37 Indian Ocean (3rd Largest ocean) “Introduction, Marginal Seas, Geology, Bottom relief features, Surface Features, climatic condition, Hydrological Condition, Economic aspects”.


The Indian Ocean, a body of saltwater, accounts for about one-fifth of the total area of the world’s oceans. It is the smallest in the region, the smallest in geology, and the most complex in physics of the three oceans in the world. With an area of 3,340,000 square miles, it extends to more than 10,000 unpaved beaches including the southern tip of Africa and Australia. Indian ocean average depth is near about lies in 12990 feet and the lowest point in the Far Sunda Trench off the southern coast of the island of Java (Indonesia) is 24,442 feet. feet (7,450 meters).

Indian Ocean Bounded:-

The extension of the Indian Ocean is north to Iran, Pakistan, India, and Bangladesh; The Malay Peninsula, the former Sunda Islands of Indonesia and Australia; and extension in South Antarctica; And Africa and the Arabian Peninsula to the west. In the southwest, it connects with the Atlantic Ocean at the southern tip of southern Africa and to the east and most of the waters with these parts of the Pacific Ocean.

Indian Ocean

Fig 1: Indian Ocean

Limits of the Indian Ocean:

Defining the boundaries of the Indian Ocean is complex and remains a challenge. This is the clearest and most frequently agreed border with the Atlantic Ocean, extending from Cape Agoulias, on the southern tip of Africa, south of 20 ° E. to the coast of Antarctica. The southeastern border with Minch is usually drawn from the Southeastern Cape on the island of Tasmania south of the 147 ° E meridian. to Antarctica.

Bass Street, between Tasmania and Australia, is considered part of the Indian Ocean and other parts of the Pacific Ocean. The most difficult definition is the northeastern border. One of the most common routes flows northwest of Cape Londonderry in Australia through the Timor Sea, along the south coast of the Little Sunda Islands and Java, and then across the Sunda Strait to the river o Sumatra. The border between Sumatra and the Malay Peninsula is usually drawn beyond Singapore Street.

Indian Ocean: Marginal Seas:

The Indian Ocean has the lowest marginal ocean of the largest oceans. Inland to the north is the Red Sea and the Persian Gulf. The Arabian Sea is located in the northwest and the Andaman Sea to the northeast. The Great Aden and the Gulf of Oman are located in the northwest, the Gulf of Bengal in East India, and the Gulf of Australia on the south coast of Australia.


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Terms of Physiography and Geology


The rise and development of the Indian Ocean is the most complex of the three. Its establishment was the result of the emergence of the great southern subcontinent Gondwana (or Gondwanaland), which began about 180 million years ago; The Northeast Indian subcontinent movement (started about 125 million years ago) began to engage Europe almost 50 million years ago. About 53 million years ago, the West African movement and Australia’s separation from Antarctica began. The Indian Ocean replaced it 36 million years ago. Although it opened about 140 million years ago, the length of the sea in southern India is less than 80 years.

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Submarine Features

Oceanic Ridges & Fracture Zones:

Ocean ridges are made up of rough, seismically active mountain ranges that are part of the global ocean ridge system and still contain seabed centers that extend to several locations. The ridges traverse the Y at the bottom of the ocean, starting from the upper northwest of the Carlsberg Range in the Arabian Sea, bypassing the Chagos-Lakadiv Plateau to form the Middle Indian (or Central Indian), Range. Branches of the mountain range southeast of Madagascar.

The south-western Indian subcontinent continues south-west until it merges with the South Atlantic-Indian subcontinent of Africa; The most shocking is the seismic (virtually earthquake-free) the Ninety East Ridge, which is the longest and straightest in the world’s oceans. It was first discovered in 1962 and stretches north along the east 90 ° corridor (hence its name) at 3,100 H and 9 ° H from an area where violations of 4500 km are broken. then follow the attachment.

The Bay of Bengal. Other possible earthquake regions are the Chagos-Lakadiv, Madagascar, and Mozambique plateaus, which are not part of the Arctic Ocean. The breakaway areas of the Indian Ocean weigh heavily on the edge of the sea mostly in the north-south direction. Notable are Owen, Prince Edward, Vema, and the surrounding Amsterdam area, with the largest Diamantina area found in southwestern Australia.


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Seamounts are underwater volcanoes that end in a mostly flat structure. Suddenly they rise from the bottom of the pit to a height of at least 3,300 feet (1,000 meters) above sea level. In the Indian Ocean, sailors are particularly popular between Réunion and Seychelles and the Vening Meinesz group near the Wharton Basin. The Bardin, Kohler, Nikitin, and Williams seamounts are one example.


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Ocean Basins

Ocean basins are characterized by smooth, flat, thick sedimentary plains with deep hills (i.e., properties less than 3,300 feet) at the lower edge of ocean ridges. The Indian Ocean ridge’s intricate topography culminated in the creation of many basins varying in diameter from 200 to 5,600 miles (320 to 9,000 km). The Arab, Somali, Mascarene, Madagascar, Mozambique, Agulhas, and Crozet basins are located in the west, while Central India (largest), Wharton, and South Australian basins are located in the east.

Continental Rise, Slope, and Shelf

The average width of the continental shelf is about 120 miles (120 km) in the Indian Ocean, with its widest points (300 km) near Mumbai (Bombay), off the west coast of India, and in northwestern Australia. The shelves on the island are only about 300 meters wide.

The shelf rupture is about 140 meters deep. Low-lying vessels pull back the steep slope during breakage. The Ganges (Ganga) and Indus rivers in Asia and the Zambezi River in Africa carve special large canyons. Their angry loads extend beyond the shelf, sliding down the slope, and contributing to the depth of their bowls. The Ganges sedimentary cone is the widest and widest in the world.


The Indian Ocean has fewer holes than any other sea in the world. The narrow (50 miles [80 km]), volcanic, and seismically Java Trench is the second-longest in the world, reaching 2,800 miles (4,500 km) southwest of Java and continuing north. the Sunda Trench passes through Sumatra, with an extension to the Andaman and Nicobar Islands. Part of the system adjacent to Sumatra is the epicenter of a major 2004 earthquake (9.1 magnitudes) that affected approximately 600 miles (1,000 km) in the area. The epicenter was reported below the Pacific Ocean floor, however, no tsunami alert was issued.

Bottom deposits

The severity of the discharge of water from the rivers into the Indian Ocean is the largest of our oceans, and nearly half of it comes from the Indian subcontinent alone. These dangerous occurrences occur most often in continuous soils, small areas, and climbs, and they enter flat soils. Cones of the thickness of at least 1 mile (1.6 km) are found in the Bay of Bengal, the Arabian Sea, and the Somali and Mozambique regions. The Wharton Basin in northern Australia has several artifacts. In the Ganges-Brahmaputra cone, there is a separation of 14 km in thickness and height up to 10 ° C.

Small hills emerged along with the southern Sunda Islands, perhaps because the Java Channel seemed a threat; instead, there was an ash fire of ashes. The reddish and reddish soils make a shallow depth between 10 ° C and 40 ° S between islands and land and up to 300 meters in thickness. Equator County is rich in seafood, marijuana, and so on.

To the south and below the Antarctic Convergence (approximately 50 ° S), an area with high yields, with the diatomaceous algal flow. The demons are no more than 70 km above sea level, and their wings are slightly covered. The bottom of the ocean is formed by basalt in various stages of transformation. Large authentic mineral phosphors (formed in the sea) are found at a depth of 40 to 400 meters, ferromanganese crusts at a depth of 3300 to 8200 feet (1,000 to 2,500 meters), ferromanganese swellings at depths of over 10,000 meters (3,000 meters)), and metalliferous hydrothermal sediments on the Carlsberg and Central Indian ridges.

Surface Features


It describes some of the coastal areas found in the Indian Ocean: estuaries, deltas, marshes, mangrove marshes, cliffs, coral reefs and fortified island landscapes, lagoons, beaches, and sandy beaches. An important part of the Hugli (Hooghly) complex is the three branches of the Hugli River in the Bay of Bengal near Kolkata (Calcutta). Pakistan combines one of the largest remote beaches in the world with the 190-mile-wide Indus river delta, where mud and salt marshes are often flooded.

The Indian Ocean has the widest coastline (more than half its coastline). Mangroves are found in many estuaries and deltas. Sundarbans delta, at the foot of the Ganges, has the highest mangrove forest in the world, and in 1987 many areas were designated a UNESCO World Heritage Site. Swimming – in any case, barbed wire, or atoll-shaped – is common on tropical islands and is also found on the southern coasts of Bangladesh, Myanmar (Burma), and India, and the east coast of Africa.


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There are more islands in the Indian Ocean than in the Atlantic and Pacific Oceans. Madagascar is the fourth largest island in the world – the Maldives, Seychelles, Sota, and parts of the Sri Lankan contingent. Other islands, including Christmas, Cocos, Farcad, Prince Edward, St. Paul, and Amsterdam. Amirante, Andaman and Nicobar, Chagos, Kroset, Cargulan, Sunda, Comoros, Lakshadweep (Lacadive, Minicay, Amandivi Islands), Mauritius, and Rhinoceros vol. Adjacent to the Andaman Sea and Sunds Arc, the islands are a sub-system of the arc.


The Indian Ocean can be divided into four broad geographical regions according to its climatic distribution: monsoon, industrial winds, tropical and subtropical and sub-Antarctic, and the Antarctic.

Monsoon Zone

The first region, which stretches north of latitudes of 10 ° C, has a monsoon climate (characterized by reverse winds in the middle of the year). In the “summer” of the northern hemisphere (May – October) there is a monsoon in the southwest due to low atmospheric pressure with Asia and pressure over Australia, with wind speeds of 45 km / h and South Asia. the season is wet. In the northern “winter” (November-April), high pressures over Asia and low pressures from 10 ° north to northern Australia cause northeast monsoon edges as well as wet northern parts of Indonesia and Australia.

Although the southwest monsoon repeats itself regularly, the date and intensity of its occurrence are characterized by high annual variability, and none of them can be accurately predicted. The dynamics of the monsoon are related to the current anomalies of El Niño and La Niña, as well as the atmospheric pattern of the southern oscillations in the South Pacific. The region is prone to destructive tropical cyclones that form over the open ocean and usually head west towards the coast. These storms usually occur just before and after the southwest monsoon, with the west coast usually hitting the hardest.

One such storm, the Ganges-Brahmaputra cyclone in November 1970, was particularly devastating, killing hundreds of thousands of people. The northwestern part of the region has the driest climate, with some regions receiving less than 10 inches (250 mm) of rainfall per year; In contrast, the equatorial regions are the highest, averaging 80 inches (2000 mm).

In summer months, sea temperatures range from 77 to 82 ° F (25–28 ° C), but along the north-east coast of Africa, cold deep waters rise to 73 ° F (23 ° C). Winter temperatures plunge to 72 ° F (22 ° C) in the Northern Ocean, remaining largely unchanged further south along the equator. The sky is cloudy, 60 to 70 percent on summer days and 10 to 30 percent in winter during the rainy season.


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Trade-Winds Zone

The second zone, the trade wind zone, is located between 10 ° and 30 ° S latitude. Here stable southeastern trade winds prevail throughout the year and are strongest from June to September. The Cyclones were also found east of Madagascar between December and March. In the northern part of the zone, temperatures average 77 ° F (25 ° C) during the southern “winter” (May-October) and slightly warmer the rest of the time; At latitude 30 ° S, winter temperatures are 61-63 ° F (16-17) C) and tropical “summer” (November-April) 68-72 ° F (20-22 ° C). The warm ocean currents raise the westerly trade wind temperature by about 4-6 ° F (2-3 ° C) compared to the east. Precipitation drops from north to south.


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Subtropical and Temperate Zone

The third zone is located in the subtropical and temperate latitudes of the Southern Hemisphere, between 30 ° and 45 ° S. The main winds in the north of the area are light and variable, while in the south the winds are moderate or strong in the west. The average air temperature decreases as the southern latitude increases: 68 to 22 ° C between 68 and 72 ° F (10 ° C) to 50 ° F (austral summer (December-February) and 16 to 17 ° C). ° F (6 and 7 ° C) in winter (June-August). Rainfall is moderate and evenly distributed.

Sub Antarctic and Antarctic Zone

The fourth zone, or sub-Antarctic and Antarctic, covers a wide zone between 45 ° S latitude and the Antarctic continent. Stable westerly winds prevail, and sometimes, passing through low-pressure areas of Antarctica, gain gale strength. The average winter air temperature varies between 43 and 45 ° F (6 to 7 ° C) in the north close to the continent. Suitable summer temperatures range from 10 to -4 ° C (50 to 25 ° F). Precipitation is common and decreases in the south, while snow is common in the far south.


The water quality of the Indian Ocean is based on the interaction of climates (water, wind, and solar energy) with the surface, its water features, and the deep circulation (thermohaline), which together often form straight lines of water. Each section has different temperatures and salt mixtures that create discrete water cells of different shades, with clearer water than excess water. The water surface temperature varies with the time, latitude, and orbit of the planet; the salt above the ground is present between rain, flow, and runoff of the river.

Surface Currents

The circulation of the ocean surface is driven by the wind. In the monsoon zone, the surface circulation reverses every six months and features two opposing eddies (i.e. semi-closed current systems showing spiral motion) that are separated from the Indian subcontinent. During the northeast monsoon, a faint counterclockwise vortex develops in the Arabian Sea and a strong clockwise vortex forms in the Bay of Bengal. During the southwestern monsoon, currents change the direction of the two seas, creating hot and cold storms in the Arabian Sea.

In southern Sri Lanka, during the northeastern monsoon, the northern equatorial current flows westward, turns southward off the coast of Somalia, and returns eastward as an equatorial countercurrent between latitudes 2 ° and 10 ° C. Equatorial current flows to the east to a greater depth. then 500 feet (150 meters). During the South-West Monsoon, Now the North Equator changes direction to the Monun current flowing rails.

Some of the southern equatorial currents appear north along the coast of Somalia and become strong currents of Somalia. The bright front, typical of the Indian Ocean, at 10 ° C, determines the boundary effect of the monsoon.

Deep (Thermohaline) Circulation

Under the influence of surface water flow, the flow of water is slow and irregular. Two high-salinity water sources enter the Indian Ocean through the Arabian Sea, one from the Persian Gulf and the other from the Red Sea, and then sink below the fresher surface water, forming a North Indian high-salinity intermediate water between 2,000 and 3,300 feet (600 and 1,000 meters). This layer extends eastward to the Bay of Bengal and southward to Madagascar and Sumatra.

Below this part of the Antarctic central water level at 5,000 feet. The deep waters of the North Atlantic Ocean (named for the cause of the reef) are between 5,000 and 10,000 feet (1,500 to 3,000 m), and less than 10,000 feet of Antarctic waters below the Wade Sea. These cold, dense waves slowly creep north from their origins to the Antarctic Circumpolar Region, making them an almost anoxic (oxygen-deficient) journey. Unlike the Atlantic Ocean and the Pacific Ocean, the Indian Ocean has no various underwater resources.


The increase is a seasonal phenomenon in the Indian Ocean due to the monsoon regime. During the southwest monsoon, renovations will take place off the coasts of Somalia and Arabia, as well as in southern Java. The most intense is between 5 ° and 11 ° N, with warmer surface water being replaced by 14 ° C (57 ° F). During the northeast monsoon, there was a strong rise off the west coast of India. Midocean warming occurs at a time of 5 ° south, where the northern equatorial current and the equatorial countercurrent flow in opposite directions.

Surface Temperatures

Zonal asymmetry is observed in the distribution of surface water temperature in summer flying north of latitude 20 ° C. Summer surface temperatures are higher in the eastern part of the region than in the west. In the Bay of Bengal, the maximum temperature is around 82 ° F (28 ° C). The minimum temperature is around 72 ° F (22 ° C) in the area of Cape Guardafui, in the Horn of Africa, and is associated with the ascent along the African coast.

In the Antarctic region, surface water temperatures steadily decrease south of latitude 20 ° S as latitude increases from 72-75 ° F (22-24 ° C) to 30 ° F (-1 ° C). Near the equator, in the Tokai and northern Arabian Seas, winter surface temperatures exceed 28 ° C. Winter surface temperatures range from 22 to 23 ° C (72 to 73 ° F). 77 ° F (25 ° C) in the Bay of Bengal. The temperature at 20 ° S is about 72 to 75 ° F (22 to 24 ° C). On the 40th parallel, 14-16 ° C (57-61 ° F). On the coast of Antarctica, -1 to 0 ° C (30 to 32 ° F).


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Surface Salinity

In total, the surface salt content of the Indian Ocean varies between 32 and 37 ppm, with significant regional differences. The Arabian Sea is very densely populated, with high salt content (37 parts per mile) to a depth of about 400 feet (120 meters) due to its hot climate and underwater during seasonal changes. Salinity and the Bay of Bengal area are small, sometimes less than 32 thousand, due to the high water content in the river.

High salt content (more than 35 parts per thousand) is also found in the southern suburbs of the South Hemisphere between 25 ° C and 35 ° C; where the salinity zone extends over a maximum of 10 ° S from Indonesia to Madagascar. The salinity of the Antarctic water is usually below 34 parts per thousand.


Ice forms in the southern part of the Antarctic during the winter months. Between January and February, the melting ice along the Antarctic coast was broken by severe storms and, in the form of large blocks and wide-open spaces, was carried by wind and currents into the open sea. In other coastal areas, the ice tongue is broken on the ice to produce ice. To the west of the 90 ° E meridian, the northern boundary of the rotating ice is around 65 ° latitude. To the east of this meridian, however, ice of up to 60 ° S is usually found; icebergs are sometimes found as far north as 40 ° S.


Examples of all three types of waves: daily (daily), semi-annually (twice daily) և mixed, can be found in the Indian Ocean, although semi-annual are the most common. Biennial waves occur on the east coast of Africa as far as the Equatorial Bay of Bengal. The waves mix in the Arabian Sea ներքին in the interior of the Persian Gulf. The southwest coast of Australia has relatively small areas with high tides, such as the Andaman Sea in Thailand and the south coast of the Central Persian Gulf.

Tidal areas in the Indian Ocean and adjacent seas vary significantly in places. In Port Louis, Mauritius, for example, there is a spring tide range of only 0.5 meters typical of the open ocean islands. Other low-lying areas are Chennai (Madras), India (1.3 meters), and Colombo, Sri Lanka (2.3 feet [0.7 meters]).

The largest tidal areas are in the Arabian Sea, especially in Bhavanagar, India, in Khambhat Bay (11.6 meters] at 38 feet, at Navlakhi (Kachchh Bay) (7.5 meters) There is a high tidal range in the eastern part of the ocean; 3 meters, Yangon (Rangoon), Myanmar, and 18.4 feet (5.6 meters) meters at the northern end of the Andaman Sea. Moderate provinces are found in Durban, South Africa, and Karachi, Pakistan (both about 2.3 meters], and Shatt Al-’Arab, Iraq (3.4 meters).

Economic Aspects

Mineral resources

The most valuable mineral resource is by far oil, and the Persian Gulf is the largest oil-producing region in the world. Offshore oil and gas exploration is also underway in the Arabian Sea and the Bay of Bengal, both of which have large reserves. Other sites for research activities are located off the northwest coast of Australia, the Andaman Sea, off the coast of Africa south of the Equator, and off the southwest coast of Madagascar. Apart from the countries of the Persian Gulf, only India produces large quantities of oil from distant countries, and most of its production comes from land off the coast of Mumbai.

Other gas is produced from land in northeastern Australia. Another potentially valuable resource is manganese nodules, which are abundant in the Indian Ocean. Experimental sites in the middle of the ocean, as far as South Africa, and east of the South Australian Basin have been found to have nodules; manganese content was highest in the east and low in the northwest. The difficulty in digging and operating those minerals, despite advances in technology, has prevented their business isolation. Other potential commercial minerals are ilmenite (a mixture of iron and titanium oxide), tin, monazite (rare earth), zircon, and chromite, all of which are found on the beach one.


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Biological Resources

The bulk of the Indian Ocean waters lie within hot and temperate zones. The shallow waters of the tropics are represented by the abundance of corals and other living things that can build homes – along with cool red algae – reefs and islands of corals. The enclosed buildings are habitats that protect marine life including bats, worms, crabs, mollusks, sea urchins, squirrels, sea stars, and small fish that are very bright in color.

Much of the tropical coast is covered with flat forests and wildlife. Working mangroves stabilize the land along the coast and it is important to develop it with a nursery class for outdoor animals. Fruits on most of the islands of the Indian Ocean include various types of palms and baths. Little crustaceans, comprising more than a hundred minutes of cod, build a large animal life, followed by soft tissues, jellyfish, and polyps, and other invertebrates circulating from single-cell Radiolaria to Portuguese adults – importantly, the buildings can reach as long as possible. 165 feet (50 meters).


The upgrades that occur in several coastal regions of the Indian Ocean – particularly in the northern Arabian Sea and along the coast of South Africa – contribute to nutrient concentrations in surface waters. This phenomenon, in turn, produces huge amounts of phytoplankton which is the basis for large populations of commercially valuable marine animals. Despite the great fishing potential, however, most commercial fishing is done by small-scale fishermen, at lower depths, although deep-sea resources (other than tuna) still fish poorly. Littoral countries capture the main coastal species – shrimp, crocuses, snappers, skates, and grouse – and higher value pelagic fish – including tuna and tuna species such as billed fish found in tropical and subtropical waters – are caught in large quantities.

of mostly world fishing countries (e.g., Japan, South Korea, and Russia). Shrimp is the most important commercial species for coastal countries, with India being the largest catch. Literary states use smaller amounts of sardines, mackerel, and anchovies. Because coastal nations can claim sovereignty over resources within an exclusive economic zone that stretches 200 nautical miles (230 nautical miles, or 370 km) from their coasts, small countries like the Maldives can increase national income through fishing rights to sell. in their zones in large fishing, countries have capital and technology using pelagic resources.


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Trade and Transportation

The economic development of littoral countries since the middle of the 20th century has been uneven, following the acquisition of independence by many states. The formation of trade segments led to an increase in sea trade and the development of new products. Many Indian states of India have continued to export raw materials and imports of manufactured goods to other locations, with a few exceptions such as Australia, India, and South Africa.

Oil regulation business, since the Indian Ocean, has become an important means of transporting unsafe oil in Europe, North America, and East Asia. Other important products include iron, coal, leather, and tea. Iron ore from Western Australia and India and South Africa is transported to Japan, while coal is transported to the UK from Australia via the Indian Ocean. Marine samples have emerged as an important export and export product. In addition, tourism is growing rapidly on many islands.


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