IV.

Islands

The largest islands, in the western region, form volcanic island arcs that rise from the broad continental shelf along the eastern edge of the Eurasian Plate. They include Japan, Taiwan, the Philippines, Indonesia, New Guinea, and New Zealand. The oceanic islands, collectively called Oceania, are the tops of mountains built up from the ocean basin by extruding molten rock. The Pacific Ocean contains more than 30,000 islands of this type; their total land area, however, amounts to only one-quarter of one per cent of the ocean's surface area. The mountains that remain submerged are called seamounts. In many areas, particularly the South Pacific, the land features above the sea surface are accretions of coral reef. Along the eastern edge of the Pacific, the continental shelf is narrow and steep, with few island areas. The major groups are the Galápagos at the equator, which rise from the Nazca Plate, the Aleutians in the north, which are part of the North American continental shelf, and the islands of Hawaii, which rise some 5,550 m (more than 18,000 ft) from the seafloor of the central Pacific, reaching in Mauna Kea a height of 4,205 m (13,796 ft) above sea level.