Report on Bezymianny (Russia) — 8 August-14 August 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 8 August-14 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, 8 August-14 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)
Volcanic activity decreased after an eruption at Bezymianny on 7 August at 1128. Later in the day, smaller explosions produced ash clouds that rose to 2 km above the dome. Seismic activity was above background levels on 7-8 August, with many small earthquakes occurring within the volcano's edifice and several different seismic signals (explosion, avalanche, collapse) recorded locally. On 9 August a three-pixel thermal anomaly was visible on satellite imagery. The anomaly represented a viscous lava flow that had formed at the dome of the volcano. On 9 August the Concern Color Code was reduced from Red (the highest level) to Yellow and was further reduced on 10 August to Green (the lowest level).
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.