KVERT reported that seismic activity at Shiveluch was above background levels during 25 December-2 January. Based on interpretations of seismic data, ash plumes rose to an altitude of 7 km (23,000 ft) a.s.l. on 25 and 26 December, and to an altitude of 5.5 km (18,000 ft) a.s.l. on the other days during the reporting period. An ash plume was seen on 25 December at an altitude of 5.5 km (18,000 ft) a.s.l. and gas-and-steam emissions were noted on 25 and 30 December, and on 1 January. Analysis of satellite imagery revealed a daily thermal anomaly on the lava dome and an ash plume that drifted 40 km NW on 30 December. The Level of Concern Color Code remained at Orange.

Based on information from KEMSD and analysis of satellite imagery, the Tokyo VAAC reported that during 1, 2, 5, and 6 January eruptions produced plumes to altitudes of 4.6-5.8 km (15,000-19,000 ft) a.s.l.

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)