Mount Chausu Crater & Fumaroles was added to Your Favorites!
Nikko NP, Tochigi
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The bare summit is surprisingly young: eruptions in 1408–1410 built the andesite lava dome that forms Chausu’s peak today—a medieval volcanic landmark, not an ancient cone.
In 1408, sulfur fell from the sky and the Nakagawa River stayed yellow for years. Records report more than 180 deaths and heavy livestock losses in the 1410 eruption.
The crater inside Chausu’s summit dome is not where the strongest steaming occurs: the Japan Meteorological Agency locates the most active fumaroles in 2 separate explosion craters on the west slope.
A steam blast in 1881 formed Mugen Jigoku and sent ash about 20 km to Shirakawa. Ash that reached the Nakagawa River killed fish, though no people died in the eruption.
Chausu’s last recorded eruption was in 1963, but Mugen Jigoku has continued to vent since its 1881 crater formed. Park rangers have reported a deep rumble and strong sulfur smell nearby.
Some fumarole gases reach around 90°C. Sulfur crystals tint the barren rocks yellow, while vapor clouds and a strong sulfur smell help explain the name Mugen Jigoku, or “Infinite Hell.”
Chausu’s heat reaches well beyond its summit: more than 150 hot springs have been found around Nasu, and most are heated by magma beneath the mountain.
