Seismicity was above background levels at Shiveluch during 26-31 January, but on 1 February at 1859 it increased. During the following 2 hours spasmodic tremor occurred and seismic data suggested that an ash-and-gas plume rose to 2.5 km above the lava dome. Afterwards, seismicity returned to levels seen before the increase. During 25 January-2 February several clouds composed of ash, steam, and/or gas were seen, with the highest rising 2 km above the dome. Thermal anomalies were visible on satellite imagery. The Color Concern Code remained at Yellow ("volcano is restless").

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: Tokyo Volcanic Ash Advisory Center (VAAC), Kamchatkan Volcanic Eruption Response Team (KVERT)