Explosive activity from summit and flank vents emitted ash and lava October-December 1989 and January 1990. Up to 5 ejections/minute from three vents in the summit crater sent ash to 2 km above the summit in December, with a visible plume stretching 20 km from the volcano. Lava fountaining, 30-50 m high from SE flank vents at 4100-4200 m altitude, fed two lava flows that moved SE and E to 2,500 m altitude. Violent explosive activity from the summit crater resumed 29 January, ejecting a 6-km ash plume that extended 60 km from the volcano [see also 15:3]. An incandescent cloud 600-1,500 m high pulsated at the base of the plume, which generated lightning at its top. Ashfall on the Bering Islands (~375 km SE of the volcano) was reported 1 February. Activity also occurred from a SE-flank crater.

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 and E. Zhdanova, IV.