KVERT reported that seismic activity in the area of Gorely and Mutnovsky volcanoes increased on 13 June. There is only one seismic station in the area of the two volcanoes, so the source of the seismicity could not be determined. Activity was not visually noted and satellite imagery was not available at the time of the seismicity increase. The level of Concern Color Code was raised to Yellow on 14 June.

Geological Summary. Gorely volcano consists of five small overlapping stratovolcanoes constructed along a WNW-ESE line within a large 9 x 13 km caldera. The caldera formed about 38,000-40,000 years ago accompanied by the eruption of about 100 km3 of tephra. The massive complex includes about 40 cinder cones, some of which contain acid or freshwater crater lakes; three major rift zones cut the complex. Another Holocene stratovolcano is located on the SW flank. Activity during the Holocene was characterized by frequent mild-to-moderate explosive eruptions along with a half dozen episodes of major lava extrusion. Early Holocene explosive activity, along with lava flows filled in much of the caldera. Quiescent periods became longer between 6,000 and 2,000 years ago, after which the activity was mainly explosive. About 600-650 years ago intermittent strong explosions and lava flow effusion accompanied frequent eruptions. Historical eruptions have consisted of moderate Vulcanian and phreatic explosions.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)