Report on Sheveluch (Russia) — 10 July-16 July 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 10 July-16 July 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, 10 July-16 July 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 5-12 July, seismicity generally continued to decline at Shiveluch, but remained above background levels. Earthquakes less than M 1.7 occurred at depths of 0-6 km accompanied by many local shallow seismic signals from possible avalanches or weak gas-and-ash explosions. During the report period the level of volcanic tremor increased; there was a tremor episode on the 9th from 0510 to 0540 in which the amplitude sharply increased to 10 times the previous level. Several short-lived explosions produced ash-and-gas plumes ~1-1.5 km above the lava dome. Some explosions were accompanied by rock avalanches and pyroclastic flows. Gas-and-steam plumes rose 0.2-1.5 km above the dome. Thermal anomalies were visible on satellite imagery, but ash was not. The Concern Color Code remained at Yellow ("volcano is restless").
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.