KVERT reported that the eruption at Bezymianny continued, characterized by strong fumarolic emissions, lava-dome incandescence, explosions, and hot avalanches. Seismicity increased during 23-28 May. Multiple and notable collapses of hot avalanches on the E flank produced ash plumes that rose to 4-5 km (13,100-16,400 ft) a.s.l. and drifted 70-320 km in multiple directions.

Activity significantly increased on 28 May, local time. According to Kamchatka Volcanological Station (Volkstat), observers saw ash plumes from Bezymianny rising over Klyuchevsky volcano around lunchtime. The plume altitudes gradually increased and late in the evening a large, strong, explosive event occurred; ash plumes rose to 11 km (36,100 ft) a.s.l. and drifted E. According to KVERT satellite data showed ash plumes rising 10-12 km (32,800-39,400 ft) a.s.l. and drifting ESE at 1920. The Aviation Color Code was raised to Red (the highest level on a four-color scale). By 2010 the ash plumes had risen to 15 km (49,000 ft) a.s.l., and previous ash emissions had drifted 365 km SE. Volkstat observers noted that activity began to decline by about 2020 and plume altitudes did not exceed 6 km (19,700 ft) a.s.l. and drifted SE. At 2207 KVERT issued a VONA noting that the Aviation Color Code was lowered to Orange as the most intense phase of the explosive eruption had ended. Ash plumes continued to be emitted, though they rose no higher than 5 km based on webcam views. Two ash plumes were identified in satellite images; the first was drifting 212 km SE at an altitude of 9.5 km (31,200 ft) a.s.l. and the second was drifting 650 km SE at unspecified altitudes. On 29 May at 1000 gas-and-steam plumes with some ash were visible in webcam images rising as high as 4.5 km a.s.l. and drifting 45 km SE. Satellite images showed that the large ash cloud from the day before had drifted 1,635 km SE.

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), Kamchatka Volcanological Station