Based on satellite image observations, the Tokyo VAAC reported that a possible eruption at Chirinkotan on 21 July may have produced an ash plume that rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted SE. A subsequent notice stated that ash was observed in images and then dissipated. SVERT reported that on 22 July a thermal anomaly over Chirinkotan was detected in satellite images as well as steam-and-gas emissions. The Aviation Color Code was raised to Yellow.

Geological Summary. The small, mostly unvegetated 3-km-wide island of Chirinkotan occupies the far end of an E-W volcanic chain that extends nearly 50 km W of the central part of the main Kuril Islands arc. It is the emergent summit of a volcano that rises 3000 m from the floor of the Kuril Basin. A small 1-km-wide caldera about 300-400 m deep is open to the SW. Lava flows from a cone within the breached crater reached the shore of the island. Historical eruptions have been recorded since the 18th century. Lava flows were observed by the English fur trader Captain Snow in the 1880s.

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