Seismic activity at Karymsky was above background levels during 24-31 August, with 100-280 shallow earthquakes occurring daily. Based on seismic interpretation, ash plumes may have risen to an altitude of 5.9 km (19,400 ft) a.s.l. Observations of satellite imagery revealed that a thermal anomaly was present in the crater on 24 and 30 August. Ash plumes were also present and drifted SE on 24 August and NE during 28-30 August. The Level of Concern Color Code remained at Orange.

Based on information from KEMSD, satellite imagery, observations in the Petropavlovsk-Kamchatsky Flight Information Region (FIR), and KVERT, the Tokyo VAAC reported that ash plumes rose to altitudes of 4.3-6.1 km (14,000-20,000 ft) a.s.l. during 31 August and 2-3 September. Ash was not identified on satellite imagery on 31 August.

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