Seismicity under the volcano was about at background levels from December 1998 through February 1999. On 2 February a M 2 earthquake was located at 23 km depth. Weak volcanic tremor and small earthquakes were registered during the first half of February, and on 21 February a 6-minutes series of shallow earthquakes was detected. The Level of Concern Color Code remained Green.

The volcano was frequently obscured by clouds, making observations only intermittently possible. Fumarolic plumes rising 50-400 m were noted on 10 December, 8, 13-14, and 20 January, 6-7, 13, 16-18, and 22 February. Higher plumes, in the range of 700-800 m above the summit, were observed on 21 and 23 January, and 5 February. On 10 and 15 February fumarolic plumes rose 1,000 m.

Geological Summary. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1,300 km3 andesitic volcano is one of Kamchatka's largest and most active volcanic structures, with at least 60 large eruptions during the Holocene. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes occur on its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large open caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

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.