Onioshidashi Lava Field was added to Your Favorites!
Joshin’etsukogen NP, Gunma
Claim this place to tell your story your way.
This is not a conventional river of molten rock: studies suggest Onioshidashi began as hot fragments blasted from a volcanic fountain, which piled up and welded together as they moved.
Nearby Kanbara’s 477 deaths came when a debris avalanche buried the village and a downstream mudflow surged along the rivers. The jagged lava field is another deposit from the same 1783 eruption.
At the park’s Setsubun, oni are allies, not targets: celebrants call “Fuku wa uchi!” (“Welcome good fortune!”) without “Oni wa soto,” and toss peanuts rather than soybeans.
From Asama’s summit crater, Onioshidashi extends about 5.5 km north and covers 6.8 km². All that immense, jumbled rock formed during the volcano’s 1783 eruption.
At the lava flow’s lower end, gaps between piled rocks hide cold-air vents and a spring. Researchers recorded vent temperatures near 0°C from early April to early June, as melt-season ice chilled the air.
The 1783 lava has not greened over evenly: researchers found 6 plant communities, even at similar elevations. Loose, dry gravel and stable, moist cracks in the lava favor different plants.
Asama Kannon Hall was built among the lava in 1958, 175 years after the eruption, to commemorate those lost and pray for disaster recovery. Its sacred Kannon image came from Tokyo’s Kan’eiji Temple.
No one knows who coined “Onioshidashi.” Local tradition imagines Asama’s ogres pushing rocks from the crater; Gunma’s Jomo Karuta later immortalized the image in its line “Asama’s mischief: the oni’s push-out.”
Asama’s 1783 eruption lasted about 90 days, but its final climactic phase lasted roughly 15 hours. The lava formed amid the same finale that sent out pumice and generated pyroclastic flows.
Scientists pieced together the 1783 eruption that produced this flow from 166 historical documents. Reports from more than 100 km away recorded rumbling and shaking that matched explosive events at Asama.
