KVERT reported that during 4-11 May, seismic activity at Kliuchevskoi continued above background levels and a thermal anomaly in the crater was detected on satellite imagery. Lava flows continued to advance on the NW flank. Phreatic activity and ash plumes from lava-flow fronts were noted. Gas-and-steam plumes containing ash rose to altitudes of 6.7 km (22,000 ft) a.s.l. and drifted N during 4-7 May. Ash plumes were seen on satellite imagery drifting NE, NW, W, and E during the reporting period. Ashfall was reported on 4 May and explosions were heard during 3-6 May in the town of Klyuchi, about 30 km to the NE. Based on information from KEMSD and satellite imagery, the Tokyo VAAC reported that on 11 May ash plumes rose to altitudes of 7.6 km (25,000 ft) a.s.l. and drifted SE and E. On 12 May, the Anchorage VAAC reported that ash plumes were visible on satellite imagery. On 15 May, the Tokyo VAAC reported that an eruption plume was possibly seen on satellite imagery to an altitude of 5.2 km (17,000 ft) a.s.l. drifting N. The Level of Concern Color Code 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: Tokyo Volcanic Ash Advisory Center (VAAC), Kamchatkan Volcanic Eruption Response Team (KVERT), Anchorage Volcanic Ash Advisory Center (VAAC)