A lava dome continued to grow in the active crater at Shiveluch (also called Sheveluch). In accord with the hazard associated with lava dome growth, the level of concern from 7 November 2003 to 2 January 2004 was yellow. During this ~ 2-month interval, US and Russian satellites recorded thermal anomalies averaging 1-3 pixels.

Increasing seismicity in December was accompanied by gas-steam plumes with varying heights of 50-800 m. Sometimes the plumes extended over 10-30 km to the E, as was noted on 30 November and 2-3 December.

Seismicity was at background levels during most of November. On 29-30 November instruments detected a series of shallow events lasting 3-4 minutes. On November 29-30 and December 1-4, weak shallow earthquakes were registered. Similar earthquakes also occurred at depths of 0-5 km beneath the active dome during 19 December 2003 to 2 January 2004.

On 13 December geophysicists noted a series of weak, local, and continuous seismic events interpreted as possibly resulting from the descent of hot avalanches, but visual observations revealed only weak fumarolic activity. Later, on 11, 12, 15, and 16 December, people in the town of Klyuchi saw gas-steam plumes rise up to 100-400 m above the dome.

Eight strong earthquakes registered in December. Two occurred on 14 and 16 December; ;they were of ML over 2.25 in the depth range 0-5 km. Three occurred on 20 December; they were of ML 1.9-2.0 in the depth range 0-10 km. Three total earthquakes occurred in the two days 28 December and 1 January; they were of ML 1.7-2.5 in the depth range 2-5 km.

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 Girina, Kamchatka Volcanic Eruptions Response Team (KVERT), a cooperative program of the Institute of Volcanic Geology and Geochemistry, Far East Division, Russian Academy of Sciences, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia, the Kamchatka Experimental and Methodical Seismological Department (KEMSD), GS RAS (Russia), and the Alaska Volcano Observatory (USA); Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), the Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and the Alaska Division of Geological and Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.