KVERT reported that seismic activity at Karymsky was above background levels on 11 and 12 May and at background levels the other days during 9-16 May. Gas-and-ash explosions that produced plumes to an altitude of 3.1 km (10,200 ft) a.s.l. may have occurred on 11 and 12 May. Observations of satellite imagery revealed that on 13 May a thermal anomaly was present in the crater and a steam plume drifted 7 km ESE. An ash plume at an altitude of 2 km (6,600 ft) a.s.l. was spotted on 15 May and drifted E. The Level of Concern Color Code remained at Orange.

Based on observations of sateliite imagery, the Tokyo VAAC reported that on 20 May an eruption plume rose to an altitude of 3.4 km (11,000 ft) a.s.l.

Geological Summary. Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT), Tokyo Volcanic Ash Advisory Center (VAAC)