Report on Sheveluch (Russia) — 25 September-1 October 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 25 September-1 October 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Sheveluch (Russia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 25 September-1 October 2002. Smithsonian Institution and US Geological Survey.
56.653°N, 161.36°E; summit elev. 3283 m
All times are local (unless otherwise noted)
During 20-27 September, volcanic and seismic activity at Shiveluch were above background levels. There were four earthquakes with magnitudes 2-2.1, and many smaller ones. Seismic data indicated possible avalanches and ash-and-gas explosions that may have sent material to 5.5 km a.s.l. On 25 September continuous spasmodic volcanic tremor was recorded for 27 minutes. Short-lived gas-and-steam plumes were observed rising to 6.5 km a.s.l. Thermal anomalies were visible on satellite imagery during several days, but ash was not. Shiveluch remained at Concern Color Code Yellow.
Geologic Background. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 volcano is one of Kamchatka's largest and most active volcanic structures. 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 dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. 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.