During 5-12 October, KVERT reported that seismic activity at Bezymianny was at background levels. Based on observations of satellite imagery, a thermal anomaly was present in the crater on 4, 6, 8, and 11 October. Fumarolic activity was observed during 6-7 and 10-11 October. Based on seismic interpretation, a hot avalanche probably occurred on 10 October.

Based on observations of satellite imagery and seismic interpretation, a small eruption occurred on 15 October. Ash plumes drifted SE and a strong thermal anomaly was present in the crater. Based on information from KEMSD and observations of satellite imagery, the Tokyo VAAC reported that an ash plume rose to altitudes of 7.3-9.1 km (24,000-30,000 ft) a.s.l. and drifted E and SE. The level of Concern Color Code was raised from Yellow to Red.

No ash plumes were present on 16 October, and seismicity was only slightly above background levels. The level of Concern Color Code was lowered to Orange.

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.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT), Tokyo Volcanic Ash Advisory Center (VAAC)