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Fuji-Hakone-Izu NP, Kanagawa
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About 3,000 years ago, Kamiyama’s northwestern flank collapsed. The debris avalanche blocked the Hayakawa River, creating Lake Ashi, while its deposits spread into Sengokuhara.
Around Ubako, boulders such as Kintaro-iwa and Funami-iwa are chunks of Kamiyama carried downhill by that ancient avalanche. These stranded, hummock-like landforms are called nagare-yama, or “flow hills.”
Kamiyama is revered as Hakone’s sacred mountain. At the October 24 festival on neighboring Komagatake, a sacred flame descends by ropeway, crosses Lake Ashi by boat, then travels to shrines around Hakone.
Kamiyama’s great collapse did not leave an empty scar: magma later rose there and built nearby Kanmurigatake. Pyroclastic flows from this activity crossed Nagao Pass into Shizuoka Prefecture.
On Kamiyama’s exposed western summit slope, the rare Hakone kometsutsuji azalea grows in tiny patches on rock. Its range is limited to the Fuji volcanic belt and Chichibu, and forestry officials protect its habitat.
After Kamiyama’s last magma eruption about 3,200 years ago, geologists identified 5 later steam-driven explosions in the Hakone volcanic area—including 3 clustered between the late 12th and 13th centuries.
