During September and the first half of October, seismicity remained above background and was indicative of continued low-level Strombolian eruptive activity. Gas-and-ash explosions occurred every 3-25 minutes, commonly generating ash-and-steam plumes 300-700 m high. However, the eruptive activity increased on 13 October. Volcanic bombs were ejected to 500 m above the crater; eruptive plumes from separate explosions rose to 3-5 km above Karymsky and extended >200 km NE and E. AVO analysis of satellite imagery confirmed a hot spot at the volcano.

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.

Information Contacts: Tom Miller, Alaska Volcano Observatory; Vladimir Kirianov, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry.