Hiuchi initially formed around 350,000 years ago. Around 160,000–170,000 years ago, Hiuchi erupted, creating a large pyroclastic flow deposit. At the summit of the volcano lie two lava domes, Akanagure (赤ナグレ) and Mi-ike (御池岳). Akanagure, the southern dome, produced a series of viscouslava flows that flowed down the southern and western parts of the volcano about 3500 years ago. Mi-ike is responsible for the only recorded activity.
Historic eruptions
1544 eruptions
The only recorded activity was on July 28, 1544. A moderate phreatic eruption at the Mi-ike Lava Dome produced lahars and an associated tephra layer.[1][5]
