Report on Bezymianny (Russia) — 19 December-25 December 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 19 December-25 December 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Bezymianny (Russia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 19 December-25 December 2001. Smithsonian Institution and US Geological Survey.
55.972°N, 160.595°E; summit elev. 2882 m
All times are local (unless otherwise noted)
During 14-21 December, many weak shallow earthquakes occurred within the edifice of Bezymianny and other local shallow seismic events (possible avalanches) were registered. In addition, several gas-and-steam explosions occurred, with the highest reported plume rising 4 km a.s.l. and extending 60 km to the NW on 16 December at 0845. During the week, thermal anomalies were visible on satellite imagery. By 25 December a decrease in seismicity led KVERT to reduce the Concern Color Code from Orange ("eruption may occur at any time") to Yellow ("volcano is restless").
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.