SVERT reported that a weak thermal anomaly over Sarychev Peak was visible in satellite images on 10, 12, and 17 May. At 0830 on 16 May satellite images showed an ash plume drifting 50 km SE at an altitude as high as 2.5 km (8,200 ft) a.s.l. The Aviation Color Code was raised to Yellow on 16 May.

Geological Summary. Sarychev Peak, one of the most active volcanoes of the Kuril Islands, occupies the NW end of Matua Island in the central Kuriles. The andesitic central cone was constructed within a 3-3.5-km-wide caldera, whose rim is exposed only on the SW side. A dramatic 250-m-wide, very steep-walled crater with a jagged rim caps the volcano. The substantially higher SE rim forms the 1496 m high point of the island. Fresh-looking lava flows, prior to activity in 2009, had descended in all directions, often forming capes along the coast. Much of the lower-angle outer flanks of the volcano are overlain by pyroclastic-flow deposits. Eruptions have been recorded since the 1760s and include both quiet lava effusion and violent explosions. Large eruptions in 1946 and 2009 produced pyroclastic flows that reached the sea.

Source: Sakhalin Volcanic Eruption Response Team (SVERT)