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
Gareloi Volcano Gareloi Volcano The Gareloi Volcano is a stratovolcano in the Aleutian Islands of Alaska, United States, about from Anchorage. Gareloi is located on Gareloi Island, and comprises most of its land mass. The island also has two small glaciers which protrude to the northwest and southeast. The volcano is by at its base, possessing two summits. The southern crater is far greater in size, wide with fumaroles, which can be attributed to edifice failure in the southern wall, while Gareloi's northern crater is enclosed. Vitus Bering had been a prominent sailor in Russia. After successful expeditions in 1725, 1728, and