KVERT reported that a thermal anomaly over Karymsky was visible in satellite images during 15-22 April. Explosions during 17-19 and 21 April generated ash plumes that rose as high as 7.5 km (24,600 ft) a.s.l. and drifted 500 km NE. SE, and E. A powerful explosion at 0805 on 20 April (local time) generated ash plumes that rose as high as 11 km (36,100 ft) a.s.l. and drifted more than 2,000 km NE. KVERT raised the Aviation Color Code to Red (the highest level on a four-color scale). Ashfall was reported in the territory of the Kronotsky Reserve (Semyachinsky, Valley of Geysers), 50 km NE, and at Cape Nalychevo, 100 km S. Explosions continued through the day; ash plumes rising to 5 km (16,400 ft) a.s.l. were visible in satellite images at 1500, local time. The previous ash plume was about 505 x 130 km and drifted NE, S, and SE at an altitude of 8.7 km (28,500 ft) a.s.l. The Aviation Color Code was lowered to Orange by 1544, local time, on 20 April.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

Geological Summary. Karymsky is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the S side of the Pleistocene Dvor volcano and is located outside the N 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 enclosing caldera formed about 7,600-7,700 radiocarbon years ago; construction of the stratovolcano began about 2,000 years later. The latest eruptive period began about 500 years ago, following a 2,300 years of quiescence. Much of the cone is covered by lava flows less than 200 years old. Recorded eruptions have been Vulcanian or Vulcanian-Strombolian with moderate explosive activity and occasional lava flows from the summit crater.