Kikai Caldera

Kikai Caldera
鬼界カルデラ
Highest point
Peak	Mount Iō (Iōjima) (Iōjima)
Elevation	704 m (2,310 ft)
Dimensions
Length	17 km (11 mi) NS
Width	20 km (12 mi) EW
Geography
Country	Japan
State	Kagoshima Prefecture
Region	Ōsumi Islands
District	Kagoshima District
Geology
Age of rock	6,300 to 95,000 years ago

Not to be confused with the island Kikaijima nor the town on it Kikai, Kagoshima

Kikai Caldera (鬼界カルデラ, Kikai karudera^?) is a massive, mostly submerged caldera up to 19 kilometres (12 mi) in diameter in the Ōsumi Islands of Kagoshima Prefecture, Japan. It is the remains of the ancient eruption of a gigantic volcano. Its geographic coordinates are: Latitude (dd.) 30.79 and Longitude (dd.) 130.31

Kikai Caldera was the source of the Akahoya eruption, one of the largest eruptions during the Holocene (10,000 years ago to present). About 6,300 years ago, pyroclastic flows from that eruption reached the coast of southern Kyūshū up to 100 km (62 mi) away, and ash fell as far as Hokkaidō. The eruption produced about 150 km³ of tephra, giving it a Volcanic Explosivity Index of 7 and making it one of the most explosive in the last 10,000 years, ranking alongside Santorini, Changbaishan, Crater Lake, Kurile Lake and Tambora.

Kikai is still an active volcano. Minor eruptions occur frequently on Mount Iō (硫黄岳, Iō-dake^?), one of the post-caldera subaerial volcanic peaks on Iōjima (硫黄島, Iō-jima^?). Iōjima is one of three volcanic islands, two of which lie on the caldera rim. The most recent eruptions occurred in 2013. On June 4, 2013, weak tremors were recorded. Shortly after, eruptions began and continued off-and-on for several hours. Due to this activity, an ash cloud formed and moved west. The Japan Meteorological Agency (JMA) raised the Alert Level from 1-2 (on a scale of 5) and released a warning for potentially hazardous conditions both on the leeward side of the island and the area within 1km from the summit.

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Wikipedia