Report on Sheveluch (Russia) — 20 March-26 March 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 20 March-26 March 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, 20 March-26 March 2002. Smithsonian Institution and US Geological Survey.
56.653°N, 161.36°E; summit elev. 3283 m
All times are local (unless otherwise noted)
A decrease in the level of activity at Shiveluch during 15-22 March led KVERT to reduce the Concern Color Code from Orange ("eruption may occur at anytime") to Yellow ("volcano is restless"). During the week, several gas-and-steam eruption clouds rose 300-1,500 m above the volcano's lava dome. Seismicity included earthquakes with magnitudes less than or equal to 2.2 at depths of 0-9 km, many local shallow seismic signals (from possible avalanches or weak gas-ash explosions), and episodes of weak intermittent volcanic tremor. Thermal anomalies were observed on AVHRR satellite imagery and no ash was detected.
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.