Information about the Indian Ocean short message. All about sharks

Ocean area – 76.2 million sq. km;
Maximum depth – Sunda Trench, 7729 m;
Number of seas – 11;
The largest seas are the Arabian Sea, the Red Sea;
The largest bay is the Bay of Bengal;
The largest islands are the island of Madagascar, Sri Lanka;
The strongest currents:
- warm - South Passatnoe, Monsoon;
- cold - Western Winds, Somali.

The Indian Ocean ranks third in size. Most of it is located in the Southern Hemisphere. In the north it washes the shores of Eurasia, in the west – Africa, in the south – Antarctica, and in the east – Australia. The coastline of the Indian Ocean is slightly indented. On the northern side, the Indian Ocean is seemingly shrouded in land, making it the only ocean that is not connected to the Arctic Ocean.
The Indian Ocean was formed as a result of the splitting of the ancient continent of Gondwana into parts. It lies on the boundary of three lithospheric plates - the Indo-Australian, African and Antarctic. The mid-ocean ridges of the Arabian-Indian, West Indian and Australian-Antarctic are the boundaries between these plates. Underwater ridges and elevations divide the ocean floor into separate basins. The ocean shelf zone is very narrow. Most of the ocean lies within the boundaries of the bed and has considerable depth.

From the north, the Indian Ocean is reliably protected by mountains from the penetration of cold air masses. Therefore, the temperature of surface waters in the northern part of the ocean reaches +29 ˚С, and in the summer in the Persian Gulf it rises to +30...+35 ˚С.
An important feature of the Indian Ocean is the monsoon winds and the monsoon current created by them, which changes its direction seasonally. Hurricanes are frequent, especially around the island of Madagascar.
The coldest areas of the ocean are in the south, where the influence of Antarctica is felt. Icebergs are found in this part of the Pacific Ocean.
The salinity of surface waters is higher than in the World Ocean. A salinity record was recorded in the Red Sea - 41%.
The organic world of the Indian Ocean is diverse. Tropical water masses are rich in plankton. The most common fish include: sardinella, mackerel, tuna, mackerel, flounder, flying fish and numerous sharks.
Shelf areas and coral reefs are especially rich in life. In the warm waters of the Pacific Ocean there are giant sea turtles, sea snakes, a lot of squid, cuttlefish, and starfish. Whales and seals are found closer to Antarctica. Pearls are mined in the Persian Gulf near the island of Sri Lanka.
Important shipping routes pass through the Indian Ocean, mostly in its northern part. The Suez Canal, dug at the end of the 19th century, connects the Indian Ocean with the Mediterranean Sea.
The first information about the Indian Ocean was collected 3 thousand years BC by Indian, Egyptian and Phoenician sailors. The first sailing routes in the Indian Ocean were drawn up by the Arabs.
Vasco da Gama, after the discovery of India in 1499, Europeans began to explore the Indian Ocean. During an expedition, the English navigator James Cook made the first measurements of the depth of the ocean.
A comprehensive study of the nature of the Indian Ocean begins at the end of the nineteenth century.
Nowadays, warm waters and picturesque coral islands of the Indian Ocean, which attract the attention of tourists from different countries world, are carefully studied by numerous scientific expeditions from all over the world.

The message about the Indian Ocean will briefly tell you about the ocean, which is the third largest after the Pacific and Atlantic oceans. The report on the Indian Ocean can also be used to prepare for the lesson.

Message about the Indian Ocean

Indian Ocean: geographical location

The Indian Ocean is located in the eastern hemisphere. In the northeast and north it is limited by Eurasia, Africa in the west, the Antarctic convergence zone in the southeast, in the south by the eastern coast of Africa, in the east by the western coast of Oceania and Australia. This ocean is the third largest after the Atlantic and Pacific oceans. Its area is 76.2 million km 2, and the volume of water is 282.6 million km 3.

Features of the Indian Ocean

It was from the Indian Ocean that the exploration of water spaces began. Of course, the population ancient civilizations didn't swim far in open waters and considered the ocean to be a huge sea. The Indian Ocean is quite warm: the water temperature near the coast of Australia is +29 0 C, in the subtropics +20 0 C.

A small number of rivers flow into this ocean, unlike other oceans. Mainly in the north. Rivers carry a large amount of sediment into it, so the northern part of the ocean is quite polluted. The southern Indian Ocean is much cleaner as there are no freshwater arteries. Therefore, the water is crystal clear with a dark, blue tint. It is the lack of desalination and high evaporation that is the reason why the salinity of the Indian Ocean is much higher than in other oceans. The saltiest part of the Indian Ocean is the Red Sea. Its salinity is 42% 0. The salinity of the ocean is also affected by icebergs that swim far into the depths. Up to 40 0 south latitude, the average water salinity is 32% 0.

Also in this ocean there is a huge speed of trade winds and monsoons. Therefore, large surface currents are formed here, changing every season. The largest of them is the Somali Current, flowing in winter from north to south, and with the onset of summer it changes direction.

Topography of the Indian Ocean

The bottom topography is varied and complex. In the southeast and northwest there is a divergent system of mid-ocean ridges. They are characterized by the presence of rifts, transverse faults, seismicity and submarine volcanism. Between the ridges there are numerous deep-sea basins. The shelf on the ocean floor is mostly small, but off the coast of Asia it expands.

Natural resources of the Indian Ocean

The Indian Ocean contains many minerals, emeralds, diamonds, pearls and other precious stones. The largest oil field developed by man is located in the Persian Gulf.

Indian Ocean climate

Since the Indian Ocean borders continents, climatic conditions are to some extent determined by the surrounding land. It has the unofficial status of “monsoon”. The fact is that the sharp contrast over sea and land strong winds, monsoons.

In summer, in the northern ocean, the land becomes very hot and a low pressure area appears, which causes heavy precipitation over the ocean and continent. This phenomenon was called the “southwest equatorial monsoon.” In winter, the weather is harsher: destructive hurricanes are observed in the ocean and floods on land. A high pressure area and trade winds dominate over Asia.

Organic world of the Indian Ocean

The fauna is quite diverse and rich, especially in coastal areas and tropical parts. Coral reefs stretch along the entire Indian Ocean and continue into the Pacific. There are many thickets of mangroves in the coastal waters. In the tropical region there is a large amount of plankton, which, in turn, serves as food for larger fish (sharks, tuna). Sea turtles and snakes swim in the waters.

Anchovy, sardinella, mackerel, coryphaena, flying fish, tuna, and shark swim in the northern part. In the south there are white-blooded and nototheniid fish, cetaceans and pinnipeds. In the thickets there is a large accumulation of shrimp, lobsters, and krill.

It is interesting that against the backdrop of such a vast diversity of fauna, the southern Indian Ocean is an oceanic desert where life forms are minimal.

Indian Ocean interesting facts

The surface of the Indian Ocean is covered with luminous circles from time to time. They disappear and then appear again. Scientists have not yet come to a consensus regarding the nature of these circles, but they suggest that they appear due to a huge concentration of plankton floating to the surface of the water.
The saltiest ocean on the planet (after the Dead Sea) is located in the ocean - the Red Sea. No river flows into it, so it is not only salty, but also transparent.
The Indian Ocean is home to the most dangerous poisoner - the blue-ringed octopus. It is no bigger than a golf ball. However, after being struck by it, a person begins to experience suffocation within 5 minutes and dies after 2 hours.
This is the warmest ocean on the planet.
Near the island of Mauritius you can observe an interesting natural phenomenon - an underwater waterfall. From the outside it seems real. This illusion occurs due to the runoff of sand in the water and silt deposits.

We hope that the message about the Indian Ocean helped you prepare for the lesson. And you can add to the story about the Indian Ocean using the comment form below.

What is the area of the Indian Ocean? The very name of the water area implies enough big numbers. It is immediately worth paying attention to the fact that the Indian Ocean ranks third in size among similar bodies of water on our planet. In the widest part of the ocean, the distance is about 10 thousand km. This meaning visually connects the southern points of Africa and Australia. It is located between four continents: Antarctica, Eurasia, Africa and Australia. So, what is the area of the Indian Ocean (million km2)? This figure is 76.174 million square meters. km.

Let's look into history

The Indian Ocean in the north cuts so far into the land that the people of the ancient world defined it as a very large sea. It was in these waters that humanity began its first long journeys.

On ancient maps it (or rather, the western part) was called the “Eritrean Sea”. And the ancient Russians called him Black. In the 4th century, a name consonant with the current one began to appear for the first time: the Greek “Indikon pelagos” - “Indian Sea”, the Arabic Bar-el-Hind - “Indian Ocean”. And already in the 16th century, the hydronym, which was proposed by a Roman scientist, was officially assigned to the ocean.

Geography

The Indian Ocean, whose area is smaller than the Pacific and Atlantic, is younger and much warmer than these bodies of water. This body of water receives many rivers in the region, the largest of which are the Limpopo, Tigris, Ganges and Euphrates. The near-continental waters of the ocean are muddy due to the abundance of clay and sand that rivers carry into them, but its open water is surprisingly clean. There are many islands in the Indian Ocean. Some of them are debris. The largest are Madagascar, Sri Lanka, Comoros, Maldives, Seychelles and many others.

The Indian Ocean has seven seas and six bays, as well as several straits. Their area is more than 11 million square meters. km. The most famous are the Red Sea (the saltiest in the world), the Arabian Sea, the Andaman Sea, the Persian Sea and
The ocean sits above ancient tectonic plates that are still moving today. Because of this, tsunamis and underwater volcanic eruptions are common in the region.

Climate indicators

The Indian Ocean, whose area is more than 76 million square meters. km, located in four climatic zones. The north of the water basin is influenced by the Asian continent, which is why frequent tsunamis with characteristic tsunamis are observed here. Thanks to high temperatures, the water heats up well, so the seas and bays there are the warmest. In the south, the southeast trade wind prevails with its cold air. Tropical hurricanes often form in the middle part.

The entire weather background is formed by monsoons - winds that change direction depending on the season. There are two of them: summer - hot and rainy and winter, with sudden changes weather, often accompanied by storms and floods.

World of flora and fauna

The Indian Ocean, whose area is quite large, has an extremely diverse fauna and flora, both on land and in the aquatic part. The tropics are rich in plankton, which, unlike the Pacific, is abundant in luminous organisms. A huge number of crustaceans, jellyfish and squid. The most common fish are flying species, poisonous sea snakes, tuna, and some types of sharks. In the waters you can see whales, seals and dolphins. The coast is favored by giant turtles and elephant seals.

Among the variety of birds, albatross and frigatebirds can be distinguished. And in southern Africa there are various populations of penguins. Corals grow in shallow waters, sometimes forming entire islands. Among these beautiful structures live many representatives of this region - sea urchin and starfish, crabs, sponges, coral fish.

Like any other body of water, the Indian Ocean abounds in numerous species of algae. For example, sargassum, which is also found in the Pacific region. There are also lush and strong lithothamnias and halimedas, which help the corals build atolls, turbinaria and caulerpas, forming entire underwater jungles. The tidal zone is favored by mangroves - dense, always green forests.

Economic characteristics of the Indian Ocean

The Indian Ocean is shared by 28 mainland and 8 island states. With some on the brink of extinction, what was once a highly developed species is fading away. Fishing takes up a small percentage of the economy of this region. Mother-of-pearl and pearls are mined off the coast of Australia, Bahrain and Sri Lanka.

The ocean is the largest transport artery for ships in the region. The main maritime transport hub is the Suez Canal, connecting the Indian Ocean with the Atlantic. From there the path to Europe and America opens. Almost most of the region's business life is concentrated in port cities - Mumbai, Karachi, Durban, Colombo, Dubai and others.

With an area of over 76 million km2, the Indian Ocean is home to a huge number of mineral deposits. Huge deposits of non-ferrous metals and ores. But the main wealth, of course, is the richest oil and gas deposits. They are concentrated mainly on the shallows of the Persian and Suez Gulfs.

Unfortunately, human activity is becoming a threat to the integrity and preservation of this world. Tankers and industrial vessels ply in large numbers across the Indian Ocean. Any leak, even a small one, can become a disaster for the entire region.

The Indian Ocean ranks third in area after the Pacific and Atlantic. The average depth is about 4 km, and the maximum is recorded in the Java Trench and is 7,729 m.

The Indian Ocean washes the shores of the most ancient centers of civilization and it is believed that it was the very first to be explored. The routes of the first voyages did not go far into open waters, so the ancients who lived on the ocean considered it simply a huge sea.

The Indian Ocean appears to be the most populous of animals. Fish stocks have always been famous for their abundance. Northern waters served as almost the only source of food for people. Pearls, diamonds, emeralds and other precious stones - they are all found in the Indian Ocean.

The ocean is also rich in minerals. The Persian Gulf contains one of the largest oil fields developed by man.

A small number of rivers flow into the Indian Ocean, mainly in the north. These rivers carry a lot of sediment into the ocean, so this part of the ocean cannot boast of cleanliness. Things are different in the south, where the ocean has no freshwater arteries. The water appears crystal clear to the observer, with a dark blue tint.

The lack of sufficient desalination, as well as high evaporation, explains why the salinity of its waters is slightly higher compared to other oceans. The saltiest part of the Indian Ocean is the Red Sea (42%).

Climate

Since the Indian Ocean has extensive borders with continents, the climatic conditions are largely determined by the surrounding land. The status of " monsoon"The pressure contrast over land and sea causes strong winds - monsoons. In summer, when the land in the northern ocean is very hot, a large area of low pressure occurs, causing heavy precipitation over both the continent and the ocean. This is the so-called southwest equatorial monsoon".

In contrast, winter is characterized by harsher weather in the form of destructive hurricanes and flooding on land. An area of high pressure over Asia causes trade winds.

The speed of the monsoons and trade winds is so fast that they form large surface currents that change every season. The largest such current is Somali, which flows from north to south in winter and changes its direction in summer.

The Indian Ocean is quite warm. The water surface temperature in Australia reaches 29 degrees, but in the subtropics it is colder, around 20. Icebergs, which can float quite high, up to 40 degrees south latitude, have a minor but quite noticeable effect on the water temperature, as well as on its salinity. . Before this area, salinity averages 32% and increases closer to the north.

INDIAN OCEAN, the third largest ocean on Earth (after the Pacific and Atlantic), part of the World Ocean. Located between Africa in the northwest, Asia in the north, Australia in the east and Antarctica in the south.

Physiographical sketch

General information. The border of the Indian Ocean in the west (with the Atlantic Ocean south of Africa) is drawn along the meridian of Cape Agulhas (20° east longitude) to the coast of Antarctica (Donning Maud Land), in the east (with the Pacific Ocean south of Australia) - along the eastern border of Bass Strait to the island of Tasmania , and then along the meridian 146°55' east longitude to Antarctica, in the northeast (with the Pacific Ocean) - between the Andaman Sea and the Strait of Malacca, then along the southwestern shores of the island of Sumatra, the Sunda Strait, the southern coast of the island of Java, the southern the borders of the Bali and Savu seas, the northern border of the Arafura Sea, the southwestern shores of New Guinea and the western border of the Torres Strait. The southern high-latitude part of the Indian Ocean is sometimes referred to as the Southern Ocean, which combines the Antarctic sectors of the Atlantic, Indian and Pacific oceans. However, such geographical nomenclature is not generally accepted, and, as a rule, the Indian Ocean is considered within its usual boundaries. The Indian Ocean is the only ocean that is located mostly in the Southern Hemisphere and is bounded in the north by a powerful land mass. Unlike other oceans, its mid-ocean ridges form three branches radiating in different directions from the central part of the ocean.

The area of the Indian Ocean with seas, bays and straits is 76.17 million km2, the volume of water is 282.65 million km3, the average depth is 3711 m (2nd place after the Pacific Ocean); without them - 64.49 million km 2, 255.81 million km 3, 3967 m. The greatest depth in the deep-sea Sunda Trench is 7729 m at the point of 11°10' south latitude and 114°57' east longitude. The shelf zone of the ocean (conditionally depths up to 200 m) occupies 6.1% of its area, the continental slope (from 200 to 3000 m) 17.1%, the bed (over 3000 m) 76.8%. See the map.

Seas. There are almost three times fewer seas, bays and straits in the Indian Ocean than in the Atlantic or Pacific Oceans; they are mainly concentrated in its northern part. Seas of the tropical zone: Mediterranean - Red; marginal - Arabian, Laccadive, Andaman, Timor, Arafura; Antarctic zone: marginal - Davis, D'Urville, Cosmonauts, Riiser-Larsen, Commonwealth (see separate articles on the seas). The largest bays: Bengal, Persian, Aden, Oman, Great Australian, Carpentaria, Prydz. Straits: Mozambique, Babel-Mandeb, Bass, Hormuz, Malacca, Polk, Tenth Degree, Great Channel.

Islands. Unlike other oceans, the islands are few in number. The total area is about 2 million km 2. The largest islands of mainland origin are Socotra, Sri Lanka, Madagascar, Tasmania, Sumatra, Java, Timor. Volcanic islands: Reunion, Mauritius, Prince Edward, Crozet, Kerguelen, etc.; coral - Laccadive, Maldives, Amirante, Chagos, Nicobar, most of Andaman, Seychelles; The coral Comoros, Mascarene, Cocos and other islands rise on volcanic cones.

Shores. The Indian Ocean has a relatively indented coastline with the exception of the northern and northeastern parts, where most of the seas and the main large bays are located; There are few convenient bays. The coasts of Africa in the western part of the ocean are alluvial, weakly dissected, and often surrounded by coral reefs; in the northwestern part - indigenous. In the north, low, weakly dissected shores with lagoons and sand bars, in places with mangroves, bordered on the landward side by coastal lowlands (Malabar Coast, Coromandel Coast) predominate; abrasion-accumulative (Konkan coast) and deltaic shores are also common. In the east, the shores are indigenous; in Antarctica, they are covered with glaciers descending to the sea, ending in ice cliffs several tens of meters high.

Bottom relief. In the bottom topography of the Indian Ocean, four main elements of geotexture are distinguished: the underwater continental margins (including the shelf and continental slope), transition zones, or island arc zones, the ocean floor and mid-ocean ridges. The area of the underwater continental margins in the Indian Ocean is 17,660 thousand km 2. The underwater margin of Africa is distinguished by a narrow shelf (from 2 to 40 km), its edge is located at a depth of 200-300 m. Only near the southern tip of the continent does the shelf expand significantly and in the area of the Agulhas Plateau extends up to 250 km from the coast. Significant areas of the shelf are occupied by coral structures. The transition from the shelf to the continental slope is expressed by a clear bend of the bottom surface and a rapid increase in its slope to 10-15°. The underwater margin of Asia off the coast of the Arabian Peninsula also has a narrow shelf, gradually expanding on the Malabar coast of Hindustan and off the coast of the Bay of Bengal, while the depth on its outer border increases from 100 to 500 m. The continental slope is clearly visible everywhere along the characteristic slopes of the bottom (height up to 4200 m, Sri Lanka island). The shelf and continental slope in some areas are cut through by several narrow and deep canyons, the most pronounced canyons being underwater continuations of the channels of the Ganges rivers (together with the Brahmaputra River, it annually carries about 1,200 million tons of suspended and tractional sediment into the ocean, forming a sediment layer over 3,500 m thick ) and Ind. Australia's submarine margin is characterized by an extensive shelf, especially in the northern and northwestern parts; in the Gulf of Carpentaria and the Arafura Sea up to 900 km wide; maximum depth 500 m. The continental slope to the west of Australia is complicated by underwater ledges and individual underwater plateaus (maximum height 3600 m, Aru Islands). On the underwater outskirts of Antarctica, there are everywhere traces of the influence of the ice load of the huge glacier covering the continent. The shelf here belongs to a special glacial type. Its outer boundary almost coincides with the 500 m isobath. The shelf width is from 35 to 250 km. The continental slope is complicated by longitudinal and transverse ridges, individual ridges, valleys and deep trenches. At the foot of the continental slope, an accumulative plume composed of terrigenous material brought by glaciers is almost everywhere observed. The largest bottom slopes are observed in the upper part; with increasing depth, the slope gradually flattens out.

The transition zone on the floor of the Indian Ocean is distinguished only in the area adjacent to the Sunda Islands arc, and represents the southeastern part of the Indonesian transition region. It includes: the Andaman Sea basin, the Sunda Islands island arc and deep-sea trenches. The most morphologically pronounced in this zone is the deep-sea Sunda Trench with a slope steepness of 30° or more. Relatively small deep-sea trenches are identified to the southeast of the island of Timor and east of the Kai Islands, but due to the thick sedimentary layer, their maximum depths are relatively small - 3310 m (Timor Trench) and 3680 m (Kai Trench). The transition zone is extremely seismically active.

The mid-ocean ridges of the Indian Ocean form three submarine mountain ranges radiating from the area at 22°S and 68°E to the northwest, southwest and southeast. Each of the three branches is divided according to morphological characteristics into two independent ridges: the northwestern - into the Middle Aden Ridge and the Arabian-Indian Ridge, the southwestern - into the West Indian Ridge and the African-Antarctic Ridge, the southeastern - into the Central Indian Ridge and Australian-Antarctic Rise. Thus, the median ridges divide the floor of the Indian Ocean into three large sectors. The median ridges are vast uplifts, fragmented by transform faults into separate blocks, with a total length of over 16 thousand km, the foothills of which are located at depths of the order of 5000-3500 m. The relative height of the ridges is 4700-2000 m, width 500-800 km, depth of rift valleys up to 2300 m .

In each of the three sectors of the ocean floor of the Indian Ocean, characteristic relief forms are distinguished: basins, individual ridges, plateaus, mountains, trenches, canyons, etc. In the western sector there are the largest basins: Somalia (with depths of 3000-5800 m), Mascarene (4500 -5300 m), Mozambique (4000-6000 m), Madagascar Basin (4500-6400 m), Agulhas (4000-5000 m); underwater ridges: Mascarene Ridge, Madagascar, Mozambique; plateau: Agulhas, Mozambican plateau; individual mountains: Equator, Africana, Vernadsky, Hall, Bardin, Kurchatov; Amirante Trench, Mauritius Trench; Canyons: Zambezi, Tanganyika and Tagela. In the northeastern sector there are basins: Arabian (4000-5000 m), Central (5000-6000 m), Coconut (5000-6000 m), North Australian (5000-5500 m), Western Australian Basin (5000-6500 m). m), Naturalista (5000-6000 m) and South Australian Basin (5000-5500 m); underwater ridges: Maldives Ridge, East Indian Ridge, Western Australian; Cuvier mountain range; Exmouth plateau; Mill Hill; individual mountains: Moscow State University, Shcherbakova and Afanasy Nikitin; East Indian Trench; Canyons: Indus, Ganges, Seatown and Murray rivers. In the Antarctic sector there are basins: Crozet (4500-5000 m), African-Antarctic Basin (4000-5000 m) and Australian-Antarctic Basin (4000-5000 m); plateaus: Kerguelen, Crozet and Amsterdam; separate mountains: Lena and Ob. The shapes and sizes of the basins are different: from round with a diameter of about 400 km (Comoros) to oblong giants with a length of 5500 km (Central), the degree of their isolation and the bottom topography are different: from flat or gently undulating to hilly and even mountainous.

Geological structure. The peculiarity of the Indian Ocean is that its formation occurred both as a result of the split and subsidence of continental masses, and as a result of the spreading of the bottom and the new formation of oceanic crust within the mid-ocean (spreading) ridges, the system of which was repeatedly rebuilt. Modern system The mid-ocean ridges consist of three branches that converge at the Rodriguez Triple Junction. In the northern branch, the Arabian-Indian Ridge continues northwest of the Owen transform fault zone with the Gulf of Aden and Red Sea rift systems and connects with the intracontinental rift systems of East Africa. In the southeastern branch, the Central Indian Ridge and the Australian-Antarctic Rise are separated by the Amsterdam fault zone, which is connected to the plateau of the same name with the volcanic islands of Amsterdam and Saint-Paul. The Arabian-Indian and Central Indian ridges are slow-spreading (spreading speed is 2-2.5 cm/year), have a well-defined rift valley, and are crossed by numerous transform faults. The wide Australasian-Antarctic Rise does not have a pronounced rift valley; the spreading rate on it is higher than in other ridges (3.7-7.6 cm/year). To the south of Australia, the uplift is broken up by the Australian-Antarctic fault zone, where the number of transform faults increases and the spreading axis shifts along the faults in a southerly direction. The ridges of the southwestern branch are narrow, with a deep rift valley, densely crossed by transform faults oriented at an angle to the strike of the ridge. It is very common for them low speed spreading (about 1.5 cm/year). The West Indian Ridge is separated from the African-Antarctic Ridge by the Prince Edward, Du Toit, Andrew-Bain and Marion fault systems, which shift the ridge axis almost 1000 km to the south. The age of the oceanic crust within the spreading ridges is predominantly Oligocene-Quaternary. The West Indian Ridge, which penetrates like a narrow wedge into the structures of the Central Indian Ridge, is considered the youngest.

Spreading ridges divide the ocean floor into three sectors - African in the west, Asian-Australian in the northeast and Antarctic in the south. Within the sectors there are various types of intra-oceanic uplift, represented by “aseismic” ridges, plateaus and islands. Tectonic (block) uplifts have a block structure with varying crustal thickness; often include continental remains. Volcanic uplifts are mainly associated with fault zones. The uplifts are the natural boundaries of deep-sea basins. The African sector is distinguished by the predominance of fragments of continental structures (including microcontinents), within which the thickness of the earth's crust reaches 17-40 km (the Agulhas and Mozambican plateaus, the Madagascar ridge with the island of Madagascar, individual blocks of the Mascarene plateau with the Bank of the Seychelles Islands and the Saya de Bank -Malya). Volcanic uplifts and structures include the Comoros underwater ridge, crowned by archipelagos of coral and volcanic islands, the Amirante Range, the Reunion Islands, Mauritius, Tromelin, and the Farquhar Massif. In the western part of the African sector of the Indian Ocean (western part of the Somali Basin, northern part of the Mozambique Basin), adjacent to the eastern underwater margin of Africa, the age of the earth's crust is predominantly Late Jurassic-Early Cretaceous; in the central part of the sector (Mascarene and Madagascar basins) - Late Cretaceous; in the northeastern part of the sector (eastern part of the Somali Basin) - Paleocene-Eocene. Ancient spreading axes and transform faults intersecting them have been identified in the Somali and Mascarene basins.

The northwestern (near-Asian) part of the Asian-Australian sector is characterized by meridional “aseismic” ridges of a block structure with an increased thickness of the oceanic crust, the formation of which is associated with a system of ancient transform faults. These include the Maldives range, crowned by archipelagos of coral islands - Laccadive, Maldives and Chagos; the so-called 79° ridge, the Lanka ridge with Mount Afanasia Nikitin, the East Indian (the so-called 90° ridge), Investigator, etc. Thick (8-10 km) sediments of the Indus, Ganges and Brahmaputra rivers in the northern part of the Indian Ocean partially overlap the extending in this direction there are ridges, as well as structures of the transition zone between the Indian Ocean and the southeastern edge of Asia. The Murray Ridge in the northern part of the Arabian Basin, bounding the Oman Basin from the south, is a continuation of folded land structures; falls within the Owen fault zone. South of the equator, a sublatitudinal zone of intraplate deformations up to 1000 km wide has been identified, which is characterized by high seismicity. It stretches in the Central and Cocos Basins from the Maldives Ridge to the Sunda Trench. The Arabian Basin is underlain by crust of Paleocene-Eocene age, the Central Basin by crust of Late Cretaceous - Eocene age; the crust is youngest in the southern part of the basins. In the Cocos Basin, the crust ranges in age from Late Cretaceous in the south to Eocene in the north; in its northwestern part, an ancient spreading axis was established, which separated the Indian and Australian lithospheric plates until the mid-Eocene. The Coconut Rise, a latitudinal rise with numerous seamounts and islands (including the Cocos Islands) towering above it, and the Ru rise, adjacent to the Sunda Trench, separate the southeastern (Australian) part of the Asian-Australian sector. The Western Australian Basin (Wharton) in the central part of the Asian-Australian sector of the Indian Ocean is underlain by Late Cretaceous crust in the northwest and Late Jurassic in the east. Submerged continental blocks (marginal plateaus of Exmouth, Cuvier, Zenith, Naturalista) divide the eastern part of the basin into separate depressions - Cuvier (north of the Cuvier plateau), Perth (north of the Naturalista plateau). The crust of the North Australian Basin (Argo) is the oldest in the south (Late Jurassic); becomes younger in a northern direction (until the Early Cretaceous). The age of the crust of the South Australian Basin is Late Cretaceous - Eocene. The Brocken Plateau is an intra-oceanic rise with increased (from 12 to 20 km, according to various sources) crustal thickness.

In the Antarctic sector of the Indian Ocean there are mainly volcanic intra-oceanic rises with increased thickness of the earth's crust: the Kerguelen, Crozet (Del Caño) and Conrad plateaus. Within the largest Kerguelen plateau, presumably founded on an ancient transform fault, the thickness of the earth’s crust (according to some data, Early Cretaceous age) reaches 23 km. Rising above the plateau, the Kerguelen Islands are a multiphase volcanoplutonic structure (composed of alkali basalts and syenites of Neogene age). On Heard Island there are Neogene-Quaternary alkaline volcanics. In the western part of the sector there are the Conrad plateau with the volcanic mountains Ob and Lena, as well as the Crozet plateau with a group of volcanic islands Marion, Prince Edward, Crozet, composed of Quaternary basalts and intrusive massifs of syenites and monzonites. The age of the earth's crust within the African-Antarctic, Australian-Antarctic basins and the Late Cretaceous Crozet Basin is Eocene.

The Indian Ocean is characterized by the predominance of passive margins (continental margins of Africa, the Arabian and Hindu peninsulas, Australia, Antarctica). An active margin is observed in the northeastern part of the ocean (the Sunda transition zone between the Indian Ocean and Southeast Asia), where subduction of the ocean lithosphere occurs under the Sunda island arc. A subduction zone of limited extent, the Makran subduction zone, has been identified in the northwestern part of the Indian Ocean. Along the Agulhas Plateau, the Indian Ocean borders the African continent along a transform fault.

The formation of the Indian Ocean began in the mid-Mesozoic during the breakup of the Gondwanan part (see Gondwana) of the supercontinent Patea, which was preceded by continental rifting during the Late Triassic - Early Cretaceous. The formation of the first sections of oceanic crust as a result of the separation of continental plates began in the Late Jurassic in the Somali (about 155 million years ago) and North Australian (151 million years ago) basins. In the Late Cretaceous, the northern part of the Mozambique Basin experienced the spreading of the bottom and the new formation of oceanic crust (140-127 million years ago). The separation of Australia from Hindustan and Antarctica, accompanied by the opening of basins with oceanic crust, began in the Early Cretaceous (about 134 million years ago and about 125 million years ago, respectively). Thus, in the Early Cretaceous (about 120 million years ago), narrow ocean basins arose, cutting into the supercontinent and dividing it into separate blocks. In the middle of the Cretaceous period (about 100 million years ago), the ocean floor began to grow intensively between Hindustan and Antarctica, which led to the drift of Hindustan in a northerly direction. In the time interval of 120-85 million years ago, the spreading axes that existed north and west of Australia, off the coast of Antarctica and in the Mozambique Channel, died out. In the Late Cretaceous (90-85 million years ago), a split began between Hindustan with the Mascarene-Seychelles block and Madagascar, which was accompanied by bottom spreading in the Mascarene, Madagascar and Crozet basins, as well as the formation of the Australian-Antarctic Rise. At the Cretaceous-Paleogene boundary, Hindustan separated from the Mascarene-Seychelles block; the Arabian-Indian spreading ridge arose; the extinction of spreading axes occurred in the Mascarene and Madagascar basins. In the middle of the Eocene, the Indian lithospheric plate merged with the Australian one; the still developing system of mid-ocean ridges was formed. The Indian Ocean acquired its appearance close to its modern one in the early - middle Miocene. In the mid-Miocene (about 15 million years ago), during the split of the Arabian and African plates, new formation of oceanic crust began in the Gulf of Aden and the Red Sea.

Modern tectonic movements in the Indian Ocean are noted in mid-ocean ridges (associated with shallow earthquakes), as well as in individual transform faults. The area of intense seismicity is the Sunda island arc, where deep-focus earthquakes are caused by the presence of a seismofocal zone plunging in the northeast direction. During earthquakes on the northeastern edge of the Indian Ocean, a tsunami may form.

Bottom sediments. Sedimentation rates in the Indian Ocean are generally lower than those in the Atlantic and Pacific oceans. The thickness of modern bottom sediments varies from a discontinuous distribution at mid-ocean ridges to several hundred meters in deep-sea basins and 5000-8000 m at the foot of continental slopes. The most widespread are calcareous (mainly foraminiferal-coccolithic) silts, covering over 50% of the ocean floor area (on continental slopes, ridges and the bottom of basins at depths of up to 4700 m) in warm oceanic areas from 20° north latitude to 40° south latitude with high biological productivity of water. Polygenic sediments - red deep-sea oceanic clays - occupy 25% of the bottom area at depths of over 4700 m in the eastern and southeastern parts of the ocean from 10° north latitude to 40° south latitude and in areas of the bottom remote from islands and continents; in the tropical region, red clays alternate with siliceous radiolarian silts covering the bottom of deep-sea basins of the equatorial belt. Ferromanganese nodules are present in deep-sea sediments in the form of inclusions. Siliceous, predominantly diatomaceous, silts occupy about 20% of the Indian Ocean floor; distributed at great depths south of 50° south latitude. The accumulation of terrigenous sediments (pebbles, gravel, sands, silts, clays) occurs mainly along the coasts of continents and within their underwater margins in areas of river and iceberg runoff and significant wind removal of material. The sediments covering the African shelf are mainly of shell and coral origin; phosphorite nodules are widely developed in the southern part. Along the northwestern periphery of the Indian Ocean, as well as in the Andaman Basin and the Sunda Trench, bottom sediments are represented mainly by deposits of turbidity (turbidity) flows - turbidites with the participation of products of volcanic activity, underwater landslides, landslides, etc. Sediments of coral reefs are widespread in western parts of the Indian Ocean from 20° south latitude to 15° north latitude, and in the Red Sea - up to 30° north latitude. In the rift valley of the Red Sea, outcrops of metal-bearing brines with temperatures up to 70°C and salinity up to 300‰ were discovered. Metalliferous sediments formed from these brines contain a high content of non-ferrous and rare metals. On continental slopes, seamounts, and mid-ocean ridges, there are outcrops of bedrock (basalts, serpentinites, peridotites). Bottom sediments around Antarctica are classified as a special type of iceberg sediment. They are characterized by a predominance of a variety of clastic material, ranging from large boulders to silts and fine silts.

Climate. Unlike the Atlantic and Pacific oceans, which have a meridional extension from the coast of Antarctica to the Arctic Circle and communicate with the Arctic Ocean, the Indian Ocean in the northern tropical region is bordered by a land mass, which largely determines the characteristics of its climate. The uneven heating of land and ocean leads to seasonal changes in extensive minimums and maximums of atmospheric pressure and to seasonal shifts of the tropical atmospheric front, which in the winter of the Northern Hemisphere retreats south to almost 10° south latitude, and in the summer is located in the foothills of southern Asia. As a result, the northern part of the Indian Ocean is dominated by a monsoon climate, which is primarily characterized by changes in wind direction throughout the year. The winter monsoon with relatively weak (3-4 m/s) and stable northeast winds operates from November to March. During this period, calms are common north of 10° south latitude. The summer monsoon with southwest winds occurs from May to September. In the northern tropical region and in the equatorial zone of the ocean, the average wind speed reaches 8-9 m/s, often reaching storm force. In April and October, a restructuring of the pressure field usually occurs, and during these months the wind situation is unstable. Against the backdrop of the prevailing monsoon atmospheric circulation over the northern Indian Ocean, possible individual manifestations cyclonic activity. During the winter monsoon, there are known cases of cyclones developing over the Arabian Sea, and during the summer monsoon - over the waters of the Arabian Sea and the Bay of Bengal. Strong cyclones in these areas sometimes form during periods of monsoon change.

At approximately 30° south latitude in the central Indian Ocean there is a stable area of high pressure, the so-called South Indian High. This stationary anticyclone - part of the southern subtropical high pressure area - persists throughout the year. The pressure at its center varies from 1024 hPa in July to 1020 hPa in January. Under the influence of this anticyclone, stable southeastern trade winds blow throughout the latitudinal band between 10 and 30° south latitude throughout the year.

South of 40° south latitude, atmospheric pressure uniformly decreases in all seasons from 1018-1016 hPa at the southern periphery of the South Indian High to 988 hPa at 60° south latitude. Under the influence of the meridional pressure gradient in the lower layer of the atmosphere, a stable westerly air transport is maintained. The highest average wind speed (up to 15 m/s) is observed in the middle of winter in the Southern Hemisphere. The higher southern latitudes of the Indian Ocean are characterized by storm conditions throughout most of the year, in which winds with speeds of more than 15 m/s, causing waves above 5 m in height, have a frequency of 30%. South of 60° south latitude along the coast of Antarctica, easterly winds and two to three cyclones per year are usually observed, most often in July - August.

In July, the highest air temperatures in the surface layer of the atmosphere are observed at the top of the Persian Gulf (up to 34°C), the lowest - off the coast of Antarctica (-20°C), over the Arabian Sea and the Bay of Bengal on average 26-28°C. Over the Indian Ocean, air temperature almost everywhere varies in accordance with geographic latitude.

In the southern part of the Indian Ocean, it gradually decreases from north to south by about 1°C for every 150 km. In January, the highest air temperatures (26-28°C) are observed in the equatorial belt, near the northern coasts of the Arabian Sea and the Bay of Bengal - about 20°C. In the southern part of the ocean, the temperature gradually decreases from 26 ° C in the Southern Tropics to 0 ° C and slightly lower at the latitude of the Antarctic Circle. The amplitude of annual air temperature fluctuations over most of the Indian Ocean is on average less than 10°C and only off the coast of Antarctica increases to 16°C.

The greatest amount of precipitation per year falls in the Bay of Bengal (over 5500 mm) and off the eastern coast of the island of Madagascar (over 3500 mm). The northern coastal part of the Arabian Sea receives the least amount of precipitation (100-200 mm per year).

The northeastern Indian Ocean is located in seismically active areas. The eastern coast of Africa and the island of Madagascar, the shores of the Arabian Peninsula and the Hindustan Peninsula, almost all island archipelagos of volcanic origin, western shores Australia, especially the Sunda Islands arc, has in the past been repeatedly exposed to tsunami waves of varying strength, up to catastrophic ones. In 1883, after the explosion of the Krakatau volcano in the Jakarta area, a tsunami with a wave height of over 30 m was recorded; in 2004, a tsunami caused by an earthquake in the area of the island of Sumatra had catastrophic consequences.

Hydrological regime. Seasonality in changes in hydrological characteristics (primarily temperature and currents) is most clearly manifested in the northern part of the ocean. The summer hydrological season here corresponds to the duration of the southwest monsoon (May - September), the winter - to the northeast monsoon (November - March). A feature of the seasonal variability of the hydrological regime is that the restructuring of hydrological fields is somewhat delayed relative to the meteorological fields.

Water temperature. In the winter of the Northern Hemisphere, the highest water temperatures in the surface layer are observed in the equatorial zone - from 27°C off the coast of Africa to 29°C or more east of the Maldives. In the northern regions of the Arabian Sea and Bay of Bengal, the water temperature is about 25°C. The southern part of the Indian Ocean is characterized by a zonal temperature distribution, which gradually decreases from 27-28°C at 20°S latitude to negative values at the edge of the drifting ice, located at approximately 65-67°S latitude. In the summer season, the highest water temperatures in the surface layer are observed in the Persian Gulf (up to 34°C), in the north-west of the Arabian Sea (up to 30°C), and in the eastern part of the equatorial zone (up to 29°C). In the coastal areas of the Somali and Arabian peninsulas, abnormally low values (sometimes less than 20°C) are observed at this time of year, which is the result of the rise to the surface of cooled deep waters in the Somali Current system. In the southern part of the Indian Ocean, the distribution of water temperature throughout the year remains zonal, with the difference that its negative values in the winter of the Southern Hemisphere are found much further north, already around 58-60° south latitude. The amplitude of annual fluctuations in water temperature in the surface layer is small and averages 2-5°C; only in the area of the Somali coast and in the Gulf of Oman in the Arabian Sea does it exceed 7°C. The water temperature quickly decreases vertically: at a depth of 250 m it almost everywhere drops below 15°C, deeper than 1000 m - below 5°C. At a depth of 2000 m, temperatures above 3°C are observed only in the northern part of the Arabian Sea, in the central regions - about 2.5°C, in the southern part it decreases from 2°C at 50° south latitude to 0°C off the coast of Antarctica. Temperatures in the deepest (over 5000 m) basins range from 1.25°C to 0°C.

The salinity of surface waters of the Indian Ocean is determined by the balance between the amount of evaporation and the total amount of precipitation and river flow for each region. The absolute maximum salinity (over 40‰) is observed in the Red Sea and the Persian Gulf, in the Arabian Sea everywhere, with the exception of a small area in the southeastern part, salinity is above 35.5‰, in the band of 20-40° south latitude - more than 35‰ . The area of low salinity is located in the Bay of Bengal and in the area adjacent to the Sunda Islands arc, where fresh river flow and precipitation are high. greatest number precipitation. In the northern part of the Bay of Bengal in February, salinity is 30-31‰, in August - 20‰. A vast tongue of water with salinity up to 34.5‰ at 10° south latitude extends from the island of Java to 75° east longitude. In Antarctic waters, salinity is everywhere below the average oceanic value: from 33.5‰ in February to 34.0‰ in August, its changes are determined by slight salinization during the formation of sea ice and corresponding freshening during the melting of ice. Seasonal changes in salinity are noticeable only in the upper, 250-meter layer. With increasing depth, not only seasonal fluctuations fade, but also spatial variability of salinity; deeper than 1000 m it fluctuates between 35-34.5‰.

Density. The highest density of water in the Indian Ocean is observed in the Suez and Persian Gulfs (up to 1030 kg/m3) and in the cold Antarctic waters (1027 kg/m3), the average is in the warmest and saltiest waters in the northwest (1024-1024. 5 kg/m3), the smallest - in the most desalinated waters in the northeastern part of the ocean and in the Bay of Bengal (1018-1022 kg/m3). With depth, mainly due to a decrease in water temperature, its density increases, sharply increasing in the so-called jump layer, which is most noticeably expressed in the equatorial zone of the ocean.

Ice mode. The severity of the climate in the southern Indian Ocean is such that the formation of sea ice (at air temperatures below -7°C) can occur almost all year round. The ice cover reaches its greatest development in September - October, when the width of the drifting ice belt reaches 550 km, the smallest - in January - February. Ice cover is characterized by great seasonal variability and its formation occurs very quickly. The ice edge moves north at a speed of 5-7 km/day, and retreats just as quickly (up to 9 km/day) to the south during the melting period. Fast ice is established annually, reaches an average width of 25-40 km and almost completely melts by February. Drifting ice off the coast of the continent moves under the influence of katabatic winds in a general direction to the west and northwest. Near the northern edge, the ice drifts eastward. A characteristic feature of the Antarctic ice sheet is the large number of icebergs breaking off from the outlet and shelf glaciers of Antarctica. Table-shaped icebergs are especially large, which can reach a gigantic length of several tens of meters, rising 40-50 m above the water. Their number quickly decreases as they move away from the shores of the mainland. The average lifespan of large icebergs is 6 years.

Currents. The circulation of surface waters in the northern part of the Indian Ocean is formed under the influence of monsoon winds and therefore varies significantly from the summer to the winter season. In February, from 8° north latitude near the Nicobar Islands to 2° north latitude off the coast of Africa, the surface winter Monsoon current passes at speeds of 50-80 cm/s; with a core passing approximately 18° south latitude, the Southern Trade Wind Current propagates in the same direction, having an average speed on the surface of about 30 cm/s. Connecting off the coast of Africa, the waters of these two streams give rise to the Intertrade Countercurrent, which carries its waters to the east with velocities in the core of about 25 cm/s. Along the North African coast, with a general direction to the south, the waters of the Somali Current move, partially turning into the Intertrade Countercurrent, and to the south - the Mozambique and Cape Agulhas currents, moving south at speeds of about 50 cm/s. Part of the South Trade Wind Current off the eastern coast of the island of Madagascar turns south along it (Madagascar Current). South of 40° south latitude, the entire ocean area is crossed from west to east by the flow of the longest and most powerful current in the World Ocean, the Western Winds (Antarctic Circumpolar Current). The velocities in its rods reach 50 cm/s, and the flow rate is about 150 million m 3 /s. At 100-110° east longitude, a stream branches off from it, heading north and giving rise to the Western Australian Current. In August, the Somali Current follows a general direction to the northeast and, at a speed of up to 150 cm/s, pushes water into the northern part of the Arabian Sea, from where the Monsoon Current, skirting the western and southern shores of the Hindustan Peninsula and the island of Sri Lanka, carries water to the shores of the island Sumatra turns south and merges with the waters of the South Trade Wind Current. Thus, an extensive clockwise gyre is created in the northern part of the Indian Ocean, consisting of the Monsoon, South Trade Wind and Somali currents. In the southern part of the ocean, the pattern of currents changes little from February to August. Off the coast of Antarctica, in a narrow coastal strip, a current caused by katabatic winds and directed from east to west is observed all year round.

Water masses. In the vertical structure of the water masses of the Indian Ocean, according to hydrological characteristics and depth, surface, intermediate, deep and bottom waters are distinguished. Surface water distributed in a relatively thin surface layer and on average occupy the upper 200-300 m. From north to south, water masses are distinguished in this layer: Persian and Arabian in the Arabian Sea, Bengal and South Bengal in the Bay of Bengal; further, south of the equator - Equatorial, Tropical, Subtropical, Subantarctic and Antarctic. As the depth increases, the differences between neighboring water masses decrease and their number decreases accordingly. Thus, in intermediate waters, the lower limit of which reaches 2000 m in temperate and low latitudes and up to 1000 m in high latitudes, the Persian and Red Sea in the Arabian Sea, the Bengal in the Bay of Bengal, the Subantarctic and Antarctic intermediate water masses are distinguished. Deep waters are represented by the North Indian, Atlantic (in the western part of the ocean), Central Indian (in the eastern part) and Circumpolar Antarctic water masses. Bottom waters everywhere, except the Bay of Bengal, are represented by one Antarctic bottom water mass, filling all deep-sea basins. The upper limit of bottom water is located on average at a horizon of 2500 m off the coast of Antarctica, where it is formed, up to 4000 m in the central regions of the ocean and rises to almost 3000 m north of the equator.

Tides and swells. Semidiurnal and irregular semidiurnal tides are most common on the shores of the Indian Ocean. Semidiurnal tides are observed on the African coast south of the equator, in the Red Sea, off the northwestern coast of the Persian Gulf, in the Bay of Bengal, and off the northwestern coast of Australia. Irregular semidiurnal tides - off the Somali Peninsula, in the Gulf of Aden, off the coast of the Arabian Sea, in the Persian Gulf, off the southwestern coast of the Sunda island arc. Diurnal and irregular tides occur off the western and southern coasts of Australia. The highest tides are off the northwestern coast of Australia (up to 11.4 m), in the mouth zone of the Indus (8.4 m), in the mouth zone of the Ganges (5.9 m), off the coast of the Mozambique Strait (5.2 m) ; in the open ocean, tides vary from 0.4 m near the Maldives to 2.0 m in the southeastern Indian Ocean. The excitement reaches greatest strength in temperate latitudes in the zone of action of westerly winds, where the frequency of waves over 6 m in height is 17% per year. Waves with a height of 15 m and a length of 250 m were recorded near the Kerguelen Island, and 11 m and 400 m, respectively, off the coast of Australia.

Flora and fauna. The main part of the Indian Ocean is located within the tropical and southern temperate zones. The absence of a northern high-latitude region in the Indian Ocean and the action of monsoons lead to two differently directed processes that determine the characteristics of the local flora and fauna. The first factor complicates deep-sea convection, which negatively affects the renewal of deep waters of the northern part of the ocean and the increase in oxygen deficiency in them, which is especially pronounced in the Red Sea intermediate water mass, which leads to a depletion of species composition and reduces the total biomass of zooplankton in the intermediate layers. When oxygen-poor waters in the Arabian Sea reach the shelf, local death occurs (death of hundreds of thousands of tons of fish). At the same time, the second factor (monsoons) creates favorable conditions for high biological productivity in coastal areas. Under the influence of the summer monsoon, water is driven along the Somali and Arabian coasts, which causes powerful upwelling, bringing water rich in nutritious salts to the surface. The winter monsoon, although to a lesser extent, leads to seasonal upwelling with similar consequences off the western coast of the Indian subcontinent.

The coastal zone of the ocean has the greatest species diversity. The shallow waters of the tropical zone are characterized by numerous 6- and 8-rayed madrepore corals and hydrocorals that, together with red algae, can create underwater reefs and atolls. Among the powerful coral structures lives a rich fauna of various invertebrates (sponges, worms, crabs, mollusks, sea urchins, brittle stars and starfish), small but brightly colored coral reef fish. Most of the coasts are occupied by mangroves. At the same time, the fauna and flora of beaches and rocks that dry out at low tide are quantitatively depleted due to the inhibitory effect sun rays. In the temperate zone, life on such sections of the coast is much richer; Dense thickets of red and brown algae (kelp, fucus, macrocystis) develop here, and a variety of invertebrates are abundant. According to L.A. Zenkevich (1965), over 99% of all species of bottom and benthic animals living in the ocean live in the littoral and sublittoral zones.

The open spaces of the Indian Ocean, especially the surface layer, are also characterized by a rich flora. The food chain in the ocean begins with microscopic single-celled plant organisms - phytoplankton, which inhabit mainly the uppermost (about 100-meter) layer of ocean waters. Among them, several species of peridinian and diatom algae predominate, and in the Arabian Sea - cyanobacteria (blue-green algae), which often cause so-called water blooms when they develop en masse. In the northern Indian Ocean, there are three areas of highest phytoplankton production: the Arabian Sea, Bay of Bengal and Andaman Sea. The greatest production is observed off the coast of the Arabian Peninsula, where the number of phytoplankton sometimes exceeds 1 million cells/l (cells per liter). Its high concentrations are also observed in the subantarctic and Antarctic zones, where during the spring flowering period there are up to 300,000 cells/l. The lowest phytoplankton production (less than 100 cells/l) is observed in the central part of the ocean between parallels 18 and 38° south latitude.

Zooplankton inhabits almost the entire thickness of oceanic waters, but its quantity quickly decreases with increasing depth and decreases by 2-3 orders of magnitude towards the bottom layers. The food for most zooplankton, especially those living in the upper layers, is phytoplankton, so the patterns of spatial distribution of phyto- and zooplankton are largely similar. The highest levels of zooplankton biomass (from 100 to 200 mg/m3) are observed in the Arabian and Andaman seas, the Bengal, Aden and Persian Gulfs. The main biomass of ocean animals consists of copepod crustaceans (more than 100 species), with slightly less pteropods, jellyfish, siphonophores and other invertebrate animals. Radiolarians are typical of unicellular organisms. The Antarctic region of the Indian Ocean is characterized by a huge number of euphausian crustaceans of several species, collectively called “krill”. Euphausiids create the main food supply for the largest animals on Earth - baleen whales. In addition, fish, seals, cephalopods, penguins and other bird species feed on krill.

Organisms that move freely in the marine environment (nekton) are represented in the Indian Ocean mainly by fish, cephalopods, and cetaceans. Among the cephalopods common in the Indian Ocean are cuttlefish, numerous squids and octopuses. Of the fish, the most abundant are several species of flying fish, luminous anchovies (coryphaenas), sardinella, sardine, mackerel, nototheniids, groupers, several types of tuna, blue marlin, grenadier, sharks, and rays. Warm waters are home to sea turtles and poisonous sea snakes. The fauna of aquatic mammals is represented by various cetaceans. The most common baleen whales are: blue whale, sei whale, fin whale, humpback whale, Australian (Cape) and Chinese whales. Toothed whales are represented by sperm whales and several species of dolphins (including killer whales). In the coastal waters of the southern part of the ocean, pinnipeds are widespread: the Weddell seal, the crabeater seal, fur seals - Australian, Tasmanian, Kerguelen and South African, Australian sea lion, leopard seal, etc. Among the birds, the most typical are the wandering albatross, petrels, great frigatebird, phaetons , cormorants, gannets, skuas, terns, gulls. South of 35° south latitude, on the coasts of South Africa, Antarctica and the islands, there are numerous colonies of several species of penguins.

In 1938, a unique biological phenomenon was discovered in the Indian Ocean - a living lobe-finned fish, Latimeria chalumnae, which was considered extinct tens of millions of years ago. “Fossil” coelacanth lives at a depth of over 200 m in two places - near the Comoros Islands and in the waters of the Indonesian archipelago.

History of the study

The northern coastal areas, especially the Red Sea and the deeply incised bays, began to be used by humans for navigation and fishing already in the era of ancient civilizations, several thousand years BC. 600 years BC, Phoenician sailors, in the service of the Egyptian pharaoh Necho II, circumnavigated Africa. In 325-324 BC, Alexander the Great's comrade Nearchus, commanding a fleet, sailed from India to Mesopotamia and compiled the first descriptions of the coastline from the mouth of the Indus River to the top of the Persian Gulf. In the 8th-9th centuries, the Arabian Sea was intensively explored by Arab navigators, who created the first sailing directions and navigation guides for this area. In the 1st half of the 15th century, Chinese sailors under the leadership of Admiral Zheng He made a series of voyages along the Asian coast to the west, reaching the coast of Africa. In 1497-99, the Portuguese Gama (Vasco da Gama) paved the sea route for Europeans to India and to the countries South-East Asia. A few years later, the Portuguese discovered the island of Madagascar, Amirante, Comoros, Mascarene and Seychelles. Following the Portuguese, the Dutch, French, Spanish and British entered the Indian Ocean. The name "Indian Ocean" first appeared on European maps in 1555. In 1772-75, J. Cook penetrated the Indian Ocean to 71° south latitude and made the first deep-sea measurements. Oceanographic research in the Indian Ocean began with systematic measurements of water temperature during the circumnavigation of the Russian ships "Rurik" (1815-18) and "Enterprise" (1823-26). In 1831-36, an English expedition took place on the ship Beagle, on which Charles Darwin carried out geological and biological work. Complex oceanographic measurements in the Indian Ocean were carried out during the British expedition on the Challenger ship in 1873-74. Oceanographic work in the northern part of the Indian Ocean was carried out in 1886 by S. O. Makarov on the ship “Vityaz”. In the 1st half of the 20th century, oceanographic observations began to be made regularly, and by the 1950s they were carried out at almost 1,500 deep-sea oceanographic stations. In 1935, P. G. Schott’s monograph “Geography of the Indian and Pacific Oceans” was published - the first major publication that summarized the results of all previous studies in this region. In 1959, the Russian oceanographer A. M. Muromtsev published a fundamental work - “The Main Features of the Hydrology of the Indian Ocean.” In 1960-65, UNESCO's Scientific Committee on Oceanography conducted the International Indian Ocean Expedition (IIOE), the largest of those previously operating in the Indian Ocean. Scientists from more than 20 countries of the world (USSR, Australia, Great Britain, India, Indonesia, Pakistan, Portugal, USA, France, Germany, Japan, etc.) took part in the MIOE program. During MIOE, large geographical discoveries: discovered underwater West Indian and East Indian ridges, tectonic fault zones - Owen, Mozambique, Tasmanian, Diamantina, etc., underwater mountains - Ob, Lena, Afanasia Nikitina, Bardina, Zenit, Equator, etc., deep-sea trenches - Ob , Chagos, Vima, Vityaz, etc. In the history of the study of the Indian Ocean, the results of research carried out in 1959-77 by the research vessel “Vityaz” (10 voyages) and dozens of other Soviet expeditions on ships of the Hydrometeorological Service and the State Fisheries Committee stand out. Since the early 1980s, ocean research has been carried out in 20 international projects. Research in the Indian Ocean was especially intensified during the World Ocean Circulation Experiment (WOCE). Since its successful completion in the late 1990s, the amount of current oceanographic information on the Indian Ocean has doubled.

Economic use

The coastal zone of the Indian Ocean is exceptionally high density population. There are over 35 states on the coasts and islands of the ocean, home to about 2.5 billion people (over 30% of the Earth's population). The bulk of the coastal population is concentrated in South Asia (more than 10 cities with a population of over 1 million people). In most countries in the region, there are acute problems of finding living space, creating jobs, providing food, clothing and housing, and medical care.

The Indian Ocean, like other seas and oceans, is used in several main areas: transport, fishing, mining, and recreation.

Transport. The role of the Indian Ocean in maritime transport increased significantly with the creation of the Suez Canal (1869), which opened a short sea route for communication with states washed by the waters of the Atlantic Ocean. The Indian Ocean is an area for transit and export of all kinds of raw materials, in which almost all major seaports are of international importance. In the northeastern part of the ocean (in the Malacca and Sunda Straits) there are routes for ships traveling to the Pacific Ocean and back. The main export item to the USA, Japan and Western European countries is crude oil from the Persian Gulf region. In addition, products are exported Agriculture- natural rubber, cotton, coffee, tea, tobacco, fruits, nuts, rice, wool; wood; mineral raw materials - coal, iron ore, nickel, manganese, antimony, bauxite, etc.; machinery, equipment, tools and hardware, chemical and pharmaceutical products, textiles, processed gemstones and jewelry. The Indian Ocean accounts for about 10% of global shipping traffic; at the end of the 20th century, about 0.5 billion tons of cargo were transported through its waters per year (according to IOC). According to these indicators, it ranks 3rd after the Atlantic and Pacific oceans, inferior to them in terms of shipping intensity and total volume of cargo transportation, but surpassing all other sea transport communications in terms of oil transportation volume. The main transport routes along the Indian Ocean are towards the Suez Canal, the Strait of Malacca, the southern tips of Africa and Australia and along the northern coast. Shipping is most intense in the northern regions, although limited by storm conditions during the summer monsoon, and less intense in the central and southern regions. The growth of oil production in the Persian Gulf countries, Australia, Indonesia and other places contributed to the construction and modernization of oil ports and the appearance of giant tankers in the Indian Ocean.

The most developed transport routes for the transportation of oil, gas and petroleum products: Persian Gulf - Red Sea - Suez Canal - Atlantic Ocean; Persian Gulf - Strait of Malacca - Pacific Ocean; Persian Gulf - southern tip of Africa - Atlantic Ocean (especially before the reconstruction of the Suez Canal, 1981); Persian Gulf - Australian coast (port of Fremantle). Mineral and agricultural raw materials, textiles, precious stones, jewelry, equipment, and computer equipment are transported from India, Indonesia, and Thailand. From Australia, coal, gold, aluminum, alumina, iron ore, diamonds, uranium ores and concentrates, manganese, lead, zinc are transported; wool, wheat, meat products, as well as internal combustion engines, passenger cars, electrical products, river boats, glass products, rolled steel, etc. The oncoming flows are dominated by industrial goods, cars, electronic equipment, etc. An important place in the transport use of Indian The ocean is occupied by the transportation of passengers.

Fishing. Compared to other oceans, the Indian Ocean has relatively low biological productivity; fish and other seafood production accounts for 5-7% of the total world catch. Fishing and non-fishery fishing is concentrated mainly in the northern part of the ocean, and in the west it is twice as much as in the eastern part. The largest volumes of bioproduct production are observed in the Arabian Sea off the western coast of India and off the coast of Pakistan. Shrimp are harvested in the Persian and Bengal Bays, and lobsters are harvested off the east coast of Africa and on tropical islands. In open ocean areas in the tropical zone, tuna fishing is widely developed, carried out by countries with well-developed fishing fleets. In the Antarctic region, nototheniids, icefish and krill are caught.

Mineral resources. Deposits of oil and natural combustible gas or oil and gas shows have been identified almost throughout the entire shelf area of the Indian Ocean. The most industrially important are the actively developed oil and gas fields in the Gulfs: Persian (Persian Gulf oil and gas basin), Suez (oil and gas basin of the Gulf of Suez), Cambay (Kambay oil and gas basin), Bengal (Bengal oil and gas basin); off the northern coast of the island of Sumatra (North Sumatra oil and gas basin), in the Timor Sea, off the northwestern coast of Australia (Carnarvon oil and gas basin), in Bass Strait (Gippsland oil and gas basin). Gas deposits have been explored in the Andaman Sea, oil and gas bearing areas in the Red Sea, Gulf of Aden, and along the coast of Africa. Coastal-sea placers of heavy sands are developed off the coast of the island of Mozambique, along the southwestern and northeastern coasts of India, off the northeastern coast of the island of Sri Lanka, along the southwestern coast of Australia (mining ilmenite, rutile, monazite and zircon); in the coastal areas of Indonesia, Malaysia, Thailand (cassiterite mining). Industrial accumulations of phosphorites have been discovered on the shelves of the Indian Ocean. Large fields of ferromanganese nodules, a promising source of Mn, Ni, Cu, and Co, have been established on the ocean floor. In the Red Sea, metal-bearing brines and sediments identified are potential sources for the production of iron, manganese, copper, zinc, nickel, etc.; There are deposits of rock salt. In the coastal zone of the Indian Ocean, sand, gravel, and limestone are mined for construction and glass production.

Recreational resources. Since the 2nd half of the 20th century, the use of ocean recreational resources has been of great importance for the economies of coastal countries. Old resorts are being developed and new ones are being built on the coasts of continents and on numerous tropical islands in the ocean. The most visited resorts are in Thailand (Phuket Island, etc.) - over 13 million people a year (together with the coast and islands of the Gulf of Thailand in the Pacific Ocean), in Egypt [Hurghada, Sharm el-Sheikh (Sharm el-Sheikh), etc. ] - over 7 million people, in Indonesia (the islands of Bali, Bintan, Kalimantan, Sumatra, Java, etc.) - over 5 million people, in India (Goa, etc.), in Jordan (Aqaba), in Israel (Eilat) , in the Maldives, in Sri Lanka, in the Seychelles, on the islands of Mauritius, Madagascar, South Africa, etc.

Sharm el-Sheikh. Hotel Concorde.

Port cities. On the shores of the Indian Ocean there are specialized oil loading ports: Ras Tanura (Saudi Arabia), Kharq (Iran), Ash-Shuaiba (Kuwait). The largest ports of the Indian Ocean: Port Elizabeth, Durban (South Africa), Mombasa (Kenya), Dar es Salaam (Tanzania), Mogadishu (Somalia), Aden (Yemen), Kuwait City (Kuwait), Karachi (Pakistan), Mumbai, Chennai, Kolkata, Kandla (India), Chittagong (Bangladesh), Colombo (Sri Lanka), Yangon (Myanmar), Fremantle, Adelaide and Melbourne (Australia).

Lit.: Geological and geophysical atlas of the Indian Ocean. M., 1975; Kanaev V.F. Relief of the bottom of the Indian Ocean. M., 1979; Indian Ocean. L., 1982; Udintsev G. B. Regional geomorphology of the ocean floor. Indian Ocean. M., 1989; Lithosphere of the Indian Ocean: according to geophysical data / Ed. A. V. Chekunov, Yu. P. Neprochnov. K., 1990; Neiman V. G., Burkov V. A., Shcherbinin A. D. Dynamics of Indian Ocean waters. M., 1997; Pushcharovsky Yu. M. Tectonics of the Earth. Favorite works. M., 2005. T. 2: Tectonics of the oceans.

M. G. Deev; N. N. Turko (geological structure).