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Kirishima Kinkowan NP, Kagoshima
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About 45,000 years ago, the eruption that shaped Onamiike sent pumice and ash roughly 50 km east to the Miyazaki Plain, where deposits reached 20 cm. It happened before many of Kirishima’s famous peaks formed.
Onamiike’s water surface sits at 1,239 m—the highest elevation for a summit crater lake in Japan. The lake is about 650 m across, inside a crater roughly 1 km wide.
Despite being in southern Kyushu, Onamiike can freeze completely in winter. At 1,239 m, it gets cold enough for ice to cover the lake while hoarfrost coats nearby trees.
In Kirishima’s local legend, a childless village headman and his wife prayed for a child and raised a daughter named Onami. She was said to be the dragon king’s incarnation, and the lake became known as “Onami’s Pond.”
No stream visibly flows into Onamiike, yet its water level stays almost constant through the year. The explanation lies underground: the crater floor sits below the water table, allowing groundwater to fill the basin.
Onamiike’s last eruption was about 45,000 years ago, giving forest succession time to develop. Beech and oak grow among fir and hemlock here; nearby, more recently active craters have less-developed vegetation.
Early in spring, yellow, ribbon-petaled witch hazel (mansaku) blooms in a notable colony along Onamiike’s eastern rim trail. Its bright flowers stand out against the blue lake before the season’s better-known blooms arrive.
