KVERT reported that 27 August-3 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. On 27 August, activity increased; ash plumes rose to an altitude of 6 km (19,700 ft) a.s.l. and drifted 120 km SE. Strombolian activity was observed during 27-30 August. Phreatic explosions occurred on the SW flank on 29 and 30 August. Ash plumes rose to an altitude of 6.5 km (21,300 ft) a.s.l. on 30 August and drifted 278 km SE.

Based on analyses of satellite imagery and information from the Yelizovo Airport (UHPP), the Tokyo VAAC reported a possible eruption on 3 September. Subsequent images showed continuing emissions. Later that day a notice stated that ash had dissipated. Another possible eruption that day produced a plume that rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted E. During 4-7 September eruptions reported by KVERT and seen in satellite imagery produced ash plumes that rose to altitudes of 5.2-7 km (17,000-23,000 ft) a.s.l. and drifted NW, E, and SE. The Aviation Color Code level remained at Orange.

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)