During 10-17 May seismicity was above background levels at Karymsky and the rate of earthquakes slightly increased in the middle of the report week. The character of seismicity suggested that weak ash-and-gas explosions, gas blow-outs, and debris avalanches occurred. Observations from a helicopter on 10 May revealed that a new ~100-m-high cone had grown inside the crater and a lava flow was seen on the volcano's SSE slope. Thermal anomalies and an ash-and-steam plume were visible on satellite imagery. Karymsky remained at Concern Color Code Yellow ("volcano is restless").

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)