KVERT reported that eruptive activity at Bezymianny continued during 18-23 October. Large collapses on the E flanks of the lava dome that began on 17 October continued the next day. A VONA issued at 1616 on 18 October described continuing large collapses and subsequent ash plumes that rose 4.5-5 km (14,800-16,400 ft) a.s.l. and drifted 32 km NW. A large explosion at 1630 produced ash plumes that rose 10-11 km (32,800-36,100 ft) a.s.l. and drifted 50 km NNE, prompting KVERT to raise the Aviation Color Code to Red (the highest level on a four-color scale). According to the Kamchatka Volcanological Station, inclement weather clouds hindered views of the volcano but a roar was heard at about 1650 and a dark ash cloud was visible. KVERT noted that by 2030 the ash cloud had detached and was 250 m long and 70 km wide; the cloud continued to drift NNE at an altitude of 8 km (26,200 ft) a.s.l. At 2117 the Aviation Color Code was lowered to Orange. Within two days, the ash cloud drifted NE and then NW as far as 850 km. Minor ashfall was reported in Kozyrevsk, 45 km W. At 0820 on 20 October an ash plume was identified in satellite images drifting 100 km ENE at altitudes of 4-4.5 km (13,100-14,800 ft) a.s.l. At 0903 the Aviation Color Code was lowered to Yellow. Lava effusion continued; fumarolic activity and dome incandescence were 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.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT), Kamchatka Volcanological Station