Conical Atsonupuri stratovolcano, it summit dappled by light snowfall, is seen here from the SW. The volcano forms a prominent peninsula joined to the SW side of Iturup Island. A 2-km-wide caldera was subsequently largely overtopped by a central cone that forms the present 1206-m-high summit. Strombolian eruptions have dominated the history of this basaltic volcano, leaving slopes susceptible to slumping and erosion. Only two historical eruptions are known at Atsonupuri, during 1812 and 1932. Photo by Alexander Rybin, 2001 (Institute of Marine Geology and Geophysics, Yuzhno-Sakhalin).
On 6 August, AVO raised the Volcano Alert Level for Kasatochi to Advisory and the Aviation Color Code to Yellow based on increased seismicity detected that day by instruments in the area and by field crews on the island the previous few days. On 7 August, earthquake activity continued. Crews reported rockfalls, ground shaking lasting 5-10 minutes, and a strong sulfur smell. Later that day, an ash plume at an altitude of at least 10.7 km (35,000 ft) a.s.l. was detected on satellite imagery drifting SSW.
On 10 August, a mild explosion from Mayon produced an ash plume to an altitude of 2.7 km (8,900 ft) a.s.l. and drifted ENE.
The Smithsonian's Global Volcanism Program seeks better understanding of all volcanoes through documenting their eruptions — small as well as large — during the past 10,000 years.
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