KVERT reported that seismic activity at Kliuchevskoi was above background levels during 12-19 December. Strombolian activity was noted on 12, 13, 14, and 16 December, and lava effusion on the NW flank continued. Gas-and-steam plumes containing ash rose to an altitude of 8 km (26,200 ft) a.s.l. during 12-14 and 18 December. Analysis of satellite imagery revealed a large daily thermal anomaly in the crater. Ash plumes rose to altitudes of 4-8 km (13,100-26,200 ft) a.s.l. and drifted 500 km E, NE, and SE during 12-14 and 16-18 December.

Based on analysis of satellite imagery, the Tokyo VAAC reported that on 21 December a possible eruption produced a plume to an altitude of 5.2 km (17,000 ft) a.s.l. The plumes drifted N. Ash emissions continued the next day. An eruption on 23 December produced an ash plume to an altitude of 5.2 km (17,000 ft) a.s.l. and drifted NE.

Geological Summary. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

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