Report on Klyuchevskoy (Russia) — August 1998
Bulletin of the Global Volcanism Network, vol. 23, no. 8 (August 1998)
Managing Editor: Richard Wunderman.
Klyuchevskoy (Russia) Gas-and-ash explosions during 23-25 July
Please cite this report as:
Global Volcanism Program, 1998. Report on Klyuchevskoy (Russia). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 23:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199808-300260.
56.056°N, 160.642°E; summit elev. 4754 m
All times are local (unless otherwise noted)
During 27 July-1 September seismicity under the volcano was generally above background. Hypocenters of earthquakes were concentrated at two levels: near the summit crater and at depths of 25-30 km. Shallow events were more numerous than deeper ones. Clouds often prevented direct summit observations. The level-of-concern fluctuated between Yellow and Green throughout the period.
Beginning on the afternoon of 23 July gas-and-ash explosions occurred every 15-20 minutes. A plume rose 300-500 m over the summit. No unusual changes in seismicity were recorded until noon on 25 July, when earthquake numbers and energy abruptly decreased, and tremor amplitude increased. During the first two weeks of August, earthquakes were concentrated near the summit accompanied by weak tremor. On 19 August tremor decreased but the number of shallow earthquakes increased. No tremor was recorded after 21 August, but on 23 August there was a 23-minute series of shallow earthquakes.
Fumarolic plumes rose to only 50 m above the volcano on 2 August, but some rose to 100 m by 9 August. Plumes rising to 400 m and extending 10 km NE were seen on 18 August. No plumes were seen on 11 and 16 August. On other days the summit was obscured by clouds.
Geologic Background. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.
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.