Symmetrical Prevo Peak, also known as Simushiru-Fuji for its resemblance to Japan's noted volcano, is capped by a 500 x 600 m summit crater. A nested inner cone contains a deep 350-m-wide crater with a small lake. Lava flows reach both coasts of central Simushir Island. Two small pyroclastic cones on the western flank produced lava flows that reached to or near the Sea of Okhotsk. A large eruption during the 1760s produced pyroclastic flows that destroyed all vegetation at the foot of the volcano. Weak explosive activity occurred during the most recent eruption, which took place during the first half of the 19th century.