Eruptive activity continued through August. During periods of maximum activity ash was ejected to 5 km and bombs to 1 km above the crater rim. Lava flowed to the NW, NE, and SW from the central crater; the largest flow advanced along the NW valley to about 3 km above sea level and crossed a glacier, forming mud flows. A cinder cone has formed inside the central crater.

On 17 August between 0733 and 1027, high-resolution thermal infrared and visual images from polar orbiting weather satellites showed a plume extending about 200 km SE from the volcano below about 6 km altitude. Soviet volcanologists confirmed these observations, reporting that on 16-17 August a 15 km-wide ash plume extended 200 km from the volcano.

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: B. Ivanov, IVP.