During a 13 May visit, two explosions (at 1130 and 1428) ejected ash clouds to 1,000 m above the summit. A third explosion was noted at 0140 the next day, but no additional activity was observed during the 14-15 May journey from the volcano.

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: H. Gaudru, SVE, Switzerland; G. de St. Cyr, T. de St. Cyr, and I. de St. Cyr, A.V. Lyon, France; T. Vaudelin, Genève, Switzerland.