Based on analyses of satellite imagery, KVERT reported that during 22-29 April a large bright thermal anomaly was detected over Kizimen daily and ash plumes drifted 135 km in multiple directions. Ground-based observations indicated that gas-and-steam plumes with a small amount of ash rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted W during 20-21 April. The Aviation Color Code remained at Orange. On 3 May seismic data indicated a possible series of ash plumes and avalanches. An ash plume may have risen to an altitude of 10 km (33,000 ft) a.s.l. The Aviation Color Code was raised to Red. On 4 May seismicity decreased but remained high. Satellite imagery showed ash plumes at altitudes of 4-6 km (13,100-19,700 ft) a.s.l. The Aviation Color Code was lowered to Orange.

Geological Summary. Kizimen is an isolated, conical stratovolcano that is morphologically similar to St. Helens prior to its 1980 eruption. The summit consists of overlapping lava domes, and blocky lava flows descend the flanks of the volcano, which is the westernmost of a volcanic chain north of Kronotsky volcano. The 2334-m-high edifice was formed during four eruptive cycles beginning about 12,000 years ago and lasting 2000-3500 years. The largest eruptions took place about 10,000 and 8300-8400 years ago, and three periods of long-term lava dome growth have occurred. The latest eruptive cycle began about 3000 years ago with a large explosion and was followed by intermittent lava dome growth lasting about 1000 years. An explosive eruption about 1100 years ago produced a lateral blast and created a 1.0 x 0.7 km wide crater breached to the NE, inside which a small lava dome (the fourth at Kizimen) has grown. Prior to 2010, only a single explosive eruption, during 1927-28, had been recorded in historical time.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)