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
McDonald Islands (volcano) McDonald Islands (volcano) The McDonald Islands () are the peaks of a volcano in the southern Indian Ocean in the vicinity of Heard Island (). The islands are Australian external territory. Prior to 1992, the volcano had not erupted in the previous 75,000 years. The McDonald Islands volcano comprises three islands: McDonald Island, Flat Island (which later merged with McDonald Island) and Meyer Rock. The islands are mostly composed of phonolitic low-silica pumice, dikes and lava domes, and sit atop a submarine plateau, the Kerguelen plateau. They are located about 75 km from Heard Island. McDonald Island is the largest