Mount Bezymianny is an extremely active stratovolcano on the central part of the Kamchatka Peninsula in the Russian Far East. The volcano was thought to be extinct until 1955, when it began a volcanic cycle that ended in 1956 with an explosive eruption caused the summit to collapse and created a large horseshoe-shaped crater. This has subsequently been filled in by further eruptive episodes on Bezymianny. The current summit is 2882 m high, but it is overshadowed by the nearby Kamen and Kluchevskaya volcanoes at 4579 m and 4750 m respectively.
Mount Bezymianny in 1957 (top) and the late 1980s (bottom) showing the growth of a new summit within the 1956 crater. Top image G.Y. Bogoyavlenskaya/Oregon State University. Bottom image Yuri Doubik/Institute of Volcanology, Petropavlovsk/Oregon State University.
Bezymianny is thought to have formed about 4700 years ago, on the remains on an older, Pleistocene, volcano active between 11 000 and 7000 years ago. It has undergone three periods of intense activity since its formation, but was apparently inactive for about a thousand years prior to its 1955 reactivation.
Bezymianny last erupted in 2011, but underwent a period of seismic activity (earthquakes) in February-March 2012. On 24 August 2012 the Kamchatka Volcanic Eruption Response Team detected a resumption in seismic activity, followed by the onset of fumarole activity (gas emissions) on 25 August. An explosive eruption occurred on 2 September, causing to an ash cloud rising to a height of 10-12 km, which then drifted 1500 km to the northeast. This was followed on 3 September by lava flows and ash avalanches.
Ash cloud from Mount Bezymianny. Kamchatka Volcanic Eruption Response Team.
See also Seismic activity on Little Sitkin, Eruption on Ivan Grozny, Massive deep Earthquake beneath the Sea of Okhotsk, Earthquake shakes the Kamchatka Peninsula and Volcanoes on Sciency Thoughts YouTube.
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