KVERT reported that Karymsky's seismicity was above background during the week ending 25 April, an interval when instruments registered ~40-100 volcanic earthquakes per day. The character of the seismicity suggested ash-and-gas explosions up to 1,000 m above the volcano's crater. According to Russian satellite data, ash deposits were detected ~35 km away in various directions from the volcano; these were noted the previous week, on 19-22 April, but not previously reported here. According to other observers on 21 April, an ash-and-gas plume rose 1,500 m above the volcano's crater. The level of concern color code stood at 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)