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Akan-Mashū NP, Hokkaido
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Atosa-nupuri means “bare mountain” in Ainu. Long before commercial mining, Ainu people used its sulfur as tinder; a local merchant began trial mining in 1876, and full-scale extraction followed in 1877.
In 1887, about 300 laborers and 300 prisoners built a roughly 41-km sulfur railway between Atosanupuri and Shibecha in just 8 months. It was Hokkaido’s second railway, after the Horonai line.
The dark alpine crowberries around Tsutsujigahara once supplied dye for Ainu clothing; local gatherers now turn the same distinctive berries into jam.
Atosanupuri’s sulfur boom came at a terrible cost: prisoners from the Kushiro prison camp at Shibecha were sent to mine here, and sulfurous gas and dust caused eye disease and blindness.
Before the railway, merchant Sano brought in 400 horses to haul sulfur: 300 worked each day on the route to Shibecha while 100 rested. From there, the cargo continued to Kushiro by boat.
Atosanupuri’s acidic, gas-affected ground creates an upside-down alpine scene: Japanese stone pine and marsh tea grow at only about 150 m, and the plant communities shift noticeably as the trail nears the volcano.
The volcano’s heat reaches the menu: the rest house at Mount Io serves onsen eggs prepared with water from Kawayu’s hot-spring source.
Atosanupuri sulfur traveled as far as the United States. Its export trade helped Kushiro gain special-export-port status in 1890 and supported the growth of the area’s coal and paper industries.
In the forest below the mountain, a surviving rail from the old sulfur-mining railway is caught in a tree trunk and lifted above the ground as the tree grows.
Spotted nutcrackers feed on Japanese stone-pine seeds here, then push seeds into cracks in rocks to stash food for the harsh winter.
Small red flecks on the ground near the volcano may look like flowers, but they are lichen. This hardy organism traps volcanic ash and helps keep it from filtering into Tsutsujigahara’s soil.
Atosanupuri sits inside a roughly 4-km-wide caldera nested within the much larger Kussharo Caldera. The broader volcanic complex includes 10 lava domes—this steaming peak is one member of the family.
The latest eruption identified in Atosanupuri’s geologic record was a steam-driven explosion several hundred years ago. It formed the explosive crater known as Kumaotoshi.
