Report on Bezymianny (Russia) — 25 July-31 July 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 July-31 July 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, 25 July-31 July 2001. Smithsonian Institution and US Geological Survey.
55.972°N, 160.595°E; summit elev. 2882 m
All times are local (unless otherwise noted)
KVERT raised the Concern Color Code from Green to Orange on 27 July after seismic and satellite data revealed that an extrusive process began at Bezymianny's lava dome. On 23 and 24 July gas-and-steam plumes rose 200-700 m above the dome. On 25 July seismic activity at the volcano increased above background levels as shallow earthquakes and weak, long local seismic events (possible collapses and/or avalanches) were recorded. On 26 July a linear three-pixel thermal anomaly was visible on satellite imagery trending SE from the summit. The Concern Color Code was reduced to Yellow on 31 July because seismic activity was at background levels during 28-31 July and only weak fumarolic activity was observed.
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.