Indian Ocean
The Indian Ocean is the third largest ocean. It is surrounded by southern Asia, the Arabian Peninsula, Africa, the Malay Peninsula, the Sunda Islands, Australia and Antartica. The 20° E meridian divides it from the Atlantic and the 147° E meridian divides it from the Pacific below Australia. The Continental Shelves of the Indian Ocean are narrow compared to those of the other oceans. The Indian Ocean has an area of 73,556,000 sq km. At its widest point, between Southern Africa and Australia, it is nearly 10,000 km wide.
The Indian Ocean is divided into three major sections by the Mid-Oceanic Ridge which runs from Asia to Antarctica in an upside down Y shape. The sections are, the African, the Antardis, and the Australasian. The Mid-Oceanic Ridge rises to an average of 3,000 m, with some of its peaks rising to form islands. Many deep sea basins are enclosed by the Mid-Oceanic Ridge. The deepest among these is the Java Trench which reaches a depth of 7,450 m.
The Indian Ocean has two water circulation systems. The northern system circulates clockwise except during the winter monsoon season when the currents are reversed. Low atmospheric pressure over southwest Asia from hot, rising, summer air results in the southwest monsoon and clockwise winds and currents. High pressure over northern Asia from cold, falling, winter air results in the northeast monsoon and counterclockwise winds and currents. In the southern portion of the Indian Ocean, currents travel in a counterclockwise direction.
The main importance of the Indian Ocean has been as a trade route between Africa and Asia. Petroleum, extracted mainly from the Persian Gulf area is also important. Relatively warm surface temperatures keep the growth of phytoplankton low, which limits ocean life. Fishing is only done at the subsistence level.