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Joshin’etsukogen NP, Nagano / Gunma
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At Kamahara Kannon-do, the 1783 avalanche buried 35 of 50 steps; 93 villagers survived by reaching its raised hall. Excavation later found 2 women at the bottom, one apparently carrying the other.
Edo residents misidentified Asama’s 1783 ash as coming from Nikkō or Tsukuba. A surviving account says they reasoned that, since it fell more heavily than Sakurajima’s ash, the volcano must be nearer.
On Asama’s Gunma foothills, Tsumagoi’s volcanic-ash black soil and cool summers nurture cabbages. The village ranked Japan’s No. 1 summer-autumn cabbage shipper in 2023, according to its agricultural cooperative.
The early-Heian Tales of Ise already celebrates Asama’s smoke: travelers wonder whether people near and far will notice the plume. Later readers also used its rising smoke as an image of love too strong to hide.
At Asama’s north foot, the “lava tree molds” formed not from lava but when 1783 pyroclastic flows hardened around trees. About 500 vertical hollows remain, up to 7m deep; the site is a Special Natural Monument.
At Onioshidashi Park, a memorial to the 1783 eruption began with local innkeeper Kuroiwa Chōzaemon, who used his own wealth to help survivors. He asked comic poet Shokusanjin to compose it; his son erected it in 1816.
On Asama’s high rocky slopes, kuromame-no-ki berries are nicknamed Asama-budō, “Asama grapes.” A local nature guide notes that these dark berries are gathered for jam.
Before the present peak, Asama had an older giant: Kurofu volcano lost its eastern half in a huge collapse about 27,000 years ago. The resulting crescent-shaped caldera still forms the mountain’s outer rim.
The jagged 1783 lava field north of Asama is called Onioshidashi—“pushed out by demons.” A local explanation says the rocks looked as though an oni had shoved them from the crater.
1783’s destruction spread far beyond the mountain: debris entered the Agatsuma and Tone rivers, raised the Tone’s bed, and helped intensify flooding across its basin 3 years later.
An Asama explosion was heard 240km away in 1911—the year Japan opened its first permanent volcano observatory on the mountain. The observatory’s Aug 26 anniversary became Japan’s Volcano Disaster Prevention Day in 2024.
Today’s summit cone is surprisingly young: the 1783 eruption built the Kamayama pyroclastic cone around Asama’s active crater, which spans about 500m. Its crater floor can rise or sink substantially with volcanic activity.
In May, melting snow traces a carp on Asama’s south slope, called Nobori-koi, “ascending carp.” Saku-area farmers read the pattern’s development as a seasonal signal for sowing rice nurseries and transplanting.
