HR: 0800h
AN: V31E-0719    [Abstracts]
TI: The 2006 Eruption of Fourpeaked Volcano, Katmai National Park, Alaska
AU: * Cervelli, P F
EM: pcervelli@usgs.gov
AF: U.S. Geological Survey, Alaska Volcano Observatory, Alaska Science Center 4200 University Drive, Anchorage, AK 99508, United States
AU: West, M
EM: west@gi.alaska.edu
AF: Geophysical Institute, Alaska Volcano Observatory, University of Alaska, Fairbanks, Fairbanks, AK 99775, United States
AB: On September 17, 2006 Fourpeaked Mountain, a glacier-clad stratovolcano with no known Holocene activity, produced a plume of steam, ash, and SO₂, which rose to 6000 m above sea level. The plume was observed by eye-witnesses, seen on weather radar, and also appeared in SO₂-sensitive satellite imagery. Concurrent with the plume, regional seismic stations recorded a swarm of volcano-tectonic earthquakes while an atmospheric infrasound signal was recorded 800 km away. Air and ground reconnaissance revealed a linear series of vigorously steaming vents in the summit glacier, stretching about 1 km down the north flank of the volcano. Debris flows, emanating from disrupted glacial ice, extended many kilometers downslope and contained hydrothermally altered clasts and clay minerals mixed with ice; the largest clasts approached 5 meters in diameter. Airborne gas measurements indicated SO₂ emission rates of thousands of tonnes per day. Ash collected from the glacier surface contained crystal fragments and dense rock particles. Neither the ash nor the debris flows show evidence of juvenile material; most clasts appear to consist of hydrothermally altered material likely derived from rock similar to outcrops exposed near the summit. The eruption response over subsequent weeks and months included regular visual and gas observations and the installation of a basic seismic network and web camera. The ensuing weeks saw continued disruption of the summit glacier, day-long seismic swarms, and the continuation of notable SO₂ levels. As of mid-2007, SO₂ levels had dropped by more than 90% and seismic swarms have been replaced by scattered earthquake activity. Steam plumes continue, but have diminished in vigor dramatically over the last year. The entire staff of the Alaska Volcano Observatory, as well as other collaborators, contributed to this abstract and the Fourpeaked eruption response. The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.
DE: 1817 Extreme events
DE: 8419 Volcano monitoring (7280)
DE: 8430 Volcanic gases
DE: 8488 Volcanic hazards and risks
DE: 8499 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting