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
Reef Islands Reef Islands The Reef Islands are a loose collection of 16 islands in the northwestern part of the Solomon Islands province of Temotu. These islands have historically also been known by the names of Swallow Islands and Matema Islands. The islands lie about north of Nendo, the largest of the Santa Cruz Islands. The center of the group is at approximately 10°12'36" S lat., 166°10'12" E. long. The islands are raised some five metres on the east and tilted west. The islands are subject to tidal surges caused by cyclones and volcanic activity from nearby Tinakula volcano. The island soils