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
Tori-shima (Izu Islands) Tori-shima (Izu Islands) , literally meaning "Bird Island", is an uninhabited Japanese island in the Pacific Ocean. The volcanic island is part of the Izu Islands. Tori-shima is located in the Philippine Sea approximately south of Tokyo and north of Lot's Wife. The roughly circular-shaped island is listed as a Class A active volcano by the Japan Meteorological Agency. The island is the above-water portion of a submarine volcano, whose submerged caldera portion to the north of the island continues to erupt underwater. Volcanic activity on the island itself was last recorded in 2002, accompanied by earthquake swarms. The main