|Mountain name required|
Koryaksky or Koryakskaya Sopka (Russian: Коря́кская со́пка) is a volcano on the Kamchatka Peninsula in the far east of Russia. It lies within sight of Kamchatka Krai's administrative centre, Petropavlovsk-Kamchatsky. Together with neighbouring Avachinsky, it has been designated a Decade Volcano, worthy of particular study in light of its history of explosive eruptions and proximity to populated areas.
Koryaksky lies on the Pacific Ring of Fire, at a point where the Pacific Plate is sliding underneath the Eurasian Plate at a rate of about 80 mm/year. A wedge of mantle material lies between the subducting Pacific Plate and the overlying Eurasian Plate is the source of dynamic volcanism over the whole Kamchatka Peninsula.
The volcano has probably been active for tens of thousands of years. Geological records indicate that there have been three major eruptions in the last 10,000 years, at 5500 BC, 1950 BC and 1550 BC. These three eruptions seem to have been mainly effusive, generating extensive lava flows.
Koryaksky erupted for the first time in recorded history in 1890, in an eruption characterised by the emission of lava from fissures which opened up on the south western flank of the volcano, and phreatic explosions. It was thought to have erupted again five years later, but it was later shown that no eruption had occurred; what was thought to be an eruption column was simply steam generated by strong fumarolic activity.
Another brief, moderately explosive eruption occurred in 1926, after which the volcano was dormant until 1956. The 1956 eruption was more explosive than the previous known eruptions, with VEI=3, and generated pyroclastic flows and lahars. The eruption continued until June 1957.
Since then, the volcano has seen no further eruptions, but occasional seismic activity and ongoing fumarolic activity has indicated that the volcano is still active. In light of its proximity to Petropavlovsk-Kamchatsky, Koryaksky was designated a Decade Volcano in 1996 as part of the United Nations' International Decade for Natural Disaster Reduction, together with the nearby Avachinsky volcano.