Mount Mihara (三原山 Mihara-yama) is an active volcano on the Japanese isle of Izu Ōshima. Although the volcano is predominantly basaltic, major eruptions have occurred at intervals of 100–150 years. Mount Mihara's major eruption in 1986 saw lava fountains up to 1.6 kilometres (1.0 mi) high. The eruption had a Volcanic Explosivity Index of 3, and involved a central vent eruption, radial fissure eruption, explosive eruption, lava flows, and a lava lake eruption. There was also a 16 km high subplinian plume. All of the island's 12,000 inhabitants were evacuated by dozens of vessels consisting of both the military and civilian volunteers.