During the period 13 April-25 May, seismicity under the volcano remained above background level and earthquakes at depths of 25-30 km were recorded. Fumarolic plumes rose 50-200 m above the volcano during 6-9, and 11-16 April. These plumes were seen to move 5 km to the SE of the volcano.

At 1608 on 17 April, a series of shallow earthquakes of up to M 2 were recorded. The following day there was no measurable activity. A series of strong, explosive earthquakes lasting up to 10 minutes was recorded as far as 70 km from the volcano on 22 April. Hypocenters of earthquakes recorded in late May were concentrated at two levels: near the summit crater and at depths of 25-30 km. Starting at 2300 local time 24 May, a series of shallow earthquakes in the M 1.5-2.0 range were recorded.

Fumarolic plumes were seen 50-500 m above the volcano on 24, and 26 April, although clouds prevented observation during most of the week 20-27 April. Plumes 50-100 m above the summit were recorded on 27-29 April, and 11 and 14 May. During 13-24 May, a fumarolic plume rose 50-100 m above the volcano and drifted 1-5 km S and SE. On 25 May the plume rose 50 m above the summit.

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.