HR: 14:40h
AN: V13F-05 INVITED     [Abstracts]
TI: Living on the edge: Volcanic edifice failures along the north edge of the Aleutian Ridge
AU: * Coombs, M L
EM: mcoombs@usgs.gov
AF: Alaska Volcano Observatory, U.S. Geological Survey 4200 University Drive, Anchorage, AK 99508 United States
AU: White, S
EM: swhite@geol.sc.edu
AF: Department of Geological Sciences, 701 Sumter Street University of South Carolina, Columbia, SC 29208 United States
AU: Scholl, D W
EM: dscholl@usgs.gov
AF: Moss Landing Marine Laboratories, 8272 Moss Landing Road, Moss Landing, CA 95039 United States
AU: Yogodzinski, G M
EM: gyogodzin@geol.sc.edu
AF: Department of Geological Sciences, 701 Sumter Street University of South Carolina, Columbia, SC 29208 United States
AB: Many Quaternary volcanoes in the Aleutian Island arc show evidence for catastrophic collapse and subsequent debris avalanche deposition on the seafloor. Active volcanoes in the central and western portions of the arc (177°E to 175°W) sit atop the northern edge of the ~4000 m-high Aleutian Ridge, constructed by arc volcanism starting at ~40 ma. This ridge drops off steeply to the north, providing significant runout potential for debris avalanches that flow into the Bering Sea. Reconnaissance studies have found subaerial evidence for large-scale collapse events at many of the volcanically active islands. The position of the Quaternary stratocones relative to the edge of the Aleutian ridge apparently controls their likelihood for collapse. Based on the absence of large pyroclastic sheets on the best-studied islands, most collapses were not accompanied by large-scale explosive eruptions, and thus were likely driven by gravitational failure instead of magmatic injection and caldera formation. GLORIA sidescan sonar data collected in the 1980s image hummocky debris on the seafloor north of several islands, notably Kiska, Gareloi, Tanaga, Kanaga, and Great Sitkin. Multibeam and backscatter data, acquired during the summer of 2005 with the 30 kHz Simrad EM300 system, corroborate the slide profile of several deposits first imaged by GLORIA. A debris avalanche deposit north of Kiska Island (177.6°E, 52.1°N), mapped in the greatest detail, has a hummocky surface that extends 40 km from the north flank of the volcano and covers an area of ~380 km². A 24-channel seismic profile across the short axis of the deposit documents a 500 m-thick, chaotic unit that appears to have either cut into or disturbed a sequence of well-bedded sediments. Despite its thickness, the chaotic unit has only a few tens of meters of surface elevation above the surrounding seafloor. The volume of the debris-avalanche deposit could be as much as 190 km³. This suggests that estimating volumes solely by bathymetric data may underestimate total volumes of debris deposition in areas of easily eroded/deformed sedimentary sequences.
DE: 3022 Marine sediments: processes and transport
DE: 3060 Subduction zone processes (1031, 3613, 8170, 8413)
DE: 3070 Submarine landslides
DE: 8404 Volcanoclastic deposits
DE: 8440 Calderas
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005