Eruptions associated with extrusion of viscous lavas continued at Bezymianny into June 2004. Since observers last reported on Bezymianny (BGVN 29:03) they noted substantial ash plumes occurring in June 2004 (table 2). The summary below chiefly comes from weekly reports made by Kamchatka Volcanic Eruptions Response Team (KVERT) and disseminated through the Alaska Volcano Observatory (AVO).

Table 2. A synopsis of some recent eruptions distinguished at Bezymianny (the first three were previously discussed, BGVN 28:10 and 29:03). Taken from KVERT reports.

This report concerns the most recent eruption of Bezymianny which occurred on 19 June 2004. Increased activity on the volcano began during 11 to 14 June, when seismicity rose above background level and 2-3 shallow earthquakes occurred daily.

By 16 June, KVERT elevated Bezymianny's hazard status, raising the Concern Color Code from Yellow to Orange (table 3), signifying that an eruption could occur at any time. On 19 June, the Code was raised to Red, the highest level.

Table 3. The significance of various hazard status categories on the KVERT Concern Color Code Key. This key is regularly posted with their reports.

Explosive activity began at 0840 on 19 June, and according to seismic data, it produced an ash plume that rose ~8-10 km altitude. Satellite imagery revealed that by 1319, the plume had extended ~200 km. The more concentrated portion of the plume was in the zone of ~ 167-189 km from the volcano. At 1439, a large local ash cloud moved to the NNE towards Bering Island. Later in the day, the seismicity level decreased, and KVERT reduced the Concern Color Code to Orange. During 18 to 19 June, an ash cloud extended over 1,000 km E and SE of the volcano, and "possible ash deposits" were inferred 190 km SE of the lava dome. The last time an ash cloud was noted near Korovin Island was on 20 June.

Around this time KVERT noted viscous lava flows at the lava dome. They documented weak, 1- to 4-pixel thermal anomalies over the dome. In the wake of the eruption KVERT reported gas-steam plumes extending ~3.5 km S, NE, and ESE. Following that, they reported no other activity as recently as 25 June.

Geological Summary. The modern Bezymianny, much smaller than its massive neighbors Kamen and Kliuchevskoi on the Kamchatka Peninsula, was formed about 4,700 years ago over a late-Pleistocene lava-dome complex and an edifice built about 11,000-7,000 years ago. Three periods of intensified activity have occurred during the past 3,000 years. The latest period, which was preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large open crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

Information Contacts: Olga A. 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.