KVERT reported that seismic activity at Koryaksky was elevated on 7 and 8 April and at background levels on the other days during 3-10 April. Weak volcanic tremor was detected on 7 April. Gas plumes containing a small amount of ash originating from two vents on the NW flank rose to an altitude of 5.4 km (17,700 ft) a.s.l. and drifted NE, NW, SE, and SW during the reporting period. Gas-and-ash plumes were also seen on satellite imagery and drifted 290 km in multiple directions. On 11 April, KVERT staff reported ashfall in Petropavlovsk-Kamchatsky (30 km S). Ash accumulated to 0.1-2.5 cm thickness near the Institute of Volcanology and Seismology (IVS) FED RAS. The Level of Concern Color Code remained Orange.

Geological Summary. The large symmetrical Koryaksky stratovolcano is the most prominent landmark of the NW-trending Avachinskaya volcano group, which towers above Kamchatka's largest city, Petropavlovsk. Erosion has produced a ribbed surface on the eastern flanks of the 3430-m-high volcano; the youngest lava flows are found on the upper W flank and below SE-flank cinder cones. Extensive Holocene lava fields on the western flank were primarily fed by summit vents; those on the SW flank originated from flank vents. Lahars associated with a period of lava effusion from south- and SW-flank fissure vents about 3900-3500 years ago reached Avacha Bay. Only a few moderate explosive eruptions have occurred during historical time, but no strong explosive eruptions have been documented during the Holocene. Koryaksky's first historical eruption, in 1895, also produced a lava flow.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)