The Indian ocean

The Indian Ocean is the third largest of the world's five oceans (after the Pacific Ocean and Atlantic Ocean, but larger than the Southern Ocean and Arctic Ocean). Four critically important access waterways are the Suez Canal (Egypt), Bab el Mandeb (Djibouti-Yemen), Strait of Hormuz (Iran-Oman), and Strait of Malacca (Indonesia-Malaysia). The decision by the International Hydrographic Organization in the spring of 2000 to delimit a fifth ocean, the Southern Ocean, removed the portion of the Indian Ocean south of 60 degrees south.

It includes includes Andaman Sea, Arabian Sea, Bay of Bengal, Flores Sea, Great Australian Bight, Gulf of Aden, Gulf of Oman, Java Sea, Mozambique Channel, Persian Gulf, Red Sea, Savu Sea, Strait of Malacca, Timor Sea, and other tributary water bodies

The average depth of the Indian Icean is 3890 m. The deepest point is the Java Trench off Java, in Indonesia, which is 7450 m deep. It marks the line where the Australian plate is being subducted under the Eurasian plate.

The occean's surface is dominated by counterclockwise gyre (broad, circular system of currents) in the southern Indian Ocean; unique reversal of surface currents in the northern Indian Ocean; low atmospheric pressure over southwest Asia from hot, rising, summer air results in the southwest monsoon and southwest-to-northeast winds and currents, while high pressure over northern Asia from cold, falling, winter air results in the northeast monsoon and northeast-to-southwest winds and currents; ocean floor is dominated by the Mid-Indian Ocean Ridge and subdivided by the Southeast Indian Ocean Ridge, Southwest Indian Ocean Ridge, and Ninetyeast Ridge

The Indian Ocean is 10,000 km across at its widest point between Africa and Australia.

Scientists believe that the Indian Ocean began to form about 200 million years ago when Australia broke from Africa, followed by India.

The Indian Ocean is scattered with thousands of tropical islands such as the Seychelles and Maldives. The Maldives are so low lying that they may be swamped if global warming melts the polar ice.

Unlike in other oceans, currents in the Indian Ocean change course twice a year. They are blown by monsoon winds towards Africa in winter, and then in the other direction towards India in summer.