Kamchatka is situated on the Pacific 'Rim of Fire' and is best known for its volcanoes that cause the peninsula to practically percolates with geothermal activity. There are over 200 volcanoes, many of them still active, that contain huge calderas, acid lakes, geysers and natural thermal springs.

Avacha is an active conical stratovolcano, 2741 m high, that is very prominent from down-town Petropavlovsk. A powerful eruption in 1945 left a crater 250 m deep and 330 m across, although the most recent eruption was in 1991, when lava filled the crater and overtopped the rim to produce a flow a kilometre long down the southern slope. This lava plug is still warm, and is likely to be removed explosively within the next 100 years.