Report on Bezymianny (Russia) — 1 August-7 August 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 1 August-7 August 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, 1 August-7 August 2001. 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 was raised from Yellow to Red (the highest level) on 7 August after a relatively large eruption occurred that day. Prior to the eruption, during 28 July-3 August, seismic activity was at background levels; weak, long local seismic events (possible collapses and/or avalanches) were recorded, and weak fumarolic activity was observed. On 6 August AVHRR imagery showed a three-pixel thermal anomaly on the volcano. On 7 August at 1128 an ash cloud was observed from the town of Klyuchi rising 5 km above the volcano and drifting to the ESE. By 1215 the ash cloud was at a maximum height of 10 km.
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.