Weak volcanic tremor (0.6-1.3 hours/day) and 1-3 volcanic earthquakes/day were registered in mid-February. During late February and early March, weak tremor continued and the number of seismic events increased slightly (2-5/day). Weak volcanic tremor was consistently registered for 1-3 hours/day throughout March, although it was slightly higher (<=4.5 hours/day) during the third week. Shallow volcanic earthquakes were more variable, ranging from 2 to 18 events/day. Seismic activity during the last week of March included both deep (3-13 events/day) and shallow (1-2 events/day) earthquakes, as well as weak volcanic tremor (4.5-6 hours/day). Weak fumarolic activity from the central crater was observed throughout most of March, and on 29 March a plume extended ~1 km above the crater.

Seismicity continued to increase in the first half of April, consisting of weak deep and shallow earthquakes (4-37 events/day) and weak volcanic tremor (0.5-6 hours/day). Weak fumarolic activity was observed in the central crater on 1-4 and 13 April, and the gas-and-steam plume reached as high as 800 m above the crater.

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.