Sample records for aleutian islands erupted
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DeGange, Anthony R.; Byrd, G. Vernon; Walker, Lawrence R.; Waythomas, C.F.
2010-01-01
The Aleutian Islands are situated on the northern edge of the so-called “Pacific Ring of Fire,” a 40,000-km-long horseshoe-shaped assemblage of continental landmasses and islands bordering the Pacific Ocean basin that contains many of the world's active and dormant volcanoes. Schaefer et al. (2009) listed 27 historically active volcanoes in the Aleutian Islands, of which nine have had at least one major eruptive event since 1990. Volcanic eruptions are often significant natural disturbances, and ecosystem responses to volcanic eruptions may vary markedly with eruption style (effusive versus explosive), frequency, and magnitude of the eruption as well as isolation of the disturbed sites from potential colonizing organisms (del Moral and Grishin, 1999). Despite the relatively high frequency of volcanic activity in the Aleutians, the response of island ecosystems to volcanic disturbances is largely unstudied because of the region's isolation. The only ecological studies in the region that address the effects of volcanic activity were done on Bogoslof Island, a remote, highly active volcanic island in the eastern Aleutians, which grew from a submarine eruption in 1796 (Merriam, 1910; Byrd et al., 1980; Byrd and Williams, 1994). Nevertheless, in the 214 years of Bogoslof's existence, the island has been visited only intermittently.Kasatochi Island is a small (2.9 km by 2.6 km, 314 m high) volcano in the central Aleutian Islands of Alaska (52.17°N latitude, 175.51°W longitude; Fig. 1) that erupted violently on 7-8 August 2008 after a brief, but intense period of precursory seismic activity (Scott et al., 2010 [this issue]; Waythomas et al., in review). The island is part of the Aleutian arc volcanic front, and is an isolated singular island. Although the immediate offshore areas are relatively shallow (20–50 m water depth), the island is about 10 km south of the 2000 m isobath, north of which, ocean depths increase markedly. Kasatochi is located between the
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Jessica Larsen,; Neal, Christina; Schaefer, Janet R.; Kaufman, Max; Lu, Zhong
2015-01-01
Okmok volcano, Aleutian Islands, Alaska, explosively erupted over a five-week period between July 12 and August 23, 2008. The eruption was predominantly phreatomagmatic, producing fine-grained tephra that covered most of northeastern Umnak Island. The eruption had a maximum Volcanic Explosivity Index (VEI) of 4, with eruption column heights up to 16 km during the opening phase. Several craters and a master tuff cone formed in the caldera as a result of phreatomagmatic explosions and accumulated tephra-fall and surge deposits. Ascending magma continuously interacted with an extensive shallow groundwater table in the caldera, resulting in the phreatomagmatic character of the eruption. Syneruptive explosion and collapse processes enlarged a pre-existing lake, created a second, entirely new lake, and formed new, deep craters. A field of ephemeral collapse pits and collapse escarpments formed where rapid groundwater withdrawal removed material from beneath capping lava flows. This was the first significant phreatomagmatic event in the U.S. since the Ukinrek Maars eruption in 1977.
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Coombs, Michelle L.; Larsen, Jessica F.; Neal, Christina A.
2018-02-14
Semisopochnoi Island, located in the Rat Islands group of the western Aleutian Islands and Aleutian volcanic arc, is a roughly circular island composed of scattered volcanic vents, the prominent caldera of Semisopochnoi volcano, and older, ancestral volcanic rocks. The oldest rocks on the island are gently radially dipping lavas that are the remnants of a shield volcano and of Ragged Top, which is an eroded stratocone southeast of the current caldera. None of these oldest rocks have been dated, but they all are likely Pleistocene in age. Anvil Peak, to the caldera’s north, has the morphology of a young stratocone and is latest Pleistocene to early Holocene in age. The oldest recognized Holocene deposits are those of the caldera-forming eruption, which produced the 7- by 6-km caldera in the center of the island, left nonwelded ignimbrite in valleys below the edifice, and left welded ignimbrite high on its flanks. The caldera-forming eruption produced rocks showing a range of intermediate whole-rock compositions throughout the eruption sequence, although a majority of clasts analyzed form a fairly tight cluster on SiO2-variation diagrams at 62.9 to 63.4 weight percent SiO2. This clustering of compositions at about 63 weight percent SiO2 includes black, dense, obsidian-like clasts, as well as tan, variably oxidized, highly inflated pumice clasts. The best estimate for the timing of the eruption is from a soil dated at 6,920±60 14C years before present underlying a thin facies of the ignimbrite deposit on the island’s north coast. Shortly after the caldera-forming eruption, two scoria cones on the northwest flank of the volcano outside the caldera, Ringworm crater and Threequarter Cone, simultaneously erupted small volumes of andesite.The oldest intracaldera lavas, on the floor of the caldera, are andesitic to dacitic, but are mostly covered by younger lavas and tephras. These intracaldera lavas include the basaltic andesites of small Windy cone, as well as the
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The 7-8 August 2008 eruption of Kasatochi Volcano, central Aleutian Islands, Alaska
NASA Astrophysics Data System (ADS)
Waythomas, Christopher F.; Scott, William E.; Prejean, Stephanie G.; Schneider, David J.; Izbekov, Pavel; Nye, Christopher J.
2010-12-01
Kasatochi volcano in the central Aleutian Islands erupted unexpectedly on 7-8 August 2008. Kasatochi has received little study by volcanologists and has had no confirmed historical eruptions. The island is an important nesting area for seabirds and a long-term biological study site of the U.S. Fish and Wildlife Service. After a notably energetic preeruptive earthquake swarm, the volcano erupted violently in a series of explosive events beginning in the early afternoon of 7 August. Each event produced ash-gas plumes that reached 14-18 km above sea level. The volcanic plume contained large amounts of SO2 and was tracked around the globe by satellite observations. The cumulative volcanic cloud interfered with air travel across the North Pacific, causing many flight cancelations that affected thousands of travelers. Visits to the volcano in 2008-2009 indicated that the eruption generated pyroclastic flows and surges that swept all flanks of the island, accumulated several tens of meters of pyroclastic debris, and increased the diameter of the island by about 800 m. Pyroclastic flow deposits contain abundant accidental lithic debris derived from the inner walls of the Kasatochi crater. Juvenile material is crystal-rich silicic andesite that ranges from slightly pumiceous to frothy pumice. Fine-grained pyroclastic surge and fall deposits with accretionary lapilli cover the lithic-rich pyroclastic flow deposits and mark a change in eruptive style from episodic explosive activity to more continuous ash emission with smaller intermittent explosions. Pyroclastic deposits completely cover the island, but wave erosion and gully development on the flanks have begun to modify the surface mantle of volcanic deposits.
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Aleutian volcanic eruption taken by Expedition 13 crewmember
2006-05-23
ISS013-E-24184 (23 May 2006) --- Eruption of Cleveland Volcano, Aleutian Islands, Alaska is featured in this image photographed by an Expedition 13 crewmember on the International Space Station. This most recent eruption was first reported to the Alaska Volcano Observatory by astronaut Jeffrey N. Williams, NASA space station science officer and flight engineer, at 3:00 p.m. Alaska Daylight Time (23:00 GMT). This image, acquired shortly after the beginning of the eruption, captures the ash plume moving west-southwest from the summit vent. The eruption was short-lived; the plume had completely detached from the volcano summit two hours later.
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Gabbroic and Peridotitic Enclaves from the 2008 Kasatochi Eruption, Aleutian Islands, Alaska
NASA Astrophysics Data System (ADS)
Kentner, A.; Nadin, E. S.; Izbekov, P. E.; Nye, C. J.; Neill, O. K.
2012-12-01
Kasatochi volcano of the Andreanof Islands in the western Aleutian Arc violently erupted over a two day period from August 7-8, 2008. The eruption involved multiple explosive events generating pyroclastic flows, which included abundant mafic and ultramafic enclaves that have since weathered out and accumulated in talus along the coast. These and other mafic enclaves sampled by modern island arc lavas provide insight into subduction magmatism because they emerge from a section of the subduction system that is less likely than shallower zones to be modified by magmatic processes such as mixing, assimilation, or fractionation. We present new whole rock, clinopyroxene, amphibole, plagioclase, and melt compositions from Kasatochi enclaves of the 2008 eruption. The highly crystalline (~40 vol. % phenocryst content), medium-K basaltic andesite host rock contains ~52-55 wt. % SiO2 and 0.6-0.9 wt. % K2O, and is composed of plagioclase, ortho- and clinopyroxene, amphibole, and Ti-magnetite in a microlite-rich groundmass. Upon eruption, this magma sampled two distinct enclave populations: gabbro and peridotite. The gabbro has abundant amphibole (mostly magnesio-hastingsite) and plagioclase with minor clinopyroxene, olivine, and magnetite, while the peridotite is composed of olivine with minor amounts of clinopyroxene and orthopyroxene. There is little textural variation amongst the peridotitic samples collected, but the gabbroic samples vary from layered to massive and cover a range in grain size from fine-grained to pegmatitic. The layered gabbros display centimeter-scale bands of alternating plagioclase- and amphibole-rich layers, with a strong preferential alignment of the amphibole grains. The coarser-grained samples are very friable, with ~10% pore space; disaggregation of these upon host-magma ascent likely formed the amphibole and plagioclase xenocrysts in the andesitic host. Based on the textural and compositional differences, we divide the enclaves into four groups
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2014-05-21
Remote, rugged and extraordinarily beautiful, Alaska’s Aleutian Islands are best known for wildlife reserves, military bases, fishing, furs and fog. The sprawling volcanic archipelago was brought into the spotlight by the Russian-supported expedition of Alexey Chirikov and Vitus Bering in 1741, and soon became controlled by the Russian-American Fur Company. In 1867 the United States purchased Alaska, including the Aleutian Islands, from Russia. By 1900 the port in Unalaska was well established as a shipping port for Alaska gold. The archipelago sweeps about 1,200 miles (1,800 km) from the tip of the Alaskan Peninsula to Attu, the most westward island. Four major island groups hold 14 large islands, about 55 smaller islands, and a large number of islets, adding up to roughly 150 islands/islets in total. This chain separates the Bering Sea (north) from the Pacific Ocean (south) and the islands are connected by the Marine Highway Ferry – at least as far as Unalaska. For the most remote islands, such as birding paradise of Attu, the western-most Aleutian Island, travel becomes trickier and relies primarily on custom charter. The Moderate Resolution Imaging Spectroradiometer (MODIS) flew over the region and captured this spectacular true-color image of the eastern Aleutian Islands on May 15, 2014. In this image, the Alaskan Peninsula protrudes from the mainland and sweeps to the southwest. The first set of islands are called the Fox Island group. Unalaska Island is part of this group and can be identified, with some imagination, as an island formed in the shape of a flying cherub, with two arms (peninsulas) outstretched towards the northeast, seemingly reaching for the round “balls” of Akutan and Akun Islands. The smallest islands in the west of the image belong to the group known as the Islands of Four Mountains. The Aleutians continue far to the west of this image. Fog surrounds the Aleutians, stretching from just off the southwestern Alaska mainland to the
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NASA Astrophysics Data System (ADS)
Martin, C.; Nicolaysen, K. P.; McConville, K.; Hatfield, V.; West, D.
2013-12-01
By examining the existing geological and archeological record of radiocarbon dated Aleutian tephras of the last 12,000 years, this study sought to determine whether there were spatial or temporal patterns of explosive eruptive activity. The Holocene tephra record has important implications because two episodes of migration and colonization by humans of distinct cultures established the Unangan/Aleut peoples of the Aleutian Islands concurrently with the volcanic activity. From Aniakchak Volcano on the Alaska Peninsula to the Andreanof Islands (158 to 178° W longitude), 55 distinct tephras represent significant explosive eruptions of the last 12,000 years. Initial results suggest that the Andreanof and Fox Island regions of the archipelago have had frequent explosive eruptions whereas the Islands of Four Mountains, Rat, and Near Island regions have apparently had little or no eruptive activity. However, one clear result of the investigation is that sampling bias strongly influences the apparent spatial patterns. For example field reconnaissance in the Islands of Four Mountains documents two Holocene calderas and a minimum of 20 undated tephras in addition to the large ignimbrites. Only the lack of significant explosive activity in the Near Islands seems a valid spatial result as archeological excavations and geologic reports failed to document Holocene tephras there. An intriguing preliminary temporal pattern is the apparent absence of large explosive eruptions across the archipelago from ca. 4,800 to 6,000 yBP. To test the validity of apparent patterns, a statistical treatment of the compiled data grappled with the sampling bias by considering three confounding variables: larger island size allows more opportunity for geologic preservation of tephras; larger magnitude eruption promotes tephra preservation by creating thicker and more widespread deposits; the comprehensiveness of the tephra sampling of each volcano and island varies widely because of logistical and
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InSAR imaging of volcanic deformation over cloud-prone areas - Aleutian islands
Lu, Zhong
2007-01-01
Interferometric synthetic aperture radar (INSAR) is capable of measuring ground-surface deformation with centimeter-tosubcentimeter precision and spatial resolution of tens-of meters over a relatively large region. With its global coverage and all-weather imaging capability, INSAR is an important technique for measuring ground-surface deformation of volcanoes over cloud-prone and rainy regions such as the Aleutian Islands, where only less than 5 percent of optical imagery is usable due to inclement weather conditions. The spatial distribution of surface deformation data, derived from INSAR images, enables the construction of detailed mechanical models to enhance the study of magmatic processes. This paper reviews the basics of INSAR for volcanic deformation mapping and the INSAR studies of ten Aleutian volcanoes associated with both eruptive and noneruptive activity. These studies demonstrate that all-weather INSAR imaging can improve our understanding of how the Aleutian volcanoes work and enhance our capability to predict future eruptions and associated hazards.
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Preliminary volcano-hazard assessment for Akutan Volcano east-central Aleutian Islands, Alaska
Waythomas, Christopher F.; Power, John A.; Richter, Donlad H.; McGimsey, Robert G.
1998-01-01
Akutan Volcano is a 1100-meter-high stratovolcano on Akutan Island in the east-central Aleutian Islands of southwestern Alaska. The volcano is located about 1238 kilometers southwest of Anchorage and about 56 kilometers east of Dutch Harbor/Unalaska. Eruptive activity has occurred at least 27 times since historical observations were recorded beginning in the late 1700?s. Recent eruptions produced only small amounts of fine volcanic ash that fell primarily on the upper flanks of the volcano. Small amounts of ash fell on the Akutan Harbor area during eruptions in 1911, 1948, 1987, and 1989. Plumes of volcanic ash are the primary hazard associated with eruptions of Akutan Volcano and are a major hazard to all aircraft using the airfield at Dutch Harbor or approaching Akutan Island. Eruptions similar to historical Akutan eruptions should be anticipated in the future. Although unlikely, eruptions larger than those of historical time could generate significant amounts of volcanic ash, fallout, pyroclastic flows, and lahars that would be hazardous to life and property on all sectors of the volcano and other parts of the island, but especially in the major valleys that head on the volcano flanks. During a large eruption an ash cloud could be produced that may be hazardous to aircraft using the airfield at Cold Bay and the airspace downwind from the volcano. In the event of a large eruption, volcanic ash fallout could be relatively thick over parts of Akutan Island and volcanic bombs could strike areas more than 10 kilometers from the volcano.
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Clouds off the Aleutian Islands
2017-12-08
March 23, 2010 - Clouds off the Aleutian Islands Interesting cloud patterns were visible over the Aleutian Islands in this image, captured by the MODIS on the Aqua satellite on March 14, 2010. Turbulence, caused by the wind passing over the highest points of the islands, is producing the pronounced eddies that swirl the clouds into a pattern called a vortex "street". In this image, the clouds have also aligned in parallel rows or streets. Cloud streets form when low-level winds move between and over obstacles causing the clouds to line up into rows (much like streets) that match the direction of the winds. At the point where the clouds first form streets, they're very narrow and well-defined. But as they age, they lose their definition, and begin to spread out and rejoin each other into a larger cloud mass. The Aleutians are a chain of islands that extend from Alaska toward the Kamchatka Peninsula in Russia. For more information related to this image go to: modis.gsfc.nasa.gov/gallery/individual.php?db_date=2010-0... For more information about Goddard Space Flight Center go here: www.nasa.gov/centers/goddard/home/index.html
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Perspective View of Umnak Island, Aleutian Islands, Alaska #2
2001-11-04
This image is a perspective view acquired by NASA Airborne Synthetic Aperture Radar AIRSAR in 2001, is of Umnak Island, one of Alaska Aleutian Islands. The active Okmok volcano appears in the center of the island.
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Perspective View of Umnak Island, Aleutian Islands, Alaska #1
2001-11-04
This image is a perspective view acquired by NASA Airborne Synthetic Aperture Radar AIRSAR in 2001, is of Umnak Island, one of Alaska Aleutian Islands. The active Okmok volcano appears in the center of the island.
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Drew, Gary S.; Piatt, John F.; Williams, Jeffrey C.
2018-01-01
Crested Auklets (Aethia cristatella) and Least Auklets (A. pusilla) are crevice-nesting birds that breed in large mixed colonies at relatively few sites in the Aleutian Island archipelago, Bering Sea, Gulf of Alaska, and Sea of Okhotsk. Many of these colonies are located on active volcanic islands. The eruption of Kasatochi volcano, in the central Aleutians, on August 7, 2008, completely buried all crevice-nesting seabird habitat on the island. This provided an opportunity to examine the response of a large, mixed auklet colony to a major geological disturbance. Time-lapse imagery of nesting habitat indicated that both species returned to the largest pre-eruption colony site for several years, but subsequently abandoned it within 5 yr after the eruption. In 2010, a rockfall site in a cove north of the old colony site began to accumulate talus, and groups of auklets were observed using the site in 2011. Use of the new colony appeared to coincide with the abandonment of the old colony site by both species, though surface counts suggested that Least Auklets shifted to the new colony sooner than Crested Auklets. At-sea surveys of seabirds before and after the eruption indicated that both Crested and Least auklets shifted their at-sea distributions from the waters around Kasatochi Island to nearby Koniuji Island. In combination, at-sea counts and colony time-lapse imagery indicated that Crested and Least auklets using Kasatochi responded to the volcanic disturbance and complete loss of nesting habitat at the main colony on Kasatochi with dispersal either to newly created habitat on Kasatochi or to an alternate colony on a nearby island.
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The nearshore benthic community of Kasatochi Island, one year after the 2008 volcanic eruption
Jewett, S.C.; Bodkin, James L.; Chenelot, H.; Esslinger, George G.; Hoberg, M.K.
2010-01-01
A description is presented of the nearshore benthic community of Kasatochi Island 10–12 months after a catastrophic volcanic eruption in 2008. The eruption extended the coastline of the island approximately 400 m offshore, mainly along the south, southeast, and southwest shores, to roughly the 20 m isobath. Existing canopy kelp of Eualaria (Alaria) fistulosa, as well as limited understory algal species and associated fauna (e.g., urchin barrens) on the hard substratum were apparently buried following the eruption. Samples and observations revealed the substrate around the island in 2009 was comprised almost entirely of medium and coarse sands with a depauperate benthic community, dominated by opportunistic pontogeneiid amphipods. Comparisons of habitat and biological communities with other nearby Aleutian Islands, as well as with the Icelandic volcanic island of Surtsey, confirm dramatic reductions in flora and fauna consistent with an early stage of recovery from a large-scale disturbance event.
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NASA Astrophysics Data System (ADS)
Zeglin, L. H.; Rainey, F.; Wang, B.; Waythomas, C.; Talbot, S. L.
2013-12-01
Microorganisms are abundant and diverse in soil and their integrated activity drives nutrient cycling on the ecosystem scale. Organic matter (OM) inputs from plant production support microbial heterotrophic life, and soil geochemistry constrains microbial activity and diversity. As vegetation and soil develops over time, these factors change, modifying the controls on microbial heterogeneity. Following a volcanic eruption, ash deposition creates new surfaces where both organismal growth and weathering processes are effectively reset. The trajectory of microbial community development following this disturbance depends on both organic matter accumulation and geochemical constraints. Also, dispersal of microbial cells to the sterile ash surface may determine microbial community succession. The Aleutian Islands (Alaska, USA) are a dynamic volcanic region, with active and dormant volcanoes distributed across the volcanic arc. One of these volcanoes, Kasatochi, erupted violently in August 2008, burying a small lush island in pryoclastic flows and fine ash. Since, plants and birds are beginning to re-establish on developing surfaces, including legacy soils exposed by rapid erosion of pyroclastic deposits, suggesting that recovery of microbial life is also proceeding. However, soil microbial diversity and function has not been examined on Kasatochi Island or across the greater Aleutian region. The project goal is to address these questions: How is soil microbial community structure and function developing following the Kasatochi eruption? What is the relative importance of dispersal, soil OM and geochemistry to microbial community heterogeneity across the Aleutians? Surface mineral soil (20-cm depth) samples were collected from Kasatochi Island in summer 2013, five years after the 2008 eruption, and from eight additional Aleutian islands. On Kasatochi, pryoclastic deposits, exposed legacy soils supporting regrowth of remnant dune wild-rye (Leymus mollis) and mesic meadow
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46 CFR 7.170 - Alaska Peninsula, AK to Aleutian Islands, AK.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 46 Shipping 1 2014-10-01 2014-10-01 false Alaska Peninsula, AK to Aleutian Islands, AK. 7.170 Section 7.170 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY PROCEDURES APPLICABLE TO THE PUBLIC BOUNDARY LINES Alaska § 7.170 Alaska Peninsula, AK to Aleutian Islands, AK. (a) A line drawn from the...
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46 CFR 7.170 - Alaska Peninsula, AK to Aleutian Islands, AK.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 46 Shipping 1 2011-10-01 2011-10-01 false Alaska Peninsula, AK to Aleutian Islands, AK. 7.170 Section 7.170 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY PROCEDURES APPLICABLE TO THE PUBLIC BOUNDARY LINES Alaska § 7.170 Alaska Peninsula, AK to Aleutian Islands, AK. (a) A line drawn from the...
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46 CFR 7.170 - Alaska Peninsula, AK to Aleutian Islands, AK.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 46 Shipping 1 2013-10-01 2013-10-01 false Alaska Peninsula, AK to Aleutian Islands, AK. 7.170 Section 7.170 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY PROCEDURES APPLICABLE TO THE PUBLIC BOUNDARY LINES Alaska § 7.170 Alaska Peninsula, AK to Aleutian Islands, AK. (a) A line drawn from the...
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Modeling potential tsunami sources for deposits near Unalaska Island, Aleutian Islands
NASA Astrophysics Data System (ADS)
La Selle, S.; Gelfenbaum, G. R.
2013-12-01
In regions with little seismic data and short historical records of earthquakes, we can use preserved tsunami deposits and tsunami modeling to infer if, when and where tsunamigenic earthquakes have occurred. The Aleutian-Alaska subduction zone in the region offshore of Unalaska Island is one such region where the historical and paleo-seismicity is poorly understood. This section of the subduction zone is not thought to have ruptured historically in a large earthquake, leading some to designate the region as a seismic gap. By modeling various historical and synthetic earthquake sources, we investigate whether or not tsunamis that left deposits near Unalaska Island were generated by earthquakes rupturing through Unalaska Gap. Preliminary field investigations near the eastern end of Unalaska Island have identified paleotsunami deposits well above sea level, suggesting that multiple tsunamis in the last 5,000 years have flooded low-lying areas over 1 km inland. Other indicators of tsunami inundation, such as a breached cobble beach berm and driftwood logs stranded far inland, were tentatively attributed to the March 9, 1957 tsunami, which had reported runup of 13 to 22 meters on Umnak and Unimak Islands, to the west and east of Unalaska. In order to determine if tsunami inundation could have reached the runup markers observed on Unalaska, we modeled the 1957 tsunami using GeoCLAW, a numerical model that simulates tsunami generation, propagation, and inundation. The published rupture orientation and slip distribution for the MW 8.6, 1957 earthquake (Johnson et al., 1994) was used as the tsunami source, which delineates a 1200 km long rupture zone along the Aleutian trench from Delarof Island to Unimak Island. Model results indicate that runup and inundation from this particular source are too low to account for the runup markers observed in the field, because slip is concentrated in the western half of the rupture zone, far from Unalaska. To ascertain if any realistic
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Cranial suture biology of the Aleutian Island inhabitants.
Cray, James; Mooney, Mark P; Siegel, Michael I
2011-04-01
Research on cranial suture biology suggests there is biological and taxonomic information to be garnered from the heritable pattern of suture synostosis. Suture synostosis along with brain growth patterns, diet, and biomechanical forces influence phenotypic variability in cranial vault morphology. This study was designed to determine the pattern of ectocranial suture synostosis in skeletal populations from the Aleutian Islands. We address the hypothesis that ectocranial suture synostosis pattern will differ according to cranial vault shape. Ales Hrdlicka identified two phenotypes in remains excavated from the Aleutian Island. The Paleo-Aleutians, exhibiting a dolichocranic phenotype with little prognathism linked to artifacts distinguished from later inhabitants, Aleutians, who exhibited a brachycranic phenotype with a greater amount of prognathism. A total of 212 crania representing Paleo-Aleuts and Aleutian as defined by Hrdlicka were investigated for suture synostosis pattern following standard methodologies. Comparisons were performed using Guttmann analyses. Results revealed similar suture fusion patterns for the Paleo-Aleut and Aleutian, a strong anterior to posterior pattern of suture fusion for the lateral-anterior suture sites, and a pattern of early termination at the sagittal suture sites for the vault. These patterns were found to differ from that reported in the literature. Because these two populations with distinct cranial shapes exhibit similar patterns of suture synostosis it appears pattern is independent of cranial shape in these populations of Homo sapiens. These findings suggest that suture fusion patterns may be population dependent and that a standardized methodology, using suture fusion to determine age-at-death, may not be applicable to all populations. Copyright © 2011 Wiley-Liss, Inc.
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-07-07
.... 0910131363-0087-02] RIN 0648-XX17 Fisheries of the Exclusive Economic Zone Off Alaska; Greenland Turbot in the Aleutian Islands Subarea of the Bering Sea and Aleutian Islands Management Area AGENCY: National... Islands subarea of the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary to...
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Talbot, S. S.; Talbot, S.L.; Walker, L.R.
2010-01-01
We studied the vegetation of Kasatochi Island, central Aleutian Islands, to provide a general field assessment regarding the survival of plants, lichens, and fungi following a destructive volcanic eruption that occurred in 2008. Plant community data were analyzed using multivariate methods to explore the relationship between pre- and post-eruption plant cover; 5 major vegetation types were identified: Honckenya peploides beach, Festuca rubra cliff shelf, Lupinus nootkatensisFestuca rubra meadow, Leymus mollis bluff ridge (and beach), and Aleuria aurantia lower slope barrens. Our study provided a very unusual glimpse into the early stages of plant primary succession on a remote island where most of the vegetation was destroyed. Plants that apparently survived the eruption dominated early plant communities. Not surprisingly, the most diverse post-eruption community most closely resembled a widespread pre-eruption type. Microhabitats where early plant communities were found were distinct and apparently crucial in determining plant survival. Comparison with volcanic events in related boreal regions indicated some post-eruption pattern similarities. ?? 2010 Regents of the University of Colorado.
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-03-12
...-BC25 Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and Aleutian Islands Crab... Amendment 42 to the Fishery Management Plan for Bering Sea/Aleutian Islands King and Tanner Crabs (FMP) for... economic zone of the Bering Sea and Aleutian Islands (BSAI) are managed under the FMP. The FMP was prepared...
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Molecular genetic status of Aleutian Canada Geese from Buldir and the Semidi Islands, Alaska
Pierson, Barbara J.; Pearce, John M.; Talbot, Sandra L.; Shields, Gerald F.; Scribner, Kim T.
2000-01-01
We conducted genetic analyses of Aleutian Canada Geese (Branta canadensis leucopareia) from Buldir Island in the western Aleutians and the Semidi Islands in the eastern portion of their breeding range. We compared data from seven microsatellite DNA loci and 143 base pairs of the control region of mitochondrial DNA from the two populations of Aleutian Canada Geese and another small-bodied subspecies, the Cackling Canada Goose (B. c. minima) which nests in western Alaska. The widely separated island-nesting Aleutian geese were genetically more closely related to each other than to mainland-nesting small-bodied geese. The populations of Aleutian geese were genetically differentiated from one another in terms of mitochondrial DNA haplotype and microsatellite allele frequencies, suggesting limited contemporary gene flow and/or major shifts in gene frequency through genetic drift. The degree of population genetic differentiation suggests that Aleutian Canada Goose populations could be considered separate management units. There was some evidence of population bottlenecks, although we found no significant genetic evidence of non-random mating or inbreeding.
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50 CFR 600.1103 - Bering Sea and Aleutian Islands (BSAI) Crab species program.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 50 Wildlife and Fisheries 12 2014-10-01 2014-10-01 false Bering Sea and Aleutian Islands (BSAI... PROVISIONS Specific Fishery or Program Fishing Capacity Reduction Regulations § 600.1103 Bering Sea and... Fishery Management Plan for the Bering Sea/Aleutian Islands King and Tanner Crabs pursuant to § 679.2 of...
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50 CFR 600.1103 - Bering Sea and Aleutian Islands (BSAI) Crab species program.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 50 Wildlife and Fisheries 12 2013-10-01 2013-10-01 false Bering Sea and Aleutian Islands (BSAI... PROVISIONS Specific Fishery or Program Fishing Capacity Reduction Regulations § 600.1103 Bering Sea and... Fishery Management Plan for the Bering Sea/Aleutian Islands King and Tanner Crabs pursuant to § 679.2 of...
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50 CFR 600.1103 - Bering Sea and Aleutian Islands (BSAI) Crab species program.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 50 Wildlife and Fisheries 8 2010-10-01 2010-10-01 false Bering Sea and Aleutian Islands (BSAI... PROVISIONS Specific Fishery or Program Fishing Capacity Reduction Regulations § 600.1103 Bering Sea and... Fishery Management Plan for the Bering Sea/Aleutian Islands King and Tanner Crabs pursuant to § 679.2 of...
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50 CFR 600.1103 - Bering Sea and Aleutian Islands (BSAI) Crab species program.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 50 Wildlife and Fisheries 12 2012-10-01 2012-10-01 false Bering Sea and Aleutian Islands (BSAI... PROVISIONS Specific Fishery or Program Fishing Capacity Reduction Regulations § 600.1103 Bering Sea and... Fishery Management Plan for the Bering Sea/Aleutian Islands King and Tanner Crabs pursuant to § 679.2 of...
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50 CFR Figure 8 to Part 679 - Aleutian Islands Chinook Salmon Savings Area
Code of Federal Regulations, 2010 CFR
2010-10-01
... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Aleutian Islands Chinook Salmon Savings Area 8 Figure 8 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL... ECONOMIC ZONE OFF ALASKA Pt. 679, Fig. 8 Figure 8 to Part 679—Aleutian Islands Chinook Salmon Savings Area...
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50 CFR Figure 8 to Part 679 - Aleutian Islands Chinook Salmon Savings Area
Code of Federal Regulations, 2011 CFR
2011-10-01
... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Aleutian Islands Chinook Salmon Savings Area 8 Figure 8 to Part 679 Wildlife and Fisheries FISHERY CONSERVATION AND MANAGEMENT, NATIONAL... ECONOMIC ZONE OFF ALASKA Pt. 679, Fig. 8 Figure 8 to Part 679—Aleutian Islands Chinook Salmon Savings Area...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-09-28
.... 101126521-0640-2] RIN 0648-XA734 Fisheries of the Exclusive Economic Zone Off Alaska; ``Other Rockfish'' in the Aleutian Islands Subarea of the Bering Sea and Aleutian Islands Management Area AGENCY: National... subarea of the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary because...
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Waythomas, C.F.
1999-01-01
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 Island. During these studies new information was obtained about the Holocene eruptive history of the volcano on the basis of stratigraphic studies of volcaniclastic deposits and radiocarbon dating of associated buried soils and peat. A black, scoria-bearing, lapilli tephra, informally named the 'Akutan tephra,' is up to 2 m thick and is found over most of the island, primarily east of the volcano summit. Six radiocarbon ages on the humic fraction of soil A-horizons beneath the tephra indicate that the Akutan tephra was erupted approximately 1611 years B.P. At several locations the Akutan tephra is within a conformable stratigraphic sequence of pyroclastic-flow and lahar deposits that are all part of the same eruptive sequence. The thickness, widespread distribution, and conformable stratigraphic association with overlying pyroclastic-flow and lahar deposits indicate that the Akutan tephra likely records a major eruption of Akutan Volcano that may have formed the present summit caldera. Noncohesive lahar and pyroclastic-flow deposits that predate the Akutan tephra occur in the major valleys that head on the volcano and are evidence for six to eight earlier Holocene eruptions. These eruptions were strombolian to subplinian events that generated limited amounts of tephra and small pyroclastic flows that extended only a few kilometers from the vent. The pyroclastic flows melted snow and ice on the volcano flanks and formed lahars that traveled several kilometers down broad, formerly glaciated valleys, reaching the coast as thin, watery, hyperconcentrated flows or water floods. Slightly
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NASA's MISR Spots Alaskan Volcano's Latest Eruption
2017-06-02
The tiny Aleutian island of Bogoslof in Alaska, erupting regularly since December 2016, produced fresh activity on Sunday, May 28, 2017. Bogoslof is a stratovolcano fueled by the subduction of the Pacific Plate under the North American Plate and forms part of the larger Aleutian Arc, which includes more than 60 volcanoes on the Aleutian Islands and the Aleutian Range on the Alaska mainland. Previous to its recent period of activity, Bogoslof had last erupted in 1992, and its above-water surface area was a mere 0.11 square miles (0.29 square kilometers). As of March 11, the most recent data available, the area of the island had tripled to 0.38 square miles (0.98 square kilometers). The event on May 28 produced an ash cloud that reached 40,000 feet (12 km) in altitude, causing the Alaskan Volcano Observatory to issue a red alert for air travel in the area. Volcanic ash can cause major damage to aircraft engines, and the region is close to several major air routes between North America and Asia. On May 28, 2017, at approximately 2:23 p.m. local time, NASA's Terra satellite passed over Bogoslof, less than 10 minutes after the eruption began. MISR has nine cameras that view Earth at different angles. It takes slightly less than seven minutes for all nine cameras to view the same location on Earth. An animation made from the images from the nine MISR cameras, captured between 2:19 and 2:26 p.m., demonstrates how the angled views give a glimpse of the underside of the growing plume of volcanic ash, showing the eruption column widening into the cloud at the top. The animation is available at https://photojournal.jpl.nasa.gov/catalog/PIA21655
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A new sea star of the genus Leptasterias (Asteroidea: Asteriidae) from the Aleutian Islands.
Clark, Roger N; Jewett, Stephen C
2015-04-02
A new species of asteriid sea star of the genus Leptasterias (Order Forcipulatida) is described from the nearshore waters of the Aleutian Islands. Leptaterias tatei sp. nov. is distinguished from Leptasterias stolacantha Fisher, 1930, by the characteristics of the spines and pedicellariae. Geographic distribution is discussed and a key to the five-rayed Leptasterias of the Aleutian Islands is provided.
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-11-04
.... SUMMARY: NMFS issues regulations implementing Amendment 93 to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian Islands Management Area (FMP). These regulations amend the Bering Sea... Aleutian Islands Management Area; Limited Access Privilege Program AGENCY: National Marine Fisheries...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-02-01
... quota (IPQ) in the Western Aleutian Islands golden king crab fishery from the West regional delivery requirements. Federal regulations require West-designated golden king crab IFQ to be delivered to a processor... disruption to the Western Aleutian Islands golden king crab fishery, while providing for the sustained...
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Volcanoes of the Alaska Peninsula and Aleutian Islands, Alaska: selected photographs
Neal, Christina A.; McGimsey, Robert G.
2002-01-01
This CD-ROM contains 97 digital images of volcanoes along the Aleutian volcanic arc in Alaska. Perspectives include distant aerial shots, ground views of volcanic products and processes, and dramatic views of eruptions in progress. Each image is stored as a .PCD file in five resolutions. Brief captions, a location map, and glossary are included.
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Massive edifice failure at Aleutian arc volcanoes
Coombs, M.L.; White, S.M.; Scholl, D. W.
2007-01-01
Along the 450-km-long stretch of the Aleutian volcanic arc from Great Sitkin to Kiska Islands, edifice failure and submarine debris-avalanche deposition have occurred at seven of ten Quaternary volcanic centers. Reconnaissance geologic studies have identified subaerial evidence for large-scale prehistoric collapse events at five of the centers (Great Sitkin, Kanaga, Tanaga, Gareloi, and Segula). Side-scan sonar data collected in the 1980s by GLORIA surveys reveal a hummocky seafloor fabric north of several islands, notably Great Sitkin, Kanaga, Bobrof, Gareloi, Segula, and Kiska, suggestive of landslide debris. Simrad EM300 multibeam sonar data, acquired in 2005, show that these areas consist of discrete large blocks strewn across the seafloor, supporting the landslide interpretation from the GLORIA data. A debris-avalanche deposit north of Kiska Island (177.6?? E, 52.1?? N) was fully mapped by EM300 multibeam revealing a hummocky surface that extends 40??km from the north flank of the volcano and covers an area of ??? 380??km2. A 24-channel seismic reflection profile across the longitudinal axis of the deposit reveals a several hundred-meter-thick chaotic unit that appears to have incised into well-bedded sediment, with only a few tens of meters of surface relief. Edifice failures include thin-skinned, narrow, Stromboli-style collapse as well as Bezymianny-style collapse accompanied by an explosive eruption, but many of the events appear to have been deep-seated, removing much of an edifice and depositing huge amounts of debris on the sea floor. Based on the absence of large pyroclastic sheets on the islands, this latter type of collapse was not accompanied by large eruptions, and may have been driven by gravity failure instead of magmatic injection. Young volcanoes in the central and western portions of the arc (177?? E to 175?? W) are located atop the northern edge of the ??? 4000-m-high Aleutian ridge. The position of the Quaternary stratocones relative to the
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Aleutian Arc Magmatism: Continuous or Episodic?
NASA Astrophysics Data System (ADS)
Stone, D. B.; Layer, P. W.
2004-05-01
For essentially all of Cenozoic time, the plates of the north Pacific - the Pacific, Kula and Faralon plates - have had a generally northward motion. Most models show that rates of subduction perpendicular to the Alaska Peninsula and eastern Aleutian arc were substantial, and do not show any interruptions in expected rates and directions. In contrast, the eastern Aleutian arc (the arc bounded on both sides by oceanic depths) and to some extent the Alaska Peninsula (the parts of the arc built on continental material) appear to have significant gaps in the geologic record of volcanism. In addition to these arc-wide, generally long period gaps in volcanism, individual volcanic centers also appear to have significant temporal gaps (of shorter duration) in their eruptive histories. The most obvious example is the lack of volcanic rocks associated with today's volcanoes that are older than 2 Ma. Paleomagnetic data from Aleutian volcanoes show only one reversal, which would suggest that the bulk of the volcanic rocks were erupted during the Bruhnes normal polarity chron (roughly 700 ka to the present). The earth's field in Cenozoic time spends equal time in each polarity with an average polarity interval of about .25Ma. If eruptive activity was spread uniformly over time, more reversals would be expected. On longer timescales, available radiometric ages for volcanic and plutonic rocks from the eastern Aleutian islands divide roughly into four groups; 0-2Ma, rocks associated with the modern volcanic chain; 5-6Ma, flows, dikes and other intrusives not associated with modern volcanoes; 10-17Ma, mainly small intrusive bodies; 30-40(?)Ma, mainly isolated flow units, dikes and other intrusive rocks. This leaves gaps in the record of igneous rocks ranging from about 3Ma to 15Ma. An analogous but more complex distribution of ages is seen on the Alaska Peninsula where the arc has been built on continental crust. If the chronology and geologic history of the arc is more
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-03-21
.... 120806311-3213-01] RIN 0648-BC25 Fisheries of the Exclusive Economic Zone Off Alaska; Bering Sea and... Bering Sea/Aleutian Islands King and Tanner Crabs (FMP). If approved, these regulations would revise the... of the CR Program were analyzed in the Bering Sea/Aleutian Islands Crab Fisheries Final EIS. Due to...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-02-18
... due to a recent unforeseen event, no processing facility is open in the West region. This emergency... Magnuson-Stevens Fishery Conservation and Management Act, the Fishery Management Plan for Bering Sea... and Aleutian Islands (BSAI) are managed under the Fishery Management Plan for Bering Sea/Aleutian...
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Avian mortality associated with a volcanic gas seep at Kiska Island, Aleutian Islands, Alaska
Bond, Alexander L.; Evans, William C.; Jones, Ian L.
2012-01-01
We identified natural pits associated with avian mortality at the base of Kiska Volcano in the western Aleutian Islands, Alaska in 2007. Living, moribund, and dead birds were regularly found at low spots in a canyon between two lava flows during 2001–2006, but the phenomenon was attributed to natural trapping and starvation of fledgling seabirds (mostly Least Auklets, Aethia pusilla) at a colony site with >1 million birds present. However, 302 birds of eight species, including passerines, were found dead at the site during 2007–2010, suggesting additional factors were involved. Most carcasses showed no signs of injury and concentrations of dead birds had accumulated in a few distinctive low pits in the canyon. Gas samples from these locations showed elevated CO2 concentrations in late 2010. Analysis of carcasses indicated no evidence of blunt trauma or internal bleeding. Volcanic gases accumulating at these poorly ventilated sites may have caused the observed mortality, but are temporally variable. Most auklets breeding in the Aleutian Islands do so in recent lava flows that provide breeding habitat; our study documents a cost of this unusual habitat selection.
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NASA Astrophysics Data System (ADS)
Waythomas, C. F.; Wallace, K. L.; Schwaiger, H.
2012-12-01
Akutan Volcano in the eastern Aleutian Islands of Alaska is one of the most historically active volcanoes in the Aleutian arc (43 eruptions in about the past 250 years). Explosive eruptions pose major hazards to aircraft flying north Pacific air routes and to local infrastructure on Akutan and neighboring Unalaska Island. Air travel, infrastructure, and population in the region have steadily increased during the past several decades, and thus it is important to better understand the frequency, magnitude, and characteristics of tephra-producing eruptions. The most recent eruption was a VEI 2 event on March 8-May 21, 1992 that resulted in minor ash emissions and trace amounts of proximal fallout. Nearly continuous low-level emission of ash and steam is typical of historical eruptions, and most of the historical events have been similar in magnitude to the 1992 event. The most recent major eruption occurred about 1600 yr. B.P. and likely produced the ca. 2-km diameter summit caldera and inundated valleys that head on the volcano with pyroclastic-flow and lahar deposits that are tens of meters thick. The 1600 yr. B.P. eruption covered most of Akutan Island with up to 2.5 m of coarse scoriaceous tephra fall, including deposits 0.5-1 m thick near the City of Akutan. Tephra-fall deposits associated with this eruption exhibit a continuous sequence of black, fine to coarse scoriaceous lapilli overlain by a lithic-rich facies and finally a muddy aggregate-rich facies indicating water involvement during the latter stages of the eruption. Other tephra deposits of Holocene age on Akutan Island include more than a dozen discrete fine to coarse ash beds and 3-6 beds of scoriaceous, coarse lapilli tephra indicating that there have been several additional major eruptions (>VEI 3) of Akutan Volcano during the Holocene. Radiocarbon dates on these events are pending. In addition to tephra falls from Akutan, other fine ash deposits are found on the island that originated from other
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Code of Federal Regulations, 2013 CFR
2013-10-01
... 50 Wildlife and Fisheries 13 2013-10-01 2013-10-01 false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table 24 to Part 679... Table 24 to Part 679—Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open...
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Code of Federal Regulations, 2010 CFR
2010-10-01
... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table 24 to Part 679 Wildlife and... 24 to Part 679—Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to...
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Kenney, Leah A; von Hippel, Frank A; Willacker, James J; O'Hara, Todd M
2012-11-01
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 δ(13)C stable isotope ratios of stickleback collected from seabird lakes suggest an input of marine-derived nutrients and/or marine-derived Hg. Copyright © 2012 SETAC.
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Andesites from northeastern Kanaga Island, Aleutians
NASA Astrophysics Data System (ADS)
Brophy, James G.
1990-04-01
Kanaga island is located in the central Aleutian island arc. Northeastern Kanaga is a currently active late Tertiary to Recent calc-alkaline volcanic complex. Basaltic andesite to andesite lavas record three episodes (series) of volcanic activity. Series I and Series II lavas are all andesite while Series III lavas are basaltic andesite to andesite. Four Series II andesites contain abundant quenched magmatic inclusions ranging in composition from high-MgO low-alumina basalt to low-MgO highalumina basalt. The spectrum of lava compositions is due primarily to fractional crystallization of a parental low-MgO high-alumina basalt but with variable degrees of crustal contamination and magma mixing. The earliest Series I lavas represent mixing between high-alumina basalt and silicic andesite with maximum SiO2 contents of 65 67 wt %. Later Series I and all Series II lavas are due to mixing of andesite magmas of similar composition. The maximum SiO2 content of the pre-mixed andesites magmas is estimated at 60 63 wt %. The youngest lavas (Series III) are all non-mixed and have maximum estimated SiO2 contents of 59 wt %. The earliest Series I lavas contain a significant crustal component while all later lavas do not. It is concluded that the maximum SiO2 contents of silicic magmas, the contribution of crustal material to silicic magma generation, and the role of magma mixing all decrease with time. Furthermore, silicic magmas generated by fractional crystallization at this volcanic center have a maximum SiO2 content of 63 wt %. All of these features have also been documented at the central Aleutian Cold Bay Volcanic Center (Brophy 1987). Based on data from these two centers a model of Aleutian calc-alkaline magma chamber development is proposed. The main features are: (1) a single low pressure magma chamber is continuously supplied by primitive low-alumina basalt; (2) non-primary high-alumina basalt is formed along the chamber margins by selective gravitational settling of
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Geologic framework of the Aleutian arc, Alaska
Vallier, Tracy L.; Scholl, David W.; Fisher, Michael A.; Bruns, Terry R.; Wilson, Frederic H.; von Huene, Roland E.; Stevenson, Andrew J.
1994-01-01
The Aleutian arc is the arcuate arrangement of mountain ranges and flanking submerged margins that forms the northern rim of the Pacific Basin from the Kamchatka Peninsula (Russia) eastward more than 3,000 km to Cooke Inlet (Fig. 1). It consists of two very different segments that meet near Unimak Pass: the Aleutian Ridge segment to the west and the Alaska Peninsula-the Kodiak Island segment to the east. The Aleutian Ridge segment is a massive, mostly submerged cordillera that includes both the islands and the submerged pedestal from which they protrude. The Alaska Peninsula-Kodiak Island segment is composed of the Alaska Peninsula, its adjacent islands, and their continental and insular margins. The Bering Sea margin north of the Alaska Peninsula consists mostly of a wide continental shelf, some of which is underlain by rocks correlative with those on the Alaska Peninsula.There is no pre-Eocene record in rocks of the Aleutian Ridge segment, whereas rare fragments of Paleozoic rocks and extensive outcrops of Mesozoic rocks occur on the Alaska Peninsula. Since the late Eocene, and possibly since the early Eocene, the two segments have evolved somewhat similarly. Major plutonic and volcanic episodes, however, are not synchronous. Furthermore, uplift of the Alaska Peninsula-Kodiak Island segment in late Cenozoic time was more extensive than uplift of the Aleutian Ridge segment. It is probable that tectonic regimes along the Aleutian arc varied during the Tertiary in response to such factors as the directions and rates of convergence, to bathymetry and age of the subducting Pacific Plate, and to the volume of sediment in the Aleutian Trench.The Pacific and North American lithospheric plates converge along the inner wall of the Aleutian trench at about 85 to 90 mm/yr. Convergence is nearly at right angles along the Alaska Peninsula, but because of the arcuate shape of the Aleutian Ridge relative to the location of the plates' poles of rotation, the angle of convergence
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Madison, Erica N.; Piatt, John F.; Arimitsu, Mayumi L.; Romano, Marc D.; van Pelt, Thomas I.; Nelson, S. Kim; Williams, Jeffrey C.; DeGange, Anthony R.
2011-01-01
The Kittlitz's Murrelet Brachyramphus brevirostris is adapted for life in glacial-marine ecosystems, being concentrated in the belt of glaciated fjords in the northern Gulf of Alaska from Glacier Bay to Cook Inlet. Most of the remaining birds are scattered along coasts of the Alaska Peninsula and Aleutian Islands, where they reside in protected bays and inlets, often in proximity to remnant glaciers or recently deglaciated landscapes. We summarize existing information on Kittlitz's Murrelet in this mainly unglaciated region, extending from Kodiak Island in the east to the Near Islands in the west. From recent surveys, we estimated that ~2400 Kittlitz's Murrelets were found in several large embayments along the Alaska Peninsula, where adjacent ice fields feed silt-laden water into the bays. On Kodiak Island, where only remnants of ice remain today, observations of Kittlitz's Murrelets at sea were uncommon. The species has been observed historically around the entire Kodiak Archipelago, however, and dozens of nest sites were found in recent years. We found Kittlitz's Murrelets at only a few islands in the Aleutian chain, notably those with long complex shorelines, high mountains and remnant glaciers. The largest population (~1600 birds) of Kittlitz's Murrelet outside the Gulf of Alaska was found at Unalaska Island, which also supports the greatest concentration of glacial ice in the Aleutian Islands. Significant populations were found at Atka (~1100 birds), Attu (~800) and Adak (~200) islands. Smaller numbers have been reported from Unimak, Umnak, Amlia, Kanaga, Tanaga, Kiska islands, and Agattu Island, where dozens of nest sites have been located in recent years. Most of those islands have not been thoroughly surveyed, and significant pockets of Kittlitz's Murrelets may yet be discovered. Our estimate of ~6000 Kittlitz's Murrelets along the Alaska Peninsula and Aleutian Islands is also likely to be conservative because of the survey protocols we employed (i.e. early
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-11-14
...NMFS proposes regulations to implement Amendment 102 to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian Islands Management Area (BSAI FMP), and amend the Individual Fishing Quota Program for the Fixed-Gear Commercial Fisheries for Pacific Halibut and Sablefish in Waters in and off Alaska (IFQ Program). Amendment 102 and its proposed implementing regulations would create a Community Quota Entity (CQE) Program in halibut IFQ regulatory area 4B (Area 4B) and the sablefish Aleutian Islands regulatory area that is similar to the existing CQE Program in the Gulf of Alaska (GOA). Amendment 102 would also allow an eligible community in Area 4B and in the Aleutian Islands to establish a non-profit organization as a CQE to purchase halibut catcher vessel quota share (QS) assigned to Area 4B and sablefish QS assigned to the Aleutian Islands. The CQE could assign the resulting annual halibut and sablefish IFQ to participants according to defined CQE Program elements. An additional proposed revision to the IFQ Program regulations would allow IFQ derived from D share halibut QS to be fished on Category C vessels in Area 4B. These actions are necessary to provide additional fishing opportunities for residents of fishery dependent communities and sustain participation in the halibut and sablefish IFQ fisheries. These actions are intended to promote the goals and objectives of the Magnuson-Stevens Fishery Conservation and Management Act, the Northern Pacific Halibut Act of 1982, the BSAI FMP, and other applicable law.
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-11-03
... Aleutian Islands (AI) directed pollock fishery to the Aleut Corporation for economic development of Adak... necessary for conducting the AI directed pollock fishery. Management provisions for the AI directed pollock fishery include: restrictions on the harvest specifications for the AI directed pollock fishery...
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Vegetation of eastern Unalaska Island, Aleutian Islands, Alaska
Talbot, Stephen S.; Schofield, Wilfred B.; Talbot, Sandra L.; Daniëls, Fred J. A.
2010-01-01
Plant communities of Unalaska Island in the eastern Aleutian Islands of western Alaska, and their relationship to environmental variables, were studied using a combined Braun-Blanquet and multivariate approach. Seventy relevés represented the range of structural and compositional variation in the matrix of vegetation and landform zonation. Eleven major community types were distinguished within six physiognomic–ecological groups: I. Dry coastal meadows: Honckenya peploides beach meadow, Leymus mollis dune meadow. II. Mesic meadows: Athyrium filix-femina – Aconitum maximum meadow, Athyrium filix-femina – Calamagrostis nutkaensis meadow, Erigeron peregrinus – Thelypteris quelpaertensis meadow. III. Wet snowbed meadow: Carex nigricans snowbed meadow. IV. Heath: Linnaea borealis – Empetrum nigrum heath, Phyllodoce aleutica heath, Vaccinium uliginosum – Thamnolia vermicularis fellfield. V. Mire: Carex pluriflora – Plantago macrocarpa mire. VI. Deciduous shrub thicket: Salix barclayi – Athyrium filix-femina thicket. These were interpreted as a complex gradient primarily influenced by soil moisture, elevation, and pH. Phytogeographical and syntaxonomical analysis of the plant communities indicated that the dry coastal meadows, most of the heaths, and the mire vegetation belonged, respectively, to the widespread classes Honckenyo–Elymetea, Loiseleurio–Vaccinietea, and Scheuchzerio–Caricetea, characterized by their circumpolar and widespread species. Amphi-Beringian species were likely diagnostic of amphi-Beringian syntaxa, many of these yet to be described.
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Historic hydrovolcanism at Deception Island (Antarctica): implications for eruption hazards
NASA Astrophysics Data System (ADS)
Pedrazzi, Dario; Németh, Károly; Geyer, Adelina; Álvarez-Valero, Antonio M.; Aguirre-Díaz, Gerardo; Bartolini, Stefania
2018-01-01
Deception Island (Antarctica) is the southernmost island of the South Shetland Archipelago in the South Atlantic. Volcanic activity since the eighteenth century, along with the latest volcanic unrest episodes in the twentieth and twenty-first centuries, demonstrates that the volcanic system is still active and that future eruptions are likely. Despite its remote location, the South Shetland Islands are an important touristic destination during the austral summer. In addition, they host several research stations and three summer field camps. Deception Island is characterised by a Quaternary caldera system with a post-caldera succession and is considered to be part of an active, dispersed (monogenetic), volcanic field. Historical post-caldera volcanism on Deception Island involves monogenetic small-volume (VEI 2-3) eruptions such forming cones and various types of hydrovolcanic edifices. The scientific stations on the island were destroyed, or severely damaged, during the eruptions in 1967, 1969, and 1970 mainly due to explosive activity triggered by the interaction of rising (or erupting) magma with surface water, shallow groundwater, and ice. We conducted a detailed revision (field petrology and geochemistry) of the historical hydrovolcanic post-caldera eruptions of Deception Island with the aim to understand the dynamics of magma-water interaction, as well as characterise the most likely eruptive scenarios from future eruptions. We specifically focused on the Crimson Hill (estimated age between 1825 and 1829), and Kroner Lake (estimated age between 1829 and 1912) eruptions and 1967, 1969, and 1970 events by describing the eruption mechanisms related to the island's hydrovolcanic activity. Data suggest that the main hazards posed by volcanism on the island are due to fallout, ballistic blocks and bombs, and subordinate, dilute PDCs. In addition, Deception Island can be divided into five areas of expected activity due to magma-water interaction, providing additional
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NASA Astrophysics Data System (ADS)
Littell, J. S.; Poe, A.; van Pelt, T.
2015-12-01
Climate change is already affecting the Bering Sea and Aleutian Island region of Alaska. Past and present marine research across a broad spectrum of disciplines is shedding light on what sectors of the ecosystem and the human dimension will be most impacted. In a grassroots approach to extend existing research efforts, leveraging recently completed downscaled climate projections for the Bering Sea and Aleutian Islands region, we convened a team of 30 researchers-- with expertise ranging from anthropology to zooplankton to marine mammals-- to assess climate projections in the context of their expertise. This Aleutian-Bering Climate Vulnerability Assessment (ABCVA) began with researchers working in five teams to evaluate the vulnerabilities of key species and ecosystem services relative to projected changes in climate. Each team identified initial vulnerabilities for their focal species or services, and made recommendations for further research and information needs that would help managers and communities better understand the implications of the changing climate in this region. Those draft recommendations were shared during two focused, public sessions held within two hub communities for the Bering and Aleutian region: Unalaska and St. Paul. Qualitative insights about local concerns and observations relative to climate change were collected during these sessions, to be compared to the recommendations being made by the ABCVA team of researchers. Finally, we used a Structured Decision Making process to prioritize the recommendations of participating scientists, and integrate the insights shared during our community sessions. This work brought together residents, stakeholders, scientists, and natural resource managers to collaboratively identify priorities for addressing current and expected future impacts of climate change. Recommendations from this project will be incorporated into future research efforts of the Aleutian and Bering Sea Islands Landscape Conservation
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-09-28
... among harvesters, processors, and coastal communities and monitors the ``economic stability for... Collection; Comment Request; Alaska Region Bering Sea & Aleutian Islands (BSAI) Crab Economic Data Reports... CR Program's mandatory economic data collection report (EDR) used to assess the efficacy of the CR...
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Kaler, Robb S.A.; Kenney, Leah A.; Bond, Alexander L.; Eagles-Smith, Collin A.
2014-01-01
Mercury (Hg) is a toxic element distributed globally through atmospheric transport. Agattu Island, located in the western Aleutian Islands, Alaska, has no history of point-sources of Hg contamination. We provide baseline levels of total mercury (THg) concentrations in breast feathers of three birds that breed on the island. Geometric mean THg concentrations in feathers of fork-tailed storm-petrels (Oceanodroma furcata; 6703 ± 1635, ng/g fresh weight [fw]) were higher than all other species, including snowy owl (Bubo scandiacus; 2105 ± 1631, ng/g fw), a raptor with a diet composed largely of storm-petrels at Agattu Island. There were no significant differences in mean THg concentrations of breast feathers among adult Kittlitz’s murrelet (Brachyramphus brevirostris; 1658 ± 1276, ng/g fw) and chicks (1475 ± 671, ng/g fw) and snowy owls. The observed THg concentrations in fork-tailed storm-petrel feathers emphasizes the need for further study of Hg pollution in the western Aleutian Islands.
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Kaler, Robb S A; Kenney, Leah A; Bond, Alexander L; Eagles-Smith, Collin A
2014-05-15
Mercury (Hg) is a toxic element distributed globally through atmospheric transport. Agattu Island, located in the western Aleutian Islands, Alaska, has no history of point-sources of Hg contamination. We provide baseline levels of total mercury (THg) concentrations in breast feathers of three birds that breed on the island. Geometric mean THg concentrations in feathers of fork-tailed storm-petrels (Oceanodroma furcata; 6703 ± 1635, ng/g fresh weight [fw]) were higher than all other species, including snowy owl (Bubo scandiacus; 2105 ± 1631, ng/g fw), a raptor with a diet composed largely of storm-petrels at Agattu Island. There were no significant differences in mean THg concentrations of breast feathers among adult Kittlitz's murrelet (Brachyramphus brevirostris; 1658 ± 1276, ng/g fw) and chicks (1475 ± 671, ng/g fw) and snowy owls. The observed THg concentrations in fork-tailed storm-petrel feathers emphasizes the need for further study of Hg pollution in the western Aleutian Islands. Published by Elsevier Ltd.
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NASA Technical Reports Server (NTRS)
2002-01-01
On January 16, 2002, lava that had begun flowing on January 5 from the Piton de la Fournaise volcano on the French island of Reunion abruptly decreased, marking the end of the volcano's most recent eruption. These false color MODIS images of Reunion, located off the southeastern coast of Madagascar in the Indian Ocean, were captured on the last day of the eruption (top) and two days later (bottom). The volcano itself is located on the southeast side of the island and is dark brown compared to the surrounding green vegetation. Beneath clouds (light blue) and smoke, MODIS detected the hot lava pouring down the volcano's flanks into the Indian Ocean. The heat, detected by MODIS at 2.1 um, has been colored red in the January 16 image, and is absent from the lower image, taken two days later on January 18, suggesting the lava had cooled considerably even in that short time. Earthquake activity on the northeast flank continued even after the eruption had stopped, but by January 21 had dropped to a sufficiently low enough level that the 24-hour surveillance by the local observatory was suspended. Reunion is essentially all volcano, with the northwest portion of the island built on the remains of an extinct volcano, and the southeast half built on the basaltic shield of 8,630-foot Piton de la Fournaise. A basaltic shield volcano is one with a broad, gentle slope built by the eruption of fluid basalt lava. Basalt lava flows easily across the ground remaining hot and fluid for long distances, and so they often result in enormous, low-angle cones. The Piton de la Fournaise is one of Earth's most active volcanoes, erupting over 150 times in the last few hundred years, and it has been the subject of NASA research because of its likeness to the volcanoes of Mars. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC
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Seismicity of the Earth 1900-2010 Aleutian arc and vicinity
Benz, Harley M.; Herman, Matthew; Tarr, Arthur C.; Hayes, Gavin P.; Furlong, Kevin P.; Villaseñor, Antonio; Dart, Richard L.; Rhea, Susan
2011-01-01
This map shows details of the Aleutian arc not visible in an earlier publication. The Aleutian arc extends about 3,000 km from the Gulf of Alaska to the Kamchatka Peninsula. It marks the region where the Pacific plate subducts into the mantle beneath the North America plate. This subduction is responsible for the generation of the Aleutian Islands and the deep offshore Aleutian Trench. Relative to a fixed North America plate, the Pacific plate is moving northwest at a rate that increases from about 55 mm per year at the arc's eastern edge to 75 mm per year near its western terminus. In the east, the convergence of the plates is nearly perpendicular to the plate boundary. However, because of the boundary's curvature, as one travels westward along the arc, the subduction becomes more and more oblique to the boundary until the relative plate motion becomes parallel to the arc at the Near Islands near its western edge. Subduction zones such as the Aleutian arc are geologically complex and produce numerous earthquakes from multiple sources. Deformation of the overriding North America plate generates shallow crustal earthquakes, whereas slip at the interface of the plates generates interplate earthquakes that extend from near the base of the trench to depths of 40 to 60 km. At greater depths, Aleutian arc earthquakes occur within the subducting Pacific plate and can reach depths of 300 km. Since 1900, six great earthquakes have occurred along the Aleutian Trench, Alaska Peninsula, and Gulf of Alaska: M8.4 1906 Rat Islands; M8.6 1938 Shumagin Islands; M8.6 1946 Unimak Island; M8.6 1957 Andreanof Islands; M9.2 1964 Prince William Sound; and M8.7 1965 Rat Islands. Several relevant tectonic elements (plate boundaries and active volcanoes) provide a context for the seismicity presented on the main map panel. The plate boundaries are most accurate along the axis of the Aleutian Trench and more diffuse or speculative in extreme northeastern Russia. The active volcanoes parallel
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Preliminary Volcano-Hazard Assessment for Gareloi Volcano, Gareloi Island, Alaska
Coombs, Michelle L.; McGimsey, Robert G.; Browne, Brandon L.
2008-01-01
Gareloi Volcano (178.794 degrees W and 51.790 degrees N) is located on Gareloi Island in the Delarof Islands group of the Aleutian Islands, about 2,000 kilometers west-southwest of Anchorage and about 150 kilometers west of Adak, the westernmost community in Alaska. This small (about 8x10 kilometer) volcano has been one of the most active in the Aleutians since its discovery by the Bering expedition in the 1740s, though because of its remote location, observations have been scant and many smaller eruptions may have gone unrecorded. Eruptions of Gareloi commonly produce ash clouds and lava flows. Scars on the flanks of the volcano and debris-avalanche deposits on the adjacent seafloor indicate that the volcano has produced large landslides in the past, possibly causing tsunamis. Such events are infrequent, occurring at most every few thousand years. The primary hazard from Gareloi is airborne clouds of ash that could affect aircraft. In this report, we summarize and describe the major volcanic hazards associated with Gareloi.
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An introduced predator alters Aleutian Island plant communities by thwarting nutrient subsidies
Maron, J.L.; Estes, J.A.; Croll, D.A.; Danner, E.M.; Elmendorf, S.C.; Buckelew, S.L.
2006-01-01
The ramifying effects of top predators on food webs traditionally have been studied within the framework of trophic cascades. Trophic cascades are compelling because they embody powerful indirect effects of predators on primary production. Although less studied, indirect effects of predators may occur via routes that are not exclusively trophic. We quantified how the introduction of foxes onto the Aleutian Islands transformed plant communities by reducing abundant seabird populations, thereby disrupting nutrient subsidies vectored by seabirds from sea to land. We compared soil and plant fertility, plant biomass and community composition, and stable isotopes of nitrogen in soil, plants, and other organisms on nine fox-infested and nine historically fox-free islands across the Aleutians. Additionally, we experimentally augmented nutrients on a fox-infested island to test whether differences in plant productivity and composition between fox-infested and fox-free islands could have arisen from differences in nutrient inputs between island types. Islands with historical fox infestations had soils low in phosphorus and nitrogen and plants low in tissue nitrogen. Soils, plants, slugs, flies, spiders, and bird droppings on these islands had low d15N values indicating that these organisms obtained nitrogen from internally derived sources. In contrast, soils, plants, and higher trophic level organisms on fox-free islands had elevated d15N signatures indicating that they utilized nutrients derived from the marine environment. Furthermore, soil phosphorus (but not nitrogen) and plant tissue nitrogen were higher on fox-free than fox-infested islands. Nutrient subsidized fox-free islands supported lush, high biomass plant communities dominated by graminoids. Fox-infested islands were less graminoid dominated and had higher cover and biomass of low-lying forbs and dwarf shrubs. While d15N profiles of soils and plants and graminoid biomass varied with island size and distance from
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The 2011 submarine volcanic eruption of El Hierro Island (Canary Islands, Spain)
NASA Astrophysics Data System (ADS)
López, C.; Blanco, M. J.
2012-04-01
On 10 October 2011 a submarine volcanic eruption began 2 km SW of La Restinga village in the South coast of El Hierro Island (Spain). It became the first submarine eruption reported in 500 years of historical record in the Canary Islands. The eruption took place after three months of intensive seismic activity and ground deformation. The first signal evidencing the eruption was a harmonic tremor signal, located somewhere in the South sector of El Hierro Island and registered in every seismic station on the island. On the following day, the tremoŕs amplitude increased up enough to be felt by the residents of La Restinga. The first visual evidence of the eruption was observed during the afternoon of 12 October, a large light-green coloured area on the sea surface, 2 km to the SW of La Restinga. Three days later, steaming lava fragments were observed floating on the sea, in the area where the vent was supposed to be located. These fragments had a bomb-like shape and their sizes ranged between 10 and 40 cm long. They were bicoloured, a black outer part with a basaltic composition, and a white inner part, highly vesiculated and rich in silica content (>60%). This type of fragments was only observed during the first days of the eruption. Within the next two months further emission episodes have been observed with turbulent water, foam rings and large bubbles on the sea surface. On the 27th of November new lava fragments were observed while floating and degassing on the sea surface. Most of them were "lava balloons" or hollow fragments of lavas, with sizes between 30 and 200 cm, and highly vesiculated outer crust of basaltic-basanitic and sideromelane composition. The emission of these products continues intermitently up to date (January 2012) During the eruption, the GPS monitoring network detected episodes of inflation-deflation and a maximum vertical deformation of 4 cm. The horizontal deformation, which had reached up to 5 cm before the eruption, remains stable. The
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Genetic structure of the Common Eider in the western Aleutian Islands prior to fox eradication
Sonsthagen, Sarah A.; Talbot, Sandra L.; Wilson, Robert E.; Petersen, Margaret R.; Williams, Jeffrey C.; Byrd, G. Vernon; McCracken, Kevin G.
2013-01-01
Since the late 18th century bird populations residing in the Aleutian Archipelago have been greatly reduced by introduced arctic foxes (Alopex lagopus). We analyzed data from microsatellite, nuclear intron, and mitochondrial (mtDNA) loci to examine the spatial genetic structure, demography, and gene flow among four Aleutian Island populations of the Common Eider (Somateria mollissima) much reduced by introduced foxes. In mtDNA, we found high levels of genetic structure within and between island groups (ΦST = 0.643), but we found no population subdivision in microsatellites or nuclear introns. Differences in genetic structure between the mitochondrial and nuclear genomes are consistent with the Common Eider's breeding and winter biology, as females are highly philopatric and males disperse. Nevertheless, significant differences between islands in the mtDNA of males and marginal significance (P =0.07) in the Z-linked locus Smo 1 suggest that males may also have some level of fidelity to island groups. Severe reduction of populations by the fox, coupled with females' high philopatry, may have left the genetic signature of a bottleneck effect, resulting in the high levels of genetic differentiation observed in mtDNA (ΦST = 0.460–0.807) between islands only 440 km apart. Reestablishment of the Common Eider following the fox's eradication was likely through recruitment from within the islands and bolstered by dispersal from neighboring islands, as suggested by the lack of genetic structure and asymmetry in gene flow between Attu and the other Near Islands.
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NASA Astrophysics Data System (ADS)
Larsen, Jessica F.
2016-11-01
The magmatic systems feeding arc volcanoes are complex, leading to a rich diversity in eruptive products and eruption styles. This review focuses on examples from the Aleutian subduction zone, encompassed within the state of Alaska, USA because it exhibits a rich diversity in arc structure and tectonics, sediment and volatile influx feeding primary magma generation, crustal magma differentiation processes, with the resulting outcome the production of a complete range in eruption styles from its diverse volcanic centers. Recent and ongoing investigations along the arc reveal controls on magma production that result in diversity of eruptive products, from crystal-rich intermediate andesites to phenocryst-poor, melt-rich silicic and mafic magmas and a spectrum in between. Thus, deep to shallow crustal "processing" of arc magmas likely greatly influences the physical and chemical character of the magmas as they accumulate in the shallow crust, the flow physics of the magmas as they rise in the conduit, and eruption style through differences in degassing kinetics of the bubbly magmas. The broad spectrum of resulting eruption styles thus depends on the bulk magma composition, melt phase composition, and the bubble and crystal content (phenocrysts and/or microlites) of the magma. Those fundamental magma characteristics are in turn largely determined by the crustal differentiation pathway traversed by the magma as a function of tectonic location in the arc, and/or the water content and composition of the primary magmas. The physical and chemical character of the magma, set by the arc differentiation pathway, as it ascends towards eruption determines the kinetic efficiency of degassing versus the increasing internal gas bubble overpressure. The balance between degassing rate and the rate at which gas bubble overpressure builds then determines the conditions of fragmentation, and ultimately eruption intensity.
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Seitz, A.C.; Loher, Timothy; Norcross, Brenda L.; Nielsen, J.L.
2011-01-01
Currently, it is assumed that eastern Pacific halibut Hippoglossus stenolepis belong to a single, fully mixed population extending from California through the Bering Sea, in which adult halibut disperse randomly throughout their range during their lifetime. However, we hypothesize that hali but dispersal is more complex than currently assumed and is not spatially random. To test this hypo thesis, we studied the seasonal dispersal and behavior of Pacific halibut in the Bering Sea and Aleutian Islands (BSAI). Pop-up Archival Transmitting tags attached to halibut (82 to 154 cm fork length) during the summer provided no evidence that individuals moved out of the Bering Sea and Aleutian Islands region into the Gulf of Alaska during the mid-winter spawning season, supporting the concept that this region contains a separate spawning group of adult halibut. There was evidence for geographically localized groups of halibut along the Aleutian Island chain, as all of the individuals tagged there displayed residency, with their movements possibly impeded by tidal currents in the passes between islands. Mid-winter aggregation areas of halibut are assumed to be spawning grounds, of which 2 were previously unidentified and extend the species' presumed spawning range ~1000 km west and ~600 km north of the nearest documented spawning area. If there are indeed independent spawning groups of Pacific halibut in the BSAI, their dynamics may vary sufficiently from those of the Gulf of Alaska, so that specifically accounting for their relative segregation and unique dynamics within the larger population model will be necessary for correctly predicting how these components may respond to fishing pressure and changing environmental conditions.?? Inter-Research 2011.
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Aleutian terranes from Nd isotopes
NASA Technical Reports Server (NTRS)
Kay, R. W.; Kay, S. M.; Rubenstone, J. L.
1986-01-01
Nd isotope ratios substantiate the identification of oceanic crustal terranes within the continental crustal basement of the Aleutian island arc. The oceanic terranes are exposed in the westernmost Aleutians, but to the east, they are completely buried by isotopically distinct arc-volcanic rocks. Analogous oceanic terranes may be important components of the terrane collages that comprise the continents.
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Volcanic Tsunami Generation in the Aleutian Arc of Alaska
NASA Astrophysics Data System (ADS)
Waythomas, C. F.; Watts, P.
2003-12-01
, geological evidence of tsunamis, such as tsunami deposits on land, should be found in the area around Augustine Island. Paradoxically, unequivocal evidence for tsunami inundation has been found. Augustine Volcano is the most historically active volcano in the Cook Inlet region and a future tsunami from the volcano would have devastating consequences to villages, towns, oil-production facilities, and the fishing industry, especially if it occurred at high tide (the tidal range in this area is about 5 m). Numerical simulation experiments of tsunami generation, propagation and inundation using a subaerial debris avalanche source at Augustine volcano indicate only modest wave generation because of the shallow water surrounding the volcano (maximum water depth about 25 m). Lahar flows produced during eruptions at snow and ice clad volcanoes in the Aleutian arc also deliver copious amounts of sediment to the sea. These flows only rarely transform to subaqueous debris flows that may become tsunamigenic. However, the accumulation of loose, unconsolidated sediment on the continental shelf may lead to subaqueous debris flows and landslides if these deposits become mobilized by large earthquakes. Tsunamis produced by this mechanism could potentially reach coastlines all along the Pacific Rim. Finally, recent work in the western Aleutian Islands indicates that many of the island volcanoes in this area have experienced large-scale flank collapse. Because these volcanoes are surrounded by deep water, the tsunami hazard associated with a future sector collapse could be significant.
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Neal, Christina A.; Herrick, Julie; Girina, O.A.; Chibisova, Marina; Rybin, Alexander; McGimsey, Robert G.; Dixon, Jim
2014-01-01
The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, volcanic unrest or suspected unrest at 12 volcanic centers in Alaska during 2010. The most notable volcanic activity consisted of intermittent ash emissions from long-active Cleveland volcano in the Aleutian Islands. AVO staff also participated in hazard communication regarding eruptions or unrest at seven volcanoes in Russia as part of an ongoing collaborative role in the Kamchatka and Sakhalin Volcanic Eruption Response Teams.
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NASA Astrophysics Data System (ADS)
Butler, Rhett; Frazer, L. Neil; Templeton, William J.
2016-05-01
We use the global rate of Mw ≥ 9.0 earthquakes, and standard Bayesian procedures, to estimate the probability of such mega events in the Aleutian Islands, where they pose a significant risk to Hawaii. We find that the probability of such an earthquake along the Aleutians island arc is 6.5% to 12% over the next 50 years (50% credibility interval) and that the annualized risk to Hawai'i is about $30 M. Our method (the regionally scaled global rate method or RSGR) is to scale the global rate of Mw 9.0+ events in proportion to the fraction of global subduction (units of area per year) that takes place in the Aleutians. The RSGR method assumes that Mw 9.0+ events are a Poisson process with a rate that is both globally and regionally stationary on the time scale of centuries, and it follows the principle of Burbidge et al. (2008) who used the product of fault length and convergence rate, i.e., the area being subducted per annum, to scale the Poisson rate for the GSS to sections of the Indonesian subduction zone. Before applying RSGR to the Aleutians, we first apply it to five other regions of the global subduction system where its rate predictions can be compared with those from paleotsunami, paleoseismic, and geoarcheology data. To obtain regional rates from paleodata, we give a closed-form solution for the probability density function of the Poisson rate when event count and observation time are both uncertain.
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NASA Astrophysics Data System (ADS)
Jewett, S. C.; Drew, G. S.
2014-03-01
The intertidal and nearshore benthic communities of Kasatochi Island are described following a catastrophic volcanic eruption in 2008. Prior to the eruption, the island was surrounded by a dense bed of canopy-forming dragon kelp Eualaria fistulosa which supported a productive nearshore community. The eruption extended the coastline of the island approximately 400 m offshore to roughly the 20 m isobath. One year following the eruption a reconnaissance survey found the intertidal zone devoid of life. Subtidally, the canopy kelp, as well as limited understory algal species and associated benthic fauna on the hard substratum, were buried by debris from the eruption. The resulting substrate was comprised almost entirely of medium and coarse sands with a depauperate benthic community. Comparisons of habitat and biological communities with other nearby Aleutian Islands and the Icelandic submarine volcanic eruption of Surtsey confirm dramatic reductions in flora and fauna consistent with the initial stages of recovery from a large-scale disturbance event. Four and five years following the eruption brief visits revealed dramatic intertidal and subtidal recolonization of the flora and fauna in some areas. Signs of nesting and fledging of young pigeon guillemots Cepphus columba suggest that the recovery of the nearshore biota may have begun affecting higher trophic levels. Recolonization or lack thereof was tied to bathymetric changes from coastal and nearshore erosion over the study period.
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-12-27
... information collected during 2011, such as revised stock assessments and catch data. The Plan Team compiled... and socioeconomic data, including projected biomass trends, information on assumed distribution of..., skates, sculpins, and octopuses. Section 679.20(a)(5)(iii)(B)(1) requires the Aleutian Islands (AI...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-02-19
... and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS), National... fishery in the BSAI is 1,248,494 animals as established by the final 2009 and 2010 harvest specifications.... Emily H. Menashes, Acting Director, Office of Sustainable Fisheries, National Marine Fisheries Service...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-08-17
... West region of the Aleutian Islands. An emergency exists because, due to a recent unforeseen event, no... objectives of the Magnuson-Stevens Fishery Conservation and Management Act, the Fishery Management Plan for... and Management Act (Magnuson-Stevens Act) provides authority for rulemaking to address an emergency...
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Code of Federal Regulations, 2010 CFR
2010-10-01
... endorsement for Norton Sound red king. More specifically, the reduction endorsement fisheries, and the crab... endorsement fisheries, are: (1) Bristol Bay red king (the corresponding crab rationalization fishery is Bristol Bay red king crab), (2) Bering Sea and Aleutian Islands Area C. opilio and C. bairdi (the...
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Code of Federal Regulations, 2011 CFR
2011-10-01
... endorsement for Norton Sound red king. More specifically, the reduction endorsement fisheries, and the crab... endorsement fisheries, are: (1) Bristol Bay red king (the corresponding crab rationalization fishery is Bristol Bay red king crab), (2) Bering Sea and Aleutian Islands Area C. opilio and C. bairdi (the...
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NASA Satellite Tracks Underwater Volcanic Eruption in Canary Islands
2011-11-02
In July 2011, volcanic tremors began on the Island of El Hierro in the Canary Islands; by September, many tourists evacuated the resort island, fearing a volcanic eruption. This image is from NASA Terra spacecraft.
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Jewett, S.C.; Drew, Gary S.
2014-01-01
The intertidal and nearshore benthic communities of Kasatochi Island are described following a catastrophic volcanic eruption in 2008. Prior to the eruption, the island was surrounded by a dense bed of canopy-forming dragon kelp Eualaria fistulosa which supported a productive nearshore community. The eruption extended the coastline of the island approximately 400 m offshore to roughly the 20 m isobath. One year following the eruption a reconnaissance survey found the intertidal zone devoid of life. Subtidally, the canopy kelp, as well as limited understory algal species and associated benthic fauna on the hard substratum, were buried by debris from the eruption. The resulting substrate was comprised almost entirely of medium and coarse sands with a depauperate benthic community. Comparisons of habitat and biological communities with other nearby Aleutian Islands and the Icelandic submarine volcanic eruption of Surtsey confirm dramatic reductions in flora and fauna consistent with the initial stages of recovery from a large-scale disturbance event. Four and five years following the eruption brief visits revealed dramatic intertidal and subtidal recolonization of the flora and fauna in some areas. Signs of nesting and fledging of young pigeon guillemots Cepphus columba suggest that the recovery of the nearshore biota may have begun affecting higher trophic levels. Recolonization or lack thereof was tied to bathymetric changes from coastal and nearshore erosion over the study period.
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NASA Technical Reports Server (NTRS)
Murray, John J.; Hudnall, L. A.; Matus, A.; Krueger, A. J.; Trepte, C. r.
2010-01-01
The Aleutian Islands of Alaska are home to a number of major volcanoes which periodically present a significant hazard to aviation. During summer of 2008, the Okmok and Kasatochi volcanoes experienced moderate eruptive events. These were followed a dramatic, major eruption of Mount Redoubt in late March 2009. The Redoubt case is extensively covered in this paper. Volcanic ash and SO2 from each of these eruptions dispersed throughout the atmosphere. This created the potential for major problems for air traffic near the ash dispersions and at significant distances downwind. The NASA Applied Sciences Weather Program implements a wide variety of research projects to develop volcanic ash detection, characterization and tracking applications for NASA Earth Observing System and NOAA GOES and POES satellites. Chemistry applications using NASA AURA satellite Ozone Monitoring System (OMI) retrievals produced SO2 measurements to trace the dispersion of volcanic aerosol. This work was complimented by advanced multi-channel imager applications for the discrimination and height assignment of volcanic ash using NASA MODIS and NOAA GOES and POES imager data. Instruments similar to MODIS and OMI are scheduled for operational deployment on NPOESS. In addition, the NASA Calipso satellite provided highly accurate measurements of aerosol height and dispersion for the calibration and validation of these algorithms and for corroborative research studies. All of this work shortens the lead time for transition to operations and ensures that research satellite data and applications are operationally relevant and utilized quickly after the deployment of operational satellite systems. Introduction
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Federal Register 2010, 2011, 2012, 2013, 2014
2012-07-27
... of a zero (0) percent fee for cost recovery under the Bering Sea and Aleutian Islands Crab... Program includes a cost recovery provision to collect fees to recover the actual costs directly related to... processing sectors to each pay half the cost recovery fees. Catcher/processor quota share holders are...
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Material culture across the Aleutian archipelago.
Hatfield, Virginia L
2010-12-01
The material evidence from sites across the Aleutian Islands reflects colonization events, subsequent adaptations, and influxes of ideas and/or people from the east. The occurrence in the eastern Aleutians of bifacial technology around 7000 BP, of artifacts similar to the Arctic Small Tool tradition between 4000 and 3500 BP, and of slate and jet objects around 1000 BP reflects repeated surges of influence or movement of peoples from further east into the eastern end of the chain. In the central and western Aleutians, influence or perhaps colonization from east of the Aleutians is also marked by the occurrence of bifacial technology about 6500 BP and the appearance of slate artifacts after 1000 BP, suggesting the movement of ideas or people from further east. Basic trends across the archipelago include a decrease in formal chipped-stone tools, an increase in the use and the complexity of bone technology, and the increase in use and variety of ground-stone tools. In addition, increasing village site sizes and denser midden deposits are seen later in time throughout the archipelago. The similarity in sites and assemblages, albeit with regional variations, reflects trends that are seen across the chain and indicates that these island communities were not isolated from one another or from mainland Alaska.
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NASA Astrophysics Data System (ADS)
Roman, D.; Plank, T. A.; Hauri, E. H.; Rasmussen, D. J.; Power, J. A.; Lyons, J. J.; Haney, M. M.; Werner, C. A.; Kern, C.; Lopez, T. M.; Izbekov, P. E.; Stelling, P. L.
2016-12-01
We present initial results from an integrated geochemical-geophysical study of the Unimak-Cleveland corridor of the Aleutian volcanic arc, which encompasses six volcanoes spanning 450 km of the arc that have erupted in the past 25 years with a wide range of magmatic water contents. This relatively small corridor also exhibits a range of deep and upper-crustal seismicity, apparent magma storage depths, and depths to the subducting tectonic plate. The ultimate goal of this study is to link two normally disconnected big-picture problems: 1) the deep origin of magmas and volatiles, and 2) the formation and eruption of crustal magma reservoirs, which we will do by establishing the depth(s) of crustal magma reservoirs and pre-eruptive volatile contents throughout the corridor. Our preliminary work focuses on the geographic end members Shishaldin Volcano, which last erupted in 2014-2015, and Cleveland Volcano, which last erupted in April-May of this year (2016). Both systems are persistently degassing, open-vent volcanoes whose frequent eruptions are typically characterized by minimal precursory seismicity, making eruption forecasting challenging. At Cleveland, we analyze data from a 12-station broadband seismic network deployed from August 2015-July 2016, which is complemented by two permanent seismo-acoustic stations operated by the Alaska Volcano Observatory (AVO). We also analyze tephras from recent eruptions (including 2016) and conducted ground- and helicopter-based gas emission surveys. At Shishaldin, we analyze data from the permanent AVO network, which is comprised of mainly short-period, single-component seismic stations. We also present preliminary analyses of samples of recent eruptive deposits and gas emission data. Through integration of these various datasets we present preliminary interpretations related to the origin, storage, ascent and eruption of volatile-bearing magmas at Cleveland and Shishaldin volcanoes.
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Code of Federal Regulations, 2014 CFR
2014-10-01
... Pribilof blue king (the corresponding crab rationalization fishery is Pribilof red king and blue king crab), and (6) St. Matthew blue king (the corresponding crab rationalization fishery is also St. Matthew blue... Aleutian Islands red king, $237,588.04; (5) For Pribilof red king and Pribilof blue king, $1,571,216.35...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-07-23
... of a 2.67-percent fee for cost recovery under the Bering Sea and Aleutian Islands Crab... for the 2010/2011 crab fishing year so they can calculate the required payment for cost recovery fees...-Stevens Act). The Program includes a cost recovery provision to collect fees to recover the actual costs...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-07-21
... of a 1.23-percent fee for cost recovery under the Bering Sea and Aleutian Islands Crab... for the 2011/2012 crab fishing year so they can calculate the required payment for cost recovery fees...-Stevens Act). The Program includes a cost recovery provision to collect fees to recover the actual costs...
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-08-01
... of a 0.69-percent fee for cost recovery under the Bering Sea and Aleutian Islands Crab... for the 2013/2014 crab fishing year so they can calculate the required payment for cost recovery fees... Program includes a cost recovery provision to collect fees to recover the actual costs directly related to...
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Seismic array observations for monitoring phreatic eruptions in Iwojima Island, Japan
NASA Astrophysics Data System (ADS)
Ueda, H.; Kawaguchi, R.; Chiba, K.; Fujita, E.; Tanada, T.
2015-12-01
Iwojima is an active volcanic island located within a 10 km wide submarine caldera about 1250 km to the south of Tokyo, Japan. The volcanic activity is characterized by intensive earthquake activity associated with an island-wide uplift with high uplift rate (30~40 cm/year) and hydrothermal activity. In the last 10 years, phreatic eruptions took place in and near the island in 2012, 2013, and 2015. In such restless volcano, predictions and detections of occurrence points of phreatic eruptions are important for ensuring safety of residents. In the previous studies, we found that the earthquake activity of Iwojima highly correlates with the island wide large uplift, but the precursory activity of the phreatic eruption in 2012 was deviated from the correlation (Ueda et al. 2013 AGU Fall Meeting). For prediction of occurrence points of phreatic eruptions and investigation of the eruption mechanism, we began observation by seismic arrays at two areas in December 2014. The seismic arrays enable to locate epicenters of volcanic tremors, which are not well located by existing seismic stations. In May and June 2015, Japan Maritime Self-Defense Force stayed in Iwojima and a live camera of Japan Meteorological Agency found very small phreatic eruptions occurred at the northern beach. Existing seismic stations could not detect seismic signals related with the eruptions. The seismic array could detect weak seismic signals related with the eruptions. Although the seismic arrays could not detect precursory signals because of too small eruption, we expect the seismic arrays can detect precursory seismic signals suggesting occurrence points of small or medium-sized phreatic eruptions. The seismic arrays also detected epicenters of harmonic and monotonic tremors took place at an active fumarolic field in the north earthen part of Iwojima. The apparent velocity of seismic waves (~1km/s) strongly suggests that the tremors relate with hydrothermal activity near ground surface.
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Maley, Blaine
2016-05-01
The number of distinct human migrations into the Aleutian Islands during the Holocene has been a recurrent debate in the anthropological literature. Stemming from Hrdlička's sorting of the prehistoric remains into two distinct populations based on archaeological context and cranial measurements, the human occupation of the Aleutian Islands has long been thought to be the consequence of two distinct human migrations, a Paleo-Aleut migration that provided the initial settlement of the islands, and a Neo-Aleut migration that replaced the original settlers around 1000 BP. This study examines the relationship of the Aleut cranial assemblages in the context of greater Alaskan population variability to assess the evidence for a substantial migration into the Aleutian Islands during the late Holocene. A battery of 29 cranial measurements that quantify global cranial shape were analyzed using Euclidean morphometric methods and quantitative genetic permutation methods to examine the plausibility for two distinct Aleut occupations ("Paleo-Aleut" and "Neo-Aleut"), the latter of which is held to share closer phenetic affinities to mainland Alaskan populations than the former. The Aleut skeletal assemblages were arranged according to temporal association, geographic location, and cranial typology, and analyzed within a comparative framework of mainland Alaskan samples using principal coordinates, biological distance and random skewers permutation methods. Regardless of how the Aleut assemblages are divided, they show greater similarity to each other than to any of the mainland Alaskan assemblages. These findings are consistent across the methodological approaches. The results obtained in this study provide no support for a cranial morphology-based subdivision of the Aleuts into two distinct samples, Hence, there is no evidence for a substantial population migration of so-called Neo-Aleuts, nor for a population replacement event of an extant Paleo-Aleut population by a mainland
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Wang, B.; Michaelson, G.; Ping, C.-L.; Plumlee, G.; Hageman, P.
2010-01-01
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.
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Federal Register 2010, 2011, 2012, 2013, 2014
2012-07-27
... manages the groundfish fishery in the BSAI exclusive economic zone according to the Fishery Management.... 111213751-2102-02] RIN 0648-XC119 Fisheries of the Exclusive Economic Zone Off Alaska; Squid in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS), National...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-09-07
.... 101126521-0640-02] RIN 0648-XA683 Fisheries of the Exclusive Economic Zone Off Alaska; Octopus in the Bering... retention of octopus in the Bering Sea and Aleutian Islands (BSAI). This action is necessary because the 2011 total allowable catch of octopus in the BSAI has been reached. DATES: Effective 1200 hrs, Alaska...
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NASA Astrophysics Data System (ADS)
Zelenak, G.; Key, K.; Bennington, N. L.; Bedrosian, P.
2015-12-01
Understanding the factors controlling the release of volatiles from the downgoing slab, the subsequent generation of melt in the overlying mantle wedge, the migration of melt to the crust, and its evolution and emplacement within the crust are important for advancing our understanding of arc magmatism and crustal genesis. Because melt and aqueous fluids are a few orders of magnitude more electrically conductive than unmelted peridotite, the conductivity-mapping magnetotelluric (MT) method is well-suited to imaging fluids and melt beneath arc volcanoes. Here we present conductivity results from an amphibious MT profile crossing Okmok volcano in the central Aleutian arc. The Aleutian arc is one of the most volcanically active regions in North America, making it an ideal location for studying arc magnetism. Okmok volcano, located on the northeastern portion of Umnak Island, is among the most active volcanoes in the Aleutian chain. In addition to two caldera-forming events in the Holocene, numerous eruptions in the past century indicate a robust magmatic supply. Previous coarse resolution seismic studies have inferred a crustal magma reservoir. In order to investigate the role fluids play in melting the mantle wedge, how melts ascend through the corner flow regime of the mantle wedge, how melt migrates and is stored within the upper mantle and crust, and how this impacts explosive caldera forming eruptions, we carried out an amphibious geophysical survey across the arc in June-July 2015. Twenty-nine onshore MT stations and 10 offshore stations were collected in a 3D array covering Okmok, and 43 additional offshore MT stations completed a 300 km amphibious profile starting at the trench, crossing the forearc, arc and backarc. Thirteen onshore passive seismic stations were also installed and will remain in place for one year to supplement the twelve permanent stations on the island. Data collected by this project will be used to map seismic velocity and electrical
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Eruption of soufriere volcano on st. Vincent island, 1971-1972.
Aspinall, W P; Sigurdsson, H; Shepherd, J B
1973-07-13
The Soufrière volcano in St. Vincent erupted from October 1971 to March 1972, as 80 x 10(6) m(3) of basaltic andesite lava was quietly extruded inside the mile-wide crater. The eruption was largely subaqueous, taking place in the 180-m-deep crater lake, and resulted in the emergence of a steep-sided island. The mild character of the eruption and the absence of seismic activity stand in direct contrast to the highly explosive character of the eruption of 1902 to 1903.
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Multi-stage volcanic island flank collapses with coeval explosive caldera-forming eruptions.
Hunt, James E; Cassidy, Michael; Talling, Peter J
2018-01-18
Volcanic flank collapses and explosive eruptions are among the largest and most destructive processes on Earth. Events at Mount St. Helens in May 1980 demonstrated how a relatively small (<5 km 3 ) flank collapse on a terrestrial volcano could immediately precede a devastating eruption. The lateral collapse of volcanic island flanks, such as in the Canary Islands, can be far larger (>300 km 3 ), but can also occur in complex multiple stages. Here, we show that multistage retrogressive landslides on Tenerife triggered explosive caldera-forming eruptions, including the Diego Hernandez, Guajara and Ucanca caldera eruptions. Geochemical analyses were performed on volcanic glasses recovered from marine sedimentary deposits, called turbidites, associated with each individual stage of each multistage landslide. These analyses indicate only the lattermost stages of subaerial flank failure contain materials originating from respective coeval explosive eruption, suggesting that initial more voluminous submarine stages of multi-stage flank collapse induce these aforementioned explosive eruption. Furthermore, there are extended time lags identified between the individual stages of multi-stage collapse, and thus an extended time lag between the initial submarine stages of failure and the onset of subsequent explosive eruption. This time lag succeeding landslide-generated static decompression has implications for the response of magmatic systems to un-roofing and poses a significant implication for ocean island volcanism and civil emergency planning.
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Duarte, Adam; Wolcott, Daniel M.; Chow, T. Edwin
2012-01-01
The Aleutian shield fern Polystichum aleuticum is endemic to the Aleutian archipelago of Alaska and is listed as endangered pursuant to the U.S. Endangered Species Act. Despite numerous efforts to discover new populations of this species, only four known populations are documented to date, and information is needed to prioritize locations for future surveys. Therefore, we incorporated topographical habitat characteristics (elevation, slope, aspect, distance from coastline, and anthropogenic footprint) found at known Aleutian shield fern locations into a Geographical Information System (GIS) model to create a habitat suitability map for the entirety of the Andreaonof Islands. A total of 18 islands contained 489.26 km2 of highly suitable and moderately suitable habitat when weighting each factor equally. This study reports a habitat suitability map for the endangered Aleutian shield fern using topographical characteristics, which can be used to assist current and future recovery efforts for the species.
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A tectonic earthquake sequence preceding the April-May 1999 eruption of Shishaldin Volcano, Alaska
Moran, S.C.; Stihler, S.D.; Power, J.A.
2002-01-01
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 or not the eruption caused the mainshock by computing the Coulomb stress change caused by an inflating dike on fault planes oriented parallel to the mainshock focal mechanism. We found Coulomb stress increases of ???0.1 MPa in the region of the mainshock, suggesting that magma intrusion prior to the eruption could have caused the mainshock. Satellite and seismic data indicate that magma was moving upwards beneath Shishaldin well before the mainshock. indicating that, in an overall sense, the mainshock cannot be said to have caused the eruption. However, observations of changes at the volcano following the mainshock and several large aftershocks suggest that the earthquakes may, in turn, have influenced the course of the eruption.
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Witter, Robert C.; Briggs, Richard W.; Engelhart, Simon E.; Gelfenbaum, Guy R.; Koehler, Richard D.; Barnhart, William D.
2014-01-01
Can a predominantly creeping segment of a subduction zone generate a great (M > 8) earthquake? Despite Russian accounts of strong shaking and high tsunamis in 1788, geodetic observations above the Aleutian megathrust indicate creeping subduction across the Shumagin Islands segment, a well-known seismic gap. Seeking evidence for prehistoric great earthquakes, we investigated Simeonof Island, the archipelago's easternmost island, and found no evidence for uplifted marine terraces or subsided shorelines. Instead, we found freshwater peat blanketing lowlands, and organic-rich silt and tephra draping higher glacially smoothed bedrock. Basal peat ages place glacier retreat prior to 10.4 ka and imply slowly rising (<0.2 m/ka) relative sea level since ~3.4 ka. Storms rather than tsunamis probably deposited thin, discontinuous deposits in coastal sites. If rupture of the megathrust beneath Simeonof Island produced great earthquakes in the late Holocene, then coseismic uplift or subsidence was too small (≤0.3 m) to perturb the onshore geologic record.
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Psychological aspects in a volcanic crisis: El Hierro Island eruption (October, 2011).
NASA Astrophysics Data System (ADS)
Lopez, P.; Llinares, A.; Garcia, A.; Marrero, J. M.; Ortiz, R.
2012-04-01
The recent eruption on the El Hierro Island (Canary Islands, Spain) has shown that Psychology plays an important role in the emergence management of a natural phenomenon. However, Psychology continues to have no social coverage it deserves in the mitigation of the effects before, during and after the occurrence of a natural phenomenon. Keep in mind that an unresolved psychological problem involves an individual and collective mismatch may become unrecoverable. The population of El Hierro has been under a state of alert since July 2011, when seismic activity begins, until the occurrence of submarine eruption in October 2011 that is held for more than three months. During this period the inhabitants of the small island have gone through different emotional states ranging from confusion to disappointment. A volcanic eruption occurs not unexpectedly, allowing to have a time of preparation / action before the disaster. From the psychological point of view people from El Hierro Island have responded to different stages of the same natural process. Although the island of El Hierro is of volcanic origin, the population has no historical memory since the last eruption occurred in 1793. Therefore, the educational system does not adequately address the formation in volcanic risk. As a result people feel embarrassment when the seismovolcanic crisis begins, although no earthquakes felt. As an intermediate stage, when the earthquakes are felt by the population, scientists and operational Emergency Plan care to inform and prepare actions in case of a possible eruption. The population feel safe despite the concerns expressed by not knowing where, how and when the eruption will occur. Once started the submarine eruption, taking into account that all the actions (evacuation, relocation, etc.) have worked well and that both their basic needs and security are covered there are new states of mind. These new emotional states ranging from disenchantment with the phenomenology of the
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NASA Astrophysics Data System (ADS)
Nelson, A. R.; Briggs, R. W.; Kemp, A.; Haeussler, P. J.; Engelhart, S. E.; Dura, T.; Angster, S. J.; Bradley, L.
2012-12-01
Uncertainty in earthquake and tsunami prehistory of the Aleutian-Alaska megathrust westward of central Kodiak Island limit assessments of southern Alaska's earthquake hazard and forecasts of potentially damaging tsunamis along much of North America's west coast. Sitkinak Island, one of the Trinity Islands off the southwest tip of Kodiak Island, lies at the western end of the rupture zone of the 1964 Mw9.2 earthquake. Plafker reports that a rancher on the north coast of Sitkinak Island observed ~0.6 m of shoreline uplift immediately following the 1964 earthquake, and the island is now subsiding at about 3 mm/yr (PBO GPS). Although a high tsunami in 1788 caused the relocation of the first Russian settlement on southwestern Kodiak Island, the eastern extent of the megathrust rupture accompanying the tsunami is uncertain. Interpretation of GPS observations from the Shumagin Islands, 380 km southwest of Kodiak Island, suggests an entirely to partially creeping megathrust in that region. Here we report the first stratigraphic evidence of tsunami inundation and land-level change during prehistoric earthquakes west of central Kodiak Island. Beneath tidal and freshwater marshes around a lagoon on the south coast of Sitkinak Island, 27 cores and tidal outcrops reveal the deposits of four to six tsunamis in 2200 years and two to four abrupt changes in lithology that may correspond with coseismic uplift and subsidence over the past millennia. A 2- to 45-mm-thick bed of clean to peaty sand in sequences of tidal sediment and freshwater peat, identified in more than one-half the cores as far inland as 1.5 km, was probably deposited by the 1788 tsunami. A 14C age on Scirpus seeds, double 137Cs peaks at 2 cm and 7 cm depths (Chernobyl and 1963?), a consistent decline in 210Pb values, and our assumption of an exponential compaction rate for freshwater peat, point to a late 18th century age for the sand bed. Initial 14C ages suggest that two similar extensive sandy beds, identified
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2015 Volcanic activity in Alaska—Summary of events and response of the Alaska Volcano Observatory
Dixon, James P.; Cameron, Cheryl E.; Iezzi, Alexandra M.; Wallace, Kristi
2017-09-28
The Alaska Volcano Observatory (AVO) responded to eruptions, volcanic unrest or suspected unrest, and seismic events at 14 volcanic centers in Alaska during 2015. The most notable volcanic activity consisted of continuing intermittent ash eruptions from Cleveland and Shishaldin volcanoes in the Aleutian Islands. Two eruptive episodes, at Veniaminof and Pavlof, on the Alaska Peninsula ended in 2015. During 2015, AVO re-established the seismograph network at Aniakchak, installed six new broadband seismometers throughout the Aleutian Islands, and added a Multiple component Gas Analyzer System (MultiGAS) station on Augustine.
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NASA Astrophysics Data System (ADS)
Ghosh, A.; LI, B.
2016-12-01
Alaska-Aleutian subduction zone is one of the most seismically active subduction zones in this planet. It is characterized by remarkable along-strike variations in seismic behavior, more than 50 active volcanoes, and presents a unique opportunity to serve as a natural laboratory to study subduction zone processes including fault dynamics. Yet details of the seismicity pattern, spatiotemporal distribution of slow earthquakes, nature of interaction between slow and fast earthquakes and their implication on the tectonic behavior remain unknown. We use a hybrid seismic network approach and install 3 mini seismic arrays and 5 stand-alone stations to simultaneously image subduction fault and nearby volcanic system (Makushin). The arrays and stations are strategically located in the Unalaska Island, where prolific tremor activity is detected and located by a solo pilot array in summer 2012. The hybrid network is operational between summer 2015 and 2016 in continuous mode. One of the three arrays starts in summer 2014 and provides additional data covering a longer time span. The pilot array in the Akutan Island recorded continuous seismic data for 2 months. An automatic beam-backprojection analysis detects almost daily tremor activity, with an average of more than an hour per day. We imaged two active sources separated by a tremor gap. The western source, right under the Unalaska Island shows the most prolific activity with a hint of steady migration. In addition, we are able to identify more than 10 families of low frequency earthquakes (LFEs) in this area. They are located within the tremor source area as imaged by the bean-backprojection technique. Application of a match filter technique reveals that intervals between LFE activities are shorter during tremor activity and longer during quiet time period. We expect to present new results from freshly obtained data. The experiment A-cubed is illuminating subduction zone processes under Unalaska Island in unprecedented
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Deformation associated with the 1997 eruption of Okmok volcano, Alaska
Mann, Dorte; Freymueller, Jeffrey T.; Lu, Z.
2002-01-01
Okmok volcano, located on Umnak Island in the Aleutian chain, Alaska, is the most eruptive caldera system in North America in historic time. Its most recent eruption occurred in 1997. Synthetic aperture radar interferometry shows deflation of the caldera center of up to 140 cm during this time, preceded and followed by inflation of smaller magnitude. The main part of the observed deformation can be modeled using a pressure point source model. The inferred source is located between 2.5 and 5.0 km beneath the approximate center of the caldera and ???5 km from the eruptive vent. We interpret it as a central magma reservoir. The preeruptive period features inflation accompanied by shallow localized subsidence between the caldera center and the vent. We hypothesize that this is caused by hydrothermal activity or that magma moved away from the central chamber and toward the later vent. Since all historic eruptions at Okmok have originated from the same cone, this feature may be a precursor that indicates an upcoming eruption. The erupted magma volume is ???9 times the volume that can be accounted for by the observed preeruptive inflation. This indicates a much longer inflation interval than we were able to observe. The observation that reinflation started shortly after the eruption suggests that inflation spans the whole time interval between eruptions. Extrapolation of the average subsurface volume change rate is in good agreement with the long-term eruption frequency and eruption volumes of Okmok.
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Ongoing Uplift Rates and Topography Across the Aleutian Forearc Region on Kodiak Island, Alaska.
NASA Astrophysics Data System (ADS)
Sauber, J. M.; Carver, G. A.
2002-12-01
The Kodiak Islands are part of a large subduction complex that comprises the eastern Aleutian forearc; the islands form the subaerial part of a broad topographic ridge that includes a Mesozoic-Cenozoic accretionary complex. To explore the relation between the ongoing subduction process, uplift rates and topographic characteristics, we have used a 30 m digital elevation map (DEM) derived from the Shuttle Radar Topography Mission (SRTM), an older 90 m DEM and ocean bathymetry. The topographic characteristics of Kodiak Island vary along strike and as a function of distance from the trench. From the northern to southern part of island, the distance from the 5800 m bathymetric contour (Aleutian Trench) and the eastern coast of Kodiak Island, as well as the width of the island, narrows by about 10% and probably reflects a steepening of the dip of the downgoing Pacific plate under the southern part of the island. The northern and central part of the island have similar topographic profiles as a function of distance from the trench; the highest peaks are located in the central part of the island. Although most of the island was glaciated during the last glacial maximum, the southwest portion of the island remained unglaciated; this region is distinctly less dissected. Preliminary uplift rates across the forearc region have been estimated from coastal marine terraces and short-term geodetic observations. Elevation changes over the last 103 - 104 years are being obtained from kinematic GPS observations across two sets of Holocene marine terrace sequences and from elevation measurements in northern Kodiak of an extensive late Pleistocene marine terrace (probably an oxygen isotope stage 5a, 120 - 130 ka). Initial measurements from the older terrace in northern Kodiak suggest an average uplift rate for the eastern side of Kodiak, above the down-dip end of the locked zone on the megathrust, to be about 1.2 mm/yr; on the western side of the island the uplift rate decreases by an
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-02-25
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-05-03
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-01-25
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2010-02-08
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2012-07-03
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2013-05-20
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-11-15
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Federal Register 2010, 2011, 2012, 2013, 2014
2012-05-03
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2013-06-14
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-10-25
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The eruption of Mount Pagan volcano, Mariana Islands, 15 May 1981
Banks, N.G.; Koyanagi, R.Y.; Sinton, J.M.; Honma, K.T.
1984-01-01
A major explosive eruption occurred 15 May 1981 at Mount Pagan Volcano, the larger of two historic eruptive centers on Pagan Island, Mariana Islands. The eruption was preceded by increased numbers of locally felt earthquakes beginning in late March or early April and by new ground cracks, new sublimates, and increased gas emissions. A swarm of felt earthquakes began at 0745h (local time = UCT+10 hours) 15 May, and at 0915 h, closely following a loud sonic boom, a strong plinian column issued from the volcano. The high-altitude ash cloud (at least 13.5 km) travelled south-southeast, but ash and scoria deposits were thickest (> 2 m) in the NW sector of the island because of the prevailing low-altitude southeasterly winds. The early activity of 15 May probably involved magmatic eruption along a fissure system oriented about N10??E. However, the eruption became hydromagmatic, possibly within minutes, and was largely restricted to three long-lived vents. The northernmost of these built a substantial new scoria-ash cinder cone. Flows and air-fall deposits, consisting almost entirely of juvenile material, exceeded 105 ?? 106 m3 in volume (75 ?? 106 m3 of magma) on land and at least 70-100 ?? 606 m3 at sea. An unknown volume was carried away by stratospheric winds. Lithic blocks and juvenile bombs as large as 1 m in diameter were thrown more than 2 km from the summit, and evidence for base-surge was observed in restricted corridors as low as 200 m elevation on the north and south slopes of the volcano. Neither of these events resulted in serious injuries to the 54 residents of the island, nor did the eruption produce serious chemical hazards in their water supply. Weak eruptions occurred during the ensuing month, and some of these were monitored by ground observations, seismic monitoring, and deformation studies. Precursory seismicity and possibly deformation occurred with some of the observed eruptions. More vigorous eruptions were reported by visiting residents in late
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Repeated magmatic intrusions at El Hierro Island following the 2011-2012 submarine eruption
NASA Astrophysics Data System (ADS)
Benito-Saz, Maria A.; Parks, Michelle M.; Sigmundsson, Freysteinn; Hooper, Andrew; García-Cañada, Laura
2017-09-01
After more than 200 years of quiescence, in July 2011 an intense seismic swarm was detected beneath the center of El Hierro Island (Canary Islands), culminating on 10 October 2011 in a submarine eruption, 2 km off the southern coast. Although the eruption officially ended on 5 March 2012, magmatic activity continued in the area. From June 2012 to March 2014, six earthquake swarms, indicative of magmatic intrusions, were detected underneath the island. We have studied these post-eruption intrusive events using GPS and InSAR techniques to characterize the ground surface deformation produced by each of these intrusions, and to determine the optimal source parameters (geometry, location, depth, volume change). Source inversions provide insight into the depth of the intrusions ( 11-16 km) and the volume change associated with each of them (between 0.02 and 0.13 km3). During this period, > 20 cm of uplift was detected in the central-western part of the island, corresponding to approximately 0.32-0.38 km3 of magma intruded beneath the volcano. We suggest that these intrusions result from deep magma migrating from the mantle, trapped at the mantle/lower crust discontinuity in the form of sill-like bodies. This study, using joint inversion of GPS and InSAR data in a post-eruption period, provides important insight into the characteristics of the magmatic plumbing system of El Hierro, an oceanic intraplate volcanic island.
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Feasibility of Tidal and Ocean Current Energy in False Pass, Aleutian Islands, Alaska final report
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wright, Bruce Albert
The Aleutian Pribilof Islands Association was awarded a U.S. Department of Energy Tribal Energy Program grant (DE-EE0005624) for the Feasibility of Tidal and Ocean Current Energy in False Pass, Aleutian Islands, Alaska (Project). The goal of the Project was to perform a feasibility study to determine if a tidal energy project would be a viable means to generate electricity and heat to meet long-term fossil fuel use reduction goals, specifically to produce at least 30% of the electrical and heating needs of the tribally-owned buildings in False Pass. The Project Team included the Aleut Region organizations comprised of the Aleutianmore » Pribilof Island Association (APIA), and Aleutian Pribilof Island Community Development Association (APICDA); the University of Alaska Anchorage, ORPC Alaska a wholly-owned subsidiary of Ocean Renewable Power Company (ORPC), City of False Pass, Benthic GeoScience, and the National Renewable Energy Laboratory (NREL). The following Project objectives were completed: collected existing bathymetric, tidal, and ocean current data to develop a basic model of current circulation at False Pass, measured current velocities at two sites for a full lunar cycle to establish the viability of the current resource, collected data on transmission infrastructure, electrical loads, and electrical generation at False Pass, performed economic analysis based on current costs of energy and amount of energy anticipated from and costs associated with the tidal energy project conceptual design and scoped environmental issues. Utilizing circulation modeling, the Project Team identified two target sites with strong potential for robust tidal energy resources in Isanotski Strait and another nearer the City of False Pass. In addition, the Project Team completed a survey of the electrical infrastructure, which identified likely sites of interconnection and clarified required transmission distances from the tidal energy resources. Based on resource and
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U.S. Geological Survey (USGS) Western Region Kasatochi Volcano Coastal and Ocean Science
DeGange, Anthony
2010-01-01
Alaska is noteworthy as a region of frequent seismic and volcanic activity. The region contains 52 historically active volcanoes, 14 of which have had at least one major eruptive event since 1990. Despite the high frequency of volcanic activity in Alaska, comprehensive studies of how ecosystems respond to volcanic eruptions are non-existent. On August 7, 2008, Kasatochi Volcano, in the central Aleutian Islands, erupted catastrophically, covering the island with ash and hot pyroclastic flow material. Kasatochi Island was an annual monitoring site of the U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife Refuge (AMNWR); therefore, features of the terrestrial and nearshore ecosystems of the island were well known. In 2009, the U.S. Geological Survey (USGS), AMNWR, and University of Alaska Fairbanks began long-term studies to better understand the effects of the eruption and the role of volcanism in structuring ecosystems in the Aleutian Islands, a volcano-dominated region with high natural resource values.
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The eruption of Mount Pagan volcano, Mariana Islands, 15 May 1981
NASA Astrophysics Data System (ADS)
Banks, Norman G.; Koyanagi, Robert Y.; Sinton, John M.; Honma, Kenneth T.
1984-10-01
A major explosive eruption occurred 15 May 1981 at Mount Pagan Volcano, the larger of two historic eruptive centers on Pagan Island, Mariana Islands. The eruption was preceded by increased numbers of locally felt earthquakes beginning in late March or early April and by new ground cracks, new sublimates, and increased gas emissions. A swarm of felt earthquakes began at 0745h (local time = UCT+10 hours) 15 May, and at 0915 h, closely following a loud sonic boom, a strong plinian column issued from the volcano. The high-altitude ash cloud (at least 13.5 km) travelled south-southeast, but ash and scoria deposits were thickest (> 2 m) in the NW sector of the island because of the prevailing low-altitude southeasterly winds. The early activity of 15 May probably involved magmatic eruption along a fissure system oriented about N10°E. However, the eruption became hydromagmatic, possibly within minutes, and was largely restricted to three long-lived vents. The northernmost of these built a substantial new scoria-ash cinder cone. Flows and air-fall deposits, consisting almost entirely of juvenile material, exceeded 105 × 10 6 m 3 in volume (75 × 10 6 m 3 of magma) on land and at least 70-100 × 60 6 m 3 at sea. An unknown volume was carried away by stratospheric winds. Lithic blocks and juvenile bombs as large as 1 m in diameter were thrown more than 2 km from the summit, and evidence for base-surge was observed in restricted corridors as low as 200 m elevation on the north and south slopes of the volcano. Neither of these events resulted in serious injuries to the 54 residents of the island, nor did the eruption produce serious chemical hazards in their water supply. Weak eruptions occurred during the ensuing month, and some of these were monitored by ground observations, seismic monitoring, and deformation studies. Precursory seismicity and possibly deformation occurred with some of the observed eruptions. More vigorous eruptions were reported by visiting residents in
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Water-magma interaction and plume processes in the 2008 Okmok eruption, Alaska
Unema, Joel; Ort, Michael H.; Larsen, Jessica D; Neal, Christina; Schaefer, Janet R.
2016-01-01
Eruptions of similar explosivity can have divergent effects on the surroundings due to differences in the behavior of the tephra in the eruption column and atmosphere. Okmok volcano, located on Umnak Island in the eastern Aleutian Islands, erupted explosively between 12 July and 19 August 2008. The basaltic andesitic eruption ejected ∼0.24 km3dense rock equivalent (DRE) of tephra, primarily directed to the northeast of the vent area. The first 4 h of the eruption produced dominantly coarse-grained tephra, but the following 5 wk of the eruption deposited almost exclusively ash, much of it very fine and deposited as ash pellets and ashy rain and mist. Meteorological storms combined with abundant plume water to efficiently scrub ash from the eruption column, with a rapid decrease in deposit thickness with distance from the vent. Grain-size analysis shows that the modes (although not their relative proportions) are very constant throughout the deposit, implying that the fragmentation mechanisms did not vary much. Grain-shape features consistent with molten fuel-coolant interaction are common. Surface and groundwater drainage into the vents provided the water for phreatomagmatic fragmentation. The available water (water that could reach the vent area during the eruption) was ∼2.8 × 1010 kg, and the erupted magma totaled ∼7 × 1011 kg, which yield an overall water:magma mass ratio of ∼0.04, but much of the water was not interactive. Although magma flux dropped from 1 × 107 kg/s during the initial 4 h to 1.8 × 105 kg/s for the remainder of the eruption, most of the erupted material was ejected during the lower-mass-flux period due to its much greater length, and this tephra was dominantly deposited within 10 km downwind of the vent. This highlights the importance of ash scrubbing in the evaluation of hazards from explosive eruptions.
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MAGNETIC-ISLAND CONTRACTION AND PARTICLE ACCELERATION IN SIMULATED ERUPTIVE SOLAR FLARES
DOE Office of Scientific and Technical Information (OSTI.GOV)
Guidoni, S. E.; DeVore, C. R.; Karpen, J. T.
The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission in solar flares is not well understood. Drake et al. proposed a mechanism for accelerating electrons in contracting magnetic islands formed by kinetic reconnection in multi-layered current sheets (CSs). We apply these ideas to sunward-moving flux ropes (2.5D magnetic islands) formed during fast reconnection in a simulated eruptive flare. A simple analytic model is used to calculate the energy gain of particles orbiting the field lines of the contracting magnetic islands in our ultrahigh-resolution 2.5D numerical simulation. We find that the estimated energy gainsmore » in a single island range up to a factor of five. This is higher than that found by Drake et al. for islands in the terrestrial magnetosphere and at the heliopause, due to strong plasma compression that occurs at the flare CS. In order to increase their energy by two orders of magnitude and plausibly account for the observed high-energy flare emission, the electrons must visit multiple contracting islands. This mechanism should produce sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each magnetohydrodynamic-scale island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare CS is a promising candidate for electron acceleration in solar eruptions.« less
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Magnetic-Island Contraction and Particle Acceleration in Simulated Eruptive Solar Flares
NASA Technical Reports Server (NTRS)
Guidoni, S. E.; Devore, C. R.; Karpen, J. T.; Lynch, B. J.
2016-01-01
The mechanism that accelerates particles to the energies required to produce the observed high-energy impulsive emission in solar flares is not well understood. Drake et al. proposed a mechanism for accelerating electrons in contracting magnetic islands formed by kinetic reconnection in multi-layered current sheets (CSs). We apply these ideas to sunward-moving flux ropes (2.5D magnetic islands) formed during fast reconnection in a simulated eruptive flare. A simple analytic model is used to calculate the energy gain of particles orbiting the field lines of the contracting magnetic islands in our ultrahigh-resolution 2.5D numerical simulation. We find that the estimated energy gains in a single island range up to a factor of five. This is higher than that found by Drake et al. for islands in the terrestrial magnetosphere and at the heliopause, due to strong plasma compression that occurs at the flare CS. In order to increase their energy by two orders of magnitude and plausibly account for the observed high-energy flare emission, the electrons must visit multiple contracting islands. This mechanism should produce sporadic emission because island formation is intermittent. Moreover, a large number of particles could be accelerated in each magneto hydro dynamic-scale island, which may explain the inferred rates of energetic-electron production in flares. We conclude that island contraction in the flare CS is a promising candidate for electron acceleration in solar eruptions.
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Environmental contaminants in bald eagle eggs from the Aleutian archipelago
Anthony, R.G.; Miles, A.K.; Ricca, M.A.; Estes, J.A.
2007-01-01
We collected 136 fresh and unhatched eggs from bald eagle (Haliaeetus leucocephalus) nests and assessed productivity on eight islands in the Aleutian archipelago, 2000 to 2002. Egg contents were analyzed for a broad spectrum of organochlorine (OC) contaminants, mercury (Hg), and stable isotopes of carbon (??13C) and nitrogen (??15N). Concentrations of polychlorinated biphenyls (??PCBs), p,p???- dichlorodiphenyldichloroethylene (DDE), and Hg in bald eagle eggs were elevated throughout the archipelago, but the patterns of distribution differed among the various contaminants. Total PCBs were highest in areas of past military activities on Adak and Amchitka Islands, indicating local point sources of these compounds. Concentrations of DDE and Hg were higher on Amchitka Island, which was subjected to much military activity during World War II and the middle of the 20th century. Concentrations of ??PCBs also were elevated on islands with little history of military activity (e.g., Amlia, Tanaga, Buldir), suggesting non-point sources of PCBs in addition to point sources. Concentrations of DDE and Hg were highest in eagle eggs from the most western Aleutian Islands (e.g., Buldir, Kiska) and decreased eastward along the Aleutian chain. This east-to-west increase suggested a Eurasian source of contamination, possibly through global transport and atmospheric distillation and/or from migratory seabirds. Eggshell thickness and productivity of bald eagles were normal and indicative of healthy populations because concentrations of most contaminants were below threshold levels for effects on reproduction. Contrary to our predictions, contaminant concentrations were not correlated with stable isotopes of carbon (??13C) or nitrogen (??15N) in eggs. These latter findings indicate that contaminant concentrations were influenced more by point sources and geographic location than trophic status of eagles among the different islands. ?? 2007 SETAC.
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Code of Federal Regulations, 2014 CFR
2014-10-01
... 50 Wildlife and Fisheries 13 2014-10-01 2014-10-01 false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table 24 to Part 679... to Nonpelagic Trawl Fishing ER19FE08.009 ER19FE08.010 ER19FE08.011 ER19FE08.012 ER19FE08.013 ER19FE08...
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Code of Federal Regulations, 2012 CFR
2012-10-01
... 50 Wildlife and Fisheries 13 2012-10-01 2012-10-01 false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table 24 to Part 679... to Nonpelagic Trawl Fishing ER19FE08.009 ER19FE08.010 ER19FE08.011 ER19FE08.012 ER19FE08.013 ER19FE08...
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Code of Federal Regulations, 2011 CFR
2011-10-01
... 50 Wildlife and Fisheries 11 2011-10-01 2011-10-01 false Except as Noted, Locations in the Aleutian Islands Habitat Conservation Area Open to Nonpelagic Trawl Fishing 24 Table 24 to Part 679... to Nonpelagic Trawl Fishing ER19FE08.009 ER19FE08.010 ER19FE08.011 ER19FE08.012 ER19FE08.013 ER19FE08...
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The May 2010 submarine eruption from South Sarigan seamount, Northern Mariana Islands
NASA Astrophysics Data System (ADS)
McGimsey, R. G.; Neal, C. A.; Searcy, C. K.; Camacho, J. T.; Aydlett, W. B.; Embley, R. W.; Trusdell, F.; Paskievitch, J. F.; Schneider, D. J.
2010-12-01
A sudden submarine explosive eruption occurred on May 29, 2010, from a seamount south of Sarigan Island in the Northern Mariana Islands, propelling a diffuse steam and ash cloud to high altitude. Pre-eruptive seismicity was recorded in early April by stations located on Sarigan and Anatahan Island, 42 km to the south, and indicated a source ~12-16 km south of Sarigan. On May 27-28, a change in seismicity—the appearance of tremor-like waveforms—may have marked the onset of volcanic activity. Also on May 27, an elongate patch of discolored ocean water and possible light-colored floating debris about 8-11 km south of Sarigan was observed from a helicopter. This material was likely produced during low-intensity eruptive activity, and an Information Statement from the Commonwealth of the Northern Mariana Islands (CNMI) Emergency Management Office (EMO) and USGS issued at 2353 UTC May 28 described the observation. The Guam Weather Forecast Office of the National Weather Service reported that the area of discoloration, visible on satellite images at 2313 and 2330 UTC on May 28, was about 10 km2, about twice the size of Sarigan Island. Pulses of tremor merged into a nearly continuous signal by 0305 UTC on May 29, lasting for ~4.5 hours followed by nearly 4.5 hours of quiescence. The EMO issued a declaration closing the region south of Sarigan to all local boating traffic and issued an advisory to aircraft. The explosive onset of the main plume-producing event occurred at ~1148 UTC as confirmed by seismic records on Anatahan Island, with the strongest phase ending ~1200 UTC. Soon after, the Washington Volcanic Ash Advisory Center reported an eruption cloud reaching an estimated 40,000 feet (12 km) ASL that diminished rapidly on satellite imagery suggesting it was water-vapor dominated. Winds carried the cloud southwest over Guam, and although no ash fall was reported, the cloud was visible and was detected in Aura/OMI aerosol index imagery. Biologists on Sarigan Island
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The 1999 eruption of Shishaldin Volcano, Alaska: Monitoring a distant eruption
Nye, C.J.; Keith, T.E.C.; Eichelberger, J.C.; Miller, T.P.; McNutt, S.R.; Moran, S.; Schneider, D.J.; Dehn, J.; Schaefer, J.R.
2002-01-01
Shishaldin Volcano, in the central Aleutian volcanic arc, became seismically restless during the summer of 1998. Increasing unrest was monitored using a newly installed seismic network, weather satellites, and rare local visual observations. The unrest culminated in large eruptions on 19 April and 22-23 April 1999. The opening phase of the 19 April eruption produced a sub-Plinian column that rose to 16 km before rapidly dissipating. About 80 min into the 19 April event we infer that the eruption style transitioned to vigorous Strombolian fountaining. Exceptionally vigorous seismic tremor heralded the 23 April eruption, which produced a large thermal anomaly observable by satellite, but only a modest, 6-km-high plume. There are no ground-based visual observations of this eruption; however we infer that there was renewed, vigorous Strombolian fountaining. Smaller low-level ash-rich plumes were produced through the end of May 1999. The lava that erupted was evolved basalt with about 49% SiO2. Subsequent field investigations have been unable to find a distinction between deposits from each of the two major eruptive episodes.
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Nature and Significance of the High-Sr Aleutian Lavas
NASA Astrophysics Data System (ADS)
Yogodzinski, G. M.; Arndt, S.; Turka, J. R.; Kelemen, P. B.; Vervoort, J. D.; Portnyagin, M.; Hoernle, K.
2011-12-01
Results of the Western Aleutian Volcano Expedition and German-Russian KALMAR cruises include the discovery of seafloor volcanism at the Ingenstrem Depression and at unnamed seamounts 300 km west of Buldir, the westernmost emergent volcano in the Aleutian arc. These discoveries indicate that the surface expression of active Aleutian volcanism goes below sea level just west of Buldir, but is otherwise continuous along the full length of the arc. Many lavas dredged from western Aleutian seamounts are basalts, geochemically similar to basalts from elsewhere in Aleutians and other arcs (La/Yb 4-8, Sr/Y<30, 87Sr/86Sr=0.7031-0.7033). Western Aleutian dredge samples also include high-Sr lavas (>700 ppm Sr), which are mostly plagioclase-hornblende andesites and dacites with low Y and middle-heavy rare-earth elements, fractionated trace element patterns (Sr/Y=50-200, La/Yb=9-25) and MORB-like isotopes (87Sr/86Sr < 0.7028). The endmember Sr-rich lavas are magnesian rhyodacites (SiO2~68%, Mg# >0.65) with 1250-1700 ppm Sr, 4-7 ppm Y, low abundances of all rare-earth elements (La<7 ppm, Yb<0.4 ppm) and 87Sr/86Sr < 0.70266. The high silica and primitive (high Mg#) character of the high-Sr lavas, combined with their strongly fractionated trace element patterns and MORB-like isotopes are consistent with a source predominantly of subducted basalt and a melt residue that contained garnet. The high-Sr lavas have some characteristics of MORB fluids (low Ce/Pb and unradiogenic Pb), and their highly calc-alkaline nature implies high pre-eruptive water contents[1], but low 87Sr/86Sr indicates that their source was in MORB, not seawater-altered MORB. The high-Sr endmember is clearly present in andesites from some emergent volcanoes in the western Aleutians, and mixing arrays indicate that it may be present in all Aleutian lavas (e.g., 87Sr/86Sr vs. La/Yb or Sr/Y); however, radiogenic Pb and Sr from subducted sediment renders the high-Sr endmember isotopically invisible in most central and
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NASA Astrophysics Data System (ADS)
Tarff, R.; Day, S. J.; Downes, H.; Seghedi, I.
2015-12-01
Groundwater heating and pressurization of aquifers trapped between dikes in ocean island volcanoes has been proposed as a mechanism for destabilizing and triggering large-volume flank collapses. Previous modelling has indicated that heat transfer from sustained magma flow through dikes during eruption has the potential to produce destabilizing levels of pressure on time scales of 4 to 400 days, if the aquifers remain confined. Here we revisit this proposal from a different perspective. We examine evidence for pressure variations in dike-confined aquifers during eruptions at high elevation vents on ocean island volcanoes. Initially magmatic, these eruptions change to mostly small-volume explosive phreatomagmatic activity. A recent example is the 1949 eruption on La Palma, Canary Islands. Some such eruptions involve sequences of larger-volume explosive phases or cycles, including production of voluminous low-temperature, pyroclastic density currents (PDC). Here we present and interpret data from the Cova de Paul crater eruption (Santo Antao, Cape Verde Islands). The phreatomagmatic part of this eruption formed two cycles, each culminating with eruption of PDCs. Compositional and textural variations in the products of both cycles indicate that the diatreme fill began as coarse-grained and permeable which allowed gas to escape. During the eruption, the fill evolved to a finer grained, poorly sorted, less permeable material, in which pore fluid pressures built up to produce violent explosive phases. This implies that aquifers adjacent to the feeder intrusion were not simply depressurized at the onset of phreatomagmatic explosivity but experienced fluctuations in pressure throughout the eruption as the vent repeatedly choked and emptied. In combination with fluctuations in magma supply rate, driving of aquifer pressurization by cyclical vent choking will further complicate the prediction of flank destabilization during comparable eruptions on ocean island volcanoes.
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Rybin, A.; Chibisova, M.; Webley, P.; Steensen, T.; Izbekov, P.; Neal, C.; Realmuto, V.
2011-01-01
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.
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Stewart, Nathan L.; Konar, Brenda; Tinker, M. Tim
2015-01-01
Sea otters (Enhydra lutris) inhabiting the Aleutian Islands have stabilized at low abundance levels following a decline and currently exhibit restricted habitat-utilization patterns. Possible explanations for restricted habitat use by sea otters can be classified into two fundamentally different processes, bottom-up and top-down forcing. Bottom-up hypotheses argue that changes in the availability or nutritional quality of prey resources have led to the selective use of habitats that support the highest quality prey. In contrast, top-down hypotheses argue that increases in predation pressure from killer whales have led to the selective use of habitats that provide the most effective refuge from killer whale predation. A third hypothesis suggests that current restricted habitat use is based on a need for protection from storms. We tested all three hypotheses for restricted habitat use by comparing currently used and historically used sea otter foraging locations for: (1) prey availability and quality, (2) structural habitat complexity, and (3) exposure to prevailing storms. Our findings suggest that current use is based on physical habitat complexity and not on prey availability, prey quality, or protection from storms, providing further evidence for killer whale predation as a cause for restricted sea otter habitat use in the Aleutian Islands.
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Stewart, Nathan L; Konar, Brenda; Tinker, M Tim
2015-03-01
Sea otters (Enhydra lutris) inhabiting the Aleutian Islands have stabilized at low abundance levels following a decline and currently exhibit restricted habitat-utilization patterns. Possible explanations for restricted habitat use by sea otters can be classified into two fundamentally different processes, bottom-up and top-down forcing. Bottom-up hypotheses argue that changes in the availability or nutritional quality of prey resources have led to the selective use of habitats that support the highest quality prey. In contrast, top-down hypotheses argue that increases in predation pressure from killer whales have led to the selective use of habitats that provide the most effective refuge from killer whale predation. A third hypothesis suggests that current restricted habitat use is based on a need for protection from storms. We tested all three hypotheses for restricted habitat use by comparing currently used and historically used sea otter foraging locations for: (1) prey availability and quality, (2) structural habitat complexity, and (3) exposure to prevailing storms. Our findings suggest that current use is based on physical habitat complexity and not on prey availability, prey quality, or protection from storms, providing further evidence for killer whale predation as a cause for restricted sea otter habitat use in the Aleutian Islands.
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Post-eruptive inflation of Okmok Volcano, Alaska, from InSAR, 2008–2014
Qu, Feifei; Lu, Zhong; Poland, Michael; Freymueller, Jeffrey T.; Zhang, Qin; Jung, Hyung-Sup
2016-01-01
Okmok, a ~10-km wide caldera that occupies most of the northeastern end of Umnak Island, is one of the most active volcanoes in the Aleutian arc. The most recent eruption at Okmok during July-August 2008 was by far its largest and most explosive since at least the early 19th century. We investigate post-eruptive magma supply and storage at the volcano during 2008–2014 by analyzing all available synthetic aperture radar (SAR) images of Okmok acquired during that time period using the multi-temporal InSAR technique. Data from the C-band Envisat and X-band TerraSAR-X satellites indicate that Okmok started inflating very soon after the end of 2008 eruption at a time-variable rate of 48-130 mm/y, consistent with GPS measurements. The “model-assisted” phase unwrapping method is applied to improve the phase unwrapping operation for long temporal baseline pairs. The InSAR time-series is used as input for deformation source modeling, which suggests magma accumulating at variable rates in a shallow storage zone at ~3.9 km below sea level beneath the summit caldera, consistent with previous studies. The modeled volume accumulation in the 6 years following the 2008 eruption is ~75% of the 1997 eruption volume and ~25% of the 2008 eruption volume.
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NASA Astrophysics Data System (ADS)
Ko, Bokyun; Yun, Sung-Hyo
2016-04-01
Jeju Island located in the southwestern part of Korea Peninsula is a volcanic island composed of lavaflows, pyroclasts, and around 450 monogenetic volcanoes. The volcanic activity of the island commenced with phreatomagmatic eruptions under subaqueous condition ca. 1.8-2.0 Ma and lasted until ca. 1,000 year BP. For evaluating volcanic activity of the most recently erupted volcanoes with reported age, volcanic explosivity index (VEI) and volcanic sulfur dioxide index (VSI) of three volcanoes (Ilchulbong tuff cone, Songaksan tuff ring, and Biyangdo scoria cone) are inferred from their eruptive volumes. The quantity of eruptive materials such as tuff, lavaflow, scoria, and so on, is calculated using a model developed in Auckland Volcanic Field which has similar volcanic setting to the island. The eruptive volumes of them are 11,911,534 m3, 24,987,557 m3, and 9,652,025 m3, which correspond to VEI of 3, 3, and 2, respectively. According to the correlation between VEI and VSI, the average quantity of SO2 emission during an eruption with VEI of 3 is 2-8 × 103 kiloton considering that the island was formed under intraplate tectonic setting. Jeju Island was regarded as an extinct volcano, however, several studies have recently reported some volcanic eruption ages within 10,000 year BP owing to the development in age dating technique. Thus, the island is a dormant volcano potentially implying high probability to erupt again in the future. The volcanoes might have explosive eruptions (vulcanian to plinian) with the possibility that SO2 emitted by the eruption reaches stratosphere causing climate change due to backscattering incoming solar radiation, increase in cloud reflectivity, etc. Consequently, recommencement of volcanic eruption in the island is able to result in serious volcanic hazard and this study provides fundamental and important data for volcanic hazard mitigation of East Asia as well as the island. ACKNOWLEDGMENTS: This research was supported by a grant [MPSS
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Aleutian Pribilof Islands Wind Energy Feasibility Study
DOE Office of Scientific and Technical Information (OSTI.GOV)
Bruce A. Wright
2012-03-27
Under this project, the Aleutian Pribilof Islands Association (APIA) conducted wind feasibility studies for Adak, False Pass, Nikolski, Sand Point and St. George. The DOE funds were also be used to continue APIA's role as project coordinator, to expand the communication network quality between all participants and with other wind interest groups in the state and to provide continued education and training opportunities for regional participants. This DOE project began 09/01/2005. We completed the economic and technical feasibility studies for Adak. These were funded by the Alaska Energy Authority. Both wind and hydro appear to be viable renewable energy optionsmore » for Adak. In False Pass the wind resource is generally good but the site has high turbulence. This would require special care with turbine selection and operations. False Pass may be more suitable for a tidal project. APIA is funded to complete a False Pass tidal feasibility study in 2012. Nikolski has superb potential for wind power development with Class 7 wind power density, moderate wind shear, bi-directional winds and low turbulence. APIA secured nearly $1M from the United States Department of Agriculture Rural Utilities Service Assistance to Rural Communities with Extremely High Energy Costs to install a 65kW wind turbine. The measured average power density and wind speed at Sand Point measured at 20m (66ft), are 424 W/m2 and 6.7 m/s (14.9 mph) respectively. Two 500kW Vestas turbines were installed and when fully integrated in 2012 are expected to provide a cost effective and clean source of electricity, reduce overall diesel fuel consumption estimated at 130,000 gallons/year and decrease air emissions associated with the consumption of diesel fuel. St. George Island has a Class 7 wind resource, which is superior for wind power development. The current strategy, led by Alaska Energy Authority, is to upgrade the St. George electrical distribution system and power plant. Avian studies in Nikolski
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Fraile-Nuez, E.; González-Dávila, M.; Santana-Casiano, J. M.; Arístegui, J.; Alonso-González, I. J.; Hernández-León, S.; Blanco, M. J.; Rodríguez-Santana, A.; Hernández-Guerra, A.; Gelado-Caballero, M. D.; Eugenio, F.; Marcello, J.; de Armas, D.; Domínguez-Yanes, J. F.; Montero, M. F.; Laetsch, D. R.; Vélez-Belchí, P.; Ramos, A.; Ariza, A. V.; Comas-Rodríguez, I.; Benítez-Barrios, V. M.
2012-01-01
On October 10 2011 an underwater eruption gave rise to a novel shallow submarine volcano south of the island of El Hierro, Canary Islands, Spain. During the eruption large quantities of mantle-derived gases, solutes and heat were released into the surrounding waters. In order to monitor the impact of the eruption on the marine ecosystem, periodic multidisciplinary cruises were carried out. Here, we present an initial report of the extreme physical-chemical perturbations caused by this event, comprising thermal changes, water acidification, deoxygenation and metal-enrichment, which resulted in significant alterations to the activity and composition of local plankton communities. Our findings highlight the potential role of this eruptive process as a natural ecosystem-scale experiment for the study of extreme effects of global change stressors on marine environments. PMID:22768379
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Large-scale deformation related to the collision of the Aleutian Arc with Kamchatka
Gesit, Eric L.; Scholl, David W.
1994-01-01
The far western Aleutian Island Arc is actively colliding with Kamchatka. Westward motion of the Aleutian Arc is brought about by the tangential relative motion of the Pacific plate transferred to major, right-lateral shear zones north and south of the arc. Early geologic mapping of Cape Kamchatka (a promontory of Kamchatka along strike with the Aleutian Arc) revealed many similarities to the geology of the Aleutian Islands. Later studies support the notion that Cape Kamchatka is the farthest west Aleutian “island” and that it has been accreted to Kamchatka by the process of arc-continent collision. Deformation associated with the collision onshore Kamchatka includes gravimetrically determined crustal thickening and formation of a narrow thrust belt of intensely deformed rocks directly west of Cape Kamchatka. The trend of the thrust faults is concave toward the collision zone, indicating a radial distribution of maximum horizontal compressive stress. Offshore, major crustal faults trend either oblique to the Kamchatka margin or parallel to major Aleutian shear zones. These offshore faults are complex, accommodating both strike-slip and thrust displacements as documented by focal mechanisms and seismic reflection data. Earthquake activity is much higher in the offshore region within a zone bounded to the north by the northernmost Aleutian shear zone and to the west by an apparent aseismic front. Analysis of focal mechanisms in the region indicate that the present-day arc-continent “contact zone” is located directly east of Cape Kamchatka. In modeling the dynamics of the collision zone using thin viscous sheet theory, the rheological parameters are only partially constrained to values of n (the effective power law exponent) ≥ 3 and Ar(the Argand number) ≤ 30. These values are consistent with a forearc thermal profile of Kamchatka, previously determined from heat flow modeling. The thin viscous sheet modeling also indicates that onshore thrust faulting
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Using volcanic tremor for eruption forecasting at White Island volcano (Whakaari), New Zealand
NASA Astrophysics Data System (ADS)
Chardot, Lauriane; Jolly, Arthur D.; Kennedy, Ben M.; Fournier, Nicolas; Sherburn, Steven
2015-09-01
Eruption forecasting is a challenging task because of the inherent complexity of volcanic systems. Despite remarkable efforts to develop complex models in order to explain volcanic processes prior to eruptions, the material Failure Forecast Method (FFM) is one of the very few techniques that can provide a forecast time for an eruption. However, the method requires testing and automation before being used as a real-time eruption forecasting tool at a volcano. We developed an automatic algorithm to issue forecasts from volcanic tremor increase episodes recorded by Real-time Seismic Amplitude Measurement (RSAM) at one station and optimised this algorithm for the period August 2011-January 2014 which comprises the recent unrest period at White Island volcano (Whakaari), New Zealand. A detailed residual analysis was paramount to select the most appropriate model explaining the RSAM time evolutions. In a hindsight simulation, four out of the five small eruptions reported during this period occurred within a failure window forecast by our optimised algorithm and the probability of an eruption on a day within a failure window was 0.21, which is 37 times higher than the probability of having an eruption on any day during the same period (0.0057). Moreover, the forecasts were issued prior to the eruptions by a few hours which is important from an emergency management point of view. Whereas the RSAM time evolutions preceding these four eruptions have a similar goodness-of-fit with the FFM, their spectral characteristics are different. The duration-amplitude distributions of the precursory tremor episodes support the hypothesis that several processes were likely occurring prior to these eruptions. We propose that slow rock failure and fluid flow processes are plausible candidates for the tremor source of these episodes. This hindsight exercise can be useful for future real-time implementation of the FFM at White Island. A similar methodology could also be tested at other
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Surface wind characteristics of some Aleutian Islands. [for selection of windpowered machine sites
NASA Technical Reports Server (NTRS)
Wentink, T., Jr.
1973-01-01
The wind power potential of Alaska is assessed in order to determine promising windpower sites for construction of wind machines and for shipment of wind derived energy. Analyses of near surface wind data from promising Aleutian sites accessible by ocean transport indicate probable velocity regimes and also present deficiencies in available data. It is shown that winds for some degree of power generation are available 77 percent of the time in the Aleutians with peak velocities depending on location.
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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, David R.
2005-01-01
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
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-02-28
... economic zone according to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian.... 0910131363-0087-02] RIN 0648-XA252 Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS...
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NASA Astrophysics Data System (ADS)
García, A.; Fernández-Ros, A.; Berrocoso, M.; Marrero, J. M.; Prates, G.; De la Cruz-Reyna, S.; Ortiz, R.
2014-04-01
Significant deformations, followed by increased seismicity detected since 2011 July at El Hierro, Canary Islands, Spain, prompted the deployment of additional monitoring equipment. The climax of this unrest was a submarine eruption first detected on 2011 October 10, and located at about 2 km SW of La Restinga, southernmost village of El Hierro Island. The eruption ceased on 2012 March 5, after the volcanic tremor signals persistently weakened through 2012 February. However, the seismic activity did not end with the eruption, as several other seismic crises followed. The seismic episodes presented a characteristic pattern: over a few days the number and magnitude of seismic event increased persistently, culminating in seismic events severe enough to be felt all over the island. Those crises occurred in 2011 November, 2012 June and September, 2012 December to 2013 January and in 2013 March-April. In all cases the seismic unrest was preceded by significant deformations measured on the island's surface that continued during the whole episode. Analysis of the available GPS and seismic data suggests that several magma displacement processes occurred at depth from the beginning of the unrest. The first main magma movement or `injection' culminated with the 2011 October submarine eruption. A model combining the geometry of the magma injection process and the variations in seismic energy release has allowed successful forecasting of the new-vent opening.
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Sea birds as proxies of marine habitats and food webs in the western Aleutian Arc
Springer, Alan M.; Piatt, John F.; Van Vliet, Gus B.
1996-01-01
We propose that ocean conditions of the Near Islands in the western Aleutian Arc mimic those of the shallow continental shelf of the eastern Bering Sea to the extent that the marine community, including assemblages of forage fishes and their avian predators, has distinctly coastal characteristics. In contrast, marine avifauna and their prey at neighbouring Buldir Island are distinctly oceanic. For example, at the Near Islands, the ratio of thick-billed to common murres, Vria lomvia and U. aalge, is low and black-legged kittiwakes, Rissa tridactyla, but not red-legged kittiwakes, R. brevirostris, nest there. Diets of murres and kittiwakes are dominated by sand lance, Ammodytes hexapterus, an abundant coastal species. At Buldir Island, thick-billed murres greatly outnumber common murres, red-legged kittiwakes and black-legged kittiwakes are both abundant, and diets of the birds consist primarily of oceanic squid and lantern-fish (Myctophidae). This mesoscale difference in food webs is apparently a consequence of the local physiography. A broad escarpment on the Near physiographic block creates a comparatively expansive, shallow, shelflike habitat around the Near Islands, where a pelagic community typical of coastal regions flourishes. Buldir Island is the only emergent feature of the Buldir physiographic block, with little shallow water surrounding it and, apparently, little opportunity for other than oceanic species to exist. Patterns in the distribution of fishes, and thus of sea birds, throughout the Aleutian Islands might be largely explained by the presence or absence of shelf-like habitat and the relationship between physical environments and food webs. In the larger context of fisheries oceanography, this model for the Aleutian Islands improves our ability to interpret physical and biological heterogeneity in the ocean and its relationship to regional community dynamics and trends in the abundance and productivity of individual species at higher trophic levels.
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The 1997 eruption of Okmok Volcano, Alaska: A synthesis of remotely sensed imagery
Patrick, M.R.; Dehn, J.; Papp, K.R.; Lu, Z.; Dean, K.; Moxey, L.; Izbekov, P.; Guritz, R.
2003-01-01
Okmok Volcano, in the eastern Aleutian Islands, erupted in February and March of 1997 producing a 6-km-long lava flow and low-level ash plumes. This caldera is one of the most active in the Aleutian Arc, and is now the focus of international multidisciplinary studies. A synthesis of remotely sensed data (AirSAR, derived DEMs, Landsat MSS and ETM+ 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 were used to create a 5-m resolution DEM mosaic of Okmok Volcano. AVHRR nighttime imagery has been analyzed between February 13 and April 11, 1997. Landsat imagery and SAR data recorded prior to and after the eruption allowed us to accurately determine the extent of the new flow. The flow was first observed on February 13 without precursory thermal anomalies. At this time, the flow was a large single lobe flowing north. According to AVHRR Band 3 and 4 radiance data and ground observations, the first lobe continued growing until mid to late March, while a second, smaller lobe began to form sometime between March 11 and 12. This is based on a jump in the thermal and volumetric flux determined from the imagery, and the physical size of the thermal anomalies. Total radiance values waned after March 26, indicating lava effusion had ended and a cooling crust was growing. The total area (8.9 km2), thickness (up to 50 m) and volume (1.54×108 m3) of the new lava flow were determined by combining observations from SAR, Landsat ETM+, and AirSAR DEM data. While the first lobe of the flow ponded in a pre-eruption depression, our data suggest the second lobe was volume-limited. 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 methods to monitor potentially dangerous ones.
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Pacific Basin tsunami hazards associated with mass flows in the Aleutian arc of Alaska
Waythomas, Christopher F.; Watts, Philip; Shi, Fengyan; Kirby, James T.
2009-01-01
We analyze mass-flow tsunami generation for selected areas within the Aleutian arc of Alaska using results from numerical simulation of hypothetical but plausible mass-flow sources such as submarine landslides and volcanic debris avalanches. The Aleutian arc consists of a chain of volcanic mountains, volcanic islands, and submarine canyons, surrounded by a low-relief continental shelf above about 1000–2000 m water depth. Parts of the arc are fragmented into a series of fault-bounded blocks, tens to hundreds of kilometers in length, and separated from one another by distinctive fault-controlled canyons that are roughly normal to the arc axis. The canyons are natural regions for the accumulation and conveyance of sediment derived from glacial and volcanic processes. The volcanic islands in the region include a number of historically active volcanoes and some possess geological evidence for large-scale sector collapse into the sea. Large scale mass-flow deposits have not been mapped on the seafloor south of the Aleutian Islands, in part because most of the area has never been examined at the resolution required to identify such features, and in part because of the complex nature of erosional and depositional processes. Extensive submarine landslide deposits and debris flows are known on the north side of the arc and are common in similar settings elsewhere and thus they likely exist on the trench slope south of the Aleutian Islands. Because the Aleutian arc is surrounded by deep, open ocean, mass flows of unconsolidated debris that originate either as submarine landslides or as volcanic debris avalanches entering the sea may be potential tsunami sources. To test this hypothesis we present a series of numerical simulations of submarine mass-flow initiated tsunamis from eight different source areas. We consider four submarine mass flows originating in submarine canyons and four flows that evolve from submarine landslides on the trench slope. The flows have lengths
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Coccidia of Aleutian Canada geese
Greiner, E.C.; Forrester, Donald J.; Carpenter, J.W.; Yparraguirre, D.R.
1981-01-01
Fecal samples from 122 captive and 130 free-ranging Aleutian Canada geese (Branta canadensis leucopareia) were examined for oocysts of coccidia. Freeranging geese sampled on the spring staging ground near Crescent City, California were infected with Eimeria hermani, E. truncata, E. magnalabia, E. fulva, E. clarkei and Tyzzeria parvula. Except for E. clarkei, the same species of coccidia were found in geese on their breeding grounds in Alaska. Most of the coccidial infections in captive geese from Amchitka Island, Alaska and Patuxent Wildlife Research Center, Maryland, consisted of Tyzzeria.
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Hair methylmercury levels of mummies of the Aleutian Islands, Alaska
DOE Office of Scientific and Technical Information (OSTI.GOV)
Egeland, G.M.; Ponce, Rafael; Bloom, Nicolas S.
2009-04-15
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).more » 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.« less
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NASA Astrophysics Data System (ADS)
Cai, Y.; Kelemen, P. B.; Goldstein, S. L.; Yogodzinski, G. M.; Hemming, S. R.; Rioux, M. E.; Cooperdock, E. H. G.
2016-12-01
On average, arc volcanics are compositionally different from the bulk continental crust. The relatively little known plutonic part of intra-oceanic arcs is more similar to continental crust, and may play a significant role for understanding continental crust formation. Our pilot study [1] demonstrated that in the central and eastern Aleutian islands, predominantly tholeiitic Quaternary volcanic rocks have statistically different Pb-Nd-Sr-Hf isotopic signatures than predominantly calc-alkaline Miocene and older plutonic rocks, showing that these plutonics and volcanics were derived from compositionally different sources. However, studies of older volcanics are needed to determine whether (1) there was a change in magma chemistry in the central and eastern Aleutian arc between the Miocene and the present-day, or (2) coeval plutonics and volcanics are compositionally different, and formed by different processes. For example, silica- and water-rich calc-alkaline magmas may preferentially stall and form plutons after extensive degassing and rapid viscosity increase in the mid-crust, while silica- and water-poor tholeiitic magmas tend to erupt at the surface. Here we report new geochronological and geochemical results on samples collected during the 2015 GeoPRISMS shared logistics field campaign. We collected more than 500 volcanic and plutonic samples from Unalaska, Umnak and Atka islands, including pillow lavas, sills, and larger plutons. A subset of 50 samples has been analyzed for major and trace element chemistry, Pb-Nd-Sr-Hf isotopes, and Ar-Ar geochronology. So far,40Ar/39Ar cooling dates measured for the volcanics span a wide range, from zero to 35 Ma, which is comparable to the age distribution of the plutons ( 9 Ma to 39 Ma) from these islands. The forthcoming, combined geochronology and geochemistry of coeval plutonics and volcanics will contribute to our understanding of the connections between arc magmatism and continental crust formation. [1] Cai et al
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NASA Astrophysics Data System (ADS)
Wade, J. A.; Plank, T.; Stern, R.; Hilton, D.; Fischer, T. P.; Moore, R.; Trusdell, F.; Sako, M.
2003-12-01
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
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2011 volcanic activity in Alaska: summary of events and response of the Alaska Volcano Observatory
McGimsey, Robert G.; Maharrey, J. Zebulon; Neal, Christina A.
2014-01-01
The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, and volcanic unrest at or near three separate volcanic centers in Alaska during 2011. The year was highlighted by the unrest and eruption of Cleveland Volcano in the central Aleutian Islands. AVO annual summaries no longer report on activity at Russian volcanoes.
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NASA Astrophysics Data System (ADS)
Pedrazzi, Dario; Martí, Joan; Geyer, Adelina
2013-07-01
The tuff cone of El Golfo on the western coast of Lanzarote (Canary Islands) is a typical hydrovolcanic edifice. Along with other edifices of the same age, it was constructed along a fracture oriented NEE-SWW that coincides with the main structural trend of recent volcanism in this part of the island. We conducted a detailed stratigraphic study of the succession of deposits present in this tuff cone and here interpret them in light of the depositional processes and eruptive dynamics that we were able to infer. The eruptive sequence is represented by a succession of pyroclastic deposits, most of which were emplaced by flow, plus a number of air-fall deposits and ballistic blocks and bombs. We distinguished five different eruptive/depositional stages on the basis of differences in inferred current flow regimes and fragmentation efficiencies represented by the resulting deposits; the different stages may be related to variations in the explosive energy. Eight lithofacies were identified based on sedimentary discontinuities, grain size, components, variations in primary laminations and bedforms. The volcanic edifice was constructed very rapidly around the vent, and this is inferred to have controlled the amount of water that was able to enter the eruption conduit. The sedimentological characteristics of the deposits and the nature and distribution of palagonitic alteration suggest that most of the pyroclastic succession in El Golfo was deposited in a subaerial environment. This type of hydrovolcanic explosive activity is common in the coastal zones of Lanzarote and the other Canary Islands and is one of the main potential hazards that could threaten the human population of this archipelago. Detailed studies of these hydrovolcanic eruptions such as the one we present here can help volcanologists understand the hazards that this type of eruption can generate and provide essential information for undertaking risk assessment in similar volcanic environments.
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NASA Astrophysics Data System (ADS)
White, James D. L.; Schmincke, Hans-Ulrich
1999-12-01
In 1949, a 5-week-long magmatic and phreatomagmatic eruption took place along the active volcanic ridge of La Palma (Canary Islands). Two vents, Duraznero and Hoyo Negro, produced significant pyroclastic deposits. The eruption began from Duraznero vent, which produced a series of deposits with an upward decrease in accidental fragments and increase in fluidal ash and spatter, together inferred to indicate decreasing phreatomagmatic interaction. Hoyo Negro erupted over a 2-week period, producing a variety of pyroclastic density currents and ballistic blocks and bombs. Hoyo Negro erupted within and modified an older crater having high walls on the northern to southeastern edges. Southwestern to western margins of the crater lay 50 to 100 m lower. Strongly contrasting deposits in the different sectors (N-SE vs. SW-W) were formed as a result of interaction between topography, weak eruptive columns and stratified pyroclastic density currents. Tephra ring deposits are thicker and coarser-grained than upper rim deposits formed along the higher edges of the crater, and beyond the crater margin, valley-confined deposits are thicker than more thinly bedded mantling deposits on higher topography. These differences indicate that the impact zone for the bulk of the collapsing, tephra-laden column lay within the crater and that the high crater walls inhibited escape of pyroclastic density currents to the north and east. The impact zone lay outside the low SW-W rims, however, thus allowing stratified pyroclastic density currents to move freely away from the crater in those directions, depositing thin sections (<30 cm) of well-bedded ash (mantling deposits) on ridges and thicker sections (1-3 m) of structureless ash beds in valleys and small basins. Such segregation of dense pyroclastic currents from more dilute ones at the crater wall is likely to be common for small eruptions from pre-existing craters and is an important factor to be taken into account in volcanic hazards
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Jicha, Brian R.; Coombs, Michelle L.; Calvert, Andrew T.; Singer, Brad S.
2012-01-01
We used geologic mapping and geochemical data augmented by 40Ar/39Ar dating to establish an eruptive chronology for the Tanaga volcanic cluster in the western Aleutian arc. The Tanaga volcanic cluster is unique in comparison to other central and western Aleutian volcanoes in that it consists of three closely spaced, active, volumetrically significant edifices (Sajaka, Tanaga, and Takawangha), the eruptive products of which have unusually high K2O contents. Thirty-five new 40Ar/39Ar ages obtained in two different laboratories constrain the duration of Pleistocene–Holocene subaerial volcanism to younger than 295 ka. The eruptive activity has been mostly continuous for the last 150 k.y., unlike most other well-characterized arc volcanoes, which tend to grow in discrete pulses. More than half of the analyzed Tanaga volcanic cluster lavas are basalts that have erupted throughout the lifetime of the cluster, although a considerable amount of basaltic andesite and basaltic trachyandesite has also been produced since 200 ka. Major- and trace-element variations suggest that magmas from Sajaka and Tanaga volcanoes are likely to have crystallized pyroxene and/or amphibole at greater depths than the older Takawangha magmas, which experienced a larger percentage of plagioclase-dominated fractionation at shallower depths. Magma output from Takawangha has declined over the last 86 k.y. At ca. 19 ka, the focus of magma flux shifted to the west beneath Tanaga and Sajaka volcanoes, where hotter, more mafic magma erupted.
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Gómez-Letona, M; Arístegui, J; Ramos, A G; Montero, M F; Coca, J
2018-03-16
The eruption of a submarine volcano south of El Hierro Island (Canary Islands) in October 2011 led to major physical and chemical changes in the local environment. Large amounts of nutrients were found at specific depths in the water column above the volcano associated with suboxic layers resulting from the oxidation of reduced chemical species expelled during the eruptive phase. It has been suggested that the fertilization with these compounds enabled the rapid restoration of the ecosystem in the marine reserve south of the island once the volcanic activity ceased, although no biological evidence for this has been provided yet. To test the biological fertilization hypothesis on the pelagic ecosystem, we studied the evolution and variability in chlorophyll a, from in situ and remote sensing data, combined with information on phytoplankton and bacterial community structure during and after the eruptive episode. Remote sensing and in situ data revealed that no phytoplankton bloom took place neither during nor after the eruptive episode. We hypothesize that the fertilization by the volcano did not have an effect in the phytoplankton community due to the strong dilution of macro- and micronutrients caused by the efficient renewal of ambient waters in the zone.
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NASA Astrophysics Data System (ADS)
Sobradelo, R.; Martí, J.; Mendoza-Rosas, A. T.; Gómez, G.
2012-04-01
The Canary Islands are an active volcanic region densely populated and visited by several millions of tourists every year. Nearly twenty eruptions have been reported through written chronicles in the last 600 years, suggesting that the probability of a new eruption in the near future is far from zero. This shows the importance of assessing and monitoring the volcanic hazard of the region in order to reduce and manage its potential volcanic risk, and ultimately contribute to the design of appropriate preparedness plans. Hence, the probabilistic analysis of the volcanic eruption time series for the Canary Islands is an essential step for the assessment of volcanic hazard and risk in the area. Such a series describes complex processes involving different types of eruptions over different time scales. Here we propose a statistical method for calculating the probabilities of future eruptions which is most appropriate given the nature of the documented historical eruptive data. We first characterise the eruptions by their magnitudes, and then carry out a preliminary analysis of the data to establish the requirements for the statistical method. Past studies in eruptive time series used conventional statistics and treated the series as an homogeneous process. In this paper, we will use a method that accounts for the time-dependence of the series and includes rare or extreme events, in the form of few data of large eruptions, since these data require special methods of analysis. Hence, we will use a statistical method from extreme value theory. In particular, we will apply a non-homogeneous Poisson process to the historical eruptive data of the Canary Islands to estimate the probability of having at least one volcanic event of a magnitude greater than one in the upcoming years. Shortly after the publication of this method an eruption in the island of El Hierro took place for the first time in historical times, supporting our method and contributing towards the validation of
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Near-field survey of the 1946 Aleutian tsunami on Unimak and Sanak Islands
Okal, E.A.; Plafker, G.; Synolakis, C.E.; Borrero, J.C.
2003-01-01
The 1946 Aleutian earthquake stands out among tsunamigenic events because it generated both very high run-up near the earthquake source region and a destructive trans-Pacific tsunami. We obtained new data on the distribution of its tsunami in the near field along south-facing coasts between Unimak Pass on the west and Sanak Island on the east by measuring the height of driftwood and beach materials that were deposited by the tsunami above the extreme storm tide level. Our data indicate that (1) the highest measured run-up, which is at the Scotch Cap lighthouse, was 42 m above tide level or about 37 m above present storm tide elevation; (2) run-up along the rugged coast from Scotch Cap for 12 km northwest to Sennett Point is 12-18 m, and for 30 km east of Scotch Cap to Cape Lutke it is 24-42 m; (3) run-up along the broad lowlands bordering Unimak Bight is 10-20 m, and in-undation is locally more than 2 km; (5) run-up diminishes to 8 m or less at the southeast corner of Unimak Island; (6) no evidence was found for run-up above present storm tides (about 4-5 m above MLLW) on the Ikatan Peninsula or areas along the coast to the west; and (7) run-up above storm tide level in the Sanak Island group is restricted to southwest-facing coasts of Sanak, Long, and Clifford Islands, where it is continuous and locally up to 24 m high. Generation of the tsunami by one or more major earthquake-triggered submarine landslides near the shelf edge south of Unimak Island seems to be the only viable mechanism to account for the data on wave arrival time, run-up heights, and distribution, as well as for unconfirmed anecdotal reports of local postquake increases in water depth and diminished bottom-fisheries productivity. A preliminary hydrodynamic simulation of the local tsunami propagation and run-up using a dipolar model of a possible landslide off Davidson Bank provides an acceptable fit to the characteristics of the distribution of local run-up, with a value at 34 m at the Scotch Cap
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Magmatic sill intrusions beneath El Hierro Island following the 2011-2012 submarine eruption
NASA Astrophysics Data System (ADS)
Benito-Saz, María Á.; Sigmundsson, Freysteinn; Parks, Michelle M.; García-Cañada, Laura; Domínguez Cerdeña, Itahiza
2016-04-01
El Hierro, the most southwestern island of Canary Islands, Spain, is a volcano rising from around 3600 m above the ocean floor and up to of 1500 m above sea level. A submarine eruption occurred off the coast of El Hierro in 2011-2012, which was the only confirmed eruption in the last ~ 600 years. Activity continued after the end of the eruption with six magmatic intrusions occurring between 2012-2014. Each of these intrusions was characterized by hundreds of earthquakes and 3-19 centimeters of observed ground deformation. Ground displacements at ten continuous GPS sites were initially inverted to determine the optimal source parameters (location, geometry, volume/pressure change) that best define these intrusions from a geodetic point of view. Each intrusive period appears to be associated with the formation of a separate sill, with inferred volumes between 0.02 - 0.3 km3. SAR images from the Canadian RADARSAT-2 satellite and the Italian Space Agency COSMO-SkyMed constellation have been used to produce high-resolution detailed maps of line-of-sight displacements for each of these intrusions. These data have been combined with the continuous GPS observations and a joint inversion undertaken to gain further constraints on the optimal source parameters for each of these separate intrusive events. The recorded activity helps to understand how an oceanic intraplate volcanic island grows through repeated sill intrusions; well documented by seismic, GPS and InSAR observations in the case of the El Hierro activity.
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NASA Astrophysics Data System (ADS)
Troll, V. R.; Klügel, A.; Longpré, M.-A.; Burchardt, S.; Deegan, F. M.; Carracedo, J. C.; Wiesmaier, S.; Kueppers, U.; Dahren, B.; Blythe, L. S.; Hansteen, T. H.; Freda, C.; Budd, D. A.; Jolis, E. M.; Jonsson, E.; Meade, F. C.; Harris, C.; Berg, S. E.; Mancini, L.; Polacci, M.; Pedroza, K.
2012-03-01
A submarine eruption started off the south coast of El Hierro, Canary Islands, on 10 October 2011 and continues at the time of this writing (February 2012). In the first days of the event, peculiar eruption products were found floating on the sea surface, drifting for long distances from the eruption site. These specimens, which have in the meantime been termed "restingolites" (after the close-by village of La Restinga), appeared as black volcanic "bombs" that exhibit cores of white and porous pumice-like material. Since their brief appearance, the nature and origin of these "floating stones" has been vigorously debated among researchers, with important implications for the interpretation of the hazard potential of the ongoing eruption. The "restingolites" have been proposed to be either (i) juvenile high-silica magma (e.g. rhyolite), (ii) remelted magmatic material (trachyte), (iii) altered volcanic rock, or (iv) reheated hyaloclastites or zeolite from the submarine slopes of El Hierro. Here, we provide evidence that supports yet a different conclusion. We have analysed the textures and compositions of representative "restingolites" and compared the results to previous work on similar rocks found in the Canary Islands. Based on their high-silica content, the lack of igneous trace element signatures, the presence of remnant quartz crystals, jasper fragments and carbonate as well as wollastonite (derived from thermal overprint of carbonate) and their relatively high oxygen isotope values, we conclude that "restingolites" are in fact xenoliths from pre-island sedimentary layers that were picked up and heated by the ascending magma, causing them to partially melt and vesiculate. As they are closely resembling pumice in appearance, but are xenolithic in origin, we refer to these rocks as "xeno-pumice". The El Hierro xeno-pumices hence represent messengers from depth that help us to understand the interaction between ascending magma and crustal lithologies beneath the
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Catalog of the historically active volcanoes of Alaska
Miller, T.P.; McGimsey, R.G.; Richter, D.H.; Riehle, J.R.; Nye, C.J.; Yount, M.E.; Dumoulin, Julie A.
1998-01-01
Alaska hosts within its borders over 80 major volcanic centers that have erupted during Holocene time (< 10,000 years). At least 29 of these volcanic centers (table 1) had historical eruptions and 12 additional volcanic centers may have had historical eruptions. Historical in Alaska generally means the period since 1760 when explorers, travelers, and inhabitants kept written records. These 41 volcanic centers have been the source for >265 eruptions reported from Alaska volcanoes. With the exception of Wrangell volcano, all the centers are in, or near, the Aleutian volcanic arc, which extends 2500 km from Hayes volcano 145 km west of Anchorage in the Alaska-Aleutian Range to Buldir Island in the western Aleutian Islands (fig. 1). The volcanic arc, a subduction-related feature associated with underthrusting of the Pacific plate beneath the North American plate is divided between oceanic island arc and continental margin segments, the boundary occurring at about 165° W longitude (fig. 1). An additional 7 volcanic centers in the Aleutian arc (table 2; fig. 1 A) have active fumarole fields but no reported historical eruptions.This report discusses the location, physiography and structure, eruptive history, and geology of those volcanoes in Alaska that have experienced one or more eruptions that have been recorded in the written history (i.e., in historical time). It is part of the group of catalogs entitled Catalogue of Active Volcanoes of the World published beginning in 1951 under the auspices of the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI). A knowledge of the information contained in such catalogs aids in understanding the type and scale of activity that might be expected during a particular eruption, the hazards the eruption may pose, and even the prediction of eruptions. The catalog will thus be of value not only to the inhabitants of Alaska but to government agencies concerned with emergency response, air traffic
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The 2014 eruptions of Pavlof Volcano, Alaska
Waythomas, Christopher F.; Haney, Matthew M.; Wallace, Kristi; Cameron, Cheryl E.; Schneider, David J.
2017-12-22
Pavlof Volcano is one of the most frequently active volcanoes in the Aleutian Island arc, having erupted more than 40 times since observations were first recorded in the early 1800s . The volcano is located on the Alaska Peninsula (lat 55.4173° N, long 161.8937° W), near Izembek National Wildlife Refuge. The towns and villages closest to the volcano are Cold Bay, Nelson Lagoon, Sand Point, and King Cove, which are all within 90 kilometers (km) of the volcano (fig. 1). Pavlof is a symmetrically shaped stratocone that is 2,518 meters (m) high, and has about 2,300 m of relief. The volcano supports a cover of glacial ice and perennial snow roughly 2 to 4 cubic kilometers (km3) in volume, which is mantled by variable amounts of tephra fall, rockfall debris, and pyroclastic-flow deposits produced during historical eruptions. Typical Pavlof eruptions are characterized by moderate amounts of ash emission, lava fountaining, spatter-fed lava flows, explosions, and the accumulation of unstable mounds of spatter on the upper flanks of the volcano. The accumulation and subsequent collapse of spatter piles on the upper flanks of the volcano creates hot granular avalanches, which erode and melt snow and ice, and thereby generate watery debris-flow and hyperconcentrated-flow lahars. Seismic instruments were first installed on Pavlof Volcano in the early 1970s, and since then eruptive episodes have been better characterized and specific processes have been documented with greater certainty. The application of remote sensing techniques, including the use of infrasound data, has also aided the study of more recent eruptions. Although Pavlof Volcano is located in a remote part of Alaska, it is visible from Cold Bay, Sand Point, and Nelson Lagoon, making distal observations of eruptive activity possible, weather permitting. A busy air-travel corridor that is utilized by a numerous transcontinental and regional air carriers passes near Pavlof Volcano. The frequency of air travel
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The Eggøyan eruption in 1732, Jan Mayen; an emerging ankaramitic surtseyjan type eruption
NASA Astrophysics Data System (ADS)
Gjerlxw, E.; Hoskuldsson, A.; Pedersen, R. B.; Thorseth, I. H.
2011-12-01
Jan Mayen is a volcanic island situated at 71°N and 8°W. The Island is build up of two main edifices, Sør Jan and Nord Jan (Beerenberg). Volcanic activity on the island is little known, and however at least 4 eruptions are documented at the island since early 18th century. An expedition to the island in summer 2011 reveals that first of these eruptions formed the tuffcone Eggøyan in 1732 AD. The Eggøyan tuffcone is situated at the north east foot of Beerenberg volcano, about 2.5 km from the coastline marked by Valberget. The tuffcone is about 1.5 km in diameter and emerges from about 35 m depth to reach the altitude of at least 217 m above sea level. Pre Eggøyan Lava flows on the sandy coast west of the edifice are covered by up to 1.6 m of ash some 3 km from the vent. These lava flows have been suggested to be formed in the 1732 eruption and the 1818 eruption of Jan Mayen. However, they are covered with the Eggøyan tephra and thus considerable older. Volcanic tephra from the Eggøyan eruption forms the uppermost tephra layer on the Eastern flanks of Beerenberg. Contemporary description of the 1732 eruption, tell of violent explosive eruption at the east side of Beerenberg observed by German whalers for 28 hours, while sailing past the island in May that year. A Dutch wailer group arriving to the island in June that year, report fine ash covering the island in such a way they sink up to mid leg into it. Our study this summer shows that the only eruption these descriptions can report to are the Eggøyan eruption, dating it precisely to the spring 1732. The eruptive products are made up of frothy glass and ol, cpx and opx crystals, which characterize the flank eruptions of Beerenberg. In this presentation we shall present first results of intense fragmentation of deep gas rich ankaramitic magma from the Jan Mayen are and its interaction with seawater in shallow coastal settings.
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NASA Astrophysics Data System (ADS)
Di Roberto, A.; Bertagnini, A.; Del Carlo, P.; Meletlidis, S.; Pompilio, M.
2016-12-01
The last eruption on Tenerife (Canary Islands, Spain) started on 18 November 1909 from the El Chinyero vent on the northwestern Santiago rift. This fissural eruption was well documented by scientists and eyewitnesses, but there is a lack of data on the high-energy phase that produced the most significant emissions of ash and lapilli at the onset of the eruption. Here, we review historical documents (e.g. newspapers, dispatches, telegrams); eyewitness accounts and scientific reports were reviewed from a volcanological perspective and integrated with data from the analysis of deposit features, allowing an accurate reconstruction of the eruption and its dynamics. The 1909 eruption of Chinyero was fed by a compositionally discrete magma batch that ascended rapidly within the crust, producing rather violent pulsating Strombolian explosive activity in the early phases of the eruption. This activity produced a ca. 80 m high scoria cone and heavy fallout of lapilli and ash over the entire northern sector of the island of Tenerife. The energy of explosive activity waned after 3 days, giving way to the weak Strombolian explosive activity that contributed to a lesser extent to the buildup of the pyroclastic pile. Eruptions such as those from the Chinyero vent in 1909 are representative of rift activity on Tenerife and constitute a volcanic hazard for present-day inhabitants.
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NASA Astrophysics Data System (ADS)
Padrón, Eleazar; Hernández, Pedro A.; Melián, Gladys V.; Barrancos, José; Padilla, Germán; Pérez, Nemesio M.; Dionis, Samara; Rodríguez, Fátima; Asensio-Ramos, María; Calvo, David
2015-04-01
El Hierro Island (278 km2) is the youngest and the SW-most of the Canary Islands. On July 16, 2011, a seismic-volcanic crisis started with the occurrence of more than 11,900 seismic events and significant deformation along the island, culminating with the eruption onset in October 12. Since at El Hierro Islands there are not any surface geothermal manifestation (fumaroles, etc), we have focused our studies on soil degassing surveys. Between July 2011 to March 2012, seventeen diffuse CO2 and He emissions soil gas surveys were undertaken at El Hierro volcanic system (600 observation sites) with the aim to investigate the relationship between their temporal variations and the volcanic activity (Padrón et al., 2013; Melián et al., 2014). Based on the diffuse He/CO2 emission ratio, a sharp increase before the eruption onset was observed, reaching the maximum value on September 26 (6.8×10-5), sixteen days before the occurrence of the eruption. This increase coincided with an increase in seismic energy release during the volcanic unrest and occurred together with an increase on the 3He/4He isotopic ratio in groundwaters from a well in El Hierro Island (Padrón et al., 2013; from 2-3 RA to 7.2 RA where RA = 3He/4He ratio in air), one month prior to the eruption onset. Early degassing of new gas-rich magma batch at depth could explain the observed increase on the He/CO2 ratio, causing a preferential partitioning of CO2 in the gas phase with respect to the He, due to the lower solubility of CO2 than that of He in basaltic magmas. During the eruptive period (October 2011-March 2012) the prevalence of a magmatic CO2-dominated component is evident, as indicated by the generally lower He/CO2 ratios and high 3He/4He values (Padrón et al., 2013). The onset of the submarine eruption might have produced a sudden release of volcanic gases, and consequently, a decrease in the volcanic gas pressure of the magma bodies moving beneath the island, reflected by a drastic decrease in
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NASA Astrophysics Data System (ADS)
Fraile-Nuez, E.; Santana-Casiano, J.; Gonzalez-Davila, M.
2013-12-01
On October 10 2011 an underwater eruption gave rise to a novel shallow submarine volcano south of the island of El Hierro, Canary Islands, Spain. During the eruption large quantities of mantle-derived gases, solutes and heat were released into the surrounding waters. In order to monitor the impact of the eruption on the marine ecosystem, periodic multidisciplinary cruises were carried out. Here, we present an initial report of the extreme physical-chemical perturbations caused by this event, comprising thermal changes, water acidification, deoxygenation and metal-enrichment, which resulted in significant alterations to the activity and composition of local plankton communities. Our findings highlight the potential role of this eruptive process as a natural ecosystem-scale experiment for the study of extreme effects of global change stressors on marine environments. (A) Natural color composite from the MEdium Resolution Imaging Spectrometer (MERIS) instrument aboard ENVISAT Satellite (European Space Agency), (November 9, 2011 at 14:45 UTC). Remote sensing data have been used to monitor the evolution of the volcanic emissions, playing a fundamental role during field cruises in guiding the Spanish government oceanographic vessel to the appropriate sampling areas. The inset map shows the position of Canary Islands west of Africa and the study area (solid white box). (B) Location of the stations carried out from November 2011 to February 2012 at El Hierro. Black lines denote transects A-B and C-D.
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New constraints on subduction inputs and volatile outputs along the Aleutian Arc
NASA Astrophysics Data System (ADS)
Lopez, T. M.; Fischer, T. P.; Plank, T. A.; Rizzo, A. L.; Rasmussen, D. J.; Cottrell, E.; Werner, C. A.; Kern, C.; Ilanko, T.; Buff, L.; Andrys, J.; Kelley, K. A.
2017-12-01
Volatile cycling drives volcanism in subduction zone settings. At arcs, volatiles can originate from the subducted slab, mantle wedge and/or crust. Each region has characteristic isotopic signatures, which can be used to fingerprint volatile provenance. We speculate that differences in subduction parameters, such as convergence angle, plate coupling and subducted sediment fluxes, may lead to differences in volatile provenance, which may in turn influence volcanic eruption style and frequency. Here we combine updated constraints on subduction inputs and volatile outputs to provide new insights into volatile cycling within the Aleutian Arc. The high proportion of organic carbon (80-100% to total carbon) in sediments subducting at the Aleutian trench stands out globally and predicts a light carbon isotopic composition of recycled volcanic fluids. We assess volatile outputs on volcanic timescales and along the arc by combining carbon (C), nitrogen (N) and helium (He) isotopic compositions of volcanic gases and new analyses of He and, where possible, C isotopes in olivine-hosted fluid inclusions. From our preliminary isotopic analyses of volcanic gases, we find a greater proportion of mantle-derived volatiles released from the Western segment of the Aleutian Arc (>40% mantle) compared with other volcanic arcs around the world (<30% mantle), where volatiles are sourced primarily from subducted or upper crustal carbonates. This trend may be due to the oblique convergence and low subducted sediment input in this region. The Aleutian Arc also exhibits among the lightest carbon isotope ratios of arcs worldwide (δ13C = -10 to -15‰), especially in the central part of the arc, where organic-bearing terrigneous sediment fills the trench and the convergence rate is high. New constraints on subduction inputs and outputs presented here will help discriminate between upper crustal and subducted carbon sources, and provide further insights into volatile cycling and subduction
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Chronology of the 2014 volcanic eruption on the island of Fogo, Cape Verde
NASA Astrophysics Data System (ADS)
Silva, Sónia; Cardoso, Nadir; Alfama, Vera; Cabral, Jeremias; Semedo, Helio; Pérez, Nemesio M.; Dionis, Samara; Hernández, Pedro A.; Barrancos, José; Melián, Gladys V.; Pereira, José Manuel; Rodríguez, Fátima
2015-04-01
Twenty seven historical eruptions have ocurred at Fogo Island since its discovery and settlement (Ribeiro, 1960; Torres et al., 1997). This summary covers the events of the 27th eruption, which started on November 23, 2014, in Cha das Caldeiras, Fogo Island, along a NNE-SSW fissure on the east flank of the 1995 Pico Novo vent with the appearance of four eruptive vents and emissions of gases, pyroclastic rocks and lava. The eruptive column reached an estimated altitude of 6000 m, with aa lavas spilled over and ash fall in Cha das Caldeiras and other locations in the islands of Fogo and Brava (which lies 17km from Fogo). The Hawaiian style fissural stage originated about seven craters with gas and lava emission, that formed two lava flows of aa and pahoehoe style who started the destruction of Portela village, with average speeds of 1-3 meters/hour to 8-10 meters/hour with faster paces up to 1 meter/3 minutes, with thicknesses ranging between 1.5 meters to 10 meters, and temperatures of around 800 ° C. The Strombolian stage, gave rise to a main crater (from the coalescence of small craters) and three small craters or emmision vents, which released aa lava flows with development of lava fronts from one or two lava tubes at the base of the volcanic cone which also reached maximum lengths of 300 to 500 meters at estimated speeds of 20-30 meters/minute to 8-10 meters/minute, that destroyed the Portela and Bangaeira villages. Loud explosions and strong rumbling was also heard at the eruption site. A pahoehoe lava flow developed to the Ilhéu de Losna site, at an average speed of 1 meter/2minutes and a width of about 3 m which was divided into two fronts (north and south of this location) having buried all crop fields (vineyards and other crops) and some houses. The eruption is ongoing in the main vent, with the emission of gases and ash (dark color fumaroles), scorias, spatter and ballistics up to 30-40 feet high, forming eruptive columns with height of 200-1000 meters
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NASA Astrophysics Data System (ADS)
Troll, V. R.; Klügel, A.; Longpré, M.-A.; Burchardt, S.; Deegan, F. M.; Carracedo, J. C.; Wiesmaier, S.; Kueppers, U.; Dahren, B.; Blythe, L. S.; Hansteen, T.; Freda, C.; Budd, D. A.; Jolis, E. M.; Jonsson, E.; Meade, F.; Berg, S.; Mancini, L.; Polacci, M.
2011-12-01
The eruption that started off the south coast of El Hierro, Canary Islands, in October 2011 has emitted intriguing eruption products found floating in the sea. These specimens appeared as floating volcanic "bombs" that have in the meantime been termed "restingolites" (after the close-by village of La Restinga) and exhibit cores of white and porous pumice-like material. Currently the nature and origin of these "floating stones" is vigorously debated among researchers, with important implications for the interpretation of the hazard potential of the ongoing eruption. The "restingolites" have been proposed to be either (i) juvenile high-silica magma (e.g. rhyolite), (ii) remelted magmatic material (trachyte), (iii) altered volcanic rock, or (iv) reheated hyaloclastites or zeolite from the submarine slopes of El Hierro. Here, we provide evidence that supports yet a different conclusion. We have collected and analysed the structure and composition of samples and compared the results to previous work on similar rocks found in the archipelago. Based on their high silica content, the lack of igneous trace element signatures, and the presence of remnant quartz crystals, jasper fragments and carbonate relicts, we conclude that "restingolites" are in fact xenoliths from pre-island sedimentary rocks that were picked up and heated by the ascending magma causing them to partially melt and vesiculate. They hence represent messengers from depth that help us to understand the interaction between ascending magma and crustal lithologies in the Canary Islands as well as in similar Atlantic islands that rest on sediment/covered ocean crust (e.g. Cape Verdes, Azores). The occurrence of these "restingolites" does therefore not indicate the presence of an explosive high-silica magma that is involved in the ongoing eruption.
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Miles, A. Keith; Ricca, Mark A.; Anthony, Robert G.; Estes, James A.
2009-01-01
Organochlorines were examined in liver and stable isotopes in muscle of fishes from the western Aleutian Islands, Alaska, in relation to islands or locations affected by military occupation. Pacific cod (Gadus macrocephalus), Pacific halibut (Hippoglossus stenolepis), and rock greenling (Hexagrammos lagocephalus) were collected from nearshore waters at contemporary (decommissioned) and historical (World War II) military locations, as well as at reference locations. Total (Σ) polychlorinated biphenyls (PCBs) dominated the suite of organochlorine groups (ΣDDTs, Σchlordane cyclodienes, Σother cyclodienes, and Σchlorinated benzenes and cyclohexanes) detected in fishes at all locations, followed by ΣDDTs and Σchlordanes; dichlorodiphenyldi-chloroethylene (p,p′DDE) composed 52 to 66% of ΣDDTs by species. Organochlorine concentrations were higher or similar in cod compared to halibut and lowest in greenling; they were among the highest for fishes in Arctic or near Arctic waters. Organochlorine group concentrations varied among species and locations, but ΣPCB concentrations in all species were consistently higher at military locations than at reference locations. Moreover, all organochlorine group concentrations were higher in halibut from military locations than those from reference locations. A wide range of molecular weight organochlorines was detected at all locations, which implied regional or long-range transport and deposition, as well as local point-source contamination. Furthermore, a preponderance of higher-chlorinated PCB congeners in fishes from contemporary military islands implied recent exposure. Concentrations in all organochlorine groups increased with δ15N enrichment in fishes, and analyses of residual variation provided further evidence of different sources of ΣPCBs and p,p′DDE among species and locations.
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Burger, Joanna; Gochfeld, Michael; Kosson, David S; Powers, Charles W; Friedlander, Barry; Eichelberger, John; Barnes, David; Duffy, Lawrence K; Jewett, Stephen C; Volz, Conrad D
2005-05-01
With the ending of the Cold War, the US Department of Energy is responsible for the remediation of radioactive waste and disposal of land no longer needed for nuclear material production or related national security missions. The task of characterizing the hazards and risks from radionuclides is necessary for assuring the protection of health of humans and the environment. This is a particularly daunting task for those sites that had underground testing of nuclear weapons, where the radioactive contamination is currently inaccessible. Herein we report on the development of a Science Plan to characterize the physical and biological marine environment around Amchitka Island in the Aleutian chain of Alaska, where three underground nuclear tests were conducted (1965-1971). Information on the ecology, geology, and current radionuclide levels in biota, water, and sediment is necessary for evaluating possible current contamination and to serve as a baseline for developing a plan to ensure human and ecosystem health in perpetuity. Other information required includes identifying the location of the salt water/fresh water interface where migration to the ocean might occur in the future and determining groundwater recharge balances, as well as assessing other physical/geological features of Amchitka near the test sites. The Science Plan is needed to address the confusing and conflicting information available to the public about radionuclide risks from underground nuclear blasts in the late 1960s and early 1970s, as well as the potential for volcanic or seismic activity to disrupt shot cavities or accelerate migration of radionuclides into the sea. Developing a Science Plan involved agreement among regulators and other stakeholders, assignment of the task to the Consortium for Risk Evaluation with Stakeholder Participation, and development of a consensus Science Plan that dealt with contentious scientific issues. Involvement of the regulators (State of Alaska), resource
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NASA Astrophysics Data System (ADS)
Nishimura, T.; Ozawa, S.; Murakami, M.; Sagiya, T.; Yarai, H.; Tada, T.; Kaidzu, M.
2001-12-01
Miyakejima is located in the northern part of the Izu Islands lying along the boundary between the Pacific plate and the Philippine Sea plate. Miyakejima volcano erupted on Miyakejima is located in the northern part of the Izu Islands which are a chain of volcanoes lying along the boundary between the Pacific plate and the Philippine Sea plate. Miyakejima volcano erupted on June 27, 2000 after the quiescence of 17 years. First eruption is a small submarine eruption 1.5km off the western coast of Miyakejima. Subsequently, several summit eruptions as tephra ejecta occurred in July and August 2000. The summit collapsed just after the first summit eruption and a caldera was formed for 40 days. Collapsed volume and erupted volume are estimated to be 0.6km3 and 0.02km3, respectively. In September 2000, the collapse caldera started emitting a large amount of volcanic gasses. A peak amount of degassing SO2 is ~70000 ton/day in the period from October to December 2000. Amount of volcanic gas is decreasing gradually and is 15000 ton/day (SO2 ) now. However, it is still larger than other active volcanoes. Permanent GPS data reveals the spatial pattern and time evolution of ground deformation. Inflation of Miyakejima was observed by continuous GPS and leveling before the 2000 eruption. The observed displacements associated with the 2000 eruption show radial pattern suggesting shrinking of the island and subsidence. This pattern continues for 14 months from July 2000. Though the rate of crustal deformation is almost constant from July to August 2000, it is decreasing exponentially with a time constant of ~150days from September 2000. We assumed a point deflation source and inverted the observed displacement to estimate parameters of the point source. Volume decrease and depth of the deflation source is 0.12km3 and 4.2km from July to August 2000. We interpret that it is the squeezing of magma from a magma chamber of Miyakejima volcano. The displacement observed in neighbor
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Palaeomagnetic constraints on the age of Lomo Negro volcanic eruption (El Hierro, Canary Islands)
NASA Astrophysics Data System (ADS)
Villasante-Marcos, Víctor; Pavón-Carrasco, Francisco Javier
2014-12-01
A palaeomagnetic study has been carried out in 29 cores drilled at six different sites from the volcanic products of Lomo Negro eruption (El Hierro, Canary Islands, Spain). Systematic thermal and alternating field demagnetization of the samples' natural remanent magnetization revealed a northward, stable palaeomagnetic direction similar in all the samples. Rock magnetic experiments indicate that this palaeomagnetic component is carried by a mixture of high-Ti and low-Ti titanomagnetite crystals typical of basaltic lithologies that have experienced a significant degree of oxyexsolution during subaerial cooling. The well constrained palaeomagnetic direction of Lomo Negro lavas was used to perform a palaeomagnetic dating of the volcanic event, using the SHA.DIF.14k global geomagnetic model restricted for the last 3000 yr. It can be unambiguously concluded that Lomo Negro eruption occurred well before the previously proposed date of 1793 AD, with three different age ranges being statistically possible during the last 3 ka: 115 BC-7 AD, 410-626 AD and 1499-1602 AD. The calibration of a previously published non-calibrated 14C dating suggests a XVI c. date for Lomo Negro eruption. This conclusion leaves open the possibility that the seismic crisis occurred at El Hierro in 1793 AD was related to an intrusive magmatic event that either did not reach the surface or either culminated in an unregistered submarine eruption similar to the one occurred in 2011-2012 at the southern off-shore ridge of the island.
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Earth observation views of the Aleutian Mt. Range taken during STS-99
2000-03-16
STS099-749-089 (11-22 February 2000) ---As evidenced by this 70mm frame from the Space Shuttle Endeavour, the Alaska Peninsula and Aleutian Islands form a long arc that intervenes between the Bering Sea and the northern Pacific Ocean. This view is of the snowy south coast of the peninsula, from Chignik Bay and Cape Kumliun (on the triangular peninsula) northeastward to Chiginagak Bay and David Island. Port Heiden is the darker area of little ice on the north coast. Within the rim of the Aniakchak volcanic crater (4,450 feet at highest point) the frozen waters of Surprise Lake are visible. The North American and Pacific tectonic plates are converging in this region at a rate of about 5 centimeters a year. The Pacific plate descends beneath North America, producing a deep trench along the south coast; the Aleutian Trench reaches depths greater than 25,000 ft. In such regions (subduction zones) volcanoes form on the overriding plate -- the North American plate in this instance; Aniakchak is one of the many young volcanoes in this arc.
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Bond, Alexander L; Jones, Ian L; Williams, Jeffrey C; Byrd, G Vernon
2010-08-01
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. Copyright 2010 Elsevier Ltd. All rights reserved.
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NASA Astrophysics Data System (ADS)
Kato, T.; Matsushima, T.; Nakada, S.; Watanabe, T.; Tabei, T.; Camacho, J. T.; Chong, R.
2003-12-01
A GPS observation project in the Northern Mariana Islands started in 1992 by a joint team of Japan, US and Saipan, CNMI. We have repeated surveys in the area for several times until 2003. Previous results until 1999 showed clear evidence of back arc spreading at the Mariana Trough with velocities of 4-6cm/yr with respect to the Philippine Sea plate. There was no significant volcanic activity in this time periods. Anatahan Island erupted about three months after the latest resurvey of January 2003. In order to investigate crustal deformations of the island related to this eruption, we established a permanent site in Anatahan (ANAT). The site is located about 7km WNW of the active crater in the eastern caldera. Solar panel and a lead battery are used for power and a small PC is used for automatic data archive. A special stainless pillar was designed to set up right above the pre-occupied benchmark. We also established a new permanent site in Saipan on the roof of EMO (EMO1). For a tie to the old site in Saipan, we conducted a survey at MPLC site that have been repeatedly occupied. For a preliminary analysis, we used data sets of 1994, 1998, 1999 and January and July of 2003 for a baseline MPLC - ANAT. The obtained results suggest that Anatahan has linearly drifted to northwest relative to Saipan at least until January 2003 with a rate of about 6.5mm/yr. There was no clear long-term vertical motion of Anatahan Island until January 2003. Comparison of position of ANAT relative to MPLC between January and July, 2003 suggests about 19cm subsidence of the island. Horizontal displacement may not be significant though a few centimeters of offset toward north could be visible. Large subsidence may be due to the spouting of magma. In order to monitor the crustal deformation during the volcanic activity, we are continuing GPS tracking at the established two permanent sites for a while.
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NASA Astrophysics Data System (ADS)
Meletlidis, Stavros; Di Roberto, Alessio; Domínguez Cerdeña, Itahiza; Pompilio, Massimo; García-Cañada, Laura; Bertagnini, Antonella; Benito Saz, Maria Angeles; Del Carlo, Paola; Sainz-Maza Aparicio, Sergio; Lopez Moreno, Carmen; Moure García, David
2014-05-01
A shallow submarine eruption took place on 10th October 2011, about 1.8 km off the coast of La Restinga, a small village located in El Hierro (Canary Islands, Spain). The eruption lasted for about four months and ended by early March 2012. The eruption was preceded by an unrest episode that initiated about three months before, in July 2011, and characterized by more than 10,000 localized earthquakes accompanied by up to 5 cm of vertical ground deformation. In the Canary Islands, this event represents the first case of an eruption that was monitored since the unrest to the end by the monitoring network of IGN (Instituto Geográfico National), providing a huge dataset that includes geophysical (seismic, magnetic and gravimetric), geodetic, geochemistry and petrological data. In this work we use the seismic, GPS and gravity records collected by IGN along with the petrological data derived from the study of various lava balloons, scoriaceous fragments and ash.Geophysical and geochemical monitoring tools provide a variety of information that need to be interpreted in terms of magma movement and/or interaction of magma with host rocks. We present a model, based on this data, which describes the intrusion and ascent of the magma. According to this model, a major intrusion beneath and around preexisting high-density magmatic bodies, localized in the central sector of the island, led to an eruption in the Southern sector of the island. After a failed attempt to reach the surface, while various dykes were emplaced, through a low fractured area in the Central and Northern parts of the island, the ascending magma finally found its way in the submarine area of La Restinga, in the South rift zone, at a depth of 350 m below sea level. Feeding of the eruption was achieved by the ascension of an important volume of material from the upper mantle which was emplaced near the crust-mantle boundary. However, the very energetic post-eruptive unrests - we had five episodes up today with
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Eruption of Alaska volcano breaks historic pattern
Larsen, Jessica; Neal, Christina A.; Webley, Peter; Freymueller, Jeff; Haney, Matthew; McNutt, Stephen; Schneider, David; Prejean, Stephanie; Schaefer, Janet; Wessels, Rick L.
2009-01-01
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.
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Eruption of Alaska Volcano Breaks Historic Pattern
NASA Astrophysics Data System (ADS)
Larsen, Jessica; Neal, Christina; Webley, Peter; Freymueller, Jeff; Haney, Matthew; McNutt, Stephen; Schneider, David; Prejean, Stephanie; Schaefer, Janet; Wessels, Rick
2009-05-01
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.
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NASA Astrophysics Data System (ADS)
Sohn, Y. K.
1995-02-01
Detailed mapping of Tok Island, located in the middle of the East Sea (Sea of Japan), along with lithofacies analysis and K-Ar age determinations reveal that the island is of early to late Pliocene age and comprises eight rock units: Trachyte I, Unit P-I, Unit P-II, Trachyandesite (2.7±0.1 Ma), Unit P-III, Trachyte II (2.7±0.1 Ma), Trachyte III (2.5±0.1 Ma) and dikes in ascending stratigraphic order. Trachyte I is a mixture of coherent trachytic lavas and breccias that are interpreted to be subaqueous lavas and related hyaloclastites. Unit P-I comprises massive and inversely graded basaltic breccias which resulted from subaerial gain flows and subaqueous debris flows. A basalt clast from the unit, derived from below Trachyte I, has an age of 4.6±0.4 Ma. Unit P-II is composed of graded and stratified lapilli tuffs with the characteristics of proximal pyroclastic surge deposits. The Trachyandesite is a massive subaerial lava ponded in a volcano-tectonic depression, probably a summit crater. A pyroclastic sequence containing flattened scoria clasts (Unit P-III) and a small volume subaerial lava (Trachyte II) occur above the Trachyandesite, suggesting resumption of pyroclastic activity and lava effusion. Afterwards, shallow intrusion of magma occurred, producing Trachyte III and trachyte dikes. The eight rock units provide an example of the changing eruptive and depositional processes and resultant succession of lithofacies as a seamount builds up above sea level to form an island volcano: Trachyte I represents a wholly subaqueous and effusive stage; Units P-I and P-II represent Surtseyan and Taalian eruptive phases during an explosive transitional (subaqueous to emergent) stage; and the other rock units represent later subaerial effusive and explosive stages. Reconstruction of volcano morphology suggests that the island is a remnant of the south-western crater rim of a volcano the vent of which lies several hundred meters to the north-east.
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Seasonal and distributional patterns of seabirds along the Aleutian Archipelago
Renner, M.; Hunt, G.L.; Piatt, John F.; Byrd, G.V.
2008-01-01
The Aleutian Archipelago is of global importance to seabirds during the northern summer, but little is known about seabird use of these waters during winter. We compare summer and winter abundances of seabirds around 3 islands: Buldir in the western, Kasatochi in the central, and Aiktak in the eastern Aleutians. The density of combined seabird biomass in nearshore marine waters was higher in summer than in winter at Buldir and Kasatochi, but was higher in winter at Aiktak, despite the departure of abundant migratory species. Comparing foraging guilds, we found that only piscivores increased at the western and central sites in winter, whereas at the eastern site several planktivorous species increased as well. The only planktivore remaining in winter at the central and western sites in densities comparable to summer densities was whiskered auklet Aethia pygmaea. Crested auklet Aethia cristatella and thick-billed murre Uria lomvia showed the greatest proportional winter increase at the eastern site. The seasonal patterns of the seabird communities suggest a winter breakdown of the copepod-based food web in the central and western parts of the archipelago, and a system that remains rich in euphausiids in the eastern Aleutians. We suggest that in winter crested auklets take the trophic role that short-tailed shearwaters Puffinus tenuirostris occupy during summer. We hypothesize that advection of euphausiids in the Aleutian North Slope Current is important for supporting the high biomass of planktivores that occupy the Unimak Pass region on a year-round basis. ?? Inter-Research 2008.
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NASA Astrophysics Data System (ADS)
Ueda, Hideki; Nagai, Masashi; Tanada, Toshikazu
2018-03-01
On Ioto Island (Iwo-jima), 44 phreatic eruptions have been recorded since 1889, when people began to settle there. Four of these eruptions, after the beginning of continuous observation by seismometers in 1976, were accompanied by intense seismic activity and rapid crustal deformation beforehand. Other eruptions on Ioto were without obvious crustal activities. In this paper, we discuss the mechanisms of phreatic eruptions on Ioto. Regular geodetic surveys and continuous GNSS observations show that Ioto intermittently uplifts at an abnormally high rate. All of the four eruptions accompanied by the precursors took place during intermittent uplifts. The crustal deformation before and after one of these eruptions revealed that a sill-like deformation source in the shallow part of Motoyama rapidly inflated before and deflated after the beginning of the eruption. From the results of a seismic array and a borehole survey, it is estimated that there is a layer of lava at a depth of about 100-200 m, and there is a tuff layer about 200-500 m beneath it. The eruptions accompanied by the precursors probably occurred due to abrupt boiling of hot water in hydrothermal reservoirs in the tuff layer, sealed by the lava layer and triggered by intermittent uplift. For the eruptions without precursors, the hydrothermal systems are weakly sealed by clay or probably occurred on the same principle as a geyser because phreatic eruptions had occurred beforehand and hydrostatic pressure is applied to the hydrothermal reservoirs.
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Analysis of Ballistic Blocks and Eruption History of Montaña Colorada, Lanzarote, Canary Islands
NASA Astrophysics Data System (ADS)
Semple Domagall, A. M.; Kobs-Nawotniak, S. E.
2015-12-01
From September 1730 to April 1736, more than 30 vents formed along a ~18 km long rift on the island of Lanzarote in the Canary Islands. Little actual data of these eruptions exist with the exception of court records and the diary of a priest from Yaiza. Previous research has broken this five and a half year period into 5 major eruptive phases (Carracedo et al., 1992).Montaña Colorada - a 150 m-tall, 600 m wide cinder cone - is the final vent associated with this eruption, and likely formed in <10 days (Carracedo et al., 1992). A'a lava flows (including one >10 km long), large spatter clasts, spatter within the cinder cone, and a minor ash blanket are associated with this vent. These are typical of the 1730-1736 vents on Lanzarote. Unique to Montaña Colorada is the presence of a solidified lava pond within the vent, and an array of large (~1-4 m diameter), dense (2800 kg/m3), basaltic blocks roughly 500-1000 m from the vent. Additionally, peridotite nodules (up to 15 cm diameter) are found both within the lava flows and the tephra: the nodules are seen only here and at the, nearby, first vent associated with the eruptions. Lava flows, possibly from a fissure vent, started the eruption at Montaña Colorada: an effusion rate of 74.9 ± 25.9 m3s-1 is estimated for the 10.6 km-long, peridotite-bearing, flow, giving an emplacement time of ~1-3 days. As the eruption rate decreased, agglutinated spatter collected closer to the vent with loose tephra distally forming the main cinder cone. Towards the end of the eruption it appears the vent was filled with a lava pond, which breached to the north. The large, dense, blocks surrounding Montaña Colorada are here suggested to be the result of a transient explosion of a previous lava pond that occupied the vent. A lack of peridotite nodules or vesicles would be consistent with basalt that had pooled within the vent for some time. Eruption velocities on the order of 70-300 ms-1 are calculated for these blocks.
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Fertility of the early post-eruptive surfaces of Kasatochi Island volcano
Michaelson, G. J.; Wang, Bronwen; Ping, C. L.
2016-01-01
In the four years after the 2008 eruption and burial of Kasatochi Island volcano, erosion and the return of bird activity have resulted in new and altered land surfaces and initiation of ecosystem recovery. We examined fertility characteristics of the recently deposited pyroclastic surfaces, patches of legacy pre-eruptive surface soil (LS), and a post-eruptive surface with recent bird roosting activity. Pyroclastic materials were found lacking in N, but P, K, and other macronutrients were in sufficient supply for plants. Erosion and leaching are moving mobile P and Fe downslope to deposition fan areas. Legacy soil patches that currently support plants have available-N at levels (10–22 mg N kg-1) similar to those added by birds in a recent bird roosting area. Roosting increased surface available N from <1 mg N kg-1 in the new pyroclastic surfaces to up to 42 mg N kg-1 and increased soil biological respiration of CO2 from essentially zero to a level about 40% that of the LS surface. Laboratory plant growth trials using Lupinus nootkatensis and Leymus mollis indicated that the influence of eroded and redeposited LS in amounts as little as 10% by volume mixed with new pyroclastic materials could aid plant recovery by supplying vital N and soil biota to plants as propagules are introduced to the new surface. Erosion-exposure of fertile pre-eruptive soils and erosion-mixing of pre-eruptive soils with newly erupted materials, along with inputs of nutrients from bird activities, each will exert significant influences on the surface fertility and recovery pattern of the new post-eruptive Kasatochi volcano. For this environment, these influences could help to speed recovery of a more diverse plant community by providing N (LS and bird inputs) as alternatives to relying most heavily on N-fixing plants to build soil fertility.
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Sea otter population declines in the Aleutian Archipelago
Doroff, Angela M.; Estes, James A.; Tinker, M. Tim; Burn, Douglas M.; Evans, Thomas J.
2003-01-01
Sea otter (Enhydra lutris) populations were exploited to near extinction and began to recover after the cessation of commercial hunting in 1911. Remnant colonies of sea otters in the Aleutian archipelago were among the first to recover; they continued to increase through the 1980s but declined abruptly during the 1990s. We conducted an aerial survey of the Aleutian archipelago in 2000 and compared results with similar surveys conducted in 1965 and 1992. The number of sea otters counted decreased by 75% between 1965 and 2000; 88% for islands at equilibrial density in 1965. The population decline likely began in the mid-1980s and declined at a rate of 17.5%/year in the 1990s. The minimal population estimate was 8,742 sea otters in 2000. The population declined to a uniformly low density in the archipelago, suggesting a common and geographically widespread cause. These data are in general agreement with the hypothesis of increased predation on sea otters. These data chronicle one of the most widespread and precipitous population declines for a mammalian carnivore in recorded history.
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NASA Astrophysics Data System (ADS)
Ozawa, S.; Miyazaki, S.; Nishimura, T.; Murakami, M.; Kaidzu, M.; Imakiire, T.; Ji, X.
2004-02-01
Analysis of Global Positioning System data shows shrinkage of Miyake Island and the widening between Nijima and Kozu Islands during the period of the Miyake island volcanic activity and the ensuing Izu islands earthquakes in 2000. The estimated time evolution of a model consisting of a dike, creeping faults, and a Mogi source suggests that a crack opening on Miyake Island occurred immediately after the start of the seismic activities on 26 June and ended within several days at the west coast of Miyake Island. After the seabed eruption on 27 June, magma migrated from Miyake Island to Kozu and Nijima Islands within several days. The estimated volume of intruded magma totals around 1.2 × 109 m3. Associated with the magma intrusion between Miyake and Kozu Islands, left-lateral and right-lateral creep motions occurred in regions off the west coast of Miyake Island and near Kozu Island. The accumulated moment energy is equivalent to an earthquake of Mw 6.6 and 6.6 for right-lateral and left-lateral creeping faults, respectively. The estimated magma chamber continued deflation beneath the southwestern part of Miyake Island from 26 June, totaling around 0.12 × 109 m3 in volume change, in addition to the collapse volume of 0.6 × 109 m3 at the summit of Mount Oyama on Miyake Island. The volume change on Miyake Island can be compensated by the migrated magma toward Kozu Island from the deflation source beneath Miyake Island. The deflation speed of the magma chamber beneath Miyake Island decreased and increased before and after the eruption of 14-15 July and 18 August, suggesting a change in balance of mass influx and draining out rate of the magma chamber.
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Nelson, Alan R.; Briggs, Richard; Dura, Tina; Engelhart, Simon E.; Gelfenbaum, Guy; Bradley, Lee-Ann; Forman, S.L.; Vane, Christopher H.; Kelley, K.A.
2015-01-01
cannot estimate source earthquake locations or magnitudes for most tsunami-deposited beds. We infer that no more than 3 of the 23 possible tsunamis beds at both sites were deposited following upper plate faulting or submarine landslides independent of megathrust earthquakes. If so, the Semidi segment of the Alaska-Aleutian megathrust near Chirikof Island probably sent high tsunamis southward every 180–270 yr for at least the past 3500 yr.
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Pallister, J.S.; Trusdell, F.A.; Brownfield, I.K.; Siems, D.F.; Budahn, J.R.; Sutley, S.F.
2005-01-01
Stratigraphic and field data are used in conjunction with textural and chemical evidence (including data from scanning electron microscope, electron microprobe, X-ray fluorescence, X-ray diffraction, and instrumental neutron activation analysis) to establish that the 2003 eruption of Anatahan volcano was mainly phreatomagmatic, dominated by explosive interaction of homogeneous composition low-viscosity crystal-poor andesite magma with water. The hydromagmatic mode of eruption contributed to the significant height of initial eruptive columns and to the excavation and eruption of altered rock debris from the sub-volcanic hydrothermal system. Volatile contents of glass inclusions in equilibrium phenocrysts less abundances of these constituents in matrix glass times the estimated mass of juvenile magma indicate minimum emissions of 19 kt SO2 and 13 kt Cl. This petrologic estimate of SO2 emission is an order-of-magnitude less than an estimate from TOMS. Similarly, inferred magma volumes from the petrologic data are an order of magnitude greater than those modeled from deformation data. Both discrepancies indicate additional sources of volatiles, likely derived from a separate fluid phase in the magma. The paucity of near-source volcanic-tectonic earthquakes preceding the eruption, and the dominance of sustained long-period tremor are attributed to the ease of ascent of the hot low-viscosity andesite, followed by a shallow phreatomagmatic mode of eruption. Phreatomagmatic eruptions are probably more common at emergent tropical island volcanoes, where shallow fresh-water lenses occur at near-sea-level vents. These relations suggest that phreatomagmatic explosions contributed to the formation of many of the near-sea-level craters and possibly even to the small calderas at the other Mariana islands.
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Chadwick, W.W.; Howard, K.A.
1991-01-01
Maps of the eruptive vents on the active shield volcanoes of Fernandina and Isabela islands, Galapagos, made from aerial photographs, display a distinctive pattern that consists of circumferential eruptive fissures around the summit calderas and radial fissures lower on the flanks. On some volcano flanks either circumferential or radial eruptions have been dominant in recent time. The location of circumferential vents outside the calderas is independent of caldera-related normal faults. The eruptive fissures are the surface expression of dike emplacement, and the dike orientations are interpreted to be controlled by the state of stress in the volcano. Very few subaerial volcanoes display a pattern of fissures similar to that of the Galapagos volcanoes. Some seamounts and shield volcanoes on Mars morphologically resemble the Galapagos volcanoes, but more specific evidence is needed to determine if they also share common structure and eruptive style. ?? 1991 Springer-Verlag.
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Ariza, Alejandro; Kaartvedt, Stein; Røstad, Anders; Garijo, Juan Carlos; Arístegui, Javier; Fraile-Nuez, Eugenio; Hernández-León, Santiago
2014-01-01
The submarine volcano eruption off El Hierro Island (Canary Islands) on 10 October 2011 promoted dramatic perturbation of the water column leading to changes in the distribution of pelagic fauna. To study the response of the scattering biota, we combined acoustic data with hydrographic profiles and concurrent sea surface turbidity indexes from satellite imagery. We also monitored changes in the plankton and nekton communities through the eruptive and post-eruptive phases. Decrease of oxygen, acidification, rising temperature and deposition of chemicals in shallow waters resulted in a reduction of epipelagic stocks and a disruption of diel vertical migration (nocturnal ascent) of mesopelagic organisms. Furthermore, decreased light levels at depth caused by extinction in the volcanic plume resulted in a significant shallowing of the deep acoustic scattering layer. Once the eruption ceased, the distribution and abundances of the pelagic biota returned to baseline levels. There was no evidence of a volcano-induced bloom in the plankton community. PMID:25047077
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Ariza, Alejandro; Kaartvedt, Stein; Røstad, Anders; Garijo, Juan Carlos; Arístegui, Javier; Fraile-Nuez, Eugenio; Hernández-León, Santiago
2014-01-01
The submarine volcano eruption off El Hierro Island (Canary Islands) on 10 October 2011 promoted dramatic perturbation of the water column leading to changes in the distribution of pelagic fauna. To study the response of the scattering biota, we combined acoustic data with hydrographic profiles and concurrent sea surface turbidity indexes from satellite imagery. We also monitored changes in the plankton and nekton communities through the eruptive and post-eruptive phases. Decrease of oxygen, acidification, rising temperature and deposition of chemicals in shallow waters resulted in a reduction of epipelagic stocks and a disruption of diel vertical migration (nocturnal ascent) of mesopelagic organisms. Furthermore, decreased light levels at depth caused by extinction in the volcanic plume resulted in a significant shallowing of the deep acoustic scattering layer. Once the eruption ceased, the distribution and abundances of the pelagic biota returned to baseline levels. There was no evidence of a volcano-induced bloom in the plankton community.
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Nannofossils in 2011 El Hierro eruptive products reinstate plume model for Canary Islands
NASA Astrophysics Data System (ADS)
Zaczek, Kirsten; Troll, Valentin R.; Cachao, Mario; Ferreira, Jorge; Deegan, Frances M.; Carracedo, Juan Carlos; Soler, Vicente; Meade, Fiona C.; Burchardt, Steffi
2015-01-01
The origin and life cycle of ocean islands have been debated since the early days of Geology. In the case of the Canary archipelago, its proximity to the Atlas orogen led to initial fracture-controlled models for island genesis, while later workers cited a Miocene-Quaternary east-west age-progression to support an underlying mantle-plume. The recent discovery of submarine Cretaceous volcanic rocks near the westernmost island of El Hierro now questions this systematic age-progression within the archipelago. If a mantle-plume is indeed responsible for the Canaries, the onshore volcanic age-progression should be complemented by progressively younger pre-island sedimentary strata towards the west, however, direct age constraints for the westernmost pre-island sediments are lacking. Here we report on new age data obtained from calcareous nannofossils in sedimentary xenoliths erupted during the 2011 El Hierro events, which date the sub-island sedimentary rocks to between late Cretaceous and Pliocene in age. This age-range includes substantially younger pre-volcanic sedimentary rocks than the Jurassic to Miocene strata known from the older eastern islands and now reinstate the mantle-plume hypothesis as the most plausible explanation for Canary volcanism. The recently discovered Cretaceous submarine volcanic rocks in the region are, in turn, part of an older, fracture-related tectonic episode.
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Nannofossils in 2011 El Hierro eruptive products reinstate plume model for Canary Islands.
Zaczek, Kirsten; Troll, Valentin R; Cachao, Mario; Ferreira, Jorge; Deegan, Frances M; Carracedo, Juan Carlos; Soler, Vicente; Meade, Fiona C; Burchardt, Steffi
2015-01-22
The origin and life cycle of ocean islands have been debated since the early days of Geology. In the case of the Canary archipelago, its proximity to the Atlas orogen led to initial fracture-controlled models for island genesis, while later workers cited a Miocene-Quaternary east-west age-progression to support an underlying mantle-plume. The recent discovery of submarine Cretaceous volcanic rocks near the westernmost island of El Hierro now questions this systematic age-progression within the archipelago. If a mantle-plume is indeed responsible for the Canaries, the onshore volcanic age-progression should be complemented by progressively younger pre-island sedimentary strata towards the west, however, direct age constraints for the westernmost pre-island sediments are lacking. Here we report on new age data obtained from calcareous nannofossils in sedimentary xenoliths erupted during the 2011 El Hierro events, which date the sub-island sedimentary rocks to between late Cretaceous and Pliocene in age. This age-range includes substantially younger pre-volcanic sedimentary rocks than the Jurassic to Miocene strata known from the older eastern islands and now reinstate the mantle-plume hypothesis as the most plausible explanation for Canary volcanism. The recently discovered Cretaceous submarine volcanic rocks in the region are, in turn, part of an older, fracture-related tectonic episode.
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NASA Astrophysics Data System (ADS)
de Vita, Sandro; Foresta Martin, Franco
2017-04-01
This research focuses on the effects of the last eruption at Ustica (Suthern Tyrrhenian Sea, Italy), which formed the Falconiera tuff-cone at around 130 ka BP in the north-eastern tip of the island. This eruption was mainly explosive and phreatomagmatic, and emplaced a series of pyroclastic surge beds that formed an asymmetric tuff cone. This is the most easily recognizable volcanic edifice on Ustica, although its north-eastern sector has been partially eroded. A section of the feeding conduit is exposed northward, and is composed of lavas that fed the last stages of the eruption characterized by an intracrateric lava lake and a Strombolian scoria-fallout deposit. The eruption occurred during Upper Pleistocene Marine Isotopic Substage 5.5, a warm period characterized by a high sea-level stand (6±3 m above the present sea level in stable areas) and the diffusion of subtropical flora and fauna across the Mediterranean sea. This eruption slightly modified the morphology of Ustica, but impacted both marine and terrestrial environments, burying beach deposits rich in mollusk shells (i.e. Strombus bubonius, Conus testudinarius, Brachidontes puniceus), colonies of corals (Cladocora caespitosa) and subaerial plants (Chamaerops humilis). These organisms, found in some cases in their life position, along with other lines of evidence, provide information on the palaeogeography of this sector of the island at the time of the eruption, and on the local impact of this event on the environment.
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A Reappraisal of Seismicity and Eruptions of Pantelleria Island and the Sicily Channel (Italy)
NASA Astrophysics Data System (ADS)
Spampinato, Salvatore; Ursino, Andrea; Barbano, Maria Serafina; Pirrotta, Claudia; Rapisarda, Salvatore; Larocca, Graziano; Platania, Pier Raffaele
2017-07-01
Three main tectonic depressions (the Pantelleria, Linosa and Malta troughs), the expression of a continental rift, characterize the Sicily Channel, a region with recent volcanic activity attested by the Pantelleria and Linosa volcanic islands, as well as numerous seamounts. To understand the seismic and eruptive behaviour of this area, we compare historical and instrumental seismicity retrieved from catalogues with recordings from both a mobile seismic network and a permanent station deployed at Pantelleria. A review of historical eruptions affecting the Sicily Channel is also presented. Recent instrumental seismicity shows that the Sicily Channel is characterized by a low level of seismicity, with earthquakes mainly occurring as isolated events, rather than swarms as observed during the few documented eruptive periods. The results of a seismic survey in 2006-2007, as well as the signals recorded by a permanent station in 2010-2014, enable stating that also Pantelleria is characterized by a very low rate of seismicity. The available, though scant, historical information suggests a recurrence time of about a century for the volcanic activity and that eruptions are usually preceded by seismic swarms. In the only historical known eruption of Pantelleria, in addition to shocks, uplifting and increasing fumarole activity, were observed. Notwithstanding the lack of eruptions over the past century, and despite the low recent seismic rate, we believe that the geophysical monitoring of the Sicily Channel needs improving since it is an area of potentially high seismic and volcanic hazard given the presence of several active submarine eruptive centres.
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Subsidence at Kiska volcano, Western Aleutians, detected by satellite radar interferometry
Lu, Z.; Masterlark, Timothy; Power, J.; Dzurisin, D.; Wicks, Charles
2002-01-01
Sequential interferometric synthetic aperture radar images of Kiska, the westernmost historically active volcano in the Aleutian arc, show that a circular area about 3 km in diameter centered near the summit subsided by as much as 10 cm from 1995 to 2001, mostly during 1999 and 2000. An elastic Mogi-type deformation model suggests that the source is within 1 km of the surface. Based on the shallow source depth, the copious amounts of steam during recent eruptions, and recent field reports of vigorous steaming and persistent ground shaking near the summit area, we attribute the subsidence to decreased pore-fluid pressure within a shallow hydrothermal system beneath the summit area.
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NASA Astrophysics Data System (ADS)
Pedrazzi, D.; Marti, J.; Geyer, A.
2012-04-01
The El Golfo tuff cone is an example of phreatomagmatic edifice, developed in the western coast of Lanzarote (Canary Islands). El Golfo, together with other edifices of the same age, is aligned along a fracture oriented NEE-SWW coinciding with the main lineation of the historic volcanism in this part of the island. In this contribution we present a detailed stratigraphic study of the succession of deposits and we interpret them in terms of depositional processes and eruptive dynamics. The eruptive sequence is exclusively represented by a succession of pyroclastic deposits, and we infer it according to variations in flow regime and the magma-water interaction. Several pyroclastic units were identified according to facies variations based on sedimentary discontinuities, grain size, components, variations in primary laminations and bedforms following the facies model proposed by Chough and Sohn (1990). The growth of the El Golfo tuff cone involved several stages based on variations in depositional processes. The edifice was constructed very rapidly around the vent controlling the amount of water that got access to the eruption conduit. Although the invariable phreatomagmatic character of most of the pyroclastic sequence, it is possible to deduce variations in the explosive energy, with a general increment upwards, according to the increase in the degree of fragmentation of pyroclasts, The absence of hyaloclastites, the nature of the palagonite alteration and the observed sedimentary structures, demonstrate the subaereal character of most of the deposits
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NASA Astrophysics Data System (ADS)
López, Carmen; Martí, Joan; Abella, Rafael; Tarraga, Marta
2014-07-01
The impossibility of observing magma migration inside the crust obliges us to rely on geophysical data and mathematical modelling to interpret precursors and to forecast volcanic eruptions. Of the geophysical signals that may be recorded before and during an eruption, deformation and seismicity are two of the most relevant as they are directly related to its dynamic. The final phase of the unrest episode that preceded the 2011-2012 eruption on El Hierro (Canary Islands) was characterized by local and accelerated deformation and seismic energy release indicating an increasing fracturing and a migration of the magma. Application of time varying fractal analysis to the seismic data and the characterization of the seismicity pattern and the strain and the stress rates allow us to identify different stages in the source mechanism and to infer the geometry of the path used by the magma and associated fluids to reach the Earth's surface. The results obtained illustrate the relevance of such studies to understanding volcanic unrest and the causes that govern the initiation of volcanic eruptions.
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49 CFR 71.12 - Hawaii-Aleutian zone.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 49 Transportation 1 2010-10-01 2010-10-01 false Hawaii-Aleutian zone. 71.12 Section 71.12 Transportation Office of the Secretary of Transportation STANDARD TIME ZONE BOUNDARIES § 71.12 Hawaii-Aleutian zone. The seventh zone, the Hawaii-Aleutian standard time zone, includes the entire State of Hawaii and...
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2014 volcanic activity in Alaska: Summary of events and response of the Alaska Volcano Observatory
Cameron, Cheryl E.; Dixon, James P.; Neal, Christina A.; Waythomas, Christopher F.; Schaefer, Janet R.; McGimsey, Robert G.
2017-09-07
The Alaska Volcano Observatory (AVO) responded to eruptions, possible eruptions, volcanic unrest or suspected unrest, and seismic events at 18 volcanic centers in Alaska during 2014. The most notable volcanic activity consisted of intermittent ash eruptions from long-active Cleveland and Shishaldin Volcanoes in the Aleutian Islands, and two eruptive episodes at Pavlof Volcano on the Alaska Peninsula. Semisopochnoi and Akutan volcanoes had seismic swarms, both likely the result of magmatic intrusion. The AVO also installed seismometers and infrasound instruments at Mount Cleveland during 2014.
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Man against volcano: The eruption on Heimaey, Vestmann Islands, Iceland
Williams, R.S.; Moore, J.G.
1976-01-01
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.
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NASA Astrophysics Data System (ADS)
Sheth, Hetu C.; Ray, Jyotiranjan S.; Bhutani, Rajneesh; Kumar, Alok; Smitha, R. S.
2009-11-01
Barren Island (India) is a relatively little studied, little known active volcano in the Andaman Sea, and the northernmost active volcano of the great Indonesian arc. The volcano is built of prehistoric (possibly late Pleistocene) lava flows (dominantly basalt and basaltic andesite, with minor andesite) intercalated with volcaniclastic deposits (tuff breccias, and ash beds deposited by pyroclastic falls and surges), which are exposed along a roughly circular caldera wall. There are indications of a complete phreatomagmatic tephra ring around the exposed base of the volcano. A polygenetic cinder cone has existed at the centre of the caldera and produced basalt-basaltic andesite aa and blocky aa lava flows, as well as tephra, during historic eruptions (1787-1832) and three recent eruptions (1991, 1994-95, 2005-06). The recent aa flows include a toothpaste aa flow, with tilted and overturned crustal slabs carried atop an aa core, as well as locally developed tumuli-like elliptical uplifts having corrugated crusts. Based on various evidence we infer that it belongs to either the 1991 or the 1994-95 eruptions. The volcano has recently (2008) begun yet another eruption, so far only of tephra. We make significantly different interpretations of several features of the volcano than previous workers. This study of the volcanology and eruptive styles of the Barren Island volcano lays the ground for detailed geochemical-isotopic and petrogenetic work, and provides clues to what the volcano can be expected to do in the future.
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Geyer, A; Marti, A; Giralt, S; Folch, A
2017-11-28
Ash emitted during explosive volcanic eruptions may disperse over vast areas of the globe posing a threat to human health and infrastructures and causing significant disruption to air traffic. In Antarctica, at least five volcanoes have reported historic activity. However, no attention has been paid to the potential socio-economic and environmental consequences of an ash-forming eruption occurring at high southern latitudes. This work shows how ash from Antarctic volcanoes may pose a higher threat than previously believed. As a case study, we evaluate the potential impacts of ash for a given eruption scenario from Deception Island, one of the most active volcanoes in Antarctica. Numerical simulations using the novel MMB-MONARCH-ASH model demonstrate that volcanic ash emitted from Antarctic volcanoes could potentially encircle the globe, leading to significant consequences for global aviation safety. Results obtained recall the need for performing proper hazard assessment on Antarctic volcanoes, and are crucial for understanding the patterns of ash distribution at high southern latitudes with strong implications for tephrostratigraphy, which is pivotal to synchronize palaeoclimatic records.
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Variations in Melt Generation and Migration along the Aleutian Arc (Invited)
NASA Astrophysics Data System (ADS)
Plank, T. A.; Van Keken, P. E.
2013-12-01
The generation and ascent of mantle melt beneath volcanic arcs sets the course for how magmas differentiate to form the continental crust and erupt explosively from volcanoes. Although the basic framework of melting at subduction zones is understood to involve the convective influx of hot mantle (Tp ≥ 1300°C) and advective transport of water-rich fluids from the subducting slab, the P-T paths that melts follow during melt generation and migration are still not well known. The Aleutian Arc provides an opportunity to explore the conditions of mantle melting in the context of volcanoes that span an unusually large range in the depth to the slab, from Seguam island, with among the shallowest depths to the slab worldwide (~65 km, [1]) to Bogoslof island, behind the main volcanic front and twice the depth to the slab (~130 km). Here we combine thermal models tuned to Aleutian subduction parameters [after 2] with petrological estimates of the T and P of mantle-melt equilibration, using a major element geothermometer [3] and estimates of H2O and fO2 from olivine-hosted melt inclusion measurements [4] for basaltic magmas from 6 volcanoes in the central Aleutians (Korovin, Seguam, Bogoslof, Pakushin, Akutan, Shishaldin). We find mantle-melt equilibration conditions to vary systematically as a function of the depth to the slab, from 30 km and 1220°C (for Seguam) to 60 km and 1300°C (for Bogoslof). Such shallow depths, which extend up to the Moho, define a region perched well above the hot core of the mantle wedge predicted from thermal models, even considering the shallow depths of slab-mantle coupling (< 60 km) required to supply hot mantle beneath Seguam. Thus, even though the greatest melt production will occur in the hot core of the wedge (50-100 km depth), melts apparently ascend and re-equilibrate in the shallowest mantle. Volcanoes that overlie the greatest depth to the slab, and lie furthest from the wedge corner, stall at greater depths (~60 km), at the base of
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NASA Astrophysics Data System (ADS)
Longpre, M. A.; Muller, J.; Beaudry, P.; Andronikides, A.; Felpeto, A.
2017-12-01
Since the 16th century, at least 13 volcanic eruptions have occurred in the Canary Islands that formed monogenetic cinder cones and lava flow fields: 2 on Lanzarote, 4 on Tenerife, 6 on La Palma, and 1 on the submarine flank of El Hierro. Here we present a comprehensive new dataset of tephra composition for all 13 eruptions, comprising major and trace element data for bulk rocks and matrix glasses, as well as vesicularity and crystallinity measurements. In addition, we compile available volcanological and petrological information for specific eruptions, including estimates of lava flow area and volume. All lapilli samples show a vesicularity of 40-50 vol% and a vesicle-free crystallinity (crystals ≥ 250 µm) of 5-15 vol%. Modal mineralogy varies significantly between samples, typically consisting of olivine ± clinopyroxene ± Fe-Ti oxide ± plagioclase ± amphibole in different proportions. All but 2 tephras have basanite-tephrite bulk rock compositions. Lapilli from vents of the AD 1730-1736 Timanfaya eruption, Lanzarote, largely are basaltic, whereas the AD 1798 Chahorra eruption, Tenerife, produced phonotephrite tephra. These results are in agreement with published bulk lava flow data. Unsurprisingly, glass compositions are more evolved than bulk rocks and MgOglass is weakly positively correlated to MgObulk (MgOglass = 0.30*MgObulk + 2.11, R2 = 0.54). Both bulk rocks and glasses show strikingly similar multi-element diagram patterns, with strong enrichment relative to the bulk-silicate Earth and marked positive Nb and Ta and negative Pb anomalies — typical for ocean island basalts. Glass/bulk rock elemental ratios reveal systematic differences between samples that relate to their mineralogy; for example, Lanzarote tephras that lack significant clinopyroxene and Fe-Ti oxide crystals have higher Scglass/Scbulk and Vglass/Vbulk than Tenerife, La Palma and El Hierro samples that typically contain these minerals. Among all elements, K and P display the greatest
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Experimental constraints on phreatic eruption processes at Whakaari (White Island volcano)
NASA Astrophysics Data System (ADS)
Mayer, Klaus; Scheu, Bettina; Gilg, H. Albert; Heap, Michael J.; Kennedy, Ben M.; Lavallée, Yan; Letham-Brake, Mark; Dingwell, Donald B.
2015-09-01
Vigorous hydrothermal activity interspersed by sequences of phreatic and phreatomagmatic eruptions occur at Whakaari (White Island volcano), New Zealand. Here, we investigate the influence of sample type (hydrothermally altered cemented ash tuffs and unconsolidated ash/lapilli) and fragmentation mechanism (steam flashing versus gas expansion) on fragmentation and ejection velocities as well as on particle-size and shape. Our rapid decompression experiments show that fragmentation and ejection speeds of two ash tuffs, cemented by alunite and amorphous opal, increase with increasing porosity and that both are significantly enhanced in the presence of steam flashing. Ejection speeds of unconsolidated samples are higher than ejection speeds of cemented tuffs, as less energy is consumed by fragmentation. Fragmentation dominated by steam flashing results in increased fragmentation energy and a higher proportion of fine particles. Particle shape analyses before and after fragmentation reveal that both steam flashing and pure gas expansion produce platy or bladed particles from fracturing parallel to the decompression front. Neither fragmentation mechanisms nor sample type show a significant influence on the shape. Our results emphasize that, under identical pressure and temperature conditions, eruptions accompanied by the process of liquid water flashing to steam are significantly more violent than those driven simply by gas expansion. Therefore, phase changes during decompression and cementation are both important considerations for hazard assessment and modeling of eruptions in hydrothermally active environments.
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Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust
Witter, Robert C.; Carver, G.A.; Briggs, Richard; Gelfenbaum, Guy R.; Koehler, R.D.; La Selle, SeanPaul M.; Bender, Adrian M.; Engelhart, S.E.; Hemphill-Haley, E.; Hill, Troy D.
2016-01-01
Current models used to assess earthquake and tsunami hazards are inadequate where creep dominates a subduction megathrust. Here we report geological evidence for large tsunamis, occurring on average every 300–340 years, near the source areas of the 1946 and 1957 Aleutian tsunamis. These areas bookend a postulated seismic gap over 200 km long where modern geodetic measurements indicate that the megathrust is currently creeping. At Sedanka Island, evidence for large tsunamis includes six sand sheets that blanket a lowland facing the Pacific Ocean, rise to 15 m above mean sea level, contain marine diatoms, cap terraces, adjoin evidence for scour, and date from the past 1700 years. The youngest sheet, and modern drift logs found as far as 800 m inland and >18 m elevation, likely record the 1957 tsunami. Modern creep on the megathrust coexists with previously unrecognized tsunami sources along this part of the Aleutian Subduction Zone.
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NASA Astrophysics Data System (ADS)
Padrón, E.; Pérez, N. M.; Hernández, P. A.; Melián, G. V.; Padilla, G. D.; Barrancos, J.; Dionis, S.; Rodríguez, F.; Nolasco, D.; Calvo, D.; Hernández, I.; Peraza, M. D.
2012-04-01
El Hierro Island is the southwesternmost and the youngest island of the Canary archipelago. Since 16 July, an anomalous seismicity at El Hierro island was recorded by IGN seismic network. After the occurrence of more than 10,000 seismic events, volcanic tremor was recorded since 05:15 of the October 10, by all of the seismic stations on the island, with highest amplitudes recorded in the southernmost station. During the afternoon of 12 October a large light-green coloured area was observed in the sea to the souht of La Restinga village (at the southernmost part of El Hierro island), suggesting the existence of a submarine eruption. Since October 12, frequent episodes of, turbulent gas emission and foaming, and the appearance of steamy lava fragments has been observed on the sea surface. As part of the volcanic surveillance of the island, the Instituto Volcanologico de Canarias (INVOLCAN) geochemical monitoring program is carrying out diffuse helium surveys on the surface environment of El Hierro (soil atmosphere). This nobel gas has been investigated because it has been considered an almost ideal geochemical indicator because it is chemically inert, physically stable, nonbiogenic, sparingly soluble in water under ambient conditions and almost non-adsorbable. At each survey, 600 sampling sites covering the whole island and following an homogeneous distribution are selected for helium measurements in the soil gases, The helium concentration gradients with respect to its value on air (5.24 ppm) allow us to estimate a pure diffusive emission rate of helium throughout the island. The first survey was carried out on the summer of 2003, when the island was on a quiescence period. At this survey, the amount of helium released by the volcanic system of El Hierro was estimated in 6 kg/d. Since the beginning of the seismic unrest, 13 helium emission surveys have been carried out. The helium emission rate has shown an excellent agreement with the evolution of the volcanic
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NASA Astrophysics Data System (ADS)
Langmann, Baerbel; ZakšEk, Klemen; Hort, Matthias
2010-01-01
In August 2008, Kasatochi volcano on the Aleutian Islands erupted without much advance warning. Volcanic ash released during this eruption quickly settled out of the atmosphere, mainly into the NE Pacific Ocean. The amount of volcanic ash, as well as the ash fall area and volume into the NE Pacific Ocean, remains speculative, as only a limited number of measurements is available. We used a three-dimensional atmosphere/chemistry-aerosol model to determine the atmospheric distribution of SO2 and volcanic ash and its fallout after the eruption of Kasatochi volcano. In a first step, modeled atmospheric SO2 distributions are compared with satellite data, thereby evaluating the model capabilities to reasonably reproduce atmospheric transport patterns. For modeled volcanic ash mass a considerable reduction of the atmospheric content already occurred by 10 August, the second day after the eruption in accordance with satellite observations. Gravitational settling is the most efficient removal process for volcanic ash mass, exceeding dry and wet deposition by far. Assuming an ash volume of 0.3 km3 released during the eruption of Kasatochi volcano and a median ash particle diameter of 4 μm, the mass of volcanic ash removed at ground within the 0.1 mm isopach covers an area of 7.6 × 105 km2 over the NE Pacific Ocean and makes up 49% of the removed material out of the atmosphere. The amount of ash and that of iron attached to it is sufficient to explain measured seawater CO2 decrease at the ocean station Papa in August 2008 induced by iron fertilization and subsequent phytoplankton production.
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NASA Astrophysics Data System (ADS)
Edwards, Matt; Kennedy, Ben; Jolly, Art; Scheu, Bettina; Taddeucci, Jacopo; Jousset, Philippe; Schmid, Di
2015-04-01
Micro-eruptions are potentially modulated by hydrothermal systems and crater lakes but to date have not been well studied. In January/February 2013 White Island (Whakaari), New Zealand, experienced an about three week long period of atypical, frequent micro-eruptions within its crater lake. Many of these micro-eruptions were recorded by tour operators and GNS personnel monitoring the lake activity. Analysis of this video footage reveals an increasingly energetic eruption style. Deformation of the muddy lake surface by ascending bubbles begins as irregularly shaped bursts, producing liquid strings of mud ejected to heights of less than 10m at 10-15m/s. As the episode progresses, eruption frequency is maintained at semi-regular <10s intervals. Each eruption however starts with an increasingly hemispheric surface deformation ~6m in diameter, and bursts occur as "star-bursts" with ejection of less fluidal ash/mud clots. In addition, these bursts are commonly followed within 2s by a more vertical and energetic secondary ejection of material, which occasionally ejects through the deformed hemispheric surface up to >100m high, and reaches ejection velocities up to 45m/s. The period of frequent "star-bursts" is then followed by a two day phase of constant ~30-75m high ash ejection resulting in the formation of a tuff cone with a central open conduit of 6m within the former crater lake. We theorise that this behaviour is influenced by evolving bubble overpressure/volume, including the presence or absence of a trailing wake of smaller bubbles and is modulated over the eruption episode by the viscosity of the crater lake. In the early stages of the episode a lower viscosity lake provides little resistance to rising gas/ash mixtures. Bubble coalescence and/or overpressure development is therefore minimised, resulting in low energy bursts. Over the course of this episode the viscosity of the lake increases due to addition of ash from ash-carrying gas flux and fluid loss by
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Wilson, Frederic H.; White, Willis H.; Detterman, Robert L.
1988-01-01
Geologic mapping of the Port Moller, Stepovak Bay, and Simeonof Island quadrangles was begun under the auspices of the Alaska Mineral Resource Assessment Program (AMRAP) in 1983 . Two important mineral deposits are located in the Port Moller quadrangle; the Pyramid prospect is the largest copper porphyry system in the Aleutian Arc, and the Apollo Mine is the only gold mine to reach production status in the Aleutian Arc.
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Mangan, M.; Miller, T.; Waythomas, C.; Trusdell, F.; Calvert, A.; Layer, P.
2009-01-01
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
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Lozano-Bilbao, Enrique; Gutiérrez, Ángel José; Hardisson, Arturo; Rubio, Carmen; González-Weller, Dailos; Aguilar, Natacha; Escánez, Alejandro; Espinosa, José María; Canales, Paula; Lozano, Gonzalo
2018-04-01
This work investigates whether a submarine volcanic eruption off El Hierro (Canary Islands) in October 2011 influenced the metal contents of two deep water cephalopod species: Abraliopsis morisii and Pyroteuthis margaritifera. This was assessed by comparing metal contents in specimens collected off the island of El Hierro and in the neighbouring islands of La Palma and Tenerife during an experimental deep water fishing trip. The concentration of 20 heavy metals was analyzed in 180 specimens of A. morisii and P. margaritifera collected around the three islands to test for inter-island differences for each species and metal. While both species showed geographical differences in metal concentrations, the main finding was that A. morisii could be a bioindicator species for metals such as Li, Sr and Ca. Copyright © 2017 Elsevier Ltd. All rights reserved.
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Strong hydrothermal eruption 600 BP inside Golovnin caldera, Kunashir Island, Kurile arc
NASA Astrophysics Data System (ADS)
Belousov, Alexander; Belousova, Marina; Kozlov, Dmitry
2017-04-01
Hydrothermal explosions are difficult to predict and thus they pose serious hazard to visitors of hydrothermal areas. Here we present results of mapping of airfall deposit of strong prehistoric hydrothermal eruption that was the latest eruptive event in the limits of Golovnin caldera in the southern part of Kunashir Island, Kurile arc. This caldera was formed 30 Ka BP (Razhigaeva et al. 1998) that was followed by extrusion of two dacitic lava domes in the central part of the caldera. The studied hydrothermal eruption occurred at active hydrothermal area located at the southern foot of the Vostochny (Eastern) lava dome. This eruption formed a 350-m wide and 40 m deep crater surrounded by low-profile ring of the ejected material. Part of the crater is occupied by 17-m-deep Kipiashee Lake having intensive hydrothermal discharge on its bottom. The ejected material is represented by yellow-white and yellow-brown poorly sorted sandy gravels and sands with admixture of clay. This clastic material was formed by fragmentation of hydrothermally altered pumice tuffs (former sediments of the intracaldera lake). The airfall deposit has nearly circular distribution around the crater. The deposit thickness decreases from 5-7 m at the crater rim to 5 cm on the distances 2-3 km; thickness half-distance (bt) is estimated as 4.1. Volume of the deposit calculated by the method of Fierstein and Nathenson (1992) is 0.007 cub.km. Radiocarbon dating of soil buried directly under the deposit provided calibrated age 1300-1420 AD. This eruption can be considered as a model for future hydrothermal explosions inside the Golovnin caldera. This study was supported by grant of Russian Science Foundation #15-17-20011.
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NASA Astrophysics Data System (ADS)
Berrocoso, M.; Fernandez-Ros, A.; Prates, G.; Martin, M.; Hurtado, R.; Pereda, J.; Garcia, M. J.; Garcia-Cañada, L.; Ortiz, R.; Garcia, A.
2012-04-01
The surface deformation has been an essential parameter for the onset and evolution of the eruptive process of the island of El Hierro (October 2011) as well as for forecasting changes in seismic and volcanic activity during the crisis period. From GNSS-GPS observations the reactivation is early detected by analizing the change in the deformation of the El Hierro Island regional geodynamics. It is found that the surface deformation changes are detected before the occurrence of seismic activity using the station FRON (GRAFCAN). The evolution of the process has been studied by the analysis of time series of topocentric coordinates and the variation of the distance between stations on the island of El Hierro (GRAFCAN station;IGN network; and UCA-CSIC points) and LPAL-IGS station on the island of La Palma. In this work the main methodologies and their results are shown: •The location (and its changes) of the litospheric pressure source obtained by applying the Mogi model. •Kalman filtering technique for high frequency time series, used to make the forecasts issued for volcanic emergency management. •Correlations between deformation of the different GPS stations and their relationship with seismovolcanic settings.
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NASA Astrophysics Data System (ADS)
Losic, M.; Robock, A.
2010-12-01
It is well-understood that the effects of volcanic aerosol loading into the stratosphere are transient, with global cooling lasting only a few years after a single large eruption. Geological evidence collected from Northern Baffin Island, Canada, suggests ice cap growth began soon after a succession of several large eruptions in the 13th century, and they did not start to melt until roughly a century ago. We investigate which feedbacks allowed these ice caps to be maintained long after the transient forcing of the volcanic aerosols, by conducting sensitivity studies with the Weather Research and Forecasting (WRF) Model and Polar WRF, a version of WRF developed specifically for the polar regions. Results from an ensemble of month-long regional simulations over Baffin Island suggest that better treatment of snow and ice in Polar WRF improves our regional climate simulations. Thus, sensitivity test results from decade-long runs with imposed changes to boundary condition temperatures and carbon dioxide concentrations using Polar WRF are presented. Preliminary findings suggest that not only large scale but localized climate feedbacks play an important role in the responses of the ice caps after temperature and carbon dioxide forcings are applied. The results from these and further sensitivity tests will provide insight into the influence of regional feedbacks on the persistence of these ice caps long after the 13th century eruptions.
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-09-28
... manages the groundfish fishery in the GOA exclusive economic zone according to the Fishery Management Plan.... 101126521-0640-2] RIN 0648-XA731 Fisheries of the Exclusive Economic Zone Off Alaska; Skates in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS), National...
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Moran, S.C.; Kwoun, O.; Masterlark, Timothy; Lu, Z.
2006-01-01
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 interval. All interferograms lack coherence within ∼5 km of the summit, primarily due to persistent snow and ice cover on the edifice. Remarkably, in the 5–15 km distance range where interferograms are coherent, the InSAR images show no intrusion- or withdrawal-related deformation at Shishaldin during this entire time period. However, several InSAR images do show deformation associated with a shallow ML 5.2 earthquake located ∼14 km west of Shishaldin that occurred 6 weeks before the 1999 eruption. We use a theoretical model to predict deformation magnitudes due to a volumetric expansion source having a volume equivalent to the 1999 erupted volume, and find that deformation magnitudes for sources shallower than 10 km are within the expected detection capabilities for interferograms generated from C-band ERS 1/2 and RADARSAT-1 synthetic aperture radar images. We also find that InSAR images cannot resolve relatively shallow deformation sources (1–2 km below sea level) due to spatial gaps in the InSAR images caused by lost coherence. The lack of any deformation, particularly for the 1999 eruption, leads us to speculate that magma feeding eruptions at the summit moves rapidly (at least 80m/day) from > 10 km depth, and that the intrusion–eruption cycle at Shishaldin does not produce significant permanent deformation at the surface.
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Ferrera, Isabel; Arístegui, Javier; González, José M; Montero, María F; Fraile-Nuez, Eugenio; Gasol, Josep M
2015-01-01
The submarine volcanic eruption occurring near El Hierro (Canary Islands) in October 2011 provided a unique opportunity to determine the effects of such events on the microbial populations of the surrounding waters. The birth of a new underwater volcano produced a large plume of vent material detectable from space that led to abrupt changes in the physical-chemical properties of the water column. We combined flow cytometry and 454-pyrosequencing of 16S rRNA gene amplicons (V1-V3 regions for Bacteria and V3-V5 for Archaea) to monitor the area around the volcano through the eruptive and post-eruptive phases (November 2011 to April 2012). Flow cytometric analyses revealed higher abundance and relative activity (expressed as a percentage of high-nucleic acid content cells) of heterotrophic prokaryotes during the eruptive process as compared to post-eruptive stages. Changes observed in populations detectable by flow cytometry were more evident at depths closer to the volcano (~70-200 m), coinciding also with oxygen depletion. Alpha-diversity analyses revealed that species richness (Chao1 index) decreased during the eruptive phase; however, no dramatic changes in community composition were observed. The most abundant taxa during the eruptive phase were similar to those in the post-eruptive stages and to those typically prevalent in oceanic bacterioplankton communities (i.e. the alphaproteobacterial SAR11 group, the Flavobacteriia class of the Bacteroidetes and certain groups of Gammaproteobacteria). Yet, although at low abundance, we also detected the presence of taxa not typically found in bacterioplankton communities such as the Epsilonproteobacteria and members of the candidate division ZB3, particularly during the eruptive stage. These groups are often associated with deep-sea hydrothermal vents or sulfur-rich springs. Both cytometric and sequence analyses showed that once the eruption ceased, evidences of the volcano-induced changes were no longer observed.
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Ferrera, Isabel; Arístegui, Javier; González, José M.; Montero, María F.; Fraile-Nuez, Eugenio; Gasol, Josep M.
2015-01-01
The submarine volcanic eruption occurring near El Hierro (Canary Islands) in October 2011 provided a unique opportunity to determine the effects of such events on the microbial populations of the surrounding waters. The birth of a new underwater volcano produced a large plume of vent material detectable from space that led to abrupt changes in the physical-chemical properties of the water column. We combined flow cytometry and 454-pyrosequencing of 16S rRNA gene amplicons (V1–V3 regions for Bacteria and V3–V5 for Archaea) to monitor the area around the volcano through the eruptive and post-eruptive phases (November 2011 to April 2012). Flow cytometric analyses revealed higher abundance and relative activity (expressed as a percentage of high-nucleic acid content cells) of heterotrophic prokaryotes during the eruptive process as compared to post-eruptive stages. Changes observed in populations detectable by flow cytometry were more evident at depths closer to the volcano (~70–200 m), coinciding also with oxygen depletion. Alpha-diversity analyses revealed that species richness (Chao1 index) decreased during the eruptive phase; however, no dramatic changes in community composition were observed. The most abundant taxa during the eruptive phase were similar to those in the post-eruptive stages and to those typically prevalent in oceanic bacterioplankton communities (i.e. the alphaproteobacterial SAR11 group, the Flavobacteriia class of the Bacteroidetes and certain groups of Gammaproteobacteria). Yet, although at low abundance, we also detected the presence of taxa not typically found in bacterioplankton communities such as the Epsilonproteobacteria and members of the candidate division ZB3, particularly during the eruptive stage. These groups are often associated with deep-sea hydrothermal vents or sulfur-rich springs. Both cytometric and sequence analyses showed that once the eruption ceased, evidences of the volcano-induced changes were no longer observed
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Seismicity associated with the May 2010 eruption of South Sarigan Seamount, Northern Mariana Islands
Searcy, Cheryl
2013-01-01
On 29 May 2010, at approximately 11:48 UTC, an undersea volcano south of Sarigan in the Northern Mariana Islands (Figs. 1 and 2) erupted sending a cloud of volcanic ash and water vapor to 40,000 feet (12 km; Washington Volcanic Ash Advisory Center). Bathymetric data (Stern and Smoot, 1998; Embley et al., 2007) indicate an undersea vent exists at approximately 16.582° N and 145.821° E or about 12 km southwest of Sarigan and about 30 km northeast of Anatahan (Fig. 3). The vent depth is estimated to be 184 m below sea level. Based on physical observations of water discoloration (Juan Camacho, personal comm., 2010) and satellite imagery, the eruption plume is attributed to this undersea seamount.
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-10-21
... manages the groundfish fishery in the BSAI exclusive economic zone according to the Fishery Management.... 0910131363-0087-01] RIN 0648-XZ85 Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-03-26
... the groundfish fishery in the BSAI exclusive economic zone according to the Fishery Management Plan.... 0910131363-0087-02] RIN 0648-XV52 Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-09-01
... the groundfish fishery in the BSAI exclusive economic zone according to the Fishery Management Plan.... 0910131363-0087-02] RIN 0648-XY62 Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS...
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-01-28
... groundfish fishery in the BSAI exclusive economic zone according to the Fishery Management Plan for.... 0810141351-9087-02] RIN 0648-XU11 Fisheries of the Exclusive Economic Zone Off Alaska; Atka Mackerel in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS...
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NASA Astrophysics Data System (ADS)
Prates, G.; Berrocoso, M.; Fernández-Ros, A.; García, A.; Ortiz, R.
2012-04-01
El Hierro Island (Canary Islands, Spain) has undergone a submarine eruption a few kilometers to its southeast, detected October 10, on the rift alignment that cuts across the island. However, the seismicity level suddenly increased around July 17 and ground deformation was detected by the only continuously observed GNSS-GPS (Global Navigation Satellite Systems - Global Positioning System) benchmark FRON in the El Golfo area. Based on that information several other GNSS-GPS benchmarks were installed, some of which continuously observed as well. A normal vector analysis was applied to these collected data. The normal vector magnitude variation identified local extension-compression regimes, while the normal vector inclination showed the relative height variation between the three benchmarks that define the plan to which normal vector is analyzed. To accomplish this analysis the data was previously processed to achieve positioning solutions every 30 minutes using the Bernese GPS Software 5.0, further enhanced by a Discrete Kalman Filter, giving an overall millimeter level precision. These solutions were reached using the IGS (International GNSS Service) ultra-rapid orbits and the double-differenced ionosphere-free combination. With this strategy the positioning solutions were attained in near real-time. Later with the IGS rapid orbits the data was reprocessed to provide added confidence to the solutions. Two triangles were then considered, a smaller one located in the El Golfo area within the historically collapsed caldera, and a larger one defined by benchmarks placed in Valverde, El Golfo and La Restinga, the town closest to the eruption's location, covering almost the entire Island's surface above sea level. With these two triangles the pre-eruption and post-eruption deformation suffered by El Hierro's surface will be further analyzed.
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-06-08
... fishery in the (BSAI) exclusive economic zone according to the Fishery Management Plan for Groundfish of.... 101126521-0640-02] RIN 0648-XA483 Fisheries of the Exclusive Economic Zone Off Alaska; Alaska Plaice in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-06-08
.... 101126521-0640-02] RIN 0648-XA482 Fisheries of the Exclusive Economic Zone Off Alaska; Alaska Plaice in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries Service (NMFS... management area (BSAI). This action is necessary to prevent exceeding the 2011 Alaska plaice total allowable...
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Aleutian tholeiitic and calc-alkaline magma series I: The mafic phenocrysts
NASA Astrophysics Data System (ADS)
Kay, S. Mahlburg; Kay, Robert W.
1985-07-01
Diagnostic mafic silicate assemblages in a continuous spectrum of Aleutian volcanic rocks provide evidence for contrasts in magmatic processes in the Aleutian arc crust. Tectonic segmentation of the arc exerts a primary control on the variable mixing, fractional crystallization and possible assimilation undergone by the magmas. End members of the continuum are termed calc-alkaline (CA) and tholeiitic (TH). CA volcanic rocks (e.g., Buldir and Moffett volcanoes) have low FeO/MgO ratios and contain compositionally diverse phenocryst populations, indicating magma mixing. Their Ni and Cr-rich magnesian olivine and clinopyroxene come from mantle-derived mafic olivine basalts that have mixed with more fractionated magmas at mid-to lower-crustal levels immediately preceding eruption. High-Al amphibole is associated with the mafic end member. In contrast, TH lavas (e.g., Okmok and Westdahl volcanoes) have high FeO/MgO ratios and contain little evidence for mixing. Evolved lavas represent advanced stages of low pressure crystallization from a basaltic magma. These lavas contain groundmass olivine (FO 40 50) and lack Ca-poor pyroxene. Aleutian volcanic rocks with intermediate FeO/MgO ratios are termed transitional tholeiitic (TTH) and calc-alkaline (TCA). TCA magmas are common (e.g., Moffett, Adagdak, Great Sitkin, and Kasatochi volcanoes) and have resulted from mixing of high-Al basalt with more evolved magmas. They contain amphibole (high and low-Al) or orthopyroxene or both and are similar to the Japanese hypersthene-series. TTH magmas (e.g., Okmok and Westdahl) contain orthopyroxene or pigeonite or both, and show some indication of upper crustal mixing. They are mineralogically similar to the Japanese pigeonite-series. High-Al basalt lacks Mg-rich mafic phases and is a derivative magma produced by high pressure fractionation of an olivine tholeiite. The low pressure mineral assemblage of high-Al basalt results from crystallization at higher crustal levels.
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Federal Register 2010, 2011, 2012, 2013, 2014
2013-09-17
.... 121018563-3418-02] RIN 0648-XC872 Fisheries of the Exclusive Economic Zone Off Alaska; Sharks in the Bering... prohibiting retention of sharks in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary because the 2013 total allowable catch (TAC) of sharks in the BSAI has been reached. DATES...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-09-28
.... 101126521-0640-2] RIN 0648-XA733 Fisheries of the Exclusive Economic Zone Off Alaska; Sharks in the Bering... prohibiting retention of sharks in the Bering Sea and Aleutian Islands management area (BSAI). This action is necessary because the 2011 total allowable catch (TAC) of sharks in the BSAI has been reached. DATES...
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New insight on the Toba volcano super eruption (Sumatra Island, Indonesia) from BAR-9425 core.
NASA Astrophysics Data System (ADS)
Caron, B.; del Manzo, G.; Moreno, E.; Annachiara, B.; Baudin, F.; Bassinot, F. C.; Villemant, B.
2017-12-01
The famous 73 ka Toba eruption has produced about 2800 km3 of magma and is considered as one of the largest known eruptions during the Quaternary (Rose and Chesner, 1990). The BAR-9425 piston core collected during the 1994 joint French-Indonesian BARAT Cruise in the north Sumatra Island has recorded the volcano history of Toba from 60 to 100 ka (including the 73 ka Young Toba Tuff (YTT)). Tephra layers within this sediment core have been systematically studied using a combined analysis including stable isotope (δ18O, van der Kaars et al., 2012), high resolution tephrostratigraphic, morphological and a major-trace element studies. Our preliminary results show that not only one major eruption occurred between 60 and 100 ka but probably 11 distinct eruptions occurred. The 11 eruptions display an homogeneous major element composition. The oldest tephra with an estimated age of 101 ka, have a rhyolitic composition and 30% of relative abundance of volcanic glass shards. The other eruptive phases are dated at: 91,5-89,2 ka with a maximum of 16% of volcanic tephra; 85,7-84,8 ka with 64%; 81,8 ka with 22%; 74,4 ka with 43%, 72,3 ka with 89%, 71,4 ka with 92%; 68,9% with 96%; 66,5 ka with 94%; 65,2 ka with 75% and 63,1-60,3 ka with a maximum of 96% of volcanic tephra respectively (ages were calculated with a constant sediment rate of 4,3 cm/ka from data from van der Kaars et al., 2012). Some of these eruptions have had direct effect on regional vegetation as suggested by Van der Kaars et al. (2012) who propose that the gradual expansion of pine cover for the 7000 years following the eruption, is a consequence of the ash deposit from the 89 ka eruption. Our detailed tephrostratigraphy study of Toba eruptions will help to understand the impact on the ecosystems of northern Sumatra and on global climate change. Moreover, we expect to correlate the new tephra layers of Toba volcano to other sites by using AL-ICP-MS traces analyses and to use it as chronological makers.
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Assessing qualitative long-term volcanic hazards at Lanzarote Island (Canary Islands)
NASA Astrophysics Data System (ADS)
Becerril, Laura; Martí, Joan; Bartolini, Stefania; Geyer, Adelina
2017-07-01
Conducting long-term hazard assessment in active volcanic areas is of primary importance for land-use planning and defining emergency plans able to be applied in case of a crisis. A definition of scenario hazard maps helps to mitigate the consequences of future eruptions by anticipating the events that may occur. Lanzarote is an active volcanic island that has hosted the largest (> 1.5 km3 DRE) and longest (6 years) eruption, the Timanfaya eruption (1730-1736), on the Canary Islands in historical times (last 600 years). This eruption brought severe economic losses and forced local people to migrate. In spite of all these facts, no comprehensive hazard assessment or hazard maps have been developed for the island. In this work, we present an integrated long-term volcanic hazard evaluation using a systematic methodology that includes spatial analysis and simulations of the most probable eruptive scenarios.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Amundsen, C.C.
1985-01-01
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 Elymusmore » 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.« less
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-03-29
.... 101126521-0640-02] RIN 0648-XA322 Fisheries of the Exclusive Economic Zone Off Alaska; Octopus in the Bering... allowable catch of octopus in the Bering Sea and Aleutian Islands (BSAI). This action is necessary to allow... subpart H of 50 CFR part 600 and 50 CFR part 679. The 2011 initial total allowable catch (ITAC) of octopus...
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NASA Astrophysics Data System (ADS)
Yang, Zhongkang; Long, Nanye; Wang, Yuhong; Zhou, Xin; Liu, Yi; Sun, Liguang
2017-02-01
The contents of Ti, Al and Fe 2 O 3 in a lacustrine sediment core (DY6) collected from Dongdao Island, South China Sea (SCS), were determined to be much higher than those in the three major sediment end-members (coral sand, guano and plants), and their likely sources include terrigenous dust and volcanic ash. At 61 cm (˜AD 1300), the contents of Ti, Al and Fe 2 O 3 have an abnormally high spike, which cannot be explained by terrigenous dust. The Sr and Nd isotope compositions at 61 cm are in excellent agreement with those in volcanic materials, but they are significantly different from those in terrigenous dust, implying a possible material input from historical volcanic eruptions in the lacustrine sediment DY6. The documented great Samalas volcanic eruption at AD 1257 in Indonesia is likely the candidate for this volcanic eruption.
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DSCOVR/EPIC observations of SO2 reveal dynamics of young volcanic eruption clouds
NASA Astrophysics Data System (ADS)
Carn, S. A.; Krotkov, N. A.; Taylor, S.; Fisher, B. L.; Li, C.; Bhartia, P. K.; Prata, F. J.
2017-12-01
Volcanic emissions of sulfur dioxide (SO2) and ash have been measured by ultraviolet (UV) and infrared (IR) sensors on US and European polar-orbiting satellites since the late 1970s. Although successful, the main limitation of these observations from low Earth orbit (LEO) is poor temporal resolution (once per day at low latitudes). Furthermore, most currently operational geostationary satellites cannot detect SO2, a key tracer of volcanic plumes, limiting our ability to elucidate processes in fresh, rapidly evolving volcanic eruption clouds. In 2015, the launch of the Earth Polychromatic Imaging Camera (EPIC) aboard the Deep Space Climate Observatory (DSCOVR) provided the first opportunity to observe volcanic clouds from the L1 Lagrange point. EPIC is a 10-band spectroradiometer spanning UV to near-IR wavelengths with two UV channels sensitive to SO2, and a ground resolution of 25 km. The unique L1 vantage point provides continuous observations of the sunlit Earth disk, from sunrise to sunset, offering multiple daily observations of volcanic SO2 and ash clouds in the EPIC field of view. When coupled with complementary retrievals from polar-orbiting UV and IR sensors such as the Ozone Monitoring Instrument (OMI), the Ozone Mapping and Profiler Suite (OMPS), and the Atmospheric Infrared Sounder (AIRS), we demonstrate how the increased observation frequency afforded by DSCOVR/EPIC permits more timely volcanic eruption detection and novel analyses of the temporal evolution of volcanic clouds. Although EPIC has detected several mid- to high-latitude volcanic eruptions since launch, we focus on recent eruptions of Bogoslof volcano (Aleutian Islands, AK, USA). A series of EPIC exposures from May 28-29, 2017, uniquely captures the evolution of SO2 mass in a young Bogoslof eruption cloud, showing separation of SO2- and ice-rich regions of the cloud. We show how analyses of these sequences of EPIC SO2 data can elucidate poorly understood processes in transient eruption
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NASA Astrophysics Data System (ADS)
Pimentel, A.; Zanon, V.; de Groot, L. V.; Hipólito, A.; Di Chiara, A.; Self, S.
2016-03-01
The AD 1761 eruption on Terceira was the only historical subaerial event on the island and one of the last recorded in the Azores. The eruption occurred along the fissure zone that crosses the island and produced a trachybasalt lava flow and scoria cones. Small comenditic trachyte lava domes (known as Mistérios Negros) were also thought by some to have formed simultaneously on the eastern flank of Santa Bárbara Volcano. Following a multidisciplinary approach, we combined geological mapping, paleomagnetic, petrographic, mineral and whole-rock geochemical and structural analyses to study this eruption. The paleomagnetic dating method compared geomagnetic vectors (directions and intensities) recorded by both the AD 1761 lava flow and Mistérios Negros domes and revealed that the two events were indeed coeval. Based on new data and interpretation of historical records, we have accordingly reconstructed the AD 1761 eruptive dynamics and distinguished three phases: (1) a precursory phase characterized by decreased degassing in the fumarolic field of Pico Alto Volcano and a gradual increase of seismic activity, which marked the intrusion of trachybasalt magma; (2) a first eruptive phase that started with phreatic explosions on the eastern flank of Santa Bárbara Volcano, followed by the inconspicuous effusion of comenditic trachyte (66 wt% SiO2), forming a WNW-ESE-oriented chain of lava domes; and (3) a second eruptive phase on the central part of the fissure zone, where a Hawaiian to Strombolian-style eruption formed small scoria cones (E-W to ENE-WSW-oriented) and a trachybasalt lava flow (50 wt% SiO2) which buried 27 houses in Biscoitos village. Petrological analyses show that the two batches of magma were emitted independently without evidence of interaction. We envisage that the dome-forming event was triggered by local stress changes induced by intrusion of the trachybasalt dyke along the fissure zone, which created tensile stress conditions that promoted ascent
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Burger, Joanna; Gochfeld, Michael; Jewett, Stephen C
2007-05-01
Concentrations of 13 radionuclides (137Cs, 129I, 60Co, 152Eu, 90Sr, 99Tc, 241Am, 238Pu, 239,249Pu, 234U, 235U, 236U, 238U) were examined in seven species of invertebrates from Amchitka and Kiska Islands, in the Aleutian Chain of Alaska, using gamma spectroscopy, inductively coupled plasma mass spectroscopy, and alpha spectroscopy. Amchitka Island was the site of three underground nuclear test (1965-1971), and we tested the null hypotheses that there were no differences in radionuclide concentrations between Amchitka and the reference site (Kiska) and there were no differences among species. The only radionuclides where composite samples were above the Minimum Detectable Activity (MDA) were 137Cs, 241Am, 239,249Pu, 234U, 235U, 236U, and 238U. Green sea urchin (Strongylocentrotus polyacanthus), giant chiton (Cryptochiton stelleri), plate limpets (Tectura scutum) and giant Pacific octopus (Enteroctopus dofleini) were only tested for 137Cs; octopus was the only species with detectable levels of 137Cs (0.262 +/- 0.029 Bq/kg, wet weight). Only rock jingle (Pododesmus macroschisma), blue mussel (Mytilus trossulus) and horse mussel (Modiolus modiolus) were analyzed for the actinides. There were no interspecific differences in 241Am and 239,240Pu, and almost no samples above the MDA for 238Pu and 236U. Horse mussels had significantly higher concentrations of 234U (0.844 +/- 0.804 Bq/kg) and 238U (0.730 +/- 0.646) than the other species (both isotopes are naturally occurring). There were no differences in actinide concentrations between Amchitka and Kiska. In general, radionuclides in invertebrates from Amchitka were similar to those from uncontaminated sites in the Northern Hemisphere, and below those from the contaminated Irish Sea. There is a clear research need for authors to report the concentrations of radionuclides by species, rather than simply as 'shellfish', for comparative purposes in determining geographical patterns, understanding possible effects, and for
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The ten-year eruption of Kilauea Volcano
Clague, D.A.; Heliker, C.
1992-01-01
About 1 km3 of lava erupted during the first 0 years of the eruption. Lava flows have destroyed 181 houses and severed the coastal highway along the volcano's south flank, severely restricting transportation on this part of the island of Hawaii. the eruption consisted of many distinct episodes characterized by activity at different vents and by different eruptive styles. the following summarizes the first 10 years of the eruption, starting with the initial outbreak in 1983.
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Heavy metals in fish from the Aleutians: Interspecific and locational differences
DOE Office of Scientific and Technical Information (OSTI.GOV)
Burger, Joanna, E-mail: burger@biology.rutgers.edu; Environmental and Occupational Health Sciences Institute, Rutgers University, Piscataway, NJ; Consortium for Risk Evaluation with Stakeholder Participation, Vanderbilt University, Nashville, TN 37235
The objectives of this study were to examine levels of arsenic, cadmium, lead, mercury and selenium in edible tissue of seven species of marine fish collected from several Aleutian islands (in 2004) to determine: (1) interspecific differences, (2) locational differences (among Aleutian Islands), (3) size-related differences in any metal levels within a species, and (4) potential risk to the fish or to predators on the fish, including humans. We also compared metals levels to those of three other fish species previously examined in detail, as well as examining metals in the edible tissue of octopus (Octopus dofleini). Octopus did notmore » have the highest levels of any metal. There were significant interspecific differences in all metal levels among the fish species, although the differences were less than an order of magnitude, except for arsenic (mean of 19,500 ppb in Flathead sole, Hippoglossoides elassodon). Significant intraisland variation occurred among the four sites on Amchitka, but there was not a consistent pattern. There were significant interisland differences for some metals and species. Mercury levels increased significantly with size for several species; lead increased significantly for only one fish species; and cadmium and selenium decreased significantly with size for halibut (Hippoglossus stenolepis). The Alaskan Department of Health and Social Services supports unrestricted consumption of most Alaskan fish species for all people, including pregnant women. Most mean metal concentrations were well below the levels known to adversely affect the fish themselves, or predators that consume them (including humans), except for mercury in three fish species (mean levels just below 0.3 ppm), and arsenic in two fish species. However, even at low mercury levels, people who consume fish almost daily will exceed guideline values from the Centers for Disease Control and the Environmental Protection Agency. - Highlights: • Cadmium, lead, mercury and
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Chronology and volcanology of the 1949 multi-vent rift-zone eruption on La Palma (Canary Islands)
NASA Astrophysics Data System (ADS)
Klügel, A.; Schmincke, H.-U.; White, J. D. L.; Hoernle, K. A.
1999-12-01
The compositionally zoned San Juan eruption on La Palma emanated from three eruptive centers located along a north-south-trending rift zone in the south of the island. Seismic precursors began weakly in 1936 and became strong in March 1949, with their foci progressing from the north of the rift zone towards its south. This suggests that magma ascended beneath the old Taburiente shield volcano and moved southward along the rift. The eruption began on June 24, 1949, with phreatomagmatic activity at Duraznero crater on the ridgetop (ca. 1880 m above sea level), where five vents erupted tephritic lava along a 400-m-long fissure. On June 8, the Duraznero vents shut down abruptly, and the activity shifted to an off-rift fissure at Llano del Banco, located at ca. 550 m lower elevation and 3 km to the northwest. This eruptive center issued initially tephritic aa and later basanitic pahoehoe lava at high rates, producing a lava flow that entered the sea. Two days after basanite began to erupt at Llano del Banco, Hoyo Negro crater (ca. 1880 m asl), located 700 m north of Duraznero along the rift, opened on July 12 and produced ash and bombs of basanitic to phonotephritic composition in violent phreatomagmatic explosions ( White and Schmincke, 1999). Llano del Banco and Hoyo Negro were simultaneously active for 11 days and showed a co-variance of their eruption rates indicating a shallow hydraulic connection. On July 30, after 3 days of quiescence at all vents, Duraznero and Hoyo Negro became active again during a final eruptive phase. Duraznero issued basanitic lava at high rates for 12 h and produced a lava flow that descended towards the east coast. The lava contains ca. 1 vol.% crustal and mantle xenoliths consisting of 40% tholeiitic gabbros from the oceanic crust, 35% alkaline gabbros, and 20% ultramafic cumulates. The occurrence of xenoliths almost exclusively in the final lava is consistent with their origin by wall-rock collapse at depth near the end of the eruption
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2013-12-30
On December 10, 2013 the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite flew across the central Atlantic Ocean and captured a true-color image of the Canary Islands. Lying off of the coast of Western Sahara and Morocco, the islands were created by successive submarine volcanic eruptions which raised the ocean floor vertically until some of land rose above sea level. The oldest islands lie in the east and the youngest in the west. From east to west, the major islands seen in this image are: Lanzarote, Fuerteventura, Gran Canaria, Tenerife, La Gomera, La Palmera and El Hierro. While the creation of the islands began in the Late Cretaceous Period (70 – 80 million years ago), active volcanic activity continues. In 2011, a spectacular submarine eruption occurred just off the shore of El Hierro. The volcano became quiet again, but very recently increasing earthquakes and changing height of El Hierro suggested the volcano may again be entering an active eruptive phase. On December 27 the island’s volcano monitoring agency had raised the volcanic eruption risk for El Hierro to “yellow” – a code that means increasing activity but no eruption imminent. That afternoon a magnitude 5.1 earthquake struck offshore at El Hierro. The epicenter was 9 miles (15 km) deep, and it was one of the largest quakes ever recorded at the island. Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram
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NASA Astrophysics Data System (ADS)
Maksimovich, I. A.; Smirnov, S. Z.; Kotov, A. A.; Timina, T. Yu; Shevko, A. V.
2017-12-01
The Vetrovoy Isthmus and the Lvinaya Past’ Bay on the Iturup island (Kuril island arc) are the results of large Plinian eruptions of compositionally similar dacitic magmas. This study is devoted to a comparative analysis of the storage and crystallization conditions for magma reservoirs, which were a source of large-scale explosive eruptions. The plagioclase is most informative mineral in studying of the melt evolution. The studied plagioclases possess a complex zoning patterns, which are not typical for silicic rocks in island-arc systems. It was shown that increase of Ca in the plagioclase up to unusually high An95 is related to increase of H2O pressure in both volcanic magma chambers. The study revealed that minerals of the Vetrovoy Isthmus and Lvinaya Past’ crystallized from compositionally similar melts. Despite the compositional similarity of the melts, the phenocryst assemblage of the Lvinaya Past’ differs from the Vetrovoy Isthmus by the presence of the amphibole, which indicates that the pressure in the magmatic chamber exceeded 1-2 kbar at a 4-6 wt. % of H2O in the melt. The rocks of the Vetrovoy Isthmus do not contain amphibole phenocrysts, but melt and fluid inclusions assemblages in plagioclase demonstrate that the magma degassed in the course of evolution. This is an indication that the pressure did not exceed significantly 1-2 kbar.
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Introduction to Augustine Volcano and Overview of the 2006 Eruption
NASA Astrophysics Data System (ADS)
Nye, C. J.
2006-12-01
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
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GLORIA imagery links sedimentation in Aleutian Trench to Yakutat margin via surveyor channel
DOE Office of Scientific and Technical Information (OSTI.GOV)
Carlson, P.R.; Bruns, T.R.; Mann, D.M.
1990-06-01
GLORIA side-scan sonar imagery shows that the continental slope developing along the active margin of the Gulf of Alaska is devoid of large submarine canyons, in spite of the presence of large glacially formed sea valleys that cross the continental shelf. In the western and northern Gulf, discontinuous, actively growing deformation structures disrupt or divert the downslope transport of sediment into the Aleutian Trench. To the east of Middleton Island, the slope is intensively gullied and incised only by relatively small canyons. At the base of the gullied slope between Pamplona Spur and Alsek Valley, numerous small slope gullies coalescemore » into three turbidity current channels that merge to form the Surveyor deep-sea channel. About 350 km from the margin, the channel crosses the structural barrier formed by the Kodiak-Bowie Seamount chain and heads south for another 150 km where it bends northerly, perhaps influenced by the oceanic basement relief of the Patton Seamounts. The channel, now up to 5 km wide and deeply entrenched to 450 m, continues northerly for 200 km where it intercepts the Aleutian Trench, some 700 km from the Yakutat margin. South of Surveyor Channel, GLORIA imagery revealed evidence of another older channel. The older channel meanders through a gap in the seamount chain and eventually bends northwesterly. This now inactive, largely buried channel may have carried turbidity currents to the Aleutian Trench concurrent with the active Surveyor Channel.« less
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Sydeman, William J.; Thompson, Sarah Ann; Piatt, John F.; García-Reyes, Marisol; Zador, Stephani; Williams, Jeffrey C.; Romano, Marc; Renner, Heather
2017-01-01
Seabirds are thought to be reliable, real-time indicators of forage fish availability and the climatic and biotic factors affecting pelagic food webs in marine ecosystems. In this study, we tested the hypothesis that temporal trends and interannual variability in seabird indicators reflect simultaneously occurring bottom-up (climatic) and competitor (pink salmon) forcing of food webs. To test this hypothesis, we derived multivariate seabird indicators for the Bering Sea–Aleutian Island (BSAI) ecosystem and related them to physical and biological conditions known to affect pelagic food webs in the ecosystem. We examined covariance in the breeding biology of congeneric pelagic gulls (kittiwakes Rissa tridactyla and R. brevirostris) andauks (murres Uria aalge and U. lomvia), all of whichare abundant and well-studiedinthe BSAI. At the large ecosystem scale, kittiwake and murre breeding success and phenology (hatch dates) covaried among congeners, so data could be combined using multivariate techniques, but patterns of responsedifferedsubstantially betweenthe genera.Whiledata fromall sites (n = 5)inthe ecosystemcould be combined, the south eastern Bering Sea shelf colonies (St. George, St. Paul, and Cape Peirce) provided the strongest loadings on indicators, and hence had the strongest influence on modes of variability. The kittiwake breeding success mode of variability, dominated by biennial variation, was significantly related to both climatic factors and potential competitor interactions. The murre indicator mode was interannual and only weakly related to the climatic factors measured. The kittiwake phenology indicator mode of variability showed multi-year periods (“stanzas”) of late or early breeding, while the murre phenology indicator showed a trend towards earlier timing. Ocean climate relationships with the kittiwake breeding success indicator suggestthat early-season (winter–spring) environmental conditions and the abundance of pink salmon affect the
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NASA Astrophysics Data System (ADS)
Barrancos, J.; Padilla, G.; Hernandez Perez, P. A.; Padron, E.; Perez, N.; Melian Rodriguez, G.; Nolasco, D.; Dionis, S.; Rodriguez, F.; Calvo, D.; Hernandez, I.
2012-12-01
El Hierro is the youngest and southernmost island of the Canarian archipelago and represents the summit of a volcanic shield elevating from the surrounding seafloor at depth of 4000 m to up to 1501 m above sea level. The island is believed to be near the present hotspot location in the Canaries with the oldest subaerial rocks dated at 1.12 Ma. The subaerial parts of the El Hierro rift zones (NE, NW and S Ridges) are characterized by tightly aligned dyke complexes with clusters of cinder cones as their surface expressions. Since July 16, 2011, an anomalous seismicity at El Hierro Island was recorded by IGN seismic network. Volcanic tremor started at 05:15 hours on October 10, followed on the afternoon of October 12 by a green discolouration of seawater, strong bubbling and degassing indicating the initial stage of submarine volcanic eruption at approximately 2 km off the coast of La Restinga, El Hierro. Soil gas 222Rn and 220Rn activities were continuously measured during the period of the recent volcanic unrest occurred at El Hierro, at two different geochemical stations, HIE02 and HIE03. Significant increases in soil 222Rn activity and 222Rn/220Rn ratio from the soil were observed at both stations prior the submarine eruption off the coast of El Hierro, showing the highest increases before the eruption onset and the occurrence of the strongest seismic event (M=4.6). A statistical analysis showed that the long-term trend of the filtered data corresponded closely to the seismic energy released during the volcanic unrest. The observed increases of 222Rn are related to the rock fracturing processes (seismic activity) and the magmatic CO2 outflow increase, as observed in HIE03 station. Under these results, we find that continuous soil radon studies are important for evaluating the volcanic activity of El Hierro and they demonstrate the potential of applying continuous monitoring of soil radon to improve and optimize the detection of early warning signals of future
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Russian eruption warning systems for aviation
Neal, C.; Girina, O.; Senyukov, S.; Rybin, A.; Osiensky, J.; Izbekov, P.; Ferguson, G.
2009-01-01
More than 65 potentially active volcanoes on the Kamchatka Peninsula and the Kurile Islands pose a substantial threat to aircraft on the Northern Pacific (NOPAC), Russian Trans-East (RTE), and Pacific Organized Track System (PACOTS) air routes. The Kamchatka Volcanic Eruption Response Team (KVERT) monitors and reports on volcanic hazards to aviation for Kamchatka and the north Kuriles. KVERT scientists utilize real-time seismic data, daily satellite views of the region, real-time video, and pilot and field reports of activity to track and alert the aviation industry of hazardous activity. Most Kurile Island volcanoes are monitored by the Sakhalin Volcanic Eruption Response Team (SVERT) based in Yuzhno-Sakhalinsk. SVERT uses daily moderate resolution imaging spectroradiometer (MODIS) satellite images to look for volcanic activity along this 1,250-km chain of islands. Neither operation is staffed 24 h per day. In addition, the vast majority of Russian volcanoes are not monitored seismically in real-time. Other challenges include multiple time-zones and language differences that hamper communication among volcanologists and meteorologists in the US, Japan, and Russia who share the responsibility to issue official warnings. Rapid, consistent verification of explosive eruptions and determination of cloud heights remain significant technical challenges. Despite these difficulties, in more than a decade of frequent eruptive activity in Kamchatka and the northern Kuriles, no damaging encounters with volcanic ash from Russian eruptions have been recorded. ?? Springer Science+Business Media B.V. 2009.
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Precursory diffuse CO2 emission signature of the 2011 El Hierro submarine eruption, Canary Islands
NASA Astrophysics Data System (ADS)
Pérez, N. M.; Padilla, G. D.; Padrón, E.; Hernández, P. A.; Melián, G. V.; Barrancos, J.; Dionis, S.; Rodríguez, F.; Nolasco, D.; Calvo, D.; Hernández, I.; Peraza, M. D.
2012-04-01
El Hierro is the youngest and southernmost island of the Canarian archipelago and represents the summit of a volcanic shield elevating from the surrounding seafloor at depth of 4000 m to up to 1501 m above sea level. The island is believed to be near the present hotspot location in the Canaries with the oldest subaerial rocks dated at 1.12 Ma. The subaerial parts of the El Hierro rift zones (NE, NW and S Ridges) are characterized by tightly aligned dyke complexes with clusters of cinder cones as their surface expressions. Since 16 July, an anomalous seismicity at El Hierro Island was recorded by IGN seismic network. Volcanic tremor started at 05:15 on 10 October, followed on the afternoon of 12 October by a green discolouration of seawater, strong bubbling and degassing, and abundant bombs on a decimetre scale found floating on the ocean surface offshore, southwest of La Restinga village, indicating the occurrence of a submarine volcanic eruption at approximately 2 km far the coast line of La Restinga. Further episodes have occurred during November, December 2011 and January 2012, with turbulent water, foam rings, and volcanic material again reaching the sea surface. In order to improve the volcanic surveillance program of El Hierro Island and to provide a multidisciplinary approach, a continuous geochemical station to measure CO2 efflux was installed on September 2003 in Llanos de Guillen, the interception center of the three volcanic-rift zones of the island, with the aim of detecting changes in the diffuse emission of CO2 related to the seismic or volcanic activity. The station measures on an hourly basis the CO2 and H2S efflux, the CO2 and H2S air concentrations, the soil water content and temperature and the atmospheric parameters: wind speed and direction, air temperature and humidity and barometric pressure. The meteorological parameters together with the air CO2 concentration are measured 1 m above the ground and the soil water content and soil temperature
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Modeling post-eruptive deformation at Okmok volcano from GPS and InSAR using unscented Kalman filter
NASA Astrophysics Data System (ADS)
Xue, X.; Freymueller, J. T.
2017-12-01
Okmok, occupies most of northeastern Umnak Island in the Aleutian arc, started inflating soon after the 2008 eruption. Seven GPS sites have been operated after the eruption. Two of them are located within the caldera, three are around the rim of the caldera and two are out of the caldera. The InSAR timeseries have been generated using data from the C-band Envisat and X-band TerraSAR-X satellites (Qu et al., 2015). Both GPS and InSAR indicate more than 0.6 m uplift within the caldera and subtle subsidence outside the caldera. Based on single Mogi source, an unscented Kalman filter was successfully used to model the deformation at Okmok detected by GPS during 2000-2007. We have expanded it to be able to model multiple Mogi sources at different depths and integrate the InSAR observations. Before applying the Kalman filter, We remove a time-independent Mogi source and phase ramp from each InSAR image and obtain its variance-covariance information from the residual. We also determine the relative weight between GPS and InSAR data using variance component estimation. The GPS and InSAR timeseries can then be combined for the Kalman filter. Preliminary results show that two Mogi sources are more likely beneath Okmok volcano. The deep source is located at 8.5 km depth which deflated 0.016 km3 during the first 3 years after the eruption then reached a stable state. The deflating source explains the subsidence outside the caldera which can not be modeled with only one inflating source in any way. The shallow source, migrating 0.5 km from north to south, is located at 2 km depth within the caldera where is close to the source position before the eruption (Freymueller et al., 2010). The magma volume accumulation of the shallow source in the following 7 years from the 2008 eruption is 0.035 km3.
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NASA Astrophysics Data System (ADS)
Rath, C. A.; Browne, B. L.
2011-12-01
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
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Microbial consortia of gorgonian corals from the Aleutian islands
Gray, Michael A.; Stone, R.P.; McLaughlin, M.R.; Kellogg, C.A.
2011-01-01
Gorgonians make up the majority of corals in the Aleutian archipelago and provide critical fish habitat in areas of economically important fisheries. The microbial ecology of the deep-sea gorgonian corals Paragorgea arborea, Plumarella superba, and Cryogorgia koolsae was examined with culture-based and 16S rRNA gene-based techniques. Six coral colonies (two per species) were collected. Samples from all corals were cultured, and clone libraries were constructed from P. superba and C. koolsae. Cultured bacteria were dominated by the Gammaproteobacteria, especially Vibrionaceae, with other phyla comprising <6% of the isolates. The clone libraries showed dramatically different bacterial communities between corals of the same species collected at different sites, with no clear pattern of conserved bacterial consortia. Two of the clone libraries (one from each coral species) were dominated by Tenericutes, with Alphaproteobacteria dominating the remaining sequences. The other libraries were more diverse and had a more even distribution of bacterial phyla, showing more similarity between genera than within coral species. Here we report the first microbiological characterization of P. arborea, P. superba, and C. koolsae. FEMS Microbiology Ecology ?? 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. No claim to original US government works.
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NASA Technical Reports Server (NTRS)
Munro, Duncan C.; Mouginis-Mark, Peter J.
1990-01-01
SPOT-1 HRV, and large format-camera images were used to investigate the distribution and structure of erupted materials on Isla Fernandina, Galapagos Islands. Maps of lava flows, fissures, cones and topography derived from these data allow the first study of the entire subaerial segment of this geographically remote and ecologically sensitive volcano. No significant departure from a uniform distribution of erupted lava with azimuth can be detected. Short (less than 4 km) lava flows commonly have their source in the summit region and longer (greater than 8 km) lava flows originate from vents at lower elevations. Catastrophic landslides are proposed as a possible explanation for the asymmetry of the coastline with respect to the caldera.
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Bacon, C.R.; Sison, T.W.; Mazdab, F.K.
2007-01-01
Mount Veniaminof volcano, Alaska Peninsula, provides an opportunity to relate Quaternary volcanic rocks to a coeval intrusive complex. Veniaminof erupted tholeiitic basalt through dacite in the past ???260 k.y. Gabbro, diorite, and miarolitic granodiorite blocks, ejected 3700 14C yr B.P. in the most recent caldera-forming eruption, are fragments of a shallow intrusive complex of cumulate mush and segregated vapor-saturated residual melts. Sensitive high-resolution ion microprobe (SHRIMP) analyses define 238U-230Th isochron ages of 17.6 ?? 2.7 ka, 5+11/-10 ka, and 10.2 ?? 4.0 ka (2??) for zircon in two granodiorites and a diorite, respectively. Sparse zircons from two gabbros give 238-230Th model ages of 36 ?? 8 ka and 26 ?? 7 ka. Zircons from granodiorite and diorite crystallized in the presence of late magmatic aqueous fluid. Although historic eruptions have been weakly explosive Strombolian fountaining and small lava effusions, the young ages of plutonic blocks, as well as late Holocene dacite pumice, are evidence that the intrusive complex remains active and that evolved magmas can segregate at shallow levels to fuel explosive eruptions. ?? 2007 The Geological Society of America.
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Ryan, Holly F.; von Huene, Roland E.; Wells, Ray E.; Scholl, David W.; Kirby, Stephen; Draut, Amy E.; Dumoulin, Julie A.; Dusel-Bacon, C.
2012-01-01
During the past several years, devastating tsunamis were generated along subduction zones in Indonesia, Chile, and most recently Japan. Both the Chile and Japan tsunamis traveled across the Pacific Ocean and caused localized damage at several coastal areas in California. The question remains as to whether coastal California, in particular the California Continental Borderland, is vulnerable to more extensive damage from a far-field tsunami sourced along a Pacific subduction zone. Assuming that the coast of California is at risk from a far-field tsunami, its coastline is most exposed to a trans-Pacific tsunami generated along the eastern Aleutian-Alaska subduction zone. We present the background geologic constraints that could control a possible giant (Mw ~9) earthquake sourced along the eastern Aleutian-Alaska megathrust. Previous great earthquakes (Mw ~8) in 1788, 1938, and 1946 ruptured single segments of the eastern Aleutian-Alaska megathrust. However, in order to generate a giant earthquake, it is necessary to rupture through multiple segments of the megathrust. Potential barriers to a throughgoing rupture, such as high-relief fracture zones or ridges, are absent on the subducting Pacific Plate between the Fox and Semidi Islands. Possible asperities (areas on the megathrust that are locked and therefore subject to infrequent but large slip) are identified by patches of high moment release observed in the historical earthquake record, geodetic studies, and the location of forearc basin gravity lows. Global Positioning System (GPS) data indicate that some areas of the eastern Aleutian-Alaska megathrust, such as that beneath Sanak Island, are weakly coupled. We suggest that although these areas will have reduced slip during a giant earthquake, they are not really large enough to form a barrier to rupture. A key aspect in defining an earthquake source for tsunami generation is determining the possibility of significant slip on the updip end of the megathrust near
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Federal Register 2010, 2011, 2012, 2013, 2014
2012-10-01
...NMFS publishes regulations to implement Amendment 97 to the Fishery Management Plan for Groundfish of the Bering Sea and Aleutian Islands Management Area (FMP). Amendment 97 allows the owner of a trawl catcher/processor vessel authorized to participate in the Amendment 80 catch share program to replace that vessel with a vessel that meets certain requirements. This action establishes the regulatory process for replacement of vessels in the Amendment 80 fleet and the requirements for Amendment 80 replacement vessels, such as a limit on the overall length of a replacement vessel, a prohibition on the use of an AFA vessel as a replacement vessel, measures to prevent a replaced vessel from participating in Federal groundfish fisheries off Alaska that are not Amendment 80 fisheries, and measures that extend specific catch limits (known as Amendment 80 sideboards) to a replacement vessel. This action is necessary to promote safety-at-sea by allowing Amendment 80 vessel owners to replace their vessels for any reason at any time and by requiring replacement vessels to meet certain U.S. Coast Guard vessel safety standards, and to improve the retention and utilization of groundfish catch by these vessels by facilitating an increase in the processing capabilities of the fleet. This action is intended to promote the goals and objectives of the Magnuson-Stevens Fishery Conservation and Management Act, the FMP, and other applicable laws.
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National-level long-term eruption forecasts by expert elicitation
NASA Astrophysics Data System (ADS)
Bebbington, Mark S.; Stirling, Mark W.; Cronin, Shane; Wang, Ting; Jolly, Gill
2018-06-01
Volcanic hazard estimation is becoming increasingly quantitative, creating the potential for land-use decisions and engineering design to use volcanic information in an analogous manner to seismic codes. The initial requirement is to characterize the possible hazard sources, quantifying the likely timing, magnitude and location of the next eruption in each case. This is complicated by the extremely different driving processes at individual volcanoes, and incomplete and uneven records of past activity at various volcanoes. To address these issues, we carried out an expert elicitation approach to estimate future eruption potential for 12 volcanoes of interest in New Zealand. A total of 28 New Zealand experts provided estimates that were combined using Cooke's classical method to arrive at a hazard estimate. In 11 of the 12 cases, the elicited eruption duration increased with VEI, and was correlated with expected repose, differing little between volcanoes. Most of the andesitic volcanoes had very similar elicited distributions for the VEI of a future eruption, except that Taranaki was expected to produce a larger eruption, due to the current long repose. Elicited future vent locations for Tongariro and Okataina reflect strongly the most recent eruptions. In the poorly studied Bay of Islands volcanic field, the estimated vent location distribution was centred on the centroid of the previous vent locations, while in the Auckland field, it was focused on regions within the field without past eruptions. The elicited median dates for the next eruptions ranged from AD2022 (Whakaari/White Island) to AD4390 (Tuhua/Mayor Island).
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NASA Astrophysics Data System (ADS)
Go, S. Y.; Kim, G. B.; Jeong, J. O.; Sohn, Y. K.
2017-03-01
The Songaksan tuff ring, Jeju Island, Korea, which erupted ca. 3.7 ka BP in a coastal setting, provides an unusual opportunity to study the processes of phreatomagmatic eruption and the formation of a diatreme because of the exceptionally well-preserved ejecta beds and well-known subsurface geology. The tuff sequence can be divided into four units (A to D), which have distinctly different accidental componentry (quartz-rich vs. quartz-poor), grain surface features (abraded and ash-coated vs. unabraded and uncoated), and chemical compositions of juvenile particles. The basal tephra bed of unit A, which probably erupted after the removal of the relatively hard shallow-level (<120 m deep) substrate by initial cratering, comprises only unabraded and uncoated grains and contains abundant relatively deep-derived (>120 m deep) accidental grains, suggesting that the early erupted tephra had not yet experienced recycling and pre-eruption mixing in the diatreme. On the other hand, the overlying tephra beds of units A, B, and D contain an abundance of abraded and ash-coated juvenile/accidental grains, suggesting that the tephra comprised significant proportions of "recycled" or "premixed" materials from previous eruptions or subsurface explosions, which participated in the explosion-driven mixing in the diatreme before eventual ejection from the diatreme. Unit C is unusual in that it comprises extremely rare accidental grains and ash-coated juvenile/accidental grains. We interpret that the supply of solid materials, either accidental or juvenile, to the diatreme was greatly reduced because of temporary stabilization of the diatreme and the reduction in magma flux to the diatreme. The diatreme is therefore envisaged to have been filled with a water-saturated slurry, in which particle abrasion and adhesion were inhibited. We also infer that the diatreme fill was temporarily removed by a powerful explosion before eruption of unit C on the basis of the near absence of the tephra
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Satellite observations of a surtseyan eruption: Hunga Ha'apai, Tonga
Vaughan, R.G.; Webley, P.W.
2010-01-01
On March 17, 2009, a surtseyan eruption occurred around Hunga Ha'apai Island, Tonga. A series of observations from the high-spatial resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), and the high-temporal resolution Moderate Resolution Imaging Spectroradiometer (MODIS), was used to estimate the magnitude, location, start time, and duration of the eruption, and measure the evolving characteristics of the new Hunga Ha'apai Island. The eruption start time was estimated to be between 01:50 and 11:10 local time, on March 17, 2009 (i.e., between 12:50 and 22:10UTC, March 16). The initial explosive phase lasted 3-5days and consisted of multiple steam and tephra explosions from two distinct vent sources, one on the northwest side, and another about 100m off the south shore of the pre-existing island. The eruption plume reached 4.0 to 7.6km altitude above sea level, and tephra added new land around each of the vents, initially tripling the area of the pre-existing island. The next phase of steaming from newly formed crater lakes around the vents lasted a few days. Three warm crater lakes formed initially, but disappeared with time as the shoreline eroded. After ~2months, vegetation that was initially buried by tephra was recovering; after ~10months, the size of the island had eroded down to ~twice that of the pre-existing island, and the one remaining crater lake had a temperature of ~68??17??C. The volume of erupted material was estimated to be ~0.0176km3 and the volcanic explosivity index (VEI) was estimated to be VEI=2. ?? 2010.
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NASA Astrophysics Data System (ADS)
Becerril, L.; Galindo, I.; Martí, J.; Gudmundsson, A.
2015-04-01
Using new surface structural data as well as subsurface structural data obtained from seventeen water galleries, we provide a comprehensive model of the volcano-tectonic evolution of El Hierro (Canary Islands). We have identified, measured and analysed more than 1700 volcano-structural elements including vents, eruptive fissures, dykes and faults. The new data provide important information on the main structural patterns of the island and on its stress and strain fields, all of which are crucial for reliable hazard assessments. We conducted temporal and spatial analyses of the main structural elements, focusing on their relative age and association with the three main cycles in the construction of the island: the Tiñor Edifice, the El Golfo-Las Playas Edifice, and the Rift Volcanism. A radial strike distribution, which can be related to constructive episodes, is observed in the on-land structures. A similar strike distribution is seen in the submarine eruptive fissures, which are radial with respect to the centre of the island. However, the volcano-structural elements identified onshore and reflecting the entire volcano-tectonic evolution of the island also show a predominant NE-SW strike, which coincides with the main regional trend of the Canary archipelago as a whole. Two other dominant directions of structural elements, N-S and WNW-ESE, are evident from the establishment of the El Golfo-Las Playas edifice, during the second constructive cycle. We suggest that the radial-striking structures reflect comparatively uniform stress fields during the constructive episodes, mainly conditioned by the combination of overburden pressure, gravitational spreading, and magma-induced stresses in each of the volcanic edifices. By contrast, in the shallower parts of the edifice the NE-SW, N-S and WNW-ESE-striking structures reflect local stress fields related to the formation of mega-landslides and masking the general and regional radial patterns.
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NASA Technical Reports Server (NTRS)
2001-01-01
An Expedition Two crewmember aboard the International Space Station (ISS) captured this overhead look at the smoke and ash regurgitated from the erupting volcano Mt. Etna on the island of Sicily, Italy. At an elevation of 10,990 feet (3,350 m), the summit of the Mt. Etna volcano, one of the most active and most studied volcanoes in the world, has been active for a half-million years and has erupted hundreds of times in recorded history.
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Eruption Forecasting in Alaska: A Retrospective and Test of the Distal VT Model
NASA Astrophysics Data System (ADS)
Prejean, S. G.; Pesicek, J. D.; Wellik, J.; Cameron, C.; White, R. A.; McCausland, W. A.; Buurman, H.
2015-12-01
United States volcano observatories have successfully forecast most significant US eruptions in the past decade. However, eruptions of some volcanoes remain stubbornly difficult to forecast effectively using seismic data alone. The Alaska Volcano Observatory (AVO) has responded to 28 eruptions from 10 volcanoes since 2005. Eruptions that were not forecast include those of frequently active volcanoes with basaltic-andesite magmas, like Pavlof, Veniaminof, and Okmok volcanoes. In this study we quantify the success rate of eruption forecasting in Alaska and explore common characteristics of eruptions not forecast. In an effort to improve future forecasts, we re-examine seismic data from eruptions and known intrusive episodes in Alaska to test the effectiveness of the distal VT model commonly employed by the USGS-USAID Volcano Disaster Assistance Program (VDAP). In the distal VT model, anomalous brittle failure or volcano-tectonic (VT) earthquake swarms in the shallow crust surrounding the volcano occur as a secondary response to crustal strain induced by magma intrusion. Because the Aleutian volcanic arc is among the most seismically active regions on Earth, distinguishing distal VT earthquake swarms for eruption forecasting purposes from tectonic seismicity unrelated to volcanic processes poses a distinct challenge. In this study, we use a modified beta-statistic to identify pre-eruptive distal VT swarms and establish their statistical significance with respect to long-term background seismicity. This analysis allows us to explore the general applicability of the distal VT model and quantify the likelihood of encountering false positives in eruption forecasting using this model alone.
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NASA Astrophysics Data System (ADS)
Miller, H.; Lopez, T. M.; Fischer, T. P.; Schrenk, M. O.
2016-12-01
Subduction-related processes, including the movement and alteration of carbon compounds, are an important component of global geochemical cycles. Actively degassing volcanoes of the Aleutian Island arc offer interesting opportunities to not only characterize the composition and abundance of volatiles, but also to identify the origin of the discharging gases (e.g. mantle, organic matter, or carbonates). Taking this approach a step further, microbial activities in and around volcanic fumarole areas may impact the composition and flux of reduced volcanic gases, either through their modification or their assimilation into fixed biomass. Microbiological studies of these systems can be used to develop predictive models to complement those based upon geochemical data while providing greater understanding of the causal relationships between microbial populations and their environment, and ultimately refine estimates of volcanic outgassing. Coupled fumarole soil and gas samples were collected from several Aleutian Island volcanoes in 2015 (Gareloi, Kanaga, Kiska, Little Sitkin) and 2016 (Okmok, Resheschnoi). DNA was extracted from the soil and used to describe microbial community composition, while gas samples were analyzed through chromatography and mass spectrometry. Preliminary data suggests a relationship between the abundance of specific groups of prokaryotes known to metabolize reduced gases, such as sulfur-oxidizers and methanotrophs, and the abundances of the degassing volatiles, including sulfur dioxide and methane. Ongoing studies aimed at investigating the relationship between the genomic composition of the fumarolic microbial community and the physical and chemical properties of the soil (i.e. mineralogy, bulk geochemistry, nutrient concentration, gas flux, and environmental measurements) are underway. These data will be used to evaluate the potential for microbial communities to remove volcanic carbon and store it as biomass, or to modify the volatile carbon
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Microbial consortia of gorgonian corals from the Aleutian islands.
Gray, Michael A; Stone, Robert P; McLaughlin, Molly R; Kellogg, Christina A
2011-04-01
Gorgonians make up the majority of corals in the Aleutian archipelago and provide critical fish habitat in areas of economically important fisheries. The microbial ecology of the deep-sea gorgonian corals Paragorgea arborea, Plumarella superba, and Cryogorgia koolsae was examined with culture-based and 16S rRNA gene-based techniques. Six coral colonies (two per species) were collected. Samples from all corals were cultured, and clone libraries were constructed from P. superba and C. koolsae. Cultured bacteria were dominated by the Gammaproteobacteria, especially Vibrionaceae, with other phyla comprising <6% of the isolates. The clone libraries showed dramatically different bacterial communities between corals of the same species collected at different sites, with no clear pattern of conserved bacterial consortia. Two of the clone libraries (one from each coral species) were dominated by Tenericutes, with Alphaproteobacteria dominating the remaining sequences. The other libraries were more diverse and had a more even distribution of bacterial phyla, showing more similarity between genera than within coral species. Here we report the first microbiological characterization of P. arborea, P. superba, and C. koolsae. FEMS Microbiology Ecology © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. No claim to original US government works.
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NASA Astrophysics Data System (ADS)
Telesca, Luciano; Lovallo, Michele; Martì Molist, Joan; López Moreno, Carmen; Abella Meléndez, Rafael
2015-02-01
The Multifractal Detrended Fluctuation Analysis (MF-DFA) is an effective method that allows detecting multifractality in non-stationary signals. We applied the MF-DFA to the continuous seismic signal recorded at El Hierro volcano (Canary Islands), which was affected by a submarine monogenetic eruption in October 2011. We investigated the multifractal properties of the continuous seismic signal before the onset of the eruption and after. We analysed three frames of the signal, one measured before the onset of eruption that occurred on October 10, 2011; and two after, but corresponding to two distinct eruptive episodes, the second one started on November 22, 2011 and lasting until late February 2012. The results obtained show a striking difference in the width of the multifractal spectrum, which is generally used to quantify the multifractal degree of a signal: the multifractal spectra of the signal frames recorded during the eruptive episodes are almost identical and much narrower than that of the signal frame measured before the onset of the eruption. Such difference indicates that the seismic signal recorded during the unrest reflects mostly the fracturing of the host rock under the overpressure exerted by the intruding magma, while that corresponding to the eruptive phases was mostly influenced by the flow of magma through the plumbing system, even some fracturing remains, not being possible to distinguish among the two eruptive episodes in terms of rock fracture mechanics.
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NASA Astrophysics Data System (ADS)
Vieira, D.; Teodoro, A.; Gomes, A.
2016-10-01
Land Surface Temperature (LST) is an important parameter related to land surface processes that changes continuously through time. Assessing its dynamics during a volcanic eruption has both environmental and socio-economical interest. Lava flows and other volcanic materials produced and deposited throughout an eruption transform the landscape, contributing to its heterogeneity and altering LST measurements. This paper aims to assess variations of satellite-derived LST and to detect patterns during the latest Fogo Island (Cape Verde) eruption, extending from November 2014 through February 2015. LST data was obtained through four processed Landsat 8 images, focused on the caldera where Pico do Fogo volcano sits. QGIS' plugin Semi-Automatic Classification was used in order to apply atmospheric corrections and radiometric calibrations. The algorithm used to retrieve LST values is a single-channel method, in which emissivity values are known. The absence of in situ measurements is compensated by the use of MODIS sensor-derived LST data, used to compare with Landsat retrieved measurements. LST data analysis shows as expected that the highest LST values are located inside the caldera. High temperature values were also founded on the south-facing flank of the caldera. Although spatial patterns observed on the retrieved data remained roughly the same during the time period considered, temperature values changed throughout the area and over time, as it was also expected. LST values followed the eruption dynamic experiencing a growth followed by a decline. Moreover, it seems possible to recognize areas affected by lava flows of previous eruptions, due to well-defined LST spatial patterns.
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Ruppert, Natalia G.; Prejean, Stephanie G.; Hansen, Roger A.
2011-01-01
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 eruptive activity. The largest earthquake measured as moment magnitude 5.8, and a dozen additional earthquakes were larger than magnitude 4. The swarm exhibited both tectonic and volcanic characteristics. Its shear failure earthquake features were b value = 0.9, most earthquakes with impulsive P and S arrivals and higher-frequency content, and earthquake faulting parameters consistent with regional tectonic stresses. Its volcanic or fluid-influenced seismicity features were volcanic tremor, large CLVD components in moment tensor solutions, and increasing magnitudes with time. Earthquake location tests suggest that the earthquakes occurred in a distributed volume elongated in the NS direction either directly under the volcano or within 5-10 km south of it. Following the MW 5.8 event, earthquakes occurred in a new crustal volume slightly east and north of the previous earthquakes. The central Aleutian Arc is a tectonically active region with seismicity occurring in the crusts of the Pacific and North American plates in addition to interplate events. We postulate that the Kasatochi seismic swarm was a manifestation of the complex interaction of tectonic and magmatic processes in the Earth's crust. Although magmatic intrusion triggered the earthquakes in the swarm, the earthquakes failed in context of the regional stress field.
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NASA Astrophysics Data System (ADS)
Tarff, R. W.; Day, S. J.
2011-12-01
Episodes of hazardous phreatomagmatic explosive activity, including Surtseyan activity, occur within otherwise less dangerous effusive to mildly explosive magmatic eruptions at high-elevation vents on many oceanic island volcanoes. The water driving these explosions is sourced from freshwater aquifers within the volcanic edifices. Understanding volcanic and geophysical precursors to, and mechanisms of, the (frequently abrupt) transitions to explosive activity is required as a basis for effective warning and mitigation of the resulting hazards. Here we describe near-vent deposits around the large Cova de Paúl crater on the island of Santo Antão, Cape Verde Islands, which provide some insights into a transition from mild magmatic to violently explosive phreatomagmatic activity in one such eruption. This pre-historic but well-preserved crater formed in a single eruption that produced extensive low-temperature, lithic-rich phreatomagmatic pyroclastic flows and surge deposits; these are interbedded in proximal outcrops with airfall breccia and ash beds containing varying proportions of lithic and juvenile clasts, pointing to a series of climactic explosions within an extended period of milder explosive activity of broadly Surtseyan type. Prior to the transition to phreatomagmatic activity, the eruption had been characterized by mild Strombolian activity that produced scoria and spatter deposits of broadly tephritic composition. The Strombolian deposits contain a distinct population of strongly banded, low-vesicularity angular clasts with strongly prolate vesicles and a notably glassy appearance. These became markedly larger and more abundant just below the transition to the phreatomagmatic deposits. Comparisons of these clasts with the Strombolian scoria suggest that they are fragments of flow-banded chilled margins from the walls of the eruptive conduit. Thermal shattering of these margins to produce the angular glassy clasts may record the onset of groundwater flow
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Ricca, Mark A.; Miles, A. Keith; Anthony, Robert G.
2008-01-01
Persistent organochlorine compounds and mercury (Hg) have been detected in numerous coastal organisms of the Aleutian archipelago of Alaska, yet sources of these contaminants are unclear. We collected glaucous-winged gulls, northern fulmars, and tufted puffins along a natural longitudinal gradient across the western and central Aleutian Islands (Buldir, Kiska, Amchitka, Adak), and an additional 8 seabird species representing different foraging and migratory guilds from Buldir Island to evaluate: 1) point source input from former military installations, 2) westward increases in contaminant concentrations suggestive of distant source input, and 3) effects of trophic status (δ15N) and carbon source (δ13C) on contaminant accumulation. Concentrations of Σ polychlorinated biphenyls (PCBs) and most chlorinated pesticides in glaucous-winged gulls consistently exhibited a ‘U’-shaped pattern of high levels at Buldir and the east side of Adak and low levels at Kiska and Amchitka. In contrast, concentrations of Σ PCBs and chlorinated pesticides in northern fulmars and tufted puffins did not differ among islands. Hg concentrations increased westward in glaucous-winged gulls and were highest in northern fulmars from Buldir. Among species collected only at Buldir, Hg was notably elevated in pelagic cormorants, and relatively high Σ PCBs were detected in black-legged kittiwakes. Concentrations of Σ PCBs, dichlorodiphenyldichloroethylene (p,p′ DDE), and Hg were positively correlated with δ15N across all seabird species, indicating biomagnification across trophic levels. The east side of Adak Island (a former military installation) was a likely point source of Σ PCBs and p,p′ DDE, particularly in glaucous-winged gulls. In contrast, elevated levels of these contaminants and Hg, along with PCB congener and chlorinated pesticide compositional patterns detected at Buldir Island indicated exposure from distant sources influenced by a combination of atmospheric
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USDA-ARS?s Scientific Manuscript database
Burned stone slabs, historically called griddlestones, were recovered from Components 1 (2390-2590 RCYPB) and 2 (170-415 RCYBP) at archaeological site ADK-011 on Adak Island, Aleutian Islands, Alaska. The griddlestones show evidence of fire exposure and have a dark, often greasy, matrix of decompose...
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NASA Astrophysics Data System (ADS)
Edwards, M. J.; Kennedy, B. M.; Jolly, A. D.; Scheu, B.; Jousset, P.
2017-02-01
White Island volcano, New Zealand was a host to multiple hydrothermal eruptive episodes within a mud-sulphur pool in 2013. Although hydrothermal activity is common at White Island, past events have largely gone undescribed in favour of the larger phreatomagmatic and magmatic eruptions. Here, we detail the first and longest hydrothermal episode of 2013, lasting from 15 January to 7 February using video and photo analysis from tour operators and staff responsible for monitoring the volcano. Differences in the dominant bubble burst style across this episode led to the classification of four distinct eruption regimes: (1) multiple irregular bursts on the pool surface, (2) larger distinct symmetric hemispheres with starbursts and/or followed by mud heaves, (3) no initial pool surface deformation but a vertical steam jet followed by a sometimes large directed mud heave and (4) no lake and continuous pulsating dry ash and block venting. The progression through these regimes is associated with a lowering lake level and a concomitantly increasing viscosity of the pool, which initially comprises a low viscosity muddy water, and partially evaporates to yield a shallow layer of high viscosity mud that ends with the complete drying up of the mud pool. Formation of primary mud hemispheres or gas jets is followed by heaves or secondary upheaval events. The heights of these heaves are used as a measure of explosivity. Heights increase from ˜8 m during regime 1 on 15 January to ˜102 m during regime 3 on 28 January. Venting of dry mud during regime 4 developed on 29 January before a regression back to regime 1 took place on 7 February as the pool re-established. Through observations of the shapes of ejected mud clots, we propose that the increasing explosivity of higher number regimes is primarily due to increasing slug bubble lengths teamed with increasing mud pool viscosity. We attribute a lesser control to the decreasing depth of the pool during its progressive desiccation
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NASA Astrophysics Data System (ADS)
Bryan, S. E.; Cas, R. A. F.; Martí, J.
2000-12-01
The Granadilla Member is one of the most widely dispersed and largest volume pyroclastic units at Tenerife (Canary Islands) and represents the culminating eruption to a second cycle of explosive volcanism of the Las Cañadas edifice. The member, dated at 0.57 Ma, comprises a plinian fall deposit, the Granadilla pumice, which is overlain by ignimbrite up to 30 m thick. The Granadilla pumice is up to 9 m thick approximately 10 km from source (Pyle bt value is 5.35 km), and is subdivided into four fall units. Unit 1 is up to 1.2 m thick and is further divisible into another four pumice fall subunits, based on bedding and grainsize differences. Unit 2 is a thin but distinctive ash layer (˜2 cm thick), and its wide dispersal (>550 km2), constant thickness, planar laminations and ash aggregate textures collectively indicate a phreatoplinian fall origin. The lithic-rich nature and abundance of unaltered lithic fragments reflect magma interaction with aquifer-derived water at depth. Unit 3 (≤1.8 m thick), records a reversal to dry plinian eruptive activity. Unit 4, the thickest of the fall units (up to 6.3 m thick), records the maximum dispersal and intensity of the eruption (Pyle bt and bc values are 5.7 and 6.3 km, respectively), best illustrated by the presence of large pumice bombs up to 30 cm diameter (at distances up to 20 km from vent), and reverse grading of lithic and pumice clasts. The widespread (>500 km2), nonwelded and pumice-rich Granadilla ignimbrite (unit 5) records the collapse of the plinian eruption column. The ignimbrite has a simple sheet-like geometry, but exhibits a complex internal stratigraphy. The base of the ignimbrite locally cuts down through the underlying Granadilla pumice removing it entirely, indicating up to 9 m of erosion by the pyroclastic flows. A coarse, vent-derived lithic breccia horizon towards the top of the ignimbrite is interpreted to record the onset of caldera collapse late in the eruption. Minimum volume estimates for the
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Satellite View of Kilauea Eruption
2018-05-07
This image from NASA's Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra spacecraft show recent eruptions of Kilauea volcano on the island of Hawaii (the Big Island). Following days of increased seismic activity, Kilauea erupted May 3, 2018, and triggered a number of additional fissure eruptions along the East Rift Zone. The eruptions and high level of sulfur dioxide gas (SO2) prompted evacuations in the area, including the Leilani Estates subdivision near the town of Pahoa. The ASTER images, acquired on May 6, 2018, show different aspects of the eruption. A color composite depicts vegetation in red, and old lava flows in black and gray. Superimposed on the image in yellow are hotspots detected on the thermal infrared bands. The easternmost hot spots show the newly formed fissures and the lava flow spilling to the northwest. The middle spots are Pu'u O'o crater, and lava flows descending the slopes to the southeast. The westernmost area is the crater and lava lake on Kilauea's summit. The greenish area southwest of Pu'u O'o is ash deposits from its short eruption on Friday. The inset shows the massive sulfur dioxide plume is shown in yellow and yellow-green, extracted from ASTER's multiple thermal bands. A smaller, but thicker, sulfur dioxide gas plume can be seen coming from Kilauea. The prevailing trade winds blow the plumes to the southwest, out over the ocean. The images cover an area of 57.8 by 63 kilometers, and are located at 19.3 degrees North, 155.1 degrees West. https://photojournal.jpl.nasa.gov/catalog/PIA22450
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NASA Technical Reports Server (NTRS)
1988-01-01
In this view of the entire Hawaiian Island Archipelago (21.0N, 157.0W), the islands perturb the prevailing northeastewrly winds producing extensive cloud wakes in the lee of the islands. The atmospheric haze within the wake is a result of the near continuous eruptions of Kilauea volcano on the southeast coast of the big island of Hawaii.
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NASA Astrophysics Data System (ADS)
Kueppers, U.; Queiroz, M. G.; Pacheco, J. M.
2007-12-01
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 island in the 15{th} century. The Eastern part of the island is considered extinct. The oldest dated subaerial rocks of Sete Cidades exhibit an age of 210 ka. Morphology of the present summit caldera (5 km diameter, up to 350 m deep), stratigraphy, and distribution of the deposits suggest a multiple-stage evolution and at least three caldera-forming eruptions (CFE) are assumed to have occurred. 14C-dating revealed ages of 36, 29, and 16 ka, respectively, for the most recent ones. Today, the average slope angle is 12° and the maximum distance of the coastline from the caldera rim approx. 5 km. Assuming a comparable situation at the time of the CFE, a large portion of the eruptive products has probably not been deposited on land. After a pause of several thousand years, eruptive activity resumed approx. 5 ka ago and started filling the caldera. As deposits of minor thickness and distribution can be found between the deposits of the CFE, it is unclear whether the caldera formation is completely finished. Climatic factors (e.g. precipitation, air humidity) have affected the deposits by erosion, weathering, and possibly significant reworking and caused dense vegetation on all flanks of the volcano. Still, it was possible to establish distribution and thickness of the deposits of the CFE and constrain differences in eruptive behaviour and transport/emplacement mechanisms. They are composed of air-fall deposits and pyroclastic density currents but show significant differences amongst them: (1) Degree of pre- and syn-eruptive magma-magma interaction and syn-eruptive magma
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From 3D to 4D seismic tomography at El Hierro Island (Canary Islands, Spain)
NASA Astrophysics Data System (ADS)
Garcia-Yeguas, A.; Koulakov, I.; Jakovlev, A.; Ibáñez, J. M.
2012-04-01
In this work we are going to show the advantages of a dynamic tomography 4D, versus a static image 3D related with a volcanic reactivation and eruption at El Hierro island (Canary Islands, Spain). In this process a high number of earthquakes before and during the eruptive processes have been registered. We are going to show a 3D image as an average of the velocity structure and then the characteristics and physical properties on the medium, including the presence or not of magma. This image will be complemented with its evolution along the time, observing its volcanic dynamic and its influence over the medium properties, including its power as an important element on early warnings protocols. After more than forty years of quiet at Canary Islands, since 1971 with Teneguía eruption at La Palma Island, and more than 200 years on El Hierro Island (The last eruption known at El Hierro took place in 1793, volcán de Lomo Negro), on 19th July on 2011 the Spanish seismic national network, administered by IGN (Instituto Geográfico Nacional), detected an increase of local seismic activity below El Hierro island (Canary Islands, Spain). Since this moment an intense swarm took place, with more than 11000 events, until 11th December, with magnitudes (MLg) from 0.2 to 4.4. In this period two eruptive processes have been declared in front of the South coast of El Hierro island, and they have not finished yet. This seismic swarm has allowed carrying out a 3D seismic tomography, using P and S waves traveltimes. It has showed a low velocity from the North to the South. On the other hand, we have performed a 4D seismic tomography, taking the events occurred at different intervals of time. We can observe the evolution of the negative anomaly along the time, from the North to the South, where has taken place La Restinga submarine eruption. 4D seismic tomography is an innovative and powerful tool able to show the evolution in time of a volcanic process.
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Buldir Depression - A Late Tertiary graben on the Aleutian Ridge, Alaska
Marlow, M. S.; Scholl, D. W.; Buffington, E.C.; Boyce, R.E.; Alpha, T.R.; Smith, P.J.; Shipek, C.J.
1970-01-01
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.
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NASA Astrophysics Data System (ADS)
Marti, Joan; Geyer, Adelina
2016-04-01
The quantification of hazard in volcanic systems characterised by long repose period is difficult because the lack of knowledge of the past volcanic history and also because in many cases volcanism is not perceived as a potential problem, being only regarded as an attraction for tourism or a source of economic benefit, thus hiding the need to conduct hazard assessment. Teide, in the island of Tenerife (Canary Islands), is not an exception to this general rule and, despite being one of the largest composite volcanoes in the World, it is generally considered as a non-active volcano by population, visitors and even by some scientists. However, geological and geophysical evidence, including a large diversity of monitoring signals recorded during last decades, as well as a simple comparison with similar volcanoes that have erupted in recent times after hundreds or even thousands of years of quiescence, recommend to consider Teide as an active volcano and to take the necessary precaution in an island with nearly one million of permanent inhabitants and nearly 5 millions of visitors per year. What is the potential of Teide to erupt again? is the question that relies behind the fact of considering it as active, and that needs to be answered first. Based on the current volcanological, petrological and geophysical knowledge We propose a conceptual model on the magma recharge mechanisms, structure of the plumbing system, and eruption triggers and dynamics of Teide volcano that helps to understand its behaviour and to anticipate future activity. Ramón y Cajal contract (RYC-2012-11024)
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NASA Astrophysics Data System (ADS)
Garcia, A.; Berrocoso, M.; Marrero, J. M.; Ortiz, R.
2012-04-01
The FFM (Failure Forecast Method) is developed from the eruption of St. Helens, being repeatedly applied to forecast eruptions and recently to the prediction of seismic activity in active volcanic areas. The underwater eruption of El Hierro Island has been monitored from three months before starting (October 10, 2011). This allowed a large catalogue of seismic events (over 11000) and continuous recording seismic signals that cover the entire period. Since the beginning of the seismic-volcanic crisis (July 2011), the FFM was applied to the SSEM signal of seismic records. Mainly because El Hierro is a very small island, the SSEM has a high noise (traffic and oceanic noise). To improve the signal / noise ratio has been used a Kalman filter. The Kalman filter coefficients are adjusted using an inversion process based on forecasting errors occurred in the twenty days preceding. The application of this filter has been a significant improvement in the reliability of forecasts. The analysis of the results shows, before the start of the eruption, that 90% of the forecasts are obtained with errors less than 10 minutes with more than 24 hours in advance. It is noteworthy that the method predicts the events of greater magnitude and especially the beginning of each swarm of seismic events. At the time the eruption starts reducing the efficiency of the forecast 50% with a dispersion of more than one hour. This fact is probably due to decreased detectability by saturation of some of the seismic stations and decreased the average magnitude. However, the events of magnitude greater than 4 were predicted with an error less than 20 minutes.
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Alaska Volcano Observatory's satellite remote sensing of the Okmok and Kasatochi 2008 eruptions
NASA Astrophysics Data System (ADS)
Dean, K.; Webley, P. W.; Lovick, J.; Puchrik, R.; Bailey, J. E.; Dehn, J.; Valcic, L.
2008-12-01
In July and August 2008, Okmok and Kasatochi volcanoes erupted explosively, both sending ash clouds up to 15 km above sea level (ASL). Okmok volcano last showed signs of volcanic activity in 1997 and Kasatochi in 1899, and then only with suggested steaming. Prior to erupting neither eruption showed any thermal precursors in infrared satellite data, as is common for Aleutian volcanoes. Okmok volcano (53.4 N, 168.2 W, 1073 m ASL) erupted on July 12 at 19:43 UTC, with a phreatomagmatic eruption and within a few hours the ash cloud had reached several 100 km from the volcano. The initial ash cloud reached 16 km ASL, effecting air traffic in the region and caused evacuations of local communities. By July 13, the eruption showed a bifurcated plume with the ash portions at lower elevations than the water rich portion. Kasatochi volcano (52.17 N, 175.51 W, 314 m ASL) erupted on August 7 at approx 22:00 UTC, with two more explosive events on August 8 at 02:00 and 04:35 UTC. The initial plume heights for these events were from 12 to 15 km ASL. From August 7 to 11, the volcanic ash cloud was seen to track across the northeastern portion of the Pacific Ocean and in combination with the sulfur dioxide detected cloud and dispersion modeling predictions resulted in cancellations of numerous flights into Alaska. Here, we show the remote sensing data collected during these two volcanic eruptions, illustrating the strength of the ash signal during the Kasatochi event and also the effect the water rich plume had on the ash detection during the beginning of the Okmok eruption.
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Ruppert, N.A.; Prejean, S.; Hansen, R.A.
2011-01-01
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 eruptive activity. The largest earthquake measured as moment magnitude 5.8, and a dozen additional earthquakes were larger than magnitude 4. The swarm exhibited both tectonic and volcanic characteristics. Its shear failure earthquake features were b value = 0.9, most earthquakes with impulsive P and S arrivals and higher-frequency content, and earthquake faulting parameters consistent with regional tectonic stresses. Its volcanic or fluid-influenced seismicity features were volcanic tremor, large CLVD components in moment tensor solutions, and increasing magnitudes with time. Earthquake location tests suggest that the earthquakes occurred in a distributed volume elongated in the NS direction either directly under the volcano or within 5-10 km south of it. Following the MW 5.8 event, earthquakes occurred in a new crustal volume slightly east and north of the previous earthquakes. The central Aleutian Arc is a tectonically active region with seismicity occurring in the crusts of the Pacific and North American plates in addition to interplate events. We postulate that the Kasatochi seismic swarm was a manifestation of the complex interaction of tectonic and magmatic processes in the Earth's crust. Although magmatic intrusion triggered the earthquakes in the swarm, the earthquakes failed in context of the regional stress field. Copyright ?? 2011 by the American Geophysical Union.
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NASA Astrophysics Data System (ADS)
Staudacher, Thomas; Peltier, Aline; Boissier, Patrice; di Muro, Andrea
2010-05-01
The Piton de la Fournaise volcano at La Réunion Island in the western Indian Ocean is one of the most active volcanoes in the world. Its average eruption rate over the last 2 centuries is one eruption every 9 months. Between 1998 and 2010 thirty eruptions occurred and produced some 300×106 m3 of lava flows. Since the 2007 collapse of 340 m of the Dolomieu caldera, the eruptive activity of the volcano changed with mainly the occurrence of numerous shallow intrusions preceding days or weeks small summit eruptions. In 2009-2010, Piton de la Fournaise erupted successively in November 5, December 14, 2009 and in January 2, 2010. The one day lasting November and December 2009 eruptions started from en echelon fissures close to the summit around its eastern and southern rims, respectively, whereas the January 2010 eruptive fissure opened on the western flank inside of the Dolomieu crater. These three eruptions produced less than 106 m3 of lava, but generated large ground deformation, of up to 70 cm, recorded by the cGPS network of the volcano observatory and by cinematic GPS measurements. The long term survey showed a small extent of the ground deformation field and the small ratios of base/summit displacements and vertical/horizontal displacements reveal the involvement of shallow dykes to fed these successive eruptions. The cGPS network allowed us to follow up precisely the pre eruptive ground deformations, the 40 to 90 minutes dyke propagation toward the surface, as well as the ground deformations after the vent opening. For the November and December 2009 eruptions, the dyke started below the western part of the Dolomieu crater, before propagating to the east and the south, respectively. For the January eruption, the dyke propagated along a more or less vertical pathway directly to the western part of the Dolomieu crater. The two previous dyke injections of November and December had increased the horizontal compressive stress of the eastern side of the Dolomieu
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An isolated population of small Canada geese on Kaliktagik Island, Alaska
Hatch, Scott A.; Hatch, Martha A.
1983-01-01
Recently we discovered that a small form of the Canada Goose Branta canadensis breeds on Kaliktagik Island, one of the Semidi Islands, about 80 km south of the Alaska Peninsula near longitude 157°W (Figure 1). The unexpected occurrence of geese on this oceanic island and the possibility that they are closely allied with the endangered Aleutian race of Canada Geese B. c. leucopareia prompt this summary of observations made between 1977 and 1981, in the course of field studies on seabirds of the area.
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Long-term volcanic hazard assessment on El Hierro (Canary Islands)
NASA Astrophysics Data System (ADS)
Becerril, L.; Bartolini, S.; Sobradelo, R.; Martí, J.; Morales, J. M.; Galindo, I.
2014-07-01
Long-term hazard assessment, one of the bastions of risk-mitigation programs, is required for land-use planning and for developing emergency plans. To ensure quality and representative results, long-term volcanic hazard assessment requires several sequential steps to be completed, which include the compilation of geological and volcanological information, the characterisation of past eruptions, spatial and temporal probabilistic studies, and the simulation of different eruptive scenarios. Despite being a densely populated active volcanic region that receives millions of visitors per year, no systematic hazard assessment has ever been conducted on the Canary Islands. In this paper we focus our attention on El Hierro, the youngest of the Canary Islands and the most recently affected by an eruption. We analyse the past eruptive activity to determine the spatial and temporal probability, and likely style of a future eruption on the island, i.e. the where, when and how. By studying the past eruptive behaviour of the island and assuming that future eruptive patterns will be similar, we aim to identify the most likely volcanic scenarios and corresponding hazards, which include lava flows, pyroclastic fallout and pyroclastic density currents (PDCs). Finally, we estimate their probability of occurrence. The end result, through the combination of the most probable scenarios (lava flows, pyroclastic density currents and ashfall), is the first qualitative integrated volcanic hazard map of the island.
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Isabela Island, Galapagos Islands
1996-01-20
STS072-732-072 (11-20 Jan. 1996) --- Three of the nineteen Galapagos Islands are visible in this image, photographed from the Earth-orbiting Space Shuttle Endeavour. The Galapagos Islands are located 600 miles (1,000 kilometers) to the west of Ecuador. The largest of the islands, Isabela, is at center (north is toward the upper right corner). The numerous circular features on the island, highlighted by clouds, are volcanoes. The Galapagos Islands owe their existence to a hot spot, or persistent heat source in the mantle, which also is located over a rift, or place where plates are separating and new crust is being created. The rift is located between the Cocos and Nazca Plates. The dark linear features on the islands are lava flows from past eruptions. The island to the left of Isabela is Fernandina, while the island to the right is San Salvador. The Galapagos Islands were visited by the English naturalist Charles Darwin in 1835.
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GLORIA side-scan imagery of Aleutian basin, Bering Sea slope and Abyssal plain
DOE Office of Scientific and Technical Information (OSTI.GOV)
Carlson, P.R.; Cooper, A.K.; Gardner, J.V.
1987-05-01
During July-September 1986, about 700,000 km/sup 2/ of continental slope and abyssal plain of the Aleutian basin, Bering Sea, were insonified with GLORIA (Geological Long Range Inclined Asdic) side-scane sonar. A sonar mosaic displays prominent geomorphic features including the massive submarine canyons of the Beringian and the northern Aleutian Ridge slopes and shows well-defined sediment patterns including large deep-sea channels and fan systems on the Aleutian basin abyssal plain. Dominant erosional and sediment transport processes on both the Beringian and the Aleutian Ridge slopes include varieties of mass movement that range from small debris flows and slides to massive slidesmore » and slumps of blocks measuring kilometers in dimension. Sediment-flow patterns that appear to be formed by sheet flow rather than channelized flow extend basinward from the numerous canyons and gullies that incise the slopes of the Beringian margin and of Bowers Ridge and some places along the Aleutian Ridge. These Beringian and Bowers canyon sediment sources, however, appear to have contributed less modern sediment to the Aleutian basin than the large, well-defined channel systems that emanate from Bering, Umnak, and Amchitka submarine canyons and extend for several hundred kilometers across the abyssal plain. This GLORIA imagery emphasizes the important contribution of the Aleutian Ridge to modern sedimentation in the deep Bering Sea.« less
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Impacts of a volcanic eruption on the forest birdcommunity of Montserrat, Lesser Antilles.
B. DALSGAARD; G. M. HILTON; G. A. L. GRAY; L. AYMER; J. BOATSWAIN; J. FENTON DALEY; J. MARTIN; L. MARTIN; P. MURRAIN; W. J. ARENDT; W. OLESEN GIBBONSD
2007-01-01
Volcanic eruptions are an important and natural source of catastrophic disturbance to ecological communities. However, opportunities to study them are relatively rare. Here we report on the effects of the eruption of the Soufrière Hills volcano on the forest bird community of the Lesser Antillean island of Montserrat. The islandâs species-poor avifauna includes 11...
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NASA Astrophysics Data System (ADS)
Padrón, Eleazar; Padilla, Germán; Hernández, Pedro A.; Pérez, Nemesio M.; Calvo, David; Nolasco, Dácil; Barrancos, José; Melián, Gladys V.; Dionis, Samara; Rodríguez, Fátima
2013-01-01
We report herein the first results of an extensive soil gas survey performed on Timanfaya volcano on May 2011. Soil gas composition at Timanfaya volcano indicates a main atmospheric source, slightly enriched in CO2 and He. Soil CO2 concentration showed a very slight deep contribution of the Timanfaya volcanic system, with no clear relation to the main eruptive fissures of the studied area. The existence of soil helium enrichments in Timanfaya indicates a shallow degassing of crustal helium and other possible deeper sources probably form cooling magma bodies at depth. The main soil helium enrichments were observed in good agreement with the main eruptive fissures of the 1730-36 eruption, with the highest values located at those areas with a higher density of recent eruptive centers, indicating an important structural control for the leakage of helium at Timanfaya volcano. Atmospheric air slightly polluted by deep-seated helium emissions, CO2 degassed from a cooling magma body, and biogenic CO2, might be the most plausible explanation for the existence of soil gas. Helium is a deep-seated gas, exhibiting important emission rates along the main eruptive fissure of the 1730-36 eruption of Timanfaya volcano.
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Ambient air quality effects of the 2008-2009 Halema`uma`u eruption on the Island of Hawai`i
NASA Astrophysics Data System (ADS)
Elias, T.; Sutton, A. J.; Kauahikaua, J. P.; Ray, J. D.; Babb, J. L.
2009-12-01
While the Halema`uma`u eruption has enlivened volcanologists with the rare opportunity to observe eruptive processes at Kilauea’s summit, it has also caused significant environmental impact on the Island of Hawai`i. Since the beginning of 2008, the combined SO2 emissions from the east rift zone (ERZ) and summit of Kilauea have increased by ~40% as compared to the 2003-2007 long-term average. However, emissions from Kilauea’s summit have increased ~6-fold, averaging 850 t/d during January 2008-August 2009. Although average emissions from the ERZ during this period have been 1-2 times that of the summit, the relative impact of summit emissions is disproportionately large due to the location of the vent and the plume dispersal pattern to downwind communities. Ambient air quality data show that federal standards have been exceeded frequently in various communities on the south half of the island. Between April 2008 and August 2009, primary health standards for SO2 and PM2.5 were exceeded on 41 and 19 occasions respectively in Pahala, located ~30 km downwind of the Kilauea summit under prevailing trade wind conditions. Pahala, which exceeded the SO2 annual standard for 2008, had not exceeded standards prior to the opening of the Halema`uma`u vent in March 2008. In July 2008, the U.S. Secretary of Agriculture designated Hawai`i County a primary natural disaster area due to agricultural losses from volcanic emissions. Many growers of exotic flower crops in the Ka`u district suffered irrecoverable losses. Coffee and macadamia nut farmers also reported damage to their fields. While some livestock farmers reported eye irritation in cattle, more significant damage was observed in the accelerated deterioration of galvanized fencing, gates, pipelines and other infrastructure. The increase in volcanic pollution has spurred health concerns. A rise in respiratory emergencies for visitors to Kilauea caldera in early 2008 led Hawai`i Volcanoes National Park to close areas
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1985-06-24
The entire Hawaiian Island Archipelago (21.5N, 158.0W) is seen in this single view. The islands are a favorite international resort and tourist attraction drawing visitors from all over the world to enjoy the tropical climate, year round beaches and lush island flora. Being volcanic in origin, the islands' offer a rugged landscape and on the big island of Hawaii, there is still an occasional volcanic eruption of lava flows and steam vents.
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Geochronological constraints on the evolution of El Hierro (Canary Islands)
NASA Astrophysics Data System (ADS)
Becerril, Laura; Ubide, Teresa; Sudo, Masafumi; Martí, Joan; Galindo, Inés; Galé, Carlos; Morales, Jose María; Yepes, Jorge; Lago, Marceliano
2016-01-01
New age data have been obtained to time constrain the recent Quaternary volcanism of El Hierro (Canary Islands) and to estimate its recurrence rate. We have carried out 40Ar/39Ar geochronology on samples spanning the entire volcanostratigraphic sequence of the island and 14C geochronology on the most recent eruption on the northeast rift of the island: 2280 ± 30 yr BP. We combine the new absolute data with a revision of published ages onshore, some of which were identified through geomorphological criteria (relative data). We present a revised and updated chronology of volcanism for the last 33 ka that we use to estimate the maximum eruptive recurrence of the island. The number of events per year determined is 9.7 × 10-4 for the emerged part of the island, which means that, as a minimum, one eruption has occurred approximately every 1000 years. This highlights the need of more geochronological data to better constrain the eruptive recurrence of El Hierro.
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Parvovirus-associated syndrome (Aleutian disease) in two ferrets.
Palley, L S; Corning, B F; Fox, J G; Murphy, J C; Gould, D H
1992-07-01
There is a paucity of information regarding natural Aleutian disease, caused by a parvovirus in ferrets. With the increasing popularity of ferrets as household pets and laboratory animals, and with the advent of a USDA-approved rabies vaccine, the occurrence and the etiopathogenesis of naturally acquired diseases in ferrets needs to be documented. We present the clinical and laboratory findings associated with Aleutian disease in 2 domestic ferrets, one with the chronic wasting form of the disease and one with the central nervous system form.
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Zeglin, Lydia H.; Wang, Bronwen; Waythomas, Christopher F.; Rainey, Frederick; Talbot, Sandra L.
2016-01-01
In August 2008, Kasatochi volcano erupted and buried a small island in pyroclastic deposits and fine ash; since then, microbes, plants and birds have begun to re-colonize the initially sterile surface. Five years post-eruption, bacterial 16S rRNA gene and fungal internal transcribed spacer (ITS) copy numbers and extracellular enzyme activity (EEA) potentials were one to two orders of magnitude greater in pyroclastic materials with organic matter (OM) inputs relative to those without, despite minimal accumulation of OM (< 0.2%C). When normalized by OM levels, post-eruptive surfaces with OM inputs had the highest β-glucosidase, phosphatase, NAGase and cellobiohydrolase activities, and had microbial population sizes approaching those in reference soils. In contrast, the strongest factor determining bacterial community composition was the dominance of plants versus birds as OM input vectors. Although soil pH ranged from 3.9 to 7.0, and %C ranged 100×, differentiation between plant- and bird-associated microbial communities suggested that cell dispersal or nutrient availability are more likely drivers of assembly than pH or OM content. This study exemplifies the complex relationship between microbial cell dispersal, soil geochemistry, and microbial structure and function; and illustrates the potential for soil microbiota to be resilient to disturbance.
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NASA Technical Reports Server (NTRS)
2002-01-01
Expedition Five crew members aboard the International Space Station (ISS) captured this overhead look at the smoke and ash regurgitated from the erupting volcano Mt. Etna on the island of Sicily, Italy in October 2002. Triggered by a series of earthquakes on October 27, 2002, this eruption was one of Etna's most vigorous in years. This image shows the ash plume curving out toward the horizon. The lighter-colored plumes down slope and north of the summit seen in this frame are produced by forest fires set by flowing lava. At an elevation of 10,990 feet (3,350 m), the summit of the Mt. Etna volcano, one of the most active and most studied volcanoes in the world, has been active for a half-million years and has erupted hundreds of times in recorded history.
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Searching for a paleotsunami record in the Hawaiian Islands
NASA Astrophysics Data System (ADS)
La Selle, S.; Richmond, B. M.; Arcos, M. E. M.; Jaffe, B. E.; Lunghino, B.; Kane, H. H.; Bishop, J. M.; Habel, S. L.
2016-12-01
Historical records of tsunamis over the last 200 years in the state of Hawai'i demonstrate that earthquakes in subduction zones around the Pacific (Aleutian, Kuril-Kamchatka, Chile, Japan, and Alaska) can cause significant tsunami inundation on multiple Hawaiian islands. Deposits found along these subduction zones provide evidence for older tsunamis, but it is unclear if any of these prehistoric far-field events have impacted the Hawaiian islands because no study has successfully correlated Hawaiian paleotsunami deposits between sites or islands. We cored coastal marshlands on Óahu, Maui, and Kauái searching for tsunami deposits in order to determine the viability of extending the record of tsunami inundation in the state of Hawai'i. Sites were selected based on historical tsunami runup, numerical inundation modeling results, the presence of a coastal marsh in close proximity to a sandy shoreline, the extent of undisturbed wetlands, and the breadth of prior geological investigations. Several possible tsunami deposits were identified on the north and northeast shores of Kauái and Óahu as marine sand layers within marsh peat or mud. At some sites, the presence of deposits from the 1946 and 1957 Aleutian tsunamis aided identification of the deeper candidate tsunami deposits. Radiocarbon ages of the deeper sand layers suggest deposition around 800-600 cal yr B.P., which may coincide with a tsunami deposit in the eastern Aleutians that was deposited 660-560 cal yr B.P. (Witter et al., 2016). Further dating and analyses of the deposits is needed to determine whether or not deposition was synchronous on O'ahu and Kaua'i and to determine from sedimentological and micropaleontological characteristics that a tsunami formed the deposits.
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Engdahl, E.R.; Billington, S.; Kisslinger, C.
1989-01-01
The Andreanof Islands earthquake (Mw 8.0) is the largest event to have occurred in that section of the Aleutian arc since the March 9, 1957, Aleutian Islands earthquake (Mw 8.6). Teleseismically well-recorded earthquakes in the region of the 1986 earthquake are relocated with a plate model and with careful attention to the focal depths. The data set is nearly complete for mb???4.7 between longitudes 172??W and 179??W for the period 1964 through April 1987 and provides a detailed description of the space-time history of moderate-size earthquakes in the region for that period. Additional insight is provided by source parameters which have been systematically determined for Mw???5 earthquakes that occurred in the region since 1977 and by a modeling study of the spatial distribution of moment release on the mainshock fault plane. -from Authors
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Billington, Serena; Engdahl, E.R.; Price, Stephanie
1981-01-01
On November 4 1977, a magnitude Ms 6.7 (mb 5.7) shallow-focus thrust earthquake occurred in the vicinity of the Adak seismographic network in the central Aleutian island arc. The earthquake and its aftershock sequence occurred in an area that had not experienced a similar sequence since at least 1964. About 13 1/2 months before the main shock, the rate of occurrence of very small magnitude earthquakes increased abruptly in the immediate vicinity of the impending main shock. To search for possible variations in the focal mechanism of small events preceding the main shock, a method was developed that objectively combines first-motion data to generate composite focal-mechanism information about events occurring within a small source region. The method could not be successfully applied to the whole study area, but the results show that starting about 10 1/2 months before the November 1977 earthquake, there was a change in the mechanism of small- to moderate-sized earthquakes in the immediate vicinity of the hypocenter and possibly in other parts of the eventual aftershock zone, but not in the surrounding regions.
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NASA Astrophysics Data System (ADS)
Lerner, Allan H.; Crowley, Peter D.; Nicolaysen, Kirsten P.; Hazlett, Richard W.
2018-05-01
Makushin Volcano on Unalaska Island, Alaska, threatens the Aleutian's largest population centers (Unalaska and Dutch Harbor), yet its eruption mechanisms are poorly known. This study presents a detailed stratigraphic and geochemical investigation of Makushin's most recent highly explosive event: the ca. 8.5 ka Driftwood Pumice eruption. The Driftwood Pumice has measured thicknesses of over 2.5 m, and isopach reconstructions estimate a total deposit volume of 0.3 to 1.6 km3, indicating a VEI 4-5 eruption. Proximal deposits consist of normally-graded, tan, dacitic to andesitic pumice, capped by a thinner dark layer of lower-silica andesitic scoria mixed with abundant lithic fragments. This stratigraphy is interpreted as an initial vent-clearing eruption that strengthened into a climactic ejection of pumice and ash and concluded with vent destabilization and the eruption of somewhat more mafic, gas-poor magma. Within the pumice, geochemical trends, disequilibrium mineral populations, and mineral zonation patterns show evidence of magma mixing between a bulk silicic magma and a mafic melt. Euhedral high-Ca plagioclase (An68-91) and high-Mg olivine (Fo69-77) phenocrysts are in disequilibrium with trachydacitic glass (65-68 wt% SiO2) and more abundant sodic plagioclase (An34-55), indicating the former originally crystallized in a more mafic melt. Tephra whole rock compositions become more mafic upwards through the deposit, ranging from a basal low-silica dacite to an andesite (total range: 60.8-63.3 wt% SiO2). Collectively, these compositional variations suggest magma mixing in the Driftwood Pumice (DWP) magma reservoir, with a systematic increase in the amount of a mafic component (up to 25%) upward through the deposit. Olivine-liquid and liquid-only thermometry indicate the mafic magma intruded at temperatures 140-200 °C hotter than the silicic magma. Diffusion rates calculated for 5-7 μm thick, lower-Mg rims on the olivine phenocrysts (Fo60 rim vs Fo76 bulk) suggest
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Inception and Early Evolution of the Aleutian Arc
NASA Astrophysics Data System (ADS)
Bezard, R.; Hoernle, K.; Hauff, F.; Portnyagin, M.; Werner, R.; Yogodzinski, G.; Jicha, B.; Garbe-Schönberg, D.; Turner, S.; Schaefer, B. F.
2017-12-01
Constraining the timing and style of subduction initiation in the Aleutian system is critical to model the Cenozoic geodynamic evolution of the Pacific. Until now, the oldest ages for the Aleutian arc suggest a subduction inception at c.a. 46-47 Ma. However, the compositions of these samples (arc tholeiites and calc-alkaline rocks) are different from those of typical early-arc sequences found at extensively studied subduction systems (Izu-Bonin-Mariana), dominated by FABs and boninites. Thus, if the FAB/boninite model applies to the Aleutian, the oldest units might not have been recovered yet and the arc inception could have occurred earlier than 47 Ma. To test this hypothesis, we have sampled the lowermost submarine Aleutian sequences at ten forearc and rear-arc localities during the R/V SONNE Cruise 249. We present preliminary whole-rock major and trace element concentrations, Sr-Nd-Hf-Pb isotopes as well as U-Pb zircon dating on the recovered igneous rocks. The sample compositions range from tholeiitic to calc-alkaline. No boninites were found. Most of the samples show strong subduction signatures. However, the remaining rocks present no or minor arc-type trace element features. These samples are either depleted tholeiites with similar trace element characteristics to FABs or enriched calc-alkaline rocks. Preliminary zircon dating suggests an age of 47.2 ± 1.2 Ma for one of the samples with strong arc signatures, consistent with the oldest published ages for the Aleutian so far. However, based on their compositional similarities to FABs, the depleted tholeiites should be older than the arc-type rocks, suggesting that subduction initiation could have occurred earlier than the above-mentioned age. The absence of boninite could either reflect an incomplete sampling of the early-arc sequences or a different initiation style compared to other Pacific subduction zones. Further ages and radiogenic isotope data should refine these interpretations.
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Infrasonic Influence of Volcanos
NASA Astrophysics Data System (ADS)
Hosman, Ashley
2014-03-01
My presentation will consist of a poster on the use of ring laser interferometers to detect infrasound. The research was performed during the summer of 2013 and it focused on the finding infrasound emissions created by volcanic activity. I will explain how a ring laser works and discuss how I analyze the collected data using Fast Fourier Transforms. Due to the extreme distances over which infrasound can travel, I will also stress the need to compare the detected responses to specific volcanic eruptions. Finally, I will purpose practical applications of my research. One of the more promising applications is to use ring lasers to detect volcanic activity in remote areas such as parts of the Aleutian Islands. There is considerable air traffic over the Aleutian Islands. Volcanic plumes are a significant aviation hazard and can damage jet engines to the extent that they will no longer operate. Thank you to the NSF ans NASA foundations for providing funding for this reseach.
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Towards a Proactive Risk Mitigation Strategy at La Fossa Volcano, Vulcano Island
NASA Astrophysics Data System (ADS)
Biass, S.; Gregg, C. E.; Frischknecht, C.; Falcone, J. L.; Lestuzzi, P.; di Traglia, F.; Rosi, M.; Bonadonna, C.
2014-12-01
A comprehensive risk assessment framework was built to develop proactive risk reduction measures for Vulcano Island, Italy. This framework includes identification of eruption scenarios; probabilistic hazard assessment, quantification of hazard impacts on the built environment, accessibility assessment on the island and risk perception study. Vulcano, a 21 km2 island with two primary communities host to 900 permanent residents and up to 10,000 visitors during summer, shows a strong dependency on the mainland for basic needs (water, energy) and relies on a ~2 month tourism season for its economy. The recent stratigraphy reveals a dominance of vulcanian and subplinian eruptions, producing a range of hazards acting at different time scales. We developed new methods to probabilistically quantify the hazard related to ballistics, lahars and tephra for all eruption styles. We also elaborated field- and GIS- based methods to assess the physical vulnerability of the built environment and created dynamic models of accessibility. Results outline the difference of hazard between short and long-lasting eruptions. A subplinian eruption has a 50% probability of impacting ~30% of the buildings within days after the eruption, but the year-long damage resulting from a long-lasting vulcanian eruption is similar if tephra is not removed from rooftops. Similarly, a subplinian eruption results in a volume of 7x105 m3 of material potentially remobilized into lahars soon after the eruption. Similar volumes are expected for a vulcanian activity over years, increasing the hazard of small lahars. Preferential lahar paths affect critical infrastructures lacking redundancy, such as the road network, communications systems, the island's only gas station, and access to the island's two evacuation ports. Such results from hazard, physical and systemic vulnerability help establish proactive volcanic risk mitigation strategies and may be applicable in other island settings.
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Can rain cause volcanic eruptions?
Mastin, Larry G.
1993-01-01
Volcanic eruptions are renowned for their violence and destructive power. This power comes ultimately from the heat and pressure of molten rock and its contained gases. Therefore we rarely consider the possibility that meteoric phenomena, like rainfall, could promote or inhibit their occurrence. Yet from time to time observers have suggested that weather may affect volcanic activity. In the late 1800's, for example, one of the first geologists to visit the island of Hawaii, J.D. Dana, speculated that rainfall influenced the occurrence of eruptions there. In the early 1900's, volcanologists suggested that some eruptions from Mount Lassen, Calif., were caused by the infiltration of snowmelt into the volcano's hot summit. Most such associations have not been provable because of lack of information; others have been dismissed after careful evaluation of the evidence.
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Ash from Kilauea Eruption Viewed by NASA's MISR
2018-05-09
On May 3, 2018, a new eruption began at a fissure of the Kilauea volcano on the Island of Hawaii. Kilauea is the most active volcano in the world, having erupted almost continuously since 1983. Advancing lava and dangerous sulfur dioxide gas have forced thousands of residents in the neighborhood of Leilani Estates to evacuate. A number of homes have been destroyed, and no one can say how soon the eruption will abate and evacuees can return home. On May 6, 2018, at approximately 11 a.m. local time, the Multi-angle Imaging SpectroRadiometer (MISR) instrument on NASA's Terra satellite captured this view of the island as it passed overhead. Much of the island was shrouded by clouds, including the fissure on its eastern point. However, an eruption plume is visible streaming southwest over the ocean. The MISR instrument is unique in that it has nine cameras that view Earth at different angles: one pointing downward, four at various angles in the forward direction, and four in the backward direction. This image shows the view from one of MISR's forward-pointing cameras (60 degrees), which shows the plume more distinctly than the near-vertical views. The information from the images acquired at different view angles is used to calculate the height of the plume, results of which are superimposed on the right-hand image. The top of the plume near the fissure is at approximately 6,500 feet (2,000 meters) altitude, and the height of the plume decreases as it travels south and west. These relatively low altitudes mean that the ash and sulfur dioxide remained near the ground, which can cause health issues for people on the island downwind of the eruption. The "Ocean View" air quality monitor operated by the Clean Air Branch of the State of Hawaii Department of Health recorded a concentration of 18 μg/m3 of airborne particles less than 2.5 micrometers in diameter at 11 a.m. local time. This amount corresponds to an air quality rating of "moderate" and supports the MISR results
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Mt. Pinatubo Volcano - Post Eruption, Luzon, Philippines
1992-08-08
Mt. Pinatubo on the island of Luzon (15.0N, 120.0E) erupted catastrophically in June 1991 after over 600 years of inactivity. In this vertical view, the full extent of the eruption is obvious. Thick layers of ash completely surrounds the crater and the effect of mudflows in this previously heavily forested and agricultural region can be traced as ribbons flowing downhill. Clark AFB, once the crossroads of the SW Pacific can only partially be seen.
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Tephra from the 1979 soufriere explosive eruption.
Sigurdsson, H
1982-06-04
The explosive phase of the 1979 Soufriere eruption produced 37.5 x 10(6) cubic meters (dense-rock equivalent) of tephra, consisting of about 40 percent juvenile basaltic andesite and 60 percent of a nonjuvenile component derived from the fragmentation of the 1971-1972 lava island during phreatomagmatic explosions. The unusually fine grain size, poor sorting, and bimodality of the land deposit are attributed to particle aggregation and the formation of accretionary lapilli in a wet eruption column.
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Earth Observations taken by Expedition 38 crewmember
2013-11-15
ISS038-E-003612 (15 Nov. 2013) --- Islands of the Four Mountains are featured in this image photographed by an Expedition 38 crew member on the International Space Station. Morning sunlight illuminates the southeast-facing slopes of the islands in the photograph. The islands, part of the Aleutian Island chain, are actually the upper slopes of volcanoes rising from the sea floor; Carlisle, Cleveland, Herbert, and Tana. Carlisle and Herbert volcanoes are distinct cones and form separate islands. Cleveland volcano and the Tana volcanic complex form the eastern and western ends respectively of Chuginadak Island; a cloud bank obscures the connecting land mass in this image. Cleveland volcano (peak elevation 1,730 meters above sea level) is one of the most active in the Aleutian chain, with its most recent activity--eruptions and lava flow emplacement--taking place in May of 2013. The northernmost of the islands, Carlisle volcano's (peak elevation 1,620 meters above sea level) last confirmed eruption occurred in 1828, with unconfirmed reports of activity in 1987. Herbert volcano (peak elevation 1,280 meters above sea level) to the southwest displays a classic cone structure breached by a two-kilometer wide summit caldera (upper right), but there are no historical records of volcanic activity. The easternmost peak, Tana (1,170 meters above sea level) is a volcanic complex comprised of two east-west trending volcanoes and associated younger cinder cones; like Herbert volcano, there is no historical record of activity at Tana. A layer of low clouds and/or fog obscures much of the lower elevations of the islands and the sea surface, but the clouds also indicate the general airflow pattern around and through the islands. Directly to the south-southeast of Cleveland volcano a Von Karman vortex "street" is visible. Shadows cast by the morning sun extend from the peaks towards the northwest. The peaks of all of the Four Islands have snow cover; this is distinct from the clouds
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Zeglin, Lydia H; Wang, Bronwen; Waythomas, Christopher; Rainey, Frederick; Talbot, Sandra L
2016-01-01
In August 2008, Kasatochi volcano erupted and buried a small island in pyroclastic deposits and fine ash; since then, microbes, plants and birds have begun to re-colonize the initially sterile surface. Five years post-eruption, bacterial 16S rRNA gene and fungal internal transcribed spacer (ITS) copy numbers and extracellular enzyme activity (EEA) potentials were one to two orders of magnitude greater in pyroclastic materials with organic matter (OM) inputs relative to those without, despite minimal accumulation of OM (< 0.2%C). When normalized by OM levels, post-eruptive surfaces with OM inputs had the highest β-glucosidase, phosphatase, NAGase and cellobiohydrolase activities, and had microbial population sizes approaching those in reference soils. In contrast, the strongest factor determining bacterial community composition was the dominance of plants versus birds as OM input vectors. Although soil pH ranged from 3.9 to 7.0, and %C ranged 100×, differentiation between plant- and bird-associated microbial communities suggested that cell dispersal or nutrient availability are more likely drivers of assembly than pH or OM content. This study exemplifies the complex relationship between microbial cell dispersal, soil geochemistry, and microbial structure and function; and illustrates the potential for soil microbiota to be resilient to disturbance. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.
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Drew, Gary S.; Piatt, John F.; Byrd, G. Vernon; Dragoo, Donald E.
2003-01-01
Although islands in the Aleutians are known to support some of the highest densities of seabirds in the world, their remoteness has limited systematic research on the at-sea distribution of seabirds near these colonies. Kasatochi, Koniuji, and Ulak islands, in the central Aleutian Islands, together comprise one of nine ecological sites monitored once every 5 years on an annual rotation since 1996 by the Alaska Maritime National Wildlife Refuge (AMNWR). To supplement annual colony monitoring and examine seabird distribution away from colony sites, the AMNWR personnel in conjunction with U.S. Geological Survey (USGS) researchers, conducted a pelagic survey of the waters around these 3 islands in 1996.Previous research in this area has focused on the seabird colony sites located on Kasatochi, Koniuji, and Ulak islands. Although boat-based circumnavigations have been used to evaluate colony populations (Early et al. 1981; Bailey and Trapp 1986; Byrd and Williams 1994; Byrd 1995a, 1995b), wide ranging pelagic surveys to examine foraging patterns had not previously been conducted near the islands. The goal of this survey was to examine foraging patterns of the seabirds nesting in the study area and identify factors that may explain seabird distribution patterns.
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Trusdell, F.A.; Moore, R.B.; Sako, M.; White, R.A.; Koyanagi, S.K.; Chong, R.; Camacho, J.T.
2005-01-01
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
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Kilauea volcano eruption seen from orbit
NASA Technical Reports Server (NTRS)
1993-01-01
The STS-51 crew had a clear view of the erupting Kilauea volcano during the early morning pass over the Hawaiian islands. Kilauea, on the southwest side of the island of Hawaii, has been erupting almost continuously since January, 1983. Kilauea's summit caldera, with the smaller Halemaumau crater nestled within, is highlighted in the early morning sun (just above the center of the picture). The lava flows which covered roads and subdivisions in 1983-90 can be seen as dark flows to the east (toward the upper right) of the steam plumes on this photo. The summit crater and lava flows of Mauna Loa volcano make up the left side of the photo. Features like the Volcano House and Kilauea Visitor Center on the edge of the caldera, the small subdivisions east of the summit, Ola's Rain Forest north of the summit, and agricultural land along the coast are easily identified.
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Dome growth at Mount Cleveland, Aleutian Arc, quantified by time-series TerraSAR-X imagery
Wang, Teng; Poland, Michael; Lu, Zhong
2016-01-01
Synthetic aperture radar imagery is widely used to study surface deformation induced by volcanic activity; however, it is rarely applied to quantify the evolution of lava domes, which is important for understanding hazards and magmatic system characteristics. We studied dome formation associated with eruptive activity at Mount Cleveland, Aleutian Volcanic Arc, in 2011–2012 using TerraSAR-X imagery. Interferometry and offset tracking show no consistent deformation and only motion of the crater rim, suggesting that ascending magma may pass through a preexisting conduit system without causing appreciable surface deformation. Amplitude imagery has proven useful for quantifying rates of vertical and areal growth of the lava dome within the crater from formation to removal by explosive activity to rebirth. We expect that this approach can be applied at other volcanoes that host growing lava domes and where hazards are highly dependent on dome geometry and growth rates.
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NASA Technical Reports Server (NTRS)
Munro, Duncan C.; Rowland, Scott K.; Mouginis-Mark, Peter J.; Wilson, Lionel; Oviedo-Perez, Victor-Hugo
1991-01-01
Recent volcanic activity in the Galapagos Islands is concentrated on the two westernmost islands, Isla Isabela and Isla Fernandina. Difficult access has thus far prevented comprehensive geological field studies, so we examine the potential of remotely sensed data as a means of studying volcanic processes in the region. Volcan Wolf is used as an example of the analysis of SPOT HRV-1 data undertaken for each volcano. Landsat TM data are analyzed in an attempt to construct a relative age sequence for the recent eruptive activity on Isla Fernandina. No systematic variation in the surface reflectance of lava flows as a function of age could be detected with these data. Thus it was not possible to complete a study of the temporal distribution of volcanic activity.
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Hardell, Sara; Tilander, Hanna; Welfinger-Smith, Gretchen; Burger, Joanna; Carpenter, David O.
2010-01-01
Background Persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs) and chlorinated pesticides, have been shown to have many adverse human health effects. These contaminants therefore may pose a risk to Alaska Natives that follow a traditional diet high in marine mammals and fish, in which POPs bioaccumulate. Methods and Findings This study examined the levels of PCBs and three pesticides [p, p′-DDE, mirex, and hexachlorobenzene (HCB)] in muscle tissue from nine fish species from several locations around the Aleutian Islands of Alaska. The highest median PCB level was found in rock sole (Lepidopsetta bilineata, 285 ppb, wet weight), while the lowest level was found in rock greenling (Hexagrammos lagocephalus, 104 ppb, wet weight). Lipid adjusted PCB values were also calculated and significant interspecies differences were found. Again, rock sole had the highest level (68,536 ppb, lipid weight). Concerning the PCB congener patterns, the more highly chlorinated congeners were most common as would be expected due to their greater persistence. Among the pesticides, p, p′-DDE generally dominated, and the highest level was found in sockeye salmon (Oncorhynchus nerka, 6.9 ppb, wet weight). The methodology developed by U.S. Environmental Protection Agency (USEPA) was used to calculate risk-based consumption limits for the analyzed fish species. For cancer health endpoints for PCBs, all species would trigger strict advisories of between two and six meals per year, depending upon species. For noncancer effects by PCBs, advisories of between seven and twenty-two meals per year were triggered. None of the pesticides triggered consumption limits. Conclusion The fish analyzed, mainly from Adak, contain significant concentrations of POPs, in particular PCBs, which raises the question whether these fish are safe to eat, particularly for sensitive populations. However when assessing any risk of the traditional diet, one must also consider the many health
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Seismicity and tilt associated with the 2003 Anatahan eruption sequence
Pozgay, S.H.; White, R.A.; Wiens, D.A.; Shore, P.J.; Sauter, A.W.; Kaipat, J.L.
2005-01-01
On May 10, 2003, the first historical eruption of Anatahan volcano in the western Pacific Mariana Islands was fortuitously recorded by a broadband seismograph installed on the island only 4 days prior to the eruption. This station, located 7 km WNW of the active crater, together with another broadband seismograph on Sarigan Island 45 km to the north, continued to operate throughout the 2-month period of major eruptive activity in May and June and throughout the majority of the following year. In June 2003, the Saipan Emergency Management Office and the US Geological Survey installed two telemetered high-gain short-period seismic stations to monitor the activity in real-time. The only earthquakes detected in the 4-day period from the initial seismograph installation until 6 h prior to the eruption occurred approximately 20 km to the northeast of the island on May 8. The first volcano-tectonic (VT) event located near the volcano occurred at 01:53 GMT on May 10. The number of events per hour then increased dramatically and a period of about 80 discrete earthquakes per hour commenced at about 06:20 GMT, immediately prior to the estimated eruption time of 07:30 from the Volcanic Ash Advisory Center. A long-period tilt signal recorded on the horizontal components of the broadband seismograph, indicating upward movement of the crater region, also commenced at about 06:20. Inflation continued until 09:30, when the direction of tilt reversed. Deflation continued until 17:50, coinciding with a reduction in the number of VT events. The larger VT events were located with a linearized least-squares location algorithm. Magnitudes of located VT events on May 10 ranged from 2.0 to 3.2, but a period of larger VT events were recorded on May 11, with the largest M 4.2. After about 36 h of intense earthquake activity, the number of discrete VT events declined and was replaced by nearly continuous volcanic tremor for the next 6 weeks. Differing types of very long-period events may
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Seismicity and tilt associated with the 2003 Anatahan eruption sequence
NASA Astrophysics Data System (ADS)
Pozgay, Sara H.; White, Randall A.; Wiens, Douglas A.; Shore, Patrick J.; Sauter, Allan W.; Kaipat, Jose L.
2005-08-01
On May 10, 2003, the first historical eruption of Anatahan volcano in the western Pacific Mariana Islands was fortuitously recorded by a broadband seismograph installed on the island only 4 days prior to the eruption. This station, located 7 km WNW of the active crater, together with another broadband seismograph on Sarigan Island 45 km to the north, continued to operate throughout the 2-month period of major eruptive activity in May and June and throughout the majority of the following year. In June 2003, the Saipan Emergency Management Office and the US Geological Survey installed two telemetered high-gain short-period seismic stations to monitor the activity in real-time. The only earthquakes detected in the 4-day period from the initial seismograph installation until 6 h prior to the eruption occurred approximately 20 km to the northeast of the island on May 8. The first volcano-tectonic (VT) event located near the volcano occurred at 01:53 GMT on May 10. The number of events per hour then increased dramatically and a period of about 80 discrete earthquakes per hour commenced at about 06:20 GMT, immediately prior to the estimated eruption time of 07:30 from the Volcanic Ash Advisory Center. A long-period tilt signal recorded on the horizontal components of the broadband seismograph, indicating upward movement of the crater region, also commenced at about 06:20. Inflation continued until 09:30, when the direction of tilt reversed. Deflation continued until 17:50, coinciding with a reduction in the number of VT events. The larger VT events were located with a linearized least-squares location algorithm. Magnitudes of located VT events on May 10 ranged from 2.0 to 3.2, but a period of larger VT events were recorded on May 11, with the largest M 4.2. After about 36 h of intense earthquake activity, the number of discrete VT events declined and was replaced by nearly continuous volcanic tremor for the next 6 weeks. Differing types of very long-period events may
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FOGO-2014: Monitoring the Fogo 2014 Eruption, Cape Verde
NASA Astrophysics Data System (ADS)
Fernandes, Rui; Faria, Bruno
2015-04-01
Fogo volcano, located in the Cape Verde Archipelago offshore Western Africa, is a complete stratovolcano system that was created by the Cape Verde hotspot, forming the island of Fogo. The top (Pico do Fogo) reaches ~2830m above sea level, and raises ~1100m above Chã das Caldeiras, an almost flat circular area with approximately 10 kilometres in the north-south direction and 7 kilometres in the east-west direction. Chã das Caldeiras, surrounded towards the West by the ~1000m high Bordeira rampart, has been inhabited since the early 20th Century, because it is one of the most productive agricultural areas in this semi-arid country. Fogo volcano erupted on November 23, 2014 (~10:00UTC) on a subsidiary vent of the main cone, after 19 years of inactivity. C4G (Collaboratory for Geosciences), a distributed research infrastructure created in 2014 in the framework of the Portuguese Roadmap for Strategic Research Infrastructures, immediately offered support to the Cape Verdean authorities, with the goal of complementing the permanent geophysical monitoring network operated in Fogo island by INMG, the Cape Verdean Meteorological and Geophysical Institute. This permanent network is composed of seven seismographic stations and three tiltmeter stations, and the data is transmitted in real time to the INMG geophysical laboratory in São Vicente Island, where it is analysed on a routine basis. Pre-eruptive activity started to be detected by the permanent monitoring network on October 2014, with earthquakes occurring at depths larger than 15 km. These events led to a first volcanic warning to the Cape Verdean Civil Protection Agency. On November 22 several volcano-tectonic earthquakes were recorded at shallow depths, indicating shallow fracturing. On the basis of this activity, INMG issued a formal alert of an impending eruption to the Civil Protection Agency, ~24 hours before the onset of the eruption. Volcanic tremor and clear tiltmeter signals were recorded about one hour
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Runoff process in the Miyake-jima Island after Eruption in 2000
NASA Astrophysics Data System (ADS)
Tagata, Satoshi; Itoh, Takahiro; Miyamoto, Kuniaki; Ishizuka, Tadanori
2014-05-01
Hydrological environment in a basin can be changed completely due to volcanic eruption. Huge volume of tephra was yielded due to eruptions in 2000 in the Miyake-jima Island, Japan. Hydrological monitoring was conducted at four observation sites with several hundred m2 in a basin. Those were decided by the distribution of thickness and the grain size of the tephra. Rainfall intensity was measured by a tipping bucket type raingauge and flow discharge was calculated by the over flow depth in a flow gauging weir in the monitoring. However, the runoff rate did not relate to the grain size of tephra and the thickness of tephra deposition, according to measured data of rainfall intensity and runoff discharge. Supposing that if total runoff in one rainfall event is equal to the summation of rainfall over a threshold, the value of the threshold must be the loss rainfall intensity, the value of the threshold corresponds to the infiltration for the rainfall intensity. The relationships between loss rainfall intensity and the antecedent precipitation are calculated using measured rainfall and runoff data in every rainfall event, focusing on that the antecedent precipitation before occurrence of surface runoff approximately corresponds to the water contents under the slope surface. In present study, the results obtained through data analyses are summarized as follows: (1) There are some values for the threshold values, and the loss rainfall intensity approaches to some constant value if the value of the antecedent precipitation increases. The constant value corresponds to the saturated infiltration. (2) The loss rainfall intensity must be vertical unsaturated infiltration, and observed data for water runoff can express that the runoff is given by the excess rainfall intensity more than the loss rainfall intensity. (3) There are two antecedent times for rainfall with several hours and several days, and the saturation ratio before antecedent time at four observation sites can be
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Analyses of Etna Eruptive Activity From 18th Century and Characterization of Flank Eruptions
NASA Astrophysics Data System (ADS)
del Carlo, P.; Branca, S.; Coltelli, M.
2003-12-01
to fire fountain. This activity produced abundant ash fall in the whole volcano area reaching the Calabria region and Malta Island. Generally, some of these periods preceded important flank eruptions. Concerning the occurrence of the higher magnitude explosive events, we observe that at least one subplinian eruption occurred both in the 18th and 19th centuries. In the 20th century the increased quality of the scientific reports has allowed to recognize 6 subplinian eruptions from summit craters.
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NASA Astrophysics Data System (ADS)
Klügel, Andreas; Hoernle, Kaj A.; Schmincke, Hans-Ulrich; White, James D. L.
2000-03-01
The 1949 rift zone eruption along the Cumbre Vieja ridge on La Palma involved three eruptive centers, 3 km spaced apart, and was chemically and mineralogically zoned. Duraznero crater erupted tephrite for 14 days and shut down upon the opening of Llano del Banco, a fissure that issued first tephrite and, after 3 days, basanite. Hoyo Negro crater opened 4 days later and erupted basanite, tephrite, and phonotephrite, while Llano del Banco continued to issue basanite. The eruption ended with Duraznero erupting basanite with abundant crustal and mantle xenoliths. The tephrites and basanites from Duraznero and Llano del Banco show narrow compositional ranges and define a bimodal suite. Each batch ascended and evolved separately without significant intermixing, as did the Hoyo Negro basanite, which formed at lower degrees of melting. The magmas fractionated clinopyroxene +olivine±kaersutite±Ti-magnetite at 600-800 MPa and possibly 800-1100 MPa. Abundant reversely zoned phenocrysts reflect mixing with evolved melts at mantle depths. Probably as early as 1936, Hoyo Negro basanite entered the deep rift system at 200-350 MPa. Some shallower pockets of this basanite evolved to phonotephrite through differentiation and assimilation of wall rock. A few months prior to eruption, a mixing event in the mantle may have triggered the final ascent of the magmas. Most of the erupted tephrite and basanite ascended from mantle depths within hours to days without prolonged storage in crustal reservoirs. The Cumbre Vieja rift zone differs from the rift zones of Kilauea volcano (Hawaii) in lacking a summit caldera or a summit reservoir feeding the rift system and in being smaller and less active with most of the rift magma solidifying between eruptions.
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The ongoing Puʻu ʻŌʻō eruption of Kīlauea Volcano, Hawaiʻi: 30 years of eruptive activity
Orr, Tim R.; Heliker, Christina; Patrick, Matthew R.
2013-01-01
The Puʻu ʻŌʻō eruption of Kīlauea Volcano is its longest rift-zone eruption in more than 500 years. Since the eruption began in 1983, lava flows have buried 48 square miles (125 square kilometers) of land and added about 500 acres (200 hectares) of new land to the Island of Hawaiʻi. The eruption not only challenges local communities, which must adapt to an ever-changing and sometimes-destructive environment, but has also drawn millions of visitors to Hawaiʻi Volcanoes National Park. U.S. Geological Survey (USGS) scientists closely monitor and evaluate hazards at Hawaiʻi’s volcanoes and also work with park rangers to help ensure safe lava viewing for visitors.
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NASA Astrophysics Data System (ADS)
Abella, R.; Almendros, J.; Carmona, E.; Martin, R.
2012-04-01
On 17 July 2011 there was an important increase of the seismic activity at El Hierro (Canary Islands, Spain). This increase was detected by the Volcano Monitoring Network (Spanish national seismic network) run by the Instituto Geográfico Nacional (IGN). As a consequence, the IGN immediately deployed a dense, complete monitoring network that included seismometers, GPS stations, geochemical equipment, magnetometers, and gravity meters. During the first three months of activity, the seismic network recorded over ten thousand volcano-tectonic earthquakes, with a maximum magnitude of 4.6. On 10 October 2011 an intense volcanic tremor started. It was a monochromatic signal, with variable amplitude and frequency content centered at about 1-2 Hz. The tremor onset was correlated with the initial stages of the submarine eruption that occurred from a vent located south of El Hierro island, near the village of La Restinga. At that point the IGN, in collaboration with the Instituto Andaluz de Geofísica, deployed a seismic array intended for volcanic tremor monitoring and analysis. The seismic array is located about 7 km NW of the submarine vent. It has a 12-channel, 24-bit data acquisition system sampling each channel at 100 sps. The array is composed by 1 three-component and 9 vertical-component seismometers, distributed in a flat area with an aperture of 360 m. The data provided by the seismic array are going to be processed using two different approaches: (1) near-real-time, to produce information that can be useful in the management of the volcanic crisis; and (2) detailed investigations, to study the volcanic tremor characteristics and relate them to the eruption dynamics. At this stage we are mostly dedicated to produce fast, near-real-time estimates. Preliminary results have been obtained using the maximum average cross-correlation method. They indicate that the tremor wavefronts are highly coherent among array stations and propagate across the seismic array with an
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Guffanti, M.; Ewert, J.W.; Gallina, G.M.; Bluth, G.J.S.; Swanson, G.L.
2005-01-01
Within the Commonwealth of the Northern Mariana Islands (CNMI), Anatahan is one of nine active subaerial volcanoes that pose hazards to major air-traffic routes from airborne volcanic ash. The 2003-2004 eruptive activity of Anatahan volcano affected the region's aviation operations for 3 days in May 2003. On the first day of the eruption (10 May 2003), two international flights from Saipan to Japan were cancelled, and several flights implemented ash-avoidance procedures. On 13 May 2003, a high-altitude flight through volcanic gas was reported, with no perceptible damage to the aircraft. TOMS and MODIS analysis of satellite data strongly suggests that no significant ash and only minor amounts of SO2 were involved in the incident, consistent with crew observations. On 23 May 2003, airport operations were disrupted when tropical-cyclone winds dispersed ash to the south, dusting Saipan with light ashfall and causing flight cancellations there and at Guam 320 km south of the volcano. Operational (near-real-time) monitoring of ash clouds produced by Anatahan has been conducted since the first day of the eruption on 10 May 2003 by the Washington Volcanic Ash Advisory Center (VAAC). The VAAC was among the first groups outside of the immediate area of the volcano to detect and report on the unexpected eruption of Anatahan. After being contacted about an unusual cloud by National Weather Service forecasters in Guam at 1235 UTC on 10 May 2003, the VAAC analyzed GOES 9 images, confirming Anatahan as the likely source of an ash cloud and estimating that the eruption began at about 0730 UTC. The VAAC issued its first Volcanic Ash Advisory for Anatahan at 1300 UTC on 10 May 2003 more than 5 h after the start of the eruption, the delay reflecting the difficulty of detecting and confirming a surprise eruption at a remote volcano with no in situ real-time geophysical monitoring. The initial eruption plume reached 10.7-13.4 km (35,000-44,000 ft), well into jet cruise altitudes
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NASA Astrophysics Data System (ADS)
Guffanti, Marianne; Ewert, John W.; Gallina, Gregory M.; Bluth, Gregg J. S.; Swanson, Grace L.
2005-08-01
Within the Commonwealth of the Northern Mariana Islands (CNMI), Anatahan is one of nine active subaerial volcanoes that pose hazards to major air-traffic routes from airborne volcanic ash. The 2003-2004 eruptive activity of Anatahan volcano affected the region's aviation operations for 3 days in May 2003. On the first day of the eruption (10 May 2003), two international flights from Saipan to Japan were cancelled, and several flights implemented ash-avoidance procedures. On 13 May 2003, a high-altitude flight through volcanic gas was reported, with no perceptible damage to the aircraft. TOMS and MODIS analysis of satellite data strongly suggests that no significant ash and only minor amounts of SO 2 were involved in the incident, consistent with crew observations. On 23 May 2003, airport operations were disrupted when tropical-cyclone winds dispersed ash to the south, dusting Saipan with light ashfall and causing flight cancellations there and at Guam 320 km south of the volcano. Operational (near-real-time) monitoring of ash clouds produced by Anatahan has been conducted since the first day of the eruption on 10 May 2003 by the Washington Volcanic Ash Advisory Center (VAAC). The VAAC was among the first groups outside of the immediate area of the volcano to detect and report on the unexpected eruption of Anatahan. After being contacted about an unusual cloud by National Weather Service forecasters in Guam at 1235 UTC on 10 May 2003, the VAAC analyzed GOES 9 images, confirming Anatahan as the likely source of an ash cloud and estimating that the eruption began at about 0730 UTC. The VAAC issued its first Volcanic Ash Advisory for Anatahan at 1300 UTC on 10 May 2003 more than 5 h after the start of the eruption, the delay reflecting the difficulty of detecting and confirming a surprise eruption at a remote volcano with no in situ real-time geophysical monitoring. The initial eruption plume reached 10.7-13.4 km (35,000-44,000 ft), well into jet cruise altitudes
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Compound Antidunes: a Key to Detect Catastrophic Volcanic Eruptions
NASA Astrophysics Data System (ADS)
Yoshida, S.; Nemoto, Y.
2008-12-01
Antidunes are common in pyroclastic flow and surge deposits. However, the compound or nested occurrence of antidunes, where smaller antidunes reside within a larger-scale antidune, has seldom been documented or discussed in both pyroclastic and siliciclastic depositional settings. Without realizing this complexity, the frequency and magnitude of volcanic eruptions estimated from pyroclastic deposits are severely unrealistic. We have documented the Holocene outcrops of the antidune-bearing pyroclastites in Niijima Island, 100 miles SSW of Tokyo, Japan. The pyroclastites were formed by the eruptions in 886 AD Along the Habushiura coast in the southeastern part of the island, these outcrops form up to 50 m high cliffs, and are laterally traceable over 5 km from the volcano crater that shed the pyroclastites in the northward (downcurrent) direction. These pyroclastites were previously interpreted as recording about 30 small eruptions, each forming a 0.5-2 meter thick subhorizontal couplet of pumice (inversely grading) and lithic (normal grading) debris, with cm-m thick antidunes. However, we postulate that each of these couplets does not record a single volcanic eruption, but a much shorter time. These couplets occur between concave-up vertical accretion surfaces, which have both upstream- and downstream-migration components, within a 5-15 meter thick compound antidune (our "rank-1" antidune). Three erosively stacked compound antidunes form the coastal cliffs in the Habushiura coast, and each compound antidune is about ten times thicker than antidunes reported by earlier workers (corresponding to our "rank-2 antidunes" that nest within a rank-1 antidune, and "rank-3 antidunes" that nest within a rank-2 antidune). Hence, the Habushiura cliffs represent only three eruption events (instead of 30 events), but each representing much larger magnitude of eruptions. The geometry of these antidunes is comparable to "sediment waves" or "cyclic steps" of siliciclastic deposits
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Depth of origin of magma in eruptions.
Becerril, Laura; Galindo, Ines; Gudmundsson, Agust; Morales, Jose Maria
2013-09-26
Many volcanic hazard factors--such as the likelihood and duration of an eruption, the eruption style, and the probability of its triggering large landslides or caldera collapses--relate to the depth of the magma source. Yet, the magma source depths are commonly poorly known, even in frequently erupting volcanoes such as Hekla in Iceland and Etna in Italy. Here we show how the length-thickness ratios of feeder dykes can be used to estimate the depth to the source magma chamber. Using this method, accurately measured volcanic fissures/feeder-dykes in El Hierro (Canary Islands) indicate a source depth of 11-15 km, which coincides with the main cloud of earthquake foci surrounding the magma chamber associated with the 2011-2012 eruption of El Hierro. The method can be used on widely available GPS and InSAR data to calculate the depths to the source magma chambers of active volcanoes worldwide.
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Cause and risk of catastrophic eruptions in the Japanese Archipelago.
Tatsumi, Yoshiyuki; Suzuki-Kamata, Keiko
2014-01-01
The Japanese Archipelago is characterized by active volcanism with variable eruption styles. The magnitude (M)-frequency relationships of catastrophic caldera-forming eruptions (M ≥ 7) are statistically different from those of smaller eruptions (M ≤ 5.7), suggesting that different mechanisms control these eruptions. We also find that volcanoes prone to catastrophic eruptions are located in regions of low crustal strain rate (<0.5 × 10(8)/y) and propose, as one possible mechanism, that the viscous silicic melts that cause such eruptions can be readily segregated from the partially molten lower crust and form a large magma reservoir in such a tectonic regime. Finally we show that there is a ∼1% probability of a catastrophic eruption in the next 100 years based on the eruption records for the last 120 ky. More than 110 million people live in an area at risk of being covered by tephra >20 cm thick, which would severely disrupt every day life, from such an eruption on Kyushu Island, SW Japan.
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Cause and risk of catastrophic eruptions in the Japanese Archipelago
TATSUMI, Yoshiyuki; SUZUKI-KAMATA, Keiko
2014-01-01
The Japanese Archipelago is characterized by active volcanism with variable eruption styles. The magnitude (M)-frequency relationships of catastrophic caldera-forming eruptions (M ≥ 7) are statistically different from those of smaller eruptions (M ≤ 5.7), suggesting that different mechanisms control these eruptions. We also find that volcanoes prone to catastrophic eruptions are located in regions of low crustal strain rate (<0.5 × 108/y) and propose, as one possible mechanism, that the viscous silicic melts that cause such eruptions can be readily segregated from the partially molten lower crust and form a large magma reservoir in such a tectonic regime. Finally we show that there is a ∼1% probability of a catastrophic eruption in the next 100 years based on the eruption records for the last 120 ky. More than 110 million people live in an area at risk of being covered by tephra >20 cm thick, which would severely disrupt every day life, from such an eruption on Kyushu Island, SW Japan. PMID:25391319
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Ash from Kilauea Eruption Viewed by NASA's MISR
Atmospheric Science Data Center
2018-06-07
... title: Ash from Kilauea Eruption Viewed by NASA's MISR View Larger Image Ash ... Multi-angle Imaging SpectroRadiometer (MISR) instrument on NASA's Terra satellite captured this view of the island as it passed overhead. ...
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Long-term eruptive activity at a submarine arc volcano.
Embley, Robert W; Chadwick, William W; Baker, Edward T; Butterfield, David A; Resing, Joseph A; de Ronde, Cornel E J; Tunnicliffe, Verena; Lupton, John E; Juniper, S Kim; Rubin, Kenneth H; Stern, Robert J; Lebon, Geoffrey T; Nakamura, Ko-ichi; Merle, Susan G; Hein, James R; Wiens, Douglas A; Tamura, Yoshihiko
2006-05-25
Three-quarters of the Earth's volcanic activity is submarine, located mostly along the mid-ocean ridges, with the remainder along intraoceanic arcs and hotspots at depths varying from greater than 4,000 m to near the sea surface. Most observations and sampling of submarine eruptions have been indirect, made from surface vessels or made after the fact. We describe here direct observations and sampling of an eruption at a submarine arc volcano named NW Rota-1, located 60 km northwest of the island of Rota (Commonwealth of the Northern Mariana Islands). We observed a pulsating plume permeated with droplets of molten sulphur disgorging volcanic ash and lapilli from a 15-m diameter pit in March 2004 and again in October 2005 near the summit of the volcano at a water depth of 555 m (depth in 2004). A turbid layer found on the flanks of the volcano (in 2004) at depths from 700 m to more than 1,400 m was probably formed by mass-wasting events related to the eruption. Long-term eruptive activity has produced an unusual chemical environment and a very unstable benthic habitat exploited by only a few mobile decapod species. Such conditions are perhaps distinctive of active arc and hotspot volcanoes.
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Long-term eruptive activity at a submarine arc volcano
Embley, R.W.; Chadwick, W.W.; Baker, E.T.; Butterfield, D.A.; Resing, J.A.; de Ronde, Cornel E. J.; Tunnicliffe, V.; Lupton, J.E.; Juniper, S.K.; Rubin, K.H.; Stern, R.J.; Lebon, G.T.; Nakamura, K.-I.; Merle, S.G.; Hein, J.R.; Wiens, D.A.; Tamura, Y.
2006-01-01
Three-quarters of the Earth's volcanic activity is submarine, located mostly along the mid-ocean ridges, with the remainder along intraoceanic arcs and hotspots at depths varying from greater than 4,000 m to near the sea surface. Most observations and sampling of submarine eruptions have been indirect, made from surface vessels or made after the fact. We describe here direct observations and sampling of an eruption at a submarine arc volcano named NW Rota-1, located 60 km northwest of the island of Rota (Commonwealth of the Northern Mariana Islands). We observed a pulsating plume permeated with droplets of molten sulphur disgorging volcanic ash and lapilli from a 15-m diameter pit in March 2004 and again in October 2005 near the summit of the volcano at a water depth of 555 m (depth in 2004). A turbid layer found on the flanks of the volcano (in 2004) at depths from 700 m to more than 1,400 m was probably formed by mass-wasting events related to the eruption. Long-term eruptive activity has produced an unusual chemical environment and a very unstable benthic habitat exploited by only a few mobile decapod species. Such conditions are perhaps distinctive of active arc and hotspot volcanoes. ?? 2006 Nature Publishing Group.
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Indirect food web interactions: Sea otters and kelp forest fishes in the Aleutian archipelago
Reisewitz, S.E.; Estes, J.A.; Simenstad, C.A.
2006-01-01
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
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Federal Register 2010, 2011, 2012, 2013, 2014
2010-09-14
... Yellowfin Sole in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries... allowable catch (TAC) assigned to the Bering Sea and Aleutian Islands trawl limited access sector to the Amendment 80 cooperative in the Bering Sea and Aleutian Islands management area (BSAI). This action is...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-10-12
... Yellowfin Sole in the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine Fisheries... allowable catch (TAC) assigned to the Bering Sea and Aleutian Islands trawl limited access sector to the Amendment 80 cooperative in the Bering Sea and Aleutian Islands management area (BSAI). This action is...
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-11-17
... the Bering Sea Subarea of the Bering Sea and Aleutian Islands Management Area AGENCY: National Marine... Bering Sea subarea of the Bering Sea and Aleutian Islands management area. This action is necessary to... management plan for the Bering Sea and Aleutian Islands management area. DATES: Effective November 14, 2011...
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Spatial vent opening probability map of El Hierro Island (Canary Islands, Spain)
NASA Astrophysics Data System (ADS)
Becerril, Laura; Cappello, Annalisa; Galindo, Inés; Neri, Marco; Del Negro, Ciro
2013-04-01
The assessment of the probable spatial distribution of new eruptions is useful to manage and reduce the volcanic risk. It can be achieved in different ways, but it becomes especially hard when dealing with volcanic areas less studied, poorly monitored and characterized by a low frequent activity, as El Hierro. Even though it is the youngest of the Canary Islands, before the 2011 eruption in the "Las Calmas Sea", El Hierro had been the least studied volcanic Island of the Canaries, with more historically devoted attention to La Palma, Tenerife and Lanzarote. We propose a probabilistic method to build the susceptibility map of El Hierro, i.e. the spatial distribution of vent opening for future eruptions, based on the mathematical analysis of the volcano-structural data collected mostly on the Island and, secondly, on the submerged part of the volcano, up to a distance of ~10-20 km from the coast. The volcano-structural data were collected through new fieldwork measurements, bathymetric information, and analysis of geological maps, orthophotos and aerial photographs. They have been divided in different datasets and converted into separate and weighted probability density functions, which were then included in a non-homogeneous Poisson process to produce the volcanic susceptibility map. Future eruptive events on El Hierro is mainly concentrated on the rifts zones, extending also beyond the shoreline. The major probabilities to host new eruptions are located on the distal parts of the South and West rifts, with the highest probability reached in the south-western area of the West rift. High probabilities are also observed in the Northeast and South rifts, and the submarine parts of the rifts. This map represents the first effort to deal with the volcanic hazard at El Hierro and can be a support tool for decision makers in land planning, emergency plans and civil defence actions.
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Long- and short-term triggering and modulation of mud volcano eruptions by earthquakes
NASA Astrophysics Data System (ADS)
Bonini, Marco; Rudolph, Maxwell L.; Manga, Michael
2016-03-01
Earthquakes can trigger the eruption of mud. We use eruptions in Azerbaijan, Italy, Romania, Japan, Andaman Islands, Pakistan, Taiwan, Indonesia, and California to probe the nature of stress changes that induce new eruptions and modulate ongoing eruptions. Dynamic stresses produced by earthquakes are usually inferred to be the dominant triggering mechanism; however static stress changes acting on the feeder systems of mud volcanoes may also play a role. In Azerbaijan, eruptions within 2-10 fault lengths from the epicenter are favored in the year following earthquakes where the static stress changes cause compression of the mud source and unclamp feeder dikes. In Romania, Taiwan, and some Italian sites, increased activity is also favored where the static stress changes act to unclamp feeder dikes, but responses occur within days. The eruption in the Andaman Islands, and those of the Niikappu mud volcanoes, Japan are better correlated with amplitude of dynamic stresses produced by seismic waves. Similarly, a new island that emerged off the coast of Pakistan in 2013 was likely triggered by dynamic stresses, enhanced by directivity. At the southern end of the Salton Sea, California earthquakes increase the gas flux at small mud volcanoes. Responses are best correlated with dynamic stresses. The comparison of responses in these nine settings indicates that dynamic stresses are most often correlated with triggering, although permanent stress changes as small as, and possibly smaller than, 0.1 bar may be sufficient to also influence eruptions. Unclamping stresses with magnitude similar to Earth tides (0.01 bar) persist over time and may play a role in triggering delayed responses. Unclamping stresses may be important contributors to short-term triggering only if they exceed 0.1-1 bar.
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Petersen, Margaret R.; Sonsthagen, Sarah A.; Sexson, Matthew G.
2015-01-01
Islands provide refuges for populations of many species where they find safety from predators, but the introduction of predators frequently results in elimination or dramatic reductions in island-dwelling organisms. When predators are removed, re-colonization for some species occurs naturally, and inter-island phylogeographic relationships and current movement patterns can illuminate processes of colonization. We studied a case of re-colonization of common eiders Somateria mollissima following removal of introduced arctic foxes Vulpes lagopus in the Aleutian Archipelago, Alaska. We expected common eiders to resume nesting on islands cleared of foxes and to re-colonize from nearby islets, islands, and island groups. We thus expected common eiders to show limited genetic structure indicative of extensive mixing among island populations. Satellite telemetry was used to record current movement patterns of female common eiders from six islands across three island groups. We collected genetic data from these and other nesting common eiders at 14 microsatellite loci and the mitochondrial DNA control region to examine population genetic structure, historical fluctuations in population demography, and gene flow. Our results suggest recent interchange among islands. Analysis of microsatellite data supports satellite telemetry data of increased dispersal of common eiders to nearby areas and little between island groups. Although evidence from mtDNA is suggestive of female dispersal among island groups, gene flow is insufficient to account for recolonization and rapid population growth. Instead, near-by remnant populations of common eiders contributed substantially to population expansion, without which re-colonization would have likely occurred at a much lower rate. Genetic and morphometric data of common eiders within one island group two and three decades after re-colonization suggests reduced movement of eiders among islands and little movement between island groups after
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Barren Island west of Malaysia as seen from STS-67 Endeavour
1995-03-14
Barren Island, a small volcanic island which is part of the Andaman Island group in the Andaman Sea west of Malaysia, began a new eruptive phase late in 1994. The STS-67 crew noticed the volcanic plume early in their flight, and had several opportunities to document the on-going eruption. This view, taken March 14, 1995, shows a healthy volcanic plume rising several thousand feet into the atmosphere. The main plume drifts westward over Andaman Island, although a smaller plume close to the ground is being dispersed to the south.
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Federal Register 2010, 2011, 2012, 2013, 2014
2011-11-07
... in the Bering Sea Subarea of the Bering Sea and Aleutian Islands Management Area AGENCY: National... Pacific ocean perch in the Bering Sea subarea of the Bering Sea and Aleutian Islands management area. This... Bering Sea subarea of the Bering Sea and Aleutian Islands management area. DATES: Effective 1200 hrs...
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50 CFR 679.64 - Harvesting sideboard limits in other fisheries.
Code of Federal Regulations, 2013 CFR
2013-10-01
... Pacific ocean perch. (A) The Aleutian Islands Pacific ocean perch harvest limit will be equal to the 1996 through 1997 aggregate retained catch of Aleutian Islands Pacific ocean perch by catcher/processors listed... sum of the Aleutian Islands Pacific ocean perch catch in 1996 and 1997 multiplied by the remainder of...
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50 CFR 679.64 - Harvesting sideboard limits in other fisheries.
Code of Federal Regulations, 2014 CFR
2014-10-01
... area or subarea of the BSAI as follows: (i) Aleutian Islands Pacific ocean perch. (A) The Aleutian Islands Pacific ocean perch harvest limit will be equal to the 1996 through 1997 aggregate retained catch of Aleutian Islands Pacific ocean perch by catcher/processors listed in Sections 208(e)(1) through...
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50 CFR 679.64 - Harvesting sideboard limits in other fisheries.
Code of Federal Regulations, 2012 CFR
2012-10-01
... Pacific ocean perch. (A) The Aleutian Islands Pacific ocean perch harvest limit will be equal to the 1996 through 1997 aggregate retained catch of Aleutian Islands Pacific ocean perch by catcher/processors listed... sum of the Aleutian Islands Pacific ocean perch catch in 1996 and 1997 multiplied by the remainder of...
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Geological and biological heterogeneity of the Aleutian margin (1965-4822 m)
NASA Astrophysics Data System (ADS)
Rathburn, A. E.; Levin, L. A.; Tryon, M.; Gieskes, J. M.; Martin, J. B.; Pérez, M. E.; Fodrie, F. J.; Neira, C.; Fryer, G. J.; Mendoza, G.; McMillan, P. A.; Kluesner, J.; Adamic, J.; Ziebis, W.
2009-01-01
Geological, biological and biogeochemical characterization of the previously unexplored margin off Unimak Island, Alaska between 1965 and 4822 m water depth was conducted to examine: (1) the geological processes that shaped the margin, (2) the linkages between depth, geomorphology and environmental disturbance in structuring benthic communities of varying size classes and (3) the existence, composition and nutritional sources of methane seep biota on this margin. The study area was mapped and sampled using multibeam sonar, a remotely operated vehicle (ROV) and a towed camera system. Our results provide the first characterization of the Aleutian margin mid and lower slope benthic communities (microbiota, foraminifera, macrofauna and megafauna), recognizing diverse habitats in a variety of settings. Our investigations also revealed that the geologic feature known as the “Ugamak Slide” is not a slide at all, and could not have resulted from a large 1946 earthquake. However, sediment disturbance appears to be a pervasive feature of this margin. We speculate that the deep-sea occurrence of high densities of Elphidium, typically a shallow-water foraminiferan, results from the influence of sediment redeposition from shallower habitats. Strong representation of cumacean, amphipod and tanaid crustaceans among the Unimak macrofauna may also reflect sediment instability. Although some faunal abundances decline with depth, habitat heterogeneity and disturbance generated by canyons and methane seepage appear to influence abundances of biota in ways that supercede any clear depth gradient in organic matter input. Measures of sediment organic matter and pigment content as well as C and N isotopic signatures were highly heterogeneous, although the availability of organic matter and the abundance of microorganisms in the upper sediment (1-5 cm) were positively correlated. We report the first methane seep on the Aleutian slope in the Unimak region (3263-3285 m), comprised of
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Selected 1970 Census Data for Alaska Communities. Part 4 - Bristol Bay-Aleutian Region.
ERIC Educational Resources Information Center
Alaska State Dept. of Community and Regional Affairs, Juneau. Div. of Community Planning.
As 1 of 6 regional reports supplying statistical information on Alaska's incorporated and unincorporated communities (those of 25 or more people), this report on Alaska's Bristol Bay-Aleutian Region presents data derived from the 1970 U.S. Census first-count microfilm. Organized via the 3 Bristol Bay-Aleutian census divisions, data are presented…
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Depth of origin of magma in eruptions
Becerril, Laura; Galindo, Ines; Gudmundsson, Agust; Morales, Jose Maria
2013-01-01
Many volcanic hazard factors - such as the likelihood and duration of an eruption, the eruption style, and the probability of its triggering large landslides or caldera collapses - relate to the depth of the magma source. Yet, the magma source depths are commonly poorly known, even in frequently erupting volcanoes such as Hekla in Iceland and Etna in Italy. Here we show how the length-thickness ratios of feeder dykes can be used to estimate the depth to the source magma chamber. Using this method, accurately measured volcanic fissures/feeder-dykes in El Hierro (Canary Islands) indicate a source depth of 11–15 km, which coincides with the main cloud of earthquake foci surrounding the magma chamber associated with the 2011–2012 eruption of El Hierro. The method can be used on widely available GPS and InSAR data to calculate the depths to the source magma chambers of active volcanoes worldwide. PMID:24067336
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50 CFR 679.64 - Harvesting sideboard limits in other fisheries.
Code of Federal Regulations, 2010 CFR
2010-10-01
.../processors be calculated? Except for Aleutian Islands pollock and BSAI Pacific cod, the Regional... group in which a TAC is specified for an area or subarea of the BSAI as follows: (i) Aleutian Islands Pacific ocean perch. (A) The Aleutian Islands Pacific ocean perch harvest limit will be equal to the 1996...
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George, R.; Turner, S.; Hawkesworth, C.; Bacon, C.R.; Nye, C.; Stelling, P.; Dreher, S.
2004-01-01
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.
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NASA Astrophysics Data System (ADS)
Pérez, Nemesio M.; Padilla, Germán D.; Padrón, Eleazar; Hernández, Pedro A.; Melián, Gladys V.; Barrancos, José; Dionis, Samara; Nolasco, Dácil; Rodríguez, Fátima; Calvo, David; Hernández, Íñigo
2012-08-01
On October 12, 2011, a submarine eruption began 2 km off the coast of La Restinga, south of El Hierro Island. CO2 and H2S soil efflux were continuously measured during the period of volcanic unrest by using the accumulation chamber method at two different geochemical stations, HIE01 and HIE07. Recorded CO2 and H2S effluxes showed precursory signals that preceded the submarine eruption. Beginning in late August, the CO2 efflux time series started increasing at a relatively constant rate over one month, reaching a maximum of 19 gm-2d-1 one week before the onset of the submarine volcanic eruption. The H2S efflux time series at HIE07 showed a pulse in H2S emission just one day before the initiation of the submarine eruption, reaching peak values of 42 mg m-2 d-1, 10 times the average H2S efflux recorded during the observation period. Since CO2 and H2S effluxes are strongly influenced by external factors, we applied a multiple regression analysis to remove their contribution. A statistical analysis showed that the long-term trend of the filtered data is well correlated with the seismic energy. We find that these geochemical stations are important monitoring sites for evaluating the volcanic activity of El Hierro and that they demonstrate the potential of applying continuous monitoring of soil CO2 and H2S efflux to improve and optimize the detection of early warning signals of future volcanic unrest episodes at El Hierro. Continuous diffuse degassing studies would likely prove useful for monitoring other volcanoes during unrest episodes.
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Aseismic inflation of Westdahl volcano, Alaska, revealed by satellite radar interferometry
Lu, Z.; Wicks, Charles; Dzurisin, D.; Thatcher, W.; Freymueller, J.T.; McNutt, S.R.; Mann, Dorte
2000-01-01
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.
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NASA Astrophysics Data System (ADS)
DeGrandpre, K.; Pesicek, J. D.; Lu, Z.
2017-12-01
During the summer of 2014 and the early spring of 2015 two notable increases in seismic activity at Semisopochnoi Island in the western Aleutian islands were recorded on AVO seismometers on Semisopochnoi and neighboring islands. These seismic swarms did not lead to an eruption. This study employs interferometric synthetic aperture radar (InSAR) techniques using TerraSAR-X images in conjunction with more accurately relocating the recorded seismic events through simultaneous inversion of event travel times and a three-dimensional velocity model using tomoDD. The InSAR images exhibit surprising coherence and an island wide spatial distribution of inflation that is then used in Mogi, Okada, spheroid, and ellipsoid source models in order to define the three-dimensional location and volume change required for a source at the volcano to produce the observed surface deformation. The tomoDD relocations provide a more accurate and realistic three-dimensional velocity model as well as a tighter clustering of events for both swarms that clearly outline a linear seismic void within the larger group of shallow (<10 km) seismicity. The source models are fit to this void and pressure estimates from geochemical analysis are used to verify the storage depth of magmas at Semisopochnoi. Comparisons of calculated source cavity, magma injection, and surface deformation volumes are made in order to assess the reality behind the various modelling estimates. Incorporating geochemical and seismic data to provide constraints on surface deformation source inversions provides an interdisciplinary approach that can be used to make more accurate interpretations of dynamic observations.
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Mercury levels and potential risk from subsistence foods from the Aleutians.
Burger, Joanna; Gochfeld, Michael; Jeitner, Christian; Burke, Sean; Stamm, Tim; Snigaroff, Ronald; Snigaroff, Dan; Patrick, Robert; Weston, Jim
2007-10-01
Considerable attention has been devoted to contaminants (mainly PCBs and mercury) in subsistence foods (particularly fish) from various parts of the world. However, relatively little attention has been devoted to examining mercury levels in a full range of subsistence foods from a particular region. While managers and scientists compute risk based on site-specific data on contaminant levels and consumption rates, a first step in making risk decisions by subsistence peoples is knowledge about the relative levels of mercury in the foods they eat. This study examined levels of mercury in subsistence foods (edible components) from several islands in the western Aleutians of Alaska, including algae (4 species), invertebrates (9 species), fish (15 species) and birds (5 species). Samples were gathered by both subsistence hunters/fishers and by scientists using the same equipment. Another objective was to determine if there were differences in mercury levels in subsistence foods gathered from different Aleutian islands. We tested the null hypotheses that there were no interspecific and interisland differences in mercury levels. Because of variation in distribution and the nature of subsistence hunting and fishing, not all organisms were collected from each of the islands. There were significant and important differences in mercury levels among species, but the locational differences were rather small. There was an order of magnitude difference between algae/some invertebrates and fish/birds. Even within fish, there were significant differences. The highest mean mercury levels were in flathead sole (Hippoglossoides elassodon, 0.277 ppm), yellow irish lord (Hemilepidotus jardani, 0.281 ppm), great sculpin (Myoxocephalus polyacanthocephalus, 0.366 ppm), glaucous-winged gull (Larus glaucescens, 0.329 ppm) and its eggs (0.364 ppm), and pigeon guillemot (Cepphus columba, 0.494 ppm). Mercury levels increased with increasing weight of the organisms for limpets (Tectura scutum
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NASA Astrophysics Data System (ADS)
Suleimani, E.; Nicolsky, D.; Freymueller, J. T.; Koehler, R.
2013-12-01
The Alaska Earthquake Information Center conducts tsunami inundation mapping for coastal communities in Alaska along several segments of the Aleutian Megathrust, each having a unique seismic history and tsunami generation potential. Accurate identification and characterization of potential tsunami sources is a critical component of our project. As demonstrated by the 2011 Tohoku-oki tsunami, correct estimation of the maximum size event for a given segment of the subduction zone is particularly important. In that event, unexpectedly large slip occurred approximately updip of the epicenter of the main shock, based on seafloor GPS and seafloor pressure gage observations, generating a much larger tsunami than anticipated. This emphasizes the importance of the detailed knowledge of the region-specific subduction processes, and using the most up-to-date geophysical data and research models that define the magnitude range of possible future tsunami events. Our study area extends from the eastern half of the 1957 rupture zone to Kodiak Island, covering the 1946 and 1938 rupture areas, the Shumagin gap, and the western part of the 1964 rupture area. We propose a strategy for generating worst-case credible tsunami scenarios for locations that have a short or nonexistent paleoseismic/paleotsunami record, and in some cases lack modern seismic and GPS data. The potential tsunami scenarios are built based on a discretized plate interface model fit to the Slab 1.0 model geometry. We employ estimates of slip deficit along the Aleutian Megathrust from GPS campaign surveys, the Slab 1.0 interface surface, empirical magnitude-slip relationships, and a numerical code that distributes slip among the subfault elements, calculates coseismic deformations and solves the shallow water equations of tsunami propagation and runup. We define hypothetical asperities along the megathrust and in down-dip direction, and perform a set of sensitivity model runs to identify coseismic deformation
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Amchitka Island, Alaska, Biological Monitoring Report 2011 Sampling Results
DOE Office of Scientific and Technical Information (OSTI.GOV)
None
The Long-Term Surveillance and Maintenance (LTS&M) Plan for the U.S. Department of Energy (DOE) Office of Legacy Management (LM) Amchitka Island sites describes how LM plans to conduct its mission to protect human health and the environment at the three nuclear test sites located on Amchitka Island, Alaska. Amchitka Island, near the western end of the Aleutian Islands, is approximately 1,340 miles west-southwest of Anchorage, Alaska. Amchitka is part of the Aleutian Island Unit of the Alaska Maritime National Wildlife Refuge, which is administered by the U.S. Fish and Wildlife Service (USFWS). Since World War II, Amchitka has been usedmore » by multiple U.S. government agencies for various military and research activities. From 1943 to 1950, it was used as a forward air base for the U.S. Armed Forces. During the middle 1960s and early 1970s, the U.S. Department of Defense (DOD) and the U.S. Atomic Energy Commission (AEC) used a portion of the island as a site for underground nuclear tests. During the late 1980s and early 1990s, the U.S. Navy constructed and operated a radar station on the island. Three underground nuclear tests were conducted on Amchitka Island. DOD, in conjunction with AEC, conducted the first nuclear test (named Long Shot) in 1965 to provide data that would improve the United States' capability of detecting underground nuclear explosions. The second nuclear test (Milrow) was a weapons-related test conducted by AEC in 1969 as a means to study the feasibility of detonating a much larger device. Cannikin, the third nuclear test on Amchitka, was a weapons-related test detonated on November 6, 1971. With the exception of small concentrations of tritium detected in surface water shortly after the Long Shot test, radioactive fission products from the tests remain in the subsurface at each test location As a continuation of the environmental monitoring that has taken place on Amchitka Island since before 1965, LM in the summer of 2011 collected
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Early signs of geodynamic activity before the 2011-2012 El Hierro eruption
NASA Astrophysics Data System (ADS)
López, Carmen; García-Cañada, Laura; Martí, Joan; Domínguez Cerdeña, Itahiza
2017-04-01
The potential relation between mantle plume dynamics, regional tectonics and eruptive activity in the Canary Islands has not been studied yet through the analysis of long-time series of geophysical observational data. The existence of highly reliable seismic and GNSS data has enabled us to study from 1996 to 2014 the geodynamic evolution of the North Atlantic Azores-Gibraltar region and its relationship with recent volcanic activity in El Hierro (Canary Islands, Spain). We compiled a new and unified regional seismic catalog and used long time-series of surface displacements recorded by permanent GNSS stations in the region. A regional- and local-scale analysis based on these data enabled us to identify signs of anomalous tectonic activity from 2003 onwards, whose intensity increased in 2007 and finally accelerated three months before the onset of the volcanic eruption on El Hierro in October 2011. This activity includes a regional extension and an uplift process that affects the southern Iberian Peninsula, NW Africa, and the Canary Islands. We interpret these observations as early signs of the geodynamic activity, which led to El Hierro eruption and the subsequent episodes of magma intrusion. Results point to the significant contribution of the mantle plume dynamics (i.e. external forces) in this renewed volcanic activity in the Canary Islands and emphasize the role of mantle dynamics in controlling regional tectonics.
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Lidar Observations of Stratospheric Aerosol Layer After the Mt. Pinatubo Volcanic Eruption
NASA Technical Reports Server (NTRS)
Nagai, Tomohiro; Uchino, Osamu; Fujimoto, Toshifumi
1992-01-01
The volcano Mt. Pinatubo located on the Luzon Island, Philippines, had explosively erupted on June 15, 1991. The volcanic eruptions such as volcanic ash, SO2 and H2O reached into the stratosphere over 30 km altitude by the NOAA-11 satellite observation and this is considered one of the biggest volcanic eruptions in this century. A grandiose volcanic eruption influences the atmosphere seriously and causes many climatic effects globally. There had been many impacts on radiation, atmospheric temperature and stratospheric ozone after some past volcanic eruptions. The main cause of volcanic influence depends on stratospheric aerosol, that stay long enough to change climate and other meteorological conditions. Therefore it is very important to watch stratospheric aerosol layers carefully and continuously. Standing on this respect, we do not only continue stratospheric aerosol observation at Tsukuba but also have urgently developed another lidar observational point at Naha in Okinawa Island. This observational station could be thought valuable since there is no lidar observational station in this latitudinal zone and it is much nearer to Mt. Pinatubo. Especially, there is advantage to link up these two stations on studying the transportation mechanism in the stratosphere. In this paper, we present the results of lidar observations at Tsukuba and Naha by lidar systems with Nd:YAG laser.
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Wright, Heather M.; Vazquez, Jorge A.; Champion, Duane E.; Calvert, Andrew T.; Mangan, Margaret T.; Stelten, Mark E.; Cooper, Kari M.; Herzig, Charles; Schriener Jr., Alexander
2015-01-01
In the Salton Trough, CA, five rhyolite domes form the Salton Buttes: Mullet Island, Obsidian Butte, Rock Hill, North and South Red Hill, from oldest to youngest. Results presented here include 40Ar/39Ar anorthoclase ages, 238U-230Th zircon crystallization ages, and comparison of remanent paleomagnetic directions with the secular variation curve, which indicate that all domes are Holocene. 238U-230Th zircon crystallization ages are more precise than but within uncertainty of 40Ar/39Ar anorthoclase ages, suggesting that zircon crystallization proceeded until shortly before eruption in all cases except one. Remanent paleomagnetic directions require three eruption periods: (1) Mullet Island, (2) Obsidian Butte, and (3) Rock Hill, North Red Hill, and South Red Hill. Borehole cuttings logs document up to two shallow tephra layers. North and South Red Hills likely erupted within 100 years of each other, with a combined 238U-230Th zircon isochron age of: 2.83 ± 0.60 ka (2 sigma); paleomagnetic evidence suggests this age predates eruption by hundreds of years (1800 cal BP). Rock Hill erupted closely in time to these eruptions. The Obsidian Butte 238U-230Th isochron age (2.86 ± 0.96 ka) is nearly identical to the combined Red Hill age, but its Virtual Geomagnetic Pole position suggests a slightly older age. The age of aphyric Mullet Island dome is the least well constrained: zircon crystals are resorbed and the paleomagnetic direction is most distinct; possible Mullet Island ages include ca. 2300, 5900, 6900, and 7700 cal BP. Our results constrain the duration of Salton Buttes volcanism to between ca. 5900 and 500 years.
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Volcanic Island Appears Near Tonga
NASA Astrophysics Data System (ADS)
Zielinski, Sarah
2006-11-01
A volcano known as Home Reef is now believed to be the source of a small island that appeared recently in Tonga, accordingto scientists from the Smithsonian Institution's Global Volcanism Program who had initially placed the location of the eruption and resulting island at nearby Metis Shoal. Mariners onboard the yacht Maiken
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Eruption style at Kīlauea Volcano in Hawai‘i linked to primary melt composition
Sides. I.R.,; Edmonds, M.; Maclennan, J.; Swanson, Don; Houghton, Bruce F.
2014-01-01
Explosive eruptions at basaltic volcanoes have been linked to gas segregation from magmas at shallow depths in the crust. The composition of primary melts formed at greater depths was thought to have little influence on eruptive style. Ocean island basaltic volcanoes are the product of melting of a geochemically heterogeneous mantle plume and are expected to give rise to heterogeneous primary melts. This range in primary melt composition, particularly with respect to the volatile components, will profoundly influence magma buoyancy, storage and eruption style. Here we analyse the geochemistry of a suite of melt inclusions from 25 historical eruptions at the ocean island volcano of Kīlauea, Hawai‘i, over the past 600 years. We find that more explosive styles of eruption at Kīlauea Volcano are associated statistically with more geochemically enriched primary melts that have higher volatile concentrations. These enriched melts ascend faster and retain their primary nature, undergoing little interaction with the magma reservoir at the volcano’s summit. We conclude that the eruption style and magma-supply rate at Kīlauea are fundamentally linked to the geochemistry of the primary melts formed deep below the volcano. Magmas might therefore be predisposed towards explosivity right at the point of formation in their mantle source region.
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Volcanism in Iceland in historical time: Volcano types, eruption styles and eruptive history
NASA Astrophysics Data System (ADS)
Thordarson, T.; Larsen, G.
2007-01-01
The large-scale volcanic lineaments in Iceland are an axial zone, which is delineated by the Reykjanes, West and North Volcanic Zones (RVZ, WVZ, NVZ) and the East Volcanic Zone (EVZ), which is growing in length by propagation to the southwest through pre-existing crust. These zones are connected across central Iceland by the Mid-Iceland Belt (MIB). Other volcanically active areas are the two intraplate belts of Öræfajökull (ÖVB) and Snæfellsnes (SVB). The principal structure of the volcanic zones are the 30 volcanic systems, where 12 are comprised of a fissure swarm and a central volcano, 7 of a central volcano, 9 of a fissure swarm and a central domain, and 2 are typified by a central domain alone. Volcanism in Iceland is unusually diverse for an oceanic island because of special geological and climatological circumstances. It features nearly all volcano types and eruption styles known on Earth. The first order grouping of volcanoes is in accordance with recurrence of eruptions on the same vent system and is divided into central volcanoes (polygenetic) and basalt volcanoes (monogenetic). The basalt volcanoes are categorized further in accordance with vent geometry (circular or linear), type of vent accumulation, characteristic style of eruption and volcanic environment (i.e. subaerial, subglacial, submarine). Eruptions are broadly grouped into effusive eruptions where >95% of the erupted magma is lava, explosive eruptions if >95% of the erupted magma is tephra (volume calculated as dense rock equivalent, DRE), and mixed eruptions if the ratio of lava to tephra occupy the range in between these two end-members. Although basaltic volcanism dominates, the activity in historical time (i.e. last 11 centuries) features expulsion of basalt, andesite, dacite and rhyolite magmas that have produced effusive eruptions of Hawaiian and flood lava magnitudes, mixed eruptions featuring phases of Strombolian to Plinian intensities, and explosive phreatomagmatic and magmatic
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NASA Astrophysics Data System (ADS)
Spieker, Kathrin; Rondenay, Stéphane; Sawade, Lucas
2016-04-01
The Circum-Pacific belt, also called the Pacific Ring of Fire, is the most seismically active region on Earth. Multiple plate boundaries form a zone characterized by frequent volcanic eruptions and seismicity. While convergent plate boundaries such as the Peru-Chile trench dominate the Circum-Pacific belt, divergent and transform boundaries are present as well. The eastern section of the Circum-Pacific belt extends from the Aleutian arc, through the Cascadia subduction zone, San Andreas Fault, middle America trench and the Andean margin down to Tierra del Fuego. Due to the significant hazards posed by this tectonic activity, the region has been densely instrumented by thousands of seismic stations deployed across fifteen countries, over a distance of more than 15000 km. Various seismological studies, including receiver function analyses, have been carried out to investigate the crustal and mantle structure beneath local segments of the eastern Circum-Pacific belt (i.e., at ~100-500 km scale). However, to the best of our knowledge, no study to date has ever attempted to combine all available seismic data from the eastern Circum-Pacific belt to generate a continuous profile of seismic discontinuities extending from the Aleutians to Tierra del Fuego. Here, we use results from the "Global Imaging using Earthquake Records" (GLImER) P-wave receiver function database to create a long-range profile of crustal and upper mantle discontinuities across the entire eastern portion of the Circum-Pacific belt. We image intermittent crustal and mantle discontinuities along the profile, and examine them with regard to their behaviour and properties across transitions between different tectonic regimes.
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Diverse Water-Magma Interactions In The Conduit And Column During The 2008 Okmok Eruption, Alaska
NASA Astrophysics Data System (ADS)
Ort, M. H.; Unema, J. A.; Neal, C. A.; Larsen, J. F.; Schaefer, J. R.
2015-12-01
Ground, surface, and atmospheric water affected the Okmok (central Aleutians, Alaska) 2008 eruption in diverse ways. An initial 16-km-high column produced a widespread coarse fallout. Explosion breccias and lithic-rich fallout overlie this deposit proximally, topped by an ash with abundant accretionary lapilli and ash pellets. After this, a water-rich flood, likely from ejected lake water, left deposits in the eastern caldera. Pyroclastic density currents traveled northward in the caldera, leaving both coarse-ash dune forms and massive unsorted deposits. We interpret these to mark vent opening or widening, with diverse currents forming in different sectors due to directed explosions and partial column collapse. The rest of the eruption was characterized by water-rich ash and steam columns 1-4 km high, with brief <9-km-high periods. Several vents formed during the eruption; one enlarged a pre-existing lake and others formed a new lake, a small tuff ring, and a 300-m-high tuff cone. Surface water, shallow groundwater in coarse sediments, and atmospheric water were abundantly available throughout the eruption. Cone D Lake (13.6 Mm3 volume) drained into the North vent 7-10 days into the eruption, with massive groundwater and sediment removal. Nearby pit craters have no ejecta; surficial lava collapsed when underlying sediments were removed. The eruption column was typically gray or white, rarely black, and ashfall dominates the deposits at all localities, reflecting efficient fragmentation and deposition. Scrubbing of the plume by erupted and atmospheric water caused rapid deposition of the ash, so deposits thin rapidly away from the vent. Laminae and thin lenses dominate the deposits outside the caldera whereas some intracaldera deposits are massive beds up to several decimeters thick. Wind-blown ash-laden mist made low-angle ripples and discontinuous laminae; ash rain deposited continuous laminae. A capping vesicular ash (Av soil horizon) formed as a water
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Monitoring El Hierro submarine volcanic eruption events with a submarine seismic array
NASA Astrophysics Data System (ADS)
Jurado, Maria Jose; Molino, Erik; Lopez, Carmen
2013-04-01
A submarine volcanic eruption took place near the southernmost emerged land of the El Hierro Island (Canary Islands, Spain), from October 2011 to February 2012. The Instituto Geografico Nacional (IGN) seismic stations network evidenced seismic unrest since July 2012 and was a reference also to follow the evolution of the seismic activity associated with the volcanic eruption. From the beginning of the eruption a geophone string was installed less than 2 km away from the new volcano, next to La Restinga village shore, to record seismic activity related to the volcanic activity, continuously and with special interest on high frequency events. The seismic array was endowed with 8, high frequency, 3 component, 250 Hz, geophone cable string with a separation of 6 m between them. The analysis of the dataset using spectral techniques allows the characterization of the different phases of the eruption and the study of its dynamics. The correlation of the data analysis results with the observed sea surface activity (ash and lava emission and degassing) and also with the seismic activity recorded by the IGN field seismic monitoring system, allows the identification of different stages suggesting the existence of different signal sources during the volcanic eruption and also the posteruptive record of the degassing activity. The study shows that the high frequency capability of the geophone array allow the study of important features that cannot be registered by the standard seismic stations. The accumulative spectral amplitude show features related to eruptive changes.
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NASA Astrophysics Data System (ADS)
Bai, Yefei; Yamazaki, Yoshiki; Cheung, Kwok Fai
2018-04-01
The latest tsunami evacuation maps of Hawaii include an extreme scenario triggered by an Mw 9.3 Aleutian earthquake with large near-trench rupture. The tectonic plate motion produces concentrated seafloor uplift toward the deepest part of the trench generating a tsunami with strong non-hydrostatic characters. A parametric study shows the skewed seafloor uplift produces a dispersive leading crest followed by a prominent trough in the form of an N-wave. The trough maintains its depth across the ocean in the absence of side lobes and dispersion. Shifting of the uplift toward the trench tends to deepen the trough, but has diminishing effects on the wave crest away from the source. While the attenuated leading crest produces relatively moderate runup on north-facing shores of the Hawaiian Islands, with matching of the N-wave and shelf resonance periods, the trough produces an impulsive drawdown followed by an energetic upswing with unprecedented runup for a far-field tsunami. A set of control computations without dispersion reaffirms that a non-hydrostatic model is essential to account for these complex wave processes from the source to the shore. This case study highlights the unique tsunami hazards posed by the Aleutians to Hawaii and the role of wave troughs in delineating the impacts for hazard assessment and engineering design.
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NASA Astrophysics Data System (ADS)
Rooper, Christopher N.; Wilkins, Mark E.; Rose, Craig S.; Coon, Catherine
2011-11-01
The abundance of some marine fish species are correlated to the abundance of habitat-forming benthic organisms such as sponges and corals. A concern for fisheries management agencies is the recovery of these benthic invertebrates from removal or mortality from bottom trawling and other commercial fisheries activities. Using a logistic model, observations of available substrate and data from bottom trawl surveys of the Aleutian Islands, Alaska, we estimated recovery rates of sponges and corals following removal. The model predicted the observed sponge and coral catch in bottom trawl surveys relatively accurately ( R2=0.38 and 0.46). For sponges, the results show that intrinsic growth rates were slow ( r=0.107 yr -1). Results show that intrinsic growth rates of corals were also slow ( r=0.062 yr -1). The best models for corals and sponges were models that did not include the impacts of commercial fishing removals. Subsequent recovery times for both taxa were also predicted to be slow. Mortality of 67% of the initial sponge biomass would recover to 80% of the original biomass after 20 years, while mortality of 67% of the coral biomass would recover to 80% of the original biomass after 34 years. The modeled recovery times were consistent with previous studies in estimating that recovery times were of the order of decades, however improved data from directed studies would no doubt improve parameter estimates and reduce the uncertainty in the model results. Given their role as a major ecosystem component and potential habitat for marine fish, damage and removal of sponges and corals must be considered when estimating the impacts of commercial bottom trawling on the seafloor.
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Attaining high-resolution eruptive histories for active arc volcanoes with argon geochronology
NASA Astrophysics Data System (ADS)
Calvert, A. T.
2012-04-01
Geochronology of active arc volcanoes commonly illuminates eruptive behavior over tens to hundreds of thousands of years, lengthy periods of repose punctuated by short eruptive episodes, and spatial and compositional changes with time. Despite the >1 Gyr half-life of 40K, argon geochronology is an exceptional tool for characterizing Pleistocene to Holocene eruptive histories and for placing constraints on models of eruptive behavior. Reliable 40Ar/39Ar ages of calc-alkaline arc rocks with rigorously derived errors small enough (± 500 to 3,000 years) to constrain eruptive histories are attainable using careful procedures. Sample selection and analytical work in concert with geologic mapping and stratigraphic studies are essential for determining reliable eruptive histories. Preparation, irradiation and spectrometric techniques have all been optimized to produce reliable, high-precision results. Examples of Cascade and Alaska/Aleutian eruptive histories illustrating duration of activity from single centers, eruptive episodicity, and spatial and compositional changes with time will be presented: (1) Mt. Shasta, the largest Cascade stratovolcano, has a 700,000-year history (Calvert and Christiansen, 2011 Fall AGU). A similar sized and composition volcano (Rainbow Mountain) on the Cascade axis was active 1200-950 ka. The eruptive center then jumped west 15 km to the south flank of the present Mt. Shasta and produced a stratovolcano from 700-450 ka likely rivaling today's Mt. Shasta. The NW portion of that edifice failed in an enormous (>30 km3) debris avalanche. Vents near today's active summit erupted 300-135 ka, then 60-15 ka. A voluminous, but short-lived eruptive sequence occurred at 11 ka, including a summit explosion producing a subplinian plume, followed by >60 km3 andesite-dacite Shastina domes and flows, then by the flank dacite Black Butte dome. Holocene domes and flows subsequently rebuilt the summit and flowed to the north and east. (2) Mt. Veniaminof on
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NASA Astrophysics Data System (ADS)
Faria, B.; Fonseca, J. F. B. D.
2014-02-01
We describe a new geophysical network deployed in the Cape Verde Archipelago for the assessment and monitoring of volcanic hazards as well as the first results from the network. Across the archipelago, the ages of volcanic activity range from ca. 20 Ma to present. In general, older islands are in the east and younger ones are in the west, but there is no clear age progression of eruptive activity as widely separated islands have erupted contemporaneously on geological timescales. The overall magmatic rate is low, and there are indications that eruptive activity is episodic, with intervals between episodes of intense activity ranging from 1 to 4 Ma. Although only Fogo Island has experienced eruptions (mainly effusive) in the historic period (last 550 yr), Brava and Santo Antão have experienced numerous geologically recent eruptions, including violent explosive eruptions, and show felt seismic activity and geothermal activity. Evidence for recent volcanism in the other islands is more limited and the emphasis has therefore been on monitoring of the three critical islands of Fogo, Brava and Santo Antão, where volcanic hazard levels are highest. Geophysical monitoring of all three islands is now in operation. The first results show that on Fogo, the seismic activity is dominated by hydrothermal events and volcano-tectonic events that may be related to settling of the edifice after the 1995 eruption; in Brava by volcano-tectonic events (mostly offshore), and in Santo Antão by volcano-tectonic events, medium-frequency events and harmonic tremor. Both in Brava and in Santo Antão, the recorded seismicity indicates that relatively shallow magmatic systems are present and causing deformation of the edifices that may include episodes of dike intrusion.
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Deep intrusions, lateral magma transport and related uplift at ocean island volcanoes
NASA Astrophysics Data System (ADS)
Klügel, Andreas; Longpré, Marc-Antoine; García-Cañada, Laura; Stix, John
2015-12-01
Oceanic intraplate volcanoes grow by accumulation of erupted material as well as by coeval or discrete magmatic intrusions. Dykes and other intrusive bodies within volcanic edifices are comparatively well studied, but intrusive processes deep beneath the volcanoes remain elusive. Although there is geological evidence for deep magmatic intrusions contributing to volcano growth through uplift, this has rarely been demonstrated by real-time monitoring. Here we use geophysical and petrological data from El Hierro, Canary Islands, to show that intrusions from the mantle and subhorizontal transport of magma within the oceanic crust result in rapid endogenous island growth. Seismicity and ground deformation associated with a submarine eruption in 2011-2012 reveal deep subhorizontal intrusive sheets (sills), which have caused island-scale uplift of tens of centimetres. The pre-eruptive intrusions migrated 15-20 km laterally within the lower oceanic crust, opening pathways that were subsequently used by the erupted magmas to ascend from the mantle to the surface. During six post-eruptive episodes between 2012 and 2014, further sill intrusions into the lower crust and upper mantle have caused magma to migrate up to 20 km laterally, resulting in magma accumulation exceeding that of the pre-eruptive phase. A comparison of geobarometric data for the 2011-2012 El Hierro eruption with data for other Atlantic intraplate volcanoes shows similar bimodal pressure distributions, suggesting that eruptive phases are commonly accompanied by deep intrusions of sills and lateral magma transport. These processes add significant material to the oceanic crust, cause uplift, and are thus fundamentally important for the growth and evolution of volcanic islands. We suggest that the development of such a magma accumulation zone in the lower oceanic crust begins early during volcano evolution, and is a consequence of increasing size and complexity of the mantle reservoir system, and potentially
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Ryan, Holly F.; Draut, Amy E.; Keranen, Katie M.; Scholl, David W.
2012-01-01
During Pliocene to Quaternary time, the central Aleutian forearc basin evolved in response to a combination of tectonic and climatic factors. Initially, along-trench transport of sediment and accretion of a frontal prism created the accommodation space to allow forearc basin deposition. Transport of sufficient sediment to overtop the bathymetrically high Amlia fracture zone and reach the central Aleutian arc began with glaciation of continental Alaska in the Pliocene. As the obliquely subducting Amlia fracture zone swept along the central Aleutian arc, it further affected the structural evolution of the forearc basins. The subduction of the Amlia fracture zone resulted in basin inversion and loss of accommodation space east of the migrating fracture zone. Conversely, west of Amlia fracture zone, accommodation space increased arcward of a large outer-arc high that formed, in part, by a thickening of arc basement. This difference in deformation is interpreted to be the result of a variation in interplate coupling across the Amlia fracture zone that was facilitated by increasing subduction obliquity, a change in orientation of the subducting Amlia fracture zone, and late Quaternary intensification of glaciation. The change in coupling is manifested by a possible tear in the subducting slab along the Amlia fracture zone. Differences in coupling across the Amlia fracture zone have important implications for the location of maximum slip during future great earthquakes. In addition, shaking during a great earthquake could trigger large mass failures of the summit platform, as evidenced by the presence of thick mass transport deposits of primarily Quaternary age that are found in the forearc basin west of the Amlia fracture zone.
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Post-eruptive flooding of Santorini caldera and implications for tsunami generation.
Nomikou, P; Druitt, T H; Hübscher, C; Mather, T A; Paulatto, M; Kalnins, L M; Kelfoun, K; Papanikolaou, D; Bejelou, K; Lampridou, D; Pyle, D M; Carey, S; Watts, A B; Weiß, B; Parks, M M
2016-11-08
Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The caldera-forming eruption of Santorini in the Late Bronze Age is known to have been tsunamigenic, and caldera collapse has been proposed as a mechanism. Here, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Inflow of water and associated landsliding cut a deep, 2.0-2.5 km 3 , submarine channel, thus filling the caldera in less than a couple of days. If, as at most such volcanoes, caldera collapse occurred syn-eruptively, then it cannot have generated tsunamis. Entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations, were the main mechanisms of tsunami production.
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Post-eruptive flooding of Santorini caldera and implications for tsunami generation
NASA Astrophysics Data System (ADS)
Nomikou, P.; Druitt, T. H.; Hübscher, C.; Mather, T. A.; Paulatto, M.; Kalnins, L. M.; Kelfoun, K.; Papanikolaou, D.; Bejelou, K.; Lampridou, D.; Pyle, D. M.; Carey, S.; Watts, A. B.; Weiß, B.; Parks, M. M.
2016-11-01
Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The caldera-forming eruption of Santorini in the Late Bronze Age is known to have been tsunamigenic, and caldera collapse has been proposed as a mechanism. Here, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Inflow of water and associated landsliding cut a deep, 2.0-2.5 km3, submarine channel, thus filling the caldera in less than a couple of days. If, as at most such volcanoes, caldera collapse occurred syn-eruptively, then it cannot have generated tsunamis. Entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations, were the main mechanisms of tsunami production.
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Post-eruptive flooding of Santorini caldera and implications for tsunami generation
Nomikou, P.; Druitt, T. H.; Hübscher, C.; Mather, T. A.; Paulatto, M.; Kalnins, L. M.; Kelfoun, K.; Papanikolaou, D.; Bejelou, K.; Lampridou, D.; Pyle, D. M.; Carey, S.; Watts, A. B.; Weiß, B.; Parks, M. M.
2016-01-01
Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The caldera-forming eruption of Santorini in the Late Bronze Age is known to have been tsunamigenic, and caldera collapse has been proposed as a mechanism. Here, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Inflow of water and associated landsliding cut a deep, 2.0–2.5 km3, submarine channel, thus filling the caldera in less than a couple of days. If, as at most such volcanoes, caldera collapse occurred syn-eruptively, then it cannot have generated tsunamis. Entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations, were the main mechanisms of tsunami production. PMID:27824353
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Preliminary volcano-hazard assessment for Kanaga Volcano, Alaska
Waythomas, Christopher F.; Miller, Thomas P.; Nye, Christopher J.
2002-01-01
Kanaga Volcano is a steep-sided, symmetrical, cone-shaped, 1307 meter high, andesitic stratovolcano on the north end of Kanaga Island (51°55’ N latitude, 177°10’ W longitude) in the western Aleutian Islands of Alaska. Kanaga Island is an elongated, low-relief (except for the volcano) island, located about 35 kilometers west of the community of Adak on Adak Island and is part of the Andreanof Islands Group of islands. Kanaga Volcano is one of the 41 historically active volcanoes in Alaska and has erupted numerous times in the past 11,000 years, including at least 10 eruptions in the past 250 years (Miller and others, 1998). The most recent eruption occurred in 1993-95 and caused minor ash fall on Adak Island and produced blocky aa lava flows that reached the sea on the northwest and west sides of the volcano (Neal and others, 1995). The summit of the volcano is characterized by a small, circular crater about 200 meters in diameter and 50-70 meters deep. Several active fumaroles are present in the crater and around the crater rim. The flanking slopes of the volcano are steep (20-30 degrees) and consist mainly of blocky, linear to spoonshaped lava flows that formed during eruptions of late Holocene age (about the past 3,000 years). The modern cone sits within a circular caldera structure that formed by large-scale collapse of a preexisting volcano. Evidence for eruptions of this preexisting volcano mainly consists of lava flows exposed along Kanaton Ridge, indicating that this former volcanic center was predominantly effusive in character. In winter (October-April), Kanaga Volcano may be covered by substantial amounts of snow that would be a source of water for lahars (volcanic mudflows). In summer, much of the snowpack melts, leaving only a patchy distribution of snow on the volcano. Glacier ice is not present on the volcano or on other parts of Kanaga Island. Kanaga Island is uninhabited and is part of the Alaska Maritime National Wildlife Refuge, managed by
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Eruption Dynamics and Flow Morphology during the 2005 Sierra Negra Eruption, Galapagos Islands
NASA Astrophysics Data System (ADS)
Rader, E.; Harpp, K.; Geist, D.
2006-12-01
Sierra Negra volcano began erupting on October 22nd, 2005. The eruption lasted nine days and provided an opportunity to examine emplacement of lava flows and their morphology. During the first two days, fire fountaining produced a broad, unchannelized flow that coated the northern caldera wall and benches directly below the vents as it moved onto the eastern caldera floor. After the first day of the eruption, the caldera floor a'a flow grew primarily by inflation, lateral spreading along linear upwelling regions, and pahoehoe breakouts at the perimeter. Simultaneously, four 4km long rootless flows formed on the northern flanks of the volcano, supplied by spatter from the vents inboard of the caldera rim. Samples from different morphological types of lava from the caldera floor, bench, and outer flanks were collected and examined by BSE imaging. Transitions from pahoehoe to a'a and back to pahoehoe were observed in a low viscosity flow on the caldera bench that cascaded over a steep escarpment. Plagioclase microlite content in the bench flow varies little, with 27% in pahoehoe and 33% in a'a, on average. Consequently, we propose that the transformation was driven by changes in strain rate rather than cooling. As the lava first flowed over the bench edge, the increased strain rate caused it to become a'a. The elevation drop was small enough, however, that the flow remained sufficiently hot to revert to pahoehoe as it pooled on the flat surface at the base of the drop; comparable flows have been described on Kilauea. Similarly, pahoehoe breakouts from the caldera floor a'a flow were driven by pressure from the inflating flow, causing well-insulated lava to emerge from the a'a body as pahoehoe. Quenched lava collected from the incandescent breakouts have higher crystal contents than those collected closer to the vents, indicating that they experienced ~30° cooling during transport within the inflating flow. At the southern tip of the caldera floor flow, several km
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Early signs of geodynamic activity before the 2011-2012 El Hierro eruption
NASA Astrophysics Data System (ADS)
López, Carmen; García-Cañada, Laura; Martí, Joan; Domínguez Cerdeña, Itahiza
2017-02-01
The potential relation between mantle plume dynamics, regional tectonics and eruptive activity in the Canary Islands has not been studied yet through the analysis of long-time series of geophysical observational data. The existence of highly reliable seismic and geodetic data has enabled us to study from 1996 to 2014 the geodynamic evolution of the North Atlantic Azores-Gibraltar region (including the NW African margin) and its relationship with recent volcanic activity in El Hierro (Canary Islands). We compiled a new and unified regional seismic catalog and used long time-series of digital 3D surface displacements recorded by permanent GPS stations in the region. A joint regional- and local-scale analysis based on these data enabled us to identify signs of anomalous tectonic activity from 2003 onwards, whose intensity increased in 2007 and finally accelerated three months before the onset of the volcanic eruption on El Hierro in October 2011. Activity included the occurrence of regional extension and an uplift process affecting the southern Iberian Peninsula, NW Africa, and the Canary Islands. We interpret these observations as early signs of the geodynamic activity, which led to El Hierro eruption and the subsequent episodes of magma intrusion. Results point to the significant contribution of the mantle plume dynamics (i.e. external forces) in this renewed volcanic activity in the Canary Islands and emphasize the role of mantle dynamics in controlling regional tectonics.
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NASA Astrophysics Data System (ADS)
Bègue, Nelson; Vignelles, Damien; Berthet, Gwenaël; Portafaix, Thierry; Payen, Guillaume; Jégou, Fabrice; Benchérif, Hassan; Jumelet, Julien; Vernier, Jean-Paul; Lurton, Thibaut; Renard, Jean-Baptiste; Clarisse, Lieven; Duverger, Vincent; Posny, Françoise; Metzger, Jean-Marc; Godin-Beekmann, Sophie
2017-12-01
After 43 years of inactivity, the Calbuco volcano, which is located in the southern part of Chile, erupted on 22 April 2015. The space-time evolutions (distribution and transport) of its aerosol plume are investigated by combining satellite (CALIOP, IASI, OMPS), in situ aerosol counting (LOAC OPC) and lidar observations, and the MIMOSA advection model. The Calbuco aerosol plume reached the Indian Ocean 1 week after the eruption. Over the Reunion Island site (21° S, 55.5° E), the aerosol signal was unambiguously enhanced in comparison with
background
conditions, with a volcanic aerosol layer extending from 18 to 21 km during the May-July period. All the data reveal an increase by a factor of ˜ 2 in the SAOD (stratospheric aerosol optical depth) with respect to values observed before the eruption. The aerosol mass e-folding time is approximately 90 days, which is rather close to the value ( ˜ 80 days) reported for the Sarychev eruption. Microphysical measurements obtained before, during, and after the eruption reflecting the impact of the Calbuco eruption on the lower stratospheric aerosol content have been analyzed over the Reunion Island site. During the passage of the plume, the volcanic aerosol was characterized by an effective radius of 0.16 ± 0.02 µm with a unimodal size distribution for particles above 0.2 µm in diameter. Particle concentrations for sizes larger than 1 µm are too low to be properly detected by the LOAC OPC. The aerosol number concentration was ˜ 20 times higher that observed before and 1 year after the eruption. According to OMPS and lidar observations, a tendency toward conditions before the eruption was observed by April 2016. The volcanic aerosol plume is advected eastward in the Southern Hemisphere and its latitudinal extent is clearly bounded by the subtropical barrier and the polar vortex. The transient behavior of the aerosol layers observed above Reunion Island between May and July 2015 reflects an inhomogeneous spatio -
Multi-disciplinary Monitoring of the 2014 Eruption of Fogo Volcano, Cape Verde
NASA Astrophysics Data System (ADS)
Fernandes, R. M. S.; Faria, B. V. E.
2015-12-01
The Fogo volcano, located in the Cape Verde Archipelago (offshore Western Africa), is a complete stratovolcano system. It is the most recent expression of the Cape Verde hotspot, that has formed the archipelago. The summit reaches ~2830m above sea level, and raises 1100m above Chã das Caldeiras, an almost flat circular area. The last eruption of Fogo started on November 23, 2014 (~10:00UTC), after 19 years of inactivity. C4G, a distributed research infrastructure created in 2014 in the framework of the Portuguese Roadmap for Strategic Research Infrastructures, collaborated immediately with INMG, the Cape Verdean Meteorological and Geophysical Institut with the goal of complementing the permanent geophysical monitoring network in operation on Fogo island. The INMG permanent network is composed of seven seismographic stations and three tiltmeter stations, with real-time data transmitted. On the basis of increased pre-event activity (which started in October 2014), INMG issued a formal alert of an impending eruption to the Civil Protection Agency, about 24 hours before the onset of the eruption. Although the eruption caused no casualties or personal injuries due to the warnings issued, the lava expelled by the eruption (which last until the end of January) destroyed the two main villages in the caldera (~1000 inhabitants) and covered vast areas of agricultural land, causing very large economic losses and an uncertain future of the local populations. The C4G team installed a network of seven GNSS receivers and nine seismometers, distributed by the entire island. The data collection started on 28th November 2014, and continued until the end of January 2015. The mission also included a new detailed gravimetric survey of the island, the acquisition of geological samples, and the analysis of the air quality during the eruption. We present here a detailed description of the monitoring efforts carried out during the eruption as well as initial results of the analysis of the
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Gochfeld, Michael
2014-01-01
We analyzed arsenic, cadmium, chromium, lead, manganese, mercury, and selenium in the feathers of common eiders (Somateria mollissima) and tufted puffins (Fratercula cirrhata) from Amchitka and Kiska islands (Aleutians). Between species, puffins had 10 times higher chromium (arithmetic mean = 1820 ppb), 7.5 times higher selenium (mean = 6600 ppb), and 3 times higher mercury (mean = 2540 ppb) than eiders. Eiders had significantly higher levels of manganese than puffins. Puffins are higher on the food chain than eiders, which is reflected in their generally higher levels of metals in their feathers. Interisland differences were generally small, and there were few significant differences as a function of the three nuclear test locations on Amchitka. The only sex-related difference was that female puffins had higher mercury than males (arithmetic mean of 3060 ppb vs. 2270 ppb). Mean levels of metals in the feathers of puffins and eiders from the Aleutians were low compared with comparable studies elsewhere, and the relatively low levels of metals do not indicate the potential for adverse behavioral or reproductive effects in the birds themselves, nor pose concern for other consumers, including subsistence hunters. PMID:18712499
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Post-eruptive Submarine Terrace Development of Capelinhos, Azores
NASA Astrophysics Data System (ADS)
Zhongwei Zhao, Will; Mitchell, Neil; Quartau, Rui; Tempera, Fernando; Bricheno, Lucy
2017-04-01
Erosion of the coasts of volcanic islands by waves creates shallow banks, but how erosion proceeds with time to create them and how it relates to wave climate is unclear. In this study, historical and recent marine geophysical data collected around the Capelinhos promontory (western Faial Island, Azores) offer an unusual opportunity to characterize how a submarine terrace developed after the eruption. The promontory was formed in 1957/58 during a Surtseyan eruption that terminated with extensive lava forming new rocky coastal cliffs. Historical measurements of coastline position are supplemented here with coastlines measured from 2004 and 2014 Google Earth images in order to characterize coastline retreat rate and distance for lava- and tephra-dominated cliffs. Swath mapping sonars were used to characterize the submarine geometry of the resulting terrace (terrace edge position, gradient and morphology). Limited photographs are available from a SCUBA dive and drop-down camera deployments to ground truth the submarine geomorphology. The results reveal that coastal retreat rates have decreased rapidly with the time after the eruption, possibly explained by the evolving resistance to erosion of cliff base materials. Surprisingly, coastline retreat rate decreases with terrace width in a simple inverse power law with terrace width. We suspect this is only a fortuitous result as wave attenuation over the terrace will not obviously produce the variation, but nevertheless it shows how rapidly the retreat rate declines. Understanding the relationship between terrace widening shelf and coastal cliff retreat rate may be more widely interesting if they can be used to understand how islands evolve over time into abrasional banks and guyots.
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Quantitative evaluation of variance in secondary dentition eruption among ethnic groups in Hawai'i.
Greer, Mark H K; Loo, Kevin J
2003-03-01
Though little scientific evidence existed to support the belief among dentists who treat Pacific Islander populations that many children of the region erupt secondary teeth earlier and at an eruption rate which exceeds Caucasian children. Based upon a data set created in Hawai'i during the 1998-1999 school year, of 26,097 public school children, the opportunity presented itself to examine for variance in eruption timing and sequence. Hawai'i is an ethnic diverse community, with a majority population comprised of Asians and Pacific Islanders. Children, 5 through 9 years of age, were examined for gender and ethnic variance. In the aggregate, at all ages, girls erupted teeth earlier than boys, however, while generally true among individual tooth types, that variance was not always statistically significant. By ethnic group, African Americans exhibited earlier eruption by contrast with Caucasians, however, Caucasian children caught up by nine years of age. Native Hawaiian, Samoan and Tongan children exhibited earlier and high rates of secondary dentition eruption than Caucasian or African American children. Children of various Asian cohorts did not exhibit significant variance by contrast with Caucasians. Based upon these findings, the authors recommend that dietary fluoride supplementation of Native Hawaiian, Samoan and Tongan children begin at birth rather than 6 months of age and that these children be targeted for pit & fissure sealants as early as five years of age.
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A Summary of the History and Achievements of the Alaska Volcano Observatory.
NASA Astrophysics Data System (ADS)
Smith, R. W.
2008-12-01
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.
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Rowland, S.K.; Lockwood, J.P.; Trusdell, F.A.; Moore, R.B.; Sako, M.K.; Koyanagi, R.Y.; Kojima, G.
2005-01-01
Anatahan island is 9.5 km east-west by 3.5 km north-south and truncated by an elongate caldera 5 km east-west by 2.5 km north-south. A steep-walled pit crater ???1 km across and ???200 m deep occupies the eastern part of the caldera. The island is the summit region of a mostly submarine stratovolcano. The oldest subaerial rocks (stage 1) are exposed low on the outer flanks and in the caldera walls. These include thick (???10 m) and thin (2-3 m) lava flows, well-indurated tuffs, and scoria units that make up the bulk of the island. Rock compositions range from basaltic andesite to dacite, and most are plagioclase-phyric. On the steep north and south flanks of the volcano, these rocks are cut by numerous east-west-oriented, few-hundred-m-long lineaments of undetermined origin. Indurated breccias unconformably overlie scarps cut into stage 1 units low on the south flank. Intermediate-age eruptive units (stage 2) include caldera-filling lava flows and pyroclastic deposits and, on the outer flanks, vents and valley-filling lava flows. The youngest pre-2003 volcanic unit on Anatahan (stage 3) is a hydromagmatic surge and fall deposit rich in accretionary lapilli. Prior to 2003, this unit was found over almost the entire island, and in many places original depositional surfaces and outcrops could be found in high-energy environments along the coast, indicating a young (but undetermined) age. During reconnaissance visits in 1990, 1992, 1994, and 2001, geothermal activity (fumaroles as well as pits with boiling, sediment-laden pools) was observed in the southern part of the pit crater. In March and April 1990, increased local seismicity, a large regional earthquake, and reported increased fumarolic activity in the pit crater prompted evacuation of Anatahan village, at the west end of the island. Our first field investigation took place in late April 1990 to assess the level of volcanic unrest, conduct reconnaissance geological observations, collect rock and geothermal water
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ASTER-SRTM Perspective of Mount Oyama Volcano, Miyake-Jima Island, Japan
2000-08-10
Mount Oyama is a 820-meter-high (2,700 feet) volcano on the island of Miyake-Jima, Japan. In late June 2000, a series of earthquakes alerted scientists to possible volcanic activity. On June 27, authorities evacuated 2,600 people, and on July 8 the volcano began erupting and erupted five times over that week. The dark gray blanket covering green vegetation in the image is the ash deposited by prevailing northeasterly winds between July 8 and 17. This island is about 180 kilometers (110 miles) south of Tokyo and is part of the Izu chain of volcanic islands that runs south from the main Japanese island of Honshu. Miyake-Jima is home to 3,800 people. The previous major eruptions of Mount Oyama occurred in 1983 and 1962, when lava flows destroyed hundreds of houses. An earlier eruption in 1940 killed 11 people. This image is a perspective view created by combining image data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) aboard NASA's Terra satellite with an elevation model from the Shuttle Radar Topography Mission (SRTM). Vertical relief is exaggerated, and the image includes cosmetic adjustments to clouds and image color to enhance clarity of terrain features. http://photojournal.jpl.nasa.gov/catalog/PIA02771
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NASA Astrophysics Data System (ADS)
Calabozo, Fernando M.; Strelin, Jorge A.; Orihashi, Yuji; Sumino, Hirochika; Keller, Randall A.
2015-05-01
We present here the results of detailed mapping, lithofacies analysis and stratigraphy of the Neogene James Ross Island Volcanic Group (Antarctic Peninsula) in the Cerro Santa Marta area (northwest of James Ross Island), in order to give constraints on the evolution of a glaciated volcanic island. Our field results included recognition and interpretation of seventeen volcanic and glacial lithofacies, together with their vertical and lateral arrangements, supported by four new unspiked K-Ar ages. This allowed us to conclude that the construction of the volcanic pile in this area took place during two main eruptive stages (Eruptive Stages 1 and 2), separated from the Cretaceous bedrock and from each other by two major glacial unconformities (U1 and U2). The U1 unconformity is related to Antarctic Peninsula Ice sheet expansion during the late Miocene (before 6.2 Ma) and deposition of glacial lithofacies in a glaciomarine setting. Following this glacial advance, Eruptive Stage 1 (6.2-4.6 Ma) volcanism started with subaerial extrusion of lava flows from an unrecognized vent north of the study area, with eruptions later fed from vent/s centered at Cerro Santa Marta volcano, where cinder cone deposits and a volcanic conduit/lava lake are preserved. These lava flows fed an extensive (> 7 km long) hyaloclastite delta system that was probably emplaced in a shallow marine environment. A second unconformity (U2) was related to expansion of a local ice cap, centered on James Ross Island, which truncated all the eruptive units of Eruptive Stage 1. Concomitant with glacier advance, renewed volcanic activity (Eruptive Stage 2) started after 4.6 Ma and volcanic products were fed again by Cerro Santa Marta vents. We infer that glaciovolcanic eruptions occurred under a moderately thin (~ 300 m) glacier, in good agreement with previous estimates of paleo-ice thickness for the James Ross Island area during the Pliocene.
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NASA Astrophysics Data System (ADS)
Asensio-Ramos, María; Alonso, Mar; Sharp, Emerson; Woods, Hannah; Barrancos, José; Pérez, Nemesio M.
2016-04-01
We report herein the latest results of a diffuse CO2 efflux survey at El Hierro volcanic system carried out during the summer period of 2015 to constrain the total CO2 output from the studied area a during post-eruptive period. El Hierro Island (278 km2) is the youngest and the SW-most of the Canary Islands. On July 16, 2011, a seismic-volcanic crisis started with the occurrence of more than 11,900 seismic events and significant deformation along the island. On October 10, 2011, the dominant character of seismicity changed dramatically from discrete earthquakes to continuous tremor, a clear indication that magma was rapidly approaching the surface immediately before the onset of the eruption, October 12. Eruption was declared over on 5 March, 2012. In order to monitor the volcanic activity of El Hierro Island, from 1998 to 2015 diffuse CO2 emission studies have been performed at El Hierro volcanic system in a yearly basis (˜600 observation sites) according to the accumulation chamber method. Spatial distribution maps were constructed following the sequential Gaussian simulation (sGs) procedure. To quantify the total CO2 emission from the studied area, 100 simulations for each survey have been performed. During the eruption period, soil CO2 efflux values range from non-detectable (˜0.5 g m-2 d-1) up to 457 g m-2 d-1, reaching in November 27, 2011, the maximum CO2 output estimated value of all time series, 2,398 t d-1, just before the episodes of maximum degassing observed as vigorous bubbling at the sea surface and an increment in the amplitude of the tremor signal. During the 2015 survey, soil CO2 efflux values ranged from non-detectable up to 41 g m-2 d-1. The spatial distribution of diffuse CO2 emission values seemed to be controlled by the main volcano structural features of the island. The total diffuse CO2 output released to atmosphere was estimated at 575 ± 24 t d-1, value slightly higher that the background CO2 emission estimated at 422 t d-1 (Melián et
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NASA Astrophysics Data System (ADS)
Suwarsono, Hidayat, Suprapto, Totok; Prasasti, Indah; Parwati, Rokhis Khomarudin, M.
2017-07-01
At the end of October to early November 2015, Rinjani Volcano that is located in Lombok Island was erupted and has catapulted the ash, pyroclastic and lava flow. The dispersion of this volcanic ash in the atmosphere has been disrupting flights and the three closest airports to be closed for a while. The existence of Rinjani Volcano geographically plays an important role in the survival of life on the island of Lombok, because large areas of land on the island are a part of the Rinjani Volcano landscape. Based on the experience of violent eruptions that have occurred in the 13th century ago, the monitoring of the volcanism activity of this volcano needs to be done intensively and continuously. This is something important to do an early detection efforts of the volcanic eruption. These efforts need to be done as a preparedness effort in order to minimize adverse impacts that may occur as a result of this eruption. This research tries to detect the volcanic eruption precursor based on changes in temperature conditions of the crater and the surrounding area. We use the medium resolution satellite data, Thermal Infra Red Scanner (TIRS), on board Landsat-8, to monitor the brightness temperature as a representative of surface temperature of the volcanic region. The results showed that the brightness temperature derived from Landsat-8 TIRS is very usefull to predict the strombolian eruption which will occur in the near future. The use of multitemporal image data is important to understand the dynamics of volcanism activity over time.
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Proceedings of the North Aleutian Basin information status and research planning meeting.
DOE Office of Scientific and Technical Information (OSTI.GOV)
LaGory, K. E.; Krummel, J. R.; Hayse, J. W.
2007-10-26
The North Aleutian Basin Planning Area of the Minerals Management Service (MMS) is a large geographic area with significant ecological and natural resources. The Basin includes most of the southeastern part of the Bering Sea continental shelf including all of Bristol Bay. The area supports important habitat for a wide variety of species and globally significant habitat for birds and marine mammals including federally listed species. Villages and communities of the Alaska Peninsula and other areas bordering or near the Basin rely on its natural resources (especially commercial and subsistence fishing) for much of their sustenance and livelihood. The offshoremore » area of the North Aleutian Basin is considered to have important hydrocarbon reserves, especially natural gas. In 2006, the MMS released a draft proposed program, Outer Continental Shelf Oil and Gas Leasing Program, 2007-2012 and an accompanying draft programmatic environmental impact statement (EIS). The draft proposed program identified two lease sales proposed in the North Aleutian Basin in 2010 and 2012, subject to restrictions. The area proposed for leasing in the Basin was restricted to the Sale 92 Area in the southwestern portion. Additional EISs will be needed to evaluate the potential effects of specific lease actions, exploration activities, and development and production plans in the Basin. A full range of updated multidisciplinary scientific information will be needed to address oceanography, fate and effects of oil spills, marine ecosystems, fish, fisheries, birds, marine mammals, socioeconomics, and subsistence in the Basin. Scientific staff at Argonne National Laboratory (Argonne) were contracted to assist the MMS Alaska Outer Continental Shelf (OCS) Region in identifying and prioritizing information needs related to the North Aleutian Basin and potential future oil and gas leasing and development activities. The overall approach focused on three related but separate tasks: (1
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NASA Astrophysics Data System (ADS)
D'Oriano, Claudia; Landi, Patrizia; Pimentel, Adriano; Zanon, Vittorio
2017-11-01
The Lajes Ignimbrite on Terceira Island (Azores) records the last major pyroclastic density current-forming eruption of Pico Alto Volcano that occurred ca. 21 kyrs ago. This comenditic trachyte ignimbrite contains up to 30 vol% of crystals, mostly anorthoclase. Geochemical investigation of the products collected throughout two key outcrops reveals that major element compositions are poorly variable, whereas trace elements show significant variability, pointing to the presence of a zoned magma reservoir. Thermometry and oxygen fugacity estimations yielded pre-eruptive temperatures of 850-900 °C and ΔNNO from - 2.4 to - 1.8. Melt-alkali-feldspar hygrometer indicates magmatic H2O contents ranging from 5.8 wt% in the upper part of the reservoir to 3.6 wt% at the bottom, indicating that the magma reservoir (confined at 4 km depth) was mainly water-undersaturated before the eruption, except for the topmost portion. Two types of anorthoclase crystals were identified. Type 1 crystals show reverse to oscillatory zoning with An contents of 0.4-2.1 mol% and Ba of 200-2000 ppm. They formed in the middle/upper portion of the reservoir, where fractional crystallization processes dominated. Type 2 crystals, mainly present in the less evolved products, are characterized by patchy-zoned cores with large dissolution pockets surrounded by thick oscillatory-zoned rims and show a wide compositional range (An of 0.5-4.7 mol% and Ba of 142-4824 ppm). Their zoning patterns, together with whole-rock and glass compositions of the juvenile clasts, are consistent with the involvement of an anorthoclase-bearing cumulate from the bottom of the reservoir that underwent partial melting. Crystal dissolution was likely induced by the presence of a heat source at depth, without any mass transfer to the eruptible magma, as suggested by the lack of petrographic and chemical evidences of mixing between the resident comenditic trachyte and a mafic/intermediate magma. Thermal instability generated
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Current Sheet Properties and Dynamics During Sympathetic Breakout Eruptions
NASA Astrophysics Data System (ADS)
Lynch, B. J.; Edmondson, J. K.
2013-12-01
We present the continued analysis of the high-resolution 2.5D MHD simulations of sympathetic magnetic breakout eruptions from a pseudostreamer source region. We examine the generation of X- and O-type null points during the current sheet tearing and track the magnetic island formation and evolution during periods of reconnection. The magnetic breakout eruption scenario forms an overlying 'breakout' current sheet that evolves slowly and removes restraining flux from above the sheared field core that will eventually become the center of the erupting flux rope-like structure. The runaway expansion from the expansion-breakout reconnection positive feedback enables the formation of the second, vertical/radial current sheet underneath the rising sheared field core as in the standard CHSKP eruptive flare scenario. We will examine the flux transfer rates through the breakout and flare current sheets and compare the properties of the field and plasma inflows into the current sheets and the reconnection jet outflows into the flare loops and flux rope ejecta.
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Weather as the Decisive Factor of the Aleutian Campaign, June 1942 - August 1943
1993-01-01
examine the effect of weather on the living and fighting conditions during the campaign. The Delimitations The study will not examine prewar...airstrip the engineers drained and filled a flooded tidal basin . 52 An innovation available to the Americans and not Japan or Germany was "Marston mat...p, 47. 30 See Aleutians Cawnpaign, p. 87; Army Air Force in World War II, Vol 4, p. 383. ൯ See Aleutians Campaign, pp. 88-89; Argy Air Force in
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Poly IC therapy in aleutian disease of mink.
Russell, A S; Percy, J S; Cho, H J
1975-01-01
Twenty-four virgin female aleutian mink were infected with aleutian disease agent and after 24 hours, 12 of these were treated with a course of polyinosinic acid-polycytidilic acid (Poly IC) injections. After six weeks the gammaglobulin level was significantly lower in the treated group but at 12 weeks this difference was no longer present. Four of the treated mink had normal target organ histology when killed at 20 weeks. The untreated group all showed moderate to marked changes but this difference was not statistically significant. There was a marked increase in the reactive lymphocyte blastogenesis index during the first weeks of infection and the phytohaemagglutinin response was seen to fall progressively. The antiglobulin reaction usually became positive after infection but neither antinuclear nor antierythrocyte antibodies were found. Precipitating antibodies to several polynucleotides were frequently present and were unrelated to infection or to Poly IC treatment. Images Fig. 1. Fig. 2A Fig. 2B. PMID:1095164
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NASA Astrophysics Data System (ADS)
Faria, B.; Fonseca, J. F. B. D.
2013-09-01
We describe a new geophysical network deployed in the Cape Verde archipelago for the assessment and monitoring of volcanic hazards, and the first results from the network. Across the archipelago, the ages of volcanic activity range from ca. 20 Ma to present. In general, older islands are in the east and younger ones are in the west, but there is no clear age progression and widely-separated islands have erupted contemporaneously on geological time scales. The overall magmatic rate is low, and there are indications that eruptive activity is episodic, with intervals between episodes of intense activity ranging from 1 to 4 Ma. Although only Fogo island has experienced eruptions (mainly effusive) in the historic period (last 550 yr), Brava and Santo Antão have experienced numerous geologically recent eruptions including violent explosive eruptions, and show felt seismic activity and geothermal activity. Evidence for recent volcanism in the other islands is more limited and the emphasis has therefore been on monitoring of the three critical islands of Fogo, Brava and Santo Antão, where volcanic hazard levels are highest. Geophysical monitoring of all three islands is now in operation. The first results show that in Fogo the seismic activity is dominated by hydrothermal events and volcano-tectonic events that may be related to settling of the edifice after the 1995 eruption; in Brava by volcano-tectonic events (mostly offshore), and in Santo Antão by volcano-tectonic events, medium frequency events and harmonic tremor. Both in Brava and in Santo Antão, the recorded seismicity indicates that relatively shallow magmatic systems are present and causing deformation of the edifices that may include episodes of dike intrusion.
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Towards reconstruction of the lost Late Bronze Age intra-caldera island of Santorini, Greece.
Karátson, Dávid; Gertisser, Ralf; Telbisz, Tamás; Vereb, Viktor; Quidelleur, Xavier; Druitt, Timothy; Nomikou, Paraskevi; Kósik, Szabolcs
2018-05-04
During the Late Bronze Age, the island of Santorini had a semi-closed caldera harbour inherited from the 22 ka Cape Riva Plinian eruption, and a central island referred to as 'Pre-Kameni' after the present-day Kameni Islands. Here, the size and age of the intracaldera island prior to the Late Bronze Age (Minoan) eruption are constrained using a photo-statistical method, complemented by granulometry and high-precision K-Ar dating. Furthermore, the topography of Late Bronze Age Santorini is reconstructed by creating a new digital elevation model (DEM). Pre-Kameni and other parts of Santorini were destroyed during the 3.6 ka Minoan eruption, and their fragments were incorporated as lithic clasts in the Minoan pyroclastic deposits. Photo-statistical analysis and granulometry of these lithics, differentiated by lithology, constrain the volume of Pre-Kameni to 2.2-2.5 km 3 . Applying the Cassignol-Gillot K-Ar dating technique to the most characteristic black glassy andesite lithics, we propose that the island started to grow at 20.2 ± 1.0 ka soon after the Cape Riva eruption. This implies a minimum long-term lava extrusion rate of ~0.13-0.14 km 3 /ky during the growth of Pre-Kameni.
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The 1902-3 eruptions of the Soufrière, St Vincent: Impacts, relief and response
NASA Astrophysics Data System (ADS)
Pyle, David M.; Barclay, Jenni; Armijos, Maria Teresa
2018-05-01
Retrospective analysis of the contemporary colonial and scientific records of a major explosive eruption of the Soufrière of St Vincent from 1902 to 1903 reveals how this significant and prolonged event presented challenges to the authorities charged with managing the crisis and its aftermath. In a small-island setting vulnerable to multiple hazards, the spatial footprint of the volcanic hazard and the nature and intensity of the hazard effects were rather different to those of other recurrent hazards such as hurricanes. The eruption affected the same parts of the island that had been impacted by prior explosive eruptions in 1718 and 1812, and hurricanes in 1831 and 1898, with consequences that disproportionately affected those working in and around the large sugar estates. The official response to the eruption, both in terms of short-term relief and remediation, was significantly accelerated by the existence of mature plans for land-reform following the collapse of the sugar market, and ongoing plans for rebuilding in the aftermath of the destructive hurricane of 1898. The picture that this analysis helps to illuminate provides insights both into the nature of the particular eruptive episode, and the human and social response to that episode. This not only informs discussion and planning for future explosive eruptions on St Vincent, but provides important empirical evidence for building effective responses in similar multihazard contexts.
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Volcanic hazard assessment for the Canary Islands (Spain) using extreme value theory
NASA Astrophysics Data System (ADS)
Sobradelo, R.; Martí, J.; Mendoza-Rosas, A. T.; Gómez, G.
2011-10-01
The Canary Islands are an active volcanic region densely populated and visited by several millions of tourists every year. Nearly twenty eruptions have been reported through written chronicles in the last 600 yr, suggesting that the probability of a new eruption in the near future is far from zero. This shows the importance of assessing and monitoring the volcanic hazard of the region in order to reduce and manage its potential volcanic risk, and ultimately contribute to the design of appropriate preparedness plans. Hence, the probabilistic analysis of the volcanic eruption time series for the Canary Islands is an essential step for the assessment of volcanic hazard and risk in the area. Such a series describes complex processes involving different types of eruptions over different time scales. Here we propose a statistical method for calculating the probabilities of future eruptions which is most appropriate given the nature of the documented historical eruptive data. We first characterize the eruptions by their magnitudes, and then carry out a preliminary analysis of the data to establish the requirements for the statistical method. Past studies in eruptive time series used conventional statistics and treated the series as an homogeneous process. In this paper, we will use a method that accounts for the time-dependence of the series and includes rare or extreme events, in the form of few data of large eruptions, since these data require special methods of analysis. Hence, we will use a statistical method from extreme value theory. In particular, we will apply a non-homogeneous Poisson process to the historical eruptive data of the Canary Islands to estimate the probability of having at least one volcanic event of a magnitude greater than one in the upcoming years. This is done in three steps: First, we analyze the historical eruptive series to assess independence and homogeneity of the process. Second, we perform a Weibull analysis of the distribution of repose
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2017-01-06
Lanzarote is the easternmost of the Canary Islands, 125 km off the coast of Africa, and is the fourth largest of the archipelago, with an area of 846 square kilometers. Like all of the Canary Islands, its volcanic origin dates to about 15 million years ago. The largest historic eruption occurred in the 1730s. The island was first recorded by Pliny the Elder, though it may have been originally settled by the Phoenicians (Wikipedia). The image was acquired 12 March 2015, covers an area of 50.5 by 55.1 km, and is located near 29 degrees north, 13.6 degrees west. http://photojournal.jpl.nasa.gov/catalog/PIA21284
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Tephro- and chemo-stratigraphy of the Vulcanello Peninsula (Vulcano, Aeolian Islands)
NASA Astrophysics Data System (ADS)
Rosi, M.; Fusillo, R.; di Traglia, F.; Pistolesi, M.; Todman, A.; Menzies, M. A.
2009-12-01
New stratigraphic studies of the Vulcanello Peninsula have been used to better define the small-scale evolution of this young (1000 AD and 325±100 BP) volcanic center and to re-investigate the last 1000 years of volcanic history for the Island of Vulcano (Aeolian Islands, Southern Italy). Vulcanello Peninsula is the northern-most part of the Island of Vulcano. It comprises a shoshonitic lava platform and a volcanic edifice made up of three overlying cones, which are shoshonitic to trachytic in composition. Volcanic activity in this area was coeval with the recent eruptions of the La Fossa Cone, the present-day active center of the island. Our goal is to constrain the recent volcanic development of this mafic volcano and to focus on the historic eruptive activity of the two other recent or active centres in the southern Aeolian Islands, Mt. Pilato (Island of Lipari) and La Fossa Cone. In order to do so, we reconstructed the stratigraphical setting of the proximal deposits of the three Vulcanello cones, through the investigation of 25 outcrops. We analyzed the stratigraphy of the tephra blankets deposited on the lava platform, studying 10 trenches. Our intention is to integrate morphological, textural and chemical data in order to correlate these deposits with the Vulcanello, La Fossa Cone or Mt Pilato. LA-MC-ICPMS (RHUL) analysis of juvenile clasts is underway in order to investigate the evolution of the Vulcanello juvenile clasts. In addition 14C dating is planned on selected organic matter from the volcanostratigraphic sections. Our preliminary data for the Vulcanello proximal deposits suggest that each of the three cones experienced several eruptions, with a wide spectrum of eruptive styles and a diversity of chemistry. The oldest cone (Vulcanello I) is characterised by four different eruptions separated by minor unconformities or reworking material indicative of little or not time breaks in the eruptive cycle. The eruptions shift from Violent Strombolian to
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Evaluation of Kilauea Eruptions By Using Stable Isotope Analysis
NASA Astrophysics Data System (ADS)
Rahimi, K. E.; Bursik, M. I.
2016-12-01
Kilauea, on the island of Hawaii, is a large volcanic edifice with numerous named vents scattered across its surface. Halema`uma`u crater sits with Kilauea caldera, above the magma reservoir, which is the main source of lava feeding most vents on Kilauea volcano. Halema`uma`u crater produces basaltic explosive activity ranging from weak emission to sub-Plinian. Changes in the eruption style are thought to be due to the interplay between external water and magma (phreatomagmatic/ phreatic), or to segregation of gas from magma (magmatic) at shallow depths. Since there are three different eruption mechanisms (phreatomagmatic, phreatic, and magmatic), each eruption has its own isotope ratios. The aim of this study is to evaluate the eruption mechanism by using stable isotope analysis. Studying isotope ratios of D/H and δ18O within fluid inclusion and volcanic glass will provide an evidence of what driven the eruption. The results would be determined the source of water that drove an eruption by correlating the values with water sources (groundwater, rainwater, and magmatic water) since each water source has a diagnostic value of D/H and δ18O. These results will provide the roles of volatiles in eruptions. The broader application of this research is that these methods could help volcanologists forecasting and predicting the current volcanic activity by mentoring change in volatiles concentration within deposits.
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Eruptive history of Earth's largest Quaternary caldera (Toba, Indonesia) clarified
DOE Office of Scientific and Technical Information (OSTI.GOV)
Chesner, C.A.; Rose, W.I.; Drake, R.
1991-03-01
Single-grain laser-fusion {sup 40}Ar/{sup 39}Ar analyses of individual sanidine phenocrysts from the two youngest Toba (Indonesia) tuffs yield mean ages of 73{plus minus}4 and 501{plus minus}5 ka. In addition, glass shards from Toba ash deposited in Malaysia were dated at 68{plus minus}7 ka by the isothermal plateau fission-track technique. These new determinations, in conjunction with previous ages for the two oldest tuffs at Toba, establish the chronology of four eruptive events from the Toba caldera complex over the past 1.2 m.y. Ash-flow tuffs were erupted from the complex every 0.34 to 0.43 m.y., culminating with the enormous (2500-3000 km{sup 3})more » Youngest Toba tuff eruption, caldera formation, and subsequent resurgence of Samosir Island. Timing of this last eruption at Toba is coincident with the early Wisconsin glacial advance. The high-precision {sup 40}Ar/{sup 39}Ar age eruption of such magnitude may provide an important marker horizon useful as a baseline for research and modeling of the worldwide climatic impact of exceptionally large explosive eruptions.« less
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NASA Astrophysics Data System (ADS)
Hernández, Pedro A.; Norrie, Janice; Withoos, Yannick; García-Merino, Marta; Melián, Gladys; Padrón, Eleazar; Barrancos, José; Padilla, Germán; Rodríguez, Fátima; Pérez, Nemesio M.
2017-04-01
Even during repose periods, volcanoes release large amounts of gases from both visible (fumaroles, solfataras, plumes) and non-visible emanations (diffuse degassing). In the last 20 years, there has been considerable interest in the study of diffuse degassing as a powerful tool in volcano monitoring programs, particularly in those volcanic areas where there are no visible volcanic-hydrothermal gas emissions. Historically, soil gas and diffuse degassing surveys in volcanic environments have focused mainly on CO2 because it is, after water vapor, the most abundant gas dissolved in magma. As CO2 travels upward by advective-diffusive transport mechanisms and manifests itself at the surface, changes in its flux pattern over time provide important information for monitoring volcanic and seismic activity. Since 1998, diffuse CO2 emission has been monitored at El Hierro Island, the smallest and south westernmost island of the Canarian archipelago with an area of 278 km2. As no visible emanations occur at the surface environment of El Hierro, diffuse degassing studies have become the most useful geochemical tool to monitor the volcanic activity in this volcanic island. The island experienced a volcano-seismic unrest that began in July 2011, characterized by the location of a large number of relatively small earthquakes (M<2.5) beneath El Hierro at depths between 8 and 15 km. On October 12, 2011, a submarine eruption was confirmed during the afternoon of October 12, 2011 by visual observations off the coast of El Hierro, about 2 km south of the small village of La Restinga in the southernmost part of the island. During the pre-eruptive and eruptive periods, the time series of the diffuse CO2 emission released by the whole island experienced two significant increases. The first started almost 2 weeks before the onset of the submarine eruption, reflecting a clear geochemical anomaly in CO2 emission, most likely due to increasing release of deep seated magmatic gases to the
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Geist, Eric L.; Vallier, Tracy L.; Scholl, David W.
1994-01-01
consequence of either infra-oceanic transport or coastwise translation is that an open corridor between the western terminus of the Aleutian Arc and Kamchatka must have existed until middle to late Eocene time. Spreading within the Komandorsky Basin, subduction of sea-mounts, and collision of the Aleutian Arc with Kamchatka are proposed to have instigated the second Miocene phase of deformation, which uplifted and reexposed the island-arc terrane.
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Santana-Casiano, J. M.; González-Dávila, M.; Fraile-Nuez, E.; de Armas, D.; González, A. G.; Domínguez-Yanes, J. F.; Escánez, J.
2013-01-01
The shallow submarine eruption which took place in October 10th 2011, 1.8 km south of the island of El Hierro (Canary Islands) allowed the study of the abrupt changes in the physical-chemical properties of seawater caused by volcanic discharges. In order to monitor the evolution of these changes, seven oceanographic surveys were carried out over six months (November 2011-April 2012) from the beginning of the eruptive stage to the post-eruptive phase. Here, we present dramatic changes in the water column chemistry including large decreases in pH, striking effects on the carbonate system, decreases in the oxygen concentrations and enrichment of Fe(II) and nutrients. Our findings highlight that the same volcano which was responsible for the creation of a highly corrosive environment, affecting marine biota, has also provided the nutrients required for the rapid recuperation of the marine ecosystem. PMID:23355953
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NASA Astrophysics Data System (ADS)
Jordan, Nina J.; Rotolo, Silvio G.; Williams, Rebecca; Speranza, Fabio; McIntosh, William C.; Branney, Michael J.; Scaillet, Stéphane
2018-01-01
A new, pre-Green Tuff (46 ka) volcanic stratigraphy is presented for the peralkaline Pantelleria Volcano, Italy. New 40Ar/39Ar and paleomagnetic data are combined with detailed field studies to develop a comprehensive stratigraphic reconstruction of the island. We find that the pre-46 ka succession is characterised by eight silica-rich peralkaline (trachyte to pantellerite) ignimbrites, many of which blanketed the entire island. The ignimbrites are typically welded to rheomorphic, and are commonly associated with lithic breccias and/or pumice deposits. They record sustained radial pyroclastic density currents fed by low pyroclastic fountains. The onset of ignimbrite emplacement is typically preceded (more rarely followed) by pumice fallout with limited dispersal, and some eruptions lack any associated pumice fall deposit, suggesting the absence of tall eruption columns. Particular attention is given to the correlation of well-developed lithic breccias in the ignimbrites, interpreted as probable tracers of caldera collapses. They record as many as five caldera collapse events, in contrast to the two events reported to date. Inter-ignimbrite periods are characterised by explosive and effusive eruptions with limited dispersal, such as small pumice cones, as well as pedogenesis. These periods have similar characteristics as the current post-Green Tuff activity on the island, and, while not imminent, it is reasonable to postulate the occurrence of another ignimbrite-forming eruption sometime in the future.
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Nye, C.J.
1987-12-01
The Spurr Volcanic Complex (SVC) is a calcalkaline, medium-K, sequence of andesites erupted over the last quarter of a million years by the easternmost currently active volcanic center in the Aleutian Arc. The ancestral Mt. Spurr was built mostly of andesites of uniform composition (58 to 60% SiO/sub 2/), although andesite production was episodically interrupted by the introduction of new batches of more mafic magma. Near the end of the Pleistocene the ancestral Mt. Spurr underwent Bezyianny-type avalanche caldera formation, resulting in the production of a volcanic debris avalanche with overlying ashflows. Immediately afterward, a large dome (the present Mt.more » Spurr) was emplaced in the caldera. Both the ashflows and dome are made of acid andesite more silicic than any analyzed lavas from the ancestral Mt. Spurr (60 to 63% SiO/sub 2/), yet contain olivine and amphibole xenocrysts derived from more mafic magma. The mafic magma (53 to 57% SiO/sub 2/) erupted during and after dome emplacement, forming proto-Crater Peak and Crater Peak. Hybrid pyroclastic flows and lavas were also produced. Proto-Crater Peak underwent glacial dissection prior to the formation of Crater Peak in approximately the same location. Appendices II through VIII contain a summary of mineral compositions; Appendix I contains geochemical data. Appendix IX by R.J. Motyka and C.J. Nye describes the chemistry of geothermal fluids. 78 refs., 16 figs., 3 tabs.« less
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NASA Astrophysics Data System (ADS)
Lindquist, Kent Gordon
We constructed a near-real-time system, called Iceworm, to automate seismic data collection, processing, storage, and distribution at the Alaska Earthquake Information Center (AEIC). Phase-picking, phase association, and interprocess communication components come from Earthworm (U.S. Geological Survey). A new generic, internal format for digital data supports unified handling of data from diverse sources. A new infrastructure for applying processing algorithms to near-real-time data streams supports automated information extraction from seismic wavefields. Integration of Datascope (U. of Colorado) provides relational database management of all automated measurements, parametric information for located hypocenters, and waveform data from Iceworm. Data from 1997 yield 329 earthquakes located by both Iceworm and the AEIC. Of these, 203 have location residuals under 22 km, sufficient for hazard response. Regionalized inversions for local magnitude in Alaska yield Msb{L} calibration curves (logAsb0) that differ from the Californian Richter magnitude. The new curve is 0.2\\ Msb{L} units more attenuative than the Californian curve at 400 km for earthquakes north of the Denali fault. South of the fault, and for a region north of Cook Inlet, the difference is 0.4\\ Msb{L}. A curve for deep events differs by 0.6\\ Msb{L} at 650 km. We expand geographic coverage of Alaskan regional seismic monitoring to the Aleutians, the Bering Sea, and the entire Arctic by initiating the processing of four short-period, Alaskan seismic arrays. To show the array stations' sensitivity, we detect and locate two microearthquakes that were missed by the AEIC. An empirical study of the location sensitivity of the arrays predicts improvements over the Alaskan regional network that are shown as map-view contour plots. We verify these predictions by detecting an Msb{L} 3.2 event near Unimak Island with one array. The detection and location of four representative earthquakes illustrates the expansion
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Population genetic structure and conservation of marbled murrelets (Brachyramphus marmoratus)
Friesen, Vicki L.; Birt, T.P.; Piatt, John F.; Golightly, R.T.; Newman, S.H.; Hebert, P.N.; Congdon, B.C.; Gissing, G.
2005-01-01
Marbled murrelets (Brachyramphus marmoratus) are coastal seabirds that nest from California to the Aleutian Islands. They are declining and considered threatened in several regions. We compared variation in the mitochondrial control region, four nuclear introns and three microsatellite loci among 194 murrelets from throughout their range except Washington and Oregon. Significant population genetic structure was found: nine private control region haplotypes and three private intron alleles occurred at high frequency in the Aleutians and California; global estimates of FST or ??ST and most pairwise estimates involving the Aleutians and/or California were significant; and marked isolation-by-distance was found. Given the available samples, murrelets appear to comprise five genetic management units: (1) western Aleutian Islands, (2) central Aleutian Islands, (3) mainland Alaska and British Columbia, (4) northern California, and (5) central California.
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1988-10-03
STS026-43-082 (29 Sept. - 3 Oct. 1988) --- This 70mm northerly oriented frame over the Pacific Ocean features the Hawaiian Islands chain. The islands perturb the prevailing northeasterly winds producing extensive cloud wakes in the lee of the islands. Photo experts feel that atmospheric haze in the Hawaii wake is probably a result of the continuing eruptions of Kilauea volcano on the southeast coast. From the lower right corner in a diagonal directed upward to the north are the islands of Nihau, Kauai, Oahu, Molokai, Lanai, Maui, Kahoolawe, and Hawaii. This photo was shown during the post-flight press conference on October 11, 1988 by the STS-26 astronauts, who at one time during the flight wore Hawaiian attire to pay tribute to the working staff of the Hawaii tracking station.
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Burger, Joanna
2007-11-01
World War II and the Cold War have left the Unites States, and other Nations, with massive cleanup and remediation tasks for radioactive and other legacy hazardous wastes. While some sites can be cleaned up to acceptable residential risk levels, others will continue to hold hazardous wastes, which must be contained and monitored to protect human health and the environment. While media (soil, sediment, groundwater) monitoring is the usual norm at many radiological waste sites, for some situations (both biological and societal), biomonitoring may provide the necessary information to assure greater peace of mind for local and regional residents, and to protect ecologically valuable buffer lands or waters. In most cases, indicators are selected using scientific expertise and a literature review, but not all selected indicators will seem relevant to stakeholders. In this paper, I provide a model for the inclusion of stakeholders in the development of bioindicators for assessing radionuclide levels of biota in the marine environment around Amchitka Island, in the Aleutian Chain of Alaska. Amchitka was the site of three underground nuclear tests from 1965 to 1971. The process was stakeholder-initiated, stakeholder-driven, and included stakeholders during each phase. Phases included conceptualization, initial selection of biota and radionuclides, refinement of biota and radionuclide target lists, collection of biota, selection of biota and radionuclides for analysis, and selection of biota, tissues, and radionuclides for bioindicators. The process produced site-specific information on biota availability and on radionuclide levels that led to selection of site-appropriate bioindicators. I suggest that the lengthy, iterative, stakeholder-driven process described in this paper results in selection of bioindicators that are accepted by biologists, public health personnel, public-policy makers, resource agencies, regulatory agencies, subsistence hunters/fishers, and a wide
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Lu, Zhong; Wicks, Charles W.; Dzurisin, Daniel; Thatcher, Wayne R.; Freymueller, Jeffrey T.; McNutt, Stephen R.; Mann, Dorte
2000-01-01
Westdahl is a broad shield volcano at the western end of Unimak Island in the Aleutian chain. It has apparently been dormant since a 1991-92 eruption and seismicity levels have been low. However, satellite radar imaging shows that in the years following 1992 the upper flanks of Westdahl have risen several centimeters, probably from the influx of new magma deep below its summit. Until now, deep magma reservoirs have been difficult to detect beneath most volcanoes. But using space geodetic technologies, specifically interferometric synthetic aperture radar (InSAR), we have discovered a deep magmatic source beneath Westdahl.
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NASA Astrophysics Data System (ADS)
Padilla, G.; Hernández, P. A.; Padrón, E.; Barrancos, J.; Melián, G.; Dionis, S.; Rodríguez, F.; Nolasco, D.; Calvo, D.; Hernández, I.; Pereza, M. D.; Pérez, N. M.
2012-04-01
El Hierro (278 km2) is the southwesternmost island of the Canarian archipelago. From June 19, 2011 to January 2012, more than 11,950 seismic events have been detected by the seismic network of IGN. On 10 October 2011 the earthquake swarm changed its behaviour and produced a harmonic tremor due to magma movement, indicating that a submarine eruption located at 2 km south of La Restinga had started which is still in progress. Since 2003, the ITER Environmental Research Division now integrated in the Instituto Volcanológico de Canarias, INVOLCAN, has regularly performed soil gas surveys at El Hierro as a geochemical tool for volcanic surveillance. Among the investigated gases, soil gas radon (222Rn) and thoron (220Rn) have played a special attention. Both gases are characterized to ascend towards the surface mainly through cracks or faults via diffusion or advection, mechanisms dependent of both soil porosity and permeability, which in turn vary as a function of the stress/strain changes at depth. Years before the starts of the volcanic-seismic crisis on July 17, 2011, a volcanic multidisciplinary surveillance program was implemented at El Hierro including discrete and continuous measurements of 222Rn and 220Rn. Two soil gas 222Rn surveys had been carried out at El Hierro in 2003 and 2011, and four continuous geochemical monitoring stations for 222Rn and 220Rn measurements had been installed (HIE02, HIE03, HIE04 and HIE08). Soil gas 222Rn surveys were carried out at the surface environment of El Hierro after selecting 600 sampling observation sites (about 40 cm depth). Geochemical stations measure 222Rn and 220Rn activities by pumping the gas from a PVC pipe inserted 1m in the ground and thermally isolated. The results of the 2003 and 2011 soil gas 222Rn surveys show clearly a relatively higher observed 222Rn activities in the surface environment on 2011 than those observed on 2003 when no anomalous seismicity were taking place beneath El Hierro. The observed
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Effects of a submarine eruption on the performance of two brown seaweeds
NASA Astrophysics Data System (ADS)
Betancor, Séfora; Tuya, Fernando; Gil-Díaz, Teba; Figueroa, Félix L.; Haroun, Ricardo
2014-03-01
World oceans are becoming more acidic as a consequence of CO2 anthropogenic emissions, with multiple physiological and ecological implications. So far, our understanding is mainly limited to some species through in vitro experimentation. In this study, we took advantage of a recent submarine eruption (from October 2011 to March 2012) at ~ 1 nautical mile offshore El Hierro Island (Canary Islands, central east Atlantic) to determine whether altered physical-chemical conditions, mainly sudden natural ocean acidification, affected the morphology, photosynthesis (in situ Chl-a fluorescence) and physiological performance (photo-protective mechanisms and oxidative stress) of the conspicuous brown seaweeds Padina pavonica-a species with carbonate deposition - and Lobophora variegata-a species without carbonate on thallus surfaces - , both with similar morphology. Seaweeds were sampled twice: November 2011 (eruptive phase with a pH drop of ca. 1.22 units relative to standard conditions) and March 2012 (post-eruptive phase with a pH of ca. 8.23), on two intertidal locations adjacent to the eruption and at a control location. P. pavonica showed decalcification and loss of photo-protective compounds and antioxidant activity at locations affected by the eruption, behaving as a sun-adapted species during lowered pH conditions. At the same time, L. variegata suffered a decrease in photo-protective compounds and antioxidant activity during the volcanic event, but its photosynthetic performance remained unaltered. These results reinforce the idea that calcareous seaweeds, as a whole, are more sensitive than non-calcareous seaweeds to alter their performance under scenarios of reduced pH.
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Dove, C.J.; Peurach, S.C.; Frohlich, Bruno; Harper, Albert B.; Gilberg, Rolf
2002-01-01
Human mummified remains of 34 different infant and adult individuals from Kagamil Island, Alaska, are accessioned in the Department of Anthropology, National Museum of Natural History, Smithsonian Institution. Kagamil Island is one of the small islands in the Island of Four Mountains group of the Aleutian Islands, Alaska and is well known for the mummy caves located on the southwest coast of the island. The Kagamil mummy holdings at the Smithsonian represent one of the largest, best documented and preserved collections of this type. Although these specimens are stored in ideal conditions, many small feather and hair fragments have become loose or disassociated from the actual mummies over the years. This preliminary investigation of fragmentary fiber material retrieved from these artifacts is the first attempt to identify bird and mammal species associated with the mummified remains of the Kagamil Island, Alaska collection and is part of the ongoing research connected with these artifacts.
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NASA Astrophysics Data System (ADS)
Morgan, K.; Ort, M. H.; Di Muro, A.; Parnell, R. A.; Huff, W. D.
2017-12-01
Piton de la Fournaise (PdF) is an active basaltic volcano on La Réunion island. The Bellecombe Tephra was deposited from at least three unusually explosive eruptions between 3000-5000 ka. The Bellecombe eruptions were interpreted recently to have been due to rapid depressurization of the hydrothermal system when a deep fracture opened after lateral, seaward-directed sliding of the eastern flank, late in a large effusive eruption. This project tests this hypothesis by physically, mineralogically, and chemically characterizing the Bellecombe Tephra to look for evidence of the involvement of the PdF hydrothermal system in the eruptions and understand where the eruptions initiated. The Bellecombe tephra consists of three units separated by incipient soils. Both the Upper and Lower Bellecombe deposits are mostly medium to very fine ash. Lower Bellecombe deposits, from the first two eruptions, are mostly beds of glassy ash containing minor lithic grains and olivine crystals. Hydrothermal minerals, mostly smectite, are present in a few Lower Bellecombe beds. Since these minerals are only present in some beds, the smectite formed before deposition rather than as a product of surficial alteration. The Upper Bellecombe deposits record a third eruption and vary between clast-supported crystal- and lithic-rich lapilli beds and ash beds with abundant ash pellets. The crystals are mostly olivine, with lesser pyroxene and plagioclase and sparse hydrothermal quartz. Gabbro and oceanite clasts are abundant and trachytic pumice rare in these deposits. Hydrothermal minerals are common in most Upper Bellecombe beds. The presence of smectite in some of the Lower Bellecombe beds suggests these deposits came from a system below 200 ºC. Clays in the Upper Bellecombe beds - smectite and mixed layer R0 illite/smectite - imply a system at 40-140 ºC. The hydrothermal system was involved, but might not have been the primary impetus for these eruptions, since hydrothermal minerals are not
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Tao-Rusyr Caldera, Onekotan Island, Kuril Islands
2017-12-08
More than 9,000 years ago, a catastrophic volcanic eruption created a huge caldera on the southern end of Onekotan Island, one of the Kuril Islands, located off the southern tip of Russia’s Kamchatka Peninsula. Today, the ancient Tao-Rusyr Caldera is filled by the deep blue waters of Kal’tsevoe Lake. The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite acquired this true-color image of southern Onekotan on June 10, 2009. In this late-spring shot, snow or ice lingers on the land, forming white streaks on a brown-and-green land surface. In the northwest quadrant of the caldera is Krenitzyn Peak, which rises to a height of 1,325 meters (4,347 feet). Like the other Kuril Islands, Onekotan lies along the Pacific “Ring of Fire.” The Kuril Island volcanoes are fueled by magma generated by the subduction of the Pacific Plate under the Eurasian Plate, which takes place along a deep trench about 200 kilometers (120 miles) to the islands’ east. The only historical eruption at Krenitzyn Peak occurred in 1952, a week after a magnitude 9.0 earthquake along the subduction fault. NASA Earth Observatory image created by Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Caption by Michon Scott and Rebecca Lindsey. NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram
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Estes, James A.; Tinker, M. Tim; Bodkin, James L.
2010-01-01
Recovery criteria for depleted species or populations normally are based on demographic measures, the goal being to maintain enough individuals over a sufficiently large area to assure a socially tolerable risk of future extinction. Such demographically based recovery criteria may be insufficient to restore the functional roles of strongly interacting species. We explored the idea of developing a recovery criterion for sea otters (Enhydra lutris) in the Aleutian archipelago on the basis of their keystone role in kelp forest ecosystems. We surveyed sea otters and rocky reef habitats at 34 island-time combinations. The system nearly always existed in either a kelp-dominated or deforested phase state, which was predictable from sea otter density. We used a resampling analysis of these data to show that the phase state at any particular island can be determined at 95% probability of correct classification with information from as few as six sites. When sea otter population status (and thus the phase state of the kelp forest) was allowed to vary randomly among islands, just 15 islands had to be sampled to estimate the true proportion that were kelp dominated (within 10%) with 90% confidence. We conclude that kelp forest phase state is a more appropriate, sensitive, and cost-effective measure of sea otter recovery than the more traditional demographically based metrics, and we suggest that similar approaches have broad potential utility in establishing recovery criteria for depleted populations of other functionally important species.
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NASA Astrophysics Data System (ADS)
Rodriguez-Losada, Jose A.; Eff-Darwich, Antonio; Hernandez, Luis E.; Viñas, Ronaldo; Pérez, Nemesio; Hernandez, Pedro; Melián, Gladys; Martinez-Frías, Jesús; Romero-Ruiz, M. Carmen; Coello-Bravo, Juan Jesús
2015-02-01
This paper describes the main physical, petrological and geochemical features of the floating fragments that were emitted in the initial stages of the 2011-2012 submarine eruption off the coast of the Canarian island of El Hierro, located 380 km from the Northwest African Coast. It attempts to assess the potential of radiometric analyses to discern the intriguing origin of the floating fragments and the differences between their constituent parts. In this regard, the material that conforms the core of the fragments contains the largest concentration of uranium (U) ever found in volcanic rocks of the Canary Islands. This enrichment in U is not found in the content of thorium (Th), hence the floating fragments have an unusual U/Th ratio, namely equal to or larger than 3. Although the origin of this material is under discussion, it is proposed that the enrichment in U is the result of hydrothermal processes.
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Airborne lidar measurements of the soufriere eruption of 17 april 1979.
Fuller, W H; Sokol, S; Hunt, W H
1982-06-04
At the time of the Soufriere, St. Vincent, volcanic eruption of 17 April 1979, a NASA P-3 aircraft with an uplooking lidar (light detection and ranging) system onboard was airborne 130 kilometers east of the island. Lidar measurements of the fresh volcanic ash were made approximately 2 hours after the eruption, 120 kilometers to the northeast and east. On the evening of 18 April, the airborne lidar, on a southerly flight track, detected significant amounts of stratospheric material in layers at 16, 17, 18, and 19.5 kilometers. These data, and measurements to the north on 19 April, indicate that the volcanic plume penetrated the stratosphere to an altitude of about 20 kilometers and moved south during the first 48 hours after the eruption.
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Airborne lidar measurements of the Soufriere eruption of 17 April 1979
NASA Technical Reports Server (NTRS)
Fuller, W. H., Jr.; Sokol, S.; Hunt, W. H.
1982-01-01
At the time of the Soufriere, St. Vincent, volcanic eruption of April 17, 1979, a NASA P-3 aircraft with an uplooking lidar (light detection and ranging) system onboard was airborne 130 kilometers east of the island. Lidar measurements of the fresh volcanic ash were made approximately 2 hours after the eruption, 120 kilometers to the northeast and east. On the evening of April 18, the airborne lidar, on a southerly flight track, detected significant amounts of stratospheric material in layers at 16, 17, 18, and 19.5 kilometers. These data, and measurements to the north on April 19, indicate that the volcanic plume penetrated the stratosphere to an altitude of about 20 kilometers and moved south during the first 48 hours after the eruption.
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NASA Technical Reports Server (NTRS)
2002-01-01
This true-color image of the Galapagos Islands was acquired on March 12, 2002, by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA's Terra satellite. The Galapagos Islands, which are part of Ecuador, sit in the Pacific Ocean about 1000 km (620 miles) west of South America. As the three craters on the largest island (Isabela Island) suggest, the archipelago was created by volcanic eruptions, which took place millions of years ago. Unlike most remote islands in the Pacific, the Galapagos have gone relatively untouched by humans over the past few millennia. As a result, many unique species have continued to thrive on the islands. Over 95 percent of the islands' reptile species and nearly three quarters of its land bird species cannot be found anywhere else in the world. Two of the more well known are the Galapagos giant tortoise and marine iguanas. The unhindered evolutionary development of the islands' species inspired Charles Darwin to begin The Origin of Species eight years after his visit there. To preserve the unique wildlife on the islands, the Ecuadorian government made the entire archipelago a national park in 1959. Each year roughly 60,000 tourists visit these islands to experience what Darwin did over a century and a half ago. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC
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2018-05-25
Tristan da Cunha is both a remote group of volcanic islands in the south Atlantic, and the main island. It is the most remote inhabited island group in the world, 2400 km from the nearest inhabited land. Tristan has a population of about 250 inhabitants, and is part of the British overseas territory of Saint Helena, Ascension and Tristan da Cunha. In 1961 the eruption of Queen Mary's Peak forced the evacuation of the entire population for two years. The image was acquired October 7, 2017, and is located at 37.1 degrees south, 12.3 degrees west. https://photojournal.jpl.nasa.gov/catalog/PIA22506
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Amchitka Island, Alaska, special sampling project 1997
DOE Office of Scientific and Technical Information (OSTI.GOV)
U.S. Department of Energy, Nevada Operations Office
2000-06-28
This 1997 special sampling project represents a special radiobiological sampling effort to augment the 1996 Long-Term Hydrological Monitoring Program (LTHMP) for Amchitka Island in Alaska. Lying in the western portion of the Aleutian Islands arc, near the International Date Line, Amchitka Island is one of the southernmost islands of the Rat Island Chain. Between 1965 and 1971, the U.S. Atomic Energy Commission conducted three underground nuclear tests on Amchitka Island. In 1996, Greenpeace collected biota samples and speculated that several long-lived, man-made radionuclides detected (i.e., americium-241, plutonium-239 and -240, beryllium-7, and cesium-137) leaked into the surface environment from underground cavitiesmore » created during the testing. The nuclides of interest are detected at extremely low concentrations throughout the environment. The objectives of this special sampling project were to scientifically refute the Greenpeace conclusions that the underground cavities were leaking contaminants to the surface. This was achieved by first confirming the presence of these radionuclides in the Amchitka Island surface environment and, second, if the radionuclides were present, determining if the source is the underground cavity or worldwide fallout. This special sampling and analysis determined that the only nonfallout-related radionuclide detected was a low level of tritium from the Long Shot test, which had been previously documented. The tritium contamination is monitored and continues a decreasing trend due to radioactive decay and dilution.« less
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Preliminary geologic map of Kanaga Volcano, Alaska
Miller, T.P.; Waythomas, C.F.; Nye, C.J.
2003-01-01
Kanaga Volcano is a 1,300 m (4,287-foot) high, historically active cone-shaped stratovolcano located on the north end of Kanaga Island in the Andreanof Islands Group of the Aleutian Islands. The volcano is undissected, symmetrical in profile, and is characterized by blocky andesitic lava flows, with well-developed levees and steep flow fronts, that emanate radially from, or near, the 200-m-wide summit crater. The lack of dissection of the cone suggests the entire edifice was constructed in post-glacial Holocene time. Historical eruptions were reported in 1791, 1827, 1829, 1904-1906, and 1993-95 (Miller and others, 1998); questionable eruptions occurred in 1763, 1768, 1786, 1790, and 1933. The upper flanks of the cone are very steep (>30°) and flows moving down these steep flows commonly fragment into breccias and lahars. A non-vegetated lahar, or group of lahars, extends from high on the southeast flank of the cone down to the northeast shore of the intracaldera lake. This lahar deposit was observed in 1999 but does not appear to be present on aerial photos taken in 1974 and is assumed to be part of the 1994-95 eruption. Most recent eruptions of Kanag a, including the 1994-95 eruption, were primarily effusive in character with a subordinate explosive component. Lava was extruded from, or near, the summit vent and moved down the flank of the cone in some cases reaching the ocean. In 1994, lava flows going down the very steep north and west flanks broke up into incandescent avalanches tumbling over steep truncated sea cliffs into the Bering Sea. A common feature of Kanaga central vent eruptions is the occurrence of widespread ballistics and accompanying craters. Steam and fine ash plumes rose to 7.5 km ASL and drifted a few tens of kilometers downwind. Plumes such as these are unlikely to deposit significant (i.e., sufficiently thick to leave a permanent record) tephras on other islands downwind.
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Cascades/Aleutian Play Fairway Analysis: Data and Map Files
Lisa Shevenell
2015-11-15
Contains Excel data files used to quantifiably rank the geothermal potential of each of the young volcanic centers of the Cascade and Aleutian Arcs using world power production volcanic centers as benchmarks. Also contains shapefiles used in play fairway analysis with power plant, volcano, geochemistry and structural data.
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Explosive eruption, flank collapse and megatsunami at Tenerife ca. 170 ka.
Paris, Raphaël; Bravo, Juan J Coello; González, María E Martín; Kelfoun, Karim; Nauret, François
2017-05-15
Giant mass failures of oceanic shield volcanoes that generate tsunamis potentially represent a high-magnitude but low-frequency hazard, and it is actually difficult to infer the mechanisms and dynamics controlling them. Here we document tsunami deposits at high elevation (up to 132 m) on the north-western slopes of Tenerife, Canary Islands, as a new evidence of megatsunami generated by volcano flank failure. Analyses of the tsunami deposits demonstrate that two main tsunamis impacted the coasts of Tenerife 170 kyr ago. The first tsunami was generated during the submarine stage of a retrogressive failure of the northern flank of the island, whereas the second one followed the debris avalanche of the subaerial edifice and incorporated pumices from an on-going ignimbrite-forming eruption. Coupling between a massive retrogressive flank failure and a large explosive eruption represents a new type of volcano-tectonic event on oceanic shield volcanoes and a new hazard scenario.
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Explosive eruption, flank collapse and megatsunami at Tenerife ca. 170 ka
Paris, Raphaël; Bravo, Juan J. Coello; González, María E. Martín; Kelfoun, Karim; Nauret, François
2017-01-01
Giant mass failures of oceanic shield volcanoes that generate tsunamis potentially represent a high-magnitude but low-frequency hazard, and it is actually difficult to infer the mechanisms and dynamics controlling them. Here we document tsunami deposits at high elevation (up to 132 m) on the north-western slopes of Tenerife, Canary Islands, as a new evidence of megatsunami generated by volcano flank failure. Analyses of the tsunami deposits demonstrate that two main tsunamis impacted the coasts of Tenerife 170 kyr ago. The first tsunami was generated during the submarine stage of a retrogressive failure of the northern flank of the island, whereas the second one followed the debris avalanche of the subaerial edifice and incorporated pumices from an on-going ignimbrite-forming eruption. Coupling between a massive retrogressive flank failure and a large explosive eruption represents a new type of volcano-tectonic event on oceanic shield volcanoes and a new hazard scenario. PMID:28504256
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Thornton, I W; Zann, R A; Rawlinson, P A; Tidemann, C R; Adikerana, A S; Widjoya, A H
1988-01-01
MacArthur and Wilson [MacArthur, R. H. & Wilson, E. O. (1967) The Theory of Island Biogeography (Princeton Univ. Press, Princeton, NJ)] used the rate of recolonization of the Krakatau Islands (sterilized in the cataclysmic 1883 eruption) by birds and vascular plants to test their equilibrium model of immigration and extinction processes on islands. Working with data only up to 1933, they concluded that the number of resident land bird species had approached equilibrium by 1908-1919, 25-36 years after the eruption, when the number of vascular plant species was still increasing. Recent surveys of vertebrates on the archipelago show continuing colonization, as well as species turnover. Nonmigrant nonmarine birds and reptiles are only now approaching equilibrium species numbers; archipelago acquisition rates for these groups are lower than in the 40 years following the 1883 eruption. Apparent (minimal) annual extinction rates are an order of magnitude lower than those calculated for equilibrium by MacArthur and Wilson. The active volcano Anak Krakatau emerged in 1930 and suffered an eruption in 1952 that destroyed the vegetation. It is still at an early stage of succession and on the threshold of major vegetational change. This island and a physically dynamic, ever-young spit on Sertung I, also held at an early successional stage, may provide (i) ecological refuges for some species whose optimal habitat on the older islands is being extirpated by vegetational succession and (ii) ecological "windows" through which such species may still establish from the mainland, thus postponing their extinction on the archipelago. PMID:3422440
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Uplift and subsidence reveal a nonpersistent megathrust rupture boundary (Sitkinak Island, Alaska)
Briggs, Richard W.; Engelhart, Simon E.; Nelson, Alan R.; Dura, Tina; Kemp, Andrew C.; Haeussler, Peter J.; Corbett, D. Reide; Angster, Stephen J.; Bradley, Lee-Ann
2014-01-01
We report stratigraphic evidence of land-level change and tsunami inundation along the Alaska-Aleutian megathrust during prehistoric and historical earthquakes west of Kodiak Island. On Sitkinak Island, cores and tidal outcrops fringing a lagoon reveal five sharp lithologic contacts that record coseismic land-level change. Radiocarbon dates, 137Cs profiles, CT scans, and microfossil assemblages are consistent with rapid uplift ca. 290-0, 520-300, and 1050-790 cal yr BP, and subsidence in AD 1964 and ca. 640-510 cal yr BP. Radiocarbon, 137Cs, and 210Pb ages bracketing a sand bed traced 1.5 km inland and evidence for sudden uplift are consistent with Russian accounts of an earthquake and tsunami in AD 1788. The mixed uplift and subsidence record suggests that Sitkinak Island sits above a non-persistent boundary near the southwestern limit of the AD 1964 Mw 9.2 megathrust rupture.
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Using gravimetry to probe small to large scale lithospheric structure at Fogo Island (Cape Verde)
NASA Astrophysics Data System (ADS)
Fernandes, R.; Bos, M. S.; Dumont, S.; Oliveira, C. S.; Miranda, E. H.; Almeida, P. G.
2017-12-01
The Fogo volcano is located on one of the Cape Verde islands in the Atlantic Ocean. Its last eruption was from November 2014 to February 2015 and destroyed two villages. To better understand its volcanic plumbing system, but also its eruptive dynamics that would contribute to hazard assessment and risk mitigation, the project "FIRE - Fogo Island volcano: multi-disciplinary Research on 2014/15 Eruption" was rapidly conceived in collaboration with local institutions. Despite a regular eruptive activity in the last centuries ( 20 years), no magmatic chamber has been evidenced yet and this is what we are investigating using gravimetry in the FIRE project. Approximately 70 relative new gravity observations were made by the C4G mission during the 2014 eruption, using a SCINTREX CG3M gravimeter. The spacing between observation points was around 5 km for most of the island and around 2 km in Chã das Caldeiras, close to the 2014 eruption vent. In January 2017, 48 additional observations were made which densified the post-eruption observations in Chã das Caldeiras. The exact location of each observation point was determined with an accuracy of <10 cm from colocated GNSS receivers. The gravity residuals are fitted to the predicted gravity effect from modelled magma chambers with various diameters, depths and density contrasts in order to investigate if such a chamber can explain the measurements. A digital terrain model of the island, refined with a high-resolution terrain model of 10m resolution in the Chã das Caldeiras produced as part of the project, will be used to remove the gravitational effect of the topography. In addition, the new gravity observations can be used to improve global geopotential models such as EGM2008/EIGEN6C4 over the island and to compute a new elastic thickness of the crust underneath the island. Pim (2006) estimated that the elastic thickness Te is around 30 km in this region which is normal for the age of lithosphere, suggesting that it has
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Trusdell, Frank A.; Moore, Richard B.; Sako, Maurice K.
2006-01-01
Pagan Island is the subaerial portion of two adjoining Quaternary stratovolcanoes near the middle of the active Mariana Arc, [FAT1]north of Saipan. Pagan and the other volcanic islands that constitute part of the Arc form the northern half of the East Mariana Ridge[FAT2], which extends about 2-4 km above the ocean floor. The > 6-km-deep Mariana Trench adjoins the East Mariana Ridge on the east, and the Mariana Trough, partly filled with young lava flows and volcaniclastic sediment, lies on the west of the Northern Mariana Islands (East Mariana Ridge. The submarine West Mariana Ridge, Tertiary in age, bounds the western side of the Mariana Trough. The Mariana Trench and Northern Mariana Islands (East Mariana Ridge) overlie an active subduction zone where the Pacific Plate, moving northwest at about 10.3 cm/year, is passing beneath the Philippine Plate, moving west-northwest at 6.8 cm/year. Beneath the Northern Mariana Islands, earthquake hypocenters at depths of 50-250 km identify the location of the west-dipping subduction zone, which farther west becomes nearly vertical and extends to 700 km depth. During the past century, more than 40 earthquakes of magnitude 6.5-8.1 have shaken the Mariana Trench. The Mariana Islands form two sub-parallel, concentric, concave-west arcs. The southern islands comprise the outer arc and extend north from Guam to Farallon de Medinilla. They consist of Eocene to Miocene volcanic rocks and uplifted Tertiary and Quaternary limestone. The nine northern islands extend from Anatahan to Farallon de Pajaros and form part of the inner arc. The active inner arc extends south from Anatahan, where volcanoes, some of which are active, form seamounts west of the older outer arc. Other volcanic seamounts of the active arc surmount the East Mariana Ridge in the vicinity of Anatahan and Sarigan and north and south of Farallon de Pajaros. Six volcanoes (Farallon de Pajaros, Asuncion, Agrigan, Mount Pagan, Guguan, and Anatahan) in the northern islands
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Kenney, Leah A.; Eagles-Smith, Collin A.; Ackerman, Joshua T.; von Hippel, Frank A.
2014-01-01
We assessed temporal variation in mercury (Hg) concentrations of threespine stickleback (Gasterosteus aculeatus) from Agattu Island, Aleutian Archipelago, Alaska. Total Hg concentrations in whole-bodied stickleback were measured at two-week intervals from two sites in each of two lakes from June 1 to August 10, 2011 during the time period when lakes were ice-free. Across all sites and sampling events, stickleback Hg concentrations ranged from 0.37–1.07 µg/g dry weight (dw), with a mean (± SE) of 0.55±0.01 µg/g dw. Mean fish Hg concentrations declined by 9% during the study period, from 0.57±0.01 µg/g dw in early June to 0.52±0.01 µg/g dw in mid-August. Mean fish Hg concentrations were 6% higher in Loon Lake (0.56±0.01 µg/g dw) than in Lake 696 (0.53±0.01 µg/g dw), and 4% higher in males (0.56±0.01 µg/g dw) than in females (0.54±0.01 µg/g dw). Loon Lake was distinguished from Lake 696 by the presence of piscivorous waterbirds during the breeding season. Mercury concentrations in stickleback from Agattu Island were higher than would be expected for an area without known point sources of Hg pollution, and high enough to be of concern to the health of piscivorous wildlife.
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NASA Astrophysics Data System (ADS)
Melián, Gladys; Hernández, Pedro A.; Padrón, Eleazar; Pérez, Nemesio M.; Barrancos, José; Padilla, Germán.; Dionis, Samara; Rodríguez, Fátima; Calvo, David; Nolasco, Dacil
2014-09-01
We report herein the results of extensive diffuse CO2 emission surveys performed on El Hierro Island in the period 1998-2012. More than 17,000 measurements of the diffuse CO2 efflux were carried out, most of them during the volcanic unrest period that started in July 2011. Two significant precursory signals based on geochemical and geodetical studies suggest that a magma intrusion processes might have started before 2011 in El Hierro Island. During the preeruptive and eruptive periods, the time series of the diffuse CO2 emission released by the whole island experienced two significant increases. The first started almost 2 weeks before the onset of the submarine eruption, reflecting a clear geochemical anomaly in CO2 emission, most likely due to increasing release of deep-seated magmatic gases to the surface. The second one, between 24 October and 27 November 2011, started before the most energetic seismic events of the volcanic-seismic unrest. The data presented here demonstrate that combined continuous monitoring studies and discrete surveys of diffuse CO2 emission provide important information to optimize the early warning system in volcano monitoring programs and to monitor the evolution of an ongoing volcanic eruption, even though it is a submarine eruption.
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NASA Astrophysics Data System (ADS)
Poret, M.; Costa, A.; Folch, A.; Martí, A.
2017-11-01
On the 26th April 1979, La Soufrière St. Vincent volcano (West Indies) erupted producing a tephra fallout that blanketed the main island and the neighboring Bequia Island, located southwards. Using deposit measurements and the available observations reported in Brazier et al. (1982), we estimated the optimal Eruption Source Parameters, such as the Mass Eruption Rate (MER), the Total Erupted Mass (TEM) and the Total Grain-Size Distribution (TGSD) by means of a computational inversion method. Tephra transport and deposition were simulated using the 3D Eulerian model FALL3D. The field-based TGSD reconstructed by Brazier et al. (1982) shows a bi-modal pattern having a coarse and a fine population with modes around 0.5 and 0.06 mm, respectively. A significant amount of aggregates was observed during the eruption. To quantify the relevance of aggregation processes on the bulk tephra deposit, we performed a comparative study in which we accounted for aggregation using three different schemes, computing ash aggregation within the plume under wet conditions, i.e. considering both the effects of air moisture and magmatic water, consistently with the eruptive phreatomagmatic eruption features. The sensitivity to the driving meteorological model (WRF/ARW) was also investigated by considering two different spatial resolutions (5 and 1 km) and model output frequencies. Results show that, for such short-lived explosive eruptions, high-resolution meteorological data are critical. Optimal results best-fitting all available observations indicate a column height of 12 km above the vent, a MER of 7.8 × 106 kg/s which, for an eruption duration of 370 s, gives a TEM of 2.8 × 109 kg. The optimal aggregate mean diameter obtained is 1.5Φ with a density of 350 kg/m3, contributing to 22% of the deposit mass.
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NASA Astrophysics Data System (ADS)
Rubin, K. H.; Jurado-Chichay, Z.; Urrutia-Fucugauchi, J.
2002-12-01
The Koko Rift Zone (KRZ), eastern Oahu, is generally regarded as among the youngest volcanic features on the island. Previous workers have suggested that the 9 or 10 vents of this rift erupted near-simultaneously. However, K-Ar data in the literature (32-39 ka vs 320 ka) provide only general guidance on the youthfulness of these eruptions. We present new age constraints on KRZ volcanism using deposits of the phreatomagmatic eruption that produced Hanauma Bay (a popular snorkeling spot) and spatially associated lava flows. Numerous continuous basaltic ash units within the walls of Hanauma crater contain lithic fragments of well-preserved coral reef, beach rock, and marine mollusks, indicating that the eruption occurred in a near shore environment. 238U-234U-230Th dating of coral clasts in the deposit demonstrates that the eruption breached reef of MIS stage 7 age (200 +/- 30 ka), thereby ruling out the K-Ar age of 320 ka. U-series nuclides in "normal" MIS 7 coral lithics are indistinguishable from those in the island encircling Waianae Reef of the same age. However, U-series components in some originally aragonitic coral clasts were offset during the eruption when the rims recrystallized to calcite. 87Sr/86Sr, 234U/238U and Sr and U concentration indicate chemical mixing with host basaltic ash during this event, from which potential ages of the eruption can be constructed using isochron methods. More modeling of the data remains to be done but our preliminary estimate places the eruption at less than 100 ka. This result is consistent with new data on paleointensity and paleomagnetic secular variation within the lava flows exposed in or around the crater. This U-series dating approach should prove useful for eruptions in other locales where carbonate bioclast lithics are present in the deposits.
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Bald eagles and sea otters in the Aleutian Archipelago: indirect effects of trophic cascades.
Anthony, R.G.; Estes, J.A.; Ricca, M.A.; Miles, A.K.; Forsman, E.D.
2008-01-01
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 and 2000–2002, when sea otters were abundant and scarce, respectively. Bald Eagles depend on nearshore marine communities for most of their prey in this ecosystem, so we predicted that the recent decline in otter populations would have an indirect negative effect on diets and demography of Bald Eagles. Contrary to our predictions, we found no effects on density of breeding pairs on four islands from 1993–1994 to 2000–2002. In contrast, diets and diet diversity of Bald Eagles changed considerably between the two time periods, likely reflecting a change in prey availability resulting from the increase and subsequent decline in sea otter populations. The frequency of sea otter pups, rock greenling (Hexagammus lagocephalus), and smooth lumpsuckers (Aptocyclus ventricosus) in the eagle's diet declined with corresponding increases in Rock Ptarmigan (Lagopus mutus), Glaucous-winged Gulls (Larus glaucescens), Atka mackerel (Pleurogrammus monopterygius), and various species of seabirds during the period of the recent otter population decline. Breeding success and productivity of Bald Eagles also increased during this time period, which may be due to the higher nutritional quality of avian prey consumed in later years. Our results provide further evidence of the wide-ranging indirect effects of sea otter predation on nearshore marine communities and another apex predator, the Bald Eagle. Although the indirect effects of sea otters are widely known, this example is unique because the food-web pathway transcended five species and several trophic levels in linking one apex
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The first five years of Kīlauea’s summit eruption in Halema‘uma‘u Crater, 2008–2013
Patrick, Matthew R.; Orr, Tim R.; Sutton, A.J.; Elias, Tamar; Swanson, Donald A.
2013-01-01
The eruption in Halema‘uma‘u Crater that began in March 2008 is the longest summit eruption of Kīlauea Volcano, on the Island of Hawai‘i, since 1924. From the time the eruption began, the new "Overlook crater" inside Halema‘uma‘u has exhibited fluctuating lava lake activity, occasional small explosive events, and a persistent gas plume. The beautiful nighttime glow impresses and thrills visitors in Hawai‘i Volcanoes National Park, but the continuous emission of sulfur dioxide gas produces "vog" (volcanic smog) that can severely affect communities and local agriculture downwind. U.S. Geological Survey scientists continue to closely monitor the eruption and assess ongoing hazards.
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NASA Astrophysics Data System (ADS)
Sibrant, A. L. R.; Hildenbrand, A.; Marques, F. O.; Weiss, B.; Boulesteix, T.; Hübscher, C.; Lüdmann, T.; Costa, A. C. G.; Catalão, J. C.
2015-08-01
The evolution of volcanic islands is generally marked by fast construction phases alternating with destruction by a variety of mass-wasting processes. More specifically, volcanic islands located in areas of intense regional deformation can be particularly prone to gravitational destabilisation. The island of S. Miguel (Azores) has developed during the last 1 Myr inside the active Terceira Rift, a major tectonic structure materializing the present boundary between the Eurasian and Nubian lithospheric plates. In this work, we depict the evolution of the island, based on high-resolution DEM data, stratigraphic and structural analyses, high-precision K-Ar dating on separated mineral phases, and offshore data (bathymetry and seismic profiles). The new results indicate that: (1) the oldest volcanic complex (Nordeste), composing the easternmost part of the island, was dominantly active between ca. 850 and 750 ka, and was subsequently affected by a major south-directed flank collapse. (2) Between at least 500 ka and 250 ka, the landslide depression was massively filled by a thick lava succession erupted from volcanic cones and domes distributed along the main E-W collapse scar. (3) Since 250 kyr, the western part of this succession (Furnas area) was affected by multiple vertical collapses; associated plinian eruptions produced large pyroclastic deposits, here dated at ca. 60 ka and less than 25 ka. (4) During the same period, the eastern part of the landslide scar was enlarged by retrogressive erosion, producing the large Povoação valley, which was gradually filled by sediments and young volcanic products. (5) The Fogo volcano, in the middle of S. Miguel, is here dated between ca. 270 and 17 ka, and was affected by, at least, one southwards flank collapse. (6) The Sete Cidades volcano, in the western end of the island, is here dated between ca. 91 and 13 ka, and experienced mutliple caldera collapses; a landslide to the North is also suspected from the presence of a
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NASA Astrophysics Data System (ADS)
Coussens, Maya; Wall-Palmer, Deborah; Talling, Peter. J.; Watt, Sebastian. F. L.; Cassidy, Michael; Jutzeler, Martin; Clare, Michael A.; Hunt, James. E.; Manga, Michael; Gernon, Thomas. M.; Palmer, Martin. R.; Hatter, Stuart. J.; Boudon, Georges; Endo, Daisuke; Fujinawa, Akihiko; Hatfield, Robert; Hornbach, Matthew. J.; Ishizuka, Osamu; Kataoka, Kyoko; Le Friant, Anne; Maeno, Fukashi; McCanta, Molly; Stinton, Adam. J.
2016-07-01
Hole U1395B, drilled southeast of Montserrat during Integrated Ocean Drilling Program Expedition 340, provides a long (>1 Ma) and detailed record of eruptive and mass-wasting events (>130 discrete events). This record can be used to explore the temporal evolution in volcanic activity and landslides at an arc volcano. Analysis of tephra fall and volcaniclastic turbidite deposits in the drill cores reveals three heightened periods of volcanic activity on the island of Montserrat (˜930 to ˜900 ka, ˜810 to ˜760 ka, and ˜190 to ˜120 ka) that coincide with periods of increased volcano instability and mass-wasting. The youngest of these periods marks the peak in activity at the Soufrière Hills volcano. The largest flank collapse of this volcano (˜130 ka) occurred toward the end of this period, and two younger landslides also occurred during a period of relatively elevated volcanism. These three landslides represent the only large (>0.3 km3) flank collapses of the Soufrière Hills edifice, and their timing also coincides with periods of rapid sea level rise (>5 m/ka). Available age data from other island arc volcanoes suggest a general correlation between the timing of large landslides and periods of rapid sea level rise, but this is not observed for volcanoes in intraplate ocean settings. We thus infer that rapid sea level rise may modulate the timing of collapse at island arc volcanoes, but not in larger ocean-island settings.
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McGimsey, R.G.; Neal, C.A.; Dixon, J.P.; Ushakov, Sergey
2008-01-01
The Alaska Volcano Observatory (AVO) responded to eruptive activity or suspected volcanic activity at or near 16 volcanoes in Alaska during 2005, including the high profile precursory activity associated with the 2005?06 eruption of Augustine Volcano. AVO continues to participate in distributing information about eruptive activity on the Kamchatka Peninsula, Russia, and in the Kurile Islands of the Russian Far East, in conjunction with the Kamchatkan Volcanic Eruption Response Team (KVERT) and the Sakhalin Volcanic Eruption Response Team (SVERT), respectively. In 2005, AVO helped broadcast alerts about activity at 8 Russian volcanoes. The most serious hazard posed from volcanic eruptions in Alaska, Kamchatka, or the Kurile Islands is the placement of ash into the atmosphere at altitudes traversed by jet aircraft along the North Pacific and Russian Trans East air routes. AVO, KVERT, and SVERT work collaboratively with the National Weather Service, Federal Aviation Administration, and the Volcanic Ash Advisory Centers to provide timely warnings of volcanic eruptions and the production and movement of ash clouds.
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Ionospheric disturbance excited by the 2015 Kuchinoerabu-jima, southwest Japan, eruption
NASA Astrophysics Data System (ADS)
Aoki, Y.; Nishida, K.; Nakashima, Y.; Heki, K.
2015-12-01
Vertical displacements excited by volcanic eruptions, earthquakes, or tsunamis excites pressure waves in the atmosphere. The excited oscillation propagates to ionosphere where solar radiation ionize a part of atmosphere, resulting in a disturbance of the total electron content (TEC). Where numerous studies have reported ionospheric disturbance excited by earthquakes or tsunamis, much smaller number of studies have investigated that excited by volcanic eruptions. This study reports on the ionospheric disturbance excited by the 2015 Kuchinoerabu-jima eruption observed by continuous GPS observations. The 2015 Kuchinoerabu-jima eruption is a phreatomagmatic eruption occurred on 29 May 2015. The eruption is explosive with a column height up to 10,000 meters above the vent. The disturbance of TEC started from about 10 minutes after the eruption at approximately 100 km from the volcano. The disturbance then propagates outward for about 10 minutes. The velocity of pressure wave is estimated to be about 500 m/s, consistent with the average acoustic velocity in the ionosphere. The dominant frequency of the observed disturbance is about 11 mHz, much higher than the eigenfrequencies of Earth's atmosphere, 3.7 mHz and 4.4 mHz. The dominant frequency observed here might be related to the dominant frequency of the acoustic wave excited by the eruption and the dissipation of the medium. While the ionospheric disturbance associated with the 2003 Soufrière Hills lasted more than an hour, that in this study lasted only up to a few minutes. This difference might correspond to the difference in time scale of the excitation. The pressure wave excited by the eruption is also recorded by broadband seismometers in the Japanese islands. Our goal is thus to gain more insights into the mechanics of lithosphere-atmosphere-ionosphere coupling as well that of the 2015 Kuchinoerabu-jima eruption consisent with both seismic and GPS observations.
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Post-eruptive flooding of Santorini caldera and implications for tsunami generation
NASA Astrophysics Data System (ADS)
Nomikou, Paraskevi; Druitt, Tim; Hübscher, Christian; Mather, Tamsin; Paulatto, Michele; Kalnins, Lara; Kelfoun, Karim; Papanikolaou, Dimitris; Bejelou, Konstantina; Lampridou, Danai; Pyle, David; Carey, Steven; Watts, Anthony; Weiß, Benedikt; Parks, Michelle
2017-04-01
Caldera-forming eruptions of island volcanoes generate tsunamis by the interaction of different eruptive phenomena with the sea. Such tsunamis are a major hazard, but forward models of their impacts are limited by poor understanding of source mechanisms. The eruption of Santorini 3600 years ago was one of the largest of eruptions known worldwide from the past 10,000 years - and was at least 3 times larger than the catastrophic eruption of Krakatoa. This huge eruption evacuated large volumes of magma, causing collapse of the large caldera, which is now filled with seawater. Tsunamis from this eruption have been proposed to have played a role in the demise of the Minoan culture across the southern Aegean, through damage to coastal towns, harbors, shipping and maritime trade. Before the eruption, there was an older caldera in the northern part of Santorini, partly filled with a shallow lagoon. In our study, we present bathymetric and seismic evidence showing that the caldera was not open to the sea during the main phase of the eruption, but was flooded once the eruption had finished. Following subsidence of the caldera floor, rapid inflow of seawater and landslides cut a deep 2.0-2.5 km3 submarine channel into the northern flank of the caldera wall. Hydrodynamic modelling indicates that the caldera was flooded through this breach in less than a couple of days. It was previously proposed that collapse of the caldera could have led to the formation of a major tsunami; but this is ruled out by our new evidence. Any tsunami's generated were most likely caused by entry of pyroclastic flows into the sea, combined with slumping of submarine pyroclastic accumulations. This idea is consistent with previous assertions that pyroclastic flows were the main cause of tsunamis at Krakatau.
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2010-09-14
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NASA Astrophysics Data System (ADS)
Domínguez Cerdeña, Itahiza; García-Cañada, Laura; Ángeles Benito Saz, María; Del Fresno, Carmen
2017-04-01
The last volcanic eruption in the Canary Islands took place in 2011 less than 2 km offshore El Hierro island, after 3 months of measuring surface deformation (up to 5 cm) and locating more than 10 000 earthquakes. In the two years following the end of the submarine eruption on 5 March 2012, six deep magmatic intrusions were recorded beneath the island. Despite the short time duration of these intrusions, these events have been more energetic that the 2011 pre-eruptive intrusive event but none of them ended in a new eruption. These post-eruptive reactivations are some of the few examples in the world of well monitored magmatic intrusions related with monogenetic volcanism. In order to understand these processes we have analyzed the geodetic and seismic data with different techniques. First, we did a joint hypocentral relocation of the six seismic swarms, including more than 6 300 events, to analyze the relative distribution of the earthquakes from different intrusions. The uncertainties of the earthquakes relocations was reduced to an average value of 300 m. New earthquakes' distribution shows the alignments of the different intrusions and a temporal migration of the events to larger depths. Moreover, we show the results of the ground deformation using GPS data from the network installed on the island (for each of the six intrusive events) and their inversion considering spherical models. In most of the intrusions the optimal source model was shallower and southern than the corresponding seismicity hypocenters. The intruded magma volume ranges from 0.02 to 0.13 km3. Finally, we also computed the b value from the Gutenberg Richter equation by means of a bootstrap method. The spatial and temporal evolution of the b value for the seismicity show a clear correlation with the temporal evolution of the crustal deformation. The six magma intrusions can be grouped, depending on their location, in three pairs each one associated with each of the three active rifts of El
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A submarine volcanic eruption leads to a novel microbial habitat.
Danovaro, Roberto; Canals, Miquel; Tangherlini, Michael; Dell'Anno, Antonio; Gambi, Cristina; Lastras, Galderic; Amblas, David; Sanchez-Vidal, Anna; Frigola, Jaime; Calafat, Antoni M; Pedrosa-Pàmies, Rut; Rivera, Jesus; Rayo, Xavier; Corinaldesi, Cinzia
2017-04-24
Submarine volcanic eruptions are major catastrophic events that allow investigation of the colonization mechanisms of newly formed seabed. We explored the seafloor after the eruption of the Tagoro submarine volcano off El Hierro Island, Canary Archipelago. Near the summit of the volcanic cone, at about 130 m depth, we found massive mats of long, white filaments that we named Venus's hair. Microscopic and molecular analyses revealed that these filaments are made of bacterial trichomes enveloped within a sheath and colonized by epibiotic bacteria. Metagenomic analyses of the filaments identified a new genus and species of the order Thiotrichales, Thiolava veneris. Venus's hair shows an unprecedented array of metabolic pathways, spanning from the exploitation of organic and inorganic carbon released by volcanic degassing to the uptake of sulfur and nitrogen compounds. This unique metabolic plasticity provides key competitive advantages for the colonization of the new habitat created by the submarine eruption. A specialized and highly diverse food web thrives on the complex three-dimensional habitat formed by these microorganisms, providing evidence that Venus's hair can drive the restart of biological systems after submarine volcanic eruptions.
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Impact of the 1815 Tambora Eruption to global climate change
NASA Astrophysics Data System (ADS)
Djumarma Wirakusumah, Achmad; Rachmat, Heryadi
2017-06-01
Tambora volcano is located at Sumbawa island, Indonesia. Geological study shows a successive of geomorphological development of Tambora Volcano. During 190 to 86 K-Years BP, shield-like or effusive volcano were formed; During 86 to 4 K-Years BP, a strato or explosive-volcano was formed; However, during 80 to 4 K-Years BP flank eruptions occurred intermittently and cinders were formed; In April 1815, a paroxysmal destructive eruption occurred which were followed by caldera forming; Since 1815, lava domes and solphataric fields were formed. The 1815 Tambora eruption emitted 60 to 80 megatons of SO2 to the stratosphere (44 km high). The SO2 spread the tropics, circled the world and it was oxidized to form H2SO4 so called sulphate aerosols protecting the sunlight to reach the earth surface causing global change effects. The Year of 1816 as the year without summer in Europe, the depressed situation in Europe, the epidemic disease of Benggal were three of examples of the impacts of the 1815 Tambora paroxysmal eruption. Therefore, characteristics of Tambora activity before paroxysmal should be learned for mitigation purposes.
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2011-04-20
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2011-04-14
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2010-12-13
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2010-11-12
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2013-02-08
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2012-10-09
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2011-03-07
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NASA Astrophysics Data System (ADS)
Greve, Annika; Turner, Gillian M.; Conway, Chris E.; Townsend, Dougal B.; Gamble, John A.; Leonard, Graham S.
2016-11-01
We present a detailed palaeomagnetic study from 35 sites on Holocene lava flows of the Tongariro Volcanic Centre, central North Island, New Zealand. Prior to the study the eruption ages of these flows were constrained to within a few thousand years by recently published high-precision 40Ar/39Ar geochronological data and tephrostratigraphic controls. Correlation of flow mean palaeomagnetic directions with a recently published continuous sediment record from Lake Mavora, Fiordland, allows us to reduce the age uncertainty to 300-500 yr in some cases. Our refined ages significantly improve the chronology of Holocene effusive eruptions of the volcanoes of the Tongariro Volcanic Centre. For instance, differences in the palaeomagnetic directions recorded by lavas from the voluminous Iwikau and Rangataua members suggest that individual effusive periods lasted up to thousands of years and that these bursts have been irregularly spaced over time. While over the last few millennia the effusive eruptive activity from Mt Ruapehu has been relatively quiet, the very young age (200-500 BP) of a Red Crater sourced flow suggests that effusive activity around Mt Tongariro lasted into the past few centuries. This adds an important hazard context to the historical record, which has otherwise comprised frequent relatively small, tephra producing, explosive eruptions without the production of lava flows.
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NASA Astrophysics Data System (ADS)
Needham, A. J.; Lindsay, J. M.; Smith, I. E. M.; Augustinus, P.; Shane, P. A.
2011-04-01
Rangitoto Volcano is the youngest and largest eruptive centre in the monogenetic intraplate Auckland Volcanic Field (AVF). The stratigraphy of Rangitoto pyroclastic deposits that have been preserved in swamps on nearby Motutapu Island and in Lake Pupuke on the mainland reveals that the volcano erupted twice; radiocarbon dating of 10 samples from the two tephra units in the swamps indicates eruption ages of 553 ± 7 and 504 ± 5 Cal years BP, for the lower and upper tephra layers, respectively. Geochemistry of the lava field and various scoria cones on Rangitoto Island itself reveals two distinct compositional groups: an alkaline olivine basalt group (that correlates geochemically with the lower tephra layer) and a group that is sub-alkaline and transitional to tholeiite (that correlates geochemically with the upper tephra layer). Based on this data, we infer that, following a phreatomagmatic vent-clearing phase, the early magmatic eruption of Rangitoto Volcano was Strombolian in character and produced an alkaline olivine basalt scoria cone and an associated thick ash deposit on nearby Motutapu Island. This was followed by a time gap of up to several decades, after which a second eruptive phase built the current summit scoria cone together with an encircling lava field. We suggest this later, sub-alkaline eruptive period was associated with the deposition of the thin upper tephra layer on Motutapu Island. The two suites of Rangitoto samples are chemically quite distinct, and each is associated with a distinct parental composition. Trace element modelling indicates the alkaline and sub-alkaline parental melts could have been derived by ~ 1 and 6 wt.% partial melting of an anhydrous garnet peridotite source at ~ 80 and 65 km depth, respectively. The compositional range within each suite is similar, and can be explained by mainly olivine together with minor clinopyroxene fractionation within a relatively simple conduit system in which mixing and mingling were not
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NASA Astrophysics Data System (ADS)
García-Yeguas, Araceli; Ibáñez, Jesús M.; Koulakov, Ivan; Jakovlev, Andrey; Romero-Ruiz, M. Carmen; Prudencio, Janire
2014-12-01
We present a 3-D model of P and S velocities beneath El Hierro Island, constructed using the traveltime data of more than 13 000 local earthquakes recorded by the Instituto Geográfico Nacional (IGN, Spain) in the period from 2011 July to 2012 September. The velocity models were performed using the LOTOS code for iterative passive source tomography. The results of inversion were thoroughly verified using different resolution and robustness tests. The results reveal that the majority of the onshore area of El Hierro is associated with a high-velocity anomaly observed down to 10-12-km depth. This anomaly is interpreted as the accumulation of solid igneous rocks erupted during the last 1 Myr and intrusive magmatic bodies. Below this high-velocity pattern, we observe a low-velocity anomaly, interpreted as a batch of magma coming from the mantle located beneath El Hierro. The boundary between the low- and high-velocity anomalies is marked by a prominent seismicity cluster, thought to represent anomalous stresses due to the interaction of the batch of magma with crust material. The areas of recent eruptions, Orchilla and La Restinga, are associated with low-velocity anomalies surrounding the main high-velocity block. These eruptions took place around the island where the crust is much weaker than the onshore area and where the melted material cannot penetrate. These results put constraints on the geological model that could explain the origin of the volcanism in oceanic islands, such as in the Canaries, which is not yet clearly understood.
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Historical evidence for a connection between volcanic eruptions and climate change
NASA Technical Reports Server (NTRS)
Rampino, Michael R.
1991-01-01
The times of historical volcanic aerosol clouds were compared with changes in atmospheric temperatures on regional, hemispheric, and global scales. These involve either a direct comparison of individual significant eruption years with temperature records, or a comparison of eruption years with composited temperature records for several years before and after chosen sets of eruptions. Some studies have challenged the connection between individual eruptions and climate change. Mass and Portman (1989) recently suggested that the volcanic signal was present, but smaller than previously thought. In a study designed to test the idea that eruptions could cause small changes in climate, Hansen and other (1978) chose one of the best monitored eruptions at the time, the 1963 eruption of Agung volcano on the island of Bali. Using a simple radiation-balance model, in which an aerosol cloud in the tropics was simulated, this basic pattern of temperature change in the tropics and subtropics was reproduced. There may be natural limits to the atmospheric effects of any volcanic eruption. Self-limiting physical and chemical effects in eruption clouds were proposed. Model results suggest that aerosol microphysical processes of condensation and coagulation produce larger aerosols as the SO2 injection rate is increased. The key to discovering the greatest effects of volcanoes on short-term climate may be to concentrate on regional temperatures where the effects of volcanic aerosol clouds can be amplified by perturbed atmospheric circulation patterns, especially changes in mid-latitudes where meridional circulation patterns may develop. Such climatic perturbations can be detected in proxy evidence such as decreases in tree-ring widths and frost damage rings in climatically sensitive parts of the world, changes in treelines, weather anomalies such as unusually cold summers, severity of sea-ice in polar and subpolar regions, and poor grain yields and crop failures.
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Earth observations of the Galapagos Islands taken from OV-105 during STS-99.
2000-03-28
STS099-753-032 (11-22 February 2000) ---This 70mm photograph, photographed from the Space Shuttle Endeavour, centers on the two westernmost Galapagos Islands--seahorse-shaped Isla Isabela and the smaller round Isla Fernandina to its west. All of the 19 islands in the chain are volcanic in origin, and the craters of several of the shield volcanoes are visible as circular features on each of the islands. The two islands shown in this picture contain the most active volcanoes of the Galapagos. Fernandina last erupted in January-February 1995, with red-hot lava pouring into the sea. After 20 years of inactivity, Cerro Azul on Isla Isabela, last erupted in September-October 1998. Cerro Azul is the southwesternmost volcano on Isla Isabela. At 82 miles long, Isla Isabela is the largest of the islands, and comprises half of the land area of the archipelago. The islands are famous for their unique flora and fauna. Charles Darwin's observations of these species in 1835 contributed to the formation of his ideas on natural selection. Some of the most unique species include flightless cormorants, Galapagos penguins, giant land tortoises, and Galapagos finches. The range of Galapagos penguins is restricted to these western islands where upwelling enriches the ocean productivity, and the adaptation of a typically Antarctic bird family to the equator is an ecological marvel. Giant land tortoises are thought to have the oldest lifespans of any animal on Earth, but, scientists say, they have been driven near to extinction. During the most recent eruption of Cerro Azul, one tortoise was killed and many had to be relocated. The 13 species of Galapagos finches on the islands, although varied in form and lifestyle, are the descendants of an ancestor that happened to colonize this isolated archipelago. The human population of the entire archipelago is about 10,000.
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NASA Astrophysics Data System (ADS)
Hernández, P. A.; Calvari, S.; Calvo, D.; Marquez, A.; Padron, E.; Pérez, N.; Melian, G.; Padilla, G.; Barrancos, J.; Dionis, S.; Rodríguez, F.; Nolasco, D.; Hernández, I.
2012-04-01
El Hierro represents the summit of a volcanic shield elevating from the surrounding seafloor at depth of 4000 m to up to 1501 m above sea level. The island is believed to be near the present hotspot location in the Canaries with the oldest subaerial rocks dated at 1.12 Ma. The subaerial parts of the El Hierro rift zones (NE, NW and S Ridges) are characterized by tightly aligned dyke complexes with clusters of cinder cones as their surface expressions. Since 16 July, an anomalous seismicity at El Hierro Island was recorded by IGN seismic network. After the occurrence of more than 10,000 seismic events, volcanic tremor started at 05:15 on 10 October, followed on the afternoon of 12 October by a green discolouration of seawater, strong bubbling and degassing, and abundant bombs on a decimetre scale found floating on the ocean surface offshore, southwest of La Restinga village. The Canary Government raised the alert level from green to yellow on 10 October (3 colour basis: green, yellow, and red). Further episodes have occurred during November, December 2011 and January 2012, with turbulent water, foam rings, and volcanic material again reaching the sea surface. Colour of the discoloured area has changed frequently from light green to dark brown, depending on the eruptive activity. During the whole eruptive period, The Volcanological Institute of Canary Islands and the Helicopter Unit of the Spanish Civil Guard have carried out regularly thermal surveys with a hand held FLIR Thermal Camera P65. The images have been collected taking care of avoiding solar reflection (with cloudy weather) or at times of the day without direct sun light. Air temperature and humidity were measured with a handled thermo-hygrometer every time before the thermal image collection, and measurements were always performed at two fixed heights: 2000 and 1000 feet, and images were collected as perpendicular as possible to the surface. Together with thermal images, digital photos of the surface have
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The 1845 Hekla eruption: Grain-size characteristics of a tephra layer
NASA Astrophysics Data System (ADS)
Gudnason, Jonas; Thordarson, Thor; Houghton, Bruce F.; Larsen, Gudrun
2018-01-01
The 1845 eruption is commonly viewed as a typical Hekla eruption. It is a key event in the eruptive history of the volcano, as it is one of the best documented Hekla eruptions, in terms of contemporary accounts and observations. The eruption started on 2 September 1845 with an intense, hour long explosive Plinian phase that passed into effusive activity, ending on the 16 March 1846. The amount of tephra produced in the opening phase was 0.13 km3/7.5 × 1010 kg. The total grain-size distribution of the deposit is bimodal with a dominant coarse mode at - 2.5 φ (5.6 mm) and a broad finer mode at 3 to 4.5 φ (0.125 to 0.045 mm). At individual sites, the grain-size distribution of the tephra from the Plinian opening phase is also commonly (not always) bimodal. Deconvolved grain-size distributions exhibit distinctly different sedimentation patterns of the coarse and fine subpopulations. The lapilli-dominated subpopulation fines rapidly with transport, while the ash-dominated subpopulation shows less changes with distance, indicating premature sedimentation of fines by aggregation from the 1845 volcanic plume. Tephra deposition was to the ESE of the volcano from a 19 km (a.s.l.) high eruption plume. The plume front travelled at speeds of 16-19 m s- 1. Reports of ash deposition onto ships near the Faroe and Shetland Islands, 700 to 1100 km away from Hekla, demonstrate that even moderate-sized Hekla eruptions can affect very large parts of European air-space.
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NASA Astrophysics Data System (ADS)
Tudino, T.; Bortoluzzi, G.; Aliani, S.
2014-03-01
Marine water dynamics in the near field of a massive gas eruption near Panarea (Aeolian Islands volcanic arc, SE Tyrrhenian Sea) is described. ADCP current-meters were deployed during the paroxysmal phase in 2002 and 2003 a few meters from the degassing vent, recording day-long time series. Datasets were sorted to remove errors and select good quality ensembles over the entire water column. Standard deviation of error velocity was considered a proxy for inhomogeneous velocity fields over beams. Time series intervals had been selected when the basic ADCP assumptions were fulfilled and random errors minimized. Backscatter data were also processed to identify bubbles in the water column with the aim of locating bubble-free ensembles. Reliable time series are selected combining these data. Two possible scenarios have been described: firstly, a highly dynamic situation with visible surface diverging rings of waves, entrainment on the lower part of the gas column, detrainment in the upper part and a stagnation line (SL) at mid depth where currents were close to zero and most of the gas bubbles spread laterally; secondly, a less dynamic situation with water entraining into the gas plume at all depths and no surface rings of diverging waves. Reasons for these different dynamics may be ascribed to changes in gas fluxes (one order of magnitude higher in 2002). Description of SL is important to quantify its position in the water column and timing for entrainment-detrainment, and it can be measured by ADCP and calculated from models.
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First high resolution P wave velocity structure beneath Tenerife Island, (Canary Islands, Spain)
NASA Astrophysics Data System (ADS)
Garcia-Yeguas, Araceli; Ivan, Koulakov; Ibañez Jesus, M.; Valenti, Sallarès.
2010-05-01
3D velocity structure distribution has been imaged for first time using high resolution traveltime seismic tomography of the active volcano of Tenerife Island (Canary Islands, Spain). It is located in the Atlantic Ocean. In this island is situated the Teide stratovolcano (3718 m high) that is part of the Cañadas-Teide-Pico Viejo volcanic complex. Las Cañadas is a caldera system more than 20 kilometers wide where at least four distinct caldera processes have been identified. Evidence for many explosive eruptions in the volcanic complex has been found; the last noticeable explosive eruption (sub-plinean) occurred at Montaña Blanca around 2000 years ago. During the last 300 years, six effusive eruptions have been reported, the last of which took place at Chinyero Volcano on 18 November 1909. In January 2007, a seismic active experiment was carried out as part of the TOM-TEIDEVS project. About 6850 air gun shots were fired on the sea and recorded on a dense local seismic land network consisting of 150 independent (three component) seismic stations. The good quality of the recorded data allowed identifying P-wave arrivals up to offsets of 30-40 km obtaining more than 63000 traveltimes used in the tomographic inversion. The images have been obtained using ATOM-3D code (Koulakov, 2009). This code uses ray bending algorithms in the ray tracing for the forward modelling and in the inversion step it uses gradient methods. The velocity models show a very heterogeneous upper crust that is usual in similar volcanic environment. The tomographic images points out the no-existence of a magmatic chamber near to the surface and below Pico Teide. The ancient Las Cañadas caldera borders are clearly imaged featuring relatively high seismic velocity. Moreover, we have found a big low velocity anomaly in the northwest dorsal of the island. The last eruption took place in 1909 in this area. Furthermore, in the southeast another low velocity anomaly has been imaged. Several resolution
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DOE Office of Scientific and Technical Information (OSTI.GOV)
Stevenson, A.J.; Scholl, D.W.; Vallier, T.L.
1990-05-01
The central segment of the Aleutian Trench (162{degree}W to 175{degree}E) is an intraoceanic subduction zone that contains an anomalously thick sedimentary fill (4 km maximum). The fill is an arcward-thickening and slightly tilted wedge of sediment characterized acoustically by laterally continuous, closely spaced, parallel reflectors. These relations are indicative of turbidite deposition. The trench floor and reflection horizons are planar, showing no evidence of an axial channel or any transverse fan bodies. Cores of surface sediment recover turbidite layers, implying that sediment transport and deposition occur via diffuse, sheetlike, fine-grained turbidite flows that occupy the full width of the trench.more » The mineralogy of Holocene trench sediments document a mixture of island-arc (dominant) and continental source terranes. GLORIA side-scan sonar images reveal a westward-flowing axial trench channel that conducts sediment to the eastern margin of the central segment, where channelized flow cases. Much of the sediment transported in this channel is derived from glaciated drainages surrounding the Gulf of Alaska which empty into the eastern trench segment via deep-sea channel systems (Surveyor and others) and submarine canyons (Hinchinbrook and others). Insular sediment transport is more difficult to define. GLORIA images show the efficiency with which the actively growing accretionary wedge impounds sediment that manages to cross a broad fore-arc terrace. It is likely that island-arc sediment reaches the trench either directly via air fall, via recycling of the accretionary prism, or via overtopping of the accretionary ridges by the upper parts of thick turbidite flows.« less
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Volcano-tectonic earthquakes: A new tool for estimating intrusive volumes and forecasting eruptions
White, Randall A.; McCausland, Wendy
2016-01-01
Notable cases in which distal VT events preceded eruptions at long-dormant volcanoes include: Nevado del Ruiz (1984–1985), Pinatubo (1991), Unzen (1989–1995), Soufriere Hills (1995), Shishaldin (1989–1999), Tacana' (1985–1986), Pacaya (1980–1984), Rabaul (1994), and Cotopaxi (2001). Additional cases are recognized at frequently active volcanoes including Popocateptl (2001–2003) and Mauna Loa (1984). We present four case studies (Pinatubo, Soufriere Hills, Unzen, and Tacana') in which we demonstrate the above mentioned VT characteristics prior to eruptions. Using regional data recorded by NEIC, we recognized in near-real time that a huge distal VT swarm was occurring, deduced that a proportionately huge magmatic intrusion was taking place beneath the long dormant Sulu Range, New Britain Island, Papua New Guinea, that it was likely to lead to eruptive activity, and warned Rabaul Volcano Observatory days before a phreatic eruption occurred. This confirms the value of this technique for eruption forecasting. We also present a counter-example where we deduced that a VT swarm at Volcan Cosiguina, Nicaragua, indicated a small intrusion, insufficient to reach the surface and erupt. Finally, we discuss limitations of the method and propose a mechanism by which this distal VT seismicity is triggered by magmatic intrusion.
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Aerosols from the soufriere eruption plume of 17 april 1979.
Sedlacek, W A; Heiken, G; Zoller, W H; Germani, M S
1982-06-04
Aerosol samples collected from the 17 April 1979 eruption plume of Soufriere, St. Vincent, at altitudes between 1.8 and 5.5 kilometers were physically and chemically very similar to the ash that fell on the island. Higher altitude samples (7.3 and 9.5 kilometers) had a much lower ash content but comparable concentrations of sulfate, which were above the background concentration found at these altitudes.
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Aerosols from the Soufriere eruption plume of 17 April 1979
NASA Technical Reports Server (NTRS)
Sedlacek, W. A.; Heiken, G.; Zoller, W. H.; Germani, M. S.
1982-01-01
Aerosol samples collected from the April 17, 1979 eruption plume of Soufriere, St. Vincent, at altitudes between 1.8 and 5.5 kilometers were physically and chemically very similar to the ash that fell on the island. Higher altitude samples (7.3 and 9.5 kilometers) had a much lower ash content but comparable concentrations of sulfate, which were above the background concentration found at these altitudes.
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2011-03-30
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2010-04-01
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Perspective View, Mt. Etna, Italy & the Aeolian Islands
2002-11-01
Italy's Mount Etna and the Aeolian Islands are the focus of this perspective view made from an Advanced Spaceborne Thermal and Emission Radiometer (ASTER) image from NASA's Terra spacecraft overlaid on Shuttle Radar Topography Mission (SRTM) topography. The image is looking south with the islands of Lipari and Vulcano in the foreground and Etna with its dark lava flows on the skyline. Vulcano also hosts an active volcano, the cone of which is prominent. In late October 2002, Etna erupted again, sending lava flows down the north and south sides of the volcano. The north flows are near the center of this view, but the ASTER image is from before the eruption. In addition to the terrestrial applications of these data for understanding active volcanoes and hazards associated with them such as lava flows and explosive eruptions, geologists studying Mars find these data useful as an analog to martian landforms and geologic processes. In late September 2002, a field conference with the theme of Terrestrial Analogs to Mars focused on Mount Etna allowing Mars geologists to see in person the types of features they can only sample remotely. http://photojournal.jpl.nasa.gov/catalog/PIA03370
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Nicolsky, D. J.; Freymueller, J.T.; Witter, R.C.; Suleimani, E. N.; Koehler, R.D.
2016-01-01
We reassess the slip distribution of the 1957 Andreanof Islands earthquake in the eastern part of the aftershock zone where published slip models infer little or no slip. Eyewitness reports, tide gauge data, and geological evidence for 9–23 m tsunami runups imply seafloor deformation offshore Unalaska Island in 1957, in contrast with previous studies that labeled the area a seismic gap. Here, we simulate tsunami dynamics for a suite of deformation models that vary in depth and amount of megathrust slip. Tsunami simulations show that a shallow (5–15 km deep) rupture with ~20 m of slip most closely reproduces the 1957 Dutch Harbor marigram and nearby >18 m runup at Sedanka Island marked by stranded drift logs. Models that place slip >20 km predict waves that arrive too soon. Our results imply that shallow slip on the megathrust in 1957 extended east into an area that presently creeps.
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NASA Astrophysics Data System (ADS)
Nemeth, Karoly; Geshi, Nobuo
2017-04-01
On near summit flank eruptions on stratovolcanoes it is commonly inferred that external water to have little or no influence on the course of the eruptions. Hence eruptions are typicaly "dry" that form spatter-dominated fissures and scoria cones. This assumption is based on that in elevated regions - especially on steep slopes - the hydrogeological conditions are not favourable to store large volume of ground water that can have effect on the eruptions. However there is some controversial trend of eruption progression from an early dry eruption below the summit that later turn to be phreatomagmatic as the eruption locus migrates toward the summit. The Suoana Ccrater on top of Miyakejima Island's mafic stratovolcano is a fine example to demonstrate such process. Suona Crater is the topmost crater of the 3 km long fissure aligned chain of small-volume volcanoes that formed in the 7th century flank of the summit region of the Miyakejima mafic stratovolcano. The oval shape crater of Suona (400 x 300 m) is surrounded by a tuff ring that developed over lava flows and epiclastic deposits accumulated in an older caldera forming about a tuff ring that is about 25 m in its thickest section with a basal consistent lava spatter dominated unit gradually transforming into a more scoria-dominated middle unit. A caldera-forming eruption in AD 2000 half-sectioned the Suona Crater exposing of its internal diatreme - crater in-fill - tephra rim succession providing a unique opportunity to understand the 3D architecture of the volcano. Toward the top of the preserved and exposed tuff ring section a clear gradual transition can be seen toward more abundance of chilled dark juvenile particles providing a matrix of a coarse ash that commonly hold cauliflower lapilli and bomb. This transition indicates that the eruption progressed from an early dry explosive phase such as lava fountaining to be a more Strombolian style explosive eruption that later on turned to be heavily influenced by
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ELECTRON ACCELERATION IN CONTRACTING MAGNETIC ISLANDS DURING SOLAR FLARES
DOE Office of Scientific and Technical Information (OSTI.GOV)
Borovikov, D.; Tenishev, V.; Gombosi, T. I.
Electron acceleration in solar flares is well known to be efficient at generating energetic particles that produce the observed bremsstrahlung X-ray spectra. One mechanism proposed to explain the observations is electron acceleration within contracting magnetic islands formed by magnetic reconnection in the flare current sheet. In a previous study, a numerical magnetohydrodynamic simulation of an eruptive solar flare was analyzed to estimate the associated electron acceleration due to island contraction. That analysis used a simple analytical model for the island structure and assumed conservation of the adiabatic invariants of particle motion. In this paper, we perform the first-ever rigorous integrationmore » of the guiding-center orbits of electrons in a modeled flare. An initially isotropic distribution of particles is seeded in a contracting island from the simulated eruption, and the subsequent evolution of these particles is followed using guiding-center theory. We find that the distribution function becomes increasingly anisotropic over time as the electrons’ energy increases by up to a factor of five, in general agreement with the previous study. In addition, we show that the energized particles are concentrated on the Sunward side of the island, adjacent to the reconnection X-point in the flare current sheet. Furthermore, our analysis demonstrates that the electron energy gain is dominated by betatron acceleration in the compressed, strengthened magnetic field of the contracting island. Fermi acceleration by the shortened field lines of the island also contributes to the energy gain, but it is less effective than the betatron process.« less
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2010-02-19
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Teleseismic traveltime tomography of Jeju Island, South Korea
NASA Astrophysics Data System (ADS)
Song, J.; Rhie, J.; Kim, S.; Lee, S. H.
2017-12-01
Jeju Island is the largest volcanic island in South Korea, which lies off the south coast of the Korean Peninsula. It is well known that the volcanism started in the Early Pleistocene (c. 1.7 Ma) and subsequent eruptions during Late Pleistocene to Holocene formed the bulk of the island with a number of small cones. However, the origin of magma and detailed mechanism of eruptions have not been fully understood yet. To address these issues, we applied teleseismic travel time tomography to image the underlying crust and upper mantle of the island. We carefully analyzed 185 teleseismic earthquakes (5.5 < Mw < 7.9) that occurred between Oct. 2013 and Nov. 2015. Broadband waveforms recorded by 23 seismic stations covering the whole island were used to measure travel time residuals of P and S waves using semi-automated adaptive stacking technique. The residuals are mapped as three-dimensional perturbations of velocity using iterative non-linear tomographic process with a subspace inversion technique and the fast marching method for grid based eikonal solver. We used AK135 global reference model as a starting velocity model for tomography inversion. The resulting P wave tomographic images exhibit relatively low velocity anomaly in the upper mantle, which extends to depths of nearly 60 km under the summit of the island, Mt. Halla. The anomaly is likely related to a relatively high-temperature magmatic body, which might be associated to the volcanism lasted until late Cenozoic. To better constrain possible compositions of the anomalies and the existence of melt fractions, we will continue to examine perturbation of Vp/Vs ratios and discuss the evolution of the volcanic island.
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Chadwick, William W.; Geist, Dennis J.; Jonsson, Sigurjon; Poland, Michael P.; Johnson, Daniel J.; Meertens, Charles M.
2006-01-01
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 total uplift since 1992, the largest precursory inflation ever recorded at a basaltic caldera. This extraordinary uplift was accommodated in part by repeated trapdoor faulting, and coseismic CGPS data provide strong constraints for improved deformation models. These results highlight the feedbacks between inflation, faulting, and eruption at a basaltic volcano, and demonstrate that faulting above an intruding magma body can relieve accumulated strain and effectively postpone eruption.
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Mauna Loa eruptive history—The preliminary radiocarbon record
NASA Astrophysics Data System (ADS)
Lockwood, John P.
Radiocarbon dating of charcoal from beneath lava flows of Mauna Loa has provided the most detailed prehistoric eruptive chronology of any volcano on Earth. Three hundred and fifty-five 14C dates have been reviewed, stratigraphically contradictory dates have been rejected, and multiple dates on single flows averaged to give "reliable" ages on 170 separate lava flows (about 35% of the total number of prehistoric Mauna Loa flows mapped to date). The distribution of these ages has revealed fundamental variations in the time and place of Mauna Loa eruptive activity, particularly for Holocene time. As lava flow activity from Mauna Loa's summit waxes, activity on the rift zones wanes. A cyclic model is proposed which involves a period of concentrated summit shield-building activity associated with long-lived lava lakes and frequent overflows of pahoehoe lavas on the north and southeast flanks. At this time, compressive stresses across Mauna Loa's rift zones are relatively high, inhibiting eruptions in these areas. This period is then followed by a relaxation of stresses across Mauna Loa's rift zones and a long period of frequent rift zone eruptions as magma migrates downrift. This change of eruptive style is marked by summit caldera collapse (possibly associated with massive eruptions of picritic lavas low on the rift zones). Concurrent with this increased rift zone activity, the summit caldera is gradually filled by repeated summit eruptions, stress across the rift zones increases, magma rises more easily to the summit, rift activity wanes, and the cycle repeats itself. Two such cycles are suggested within the late Holocene, each lasting 1,500-2,000 years. Earlier evidence for such cycles is obscure. Mauna Loa appears to have been quiescent between 6-7 ka, for unknown reasons. A period of increased eruptive activity marked the period 8-11 ka, coincident with the Pleistocene-Holocene boundary. Other volcanoes on the Island of Hawaii for which (limited) radiocarbon dating
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Moles, A; Heintz, R A
2007-07-01
Fish serve as intermediate hosts for a number of larval parasites that have the potential of maturing in marine mammals such as Steller sea lions (Eumetopias jubatus). We examined the prevalence of parasites from 229 fish collected between March and July 2002 near two islands used by Steller sea lions in Southeast Alaska and island habitats in the Aleutian Islands. Sea lion populations have remained steady in Southeast Alaska but have been declining over the last 30 yr in the Aleutian Islands. Even though the fish samples near the Southeast Alaska haul-outs were composed of numerous small species of fish and the Aleutian Islands catch was dominated by juveniles of commercially harvested species, the parasite fauna was similar at all locations. Eleven of the 20 parasite taxa identified were in their larval stage in the fish hosts, several of which have been described from mammalian final hosts. Four species of parasite were more prevalent in Southeast Alaska fish samples, and seven parasite species, including several larval forms capable of infecting marine mammals, were more prevalent in fish from the Aleutian Islands. Nevertheless, parasites available to Steller sea lions from common fish prey are not likely to be a major factor in the decline of this marine mammal species.
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Ocean Island Volcanoes—Just How Similar Are They?
NASA Astrophysics Data System (ADS)
Poland, M. P.; Peltier, A.; Bonforte, A.; Puglisi, G.
2016-12-01
Basaltic ocean island volcanoes are exceptional natural laboratories for volcanology. They present a range of eruptive styles, unrest and eruptions are frequent, and good accessibility facilitates detailed observation. The most important factors controlling the style and composition of volcanism at ocean islands are the tectonic setting and magma supply. Hawaíi represents an end member in this respect, located in the middle of an old and rapidly moving plate and with the highest magma supply of any ocean island hot spot. Hawaiian volcanoes are thus large, prone to collapse, and have a compositional evolution that reflects varying degrees of partial melt as they pass over the source hot spot. The Galápagos, in contrast, fall at the other end of the spectrum in most respects—the islands are on a young plate near a spreading center and have comparatively low magma supply. Collapse of Galápagos volcanoes is not common, the edifices are much smaller than their Hawaiian counterparts, and compositional evolution is spatially variable due to thin lithosphere and interaction between hot spot and mid-ocean ridge melts. La Réunion is something of a mix between these extremes, being located in the middle of an old but slow-moving plate and with a low magma supply. The resulting volcanoes have a straightforward compositional evolution, are relatively small in size but long-lived, and have unstable flanks. The broad context of magma supply and tectonic setting provides a useful means of interpreting the characteristics of ocean island volcanism. Gross similarities in volcano morphology (shield structure) and eruptive activity (effusive lava flows) create a perception that these volcanoes are analogs for one another. While it is certainly true that insights from Kīlauea have potential application at Piton de la Fournaise, for example, such lessons should not be applied without a good understanding of the substantial differences between volcanoes.
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Literature and information related to the natural resources of the North Aleutian Basin of Alaska.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Stull, E.A.; Hlohowskyj, I.; LaGory, K. E.
The North Aleutian Basin Planning Area of the Minerals Management Service (MMS) is a large geographic area with significant natural resources. The Basin includes most of the southeastern part of the Bering Sea Outer Continental Shelf, including all of Bristol Bay. The area supports important habitat for a wide variety of species and globally significant habitat for birds and marine mammals, including several federally listed species. Villages and communities of the Alaska Peninsula and other areas bordering or near the Basin rely on its natural resources (especially commercial and subsistence fishing) for much of their sustenance and livelihood. The offshoremore » area of the North Aleutian Basin is considered to have important hydrocarbon reserves, especially natural gas. In 2006, the MMS released a draft proposed program, 'Outer Continental Shelf Oil and Gas Leasing Program, 2007-2012' and an accompanying draft programmatic environmental impact statement (EIS). The draft proposed program identified two lease sales proposed in the North Aleutian Basin in 2010 and 2012, subject to restrictions. The area proposed for leasing in the Basin was restricted to the Sale 92 Area in the southwestern portion. Additional EISs will be needed to evaluate the potential effects of specific lease actions, exploration activities, and development and production plans in the Basin. A full range of updated multidisciplinary scientific information will be needed to address oceanography, fate and effects of oil spills, marine ecosystems, fish, fisheries, birds, marine mammals, socioeconomics, and subsistence in the Basin. Scientific staff at Argonne National Laboratory were contracted to assist MMS with identifying and prioritizing information needs related to potential future oil and gas leasing and development activities in the North Aleutian Basin. Argonne focused on three related tasks: (1) identify and gather relevant literature published since 1996, (2) synthesize and summarize
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Spatial analysis of the impacts of the Chaitén volcano eruption (Chile) in three fluvial systems
NASA Astrophysics Data System (ADS)
Ulloa, H.; Iroumé, A.; Picco, L.; Mohr, C. H.; Mazzorana, B.; Lenzi, M. A.; Mao, L.
2016-08-01
The eruption of the Chaitén volcano in May 2008 generated morphological and ecological disturbances in adjacent river basins, and the magnitude of these disturbances depended on the type of dominant volcanic process affecting each of them. The aim of this study is to analyse the morphological changes in different periods in river segments of the Blanco, El Amarillo and Rayas river basins located near the Chaitén volcano. These basins suffered disturbances of different intensity and spatial distribution caused by tephra fall, dome collapses and pyroclastic density currents that damaged hillslope forests, widened channels and destroyed island and floodplain vegetation. Changes continued to occur in the fluvial systems in the years following the eruption, as a consequence of the geomorphic processes indirectly induced by the eruption. Channel changes were analyzed by comparing remote images of pre and post-eruption conditions. Two periods were considered: the first from 2008 to 2009-2010 associated with the explosive and effusive phases of the eruption and the second that correspond to the post-eruption stage from 2009-2010 to 2013. Following the first phases channel segments widened 91% (38 m/yr), 6% (7 m/yr) and 7% (22 m/yr) for Blanco, Rayas and El Amarillo Rivers, respectively, compared to pre-eruption condition. In the second period, channel segments additionally widened 42% (8 m/yr), 2% (2 m/yr) and 5% (4 m/yr) for Blanco, Rayas and El Amarillo Rivers, respectively. In the Blanco River 62 and 82% of the islands disappeared in the first and second period, respectively, which is 6-8 times higher than in the El Amarillo approximately twice the Rayas. Sinuosity increased after the eruption only in the Blanco River but the three study channels showed a high braiding intensity mainly during the first post-eruption period. The major disturbances occurred during the eruptive and effusive phases of Chaitén volcano, and the intensity of these disturbances reflects the
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Tambora Caldera, Sumbawa Island, Indonesia
1988-10-03
STS026-038-056 (29 Sept. - 3 Oct. 1988) --- Tambora Caldera, Sumbawa Island, Indonesia as photographed with a 70mm handheld Hasselblad camera. Tambora is a 6-kilometer-wide and 650-meter-deep Caldera formed in 1815 as a result of a huge volcanic eruption. Gases from the eruption were ejected high into Earth's atmosphere and transported around the globe. The atmospheric gases trapped part of the incoming sunglint, resulting in extremely cold weather. In New England, snow fell in June, and freezes occurred throughout the summer of 1816, which became known as "the year without a summer." This photo was shown by the STS-26 astronaut crew during its Oct. 11, l988 post-flight press conference.
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Waythomas, C.F.
2001-01-01
The formation of lahars and a debris avalanche during Holocene eruptions of the Spurr volcanic complex in south-central Alaska have led to the development of volcanic debris dams in the Chakachatna River valley. Debris dams composed of lahar and debris-avalanche deposits formed at least five times in the last 8000-10,000 years and most recently during eruptions of Crater Peak vent in 1953 and 1992. Water impounded by a large debris avalanche of early Holocene (?) age may have destabilized an upstream glacier-dammed lake causing a catastrophic flood on the Chakachatna River. A large alluvial fan just downstream of the debris-avalanche deposit is strewn with boulders and blocks and is probably the deposit generated by this flood. Application of a physically based dam-break model yields estimates of peak discharge (Qp) attained during failure of the debris-avalanche dam in the range 104 < Qp < 106 m3 s-1 for plausible breach erosion rates of 10-100 m h-1. Smaller, short-lived, lahar dams that formed during historical eruptions in 1953, and 1992, impounded smaller lakes in the upper Chakachatna River valley and peak flows attained during failure of these volcanic debris dams were in the range 103 < Qp < 104 m3 s-1 for plausible breach erosion rates. Volcanic debris dams have formed at other volcanoes in the Cook Inlet region, Aleutian arc, and Wrangell Mountains but apparently did not fail rapidly or result in large or catastrophic outflows. Steep valley topography and frequent eruptions at volcanoes in this region make for significant hazards associated with the formation and failure of volcanic debris dams. Published by Elsevier Science B.V.
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Unravelling the magmatic processes behind zoned fall units on Ascension Island, South Atlantic
NASA Astrophysics Data System (ADS)
Chamberlain, K. J.; Barclay, J.; Preece, K.; Brown, R. J.; Davidson, J.
2015-12-01
Ascension Island, an isolated composite volcano in the south Atlantic, has a wide spectrum of explosive and effusive deposits. Eruptions on the island have produced ash and pumice fall deposits, ignimbrites, scoria cones, lava flows and lava domes, which vary in composition from basalt to rhyolite. We report, for the first time, the presence of multiple, zoned pumice fall deposits. These deposits grade upwards (stepwise or gradationally) from pumice to scoria. We present detailed observations of two key deposits which typify the range in zonation observed in the unusual fall units. Forensic examination of these deposits and their petrological and geochemical characteristics provide critical information about the interactions and processes behind the wide spectrum of magma compositions and past eruptive behaviour on Ascension Island. The first deposit changes gradationally from fayalite-bearing trachytic pumice fall (61.1 wt.% SiO2) at the base, to basaltic trachy-andesite scoria fall (54.5 wt.% SiO2) at the top. The second deposit is more complex. It contains mingled pumice-scoria clasts, has a rapid transition from pumice to scoria and no intermediate clasts were observed. New analyses of H2O, CO2 and key trace elements within melt inclusions combined with systematic whole rock and phenocryst analyses enable us to probe the relationship of these co-erupted magmas to other deposits on the island. This has yielded insights into the magma plumbing system; and improved understanding of the roles that fractional crystallisation and magma mixing play in generating the range in compositions observed at this unique ocean island volcano.
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Searching for structural medium changes during the 2011 El Hierro (Spain) submarine eruption
NASA Astrophysics Data System (ADS)
Sánchez-Pastor, Pilar S.; Schimmel, Martin; López, Carmen
2017-04-01
Submarine volcanic eruptions are often difficult to study due to their restricted access that usually inhibits direct observations. That happened with the 2011 El Hierro eruption, which is the first eruption that has been tracked in real time in Canary Islands. For instance, despite the real-time tracking it was not possible to determine the exact end of the eruption. Besides, volcanic eruptions involve many dynamic (physical and chemical) processes, which cause structural changes in the surrounding medium that we expect to observe and monitor through passive seismic approaches. The purpose of this study is to detect and analyse these changes as well as to search for precursory signals to the eruption itself using ambient noise auto and cross-correlations. We employ different correlation strategies (classical and phase cross-correlation) and apply them to field data recorded by the IGN network during 2011 and 2012. The different preprocessing and processing steps are tested and compared to better understand the data, to find the robust signatures, and to define a routine work procedure. One of the problems we face is the presence of volcanic tremors, which cause a varying seismic response that we can not attribute to structural changes. So far, structural changes could not be detected unambiguously and we present our ongoing research in this field.
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Walker, Lawrence R.; Sikes, Derek S.; DeGange, Anthony R.; Jewett, Stephen C.; Michaelson, Gary; Talbot, Sandra L.; Talbot, Stephen S.; Wang, Bronwen; Williams, Jeffrey C.
2014-01-01
Attempts to understand how communities assemble following a disturbance are challenged by the difficulty of determining the relative importance of stochastic and deterministic processes. Biological legacies, which result from organisms that survive a disturbance, can favour deterministic processes in community assembly and improve predictions of successional trajectories. Recently disturbed ecosystems are often so rapidly colonized by propagules that the role of biological legacies is obscured. We studied biological legacies on a remote volcanic island in Alaska following a devastating eruption where the role of colonization from adjacent communities was minimized. The role of biological legacies in the near shore environment was not clear, because although some kelp survived, they were presumably overwhelmed by the many vagile propagules in a marine environment. The legacy concept was most applicable to terrestrial invertebrates and plants that survived in remnants of buried soil that were exposed by post-eruption erosion. If the legacy concept is extended to include ex situ survival by transient organisms, then it was also applicable to the island's thousands of seabirds, because the seabirds survived the eruption by leaving the island and have begun to return and rebuild their nests as local conditions improve. Our multi-trophic examination of biological legacies in a successional context suggests that the relative importance of biological legacies varies with the degree of destruction, the availability of colonizing propagules, the spatial and temporal scales under consideration, and species interactions. Understanding the role of biological legacies in community assembly following disturbances can help elucidate the relative importance of colonists versus survivors, the role of priority effects among the colonists, convergence versus divergence of successional trajectories, the influence of spatial heterogeneity, and the role of island biogeographical concepts.
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Multi-segment earthquakes and tsunami potential of the Aleutian megathrust
Shennan, I.; Bruhn, R.; Plafker, G.
2009-01-01
Large to great earthquakes and related tsunamis generated on the Aleutian megathrust produce major hazards for both the area of rupture and heavily populated coastlines around much of the Pacific Ocean. Here we use paleoseismic records preserved in coastal sediments to investigate whether segment boundaries control the largest ruptures or whether in some seismic cycles segments combine to produce earthquakes greater than any observed since instrumented records began. Virtually the entire megathrust has ruptured since AD1900, with four different segments generating earthquakes >M8.0. The largest was the M9.2 great Alaska earthquake of March 1964 that ruptured ???800 km of the eastern segment of the megathrust. The tsunami generated caused fatalities in Alaska and along the coast as far south as California. East of the 1964 zone of deformation, the Yakutat microplate experienced two >M8.0 earthquakes, separated by a week, in September 1899. For the first time, we present evidence that earthquakes ???900 and ???1500 years ago simultaneously ruptured adjacent segments of the Aleutian megathrust and the Yakutat microplate, with a combined area ???15% greater than 1964, giving an earthquake of greater magnitude and increased tsunamigenic potential. ?? 2008 Elsevier Ltd. All rights reserved.
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Slow Earthquakes in the Alaska-Aleutian Subduction Zone Detected by Multiple Mini Seismic Arrays
NASA Astrophysics Data System (ADS)
LI, B.; Ghosh, A.; Thurber, C. H.; Lanza, F.
2017-12-01
The Alaska-Aleutian subduction zone is one of the most seismically and volcanically active plate boundaries on earth. Compared to other subduction zones, the slow earthquakes, such as tectonic tremors (TTs) and low frequency earthquakes (LFEs), are relatively poorly studied due to the limited data availability and difficult logistics. The analysis of two-months of continuous data from a mini array deployed in 2012 shows abundant tremor and LFE activities under Unalaska Island that is heterogeneously distributed [Li & Ghosh, 2017]. To better study slow earthquakes and understand their physical characteristics in the study region, we deployed a hybrid array of arrays, consisting of three well-designed mini seismic arrays and five stand alone stations, in the Unalaska Island in 2014. They were operational for between one and two years. Using the beam back-projection method [Ghosh et al., 2009, 2012], we detect continuous tremor activities for over a year when all three arrays are running. The sources of tremors are located south of the Unalaska and Akutan Islands, at the eastern and down-dip edge of the rupture zone of the 1957 Mw 8.6 earthquake, and they are clustered in several patches, with a gap between the two major clusters. Tremors show multiple migration patterns with propagation in both along-strike and dip directions and a wide range of velocities. We also identify tens of LFE families and use them as templates to search for repeating LFE events with the matched-filter method. Hundreds to thousands of LFEs for each family are detected and their activities are spatiotemporally consistent with tremor activities. The array techniques are revealing a near-continuous tremor activity in this area with remarkable spatiotemporal details. It helps us to better recognize the physical properties of the transition zone, provides new insights into the slow earthquake activities in this area, and explores their relation with the local earthquakes and the potential slow