The volcano has five crater lakes, with Ni no Ike(二ノ池?) at 2,905 m (9,531 ft) being the highest mountain lake in Japan.
Ontake is a major sacred mountain, and following older shamanistic practices, actors and artists have gone to the mountain to put themselves into trances in order to get divine inspiration for their creative activities.
Mount Ontake seen from Kurakake Pass on October 11, 2014.
Ontake was thought to be inactive until October 1979, when it underwent a series of explosive phreatic eruptions (VEI2), ejecting 200,000 tons of ash in total.
There were minor non-explosive (VEI0) phreatic eruptions in 1991 and 2007.
On Saturday, September 27, 2014, at around 11:53 a.m. Japan Standard Time (UTC +9), the volcano erupted with a VEI of 3 or 4. There were no significant earthquakes that might have warned authorities in the lead up to the phreatic eruption—caused by ground water flashing to steam in a hydrothermal explosion. The Mount Ontake volcano eruption was an extremely rare phenomenon which made it impossible to take precautionary measures. At least 40 people were injured, and another 32 were believed to be missing. The Japan Self-Defense Forces began carrying out helicopter searches for missing people after the eruption. On October 7, the total confirmed death count stood at 54.