Karymsky exhibited decreased volcanism from late October 2018 through mid-February 2019. Previously reported activity consisted of thermal anomalies, gas-and-steam emissions, and ash plumes. Moderate eruptive activity last occurred in September to early October 2018, which featured thermal anomalies and some ash plumes. Activity then decreased, involving primarily moderate gas-and-steam activity. This reporting period of February-April 2019 describes renewed volcanism involving moderate explosive-eruptive activity, thermal anomalies, and moderate gas-and-steam emissions, according to the Kamchatka Volcanic Eruptions Response Team (KVERT).

Volcanism increased on 16 February 2019 when moderate eruptive activity produced an ash plume that extended for about 55 km SE; KVERT reported that satellite data showed the appearance of a thermal anomaly. Moderate explosive activity and moderate gas-and-steam emissions continued through April 2019. On 22 and 24-26 February 2019, ash plumes rose to an altitude of 3.5 km; satellite data showed ash clouds drifting up to a maximum 216 km, generally E (figure 43). Ash plumes tended to drift 17-190 km during this reporting period. During 8-12 March an ash plume rose to a maximum altitude of 4 km, drifting 100 km E from the volcano.

Figure 43. An ash plume from Karymsky, as seen from the Uzon caldera, on 27 March 2019. Photo by E. Subbotina, Kronotsky Reserve; courtesy of Institute of Volcanology and Seismology (IVS FEB RAS).

Thermal anomalies were registered by KVERT satellite data on ten days in February, six days in March, and 11 days in April. Low-power thermal anomalies identified by MIROVA continued to appear intermittently throughout the reporting period. Thermal alerts based on MODIS satellite instruments analyzed using the MODVOLC algorithm were rare; the only hotspot pixel recorded during this report period was on 10 March 2019, located proximal to the crater summit.

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: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).