Tokyo VAAC reported a possible eruption took place at Ketoi stratovolcano in Russia's Kuril Islands at 23:30 UTC on September 20, 2018. The last eruption of this volcano took place in 1960.
Volcanic ash was not identifiable in satellite imagery and there was no notable additional information supplied.
Thermal anomaly was detected at the volcano during July and August 2013 as well as occasional gas and steam emissions.
Increased fumarolic activity from Ketoi was noted in satellite imagery on May 4, 2010.
The first historical eruption at the volcano took place from 1843 (July) to 1846. It had Volcanic Explosivity Index of 2 and is still its largest known eruption.
Other confirmed eruptions took place in 1924 and 1960. Both VEI2.
The circular, 10-km-wide (6.2 miles)Ketoi island, which rises across the 19-km-wide (11.8 miles) Diana Strait from Simushir Island, hosts of one of the most complex volcanic structures of the Kuril Islands.
The rim of a 5-km-wide (3.1 miles) Pleistocene caldera is exposed only on the NE side. A younger 1172-m-high (3 845 feet) stratovolcano forming the NW part of the island is cut by a horst-and-graben structure containing two solfatara fields.
A 1.5-km-wide (0.9 miles) freshwater lake fills an explosion crater in the center of the island. Pallas Peak, a large andesitic cone in the NE part of the caldera, is truncated by a 550-m-wide (1 804 feet) crater containing a brilliantly colored turquoise crater lake. Lava flows from Pallas Peak overtop the caldera rim and descend nearly 5 km (3.1 miles)to the SE coast.
The first historical eruption of Pallas Peak, during 1843-46, was its largest.
Featured image credit: NASA