KVERT reported that seismic activity was at background levels at Karymsky until 0905 to 0915 on 20 December when shallow earthquakes registered under the volcano were accompanied by short-lived explosions. At 2150 the same day, a pilot confirmed the presence of ash at the summit of the volcano and mud traces from melting snow on the edifice slopes. On 21 and 22 December (the end of KVERT's report period) seismicity was above background levels. The Concern Color Code was raised from Green to Yellow.

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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)