Report on Veniaminof (United States) — May 2008
Bulletin of the Global Volcanism Network, vol. 33, no. 5 (May 2008)
Managing Editor: Richard Wunderman.
Veniaminof (United States) Minor ash bursts during February 2008
Please cite this report as:
Global Volcanism Program, 2008. Report on Veniaminof (United States). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 33:5. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.BGVN200805-312070.
56.17°N, 159.38°W; summit elev. 2507 m
All times are local (unless otherwise noted)
Our previous report on Veniaminof (BGVN 31:08) noted the relative quiescence of the volcano through 15 September 2006, with the seismicity remaining low, but above earlier background levels. We received no subsequent reports of seismicity until 11 February 2008, when the Alaska Volcano Observatory (AVO) noted sporadic increases in seismic activity, including tremor episodes that lasted 1-2 minutes and occurred several times per hour.
On 22 February several minor ash bursts from Veniaminof were recorded by the seismic network and observed on web camera footage. The bursts rose to an altitude below 2.7 km; fallout was confined to the crater. Steam plumes emitted from the intra-caldera cone were seen on video footage during 23-25 February and seismic levels were elevated during 23-26 February.
On 27 February, web camera views showed steaming from the cone and occasional small ash bursts that rose to 200 m above the crater. The Aviation color code was raised to Yellow and the Alert Level was raised to Advisory. During 28 February-3 March, views were obscured by cloud cover. However, the elevated seismic activity continued to 4 March and low-level steaming was seen on 29 February during a break in the weather.
Subsequent to the February-March activity, the volcano returned to its quiescent state. AVO reported on 3 May that the Volcanic Alert Level for Veniaminof was lowered to Normal and the Aviation Color Code was lowered to Green due to the absence of ash emissions and elevated surface temperatures in satellite data and webcast imagery. Seismicity was still above past background levels, but the rate and intensity had declined over the previous several weeks.
Web camera imagery of Veniaminof volcano showed that occasional light steaming continued.
Geologic Background. Massive Veniaminof volcano, one of the highest and largest volcanoes on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3700 years ago. The caldera rim is up to 520 m high on the north, is deeply notched on the west by Cone Glacier, and is covered by an ice sheet on the south. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.
Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA; Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA; and Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.avo.alaska.edu/).