The Indian Ocean
is the third largest of the
divisions, covering about 20%
of the water
on the Earth
's surface. It is bounded on the north by South Asia (including India, after which
it is named); on the west by Africa; on the
east by Indochina, 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, and from the Pacific by the
meridian of 146°55' east. The northernmost extent of the Indian
Ocean is approximately 30° north
in the Persian
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
Sea and the Persian Gulf.
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 Madagascar, the world's fourth largest island; Reunion Island; Comoros; Seychelles; Maldives; Mauritius; and Sri
Lanka. The archipelago of Indonesia borders the ocean on the east.
importance as a transit route between Asia
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 Kingdom controlled much of the surrounding
The African, Indian, and Antarctic crustal plates
converge in the Indian Ocean at the
Rodrigues Triple Point
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.
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).
deepest point, is in the Java Trench.
North of 50°
, 86% of the main basin is covered by pelagic
sediments, of which more than half is
. The remaining 14% is
layered with terrigenous
Glacial outwash dominates the extreme southern latitudes.
2000 decision by the International
Hydrographic Organisation delimited a fifth world ocean, stripping the southern portions of the Indian
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.
choke points include Bab el Mandeb, Strait of
Hormuz, the Lombok Strait, the Strait of Malacca and the Palk Strait. Seas include Gulf of Aden, Andaman
Sea, Bay of
Bengal, Great Australian Bight, Laccadive Sea,
Mannar, Mozambique Channel, Gulf of
Sea, and other tributary water bodies.
artificially connected to the Mediterranean Sea via the Suez Canal, accessible via the Red Sea.
The climate north of the equator
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 Sea the violent Monsoon brings rain to the Indian
In the southern hemisphere the winds are
generally milder, but summer storms near Mauritius can be severe.
Monsoon winds change, cyclones sometimes strike the shores of the
Arabian Sea and the Bay of
The Indian Ocean is the warmest ocean in
few large rivers flowing into the Indian Ocean are the Zambezi, Shatt
al-Arab, Indus, Ganges, Brahmaputra, Jubba and
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.
water circulation is controlled primarily by inflows from the
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°
, temperatures drop quickly. Surface water
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
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
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
The Kerguelen Plateau
is a large
submerged continent, of volcanic origin, in the southern Indian
Mascarene Plateau is 2000 km
long undersea plateau that lies east of Madagascar.
The Indian Ocean provides major sea routes connecting the Middle East
and the Americas
carries a particularly heavy traffic of petroleum and petroleum products from the oil
fields of the Persian
Gulf and Indonesia. Large reserves of hydrocarbons are being
tapped in the offshore areas of Saudi Arabia, Iran, India, and Western
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 fringe and in a few scattered spots elsewhere; life in the
ocean is thus limited. Fishing
to subsistence levels. Its fish are of great and growing importance
to the bordering countries for domestic consumption and export.
fleets from Russia, Japan, South Korea, and Taiwan also
exploit the Indian Ocean, mainly for shrimp
Endangered marine species include the dugong
ship pollution threatens the Arabian Sea, Persian
Gulf, and Red
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
second or first century BC, Eudoxus
of Cyzicus was the first Greek to cross
the Indian Ocean. Hippalus
to have discovered the direct route from Arabia
to India around this time. During the first
and second centuries intensive trade
developed between Roman
and the Tamil kingdoms
. Like the Indonesian
peoples above, the western sailors used the monsoon to cross the
ocean. The unknown author of the Periplus of the Erythraean
describes this route and the ports and trade goods
along the coasts of Africa and India around AD 70.
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
Vasco da Gama rounded the Cape of Good
Hope and became the first European to sail to
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.
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.
opening of the Suez
Canal in 1869 revived European interest in the East, but
no nation was successful in establishing trade dominance.
World War II the United Kingdom has withdrawn from the area, to be
only partially replaced by India, the USSR, and the
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 Garcia atoll in the middle of the Indian
December 26, 2004, the countries surrounding the Indian Ocean were
hit by a tsunami caused by the 2004 Indian
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
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
Port Louis is the largest container handling facility in the
Indian Ocean and can accommodate fourth and fifth generation
container vessels. At present, only Cape Town and Port Louis can achieve that in Sub-Saharan