KVERT reported that seismic activity at Karymsky was at background levels during 25 April-2 May. Possible activity was characterized by gas-and-ash plumes that rose to altitudes of 2-2.5 km (6,600-8,200 ft) a.s.l. Based on seismic interpretation, a gas-and-ash explosion may have occurred on 26 April. Observations of satellite imagery revealed that a thermal anomaly was present in the crater on 25, 27, and 28 April. Based on airport data and information from KEMSD, the Tokyo VAAC reported that an eruption plume rose to altitudes of 3.7 km (10,000-17,000 ft) a.s.l. during 6-7 May. Ash was not detected on satellite imagery. The Level of Concern Color Code remained at Orange.

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)