KVERT reported that during 20-27 May seismic activity at Shiveluch did not exceed background levels. Strong gas-and-steam activity was observed on 21 May; cloud cover prevented ground-based observations on the other days. Satellite imagery showed ash plumes drifting 58 km SW on 20 May and a thermal anomaly over the lava dome during 19-21 and 24 May. The Aviation Color Code remained at Orange.

Based on information from KEMSD, the Tokyo VAAC reported that during 30-31 May eruptions produced plumes that rose to altitudes of 7.6-8.2 km (25,000-27,000 ft) a.s.l. and drifted S. According to news articles, ash plumes caused authorities to reroute a number of international flights in the region.

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.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT), BNO News, Tokyo Volcanic Ash Advisory Center (VAAC)