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 much more frequent. Japanese songs such as "Masaharu Gunto" were written in the 1930s and reflected of romantic associations between Japanese men and Marshallese women. Ethnic suspicion and hatred by the Marshallese against the Japanese settlers developed during the Second World War, as the Japanese civilian government placed increased emphasis on militarism and forcibly conscripted many Marshallese to menial labour during the Second World War. Shortly before the end of the war, a few Marshallese led independent and isolated attacks against Japanese military personnel wherever possible. Japanese settlement in the Marshall Islands Japanese settlement in the Marshall Islands was spurred