Report on Bezymianny (Russia) — February 1999
Bulletin of the Global Volcanism Network, vol. 24, no. 2 (February 1999)
Managing Editor: Richard Wunderman.
Bezymianny (Russia) Explosions on 25 February send gas-and-ash plume 5 km above the summit
Please cite this report as:
Global Volcanism Program, 1999. Report on Bezymianny (Russia) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 24:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199902-300250.
55.972°N, 160.595°E; summit elev. 2882 m
All times are local (unless otherwise noted)
During February, seismic and volcanic activity at Bezymianny increased in intensity, causing the hazard status to be raised from Green to Yellow on 16 February and then to Orange on 25 February. The activity decreased on the 26th and the "Level of Concern Color Code" was reduced to Yellow. In the first two weeks of the month, numerous weak earthquakes were registered under the volcano, and fumarolic plumes rising up to a few hundred meters above the summit occurred frequently.
Starting on 15 February and continuing the following week, seismicity rose above background levels and 20-40 shallow earthquakes were registered every day. The hazard status was raised to Yellow. Fumarolic plumes continued to rise to a few hundred meters above the summit, and could be seen when not obscured by clouds. Satellite images during the week indicated a persistent thermal anomaly possibly caused by rock avalanches from the summit dome.
The hazard status was raised to Orange on 25 February after volcanic tremor began under the volcano and continued for ~6 hours. Two large explosions during that period each lasted several minutes and a gas-and-ash plume rose 5 km above the summit. Satellite images that morning showed an ash-rich plume heading SE. Over the next few days, using satellite imagery, the ash cloud was tracked for 1,500 km to the SE, but by early on the 27th the cloud had dissipated. Activity declined after the 25th and the hazard status was reduced to Yellow.
On 27-28 February the seismicity was above background levels. Low-level spasmodic tremor continued to be recorded. On the morning of 28 February a steam-and-gas plume rose 300 m. The volcano was obscured by clouds after 28 February.
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.
Information Contacts: Olga Chubarova, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Tom Miller, Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.