed on Unalaska, we modeled the 1957 tsunami using GeoCLAW, a numerical model that simulates tsunami generation, propagation, and inundation. The published rupture orientation and slip distribution for the MW 8.6, 1957 earthquake (Johnson et al., 1994) was used as the tsunami source, which delineates a 1200 km long rupture zone along the Aleutian trench from Delarof Island to Unimak Island. Model results indicate that runup and inundation from this particular source are too low to account for the runup markers observed in the field, because slip is concentrated in the western half of the rupture zone, far from Unalaska. To ascertain if any realistic, earthquake-generated tsunami could account for the observed runup, we modeled tsunami inundation from synthetic MW 9.2 earthquakes rupturing along the trench between Atka and Unimak Islands, which indicate that the deposit runup observed on Unalaska is possible from a source of this size and orientation. Further modeling efforts will examine the April 1, 1946 Aleutian tsunami, as well as other synthetic tsunamigenic earthquake sources of varying size and location, which may provide insight into the rupture history of the Aleutian-Alaska subduction zone, especially in combination with more data from paleotsunami deposits. Johnson, Jean M., Tanioka, Yuichiro, Ruff, Larry J., Satake, Kenji, Kanamori, Hiroo, Sykes, Lynn R. "The 1957 great Aleutian earthquake." Pure and Applied Geophysics 142.1 (1994): 3-28.

La Selle, S.; Gelfenbaum, G. R.

2013-12-01

36

Three new species of heteroderoidea (nematoda) from the Aleutian Islands  

SciTech Connect

Three new species of Heteroderoidea are described from Adak and Amchitka Islands in the Aleutian chain. Second-stage juveniles of Thecavermiculatus crassicrustata, n. sp., differ from those of T. gracililancea Robbins by having longer stylets (40 to 50 ..mu..m vs 19 to 22 ..mu..m). The female of T. crassicrustata has a longer neck, a more posterior excretory pore, and lacks a posterior protuberance. Meloidodera eurytyla, n. sp., differs from other Meloidodera spp. in that second-stage juveniles have longer stylets (32 to 35 ..mu..m) and much more massive styletknobs, while males have a longitudinally striated basal head annule. Meloidogyne subarctica, n. sp., can be separated from other Meloidogyne spp. by combinations of the following characteristics: perineal pattern with large oval areas in the tail region devoid of striae, arch with few unbroken striae; female excretory pore 1.5 to 2.5 x the stylet length from the anterior end; haploid chromosome number = 18; the spermatheca filled with sperm; stylet length of second-stage juveniles 13.5 to 15.4 ..mu..m.

Bernard, E.C.

1981-10-01

37

Hair methylmercury levels of mummies of the Aleutian Islands, Alaska  

SciTech Connect

Ancient human hair specimens can shed light on the extent of pre-historic exposures to methylmercury and provide valuable comparison data with current-day exposures, particularly for Indigenous Peoples who continue to rely upon local traditional food resources. Human hair from ancient Aleutian Island Native remains were tested for total and methylmercury (Hg, MeHg) and were radiocarbon dated. The remains were approximately 500 years old (1450 A.D.). For four adults, the mean and median total hair mercury concentration was 5.8 ppm (SD=0.9). In contrast, MeHg concentrations were lower with a mean of 1.2 ppm (SD=1.8) and a median of 0.54 ppm (0.12-3.86). For the five infants, the mean and median MeHg level was 1.2 ppm (SD=1.8) and 0.20 ppm (0.007-4.61), respectively. Segmental analyses showed variations in MeHg concentrations in 1-cm segments, consistent with fluctuations in naturally occurring exposure to mercury through dietary sources. The levels are comparable to or lower than those found in fish and marine mammal-eating populations today who rely far less on subsistence food than pre-historic humans. The findings are, therefore, compatible with increased anthropogenic release of trace metals during the past several centuries.

Egeland, G.M. [Centre for Indigenous Peoples' Nutrition and Environment (CINE), McGill University, 21, 111 Lakeshore Road, Ste-Anne-de-Bellevue, QC, H9X 3V9 (Canada)], E-mail: grace.egeland@mcgill.ca; Ponce, Rafael [Toxicology, Amgen WA, 1201 Amgen Court West, Seattle, WA 981119 (United States)], E-mail: rponce@amgen.com; Bloom, Nicolas S. [Studio Geochimica, 4744 University Way NE, Seattle, WA 98105 (United States)], E-mail: nicolasb@nickslab.org; Knecht, Rick [Department of Alaska Native and Rural Development, University of Alaska, Fairbanks, 221 E. Northern Lights Boulevard, Suite 213, Anchorage, AK 99508-4143 (United States)], E-mail: Knecht@palaunet.com; Loring, Stephen [Arctic Studies Center, Smithsonian Institution, National Museum of Natural History, P.O. Box 37012, Washington, DC 20013-7012 (United States)], E-mail: lorings@si.edu; Middaugh, John P. [Nevada Department of Health and Human Services, 4150 Technology Way, Carson City, NV 89706 (United States)], E-mail: middaugh@SNHDMAIL.ORG

2009-04-15

38

Three New Species of Heteroderoidea (Nematoda) from the Aleutian Islands  

PubMed Central

Three new species of Heteroderoidea are described from Adak and Amchitka Islands in the Aleutian chain. Second-stage juveniles of Thecavermiculatus crassicrustata, n. sp., differ from those of T. gracililancea Robbins by having longer stylets (40-45 ?m vs 19-22 ?m). The female of T. crassicrustata has a longer neck, a more posterior excretory pore, and lacks a posterior protuberance. Meloidodera eurytyla, n. sp., differs from other Meloidodera spp. in that second-stage juveniles have longer stylets (32-35 ?m) and much more massive stylet knobs, while males have a longitudinally striated basal head annule. Meloidogyne subarctica, n. sp., can be separated from other Meloidogyne spp. by combinations of the following characteristics: perineal pattern with large oval areas in the tail region devoid of striae, arch with few unbroken striae; female excretory pore 1.5-2.5 × the stylet length from the anterior end; haploid chromosome number = 18; the spermatheca filled with sperm; stylet length of second-stage juveniles 13.5-15.4 ?m. PMID:19300796

Bernard, E. C.

1981-01-01

39

50 CFR Table 24 to Part 679 - Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic...  

Code of Federal Regulations, 2013 CFR

...false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table...679—Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing...

2013-10-01

40

50 CFR Table 24 to Part 679 - Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic...  

Code of Federal Regulations, 2012 CFR

...false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table...679—Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing...

2012-10-01

41

50 CFR Table 24 to Part 679 - Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic...  

Code of Federal Regulations, 2010 CFR

...false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table...679—Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing...

2010-10-01

42

50 CFR Table 24 to Part 679 - Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic...  

Code of Federal Regulations, 2011 CFR

...false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table...679—Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing...

2011-10-01

43

The tsunamigenic earthquake of April 1, 1946, in the Fox Islands (Aleutian island arc)  

NASA Astrophysics Data System (ADS)

An interpretation of the type, size, and location of the source of the Aleutian earthquake on April 1, 1946, which was characterized by the highest intensity ( I = 4), is proposed. The earthquake source is a subvertical reverse fault striking along the island arc and dipping at an angle of 85° toward the deep-sea trench. The reverse fault is located in the lower part of the island slope, within the eastern termination of the Aleutian terrace. The western end of the reverse fault is located in the area of the Krenitsyn Islands (? ˜ 165°W), where the pattern of isobaths changes, and an abrupt widening of the shelf part of the Fox Islands takes place. Large ( M S ˜ 7) shocks, preceding the 1946 earthquake, occurred here in 1940, 1942, and 1944. Structural inhomogeneities in the island slope in the area of the Sanak Islands (? ˜ 162°W) determine the eastern edge of the source-reverse fault, whose length within the specified boundaries is about 200 km. The mean magnitude of the earthquake corresponding to such a source is ˜8.3. According to the regular relation between the rupture length and the mean movement, the vertical displacement of the ocean floor in the source region could attain 5-6 m. A significant vertical displacement of the ocean floor over its large length (˜200 km) was responsible for the high tsunamigenic ability of this earthquake. A favorable combination in the source area of the topographic and other conditions necessary for the tsunami formation could additionally contribute to an increase in the intensity of the tsunami. The earthquake of April 1, 1946, in the Fox Islands, as well as the tsunamigenic earthquakes of March 9, 1957, in the Andreanof Islands and February 4, 1965, in the Rat Islands, does not belong to the class of “slow” earthquakes.

Balakina, L. M.; Moskvina, A. G.

2010-06-01

44

76 FR 55276 - Fisheries of the Exclusive Economic Zone Off Alaska; Octopus in the Bering Sea and Aleutian Islands  

Federal Register 2010, 2011, 2012, 2013, 2014

...the Exclusive Economic Zone Off Alaska; Octopus in the Bering Sea and Aleutian Islands...SUMMARY: NMFS is prohibiting retention of octopus in the Bering Sea and Aleutian Islands...because the 2011 total allowable catch of octopus in the BSAI has been reached....

2011-09-07

45

Spawning phenology and geography of Aleutian Islands and eastern Bering Sea Pacific cod (Gadus macrocephalus)  

NASA Astrophysics Data System (ADS)

Pacific cod (Gadus macrocephalus) is an economically and ecologically important species in the southeastern Bering Sea and Aleutian Islands, yet little is known about the spawning dynamics of Pacific cod in these regions. To address this knowledge gap, we applied a gross anatomical maturity key for Pacific cod to describe temporal and spatial patterns of reproductive status over three winter spawning seasons: 2005, 2006, and 2007. Maturity status of female Pacific cod was assessed by fishery observers during sampling of commercial catches and used to construct maps showing spawning activity in the Bering Sea and Aleutian Islands. Most spawning activity was observed on the Bering Sea shelf and Aleutian Island plateaus between 100 and 200 m depth. Data for those days when a high percentage of spawning stage fish were observed were used to identify areas with concentrations of spawning fish. Spawning concentrations were identified north of Unimak Island, in the vicinity of the Pribilof Islands, at the shelf break near Zhemchug Canyon, and adjacent to islands in the central and western Aleutian Islands along the continental shelf. The spawning season was found to begin in the last days of February or early March and extend through early to mid-April. Variation in spawning time (averaging ~10 days between years) may have been associated with a change from warm (2005) to cold (2007) climate conditions during the study period. Our information on Pacific cod spawning patterns will help inform fishery management decisions, models of spawning and larval dispersal and the spatial structure of the stock.

Neidetcher, Sandra K.; Hurst, Thomas P.; Ciannelli, Lorenzo; Logerwell, Elizabeth A.

2014-11-01

46

Abundance, trends and distribution of baleen whales off Western Alaska and the central Aleutian Islands  

Microsoft Academic Search

Large whales were extensively hunted in coastal waters off Alaska, but current distribution, population sizes and trends are poorly known. Line transect surveys were conducted in coastal waters of the Aleutian Islands and the Alaska Peninsula in the summer of 2001–2003. Abundances of three species were estimated by conventional and multiple covariate distance sampling (MCDS) methods. Time series of abundance

Alexandre N. Zerbini; Janice M. Waite; Jeffrey L. Laake; Paul R. Wade

2006-01-01

47

Enormous Tsunamis in Hawaii from Great Earthquakes in the Aleutians Islands  

E-print Network

Enormous Tsunamis in Hawaii from Great Earthquakes in the Aleutians Islands Rhett Butler Hawaii earthquake of March 11, 2011 was much larger than anticipated, and generated a devastating tsunami along from Mw 8.6 earthquakes in 1946 and 1957. Since Tohoku, my research has focused on determining

Frandsen, Jannette B.

48

Chemical versus temporal controls on the evolution of tholeiitic and calc-alkaline magmas at two volcanoes in the Alaska-Aleutian arc  

USGS Publications Warehouse

The Alaska-Aleutian island arc is well known for erupting both tholeiitic and calc-alkaline magmas. To investigate the relative roles of chemical and temporal controls in generating these contrasting liquid lines of descent we have undertaken a detailed study of tholeiitic lavas from Akutan volcano in the oceanic A1eutian arc and calc-alkaline products from Aniakchak volcano on the continental A1askan Peninsula. The differences do not appear to be linked to parental magma composition. The Akutan lavas can be explained by closed-system magmatic evolution, whereas curvilinear trace element trends and a large range in 87 Sr/86 Sr isotope ratios in the Aniakchak data appear to require the combined effects of fractional crystallization, assimilation and magma mixing. Both magmatic suites preserve a similar range in 226 Ra-230 Th disequilibria, which suggests that the time scale of crustal residence of magmas beneath both these volcanoes was similar, and of the order of several thousand years. This is consistent with numerical estimates of the time scales for crystallization caused by cooling in convecting crustal magma chambers. During that time interval the tholeiitic Akutan magmas underwent restricted, closed-system, compositional evolution. In contrast, the calc-alkaline magmas beneath Aniakchak volcano underwent significant open-system compositional evolution. Combining these results with data from other studies we suggest that differentiation is faster in calc-alkaline and potassic magma series than in tholeiitic series, owing to a combination of greater extents of assimilation, magma mixing and cooling.

George, R.; Turner, S.; Hawkesworth, C.; Bacon, C.R.; Nye, C.; Stelling, P.; Dreher, S.

2004-01-01

49

Oxygen isotopic evidence for meteoric water interaction with the Captains Bay pluton, Aleutian Islands  

Microsoft Academic Search

Low 18O\\/16O values have been found in rocks from the Captains Bay pluton and surrounding country rocks on Unalaska Island in the Aleutian Islands. The pluton is surrounded by a metamorphic aureole in which the country rocks have been domed, faulted and chaotically fractured. Samples with lower 18O\\/16O values (delta 18O = -4.1 to +2.70\\/00, SMOW) commonly have interstitial micrographic

Michael R. Perfit; James R. Lawrence

1979-01-01

50

Contrasting timescales of crystallization and magma storage beneath the Aleutian Island arc  

Microsoft Academic Search

Geologic, chronologic, and U–Th isotope data from Pleistocene–Recent basaltic to rhyolitic lavas and their phenocrysts constrain the long-term evolution of magmatic processes at Seguam Island, Aleutian Island arc, and suggest a model in which erupted magmas were derived from a single, deep seated reservoir for ?130 kyrs of its eruptive history. The monotonic evolution in (230Th\\/232Th)0 ratios is consistent with

Brian R. Jicha; Brad S. Singer; Brian L. Beard; Clark M. Johnson

2005-01-01

51

Scrubbing masks magmatic degassing during repose at Cascade-Range and Aleutian-Arc volcanoes  

USGS Publications Warehouse

Between 1992 and 1998, we sampled gas discharges from ?173°C fumaroles and springs at 12 quiescent but potentially restless volcanoes in the Cascade Range and Aleutian Arc (CRAA) including Mount Shasta, Mount Hood, Mount St. Helens, Mount Rainier, Mount Baker, Augustine Volcano, Mount Griggs, Trident, Mount Mageik, Aniakchak Crater, Akutan, and Makushin. For each site, we collected and analyzed samples to characterize the chemical (H2O, CO2, H2S, N2, CH4, H2, HCl, HF, NH3, Ar, O2, He) and isotopic (?13C of CO2, 3He/4He, 40Ar/36Ar, ?34S, ?13C of CH4, ?15N, and ?D and ?18O of water) compositions of the gas discharges, and to create baseline data for comparison during future unrest. The chemical and isotopic data show that these gases contain a magmatic component that is heavily modified from scrubbing by deep hydrothermal (150° - 350°C) water (primary scrubbing) and shallow meteoric water (secondary scrubbing). The impact of scrubbing is most pronounced in gas discharges from bubbling springs; gases from boiling-point fumaroles and superheated vents show progressively less impact from scrubbing. The most effective strategies for detecting gas precursors to future CRAA eruptions are to measure periodically the emission rates of CO2 and SO2, which have low and high respective solubilities in water, and to monitor continuously CO2 concentrations in soils around volcanic vents. Timely resampling of fumaroles can augment the geochemical surveillance program by watching for chemical changes associated with drying of fumarolic pathways (all CRAA sites), increases in gas geothermometry temperatures (Mount Mageik, Trident, Mount Baker, Mount Shasta), changes in ?13C of CO2 affiliated with magma movement (all CRAA site), and increases in 3He/4He coupled with intrusion of new magma (Mount Rainier, Augustine Volcano, Makushin, Mount Shasta). Repose magmatic degassing may discharge substantial amounts of S and Cl into the edifices of Mount Baker and several other CRAA volcanoes that is trapped by primary and secondary scrubbing. The consequent acidic fluids produce ongoing alteration in the 0.2- to 3-km-deep hydrothermal systems and in fields of boiling-point fumaroles near the surface. Such alteration may influence edifice stability and contribute to the formation of more-hazardous cohesive debris flows. In particular, we recommend further investigation of the volume, extent, and hazards of hydrothermal alteration at Mount Baker. Other potential hazards associated with the CRAA volcano hydrothermal systems include hydrothermal eruptions and, for deeper systems intruded by magma, deep-seated edifice collapse.

Symonds, Robert B.; Janik, C.J.; Evans, W.C.; Ritchie, B.E.; Counce, Dale; Poreda, R.J.; Iven, Mark

2003-01-01

52

76 FR 49423 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013, 2014

...DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 680...Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab Rationalization Program...Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA),...

2011-08-10

53

76 FR 80782 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands; Proposed...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Tuesday, December 27, 2011)] [Rules and Regulations] [Pages 80782-80802...DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 679...Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands; Proposed 2012 and...

2011-12-27

54

78 FR 36122 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013, 2014

...116 (Monday, June 17, 2013)] [Rules and Regulations] [Pages 36122-36128...DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 680...Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab Rationalization...

2013-06-17

55

77 FR 72791 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands; 2013 and...  

Federal Register 2010, 2011, 2012, 2013, 2014

...DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration 50 CFR Part 679 [Docket...the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands; 2013 and 2014 Harvest Specifications for Groundfish...

2012-12-06

56

SURFACE REMEDIATION IN THE ALEUTIAN ISLANDS: A CASE STUDY OF AMCHITKA ISLAND, ALASKA  

SciTech Connect

Amchitka Island, Alaska, was at one time an integral player in the nation's defense program. Located in the North Pacific Ocean in the Aleutian Island archipelago, the island was intermittently inhabited by several key government agencies, including the U.S. Army, the U.S. Atomic Energy Commission (predecessor agency to the U.S. Department of Energy), and the U.S. Navy. Since 1993, the U.S. Department of Energy (DOE) has conducted extensive investigations on Amchitka to determine the nature and extent of contamination resulting from historic nuclear testing. The uninhabited island was the site of three high-yield nuclear tests from 1965 to 1971. These test locations are now part of the DOE's National Nuclear Security Administration Nevada Operations Office's Environmental Management Program. In the summer of 2001, the DOE launched a large-scale remediation effort on Amchitka to perform agreed-upon corrective actions to the surface of the island. Due to the lack of resources available on Amchitka and logistical difficulties with conducting work at such a remote location, the DOE partnered with the Navy and U.S. Army Corps of Engineers (USACE) to share certain specified costs and resources. Attempting to negotiate the partnerships while organizing and implementing the surface remediation on Amchitka proved to be a challenging endeavor. The DOE was faced with unexpected changes in Navy and USACE scope of work, accelerations in schedules, and risks associated with construction costs at such a remote location. Unfavorable weather conditions also proved to be a constant factor, often slowing the progress of work. The Amchitka Island remediation project experience has allowed the DOE to gain valuable insights into how to anticipate and mitigate potential problems associated with future remediation projects. These lessons learned will help the DOE in conducting future work more efficiently, and can also serve as a guide for other agencies performing similar work.

Giblin, M. O.; Stahl, D. C.; Bechtel, J. A.

2002-02-25

57

Volatile Contents in Mafic Magmas from two Aleutian volcanoes: Augustine and Makushin  

NASA Astrophysics Data System (ADS)

There are several competing theories for the origin of tholeiitic (TH) vs. calc-alkaline (CA) fractionation trends in arc magmas. One relates to water (TH-dry magma, CA-wet magma), another to pressure (TH-low pressure crystallization, CA-high pressure), and a third to primary magma composition (TH-low Si/Fe#, CA-hi Si/Fe#) These theories have been difficult to test without quantitative measures of the water contents and pressures of crystallization of arc magmas. We are in the process of studying several Aleutian arc tephra suites (phenocrysts and melt inclusions) with the aim of obtaining volatile element concentrations (by SIMS), major and trace element concentrations and thermobarometric data (by EMP and laser-ICPMS). We report preliminary results on olivine-hosted melt inclusions from Augustine and Makushin volcanoes that support the role of water in calc-alkaline fractionation. Basaltic melt inclusions from Augustine, a low-K2O, calc-alkaline volcano, are hosted in Fo80-82 olivine. The inclusions yield high water contents, up to 5 wt%, and contain 60-90 ppm CO2, 3000-4500 ppm S, and 3000-6000 ppm Cl. Inclusions record vapor-saturation pressures near 2 kbar. Cl/K2O ratios in Augustine inclusions (ave. 1.9) are among the highest documented in an arc setting, and likely record a Cl- and H2O- rich fluid from the subducting plate. High water contents in Augustine primary melts may have contributed to the strong calc-alkaline trend observed at this volcano. Basaltic melt inclusions from Pakushin, a medium-K2O, tholeiitic cone on the flanks of Makushin volcano, are hosted in Fo80-86 olivine. These inclusions have low water contents (<0.15 wt%) and low CO2 contents (<125 ppm), and record shallow vapor saturation pressures (<300 bars). The high sulfur (2000-4000 ppm) and Cl (>2000 ppm) in Pakushin melt inclusions, however, indicate that degassing was minimal. The low water contents and low vapor saturation pressures recorded in Pakushin melt inclusions are consistent with development of its tholeiitic trend, but we cannot distinguish whether the low water contents at Pakushin reflect a difference in the primary magma, or in crustal stresses that favor low pressure fractionation and degassing. These questions will be addressed with further work on the trace element contents of the melt inclusions and on phenocryst-melt geobarometers.

Zimmer, M. M.; Plank, T.; Hauri, E. H.; Nye, C.; Faust Larsen, J.; Kelemen, P. B.

2004-12-01

58

Abundance, trends and distribution of baleen whales off Western Alaska and the central Aleutian Islands  

NASA Astrophysics Data System (ADS)

Large whales were extensively hunted in coastal waters off Alaska, but current distribution, population sizes and trends are poorly known. Line transect surveys were conducted in coastal waters of the Aleutian Islands and the Alaska Peninsula in the summer of 2001-2003. Abundances of three species were estimated by conventional and multiple covariate distance sampling (MCDS) methods. Time series of abundance estimates were used to derive rates of increase for fin whales ( Balaenoptera physalus) and humpback whales ( Megaptera novaeangliae). Fin whales occurred primarily from the Kenai Peninsula to the Shumagin Islands, but were abundant only near the Semidi Islands and Kodiak. Humpback whales were found from the Kenai Peninsula to Umnak Island and were more abundant near Kodiak, the Shumagin Islands and north of Unimak Pass. Minke whales ( B. acutorostrata) occurred primarily in the Aleutian Islands, with a few sightings south of the Alaska Peninsula and near Kodiak Island. Humpback whales were observed in large numbers in their former whaling grounds. In contrast, high densities of fin whales were not observed around the eastern Aleutian Islands, where whaling occurred. Average abundance estimates (95% CI) for fin, humpback and minke whales were 1652 (1142-2389), 2644 (1899-3680), and 1233 (656-2315), respectively. Annual rates of increase were estimated at 4.8% (95% CI=4.1-5.4%) for fin and 6.6% (5.2-8.6%) for humpback whales. This study provides the first estimate of the rate of increase of fin whales in the North Pacific Ocean. The estimated trends are consistent with those of other recovering baleen whales. There were no sightings of blue or North Pacific right whales, indicating the continued depleted status of these species.

Zerbini, Alexandre N.; Waite, Janice M.; Laake, Jeffrey L.; Wade, Paul R.

2006-11-01

59

The Detection, Characterization and Tracking of Recent Aleutian Island Volcanic Ash Plumes and the Assessment of Their Impact on Aviation  

NASA Technical Reports Server (NTRS)

The Aleutian Islands of Alaska are home to a number of major volcanoes which periodically present a significant hazard to aviation. During summer of 2008, the Okmok and Kasatochi volcanoes experienced moderate eruptive events. These were followed a dramatic, major eruption of Mount Redoubt in late March 2009. The Redoubt case is extensively covered in this paper. Volcanic ash and SO2 from each of these eruptions dispersed throughout the atmosphere. This created the potential for major problems for air traffic near the ash dispersions and at significant distances downwind. The NASA Applied Sciences Weather Program implements a wide variety of research projects to develop volcanic ash detection, characterization and tracking applications for NASA Earth Observing System and NOAA GOES and POES satellites. Chemistry applications using NASA AURA satellite Ozone Monitoring System (OMI) retrievals produced SO2 measurements to trace the dispersion of volcanic aerosol. This work was complimented by advanced multi-channel imager applications for the discrimination and height assignment of volcanic ash using NASA MODIS and NOAA GOES and POES imager data. Instruments similar to MODIS and OMI are scheduled for operational deployment on NPOESS. In addition, the NASA Calipso satellite provided highly accurate measurements of aerosol height and dispersion for the calibration and validation of these algorithms and for corroborative research studies. All of this work shortens the lead time for transition to operations and ensures that research satellite data and applications are operationally relevant and utilized quickly after the deployment of operational satellite systems. Introduction

Murray, John J.; Hudnall, L. A.; Matus, A.; Krueger, A. J.; Trepte, C. r.

2010-01-01

60

Geology and geochemistry of the Geyser Bight Geothermal Area, Umnak Island, Aleutian Islands, Alaska  

SciTech Connect

The Geyser Bight geothermal area is located on Umnak Island in the central Aleutian Islands. It contains one of the hottest and most extensive areas of thermal springs and fumaroles in Alaska, and is only documented site in Alaska with geysers. The zone of hot springs and fumaroles lies at the head of Geyser Creek, 5 km up a broad, flat, alluvial valley from Geyser Bight. At present central Umnak is remote and undeveloped. This report describes results of a combined program of geologic mapping, K-Ar dating, detailed description of hot springs, petrology and geochemistry of volcanic and plutonic rock units, and chemistry of geothermal fluids. Our mapping documents the presence of plutonic rock much closer to the area of hotsprings and fumaroles than previously known, thus increasing the probability that plutonic rock may host the geothermal system. K-Ar dating of 23 samples provides a time framework for the eruptive history of volcanic rocks as well as a plutonic cooling age.

Nye, C.J. (Alaska Univ., Fairbanks, AK (USA). Geophysical Inst. Alaska Dept. of Natural Resources, Fairbanks, AK (USA). Div. of Geological and Geophysical Surveys); Motyka, R.J. (Alaska Dept. of Natural Resources, Juneau, AK (USA). Div. of Geological and Geophysical Surveys); Turner, D.L. (Alaska Univ., Fairbanks, AK (USA). Geophysical Inst.); Liss, S.A. (Alaska Dept. of Natural Resources, Fairba

1990-10-01

61

Divergence in an archipelago and its conservation consequences in Aleutian Island rock ptarmigan  

Microsoft Academic Search

The identification and assessment of island endemics is a conservation priority. We genotyped 115 rock ptarmigan from five\\u000a insular populations in the Aleutian-Commander archipelago and two Alaska mainland populations to identify conservation units,\\u000a assess genetic diversity and gene flow, and to determine whether populations have declined over time. We found four distinct\\u000a populations that appear to be completely isolated and

Christin L. PruettTyler; Tyler N. Turner; Carrie M. Topp; Sergey V. Zagrebelny; Kevin Winker

2010-01-01

62

A new population of Aleutian shield fern (Polystichum aleuticum C. Christens.) on Adak Island, Alaska  

USGS Publications Warehouse

We report and describe a new population of the endangered Aleutian shield fern (Polystichum aleuticum C. Christens.) discovered on Mount Reed, Adak Island, Alaska. The new population is located at a lower elevation than the other known populations, placing the species' known elevational range between 338 m and 525 m. The discovery of this population is significant because it increases the total number of known populations and individuals for the species.

Talbot, S.L.; Talbot, S.S.

2002-01-01

63

Timing of Volcanism on Yunaska Island, Central Aleutian arc, Alaska: an Investigation Applying Multi-temporal Synthetic Aperture Radar  

NASA Astrophysics Data System (ADS)

The volcanoes of the central Aleutian arc remain largely uninstrumented and unstudied despite numerous eruptions within the last century. Many of these eruptions are not documented and others may not have been observed. Previous synthetic aperture radar (SAR) studies at Westdahl volcano show that radar can be used to relatively date a'a lava flows and to suggest whether some flows are "historic" though not recorded. This is accomplished through comparison of semi-quantitative measurements of surface roughness for young, unvegetated lavas. Because a'a lavas typically become smoother as they weather, they produce less radar backscatter. Thus, lavas that exhibit higher radar backscatter intensities are younger than those with lower backscatter intensities for regions of similar relief and aspect. Located 305 km west of Dutch Harbor, Yunaska has six volcanic centers, of which three have probably been active in the Quaternary. Based on field observations, recent volcanism on Yunaska is associated with the younger of two nested calderas and several smaller vents and cones on the eastern half of the island. Although there is a reported 1937 eruption, it is not clear if this came from fissures north of the caldera or created the intracaldera cinder cone and lava flows. Using a twenty-year composite of SAR data, we establish relative ages for five basaltic andesite lavas from these fissures and from within the young caldera. Clear stratigraphic relationships among three lavas within the caldera provide a check on the accuracy of this technique. The use of SAR to differentiate between young lavas allows us to better document the eruption history of remote volcanoes and to mitigate their hazards.

Brown, M. E.; Nicolaysen, K. P.; Dehn, J.; Myers, J. D.

2003-12-01

64

Deep, Carbon Dioxide-Rich Degassing of Pavlof Volcano, Aleutian arc  

NASA Astrophysics Data System (ADS)

Pavlof is the most active volcanic center in the Aleutian arc with more than 40 eruptions in the last 250 years. Lava fountains and strombolian-to-vulcanian activity since the late Pleistocene built a steep-sided basaltic- andesite stratovolcano rising 2733 m a.s.l. Seismic monitoring (in place since the 1970's) shows the tendency of Pavlof to erupt without extensive precursors. Of the 22 monitored eruptions between 1973 and 1996, 18 occurred with < 24 hours of above-background seismicity (McNutt, 1989; Neal and McGimsey, 1997). Upper mantle to lower crustal long-period (LP) earthquakes are a notable geophysical feature of Pavlof (and other Aleutian volcanoes) during repose periods (Power et al, 2004). LP earthquakes, with their emergent onsets, extended codas and narrow frequency spectra (1-3 Hz), are widely attributed to the motions of fluid (melt, gas, or aqueous) in fractures or reservoirs. At Pavlof, LPs are detected as sporadic single events at depths of 18-36 km or as clusters with co-located volcano-tectonic earthquakes (VTs) typical of brittle fracture. Rapid injection (VT) and degassing (LP) of CO2-H2O saturated Pavlof magmas may account for deep LP-VT clusters. We are in the early stages of an experimental study of CO2-rich degassing of Pavlof magma with the aim of quantifying the physiochemical mechanisms of deep, fluid-driven seismicity in active volcanic regions. We use newly developed methods for conducting controlled decompressions (1200 to 400 MPa) of volatile-added silicate melts in piston-cylinder presses. At 1200 MPa and 1125°C, a vapor-saturated Pavlof basaltic- andesite melt with 2 wt% dissolved H2O has 8500 ppm dissolved CO2 (FTIR). Rapid decompression of these mixed-volatile melts to 400 MPa triggers nucleation and growth of bubbles containing nearly pure CO2 vapor. Equilibrium between melt and vapor is re-established after ~ 1 hr at the final pressure with dissolved volatile concentrations of 2 wt% H2O and 2000 ppm CO2, and 5 vol% coexisting bubbles. The experiments are visually compelling with an initially homogeneous bubble suspension (7E6-2E7 bubbles/cm3melt) that rapidly becomes unstable. The instability is two-stage (bubble wave feeds secondary plumes), and results in a foam layer at the top of the capsule. We are struck by the speed at which this process occurs (< 1 hr). The hydrodynamics of bubble wave and secondary plume instabilities was modeled numerically in the context of vesicle layers observed in lava flows (Manga, 1996). It may also have application to the rapid-fire magma injection and gas expulsion scenario needed to explain VT-LP clustering.

Mangan, M.; Sisson, T.; Hankins, B.

2006-12-01

65

Microbial consortia of gorgonian corals from the Aleutian islands  

USGS Publications Warehouse

Gorgonians make up the majority of corals in the Aleutian archipelago and provide critical fish habitat in areas of economically important fisheries. The microbial ecology of the deep-sea gorgonian corals Paragorgea arborea, Plumarella superba, and Cryogorgia koolsae was examined with culture-based and 16S rRNA gene-based techniques. Six coral colonies (two per species) were collected. Samples from all corals were cultured, and clone libraries were constructed from P. superba and C. koolsae. Cultured bacteria were dominated by the Gammaproteobacteria, especially Vibrionaceae, with other phyla comprising <6% of the isolates. The clone libraries showed dramatically different bacterial communities between corals of the same species collected at different sites, with no clear pattern of conserved bacterial consortia. Two of the clone libraries (one from each coral species) were dominated by Tenericutes, with Alphaproteobacteria dominating the remaining sequences. The other libraries were more diverse and had a more even distribution of bacterial phyla, showing more similarity between genera than within coral species. Here we report the first microbiological characterization of P. arborea, P. superba, and C. koolsae. FEMS Microbiology Ecology ?? 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. No claim to original US government works.

Gray, Michael A.; Stone, R.P.; McLaughlin, M.R.; Kellogg, C.A.

2011-01-01

66

Defining Essential Fish Habitat for Atka Mackerel with Respect to Feeding within and Adjacent to Aleutian Islands Trawl Exclusion Zones  

Microsoft Academic Search

The distribution patterns of Atka mackerel Pleurogrammus monopterygius were examined, both seasonally and spatially, to identify essential feeding habitat and to add to existing knowledge of diet composition. The study focused on two local aggregations in the Aleutian Islands, Alaska: one at Seguam Pass and one near Amchitka Island. At each locale, we examined the mean stomach fullness (i.e., feeding

Kimberly M. Rand; Sandra A. Lowe

2011-01-01

67

Dispersal and behavior of pacific halibut hippoglossus stenolepis in the bering sea and Aleutian islands region  

USGS Publications Warehouse

Currently, it is assumed that eastern Pacific halibut Hippoglossus stenolepis belong to a single, fully mixed population extending from California through the Bering Sea, in which adult halibut disperse randomly throughout their range during their lifetime. However, we hypothesize that hali but dispersal is more complex than currently assumed and is not spatially random. To test this hypo thesis, we studied the seasonal dispersal and behavior of Pacific halibut in the Bering Sea and Aleutian Islands (BSAI). Pop-up Archival Transmitting tags attached to halibut (82 to 154 cm fork length) during the summer provided no evidence that individuals moved out of the Bering Sea and Aleutian Islands region into the Gulf of Alaska during the mid-winter spawning season, supporting the concept that this region contains a separate spawning group of adult halibut. There was evidence for geographically localized groups of halibut along the Aleutian Island chain, as all of the individuals tagged there displayed residency, with their movements possibly impeded by tidal currents in the passes between islands. Mid-winter aggregation areas of halibut are assumed to be spawning grounds, of which 2 were previously unidentified and extend the species' presumed spawning range ~1000 km west and ~600 km north of the nearest documented spawning area. If there are indeed independent spawning groups of Pacific halibut in the BSAI, their dynamics may vary sufficiently from those of the Gulf of Alaska, so that specifically accounting for their relative segregation and unique dynamics within the larger population model will be necessary for correctly predicting how these components may respond to fishing pressure and changing environmental conditions.?? Inter-Research 2011.

Seitz, A.C.; Loher, T.; Norcross, B.L.; Nielsen, J.L.

2011-01-01

68

An introduced predator alters Aleutian Island plant communities by thwarting nutrient subsidies  

USGS Publications Warehouse

The ramifying effects of top predators on food webs traditionally have been studied within the framework of trophic cascades. Trophic cascades are compelling because they embody powerful indirect effects of predators on primary production. Although less studied, indirect effects of predators may occur via routes that are not exclusively trophic. We quantified how the introduction of foxes onto the Aleutian Islands transformed plant communities by reducing abundant seabird populations, thereby disrupting nutrient subsidies vectored by seabirds from sea to land. We compared soil and plant fertility, plant biomass and community composition, and stable isotopes of nitrogen in soil, plants, and other organisms on nine fox-infested and nine historically fox-free islands across the Aleutians. Additionally, we experimentally augmented nutrients on a fox-infested island to test whether differences in plant productivity and composition between fox-infested and fox-free islands could have arisen from differences in nutrient inputs between island types. Islands with historical fox infestations had soils low in phosphorus and nitrogen and plants low in tissue nitrogen. Soils, plants, slugs, flies, spiders, and bird droppings on these islands had low d15N values indicating that these organisms obtained nitrogen from internally derived sources. In contrast, soils, plants, and higher trophic level organisms on fox-free islands had elevated d15N signatures indicating that they utilized nutrients derived from the marine environment. Furthermore, soil phosphorus (but not nitrogen) and plant tissue nitrogen were higher on fox-free than fox-infested islands. Nutrient subsidized fox-free islands supported lush, high biomass plant communities dominated by graminoids. Fox-infested islands were less graminoid dominated and had higher cover and biomass of low-lying forbs and dwarf shrubs. While d15N profiles of soils and plants and graminoid biomass varied with island size and distance from shore, after accounting for these effects differences between fox-infested and fox-free islands still existed. Fertilization over four years caused a 24-fold increase in graminoid biomass and a shift toward a more graminoid dominated plant community typical of fox-free islands. These results indicate that apex predators can influence plant productivity and composition through complex interaction web pathways involving both top-down forcing and bottom-up nutrient exchanges across systems. ?? 2006 by the Ecological Society of America.

Maron, J.L.; Estes, J.A.; Croll, D.A.; Danner, E.M.; Elmendorf, S.C.; Buckelew, S.L.

2006-01-01

69

The petrology of the Las Canadas volcanoes, Tenerife, Canary islands  

Microsoft Academic Search

Tenerife is the largest of the seven Tertiary to Recent volcanic islands that make up the Canary Archipelago. The island is composed of volcanics belonging to the basanitetrachyte-phonolite assemblage that characterises many Atlantic islands. The most voluminous development of intermediate and salic volcanics has been in the centre of the island where the Las Canadas volcanoes arose upon a basement

William Ian Ridley

1970-01-01

70

Status and distribution of the Kittlitz's Murrelet Brachyramphus brevirostris along the Alaska Peninsula and Kodiak and Aleutian Islands, Alaska  

USGS Publications Warehouse

The Kittlitz's Murrelet Brachyramphus brevirostris is adapted for life in glacial-marine ecosystems, being concentrated in the belt of glaciated fjords in the northern Gulf of Alaska from Glacier Bay to Cook Inlet. Most of the remaining birds are scattered along coasts of the Alaska Peninsula and Aleutian Islands, where they reside in protected bays and inlets, often in proximity to remnant glaciers or recently deglaciated landscapes. We summarize existing information on Kittlitz's Murrelet in this mainly unglaciated region, extending from Kodiak Island in the east to the Near Islands in the west. From recent surveys, we estimated that ~2400 Kittlitz's Murrelets were found in several large embayments along the Alaska Peninsula, where adjacent ice fields feed silt-laden water into the bays. On Kodiak Island, where only remnants of ice remain today, observations of Kittlitz's Murrelets at sea were uncommon. The species has been observed historically around the entire Kodiak Archipelago, however, and dozens of nest sites were found in recent years. We found Kittlitz's Murrelets at only a few islands in the Aleutian chain, notably those with long complex shorelines, high mountains and remnant glaciers. The largest population (~1600 birds) of Kittlitz's Murrelet outside the Gulf of Alaska was found at Unalaska Island, which also supports the greatest concentration of glacial ice in the Aleutian Islands. Significant populations were found at Atka (~1100 birds), Attu (~800) and Adak (~200) islands. Smaller numbers have been reported from Unimak, Umnak, Amlia, Kanaga, Tanaga, Kiska islands, and Agattu Island, where dozens of nest sites have been located in recent years. Most of those islands have not been thoroughly surveyed, and significant pockets of Kittlitz's Murrelets may yet be discovered. Our estimate of ~6000 Kittlitz's Murrelets along the Alaska Peninsula and Aleutian Islands is also likely to be conservative because of the survey protocols we employed (i.e. early seasonal timing of surveys, strip transects).

Madison, Erica N.; Piatt, John F.; Arimitsu, Mayumi L.; Romano, Marc D.; van Pelt, Thomas I.; Nelson, S. Kim; Williams, Jeffrey C.; DeGange, Anthony R.

2011-01-01

71

Alaska Open-file Report 144 Assessment of Thermal Springs Sites Aleutian Arc, Atka Island to Becherof Lake -- Preliminary Results and Evaluation  

SciTech Connect

Twenty of more than 30 thermal spring areas reported to exist in the Aleutian arc extending from Atka Island to Becherof Lake were investigated during July and August, 1980. Thermal activity of three of these sites had diminished substantially or no longer existed. At least seven more sites where thermal-spring activity is probable or certain were not visited because of their remoteness or because of time constraints. The existence of several other reported thermal spring sites could not be verified; these sites are considered questionable. On the basis of geothermometry, subsurface reservoir temperatures in excess of 150 C are estimated for 10 of the thermal spring sites investigated. These sites all occur in or near regions of Recent volcanism. Five of the sites are characterized by fumaroles and steaming ground, indicating the presence of at least a shallow vapor-dominated zone. Two, the Makushin Valley and Glacier Valley thermal areas, occur on the flanks of active Mukushin Volcano located on Unalaska Island, and may be connected to a common source of heat. Gas geothermometry suggests that the reservoir feeding the Kliuchef thermal field, located on the flanks of Kliuchef volcano of northeast Atka Island, may be as high as 239 C.

Motyka, R.J.; Moorman, M.A.; Liss, S.A.

1981-12-01

72

Insights Into Aleutian Volcanism from Insar Observations  

NASA Astrophysics Data System (ADS)

With its global coverage and all-weather imaging capability, interferometric synthetic aperture radar (InSAR) has become an increasingly important technique for studying magma dynamics at volcanoes in remote regions, such as the Aleutian Islands. The spatial distribution of surface deformation derived from InSAR data enables the construction of detailed mechanical models to enhance the study of magmatic processes. To study Aleutian volcanism, we processed nearly 12,000 SAR images acquired by ERS-1, JERS-1, ERS-2, Radarsat-1, Envisat, ALOS, and TerraSAR-X from the early 1990s to 2010. We combined these SAR images to produce about 25,000 interferograms, which we analyzed for evidence of surface deformation at most of the arc's Holocene volcanoes. Where surface displacements were sufficiently strong, we used analytical models to estimate the location, shape, and volume change of deformation sources. This paper summarizes deformation processes at Aleutian volcanoes observed with InSAR, including: (1) time-variant volcanic inflation and magmatic intrusion, (2) deformation preceding and accompanying seismic swarms , (3) persistent volcano-wide subsidence at calderas that last erupted tens of years ago, (4) episodic magma intrusion and associated tectonic stress release, (5) subsidence caused by a decrease in pore fluid pressure in active hydrothermal systems, (6) subsidence of surface lava and pyroclastic flows, and (7) a lack of deformation at some volcanoes with recent eruptions, where deformation might be expected. Among the inferred mechanisms are magma accumulation in and withdrawal from crustal magma reservoirs, pressurization/depressurization of hydrothermal systems, and thermo-elastic contraction of young lava flows. Our work demonstrates that deformation patterns and associated magma supply mechanisms at Aleutian volcanoes are diverse and vary in both space and time. By combining InSAR results with information from the geologic record, accounts of historical eruptions, and data from seismology, petrology, gas geochemistry, and other sources, we have developed conceptual models for the magma plumbing systems and behaviors of many volcanoes in the Aleutian arc. We realize that these models are simplistic, but it is our hope that they will serve as foundations that will be refined as additional information becomes available. Finally, we have compared our InSAR observations from the Aleutians with those from the Andes and Indonesia to highlight the similarities and differences in volcanism between volcanic arcs [Lu and Dzurisin, 2013]. Lu, Z., and D. Dzurisin, InSAR Imaging of Aleutian Volcanoes: Monitoring a Volcanic Arc from Space', Springer Praxis Books, Geophysical Sciences, ISBN 978-3-642-00347-9, December 2013.

Lu, Z.; Dzurisin, D.

2013-12-01

73

77 FR 44172 - Fisheries of the Exclusive Economic Zone Off Alaska; Squid in the Bering Sea and Aleutian Islands...  

Federal Register 2010, 2011, 2012, 2013, 2014

NMFS apportions an amount of the non-specified reserve to the initial total allowable catch of squid in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary to allow the fisheries to continue operating. It is intended to promote the goals and objectives of the fishery management plan for the...

2012-07-27

74

Pyroxenite is a possible cause of enriched magmas in island arc settings: Gorely volcano (Kamchatka)  

NASA Astrophysics Data System (ADS)

Kamchatka peninsula (Russia) is an island-arc with a complex geological history and structure. It has three distinct volcanic fronts, whose origins are still debated. Moreover, a junction with the Aleutian Arc (at ~56oN) complicates the understanding of geodynamics at the region. The process of magma generation in Kamchatka involves several components: N-MORB mantle wedge (variably depleted), slab fluids and melts, and enriched mantle [Churikova et al. 2001, 2007; Yogodzinsky et al. 2001; Volynets et al. 2010]. Two of these end members (mantle wedge, slab fluids) are well studied [Portnyagin et al. 2007; Duggen et al. 2007]. However, the nature/genesis of the enriched magmas is unclear. In the standard model of arc volcanism depleted mantle peridotite in the mantle wedge partially melts to form parental basalts. However, evidence for pyroxenite melting in the arc environment was reported for the Mexican Volcanic Belt [Straub et al, 2008; Straub et al, 2013] and for Kamchatka [Portnyagin, 2009; Portnyagin, 2011; Bryant et al., 2011; Gavrilenko, 2012]. High precision Ni, Ca, and Mn contents of olivines from Gorely volcano confirm the existence of pyroxenite source in the mantle wedge [Gavrilenko, 2013]. Our forward modeling using Arc Basalt Simulator 4.0 (ABS) by [Kimura et al. 2011]) shows that we have primitive mantle as a source for Gorely volcano, a mantle more enriched than the DMM in the standard model for arc magmatism) REE inverse modeling [after Feigenson et al, 1983] agrees with the ABS forward model, returning the same REE pattern for the source. In contrast, ABS modeling for Mutnovsky volcano (next to Gorely, but closer to the trench) shows standard DMM as the source for the volcano. We conclude that DMM is the composition for the mantle wedge rocks beneath Gorely volcano, but the enrichment of the parental melts at Gorely volcano is caused by reaction of DMM peridotite with slab melts/fluids to produce pyroxenite.

Gavrilenko, M.; Carr, M. J.; Herzberg, C. T.; Ozerov, A.

2013-12-01

75

Little late Holocene strain accumulation and release on the Aleutian megathrust below the Shumagin Islands, Alaska  

NASA Astrophysics Data System (ADS)

a predominantly creeping segment of a subduction zone generate a great (M > 8) earthquake? Despite Russian accounts of strong shaking and high tsunamis in 1788, geodetic observations above the Aleutian megathrust indicate creeping subduction across the Shumagin Islands segment, a well-known seismic gap. Seeking evidence for prehistoric great earthquakes, we investigated Simeonof Island, the archipelago's easternmost island, and found no evidence for uplifted marine terraces or subsided shorelines. Instead, we found freshwater peat blanketing lowlands, and organic-rich silt and tephra draping higher glacially smoothed bedrock. Basal peat ages place glacier retreat prior to 10.4 ka and imply slowly rising (<0.2 m/ka) relative sea level since ~3.4 ka. Storms rather than tsunamis probably deposited thin, discontinuous deposits in coastal sites. If rupture of the megathrust beneath Simeonof Island produced great earthquakes in the late Holocene, then coseismic uplift or subsidence was too small (?0.3 m) to perturb the onshore geologic record.

Witter, Robert C.; Briggs, Richard W.; Engelhart, Simon E.; Gelfenbaum, Guy; Koehler, Richard D.; Barnhart, William D.

2014-04-01

76

Feasibility of Tidal and Ocean Current Energy in False Pass, Aleutian Islands, Alaska FINAL REPORT  

SciTech Connect

The Aleutian Pribilof Islands Association was awarded a U.S. Department of Energy Tribal Energy Program grant (DE-EE0005624) for the Feasibility of Tidal and Ocean Current Energy in False Pass, Aleutian Islands, Alaska (Project). The goal of the Project was to perform a feasibility study to determine if a tidal energy project would be a viable means to generate electricity and heat to meet long-term fossil fuel use reduction goals, specifically to produce at least 30% of the electrical and heating needs of the tribally-owned buildings in False Pass. The Project Team included the Aleut Region organizations comprised of the Aleutian Pribilof Island Association (APIA), and Aleutian Pribilof Island Community Development Association (APICDA); the University of Alaska Anchorage, ORPC Alaska a wholly-owned subsidiary of Ocean Renewable Power Company (ORPC), City of False Pass, Benthic GeoScience, and the National Renewable Energy Laboratory (NREL). The following Project objectives were completed: collected existing bathymetric, tidal, and ocean current data to develop a basic model of current circulation at False Pass, measured current velocities at two sites for a full lunar cycle to establish the viability of the current resource, collected data on transmission infrastructure, electrical loads, and electrical generation at False Pass, performed economic analysis based on current costs of energy and amount of energy anticipated from and costs associated with the tidal energy project conceptual design and scoped environmental issues. Utilizing circulation modeling, the Project Team identified two target sites with strong potential for robust tidal energy resources in Isanotski Strait and another nearer the City of False Pass. In addition, the Project Team completed a survey of the electrical infrastructure, which identified likely sites of interconnection and clarified required transmission distances from the tidal energy resources. Based on resource and electrical data, the Project Team developed a conceptual tidal energy project design utilizing ORPC’s TidGen® Power System. While the Project Team has not committed to ORPC technology for future development of a False Pass project, this conceptual design was critical to informing the Project’s economic analysis. The results showed that power from a tidal energy project could be provided to the City of False at a rate at or below the cost of diesel generated electricity and sold to commercial customers at rates competitive with current market rates, providing a stable, flat priced, environmentally sound alternative to the diesel generation currently utilized for energy in the community. The Project Team concluded that with additional grants and private investment a tidal energy project at False Pass is well-positioned to be the first tidal energy project to be developed in Alaska, and the first tidal energy project to be interconnected to an isolated micro grid in the world. A viable project will be a model for similar projects in coastal Alaska.

Wright, Bruce Albert [Aleutian Pribilof Islands Association] [Aleutian Pribilof Islands Association

2014-05-07

77

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

USGS Publications Warehouse

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.

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

2014-01-01

78

Late Holocene coastal stratigraphy of Sitkinak Island reveals Aleutian-Alaska megathrust earthquakes and tsunamis southwest of Kodiak Island  

NASA Astrophysics Data System (ADS)

Uncertainty in earthquake and tsunami prehistory of the Aleutian-Alaska megathrust westward of central Kodiak Island limit assessments of southern Alaska's earthquake hazard and forecasts of potentially damaging tsunamis along much of North America's west coast. Sitkinak Island, one of the Trinity Islands off the southwest tip of Kodiak Island, lies at the western end of the rupture zone of the 1964 Mw9.2 earthquake. Plafker reports that a rancher on the north coast of Sitkinak Island observed ~0.6 m of shoreline uplift immediately following the 1964 earthquake, and the island is now subsiding at about 3 mm/yr (PBO GPS). Although a high tsunami in 1788 caused the relocation of the first Russian settlement on southwestern Kodiak Island, the eastern extent of the megathrust rupture accompanying the tsunami is uncertain. Interpretation of GPS observations from the Shumagin Islands, 380 km southwest of Kodiak Island, suggests an entirely to partially creeping megathrust in that region. Here we report the first stratigraphic evidence of tsunami inundation and land-level change during prehistoric earthquakes west of central Kodiak Island. Beneath tidal and freshwater marshes around a lagoon on the south coast of Sitkinak Island, 27 cores and tidal outcrops reveal the deposits of four to six tsunamis in 2200 years and two to four abrupt changes in lithology that may correspond with coseismic uplift and subsidence over the past millennia. A 2- to 45-mm-thick bed of clean to peaty sand in sequences of tidal sediment and freshwater peat, identified in more than one-half the cores as far inland as 1.5 km, was probably deposited by the 1788 tsunami. A 14C age on Scirpus seeds, double 137Cs peaks at 2 cm and 7 cm depths (Chernobyl and 1963?), a consistent decline in 210Pb values, and our assumption of an exponential compaction rate for freshwater peat, point to a late 18th century age for the sand bed. Initial 14C ages suggest that two similar extensive sandy beds, identified in eight cores at higher tidal and freshwater sites, date from about 1.5 ka and 2.0 ka, respectively. A younger silty sand bed, <10 cm beneath the now-eroding low marsh around the lagoon, may record the 1964 tsunami. Correlations of two to three other sandy beds are too uncertain to infer their deposition by tsunamis. Stratigraphic contacts found only in cores and outcrops of the <0.8- to 1-ka tidal section fringing the lagoon may mark coseismic uplift (peat over tidal mud, sometimes with intervening sand) or subsidence (tidal mud over peat, sometimes with intervening sand). We collected samples of modern tidal foraminifera along three elevational transects for the baseline dataset needed to use fossil assemblages to measure the amount of uplift or subsidence recorded by contacts. Foraminiferal assemblages above and below one contact confirm rapid uplift a few hundred years before the 1788 tsunami, but cores are too few to correlate this contact with any of the sandy beds that we infer were deposited by tsunamis farther inland. These initial results demonstrate the promise of this previously unexplored island and similar sites for using stratigraphic evidence of sudden land-level changes and high tsunamis to map prehistoric ruptures of the Aleutian-Alaskan megathrust.

Nelson, A. R.; Briggs, R. W.; Kemp, A.; Haeussler, P. J.; Engelhart, S. E.; Dura, T.; Angster, S. J.; Bradley, L.

2012-12-01

79

Living on Active Volcanoes - The Island of Hawaii  

NSDL National Science Digital Library

This United States Geological Survey (USGS) on-line publication highlights the volcanic hazards facing the people living on the Island of Hawaii. These hazards include lava flows, explosive eruptions, volcanic smog, earthquakes and tsunamis. This report discusses these hazards, the volcanoes of Mauna Loa and Kilauea, and the work of the Hawaiian Volcano Observatory to monitor and issue warnings to the people affected by these hazards.

Heliker, Christina; Stauffer, Peter; Hendley Ii., James

80

The 1817 Eruption of Okmok Caldera, Umnak Island, Alaska: New Insights Into a Complex Historical Eruption in the Eastern Aleutians  

Microsoft Academic Search

Okmok is a 10-km-diameter, late-Holocene caldera on Umnak Island in the eastern Aleutians, 1400 km southwest of Anchorage. The most recent eruption in 1997 was strombolian in character, producing a basaltic-andesite lava flow within the caldera and localized ash fall. Since caldera-formation approximately 2050 14C yrs BP, however, more violent eruptions from vents within the caldera have impacted all flanks

C. A. Neal; J. Beget; D. Grey; B. Wolfe

2003-01-01

81

Science, policy, and stakeholders: developing a consensus science plan for Amchitka Island, Aleutians, Alaska.  

PubMed

With the ending of the Cold War, the US Department of Energy is responsible for the remediation of radioactive waste and disposal of land no longer needed for nuclear material production or related national security missions. The task of characterizing the hazards and risks from radionuclides is necessary for assuring the protection of health of humans and the environment. This is a particularly daunting task for those sites that had underground testing of nuclear weapons, where the radioactive contamination is currently inaccessible. Herein we report on the development of a Science Plan to characterize the physical and biological marine environment around Amchitka Island in the Aleutian chain of Alaska, where three underground nuclear tests were conducted (1965-1971). Information on the ecology, geology, and current radionuclide levels in biota, water, and sediment is necessary for evaluating possible current contamination and to serve as a baseline for developing a plan to ensure human and ecosystem health in perpetuity. Other information required includes identifying the location of the salt water/fresh water interface where migration to the ocean might occur in the future and determining groundwater recharge balances, as well as assessing other physical/geological features of Amchitka near the test sites. The Science Plan is needed to address the confusing and conflicting information available to the public about radionuclide risks from underground nuclear blasts in the late 1960s and early 1970s, as well as the potential for volcanic or seismic activity to disrupt shot cavities or accelerate migration of radionuclides into the sea. Developing a Science Plan involved agreement among regulators and other stakeholders, assignment of the task to the Consortium for Risk Evaluation with Stakeholder Participation, and development of a consensus Science Plan that dealt with contentious scientific issues. Involvement of the regulators (State of Alaska), resource trustees (U S Fish and Wildlife Service), representatives of the Aleut and Pribilof Island communities, and other stakeholders was essential for plan development and approval, although this created tensions because of the different objectives of each group. The complicated process of developing a Science Plan involved iterations and interactions with multiple agencies and organizations, scientists in several disciplines, regulators, and the participation of Aleut people in their home communities, as well as the general public. The importance of including all parties in all phases of the development of the Science Plan was critical to its acceptance by a broad range of regulators, agencies, resource trustees, Aleutian/Pribilof communities, and other stakeholders. PMID:15886955

Burger, Joanna; Gochfeld, Michael; Kosson, David S; Powers, Charles W; Friedlander, Barry; Eichelberger, John; Barnes, David; Duffy, Lawrence K; Jewett, Stephen C; Volz, Conrad D

2005-05-01

82

Rift zone reorganization through flank instability in ocean island volcanoes: an example from Tenerife, Canary Islands  

Microsoft Academic Search

The relationship between rift zones and flank instability in ocean island volcanoes is often inferred but rarely documented. Our field data, aerial image analysis, and 40Ar\\/39Ar chronology from Anaga basaltic shield volcano on Tenerife, Canary Islands, support a rift zone—flank instability relationship. A single rift zone dominated the early stage of the Anaga edifice (~6–4.5 Ma). Destabilization of the northern sector

T. R. Walter; V. R. Troll; B. Cailleau; A. Belousov; H.-U. Schmincke; F. Amelung; P. v. d. Bogaard

2005-01-01

83

Mercury concentrations in breast feathers of three upper trophic level marine predators from the western Aleutian Islands, Alaska  

USGS Publications Warehouse

Mercury (Hg) is a toxic element distributed globally through atmospheric transport. Agattu Island, located in the western Aleutian Islands, Alaska, has no history of point-sources of Hg contamination. We provide baseline levels of total mercury (THg) concentrations in breast feathers of three birds that breed on the island. Geometric mean THg concentrations in feathers of fork-tailed storm-petrels (Oceanodroma furcata; 6703 ± 1635, ng/g fresh weight [fw]) were higher than all other species, including snowy owl (Bubo scandiacus; 2105 ± 1631, ng/g fw), a raptor with a diet composed largely of storm-petrels at Agattu Island. There were no significant differences in mean THg concentrations of breast feathers among adult Kittlitz’s murrelet (Brachyramphus brevirostris; 1658 ± 1276, ng/g fw) and chicks (1475 ± 671, ng/g fw) and snowy owls. The observed THg concentrations in fork-tailed storm-petrel feathers emphasizes the need for further study of Hg pollution in the western Aleutian Islands.

Kaler, Robb S.A.; Kenney, Leah A.; Bond, Alexander L.; Eagles-Smith, Collin A.

2014-01-01

84

Mercury concentrations in breast feathers of three upper trophic level marine predators from the western Aleutian Islands, Alaska.  

PubMed

Mercury (Hg) is a toxic element distributed globally through atmospheric transport. Agattu Island, located in the western Aleutian Islands, Alaska, has no history of point-sources of Hg contamination. We provide baseline levels of total mercury (THg) concentrations in breast feathers of three birds that breed on the island. Geometric mean THg concentrations in feathers of fork-tailed storm-petrels (Oceanodroma furcata; 6703 ± 1635, ng/g fresh weight [fw]) were higher than all other species, including snowy owl (Bubo scandiacus; 2105 ± 1631, ng/g fw), a raptor with a diet composed largely of storm-petrels at Agattu Island. There were no significant differences in mean THg concentrations of breast feathers among adult Kittlitz's murrelet (Brachyramphus brevirostris; 1658 ± 1276, ng/g fw) and chicks (1475 ± 671, ng/g fw) and snowy owls. The observed THg concentrations in fork-tailed storm-petrel feathers emphasizes the need for further study of Hg pollution in the western Aleutian Islands. PMID:24656750

Kaler, Robb S A; Kenney, Leah A; Bond, Alexander L; Eagles-Smith, Collin A

2014-05-15

85

Near-field survey of the 1946 Aleutian tsunami on Unimak and Sanak Islands  

USGS Publications Warehouse

The 1946 Aleutian earthquake stands out among tsunamigenic events because it generated both very high run-up near the earthquake source region and a destructive trans-Pacific tsunami. We obtained new data on the distribution of its tsunami in the near field along south-facing coasts between Unimak Pass on the west and Sanak Island on the east by measuring the height of driftwood and beach materials that were deposited by the tsunami above the extreme storm tide level. Our data indicate that (1) the highest measured run-up, which is at the Scotch Cap lighthouse, was 42 m above tide level or about 37 m above present storm tide elevation; (2) run-up along the rugged coast from Scotch Cap for 12 km northwest to Sennett Point is 12-18 m, and for 30 km east of Scotch Cap to Cape Lutke it is 24-42 m; (3) run-up along the broad lowlands bordering Unimak Bight is 10-20 m, and in-undation is locally more than 2 km; (5) run-up diminishes to 8 m or less at the southeast corner of Unimak Island; (6) no evidence was found for run-up above present storm tides (about 4-5 m above MLLW) on the Ikatan Peninsula or areas along the coast to the west; and (7) run-up above storm tide level in the Sanak Island group is restricted to southwest-facing coasts of Sanak, Long, and Clifford Islands, where it is continuous and locally up to 24 m high. Generation of the tsunami by one or more major earthquake-triggered submarine landslides near the shelf edge south of Unimak Island seems to be the only viable mechanism to account for the data on wave arrival time, run-up heights, and distribution, as well as for unconfirmed anecdotal reports of local postquake increases in water depth and diminished bottom-fisheries productivity. A preliminary hydrodynamic simulation of the local tsunami propagation and run-up using a dipolar model of a possible landslide off Davidson Bank provides an acceptable fit to the characteristics of the distribution of local run-up, with a value at 34 m at the Scotch Cap lighthouse.

Okal, E.A.; Plafker, G.; Synolakis, C.E.; Borrero, J.C.

2003-01-01

86

High prevalence of Aleutian mink disease virus in free-ranging mink on a remote Danish island.  

PubMed

Aleutian mink disease virus (AMDV) causes severe disease in farmed mink (Neovison vison) worldwide. In Denmark, AMDV in farmed mink has been confined to the northern part of the mainland since 2002. From 1998 to 2009, samples from 396 free-ranging mink were collected from mainland Denmark, and a low AMDV antibody prevalence (3% of 296) was found using countercurrent immune electrophoresis. However, on the island of Bornholm in the Baltic Sea, a high prevalence (45% of 142 mink) was detected in the free-ranging mink. Aleutian mink disease virus was detected by polymerase chain reaction in 32 of 49 antibody-positive free-ranging mink on Bornholm, but not in mink collected from other parts of Denmark. Sequence analysis of 370 base pairs of the nonstructural gene of the AMDV of 17 samples revealed two clusters with closest similarity to Swedish AMDV strains. PMID:22493130

Jensen, Trine H; Christensen, Laurids S; Chriél, Mariann; Harslund, Jakob; Salomonsen, Charlotte M; Hammer, Anne Sofie

2012-04-01

87

Depths of Magma Storage Beneath Fogo Volcano, Cape Verde Islands  

Microsoft Academic Search

Fogo is one of the most active oceanic volcanoes of the world in present time and the only island of the Cape Verde archipelago with historic volcanic activity. We have carried out a barometric study of basanitic to tephriphonolitic volcanic rocks of the 1995 eruption of Fogo in order to reconstruct the depths of magma reservoirs and magma pathways prior

E. Hildner; A. Klügel

2008-01-01

88

Characterization of the seismogenic process in the Aleutian island arc: I. Source relations of the large earthquakes of 1957, 1986, and 1996 in the Andreanof Islands  

NASA Astrophysics Data System (ADS)

An interpretation of the type, size, and interrelations of sources is proposed for the three large Aleutian earthquakes of March 9, 1957, May 7, 1986, and June 10, 1996, which occurred in structures of the Andreanof Islands. According to our interpretation, the earthquakes were caused by steep reverse faults confined to different structural units of the southern slope of the Andreanof Islands and oriented along the strike of these structures. An E-W reverse fault that generated the largest earthquake of 1957 is located within the Aleutian Terrace and genetically appears to be associated with the development of the submarine Hawley Ridge. The western and eastern boundaries of this source are structurally well expressed by the Adak Canyon in the west (˜177°W) and an abrupt change in isobaths in the east (˜173°W). The character of the boundaries is reflected in the focal mechanisms. The source of the earthquake of 1957 extends for about 300 km, which agrees well with modern estimates of its magnitude ( M w = 8.6). Because the earthquake of 1957 caused, due to its high strength, seismic activation of adjacent areas of the Aleutian island arc, its aftershock zone appreciably exceeded in size the earthquake source. Reverse faults that activated the seismic sources of the earthquakes of 1986 and 1996 were located within the southern slope of the Andreanof Islands, higher than the Aleutian Terrace, outside the seismic source of the 1957 earthquake. The boundaries of these sources are also well expressed in structures and focal mechanisms. According to our estimate, the length of the 1986 earthquake source does not exceed 130 140 km, which does not contradict its magnitude ( M w = 8). The length of the 1996 earthquake source is ˜100 km, which also agrees with the magnitude of the earthquake ( M w = 7.8).

Balakina, L. M.; Moskvina, A. G.

2008-08-01

89

The geomorphology of an Aleutian volcano following a major eruption: The 7-8 August 2008 eruption of Kasatochi Volcano, Alaska, and its aftermath  

USGS Publications Warehouse

Analysis of satellite images of Kasatochi volcano and field studies in 2008 and 2009 have shown that within about one year of the 78 August 2008 eruption, significant geomorphic changes associated with surface and coastal erosion have occurred. Gully erosion has removed 300,000 to 600,000 m3 of mostly fine-grained volcanic sediment from the flanks of the volcano and much of this has reached the ocean. Sediment yield estimates from two representative drainage basins on the south and west flanks of the volcano, with drainage areas of 0.7 and 0.5 km2, are about 104 m3 km-2 yr-1 and are comparable to sediment yields documented at other volcanoes affected by recent eruptive activity. Estimates of the retreat of coastal cliffs also made from analysis of satellite images indicate average annual erosion rates of 80 to 140 m yr-1. If such rates persist it could take 35 years for wave erosion to reach the pre-eruption coastline, which was extended seaward about 400 m by the accumulation of erupted volcanic material. As of 13 September 2009, the date of the most recent satellite image of the island, the total volume of material eroded by wave action was about 106 m3. We did not investigate the distribution of volcanic sediment in the near shore ocean around Kasatochi Island, but it appears that erosion and sediment dispersal in the nearshore environment will be greatest during large storms when the combination of high waves and rainfall runoff are most likely to coincide. ?? 2010 Regents of the University of Colorado.

Waythomas, C.F.; Scott, W.E.; Nye, C.J.

2010-01-01

90

77 FR 64918 - Fisheries of the Exclusive Economic Zone Off Alaska; “Other Rockfish” in the Aleutian Islands...  

Federal Register 2010, 2011, 2012, 2013, 2014

...2012)] [Rules and Regulations] [Page 64918] [FR...Off Alaska; ``Other Rockfish'' in the Aleutian...allowable catch of ``other rockfish'' in the Aleutian...and Management Act. Regulations governing fishing by...TAC) of ``other rockfish'' Aleutian...

2012-10-24

91

Geodetic Volcano Monitoring Research in Canary Islands: Recent Results  

NASA Astrophysics Data System (ADS)

The Canarian Archipelago is an oceanic island volcanic chain with a long-standing history of volcanic activity (> 40 Ma). It is located off the NW coast of the African continent, lying over a transitional crust of the Atlantic African passive margin. At least 12 eruptions have been occurred on the islands of Lanzarote, Tenerife and La Palma in the last 500 years. Volcanism manifest predominantly as basaltic strombolian monogenetic activity (whole archipelago) and central felsic volcanism (active only in Tenerife Island). We concentrate our studies in the two most active islands, Tenerife and La Palma. In these islands, we tested different methodologies of geodetic monitoring systems. We use a combination of ground- and space-based techniques. At Tenerife Island, a differential interferometric study was performed to detect areas of deformation. DInSAR detected two clear areas of deformation, using this results a survey-based GPS network was designed and optimized to control those deformations and the rest of the island. Finally, using SBAS DInSAR results weak spatial long- wavelength subsidence signals has been detected. At La Palma, the first DInSAR analysis have not shown any clear deformation, so a first time series analysis was performed detecting a clear subsidence signal at Teneguia volcano, as for Tenerife a GPS network was designed and optimized taking into account stable and deforming areas. After several years of activities, geodetic results served to study ground deformations caused by a wide variety of sources, such as changes in groundwater levels, volcanic activity, volcano-tectonics, gravitational loading, etc. These results proof that a combination of ground-based and space-based techniques is suitable tool for geodetic volcano monitoring in Canary Islands. Finally, we would like to strength that those results could have serious implications on the continuous geodetic monitoring system design and implementation for the Canary Islands which is under development nowadays.

Fernandez, J.; Gonzalez, P. J.; Arjona, A.; Camacho, A. G.; Prieto, J. F.; Seco, A.; Tizzani, P.; Manzo, M. R.; Lanari, R.; Blanco, P.; Mallorqui, J. J.

2009-05-01

92

Radionuclide concentrations in benthic invertebrates from Amchitka and Kiska Islands in the Aleutian Chain, Alaska.  

PubMed

Concentrations of 13 radionuclides (137Cs, 129I, 60Co, 152Eu, 90Sr, 99Tc, 241Am, 238Pu, 239,249Pu, 234U, 235U, 236U, 238U) were examined in seven species of invertebrates from Amchitka and Kiska Islands, in the Aleutian Chain of Alaska, using gamma spectroscopy, inductively coupled plasma mass spectroscopy, and alpha spectroscopy. Amchitka Island was the site of three underground nuclear test (1965-1971), and we tested the null hypotheses that there were no differences in radionuclide concentrations between Amchitka and the reference site (Kiska) and there were no differences among species. The only radionuclides where composite samples were above the Minimum Detectable Activity (MDA) were 137Cs, 241Am, 239,249Pu, 234U, 235U, 236U, and 238U. Green sea urchin (Strongylocentrotus polyacanthus), giant chiton (Cryptochiton stelleri), plate limpets (Tectura scutum) and giant Pacific octopus (Enteroctopus dofleini) were only tested for 137Cs; octopus was the only species with detectable levels of 137Cs (0.262 +/- 0.029 Bq/kg, wet weight). Only rock jingle (Pododesmus macroschisma), blue mussel (Mytilus trossulus) and horse mussel (Modiolus modiolus) were analyzed for the actinides. There were no interspecific differences in 241Am and 239,240Pu, and almost no samples above the MDA for 238Pu and 236U. Horse mussels had significantly higher concentrations of 234U (0.844 +/- 0.804 Bq/kg) and 238U (0.730 +/- 0.646) than the other species (both isotopes are naturally occurring). There were no differences in actinide concentrations between Amchitka and Kiska. In general, radionuclides in invertebrates from Amchitka were similar to those from uncontaminated sites in the Northern Hemisphere, and below those from the contaminated Irish Sea. There is a clear research need for authors to report the concentrations of radionuclides by species, rather than simply as 'shellfish', for comparative purposes in determining geographical patterns, understanding possible effects, and for estimating risk to humans from consuming different biota. PMID:17057992

Burger, Joanna; Gochfeld, Michael; Jewett, Stephen C

2007-05-01

93

Phonolitic Diatremes within the Dunedin Volcano, South Island, New Zealand  

Microsoft Academic Search

The Port Chalmers Breccia is a vent-filling, clastic volcanic unit exposed within the Miocene Dunedin Volcano of South Island, New Zealand. Clasts (up to in excess of 1m but generally 520cm) are supported in ash and fine lapilli of phonolitic (ne-benmoreite or tephro-phonolite) composition and the dominant clast type (55 to almost 100%) is also phonolitic. Less abundant lithologies include

RICHARD C. PRICE; ALAN F. COOPER; JON D. WOODHEAD; IAN CARTWRIGHT

2003-01-01

94

Long term volcano monitoring by using advanced Persistent Scatterer SAR Interferometry technique: A case study at Unimak Island, Alaska  

NASA Astrophysics Data System (ADS)

Unimak Island, the largest island in the eastern Aleutians of Alaska, is home to three major active volcanoes: Shishaldin, Fisher, and Westdahl. Shishaldin and Westdahl erupted within the past 2 decades and Fisher has shown persistent hydrothermal activity (Mann and Freymueller, 2003). Therefore, Unimak Island is of particular interest to geoscientists. Surface deformation on Unimak Island has been studied in several previous efforts. Lu et al. (2000, 2003) applied conventional InSAR techniques to study surface inflation at Westdahl during 1991 and 2000. Mann and Freymueller (2003) used GPS measurements to analyze inflation at Westdahl and subsidence at Fisher during 1998-2001. Moran et al., ( 2006) reported that Shishaldin, the most active volcano in the island , experienced no significant deformation during the 1993 to 2003 period bracketing two eruptions. In this paper, we present deformation measurements at Unimak Islank during 2003-2010 using advanced persistent scatterer InSAR (PSI). Due to the non-urban setting in a subarctic environment and the limited data acquisition, the number of images usable for PSI processing is limited to about 1-3 acquisitions per year. The relatively smaller image stack and the irregular acquisition distribution in time pose challenges in the PSI time-series processing. Therefore, we have developed a modified PSI technique that integrates external atmospheric information from numerical weather predication models to assist in the removal of atmospheric artifacts [1]. Deformation modeling based on PSI results will be also presented. Our new results will be combined with previous findings to address the magma plumbing system at Unimak Island. 1) W. Gong, F. J. Meyer (2012): Optimized filter design for irregular acquired data stack in Persistent Scatterers Synthetic Aperture Radar Interferometry, Proceeding of Geosciences and Remote Sensing Symposium (IGARSS), 2012 IEEE International, Munich, Germany.

Gong, W.; Meyer, F. J.; Freymueller, J. T.; Lu, Z.

2012-12-01

95

Seismic monitoring at Deception Island volcano (Antarctica): Recent advances  

NASA Astrophysics Data System (ADS)

Deception Island (South Shetland Island, Antarctica) is an active volcano with recent eruptions (e.g. 1967, 1969 and 1970). It is also among the Antarctic sites most visited by tourists. Besides, there are currently two scientific bases operating during the austral summers, usually from late November to early March. For these reasons it is necessary to deploy a volcano monitoring system as complete as possible, designed specifically to endure the extreme conditions of the volcanic environment and the Antarctic climate. The Instituto Andaluz de Geofísica of University of Granada, Spain (IAG-UGR) performs seismic monitoring on Deception Island since 1994 during austral summer surveys. The seismicity basically includes volcano-tectonic earthquakes, long-period events and volcanic tremor, among other signals. The level of seismicity is moderate, except for a seismo-volcanic crisis in 1999. The seismic monitoring system has evolved during these years, following the trends of the technological developments and software improvements. Recent advances have been mainly focused on: (1) the improvement of the seismic network introducing broadband stations and 24-bit data acquisition systems; (2) the development of a short-period seismic array, with a 12-channel, 24-bit data acquisition system; (3) the implementation of wireless data transmission from the network stations and also from the seismic array to a recording center, allowing for real-time monitoring; (4) the efficiency of the power supply systems and the monitoring of the battery levels and power consumption; (5) the optimization of data analysis procedures, including database management, automated event recognition tools for the identification and classification of seismo-volcanic signals, and apparent slowness vector estimates using seismic array data; (6) the deployment of permanent seismic stations and the transmission of data during the winter using a satellite connection. A single permanent station is operating at Deception Island since 2008. In the current survey we collaborate with the Spanish Army to add another permanent station that will be able to send to the IAG-UGR seismic information about the activity of the volcano during the winter, using a communications satellite (SPAINSAT). These advances simplify the field work and the data acquisition procedures, and allow us to obtain high-quality seismic data in real-time. These improvements have a very important significance for a better and faster interpretation of the seismo-volcanic activity and assessment of the volcanic hazards at Deception Island volcano.

Carmona, E.; Almendros, J.; Martín, R.; Cortés, G.; Alguacil, G.; Moreno, J.; Martín, B.; Martos, A.; Serrano, I.; Stich, D.; Ibáñez, J. M.

2012-04-01

96

Auklet (Charadriiformes: Alcidae, Aethia spp.) chick meals from the Aleutian Islands, Alaska, have a very low incidence of plastic marine debris  

E-print Network

t i c l e i n f o Keywords: Plastic Marine debris North Pacific Ocean Auklet Aethia Aleutian Islands in the world's oceans (Moore, 2008). This anthropogenic pollution may be mistaken for food by foraging seabirds; Ryan, 1988). In the North Pacific Ocean, incidences of plastic ingestion in a wide variety of seabirds

Jones, Ian L.

97

Scotch Cap Light Station on Unimak Island in the Alaskan Aleutian chain after destruction by the Tsunami of April1, 1946. The Tsunami claimed the lives of  

E-print Network

on Unimak Island in the Alaskan Aleutian chain after destruction by the Tsunami of April1, 1946. The Tsunami.) #12;TSUNAMI RESEARCH OPPORTUNITIES An Assessment and Comprehensive Guide National Science Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Figure 1 -Tsunami Data (1876-1976) .. . . . . .. .. .. .. .. . .. . .. 3 Table I - Major Tsunami

98

Origin of Immature Chum Salmon Collected in the Eastern Bering Sea and Aleutian Islands during the F\\/V Northwest Explorer BASIS Survey, Fall 2002  

Microsoft Academic Search

Immature chum salmon were collected by the F\\/V Northwest Explorer between September 5 and October 8, during the 2002 BASIS survey across the eastern Bering Sea shelf and Aleutian Islands (for details, see Murphy et al. 2003). Approximately 1,600 fish were aged, checked for the presence of hatchery thermal marks, and genotyped for allozyme loci. Scale aging and otolith mark

Christine M. Kondzela; James M. Murphy; Richard L. Wilmot

99

Volcanoes  

NSDL National Science Digital Library

This resource provides general information about volcanoes. It illustrates the growth of a volcano, using Paricutin and Mt. St. Helens as examples of an active volcano and a lava dome. The terms extinct and dormant are also discussed. This site provides an explanation of why and how volcanoes form, zones of subduction, mid-ocean ridges, and hot spots. Deadly dangers associated with eruptions are discussed as is the use of a tiltmeter for prediction. The content center lesson describes a possible connection between the lost continent of Atlantis and the island of Santorini. Dissolved gasses in magma and the creation of a lava dome are both demonstrated in the hands-on section.

Johnson, Scott

100

76 FR 59923 - Fisheries of the Exclusive Economic Zone Off Alaska; “Other Rockfish” in the Aleutian Islands...  

Federal Register 2010, 2011, 2012, 2013, 2014

...2011)] [Rules and Regulations] [Page 59923] [FR...Off Alaska; ``Other Rockfish'' in the Aleutian...TAC) of ``other rockfish'' in the Aleutian...and Management Act. Regulations governing fishing by...2011 TAC of ``other rockfish'' in the...

2011-09-28

101

Ritter Island Volcano-lateral collapse and the tsunami of 1888  

Microsoft Academic Search

In the early morning of 1888 March 13, roughly 5 km3 of Ritter Island Volcano fell violently into the sea northeast of New Guinea. This event, the largest lateral collapse of an island volcano to be recorded in historical time, flung devastating tsunami tens of metres high on to adjacent shores. Several hundred kilometres away, observers on New Guinea chronicled

Steven N. Ward; Simon Day

2003-01-01

102

Aleutian terranes from Nd isotopes  

NASA Technical Reports Server (NTRS)

Nd isotope ratios substantiate the identification of oceanic crustal terranes within the continental crustal basement of the Aleutian island arc. The oceanic terranes are exposed in the westernmost Aleutians, but to the east, they are completely buried by isotopically distinct arc-volcanic rocks. Analogous oceanic terranes may be important components of the terrane collages that comprise the continents.

Kay, R. W.; Kay, S. M.; Rubenstone, J. L.

1986-01-01

103

Hydrochemical fluxes from Baransky volcano, Iturup, Kuril Islands  

NASA Astrophysics Data System (ADS)

The Sernaya River and its tributary the Kipyashaya River are the only rivers that drain all thermal waters coming down the Baransky volcano (Iturup, the Kuril Islands). Hydrological parameters and a chemical composition relating to these rivers and all inflow streams coming from the volcano were measured from August to October 2013. The main aims of this investigation were to develop a data baseline for the catchment of the Sernaya River in order to monitor the Baransky volcano, to estimate total discharge of solute elements and finally to identify thermal groundwater inflow. Since the Kipyashaya River and the Sernaya River receive all water streams coming along the south-west and south flanks of the Baransky volcano within approximately 10 kilometers we can suggest that the whole thermal discharge runs into the Kipyashaya River. Thus a frequent sampling of the rivers presents the best way to monitor the volcano as they comprise a mix of all thermal waters from the Baransky volcano. The Sernaia River, at the end of its course along the flanks of the Baransky volcano, has a total flux of 12 m³/s ± 1%. Multiplication of the discharge by the concentration in main ions of the river at this point yields an aggregate flux of ~130 tons/day ± 10%. This flux performs the dissolution flux as a result of rocks dissolution beneath the active crater and in the aquifer of the Kipyashaya River. Cl total discharge was estimated at ~33 tons/day ± 10%, SO4 ~67 tons/day ± 10%, and total cation discharge ~28 tons/day ± 10%. The Kipyashaya River brings in to the Sernaya River 15 tons/day ± 10% of Cl, ~30 tons/day ± 10% of SO4, and ~3,5 tons/day ± 10% cations average. Several thermal springs with low water discharge are located on the right waterside of the Sernaya River 100 m up and down from the Kipyashaya River influx. These thermal springs with Cl discharge ~ 5g/s have significant concentrations of Ca due to water-rock interaction with basement rocks. The way of sampling streams at the end of their course, just before confluence with the Sernaia River, provides more representative chemical composition of the Baransky volcano waters than a punctual sampling of springs and indicates the existing thermal groundwater inflow. It is argued that a renewal in the activity of the Baransky volcano is a result of the changes in chemical ratios and Cl discharge. Studying the network of the Sernaya River presents one of the best ways of detection such pre-eruptive periods. The work was supported by RFBR grants 13-05-00544A, 14-05-00243, 14-05-00171 and FEB RAS grant 12-III-A-08-161.

Chelnokov, George; Zharkov, Rafael; Bragin, Ivan; Kharitonova, Natalia

2014-05-01

104

First Recorded Eruption of Mount Belinda Volcano, South Sandwich Islands  

NASA Astrophysics Data System (ADS)

The MODVOLC satellite monitoring system at the University of Hawaii Manoa has revealed the first recorded eruption of Mount Belinda volcano, on Montagu Island in the remote South Sandwich Islands. Here we present some initial qualitative observations gleaned from the relatively limited amount of satellite imagery available throughout the eruption, including MODIS, Landsat 7 ETM+ and ASTER data. The eruption started some time between September 12 and October 20, 2001, with low-level ash effusion. In January 2002 a Landsat 7 ETM+ image indicated possible collapse structures in the surface of the continuous ice cover within the caldera, suggesting some degree of subglacial volcanism. By May 2002, a broad area of lava or ash was observed close to the subaerial erupting centre, and activity subsequently increased to its highest observed levels in August 2002. Observations in February and March 2003, from a British Antarctic Survey ship and an aircraft of the British Royal Navy, provided the first visual confirmation of the eruption. Minor thermal anomalies continued to be observed in MODIS imagery throughout August 2003, indicating a prolonged low-level eruption or the establishment of a persistent summit lake possibly similar to that believed to occupy the summit crater (Mount Michael) on nearby Saunders Island. A dynamic lava lake on Saunders Island was first reported in 2001 and remains active.

Smellie, J.; Patrick, M.; Harris, A.; Garbeil, H.; Pilger, E.

2003-12-01

105

Kahoolawe Island, Hawaii: The role of an ‘inaccessible’ shield volcano in the petrology of the Hawaiian islands and plume  

Microsoft Academic Search

Kahoolawe volcano (?10×17km) forms one of the eight major Hawaiian islands. Access for geologic sampling has long been restricted due to military and preservation policies. However, limited visits to Kahoolawe in the 1980s yielded >200 samples, many of which have since been used to study the volcano within the framework of Hawaiian shield and mantle source geochemistry, petrology, mineralogy, and

R. V. Fodor; G. R. Bauer

2010-01-01

106

Near-field survey of the 1946 Aleutian tsunami on Unimak and Sanak Islands  

E-print Network

-up and inundation points through the interview of 48 elderly survivors on 8 islands deprived of coral reefs field, where it killed 159 people in Hawaii, inflicted severe damage in the Marquesas Islands

Synolakis, Costas E.

107

A submarine canyon as the cause of a mud volcano Liuchieuyu Island in Taiwan  

E-print Network

A submarine canyon as the cause of a mud volcano Ð Liuchieuyu Island in Taiwan J. Chowa,*, J, we also discuss the relationship between a nearby submarine canyon (Kaoping Submarine Canyon¯ection; Submarine canyon; Mud volcano 1. Introduction In the early Pliocene, the paleoenvironment of the offshore

Lin, Andrew Tien-Shun

108

First recorded eruption of Mount Belinda volcano (Montagu Island), South Sandwich Islands  

NASA Astrophysics Data System (ADS)

The MODVOLC satellite monitoring system has revealed the first recorded eruption of Mount Belinda volcano, on Montagu Island in the remote South Sandwich Islands. Here we present some initial qualitative observations gleaned from a collection of satellite imagery covering the eruption, including MODIS, Landsat 7 ETM+, ASTER, and RADARSAT-1 data. MODVOLC thermal alerts indicate that the eruption started sometime between 12 September and 20 October 2001, with low-intensity subaerial explosive activity from the island’s summit peak, Mount Belinda. By January 2002 a small lava flow had been emplaced near the summit, and activity subsequently increased to some of the highest observed levels in August 2002. Observations from passing ships in February and March 2003 provided the first visual confirmation of the eruption. ASTER images obtained in August 2003 show that the eruption at Mount Belinda entered a new phase around this time, with fresh lava effusion into the surrounding icefield. MODIS radiance trends also suggest that the overall activity level increased significantly after July 2003. Thermal anomalies continued to be observed in MODIS imagery in early 2004, indicating a prolonged low-intensity eruption and the likely establishment of a persistent summit lava lake, similar to that observed on neighboring Saunders Island in 2001. Our new observations also indicate that lava lake activity continues on Saunders Island.

Patrick, Matthew R.; Smellie, John L.; Harris, Andrew J. L.; Wright, Robert; Dean, Ken; Izbekov, Pavel; Garbeil, Harold; Pilger, Eric

2005-06-01

109

Volcanic Tsunami Generation in the Aleutian Arc of Alaska  

NASA Astrophysics Data System (ADS)

Many of the worlds active volcanoes are situated on or near coastlines, and during eruptions the transfer of mass from volcano to sea is a potential source mechanism for tsunamis. Flows of granular material off of volcanoes, such as pyroclastic flow, debris avalanche, and lahar, often deliver large volumes of unconsolidated debris to the ocean that have a large potential tsunami hazard. The deposits of both hot and cold volcanic grain flows produced by eruptions of Aleutian arc volcanoes are exposed at many locations along the coastlines of the Bering Sea, North Pacific Ocean, and Cook Inlet indicating that the flows entered the sea and in some cases may have initiated tsunamis. We evaluate the process of tsunami generation by granular subaerial volcanic flows using examples from Aniakchak volcano in southwestern Alaska, and Augustine volcano in southern Cook Inlet. Evidence for far-field tsunami inundation coincident with a major caldera-forming eruption of Aniakchak volcano ca. 3.5 ka has been described and is the basis for one of our case studies. We perform a numerical simulation of the tsunami using a large volume pyroclastic flow as the source mechanism and compare our results to field measurements of tsunami deposits preserved along the north shore of Bristol Bay. Several attributes of the tsunami simulation, such as water flux and wave amplitude, are reasonable predictors of tsunami deposit thickness and generally agree with the field evidence for tsunami inundation. At Augustine volcano, geological investigations suggest that as many as 14 large volcanic-rock avalanches have reached the sea in the last 2000 years, and a debris avalanche emplaced during the 1883 eruption may have initiated a tsunami observed about 80 km east of the volcano at the village of English Bay (Nanwalek) on the coast of the southern Kenai Peninsula. By analogy with the 1883 event, previous studies concluded that tsunamis could have been generated many times in the past. If so, geological evidence of tsunamis, such as tsunami deposits on land, should be found in the area around Augustine Island. Paradoxically, unequivocal evidence for tsunami inundation has been found. Augustine Volcano is the most historically active volcano in the Cook Inlet region and a future tsunami from the volcano would have devastating consequences to villages, towns, oil-production facilities, and the fishing industry, especially if it occurred at high tide (the tidal range in this area is about 5 m). Numerical simulation experiments of tsunami generation, propagation and inundation using a subaerial debris avalanche source at Augustine volcano indicate only modest wave generation because of the shallow water surrounding the volcano (maximum water depth about 25 m). Lahar flows produced during eruptions at snow and ice clad volcanoes in the Aleutian arc also deliver copious amounts of sediment to the sea. These flows only rarely transform to subaqueous debris flows that may become tsunamigenic. However, the accumulation of loose, unconsolidated sediment on the continental shelf may lead to subaqueous debris flows and landslides if these deposits become mobilized by large earthquakes. Tsunamis produced by this mechanism could potentially reach coastlines all along the Pacific Rim. Finally, recent work in the western Aleutian Islands indicates that many of the island volcanoes in this area have experienced large-scale flank collapse. Because these volcanoes are surrounded by deep water, the tsunami hazard associated with a future sector collapse could be significant.

Waythomas, C. F.; Watts, P.

2003-12-01

110

Toothpaste lava from the Barren Island volcano (Andaman Sea)  

NASA Astrophysics Data System (ADS)

Toothpaste lava is a basaltic lava flow type transitional between pahoehoe and aa and has been described from Paricutin, Kilauea and Etna volcanoes. Here we describe a spectacular example of toothpaste lava, forming part of a recent (possibly 1994-95) aa flow on the active volcano of Barren Island (Andaman Sea). This flow of subalkalic basalt shows abundant squeeze-ups of viscous toothpasate lava near its entry into the sea. The squeeze-ups are sheets and slabs, up to several meters across and tens of centimeters thick, extruded from boccas. They are often prominently curved, have striated upper surfaces with close-spaced, en echelon linear ridges and grooves, broad wave-like undulations perpendicular to the striations, and sometimes, clefts. Textural, geochemical, and Sr-Nd isotopic data on the squeeze-ups and the exposed aa flow core indicate very crystal-rich, viscous, and isotopically very homogeneous lava. We envisage that a greatly reduced speed of this viscous flow at the coastline, possibly aided by a shallowing of the basal slope, led to lateral spreading of the flow, which caused tension in its upper parts. This, with continued (albeit dwindling) lava supply at the back, led to widespread tearing of the flow surface and extrusion of the squeeze-ups. The larger slabs, while extruding in a plastic condition, curved under their own weight, whereas their surfaces experienced brittle deformation, forming the en echelon grooves. The extruded, detached, and rotated sheets and slabs were carried forward for some distance atop the very slowly advancing aa core, before the flow solidified.

Sheth, Hetu C.; Ray, Jyotiranjan S.; Kumar, Alok; Bhutani, Rajneesh; Awasthi, Neeraj

2011-04-01

111

The First Historical Eruption of Anatahan Volcano, Mariana Islands  

NASA Astrophysics Data System (ADS)

The first historical eruption of Anatahan volcano occurred on May 10, 2003. The MARGINS office responded by authorizing helicopter surveillance and ship deployment to visit the volcano. The helicopter flight on May 19 allowed visual observations and identification of the east crater as the source of the eruption. The top of the plume was estimated to be at 10,000 ft - significantly less than the 30,000 ft of the initial blast. No bombs were ejected out of the east crater at this time but were falling back into the crater. The bombs looked irregular in shape, massive and were estimated to be a few m in diameter. Bombs and tephra samples were collected from the eastern side of the island when blasts were occurring at a rate of approx. 1 per 5min. The ship visit followed on May 21 to the western side of the island for collection of samples and SO2 flux measurements, along with maintenance of a previously deployed seismometer. Volcanic samples collected on Anatahan consisted of bombs, ash and scoria from the present eruption and old lavas (age unknown). The ash section on the western shore was 25 cm thick and consisted of the following sequence (bottom to top): 0-5 inversely? graded dark ash with scoria and pumice clasts (1-2 cm), 20-25 cm: well sorted clast-supported scoria (max 2 cm) with some fine ash. The maximum total thickness measured at a site 6 km from the east crater was approximately 45 cm. The sequence is interpreted as 1) initial blast 2) interaction of magma with water (from pre-existing hydrothermal system) as evidenced by accretionary lapilli 3) magmatic phase of the eruption producing juvenile material. Electron microprobe analyses of the pumice and scoria show uniform compositions of ~ 60wt% SiO2 in the glass; zoned plagioclase with average composition of 61% An, 37.7% Ab, 1.2% Or; pyroxenes (19.4% Wo, 53.4% En, 26.7% Fs) and Fe-Ti oxides. Sulfur and Cl contents are approx. 100 and 1500 ppm, respectively. Water content of the glass may be several wt% based on analytical totals. Volatile emissions from the volcano were measured by traversing under the plume with a ship-based COSPEC. Using wind speed data from NOAA (10-15 knots on May 21), we estimate the daily SO2 flux to be 3000 - 4500 tons. Our observations are consistent with the idea that the initial phreatic eruption evolved rapidly into a magmatic phase producing juvenile (and vesicular) material accompanied by a high SO2 flux. Details on the eruption products, chemical analyses, seismic measurements, and current monitoring efforts can be found in accompanying posters.

Fischer, T. P.; Hilton, D. R.; Demoor, J.; Jaffe, L.; Spilde, M. N.; Counce, D.; Camacho, J. T.

2003-12-01

112

78 FR 56837 - Fisheries of the Exclusive Economic Zone Off Alaska; “Other Rockfish” in the Aleutian Island...  

Federal Register 2010, 2011, 2012, 2013, 2014

...2013)] [Rules and Regulations] [Pages 56837-56838...Off Alaska; ``Other Rockfish'' in the Aleutian...TAC) of ``other rockfish'' in the BSAI has...and Management Act. Regulations governing fishing by...The 2013 TAC ``other rockfish'' in the...

2013-09-16

113

APRIL 2009 FERNANDINA VOLCANO ERUPTION, GALAPAGOS ISLANDS, ECUADOR: THERMAL MAPPING OF THE LAVA FLOWS EMITTED  

E-print Network

B APRIL 2009 FERNANDINA VOLCANO ERUPTION, GALAPAGOS ISLANDS, ECUADOR: THERMAL MAPPING OF THE LAVA Politécnica Nacional (IG-EPN), Quito, Ecuador 2. Institut de Recherche pour le Développement, Clermont, no earthquakes were associated with this eruption. Fernandina Island is about 32 km in diameter,a maximum

Geist, Dennis

114

Surface Pressure Gradient and Carbon Dioxide Degassing Survey at Cumbre Vieja Volcano, La Palma, Canary Islands  

Microsoft Academic Search

La Palma (730 Km2) is one of the youngest island of the Canarian archipelago. Recent volcanic activity is concentrated on the southern part of the island, where Cumbre Vieja volcano (220 Km2) has been constructed during the last 1 Ma reaching an elevation of 1,898 m above sea level. Six historical eruptions had occurred at Cumbre Vieja, and the most

A. Alfaya; F. López; E. Padron; P. A. Hernández; J. M. Salazar; N. M. Pérez

2002-01-01

115

A model for selecting bioindicators to monitor radionuclide concentrations using Amchitka Island in the Aleutians as a case study.  

PubMed

World War II and the Cold War have left the Unites States, and other Nations, with massive cleanup and remediation tasks for radioactive and other legacy hazardous wastes. While some sites can be cleaned up to acceptable residential risk levels, others will continue to hold hazardous wastes, which must be contained and monitored to protect human health and the environment. While media (soil, sediment, groundwater) monitoring is the usual norm at many radiological waste sites, for some situations (both biological and societal), biomonitoring may provide the necessary information to assure greater peace of mind for local and regional residents, and to protect ecologically valuable buffer lands or waters. In most cases, indicators are selected using scientific expertise and a literature review, but not all selected indicators will seem relevant to stakeholders. In this paper, I provide a model for the inclusion of stakeholders in the development of bioindicators for assessing radionuclide levels of biota in the marine environment around Amchitka Island, in the Aleutian Chain of Alaska. Amchitka was the site of three underground nuclear tests from 1965 to 1971. The process was stakeholder-initiated, stakeholder-driven, and included stakeholders during each phase. Phases included conceptualization, initial selection of biota and radionuclides, refinement of biota and radionuclide target lists, collection of biota, selection of biota and radionuclides for analysis, and selection of biota, tissues, and radionuclides for bioindicators. The process produced site-specific information on biota availability and on radionuclide levels that led to selection of site-appropriate bioindicators. I suggest that the lengthy, iterative, stakeholder-driven process described in this paper results in selection of bioindicators that are accepted by biologists, public health personnel, public-policy makers, resource agencies, regulatory agencies, subsistence hunters/fishers, and a wide range of other stakeholders. The process is applicable to other sites with ecologically important buffer lands or waters, or where contamination issues are contentious. PMID:17698056

Burger, Joanna

2007-11-01

116

A model for selecting bioindicators to monitor radionuclide concentrations using Amchitka Island in the Aleutians as a case study  

SciTech Connect

World War II and the Cold War have left the Unites States, and other Nations, with massive cleanup and remediation tasks for radioactive and other legacy hazardous wastes. While some sites can be cleaned up to acceptable residential risk levels, others will continue to hold hazardous wastes, which must be contained and monitored to protect human health and the environment. While media (soil, sediment, groundwater) monitoring is the usual norm at many radiological waste sites, for some situations (both biological and societal), biomonitoring may provide the necessary information to assure greater peace of mind for local and regional residents, and to protect ecologically valuable buffer lands or waters. In most cases, indicators are selected using scientific expertise and a literature review, but not all selected indicators will seem relevant to stakeholders. In this paper, I provide a model for the inclusion of stakeholders in the development of bioindicators for assessing radionuclide levels of biota in the marine environment around Amchitka Island, in the Aleutian Chain of Alaska. Amchitka was the site of three underground nuclear tests from 1965 to 1971. The process was stakeholder-initiated, stakeholder-driven, and included stakeholders during each phase. Phases included conceptualization, initial selection of biota and radionuclides, refinement of biota and radionuclide target lists, collection of biota, selection of biota and radionuclides for analysis, and selection of biota, tissues, and radionuclides for bioindicators. The process produced site-specific information on biota availability and on radionuclide levels that led to selection of site-appropriate bioindicators. I suggest that the lengthy, iterative, stakeholder-driven process described in this paper results in selection of bioindicators that are accepted by biologists, public health personnel, public-policy makers, resource agencies, regulatory agencies, subsistence hunters/fishers, and a wide range of other stakeholders. The process is applicable to other sites with ecologically important buffer lands or waters, or where contamination issues are contentious.

Burger, Joanna [Division of Life Sciences, Environmental and Occupational Health Sciences Institute, and Consortium for Risk Evaluation with Stakeholder Participation, Rutgers University, Piscataway, NJ (United States)], E-mail: burger@biology.rutgers.edu

2007-11-15

117

Depths of Magma Storage Beneath Fogo Volcano, Cape Verde Islands  

NASA Astrophysics Data System (ADS)

Fogo is one of the most active oceanic volcanoes of the world in present time and the only island of the Cape Verde archipelago with historic volcanic activity. We have carried out a barometric study of basanitic to tephriphonolitic volcanic rocks of the 1995 eruption of Fogo in order to reconstruct the depths of magma reservoirs and magma pathways prior to eruption. The pyroclastic rocks and lavas studied span the whole temporal and compositional range of this eruption. Clinopyroxene-melt thermobarometry of 75 clinopyroxenes in 9 samples yields a well-defined pressure range of 500-630 MPa (average 550 MPa). This pressure range is interpreted to reflect a major fractionation level at ca. 17-22 km depth, within the uppermost mantle, where melt and phenocrysts last equilibrated. Microthermometry of CO2-rich fluid inclusions in clinopyroxene and olivine phenocrysts indicates a broader pressure range with two apparent frequency maxima. The higher pressure range, between 430 and 510 MPa (average 480 MPa), partly overlaps with the clinopyroxene-melt barometry data. The lower pressure range, between 250 and 430 MPa (average 375 MPa), is within the lower crust to Moho and may reflect short-term stagnation of magma at 9-16 km depth prior to eruption. Our data suggest that the 1995 magmas ascended from mantle depth to the surface with residence times at shallow levels probably being restricted to less than a day. This conclusion is in accordance with the absence of plagioclase phenocrysts and microphenocrysts in the 1995 and most other recent lavas.

Hildner, E.; Klügel, A.

2008-12-01

118

Monitoring the evolution of Deception Island volcano from magnetic anomaly data (South Shetland Islands, Antarctica)  

NASA Astrophysics Data System (ADS)

Deception Island is a young and active volcano located in the south-western part of Bransfield back-arc basin. During the last twenty years the Royal Observatory of the Spanish Navy has carried out geophysical surveys in the area. In addition, an unmanned aerial vehicle flight was conducted in 2011 at 800 m height on the northern half of Deception Island. Analysing and comparing magnetic grids obtained in different periods and tie point readings allow us to detect temporal changes and isolate signals of volcanic origin. Magnetic survey cruises performed in Deception Island's inner bay (1988, 1999 and 2008), and the study of its outer area's magnetic anomaly changes, point to a period of high variations concentrated between December 1989 and December 1999 that may be related to the two main recent periods of seismic activity (1992 and January 1999). From December 1999 to December 2008, there were no significant changes in seismic activity; nevertheless, our data show some magnetic alterations, which might signal the slow progress of a volcanic environment towards equilibrium. Interpreting these magnetic changes called for the construction of several forward models. Additionally, we put forth this kind of study as a suitable, economical and easy method for monitoring an active volcanic system whenever it is possible to measure the magnetic field with accurate positioning, and if the external field components are removed correctly.

Catalán, Manuel; Martos, Yasmina M.; Galindo-Zaldívar, Jesús; Funaki, Minoru

2014-12-01

119

Embedded ARM system for volcano monitoring in remote areas: application to the active volcano on Deception Island (Antarctica).  

PubMed

This paper describes the development of a multi-parameter system for monitoring volcanic activity. The system permits the remote access and the connection of several modules in a network. An embedded ARM™ processor has been used, allowing a great flexibility in hardware configuration. The use of a complete Linux solution (Debian™) as Operating System permits a quick, easy application development to control sensors and communications. This provides all the capabilities required and great stability with relatively low energy consumption. The cost of the components and applications development is low since they are widely used in different fields. Sensors and commercial modules have been combined with other self-developed modules. The Modular Volcano Monitoring System (MVMS) described has been deployed on the active Deception Island (Antarctica) volcano, within the Spanish Antarctic Program, and has proved successful for monitoring the volcano, with proven reliability and efficient operation under extreme conditions. In another context, i.e., the recent volcanic activity on El Hierro Island (Canary Islands) in 2011, this technology has been used for the seismic equipment and GPS systems deployed, thus showing its efficiency in the monitoring of a volcanic crisis. PMID:24451461

Peci, Luis Miguel; Berrocoso, Manuel; Fernández-Ros, Alberto; García, Alicia; Marrero, José Manuel; Ortiz, Ramón

2014-01-01

120

Embedded ARM System for Volcano Monitoring in Remote Areas: Application to the Active Volcano on Deception Island (Antarctica)  

PubMed Central

This paper describes the development of a multi-parameter system for monitoring volcanic activity. The system permits the remote access and the connection of several modules in a network. An embedded ARM™™ processor has been used, allowing a great flexibility in hardware configuration. The use of a complete Linux solution (Debian™) as Operating System permits a quick, easy application development to control sensors and communications. This provides all the capabilities required and great stability with relatively low energy consumption. The cost of the components and applications development is low since they are widely used in different fields. Sensors and commercial modules have been combined with other self-developed modules. The Modular Volcano Monitoring System (MVMS) described has been deployed on the active Deception Island (Antarctica) volcano, within the Spanish Antarctic Program, and has proved successful for monitoring the volcano, with proven reliability and efficient operation under extreme conditions. In another context, i.e., the recent volcanic activity on El Hierro Island (Canary Islands) in 2011, this technology has been used for the seismic equipment and GPS systems deployed, thus showing its efficiency in the monitoring of a volcanic crisis. PMID:24451461

Peci, Luis Miguel; Berrocoso, Manuel; Fernández-Ros, Alberto; García, Alicia; Marrero, José Manuel; Ortiz, Ramón

2014-01-01

121

A submarine canyon as the cause of a mud volcano — Liuchieuyu Island in Taiwan  

Microsoft Academic Search

In this paper, based on 3.5kHz, UNIBOOM and conventional seismic data, we propose a model for the creation of Liuchieuyu Island, a near-shore mud volcano off the southwestern coast of Taiwan. In support of this model, we also discuss the relationship between a nearby submarine canyon (Kaoping Submarine Canyon) and the mud diapirs and mud volcanoes in the region. Seismic

J. Chow; J. S. Lee; C. S. Liu; B. D. Lee; J. S. Watkins

2001-01-01

122

Specification of Tectonic Tsunami Sources Along the Eastern Aleutian Island Arc and Alaska Peninsula for Inundation Mapping and Hazard Assessment  

NASA Astrophysics Data System (ADS)

The Alaska Earthquake Information Center conducts tsunami inundation mapping for coastal communities in Alaska along several segments of the Aleutian Megathrust, each having a unique seismic history and tsunami generation potential. Accurate identification and characterization of potential tsunami sources is a critical component of our project. As demonstrated by the 2011 Tohoku-oki tsunami, correct estimation of the maximum size event for a given segment of the subduction zone is particularly important. In that event, unexpectedly large slip occurred approximately updip of the epicenter of the main shock, based on seafloor GPS and seafloor pressure gage observations, generating a much larger tsunami than anticipated. This emphasizes the importance of the detailed knowledge of the region-specific subduction processes, and using the most up-to-date geophysical data and research models that define the magnitude range of possible future tsunami events. Our study area extends from the eastern half of the 1957 rupture zone to Kodiak Island, covering the 1946 and 1938 rupture areas, the Shumagin gap, and the western part of the 1964 rupture area. We propose a strategy for generating worst-case credible tsunami scenarios for locations that have a short or nonexistent paleoseismic/paleotsunami record, and in some cases lack modern seismic and GPS data. The potential tsunami scenarios are built based on a discretized plate interface model fit to the Slab 1.0 model geometry. We employ estimates of slip deficit along the Aleutian Megathrust from GPS campaign surveys, the Slab 1.0 interface surface, empirical magnitude-slip relationships, and a numerical code that distributes slip among the subfault elements, calculates coseismic deformations and solves the shallow water equations of tsunami propagation and runup. We define hypothetical asperities along the megathrust and in down-dip direction, and perform a set of sensitivity model runs to identify coseismic deformation patterns resulting in highest runup at a given community. Because of the extra fine discretization of the interface, we can prescribe variable slip patterns, using simple parameters to describe slip variations in the along-strike and down-dip directions. Since it was demonstrated by studies of the 1964 tsunami that changes in slip distribution result in significant variations in the local tsunami wave field, we expect that the near-field tsunami runup in target communities will be highly sensitive to variability of slip along the rupture area. We perform simulations for each source scenario using AEIC's numerical model of tsunami propagation and runup, which is validated through a set of analytical benchmarks and tested against laboratory and field data. Results of numerical modeling combined with historical observations are compiled on inundation maps and used for site-specific tsunami hazard assessment by local emergency planners.

Suleimani, E.; Nicolsky, D.; Freymueller, J. T.; Koehler, R.

2013-12-01

123

Ritter Island Volcano-lateral collapse and the tsunami of 1888  

NASA Astrophysics Data System (ADS)

In the early morning of 1888 March 13, roughly 5 km3 of Ritter Island Volcano fell violently into the sea northeast of New Guinea. This event, the largest lateral collapse of an island volcano to be recorded in historical time, flung devastating tsunami tens of metres high on to adjacent shores. Several hundred kilometres away, observers on New Guinea chronicled 3 min period waves up to 8 m high, that lasted for as long as 3 h. These accounts represent the best available first-hand information on tsunami generated by a major volcano lateral collapse. In this article, we simulate the Ritter Island landslide as constrained by a 1985 sonar survey of its debris field and compare predicted tsunami with historical observations. The best agreement occurs for landslides travelling at 40 m s-1, but velocities up to 80 m s-1 cannot be excluded. The Ritter Island debris dropped little more than 800 m vertically and moved slowly compared with landslides that descend into deeper water. Basal friction block models predict that slides with shorter falls should attain lower peak velocities and that 40+ m s-1 is perfectly compatible with the geometry and runout extent of the Ritter Island landslide. The consensus between theory and observation for the Ritter Island waves increases our confidence in the existence of mega-tsunami produced by oceanic volcano collapses two to three orders of magnitude larger in scale.

Ward, Steven N.; Day, Simon

2003-09-01

124

Testing the nutritional-limitation, predator-avoidance, and storm-avoidance hypotheses for restricted sea otter habitat use in the Aleutian Islands, Alaska  

USGS Publications Warehouse

Sea otters (Enhydra lutris) inhabiting the Aleutian Islands have stabilized at low abundance levels following a decline and currently exhibit restricted habitat-utilization patterns. Possible explanations for restricted habitat use by sea otters can be classified into two fundamentally different processes, bottom-up and top-down forcing. Bottom-up hypotheses argue that changes in the availability or nutritional quality of prey resources have led to the selective use of habitats that support the highest quality prey. In contrast, top-down hypotheses argue that increases in predation pressure from killer whales have led to the selective use of habitats that provide the most effective refuge from killer whale predation. A third hypothesis suggests that current restricted habitat use is based on a need for protection from storms. We tested all three hypotheses for restricted habitat use by comparing currently used and historically used sea otter foraging locations for: (1) prey availability and quality, (2) structural habitat complexity, and (3) exposure to prevailing storms. Our findings suggest that current use is based on physical habitat complexity and not on prey availability, prey quality, or protection from storms, providing further evidence for killer whale predation as a cause for restricted sea otter habitat use in the Aleutian Islands.

Stewart, Nathan L.; Konar, Brenda; Tinker, M. Tim

2014-01-01

125

Testing the nutritional-limitation, predator-avoidance, and storm-avoidance hypotheses for restricted sea otter habitat use in the Aleutian Islands, Alaska.  

PubMed

Sea otters (Enhydra lutris) inhabiting the Aleutian Islands have stabilized at low abundance levels following a decline and currently exhibit restricted habitat-utilization patterns. Possible explanations for restricted habitat use by sea otters can be classified into two fundamentally different processes, bottom-up and top-down forcing. Bottom-up hypotheses argue that changes in the availability or nutritional quality of prey resources have led to the selective use of habitats that support the highest quality prey. In contrast, top-down hypotheses argue that increases in predation pressure from killer whales have led to the selective use of habitats that provide the most effective refuge from killer whale predation. A third hypothesis suggests that current restricted habitat use is based on a need for protection from storms. We tested all three hypotheses for restricted habitat use by comparing currently used and historically used sea otter foraging locations for: (1) prey availability and quality, (2) structural habitat complexity, and (3) exposure to prevailing storms. Our findings suggest that current use is based on physical habitat complexity and not on prey availability, prey quality, or protection from storms, providing further evidence for killer whale predation as a cause for restricted sea otter habitat use in the Aleutian Islands. PMID:25416538

Stewart, Nathan L; Konar, Brenda; Tinker, M Tim

2014-11-22

126

Volcanoes  

NSDL National Science Digital Library

Create a poster about volcanoes Directions: Make a poster about volcanoes. (20 points) Include at least (1) large picture (15 points) on your poster complete with labels of every part (10 points). (15 points) Include at least three (3) facts about volcanoes. (5 points each) (15 points) Write at least a three sentence summary of your poster and volcanoes. (5 points) Use at ...

Mrs. Walls

2011-01-30

127

76 FR 68354 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...  

Federal Register 2010, 2011, 2012, 2013, 2014

...NMFS determined the amount of QS issued based on the catch history of...sole, Pacific cod, rock sole, and yellowfin sole) in the Bering Sea and Aleutian...allocation, and may have little incentive to coordinate...unique persons and nine QS permits must...

2011-11-04

128

Cumbre Vieja Volcano-Potential collapse and tsunami at La Palma, Canary Islands  

Microsoft Academic Search

Geological evidence suggests that during a future eruption, Cumbre Vieja Volcano on the Island of La Palma may experience a catastrophic failure of its west flank, dropping 150 to 500 km3 of rock into the sea. Using a geologically reasonable estimate of landslide motion, we model tsunami waves produced by such a collapse. Waves generated by the run-out of a

Steven N. Ward; Simon Day

2001-01-01

129

Volcanoes  

ERIC Educational Resources Information Center

Describes the forces responsible for the eruptions of volcanoes and gives the physical and chemical parameters governing the type of eruption. Explains the structure of the earth in relation to volcanoes and explains the location of volcanic regions. (GS)

Kunar, L. N. S.

1975-01-01

130

Volcanoes  

SciTech Connect

This book describes volcanoes although the authors say they are more to be experienced than described. This book poses more question than answers. The public has developed interest and awareness in volcanism since the first edition eight years ago, maybe because since the time 120 volcanoes have erupted. Of those, the more lethal eruptions were from volcanoes not included in the first edition's World's 101 Most Notorious Volcanoes.

Decker, R.W.; Decker, B.

1989-01-01

131

Volcanoes  

NSDL National Science Digital Library

In this lesson, students investigate the processes that build volcanoes, the types of rocks they create, the factors that influence different eruption types, and the threats volcanoes pose to their surrounding environments. They will also create a notebook of volcano characteristics and use what they have learned to identify physical features and eruption types in some real-life documented volcanic episodes.

2005-01-01

132

Volcanoes.  

ERIC Educational Resources Information Center

One of a series of general interest publications on science topics, this booklet provides a non-technical introduction to the subject of volcanoes. Separate sections examine the nature and workings of volcanoes, types of volcanoes, volcanic geological structures such as plugs and maars, types of eruptions, volcanic-related activity such as geysers…

Tilling, Robert I.

133

The petrogenesis of sodic island arc magmas at Savo volcano, Solomon Islands  

NASA Astrophysics Data System (ADS)

Savo, Solomon Islands, is a historically active volcano dominated by sodic, alkaline lavas, and pyroclastic rocks with up to 7.5 wt% Na2O, and high Sr, arc-like trace element chemistry. The suite is dominated by mugearites (plagioclase-clinopyroxene-magnetite ± amphibole ± olivine) and trachytes (plagioclase-amphibole-magnetite ± biotite). The presence of hydrous minerals (amphibole, biotite) indicates relatively wet magmas. In such melts, plagioclase is relatively unstable relative to iron oxides and ferromagnesian silicates; it is the latter minerals (particularly hornblende) that dominate cumulate nodules at Savo and drive the chemical differentiation of the suite, with a limited role for plagioclase. This is potentially occurring in a crustal “hot zone”, with major chemical differentiation occurring at depth. Batches of magma ascend periodically, where they are subject to decompression, water saturation and further cooling, resulting in closed-system crystallisation of plagioclase, and ultimately the production of sodic, crystal and feldspar-rich, high-Sr rocks. The sodic and hydrous nature of the parental magmas is interpreted to be the result of partial melting of metasomatised mantle, but radiogenic isotope data (Pb, Sr, Nd) cannot uniquely identify the source of the metasomatic agent.

Smith, D. J.; Petterson, M. G.; Saunders, A. D.; Millar, I. L.; Jenkin, G. R. T.; Toba, T.; Naden, J.; Cook, J. M.

2009-12-01

134

Continuous Monitoring of Diffuse Gas Emission From Teide Volcano, Tenerife, Canary Islands  

Microsoft Academic Search

Teide volcano (3,717 m a.s.l.) is located in the central part of Tenerife island, at the intersection of three major volcanic rift-zones. Low temperature fumaroles (81-85°C) occur in the summit cone, where significant amounts of diffuse CO2 degassing have been measured about 400 of tons per day (Hernandez et al., 1998; Gonzalez et al., 2001). Chemical and isotopic composition of

J. Salazar; R. Lima; G. Melian; I. Galindo; E. Padron; P. Hernandez; N. Perez

2002-01-01

135

Identifying rift zones on volcanoes: an example from La Réunion island, Indian Ocean  

Microsoft Academic Search

We describe a methodology for identifying complex rift zones on recent or active volcanoes, where structures hidden by recent\\u000a deposits and logistical conditions might prevent carrying out detailed fieldwork. La Réunion island was chosen as a test-site.\\u000a We used georeferenced topographic maps, aerial photos and digital terrain models to perform a statistical analysis of several\\u000a morphometric parameters of pyroclastic cones.

Fabio Luca Bonali; Claudia Corazzato; Alessandro Tibaldi

2011-01-01

136

Evidence for two shield volcanoes exposed on the island of Kauai, Hawaii  

USGS Publications Warehouse

The island of Kauai has always been interpreted as a single shield volcano, but lavas of previously correlated reversed-to-normal magnetic-polarity transitions on opposite sides of the island differ significantly in isotopic composition. Samples from west Kauai have 87Sr/86Sr 18.25; samples from east Kauai have 87Sr/86Sr > 0.7037, ??Nd ??? 6.14, and 206Pb/204Pb < 18.25. Available data suggest that a younger eastern shield grew on the collapsed flank of an older western one.

Holcomb, R.T.; Reiners, P.W.; Nelson, B.K.; Sawyer, N.-L.E.

1997-01-01

137

VOLInSAR-PF, the InSAR Volcano Observatory Service at Piton de la Fournaise Volcano (La Reunion Island).  

NASA Astrophysics Data System (ADS)

Since 2003, we carry out a systematic InSAR survey of the Piton de la Fournaise volcano, Reunion Island, in the framework of an AO-ENVISAT project. Since 2005 this activity gets the status of Observatory Service of the Observatoire de Physique du Globe de Clermont-Ferrand (OPGC). From 375 ASAR images acquired between 2003 and 2010, we have produced more than 2100 interferograms that allowed us to map the deformations related to 21 eruptions and thus to better understand the internal processes acting during each eruption. In the same time, we have developed an automatic procedure to provide full resolution interferograms, trough a dedicated WEB site, to the Volcano Observatory of Piton de la Fournaise (OVPF), and our other partners, within a few hours after receiving the ASAR images. In this way, our work is a first step toward an operational system of InSAR monitoring of volcanic activity. Since the beginning of 2010, the VOLInSAR-PF database is also open to the entire community, trough an anonymous login that gives access to slightly reduced resolution interferograms. We will present the VOLInSAR-PF database, the main results it provides concerning the way Piton de la Fournaise is deforming, and the main perspectives for monitoring provided by the new InSAR data (PALSAR-ALOS, TerraSAR-X, RADARSAT-2, COSMO-Skymed) we are beginning to integrate in the database.

Froger, Jean-Luc; Cayol, Valérie; Augier, Aurélien; Souriot, Thierry

2010-05-01

138

Bathymetric constraints on the tectonic and volcanic evolution of Deception Island Volcano, South Shetland Islands  

E-print Network

basin situated behind the extinct South Shetland Islands arc. Deception Island has been well studied but its submerged flanks have not. A multibeam bathymetry survey was conducted around the island in 2005 Shetland island arc or of simple shear between the Scotia and Antarctic plates (Lawver et al. 1996, Barker

Wilcock, William

139

Central Aleutian tundra: ecological manifestations of maritime tundra landscapes in the Central Aleution Islands (Amchitka, Adak) Alaska. Final report, 1 April 1971-15 November 1985  

SciTech Connect

Measured and inferred ecological characteristics and holocoenotic factors which affect the dynamics and manifestations of central Aleutian maritime tundra and beach-dune vegetational expressions of Adak and Amchitka Islands are discussed. The known vascular flora is enumerated and predominant taxa are grouped into communities and topoedaphic units. Stability of community composition and structure is elaborated and the absence of ecological succession demonstrated. Perturbations occasioned by human activities which impinge on these remote islands are detailed. The testing and monitoring of subsequent passive and managed recovery of stable vegetation on disturbed areas is described. Selection, preparation and utilization of transplants of Elymus mollis Trin. is documented. Transplants of rhizomes of E. mollis are successful in the reestablishment of vegetative cover in disturbed habitats which are topoedaphically suitable for graminoid success. The responses of plant population stands to environmental processes and habitat insults are reported. The relatively limited but stable biota and the lethargic ecological response as defined by extant vegetational expressions provide field test potentials which mandate further basic and applied research.

Amundsen, C.C.

1985-01-01

140

Comprehensive study of the seismotectonics of the eastern Aleutian arc and associated volcanic systems. Annual progress report, March 1, 1980-February 28, 1981  

SciTech Connect

Refined hypocenter locations beneath the Shumagin Islands seismic network of the eastern Aleutian arc, Alaska, provide for the first time conclusive evidence for a double-sheeted dipping seismic (Benioff) zone in this arc. This refined seismicity structure was obtained in the arc section centered on the Shumagin seismic gap. A thorough review of three seismic gaps in the eastern Aleutian arc shows a high potential for great earthquakes within the next one to two decades in the Shumagin and Yakataga seismic gaps, and a less certain potential for a large or great earthquake in the possible Unalaska gap. A tilt reversal was geodetically observed to have occurred in 1978/79 in the forearc region of the Shumagin gap and could indicate the onset of a precursory strain relief episode prior to a great quake. A comparative study of the Pavlof volcano seismicity with that of other recently active volcanoes (i.e., Mt. St. Helens) indicates that island-arc (explosive-type) volcanoes respond to small ambient, periodic stress changes (i.e., tides). Stress drop measurements from earthquakes on the main thrust zone indicate high stress drops within the seismic gap regions of the Aleutian arc and low stress drops outside the gap region.

Jacob, K.H.; Davies, J.N.; House, L.

1981-01-01

141

High CO2 Levels in Boreholes at El Teide Volcano Complex (Tenerife, Canary Islands): Implications for Volcanic  

E-print Network

High CO2 Levels in Boreholes at El Teide Volcano Complex (Tenerife, Canary Islands): Implications emissions at numerous water prospection drillings in the volcanic island of Tenerife. Large concentrations Consejo Insular de Aguas (CIA) , Cabildo de Tenerife, Santa Cruz de Tenerife, Spain. 6 Servicio Electro

Long, Bernard

142

Hydrogeochemical, Stable Isotopes and Hydrology of Fogo Volcano Perched Aquifers: São Miguel Island, Azores (Portugal)  

NASA Astrophysics Data System (ADS)

Fogo Volcano is located at central part of São Miguel Island and corresponds to a polygenetic volcano with a caldera made by an intercalated accumulation of volcaniclastic deposits and lava flows. São Miguel Island is one of the nine volcanic islands that form the Azores Archipelago. The volcano is 950 meters high, with a caldera diameter of 3.2 Km, which holds a lake inside. The last eruption occurred in 1563-1564, as one of a group of seven traquitic eruptions occurring within the last 5000 years. The volcanic activity is related to hydrothermal activity in a geothermal field located in the volcanoes North flank. The hydrology of Fogo Volcano is characterized by a series of perched-water bodies drained by a large number of springs grouped at different altitudes on the volcano flanks. It is possible to identify three types of water (1) Fresh water, cold temperature (12 - 17 C) with low dissolved solids contents (average conductivity of 179 ?S/cm), pH range between 6.60 and 7.82, dominated by the major ions Na, K, HCO3, and Cl, and correspond mainly to sodium bicarbonate type water. (2) Mineral water, cold temperature (12.5 - 19.4 C) with low dissolved solids contents (average conductivity of 261 ?S/cm), acid pH range between 4.62 and 6.79, and correspond mainly to sodium bicarbonate type water. (3) Thermal water, with temperature of 32 C, high dissolved solids content (4.62 mS/cm), with a pH around 4.50 and belongs to sodium sulfate type water. South Fogo volcano have only fresh water springs and at high elevation, springs drained from pumice fall deposits near 700 m of altitude. Water dissolved solids contents increased slightly with springs at lower altitude due to water-rock interaction. Springs sampled around 700 m high have a conductivity average of 85 ?S/cm, at 520 m an average of 129 ?S/cm, at 430 m an average of 182 ?S/cm, at 200 m an average of 192 ?S/cm and at 12 m high sea level and average of 472 ?S/cm. This trend is observed at North Fogo volcano flank for fresh water springs. Mineral and thermal waters show an influence of magmatic input, a natural water pollution source in areas with volcanic activity. Rainwater isotopic composition showed elevation effect variation with lighter ?18O and ?D values and recharge appear to be at highest altitudes with influence of sea salt from atmospheric contamination. Evaporation is clearly associated with mineral and thermal waters. Hydrogeochemistry differentiates the low altitude springs at South volcano flank where they are separated by ultramafic intrusions supporting the existence of dike impounded aquifers as Peterson (1972) proposed with the Hawaiian conceptual model for volcanic islands.

Antunes, P. C.; Boutt, D. F.; Martini, A. M.; Ferstad, J.; Rodrigues, F. C.

2012-12-01

143

Active Volcanoes of the Kurile Islands: A Reference Guide for Aviation Users  

USGS Publications Warehouse

Introduction: The many volcanoes of the remote and mostly uninhabited Kurile Island arc (fig. 1; table 1) pose a serious hazard for air traffic in the North Pacific. Ash clouds from Kurile eruptions can impact some of the busiest air travel routes in the world and drift quickly into airspace managed by three countries: Russia, Japan, and the United States. Prevailing westerly winds throughout the region will most commonly send ash from any Kurile eruption directly across the parallel North Pacific airways between North America and Asia (Kristine A. Nelson, National Weather Service, oral commun., 2006; fig. 1). This report presents maps showing locations of the 36 most active Kurile volcanoes plotted on Operational Navigational Charts published by the Defense Mapping Agency (map sheets ONC F-10, F-11, and E-10; figs. 1, 2, 3, 4). These maps are intended to assist aviation and other users in the identification of restless Kurile volcanoes. A regional map is followed by three subsections of the Kurile volcanic arc (North, Central, South). Volcanoes and selected primary geographic features are labeled. All maps contain schematic versions of the principal air routes and selected air navigational fixes in this region.

Neal, Christina A.; Rybin, Alexander; Chibisova, Marina; Miller, Edward

2008-01-01

144

Discovery of an Active Submarine Mud Volcano Along the Nootka Fault West of Vancouver Island  

NASA Astrophysics Data System (ADS)

Submarine mud volcanoes are a common feature in margin environments, but few of them have been documented in the Northeast Pacific. However, during a Hydrosweep bathymetric survey in July, 2001, and a follow-on sub-surface seismic survey in August two mud volcanoes were imaged along the Nootka Fault, 16-18 km west of Vancouver Island at a water depth of 2500 m. The southern volcano, called Maquinna, lies directly along the southern expression of the left lateral, strike slip Nootka Fault. It is 1.5 km across, has a breached caldera and two small summit craters, and it stands about 30 m above the seafloor. The base is bounded by a narrow moat, partially filled by Holocene sediments that are flat lying; older, underlying sediments show steep downwarping towards the sides of the volcano. Subsurface imaging shows a dramatic loss of reflectivity beneath the volcano mound, which may indicate significant mobilization of material. However, a very bright reflector is seen at about 400 m depth below the volcano. This reflector is too deep for stability of methane clathrate, and is interpreted as a zone of high fluid content. A CTD vertical cast above the summit of the volcano showed strong, co-registered thermal, particulate, and oxygen anomalies that extend 50 m up into the overlying water column. These data indicate that the volcano is actively venting warm hydrothermal fluids. The fluids are depleted in CO2, contain background concentrations of CH4, but show elevated H2 concentrations above ocean background water. Microscopic examination of the Nootka hydrothermal samples shows that they contain dense and morphologically diverse microbial communities in comparison to background seawater with cell densities of 106 cells/ml. Enrichment culturing indicates that these communities include both anaerobic and aerobic organisms, some of which are thermophilic with optimal growth temperatures in excess of 50 deg C. Some of these cultures can use methane oxidation as an energy source. Additional culturing experiments and analysis of preserved samples are underway to further characterize the microbes. To further understand the biogeochemical cycles at these sites, samples recently taken from piston cores and CTD casts in this region, are being surveyed for stable and radio carbon isotope signatures of CH4, dissolved inorganic carbon, organic carbon and phospholipid bacterial biomarkers. A second volcano lies ~ 8 km to the northwest of the Maquinna that has a less well defined seafloor expression. However, like Maquinna, seismic reflectivity is lost nearly completely beneath the mound, except for a very bright reflector at about 800 m depth. It is not yet known if this volcano is hydrothermally active. It is likely that high sediment accumulation and lateral tectonic compression associated with accretionary prism formation along the west coast of Vancouver Island support overpressuring of fluids at depth along the Nootka Fault zone, resulting in growth of the two volcanoes.

Riedel, M.; Riedel, M.; Kelly, D. S.; Delaney, J. R.; Spence, G. D.; Hyndman, R. D.; Hyndman, R. D.; Mayer, L.; Calder, B.; Lilley, M. D.; Olson, E. O.; Schrenk, M. O.; Coffin, R.

2001-12-01

145

Space imaging of a 300 years old cooling magma chamber: Timanfaya volcano (Lanzarote, Canary Islands)  

NASA Astrophysics Data System (ADS)

Multitemporal space radar interferometry analysis between 1992 and 2000 revealed significantly deforming areas with a magnitude of 4-6 mm/yr of lengthening in the radar line of sight at Timanfaya volcano (Lanzarote, Canary Island). Timanfaya volcano erupted almost 300 years ago (1730-1736), along a 15 km-long fissure-feeding magmatic system, resulting in the longest and largest historical eruption of the Canarian archipelago to date, with >1 km3 of erupted basaltic lavas covering 200 km2. High surficial temperature (600 degrees-C at 13 m) and high heat flux measurements (150 mW/m2) suggest that the remnants of the magmatic chamber that fed the 1730-1736 are still partly molten. Here, we present preliminary models of the subsidence taking into account all available data, including geophysical data (heat flux, seismic, magnetotelluric and gravity), the geochemistry of freshly erupted lavas, upper mantle and crustal xenoliths, and structural geology.

Gonzalez, P. J.; Tiampo, K. F.

2010-12-01

146

Long-distance lateral magma transport from intra-oceanic island arc volcanoes  

NASA Astrophysics Data System (ADS)

Long-distance lateral magma transport in oceanic island arc volcanoes is emerging as a common phenomenon where the regional stress regime is favorable. It should also be recognized as an important factor in the construction and growth of island arcs. In this contribution, we report on recent investigations into the magma plumbing of Izu-Oshima volcano: an active basaltic volcano with an extensive fissure system. Geophysical observations in the Izu-Bonin intra-oceanic island arc indicate that magma is transported long distances laterally from the main basaltic composite volcano. When Miyakejima erupted in 2000, seismic activity migrated about 30km northwestward from the volcanic centre (Geshi et al., 2002). This event is interpreted to reflect northwestward dike injection and propagation from Miyakejima, transporting magma at a depth range between 12 and 20km (Kodaira et al., 2002). We demonstrated that long-distance lateral magma transport also occurred at the Nishiyama volcano on Hachijojima Island using petrological, geochemical and structural studies of satellite vents (Ishizuka et al., 2008). Nishiyama provided evidence for two types of magma transport. In the first type, primitive magma moved laterally NNW for at least 20km in the middle to lower crust (10-20km deep). The other type is characterized by magmas that have experienced differentiation in a shallow magma chamber beneath Nishiyama and have been transported short distances (<5km). The long-distance magma transport seems to be controlled by a regional extensional stress regime, while short distance transport may be controlled by local stress regime affected by the load generated by the main volcanic edifice. Izu-Oshima volcano comprises numerous, subparallel NW-SE trending submarine ridges extending up to 22 km to the NW and SE from the summit of Izu-Oshima. A recent diving survey has revealed that: 1) NW-SE trending ridges are fissures which erupted basaltic spatter and lava flows. 2) Basaltic effusives are petrographically similar among each ridge, while there are noticeable differences between ridges. 3) The ridges are petrographically distinct from interspersed seamounts. These seamounts are identical to the Higashi-Izu-Oki monogenetic volcanoes (HIMV) found across this area of the rear-arc. Geochemically there is a close similarity between the submarine ridges and the corresponding subaerial chains, implying that each chain represents an episode of magma transport away from the main Izu-Oshima edifice. This scenario also explains the overlapping distribution of the HIMV and NW-SE chains which have clearly distinct magma sources. HIMV appear to be fed by an "in-situ" source, while the NW-SE chains are fed by lateral magma transport from the Izu-Oshima plumbing system. Unlike the Nishiyama volcano, Izu-Oshima does not show a compositional variation along the length of the volcanic chains, and has no evidence of any primitive magmas. Hence, the magma transport from Izu-Oshima seems to occur from a shallow crustal magma chamber where extensive crystal fractionation and plagioclase accumulation has taken place.

Ishizuka, O.; Geshi, N.; Kawanabe, Y.; Ogitsu, I.; Tuzino, T.; Nakano, S.; Arai, K.; Sakamoto, I.; Taylor, R. N.; Sano, K.; Yamamoto, T.

2011-12-01

147

Investigation of the Influence of the Amlia Fracture Zone on the Islands of Four Mountains Region of the Aleutian Arc, AK  

NASA Astrophysics Data System (ADS)

Regional isotopic and trace element investigations of the magmatic source characteristics of the Aleutian arc have attributed regional patterns to variations in the contribution of eclogite through slab melting, to increased proportions of sediment melts, and to variation in the amount of fluid derived by progressive metamorphism of the downgoing slab. Currently the Amlia Fracture Zone (AFZ) is located between the islands of Atka and Seguam and marks a prominent boundary between subduction of large quantities of trench sediments to the east versus sediment impoverished subduction to the west of the AFZ. This boundary is not stationary through time. Instead oblique subduction of the Pacific plate moves the AFZ westward along the arc front, causing sequential subduction beneath the islands of Chuginadak, Yunaska and Seguam circa 5, 2.5 and 1 million years ago, respectively. Lavas from Atka Island, which has not yet received the sediment and fluid spike from the AFZ, act as reference compositions. Comparison of bulk rock trace element ratios and Sr, Nd, Hf, and Pb isotopic compositions for lavas from these islands relative to Atka show that contributions from melted subducted sediment are important in the genesis of Holocene and Pleistocene lavas erupted in the Islands of Four Mountains region of the arc. Sr and Pb isotopic compositions for Yunaska and Chuginadak lavas are as high or higher than Seguam values and trend in the direction of sediment values. La/Nb ratios similarly indicate sediment melting is important for all these lavas. Comparison of values for Holocene relative to Pleistocene values indicate that once sediments are introduced to the magma source, they persist in affecting magma compositions. Comparison of higher Mg# lavas (molar Mg#>50) shows that a group of the oldest sampled lavas on Chuginadak have much lower 208Pb/204Pb, 206Pb/204Pb, and 87Sr/86Sr and higher 143Nd/144Nd, Zr/Y and Zn/Mn relative to all sampled Holocene and Pleistocene lavas from Seguam and Yunaska, suggesting that the earliest period of volcanism on Chuginadak occurred prior to the subduction of the AFZ.

Nicolaysen, K. P.; Myers, J. D.; Weis, D.

2013-12-01

148

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

149

What drives centuries-long polygenetic scoria cone activity at Barren Island volcano?  

NASA Astrophysics Data System (ADS)

Barren Island in the Andaman Sea is an active mafic stratovolcano, which had explosive and effusive eruptions, followed by caldera formation, in prehistoric time (poorly dated). A scoria cone within the caldera, marking volcanic resurgence, was active periodically from 1787 to 1832 (the historic eruptions). Since 1991, the same scoria cone has produced six eruptions, commonly including lava flows. Links between Barren Island's eruptions and giant earthquakes (such as the 26 December 2004 Great Sumatra megathrust earthquake) have been suggested, though there is no general correlation between them. The ? 227-year-long activity of the scoria cone, named here Shanku ("cone"), is normally driven by purely magmatic processes. I present a "source to surface" model for Barren Island and Shanku, including the source region, deeper and shallow magma chambers, volcanotectonics, dyking from magma chambers, and eruptions and eruptive style as controlled by crustal stresses, composition and volatile content. Calculations show that dykes ~ 0.5 m thick and a few hundred meters long, originating from shallow-level magma chambers (~ 5 km deep), are suitable feeders of the Shanku eruptions. Shanku, a polygenetic scoria cone (at least 13 eruptions since 1787), has three excellent analogues, namely Anak Krakatau (40 eruptions since 1927), Cerro Negro (23 eruptions since 1850), and Yasur (persistent activity for the past hundreds of years). This is an important category of volcanoes, gradational between small "monogenetic" scoria cones and larger "polygenetic" volcanoes.

Sheth, Hetu

2014-12-01

150

Man against volcano: The eruption on Heimaey, Vestmann Islands, Iceland  

USGS Publications Warehouse

The U.S. Geological Survey carries out scientific studies in the geological, hydrological, and cartographic sciences generally within the 50 states, but also in cooperation with scientific organizations in many foreign countries for the investigation of unusual earth science phenomena throughout the world. The following material discusses the impact of the 1973 volcanic eruption of Eldfell on the fishing port of Vestmannaeyjar on the island of Heimaey, Iceland. Before the eruption was over, approximately one-third of the town of Vestmannaeyjar had been obliterated but, more importantly, the potential damage had been reduced markedly by the spraying of seawater onto the advancing lava flows, causing them to be slowed, stopped, or diverted from the undamaged portion of the town. The Survey's interest and involvement in the Heimaey eruption in Iceland was occasioned by the possibility that the procedures used to control the course of the flowing lava and to reduce the damage in a modern town may some day be needed in Hawaii and possibly even in the continental United States. This publication is based on the observations of two USGS geologists, Richard S. Williams, Jr. and James G. Moore, as well as on information from the Icelandic Ministry for Foreign Affairs, Icelandic scientists' reports through the Center for Short-Lived Phenomena, and other published scientific reports. A number of Icelandic scientists studied the scientific aspects of the eruption and the engineering aspects of the control of lava flows, in particular, Professors Thorbjb'rn Sigurgeirsson and Sigurdur Thorarinsson of the University of Iceland Science Institute. Also, Icelandic governmental officials provided logistical and other support, in particular, Mr. Steingnmur Hermannsson, Director, Icelandic National Research Council and Professor Magnus Magnusson, Director, University of Iceland Science Institute.

Williams, R.S., Jr.; Moore, J.G.

1976-01-01

151

Hydrothermal history of Piton des Neiges volcano (Reunion Island, Indian Ocean)  

NASA Astrophysics Data System (ADS)

The Piton des Neiges volcano on Reunion Island represents a unique example of an oceanic volcano where the extreme development of amphitheatre-headed valley erosion has led to the formation of three large cirques. They are so large that the island's volcano-structural and petrological history can be traced from its emergence to the latest stages of its sub-aerial evolution (> 2.1 m.y. to 22,000 years ago). The various magmatic series of the Piton des Neiges are, moreover, abundantly invaded by hydrothermal mineralization. It is this post-magmatic feature, represented by the hydrothermal alteration of the series, which is examined here. Mineralogical studies (X-ray, microprobe, scanning electron microscope) reveal a large number of hydrothermal species. Of these, zeolites are the most common and five are described here for the first time in Reunion (gonnardite, levynite, erionite, garronite, herschelite). Six hydrothermal facies characteristic of weak metamorphism are defined: chabazitephillipsite, natrolite-thomsonite, analcime-thomsonite, laumontite-thomsonite, albiteprehnite and prehnite-pumpellyite. The paleo-temperatures covered by these facies range from 0 to 380°C. On the basis of these data and supporting field observations, three main hydrothermal phases were determined and fitted into the known chronostratigraphy. These three phases have succeeded one another over the last two million years in the Piton des Neiges massif. The extent and mineralogical facies of each phase can be related to the volcanotectonic structures. This sequence has been directly linked to the geological evolution of the massif. The progressive restriction with time of the hydrothermal manifestations to the present Piton des Neiges occurred alongside the focusing of volcanism centralized on this same relief. An attempt is made to reconstruct the island's hydrothermal history.

Rançon, J. Ph.

1985-12-01

152

Eruption of soufriere volcano on st. Vincent island, 1971-1972.  

PubMed

The Soufrière volcano in St. Vincent erupted from October 1971 to March 1972, as 80 x 10(6) m(3) of basaltic andesite lava was quietly extruded inside the mile-wide crater. The eruption was largely subaqueous, taking place in the 180-m-deep crater lake, and resulted in the emergence of a steep-sided island. The mild character of the eruption and the absence of seismic activity stand in direct contrast to the highly explosive character of the eruption of 1902 to 1903. PMID:17746610

Aspinall, W P; Sigurdsson, H; Shepherd, J B

1973-07-13

153

1994 Volcanic activity in Alaska: summary of events and response of the Alaska Volcano Observatory  

USGS Publications Warehouse

During 1994, the Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, or false alarms at nine volcanic centers-- Mount Sanford, Iliamna, the Katmai group, Kupreanof, Mount Veniaminof, Shishaldin, Makushin, Mount Cleveland and Kanaga (table 1). Of these volcanoes, AVO has a real time, continuously recording seismic network only at Iliamna, which is located in the Cook Inlet area of south-central Alaska (fig. 1). AVO has dial-up access to seismic data from a 5-station network in the general region of the Katmai group of volcanoes. The remaining unmonitored volcanoes are located in sparsely populated areas of the Wrangell Mountains, the Alaska Peninsula, and the Aleutian Islands (fig. 1). For these volcanoes, the AVO monitoring program relies chiefly on receipt of pilot reports, observations of local residents and analysis of satellite imagery.

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

1995-01-01

154

Surface Pressure Gradient and Carbon Dioxide Degassing Survey at Cumbre Vieja Volcano, La Palma, Canary Islands  

NASA Astrophysics Data System (ADS)

La Palma (730 Km2) is one of the youngest island of the Canarian archipelago. Recent volcanic activity is concentrated on the southern part of the island, where Cumbre Vieja volcano (220 Km2) has been constructed during the last 1 Ma reaching an elevation of 1,898 m above sea level. Six historical eruptions had occurred at Cumbre Vieja, and the most recent event took place in the southern part of the volcano (Teneguía volcano, 1971). The main structural features are three major volcanic rift-zones of N-S, NE, and NW orientations. Since fumarolic activity is absent at Cumbre Vieja, coupled surface pressure gradient and carbon dioxide degassing monitoring could be potential geophysical and geochemical tools for its volcanic surveillance. Surface pressure gradient and carbon dioxide degassing survey of 619 observation sites was carried out from July 19 to August 13, 2002, at Cumbre Vieja volcano. Pressure gradient measurements were performed by means of a Setra 239 Model pressure transducer, and soil CO2 efflux measurements were performed by means of a portable NDIR sensor according to the accumulation chamber method. At each sampling site, soil gas samples were collected at 40 cm deep using a metallic probe and analyzed for CO2 contents by means of a Omnistar QMS within 24 hours. Surface pressure gradient ranged from -36 to 90 Pam-1. Soil CO2 efflux ranged from negligible values to 1,300 gm-2d-1, and soil gas CO2 content ranged from 0.03 to 1.1 %V. Statistical graphical analysis showed two different populations for the CO2 efflux data and their mean values are 1.4 and 52 gm-2d-1, respectively. For this 2002 survey, the total output of diffuse CO2 emission was estimated about 1,340 td-1, which lies within the range of previous surveys (1,250-2,500 td-1). Spatial distribution of the data showed an excellent agreement between surface pressure gradient and CO2 degassing at Cumbre Vieja, where the highest observed values were detected in and around the volcanic vent related to the most recent eruption at Cumbre Vieja volcano.

Alfaya, A.; López, F.; Padron, E.; Hernández, P. A.; Salazar, J. M.; Pérez, N. M.

2002-12-01

155

Shield volcanoes of Marie Byrd Land, West Antarctic rift: oceanic island similarities, continental signature, and tectonic controls  

NASA Astrophysics Data System (ADS)

The Marie Byrd Land volcanic province is largely defined by 18 large (up to ~1,800 km3) alkaline shield volcanoes, each surmounted by a summit section of varied felsic rocks dominated by trachytic flows. They are distributed over a 500 × 800-km block-faulted dome within the West Antarctic rift. The basement contact of volcanic sections is ~500 masl at one site and 3,000 mbsl at another, 70 km away, which illustrates the scale of block faulting but complicates an understanding of volcanic structure. Furthermore, the continental ice sheet buries 16 volcanoes to progressively greater heights inland. However, five are sufficiently exposed to allow meaningful comparisons with alkaline oceanic island volcanoes; these comparisons are used as a guide to estimate the structure of Marie Byrd Land volcanoes. The type example for this study is Mt. Murphy, the most completely exposed volcano. It consists of a 1,400-m section of alkaline basalt overlain by trachyte and benmoreite flows that make up ~7-13 % of the volcano volume. In gross structure and composition, Mt. Murphy is similar to Gran Canaria volcano, Canary Islands, but the percent of felsic rock may be three times that of Gran Canaria, if the estimate is approximately correct. Departures from the oceanic island example are believed to represent the imprint of the Marie Byrd Land lithosphere and tectonic environment on volcano evolution. These include a lack of order in the sequence of felsic rock types, lack of progression toward more silica undersaturated compositions with time, absence of a highly undersaturated mafic resurgent stage, and perhaps, a relatively large volume of felsic rock.

LeMasurier, Wesley

2013-06-01

156

Volcanoes  

NSDL National Science Digital Library

This module include four problem-based learning scenarios related to volcanoes and emphasize different kinds of volcanic hazards and geologic processes. The four scenarios are: whether to build a new high school in the shadow of a restless volcanic giant, Mt. Rainier; Kilauea in Hawaii shows signs of activity. What are the prospects for the nearby population?; Mt. Hood is starting to act like Mt. St. Helens did in 1980, but Mt. Hood is just 40 miles from the metropalitan area. How might an eruption impact this populated area?; and America's largest volcano in Yellowstone National Park is stirring. Are we facing an eruption as devastating as a nuclear attack? This module is from Exploring the Environment.

2012-08-03

157

Dynamics of diffuse helium degassing from Cumbre Vieja volcano, La Palma, Canary Islands  

NASA Astrophysics Data System (ADS)

La Palma island (730 km2) is the northwestern most island of the Canarian archipelago. Cumbre Vieja volcano (220 km2) is the result of the volcanic activity in the southern part of the island during the last 1 Ma. Six historical eruptions had occurred at Cumbre Vieja, and the most recent one took place at the extreme south of this volcano in 1971. Three major volcanic rift-zones trending N-S, NW-SE and NE-SW constitute Cumbre Vieja\\'{ }s major structural features. The aim of this study is evaluate the use of diffuse helium degassing for monitoring Cumbre Vieja volcano since (1) diffuse degassing studies seems to become a powerful geochemical tool for volcano surveillance (Hernández et al., 2001), and (2) helium is an ideal geochemical gas tracer because it is chemically inert, physically stable, sparingly soluble in water under ambient conditions. Since 1997 diffuse degassing surveys are regularly performed at Cumbre Vieja. During the last 2 years these surveys have investigated helium in the soil atmosphere. Soil gas samples were collected at 40 cm deep using a metallic probe and stored in vacutainers by means of water displacement technique. Soil gas samples were analyzed for 4He and CO2 contents by means of a QMS within 24 hours. CO2 efflux measurements were also performed by means of a portable NDIR sensor according to the accumulation chamber method. ? He contour maps (? He = He{soil atmosphere}-Heair) were constructed using kriging as interpolation method. Both surveys showed a good spatial agreement for ? He, and their peak values (> 1,800 ppbV) were mainly observed at the summit area of Cumbre Vieja along the N-S rift-zone, suggesting a deep origin for the degassing through this major structure. The total output for diffuse 4He emission rate at Cumbre Vieja was estimated by multiplying CO2 efflux times ? He /? CO2 ratio at each sampling site. The results showed an increase on the diffuse 4He emission rate from 67 to 167 kg d-1. Monitoring these results could be useful for the volcanic surveillance.

Alfaya, A.; Robles, J.; Padron, E.; Salazar, J.; Hernandez, P.; Perez, N.

2003-12-01

158

Diffuse Helium Degassing at Cumbre Vieja Volcano, La Palma, Canary Islands  

NASA Astrophysics Data System (ADS)

La Palma (730 Km2) is the northwestern most island of the Canarian archipelago. Cumbre Vieja (<1 Ma) is situated in the southern part of La Palma, and is the most active basaltic volcano in the Canaries where the most recent eruption occurred in 1971, Teneguía volcano. The main structural features of Cumbre Vieja (220 Km2) are three major volcanic rift-zones of N-S, NE, and NW orientations. Diffuse CO2 degassing studies is becoming a useful geochemical tool for volcano monitoring (Hernández et al., 2001). Since (1) helium is an ideal geochemical indicator because it is chemically inert, physically stable, sparingly soluble in water under ambient conditions and almost non-adsorbable, and (2) helium-3 is the best fingerprint for magmatic activity and reach levels up to 9.6 Ra at La Palma (Pérez et al., 1994), the goal of this study is evaluate the use of diffuse helium emission for volcano monitoring of Cumbre Vieja. Diffuse degassing survey of 619 sampling sites was carried out from July 19 to August 13, 2002, at Cumbre Vieja volcano. Soil CO2 efflux measurements were performed by means of a portable NDIR sensor and according to the accumulation chamber method. At each sampling site, soil gas samples were collected at 40 cm deep using a metallic probe and analyzed for 4He and CO2 contents by means of a Omnistar QMS within 24 hours. Spatial distribution of soil gas helium expressed as ?He (?He = He{soil atmosphere} - Heair) showed that relatively high ?He values (> 1,800 ppb) occurred in the summit zone of Cumbre Vieja along the N-S rift-zone, suggesting a deep origin for the degassing through this major structure. Soil He efflux was estimated by multiplying soil CO2 efflux times ?He/?CO2 ratio at each sampling site. Taking into consideration the spatial distribution of estimated soil He efflux and the volcanic area, the total output of diffuse He emission is estimated about 59 Kg/d for Cumbre Vieja volcano. Monitoring these results could be useful for the volcanic surveillance.

Padron, E.; Fuentes, L.; Salazar, J. M.; Hernandez, P. A.; Perez, N. M.

2002-12-01

159

Magma Genesis of Sakurajima, the Quaternary post- Aira caldera volcano, southern Kyushu Island, Japan  

NASA Astrophysics Data System (ADS)

Sakurajima volcano is the Quaternary post-caldera volcano of Aira caldera, which was caused by the eruption of huge amount of silicic pyroclastics, situated on Ryukyu arc, southern Kyushu Island, Japan. This volcano is quite active, so it can be considered that the preparation of next caldera-forming eruption with huge amount of silicic magma is proceeding. It is, therefore, expected that the investigation of magma genesis of Sakurajima volcano give us information for the mechanism generating huge amount of silicic magma, which cause the caldera formation. We analyzed major and trace elements with Sr, Nd and Pb isotopic compositions of volcanic rocks from Sakurajima volcano. We sampled (ol) - opx - cpx - pl andesite and dacite from almost all the volcanic units defined by Fukuyama and Ono (1981). In addition to Sakurajima samples, we also studied basaltic rocks erupted at pre-caldera stage of the Aira caldera to estimate the primary magma of Sakurajima volcano. Major and trace element variations generally show linear trends on the Harker diagrams, with the exception of P2O5 and TiO2. Based on the trend of P2O5 vs.SiO2, we divided studied samples low-P (P2O5 < 0.15 wt. %) and high-P (P2O5 > 0.15 wt. %) groups and these groups also display two distinct trends on TiO2-SiO2 diagram. The composition of trace elements shows typical island arc character as depletion of Nb and enrichments of Rb, K and Pb, suggesting addition of aqueous fluids to the mantle wedge. The Zr and Nb concentrations make a liner trend (Zr/Nb = 27) and this trend across from tend of MORB (Zr/Nb = 35) to that of crustal materials (Zr/Nb=17). The Sr, Nd and Pb isotopic compositions broadly plot to on the mixing curve connecting MORB-type mantle and sediments of the Philippine Sea Plate, indicating that the primary magma was generated by partial melting of MORB-type mantle wedge, which was hydrated with fluids derived from the subducted Philippine Sea sediments. But we found that our data plot apart from the mixing curve to the direction of being more radiogenic when we observe in more detail. This observation supports our conclusion that the crustal materials contribute the magma genesis of Sakurajima volcano emphasized from Zr/Nb ratios. Low-P and high-P groups show different trends of SiO2, P2O5, TiO2 concentrations and 87Sr/86Sr ratios relative to plagioclase modal abundances. The high-P group samples show continuous trends, and their 87Sr/86Sr ratios increase with decreasing plagioclase, representing simple AFC process. The SiO2 content of low-P group rapidly increases from 63 to 66 wt. % at the modal abundance of pl is nearly 20 vol. %. The Sr isotope ratios of low-P group with < 20 vol. % of pl are obviously high (87Sr/86Sr = 0.70556 to 0.70569) compared to those of high-P group (87Sr/86Sr = 0.705136 to 0.705285). From these observations, we conclude that the rapid increase of SiO2 with high 87Sr/87Sr ratio infer involvement of crustal materials to the magma chamber, in which the ACF process is proceeding.

Shibata, T.; Suzuki, J.; Yoshikawa, M.; Kobayashi, T.; Miki, D.; Takemura, K.

2012-12-01

160

Secular and Spatial Variations of Diffuse CO2 Degassing From Cumbre Vieja Volcano, La Palma, Canary Islands, Spain  

Microsoft Academic Search

La Palma (730 Km2) is the northwestmost island of the Canarian archipielago and rises 6.5 Km from the oceanic basement. Constructive and destructive geological processes are responsible for the actual geomorphology of La Palma (Navarro, 1992; Ancochea et al., 1994). Recent volcanic activity is mainly concentrated at Cumbre Vieja volcano, in the southern part of La Palma. The most recent

L. Fuentes; A. Mena; A. Alfaya; E. Padron; G. Melian; J. Salazar; P. Hernandez; N. Perez

2001-01-01

161

ASTER-SRTM Perspective of Mount Oyama Volcano, Miyake-Jima Island, Japan  

NASA Technical Reports Server (NTRS)

Mount Oyama is a 820-meter-high (2,700 feet) volcano on the island of Miyake-Jima, Japan. In late June 2000, a series of earthquakes alerted scientists to possible volcanic activity. On June 27, authorities evacuated 2,600 people, and on July 8 the volcano began erupting and erupted five times over that week. The dark gray blanket covering green vegetation in the image is the ash deposited by prevailing northeasterly winds between July 8 and 17. This island is about 180 kilometers (110 miles) south of Tokyo and is part of the Izu chain of volcanic islands that runs south from the main Japanese island of Honshu. Miyake-Jima is home to 3,800 people. The previous major eruptions of Mount Oyama occurred in 1983 and 1962, when lava flows destroyed hundreds of houses. An earlier eruption in 1940 killed 11 people.

This image is a perspective view created by combining image data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) aboard NASA's Terra satellite with an elevation model from the Shuttle Radar Topography Mission (SRTM). Vertical relief is exaggerated, and the image includes cosmetic adjustments to clouds and image color to enhance clarity of terrain features.

The ASTER instrument is a cooperative project between NASA, JPL, and the Japanese Ministry of International Trade and Industry.

Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on February 11,2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise,Washington, DC.

Size: Island is approximately 8 kilometers (5 miles) in diameter Location: 34.1 deg. North lat., 139.5 deg. East lon. Orientation: View toward the west-southwest. Image Data: ASTER visible and near infrared Date Acquired: February 20, 2000 (SRTM), July 17, 2000 (ASTER)

2000-01-01

162

Aleutian Disease of Mink  

PubMed Central

A suspension of tissues from field cases of Aleutian disease was used successfully to reproduce the disease in Aleutian mink. Similarly, suspensions of diseased tissues from the experimentally infected mink were used to transmit the agent of Aleutian disease to both Aleutian mink and standard dark mink. Seitz and millipore filtrates prepared from these tissue suspensions were also infective; a suggestion that the etiologic agent is a virus. Genetic factors and hypersensitivity are discussed as possibly contributing to development of the disease. PMID:17649371

Karstad, Lars; Pridham, T. J.

1962-01-01

163

Morphology of Piton de la Fournaise basaltic shield volcano (La Réunion Island): Characterization and implication in the volcano evolution  

Microsoft Academic Search

The topography of Piton de la Fournaise volcano (PdF) differs from the classic view of basaltic shield volcanoes as it is characterized by (1) several steep slope zones on its flanks and (2) a large U-shaped caldera, the Enclos-Grand Brûlé structure (EGBS). Most of these structures were previously interpreted as the scars of lateral landslides, the deposits of which cover

Laurent Michon; Francky Saint-Ange

2008-01-01

164

Lithospheric normal faulting beneath the Aleutian trench  

Microsoft Academic Search

The focal process of the Rat Island earthquake of March 30, 1965, which occurred beneath the Aleutian trench, is studied on the basis of the long-period surface-wave data and the spatial distribution of the aftershocks. The Rat Island earthquake is represented by a normal faulting with some left-lateral strike-slip component. The spatial distribution of the aftershocks shows a remarkable plane-like

Katsuyuki Abe

1972-01-01

165

CO2 budget from active volcanoes of central Mediterranean: preliminary estimate for Ischia Island (Italy).  

NASA Astrophysics Data System (ADS)

Ischia Island (46 km2) is an active volcano located a few kilometres northwest of the bay of Naples (Central Italy). It last erupted in 1302 A.D. and its activity is currently characterised only by low-temperature (T° max. = 100° C) gas emissions, such as fumaroles and anomalous soil degassing. A geothermal reservoir (estimated reservoir temperature near 280° C; Inguaggiato et al., 2000) is also present in the island. The emitted gases are mostly water vapour and CO2. Also H2 is present in appreciable amounts (up to 2.5 % v/v of dry gas), together with minor concentrations of CH4 He and CO. Based on helium and carbon isotopic ratios (R/Ra ˜ 3.6; ? 13C(CO2) ˜ -2 \\permil), a magmatic source can be inferred for these gases. The present study was mainly aimed at carrying out a preliminary estimate of the total output of magmatic CO2 from Ischia, considering all types of fluids emitted there. Soil CO2 fluxes (measured with the accumulation chamber) gave a value of about 2.5 Mt a-1, that is much lower than the amount estimated at Mt. Etna (13 to 25 Mt a-1; Allard et al., 1991; D'Alessandro et al., 1997), but more than an order of magnitude higher than that estimated at Pantelleria Island and at Vulcano (Favara et al., 2001). The amount of CO2 dissolved into ground water as carbonatic species is only 0.025 Mt a-1, considering an annual volume of infiltrated water of about 8 x 106 m3. The overall output of CO2 from Ischia indicates that this island is site of active volcanic degassing and deserves a more careful volcanological monitoring.

Pecoraino, G.; Brusca, L.; D'Alessandro, W.; Giammanco, S.; Inguaggiato, S.; Longo, M.

2003-12-01

166

Pacific Basin tsunami hazards associated with mass flows in the Aleutian arc of Alaska  

USGS Publications Warehouse

We analyze mass-flow tsunami generation for selected areas within the Aleutian arc of Alaska using results from numerical simulation of hypothetical but plausible mass-flow sources such as submarine landslides and volcanic debris avalanches. The Aleutian arc consists of a chain of volcanic mountains, volcanic islands, and submarine canyons, surrounded by a low-relief continental shelf above about 1000–2000 m water depth. Parts of the arc are fragmented into a series of fault-bounded blocks, tens to hundreds of kilometers in length, and separated from one another by distinctive fault-controlled canyons that are roughly normal to the arc axis. The canyons are natural regions for the accumulation and conveyance of sediment derived from glacial and volcanic processes. The volcanic islands in the region include a number of historically active volcanoes and some possess geological evidence for large-scale sector collapse into the sea. Large scale mass-flow deposits have not been mapped on the seafloor south of the Aleutian Islands, in part because most of the area has never been examined at the resolution required to identify such features, and in part because of the complex nature of erosional and depositional processes. Extensive submarine landslide deposits and debris flows are known on the north side of the arc and are common in similar settings elsewhere and thus they likely exist on the trench slope south of the Aleutian Islands. Because the Aleutian arc is surrounded by deep, open ocean, mass flows of unconsolidated debris that originate either as submarine landslides or as volcanic debris avalanches entering the sea may be potential tsunami sources. To test this hypothesis we present a series of numerical simulations of submarine mass-flow initiated tsunamis from eight different source areas. We consider four submarine mass flows originating in submarine canyons and four flows that evolve from submarine landslides on the trench slope. The flows have lengths that range from 40 to 80 km, maximum thicknesses of 400–800 m, and maximum widths of 10–40 km. We also evaluate tsunami generation by volcanic debris avalanches associated with flank collapse, at four locations (Makushin, Cleveland, Seguam and Yunaska SW volcanoes), which represent large to moderate sized events in this region. We calculate tsunami sources using the numerical model TOPICS and simulate wave propagation across the Pacific using a spherical Boussinesq model, which is a modified version of the public domain code FUNWAVE. Our numerical simulations indicate that geologically plausible mass flows originating in the North Pacific near the Aleutian Islands can indeed generate large local tsunamis as well as large transoceanic tsunamis. These waves may be several meters in elevation at distal locations, such as Japan, Hawaii, and along the North and South American coastlines where they would constitute significant hazards.

Waythomas, Christopher F.; Watts, Philip; Shi, Fengyan; Kirby, James T.

2009-01-01

167

Anthropogenic and natural radionuclides in caribou and muskoxen in the western Alaskan Arctic and marine fish in the Aleutian Islands in the first half of 2000s.  

PubMed

A number of caribou and muskoxen samples from the western Alaskan Arctic and fish samples from the Aleutian Islands were collected between 1998 and 2006 and analyzed for anthropogenic ((90)Sr and (137)Cs) and natural radionculides ((40)K, (210)Pb and (226)Ra), as part of the radiological assessment for the regional subsistence hunting communities in the first half of 2000s. We examined the relationship between the activities of these nuclides with the size of the fish. In caribou samples, concentration of (90)Sr in muscle was below the detection limit of 0.14 Bq kg(-1) and (137)Cs concentration in bones was below the detection limit of 0.15 Bq kg(-1). (137)Cs activity varied over an order of magnitude in caribou muscle samples with an average value of 2.5 Bq/kg wet wt. Average (137)Cs activity in muskoxen muscle was found to be 9.7 Bq/kg wet wt. However, there were a little variation (less than 60%) in (210)Pb, (40)K, and (226)Ra in both muscle and bone of both caribou and muskoxen. The activities of total (210)Pb in caribou and muskox bones were found to be 1-2 orders of magnitude higher than that of parent-supported (210)Pb indicating the potential for dating of bones of terrestrial mammals (time elapsed since the death of the animal) based on the excess (210)Pb method exists. In fish muscle samples, (137)Cs activity varied from below detection limit to 154 mBq/kg wet wt. and its content increased with the size of the fish due to its transfer through the food chain. Among the seven fish species investigated, (210)Pb activities varied almost an order of magnitude; however, (40)K and (226)Ra activities varied less than a factor of two. Total annual effective dose due to (90)Sr and (137)Cs from the ingestion of those terrestrial and marine meats was estimated to be negligible (ca. 9 ?SV/a) compared to the natural radionuclides present thus posing negligible radiological threat to humans. PMID:21774963

Hong, Gi Hoon; Baskaran, Mark; Molaroni, Shannon Marie; Lee, Hyun-Mi; Burger, Joanna

2011-09-01

168

Are There Spatial or Temporal Patterns to Holocene Explosive Eruptions in the Aleutian Archipelago? A Work in Progress  

NASA Astrophysics Data System (ADS)

By examining the existing geological and archeological record of radiocarbon dated Aleutian tephras of the last 12,000 years, this study sought to determine whether there were spatial or temporal patterns of explosive eruptive activity. The Holocene tephra record has important implications because two episodes of migration and colonization by humans of distinct cultures established the Unangan/Aleut peoples of the Aleutian Islands concurrently with the volcanic activity. From Aniakchak Volcano on the Alaska Peninsula to the Andreanof Islands (158 to 178° W longitude), 55 distinct tephras represent significant explosive eruptions of the last 12,000 years. Initial results suggest that the Andreanof and Fox Island regions of the archipelago have had frequent explosive eruptions whereas the Islands of Four Mountains, Rat, and Near Island regions have apparently had little or no eruptive activity. However, one clear result of the investigation is that sampling bias strongly influences the apparent spatial patterns. For example field reconnaissance in the Islands of Four Mountains documents two Holocene calderas and a minimum of 20 undated tephras in addition to the large ignimbrites. Only the lack of significant explosive activity in the Near Islands seems a valid spatial result as archeological excavations and geologic reports failed to document Holocene tephras there. An intriguing preliminary temporal pattern is the apparent absence of large explosive eruptions across the archipelago from ca. 4,800 to 6,000 yBP. To test the validity of apparent patterns, a statistical treatment of the compiled data grappled with the sampling bias by considering three confounding variables: larger island size allows more opportunity for geologic preservation of tephras; larger magnitude eruption promotes tephra preservation by creating thicker and more widespread deposits; the comprehensiveness of the tephra sampling of each volcano and island varies widely because of logistical and financial limitations. This initial statistical investigation proposes variables to mitigate the effects of sampling bias and makes recommendations for sampling strategies to enable statistically valid examination of research questions. Further, though caldera-forming eruptions occurred throughout the Holocene - and several remain undated - four of six dated eruptions occurred throughout the archipelago between 8,000-9,100 yBP, a period coinciding with some of the earliest human occupation (Early Anangula Phase) of the eastern Aleutians.

Martin, C.; Nicolaysen, K. P.; McConville, K.; Hatfield, V.; West, D.

2013-12-01

169

Volcanic-ash hazard to aviation during the 2003–2004 eruptive activity of Anatahan volcano, Commonwealth of the Northern Mariana Islands  

Microsoft Academic Search

Within the Commonwealth of the Northern Mariana Islands (CNMI), Anatahan is one of nine active subaerial volcanoes that pose hazards to major air-traffic routes from airborne volcanic ash. The 2003–2004 eruptive activity of Anatahan volcano affected the region's aviation operations for 3 days in May 2003. On the first day of the eruption (10 May 2003), two international flights from

Marianne Guffanti; John W. Ewert; Gregory M. Gallina; Gregg J. S. Bluth; Grace L. Swanson

2005-01-01

170

Volcanic-ash hazard to aviation during the 2003 2004 eruptive activity of Anatahan volcano, Commonwealth of the Northern Mariana Islands  

Microsoft Academic Search

Within the Commonwealth of the Northern Mariana Islands (CNMI), Anatahan is one of nine active subaerial volcanoes that pose hazards to major air-traffic routes from airborne volcanic ash. The 2003 2004 eruptive activity of Anatahan volcano affected the region's aviation operations for 3 days in May 2003. On the first day of the eruption (10 May 2003), two international flights

Marianne Guffanti; John W. Ewert; Gregory M. Gallina; Gregg J. S. Bluth; Grace L. Swanson

2005-01-01

171

Construction and destruction rates of volcanoes within tropical environment: Examples from the Basse-Terre Island (Guadeloupe, Lesser Antilles)  

NASA Astrophysics Data System (ADS)

In order to better constrain the construction and the erosion rate affecting the volcanic island of Basse-Terre Island (Guadeloupe, F.W.I.), an enlarged K-Ar age dataset has been combined with reconstruction of the paleo-topography. Two different methods of interpolation of the present topography have been cross-checked to better support the erosion rates obtained and their associated uncertainties. The present study focusses on the Monts-Caraïbes volcanoes and on the main geomorphic feature of the Piton de Bouillante volcano, the Beaugendre Valley. The Monts-Caraïbes volcanoes were constructed in 83 kyr at a rate of 0.12 ± 0.04 km3/kyr. During the last 450 kyr, they have experienced an erosion rate of 610 ± 550 t/km2/yr. In the Piton de Bouillante volcano eleven new K-Ar ages have been obtained, constraining the duration of its volcanic activity between 880 ± 14 and 712 ± 12 ka, and involving a construction rate of 0.70 ± 0.20 km3/kyr. For this volcano, an erosion rate of 1220 ± 700 t/km2/yr has been obtained for the last 700 kyr. Our study also shows, based on the contemporaneity of the ages in the entire Beaugendre Valley added to the mean erosion rate of 1350 ± 550 t/km2/yr, that the flank collapse hypothesis cannot explain the formation of this valley. Finally, the similarity of the erosion rates computed for different locations of the Basse-Terre Island shows that the time-integrated erosion appears independent to the trade wind effect and suggests that the barrier effect due to the relief is not present here.

Ricci, Julia; Lahitte, Pierre; Quidelleur, Xavier

2015-01-01

172

Two Decades of Degassing at Kilauea Volcano, Hawai`i: Perspectives on Island Impacts  

NASA Astrophysics Data System (ADS)

The ongoing eruption of Kilauea provides an opportunity to examine how volcanic emissions impact the natural and human environment of the island of Hawai`i. Kilauea has released ˜ 13 megatons of SO2 gas into the troposphere since the current eruption began in 1983, more than any single anthropogenic source in the U.S. During prevailing trade wind conditions, measurements of SO2 gas, aerosol mass, and aerosol acidity downwind of Kilauea document the conversion of SO2 to acid aerosol as the plume propagates to the leeward side of the island. Lidar measurements suggest a gas-to-particle conversion rate (t1/2) of 6 hours. When trade winds are disrupted, ambient SO2 and particle measurements in Hawai`i Volcanoes National Park have shown episodes of particle concentrations of ˜ 100 ? g/m3 and SO2 concentrations in excess of 4000 ppb. Federal health standards and WHO guidelines for SO2 have been exceeded repeatedly at this near-source location. Documented effects from volcanic emissions on the island of Hawai`i include the rapid corrosion of metal objects, degradation of domestic water quality, agricultural crop damage, and adverse impacts on human respiratory and pulmonary function. Other impacts may include decreases in local rainfall and increased mortality of asthmatics. For the period 1986 to 1993, after the eruption became continuous, deaths from asthma on the island of Hawai`i increased by a factor of ten. Three current health studies seek to investigate the relationship between exposure to volcanic pollution and health effects. In addition to measuring gas and particle exposures, these studies examine lung development in children around the island, disease prevalence in adults residing in communities downwind of volcanic degassing sources, and acute effects in asthmatic children and healthy children and adults. In the absence of conclusive evidence linking exposure and health effects, the USGS, in collaboration with the National Park Service, has developed a real-time advisory for heavily visited park areas known to exceed U.S. Air Quality Standards. This color-coded system informs and advises park visitors and employees when ambient SO2 concentrations exceed predetermined levels.

Elias, T.; Sutton, A. J.

2003-12-01

173

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

USGS Publications Warehouse

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.

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

2008-01-01

174

Electric and magnetic phenomena observed before the volcano-seismic activity in 2000 in the Izu Island Region, Japan  

PubMed Central

Significant anomalous changes in the ultra low frequency range (?0.01 Hz) were observed in both geoelectric and geomagnetic fields before the major volcano-seismic activity in the Izu Island region, Japan. The spectral intensity of the geoelectric potential difference between some electrodes on Niijima Island and the third principal component of geomagnetic field variations at an array network in Izu Peninsula started to increase from a few months before the onset of the volcano-seismic activity, culminating immediately before nearby magnitude 6 class earthquakes. Appearance of similar changes in two different measurements conducted at two far apart sites seems to provide information supporting the reality of preseismic electromagnetic signals. PMID:12032286

Uyeda, S.; Hayakawa, M.; Nagao, T.; Molchanov, O.; Hattori, K.; Orihara, Y.; Gotoh, K.; Akinaga, Y.; Tanaka, H.

2002-01-01

175

A review of historical lahars, floods, and landslides in the Prcheur river catchment (Montagne Pele volcano, Martinique island, Lesser Antilles)  

E-print Network

to the Montagne Pelée volcano massif located in the north of Martinique island, in the Lesser Antilles arc Martinique, dans l'arc des Petites Antilles. Les 19 et 20 juin 2010, deux lahars de forts débits ont débordé capable d'endommager partiellement ou de submerger le pont se produisent tous les 10,3 ans en moyenne

Clouard, Valerie

176

On the time-scales of magmatism at island-arc volcanoes.  

PubMed

Precise information on time-scales and rates of change is fundamental to an understanding of natural processes and the development of quantitative physical models in the Earth sciences. U-series isotope studies are revolutionizing this field by providing time information in the range 10(2)-10(4) years, which is similar to that of many modern Earth processes. I review how the application of U-series isotopes has been used to constrain the time-scales of magma formation, ascent and storage beneath island-arc volcanoes. Different elements are distilled-off the subducting plate at different times and in different places. Contributions from subducted sediments to island-arc lava sources appear to occur some 350 kyr to 4 Myr prior to eruption. Fluid release from the subducting oceanic crust into the mantle wedge may be a multi-stage process and occurs over a period ranging from a few hundred kyr to less than one kyr prior to eruption. This implies that dehydration commences prior to the initiation of partial melting within the mantle wedge, which is consistent with recent evidence that the onset of melting is controlled by an isotherm and thus the thermal structure within the wedge. U-Pa disequilibria appear to require a component of decompression melting, possibly due to the development of gravitational instabilities. The preservation of large (226)Ra disequilibria permits only a short period of time between fluid addition and eruption. This requires rapid melt segregation, magma ascent by channelled flow and minimal residence time within the lithosphere. The evolution from basalt to basaltic andesite probably occurs rapidly during ascent or in magma reservoirs inferred from some geophysical data to lie within the lithospheric mantle. The flux across the Moho is broadly andesitic, and some magmas subsequently stall in more shallow crustal-level magma chambers, where they evolve to more differentiated compositions on time-scales of a few thousand years or less. PMID:12626270

Turner, S P

2002-12-15

177

Evidence for a Great Aleutian Paleotsunami on Kaua`i  

NASA Astrophysics Data System (ADS)

The Hawaiian Islands location amid the Pacific Ocean is threatened by tsunamis from great earthquakes in nearly all directions. Historical great earthquakes Mw>8.5 in the last 100 years have produced large inundations and loss of life in the Islands, but have not accounted for a substantial (>100 m^3) paleotsunami deposit in the Makauwahi sinkhole at Maha`ulepu on the Island of Kaua`i. High-resolution, digital elevation models of bathymetry and topography have been used in conjunction with a non-linear, hydrostatic tsunami model to simulate inundations from giant earthquakes in the Aleutian Islands and elsewhere to estimate the extent of tsunami threats to the State of Hawaii. We model the inundation of the sinkhole by an earthquake with a minimum moment-magnitude of Mw 9.2 located within the eastern Aleutians, where the tsunami energy is focused toward Hawaii. An alternative hypothesis wherein the deposit entered through a small cave entrance is not consistent with fine speleothems, intact in the cave, that pre-date the deposit. The results indicate that a giant earthquake in the eastern Aleutian Islands circa 1425-1665 AD, located between the source regions of the 1946 and 1957 great tsunamigenic earthquakes, generated a tsunami in Hawaii much larger than the historical record. A tsunami deposit in the Aleutians dated circa ~1550 AD is consistent with this eastern Aleutian source region.

Butler, R.; Bai, Y.; Burney, D. A.; Cheung, K.; Yamazaki, Y.

2013-12-01

178

Secular and Spatial Variations of Diffuse CO2 Degassing From Cumbre Vieja Volcano, La Palma, Canary Islands, Spain  

NASA Astrophysics Data System (ADS)

La Palma (730 Km2) is the northwestmost island of the Canarian archipielago and rises 6.5 Km from the oceanic basement. Constructive and destructive geological processes are responsible for the actual geomorphology of La Palma (Navarro, 1992; Ancochea et al., 1994). Recent volcanic activity is mainly concentrated at Cumbre Vieja volcano, in the southern part of La Palma. The most recent eruption occurred in the southernmost part of Cumbre Vieja volcano along its N-S rift zone in October 1971, and lasted for 32 days. Since fumarolic degassing is not present at Cumbre Vieja volcano, diffuse degassing studies are useful geochemical tools for monitoring magma movement and seismicity changes. The purpose of this study is to evaluate the spatial and temporal variations of diffuse CO2 degassing rates at Cumbre Vieja volcano. Soil CO2 efflux surveys of approximately 600 observation sites were carried out during the 2000 and 2001 summer periods. Soil CO2 efflux measurements were performed with the accumulation chamber method by using a portable NDIR sensor and a PC. Statistical-graphical analysis showed three overlapping geochemical populations for both surveys. CO2 efflux peak populations, the geometric means were 271 and 58.6 gm-2d-1 for the 2000 and 2001 surveys, respectively. Most of Cumbre Vieja volcano showed background diffuse CO2 degassing rates. Anomalous CO2 efflux values are spatially related to the volcanic rift-zones. Carbon isotopic signatures showed a mixing of deep and shallow seated CO2. Diffuse CO2 emission rates from Cumbre Vieja volcano were 2,925 and 1,165 td-1 for the 2000 and 2001 surveys, respectively. These results are useful for Cumbre Vieja seismic-volcanic monitoring.

Fuentes, L.; Mena, A.; Alfaya, A.; Padron, E.; Melian, G.; Salazar, J.; Hernandez, P.; Perez, N.

2001-12-01

179

Role of the structural inheritance of the oceanic lithosphere in the magmato-tectonic evolution of Piton de la Fournaise volcano (La Réunion Island)  

Microsoft Academic Search

La Réunion Island is located east of Madagascar, on the eastern rim of the tectonically inactive Mascarene Basin. This island is composed of three shield volcanoes of which only Piton de la Fournaise is currently active. Although the magmatic activity is restricted to Piton de la Fournaise, a scattered seismicity occurs on the whole 200 km wide volcanic edifice and

Laurent Michon; Francky Saint-Ange; Patrick Bachelery; Nicolas Villeneuve; Thomas Staudacher

2007-01-01

180

Zn isotope compositions of the thermal spring waters of La Soufrière volcano, Guadeloupe Island  

NASA Astrophysics Data System (ADS)

To trace the sources and pathways of Zn in hydrothermal systems, the Zn isotope compositions of seventeen water samples from eight thermal springs and six gas samples from two fumaroles from La Soufrière, an active volcano on Guadeloupe Island (French West Indies, FWI), were analyzed using a method adapted for purifying Zn from Fe- and SO4-enriched thermal solutions. The fumaroles are enriched in Zn 100 to 8000 times compared to the local bedrock and have isotopic compositions (?66Zn values from +0.21‰ to +0.35‰) similar to or slightly higher than fresh andesite (+0.21‰). The enrichment of Zn in the thermal springs compared with the surface waters shows that Zn behaves as a soluble element during hydrothermal alteration but is significantly less mobile than Na. The ?66Zn values of most of the spring waters are relatively constant (approximately 0.70‰), indicating that the thermal springs from La Soufrière are enriched in heavy isotopes (i.e., 66Zn) compared to the host rocks (from -0.14‰ to +0.42‰). Only three thermal springs have lower ?66Zn values (as low as -0.43%). While the Zn in the fumaroles is essentially derived from magma degassing, which is consistent with a previous study on Merapi volcano (Toutain et al., 2008), we show that the Zn in the thermal springs is mainly derived from water-rock interactions. The 66Zn-enriched isotopic signature in most of the spring waters can be explained qualitatively by the precipitation at depth of sulfide minerals that preferentially incorporate the light isotopes. This agrees with the isotopic fractionation that was recently calculated for aqueous complexes of Zn. The few thermal springs with lower ?66Zn values also have low Zn concentrations, indicating the preferential scavenging of heavy Zn isotopes in the hydrothermal conduits. This study shows that unlike chemical weathering under surface conditions, hydrothermal alteration at high temperatures significantly fractionates Zn isotopes and enriches thermal waters in heavy Zn isotopes (e.g., 66Zn). Continental hydrothermal systems therefore constitute a source of heavy Zn isotopes to the oceans; this should be taken into account in the global oceanic budget of Zn.

Chen, Jiu-Bin; Gaillardet, Jérôme; Dessert, Céline; Villemant, Benoit; Louvat, Pascale; Crispi, Olivier; Birck, Jean-Louis; Wang, Yi-Na

2014-02-01

181

76 FR 17360 - Fisheries of the Exclusive Economic Zone Off Alaska; Octopus in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013, 2014

...the Exclusive Economic Zone Off Alaska; Octopus in the Bering Sea and Aleutian Islands...to the initial total allowable catch of octopus in the Bering Sea and Aleutian Islands...initial total allowable catch (ITAC) of octopus in the BSAI was [[Page 17361

2011-03-29

182

Handbook for Central Aleutian Site: The Aleuts of the Eighteenth Century, Social Studies Unit, Book IV.  

ERIC Educational Resources Information Center

Artifacts and animal remains found at the Central Aleutian Site are described. The site consists of a house pit and a midden, or refuse pile. The house and artifacts, used in the mid-1700s, were abandoned about the time the Russians first came to the Aleutian Islands. The following information is given for the different types of artifacts:…

Partnow, Patricia H.

183

Genetic and archaeological evidence for a former breeding population of Aleutian Cackling Goose  

E-print Network

(Branta hutchinsii leucopareia) on Adak Island, central Aleutians, Alaska B.J. Wilson, S.J. Crockford, J (Branta hutchinsii leucopareia (Brandt, 1836)) breeds elsewhere in the Aleutians but does not currently (Branta hutchinsii leucopareia (Brandt, 1836)) se reproduit ailleurs dans les Aléoutiennes; elle ne se

Kemp, Brian M.

184

Seismic monitoring at Deception Island volcano (Antarctica): the 2010-2011 survey  

NASA Astrophysics Data System (ADS)

As an example of the recent advances introduced in seismic monitoring of Deception Island volcano (Antarctica) during recent years, we describe the instrumental network deployed during the 2010-2011 survey by the Instituto Andaluz de Geofísica of University of Granada, Spain (IAG-UGR). The period of operation extended from December 19, 2010 to March 5, 2011. We deployed a wireless seismic network composed by four three-component seismic stations. These stations are based on 24-bit SL04 SARA dataloggers sampling at 100 sps. They use a PC with embedded linux and SEISLOG data acquisition software. We use two types of three-component seismometers: short-period Mark L4C with natural frequency of 1 Hz and medium-period Lennartz3D/5s with natural frequency of 0.2 Hz. The network was designed for an optimum spatial coverage of the northern half of Deception, where a magma chamber has been reported. Station locations include the vicinity of the Spanish base "Gabriel de Castilla" (GdC), Obsidianas Beach, a zone near the craters from the 1970 eruptions, and the Chilean Shelter located south of Pendulum Cove. Continuous data from the local seismic network are received in real-time in the base by wifi transmission. We used Ubiquiti Networks Nanostation2 antennas with 2.4 GHz, dual-polarity, 10 dBi gain, and 54 Mbps transmission rate. They have shown a great robustness and speed for real-time applications. To prioritize data acquisition when the battery level is low, we have designed a circuit that allows independent power management for the seismic station and wireless transmission system. The reception antenna located at GdC is connected to a computer running SEISCOMP. This software supports several transmission protocols and manages the visualization and recording of seismic data, including the generation of summary plots to show the seismic activity. These twelve data channels are stored in miniseed format and displayed in real time, which allows for a rapid evaluation of the seismic activity and an efficient seismo-volcanic surveillance. The data are processed and analyzed using the SEISAN database management software. In addition to the seismic network, we deployed a small-aperture seismic array south of Fumarole Bay. It is composed by 9 vertical and 1 three-component short-period stations. The 24-bit data acquisition system samples these 12 channels at 100 sps. There is also a permanent seismic station operating since 2008 and located near GdC, that is very useful for the preliminary evaluation of the seismicity at the start of the survey. This station is composed by a 16-s electrolytic seismometer (Eentec SP400) and a 24-bit datalogger (Eentec DR4000) sampling at 100 sps. During the 2010-2011 survey we identified 33 regional earthquakes, 80 volcano-tectonic (VT) earthquakes, and 929 long-period (LP) events. The volcanic alert system has remained green (the lowest level) at all times. The seismic activity has been similar to previous surveys and remained within limits that are normal for the island.

Martín, R.; Carmona, E.; Almendros, J.; Serrano, I.; Villaseñor, A.; Galeano, J.

2012-04-01

185

Studies Of Volcanoes Of Alaska By Satellite Radar Interferometry  

E-print Network

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

Zhong Lu; Charles Wicks, Jr.; Daniel Dzurisin; Wayne Thatcher; John Power

186

Methods of InSAR atmosphere correction for volcano activity monitoring  

USGS Publications Warehouse

When a Synthetic Aperture Radar (SAR) signal propagates through the atmosphere on its path to and from the sensor, it is inevitably affected by atmospheric effects. In particular, the applicability and accuracy of Interferometric SAR (InSAR) techniques for volcano monitoring is limited by atmospheric path delays. Therefore, atmospheric correction of interferograms is required to improve the performance of InSAR for detecting volcanic activity, especially in order to advance its ability to detect subtle pre-eruptive changes in deformation dynamics. In this paper, we focus on InSAR tropospheric mitigation methods and their performance in volcano deformation monitoring. Our study areas include Okmok volcano and Unimak Island located in the eastern Aleutians, AK. We explore two methods to mitigate atmospheric artifacts, namely the numerical weather model simulation and the atmospheric filtering using Persistent Scatterer processing. We investigate the capability of the proposed methods, and investigate their limitations and advantages when applied to determine volcanic processes. ?? 2011 IEEE.

Gong, W.; Meyer, F.; Webley, P.W.; Lu, Z.

2011-01-01

187

Aseismic inflation of Westdahl volcano, Alaska, revealed by satellite radar interferometry  

USGS Publications Warehouse

Westdahl volcano, located at the west end of Unimak Island in the central Aleutian volcanic arc, Alaska, is a broad shield that produced moderate-sized eruptions in 1964, 1978-79, and 1991-92. Satellite radar interferometry detected about 17 cm of volcano-wide inflation from September 1993 to October 1998. Multiple independent interferograms reveal that the deformation rate has not been steady; more inflation occurred from 1993 to 1995 than from 1995 to 1998. Numerical modeling indicates that a source located about 9 km beneath the center of the volcano inflated by about 0.05 km3 from 1993 to 1998. On the basis of the timing and volume of recent eruptions at Westdahl and the fact that it has been inflating for more than 5 years, the next eruption can be expected within the next several years.

Lu, Z.; Wicks, C.; Dzurisin, D.; Thatcher, W.; Freymueller, J.T.; McNutt, S.R.; Mann, D.

2000-01-01

188

Instrumentation Recommendations for Volcano Monitoring at U.S. Volcanoes Under the National Volcano Early Warning System  

USGS Publications Warehouse

As magma moves toward the surface, it interacts with anything in its path: hydrothermal systems, cooling magma bodies from previous eruptions, and (or) the surrounding 'country rock'. Magma also undergoes significant changes in its physical properties as pressure and temperature conditions change along its path. These interactions and changes lead to a range of geophysical and geochemical phenomena. The goal of volcano monitoring is to detect and correctly interpret such phenomena in order to provide early and accurate warnings of impending eruptions. Given the well-documented hazards posed by volcanoes to both ground-based populations (for example, Blong, 1984; Scott, 1989) and aviation (for example, Neal and others, 1997; Miller and Casadevall, 2000), volcano monitoring is critical for public safety and hazard mitigation. Only with adequate monitoring systems in place can volcano observatories provide accurate and timely forecasts and alerts of possible eruptive activity. At most U.S. volcanoes, observatories traditionally have employed a two-component approach to volcano monitoring: (1) install instrumentation sufficient to detect unrest at volcanic systems likely to erupt in the not-too-distant future; and (2) once unrest is detected, install any instrumentation needed for eruption prediction and monitoring. This reactive approach is problematic, however, for two reasons. 1. At many volcanoes, rapid installation of new ground-1. based instruments is difficult or impossible. Factors that complicate rapid response include (a) eruptions that are preceded by short (hours to days) precursory sequences of geophysical and (or) geochemical activity, as occurred at Mount Redoubt (Alaska) in 1989 (24 hours), Anatahan (Mariana Islands) in 2003 (6 hours), and Mount St. Helens (Washington) in 1980 and 2004 (7 and 8 days, respectively); (b) inclement weather conditions, which may prohibit installation of new equipment for days, weeks, or even months, particularly at midlatitude or high-latitude volcanoes; (c) safety factors during unrest, which can limit where new instrumentation can safely be installed (particularly at near-vent sites that can be critical for precursor detection and eruption forecasting); and (d) the remoteness of many U.S. volcanoes (particularly those in the Aleutians and the Marianas Islands), where access is difficult or impossible most of the year. Given these difficulties, it is reasonable to anticipate that ground-based monitoring of eruptions at U.S. volcanoes will likely be performed primarily with instruments installed before unrest begins. 2. Given a growing awareness of previously undetected 2. phenomena that may occur before an eruption begins, at present the types and (or) density of instruments in use at most U.S. volcanoes is insufficient to provide reliable early warning of volcanic eruptions. As shown by the gap analysis of Ewert and others (2005), a number of U.S. volcanoes lack even rudimentary monitoring. At those volcanic systems with monitoring instrumentation in place, only a few types of phenomena can be tracked in near-real time, principally changes in seismicity, deformation, and large-scale changes in thermal flux (through satellite-based remote sensing). Furthermore, researchers employing technologically advanced instrumentation at volcanoes around the world starting in the 1990s have shown that subtle and previously undetectable phenomena can precede or accompany eruptions. Detection of such phenomena would greatly improve the ability of U.S. volcano observatories to provide accurate early warnings of impending eruptions, and is a critical capability particularly at the very high-threat volcanoes identified by Ewert and others (2005). For these two reasons, change from a reactive to a proactive volcano-monitoring strategy is clearly needed at U.S. volcanoes. Monitoring capabilities need to be expanded at virtually every volcanic center, regardless of its current state of

Moran, Seth C.; Freymueller, Jeff T.; LaHusen, Richard G.; McGee, Kenneth A.; Poland, Michael P.; Power, John A.; Schmidt, David A.; Schneider, David J.; Stephens, George; Werner, Cynthia A.; White, Randall A.

2008-01-01

189

InSAR observations of the 1995 Fogo, Cape Verde, eruption: Implications for the effects of collapse events upon island volcanoes  

Microsoft Academic Search

Fogo volcano, Cape Verde Islands, erupted in April 1995 after 43 years of dormancy. About 46 106 m3 of lava erupted during 7.5 weeks from vents on the SW flank of Pico do Fogo into Cha das Caldeiras. Interferograms obtained from 1993–1998 ERS SAR data show ground deformation due to the feeder dike but lack evidence for any volcano-wide deformation

Falk Amelung; Simon Day

2002-01-01

190

InSAR observations of the 1995 Fogo, Cape Verde, eruption: Implications for the effects of collapse events upon island volcanoes  

Microsoft Academic Search

Fogo volcano, Cape Verde Islands, erupted in April 1995 after 43 years of dormancy. About 46 106 m3 of lava erupted during 7.5 weeks from vents on the SW flank of Pico do Fogo into Cha das Caldeiras. Interferograms obtained from 1993-1998 ERS SAR data show ground deformation due to the feeder dike but lack evidence for any volcano-wide deformation

Falk Amelung; Simon Day

2002-01-01

191

The 1998-1999 Seismic Series At Deception Island Volcano, Antarctica.  

NASA Astrophysics Data System (ADS)

During the 1998-1999 Antarctic summer, the pattern of seismic activity at Deception Island volcano suffered a significant change with respect to the previous years. This change was characterized by the occurrence of an intense swarm of local earthquakes. More than 2000 local earthquakes with S-P time smaller than 4 s were recorded in the period January-February 1999. Pure volcanic events have been also detected, spe- cially long period (LP) events and volcanic tremor, and some hybrid events. Seismic monitoring was performed using two short-period small-aperture arrays, among other instruments. We selected for the analysis 863 local earthquakes, 350 LP events and tremor episodes, and 9 hybrid events, based on their signal-to-noise ratios. Propaga- tion parameters (apparent slowness and back-azimuth) for all events were estimated using the zero lag cross-correlation (ZLCC) array technique. Combining this infor- mation with measures of S-P times and other indirect evidences, two different source regions have been identified. LP seismicity is located southwestward from the Fuma- role array site at distances smaller than 1-1.5 km. In this region we find the presence of glaciers, important fractures, and thermal anomalies, which supports the hypothesis of a hydrothermal origin. Local earthquakes and hybrid events are located in a region beneath Port Foster, the inner Bay of Deception Island. This region extends from the array site to the Northeast, between depths of 0.3 and 10 km. The epicentral distances range between 0.5 and 12 km. Most hypocenters are clustered in a small volume of around 8 km3 centered at 1.5 km depth and 1.5 km Northeast of the Fumarole ar- ray. The sources of the LP seismicity and the local earthquakes are spatially distinct, which indicates that they are not produced by the same mechanisms. Moment mag- nitude analyses of the local earthquakes show an energetic uniformity in the seismic series, with average magnitude of 0.5 and very low average stress drop, around 1 bar. The study of the spatial distribution of the first motion of the P-waves suggests that dif- ferent source mechanisms acted in a very small volume. The complexity of the source region is also evidenced by the identification of distinct families of events with the same waveforms inside the main source region. The occurrence of repeatable fracture processes with low stress drop and small fault dimensions can be explained by the lu- brication of pre-existing zones of weakness by pressurized fluids. Three mechanisms could be invoked to explain the generation of the recorded seismic series at Decep- 1 tion Island: 1) a classical tectonic seismic swarm caused by a regional stress field; 2) a seismic swarm produced directly by the actual movement of magma through the source region; and 3) a seismic series caused by the stress generated by the uplift of the source area due to a magmatic injection in depth. We favor the last hypothesis since it is compatible with the majority of the characteristics of the seismicicty and explains the spatial and temporal behavior of the series. 2

Ibáñez, J. M.; Carmona, E.; Almendros, J.; Saccorotti, G.; del Pezzo, E.; Abril, M.; Ortiz, R.; Martínez-Arévalo, C.

192

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

PubMed Central

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

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

2012-01-01

193

Ground deformation associated with the March 1996 earthquake swarm at Akutan volcano, Alaska, revealed by satellite radar interferometry  

USGS Publications Warehouse

In March 1996 an intense swarm of volcano-tectonic earthquakes (???3000 felt by local residents, Mmax = 5.1, cumulative moment of 2.7 ??1018 N m) beneath Akutan Island in the Aleutian volcanic arc, Alaska, produced extensive ground cracks but no eruption of Akutan volcano. Synthetic aperture radar interferograms that span the time of the swarm reveal complex island-wide deformation: the western part of the island including Akutan volcano moved upward, while the eastern part moved downward. The axis of the deformation approximately aligns with new ground cracks on the western part of the island and with Holocene normal faults that were reactivated during the swarm on the eastern part of the island. The axis is also roughly parallel to the direction of greatest compressional stress in the region. No ground movements greater than 2.83 cm were observed outside the volcano's summit caldera for periods of 4 years before or 2 years after the swarm. We modeled the deformation primarily as the emplacement of a shallow, east-west trending, north dipping dike plus inflation of a deep, Mogi-type magma body beneath the volcano. The pattern of subsidence on the eastern part of the island is poorly constrained. It might have been produced by extensional tectonic strain that both reactivated preexisting faults on the eastern part of the island and facilitated magma movement beneath the western part. Alternatively, magma intrusion beneath the volcano might have been the cause of extension and subsidence in the eastern part of the island. We attribute localized subsidence in an area of active fumaroles within the Akutan caldera, by as much as 10 cm during 1992-1993 and 1996-1998, to fluid withdrawal or depressurization of the shallow hydrothermal system. Copyright 2000 by the American Geophysical Union.

Lu, Z.; Wicks, C., Jr.; Power, J.A.; Dzurisin, D.

2000-01-01

194

Argon geochronology of late Pleistocene to Holocene Westdahl volcano, Unimak Island, Alaska  

USGS Publications Warehouse

High-precision 40Ar/39Ar geochronology of selected lavas from Westdahl Volcano places time constraints on several key prehistoric eruptive phases of this large active volcano. A dike cutting old pyroclastic-flow and associated lahar deposits from a precursor volcano yields an age of 1,654+/-11 k.y., dating this precursor volcano as older than early Pleistocene. A total of 11 geographically distributed lavas with ages ranging from 47+/-14 to 127+/-2 k.y. date construction of the Westdahl volcanic center. Lava flows cut by an apparent caldera-rim structure yielded ages of 81+/-5 and 121+/-8 k.y., placing a maximum date of 81 ka on caldera formation. Late Pleistocene and Holocene lavas fill the caldera, but most of them are obscured by the large summit icecap.

Calvert, Andrew T.; Moore, Richard B.; McGimsey, Robert G.

2005-01-01

195

Magnetic structure of Loihi Seamount, an active hotspot volcano in the Hawaiian Island chain  

E-print Network

them difficult to investigate. Because undersea volcanoes are made up of highly magnetic basaltic rock, it is possible to use variations in the magnetic field to explore the internal structure of such edifices. This study combines magnetic survey data...

Lamarche, Amy J.

2004-09-30

196

Controlled-source seismic investigations of the crustal structure beneath Erebus volcano and Ross Island, Antarctica: Preliminary Results  

NASA Astrophysics Data System (ADS)

During the 2008-09 Austral summer field season we undertook a controlled-source seismic experiment (Tomo-Erebus, TE) to examine the shallow magmatic system beneath the active Erebus volcano (TE-3D) and the crustal structure beneath Ross Island. Here we report on the TE-2D component, which was designed to produce a two-dimensional P-wave velocity model along an east-west profile across Ross Island. Marine geophysical observations near Ross Island have identified the north-south trending Terror Rift within the older and broader Victoria Land Basin, which are a component of the intraplate West Antarctic Rift System. Mount Erebus and Ross Island are circumstantially associated with the Terror Rift and its thin (~20 km) crust. The nature, extent and role of the Terror Rift in controlling the evolution of Ross Island volcanism and the on-going eruptive activity of Erebus volcano are unknown. In TE-2D, we deployed 21 seismic recorders (Ref Tek 130) with three-component 4.5 Hz geophones (Sercel L-28-3D) along a 90-km east-west line between Capes Royds and Crozier. These were supplemented by 79 similar instruments deployed for the high-resolution TE-3D experiment within a 3 x 3 km grid around the summit crater of Erebus, an array of 8 permanent short period and broadband sensors used to monitor the activity of Erebus and 23 three-component sensors (Guralp CMG-40T, 30s-100 Hz) positioned around the flanks and summit of Erebus. Fifteen chemical sources were loaded in holes drilled about 15 m deep in the snow and ice. The size of these shots ranged from 75 to 600 kg of ANFO with the largest shots at the ends of the profile. An additional shot was detonated in the sea (McMurdo Sound) using 200 kg of dynamite. Due to the rugged terrain, short field seasons and large area to be covered, the seismometer spacing along the TE-2D profile is quite large (~ 5 km spacing), resulting in poor near-surface data resolution. However, the data have a high signal to noise ratio with clear first arrivals and wide-angle reflections across the array. We will present a preliminary P-wave velocity model of the TE-2D data to constrain the middle to lower crust and upper mantle beneath Ross Island.

Maraj, S.; Kyle, P. R.; Zandomeneghi, D.; Knox, H. A.; Aster, R. C.; Snelson, C. M.; Miller, P. E.; Kaip, G. M.

2009-12-01

197

InSAR observations of the 1995 Fogo, Cape Verde, eruption: Implications for the effects of collapse events upon island volcanoes  

NASA Astrophysics Data System (ADS)

Fogo volcano, Cape Verde Islands, erupted in April 1995 after 43 years of dormancy. About 46 106 m3 of lava erupted during 7.5 weeks from vents on the SW flank of Pico do Fogo into Cha das Caldeiras. Interferograms obtained from 1993-1998 ERS SAR data show ground deformation due to the feeder dike but lack evidence for any volcano-wide deformation related to volume changes of a shallow magma reservoir. This suggests that Fogo is fed from a relatively deep, mantle-lithospheric source (>16.5 km depth), consistent with petrological data. This supports the concept that Cha das Caldeiras is the fill of a collapse scar created by a giant landslide, and not a collapse caldera overlying a central, shallow magma chamber. The disturbance of the magmatic system by giant landslides may explain why some oceanic island volcanoes with high magma supply rates currently lack well-developed shallow reservoirs.

Amelung, Falk; Day, Simon

2002-06-01

198

INVASION NOTE Range expansion of nonindigenous caribou in the Aleutian  

E-print Network

) 2012 Abstract Caribou (Rangifer tarandus) are nonin- digenous to all but the eastern-most island are devoid of indigenous land mammals. However, introductions of caribou (Rangifer taran- dusINVASION NOTE Range expansion of nonindigenous caribou in the Aleutian archipelago of Alaska Mark A

Aspbury, Andrea S. - Department of Biology, Texas State University

199

Improvement in TDEM sounding interpretation in presence of induced polarization. A case study in resistive rocks of the Fogo volcano, Cape Verde Islands  

Microsoft Academic Search

A Time Domain Electromagnetic (TDEM) survey was carried out in and around the caldera of the Fogo volcano, Cape Verde Islands, to detect the low resistive structures that could be related to groundwater. A sign reversal in the sounding curves was encountered in central-loop measurements for the soundings located in the centre of the caldera along three main radial profiles.

Marc Descloitres; Roger Guérin; Yves Albouy; Alain Tabbagh; Michel Ritz

2000-01-01

200

Unravelling the Geometry of Unstable Flanks of Submarine Volcanoes by Magnetic Investigation: the Case of the "sciara del Fuoco" Scar (stromboli Volcano, Aeolian Islands)  

NASA Astrophysics Data System (ADS)

Stromboli is the easternmost island of the Aeolian Archipelago (Tyrrhenian Sea) and one of the most active Mediterranean volcanoes. The volcanic edifice rises over 3000 m above the surrounding seafloor, from a depth of about 2000 m b.s.l. to 924 m a.s.l. The north-western flank of volcano is deeply scarred by a destructive collapse event occurred ca. 5000 years ago, and forming a big horseshoe-shaped depression, known as "Sciara del Fuoco" (SdF). This depression, 3 Km long and 2 Km wide, is supposed to extend into the sea down to 700 m b.s.l., while further basinward it turns into a fan-shaped mounted deposit down to about 2600 m b.s.l., where it merges the so-called "Stromboli Canyon". Since its formation, emerged and submerged portions of the SdF have been progressively filled by the volcanic products of the persistent activity of the Stromboli Volcano. In the last 10 years, two paroxysmal eruptions occurred in the Stromboli Volcano, during 2002-2003 and February-April 2007. During both events, the SdF has been partially covered by lava flows and affected by slope failures, also causing (for the 2002-2003 event) a local tsunami. Since the 1990's, and especially after the last two paroxysms, the submerged extension of the SdF has been intensively investigated by using swath bathymetry data. We focused principally on the magnetic anomaly pattern of the submerged SdF since the chaotic depositional system virtually cancels magnetic remanence (which at Stromboli can reach 5-10 A/m values), thus lowering magnetic residual intensity. On July 2012 we acquired new detailed sea-surface magnetic data of the SdF from the shoreline to about 7 km offshore, where the depth is more than 1800 m b.s.l. We collected data thanks to the Italian Navy ship "Nave Aretusa" and by using the Marine Magnetics SeaSPY magnetometer. At the same time, new bathymetric data were acquired in the same area by using a Kongsberg Marine multibeam systems. Although the morphologic features of the submarine prosecution of the SdF system were already studied and unveiled, the complete description of the in-depth extension of the system and the overall volume estimation is still poorly known. This has important implications for the hazard assessment of the landslide structure and most generally of the entire volcanic edifice. The application of a classical geomagnetic prospection to describe a landslide feature is an uncommon procedure yet it can be considered as innovative approach, having the advantages of effectiveness, low cost and expedition typical of the geomagnetic survey. Here we present the interpretation of the newly acquired high-resolution magnetic dataset, thanks to susceptibility and magnetic remanence values gathered from on-land rock samples at Stromboli. A 3D inverse model is here proposed, allowing a full definition of the submerged SdF structure geometry.

Muccini, F.; Cocchi, L.; Carmisciano, C.; Speranza, F.; Marziani, F.

2012-12-01

201

Tsunami deposits in Santiago Island (Cape Verde archipelago) as possible evidence of a massive flank failure of Fogos volcano  

NASA Astrophysics Data System (ADS)

Massive flank failures of volcanic edifices generate tsunami waves. These low-frequency but high magnitude hazards remain poorly documented because of the scarcity of observations. Offshore deposits are studied only by geophysical surveys and the failure rheologies are poorly constrained. Marine conglomerates found at unusually high elevations in Hawaii and in the Canary Islands were previously interpreted as being the result of giant tsunami waves generated by massive flank failures. This study focuses on the search for, and interpretation of, sedimentary evidence of a tsunami around the coastline of Santiago Island, which is located 55 km east of the active Fogo volcano. The Bordeira caldera in Fogo Island, which opens to the east, was formed by the Monte Amarelo flank collapse, and the active edifice is now nested in the failure's scar. The only evidence of a tsunami was found north of Tarrafal Bay. The deposits display many similarities with the tsunami conglomerate described in Hawaii and the Canary Islands: erosive contact with the substratum; rip-up clasts of paleo-soil; marine bioclasts never found in growth or live position; internal organisation into different facies with distinct characteristics of clast-size (up to boulders), sorting (from moderately to very poorly sorted) and clast-fabrics (landward or seaward orientations). This organisation suggests that the tsunami consisted of two main waves. The absence of tsunami deposits elsewhere on Santiago Island, coupled with the relatively low elevation of the conglomerate in Tarrafal (< 15 m), indicate retrogressive failures, rather than a single massive failure. The marine fauna in the tsunami conglomerate is not typical of warm fauna such as the Senegalese fauna (interglacial stages). The age of the tsunami is bracketed by the ages of a coral branch in the conglomerate (123.6 ± 3.9 ka U-Th age) and a post-collapse lava along the Bordeira caldera in Fogo (86 ± 3 ka K-Ar age).

Paris, Raphaël; Giachetti, Thomas; Chevalier, Joël; Guillou, Hervé; Frank, Norbert

2011-08-01

202

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

NASA Astrophysics Data System (ADS)

On October 10 2011 an underwater eruption gave rise to a novel shallow submarine volcano south of the island of El Hierro, Canary Islands, Spain. During the eruption large quantities of mantle-derived gases, solutes and heat were released into the surrounding waters. In order to monitor the impact of the eruption on the marine ecosystem, periodic multidisciplinary cruises were carried out. Here, we present an initial report of the extreme physical-chemical perturbations caused by this event, comprising thermal changes, water acidification, deoxygenation and metal-enrichment, which resulted in significant alterations to the activity and composition of local plankton communities. Our findings highlight the potential role of this eruptive process as a natural ecosystem-scale experiment for the study of extreme effects of global change stressors on marine environments. (A) Natural color composite from the MEdium Resolution Imaging Spectrometer (MERIS) instrument aboard ENVISAT Satellite (European Space Agency), (November 9, 2011 at 14:45 UTC). Remote sensing data have been used to monitor the evolution of the volcanic emissions, playing a fundamental role during field cruises in guiding the Spanish government oceanographic vessel to the appropriate sampling areas. The inset map shows the position of Canary Islands west of Africa and the study area (solid white box). (B) Location of the stations carried out from November 2011 to February 2012 at El Hierro. Black lines denote transects A-B and C-D.

Fraile-Nuez, E.; Santana-Casiano, J.; Gonzalez-Davila, M.

2013-12-01

203

Volcano-structural evolution of Teide (Tenerife, Canary Islands): field data constraints.  

NASA Astrophysics Data System (ADS)

Teide is the only active stratovolcano in the Canaries. Its outstanding morphology strongly departs from a typical stratovolcano, having two prominent NE and NW flank bulges, and a flat summit area. Different hypotheses of Teide evolution disagree on the role of deformation processes in controlling volcano morphology. We present field structural and stratigraphic data, as well as analogue models, to test the hypothesis on the volcano's structural evolution. On the NE bulge the oldest lava flows have clear morphological evidence that they are younger than the slope break. We have found several tumuli on these lava flows and discard their previously proposed origin as dome eruptive vents, one of the main alleged evidences for an origin of the NE bulge as a covered flank vent. On the N flank the same "tumuli-forming" lava flows unit crop out below other lava flows cut by the northern summit scarp. These stratigraphic relationships point to a younger age for the summit scarp than for the NE bulge, which argues against both structures being genetically related by flank spreading. However, our analogue models of volcano deformation over a weak core indicate that summit faulting still occurs in the late deformation stages when lateral bulge has fully developed. "Tumuli-forming" lava flows could be contemporaneous to NE flank spreading and could have covered the flank bulge, only to be later faulted by summit structures. On the NW bulge the morphology of flank covering block-and-ash flow deposits and inter-bedded lava flows (Las Calvas unit) indicate their emplacement on a steep slope, post-dating the bulge formation. Moreover, we find penetrative fractures affecting these volcanoclastic and lava flow deposits. The extensional nature of this radial and tangential fracturing could be caused by bulging of the deposits, indicating long-lived progressive bulging of this flank. On the flat summit area we have found structural evidence of bulging due to a cryptodome intrusion that could also have contributed to the formation of the bounding scarps. There is other field evidence of dome intrusions at different altitudes along the volcano eastern flank in the same ENE-WSW structural direction of the Teide-Pico Viejo alignment and of the dykes at the Pico Viejo crater walls. Our field data provide some new constraints for the debate of the structural evolution of Teide volcano, and seem to point to a prominent role for flank spreading and dome intrusion. However, radiometric dating of selected units and further analogue modelling are necessary to integrate our field observations in a coherent model of Teide volcano structural evolution.

Marquez, Alvaro; Herrera, Raquel; Granja Bruña, Jose Luis; van Wyk de Vries, Benjamin; Llanes, Pilar; Rincón, Marta

2014-05-01

204

Vertical Movements of Ocean Island Volcanoes: Insights from a Stationary Plate  

Microsoft Academic Search

\\u000a The origin of hotspot swells is still controversial and their development is at present poorly constrained and strongly model-dependent.\\u000a However, since islands are built on top of these structures, the role of swell development in island uplift\\/subsidence should\\u000a be assessed.

Ricardo Alexandre dos Santos Ramalho

205

GPS and Gravity Surveying at Fogo Volcano, Cape Verde Islands, 1998-2001  

Microsoft Academic Search

Fogo Island, in the Cape verde archipelago (North Atlantic), is a roughly conical volcanic edifice with 25 Km of base diameter and a summit that reaches an altitude of about 3000 m. Volcanic eruptions in the island are reported since the settlement in the 16th century, at average intervals of about 20 years. In the 20th century the activity subsided,

J. N. Lima; C. Lazaro; S. I. Heleno; J. F. Fonseca; I. Barros; J. Matos; M. Baio; J. Osorio

2001-01-01

206

O-saturated island arc low-K tholeiite magmas: a case study of the Izu-Oshima volcano in the Izu arc  

NASA Astrophysics Data System (ADS)

Island arc low-K tholeiites are basaltic magmas erupting from frontal arc volcanoes of juvenile arcs associated with the subduction of old and cold plates. We investigated the origins of geochemical variation in volcanic rocks having multiple phase saturated liquid compositions from the Izu-Oshima volcano in the northern Izu arc. The geochemical variations in the liquids fall between two endmember trends, namely higher- and lower-Al/Si trends. Polybaric differentiation of H2O-saturated melts between a 4-km-deep magma chamber and degassed melts near the surface should be responsible for the observed variation in the liquids.

Hamada, Morihisa; Okayama, Yuko; Kaneko, Takayuki; Yasuda, Atsushi; Fujii, Toshitsugu

2014-12-01

207

Variations in Melt Generation and Migration along the Aleutian Arc (Invited)  

NASA Astrophysics Data System (ADS)

The generation and ascent of mantle melt beneath volcanic arcs sets the course for how magmas differentiate to form the continental crust and erupt explosively from volcanoes. Although the basic framework of melting at subduction zones is understood to involve the convective influx of hot mantle (Tp ? 1300°C) and advective transport of water-rich fluids from the subducting slab, the P-T paths that melts follow during melt generation and migration are still not well known. The Aleutian Arc provides an opportunity to explore the conditions of mantle melting in the context of volcanoes that span an unusually large range in the depth to the slab, from Seguam island, with among the shallowest depths to the slab worldwide (~65 km, [1]) to Bogoslof island, behind the main volcanic front and twice the depth to the slab (~130 km). Here we combine thermal models tuned to Aleutian subduction parameters [after 2] with petrological estimates of the T and P of mantle-melt equilibration, using a major element geothermometer [3] and estimates of H2O and fO2 from olivine-hosted melt inclusion measurements [4] for basaltic magmas from 6 volcanoes in the central Aleutians (Korovin, Seguam, Bogoslof, Pakushin, Akutan, Shishaldin). We find mantle-melt equilibration conditions to vary systematically as a function of the depth to the slab, from 30 km and 1220°C (for Seguam) to 60 km and 1300°C (for Bogoslof). Such shallow depths, which extend up to the Moho, define a region perched well above the hot core of the mantle wedge predicted from thermal models, even considering the shallow depths of slab-mantle coupling (< 60 km) required to supply hot mantle beneath Seguam. Thus, even though the greatest melt production will occur in the hot core of the wedge (50-100 km depth), melts apparently ascend and re-equilibrate in the shallowest mantle. Volcanoes that overlie the greatest depth to the slab, and lie furthest from the wedge corner, stall at greater depths (~60 km), at the base of the conductive upper plate (i.e., lithosphere). The conductive lid and isotherms shallow toward the wedge corner. This leads to shallower depths of melt equilibration at shallower depths to the slab. A second effect is infiltration of melt into the thinning lithosphere, likely due to the increase in strain-rate toward the wedge corner, which favors melt segregation, migration, and shallow equilibration [5]. Such a process is developed most beneath Seguam, where melts collect at the Moho (~ 30km), but are still > 1200°C. Such equilibration depths in the uppermost mantle (30-60 km) and temperatures typical of the base of the conductive lid appear to characterize most modeled primary arc magmas [6], and point to a final re-setting point in the mantle that controls the composition of bulk arc crust. [1] Syracuse & Abers, 2006, G3. [2] Syracuse, van Keken, Abers, (2010) PEPI. [3] Lee, Luffi, Plank, Dalton, Leeman (2009) EPSL. [4] Zimmer et al. (2010) J.Pet. [5] Holzman & Kendall (2010). [6] Ruscitto et al. (2012) G3.

Plank, T. A.; Van Keken, P. E.

2013-12-01

208

TECTONIC CONTROLS ON THOLEIITIC AND CALC-ALKALINE MAGMATISM IN THE ALEUTIAN ARC  

Microsoft Academic Search

The tectonic position of Aleutian arc volcanic centers and their magmatic differ- entiation trends (calc-alkaline or tholeiitic) appear to correlate. From 160øW to 175øE, the volcanoes form four major arc segments that coincide with earthquake aftershock zones and major geographic features on both the upper and lower plates. The tholeiitic volcanoes are large, primarily basaltic centers that occur between or

S. Mahlburg Kay; R. W. Kay; G. P. Citron

1982-01-01

209

Movement of shallow magmatic sources inferred from volcano-tectonic faults: An example from Shinjima Island nearby Sakurajima volcano, Kyushu, Japan  

Microsoft Academic Search

Uplift and subsidence due to magma movement involve complex fault system at the surface of a volcano. Conversely, mapping volcano-tectonic faults and surface deformation allows us to infer the feeding system of magma and eruption process in the past. Here we represent a case study of such deformation and a complex fault system associated with prehistoric and historic volcanic uplifts

Y. Yoshinaga; T. Haraguchi; S. Toda; D. Miki; R. Imura

2006-01-01

210

Enhancement of sub-daily positioning solutions for surface deformation surveillance at El Hierro volcano (Canary Islands, Spain)  

NASA Astrophysics Data System (ADS)

El Hierro Island in the Canary Archipelago recently experienced a submerged eruption a few kilometers off its southern shore, detected 2011 October 10 on the island's south-rift alignment. The seismic activity suddenly increased around mid 2011 July, and ground deformation was then detected on the only geodetic benchmark that is continuously observed by global navigation satellite systems techniques and provides public data access. Based on that information, several other global navigation satellite system signal receivers were deployed on the island to provide continuous observation. For data collected by these receivers, a processing strategy was applied to achieve millimeter-level half-hourly positioning solutions. Position updates every 24 h are satisfactory to determine tectonic-plates' velocities. Updates near 1 s or less are required to characterize seismic waves. In between, minute-level updates are well suited for monitoring active volcano's inflation or deflation, providing an optimal time resolution of the local ground deformation. In half-hourly positioning solutions, the heterogeneous satellites' distribution in their orbital planes gives different constraints during satellite-constellation revolution, which can bias the solutions. Also, several geophysical influences can bias the solutions, including those related to gravitational movements. These influences have mostly semi-diurnal periodicities and may be considered Gaussian colored noise on the position's time series. Daily solutions that average out these influences can be applied in active volcanoes, but they can impose some limitations because they average the daily deformation, and the update waiting time is not suitable when near real-time surveillance is mandatory. These semi-diurnal biases do need to be removed or minimized to achieve millimeter-level sub-daily positioning solutions, however, and to do so, a discrete Kalman filter was applied to enhance the half-hourly positioning solutions required during El Hierro's 2011-2012 unrest and eruption. Throughout El Hierro's volcanic activity, there were correlations between ground deformation and seismic activity. Many times the deformation preceded the earthquakes, though at other times the seismic activity was followed by the ground deformation response. This correlation is the outcome of ground deformation taking place as the result of energy accommodation, whereas seismic events correspond to energy release. Hence, those observed correlations indicate that the Kalman filter-enhanced half-hourly positioning solutions measured local ground deformation accurately; they were not a mathematical "trick" producing a spurious precision.

Prates, G.; García, A.; Fernández-Ros, A.; Marrero, J. M.; Ortiz, R.; Berrocoso, M.

2013-06-01

211

Identifying potential habitat for the endangered Aleutian shield fern using topographical characteristics  

USGS Publications Warehouse

The Aleutian shield fern Polystichum aleuticum is endemic to the Aleutian archipelago of Alaska and is listed as endangered pursuant to the U.S. Endangered Species Act. Despite numerous efforts to discover new populations of this species, only four known populations are documented to date, and information is needed to prioritize locations for future surveys. Therefore, we incorporated topographical habitat characteristics (elevation, slope, aspect, distance from coastline, and anthropogenic footprint) found at known Aleutian shield fern locations into a Geographical Information System (GIS) model to create a habitat suitability map for the entirety of the Andreaonof Islands. A total of 18 islands contained 489.26 km2 of highly suitable and moderately suitable habitat when weighting each factor equally. This study reports a habitat suitability map for the endangered Aleutian shield fern using topographical characteristics, which can be used to assist current and future recovery efforts for the species.

Duarte, Adam; Wolcott, Daniel M.; Chow, T. Edwin, Ricca, Mark A.

2012-01-01

212

The 1957 great Aleutian earthquake  

NASA Astrophysics Data System (ADS)

The 9 March 1957 Aleutian earthquake has been estimated as the third largest earthquake this century and has the longest aftershock zone of any earthquake ever recorded—1200 km. However, due to a lack of high-quality seismic data, the actual source parameters for this earthquake have been poorly determined. We have examined all the available waveform data to determine the seismic moment, rupture area, and slip distribution. These data include body, surface and tsunami waves. Using body waves, we have estimated the duration of significant moment release as 4 min. From surface wave analysis, we have determined that significant moment release occurred only in the western half of the aftershock zone and that the best estimate for the seismic moment is 50 100×1020 Nm. Using the tsunami waveforms, we estimated the source area of the 1957 tsunami by backward propagation. The tsunami source area is smaller than the aftershock zone and is about 850 km long. This does not include the Unalaska Island area in the eastern end of the aftershock zone, making this area a possible seismic gap and a possible site of a future large or great earthquake. We also inverted the tsunami waveforms for the slip distribution. Slip on the 1957 rupture zone was highest in the western half near the epicenter. Little slip occurred in the eastern half. The moment is estimated as 88×1020 Nm, or M w =8.6, making it the seventh largest earthquake during the period 1900 to 1993. We also compare the 1957 earthquake to the 1986 Andreanof Islands earthquake, which occurred within a segment of the 1957 rupture area. The 1986 earthquake represents a rerupturing of the major 1957 asperity.

Johnson, Jean M.; Tanioka, Yuichiro; Ruff, Larry J.; Satake, Kenji; Kanamori, Hiroo; Sykes, Lynn R.

1994-03-01

213

Pacific Basin tsunami hazards associated with mass flows in the Aleutian arc of Alaska  

Microsoft Academic Search

We analyze mass-flow tsunami generation for selected areas within the Aleutian arc of Alaska using results from numerical simulation of hypothetical but plausible mass-flow sources such as submarine landslides and volcanic debris avalanches. The Aleutian arc consists of a chain of volcanic mountains, volcanic islands, and submarine canyons, surrounded by a low-relief continental shelf above about 1000–2000m water depth. Parts

Christopher F. Waythomas; Philip Watts; Fengyan Shi; James T. Kirby

2009-01-01

214

The Submarine Volcano Eruption off El Hierro Island: Effects on the Scattering Migrant Biota and the Evolution of the Pelagic Communities  

PubMed Central

The submarine volcano eruption off El Hierro Island (Canary Islands) on 10 October 2011 promoted dramatic perturbation of the water column leading to changes in the distribution of pelagic fauna. To study the response of the scattering biota, we combined acoustic data with hydrographic profiles and concurrent sea surface turbidity indexes from satellite imagery. We also monitored changes in the plankton and nekton communities through the eruptive and post-eruptive phases. Decrease of oxygen, acidification, rising temperature and deposition of chemicals in shallow waters resulted in a reduction of epipelagic stocks and a disruption of diel vertical migration (nocturnal ascent) of mesopelagic organisms. Furthermore, decreased light levels at depth caused by extinction in the volcanic plume resulted in a significant shallowing of the deep acoustic scattering layer. Once the eruption ceased, the distribution and abundances of the pelagic biota returned to baseline levels. There was no evidence of a volcano-induced bloom in the plankton community. PMID:25047077

Ariza, Alejandro; Kaartvedt, Stein; Røstad, Anders; Garijo, Juan Carlos; Arístegui, Javier; Fraile-Nuez, Eugenio; Hernández-León, Santiago

2014-01-01

215

The submarine volcano eruption off El Hierro Island: effects on the scattering migrant biota and the evolution of the pelagic communities.  

PubMed

The submarine volcano eruption off El Hierro Island (Canary Islands) on 10 October 2011 promoted dramatic perturbation of the water column leading to changes in the distribution of pelagic fauna. To study the response of the scattering biota, we combined acoustic data with hydrographic profiles and concurrent sea surface turbidity indexes from satellite imagery. We also monitored changes in the plankton and nekton communities through the eruptive and post-eruptive phases. Decrease of oxygen, acidification, rising temperature and deposition of chemicals in shallow waters resulted in a reduction of epipelagic stocks and a disruption of diel vertical migration (nocturnal ascent) of mesopelagic organisms. Furthermore, decreased light levels at depth caused by extinction in the volcanic plume resulted in a significant shallowing of the deep acoustic scattering layer. Once the eruption ceased, the distribution and abundances of the pelagic biota returned to baseline levels. There was no evidence of a volcano-induced bloom in the plankton community. PMID:25047077

Ariza, Alejandro; Kaartvedt, Stein; Røstad, Anders; Garijo, Juan Carlos; Arístegui, Javier; Fraile-Nuez, Eugenio; Hernández-León, Santiago

2014-01-01

216

Mt. St. Augustine, Alaska: Geochemical evolution of an eastern Aleutian volcanic center  

SciTech Connect

Mt. St. Augustine is a calc-alkaline Quaternary volcano, situated within Cook Inlet, Alaska. The island is composed of low- to medium-K andesite and dacite domes and pyroclastic flows. Major element variations indicate the magmatic evolution is dominantly influenced by fractionation and magma-mixing processes. Incompatible element and isotopic compositions suggest that despite its continental location, crustal assimilation is not significant factor in magmatic evolution. Alkali contents for Augustine are generally lower than elsewhere in the Aleutians (e.g. Augustine Cs/Rb = 0.016--0.024, K/Rb = 372--553; Aleutians Cs/Rb = 0.016--0.17, K/Rb = 231--745). Sr- and Nd-isotope ratios encompass narrow ranges ([sup 87]Sr/[sup 86]Sr = 0.70317--0.70343; [sup 143]Nd/[sup 144]Nd = 0.513011--0.513085), characteristic of uncontaminated mantle-derived melts. U-Th disequilibrium isotopic values also indicate little or no assimilation of evolved continental crust. Pb-isotopic ranges are also relatively restricted ([sup 206]Pb/[sup 204]Pb = 18.62--18.82; [sup 207]Pb/[sup 204]Pb = 15.54--15.57; [sup 208]Pb/[sup 204]Pb = 38.18--38.34) and comparison with north Pacific enriched (OIB) and depleted (MORB) mantle sources suggest the incorporation of only a small percentage of subducted terrigenous sediments. A model for Augustine magma genesis is proposed where parental magmas are generated by 5--20% partial melting of a lherzolite mantle with up to a 5% subducted terrigenous sediment component. The major influence of the thickened continental crust is to prevent the ascent and eruption of basaltic magma. The data exhibit no temporal variations, indicating that the magmatic system which produced the historic eruptions is well established.

Johnson, K.E. (Univ. of Florida, Gainesville, FL (United States). Dept. of Geology); Harmon, R.S. (NERC Isotope Geosciences Lab., Keyworth (United Kingdom). Kingsley Dunham Centre); Moorbath, S. (Univ. of Oxford (United Kingdom). Dept. of Earth Sciences); Sigmarsson, O. (Univ. Blaise Pascal and CNRS, Clermont-Ferrand (France))

1993-04-01

217

Eruption Forecasting: Success and Surprise at Kasatochi and Okmok Volcanoes  

NASA Astrophysics Data System (ADS)

In the summer of 2008, the Alaska Volcano Observatory (AVO) successfully forecast eruption at an unmonitored volcano, Kasatochi, and was unable to forecast eruption at a well monitored volcano, Okmok. We use these case studies to explore the limitations and opportunities of seismically monitored and unmonitored systems and to evaluate situations when we can expect to succeed and when we must expect to fail in eruption forecasting. Challenges in forecasting eruptions include interpreting seismicity in context of volcanic history, developing a firm understanding of distance scales over which pre- and co-eruptive seismic signals are observed, and improving our ability to discriminate processes causing tremor. Kasatochi Volcano is a 3 km wide island in the central Aleutian Islands with no confirmed historical activity. Little is known about the eruptive history of the volcano. It was not considered an immediate threat until 3 days prior to eruption. A report of ground shaking by a biology field crew on the island on August 4 was the first indication of unrest. On August 6 a vigorous seismic swarm became apparent on the nearest seismic stations 40 km distant. The aviation color code/volcano alert level at Kasatochi was increased to Yellow/Advisory in response to increasing magnitude and frequency of earthquakes. The color code/alert level was increased to Orange/Watch on August 7 when volcanic tremor was observed in the wake of the largest earthquake in the sequence, a M 5.6. Three hours after the onset of volcanic tremor, eruption was confirmed by satellite data and the color code/alert level increased to Red/Warning. Eruption forecasting was possible only due to the exceptionally large moment release of pre-eruptive seismicity. The key challenge in evaluating the situation was distinguishing between tectonic activity and a volcanic swarm. It is likely there were weeks to months of precursory seismicity, however little instrumental record exists due to the lack of a seismic network on Kasatochi Island. Unlike Kasatochi, Okmok volcano, also located in the central Aleutian Islands, hosts 13 telemetered seismic stations and several telemetered GPS stations. The volcano has received considerable study by AVO, and the record of historical eruptions is well known. Despite regular scrutiny of Okmok data, the 2008 eruption was a surprise as there were fewer than 3 hours of clear pre-eruptive seismicity. The color code/alert level at Okmok went directly from Green/Normal to Red/Warning on July 12 after eruptive activity began. Interpretation of co-eruptive seismicity remained a challenge through the course of the eruption as bursts of volcanic tremor often did not correlate immediately with ash output at the vent as observed in satellite data.

Prejean, S.; Power, J.; Brodsky, E.

2008-12-01

218

Volcano-stratigraphic and structural evolution of Brava Island (Cape Verde) based on 40Ar\\/ 39Ar, U–Th and field constraints  

Microsoft Academic Search

Three volcano-stratigraphic units were identified at Brava Island in the Cape Verde Archipelago on the basis of field relationships, geologic mapping and 40Ar\\/39Ar and U–Th ages. The Lower Unit comprises a 2-to-3Ma-old submarine volcanic sequence that represents the seamount stage. It is composed of nephelinitic\\/ankaramitic hyaloclastites and pillow lavas, which are cut by abundant co-genetic dikes. Plutonic rocks of an

José Madeira; João Mata; Cyntia Mourão; António Brum da Silveira; Sofia Martins; Ricardo Ramalho; Dirk L. Hoffmann

2010-01-01

219

Middle Archean island arc volcano-hydrothermal sequence: 3.2-Ga Dixon Island Formation, coastal Pilbara terrane, Australia  

NASA Astrophysics Data System (ADS)

The 3.2-Ga Dixon Island Formation in the Cleaverville Group of the coastal Pilbara terrane, Australia, is one of the most complete and best-preserved examples of middle Archean oceanic stratigraphy. Field observations and geochemical evidence suggest that this formation contains a low-temperature hydrothermal-vent system with a biogenic microbial colony from the Archean ocean. The Dixon Island Formation is approximately 350 m thick and consists of the Rhyolite Tuff, Black Chert and Varicolored Chert members, in ascending order. The Rhyolite Tuff Member contains many vein swarms, such as fine quartz vein and two black-chert veins with in highly altered rhyolite tuff layers. This vein rich and highly altered vein zones are identified as an underground bypass zone for circulating hydrothermal fluid. The Black Chert Member, which is 10 - 15 m thick, is composed of massive black chert, laminated black chert, dark greenish siliceous shale, stromatolite-like biomat bed and tuffaceous laminated chert. The absence of detrital sediment of continental origin and the many vein injections imply that this sedimentary facies represents a pelagic hydrothermal environment at about 500 - 2000 m in paleodepth, and may have been on the slope of an immature island arc. More then 500 samples of detail chemical anarysis from black chert veins and black chert bed suggest that the total organic carbon (TOC) value of massive black chert in the lower part of the Black Chert Member is higher (TOC=0.15-0.45%) than that of the overlying laminated chert section (TOC=0.02-0.15%) and the black chert vein (TOC=0.1-0.13). The carbon isotope (delta13C) values of this lithology (-33 - -27 per mil) are also lighter than for the black-chert veins (-29--26 per mill) and the laminated black chert in the upper part of the Black Chert Member and the Vari-colored Chert Member (-27 - -13 per mil). Especially, -40 per mill carbon isotope identified near the biomat beds. These evidences suggest that the carbonaceous grains bearing massive black chert in the lower part of the Black Chert Member is identified as directory from the black chert vein. On the other hand, biogenic materials, biomat bed and very low carbon isotope suggest the biogenic activity formed above a low-temperature hydrothermal vent. The microbial colony may have been rapidly fossilized by silicification related to hydrothermal activity. Laminated black chert in the upper part of the Black Chert and the Varicolored Chert members may have formed by cyanobacterial sedimentation from the ocean surface.

Kiyokawa, S.; Katagami, A.; Ito, T.; Ikehara, M.; Kitajima, F.

2005-12-01

220

Deployment of a seismic array for volcano monitoring during the ongoing submarine eruption at El Hierro, Canary Islands  

NASA Astrophysics Data System (ADS)

On 17 July 2011 there was an important increase of the seismic activity at El Hierro (Canary Islands, Spain). This increase was detected by the Volcano Monitoring Network (Spanish national seismic network) run by the Instituto Geográfico Nacional (IGN). As a consequence, the IGN immediately deployed a dense, complete monitoring network that included seismometers, GPS stations, geochemical equipment, magnetometers, and gravity meters. During the first three months of activity, the seismic network recorded over ten thousand volcano-tectonic earthquakes, with a maximum magnitude of 4.6. On 10 October 2011 an intense volcanic tremor started. It was a monochromatic signal, with variable amplitude and frequency content centered at about 1-2 Hz. The tremor onset was correlated with the initial stages of the submarine eruption that occurred from a vent located south of El Hierro island, near the village of La Restinga. At that point the IGN, in collaboration with the Instituto Andaluz de Geofísica, deployed a seismic array intended for volcanic tremor monitoring and analysis. The seismic array is located about 7 km NW of the submarine vent. It has a 12-channel, 24-bit data acquisition system sampling each channel at 100 sps. The array is composed by 1 three-component and 9 vertical-component seismometers, distributed in a flat area with an aperture of 360 m. The data provided by the seismic array are going to be processed using two different approaches: (1) near-real-time, to produce information that can be useful in the management of the volcanic crisis; and (2) detailed investigations, to study the volcanic tremor characteristics and relate them to the eruption dynamics. At this stage we are mostly dedicated to produce fast, near-real-time estimates. Preliminary results have been obtained using the maximum average cross-correlation method. They indicate that the tremor wavefronts are highly coherent among array stations and propagate across the seismic array with an apparent slowness of ~0.8 s/km and a back-azimuth of 135°N. These estimates have remained approximately constant since the onset of volcanic tremor, indicating a unique source and thus a single, continuing eruptive center.

Abella, R.; Almendros, J.; Carmona, E.; Martin, R.

2012-04-01

221

Edifice growth, deformation and rift zone development in basaltic setting: Insights from Piton de la Fournaise shield volcano (Réunion Island)  

Microsoft Academic Search

The overall morphology of basaltic volcanoes mainly depends on their eruptive activity (effusive vs. explosive), the geometry of the rift zones and the characteristics of both endogenous and exogenous growth processes. The origin of the steep geometry of the central cone of Piton de la Fournaise volcano, which is unusual for a basaltic effusive volcano, and its deformation are examined

Laurent Michon; Valérie Cayol; Ludovic Letourneur; Aline Peltier; Nicolas Villeneuve; Thomas Staudacher

2009-01-01

222

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

USGS Publications Warehouse

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

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

2005-01-01

223

Long- and short-term temporal variations of the diffuse CO2 emission from Timanfaya volcano, Lanzarote, Canary Islands  

NASA Astrophysics Data System (ADS)

Lanzarote Island is an emergent part of the East Canary Ridge and it is situated approximately 100 km from the NW coast of Morocco, covering an area of about 795km2. The largest historical eruption of the Canary Islands, Timanfaya, took place during 1730-36 in this island when long-term eruptions from a NE-SW-trending fissure formed the Montañas del Fuego. The last eruption at Lanzarote Island occurred during 1824, Tinguaton volcano, and produced a much smaller lava flow that reached the SW coast. At present, one of the most prominent phenomena at Timanfaya volcanic field is the high maintained superficial temperatures occurring in the area since the 1730 volcanic eruption. The maximum temperatures recorded in this zone are 605°C, taken in a slightly inclined well 13 m deep. Since fumarolic activity is absent at the surface environment of Lanzarote, to study the diffuse CO2 emission becomes an ideal geochemical tool for monitoring its volcanic activity. Soil CO2 efflux surveys were conducted throughout Timanfaya volcanic field and surrounding areas during the summer periods of 2006, 2007, 2008, 2009, fall period of 2010 and winter, spring and summer periods of 2011 to investigate long and short-term temporal variations of the diffuse CO2 emission from Timanfaya volcano. Soil CO2 efflux surveys were undertaken at Timanfaya volcanic field always under stable weather conditions to minimize effects of meteorological conditions on the CO2 at the soil atmosphere. Approximately 370-430 sampling sites were selected at the surface environment of Timanfaya to obtain an even distribution of the sampling points over the study area. The accumulation chamber method (Parkinson et al., 1981) was used to perform soil CO2 efflux measurements in-situ by means of a portable non dispersive infrared (NDIR) CO2 analyzer, which was interfaced to a hand size computer that runs data acquisition software. At each sampling site, soil temperature at 15 and 40cm depth was also measured by means of a thermocouple together with soil gas samples collected during the campaign of 2010 to evaluate the chemical and isotopic composition of soil gases. Diffuse CO2 emission values have ranged between non detectable values to 34 g m-2 d-1, and most of the study area have shown relatively low values, around the detection limit of the instrument (~0,5 g m-2 d-1). Higher soil CO2 diffuse emission values were observed where thermal anomalies occur, indicating a convective mechanism transport of gas from depth at these areas. Total CO2 outputs of the study area have been estimated in the range 41-518 t d-1 during the study period. Long-term temporal variation on total CO2 diffuse emission shows a peak recorded on winter 2011, suggesting a seasonal control on the CO2 emission. As part of the volcanic surveillance program and to understand the dynamics of CO2 diffuse emission at Timanfaya volcanic zone, an automatic geochemical station was installed in July 2010 to monitor the CO2 emission and investigate the short-term temporal variation. Time series of soil CO2 efflux shows also a close relationship with seasonal changes mainly due to rainfall.

Hernández, P. A.; Padilla, G.; Calvo, D.; Padrón, E.; Melian, G.; Dionis, S.; Nolasco, D.; Barrancos, J.; Rodríguez, F.; Pérez, N.

2012-04-01

224

Relationships between tectonism, volcano-tectonism and volcanism: the Ischia island (Italy) case.  

NASA Astrophysics Data System (ADS)

The resurgent calderas of Ischia, Campi Flegrei and Pantelleria are characterized by differentially displaced blocks, and distribution of later eruption vents in a well defined sector of the resurgent area. These features suggest a simple shearing block resurgence mechanism. Moreover, the studies carried out on Ischia and Campi Flegrei evidenced a very complex structural pattern due to deformation related to the local stress regime induced by magmatism and volcanism and also to reactivation of regional structures. In order to better define the relationships among tectonic, volcano-tectonic and caldera resurgence mechanism, a structural study has been carried out at Ischia, where the Mt. Epomeo has been uplifted of about 900 m in the past 30 ka. The measures taken on 1,400 planar surfaces (faults, joints and fracture cleavages) show that the resurgent area is composed of differentially displaced blocks whose uplifting is maximum for the Mt. Epomeo and decreases southeastward. The resurgent area has a poligonal shape resulting from the reactivation of regional faults and by the activation of faults directly related to volcano-tectonism. The limit of the resurgent area is not defined towards the north, as beach deposits displaced at variable elevation by E-W and NW-SE trending faults, are exposed along the coastline. The western sector is bordered by inward-dipping, high-angle reverse faults, whose directions vary from N40E to NS and N50W from NW to SW of the block, testifying a compressional stress regime active in this area. These features are cut by late outward-dipping normal faults due to gravitational readjustment of the slopes. Vertical faults border the block at NE ad SW with right transtensive and left transpressive movements, respectively. The area located to the east of the most uplifted block, characterized by a tensile stress regime, has been deformed by N-S, N40-70E and N15W trending normal faults, with maximum elongation direction along N50W. The results of our study and the volcanological data of the past 3 ka, suggest that the eastern part of the resurgent block is the area with highest probability of vent opening in case of renewal of volcanism. Occurrence of landslides just before and after eruptions, suggest that resurgence occurs through discontinuous vertical movements which likely trigger the volcanic activity.

Marotta, E.; de Vita, S.; Orsi, G.; Sansivero, F.

2005-12-01

225

Observations on basaltic lava streams in tubes from Kilauea Volcano, island of Hawai'i  

USGS Publications Warehouse

From 1986 to 1997, the Pu'u 'O'o-Kupaianaha eruption of Kilauea produced a vast pahoehoe flow field fed by lava tubes that extended 10-12 km from vents on the volcano's east rift zone to the ocean. Within a kilometer of the vent, tubes were as much as 20 m high and 10-25 m wide. On steep slopes (4-10??) a little farther away from the vent, some tubes formed by roofing over of lava channels. Lava streams were typically 1-2 m deep flowing within a tube that here was typically 5 m high and 3 m wide. On the coastal plain (<1??), tubes within inflated sheet flows were completely filled, typically 1-2 m high, and several tens of meters wide. Tubes develop as a flow's crust grows on the top, bottom, and sides of the tubes, restricting the size of the fluid core. The tubes start out with nearly elliptical cross-sectional shapes, many times wider than high. Broad, flat sheet flows evolve into elongate tumuli with an axial crack as the flanks of the original flow were progressively buried by breakouts. Temperature measurements and the presence of stalactites in active tubes confirmed that the tube walls were above the solidus and subject to melting. Sometimes, the tubes began downcutting. Progressive downcutting was frequently observed through skylights; a rate of 10 cm/d was measured at one skylight for nearly 2 months.

Kauahikaua, J.; Cashman, K.V.; Mattox, T.N.; Christina, Heliker C.; Hon, K.A.; Mangan, M.T.; Thornber, C.R.

1998-01-01

226

GPS and Gravity Surveying at Fogo Volcano, Cape Verde Islands, 1998-2001  

NASA Astrophysics Data System (ADS)

Fogo Island, in the Cape verde archipelago (North Atlantic), is a roughly conical volcanic edifice with 25 Km of base diameter and a summit that reaches an altitude of about 3000 m. Volcanic eruptions in the island are reported since the settlement in the 16th century, at average intervals of about 20 years. In the 20th century the activity subsided, with only two eruptions in 1951 and 1995. Fogo comprises 33000 inhabitants, of which 800 live inside the 9km-wide ancient collapse caldera, which is open towards the East. A joint effort has been made to implement basic monitoring capabilities in Fogo. A permanent network for real-time monitoring of seismicity and tilt was installed in 1999 (Faria et al., this conference). This presentation describes the repeated GPS and microgravity surveys carried out in Fogo island between 1998 and 2001. Until present, five GPS and three microgravity surveys were made, with a repeat period of about 7 months. A network composed of 23 geodetic monuments, with stable reinforced concrete foundations, was previously implemented for this purpose, covering the entire island with basis lengths between 2 and 8 Kms. For the GPS surveys, seven GPS Trimble 4000 SSE receivers were used, and the observations were processed with Bernese 4.2 software. Two LaCoste & Romberg G gravimeters were used together with the GPS observations for three of the five campaigns. The results from the GPS surveys show significant vertical and horizontal deformation. The clearest observations are as follows: 1. between Sep 98 and Apr 99, uplit (up to 5 cm) of the points inside the collapse caldera; 2. between Apr 99 and Nov 99, dislocation towards the East of the monuments inside the caldera and on the East coast; 3. between Nov 99 and Jun 00, movement towards the West of the points inside the caldera and on the East coast. The microgravity survey carried out between Nov 99 and Jun 00 points to density increase coupled with surface uplift. Different mechanisms to explain the observations are discussed, namely subsurface magma movements, gravitic instability of the volcanic edifice and variations of the water-table geometry.

Lima, J. N.; Lazaro, C.; Heleno, S. I.; Fonseca, J. F.; Barros, I.; Matos, J.; Baio, M.; Osorio, J.; Osorio, J.

2001-12-01

227

Spatio-temporal evolution of a dispersed magmatic system and its implications for volcano growth, Jeju Island Volcanic Field, Korea  

NASA Astrophysics Data System (ADS)

Jeju Island is the emergent portion of a basaltic volcanic field developed over the last c. 1.8 Ma on continental crust. Initial volcanism comprised dispersed, small-volume (< 0.01 km3) alkali basaltic eruptions that incrementally constructed a tuff pile. Lavas and scoria from continuing small-scaled monogenetic volcanism capped this foundation. From c. 0.4 Ma large-volume (> 1 km3) eruptions began, with lavas building a composite shield. Three magma suites can be recognized: Early Pleistocene high-Al alkali (HAA), and Late Pleistocene to Holocene low-Al alkali (LAA) and subalkali (SA). The chemical similarity between small-volume and primitive large-volume eruptions suggests analogous parent magmas and fractionation histories that are independent of erupted volumes. The large-volume magmas evolved to trachyte, which erupted in two distinct episodes: the HAA Sanbangsan suite at c. 750 ka and the LAA Hallasan suite at c. 25 ka. Sr and Nd isotopes indicate that the early trachytes were contaminated by upper crustal material, whereas the later magmas were not. Both suites bear a Nd isotope signature indicative of lower crustal interaction. Sub-suites transitional between HAA and LAA, and between LAA and SA, indicate that melting occurred in discrete, but adjacent, mantle domains. Throughout the evolution of this volcano, each magma batch erupted separately, and a centralized plumbing system was never created. The Island's central peak (Mt. Halla 1950 m a.s.l.) is therefore not a sensu stricto stratovolcano, but marks the point of peak magma output in a distributed magmatic system. Jeju's shape and topography thus represent the spatial variation of fertility of the mantle below it. An increase in melt production in the Late Pleistocene was related to a deepening of the melting zone due to regional tectonic rearrangements. Temporal coincidences between magmatic pulses on Jeju and large-scale caldera eruptive events along the nearest subduction system in Kyushu, Japan, suggest that tectonic extension and changing strain rates may drive volcanism on a regional basis, influencing the intraplate volcanism of Jeju Island.

Brenna, Marco; Cronin, Shane J.; Smith, Ian E. M.; Sohn, Young Kwan; Maas, Roland

2012-09-01

228

GPS monitoring of Hawaiian Volcanoes  

USGS Multimedia Gallery

The USGS Hawaiian Volcano Observatory uses a variety of ground- and satellite-based techniques to monitor Hawai‘i’s active volcanoes.  Here, an HVO scientist sets up a portable GPS receiver to track surface changes during an island-wide survey of Hawai‘i’s volcanoes. &n...

229

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

USGS Publications Warehouse

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.

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

2014-01-01

230

The September 1988 intracaldera avalanche and eruption at Fernandina volcano, Galapagos Islands  

USGS Publications Warehouse

During 14-16 September 1988, a large intracaldera avalanche and an eruption of basaltic tephra and lava at Fernandina volcano, Galapagos, produced the most profound changes within the caldera since its collapse in 1968. A swarm of eight earthquakes (mb 4.7-5.5) occurred in a 14 h period on 24 February 1988 at Fernandina, and two more earthquakes of this size followed on 15 April and 20 May, respectively. On 14 September 1988, another earthquake (mb 4.6) preceded a complex series of events. A debris avalanche was generated by the failure of a fault-bounded segment of the east caldera wall, approximately 2 km long and 300 m wide. The avalanche deposit is up to 250 m thick and has an approximate volume of 0.9 km3. The avalanche rapidly displaced a preexisting lake from the southeast end of the caldera floor to the northwest end, where the water washed up against the lower part of the caldera wall, then gradually seeped into the avalanche deposit and was completely gone by mid-January 1989. An eruption began in the caldera within about 1-2 h of the earthquake, producing a vigorous tephra plume for about 12 h, then lava flows during the next two days. The eruption ended late on 16 September. Most of the eruptive activity was from vents on the caldera floor near the base of the new avalanche scar. Unequivocal relative timing of events is difficult to determine, but seismic records suggest that the avalanche may have occurred 1.6 h after the earthquake, and field relations show that lava was clearly erupted after the avalanche was emplaced. The most likely sequence of events seems to be that the 1988 feeder dike intruded upward into the east caldera wall, dislocated the unstable wall block, and triggered the avalanche. The avalanche immediately exposed the newly emplaced dike and initiated the eruption. The exact cause of the earthquakes is unknown. ?? 1991 Springer-Verlag.

Chadwick, W.W., Jr.; De Roy, T.; Carrasco, A.

1991-01-01

231

Environmental contaminants in bald eagle eggs from the Aleutian archipelago  

USGS Publications Warehouse

We collected 136 fresh and unhatched eggs from bald eagle (Haliaeetus leucocephalus) nests and assessed productivity on eight islands in the Aleutian archipelago, 2000 to 2002. Egg contents were analyzed for a broad spectrum of organochlorine (OC) contaminants, mercury (Hg), and stable isotopes of carbon (??13C) and nitrogen (??15N). Concentrations of polychlorinated biphenyls (??PCBs), p,p???- dichlorodiphenyldichloroethylene (DDE), and Hg in bald eagle eggs were elevated throughout the archipelago, but the patterns of distribution differed among the various contaminants. Total PCBs were highest in areas of past military activities on Adak and Amchitka Islands, indicating local point sources of these compounds. Concentrations of DDE and Hg were higher on Amchitka Island, which was subjected to much military activity during World War II and the middle of the 20th century. Concentrations of ??PCBs also were elevated on islands with little history of military activity (e.g., Amlia, Tanaga, Buldir), suggesting non-point sources of PCBs in addition to point sources. Concentrations of DDE and Hg were highest in eagle eggs from the most western Aleutian Islands (e.g., Buldir, Kiska) and decreased eastward along the Aleutian chain. This east-to-west increase suggested a Eurasian source of contamination, possibly through global transport and atmospheric distillation and/or from migratory seabirds. Eggshell thickness and productivity of bald eagles were normal and indicative of healthy populations because concentrations of most contaminants were below threshold levels for effects on reproduction. Contrary to our predictions, contaminant concentrations were not correlated with stable isotopes of carbon (??13C) or nitrogen (??15N) in eggs. These latter findings indicate that contaminant concentrations were influenced more by point sources and geographic location than trophic status of eagles among the different islands. ?? 2007 SETAC.

Anthony, R.G.; Miles, A.K.; Ricca, M.A.; Estes, J.A.

2007-01-01

232

Environmental contaminants in bald eagle eggs from the Aleutian archipelago.  

PubMed

We collected 136 fresh and unhatched eggs from bald eagle (Haliaeetus leucocephalus) nests and assessed productivity on eight islands in the Aleutian archipelago, 2000 to 2002. Egg contents were analyzed for a broad spectrum of organochlorine (OC) contaminants, mercury (Hg), and stable isotopes of carbon (delta13C) and nitrogen (delta15N). Concentrations of polychlorinated biphenyls (SigmaPCBs), p,p'-dichlorodiphenyldichloroethylene (DDE), and Hg in bald eagle eggs were elevated throughout the archipelago, but the patterns of distribution differed among the various contaminants. Total PCBs were highest in areas of past military activities on Adak and Amchitka Islands, indicating local point sources of these compounds. Concentrations of DDE and Hg were higher on Amchitka Island, which was subjected to much military activity during World War II and the middle of the 20th century. Concentrations of SigmaPCBs also were elevated on islands with little history of military activity (e.g., Amlia, Tanaga, Buldir), suggesting non-point sources of PCBs in addition to point sources. Concentrations of DDE and Hg were highest in eagle eggs from the most western Aleutian Islands (e.g., Buldir, Kiska) and decreased eastward along the Aleutian chain. This east-to-west increase suggested a Eurasian source of contamination, possibly through global transport and atmospheric distillation and/or from migratory seabirds. Eggshell thickness and productivity of bald eagles were normal and indicative of healthy populations because concentrations of most contaminants were below threshold levels for effects on reproduction. Contrary to our predictions, contaminant concentrations were not correlated with stable isotopes of carbon (delta13C) or nitrogen (delta15N) in eggs. These latter findings indicate that contaminant concentrations were influenced more by point sources and geographic location than trophic status of eagles among the different islands. PMID:17702538

Anthony, Robert G; Miles, A Keith; Ricca, Mark A; Estes, James A

2007-09-01

233

Fogo Volcano, Cape Verde Islands: seismicity-derived constraints on the mechanism of the 1995 eruption  

NASA Astrophysics Data System (ADS)

Seismic data recorded in the vicinity of the active vent of the 1995 Fogo eruption [Global Volcanism Network Bulletin, 1995, 20(3) 2-4.] is used to constrain the associated stress field and deformation. Using the frequency content of the seismograms to distinguish between brittle fracture of cold host rock and deformation in the vicinity of the intruding magma, a sub-vertical dyke with 060° strike is identified as the feeder of the eruption, and delineated down to a depth of about 4 km. The local stress field during the eruption is estimated from composite focal mechanisms. Besides the expected ?3 direction normal to the dyke, a group of focal solutions point to a stress field with nearly dyke-parallel ?3, which is interpreted as a re-adjustment of the edifice following the eruption, maybe partially controlled by gravity. This effect may have increased the instability of the steep eastern flank of the island, since the deformation detected during the magma drainback is compatible with predominantly dip-slip motion on east-dipping surfaces.

Heleno da Silva, S. I. N.; Day, S. J.; Fonseca, J. F. B. D.

1999-12-01

234

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

USGS Publications Warehouse

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.

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

2011-01-01

235

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

USGS Publications Warehouse

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.

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

2011-01-01

236

Flow-By-Flow Mapping on Fogo, Cape Verde Islands, Reveals Long Term Variations in Eruption Distributions and Volcanic Edifice Structure at a Shield-Stage Oceanic Island Volcano  

NASA Astrophysics Data System (ADS)

Most maps of large oceanic island shield volcanoes show the lava flows and scoria cones of individual historic and subhistoric eruptions as individual units but then resort to grouping older rocks into larger stratigraphic units. This grouping makes it difficult to characterize long-term progressive trends in volumes of individual eruptions and distributions of eruptive vents, but is commonly made necessary by poor exposure, limited compositional variation between individual eruptions, and burial of older by younger volcanic rocks. In contrast, work on Fogo, Cape Verde Islands has involved flow-by-flow mapping of rocks erupted over an extended period of tens of thousands of years, as part of the process of mapping the island and producing a 1:25 000 scale geological map for research and hazard management purposes. Around three-quarters of the island is characterized by low rainfall and limited vegetation cover, with erosion restricted to narrow gullies. Only in small areas on the windward side of the island do higher rainfall, thick vegetation and deeper erosion combine to prevent flow-by-flow mapping. The map of the island is accompanied by a rigorous representation of direct and inferred age relationships between lavas and scoria cones of different eruptions using a novel type of age correlation diagram. The time period covered by the flow-by-flow mapping includes both the final stages of growth of an older shield volcano (Monte Amarelo volcano) prior to its collapse and the subsequent growth of a new volcano (Cha das Caldeiras volcano). The latter forms a thick infill and summit cone within the Monte Amarelo collapse scar together with partial covering of the outer flanks of the Monte Amarelo volcano with a veneer of younger lavas and scoria cones. The erupted rocks are compositionally varied (ankaramitic nephelinites, basanites, tephrites) and often highly porphyritic. Petrographic criteria were therefore used to aid field mapping, define lithostratigraphic units and demonstrate systematic changes in compositions of erupted magmas through time. Some of these changes, particularly eruptions of ankaramitic magmas, coincide with similar sequences of volcano-structural changes that have occurred prior to the Monte Amarelo collapse and again during the Holocene (beginning around 11 000 years before present; Foeken et al, 2009). The flow-by-flow mapping approach has allowed reconstruction and comparison of the sequences of these structural changes, and thus provides insights into the inferred progressive destabilization of the eastern flank of Fogo during the Holocene, as well as into wide variations in eruption and resurfacing rates that have occurred on decade to century timescales in more recent times. Foeken, J.P.T., Day, S.J. & Stuart, F.M. (2009) Cosmogenic 3He exposure dating of the Quaternary basalts from Fogo, Cape Verdes: Implications for rift zone and magmatic reorganization. Quaternary Geology 4 (2009) 37 - 49.

Day, S. J.

2011-12-01

237

At-sea observations of marine birds and their habitats before and after the 2008 eruption of Kasatochi volcano, Alaska  

USGS Publications Warehouse

Kasatochi volcano, an island volcano in the Aleutian chain, erupted on 7-8 August 2008. The resulting ash and pyroclastic flows blanketed the island, covering terrestrial habitats. We surveyed the marine environment surrounding Kasatochi Island in June and July of 2009 to document changes in abundance or distribution of nutrients, fish, and marine birds near the island when compared to patterns observed on earlier surveys conducted in 1996 and 2003. Analysis of SeaWiFS satellite imagery indicated that a large chlorophyll-a anomaly may have been the result of ash fertilization during the eruption. We found no evidence of continuing marine fertilization from terrestrial runoff 10 months after the eruption. At-sea surveys in June 2009 established that the most common species of seabirds at Kasatochi prior to the eruption, namely crested auklets (Aethia cristatella) and least auklets (Aethia pusilla) had returned to Kasatochi in relatively high numbers. Densities from more extensive surveys in July 2009 were compared with pre-eruption densities around Kasatochi and neighboring Ulak and Koniuji islands, but we found no evidence of an eruption effect. Crested and least auklet populations were not significantly reduced by the initial explosion and they returned to attempt breeding in 2009, even though nesting habitat had been rendered unusable. Maps of pre- and post-eruption seabird distribution anomalies indicated considerable variation, but we found no evidence that observed distributions were affected by the 2008 eruption. ?? 2010 Regents of the University of Colorado.

Drew, G.S.; Dragoo, D.E.; Renner, M.; Piatt, J.F.

2010-01-01

238

2006 Volcanic Activity in Alaska, Kamchatka, and the Kurile Islands: Summary of Events and Response of the Alaska Volcano Observatory  

USGS Publications Warehouse

The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, and volcanic unrest at or near nine separate volcanic centers in Alaska during 2006. A significant explosive eruption at Augustine Volcano in Cook Inlet marked the first eruption within several hundred kilometers of principal population centers in Alaska since 1992. Glaciated Fourpeaked Mountain, a volcano thought to have been inactive in the Holocene, produced a phreatic eruption in the fall of 2006 and continued to emit copious amounts of volcanic gas into 2007. 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.

Neal, Christina A.; McGimsey, Robert G.; Dixon, James P.; Manevich, Alexander; Rybin, Alexander

2008-01-01

239

Lab7: Volcanoes I. --Their Geographic Distribution Introduction  

E-print Network

1 Lab7: Volcanoes I. -- Their Geographic Distribution Introduction Active volcanoes present in understanding these hazards is to realize where active volcanoes actually occur on the Earth's surface. Pacuritin Volcano, Mexico Active Volcanoes of the World South Sandwich Islands. Also known as the Scotia arc

Chen, Po

240

49 CFR 71.12 - Hawaii-Aleutian zone.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 2013-10-01 false Hawaii-Aleutian zone. 71.12 Section 71...STANDARD TIME ZONE BOUNDARIES § 71.12 Hawaii-Aleutian zone. The seventh zone, the Hawaii-Aleutian standard time zone, includes...

2013-10-01

241

49 CFR 71.12 - Hawaii-Aleutian zone.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 2010-10-01 false Hawaii-Aleutian zone. 71.12 Section 71...STANDARD TIME ZONE BOUNDARIES § 71.12 Hawaii-Aleutian zone. The seventh zone, the Hawaii-Aleutian standard time zone, includes...

2010-10-01

242

49 CFR 71.12 - Hawaii-Aleutian zone.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 2011-10-01 false Hawaii-Aleutian zone. 71.12 Section 71...STANDARD TIME ZONE BOUNDARIES § 71.12 Hawaii-Aleutian zone. The seventh zone, the Hawaii-Aleutian standard time zone, includes...

2011-10-01

243

49 CFR 71.12 - Hawaii-Aleutian zone.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 2012-10-01 false Hawaii-Aleutian zone. 71.12 Section 71...STANDARD TIME ZONE BOUNDARIES § 71.12 Hawaii-Aleutian zone. The seventh zone, the Hawaii-Aleutian standard time zone, includes...

2012-10-01

244

49 CFR 71.12 - Hawaii-Aleutian zone.  

Code of Federal Regulations, 2014 CFR

... 2014-10-01 2014-10-01 false Hawaii-Aleutian zone. 71.12 Section 71...STANDARD TIME ZONE BOUNDARIES § 71.12 Hawaii-Aleutian zone. The seventh zone, the Hawaii-Aleutian standard time zone, includes...

2014-10-01

245

Volcanic Unrest of Fogo Volcano in 2011-2012, S.Miguel Island, Azores, Observed by Continuous and Campaign GPS Analysis  

NASA Astrophysics Data System (ADS)

Volcanic eruptions can occur after long time of dormancy as has been seen from the recent examples: Mount St. Helens 1980, Pinatubo 1991, Unzen 1991, Soufrière Hills volcano 1995, Chaitén 2008, and Eyjafjallajökull 2010. By utilizing space geodesy techniques, namely GNSS and InSAR, it has been reported that the inflation-deflation processes exist at several dormant volcanoes in the world, but the mechanism responsible for this phenomena is still controversial. Fundamental questions such as magma vs. hydrothermal fluids and volcanic vs. tectonic process remain unanswered in many cases. In this study, we analyze both continuous and campaign GPS data from Fogo volcano, S. Miguel Island, Azores. Although no geochemical and hydrothermal evidences for a magmatic intrusion were reported during the past seismic swarm episodes (1989, 2003-2006, and 2011-2012), geophysical data, both seismic and ground deformation, indicate possible volcanic sources. GPS time series spanned 2008-2013 period characterize tectonic plate divergence between Eurasian and Nubian, and reveal two different types of ground deformation associated with the 2011-2012 volcanic unrest of Fogo. One is the permanent edifice-scale inflation centered at NE summit which corresponds to the increase of volcano-tectonic events. Another is the subsequent minor-scale inflation-deflation reversals between Congro, a trachyte maar, east of Fogo and Furnas volcano. Calculated strain rates and GPS campaign results indicate that the 2011-2012 deformation is one order smaller than the previous unrest episode. A strong similarity exists to Matsushiro earthquake swarm (1965-1966) and Campi Flegrei volcanic unrests (1969-1972 and 1982-1984), which is the coexistence of an edifice-scale main inflation associated with intense volcano-tectonic earthquakes with inflation to deflation reversal that coincided with a sharp drop of seismicity. High recovery rate of inflation-deflation may be an indicator for the existence of hydrothermal fluids in the highly heterogeneous/porous media. We propose the following hypothesis for the 2011-2012 volcanic unrest of Fogo - (1) a minor magmatic intrusion beneath Fogo which acts as a heat source encourages lateral diffusion of fluids, (2) the fluids are transported through the existing cracks/fissures which are sustained by regional extension due to plate divergence, (3) influx of fluids increases pressure in cracks/fissures and generates lower-frequency earthquakes, and (4) discharge of fluids causes sudden pressure decrease and dilatancy recovery which leads seismic quiescence. Fogo volcano represents 450 years of dormancy since 1563-1564 when the last eruptions took place at the summit caldera. However, we show that the volcano has been experiencing intermittent magma ascents (i.e. repeating "failed eruptions") even its dormant period. Further researches are needed in order to understand the eruption triggering conditions. Nevertheless, we have a continuous GPS network that can detect small changes in the volcano roots and provide important contribution to evaluate future unrest episodes at Azores.

Okada, Jun; Sigmundsson, Freysteinn; Ofeigsson, Benedikt; Ferreira, Teresa; Gaspar, Joao; Lorenzo, Maria; Araujo, Joao; Rodriques, Rita

2014-05-01

246

Earth's Active Volcanoes by Geographic Region  

NSDL National Science Digital Library

This site describes active volcanoes from around the world by using the volcano links from the Michigan Technological University and the homepages of observatories at active volcanoes. Each volcano section contains photo images, maps, and reference text. Some sections contain bibliographies, volcano reports, and video clips of lahars. The volcanoes are organized by the following geographic regions: Africa and surrounding islands; the Southwest Pacific, Southeast Asia, and India; East Asia including Japan and Kamchatka; Antarctica; the North Atlantic and Iceland; the Mediterranean; South America and surrounding islands; Central Pacific, South Pacific and New Zealand; Alaska and the Northern Pacific Region; North America; and Central America.

247

Aleutian Ancorinidae (Porifera, Astrophorida): Description of three new species from the genera Stelletta and Ancorina.  

PubMed

Two new species of the genus Stelletta and one new species of Ancorina are described from the Aleutian Islands of Alaska and compared to congeners of the region. This is the first record of the genus Ancorina in the North Pacific Ocean. Stelletta ovalae Tanita 1965 is also reported for the first time from the Bering Sea and Alaska.  PMID:24990051

Lehnert, Helmut; Stone, Robert P

2014-01-01

248

Minkin Aleutian taudin ELISA-testin tuotteistaminen : Insinöörityö.  

E-print Network

??Aleutian tauti on minkin (Mustela vison) plasmasytoosisairaus. Sen aiheuttaa Aleutian mink disease virus, AMDV, joka on parvovirus. AMDV:n käyttäytyminen on kuitenkin epätyypillistä parvoviruksille. Taudin oireita… (more)

Poikulainen, Emmi

2014-01-01

249

Insights from geophysical monitoring into the volcano structure and magma supply systems at three very different oceanic islands in the Cape Verde archipelago  

NASA Astrophysics Data System (ADS)

Three oceanic volcano islands in the west of the Cape Verde archipelago are considered to have the highest levels of volcanic hazard in the archipelago: Fogo, Brava, and Santo Antao. Fogo has had frequent mainly effusive eruptions in historic time, the most recent in 1995, whilst Brava and Santo Antao have ongoing geothermal activity and felt earthquakes, and have experienced geologically recent violent explosive eruptions. Therefore, these three islands have been the focus of recent efforts to set up seismic networks to monitor their activity. Here we present the first results from these networks, and propose interpretations of the monitored seismic activity in terms of subsurface volcano structures, near-surface intrusive activity and seasonal controls on geothermal activity. In Fogo, most recorded seismic events are hydrothermal events. These show a strong seasonal variation, increasing during the summer rain season and decreasing afterwards. Rare volcano-tectonic (VT) events (0.1island due to the 1995 eruption. Brava experiences frequent swarms of VT events. These are located mostly offshore, with a small proportion of on-shore events. The positions of offshore events are strongly correlated with seamounts and hence are interpreted as due to submarine volcanic processes. Onshore events (0.7island that has been indicated by previous geological studies, and may be due to inflation of a magma reservoir in the edifice. S. Antão is characterized by frequent seismic swarms composed of VT earthquakes (0.1volcanoes on Santo Antao, which are most probably also the sources of the associated MF events and harmonic tremor as well. These onshore swarms likely record dike intrusions into the volcanic rift zones. In conclusion, we note that each island has its own distinctive pattern of seismic activity, perhaps reflecting its different stage of evolution. Full understanding of the seismic activity and how it can be interpreted in mechanistic terms, as a basis for future volcanic hazard models and eruption forecasts, will therefore require more detailed geological and geophysical investigations of each island, with different priorities in each case.

Faria, B. V.; Day, S.; Fonseca, J. F.

2013-12-01

250

Internal structure of the western flank of the Cumbre Vieja volcano, La Palma, Canary Islands, from land  

E-print Network

in the future [Day et al., 1999a, 1999b]. In the particular cases of La Palma (Canary Islands) and Fogo (Cape lithosphere (such as Hawaii and Reunion Island) and those formed on slow moving litho- sphere (such as Cape Verde and the Canary Islands). A number of mechanical explanations exists for this contrast in behavior

Jones, Alan G.

251

Adventive hydrothermal circulation on Stromboli volcano (Aeolian Islands, Italy) revealed by geophysical and geochemical approaches: Implications for general fluid flow models on volcanoes  

NASA Astrophysics Data System (ADS)

On March 15th 2007 a paroxysmal explosion occurred at the Stromboli volcano. This event generated a large amount of products, mostly lithic blocks, some of which impacted the ground as far as down to 200 m a.s.l., about 1.5 km far away from the active vents. Two days after the explosion, a new vapour emission was discovered on the north-eastern flank of the volcanic edifice, at 560 m a.s.l., just above the area called "Nel Cannestrà". This new vapour emission was due to a block impact. In order to investigate the block impact area to understand the appearance of the vapour emission, we conducted on May 2008 a multidisciplinary study involving Electrical Resistivity Tomography (ERT), Ground Penetrating Radar (GPR), Self-Potential (SP), CO 2 soil diffuse degassing and soil temperature surveys. This complementary data set revealed the presence of an anomalous conductive body, probably related to a shallow hydrothermal level, at about 10-15 m depth, more or less parallel to the topography. It is the first time that such a hydrothermal fluid flow, with a temperature close to the water boiling point (76 °C) has been evidenced at Stromboli at this low elevation on the flank of the edifice. The ERT results suggest a possible link between (1) the main central hydrothermal system of Stromboli, located just above the plumbing system feeding the active vents, with a maximum of subsurface soil temperature close to 90 °C and limited by the NeoStromboli summit crater boundary and (2) the investigated area of Nel Cannestrà, at ~ 500 m a.s.l., a buried eruptive fissure active 9 ka ago. In parallel, SP and CO 2 soil diffuse degassing measurements suggest in this sector at slightly lower elevation from the block impact crater a magmatic and hydrothermal fluid rising system along the N41° regional fault. A complementary ERT profile, on May 2009, carried out from the NeoStromboli crater boundary down to the block impact crater displayed a flank fluid flow apparently connected to a deeper system. The concept of shallow hydrothermal level have been compared to similar ERT results recently obtained on Mount Etna and La Fossa cone of Vulcano. This information needs to be taken into account in general fluid flow models on volcanoes. In particular, peripheral thermal waters (as those bordering the north-eastern coast of Stromboli) could be contaminated by hydrothermal and magmatic fluids coming from regional faults but also from the summit.

Finizola, A.; Ricci, T.; Deiana, R.; Cabusson, S. Barde; Rossi, M.; Praticelli, N.; Giocoli, A.; Romano, G.; Delcher, E.; Suski, B.; Revil, A.; Menny, P.; Di Gangi, F.; Letort, J.; Peltier, A.; Villasante-Marcos, V.; Douillet, G.; Avard, G.; Lelli, M.

2010-09-01

252

Coeval giant landslides in the Canary Islands: Implications for global, regional and local triggers of giant flank collapses on oceanic volcanoes  

NASA Astrophysics Data System (ADS)

Giant landslides are an important part of the evolution of most intra-plate volcanic islands. They often proceed in catastrophic events, likely to generate voluminous debris avalanches and eventually trigger destructive tsunamis. Although knowledge of the timing of their recurrence is a key factor regarding the hazard assessment in coastal environments, only a few of them have been well dated. In this contribution, we focus on the La Orotava event on Tenerife, which we date with the unspiked K-Ar technique, between 534 and 523 ka. Such narrow temporal interval is compatible, within uncertainties, with the age of the Cumbre Nueva collapse on the neighboring island of La Palma. We thus examine here the possible common triggering mechanisms at the global, regional and local scales. Both events occurred shortly after the climax of the oxygen isotopic stage 14, during the rapid transition towards the interglacial stage 13, reinforcing the hypothesis of a control from global paleoclimatic changes on the destabilization of oceanic islands. Intense volcanic pulses at the regional scale also lead to the synchronous overgrowth of several volcanic islands in the archipelago, but coeval destabilization on Tenerife and La Palma appears significantly controlled by the intrinsic morphology of the edifices, with contrasted instability thresholds for shield volcanoes and volcanic ridges respectively. Finally, we propose that the two events may be genetically linked. Dynamic transfer of voluminous debris avalanches during a giant landslide episode can induce isostatic readjustments, generate significant ground acceleration and finally produce a large tsunami, three processes which can concur to trigger large scale flank collapse on a neighboring mature unstable volcanic island.

Boulesteix, Thomas; Hildenbrand, Anthony; Soler, Vicente; Quidelleur, Xavier; Gillot, Pierre-Yves

2013-05-01

253

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

USGS Publications Warehouse

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

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

2013-01-01

254

GPS Application to the Study of Ground Deformation in the Volcano Tectonic System of the Graciosa Island (Azores)  

Microsoft Academic Search

The Azores archipelago is located in North Atlantic Ocean, in the junction of Eurasian, American and African plates, which reflect the existence of a complex system of fractures, namely the Mid-Atlantic Ridge, the Eastern Azorean fracture zone, the Terceira Rift and the Gloria Fault. The Azores are, therefore, an excellent place for the application and development of various volcano tectonic

R. Rodrigues; T. Ferreira; J. L. Gaspar

2009-01-01

255

Volcanic-ash hazard to aviation during the 2003 2004 eruptive activity of Anatahan volcano, Commonwealth of the Northern Mariana Islands  

NASA Astrophysics Data System (ADS)

Within the Commonwealth of the Northern Mariana Islands (CNMI), Anatahan is one of nine active subaerial volcanoes that pose hazards to major air-traffic routes from airborne volcanic ash. The 2003-2004 eruptive activity of Anatahan volcano affected the region's aviation operations for 3 days in May 2003. On the first day of the eruption (10 May 2003), two international flights from Saipan to Japan were cancelled, and several flights implemented ash-avoidance procedures. On 13 May 2003, a high-altitude flight through volcanic gas was reported, with no perceptible damage to the aircraft. TOMS and MODIS analysis of satellite data strongly suggests that no significant ash and only minor amounts of SO 2 were involved in the incident, consistent with crew observations. On 23 May 2003, airport operations were disrupted when tropical-cyclone winds dispersed ash to the south, dusting Saipan with light ashfall and causing flight cancellations there and at Guam 320 km south of the volcano. Operational (near-real-time) monitoring of ash clouds produced by Anatahan has been conducted since the first day of the eruption on 10 May 2003 by the Washington Volcanic Ash Advisory Center (VAAC). The VAAC was among the first groups outside of the immediate area of the volcano to detect and report on the unexpected eruption of Anatahan. After being contacted about an unusual cloud by National Weather Service forecasters in Guam at 1235 UTC on 10 May 2003, the VAAC analyzed GOES 9 images, confirming Anatahan as the likely source of an ash cloud and estimating that the eruption began at about 0730 UTC. The VAAC issued its first Volcanic Ash Advisory for Anatahan at 1300 UTC on 10 May 2003 more than 5 h after the start of the eruption, the delay reflecting the difficulty of detecting and confirming a surprise eruption at a remote volcano with no in situ real-time geophysical monitoring. The initial eruption plume reached 10.7-13.4 km (35,000-44,000 ft), well into jet cruise altitudes; thereafter, the maximum plume height decreased and during the rest of the eruption usually did not exceed ˜5 km (˜17,000 ft), which lessened the potential hazard to aircraft at higher cruise altitudes. Drifting ash clouds commonly extended hundreds of kilometers from the volcano, occasionally as far west as the Philippines. Over the course of the eruptive activity in 2003-2004, the VAAC issued 323 advisories (168 with graphical depictions of ash clouds) for Anatahan, serving as a reliable source of ash-cloud information for aviation-related meteorological offices and air carriers. With a record of frequent eruptions in the CNMI, continued satellite and in situ real-time geophysical monitoring is needed at Anatahan and other Marianas volcanoes so that potential hazards to aviation from any future eruptive activity can be quickly and correctly assessed.

Guffanti, Marianne; Ewert, John W.; Gallina, Gregory M.; Bluth, Gregg J. S.; Swanson, Grace L.

2005-08-01

256

Man Against Volcano: The Eruption on Heimaey,  

E-print Network

Man Against Volcano: The Eruption on Heimaey, Vestmannaeyjar, Iceland This booklet was originally published in 1976 under the title "Man Against Volcano:The Eruption on Heimaey, Vestmann Islands, Iceland:Town of Vestmannaeyjar with Helgafell in the right back- ground (photo courtesy of Sólarfilma). #12;Man Against Volcano

Ingólfsson, �lafur

257

Calderas, landslides and paleo-canyons on Piton de la Fournaise volcano (La Réunion Island, Indian Ocean)  

Microsoft Academic Search

Based upon a re-interpretation of previous data and a new field campaign, a structural evolution is proposed for the early history of Piton de la Fournaise volcano from 500,000 to 50,000years. Conceptually, it is shown that the formation of a caldera in which lava flows are contained inside the caldera depression, gives time for erosion to excavate deep canyons on

Olivier Merle; Philippe Mairine; Laurent Michon; Patrick Bachèlery; Magali Smietana

2010-01-01

258

Nicaraguan Volcanoes  

Atmospheric Science Data Center

article title:  Nicaraguan Volcanoes     View Larger Image Nicaraguan volcanoes, February 26, 2000 . The true-color image at left is a ... February 26, 2000 - Plumes from the San Cristobal and Masaya volcanoes. project:  MISR category:  gallery ...

2013-04-18

259

Eruption of Alaska volcano breaks historic pattern  

USGS Publications Warehouse

In the late morning of 12 July 2008, the Alaska Volcano Observatory (AVO) received an unexpected call from the U.S. Coast Guard, reporting an explosive volcanic eruption in the central Aleutians in the vicinity of Okmok volcano, a relatively young (~2000-year-old) caldera. The Coast Guard had received an emergency call requesting assistance from a family living at a cattle ranch on the flanks of the volcano, who reported loud "thunder," lightning, and noontime darkness due to ashfall. AVO staff immediately confirmed the report by observing a strong eruption signal recorded on the Okmok seismic network and the presence of a large dark ash cloud above Okmok in satellite imagery. Within 5 minutes of the call, AVO declared the volcano at aviation code red, signifying that a highly explosive, ash-rich eruption was under way.

Larsen, Jessica; Neal, Christina; Webley, Peter; Freymueller, Jeff; Haney, Matthew; McNutt, Stephen; Schneider, David; Prejean, Stephanie; Schaefer, Janet; Wessels, Rick

2009-01-01

260

Volcano-stratigraphic and structural evolution of Brava Island (Cape Verde) based on 40Ar/ 39Ar, U-Th and field constraints  

NASA Astrophysics Data System (ADS)

Three volcano-stratigraphic units were identified at Brava Island in the Cape Verde Archipelago on the basis of field relationships, geologic mapping and 40Ar/ 39Ar and U-Th ages. The Lower Unit comprises a 2-to-3 Ma-old submarine volcanic sequence that represents the seamount stage. It is composed of nephelinitic/ankaramitic hyaloclastites and pillow lavas, which are cut by abundant co-genetic dikes. Plutonic rocks of an alkaline-carbonatite complex, which intruded the submarine sequence 1.8 to 1.3 Ma ago, constitute the Middle Unit. A major erosional surface developed between 1.3 and ~ 0.25 Ma. The post-erosional volcanism recorded in the Upper Unit started 0.25 Ma ago and is dominated by phonolitic magmatism. This phase is characterised by explosive phreato-magmatic and magmatic activity that produced block and ash flow, surge, and pyroclastic fall deposits and numerous phreato-magmatic craters. Effusive events are represented by lava domes and coulées. One peculiarity of Brava is the occurrence of carbonatites in both the plutonic complex and the post-erosional phase as extrusive volcanics. The intrusive carbonatites are younger than those occurring on Fogo, Santiago and Maio islands. Young (Upper Pleistocene to Holocene) extrusive carbonatites occurring in the late stages of volcanism are unknown in other Cape Verde islands. The occurrence of pillow lavas and hyaloclastites above the present sea level (up to 400 m) and raised Upper Pleistocene beaches indicates continuous uplift of Brava since the seamount stage. By dating raised marine markers, uplift rates were estimated at between 0.2 and 0.4 mm/a. The evolution of Brava was controlled by faults with directions similar to those described for Fogo, suggesting a common stress field. A detailed geological map (1/25,000) of Brava is presented.

Madeira, José; Mata, João; Mourão, Cyntia; Brum da Silveira, António; Martins, Sofia; Ramalho, Ricardo; Hoffmann, Dirk L.

2010-10-01

261

Distribution of bivalve mollusks Macoma golikovi Scarlato and Kafanov, 1988 and Macoma calcarea (Gmelin, 1791) in the shallow-water hydrothermal ecosystem of Kraternaya Bight (Yankich Island, Kuril Islands): connection with feeding type and hydrothermal activity of Ushishir Volcano  

NASA Astrophysics Data System (ADS)

Kraternaya Bight (Yankich Island, the Kuril Islands) is a submerged crater of the active Ushishir Volcano characterized by terrestrial and underwater gasohydrothermal activity. The gasohydrothermal activity of the volcano produces a great influence on the physico-chemical characteristics of water column, as well as planktonic and bottom communities of marine organisms of the bight. The bivalve mollusks Macoma golikovi and Macoma calcarea are dominant macrobenthos species of Kraternaya Bight, which inhabit all the zones of underwater volcanic activity. Macoma golikovi occurs at a depth of 1-45 m. This species forms the densest aggregations (with an average biomass of 500-800 g m -2 and a population density of 500-700 ind. m -2) at a depth of 3-15 m, on steep underwater crater slopes (40-45°), on slightly silted gravel. The majority of gasohydrothermal vents are located at that depth. Macoma calcarea occurs at a depth of 5-55 m. In contrast to Macoma golikovi, this species is dominant at a depth of 25-40 m, on gentle slopes of the crater (to 20°), on silt and silty sand. That depth is less subjected to the influence of volcanic products. Its average biomass is 450-750 g m -2 with a population density of 200-450 ind. m -2 there. It is assumed that the differences in the distribution are due the fact that Macoma golikovi is mainly a suspension-feeder in Kraternaya Bight, and Macoma calcarea is a deposit-feeder. The studies conducted between 1987 and 1997 on the quantitative distribution of Macoma golikovi and Macoma calcarea in four areas of the bight, which had different intensity, temperature and chemical composition of gasohydrothermal vents and volcanic water seeping showed that both species formed settlements with lesser density in the area of the gasohydrothermal vents containing hydrogen sulfide. Beyond the area of volcanic activity, these species were most abundant. In 1993 and 1995, the mortality of the populations of the bivalve mollusks was observed in the areas of hydrogen sulfide gasohydrothermal vents and volcanic water seeping. In other areas of the bight, their abundance decreased sharply suggesting a relationship to the gasohydrothermal activity of the volcano in those years. Circumstantial evidence for this suggestion was that in 1993, the maximal concentrations of Fe, Zn, Cd, and Mn were observed in the tissues of both species. Macoma golikovi accumulated 5-10 times more Zn than Macoma calcarea. The concentration of Zn in the tissues of Macoma golikovi reached 2000 ?g g -1.

Kamenev, G. M.; Kavun, V. Ya; Tarasov, V. G.; Fadeev, V. I.

2004-01-01

262

The growth of Ritter Island volcano, Papua New Guinea, and the lateral collapse landslide and tsunami of 1888: new insights from eyewitness accounts  

NASA Astrophysics Data System (ADS)

We present a case study of the 1888 edifice lateral collapse landslide and tsunami event at Ritter Island volcano, using a more complete set of primary and secondary eyewitness accounts than has been used in previous studies. The collapse, early in the morning of March 13th, 1888, removed most of the island and its western submarine flank down to the base of the edifice some 900 m below sea level. The resulting tsunami is believed to have eradicated entire coastal communities on the surrounding islands and was recorded by German colonists in several locations around the Bismarck Sea and on adjacent coasts. Our analysis, based in particular upon new and complete translation of the German accounts, considers the evolution of the island over the previous two centuries and the events of March 1888, with the aim of clarifying the constraints that exist upon the cause, kinematics and mechanisms of the lateral collapse. Our analysis indicates that the pre-collapse Ritter edifice produced frequent strombolian eruptions and steam emissions, building an approximately 1700 m wide, notably steep-sided edifice with a N-S elongated oval shape in plan, by the late 1800s. Most activity was concentrated at a group of summit craters some 800 m above sea level, possibly also in a north-south line, with lesser flank fissure activity. The accounts of the tsunami indicate that the 1888 collapse involved a single large-scale catastrophic landslide, but descriptions of the island in the following days indicate a period in which there were many small landslides from the newly formed and unstable collapse scar. There is no evidence for a sequence of large landslides during this event and there is no clear evidence for a coincident or causal magmatic explosive eruption. One report suggests that there was activity (perhaps phreatic or phreatomagmatic explosions?) prior to the collapse that lead some of the resident local communities to seek higher ground, but evidence for precursory flank movements or changes in eruptive style have not been found in the historical accounts.

Ray, Melanie Jane; Day, Simon; Downes, Hilary

2014-05-01

263

How changes in pore pressure affect fluid circulation in volcanoes: three examples from Vulcano Island, Mt. Etna and Mt Vesuvius (Italy)  

NASA Astrophysics Data System (ADS)

Fluids circulating in volcanic edifices are attracting increasing interest from scientists, mostly because their role in triggering flank instability, phreatic explosions, and eruptions has been documented in several cases worldwide [Newhall et al. 2001, Thomas et al. 2004]. Fluid pore pressure can change as an effect of either external (meteoric recharge, variation of the stress field), or endogenous causes (e.g. internal pressurization of magmatic volatiles and hydrothermal systems). The reciprocal roles of tectonics and magmatic/hydrothermal activity are still under investigation [Gottsman et al. 2007, Roeloffs et al. 2003]. We discuss the results of decennial data records collected in the aquifers of Mt Etna, Vulcano Island and Mt Vesuvius, and get insights on the role of tectonics and volcanic activity on the observed variations of water level and chemical composition. In Vulcano Island, the shallow thermal aquifer is deeply concerned by deep volcanic fluids. The most significant variations were observed during the 1988-96 crisis, due to the large input of steam and acidic gases from depth. In addition, the record of the water table elevation provided remarkable insights on the pressure of the volcano-hydrothermal system, which can be envisaged as the cause for the onset of the phase of higher vapor output in the fumarolic field in late 2004. On Mt. Vesuvius, the geochemical behavior of the aquifer appears strictly controlled by the input of volcanic gases and variations in the stress field. These latter, which were responsible for the seismic crisis of 1999, and the almost simultaneous increased input of CO2-rich vapor, significantly affected water chemistry and temperature, until 2006. The recent observations of low salinity, temperature, and dissolved carbon contents in groundwater provide strong evidence for reduced pressure in the volcano-hydrothermal system. The record of water chemistry available on Mt. Etna since 1994 shows coeval changes in almost all monitored sites, ascribed to the variable contribution over time of waters with different temperature and composition. In addition, the dissolved CO2 content is chiefly affected by the input of volcanic CO2. Given the intense dynamics of the volcano, with frequent eruptions and periodic inflation-deflation phases, as well as the uneven deformation of the edifice, changes in water chemistry can be attributed, at least in part, to stress-related changes in pore pressure. Changes of pore pressure and micro-fracturation are controlling fluid movement (water and gases) within the volcano, producing part of the observed geochemical variations. The accurate modeling of the proposed process of fluid pressure increase, fracturing, and drainage of deep fluids will benefit of a multidisciplinary approach, able to clarify the cause-effect relationship and critical conditions. Newhall CG et al. 2001. J. Geol. Soc. Philipp., 56, 69-84. Thomas ME et al. 2004. Terra Nova, 16, 312-317. Gottsmann J. et al. 2007. GRL 34, L07307. Roeloffs E. et al. 2003. JVGR 127, 269-303.

Federico, C.; Madonia, P.; Capasso, G.; D'Alessandro, W.; Bellomo, S.; Brusca, L.; Cusano, P.; Longo, M.; Paonita, A.; Petrosino, S.

2013-05-01

264

Time variability of low-temperature fumaroles at Stromboli island (Italy) and its application to volcano monitoring  

NASA Astrophysics Data System (ADS)

The constant and mild activity of Stromboli volcano (Italy) is occasionally interrupted by effusive events and/or more energetic explosions, referred to as major explosions and paroxysms, which are potentially dangerous for the human community. Although several premonitory signals for effusive phases have been identified, precursors of major explosions and paroxysms still remain poorly understood. With the aim of contributing to the identification of possible precursors of energetic events, this work discusses soil temperature data acquired in low-temperature fumaroles at Stromboli in the period 2006-2010. Data analysis revealed that short-term anomalies recorded in the thermal signal are potentially useful in predicting state changes of the volcano. In particular, sudden changes in fumarole temperatures and their hourly gradients were observed from several days to a few hours prior to fracturing and paroxysmal events, heralded by peculiar waveforms of the recorded signals. The qualitative interpretation is supported by a quantitative, theoretical treatment that uses circuit theory to explain the time dependence of the short-period temperature variations, showing a good agreement between theoretical and observational data.

Madonia, Paolo; Fiordilino, Emilio

2013-12-01

265

Variability of passive gas emissions, seismicity, and deformation during crater lake growth at White Island Volcano, New Zealand, 2002-2006  

USGS Publications Warehouse

We report on 4 years of airborne measurements of CO2, SO2, and H2S emission rates during a quiescent period at White Island volcano, New Zealand, beginning in 2003. During this time a significant crater lake emerged, allowing scrubbig processes to be investigated. CO2 emissions varied from a baseline of 250 to >2000 t d-1 and demonstrated clear annual cycling that was consistent with numbers of earthquake detections and annual changes in sea level. The annual variability was found to be most likely related to increases in the strain on the volcano during sea level highs, temporarily causing fractures to reduce in size in the upper conduit. SO2 emissions varied from 0 to >400 t d-1 and were clearly affected by scrubbing processes within the first year of take development. Scrubbing caused increases of SO42- and Cl- in lake waters, and the ratio of carbon to total sulphur suggested that elemental sulphur deposition was also significant in the lake during the first year. Careful measurements of the lake level and chemistry allowed estimates of the rate of H2O(g) and HCl(g) input into the lake and suggested that the molar abundances of major gas species (H2O, CO2, SO2, and HCl) during this quiescent phase were similar to fumarolic ratios observed between earlier eruptive periods. The volume of magma estimated from CO2 emissions (0.0 15-0.04 km3) was validated by Cl- increases in the lake, suggesting that the gas and magma are transported from deep to shallow depths as a closed system and likely become open in the upper conduit region. The absence of surface deformation further leads to a necessity of magma convection to supply and remove magma from the degassing depths. Two models of convection configurations are discussed. Copyright 2008 by the American Geophysical Union.

Werner, C.; Hurst, T.; Scott, B.; Sherburn, S.; Christenson, B.W.; Britten, K.; Cole-Baker, J.; Mullan, B.

2008-01-01

266

Intra-caldera Events: A Look at the Hydrovolcanic Deposit Stratigraphically Located Between two Caldera-Forming Eruptions of Okmok Volcano, Umnak Island, Alaska  

NASA Astrophysics Data System (ADS)

Within the 10 km diameter caldera that characterizes Okmok Volcano, a field of post-caldera cones and deposits demonstrate many features associated with water-magma interactions. A unit deposited prior to the formation of the present caldera provides evidence for large explosive hydrovolcanic eruptions in the past as well. This unit is referred to as the Middle Scoria Unit as it is stratigraphically located between the ~9000 BP Okmok I and 2050 BP Okmok II caldera-forming events. Here, we present data on the stratigraphy, geochemistry, and eruptive mechanisms of the Middle Scoria Unit, which averages a thickness of 2.5 meters. The basal layer of the Middle Scoria consists of moderately well sorted, highly inflated juvenile clasts of basaltic composition (53.88 wt.% SiO2) that average 3 to 5 cm in size. Capping the base is a sequence of layers alternating between oxidized reddish lithic fragments and poorly vesicular scoria averaging 1 mm to 3 cm in size. The contacts between the scoria and lithic layers are less discrete in the top section, with a higher proportion of mixing averaging up to 75% for a clast-rich layer. The upper layers of the unit also show reverse grading and contain dense, poorly vesicular scoria fragments and lithic fragments of 2 mm to 1.5 cm in size. The Middle Scoria unit has been found on the neighboring Unalaska Island, approximately 30 km to the East, revealing a wide dispersal. Our results indicate that this eruption began as a highly explosive, purely magmatic and rare basaltic Plinian eruption. With time, the eruptive series evolved to incorporate external water, as demonstrated by the successions of oxidized lithic lapilli and poorly vesicular scoria layers. Our preliminary interpretations of the Middle Scoria indicate that Okmok Volcano may be capable of highly explosive basaltic Plinian and hydrovolcanic eruptions.

Wong, L. J.

2002-12-01

267

Island of Timor, Indonesia  

NASA Technical Reports Server (NTRS)

This almost totally cloud free, photo of the island of Timor, Indonesia (9.0S, 125.0E) illustrates the volcanic origin of the over 1500 islands of Indonesia. Close examination of the photo reveals several eroded volcanoes on the Island of Timor and several of the adjacent islands. The linear alignment of the volcanoes, as seen from space, indicates the edges of the tectonic plates of the Earth's crust where volcanic activity is most common.

1989-01-01

268

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

NASA Astrophysics Data System (ADS)

In addition to hosting one of the most active volcanoes in the Aleutian Arc, Akutan Island, Alaska, is the site of a significant geothermal resource within Hot Springs Bay Valley (HSBV). We deployed 15 broadband (30 s to 50 Hz) seismometers in and around HSBV during July 2012 as part of an effort to establish a baseline for background seismic activity in HSBV prior to geothermal production on the island. The stations recorded data on-site and were retrieved in early September 2012. Additional targets for the array include the tracking of deep tectonic tremor known to occur within the Aleutian subduction zone and the characterization of volcano-tectonic (VT) and deep long period (DLP) earthquakes from Akutan Volcano. Because 13 of the stations in the array sit within an area roughly 1.5 km by 1.5 km, we plan to apply methods based on stacking and beamforming to analyze the waveforms of extended signals lacking clear phase arrivals (e.g., tremor). The average spacing of the seismometers, roughly 350 m, provides sensitivity to frequencies between 2-8 Hz. The stacking process also increases the signal-to-noise ratio of small amplitude signals propagating across the array (e.g., naturally occurring geothermal seismicity). As of August 2012, several episodes of tectonic tremor have been detected in the vicinity of Akutan Island during the array deployment based on recordings from nearby permanent stations operated by the Alaska Volcano Observatory (AVO). This is the first small-aperture array deployed in the Aleutian Islands and the results should serve as a guide for future array deployments along the Aleutian Arc as part of the upcoming EarthScope and GeoPRISMS push into Alaska. We demonstrate the power of array methods based on stacking at Akutan Volcano using a sequence of DLP earthquakes from June 11, 2012 that were recorded on the permanent AVO stations. We locate and characterize the lowest frequency portion of the signals at 0.5 Hz. At these low frequencies, the traditional "sparse" local network at Akutan effectively becomes a small-aperture array relative to the wavelength. We exploit the coherency among the stations and locate the DLPs by using a novel stacking method. The crux of the method involves scanning over all possible source locations and relative polarity combinations between the local stations to find the one that maximizes the stacked power at a well-defined region in the subsurface. As a result, the method is applicable even in the presence of mixed polarities. We discover that two of the stations at Akutan have DLP waveforms with opposite polarities compared to the other stations. Accounting for this polarity variation gives a DLP source location at 10 km depth, to the west-southwest of the Akutan summit caldera. These results give clear evidence for non-isotropic radiation patterns associated with DLPs and show the promise of array methods based on waveform stacking for providing future insights into the origin of volcanic as well as geothermal and tectonic seismicity.

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

2012-12-01

269

Tsunami deposits in Santiago Island (Cape Verde archipelago) as possible evidence of a massive flank failure of Fogos volcano  

Microsoft Academic Search

Massive flank failures of volcanic edifices generate tsunami waves. These low-frequency but high magnitude hazards remain poorly documented because of the scarcity of observations. Offshore deposits are studied only by geophysical surveys and the failure rheologies are poorly constrained. Marine conglomerates found at unusually high elevations in Hawaii and in the Canary Islands were previously interpreted as being the result

Raphaël Paris; Thomas Giachetti; Joël Chevalier; Hervé Guillou; Norbert Frank

2011-01-01

270

Don Swanson at Ash Outcrop Near Volcano Observatory  

USGS Multimedia Gallery

Don Swanson (USGS Hawaiian Volcano Observatory) shows scientists in the CSAV International class how layers of ash outside of HVO indicate past explosive eruptions of Kilauea. Hawaiian Volcano Observatory, Hawaii Island, Hawaii...

271

Macrobenthos of the nearshore Aleutian Archipelago, with emphasis on invertebrates associated with Clathromorphum nereostratum (Rhodophyta, Corallinaceae)  

Microsoft Academic Search

In the Aleutian Islands, Alaska, crustose coralline algae can be widespread in the low intertidal and shallow subtidal regions,\\u000a and cover most available hard substrates. The longevity and slow growth-rate of coralline algae make them vulnerable to major\\u000a disturbances, including anthropogenic disturbances and ocean acidification. Subtidal habitats dominated by crustose coralline\\u000a algae are often associated with sea urchin-barren grounds and

Heloise Chenelot; Stephen C. Jewett; Max K. Hoberg

272

The role of slab melting in the petrogenesis of high-Mg andesites: evidence from Simbo Volcano, Solomon Islands  

Microsoft Academic Search

The petrogenesis of high-Mg andesites (HMA) in subduction zones involves shallow melting of refractory mantle sources or, alternatively, the interaction of ascending slab-derived melts with mantle peridotite. To unravel the petrogenesis of HMA, we report major, trace element and Sr–Nd–Hf–Pb isotope data for a newly found occurrence of HMA in the New Georgia group, Solomon Islands, SW-Pacific. Volcanism in the

S. König; S. Schuth; C. Münker; C. Qopoto

2007-01-01

273

Causation or coincidence? The correlations in time and space of the 2008 eruptions of Cleveland, Kasatochi, and Okmok Volcanoes, Alaska  

NASA Astrophysics Data System (ADS)

In mid-summer 2008, three significant volcanic eruptions occurred in the Andreanof Islands of the Aleutian Arc, Alaska. Okmok volcano began erupting on July 12, followed by Cleveland on July 21, and then by Kasatochi on August 7. In addition to this temporal correlation, there is also a geographic correlation: the eruptions occurred in a 525 km region representing only about 20% of the arc's length. Given these close proximities in space and time, it is natural to speculate about whether an underlying process is at work. Ultimately, the arc exists because of subduction, but the question remains if a more immediate trigger may be responsible for the concurrence. We began our inquiry into whether a link exists among the three eruptions by posing the following question: What is the probability that, by chance alone, Okmok, Kasatochi and Cleveland could simultaneously erupt? Answering this question requires both a statistical model for eruption frequency and empirical data of where and when eruptions have occurred in the past. We assume that eruptions follow a Poisson distribution, and estimate the expected number of eruptions per time interval for each volcano in the arc from the geologic record and observations contained in the Alaska Volcano Observatory's GeoDIVA database. We then perform a Monte Carlo experiment, simulating 10,000 years of eruptive activity at 30 day intervals. The results of the simulation indicate that the phenomenon of three eruptions beginning in a single month happens about once every 90 years. A spatial constraint requiring that the maximum separation among the volcanoes be less than 525 km increases this interval to about once every 900 years. Though these intervals are not so long as to rule out coincidence, they are long enough to warrant further investigation into the possibility of a common origin. Several candidates for a prospective cause are: (1) the Great Aleutian Earthquake of 1957, which includes the region of the three recent eruptions, may have triggered a period of increased volcanic activity that still persists; (2) a slow slip event, with associated non- volcanic tremor, have may have resulted in static stress changes favorable to volcanic eruptions; or (3) nearby volcanoes may interact with one another in such a way as to increase the chance of clustered eruptions. We consider each of these scenarios (as well as other more remote possibilities) and weigh their relative likelihoods against the probability of random correlation. In the end, no definitive answer emerges, though pure coincidence remains a simple and plausible explanation for this remarkable event.

Cervelli, P. F.; Cameron, C. E.

2008-12-01

274

The EarthScope Plate Boundary Observatory: Bringing Low Latency Data From Unimak Island, Alaska  

NASA Astrophysics Data System (ADS)

The Plate Boundary Observatory (PBO), part of the NSF-funded EarthScope project, will complete the installation of a fourteen station GPS network on Unimak Island, Alaska in August, 2008. The primary data communications goal of the project is to design and implement a robust data communications network capable of downloading 15-sec daily GPS files and streaming 1 Hz GPS data, via Ustream, from Unimak Island to three data relay points in the Aleutian chain. As part of the permitting agreement with the landowner, PBO will co-locate the GPS stations with existing USGS seismic stations. The technical challenges involved in optimizing the data communications network for both the GPS data and the seismic data will be presented. From Unimak island, there will be three separate data telemetry paths: 1) West through a radio repeater on Akutan volcano to a VSAT in Akutan village, 2) East through a radio repeater to a T1 connection in Cold Bay, AK, 3) South through a radio repeater to a VSAT at an existing PBO GPS station in King Cove, AK. The difficulties involved in the project include complex network geometries with multiple radio repeaters, long distance RF transmission over water, hardware bandwidth limitations, power limitations, space limitations, as well as working in bear country on an incredibly remote and active volcano.

Feaux, K.; Mencin, D.; Jackson, M.; Gallaher, W.; Pauk, B.; Smith, S.

2008-05-01

275

Vertical Motions of Oceanic Volcanoes  

NASA Astrophysics Data System (ADS)

Oceanic volcanoes offer abundant evidence of changes in their elevations through time. Their large-scale motions begin with a period of rapid subsidence lasting hundreds of thousands of years caused by isostatic compensation of the added mass of the volcano on the ocean lithosphere. The response is within thousands of years and lasts as long as the active volcano keeps adding mass on the ocean floor. Downward flexure caused by volcanic loading creates troughs around the growing volcanoes that eventually fill with sediment. Seismic surveys show that the overall depression of the old ocean floor beneath Hawaiian volcanoes such as Mauna Loa is about 10 km. This gross subsidence means that the drowned shorelines only record a small part of the total subsidence the islands experienced. In Hawaii, this history is recorded by long-term tide-gauge data, the depth in drill holes of subaerial lava flows and soil horizons, former shorelines presently located below sea level. Offshore Hawaii, a series of at least 7 drowned reefs and terraces record subsidence of about 1325 m during the last half million years. Older sequences of drowned reefs and terraces define the early rapid phase of subsidence of Maui, Molokai, Lanai, Oahu, Kauai, and Niihau. Volcanic islands, such as Maui, tip down toward the next younger volcano as it begins rapid growth and subsidence. Such tipping results in drowned reefs on Haleakala as deep as 2400 m where they are tipped towards Hawaii. Flat-topped volcanoes on submarine rift zones also record this tipping towards the next younger volcano. This early rapid subsidence phase is followed by a period of slow subsidence lasting for millions of years caused by thermal contraction of the aging ocean lithosphere beneath the volcano. The well-known evolution along the Hawaiian chain from high to low volcanic island, to coral island, and to guyot is due to this process. This history of rapid and then slow subsidence is interrupted by a period of minor uplift lasting a few hundred thousand years as the island migrates over a broad flexural arch related to isostatic compensation of a nearby active volcano. The arch is located about 190±30 km away from the center of volcanic activity and is also related to the rejuvenated volcanic stage on the islands. Reefs on Oahu that are uplifted several tens of m above sea level are the primary evidence for uplift as the islands over-ride the flexural arch. At the other end of the movement spectrum, both in terms of magnitude and length of response, are the rapid uplift and subsidence that occurs as magma is accumulated within or erupted from active submarine volcanoes. These changes are measured in days to years and are of cm to m variation; they are measured using leveling surveys, tiltmeters, EDM and GPS above sea level and pressure gauges and tiltmeters below sea level. Other acoustic techniques to measure such vertical movement are under development. Elsewhere, evidence for subsidence of volcanoes is also widespread, ranging from shallow water carbonates on drowned Cretaceous guyots, to mapped shoreline features, to the presence of subaerially-erupted (degassed) lavas on now submerged volcanoes. Evidence for uplift is more limited, but includes makatea islands with uplifted coral reefs surrounding low volcanic islands. These are formed due to flexural uplift associated with isostatic loading of nearby islands or seamounts. In sum, oceanic volcanoes display a long history of subsidence, rapid at first and then slow, sometimes punctuated by brief periods of uplift due to lithospheric loading by subsequently formed nearby volcanoes.

Clague, D. A.; Moore, J. G.

2006-12-01

276

Savage Earth: Out of the Inferno - Volcanoes  

NSDL National Science Digital Library

This article, entitled Mountains of Fire, describes the relationship between the types of volcanic activity and plate movement and the connection between types of volcanoes and how they erupt. The article is supported by a video of an erupting volcano, a photograph of an eruption and an animation depicting pyroclastic flow and the formation of a composite volcano. It is also supported by three sidebars, called Volcanoes of North America, Montserrat: An Island Under Siege, and Volcanoes on other Planets. These sidebars also have videos or photographs to enhance their message.

277

Evidence of flank failure deposit reactivation in a shield volcano. A favorable context for deep-seated landslide activation (La Réunion Island)  

NASA Astrophysics Data System (ADS)

Giant flank failures are recurrent features of shield volcanoes, and their deposits (i.e. breccia), constitute a significant volume in a volcanic edifice. On La Réunion Island, the growth and development of Piton des Neiges volcano has been punctuated by several flank failure episodes. One of these failures is a deep-seated landslide (>200 Mm3) occurring nowadays in Grand Ilet, a plateau inhabited by 1 000 people in the cirque of Salazie, on the northern flank of Piton des Neiges. Here we present the results of a multidisciplinary study (structural geology and field mapping, GNSS monitoring, borehole logging) performed to characterize the geological structure the Grand Ilet landslide, and identify the instability factors that control this category of destabilization. Basic breccia deposits, up to 160 meters thick, constitute the main geological formation of the unstable mass. This breccia are cut by the headwall scar of the landslide, and covered by lava flows, indicating a minimum age of 200 kyr for the destabilization that produced the deposits. The breccia is consolidated out of the landslide area. The NE toe of the landslide is evidenced by an important compressional deformation of the base of the breccia, and striated surfaces in this deformed volume indicate a NE-direction of transport. In this deformed bulge, a clay-rich layer at the base of the breccia has been identified as the main slip plane. Using a video inspection of drill casings on three exploration boreholes, we reconstructed the 3D geometry of the slip plane at the base of the breccia. This reconstruction shows that the landslide plane has an average dip of 6° toward the NE. The displacement monitoring network shows that the unstable mass has a 5.5 km2 extension, with a variable azimuth of movement direction (N140° for the SW sector, and N45° for the NE sector). The planimetric displacements velocities range between 2 cm/year in the inner part of the unstable mass to 52 cm/year at the landslide toe. The dip of displacement vectors vary from 34° ± 9 uphill to 7° ± 2 downhill near the landslide toe. This displacement field, the topography and the drill casings inspection show that secondary shear zones are located inside the landslide mass, characterized by a lower deformation rate than the basal shear zone. However heterogeneous is the deformation, it more important at the base of the breccia (locally in the clay layer). Ultimately, our study suggests that the main slip plane has localized at the base of the breccia despite its induration. Thus we conclude that the Grand Ilet landslide is in fact a present-day reactivation of an old destabilization.

Belle, Pierre; Aunay, Bertrand; Famin, Vincent; Join, Jean-Lambert

2014-05-01

278

Craniometric variation in the Aleutians: integrating morphological, molecular, spatial, and temporal data.  

PubMed

Several hypotheses have been put forward about the origins and evolution of the inhabitants of the Aleutian Islands. Both Hrdli?ka [The Aleutian and Commander Islands and Their Inhabitants (Philadelphia: Wistar Institute of Anatomy and Biology, 1945)] and Laughlin ["The Alaska gateway viewed from the Aleutian Islands," in Papers on the Physical Anthropology of the American Indian, W. S. Laughlin, ed. (New York: Viking Fund, 1951), 98-126] analyzed cranial morphology and came to somewhat different conclusions using a typological approach and limited analytical methods. Subsequent investigations using morphological data have not significantly improved our understanding of Aleut prehistory. More recently, radiocarbon dating and mitochondrial DNA analyses have shed light on Aleut genetic variation and changes over time, but better morphological methods using multivariate statistical analysis have not yet been used. We analyzed craniometric data using multivariate procedures and found that Aleuts demonstrate significant changes in cranial morphology over time, and these changes correspond to Hrdli?ka's observations but may not necessarily reflect in-migration. The morphological changes were concentrated in the very aspects of morphology that are easily observable and that Hrdli?ka most often measured, namely, cranial length, breadth, and height, but they were obscured when craniometric variation as a whole was analyzed. Also, we found that the morphological changes over time were not related to the changes in haplogroup frequencies over time, suggesting that migration into the Aleutians did not play a significant role in producing the morphological changes. However, craniometric variability apparently increases over time, suggesting in-migration, localized selection, and/or greater environmental heterogeneity. Our results contradict Laughlin's observations but may be more in line with his hypothesis of in situ evolutionary changes absent gene flow. In addition to selection, gene flow, and gene drift, however, sociocultural changes must also be considered as a factor in why morphology changed over time. PMID:21417887

Ousley, Stephen D; Jones, Erica B

2010-12-01

279

Under the volcano: phylogeography and evolution of the cave-dwelling Palmorchestia hypogaea (Amphipoda, Crustacea) at La Palma (Canary Islands)  

PubMed Central

Background The amphipod crustacean Palmorchestia hypogaea occurs only in La Palma (Canary Islands) and is one of the few terrestrial amphipods in the world that have adapted to a strictly troglobitic life in volcanic cave habitats. A surface-dwelling closely related species (Palmorchestia epigaea) lives in the humid laurel forest on the same island. Previous studies have suggested that an ancestral littoral Orchestia species colonized the humid forests of La Palma and that subsequent drought episodes in the Canaries reduced the distribution of P. epigaea favouring the colonization of lava tubes through an adaptive shift. This was followed by dispersal via the hypogean crevicular system. Results P. hypogaea and P. epigaea did not form reciprocally monophyletic mitochondrial DNA clades. They showed geographically highly structured and genetically divergent populations with current gene flow limited to geographically close surface locations. Coalescence times using Bayesian estimations assuming a non-correlated relaxed clock with a normal prior distribution of the age of La Palma, together with the lack of association of habitat type with ancestral and recent haplotypes, suggest that their adaptation to cave life is relatively ancient. Conclusion The data gathered here provide evidence for multiple invasions of the volcanic cave systems that have acted as refuges. A re-evaluation of the taxonomic status of the extant species of Palmorchestia is needed, as the division of the two species by habitat and ecology is unnatural. The information obtained here, and that from previous studies on hypogean fauna, shows the importance of factors such as the uncoupling of morphological and genetic evolution, the role of climatic change and regressive evolution as key processes in leading to subterranean biodiversity. PMID:18234125

Villacorta, Carlos; Jaume, Damià; Oromí, Pedro; Juan, Carlos

2008-01-01

280

Decade Volcanoes  

NSDL National Science Digital Library

In the 1990s, the International Association of Volcanology and Chemistry of the Earth's Interior started the Decade Volcano Project. As part of their work, they designated sixteen volcanoes particularly worthy of study "because of their explosive histories and close proximity to human populations." The group recently teamed up with National Geographic to create a guide to these volcanoes via this interactive map. Navigating through the map, visitors can learn about Mount Rainier, Colima, Galeras, Santorini, and other prominent volcanoes. For each volcano, there's a brief sketch that gives the date of its last eruption, its elevation, nearby population centers, and a photograph.

281

Improvement in TDEM sounding interpretation in presence of induced polarization. A case study in resistive rocks of the Fogo volcano, Cape Verde Islands  

NASA Astrophysics Data System (ADS)

A Time Domain Electromagnetic (TDEM) survey was carried out in and around the caldera of the Fogo volcano, Cape Verde Islands, to detect the low resistive structures that could be related to groundwater. A sign reversal in the sounding curves was encountered in central-loop measurements for the soundings located in the centre of the caldera along three main radial profiles. The negative transients are recorded in the early channels between 6.8 and 37 ?s. Negative values in an early time transient is an unusual field observation, and consequently the first step was to check the data to ascertain their accuracy and quality. In the second step, three-dimensional (3D) effects are evaluated and ruled out in this zone, while an Induced Polarization (IP) phenomenon is observed using Direct Current (DC) sounding measurements. In the third step, the IP effect is called upon to explain the TDEM distortions; a Cole-Cole dispersive conductivity is found to be adequate to fit the field data. However, the more relevant one-dimensional (1D) model is recovered when both central-loop and offset-loop data are jointly taken into account, thus indicating that an effect of dispersive conductivity is necessary to explain the field data. The 1D electrical structure exhibits four layers, with decreasing resistivity with depth. Only the first layer is polarizable and its Cole-Cole parameters are m=0.85, c=0.8 and ?=0.02 ms for chargeability, frequency dependence and time constant, respectively. However, the Cole-Cole parameters deduced from TDEM forward modelling remain different from those deduced from DC/IP sounding. In this volcanic setting, this IP effect may be caused by the presence of small grains of magnetite and/or by the granularity of effusive products (lapillis). As a conclusion, it is shown that a modelling using different TDEM data sets is essential to recover the electrical structure of this area.

Descloitres, Marc; Guérin, Roger; Albouy, Yves; Tabbagh, Alain; Ritz, Michel

2000-08-01

282

Mingling processes at Panarea Volcano (Aeolian Islands, Italy): results from M73/2 cruise drilled cores  

NASA Astrophysics Data System (ADS)

The last Meteor 73/2 cruise drilled several lava cores in the southern Tyrrhenian Sea, close to Panarea Island and surrounding islets (Aeolian archipelago, Italy), at depths comprised between 50 and 70 m bsl. These rocks - unconformably covered by unconsolidated lapilli tuffs - revealed different lithologies and mineralogical assemblages corresponding to different compositions (hereafter A & B), as then evidenced by ICP-MS analyses (major and trace elements) performed on selected rock-samples. The cores also displayed several, cm-sized, rounded enclaves of the A-type dispersed in the B-type. The petrographic study on textures and microprobe analyses on glass shards and mineral phases finally concurred in identifying two magmas with different history and quite complex interaction. Rock A is a holocrystalline shoshonite (SHO) - showing plagioclase (pl - An%=62-74) and clinopyroxene (cpx) as main phases, plus subordinate amphibole and biotite phenocrysts, rare and small olivines (Fo?89%) - which represents the first magma, usually in form of enclaves. Notably, the SHO shows intersertal vesicularity and scarce glass. Rock B is a porphyritic rhyodacite (RD) characterized by pl (An%=32-52), and biotite phenocrysts, with minor cpx phenocrysts and microphenocrysts. Pl and cpx show both alternate and normal zoning, and the former have frequent K-rich reaction rims. Similar mineral phases and frequent sanidine microlites characterize the alkali-trachyte glassy groundmass of rock B. This rock hosts the SHO and represent the most voluminous magma. Overall, these features indicate a quite complex history of magma interaction(s) as well as a polybaric crystallization, which lead the volatiles abundance and behaviour. From the study of the highly irregular edges observed along their contacts, we argue intrusive and visco-plastic relationships between A and B. Moreover, the presence of irregular vesicles and vugs bounded by pl microlites suggest an emplacement at shallow level where cooling favoured both slow degassing and pervasive crystallization. Textural and compositional data concur in indicating that the two magmas mingled at depth. Noteworthy, enclaves of a third rock type - very limited in volume - is present along some of the collected cores. It is a reddish low-porphyritic lava similar to the RD lava in terms of mineralogical composition, but showing a higher amount of microlites with smaller size if compared to the main RD host-rock. This could indicate that at some extent also mixing occurred. The multiple similarities of our rocks with lavas of the Panarea islets or other acid volcanics containing mafic-intermediate enclaves and outcropping on other Aeolian Islands, suggest that mafic magma uprising "within" resident magma with subsequent mingling is a recurrent process in these volcanic systems and may be the trigger for the eruption of acid melts.

De Benedetti, A. A.; De Astis, G.; Raffaele, V.; Esposito, A.; Giordano, G.; Petersen, S.; Monecke, T.

2012-04-01

283

Plant Diversity Changes during the Postglacial in East Asia: Insights from Forest Refugia on Halla Volcano, Jeju Island  

PubMed Central

Understanding how past climate changes affected biodiversity is a key issue in contemporary ecology and conservation biology. These diversity changes are, however, difficult to reconstruct from paleoecological sources alone, because macrofossil and pollen records do not provide complete information about species assemblages. Ecologists therefore use information from modern analogues of past communities in order to get a better understanding of past diversity changes. Here we compare plant diversity, species traits and environment between late-glacial Abies, early-Holocene Quercus, and mid-Holocene warm-temperate Carpinus forest refugia on Jeju Island, Korea in order to provide insights into postglacial changes associated with their replacement. Based on detailed study of relict communities, we propose that the late-glacial open-canopy conifer forests in southern part of Korean Peninsula were rich in vascular plants, in particular of heliophilous herbs, whose dramatic decline was caused by the early Holocene invasion of dwarf bamboo into the understory of Quercus forests, followed by mid-Holocene expansion of strongly shading trees such as maple and hornbeam. This diversity loss was partly compensated in the Carpinus forests by an increase in shade-tolerant evergreen trees, shrubs and lianas. However, the pool of these species is much smaller than that of light-demanding herbs, and hence the total species richness is lower, both locally and in the whole area of the Carpinus and Quercus forests. The strongly shading tree species dominating in the hornbeam forests have higher leaf tissue N and P concentrations and smaller leaf dry matter content, which enhances litter decomposition and nutrient cycling and in turn favored the selection of highly competitive species in the shrub layer. This further reduced available light and caused almost complete disappearance of understory herbs, including dwarf bamboo. PMID:22438890

Dolezal, Jiri; Altman, Jan; Kopecky, Martin; Cerny, Tomas; Janecek, Stepan; Bartos, Michael; Petrik, Petr; Srutek, Miroslav; Leps, Jan; Song, Jong-Suk

2012-01-01

284

Volcano watch Monitoring risk on Auckland's volcanic field  

E-print Network

Volcano watch Monitoring risk on Auckland's volcanic field Lest we forget Our Memory Lab@auckland.ac.nz Volcano watchThe recent eruptions at Mt Tongariro and White Island are a timely reminder for Auckland (pictured with Lucy McGee, who has recently completed her doctorate) is dating the city's 50 volcanoes

Auckland, University of

285

Living with Volcanoes: Year Eleven Teaching Resource Unit.  

ERIC Educational Resources Information Center

Presents a unit on volcanoes and experiences with volcanoes that helps students develop geography skills. Focuses on four volcanoes: (1) Rangitoto Island; (2) Lake Pupuke; (3) Mount Smart; and (4) One Tree Hill. Includes an answer sheet and resources to use with the unit. (CMK)

Le Heron, Kiri; Andrews, Jill; Hooks, Stacey; Larnder, Michele; Le Heron, Richard

2000-01-01

286

Seismic cycles along the Aleutian arc: Analysis of seismicity from 1957 through 1991  

NASA Astrophysics Data System (ADS)

We catalog and relocate Aleutian arc seismicity. Between 1957 and 1991, two great earthquakes ruptured the same 250-km-long portion of the central Aleutian arc: the 1957 Aleutian Islands earthquake and the 1986 Andreanof Islands earthquake. Because accurate estimates of the moment distribution of the 1957 earthquake are not available, the spatial distribution of aftershocks for each of these events is compared and tested against models describing the modes of occurrence of great subduction zone earthquakes. Earthquake relocations are based on P wave arrival times published in the International Seismological Summary, the Bureau Central International Seismologique, and the International Seismological Centre bulletins and include corrections for the near-source velocity structure associated with the down-going slab. Magnitude estimates are extracted from bulletins and prior to 1964 are estimated by us from microfilmed records. Our catalog is complete above magnitude 5.5. Aftershocks associated with the 1957 and 1986 earthquakes appear to occur in different areas. East of the main shock epicenters, aftershock locations are anticorrelated. West of the main shock epicenter, aftershocks of the 1986 earthquake tended to concentrate along the updip edge of aftershock clusters associated with the 1957 earthquake. If we assume aftershocks rim the distribution of seismic moment release associated with each event, these observations imply that the moment distribution of the 1986 earthquake was different from that of the 1957 earthquake. This suggests that we should use caution in identifying mechanically strong portions of a fault, asperities, by simply mapping the moment distribution of a single great earthquake. A fundamental tenet of the asperity model, that rupture always occurs on the strongest portions of the fault with weaker portions rupturing either aseismically or dynamically as a result of rupture on a strong fault patch, may in the case of the central Aleutian arc not be correct. Thus observing the moment distribution from a single great earthquake may tell us little about what the distribution of moment release will look like during the next earthquake.

Boyd, Thomas M.; Engdahl, E. Robert; Spence, William

1995-01-01

287

Hawaii's volcanoes revealed  

USGS Publications Warehouse

Hawaiian volcanoes typically evolve in four stages as volcanism waxes and wanes: (1) early alkalic, when volcanism originates on the deep sea floor; (2) shield, when roughly 95 percent of a volcano's volume is emplaced; (3) post-shield alkalic, when small-volume eruptions build scattered cones that thinly cap the shield-stage lavas; and (4) rejuvenated, when lavas of distinct chemistry erupt following a lengthy period of erosion and volcanic quiescence. During the early alkalic and shield stages, two or more elongate rift zones may develop as flanks of the volcano separate. Mantle-derived magma rises through a vertical conduit and is temporarily stored in a shallow summit reservoir from which magma may erupt within the summit region or be injected laterally into the rift zones. The ongoing activity at Kilauea's Pu?u ?O?o cone that began in January 1983 is one such rift-zone eruption. The rift zones commonly extend deep underwater, producing submarine eruptions of bulbous pillow lava. Once a volcano has grown above sea level, subaerial eruptions produce lava flows of jagged, clinkery ?a?a or smooth, ropy pahoehoe. If the flows reach the ocean they are rapidly quenched by seawater and shatter, producing a steep blanket of unstable volcanic sediment that mantles the upper submarine slopes. Above sea level then, the volcanoes develop the classic shield profile of gentle lava-flow slopes, whereas below sea level slopes are substantially steeper. While the volcanoes grow rapidly during the shield stage, they may also collapse catastrophically, generating giant landslides and tsunami, or fail more gradually, forming slumps. Deformation and seismicity along Kilauea's south flank indicate that slumping is occurring there today. Loading of the underlying Pacific Plate by the growing volcanic edifices causes subsidence, forming deep basins at the base of the volcanoes. Once volcanism wanes and lava flows no longer reach the ocean, the volcano continues to submerge, while erosion incises deep river valleys, such as those on the Island of Kaua?i. The edges of the submarine terraces that ring the islands, thus, mark paleocoastlines that are now as much as 2,000 m underwater, many of which are capped by drowned coral reefs.

Eakins, Barry W.; Robinson, Joel E.; Kanamatsu, Toshiya; Naka, Jiro; Smith, John R.; Takahashi, Eiichi; Clague, David A.

2003-01-01

288

Seismic Variability Study of Eastern Alaska/Aleutian Megathrust  

NASA Astrophysics Data System (ADS)

The Eastern Alaska/Aleutian megathrust has ruptured in a number of >M8.0 earthquakes in the 20th century on multiple segments, causing strong ground shaking and generating Pacific-wide trunamis. Seismic variability along the arc within the Semidi-Shumagin segments, considered locked and creeping sections respectively, may be attributable to structural variations in the megathrust. We placed eight seismometers (6 broadband and 2 short-period) throughout the Alaska peninsula for the summer of 2011 to both record local seismicity and to serve as an onshore component to the Langseth ALEUT cruise. We combine these data with data from selected stations of the Alaska Earthquake Information Center (AEIC) and the Alaska Volcano Observatory (AVO) to locate local seismicity, to define the megathrust boundary, and to develop a velocity model of the arc in this region. So far, ~550 events during the two-month period were located using P- and S-phases and a local velocity model. Data from OBS's deployed during the ALEUT cruise will improve accuracy of locations along the megathrust.

Mattei, G. A.; Keranen, K. M.; Abers, G. A.; Shillington, D. J.; Becel, A.

2012-12-01

289

How Are Islands Formed?  

NSDL National Science Digital Library

This lesson provides students with information about how islands are formed, including a basic knowledge of plate tectonics. Using the islands of Hawaii as an example, students learn about the earth processes that cause the formation of islands over time, including volcanoes and hot spots.

2001-01-01

290

Long magma residence times at an island arc volcano (Soufriere, St. Vincent) in the Lesser Antilles: evidence from 238U- 230Th isochron dating  

NASA Astrophysics Data System (ADS)

High-precision (TIMS) measurements of U and Th isotope concentrations have been determined on whole rocks and mineral separates from Soufriere volcano on St. Vincent in the Lesser Antilles island arc. The whole rocks display relatively constant U/Th ratios (˜0.5), and are characterised by excess 238U relative to 230Th which is attributed to the addition of U-rich fluids from the subducting slab to the mantle source of the magmas. Mineral isochrons for four recently erupted (<4 ka) rocks yield ages of 46-77 ka and the combined data have an age of 58±7 ka with an initial ( 230Th/ 230Th) ratio of 1.05. Mixing of young magmas, or magma-cumulate mixing, are unlikely to be responsible for these isochronous relationships. Contamination of young, phenocrystic magmas with previously crystallised magma could produce the isochrons, in which case the ages provide maximum and minimum ages, respectively, for these two components. However, no lavas with ( 230Th/ 230Th) ratios of 1.054 have been found and there is no petrographic evidence for mixing or phenocryst-magma disequilibrium. Our preferred interpretation is that the isochrons reflect long magma residence times within the arc crust. Following initial crystallisation, due to heat loss to the wall rocks, the magmas were maintained at a temperature close to their liquidus while 230Th-ingrowth occurred in both the magma and the crystals. Maintenance of a relatively constant temperature requires good insulation by cumulate layers and probably heating from below by influxes of fresh magma which either did not mix with the resident magma or else had an essentially indistinguishable composition. Subtraction of the residence times from the ˜90 ka inferred to have elapsed since fluid addition to the mantle wedge leaves ˜30 ka for transfer through the wedge. Long residence times may typify more evolved lavas that develop in thicker arc crust whereas tholeiitic arc lavas are inferred to have trivial crustal residence times but similar transfer times through the mantle wedge.

Heath, E.; Turner, S. P.; Macdonald, R.; Hawkesworth, C. J.; van Calsteren, P.

1998-07-01

291

Volcano Activity  

NSDL National Science Digital Library

Part of Prentice Hall's Planet Diary, this computer activity covers volcanic activity. Students research the most recent volcanic activity and the locations and names of each volcano. They then find out which tectonic plates the volcanoes are located on or if they are hot spots, and if any are part of the Ring of Fire.

292

Redoubt Volcano  

USGS Multimedia Gallery

Ascending eruption cloud from Redoubt Volcano as viewed to the west from the Kenai Peninsula. The mushroom-shaped plume rose from avalanches of hot debris (pyroclastic flows) that cascaded down the north flank of the volcano. A smaller, white steam plume rises from the summit crater. ...

293

Geochemical and temporal relationships between plutonic and volcanic rocks from the Aleutian arc: a pilot study  

NASA Astrophysics Data System (ADS)

Aleutian arc volcanics are predominantly basaltic while known plutonic rocks are systematically more felsic and have compositions that overlap estimates for the bulk composition of the continental crust. The Aleutian arc is unique among active intra-oceanic arcs in its widespread exposure of Paleogene and Neogene mid-crustal plutonic rocks, as well as the lavas and sediments that these plutons intruded. Thus, understanding the genesis of Aleutian plutonic rocks is a key to understanding continental genesis and evolution via arc magmatism. We have measured major, trace element contents and Sr-Nd-Hf-Pb isotope compositions of 26 mafic to intermediate plutonic rocks, ranging in age from ~32-9 Ma, across the Aleutian arc and compared them with spatially associated Quaternary volcanic rocks. The samples cover a large range of Mg# (73 to 35). Most samples do not show substantial Eu anomalies, and they represent primary magmas rather than differentiated cumulates. Compared to associated volcanics, the plutonic rocks show similar to slightly higher SiO2 and K2O contents at a given Mg#. For many trace elements, the plutonic and volcanic rocks are similar (e.g., elemental concentrations and La/Sm, Th/Nd, Lu/Hf, Dy/Yb ratios). However, the plutonic rocks show on average higher Nd and Hf isotope ratios and lower Pb isotope ratios than volcanic rocks from the same island. The difference in isotope compositions between the plutonic rocks and their volcanic neighbors indicates differences in the mantle sources. This could reflect temporal variation of mantle composition under the Aleutians. Based on U-Pb zircon geochronology of representative samples, the data may indicate decreasing Nd (-Hf) isotope ratios of the sub-Aleutians mantle through time in some regions. However, more data is necessary from plutonic rocks to determine if this will hold up. Alternatively, the compositional differences (e.g. higher Si and K) between the plutonics and the volcanics could reflect different modes of magma transport and emplacement, possibly related to the different mantle sources.

Cai, Y.; Rioux, M. E.; Kelemen, P. B.; Goldstein, S. L.

2013-12-01

294

A magmatic source for fumaroles and diffuse degassing from the summit crater of Teide Volcano (Tenerife, Canary Islands): a geochemical evidence for the 2004-2005 seismic-volcanic crisis  

NASA Astrophysics Data System (ADS)

The present work reports the results of 15 studies of diffuse CO2 degassing performed at Teide Volcano crater (Canary Island, Spain) and the chemical and isotopic compositions of fluids discharged from a fumarolic field located at the top of the volcano as measured between 1991 and 2010. A higher contribution of magmatic gases accompanied by enhanced total diffuse CO2 emissions were observed in relation with a seismic crisis that occurred in Tenerife Island between 2001 and 2005, with the main peak of seismic activity between April and June 2004. A significant pulse in total diffuse CO2 emission was observed at the crater of Teide (up to 26.3 t day-1) in 2001. In December 2003, the chemical composition of the Teide fumarole changed significantly, including the appearance of SO2, an increase in the HCl and CO concentrations and in the C2H6/C2H4 and C3H8/C3H6 ratios, and a decrease in the H2S, CH4, and C6H6 concentrations and in the gas/steam ratio. A few months after a drastic decrease in seismic activity, the SO2, HCl, and CO concentrations and the C2H6/C2H4 and C3H8/C3H6 ratios strongly decreased, whereas the CH4 and C6H6 concentrations and the gas/steam ratios increased. According to the trends shown by both the geochemical parameters and the seismic signals late in the observation period, the risk of a rejuvenation of volcanic activity at Teide is considered to be low. The associated temporal changes in seismic activity and magmatic degassing indicate that geophysical and fluid geochemistry signals in this system are related. Future monitoring programs aimed at mitigating volcanic hazard on Tenerife Island should involve coupled geophysical and geochemical studies.

Melián, G.; Tassi, F.; Pérez, N.; Hernández, P.; Sortino, F.; Vaselli, O.; Padrón, E.; Nolasco, D.; Barrancos, J.; Padilla, G.; Rodríguez, F.; Dionis, S.; Calvo, D.; Notsu, K.; Sumino, H.

2012-08-01

295

Cascade Volcanoes  

USGS Multimedia Gallery

The volcanoes from closest to farthest are Mt. Washington, Three Fingered Jack, Mt. Jefferson. This picture is taken from Middle Sister looking north in the Cascade Range, Three Sisters Wilderness Area, Deschutes National Forest, Oregon....

296

Volcano Preparedness  

MedlinePLUS

... Safety Hurricane Landslide Pet Safety Poisoning Power Outage Terrorism Thunderstorm Tornado Tsunami Volcano Water Safety Wildfire Winter ... all windows, doors, and dampers. Put all machinery inside a garage or barn. Bring animals and livestock ...

297

Management and Conservation Article Expensive Traditions: Energy Expenditure of Aleutian  

E-print Network

a coordinated hazing plan to scare Aleutian cackling geese (Branta hutchinsii leucopareia) from private lands, Branta hutchinsii leucopareia, disturbance, energy expenditure, foraging behavior, hazing, northwestern distributed (sensu Suther- land et al. 2002, Black et al. 2007). Aleutian cackling geese (Branta hutchinsii

Black, Jeff

298

Atmospheric distribution and removal of volcanic ash after the eruption of Kasatochi volcano: A regional model study  

NASA Astrophysics Data System (ADS)

In August 2008, Kasatochi volcano on the Aleutian Islands erupted without much advance warning. Volcanic ash released during this eruption quickly settled out of the atmosphere, mainly into the NE Pacific Ocean. The amount of volcanic ash, as well as the ash fall area and volume into the NE Pacific Ocean, remains speculative, as only a limited number of measurements is available. We used a three-dimensional atmosphere/chemistry-aerosol model to determine the atmospheric distribution of SO2 and volcanic ash and its fallout after the eruption of Kasatochi volcano. In a first step, modeled atmospheric SO2 distributions are compared with satellite data, thereby evaluating the model capabilities to reasonably reproduce atmospheric transport patterns. For modeled volcanic ash mass a considerable reduction of the atmospheric content already occurred by 10 August, the second day after the eruption in accordance with satellite observations. Gravitational settling is the most efficient removal process for volcanic ash mass, exceeding dry and wet deposition by far. Assuming an ash volume of 0.3 km3 released during the eruption of Kasatochi volcano and a median ash particle diameter of 4 ?m, the mass of volcanic ash removed at ground within the 0.1 mm isopach covers an area of 7.6 × 105 km2 over the NE Pacific Ocean and makes up 49% of the removed material out of the atmosphere. The amount of ash and that of iron attached to it is sufficient to explain measured seawater CO2 decrease at the ocean station Papa in August 2008 induced by iron fertilization and subsequent phytoplankton production.

Langmann, Baerbel; ZakšEk, Klemen; Hort, Matthias

2010-01-01

299

Oxygen isotope constraints on the petrogenesis of Aleutian arc magmas  

SciTech Connect

The first measurement of {sup 18}O/{sup 16}O ratios of plagioclase, clinopyroxene, orthopyroxene, and titanomagnetite phenocrysts from modern Aleutian island-arc lavas provides new insight and independent constraints on magma sources and intracrustal processes. Basalts are heterogeneous on the scale of the entire arc and individual volcanic centers. Combined with Sr isotope and trace element data {delta}{sup 18}O{sub plag} values suggest a variable magma source characterized by differences in the mantle wedge or the subducted sediment component along the volcanic front. Seven tholeiitic basalt to rhyodacite lavas from the Seguam volcanic center have nearly identical {delta}{sup 18}O{sub plag} values of 6.0{per thousand} {plus minus} 0.2{per thousand}, reflecting extensive closed-system plagioclase-dominated crystal fractionation. Oxygen isotope thermometry and pyroxene and oxide equilibria indicate that differentiation occurred between 1,150 {plus minus} 100C (basalt) and 950 {plus minus} 100C (rhyodacite). In contrast, {delta}{sup 18}O{sub plag} values of 12 calc-alkalic basaltic andesites and andesites from the smaller Kanaga volcanic center span a broader range of 5.9{per thousand}-6.6{per thousand}, and consist of mostly higher values. Isotopic disequilibrium in the Kanaga system is manifest in two ways: two types of basaltic inclusions with contrasting {delta}{sup 18}O values occur in one andesite, and in two other andesites plagioclase-titanomagnetite and clinopyroxene-titanomagnetite oxygen isotope temperatures are inconsistent.

Singer, B.S.; O'Neil, J.R. (Univ. of Michigan, Ann Arbor (United States)); Brophy, J.G. (Indiana Univ., Bloomington (United States))

1992-04-01

300

Plume Structures in the Central Aleutian Basin  

NASA Astrophysics Data System (ADS)

It is widely accepted that deep ocean basins are suitable for gas hydrate formation with appropriate temperature and pressure conditions but the assumption has been that they lack a sufficient source of methane and thus cannot generate gas hydrates. The Aleutian Basin of the Bering Sea, however, may be an exception due to the influx of methane-generating sediment in the region. The basin is unique in this respect because it is enclosed by the Aleutian Arc on the south as well as land on the north. Terrigenous sediments from these land masses reach the basin, and through accumulation over time, become sources of methane. In this study, we are analyzing a newly acquired seismic data set (Scholl et al, 2012) from the central Aleutian Basin to test for the presence of gas hydrates in the region. Previous seismic evidence from the region led to the discovery of VAMPs - velocity amplitude anomaly structures - characterized by pull-ups and push-downs in the seismic horizons. This study is aimed at testing the hypothesis first proposed by Scholl and Hart (1993) that methane plumes are responsible for the velocity push-downs, while gas hydrates (which condense above the plume) cause the pull-ups. We have constructed geologic models based on a velocity analysis obtained from performing inversions on the pre-stack CMP gathers (using GDMI, a recently developed inversion code from the Naval Research Laboratory). We present a one-dimensional geologic model of rock properties for a region within the study area adjacent to a VAMP structure (but itself lacking the characteristic velocity anomalies). We also show a two-dimensional geologic model for the region in which the VAMP structure is present. The interpretation of a flat-lying geology incorporating a methane hydrate plume guided the creation of the two-dimensional model from the velocity analysis. Our next goal, using full-waveform forward seismic modeling (TESSERAL software), is to generate a synthetic seismic section that reproduces the velocity pull-ups and push-downs present in the field data. Ultimately, this study will yield a much better understanding of the geology of the Aleutian Basin as well as its potential for gas hydrates.

Yankovsky, E. A.; Terry, D. A.; Knapp, C. C.

2013-12-01

301

Mass Wasting in the Western Galapagos Islands  

E-print Network

Oceanic island volcanoes such as those in the Hawaiian, Canary and Galapagos Islands are known to become unstable, causing failures of the subaerial and submarine slopes of the volcanic edifices. These mass wasting events appear to be the primary...

Hall, Hillary

2012-10-19

302

Volcano Baseball  

NSDL National Science Digital Library

In this game, learners are volcanoes that must complete several steps to erupt. Starting at home plate, learners draw cards until they have enough points to move to first base. This process repeats for each learner at each base, and each base demonstrates a different process in a volcano's eruption. The first learner to make it back to home plate erupts and is the winner. This is a good introduction to volcanoes. When learners set up a free account at Kinetic City, they can answer bonus questions at the end of the activity as a quick assessment. As a larger assessment, learners can complete the Smart Attack game after they've completed several activities.

Science, American A.

2009-01-01

303

Seismic-hazard maps for Alaska and the Aleutian Islands  

USGS Publications Warehouse

Probabilistic seismic hazard maps were prepared for Alaska portraying peak horizontal ground acceleration and horizontal spectral response acceleration for 0.2, 0.3, and 1.0 second periods with probabilities of exceedance of 10% in 50 years and 2% in 50 years. This particular data set is for horizontal spectral response acceleration for 1.0 second period with a 10% probability of exceedance in 50 years. All of the maps were prepared by combining hazard derived from spatially- smoothed historic seismicity with hazard from fault-specific sources. The acceleration values contoured are the random horizontal component. The reference site condition is firm rock, defined as having an average shear-wave velocity of 760 m/sec in the top 30 meters corresponding to the boundary between NEHRP site classes B and C. This data set represents the results of calculations of hazard curves for a grid of points with a spacing of 0.1 degrees in latitude and longitude. The grid of points were contoured to produce the final representation of the seismic-hazard.

Wesson, Robert L.; Frankel, Arthur D.; Mueller, Charles S.; Harmsen, Stephen C.

1999-01-01

304

BERING SEA AND ALEUTIAN ISLANDS MANAGEMENT AREA (BSAI) GROUNDFISH FISHERY  

E-print Network

Permit (EFP), and the provisions of the Magnuson-Stevens Act and 50 CFR parts 600 and 679, except, and an authorized representative for each participating vessel, unless terminated earlier by provisions of this EFP Vessels The vessels authorized to participate in this Exempted Fishing Permit (EFP) experiment

305

Mantle and Crustal Sources of Carbon, Nitrogen, and Noble gases in Cascade-Range and Aleutian-Arc Volcanic gases  

USGS Publications Warehouse

Here we report anhydrous chemical (CO2, H2S, N2, H2, CH4, O2, Ar, He, Ne) and isotopic (3He/4He, 40Ar/36Ar, ?13C of CO2, ?13C of CH4, ?15N) compositions of virtually airfree gas samples collected between 1994 and 1998 from 12 quiescent but potentially restless volcanoes in the Cascade Range and Aleutian Arc (CRAA). Sample sites include ?173°C fumaroles and springs at Mount Shasta, Mount Hood, Mount St. Helens, Mount Rainier, Mount Baker, Augustine Volcano, Mount Griggs, Trident, Mount Mageik, Aniakchak Crater, Akutan, and Makushin. The chemical and isotopic data generally point to magmatic (CO2, Ar, He), shallow crustal sedimentary (hereafter, SCS) (CO2, N2, CH4), crustal (He), and meteoric (N2, Ar) sources of volatiles. CH4 clearly comes from SCS rocks in the subvolcanic systems because CH4 cannot survive the higher temperatures of deeper potential sources. Further evidence for a SCS source for CH4 as well as for non-mantle CO2 and non-meteoric N2 comes from isotopic data that show wide variations between volcanoes that are spatially very close and similar isotopic signatures from volcanoes from very disparate areas. Our results are in direct opposition to many recent studies on other volcanic arcs (Kita and others, 1993; Sano and Marty, 1995; Fischer and others, 1998), in that they point to a dearth of subducted components of CO2 and N2 in the CRAA discharges. Either the CRAA volcanoes are fundamentally different from volcanoes in other arcs or we need to reevaluate the significance of subducted C and N recycling in convergent-plate volcanoes.

Symonds, Robert B.; Poreda, Robert J.; Evans, William C.; Janik, Cathy J.; Ritchie, Beatrice E.

2003-01-01

306

Active submarine volcano sampled  

NASA Astrophysics Data System (ADS)

On June 4, 1982, two full dredge hauls of fresh olivine basalt were recovered from the upper flanks of Kavachi submarine volcano, Solomon Islands, from water depths of 400 and 900 m. The shallower dredge site was within one-half mile of the active submarine vent evidenced at the surface by an area of slick water, probably caused by gas emissions. Kavachi is a composite stratovolcano located on the ‘trench-slope break’ or ‘outer-arc high’ of the New Georgia Group, approximately 35 km seaward of the main volcanic line and only 30 km landward of the base of the trench inner wall. The volcano has been observed to erupt every year or two for at least the last 30 years (see cover photographs). An island formed in 1952, 1961, 1965, and 1978, but in each case it rapidly eroded below sea level. The latest eruption was observed by Solair pilots during the several weeks up to and including May 18, 1982.

Taylor, Brian

307

Klyuchevskaya Volcano  

NASA Technical Reports Server (NTRS)

The Klyuchevskaya Volcano on Russia's Kamchatka Peninsula continued its ongoing activity by releasing another plume on May 24, 2007. The same day, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this image, at 01:00 UTC. In this image, a hotspot marks the volcano's summit. Outlined in red, the hotspot indicates where MODIS detected unusually warm surface temperatures. Blowing southward from the summit is the plume, which casts its shadow on the clouds below. Near the summit, the plume appears gray, and it lightens toward the south. With an altitude of 4,835 meters (15,863 feet), Klyuchevskaya (sometimes spelled Klyuchevskoy or Kliuchevskoi) is both the highest and most active volcano on the Kamchatka Peninsula. As part of the Pacific 'Ring of Fire,' the peninsula experiences regular seismic activity as the Pacific Plate slides below other tectonic plates in the Earth's crust. Klyuchevskaya is estimated to have experienced more than 100 flank eruptions in the past 3,000 years. Since its formation 6,000 years ago, the volcano has seen few periods of inactivity. NASA image courtesy the MODIS Rapid Response Team at NASA GSFC. The Rapid Response Team provides daily images of this region.

2007-01-01

308

Iceland Volcano  

Atmospheric Science Data Center

... of which are so thick that they block the penetration of light from CALIPSO's lidar to the surface. The yellow layer near the surface over France is believed to be primarily air pollution, but could also contain ash from the volcano. Highlighting its ...

2013-04-23

309

Dynamics of Carbon Diffuse Degassing Species (CO2, CO & CH4) From the Summit Cone of Teide Volcano, Tenerife, Canary Islands  

NASA Astrophysics Data System (ADS)

CO2 is the predominant carbon component in volcanic gases, and it is the least soluble of the major species in magmatic melts. The two remaining carbon components are CO and CH4. Most of the diffuse emission studies on volcanoes are related to CO2 but significant amounts of other C species in volcanic gases could be emited through the surface environment of volcanoes in a diffuse form. To understand the dynamics of diffuse CO2, CH4 and CO degassing from Teide volcano (3,716 m), soil flux surveys had been performed to evaluate spatial and temporal variations. Diffuse CO2 degassing surveys were yearly performed by means of a portable NDIR sensor since 1999 during the summer term. The observed highest diffuse CO2 emission rates were 3,0 (1999), 12,0 (2000) and 12,6 (2001) Kgm-2d-1. Soil gas samples were also collected at 40 cm depth using a metallic a metallic probe and analyzed within 24 hours by means of VARIAN 2002P and 2003P microGCs. Diffuse CH4 and CO degassing rates were estimated by multiplying CO2 efflux times CH4/CO2 and CO/CO2 ratios at each sampling site, respectively. CH4 efflux showed values of 23 (1999), 123 (2000) and 3,761 (2001) gm-2d-1. For CO efflux, the observed highest values were 1.3 (2000) and 31.4 (2001) gm-2d-1. Diffuse CO2, CH4 and CO degassing spatial distribution seem to be afected by deep processes as well as meteorological fluctuations, specially wind speed. The total output of diffuse CO2 emission for the 2001 survey was 399 td-1 which is relatively higher than previous surveys: 100 (1997), 168 (1999), and 43 (2000) td-1. In the case of CO, diffuse degassing rates from the study area were 7.2 and 136 Kg/d for the 2000 and 2001 surveys, respectively. Diffuse CO/CO2 degassing ratio were similar for both recent surveys: 1.6x10-4 (2000) and 3.4x10-4 (2001). These results are useful for Teide volcano monitoring program.

Gonzalez, P.; Marrero, R.; Melian, G.; Lima, R.; Salazar, J.; Hernandez, P.; Perez, N.

2001-12-01

310

Indirect food web interactions: Sea otters and kelp forest fishes in the Aleutian archipelago  

USGS Publications Warehouse

Although trophic cascades - the effect of apex predators on progressively lower trophic level species through top-down forcing - have been demonstrated in diverse ecosystems, the broader potential influences of trophic cascades on other species and ecosystem processes are not well studied. We used the overexploitation, recovery and subsequent collapse of sea otter (Enhydra lutris) populations in the Aleutian archipelago to explore if and how the abundance and diet of kelp forest fishes are influenced by a trophic cascade linking sea otters with sea urchins and fleshy macroalgae. We measured the abundance of sea urchins (biomass density), kelp (numerical density) and fish (Catch per unit effort) at four islands in the mid-1980s (when otters were abundant at two of the islands and rare at the two others) and in 2000 (after otters had become rare at all four islands). Our fish studies focused on rock greenling (Hexagrammos lagocephalus), the numerically dominant species in this region. In the mid-1980s, the two islands with high-density otter populations supported dense kelp forests, relatively few urchins, and abundant rock greenling whereas the opposite pattern (abundant urchins, sparse kelp forests, and relatively few rock greenling) occurred at islands where otters were rare. In the 2000, the abundances of urchins, kelp and greenling were grossly unchanged at islands where otters were initially rare but had shifted to the characteristic pattern of otter-free systems at islands where otters were initially abundant. Significant changes in greenling diet occurred between the mid-1980s and the 2000 although the reasons for these changes were difficult to assess because of strong island-specific effects. Whereas urchin-dominated communities supported more diverse fish assemblages than kelp-dominated communities, this was not a simple effect of the otter-induced trophic cascade because all islands supported more diverse fish assemblages in 2000 than in the mid-1980s. ?? Springer-Verlag 2005.

Reisewitz, S.E.; Estes, J.A.; Simenstad, C.A.

2006-01-01

311

Eruptions of Hawaiian Volcanoes: Past, Present, and Future  

NSDL National Science Digital Library

The origin of the Hawaiian Islands, recorded eruptions, and eruption patterns are discussed in this United States Geological Survey (USGS) publication. The on-line book also covers volcano monitoring and research, landforms and structures, hazards and benefits, and a discussion of Loihi, Hawaii's newest volcano.

Robert Tilling

312

Space-geodetic evidence for multiple magma reservoirs and subvolcanic lateral intrusions at Fernandina Volcano,  

E-print Network

at Fernandina Volcano, Galápagos Islands Marco Bagnardi1 and Falk Amelung1 Received 23 May 2012; revised 12 Aperture Radar (InSAR) measurements of the surface deformation at Fernandina Volcano, Galápagos (Ecuador magmatic system of the volcano. Through the analysis of spatial and temporal variations of the measured

Amelung, Falk

313

New volcano newsletter planned  

NASA Astrophysics Data System (ADS)

In the beginning, there was Volcano News, an interdisciplinary forum where volcanophiles of all stripes—4professional and amateur, “hard” and “soft” scientists alike— could exchange information. Unfortunately, Volcano News became extinct when editor-publisher Chuck Wood became involved in editing Volcanoes of North America. Janet Cullen Tanaka, a former contributing associate editor of Volcano News is planning the publication of a new interdisciplinary volcano newsletter to cover all facets of volcano studies, from geophysics to emergency management.

314

Hawaiian Volcano Observatory  

USGS Publications Warehouse

Lava from Kilauea volcano flowing through a forest in the Royal Gardens subdivision, Hawai'i, in February 2008. The Hawaiian Volcano Observatory (HVO) monitors the volcanoes of Hawai'i and is located within Hawaiian Volcanoes National Park. HVO is one of five USGS Volcano Hazards Program observatories that monitor U.S. volcanoes for science and public safety. Learn more about Kilauea and HVO at http://hvo.wr.usgs.gov.

Venezky, Dina Y.; Orr, Tim

2008-01-01

315

The petrogenesis of island arc basalts from Gunung Slamet volcano, Indonesia: Trace element and sup 87 Sr/ sup 86 Sr constraints  

SciTech Connect

Selected major and trace elements, rare earth element (REE) and {sup 87}Sr/{sup 86}Sr data are presented for arc basalts from Gunung Slamet volcano, Java, Indonesia. On the basis of stratigraphy, trace element content, Zr/Nb, and {sup 87}Sr/{sup 86}Sr ratios, Slamet basalts can be broadly categorized into high abundance magma (HAM) and low abundance magma (LAM) types. Provided the quantities of immobile trace elements (in aqueous systems) such as Nb, Hf and Zr in the mantle wedge and ensuing magmas are unaffected by additions from subducted lithosphere or overlying arc crust, a model may be developed whereby LAM are generated by higher degrees of melting in the mantle wedge (13%) compared to HAM (7%). Hf/Nb or Zr/Nb ratio systematics indicate that prior to metasomatism by the underlying lithosphere, the Slamet mantle wedge was similar in chemical character to transitional-MORB source mantle.

Vukadinovic, D.; Nicholls, I.A. (Monash Univ., Victoria (Australia))

1989-09-01

316

A spatter-forming, large-scale paroxysm at Stromboli Volcano (Aeolian Islands, Italy): insight into magma evolution and eruption dynamics  

NASA Astrophysics Data System (ADS)

This study focuses on a pyroclastic sequence related to a large-scale paroxysm that occurred during the seventeenth century ad and which can be considered one of the most powerful and hazardous explosive events at the volcano in the past few centuries. Paroxysms are energetic, short-lived explosions which sporadically interrupt normal Strombolian activity at Stromboli and commonly erupt a deep-derived, volatile-rich crystal-poor high-potassium basalt ("low porphyricity" (LP)), together with a shallow, degassed crystal-rich high-potassium to shoshonitic basalt ("high porphyricity" (HP)), which feed normal activity at the volcano. The studied deposit, crops out along the flanks of Sciara del Fuoco and, from base to top, consists of: (1) a layer of HP and LP ash and lapilli; (2) an unwelded layer of coarse HP lapilli and flattened dark scoriae; (3) weakly welded spatter made up of dense HP pyroclasts at the base, overlain by strongly vesicular LP clasts. The textural and chemical zoning of minerals and the glass chemistry of the LP products record repeated mafic recharge events, mixing with an old mushy body and episodes of rapid crystallization due to sudden degassing. Collapse of a foam layer originated by deep degassing probably triggered this large-scale, spatter-forming paroxysm. Decompression induced rapid degassing and vesiculation of the deep volatile-rich magma. The rapid ascent of the foamy magma blob pushed the shallow HP magma out and finally produced a fire fountain that emplaced the LP portion of the spatter.

La Felice, Sonia; Landi, Patrizia

2011-11-01

317

The Anatahan volcano-monitoring system  

Microsoft Academic Search

A real-time 24\\/7 Anatahan volcano-monitoring and eruption detection system is now operational. There had been no real-time seismic monitoring on Anatahan during the May 10, 2003 eruption because the single telemetered seismic station on Anatahan Island had failed. On May 25, staff from the Emergency Management Office (EMO) of the Commonwealth of the Northern Mariana Islands and the U. S.

J. N. Marso; A. B. Lockhart; R. A. White; S. K. Koyanagi; F. A. Trusdell; J. T. Camacho; R. Chong

2003-01-01

318

Volcano Lovers  

NSDL National Science Digital Library

This Why Files article explores volcanoes and volcanic eruptions. Topics covered include: Alaska's Pavlof and its threat to jet engines; Mexico City's restless neighbor, Popocatepetl (El Popo); underground volcanic processes; modern forecasting of eruptions; various volcanic phenomena and features; large flood basalt areas around the world; California's volcanically active area, Long Valley Caldera and Mammoth Mountain; Indonesia's Krakatau eruption in 1883, which was the world's largest historical eruption; Krakatau's ecological contribution to the study of colonization of sterile lands; and central Mexico's Paricutin which was witnessed emerging from a farmer's field in 1943. Three scientists were interviewed for this article.

Tenenbaum, David

1997-01-02

319

Interactions Between Separated Volcanoes  

NASA Astrophysics Data System (ADS)

The Japan Meteorological Agency installed and operates a network of borehole strainmeters in south-east Honshu. One of these instruments is on Izu-Oshima, a volcanic island at the northern end of the Izu-Bonin arc. That strainmeter recorded large strain changes associated with the 1986 eruption of Miharayama on the island. Miyake-jima, about 70 km south of Izu-Oshima, erupted in 1983. No deformation monitoring was available on Miyake-jima but several changes occurred in the strain record at Izu-Oshima. There was a clear change in the long-term strain rate 2 days before the Miyake eruption. Frequent short period events recorded by the strainmeter showed a marked change in their character. The Izu-Oshima strainmeter showed that, over the period from 1980 to the 1986 eruption, the amplitude of the solid earth tides increased by almost a factor of two. At the time of the Miyake eruption, the rate of increase of the tidal amplitude also changed. While all of these changes were observed on a single instrument, they are very different types of change. From a number of independent checks, we can be sure that the strainmeter did not experience any change in performance at that time. Thus it recorded a change in deformation behavior in three very different frequency bands: over very long term, at tidal periods ( ~ day) and at very short periods (minutes). It appears that the distant eruption in 1984 had an effect on the magmatic system under Izu-Oshima. More recent tomographic and seismic attenuation work in the Tohoku (northern Honshu) area has show the existence of a low velocity, high attenuation horizontally elongated structure under the volcanic front. If such a structure exists in the similar tectonic setting for these volcanoes, it could provide a mechanism for communication between the volcanoes.

Linde, A. T.; Sacks, I. S.; Kamigaichi, O.

2002-05-01

320

Newberry Volcano—Central Oregon's Sleeping Giant  

USGS Publications Warehouse

Hidden in plain sight, Oregon's massive Newberry Volcano is the largest volcano in the Cascades volcanic arc and covers an area the size of Rhode Island. Unlike familiar cone-shaped Cascades volcanoes, Newberry was built into the shape of a broad shield by repeated eruptions over 400,000 years. About 75,000 years ago a major explosion and collapse event created a large volcanic depression (caldera) at its summit. Newberry last erupted about 1,300 years ago, and present-day hot springs and geologically young lava flows indicate that it could reawaken at any time. Because of its proximity to nearby communities, frequency and size of past eruptions, and geologic youthfulness, U.S. Geological Survey scientists are working to better understand volcanic activity at Newberry and closely monitor the volcano for signs of unrest.

Donnelly-Nolan, Julie M.; Stovall, Wendy K.; Ramsey, David W.; Ewert, John W.; Jensen, Robert A.

2011-01-01

321

Wildfowl & Wetlands Trust Wildfowl (2011) 61: 329 Recovery of the Aleutian Cackling Goose  

E-print Network

Branta hutchinsii leucopareia: 10-year review and future prospects ANNE E. MINI1,2, DOMINIC C. BACHMAN1-mail: Jeff.Black@humboldt.edu Abstract Aleutian Cackling Geese Branta hutchinsii leucopareia were feared are especially important. The Aleutian Cackling Goose Branta hutchinsii leucopareia (formerly the Aleutian Canada

Black, Jeff

322

Nyiragonga Volcano  

NASA Technical Reports Server (NTRS)

This image of the Nyiragonga volcano eruption in the Congo was acquired on January 28, 2002 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters about 50 to 300 feet ), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet.

Image: A river of molten rock poured from the Nyiragongo volcano in the Congo on January 18, 2002, a day after it erupted, killing dozens, swallowing buildings and forcing hundreds of thousands to flee the town of Goma. The flow continued into Lake Kivu. The lave flows are depicted in red on the image indicating they are still hot. Two of them flowed south form the volcano's summit and went through the town of Goma. Another flow can be seen at the top of the image, flowing towards the northwest. One of Africa's most notable volcanoes, Nyiragongo contained an active lava lake in its deep summit crater that drained catastrophically through its outer flanks in 1977. Extremely fluid, fast-moving lava flows draining from the summit lava lake in 1977 killed 50 to 100 people, and several villages were destroyed. The image covers an area of 21 x 24 km and combines a thermal band in red, and two infrared bands in green and blue.

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

2001-01-01

323

Characterization of Aleutian disease virus as a parvovirus.  

PubMed Central

We characterized a strain of Aleutian disease virus adapted to growth in Crandall feline kidney cells at 31.8 degrees C. When purified from infected cells, Aleutian disease virus had a density in CsCl of 1.42 to 1.44 g/ml and was 24 to 26 nm in diameter. [3H]thymidine could be incorporated into the viral genome, and the viral DNA was then studied. In alkaline sucrose gradients, Aleutian disease virus DNA was a single species that cosedimented at 15.5S with single-stranded DNA from adeno-associated virus. When the DNA was analyzed on neutral sucrose gradients, a single species was again observed, which sedimented at 21S and was clearly distinct from 16S duplex adeno-associated virus DNA. A similar result was obtained even after incubation under annealing conditions, implying that the bulk of Aleutian disease virus virions contained a single non-complementary strand with a molecular weight of about 1.4 X 10(6). In addition, two major virus-associated polypeptides with molecular weights of 89,100 and 77,600 were demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of virus purified from infected cultures labeled with [35S]methionine. These data suggest that Aleutian disease virus is a nondefective parvovirus. Images PMID:6252342

Bloom, M E; Race, R E; Wolfinbarger, J B

1980-01-01

324

Soufriere Hills Volcano  

NASA Technical Reports Server (NTRS)

In this ASTER image of Soufriere Hills Volcano on Montserrat in the Caribbean, continued eruptive activity is evident by the extensive smoke and ash plume streaming towards the west-southwest. Significant eruptive activity began in 1995, forcing the authorities to evacuate more than 7,000 of the island's original population of 11,000. The primary risk now is to the northern part of the island and to the airport. Small rockfalls and pyroclastic flows (ash, rock and hot gases) are common at this time due to continued growth of the dome at the volcano's summit.

This image was acquired on October 29, 2002 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER images Earth to map and monitor the changing surface of our planet.

ASTER is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring of dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Bjorn Eng of JPL is the project manager. The Terra mission is part of NASA's Earth Science Enterprise, a long- term research effort to understand and protect our home planet. Through the study of Earth, NASA will help to provide sound science to policy and economic decision-makers so as to better life here, while developing the technologies needed to explore the universe and search for life beyond our home planet.

Size: 40.5 x 40.5 km (25.1 x 25.1 miles) Location: 16.7 deg. North lat., 62.2 deg. West long. Orientation: North at top Image Data: ASTER bands 1,2, and 3. Original Data Resolution: 15 m Date Acquired: October 29, 2002

2002-01-01

325

Rifting, recurrent landsliding and Miocene structural reorganization on NW-Tenerife (Canary Islands)  

Microsoft Academic Search

We studied mechanisms of structural destabilization of ocean island flanks by considering the linkage between volcano construction and volcano destruction, exemplified by the composite Teno shield volcano on Tenerife (Canary Islands). During growth, Tenerife episodically experienced giant landslides, genetically associated with rifting and preferentially located between two arms of a three-armed rift system. The deeply eroded late Miocene Teno massif

T. Walter; H.-U. Schmincke

2002-01-01

326

Episodes of Aleutian Ridge explosive volcanism  

USGS Publications Warehouse

Earlier workers have overlooked deep-sea bentonite beds when unraveling the Cenozoic volcanic history of an area. In the North Pacific, identification of Miocene and older volcanic episodes is possible only if both altered (bentonite) and unaltered ash beds are recognized. Our study, which includes bentonite beds, shows that volcanism on the Aleutian Ridge and Kamchatka Peninsula has been cyclic. Volcanic activity seems to have increased every 2.5 ?? 10 6 years for the past 10 ?? 106 years and every 5.0 ?? 106 years for the time span from 10 to 20 ?? 10 6 years ago. The middle and late Miocene and the Quaternary were times of greatly increased volcanic activity in the North Pacific and elsewhere around the Pacific Basin. The apparent absence of a volcanic record before the late Miocene at Deep Sea Drilling Project site 192 is the result not of plate motion, as suggested by Stewart and by Ninkovich and Donn, but rather of the diagenesis of ash layers. Major, apparently global volcanic episodes occurred at least twice in the last 20 ?? 106 years. Yet, only one major glacial epoch (the Pleistocene) has occurred. Therefore, even though glaciation coincided with an increase in Quaternary volcanism, the increased volcanism itself may not have been the primary cause of global cooling. Copyright ?? 1978 AAAS.

Hein, J.R.; Scholl, D. W.; Miller, J.

1978-01-01

327

Comparison of the submarine landslide by the sector collapse of Oshima-Oshima island in the northern part of Japan with the debris avalanche of off Kaimon volcano in the southern part of Japan and several landslide.  

NASA Astrophysics Data System (ADS)

Oshima-Oshima island is an active volcano located in the eastern margin of the Japan Sea off Hokkaido. Oshima-Oshima consists of Higashi-yama somma, Nishi-yama somma, and the central cone. The latest eruption occurred at the 18th century. In a huge eruption on August 1741 , Nishiyama of western part of Oshima- Oshima collapsed toward the northern submarine slope , and the horseshoe shape caldera was formed. It is proposed by Katsui et al.(1977) , Satake and Kato(2001) that Japan Sea tsunami in 1741 was generated by this collapse. Detailed swath bathymetry surveys have been conducted around Oshima-Oshima by Hydrographic and Oceanographic Department of Japan in 1993. As a result, a large area of debris avalanche deposits has been discovered on the northern submarine flanks of Oshima-Oshima island. In addition, sidescan sonar surveys was also conducted by Hydrographic and Oceanographic Department of Japan and University of Tokyo in 1995. In 1997, the lower part of the debris avalanche deposit was investigated using submersible 'Shinkai 2000' by JAMSTEC(Japan Agency for Marine-Earth Science and Technology). It was confirmed that those deposits were Oshima origins (Kato,1997). We compiled and analyzed using these detailed bathymetry data and sidescan data. As a result , we clarified a detailed geographical features of debris avalanche and the limit of their distribution. Scarp of caldera rim continues to approximately 1100m under the sea. Oshima-Oshima has diameter of approximately 16km. Oshima-Oshima has also an estimated total edifice volume (subaerial and submarine) of 127km3 and rises about 2200m from its base in 1500m depth of water. Northern part of Oshima-Oshima, the scarp of caldera rim on the subaerial area consecutively continues up to about 1100m of depth. The scarp has 100m-300m high, and width of landslide valley is about 2km. Hammocky surface starts from 1100m depth of water. Sea mount of like spur is composed of the collapse deposits has almost extended to the whole area in the trough deeper than 1100m. Debris avalanche deposits have been identified up to 2200m depth and 24km from Oshima-Oshima island, H/L is approximately 0.12. Maximum sizes of debris avalanche block is up to 1-2km width and 100m high. We divided the debris avalanche deposits into three areas (Type A-C) by the topography. Type-A is the main sedimentary area in front of the collapse area and the form is like a spur with 100 to 130m height. Type-B has a form like a knoll or block. Type-C shows gradual slope containing a small rise. We compared these feature with debris avalanche of off Kaimon volcano in the southern part of Japan and the other debris avalanche (landslide, submarine landslide).

Kaji, T.; Yamazaki, H.; Kato, Y.

2007-12-01

328

Heavy metals in fish from the Aleutians: interspecific and locational differences.  

PubMed

The objectives of this study were to examine levels of arsenic, cadmium, lead, mercury and selenium in edible tissue of seven species of marine fish collected from several Aleutian islands (in 2004) to determine: (1) interspecific differences, (2) locational differences (among Aleutian Islands), (3) size-related differences in any metal levels within a species, and (4) potential risk to the fish or to predators on the fish, including humans. We also compared metals levels to those of three other fish species previously examined in detail, as well as examining metals in the edible tissue of octopus (Octopus dofleini). Octopus did not have the highest levels of any metal. There were significant interspecific differences in all metal levels among the fish species, although the differences were less than an order of magnitude, except for arsenic (mean of 19,500 ppb in Flathead sole, Hippoglossoides elassodon). Significant intraisland variation occurred among the four sites on Amchitka, but there was not a consistent pattern. There were significant interisland differences for some metals and species. Mercury levels increased significantly with size for several species; lead increased significantly for only one fish species; and cadmium and selenium decreased significantly with size for halibut (Hippoglossus stenolepis). The Alaskan Department of Health and Social Services supports unrestricted consumption of most Alaskan fish species for all people, including pregnant women. Most mean metal concentrations were well below the levels known to adversely affect the fish themselves, or predators that consume them (including humans), except for mercury in three fish species (mean levels just below 0.3 ppm), and arsenic in two fish species. However, even at low mercury levels, people who consume fish almost daily will exceed guideline values from the Centers for Disease Control and the Environmental Protection Agency. PMID:24727640

Burger, Joanna; Gochfeld, Michael; Jeitner, Christian; Pittfield, Taryn; Donio, Mark

2014-05-01

329

Super Volcano  

NSDL National Science Digital Library

Deep beneath the surface of Earth lies one of the most destructive and yet least understood of the natural forces on the planet: the super volcano. This radio broadcast presents discussions with scientists at Yellowstone National Park who are investigating this potentially devastating natural phenomenon. Yellowstone National Park is one of the largest supervolcanoes in the world. It last erupted 640,000 years ago and scientists are now predicting that the next eruption may not be far off. To discover more, a new volcanic observatory has been built in the park to monitor the extreme volcanic activity going on beneath the surface of this much visited destination. The broadcast is 30 minutes in length.

330

Tsunami deposits related to Fogo flank failure (Cape Verde Islands)  

Microsoft Academic Search

Oceanic shield volcanoes are prone to massive flank failures involving dozens to hundreds of km³. Fogo active volcano (Cape Verde Islands) is nested in a large horseshoe shaped caldera opened to the east. This volcano-tectonic structure could be the result of past failures of the edifice (Day et al., 1999). Debris avalanche deposits were identified offshore (Masson et al., 2008).

Raphael Paris; Joel Chevalier; Franck Lavigne

2010-01-01

331

4D seismic structure beneath Spurr volcano, Alaska  

NASA Astrophysics Data System (ADS)

Mount Spurr is a large volcano located 125 km west of Anchorage, Alaska. This dominantly andesitic stratovolcano with summit elevation of 3374 m is the highest volcano of the Aleutian Arc. Two historical eruptions of Spurr volcano have occurred in 1953 and 1992. Moreover, from July 2004 to February 2006 continuous non-eruptive activity was observed. Since 1988 the Alaska Volcano Observatory (AVO) collects information about Alaska seismicity. In this work we present evolution of the seismic structure beneath Spurr volcano obtained from 4D seismic tomography. In total 222605 rays (129387 P and 93218 S rays) coming from 17068 earthquakes and registered by 26 station of AVO seismic network were used for the tomographic inversion. After analysis of the seismic and volcano activity, 5 time periods were chosen. Variations of P and S wave velocity anomalies and Vp/Vs ratio in this 5 time periods were obtained after simultaneous iterative inversion of one combined matrix. Smoothness of the velocity anomalies variation in space and time are controlled by two additional matrix block. Results reveal clear correlation of the seismic structure and volcanic activity. In the first (October 1989 - July 1996) and fourth (January 2004 - January 2007) time periods, characterized by high activity, a prominent vertical channel directly beneath volcano is observed on the vertical sections. This channel is characterized by very high values of Vp/Vs ratio (increased P wave and decreased S wave velocities). During the three other periods with no volcanic activity, when the relaxation of the media took place, seismic structure becomes more homogeneous without strong velocity anomalies. Special attention is paid to estimation of the model resolution in different time periods and analysis of possible artifacts due to different ray coverage in different periods. Therefore a lot synthetic and real data tests were performed.

Jakovlev, Andrey; Koulakov, Ivan; West, Michael

2013-04-01

332

Seismicity and seismic structure at Okmok Volcano, Alaska  

USGS Publications Warehouse

Okmok volcano is an active volcanic caldera located on the northeastern portion of Umnak Island in the Aleutian arc, with recent eruptions in 1997 and 2008. The Okmok area had ~900 locatable earthquakes between 2003 and June 2008, and an additional ~600 earthquakes from the beginning of the 2008 eruption to mid 2009, providing an adequate dataset for seismic tomography. To image the seismic velocity structure of Okmok, we apply waveform cross-correlation using bispectrum verification and double-difference tomography to a subset of these earthquakes. We also perform P-wave attenuation tomography using a spectral decay technique. We examine the spatio-temporal characteristics of seismicity in the opening sequence of the 2008 eruption to investigate the path of magma migration during the establishment of a new eruptive vent. We also incorporate the new earthquake relocations and three-dimensional (3D) velocity model with first-motion polarities to compute focal mechanisms for selected events in the 2008 pre-eruptive and eruptive periods. Through these techniques we obtain precise relocations, a well-constrained 3D P-wave velocity model, and a marginally resolved S-wave velocity model. We image a main low Vp and Vs anomaly directly under the caldera consisting of a shallow zone at 0–2 km depth connected to a larger deeper zone that extends to about 6 km depth. We find that areas of low Qp are concentrated in the central to southwestern portion of the caldera and correspond fairly well with areas of low Vp. We interpret the deeper part of the low velocity anomaly (4–6 km depth) beneath the caldera as a magma body. This is consistent with results from ambient noise tomography and suggests that previous estimates of depth to Okmok's magma chamber based only on geodetic data may be too shallow. The distribution of events preceding the 2008 eruption suggest that a combination of overpressure in the zone surrounding the magma chamber and the introduction of new material from below were jointly responsible for the explosive eruption. Magma escaping from the top of the main magma chamber likely reacted with both a smaller shallow pod of magma and groundwater on its way up below the Cone D area. The earthquakes in the 2008 pre-eruptive and eruptive periods are found to have a mixture of strike-slip, oblique normal, and oblique thrust mechanisms, with a dominant P-axis orientation that is nearly perpendicular to the regional tectonic stress. This may indicate that the stresses related to magmatic activity locally dominated regional tectonic forces during this time period.

Ohlendorf, Summer J.; Thurber, Clifford H.; Pesicek, Jeremy D.; Prejean, Stephanie G.

2014-01-01

333

Types of Volcanoes  

NSDL National Science Digital Library

This volcano resource introduces the six-type classification system and points out weaknesses of the classic three-type system. The six types of volcanoes are shield volcanoes, strato volcanoes, rhyolite caldera complexes, monogenetic fields, flood basalts, and mid-ocean ridges. For each type of volcano there is a description of both structure and dynamics along with examples of each. You can account for more than ninty percent of all volcanoes with these six types. Additionally, any system will be more useful if you use modifiers from the other potential classification schemes with the morphological types.

334

Eruption dynamics of the 7.7 ka Driftwood pumice-fall suggest mafic injection is a common eruption mechanism for Makushin Volcano, Alaska  

NASA Astrophysics Data System (ADS)

Makushin Volcano on Unalaska Island, AK is potentially the most threatening volcano in the Aleutian chain, being close to the largest Aleutian towns of Dutch Harbor and Unalaska. This study reports the eruption chronology and triggering mechanism for the most recent highly explosive event, the 7.7 ka Driftwood Pumice-fall event. The Driftwood Pumice reaches thicknesses of over 2 m, and isopach contours estimate a total deposit volume of 0.3-0.9 km3, covering an area of at least 8100 km2. These reconstructions show an eruption on the scale of the 1980 Mt. St. Helens eruption, with a VEI of 4-5. In the field, the deposit was divided into four stratigraphic horizons from bottom to top, and tephra within these layers becomes systematically more mafic upward through the section, ranging from a basal low-SiO2 dacite (64 wt.% SiO2) to an upper medium-SiO2 andesite (61.5 wt.% SiO2). High-Ca plagioclase (An75-83) and high-Mg olivine (Mg69-75) grains within the pumice are in great disequilibrium with the dacitic glass (64-69 wt.% SiO2), suggesting their origin in a more mafic magma. Geochemical trends, disequilibrium mineral populations, and mineral zonation patterns within these plagioclase and olivine xenocrysts show evidence of magma mixing between a bulk siliceous magma chamber and a mafic injection. The amount of the mafic component increases upward within the deposit, ranging from 0-25% throughout the section. The mafic injection is calculated to have been ~110-200 °C hotter than the siliceous magma chamber. The thermal pulse provided by the injection likely initiated convection and volatile exsolution within the siliceous magma body, ultimately causing the Driftwood Pumice eruption. Diffusion rates based on the thickness of lower-Mg rim zonations (<10 µm thick rims of Mg64) in the olivine xenocrysts show a lag-time of ~1 year between the basaltic injection and the resulting eruption. Similar delays between mafic injections and eruptions are seen in numerous other volcanic systems where magma mixing has been cited as the eruption trigger. The Driftwood Pumice is stratigraphically sandwiched between numerous smaller ashfalls, many of which consist of light-dark ash couplets. The color and compositional differences between the layers of these ash couplets are similar to differences within the Driftwood Pumice horizons, though the Driftwood Pumice is significantly thicker than the couplets. The repeated occurrences of light tephra overlain by dark, more mafic tephra suggest that magma mixing via a mafic injection is a common mechanism for sparking Makushin eruptions.

Lerner, A.; Crowley, P.; Hazlett, R. W.; Nicolaysen, K. E.

2010-12-01

335

MTU Volcanoes Page  

NSDL National Science Digital Library

Michigan Technological University Volcanoes Page, which is sponsored by the Keweenaw Volcano Observatory, aims to provide information about volcanoes to the public and to complement other informational sites on the Web. Visitors will find information on what a volcano is, currently active volcanoes throughout the world, remote sensing of volcanoes, volcanic humor, and much more. The volcano hazard section of the site contains primarily original content that provides a Basic Guide to Volcanic Hazards and details Volcanic Cloud Hazards to Aviation, while offering volcano safety recommendations to the public. Although the site could use an update to its layout and organization, it does do a good job of presenting an interesting mix of unique information.

336

Geography World - Volcanoes  

NSDL National Science Digital Library

This portal provides links to an extensive list of volcano-related websites for the United States and around the world. Users can access articles, maps, glossaries, webcams, a dictionary of volcanoes, and many other resources.

337

Ol Doinyo Lengai Volcano  

USGS Multimedia Gallery

Scientists from the Volcano Disaster Assistance Program team and the Geological Survey of Tanzania take a sample of the most recent ashfall from Ol Doinyo Lengai as the volcano looms in the background....

338

Volcanoes: Annenberg Media Project  

NSDL National Science Digital Library

Volcanoes is an exhibit from the Annenberg Media Project that provides a wealth of information about volcanoes and includes sections such as Melting Rocks, the Dynamic Earth, and Forecasting. Interactive exercises enable the user to learn how rock turns into magma, how to locate volcanoes, and how to decide if building a project near a volcano is safe. Quicktime videos are used for each of the six categories to illustrate the points outlined in the text.

339

Modelling and Remote Sensing of Ash and Sulfur Dioxide from the 2008 Kasatochi Volcano Eruption  

NASA Astrophysics Data System (ADS)

We simulated the formation, evolution and transport of volcanic ash and sulfur dioxide (SO2) from the 2008 eruption of Kasatochi volcano using the Weather Research Forecasting (WRF) with inline Chemistry (WRF-Chem). The volcano is located at the western Aleutian arc, and the ash and SO2 plume dispersed well over the North American continent. Using the Regional Acid Deposition Model, version 2 (RADM2) within WRF-Chem, we describe the conversion of sulfur dioxide to sulfate aerosols. WRF-Chem was further set up to use the GOCART aerosol module for predicting the fate of the sulfate aerosol downwind from the volcano. We validated model output with temporal and spatial comparisons to data available from various satellite borne sensors, including OMI, AIRS and MODIS. Temporal and special agreement between WRF and sensor data is discussed and the feasibility of using WRF-Chem as a tool for volcanic sulfur dioxide and ash prediction is assessed.

Egan, S.; Stuefer, M.

2013-12-01

340

Monitoring Active Volcanoes  

NSDL National Science Digital Library

This United States Geological Survey (USGS) publication discusses the historic and current monitoring of active volcanoes around the globe. Techniques to measure deviations in pressure and stress induced by subterranean magma movement, as well as other technologies, explain the ways in which researchers monitor and predict volcanoes. Case studies of volcanoes such as Mt. St. Helens, El Chichon, Mauna Loa, and others are discussed.

Tilling, Robert

341

A Scientific Excursion: Volcanoes.  

ERIC Educational Resources Information Center

Reviews an educationally valuable and reasonably well-designed simulation of volcanic activity in an imaginary land. VOLCANOES creates an excellent context for learning information about volcanoes and for developing skills and practicing methods needed to study behavior of volcanoes. (Author/JN)

Olds, Henry, Jr.

1983-01-01

342

Where are the Volcanoes?  

NSDL National Science Digital Library

This formative assessment item discusses common misconceptions about volcano location around the world. Resources include background and content information as well as alignment to the National Science Education Standards. The probe could easily be modified to be used with a study of earthquakes instead of volcanoes. Teachers can access other resources including facts about volcanoes and lesson ideas.

Jessica Fries-Gaither

343

How Volcanoes Work  

NSDL National Science Digital Library

This educational resource describes the science behind volcanoes and volcanic processes. Topics include volcanic environments, volcano landforms, eruption dynamics, eruption products, eruption types, historical eruptions, and planetary volcanism. There are two animations, over 250 images, eight interactive tests, and a volcano crossword puzzle.

344

USGS Hawaiian Volcano Observatory  

USGS Multimedia Gallery

The USGS Hawaiian Volcano Observatory is perched on the rim of Kilauea Volcano's summit caldera (next to the Thomas A. Jaggar Museum in Hawai'i Volcanoes National Park), providing a spectacular view of the active vent in Halema‘uma‘u Crater....

345

How Volcanoes Work: Historical Eruptions  

NSDL National Science Digital Library

This information about major volcanic eruptions in history covers events from the civilization-destroying explosion at Santorini in about 1630 BC, to the killing cloud of carbon dioxide at Lake Nyos Cameroon in 1986. The site documents the seven deadliest eruptions in history. Other eruptions include Mount Pelee on the island of Martinique in 1902, Mount Saint Helens in Washington State in 1980, Nevado Del Ruiz Columbia in 1985, the Mexican eruption of Paricutin in 1943, and the 1883 explosion that nearly obliterated the island of Krakatau in what is now Indonesia. For each eruption the site offers information about the type of volcano, the type of eruption, the products of the eruption, and the relation to plate tectonics. In addition, historical background is provided when appropriate.

Victor Camp

346

Ice-volcano interactions Eyjafjallajkull volcano, Iceland  

E-print Network

Ice-volcano interactions in Eyjafjallajökull volcano, Iceland Eyjólfur Magnússon1, Magnús Tumi Sciences, University of Iceland, Reykjavík, Iceland 2. Institute of Earth Sciences, University of Iceland, Reykjavík, Iceland 3. Icelandic Coast Guard SPIRIT workshop 29&30 April 2010, Toulouse Picture by Eyjólfur

Berthier, Etienne

347

Volcano Vents  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Released 5 May 2003

This low-relief shield volcano imaged with the THEMIS visible camera has two large vents which have erupted several individual lava flows. The positions of the origins of many of the flows indicate that it is probable that the vents are secondary structures that formed only after the shield was built up by eruptions from a central caldera.

Image information: VIS instrument. Latitude 17.6, Longitude 243.6 East (116.4 West). 19 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

2003-01-01

348

Identification of a nonvirion protein of Aleutian disease virus: mink with Aleutian disease have antibody to both virion and nonvirion proteins.  

PubMed Central

We studied Aleutian disease virus polypeptides in Crandall feline kidney (CRFK) cells. When CRFK cells labeled with [35S]methionine at 60 h postinfection were studied by immunoprecipitation with sera from infected mink, the major Aleutian disease virus virion polypeptides (p85 and p75) were consistently identified, as was a 71,000-dalton nonvirion protein (p71). The peptide maps of p85 and p75 were similar, but the map of p71 was different. p85, p75, and p71 were all precipitated by sera from Aleutian disease virus-infected mink, including those with signs of progressive disease, but heterologous sera raised against purified Aleutian disease virus did not precipitate the nonvirion p71. These results indicated that the nonvirion p71 was unrelated to p85 and p75 and further suggested that mink infected with Aleutian disease virus develop antibody to nonvirion, as well as structural, viral proteins. Images PMID:6287034

Bloom, M E; Race, R E; Wolfinbarger, J B

1982-01-01

349

Volcanic geology of Furnas Volcano, São Miguel, Azores  

Microsoft Academic Search

Furnas is the easternmost of the three active central volcanoes on the island of São Miguel in the Azores. Unlike the other two central volcanoes, Sete Cidades and Fogo, Furnas does not have a well-developed edifice, but consists of a steep-sided caldera complex 8×5 km across. It is built on the outer flanks of the Povoação\\/Nordeste lava complex that forms

J. E Guest; J. L Gaspar; P. D Cole; G Queiroz; A. M Duncan; N Wallenstein; T Ferreira; J.-M Pacheco

1999-01-01

350

The Anatahan volcano-monitoring system  

NASA Astrophysics Data System (ADS)

A real-time 24/7 Anatahan volcano-monitoring and eruption detection system is now operational. There had been no real-time seismic monitoring on Anatahan during the May 10, 2003 eruption because the single telemetered seismic station on Anatahan Island had failed. On May 25, staff from the Emergency Management Office (EMO) of the Commonwealth of the Northern Mariana Islands and the U. S. Geological Survey (USGS) established a replacement telemetered seismic station on Anatahan whose data were recorded on a drum recorder at the EMO on Saipan, 130 km to the south by June 5. In late June EMO and USGS staff installed a Glowworm seismic data acquisition system (Marso et al, 2003) at EMO and hardened the Anatahan telemetry links. The Glowworm system collects the telemetered seismic data from Anatahan and Saipan, places graphical display products on a webpage, and exports the seismic waveform data in real time to Glowworm systems at Hawaii Volcano Observatory and Cascades Volcano Observatory (CVO). In early July, a back-up telemetered seismic station was placed on Sarigan Island 40 km north of Anatahan, transmitting directly to the EMO on Saipan. Because there is currently no population on the island, at this time the principal hazard presented by Anatahan volcano would be air traffic disruption caused by possible erupted ash. The aircraft/ash hazard requires a monitoring program that focuses on eruption detection. The USGS currently provides 24/7 monitoring of Anatahan with a rotational seismic duty officer who carries a Pocket PC-cell phone combination that receives SMS text messages from the CVO Glowworm system when it detects large seismic signals. Upon receiving an SMS text message notification from the CVO Glowworm, the seismic duty officer can use the Pocket PC - cell phone to view a graphic of the seismic traces on the EMO Glowworm's webpage to determine if the seismic signal is eruption related. There have been no further eruptions since the monitoring system was installed, but regional tectonic earthquakes have provided frequent tests of the system. Reliance on a Pocket PC - cell phone requires that the seismic duty officer remain in an area with cell phone coverage. With this monitoring method, the USGS is able to provide rapid notice of an Anatahan eruption to the EMO and the Washington Volcano Ash Advisory Center. Reference Marso, J.N., Murray, T.L., Lockhart, A.B., Bryan, C.J., Glowworm: An extended PC-based Earthworm system for volcano monitoring. Abstracts, Cities On Volcanoes III, Hilo Hawaii, July 2003.

Marso, J. N.; Lockhart, A. B.; White, R. A.; Koyanagi, S. K.; Trusdell, F. A.; Camacho, J. T.; Chong, R.

2003-12-01

351

Alaska Volcano Observatory  

USGS Publications Warehouse

Steam plume from the 2006 eruption of Augustine volcano in Cook Inlet, Alaska. Explosive ash-producing eruptions from Alaska's 40+ historically active volcanoes pose hazards to aviation, including commercial aircraft flying the busy North Pacific routes between North America and Asia. The Alaska Volcano Observatory (AVO) monitors these volcanoes to provide forecasts of eruptive activity. AVO is a joint program of the U.S. Geological Survey (USGS), the Geophysical Institute of the University of Alaska Fairbanks (UAFGI), and the State of Alaska Division of Geological and Geophysical Surveys (ADGGS). AVO is one of five USGS Volcano Hazards Program observatories that monitor U.S. volcanoes for science and public safety. Learn more about Augustine volcano and AVO at http://www.avo.alaska.edu.

Venezky, Dina Y.; Murray, Tom; Read, Cyrus

2008-01-01

352

Island of Hawaii, Hawaiian Archipelago  

NASA Technical Reports Server (NTRS)

This single photo covers almost all of the big island of Hawaii (19.5N, 155.5E) in the Hawaiian Archipelago. The active Kilauea Volcano and lava flow is under clouds and hardly visible at the lower right edge but the Mauna Loa volcano crater and its older lava flow is at the bottom center. The Kona Coast, that produces the only coffee grown in the United States, is to the left. Mauna Kea is the extinct volcano and lava flow in the right center.

1983-01-01

353

Managing grassland pastures at Humboldt Bay National Wildlife Refuge for Aleutian geese.  

E-print Network

??An increasing population of Aleutian cackling geese (Branta hutchinsii leucopareia) has sparked concerns over goose population and public land management in Northwestern California. Strategies are… (more)

Bachman, Dominic

2008-01-01

354

Active volcanoes guided Tsunamigenic earthquakes from Andaman –  

E-print Network

The Indian Ocean Tsunami of Northern Sumatra Great Earthquake disastrous event (Mw 9.3) on 26th December 2004, had initiated release of trains of aftershocks in different directions. The above events resulted in explosions of series of Volcanoes of Andaman and Indonesian Island Arc Belt. After the tsunamigenic Northern Sumatra Great Earthquake of 2004, consecutive many tsunamigenerations were formed from the following regions viz West

unknown authors

355

Lifetime of an ocean island volcano feeder zone: constraints from U-Pb dating on coexisting zircon and baddeleyite, and 40/39Ar age determinations, Fuerteventura, Canary Islands  

USGS Publications Warehouse

High-precision isotope dilution - thermal ionization mass spectrometry (ID-TIMS) U-Pb zircon and baddeleyite ages from the PX1 vertically layered mafic intrusion Fuerteventura, Canary Islands, indicate initiation of magma crystallization at 22.10 ± 0.07 Ma. The magmatic activity lasted a minimum of 0.52 Ma. 40Ar/39Ar amphibole dating yielded ages from 21.9 ± 0.6 to 21.8 ± 0.3, identical within errors to the U-Pb ages, despite the expected 1% theoretical bias between 40Ar/39Ar and U-Pb dates. This overlap could result from (i) rapid cooling of the intrusion (i.e., less than the 0.3 to 0.6 Ma 40Ar/39Ar age uncertainties) from closure temperatures (Tc) of zircon (699-988 °C) to amphibole (500-600 °C); (ii) lead loss affecting the youngest zircons; or (iii) excess argon shifting the plateau ages towards older values. The combination of the 40Ar/39Ar and U/Pb datasets implies that the maximum amount of time PX1 intrusion took to cool below amphibole Tc is 0.8 Ma, suggesting PX1 lifetime of 520,000 to 800,000 Ma. Age disparities among coexisting baddeleyite and zircon (22.10 ± 0.07/0.08/0.15 Ma and 21.58 ± 0.15/0.16/0.31 Ma) in a gabbro sample from the pluton margin suggest complex genetic relationships between phases. Baddeleyite is found preserved in plagioclase cores and crystallized early from low silica activity magma. Zircon crystallized later in a higher silica activity environment and is found in secondary scapolite and is found close to calcite veins, in secondary scapolite that recrystallised from plagioclase. close to calcite veins. Oxygen isotope ?18O values of altered plagioclase are high (+7.7), indicating interaction with fluids derived from host-rock carbonatites. The coexistence of baddeleyite and zircon is ascribed to interaction of the PX1 gabbro with CO2-rich carbonatite-derived fluids released during contact metamorphism.

Allibon, James; Ovtcharova, Maria; Bussy, Francois; Cosca, Michael; Schaltegger, Urs; Bussien, Denise; Lewin, Eric

2011-01-01

356

75 FR 69601 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch in the Western Aleutian...  

Federal Register 2010, 2011, 2012, 2013, 2014

...Exclusive Economic Zone Off Alaska; Pacific Ocean Perch in the Western Aleutian District...prohibiting directed fishing for Pacific ocean perch in the Western Aleutian District...exceeding the 2010 allocation of Pacific ocean perch in this area allocated to...

2010-11-15

357

History of earthquakes and tsunamis along the eastern Aleutian-Alaska megathrust, with implications for tsunami hazards in the California Continental Borderland  

USGS Publications Warehouse

During the past several years, devastating tsunamis were generated along subduction zones in Indonesia, Chile, and most recently Japan. Both the Chile and Japan tsunamis traveled across the Pacific Ocean and caused localized damage at several coastal areas in California. The question remains as to whether coastal California, in particular the California Continental Borderland, is vulnerable to more extensive damage from a far-field tsunami sourced along a Pacific subduction zone. Assuming that the coast of California is at risk from a far-field tsunami, its coastline is most exposed to a trans-Pacific tsunami generated along the eastern Aleutian-Alaska subduction zone. We present the background geologic constraints that could control a possible giant (Mw ~9) earthquake sourced along the eastern Aleutian-Alaska megathrust. Previous great earthquakes (Mw ~8) in 1788, 1938, and 1946 ruptured single segments of the eastern Aleutian-Alaska megathrust. However, in order to generate a giant earthquake, it is necessary to rupture through multiple segments of the megathrust. Potential barriers to a throughgoing rupture, such as high-relief fracture zones or ridges, are absent on the subducting Pacific Plate between the Fox and Semidi Islands. Possible asperities (areas on the megathrust that are locked and therefore subject to infrequent but large slip) are identified by patches of high moment release observed in the historical earthquake record, geodetic studies, and the location of forearc basin gravity lows. Global Positioning System (GPS) data indicate that some areas of the eastern Aleutian-Alaska megathrust, such as that beneath Sanak Island, are weakly coupled. We suggest that although these areas will have reduced slip during a giant earthquake, they are not really large enough to form a barrier to rupture. A key aspect in defining an earthquake source for tsunami generation is determining the possibility of significant slip on the updip end of the megathrust near the trench. Large slip on the updip part of the eastern Aleutian-Alaska megathrust is a viable possibility owing to the small frontal accretionary prism and the presence of arc basement relatively close to the trench along most of the megathrust.

Ryan, Holly F.; von Huene, Roland; Wells, Ray E.; Scholl, David W.; Kirby, Stephen; Draut, Amy E.

2012-01-01

358

Fumarole\\/plume and diffuse CO2 emission from Sierra Negra volcano, Galapagos archipelago  

Microsoft Academic Search

The active shield-volcano Sierra Negra is part of the Galapagos hotspot. Sierra Negra is the largest shield volcano of Isabela Island, hosting a 10 km diameter caldera. Ten historic eruptions have occurred and some involved a frequently visited east caldera rim fissure zone called Volcan Chico. The last volcanic event occurred in October 2005 and lasted for about a week,

E. Padron; P. A. Hernandez Perez; N. Perez; T. Theofilos; G. Melian; J. Barrancos; G. Virgil; H. Sumino; K. Notsu

2009-01-01

359

Long term dismantling of a basaltic volcano (Piton des Neiges, La Réunion hotspot)  

Microsoft Academic Search

We present a structural investigation of destabilization processes at the Piton des Neiges, the extinct volcano of La Reunion Island. We focus on the Cirque of Cilaos (a large erosional depression south of the volcano summit), where the exposed internal structure of Piton des Neiges is made of pahoehoe lava flows of the shield building stage (unknown thickness) and breccias

Marie Chaput; Vincent Famin; Laurent Michon; Thibault Catry

2010-01-01

360

The Ninole Basalt — Implications for the structural evolution of Mauna Loa volcano, Hawaii  

Microsoft Academic Search

Lava flows of the Ninole Basalt, the oldest rocks exposed on the south side of the island of Hawaii, provide age and compositional constraints on the evolution of Mauna Loa volcano and the southeastward age progression of Hawaiian volcanism. Although the tholeiitic Ninole Basalt differs from historic lavas of Mauna Loa volcano in most major-element contents (e.g., variably lower K,

Peter W Lipman; J M Rhodes; G Brent Dalrymple

1991-01-01

361

The Volcano Adventure Guide  

NASA Astrophysics Data System (ADS)

Adventure travels to volcanoes offer chance encounters with danger, excitement, and romance, plus opportunities to experience scientific enlightenment and culture. To witness a violently erupting volcano and its resulting impacts on landscape, climate, and humanity is a powerful personal encounter with gigantic planetary forces. To study volcano processes and products during eruptions is to walk in the footsteps of Pliny himself. To tour the splendors and horrors of 25 preeminent volcanoes might be the experience of a lifetime, for scientists and nonscientists alike. In The Volcano Adventure Guide, we now have the ultimate tourist volume to lead us safely to many of the world's famous volcanoes and to ensure that we will see the important sites at each one.

Goff, Fraser

2005-05-01

362

Pb, Hf and Nd isotope compositions of the two Runion volcanoes (Indian Ocean): A tale of two small-scale mantle "blobs"?  

E-print Network

Pb, Hf and Nd isotope compositions of the two Réunion volcanoes (Indian Ocean): A tale of two small of basaltic lavas from the two Réunion Island volcanoes are reported in order to examine the origin of the sources feeding these volcanoes and to detect possible changes through time. Samples, chosen to cover

Demouchy, Sylvie

363

Hazardous Phenomena at Volcanoes  

USGS Publications Warehouse

Volcanoes generate a wide variety of phenomena that can alter the Earth's surface and atmosphere and endanger people and property. While most of the natural hazards illustrated and described in this fact sheet are associated with eruptions, some, like landslides, can occur even when a volcano is quiet. Small events may pose a hazard only within a few miles of a volcano, while large events can directly or indirectly endanger people and property tens to hundreds of miles away.

Myers, Bobbie M.; Brantley, Steven R.

1995-01-01

364

Volcanoes: On-Line Edition  

NSDL National Science Digital Library

This is the on-line version of a general interest publication prepared by the United States Geological Survey (USGS). It provides a general introduction to volcanoes and volcanology. Topics include types of volcanoes; types of eruptions; submarine volcanoes; and features associated with volcanic terrains (geysers, hot springs, etc.). There is also discussion of volcanoes and their association to plate tectonics, extraterrestrial volcanoes, monitoring and research efforts, and the impacts of volcanoes on human populations. A text-only version is also available.

365

Yellowstone Volcano Observatory  

USGS Publications Warehouse

Eruption of Yellowstone's Old Faithful Geyser. Yellowstone hosts the world's largest and most diverse collection of natural thermal features, which are the surface expression of magmatic heat at shallow depths in the crust. The Yellowstone system is monitored by the Yellowstone Volcano Observatory (YVO), a partnership among the U.S. Geological Survey (USGS), Yellowstone National Park, and the University of Utah. YVO is one of five USGS Volcano Hazards Program observatories that monitor U.S. volcanoes for science and public safety. Learn more about Yellowstone and YVO at http://volcanoes.usgs.gov/yvo.

Venezky, Dina Y.; Lowenstern, Jacob

2008-01-01

366

First breeding records of whooping swan and brambling in North America at Attu Island, Alaska  

USGS Publications Warehouse

We document the first breeding records of Whooper Swan (Cygnus cygnus) and Brambling (Fringilla montifringilla) in Alaska and North America on Attu Island in the Western Aleutians in the spring of 1996. Five cygnets were seen with adults and the nest located, and a territorial pair of Bramblings was observed and a nest with eggs found.

Sykes, P.W., Jr.; Sonneborn, D.W.

1998-01-01

367

Genetic Architecture of a Small, Recently Aggregated Aleut Population: Bering Island  

E-print Network

of the Aleutian archipelago. The purpose of this study is to characterize the genetic variation of Bering Island inhabitants for autosomal, mitochondrial, and Y-chromosome DNA and classic genetic markers and to investigate the genetic impact of the 19th...

Rubicz, Rohina C.; Zlojutro, Mark; Sun, Guangyun; Spitsyn, Victor; Deka, Ranjan; Young, Kristin Leigh; Crawford, Michael H.

2010-01-01

368

Numerical simulation of tsunami generation by cold volcanic mass flows at Augustine Volcano, Alaska  

USGS Publications Warehouse

Many of the world's active volcanoes are situated on or near coastlines. During eruptions, diverse geophysical mass flows, including pyroclastic flows, debris avalanches, and lahars, can deliver large volumes of unconsolidated debris to the ocean in a short period of time and thereby generate tsunamis. Deposits of both hot and cold volcanic mass flows produced by eruptions of Aleutian arc volcanoes are exposed at many locations along the coastlines of the Bering Sea, North Pacific Ocean, and Cook Inlet, indicating that the flows entered the sea and in some cases may have initiated tsunamis. We evaluate the process of tsunami generation by cold granular subaerial volcanic mass flows using examples from Augustine Volcano in southern Cook Inlet. Augustine Volcano is the most historically active volcano in the Cook Inlet region, and future eruptions, should they lead to debris-avalanche formation and tsunami generation, could be hazardous to some coastal areas. Geological investigations at Augustine Volcano suggest that as many as 12-14 debris avalanches have reached the sea in the last 2000 years, and a debris avalanche emplaced during an A.D. 1883 eruption may have initiated a tsunami that was observed about 80 km east of the volcano at the village of English Bay (Nanwalek) on the coast of the southern Kenai Peninsula. Numerical simulation of mass-flow motion, tsunami generation, propagation, and inundation for Augustine Volcano indicate only modest wave generation by volcanic mass flows and localized wave effects. However, for east-directed mass flows entering Cook Inlet, tsunamis are capable of reaching the more populated coastlines of the southwestern Kenai Peninsula, where maximum water amplitudes of several meters are possible.

Waythomas, C.F.; Watts, P.; Walder, J.S.

2006-01-01

369

Alaska Volcano Observatory  

NSDL National Science Digital Library

This is the homepage of the Alaska Volcano Observatory, a joint program of the United States Geological Survey (USGS), the Geophysical Institute of the University of Alaska Fairbanks (UAFGI), and the State of Alaska Division of Geological and Geophysical Surveys (ADGGS). Users can access current information on volcanic activity in Alaska and the Kamchatka Penninsula, including weekly and daily reports and information releases about significant changes in any particluar volcano. An interactive map also directs users to summaries and activity notifications for selected volcanoes, or through links to webcams and webicorders (recordings of seismic activity). General information on Alaskan volcanoes includes descriptions, images, maps, bibliographies, and eruptive histories. This can be accessed through an interactive map or by clicking on an alphabetic listing of links to individual volcanoes. There is also an online library of references pertinent to Quaternary volcanism in Alaska and an image library.

370

Pyroclastic deposits and volcanic history of Mayor Island  

Microsoft Academic Search

The emergent summit of Mayor Island, Bay of Plenty, New Zealand, is a peralkaline rhyolite volcano constructed by: a sequence of lava flows, the Tutaretare Rhyolite Formation (new); and pyroclastic deposits, the Oira Pyroclastite Formation (new). These 2 formations constitute the Mayor Island Group (new). The pyroclastic deposits mantle most of the outer slopes of the island, in places exceeding

M. D. Buck; R. M. Briggs; Campbell S. Nelson

1981-01-01

371

Mauna Loa--history, hazards and risk of living with the world's largest volcano  

USGS Publications Warehouse

Mauna Loa on the Island Hawai?i is the world’s largest volcano. People residing on its flanks face many hazards that come with living on or near an active volcano, including lava flows, explosive eruptions, volcanic smog, damaging earthquakes, and local tsunami (giant seawaves). The County of Hawai?i (Island of Hawai?i) is the fastest growing County in the State of Hawaii. Its expanding population and increasing development mean that risk from volcano hazards will continue to grow. U.S. Geological Survey (USGS) scientists at the Hawaiian Volcano Observatory (HVO) closely monitor and study Mauna Loa Volcano to enable timely warning of hazardous activity and help protect lives and property.

Trusdell, Frank A.

2012-01-01

372

Dyke and sill injections: what mostly trigger volcano flank collapse?  

Microsoft Academic Search

There is a large number of evidences that the morphostructural evolution of basaltic oceanic volcanoes (e.g. Stromboli, Hawaï and Canary Islands) results of alternating phases of growth and destruction. Among dismantling processes, flank collapses have been largely documented and interpreted as gravitational destabilization triggered by vertical injections of magma (dykes). In most cases, this interpretation has not been sustained by

Thibault Catry; Valérie Cayol; Laurent Michon; Vincent Famin; Claudia Romagnoli; Marie Chaput

2010-01-01

373

Eastern Aleutian volcanic arc digital model - version 1.0  

USGS Publications Warehouse

A 3-dimensional model (Figure 1) of the interaction of oceanic and continental tectonic plates along the eastern portion of the Aleutian volcanic arc helps in the visualization of basic tectonic, geodetic, and geophysical data in this active plate boundary region. The model is constrained by topographic, bathymetric, and seismic data and by the principle of isostasy. Examination of free-air gravity anomalies over the region indicates where the flexural strength of the down-going oceanic slab disturbs local isostatic balance and where low-density sediments have accumulated in the trench and forearc regions.

Saltus, R.W.; Barnett, Adrienne

2000-01-01

374

Geologic implications of great interplate earthquakes along the Aleutian arc  

SciTech Connect

We present new marine geophysical observations and synthesize previous geologic interpretations of the Aleutian arc to show that the epicenters of these great thrust-type earthquakes coincide with upper plate segments of the arc characterized by a coherent forearc structural fabric. We propose that variations in upper plate structural strength and mobility affect the mechanical properties of the interplate thrust zone and need to be considered in localizing interplate asperities. Forearc tectonic segmentaion associated with the partitioning of strike-slip and thrust motions may exert long-term controls on the rates of seismic moment release.

Ryan, H.F.; Scholl, D.W. [Geological Survey, Menlo Park, CA (United States)

1993-12-01

375

A past giant lateral collapse and present-day flank instability of Fogo, Cape Verde Islands  

Microsoft Academic Search

Fogo island is a large and extremely steepsided oceanic island volcano in the Cape Verde archipelago. It has a large (ca. 9 km across) east facing summit collapse structure, the Monte Amarelo collapse, with a probable volume of at least 150–200 km3. For most of its history the Monte Amarelo volcano had a small but productive central vent complex and

S. J. Day; S. I. N. Heleno da Silva; J. F. B. D. Fonseca

1999-01-01

376

GLORIA side-scan imagery of Aleutian basin, Bering Sea slope and Abyssal plain  

SciTech Connect

During July-September 1986, about 700,000 km/sup 2/ of continental slope and abyssal plain of the Aleutian basin, Bering Sea, were insonified with GLORIA (Geological Long Range Inclined Asdic) side-scane sonar. A sonar mosaic displays prominent geomorphic features including the massive submarine canyons of the Beringian and the northern Aleutian Ridge slopes and shows well-defined sediment patterns including large deep-sea channels and fan systems on the Aleutian basin abyssal plain. Dominant erosional and sediment transport processes on both the Beringian and the Aleutian Ridge slopes include varieties of mass movement that range from small debris flows and slides to massive slides and slumps of blocks measuring kilometers in dimension. Sediment-flow patterns that appear to be formed by sheet flow rather than channelized flow extend basinward from the numerous canyons and gullies that incise the slopes of the Beringian margin and of Bowers Ridge and some places along the Aleutian Ridge. These Beringian and Bowers canyon sediment sources, however, appear to have contributed less modern sediment to the Aleutian basin than the large, well-defined channel systems that emanate from Bering, Umnak, and Amchitka submarine canyons and extend for several hundred kilometers across the abyssal plain. This GLORIA imagery emphasizes the important contribution of the Aleutian Ridge to modern sedimentation in the deep Bering Sea.

Carlson, P.R.; Cooper, A.K.; Gardner, J.V.; Karl, H.A.; Marlow, M.S.; Stevenson, A.J.; Huggett, Q.; Kenyon, N.; Parson, L.

1987-05-01

377

Molecular epidemiology of Aleutian mink disease virus in China.  

PubMed

Aleutian mink disease (mink plasmacytosis) is a very severe immune-complex-mediated disease affecting minks. It is caused by the Aleutian mink disease virus (AMDV). To obtain a better understanding of the molecular epidemiology of AMDV in China, a total of 420 samples were collected from mink farms in five major mink-farming provinces in China. After testing serum antibodies using counterimmunoelectrophoresis (CIEP), 23 of the 340 positive samples were randomly selected and analyzed. The full length of the major structural protein gene (VP2) from all the samples was amplified and sequenced. The sequences in the twenty-three samples from 5 farms in 5 provinces were phylogenetically analyzed, and eleven were found to have homologous sequences in GenBank. A rooted phylogenetic tree was constructed using the unweighted pair-group method with arithmetic (UPGMA) method. Phylogenetic analysis showed that the AMDV strains formed five groups (I-VI), and four of them contained Chinese strains. The tree showed that the two AMVD lineages had been introduced to China independently. Over 70% of the Chinese isolates were classified into two groups, all of which contained Chinese strains. The results of the analysis suggested that the distribution of the AMDV strains was not based on geographical origin, and both indigenous AMDV and imported AMDV were prevalent in the primary mink production areas in China. PMID:24561116

Wang, Zhenjun; Wu, Wei; Hu, Bo; Zhang, Hailing; Bai, Xue; Zhao, Jianjun; Zhang, Lei; Yan, Xijun

2014-05-12

378

Shaking up volcanoes  

USGS Publications Warehouse

Most volcanic eruptions that occur shortly after a large distant earthquake do so by random chance. A few compelling cases for earthquake-triggered eruptions exist, particularly within 200 km of the earthquake, but this phenomenon is rare in part because volcanoes must be poised to erupt in order to be triggered by an earthquake (1). Large earthquakes often perturb volcanoes in more subtle ways by triggering small earthquakes and changes in spring discharge and groundwater levels (1, 2). On page 80 of this issue, Brenguier et al. (3) provide fresh insight into the interaction of large earthquakes and volcanoes by documenting a temporary change in seismic velocity beneath volcanoes in Honshu, Japan, after the devastating Tohoku-Oki earthquake in 2011.

Prejean, Stephanie G.; Haney, Matthew M.

2014-01-01

379

EDGE deep seismic reflection transect of the eastern Aleutian arc-trench layered lower crust reveals underplating and continental growth  

SciTech Connect

An EDGE deep crustal seismic reflection transect of the eastern Aleutian arc-trench traces oceanic crust and Moho more than 200 km beneath the accretionary prism to depths of more than 30 km. These horizons project beneath a prominent sequence of layered reflectors that extends from about 9 to 35 km beneath the Mesozoic core of the prism. Earthquake hypocenters imply continuity of the downgoing lithosphere from the base of the layered reflectors to beneath and beyond the active Augustine volcano. Rapid lateral growth of the prism in eocene-Oligocene time coincided with uplift of the Mesozoic core of the prism. During lateral growth, maintenance of critical taper requires thickening, either by internal deformation or underplating. Because exposed rocks show only modest postemplacement shortening, thickening most likely occurred by underplating, probably of the layered reflectors. The overall geometry of the layered reflectors is reminiscent of nappe structures, and their emplacement may represent crustal-scale duplexing associated with underplating. The EDGE reflection data and borehole results indicate that the self edge is marked by an active out-of-sequence thrust that separates the Paleogene and Neogene prisms. This thrust apparently developed in response to the prism's need to maintain critical taper and demonstrates that contrasts in lithology can result from mechanisms other than terrane emplacement.

Moore, J.C. (Univ. of California, Santa Cruz (USA)); Sample, J. (Univ. of California, Los Angeles (USA)); Diebold, J. (Columbia Univ., Palisades, NY (USA)); Fisher, M.A.; Brocher, T.; Stevens, C. (Geological Survey, Menlo Park, CA (USA)); Talwani, M.; Ewing, J. (Houston Research Center, Woodlands, TX (USA)); von Huene, R. (Geomar, Keil (West Germany)); Rowe, C.; Stone, D. (Univ. of Alaska, Fairbanks (USA)); Sawyer, D. (Rice Univ., Houston, TX (USA))

1991-05-01

380

Low pressure fractionation in arc volcanoes: an example from Augustine Volcano, Alaska  

SciTech Connect

Augustine Volcano, situated between the Cook and Katmai segments of the Eastern Aleutian Volcanic Arc, has erupted 5 times since its discovery in 1778. Eruptions are characterized by early vent-clearing eruptions with accompanying pyroclastic flows followed by dome-building and more pyroclastic flows. Bulk rock chemistry of historic and prehistoric lavas shows little variability. The lavas are calc-alkaline, low to medium K, porphyritic acid andesites, rare basalt, and minor dacite pumice. FeO*/MgO averages 1.6 over this silica range. Plagioclase phenocrysts show complicated zoning patterns, but olivine, orthopyroxene, and clinopyroxene phenocrysts show little compositional variation. Hornblende, where present, is ubiquitously oxidized and was clearly out of equilibrium during the last stages of fractionation. Evolved liquid compositions of vitriophyric domes are rhyolitic, and of pumices are slightly less evolved suggesting that individual eruptions become more fractionated with time. Comparison of glass compositions with experimental results is consistent with low pressure fractionation of a relatively dry silicate melt. Disequilibrium of amphiboles and the evolved nature of glasses indicate that shallow level fractionation plays a significant role in the evolution of Augustine magmas. This model is consistent with a shallow magma chamber inferred from geophysical models of the Augustine system and also with its simple, predictable eruption pattern.

Daley, E.E.; Swanson, S.E.

1985-01-01

381

The diversity of mud volcanoes in the landscape of Azerbaijan  

NASA Astrophysics Data System (ADS)

As the natural phenomenon the mud volcanism (mud volcanoes) of Azerbaijan are known from the ancient times. The historical records describing them are since V century. More detail study of this natural phenomenon had started in the second half of XIX century. The term "mud volcano" (or "mud hill") had been given by academician H.W. Abich (1863), more exactly defining this natural phenomenon. All the previous definitions did not give such clear and capacious explanation of it. In comparison with magmatic volcanoes, globally the mud ones are restricted in distribution; they mainly locate within the Alpine-Himalayan, Pacific and Central Asian mobile belts, in more than 30 countries (Columbia, Trinidad Island, Italy, Romania, Ukraine, Georgia, Azerbaijan, Turkmenistan, Iran, Pakistan, Indonesia, Burma, Malaysia, etc.). Besides it, the zones of mud volcanoes development are corresponded to zones of marine accretionary prisms' development. For example, the South-Caspian depression, Barbados Island, Cascadia (N.America), Costa-Rica, Panama, Japan trench. Onshore it is Indonesia, Japan, and Trinidad, Taiwan. The mud volcanism with non-accretionary conditions includes the areas of Black Sea, Alboran Sea, the Gulf of Mexico (Louisiana coast), Salton Sea. But new investigations reveal more new mud volcanoes and in places which were not considered earlier as the traditional places of mud volcanoes development (e.g. West Nile Rive delta). Azerbaijan is the classic region of mud volcanoes development. From over 800 world mud volcanoes there are about 400 onshore and within the South-Caspian basin, which includes the territory of East Azerbaijan (the regions of Shemakha-Gobustan and Low-Kura River, Absheron peninsula), adjacent water area of South Caspian (Baku and Absheron archipelagoes) and SW Turkmenistan and represents an area of great downwarping with thick (over 25 km) sedimentary series. Generally, in the modern relief the mud volcanoes represent more or less large uplifts on surface, often of plane-conical shape, rising for 5 to 400 m and more over the country (for example, mud volcano Toragay, 400 m height). The base diameter is from 100 m to 3-4 km and more. Like the magmatic ones, the mud volcanoes are crowned with crater of convex-plane or deeply-seated shape. In Azerbaijan there are all types of mud volcanoes: active, extinct, buried, submarine, island, abundantly oil seeping. According to their morphology they are defined into cone-shaped, dome-shaped, ridge-shaped, plateau-shaped. The crater shapes are also various: conical, convex-plane, shield-shaped, deeply-seated, caldera-like. The most complete morphological classification was given in "Atlas of mud volcanoes of Azerbaijan" (Yakubov et al., 1971). Recently (Aliyev Ad. et al., 2003) it was proposed a quite new morphological classification of mud volcanoes of Azerbaijan. For the first time the mud volcanic manifestations had been defined. Volcanoes are ranged according to morphological signs, crater shape and type of activity.

Rashidov, Tofig

2014-05-01

382

Remote Telemetered and Time-Lapse Cameras at Augustine Volcano  

USGS Publications Warehouse

Before and during the 2006 eruption of Augustine Volcano, the Alaska Volcano Observatory (AVO) installed a network of telemetered and nontelemetered cameras in Homer, Alaska, and on Augustine Island. On December 1, 2005, a network camera was installed at the Homer Field Station, a University of Alaska Fairbanks Geophysical Institute (UAF/GI) facility on a bluff near Homer, where telemetered Augustine data are received. The camera placed there provides observations of the volcano from a distance of 126 km (78 miles) in daylight hours during clear sky conditions. On January 9, 2006, a radio-telemetered network camera was installed on the lower eastern flank of the volcano at 'Mound,' 4.4 km (2.7 miles) from the summit. The proximity of this camera provided for near-field images of the volcano. A nontelemetered camera with onsite recording was installed 3.8 km (2.4 miles) north of the volcano's summit near Burr Point on December 17, 2005. This camera recorded high-resolution images at a rate of 4 images per hour through much of the eruptive sequence. A low-light camera was installed on February 8, 2006, at the Homer facility to augment the extreme low-light camera installed by the UAF/GI (Sentman and others, this volume). On September 10, 2006, a second radio-telemetered network camera was installed at Lagoon camp on the west side of Augustine Island, 5.4 km (3.3 miles) west-northwest of the summit. The installation of these camera systems proved valuable for assessing volcanic activity, determining ground hazards and on-island weather for visiting field teams, and deciphering depositional history after the eruption.

Paskievitch, John; Read, Cyrus; Parker, Thomas

2010-01-01

383

Forearc structure from legacy multichannel seismic data linked to mechanical variability and rupture segmentation on the central Alaska-Aleutian subduction zone  

NASA Astrophysics Data System (ADS)

The historical earthquake record, geodetic observations, and modern interseismic seismicity patterns indicate along-strike variability in the mechanical behavior of the subduction zone extending from the central Alaska peninsula west to the eastern Aleutian Islands. This region spans the rupture areas of several historical megathrust earthquakes, including the 1938 M8.3 Semidi Islands event, the 1946 M8.5 earthquake near Unimak Pass, and the 1957 M8.6 Andreanof Islands earthquake. Each of these events produced tsunamis that affected Alaska and/or far-field coastal regions in Hawaii and the mainland U.S. The '38 and '46 rupture areas are separated by a segment of the subduction zone in the vicinity of the Shumagin Islands where, based on plate velocities from GPS, plate coupling decreases from nearly fully locked in the east, to very low coupling in the western Shumagins, indicating an important change in seismic style along-strike. Changes in the degree of interseismic coupling are often attributed to variability in the mechanical strength of the thrust interface, influenced by heterogeneity in the material properties and subducted topographic relief. Furthermore, the expression of forearc structural features along the margin may indicate the width and up-dip limit of the locked zone. We explore structural characteristics of the shallow portion of the subduction system related to variations in the mechanical properties of the megathrust and interseismic coupling using legacy multichannel seismic (MCS) data from several segments along the Alaska-Aleutian subduction zone. Critical images were reprocessed with modern seismic processing systems. We characterize structural features of the downgoing plate and forearc, including the variation in thickness and character of subducted sediment, the geometry of the upper plate wedge, the distribution of imbricate thrust faults, the transition from outer prism to margin rock framework and extensional faulting. These interpretations of recently reprocessed MCS data from the USGS R/V Lee and R/V Ewing are considered in the context of the seismogenic properties of several distinct rupture segments. We consider variations in wedge geometry along-strike to gain some insight into changes in the mechanical strength of the interface. Interseismic seismicity patterns associated with small magnitude, shallow interplate earthquakes and seismicity in the overriding plate also provide information about potential changes in the mechanical properties of the subduction zone along-strike that correlate with variations in forearc structure at the Alaska-Aleutian margin.

Roland, E. C.; von Huene, R.; Miller, J.; Haeussler, P. J.; Scholl, D. W.; Ryan, H. F.; Kirby, S. H.

2012-12-01

384

Investigation of the Dashigil mud volcano (Azerbaijan) using beryllium-10  

NASA Astrophysics Data System (ADS)

We collected and analyzed five sediments from three mud volcano (MV) vents and six suspended and bottom sediment samples from the adjoining river near the Dashgil mud volcano in Azerbaijan for 10Be. These three MV are found among the 190 onshore and >150 offshore MV in this region which correspond to the western flank of the South Caspian depression. These MVs overlie the faulted and petroleum-bearing anticlines. The 10Be concentrations and 10Be/9Be ratios are comparable to the values reported for mud volcanoes in Trinidad Island. It appears that the stable Be concentrations in Azerbaijan rivers are not perturbed by anthropogenic effects and are comparable to the much older sediments (mud volcano samples). The 10Be and 9Be concentrations in our river sediments are compared to the global data set and show that the 10Be values found for Kura River are among the lowest of any river for which data exist. We attribute this low 10Be concentration to the nature of surface minerals which are affected by the residual hydrocarbon compounds that occur commonly in the study area in particular and Azerbaijan at large. The concentrations of 40K and U-Th-series radionuclides (234Th, 210Pb, 226Ra, and 228Ra) indicate overall homogeneity of the mud volcano samples from the three different sites. Based on the 10Be concentrations of the mud volcano samples, the age of the mud sediments could be at least as old as 4 myr.

Kim, K. J.; Baskaran, M.; Jweda, J.; Feyzullayev, A. A.; Aliyev, C.; Matsuzaki, H.; Jull, A. J. T.

2013-01-01

385

Volcanoes: Coming Up from Under.  

ERIC Educational Resources Information Center

Provides specific information about the eruption of Mt. St. Helens in March 1980. Also discusses how volcanoes are formed and how they are monitored. Words associated with volcanoes are listed and defined. (CS)

Science and Children, 1980

1980-01-01

386

Comparative pathogenicity of four strains of Aleutian disease virus for pastel and sapphire mink.  

PubMed Central

Information was sought on the comparative pathogenicity of four North American strains (isolates) of Aleutian disease virus for royal pastel (a non-Aleutian genotype) and sapphire (an Aleutian genotype) mink. The four strains (Utah-1, Ontario [Canada], Montana, and Pullman [Washington]), all of mink origin, were inoculated intraperitoneally and intranasally in serial 10-fold dilutions. As indicated by the appearance of specific antibody (counterimmunoelectrophoresis test), all strains readily infected both color phases of mink, and all strains were equally pathogenic for sapphire mink. Not all strains, however, regularly caused Aleutian disease in pastel mink. Infection of pastel mink with the Utah-1 strain invariably led to fatal disease. Infection with the Ontario strain caused fatal disease nearly as often. The Pullman strain, by contrast, almost never caused disease in infected pastel mink. The pathogenicity of the Montana strain for this color phase was between these extremes. These findings emphasize the need to distinguish between infection and disease when mink are exposed to Aleutian disease virus. The distinction has important implications for understanding the natural history of Aleutian disease virus infection in ranch mink. PMID:6193063

Hadlow, W J; Race, R E; Kennedy, R C

1983-01-01

387

GlobVolcano pre-operational services for global monitoring active volcanoes  

NASA Astrophysics Data System (ADS)

The GlobVolcano project (2007-2010) is part of the Data User Element programme of the European Space Agency (ESA). The project aims at demonstrating Earth Observation (EO) based integrated services to support the Volcano Observatories and other mandate users (e.g. Civil Protection) in their monitoring activities. The information services are assessed in close cooperation with the user organizations for different types of volcano, from various geographical areas in various climatic zones. In a first phase, a complete information system has been designed, implemented and validated, involving a limited number of test areas and respective user organizations. In the currently on-going second phase, GlobVolcano is delivering pre-operational services over 15 volcanic sites located in three continents and as many user organizations are involved and cooperating with the project team. The set of GlobVolcano offered EO based information products is composed as follows: Deformation Mapping DInSAR (Differential Synthetic Aperture Radar Interferometry) has been used to study a wide range of surface displacements related to different phenomena (e.g. seismic faults, volcanoes, landslides) at a spatial resolution of less than 100 m and cm-level precision. Permanent Scatterers SAR Interferometry method (PSInSARTM) has been introduced by Politecnico of Milano as an advanced InSAR technique capable of measuring millimetre scale displacements of individual radar targets on the ground by using multi-temporal data-sets, estimating and removing the atmospheric components. Other techniques (e.g. CTM) have followed similar strategies and have shown promising results in different scenarios. Different processing approaches have been adopted, according to data availability, characteristic of the area and dynamic characteristics of the volcano. Conventional DInSAR: Colima (Mexico), Nyiragongo (Congo), Pico (Azores), Areanal (Costa Rica) PSInSARTM: Piton de la Fournaise (La Reunion Island), Stromboli and Volcano (Italy), Hilo (Hawai), Mt. St. Helens (United States), CTM (Coherent Target Monitoring): Cumbre Vieja (La Palma) To generate products either Envisat ASAR, Radarsat 1or ALOS PALSAR data have been used. Surface Thermal Anomalies Volcanic hot-spots detection, radiant flux and effusion rate (where applicable) calculation of high temperature surface thermal anomalies such as active lava flow, strombolian activity, lava dome, pyroclastic flow and lava lake can be performed through MODIS (Terra / Aqua) MIR and TIR channels, or ASTER (Terra), HRVIR/HRGT (SPOT4/5) and Landsat family SWIR channels analysis. ASTER and Landsat TIR channels allow relative radiant flux calculation of low temperature anomalies such as lava and pyroclastic flow cooling, crater lake and low temperature fumarolic fields. MODIS, ASTER and SPOT data are processed to detect and measure the following volcanic surface phenomena: Effusive activity Piton de la Fournaise (Reunion Island); Mt Etna (Italy). Lava dome growths, collapses and related pyroclastic flows Soufrière Hills (Montserrat); Arenal - (Costa Rica). Permanent crater lake and ephemeral lava lake Karthala (Comores Islands). Strombolian activity Stromboli (Italy). Low temperature fumarolic fields Nisyros (Greece), Vulcano (Italy), Mauna Loa (Hawaii). Volcanic Emission The Volcanic Emission Service is provided to the users by a link to GSE-PROMOTE - Support to Aviation Control Service (SACS). The aim of the service is to deliver in near-real-time data derived from satellite measurements regarding SO2 emissions (SO2 vertical column density - Dobson Unit [DU]) possibly related to volcanic eruptions and to track the ash injected into the atmosphere during a volcanic eruption. SO2 measurements are derived from different satellite instruments, such as SCIAMACHY, OMI and GOME-2. The tracking of volcanic ash is accomplished by using SEVIRI-MSG data and, in particular, the following channels VIS 0.6 and IR 3.9, and along with IR8.7, IR 10.8 and IR 12.0. The GlobVolcano information system and its current experimentation represent a

Tampellini, Lucia; Ratti, Raffaella; Borgström, Sven; Seifert, Frank Martin; Peltier, Aline; Kaminski, Edouard; Bianchi, Marco; Branson, Wendy; Ferrucci, Fabrizio; Hirn, Barbara; van der Voet, Paul; van Geffen, J.

2010-05-01

388

Volcano: Tectonic Environments  

NSDL National Science Digital Library

This site describes where volcanoes are found in terms of plate tectonics and explains why they occur at those locations. S map shows that volcanoes are located mainly at plate boundaries. Then there are explanations for plate motion, mantle convection, and magma generation. The three types of plate boundaries are listed as divergent, convergent, and transform. There is also information about the relationship between types of boundaries and types of volcanism and the fact that intraplate volcanism describes volcanic eruptions within tectonic plates. The site features a diagram that depicts each type, with a link for more information about the Earth's internal heat energy and interior structure.

Victor Camp

389

The Worlds Deadliest Volcanoes  

NSDL National Science Digital Library

At this interactive site the student attempts to rate the eruption of a volcano according to the Volcanic Explosive Index (VEI). After seeing the step by step eruption of an actual volcano, the student is introduced to VEI scale, which includes a description of the eruption, volume of ejected material, plume height, eruption type, duration, total known eruptions with that VEI, and an example. Each factor is linked to a section where it is explained in detail. After evaluating all of the factors and rating them, the student selects a VEI number and clicks for feedback. The correct answer is given with an explanation.

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Mercury and Other Metals in Feathers of Common Eider (Somateria mollissima) and Tufted Puffin (Fratercula cirrhata) from the Aleutian Chain of Alaska  

PubMed Central

We analyzed arsenic, cadmium, chromium, lead, manganese, mercury, and selenium in the feathers of common eiders (Somateria mollissima) and tufted puffins (Fratercula cirrhata) from Amchitka and Kiska islands (Aleutians). Between species, puffins had 10 times higher chromium (arithmetic mean = 1820 ppb), 7.5 times higher selenium (mean = 6600 ppb), and 3 times higher mercury (mean = 2540 ppb) than eiders. Eiders had significantly higher levels of manganese than puffins. Puffins are higher on the food chain than eiders, which is reflected in their generally higher levels of metals in their feathers. Interisland differences were generally small, and there were few significant differences as a function of the three nuclear test locations on Amchitka. The only sex-related difference was that female puffins had higher mercury than males (arithmetic mean of 3060 ppb vs. 2270 ppb). Mean levels of metals in the feathers of puffins and eiders from the Aleutians were low compared with comparable studies elsewhere, and the relatively low levels of metals do not indicate the potential for adverse behavioral or reproductive effects in the birds themselves, nor pose concern for other consumers, including subsistence hunters. PMID:18712499

Gochfeld, Michael

2014-01-01

391

A Submarine Perspective on Hawaiian Volcanoes  

NASA Astrophysics Data System (ADS)

Postwar improvements in navigation, sonar-based mapping, and submarine photography enabled the development of bathymetric maps, which revealed submarine morphologic features that could be dredged or explored and sampled with a new generation of manned and unmanned submersibles. The maps revealed debris fields from giant landslides, the great extent of rift zones radiating from volcanic centers, and two previously unknown submarine volcanoes named Mahukona and Loihi, the youngest Hawaiian volcano. About 70 major landslides cover half the flanks of the Hawaiian Ridge out to Midway Island. Some of the landslides attain lengths of 200 km and have volumes exceeding 5,000 km3. More recent higher resolution bathymetry and sidescan data reveal that many submarine eruptions construct circular, flat-topped, monogenetic cones; that large fields of young strongly alkalic lava flows, such as the North Arch and South Arch lava fields, erupt on the seafloor within several hundred km of the islands; and that alkalic lavas erupt during the shield stage on Kilauea and Mauna Loa. The North Arch flow field covers about 24,000 km2, has an estimated volume between about 1000 and 1250 km3, has flows as long as 108 km, and erupted from over 100 vents. The source and melting mechanisms for their production is still debated. The maps also displayed stair-step terraces, mostly constructed of drowned coral reefs, which form during early rapid subsidence of the volcanoes during periods of oscillating sea level. The combination of scuba and underwater photography facilitated the first motion pictures of the mechanism of formation of pillow lava in shallow water offshore Kilauea. The age progression known from the main islands was extended westward along the Hawaiian Ridge past Midway Island, around a bend in the chain and northward along the Emperor Seamounts. Radiometric dating of dredged samples from these submarine volcanoes show that the magma source that built the chain has been active for over 80 Ma and established the remarkable linearity of the age-progression along the chain. Glass rinds on submarine lava quenched at depth contain initial magmatic volatiles and yield data on the juvenile water, sulfur, CO2, and rare gas contents of basaltic magmas, and continue to reveal nuances of the volatile contents of lava. Rock sampling at Loihi Seamount led to the discovery of the pre-shield alkalic phase of Hawaiian volcanism, which mirrors the well-known post-shield alkalic phase. Lava compositions from the Hawaiian Ridge and Emperor Seamounts have clear affinities to present-day Hawaiian lavas, but subtle source differences as well. The progression from small to large and back to small degrees of melting at individual volcanoes and the compositional changes along the chain constrain the melting processes and source compositions of Hawaiian volcanism. Coupling the age of lavas with that of submerged coral reefs has provided data on the growth and subsidence of volcanic centers. This information has meshed nicely with the age, composition, and morphology of lavas from the 3.2-km-deep Hawaiian Scientific Drill Hole. Submarine studies have taught us much about the workings of Hawaiian Volcanoes, and in the process have stimulated new work and concepts on marine volcanism worldwide.

Clague, D. A.; Moore, J. G.

2011-12-01

392

Influence of fortnightly earth tides at Kilauea Volcano, Hawaii.  

USGS Publications Warehouse

Analysis of 52 historic eruptions confirms the premise that fortnightly earth tides play a significant role in triggering activity at Kilauea Volcano, Hawaii. Since January 1832, nearly twice as many eruptions have occurred nearer fortnightly tidal maximum than tidal minimum (34 vs. 18). A straightforward significance test indicates that the likelihood of a fortnightly tidal influence on Kilauea eruptions is roughly 90%. This is not the case for Mauna Loa Volcano, where 37 historic eruptions have been distributed randomly with respect to the fortnightly tide. At Kilauea, stresses induced by fortnightly earth tides presumably act in concert with volcanic and tectonic stresses to trigger shallow magma movements along preexisting zones of weakness. Differences in structure or internal plumbing may limit the effectiveness of this mechanism at Mauna Loa. Tidal effects seem to be less marked at shields than at some island-arc volcanoes, possibly because higher average volcanic stress rates in Hawaii more often override the effects of tidal stresses.-Author

Dzurisin, D.

1980-01-01

393

Shallow S wave attenuation and actively degassing magma beneath Taal Volcano, Philippines  

NASA Astrophysics Data System (ADS)

Volcano, Philippines, is one of the world's most dangerous volcanoes given its history of explosive eruptions and its close proximity to populated areas. A real-time broadband seismic network was recently deployed and has detected volcano-tectonic events beneath Taal. Our source location analysis of these volcano-tectonic events, using onset arrival times and high-frequency seismic amplitudes, points to the existence of a region of strong attenuation near the ground surface beneath the east flank of Volcano Island in Taal Lake. This region is beneath the active fumarolic area and above sources of pressure contributing inflation and deflation, and it coincides with a region of high electrical conductivity. The high-attenuation region matches that inferred from an active-seismic survey conducted at Taal in 1993. These features strongly suggest that the high-attenuation region represents an actively degassing magma body near the surface that has existed for more than 20 years.

Kumagai, Hiroyuki; Lacson, Rudy; Maeda, Yuta; Figueroa, Melquiades S.; Yamashina, Tadashi

2014-10-01

394

Catalog of Earthquake Hypocenters at Alaskan Volcanoes: January 1 through December 31, 2007  

USGS Publications Warehouse

Between January 1 and December 31, 2007, AVO located 6,664 earthquakes of which 5,660 occurred within 20 kilometers of the 33 volcanoes monitored by the Alaska Volcano Observatory. Monitoring highlights in 2007 include: the eruption of Pavlof Volcano, volcanic-tectonic earthquake swarms at the Augustine, Illiamna, and Little Sitkin volcanic centers, and the cessation of episodes of unrest at Fourpeaked Mountain, Mount Veniaminof and the northern Atka Island volcanoes (Mount Kliuchef and Korovin Volcano). This catalog includes descriptions of : (1) locations of seismic instrumentation deployed during 2007; (2) earthquake detection, recording, analysis, and data archival systems; (3) seismic velocity models used for earthquake locations; (4) a summary of earthquakes located in 2007; and (5) an accompanying UNIX tar-file with a summary of earthquake origin times, hypocenters, magnitudes, phase arrival times, location quality statistics, daily station usage statistics, and all files used to determine the earthquake locations in 2007.

Dixon, James P.; Stihler, Scott D.; Power, John A.

2008-01-01

395

Numerical simulation of tsunami generation by pryoclastic flow at Aniakchak Volcano, Alaska  

USGS Publications Warehouse

Pyroclastic flows entering the sea are plausible mechanisms for tsunami generation at volcanic island arcs worldwide. We evaluate tsunami generation by pyroclastic flow using an example from Aniakchak volcano in Alaska where evidence for tsunami inundation coincident with a major, caldera-forming eruption of the volcano ca. 3.5 ka has been described. Using a numerical model, we simulate the tsunami and compare the results to field estimates of tsunami run up.

Waythomas, C.F.; Watts, P.

2003-01-01

396

Tech trek: Viewing volcanoes  

NSDL National Science Digital Library

Help students make real-world connections to Earth science concepts such as volcanoes with the help of modern technology. This article enumerates several websites where students can explore these forces of nature in a variety of ways - all from a safe distance!

Christmann, Edwin P.; Wighting, Mervyn J.; Lucking, Robert A.

2005-03-01

397

The Super Volcano Game  

NSDL National Science Digital Library

How would you handle a volcano diasater? In this game, you've just been appointed chief of the Emergency Management Agency for Bluebear County. Everyone is counting on you to handle the eruption of Mount Spur. Download this game to find out. Before you play, make sure Flash is installed on your computer.

British Broadcasting Corporation

398