During 13 October-29 December, seismicity under Kliuchevskoi was above background level. During 13 October- 2 November the activity occurred at depths of 20-30 km, but during 3-16 November, hypocenters were concentrated both near the summit crater and at depths of 25-30 km. Volcanic tremor recorded on 10-16 November was followed by tremor under the volcano and earthquake hypocenters 25-30 km deep during 17 November-14 December.

Gas-and-steam plumes rose 100 m above the crater on 18, 25, and 30 October, and on 1-2, 17-18, 23, and 28 November. A gas-and-steam plume rose 70 m above the summit crater on 6-7 November; by 8 November the plume rose 1 km above the crater and extended 5 km NW. By 9 November, the plume returned to a more typical height of 50-100 m. On 11-12 and 14-16 November, gas-and-steam plumes rose 100-200 m. During 2-6 December a gas-and- steam plume rose 300-1,000 m and extended 5-10 km SE to SW. On 7 December, a fumarolic plume rose less than 300 m above the summit crater. A gas-and-steam plume rose 300-700 m above the summit crater and extended 3-10 km NE and SW on 8-9 and 12 December. On 23, 24, and 28 December, a gas- and-steam plume rose 100-300 m and extended 3-5 km SE to SW. A fumarolic plume rose 2 km above the volcano on 25 December.

The level of concern was upgraded to yellow from green during 3-16 November, indicating that normal activity could possibly change into an eruption. During 17-23 November, although seismicity continued above background, the level of concern returned to green. On 1 December, the level of concern was again upgraded to yellow but returned to green as of 15 December.

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- Kamchatskiy 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.