Two stratovolcanoes are located on the island: Mount Reaumur and Cerisy Peak. The summit of the volcanic complex collapsed during at least three major explosive eruptions, about 16,000, 4000, and 300 years ago. These produced a large caldera 10 x 12.5 km in size, now filled with a freshwater crater lake, Lake Wisdom. In 1953-1954 and 1968, volcanic activity created Motmot Island on the crater lake, 200 x 200 m in size. The 1660 eruption was one of the largest in Papua New Guinea's recent history with an estimated air-fall volume in excess of 11 cu km, comparable to the 1991 eruption of Mount Pinatubo, but the Global Volcanism Program gives a much higher estimate of 30 cu km. This cataclysmic event prompted legends of a Time of Darkness. The most recent (and a smaller) eruption occurred in 1993.