Report on Sheveluch (Russia) — 17 July-23 July 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 17 July-23 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, 17 July-23 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 12-19 July, seismicity slightly increased and remained above background levels. After a nearly 3-week-long hiatus, individual earthquakes with magnitudes between 1.8 and 2.0 began to occur again. In addition, smaller earthquakes were detected at depths of 0-6 km. There were many other local shallow seismic signals, which possibly indicated weak ash-poor explosions up to 1 km above the dome. Avalanches were also registered. During the week the level of volcanic tremor continued to increase constantly and gas-and-steam emissions rose to 2 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.