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The Indian Ocean is the third largest of the world's oceanic divisions, covering about 20% of the water on the Earth's surface. It is bounded on the north by South Asia (including Indiamarker, after which it is named); on the west by Africa; on the east by Indochina, the Sunda Islandsmarker, and Australia; and on the south by the Southern Oceanmarker (or, traditionally, by Antarcticamarker). One component of the all-encompassing World Ocean, the Indian Ocean is delineated from the Atlantic Oceanmarker by the 20° east meridian running south from Cape Agulhasmarker, and from the Pacificmarker by the meridian of 146°55' east. The northernmost extent of the Indian Ocean is approximately 30° north in the Persian Gulfmarker. The Indian Ocean 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 73,556,000 square kilometres (28,400,000 mi²), including the Red Seamarker and the Persian Gulfmarker.

The ocean's volume is estimated to be 292,131,000 cubic kilometres (70,086,000 mi³). Small islands dot the continental rims. Island nations within the ocean are Madagascarmarker, the world's fourth largest island; Reunion Islandmarker; Comorosmarker; Seychellesmarker; Maldivesmarker; Mauritiusmarker; and Sri Lankamarker. The archipelago of Indonesiamarker borders the ocean on the east. 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 successfully dominated most of it until the early 1800s when the United Kingdommarker controlled much of the surrounding land.



Geography

The African, Indian, and Antarctic crustal plates converge in the Indian Ocean at the Rodrigues Triple Point. 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 Mumbaimarker, Indiamarker. The eastern, western, and southern basins thus formed are subdivided into smaller basins by ridges. The ocean's continental shelves are narrow, averaging 200 kilometers (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). Its deepest point, is in the Java Trenchmarker. 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 oceanmarker, 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. In Australia the Southern Ocean is considered to comprise all of the ocean south of the continent. This is obviously out of step with prevailing views in the rest of the world. The Indian Ocean remains the third-largest of the world's five oceans.

Major choke points include Bab el Mandebmarker, Strait of Hormuzmarker, the Lombok Straitmarker, the Strait of Malaccamarker and the Palk Straitmarker. Seas include Gulf of Adenmarker, Andaman Seamarker, Arabian Seamarker, Bay of Bengalmarker, Great Australian Bightmarker, Laccadive Sea, Gulf of Mannarmarker, Mozambique Channelmarker, Gulf of Omanmarker, Persian Gulfmarker, Red Seamarker, and other tributary water bodies. It is artificially connected to the Mediterranean Seamarker via the Suez Canalmarker, accessible via the Red Sea.



Climate

The climate north of the equator is affected by a Monsoon climate. Strong north-east winds blow from October until April; from May until October south and west winds prevail. In the Arabian Seamarker the violent Monsoon brings rain to the Indian subcontinent. In the southern hemisphere the winds are generally 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 Bengalmarker. The Indian Ocean is the warmest ocean in the world.

Hydrology

Among the few large rivers flowing into the Indian Ocean are the Zambezimarker, Shatt al-Arabmarker, Indusmarker, Gangesmarker, Brahmaputramarker, Jubbamarker and Ayeyarwady Rivermarker. 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 Oceanmarker, the Red Seamarker, 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.

Sub surface features

As the youngest of the major oceans it has active spreading ridges that are part of the worldwide system of mid-ocean ridges :-

The Ninety East Ridge runs north-south at meridian 90E, dissecting the Indian Ocean into eastern and western halves. Another submerged mountain range runs approximately north-south between the Atolls of the Maldives and the Chagos Archipelagomarker.

The Kerguelen Plateau is a large submerged continent, of volcanic origin, in the southern Indian Ocean.

The Mascarene Plateau is 2000 km long undersea plateau that lies east of Madagascarmarker.

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 oil fields of the Persian Gulfmarker and Indonesiamarker. Large reserves of hydrocarbons are being tapped in the offshore areas of Saudi Arabiamarker, Iranmarker, Indiamarker, 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 Indiamarker, South Africa, Indonesiamarker, Sri Lankamarker, and Thailandmarker.

The warmth of the Indian Ocean keeps phytoplankton production low, except along the northern fringe 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 Russiamarker, Japanmarker, South Koreamarker, and Taiwanmarker also exploit the Indian Ocean, mainly for shrimp and tuna.

Endangered marine species include the dugong, seal, turtles, and whales.

Oil and ship pollution threatens the Arabian Seamarker, Persian Gulfmarker, and Red Seamarker,

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 Tigrismarker-Euphrates, Nile and Indusmarker rivers respectively, had all developed around the Indian Ocean. Civilizations soon arose in Persiamarker (beginning with Elammarker) and later in Southeast Asia (beginning with Funan). During Egyptmarker's first dynasty (c. 3000 BC), sailors were sent out onto its waters, journeying to Punt, thought to be part of present-day Somaliamarker. 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. Phoeniciansmarker 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 Pacificmarker 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 Indonesianmarker peoples to cross the Indian Ocean to settle in Madagascar.

In the second or first century BC, Eudoxus of Cyzicus was the first Greekmarker 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 Dynastymarker 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 Hopemarker and became the first European to sail to India. The European ships, armed with heavy cannon, quickly dominated trade. Portugalmarker 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. Francemarker 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 Canalmarker 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 USSRmarker, and the United Statesmarker. The last two 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 Garciamarker 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 earthquakemarker. The waves resulted in more than 226,000 deaths and over 1 million people were left homeless.

Culture and literature

The Indian Ocean is known as Ratnakara in the ancient Sanskrit literature. Ratnakara means "the maker(creator) of pearls".
See Culture of the Indian Ocean Islands and Indian Ocean literature.


Major ports and harbours

Mumbai is the chief Indian trading port on the coast of Indian Ocean. It is often known as "The Gateway of India". The port of Kochi from the Southern Indian is known as "The Queen Arabian Sea". It is the finest natural harbour of India. Kolkata and Chennai are other important ports of India. They control the Indian goods flowing towards the east. Aden is the important Arabian port controled by the country of Yemen. Perth is the important Australian port.

Port Louismarker is the largest container handling facility in the Indian Ocean and can accommodate fourth and fifth generation container vessels. At present, only Cape Townmarker and Port Louis can achieve that in Sub-Saharan Africa.

See also



References

External links




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