Report on Akutan (United States) — April 1996
Bulletin of the Global Volcanism Network, vol. 21, no. 4 (April 1996)
Managing Editor: Richard Wunderman.
Akutan (United States) Seismicity decreases and remains low
Please cite this report as:
Global Volcanism Program, 1996. Report on Akutan (United States). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 21:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199604-311320.
54.134°N, 165.986°W; summit elev. 1303 m
All times are local (unless otherwise noted)
The rate of seismicity after 19 April continued to be <5 recorded earthquakes per day, a significant decrease from the number of earthquakes recorded during the seismic crisis of mid-March (BGVN 21:02 and 21:03). Background seismicity had not yet stabilized, but the small number of daily earthquakes through 3 May allowed the level of concern to be downgraded to Green at that time. The daily number of recorded earthquakes continued to be low, with some fluctuations, through 17 May.
Geologic Background. One of the most active volcanoes of the Aleutian arc, Akutan contains 2-km-wide caldera with an active intracaldera cone. An older, largely buried caldera was formed during the late Pleistocene or early Holocene. Two volcanic centers are located on the NW flank. Lava Peak is of Pleistocene age, and a cinder cone lower on the flank produced a lava flow in 1852 that extended the shoreline of the island and forms Lava Point. The 60-365 m deep younger caldera was formed during a major explosive eruption about 1600 years ago and contains at least three lakes. The currently active large cinder cone in the NE part of the caldera has been the source of frequent explosive eruptions with occasional lava effusion that blankets the caldera floor. A lava flow in 1978 traveled through a narrow breach in the north caldera rim almost to the coast. Fumaroles occur at the base of the caldera cinder cone, and hot springs are located NE of the caldera at the head of Hot Springs Bay valley and along the shores of Hot Springs Bay.
Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.