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Last update: August 15, 2014.
1

Kanaga Volcano, Aleutian Islands, Alaska  

NSDL National Science Digital Library

These images of the Kanaga Volcano show the symmetrical cone which is characteristic of stratovolcanoes. It is also possible to see how the current volcanic edifice has grown inside an older caldera, the remains of ancient Mount Kanaton. References and links to related sites are included.

2

Perspective View of Okmok Volcano, Aleutian Islands, Alaska (#1)  

NASA Technical Reports Server (NTRS)

This perspective view shows the caldera of the Okmok volcano in Alaska's Aleutian Islands.

The shaded relief was generated from and draped over an Airsar-derived digital elevation mosaic.

Airsar collected the Alaska data as part of its PacRim 2000 Mission, which took the instrument to French Polynesia, American and Western Samoa, Fiji, New Zealand, Australia, New Guinea, Indonesia, Malaysia, Cambodia, Philippines, Taiwan, South Korea, Japan, Northern Marianas, Guam, Palau, Hawaii and Alaska. Airsar, part of NASA's Airborne Science Program, is managed for NASA's Earth Science Enterprise by JPL. JPL is a division of the California Institute of Technology in Pasadena.

2001-01-01

3

Perspective View of Okmok Volcano, Aleutian Islands, Alaska (#2)  

NASA Technical Reports Server (NTRS)

This perspective view shows the caldera of the Okmok volcano in Alaska's Aleutian Islands.

The shaded relief was generated from and draped over an Airsar-derived digital elevation mosaic.

Airsar collected the Alaska data as part of its PacRim 2000 Mission, which took the instrument to French Polynesia, American and Western Samoa, Fiji, New Zealand, Australia, New Guinea, Indonesia, Malaysia, Cambodia, Philippines, Taiwan, South Korea, Japan, Northern Marianas, Guam, Palau, Hawaii and Alaska. Airsar, part of NASA's Airborne Science Program, is managed for NASA's Earth Science Enterprise by JPL. JPL is a division of the California Institute of Technology in Pasadena.

2001-01-01

4

Preliminary volcano-hazard assessment for Akutan Volcano east-central Aleutian Islands, Alaska  

USGS Publications Warehouse

Akutan Volcano is a 1100-meter-high stratovolcano on Akutan Island in the east-central Aleutian Islands of southwestern Alaska. The volcano is located about 1238 kilometers southwest of Anchorage and about 56 kilometers east of Dutch Harbor/Unalaska. Eruptive activity has occurred at least 27 times since historical observations were recorded beginning in the late 1700?s. Recent eruptions produced only small amounts of fine volcanic ash that fell primarily on the upper flanks of the volcano. Small amounts of ash fell on the Akutan Harbor area during eruptions in 1911, 1948, 1987, and 1989. Plumes of volcanic ash are the primary hazard associated with eruptions of Akutan Volcano and are a major hazard to all aircraft using the airfield at Dutch Harbor or approaching Akutan Island. Eruptions similar to historical Akutan eruptions should be anticipated in the future. Although unlikely, eruptions larger than those of historical time could generate significant amounts of volcanic ash, fallout, pyroclastic flows, and lahars that would be hazardous to life and property on all sectors of the volcano and other parts of the island, but especially in the major valleys that head on the volcano flanks. During a large eruption an ash cloud could be produced that may be hazardous to aircraft using the airfield at Cold Bay and the airspace downwind from the volcano. In the event of a large eruption, volcanic ash fallout could be relatively thick over parts of Akutan Island and volcanic bombs could strike areas more than 10 kilometers from the volcano.

Waythomas, Christopher F.; Power, John A.; Richter, Donlad H.; McGimsey, Robert G.

1998-01-01

5

Geology and Late Quaternary Eruptive History of Kanaga Volcano, a Calc-Alkaline Stratovolcano in the Western Aleutian Islands, Alaska  

Microsoft Academic Search

Recent studies of the geology and eruptive history of Kanaga Volcano in the western Aleutian Islands of Alaska have yielded new information about the timing of Holocene eruptions and an improved understanding of the evolution of the volcano. Previous studies indicated that Kanaton Ridge, a major topographic feature on the northern part of Kanaga Island, was the rim of a

Christopher F. Waythomas; Thomas P. Miller; Christopher J. Nye

6

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

7

The 7-8 August 2008 eruption of Kasatochi Volcano, central Aleutian Islands, Alaska  

NASA Astrophysics Data System (ADS)

Kasatochi volcano in the central Aleutian Islands erupted unexpectedly on 7-8 August 2008. Kasatochi has received little study by volcanologists and has had no confirmed historical eruptions. The island is an important nesting area for seabirds and a long-term biological study site of the U.S. Fish and Wildlife Service. After a notably energetic preeruptive earthquake swarm, the volcano erupted violently in a series of explosive events beginning in the early afternoon of 7 August. Each event produced ash-gas plumes that reached 14-18 km above sea level. The volcanic plume contained large amounts of SO2 and was tracked around the globe by satellite observations. The cumulative volcanic cloud interfered with air travel across the North Pacific, causing many flight cancelations that affected thousands of travelers. Visits to the volcano in 2008-2009 indicated that the eruption generated pyroclastic flows and surges that swept all flanks of the island, accumulated several tens of meters of pyroclastic debris, and increased the diameter of the island by about 800 m. Pyroclastic flow deposits contain abundant accidental lithic debris derived from the inner walls of the Kasatochi crater. Juvenile material is crystal-rich silicic andesite that ranges from slightly pumiceous to frothy pumice. Fine-grained pyroclastic surge and fall deposits with accretionary lapilli cover the lithic-rich pyroclastic flow deposits and mark a change in eruptive style from episodic explosive activity to more continuous ash emission with smaller intermittent explosions. Pyroclastic deposits completely cover the island, but wave erosion and gully development on the flanks have begun to modify the surface mantle of volcanic deposits.

Waythomas, Christopher F.; Scott, William E.; Prejean, Stephanie G.; Schneider, David J.; Izbekov, Pavel; Nye, Christopher J.

2010-12-01

8

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

9

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

10

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, Jr. , C.; Power, J.

2008-01-01

11

Massive edifice failure at Aleutian arc volcanoes  

USGS Publications Warehouse

Along the 450-km-long stretch of the Aleutian volcanic arc from Great Sitkin to Kiska Islands, edifice failure and submarine debris-avalanche deposition have occurred at seven of ten Quaternary volcanic centers. Reconnaissance geologic studies have identified subaerial evidence for large-scale prehistoric collapse events at five of the centers (Great Sitkin, Kanaga, Tanaga, Gareloi, and Segula). Side-scan sonar data collected in the 1980s by GLORIA surveys reveal a hummocky seafloor fabric north of several islands, notably Great Sitkin, Kanaga, Bobrof, Gareloi, Segula, and Kiska, suggestive of landslide debris. Simrad EM300 multibeam sonar data, acquired in 2005, show that these areas consist of discrete large blocks strewn across the seafloor, supporting the landslide interpretation from the GLORIA data. A debris-avalanche deposit north of Kiska Island (177.6?? E, 52.1?? N) was fully mapped by EM300 multibeam revealing a hummocky surface that extends 40??km from the north flank of the volcano and covers an area of ??? 380??km2. A 24-channel seismic reflection profile across the longitudinal axis of the deposit reveals a several hundred-meter-thick chaotic unit that appears to have incised into well-bedded sediment, with only a few tens of meters of surface relief. Edifice failures include thin-skinned, narrow, Stromboli-style collapse as well as Bezymianny-style collapse accompanied by an explosive eruption, but many of the events appear to have been deep-seated, removing much of an edifice and depositing huge amounts of debris on the sea floor. Based on the absence of large pyroclastic sheets on the islands, this latter type of collapse was not accompanied by large eruptions, and may have been driven by gravity failure instead of magmatic injection. Young volcanoes in the central and western portions of the arc (177?? E to 175?? W) are located atop the northern edge of the ??? 4000-m-high Aleutian ridge. The position of the Quaternary stratocones relative to the edge of the Aleutian ridge appears to strongly control their likelihood for, and direction of, past collapse. The ridge's steep drop to the north greatly increases potential runout length for slides that originate at the island chain. ?? 2007 Elsevier B.V. All rights reserved.

Coombs, M. L.; White, S. M.; Scholl, D. W.

2007-01-01

12

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

13

Aleutian Pribilof Islands Wind Energy Feasibility Study.  

National Technical Information Service (NTIS)

Under this project, the Aleutian Pribilof Islands Association (APIA) conducted wind feasibility studies for Adak, False Pass, Nikolski, Sand Point and St. George. The DOE funds were also be used to continue APIAs role as project coordinator, to expand the...

B. Wright

2012-01-01

14

Along-strike trace element and isotopic variation in Aleutian Island arc basalt: Subduction melts sediments and dehydrates serpentine  

Microsoft Academic Search

Trace element and Sr-Nd-Pb isotope compositions of basaltic lavas from 11 volcanoes spanning 1300 km of the Aleutian Island arc provide new constraints on the recycling of elements in melts and fluids derived from subducted oceanic crust and sediment. Despite a nearly twofold variation in the flux of sediment subducted along the Aleutians, proxies indicating the presence of sediment melt

Brad S. Singer; Brian R. Jicha; William P. Leeman; Nick W. Rogers; Matthew F. Thirlwall; Jeff Ryan; Kirsten E. Nicolaysen

2007-01-01

15

Teleseismic detection in the Aleutian Island arc  

SciTech Connect

Recently it has become apparent that teleseismic detection has decreased substantially in many regions of the world. The major decrease was related to the closure of the VELA arrays in the United States during the later 1960's. This detection decrease has been recognized in South and Central America, Mexico, the Kuriles, the Caribbean, Tonga, and the New Hebrides. In this paper the effect of the closure of these arrays on the reporting of events in the Aleutian Island Arc is examined. In the Aleutians, the detection history is complicated by the short-term installation of a local network on and near Amchitka Island during the early 1970's. The temporal coincidence of the installation of this network and the closure of the VELA arrays delayed the detection decrease in the central Aleutians until the Amchitka network was closed in early 1973. Reporting in the eastern Aleutians was unaffected by the installation of the Amchitka network. In that region the detection decreased between 1968 and 1970, the times of the closure of the VELA arrays. New techniques have been developed which make it possible to determine the effect of station installation of closure on the reporting in some regions. These techniques rely on plots which show the distribution of an observed seismicity rate change in the magnitude domain. These plots make it possible to recognize probable detection changes and to determine quantititively magnitude cutoffs which avoid these changes. If one is interested in examining seismicity rates for changes which may be precursors to earthquakes, then awareness of detection-related changes and magnitude cutoffs which avoid these changes are essential for meaningful results.

Habermann, R.E.

1983-06-10

16

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

17

Double Glacier Volcano, a 'new' Quaternary volcano in the eastern Aleutian volcanic arc  

USGS Publications Warehouse

The Double Glacier Volcano (DGV) is a small dome complex of porphyritic hornblende andesite and dacite that is part of the Cook Inlet segment of Quaternary volcanoes of the eastern Aleutian arc. Its discovery reduces the previously described large volcano gap in Cook Inlet segment to a distance similar to that between other volcanoes in the area. DGV lavas are medium-K, calcalkaline andesites and dacites with concentrations of major and minor elements similar to the other Quaternary volcanoes of the Cook Inlet segment. Available K-Ar ages indicate that DGV was active 600-900 ka. ?? 1992 Springer-Verlag.

Reed, B. L.; Lanphere, M. A.; Miller, T. P.

1992-01-01

18

Two Chiefs' Houses from the Western Aleutian Islands  

Microsoft Academic Search

The earliest Russian explorers of the Aleutians described Near Island chiefs’ houses that were larger than those of ordinary people. The Russians noted that these houses were also functionally different than ordinary dwellings. Chiefs entertained guests, sheltered widows and orphans, and hosted religious ceremonies in their houses. Between 1997 and 2003, Western Aleutians Archaeological and Paleobiological Project (WAAPP) archaeologists excavated

Debra G. Corbett

2012-01-01

19

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

Federal Register 2010, 2011, 2012, 2013

...Zone Off Alaska; Bering Sea and Aleutian Islands Crab Rationalization Program AGENCY...Management Plan for Bering Sea/Aleutian Islands King and Tanner Crabs (FMP). If approved...would amend the Bering Sea/ Aleutian Islands Crab Rationalization Program by...

2011-02-15

20

78 FR 28523 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013

...Zone Off Alaska; Bering Sea and Aleutian Islands Crab Rationalization Program AGENCY...Management Plan for Bering Sea/Aleutian Islands King and Tanner Crabs (FMP). These regulations amend the Bering Sea/Aleutian Islands Crab Rationalization Program (CR...

2013-05-15

21

76 FR 68358 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013

...Zone Off Alaska; Bering Sea and Aleutian Islands Crab Rationalization Program AGENCY...Management Plan for Bering Sea/Aleutian Islands King and Tanner Crabs (FMP). Amendment 30 amends the Bering Sea/Aleutian Islands Crab Rationalization Program (CR...

2011-11-04

22

75 FR 38430 - Fisheries of the Exclusive Economic Zone Off Alaska; Greenland Turbot in the Aleutian Islands...  

Federal Register 2010, 2011, 2012, 2013

...Exclusive Economic Zone Off Alaska; Greenland Turbot in the Aleutian Islands Subarea...the initial total allowable catch of Greenland turbot in the Aleutian Islands subarea...initial total allowable catch (ITAC) of Greenland turbot in the Aleutian Islands...

2010-07-02

23

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

Federal Register 2010, 2011, 2012, 2013

...Off Alaska; ``Other Rockfish'' in the Aleutian Islands Subarea of the Bering Sea and Aleutian Islands Management Area AGENCY: National...retention of ``other rockfish'' in the Aleutian Islands subarea of the Bering Sea and...

2012-10-24

24

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

Federal Register 2010, 2011, 2012, 2013

...Off Alaska; ``Other Rockfish'' in the Aleutian Islands Subarea of the Bering Sea and Aleutian Islands Management Area AGENCY: National...retention of ``other rockfish'' in the Aleutian Island subarea of the Bering Sea and...

2011-09-28

25

76 FR 17034 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands; Final 2011...  

Federal Register 2010, 2011, 2012, 2013

...Economic Zone Off Alaska; Bering Sea and Aleutian Islands; Final 2011 and 2012 Harvest...groundfish fishery of the Bering Sea and Aleutian Islands Management Area (BSAI). Two...Pollock............. 150 150 Aleutian Islands subarea........

2011-03-28

26

75 FR 50716 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013

...Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab Rationalization Program...quota (IPQ) issued for the Western Aleutian Islands golden king crab fishery from...designation. Under the Bering Sea/Aleutian Islands Crab Rationalization...

2010-08-17

27

76 FR 45219 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...  

Federal Register 2010, 2011, 2012, 2013

...Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management Area; Limited Access...for Groundfish of the Bering Sea and Aleutian Islands Management Area (FMP) would amend the Bering Sea and Aleutian Islands Amendment 80 Program to...

2011-07-28

28

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

Federal Register 2010, 2011, 2012, 2013

...Zone Off Alaska; Bering Sea and Aleutian Islands Management Area; Limited...Groundfish of the Bering Sea and Aleutian Islands Management Area (FMP...regulations amend the Bering Sea and Aleutian Islands Amendment 80 Program...

2011-11-04

29

Plant Collecting on the Pribilof and Aleutian Islands, 1936  

Microsoft Academic Search

THE Aleutian Islands stretch from the tip of the Kenai Peninsula of Alaska for 1,200 miles westwards to Kamchatka. They comprise some fifteen larger islands and hundreds of smaller ones, and owing to their inaccessibility have been very little explored botanically.

Isobel W. Hutchison

1937-01-01

30

50 CFR 600.1103 - Bering Sea and Aleutian Islands (BSAI) Crab species program.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Bering Sea and Aleutian Islands (BSAI) Crab species program. 600...600.1103 Bering Sea and Aleutian Islands (BSAI) Crab species program. (a...Management Plan for the Bering Sea/Aleutian Islands King and Tanner Crabs pursuant to §...

2013-10-01

31

50 CFR Figure 1 to Part 679 - Bering Sea and Aleutian Islands Statistical and Reporting Areas  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Bering Sea and Aleutian Islands Statistical and Reporting Areas 1 ...to Part 679âBering Sea and Aleutian Islands Statistical and Reporting Areas ER15NO99...00â² W long, and north of the Aleutian Islands and straight lines between the...

2013-10-01

32

50 CFR 600.1103 - Bering Sea and Aleutian Islands (BSAI) Crab species program.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Bering Sea and Aleutian Islands (BSAI) Crab species program...Regulations § 600.1103 Bering Sea and Aleutian Islands (BSAI) Crab species program...Management Plan for the Bering Sea/Aleutian Islands King and Tanner Crabs...

2010-10-01

33

50 CFR Figure 1 to Part 679 - Bering Sea and Aleutian Islands Statistical and Reporting Areas  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Bering Sea and Aleutian Islands Statistical and Reporting Areas...Figure 1 to Part 679âBering Sea and Aleutian Islands Statistical and Reporting Areas...170°00â² W long, and north of the Aleutian Islands and straight lines between...

2009-10-01

34

50 CFR Figure 1 to Part 679 - Bering Sea and Aleutian Islands Statistical and Reporting Areas  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Bering Sea and Aleutian Islands Statistical and Reporting Areas...Figure 1 to Part 679âBering Sea and Aleutian Islands Statistical and Reporting Areas...170°00â² W long, and north of the Aleutian Islands and straight lines between...

2010-10-01

35

50 CFR 600.1103 - Bering Sea and Aleutian Islands (BSAI) Crab species program.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Bering Sea and Aleutian Islands (BSAI) Crab species program...Regulations § 600.1103 Bering Sea and Aleutian Islands (BSAI) Crab species program...Management Plan for the Bering Sea/Aleutian Islands King and Tanner Crabs...

2009-10-01

36

Avian mortality associated with a volcanic gas seep at Kiska Island, Aleutian Islands, Alaska  

USGS Publications Warehouse

We identified natural pits associated with avian mortality at the base of Kiska Volcano in the western Aleutian Islands, Alaska in 2007. Living, moribund, and dead birds were regularly found at low spots in a canyon between two lava flows during 2001–2006, but the phenomenon was attributed to natural trapping and starvation of fledgling seabirds (mostly Least Auklets, Aethia pusilla) at a colony site with >1 million birds present. However, 302 birds of eight species, including passerines, were found dead at the site during 2007–2010, suggesting additional factors were involved. Most carcasses showed no signs of injury and concentrations of dead birds had accumulated in a few distinctive low pits in the canyon. Gas samples from these locations showed elevated CO2 concentrations in late 2010. Analysis of carcasses indicated no evidence of blunt trauma or internal bleeding. Volcanic gases accumulating at these poorly ventilated sites may have caused the observed mortality, but are temporally variable. Most auklets breeding in the Aleutian Islands do so in recent lava flows that provide breeding habitat; our study documents a cost of this unusual habitat selection.

Bond, Alexander L.; Evans, William C.; Jones, Ian L.

2012-01-01

37

Aleutian Pribilof Islands Wind Energy Feasibility Study  

SciTech Connect

Under this project, the Aleutian Pribilof Islands Association (APIA) conducted wind feasibility studies for Adak, False Pass, Nikolski, Sand Point and St. George. The DOE funds were also be used to continue APIA's role as project coordinator, to expand the communication network quality between all participants and with other wind interest groups in the state and to provide continued education and training opportunities for regional participants. This DOE project began 09/01/2005. We completed the economic and technical feasibility studies for Adak. These were funded by the Alaska Energy Authority. Both wind and hydro appear to be viable renewable energy options for Adak. In False Pass the wind resource is generally good but the site has high turbulence. This would require special care with turbine selection and operations. False Pass may be more suitable for a tidal project. APIA is funded to complete a False Pass tidal feasibility study in 2012. Nikolski has superb potential for wind power development with Class 7 wind power density, moderate wind shear, bi-directional winds and low turbulence. APIA secured nearly $1M from the United States Department of Agriculture Rural Utilities Service Assistance to Rural Communities with Extremely High Energy Costs to install a 65kW wind turbine. The measured average power density and wind speed at Sand Point measured at 20m (66ft), are 424 W/m2 and 6.7 m/s (14.9 mph) respectively. Two 500kW Vestas turbines were installed and when fully integrated in 2012 are expected to provide a cost effective and clean source of electricity, reduce overall diesel fuel consumption estimated at 130,000 gallons/year and decrease air emissions associated with the consumption of diesel fuel. St. George Island has a Class 7 wind resource, which is superior for wind power development. The current strategy, led by Alaska Energy Authority, is to upgrade the St. George electrical distribution system and power plant. Avian studies in Nikolski and Sand Point have allowed for proper wind turbine siting without killing birds, especially endangered species and bald eagles. APIA continues coordinating and looking for funding opportunities for regional renewable energy projects. An important goal for APIA has been, and will continue to be, to involve community members with renewable energy projects and energy conservation efforts.

Bruce A. Wright

2012-03-27

38

Geological Structure of the Aleutian Trench Southwest of Kodiak Island  

Microsoft Academic Search

Geophysical data are presented and discussed for an area approximately 290 km long and 220 km wide in the Aleutian trench south of Kodiak Island. Variations in total mag- netic intensity (residual) of more than 600 - were found in the center of the trench and more than 1100 - on the southern flank. The free-air gravity values varied by

G. Peter; D. Elvers; M. Yellin

1965-01-01

39

Zooarchaeological Analysis at ADK011, Adak Island, Central Aleutian Islands, Alaska  

Microsoft Academic Search

Although William Dall explored the Central Aleutians nearly 140 years ago, surprisingly little archaeological research has occurred in this area since then. During 1999 the Western Aleutians Archaeological and Paleobiological Project excavated archaeological sites on north Adak Island, Alaska. Faunal remains from two excavation pits at ADK-011 are analyzed here. This is the first analysis of faunal remains from this

Christine Lefèvre; Dixie West; Debra G. Corbett

2012-01-01

40

Pb and Sr isotopes in volcanic rocks from the Aleutian Islands and Pribilof Islands, Alaska  

Microsoft Academic Search

The Pb and Sr isotope ratios of Plio-Pleistocene volcanic rocks from the Aleutian volcanic arc are used as tracers of the lithospheric subduction process at the converging Pacific and Bering plates. Aleutian arc lavas do not have the same Pb isotopic compositions as volcanic rocks of the subducted Pacific ocean crust or the nearby Pribilof Islands, but appear to contain

R. W. Kay; S.-S. Sun; C.-N. Lee-Hu

1978-01-01

41

Cranial suture biology of the Aleutian Island inhabitants.  

PubMed

Research on cranial suture biology suggests there is biological and taxonomic information to be garnered from the heritable pattern of suture synostosis. Suture synostosis along with brain growth patterns, diet, and biomechanical forces influence phenotypic variability in cranial vault morphology. This study was designed to determine the pattern of ectocranial suture synostosis in skeletal populations from the Aleutian Islands. We address the hypothesis that ectocranial suture synostosis pattern will differ according to cranial vault shape. Ales Hrdlicka identified two phenotypes in remains excavated from the Aleutian Island. The Paleo-Aleutians, exhibiting a dolichocranic phenotype with little prognathism linked to artifacts distinguished from later inhabitants, Aleutians, who exhibited a brachycranic phenotype with a greater amount of prognathism. A total of 212 crania representing Paleo-Aleuts and Aleutian as defined by Hrdlicka were investigated for suture synostosis pattern following standard methodologies. Comparisons were performed using Guttmann analyses. Results revealed similar suture fusion patterns for the Paleo-Aleut and Aleutian, a strong anterior to posterior pattern of suture fusion for the lateral-anterior suture sites, and a pattern of early termination at the sagittal suture sites for the vault. These patterns were found to differ from that reported in the literature. Because these two populations with distinct cranial shapes exhibit similar patterns of suture synostosis it appears pattern is independent of cranial shape in these populations of Homo sapiens. These findings suggest that suture fusion patterns may be population dependent and that a standardized methodology, using suture fusion to determine age-at-death, may not be applicable to all populations. PMID:21328563

Cray, James; Mooney, Mark P; Siegel, Michael I

2011-04-01

42

Origins of Linguistic Diversity in the Aleutian Islands  

Microsoft Academic Search

The Aleut language, currently spoken along the Aleutian chain and the Pribilof and Commander islands, is the only language in its branch of the Eskimo-Aleut language family, and traditional methods of linguistic reconstruction have neither satisfactorily explained its relationship with languages on the Asian continent nor its development from Proto-Eskimo-Aleut. Linguistic reconstruction has always been important in understanding the prehistory

Anna Berge

2010-01-01

43

78 FR 24362 - Fisheries of the Exclusive Economic Zone Off Alaska; Greenland Turbot in the Aleutian Islands...  

Federal Register 2010, 2011, 2012, 2013

...Exclusive Economic Zone Off Alaska; Greenland Turbot in the Aleutian Islands Subarea...NMFS is prohibiting directed fishing for Greenland turbot in the Aleutian Islands subarea...necessary to prevent exceeding the 2013 Greenland turbot initial total allowable...

2013-04-25

44

75 FR 38940 - Fisheries of the Exclusive Economic Zone Off Alaska; Greenland Turbot in the Aleutian Islands...  

Federal Register 2010, 2011, 2012, 2013

...Exclusive Economic Zone Off Alaska; Greenland Turbot in the Aleutian Islands Subarea...NMFS is prohibiting directed fishing for Greenland turbot in the Aleutian Islands subarea...necessary to prevent exceeding the 2010 Greenland turbot total allowable catch...

2010-07-07

45

50 CFR 600.1106 - Longline catcher processor subsector Bering Sea and Aleutian Islands (BSAI) non-pollock...  

Code of Federal Regulations, 2013 CFR

...false Longline catcher processor subsector Bering Sea and Aleutian Islands (BSAI) non-pollock groundfish species fee payment...1106 Longline catcher processor subsector Bering Sea and Aleutian Islands (BSAI) non-pollock groundfish species fee...

2013-10-01

46

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

47

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 679âAleutian Islands Chinook Salmon Savings Area ER30AU10.000 [75 FR 53069, Aug. 30,...

2013-10-01

48

46 CFR 7.170 - Alaska Peninsula, AK to Aleutian Islands, AK.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Alaska Peninsula, AK to Aleutian Islands, AK. 7.170 Section 7.170 Shipping COAST...BOUNDARY LINES Alaska § 7.170 Alaska Peninsula, AK to Aleutian Islands, AK. (a) A line drawn from the...

2013-10-01

49

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

50

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

51

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

52

78 FR 68390 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...  

Federal Register 2010, 2011, 2012, 2013

...Zone Off Alaska; Bering Sea and Aleutian Islands Management Area; Amendment 102 AGENCY...Groundfish of the Bering Sea and Aleutian Islands Management Area (BSAI FMP), and amend...Area 4B) and the sablefish Aleutian Islands regulatory area that is similar to...

2013-11-14

53

76 FR 11139 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands; Final 2011...  

Federal Register 2010, 2011, 2012, 2013

...Zone Off Alaska; Bering Sea and Aleutian Islands; Final 2011 and 2012 Harvest Specifications...fishery of the Bering Sea and Aleutian Islands management area (BSAI). This action...to the BSAI Atka mackerel and Aleutian Islands subarea Pacific cod fisheries to...

2011-03-01

54

78 FR 13813 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands; 2013 and...  

Federal Register 2010, 2011, 2012, 2013

...Zone Off Alaska; Bering Sea and Aleutian Islands; 2013 and 2014 Harvest Specifications...fishery of the Bering Sea and Aleutian Islands management area (BSAI). This action...yellowfin sole, Pacific cod, and Aleutian Islands Pacific ocean perch), 10.7...

2013-03-01

55

77 FR 10669 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands; Final 2012...  

Federal Register 2010, 2011, 2012, 2013

...Zone Off Alaska; Bering Sea and Aleutian Islands; Final 2012 and 2013 Harvest Specifications...fishery of the Bering Sea and Aleutian Islands management area (BSAI). This action...the Bering Sea subarea and the Aleutian Island subarea. This split depends on NMFS...

2012-02-23

56

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

Federal Register 2010, 2011, 2012, 2013

...Zone Off Alaska; Bering Sea and Aleutian Islands Crab Rationalization Program AGENCY...Management Plan for Bering Sea/Aleutian Islands King and Tanner Crabs (FMP). This proposed...would amend the Bering Sea/Aleutian Islands Crab Rationalization Program (CR...

2011-08-10

57

50 CFR 600.1104 - Bering Sea and Aleutian Islands (BSAI) crab species fee payment and collection system.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 false Bering Sea and Aleutian Islands (BSAI) crab species fee payment and...600.1104 Bering Sea and Aleutian Islands (BSAI) crab species fee payment and...crab), (2) Bering Sea and Aleutian Islands Area C. opilio and C. bairdi...

2013-10-01

58

78 FR 6279 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013

...Zone Off Alaska; Bering Sea and Aleutian Islands Crab Rationalization Program AGENCY...Management Plan for Bering Sea/Aleutian Islands King and Tanner Crabs (FMP). If approved...regulations will amend the Bering Sea/ Aleutian Islands Crab Rationalization Program (CR...

2013-01-30

59

78 FR 65602 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...  

Federal Register 2010, 2011, 2012, 2013

...Zone Off Alaska; Bering Sea and Aleutian Islands Management Area; Amendment 102 AGENCY...Groundfish of the Bering Sea and Aleutian Islands Management Area (BSAI FMP) for review...Program for sablefish in the Aleutian Islands regulatory area. The proposed CQE...

2013-11-01

60

75 FR 76372 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands; Proposed...  

Federal Register 2010, 2011, 2012, 2013

...Zone Off Alaska; Bering Sea and Aleutian Islands; Proposed 2011 and 2012 Harvest Specifications...fisheries of the Bering Sea and Aleutian Islands (BSAI) management area. This action...Groundfish of the Bering Sea and Aleutian Islands Management Area. The intended...

2010-12-08

61

76 FR 49417 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...  

Federal Register 2010, 2011, 2012, 2013

...Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management Area; Limited Access...for Groundfish of the Bering Sea and Aleutian Islands Management Area (FMP). This...proposed rule would amend the Bering Sea and Aleutian Islands Amendment 80 Program to...

2011-08-10

62

50 CFR 600.1104 - Bering Sea and Aleutian Islands (BSAI) crab species fee payment and collection system.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Bering Sea and Aleutian Islands (BSAI) crab species fee payment...Regulations § 600.1104 Bering Sea and Aleutian Islands (BSAI) crab species fee payment...king crab), (2) Bering Sea and Aleutian Islands Area C. opilio and C....

2009-10-01

63

50 CFR 600.1104 - Bering Sea and Aleutian Islands (BSAI) crab species fee payment and collection system.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Bering Sea and Aleutian Islands (BSAI) crab species fee payment...Regulations § 600.1104 Bering Sea and Aleutian Islands (BSAI) crab species fee payment...king crab), (2) Bering Sea and Aleutian Islands Area C. opilio and C....

2010-10-01

64

Observations of deep long-period (DLP) seismic events beneath Aleutian arc volcanoes; 1989-2002  

USGS Publications Warehouse

Between October 12, 1989 and December 31, 2002, the Alaska Volcano Observatory (AVO) located 162 deep long-period (DLP) events beneath 11 volcanic centers in the Aleutian arc. These events generally occur at mid- to lower-crustal depths (10-45 km) and are characterized by emergent phases, extended codas, and a strong spectral peak between 1.0 and 3.0 Hz. Observed wave velocities and particle motions indicate that the dominant phases are P- and S-waves. DLP epicenters often extend over broad areas (5-20 km) surrounding the active volcanoes. The average reduced displacement of Aleutian DLPs is 26.5 cm2 and the largest event has a reduced displacement of 589 cm2 (or ML 2.5). Aleutian DLP events occur both as solitary events and as sequences of events with several occurring over a period of 1-30 min. Within the sequences, individual DLPs are often separated by lower-amplitude volcanic tremor with a similar spectral character. Occasionally, volcano-tectonic earthquakes that locate at similar depths are contained within the DLP sequences. At most, Aleutian volcanoes DLPs appear to loosely surround the main volcanic vent and occur as part of background seismicity. A likely explanation is that they reflect a relatively steady-state process of magma ascent over broad areas in the lower and middle portions of the crust. At Mount Spurr, DLP seismicity was initiated by the 1992 eruptions and then slowly declined until 1997. At Shishaldin Volcano, a short-lived increase in DLP seismicity occurred about 10 months prior to the April 19, 1999 eruption. These observations suggest a link between eruptive activity and magma flux in the mid- to lower-crust and uppermost mantle.

Power, J. A.; Stihler, S. D.; White, R. A.; Moran, S. C.

2004-01-01

65

Crustal Control on Crystallization Depths? Preliminary Evidence from Mt. Cleveland, Chuginadak Island, Eastern Aleutian arc  

NASA Astrophysics Data System (ADS)

Mt. Cleveland is one of the most active volcanoes of the eastern Aleutian arc with eruptions in 2005 and 2001 and a total of 23 known eruptions in approximately the last hundred years. Several features, perhaps indicating a complex crustal geometry make Mt. Cleveland unusual. First, the Islands of Four Mountains (Herbert, Carlisle, Cleveland, Tana, Kagamil) define an area of unusually closely-spaced Quaternary stratovolcanoes relative to the central and western Aleutians. Also, the Islands of Four Moutains are closer to the trench compared to the rest of the arc. Finally, the earthquake record shows a linear cluster of earthquakes leading from Cleveland toward the trench (map view); as yet, no interpretation exists to explain how the defined linear feature may relate to a crustal structure or the downgoing slab. The crust beneath the volcano is approximately 30 km thick and is transitioning from oceanic to continental affinity. We use clinopyroxene thermobarometry to investigate the depths at which Mt. Cleveland magmas tend to stall prior to eruption to examine whether basement structure may influence the ascent of the magmas. The peak consists largely of lavas and interbedded debris flows although several cinder cones and andesitic domes have formed within five kilometers of the summit. The lavas are primarily calc-alkaline andesites and most contain two pyroxenes, plagioclase and occasionally olivine or titanomagnetite. Two of the cinder cones, in contrast, are olivine-plagioclase-clinopyroxene basaltic andesites. Preliminary data show that a Holocene flow (1994?) from Mt. Cleveland crystallized clinopyroxene at approximately 1035°C and 13+/-2 kb pressure, which corresponds nearly with the base of the crust. In contrast, the 2001 tephra essentially crystallized at 1 atm, consistent with rapid ascent through the crust. The basaltic andesite of the youngest cinder cone crystallized clinopyroxene at approximately 1300°C and 3 kb pressure, indicating some residence time in the crust.

Nicolaysen, K. P.; Bridges, D.; Swapp, S.

2005-12-01

66

Structure and composition of the Aleutian island arc and implications for continental crustal growth  

Microsoft Academic Search

We present results of a seismic reflection and refraction investigation of the Aleutian island arc, designed to test the hypothesis that volcanic arcs constitute the building blocks of continental crust. The Aleutian arc has the requisite thickness (30 km) to build continental crust, but it differs strongly from continental crust in its composition and reflectivity structure. Seismic velocities and the

W. Steven Holbrook; D. Lizarralde; S. McGeary; N. Bangs; J. Diebold

1999-01-01

67

Structure of an island-arc: Wide-angle seismic studies in the eastern Aleutian Islands, Alaska  

Microsoft Academic Search

New seismic wide-angle data from the eastern Aleutian Islands show a mafic composition and a 30-km-thick island-arc crust. Traveltimes of P and S refracted arrivals and prominent crustal and mantle reflectors observed to offsets of over 300 km were used to derive velocity models for the eastern Aleutian Arc between the islands of Atka and Unimak using a three-dimensional finite

Moritz M. Fliedner; Simon L. Klemperer

1999-01-01

68

Reconnaissance of thermal spring sites in the Aleutian arc, Atka Island to Becherof Lake  

SciTech Connect

Twenty of more than 30 thermal springs in the Aleutian arc, extending from Atka Island to Becherof Lake, were investigated July and August, 1980. Subsurface reservoir temperatures in excess of 150/sup 0/C are estimated for 10 of the thermal spring sites investigated. These sites all occur in or near regions of recent volcanism. Five thermal-spring sites have reservoir temperatures in the range of 90 to 150/sup 0/C and occur either near recent volcanoes or near lineations that suggest fracture or fault control. Three sites identified as having reservoir temperatures < 90/sup 0/C, occur at or near the coast and appear to be related to local fractures or dikes. Thermal activity at three other sites had diminished substantially or no longer existed. Three locations are highly promising for developing and using geothermal energy: Akutan Island, northern Unalaska Island, and northeast Atka Island. All three areas have high-temperature (> 150/sup 0/C) geothermal resources that are located near existing population centers with well-protected, deep-water harbors.

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

1981-10-01

69

Origins of linguistic diversity in the Aleutian Islands.  

PubMed

The Aleut language, currently spoken along the Aleutian chain and the Pribilof and Commander islands, is the only language in its branch of the Eskimo-Aleut language family, and traditional methods of linguistic reconstruction have neither satisfactorily explained its relationship with languages on the Asian continent nor its development from Proto-Eskimo-Aleut. Linguistic reconstruction has always been important in understanding the prehistory and history of the Aleuts, and new approaches in comparative linguistics, more comprehensive information on typological features of neighboring languages, and continuing language documentation allow us to propose a rich and continuous history of contact with various groups of people. I evaluate evidence that the Aleut language may have been shaped by contact with neighbors in Asia and Alaska, eventually giving rise to its differentiation from the Eskimo languages. I look at dialect differentiation along the Aleutian chain and what this differentiation reveals about the migration trends of the Aleut along the chain. I look at the colonial expansion of the Aleut-speaking area and resulting additional varieties of Aleut in the historical period. Finally, I review the effects of the Russian and American colonial periods on the Aleut language and the severe endangerment that the language faces today as a result. I conclude that there is evidence of possible Aleut contact with both neighboring peoples; however, much of this evidence has not yet been subjected to systematic comparative reconstructions. Linguistic evidence supports theories of at least two westward expansions of Aleuts along the island chain, but it is not yet clear what motivated the dialect differentiations. Finally, I offer some thoughts on directions for future dialect studies and the continuing documentation of Aleut. PMID:21417884

Berge, Anna

2010-12-01

70

Forecasters Handbook for the Bering Sea, Aleutian Islands, and Gulf of Alaska.  

National Technical Information Service (NTIS)

Weather conditions in the Bering Sea, Aleutian Islands, and Gulf of Alaska region are described. Rules of thumb and other quick reference materials are provided for use by operational forecasters. Background information is included to enhance understandin...

D. C. Perryman R. E. Englebretson R. W. Fett

1993-01-01

71

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.

Foundation, Wgbh E.

2009-02-27

72

Inferring Population Continuity Versus Replacement with aDNA: A Cautionary Tale from the Aleutian Islands  

Microsoft Academic Search

In The Aleutian and Commander Islands and Their Inhabitants (Philadelphia: Wistar Institute of Anatomy and Biology, 1945), Hrdlička proposed a population replacement event in the Aleutian Islands approximately 1,000 years ago based on a perceived temporal shift in cranial morphology. However, the archaeological record indicates cultural, and presumed population, continuity for more than 4,000 years. We use mtDNA haplogroup data

Silvia E. Smith; M. Geoffrey Hayes; Graciela S. Cabana; Chad Huff; Joan Brenner Coltrain; Dennis H. ORourke

2009-01-01

73

Inferring Population Continuity Versus Replacement with aDNA: A Cautionary Tale from the Aleutian Islands  

Microsoft Academic Search

:In The Aleutian and Commander Islands and Their Inhabitants (Philadelphia: Wistar Institute of Anatomy and Biology, 1945), Hrdlička proposed a population replacement event in the Aleutian Islands approximately 1,000 years ago based on a perceived temporal shift in cranial morphology. However, the archaeological record indicates cultural, and presumed population, continuity for more than 4,000 years. We use mtDNA haplogroup data

Silvia E. Smith; M. Geoffrey Hayes; Graciela S. Cabana; Chad Huff; Joan Brenner Coltrain; Dennis H. ORourke

2009-01-01

74

Inferring Population Continuity Versus Replacement with aDNA: A Cautionary Tale from the Aleutian Islands  

Microsoft Academic Search

In The Aleutian and Commander Islands and Their Inhabitants (Philadelphia: Wistar Institute of Anatomy and Biology, 1945), Hrdlic?ka proposed a population replacement event in the Aleutian Islands approximately 1,000 years ago based on a perceived temporal shift in cranial morphology. However, the archaeological record indicates cultural, and presumed population, continuity for more than 4,000 years. We use mtDNA haplogroup data

Silvia E. Smith; M. Geoffrey Hayes; Graciela S. Cabana; Chad Huff; Joan Brenner Coltrain; Dennis H. O'Rourke

2009-01-01

75

An Arctic fox (Alopex lagopus) captures a Least Auklet (Aethia pusilla) in the Aleutian Islands.  

NSDL National Science Digital Library

During the 100-150 years since they were introduced to the Aleutian Islands, the Arctic fox (Alopex lagopus) and Norway rat (Rattus norvegicus) have extirpated native seabirds from most of the islands through predation. Burrow nesting species have been particularly affected. The Least Auklet (Aethia pusilla) is an abundant seabird species in the Aleutian Islands. The introduction of foxes and rats to many islands and the subsequent loss of seabirds have indirectly affected other characteristics of island ecosystems, such as soil nutrient levels, plant community composition, and predominant nutrient sources (terrestrial versus marine). This photograph originally appeared on the cover of Ecological Monographs (76:1) in February of 2006.

Degange, Anthony

2010-02-16

76

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

77

Paleogene geology and chronology of southwestern Umnak Island, Aleutian Islands, Alaska ( USA).  

USGS Publications Warehouse

A slightly deformed marine sedimentary sequence reflecting volcanic arc sedimentation from late Eocene to early Oligocene is intruded by hypabyssal quartz diorite sills and small plutons with apparent ages of about 30 Ma, ie, middle Oligocene. Chemical data from igneous rocks exhibit calc-alkaline and tholeiitic volcanic arc differentiation trends. The fossil ages and radiometric dates from SW Umnak Island are similar to those reported from other central and E Aleutian islands, and indicate uniformity in the chronology and tectonic development of the archipelago during the Paleogene. Paleomagnetic data suggest possible northward movement but remain equivocal and more work is indicated. -after Authors

McLean, H.; Hein, J. R.

1984-01-01

78

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

79

Hair methylmercury levels of mummies of the Aleutian Islands, Alaska.  

PubMed

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. PMID:19195649

Egeland, G M; Ponce, Rafael; Bloom, Nicolas S; Knecht, Rick; Loring, Stephen; Middaugh, John P

2009-04-01

80

Nd and Sr isotopes in the Aleutians: multicomponent parenthood of island-arc magmas  

Microsoft Academic Search

Young volcanic rocks from different sections of the Aleutian Islands-Alaska Peninsula Arc have been measured for 87Sr\\/86Sr, 143Nd\\/144Nd and some trace elements. We found the 143Nd\\/144Nd to be highly restricted in range (?Nd=6 to 7) and low as compared to midocean ridge ba-salts (MORB). This indicates that the source of the Aleutian Arc magmas is different from MORB and remarkably

V. von Drach; B. D. Marsh; G. J. Wasserburg

1986-01-01

81

Geologic Map and Eruptive History of Veniaminof Volcano Record Aleutian Arc Processing of Mantle-Derived Melts  

Microsoft Academic Search

Mount Veniaminof, one of the largest volcanoes in the Aleutian arc, has a basal diameter of ~40 km, a volume of ~350 km3, an 8-km-diameter ice-filled caldera, and an active intracaldera cone. The geology of this tholeiitic basalt-to-dacite volcano has been mapped at 1:50,000 scale. Over 100 Quaternary volcanic map units are characterized by 600 chemical analyses of rocks and

C. R. Bacon; T. W. Sisson; A. T. Calvert; C. J. Nye

2009-01-01

82

Pacific Basin Tsunami Hazards Associated with Mass Flows in the Aleutian Islands of Alaska  

Microsoft Academic Search

The Aleutian Islands are a chain of volcanic islands formed by an intra-oceanic subduction zone. This area consists of a submerged chain of mountains, volcanic islands, and submarine canyons, surrounded by a low- relief continental shelf above about 1000-2000 m water depth. Part of the island chain is fragmented into a series of fault-bounded blocks, tens to hundreds of km

C. F. Waythomas; P. Watts; F. Shi; J. T. Kirby

2007-01-01

83

Seismic Observations of Westdahl volcano and Western Unimak Island Alaska: 1999-2005  

NASA Astrophysics Data System (ADS)

Westdahl volcano is a large basaltic shield volcano on the western end of Unimak Island Alaska in the Aleutian Island Arc. The volcano is topped by three separate vents, Pogromni Volcano, Faris Peak, and Westdahl Peak. The volcano is frequently active with known eruptions from Westdahl Peak in 1964, 1978, and 1991-92 that produced large basaltic lava flows. InSAR measurements indicate that Westdahl Volcano has been inflating at a slowly declining rate since 1992 (Lu et al., 2003). The Alaska Volcano Observatory has operated a network of six short-period seismometers on Westdahl Peak since 1998. Complementing this network are similar networks centered on Shishaldin and Akutan Volcanoes. Since 1999 more than 300 earthquakes have been located within 20 km of Westdahl Volcano. A volcano specific velocity model was determined for the western half of Uminak Island by simultaneously inverting for the velocity model and hypocentral earthquake locations using the program VELEST. Earthquakes located with the new model reveal five clusters of hypocenters: (a) a shallow cluster beneath Westdahl Peak, that largely occurred during a 24-hour period on January 7, 2004, (b) a concentration of 68 earthquakes with hypocenters ranging in depth from zero to eight km beneath Faris Peak occurring continually since 1999, (c) a diffuse cluster of long-period events northwest of Westdahl and Faris Peaks, (d) a cluster of 12 earthquakes near Pinnacle Rock, 12 km southwest of Westdahl Peak in October 2003, and (e) a cluster of 43 hypocenters near Unimak Bight, 20 km east of Westdahl Peak, that occurred between January and April 2004. Focal mechanisms were derived for four earthquakes in the Faris Peak cluster and four additional earthquakes that locate off the volcanic edifice (the four mechanisms are in the Pinnacle Rock cluster, the Unimak Bight cluster, and 20 km southeast and 30 km northeast of the volcano). Focal mechanisms in the Faris Peak cluster showed normal faulting with nodal planes trending north-south to northwest-southeast. Mechanisms of the off-volcano earthquakes are generally characterized by normal faulting with nodal planes trending southwest-northeast. These events are consistent with a stress field dominated by the Aleutian subduction zone. The Faris Peak mechanisms are not consistent with the presumed regional stress field and may reflect volcanic process. Lu et al., (2003) proposed the observed inflation of Westdahl Volcano resulted from a slowly pressurizing magma source at 6 km depth beneath Westdahl Peak. The observed seismicity is consistent with this model. Lu, Z., T. Masterlark, D. Dzurisin, and R. Rykhus, 2003, Magma supply dynamics at Westdahl volcano, Alaska, modeled from satellite radar interferometry, Alaska, J. Geophys. Res. 108, 2354, doi:10.1029/2002JB002311, 2003.

Dixon, J. P.; Power, J. A.; Stihler, S. D.

2005-12-01

84

50 CFR Figure 6 to Subpart E of... - Alaska Peninsula and Aleutian Islands Rural and Non-Rural Areas  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Alaska Peninsula and Aleutian Islands Rural and Non-Rural Areas 6 Figure 6 to Subpart... Figure 6 to Subpart E of Part 300âAlaska Peninsula and Aleutian Islands Rural and Non-Rural Areas ER04NO09.012...

2013-10-01

85

Earthquake source parameters and stress distribution in the Adak Island region of the central Aleutian Islands, Alaska  

Microsoft Academic Search

Source parameters have been sytematically determined for all earthquakes with MW>=5 that occurred between 172°W and 179°W longitude in the Adak Island region of the central Aleutian Islands during 1977-March 1987. We relocate the events using a plate velocity model developed for the region and use two alternative methods of depth determination. The first method uses arrival times of direct

Göran Ekström; E. R. Engdahl

1989-01-01

86

Muria Volcano, Island of Java, Indonesia  

NASA Technical Reports Server (NTRS)

This view of the north coast of central Java, Indonesia centers on the currently inactive Muria Volcano (6.5S, 111.0E). Muria is 5,330 ft. tall and lies just north of Java's main volcanic belt which runs east - west down the spine of the island attesting to the volcanic origin of the more than 1,500 Indonesian Islands.

1991-01-01

87

Shishaldin volcano: Aleutian high-alumina basalts and the question of plagioclase accumulation  

SciTech Connect

High-alumina basalts (HABs) from volcanic arcs commonly contain 30%-50% (modal) plagioclase. It has been suggested that they reflect plagioclase addition and are not primary compositions. In rocks from the Aleutian volcano Shishaldin, the authors search for evidence of plagioclase accumulation: Al{sub 2}O{sub 3}, CaO, and Na{sub 2}O vs. modal plagioclase; europium anomalies in HABs; plagioclase-liquid equilibrium; and the HAB groundmass. The HABs do not appear to be results of plagioclase addition to liquids of dacitic, Fe-Ti enriched, or high-Mg basaltic compositions. Plagioclase loss from HABs does appear to yield the Fe-Ti-enriched basalts. Shishaldin HABs may reflect near-primary compositions, and HAB phase equilibria may thus be useful in evaluating the origin of such arc basalts.

Fournelle, J.; Marsh, B.D. (Johns Hopkins Univ., Baltimore, Maryland (USA))

1991-03-01

88

Inferring population continuity versus replacement with aDNA: a cautionary tale from the Aleutian Islands.  

PubMed

In The Aleutian and Commander Islands and Their Inhabitants (Philadelphia: Wistar Institute of Anatomy and Biology, 1945), Hrdlicka proposed a population replacement event in the Aleutian Islands approximately 1,000 years ago based on a perceived temporal shift in cranial morphology. However, the archaeological record indicates cultural, and presumed population, continuity for more than 4,000 years. We use mtDNA haplogroup data in the series of prehistoric eastern Aleutian samples (n = 86) studied craniometrically by Hrdlicka to test alternative hypotheses regarding population continuity or replacement in the region. This molecular characterization, in conjunction with direct dating of individual specimens, provided increased resolution for hypothesis testing. Results indicate an apparent shift in mtDNA haplogroup frequencies in the eastern Aleutians approximately 1,000 years ago, in concert with changes in mortuary practices and isotopic signatures reflecting resource acquisition strategies. The earliest Aleut populations were characterized by a high frequency of haplogroup A, as are most modern populations of the North American arctic. Later prehistoric peoples in the Aleutians were characterized by a high frequency of haplogroup D and a correspondingly lower frequency of haplogroup A, a pattern typified by modern Aleut populations. PMID:20067367

Smith, Silvia E; Hayes, M Geoffrey; Cabana, Graciela S; Huff, Chad; Coltrain, Joan Brenner; O'Rourke, Dennis H

2009-08-01

89

An unusual new gorgonian coral (Anthozoa: Octocorallia) from the Aleutian Islands, Alaska  

Microsoft Academic Search

Despite the abundance and ecological importance of octocorals in Alaskan waters, most of the species in this assemblage remain unidentified and\\/or undescribed. One of the largest and most abundant species from the Aleutian Islands found at depths ranging between 125 and 512 m is a new and very unusual gorgonian coral. It has stout upright colonies that are laterally branched,

J. A. Sánchez; S. D. Cairns

2004-01-01

90

Condition of groundfish resources of the eastern Bering Sea and Aleutian Islands region in 1983  

SciTech Connect

This report contains an assessment of the condition of groundfish and squid in the eastern Bering Sea and Aleutian Islands region through 1983. The assessments are based on species-by-species analyses of the data collected from the commercial fishery and research vessel surveys. Estimates of maximum sustainable yields and equilibrium yields are presented to guide management of the 1984 fishery.

Bakkala, R.G.; Lee, L.L.; Ito, D.H.; Sample, T.M.; Narita, R.E.

1984-03-01

91

Atkamine: a new pyrroloiminoquinone scaffold from the cold water Aleutian Islands Latrunculia sponge.  

PubMed

A new pyrroloiminoquinone alkaloid, named atkamine, with an unusual scaffold was discovered from a cold, deep water Alaskan sponge Latrunculia sp. collected from the Aleutian Islands. Olefin metathesis was utilized to determine the location of the double bond in the hydrocarbon chain. The absolute configuration was determined by using computational approaches combing with the ECD (electronic circular dichroism) spectroscopy. PMID:23472820

Zou, Yike; Hamann, Mark T

2013-04-01

92

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

93

Condition of groundfish resources of the eastern Bering Sea and Aleutian Islands region in 1982  

SciTech Connect

This report contains an assessment of the condition of groundfish and squid in the eastern Bering Sea and Aleutian Islands region through 1982. The assessments are based on species-by-species analyses of the data collected from the commercial fishery and research vessel surveys. Most of the resources in the Bering Sea-Aleutians management region are in good condition, including walleye pollock, Pacific cod, the flatfishes, and Atka mackerel. Pacific cod and yellowfin sole are in excellent condition and at historic high levels of abundance.

Bakkala, R.G.; Low, L.; Ito, D.H.; Narita, R.E.; Ronholt, L.L.

1983-03-01

94

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

95

76 FR 47155 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013

...Bering Sea/Aleutian Islands crab fisheries managed under the BSAI Crab Rationalization program. The CIE, operated by Northern Taiga Ventures, Inc., provides independent peer reviews of NMFS's fisheries stock assessments and other science products....

2011-08-04

96

Influence of mesoscale anticyclonic eddies on zooplankton distribution south of the western Aleutian Islands during summer  

NASA Astrophysics Data System (ADS)

Mesoscale anticyclonic eddies have been observed south of the Aleutian Islands located between the Bering Sea and the subarctic Pacific. Eddies farther east, in the Gulf of Alaska, are known to transport coastal water and coastal zooplankton to offshore open ocean. The impacts of mesoscale anticyclonic eddies formed south of the western Aleutian Islands (Aleutian eddies) on the zooplankton community are not fully understood. In the present study, we describe zooplankton population structures within an Aleutian eddy and outside the eddy during July 2010. Our field study was conducted at seven stations along 51°15?N from 171°21?E to 174°38?E (western line) and at four stations along 50°40?N from 176°24?E to 178°44?E (eastern line) on 7-8 July 2010. At each station, environmental data (temperature, salinity and fluorescence were measured by CTD/XCTD. Zooplankton samples were collected by vertical tow of 150 m depth to the surface using 100 ?m mesh size plankton net. Based on the sea level anomaly (SLA), the western line crossed an anticyclonic eddy but the eastern line did not cross the eddy (Fig. 1). This Aleutian eddy was formed south of Attu Island (52°54?N, 172°54?E) in mid-February 2010, and it moved southeastward in the next five months. The SLA near the eddy center, representing the strength of the eddy, continuously increased, and the area oscillated at one to two month periods overlain on a general increase from ~7,000 to ~18,000 km2. Large oceanic copepods, Neocalanus cristatus, Eucalanus bungii and Metridia pacifica were more abundant inside the eddy than the outside. Inside the eddy, the life stage distribution of N. cristatus was advanced than that outside, and Neocalanus spp. had accumulated more lipids. These conditions probably reflect the greater primary production in the eddy, production enhanced by nutrients advected into the eddy. Since the Aleutian eddy was formed in offshore waters and/or eddy-eddy interaction occurred after its formation, it contained mostly oceanic copepods. The sufficient food condition in the eddy presumably induced higher growth and survival rates of these oceanic copepods, resulting in the greater abundance, advanced development stages and greater lipid accumulation. Fig. 1. Sea level anomaly along the sampling lines on 7 July 2010 south of the western Aleutian Islands.

Saito, R.; Yamaguchi, A.; Yasuda, I.; Ueno, H.; Ishiyama, H.; Imai, I.

2013-12-01

97

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

98

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

99

Geochemically Distinct Lavas from Overlapping Arc Front Volcanoes Drawing from a Common Parent, Eastern Aleutian Arc  

NASA Astrophysics Data System (ADS)

Emmons Lake Volcanic Center (ELVC) on the lower Alaska Peninsula is one of the largest and most diverse volcanic centers in the Aleutian Arc. Since the Middle Pleistocene, eruption of ~ 350 cubic kilometers of basalt through rhyolite has produced a 30 km, arc-front chain of nested calderas and overlapping stratovolcanoes. ELVC has experienced as many as five major caldera-forming eruptions, the most recent, at ~ 27 ka, produced ~ 50 cubic kilometers DRE of rhyolitic ignimbrite and ash fall. These violent silicic events were interspersed with less energetic, but prodigious, outpourings of basalt through dacite. Holocene eruptions are mostly basaltic-andesite to andesite. Historically recorded activity includes over 40 eruptions within the last 200 years, all from Pavlof volcano, the most active site in the Aleutian Arc. Geochemical and geophysical observations suggest that although all ELVC eruptions derive from a common clinopyroxene + spinel + plagioclase fractionating high-alumina basalt parent in the lower crust, magma follows one of two closely-spaced, but distinct paths to the surface. Under the eastern part of the chain, magma moves rapidly and cleanly through a relatively young (since ~28 ka), hydraulically connected dike plexus. Steady supply, short magma residence times, and limited interaction with crustal rocks preserve the geochemistry of deep crustal processes. Below the western part of the chain, magma moves haltingly through a long-lived (since ~500 ka) and complex intrusive column in which many generations of basaltic to andesitic melts have mingled and fractionated. Buoyant, silicic melts separate from the lower parts of the column (amphibole-bearing enclaves suggest silicic magma exists at or below ~15 km) to fill ephemeral reservoirs in the shallow crust that are periodically emptied by voluminous eruptions of dacite and rhyolite. Mafic magmas that reach the surface record a complicated passage through refractory cumulates and silicic differentiates as manifested by disequilibrium phenocryst textures, incompatible element enrichments, and decoupling of REEs and HFSEs ratios. Such features are absent in mafic lavas from the younger part of the chain to the east, highlighting the importance of plumbing architecture and longevity in creating petrologic diversity.

Mangan, M.; Miller, T. P.; Waythomas, C. F.; Trusdell, F.; Calvert, A. T.; Layer, P. W.

2009-12-01

100

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, M. A.; Stone, R. P.; Mclaughlin, M. R.; Kellogg, C. A.

2011-01-01

101

Microbial consortia of gorgonian corals from the Aleutian islands.  

PubMed

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. PMID:21223327

Gray, Michael A; Stone, Robert P; McLaughlin, Molly R; Kellogg, Christina A

2011-04-01

102

Mercury concentrations of a resident freshwater forage fish at Adak Island, Aleutian Archipelago, Alaska.  

PubMed

The Aleutian Archipelago is an isolated arc of over 300 volcanic islands stretching 1,600 km across the interface of the Bering Sea and North Pacific Ocean. Although remote, some Aleutian Islands were heavily impacted by military activities from World War II until recently and were exposed to anthropogenic contaminants, including mercury (Hg). Mercury is also delivered to these islands via global atmospheric transport, prevailing ocean currents, and biotransport by migratory species. Mercury contamination of freshwater ecosystems is poorly understood in this region. Total Hg (THg) concentrations were measured in threespine stickleback fish (Gasterosteus aculeatus) collected from eight lakes at Adak Island, an island in the center of the archipelago with a long military history. Mean THg concentrations for fish whole-body homogenates for all lakes ranged from 0.314 to 0.560 mg/kg dry weight. Stickleback collected from seabird-associated lakes had significantly higher concentrations of THg compared to non-seabird lakes, including all military lakes. The ?(13)C stable isotope ratios of stickleback collected from seabird lakes suggest an input of marine-derived nutrients and/or marine-derived Hg. PMID:22912068

Kenney, Leah A; von Hippel, Frank A; Willacker, James J; O'Hara, Todd M

2012-11-01

103

Earth-science studies of a nuclear test area in the Western Aleutian Islands, Alaska: an interim summary of results  

Microsoft Academic Search

Recent multi-disciplinary studies by the U. S. Geological Survey ; conducted on and near Amchitka Island in the Aleutians have contributed much to a ; better understanding of the geologic, hydrologic, and tectonic environment of the ; island as an underground nuclear test site. The work included geologic mapping, ; isotopic dating, deep drilling, geophysical surveys, hydrologic investigations, ; and

W. J. Carr; L. M. Gard; G. D. Bath; D. L. Healey

1971-01-01

104

A Summary of the History and Achievements of the Alaska Volcano Observatory  

Microsoft Academic Search

Volcanoes of the Aleutian Islands, Kamchatka and the Kurile Islands present a serious threat to aviation on routes from North America to the Far East. On March 27, 1986, an eruption of Augustine Volcano deposited ash over Anchorage and disrupted air traffic in south-central Alaska. The consequences of the colocation of an active volcano and the largest city in Alaska

R. W. Smith

2008-01-01

105

Description of the Socioeconomic and Sociocultural Systems of the Aleutian-Pribilof Islands Region. Social and Economic Studies Program Technical Report Number 118.  

National Technical Information Service (NTIS)

The goal of the research was to update information on current conditions and trends of change in the socioeconomic and sociocultural systems of the Aleutian/Pribilof Island Region. The economy of the Aleutian/Pribilof Islands region is based on extraction...

D. Burnham L. Moorehead R. Hagenstein S. R. Braund T. Holmes

1986-01-01

106

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

107

Surname distributions and their association with Y-chromosome markers in the Aleutian Islands.  

PubMed

We examine surname distribution, origin, and association with Y-chromosome haplogroups in native communities from the Aleutian archipelago. The underlying hypothesis is that surnames and Y-chromosome haplogroups should be associated because both are paternally inherited markers. We used Lasker's coefficient of relationship through isonymy (R(ib) ) to identify the distribution of 143 surnames in the Aleutian Islands. The geographic distribution of surnames was explored both through frequency distribution and through the use of Mantel tests. Multidimensional scaling, chi-square, and Mantel tests were used to examine the relationship between surname and Y-chromosome markers. Overall, we observed that the distribution of surnames in the Aleutian archipelago is culturally driven rather than being one of paternal inheritance. Surnames follow a gradient from east to west, with high frequencies of Russian surnames found in western Aleut communities and high levels of non-Russian surnames found in eastern Aleut communities. A nonsignificant correlation (r = -0.0132; P = 0.436) was found between distance matrices based on haplogroups of the nonrecombining portion of the Y chromosome and surnames, although an association was found between non-Russian surnames and the predominantly non-Russian haplogroups (R1b, I1a, and I). PMID:21417893

Graf, Orion M; Zlojutro, Mark; Rubicz, Rohina; Crawford, Michael H

2010-12-01

108

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

NASA Astrophysics Data System (ADS)

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 of the volcano with tephra fall, ballistics, pyroclastic surges and flows, and lahars. An example of these more violent intracaldera events is the 1817 eruption. Reevaluation of historical accounts of activity at Okmok combined with new geologic mapping and tephra studies suggest that an 1817 eruption included (1) early, largely hydrovolcanic, explosive activity and the production of significant pyroclastic fall and surge deposits extending down the north and east flanks of the volcano; (2) generation of a flood that reached the Bering Sea; (3) late-stage strombolian fountaining and lava flow production. Vents from the 1817 eruption form a 4-km-long arc that parallels the base of the north caldera wall and include a 50-70-m-deep, elongate maar crater erupted through pre-existing tuff cone deposits. Terrace morphology and flood deposits less than 200 14C yrs BP indicate a flooding event down Crater Creek consistent with historical accounts of Aleut village inundation at the coastline in 1817. The later part of the eruption produced a 120-m high cinder and spatter cone and a blocky a'a lava flow field that fills a shallow basin near the outlet of Crater Creek. These preliminary results indicate that Okmok is capable of eruptions far more violent than the largely effusive events of the last century.

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

2003-12-01

109

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

110

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

Microsoft Academic Search

Deception Island is the largest volcano in the actively extending Bransfield Basin, a marginal 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. Data from the flooded caldera show no evidence for recent localized resurgence. The gently-sloped

A. H. Barclay; W. S. D. Wilcock; J. M. Ibáñez

2009-01-01

111

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

Federal Register 2010, 2011, 2012, 2013

...because the 2013 total allowable catch (TAC) of ``other rockfish'' in the BSAI...part 600 and 50 CFR part 679. The 2013 TAC ``other rockfish'' in the Aleutian Islands...Administrator), has determined that the 2013 TAC of ``other rockfish'' in the...

2013-09-16

112

Gravity Field of the Northwest Pacific Ocean Basin and its Margin: Aleutian Island Arc-Trench System.  

National Technical Information Service (NTIS)

Surface-ship and pendulum sea gravity measurements have been combined with land measurements in a new free-air anomaly map of the Aleutian island arc-trench system. The most prominent features of the map are a narrow belt of large-amplitude positive anoma...

A. B. Watts

1975-01-01

113

Preliminary Seismic Tomography of Deception Island Volcano, South Shetland Islands (Antarctica)  

Microsoft Academic Search

Deception Island, 62°59' S, 60°41' W, is an active volcano located in Bransfield Strait between the Antarctic Peninsula and the main South Shetland Islands. The volcano has a basal diameter of ~30 km and rises ~1500 m from the seafloor to a maximum height of over 500 m above sea level. The 15-km-diameter emerged island is horseshoe-shaped with a flooded

D. Zandomeneghi; A. H. Barclay; T. Ben Zvi; W. Wilcock; J. M. Ibáñez; J. Almendros

2005-01-01

114

Mafic basement xenoliths from Kanaga Island and their implications for Aleutian arc initiation and evolution  

NASA Astrophysics Data System (ADS)

We currently have an understanding of the origin and evolution of the Izu Bonin-Mariana intra-oceanic arc system as decades of work have revealed the timing and compositional evolution of magmatism and provided an arc initiation model, which also serves as an analog for the Tonga Kermadec system. However, it is unclear that this model is applicable to the Central Aleutian arc where mid- to lower-crustal velocities are higher (6.5-7.3 km/s) and the crust is more continental-like. As part of understanding the evolution of the Central Aleutian arc lower crust, we have studied and dated gabbroic xenoliths from our collection of ~200 samples from two Kanaga Island localities, which are interpreted as lower crustal cumulates of basaltic to mafic andesitic arc magmas. The variable textures, mineral chemistries and isotopic ratios in these xenoliths show they experienced a complex history before being incorporated into the ~7 Ma Mg-rich arc basalt host lava. Overall, the suite includes amphibole-free, plagioclase-clinopyroxene ×orthopyroxene-titanomagnetite-bearing xenoliths with rare olivine that variously are gabbros with adcumulate textures, mafic 1 or 2 pyroxene granulites with granoblastic textures that yield temperatures of ~800-1050°C, and K and Ba enriched recrystallized and deformed granulites that yield temperatures up to 1150°C. All are characterized by cumulate REE patterns with positive Eu anomalies, arc-like Hf/La ratios, and Sr (0.7033-0.7035) and Nd (Epsilon Nd = 6.9-9) isotopic ratios that are close to those in central Aleutian plutonic rocks. Salitic clinopyroxene compositions suggest they crystallized from magmas with water contents similar to other Aleutian magmas. Extremely challenging 40Ar/39Ar incremental heating experiments due to small volume Ar releases per heating step (5-20 times above background) from low K2O (0.07 to 0.23 wt.%) plagioclases in two xenoliths provide new age constraints for their evolution. In detail, a plagioclase from a two pyroxene granulite gives a complicated Ar/Ar spectrum allowing an age of 48×4 Ma that could reflect the time of metamorphic and deformation related recrystallization of pre-existing cumulates as later mafic arc magmas intruded the lower crust. A plagioclase age near 20 Ma from another xenolith with secondary recrystallization is considered to reflect the age of high temperature recrystallization of pyroxene along fractures, deformation and partial recrystallization of plagioclase, and lowering of K/Ba ratios through interaction with hydrothermal fluids from dewatering oceanic cumulates trapped in the Aleutian crust. The absence of similar recrystallization and deformation features in all xenoliths is consistent with these events predating the incorporation of the xenoliths into the ~ 7 Ma host basalts. Overall, the features of these xenoliths support their crystallization from central Aleutian arc magmas that do not resemble Marianas-like low K arc tholeiites, boninites or depleted backarc magmas.

Kay, S. M.; Romick, J.; Jicha, B. R.; Kay, R. W.

2013-12-01

115

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

116

Volcano-Ice Interactions During Recent Eruptions of Aleutian Arc Volcanoes and Implications for Melt Water Generation  

NASA Astrophysics Data System (ADS)

Recent eruptions in Alaska (Redoubt 2009; Pavlof 2007, 2013; Veniaminof 2013) all involved ice eruptive-product interactions that led to variable amounts of melt water generation. Production of melt water during explosive eruptions is the primary mechanism for lahar generation, which is a significant and sometimes-deadly hazard at snow and ice clad volcanoes. During the 2009 eruption of Redoubt Volcano, pyroclastic flows produced by explosive destruction of lava domes swept across and eroded glacier ice and generated large quantities of melt water that formed correspondingly large lahars (107-109 m3) in the Drift River valley north of the volcano. Three of the twenty lahars generated during the eruption were large enough to threaten an oil storage facility 40 km from the volcano. During eruptions of Pavlof Volcano in 2007 and 2013 spatter-fed lava flows and minor pyroclastic flows descended over snow and ice on the upper flanks of the volcano and produced some melt water that generated lahars in the associated drainages. These lahars were smaller than those associated with the 2009 eruption of Redoubt Volcano because the melt water generation mechanism was different. At Veniaminof Volcano, a low-level eruption beginning in June 2013 produced small lava flows that flowed passively over glacier ice and produced only limited amounts of melt water. Although melt pits surrounding the lava flows eventually developed, the rate of melt water production was gradual and no significant outflows of water occurred. These eruptions and comparison with past events highlight the various mechanisms for melt water production during eruptive activity at snow and ice clad Alaskan volcanoes. Dynamic emplacement of eruptive products over glacier ice that involves significant erosion of ice and snow leads to production of large volumes of melt water. Less dynamic, but still energetic interactions such as those that have occurred at Pavlof Volcano, produce smaller amounts of melt and correspondingly smaller volume lahars whose distribution is controlled in part by changes in the location of the summit vent. Effusive, subaerial eruptions at Veniaminof Volcano result in the smallest amount of meltwater production, mainly because the lava-ice interaction is not very dynamic and only a small proportion of the heat flux goes to melt ice.

Waythomas, C. F.

2013-12-01

117

Genetic differentiation of the Kittlitz's Murrelet Brachyramphus brevirostris in the Aleutian Islands and Gulf of Alaska  

USGS Publications Warehouse

Information about the distribution of genetic variation within and among local populations of the Kittlitz's Murrelet Brachyramphus brevirostris is needed for effective conservation of this rare and declining species. We compared variation in a 429 base pair fragment of the mitochondrial control region and 11 microsatellite loci among 53 Kittlitz's Murrelets from three sites in the western Aleutian Islands (Attu Island) and Gulf of Alaska (Glacier Bay and Kachemak Bay). We found that birds in these two regions differ genetically in three assessments: (1) global and pairwise indices of genetic differentiation were significantly greater than zero, (2) mitochondrial haplotypes differed by a minimum of nine substitutions, and (3) molecular assignments indicated little gene flow between regions. The data suggest that birds in these regions have been genetically isolated for an extended period. We conclude that Kittlitz's Murrelets from Attu Island and from the Gulf of Alaska represent separate evolutionarily significant units, and should be treated as such for conservation. Genetic data for Kittlitz's Murrelets from the remainder of the breeding range are urgently needed.

Birt, T. P.; Mackinnon, D.; Piatt, J. F.; Friesen, V. L.

2011-01-01

118

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

119

Final Report: Weatherization and Energy Conservation Education and Home Energy and Safety Review in the Aleutian Islands  

Microsoft Academic Search

Aleutian\\/Pribilof Islands Association, Inc. (APIA) hired three part-time local community members that desire to be Energy Technicians. The energy technicians were trained in methods of weatherization assistance, energy conservation and home safety. They developed a listing of homes in the region that required weatherization, and conducted on-site weatherization and energy conservation education and a home energy and safety reviews in

Bruce Wright

2011-01-01

120

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

121

Organochlorine contaminants in fishes from coastal waters west of Amukta Pass, Aleutian Islands, Alaska, USA.  

PubMed

Organochlorines were examined in liver and stable isotopes in muscle of fishes from the western Aleutian Islands, Alaska, in relation to islands or locations affected by military occupation. Pacific cod (Gadus macrocephalus), Pacific halibut (Hippoglossus stenolepis), and rock greenling (Hexagrammos lagocephalus) were collected from nearshore waters at contemporary (decommissioned) and historical (World War II) military locations, as well as at reference locations. Total (Sigma) polychlorinated biphenyls (PCBs) dominated the suite of organochlorine groups (SigmaDDTs, Sigmachlordane cyclodienes, Sigmaother cyclodienes, and Sigmachlorinated benzenes and cyclohexanes) detected in fishes at all locations, followed by SigmaDDTs and Sigmachlordanes; dichlorodiphenyldichloroethylene (p,p'DDE) composed 52 to 66% of SigmaDDTs by species. Organochlorine concentrations were higher or similar in cod compared to halibut and lowest in greenling; they were among the highest for fishes in Arctic or near Arctic waters. Organochlorine group concentrations varied among species and locations, but SigmaPCB concentrations in all species were consistently higher at military locations than at reference locations. Moreover, all organochlorine group concentrations were higher in halibut from military locations than those from reference locations. A wide range of molecular weight organochlorines was detected at all locations, which implied regional or long-range transport and deposition, as well as local point-source contamination. Furthermore, a preponderance of higher-chlorinated PCB congeners in fishes from contemporary military islands implied recent exposure. Concentrations in all organochlorine groups increased with delta15N enrichment in fishes, and analyses of residual variation provided further evidence of different sources of SigmaPCBs and p,p'DDE among species and locations. PMID:19374473

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

2009-08-01

122

Paleomagnetic determination of paleolatitude and rotation of Bering Island (Komandorsky Islands) Russia: comparison with rotations in the Aleutian Islands and Kamchatka  

NASA Astrophysics Data System (ADS)

A paleomagnetic study was carried out on Paleogene sedimentary rocks from Bering Island, Komandorsky islands, located at the far western end of the Aleutian Island Arc. The age of these sediments has been debated at length, but the combination of magnetostratigraphy with the fossil record indicates that the base of the section is of early Eocene (approximately 55 Ma) and the top latest Eocene age. Paleomagnetic data were obtained from 260 samples from 60 individual bedding units. The combined data show a clockwise rotation R=26.3°±8.5°, F=8.1°±2.5° with respect to the North American Plate and R=38°±8.8°, F=8.7°±2.7° with respect to the Eurasian Plate. They also show a shallowing of the inclination which yields a paleolatitude of 53°, 12° south of its expected latitude. The shallowing may have a component due to compaction, but the wide variation in sampled lithologies, combined with internal consistency of the data set, would argue against the shallowing being significant. To compare these data with other Aleutian Arc data we compiled a comprehensive survey of all available data sets. Out of these we selected four islands for which the data passed basic reliability criteria, namely Umnak, Amlia, Amchitka and Medny islands. All four showed significant clockwise rotation with respect to both North American and Eurasian polar wander paths. Several mechanisms can generate the observed rotation, ranging from block rotation driven by oblique relative motion of the Pacific plate, through lateral transport along the curve of the arc, to whole-arc rotation about its eastern end. The distribution and age spread of the rotation data are insufficient to discriminate between mechanisms, but it seems likely that different mechanism may have operated at different times and in different locations.

Minyuk, P. S.; Stone, D. B.

2009-09-01

123

Stable isotope chemistry, population histories and Late Prehistoric subsistence change in the Aleutian Islands  

Microsoft Academic Search

Aleut population history has been a topic of debate since the earliest archaeological investigations in the region. In this paper, we use stable isotope chemistry to evaluate the hypothesis that two distinct groups of people, Paleo- and Neo-Aleut, occupied the eastern Aleutians after 1000BP. This study focuses on 80 sets of directly dated eastern Aleutian burial assemblages from Chaluka midden,

David A. Byers; David R. Yesner; Jack M. Broughton; Joan Brenner Coltrain

2011-01-01

124

Detection and location of earthquakes in the central Aleutian subduction zone using island and ocean bottom seismograph stations  

SciTech Connect

A network of eight University of Texas ocean bottom seismographs (OBS) operated for 6 weeks in 1978 about 50 km offshore of Adak Island, Alaska, and nearly islands. In 1979 a similar network of nine instruments was deployed for 7 weeks farther offshore within and up to 100 km seaward of the Aleutian trench. For shallow earthquakes on the outer trench slope, for shallow earthquakes in the thrust zone, and for intermediate-depth events we have analyzed the OBS and island-based network data and evaluated the island network's capabilities for earthquake detection and location and for focal mechanism determination. Our three major conclusions are presented. The first concerns shallow earthquakes on the outer trench slope. In 1979 about 30 earthquakes occurred within the Aleutian trench and up to 60 km seaward of the trench axis. The island network located none of these events and detected P phases for only three of them. Ray tracing shows that the islands lie in a geometric shadow zone for events on the outer trench slope. The best located events are shallower than 20 km and exhibit first motions consistent with normal faulting. Several authors have suggested that these events are caused by bending of the oceanic lithosphere at the outer rise prior to subduction. If so, then the event locations reported here show that the bending stresses exceed the strength of lithosphere only in a narrow zone extending about 10 km landward and 60 km seaward of the trench axis. The second conclusion concerns shallow earthquakes in the thrust zone. Epicenters determined by island stations alone are virtually identical to epicenters determined using data from both island and OBS stations. The third conclusion concerns earthquakes deeper than 70 km. Epicenters determined using island network stations alone lie 10 to 80 km south of those determined using OBS and island stations, with the differences between epicenters depending both on event depth and on the velocity model used.

Frohlich, C.; Billington, S.; Engdahl, E.R.; Malahoff, A.

1982-08-10

125

Adakitic volcanism in the eastern Aleutian arc: Petrology and geochemistry of Hayes volcano, Cook Inlet, Alaska  

NASA Astrophysics Data System (ADS)

Located in south-central Alaska, 135 km northwest of Anchorage, Hayes volcano is responsible for the most widespread tephra fall deposit in the regional Holocene record (~3,500 BP). Hayes is bounded to the west by the Cook Inlet volcanoes (CIV; Mt. Spurr, Redoubt, Iliamna, and Augustine) and separated from the nearest volcanism to the east, Mount Drum of the Wrangell Volcanic Field (WVF), by a 400 km-wide volcanic gap. We report initial results of the first systematic geochemical and petrologic study of Hayes volcano. Hayes eruptive products are calc-alkaline dacites and rhyolites that have anomalous characteristics within the region. Major and trace element analyses reveal that the Hayes rhyolites are more silicic (~74 wt. % SiO2) than compositions observed in other CIV, and its dacitic products possess the distinctive geochemical signatures of adakitic magmas. Key aspects of the Hayes dacite geochemistry include: 16.03 - 17.54 wt. % Al2O3, 0.97 - 2.25 wt. % MgO, Sr/Y = 60 - 78, Yb = 0.9 - 1.2 ppm, Ba/La = 31 - 79. Such signatures are consistent with melting of a metamorphosed basaltic source that leaves behind a residue of garnet ± amphibole ± pyroxene via processes such as melting of a subducting oceanic slab or underplated mafic lower crust, rather than flux melting of the mantle wedge by dehydration of the down-going slab. Additionally, Hayes tephras display a distinctive mineralogy of biotite with amphibole in greater abundance than pyroxene, a characteristic not observed at other CIV. Furthermore, Hayes rhyolites and dacites exhibit little isotopic heterogeneity (87Sr/86Sr = 0.70384 - 0.70395, 206Pb/204Pb = 18.866 - 18.889) suggesting these lavas originate from the same source. Hayes volcano is approximately situated above the western margin of the subducting Yakutat terrane and where the dip of the Pacific slab beneath Cook Inlet shallows northward. Due to its position along the margin of the subducting Yakutat terrane, it is plausible that Hayes magmas are the result of partial melting of this slab where thermal erosion and weakening of the crust occurs along the Pacific plate-Yakutat terrane transition. Additionally, flat slab subduction may be responsible for producing adakitic magmas by equilibration of the hydrous slab with ambient mantle temperatures. In contrast, it is possible that the adakitic signature at Hayes is from underplated mafic lower crust that melted as the result of pooling mantle melt at depth. Two volcanoes within the WVF, Mt. Drum and Mt. Churchill, are adakitic with an abundance of biotite and amphibole similar to Hayes volcano and have been suggested to have slab melt origins. Mt. Drum lavas have less radiogenic 87Sr/86Sr but overlapping 206Pb/204Pb signatures while Mt. Churchill, which approximately overlies the eastern edge of the Yakutat terrane, has similar 87Sr/86Sr compositions, but more radiogenic 206Pb/204Pb than Hayes. Mt. Spurr, the nearest CIV to Hayes volcano (90 km south), does not share its adakitic signature but exhibits overlapping, more heterogeneous isotopic compositions. Thus, understanding the petrogenetic history of Hayes volcano is essential not only to explain the development of an adakitic volcanic system but how this relates to regional, arc-wide volcanism.

McHugh, K.; Hart, W. K.; Coombs, M. L.

2012-12-01

126

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

127

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

128

Diverse lavas from closely spaced volcanoes drawing from a common parent: Emmons Lake Volcanic Center, Eastern Aleutian Arc  

USGS Publications Warehouse

Emmons Lake Volcanic Center (ELVC) on the lower Alaskan Peninsula is one of the largest and most diverse volcanic centers in the Aleutian Arc. Since the Middle Pleistocene, eruption of ~ 350 km3 of basalt through rhyolite has produced a 30 km, arc front chain of nested calderas and overlapping stratovolcanoes. ELVC has experienced as many as five major caldera-forming eruptions, the most recent, at ~ 27 ka, produced ~ 50 km3 of rhyolitic ignimbrite and ash fall. These violent silicic events were interspersed with less energetic, but prodigious, outpourings of basalt through dacite. Holocene eruptions are mostly basaltic andesite to andesite and historically recorded activity includes over 40 eruptions within the last 200 yr, all from Pavlof volcano, the most active site in the Aleutian Arc. Geochemical and geophysical observations suggest that although all ELVC eruptions derive from a common clinopyroxene + spinel + plagioclase fractionating high-aluminum basalt parent in the lower crust, magma follows one of two closely spaced, but distinct paths to the surface. Under the eastern end of the chain, magma moves rapidly and cleanly through a relatively young (~ 28 ka), hydraulically connected dike plexus. Steady supply, short magma residence times, and limited interaction with crustal rocks preserve the geochemistry of deep crustal processes. Below the western part of the chain, magma moves haltingly through a long-lived (~ 500 ka) and complex intrusive column in which many generations of basaltic to andesitic melts have mingled and fractionated. Buoyant, silicic melts periodically separate from the lower parts of the column to feed voluminous eruptions of dacite and rhyolite. Mafic lavas record a complicated passage through cumulate zones and hydrous silicic residues as manifested by disequilibrium phenocryst textures, incompatible element enrichments, and decoupling of REEs and HFSEs ratios. Such features are absent in mafic lavas from the younger part of the chain, highlighting the importance of plumbing architecture and longevity in creating petrologic diversity. Supplemental Data include 156 major element (XRF) and 128 trace element (ICP-MS) whole-rock analyses, 23 new 40Ar/39Ar ages, a generalized geologic map with associated unit descriptions and field photographs, and photomicrographs of key petrographic features.

Mangan, M.; Miller, T.; Waythomas, C.; Trusdell, F.; Calvert, A.; Layer, P.

2009-01-01

129

Diverse lavas from closely spaced volcanoes drawing from a common parent: Emmons Lake Volcanic Center, Eastern Aleutian Arc  

NASA Astrophysics Data System (ADS)

Emmons Lake Volcanic Center (ELVC) on the lower Alaskan Peninsula is one of the largest and most diverse volcanic centers in the Aleutian Arc. Since the Middle Pleistocene, eruption of ~ 350 km 3 of basalt through rhyolite has produced a 30 km, arc front chain of nested calderas and overlapping stratovolcanoes. ELVC has experienced as many as five major caldera-forming eruptions, the most recent, at ~ 27 ka, produced ~ 50 km 3 of rhyolitic ignimbrite and ash fall. These violent silicic events were interspersed with less energetic, but prodigious, outpourings of basalt through dacite. Holocene eruptions are mostly basaltic andesite to andesite and historically recorded activity includes over 40 eruptions within the last 200 yr, all from Pavlof volcano, the most active site in the Aleutian Arc. Geochemical and geophysical observations suggest that although all ELVC eruptions derive from a common clinopyroxene + spinel + plagioclase fractionating high-aluminum basalt parent in the lower crust, magma follows one of two closely spaced, but distinct paths to the surface. Under the eastern end of the chain, magma moves rapidly and cleanly through a relatively young (~ 28 ka), hydraulically connected dike plexus. Steady supply, short magma residence times, and limited interaction with crustal rocks preserve the geochemistry of deep crustal processes. Below the western part of the chain, magma moves haltingly through a long-lived (~ 500 ka) and complex intrusive column in which many generations of basaltic to andesitic melts have mingled and fractionated. Buoyant, silicic melts periodically separate from the lower parts of the column to feed voluminous eruptions of dacite and rhyolite. Mafic lavas record a complicated passage through cumulate zones and hydrous silicic residues as manifested by disequilibrium phenocryst textures, incompatible element enrichments, and decoupling of REEs and HFSEs ratios. Such features are absent in mafic lavas from the younger part of the chain, highlighting the importance of plumbing architecture and longevity in creating petrologic diversity. Supplemental Data include 156 major element (XRF) and 128 trace element (ICP-MS) whole-rock analyses, 23 new 40Ar/ 39Ar ages, a generalized geologic map with associated unit descriptions and field photographs, and photomicrographs of key petrographic features.

Mangan, Margaret; Miller, Thomas; Waythomas, Christopher; Trusdell, Frank; Calvert, Andrew; Layer, Paul

2009-10-01

130

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

131

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

132

Phase relations of a high-Mg basalt from the Aleutian Island Arc: Implications for primary island arc basalts and high-Al basalts  

Microsoft Academic Search

Many volcanic centers in the Aleutian Islands have erupted lavas that range in composition from high-Mg basalt (MgO>9 wt%) to more fractionated and voluminous high-Al basalts and basaltic andesites. The petrogenetic relationships between these rock types and the composition of primary magmas has been vigorously debated. The phase relations of a typical high-Mg basalt from the Makushin volcanic field on

D. A. Gust; M. R. Perfit

1987-01-01

133

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

134

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

135

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

136

InSAR observation of an arrested dike under Marchena volcano, Galapagos Islands: Implications for the magmatic systems of aging basaltic shield volcanoes  

Microsoft Academic Search

The Western Galapagos Islands are very active shield volcanoes with an average eruption rate of 3 eruptions during 10 years. The most active volcanoes are located on the islands of Isabela and Fernandina. Here we discuss interferometric data of Marchena volcano in the Northwestern part of the archipelago. Marchena erupted last in 1991. An 1992-2002 interferogram displays range decrease (uplift)

F. Amelung

2002-01-01

137

76 FR 65972 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch in the Eastern Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...Alaska; Pacific Ocean Perch in the Eastern Aleutian District of the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine...fishing for Pacific ocean perch in the Eastern Aleutian District of the Bering Sea and Aleutian...

2011-10-25

138

75 FR 69601 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch in the Western Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...Alaska; Pacific Ocean Perch in the Western Aleutian District of the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine...fishing for Pacific ocean perch in the Western Aleutian District of the Bering Sea and Aleutian...

2010-11-15

139

77 FR 34262 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch in the Western Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...Alaska; Pacific Ocean Perch in the Western Aleutian District of the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine...fishing for Pacific ocean perch in the Western Aleutian District of the Bering Sea and Aleutian...

2012-06-11

140

75 FR 69600 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch in the Eastern Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...Alaska; Pacific Ocean Perch in the Eastern Aleutian District of the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine...fishing for Pacific ocean perch in the Eastern Aleutian District of the Bering Sea and Aleutian...

2010-11-15

141

76 FR 43933 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Ocean Perch in the Western Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...Alaska; Pacific Ocean Perch in the Western Aleutian District of the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine...fishing for Pacific ocean perch in the Western Aleutian District of the Bering Sea and Aleutian...

2011-07-22

142

2003 Eruption of Chikurachki Volcano, Paramushir Island, Northern Kuriles, Russia  

NASA Astrophysics Data System (ADS)

Chikurachki Volcano in the northern Kurile Islands erupted for the second time in two years in mid-April 2003. Although the Kamchatka Volcanic Eruptions Response Team (KVERT) received word of a possible eruption from residents of Paramushir Island on April 17, poor weather precluded confirmation of volcanic activity, and the exact start date is uncertain. On April 18, during routine satellite image analysis, the Alaska Volcano Observatory (AVO) detected an ash cloud from Chikurachki in GMS data and immediately notified the Federal Aviation Administration (FAA), National Weather Service, and other agencies. Subsequent formal alerts were issued through aviation and meteorological channels as outlined in the Alaska Interagency Operating Plan for Volcanic Ash Episodes. Thermal infrared imagery and trajectory models suggested the initial cloud was relatively low-level (below 25,000 ft ASL), however this height was not well constrained. Over the next several months, activity at Chikurachki consisted largely of strombolian bursts producing intermittent ash clouds reaching heights of generally less than 10-13,000 ft. ASL. Ash fall was noted as far as 60 km downwind. The last confirmed eruptive activity was June 16, 2003. During the eruption, AVHRR, MODIS, and GMS satellites captured images of the ash cloud as far as 300 km generally east and southeast of the volcano in the region heavily traveled North Pacific air routes. The propagation of volcanic clouds was monitored using visual and infrared channels and included a routine split-window analysis. Weak thermal anomalies were detected in AVHRR images suggesting minimal effusive activity near the central vent. Over the course of the eruption, aviation and meteorological authorities in Russia, the U.S., and Japan issued official notices regarding the eruption and the position and estimated height of the ash plume. Impacts to aviation were minor due to the low-level and intermittent nature of the eruption. Chikurachki is a young, basaltic 1816-m-tall stratovolcano on the northern coast of Paramushir Island, 370 km southwest of Petropavlovsk-Kamchatsky. No seismic or other instrumentation exists near the volcano, however satellite imagery is examined at least twice daily to look for evidence of volcanic unrest. The nearest community is Severo-Kurilsk (population ~3,000), 60 km to the northeast. Previous historical eruptions have primarily consisted of VEI 1-2 strombolian eruptions, however, plinian eruptions with significant local fall deposits were recorded in 1986 and 1853. Its most recent eruption from January 25 - March 16, 2002 was similar in character to the 2003 event.

Schneider, D. J.; Girina, O. A.; Neal, C. A.; Kotenko, L.; Terentiev, N. S.; Izbekov, P.; Belousov, I.; Senyukov, S.; Ovsyannikov, A. A.

2003-12-01

143

Seismotectonic Analysis of the Seismic and Volcanic Hazards in the Pribilof Islands - Eastern Aleutian Islands Region of the Bering Sea.  

National Technical Information Service (NTIS)

The report presents and summarizes seismic and volcanic data collected by Lamont-Doherty in the eastern Aleutian arc and adjacent Bering Sea between 1973 and 1982. The data were collected with support by the NOAA-OCSEA Program during the period 1975-1982....

K. H. Jacob E. Hauksson

1983-01-01

144

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

145

Simultaneous travel time inversion for earthquake location and subduction zone structure in the central Aleutian Islands  

Microsoft Academic Search

A combined location and velocity inversion technique is applied to travel time data from 151 well-recorded central Aleutian earthquakes. The data include P and S wave arrivals at stations of a local network and P, pP, and sP wave arrivals at teleseismic stations. After correction for crustal structure at the reflection points, the depth phases pP and sP provide important

E. R. Engdahl; D. Gubbins

1987-01-01

146

Lower-Crustal and Upper-Mantle Seismicity beneath Aleutian Arc Volcanoes: A Temporal Link for Magmatic Processes between the Lower-Crust and the Surface  

NASA Astrophysics Data System (ADS)

Since 1989 the Alaska Volcano Observatory has identified more than 1,200 seismic events at upper-mantle to mid-crustal depths beneath 27 active Aleutian arc volcanic centers. Epicenters typically scatter broadly around the volcanoes at distances of as much as 25 km from the closest volcanic vent. Hypocenters for these events range typically from 15 to 45 km and the average depth is 25.1 km (?1 = 8.1 km). Magnitudes of located events range from -0.25 to 2.9 and the average magnitude is 1.22 (?1 = 0.5). Seismicity at these depths is unusual as it is generally considered below the brittle-ductile transition and suggests the involvement of pressurized fluids. These events provide some of the only direct evidence of the time history of magmatic processes in the lower-crust and upper-mantle, a portion of the magma pathway that is traditionally difficult to observe. The waveforms of these events exhibit the full range in frequency content typically seen in volcanic environments from broad spectrum (1 to 15 Hz) brittle failure, volcano-tectonic earthquakes, to peaked spectra (1 to 4 Hz), fluid resonance or long-period events. Most of the events are long-period or low-frequency in character and often have extended codas. These events occur both as solitary events and in sequences lasting from 2 to 30 minutes containing 3 to 10 individual events. Within the sequences individual events are often separated by volcanic tremor that shares the same spectral character as the seismic events themselves. All Aleutian arc volcanoes with suitable instrumentation and long-term monitoring exhibit some level of mid-crustal to upper-mantle seismicity. Spurr, Westdahl, Aniakchak and Akutan have the highest rates of upper-mantle to mid-crustal seismicity. Recent eruptions at Redoubt (2009) and Shishaldin (1999) were preceded by increases in lower-crustal seismicity as were episodes of unrest at Mount Spurr (2005), Trident (2008) and Little Sitkin (2012). The 1992 eruption of Mount Spurr initiated an increase in mid- to lower-crustal seismicity that continued until 1997. The time history of these sequences suggests a link between upper-crustal volcanic unrest and magmatic processes in upper-mantle or lower-crust that occurs at time scales of weeks to months. Tracking seismicity in the mid- to lower-crust and upper mantle may provide a means to extend forecasts of hazardous volcanic activity to an earlier stage in the eruption cycle.

Power, J. A.; Stihler, S. D.; Ketner, D. M.; Haney, M. M.; Prejean, S. G.; Parker, T. J.

2013-12-01

147

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

148

Ocean noise triggering of LP events at Deception Island volcano  

NASA Astrophysics Data System (ADS)

During the austral winter 2009, swarms of long-period (LP) events with astonishingly regular interevent times were recorded at Deception Island volcano, Antarctica. Swarm events have similar waveforms, indicating the repeated activation of a non-destructive source process. These swarms may last up to a few hours, and characteristic inter-event times range from ~10 s to ~20 s for individual swarms. The amplitudes of the periodic LPs vary significantly over a short time scale, which makes an association with a steady state internal process complicate. On the other hand, we observe that LP inter-event times are approximate integer multiples of the dominant periods of the oceanic microseism, and propose that the periodicity observed in the occurrence times of LP events is the result of dynamic triggering of the LP source process by the effect of oceanic microtremors. A positive correlation between microseism amplitude and LP periodicity supports this idea. We attribute LP periodicity to the coincidence of sustained LP activity in an unstable hydrothermal system and external forcing by ocean noise that introduces periodic pressure variations in volcano fluids. We estimate the volumetric strain change generated by the oceanic microseism at the source location and conclude that strain of order 10-7 is sufficient to introduce clear periodicity in the LP sequences.

Stich, D.; Almendros, J.; Jiménez, V.; Mancilla, F.; Carmona, E.

2012-04-01

149

Microearthquakes at St. Augustine Volcano, Alaska, Triggered by Earth Tides  

Microsoft Academic Search

Microearthquake activity at St. Augustine volcano, located at the mouth of Cook Inlet in the Aleutian Islands, has been monitored since August 1970. Both before and after minor eruptive activity on 7 October 1971, numerous shallow-foci microearthquake swarms were recorded. Plots of the hourly frequency of microearthquakes often show a diurnal peaking of activity. A cross correlation of this activity

F. J. Mauk; J. Kienle

1973-01-01

150

The seismic structure of island arc crust and reflection imaging of ultra-deep roots beneath the eastern Aleutian island arc (Invited)  

NASA Astrophysics Data System (ADS)

Seismic velocity models derived from refraction surveys are commonly used to determine the crustal thickness and to constrain the composition of oceanic island arcs. Crustal thicknesses vary from as little as 10 km in the Bonin arc to 35 km in the Aleutian and northern Izu arcs. Although globally island arcs appear to have a mafic composition, intermediate composition crust is inferred in parts of the Izu arc. Seismic velocity models are commonly poorly constrained at depths of 20-50 km beneath the arc due to the difficulty in recording first arrivals at the long offsets required to directly infer the velocity; however, the absence of a sharp velocity contrast at the Moho appears to be a first order characteristic of island arc crust, and indicates the existence of a broad crust-mantle transition zone. Multichannel seismic reflection surveys complement refraction surveys by revealing structures associated with variations of density and seismic velocity at the scale of a few hundred meters or less to depths of 60 km or more. An integrated interpretation of coincident reprocessed seismic reflection data and velocity models from the Aleutian arc shows that the eastern arc is characterized by reflectors that extend continuously from the lower arc crust to >50 km depth, which is considerably deeper than the crustal thickness of 27-35 km previously inferred from coincident wide-angle seismic surveys. Since relative to the overlying crust the upper mantle is commonly homogeneous and hence non-reflective, we interpret these reflectors to be gabbro, garnet gabbro, and pyroxenite intrusions within two 50 km-wide roots, which represent a >25 km thick heterogeneous transition from mafic lower crustal rocks to ultramafic mantle rocks. We suggest that the reflectivity is linked to repeated differentiation and intrusion of mantle-derived melts into the sub-arc lithosphere, and that the depth of these roots shows that fractionation of arc crust can extend well below the seismically determined Moho. Since these deep roots are not evident beneath the central Aleutian arc, either the roots form sporadically, perhaps as a consequence of an elevated magmatic supply, or such roots ultimately founder into the underlying mantle due to their relatively high mass density.

Calvert, A. J.; McGeary, S. E.

2013-12-01

151

78 FR 64892 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National...mackerel in the Bering Sea subarea and Eastern Aleutian district (BS/EAI) of the Bering Sea and Aleutian Islands management area (BSAI) by...

2013-10-30

152

78 FR 64891 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National...fishing for Atka mackerel in the Central Aleutian district (CAI) of the Bering Sea and Aleutian Islands management area (BSAI) by...

2013-10-30

153

75 FR 53606 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National...fishing for Atka mackerel in the Eastern Aleutian District and the Bering Sea subarea of the Bering Sea and Aleutian Islands management area (BSAI) by...

2010-09-01

154

75 FR 14498 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine...directed fishing for Atka mackerel in the Central Aleutian District of the Bering Sea and Aleutian Islands management area (BSAI) by...

2010-03-26

155

76 FR 10780 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National...mackerel in the Bering Sea subarea and Eastern Aleutian district (BS/EAI) of the Bering Sea and Aleutian Island management area (BSAI) by...

2011-02-28

156

75 FR 3873 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National...fishing for Atka mackerel in the Eastern Aleutian District and the Bering Sea subarea of the Bering Sea and Aleutian Islands management area (BSAI)...

2010-01-25

157

75 FR 6129 - Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National...fishing for Atka mackerel in the Eastern Aleutian District and the Bering Sea subarea of the Bering Sea and Aleutian Islands management area (BSAI) by...

2010-02-08

158

Modeling ground deformations of Panarea volcano hydrothermal\\/geothermal system (Aeolian Islands, Italy) from GPS data  

Microsoft Academic Search

Panarea volcano (Aeolian Islands, Italy) was considered extinct until November 3, 2002, when a submarine gas eruption began\\u000a in the area of the islets of Lisca Bianca, Bottaro, Lisca Nera, Dattilo, and Panarelli, about 2.5 km east of Panarea Island.\\u000a The gas eruption decreased to a state of low degassing by July 2003. Before 2002, the activity of Panarea volcano was

Alessandra Esposito; Marco Anzidei; Simone Atzori; Roberto Devoti; Guido Giordano; Grazia Pietrantonio

2010-01-01

159

U.S. Geological Survey (USGS) Western Region Kasatochi Volcano Coastal and Ocean Science  

USGS Publications Warehouse

Alaska is noteworthy as a region of frequent seismic and volcanic activity. The region contains 52 historically active volcanoes, 14 of which have had at least one major eruptive event since 1990. Despite the high frequency of volcanic activity in Alaska, comprehensive studies of how ecosystems respond to volcanic eruptions are non-existent. On August 7, 2008, Kasatochi Volcano, in the central Aleutian Islands, erupted catastrophically, covering the island with ash and hot pyroclastic flow material. Kasatochi Island was an annual monitoring site of the U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife Refuge (AMNWR); therefore, features of the terrestrial and nearshore ecosystems of the island were well known. In 2009, the U.S. Geological Survey (USGS), AMNWR, and University of Alaska Fairbanks began long-term studies to better understand the effects of the eruption and the role of volcanism in structuring ecosystems in the Aleutian Islands, a volcano-dominated region with high natural resource values.

DeGange, Anthony

2010-01-01

160

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

161

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

Microsoft Academic Search

Savo, Solomon Islands, is a historically active volcano dominated by sodic, alkaline lavas, and pyroclastic rocks with up\\u000a to 7.5 wt% Na2O, and high Sr, arc-like trace element chemistry. The suite is dominated by mugearites (plagioclase–clinopyroxene–magnetite ± amphibole ± olivine)\\u000a and trachytes (plagioclase–amphibole–magnetite ± biotite). The presence of hydrous minerals (amphibole, biotite) indicates\\u000a relatively wet magmas. In such melts, plagioclase is relatively unstable relative to iron oxides

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

2009-01-01

162

Preliminary Volcano-Hazard Assessment for Gareloi Volcano, Gareloi Island, Alaska.  

National Technical Information Service (NTIS)

In this report, we describe our current understanding of the hazards associated with Gareloi Volcano. The term hazard refers to danger posed by the physical events during an eruption (or less likely, physical phenomena on the volcano not directly associat...

B. L. Browne M. L. Coombs R. G. McGimsey

2008-01-01

163

Island-arc magmatic processes beneath South Pagan Volcano, Northern Mariana Islands  

NASA Astrophysics Data System (ADS)

The island-arc volcanoes that make up the Northern Mariana Islands are among the most historically active stratovolcanoes along the Pacific plate, yet they have been poorly studied due to their remote location and difficult accessibility. One of the least studied areas in the Northern Mariana Islands is Pagan Island, located near the center of the Mariana ridge. Pagan Island consists of two Holocene stratovolcanoes, Mount Pagan and South Pagan. Remarkably little is known about South Pagan including its eruptive history, potential volcanic hazards, and geochemical evolution due to a small population of inhabitants, a short and intermittent recorded history, and few geological studies. There is abundant evidence that eruption of South Pagan could pose significant hazards to both residents of the Northern Mariana Islands and to aircraft flying in the western Pacific. For example, following Mount Pagan's most recent explosive eruption (VEI = 4) in 1981, destructive rain-triggered volcanic debris flows buried large tracts of land, including the site of a village that contained a school, dispensary, church, and power generating buildings. Preliminary field studies in May 2006 by the USGS showed that a full spectrum of hazardous phenomena originated from South Pagan in the past, including pyroclastic flows and surges, caldera collapses, and volcanic debris flows. Two previously unrecognized active fumaroles near the summit of South Pagan were discovered suggesting that potential volcanic hazards currently exist in this area. A majority of the new lava samples are vesicular, clinopyroxene-plagioclase basalts with minor plagioclase xenocrysts and gabbroic xenoliths. The purpose of this study is to understand the compositional history of South Pagan and how it relates to the crustal and mantle magmatic processes beneath the central Northern Mariana Islands. Pb, Sr and Nd isotope ratios, major and trace element abundances, and mineral chemistry were determined and will be presented.

Marske, J. P.; Trusdell, F. A.; Garcia, M. O.; Pietruszka, A. J.

2007-12-01

164

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

165

Evolution and geochemistry of the Tertiary calc-alkaline plutons in the Adak Island region of the central Aleutian oceanic island arc  

NASA Astrophysics Data System (ADS)

Calc-alkaline plutons are major crustal building blocks of continental margin mountain belts like the Mesozoic to Tertiary Andes and the Sierra Nevada, but are rare in oceanic island arcs. Some of the most calc-alkaline I-type island arc plutons are in the Central Aleutians with the most extreme signatures, as indicated by FeO/MgO ratios of < ~2 at 48-70% wt. % SiO2, in the ~10 km wide Oligocene Hidden Bay pluton on southern Adak Island and the 10 km wide Miocene Kagalaska pluton to the north on eastern Adak and the adjacent Kagalaska Island. Although small compared to most continental plutons, similarities in intrusive units, mineralogy and chemistry suggest common formation processes. The Aleutian calc-alkaline plutonic rocks mainly differ from continental plutons in having more oceanic like isotopic (87Sr/86Sr = 0.703-0.7033; Epsilon Nd = 9-7.8) and LIL (e.g., higher K/Rb) ratios. The Adak region plutons differ from Tertiary plutons on Unalaska Island further east in being more K-rich and in having a more oxidized and lower-temperature mineralogy. From a regional perspective, the Adak area plutons intrude Eocene/Oligocene Finger Bay Formation mafic volcanic and sedimentary rocks and postdate the small ~38 Ma tholeiitic Finger Bay pluton. The chemistry of these older magmatic rocks is basically similar to that of young Central Aleutian magmatic rocks with boninites and arc tholeiitic magmas seemingly being absent. The formation of the calc-alkaline plutons seems to require a sufficient crustal thickness, fluid concentration and contractional stress such that magma chambers can stabilize significant amounts of pargasitic hornblende. Seismic receiver function analyses (Janiszewski et al., 2013) indicate the modern Adak crust is ~ 37 km thick. Existing and new hornblende, plagioclase and biotite Ar/Ar ages from 16 Hidden Bay pluton and Gannet Lake stock gabbro, porphyritic diorite, diorite, granodiorite, leucogranodiorite and aplite samples range from 34.6 to 30.9 Ma and indicate an ~ 4 Ma intrusion history. Biotite Ar/Ar ages for Kagalaska gabbro and granodiorite samples range from 14.7 to 13.9 Ma. The new ages are consistent with the plutons being related to several eruptive centers and forming during the waning stages of volcanism as the magmatic arc front was displaced to the north, possibly in response to accelerated periods of forearc subduction erosion. The gabbroic to leucogranodioritic units evolved in the lower to mid-crust with more silicic magmas rising buoyantly to higher levels where final crystallization and segregation of aplites occurred. Most gabbro and all mafic diorite units are largely crystal cumulates; one gabbro approaches the melt composition of a high Al basalt. The volumetrically dominant silicic diorites and granodiorites (58-63% SiO2) show the most zoning in their mineral phases and approach melt compositions. The leucogranodiorite (67-70% SiO2)unit was the last to crystallize. The silicic units are considered to be deep-crustal differentiates of high-Al basalt magmas, although partial melting of older magmatic rocks may play a role. Mafic dikes in the pluton represent the basic magmas under the dying arc front as the front moved northward.

Kay, Suzanne; Citron, Gary P.; Kay, Robert W.; Jicha, Brian; Tibbetts, Ashley

2014-05-01

166

A Summary of Geothermal Exploration and Data from Stratigraphic Test Well No. 1 Makushin Volcano, Unalaska Island  

SciTech Connect

Geothermal resource investigations have been conducted for the past four years on Unalaska Island in the Aleutian Chain. The focus of the work has been Makushin Volcano, about 12 miles from the cities of Unalaska and Dutch Harbor. In the summer of 1982, three widely spaced deep temperature gradient holes were drilled which encountered high temperatures. During the summer of 1983, a three inch diameter "slim hole" well, ST-1, was drilled to 1,949 feet. A shallow, low pressure, steam zone and a relatively productive hot water zone at total depth were encountered. The lower zone produced 47,000 lb/hr, limited by reaching critical mass velocity at the orifice. The static bottomhole pressure and temperature were 478 psig and 379{degrees}F, respectively. Analysis of transient pressure and flow data yielded a productivity inex of 3,470 lb/hr/psi and a permeability-thickness of 50,900 md-ft for the three-foot (at the wellbore) lower zone fracture. A preliminary reservoir/wellbore flow evaluation for a possible power plant indicates two commercial-size wells could fuel a 10 megawatt facility.

Campbell, Don A.; Economides, Michael J.

1983-12-15

167

The May 2003 eruption of Anatahan volcano, Mariana Islands: Geochemical evolution of a silicic island-arc volcano  

USGS Publications Warehouse

The first historical eruption of Anatahan volcano began on May 10, 2003. Samples of tephra from early in the eruption were analyzed for major and trace elements, and Sr, Nd, Pb, Hf, and O isotopic compositions. The compositions of these tephras are compared with those of prehistoric samples of basalt and andesite, also newly reported here. The May 2003 eruptives are medium-K andesites with 59-63 wt.% SiO2, and are otherwise homogeneous (varying less than 3% 2?? about the mean for 45 elements). Small, but systematic, chemical differences exist between dark (scoria) and light (pumice) fragments, which indicate fewer mafic and oxide phenocrysts in, and less degassing for, the pumice than scoria. The May 2003 magmas are nearly identical to other prehistoric eruptives from Anatahan. Nonetheless, Anatahan has erupted a wide range of compositions in the past, from basalt to dacite (49-66 wt.% SiO2). The large proportion of lavas with silicic compositions at Anatahan (> 59 wt.% SiO2) is unique within the active Mariana Islands, which otherwise erupt a narrow range of basalts and basaltic andesites. The silicic compositions raise the question of whether they formed via crystal fractionation or crustal assimilation. The lack of 87Sr/86Sr variation with silica content, the MORB-like ??18O, and the incompatible behavior of Zr rule out assimilation of old crust, altered crust, or zircon-saturated crustal melts, respectively. Instead, the constancy of isotopic and trace element ratios, and the systematic variations in REE patterns are consistent with evolution by crystal fractionation of similar parental magmas. Thus, Anatahan is a type example of an island-arc volcano that erupts comagmatic basalts to dacites, with no evidence for crustal assimilation. The parental magmas to Anatahan lie at the low 143Nd/144Nd, Ba/La, and Sm/La end of the spectrum of magmas erupted in the Marianas arc, consistent with 1-3 wt.% addition of subducted sediment to the mantle source, or roughly one third of the sedimentary column. The high Th/La in Anatahan magmas is consistent with shallow loss of the top 50 m of the sedimentary column during subduction. ?? 2005 Elsevier B.V. All rights reserved.

Wade, J. A.; Plank, T.; Stern, R. J.; Tollstrup, D. L.; Gill, J. B.; O'Leary, J. C.; Eiler, J. M.; Moore, R. B.; Woodhead, J. D.; Trusdell, F.; Fischer, T. P.; Hilton, D. R.

2005-01-01

168

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

169

Aeromagnetic Constraints on the Subsurface Structure of Stromboli Volcano, Aeolian Islands, Italy  

Microsoft Academic Search

Aeromagnetic surveys were conducted over Stromboli volcano and its surrounding areas in the Aeolian Islands, southern Italy in 2002 and 2004 to better understand the subsurface structure of the area. Observed data of those surveys were merged and aeromagnetic anomalies for Stromboli Island and its vicinity were reduced on a smoothed surface by the method, assuming equivalent anomalies below the

S. Okuma; C. Stotter; R. Supper; T. Nakatsuka; R. Furukawa

2007-01-01

170

ASTER observations of thermal anomalies preceding the April 2003 eruption of Chikurachki volcano, Kurile Islands, Russia  

Microsoft Academic Search

Chikurachki volcano (Northern Kurile Islands Chain, Paramushir Island 50° 20?N, 155° 27?E; elevation 1816 m, stratovolcano) has been in a state of unrest for over twenty years. Its most recent eruption that began in April 2003 was preceded by an eruption between January and May 2002. Thermal infrared images from the Japanese–United States' Advanced Spaceborne Thermal Emission and Reflection radiometer

David Pieri; Michael Abrams

2005-01-01

171

Geotechnical characterisation of stratocone crater wall sequences, White Island Volcano, New Zealand  

Microsoft Academic Search

Geotechnical characterisation is undertaken for 3 broad units comprising the bulk of the stratigraphy identified on White Island Volcano, Bay of Plenty, New Zealand, an active island stratovolcano. Field and laboratory measurements were used to describe rock mass characteristics for jointed lava flow units, and ring shear tests were undertaken to derive residual strength parameters for joint infilling materials within

Vicki Moon; Jennifer Bradshaw; Richard Smith; Willem de Lange

2005-01-01

172

HLA genes of Aleutian Islanders living between Alaska (USA) and Kamchatka (Russia) suggest a possible southern Siberia origin.  

PubMed

Aleuts HLA profile has been compared with that of neighboring and worldwide populations. Thirteen thousand one hundred and sixty-four chromosomes have been used for this study. Computer programs have obtained HLA allele frequencies, genetic distances between populations, NJ relatedness dendrograms, correspondence analysis and most frequent HLA extended haplotypes. Aleuts have inhabited Aleutian Islands since about 9000 years BP according to fossil and genetic (mtDNA) records. They are genetically different to Eskimo, Amerindian and Na-Dene speakers according to their HLA profile; this correlates with cultural and anthropological Aleut distinctiveness. No typical Amerindian HLA alleles have been found in a significant frequency. Their HLA relatedness to Saami (or Lapps, northern Scandinavians), Finns and Pomors (North-West Russia) indicates an ancient possible origin from the Baikal Lake Area (southern Siberia) around the present day Buryat peopling area; other origins are not discarded. Aleuts characteristic HLA profile may influence future transplantation programs in the region and be useful to study diseases linked to HLA epidemiology. PMID:17825912

Moscoso, Juan; Crawford, Michael H; Vicario, Jose L; Zlojutro, Mark; Serrano-Vela, Juan I; Reguera, Raquel; Arnaiz-Villena, Antonio

2008-02-01

173

Reconstructing palaeo-volcanic geometries using a Geodynamic Regression Model (GRM): Application to Deception Island volcano (South Shetland Islands, Antarctica)  

NASA Astrophysics Data System (ADS)

This article describes a reconstruction made of the palaeo-volcanic edifice on Deception Island (South Shetland Islands, Antarctica) prior to the formation of its present caldera. Deception Island is an active Quaternary volcano located in the Bransfield Strait, between the South Shetland Islands and the Antarctic Peninsula. The morphology of the island has been influenced mainly by the volcanic activity but geodynamics and volcanic deformation have also contributed. A volcanic reconstruction method, the Geodynamic Regression Model (GRM), which includes a terrain deformation factor, is proposed. In the case of Deception Island, the directions of this deformation are NW-SE and NE-SW, and match both the observed deformation of the Bransfield Strait and the volcanic deformation monitored over the last 20 years in the island, using Global Navigation Satellite System (GNSS) techniques. Based on these data, possible volcanic deformation values of 5-15 mm/yr in these directions have been derived. A possible coastline derived from a current bathymetry is transformed, according to values for the chosen date, to obtain the palaeo-coastline of Deception Island of 100 k years ago. Topographic, geomorphologic, volcanological and geological data in a GIS system have been considered, for computation of the outside caldera slope, palaeo-coastline, palaeo-summit height and palaeo digital elevation model (DEM). The result is a 3D palaeo-geomorphological surface model of a volcano, reaching 640 m in height, with an increase of 4 km3 in volume compared to the current edifice, covering 4 km2 more surface area and the method reveals the previous existence of parasite volcanoes. Two photorealistic images of the island are obtained by superposition of textures extracted from a current Quick Bird satellite image also. This technique for reconstructing the terrain of an existing volcano could be useful for analysing the past and future geomorphology of this island and similar locations.

Torrecillas, C.; Berrocoso, M.; Felpeto, A.; Torrecillas, M. D.; Garcia, A.

2013-01-01

174

Isotopic and incompatible element constraints on the genesis of island arc volcanics from Cold Bay and Amak Island, Aleutians, and implications for mantle structure  

NASA Astrophysics Data System (ADS)

Cold Bay and Amak Island, two Quaternary volcanic centers in the eastern Aleutians, are orthogonal relative to the trench and separated by ~50 km. Sr, Nd and Pb isotopic compositions of the calc-alkaline andesite magmas show no sign of contamination from continental crust (average 87Sr /86Sr = 0.70323 , 143Nd /144Nd = 0.51301 , 206Pb /204Pb = 18.82 , 207Pb /204Pb = 15.571 ). These samples plot within the mantle arrays for Sr-Nd and for Pb and are similar to arcs such as the Marianas and New Britain (Sr-Nd) and Marianas and Tonga (Pb). Incompatible element ratios for the Aleutian andesites (K/Rb ~ 332, K/Cs ~ 10,600, K/Sr ~ 22.4, K/Ba ~ 18.3, Ba/La ~ 60) are within the range reported for arc basalts, despite the difference in degree of fractionation. Average K content, K/Rb, K/Ba and K/Sr are approximately the same for basalts from arcs and from oceanic islands (OIB); K/Cs is a factor of 4 lower and Ba/La almost 3 times higher in arcs. Abundance ratio correlations indicate that arcs are enriched in Cs and depleted in La relative to OIB, with other incompatible element abundances very similar. Histograms of Sr and Nd isotopic compositions for MORB, OIB, and intraoceanic arcs show remarkably similar peaks and distribution patterns for intraoceanic arcs and OIB. A "plum pudding" model for the upper mantle best accommodates a) geochemical coherence of OIB and IAV, b) the existence of mantle plumes at some oceanic islands, and c) the presence of a MORB-type source at back arc spreading centers. In this model, OIB plums are imbedded in a MORB matrix; small degrees of melting generate OIB-type magmas while larger degrees of melting dilute the OIB magma with MORB matrix melts. OIB plums are merely less robust lower mantle plumes ( i.e., blobs) which are distributed throughout the upper mantle by convection. The existence of at least two types of OIB, as indicated by Sr, Nd, and Pb isotopes, suggests that nuggets of recycled oceanic lithosphère may coexist with lower-mantle plums and that both may be tapped in arcs and intraplate environments.

Morris, J. D.; Hart, S. R.

1983-11-01

175

The First Historical Eruption of Anatahan Volcano, Mariana Islands  

Microsoft Academic Search

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

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

2003-01-01

176

Shallow seismic imaging of flank collapse structures in oceanic island volcanoes: Application to the Western Canary Islands  

NASA Astrophysics Data System (ADS)

Volcanic flank collapse counts among the many hazards associated with volcanic activity. This type of event involves the mobilization of large volumes, producing debris avalanches. It affects mostly oceanic island volcanoes, involving the potential for tsunami occurrence. Geophysical imaging can illuminate subvolcanic features such as volcano-tectonic structures, magmatic plumbing systems or differences in rock type. The most commonly used geophysical methods are gravity, electromagnetics and seismics. In particular, seismic measurements quantify anomalies in seismic waves propagation velocities and can be used to obtain information on the subsurface arrangement of different materials. In the Western Canary Islands, the Cumbre Vieja volcano in La Palma (Canary Islands) has been proposed to be near the collapse stage. Previous geophysical studies that have been carried out on the flank of the volcano comprise gravity and electromagnetic methods. These types of surveys gather information on the deep structures of the volcano (1-2 km). In this project, we complement previous studies by using seismic methods to investigate the near-surface seismic structure of the Cumbre Vieja fault system (La Palma Island) and the structure of the well-developed San Andres fault system (El Hierro Island). We aim to compare the Cumbre Vieja and San Andres fault systems to infer the degree of maturity of collapse structures. We carried out reflection and refraction seismic surveys in order to image approximately the first 10 meters of the subsurface. We used 24 low frequency (4,5 Hz) geophones as receivers and a sledge hammer as the seismic source. The survey lines were located across visible parts of the fault systems at the Cumbre Vieja volcano and the San Andres fault in El Hierro. Here, we present the survey setup and results from the preliminary analysis of the data.

Sanchez, L.; González, P.; Tiampo, K. F.

2013-12-01

177

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

178

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.

Peci, Luis Miguel; Berrocoso, Manuel; Fernandez-Ros, Alberto; Garcia, Alicia; Marrero, Jose Manuel; Ortiz, Ramon

2014-01-01

179

Crustal Deformation Models and Time-Frequency Analysis of GPS Data from Deception Island Volcano (South Shetland Islands, Antarctica)  

Microsoft Academic Search

We have applied wavelet techniques to analyze GPS time-series data from REGID geodetic network, deployed at Deception Island\\u000a Volcano (South Shetland Islands, Antarctica). In the present analysis wavelets are used to detect periodic components and\\u000a to filter the data. The high frequency components can be associated to the orbital period of the satellites and to local tidal\\u000a effects, whereas the

María Ramírez; Manuel Berrocoso; María González; Alberto Fernández

180

Seismotectonic study of seismic and volcanic hazards in the Pribilof Islands, eastern Aleutian Islands region of the Bering Sea  

Microsoft Academic Search

This report presents: (1) historic seismicity maps of the Shumagin seismic gap vicinity which show the relatively low level of seismic activity in the gap, a possible offset in the Benioff zone, and a few events associated with the Bering shelf continental margin south of the Pribilof Islands; (2) a seismicity map and hypocenter cross-sections based on data from the

J. N. Davies; L. House; K. H. Jacob; R. Bilham; V. F. Cormier

1976-01-01

181

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 ...

Walls, Mrs.

2011-01-30

182

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

183

Geology and volcanic history of Pico Island Volcano, Azores  

Microsoft Academic Search

THE Azores Islands formed as a result of volcanism along a conservative plate margin1. The volcanism and seismicity of the archipelago have been described2 together with chemical analyses of lavas from many of the islands3.

D. Woodhall

1974-01-01

184

Aleutian subduction zone seismicity, volcano-trench separation, and their relation to great thrust-type earthquakes  

Microsoft Academic Search

A seismic network has been operated in the Shumagin Islands and adjacent Alaska Peninsula, Alaska, since July 1973. Hypocentral cross sections based on the first 4 years of data from this network show a well-defined Benioff zone that is about 10 km thick and extends to about 180-km depth. Focal mechanism and strong-motion accelerograph data for an mb=6.0 earthquake at

John N. Davies; Leigh House

1979-01-01

185

Preliminary Volcano-Hazard Assessment for the Tanaga Volcanic Cluster, Tanaga Island, Alaska.  

National Technical Information Service (NTIS)

The Tanaga volcanic cluster lies on the northwest part of Tanaga Island, about 100 kilometers west of Adak, Alaska, and 2,025 kilometers southwest of Anchorage, Alaska. The cluster consists of three volcanoes from west to east, they are Sajaka, Tanaga, an...

B. L. Browne M. L. Coombs R. G. McGimsey

2007-01-01

186

Evidence of two Holocene phreatomagmatic eruptions at Stromboli volcano (Aeolian Islands) from paleomagnetic data  

Microsoft Academic Search

We present detailed stratigraphic-sedimentological and paleomagnetic analyses of Holocene phreatomagmatic deposits at Stromboli volcano (Aeolian Islands, Italy). The investigated deposits belong to the Secche di Lazzaro succession (SDL) and to the Advanced Operations Center of the Department of Civil Defense (COA) succession, both lying on the Neostromboli lavas (ca. 13–5 ka). The two stratigraphic successions have similar stratigraphic position and

M. Porreca; G. Giordano; M. Mattei; P. Musacchio

2006-01-01

187

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

PubMed

The ingestion of plastic marine debris is a chronic problem for some of the world's seabird species, contributing to reduced chick survival, population declines, and deposition of contaminants via absorption in birds' gastrointestinal tract. We analysed the frequency of ingested plastic in chick meals delivered by adults in four species of auklet - Crested (Aethia cristatella), Least (A. pusilla), Parakeet (A. psittacula), and Whiskered (A. pygmaea) - from three breeding colonies in the Aleutian Islands, Alaska, USA over a 14-year period from 1993 to 2006. Among 2541 chick meals, we found plastic in only one - from a Whiskered Auklet on Buldir Island in 1993. While adult Parakeet Auklets have a high frequency of plastic ingestion (over 90%), no chick meals contained plastic. Unlike other seabirds, the planktivorous auklets do not appear to offload plastic to their chicks, and we conclude that auklet chicks are probably at a low risk of contamination from plastic debris. PMID:20627261

Bond, Alexander L; Jones, Ian L; Williams, Jeffrey C; Byrd, G Vernon

2010-08-01

188

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

189

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

190

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

191

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

192

Geology of Santa Fe island: The oldest galapagos volcano  

NASA Astrophysics Data System (ADS)

Santa Fe Island was a volcanic center when it emerged 3.9 ± 0.6 m.y. ago. Later upfaulting of a horst along the central axis of the island dominates its present morphology. Santa Fe is made up of evolved transitional lavas that are not related by fractional crystallization alone. Source heterogeneties, differing degrees of melting, or open-system magma chambers may explain the observed trace element variations. Santa Fe, Baltra, and Española make up a geologic subprovince in the central Galapagos: they are older than the other islands, and their lavas are compositionally similar. At the time of their emergence, the three islands were in a tectonic setting similar to that of the young western and central Galapagos Island.

Geist, Dennis J.; McBirney, Alexander R.; Duncan, Robert A.

1985-12-01

193

Aeromagnetic Constraints on the Subsurface Structure of Stromboli Volcano, Aeolian Islands, Italy  

NASA Astrophysics Data System (ADS)

Aeromagnetic surveys were conducted over Stromboli volcano and its surrounding areas in the Aeolian Islands, southern Italy in 2002 and 2004 to better understand the subsurface structure of the area. Observed data of those surveys were merged and aeromagnetic anomalies for Stromboli Island and its vicinity were reduced on a smoothed surface by the method, assuming equivalent anomalies below the observed surface (Nakatsuka and Okuma, 2006). Magnetic terrain corrections (Grauch, 1987) were applied to the anomalies of the study area, assuming a magnetic structure comprised of an ensemble of prism models extending from the ground surface to a depth of 3,000m below sea level: the average magnetization intensity was calculated to be 2.2 A/m by a comparison between the observed and synthetic anomalies and then the synthetic anomalies were removed from the observed. Next, apparent magnetization intensity mapping (Nakatsuka, 1995) was applied to the terrain-corrected anomalies. The apparent magnetization intensity map indicates magnetic heterogeneities among volcanic rocks which constitute the edifice of the volcano. The most obvious characteristics of the magnetization intensities is a magnetization low which occupies the center of the island where the summit craters reside closely, suggesting a demagnetization caused by the heat of conduits and/or a shallow magma chamber in addition to the thick accumulation of less magnetic pyroclastic rocks. By comparison with geologic maps, it can be seen that magnetization highs are distributed on exposures of basaltic-andesite to andesite lavas (Paleostromboli I), shoshonitic shied volcanoes (Neostromboli), at the south, north and west coasts of the volcano, respectively. Those magnetization highs further extend to offshore, implying the continuation of those volcanic rocks from land. An apparent magnetization low lies on an abrasion platform offshore of the northeastern volcano, suggesting that the platform is underlain by the hydrothermally altered center of the dissected edifice of an old volcano.

Okuma, S.; Stotter, C.; Supper, R.; Nakatsuka, T.; Furukawa, R.

2007-12-01

194

Giving birth to hotspot volcanoes: Distribution and composition of young seamounts from the seafloor near Tahiti and Pitcairn islands  

Microsoft Academic Search

Apart from being popular holiday destinations, oceanic-island volcanoes such as Hawaii, Tahiti, or the Canaries provide magmas that yield valuable information about the interior of our planet. Until recently, studies have concentrated on the easily accessible, subaerial parts of the volcanoes, largely ignoring their earlier-formed, submarine parts. These submarine parts, however, provide critical information about how the mantle begins to

C. W. Devey; K. S. Lackschewitz; D. F. Mertz; B. Bourdon; J.-L. Cheminée; J. Dubois; C. Guivel; R. Hékinian; P. Stoffers

2003-01-01

195

Evaluation of landslide susceptibility of Sete Cidades Volcano (S. Miguel Island, Azores)  

NASA Astrophysics Data System (ADS)

Sete Cidades is an active central volcano with a summit caldera located in the westernmost part of S. Miguel Island (Azores). Since the settlement of the Island, in the 15th century, many landslide events occurred in this volcano, causing extensive damages in buildings and infrastructures. The study of historical records and the observation of new occurrences showed that landslides in the region have been triggered by heavy rainfall periods, earthquakes and erosion. In order to assess landslide susceptibility at Sete Cidades Volcano, landslide scars and associated deposits were mapped through aerial photographs and field surveys. The obtained data were inserted in a GIS to produce a landslide distribution map. It was concluded that the high density landslide areas are related with (1) major scarp faults, (2) the margin of fluvial channels, (3) the sea cliffs and (4) volcanic landforms, namely the caldera wall. About 73% of the mapped events took place in areas where pyroclastic deposits are the dominant lithology and more than 77% occurred where slopes are equal or higher than 20°. These two parameters were integrated and used to generate a preliminary susceptibility map. The incorporation of vulnerability data into the GIS allowed concluding that 30% of dwellings and most of the roads on Sete Cidades Volcano are located in areas where landslide susceptibility is high to very high. Such conclusion should be taken into account for emergency and land use planning.

Gomes, A.; Gaspar, J. L.; Goulart, C.; Queiroz, G.

2005-03-01

196

Seismic signature of a phreatic explosion: Hydrofracturing damage at Karthala volcano, Grande Comore Island, Indian Ocean  

USGS Publications Warehouse

Karthala volcano is a basaltic shield volcano with an active hydrothermal system that forms the southern two-thirds of the Grande Comore Island, off the east coat of Africa, northwest of Madagascar. Since the start of volcano monitoring by the local volcano observatory in 1988, the July 11th, 1991 phreatic eruption was the first volcanic event seismically recorded on this volcano, and a rare example of a monitored basaltic shield. From 1991 to 1995 the VT locations, 0.5volcanoes, during the climax of the 1991 phreatic explosion, are due to the activation of the whole hydrothermal system, as roughly sized by the distribution of VT hypocenters. The seismicity rate in 1995 was still higher than the pre-eruption seismicity rate, and disagrees with the time pattern of thermo-elastic stress readjustment induced by single magma intrusions at basaltic volcanoes. We propose that it corresponds to the still ongoing relaxation of pressure heterogeneity within the hydrothermal system as suggested by the few LP events that still occurred in 1995. ?? Springer-Verlag 2005.

Savin, C.; Grasso, J. -R.; Bachelery, P.

2005-01-01

197

White Island volcano, New Zealand: carbon dioxide and sulfur dioxide emission rates and melt inclusion studies  

Microsoft Academic Search

CO2 and SO2 emission rates are reported for the volcanic gas plume from White Island, the most active volcano in New Zealand. SO2 emission rates were measured 16 times by correlation spectrometer (COSPEC) from 1986 to 1999 and range from 171 to 900 Mg day?1. We estimate the average SO2 emission rate was 430±70 Mg day?1 between 1983 and 1999.

Lois J. Wardell; Philip R. Kyle; Nelia Dunbar; Bruce Christenson

2001-01-01

198

Spatial variation of seismic b-values beneath Makushin Volcano, Unalaska Island, Alaska  

Microsoft Academic Search

The frequency–magnitude distribution was spatially mapped beneath Makushin Volcano, Unalaska Island, Alaska using an earthquake catalog of 491 events that occurred between July 2001 and April 2005. An area of high seismic b-values (?2.0) is found ?4 km east of Makushin's main vent at a depth between 4 and 7 km. The anomaly is statistically significant based on Utsu's p-test [T. Utsu,

David L. Bridges; Stephen S. Gao

2006-01-01

199

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

200

Geology, geochronology and geochemistry of a basanitic volcano, White Island, Ross Sea, Antarctica  

Microsoft Academic Search

White Island, Ross Sea, Antarctica is a Plio-Pleistocene basanite to tephriphonolite shield volcano, forming part of the Erebus Province, McMurdo Volcanic Group. Four new 40Ar\\/39Ar dates extend the age of surface volcanism from a previously determined 0.17 Ma to 5.05±0.31 Ma. A U\\/Pb age on zircon in an anorthoclasite nodule extends White Island magmatism back to 7.65±0.69 Ma.Volcanism was predominantly subaerial with eruption

Alan F. Cooper; Lotte J. Adam; Roseanne F. Coulter; G. Nelson Eby; William C. McIntosh

2007-01-01

201

Understanding volcano hydrothermal unrest from geodetic observations: Insights from numerical modeling and application to White Island volcano, New Zealand  

NASA Astrophysics Data System (ADS)

In this work we assess how volcano geodetic observations can be used to gain insights into hydrothermal system dynamics. We designed a range of numerical models of hydrothermal unrest and associated ground deformation caused by the thermo-poro-elastic response of the substratum. Throughout an episode of unrest, ground deformation is consistently first controlled by the poroelastic response of the substratum to pore pressure increase near the injection area. Later, thermal expansion may become the dominant process if the injection is sustained. We inverted these synthetic geodetic data using simple conventional pressure source models and compared the retrieved source characteristics with that of the synthetic hydrothermal systems. Simple pressure source models can reproduce well ground deformation caused by pore-pressure increase at depth. Most importantly, the pressure source's depth retrieved from the inversions corresponds to those of the area of injection of the hot magmatic fluids into the hydrothermal system. When the thermoelastic contribution to ground deformation becomes significant through time, simple point or spherical finite sources cannot reproduce the ground deformation signal. This allows one to determine whether observed ground deformation events due to hydrothermal unrest are distinct episodes of unrest and injection at depth, or whether one may correspond to the late, thermally-controlled phase of a previous event. Finally we applied this strategy to White Island volcano, New Zealand, to gain insights into the processes driving the last two episodes of ground uplift.

Fournier, Nicolas; Chardot, Lauriane

2012-11-01

202

Growth and collapse of the Reunion Island volcanoes  

Microsoft Academic Search

This work presents the first exhaustive study of the entire surface of the Reunion Island volcanic system. The focus is on\\u000a the submarine part, for which a compilation of all multibeam data collected during the last 20 years has been made. Different\\u000a types of submarine features have been identified: a coastal shelf, debris avalanches and sedimentary deposits, erosion canyons,\\u000a volcanic constructions

Jean-François Oehler; Jean-François Lénat; Philippe Labazuy

2008-01-01

203

Volcanoes  

USGS Publications Warehouse

Volcanoes destroy and volcanoes create. The catastrophic eruption of Mount St. Helens on May 18, 1980, made clear the awesome destructive power of a volcano. Yet, over a time span longer than human memory and record, volcanoes have played a key role in forming and modifying the planet upon which we live. More than 80 percent of the Earth's surface--above and below sea level--is of volcanic origin. Gaseous emissions from volcanic vents over hundreds of millions of years formed the Earth's earliest oceans and atmosphere, which supplied the ingredients vital to evolve and sustain life. Over geologic eons, countless volcanic eruptions have produced mountains, plateaus, and plains, which subsequent erosion and weathering have sculpted into majestic landscapes and formed fertile soils.

Tilling, Robert I.

1998-01-01

204

A Stratigraphic, Granulometric, and Textural Comparison of recent pyroclastic density current deposits exposed at West Island and Burr Point, Augustine Volcano, Alaska  

NASA Astrophysics Data System (ADS)

Augustine Volcano (Alaska) is the most active volcano in the eastern Aleutian Islands, with 6 violent eruptions over the past 200 years and at least 12 catastrophic debris-avalanche deposits over the past ~2,000 years. The frequency and destructive nature of these eruptions combined with the proximity of Augustine Volcano to commercial ports and populated areas represents a significant hazard to the Cook Inlet region of Alaska. The focus of this study examines the relationship between debris-avalanche events and the subsequent emplacement of pyroclastic density currents by comparing the stratigraphic, granulometric, and petrographic characteristics of pyroclastic deposits emplaced following the 1883 A.D. Burr Point debris-avalanche and those emplaced following the ~370 14C yr B.P. West Island debris-avalanche. Data from this study combines grain size and componentry analysis of pyroclastic deposits with density, textural, and compositional analysis of juvenile clasts contained in the pyroclastic deposits. The 1883 A.D. Burr Point pyroclastic unit immediately overlies the 1883 debris avalanche deposit and underlies the 1912 Katmai ash. It ranges in thickness from 4 to 48 cm and consists of fine to medium sand-sized particles and coarser fragments of andesite. In places, this unit is normally graded and exhibits cross-bedding. Many of these samples are fines-enriched, with sorting coefficients ranging from -0.1 to 1.9 and median grain size ranging from 0.1 to 2.4 mm. The ~370 14C yr B.P. West Island pyroclastic unit is sandwiched between the underlying West Island debris-avalanche deposit and the overlying 1912 Katmai Ash deposit, and at times a fine-grained gray ash originating from the 1883 eruption. West Island pyroclastic deposit is sand to coarse-sand-sized and either normally graded or massive with sorting coefficients ranging from 0.9 to 2.8 and median grain sizes ranging from 0.4 to 2.6 mm. Some samples display a bimodal distribution of grain sizes, while most display a fines-depleted distribution. Juvenile andesite clasts exist as either subrounded to subangular fragments with abundant vesicles that range in color from white to brown or dense clasts characterized by their porphyritic and glassy texture. Samples from neither eruption correlate in sorting or grain size with distance from the vent. Stratigraphic and granulometric data suggest differences in the manner in which these two pyroclastic density currents traveled and groundmass textures are interpreted as recording differences in how the two magmas ascended and erupted, whereas juvenile Burr Point clasts resemble other lava flows erupted from Augustine Volcano, vesicular and glassy juvenile West Island clasts bear resemblance to clasts derived from so-called "blast-generated" pyroclastic density deposits at Mt. St. Helens in 1980 and Bezymianny in 1956.

Rath, C. A.; Browne, B. L.

2011-12-01

205

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

206

76 FR 33172 - Fisheries of the Exclusive Economic Zone Off Alaska; Alaska Plaice in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...Alaska Plaice in the Bering Sea and Aleutian Islands Management Area AGENCY: National...of Alaska plaice in the Bering Sea and Aleutian Islands management area (BSAI). This...management plan for the Bering Sea and Aleutian Islands management area. DATES:...

2011-06-08

207

Preliminary Volcano-Hazard Assessment for the Tanaga Volcanic Cluster, Tanaga Island, Alaska  

USGS Publications Warehouse

Summary of Volcano Hazards at Tanaga Volcanic Cluster The Tanaga volcanic cluster lies on the northwest part of Tanaga Island, about 100 kilometers west of Adak, Alaska, and 2,025 kilometers southwest of Anchorage, Alaska. The cluster consists of three volcanoes-from west to east, they are Sajaka, Tanaga, and Takawangha. All three volcanoes have erupted in the last 1,000 years, producing lava flows and tephra (ash) deposits. A much less frequent, but potentially more hazardous phenomenon, is volcanic edifice collapse into the sea, which likely happens only on a timescale of every few thousands of years, at most. Parts of the volcanic bedrock near Takawangha have been altered by hydrothermal activity and are prone to slope failure, but such events only present a local hazard. Given the volcanic cluster's remote location, the primary hazard from the Tanaga volcanoes is airborne ash that could affect aircraft. In this report, we summarize the major volcanic hazards associated with the Tanaga volcanic cluster.

Coombs, Michelle L.; McGimsey, Robert G.; Browne, Brandon L.

2007-01-01

208

Temporal source evolution and crustal contamination at Lopevi Volcano, Vanuatu Island Arc  

NASA Astrophysics Data System (ADS)

Here we present a new geochemical study of Lopevi volcano, one the most active volcanoes in the Vanuatu island arc. We focus on the temporally well-defined sequence of lava flows emitted since 1960, and for the first time, on pre-1960 volcanic products, including high-MgO basalts and felsic andesites, the most evolved lavas sampled so far on this island. This work reports the first Pb and Hf isotopic study of lavas from Lopevi island. These lavas display correlations between differentiation indexes such as SiO2 content and isotopic ratios. The felsic andesites extend the known correlations with both the least (Sr-Pb) and the most (Nd-Hf) radiogenic isotopic compositions on the island. Our results confirm that the rising magma interacted with the sub-arc crust. Assimilation-Fractional Crystallization (AFC) quantitative modeling of trace element ratios and isotopic compositions requires 1% and 10% of assimilated partial melts of a mafic oceanic crust to account for the pre- and post-1960 lavas, respectively. The post-1960 lavas differ from the former lavas emitted ~ 20 years earlier by enrichments in fluid mobile elements (K, Ba, Rb…), Th, and Light Rare Earth Elements (LREE). We ascribe these features to slight variations in the metasomatic agent added to the sub-arc mantle and ultimately derived from the subducted lithosphere. However, the contrasting time scales involved in subducted lithosphere dehydration and magma genesis, relative to the time elapsed between eruptions of the two lava series, suggest that two different portions of mantle which have undergone slightly different metasomatism, gave birth to the Lopevi lavas. These distinct magmas are still present beneath the volcano.

Beaumais, Aurélien; Chazot, Gilles; Dosso, Laure; Bertrand, Hervé

2013-08-01

209

Ground Water in Kilauea Volcano and Adjacent Areas of Mauna Loa Volcano, Island of Hawaii  

USGS Publications Warehouse

About 1,000 million gallons of water per day moves toward or into ground-water bodies of Kilauea Volcano from the lavas of Mauna Loa Volcano. This movement continues only to the northern boundaries of the east and southwest rift zones of Kilauea, where a substantial quantity of ground water is deflected downslope to other ground-water bodies or to the ocean. In the western part of Kilauea, the kaoiki fault system, which parallels the southwest rift zone, may be the main barrier to ground-water movement. The diversion of the ground water is manifested in the western part of Kilauea by the presence of large springs at the shore end of the Kaoiki fault system, and in the eastern part by the apparently large flow of unheated basal ground water north of the east rift zone. Thus, recharge to ground water in the rift zones of Kilauea and to the areas to the south of the rift zones may be largely by local rainfall. Recharge from rainfall for all of Kilauea is about 1,250 million gallons per day. Beneath the upper slopes of the Kilauea rift zones, ground-water levels are 2,000 feet or more above mean sea level, or more than 1,000 feet below land surface. Ground-water levels are at these high altitudes because numerous and closely spaced dikes at depth in the upper slopes impound the ground water. In the lower slopes, because the number of dikes decreases toward the surface, the presence of a sufficient number of dikes capable of impounding ground water at altitudes substantially above sea level is unlikely. In surrounding basal ground-water reservoirs, fresh basal ground water floats on seawater and, through a transition zone of mixed freshwater and seawater, discharges into the sea. The hydraulic conductivity of the dike-free lavas ranges from about 3,000 to about 7,000 feet per day. The conductivity in the upper slopes of the rift ranges from about 5 to 30 feet per day and that of the lower slopes of the east rift zone was calculated at about 7,000 feet per day. The occurrence of heated basal water south of the lower east rift zone of Kilauea indicates the movement of a large quantity of geothermally heated ground water southward from the rift zone. There is little indication of similar movement of water from the upper slopes of the east rift zone, and there is no obvious movement of heated water from the lower east rift to the north because of the absence of heated ground water north of the rift zone. A broad range in temperature and chemical composition of geothermally modified ground water indicates several different sources. Four possible sources are (1) cold meteoric water, (2) cold seawater, (3) hydrothermal fluids of meteoric origin, and (4) hydrothermally modified seawater. The chloride-ion to magnesium-ion ratio of ground water indicates whether the water has been geothermally modified. A ratio greater than 15 to 1 generally denotes geothermally modified ground water.

Takasaki, Kiyoshi J.

1993-01-01

210

Ocean noise triggering of rhythmic long period events at Deception Island volcano  

NASA Astrophysics Data System (ADS)

We report on swarms of repeating long-period (LP) events with remarkably periodic occurrence at Deception Island volcano, Antarctica. The LP events show dominant frequencies near 2 Hz and characteristic inter-event times that range from ˜10 s to ˜20 s for individual swarms. We observe that LP inter-event times are approximate integer multiples of the dominant periods of the oceanic microseism, indicating a synchronization of LP activity with the phase of ocean noise. We attribute LP periodicity to the coincidence of sustained LP activity in an unstable hydrothermal system and external forcing by ocean noise that introduces periodic pressure variations in volcano fluids. We estimate the volumetric strain change generated by the oceanic microseism at the source location and conclude that strain of order 10-7 is sufficient to introduce clear periodicity in the LP sequences, and that periodicity increases with increasing strain.

Stich, Daniel; Almendros, Javier; Jiménez, Vanessa; Mancilla, Flor; Carmona, Enrique

2011-11-01

211

Multiparametric Approach in Investigating Volcano-Hydrothermal Systems: the Case Study of Vulcano (Aeolian Islands, Italy)  

NASA Astrophysics Data System (ADS)

Seismic activity, ground deformation, and soil and fumarole temperatures acquired during 2004-2007 at Vulcano (Aeolian Islands) are analysed and the time relations among the different time series are discussed. Changes in temperature of fumarolic gases took place during four "anomalous" periods (November 2004-March 2005; October 2005-February 2006; August-October 2006; July-December 2007) at the same time as an increasing number of volcano-seismic events. In particular, the temperatures at high temperature vents and at steam heated soil ranged in time from 180 to 440°C and from 20 to 90°C, respectively. The maximum daily number of volcano-seismic events was 57, reached during the second anomalous period. This seismicity, characterised by focal depth generally lower than 1 km below sea level (b.s.l.) and composed of different kinds of events associated to both resonance and shear failure processes, is related to the shallow dynamics of the hydrothermal system. During the analysed period, very few volcano-tectonic earthquakes took place and tilt recordings showed no sharp or important changes. In light of such observations, the increases in both temperature and volcano-seismic events number were associated to increases in the release of gas from a deep and stable magma body, without magma intrusions within the shallow hydrothermal system. Indeed, a greater release of gas from depth leads to increased fluid circulation, that can promote increases in volcano-seismic events number by both fracturing processes and resonance and vibration in cracks and conduits. The different trends observed in the measured geochemical and geophysical series during the anomalous periods can be due to either time changes in the medium permeability or a changing speed of gas release from a deep magma body. Finally, all the observed variations, together with the changing temporal distribution of the different seismic event kinds, suggest that the hydrothermal system at Vulcano can be considered unsteady and dynamic.

Cannata, Andrea; Diliberto, Iole Serena; Alparone, Salvatore; Gambino, Salvatore; Gresta, Stefano; Liotta, Marcello; Madonia, Paolo; Milluzzo, Vincenzo; Aliotta, Marco; Montalto, Placido

2012-01-01

212

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

213

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

214

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

215

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.

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

2002-01-01

216

CO2 degassing at Papandayan and Kelud volcanoes, Java island, Indonesia  

NASA Astrophysics Data System (ADS)

Papandayan volcano (2665 m a.s.l) is located in the western part of the island of Java. The last magmatic eruption of this volcano occurred in 1772. At that time, the NE sector of the volcano collapsed, producing a large avalanche of debris and creating a horseshoe shaped crater. The most recent activity of Papandayan occurred in November 2002 when the volcano erupted ash clouds to altitudes of about 5 km. Before this event, the volcano was in a state of passive degassing with solfatara, sulfur-pools and hot springs. Since 1994, the geochemistry of these hot springs is monitored. These springs are acid sulfate-chloride waters with pH between 1.5 and 2.5. Sulfur isotopic composition (delta 34: 8-14.5 per mil) clearly suggest the injection of magmatic volatiles (SO2) to the hydrothermal system present at depth.A survey of diffuse CO2 degassing using the accumulation chamber method was performed in August 2001. 420 uniformly distributed points were measured in the main crater (Kawah Emas) covering an area of 58,000 m2. At least, two distinct populations of values are present. Diffuse CO2 degassing show a wide range of values from background values up to fluxes as high as 6,190 g/m2/day. The total degassing flux of CO2 estimated for this area is 7,410 t/year. This survey was completed in September 2002 with measurements of soil CO2 concentrations (at 50 cm depth). Concentrations as high as 30 vol. % were measured in some areas and clearly revealed the position of active faults on the crater floor. Kelud volcano (1650 m a.s.l.) is located in the eastern part of Java island and contains a crater lake. The Kelud historical eruption consisted mainly of pyroclastic flow and surges. Kelud volcano is known for its devastating lahars and a system of drainage was build in 1920 in order to keep the volume of the lake to 2 million m3.The last magmatic eruption occurred in 1990. Periodical geochemical surveys were carried out at the lake waters since 1993 to understand the hydrothermal system of this volcano. The lake contains near neutral waters with a pH of 6. In July 2001, we conducted a preliminary CO2 survey on the lake to measure the quantities of CO2 released from the lake surface to the atmosphere. The total flux of CO2 emitted by the lake surface is estimated at 28,400 t/year. A second survey was carried out in September 2002 and showed a significant decrease in CO2 flux to 19,700 t/year. This decrease in CO2 follow a net decrease in the input of hot fluids in the crater lake where the measured temperatures dropped from 42 °C in July 2001 to 33 °C in September 2002.

Mazot, A.; Bernard, A.

2003-04-01

217

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

218

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.

219

Environmental monitoring of El Hierro Island submarine volcano, by combining low and high resolution satellite imagery  

NASA Astrophysics Data System (ADS)

El Hierro Island, located at the Canary Islands Archipelago in the Atlantic coast of North Africa, has been rocked by thousands of tremors and earthquakes since July 2011. Finally, an underwater volcanic eruption started 300 m below sea level on October 10, 2011. Since then, regular multidisciplinary monitoring has been carried out in order to quantify the environmental impacts caused by the submarine eruption. Thanks to this natural tracer release, multisensorial satellite imagery obtained from MODIS and MERIS sensors have been processed to monitor the volcano activity and to provide information on the concentration of biological, chemical and physical marine parameters. Specifically, low resolution satellite estimations of optimal diffuse attenuation coefficient (Kd) and chlorophyll-a (Chl-a) concentration under these abnormal conditions have been assessed. These remote sensing data have played a fundamental role during field campaigns guiding the oceanographic vessel to the appropriate sampling areas. In addition, to analyze El Hierro submarine volcano area, WorldView-2 high resolution satellite spectral bands were atmospherically and deglinted processed prior to obtain a high-resolution optimal diffuse attenuation coefficient model. This novel algorithm was developed using a matchup data set with MERIS and MODIS data, in situ transmittances measurements and a seawater radiative transfer model. Multisensor and multitemporal imagery processed from satellite remote sensing sensors have demonstrated to be a powerful tool for monitoring the submarine volcanic activities, such as discolored seawater, floating material and volcanic plume, having shown the capabilities to improve the understanding of submarine volcanic processes.

Eugenio, F.; Martin, J.; Marcello, J.; Fraile-Nuez, E.

2014-06-01

220

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

221

Large-scale deformation related to the collision of the Aleutian Arc with Kamchatka  

Microsoft Academic Search

The far western Aleutian Island Arc is actively colliding with Kamchatka. Westward motion of the Aleutian Arc is brought about by the tangential relative motion of the Pacific plate transferred to major, right-lateral shear zones north and south of the arc. Early geologic mapping of Cape Kamchatka (a promontory of Kamchatka along strike with the Aleutian Arc) revealed many similarities

Eric L. Geist; David W. Scholl

1994-01-01

222

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

Microsoft Academic Search

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

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

2009-01-01

223

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

224

Seismic vulnerability of dwellings at Sete Cidades Volcano (S. Miguel Island, Azores)  

NASA Astrophysics Data System (ADS)

Since the settlement of S. Miguel Island (Azores), in the XV century, several earthquakes caused important human losses and severe damages on the island. Sete Cidades Volcano area, located in the westernmost part of the island, was attained by strong seismic crises of tectonic and volcanic origin and major events reached a maximum historical intensity of IX (European Macroseismic Scale 1998) in this zone. Aiming to evaluate the impact of a future major earthquakes, a field survey was carried out in ten parishes of Ponta Delgada County, located on the flanks of Sete Cidades volcano and inside it is caldera. A total of 7019 buildings were identified, being 4351 recognized as dwellings. The total number of inhabitants in the studied area is 11429. In this work, dwellings were classified according to their vulnerability to earthquakes (Classes A to F), using the structure types table of the EMS-98, adapted to the types of constructions made in the Azores. It was concluded that 76% (3306) of the houses belong to Class A, and 17% (740) to Class B, which are the classes of higher vulnerability. If the area is affected by a seismic event with intensity IX it is estimated, that 57% (2480) to 77% (3350) of the dwellings will partially or totally collapse and 15% (652) to 25% (1088) will need to be rehabilitated. In this scenario, considering the average of inhabitants per house for each parish, 82% (9372) to 92% (10515) of the population will be affected. The number of deaths, injured and dislodged people will pose severe problems to the civil protection authorities and will cause social and economic disruption in the entire archipelago.

Gomes, A.; Gaspar, J. L.; Queiroz, G.

2006-01-01

225

Use of Precipitation and Groundwater Isotopes to Interpret Regional Hydrology on a Tropical Volcanic Island: Kilauea Volcano Area, Hawaii  

Microsoft Academic Search

Isotope tracer methods were used to determineflow paths, recharge areas, and relative age for groundwater in the Kilauea volcano area of the Island of Hawaii. A network of up to 66 precipitation collectors was emplaced in the study area and sampled twice yearly for a 3-year period. Stable isotopes in rainfall show three distinct isotopic gradients with elevation, which are

M. A. Scholl; S. E. Ingebritsen; C. J. Janik; J. P. Kauahikaua

1996-01-01

226

Use of Precipitation and Groundwater Isotopes to Interpret Regional Hydrology on a Tropical Volcanic Island: Kilauea Volcano Area, Hawaii  

Microsoft Academic Search

Isotope tracer methods were used to determine flow paths, recharge areas, and relative age for groundwater in the Kilauea volcano area of the Island of Hawaii. A network of up to 66 precipitation collectors was emplaced in the study area and sampled twice yearly for a 3-year period. Stable isotopes in rainfall show three distinct isotopic gradients with elevation, which

M. A. Scholl; S. E. Ingebritsen; C. J. Janik; J. P. Kauahikaua

1996-01-01

227

Use of precipitation and groundwater isotopes to interpret regional hydrology on a tropical volcanic island: Kilauea volcano area, Hawaii  

Microsoft Academic Search

Isotope tracer methods were used to determine flow paths, recharge areas, and relative age for groundwater in the Kilauea volcano area of the Island of Hawaii. A network of up to 66 precipitation collectors was emplaced in the study area and sampled twice yearly for a 3-year period. Stable isotopes in rainfall show three distinct isotopic gradients with elevation, which

M. A. Scholl; S. E. Ingebritsen; C. J. Janik; J. P. Kauahikaua

1996-01-01

228

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

229

76 FR 43658 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013

...Fisheries of the Exclusive Economic Zone Off Alaska; Bering...Islands Crab Rationalization Cost Recovery Program AGENCY...The Program includes a cost recovery provision to...to recover the actual costs directly related to the...Program. NMFS developed the cost recovery provision...

2011-07-21

230

78 FR 46577 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013

...Fisheries of the Exclusive Economic Zone Off Alaska; Bering...Islands Crab Rationalization Cost Recovery Program AGENCY...The Program includes a cost recovery provision to...to recover the actual costs directly related to the...Program. NMFS developed the cost recovery provision...

2013-08-01

231

77 FR 44216 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013

...Fisheries of the Exclusive Economic Zone Off Alaska; Bering...Islands Crab Rationalization Cost Recovery Program AGENCY...The Program includes a cost recovery provision to...to recover the actual costs directly related to the...Program. NMFS developed the cost recovery provision...

2012-07-27

232

75 FR 43147 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013

...Fisheries of the Exclusive Economic Zone Off Alaska; Bering...Islands Crab Rationalization Cost Recovery Program AGENCY...The Program includes a cost recovery provision to...to recover the actual costs directly related to the...Program. NMFS developed the cost recovery provision...

2010-07-23

233

Geothermal resource assessment in the Aleutian Islands and Alaska peninsula: Quarterly progress report, January 1--March 30, 1989  

SciTech Connect

In this report the authors have now completed dating work on 20 rock samples. Analytical results for the dated samples are given in the enclosed table. The results are generally in good agreement with observed stratigraphic relationships and provide a well-constrained time framework for the eruptive history of this volcanic area. The argon extraction and potassium analyses are completed and the argon sample is awaiting mass spectrometry. In addition to documenting the eruptive history of Umnak volcanoes, the K-Ar ages will provide a time framework for the chemical evolution of the magmatic system, when combined with the rock chemistry analyses presently in progress at U.C., Santa Cruz. 1 tab.

Turner, D.L.; Nye, C.J.

1989-03-30

234

Pyroclastic density currents at Stromboli volcano (Aeolian Islands, Italy): a case study of the 1930 eruption  

NASA Astrophysics Data System (ADS)

Pyroclastic density currents (PDC) related to paroxysmal eruptions have caused a large number of casualties in the recent history of Stromboli. We combine here a critical review of historical chronicles with detailed stratigraphic, textural, and petrographic analyses of PDC deposits emplaced at Stromboli over the last century to unravel the origin of currents, their flow mechanism and the depositional dynamics. We focus on the 1930 PDC as they are well described in historical accounts and because the 1930 eruption stands as the most voluminous and destructive paroxysm of the last 13 centuries. Stromboli PDC deposits are recognizable from their architecture and the great abundance of fresh, well-preserved juvenile material. General deposit features indicate that Stromboli PDC formed due to the syn-eruptive gravitational collapse of hot pyroclasts rapidly accumulated over steep slopes. Flow channelization within the several small valleys cut on the flanks of the volcano can enhance the mobility of PDC, as well as the production of fine particles by abrasion and comminution of hot juvenile fragments, thereby increasing the degree of fluidization. Textural analyses and historical accounts also indicate that PDC can be fast (15-20 m/s) and relatively hot (360-700 °C). PDC can thus flow right down the slopes of the volcano, representing a major hazard. For this reason, they must be adequately taken into account when compiling risk maps and evaluating volcanic hazard on the Island of Stromboli.

Di Roberto, A.; Bertagnini, A.; Pompilio, M.; Bisson, M.

2014-06-01

235

Volcanic emissions from soils at the base of La Fossa volcano, Vulcano island, Italy  

NASA Astrophysics Data System (ADS)

A top-sealed plastic tube with a diameter of ca. 15 cm had been buried vertically at the base of La Fossa volcano, Volcano island, Italy, next to the front of the obsidian flow. The tube had been filled with quartz wool to condense vapors emanating from the soil. At ca. 75 cm below the surface the sample had been exposed to vapors from Sept. 2005 to April 2006. The leached sample had not been in touch with the ground. Another glass wool cushion (ca. 3 cm thick) had been underneath to minimize capillary effects. Leaching of the quartz wool and ICP-MS analysis documented positive values for: Mg, Al, Si, P, K, Ca, Cr, Mn, Ni, Cu, Zn, Cd, Sn, Pb. Leaching with nitric acid documented also V and Fe. Acid leaching produced higher values for all elements, except K and Sn, than leaching with deionized water. Negative values had been obtained for As, Se, Mo. Influence from soil breathing can be excluded as the active fumaroles contain As and Se. This experiment documents for the first time an unknown element transport by vapors/gases through a volcanic edifice interacting with hydrothermal and magmatic gases. It remains unknown if elements detected are entering the atmosphere or are getting adsorbed onto the volcanic ash soil particles derived from reworked surge beds. This question is very important as soils might be an unknown filter medium to filter volcanically polluted air in case of major volcanic crises. Data can be obtained from the authors.

Obenholzner, J. H.; Parks, J. L.

2006-12-01

236

Soil CO2 emissions at Furnas volcano, São Miguel Island, Azores archipelago: Volcano monitoring perspectives, geomorphologic studies, and land use planning application  

NASA Astrophysics Data System (ADS)

Carbon dioxide (CO2) diffuse degassing structures (DDS) at Furnas volcano (São Miguel Island, Azores) are mostly associated with the main fumarolic fields, evidence that CO2 soil degassing is the surface expression of rising steam from the hydrothermal system. Locations with anomalous CO2 flux are mainly controlled by tectonic structures oriented WNW-ESE and NW-SE and by the geomorphology of the volcano, as evidenced by several DDS located in depressed areas associated with crater margins. Hydrothermal soil CO2 emissions in Furnas volcano are estimated to be ˜968 t d-1. Discrimination between biogenic and hydrothermal CO2 was determined using a statistical approach and the carbon isotope composition of the CO2 efflux. Different sampling densities were used to evaluate uncertainty in the estimation of the total CO2 flux and showed that a low density of points may not be adequate to quantify soil emanations from a relatively small DDS. Thermal energy release associated with diffuse degassing at Furnas caldera is about 118 MW (from an area of ˜4.8 km2) based on the H2O/CO2 ratio in fumarolic gas. The DDS also affect Furnas and Ribeira Quente villages, which are located inside the caldera and in the south flank of the volcano, respectively. At these sites, 58% and 98% of the houses are built over hydrothermal CO2 emanations, and the populations are at risk due to potential high concentrations of CO2 accumulating inside the dwellings.

Viveiros, FáTima; Cardellini, Carlo; Ferreira, Teresa; Caliro, Stefano; Chiodini, Giovanni; Silva, Catarina

2010-12-01

237

Comparative determination of paralytic shellfish toxins (PSTs) using five different toxin detection methods in shellfish species collected in the Aleutian Islands, Alaska.  

PubMed

Paralytic shellfish poisoning (PSP), a human illness caused by the ingestion of shellfish contaminated with paralytic shellfish toxins (PSTs), has been reported in Alaska for decades. These poisoning incidents have resulted in losses to local economies due to shellfish harvest closures. Thus the development of an effective biotoxin monitoring program designed specifically for the remote regions of Alaska would provide protection for public health and allow for a viable shellfish industry. The present study provides data useful for the development of an effective toxin screening protocol by comparing PST levels quantified in shellfish by many of the currently available PST detection techniques. Seven bivalve species were collected along beaches of the Aleutian Islands from June 2006 to September 2007. The concentration of PSTs was quantified and compared using five different analytical methods: the mouse bioassay, high performance liquid chromatography (HPLC), receptor-binding assay, the commercially available Jellett Rapid PSP Test strips, and an enzyme linked immunosorbent assay technique. The Association of Official Analytical Chemists (AOAC)-approved HPLC method proved to be valuable for characterizing the suite of individual PSTs in each species for research purposes, but was not considered practical for rapid toxin screening in remote Alaskan regions due to its time-consuming nature and requirement of expensive equipment and considerable expertise. In the present study, Jellett test strips were shown to be an effective tool for rapid screening, however due to the high percentage of false positives, subsequent validation via AOAC-approved methods would be required to prevent unnecessary closures. PMID:19450616

Costa, Pedro Reis; Baugh, Keri A; Wright, Bruce; Ralonde, Raymond; Nance, Shelly L; Tatarenkova, Natália; Etheridge, Stacey M; Lefebvre, Kathi A

2009-09-01

238

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

239

Problems in Using Underground Water Temperatures in Volcanic Surveillance: the Case of Volcano Island (Eolian Islands, Sicily, Italy)  

NASA Astrophysics Data System (ADS)

Measuring underground water temperatures in a network of wells, together with many other geochemical and geophysical data, is a useful tool in medium-long term surveillance of active volcanic areas. The study case here presented deals with Volcano Island (Eolian Islands, Sicily, Italy). About 20 years of observations are presented; they have been acquired either during spot campaigns, every 1-3 months, either by continuous monitoring (sampling period of 2 hours). Although the interested active volcanic area has an extension of few square kilometers, data analysis pointed out a surprising variability in space and time of the information acquired, and in particular: a) Monthly temperature variations show a frequency related to the hydrological cycle, except some wells located in a piezometric high (Camping Sicilia well) or in distal positions respect to the La Fossa Crater (EAS and Discarica wells). b) Some wells subjected to continuous monitoring, affected (Le Calette) or not (Camping Sicilia) by seasonal variations, show high frequency (from few hours to few days) pulsation of several Celsius degrees. The above mentioned variations are sometimes related to seismic events (Gulf of Patti earthquakes, April 2002). c) Water table elevations from sea level, measured at the same time of temperature, highlight the presence of some wells (EAS, Casamento) where the piezometric surface is normally below the sea, despite they are very near to the coast line. The elements above discussed point out the presence of a complex multi-layered aquifer, with very different interactions between fresh, sea and volcanic waters, that are reflected in space and time variations of measured B.H.T. values. The implementation of an accurate hydrogeological model is then to be considered as preventive and fundamental in order to correctly design a surveillance activity based on underground fluids monitoring in this area.

Madonia, P.; Capasso, G.; Favara, R.

2002-12-01

240

Satellite and ground observations of the June 2009 eruption of Sarychev Peak volcano, Matua Island, Central Kuriles  

NASA Astrophysics Data System (ADS)

After 33 years of repose, one of the most active volcanoes of the Kurile island arc—Sarychev Peak on Matua Island in the Central Kuriles—erupted violently on June 11, 2009. The eruption lasted 9 days and stands among the largest of recent historical eruptions in the Kurile Island chain. Satellite monitoring of the eruption, using Moderate Resolution Imaging Spectroradiometer, Meteorological Agency Multifunctional Transport Satellite, and Advanced Very High Resolution Radiometer data, indicated at least 23 separate explosions between 11 and 16 June 2009. Eruptive clouds reached altitudes of generally 8-16 km above sea level (ASL) and in some cases up to 21 km asl. Clouds of volcanic ash and gas stretched to the north and northwest up to 1,500 km and to the southeast for more than 3,000 km. For the first time in recorded history, ash fall occurred on Sakhalin Island and in the northeast sector of the Khabarovsky Region, Russia. Based on satellite image analysis and reconnaissance field studies in the summer of 2009, the eruption produced explosive tephra deposits with an estimated bulk volume of 0.4 km3. The eruption is considered to have a Volcanic Explosivity Index of 4. Because the volcano is remote, there was minimal risk to people or infrastructure on the ground. Aviation transport, however, was significantly disrupted because of the proximity of air routes to the volcano.

Rybin, Alexander; Chibisova, Marina; Webley, Peter; Steensen, Torge; Izbekov, Pavel; Neal, Christina; Realmuto, Vince

2011-11-01

241

The eruptive history of Morne Jacob volcano (Martinique Island, French West Indies): Geochronology, geomorphology and geochemistry of the earliest volcanism in the recent Lesser Antilles arc  

Microsoft Academic Search

Martinique is the Lesser Antilles Island where the most complete volcanic history of the arc can be found from the Oligocene to the present time. In this study, we focused on the construction of Morne Jacob shield volcano in Martinique, which is the largest volcano of the Lesser Antilles. We have dated twenty representative samples from the Morne Jacob, by

Aurélie Germa; Xavier Quidelleur; Shasa Labanieh; Pierre Lahitte; Catherine Chauvel

2010-01-01

242

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

243

Volcanic Activity in Alaska and Kamchatka: Summary of Events and Response of the Alaska Volcano Observatory, 2004.  

National Technical Information Service (NTIS)

The Alaska Volcano Observatory (AVO) is responsible for monitoring the more than 40 historically active volcanoes of the Aleutian arc. As of December 31, 2004, 27 of these volcanoes are instrumented with seismometers to track earthquake activity, and AVO ...

C. A. Neal R. G. McGimsey J. Dixon D. Melnikov

2005-01-01

244

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

245

Intra- and extra-caldera volcaniclastic facies and geomorphic characteristics of a frequently active mafic island–arc volcano, Ambrym Island, Vanuatu  

Microsoft Academic Search

Ambrym is one of the most voluminous active volcanoes in the Melanesian arc. It consists of a 35 by 50 km island elongated east–west, parallel with an active fissure zone. The central part of Ambrym, about 800 m above sea level, contains a 12 kilometre-wide caldera, with two active intra-caldera cone-complexes, Marum and Benbow. These frequently erupting complexes provide large volumes of tephra

Károly Németh; Shane J. Cronin; Robert B. Stewart; Douglas Charley

2009-01-01

246

Petroleum potential of volcanogenic and volcano-sedimentary rocks in ancient and recent island arcs: Caucasus, Komandorskie, and Kuril islands, eastern Kamchatka  

SciTech Connect

In the Late Cretaceous-Eocene, subduction of the Tethys oceanic plate under the island arc of the lesser Caucasus contributed to the appearance of the special conditions favorable for petroleum occurrence: (1) tectono-magmatic destruction of the crust of the Transcaucasus median massif and formation of hydrocarbon traps of different types and origins, and (2) high heat flow lasting until the recent epoch. These led flow-intensive generation of hydrocarbons in the shallow-water sediments of the paleoshelf of the Transcaucasus massif and accumulation of hydrocarbons not only in the sedimentary but also in the volcanogenic and volcano-sedimentary reservoirs (Samgori-Patardzeuli, Muradhanly fields, etc.). At the end of the Oligocene, the geodynamic setting in the northwestern margins of the Pacific Ocean was mainly similar to that within the Transcaucasus median massif. At the end of Oligocene-Miocene, such conditions determined the tectono-magmatic destruction of the continental crust and formation of the series of interarc rifts. The main fields of Japan, with accumulations in the volcanogenic and volcano-sedimentary rocks, are concentrated here. Its analog is the rift located in the southern part of a single east Kuril basin, where petroleum occurrence is only inferred. In the separate troughs, the thickness of the volcano-sedimentary cover is 4-6 km. The stratigraphic section of the cover contains the volcanic and volcano-sedimentary sediments of the Neogene-Pleistocene. The studies of the sections of the Komandorskie islands, eastern Kamchatka, Kuril Islands, and western Sakhalin indicate that distribution of reservoirs depends on the stage of evolution of the rifts and adjacent island arcs.

Levin, L.E. (VNIIZarubezhgeologia, Moscow (Russian Federation))

1993-09-01

247

Spatial variation of seismic b-values beneath Makushin Volcano, Unalaska Island, Alaska  

NASA Astrophysics Data System (ADS)

The frequency-magnitude distribution was spatially mapped beneath Makushin Volcano, Unalaska Island, Alaska using an earthquake catalog of 491 events that occurred between July 2001 and April 2005. An area of high seismic b-values (˜ 2.0) is found ˜ 4 km east of Makushin's main vent at a depth between 4 and 7 km. The anomaly is statistically significant based on Utsu's p-test [T. Utsu, On seismicity, in Report of the Joint Research Institute for Statistical Mathematics, Tokyo (1992) 139-157], and is not data processing method or parameter dependent. Interestingly, a recent InSAR interferometric study [Z. Lu, J.A. Power, V.S. McConnell, C. Wicks Jr., D. Dzurism, Preeruptive inflation and surface interferometric coherence characteristics by satellite radar interferometry at Makushin volcano, Alaska: 1993-2000, J. Geophys. Res. 107 (2002) 2266, doi:10.1029/2001JB000970] inferred a surface uplift of about 7 cm during the two-year period prior to October 1995, centered approximately in the area with the observed anomalous b-values. The uplift was caused by the volume increase of an inferred magma chamber at a depth of about 7 km. The close correspondence of the seismic and InSAR observations suggests that the heterogeneous area associated with the observed high b-values is most likely the result of increased crack density associated with the magma chamber. This study demonstrates the effectiveness of combining InSAR and seismological observations in locating magma chambers and areas of high heterogeneity in the crust.

Bridges, David L.; Gao, Stephen S.

2006-05-01

248

Possible Evidences for Abiogenic Hydrocarbons in Hydrothermal Fluids of Everman Volcano, Socorro Island, Mexico  

NASA Astrophysics Data System (ADS)

Geochemists believe that the Fischer-Tropsch reaction may be responsible for the abiogenic production of hydrocarbons (HC) in nature. Among environments where this is possible, terrestrial and submarine hydrothermal systems are main candidates. Among geochemical criteria for a natural FT process there are two most popular: Shultz-Flory distribution of alkanes and the decrease of ?13C of alkanes with increasing carbon number: the heavier alkanes should be isotopically ligher. The application of the first criterion is often wrong, because for the FT synthesis it makes sense only for n>4. The light HC products of a real FT synthesis have a maximum at C3-C4. The second rule is also not absolute, because after a heating of organic matter at >700°C the set of light alkanes formed as the result of such high-temperature thermo-degradation shows the same inverse, ``synthetic'', ?13C distribution. In the fumarolic steam of Everman volcano at Socorro island both criteria were fulfilled. Vapors from Socorro have 96° C, very high hydrogen and methane concentrations and a local minimum at ethane in the HC concentration distribution. Methane of Socorro is isotopically heavy (-9 > ?13C1 > -15 ‰ PDB) and ?13C2 > ?13C3 > ?13C4 (-21, -24, -25 permil, respectively). The source of high H2 and CH4 in Socorro gases is thought to be the serpentinization of Mg-rich gabbroid intrusive bodies inside and beneath the volcano edifice by infiltrated seawater in presence of magmatic CO2. The methane can be a mixture of isotopically heavier abiogenic CH4 and isotopically lighter thermogenic CH4. In that case, the inverse isotopic distribution could be an artifact, if most of C2+ are of thermogenic origin.

Taran, Y.

2005-12-01

249

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

PubMed

Significant anomalous changes in the ultra low frequency range (approximately 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

2002-05-28

250

Esmeralda Bank: Geochemistry of an active submarine volcano in the Mariana Island Arc  

Microsoft Academic Search

Esmeralda Bank is the southernmost active volcano in the Izu-Volcano-Mariana Arc. This submarine volcano is one of the most active vents in the western Pacific. It has a total volume of about 27 km3, rising to within 30 m of sea level. Two dredge hauls from Esmeralda recovered fresh, nearly aphyric, vesicular basalts and basaltic andesites and minor basaltic vitrophyre.

Robert J. Stern; L. D. Bibee

1984-01-01

251

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

252

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

253

Coccidia of Aleutian Canada geese  

USGS Publications Warehouse

Fecal samples from 122 captive and 130 free-ranging Aleutian Canada geese (Branta canadensis leucopareia) were examined for oocysts of coccidia. Freeranging geese sampled on the spring staging ground near Crescent City, California were infected with Eimeria hermani, E. truncata, E. magnalabia, E. fulva, E. clarkei and Tyzzeria parvula. Except for E. clarkei, the same species of coccidia were found in geese on their breeding grounds in Alaska. Most of the coccidial infections in captive geese from Amchitka Island, Alaska and Patuxent Wildlife Research Center, Maryland, consisted of Tyzzeria.

Greiner, E.C.; Forrester, D.J.; Carpenter, J.W.; Yparraguirre, D.R.

1981-01-01

254

Trace element and isotopic variations in a zoned pluton and associated volcanic rocks, Unalaska Island, Alaska: A model for fractionation in the Aleutian calcalkaline suite  

Microsoft Academic Search

Trace elements, including rare earth elements (REE), exhibit systematic variations in plutonic rocks from the Captains Bay pluton which is zoned from a narrow gabbroic rim to a core of quartz monzodiorite and granodiorite. The chemical variations parallel those in the associated Aleutian calcalkaline volcanic suite. Concentrations of Rb, Y, Zr and Ba increase as Sr and Ti decrease with

Michael R. Perfit; Hannes Brueckner; James R. Lawrence; Robert W. Kay

1980-01-01

255

Application of emulsion imaging system for cosmic-ray muon radiography to explore the internal structure of Teide and Cumbre Vieja volcanoes in the Canary Islands, Spain  

NASA Astrophysics Data System (ADS)

The internal structure of volcanoes, especially in their up per part, is product of past eruptions. Therefore, the knowledge of the internal structure of a volcano is of great importance for understanding its behaviour and to forecast the nature and style of the next eruptions. For these reasons, during past years scientists have made a big effort to investigate the internal structure of the volcanoes with different geophysical techniques, including deep drilling, passive and active seismic tomography, geoelectrics and magnetotellurics and gravimetry. One of the limits of conventional geophysical methods is the spatial resolution, which typically ranges between some tens of meters up to 1 km. In this sense, the radiography of active volcanoes based on natural muons, even if limited to the external part of the volcano, represents an important tool for investigating the internal structure of a volcano at higher spatial resolution (Macedonio and Martini, 2009). Moreover, muon radiography is able to resolve density contrasts of the order of 1-3%, significantly greater than the resolution obtained with conventional methods. As example, the experiment of muon radiography carried out at Mt. Asama volcano by Tanaka et al., 2007, allowed the reconstruction of the density map of the cone and detection of a dense region that corresponds to the position and shape of a lava deposit created during the last eruption in 2004. In the framework of a research project financed by the Canary Agency of Research, Innovation and Information Society, we will implement muon measurements at Teide volcano in Tenerife Island and Cumbre Vieja volcano in La Palma Island, Canary Islands, to radiographically image the subsurface structure of these two volcanic edifices. The data analysis will involve the study both of the shallow structure of both volcanoes and of the requirements for the implementation of the muon detectors. Both Cumbre Vieja and Teide are two active volcanoes that arouse great interest in the scientific community and society due to their volcanic features and specific hazards associated with volcanic activity.

Hernández, Iñigo; Hernández, Pedro; Pérez, Nemesio; Tanaka, Hiroyuki; Miyamoto, Seygo; Barrancos, José; Padrón, Eleazar

2013-04-01

256

Application of emulsion imaging system for cosmic-ray muon radiography to explore the internal structure of Teide and Cumbre Vieja volcanoes in the Canary Islands, Spain  

NASA Astrophysics Data System (ADS)

The internal structure of volcanoes, especially in their up per part, is product of past eruptions. Therefore, the knowledge of the internal structure of a volcano is of great importance for understanding its behaviour and to forecast the nature and style of the next eruptions. For these reasons, during past years scientists have made a big effort to investigate the internal structure of the volcanoes with different geophysical techniques, including deep drilling, passive and active seismic tomography, geoelectrics and magnetotellurics and gravimetry. One of the limits of conventional geophysical methods is the spatial resolution, which typically ranges between some tens of meters up to 1 km. In this sense, the radiography of active volcanoes based on natural muons, even if limited to the external part of the volcano, represents an important tool for investigating the internal structure of a volcano at higher spatial resolution (Macedonio and Martini, 2009). Moreover, muon radiography is able to resolve density contrasts of the order of 1-3%, significantly greater than the resolution obtained with conventional methods. As example, the experiment of muon radiography carried out at Mt. Asama volcano by Tanaka et al., 2007, allowed the reconstruction of the density map of the cone and detection of a dense region that corresponds to the position and shape of a lava deposit created during the last eruption in 2004. In the framework of a research project financed by the Canary Agency of Research, Innovation and Information Society, we will implement muon measurements at Teide volcano in Tenerife Island and Cumbre Vieja volcano in La Palma Island, Canary Islands, to radiographically image the subsurface structure of these two volcanic edifices. The data analysis will involve the study both of the shallow structure of both volcanoes and of the requirements for the implementation of the muon detectors. Both Cumbre Vieja and Teide are two active volcanoes that arouse great interest in the scientific community and society due to their volcanic features and specific hazards associated with volcanic activity.

Hernandez Perez, P. A.; Tanaka, H.; Miyamoto, S.; Perez, N.; Barrancos, J.; Padron, E.; Hernandez, I.

2012-12-01

257

Ground deformation associated with the eruption of Lumpur Sidoardjo mud volcano, eastern Java island  

NASA Astrophysics Data System (ADS)

Mud volcanism is a process that drives the extrusion of materials in the sediment to the surface. While it shares common features with magmatic eruptions; for example, eruption of mud volcanoes often results in elongated calderas and aligned vents. However, the mechanics of mud volcanism is not fully understood because of the rare occurrence. Here we take an advantage of observing ongoing eruption in Lumpur Sidoarjo (LUSI) mud volcano, eastern Java island, to gain insights into the mechanics of mud volcanism. LUSI has been erupting since May 2006 and released more than 12 million cubic meter of mud so far, buried some 20 square kilometers and forced 8000 people to evacuate. We delineated the temporal evolution of ground deformation from Synthetic Aperture Radar images taken from the ALOS satellite. We processed a total of 93 images from two ascending and three descending images between May 2006 and April 2011 using the StaMPS software (Hooper, GRL, 2008) to obtain the displacement time series of persistent scatterers. Although we were not able to obtain the time series in areas near the center of activity due to the lower coherence resulting from the mudflow, we observed an extension of line-of-sight (LOS) distance by a total of up to 200 millimeters within a few kilometers from the activity center from both ascending and descending images. This indicates that the deformation around the center of activity is dominated by subsidence. We also found an area of subsidence with a similar or even larger rate extending to the west of the activity center. This indicates that the depressurization beneath the activity center is not the only mechanism to cause this eruption but we need to consider another source to explain the observed displacement field. We also found a LOS shortening to the north of the activity center only from ascending images. This indicates an uplift and westward displacement in this area. Despite the decreasing rate of gas emission, our time series analysis shows that the deformation is quasi-linear during the time of the analysis. This suggests that the source of deformation has been stationary over time and and also it will a take long time for this eruption to cease.

Aoki, Yosuke; Purnama Sidiq, Teguh

2013-04-01

258

Ups and downs on spreading flanks of ocean-island volcanoes: Evidence from Mauna Loa and Ki??lauea  

USGS Publications Warehouse

Submarine-flank deposits of Hawaiian volcanoes are widely recognized to have formed largely by gravitationally driven volcano spreading and associated landsliding. Observations from submersibles show that prominent benches at middepths on flanks of Mauna Loa and Kilauea consist of volcaniclastic debris derived by landsliding from nearby shallow submarine and subaerial flanks of the same edifice. Massive slide breccias from the mature subaerial tholeiitic shield of Mauna Loa underlie the frontal scarp of its South Kona bench. In contrast, coarse volcaniclastic sediments derived largely from submarine-erupted preshield alkalic and transitional basalts of ancestral Kilauea underlie its Hilina bench. Both midslope benches record the same general processes of slope failure, followed by modest compression during continued volcano spreading, even though they record development during different stages of edifice growth. The dive results suggest that volcaniclastic rocks at the north end of the Kona bench, interpreted by others as distal sediments from older volcanoes that were offscraped, uplifted, and accreted to the island by far-traveled thrusts, alternatively are a largely coherent stratigraphic assemblage deposited in a basin behind the South Kona bench.

Lipman, P. W.; Eakins, B. W.; Yokose, H.

2003-01-01

259

Characteristics of Offshore Hawai';i Island Seismicity and Velocity Structure, including Lo';ihi Submarine Volcano  

NASA Astrophysics Data System (ADS)

The Island of Hawai';i is home to the most active volcanoes in the Hawaiian Islands. The island's isolated nature, combined with the lack of permanent offshore seismometers, creates difficulties in recording small magnitude earthquakes with accuracy. This background offshore seismicity is crucial in understanding the structure of the lithosphere around the island chain, the stresses on the lithosphere generated by the weight of the islands, and how the volcanoes interact with each other offshore. This study uses the data collected from a 9-month deployment of a temporary ocean bottom seismometer (OBS) network fully surrounding Lo';ihi volcano. This allowed us to widen the aperture of earthquake detection around the Big Island, lower the magnitude detection threshold, and better constrain the hypocentral depths of offshore seismicity that occurs between the OBS network and the Hawaii Volcano Observatory's land based network. Although this study occurred during a time of volcanic quiescence for Lo';ihi, it establishes a basis for background seismicity of the volcano. More than 480 earthquakes were located using the OBS network, incorporating data from the HVO network where possible. Here we present relocated hypocenters using the double-difference earthquake location algorithm HypoDD (Waldhauser & Ellsworth, 2000), as well as tomographic images for a 30 km square area around the summit of Lo';ihi. Illuminated by using the double-difference earthquake location algorithm HypoDD (Waldhauser & Ellsworth, 2000), offshore seismicity during this study is punctuated by events locating in the mantle fault zone 30-50km deep. These events reflect rupture on preexisting faults in the lower lithosphere caused by stresses induced by volcano loading and flexure of the Pacific Plate (Wolfe et al., 2004; Pritchard et al., 2007). Tomography was performed using the double-difference seismic tomography method TomoDD (Zhang & Thurber, 2003) and showed overall velocities to be slower than the regional velocity model (HG50; Klein, 1989) in the shallow lithosphere above 16 km depth. This is likely a result of thick deposits of volcaniclastic sediments and fractured pillow basalts that blanket the southern submarine flank of Mauna Loa, upon which Lo';ihi is currently superimposing (Morgan et al., 2003). A broad, low-velocity anomaly was observed from 20-40 km deep beneath the area of Pahala, and is indicative of the central plume conduit that supplies magma to the active volcanoes. A localized high-velocity body is observed 4-6 km deep beneath Lo';ihi's summit, extending 10 km to the North and South. Oriented approximately parallel to Lo';ihi's active rift zones, this high-velocity body is suggestive of intrusion in the upper crust, similar to Kilauea's high-velocity rift zones.

Merz, D. K.; Caplan-Auerbach, J.; Thurber, C. H.

2013-12-01

260

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

261

Material culture across the Aleutian archipelago.  

PubMed

The material evidence from sites across the Aleutian Islands reflects colonization events, subsequent adaptations, and influxes of ideas and/or people from the east. The occurrence in the eastern Aleutians of bifacial technology around 7000 BP, of artifacts similar to the Arctic Small Tool tradition between 4000 and 3500 BP, and of slate and jet objects around 1000 BP reflects repeated surges of influence or movement of peoples from further east into the eastern end of the chain. In the central and western Aleutians, influence or perhaps colonization from east of the Aleutians is also marked by the occurrence of bifacial technology about 6500 BP and the appearance of slate artifacts after 1000 BP, suggesting the movement of ideas or people from further east. Basic trends across the archipelago include a decrease in formal chipped-stone tools, an increase in the use and the complexity of bone technology, and the increase in use and variety of ground-stone tools. In addition, increasing village site sizes and denser midden deposits are seen later in time throughout the archipelago. The similarity in sites and assemblages, albeit with regional variations, reflects trends that are seen across the chain and indicates that these island communities were not isolated from one another or from mainland Alaska. PMID:21417883

Hatfield, Virginia L

2010-12-01

262

Deformation across the Alaska-Aleutian Subduction Zone near Kodiak  

USGS Publications Warehouse

The Kodiak-Katmai geodetic array, nine monuments distributed along a profile trending north-northwestward across Kodiak Island and the Alaska Peninsula, was surveyed in 1993, 1995 and 1997 to determine the deformation at the Alaska-Aleutian subduction zone. Velocities on Kodiak Island measured relative to the stable North American plate decrease with distance from the Alaska-Aleutian trench (distance range 106 to 250 km), whereas no appreciable deformation was measured on the Alaska Peninsula (distances 250 to 370 km from the trench). The measured deformation is reasonably well predicted by the conventional dislocation representation of subduction with the model parameters determined independently (i.e., not simply by fitting the observations). The deformation of Kodiak Island is in striking contrast to the very minor deformation measured in the similarly situated Shumagin Islands, 450 km southwest of Kodiak along the Alaska-Aleutian trench.

Savage, J. C.; Svarc, J. L.; Prescott, W. H.

1999-01-01

263

Enhancement of sub-daily positioning solutions for surface deformation monitoring at Deception volcano (South Shetland Islands, Antarctica)  

NASA Astrophysics Data System (ADS)

Deception Island is one of the most visited places in Antarctica. There are biological, geological, and archeological features that are major attractions within Port Foster, its horse shoe-shaped natural inner bay, and two scientific bases that are occupied during austral summers. Deception Island is an active volcano, however, and needs to be monitored in order to reduce risk to people on the island. Surface deformation in response to fluid pressure is one of the main volcanic activities to observe. Automated data acquisition and processing using the global navigation satellite systems allow measurements of surface deformation in near real time. Nevertheless, the positioning repeatability in sub-daily solutions is affected by geophysical influences such as ocean tidal loading, among others. Such periodic influences must be accurately modeled to achieve similar repeatability as daily solutions that average them. However, a single solution each 24 h will average out the deformation suffered during that period, and the position update waiting time can be a limitation for near real-time purposes. Throughout the last five austral summer campaigns in Deception, using simultaneous wireless communications between benchmarks, a processing strategy was developed to achieve millimeter-level half-hourly positioning solutions that have similar repeatability as those given by 24-h solutions. For these half-hourly solutions, a tidal analysis was performed to assess any mismodeling of ocean tide loading, and a discrete Kalman filter was designed and implemented to enhance the sub-daily positioning repeatability. With these solutions, the volcano-dynamic activity resulting in localized surface deformation for the last five austral summer campaigns is addressed. Although based on only three carefully located benchmarks, it is shown that Deception has been shortening and subsiding during these last 4 years. The method's accuracy in baselines up to a few hundred kilometers assures its applicability to other volcanoes worldwide.

Prates, G.; Berrocoso, M.; Fernández-Ros, A.; García, A.

2013-02-01

264

Time-space variation of volcano-seismic events at La Fossa (Vulcano, Aeolian Islands, Italy): new insights into seismic sources in a hydrothermal system  

Microsoft Academic Search

We investigated the relationship between volcano-seismic events, recorded at La Fossa crater of Vulcano (Aeolian Islands,\\u000a Italy) during 2004-2006, and the dynamics of the hydrothermal system. During the period of study, three episodes of increasing\\u000a numbers of volcano-seismic events took place at the same time as geothermal and geochemical anomalies were observed. These\\u000a geothermal and geochemical anomalies have been interpreted

Salvatore Alparone; Andrea Cannata; Salvatore Gambino; Stefano Gresta; Vincenzo Milluzzo; Placido Montalto

2010-01-01

265

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

266

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

267

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.

Fraile-Nuez, E.; Gonzalez-Davila, M.; Santana-Casiano, J. M.; Aristegui, J.; Alonso-Gonzalez, I. J.; Hernandez-Leon, S.; Blanco, M. J.; Rodriguez-Santana, A.; Hernandez-Guerra, A.; Gelado-Caballero, M. D.; Eugenio, F.; Marcello, J.; de Armas, D.; Dominguez-Yanes, J. F.; Montero, M. F.; Laetsch, D. R.; Velez-Belchi, P.; Ramos, A.; Ariza, A. V.; Comas-Rodriguez, I.; Benitez-Barrios, V. M.

2012-01-01

268

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.

Fraile-Nuez, Eugenio; Magdalena Santana-Casiano, J.; González-Dávila, Melchor

2014-05-01

269

Triggering at an Alaska-Aleutian Arc Tremor Sweet Spot  

NASA Astrophysics Data System (ADS)

Relative to other regions of the Alaska-Aleutian arc, daily routine visual scanning done for volcano monitoring notes signals with characteristics indicative of tectonic tremor most commonly at stations in the vicinity of Akutan Island. Brown et al. (2012, in press) found ambient tremor in four regions along the Alaska-Aleutian arc, and a total tremor duration in the vicinity of Akutan almost double that in any of the other regions examined. We further tested the inference that the vicinity of Akutan Island is a 'sweet spot' for tremor generation, by examining the tremor response to the nine largest amplitude seismic wavefields recorded across the region since 2006. The three largest of these posited triggering dynamic deformations originated from a M7.2 regional, the 2007 M8.1 Kuril and the M9.0 Tohoku, Japan earthquakes. Clear triggered tremor, bursts of 2-10 Hz energy in sync with passing lower-frequency surface waves, is observed only at seismic stations on Akutan and adjacent islands for the latter two earthquakes. While high frequencies from the triggering waves of the regional earthquake prevent detection of possible triggered signals at Akutan and its neighbors, no triggering is observed at any more distant stations. The only other clear triggered tremor - also at Akutan and its nearest neighbor - is associated with the 2012 M8.6 Sumatra earthquake wavefield, which curiously has smaller amplitudes than other wavefields that did not trigger tremor anywhere within the study region. Since tremor may be a proxy for slow slip on the plate-interface, we hypothesize that this observation suggests slow slip was underway at the time of the Sumatra earthquake and are testing this using GPS data. We also explore other possible explanations, such as differences in the posited triggering wavefields. We conclude that the Akutan region is indeed a sweet spot for tremor, perhaps consistent with its location above a frictionally transitional plate-interface, modeled as almost fully decoupled to the west and down-dip and coupled to the east and up-dip (bounding the down-dip edge the M8.9 1957 rupture). Curiously the Akutan region also straddles the transition between continental and oceanic crust within the overriding plate.

Gomberg, J. S.; Prejean, S. G.

2012-12-01

270

Shallow submarine volcano group in the early stage of island arc development: Geology and petrology of small islands south off Hahajima main island, the Ogasawara Islands  

NASA Astrophysics Data System (ADS)

Small Islands south off Hahajima, the southernmost of the Ogasawara Archipelago, consist of primitive basalts (<12 wt.% MgO) to dacite erupted during the transitional stage immediately following boninite volcanism on the incipient arc to sustained typical oceanic arc. Strombolian to Hawaiian fissure eruptions occurring on independent volcanic centers for the individual islands under a shallow sea produced magnesian basalt to dacite fall-out tephras, hyaloclastite and a small volume of pillow lava, which were intruded by NE-trending dikes. These volcanic strata are correlated to the upper part (<40 Ma) of the Hahajima main island. Volcanic rock samples have slightly lower FeO*/MgO ratios than the present volcanic front lavas, and are divided into three types with high, medium and low La/Yb ratios. Basalt to dacite of high- and medium-La/Yb types show both tholeiitic (TH) and calc-alkaline (CA) differentiation trends. Low-La/Yb type belongs only to TH basalt. The multiple magma types are coexistence on the each island. TH basalts have phenocrysts of olivine, clinopyroxene and plagioclase, while CA basalts are free from plagioclase phenocrysts.

Kanayama, Kyoko; Umino, Susumu; Ishizuka, Osamu

2014-05-01

271

Combining seismic and geochemical constraints on magmatic processes in the Aleutian arc (Invited)  

NASA Astrophysics Data System (ADS)

Seismic imaging provides one of the few constraints on the in situ structure and composition of island arc crust. Competing models for arc magmatic processes make different predictions for island arc structure, from lower crustal composition to the depth to crustal magma chambers. However, challenges of using seismic observations to constrain arc processes include the non-uniqueness of linking individual seismic attributes to composition and the paucity of observations worldwide. Here, we discuss the results, challenges and opportunities of seismic imaging of island arcs by discussing new and not-so-new seismic results from the Aleutian island arc, their relationship to other observations from this arc and comparisons with other oceanic island arcs worldwide. We will focus on ways to combine different types of data to extract better constraints than any single observation could provide in isolation. The Aleutian arc has a thick (>30 km) and mafic crust based on wide-angle seismic data from the central Aleutian island arc, tomography from local earthquakes, and receiver functions of widely spaced permanent seismic stations along the arc. Tomographic inversion of a sparse along-arc profile revealed that the lower crust here has notably high velocities (>7.3 km/s at depths of 20-35 km) and hinted at along-strike variations in velocity structure that related to the composition of surface volcanism. Receiver functions from a few stations also locally reveal intra-crustal conversions at 20-25 km that are consistent with a velocity step at the top of a mafic lower crust. However, Vp, alone, cannot uniquely differentiate between possible explanations for high-velocity lower crust. We present new constraints on lower crustal composition from average Vp/Vs based on sparse converted S-waves in wide-angle data. We find a low Vp/Vs of ~1.7-1.75 in the lower crust trenchward of the active arc (but within the arc platform). Using petrologic modeling, we show that no single composition is likely to explain the combination of high Vp and low Vp/Vs. Our preferred explanation is a combination of clinopyroxenite (~50-70%) and alpha-quartz bearing gabbros (~30-50%). This is consistent with Aleutian xenoliths and rocks in obducted arcs, and implies ~30-40% of the full Aleutian crust comprises ultramafic cumulates. An unexpected result is that small amounts of quartz can exert a strong influence on Vp/Vs in arc crust. At shallower levels, receiver function analysis also identifies a strong upper crustal conversion at ~10 km depth beneath Akutan, which we interpret as an upper crustal magma body. Variations in back azimuth and modeling indicate that it is best explained by a low velocity layer that extends below much of the island, and is more extensive than the eruptive edifice. These results are consistent with results from InSAR and lava geochemistry. To advance our understanding of magmatic processes in arcs, we require higher resolution imaging with diverse geophysical methods to constrain variations in the structure and composition and the distribution of magma chambers throughout the crust at the scale lengths of individual volcanoes. Additionally, closer integration of diverse seismic imaging studies (active-source refraction, receiver function, noise tomography) with each other and with petrological observations and models is essential for reducing ambiguity in interpreting composition from seismic attributes.

Shillington, D. J.; Van Avendonk, H. J.; Behn, M. D.; Janiszewski, H. A.; Abers, G. A.; Kelemen, P. B.; Jagoutz, O. E.

2013-12-01

272

78 FR 57097 - Fisheries of the Exclusive Economic Zone Off Alaska; Sharks in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...the Exclusive Economic Zone Off Alaska; Sharks in the Bering Sea and Aleutian Islands...SUMMARY: NMFS is prohibiting retention of sharks in the Bering Sea and Aleutian Islands...2013 total allowable catch (TAC) of sharks in the BSAI has been reached....

2013-09-17

273

76 FR 59924 - Fisheries of the Exclusive Economic Zone Off Alaska; Sharks in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...the Exclusive Economic Zone Off Alaska; Sharks in the Bering Sea and Aleutian Islands...SUMMARY: NMFS is prohibiting retention of sharks in the Bering Sea and Aleutian Islands...2011 total allowable catch (TAC) of sharks in the BSAI has been reached....

2011-09-28

274

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.

275

The Aleutian arc: tectonic blocks, episodic subduction, strain diffusion, and magma generation  

Microsoft Academic Search

A relocated earthquake sequence in the western Aleutian arc lasting from February 1965 through December 1968 is shown to map an episode of subduction of the Pacific plate. The February 4, 1965, Rat Island main shock (Ms=8.1) was a complex rupture involving greatest underthrusting at lock zones beneath the Aleutian arc transverse canyons. The primary tectonic consequences of the main

William Spence

1977-01-01

276

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, Jr. , C.; Power, J. A.; Dzurisin, D.

2000-01-01

277

The last 5000 years of activity at Sete Cidades volcano (São Miguel Island, Azores): Implications for hazard assessment  

NASA Astrophysics Data System (ADS)

Sete Cidades is a central volcano with a summit caldera at the western end of São Miguel Island, Azores. Its stratigraphy comprises two main geological groups: the Inferior Group, the units of which date from more than 200 000 years ago through to 36 000 years before present, consisting of thick lava flows and subaerial volcaniclastic deposits that built the base of the central volcano; and the Superior Group which comprises all the activity from the last 36 000 years, including pumice and scoria fallout and PDC deposits with minor lava flows. The volcanostratigraphy is divided into six main formations — Risco, Ajuda, Bretanha, Lombas, Santa Bárbara and Lagoas, each defined by different activity phases in the volcano's evolution. The present caldera developed in three phases associated with massive paroxysmal eruptions which occurred approximately 36 000, 29 000 and 16 000 years before present. Since the last caldera forming event, eruptive activity has been predominantly explosive and a variety of deposits have been produced by different eruptive styles, associated with three specific settings: (1) pumice fall deposits, pyroclastic density currents and hydromagmatic events from eruptions inside the caldera; (2) lava domes, cinder cones and basaltic lava flows from eruptions on the volcano flanks; (3) tuff ring and tuff deposits from surtseyan eruptions offshore. The more recent history of the volcano is marked by a change in the intracaldera activity from dominantly magmatic behaviour to a hydromagmatic character, which happened about 5000 years ago. Since then, at least 15 basaltic subaerial and submarine eruptions have occurred on the volcano flanks and 17 trachytic (s.l.) explosive eruptions have occurred within the caldera, the most recent of which took place about 700 years ago. This eruptive frequency makes Sete Cidades probably the most active volcanic centre in the Azores. In this paper we present the stratigraphy and a description of the deposits which originate from the last 5000 years, in order to delineate Sete Cidades' recent eruptive history for the purpose of estimating the hazard associated with this volcano. An event tree has been designed to systematize possible future eruptive scenarios and to aid the assessment of relative probabilities of occurrence of different potential eruptive styles. The probabilities for all nodes on the event tree, together with their associated uncertainties, were obtained by expert elicitation, providing results that accord with the geologic record. These probability estimates indicate that (1) basaltic strombolian and submarine eruptions are the most likely to occur, (2) trachytic activity from the central volcano magmatic system is more probable in the intracaldera environment than on the flanks, and (3) explosive activity is more likely than effusive for the trachytic system. Worst-case scenario and maximum expected events are identified according to the eruptive scenarios and their probabilities of occurrence.

Queiroz, G.; Pacheco, J. M.; Gaspar, J. L.; Aspinall, W. P.; Guest, J. E.; Ferreira, T.

2008-12-01

278

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

279

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

Microsoft Academic Search

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

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

2005-01-01

280

The 2003 eruption of Anatahan volcano, Commonwealth of the Northern Mariana Islands: Chronology, volcanology, and deformation  

USGS Publications Warehouse

The first historical eruption on Anatahan Island occurred on 10 May 2003 from the east crater of the volcano. The eruption was preceded by several hours of seismicity. Two and a half hours before the outbreak, the number of earthquakes surged to more than 100 events per hour. At 0730 UTC, the Washington Volcanic Ash Advisory Center issued an ash advisory. Although the eruption lasted for 3 months, the majority of erupted material was expelled during the first 2 weeks. The opening episode of the eruption resulted in a deposit of juvenile scoria and lithic clasts, the latter derived from geothermally altered colluvial fill from the vent area. The opening episode was followed by crater enlargement and deepening, which produced deposits of coarse, reddish-brown ash containing a mixture of juvenile and lithic clasts. The third episode of the eruption produced coarse ash and lapilli comprised of juvenile scoria and minor amounts of lithics. Plume heights were 4500 to 13,000 m for the initial three phases. The fourth episode, from about May 18 through early August, was characterized by smaller plume heights of 900 to 2400 m, and steam was the dominant component. Minor amounts of coarse ash and accretionary-lapilli ash comprise most of the deposits of the fourth episode, although ballistic blocks and bombs of andesite lava are also locally present. These andesite blocks were emplaced by an explosion on 14 June, which destroyed a small lava dome extruded during the first week of June. Activity waned as the summer progressed, and subsequent ash deposits accumulated in July and early August, by which time the eruption had effectively ended. In September and October, degassing and geothermal activity continued, characterized by small geysers, boiling water, and jetting steam. Noteworthy deviations from this activity were a surge event in late May-early June and the destruction of the lava dome on 14 June. We calculated on-land tephra-fall deposits to have a bulk volume of about 27.5 ?? 106 m3, covering an area of 40.6 km2. We determined the juvenile to lithic content of the deposits and corrected the bulk volume to a juvenile volume of 24.0 ?? 106 m3. We use a volume corrected density of 1.32 g/cm3 to convert the juvenile volume of 24.0 ?? 106 m3 to a magma volume of 13.2 ?? 106 m3. Using the methods of Fierstein and Nathenson (1992) [Fierstein, J., Nathenson, M., 1992. Another look at the calculation of fallout tephra volumes. Bull. Volcanology. 54, 156-167.], we computed the total eruption volume at 45.4 ?? 106 m3. Deformation surveys recorded large changes surrounding the east crater. The modeled volumetric change based on the surveys was 0.82 ?? 106 m3 of magma, which we estimate corresponds to a minimum intrusion of 10 ?? 106 m3 of magma which is in good agreement with our calculated on-land magma volume.

Trusdell, F. A.; Moore, R. B.; Sako, M.; White, R. A.; Koyanagi, S. K.; Chong, R.; Camacho, J. T.

2005-01-01

281

Hydrothermal mineralization at Kick'em Jenny submarine volcano in the Lesser Antilles island arc  

NASA Astrophysics Data System (ADS)

Kick 'em Jenny (KeJ) is an active submarine volcano located in the Lesser Antilles island arc, ~7.5 km northwest of Grenada. Of the twelve eruptions detected since 1939, most have been explosive as evidenced by eyewitness accounts in 1939, 1974, and 1988 and the dominance of explosive eruption products recovered by dredging. In 2003, vigorous hydrothermal activity was observed in the crater of KeJ. Video footage taken by a remotely operated vehicle (ROV) during the cruise RB-03-03 of the R/V Ronald Brown documented the venting of a vapor phase in the form of bubbles that ascended through the water column and a clear fluid phase in the form of shimmering water. The shimmering water generally ascended through the water column but can also been seen flowing down gradient from a fissure at the top of a fine-grained sediment mound. These fine-grained sediment mounds are the only structure associated with hydrothermal venting; spire or chimney structures were not observed. Hydrothermal venting was also observed coming from patches of coarse-grained volcaniclastic sediment on the crater floor and from talus slopes around the perimeter of the crater. Samples were collected from these areas and from areas void of hydrothermal activity. XRD and ICPMS analyses of bulk sediment were carried out to investigate the geochemical relationships between sediment types. Sediment samples from the hydrothermal mound structures are comprised of the same components (plagioclase, amphibole, pyroxene, and scoria) as sediment samples from areas void of hydrothermal activity (primary volcaniclastic sediment) in the 500-63 ?m size range. High resolution grain size analyses show that >78% of sediment in the hydrothermal mound samples are between 63-2 ?m with 6-20% clay sized (<2 ?m) whereas <40% of the primary volcaniclastic sediment is between 63-2 ?m with ~2% clay sized. The presence of clay minerals (smectite, illite, talc, and I/S mixed layer) in the hydrothermal mound samples was confirmed x-ray diffraction analysis. Differences in major oxide composition of the two sediment types (depletion in Al2O3 but enrichments in MgO and Fe2O3* in the mound sample relative to primary volcaniclastic sediment) suggest that mound sediment has experienced hydrothermal alteration/mineralization. Elevated concentrations of As, Sb and Cu in the mound sediment also indicate a strong hydrothermal contribution. The bulk composition of the mound sediment can be reasonably modeled as a mixture of ~78% primary volcaniclastic sediment, ~30% alteration clay minerals, and ~2% pyrite. The percentage of clay required in the model is ~10% greater than the fraction (~20%) observed in the hydrothermal mound sample but some of the alteration products may consist of larger grains that have not been analyzed individually.

Olsen, R.; Carey, S.; Sigurdsson, H.; Cornell, W. C.

2011-12-01

282

Imaging rapidly deforming ocean island volcanoes in the western Galápagos archipelago, Ecuador  

NASA Astrophysics Data System (ADS)

local body wave arrival-time tomography methods to determine 3-D seismic velocity structure, we imaged the plumbing system of Sierra Negra Volcano, Galápagos. This hot spot volcanic chain includes some of the fastest deforming volcanoes in the world, making this an ideal location to study shield volcano plumbing systems. We inverted P and S wave arrivals recorded on a 15-station temporary array between July 2009 and June 2011 using an a priori 1-D velocity model constrained by offshore refraction studies. With local seismicity from nearby volcanoes as well as the ring fault system, the model resolution is good between depths of 3 and 15.5 km. The propagation of S waves throughout this volume argues against any large high-melt accumulations, although a shallow melt sill may exist above 5 km. We image a broad low-velocity region (>25 km laterally) below Sierra Negra at depths ~8-15 km. No large, regional velocity increase is found within the limits of good resolution, suggesting that crust is thicker than 15 km beneath the western Galápagos archipelago. Our results are consistent with crustal accretion of mafic cumulates from a large-volume magma chamber that may span the boundary between preplume and accreted crust. The similarity between our results and those of Hawaii leave open the possibility that the crust has also been thickened by under-plating.

Tepp, Gabrielle; Ebinger, Cynthia J.; Ruiz, Mario; Belachew, Manahloh

2014-01-01

283

Use of precipitation and groundwater isotopes to interpret regional hydrology on a tropical volcanic island: Kilauea volcano area, Hawaii  

USGS Publications Warehouse

Isotope tracer methods were used to determine flow paths, recharge areas, and relative age for groundwater in the Kilauea volcano area of the Island of Hawaii. A network of up to 66 precipitation collectors was emplaced in the study area and sampled twice yearly for a 3-year period. Stable isotopes in rainfall show three distinct isotopic gradients with elevation, which are correlated with trade wind, rain shadow, and high- elevation climatological patterns. Temporal variations in precipitation isotopes are controlled more by the frequency of storms than by seasonal temperature fluctuations. Results from this study suggest that (1) sampling network design must take into account areal variations in rainfall patterns on islands and in continental coastal areas and (2) isotope/elevation gradients on other tropical islands may be predictable on the basis of similar climatology. Groundwater was sampled yearly in coastal springs, wells, and a few high-elevation springs. Areal contrasts in groundwater stable isotopes and tritium indicate that the volcanic rift zones compartmentalize the regional groundwater system, isolating the groundwater south of Kilauea's summit and rift zones. Part of the Southwest Rift gone appears to act as a conduit for water from higher elevation, but there is no evidence for downrift flow in the springs and shallow wells sampled in the lower East Rift Zone.

Scholl, M. A.; Ingebritsen, S. E.; Janik, C. J.; Kauahikaua, J. P.

1996-01-01

284

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

285

Variations in Seismic Anisotropy with time on Volcanoes in Kyushu Island, Southern Japan  

NASA Astrophysics Data System (ADS)

Using a newly developed automatic processing technique, we have calculated shear wave splitting on and near three active volcanoes in Kyushu, southern Japan (Aso, Unzen and Sakurajima). Shear wave splitting is considered to be caused by aligned cracks and microcracks. The polarisation of the first arriving phase, ?, gives a measure of the crack orientation, which is expected to align with the maximum principal stress. The delay time dt between the two phases depends upon the crack density and the path length. High quality measurements include the following: a) over 1700 from local events recorded and located near Aso Volcano between 2001 and 2008; b) over 2000 from local events recorded and located near Unzen volcano between 1988 and 1997 (spanning the most active period of seismic activity related to the large eruption in 1991); c) over 600 from regional events originating in the subducting Phillipine Sea plate recorded near Sakurajima volcano between 2003 and 2005, (during which time numerous small eruptions have occcurred, and GPS measurements have been modeled as caused by inflation of a Mogi source and a near-vertical crack). Most of the stations were located in boreholes or tunnels, providing excellent signals. Common features at all three volcanoes are that stations closest to the craters yield the fewest good measurements, and even those tend to give varying results at closely spaced stations. Scattering from the volcanic edifice may be making the S waves difficult to pick, and the local stresses may be varied. Stations on the volcanic flanks give many good measurements. Some stations yield variations in ? and dt that depend upon the earthquake location. But at each volcano, some stations show changes that are better explained by variations in time than in space. Where GPS measurements are available, the variations sometimes but not always correlate with previously-modeled inflation or deflation events. The temporal variations in ? are large, ranging from 30° at some stations to 90 ° at other stations. These results will allow us to test models of stress changes with time on the volcanoes.

Savage, M. K.; Ohkura, T.; Umakoshi, K.; Shimizu, H.; Kohno, Y.; Iguchi, M.; Wessel, A.; Mori, J.

2008-12-01

286

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

NASA Astrophysics Data System (ADS)

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 in the underlying oceanic crust. We carried out a multiscale analysis to understand (1) the origin of the seismicity in the geodynamic context and (2) the role of the oceanic lithosphere in the deformation of Piton de la Fournaise and La Réunion Island. Analysis of the magmatic system suggests that the magma ascent is controlled by large N25-30 and N125-130 fracture zones located below the Enclos depression. We also show that the orientation difference between the eruptive fissures and the related dykes result from a rotation of the main principal stress ?1 from vertical to downslope through the surface. Combining a Digital Elevation Model (DEM) analysis, field observations and the geophysical data reveals that the volcano is affected by large fault zones. The fault distribution indicates the predominance of a main N70-80 trend. Magnetic data show the same N80 orientation characterizing the remnant part of the Alizés volcano. Such parallel alignment suggests a control exerted by the underlying Alizés volcano on Piton de la Fournaise. Furthermore, the alignment between the crustal orientations and the structures determined on the island suggests a control of the crustal structures in La Réunion's volcano-tectonic activity. Contrary to several volcanic islands such as Hawaii and Tenerife, La Réunion volcanoes lie on an upbending crust. Then, we interpret the reactivation of the crustal faults as resulting from a crustal uplift related to the thermal erosion of the base of the lithosphere and/or to strong underplating. The upward deformation may prevent the spreading of the volcanoes, as no evidence of such a mechanism is observed in the bathymetry and the seismic data around the island.

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

2007-04-01

287

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

288

A Summary of the History and Achievements of the Alaska Volcano Observatory.  

NASA Astrophysics Data System (ADS)

Volcanoes of the Aleutian Islands, Kamchatka and the Kurile Islands present a serious threat to aviation on routes from North America to the Far East. On March 27, 1986, an eruption of Augustine Volcano deposited ash over Anchorage and disrupted air traffic in south-central Alaska. The consequences of the colocation of an active volcano and the largest city in Alaska were clearly evident. That event led to a three-way partnership between the US Geological Survey, the University of Alaska Geophysical Institute and the Alaska State Division of Geological and Geophysical Surveys that now maintains a continuous watch through ground instrumentation and satellite imagery providing data from which warnings of eruptions can be issued to airline operators and pilots. The eruption of Redoubt Volcano in December 1989 was AVO's first big test. It spewed volcanic ash to a height of 14,000 m (45,000 feet) and managed to catch KLM 867, a Boeing 747 aircraft in its plume under dark conditions while approaching Anchorage Airport. Further details of the early days of the Alaska Volcano Observatory will be described, along with its recent successes and challenges.

Smith, R. W.

2008-12-01

289

Potential geologic hazards of North Aleutian shelf, Bristol Bay, Alaska  

SciTech Connect

Federal OSC lease sale 92, North Aleutian shelf, Alaska, is scheduled for April 1985. The area, located in the southeastern Bering Sea, has 3 basins with sedimentary thicknesses in excess of 4 km. Six geologic conditions that could cause problems during petroleum development are: (1) seismicity, (2) recent faulting, (3) gas-charged sediment, (4) bed forms and active sediment transport, (5) scours, and (6) volcanism. Since 1953, the region has a history of at least 10 shallow earthquakes, including a 1971 back-arc event with a Richter magnitude of 5.2. The largest event impacting the entire region, a Richter magnitude 8.7 earthquake, occurred in 1938. Normal faults are located along the southern edge of the St. George basin, and on the northeastern edge of the Amak basin. Many exhibit increased offset with depth, surficial sags, and small surficial cracks. Surprising was the absence of any evidence of sea-floor sediment instability. Sonar bright spots, and possible, near-surface gas-charged sediment occur west of Amak Island and north of Unimak Island. An area of megaripples and dunes covers more than 1500 km/sup 2/. Bed forms have spacings of 20-50 m and heights of 1-3 m. Observations suggest that coarse sand may be actively transported. Thousands of scours, many linear and parallel, some greater than 800 m long, 250 m wide, and incised up to 5 m, were identified. Pavlof, an Alaskan Peninsula active volcano, located 45 km northeast of Cold Bay, has a continuous history of steam release and occasional eruption. Lahars, nuee ardentes are unknown. None of the geologic conditions identified precludes petroleum development or production. The potential impact of these factors must, however, be included in planning for future petroleum activities.

Molnia, B.F.; Schwab, W.C.

1985-02-01

290

Classification of Self-potential Anomalies on Volcanoes and Its Implication for the Hydraulic Structure Deduced From SP Surveys on 10 Island-arc Type Volcanoes in Japan  

Microsoft Academic Search

It is widely believed that the self potential (SP) anomalies on volcanoes provide information on the subsurface hydraulic and hydrothermal flow. Many studies report that the SP around active craters or fissures is relatively positive and is interpreted as a manifestation of an upward hydrothermal flow. However, there are no SP anomalies on some volcanoes in which the hydrothermal upwelling

K. Aizawa; M. Uyeshima; O. Kuwano

2006-01-01

291

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

292

Using tephrochronology to date temperate ice: correlation between ice tephras on Livingston Island and eruptive units on Deception Island volcano (South Shetland Islands, Antarctica)  

Microsoft Academic Search

Tephra layers are interstratified in the ice caps of the South Shetland Islands. Although previously poorly investigated, they are potential targets for the application of tephrochronology and, hence, may provide temporal constraints on glaciological models for the region. Several tephra layers crop out in the coastal ice-cliffs and ablation ramps of Livingston Island. Using stratigraphical position, granulometry and bulk sample

Raimon Pallàs; John L. Smellie; Josep M. Casas; Jaume Calvet

2001-01-01

293

IESID: Automatic system for monitoring ground deformation on the Deception Island volcano (Antarctica)  

NASA Astrophysics Data System (ADS)

When establishing the relative distance between two GNSS-GPS stations with sub-centimeter accuracy, it is necessary to have auxiliary data, some of which can only be collected some time after the moment of measurement. However, for monitoring highly-active geodynamic areas, such as volcanoes and landslides, data precision is not as essential as rapid availability, processing of data in real-time, and fast interpretation of the results. This paper describes the development of an integrated automatic system for monitoring volcanic deformation in quasi real-time, applied to the Deception volcano (Antarctica). This experimental system integrates two independent modules that enable researchers to monitor and control the status of the GNSS-GPS stations, and to determine a surface deformation parameter. It comprises three permanent stations, one of which serves as the reference for assessing the relative distance in relation to the other two. The availability of GNSS-GPS data in quasi real-time is achieved by means of a WiFi infrastructure and automated data processing. This system provides, in quasi real-time, a time series of varying distances that tells us the extent to which any ground deformation is taking place.

Peci, Luis Miguel; Berrocoso, Manuel; Páez, Raúl; Fernández-Ros, Alberto; de Gil, Amós

2012-11-01

294

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.

Ariza, Alejandro; Kaartvedt, Stein; R?stad, Anders; Garijo, Juan Carlos; Aristegui, Javier; Fraile-Nuez, Eugenio; Hernandez-Leon, Santiago

2014-01-01

295

Gaseous transport and deposition of gold in magmatic fluid: evidence from the active Kudryavy volcano, Kurile Islands  

NASA Astrophysics Data System (ADS)

The distribution of gold in high-temperature fumarole gases of the Kudryavy volcano (Kurile Islands) was measured for gas, gas condensate, natural fumarolic sublimates, and precipitates in silica tubes from vents with outlet temperatures ranging from 380 to 870°C. Gold abundance in condensates ranges from 0.3 to 2.4 ppb, which is significantly lower than the abundances of transition metals. Gold contents in zoned precipitates from silica tubes increase gradually with a decrease in temperature to a maximum of 8 ppm in the oxychloride zone at a temperature of approximately 300°C. Total Au content in moderate-temperature sulfide and oxychloride zones is mainly a result of Au inclusions in the abundant Fe-Cu and Zn sulfide minerals as determined by instrumental neutron activation analysis. Most Au occurs as a Cu-Au-Ag triple alloy. Single grains of native gold and binary Au-Ag alloys were also identified among sublimates, but aggregates and crystals of Cu-Au-Ag alloy were found in all fumarolic fields, both in silica tube precipitates and in natural fumarolic crusts. Although the Au triple alloy is homogeneous on the scale of microns and has a composition close to (Cu,Ni,Zn)3(Au,Ag)2, transmission electron microscopy (TEM) shows that these alloy solid solutions consist of monocrystal domains of Au-Ag, Au-Cu, and possibly Cu2O. Gold occurs in oxide assemblages due to the decomposition of its halogenide complexes under high-temperature conditions (650-870°C). In lower temperature zones (<650°C), Au behavior is related to sulfur compounds whose evolution is strongly controlled by redox state. Other minerals that formed from gas transport and precipitation at Kudryavy volcano include garnet, aegirine, diopside, magnetite, anhydrite, molybdenite, multivalent molybdenum oxides (molybdite, tugarinovite, and ilsemannite), powellite, scheelite, wolframite, Na-K chlorides, pyrrhotite, wurtzite, greenockite, pyrite, galena, cubanite, rare native metals (including Fe, Cr, Mo, Sn, Ag, and Al), Cu-Zn-Fe-In sulfides, In-bearing Pb-Bi sulfosalts, cannizzarite, rheniite, cadmoindite, and kudriavite. Although most of these minerals are fine-grained, they are strongly idiomorphic with textures such as gas channels and lamellar, banded, skeletal, and dendrite-like crystals, characteristic of precipitation from a gas phase. The identified textures and mineral assemblages at Kudryavy volcano can be used to interpret geochemical origins of both ancient and modern ore deposits, particularly gold-rich porphyry and related epithermal systems.

Yudovskaya, Marina A.; Distler, Vadim V.; Chaplygin, Ilya V.; Mokhov, Andrew V.; Trubkin, Nikolai V.; Gorbacheva, Sonya A.

2006-03-01

296

Magma storage and migration associated with the 2011-2012 El Hierro eruption: Implications for crustal magmatic systems at oceanic island volcanoes  

NASA Astrophysics Data System (ADS)

Starting in July 2011, anomalous seismicity was observed at El Hierro Island, a young oceanic island volcano. On 12 October 2011, the process led to the beginning of a submarine NW-SE fissural eruption at ~15 km from the initial earthquake loci, indicative of significant lateral magma migration. Here we conduct a multifrequency, multisensor interferometric analysis of spaceborne radar images acquired using three different satellite systems (RADARSAT-2, ENVISAT, and COSMO-SkyMed (Constellation of Small Satellites for Mediterranean Basin Observation)). The data fully captures both the pre-eruptive and coeruptive phases. Elastic modeling of the ground deformation is employed to constrain the dynamics associated with the magmatic activity. This study represents the first geodetically constrained active magmatic plumbing system model for any of the Canary Islands volcanoes, and one of the few examples of submarine volcanic activity to date. Geodetic results reveal two spatially distinct shallow (crustal) magma reservoirs, a deeper central source (9.5 ± 4.0 km), and a shallower magma reservoir at the flank of the southern rift (4.5 ± 2.0 km). The deeper source was recharged, explaining the relatively long basaltic eruption, contributing to the observed island-wide uplift processes, and validating proposed active magma underplating. The shallowest source may be an incipient reservoir that facilitates fractional crystallization as observed at other Canary Islands. Data from this eruption supports a relationship between the depth of the shallow crustal magmatic systems and the long-term magma supply rate and oceanic lithospheric age. Such a relationship implies that a factor controlling the existence/depth of shallow (crustal) magmatic systems in oceanic island volcanoes is the lithosphere thermomechanical behavior.

González, Pablo J.; Samsonov, Sergey V.; Pepe, Susi; Tiampo, Kristy F.; Tizzani, Pietro; Casu, Francesco; Fernández, José; Camacho, Antonio G.; Sansosti, Eugenio

2013-08-01

297

Aleutian Deep-Sea Channel on the Aleutian Abyssal Plain.  

National Technical Information Service (NTIS)

The Aleutian abyssal plain is a vast turbidite deposit south of the Aleutian trench. Another prominent channel trends south-westerly for more than 1,000 km across the abyssal plain. This feature consists of a series of deltaic structures extending along i...

F. P. Naugler

1970-01-01

298

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

299

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

300

Volcanogenic fluorine in rainwater around active degassing volcanoes: Mt. Etna and Stromboli Island, Italy.  

PubMed

Many studies have assessed the strong influence of volcanic activity on the surrounding environment. This is particularly true for strong gas emitters such as Mt. Etna and Stromboli volcanoes. Among volcanic gases, fluorine compounds are potentially very harmful. Fluorine cycling through rainwater in the above volcanic areas was studied analysing more than 400 monthly bulk samples. Data indicate that only approximately 1% of fluorine emission through the plume is deposited on the two volcanic areas by meteoric precipitations. Although measured bulk rainwater fluorine fluxes are comparable to and sometimes higher than in heavily polluted areas, their influence on the surrounding vegetation is limited. Only annual crops, in fact, show some damage that could be an effect of fluorine deposition, indicating that long-living endemic plant species or varieties have developed some kind of resistance. PMID:12493195

Bellomo, S; D'Alessandro, W; Longo, M

2003-01-01

301

Vapor deposition of trace elements from degassed basaltic lava, Piton de la Fournaise volcano, Reunion Island  

NASA Astrophysics Data System (ADS)

Silica-tube sublimates resulting from the cooling of high-temperature volcanic gases from degassed lava in lava tunnels have been sampled at Piton de la Fournaise volcano. Mineral phases deposited in the tube are mainly halides (Na, K and Cu chlorides, Si and K fluorides). The distribution of most of the chemical elements as a function of the temperature is mainly controlled by their volatility. Volatile elements such as Rb, Cs, Se, Pb and Tl are associated with low-temperature deposits, whereas refractory elements such as R.E.E., alkaline earth, Sc, Ta, Hf, Th and Zr are not detected. The mineral assemblages are characterized by the lack of sulfides, sulfates, native sulfur and oxides. In the same way, numerous transition and semi-metallic elements are lacking. This is interpreted as the result of the magma transport in surface lava tunnels, leading to extensive degassing upstream of the collection site.

Toutain, J. P.; Aloupogiannis, P.; Delorme, H.; Person, A.; Blanc, P.; Robaye, G.

1990-04-01

302

Long-term explosion records from two erupting submarine volcanoes in the Mariana and Tonga island-arcs  

Microsoft Academic Search

Records of explosive activity longer than a few weeks are rare for subaerial volcanoes, and nonexistent for submarine volcanoes. From February 2008 to February 2009, we recorded a year long, continuous acoustic and volcanic plume record from NW Rota-1, an erupting submarine volcano located within the Mariana Arc. From December 2008 to May 2009, we also obtained acoustic records of

R. P. Dziak; R. W. Embley; E. T. Baker; W. W. Chadwick; J. Resing; H. Matsumoto; S. L. Walker; D. R. Bohnenstiehl; H. Klink

2009-01-01

303

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

304

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

305

Tephra-Producing Eruptions of Holocene Age at Akutan Volcano, Alaska; Frequency, Magnitude, and Hazards  

NASA Astrophysics Data System (ADS)

Akutan Volcano in the eastern Aleutian Islands of Alaska is one of the most historically active volcanoes in the Aleutian arc (43 eruptions in about the past 250 years). Explosive eruptions pose major hazards to aircraft flying north Pacific air routes and to local infrastructure on Akutan and neighboring Unalaska Island. Air travel, infrastructure, and population in the region have steadily increased during the past several decades, and thus it is important to better understand the frequency, magnitude, and characteristics of tephra-producing eruptions. The most recent eruption was a VEI 2 event on March 8-May 21, 1992 that resulted in minor ash emissions and trace amounts of proximal fallout. Nearly continuous low-level emission of ash and steam is typical of historical eruptions, and most of the historical events have been similar in magnitude to the 1992 event. The most recent major eruption occurred about 1600 yr. B.P. and likely produced the ca. 2-km diameter summit caldera and inundated valleys that head on the volcano with pyroclastic-flow and lahar deposits that are tens of meters thick. The 1600 yr. B.P. eruption covered most of Akutan Island with up to 2.5 m of coarse scoriaceous tephra fall, including deposits 0.5-1 m thick near the City of Akutan. Tephra-fall deposits associated with this eruption exhibit a continuous sequence of black, fine to coarse scoriaceous lapilli overlain by a lithic-rich facies and finally a muddy aggregate-rich facies indicating water involvement during the latter stages of the eruption. Other tephra deposits of Holocene age on Akutan Island include more than a dozen discrete fine to coarse ash beds and 3-6 beds of scoriaceous, coarse lapilli tephra indicating that there have been several additional major eruptions (>VEI 3) of Akutan Volcano during the Holocene. Radiocarbon dates on these events are pending. In addition to tephra falls from Akutan, other fine ash deposits are found on the island that originated from other Aleutian arc volcanoes. Tephra deposits from typical VEI 2 historical eruptions are not well preserved on the island so tephra-fall frequency estimated from stratigraphic studies is underestimated. Akutan Island is home to the largest seafood processing plant in North America and has a workforce of more than one thousand people. Other infrastructure consists of a recently constructed paved airfield on neighboring Akun Island (25 km east of the active vent) and a new boat harbor at the head of Akutan Harbor. Plans to develop greenhouses, tourism, and increased cold storage capacity on Akutan and Akun Islands also are evolving. To support the power demands of the development efforts, The City of Akutan is considering the utilization of geothermal resources on the island that are located in Hot Springs Bay valley northwest of the city. All of the existing and planned infrastructure, water supply, and residential areas are about 12 km downwind (east) of the volcano and are at risk from ash-producing eruptions. The historical eruptive history suggests that VEI 2 eruptions are plausible in the near future and the Holocene tephra-fall record indicates that large eruptions (VEI 4 or larger) occur about every few thousand years. Numerical modeling of tephra fallout based on the record of ash-producing eruptions will be used to improve tephra-fall hazard assessments for the area.

Waythomas, C. F.; Wallace, K. L.; Schwaiger, H.

2012-12-01

306

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

307

Paleozoic subduction complex and Paleozoic-Mesozoic island-arc volcano-plutonic assemblages in the northern Sierra terrane  

USGS Publications Warehouse

This field trip provides an overview of the stratigraphic and structural evolution of the northern Sierra terrane, which forms a significant part of the wall rocks on the western side of the later Mesozoic Sierra Nevada batholith in California. The terrane consists of a pre-Late Devonian subduction complex (Shoo Fly Complex) overlain by submarine arc-related deposits that record the evolution of three separate island-arc systems in the Late Sevonian-Early Mississippian, Permian, and Late Triassic-Jurassic. The two Paleozoic are packages and the underlying Shoo Fly Complex have an important bearing on plate-tectonic processes affecting the convergent margin outboard of the Paleozoic Cordilleran miogeocline, although their original paleogeographic relations to North America are controversial. The third arc package represents an overlap assemblage that ties the terrane to North America by the Late Triassic and helps constrain the nature and timing of Mesozoic orogenesis. Several of the field-trip stops examine the record of pre-Late Devonian subduction contained in the Shoo Fly Complex, as well as the paleovolcanology of the overlying Devonian to Jurassic arc rocks. Excellent glaciated exposures provide the opportunity to study a cross section through a tilted Devonian volcano-plutonic association. Additional stops focus on plutonic rocks emplaced during the Middle Jurassic arc magmatism in the terrane, and during the main pulse of Cretaceous magmatism in the Sierra Nevada batholith to the east.

Hanson, Richard E.; Girty, Gary H.; Harwood, David S.; Schweickert, Richard A.

2000-01-01

308

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

309

The 1976 1982 Strombolian and phreatomagmatic eruptions of White Island, New Zealand: eruptive and depositional mechanisms at a `wet' volcano  

NASA Astrophysics Data System (ADS)

White Island is an active andesitic-dacitic composite volcano surrounded by sea, yet isolated from sea water by chemically sealed zones that confine a long-lived acidic hydrothermal system, within a thick sequence of fine-grained volcaniclastic sediment and ash. The rise of at least 106 m3 of basic andesite magma to shallow levels and its interaction with the hydrothermal system resulted in the longest historical eruption sequence at White Island in 1976 1982. About 107 m3 of mixed lithic and juvenile ejecta was erupted, accompanied by collapse to form two coalescing maar-like craters. Vent position within the craters changed 5 times during the eruption, but the vents were repeatedly re-established along a line linking pre-1976 vents. The eruption sequence consisted of seven alternating phases of phreatomagmatic and Strombolian volcanism. Strombolian eruptions were preceded and followed by mildly explosive degassing and production of incandescent, blocky juvenile ash from the margins of the magma body. Phreatomagmatic phases contained two styles of activity: (a) near-continuous emission of gas and ash and (b) discrete explosions followed by prolonged quiescence. The near-continuous activity reculted from streaming of magmatic volatiles and phreatic steam through open conduits, frittering juvennile shards from the margins of the magma and eroding loose lithic particles from the unconsolidated wall rock. The larger discrete explosions produced ballistic block aprons, downwind lobes of fall tephra, and cohesive ‘wet’ surge deposits confined to the main crater. The key features of the larger explosions were their shallow focus, random occurrence and lack of precursors, and the thermal heterogeneity of the ejecta. This White Island eruption was unusual because of the low discharge rate of magma over an extended time period and because of the influence of a unique physical and hydrological setting. The low rate of magma rise led to very effective separation of magmatic volatiles and high fluxes of magmatic gas even during phreatic phases of the eruption. While true Strombolian phases did occur, more frequently the decoupled magmatic gas rose to interact with the conduit walls and hydrothermal system, producing phreatomagmatic eruptions. The form of these ‘wet’ explosions was governed by a delicate balance between erosion and collapse of the weak conduit walls. If the walls were relatively stable, fine ash was slowly eroded and erupted in weak, near-continous phreatomagmatic events. When the walls were unstable, wall collapse triggered larger discrete phreatomagmatic explosions.

Houghton, B. F.; Nairn, I. A.

1991-12-01

310

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

311

Comprehensive Study of the Seismotectonics of the Aleutian Arc. Annual Progress Report, March 1, 1976--February 28, 1977.  

National Technical Information Service (NTIS)

Seismological, volcanological, and geodetic research supported by ERDA has contributed to knowledge of the seismotectonics of the Aleutian Island arc. Some of the results of research supported wholly or in part by ERDA have been presented in three papers:...

J. N. Davies L. House K. H. Jacob K. Nakamura O. Perez

1977-01-01

312

Erupting Volcano Mount Etna  

NASA Technical Reports Server (NTRS)

An Expedition Two crewmember aboard the International Space Station (ISS) captured this overhead look at the smoke and ash regurgitated from the erupting volcano Mt. Etna on the island of Sicily, Italy. At an elevation of 10,990 feet (3,350 m), the summit of the Mt. Etna volcano, one of the most active and most studied volcanoes in the world, has been active for a half-million years and has erupted hundreds of times in recorded history.

2001-01-01

313

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

314

Source of the great tsunami of 1 April 1946: a landslide in the upper Aleutian forearc  

Microsoft Academic Search

The Unimak (eastern Aleutians) earthquake of April 1, 1946 is an enigma. The earthquake (MS=7.1) produced a disproportionately large tsunami (Mt=9.3) which killed 167 people. The tsunami was highly directional, and projected its largest waves along a beam perpendicular to the Aleutian arc. Those waves passed just east of the Hawaiian Islands, ran the length of the Pacific, and were

Gerard J Fryer; Philip Watts; Lincoln F Pratson

2004-01-01

315

Mechanisms driving polymagmatic activity at a monogenetic volcano, Udo, Jeju Island, South Korea  

NASA Astrophysics Data System (ADS)

High-resolution, stratigraphically ordered samples of the Udo tuff cone and lava shield offshore of Jeju Island, South Korea, show complex geochemical variation in the basaltic magmas that fed the eruption sequence. The eruption began explosively, producing phreatomagmatic deposits with relatively evolved alkali magma. The magma became more primitive over the course of the eruption, but the last magma to be explosively erupted had shifted back to a relatively evolved composition. A separate sub-alkali magma batch was subsequently effusively erupted to form a lava shield. Absence of weathering and only minor reworking between the tuff and overlying lava implies that there was no significant time break between the eruptions of the two magma batches. Modelling of the alkali magma suggests that it was generated from a parent melt in garnet peridotite at c. 3 to 3.5 GPa and underwent mainly clinopyroxene + olivine ± spinel fractionation at c. 1.5 to 2 GPa. The sub-alkali magma was, by contrast, generated from a chemically different peridotite with residual garnet at c. 2.5 GPa and evolved through olivine fractionation at a shallower level compared to its alkali contemporary. The continuous chemostratigraphic trend in the tuff cone, from relatively evolved to primitive and back to evolved, is interpreted to have resulted from a magma batch having risen through a single dyke and erupted the batch’s head, core and margins, respectively. The alkali magma acted as a path-opener for the sub-alkali magma. The occurrence of the two distinct batches suggests that different magmatic systems in the Jeju Island Volcanic Field have interacted throughout its history. The polymagmatic nature of this monogenetic eruption has important implications for hazard forecasting and for our understanding of basaltic field volcanism.

Brenna, Marco; Cronin, Shane J.; Smith, Ian E. M.; Sohn, Young Kwan; Németh, Karoly

2010-12-01

316

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

317

The 2007 eruptions and caldera collapse of the Piton de la Fournaise volcano (La Réunion Island) from tilt analysis at a single very broadband seismic station  

NASA Astrophysics Data System (ADS)

records from La Réunion Island very broadband Geoscope station are investigated to constrain the link between the 2007 eruptive sequence and the related caldera collapse of the Piton de la Fournaise volcano. Tilt estimated from seismic records reveals that the three 2007 eruptions belong to a single inflation-deflation cycle. Tilt trend indicates that the small-volume summit eruption of 18 February occurred during a phase of continuous inflation that started in January 2007. Inflation decelerated 24 days before a second short-lived, small-volume eruption on 30 March, almost simultaneous with a sudden, large-scale deflation of the volcano. Deflation rate, which had stabilized at relatively low level, increased anew on 1 April while no magma was erupted, followed on 2 April by a major distal eruption and on 5 April by a summit caldera collapse. Long-term tilt variation suggests that the 2007 eruptive succession was triggered by a deep magma input.

Fontaine, Fabrice R.; Roult, Geneviève; Michon, Laurent; Barruol, Guilhem; Muro, Andrea Di

2014-04-01

318

The 16 ka eruption of Sete Cidades volcano, São Miguel Island (Azores, Portugal): Hazard assessment from mapping and simulation of tephra fall  

NASA Astrophysics Data System (ADS)

São Miguel, the biggest island of the Azores archipelago, accommodates three presently quiescent central volcanoes (Sete Cidades, Fogo, Furnas), connected by basaltic fissure systems. Sete Cidades volcano, located in the western part of the island, is nearly 900 m asl high, has a basal diameter of approx. 15 km (at sea level), and hosts a summit caldera of 5 km across. We studied the last caldera-forming event (CFE) of Sete Cidades (ca 16 ka BP) in detail, including morpho-tectonic analysis, deposit mapping, establishment of the stratigraphy, and grain-size distribution (GSD). Due to the restricted size of the volcanic edifice, abundant post-16 ka deposits, and a generally humid climate (fast weathering and dense vegetation), outcrops related to the last CFE are fairly sparse. The presence of magmatic mafic enclaves in juvenile pumice clasts is a characteristic feature of this eruption and unique to São Miguel. The 16 ka eruption started with a phreatic/phreatomagmatic phase producing several units of layered fall deposits. The eruption then shifted to a mostly magmatic regime, generating quasi-steady but variably energetic pyroclastic density currents (PDC) that deposited massive, unwelded ash-lapilli tuffs on all flanks of the volcano. The eruption culminated in a (sub)plinian phase and produced a well-sorted tephra fall layer that shows a slight fining upward and attains up to 4 m of thickness. Thin, discordant, ash-rich layers with rounded pumice clasts in the top of this unit indicate the simultaneous occurrence of small-scale PDC. As the fall layer is only found in a narrow sector on the N and NE flanks of the volcano, a reliable analysis of eruptive conditions (volume, VEI, magnitude, column height etc.) based on changes in GSD or isopachs is impossible. Field work furthermore identified the existence of a well sorted fall deposit (up to 50 cm thick) related to the 16 ka eruption of Sete Cidades volcano on the N-coast of Fogo volcano, at a distance of approx. 25 km. Here, we present how important eruptive parameters may be constrained by numerical simulations, trying to fit the distribution and thickness of the 16 ka (sub)plinian fall deposit. Usually, volume, vent location, column height, meteorological conditions etc. are input parameters for tephra fall models. As none of these parameters are known, we assumed a wind pattern as of today and estimated the eruptive conditions in order to achieve the best fit of the found deposit distribution. We consider that this approach can be used to better constrain the eruptive conditions in cases where these parameters can not be obtained from the geologic record. The results show that Sete Cidades volcano possibly imposes a big threat to São Miguel Island as proximal and distal deposits are likely to affect the entire island. We believe that this approach is a simplified but promising way to assess the possible hazard of explosive volcanoes, even if the deposit distribution is limited, either primarily or due to erosion.

Kueppers, U.; Pimentel, A.; Pacheco, J.

2009-04-01

319

Phreatomagmatism driven by magma withdrawal at ';open system' volcanoes: contrasting cases of Kilauea and White Island (Invited)  

NASA Astrophysics Data System (ADS)

Transitions to phreatomagmatic explosions at persistent open-system volcanoes require special conditions. One trigger can be conduit wall failure possibly accompanying magma withdrawal, promoting bulk interaction between already fragmented wall rock, magmatic volatiles and/or magma. In all cases a prerequisite is the existence of significant subsurface void spaces, on length scales of hundreds of meters, in the upper portions of the conduit. These void spaces are often abandoned conduit segments from previous eruption cycles, loosely blocked near the surface with fragmental debris. We describe here three case studies where: 1) Collapse to depths of c. 200 m did not trigger mixing with magma but temporarily blocked a major flux of magmatic volatiles, causing a impulse transient vent-clearing explosion (Halemaumau crater, Kilauea 19 March 2008), 2) Collapse following Strombolian explosions creating a 330 m by 100 m crater accompanied by significant explosive interaction between failed blocks of unconsolidated wall rock hosting a high temperature geothermal system and the retreating basic andesite magma (White Island February 1978), 3) The subsidence and disappearance of a Kilauea lava lake was followed by wall collapse and deepening of the crater to below the water table, leading to an 17-day interval characterized by approximately 80 short-lived discrete explosions (Halemaumau, May 1924). These events demonstrate the complex influence of external factors such as strength of the wall rocks and hydrology on the form of the explosions and also a clear but often over-looked role for mechanically decoupled magmatic volatiles in otherwise phreatic/phreatomagmatic eruptions.

Houghton, B. F.; Swanson, D. A.; White, J. D.

2013-12-01

320

Deformation studies at Furnas and Sete Cidades Volcanoes (São Miguel Island, Azores). Velocities and further investigations  

NASA Astrophysics Data System (ADS)

The Azores archipelago is located near the triple junction between the Nubian (NU), North America (NA), and Eurasia (EU) plates. It is characterized by a relatively strong seismicity and active volcanism. The best estimate of the current plate velocities in the area over geologic timescales comes from the NUVEL1-NNR model (DeMets et al.) . At the geodetic timescale, plate motion models (Altamimi et al., Sella et al.) including GPS, DORIS, SLR and VLBI data currently do not yet include data from the Azores. In the framework of a research project focused on the seismotectonics and volcanotectonics of São Miguel island, we have analysed GPS data collected there in 1993, 1994, 1997, 2000 and 2002. Our analysis determines both the velocity in the REVEL (Sella et al.) reference frame of São Miguel and its internal deformation. The comparison of the 2000 and 2002 coordinates indicates that São Miguel accommodates moderate WNW-ESE extension at a rate slower than 5 mm yr-1.

Trota, A.; Houlié, N.; Briole, P.; Gaspar, J. L.; Sigmundsson, F.; Feigl, K. L.

2006-08-01

321

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

322

The 3-D density structure of Stromboli volcano (Aeolian Islands, Italy) inferred by inversion of marine and land-based gravity data  

NASA Astrophysics Data System (ADS)

The first density model of Stromboli volcano was obtained by inverting land-based (543) and marine (327) gravity data. Modern positioning technology, a 1 × 1 m digital elevation model, and a 15 × 15 m bathymetric model made it possible to obtain a detailed 3-D density model through an iteratively reweighted smoothness-constrained least-squares inversion. At 125 m depth from the land surface, the mean density of the island is 2380 kg m-3, with corresponding 2.5 and 97.5 percentiles of 2200 and 2530 kg m-3 respectively. High-density anomalies found in the middle and southern parts of the island gravity model are well correlated with the two main degassing faults crossing the island (N41 and N64) that we interpret as preferential regions of dyke intrusions. Two low-density anomalies found to the NE and in the summit part of the island seem to be geographically related with paroxysmal explosive phreato-magmatic events that have played important roles in the evolution of Stromboli island, namely the Scari caldera and the NeoStromboli crater.

Linde, N.; Baron, L.; Ricci, T.; Finizola, A.; Revil, A.; Muccini, F.; Cocchi, L.; Carmisciano, C.

2013-12-01

323

Intra- and extra-caldera volcaniclastic facies and geomorphic characteristics of a frequently active mafic island-arc volcano, Ambrym Island, Vanuatu  

NASA Astrophysics Data System (ADS)

Ambrym is one of the most voluminous active volcanoes in the Melanesian arc. It consists of a 35 by 50 km island elongated east-west, parallel with an active fissure zone. The central part of Ambrym, about 800 m above sea level, contains a 12 kilometre-wide caldera, with two active intra-caldera cone-complexes, Marum and Benbow. These frequently erupting complexes provide large volumes of tephra (lapilli and ash) to fill the surrounding caldera and create an exceptionally large devegetated plateau "ash plain", as well as sediment-choked fluvial systems leading outward from the summit caldera. Deposits from fall, subordinate base surge and small-volume pyroclastic (scoria) flows dominate the volcaniclastic sequences in near vent regions. Frequent and high-intensity rainfall results in rapid erosion of freshly deposited tephra, forming small-scale debris flow- and modified grain flow-dominated deposits. Box-shaped channel systems are initially deep and narrow on the upper flanks of the composite cones and are filled bank-to-bank with lapilli-dominated debris flow deposits. These units spill out into larger channel systems forming debris aprons of thousands of overlapping and anastomosing long, narrow lobes of poorly sorted lapilli-dominated deposits. These deposits are typically remobilised by hyperconcentrated flows, debris-rich stream flows and rare debris flows that pass down increasingly shallower and broader box-shaped valleys. Lenses and lags of fines and primary fall deposits occur interbedded between the dominantly tabular hyperconcentrated flow deposits of these reaches. Aeolian sedimentation forms elongated sand dunes flanking the western rim of the ash-plain. Outside the caldera, initially steep-sided immature box-canyons are formed again, conveying dominantly hyperconcentrated flow deposits. These gradually pass into broad channels on lesser gradients in coastal areas and terminate at the coast in the form of prograding fans of ash-dominated deposits. The extra-caldera deposits are typically better sorted and contain other bedding features characteristic of more dilute fluvial flows and transitional hyperconcentrated flows. These outer flank volcaniclastics fill valleys to modify restricted portions of the dominantly constructional landscape (lava flows, and satellite cones) of Ambrym. Apparent maturity of the volcanic system has resulted in the subsidence of the present summit caldera at a similar rate to its infill by volcaniclastic deposits.

Németh, Károly; Cronin, Shane J.; Stewart, Robert B.; Charley, Douglas

2009-10-01

324

The tectonically controlled emplacement of a vertically sheeted gabbro-pyroxenite intrusion: Feeder-zone of an ocean-island volcano (Fuerteventura, Canary Islands)  

NASA Astrophysics Data System (ADS)

The Miocene PX1 gabbro-pyroxenite pluton, Fuerteventura, Canary Islands, is a 3.5 × 5.5 km shallow-level intrusion (0.15-0.2 GPa and 1100-1120 °C), interpreted as the feeder-zone to an ocean-island volcano. It displays a vertical magmatic banding expressed in five 50 to 100 metre-wide NNE-SSW trending alkaline gabbro sequences alternating with pyroxenites. This emplacement geometry was controlled by brittle to ductile shear zones, generated by a regional E-W extensional tectonic setting that affected Fuerteventura during the Miocene. At a smaller scale, the PX1 gabbro and pyroxenite bands consist of metre-thick differentiation units, which suggest emplacement by periodic injection of magma pulses as vertical dykes that amalgamated, similarly to a sub-volcanic sheeted dyke complex. Individual dykes underwent internal differentiation following a solidification front parallel to the dyke edges. This solidification front may have been favoured by a significant lateral/horizontal thermal gradient, expressed by the vertical banding in the gabbros, the fractionation asymmetry within individual dykes and the migmatisation of the wall rocks. Pyroxenitic layers result from the fractionation and accumulation of clinopyroxene ± olivine ± plagioclase crystals from a mildly alkaline basaltic liquid. They are interpreted as truncated differentiation sequences, from which residual melts were extracted at various stages of their chemical evolution by subsequent dyke intrusions, either next to or within the crystallising unit. Compaction and squeezing of the crystal mush is ascribed to the incoming and inflating magma pulses. The expelled interstitial liquid was likely collected and erupted along with the magma flowing through the newly injected dykes. Clinopyroxene mineral orientation - as evidenced by EBSD and micro X-ray tomography investigations - displays a marked pure-shear component, supporting the interpretation of the role of compaction in the generation of the pyroxenites. Conversely, gabbro sequences underwent minor melt extraction and are believed to represent crystallised coalesced magma batches emplaced at lower rates at the end of eruptive cycles. Clinopyroxene orientations in gabbros record a simple shear component suggesting syn-magmatic deformation parallel to observed NNE-SSW trending shear zones induced by the regional tensional stress field. This emplacement model implies a crystallisation time of 1 to 5 years for individual dykes, consistent with PX1 emplacement over less than 0.5 My. A minimum amount of approximately 150 km 3 of magma is needed to generate the pluton, part of it having been erupted through the Central Volcanic Centre of Fuerteventura. If the regional extensional tectonic regime controls the PX1 feeder-zone initiation and overall geometry, rates and volumes of magma depend on other, source-related factors. High injection rates are likely to induce intrusion growth rates larger than could be accommodated by the regional extension. In this case, dyke intrusion by propagation of a weak tip, combined with the inability of magma to circulate through previously emplaced and crystallised dykes could result in an increase of non-lithostatic pressure on previously emplaced mushy dyke walls; thus generating strong pure-shear compaction within the pluton feeder-zone and interstitial melt expulsion. These compaction-dominated processes are recorded by the cumulitic pyroxenite bands.

Allibon, J.; Bussy, F.; Lewin, É.; Darbellay, B.

2011-03-01

325

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

326

Compositions of melts coexisting with plagioclase, augite, and olivine,or low-calcium pyroxene, at anhydrous and hydrous conditions and pressures from 1 atm. to 8 kbar: application to the petrogenesis of Aleutian and Mariana Island arc rocks and Columbia River basalts  

SciTech Connect

Anhydrous and hydrous, 2% water in the melt, experiments have been performed on a suite of high-alumina basalts and andesites from the Aleutian and Mariana island arcs. Compositions of experimentally produced melts coexisting with plagioclase (plag), augite (aug), and olivine (ol), or low-calcium pyroxene (lpx) have been used to construct liquid lines of multiple saturation (LLMS's) on pseudoternary diagrams. Anhydrous LLMS's at 1 atm. and 8 kbar and hydrous LLMS's at 2 and 5 kbar were determined. At 1 atm. and under hydrous conditions orthopyroxene (opx) is the stable lpx; at 8 kbar pigeonite (pig) is the stable lpx. Comparison of the plotted positions of the LLMS's and the compositions of rocks from the Aleutians suggest that basaltic andesites and andesites were produced by crystal fractionation of plag+aug+ol or plag+aug+opx from basaltic magmas with less than 2% water content at pressure between 2 and 5 kbar. Comparison of the LLMS's with the compositions of Columbia River Basalts indicates that crystal fractionation of plag+aug+ol (or lpx) in magma chambers at Moho depths cannot alone account for the observed compositional trend; instead the trend is probably due to some combination of polybaric fractionation, contamination, and possibly mixing of magmas between deep and shallow magma chambers.

Baker, D.R.; Eggler, D.H.

1985-01-01

327

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.

328

Teleseismic detection in the Aleutian Island arc  

Microsoft Academic Search

Recently it has become apparent that teleseismic detection has decreased substantially in many regions of the world. The major decrease was related to the closure of the VELA arrays in the United States during the later 1960's. This detection decrease has been recognized in South and Central America, Mexico, the Kuriles, the Caribbean, Tonga, and the New Hebrides. In this

R. E. Habermann

1983-01-01

329

Comprehensive Study of the Seismotectonics of the Eastern Aleutian Arc and Associated Volcanic Systems. Annual Progress Report, March 1, 1980-February 28, 1981.  

National Technical Information Service (NTIS)

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 structur...

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

1981-01-01

330

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

331

Buldir Depression - A Late Tertiary graben on the Aleutian Ridge, Alaska  

USGS Publications Warehouse

Buldir Depression is a large, rectilinear basin that lies on the northern edge of the Aleutian Ridge and is aligned with the arcuate chain of active volcanoes on the ridge crest. The depression appears to be a volcanic-tectonic feature, which began to form in Late Tertiary time and which is still forming. It is a graben formed by extensional rifting and accompanied by contemporaneous volcanism on the Aleutian Ridge. Subsidence rates for the depression are estimated at 20-70 cm/1,000 years. Sediments in the depression are 300 m thick and are probably pelagic and turbidite deposits of Pleistocene age. The turbidites were apparently derived from the plateau area of the Aleutian Ridge surrounding the depression. Older sediments on the northern slope of the Aleutian Ridge have a maximum thickness of 550 m and are deformed and slumped toward the Bering Sea. These sediments are postulated to overlie a mid-flank terrace on the northern Aleutian Ridge that titled to the north during the formation of Buldir Depression. ?? 1970.

Marlow, M. S.; Scholl, D. W.; Buffington, E. C.; Boyce, R. E.; Alpha, T. R.; Smith, P. J.; Shipek, C. J.

1970-01-01

332

The 1957 great Aleutian earthquake  

Microsoft Academic Search

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

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

1994-01-01

333

Amplitude Comparison of Teleseismic P-Wave Phases from the Japan Subduction Zone and the South Sandwich Islands recorded at Uturuncu Volcano, Bolivia  

NASA Astrophysics Data System (ADS)

Uturuncu volcano (22° 15' S, 67° 12'W) has been shown to be inflating at a rate of 1-1.5 cm per year by a satellite geodetic survey from May 1996-present. This inflation is centered just southwest of the volcano's summit and at a depth of 15-17 km. This may be caused by the injection of magma into the system. Seismic studies performed as part of the multi-university PLUTONS project can help constrain the location and nature of this inflation. By looking at how teleseismic peak-to-peak waveform amplitudes (velocities in nm/s) vary across the network, we can begin to pinpoint the size and location of attenuating zones beneath the edifice. Analysis of 5 P-wave phases from 4 earthquakes with origins in the Japan subduction zone (NW of the network, ~155° distant) shows a consistent 'shadow zone' of decreased amplitudes in a 13.6 by 33.3 km zone to the SE of the summit. Observations from two teleseismic events originating in the South Sandwich Islands (~45° distant) show similar effects although the geometry differs with respect to individual stations. We expect this trend to hold true for events originating to the NE and SW of the volcano, which would indicate a zone of decreased amplitude in the same region SE of the summit. The attenuation of P-waves that would otherwise be of uniform amplitude could be the result of some ray paths traveling through a shallow, low-velocity and highly attenuating zone of either magma/mush, highly fractured rock, or some other cause. This attenuating zone may be located at or near the center of the inflation zone, and physical processes associated with it could well be closely related to the observed inflation.

Farrell, A. K.; McNutt, S. R.; West, M. E.

2012-12-01

334

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

USGS Publications Warehouse

Within the Commonwealth of the Northern Mariana Islands (CNMI), Anatahan is one of nine active subaerial volcanoes that pose hazards to major air-traffic routes from airborne volcanic ash. The 2003-2004 eruptive activity of Anatahan volcano affected the region's aviation operations for 3 days in May 2003. On the first day of the eruption (10 May 2003), two international flights from Saipan to Japan were cancelled, and several flights implemented ash-avoidance procedures. On 13 May 2003, a high-altitude flight through volcanic gas was reported, with no perceptible damage to the aircraft. TOMS and MODIS analysis of satellite data strongly suggests that no significant ash and only minor amounts of SO2 were involved in the incident, consistent with crew observations. On 23 May 2003, airport operations were disrupted when tropical-cyclone winds dispersed ash to the south, dusting Saipan with light ashfall and causing flight cancellations there and at Guam 320 km south of the volcano. Operational (near-real-time) monitoring of ash clouds produced by Anatahan has been conducted since the first day of the eruption on 10 May 2003 by the Washington Volcanic Ash Advisory Center (VAAC). The VAAC was among the first groups outside of the immediate area of the volcano to detect and report on the unexpected eruption of Anatahan. After being contacted about an unusual cloud by National Weather Service forecasters in Guam at 1235 UTC on 10 May 2003, the VAAC analyzed GOES 9 images, confirming Anatahan as the likely source of an ash cloud and estimating that the eruption began at about 0730 UTC. The VAAC issued its first Volcanic Ash Advisory for Anatahan at 1300 UTC on 10 May 2003 more than 5 h after the start of the eruption, the delay reflecting the difficulty of detecting and confirming a surprise eruption at a remote volcano with no in situ real-time geophysical monitoring. The initial eruption plume reached 10.7-13.4 km (35,000-44,000 ft), well into jet cruise altitudes; thereafter, the maximum plume height decreased and during the rest of the eruption usually did not exceed ???5 km (???17,000 ft), which lessened the potential hazard to aircraft at higher cruise altitudes. Drifting ash clouds commonly extended hundreds of kilometers from the volcano, occasionally as far west as the Philippines. Over the course of the eruptive activity in 2003-2004, the VAAC issued 323 advisories (168 with graphical depictions of ash clouds) for Anatahan, serving as a reliable source of ash-cloud information for aviation-related meteorological offices and air carriers. With a record of frequent eruptions in the CNMI, continued satellite and in situ real-time geophysical monitoring is needed at Anatahan and other Marianas volcanoes so that potential hazards to aviation from any future eruptive activity can be quickly and correctly assessed. ?? 2005 Elsevier B.V. All rights reserved.

Guffanti, M.; Ewert, J. W.; Gallina, G. M.; Bluth, G. J. S.; Swanson, G. L.

2005-01-01

335

Distribution and volcano-structural control of zeolites and other amygdale minerals in the island of Martinique, F.W.I.  

NASA Astrophysics Data System (ADS)

Zeolites and other amygdale minerals have a widespread occurrence in Martinique. The central and east part of the island is composed of pre-Pliocene submarine formations (hyaloclastitic tuffs, pillow lavas, swarms of dikes, and domes). Here, zeolites occur in about 10 well-defined areas where specific associations constitute discrete zones of progressive metamorphism. Four zones are established which are believed to reflect temperatures ranging from 100 to 200°C. Within the outer zone I, several of the following minerals occur together: heulandite or clinoptilolite, mordenite, chabazite, mesolite; analcime and thomsonite characterize a narrow zone II; stilbite is widespread in zone III, and laumontite characterizes inner zone IV. The Lamentin thermal area is mainly com posed of Recent monogenetic volcanoes (age < 0.7 m.y.) and alluvium overlying pre-Pliocene volcanic rocks. Hot springs (39-51°C) occur in the central part of the area, but the less restricted occurrence of zeolites, calcite and silica, and scattered crystallization of barite, tourmaline, arsenopyrite and bowlingite, emphasize the larger development of recent hydrothermal activity in the area. The distribution of zeolites and other amygdale minerals is not related to regional metamorphism brought about by burial, but rather to areas of well-defined heat flow where suitable fluids were available. Roots of deeply eroded volcanoes, shallow magmatic intrusions, and zones of intensive faulting could have provided the necessary heat required; such structures are referred to in this communications as "heat flow domes".

Westercamp, D.

1981-12-01

336

A simple approach to constrain the position and the geometry of seismogenic structures: Application to the Karthala volcano (Grande Comores Island, Mozambique Channel)  

NASA Astrophysics Data System (ADS)

A simple and quick approach is presented to constrain the position and the geometry of seismogenic structures using hypocentre locations and their associated uncertainties. It assumes that, for a given hypocentre, all other seismic events which are located inside its uncertainty ellipsoid are localised on the same structure. These can then be considered as independent measurements of the same variable which implies, from basic statistics, that the best estimate of the variable is the centroid of all these hypocentres. It is shown that the approach is robust and that it can successfully be applied even when location uncertainties are not well-constrained. When applied to the Karthala volcano (Grande Comores Island), the method, called the Best Estimate Method, constrains the direction of the main active structure. This is a plane oriented N165° and dipping close to the vertical. This result, which is in agreement with recent studies of the Karthala volcano, demonstrates the potential of this technique. It is believed that such a process could advantageously be integrated in preliminary analysis of seismological monitoring.

Bossu, Rémy

337

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

338

Geodetic Measurements From the Aleutians and Western Alaska: Examining Evidence for a Bering Block  

Microsoft Academic Search

Global Positioning System (GPS) measurements are used to examine the hypothesis of a counter clockwise rotating Bering block. Originally proposed based on seismic data, the Bering block encompasses the Bering Sea, Western Alaska, and the Aleutian Islands, with Eastern Russia defining its western boundary. Oblique convergence of 73 mm\\/yr between the subducting Pacific Plate and overriding North American Plate results

R. S. Cross

2006-01-01

339

Long-term explosion records from two erupting submarine volcanoes in the Mariana and Tonga island-arcs  

NASA Astrophysics Data System (ADS)

Records of explosive activity longer than a few weeks are rare for subaerial volcanoes, and nonexistent for submarine volcanoes. From February 2008 to February 2009, we recorded a year long, continuous acoustic and volcanic plume record from NW Rota-1, an erupting submarine volcano located within the Mariana Arc. From December 2008 to May 2009, we also obtained acoustic records of ongoing explosion and tremor activity at West Mata, a submarine volcano in the NE Lau basin near the Tofua volcanic-arc. At NW Rota-1, a hydrophone and turbidity/temperature sensor were moored ~150 m from the volcano’s summit vent (520 m deep). The volcano exhibited frequent degassing explosions lasting 60-120 s, separated by quiet periods of 10-30 s, for the entire 12-months resulting in >284,000 discrete explosion events. The explosions are broadband (1-80 Hz) with typical source levels of 191 dB re ?Pa @ 1m. Harmonic tremor is also present at times in the explosions, typically with <5 Hz fundamentals and extremely high-amplitude overtone peaks near 30 Hz. The fundamentals are likely due to resonance of the entire volcanic edifice, while the peak overtone may represent reverberation of an internal structure, possibly the conduit feeding the summit vent. The hydrophone also documents a 103 decrease in explosion amplitude over the year, marked by a sharp reduction after 6 mos, which may be part of the typical eruption cycle or due to burial of the vent by accumulated ejecta. Explosions at the summit vent produced a steady series of volcanic plumes that carried ash and hydrothermal precipitates into the water column. Hundreds of short-lived turbidity spikes are present, with no long periods of quiescence, indicating changes in explosion intensity did not affect the pattern of volcanic plume creation. Our data are the first to confirm the frequent creation and dispersal of submarine volcanic plumes on a year-long scale. In December 2008 a moored hydrophone (250 Hz) was deployed ~30 km from West Mata, a near-arc boninite volcano discovered actively erupting the month before. An ROV cruise in May 2009 deployed two short-term, high-frequency (1024 Hz) hydrophones within 50 m of the Hades volcanic vent (1208 m deep). Both the long-term and in situ hydrophones detected explosive activity as well as both mono- and polychromatic volcanic tremor throughout their records. ROV video shows the acoustic signals are from violent degassing bursts from within lava extruding at the Hades vent (summit of West Mata). The explosions exhibit both short (10s of sec) and long (2-10 min) duration modes of cyclic activity. Many explosion signals also show harmonic tremor within their codas indicative of resonance from within the volcanic edifice. Frequently the explosion records are overlapped by monochromatic tremor from a narrow band within a range from 20-100 Hz. The source of this resonance is not yet clear (although not man-made) and is possibly from a nearby, unseen vent or magma movement within the volcanic edifice.

Dziak, R. P.; Embley, R. W.; Baker, E. T.; Chadwick, W. W.; Resing, J.; Matsumoto, H.; Walker, S. L.; Bohnenstiehl, D. R.; Klink, H.

2009-12-01

340

The November 2002 eruption at Piton de la Fournaise volcano, La Réunion Island: ground deformation, seismicity, and pit crater collapse  

Microsoft Academic Search

An eruption on the eastern flank of Piton de la Fournaise volcano started on 16 November, 2002 after 10 months of quiescence.\\u000a After a relatively constant level of activity during the first 13 days of the eruption, lava discharge, volcanic tremor and\\u000a seismicity increased from 29 November to 3 December. Lava effusion suddenly ceased on 3 December while shallow earthquakes\\u000a beneath the

Marc-Antoine Longpré; Thomas Staudacher; John Stix

2007-01-01

341

Nicaraguan Volcanoes  

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

342

Earthquake swarms preceding the 2000 eruption of Miyakejima volcano, Japan  

Microsoft Academic Search

The first sign of magma accumulating beneath Miyakejima, an island volcano in the northern Izu islands, Japan, came at around 18:00 on 26 June 2000, when a swarm of earthquakes was detected by a volcano seismic network on the island. Earthquakes occurred initially beneath the southwest flank near the summit and gradually migrated west of the island, where a submarine

K. Uhira; T. Baba; H. Mori; H. Katayama; N. Hamada

2005-01-01

343

Evolution, structure, and petroleum potential of Aleutian subduction complex  

SciTech Connect

Along the southern margin of the Aleutian arc is a large accretionary wedge or subduction complex of offscraped terrigenous and pelagic sediments. The authors believe the wedge has been accumulating since the late Miocene onset of increased sediment supply to the Aleutian Trench, initiated by glaciation in Gulf of Alaska drainages. Sediment incorporated into the accretionary body was originally deposited in abyssal plain and trench axis settings, and contains both pelagic ooze and thick turbidite facies. Adjacent to the central Aleutian Islands, (long. 172/sup 0/-177/sup 0/W), a 300-km long mass of offscraped sediment (36,000 km/sup 3/) forms a tectonic wedge 6-8 km thick that contains many potential structural and stratigraphic traps for oil and gas accumulations. Seismic reflection profiles reveal antiforms, normal and reverse fault traps, and stratigraphic pinch-outs. The source potential of these deposits is low to moderate with an estimated total organic content of 0.3-0.6%. Both potential reservoir turbidite sands and clay seals exist in the accretionary complex. Heat-flow values inferred from indirect measurements place the oil-generation window at 3-6.5 km. An active water drive to sweep petroleum generated at depth into trapping structures is a likely consequence of the compaction and tectonic dewatering of the accreted trench sediment. Although prerequisite conditions exist for the formation and entrapment of oil and gas deposits in the Aleutian accretionary wedge, the actual existence of large deposits of petroleum in an active tectonic zone is impossible to predict.

Stevenson, A.J.; Vallier, T.L.

1986-07-01

344

Hydrogeology of Stromboli volcano, Aeolian Islands (Italy) from the interpretation of resistivity tomograms, self-potential, soil temperature and soil CO2 concentration measurements  

NASA Astrophysics Data System (ADS)

To gain a better insight of the hydrogeology and the location of the main tectonic faults of Stromboli volcano in Italy, we collected electrical resistivity measurements, soil CO2 concentrations, temperature and self-potential measurements along two profiles. These two profiles started at the village of Ginostra in the southwest part of the island. The first profile (4.8 km in length) ended up at the village of Scari in the north east part of the volcano and the second one (3.5 km in length) at Forgia Vecchia beach, in the eastern part of the island. These data were used to provide insights regarding the position of shallow aquifers and the extension of the hydrothermal system. This large-scale study is complemented by two high-resolution studies, one at the Pizzo area (near the active vents) and one at Rina Grande where flank collapse areas can be observed. The Pizzo corresponds to one of the main degassing structure of the hydrothermal system. The main degassing area is localized along a higher permeability area corresponding to the head of the gliding plane of the Rina Grande sector collapse. We found that the self-potential data reveal the position of an aquifer above the villages of Scari and San Vincenzo. We provide an estimate of the depth of this aquifer from these data. The lateral extension of the hydrothermal system (resistivity ˜15-60 ohm m) is broader than anticipated extending in the direction of the villages of Scari and San Vincenzo (in agreement with temperature data recorded in shallow wells). The lateral extension of the hydrothermal system reaches the lower third of the Rina Grande sector collapse area in the eastern part of the island. The hydrothermal body in this area is blocked by an old collapse boundary. This position of the hydrothermal body is consistent with low values of the magnetization (<2.5 A m-1) from previously published work. The presence of the hydrothermal body below Rina Grande raises questions about the mechanical stability of this flank of the edifice.

Revil, A.; Finizola, A.; Ricci, T.; Delcher, E.; Peltier, A.; Barde-Cabusson, S.; Avard, G.; Bailly, T.; Bennati, L.; Byrdina, S.; Colonge, J.; di Gangi, F.; Douillet, G.; Lupi, M.; Letort, J.; Tsang Hin Sun, E.

2011-09-01

345

Analysis of geometry of volcanoes and faults in Terceira Island (Azores): Evidence for reactivation tectonics at the EUR/AFR plate boundary in the Azores triple junction  

NASA Astrophysics Data System (ADS)

The late Pliocene to Quaternary (5 Ma) volcanism in the central and eastern Azores Archipelago is related to the Eurasia/Africa divergence, but a clear deformation pattern has not yet been established at this location. This work focuses on the contribution of Synthetic Aperture Radar (SAR) scenes and Digital Elevation Models (DEM), complemented with geophysical, geodetic and morpho-structural data, to establish the geometric relationships between volcanic edifices and tectonic structures in the central and eastern Azores Archipelago. Bathymetric data were also used to extend field observations to the significant submarine area of the Azores plateau. Strikes of extension fractures, directly observed or inferred from elongated volcanic vents or linear volcanic clusters in Terceira Island, indicate that volcanism is mainly controlled by regional extension as given by NUVEL-1A plate motion model. Additionally, other directions were also detected for extension fractures around the Santa Barbara volcano (defining a radial pattern) and in the central part of the island (exhibiting an S-shape pattern). Although most of the volcanic vents are controlled by extension fractures, some seem to be controlled by faulting, such as the case of the ones rooted in releasing bends along strike-slip or oblique-slip faults in the central part of the island. Concerning the Azores plateau, most of the structures have directions that do not directly fit with present-day direction of relative motion (˜ N70°) between Eurasia and Africa. Directions ranging from N110° to N125°, found mainly along the Terceira rift, are interpreted as ancient transform directions, reactivating as transtensional fault zones due to the present-day plate motion. N-S directions are also visible in the plateau, being interpreted as former middle-oceanic rift faults reactivated as left-lateral fault zones. These results contrast with the volcanic expression in other hotspot dominated oceanic islands such as the Canaries or the Hawaii islands chain, probably due to the tectonic complexity promoted by the Azores Triple Junction instability through time.

Navarro, A.; Lourenço, N.; Chorowicz, J.; Miranda, J. M.; Catalão, J.

2009-02-01

346

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

347

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

348

Time-space variation of volcano-seismic events at La Fossa (Vulcano, Aeolian Islands, Italy): new insights into seismic sources in a hydrothermal system  

NASA Astrophysics Data System (ADS)

We investigated the relationship between volcano-seismic events, recorded at La Fossa crater of Vulcano (Aeolian Islands, Italy) during 2004-2006, and the dynamics of the hydrothermal system. During the period of study, three episodes of increasing numbers of volcano-seismic events took place at the same time as geothermal and geochemical anomalies were observed. These geothermal and geochemical anomalies have been interpreted as resulting from an increasing deep magmatic component of the hydrothermal fluids. Three classes of seismic events (long period, high frequency and monochromatic events), characterised by different spectral content and various similarity of the waveforms, have been recognised. These events, clustered mainly below La Fossa crater area at depths of 0.5-1.1 km b.s.l., were space-distributed according to the classes. Based on their features, we can infer that such events at Vulcano are related to two different source mechanisms: (1) fracturing processes of rocks and (2) resonance of cracks (or conduits) filled with hydrothermal fluid. In the light of these source mechanisms, the increase in the number of events, at the same time as geochemical and geothermal anomalies were observed, was interpreted as the result of an increasing magmatic component of the hydrothermal fluids, implying an increase of their flux. Indeed, such variation caused an increase of both the pore pressure within the rocks of the volcanic system and the amount of ascending fluids. Increased pore pressures gave rise to fracturing processes, while the increased fluid flux favoured resonance and vibration processes in cracks and conduits. Finally, a gradual temporal variation of the waveform of the hybrid events (one of the subclasses of long period events) was observed, likely caused by heating and drying of the hydrothermal system.

Alparone, Salvatore; Cannata, Andrea; Gambino, Salvatore; Gresta, Stefano; Milluzzo, Vincenzo; Montalto, Placido

2010-09-01

349

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

350

Aleutian mink disease virus and humans.  

PubMed

Reports of a possible relationship between Aleutian mink disease parvovirus (AMDV) and human infection are rare. However, 2 mink farmers with vascular disease and microangiopathy similar to that in mink with Aleutian disease were found to have AMDV-specific antibodies and AMDV DNA. These findings raise the suspicion that AMDV may play a role in human disease. PMID:19961696

Jepsen, Jørgen R; d'Amore, Francesco; Baandrup, Ulrik; Clausen, Michael Roost; Gottschalck, Elisabeth; Aasted, Bent

2009-12-01

351

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

352

Volcanic Activity in Alaska and Kamchatka: Summary of Events and Response of the Alaska Volcano Observatory, 2001.  

National Technical Information Service (NTIS)

The Alaska Volcano Observatory (AVO) monitors the more than 40 historically active volcanoes of the Aleutian Arc. Of these, 22 are monitored with short-period seismic instrument networks as of the end of 2001. The AVO core monitoring program also includes...

R. G. McGimsey C. A. Neal O. Girina

2004-01-01

353

GPS application to the study of ground deformation in the volcano tectonic systems of the Terceira Island (Azores) - preliminary results  

Microsoft Academic Search

The Azores Archipelago comprises nine volcanic islands, located where the Eurasian, American and African plates meet. Due to this complex tectonic setting seismic and volcanic activities are frequent in the archipelago. Since its settlement, in the 15th century, several volcanic eruptions and destructive earthquakes have been reported causing thousands of deaths and severe damages. Last eruption in the Azores occurred

Rita Rodrigues; Teresa Ferreira; Jun Okada; António Trota; João. Gaspar

2010-01-01

354

Tremor and plate coupling in the eastern Aleutians  

NASA Astrophysics Data System (ADS)

Tectonic tremor has been observed in numerous places along the 2500 km of the Alaska subduction zone. Though not as evidently ubiquitous as in other subduction zones, some tremor activity coincided with a large slow slip event on the mainland that occurred between 1998 and 2001 [Peterson and Christensen, 2009], and there are reports of several instances of tremor along the Aleutian arc [Peterson et al., 2011; Brown et al., 2013]. However, because these studies have focused on the characterization of manually detected tremors, the full extent of where, when and how much tremor activity occurs along the margin remains unknown, along with its role in subduction. Here we perform a systematic search for tectonic tremor activity along the margin. Starting in the eastern Aleutian Islands, a 'sweet spot' known for persistent tectonic tremor (ambient and triggered), we apply an automated method to detect and locate tremor and find a nearly daily occurrence of short-duration (<20 min) ambient tremor. In 18 months of data, we find the tremor to concentrate in 3 distinct zones of activity, occurring where the plate is 50-70 km deep. Constraints on tremor depths and along-dip locations are inhibited by the linear Aleutian station geometry, but epicenters lie trenchward of the islands and are resolved well enough to be distinguished from volcanic activity. We compare these results with geodetic observations. Time histories of each of the tremor patches show nearly daily activity in the region with an along strike change in tremor rate coincident with a change in updip coupling inferred from GPS. To the southwest, downdip of where the plate is locked, the total tremor activity is half that of the northeast-most patch where the plate is unlocked updip. We suggest that this updip transition in plate coupling is controlling the tremor behavior downdip, and that the most active tremor patch is experiencing more activity because of the additional loading from above.

Wech, A.; Freymueller, J. T.

2013-12-01

355

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

356

Microearthquake activity around Kueishantao island, offshore northeastern Taiwan: Insights into the volcano-tectonic interactions at the tip of the southern Okinawa Trough  

NASA Astrophysics Data System (ADS)

Kueishantao is a volcanic island located offshore the northeastern coast of Taiwan and lies at the tip of the southern Okinawa Trough which is the back-arc basin of the Ryukyu subduction zone. Its last eruption occurred during the Holocene (~ 7 ka), hence Kueishantao can be considered as an active volcano. In an effort to better understand how magmatic processes may interact with the regional tectonics, a seismic network was installed in the area during early January 2008. This network consisted of 16 three-component seismometers located both on Kueishantao and the coast of northeastern Taiwan. One year of data was analyzed yielding 425 earthquakes whose P and S arrival times were manually picked and each event was located using a nonlinear probabilistic location method. In order to improve the location accuracy, the minimum 1-D velocity model for this dataset was derived and all earthquakes were relocated using this model. The results show a tight cluster of events near Kueishantao while the remaining earthquakes are scattered between the island and mainland Taiwan. The majority of hypocentral depths range between 2.5 and 10 km where the former depth coincides with the bottom of the shallow sedimentary layer and the latter with the ductile lower crust. Waveforms of the three largest events were also inverted for the determination of their deviatoric and full moment tensor. No statistically significant isotropic component was found, while two of the events can be explained by a double-couple source. The third event exhibited a low frequency content (< 10 Hz) and a large non-double-couple component suggesting fluid involvement at its source. A stress inversion of all available focal mechanisms in the area shows that fluid circulation in the upper crust generates a local stress field around Kueishantao facilitating the opening of cracks along the NW-SE direction of regional extension.

Konstantinou, K. I.; Pan, C.-Y.; Lin, C.-H.

2013-05-01

357

Volcanoes, Central Java, Indonesia  

NASA Technical Reports Server (NTRS)

The island of Java (8.0S, 112.0E), perhaps better than any other, illustrates the volcanic origin of Pacific Island groups. Seen in this single view are at least a dozen once active volcano craters. Alignment of the craters even defines the linear fault line of Java as well as the other some 1500 islands of the Indonesian Archipelago. Deep blue water of the Indian Ocean to the south contrasts to the sediment laden waters of the Java Sea to the north.

1992-01-01

358

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

359

Flank instability of Stromboli volcano (Aeolian Islands, Southern Italy): Integration of GB-InSAR and geomorphological observations  

NASA Astrophysics Data System (ADS)

Stromboli is characterized by frequent explosions of variable energy and periodically interrupted by more energetic blasts emitting large volumes of material. The pressurization of a volatile-poor, high-porphyritic magma column that is gas-recharged by the deep-seated, volatile-rich, low-porphyritic magma precedes such events and produces deformations on the NW flank of the volcano, Sciara del Fuoco. By integrating geomorphological observations with long-term displacements from ground-based interferometric radar since December 2007, we identified two landslides whose movements are strongly related with volcanic activity. Movement patterns obtained through a novel long-term analysis of GB-InSAR data permitted us to hypothesize the type of movement and depth for both landslides. Furthermore their position allowed us to affirm that the effusive vent formed in 2007 at 400 m a.s.l., was the result of the deflection of a feeder dike caused by landslide fractures, thus showing the important role of geomorphological discontinuities in volcanic environments.

Intrieri, Emanuele; Di Traglia, Federico; Del Ventisette, Chiara; Gigli, Giovanni; Mugnai, Francesco; Luzi, Guido; Casagli, Nicola

2013-11-01

360

Groundwater salinity and hydrochemical processes in the volcano-sedimentary aquifer of La Aldea, Gran Canaria, Canary Islands, Spain.  

PubMed

The origin of the groundwater salinity and hydrochemical conditions of a 44km(2) volcano-sedimentary aquifer in the semi-arid to arid La Aldea Valley (western Gran Canaria, Spain) has been studied, using major physical and chemical components. Current aquifer recharge is mainly the result of irrigation return flows and secondarily that of rainfall infiltration. Graphical, multivariate statistical and modeling tools have been applied in order to improve the hydrogeological conceptual model and identify the natural and anthropogenic factors controlling groundwater salinity. Groundwater ranges from Na-Cl-HCO3 type for moderate salinity water to Na-Mg-Cl-SO4 type for high salinity water. This is mainly the result of atmospheric airborne salt deposition; silicate weathering, and recharge incorporating irrigation return flows. High evapotranspiration produces significant evapo-concentration leading to relative high groundwater salinity in the area. Under average conditions, about 70% of the water used for intensive agricultural exploitation in the valley comes from three low salinity water runoff storage reservoirs upstream, out of the area, while the remaining 30% derives from groundwater. The main alluvial aquifer behaves as a short turnover time reservoir that adds to the surface waters to complement irrigation water supply in dry periods, when it reaches 70% of irrigation water requirements. The high seasonality and intra-annual variability of water demand for irrigation press on decision making on aquifer use by a large number of aquifer users acting on their own. PMID:24698802

Cruz-Fuentes, Tatiana; Cabrera, María Del Carmen; Heredia, Javier; Custodio, Emilio

2014-06-15

361

The EarthScope Plate Boundary Observatory Akutan Alaskan Volcano Tiltmeter Installation  

NASA Astrophysics Data System (ADS)

During August of 2007, the Plate Boundary Observatory (PBO) successfully installed four Applied Geomechanics Lily Self Leveling Borehole Tiltmeters on Akutan Volcano, in the central Aleutian islands of Alaska. All four stations were collocated with existing PBO Global Positioning Systems (GPS) stations installed on the volcano in 2005. The tiltmeters will aid researchers in detecting and measuring flank deformation associated with future magmatic intrusions of the volcano. All four of the tiltmeters were installed by PBO field crews with helicopter support provided by JL Aviation and logistical support from the Trident Seafood Corporation, the City of Akutan, and the Akutan Corporation. Lack of roads and drivable trails on the remote volcanic island required that all drilling equipment be transported to each site from the village of Akutan by slinging gear beneath the helicopter and with internal loads. Each tiltmeter hole was drilled to a depth of approximately 30 feet with a portable hydraulic/pneumatic drill rig. The hole was then cased with splined 2.75 inch PVC. The PVC casing was cemented in place with grout and the tiltmeters were installed and packed with fine grain sand to stabilize the tiltmeters inside the casing. The existing PBO NetRS GPS receivers were configured to collect the tiltmeter data through a spare receiver serial port at one sample per minute and 1 hour files. Data from the GPS receivers and tiltmeters is telemetered directly or through a repeater radio to a base station located in the village of Akutan that transmits the data using satellite based communications to connect to the internet and to the UNAVCO Facility data archive where it is made freely available to the public.

Pauk, B. A.; Gallaher, W.; Dittmann, T.; Smith, S.

2007-12-01

362

Fumarole-Supported Islands of Biodiversity within a Hyperarid, High-Elevation Landscape on Socompa Volcano, Puna de Atacama, Andes? †  

PubMed Central

Fumarolic activity supports the growth of mat-like photoautotrophic communities near the summit (at 6,051 m) of Socompa Volcano in the arid core of the Andes mountains. These communities are isolated within a barren, high-elevation landscape where sparse vascular plants extend to only 4,600 m. Here, we combine biogeochemical and molecular-phylogenetic approaches to characterize the bacterial and eucaryotic assemblages associated with fumarolic and nonfumarolic grounds on Socompa. Small-subunit rRNA genes were PCR amplified, cloned, and sequenced from two fumarolic soil samples and two reference soil samples, including the volcanic debris that covers most of the mountain. The nonfumarolic, dry, volcanic soil was similar in nutrient status to the most extreme Antarctic Dry Valley or Atacama Desert soils, hosted relatively limited microbial communities dominated by Actinobacteria and Fungi, and contained no photoautotrophs. In contrast, modest fumarolic inputs were associated with elevated soil moisture and nutrient levels, the presence of chlorophyll a, and 13C-rich soil organic carbon. Moreover, this soil hosted diverse photoautotroph-dominated assemblages that contained novel lineages and exhibited structure and composition comparable to those of a wetland near the base of Socompa (3,661-m elevation). Fumarole-associated eucaryotes were particularly diverse, with an abundance of green algal lineages and a novel clade of microarthropods. Our data suggest that volcanic degassing of water and 13C-rich CO2 sustains fumarole-associated primary producers, leading to a complex microbial ecosystem within this otherwise barren landscape. Finally, we found that human activities have likely impacted the fumarolic soils and that fumarole-supported photoautotrophic communities may be exceptionally sensitive to anthropogenic disturbance.

Costello, Elizabeth K.; Halloy, Stephan R. P.; Reed, Sasha C.; Sowell, Preston; Schmidt, Steven K.

2009-01-01

363

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

364

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

365

Deformation associated with the 1997 eruption of Okmok volcano, Alaska  

USGS Publications Warehouse

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

Mann, D.; Freymueller, J.; Lu, Z.

2002-01-01

366

Microearthquakes at st. Augustine volcano, alaska, triggered by Earth tides.  

PubMed

Microearthquake activity at St. Augustine volcano, located at the mouth of Cook Inlet in the Aleutian Islands, has been monitored since August 1970. Both before and after minor eruptive activity on 7 October 1971, numerous shallow-foci microearthquake swarms were recorded. Plots of the hourly frequency of microearthquakes often show a diurnal peaking of activity. A cross correlation of this activity with the calculated magnitudes of tidal acceleration exhibited two prominent phase relationships. The first, and slightly more predominant, phase condition is a phase delay in the microearthquake activity of approximately 1 hour from the time of maximum tidal acceleration. This is thought to be a direct microearthquake-triggering effect caused by tidal stresses. The second is a phase delay in the microearthquake activity of approximately 5 hours, which correlates well with the time of maximum oceanic tidal loading. Correlation of the individual peaks of swarm activity with defined components of the tides suggests that it may be necessary for tidal stressing to have a preferential orientation in order to be an effective trigger of microearthquakes. PMID:17841318

Mauk, F J; Kienle, J

1973-10-26

367

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.

368

Quantitative analysis of seismic wave propagation anomalies in azimuth and apparent slowness at Deception Island volcano (Antarctica) using seismic arrays  

NASA Astrophysics Data System (ADS)

We analyse shot data recorded by eight seismic arrays during an active-source seismic experiment carried out at Deception Island (Antarctica) in 2005 January. For each source we estimate the apparent slowness and propagation azimuth of the first wave arrival. Since both source and receiver positions are accurately known, we are able to interpret the results in terms of the effect of the heterogeneities of the medium on wave propagation. The results show the presence of significant propagation anomalies. Nearby shots produce large apparent slowness values above 0.6 s km-1, while distant shots produce small values, down to about 0.15-0.20 s km-1. These values are different for each array, which shows the importance of the local structure under the receiver. The spatial distributions of apparent slowness are not radial as we would expect in a flat-layered medium. And again, these distributions are different for each array. The azimuth anomalies defined as the difference between the empirical estimates and the values expected in a 1-D model (i.e. the source-array directions) suggest ubiquitous wave front distortions. We have detected both positive and negative anomalies. For some shot-array geometries, azimuth anomalies are quite large with values up to 60°. The distribution of the anomalies depends on the position of the array. Some of these features can be interpreted in terms of a shallow magma chamber and shallow rigid bodies imaged by high-resolution seismic tomography. However several details remain unexplained. Further work is required, including modelling of synthetic wavefields on realistic models of Deception Island and/or apparent slowness vector tomography.

Yeguas, A. García.; Almendros, J.; Abella, R.; Ibáñez, J. M.

2011-02-01

369

South from Alaska: A Pilot aDNA Study of Genetic History on the Alaska Peninsula and the Eastern Aleutians  

Microsoft Academic Search

The Aleutian Islands were colonized, perhaps several times, from the Alaskan mainland. Earlier work documented transitions in the relative frequencies of mtDNA haplogroups over time, but little is known about potential source populations for prehistoric Aleut migrants. As part of a pilot investigation, we sequenced the mtDNA first hypervariable region (HVRI) in samples from two archaeological sites on the Alaska

Jennifer Raff; Justin Tackney; Dennis H. O’Rourke

2010-01-01

370

77 FR 55735 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...overall (LOA) using hook-and-line or pot gear in the Bering Sea and Aleutian Islands...than 60 feet LOA using hook-and-line or pot gear in the BSAI. DATES: Effective 1200...than 60 feet LOA using hook-and-line or pot gear in the BSAI under Sec....

2012-09-11

371

78 FR 53369 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...overall (LOA) using hook-and-line or pot gear in the Bering Sea and Aleutian Islands...than 60 feet LOA using hook-and-line or pot gear in the BSAI. DATES: Effective 1200...than 60 feet LOA using hook-and-line or pot gear in the BSAI under Sec....

2013-08-29

372

76 FR 24404 - Fisheries of the Exclusive Economic Zone Off Alaska; Pacific Cod in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...overall (LOA) using hook-and-line or pot gear in the Bering Sea and Aleutian Islands...than 60 feet LOA using hook-and-line or pot gear in the BSAI. DATES: Effective 1200...than 60 feet LOA using hook-and-line or pot gear in the BSAI under Sec....

2011-05-02

373

Slab portal beneath the western Aleutians  

Microsoft Academic Search

Tomographic images of the distribution of shear-wave speed beneath the northwestern Pacific delineate the configuration of the subducted oceanic lithosphere beneath the western Aleutian arc. At ˜100 km depth, a fast shear-wave speed anomaly is beneath the Aleutian arc everywhere east of 173°E. Between 164°E and 173°E, however, seismic velocities at this depth are slow relative to the surrounding mantle.

Vadim Levin; Nikolai M. Shapiro; Jeffrey Park; Michael H. Ritzwoller

2005-01-01

374

Slab portal beneath the western Aleutians  

Microsoft Academic Search

Tomographic images of the distribution of shear-wave speed beneath the northwest- ern Pacific delineate the configuration of the subducted oceanic lithosphere beneath the western Aleutian arc. At ;100 km depth, a fast shear-wave speed anomaly is beneath the Aleutian arc everywhere east of 1738E. Between 1648E and 1738E, however, seismic ve- locities at this depth are slow relative to the

Vadim Levin; Nikolai M. Shapiro; Jeffrey Park; Michael H. Ritzwoller

2005-01-01

375

Short-term (1998-2002) Geochemical Evolution of the Piton de la Fournaise Volcano, Reunion Island  

NASA Astrophysics Data System (ADS)

After a six years quiet period, the Piton de La Fournaise showed an intense volcanic activity between Mars 1998 and January 2002. A long-lived eruption (six and a half months) initiated this period and was followed by eight distinct eruptive events (one week to one month long). Systematic sampling of the freshly erupted lavas was performed during the entire period. Forty-one samples covering the nine events were selected and analyzed for trace-element concentrations (ICP-MS in Grenoble) and Pb isotopic composition (MC-ICP-MS in Lyon). Three periods can be distinguished based on trace-element chemistry: I) The long-lived 1998 eruption is characterized by a 10-20% progressive increase of the most incompatible element contents (U, Th, Ba, La, Ce). La/Yb increases continuously from 8.33 to 9.45 during the eruption. II) During the six following eruptions (July 1999 - April 2001), the trace element concentrations display an overall general decrease. Within each eruption, no systematic evolution can be resolved. III) The most recent events (June 2001 and January 2002) differ by the occurrence of olivine-rich lavas less enriched in trace elements. This effect increases during the course of the two eruptions. Trace-element concentrations drop to 40-50% of the starting level in the latest lavas. During stages II and III, La/Yb oscillates between 9.3 and 10.1 (around the value reached at the end of the eruption of 1998). Lead isotopic ratios display small but systematic variations (206Pb/204Pb: 18.874-18.913, 207Pb/204Pb: 15.587-15.606 and 208Pb/204Pb: 38.975-39.032). The three stages differ in Pb isotopic signatures: stage I lavas have the highest Pb ratios and stage III lavas the lowest. Stage II samples are characterized by a distinctive correlation in 208Pb/204Pb vs. 206Pb/204Pb space. The 1998-2002 chemical and isotopic variations of Piton de la Fournaise lavas represent 20 to 40% of the total range defined by the last 530 ky activity of the volcano. The three identified periods are thought to correspond to the initiation, the steady-state regime and the vanishing stage of a plume pulse.

Vlastelic, I.; Staudacher, T.

2002-12-01

376

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

377

Volcanoes Online  

NSDL National Science Digital Library

This Thinkquest offers an encyclopedic look at plate tectonics and volcanoes. Reference sections describe the interior of the Earth, continental drift, sea floor spreading, subduction, volcano types and eruptions, lava flow, and famous volcanoes. Lesson plans cover the internal structure of Earth, plate tectonic theory, and how volcanic eruptions and earthquakes affect the human environment. There is a plasticine plates activity; a volcano-related game, crossword puzzle, and comics section; and a volcanic database containing descriptions and photographs of volcanoes around the world.

378

Erupting Volcano Mount Etna  

NASA Technical Reports Server (NTRS)

Expedition Five crew members aboard the International Space Station (ISS) captured this overhead look at the smoke and ash regurgitated from the erupting volcano Mt. Etna on the island of Sicily, Italy in October 2002. Triggered by a series of earthquakes on October 27, 2002, this eruption was one of Etna's most vigorous in years. This image shows the ash plume curving out toward the horizon. The lighter-colored plumes down slope and north of the summit seen in this frame are produced by forest fires set by flowing lava. At an elevation of 10,990 feet (3,350 m), the summit of the Mt. Etna volcano, one of the most active and most studied volcanoes in the world, has been active for a half-million years and has erupted hundreds of times in recorded history.

2002-01-01

379

Earthquakes, plate subduction, and stress reversals in the eastern Aleutian arc  

Microsoft Academic Search

Plate subduction beneath the 1500-km-long segment of the eastern Aleutian arc between Kodiak and Atka islands (154°W and 176°W longitude) is studied with observations from teleseismic data. The primary data base consists of hypocenters of earthquakes (for the period 1965-1975), carefully selected from the bulletins of the International Seismological Centre, and of 44 new focal mechanism solutions. The principal results

L. S. House; K. H. Jacob

1983-01-01

380

Volcano-seismic events during 2004-2008 at Vulcano (Aeolian Islands, Italy): clues to the dynamics of the hydrothermal system  

NASA Astrophysics Data System (ADS)

Vulcano, belonging to the Aeolian Islands, since the last eruption in 1888-1890, is characterised by fumarolic emanations of variable intensity and temperature, mainly concentrated in the La Fossa area. Different kinds of volcano-seismic events are recorded at Vulcano, whose monthly number generally changes at the same time as geothermal and geochemical anomalies. Three classes of events (long period, high frequency and monochromatic events), each comprising two subclasses and characterised by different spectral content and various similarity of the waveforms, have been recognized. These events, mainly clustered below La Fossa crater area at depth 0.5-1.1 km b.s.l. were space-distributed according to the subclasses. Based on their features, we can infer that such events at Vulcano are related to two different source mechanisms: i) fracturing processes rocks (high frequency events) and ii) resonance of cracks (or conduits) filled with hydrothermal fluid (long period and monochromatic events). In the light of these source mechanisms the increase in the number of events, at the same time as geochemical and geothermal anomalies, was interpreted as the outcome of the increasing magmatic component of the hydrothermal fluids. Such variation caused the increase of both the pore pressure within the volcanic system and the gas flux rising up. The former gave rise to fracturing processes, while the latter increased the fluid dynamics within cracks and conduits. Low frequency (LF; a subclass of long period events) and tornillos events (TR; belonging to monochromatic events), mainly occurring during 2004-2006 and 2007-2008, respectively, were studied in details. A gradual time variation of the waveform of the low frequency events was observed, likely due to processes of heating and drying of the hydrothermal system. Also tornillos events showed changes in both waveform and wavefield, interpreted to result from variations of physical-chemical features of fluids within the hydrothermal system.

Milluzzo, V.; Alparone, S.; Cammarata, L.; Cannata, A.; Gambino, S.; Gresta, S.; Hellweg, M.; Montalto, P.

2009-12-01

381

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.

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

2012-01-01

382

Plant diversity changes during the postglacial in East Asia: insights from Forest Refugia on Halla Volcano, Jeju Island.  

PubMed

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

383

Virtual Volcano  

NSDL National Science Digital Library

The Discovery Channel's website has several interactive features on volcanoes to complement its programs on Pompeii. At the homepage, visitors can explore a virtual volcano, by clicking on "Enter". The virtual volcano has several components. The first is a quickly revolving globe with red triangles and gray lines on it that represent active volcanoes and plate boundaries. Clicking on "Stop Rotation", located next to the globe, will enable a better look. Visitors can also click one of the topics below the globe, to see illustrations of "Tectonic Plates", "Ring of Fire" (no, not the Johnny Cash song), and "Layers Within". Visitors can click on "Build your Own Volcano and Watch it Erupt" on the menu on the left side of the page, where they will be given a brief explanation of two factors that affect the shape and explosiveness of volcanoes: viscosity and gas. Then they must choose, and set, the conditions of their volcano by using the arrows under the viscosity and gas headings, and clicking on "Set Conditions", underneath the arrows. Once done, a description of the type of volcano created will be given, and it's time to