According to observations, video data, and satellite imagery KVERT reported that ash plumes from Shiveluch rose to 10 km (32,800 ft) a.s.l. and drifted E on 16-17 and 20 December. Seismic activity was generally at background levels. Based on satellite imagery, the Tokyo VAAC reported that a possible eruption plume rose to an altitude of 9.1 km (30,000 ft) a.s.l. and drifted E on 24 December. Seismic and video data on 26 December indicated an ash plume above 10 km (32,800 ft.) a.s.l., extending 150 km NE in satellite imagery. The level of Concern Color Code was raised from Orange to Red.

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)