KVERT reported that seismic activity at Shiveluch continued above background levels during 13-20 April. Based on seismic interpretation, observation, and video data, ash-and-steam plumes possibly rose to altitudes of 5.5-6.5 km (18,000-21,300 ft) a.s.l. throughout the reporting period. Plumes were seen on satellite imagery drifting E, SE, and S and a thermal anomaly was present. Base on pilot reports, satellite imagery, KEMSD, and observations from the Petropavlovsk-Kamchatsky Flight Information Region (FIR), the Tokyo VAAC reported that ash plumes rose to altitudes of 4.6-6.1 km (15,000-20,000 ft) a.s.l. during 18-22 April. They drifted E. The Level of Concern Color Code remained at Orange.

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), Tokyo Volcanic Ash Advisory Center (VAAC)