Behind a waterfall lies a path.

Its deafening roar washes over you as you walk along the inner edge. You look back; light bleeds through the liquid curtain, blended through with the green of nature in the distance. This is Uramigataki, the “Look-behind” falls. True to its name, this path lets you view the waterfall “from behind.” A steaming open-air bath awaits in the nearby forest…but how can there be a hot spring here?

The answer is in the origin of Hachijō Island. Although it seems to be a single island, it is actually composed of two volcanoes: Hachijō-Fuji to the west and Mount Mihara to the east. Maps show a narrow strip of land between them, making the island look like a gourd.

The eastern Mount Mihara formed first. Around 100,000 years ago, a region of sea floor erupted. The eruptions eventually emerged to the surface as an island. Although more eruptions followed, Mount Mihara itself has been dormant since its last eruption around 3,700 years ago.

Hachijō-Fuji to the west is its much younger sibling, first becoming active 10 to 13,000 years ago. It also erupted in 1605, around 400 years ago.

As lava and volcanic ejections from young Hachijō-Fuji layered on themselves, they filled in the gap between it and the older Mount Mihara, creating a single island.

Volcanic regions retain their land’s heat underground. Mountain rains seep through cracks into the depths and are warmed by geothermal heat as they circulate over long periods of time. That water returns to the surface as a hot spring.

Uramigataki Onsen is one such blessing. Rich in sodium and chloride, its rich saline waters recall the ocean.

As for the waterfall, it was born from mountain rains and an ever-coursing river. Said river eroded the ground created by the volcano over a long time, resulting in the valley and waterfall you see today.

Water trickling underground, absorbing heat…
Water flowing along the surface, eroding stone…
Two streams along two different paths converge right here.
Listen closely while you soak in the hot spring.

Under your feet, deep beneath the earth, something rumbles, deep and long. Perhaps it’s the island’s own heartbeat, kickstarted 100,000 years ago under the sea.