A small amount of ash began to be visible in gas-and-steam emissions at Klyuchevskoy beginning at 1020 on 24 October, prompting KVERT to raise the Aviation Color Code to Yellow (the second lowest level on a four-color scale). Later that day video images showed an ash plume rising as high as 6 km (19,700 ft) a.s.l. and drifting 40 km NE. The Aviation Color Code was raised to Orange. KVERT and the Tokyo VAAC noted that during 25-28 October ash plumes rose to 5.5 km (18,000 ft) a.sl. and drifted 15-20 km SE, E, and NW. A weak thermal anomaly over the volcano was identified on 18 and 24 October.

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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)