During 20-27 December, seismicity remained above background levels at Shiveluch. Seismic data indicated that six ash-and-gas explosions reached heights of 2-3 km above the lava dome, and hot avalanches possibly occurred. Several smaller earthquakes at depths of 0-6 km were recorded. Weak, intermittent, spasmodic tremor was registered during 21-25 December. On 25 December during 1945-2045, the amplitude of volcanic tremor sharply increased. According to visual data from Klyuchi, on 19 December at 1238 and 1514, short-lived explosions sent gas-and-ash plumes to heights of ~5.5 and 5 km a.s.l., respectively. Following the first explosion, pyroclastic flows traveled SE; after the second, they traveled to the S, inside the Baidarnaya River. The runout of both pyroclastic flows was 3 km. Shiveluch remained at Concern Color Code Yellow.

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)