KVERT reported that a thermal anomaly over Sheveluch was identified in satellite images during 14-20 April. During 14-15 April ash plumes rose to 6 km (19,700 ft) a.s.l. and drifted 700 km NW. During 17-19 April plumes of unconsolidated ash resuspended from the flanks by wind rose to 4 km (13,100 ft) a.s.l. and drifted as far as 224 km NW. The sulfur dioxide gas portion of the eruption cloud produced during the notable 11-12 April activity continued to drift E; by 21 April the leading edge of the plume was over part of Greenland. The Aviation Color Code remained at Orange (the second highest level on a four-color scale). Dates are based on UTC times; specific events are in local time where noted.

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)