Maly Semiachik is a caldera. It is located in the northeast part of Sena-Soboliny caldera. A volcano sits inside the caldera in the form of a basaltic volcanic ridge. This ridge consists of three cones made of basalts and basaltic andesites. The cones to the southwest are the youngest on the ridge.
The youngest cones caldera is ~4.5 by 4.0 miles (7 by 6 km) wide. Most of the erutions from this caldera are vulcanian. The biggest of these was in 1804. The active crater has a diameter of 1640 ft (500 m) and a depth of ~560 ft (170 m). A heated lake sits in the crater. The area of this lake is about 0.15 square miles (0.25 sq km). On the banks of the lake and on the inner walls of the crater, fumaroles with temperatures of up to 194 degrees F (90 degrees C) are present. Maly Semiachik has erupted 23 times. The last was in 1952.
Sources of Information:
Erlich, Edward, "Geology of the Calderas of Kamchatka and Kurile Islands with Comparison to Calderas of Japan and the Aleutians, Alaska," United States Department of the Interior Geological Survey, Geoexplorers International, Inc., Denver, Colorado, 300 pp., 1986.