KVERT reported that during 18-25 May, seismic activity at Kliuchevskoi continued above background levels and a thermal anomaly in the crater was detected on satellite imagery. On 18 May, ashfall was reported from the town of Klyuchi, about 30 km to the NE. According to video data and visual observations, Vulcanian activity at the summit crater and phreatic bursts on the NW flank of the volcano were observed during 22-24 May. Ash plumes rose to 5-8 km (16,000-25,600 ft) a.s.l. and drifted SE. Plumes were visible on satellite imagery drifting N, NE, and SE during the reporting period. Clouds inhibited observation on other days. The Level of Concern Color Code remained at Red.

Based on satellite image observations and information from KVERT, the Tokyo VAAC reported that ash emissions produced possible plumes on 26 May to an altitude of 6.4 km (21,000 ft) a.s.l. and on 27 May to an altitude of 10.1 km (33,000 ft) a.s.l. Plumes drifted E, S, SW, and W. Ash plumes were also observed on satellite imagery during 28-29 May drifting S, SW, and W.

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), Tokyo Volcanic Ash Advisory Center (VAAC)