During 13-20 April, Strombolian activity occurred at Kliuchevskoi, based on observations and video data. Seismic activity continued above background levels and a thermal anomaly in the crater was detected on satellite imagery. Fumarolic activity intensified during 15 and 17-18 April. Gas-and-steam plumes possibly containing small amounts of ash rose to altitudes of 6.3-7.2 km (20,700-23,600 ft) a.s.l. during 15 and 17-18 April and drifted in multiple directions. Based on pilot reports, satellite imagery, and observations in the Petropavlovsk-Kamchatsky Flight Information Region (FIR), the Tokyo VAAC reported several E-drifting ash plumes. They rose to altitudes of 5.2 (17,000 ft) a.s.l. and 8.8 km (29,000 ft) on 18 and 22 April, respectively. On 24 April, KVERT reported mudflows and phreatic activity at lava flow fronts on the NW flank. Resultant ash plumes rose from the lava flow fronts to an altitude of 3.5 km (11,500 ft) a.s.l. The Level of Concern Color Code 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: Kamchatkan Volcanic Eruption Response Team (KVERT), Kamchatkan Volcanic Eruption Response Team (KVERT)