KVERT reported that seismic activity at Kliuchevskoi was above background levels 26 December-2 January. Strombolian activity was noted on 25 and 27 December, and lava effusion on the NW flank continued. On 25 December gas-and-steam plumes containing ash rose to an altitude of 5.5 km (18,000 ft) a.s.l. Analysis of satellite imagery revealed a large daily thermal anomaly in the crater. Ash plumes drifted 250 km NE during 25-26 December. On 27 December ashfall was reported in Kozyrevsk village. The Tokyo VAAC reported that on 2 January ash plumes were continuously observed on satellite imagery.

Geological Summary. Klyuchevskoy is the highest and most active volcano on the Kamchatka Peninsula. Since its origin about 6,000 years ago, this symmetrical, basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during approximately the past 3,000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 and 3,600 m elevation. Eruptions recorded since the late 17th century have resulted in frequent changes to the morphology of the 700-m-wide summit crater. These eruptions over the past 400 years have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

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