On 15 June KVERT reported that the temperature of a thermal anomaly identified in satellite images had increased, and that the webcam recorded a gas-and-steam plume rising above Bezymianny to 4 km (13,100 ft) a.s.l. and drifted SSE. Hot avalanches of material originated from the lava dome. An explosive event began at 1653 on 16 June, producing an ash cloud 28 x 25 km in size that drifted NE. The Aviation Color Code was raised to Red (the highest level on a four-color scale), but lowered back down to Orange about 5 hours later. At 2110 the ash cloud was 212 x 115 km in size and drifting E; the leading edge of the cloud was about 245 km E.

Geologic Background. Prior to its noted 1955-56 eruption, Bezymianny had been considered extinct. The modern volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large horseshoe-shaped 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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)