KVERT reported that the Strombolian eruption at Klyuchevskoy continued during 20-29 October and a daily bright thermal anomaly was identified in satellite images. Lava fountains sometimes rose as high as 500 m above the summit and fed lava flows that descended the Apakhonchichsky and Kozyrevsky drainages on the SE and S flanks. Phreatic explosions were sometimes generated from the interaction with lava and glaciers on the flanks and caused collapses of older deposits in the drainages. Plumes of the previously deposited ash generally rose as high as 7 km (23,000 ft) a.s.l. and drifted 280 km NE, E, and SE during 22-29 October, though on 23 and 29 October plumes rose as high as 8 km (26,200 ft) a.s.l. Scientists at the Kamchatka Volcanological Station visited the volcano on 28 October and noted that the cinder cone at the summit had grown. They also observed advancing lava on the E flank that extended about 2 km from the summit to 2,700 m elevation, incandescent material being ejected 500 m above the crater, and avalanches in the Apakhonchichsky drainage. Ash plumes rose more than 2 km.

Activity intensified on 31 October. Ash plumes were identified in satellite images rising as high as 10 km (32,800 ft) a.s.l., prompting KVERT to raise the Aviation Color Code to Red (the highest level on a four-color scale). Ash plumes had drifted as far as 1,300 km SSE. Dates and times are in UTC; specific events are in local time where noted.

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), Kamchatka Volcanological Station