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
Japanese settlement in the Marshall Islands Japanese settlement in the Marshall Islands Japanese settlement in the Marshall Islands was spurred on by Japanese trade in the Pacific region. The first Japanese explorers arrived in the Marshall Islands in the late 19th century, although permanent settlements were not established until the 1920s. As compared to other Micronesian islands in the South Pacific Mandate, there were fewer Japanese who settled in the islands. After the Japanese surrender in 1945, the Japanese populace were repatriated to Japan, although people of mixed Japanese–Marshallese heritage remained behind. They form a sizeable minority in the Marshall Islands' populace, and are well represented