Report on Bezymianny (Russia) — 13 April-19 April 2011
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 13 April-19 April 2011
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2011. Report on Bezymianny (Russia). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 13 April-19 April 2011. Smithsonian Institution and US Geological Survey.
55.972°N, 160.595°E; summit elev. 2882 m
All times are local (unless otherwise noted)
KVERT reported that seismic data suggesting a strong explosive eruption from Bezymianny began at 0820 on 14 April and lasted for 40 minutes. The Aviation Color Code level was raised to Red. Ash fell in Krasny Yar (45 km to the NNW). Cloud cover prevented observations. No activity was observed in satellite imagery; ash plumes may have been below meteorological clouds observed around 8 km a.s.l. The Aviation Color Code level was lowered to orange the next day.
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.