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
Davidof Volcano Davidof Volcano Davidof Volcano is an inactive stratovolcano and caldera remnant in the Aleutian Islands of Alaska, USA, from Anchorage. Located on the eponymous island, Davidof is part of the Rat Islands sub-chain. It is also part of the "Aleutian Krakatau", a group of four islands formed when a stratovolcano's caldera caved in during the late Cenozoic. Since the island is uninhabited, very little transportation is available. Transport can be found in Adak, albeit that the town is from the island. Because of the inclusion of Alaska, the United States has the largest number of active volcanoes in the world,