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 report published by a German explorer, Hambruch in 1915 mentioned that three Japanese fishermen in a junk were massacred by the Marshallese at Lae Atoll in 1910. A military administration was established when Japan annexed the Marshall Islands from Germany in 1914. The Japanese government subsequently dispatched a few administrators to the Marshall Islands. Between 1915 and 1918, a few Japanese businessmen from the South Seas Trading Company ("Nanyo Boeki") sailed to the Marshall Islands and established a few trading stations at Rongrong, Talab and Majuro village. A typhoon struck Majuro in 1918 and the businessmen relocated their trading posts