Symmetrical Prevo Peak, also known as Simushiru-Fuji for its resemblance to Japan's noted volcano, is capped by a 450 x 600 m wide summit crater.  A nested inner cone whose rim approaches the height of portions of the outer cone is itself cut by a deep, 350-m-wide crater with a small lake on its floor.  Young-looking lava flows reach both coasts of central Simushir Island, and those on the south flank (Pacific Ocean side) have a particularly youthful appearance.  Two small pyroclastic cones on the western flank have produced lava flows that reach to or near the Sea of Okhotsk.  Only two eruptions are known from Prevo Peak in historical time.  The largest of these, 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.