This report covers the period January-April 2000. As of 28 April 2000, KVERT (Kamchatkan Volcanic Eruption Response Team) temporarily suspended operations because of a lack of funding. During most of this four-month period, seismicity at the volcano was at background levels, with shallow earthquakes and weak fumarolic activity accompanied frequently by fumarolic plumes. The plumes rose from 50 to 1,500 m above the volcano and extended in various directions as far as 10 km from the vent. The volcano frequently was obscured by clouds.

Twice during the reporting period, however, the activity level increased sufficiently so that the hazard level was raised from Green to Yellow. The first of these events occurred during 29 January-3 February when seismicity was above background levels with shallow earthquakes and tremor registered. On 29 January, a fumarolic plume rose 1,500 m above the crater extending 30 km to the SE. On 30 January and 1 February, a plume rose 50-500 m above the crater and extended up to 15 km S. According to reports from pilots of Northwest and Reeve Aleutian Airlines, and an observer from Alaska Volcano Observatory on the Reeve flight, a gas-and-steam plume was observed at 1440 on 30 January rising as high as 8-10 km altitude. On the morning of 3 February the volcano was quiet. According to visual reports from from Kliuchi (~30 km NE of the volcano) and pilot reports, a short-lived eruption at 1708 on 3 February sent an ash-poor plume to altitudes of 8-9 km; instruments measured an accompanying increase in seismicity. According to analysis of a satellite image at 1825 on 3 February the plume extended 40 km SSE and contained a large amount of water or ice.

During the subsequent week (4-10 February), seismicity continued above background levels and shallow earthquakes and tremor were registered. At 1815 on 8 February, seismic data indicated that a short-lived explosion probably occurred, because a series of shallow events were recorded. On 4-5 February, a fumarolic plume rose 200-500 m above the crater and extended 3-40 km W and SW.

During the period 11 February to 2 March, seismicity at the volcano returned to near background level accompanied by typical events noted earlier. But during 3-9 March, seismicity at the volcano increased again and the hazard level was raised again to Yellow. During this period, shallow earthquakes were registered. On 3-4 March a steam-and-gas plume rose 1,500 m above the volcano. On 5-7 March, a fumarolic plume rose 100-300 m above the crater. On 8 March, a steam-and-gas plume rose 1,000 m above the volcano extending 5 km to the NW.

Seismicity returned to background levels on 13 March and the hazard level was reduced to Green. This situation prevailed throughout the remainder of March and April. Shallow earthquakes, fumarolic activity, and plumes continued as in the earlier portion of the reporting period.

Geological Summary. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Information Contacts: Olga Chubarova, 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.