Based on analyses of satellite imagery, SVERT reported that on 22 August a gas-and-ash plume rose 500 m above Grozny Group and drifted 15 km NE. Fumarolic activity increased during 23-25 August. Observers reported that an ash plume rose to 5 km (16,400 ft) a.s.l. on 25 August. That same day the Tokyo VAAC reported that a possible eruption from Etorofu-Yake-yama, a lava dome of the Grozny Group, may have produced a plume that rose to an altitude of 4 km (13,000 ft) a.s.l. and drifted E.

Geological Summary. The Etorofu-Yakeyama (Ivan Grozny) complex is located in the center of Iturup Island. It has a 3-3.5 km diameter caldera open to the south, where a large extrusive andesitic dome was emplaced. Several other lava domes of Holocene age were constructed to the NE; extrusion of these domes has constricted a former lake in the northern side of the caldera to an extremely sinuous shoreline. Recorded eruptions, the first of which took place in 1968, have been from the central Yakeyama (Grozny) dome.

Sources: Sakhalin Volcanic Eruption Response Team (SVERT), Tokyo Volcanic Ash Advisory Center (VAAC)