As reported in BGVN 31:11, after a period of moderate volcanic activity following the extensive eruption of 9 May 2006, heightened activity occurred at Bezymianny during December 2006 before returning to moderate activity through early 2007. This report covers the period from May through December 2007. It was drawn mainly from reports of the Kamchatkan Volcanic Eruption Response Team (KVERT).

Based on satellite data from 10 May 2007, KVERT reported that a large thermal anomaly with a temperature of ~ 51°C appeared over Bezymianny's summit lava dome.

At about 0330-0400 on 12 May, an explosive eruption may have occurred, according to seismic data from Kozyrevsk. Ash plumes rose to an altitude of 4 km and were visible on satellite imagery drifting in multiple directions. Ashfall was reported in the town of Klyuchi, a spot ~ 47 km NE of the volcano. On 13 May, an elongated thermal anomaly was seen on satellite imagery to the SE of the dome, which decreased in size through 17 May. That day, hunters saw a large (200 m wide) mudflow along the Sukhaya Khapitsa river.

KVERT reported that Bezymianny seismicity was at background during May-September 2007, but increased in early October. Satellite imagery observations showed a thermal anomaly in the crater on 4, 6, 8, and 11 October; fumarolic activity was observed during 6-7 and 10-11 October. Based on seismic interpretation, a hot avalanche probably occurred on 10 October and small eruptions also occurred on 14 October.

The Tokyo Volcanic Ash Advisory Center (VAAC) reported ash plumes to altitudes of ~ 10 km on 14 October. Those of 15 October reached 7.3-9.1 km altitude and drifted E and SE. A strong thermal anomaly was present in the crater around this time. Slightly elevated seismicity occurred during 16-19 October before returning to background during19-20 October. Based on observations of NOAA satellite images by the Tokyo VAAC, a stripe of ash deposits appeared on the ESE flank by 18 October.

Based on seismicity, KVERT interpreted that a series of explosions or collapses from lava flow fronts occurred on 5 November 2007. Two avalanches and an ash plume were also detected. Satellite imagery revealed a thermal anomaly over the lava dome. According to Aleksei Ozerov, the 5 November activity was caused by dome collapse. This demolished a significant section of the SE dome, involving a total volume of almost 200,000 m³. The collapse produced a debris avalanche that traveled almost 3 km downslope.

According to a TERRA MODIS image on 9 November, a very bright (probably high temperature) gas-steam plume rose to about 35 km altitude. [This unusually tall plume height has not been confirmed.] On 10 November, KVERT reported continued growth of a viscous lava flow from the summit dome.

During an overflight around this time observers saw a 4-km-long deposit on the SE flank laid down by pyroclastic flows on 5 November. Lava flow-front collapses from older lava flows on the SE flank were also evident. Visual observations and video footage analysis indicated that gas-and-steam plumes drifted NE on 9 November and S on 13 November. Based on observations of satellite imagery, the Washington VAAC reported that an ash plume at an altitude of ~6.4 km drifted E on 15 November. Visual observations and video footage showed gas-and-steam plumes on 17 and 18 November.

Seismicity was above background during 19-20 November. A thermal anomaly occurred at the crater during 16-17 and 21 November. An ash plume reached 4.3 km altitude on 2 December. Seismicity was at background through the rest of December, except during 21-25 December, when it again rose. Ash plumes up to 4.5 km altitude and avalanches were registered on 23 December.

A paroxysmal explosive eruption occurred between 0917 and 1020 UTC on 24 December 2007 and a large column rose to ~ 13.0 km altitude. According to satellite data, ash clouds extended from the volcano over 850 km to the NE on 24-25 December. According to KVERT volcanologists, who circled the volcano by helicopter with cameras, this eruption destroyed a part of lava dome.

Geological Summary. The modern Bezymianny, much smaller than its massive neighbors Kamen and Kliuchevskoi on the Kamchatka Peninsula, was formed about 4,700 years ago over a late-Pleistocene lava-dome complex and an edifice built about 11,000-7,000 years ago. Three periods of intensified activity have occurred during the past 3,000 years. The latest period, which was preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large open 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 Girina, Kamchatka Volcanic Eruptions Response Team (KVERT), a cooperative program of the Institute of Volcanic Geology and Geochemistry, Far East Division, Russian Academy of Sciences, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/), the Kamchatka Experimental and Methodical Seismological Department (KEMSD), GS RAS (Russia), and the Alaska Volcano Observatory (USA); Alaska Volcano Observatory (AVO), cooperative program of the U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), the Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and the Alaska Division of Geological and Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA; Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); Hawai'i Institute of Geophysics and Planetology (HIGP) Hot Spots System, University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Vladivostok Times (URL: http://www.vladivostoktimes.ru/).