Although more vigorous eruptions took place in May, scientists at the Institute of Volcanology (IV) reported that activity in early April was limited to moderate gas-and-steam emissions. Between 19 and 23 April, seismic stations at Zelenaya and Podkova, 14 and 23 km from the volcano, respectively, detected very low (up to 0.1 µm) tremor.

IV scientists also reported that at 0545 on 9 May an eruption plume rose to ~4 km above the crater and extended 40 km SE early in the eruption. Within two hours activity declined slightly, but pyroclastic outbursts reached 3,000 m above the crater. At 1312, Kozyrevsk and Klyuchi stations detected a strong explosion that sent an eruption column >10 km above the crater. The plume changed directions, drifted NNE, and at 1630 ashfall began in the town of Klyuchi, 47 km from the volcano. The two-hour ashfall deposited 180 g/m² of measured ash in Klyuchi.

A scientist from the Institute of Volcanic Geology and Geochemistry (IVGG) reported that the column from this event extended ENE for several tens of kilometers. He also reported that at 1600 two vents may have been active. Satellite images acquired at 1930 on 9 May indicated the plume extended ~400 km ENE.

At about 0300 on 10 May, visual observations made by IVGG volcanologists revealed that the plume rose to ~6,100 m and extended at least several tens of kilometers SE. They also reported that seismic activity had declined from the high levels recorded during the most explosive events of 9 May. At 0600 on 10 May, GMS-5 satellite imagery showed the plume extended ~700 km ENE.

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: N.A. Zharinov and Yu.V. Demyanchuk, Institute of Volcanology, 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; Vladimir Kirianov, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Bureau of Meteorology, Northern Territory Regional Office, P.O. Box 735, Darwin, NT 0801 Australia.