- This article is about the water body. For the Indian fusion music band, see Indian
Ocean (band).
The Indian Ocean is the third largest of the world's oceanic divisions, covering about
20% of the Earth's water surface. It is bounded on the north by Asia (including the Indian subcontinent, after which it is named); on
the west by Africa; on the east by the Malay Peninsula,
the Sunda Islands, and Australia; and on the south by
the Southern Ocean (or, traditionally, by Antarctica). One component of the all-encompassing World Ocean, the
Indian Ocean is delineated from the Atlantic Ocean by the 20° east meridian running south from Cape Agulhas,[1] 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 and, thus, has asymmetric ocean circulation. This ocean is nearly
10,000 kilometres (6,200 mi) wide at the southern tips of Africa and Australia; its area is [[1 E+13
m²|73,556,000 square kilometres]] (28,400,000 mi²), including the Red Sea and the
Persian Gulf.

The ocean's volume is estimated to be [[1 E+17 m³|292,131,000 cubic kilometres]] (70,086,000 mi³). Small
islands dot the continental rims. Island nations within the ocean are Madagascar (formerly Malagasy Republic), the world's fourth largest island; Comoros; Seychelles; Maldives;
Mauritius; and Sri Lanka. Indonesia borders it. 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 nation had successfully dominated most of it until the
early 1800s when the United Kingdom controlled much of the surrounding land. After the
decline of the British Empire, the ocean has been dominated by India and Australia.
Geography
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 kilometres (125 mi) in width. An exception is found off Australia's
western coast, where the shelf width exceeds 1,000 kilometres (600 mi). The average depth of the ocean is 3,890 metres
(12,760 ft) making it the deepest of the big three in median depth. Its deepest point, is in the Diamantina Deep close to the coast of south west Western
Australia. North of 50° south latitude, 86% of the main basin is covered by pelagic
sediments, of which more than half is globigerina ooze. The remaining 14% is layered with
terrigenous sediments. Glacial outwash dominates the extreme southern latitudes.
A spring 2000 decision by the International Hydrographic
Organisation delimited a fifth world ocean, stripping the southern portions of the
Indian Ocean. The new ocean extends from the coast of Antarctica north to 60° south latitude which coincides with the Antarctic
Treaty Limit. The Indian Ocean remains the third-largest of the world's five oceans.
Major choke points include Bab el Mandeb, Strait of
Hormuz, Strait of Malacca, southern access to the Suez Canal, and the Lombok Strait. Seas include Andaman Sea, Arabian Sea, Bay of
Bengal, Great Australian Bight, Gulf of
Aden, Gulf of Oman, Laccadive Sea,
Mozambique Channel, Persian Gulf,
Red Sea, Strait of Malacca, and other tributary water
bodies.
Climate
The climate north of the equator is affected by a monsoon or
tornado wind system. Strong north-east 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. The Indian Ocean happens to be the warmest ocean in the world.
Hydrology
Bathymetric map of the Indian Ocean
Among the few large rivers flowing into the Indian Ocean are the Zambezi, Shatt al-Arab, Indus, Ganges,
Brahmaputra, and Ayeyarwady River. Currents
are mainly controlled by the monsoon. Two large circular currents, one in the northern hemisphere flowing clockwise and one south
of the equator moving anticlockwise, constitute the dominant flow pattern. During the winter monsoon, however, currents in the
north are reversed. Deep water circulation is controlled primarily by inflows from the Atlantic
Ocean, the Red Sea, and Antarctic currents. North of 20° south latitude the minimum
surface temperature is 22 °C (72 °F), exceeding 28 °C (82 °F) to the east. Southward of 40° south latitude,
temperatures drop quickly. Surface water salinity ranges from 32 to 37 parts per 1000, the
highest occurring in the Arabian Sea and in a belt between southern Africa and south-western Australia. Pack ice and icebergs are
found throughout the year south of about 65° south latitude. The average northern limit of icebergs is 45° south latitude.
Economy
The Indian Ocean provides major sea routes connecting the Middle East, Africa, and
East Asia with Europe and the Americas. It carries a particularly heavy traffic of petroleum and petroleum
products from the oilfields of the Persian Gulf and Indonesia. Large reserves of hydrocarbons are being tapped in the offshore
areas of Saudi Arabia, Iran, India, and Western Australia. An estimated 40% of the world's offshore oil production comes from the Indian
Ocean. Beach sands rich in heavy minerals, and offshore placer deposits are actively exploited
by bordering countries, particularly India, South Africa,
Indonesia, Sri Lanka, and Thailand.
The warmth of the Indian Ocean keeps phytoplankton production low, except along the
northern fringes and in a few scattered spots elsewhere; life in the ocean is thus limited. Fishing is confined to subsistence levels. Its fish are of great and growing importance to the bordering
countries for domestic consumption and export. Fishing fleets from Russia, Japan, South Korea, and Taiwan also exploit
the Indian Ocean, mainly for shrimp and tuna.
Endangered marine species include the dugong, seals,
turtles, and whales.
Oil pollution threatens the Arabian Sea,
Persian Gulf, and Red Sea
History
The world's earliest civilizations in Mesopotamia (beginning with Sumer), ancient Egypt, and the Indian
subcontinent (beginning with the Indus Valley civilization), which
began along the valleys of the Tigris-Euphrates,
Nile and Indus rivers respectively, had all developed
around the Indian Ocean. Civilizations soon arose in Persia (beginning with Elam) and later in Southeast Asia (beginning with Funan). During Egypt's first dynasty (c. 3000 BC), sailors were sent out onto its
waters, journeying to Punt, thought to be part of present-day Somalia. Returning ships brought gold and myrrh. The earliest known maritime trade between Mesopotamia and the
Indus Valley (c. 2500 BC) was conducted along the Indian Ocean. Phoenicians of the late
3rd millennium BC may have entered the area, but no settlements resulted.
The Indian Ocean is far calmer and thus opened to trade earlier than the Atlantic or Pacific Oceans. The powerful monsoons also meant ships could easily sail west early in the season, then
wait a few months and return eastwards. This allowed Indonesian peoples to cross the Indian
Ocean to settle in Madagascar.
In the second or first century BC, Eudoxus of Cyzicus was the first
Greek to cross the Indian Ocean. Hippalus is said to have
discovered the direct route from Arabia to India around this time. During the first
and second centuries intensive trade relations developed between Roman Egypt and the Tamil kingdoms of the Cheras, Cholas and Pandyas
in Southern India. Like the Indonesian peoples above, the western sailors used the monsoon
to cross the ocean. The unknown author of the Periplus of the Erythraean
Sea describes this route and the ports and trade goods along the coasts of Africa and India around AD 70.
From 1405 to 1433, Admiral Zheng He led large fleets of the Ming Dynasty on several voyages to the Western Ocean (Chinese
name for the Indian Ocean) and reached the coastal country of East Africa. (see
Zheng He for reference)
In 1497, Vasco da Gama rounded the Cape of Good
Hope, and became the first European to sail to India. The European ships, armed with heavy cannon, quickly dominated
trade. Portugal at first attempted to achieve pre-eminence by setting up forts at the important
straits and ports. But the small nation was unable to support such a vast project, and they were replaced in the mid-17th century
by other European powers. The Dutch East India Company (1602-1798) sought
control of trade with the East across the Indian Ocean. France and Britain established trade
companies for the area. Eventually Britain became the principal power and by 1815 dominated the area.
The opening of the Suez Canal in 1869 revived European interest in the East, but no nation
was successful in establishing trade dominance. Since World War II the United Kingdom has withdrawn from the area, to be only
partially replaced by India, the USSR, and the United
States. The last two have tried to establish hegemony by negotiating for naval base sites. Developing countries bordering
the ocean, however, seek to have it made a "zone of peace" so that they may use its shipping lanes freely, though the United
Kingdom and United States maintain a military base on Diego Garcia atoll in the middle of
the Indian Ocean.
On December 26, 2004, the countries surrounding the Indian
Ocean were hit by a tsunami caused by the 2004
Indian Ocean earthquake. The waves resulted in more than 226,000 deaths and over 1 million were left homeless.
Culture and Literature
The Indian Ocean is known as Ratnakara in the ancient Sanskrit literature. Ratnakara
means "the place of jewels".
- See Culture of the Indian Ocean Islands and Indian Ocean literature
Major ports and harbours
-
See also
Wikimedia Commons has media related to:
References
- Braun, D., The Indian Ocean (1983)
- Chandra, S., ed., The Indian Ocean (1987);
- Chaudhuri, K. N., Trade and Civilization in the Indian Ocean (1985);
- Cousteau, Jacques-Yves, and Diole, Philippe, Life and Death in a Coral Sea
(1971);
- Cubitt, Gerald, Islands of the Indian Ocean (1975);
- Das Gupta, A., and Pearson, M.N., India and the Indian Ocean (1987);
- Dowdy, W. L., and Trood, R., eds., The Indian Ocean (1985);
- Kerr, A., ed., Resources and Development in the Indian Ocean Region (1981);
- Nairn, A. E., and Stehli, F. G., eds., The Ocean Basins and Margins, Vol. 6: The Indian Ocean (1982);
- Ostheimer, John M., ed., The Politics of the Western Indian Ocean Islands (1975);
- Torabully, Khal, Coolitude: An Anthology of the Indian Labour Diaspora (with Marina Carter, Anthem Press, London, 2002) ISBN
1843310031
- Toussaint, Auguste, The History of the Indian Ocean, trans. by June Guicharnaud (1966).
Much of this text is based on public domain text by US Naval Oceanographer at: http://oceanographer.navy.mil/indian.html
External links
Coordinates:
20° S 80°
Efrp:Ocèan
Endienbe-x-old:Індыйскі акіянzh-yue:印度洋 diq:Okyanuso Hind bat-smg:Indėjės ondenīns
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