Global Volcanism Program | Image GVP-02368
Maly Semiachik is located within several nested Pleistocene calderas and composed of three overlapping edifices along a NE-SW line. Activity migrated to the SW, eventually forming the youngest cone, Ceno-Semiachik. It contains the historically active Troitsky crater, which formed during an explosive eruption about 400 years ago. It contains a hot, acidic lake this 1972 photo.
Photo by Oleg Volynets, 1972 (Institute of Volcanology, Petropavlovsk).