Seismicity decreased in May . . . , returning to background levels by 21 May. Seismicity rose above background again on 1 June, when a few steam and ash bursts reached 400 m above the crater rim with a plume drifting to the S. A geologist from IVGG climbed to the crater rim that same day and observed a small explosive eruption from a growing cinder cone in the central crater. All volcanic bombs fell back into the crater, and no lava flows were present. Volcanic tremor was continuing as of 10 June, and there have been rare volcanic earthquakes at depths of >=10 km.

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.

Information Contacts: V. Kirianov, IVGG.