Report on Bezymianny (Russia) — 20 December-26 December 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 20 December-26 December 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Bezymianny (Russia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 20 December-26 December 2006. Smithsonian Institution and US Geological Survey.
55.972°N, 160.595°E; summit elev. 2882 m
All times are local (unless otherwise noted)
The level of Concern Color Code for Bezymianny was raised from Yellow to Orange on 24 December due to an increase in incandescent avalanches, seismicity, and the intensity of a thermal anomaly at the summit. Within a few hours, a series of ash explosions and "ash avalanches" produced plumes that rose to altitudes of 6-10 km (19,700-32,800 ft) a.s.l. and drifted NE. The level of Concern Color Code was raised to Red. On 25 December, KVERT reported that seismic activity returned to background levels and explosive activity ceased. The level of Concern Color Code was returned to Orange.
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.