Report on Sheveluch (Russia) — 26 September-2 October 2001
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 26 September-2 October 2001
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2001. Report on Sheveluch (Russia). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 26 September-2 October 2001. Smithsonian Institution and US Geological Survey.
56.653°N, 161.36°E; summit elev. 3283 m
All times are local (unless otherwise noted)
During 28-29 September seismic activity was above background levels and weak, shallow seismic signals (possible collapses and avalanches) were registered. Several small explosions occurred on 30 September, sending ash clouds to the following heights above the dome: 2.5 km at 1323, 3.5 km at 1719, 2.5 km at 1755, and 4.5 km at 1807. An explosion at 2010 produced an umbrella-shaped ash cloud that rose 9 km above the lava dome and extended ~9 km E to W. Large pyroclastic flows traveled ~5 km to the SE. The same day the Concern Color Code was raised from Orange to Red. During 28-30 September thermal anomalies in the active dome area were visible on satellite imagery. Following the eruption, during 30 September at 2100 to 1 October at 0900, seismic activity decreased and the view of the volcano was obscured by clouds. AVHRR satellite imagery at 0757 showed that the ~25-km-diameter ash cloud remained centered over the volcano. On 1 October the Concern Color Code was reduced back to Orange.
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.