In December 2006 Shiveluch underwent heightened seismic and volcanic activity of an intensity not seen since 22 September 2005. During the latter episode, plumes reached ~ 7.5 km altitude (BGVN 30:08). This report covers from September 2005 to December 2006.

Activity during 2005. Seismic levels declined in the weeks subsequent to the previously described 22 September eruption. The Kamchatka Volcanic Eruptions Response Team (KVERT) had raised the Concern Color Code level to orange due to the 22 September 2005 eruption and then lowered it to yellow at the start of November. During October, KVERT noted that weak shallow earthquakes, hot avalanches, and small fumarolic activity persisted. Incandescence at the dome was reported on 13, 15, 17, 22, and 29 October, and thermal anomalies over the lava dome were frequently registered.

On 22 October a weak ash-gas plume extended to the E. Seismic activity decreased further and did not exceed background levels in October and November, and remained at low levels in December. Weak avalanches were reported at the start of November. Weak seismicity and fumarolic activity was registered in December. Numerous thermal anomalies over the lava dome and incandescence at the dome were widely reported (specifically, on 1, 7, 8-11, 15, 17-18, 25, and 27-29 December).

Activity during 2006. The lava dome continued to grow in 2006; overall volcanism and seismicity remained low during January to May 2006. Visual and satellite observations of weak fumarolic activity and thermal anomalies were noted during periods of visibility early in 2006 (13-14, 16-17, 22, and 30-31 January and 1 February). One shallow earthquake was registered on 30 January. On 23 May a thermal anomaly was reported, and on 21, and 27-31 May moderate gas-and-steam plumes were observed.

Three deep earthquakes were recorded, one each day, on 1-2 and 5 June, and a shallow earthquakes was recorded on both 2 and 4 June. On 5 and 8 June gas-and-steam plumes rose over the volcano. A thermal anomaly from the volcanic crater was noted on 2-5 and 7-8 June. Fumarolic activity of the lava dome was observed on 23 and 29-30 June. On 16 and 19 June, gas-and-steam plumes rose to ~ 3-3.5 km altitude from the lava dome summit. A steam plume extending 9.5 km NE from the volcano was observed on a 24 July satellite image. Observers noted frequent fumarolic emissions from the dome (on 1-2, 8, 10, 17-20, 22, and 24-26 July). Frequent thermal anomalies over the dome also were noted (on 4, 7-8, 17-18, and 23-26 July).

In August and September, activity remained the same with periods of fumarolic activity and reports of thermal anomalies. Seismicity remained low except for five earthquakes in the middle of August. Several weak earthquakes were registered throughout October and November, as well as fumarolic activity of the lava dome in periods of good visibility. Sporadic thermal anomalies were recorded (on 6, 8, 14-15, 22, and 27-31 October and 1-2, 6-7, 13-15, and 19-22 November). According to visual and video data, gas-and-steam plumes rose to ~ 3.5 km altitude and extended NW on 23 October. A weak continuous spasmodic volcanic tremor was registered on 29-30 October and 2 November.

Heightened volcanic activity during December began with a strong seismic event on 4 December from 1906-1940. According to satellite data, an ash plume raising up ~ 6 km altitude and extending NW was observed at 2100, and during 2130-2400 gas-and-steam plumes containing ash extended NW at ~ 3.0 km altitude. On 4 December ashfall extended ~ 150 km. Several tens of shallow earthquakes were registered in the following days. On 5 December the level of Concern Color Code was raised from yellow to orange. On 8 December another eruption occurred with ash plumes to ~ 4 km altitude that extended NW.

On 12 December, ash explosions to a height ~ 4 km produced a plume that extended E-SE from 25-460 km, according to satellite data from various sources. According to visual and video data, two separate ash plumes rose to ~ 10 km altitude and extended NW on 16, 17, and 20 December. On subsequent days, satellite data showed ash clouds extended primarily ~ 570 km to the E, as well as to the NE.

On 26 December 2006 the Concern Color Code level was raised to red. At 2130 on 27 December, video data recorded a gas-and-steam plume rising to ~ 3.5 km altitude. An ash plume rose to ~ 10 km altitude and extended E on 25-27 December (figure 9) and N on the 28th. The Concern Color Code level lowered to orange on 28 December 2006, where it remained in early January 2007.

Figure 9. Satellite image of Shiveluch eruption taken on 27 December 2006 using the MODIS instrument on Terra satellite. The image shows a plume blowing SE. In addition, on the white ice surface resides a brownish streak, remnant of an earlier ash fall, which trends from the summit E towards the coast. Courtesy of NASA Earth Observatory.

Geological Summary. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1,300 km3 andesitic volcano is one of Kamchatka's largest and most active volcanic structures, with at least 60 large eruptions during the Holocene. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes occur on its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large open caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

Information Contacts: Olga A. 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, GS RAS (Russia), and the Alaska Volcano Observatory (AVO), a 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; Jeff Schmaltz, MODIS Land Rapid Response Team, NASA Goddard Space Flight Center (URL: http://modis.gsfc.nasa.gov/gallery/); National Aeronautics and Space Administration Earth Observatory (URL: http://earthobservatory.nasa.gov/NaturalHazards).