A KVERT report on Kliuchevskoi issued on 25 April stated that above-background seismicity, including abundant tremor, prevailed during the week. This report also revealed that the ash explosions of 17-18 April had sent material 1-2 km above the crater. Modest thermal anomalies registered in satellite data for 18-19 April and plumes around that time extended E for 20-200 km. The respective ash-bearing plumes of 20 and 23 April traveled over 10 km NE and 20 km SW. As of 25 April the Concern Color Code remained at Yellow.

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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)