During 26 September to 3 October, seismicity was above background levels at Karymsky and the Concern Color Code was raised from Yellow to Orange. During 25-29 September, 200-270 shallow earthquakes occurred that indicated possible ash-and-gas explosions to heights of 1-1.5 km above the volcano. Interpretations of seismic data suggested that on 2 October at 0633 an ash explosion began that produced a plume to 3.5 km above the volcano. A seismic pause was recorded on 2 October.

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)