Indian Ocean

Photo Courtesy of CIA World Factbook

The Indian Ocean is the third-largest body of water in the world, covering about 20% of the Earth's water surface. It is bounded on the north by southern Asia (the Indian subcontinent); on the west by the Arabian Peninsula and Africa; on the east by the Malay Peninsula, the Sunda Islands, and Australia; and on the south by the Southern Ocean. It is separated from the Atlantic Ocean by the 20° east meridian south of Africa, and from the Pacific by the 147° east meridian. The northernmost extent of the Indian Ocean is approximately 30° north latitude in the Persian Gulf. This ocean is nearly 10,000 km (6,200 mi) wide at the southern tips of Africa and Australia; its area is 73,556,000 km² (28,400,000 mi²), including the Red Sea and the Persian Gulf. The ocean's volume is estimated to be 292,131,000 km³ (70,086,000 mi³). Small islands dot the continental rims. The ocean's importance as a transit route between Asia and Africa has made it a scene of conflict. Because of its size, however, no one nation had successfully dominated until the early 1800s when Britain controlled much of the surrounding land.

The African, Indian, and Antarctic crustal plates converge in the Indian Ocean. Their junctures are marked by branches of the Mid-Oceanic Ridge forming an inverted Y, with the stem running south from the edge of the continental shelf near Mumbai, India. The eastern, western, and southern basins thus formed are subdivided into smaller basins by ridges. The ocean's continental shelves are narrow, averaging 200 km (125 mi) in width. An exception is found off Australia's western coast, where the shelf width exceeds 1,000 km (600 mi). The average depth of the ocean is 3,890 m (12,760 ft). Its deepest point, in the Java Trench, is estimated to be 7,450 m (24,442 ft). North of 50° south latitude, 86% of the main basin is covered by pelagic sediments, of which more than one-half is globigerina ooze. The remaining 14% is layered with terrigenous sediments. Glacial outwash dominates the extreme southern latitudes.

The climate north of the equator is affected by a Monsoon wind system. Strong northeast winds blow from October until April; from May until October south and west winds prevail. In the Arabian Sea the violent monsoon brings rain to the Indian subcontinent. In the southern hemisphere the winds generally are milder, but summer storms near Mauritius can be severe. When the monsoon winds change, cyclones sometimes strike the shores of the Arabian Sea and the Bay of Bengal.