SVERT reported that satellite images over Snow, a volcano of Chirpoi, detected weak steam-and-gas emissions on 25 May. A thermal anomaly was detected on 25, 28, and 30 May. Cloud cover obscured views on other days during 26 May-1 June. The Aviation Color Code remained at Yellow.

Geological Summary. Chirpoi, a small island lying between the larger islands of Simushir and Urup, contains a half dozen volcanic edifices constructed within an 8-9 km wide, partially submerged caldera. The southern rim of the caldera is exposed on nearby Brat Chirpoev Island. The symmetrical Cherny volcano, which forms the central cone of the island, erupted twice during the 18th and 19th centuries. The youngest volcano, Snow, originated between 1770 and 1810. It is composed almost entirely of lava flows, many of which have reached the sea on the southern coast. No recorded eruptions are known from Brat Chirpoev, but its youthful morphology suggests recent Strombolian activity.

Source: Sakhalin Volcanic Eruption Response Team (SVERT)