The previous report on Shiveluch (BGVN 29:05) covered activity until 27 May 2004. From May 2004 until September 2004, seismicity at Shiveluch was above background, with many shallow earthquakes recorded 0-5 km beneath the active lava dome, and Shiveluch remained at Concern Color Code Orange. Periods of continuous spasmodic tremor were recorded in May, June, July, and October 2004. Gas-and-steam plumes rising to 3-6 km altitude were frequent, sometimes drifting up to 10 km or more. A small lava flow on top of the active dome, first observed on 21 May, continued to flow until 28 May. On 19 June, a likely ash cloud was seen 10-20 km S of the volcano. The lava dome continued to grow in Shiveluch's active crater.

On 6 September at 2054 an explosion produced small pyroclastic flows and an ash plume that rose to ~ 5.5 km altitude. According to satellite data, 1- to 12-pixel thermal anomalies were registered over the lava dome on 15-16 September 2004. During 23-29 September, 26 strong shallow earthquakes up to M 2.3 were recorded. An explosion on 25 September was accompanied by small pyroclastic flows. The Kamchatka Volcanic Eruptions Response Team (KVERT),again reported seeing a new lava flow at Shiveluch's lava dome around 26 October.

Based on interpretations of seismic data, possible ash-and-gas explosions up to 7 km altitude occurred throughout October (figure 8), November, and December 2004. Possible minor ash-and-gas explosions and hot avalanches also occurred. On 28 December a gas-and-steam plume extended as far as 50 km E.

Figure 8. A dark plume of ash streamed from the Shiveluch at 0110 UTC on 20 October 2004, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this image. MODIS observed several such plumes in October. Fainter plume(s) to the SW can be seen from Bezymianny or Kliuchevskoi, both of which were emitting ash plumes during the first week of October.

During January and February 2005, seismicity decreased slightly at Shiveluch but remained above background levels, with weak shallow earthquakes occurring beneath the active dome. Possible weak ash-and-gas explosions and hot avalanches occurred throughout January and February, and gas-and-steam plumes rose up to 2-7 km altitude.

On 13 January, several ash explosions up to 5 km altitude and a pyroclastic flow probably occurred. The Tokyo Volcanic Ash Advisory Center (VAAC) reported an eruption of Shiveluch on 17 January at 1625 with a plume that rose to a height of ~ 4.5 km altitude. On 6 February a pyroclastic flow traveled ~ 2 km down the volcano's flank. On 17 February ash deposits were seen on the volcano's snow-covered lava dome extending to the SE and S.

A large eruption occurred at Shiveluch from 1825 on 27 February to 0100 on 28 February, leading KVERT to raise the Concern Color Code from Orange to Red (the highest level). Meteorological clouds obscured the volcano during the eruption. According to satellite data (NOAA 16 at 1656 UTC on 27 February), a 45-pixel thermal anomaly was registered near the dome (band 3). This anomaly was probably related to a large pyroclastic flow on the SW flank. At this time analysts detected a 45-km-long ash cloud on satellite imagery trending NW of the volcano. At 0900 on the 28th, ash deposits were noted in the town of Klyuchi, ~ 46 km from the volcano. Satellite imagery from 1205 on 28 February showed ash deposits W of Shiveluch covering an area of 24,800 km². Later that day, an ash cloud extending more than 360 km was centered over the western half of Kamchatka. On 1 March the Concern Color Code was reduced to Orange. Prior to the 27 February eruption, seismicity was above background levels and ash-and-gas plumes were seen on video rising to ~ 3 km above the lava dome.

Explosions deposited ash in Ust'-Hairyuzovo village, about 250 km to the W, on 27 and 28 February, and on 2 March. The seismic station at Shiveluch stopped working on 27 February. According to visual and video data on 2 March, part of a large pyroclastic flow was observed on the SW flank of the volcano. According to satellite data from the USA and Russia, a 2- to 23-pixel thermal anomaly was registered at the dome on 1-3 March. Clouds obscured the volcano at other times. Shiveluch remained at Concern Color Code Orange.

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, the Kamchatka Experimental and Methodical Seismological Department (KEMSD), GS RAS (Russia), and the Alaska Volcano Observatory (USA); 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; Tokyo Volcanic Ash Advisory Center, Tokyo Aviation Weather Service Center, Haneda Airport 3-3-1, Ota-ku, Tokyo 144-0041, Japan (URL: https://ds.data.jma.go.jp/svd/vaac/data/).