Through analysis of seismic data, the Kamchatkan Volcanic Eruptions Team (KVERT) detected a change in the volcano's behavior. For the past 2 years, Karymsky characteristically produced low-level Strombolian activity, including more than 100 earthquakes and gas explosions each day. After 10 July the explosive events began to accompany 1-4 minute segments of harmonic tremor.

A visit on 14-15 July disclosed gas-and-ash explosions to heights of 400-600 m above the crater every 8-10 minutes on average. More vigorous gas-and-ash explosions to 1 km occurred about every 2 hours. Lava continued to flow. During the night of 14-15 July, and the following morning, weak ashfall was observed 3.5 km from the crater. Later that morning, a series of ash explosions occurred with a periodicity of ~5 minutes. The color-coded hazard status remained 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.

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