KVERT reported that during 10-17 September seismic activity from Kliuchevskoi was above background levels and lava flowed down the SW flank. Satellite imagery analyses showed a large and intense daily thermal anomaly over the volcano. During 9-15 September ash plumes rose to altitudes of 6-7 km (19,700-23,000 ft) a.s.l. and drifted 575 km S and SE based on analyses of satellite imagery and visual observations. Strombolian activity was seen on 11 September. Based on analyses of satellite imagery and information from KEMSD, the Tokyo VAAC reported that possible eruptions on 21 and 22 September produced ash plumes that rose to altitudes of 5.2-6.1 km (17,000-20,000 ft) a.s.l. and drifted E. The Aviation Color Code level remained at Orange.

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