Shiveluch erupted at 0209 on 22 May (BGVN 26:04) and produced a mushroom-shaped ash column to an estimated altitude of ~20 km. According to reports from Klyuchi, the event destroyed both the new dome (first observed on 12 May) and the W part of the old dome. GMS satellite imagery at 1432 on 22 May showed the eruption cloud as it continued to diffuse over the Kliuchevskoi volcanoes; at that time the estimated plume area reached ~50,000 km². The hazard status remained at Red as of 22 May.

On May 23, an approximately 10-pixel anomaly with temperatures at 30-49°C was observed on satellite images. The anomaly was large and elongated to the S. It may signify a new pyroclastic-flow deposit.

By 24 May the hazard status had been lowered to Orange and, by 31 May, to Yellow. The hazard status was unchanged until 29 June, when a short-lived explosion sent an ash plume to a height of 1,200 m above the dome; associated pyroclastic flows had runouts of ~2.5-3.0 km. During the period from the end of May to the end of June, gas-and-steam plumes were observed rising 500-1,200 m above the dome. Seismic activity remained above background with earthquakes of M 2-3, and many small earthquakes within the edifice. On 8 June a short-lived explosion sent an ash plume 2,000 m above the dome accompanied by 2- and 3-minute-long, shallow seismic events.

During the week of 22-28 June, instruments registered seven M 2 earthquakes, many small earthquakes within the volcano's edifice, local seismic signals (explosions, avalanches, collapses), and episodes of weak spasmodic volcanic tremor. Based on seismicity, a possible increase in eruptive vigor occurred at 1500 on 28 June, a time when tremor and the number of shallow earthquakes increased.

At 1150 on 29 June, the aforementioned short-lived explosion occurred. The hazard status was again raised to Orange. Seismic data recorded on 29 June suggested possible explosion plumes that ascended to ~6 km above the dome (~8.5 km altitude). According to a Tokyo VAAC report, at 0300 on 30 June the ash plume attained 7.3 km altitude.

At 1250 on June 30 another short-lived explosion sent an ash plume to ~8.0 km altitude. The top part of a mushroom-like plume slowly extended to the E. Pyroclastic flows passed 5 km down the Baidarnaya River. Weak volcanic tremor and local seismic signals (avalanches) continued. Starting at 0100 on 2 July, earthquakes occurred in greater number, larger magnitudes, and at greater depth (~5 km). By 6 July the hazard status was returned to Yellow.

Subsequently, seismic activity continued above background levels. A magnitude 2 earthquake accompanied many smaller ones within the edifice, some 3-minute-long shallow seismic events, a variety of local seismic signals, and episodes of weak tremor. In mid-July this spasmodic tremor increased. At 1900 on 14 July it reached velocity-characterized amplitudes of 1.7 x 10^-6 m/s; at 2020 that day it reached 2.0 x 10^-6 m/s; at 0300 on 16 July it increased to 2.5 x 10^-6 m/s and finally, after 2300 on July 15, it attained 4.0 x 10^-6 m/s. Accordingly, the hazard status was set to Orange and visual observations from Klyuchi at 2100 on 15 July indicated that a gas plume rose 1,500 m above the dome. Seismic data suggested the plume was accompanied by explosions.

An AVHRR image (number 12.01196.05:03) at 1803 on 15 July revealed a 3-pixel thermal anomaly near the SW flank of Shiveluch. The maximum band-3 temperature was 44°C within a background near 22°C. No associated ash was observed in the imagery.

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 Chubarova, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; 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; Anchorage Volcanic Ash Advisory Center (VAAC), NOAA Alaska Aviation Weather Unit, 6930 Sand Lake Road, Anchorage, AK 99502-1845, USA (URL: http://vaac.arh.noaa.gov/); Tokyo Volcanic Ash Advisory Center, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/).