Report on Bezymianny (Russia) — September 2000
Bulletin of the Global Volcanism Network, vol. 25, no. 9 (September 2000)
Managing Editor: Richard Wunderman.
Bezymianny (Russia) Fluctuating thermal anomaly; gas-and-steam and ash(?)-gas explosions
Please cite this report as:
Global Volcanism Program, 2000. Report on Bezymianny (Russia) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 25:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200009-300250.
55.972°N, 160.595°E; summit elev. 2882 m
All times are local (unless otherwise noted)
This report summarizes activity during June-mid-October 2000. KVERT (Kamchatkan Volcanic Eruption Response Team) resumed reports on 9 June after a shutdown due to funding deficiencies. Early June seismicity was at background levels. On 3-4 and 7-8 June, fumarolic plumes rose 50-300 m above the summit crater and drifted up to 10 km to the W, NW, E, and S. Similar activity continued throughout June, with fumarolic plumes reaching 200 m above the volcano on 21 June and 100 m on 28 June.
Fumarolic activity persisted in July when a continuous plume reached 50-100 m above the summit on 2-5 July. On 16-17 July, a gas-and-steam plume rose 100 m above the dome and extended 25-30 km to the W. On the morning of 19 July, a similar plume rose 50 m above the crater and extended to the SW. Visual observations from the nearby village of Kozirevsk at 1700 on 18 July indicated a weak short-lived explosive eruption and an ash-gas(?) plume that rose about 300 m above the volcano. The plume extended 20 km to the NW. No seismicity was recorded under the volcano. By 0700 on 25 July the thermal anomaly detected on 13 April completely disappeared according to the Alaska Volcano Observatory (AVO). The hazard status for Bezymianny was upgraded from Green to Yellow on 28 July.
Seismicity in early August was above background levels, and shallow earthquakes continued to occur. By 11 August, the number of shallow earthquakes decreased, and the hazard status was downgraded from Yellow to Green. Weak fumarolic activity was observed on 17 August and 20 August, accompanied by an increase in seismicity. On 30 August, a gas-and-steam explosion rose 100 m above Bezymianny and drifted E.
During 2-4 September, a fumarolic plume reached 50 m above the summit, extending S and E. On 12 September weak fumarolic activity was not accompanied by any seismicity above background levels. Bezymianny remained quiet until 17-20 September, when weak fumarolic activity was observed. A gas-and-steam plume rose 100 m above the volcano and drifted W on 21 September. Gas-and-steam plumes seen again on 22-23 and 26-27 September rose to 50 m above the summit, extending to the E and to the W and SW respectively. Weak fumarolic activity continued on 25 September. AVO detected a new, weak 1-pixel thermal anomaly in satellite imagery at 0730 on 21 September. The anomaly persisted and grew to 4 pixels in size by 0709 on 27 September. No eruptions occurred and seismicity was rarely above background levels, so the KVERT Level of Concern Color Code remained at Green throughout the month.
Seismicity increased slightly at the beginning of October. Weak fumarolic activity was observed on 7 October. The thermal anomaly first detected by AVO on 21 September was reconfirmed on 9-10 October. By 0710 on 13 October, satellite imagery revealed that anomaly intensity had increased. The 4-pixel thermal anomaly was observed in a nighttime AVHRR image at 0704 on 18 October. One pixel was saturated at 50°C, and a recovery pixel was also present, indicating intense thermal activity. Background temperature values varied from -10 to -15°C. Thermal anomalies detected in satellite data preceded explosive eruptions of Bezymianny in 1995-2000 by days to weeks. June 1998 was an exception, however, as no explosive event occurred despite intense thermal activity. Only small earthquakes were recorded under the volcano from 14-18 October. Weak fumarolic emissions were detected on 16 October. As a result of the growing and intensifying thermal anomaly, the hazard status was increased from Green to Yellow.
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.