Report on Bezymianny (Russia) — 5 January-11 January 2005
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
5 January-11 January 2005
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2005. Report on Bezymianny (Russia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 5 January-11 January 2005. 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 at Bezymianny from Yellow to Orange on 7 January as seismicity at the volcano increased. On 11 January, the Concern Color Code was raised from Orange to Red (the highest level). According to seismic data, an explosive eruption of the volcano began at 2002 on 11 January and was inferred to have produced an ash column to 8-10 km a.s.l. No visual or satellite data were available as dense clouds obscured the volcano. Seismic activity was above background levels during the past week and increased continuously. About 60 earthquakes of magnitude 1.25-2.25, and numerous weaker, shallow events registered during 7-11 January. Intermittent volcanic tremor was recorded on 10 January.
Geological Summary. 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.