KVERT reported that a thermal anomaly over Bezymianny was identified in satellite images during 12-15 March, and intense gas-end-steam emissions continued to rise from the crater. Hot avalanches originating from the top of the lava dome were visible in webcam images at night.

Late on 15 March KVERT reported that activity continued to intensify noting that the number of hot avalanches increased and ash plumes from the avalanches drifted about 100 km SE. The temperature of the thermal anomaly also increased. The Aviation Color Code was raised to Red (the highest level on a four-color scale). Seismic data suggested that a powerful explosive eruption began at 0511 on 16 March. At 0530 webcam images recorded explosions generating ash plumes that rose as high as 15 km (49,200 ft) a.s.l. and drifted 10 km E. Thirty minutes later satellite images indicated continuing ash emissions rising to 15 km a.s.l. Ashfall was reported in Ust-Kamchatsk Village (120 km ENE) during 0650-0730. An ash plume, 79 x 65 km in dimension, was also identified drifting ENE.

Strong explosions continued to produce ash plumes on 16 March, although they were lower-altitude (5-6 km (16,400-19,700 ft) a.s.l.) and had a higher concentration of ash. The plumes drifted E. By 0930 ash plumes were rising to altitudes of 4-4.5 (13,100-14,800 ft) a.s.l.; ash plumes drifted 100 km E. A large ash plume, 120 x 130 km in dimension, continued to drift E at an altitude of 15 km. The Aviation Color Code was lowered to Orange (the second highest level on a four-color scale). By 1307 on 16 March satellite images showed ash plumes drifting 650 km E. The report noted that ashfall was likely occurring in Nikolskoye (370 km ESE) on Bering Island.

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)