Mt. Asama

Mt. Asama is an active stratovolcano straddling the border of Gunma and Nagano prefectures, roughly 150 kilometers northwest of Tokyo, and the most active volcano on the island of Honshū. Its most catastrophic recorded eruption occurred in 1783, burying surrounding villages under lava and ash and killing thousands — the event sent debris flows as far as the Tone River valley and triggered crop failures across the region. The mountain is composed primarily of andesite, giving its lava flows a characteristically viscous, slow-moving quality. The exclusion zone around the summit crater fluctuates with activity levels, continuously monitored by the Japan Meteorological Agency. On clear days, hikers approaching from the Karuizawa side are rewarded with sweeping views over the Kanto plain.