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Daisetsuzan NP, Hokkaido
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On May 24, 1926, part of Tokachidake’s central cone collapsed. Hot debris melted lingering snow into a mudflow that reached the plain 25 km away in about 25 minutes, leaving 144 people dead or missing.
In 1923, molten sulfur formed a pond in June; by August, it was spouting 7–8 m into the air. Sulfur production rose as Tokachidake’s activity intensified before the 1926 eruption.
Tokachidake’s 2,077 m summit is an older lava dome, not its youngest vent. The newer Ground Crater, central cones and active fumaroles lie northwest of the high point.
Tokachidake rises at the source of the 156-km Tokachi River. Ainu-language sources record Tokapci as the regional name, but its original meaning remains unsettled; the Obihiro museum notes several interpretations.
After the 1926 flow, Kamifurano mayor Teijiro Yoshida urged residents to reclaim sulfur-tainted fields, even though he had lost his own mother. Restoring the village’s rice paddies took 8 years.
On June 30, 1962, Tokachidake sent an ash plume 12,000 m high. Fallout reached Shiretoko and the southern Kurils, and the blast was heard as far as 190 km away.
Even the exposed upper slopes bloom: early-summer flowers include iwabukuro, iso-tsutsuji and meakan-kinbai, alpine plants known around Tokachidake for tolerating volcanic gases.
Sediment layers, tree rings and radiocarbon dating along the Furano River reveal 14 volcanic mudflows over 40,000 years, including events in 1857 and 1926. The Taisho flow is part of a much older pattern.
At the downstream Kusawake geosite, 1926 is preserved in three layers: pre-eruption farm soil, gravelly mudflow deposits, and new soil brought in afterward to make farmland productive again.
On the Biei side, a 253-hectare protected forest has regrown over the 1926 mudflow scar. Sakhalin spruce returned first; surveys found birch dominating the canopy above young spruce.
Tokachidake’s underground heat powers springs on its flanks: a source in the old crater exceeds 90°C, while Shirogane Onsen in the foothills emerges at around 50°C.
