KVERT reported that during 18-25 May explosive activity at Shiveluch continued and a thermal anomaly was observed daily in satellite imagery. Ground-based observers and satellite imagery indicated that a viscous lava flow continued to effuse in the active crater, and was accompanied by fumarolic activity and lava-dome incandescence. On 19 May seismic data indicated that possible ash plumes rose to an altitude of 9.5 km (31,200 ft) a.s.l. On 20 May observers noted ash plumes rising to altitudes of 8-9 km (26,200-29,500 ft) a.s.l.; satellite images showed ash plumes drifting 410 km SW. The Aviation Color Code remained at Orange.

Based on information from KVERT and KEMSD, and analyses of satellite images, the Tokyo VAAC reported that during 26-29 May ash plumes from eruptions and possible eruptions rose to altitudes of 7-9.1 km (23,000-30,000 ft) a.s.l. and drifted SE, W, and SW.

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