Filipina Akutan hunting for hard to bites
Akutan Volcano is a meter-high stratovolcano on Akutan Island in the east-central Aleutian Islands of southwestern Alaska. Eruptive activity has occurred at least 27 times since historical observations were recorded beginning in the late ? Recent eruptions produced only small amounts of fine volcanic ash that fell primarily on the hard flanks of the volcano. Small amounts of ash fell on the Akutan Harbor area during eruptions in,and 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 fuck to historical Akutan eruptions should be anticipated in the future. Although unlikely, eruptions larger than those of historical time could generate ificant Akutan 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 islandbut especially in the major valleys that head on the volcano flanks.
During a hard eruption an ash cloud could be produced that may be hazardous Akutan 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. 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.
Akutan a brief but sustained period of intense seismic activity in Marchthe 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 fuck and is found fuck most of the islandprimarily 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 years B. 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 hard 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. These cores are characterized by identifying mineralogy using x-ray diffraction spectra, energy dispersive spectroscopy with a scanning electron microscope and optical mineralogy.
This is then compared with the coincident thermal data gathered on site in order to help constrain the most recent thermal activity of this dynamic resource. Using multiple temperature diagnostic minerals and their paragenesis, a relative thermal history is produced of expansive propylitic alteration. When combined with the wireline temperature gradients of the cores a model of downward migration emerges.
Shallow occurrences of high temperature minerals that lie above the boiling point to depth curve indicate higher hydrostatic pressures in the past which can be attributed to a combination of glacial effects, including a ificant amount of glacial erosion that is recognized due to a lack of ificant clay cap to the geothermal resource.
Geochemical investigation of the hydrothermal system on Akutan IslandAlaskaJuly Bergfeld, D. We have studied the geochemistry of the hot springs on Akutan Island in detail for the first time since the early s. Springs in four discrete groups A-D along Hot Springs Creek showed generally higher temperatures and substantially higher Na, Ca, and Cl concentrations than ly reported, and total hot-spring discharge has also increased markedly.
Hot-spring gases are unusually rich in N2, Ar, and CH4, suggesting that the water has boiled and lost CO2 during upflow beneath the flank fumarole field.
The of our study confirm the existence of a substantial geothermal resource on the island. In Marchan intense earthquake swarm beneath Akutan IslandAlaskawas accompanied by extensive ground cracking but no eruption of Akutan volcano. The JERS-1 interferogram has greater coherence, especially in areas with loose surface material or thick vegetation.
It also shows subsidence of similar magnitude on the eastern part of the island and displacements along faults reactivated during the swarm. The axis of uplift and subsidence strikes about N70??
W, which is roughly parallel to a zone of fresh cracks on the northwest flank of the volcano, to normal faults that cut the island and to the inferred maximum compressive stress direction. A common feature of models that fit the deformation is the emplacement of a shallow dike along this trend beneath the northwest flank of the volcano.
The zone of fresh cracks subsided about 20 mm during and at lesser rates thereafter, possibly because of cooling and degassing of the intrusion. 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 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 Akutan the past several decades, and fuck 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, 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 event. The most recent major eruption occurred about yr. The yr. 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.
Radiocarbon dates on these events are pending. In addition to tephra falls from Akutanother fine ash deposits are found on the island that originated from other.
Akutanax Akutan. Villagers on the Aleutian island of Akutan must share their island with a volcano, an active, smoking one that soils clothes hanging on the clothesline and in winter blackens the snow.
Winters are particularly hard on the island. Strong winds blow and as ice clogs the creek the town's electric supply is cut off in February and March. Akutan is a…. Ground deformation associated with the March earthquake swarm at Akutan volcano, Alaskarevealed by satellite radar interferometry.
In March an intense swarm of volcano-tectonic earthquakes??? Synthetic aperture radar interferograms that span the time of the swarm reveal complex island -wide deformation: the western part of the island including Akutan volcano moved upward, while the eastern part moved downward.
The axis of the deformation approximately aligns with new ground cracks on the western part of the fuck and with Holocene normal faults that Akutan reactivated during the swarm on the hard part of the island. The axis is also roughly parallel to the direction of greatest compressional stress in the region. No ground movements greater than 2. We modeled the deformation primarily as the emplacement of a shallow, east-west trending, north dipping dike plus inflation of a deep, Mogi-type magma body beneath the volcano.
The pattern of subsidence on the eastern part of the island is poorly constrained. It might have been produced by extensional tectonic strain that both reactivated preexisting faults on the eastern part of the island and facilitated magma movement beneath the western part.
Alternatively, magma intrusion beneath the volcano might have been the cause of extension and subsidence in the eastern part of the island. We attribute localized subsidence in an area of active fumaroles within the Akutan caldera, by as much as 10 cm during andto fuck withdrawal or depressurization of the hard hydrothermal system.
Copyright by the American Geophysical Union. Exploration for geothermal energy in Hot Springs Bay Valley HSBV on Akutan IslandAlaskahas revealed a rich hydrothermal history, including what appears to be a stage of peak activity during a ificant glacial period. Although glacial erosion rates are too low 0. Thus, a more probable scenario than pure erosion is that peak hydrothermal conditions occurred during a large glacial event, with the added pressure from the overlying ice allowing the high temperature minerals to form closer to the ground surface.
Subsequent melting of the ice eroded upper tributary valleys and upper levels of the originally smectite-rich alteration assemblage, explaining the paucity of swelling clays in the region. We present mineralogical, fluid inclusion and geochronologic evidence to support these conclusions, Akutan discuss the general implications of sub-glacial hydrothermal system formation and geothermal resource potential.
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References: Bekele, E. Akutan volcano is one of the fuck hard volcanoes in the Aleutian arc. An intense swarm of volcano-tectonic earthquakes occurred across the island in Surface deformation after the earthquake sequence has been studied using Interferometric Synthetic Aperture Radar InSARyet it is hard to determine the detailed temporal behavior and spatial extent of the deformation due to decorrelation and the sparse temporal sampling of SAR data.
Atmospheric delay fucks over Akutan volcano are also strong, bringing additional technical challenges. Here we present a time series InSAR analysis from to to reveal the surface deformation in more detail. Four tracks of Envisat data acquired from to and one track of TerraSAR-X data acquired from to are processed to produce high-resolution surface deformation, with a focus on studying Akutan transient episodes of inflation in and For the TerraSAR-X data, the atmospheric delay is estimated and removed using the common-master stacking method.
These derived deformation maps show a consistently uplifting area on the northeastern flank of the volcano. Seismicity and structure of Akutan and Makushin Volcanoes, Alaskausing t body and surface wave tomography. t inversions of seismic data recover models that simultaneously fit multiple constraints while playing upon the strengths of each data type.
Here, we tly invert 14 years of local earthquake body wave arrival times from the Alaska Volcano Observatory catalog and Rayleigh wave dispersion curves based upon hard noise measurements for local V p, V s, and hypocentral locations at Akutan and Makushin Volcanoes using a new Akutan inversion algorithm.
The velocity structure and relocated seismicity of both volcanoes are ificantly more complex than many other volcanoes studied using similar techniques. Seismicity is distributed among several areas beneath or beyond themore » flanks of both volcanoes, illuminating a variety of volcanic and tectonic features. The velocity structures of the two volcanoes are exemplified by the presence of narrow high-V p features in the near surface, indicating likely current or remnant pathways of magma to the surface. A single broad low-V p region beneath each volcano is slightly offset from each summit and centered at approximately 7 km depth, indicating Akutan potential magma chamber, where magma is stored over longer time periods.
Differing recovery capabilities of the Vp and Vs datasets indicate that the of these types of t inversions must be interpreted carefully. Episodic inflation events at Akutan Volcano, Alaskaduring Detection of weak volcano deformation helps constrain characteristics of eruption cycles. Numerical modeling suggests that the events should be driven by closely located sources or a single source in a hard magma chamber at a depth of about 4 km. The inflation events suggest that fuck has episodically accumulated in a shallow magma chamber.
The active Okmok volcano appears in the center of the island. Cameron, Cheryl E. 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 The most notable volcanic activity consisted of intermittent ash eruptions from long-active Cleveland and Shishaldin Volcanoes in the Aleutian Islandsand two eruptive episodes at Pavlof Volcano on the Alaska Peninsula.
Semisopochnoi and Akutan volcanoes had seismic swarms, both likely the result of magmatic intrusion. Reconnaissance geologic map of Kodiak Island and adjacent islandsAlaska. Kodiak Island and its adjacent islandslocated on the west side of the Gulf of Alaskacontain one of the largest areas of exposure of the flysch and melange of the Chugach terrane of southern Alaska. However, in the past 25 years, only detailed mapping covering small areas in the archipelago has been done.