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Daisetsuzan NP, Hokkaido
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At Daisetsuzan’s 2,100 m Hakuundake–Koizumidake site, obsidian tools point to visits at least 3,000 years ago. Numerous arrowheads suggest hunters used this high ground, though that purpose remains a hypothesis.
Near Hiragatake, Daisetsuzan has Japan’s first reported palsa: a frozen-core peat mound just 20–100 cm tall but up to 80 m across. Peat-growth calculations suggest the field began forming 1,000–2,000 years ago.
At Hakuundake–Koizumidake, freeze–thaw cycles can push stone tools upward through the soil, then frost creep carries them downhill. The permafrost landscape has rearranged the 3,000-year-old archaeological scatter.
On Daisetsuzan’s exposed ridges, strong winter winds sweep away insulating snow and sparse plants. With less cover to shield it from cold air, the ground can stay frozen year-round in these bare patches.
Polygons, lines, lobes and steps mark Daisetsuzan’s permafrost terrain. A 2025 study found plants help shape these patterns: they colonize damp patches created by uneven snow and help stabilize shifting soil.
At Hiragatake, aerial photos show the total palsa area shrank about 36% from 1955 to 1982. Later monitoring found individual mounds still shrinking, as the seasonally thawed layer grew deeper.
At Hokkai-daira, researchers measured frost cracks widening by about 1 cm in winter 1984–85. Later monitoring at Goshikidake automated measurements of the spacing between similar freeze-crack polygons.
At a 1,755 m gravel site, researchers found seasonal frost down to about 6 m but no permafrost; exposed gravel sites above 1,800 m did have it. Deep winter frost doesn’t always last through summer.
A 2021 model estimated about 150 km² of Daisetsuzan had climate conditions suitable for permafrost in 2010. Under its high-emissions scenario, that suitable climate area disappears around 2070—not a direct map of frozen ground.
