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 Some Marshallese and Koreans reported of maltreatment by the Japanese authorities, and there was at least one case of revolt by both groups at Jelbon on Mili Atoll in which a hundred Japanese civilians and soldiers were killed. When American troops attacked the Marshall Islands between January and April 1944, Japanese troops evacuated many Japanese settlers and Korean labourers from the atolls. A few were reportedly killed in the ensuing air raids, while others who remained behind were captured as Prisoners of war after the Americans captured the atolls, together with some Japanese soldiers. After the Japanese surrender, the Japanese