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Myōkō-Togakushi Renzan NP, Niigata
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Yakeyama began erupting about 3,000 years ago. Researchers dated dead tree trunks buried in its earliest debris deposits—a remarkable natural clock for the mountain’s birth.
An ancient Yakeyama eruption sent a pyroclastic flow down the Hayakawa valley; geologists say its deposits may have reached the Sea of Japan. Its fiery reach may once have stretched from summit to coast.
In 1852, explosions opened fissures on Yakeyama’s northwest flank—not just its summit crater—and expelled abundant sulfur. Activity continued into 1853, with another eruption in 1854.
The 1974 steam eruption released an estimated 650,000 tonnes of ash. Carried northeast, it reached Fukushima Prefecture, more than 160 km away, while nearby towns were blanketed white.
At about 2:50 a.m. on July 28, 1974, Yakeyama erupted as 3 Chiba University students camped near the summit during an alpine-plant survey. All 3 were killed.
In 1974, water-rich volcanic ash swept into the river and picked up water and stones, forming a 500,000 m³ debris flow. It buried irrigation intakes, leaving about 250 hectares of farmland without water.
A local resident reported a new steam vent on Yakeyama’s east slope in May 1974. By June 25, a nature-protection officer noted stronger plumes and vents lower than usual; the town banned climbing on July 27.
Yakeyama’s ridge is part of an 827-hectare protected forest stretching from Kinzan to Hiuchiyama. It safeguards alpine dwarf-pine vegetation and habitat for Japan’s rock ptarmigan.
