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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

Stratigraphic framework of Holocene volcaniclastic deposits, Akutan Volcano, east-central Aleutian Islands, Alaska  

Microsoft Academic Search

Akutan Volcano is one of the most active volcanoes in the Aleutian arc, but until recently little was known about its history and eruptive character. Following a brief but sustained period of intense seismic activity in March 1996, the Alaska Volcano Observatory began investigating the geology of the volcano and evaluating potential volcanic hazards that could affect residents of Akutan

Christopher F. Waythomas

1999-01-01

3

Stratigraphic framework of Holocene volcaniclastic deposits, Akutan Volcano, east-central Aleutian Islands, Alaska  

Microsoft Academic Search

Akutan Volcano is one of the most active volcanoes in the Aleutian arc, but until recently little was known about its history\\u000a and eruptive character. Following a brief but sustained period of intense seismic activity in March 1996, the Alaska Volcano\\u000a Observatory began investigating the geology of the volcano and evaluating potential volcanic hazards that could affect residents\\u000a of Akutan

Christopher F. Waythomas

1999-01-01

4

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

5

The resource and development potential of the Makushin Volcano geothermal reservoir of the Aleutian Islands, Alaska  

SciTech Connect

Geological, geophysical, geochemical, and well flow-test data suggest a 13+- km/sup 3/ bulk volume, water-dominated, 195/sup 0/C geothermal reservoir that reaches a depth of 4.4+- km beneath the Makushin Volcano caldera. Through numerous fractures, this reservoir is presently discharging gases on the northern, eastern, and southern flanks of the volcano, as indicated by the occurrence of numerous fumaroles. Rising gases are also escaping directly to the surface through the caldera, as reflected by the largest fumarole field on the summit caldera.

Reeder, J.W.; Denig-Chakroff, D.N.; Economides, M.J.

1987-03-01

6

Massive edifice failure at Aleutian arc volcanoes  

NASA Astrophysics Data System (ADS)

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 km 2. 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.

Coombs, Michelle L.; White, Scott M.; Scholl, David W.

2007-04-01

7

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

8

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

Microsoft Academic Search

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

Carmelo Ferlito

2011-01-01

9

Data Report: 2006 Aleutian Islands Bottom Trawl Survey.  

National Technical Information Service (NTIS)

Tenth in a series dating from 1980, the fourth biennial groundfish assessment survey of the Aleutian Islands region was conducted during the summer of 2006 by the Alaska Fisheries Science Centers (AFSC) Resource Assessment and Conservation Engineering (RA...

C. N. Rooper

2008-01-01

10

Data Report: 2004 Aleutian Islands Bottom Trawl Survey.  

National Technical Information Service (NTIS)

Ninth in a series dating from 1980, the third biennial groundfish assessment survey of the Aleutian Islands region was conducted during the summer of 2004 by the Alaska Fisheries Science Centers (AFSC) Resource Assessment and Conservation Engineering (RAC...

C. N. Rooper M. E. Wilkins

2008-01-01

11

InSAR Imaging of Volcanic Deformation Over Aleutian Islands  

NASA Astrophysics Data System (ADS)

Interferometric synthetic aperture radar (InSAR) is capable of measuring ground-surface deformation with centimeter to subcentimeter precision and spatial resolution of tens-of-meters over relatively large regions under all weather conditions. The spatial distribution of surface deformation data, derived from InSAR images, enables the exploration of detailed mechanical models to enhance the study of volcanic and tectonic processes. This paper summarizes our InSAR studies of more than a dozen Alaskan volcanoes, associated with both eruptive and non-eruptive activity. These examples include the pre-eruption inflation, co-eruption deflation, and post-eruption inflation at Okmok Volcano; magmatic intrusion and the associated tectonic stress release at Akutan Volcano; progressive aseismic inflation of Westdahl Volcano; magmatic intrusion at Mount Peulik Volcano and its relation to an earthquake swarm 30 km away; magmatic intrusion associated with a small eruption at Makushin Volcano in 1995; complex patterns of transient deformation during and after the 1992-1993 eruption at Seguam Volcano; surface subsidence caused by a decrease in pore fluid pressure in an active hydrothermal system beneath Kiska Volcano; compaction of young pyroclastic flow deposits at Augustine Volcano; persistent volcano-wide subsidence at Aniakchak Volcano; and lack of expected deformation associated with recent eruptions at Shishaldin, Pavlof, Cleveland, and Korovin Volcanoes. We conclude that the deformation patterns and the associated magma supply mechanisms over Aleutian Volcanoes are diverse and vary between volcanoes. These studies demonstrate that InSAR can improve our understanding on how the Aleutian Volcanoes work and enhance our capability to predict future eruptions and associated hazards.

Lu, Z.; Dzurisin, D.; Wicks, C.; Power, J.; Kwoun, O.; Rykhus, R.

2005-12-01

12

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

13

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

NASA Astrophysics Data System (ADS)

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 in length, and separated from one another by distinctive fault- controlled canyons that are roughly normal to the arc axis. The canyons are geomorphically low areas between the higher relief blocks and are natural regions for the accumulation and conveyance of sediment derived from glacial and volcanic processes. The volcanic islands in the region include a number of historically active volcanoes and some possess geological evidence for large-scale sector collapse into the sea. The physical setting of the Aleutian Islands indicates that mass flows of unconsolidated debris that originate either as submarine mass flows or as subaerial debris avalanches entering the sea may be potential tsunami sources. Large scale mass-flow deposits have not been identified on the seafloor south of the Aleutian Islands, primarily because the area has never been mapped or examined at the resolution required to identify such features. Extensive submarine landslide deposits and debris flows are known on the north side of the arc and are common in similar settings elsewhere and thus they likely exist on the trench slope south of the Aleutian Islands. We suggest that tsunamigenic mass flows are a plausible geologic process in the Aleutian Islands and that the tsunamis produced by such flows may be large enough to cross the Pacific Ocean basin. To test this hypothesis we present a series of numerical simulations of submarine mass-flow initiated tsunamis from eight different source areas. We consider four submarine mass flows originating in submarine canyons and four flows that evolve from submarine landslides. The flows have lengths that range from 40-80 km, maximum thicknesses of 400-800 m, and maximum widths of 10-40 km. Although some of these hypothetical flows are large, they are not unprecedented and flows of similar dimensions are known in other continental slope settings. We calculate tsunami sources using the numerical model TOPICS and simulate wave propagation across the Pacific using a spherical Boussinesq model which is a modified version of the public domain code FUNWAVE. Our numerical simulations indicate that geologically plausible submarine mass flows originating in the North Pacific near the Aleutian Islands can indeed generate large tsunamis. These waves may be several meters in amplitude at distal locations, such as Japan, Hawaii, and along the South American coastline where they would constitute significant hazards.

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

2007-12-01

14

Subduction Controls of Hf and Nd Isotopes in Lavas of the Aleutian Island Arc  

SciTech Connect

The Hf and Nd isotopic compositions of 71 Quaternary lavas collected from locations along the full length of the Aleutian island arc are used to constrain the sources of Aleutian magmas and to provide insight into the geochemical behavior of Nd and Hf and related elements in the Aleutian subduction-magmatic system. Isotopic compositions of Aleutian lavas fall approximately at the center of, and form a trend parallel to, the terrestrial Hf-Nd isotopic array with {var_epsilon}{sub Hf} of +12.0 to +15.5 and {var_epsilon}{sub Nd} of +6.5 to +10.5. Basalts, andesites, and dacites within volcanic centers or in nearby volcanoes generally all have similar isotopic compositions, indicating that there is little measurable effect of crustal or other lithospheric assimilation within the volcanic plumbing systems of Aleutian volcanoes. Hafnium isotopic compositions have a clear pattern of along-arc increase that is continuous from the eastern-most locations near Cold Bay to Piip Seamount in the western-most part of the arc. This pattern is interpreted to reflect a westward decrease in the subducted sediment component present in Aleutian lavas, reflecting progressively lower rates of subduction westward as well as decreasing availability of trench sediment. Binary bulk mixing models (sediment + peridotite) demonstrate that 1-2% of the Hf in Aleutian lavas is derived from subducted sediment, indicating that Hf is mobilized out of the subducted sediment with an efficiency that is similar to that of Sr, Pb and Nd. Low published solubility for Hf and Nd in aqueous subduction fluids lead us to conclude that these elements are mobilized out of the subducted component and transferred to the mantle wedge as bulk sediment or as a silicate melt. Neodymium isotopes also generally increase from east to west, but the pattern is absent in the eastern third of the arc, where the sediment flux is high and increases from east to west, due to the presence of abundant terrigenous sediment in the trench east of the Amlia Fracture Zone, which is being subducting beneath the arc at Seguam Island. Mixing trends between mantle wedge and sediment end members become flatter in Hf-Nd isotope space at locations further west along the arc, indicating that the sediment end member in the west has either higher Nd/Hf or is more radiogenic in Hf compared to Nd. This pattern is interpreted to reflect an increase in pelagic clay relative to the terrigenous subducted sedimentary component westward along the arc. Results of this study imply that Hf does not behave as a conservative element in the Aleutian subduction system, as has been proposed for some other arcs.

Yogodzinski, Gene; Vervoort, Jeffery; Brown, Shaun Tyler; Gerseny, Megan

2010-08-29

15

Volcanoes as possible indicators of tectonic stress orientation — Aleutians and Alaska  

Microsoft Academic Search

A new method for obtaining from volcanic surface features the orientations of the principal tectonic stresses is applied to Aleutian and Alaskan volcanoes. The underlying concept for this method is that flank eruptions for polygenetic volcanoes can be regarded as the result of a large-scale natural magmafracturing experiment. The method essentially relies on the recognition of the preferred orientation of

Kazuaki Nakamura; Klaus H. Jacob; John N. Davies

1977-01-01

16

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

17

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

18

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

19

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

Code of Federal Regulations, 2010 CFR

...Shipping 1 2010-10-01 2010-10-01 false Alaska Peninsula, AK to Aleutian Islands, AK. 7.170 Section 7.170...THE PUBLIC BOUNDARY LINES Alaska § 7.170 Alaska Peninsula, AK to Aleutian Islands, AK. (a) A line...

2010-10-01

20

77 FR 74161 - Fisheries of the Exclusive Economic Zone Off Alaska; Allocating Bering Sea and Aleutian Islands...  

Federal Register 2010, 2011, 2012, 2013

...Bering Sea/ Aleutian Islands King and Tanner Crabs...Bering Sea and Aleutian Islands Crab Rationalization...region. Natural and man- made situations can disrupt...the Western Aleutian Islands golden king crab QS and...conditions or other natural or man-made circumstances can...

2012-12-13

21

A burial cave in the western Aleutian Islands, Alaska.  

PubMed

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

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

2003-01-01

22

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

23

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

24

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

25

Continued Magmatic Unrest: Geochemical Evolution of Recent Eruptions from Mt. Cleveland, Aleutian arc, AK  

Microsoft Academic Search

Mt. Cleveland, a previously unstudied composite volcano (1730 m) in the central Aleutians, last erupted in 1994 and 2001. Mt. Cleveland occupies an unusual tectonic setting, near the transition from sub-arc continental crust to oceanic crust further west. It and the other Islands of Four Mountains are closer to the forearc trench than any other Aleutian volcanoes, and the close

K. Nicolaysen; S. K. Allen; J. Dehn; R. B. Moore; D. Weis

2003-01-01

26

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

27

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

Federal Register 2010, 2011, 2012, 2013

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

2011-09-07

28

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

Code of Federal Regulations, 2010 CFR

...Fisheries 7 2010-10-01 2010-10-01 false Alaska Peninsula and Aleutian Islands Rural and Non-Rural Areas 6 Figure...E, Fig. 6 Figure 6 to Subpart E of Part 300âAlaska Peninsula and Aleutian Islands Rural and Non-Rural Areas...

2010-10-01

29

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

30

Mount Dutton volcano, Alaska: Aleutian arc analog to Unzen volcano, Japan  

Microsoft Academic Search

Holocene eruptions from Mount Dutton, a small Late Quaternary volcano near the tip of the Alaska Peninsula, bear strong physical and petrologic similarities to the 1990–1995 Unzen Fugendake eruption in Japan. The volcano had a protracted phase of effusive calcalkaline andesitic (54–59 wt.% SiO2) cone-building in the late Pleistocene followed by an abrupt switch to more silicic (?65 wt.% SiO2)

T. P Miller; D. G Chertkoff; J. C Eichelberger; M. L Coombs

1999-01-01

31

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

32

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

2013-03-08

33

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

Federal Register 2010, 2011, 2012, 2013

...0648-BA11 Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian...Tanner crab fisheries in the exclusive economic zone of the Bering Sea and Aleutian Islands...has taken to minimize the significant economic impact on small entities,...

2011-06-20

34

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

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

35

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

Federal Register 2010, 2011, 2012, 2013

...other flatfish,'' Alaska plaice, northern rockfish, ``other rockfish,'' squids, sharks, skates, sculpins, and octopuses. Section 679.20(a)(5)(iii)(B)(1) requires the Aleutian Islands (AI) pollock TAC to be set at...

2012-12-06

36

77 FR 59852 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...  

Federal Register 2010, 2011, 2012, 2013

...Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...participating in Federal groundfish fisheries off Alaska that are not Amendment 80 fisheries...www.regulations.gov or from the Alaska Region Web site at...

2012-10-01

37

77 FR 62482 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...  

Federal Register 2010, 2011, 2012, 2013

...Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...Administrator, Sustainable Fisheries Division, Alaska Region NMFS, Attn: Ellen Sebastian...Administrator, Sustainable Fisheries Division, Alaska Region NMFS, Attn: Ellen...

2012-10-15

38

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

Code of Federal Regulations, 2012 CFR

...opilio and C. bairdi (the corresponding crab rationalization fisheries are two separate fisheries, one for Bering Sea snow crab and another for Bering Sea Tanner crab), (3) Aleutian Islands brown king (the corresponding crab...

2012-10-01

39

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

Code of Federal Regulations, 2011 CFR

...opilio and C. bairdi (the corresponding crab rationalization fisheries are two separate fisheries, one for Bering Sea snow crab and another for Bering Sea Tanner crab), (3) Aleutian Islands brown king (the corresponding crab...

2011-10-01

40

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

Microsoft Academic Search

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

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

2010-01-01

41

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

42

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

2012-09-17

43

Satellite monitoring of remote volcanoes improves study efforts in Alaska  

Microsoft Academic Search

Satellite monitoring of remote volcanoes is greatly benefitting the Alaska Volcano Observatory (AVO), and last year's eruption of the Okmok Volcano in the Aleutian Islands is a good case in point. The facility was able to issue and refine warnings of the eruption and related activity quickly, something that could not have been done using conventional seismic surveillance techniques, since

K. Dean; M. Servilla; A. Roach; B. Foster; K. Engle

1998-01-01

44

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

Microsoft Academic Search

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

William Ian Ridley

1970-01-01

45

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

46

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

NASA Astrophysics Data System (ADS)

Adak-type andesites erupted as domes at Sheveluch volcano (Kamchatka Russia) have been associated with partial melting of the Pacific plate subducting under Kamchatka. The heat for melting at the plate edge has been proposed to be provided by an asthenosphere upwelling north of the junction of Kuril Kamchatka and Aleutian island arcs. However, Sheveluch volcano is composed of two volcano-stratigraphic units bounded by a caldera episode. The lava sequence from the pre-caldera stage of Sheveluch has not previously been considered in the petrogenetic model and in the consequent geodynamic reconstruction. New petrochemical data from the post-caldera domes and the pre-caldera lavas, together with a review of the petrochemical characteristics of northern Kamchatka volcanics reveal a more complex story. Rocks at Sheveluch display a bimodal geochemical and petrological signature, which cannot be derived from a common parent magma: the pre-caldera lavas are high-Al 2O 3 basaltic andesites, similar to the products of Kliuchevskoi and other volcanoes in northern Kamchatka, and can be associated with partial melting of the mantle wedge hydrated by the subducting slab. The post-caldera andesitic domes, with high Mg#, Cr and Ni signature, are slab primary melts which have assimilated the peridotite in the overlying mantle wedge. A possible mechanism to explain the observations is that beneath Sheveluch two distinct slabs with different subduction angle and pressure/temperature paths are responsible for the two geochemical signatures. A reappraisal of geophysical data indicates that between the western Aleutians and northern Kamchatka there is a transform zone where the Pacific plate is torn apart and decoupled. It is proposed that a portion of the slab was led to subduct at low angle north of the transform zone and travelled west for a long distance. The frictionally heated metabasalt in the slab can yield acidic melts at the amphibolite-eclogite transition ~ 70 km beneath Sheveluch. The ascending melts interact with the peridotite to produce the high Mg-andesites erupted by the present-day volcano. South of the junction, the dehydration of the Pacific slab undergoing high angle subduction would cause partial melting of the peridotite in the mantle wedge and produce melts which will evolve as high Al 2O 3 basaltic andesites erupted in the pre-caldera phase. Sheveluch volcano can therefore be considered the only known example in the world in which two paradigmatic models for magma genesis at colliding margins are not mutually exclusive but are both necessary to explain the products of two distinct evolutionary phases.

Ferlito, Carmelo

2011-03-01

47

78 FR 59908 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...  

Federal Register 2010, 2011, 2012, 2013

The North Pacific Fishery Management Council submitted Amendment 99 to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian Islands Management Area (BSAI FMP) to NMFS for review. If approved, Amendment 99 would enable the holders of license limitation program (LLP) licenses authorizing a designated vessel to catch and process Pacific cod in the BSAI hook-and-line fisheries to......

2013-09-30

48

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

Federal Register 2010, 2011, 2012, 2013

NMFS publishes a notification of a zero (0) percent fee for cost recovery under the Bering Sea and Aleutian Islands Crab Rationalization Program. This action is intended to provide holders of crab allocations with the fee percentage for the 2012/2013 crab fishing...

2012-07-27

49

78 FR 36122 - 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 Sea and Aleutian Islands Crab...www.regulations.gov or from the Alaska Region Web site at http://alaskafisheries...CR Program are available from the NMFS Alaska Region Web site at...

2013-06-17

50

Paleosecular variation and GAD studies of 0–2 Ma flow sequences from the Aleutian Islands, Alaska  

Microsoft Academic Search

A study was undertaken in the late 1960s to investigate paleosecular variations of the geomagnetic field as recorded in volcanic rocks from the Aleutian Islands. The early results were internally consistent but to be wholly credible by today's standards needed more detailed demagnetization. Complete thermal demagnetization protocols have been applied to the unmeasured archived samples from the six flow sequences

David B. Stone; Paul W. Layer

2006-01-01

51

Surface deformation associated with the March 1996 earthquake swarm at Akutan Island, Alaska, revealed by C-band ERS and L-band JERS radar interferometry  

Microsoft Academic Search

Akutan volcano, situated in the west-central part of Akutan Island in the eastern Aleutian volcanic arc, is a composite stratovolcano with an active cinder cone inside a circular summit caldera about 2 km across. Akutan is one of the most active volcanoes in the Aleutian arc, producing more than 27 small to moderate explosions from the active intracaldera cone in

Zhong Lu; Charles Wicks; O. Kwoun; J. A. Power; D. Dzurisin

2004-01-01

52

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

53

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

Microsoft Academic Search

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

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

2003-01-01

54

Interpretation of The Magnetotelluric Soundings Performed In The Junction of The Kurile-kamchatka and Aleutian Island Arcs  

NASA Astrophysics Data System (ADS)

Long-term MTS within the period range of 0.1 -15000 c have been analyzed and summarized. The interpretation is based upon he amplitude and phase curves t directed along and across the island arcs' strike. The average curves free of local galvanic effects have been obtained through statistical averaging. Using 3-D experimental models we have studied possible distortions of these curves due to large lateral geoelectrical inhomogeneities. The basis for these experimental models is maps for the geoelectrical parameters of the sedimentary -volcanogenic cover and hydrosphere as well as the current views on the deep geoelectrical section. The peculiarities have been revealed in the MTS curves behavior, which are further used for solving the inverse task using 3-D modeling. Base model has been obtained through the data of qualitative interpretation of the MTS curves and previous studies. Change of the model parameters was made by intuition. The overall geologic-geophysical information available was taken into consideration. Altogether fifteen variants have been calculated. Faster concurrency of the curves was obtained in the western part of the area where the geoelectrical section was close to the quasi- two-dimensional. It was more difficult to select parameters for the central part of the area and peninsula Kamchatsky Mys where the 3-D effects predominate. As a result of the calculations, the agreement was obtained between the model and practical curves within the limits of 15-20%. The result obtained may be thought of as a good one, taking into consideration a complexity of the model. The 3-D deep geoelectrical model of the region is a result of the MT curves inversion. The conducting zones of 8-10 ohm resistance are distinguished within the middle and lower parts of the earth's crust. The western zone stretches north-east. It is located at the depths of 25- 40 km. Central-Kamchatka volcanic belt is confined to it. The transverse conducting zone of the Aleutian (south-east) direction extending to the Pacific ocean is conjugated with the western zone. The zone is 50 km wide. It is located at the depths of 15-4- km. The Klyuchevskaya group of volcanoes is confined to the more elevated part of the zone. The astenospheric conducting layer has been revealed in the upper mantle. The roof of the layer is located at the depths of 80-120 km. Its elevated part represents the 80 km-wide zone stretching north-east. Active volcanoes of the Eastern-Kamchatka volcanic belt are confined to it at the day surface.

Moroz, Yu. F.; Nurmukhamedov, A. G.

55

Prehistoric Lahar and Tephra Sequences on Mt. Cleveland, Islands of Four Mountains, Eastern Aleutian Islands  

NASA Astrophysics Data System (ADS)

We provide the first geochronology for prehistoric activity of Mt. Cleveland, which has erupted 23 times historically and as recently as June, 2005. The lowest stratigraphically-exposed dacite indicates Cleveland already had a significant volume by 1.4+/-0.3 Ma (1 s.d.) based on a total gas age of a groundmass separate analyzed by 40Ar/39Ar. We describe two locations on the northern vegetated flank of Mt. Cleveland that expose interbedded lahar and tephra sequences that provide geochronologically-constrained comparisons with modern lahar deposits. Four calibrated radiocarbon dates were obtained by accelerator mass spectrometry (1 s.d. quoted). Beach cliffs (9 m high) on the northeast shore expose at least four debris flows, a thick ash and a probable paleosol. Three debris flows form the base of the exposure and organic material from the top finest-grained lahar gives a calibrated age of 3652+/-43 yr BP. This layer grades upward to a 2-5 cm thick, extremely hard and oxidized layer with abundant root material, some of which is burned. We interpret this to be a soil baked by an overlying fine-grained ash (50 cm thick). Charred organics from the baked soil yielded an especially important age of 2758+/-20 yr BP giving a maximum age for the eruption of the ash. Root material in a debris flow from just above the ash gives a calibrated age of 1753+/-59 yr BP, thus bracketing the eruption of the ash. The second location, located in a ravine on the north flank, is a sequence of distal lahars with at least four interbedded tephras. Coarse sand layers, some of which are oxidized, separate these ashes. Also intercalated between two ashes is a fine silt layer 20 cm thick with preserved stems and grass leaves, which yielded a calibrated age of 9082+/-58 yr BP. Previous work showed that the 2001 eruptions on the western and southern flanks emplaced debris flows that are overlain by lava and highlights the role of snowfields in creating this sequence. Unlike the recent phase, prehistoric lahars on the northern flank of Mt. Cleveland are not interbedded with lava, but instead occur with tephra sequences that will help unravel Holocene activity of the volcanoes in the Islands of Four Mountains.

Pekar, K.; Nicolaysen, K. P.; Bridges, D.; Dehn, J.

2005-12-01

56

Living on Active Volcanoes - The Island of Hawaii  

NSDL National Science Digital Library

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

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

57

Photographic mark-recapture analysis of clustered mammal-eating killer whales around the Aleutian Islands and Gulf of Alaska  

Microsoft Academic Search

We used photographic mark-recapture methods to estimate the number of mammal-eating “transient” killer whales using the coastal\\u000a waters from the central Gulf of Alaska to the central Aleutian Islands, around breeding rookeries of endangered Steller sea\\u000a lions. We identified 154 individual killer whales from 6,489 photographs collected between July 2001 and August 2003. A Bayesian\\u000a mixture model estimated seven distinct

J. DurbanD; D. Ellifrit; M. Dahlheim; J. Waite; C. Matkin; L. Barrett-Lennard; G. Ellis; R. Pitman; R. LeDuc; P. Wade

2010-01-01

58

The Earthscope Plate Boundary Observatory Akutan Alaskan Volcano Network Installation  

Microsoft Academic Search

During June and July of 2005, the Plate Boundary Observatory (PBO) installed eight permanent GPS stations on Akutan Volcano, in the central Aleutian Islands of Alaska. PBO worked closely with the Alaska Volcano Observatory and the Magmatic Systems Site Selection working group to install stations with a spatial distribution to monitor and detect both short and long term volcanic deformation

B. Pauk; M. Jackson; D. Mencin; J. Power; W. Gallaher; A. Basset; K. Kore; Z. Hargraves; T. Peterson

2005-01-01

59

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

60

The active volcanoes of Kamchatka and Paramushir Island, North Kurils in 2007  

Microsoft Academic Search

Eight strong eruptions of four Kamchatka volcanoes (Bezymyannyi, Klyuchevskoi, Shiveluch, and Karymskii) and Chikurachki Volcano\\u000a on Paramushir Island, North Kurils took place in 2007. In addition, an explosive event occurred on Mutnovskii Volcano and\\u000a increased fumarole activity was recorded on Avacha and Gorelyi volcanoes in Kamchatka and Ebeko Volcano on Paramushir Island,\\u000a North Kurils. Thanks to close cooperation with colleagues

O. A. Girina; S. V. Ushakov; N. A. Malik; A. G. Manevich; D. V. Mel’nikov; A. A. Nuzhdaev; Yu. V. Demyanchuk; L. V. Kotenko

2009-01-01

61

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

62

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

63

Depths of Magma Storage Beneath Fogo Volcano, Cape Verde Islands  

Microsoft Academic Search

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

E. Hildner; A. Klügel

2008-01-01

64

Recent structural evolution of the Cumbre Vieja volcano, La Palma, Canary Islands: volcanic rift zone reconfiguration as a precursor to volcano flank instability?  

Microsoft Academic Search

The Cumbre Vieja volcano is the youngest component of the island of La Palma. It is a very steep-sided oceanic island volcano, of a type which may undergo large-scale lateral collapse with little precursory deformation. Reconfiguration of the volcanic rift zones and underlying dyke swarms of the volcano is used to determine the present degree of instability of the volcano.

S. J. Day; J. C. Carracedo; H. Guillou; P. Gravestock

1999-01-01

65

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

Microsoft Academic Search

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

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

2003-01-01

66

Electromagnetic Imaging and Seismotectonics of Mud Volcanoes in Andaman Islands  

NASA Astrophysics Data System (ADS)

Stress perturbations from large earthquakes are capable of causing significant changes in different physical properties of the subsurface such as electrical conductivity, temperature and rheoloy. The Mw 9.0 Sumatra earthquake on December 26, 2004 has stimulated mud volcanic activity on the Island of Bartang in the Middle Andaman Islands and at Diglipur in North Andamans. Relation between large earthquakes and mud volcano eruptions are common but the exact accelerating / triggering mechanisms are little understood (Mellors et al., 2007, JGR, 112, B04304). Here, we examined Geomagnetic Depth Sounding (GDS) and Long period MagnetoTelluric (LMT) data sets that image the electrical conductivity and variations associated with the subsurface stress environment. Two profiles in middle and north Andamans brings out localized anomalies associated with mud volcano. The possible cause for this electrical conductivity anomaly could be due to presence of fluids along a fractured fault/fissure. Continous monitoring of these mud volcanoes will facilitate inferring the accumulation/built up of the stress in the study area. In the present study, we discuss and highlight the significance of EM imaging of electrical conductivity (by GDS and AMT/MT/LMT) as a marker of fluid distribution and its influence on the reactivation of rheological asperity in triggering seismic activity in Andaman Island.

Subba Rao, Pbv; Singh, Ak

2012-07-01

67

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

68

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

Code of Federal Regulations, 2010 CFR

50 Ç Wildlife and Fisheries Ç 11 Ç 2011-10-01 Ç 2011-10-01 Ç false Ç Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing Ç 24 Ç Table 24 to Part 679 Ç Wildlife and Fisheries Ç FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC...

2011-10-01

69

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

Code of Federal Regulations, 2010 CFR

50 Ç Wildlife and Fisheries Ç 13 Ç 2012-10-01 Ç 2012-10-01 Ç false Ç Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing Ç 24 Ç Table 24 to Part 679 Ç Wildlife and Fisheries Ç FISHERY CONSERVATION AND MANAGEMENT, NATIONAL OCEANIC...

2012-10-01

70

Eruption of Alkaline Basalts Prior to the Calc-alkaline Lavas of Mt. Cleveland Volcano, Aleutian Arc, Alaska  

NASA Astrophysics Data System (ADS)

Mt. Cleveland is a 1,730 m stratovolcano, located on Chuginadak Island, that has erupted at least 23 times historically, with the latest occurring in August 2005. Major, trace, and REE analyses of 63 samples from Mt. Cleveland, including 8 from proximal cinder cones and 4 from andesitic domes on the lower flanks, identify two distinct lava suites. Modern Cleveland (MC) basalts to dacites (50.5-66.7 wt.% SiO2) exhibit a calc-alkaline differentiation trend. Major element trends suggest crystal fractionation of plagioclase +/- ortho- and clinopyroxene in MC lavas and olivine in cinder cone deposits. Resorption textures on plagioclase and olivine phenocrysts and multiple populations of plagioclase predominate throughout the MC suite suggesting magma mixing is a major process at Cleveland. Frothy white xenoliths of plagioclase + quartz + biotite are encased in glass and erupted as small pumiceous fragments in 2001. The partial resorption of the xenocrysts indicates assimilation is also an active crustal process at Cleveland. MC trace element spider diagrams exhibit a typical arc pattern in which HFS elements including Nb are depleted, and Pb and LIL elements are enriched. Th/La, Sm/La, and Sr, Nd, Pb, and Hf isotopic ratios indicate both a North Pacific MORB and a sediment component in the source of modern Cleveland lavas, consistent with sediment flux estimates of 90 to 95 m3/m/yr and an updip sediment thickness of 1300 to 1400 meters. Average 206Pb/204Pb, 207Pb/204Pb, 87Sr/86Sr, and 143Nd/144Nd values for the calc-alkaline suite are 18.93, 15.58, 0.70345, and 0.51303 respectively. The second suite consists of 3 olivine-rich, mildly alkaline basalts (48.5-49.4 wt.% SiO2), of older stratigraphic position than MC lavas representing deposits from an older phase of activity (ancestral Cleveland, AC). La/Yb, Sr/Y, and Th/Nb ratios indicate lower degrees of partial melting, relative to MC lavas, and suggests presence of garnet in the source region. The AC lavas, however, are not similar to the eclogite melts that have created adakites in the western Aleutians. 206Pb/204Pb, 207Pb/204Pb, 87Sr/86Sr, and 143Nd/144Nd isotopic compositions for one of the alkali basalts are 18.60, 15.52, 0.70286, and 0.51315 respectively, which suggest, little sediment contributed to the source of AC lavas.

Bridges, D. L.; Nicolaysen, K. P.

2005-12-01

71

Crustal structure along the Aleutian island arc: New insights from receiver functions constrained by active-source data  

NASA Astrophysics Data System (ADS)

Moho depth and Vp/Vs estimates from stacking phases of receiver functions along the Aleutian island arc give new constraints on its composition and structure. They expand on the current understanding of island arcs and their relationship to continental crust production. We also present an approach for including constraints from active-source data in receiver function analysis in a region with sparse data coverage to complement this analysis. Moho depth averages 37.5 km with an average uncertainty of 2.5 km along the entire arc. Excluding the westernmost island of Attu yields an average crustal thickness of 38.5 ± 2.9 km. The Vp/Vs ratio decreases moving eastward along the arc with an average value of 1.80 in the western and central portion of the arc built on oceanic crust, but 1.63 in the eastern section built on continental crust. This may reflect tectonic and compositional changes along the arc. However, overall the arc appears more mafic than continental crust. Near-constant crustal thickness, despite significant compositional changes, may indicate that nonmagmatic processes such as erosion and isostasy act to regulate arc thickness. Additionally, strong conversions from an upper crustal magma chamber are observed beneath Akutan Island, confirming and clarifying the geometry of the magma body inferred from other techniques. They indicate a volcanic body much larger than the eruptive edifice, a feature that must persist between eruptive cycles.

Janiszewski, Helen A.; Abers, Geoffrey A.; Shillington, Donna J.; Calkins, Josh A.

2013-08-01

72

Growth and collapse of the Reunion Island volcanoes  

NASA Astrophysics Data System (ADS)

This work presents the first exhaustive study of the entire surface of the Reunion Island volcanic system. The focus is on the submarine part, for which a compilation of all multibeam data collected during the last 20 years has been made. Different types of submarine features have been identified: a coastal shelf, debris avalanches and sedimentary deposits, erosion canyons, volcanic constructions near the coast, and seamounts offshore. Criteria have been defined to differentiate the types of surfaces and to establish their relative chronology where possible. Debris avalanche deposits are by far the most extensive and voluminous formations in the submarine domain. They have built four huge Submarine Bulges to the east, north, west, and south of the island. They form fans 20-30 km wide at the coastline and 100-150 km wide at their ends, 70-80 km offshore. They were built gradually by the superimposition and/or juxtaposition of products moved during landslide episodes, involving up to several hundred cubic kilometers of material. About 50 individual events deposits can be recognized at the surface. The landslides have recurrently dismantled Piton des Neiges, Les Alizés, and Piton de La Fournaise volcanoes since 2 Ma. About one third are interpreted as secondary landslides, affecting previously emplaced debris avalanche deposits. On land, landslide deposits are observed in the extensively eroded central area of Piton des Neiges and in its coastal areas. Analysis of the present-day topography and of geology allows us to identify presumed faults and scars of previous large landslides. The Submarine Bulges are dissected and bound by canyons up to 200 m deep and 40 km long, filled with coarse-grained sediments, and generally connected to streams onshore. A large zone of sedimentary accumulation exists to the north-east of the island. It covers a zone 20 km in width, extending up to 15 km offshore. Volcanic constructions are observed near the coast on both Piton des Neiges and Piton de la Fournaise volcanoes and are continuations of subaerial structures. Individual seamounts are present on the submarine flanks and the surrounding ocean floor. A few seem to be young volcanoes, but the majority are probably old, eroded seamounts. This study suggests a larger scale and frequency of mass-wasting events on Reunion Island compared to similar islands. The virtual absence of downward flexure of the lithosphere beneath the island probably contributes to this feature. The increased number of known flank-failure events has to be taken into consideration when assessing hazards from future landslides, in particular, the probability of landslide-generated tsunamis.

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

2008-04-01

73

Ritter Island Volcano-lateral collapse and the tsunami of 1888  

Microsoft Academic Search

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

Steven N. Ward; Simon Day

2003-01-01

74

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

Microsoft Academic Search

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 ~350km3 of basalt through rhyolite has produced a 30km, arc front chain of nested calderas and overlapping stratovolcanoes. ELVC has experienced as many as five major caldera-forming eruptions, the most

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

2009-01-01

75

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

76

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

77

The 1997 Eruption of Okmok Volcano, Alaska, a Synthesis of Remotely Sensed Data  

Microsoft Academic Search

Okmok Volcano in the central Aleutian Islands erupted in February of 1997. The eruption produced a lava flow in the central caldera over 5.5 x107 m3 in volume over 7.5 km2. This caldera is the most active of the Aleutian Arc, and is now the focus of international multidisciplinary studies. A synthesis of remotely sensed data (AIRSAR, derived DEMs, Landsat

L. Moxey; J. Dehn; K. Papp; M. Patrick; R. Guritz

2001-01-01

78

Paleosecular variation and GAD studies of 0-2 Ma flow sequences from the Aleutian Islands, Alaska  

NASA Astrophysics Data System (ADS)

A study was undertaken in the late 1960s to investigate paleosecular variations of the geomagnetic field as recorded in volcanic rocks from the Aleutian Islands. The early results were internally consistent but to be wholly credible by today's standards needed more detailed demagnetization. Complete thermal demagnetization protocols have been applied to the unmeasured archived samples from the six flow sequences used in the initial study, and 40Ar/39Ar techniques have been used to improve the time resolution. The flow sequences have ages ranging from about 50 ka to 2 Ma, and the number of sequential flows in the individual sequences varies from 8 to 21. After strict selection criteria were applied (MAD < 5°, ?95 < 5°) for both demagnetization data from samples and samples within one flow, the number of acceptable flows per flow sequence dropped to between 5 and 15. With the exception of a sequence showing transitional field behavior, the between-flow dispersion and the ?95 values for the other sequences were notably low with respect to secular variation models, and their mean directions were very close to the GAD field. Since the time represented by the individual sequences is not well determined, the low dispersion could represent very short eruption times. In contrast, the lack of dispersion with respect to the GAD field can be taken to indicate good time averaging. Since the locations of the sampled flows are at roughly the same latitude (about 50°N) but are spread over about 10° of longitude, the dispersion was calculated for both the locality-means and the flow-means. These data represent the whole 2 Myr and give a dispersion which is lower than current secular variation models predict. A similar data set published for locations in western Canada that are at roughly the same latitude and overlap in age with the Aleutian sites gives dispersions that are close to the model predictions. At face value this can be interpreted as indicating low secular variation for the Aleutian sites.

Stone, David B.; Layer, Paul W.

2006-04-01

79

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

80

Remote sensing for active volcano monitoring in Barren Island, India  

SciTech Connect

The Barren Island Volcano, situated in the Andaman Sea of the Bay of Bengal, erupted recently (March, 1991) after a prolonged period of quiescence of about 188 years. This resumed activity coincides with similar outbreaks in the Philippines and Japan, which are located in an identical tectonic environment. This study addresses (1) remote sensing temporal monitoring of the volcanic activity, (2) detecting hot lava and measuring its pixel-integrated and subpixel temperatures, and (3) the importance of SWIR bands for high temperature volcanic feature detection. Seven sets of TM data acquired continuously from 3 March 1991 to 8 July 1991 have been analyzed. It is concluded that detectable pre-eruption warming took place around 25 March 1991 and volcanic activity started on 1 April 1991. It is observed that high temperature features, such as an erupting volcano, can register emitted thermal radiance in SWIR bands. Calculation of pixel-integrated and sub-pixel temperatures related to volcanic vents has been made, using the dual-band method. 6 refs.

Bhattacharya, A.; Reddy, C.S.S.; Srivastav, S.K. (National Remote Sensing Agency, Hyderabad (India))

1993-08-01

81

The forensics of sub-surface processes on island volcanoes from integrated geodetic observations: results from Tenerife and Montserrat (Invited)  

Microsoft Academic Search

Spatio-temporal variations in geodetic signals at active volcanoes provide important insight on governing subsurface processes. This contribution explores the phenomenology of volcanic unrest and eruptive activity from the perspective of both ground deformation and gravimetric investigations at an ocean island volcanic complex (Tenerife, Canary Islands) and an active andesitic arc volcano (Soufrière Hills volcano [SHV], Montserrat). Despite their marked differences

J. Gottsmann

2009-01-01

82

Economic and engineering considerations for geothermal development in the Makushin Volcano Region of Unalaska Island, Alaska  

SciTech Connect

Large vapor-dominated hydrothermal reservoirs are suspected to exist in the region marked by fumarole fields on the southeast flank of Makushin Volcano on Unalaska Island, Alaska. In this paper, economic and engineering considerations with respect to potential hydrothermal development in the Makushin Volcano region are presented.

Reeder, J.W.; Economides, M.J.; Markle, D.R.

1982-10-01

83

Diffuse emission of carbon dioxide, methane, and helium-3 from Teide volcano, Tenerife, Canary Islands  

Microsoft Academic Search

Diffuse emission of CO2, CH4 and 3He was investigated in the summit crater of Teide volcano, Tenerife, Canary Islands. The results indicate that Teide volcano releases abundant CO2 not only from its active crater, but also from its flanks as diffuse soil emanations. The spatial distribution of these emanations correlates quite closely with that of geothermal anomalies and manifestations. Our

Pedro A. Hernández; Nemesio M. Pérez; José M. Salazar; Shun'ichi Nakai; Kenji Notsu; Hiroshi Wakita

1998-01-01

84

Diffuse emission of carbon dioxide, methane, and helium-3 from Teide Volcano, Tenerife, Canary Islands  

Microsoft Academic Search

Diffuse emission of CO2, CH4 and ³He was investigated in the summit crater of Teide volcano, Tenerife, Canary Islands. The results indicate that Teide volcano releases abundant CO2 not only from its active crater, but also from its flanks as diffuse soil emanations. The spatial distribution of these emanations correlates quite closely with that of geothermal anomalies and manifestations. Our

Pedro A. Hernfindez; Nemesio M. Pérez; José M. Salazar; Shun'ichi Nakai; Kenji Notsu; Hiroshi Wakita

1998-01-01

85

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

SciTech Connect

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 the communities of Akutan, False Pass, King Cove and Nelson Lagoon. Priority was given to these smaller communities as they tend to have the residences most in need of weatherization and energy conservation measures. Local residents were trained to provide all three aspects of the project: weatherization, energy conservation education and a home energy and safety review. If the total energy saved by installing these products is a 25% reduction (electrical and heating, both of which are usually produced by combustion of diesel fuel), and the average Alaska home produces 32,000 pounds of CO2 each year, so we have saved about: 66 homes x 16 tons of CO2 each year x .25 = 264 tons of CO2 each year.

Bruce Wright

2011-08-30

86

A Location and Travel-Time Study of Aleutian Islands Explosions and Earthquakes.  

National Technical Information Service (NTIS)

Travel-time anomalies from the LONG SHOT explosion on Amchitka Island are used to locate the Flexbag explosion approximately 70 km southwest of LONG SHOT. The results obtained using anomalies and various teleseismic networks indicate location errors less ...

E. F. Chiburis R. O. Ahner

1969-01-01

87

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

88

On the absence of InSAR-detected volcano deformation spanning the 1995–1996 and 1999 eruptions of Shishaldin Volcano, Alaska  

Microsoft Academic Search

Shishaldin Volcano, a large, frequently active basaltic-andesite volcano located on Unimak Island in the Aleutian Arc of Alaska, had a minor eruption in 1995–1996 and a VEI 3 sub-Plinian basaltic eruption in 1999. We used 21 synthetic aperture radar images acquired by ERS-1, ERS-2, JERS-1, and RADARSAT-1 satellites to construct 12 coherent interferograms that span most of the 1993–2003 time

S. C. Moran; O. Kwoun; T. Masterlark; Z. Lu

2006-01-01

89

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

Code of Federal Regulations, 2011 CFR

...Islands Statistical and Reporting Areas ER15NO99.000 b. Coordinates...boundary of the Chukchi Sea, area 400, and east of 170°00... 53°18.95ⲠN, 167°51.06ⲠW. 519 South of...44.73ⲠW. 521 The area bounded by straight lines...

2011-10-01

90

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

91

Multistage mixing in subduction zones: Application to Merapi volcano (Java island, Sunda arc)  

Microsoft Academic Search

Many studies have argued for the contribution of at least three components, namely the mantle wedge, the subducted oceanic crust, and its sediment cover, to describe the geochemistry of island arc volcanics. However, isotope correlations reflecting a simple binary mixing can be observed at the scale of a single arc island or volcano. Here we investigate the possibility that these

Vinciane Debaille; Régis Doucelance; Dominique Weis; Pierre Schiano

2006-01-01

92

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

Microsoft Academic Search

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

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

2002-01-01

93

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

94

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

95

Ice record of a large eruption of Deception Island Volcano (Antarctica) in the XVIITH century  

Microsoft Academic Search

A well-marked volcanic ash layer was found at 145.9 m depth in a 154.3 m ice core recovered in 1981 on James Ross Island, Antarctic Peninsula. Ash composition analysis indicates that we are dealing with an eruption of the Deception Island volcano located some 200 km northwestward from James Ross Island. Regional lake sediments seem also to have recorded the

Alberto J. Aristarain; Robert J. Delmas

1998-01-01

96

Large Scale Failures on Volcanoes of Kurile Islands: the First Data  

Microsoft Academic Search

Investigations of air and space images of volcanoes of the Kurile arc, supplemented by observations from a vessel as well as by on-land field work on several islands, have allowed us to identify 23 active volcanoes with well-preserved horseshoe-shaped scars formed by large-scale edifice failures. Breaches of most of the scars (14 cases) range from 0.5 to 2 km wide,

A. Belousov; M. Belousova

2007-01-01

97

ERS SAR interferometry of an erupting volcano on a tropical island: Soufriere Hills volcano, Montserrat  

Microsoft Academic Search

SAR interferometry can, potentially, supply two types of useful information relevant to the 1995-99 eruption of Soufriere Hills Volcano, Montserrat: (i) the topography of the growing lava dome and its apron of pyroclastic flows, and (ii) the surface deformation of the volcano due to magma movement within. Phase information from ERS SAR data collected from July 1997 to November 1998

G. Wadge; B. Scheuchl; N. F. Stevens; D. A. Rothery; S. Blake; M. D. Palmer; C. Riley; A. Smith

1999-01-01

98

Ritter Island Volcano-lateral collapse and the tsunami of 1888  

NASA Astrophysics Data System (ADS)

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

Ward, Steven N.; Day, Simon

2003-09-01

99

The Canary Islands: An example of structural control on the growth of large oceanic-island volcanoes  

Microsoft Academic Search

Abstract Dike complexes, which are increasingly accepted as a common feature in the growth of most oceanic volcanoes, are well represented in the Canary Islands, where their deep structure can be readily observed through hundreds of infiltration galleries excavated for water mining. These intrusive complexes,have their surficial representation as narrow, clearly aligned clusters of emission centers that, cumulatively, form steep

J. c. Carracedo

1994-01-01

100

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

101

Inferring crustal structure in the Aleutian island arc from a sparse wide-angle seismic data set  

Microsoft Academic Search

Compressional seismic travel times from a relatively sparse wide-angle data set hold key information on the structure of a 800 km long section of the central Aleutian arc. Since the source and receiver locations form a swath along the arc crest that is ?50 km wide, we trace rays in 3-D for a collection of 8336 seismic refraction and reflection

Harm J. A. Van Avendonk; Donna J. Shillington; W. Steven Holbrook; Matthew J. Hornbach

2004-01-01

102

78 FR 12627 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Management...  

Federal Register 2010, 2011, 2012, 2013

...0648-BA93 Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian...fisheries of the BSAI in the Exclusive Economic Zone (EEZ) under the Fishery Management...has taken to minimize the significant economic impact on small entities...

2013-02-25

103

78 FR 15677 - Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab...  

Federal Register 2010, 2011, 2012, 2013

...0648-BC25 Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian...Amendment 42 would revise the annual economic data reports (EDRs) currently required...Council) and NMFS use to study the economic impacts of the CR Program on...

2013-03-12

104

A re-evaluation of the role of killer whales Orcinus orca in a population decline of sea otters Enhydra lutris in the Aleutian Islands and a review of alternative hypotheses  

Microsoft Academic Search

During the past 15-20 years, sea otters Enhydra lutris in the Aleutian Islands, Alaska, USA, experienced a drastic decrease in population size. It has been hypo- thesized that an increase in killer whale Orcinus orca predation was the primary cause of this decline. 2. Causation of the decline by increased killer whale predation is now considered a textbook case of

Katie KUKER; Lance BARRETT-LENNARD

2010-01-01

105

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

106

Volcanoes.  

ERIC Educational Resources Information Center

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

Tilling, Robert I.

107

Volcanoes.  

ERIC Educational Resources Information Center

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

Tilling, Robert I.

108

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

Microsoft Academic Search

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

Frank A. Trusdell; Richard B. Moore; Maurice Sako; Randall A. White; Stuart K. Koyanagi; Ramon Chong; Juan T. Camacho

2005-01-01

109

Shallow flank deformation at Cumbre Vieja volcano (Canary Islands): Implications on the stability of steep-sided volcano flanks at oceanic islands  

NASA Astrophysics Data System (ADS)

Volcano flank instability has been recognized at many volcanoes around the globe. Structural, morphological, geodetic and geophysical evidence supports the continuous deformation of their flanks. While identification of instability has been recognized in well-documented examples, until recently the initial stages of such processes have been difficult to capture. Using a combination of geological, geodetic and geophysical data analysis, we study the stability of the Cumbre Vieja. New descending radar interferometric data, covering a volcanologically quiet period between 1992 and 2008 at Cumbre Vieja, indicate movement away from the satellite on the western volcano flank. Using an inversion of stacked velocity maps, we determine the geometry and slip for a near-horizontal dislocation beneath the western flank of Cumbre Vieja. Our ground deformation modelling results (position and depth) are in agreement with a low-density anomaly constrained by gravity data. The previously undetected intereruptive ground deformation at Cumbre Vieja volcano flanks was explained as an indicator of a kinematic passive response model of the flank, where the flanks were mobilized only during periods of magmatic activity (shallow dike intrusions) and remained stable and undeformed during intereruptive periods. Here, we present new results indicating that active creeping stress release due to gravitational loading is also a dominant deformation mechanism for (current) intereruptive periods at Cumbre Vieja, which would contribute positively to the stabilization of the edifice and reduce the associated hazard related to the volcano flank dynamics. This study at Cumbre Vieja can be considered as a prototype for similar volcanoes around the Macaronesian islands group (e.g., Fogo, Teide, El Hierro, Pico) and elsewhere.

González, Pablo J.; Tiampo, Kristy F.; Camacho, Antonio G.; Fernández, José

2010-09-01

110

Mercury, arsenic, cadmium, chromium lead, and selenium in feathers of pigeon guillemots (Cepphus columba) from Prince William Sound and the Aleutian Islands of Alaska.  

PubMed

Arsenic, cadmium, chromium, lead, manganese, mercury and selenium were analyzed in the feathers of pigeon guillemots (Cepphus columba) from breeding colonies in Prince William Sound and in the Aleutian Islands (Amchitka, Kiska) to test the null hypothesis that there were no differences in metal levels as a function of location, gender, or whether the birds were from oiled or unoiled areas in Prince William Sound. Birds from locations with oil from the Exxon Valdez Oil Spill in the environment had higher levels of cadmium and lead than those from unoiled places in Prince William Sound, but otherwise there were no differences in metal levels in feathers. The feathers of pigeon guillemots from Prince William Sound had significantly higher levels of cadmium and manganese, but significantly lower levels of mercury than those from Amchitka or Kiska in the Aleutians. Amchitka had the lowest levels of chromium, and Kiska had the highest levels of selenium. There were few gender-related differences, although females had higher levels of mercury and selenium in their feathers than did males. The levels of most metals are below the known effects levels, except for mercury and selenium, which are high enough to potentially pose a risk to pigeon guillemots and to their predators. PMID:17765292

Burger, Joanna; Gochfeld, Michael; Sullivan, Kelsey; Irons, David

2007-08-31

111

Large Scale Failures on Volcanoes of Kurile Islands: the First Data  

NASA Astrophysics Data System (ADS)

Investigations of air and space images of volcanoes of the Kurile arc, supplemented by observations from a vessel as well as by on-land field work on several islands, have allowed us to identify 23 active volcanoes with well-preserved horseshoe-shaped scars formed by large-scale edifice failures. Breaches of most of the scars (14 cases) range from 0.5 to 2 km wide, indicating moderate failure volumes - around 1 km3. The two largest scars were 4 km-across (which were formed by failures with volumes about 5 km3) belong to Milne and Sinarka volcanoes. Most of the failures occurred on andesitic volcanoes which dominate in the region. At least 3 volcanoes (Harimkotan, Sinarka and Mendeleev) experienced multiple (3 or more) failures. Only two failures occurred on dominantly basaltic stratovolcanoes (Alaid and Atsonupuri). Most of the collapsed volcanoes of the Kurile arc exhibit strong hydrothermal alteration of rocks inside their horseshoe-shaped scars, and their debris avalanche deposits contain a large proportion of clayey material. This suggests that weakening of rocks composing volcanic edifices caused by hydrothermal alteration played a leading role in gravitational destabilization of the volcanoes. In 50% of the cases, failures were followed by magmatic activity; the horseshoe- shaped craters are partially filled by younger volcanic cones. This indicates that the failure surfaces intersected upper parts of feeding channels of active volcanoes, and the failures may have been triggered by magma intruding into the volcanic edifices. Apart from failures on active volcanoes there are multiple rather large scale (>0,01 km3) failures along sea cliffs of the islands which involved volcanic rocks. These cases are transitional to non-volcanic failures. Debris avalanches of all of the studied failures traveled far beyond the shore line of Okhotskoye Sea or the Pacific Ocean and thus their exact lengths and drop heights are unknown. The debris avalanches obviously generated tsunamis upon entering the sea. The studied failures have Late Pleistocene-Holocene ages; and one historical case failure of Harimkotan volcano on January 8, 1933 with the volume 0.4 km3. The failure generated a tsunami up to 20 m high with 2 reported victims on nearby Onekotan Island. The failure was followed by a strong, 5-day-long Plinian eruption with deposition of pyroclastic flows and subsequent dome growth over several months.

Belousov, A.; Belousova, M.

2007-12-01

112

Measuring deformation associated with magmatic processes at Cerro Azul Volcano, Galapagos Islands, Ecuador with InSAR  

Microsoft Academic Search

The Galapagos Islands are an active volcanic island chain in the eastern Pacific Ocean off the west coast of Ecuador. Cerro Azul volcano is located on the southern tip of Isabella Island and experienced two eruptions in 10 years. The eruptions started on September 15, 1998 and May 29, 2008 and lasted 51 days and 20 days respectively. Using radar

S. Baker; F. Amelung

2009-01-01

113

Volcanoes  

NSDL National Science Digital Library

Volcanoes is part of an online series of modules entitled Exploring the Environment. Emphasizing an integrated approach to environmental Earth Science education through problem based-learning, this module asks students to look at four different situations involving volcanoes, research the situations, and make decisions about them. Information about the three volcanic areas under exploration (Mt. Hood, Kilauea, and Yellowstone) is given through maps, movies, and videos. Additional information covers plate tectonics, locations of volcanoes, volcano monitoring and hazards, how to deal with volcano threats, lavas, eruption types, and risk analysis. Once students have gone through the information, they make real-life decisions about building near volcanoes, and the possibility of eruptions in the near future. There are teacher resources, a reference for problem-based learning, and links for more information.

114

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

Microsoft Academic Search

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,

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

2010-01-01

115

Volcanoes  

NSDL National Science Digital Library

Students investigate the processes that build volcanoes, the factors that influence different eruption types, and the threats volcanoes pose to their surrounding communities. They use what they have learned to identify physical features and eruption types of several actual volcanic episodes.

Foundation, Wgbh E.

2005-12-17

116

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

NASA Astrophysics Data System (ADS)

The topography of Piton de la Fournaise volcano (PdF) differs from the classic view of basaltic shield volcanoes as it is characterized by (1) several steep slope zones on its flanks and (2) a large U-shaped caldera, the Enclos-Grand Brûlé structure (EGBS). Most of these structures were previously interpreted as the scars of lateral landslides, the deposits of which cover the submarine flanks of PdF. We carried out a detailed analysis of the morphology of PdF, which reveals that the steep slope zones form two independent, circumferential structures that continue into the caldera. The development of circumferential steep slopes on volcano flanks may have several origins: constructive, destructive, and deformation processes. We interpret those processes acting on PdF as caused by the spreading of the volcanic edifice above a weak hydrothermal core, leading to outward displacements and a summit extensive stress field. The continuity of the steep slope on both sides of the EGBS escarpments suggests that this structure was not caused by a 4.5 ka old giant landslide as it is usually proposed but is due to a mainly vertical collapse. The recent debris avalanche deposits east of the island indicate that this event likely destabilized part of the submarine flank. We propose that the collapse of the Grand Brûlé, the lower half of the EGBS, was due to the downward drag related to the dense intrusive complex of the Alizés volcano, which is located 1 km below the Grand Brûlé. The collapse of the Enclos is interpreted as the consequence of the deformation of the hydrothermal system of the pre-Enclos volcano. Although the continuity of the geological and morphological structures between the Enclos and the Grand Brûlé suggests a narrow link between these two collapse events, their chronology and relationship are still uncertain. Finally, we hypothesize that the persistence of the NE and SE rift zones during the last 150 ka, despite the large changes of the topography related to the recurrent flank destabilizations, is linked to a deep sources, which can be either underlying crustal faults or the continuous downward subsidence of the Alizés intrusive complex.

Michon, Laurent; Saint-Ange, Francky

2008-03-01

117

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

118

3-D velocity model beneath Taal Volcano, Luzon Island Philippines  

NASA Astrophysics Data System (ADS)

We derive a three dimensional velocity model of seismic waves beneath Taal Volcano, Philippines, from about 2300 local earthquakes recorded by the Taal Volcano seismic network during the time period from March 2008 to March 2010. In the early data processing stage, with the cross-correlation functions of continuous record of station pairs, unexpected linear drifting of clock time was clearly identified. The drifting rates of each problematic station were determined and the errors were corrected before further processing. With the corrected data, we first determined initial locations by using the program HYPO71 and the reference 1-D global model ak135. 749 well-located events with 3381 P-wave and 2896 S-wave arrivals were used to derive the 'minimum 1-D velocity model' with the program VELEST developed by Kissling to further improve the 1-D velocity model and event locations. With the robust 1-D velocity model and improved event locations, we inverted a high-resolution 3-D velocity model by using the program LOTOS-10 developed by Koulakov. We present the derived 3-D model and discuss its tectonic implications.

You, S.; Konstantinou, K. I.; Gung, Y.; Lin, C.

2011-12-01

119

Geochemical Composition of Volcanic Rocks from the May 2003 Eruption of Anatahan Volcano, Mariana Islands  

Microsoft Academic Search

The first historical eruption of Anatahan volcano began on May 10, 2003, from the easternmost of the island's two craters. Samples of tephra, scoria, and bombs, collected in May by a MARGINS-supported rapid-response team, were analyzed for 34 trace elements by solution ICP-MS at Boston University and Sr-Nd-Pb isotopic composition at the University of Texas-Dallas. The new eruptive materials can

J. A. Wade; T. Plank; R. Stern; D. Hilton; T. P. Fischer; R. Moore; F. Trusdell; M. Sako

2003-01-01

120

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

Microsoft Academic Search

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

Fabio Luca Bonali; Claudia Corazzato; Alessandro Tibaldi

2011-01-01

121

Newly discovered submarine flank eruption at Stromboli volcano (Aeolian Islands, Italy)  

Microsoft Academic Search

The NW submarine portion of Stromboli volcano has been investigated by deep-towed sidescan sonar, bathymetric surveys, video camera runs and dredging during two research cruises in 2002 and 2004. The surveys resulted in the identification of an extensive pillow lava field (106-107m3) at about 2300 m of water depth and 9 km from the shoreline of Stromboli Island. The pillow

A. Di Roberto; A. Bertagnini; M. Pompilio; F. Gamberi; M. P. Marani; A. M. Rosi

2008-01-01

122

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

123

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

124

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

125

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

SciTech Connect

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

Amundsen, C.C.

1985-01-01

126

Crustal structure of Deception Island volcano from P wave seismic tomography: Tectonic and volcanic implications  

NASA Astrophysics Data System (ADS)

Deception Island (62°59'S, 60°41'W) is an active volcano located in the Bransfield Strait between the Antarctic Peninsula and the South Shetland Islands. The island is composed of rocks that date from <0.75 Ma to historical eruptions (1842, 1967, 1969, and 1970), and nowadays most of its activity is represented by vigorous hydrothermal circulation, slight resurgence of the inner bay floor, and intense seismicity, with frequent volcano-tectonic and long-period events. In January 2005 an extensive seismic survey took place in and around the island to collect high-quality data for a high-resolution P wave velocity tomography study. A total of 95 land and 14 ocean bottom seismometers were deployed, and more than 6600 air gun shots were fired. As a result of this experiment, more than 70,000 travel time data were used to obtain the velocity model, which resolves strong P wave velocity contrasts down to 5 km depth. The joint interpretation of the Vp distribution together with the results of geological, geochemical, and other geophysical (magnetic and gravimetric) measurements allows us to map and interpret several volcanic features of the island and surroundings. The most striking feature is the low P wave velocity beneath the caldera floor which represents the seismic image of an extensive region of magma beneath a sediment-filled basin. Another low-velocity zone to the east of Deception Island corresponds to seafloor sedimentary deposits, while high velocities to the northwest are interpreted as the crystalline basement of the South Shetland Islands platform. In general, in the tomographic image we observe NE-SW and NW-SE distributions of velocity contrasts that are compatible with the regional tectonic directions and suggest that the volcanic evolution of Deception Island is strongly conditioned by the Bransfield Basin geodynamics.

Zandomeneghi, Daria; Barclay, Andrew; Almendros, Javier; IbañEz Godoy, Jesús M.; Wilcock, William S. D.; Ben-Zvi, Tami

2009-06-01

127

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

128

Evidence for Deep Tectonic Tremor in the Alaska-Aleutian Subduction Zone  

NASA Astrophysics Data System (ADS)

We search for, characterize, and locate tremor not associated with volcanoes along the Alaska-Aleutian subduction zone using continuous seismic data recorded by the Alaska Volcano Observatory and Alaska Earthquake Information Center from 2005 to the present. Visual inspection of waveform spectra and time series reveal dozens of 10 to 20-minute bursts of tremor throughout the Alaska-Aleutian subduction zone (Peterson, 2009). Using autocorrelation methods, we show that these tremor signals are composed of hundreds of repeating low-frequency earthquakes (LFEs) as has been found in other circum-Pacific subduction zones. We infer deep sources based on phase arrival move-out times of less than 4 seconds across multiple monitoring networks (max. inter-station distances of 50 km), which are designed to monitor individual volcanoes. We find tremor activity is localized in 7 segments: Cook Inlet, Shelikof Strait, Alaska Peninsula, King Cove, Unalaska-Dutch Harbor, Andreanof Islands, and the Rat Islands. Locations along the Cook Inlet, Shelikof Straight and Alaska Peninsula are well constrained due to adequate station coverage. LFE hypocenters in these regions are located on the plate interface and form a sharp edge near the down-dip limit of the 1964 M 9.2 rupture area. Although the geometry, age, thermal structure, frictional and other relevant properties of the Alaska-Aleutian subduction are poorly known, it is likely these characteristics differ along its entire length, and also differ from other subduction zones where tremor has been found. LFE hypocenters in the remaining areas are also located down-dip of the most recent M 8+ megathrust earthquakes, between 60-75 km depth and almost directly under the volcanic arc. Although these locations are less well constrained, our preliminary results suggest LFE/tremor activity marks the down-dip rupture limit for megathrust earthquakes in this subduction zone. Also, we cannot rule out the possibility that our observations could be related deep magmatic processes.

Brown, J. R.; Prejean, S. G.; Beroza, G. C.; Gomberg, J. S.; Haeussler, P. J.

2010-12-01

129

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

130

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

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

131

Contrasting andesitic magmatic systems in adjacent North Island volcanoes, New Zealand: implications for predicting eruptions  

NASA Astrophysics Data System (ADS)

For active or dormant andesite volcanoes, detailed, stratigraphically controlled, geochemical and petrological information enables an understanding of the magma supply and plumbing system feeding eruptions at the surface. This can establish a basis for predictive eruption models and thus for hazard prediction and management. The potential for petrography to inform volcanic hazard management is demonstrated by comparing two andesitic volcanoes located at the southern end of the Taupo Volcanic Zone in New Zealand's North Island. Ngauruhoe has been constructed over the past 3-5 ka and last erupted in 1975. Nearby Ruapehu has a much longer eruptive history extending back beyond 230 ka B.P. Despite their close spatial proximity, the two volcanoes show geochemical contrasts suggesting that each magmatic system has operated separately. The petrology and geochemistry (major and trace element chemistry, U-series isotopes, Sr and Nd isotopes) of eruptives from each volcano reflect magma evolution in a complex magma storage and plumbing system with magma chemistry strongly influenced by fractional crystallisation and crustal assimilation but in the case of Ngauruhoe there is evidence for cyclicity in the evolution of magma batches and this appears to be driven by periodic replenishment of the magmatic system from the mantle. In contrast, the past 2 ka of eruptive history at Ruapehu reflects random tapping of shallow, volume magma reservoirs.

Price, R. C.; Smith, I. E.; Gamble, J. A.; Moebis, A.; Cronin, S. J.

2011-12-01

132

Carbon-14 ages of the past 20 ka of eruptive activity of Teide volcano, Canary Islands  

NASA Astrophysics Data System (ADS)

Teide volcano, the highest volcano on earth (3718 m a.s.l., >7 Km high) after Mauna Loa and Mauna Kea in the Hawaiian Islands, forms a volcanic complex in the centre of the Island of Tenerife. Its most recent eruptive activity (last 20 Ka) is associated with the very active NW branch of the 120º triple rift system of the island. Most of the eruptions of Tenerife during the past 20 ka have occurred along this volcanic feature, frequently in the production of extensive mafic and felsic lava flows, many of which reached the coast, crossing what is now one of the most densely populated areas of Tenerife and of any oceanic island in the world. However, despite numerous previous studies, very important basic geological information is still lacking, in particular dating of these flows to construct a geochronological framework for the evolution of the Teide-NW rift system, and a scientifically based, much needed volcanic hazard assessment. New carbon-14 ages, obtained via coupled mass spectrometer, and others in process, provide important time constraints on the evolution of Teide's volcanic system, the frequency and distribution of its eruptions, and the associated volcanic hazards. Most of the eruptions are not related to the Teide stratovolcano, which apparently had only one eruption in the last 20 Ka about 1240 ± 60 years BP, but to the Pico Viejo volcano (17570 ± 150 years BP), flank parasitic vents (Mña. Abejera upper vent, 5170 ± 110 years BP; Mña. Abejera lower vent, 4790 ± 70 years BP; Mancha Ruana, 2420 ± 70 years BP; Mña. La Angostura, 2010 ± 60 years BP and Roques Blancos, 1790 ± 60 years BP) and the NW rift (Mña. Chío, 3620 ± 70 years BP). Although the volcanic activity during the past 20 ka included the involvement of at least 7 voluminous phonolitic flank vents in the northern, more unstable slopes of the Teide, it took place without any apparent response of the volcano; on the contrary, these eruptions seemed to progressively buttress and enhance the stability of Teide Volcano. Conversely, the occurrence of these flank eruptions, combined with the Pico Viejo and NW rift eruptions, poses a very high lava-flow risk to the now densely populated areas to the north and west of Tenerife, which have been almost entirely resurfaced during the past 20.000 years.

Carracedo, J. C.; Guillou, H.; Paterne, M.; Pérez Torrado, F. J.; Paris, R.; Badiola, E. R.

2003-04-01

133

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

134

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

135

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

136

A tectonic earthquake sequence preceding the April-May 1999 eruption of Shishaldin Volcano, Alaska  

Microsoft Academic Search

On 4 March 1999, a shallow ML 5.2 earthquake occurred beneath Unimak Island in the Aleutian Arc. This earthquake was located 10-15 km west of Shishaldin Volcano, a large, frequently active basaltic-andesite stratovolcano. A Strombolian eruption began at Shishaldin roughly 1 month after the mainshock, culminating in a large explosive eruption on 19 April. We address the question of whether

S. C. Moran; S. D. Stihler; J. A. Power

2002-01-01

137

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

138

76 FR 44297 - Fisheries of the Exclusive Economic Zone Off Alaska; Allocating Bering Sea and Aleutian Islands...  

Federal Register 2010, 2011, 2012, 2013

...BSAI) Crab Rationalization Program (CR Program) allocates BSAI crab resources...Islands King and Tanner Crabs (FMP) and the CR Program to modify procedures for producing...to the FMP amended the FMP to include the CR Program. Regulations [[Page...

2011-07-25

139

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

140

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

NASA Astrophysics Data System (ADS)

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

LeMasurier, Wesley

2013-06-01

141

Volcano  

NSDL National Science Digital Library

This lesson plan is part of the DiscoverySchool.com lesson plan library for grades 6-8. It focuses on volcanoes and the destruction that results from eruptions. Students are given a scenario of massive volcanic destruction and have to come up with a plan to help those affected by the events. Included are objectives, materials, procedures, discussion questions, evaluation ideas, suggested readings, and vocabulary. There are videos available to order which complement this lesson, an audio-enhanced vocabulary list, and links to teaching tools for making custom quizzes, worksheets, puzzles and lesson plans.

Weisel, Frank

142

Living on the edge: Volcanic edifice failures along the north edge of the Aleutian Ridge  

NASA Astrophysics Data System (ADS)

Many Quaternary volcanoes in the Aleutian Island arc show evidence for catastrophic collapse and subsequent debris avalanche deposition on the seafloor. Active volcanoes in the central and western portions of the arc (177°E to 175°W) sit atop the northern edge of the ~4000 m-high Aleutian Ridge, constructed by arc volcanism starting at ~40 ma. This ridge drops off steeply to the north, providing significant runout potential for debris avalanches that flow into the Bering Sea. Reconnaissance studies have found subaerial evidence for large-scale collapse events at many of the volcanically active islands. The position of the Quaternary stratocones relative to the edge of the Aleutian ridge apparently controls their likelihood for collapse. Based on the absence of large pyroclastic sheets on the best-studied islands, most collapses were not accompanied by large-scale explosive eruptions, and thus were likely driven by gravitational failure instead of magmatic injection and caldera formation. GLORIA sidescan sonar data collected in the 1980s image hummocky debris on the seafloor north of several islands, notably Kiska, Gareloi, Tanaga, Kanaga, and Great Sitkin. Multibeam and backscatter data, acquired during the summer of 2005 with the 30 kHz Simrad EM300 system, corroborate the slide profile of several deposits first imaged by GLORIA. A debris avalanche deposit north of Kiska Island (177.6°E, 52.1°N), mapped in the greatest detail, has 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 profile across the short axis of the deposit documents a 500 m-thick, chaotic unit that appears to have either cut into or disturbed a sequence of well-bedded sediments. Despite its thickness, the chaotic unit has only a few tens of meters of surface elevation above the surrounding seafloor. The volume of the debris-avalanche deposit could be as much as 190 km3. This suggests that estimating volumes solely by bathymetric data may underestimate total volumes of debris deposition in areas of easily eroded/deformed sedimentary sequences.

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

2005-12-01

143

Variable SO2 emission rates for Anatahan volcano, the Commonwealth of the Northern Mariana Islands: Implications for deriving arc-wide volatile fluxes from erupting volcanoes  

Microsoft Academic Search

We report new spectroscopic-derived SO2 emission rates for Anatahan volcano, Mariana Islands. Measurements of SO2 fluxes reveal large fluctuations over the 2003–2005 period - from 78 kg s?1 which occurred on the same day as resurgent volcanic activity (March, 2005) to 50 kg s?1 and 25 kg s?1 made days\\/weeks after the start of eruptive sequences in 2003 and 2004

D. R. Hilton; T. P. Fischer; A. J. S. McGonigle; J. M. de Moor

2007-01-01

144

Physical volcanology and structural development of Cerro Azul Volcano, Isabela Island, Galápagos: implications for the development of Galápagos-type shield volcanoes  

Microsoft Academic Search

Cerro Azul is an active basaltic shield volcano forming the southwestern end of Isabela Island in the western Galápagos Archipelago. Ten eruptions have been witnessed between 1932 and 1998, an average of one eruption every 6.6years. Although Cerro Azul has been constructed primarily by effusive Hawaiian-style eruptions, explosive hydrovolcanic eruptions have occurred intermittently from vents on the caldera floor and

Terry Naumann; Dennis Geist

2000-01-01

145

Tephrostratigraphy and petrological study of Chikurachki and Fuss volcanoes, western Paramushir Island, northern Kurile Islands: Evaluation of Holocene eruptive activity and temporal change of magma system  

Microsoft Academic Search

A tephrostratigraphic and petrological study of the Chikurachki (1816m)-Tatarinov-Lomonosov volcanic chain (CTL volcanic chain) and Fuss (1772m), located at the southern part of Paramushir Island in the northern Kurile Islands, was carried out to reveal the explosive eruption history during the Holocene and the temporal change of the magma systems of these active volcanoes. Tephra successions were described at 54

Takeshi Hasegawa; Mitsuhiro Nakagawa; Mitsuhiro Yoshimoto; Yoshihiro Ishizuka; Wataru Hirose; Sho-ichi Seki; Vera Ponomareva; Rybin Alexander

146

Radon-222 from the island of hawaii: deep soils are more important than lava fields or volcanoes.  

PubMed

The mean flux of radon-222 atoms from the island of Hawaii is 0.45 atom per square centimeter per second. Lava fields occupy 50 percent of the land area, but their radon flux is only 1 percent of that from deep volcanic soils. The island yields approximately 10 curies of radon-222 per hour to the air surrounding it. The radon-222 contribuition of volcanoes is negligible. PMID:17781932

Wilkening, M H

1974-02-01

147

Mantle Wedge Processes from Primitive Lavas in the Western Aleutians  

NASA Astrophysics Data System (ADS)

The 2005 Western Aleutian Volcano Expedition mapped more than 19,000 sq km of Aleutian seafloor and dredged >4000 kg of fresh lava from volcanic cones and other young, constructional features along more than 1600 km of arc length. The most interesting feature is the field of active seafloor volcanism discovered in the Ingenstrem Depression - a rectangular basin, approximately 60 km in length by 10-15 km wide along the Aleutian Ridge west of Buldir island, the western-most emergent Aleutian volcano. We found more than 90 volcanic cones and associated lava flows within and on the margins of this basin, which is bounded by WNW-oriented strike-slip faults. The largest cones are 2-4 km in diameter and 300-500 m high. Some appear to be offset by strike-slip faulting, but most are un-deformed, constructional features. A striking feature of Ingenstrem dredge samples is that they include an unusually large proportion of primitive lavas with whole-rock Mg#>0.60, including basalt, andesite and dacite. Basalts and basaltic andesites have moderately enriched trace element patterns (e.g., La/Yb 4-8, Sr/Y<30) and relatively radiogenic Sr (87/86Sr=0.7031-0.7034), typical of lavas from the Aleutians and other island arcs. In contrast, Ingenstrem primitive andesites and dacites have high Sr (700-2300 ppm) and strongly fractionated trace element patterns (Sr/Y>50), with low Y (<12 ppm) and HREE. Among these, andesites and dacites with high Sr/Y also have systematically higher SiO2, lower Y, and higher Mg#, Cr and Ni. Strontium isotope ratios in Ingenstrem lavas are inversely correlated with Sr/Y and SiO2, so the most felsic samples (66-67% SiO2) have the most fractionated trace element patterns (Sr/Y>120) and the least radiogenic Sr (87Sr/86Sr<0.7029). Interestingly, samples that span the full range of geochemical variability are found in close spatial association within the Ingenstrem Depression. In one case, primitive lavas within an individual dredge span almost the entire range of SiO2 and Sr/Y. The small length scale of compositional variation in primitive lavas implies significantly different melt temperatures (basalts ~1250C vs dacites ~1000C) and source compositions (87Sr/86Sr=0.7027-0.7034), over short distances at sub-Moho depths. This, in turn, requires advective transport of cold material through a hot mantle wedge `cold plumes': e.g., Ringwood, JGSL 74; Marsh AJS 76; Kelemen et al. ToG 03; Gerya & Yuen EPSL 03) or advective transport of hot material through a cold shallow mantle conductive layer (`hot fingers': e.g., Tatsumi et al. JGR 03; Tamura et al EPSL 02). In the first case, primitive dacites with high Sr/Y could be formed by reaction between low T melts of subducting eclogite and hotter residual peridotite in the wedge. In the second case, primitive dacites could be formed by reaction between fractionating basalt in sub-crustal magma chambers and surrounding, colder residual mantle in the lithosphere.

Yogodzinski, G. M.; Kelemen, P. B.; Wyatt, W. C.

2007-12-01

148

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

149

Assessment of the exposure of islanders to ash from the Soufriere Hills volcano, Montserrat, British West Indies  

Microsoft Academic Search

Background and Aims: The Soufriere Hills volcano, Montserrat, has been erupting since July 1995 and volcanic ash has fallen on the island throughout most of the eruption. The ash contains substantial quantities of respirable particles and unusually large amounts (15–20%) of the crystalline silica mineral, cristobalite. The purpose of the surveys described here, undertaken between December 1996 and April 2000,

A Searl; A Nicholl; P J Baxter

2002-01-01

150

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

151

Geochemical Composition of Volcanic Rocks from the May 2003 Eruption of Anatahan Volcano, Mariana Islands  

NASA Astrophysics Data System (ADS)

The first historical eruption of Anatahan volcano began on May 10, 2003, from the easternmost of the island's two craters. Samples of tephra, scoria, and bombs, collected in May by a MARGINS-supported rapid-response team, were analyzed for 34 trace elements by solution ICP-MS at Boston University and Sr-Nd-Pb isotopic composition at the University of Texas-Dallas. The new eruptive materials can be compared with an extensive suite of pre-existing volcanics (basalts through dacites) from Anatahan sampled by the USGS in 1990 and 1992, and analyzed by XRF and INAA. While most Mariana volcanoes erupt basalts and basaltic andesites, Anatahan is unusual for erupting a wide range of compositions, from basalt to dacite, and thus provides the best opportunity for addressing questions of magma evolution in this classic island arc. The newly erupted scoria and pumice are andesites and dacites that are among the most silicic materials erupted in the northern Mariana islands. The recent eruptives are highly homogeneous; 13 samples vary by only 3-5% relative standard deviation for incompatible trace elements. Isotopic compositions (0.703450 +/- 2 87Sr/86Sr and 18.806 +/- 5 206Pb/204Pb) are within the range of previously measured samples from Anatahan and other volcanic centers in the Marianas. The combined dataset for Anatahan defines virtually a single liquid line of descent. This is consistent with nearly-parallel REE patterns, and small variations in the ratios of the most incompatible trace elements (e.g., Th/Rb varies by <10% over the entire fractionation trend). Low values of Th/La and Th/Zr in Anatahan volcanics provide evidence against partial melting of crustal material as a source of the silicic magmas, as these ratios are highly senstive to apatite- and zircon- saturated crustal melts. Instead, the basalts, andesites and dacites of Anatahan appear to be related predominantly by crystal fractionation with little evidence for assimilation of crustal melts. The new data can also be used to make new inferences as to the source characteristics of Anatahan magma. Trace element ratios Th/La and Sm/La distinguish island-to-island differences in the subducted sediment components incorporated into the Mariana arc magmas. Most Mariana volcanics plot on a mixing line between depleted mantle and the bulk subducting sediment Th/La (0.14). Anatahan, however, mixes to slightly higher Th/La (0.16), which could be caused by the shallow loss of the top 50 m of the sedimentary column (pelagic clay) during subduction.

Wade, J. A.; Plank, T.; Stern, R.; Hilton, D.; Fischer, T. P.; Moore, R.; Trusdell, F.; Sako, M.

2003-12-01

152

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

153

Using numerical modeling to explore the origin of intrusion patterns on Fernandina volcano, Galapagos Islands, Ecuador  

NASA Astrophysics Data System (ADS)

Using parameterized finite element models, we investigate the emplacement of both radial and circumferential intrusions in the configuration observed at Fernandina volcano in the Galapagos Islands. When situated within the edifice at depths consistent with petrological and surface displacement data, inflation of a mildly oblate magma reservoir to the point of rupture can initiate either radial or circumferential intrusions in response to minor, volcanologically plausible variations in reservoir geometry (i.e., aspect ratio). In addition, more oblate reservoirs inject lateral sills into an inflation-derived stress field consistent with rotation about their propagation axis to form gently dipping radial dikes, a mode of behavior recently inferred from InSAR data at Fernandina. All three styles of intrusion occur in near-surface configurations consistent with field observations.

Chestler, Shelley R.; Grosfils, Eric B.

2013-09-01

154

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

155

Dismantling processes of basaltic shield volcanoes - origin of the Piton des Neiges breccias - Reunion Island  

NASA Astrophysics Data System (ADS)

Reunion Island is mainly composed by two volcanic massifs: the active Piton de la Fournaise to the southeast and the Piton des Neiges to the northwest that has been inactive for about 12000 years. The latter corresponds to a dismantled volcanic massif, deeply cut by valleys and by three vast depressions, called “cirques” around the centre of the volcano. They offer the opportunity to observe the inside of a basaltic shield volcano. The first work dealing with the origin of the “cirques” very quickly showed the existence of a significant cover of breccia deposits. These breccias were often interpreted as the result of a major stage of erosion considered as partly at the origin of the “cirques” formation. Geological campaigns mainly achieved in the “cirque de Salazie” (eastern of the Piton des Neiges), allow to establish a first typology based on morphological, phenomenological and sedimentary features of the deposits. Two main complexes of breccias have been distinguished. An old complex outcropping in the internal parts of the cirque and an upper complex generally overlaying the lower complex. The old complex comprises two main units of breccias. These units show a strong alteration marked by the presence of clays, chlorites, serpentines and zeolites. In the inner part of the cirque, these breccias are closely related to the old lava formations from which they come. These units show frequent jigsaw-cracks, a chaotic stratigraphy, as well as large amounts of chlorite. The upper complex is constituted by four main units which are more or less geographically separated in the cirque of Salazie. Their limits are not yet well identified because of the significant relief and a strong vegetable cover. Several units display a very strong fracturation, jigsaw-cracks and a chaotic stratigraphy whereas many lava flows are pulverised and locally injected in scoria levels. Recent work on Saint-Gilles breccias (Fèvre et al., this meeting) allowed to identify several sub-aerials deposits of debris avalanches. These new data, the analysis of geology and sedimentary figures observed within the breccia units in the “cirque de Salazie”, evidence several major gravitational collapse affecting the northeast flank of Piton des Neiges volcano. Considering that, the “cirque de Salazie” appears as partly bounded by gravitational collapse affecting the flanks of the volcano.

Arnaud, A.; Bachèlery, B.; Cruchet, C.

2003-04-01

156

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

2011-07-20

157

The 2002–2003 submarine gas eruption at Panarea volcano (Aeolian Islands, Italy): Volcanology of the seafloor and implications for the hazard scenario  

Microsoft Academic Search

A submarine gas eruption started in November 2002 offshore of Panarea volcano (Aeolian Islands, Italy). The intensity of the gas emission and the considerable anomalies of the geochemical and geophysical parameters have alarmed the volcanological community and the Italian Civil Protection Agency on the possibility that this activity may represent a volcanic unrest at Panarea volcano. We used a high

Alessandra Esposito; Guido Giordano; Marco Anzidei

2006-01-01

158

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

159

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

USGS Publications Warehouse

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. ?? 2011 Springer-Verlag.

Rybin, A.; Chibisova, M.; Webley, P.; Steensen, T.; Izbekov, P.; Neal, C.; Realmuto, V.

2011-01-01

160

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

NASA Astrophysics Data System (ADS)

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 of agglutinated spatter-clast breccias and lava flows from vents with a NNE structural alignment. An early phase of inferred subaqueous/subglacial activity formed pillow breccias. Two nunataks in the southern part of the island comprise basanitic tuff cones, composed of poorly bedded pyroclastic deposits dominated by sideromelane lapilli, and containing horizons rich in accretionary and armoured lapilli. Many of the basanites have compositions of near-primary magmas and contain an assortment of Cr-diopside and Al-augite suite mantle nodules, lower crustal gabbros, mafic granulites, and assorted megacrysts. Peridotites are dominated by spinel facies inclusions, but include plagioclase spinel lherzolites derived from shallow mantle beneath the tectonically thinned and attenuated Ross Sea lithosphere. Mantle nodules contain accessory amounts of pale brown, metasomatic amphibole. Volcanic geochemistry is compatible with fractionation of olivine, pyroxene, titano-magnetite and minor apatite from a basanite parent yielding tephriphonolite residual liquids. Magmatism is focused along, or at the termination of, Cenozoic rift basins in the Ross Sea. The regional McMurdo Volcanic Group distribution and tectonic setting, and the history of Erebus Province volcanic centres are difficult to reconcile in terms of active mantle plumes. Instead, more randomly distributed magmatism is inferred to result from rift-related decompression melting of previously enriched mantle that may have been fertilized by plume interaction prior to Gondwana fragmentation.

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

2007-09-01

161

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

162

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

Microsoft Academic Search

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

B. F. Houghton; I. A. Nairn

1991-01-01

163

Measuring deformation associated with magmatic processes at Cerro Azul Volcano, Galapagos Islands, Ecuador with InSAR  

NASA Astrophysics Data System (ADS)

The Galapagos Islands are an active volcanic island chain in the eastern Pacific Ocean off the west coast of Ecuador. Cerro Azul volcano is located on the southern tip of Isabella Island and experienced two eruptions in 10 years. The eruptions started on September 15, 1998 and May 29, 2008 and lasted 51 days and 20 days respectively. Using radar data from Radarsat-1 and Envisat satellites, the deformation before, during, and after these eruptions was measured using interferometric synthetic aperture radar (InSAR). Radarsat-1 data cover the 1998 eruption and Envisat data is available in 2008. Compared to the 2008 data, the time coverage for the 1998 eruption is not as frequent, but still allows for measuring the deformation during the eruption. Continuous radar data coverage between the eruptions allows us to see the state of the volcano leading up to the 2008 eruption. Using data from 8 different Envisat tracks in 2008, we measured the deformation associated with two separate eruptive phases of the volcano. Acquisitions on May 30 and 31, and June 2, 3, 5 and 6 show the deformation associated with the intrusion of magma responsible for fissures on the SE flank ceased by June 5, 2008. Using these data, it is possible to measure the amount of deformation during each of the eruptive phases and model the source processes at those times.

Baker, S.; Amelung, F.

2009-12-01

164

Barren Island Volcano (NE Indian Ocean): Island-arc high-alumina basalts produced by troctolite contamination  

NASA Astrophysics Data System (ADS)

Barren Island (BI) is a subduction-related volcanic island lying in the northeastern Indian Ocean, about 750 km north of the northern tip of Sumatra. Rising from a depth of ˜2300 m on the Andaman Sea floor, BI has a submarine volume estimated at ˜400 km3, but the island is just 3 km across, reaches a maximum elevation of 355 m, and has a subaerial volume of only ˜1.3 km3. The first historical eruption began in 1787 when a cinder cone grew in the center of a pre-historical caldera 2-km in diameter and sent lava flows westward to reach the sea; activity continued intermittently until 1832. Two subsequent eruptions modified the central cone and also sent lava flows westward to reach the sea in 1991 and 1994 1995. A suite of 28 lava, scoria, and ash samples were investigated from various stages of the subaerial eruptive history of BI. Most are basalts (including all 10 samples from the 1994 1995 eruption) and basaltic andesites (including 7 of 8 samples from the 1991 eruption), but 2 pre-1787 andesites were also studied. On multi-element spider diagrams the BI suite shows subparallel trends for most elements that reflect an important role for fractional crystallization, along with the characteristic depletions of Nb Ta and enrichments of K Rb Pb found in other subduction-related island-arc suites. The typical relative enrichment of Ba is not present, likely because the subducted sediments in the Andaman arc are not Ba-rich. Wide compositional ranges for Cs, Th, Rb, U, and Pb may trace different degrees of scavenging from the underlying volcanic pile. BI basalts and basaltic andesites have variable abundances of phenocrystic microphenocrystic olivine plus Cr Al Mg spinel inclusions, plagioclase, and clinopyroxene, embedded in a matrix of glass, the same minerals, and titanomagnetite (mostly exsolved). The most remarkable mineralogical feature of certain BI basalts and basaltic andesites is the presence of abundant (to 40 vol.%) and large (to 5 mm) crystals of relatively homogeneous anorthitic plagioclase (to An95.7). These have inclusions of Mg olivine (to Fo79) and thin (10 150 ?m) normally zoned margins that reach to the more sodic compositions of the plagioclase phenocryst and microphenocryst rims. Anorthitic plagioclase crystals are common at many subduction-related volcanoes. At BI, the anorthitic plagioclase and associated olivine crystals are thought to have entered the magmas through disaggregation of troctolitic crystal mushes or plutonic xenoliths. This process affected bulk-rock compositions in many ways, including raising Al2O3 contents to values as high as 22.8 wt.% and Eu / Eu* values up to 1.05. Compared to a large petrological and geochemical database for Indonesian volcanic rocks, the BI suite falls at the most depleted end for levels of K and incompatible trace elements, and Sr, Nd, and Pb isotopic ratios. Consequently, the BI suite defines an excellent primitive baseline against which Indonesian volcanic suites can be compared.

Luhr, James F.; Haldar, Dhanapati

2006-01-01

165

Volcano-Tectonic History of the Island of Montserrat, West Indies, From Seismic Reflection Profiles  

NASA Astrophysics Data System (ADS)

Seismic reflection profiles provide a cross-sectional view of crustal layers and thus details about local sedimentation rates, chronology, and depositional materials. Based on seismic profiles collected as part of the SEA-CALIPSO seismic experiment, we apply this method to interpreting the volcanic and local tectonic history of the island of Montserrat, in the Lesser Antilles arc. In December 2007, the vessel RRS James Cook towed a tuned, 2600 cubic inch, 8-airgun array along encircling and radial lines around Montserrat. The airguns fired every 60 sec (approx. every 140 m) at a pressure of 2000 psi. The ship also towed a 600 m streamer consisting of 48 hydrophone channels. Over a period of 77 hours, the hydrophones recorded a total of 4414 shots. Onboard the ship, data were stacked to produce 26 seismic profiles. The profiles vary in length up to 15 km and allow interpretation up to a depth of approx. 2.5 km. The profiles from east of Montserrat reveal fans of coarse-grained debris flows and submarine pyroclastic flows that derive from both the older volcanic centers and the active Soufriere Hills Volcano (SHV). The flows form tapering wedges that have been overlain by younger sea-floor sediments. Older ( > 1 Ma) sedimentary rocks, containing multiple reflective layers, deflect downwards towards and beneath Montserrat, forming a moat into which the debris and pyroclastic flows have deposited. A sub-sediment volcanic basement is present offshore at approximately 1.5 km depth. Offshore on the west side of the island the prominent Belham valley fault can be traced trending NW. The new data suggest that the fault line has been active in the recent geological past; the fault has offset submarine deposits offshore and tectonic blocks onshore (Garibaldi Hill, St. Georges Hill, Roches Bluff), has caused the down-warping of ocean sediments on the east side of the island, and likely influenced the location of domes and feeding conduits at and adjacent to the SHV. Montserrat itself appears to be located at the SW boundary of a large half-graben.

Kenedi, C. L.; Sparks, S. J.; Dean, S.; Hammond, J.; Malin, P. E.; Minshull, T.; Paulatto, M.; Peirce, C.; Ryan, G.; Shalev, E.; Voight, B.

2008-12-01

166

The Galápagos Islands seen from space: the contribution of Synthetic Aperture Radar Interferometry (InSAR) to volcano monitoring  

NASA Astrophysics Data System (ADS)

Although the Galápagos volcanoes are some of the most active volcanoes on Earth, because of their geographic isolation and the difficult working conditions they have been virtually unmonitored by geodetic methods until the last 18 years. The use of detailed Interferometric Synthetic Aperture Radar (InSAR) measurements of the surface deformation provides a unique opportunity to study magmatic processes in such a location. The phase difference (interferogram) of SAR images pairs for the same area acquired at different times, provides measurements of the ground deformation along the radar line-of-sight (LOS) with centimeter to millimeter accuracy. We use SAR data acquired over the Galápagos by the European Space Agency satellites ERS-1, ERS-2, ENVISAT and by the Canadian Space Agency satellite Radarsat-1, between 1992 and 2010. In order to obtain the temporal evolution of ground deformation at each volcano, we use the selected dataset and we apply the Small Baseline Subset (SBAS) method. We present SBAS displacement time-series for Wolf, Darwin, Fernandina, Alcedo, Sierra Negra and Cerro Azul, showing that all the six volcanoes that forms Fernandina and Isabela Islands have been actively deforming during the last eighteen years. We also identify and constrain some of the sources that generate the observed surface deformation by performing non-linear inversions in a homogeneous, isotropic, elastic half-space. With the frequent acquisitions of the ENVISAT satellite, we are able to study the evolution of the latest eruptions at Cerro Azul in 2008 and at Fernandina in 2009.

Osmanoglu, B.; Baker, S.; Bagnardi, M.; Amelung, F.

2010-12-01

167

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

168

Crustal recycling and the aleutian arc  

SciTech Connect

Two types of crustal recycling transfer continental crust back into its mantle source. The first of these, upper crustal recycling, involves elements that have been fractionated by the hydrosphere-sediment system, and are subducted as a part of the oceanic crust. The subduction process (S-process) then fractionates these elements, and those not removed at shallow tectonic levels and as excess components of arc magmas are returned to the mantle. Newly determined trace element composition of Pacific oceanic sedimants are variable and mixing is necessary during the S-process, if sediment is to provide excess element in the ratios observed in Aleutian arc magmas. Only a small fraction of the total sediment subducted at the Aleutian trench is required to furnish the excess elements in Aleutian arc magmas. Ba and {sub 10}Be data indicate that this small fraction includes a contribution from the youngest subducted sediment. The second type of recycling, lower crustal recycling, involves crystal cumulates of both arc and oceanic crustal origin, and residues from crustal melting within arc crust. Unlike the silicic sediments, recycled lower crust is mafic to ultramafic in composition. Trace element analyses of xenoliths representing Aleutian arc lower crust are presented. Recycling by delamination of lower crust and attached mantle lithosphere may occur following basalt eclogite phase transformations that are facilitated by terrane suturing events that weld oceanic island arcs to the continents. The relative importance of upper and lower crustal recycling exerts a primary control on continental crustal composition.

Kay, R.W.; Kay, S.M. (Cornell Univ., Ithaca, NY (USA))

1988-06-01

169

Exploring Means of Determining Surface Deformation at Augustine Volcano  

NASA Astrophysics Data System (ADS)

The recent January 2006 eruption of Augustine Volcano followed a nearly a year of increased seismic activity, that has been actively monitored by the Alaska Volcano Observatory (AVO). The eruption has generated a topographical signal that GPS ground stations were able to monitor. This work addresses the question as to which other techniques are able to see this deformation. While we primarily use remotely sensed data, with SAR derived products and techniques as a focus, we also explore the use of ICESAT data. Deformation started in the summer of 2005, with a period of inflation leading up to the January 2006 eruption and which was then followed by a period deflation. The deformation of the flanks of Augustine island was subtle, and GPS stations at the perimeter of the island generally show less that 2cm of total deformation. The summit GPS stations show significantly greater inflation, however these stations were destroyed during the eruption. Traditional INSAR has difficulties when applied to a volcano like Augustine, due to the small area of the island, its large topographic relief, the deposition of ash over the large areas of the island and the long orbital repeat interval of current SAR satellites, all work against the technique. This does not mean however that the outlook is bleak, Permanent Scatterer (PS) INSAR related techniques show great potential. The scientific basis of each technique examined is explained along with the challenges, and limitations that are inherent therein. Deformation results obtained from each method are also presented, and compared with the GPS measurements. The following techniques are examined, 1) INSAR/DINSAR, 2) Permanent Scatterers, 3) Delta K interferometry, 4) ICESAT LIDAR integration, 5) SAR layover/shadow mapping and geometric techniques. Because eruptions at small island volcanoes are common throughout the Aleutian chain, techniques developed for the analysis of this eruption will have great applicability to these and other arc volcanoes.

Lovick, J. T.; Lawlor, O.; Dean, K.; Dehn, J.; Freymueller, J.; Atwood, D.

2006-12-01

170

Regional Variations in Aleutian Magma Composition  

NASA Astrophysics Data System (ADS)

This study is based on sample data spanning 20 years from USGS, UAF, and DGGS geologists too numerous to list here. The 2900-km long Aleutian arc contains more than 50 active and over 90 Holocene volcanoes. The arc is built on oceanic Bering-sea floor west of 166W and quasi-continental crust east of 166W. Over the past twenty years the Alaska Volcano Observatory has conducted baseline geologic mapping (or remapping) and volcanic-hazards studies of selected volcanoes - generally those targeted for geophysical monitoring. This marks the largest sustained effort to study Aleutian volcanoes in half a century; AVO scientists have logged as many as 700 person-days per field season. Geologic studies have resulted in comprehensive suites of stratigraphically constrained samples and more than 3500 new whole-rock analyses by XRF and ICP/MS from more than 30 centers, more than doubling the number of previously published analyses. Examination of the data for regional and inter-volcano variations yields a number of first-order observations. (1) The arc can be broadly divided into an eastern segment (east of 158W) of calcalkaline andesite stratocones; a central segment dominated by large, mafic, tholeiitic shield volcanoes and stratocones; and a western segment (west of 175W) of smaller volcanoes with variable morphologies and generally more andesitic compositions. (2) There are NO significant first-order compositional signals that coincide with the transition from oceanic to continental basement. (3) Individual volcanoes are often subtly distinct from neighbors, and those distinctions persist for the lifetime of the centers. (4) All centers, notably including the large basaltic centers of the central arc, are strongly affected by open-system processes significantly more complicated than mixing among sibling-fractionates of parental mafic magmas. (5) Petrogenetic pathways are long-lived; individual batches of magma are (generally) not. (6) Calcalkaline andesites have dramatically lower REE and HFSE, yet higher Cr and Ni than tholeiitic andesites, suggesting that it is overly simplistic to consider calcalkaline andesites to be simple fractionates of basalts.

Nye, C. J.

2008-12-01

171

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

172

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

173

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.

174

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

Federal Register 2010, 2011, 2012, 2013

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

2011-03-29

175

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

176

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

177

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

178

Petrology and geochemistry of plinian basaltic volcanism of Chikurachki volcano, Kurile Islands, Russia  

Microsoft Academic Search

Plinian volcanism is characterized by high eruption rates commonly erupting gas-rich magmas of rhyolitic or dacitic composition. Plinian eruptions of basaltic composition are relatively rare and poorly studied. Chikurachki volcano (1816 m above sea level), the third of the highest active volcanoes of the Kurile arc, is characterized by both strombolian and plinian types of basaltic eruptions. Our goal is

A. A. Gurenko; A. B. Belousov; A. V. Sobolev

2003-01-01

179

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

Microsoft Academic Search

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

Falk Amelung; Simon Day

2002-01-01

180

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

Microsoft Academic Search

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

Falk Amelung; Simon Day

2002-01-01

181

The shallow magmatic system of Fernandina Volcano, Galápagos Islands. Evidence of multiple magma reservoirs from Satellite Radar Interferometry  

NASA Astrophysics Data System (ADS)

In the Galápagos Islands as at other ocean island volcanoes only a fraction of the magma coming from the mantle is erupted; the remaining magma is stored in crustal magma chambers, or trapped near the crust-mantle boundary. The increase of pressure generated by these magma intrusions can inflate the volcanic edifice and trigger eruptions and earthquakes. The geometry of magma reservoirs and their connections with the surface during eruptive phases, therefore, is fundamental to the development of predictive models of volcano deformation and eruption. Among the Galápagos Islands, Fernandina can be considered the most active volcano in the archipelago, having experienced 25 eruptions since 1813 and three eruptions in the last fifteen years (1995 - 2005 - 2009). In order to investigate the deformation associated with changes in pressure in the magma storage system we use Interferometric Synthetic Aperture Radar (InSAR) data acquired over Fernandina by the European Space Agency satellites ERS-1, ERS-2 and ENVISAT between 1992 and July 2010 in four different orbits. The advantage of using different viewing geometries is that the deformation signal can be independently validated and the responsible source beneath can be better constrained. We generate more than 300 interferograms and we apply the Small Baseline Subset (SBAS) method to investigate the temporal evolution of ground deformation. The analysis of single interferograms and of mean deformation velocity maps shows that the deformation at Fernandina is characterized by an almost continuous displacement of an elliptical area clearly limited by the summit caldera rim, and occasional displacement of a larger portion of the volcano edifice outside the caldera, around the summit. We then infer the presence of multiple sources of deformation below the summit caldera and the southern flank of Fernandina demonstrating that the magmatic system is composed by multiple magma reservoirs at different depths. We also determine an unusual shallow dipping geometry for the dike that fed the eruptive fissure opened on April 10, 2009 on the southwestern flank of the volcano, confirming what inferred by Jónsson et al. (1999) for the 1995 eruption.

Bagnardi, M.; Amelung, F.; Baker, S.

2010-12-01

182

Ankaramitic Lavas and Clinopyroxene Megacrysts From the Tanganasoga Volcano, El Hierro Island (Canary Archipelago)  

NASA Astrophysics Data System (ADS)

Sometime between 134 and 21 ka, the volcanic edifice of El Hierro Island, the youngest, smallest and westernmost island of the Canary Archipelago, grew unstable and its north flank collapsed seaward to form the 15-km-wide El Golfo embayment. Since this event, eruptions at El Hierro have concentrated at the base of, and directly on, the landslide headwall and have commonly involved peculiar ankaramitic lavas rich in clinopyroxene and olivine crystals. The most striking examples of such eruptive products are located at the prominent Tanganasoga volcano, where at least ten eruptive vents have produced a large bulge in the centre-west part of the El Golfo embayment. Lava bombs from the northernmost craters reach up to ~1 m across and show extremely high crystal contents of up to 50 vol. %. Loose lapilli deposits found on the slopes of the cones contain large, often intact clinopyroxene crystals that frequently reach 1.5-2 cm, with the largest found being 3 cm across. We analyzed the whole-rock and groundmass composition of the ankaramites, as well as the composition of phenocryst phases. Moreover, four clinopyroxene megacrysts were studied in further detail, with > 300 electron microprobe spot analyses per crystal. Results indicate that groundmass and co-existing olivine and clinopyroxene crystals approach chemical equilibrium in terms of Fe-Mg exchange. Core-to-rim chemical profiles in the smaller crystals (< 1cm) reveal relatively homogeneous compositions of intra-sample crystal interiors. However, steep normal Fe-Mg zoning is common in the outermost 20-40 ?m of the crystals. In contrast, some crystals show reverse zoning towards the rim. Clinopyroxene thermobarometry indicate crystallization pressures of 700-900 MPa and temperatures of 1170-1220°C. The megacrysts show complex oscillatory zoning patterns, which, nonetheless, translate into modest chemical variations (Mg# = molar Mg/(Mg + Fetotal) = 76-80). We propose that the formation of Tanganasoga’s ankaramitic magmas and clinopyroxene megacrysts is the result of a complex interplay between prolonged magma storage, regular influx of fresh magma and efficient crystal growth, fractionation and accumulation at upper mantle depth. The eruption of such dense, crystal-rich magmas probably requires forceful triggering, and appears to be facilitated after large-scale landslide events.

Longpre, M.; Troll, V.; Hansteen, T. H.; Anderson, E.

2009-12-01

183

New insights on Mafate - Saint Gilles debris avalanche deposits (westward Piton des Neiges volcano Réunion Island)  

NASA Astrophysics Data System (ADS)

Studies of debris avalanche deposits on Reunion Island (southwestern Indian Ocean) have been started in the last decade with the bathymetric surveys offshore Piton de la Fournaise and the identification of giant submarine landslides (Lénat et al., 1989; Cochonnat et al., 1990). Since this discovery, new field investigations have been driven to characterise and understand the role of debris avalanche phenomena in the evolution of volcanic island like Reunion. The first aerial outcrop of debris avalanche deposits has been identified in the west part of Piton des Neiges volcano in 1996. It has been described has a succession of breccia events interbedded by lava flows, and localised in St Gilles area (Bachèlery et al, 2003). In the last two years, the breccia problematic has been revisited and new outcrops have been found in the northern and southern part of St Gilles area (Bret et al., 2003). In the light of new geological surveys, new debris avalanche deposits outcrops have been identified around the St Gilles area. Most of these new outcrops are situated in the main riverbeds of the western Piton des Neiges flank (Rivière des Galets, Ravine Divon, Ravine Bernica and Ravine Trois Bassins). Furthermore, similar breccia outcrops has been identified down the Maïdo cliff, in the walls of Mafate cirque, uphill St Gilles area. All these formations show common characters of debris avalanche deposits with (i) a “block facies” consisting of plurimetric to decametric shattered lava flow and dykes segments with typical jigsaw fractures packed in (ii) a “matrix facies” composed of silty to sandy heterogeneous elements. This tends to prove that previous authors have underestimated the St Gilles event lateral extent. Our new field surveys point out the new extension (obvious landslide scars) of the St Gilles well known debris avalanche deposits. These scars start in the Mafate cirque (where the landslide head is located), then continue through the Mafate wall in the north of Maïdo place and go down to the sea from Ravine Trois Bassins in the south to Rivière des Galets in the north. These discoveries associated to recent submarine DEM interpretation (Oehler, 2001) allow us to consider a new global evolution sketch of the whole Piton des Neiges west flank with a large debris-avalanche (now called Mafate - St Gilles debris avalanche deposits) that has recovered the former basaltic Piton des Neiges topography at the end of the shield building stage (around: 0.45 My).

Fèvre, F.; Bret, B.; Odon, O.; Arnaud, A.; Bachèlery, B.

2003-04-01

184

Unusual Signals Recorded by Ocean Bottom Seismometers in the Caldera of Deception Island Volcano: Biological Activity or Hydrothermally Generated Seismicity?  

NASA Astrophysics Data System (ADS)

As part of an active source land-sea tomography experiment, ocean bottom seismometers (OBSs) were deployed at Deception Island Volcano, Antarctica, in January 2005. Following the tomography study, three OBSs were left for a month inside the flooded caldera and ten on the outer slopes of the volcano to record seismo-volcanic signals. The OBS sensor package included three-orthogonal 1-Hz geophones but no hydrophone. The OBSs were deployed in water depths of 125 to 143 m inside the caldera and at depths of 119 to 475 m on the volcano's flanks. Only two volcano-tectonic earthquakes and three long period events were recorded by the network. However, the OBSs inside the caldera recorded over 4,500 unusual seismic events. These were detected by only one station at a time and were completely absent from OBSs on the flank of the volcano and from land stations deployed on the island. The signals had a dominant frequency of 5 Hz and were one to ten seconds long. Event activity in the caldera was variable with the number of events per hour ranging from 0 up to 60 and the level of activity decreasing slightly over the study period. We categorize the signals into three types based on waveform characteristics. Type 1 events have an impulsive onset and last 1 to 2 s with characteristics that are consistent with the impulse response of a poorly coupled OBS. Type 2 events typically last 2 to 4 s and comprise a low amplitude initial arrival followed less than a second later by a more energetic second phase that looks a Type 1 event. Type 3 events last up to 10 s and have more complex waveforms that appear to comprise several arrivals of varying amplitudes. Type 1 events are similar to the 'fish-bump' signals reported from previous studies that attributed them to biological activity. The consistent timing and relative amplitudes of the two arrivals for Type 2 events are difficult to explain by animals randomly touching the OBSs. Type 3 events are quite similar in frequency, duration, and signal characteristics to long-period seismic events recorded by an onshore seismic array deployed in an earlier study at Deception Island. Particle motions suggest that Type 3 events may be surface waves while the particle motions for Type 1 and Type 2 events are ambiguous and unlike any signals recorded by land arrays at the volcano. Binomial tests of the event distribution show no significant changes in the rate of events with time of day that would be indicative of a biological source. Since the events are entirely absent in biologically productive waters outside the caldera, we postulate that they may be volcanic signals related to hydrothermal flow across the seafloor in the flooded caldera of Deception Island. Future OBS deployments at Deception Island should include a hydrophone to discriminate unambiguously between biological and volcanic signals.

Bowman, D. C.; Wilcock, W. S.

2011-12-01

185

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

186

Monitoring Emissions at White Island Volcano, New Zealand; Evidence of Sustained Magmatic Degassing during Crater Lake Growth  

NASA Astrophysics Data System (ADS)

The commencement of routine monitoring of CO2 and SO2 emissions at White Island volcano in March 2003 indicated that degassing was at quiescent levels (880 and 225 td-1, respectively) similar to previous estimates of long-term (20-yr) emissions. Following an abrupt decrease in prolonged 2-5 Hz volcanic tremor in February, 2003, emissions decreased dramatically to ~250 and 0 td-1 CO2 and SO2, respectively. These decreases were coincident with the formation of a significant crater lake at the volcano. Since this time, however, CO2 emissions have increased and decreased by as much as an order of magnitude over periods of months with ~10 and 12 months between the lowest measured values. SO2 emissions also displayed similar variability, but changes were superimposed on a long term trend of increasing emissions. Likewise, SO4 concentrations in the crater lake increased steadily and also showed small deviations during periods of increased degassing. Crater lake temperatures varied primarily between 48 and 58 oC, but also displayed short-lived increases to 63 and 68 oC during periods of higher degassing. Similarly, modelled estimates of steam input to the lake, while varying, have remained relatively unchanged over the monitored period. Such changes suggest that a decrease in the magmatic mass and heat output from the volcano allowed the crater lake to form, but that overall, the mass and heat output have fluctuated about quiescent levels since the formation of the crater lake. White Island last erupted in 2000 marking the end of 25 years of episodic eruptions. We suggest that the variability of volatile output over timescales of months is related either to magma convection deep within the volcanic edifice or to changes in shallow permeability due to conduit saturation or mineral precipitation.

Werner, C. A.; Christenson, B. W.; Hurst, T.; Scott, B. J.; Britten, K.

2005-12-01

187

Spatial and temporal variations of soil CO2 flux and pressure gradient measurements at Cumbre Vieja volcano, La Palma, Canary Islands  

Microsoft Academic Search

La Palma (730 km2) is one of the youngest and the most active volcanic island of the Canarian archipelago. Volcanic activity has been concentrated on the southern part of the island, Cumbre Vieja volcano (220 km2), which had been constructed during the last 1 Ma. Three major volcanic rift-zones trending N-S, NW-SE and NE-SW constitute Cumbre Vieja's major structural features.

M. Brito; I. Martin; E. Padron; J. Salazar; P. Hernandez; N. Perez

2003-01-01

188

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

189

Aleutian Campaign, World War II: Historical Study and Current Perspective.  

National Technical Information Service (NTIS)

This work is a detailed historical study of the Aleutians Campaign conducted by U.S. Armed Forces from 3 June 1942 through 18 August 1943 to gain control of the North Pacific and eject the Japanese from Attu and Kiska Islands. The campaign, characterized ...

R. L. Johnson

1992-01-01

190

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

191

Hydrogen isotopic composition of hornblende and biotite phenocrysts from Japanese island arc volcanoes: Evaluation of alteration process of the hydrogen isotopic ratios by degassing and re-equilibration  

Microsoft Academic Search

In order to estimate hydrogen isotopic ratios (?D) of pre-eruptive island arc magma, we measured ?D, chemical compositions, and colour of hornblende and biotite phenocrysts from Japanese Quaternary volcanoes. The rock samples comprise lavas, lava domes, pyroclastic flow deposits related with lava dome collapse, air-fall pumices and pumice flow deposits. The observed ?D value ranges from ?108 to +103‰ SMOW

Isoji Miyagi; Osamu Matsubaya

2003-01-01

192

Lithospheric contributions to high-MgO basanites from the Cumbre Vieja Volcano, La Palma, Canary Islands and evidence for temporal variation in plume influence  

Microsoft Academic Search

New geochemical and isotopic data are presented from the oldest part of the Cumbre Vieja volcano, La Palma (Canary Islands), located near the assumed emergence of the Canary mantle plume. The volcanics comprise a suite dominated by basanite flows with subordinate amounts of phono-tephrite, tephri-phonolite and phonolite flows and intrusives. Two compositionally different basanite groups have been identified, both with

N.-O. Prægel; P. M. Holm

2006-01-01

193

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

194

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

NASA Astrophysics Data System (ADS)

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, Frank A.; Moore, Richard B.; Sako, Maurice; White, Randall A.; Koyanagi, Stuart K.; Chong, Ramon; Camacho, Juan T.

2005-08-01

195

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

Microsoft Academic Search

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, phi, gives a measure of the crack orientation, which is expected to align

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

2008-01-01

196

The western submerged sector of the Ischia volcanic island (Tyrrhenian Sea, Italy): new insights into its volcano-tectonic evolution  

NASA Astrophysics Data System (ADS)

The Island of Ischia is a volcanic complex located in the northern boundary of the Gulf of Naples (south-eastern Tyrrhenian Sea, Italy). The island represents only the 30% of a larger, E-W trending, volcanic ridge and likely controlled by a regional tectonic lineament. Despite the many geo-volcanological and geophysical investigations conducted on the island since long time, still little is the knowledge of its offshore. Several marine surveys have been carried out over the past 10 years from IAMC - CNR research institute (Naples, Italy) mostly in the frame of INGV and GNV projects, funded by Italy Civil Protection Department. Such surveys have largely improved the knowledge of the entire volcanic complex. Multibeam bathymetry surveys has revealed several, previously unexpected, morphological and morphostructural features. Moreover some structural patterns and volcano alignments offshore show similarities with those occurring at a regional scale in the Campania region and, locally, between the island of Procida and Phlegrean Fields. Here we report the joint interpretation of geophysical data focused on the western underwater sector of the island. Interpretation was chiefly based on processing/inversion of magnetic data in turn constrained by bathymetry and seismic reflection profiles. Magnetic data, acquired by the IAMC during two different cruises in 2000 and 2002 onboard of the Urania R/V oceanographic vessel, put in evidence that the western seafloor of Ischia is characterized by the presence of a strong residual magnetic anomaly field of complex behaviour, somewhere correlated to local bathymetry. These two last methods allowed to define and distinguish between undersea and subsurface magnetic (i.e. magmatic) basement. Interpretation was also constrained by seismological data.

Passaro, Salvatore; de Alteriis, Giovanni; Milano, Girolamo; Fedi, Maurizio; Florio, Giovanni

2010-05-01

197

Assessment of the exposure of islanders to ash from the Soufriere Hills volcano, Montserrat, British West Indies  

PubMed Central

Background and Aims: The Soufriere Hills volcano, Montserrat, has been erupting since July 1995 and volcanic ash has fallen on the island throughout most of the eruption. The ash contains substantial quantities of respirable particles and unusually large amounts (15–20%) of the crystalline silica mineral, cristobalite. The purpose of the surveys described here, undertaken between December 1996 and April 2000, was to determine levels of personal exposure of islanders to volcanic ash and cristobalite in order to inform advice on the associated risks to health and the measures required to reduce exposure. Methods: Surveys of personal exposure to respirable dust and cristobalite were undertaken using cyclone samplers. In addition, direct reading instruments (DUSTTRAK) were used to monitor ambient air concentrations of PM10 at fixed sites and also to provide information about exposures to airborne particles associated with selected activities. Results: Environmental concentrations of airborne ash have been greatest in the areas where the most ash has been deposited and during dry weather. Individual exposure to airborne ash was related to occupation, with the highest exposures among gardeners, cleaners, roadworkers, and police at roadside checkpoints. During 1997 many of these individuals were exposed to concentrations of cristobalite that exceeded the ACGIH recommended occupational exposure limit. Since the population became confined to the north of the island in October 1997, even those in relatively dusty occupations have received exposures to cristobalite well below this limit. Conclusions: Most of the 4500 people who have remained on island since the eruption began have not been exposed to sufficiently high concentrations of airborne dust for long enough to be at risk of developing silicosis. However, more than a dozen individuals continued to experience frequent high occupational exposures to volcanic ash, some of whom may have had sufficient exposure to crystalline silica to be at risk of developing mild silicosis. If volcanic activity were to deposit further ash over the occupied areas of the island during the coming years, the risks of silicosis will become more substantial.

Searl, A; Nicholl, A; Baxter, P

2002-01-01

198

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

199

Shallow Seismic Attenuation and Shear Waves Splitting In The Short Period Range of Deception Island Volcano (antarctica)  

NASA Astrophysics Data System (ADS)

The occurrence of a seismic series in Deception Island volcano (Antarctica), com- posed by hundreds of local volcano-tectonic earthquakes, has permitted us to study the seismic attenuation of such a volcanic environment in the short-distance and high- frequency range. This study has been performed using P, S and coda waves and ap- plying different, frequency dependent and independent, techniques. The methods used for this analysis have been: Spectral and Broadening of the Pulse, for direct P and S waves, Coda Normalization for S-waves and Single Back-Scattering model for coda waves. The results show that, in general, Q values are significantly smaller, for all the frequency range used (6-30 Hz), than those found in other volcanic and tectonic areas. The attenuation for P-waves is greater than for S-waves in the frequency in- dependent methods, with a Qb/QP ratio that ranges between 1.9 and 3.2. Comparing the Q factor obtained for S-waves we have observed clear differences as a function of the method used; the Coda Normalization Method has supplied significantly higher Q values (Qd) than the other two methods (Qb). These Qd values are similar to the Q factor for coda waves (Qc). We have interpreted this discrepancy as an effect of the methods: Coda Normalization and Single Back-Scattering methods eliminate the con- tribution of the near surface attenuation in their Q values. Comparing both Qb and Qd we have estimated the near surface attenuation under the recording site, named Qk. On the other hand, we have observed that Qd has an anomalous frequency dependence, with a minimum value at 21 Hz. This pattern is interpreted as an effect of strong scat- tering of the seismic waves in the source area of the earthquakes. Qc values depend clearly with frequency and lapse time, and the lapse time dependence is interpreted as a depth dependence of the seismic attenuation in Deception Island volcano. The de- rived Q values have allowed us to separate the contribution of intrinsic and scattering attenuation, deriving that the scattering attenuation is predominant over the intrinsic effects. Finally, in order to investigate how the heterogeneous medium of the volcanic island could produce other effects, we have measured the splitting of the shear waves of the same data set. The observations reveal that the arrival delay of the shear waves horizontal components varies between 0.02 and 0.14 seconds, a big amount if we take into account the short hypocentral distances (less than 5 km). The study of the polar- 1 ization direction indicates a main E-W direction. All these evidences reveal the strong heterogeneous structure of Deception Island volcano. 2

Martínez-Arévalo, C.; Bianco, F.; Ibáñez, J. M.; del Pezzo, E.

200

Magmatic and tectonic development of the Western Aleutians - An oceanic arc in a strike-slip setting  

Microsoft Academic Search

Early Tertiary magmatic histories imply that the Western Aleutians has experienced a tectonic evolution unlike that of the central and eastern arc. In this work, the geochemistry of Eocene through Mio-Pliocene tholeiitic and calcalkaline magnatic successions on Attu Island and in the Near Isands are used to investigate the changing magmatic sources and evolving tectonics of the Western Aleutian region.

G. M. Yogodzinski; J. L. Rubenstone; S. M. Kay; R. W. Kay

1993-01-01

201

Comprehensive study of the seismotectonics of the Aleutian Arc. Annual progress report, March 1, 1973February 28, 1974  

Microsoft Academic Search

Basic research is carried out to derive a coherent theory for the ; tectonic structure and geological history of the Alaska-Aleutian island arc in ; the framework of recent advancements of plate tectonics. An important part of ; this study is the evaluation of the seismic risk particularly in the eastern ; Aleutian arc which forms a major section of

Jacob

1974-01-01

202

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

Microsoft Academic Search

During 14–16 September 1988, a large intracaldera avalanche and an eruption of basaltic tephra and lava at Fernandina volcano, Galapagos, produced the most profound changes within the caldera since its collapse in 1968. A swarm of eight earthquakes (mb 4.7–5.5) occurred in a 14 h period on 24 February 1988 at Fernandina, and two more earthquakes of this size followed

William W. Chadwick; Tui Roy; Alfredo Carrasco

1991-01-01

203

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

NASA Astrophysics Data System (ADS)

The Azores archipelago is located in North Atlantic Ocean, in the junction of Eurasian, American and African plates, which reflect the existence of a complex system of fractures, namely the Mid-Atlantic Ridge, the Eastern Azorean fracture zone, the Terceira Rift and the Gloria Fault. The Azores are, therefore, an excellent place for the application and development of various volcano tectonic observation techniques (geophysics, geochemistry and geodesy) and preliminary modeling of some of the volcanic systems. In the scope of the Azores seismovolcanic monitoring programme a geodetic network was implemented in Graciosa Island. This network is composed by thirty-four geodetic benchmarks distributed according to the main volcanic and tectonic structures. A continuous GPS station installed in the island since 2003 is used as reference. In the last five years there have been eight observation campaigns, which took place between September 2003 and July 2008. For the processing of the GPS observations it was used the Bernese GPS Software 5 (developed at the University of Berne). For the GPS processing of September 2003, March 2004 and August 2004 campaigns, three processing strategies were tested to study the effect of the correction of troposphere refraction, resulting in three different solutions: one solution with pure modeling (no estimation of troposphere parameters) and two solutions with estimation of one and two troposphere parameters, using Niell's hydrostatic mapping function. A processing methodology was created, a good and reliable zero-epoch for the study of the volcanic-tectonic system of the Graciosa Island was established and a preliminary evaluation of the velocity field was obtained for Graciosa island.

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

2009-04-01

204

Beryllium geochemistry constraints on the hydraulic behavior of mud volcanoes: the Trinidad Island case  

NASA Astrophysics Data System (ADS)

To constrain Trinidad mud volcanoes hydraulic behavior, both cosmogenic 10Be (t1/2=1.5 Myr) and 9Be concentrations have been measured in fluid and associated expelled mud. As previously evidenced [A.N. Dia, M. Castrec, J. Boulègue, P. Comeau, Trinidad Mud Volcanoes: where do the expelled fluids come from? Geochim. Cosmochim. Acta 63 (1999) 1023-1038] from ?18O values and Cl concentrations, 9Be concentrations in the fluids mostly reflect the mixing of two deep components: REM I and REM II. REM I (?18O=10.5‰, Cl~275 mM and 9Be~0.05 nM) has characteristics of a continental fluid while REM II (?18O=3‰, Cl~350 mM and 9Be~1 nM) results from seawater-volcanogenic derived sediment interaction. Although 10Be concentrations in the fluid samples are close to the detection limit, the distribution of both beryllium isotopes between the hydroxylamine leachable and residual phases indicates exchange reaction with fluid younger than 15 Myr. Comparison between the lowest REM I 10Be/9Be ratio in fluid recorded by the hydroxylamine leachable phase (TD5 mud sample) and the 10Be/9Be ratio representative of meteoric contribution in the recharge area (TD8 fluid sample) yields a circulation rate of REM I fluid in the Trinidad mud volcanoes of several 10-1 m/yr.

Castrec-Rouelle, M.; Bourlès, D. L.; Boulègue, J.; Dia, A. N.

2002-11-01

205

Co-existence of two distinct magma sources in an island arc volcano: evidence from Montserrat, Lesser Antilles Arc  

NASA Astrophysics Data System (ADS)

The South Soufrière Hills (SSH), located on the southern tip of the volcanically active island of Montserrat, West Indies, hosts the most complex and interesting volcanic deposits on the island in terms of their geochemistry and volcanic history. In this study we examine the composition of submarine SSH deposits in marine sediment cores and volcanics sampled during subaerial mapping of the SSH and other volcanic centres on Montserrat. SSH volcanism is found to represent an important compositional change in the magmatic evolution of Montserrat with implications for the origin of components in the Caribbean subduction system. Marine sediment cores and subaerial field mapping of the SSH volcanic centre document voluminous multi-stage flank failures of the SSH, which successively cut into older and chemically distinct stratigraphy as the collapses progressed. Nd, Sr and high-precision double-spike Pb isotopes combined with trace element analyses and SEM imagery of the SSH deposits indicate that this volcano experienced multiple injections of mafic magma followed by magmatic differentiation and episodic explosive eruptions of andesitic pumice, which were triggered by fresh mafic pulses. We demonstrate that the SSH is chemically distinct from the rest of the volcanic centres on the island, suggesting that magmas from the Soufrière Hills and SSH come from entirely separate sources. 206Pb/204Pb plotted against ?7/4Pb and ?8/4Pb show that Montserrat falls along two differing trends; one defined by the SSH volcanic centre and the second comprising the three other volcanic centres (Silver Hills, Centre Hills and Soufrière Hills). Magma generation at these centres (excluding the SSH) reflects an input of pelagic sediment, likely in the form of partial melt as indicated by elevated Th/Nd and lower 143/144Nd. However, the SSH has more of slab-fluid rich signature relative to sediment as suggested by lower Ce/Pb, 206Pb/204Pb and ?7/4Pb combined with higher 87Sr/86Sr. The low, but stable Nb/Zr values relative to MORB, suggests that the mantle source for each volcanic centre has remained constant despite the deviation in sediment flux reflected during SSH activity. By extension from the high-precision Pb isotope results, we can suggest that subduction fluid, and sediment melt components can be discriminated within a single arc volcano.

Cassidy, M.; Taylor, R. N.; Palmer, M. R.; Trofimovs, J.

2011-12-01

206

Characterization of pyroclastic deposits and pre-eruptive soils following the 2008 eruption of Kasatochi Island Volcano, Alaska  

USGS Publications Warehouse

The 78 August 2008 eruption of Kasatochi Island volcano blanketed the island in newly generated pyroclastic deposits and deposited ash into the ocean and onto nearby islands. Concentrations of water soluble Fe, Cu, and Zn determined from a 1:20 deionized water leachate of the ash were sufficient to provide short-term fertilization of the surface ocean. The 2008 pyroclastic deposits were thicker in concavities at bases of steeper slopes and thinner on steep slopes and ridge crests. By summer 2009, secondary erosion had exposed the pre-eruption soils along gulley walls and in gully bottoms on the southern and eastern slopes, respectively. Topographic and microtopographic position altered the depositional patterns of the pyroclastic flows and resulted in pre-eruption soils being buried by as little as 1 m of ash. The different erosion patterns gave rise to three surfaces on which future ecosystems will likely develop: largely pre-eruptive soils; fresh pyroclastic deposits influenced by shallowly buried, pre-eruptive soil; and thick (>1 m) pyroclastic deposits. As expected, the chemical composition differed between the pyroclastic deposits and the pre-eruptive soils. Pre-eruptive soils hold stocks of C and N important for establishing biota that are lacking in the fresh pyroclastic deposits. The pyroclastic deposits are a source for P and K but have negligible nutrient holding capacity, making these elements vulnerable to leaching loss. Consequently, the pre-eruption soils may also represent an important long-term P and K source. ?? 2010 Regents of the University of Colorado.

Wang, B.; Michaelson, G.; Ping, C. -L.; Plumlee, G.; Hageman, P.

2010-01-01

207

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

SciTech Connect

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

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

1993-04-01

208

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

209

Evaluation of morphometry-based dating of monogenetic volcanoes—a case study from Bandas del Sur, Tenerife (Canary Islands)  

NASA Astrophysics Data System (ADS)

Morphometry-based dating provides a first-order estimate of the temporal evolution of monogenetic volcanic edifices located within an intraplate monogenetic volcanic field or on the flanks of a polygenetic volcano. Two widely used morphometric parameters, namely cone height/width ratio ( H max/ W co) and slope angle, were applied to extract chronological information and evaluate their accuracy for morphometry-based ordering. Based on these quantitative parameters extracted from contour-based Digital Elevation Models (DEMs), two event orders for the Bandas del Sur in Tenerife (Canary Islands) were constructed and compared with the existing K-Ar, paleomagnetic and stratigraphic data. The results obtained suggest that the commonly used H max/ W co ratio is not reliable, leading to inappropriate temporal order estimates, while the slope angle gives slightly better results. The overall performance of such descriptive parameters was, however, generally poor (i.e. there is no strong correlation between morphometry and age). The geomorphic/morphometric mismatches could be the result of (1) the diversity of syn-eruptive processes (i.e. diverse initial morphologies causing geomorphic/morphometric variability), (2) contrasting, edifice-specific degradation that depends partly upon the inner facies architecture of the volcanic edifices, (3) various external environmental controls (e.g. tephra mantling from pyroclastic density currents unrelated to the edifice evaluated) and (4) differences in the scale/resolution of input data. The observed degradation trend and changes in morphometric parameters over time do not support a simple degradation model for monogenetic scoria cones volcanoes.

Kereszturi, Gábor; Geyer, Adelina; Martí, Joan; Németh, Károly; Dóniz-Páez, F. Javier

2013-07-01

210

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

211

Slope instability induced by volcano-tectonics as an additional source of hazard in active volcanic areas: the case of Ischia island (Italy)  

Microsoft Academic Search

Ischia is an active volcanic island in the Gulf of Naples whose history has been dominated by a caldera-forming eruption (ca.\\u000a 55 ka) and resurgence phenomena that have affected the caldera floor and generated a net uplift of about 900 m since 33 ka.\\u000a The results of new geomorphological, stratigraphical and textural investigations of the products of gravitational movements\\u000a triggered by volcano-tectonic events

Marta Della Seta; Enrica Marotta; Giovanni Orsi; Sandro de Vita; Fabio Sansivero; Paola Fredi

2011-01-01

212

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

Microsoft Academic Search

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

B F Houghton; I A Nairn

1991-01-01

213

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

Microsoft Academic Search

High-precision (TIMS) measurements of U and Th isotope concentrations have been determined on whole rocks and mineral separates from Soufriere volcano on St. Vincent in the Lesser Antilles island arc. The whole rocks display relatively constant U\\/Th ratios (~0.5), and are characterised by excess 238 U relative to 230 Th which is attributed to the addition of U-rich fluids from

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

1998-01-01

214

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

Microsoft Academic Search

High-precision (TIMS) measurements of U and Th isotope concentrations have been determined on whole rocks and mineral separates from Soufriere volcano on St. Vincent in the Lesser Antilles island arc. The whole rocks display relatively constant U\\/Th ratios (?0.5), and are characterised by excess 238U relative to 230Th which is attributed to the addition of U-rich fluids from the subducting

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

1998-01-01

215

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

Microsoft Academic Search

We report on 4 years of airborne measurements of CO2, SO2, and H2S emission rates during a quiescent period at White Island volcano, New Zealand, beginning in 2003. During this time a significant crater lake emerged, allowing scrubbing processes to be investigated. CO2 emissions varied from a baseline of 250 to >2000 t d?1 and demonstrated clear annual cycling that

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

2008-01-01

216

Chemical composition, volatile components, and trace elements in melts of the Karymskii volcanic center, Kamchatka, and Golovnina volcano, Kunashir Island: Evidence from inclusions in minerals  

Microsoft Academic Search

Melt inclusions were examined in phenocrysts in basalt, andesite, dacite, and rhyodacite from the Karymskii volcanic center\\u000a in Kamchatka and dacite form Golovnina volcano in Kunashir Island, Kuriles. The inclusions were examined by homogenization\\u000a and by analyzing glasses in more than 80 inclusions on an electron microscope and ion microprobe. The SiO2 concentrations in the melt inclusions in plagioclase phenocrysts

V. B. Naumov; M. L. Tolstykh; E. N. Grib; V. L. Leonov; N. N. Kononkova

2008-01-01

217

Colonization of an island volcano, Long Island, Papua New Guinea, and an emergent island, Motmot, in its caldera lake. VII. Overview and  

Microsoft Academic Search

Location, aims Long Island's biota was destroyed by volcanic eruption in c. 1645, and Motmot, an emergent island in its caldera lake, was re-created in 1968, providing a nested pair of natural colonization sequences. In 1999 we surveyed the plants and vertebrates of Long and the entire biota of Motmot for comparison with previous surveys of Long (1932, 1972, birds

I. W. B. Thornton; S. Cook; J. S. Edwards; R. D. Harrison; C. Schipper; M. Shanahan

218

Petrology and geochemistry of plinian basaltic volcanism of Chikurachki volcano, Kurile Islands, Russia  

NASA Astrophysics Data System (ADS)

Plinian volcanism is characterized by high eruption rates commonly erupting gas-rich magmas of rhyolitic or dacitic composition. Plinian eruptions of basaltic composition are relatively rare and poorly studied. Chikurachki volcano (1816 m above sea level), the third of the highest active volcanoes of the Kurile arc, is characterized by both strombolian and plinian types of basaltic eruptions. Our goal is to place new petrological and geochemical constraints on the magma origin, as well as to understand the behavior of volatile components. Plinian fallout deposits resulting from the 1853, 1986 and ancient eruptions of Chikurachki volcano were a subject of this study. We analyzed major, trace and volatile (H_2O, S, Cl) elements in glass inclusions (up to 100 ?m in size) hosted in olivine (Ol, Fo72-78), orthopyroxene (Opx, mg# = 72--75), clinopyroxene (Cpx, mg# = 71--77) and plagioclase (Pl, An74-96) from glassy lapilli using EPMA and SIMS. Phenocryst crystallization occurred in the temperature range of 1140-1040^oC and oxygen fugacity around NNO. Glass inclusions have basalt to basaltic andesite composition, are enriched by LREE ([La/Sm]n = 1.2--1.5) and characterized by significant Nb depletion ([Nb/La]n = 0.18--0.27) and some Sr enrichment ([Sr/Ce]n = 2.0--3.8). Varying concentrations of H_2O (1.5--3.8 wt%), S (0.01--0.29 wt%) and Cl (0.05--0.14 wt%) suggest partial to strong degassing of the erupted magmas. The release of volatile components during eruption of such H_2O- and SO_2-rich magmas probably resulted in strongly explosive character of basaltic eruptions of Chikurachki. Trace element contents in glass inclusions were interpreted to reflect a mixture of at least two components during the magma origin: (1) a mantle component previously experienced partial melting and melt extraction and therefore depleted in LILE, LREE and Nb, and (2) a component containing H_2O and being enriched in potentially fluid-mobile elements e.g., Li, B and Ba. Neither contamination by upper crustal rocks or oceanic sediments nor by melts resulting from partial melting of the subducting slab can account the composition of the erupted magmas. The processes of fluid release from the subducting slab beneath the Kurile arc followed by metosomatism of the mantle wedge and its consequent melting are discussed.

Gurenko, A. A.; Belousov, A. B.; Sobolev, A. V.

2003-04-01

219

Geomorphic evolution of the Piton des Neiges volcano (Réunion Island, Indian Ocean): Competition between volcanic construction and erosion since 1.4 Ma  

NASA Astrophysics Data System (ADS)

Réunion Island (Indian Ocean) is a volcanic complex whose eruptive history was dominated by the activity of two main edifices: Piton des Neiges (PN) and Piton de la Fournaise (PF) volcanoes. The tropical climate induces erosion processes that permanently compete with volcanic constructional processes. Exposed to the trade winds and associated heavy rainfalls, the northeastern part of the island exhibits the most complex morphological evolution. Geomorphological analysis, performed on a 50 m DEM and associated to new K-Ar ages has clarified the overall history of PN volcano. Each massif is assigned to one of the main building stages of the edifice. In addition, the arrangement of these different massifs reveals that the eruptive phases have led to successive relief inversions and successive excavations of large central depressions in the proximal area. As a result, the younger massifs are always located in more proximal parts of the volcano, the youngest being close to the edifice center. In distal areas, early lava flows were channeled into valleys incised along the massif boundaries, leading to a more complex geochronological organization. Quantitative study of the dissection of PN volcano allows us to propose a minimum eroded volume of 101 ± 44 and 105 ± 41 km3 for the Mafate and Cilaos "Cirques" (depressions), respectively, during the last 180 kyr and a minimum average long-term erosion rate of 1.2 ± 0.4 km3/ka. This leads us to estimate the removed volume during the whole history of PN volcano (> 1000 km3) as equivalent to the volume of the deposits identified on the submarine flanks of Piton des Neiges volcano. Therefore, as regressive erosion appears to be the prevailing geomorphic process during the whole PN history, it questions the presence of major flank collapses younger than 1.4 Ma on this volcano. Erosion processes have largely been neglected in recent models, but our study emphasizes them as a key component of landscape development and a major process in the morphological evolution of Réunion Island that has to be fully integrated in future studies.

Salvany, Tiffany; Lahitte, Pierre; Nativel, Pierre; Gillot, Pierre-Yves

2012-01-01

220

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

221

Volcano Live  

NSDL National Science Digital Library

Volcano Live contains maps of volcanoes from around the world, a kids' page that provides volcano education links for teachers and students, a volcano glossary, volcano news, links to live video cams of volcanoes, geography and volcano information of countries around the world, and video clips of active volcanoes. There is also information for travelling to volcanoes, a volcano photo section, a section on the destruction of Pompeii, a volcanology section, and volcano safety rules.

Seach, John

222

Volcano-Tectonic History of the Island of Montserrat, West Indies, From Seismic Reflection Profiles  

Microsoft Academic Search

Seismic reflection profiles provide a cross-sectional view of crustal layers and thus details about local sedimentation rates, chronology, and depositional materials. Based on seismic profiles collected as part of the SEA-CALIPSO seismic experiment, we apply this method to interpreting the volcanic and local tectonic history of the island of Montserrat, in the Lesser Antilles arc. In December 2007, the vessel

C. L. Kenedi; S. J. Sparks; S. Dean; J. Hammond; P. E. Malin; T. Minshull; M. Paulatto; C. Peirce; G. Ryan; E. Shalev; B. Voight

2008-01-01

223

Volcano-tectonic implications of 3-D velocity structures derived from joint active and passive source tomography of the island of Hawaii  

NASA Astrophysics Data System (ADS)

We present a velocity model of the onshore and offshore regions around the southern part of the island of Hawaii, including southern Mauna Kea, southeastern Hualalai, and the active volcanoes of Mauna Loa, and Kilauea, and Loihi seamount. The velocity model was inverted from about 200,000 first-arrival traveltime picks of earthquakes and air gun shots recorded at the Hawaiian Volcano Observatory (HVO). Reconstructed volcanic structures of the island provide us with an improved understanding of the volcano-tectonic evolution of Hawaiian volcanoes and their interactions. The summits and upper rift zones of the active volcanoes are characterized by high-velocity materials, correlated with intrusive magma cumulates. These high-velocity materials often do not extend the full lengths of the rift zones, suggesting that rift zone intrusions may be spatially limited. Seismicity tends to be localized seaward of the most active intrusive bodies. Low-velocity materials beneath parts of the active rift zones of Kilauea and Mauna Loa suggest discontinuous rift zone intrusives, possibly due to the presence of a preexisting volcanic edifice, e.g., along Mauna Loa beneath Kilauea's southwest rift zone, or alternatively, removal of high-velocity materials by large-scale landsliding, e.g., along Mauna Loa's western flank. Both locations also show increased seismicity that may result from edifice interactions or reactivation of buried faults. New high-velocity regions are recognized and suggest the presence of buried, and in some cases, previously unknown rift zones, within the northwest flank of Mauna Loa, and the south flanks of Mauna Loa, Hualalai, and Mauna Kea.

Park, Jaewoo; Morgan, Julia K.; Zelt, Colin A.; Okubo, Paul G.

2009-09-01

224

BALD EAGLES AND SEA OTTERS IN THE ALEUTIAN ARCHIPELAGO: INDIRECT EFFECTS OF TROPHIC CASCADES  

Microsoft Academic Search

Because sea otters (Enhydra lutris) exert a wide array of direct and indirect effects on coastal marine ecosystems throughout their geographic range, we investigated the potential influence of sea otters on the ecology of Bald Eagles (Haliaeetus leucocephalus) in the Aleutian Islands, Alaska, USA. We studied the diets, productivity, and density of breeding Bald Eagles on four islands during 1993-1994

Robert G. Anthony; James A. Estes; Mark A. Ricca; A. Keith Miles; Eric D. Forsman

2008-01-01

225

Implications of Temporal-Compositional Variations in the Cerro Pajas Flow and Cone, Floreana Volcano, Galapagos Islands  

NASA Astrophysics Data System (ADS)

Floreana Island is a unique volcano in the Galapagos Islands due to its abundance of mantle xenoliths and the compositional imprint of mantle metasomatism. Floreana lavas are also the most alkaline in the archipelago and represent an enriched end-member due to their high 87Sr/86Sr and 206Pb/204Pb isotope ratios and high concentrations of incompatible trace elements. The surface exposure age of the lavas ranges from 1.52 Ma to 26 ka. Detailed mapping of a single eruptive unit, the Cerro Pajas sequence, shows 18 different eruptive units consisting of lava lobes and tephra. The age of the Pajas units is 26 ka. A suite of nineteen samples was collected from each of the flow lobes and tephra in order to assess variations over the course of the eruptive event. By studying the temporal-compositional trends of a heterogeneous eruptive sequence on Floreana, the melting mechanisms at Floreana can be assessed. Large variations in MgO concentration are seen over the course of the eruption, implying possible differences in the extent of differentiation. The beginning and end of the eruption show the highest concentrations of MgO (~11.5 wt. %). Most of the eruption, however, produced lavas with MgO concentrations of about 7.5 wt. %. The change in MgO cannot simply be attributed to different proportions of olivine phenocrysts, but must reflect changes in liquid composition. In general, concentrations of incompatible elements and ratios such as Nb/Zr increased over the course of the eruption by an amount greater than can be accounted for by fractional crystallization. This may be the result of a decrease in the degree of partial melting over the course of the eruption, and reveals that compositional heterogeneity is generated during a single melt extraction event and preserved during ascent through the lithosphere.

Sabga, M.; Ruiz Paspuel, A.; Geist, D.; Harpp, K.; Koleszar, A.

2007-12-01

226

Rock fall photogrammetric monitoring in the active crater of Piton de la Fournaise volcano, La Reunion Island  

NASA Astrophysics Data System (ADS)

The collapse of the active crater at Piton de la Fournaise volcano, La Reunion Island, 5th April 2007, offers a rare opportunity to observe frequent rock fall and granular landslides, and test new monitoring techniques. Events concern volumes ranging from single blocks to more massive cliff collapse. The purpose of the presentation is two fold: first, we present a comparison between a Digital Terrain Model (DTM) obtained prior to crater collapse and a DTM extracted from aerial photographs shot in October 2010 (before the eruptive crisis of November 2009 and January 2010). This provides an assessment of morphological changes at the scale of the crater. The second purpose is to describe slope instabilities on the south-western flank of the crater observed since October 2009. These ground-based observations were obtained from a pair of photogrammetric stations deployed along the northern and eastern edges of the crater. These works were conducted within UNDERVOLC project. With this monitoring system we mapped zones affected by rockfalls (departure and accumulation areas) and propose a first estimate of volumes of lava produced by the eruption affecting the inside of the crater since January 2.

Hibert, Clément; Dewez, Thomas; Mangeney, Anne; Grandjean, Gilles; Boissier, Patrice; Catherine, Philippe; Kowalski, Philippe

2010-05-01

227

Biodegradation of Crude Oil by Thermophilic Bacteria Isolated from a Volcano Island  

Microsoft Academic Search

One-hundred and fifty different thermophilic bacteria isolated from a volcanic island were screened for detection of an alkane\\u000a hydroxylase gene using degenerated primers developed to amplify genes related to the Pseudomonas putida and Pseudomonas oleovorans alkane hydroxylases. Ten isolates carrying the alkJ gene were further characterized by 16s rDNA gene sequencing. Nine out of ten isolates were phylogenetically affiliated with

Christos Meintanis; Kalliopi I. Chalkou; Konstantinos Ar. Kormas; Amalia D. Karagouni

2006-01-01

228

Parsing Aleutian Arc Magma Compositions  

NASA Astrophysics Data System (ADS)

The first-order subdivision of Aleutian arc magma compositions is based on SiO2, and the second-order subdivision is usually based on the change of FeOt/MgO as a function of SiO2, resulting in the additional twofold subdivision into (TH) and calcalkaline (CA) magmas. However, additional robust compositional variations exist. The two most important of these are (1) variation of the calcium number [Ca#; Ca/(Na+Ca)] as a function of SiO2, and (2) the Rate of Incompatible Trace-element Enrichment (RITE) at individual volcanic centers. Additionally, the data show that the low FeOt/MgO of CA andesite and dacite is more controlled by MgO excess than FeOt depletion. The Ca# of andesites and dacites is strongly bimodal. The low-Ca# group is "calc-alkalic", while the high-Ca# group is "calcic", using Peacock (1931) criteria. A continuum of Ca#s exists, but lavas intermediate between high-Ca# and low-Ca# are much less abundant. Ca#s merge below about 55% SiO2, and have a simple normal distribution. RITE, with rare but important exceptions, is generally constant at the temporal and spatial scale of a single volcano. Among high-RITE magmas LILE, LREE, HFSE, and Th increase ~3.5-fold, and HREE increase ~2.5-fold from basalt or basaltic-andesite through andesite to dacite. There is no strong indication that RITE is silica-dependant. High-RITE magmas develop a strong negative Eu anomaly, and are qualitatively compatible with an origin primarily involving fractionation of plagioclase-dominated mineral assemblages. Low-RITE magmas, in contrast, have nearly invariant REE and HFSE, and LILE and Th increase merely 1.5-fold over the same silica range. Low-RITE magmas are not compatible with fractionation of a plagioclase-dominant mineral assemblage. Alternative qualitatively plausible explanations (needing rigorous evaluation) include fractionation of an ultramafic mineral assemblage (Alaskan-type mafic-ultramafic bodies may be a model; see USGS Prof Paper 1564); that low-RITE basaltic-andesites through dacites are essentially unfractionated; or that low-RITE compositions are dominated by processes other than crystal fractionation, including remobilization of cumulate sludges and addition of silicic partial melts of crustal-level rocks. Low-RITE magmas are usually crystal-rich, while high-RITE magmas are usually crystal-poor - although existing modal data do not permit quantitative investigation of this relationship. There is a high degree of correlation among these chemical characteristics, resulting in two major endmember groups: Type-O suites typically have, as a function of SiO2, low Ca# (are Peacock calc-alkalic), low Mg# (are Miyashiro tholeiitic), high-RITE, are generally sparsely phyric, and are often relatively mafic on average. Type-A magma suites typically have high Ca# (Peacock calcic), high Mg# (Miyashiro calcalkaline), low-RITE, are generally very porphyritic, and usually andesitic on average. Type-O magma suites are found in the central arc - where the arc-crest appears to be under moderate extension. Type-A suites dominate the eastern arc - where the arc-crest is under compression, and are scattered among the type-O volcanoes of the central arc. The western arc is more diverse, although A-type magmas dominate.

Nye, C. J.

2011-12-01

229

The Earthscope Plate Boundary Observatory Akutan Alaskan Volcano Network Installation  

NASA Astrophysics Data System (ADS)

During June and July of 2005, the Plate Boundary Observatory (PBO) installed eight permanent GPS stations on Akutan Volcano, in the central Aleutian Islands of Alaska. PBO worked closely with the Alaska Volcano Observatory and the Magmatic Systems Site Selection working group to install stations with a spatial distribution to monitor and detect both short and long term volcanic deformation in response to magmatic intrusions at depth and magma migration through the volcano's conduit system. All eight of the GPS stations were installed by PBO field crews with helicopter support provided by Evergreen Helicopters 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 equipment be transported to each site from the village of Akutan by slinging gear beneath the helicopter and internal loads. Each station installed on the volcano consists of a standard short braced GPS monument, two solar panels mounted to an inclined structure, and a six foot high Plaschem enclosure with two solar panels mounted to one of the inclined sides. Each Plaschem houses 24 6 volt batteries that power a Trimble NetRS GPS receiver and one or two Intuicom radios. Data from each GPS receiver is telemetered directly or through a repeater radio to a base station located in the village of Akutan that transmits the data over the internet to the UNAVCO data archive at ftp://data-out.unavco.or/pub/PBO_rinex where it is made freely available to the public.

Pauk, B.; Jackson, M.; Mencin, D.; Power, J.; Gallaher, W.; Basset, A.; Kore, K.; Hargraves, Z.; Peterson, T.

2005-12-01

230

Polycyclic aromatic hydrocarbon exposure in Steller's eiders (Polysticta stelleri) and Harlequin ducks (Histronicus histronicus) in the eastern Aleutian Islands, Alaska, USA.  

PubMed

Seaducks may be affected by harmful levels of polycyclic aromatic hydrocarbons (PAHs) at seaports near the Arctic. As an indicator of exposure to PAHs, we measured hepatic enzyme 7-ethoxyresorufin-O-deethylase activity (EROD) to determine cytochrome P4501A induction in Steller's eiders (Polysticta stelleri) and Harlequin ducks (Histronicus histronicus) from Unalaska, Popof, and Unga Islands (AK, USA) in 2002 and 2003. We measured PAHs and organic contaminants in seaduck prey samples and polychlorinated biphenyl congeners in seaduck blood plasma to determine any relationship to EROD. Using Akaike's information criterion, species and site differences best explained EROD patterns: Activity was higher in Harlequin ducks than in Steller's eiders and higher at industrial than at nonindustrial sites. Site-specific concentrations of PAHs in blue mussels ([Mytilus trossilus] seaduck prey; PAH concentrations higher at Dutch Harbor, Unalaska, than at other sites) also was important in defining EROD patterns. Organochlorine compounds rarely were detected in prey samples. No relationship was found between polychlorinated biphenyl congeners in avian blood and EROD, which further supported inferences derived from Akaike's information criterion. Congeners were highest in seaducks from a nonindustrial or reference site, contrary to PAH patterns. To assist in interpreting the field study, 15 captive Steller's eiders were dosed with a PAH known to induce cytochrome P4501A. Dosed, captive Steller's eiders had definitive induction, but results indicated that wild Steller's eiders were exposed to PAHs or other inducing compounds at levels greater than those used in laboratory studies. Concentrations of PAHs in blue mussels at or near Dutch Harbor (approximately 1,180-5,980 ng/g) approached those found at highly contaminated sites (approximately 4,100-7,500 ng/g). PMID:18020694

Miles, A Keith; Flint, Paul L; Trust, Kimberley A; Ricca, Mark A; Spring, Sarah E; Arrieta, Daniel E; Hollmen, Tuula; Wilson, Barry W

2007-12-01

231

Polycyclic aromatic hydrocarbon exposure in Steller's eiders (Polysticta stelleri) and harlequin ducks (Histronicus histronicus) in the Eastern Aleutian Islands, Alaska, USA  

USGS Publications Warehouse

Seaducks may be affected by harmful levels of polycyclic aromatic hydrocarbons (PAHs) at seaports near the Arctic. As an indicator of exposure to PAHs, we measured hepatic enzyme 7-ethoxyresorufin-O-deethylase activity (EROD) to determine cytochrome P4501A induction in Steller's eiders (Polysticta stelleri) and Harlequin ducks (Histronicus histronicus) from Unalaska, Popof, and Unga Islands (AK, USA) in 2002 and 2003. We measured PAHs and organic contaminants in seaduck prey samples and polychlorinated biphenyl congeners in seaduck blood plasma to determine any relationship to EROD. Using Akaike's information criterion, species and site differences best explained EROD patterns: Activity was higher in Harlequin ducks than in Steller's eiders and higher at industrial than at nonindustrial sites. Site-specific concentrations of PAHs in blue mussels ([Mytilus trossilus] seaduck prey; PAH concentrations higher at Dutch Harbor, Unalaska, than at other sites) also was important in defining EROD patterns. Organochlorine compounds rarely were detected in prey samples. No relationship was found between polychlorinated biphenyl congeners in avian blood and EROD, which further supported inferences derived from Akaike's information criterion. Congeners were highest in seaducks from a nonindustrial or reference site, contrary to PAH patterns. To assist in interpreting the field study, 15 captive Steller's eiders were dosed with a PAH known to induce cytochrome P4501A. Dosed, captive Steller's eiders had definitive induction, but results indicated that wild Steller's eiders were exposed to PAHs or other inducing compounds at levels greater than those used in laboratory studies. Concentrations of PAHs in blue mussels at or near Dutch Harbor (???1,180-5,980 ng/g) approached those found at highly contaminated sites (???4,100-7,500 ng/g). ?? 2007 SETAC.

Miles, A. K.; Flint, P. L.; Trust, K. A.; Ricca, M. A.; Spring, S. E.; Arrieta, D. E.; Hollmen, T.; Wilson, B. W.

2007-01-01

232

Extreme Spatial Variability in Microbial Mat Communities from Submarine Hydrothermal Vents Located at Multiple Volcanoes along the Mariana Island Arc  

NASA Astrophysics Data System (ADS)

Volcanic arc systems are the most active tectonic feature in the world, but are among the least studied. The Western Pacific contains ~20,000 km of volcanic arcs, of which only ~2% have been systematically surveyed. The lack of comprehensive knowledge of volcanic arcs is compounded by the incredible variability found in relatively short distances. The complex source history of hydrothermal fluids and the variable depths of seamounts found in island arc systems result in highly variable vent chemistries and therefore unique microbial habitats within relatively short distances. The Mariana Island Arc was surveyed in 2003 and areas with suspected hydrothermal activities were identified for targeted remote operating vehicle (ROV) exploration and sampling in 2004. Sixteen microbial mat samples from five seamounts ranging from 145-1742 mbsl and from ambient to 222°C were collected and analyzed with quantitative PCR (Q-PCR), cluster analysis of terminal restriction length polymorphism (T-RFLP) community fingerprints, and by clone library analysis of small subunit ribosomal rDNA genes. The microbial mat communities from the Mariana Island Arc exhibit greater spatial variability within their community structure than microbial mats sampled from mid-ocean ridge or hotspot hydrothermal vents from a comparable scale. Microbial communities from the summit of NW Eifuku Volcano are dominated by putative iron-oxidizing phylotypes at the Yellow Top and Yellow Cone Vent sites, but are dominated by sulfur-oxidizing ?-Proteobacteria at the Champagne Vent site. Mats collected at the Mat City Vent site on E Diamante Seamount contained nearly three times as much biomass as any other mat sample collected, and is dominated by a Planctomyces phylotype. Hydrothermal sediments at the Fish Spa site located on Daikoku Seamount contained the second highest biomass detected and supported a large community of flatfish indicating a direct route for biomass being channeled up the food chain. The microbial community at Fish Spa consists of a highly diverse assemblage of Bacteroidetes, ?-Proteobacteria and Firmicutes. While in contrast, the microbial mat at the Iceberg Vent site on NW Rota I is dominated by a single phylotype of ?-Proteobacteria.

Davis, R. E.; Moyer, C. L.

2005-12-01

233

Aleutian disease in ferrets.  

PubMed Central

When 32 antibody-free ferrets were inoculated with the highly mink-virulent Utah-1 strain of Aleutian disease virus (ADV), most developed ADV antibody starting 15 days after infection, but the antibody titers were much lower than those seen in mink. Relatively small amounts of ADV were demonstrated in CRFK cell culture, using ferret spleen and lymph node homogenates only 4 to 10 days after experimental infection, but low-level viral persistence for 180 days was shown by mink inoculation. The ferrets inoculated with the Utah-1 strain of ADV did not develop elevated gamma globulin levels, but did have mild tissue lesions. Forty-two percent of a group of 214, approximately 1-year-old, recently pregnant, female ferrets were found to have antibody to ADV. An analysis of the serum proteins of the ferrets with ADV antibody showed that they had a significant, but mild, elevation of their serum gamma globulin. Serial ferret-to-ferret transmission of a ferret strain of ADV by inoculation of spleen homogenates was demonstrated, and some of these ferrets developed liver lesions. Mink inoculated with ferret ADV made antibody, but did not develop hypergammaglobulinemia or tissue lesions. Although both ferret and mink strains of ADV replicate and persist in the ferret, they fail to cause severe disease of the type usually seen in the closely related mink. Mink and ferret ADV strains appear to be biologically distinct. Images

Porter, H G; Porter, D D; Larsen, A E

1982-01-01

234

Characterization of fracture systems using precise array locations of earthquake multiplets: An example at Deception Island volcano, Antarctica  

NASA Astrophysics Data System (ADS)

Volcano-tectonic earthquakes are common seismic events in active volcanic areas. The stress produced by volcanic processes is released through fracturing of the shallow crust. Very often, these earthquakes occur in multiplets with similar waveforms, a fact which indicates common source characteristics. In this work, we introduce a method that uses array techniques to calculate precise relative locations of earthquake multiplets. We use the relative slowness estimate method to determine accurately the apparent slownesses and propagation azimuths of the earthquakes relative to a selected master event. We also obtain precise estimates of the S-P delays. This information is used to calculate precise relative locations by ray tracing in an Earth model. We applied this method to determine the characteristics of the fractures activated during the 1999 seismic series at the Deception Island volcano, Antarctica. We selected a set of 17 earthquake multiplets, initially located in a small (4 × 4 km) region a few km NE of the array site. We estimated precise locations for 14 of the clusters. In most cases, hypocenters were distributed in well-defined planar geometries. We found the best fitting planes, which we interpreted as fractures in the medium. For two clusters, the method spatially separated the earthquakes into two subgroups. Thus, we obtained two planes for each of these clusters, resulting in a total of 16 fracture planes. This is the first time that the orientations of fracture planes related to a seismic series have been obtained using a seismic array. We performed several tests to check various aspects in relation to the stability of the method and concluded that the results were robust. The dip angles indicate that the planes are mostly subvertical, while the strike angles clearly show a NW-SE trend for most of the planes and a few planes with NE-SW trends. The geometry and position of these planes suggest that the 1999 seismic series was influenced by regional tectonics, although the origin of the destabilization of the system may be related to the reactivation of a shallow magma chamber.

Carmona, E.; Almendros, J.; PeñA, J. A.; IbáñEz, J. M.

2010-06-01

235

U-series disequilibrium of basaltic rocks from Kick'em-Jenny submarine volcano, Lesser Antilles island arc  

NASA Astrophysics Data System (ADS)

Kick'em Jenny (KEJ) submarine volcano located 9 km to the north of Grenada in the Lesser Antilles volcanic arc produces lavas ranging in composition from high MgO basalts to moderately evolved andesites. We have determined U-series disequilibria in 12 porphyritic lavas erupted from KEJ volcano by TIMS and MC-ICP-MS methods to constrain the timing and identify the processes creating the magma diversity observed. The SiO2 contents of samples studied here vary from 47 to 55 wt.% SiO2 while REE patterns evolve from slightly LREE enriched, MREE/HREE = 1 patterns to strongly LREE enriched, MREE depleted concave-up patterns. Separate dissolutions of sample KEJ100 indicate an external reproducibility (1s) of 0.7% for (230Th/238U) (n=4), 0.8% for (230Th/232Th) (n=4) and 0.6% for (226Ra/230Th) (n=3), respectively. For all sample, (234U/238U) lies within 0.7% of unity, suggesting that secondary alteration by seawater has not disturbed the U-series data significantly. Sample ages for these submarine erupted samples are unknown, resulting in uncertain values for initial (226Ra/230Th); however, 10 out of 12 of the measured (226Ra/230Th) range between 3.16 and 1.13 and are thus unequivocally young with respect to decay of 230Th and 231Pa since eruption. The U (0.535 - 4.876 ppm) and Th (1.25 - 10.78 ppm) concentrations increase with SiO2 contents. (230Th/232Th) has a restricted range, varying from 0.994 to 1.093 with the exception of one sample. (230Th/238U) ranges from 0.684 to 0.875 while (231Pa/235U) ranges from 1.76 up to 2.84, among the highest 231Pa excess in island arcs yet reported. These data confirm previous observations of the unusual behavior of KEJ lavas relative to global observations in having both large 238U and 231Pa excesses. Combined with (226Ra/230Th), these disequilibria observations require that 238U excesses reflect more than solely fluid addition to the mantle wedge from the subducted oceanic slab.

Huang, F.; Lundstrom, C. C.

2005-12-01

236

K–Ar analyses of the post-caldera lavas of Bratan volcano in Bali Island, Indonesia — Ar isotope mass fractionation to light isotope enrichment  

NASA Astrophysics Data System (ADS)

The post-caldera lavas of Bratan volcano in Bali Island, Indonesia were collected for whole rock chemical analyses and K–Ar analyses. Major and trace element chemistry shows that the lavas are basalts to andesites and typical of subduction-related tectonic setting. The 38Ar/36Ar ratios are 0.1851 ± 3–0.1875 ± 2 and the 40Ar/36Ar, 294.3 ± 0.3–301.6 ± 0.1, which strongly suggest that the mass fractionation to light isotope enrichment took place. The effect of the groundwater on magma is common on the basis of systematic mass fractionation of the atmospheric Ar enriched in lighter isotopes. This case was under the mass fractionation law analyzed numerically, giving the mass fractionation correction ages (14 ± 15, 31 ± 6, 55 ± 22, 66 ± 23, 94 ± 32 and 125 ± 51 ka) consistent with the volcano stratigraphy though the magma composition that changed frequently in time.

Ryu, Sunyoung; Kitagawa, Hiroshi; Nakamura, Eizo; Itaya, Tetsumaru; Watanabe, Koichiro

2013-08-01

237

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

USGS Publications Warehouse

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

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

1991-01-01

238

Nd- and Sr-isotopic compositions of lavas from the northern Mariana and southern Volcano arcs: implications for the origin of island arc melts  

NASA Astrophysics Data System (ADS)

Nd- and Sr-isotopic data are reported for lavas from 23 submarine and 3 subaerial volcanoes in the northern Mariana and southern Volcano arcs. Values of ?Nd range from +2.4 to +9.5 whereas 87Sr/86Sr ranges from 0.70319 to 0.70392; these vary systematically between and sometimes within arc segments. The Nd-and Sr-isotopic compositions fall in the field of ocean island basalt (OIB) and extend along the mantle array. Lavas from the Volcano arc, Mariana Central Island Province and the southern part of the Northern Seamount Province have ?Nd to +10 and 87Sr/86Sr=0.7032 to 0.7039. These are often slightly displaced toward higher 87Sr/86Sr at similar ?Nd. In contrast, those lavas from the northern part of the Mariana Northern Seamount Province as far north as Iwo Jima show OIB isotopic characteristics, with ?Nd and 87Sr/86Sr=0.7035 to 0.7039. Plots of 87Sr/86Sr and ?Nd versus Ba/La and (La/Yb)n support a model in which melts from the Mariana and Volcano arcs are derived by mixing of OIB-type mantle (or melts therefrom) and a metasomatized MORB-type mantle (or melts therefrom). An alternate interpretation is that anomalous trends on the plots of Nd- and Sr-isotopic composition versus incompatible-element ratios, found in some S-NSP lavas, suggest that the addition of a sedimentary component may be locally superimposed on the two-component mixing of mantle end-members.

Lin, P. N.; Stern, R. J.; Morris, J.; Bloomer, S. H.

1990-09-01

239

High Resolution, Pb Isotope Variability Within Historic Eruptions of the Cumbre Vieja Volcano, La Palma, Canary Islands  

NASA Astrophysics Data System (ADS)

The range of time-scales over which ocean island basalt (OIB) magmatism taps different mantle heterogeneities is a fundamental dynamic of mantle plumes. The variability of long-lived radiogenic isotopes in OIB magmas erupted on time scales less than 100 years has been addressed primarily for Hawaiian magmas (e.g., Pietruszka et al., 2001). Similar data are relatively sparse for hot spots with low buoyancy fluxes. The Canary Islands have low eruption rates and have been historically active. The Cumbre Vieja volcano in southern La Palma, Canary Islands, has six, well-mapped, historic eruptions spanning the entire southern rift zone. We have investigated Pb isotope compositional variations expressed in magmas erupted in a series of events spanning 500 years (the 1480, 1585, 1677, 1712, 1949, and 1971 eruptions), and sampled in detail two of these events (the 1677 and 1712 eruptions) to document isotopic variability at the month to year time-scale as well as the 100-year time scale. Previous Pb isotope investigations of Cumbre Vieja did not reveal systematic variations (e.g., Marcantonio et al., 1995 and Ovchinnikova et al., 1995). With denser sampling (40 samples) and higher precision MC-ICP-MS analyses, we observe that radiogenic Pb isotope compositions over the 500 year eruptive history decrease systematically with time (206Pb/204Pb =19.669 -- 19.611, 207Pb/ 204Pb = 15.618 -- 15.602, 208Pb/204Pb = 39.530 -- 39.430). Detailed Pb isotope analyses of the 1677 and 1712 eruptions indicate isotopically homogeneous magmas within a single eruptive episode. However, samples from both the 1677 and 1712 eruptions display mineralogic evidence for magma mixing: 1677 samples include isotopically distinct gabbroic xenoliths, and both magmas have reversely- zoned clinopyroxene phenocrysts with corroded cores of Na-rich salite, and zoned overgrowths of Al-rich salite. With time, an increasing proportion of partial melt from a less radiogenic end-member within a heterogeneous plume explains the 500 year trend. Alternatively, higher level mixing of two magmas would require sequential recharge of a single magma chamber that feeds the entire rift zone. A single chamber is structurally unlikely, and not consistent with geochemical and petrographic trends (Klü gel, 1999). From the decompressing plume, batches of melt with homogeneous Pb isotope ratios are extracted periodically. To generate mineralogic disequilibrium, each batch must segregate into a zoned magma chamber or multiple, isolated pockets and differentiate at multiple levels. Prior to eruption, magma from these pockets may remix, producing reversely-zoned clinopyroxene phenocrysts. Isotopic homogeneity is preserved within a given magma batch. In the Canary Islands, the minimum time period for eruptive basalts to reflect resolvable mantle isotope heterogeneity is on the order of 50 - 100 years. A. Klügel, K. A. Hoernle, H.-U. Schmincke, J. D. L. White, J. Geophys. Res. 105(B3), 5997 (2000). F. Marcantonio, A. Zindler, T. R. Elliot, H. Staudigel, Earth Planet. Sci. Lett. 133, 397 (1995). G. V., Ovchinnikova, B. V., Belyatskii, I. M., Vasil'eva, L. K., Levsky, A. F., Grachev, V., Arana, I. J., Mitjavila, Petrologiya, 3, 195 (1995). A. J. Pietruszka, K. H. Rubin, M. O. Garcia, Earth Planet. Sci. Lett. 186, 15 (2001).

Locke, J. A.; Peterson, B. T.; Nelson, B. K.

2005-12-01

240

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

Microsoft Academic Search

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 200ma.s.l., about 1.5km far away from the active vents. Two days after the explosion, a new vapour emission was discovered on the north-eastern flank of the

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

2010-01-01

241

Pavlof Volcano darkens the Alaskan sky  

NASA Astrophysics Data System (ADS)

Pavlof Volcano, historically the most active volcano in the Aleutian volcanic arc and a serious potential threat to aviation safety, began a vigorous strombolian eruption in mid-September. Located 965 km southwest of Anchorage, Pavlof lies beneath the heavily traveled North Pacific jet air routes through which 10,000 passengers fly each day. During its most recent eruption in 1986-1988, an 8-hour explosive event at Pavlof sent ash more than 15 km above sea level and dropped 3 mm of ash on Cold Bay, 60 km southwest of the volcano. A similar, unanticipated explosive eruption today would pose a significant hazard to air traffic in the region.

Neal, Tina

242

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

243

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

244

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

245

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.

246

Volatile Abundances and Magma Geochemistry of Recent (2006) Through Ancient Eruptions (Less Than 2100 aBP) of Augustine Volcano, Alaska  

Microsoft Academic Search

Augustine Volcano, Cook Inlet, Alaska, is a subduction-related Aleutian arc volcano located approximately 275 km southwest of Anchorage. During the past 200 years, Augustine volcano has shown explosive eruptive behavior seven times, with the most recent activity occurring in January through March 2006. Its ash and pumice eruptions pose a threat to commercial air traffic, the local fishing industry, and

J. D. Webster; C. W. Mandeville; T. Gerard; B. Goldoff; M. L. Coombs

2006-01-01

247

The Amaknak Bridge Site: Cultural Change and the Neoglacial in the Eastern Aleutians  

Microsoft Academic Search

Evidence from a series of excavations in Unalaska Bay indicates that the onset of the Neoglacial had begun to alter the cultural and natural landscape of the Aleutian Islands as early as 4500 rcybp. By 3500 rcybp deep semi-subterranean houses with stone walls and elaborate hearth systems were constructed at the Margaret Bay site. The nearby Amaknak Bridge site was

Richard A. Knecht; Richard S. Davis

2008-01-01

248

Distribution, 14C chronology, and paleomagnetism of latest Pleistocene and Holocene lava flows at Haleakala volcano, Island of Maui, Hawai`i: A revision of lava flow hazard zones  

Microsoft Academic Search

New mapping and 60 new radiocarbon ages define the age and distribution of latest Pleistocene and Holocene (past 13,000 years) lava flows at Haleakala volcano, Island of Maui. Paleomagnetic directions were determined for 118 sites, of which 89 are in lava flows younger than 13,000 years. The paleomagnetic data, in conjunction with a reference paleosecular variation (PSV) curve for the

David R. Sherrod; Jonathan T. Hagstrum; John P. McGeehin; Duane E. Champion; Frank A. Trusdell

2006-01-01

249

Monitoring for volcano-hydrothermal activity using continuous gravity and local ground acceleration measurements: New deployments at Inferno Crater, Waimangu and White Island, New Zealand  

NASA Astrophysics Data System (ADS)

Volcanoes with crater lakes are often characterised by shallow hydrothermal systems which display cyclic behaviour (temperature, lake level, chemistry, etc.) and shallow seismic tremor. Present monitoring programmes in New Zealand include routine collection of these observables, but the associated shallow sub-surface processes are still inadequately modelled and poorly understood. Models would be better constrained with the incorporation of additional geophysical parameters. To this end, we have established a new test programme to continuously monitor for micro-gravity variations at New Zealand volcanoes. We utilise a Micro-g-LaCoste gPhone relative gravity meter having 1 Hz sample rate and a measurement precision of 1 microgal to test the viability of gravity monitoring for volcano-hydrothermal systems. We have initially tested the new sensor in a short term deployment (~2 months) at Inferno Crater, Waimangu, New Zealand. Inferno shows dramatic variations in crater lake level (> 7 m range), temperature (>40o C range) and hydrothermally derived tremor, all over a period of ~5 weeks. The amplitude and period of these observables are ideal for testing gravity variations associated with a cycling hydrothermal system because several cycles can be obtained in a relatively short campaign. We have deployed the gravity sensor into a buried vault having a stable concrete base to minimise local environmental influences. This vault is located ~20 meters from Inferno Lake edge (at high stand) and offers sufficient noise reduction to measure the gravitational effects associated with lake level changes. We will show results for the new gravity meter including raw relative gravity measurements and first order corrections (earth-tide, ocean loading, sensor level, temperature, and barometric pressure) to obtain both residual gravity and overprinted local ground accelerations (earthquakes and local tremor). To examine the effects of local ground vibrations on the gravity meter, we have co-located a broadband seismometer (100 Hz sample rate). Of particular interest in this analysis is the separation of any microgravity changes from the hydrothermal tremor signature. Future modelling of the Inferno Crater lake will incorporate gravity, lake level and temperature changes into a multi-phase spatio-temporal model of the subsurface. We anticipate that separation of the gravity and seismic signals may allow future constraint of the sub-surface hydrothermal processes which control cyclic behaviour. We also will show results of a planned deployment of the new gravity meter to White Island volcano, New Zealand which will occur in March 2010. Lessons learned from the Waimangu deployment will be incorporated to understand the long-term variations of White Islands' hydrothermal and magmatic system.

Jolly, Arthur; Fournier, Nico; Cole-Baker, Jeremy; Miller, Craig

2010-05-01

250

Eruptive history of western and central Aeolian Islands volcanoes (South Tyrrhenian Sea, Italy): temporal evolution of magmatism and of morphological structures  

NASA Astrophysics Data System (ADS)

The Aeolian Island archipelago is a complex volcanic province located on the continental margin of the Calabro-Peloritan basement. It emplaced in a geodynamic setting linked to the convergence of African and European plates. In this study, we focused on the western and central volcanoes that are respectively Alicudi-Filicudi-Salina and Lipari-Vulcano. They erupted the whole range of magmas typical of convergence settings : from calc-alkaline (CA) to potassic series (KS) through high-K CA (HKCA) and shoshonitic series (SHO). All these magma products were emitted in a span time of less than 300 ka that attests to the complexity of the volcano-tectonic evolution of this province. We report new geochronological data, based on the K/Ar Cassignol-Gillot technique, which is well suited for dating Quaternary volcanic materials. New geochemical analyses were realized on the dated samples in order to study the temporal evolution of the magmatism. These data sets were coupled with geomorphological analysis to study the relation between main morphological structures and eruptive styles. Before 180 ka, only the Filicudi, Salina and Lipari volcanoes had emerged activity. Their magmas have relatively the same CA composition, whereas some Lipari lavas have early HKCA affinity. Around 120-130 ka, Alicudi and Vulcano emerged simultaneously at the extremities of the archipelago. Alicudi products are less various and have the more primitive composition. SHO and HKCA products were emitted on Lipari and Vulcano, while only CA magmas were emplaced on Filicudi and Salina. After 40 ka, the last activity of Filicudi is characterized by mafic magmas of HKCA affinity. To the other extremity, similar products of SHO affinity were emplaced in southern Lipari and northern Vulcano. At this period, explosive activity with dacitic pumices occurred in Salina. The degree of differentiation and the K enrichment increase from western sector to central sector volcanoes and through time except at Filicudi. At the scale of the archipelago, two main magma composition changes occurred around 120 and 40 ka. However, at smaller space and time-scales, the magmatic evolution is more complex reflecting different processes specific to each volcano.

Leocat, E.; Gillot, P.; Peccerillo, A.

2010-12-01

251

The 1996 Earthquake Swarm and Intrusion at Akutan Volcano, Alaska: An Example of a Failed Eruption  

NASA Astrophysics Data System (ADS)

In March 1996, Akutan Volcano, in the central Aleutian Arc, was the source of a powerful swarm of Volcano- Tectonic (VT) earthquakes composed of more than 200 shocks greater than magnitude 3.5 (Mmax = 5.1) that produced an estimated total cumulative seismic moment of 2.7 X 1018 N m. The swarm consisted of two pulses that began on March 11 and March 14: elevated earthquake activity continued at Akutan Volcano for several months. Extensive ground cracks that striking N70W and extending discontinuously across the island from near Lava Point (the most recently active satellite vent) to the southeast side of the island formed in association with this swarm. The most extensive cracks formed a zone that is 500 m wide and 3 km long on the NW flank of the volcano between the summit and Lava Point. In this area, local graben structures show vertical displacements of 30 to 80 cm, suggesting the cracks formed in response to uplift of this portion of the volcano. Results from both C-band ERS and L-band JERS radar interferometry images that span the time of the swarm reveal a complex island-wide pattern of deformation: The western part of the island moved upward as much as 70 cm, while the eastern part moved downward a similar amount. The most plausible interpretation is that the 1996 seismic swam and associated ground deformation at Akutan resulted from an intrusion of magma beneath the northwest flank of the volcano. Modeling of the observed deformation field suggests the inflation on the northwest side of the volcano results from the intrusion of a dike with a top at 0.4 km depth, while the deflation on the island's eastern side is modeled as several dislocation planes that possibly reflect the depressurization of a known hydrothermal system in this area. Earthquake hypocenters calculated between 1996 and 2008 are consistent with this model and show (a) a prominent cluster of shallow earthquake hypocenters that occurred on the eastern side of the island near the center of subsidence in 1996, (b) a west-northwest trend in hypocenters that aligns with the observed ground cracks and extends across the island, and (c) a small cluster of low- and mixed-frequency events that locate at mid-crustal depths beneath the volcano's southwest flank. In spite of this high level of volcanic unrest in 1996 no subsequent magmatic eruption has occurred at Akutan in association with or since this swarm. The seismic moment and ground deformation observed at Akutan in 1996 greatly exceeds many sequences that precede eruptions at other volcanoes. Remarkably, no observed increases in fumorolic activity or gas emission and no obvious periods of volcanic tremor or long- period seismic events were observed in association with the 1996 seismic swarm. The lack of these key precursors played a strong role in diagnosing the unrest and formulating public warnings and advisories issued by the Alaska Volcano Observatory during the 1996 seismic crisis.

Power, J. A.; Lu, Z.; Prejean, S. G.; Wicks, C.; Dzurisin, D.

2008-12-01

252

Volcanoes Galore!  

NSDL National Science Digital Library

Here, you can check out videos and links to lots of nifty volcano stuff. Have fun! This is completely unrelated...but check it out anywho. sweet periodic table! Alaska Volcano Observatory Earthquakes and Volcanoes Check this one out for info on history\\'s most distructive volcano. Exploring Pompeii and Vesuvius Exploring the Environment: Volcanoes This will give you lots of background on how Volcanoes work, what the major parts are, and how they erupt. How Volcanoes Work A quick video on how to take a lava sample...hot! Lava Sampling on Kilauea Volcano, Hawai i A volcano in antartica? ...

Syracuse, Mr.

2008-06-11

253

Flow directions and emplacement temperatures of Holocene phreatomagmatic deposits at Stromboli volcano (Aeolian islands, Italy) inferred by paleomagnetic analyses  

NASA Astrophysics Data System (ADS)

Stromboli volcano is presently characterized by persistent mild explosive activity. However the most dangerous scenario at Stromboli is associated to the lateral sector collapse of the volcano, a less frequent event that permits the magma-water interaction producing very explosive phreatomagmatic eruptions. At Stromboli volcano, the phreatomagmatic deposits have been, up to now, related to the same eruptive event occurred in the last 15 ka. We carried out the results from an AMS (14 sites) and a TRM (8 sites) analyses on Holocene phreatomagmatic and surge deposits. Two stratigraphic sections (Secche di Lazzaro and COA) in two different localities have been recognized and investigated by means of stratigraphic, sedimentological and magnetic analyses. The magnetic fabric data suggest that the basal part of the Secche di Lazzaro deposit was emplaced from a diluted phreatomagmatic pyroclastic flow coming from the sea, whereas the middle and upper part from the summit vent. The thermal remanent magnetization data of the lava lithics demonstrate that the whole deposit was emplaced at very low temperatures (less than 140°C), whereas the basal part of the COA deposit was emplaced at temperatures between 300-350°C. The overall results suggest that the two investigated deposits are related to two distinct eruptive events, occurred in the last 15 ka. In this case, the recent phreatomagmatic activity at Stromboli should be occurred more frequently than previously believed, suggesting to reconsider the timing of recurrence of this dangerous eruptive scenario for the Stromboli volcano.

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

2006-12-01

254

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

255

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

256

Inflation and deflation modeling at Sierra Negra and Fernandina volcanoes based on GPS measurements. Galapagos Islands, Ecuador  

NASA Astrophysics Data System (ADS)

Continuous Global Positioning System (CGPS) network established since 2002 on Sierra Negra and the campaign GPS network re-measured in 2006 on Sierra Negra and Fernandina volcanoes allowed for the evaluation of ground deformation after the 2005 eruptions on each volcano. In contrast, shallow seismicity detected before the eruptions by the Galapagos seismic network (REDGAL) may be related to a shallow, pressurized magma chamber fed by a deep source on each volcano, while regional seismicity, by National Earthquake Information Center-United States Geological Survey (NEIC-USGS), plays no measurable role in the ground deformation. The ground deformation monitored by the CGPS network on Sierra Negra demonstrated fast inflation of ~ 212 cm/y immediately after the October 2005 eruption and then a deceleration at rates of ~ 73 cm/y in 2006 and ~ 48 cm/y in 2007 due the pressurization of the shallow sill. This is supported by micro-gravity surveys performed in 2006 and 2007 which record a large density increase (magma influx and/or densification) centered above the shallow sill immediately following the eruption. The density increase continued in 2007 but at a slower rate. Inversion and calculations using a simple elastic model indicates a sill ~ 2 km depth oriented northeast-southwest in agreement with InSAR data, and an average rate of magma intrusion of ~ 70 x 106 m3 /y. The campaign GPS dataset on Fernandina volcano is best explained by an average rate of magma intrusion of ~2.2 x 106 m3/y, and the deformation is best modeled by a magma chamber ~ 2 km deep in combination with a dike source produced by the May 2005 eruption. The integration of these methods allowed us to see the volcanic activity from the depth to the surface on each volcano and construct a conceptual model for each one after the 2005 eruptions.

Ruiz Paspuel, A. G.; Geist, D.; Chadwick, W.; Johnson, D.; Vigouroux-Caillibot, N.; Harpp, K. S.; Batt, S.

2010-12-01

257

The 1931 Eruption of Aniakchak Volcano, Alaska  

Microsoft Academic Search

One of the largest Aleutian Arc eruptions of the 20th century was the 1931 intracaldera eruption of Aniakchak Volcano, with an erupted volume of 0.3 to 0.5 km3. The eruption, which varied in intensity, style, and composition, persisted for approximately 6 weeks, dispersing ash as far as 600 km to the north. The eruption was first noticed when a large

R. S. Nicholson; C. A. Neal; J. E. Gardner

2002-01-01

258

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

259

HIGH TEMPERATURE VOLCANIC GAS GEOCHEMISTRY (MAJOR AND MINOR ELEMENTS) AT KUDRYAVY VOLCANO, ITURUP ISLAND, KURIL ARC, RUSSIA  

Microsoft Academic Search

Kudryavy volcano is well known for its famous Re-enrichment (Korzhinsky et al., 1994). Degassing occurs along 2 main fumarolic fields: field A enriched in Re (T= 400 to 700°C) and field B enriched in Mo (T= 600-940°C). The fO2 values of the volcanic gases are close to the Ni\\/NiO buffer. Direct fO2 measurements over the temperature range 500- 950°C approach

F. Africano; A. Bernard; M. Korzhinsky

2003-01-01

260

Constraints on magma chamber geometry at Sierra Negra Volcano, Galápagos Islands, based on InSAR observations  

Microsoft Academic Search

We investigate the problem of estimating magma chamber geometry using InSAR observations of Sierra Negra Volcano, Galápagos. Ascending and descending interferograms are combined to determine vertical and one horizontal component of displacement. The ratio of maximum horizontal to vertical displacement suggests a sill-like source. Spherical or stock-like bodies are inconsistent with the data. We estimate the geometry of the sill

S. Yun; P. Segall; H. Zebker

2006-01-01

261

Life at the extreme: meiofauna from three unexplored lakes in the caldera of the Cerro Azul volcano, Galápagos Islands, Ecuador  

Microsoft Academic Search

On Isla Isabela, Galápagos Archipelago, three so far unexplored lakes were investigated in the caldera of Cerro Azul, one\\u000a of the most active volcanoes in the world. The lakes face recurrent desiccation and eruption events and showed distinct differences\\u000a in their water chemistry. Thirty cores from the upper 15 cm of sediment indicate distinct differences in the composition of\\u000a meiobenthic communities

Daniel Muschiol; Walter Traunspurger

2009-01-01

262

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

263

New K Ar ages for calculating end-of-shield extrusion rates at West Maui volcano, Hawaiian island chain  

NASA Astrophysics Data System (ADS)

Thirty-seven new K Ar ages from West Maui volcano, Hawai‘i, are used to define the waning stages of shield growth and a brief episode of postshield volcanism. All but two samples from shield-stage strata have reversed polarity magnetization, so conceivably the exposed shield is not much older than the Olduvai Normal-Polarity subchron, or about 1.8 Ma. The oldest ages obtained are in the range 1.9 2.1 Ma but have large analytical error. Shield volcanism ended about 1.35 Ma, and postshield volcanism followed soon thereafter, persisting until about 1.2 Ma. Exposed shield-stage strata were emplaced at a rate of about 0.001 km3 per year, a rate smaller than historic Hawaiian magmatic rates by a factor of 100. Stratigraphic accumulation rates are similar to those measured previously at Wai‘anae volcano (O‘ahu) or the upper part of the Mauna Kea shield sequence (Hilo drill core, Hawai‘i). These rates diminish sharply during the final 0.3 0.5 m.y. of the shield stage. Hawaiian shield volcanoes begin waning well before their last 0.5 m.y. of life, then end quickly, geologically speaking, if West Maui is representative.

Sherrod, David R.; Murai, Takashi; Tagami, Takahiro

2007-04-01

264

New K-Ar ages for calculating end-of-shield extrusion rates at West Maui volcano, Hawaiian island chain  

USGS Publications Warehouse

Thirty-seven new K-Ar ages from West Maui volcano, Hawai'i, are used to define the waning stages of shield growth and a brief episode of postshield volcanism. All but two samples from shield-stage strata have reversed polarity magnetization, so conceivably the exposed shield is not much older than the Olduvai Normal-Polarity subchron, or about 1.8 Ma. The oldest ages obtained are in the range 1.9-2.1 Ma but have large analytical error. Shield volcanism ended about 1.35 Ma, and postshield volcanism followed soon thereafter, persisting until about 1.2 Ma. Exposed shield-stage strata were emplaced at a rate of about 0.001 km3 per year, a rate smaller than historic Hawaiian magmatic rates by a factor of 100. Stratigraphic accumulation rates are similar to those measured previously at Wai'anae volcano (O'ahu) or the upper part of the Mauna Kea shield sequence (Hilo drill core, Hawai'i). These rates diminish sharply during the final 0.3-0.5 m.y. of the shield stage. Hawaiian shield volcanoes begin waning well before their last 0.5 m.y. of life, then end quickly, geologically speaking, if West Maui is representative. ?? Springer-Verlag 2006.

Sherrod, D. R.; Murai, T.; Tagami, T.

2007-01-01

265

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

266

Volcanic Activity in Alaska and Kamchatka: Summary of Events and Response of the Alaska Volcano Observatory, 2003.  

National Technical Information Service (NTIS)

The Alaska Volcano Observatory (AVO) monitors the more than 40 historically active volcanoes of the Aleutian Arc. Of these, 24 were considered monitored in real time with short-period seismic instrument networks as of the end of 2003 (Dixon and others, 20...

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

2005-01-01

267

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

268

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

269

Structure and change of Piton de la Fournaise volcano inferred from gravity surveys (Reunion Island, Indian Ocean)  

NASA Astrophysics Data System (ADS)

A new gravity map of Piton de la Fournaise volcano has been established using new on land and offshore measurements. The data coverage allows for the differentiation of shallow and deeper structures. 3D and 2 3/4 D models have been calculated. Short wavelength positive anomalies depict the presence of piles of thick dense lava flows filling volcano-tectonic depressions. The lateral extension and the depth of paleo- depressions associated with the collapses of the Plaine des Sables-Fond de la Rivière de l'Est and of the Enclos Fouqué are thus estimated. The negative short wavelength of the Central Cone suggests it has been built by thin, highly vesisculated and fractured lava flows. Low density hydrothermally altered rock beneath the summit can also contribute to the gravity low as well as a column of fractured rocks between the surface collapse and a magma reservoir. Negative short to medium wavelength anomalies have been observed in the Rivière des Remparts-Rivière Langevin zone and above the offshore continuation of the NE and SE rift zones. We speculate that the former zone is underlain by breccias related to erosion or mass- wasting events. The offshore continuation of the rift zones is most likely built by hyaloclastites and pillow lavas. Two main deeper dense structures exist: the Grand Brûlé complex and a complex beneath the Plaine des Sables and part of the Enclos. From a deep drill-hole it has been established that the Grand Brûlé complex is a hypovolcanic complex of intrusions and cumulates. We show that this structure is disconnected from the present day Piton de la Fournaise volcano. Its interpretation as the hypovolcanic complex of the ancient concealed Les Alizés volcano remains valid. The similar nature of the other dense complex is inferred by analogy with comparable anomalies in this geological context and by the presence of frequent gabbro and peridotite xenoliths in eruptive products in this area. We suggest that this complex has developed during the Ancient Shield period of Piton de la Fournaise. The fact that this structure is apparently not offset by the fault that limits the Enclos to the west suggests that the latter is a listric fault. Observed apparent contradictions between the seismic tomographies and the gravity pattern could be resolved considering the relative sensitivity of each method. Strong shallow gravity signals significantly hide moderate signals from deeper structures. Conversely, with a moderate station and signal coverage, the seismic tomographies fail to define precisely the subsurface structures. The use of both methods increases the accuracy in the determination of the internal structure of volcanoes. Pre and post April 2007 eruptive and volcano-tectonic crisis data show a significant gravity change in the central area. The observed mass deficit can be explained by creation of the new Dolomieu crater only or by the sum of the effects of the crater formation and of the fracturing of a column of rocks between the surface and the drained magma reservoir.

Lénat, J.; Gailler, L.; Lambert, M.; Levieux, G.; Villeneuve, N.; Froger, J.

2008-12-01

270

Gravity Variations at a Dynamic Basaltic Caldera: Before and After the 2005 Eruption of Sierra Negra Volcano, Galapagos Islands  

NASA Astrophysics Data System (ADS)

Sierra Negra volcano, an active basaltic volcano in the western Galapagos, last erupted in October 2005 following a period of accelerated uplift of the central caldera floor that started in April 2003. Deformation data indicate that a shallow (~ 2 km) sill underlies the caldera floor, and an intrusion rate of 64 x 106 m3/y for the 6 months prior to eruption was calculated from a continuous GPS network installed in 2002. Micro-gravity measurements were conducted in 2005, 2006, and 2007 at three stations in the center of the caldera and one station on the outer flank of the volcano and referenced to a base station on the NE rim of the caldera. From June 2005 to June 2006, residual gravity measured in the caldera increased by 1500 microgals at the center of the caldera to 184 microgals halfway to the northern edge of the caldera. This increase in residual gravity (height corrected) was accompanied by an uplift rate of ~ 212 cm/y until February 2006 after which the uplift rate decreased to 73 cm/y in 2006 and 44 cm/y in 2007. Similarly, from June 2006 to June 2007 gravity increased less dramaticaly than in 2005-2006 with an average increase of 11 microgals at the center of the caldera and 132 microgals at the more northern part of the caldera. Interestingly, the center of maximum gravity change shifted from the center of the caldera to the northern part sometime between June 2006 and June 2007. Gravity measurements on the outer rim of the caldera showed a 300 and a 200 microgal decrease from June 2005 to June 2006 and June 2006 to June 2007, respectively accompanied by low rates of inflation (1.8 cm/y). The coupling of gravity and deformation change supports the hypothesis of significant mass increase in the central-northern part of the caldera.

Geist, D.; Vigouroux, N.; Williams-Jones, G.; Chadwick, W.; Johnson, D.

2007-12-01

271

Reawakening of the Teide volcano (Tenerife island, Spain): Monitoring the activity through the analysis of continuous seismic and GPS data.  

NASA Astrophysics Data System (ADS)

The reawakening of the Teide volcano in 2004 caused the installation of several seismic and GPS stations, operating in continuous mode. This allowed the application of different techniques of time sequence data analysis. The results of the analysis of the background seismic noise, deformation model and b parameter of located seismic events show evidences of a magmatic process in course, probably related to the central volcanic system of Tenerife. Other obtained results not only allow the occurrence of tectonic events (volcanotectonic??) forecasting, but also the establishment of a clear influence in the variation of the background noise characteristics.

Ortiz, R.; Vila, J.; García, A.; Tárraga, M.; Carniel, R.; Marrero, J. M.; Carmona, J.; Fernández-Ros, A.; Berrocoso, M.

2009-04-01

272

Low pressure fractionation in arc volcanoes: an example from Augustine Volcano, Alaska  

Microsoft Academic Search

Augustine Volcano, situated between the Cook and Katmai segments of the Eastern Aleutian Volcanic Arc, has erupted 5 times since its discovery in 1778. Eruptions are characterized by early vent-clearing eruptions with accompanying pyroclastic flows followed by dome-building and more pyroclastic flows. Bulk rock chemistry of historic and prehistoric lavas shows little variability. The lavas are calc-alkaline, low to medium

E. E. Daley; S. E. Swanson

1985-01-01

273

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

NASA Astrophysics Data System (ADS)

Using Interferometric Synthetic Aperture Radar (InSAR) measurements of the surface deformation at Fernandina Volcano, Galápagos (Ecuador), acquired between January 2003 and September 2010, we study the structure and the dynamics of the shallow magmatic system of the volcano. Through the analysis of spatial and temporal variations of the measured line-of-sight displacement we identify multiple sources of deformation beneath the summit and the southern flank. At least two sources are considered to represent permanent zones of magma storage given their persistent or recurrent activity. Elastic deformation models indicate the presence of a flat-topped magma reservoir at ˜1.1 km below sea level and an oblate-spheroid cavity at ˜4.9 km b.s.l. The two reservoirs are hydraulically connected. This inferred structure of the shallow storage system is in agreement with previous geodetic studies and previous petrological analysis of both subaerial and submarine lavas. The almost eight-year-long observation interval provides for the first time geodetic evidence for two subvolcanic lateral intrusions from the central storage system (in December 2006 and August 2007). Subvolcanic lateral intrusions could provide the explanation for enigmatic volcanic events at Fernandina such as the rapid uplift at Punta Espinoza in 1927 and the 1968 caldera collapse without significant eruption.

Bagnardi, Marco; Amelung, Falk

2012-10-01

274

The 226Ra-230Th-238U disequilibria of enigmatic magmas from Piton de la Fournaise Volcano, Reunion Island (1950-1998)  

NASA Astrophysics Data System (ADS)

We present a detailed study of the 226Ra-230Th-238U disequilibria and selected incompatible trace-element abundances of lavas from Piton de la Fournaise, a frequently active ocean-island volcano, using high-precision MC-ICP-MS. The samples erupted between 1950-1998 from vents within the summit caldera (Enclos Fouque) or along the rift zones of the volcano. The lavas display a significant range in 226Ra-230Th disequilibria (25-33% excess 226Ra) and 230Th-238U disequilibria (14-20% excess 230Th). The (230Th/232Th) ratios of the lavas are relatively constant (0.9% range) and do not correlate with either Th/U or (230Th/238U). A strong correlation (R2=0.97) between the (230Th/238U) and Th/U ratios suggests that most of the Th-U fractionation in these lavas occurred recently compared to the 76 kyr half-life of 230Th [because the effects of this fractionation are not yet reflected in the (230Th/232Th) ratios]. In contrast, the 226Ra-230Th disequilbria do not correlate with the Ba/Th ratios of the lavas (a geochemical analog). Thus, the range in Ba/Th (6.1%) and (226Ra/230Th) ratios probably results from either more than one magmatic process or a single process operating over a time scale that is longer than the half-life of 226Ra (1600 years). Unlike Hawaiian shield volcanoes, which display systematic temporal geochemical variations on a time scale of decades to centuries, the fluctuations in lava chemistry at Piton de la Fournaise do not display any coherent trends over the last 50 years. Some geochemical parameters [e.g., Ba/U, Nd/Sm or (230Th/238U)] do vary systematically over a period of a few years, but these trends are not observed consistently for the same samples and different geochemical parameters. The origin of these complex variations in lava chemistry at Piton de la Fournaise is enigmatic, but probably includes a combination of mantle (Albarede and Tamagnan, 1988, J. Petrol. v. 29) and crustal (Sigmarsson et al., 2005, EPSL v. 234; Vlastelic et al., 2005, J. Petrol. v. 46) processes. Possible explanations for the data will be explored at the meeting.

Pietruszka, A. J.; Hauri, E. H.; Albarede, F.; Blichert-Toft, J.

2005-12-01

275

Explosive activity of the summit cone of Piton de la Fournaise volcano (La Réunion island): A historical and geological review  

NASA Astrophysics Data System (ADS)

Summit explosive activity and collapses that form pit craters and calderas represent major volcanic hazards on a dominantly effusive, frequently active volcano like Piton de la Fournaise. Only three summit collapse events (1986, 2002, 2007) have been recorded since the foundation of the Piton de la Fournaise volcano observatory (OVPF) in 1979, and two of them (1986 and 2007) were associated with weak phreatic activity. At Piton de la Fournaise, the normal explosive activity consists of short-lived and mild (< 20 m-high) lava fountains, which quickly evolve into strombolian activity during the eruptions. Based on comprehensive literature review and high-resolution image analysis of surface outcrops and summit caldera walls, we reconstructed the time distribution of recent explosive events (phreatomagmatic; phreatic) and their link with summit collapses and lateral (flank) effusive eruptions. In historical time (post-1640 CE), we recognise two main clusters of explosive events. Frequent and violent phreatomagmatic to phreatic explosions occurred during the oldest cluster (1708–1878) and alternated with long-lasting periods (years to decades) of summit effusive activity. In contrast, scarce, and on average, weak explosions occurred during the youngest cluster (1897–2012), when discrete and short-lived (< 6 months) effusive eruptions represent the main eruptive dynamics. Historical summit collapses (pit craters and caldera), all localised at the top of the summit cone, were related to voluminous lateral eruptions and were followed by a significant decrease in eruptive rate. However, magma draining during lateral eruptions was not systematically associated with summit collapses or explosions. The long-lasting occurrence of magma at very shallow depth below the volcano summit, followed by a rapid lateral drainage, apparently represents a critical condition favouring magma–groundwater interaction to produce explosive activity. The prehistoric growth of the Piton de la Fournaise summit cone results chiefly from long-lasting to continuous activity, centred below its western side (Bory crater containing lava lakes). High lava fountains, long-lasting effusive activity, lava lakes, ash plumes and block ejections were common types of eruptive dynamics in the historical past, between 1640 and 1878. In this perspective, short-lived, small volume eruptions and long pauses, up to six years, during the last century of activity of Piton de la Fournaise can be considered as a lull, despite the high frequency of eruption (1 eruption/9 months on average). Temporal and spatial variations in recurrence rate and eruptive dynamics of basaltic volcanism, such as those recognised at Piton de la Fournaise, should be considered in the formulation of hazard assessments and in the interpretation of precursory patterns.

Michon, Laurent; Di Muro, Andrea; Villeneuve, Nicolas; Saint-Marc, Cécile; Fadda, Pierluigi; Manta, Fabio

2013-08-01

276

The evolution of ocean island volcanoes in a stationary plate environment and its implications concerning hotspot dynamics  

NASA Astrophysics Data System (ADS)

The evolution of oceanic hotspot systems is strongly influenced by plate velocity relative to the melting source, age/thickness of the lithosphere, proximity to a plate boundary, and melting source parameters. In fast-moving plates, volcanic loci move away from the melting source and an obvious mechanism for the waning of volcanism is established. A linear island chain is thus created and a distinct edifice evolutionary pattern is recognizable. This evolutionary pattern is strongly influenced by long-term subsidence created by flexural loading and hotspot swell decay with plate movement, albeit some small uplift when edifices cross the flexural bulge; the transition from island to guyot is essentially dictated by subsidence. Conversely, in stationary or quasi-stationary plate environments, edifices do not or barely move away from the melting source so other mechanisms must be accounted for the long-term decrease in volcanic activity and the different edifice evolution. The Cape Verde Archipelago is the type-example of a hotspot in an old, stiff plate that is stationary with respect to its melting source, making it an ideal place to study ocean island evolution and oceanic hotspot dynamics in a stationary plate environment. Observations in this archipelago suggest that island evolution in such geodynamic environments is generally characterized by long-term vertical stability or even pronounced uplift trends, prolonging the islands lifetime above sea-level; the transition from island to guyot is essentially dictated by marine erosion. Uplift reconstructions for the Cape Verde Archipelago - using dateable relative sea-level tracers such as lava deltas, submarine volcanic units and marine terraces - suggest that two processes have acted to raise the islands during their lifetime. During an initial phase, mantle processes acted to build the swell. Subsequently, magmatic intrusions in the island edifice caused up to 350 m of local uplift at the scale of individual islands and often synchronous with vigorous volcanic stages. Finally, swell-wide uplift contributed a further 100 m of surface rise. This recent swell-wide uplift is well expressed throughout the archipelago by means of Quaternary marine terraces up to ~100 m asl, even in islands without recent volcanism. These observations pose several constraints concerning oceanic hotspot dynamics: first, a seemingly episodic hotspot swell growth implies that the buoyancy source changes that act to raise the swell are probably cumulative, favoring a model that advocates for accumulation and spreading of depleted material leftover from partial melting; secondly, intrusive processes at hotspots in stationary plate environments are probably much more important than previously thought, and are the likely source of significant amounts of uplift; and thirdly, plate velocity relative to the melting source is expected to be a powerful constraint on intrusive vs extrusive processes of island building.

Ramalho, R.

2012-04-01

277

75 FR 52478 - Fisheries of the Economic Exclusive 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...meters) LOA using hook-and-line or pot gear specified for the BSAI. DATES: Effective...length overall using hook-and-line or pot gear in the BSAI under Sec....

2010-08-26

278

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

279

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

280

75 FR 19561 - Fisheries of the Economic Exclusive Zone Off Alaska; Pacific Cod in the Bering Sea and Aleutian...  

Federal Register 2010, 2011, 2012, 2013

...length overall using hook-and- line or pot gear in the Bering Sea and Aleutian Islands...length overall using hook-and-line or pot gear in the BSAI under Sec. 679.20...length overall using hook-and-line or pot gear in the BSAI. Therefore, in...

2010-04-15

281

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

Microsoft Academic Search

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

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

2011-01-01

282

The 1997 Eruption of Okmok Volcano, Alaska, a Synthesis of Remotely Sensed Data  

NASA Astrophysics Data System (ADS)

Okmok Volcano in the central Aleutian Islands erupted in February of 1997. The eruption produced a lava flow in the central caldera over 5.5 x107 m3 in volume over 7.5 km2. This caldera is the most active of the Aleutian Arc, and is now the focus of international multidisciplinary studies. A synthesis of remotely sensed data (AIRSAR, derived DEMs, Landsat MSS and TM data, AVHRR, ERS, JERS, Radarsat) has given a sequence of events for the virtually unobserved 1997 eruption. Elevation data from the AIRSAR sensor acquired in October 2000 over Okmok was used to create a 5m resolution DEM mosaic of Okmok. AVHRR night-time imagery has been analyzed between February 13 and April 11, 1997. Landsat imagery years before and after the eruption allow us to accurately determine the extent of the new flow. The flow began without precursory thermal anomalies on Feburary 13th. At this point, the flow was a large single lobe, flowing north, ranging in thickness from 4 to 20 m. The eruption rate of this flow in the early stages is estimated as 2.5 m3/s. According to AVHRR Band 3 and 4 radiance data and ground observations (overflight on Feb. 28), the first lobe had reached its maximum extent by February 28, while a second, smaller lobe began effusion sometime between March 1st - 4th. This is based on a jump in the thermal and volumetric flux determined from satellite imagery, and the physical size of the thermal anomalies. This flow continued with an eruptive rate of about 5 m3/s. The total AVHRR radiance reached a maximum on March 12, which may indicate the peak areal extent for both lobes. Total radiance values waned after March 26, indicating lava effusion had ended and a cooling crust had formed. The total volume determined by eruption rates over time (ca. 1 x 108 m3) agree well with the volume of the flow estimated using radar, Landsat, and later ground observations. Remote sensing has become an integral part of the Alaska Volcano Observatory's monitoring and hazard mitigation efforts. Studies like this allow access to remote volcanoes, and provide new methods to monitor potentially dangerous volcanoes.

Moxey, L.; Dehn, J.; Papp, K.; Patrick, M.; Guritz, R.

2001-12-01

283

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

Microsoft Academic Search

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

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

284

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

285

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

286

Cascades Volcano Observatory - Learn About Volcanoes: Frequently Asked Volcano Questions  

NSDL National Science Digital Library

This page provides the answers to frequently asked questions about volcanoes. It is created by the United States Geological Survey. Topics addressed include: What Is A Volcano? Why Do Volcanoes Occur? How Do Volcanoes Erupt? Where Do Volcanoes Occur? When Will A Volcano Erupt? How Hot Is A Volcano? Can Lava Be Diverted? Do Volcanoes Affect Weather? What Types of Volcanoes are There? Which Eruptions Were The Deadliest? 20th Century Volcanic Eruptions and Their Impact. About 60 additional questions with answers are available under MORE FAQ's -Volcano Questions and Answers, and includes some sections on volcanoes of the western United States. Other links to volcano information are also available.

287

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

288

Electrical structure beneath the eastern collapsed flank of Piton de la Fournaise volcano, Reunion Island: Implications for the quest for groundwater  

NASA Astrophysics Data System (ADS)

Time domain electromagnetic (TDEM) and tensor audiomagnetotelluric (AMT) data have been acquired at several locations on the eastern flank of Piton de la Fournaise volcano (Reunion Island) within a depressed area called Grand Brulé, interpreted as a collapse structure. The survey objectives were (1) to provide a geophysical estimate of the subsurface structure and (2) to evaluate the possibility of detecting aquifers in a volcanic environment not very known. The TDEM and the AMT data collected along two E-W traverses orthogonal to coastline on the northern and southern edges of Grand Brulé were interpreted with one-dimensional layered models. From the surface downward, the geoelectrical sections reveal two major units: very resistive, young lava flows (dry) and a shallow conductor (<500 m) which is probably primarily attributable to a clayey, poorly permeable base. A notable exception to this pattern is seen at sites close to the coast, where we found three-layered structures. There is an intermediate layer of resistivity of about 100-200 ohm m between the top resistive layer and bottom conductive layer that represents a probable freshwater lens in the southern part and an alluvial fan with resistivities substantially higher (200 ohm m) in the northern part of Grand Brulé. It is suggested that the 200 ohm m layer, interpreted as a buried paleoriver, corresponds to a drainage structure.

Descloitres, Marc; Ritz, Michel; Robineau, Bernard; Courteaud, Michel

1997-01-01

289

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

290

Eruption Rate Control On Morphology And Structure Of Submarine Monogenetic Volcanoes - Insights From Sumersible Dives Off Maui And Hawaii Islands  

Microsoft Academic Search

This paper presents the results of submersible dives off Hawaii Islands during four research cruises (R\\/V Kairei-ROV Kaiko 1998 and 2001, R\\/V Yokosuka-DSV Shinkai 1999 and 2002) by the Japan Marine Science and Technology Center. Morphologies and structures of submarine volcanic edifices were observed during dives on the Hana Ridge, submarine extension of Haleakala rift zone of East Maui and

S. Umino

2003-01-01

291

Eruptive activity of the summit cone of Piton de la Fournaise volcano (La Réunion island): a historical and geological review.  

NASA Astrophysics Data System (ADS)

Summit explosive activity and collapses represent major volcanic hazards on a dominantly effusive and frequently active volcano like Piton de la Fournaise. Only three summit collapse events (1986, 2002 and 2007) have been recorded since the foundation of the Piton de la Fournaise volcano observatory (OVPF) in 1979 and two of them (1986 and 2007) were associated with weak phreatic activity. Except during these three events, most eruptions consist in short short-lived (< 3 hours) and mild (< 20 m-high) lava fountains quickly evolving into strombolian activity. Based on a comprehensive literature review and a high-resolution image analysis of surface outcrops and summit caldera walls, we reconstructed the time distribution of recent explosive events and their link with summit collapses and lateral effusive eruptions. In historical times (post-1640 AD), we recognize two main clusters of explosive events. Frequent and violent phreatomagmatic to phreatic explosions occurred during the oldest cluster (1708-1878) characterized by long-lasting summit effusive activity. On the contrary, weak and scarce explosions occurred during the youngest cluster (1897-2012), in which discrete and often short-lived effusive eruptions represent the main eruptive dynamics. Historical summit collapses (pit craters to caldera), all localized at the top of the summit cone, were related to voluminous lateral eruptions and were followed by a significant decrease in eruptive rate. However, many lateral eruptions were not associated with summit collapses or explosions. The long-lasting occurrence of magma at very shallow depth represents thus a critical condition to produce summit explosive activity. The pre-historic building of Piton de la Fournaise summit cone results from a long-lasting to continuous activity centered below its western side (Bory crater/lava lakes). Frequent and large lava fountains and long-lasting lava lakes represented an important dynamics in this recent past. In this perspective, the last century of activity of Piton de la Fournaise can be considered as a lull, in spite of its high frequency (1 eruption / 9 months on average).

Di Muro, Andrea; Michon, Laurent; Villeneuve, Nicolas; Saint-Marc, Cecile

2013-04-01

292

Collapsing volcanoes  

Microsoft Academic Search

A series of studies has been conducted which examined Landsat images of volcanoes in the central Andes in order to identify previously unknown avalanche deposits, with attention to the Socompa volcano in Chile. The occasional, massive collapse of an unstable volcanic cone may be seen as a normal event in the life cycle of a volcano; this is especially true

Peter Francis; Stephen Self

1987-01-01

293

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

294

Monitoring and modeling ice-rock avalanches from ice-capped volcanoes: A case study of frequent large avalanches on Iliamna Volcano, Alaska  

Microsoft Academic Search

Iliamna is an andesitic stratovolcano of the Aleutian arc with regular gas and steam emissions and mantled by several large glaciers. Iliamna Volcano exhibits an unusual combination of frequent and large ice-rock avalanches in the order of 1 × 106 m3 to 3 × 107 m3 with recent return periods of 2 4 years. We have reconstructed an avalanche event

Christian Huggel; Jacqueline Caplan-Auerbach; Christopher F. Waythomas; Rick L. Wessels

2007-01-01

295

Velocity Structure and 2008 Eruptive Seismicity at Okmok Volcano, Alaska  

NASA Astrophysics Data System (ADS)

Okmok Volcano is an active volcanic caldera located on the northeastern portion of Umnak Island in the Aleutian arc, and most recently erupted in 2008. We present updated results from Okmok seismicity between January 2003 and May 2009. The volcanic caldera has been well instrumented with a network of as many as nine short-period and four broadband seismometers, providing good azimuthal coverage. Since the 2008 eruption, the volcano underwent a period of increased seismicity (addition of over 700 earthquakes) making earthquake tomography more feasible. Using a combination of waveform cross-correlation and double-difference seismic tomography, we derive refined Vp and Vs models, relocate hypocenters in them, and carry out resolution tests on the models. We image two low Vp and Vs anomalies: one directly beneath the caldera extending to 4-5 km below sea level and another to the southwest below a well known geothermal area. In addition, we re-calculate focal mechanisms in the updated model for relocated events prior to and during the 2008 eruption. We observe high focal mechanism diversity, including many reverse-faulting events. Finally, we present the 2008 relocation results in the context of satellite ash observations and seismic tremor for a detailed assessment of Okmok's seismic activity during vent formation and stabilization. The earthquakes accompanying the onset of the eruption occurred in a vertical lineation at about 4 km below sea level to the northwest of Cone D, directly below the site of the new vent, and spread slightly towards the east and west over the next few hours. Four hours after the first earthquakes, a sequence of events began near sea level. As the eruption progressed, events expanded both to greater depths and outward throughout the caldera volume, mainly westward in the direction of Cone A. The shallower and deeper groups of events seen in the early eruption remained separated by a nearly aseismic region.

Ohlendorf, S. J.; Thurber, C. H.; Prejean, S. G.

2010-12-01

296

Fumarole-supported islands of biodiversity within a hyperarid, high-elevation landscape on Socompa Volcano, Puna de Atacama, Andes.  

PubMed

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 (13)C-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 (13)C-rich CO(2) 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. PMID:19074608

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

2008-12-12

297

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

298

Factors controlling the morphology of monogenetic basaltic volcanoes: The Holocene volcanism of Gran Canaria (Canary Islands, Spain)  

NASA Astrophysics Data System (ADS)

A detailed morphometric analysis was performed on the 24 Holocene eruptions of Gran Canaria, a nearly circular island located at the centre of the Canary Islands (Spain), developed as result of the eastward movement of the African plate over a mantle hotspot. Rigorous field work was carried out to generate a palaeogeomorphological reconstruction of the Holocene eruptions of Gran Canaria to obtain pre- and post-eruption digital terrain models (DTMs). These eruptions were of Strombolian monogenetic basaltic volcanism style. With respect to the cones, feeder fissures determine their location and some morphological features as crater openings which are usually perpendicular to the slope direction. In addition, the trade winds influence the final volcanic edifice shape and the extent of the pyroclastic sheet-like fall deposits. For the lava flows, the most significant controls are the eruption rate, affecting the maximum distance travelled, and the gully slope and shape that condition their flow path. Concerning volcanic hazard and risk assessment, the applied methodology has led to a better understanding of the recent eruptions and foresees the location and nature of future eruptions.

Rodriguez-Gonzalez, A.; Fernandez-Turiel, J. L.; Perez-Torrado, F. J.; Paris, R.; Gimeno, D.; Carracedo, J. C.; Aulinas, M.

2012-01-01

299

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

PubMed Central

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

Villacorta, Carlos; Jaume, Damia; Oromi, Pedro; Juan, Carlos

2008-01-01

300

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

301

Seismic swarm associated with the 2008 eruption of Kasatochi Volcano, Alaska: Earthquake locations and source parameters  

Microsoft Academic Search

An energetic seismic swarm accompanied an eruption of Kasatochi Volcano in the central Aleutian volcanic arc in August of 2008. In retrospect, the first earthquakes in the swarm were detected about 1 month prior to the eruption onset. Activity in the swarm quickly intensified less than 48 h prior to the first large explosion and subsequently subsided with decline of

Natalia A. Ruppert; Stephanie Prejean; Roger A. Hansen

2011-01-01

302

Numerical simulation of tsunami generation by cold volcanic mass flows at Augustine Volcano, Alaska  

Microsoft Academic Search

Many of the world's active volcanoes are situated on or near coastlines. During eruptions, diverse geophysical mass flows, including pyroclastic flows, debris avalanches, and lahars, can deliver large volumes of unconsolidated debris to the ocean in a short period of time and thereby generate tsunamis. Deposits of both hot and cold volcanic mass flows produced by eruptions of Aleutian arc

C. F. Waythomas; P. Watts; J. S. Walder

2006-01-01

303

Living with Volcanoes: Year Eleven Teaching Resource Unit.  

ERIC Educational Resources Information Center

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

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

2000-01-01

304

Erupting Volcanoes!  

NSDL National Science Digital Library

This lesson presents volcanoes through the making of volcano models. While students are constructing their physical representations of volcanoes, they will be filled with questions about volcanoes as well as how to build their models. This process will provide students with a tangible reference for learning about volcanoes and give them a chance to problem-solve as they build their models. Students will be able to observe how the eruption changes the original form of their volcano model. In this way, students see first hand how this type of phenomenon creates physical change. While students at this level may struggle to understand larger and more abstract geographical concepts, they will work directly with material that will help them build a foundation for understanding concepts of phenomena that sculpt the Earth.

305

Volcano Types  

NSDL National Science Digital Library

This site lists the basic types of volcanoes: scoria cone, shield volcano, and stratovolcano. Each is described in terms of shape, composition, and eruption type, and links are available to additional information. Subordinate types listed include fissure eruptions, spatter cones, hornitos, and hydrovolcanic eruptions. The site also explains when a volcano is considered active, dormant, or extinct. In addition, generic features such as vent, central vent, edifice, magma chamber, parasitic cones, and fumaroles are listed and described.

Camp, Victor

306

Hawaii Volcanoes and Volcanics - Maps and Graphics, etc.  

NSDL National Science Digital Library

This page provides maps, "pictograms", photographs, and graphics of the Hawaiian volcanoes. Maps include volcano locations in the Hawaiian Island chain, Hawaii Island, and Maui, and a global map of the 16 Decade Volcanoes, which include Mauna Loa. Photographs or "pictograms" demonstrate a shield volcano versus a composite volcano (Mauna Loa versus Mount Rainier, Washington) and Hawaiian-Style Eruptions vs. Cascades-Style Eruptions - Pu'u O'o, Hawaii vs. Mount St. Helens, Washington. The graphic shows the profile of Mauna Loa and Kilauea versus Mount Rainier.

307

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

308

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

309

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

2012-03-16

310

Syn and posteruptive hazards of maar–diatreme volcanoes  

Microsoft Academic Search

Maar–diatreme volcanoes represent the second most common volcano type on continents and islands. This study presents a first review of syn- and posteruptive volcanic and related hazards and intends to stimulate future research in this field. Maar–diatreme volcanoes are phreatomagmatic monogenetic volcanoes. They may erupt explosively for days to 15 years. Above the preeruptive surface a relatively flat tephra ring forms.

Volker Lorenz

2007-01-01

311

Decade Volcanoes  

NSDL National Science Digital Library

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

2007-11-02

312

Geodetic Measurements and Numerical Modeling of the Deformation Cycle for Okmok Volcano, Alaska: 1993-2008  

NASA Astrophysics Data System (ADS)

Okmok Volcano is an active caldera located on Umnak Island in the Aleutian Island arc. Okmok, having recently erupted in 1997 and 2008, is well suited for multidisciplinary studies of magma migration and storage because it hosts a good seismic network and has been the subject of synthetic aperture radar (SAR) images that span the recent eruption cycle. Interferometric SAR can characterize surface deformation in space and time, while data from the seismic network provides important information about the interior processes and structure of the volcano. We conduct a complete time series analysis of deformation of Okmok with images collected by the ERS and Envisat satellites on more than 100 distinct epochs between 1993 and 2008. We look for changes in inter-eruption inflation rates, which may indicate inelastic rheologic effects. For the time series analysis, we analyze the gradient of phase directly, without unwrapping, using the General Inversion of Phase Technique (GIPhT) [Feigl and Thurber, 2009]. This approach accounts for orbital and atmospheric effects and provides realistic estimates of the uncertainties of the model parameters. We consider several models for the source, including the prolate spheroid model and the Mogi model, to explain the observed deformation. Using a medium that is a homogeneous half space, we estimate the source depth to be centered at about 4 km below sea level, consistent with the findings of Masterlark et al. [2010]. As in several other geodetic studies, we find the source to be approximately centered beneath the caldera. To account for rheologic complexity, we next apply the Finite Element Method to simulate a pressurized cavity embedded in a medium with material properties derived from body wave seismic tomography. This approach allows us to address the problem of unreasonably large pressure values implied by a Mogi source with a radius of about 1 km by experimenting with larger sources. We also compare the time dependence of the source to published results that used GPS data.

Ohlendorf, S. J.; Feigl, K.; Thurber, C. H.; Lu, Z.; Masterlark, T.

2011-12-01

313

Volcano spacing and plate rigidity  

SciTech Connect

In-plane stresses, which accompany the flexural deformation of the lithosphere under the load adjacent volcanoes, may govern the spacing of volcanoes in hotspot provinces. Specifically, compressive stresses in the vicinity of a volcano prevent new upwelling in this area, forcing a new volcano to develop at a minimum distance that is equal to the distance in which the radial stresses change from compressional to tensile (the inflection point). If a volcano is modeled as a point load on a thin elastic plate, then the distance to the inflection point is proportional to the thickness of the plate to the power of 3/4. Compilation of volcano spacing in seven volcanic groups in East Africa and seven volcanic groups of oceanic hotspots shows significant correlation with the elastic thickness of the plate and matches the calculated distance to the inflection point. In contrast, volcano spacing in island arcs and over subduction zones is fairly uniform and is much larger than predicted by the distance to the inflection point, reflecting differences in the geometry of the source and the upwelling areas.

Brink, U. (Stanford Univ., California (USA))

1991-04-01

314

Abramovite, Pb2SnInBiS7, a new mineral species from fumaroles of the Kudryavy volcano, Kurile Islands, Russia  

NASA Astrophysics Data System (ADS)

Abramovite, a new mineral species, has been found as fumarole crust on the Kudryavy volcano, Iturup Island, Kuriles, Russia. The mineral is associated with pyrrhotite, pyrite, würtzite, galena, halite, sylvite, and anhydrite. Abramovite occurs as tiny elongated lamellar crystals up to 1 mm long and 0.2 mm wide (average 300 × 50 ? m), which make up chaotic intergrowths in the narrow zone of fumarole crust formed at ˜600°C. Most crystals are slightly striated along the elongation. The new mineral is silver gray, with a metallic luster and black streak. Under reflected light, abramovite is white with a yellowish gray hue. It has weak bireflectance; anisotropy is distinct without color effects. The chemical composition (electron microprobe) is as follows, wt %: 20.66 S, 0.98 Se, 0.01 Cu, 0.03 Cd, 11.40 In, 12.11 Sn, 37.11 Pb, 17.30 Bi; the total is 99.60. The empirical formula calculated on the basis of 12 atoms is Pb1.92Sn1.09In1.06Bi0.89(S6.90Se0.13)7.03. The simplified formula is Pb2SnInBiS7. The strongest eight lines in the X-ray powder pattern [ d, Å ( I)( hkl)] are 5.90(36)(100), 3.90(100)(111), 3.84(71)(112), 3.166(26)(114), 2.921(33)(115), 2.902(16)(200), 2.329(15)(214), 2.186(18)(125). The selected area electron diffraction (SAED) patterns of abramovite are quite similar to those of the homologous cylindrite series minerals. The new mineral is characterized by noncommensurate structure composed of regularly alternated pseudotetragonal and pseudohexagonal sheets. The structure parameters determined from the SAED patterns and X-ray powder diffraction data for pseudotetragonal subcell are: a = 23.4(3), b = 5.77(2), c = 5.83(1) Å, ? = 89.1(5) °, ? = 89.9(7)°, ? = 91.5(7)°, V = 790(8) Å3; for pseudohexagonal subcell: a = 23.6(3), b = 3.6(1), c = 6.2(1) Å, ? = 91(2)°, ? = 92(1)°, ? = 90(2)°, V = 532(10) Å3. Abramovite is triclinic, space group P(1). The new mineral is named in honor of Russian mineralogist Dmitry Abramov. The type material of abramovite has been deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.

Yudovskaya, M. A.; Trubkin, N. V.; Koporulina, E. V.; Belakovsky, D. I.; Mokhov, A. V.; Kuznetsova, M. V.; Golovanova, T. I.

2008-12-01

315

Large landslides from oceanic volcanoes  

Microsoft Academic Search

GLORIA sidescan sonar surveys have shown that large landslides are ubiquitous around the submarine flanks of Hawaiian volcanoes, and GLORIA has also revealed large landslides offshore from Tristan da Cunha and El Hierro. On both of the latter islands, steep flanks formerly attributed to tilting or marine erosion have been reinterpreted as landslide headwalls mantled by younger lava flows. Large

Robin T. Holcomb; Roger C. Searle

1991-01-01

316

Collapsing volcanoes  

NASA Astrophysics Data System (ADS)

A series of studies has been conducted which examined Landsat images of volcanoes in the central Andes in order to identify previously unknown avalanche deposits, with attention to the Socompa volcano in Chile. The occasional, massive collapse of an unstable volcanic cone may be seen as a normal event in the life cycle of a volcano; this is especially true in the case of large 'stratovolcanoes', of which there are many hundreds in the 'Ring of Fire' around the Pacific rim. Stratovolcanoes are susceptible to collapse because of their association with subduction zones. Three kinds of collapse can be distinguished among stratovolcanoes.

Francis, Peter; Self, Stephen

1987-06-01

317

Model Volcanoes  

NSDL National Science Digital Library

In this lesson, students will explore volcanoes by constructing models and reflect upon their learning through drawing sketches of their models. Once they have finished making their models, they will experiment with making their volcanoes erupt. They will observe how eruption changes the original form of their volcano models. In this way, students see first hand how this type of phenomena creates physical change. While students at this level may struggle to understand larger and more abstract geographical concepts, they will work directly with material that will help them build a foundation for understanding concepts of phenomena that sculpt the earth.

318

Seismicity, topography, and free-air gravity of the Aleutian-Alaska subduction zone  

NASA Astrophysics Data System (ADS)

The Aleutian-Alaska subduction zone, extending 3400 km from the Queen Charlotte Fault to Kamchatka, has been the source of six great megathrust earthquakes in the 20th Century. Four earthquakes have ruptured the 2000-km-long Aleutian segment, where the Cenozoic Aleutian arc overlies the subducting Pacific plate. These include the 1946 M 8.6 earthquake off Unimak Is., the 1957 M 8.6 and 1986 M 8.0 earthquakes off the Andreanoff Is., and the 1965 M 8.7 Rat Is. earthquake. The source regions of these earthquakes inferred from waveform inversions underlie the well-defined Aleutian deep-sea terrace. The deep-sea terrace is about 4 km deep and is underlain by Eocene arc framework rocks, which extend nearly to the trench. It is bounded on its seaward and landward margins by strong topographic and fee-air gravity gradients. The main asperities (areas of largest slip) for the great earthquakes and nearly all of the Aleutian thrust CMT solutions lie beneath the Aleutian terrace, between the maximum gradients. Similar deep-sea terraces are characteristic of non-accretionary convergent margins globally (75% of subduction zones), and, where sampled by drilling (e.g., Japan, Peru, Tonga, Central America), are undergoing sustained subsidence. Sustained subsidence requires removal of arc crust beneath the terrace by basal subduction erosion (BSE). BSE is in part linked to the seismic cycle, as it occurs in the same location as the megathrust earthquakes. Along the eastern 1400 km of the Alaskan subduction zone, the Pacific plate subducts beneath the North American continent. The boundary between the Aleutian segment and the continent is well defined in free-air gravity, and the distinctive deep-sea terrace observed along the Aleutian segment is absent. Instead, the Alaskan margin consists of exhumed, underplated accretionary complexes forming outer arc gravity highs. Superimposed on them are broad topographic highs and lows forming forearc basins (Shumagin, Stevenson) and islands (Kodiak, Shumagin). Two great earthquakes ruptured much of this segment: the 1938 M 8.3 earthquake SW of Kodiak and the 1964 M 9.2 earthquake, which ruptured 800 km of the margin between Prince William Sound and Kodiak Island. Large slip during the 1938 event occurred under the Shumagin and Tugidak basins, but slip in 1964 is thought to have occurred on asperities under Prince William Sound and the outer arc highs off Kodiak. Seismic profiling and industry drilling indicates sustained subsidence has also occurred along the Alaska margin. BSE is probably occurring there, but the terrace structure is buried by the high sedimentation rate. At present, the inherited accretionary structures, the ongoing collision of the Yakutat terrane, and uncertainties in finite fault modeling obscure correlation of slip with topographic and gravity signatures in the 1964 source region.

Wells, R. E.; Blakely, R. J.; Scholl, D. W.; Ryan, H. F.

2011-12-01

319

Cascade Volcanoes  

USGS Multimedia Gallery

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

2009-12-08

320

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

321

Tremor Source Location at Okmok Volcano  

NASA Astrophysics Data System (ADS)

Initial results using an amplitude-based tremor location program have located several active tremor episodes under Cone A, a vent within Okmok volcano's 10 km caldera. Okmok is an andesite volcano occupying the north-eastern half of Umnak Island, in the Aleutian islands. Okmok is defined by a ~2000 y.b.p. caldera that contains multiple cinder cones. Cone A, the youngest of these, extruded lava in 1997 covering the caldera floor. Since April 2003, continuous seismic data have been recorded from eight vertical short-period stations (L4-C's) installed at distances from Cone A ranging from 2 km to 31 km. In 2004 four additional 3- component broadband stations were added, co-located with continuous GPS stations. InSAR and GPS measurements of post-eruption deformation show that Okmok experienced several periods of rapid inflation (Mann and Freymueller, 2002), from the center of the 10 km diameter caldera. While there are few locatable VT earthquakes, there has been nearly continuous low-level tremor with stronger amplitude bursts occurring at variable rates and durations. The character of occurrence remained relatively constant over the course of days to weeks until the signal ceased in mid 2005. Within any day, tremor behavior remains fairly consistent, with bursts closely resembling each other, suggesting a single main process or source location. The tremor is composed of irregular waves with a broad range of frequencies, though most energy resides between ~2 Hz and 6 Hz. Attempts to locate the tremor using traditional arrival time methods fail because the signal is emergent, with envelopes too ragged to correlate on time scales that hold much hope for a location. Instead, focus was shifted to the amplitude ratios at various stations. Candidates for the tremor source include the center of inflation and Cone A, 3 km to the south-west. For all dates on record, data were band pass filtered between 1 and 5 Hz, then evaluated in 20.48 second windows (N=2048, sampling rate=100 Hz), at 20 second intervals. Root-mean- square (rms) values were then calculated for each window of data. The ratios of these RMS amplitudes were used to investigate the tremor behavior. The ratio changes between tremor and non-tremor events suggest that the sources for episodes were closer to Cone A (and station OKCF) than they were to other locales in the caldera. Methods from Battaglia's PhD thesis (2001) were used as guidelines for a tremor location program based on amplitude decay. Written in MATLAB®, this program can be run in near-real time to estimate the tremor source location and strength. Further refinement is underway, as is an examination of all other days that have suitable data .

Reyes, C. G.; McNutt, S. R.

2007-12-01

322

Mahukona: The missing Hawaiian volcano  

SciTech Connect

New bathymetric and geochemical data indicate that a seamount west of the island of Hawaii, Mahukona, is a Hawaiian shield volcano. Mahukona has weakly alkalic lavas that are geochemically distinct. They have high {sup 3}He/{sup 4}He ratios (12-21 times atmosphere), and high H{sub 2}O and Cl contents, which are indicative of the early state of development of Hawaiian volcanoes. The He and Sr isotopic values for Mahukona lavas are intermediate between those for lavas from Loihi and Manuna Loa volcanoes and may be indicative of a temporal evolution of Hawaiian magmas. Mahukona volcano became extinct at about 500 ka, perhaps before reaching sea level. It fills the previously assumed gap in the parallel chains of volcanoes forming the southern segment of the Hawaiian hotspot chain. The paired sequence of volcanoes was probably caused by the bifurcation of the Hawaiian mantle plume during its ascent, creating two primary areas of melting 30 to 40 km apart that have persisted for at least the past 4 m.y.

Garcia, M.O.; Muenow, D.W. (Univ. of Hawaii, Honolulu (USA)); Kurz, M.D. (Woods Hole Oceanographic Institution, MA (USA))

1990-11-01

323

Evolution of elastic properties and acoustic emission, during uniaxial loading of rocks, from the Fogo Volcano in the island of Sao Miguel, Azores; Preliminary results.  

NASA Astrophysics Data System (ADS)

A Computerized Uniaxial Press working up to 250 kN was installed in the middle 2011 in the Laboratory of Microseismic Monitoring of ISEL. The system is able to record continuous time, pressure and axial strain (1 µm resolution) at 1s sampling rate. The loading platens were designed to integrate acoustic emission (AE) transducers. Signals are acquired and processed through an 8-channel ESG Hyperion Ultrasonic Monitoring System (10 MSPS, 14/16-bit ADC). The first experiments, presented here, were applied to a set of rock samples from the Fogo, an active central volcano in the island of Sao Miguel. Two different volcanic rock types were studied: a fine grained alkali basaltic rock with a porphyritic texture, a porosity of 4.5% and bulk density of 2700 kg m-3 (sample #3); and a benmoreitic rock with a trachytic texture, a porosity of 8.1 %, and bulk density of 2400 kg m-3 (sample #4). Cores from sample #3 were subjected to continuous increasing pressure, until failure. They show a uniaxial compressive strength (UCS) spanning from 60 to 85 MPa and a stress-strain curve with two phases: a first one with relative low Young's Module (YM) followed by a second phase were the YM increases roughly 3 times. The stress transition value occurs broadly in a stress level 50% of the UCS. The AE produced in the process is almost negligible until the YM transition stress level and increases after that. Important pulses of high AE rate occur, (> 100 s-1), associated with the occurrence and propagation of fractures, which are always parallel to the principal stress, showing an evident pattern of tensile fractures. About 20s before the failure, very important deformation rate is observed, the YM strongly decrease, and continuous AE events, with low rate, usually <50 s-1. The failure is accompanied with a sudden rise of AE events with rate > 200 s-1. Cycling stress experiences were also performed showing reversible stress-strain relation for axial pressure below the YM transition level, and important hysteresis for axial pressure above that level. The associated AE events show a characteristic Kaiser effect pattern. Cores from sample #4 undergo the same continuous increasing stress process, but failure is attained at a considerable lower pressure of 20-25 MPa. The stress-strain curves show an almost linear relation, but approaching the stress level of failure, the YM decreases. The AE events are constant but with a reduced rate until the decrease of the YM, when a significant rise in the AE occurs, achieving emission rates greater that 200 s-1. The fracture shows a characteristic shear pattern. Differences in stress-strain behavior, fracture mode and AE rates are associated with the very different structure of the rocks, once the basaltic sample is very fine grained with some very scattered and almost spherical vesicles or voids, while the benmoreitic core shows high values of porosity in a structure with vesicles and voids with very irregular shapes. Work supported by FCT, Portugal, projet FreeRock, PTDC/CTE-GIX/100687/2008

Moreira, M.; Wallenstein, N.

2012-04-01

324

Monitoring for volcano-hydrothermal activity using continuous gravity and local ground acceleration measurements: New deployments at Inferno Crater, Waimangu and White Island, New Zealand  

Microsoft Academic Search

Volcanoes with crater lakes are often characterised by shallow hydrothermal systems which display cyclic behaviour (temperature, lake level, chemistry, etc.) and shallow seismic tremor. Present monitoring programmes in New Zealand include routine collection of these observables, but the associated shallow sub-surface processes are still inadequately modelled and poorly understood. Models would be better constrained with the incorporation of additional geophysical

Arthur Jolly; Nico Fournier; Jeremy Cole-Baker; Craig Miller

2010-01-01

325

350 years of paleoceanographic change in the Aleutian archipelago extracted from the skeletons of a subarctic coralline alga  

NASA Astrophysics Data System (ADS)

Numerous oceanic passes along the Aleutian Island arc connect the northern North Pacific Ocean to the Bering Sea. Seawater moving through these passes is the dominant source of water along the eastern slope of the Bering Sea, an oceanographically and ecologically significant region that is already changing in response to increasing global temperatures. However, the paucity of high-quality, high-resolution instrumental seawater temperature data extending prior to the mid-20th century prevents an understanding of how these recent changes relate to longer-term climate patterns. The long-lived crustose coralline alga Clathromorphum nereostratum is proving to be a climate archive that yields proxy records able to fill this data gap. This alga is endemic to the North Pacific/Bering Sea region and forms a dominant component of the shallow seafloor along the Aleutian Island arc. Sclerochronological and geochemical measurements of the high-Mg calcite skeleton of C. nereostratum can yield sub-annually resolved, multi-centennial reconstructions of past climatic variability. Here, we measured Mg/Ca ratios across the growth axis in multiple live-collected and subfossil specimens from two Aleutian Islands as a proxy for past surface seawater temperatures. By applying chronologies developed from U/Th dates combined with counts of annual growth rings to the Mg/Ca records, we reconstructed past seawater temperature variability extending from 1658 to 2006. In the record, the significant mode of variability shifted from interdecadal to lower frequency (>50 year) oscillations around the 1850s. In addition, the record significantly correlated with climate patterns spanning from the tropical Pacific to the Arctic Ocean, highlighting the complexity of factors driving the oceanography and climate along the Aleutian archipelago.

Williams, B.; Halfar, J.; Hetzinger, S.; Lebednik, P. A.; Steneck, R. S.; Adey, W. H.; Fietzke, J.; Jacob, D.

2011-12-01

326

Spreading volcanoes  

USGS Publications Warehouse

As volcanoes grow, they become ever heavier. Unlike mountains exhumed by erosion of rocks that generally were lithified at depth, volcanoes typically are built of poorly consolidated rocks that may be further weakened by hydrothermal alteration. The substrates upon which volcanoes rest, moreover, are often sediments lithified by no more than the weight of the volcanic overburden. It is not surprising, therefore, that volcanic deformation includes-and in the long term is often dominated by-spreading motions that translate subsidence near volcanic summits to outward horizontal displacements around the flanks and peripheries. We review examples of volcanic spreading and go on to derive approximate expressions for the time volcanoes require to deform by spreading on weak substrates. We also demonstrate that shear stresses that drive low-angle thrust faulting from beneath volcanic constructs have maxima at volcanic peripheries, just where such faults are seen to emerge. Finally, we establish a theoretical basis for experimentally derived scalings that delineate volcanoes that spread from those that do not.

Borgia, A.; Delaney, P. T.; Denlinger, R. P.

2000-01-01

327

Cascade Range Volcanoes: North to South  

NSDL National Science Digital Library

This page lists Cascades Range volcanoes of British Columbia, Washington State, Oregon, and California. The user can click on the volcano name to get information on the volcano and its vicinity including Current Activity; Background and Information; Current Hazards Report; Visit a Volcano; Maps, Graphics, and Images; Items of Interest; and Useful Links. The volcanoes include: Garibaldi Lake Volcano, Meager Mountain, and Mount Garibaldi in British Columbia; Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, and Mount Adams in Washington State: Mount Hood, Mount Jefferson, Three-Fingered Jack, Mount Washington, Belknap Shield Volcano, Three Sisters (North, Middle, South), Broken Top, Mount Bachelor, Pilot Butte, Lava Butte, Newberry Caldera, Diamond Peak, Mount Bailey, Mount Thielsen, Crater Lake, Mount Mazama, Wizard Island, and Mount McLoughlin in Oregon:, and Lava Beds, Medicine Lake Volcano, Glass Mountain (Medicine Lake, California), Black Butte, Mount Shasta, and Lassen Peak in California. Links are provided to more general pages on volcanoes in the three states and in Canada.

328

Volcano Baseball  

NSDL National Science Digital Library

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

Science, American A.

2009-01-01

329

Introduction to Augustine Volcano and Overview of the 2006 Eruption  

NASA Astrophysics Data System (ADS)

This overview represents the combined efforts of scores of people, including Alaska Volcano Observatory staff from the US Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys; additional members of those agencies outside of AVO; and volcanologists from elsewhere. Augustine is a young, and therefore small island volcano in the Cook Inlet region of the eastern Aleutian arc. It is among the most active volcanoes in the arc, with six major historic eruptions, and a vigorous eruptive history going back at least 2,500 years. Eruptions typically begin explosively, and finish with the extrusion of domes and sometimes short, steep lava flows. At least 14 times (most recently in 1883) the -summit has become over-steepened and failed, producing debris avalanches which reached tidewater. Magmas within each of the well-studied eruptions are crystal-rich andesite spanning up to seven weight percent silica. Mixing and mingling are ubiquitous and occur at scales from meters to microns. In general, magmagenesis at Augustine is open, messy, and transcrustal. The 2006 eruption was broadly similar to the 20th century eruptions. Unrest began midway through 2005, with steadily increasing numbers of microearthquakes and continuous inflation of the edifice. By mid-December there were obvious morphological and thermal changes at the summit, as well as phreatic explosions and more passive venting of S-rich gasses. In mid-January 2006 phreatomagmatic explosions gave way to magmatic explosions, producing pyroclastic flows dominated by low-silica andesite, as well as lahars, followed by a small summit dome. In late January the nature of seismicity, eruptive style, and type of erupted magma all changed, and block-and-ash flows of high-silica, crystal-rich andesite were emplaced as the edifice deflated. Re-inflation well below the edifice and low-level effusion continued through February. During the second week in March there was a marked increase in extrusion, resulting in two short, steep lava flows dominantly composed of low-silica andesite. Effusion slowly waned through March and deformation ceased. Previous eruptions have had months-long repose followed be renewed effusion, but this has not yet happened during this eruption. Our ability to describe this eruption is based on a richness of data. The volcano was well instrumented with AVO seismometers and Earthscope/PBO continuous GPS instruments. Additional instruments were added as unrest increased, and substitutes for stations destroyed during initial explosions were deployed. As many as two-dozen AVHRR satellite passes were analyzed each day, providing thermal monitoring and ash-plume tracking. Overflights collected both visual and quantitative IR imagery on a regular basis. Georeferenced imagery acquired by satellite (ASTER) and repeated conventional aerial photography permitted detailed, accurate, mapping of many deposits as an aid to (but not substitute for) field mapping. Web cameras (both visual and near-IR) and conventional time-lapse cameras aided understanding of ongoing processes. Data sets less common to volcano monitoring (infrasound, lightning detection) extended our understanding.

Nye, C. J.

2006-12-01

330

Monitoring and modeling ice-rock avalanches from ice-capped volcanoes: A case study of frequent large avalanches on Iliamna Volcano, Alaska  

Microsoft Academic Search

Iliamna is an andesitic stratovolcano of the Aleutian arc with regular gas and steam emissions and mantled by several large glaciers. Iliamna Volcano exhibits an unusual combination of frequent and large ice-rock avalanches in the order of 1×106 m3 to 3×107 m3 with recent return periods of 2–4 years. We have reconstructed an avalanche event record for the past 45 years that indicates Iliamna

Christian Huggel; Jacqueline Caplan-Auerbach; Christopher F. Waythomas; Rick L. Wessels

2007-01-01

331

Mineralized microbes from Giggenbach submarine volcano  

Microsoft Academic Search

The Giggenbach submarine volcano, which forms part of the Kermadec active arc front, is located ?780 km NNE of the North Island of New Zealand. Samples collected from chimneys associated with seafloor hydrothermal vents on this volcano, at a depth of 160–180 m, contain silicified microbes and microbes entombed in reticular Fe-rich precipitates. The mineralized biota includes filamentous, rod-shaped, and

Brian Jones; C. E. J. de Ronde; Robin W. Renaut

2008-01-01

332

Zeta potential estimation of volcanic rocks on 11 island arc-type volcanoes in Japan: Implication for the generation of local self-potential anomalies  

Microsoft Academic Search

From streaming potential measurements, we deduced the zeta potential of 73 volcanic rock samples collected in 11 volcanoes where self-potential (SP) surveys had also been conducted. Experiments with crushed rock samples and 0.001 mol\\/L NaCl solution showed a large variation in streaming potential coefficient, which ranged from ?2860 to 2280 mV\\/MPa (deduced zeta potential ranged from ?45.1 to 37.2 mV).

Koki Aizawa; Makoto Uyeshima; Kenji Nogami

2008-01-01

333

Sustained long-period seismicity at Shishaldin Volcano, Alaska  

USGS Publications Warehouse

From September 1999 through April 2004, Shishaldin Volcano, Aleutian Islands, Alaska, exhibited a continuous and extremely high level of background seismicity. This activity consisted of many hundreds to thousands of long-period (LP; 1-2 Hz) earthquakes per day, recorded by a 6-station monitoring network around Shishaldin. The LP events originate beneath the summit at shallow depths (0-3 km). Volcano tectonic events and tremor have rarely been observed in the summit region. Such a high rate of LP events with no eruption suggests that a steady state process has been occurring ever since Shishaldin last erupted in April-May 1999. Following the eruption, the only other signs of volcanic unrest have been occasional weak thermal anomalies and an omnipresent puffing volcanic plume. The LP waveforms are nearly identical for time spans of days to months, but vary over longer time scales. The observations imply that the spatially close source processes are repeating, stable and non-destructive. Event sizes vary, but the rate of occurrence remains roughly constant. The events range from magnitude ???0.1 to 1.8, with most events having magnitudes <1.0. The observations suggest that the conduit system is open and capable of releasing a large amount of energy, approximately equivalent to at least one magnitude 1.8-2.6 earthquake per day. The rate of observed puffs (1 per minute) in the steam plume is similar to the typical seismic rates, suggesting that the LP events are directly related to degassing processes. However, the source mechanism, capable of producing one LP event about every 0.5-5 min, is still poorly understood. Shishaldin's seismicity is unusual in its sustained high rate of LP events without accompanying eruptive activity. Every indication is that the high rate of seismicity will continue without reflecting a hazardous state. Sealing of the conduit and/or change in gas flux, however, would be expected to change Shishaldin's behavior. ?? 2005 Elsevier B.V. All rights reserved.

Petersen, T.; Caplan-Auerbach, J.; McNutt, S. R.

2006-01-01

334

Volcano survey  

Microsoft Academic Search

SummaryA short review is made of the main means of investigation of eruption forecast, used in the few existing, accurately staffed volcanological observatories as well as during sporadic expeditions on active volcanoes, together with non-exhaustive data obtained during recent years (volcanoseismology, gravimetry, tiltmetry, geodetic measurements, magnetic and aeromagnetic surveys, chemistry of gas, waters and sublimates, geochemistry). Details of research performed

H. Tazieff

1966-01-01

335

Volcano-Tectonic Deformation at Taal Volcano, Philippines  

NASA Astrophysics Data System (ADS)

Taal Volcano, located in southern Luzon, Philippines, is an unusual, tholeiitic volcano situated within a calc-alkaline arc. It is one of the most active volcanic centers in the Philippines, with some 33 historic volcanic eruptions over the past four centuries. Volcanism at Taal is at least partly tectonically controlled, suggested by its location at the intersection of regional fault structures and by the location and shape of both Taal's caldera and Volcano Island. The alignment of modern eruption centers, are controlled by regional and local structures. Here, we review geomorphic and geodetic observations that constrain both tectonic and volcanic deformation in the vicinity of Taal volcano. We use GPS measurements from a 52-station GPS network measured from 1996 - 2001 to investigate overall plate interaction and microplate (intra-arc) deformation. The velocity field indicates that the majority of the Philippine Sea - Eurasia plate convergence is taking place west of Luzon, presumably largely by subduction at the Manila trench. A relatively small fraction of the convergence appears to be taking place within Luzon or across the East Luzon trough. The major intra-arc deformation is accommodated by strike-slip motion along the Philippine Fault, ranging from 25-40 mm/yr left-lateral slip. Detailed measurements in southern Luzon also indicate significant intra-arc deformation west of the Philippine Fault. GPS measurements in southwestern Luzon indicate significant motion within the arc, which could be explained by 11-13 mm/yr of left-lateral shear along the "Macolod Corridor", within which Taal Volcano resides. A dense network of continuous single- and dual-frequency GPS receivers at Taal Volcano, Philippines reveals highly time-variable deformation behavior, similar to that observed at other large calderas. While the caldera has been relatively quiescent for the past 2-3 years, previous deformation includes two major phases of intra-caldera deformation, including two phases of inflation and deflation in 1998-2000. The February-November 2000 period of inflation was characterized by approximately 120 mm of uplift of the center of Volcano Island relative to the northern caldera rim, at average rates up to 216 mm/yr. The source of deflation in 1999 was modeled as a contractional Mogi point source centered at 4.2 km depth beneath Volcano Island; the source of inflation in 2000 was modeled as a dilatational Mogi point source centered at 5.2 km depth beneath Volcano Island. The locations of the two sources are indistinguishable within the 95% confidence estimates. Modeling using a running four-month time window from June 1999-March 2001 reveals little evidence for source migration. We find marginal evidence for an elongate source whose long axis is oriented NW-SE, paralleling the caldera-controlling fault system. We suggest that the two periods of inflation observed at Taal represent episodic intrusions of magma into a shallow reservoir centered beneath Volcano Island whose position is controlled at least in part by regional tectonic structures.

Hamburger, M. W.; Galgana, G.; Corpuz, E.; Bartel, B.

2004-12-01

336

Volcano Instability and Dike Swarms Controlled by Local Stress Field  

Microsoft Academic Search

Hotspot volcanoes in the Hawaiian, Canary, and the Reunion islands have two or three directions of dominant rift zones, which are highly developed. Rift zones in those islands are normally underlain by a sequence of basalt flow units, and consist of dike swarms which are elongated to a specific direction (with several kilometers length). In oceanic volcanic islands(Kilauea, Mauna Loa,

O. Otaki; N. Fujii

2004-01-01

337

Mt. Erebus: A Surprising Volcano: Grades K-1: Illustrated Book  

NSDL National Science Digital Library

This informational text introduces students to Mt. Erebus, a volcano located on Ross Island, just off the coast of Antarctica. Mt. Erebus is the world's southernmost active volcano. Students read about the volcano in a simplified manner. The text is written at a kindergarten through grade one reading level. This version is a full-color PDF that can be printed, cut and folded to form a book. Each book contains color photographs and illustrations.

Fries-Gaither, Jessica

338

Eruptive and Transportation Processes During Caldera-Forming Eruptions of Sete Cidades Volcano, São Miguel, Azores  

Microsoft Academic Search

Sete Cidades volcano forms the Western part of the island of São Miguel, Azores, which is hosting three active trachytic central volcanoes (Sete Cidades, Fogo, Furnas). Volcanic activity in the archipelago exhibits a strong tectonic control and on São Miguel, the NW-SE trending basaltic Terceira Rift is intersecting the central volcanoes. All three have erupted since the settlement of the

U. Kueppers; M. G. Queiroz; J. M. Pacheco

2007-01-01

339

Mud Volcanoes Formation And Occurrence  

NASA Astrophysics Data System (ADS)

Mud volcanoes are natural phenomena, which occur throughout the globe. They are found at a greater or lesser scale in Azerbaijan, Turkmenistan, Georgia, on the Kerch and Taman peninsulas, on Sakhalin Island, in West Kuban, Italy, Romania, Iran, Pakistan, India, Burma, China, Japan, Indonesia, Malaysia, New Zealand, Mexico, Colombia, Trinidad and Tobago, Venezuela and Ecuador. Mud volcanoes are most well-developed in Eastern Azerbaijan, where more than 30% of all the volcanoes in the world are concentrated. More than 300 mud volcanoes have already been recognized here onshore or offshore, 220 of which lie within an area of 16,000 km2. Many of these mud volcanoes are particularly large (up to 400 m high). The volcanoes of the South Caspian form permanent or temporary islands, and numerous submarine banks. Many hypotheses have been developed regarding the origin of mud volcanoes. Some of those hypotheses will be examined in the present paper. Model of spontaneous excitation-decompaction (proposed by Ivanov and Guliev, 1988, 2002). It is supposed that one of major factors of the movement of sedimentary masses and formation of hydrocarbon deposits are phase transitions in sedimentary basin. At phase transitions there are abnormal changes of physical and chemical parameters of rocks. Abnormal (high and negative) pressure takes place. This process is called as excitation of the underground environment with periodicity from several tens to several hundreds, or thousand years. The relationship between mud volcanism and the generation of hydrocarbons, particularly methane, is considered to be a critical factor in mud volcano formation. At high flow rates the gas and sediment develops into a pseudo-liquid state and as flow increases the mass reaches the "so-called hover velocity" where mass transport begins. The mass of fluid moves as a quasi-uniform viscous mass through the sediment pile in a piston like manner until expelled from the surface as a "catastrophic eruption". Model of buoyancy drive (by Brown, 1990). Brown's basic hypothesis is similar to Ivanov and Guliev and may be summarized briefly as follows: -in situations where rapid sedimentation is occurring mud may be driven to the surface by buoyancy forces due to bulk density contrasts between mud and overlying sediment cover. Such density contrasts may be simply the result of compaction -disequilibrium, but more importantly may be related to gas expansion when fluids are transported to shallower depths with lower pressure and temperature conditions. Synthetic model had been proposed by I.Lerche, E.Bagirov, I.Guliyev (1997). The model includes the following studies: The starting point of the mud volcanoes begins with the formation of a zone of decompaction as a consequence of a high rate of gas generation. The mud body starts to rise under buoyancy. The excess pressure inside the mud intrusion is less than in surrounding formation. As a result, fluid flow toward the body of mud volcanoes. The body of the mud volcanoes then grows, increasing the buoyancy forces, with further drive the mud. If the rate of gas generation more thôn gas flow, causing exsolving of gas to free-phase gas. If there are open faults and fractures which cross the body of mud volcanoes, then gas and mud can penetrate through the faults, and so from gryphons and salses on the surface. A mud volcanoes can be consider as a huge accumulation of gas, where as the oil is concentrated on the flanks of the mud body.

Guliyev, I. S.

2007-12-01

340

A Direct Comparison of MODIS and COSPEC Sulfur Dioxide Measurements of the May 21, 2003 Eruption Plume of Anatahan Volcano, Mariana Islands  

NASA Astrophysics Data System (ADS)

Quantifying the SO2 burden emitted from a volcano is critical to understanding a volcano's current state of activity. Ground-based instruments such as the correlation spectrometer (COSPEC) and the mini-DOAS are most routinely employed to measure volcanic SO2. Both instruments are human operated so they must be deployed on-site to obtain SO2 estimates. This makes it difficult and costly to regularly monitor active volcanoes world- wide. Satellite-based measurements, which can provide SO2 estimates in near real-time, have increasingly been used as a tool for volcanic monitoring. The Moderate Resolution Imaging Spectrometer (MODIS) located on board the Terra and Aqua satellites provides twice daily coverage of the Earth and has the capacity to detect volcanic SO2. The ability of MODIS to accurately detect and quantify SO2 in volcanic plumes using a SO2 retrieval program, MAP_SO2, was compared with COSPEC on the May 21, 2003 plume at Anatahan volcano (16.35oN, 145.67oE). MODIS was able to clearly detect SO2 in the plume and the MAP_SO2 derived SO2 flux was calculated (independently from the COSPEC data) to be more than twice the COSPEC derived flux (10,270 t/d and 3,000 - 4,500 t/d respectively). However, calculating a flux introduces additional errors. Therefore another means of comparing the two methods is utilized: a direct comparison of plume cross-sections from these two different methods. The MODIS image used with the MAP_SO2 program was acquired at 13:25 local time. The COSPEC traverse began at 13:35 local time and ended 14:40 local time. The time of the MODIS image acquisition and the start of the COSPEC traverse occurred within 10 minutes of each other. Although the MODIS image is a snap shot in time and the COSPEC traverse took about an hour to complete, the timing is so close that these two products are ideal for the comparison. The differences in these observations are used to better quantify SO2 emissions, to assess the current mismatch between ground-based and remotely sensed retrievals, and to aid in the development of an approach to continuously and accurately monitor volcanic activity from space in near real-time.

Meier, V. L.; Scuderi, L.; Fischer, T.; Hilton, D.

2007-05-01

341

Comprehensive study of the seismotectonics of the eastern Aleutian ARC and associated volcanic systems  

NASA Astrophysics Data System (ADS)

Assessment of the seismic potential for occurrence of great earthquakes in three seismic gaps (Shumagin Islands, Unalaska Island, and Yakataga-Kayak regions) was completed. In the best instrumented seismic gap in the Shumagin Islands region, the likelihood for a great earthquake within the next two decades is high. Analysis of earthquake data collected from a telemetered network operated in the Shumagin seismic gap shows near quiescence in the shallow portion of the main thrust zone. High time resolution data (0.01 sec), and wider frequency bandpass data (0.5 to 30 Hz) are being collected. Seismic data for two eruptive sequences of Pavlof volcano were obtained.

Jacob, K. H.; Hauksson, E.; Sykes, L. R.; Davies, J.; House, L.; Morl, J.; McNutt, S.; Johnson, D.; Peterson, J.; Hauptman, J.

342

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

USGS Publications Warehouse

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

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

2006-01-01

343

Volcano Explorer: Build A Virtual Volcano  

NSDL National Science Digital Library

This website allows you to build virtual volcanoes and model their eruptions by changing gas and viscosity levels. Interactive screens define vocabulary and explain volcanic activity of three common volcano categories.

344

Tropical-North Pacific Teleconnections: a mechanistic link between the strength of the Indian monsoon strength and the Aleutian Low.  

NASA Astrophysics Data System (ADS)

Present day fluctuations in the intensity of the Indian monsoon, the position of the Intertropical Convergence Zone (ITCZ), El Niño/La Niña events, and the strength of the Aleutian Low (AL) pressure system, result in extreme weather events, large scale ecosystem shifts, and impact human life and livelihood. How these climate systems will interact as global climate changes occur is still unknown. Two new marine geochemical records of Holocene climate variability improve our understanding of past tropical - North Pacific teleconnections. The first, a Zr/Al record from the western Arabian Sea, demonstrates significant variability in soil moisture on the Horn of Africa. The second, a ?15N record from Effingham Inlet (Vancouver Island), indicates changes in the strength of the California Undercurrent and NE Pacific coastal upwelling and allows our understanding of climate change in the Pacific region to be expanded northward to include the Aleutian Low pressure system. Over the last 10 kyrs, decreased SW monsoon winds/southern ITCZ position are concurrent with an increase in El Niño events and a strengthening of the Aleutian Low. Climate models suggest that this relationship is modulated by changes in the sea surface temperature of the equatorial Pacific, which result in centennial-scale variability superimposed on the gradual Holocene decline in orbital forcing.

Ivanochko, T. S.; Ganeshram, R.; Calvert, S. E.; Bush, A. B.; Pedersen, T. F.

2008-12-01

345

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

SciTech Connect

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

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

1989-09-01

346

Seismogenic structures activated during the pre-eruptive and intrusive swarms of Piton de la Fournaise volcano (La Réunion island) between 2008 and 2011  

NASA Astrophysics Data System (ADS)

Piton de la Fournaise is a frequently active basaltic volcano with more than 30 fissure eruptions since 1998. These eruptions are always preceded by pre-eruptive swarms of volcano-tectonic earthquakes which accompany dike propagation. Occasionally, intrusion swarms occur without leading to any eruption. From October 2008 to May 2011, as part of the research project Undervolc, a temporary network of 15 broadband stations has been installed on the volcano to complement the local monitoring network. We examined in detail the 6 intrusive and 5 pre-eruptive swarms which occurred during the temporary experiment. All the crises lasted for a few hours and only included shallow events clustered below the summit craters, around and above sea level, showing no signs of deeper magma transfers. These characteristics are common to most swarms observed at Piton de la Fournaise arising questions about the origin of the seismicity which seems to be poorly linked with dike propagation. With the aim to identify the main seismogenic structures active during the swarms, we applied precise earthquake detection and classification techniques based on waveform cross-correlation. For each swarm, the onsets of all transients, including small amplitude ones, have been precisely detected at a single station by scanning the continuous data with reference waveforms. The classification of the detected transients indicates the presence of several families of similar earthquakes. The two main families (F01 and F02) include several hundred events. They are systematically activated at the beginning of each pre-eruptive swarm but are inactive during the intrusive ones. They group more than 50 percent of the detected events for the corresponding crises. The other clusters are mostly associated with single swarms. To determine the spatial characteristics of the structures corresponding to the main families, we applied precise relocation techniques. Based on the one-station classification, the events have first been picked at all available stations by cross-correlating waveforms with those of master events whose arrival times have been manually determined. All events have been located using a 3D velocity model to determine accurate hypocentral azimuths and take-off angles. Precise relative locations have been computed for each multiplet using cross-correlation delays calculated for all available stations between all pairs of events. The results indicate the presence at sea level of a major structure grouping families F01 and F02 and describing an East-West elongated pattern with sub-vertical extension. Small scale earthquake migrations, mostly horizontal, occur during the pre-eruptive swarms along that structure. The smaller multiplets define vertically elongated patterns extending around and above the main F01-F02 multiplet. Our results show that different processes are involved in pre-eruptive and intrusive crises and that a structure located around 2.5 km below the summit controls the occurrence of recent eruptions of Piton de la Fournaise volcano.

Battaglia, J.; Brenguier, F.

2011-12-01

347

New K-Ar ages and the geologic evidence against rejuvenated-stage volcanism at Haleakala??, East Maui, a postshield-stage volcano of the Hawaiian island chain  

USGS Publications Warehouse

The postshield and previously inferred rejuvenated-stage history of Haleakala?? volcano is reevaluated on the basis of 52 new K-Ar ages, 42 from the postshield Kula Volcanics and 10 from the overlying Ha??na Volcanics. Postshield extrusion was robust from 0.93 to 0.76 Ma. A period of low extrusion rate or volcanic quiescence occurred between 0.76 and 0.65 Ma, well within Kula time. A chemical change to increasingly alkalic lava occurred at this time as the volcano changed from broadly hawaiitic to basanitic in its eruptive products and robust extrusion resumed. A slightly longer period of low extrusion rate or quiescence occurred after ca. 0.4 Ma, but only trifling change in geochemical character is observed. Geochemically, the Ha??na Volcanics unit, chiefly basanitic, overlaps greatly with the upper part of the Kula Volcanics; there is a weak tendency to slightly more alkaline character among the Ha??na Volcanics. The age of the Kula/Ha??na boundary is ca. 0.15-0.12 Ma; thus, volcanic quiescence of only ???0.03 m.y. separates the two formations, much shorter than the previously known limit of 0.25-0.30 m.y. The brevity of this hiatus, coupled with coincident vent loci and broadly similar geochemical characteristics for the Ha??na and the upper part of the Kula Volcanics, indicates that the Ha??na Volcanics unit comprises deposits of postshield-stage volcanism that has waned substantially since ca. 0.4-0.3 Ma. Haleakala?? has not yet begun a classically defined rejuvenated stage. Our findings support recent numerical modeling of plume-lithosphere interactions that predict that Haleakala?? is near the end of its postshield growth.

Sherrod, D. R.; Nishimitsu, Y.; Tagami, T.

2003-01-01

348

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

NASA Astrophysics Data System (ADS)

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

La Felice, Sonia; Landi, Patrizia

2011-11-01

349

Mid-Pleistocene lavas from the Seguam volcanic center, central Aleutian arc: closed-system fractional crystallization of a basalt to rhyodacite eruptive suite  

Microsoft Academic Search

In contrast to adjacent volcanic centers of the modern central Aleutian arc, Seguam Island developed on strongly extended arc crust. K-Ar dates indicate that mid-Pleistocene, late-Pleistocene, and Holocene eruptive phases constitute Seguam. This study focuses on the petrology of the mid-Pleistocene, 1.07–07 Ma, Turf Point Formation (TPF) which is dominated by an unusual suite of porphyritic basalt and basaltic andesite

Bradley S. Singer; James D. Myers; Carol D. Frost

1992-01-01

350

Sector-zoned augite megacrysts in Aleutian high alumina basalts: implications for the conditions of basalt crystallization and the generation of calc-alkaline series magmas  

Microsoft Academic Search

Several high alumina basalts from the Aleutian volcanic centers of Cold Bay and Kanaga Island contain large (up to 1.5cm diameter) megacrysts of sector-zoned augite. The megacrysts are invariably euhedral with well developed {001}, {010} and {111} forms. All crystals display concentric bands that are rich in mineral and glass inclusions. The sector zonation typically occurs as well developed (010),

James G. Brophy; Carla S. Whittington; Young-Rok Park

1999-01-01

351

Sector-zoned augite megacrysts in Aleutian high alumina basalts: implications for the conditions of basalt crystallization and the generation of calc-alkaline series magmas  

Microsoft Academic Search

Several high alumina basalts from the Aleutian volcanic centers of Cold Bay and Kanaga Island contain large (up to 1.5?cm\\u000a diameter) megacrysts of sector-zoned augite. The megacrysts are invariably euhedral with well developed {001}, {010} and {111}\\u000a forms. All crystals display concentric bands that are rich in mineral and glass inclusions. The sector zonation typically\\u000a occurs as well developed (010),

James G. Brophy; Carla S. Whittington; Young-Rok Park

1999-01-01

352

Volcano Lovers  

NSDL National Science Digital Library

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

Tenenbaum, David

1997-01-02

353

Newberry Volcano—Central Oregon's Sleeping Giant  

USGS Publications Warehouse

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

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

2011-01-01

354

Comprehensive study of the seismotectonics of the Eastern Aleutian arc and associated volcanic systems. Annual progress report, April 1, 1985-March 31, 1986  

SciTech Connect

In the five-week period between October 9 and November 14, 1985, a sequence of 5 moderate-sized events with magnitudes m/sub b/ = 6.4, 5.0, 5.2, 5.0, and 5.6 occurred in the Shumagin Islands seismic network region of the Eastern Aleutian arc. In addition to this cluster of moderate-sized events the microseismicity rate in the Shumagin region has increased by 35 to 80% for at least a 6-months period beginning in April 1985. While we cannot be sure that these unusual seismicity patterns are part of a precursory activity to a large impending Shumagin earthquake, such a possibility must at least be considered. In addition to these observations of recent seismicity in the Eastern Aleutians, we have thoroughly reviewed the entire historic and instrumental seismicity, the tectonics and seismic hazards for most of the Alaska-Aleutian seismic zone, and have redetermined the probabilities for the occurrence of great earthquakes at this active plate boundary for the twenty year period 1985-2005. The aftershock sequence, amount of slip and magnitude Mwgreater than or equal to8.6) of the great 1957 earthquake in the central Aleutians, have been reanalyzed and its effect on the seismic potential for the Unalaska seismic gap is assessed. We find this questionable gap at present capable to sustain a Mwapprox. =8.6 event. 11 refs., 4 figs.

Jacob, K.H.; Taber, J.; Boyd, T.; McNutt, S.; Beavan, J.; Rosen, S.; Luckman, M.A.; Johnson, D.; Skinta, L.

1986-01-01

355

Eradication of Aleutian disease of mink by eliminating positive counterimmunoelectrophoresis test reactors.  

PubMed Central

The counterimmunoelectrophorsis test was applied on three Aleutian disease virus-infected mink ranches for the detection of specific Aleutian disease virus antibody. All mink on the ranches were tested during the pelting season and before the breeding season for 4 consecutive years. Aleutian disease has been eliminated from the three commercial mink ranches by culling out all mink that were positive for Aleutian disease virus antibody.

Cho, H J; Greenfield, J

1978-01-01

356

The Electronic Volcano  

NSDL National Science Digital Library

The Electronic Volcano offers links to many types of information on active volcanoes, such as maps, photographs, full texts of dissertations and a few elusive documents. The Electronic Volcano will guide you to resources in libraries or resources on other information servers including catalogs of active volcanoes, datasets for literature citations, electronic and hard-copy journals, visual information, maps, observatories and institutions, and a volcano name and country index.

357

Earth Layers and Volcanoes  

NSDL National Science Digital Library

Why do we have volcanoes? Use the information on the websites to answer the questions on the worksheet. Worksheet First, review the layers of the earth. Labeling the layers game Next, go through the maze and read the information given. Magic School Bus volcano game Now, study the different shapes of volcanoes. Click enter, then volcano types in the menu. Read about the 3 types of volcanoes. Discovery Kids Games Finally, watch ...

Brookeshallow

2011-04-13

358

Geology of the Cook Islands  

Microsoft Academic Search

The geology of the 15 Cook Islands in the south-central Pacific is briefly described and their geological history outlined. All are the summit portions of extinct Tertiary volcanoes; six of the seven Northern Group islands are atolls, four of the Southern Group are makatea-type islands, and the others include a high mountainous volcanic island, a hilly near-atoll, an atoll, and

B. L. Wood

1967-01-01

359

Rates of sulfur dioxide and particle emissions from White Island volcano, New Zealand, and an estimate of the total flux of major gaseous species  

Microsoft Academic Search

Airborne correlation spectrometry (COSPEC) was used to measure the rate of SO2 emission at White Island on three dates, i.e., November 1983, 1230 ± 300 t\\/d; November 1984, 320 ± 120 t\\/d; and January 1985, 350 ± 150 t\\/d (t = metric tons). The lower emission rates are likely to reflect the long-term emission rates, whereas the November 1983 rate

William I. Rose; Raymond L. Chuan; Werner F. Giggenbach; Philip R. Kyle; Robert B. Symonds

1986-01-01

360

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

Microsoft Academic Search

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

T. Walter; H.-U. Schmincke

2002-01-01

361

Super Volcano  

NSDL National Science Digital Library

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

362

Types of Volcanoes  

NSDL National Science Digital Library

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

363

Volcanoes, Tsunamis and the demise of the Minoans  

Microsoft Academic Search

There is considerable evidence from archaeological sites on the Greek Islands of extensive volcanic activity. The most famous example is the eruption of the island volcano of Thera (Santorini) which buried the Minoan town of Akrotiri on Thera and may have played a significant role in the replacement of the Minoan civilization on Crete by the Myceneans. The eruption of

J. J. Monaghan; P. J. Bicknell; R. J. Humble

1994-01-01

364

Interferometric synthetic aperture radar study of Okmok volcano, Alaska, 1992–2003: Magma supply dynamics and postemplacement lava flow deformation  

Microsoft Academic Search

Okmok volcano, located in the central Aleutian arc, Alaska, is a dominantly basaltic complex topped with a 10-km-wide caldera that formed circa 2.05 ka. Okmok erupted several times during the 20th century, most recently in 1997; eruptions in 1945, 1958, and 1997 produced lava flows within the caldera. We used 80 interferometric synthetic aperture radar (InSAR) images (interferograms) to study

Zhong Lu; Timothy Masterlark; Daniel Dzurisin

2005-01-01

365

Interferometric synthetic aperture radar study of Okmok volcano, Alaska, 1992-2003: Magma supply dynamics and postemplacement lava flow deformation  

Microsoft Academic Search

Okmok volcano, located in the central Aleutian arc, Alaska, is a dominantly basaltic complex topped with a 10-km-wide caldera that formed circa 2.05 ka. Okmok erupted several times during the 20th century, most recently in 1997; eruptions in 1945, 1958, and 1997 produced lava flows within the caldera. We used 80 interferometric synthetic aperture radar (InSAR) images (interferograms) to study

Zhong Lu; Timothy Masterlark; Daniel Dzurisin

2005-01-01

366

Volcanic Tsunami Generation in the Aleutian Arc of Alaska  

Microsoft Academic Search

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

C. F. Waythomas; P. Watts

2003-01-01

367

Tephra compositions from Late Quaternary volcanoes around the Antarctic Peninsula  

NASA Astrophysics Data System (ADS)

Crustal extension and rifting processes opened the Bransfield Strait between the South Shetland Islands and the Antarctic Peninsula during the last 4 Ma. Similar processes on the Peninsula's eastern side are responsible for volcanism along Larsen Rift. There are at least 11 volcanic centers with known or suspected Late Pleistocene / Holocene explosive activity (Fig. 1). Fieldwork was carried out on the islands Deception, Penguin, Bridgeman and Paulet, moreover at Melville Peak (King George Is.) and Rezen Peak (Livingston Is.). Of special importance is the second ever reported visit and sampling at Sail Rock, and the work on never before visited outcrops on the northern slopes and at the summit of Cape Purvis volcano (Fig. 1). The new bulk tephra ICP-MS geochemical data provide a reliable framework to distinguish the individual volcanic centers from each other. According to their Mg-number, Melville Peak and Penguin Island represent the most primitive magma source. Nb/Y ratios higher than 0.67 in combination with elevated Th/Yb and Ta/Yb ratios and strongly enriched LREE seem to be diagnostic to distinguish the volcanoes located along the Larsen Rift from those associated with Bransfield Rift. Sr/Y ratios discriminate between the individual Larsen Rift volcanoes, Paulet Island showing considerably higher values than Cape Purvis volcano. Along Bransfield Rift, Bridgeman Island and Melville Peak have notably lower Nb/Y and much higher Th/Nb than Deception Island, Penguin Island and Sail Rock. The latter displays almost double the Th/Yb ratio as compared to Deception Island, and also much higher LREE enrichment but extraordinarily low Ba/Th, discriminating it from Penguin Island. Such extremely low Ba/Th ratios are also typical for Melville Peak, but for none of the other volcanoes. Penguin Island has almost double the Ba/Th and Sr/Y ratios higher than any other investigated volcano. Whereas the volcanoes located in the northern part of Bransfield Strait have Zr/Hf ratios lower than N-MORB, all other volcanoes including the Larsen Rift centers display Zr/Hf higher than N-MORB. It is expected that the correlation of the new data with published data from tephra layers found in ice, lake and marine sediment cores will contribute to a better constrained timing of individual climatic events identified in the northern Antarctic Peninsula area. Late Quaternary volcanoes around the northern Antarctic Peninsula.

Kraus, S.

2009-12-01

368

Dynamic deformation of Seguam Volcano, Alaska, 1992-2007, from multi-interferogram InSAR processing  

NASA Astrophysics Data System (ADS)

Seguam Volcano, located in the central Aleutian arc, homes two major calderas. All historical eruptions (1786-1790, 1827, 1891, 1892, 1901, 1927, 1977, and 1992-1993) are thought to have emanated from or near Pyre Peak, a volcanic cone located near the center of the western caldera. A time-series ERS-1/2 and ENVISAT radar interferometric synthetic aperture radar (InSAR) images were generated to study ground surface deformation during 1992-2008. The InSAR small baseline subset (SBAS) technique was applied to retrieve time-series deformation by reducing artifacts associated with baseline uncertainties and atmospheric delay anomalies. InSAR images from two adjacent tracks were independently process to validate results. In contrast to the steady subsidence at a rate of ~1.5 cm/yr over the western Seguam Island, the eastern caldera has experienced 4 episodes of deformation: ~1.5 cm/year subsidence during June 1993 and July 1999 (stage 1), ~2.5 cm/year inflation during July 1999 and November 2000 (stage 2), ~1.5 cm/year subsidence during November 2000 and July 2005 (stage 3), and ~2 cm/year inflation during July 2005 and 2007 (stage 4). Source models suggest a static subsidence source at less than 2 km deep over the western caldera. Models of the eastern caldera indicate that the inflation source is at 3-5 km depth while the subsidence source is less than 2 km deep. We suggest that basaltic magma pulses, which intermittently flow into a storage chamber residing at 3-5 km deep, drive inflation at eastern caldera. The injected magma degasses and the volatile products accumulate in a shallow poroelastic storage chamber, resulting deflation of the eastern caldera. The steady subsidence of over the western part of Seguam Island is probably driven by thermoelastic contraction of lava flows emplaced in 1992 and previous eruptions.

Lee, C.; Lu, Z.; Won, J.; Jung, H.; Dzurisin, D.

2010-12-01

369

Volcanoes: Annenberg Media Project  

NSDL National Science Digital Library

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

1997-01-01

370

Toward sustainable ecosystem services from the Aleutian Archipelago  

Microsoft Academic Search

The new research reported in this special issue of Fisheries Oceanography expands our understanding of the Aleutian Archipelago ecosystem. Yet our know- ledge remains very limited, while the use of this eco- system for commercial activities, recreation and other purposes expands. Given this situation, how can we sustain the ecosystem services (food, fuel, fibers as well as spiritual, recreational, educational

J. D. SCHUMACHER; GORDON H. KRUSE

2005-01-01

371

Aleutian Campaign in World War II: A Strategic Perspective.  

National Technical Information Service (NTIS)

This work is a detailed historical study of the Second World War's little known Aleutian Campaign in the North Pacific, commonly referred to as the 'Forgotten War.' After describing the events that transpired in the North Pacific throughout the war, this ...

J. A. Polhamus

2005-01-01

372

A volcano bursting at the seams: Inflation, faulting, and eruption at Sierra Negra volcano, Galápagos  

Microsoft Academic Search

The results of geodetic monitoring since 2002 at Sierra Negra volcano in the Galápagos Islands show that the filling and pressurization of an ˜2-km-deep sill eventually led to an eruption that began on 22 October 2005. Continuous global positioning system (CGPS) monitoring measured >2 m of accelerating inflation leading up to the eruption and contributed to nearly 5 m of

William W. Chadwick Jr.; Dennis J. Geist; Sigurjón Jónsson; Michael Poland; Daniel J. Johnson; Charles M. Meertens

2006-01-01

373

Aerosol Lesson: Volcano Types  

NSDL National Science Digital Library

This activity has students research a list of volcanoes and then write detailed information they researched under a column that identifies that type of volcano - Cinder Cone, Composite, or Shield. Included are a worksheet and a collection of links to referential websites about specific volcanoes.

374

Where are the Volcanoes?  

NSDL National Science Digital Library

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

Fries-Gaither, Jessica

375

The Volcano Adventure Guide  

Microsoft Academic Search

Adventure travels to volcanoes offer chance encounters with danger, excitement, and romance, plus opportunities to experience scientific enlightenment and culture. To witness a violently erupting volcano and its resulting impacts on landscape, climate, and humanity is a powerful personal encounter with gigantic planetary forces. To study volcano processes and products during eruptions is to walk in the footsteps of Pliny

Fraser Goff

2005-01-01

376

A Scientific Excursion: Volcanoes.  

ERIC Educational Resources Information Center

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

Olds, Henry, Jr.

1983-01-01

377

How Volcanoes Work  

NSDL National Science Digital Library

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

2011-04-18

378

Focus: alien volcanos  

NASA Astrophysics Data System (ADS)

Part 1: Volcanoes on Earth - blowing their top; Part 2: Volcanoes of the inner Solar System - dead or alive: the Moon, Mercury, Mars, Venus; Part 3: Volcanoes of the outer Solar System - fire and ice: Io, Europa, Ganymede and Miranda, Titan, Triton, Enceladus.

Carroll, Michael; Lopes, Rosaly

2007-03-01

379

Interactive Volcano Studies and Education Using Virtual Globes  

NASA Astrophysics Data System (ADS)

Internet-based virtual globe programs such as Google Earth provide a spatial context for visualization of monitoring and geophysical data sets. At the Alaska Volcano Observatory, Google Earth is being used to integrate satellite imagery, modeling of volcanic eruption clouds and seismic data sets to build new monitoring and reporting tools. However, one of the most useful information sources for environmental monitoring is under utilized. Local populations, who have lived near volcanoes for decades are perhaps one of the best gauges for changes in activity. Much of the history of the volcanoes is only recorded through local legend. By utilizing the high level of internet connectivity in Alaska, and the interest of secondary education in environmental science and monitoring, it is proposed to build a network of observation nodes around local schools in Alaska and along the Aleutian Chain. A series of interactive web pages with observations on a volcano's condition, be it glow at night, puffs of ash, discolored snow, earthquakes, sounds, and even current weather conditions can be recorded, and the users will be able to see their reports in near real time. The database will create a KMZ file on the fly for upload into the virtual globe software. Past observations and legends could be entered to help put a volcano's long-term activity in perspective. Beyond the benefit to researchers and emergency managers, students and teachers in the rural areas will be involved in volcano monitoring, and gain an understanding of the processes and hazard mitigation efforts in their community. K-12 students will be exposed to the science, and encouraged to participate in projects at the university. Infrastructure at the university can be used by local teachers to augment their science programs, hopefully encouraging students to continue their education at the university level.

Dehn, J.; Bailey, J. E.; Webley, P.

2006-12-01

380

A precision tidal model for Montserrat (B.W.I) and insights on volcano-aquifer dynamics for the July 29, 2008 eruption at Soufrière Hills volcano  

Microsoft Academic Search

The ongoing eruption of the Soufrière Hills volcano (SHV), Montserrat, provides an unprecedented opportunity to study complex processes at an active andesitic arc volcano. There is for example evidence from geodetic measurements that volcanic activity follows a cyclic pattern. At the same time, geodetic signals on a small island such as Montserrat are prone to be affected by tidal artefacts,

Joachim Gottsmann; Michel van Camp; Nicolas Fournier

2010-01-01

381

Cascades Volcano Observatory  

NSDL National Science Digital Library

This is the homepage of the United States Geological Survey's (USGS) Cascades Volcano Observatory (CVO). The site features news and events, updates on current activity of Cascade Range volcanoes, and information summaries on each of the volcanoes in the range. There are also hazard assessment reports, maps, and a 'Living with Volcanoes' feature that provides general interest information. A set of menus provides access to more technical information, such as a glossary, information on volcano hydrology, monitoring information, a photo archive, and information on CVO research projects.

2010-09-15

382

Potential landslide activity affecting the archaeological site of Orongo (Easter Island-Chile): preliminary analysis  

Microsoft Academic Search

Easter Island forms part of the Easter Line, a continuous latitudinal chain of volcanic seamounts and islands in the Pacific Sea. The island's roughly triangular shape is determined by the merging of lava flows produced by its three main volcanoes (Rano Kau, Terevaka, Poike) which form its main mass. The Rano Kau volcano, sited in the SW vertex of the

C. Margottini; G. Delmonaco; D. Spizzichino; O. Pandolfi; R. Crisostomo; S. Nohe

2009-01-01

383

Three-dimensional velocity structure and high-precision earthquake relocations at Augustine, Akutan, and Makushin Volcanoes, Alaska  

NASA Astrophysics Data System (ADS)

Alaska contains over 100 volcanoes, 21 of which have been active within the past 20 years, including Augustine in Cook Inlet, and Akutan and Makushin in the central Aleutian arc. We incorporate 14-15 years of earthquake data from the Alaska Volcano Observatory (AVO) to obtain P-wave velocity structure and high-precision earthquake locations at each volcano. At Augustine, most relocated seismicity is beneath the summit at an average depth of 0.6 km. In the weeks leading to the 2006 eruption, seismicity shallowed and focused on a NW-SE line, suggestive of an inflating dike. Through August 2006, intermittent seismicity was observed at 1 to 4.5 km depth, pointing to an association with the transport of magma. Active-source data are also incorporated into the tomographic inversion, illuminating a high-velocity column beneath the summit, and elevated velocities on the south flank. The high-velocity column surrounds the observed deeper seismicity and is likely due to intruded volcanic material. The elevated velocities on the south flank are associated with uplifted zeolitzed sandstones. Akutan most recently erupted in 1992, before the seismic network was installed. Most seismicity is above 9 km depth, with 10% occurring between 14 to30 km depth. Seismicity is separated into two main groups that dip away from the caldera—one to the east and one to the west. The eastern group contains earthquakes from a swarm in early 1996 and the western group contains earthquakes from mid-1996 through the present that form rough lines radiating from the summit. Ongoing seismicity also occurs in a broader region beneath the caldera. Makushin most recently erupted in 1995, also prior to seismic monitoring by AVO. Relocations here show that most seismicity is at 3 to 13 km depth and either beneath the caldera or within one of two dipping clusters 20 km to the northeast. Additional seismicity occurs at up to 25 km depth beneath the summit, as well as scattered throughout the island at depths shallower than 15 km. Velocities beneath Akutan are lower than beneath Makushin at depths shallower than 7 km. Velocities are more varied beneath Makushin, with high velocities 14 km to the northeast of the summit surrounded by generally lower velocities above 5 km depth. Seismicity beneath the summit lies in a low velocity region, overlain by a northeastward-dipping high-velocity region that encompasses the cluster of dipping seismicity, indicating that these groups of earthquakes are likely caused by separate mechanisms.

Syracuse, E. M.; Thurber, C. H.; Power, J. A.; Prejean, S. G.

2010-12-01

384

Volcanic geology of Furnas Volcano, São Miguel, Azores  

Microsoft Academic Search

Furnas is the easternmost of the three active central volcanoes on the island of São Miguel in the Azores. Unlike the other two central volcanoes, Sete Cidades and Fogo, Furnas does not have a well-developed edifice, but consists of a steep-sided caldera complex 8×5 km across. It is built on the outer flanks of the Povoação\\/Nordeste lava complex that forms

J. E Guest; J. L Gaspar; P. D Cole; G Queiroz; A. M Duncan; N Wallenstein; T Ferreira; J.-M Pacheco

1999-01-01

385

Sulphur output and magma degassing budget of Stromboli volcano  

Microsoft Academic Search

STROMBOLI volcano in the Aeolian islands has been erupting continuously for more than 2,000 years1, and probably as many as 5,000, following a major flank collapse2,3. Here we describe air-borne measurements of the plume flux of SO2 during 1980-93, which show that the volcano emits very large amounts of gas, mostly by open-conduit degassing between explosive outbursts, while exuding little

P. Allard; J. Carbonnelle; N. Métrich; H. Loyer; P. Zettwoog

1994-01-01

386

Mt. Erebus: A Surprising Volcano: Grades K-1: Electronic Book  

NSDL National Science Digital Library

This informational text introduces students to Mt. Erebus, a volcano located on Ross Island, just off the coast of Antarctica. Mt. Erebus is the world's southernmost active volcano. The text is written at a kindergarten through grade one reading level. This is an onscreen version that contains recorded narration allowing students to listen to the text as they read along. Highlighted vocabulary words have individually recorded definitions heard by clicking on the links.

Fries-Gaither, Jessica

387

Mafic Plinian volcanism and ignimbrite emplacement at Tofua volcano, Tonga  

Microsoft Academic Search

Tofua Island is the largest emergent mafic volcano within the Tofua arc, Tonga, southwest Pacific. The volcano is dominated\\u000a by a distinctive caldera averaging 4 km in diameter, containing a freshwater lake in the south and east. The latest paroxysmal\\u000a (VEI 5–6) explosive volcanism includes two phases of activity, each emplacing a high-grade ignimbrite. The products are basaltic\\u000a andesites with between

J. T. Caulfield; S. J. Cronin; S. P. Turner; L. B. Cooper

388

Glaciation of Haleakala volcano, Hawaii  

SciTech Connect

Early debates regarding the large (5 [times] 10 km) summit crater'' of Haleakala volcano (3,055 m altitude) on the island of Maui attributed its origin to renting, rifting, caldera collapse, or erosion. It now is commonly assumed to have resulted from headward expansion of giant canyons by stream erosion (Stearns, 1942). Slope maps and shaded relief images based on new USGS digital elevation data point to the apparent overfit of the canyons that drain the summit depression. Studies of drowned coral reefs and terraces on the offshore east rift of Haleakala indicate that this part of the volcano has undergone submergence of about 2 km, as well as tilting, since 850 ka ago. Such subsidence indicates that the summit altitude at the end of the shield-building phase reached ca. 5,000 m, well above both the present and full-glacial snowlines. A comparison with the radiometrically dated glacial record of Mauna Kea and its reconstructed snowline history suggests that Haleakala experienced 10 or more glaciations, the most extensive during marine isotope stages 20, 18, and 16. By isotope stage 10, the summit had subsided below the full-glacial snowline. Diamictons on the south slope of the volcano, previously described as mudflows, contain lava clasts with superchilled margins, identical to margins of subglacially erupted lavas on Mauna Kea. Glacier ice that mantled the upper slopes of the volcano continuously for several hundred thousand years and intermittently thereafter, is inferred to have carved Haleakala crater and the upper reaches of large canyons radiating from it.

Moore, J.G.; Mark, R. (Geological Survey, Menlo Park, CA (United States)); Porter, S.C. (Univ. of Washington, Seattle, WA (United States). Quaternary Research Center)

1993-04-01

389

The Anatahan volcano-monitoring system  

NASA Astrophysics Data System (ADS)

A real-time 24/7 Anatahan volcano-monitoring and eruption detection system is now operational. There had been no real-time seismic monitoring on Anatahan during the May 10, 2003 eruption because the single telemetered seismic station on Anatahan Island had failed. On May 25, staff from the Emergency Management Office (EMO) of the Commonwealth of the Northern Mariana Islands and the U. S. Geological Survey (USGS) established a replacement telemetered seismic station on Anatahan whose data were recorded on a drum recorder at the EMO on Saipan, 130 km to the south by June 5. In late June EMO and USGS staff installed a Glowworm seismic data acquisition system (Marso et al, 2003) at EMO and hardened the Anatahan telemetry links. The Glowworm system collects the telemetered seismic data from Anatahan and Saipan, places graphical display products on a webpage, and exports the seismic waveform data in real time to Glowworm systems at Hawaii Volcano Observatory and Cascades Volcano Observatory (CVO). In early July, a back-up telemetered seismic station was placed on Sarigan Island 40 km north of Anatahan, transmitting directly to the EMO on Saipan. Because there is currently no population on the island, at this time the principal hazard presented by Anatahan volcano would be air traffic disruption caused by possible erupted ash. The aircraft/ash hazard requires a monitoring program that focuses on eruption detection. The USGS currently provides 24/7 monitoring of Anatahan with a rotational seismic duty officer who carries a Pocket PC-cell phone combination that receives SMS text messages from the CVO Glowworm system when it detects large seismic signals. Upon receiving an SMS text message notification from the CVO Glowworm, the seismic duty officer can use the Pocket PC - cell phone to view a graphic of the seismic traces on the EMO Glowworm's webpage to determine if the seismic signal is eruption related. There have been no further eruptions since the monitoring system was installed, but regional tectonic earthquakes have provided frequent tests of the system. Reliance on a Pocket PC - cell phone requires that the seismic duty officer remain in an area with cell phone coverage. With this monitoring method, the USGS is able to provide rapid notice of an Anatahan eruption to the EMO and the Washington Volcano Ash Advisory Center. Reference Marso, J.N., Murray, T.L., Lockhart, A.B., Bryan, C.J., Glowworm: An extended PC-based Earthworm system for volcano monitoring. Abstracts, Cities On Volcanoes III, Hilo Hawaii, July 2003.

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

2003-12-01

390

Volcano Seismology  

NASA Astrophysics Data System (ADS)

- A fundamental goal of volcano seismology is to understand active magmatic systems, to characterize the configuration of such systems, and to determine the extent and evolution of source regions of magmatic energy. Such understanding is critical to our assessment of eruptive behavior and its hazardous impacts. With the emergence of portable broadband seismic instrumentation, availability of digital networks with wide dynamic range, and development of new powerful analysis techniques, rapid progress is being made toward a synthesis of high-quality seismic data to develop a coherent model of eruption mechanics. Examples of recent advances are: (1) high-resolution tomography to image subsurface volcanic structures at scales of a few hundred meters; (2) use of small-aperture seismic antennas to map the spatio-temporal properties of long-period (LP) seismicity; (3) moment tensor inversions of very-long-period (VLP) data to derive the source geometry and mass-transport budget of magmatic fluids; (4) spectral analyses of LP events to determine the acoustic properties of magmatic and associated hydrothermal fluids; and (5) experimental modeling of the source dynamics of volcanic tremor. These promising advances provide new insights into the mechanical properties of volcanic fluids and subvolcanic mass-transport dynamics. As new seismic methods refine our understanding of seismic sources, and geochemical methods better constrain mass balance and magma behavior, we face new challenges in elucidating the physico-chemical processes that cause volcanic unrest and its seismic and gas-discharge manifestations. Much work remains to be done toward a synthesis of seismological, geochemical, and petrological observations into an integrated model of volcanic behavior. Future important goals must include: (1) interpreting the key types of magma movement, degassing and boiling events that produce characteristic seismic phenomena; (2) characterizing multiphase fluids in subvolcanic regimes and determining their physical and chemical properties; and (3) quantitatively understanding multiphase fluid flow behavior under dynamic volcanic conditions. To realize these goals, not only must we learn how to translate seismic observations into quantitative information about fluid dynamics, but we also must determine the underlying physics that governs vesiculation, fragmentation, and the collapse of bubble-rich suspensions to form separate melt and vapor. Refined understanding of such processes-essential for quantitative short-term eruption forecasts-will require multidisciplinary research involving detailed field measurements, laboratory experiments, and numerical modeling.

Chouet, B.

391

Volcanoes: Nature's Caldrons Challenge Geochemists.  

ERIC Educational Resources Information Center

Reviews various topics and research studies on the geology of volcanoes. Areas examined include volcanoes and weather, plate margins, origins of magma, magma evolution, United States Geological Survey (USGS) volcano hazards program, USGS volcano observatories, volcanic gases, potassium-argon dating activities, and volcano monitoring strategies.…

Zurer, Pamela S.

1984-01-01

392

Volcanoes: Nature's Caldrons Challenge Geochemists.  

ERIC Educational Resources Information Center

|Reviews various topics and research studies on the geology of volcanoes. Areas examined include volcanoes and weather, plate margins, origins of magma, magma evolution, United States Geological Survey (USGS) volcano hazards program, USGS volcano observatories, volcanic gases, potassium-argon dating activities, and volcano monitoring strategies.…

Zurer, Pamela S.

1984-01-01

393