Deep and shallow earthquakes, as well as volcanic tremor, continued to be recorded beneath the volcano in late May, June, and early July. In late May, between 13 and 44 events/day were recorded. The duration of volcanic tremor increased from 2.5 hours/day on 28 May to 21 hours on 30 May, but then decreased again to 2 hours on 31 May. During the first half of June, 5-20 weak, intermediate-depth earthquakes/day were detected; average duration of volcanic tremor increased from 16 to 24 hours/day during this period. This approximate level of activity continued through 25 June. In the last week of June, the number of weak intermediate-depth earthquakes increased to 18-46/day, but average tremor duration decreased to 0.3-1 hour/day. In early July, weak intermediate-depth earthquakes were recorded at a rate of 14-36/day; tremor was in the 14-24 hours/day range.

Weak fumarolic activity from the central crater was observed throughout June and early July. A steam plume on 10-11 June, possibly caused by a phreatic explosion, rose from the NW slope (2,500 m elev) to ~4,500 m altitude. A phreatic explosion on 15 June from the NE slope produced a plume that rose 2-2.5 km.

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.

Information Contacts: V. Kirianov, IVGG.