Based on Tokyo VAAC notices, KVERT reported that an explosive eruption at Bezymianny began at 0822 on 22 October and produced a large ash cloud that rose as high as 9 km (29,500 ft) a.s.l. The Aviation Color Code was raised to Red, the highest level on a four-color scale. The ash cloud identified in satellite images was 100 x 200 km in size. KVERT noted that by 1519 the eruption was over. A large ash cloud was still visible, though it had dropped to lower altitudes of 5-5.5 km (16,400-18,000 ft) a.s.l. and split into a N part (57 x 105 km) and a S part (36 x 67 km). The clouds shiftied direction and drifted as far as 811 km NW and SE. The Aviation Color Code was lowered to Orange. On 23 October a thermal anomaly over the summit was identified in satellite images and growth of a lava dome was noted. The Aviation Color Code was lowered to Yellow.

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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)