During 22-29 December, above-background seismicity prevailed under Kliuchevskoi. Gas-and-steam plumes rose 100-300 m above the crater on 23, 24, and 28 December; these extended 3-5 km from the crater, generally SE or SW. On 25 December, a gas-and-steam plume rose 2,000 m above the summit crater. Poor weather obscured observation on other days.

Volcanic tremor under the volcano caused the level of concern to be upgraded to yellow from green during 30 December to 5 January. The upgrade indicated that normal activity could possibly change into an eruption. On 30 December a plume rose 1,500 m and extended 3-5 km SE of the crater. During 31 December-2 January the plume returned to a height of 200-500 m. Poor visibility continued during 3-5 January.

On 6 January the level of concern returned to green where it remained until the end of the month. Despite persistent bad weather, gas-and-steam plumes were observed rising to typical heights of 50 m above the crater on 11 and 19 January. More such plumes were observed 21-24 January rising 100-300 m and extending 2-3 km SE or NE.

Geological Summary. Klyuchevskoy is the highest and most active volcano on the Kamchatka Peninsula. Since its origin about 6,000 years ago, this symmetrical, basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during approximately the past 3,000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 and 3,600 m elevation. Eruptions recorded since the late 17th century have resulted in frequent changes to the morphology of the 700-m-wide summit crater. These eruptions over the past 400 years have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Information Contacts: Vladimir Kirianov, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Tom Miller, 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.