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 is one of the probably five Pleistocene-to-Holocene volcanic centers on Babuyan Island (also known as Babuyan de Claro Island) with Smith, the youngest volcano on the island. The largest on the island is Babuyan Claro (also known as "Mt. Pangasun"), an active stratovolcano with two well-preserved summit craters in diameter, located in the center of the island. Babuyan Claro is about peak-to-peak southeast of Smith Volcano, which is the north-westernmost summit on the triangular-shaped island. Smith Volcano has erupted six times, the last of which was in 1924. A team of volcanologists from the Philippine Institute of Volcanology