Report on Bezymianny (Russia) — 24 December-30 December 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
24 December-30 December 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Bezymianny (Russia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 24 December-30 December 2002. Smithsonian Institution and US Geological Survey.
55.972°N, 160.595°E; summit elev. 2882 m
All times are local (unless otherwise noted)
A large explosive eruption occurred at Bezymianny on 25 December. Prior to the eruption, on 23 December, a 1-pixel-large thermal anomaly was detected on satellite imagery that increased to 7-10 pixels on 24-25 December. Seismicity was also slightly above background levels during 24-25 December, and weak intermittent spasmodic tremor was registered on the 25th. That same day at 1321 a very hot plume that probably contained ash was visible on satellite imagery. At this time the Concern Color Code was raised from Yellow to Orange. Moderate explosive activity began on the 25th around 1900. Seismic data revealed that a large explosive eruption occurred on 26 December at 0715. The resultant ash cloud rose 5 km a.s.l. and deposited ash in Kozyrevsk, 55 km NW of Bezymianny. The Concern Color Code was raised to Red.
The eruption continued through the 27th, but activity decreased. Three weak earthquakes were registered on the 26th, and the amplitude of intermittent spasmodic volcanic tremor gradually decreased. KVERT reported that a viscous lava flow was probably being emitted from the volcano's active lava dome. The Concern Color Code was reduced to Orange. On 28 December seismicity was at background levels. Meteorological clouds obscured views of the volcano during 27-28 December. On the 28th the Concern Color Code was reduced to Yellow.
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.