After a pyroclastic-flow producing eruption occurred at ~0958 on 7 May, seismic activity decreased but it remained above background levels for most of the week, a new extrusive dome formed, and the Concern Color Code was reduced. A noticeable increase in seismic activity occurred between 1820 and 1852 on 7 May, and may have corresponded to an explosion that produced an ash-and-gas plume. The plume was visible in satellite imagery rising up to 4 km a.s.l. and drifting ~40 km to the WNW. A small amount of ash fell in the town of Kliuchi, 46 km from the volcano. During 11-15 May seismic activity continued to decrease, but remained above background levels. Many small earthquakes occurred at the volcano's edifice. At 0900 on 12 May a new extrusive lava dome was observed from Kliuchi that was steaming intensely, 100 m high, 200 m wide at the upper part of the dome, and had a volume of ~10 million m3. Observers in Kliuchi reported that by 2140 on 13 May the dome had grown ~50 m higher. Weak explosions produced ash-and-steam plumes that rose up to 1 km above the new dome. On 16 May the Concern Color Code at Shiveluch was reduced from Orange to Yellow.

Geological Summary. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1,300 km3 andesitic volcano is one of Kamchatka's largest and most active volcanic structures, with at least 60 large eruptions during the Holocene. 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 occur on its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large open caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. 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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)