A strong explosive eruption that began on the afternoon of 21 October with little advance seismic warning was continuing as of 24 October. Ashfall generally obscured the volcano, but ash plumes were observed rising to 8-12 km altitude on 23-24 October and reached 15 km altitude on the afternoon of 24 October. The eruption plume extended >100 km to the ESE. The resulting ash layer was >10 mm thick at a seismic station 15 km NE, and 5 mm thick at a weather station 30 km SE. The U.S. National Weather Service observed a possible volcanic plume along the Kamchatkan coast on the morning of 22 October, but satellite imagery on 24 October showed heavy banded frontal clouds over the Kamchatka Peninsula with no definitive ash cloud visible.

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: V. Kirianov, IVGG; T. Miller, AVO; J. Lynch, SAB.