The circular, 8-km-wide island of Miyake-jima forms a low-angle stratovolcano with a 3-km-wide summit caldera partially filled by the summit cone Oyama. Parasitic craters and vents dot the volcano, including maars near the coast and radially oriented fissure vents. Frequent historical eruptions have originated at vents ranging from the summit to sea level, causing much damage. The previous eruption of Miyake-jima occurred in 1983; it forced ~4,000 residents to evacuate the island.