"Aerial inspection on 20 September of the volcanoes in the S and central Kuril Islands revealed that Tiatia's summit crater was in a state of moderate fumarolic activity. No individual distinct fumaroles were observed; vapor was being released from the whole crater surface. Numerous vapor sites were also noticed on the outer slopes near the summit crater. There were no remarkable changes near the volcano summit as compared to 1977-78. A certain increase in heat activity was observed near the subordinate vent (formed in 1973) on the S slope. Heat flow measurements made in the vent in 1981 by A. Zemtsov and A. Tron yielded values of q = 7.4 and W/m² = 1.77 cal/cm²s, 1.2 times as large as in 1978. Orange glare was observed by people in Yuzhno-Kurilsk, 50 km SW of the volcano, but we are not sure that it was related to volcanic activity."

Geological Summary. Chachadake, also known as Tiatia, consists of a beautifully symmetrical cone that rises above the broad rim of an erosionally furrowed, 2.1 x 2.4 km wide caldera. The edifice occupies the NE tip of Kunashir Island and morphologically resembles Mount Vesuvius. The pristine-looking conical central cone, mostly formed by basaltic to basaltic-andesite strombolian eruptions, rises 400 m above the floor of the caldera and contains a 400 x 250 m wide crater with two explosion vents separated by a linear septum. Fresh lava flows cover much of the SW caldera floor and have overflowed the rim, extending to the foot of the older somma, which formed during the late Pleistocene or early Holocene. A lava flow from a flank cone on the northern caldera rim reached the Sea of Okhotsk. A major explosive eruption in 1973 followed an initial historical eruption in 1812.

Information Contacts: G. Steinberg, Sakhalin Complex Institute.