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Hidakasanmyaku Erimo Tokachi NP, Hokkaido
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Plate collision lifted Hidaka’s deep island-arc rocks into view. Japan’s Environment Ministry says continuous sections from upper mantle to crust are known in only 2 places: here and Pakistan’s Kohistan Belt.
A 1966 find in a tributary of the trek’s Chiroro River became “Hidaka jade”—but its green mineral is chrome diopside, not jadeite or nephrite. Chromium gives it its color.
A stop at Akaiwa-Seigan Gorge in the separate Yubari Mountains reveals red chert made from tiny radiolarians; western-Hidaka chert accumulated on deep seafloors at about 1 mm per 1,000 years.
The itinerary includes a special-permission visit to a peridotite mine. Hidaka’s locally quarried rock is used in steelmaking and fertilizer; its quarry operator says it has also served as asteroid-research simulant soil.
The sample itinerary’s Biratori Wagyu hamburger comes with a soy-based sauce the restaurant says has been its tradition for 30 years, alongside local rice and tomatoes—a tasty link to the region’s farms.
Along the Chiroro stream, the itinerary invites guests to search for fossils and rocks, with a curator helping identify finds. Hidaka Museum displays Cretaceous ammonites, Inoceramus and corals from the region’s former seafloor.
Before heading into the field, the sample itinerary visits Hidaka Mountains Museum, where rock slices are ground to just 0.03 mm for microscopes. At that thinness, stone reveals surprising images.
At the museum stop, Hidaka’s pillow lava gets a toothpaste-like explanation: underwater lava squeezed out in rounded forms, preserving a clue that eruptions once happened beneath an ancient sea.
The Chiroro-area itinerary also follows the Saru River’s old timber route: logs were held behind tributary weirs through winter, then released with the spring melt to float downstream toward the coast.
