A gas-and-ash explosion at Kluichevskoi on 24 December led KVERT to increase the Concern Color Code from Yellow to Orange. Seismicity was above background levels during 19-25 December, with 6-9 earthquakes recorded each day at ~30-km depth. Intermittent spasmodic volcanic tremor was also recorded. On 19, 21, and 23 December gas-and-steam plumes rose 1-2 km above the crater. Visual observations and video data from the town of Klyuchi revealed that a plume from a gas-and-ash explosion on 24 December at 1210 rose 4 km above the crater and drifted WSW. By the 27th the Concern Color Code had been reduced back to Yellow.

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