Bonin Islands Pacific Plate is subducting under the Philippine Sea Plate, which creates an oceanic trench to the east of the islands: the Bonin Trench. The crust of the Ogasawara Islands was formed by volcanic activity when subduction began 45–50 million years ago, and is composed mostly of an andesitic volcanic rock called boninite, which is rich in magnesium oxide, chromium, and silicon dioxide. The Ogasawara Islands may represent the exposed parts of an ophiolite that has not yet been emplaced on oceanic crust. The rocks of the Volcano Islands are much younger; Iwo Jima is a dormant volcano characterized by rapid
Smith Volcano Smith Volcano Smith Volcano, also known as Mount Babuyan, is a cinder cone on Babuyan Island, the northernmost of the Babuyan group of islands on Luzon Strait, north of the main island of Luzon in the Philippines. The mountain is one of the active volcanoes in the Philippines, which last erupted in 1924. The volcano is politically located in the Municipality of Calayan, Cagayan province, the town that has jurisdiction over the Babuyan Islands except Fuga Island. The sparsely-vegetated cinder cone is high with a base diameter of . Layers of basaltic lava flows are evident south of the volcano.