Introduction

1.History of the formation and exploration of the Indian Ocean

2.General information about the Indian Ocean

Bottom relief.

.Characteristics of the waters of the Indian Ocean.

.Bottom sediments of the Indian Ocean and its structure

.Minerals

.Climate of the Indian Ocean

.vegetable and animal world

.Fishing and marine industry

Introduction

Indian Ocean- the youngest and warmest among the world's oceans. Most of it is in the southern hemisphere, and in the north it goes far into the mainland, which is why ancient people considered it just a big sea. It was here, in the Indian Ocean, that man began his first sea voyages.

The largest rivers of Asia belong to the Indian Ocean basin: the Salween, the Irrawaddy and the Ganges with the Brahmaputra, which flow into the Bay of Bengal; the Indus, which flows into the Arabian Sea; Tigris and Euphrates, merging a little above the confluence with the Persian Gulf. Of the major rivers of Africa, which also flow into the Indian Ocean, the Zambezi and Limpopo should be mentioned. Because of them, the water off the coast of the ocean is muddy, with a high content of sedimentary rocks - sand, silt and clay. But the open waters of the ocean are amazingly clear. The tropical islands of the Indian Ocean are famous for their cleanliness. A variety of animals have found their place on coral reefs. The Indian Ocean is home to the famous sea devils, rare whale sharks, bigmouths, sea cows, sea snakes, etc.

1. History of formation and research

Indian Oceanformed at the junction of the Jurassic and Cretaceous periods as a result of the collapse of Gondwana (130-150 million years ago). Then there was a separation of Africa and the Deccan from Australia with Antarctica, and later - Australia from Antarctica (in the Paleogene, about 50 million years ago).

The Indian Ocean and its shores remain poorly explored. The name of the Indian Ocean is found already at the beginning of the 16th century. Schöner under the name Oceanus orientalis indicus, in contrast to the Atlantic Ocean, then known as Oceanus occidentalis. Subsequent geographers called the Indian Ocean mostly the Sea of ​​India, some (Varenius) the Australian Ocean, and Fleurie recommended (in the 18th century) to call it even the Great Indian Gulf, considering it as part of the Pacific Ocean.

In ancient times (3000-1000 BC), sailors from India, Egypt and Phoenicia traveled across the northern part of the Indian Ocean. The first navigation charts were compiled by the ancient Arabs. At the end of the 15th century, the first European, the famous Portuguese Vasco da Gama, circled Africa from the south and entered the waters of the Indian Ocean. By the 16th-17th centuries, Europeans (the Portuguese, and later the Dutch, French and British) increasingly appeared in the Indian Ocean basin, and by the middle of the 19th century, most of its coasts and islands were already the property of Great Britain.

Discovery historycan be divided into 3 periods: from ancient voyages to 1772; from 1772 to 1873 and from 1873 to the present. The first period is characterized by the study of the distribution of ocean and land waters in this part of the globe. It began with the first voyages of Indian, Egyptian and Phoenician navigators, who, in 3000-1000 BC. traveled through the northern part of the Indian Ocean, and ended with the voyage of J. Cook, who in 1772-75 penetrated south to 71 ° S. sh.

The second period was marked by the beginning of deep-sea research, first conducted by Cook in 1772 and continued by Russian and foreign expeditions. The main Russian expeditions were - O. Kotzebue on the "Rurik" (1818) and Pallen on the "Cyclone" (1858-59).

The third period is characterized by complex oceanographic research. Until 1960 they were carried out on separate ships. The largest work was carried out by expeditions on the ships Challenger (English) in 1873-74, Vityaz (Russian) in 1886, Valdivia (German) in 1898-99 and Gauss (German) in 1901-03, "Discovery II" (English) in 1930-51, the Soviet expedition to the "Ob" in 1956-58, etc. In 1960-65, the Intergovernmental Oceanographic Expedition under UNESCO conducted an international Indian Ocean expedition, which collected new valuable data on hydrology, hydrochemistry, meteorology , geology, geophysics and biology of the Indian Ocean.

. General information

Indian Ocean- the third largest ocean of the Earth (after the Pacific and Atlantic), covering about 20% of its water surface. Almost all of it is in the southern hemisphere. Its area is 74917 thousand km ² ; average volume of water - 291945 thousand km ³. In the north it is bounded by Asia, in the west by the Arabian Peninsula and Africa, in the east by Indochina, the Sunda Islands and Australia, in the south by the Southern Ocean. The border between the Indian and Atlantic Oceans runs along the 20° meridian of east longitude. (meridian of the Cape of Needles), between the Indian and Pacific Ocean passes along the 147 ° meridian of east longitude (meridian southern cape islands of Tasmania). The northernmost point of the Indian Ocean is located at approximately 30° north latitude in the Persian Gulf. The width of the Indian Ocean is approximately 10,000 km between the southern points of Australia and Africa.

The greatest depth of the Indian Ocean is the Sunda, or Java Trench (7729 m), the average depth is 3700 m.

The Indian Ocean washes three continents at once: Africa from the east, Asia from the south, Australia from the north and northwest.

The Indian Ocean has the fewest seas compared to other oceans. In the northern part are located the most large seas: Mediterranean - the Red Sea and the Persian Gulf, the semi-enclosed Andaman Sea and the marginal Arabian Sea; in the eastern part - the Arafura and Timor seas.

Located in the Indian Ocean island states Madagascar (the fourth largest island in the world), Sri Lanka, Maldives, Mauritius, Comoros, Seychelles. The ocean washes in the east such states: Australia, Indonesia; in the northeast: Malaysia, Thailand, Myanmar; in the north: Bangladesh, India, Pakistan; in the west: Oman, Somalia, Kenya, Tanzania, Mozambique, South Africa. In the south it borders on Antarctica. There are relatively few islands. In the open part of the ocean, there are volcanic islands - Mascarene, Crozet, Prince Edward, etc. In tropical latitudes, coral islands rise on volcanic cones - Maldives, Laccadive, Chagos, Cocos, most of the Andaman, etc.

. Bottom relief

The ocean floor is a system of mid-ocean ridges and basins. In the region of Rodrigues Island (Mascarene Archipelago) there is a so-called triple junction, where the Central Indian and West Indian ridges converge, as well as the Australo-Antarctic Rise. The ridges consist of steep mountain ranges cut by normal or oblique faults with respect to the axes of the chains and divide the basalt ocean floor into 3 segments, and their tops are, as a rule, extinct volcanoes. The bottom of the Indian Ocean is covered with deposits of the Cretaceous and later periods, the thickness of which varies from several hundred meters to 2-3 km. The deepest of the numerous trenches of the ocean is the Yavan (4,500 km long and 29 km wide). The rivers flowing into the Indian Ocean carry with them huge amounts of sedimentary material, especially from the territory of India, creating high alluvial rapids.

The coast of the Indian Ocean is replete with cliffs, deltas, atolls, coastal coral reefs and salt marshes overgrown with mangroves. Some islands - for example, Madagascar, Socotra, Maldives - are fragments of ancient continents. Numerous islands and archipelagos of volcanic origin are scattered in the open part of the Indian Ocean. In the northern part of the ocean, many of them are crowned with coral structures. Andaman, Nicobar or Christmas Island - are of volcanic origin. The Kerguelen Plateau, located in the southern part of the ocean, also has a volcanic origin.

An underwater earthquake in the Indian Ocean on December 26, 2004 triggered a tsunami that has been recognized as the deadliest natural disaster in modern history. The magnitude of the earthquake was, according to various estimates, from 9.1 to 9.3. This is the second or third strongest earthquake on record.

The epicenter of the earthquake was located in the Indian Ocean, north of Simeulue Island, located near the north West Bank Sumatra Islands (Indonesia). The tsunami reached the shores of Indonesia, Sri Lanka, southern India, Thailand and other countries. The height of the waves exceeded 15 meters. The tsunami caused enormous destruction and a huge number of deaths, even in Port Elizabeth, South Africa, 6900 km from the epicenter. Died, according to various estimates, from 225 thousand to 300 thousand people. The true death toll is unlikely to ever be known, as many people were swept into the sea by the water.

With regard to the properties of the bottom soil, then, like in other oceans, sediments on the bottom of the Indian Ocean can be divided into three classes: coastal sediments, organic silt (globigerine, radiolar or diatom) and special clay of great depths, the so-called red clay. Coastal sediments are sand, located mostly on coastal shallows to a depth of 200 meters, green or blue silt near rocky coasts, brown in volcanic areas, but lighter and sometimes pinkish or yellowish near coral coasts due to the lime prevailing here. Globigerin silt, consisting of microscopic foraminifers, covers the deeper parts of the ocean floor almost to a depth of 4500 m; south of parallel 50°S sh. calcareous foraminiferal deposits disappear and are replaced by microscopic siliceous, from the group of algae, diatoms. With regard to the accumulation of diatom remains on the bottom, the southern part of the Indian Ocean is especially different from other oceans, where diatoms are found only in places. Red clay occurs at depths greater than 4500 m; it has the color red, or brown, or chocolate.

indian ocean climate fossil fishery

4. Characteristics of waters

Surface water circulationin the northern part of the Indian Ocean it has a monsoonal character: in summer - northeast and east currents, in winter - southwest and west currents. During the winter months between 3° and 8° S. sh. an inter-trade (equatorial) countercurrent develops. In the southern part of the Indian Ocean, water circulation forms an anticyclonic circulation, which is formed from warm currents - the South Trade Wind in the North, Madagascar and Needle in the West and cold ones - the West Winds in the South and West Australian in the East South of 55 ° S. sh. several weak cyclonic water cycles develop, closing off the coast of Antarctica with an easterly current.

Belt of the Indian Oceanbetween 10 ° from. sh. and 10 ° Yu. sh. called the thermal equator, where the surface water temperature is 28-29°C. To the south of this zone, the temperature drops, reaching ?1°C off the coast of Antarctica. In January and February, the ice along the coast of this continent melts, huge blocks of ice break off from the ice sheet of Antarctica and drift towards the open ocean. To the north, the temperature characteristics of the waters are determined by the monsoon air circulation. In summer, temperature anomalies are observed here, when the Somali current cools surface waters to a temperature of 21-23°C. In the eastern part of the ocean at the same geographical latitude, the water temperature is 28 ° C, and the highest temperature mark - about 30 ° C - was recorded in the Persian Gulf and the Red Sea. The average salinity of ocean waters is 34.8‰ fresh water carried to the seas by rivers.

The tides in the Indian Ocean, as a rule, are small (off the coast of the open ocean and on the islands from 0.5 to 1.6 m), only at the tops of some bays they reach 5-7 m; in the Gulf of Cambay 11.9 m. The tides are predominantly semi-diurnal.

Ice forms at high latitudes and is carried by winds and currents along with icebergs in a northerly direction (up to 55 ° S in August and up to 65-68 S in February).

. Bottom sediments of the Indian Ocean and its structure

Bottom sedimentsthe Indian Ocean have the greatest thickness (up to 3-4 km) at the foot of the continental slopes; in the middle of the ocean - small (about 100 m) thickness and in places where the dissected relief is distributed - discontinuous distribution. The most widely represented are foraminiferal (on the continental slopes, ridges and at the bottom of most basins at a depth of up to 4700 m), diatoms (south of 50 ° S), radiolarian (near the equator) and coral sediments. Polygenic sediments - red deep-sea clays - are distributed south of the equator at a depth of 4.5-6 km or more. Terrigenous sediments - off the coast of the continents. Chemogenic sediments are mainly represented by ferromanganese nodules, while riftogenic sediments are represented by destruction products of deep rocks. Outcrops of bedrocks are most often found on continental slopes (sedimentary and metamorphic rocks), mountains (basalts) and mid-ocean ridges, where, in addition to basalts, serpentinites and peridotites have been found, representing little-altered matter of the Earth's upper mantle.

The Indian Ocean is characterized by the predominance of stable tectonic structures both on the bed (thalassocratons) and along the periphery (continental platforms); active developing structures - modern geosynclines (Sonda arc) and georiftogenals (mid-ocean ridge) - occupy smaller areas and continue in the corresponding structures of Indochina and rifts of East Africa. These main macrostructures, which differ sharply in morphology, the structure of the earth's crust, seismic activity, and volcanism, are subdivided into smaller structures: plates, usually corresponding to the bottom of oceanic basins, blocky ridges, volcanic ridges, sometimes topped with coral islands and banks (Chagos, Maldives, etc.). .), trench-faults (Chagos, Ob, etc.), often confined to the foot of blocky ridges (East Indian, West Australian, Maldives, etc.), fault zones, tectonic ledges. Among the structures of the Indian Ocean bed, a special place (in terms of the presence of continental rocks - granites of the Seychelles and the continental type of the earth's crust) is occupied by the northern part of the Mascarene Range - a structure that is apparently part of the ancient Gondwana mainland.

. Minerals

The most important minerals of the Indian Ocean are oil and natural gas. Their deposits are found on the shelves of the Persian and Suez Gulfs, in the Bass Strait, on the shelf of the Hindustan Peninsula. In terms of reserves and production of these minerals, the Indian Ocean ranks first in the world. On the coasts of Mozambique, the islands of Madagascar and Ceylon, ilmenite, monazite, rutile, titanite and zirconium are exploited. There are deposits of barite and phosphorite off the coast of India and Australia, and deposits of cassiterite and ilmenite are exploited on an industrial scale in the shelf zones of Indonesia, Thailand and Malaysia. On the shelves - oil and gas (especially the Persian Gulf), monazite sands (the coastal region of Southwestern India), etc.; in reef zones - ores of chromium, iron, manganese, copper, etc.; on the bed - huge accumulations of ferromanganese nodules.

. Climateindian ocean

Most of the Indian Ocean is located in warm climatic zones - equatorial, subequatorial and tropical. Only its southern regions, located at high latitudes, are strongly influenced by Antarctica. The equatorial climate zone of the Indian Ocean is characterized by a constant predominance of humid warm equatorial air. Average monthly temperatures range here from 27° to 29°. The water temperature is slightly higher than the air temperature, which creates favorable conditions for convection and precipitation. Their annual amount is large - up to 3000 mm and more.

. Flora and fauna

The most dangerous mollusks in the world live in the Indian Ocean - cone snails. Inside the snail there is a rod-like container with poison, which it injects into its prey (fish, worms), its poison is also dangerous for humans.

The entire water area of ​​the Indian Ocean lies within the tropical and southern temperate zones. The shallow waters of the tropical zone are characterized by numerous 6- and 8-ray corals, hydrocorals, capable of creating islands and atolls together with calcareous red algae. The richest fauna of various invertebrates (sponges, worms, crabs, mollusks, sea ​​urchins, brittle stars and starfish), small but brightly colored coral fish. Most of the coasts are occupied by mangroves, in which the mud jumper stands out - a fish that can exist in the air for a long time. The fauna and flora of the beaches and rocks that dry out at low tide are quantitatively depleted as a result of the depressing effect of the sun's rays. In the temperate zone, life on such stretches of coasts is much richer; dense thickets of red and brown algae (kelp, fucus, reaching the huge size of microcystis) develop here, various invertebrates are abundant. For the open spaces of the Indian Ocean, especially for the surface layer of the water column (up to 100 m), rich flora is also characteristic. Of the unicellular planktonic algae, several species of peredinium and diatom algae predominate, and in the Arabian Sea - blue-green algae, often causing the so-called water bloom during mass development.

The bulk of the ocean's animals are copepods (more than 100 species), followed by pteropods, jellyfish, siphonophores, and other invertebrates. Of the unicellular, radiolarians are characteristic; numerous squids. Of the fish, the most abundant are several species of flying fish, luminous anchovies - myctophids, dolphins, large and small tuna, sailfish and various sharks, poisonous sea snakes. Sea turtles and large marine mammals (dugongs, toothed and toothless whales, pinnipeds) are common. Among the birds, the most characteristic are albatrosses and frigatebirds, as well as several species of penguins that inhabit the coast. South Africa, Antarctica and islands lying in the temperate zone of the ocean.

At night, the surface of the Indian Ocean shimmers with lights. Light is produced by small marine plants called dinoflagellates. Luminous areas sometimes have the shape of a wheel with a diameter of 1.5 m.

. Fishing and marine industry

Fishing is underdeveloped (the catch does not exceed 5% of the world catch) and is limited to the local coastal zone. Near the equator (Japan) is fishing for tuna, and in Antarctic waters - whale fishing. In Sri Lanka, on the Bahrain Islands and on the northwestern coast of Australia, pearls and mother-of-pearl are mined.

The countries of the Indian Ocean also have significant resources of other valuable types of mineral raw materials (tin, iron and manganese ores, natural gas, diamonds, phosphorites, etc.).

Bibliography:

1.Encyclopedia "Science" Dorling Kindersley.

.“I know the world. Geography” V.A. Markin

3.slovari.yandex.ru ~ TSB books / Indian Ocean /

4.Big Encyclopedic Dictionary of Brockhaus F.A., Efron I.A.

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The Indian Ocean ranks third in terms of area. At the same time, compared with others, the greatest depth of the Indian Ocean is very modest - only 7.45 kilometers.

Location

It is not difficult to find it on the map - the Asian part of Eurasia is located in the north of the ocean, Antarctica is located on the southern shores, and Australia lies on the path of the currents from the east. Africa is in the western part of it.

Most of the ocean area is located in the southern hemisphere. A very conditional line separates the Indian and - from Africa, down the twentieth meridian to Antarctica itself. It is separated from the Pacific by the Indochinese peninsulas of Malacca, the border goes to the north then along the line that on the map connects the islands of Sumatra, Java, Sumba and New Guinea. With the fourth - the Arctic - the Indian Ocean has no common borders.

Area

The average depth of the Indian Ocean is 3897 meters. At the same time, it occupies an area of ​​74,917 thousand kilometers, which allows it to be in third place in size among its "brothers". The shores of this huge reservoir are very weakly indented - this is the reason why there are few seas in its composition.

Relatively few islands lie in this ocean. The most significant of them once broke away from the mainland, so they are located close to the coastline - Socotra, Madagascar, Sri Lanka. Far from the coast, in the open part, you can find islands that originated from volcanoes. These are Crozet, Mascarensky and others. In the tropics, on the cones of volcanoes, there are islands of coral origin, such as the Maldives, Cocos, Adaman and others.

The shores in the east and northwest are indigenous, while in the west and northeast they are mostly alluvial. The edge of the coast is indented very weakly, except for its northern part. It is here that most of the large bays are concentrated.

Depth

Of course, on such a large area, the depth of the Indian Ocean cannot be the same - the maximum is 7130 meters. This point is located in the Sunda Trench. The average depth of the Indian Ocean is 3897 meters.

Sailors and water explorers cannot rely on the average figure. Therefore, scientists have long drawn up a map of the depths of the Indian Ocean. It accurately indicates the height of the bottom at various points, all the shoals, gutters, depressions, volcanoes and other features of the relief are visible.

Relief

Along the coast lies a narrow strip of continental shallows, about 100 kilometers wide. The edge of the shelf, located in the ocean, has a shallow depth - from 50 to 200 meters. Only in the northwest of Australia and along the Antarctic coast does it increase to 300-500 meters. The slope of the mainland is quite steep, in some places separated by underwater valleys of large rivers, such as the Ganges, Indus and others. In the northeast, the rather monotonous relief of the bottom of the Indian Ocean is enlivened by the Sunda Island Arc. It is here that the most significant depth of the Indian Ocean is found. The maximum point of this trough is located at 7130 meters below sea level.

Ridges, ramparts and mountains broke the bed into several basins. The most famous are the Arabian Basin, African-Antarctic and Western Australian. These depressions have formed hilly, located in the center of the ocean, and accumulative plains, located not far from the continents, in those areas where sedimentary material is supplied in sufficient quantities.

Among the large number of ridges, the East Indian is especially noticeable - its length is about 5 thousand kilometers. However, the relief of the bottom of the Indian Ocean has other significant ridges - the Western Australian, meridional and others. The bed is also rich in various volcanoes, in places forming chains and even rather large massifs.

Mid-ocean ridges - three branches mountain system dividing the ocean from the center to the north, southeast and southwest. The width of the ranges ranges from 400 to 800 kilometers, the height is 2-3 kilometers. The relief of the bottom of the Indian Ocean in this part is characterized by faults across the ridges. Along them, the bottom is most often horizontally displaced by 400 kilometers.

Unlike the ridges, the Australo-Antarctic Rise is a rampart with gentle slopes, the height of which reaches a kilometer, while the width extends up to one and a half thousand kilometers.

The predominantly tectonic structures of the bottom of this particular ocean are quite stable. Active developing structures occupy a much smaller area and flow into similar structures in Indochina and East Africa. These main macrostructures are divided into smaller ones: plates, blocky and volcanic ridges, banks and coral islands, trenches, tectonic ledges, depressions of the Indian Ocean and others.

Among the various irregularities, a special place is occupied by the north of the Mascarene Range. Presumably, this part previously belonged to the long-lost ancient mainland Gondwana.

Climate

The area and depth of the Indian Ocean make it possible to assume that the climate in its different parts will be completely different. And indeed it is. The northern part of this huge body of water has a monsoonal climate. In the summer, during a period of low pressure over mainland Asia, southwestern flows of equatorial air predominate over the water. In winter, tropical air masses from the northwest dominate here.

A little south of 10 degrees south latitude, the climate over the ocean becomes much more constant. In tropical (and subtropical in summer) latitudes, southeast trade winds rule here. In temperate - extratropical cyclones that move from west to east. Hurricanes are often found in the west of tropical latitudes. Most often they sweep in the summer and autumn.

The air in the north of the ocean warms up to 27 degrees in summer. African coasts are blown with air with a temperature of about 23 degrees. In winter, the temperature drops depending on latitude: in the south it can be below zero, while in northern Africa the thermometer does not fall below 20 degrees.

The water temperature depends on the currents. The coast of Africa is washed by the Somali current, which has rather low temperatures. This leads to the fact that the water temperature in this region is kept at about 22-23 degrees. In the north of the ocean, the upper layers of water can reach a temperature of 29 degrees, while in the southern regions, off the coast of Antarctica, it drops to -1. Of course, we are talking only about the upper layers, since the greater the depth of the Indian Ocean, the more difficult it is to draw conclusions about the water temperature.

Water

The depth of the Indian Ocean does not affect the number of seas at all. And there are fewer of them than in any other ocean. There are only two Mediterranean seas: the Red and the Persian Gulf. In addition, there is also the marginal Arabian Sea, the Andaman Sea, which is only partially enclosed. To the east of the vast waters are Timor and

The largest rivers in Asia belong to the basin of this ocean: the Ganges, Salween, Brahmaputra, Irwaddy, Indus, Euphrates and Tigris. Among the African rivers, it is worth highlighting the Limpopo and Zambezi.

Average depth Indian Ocean 3897 meters. And in this column of water a unique phenomenon occurs - a change in the direction of currents. The currents of all other oceans are unchanged from year to year, while in the Indian one the currents are subject to winds: in winter they are monsoon, in summer they prevail.

Since the deep waters originate in the Red Sea and the Persian Gulf, almost the entire body of water has an increased salinity with a low percentage of oxygen.

coast

In the west and northeast, there are mainly alluvial shores, while in the northwest and east they are bedrock. As already mentioned, the coastline is almost flat, very weakly indented almost along the entire length of this water body. The exception is the northern part - it is here that most of the seas belonging to the Indian Ocean basin are concentrated.

inhabitants

The rather small average depth of the Indian Ocean boasts a wide variety of representatives of the animal and plant worlds. The Indian Ocean is located in the tropical and temperate zones. The shallow waters are full of corals and hydrocorals, among which lives great amount types of invertebrates. These are worms, and crabs, and sea urchins, stars and other animals. An equal number of brightly colored tropical fish find shelter in these areas. The coasts are rich in mangroves, in which the mudskipper has settled - this fish can live for a very long time without water.

The flora and fauna of the beaches subject to low tide is very poor, as the hot sun rays destroy all living things here. in this sense, it is much more diverse: there is a rich selection of algae and invertebrates.

The open ocean is even richer in living beings - representatives of both the animal and plant worlds.

The main animals are copepods. More than a hundred species of them live in the waters of the Indian Ocean. Pteropods, siphonophores, jellyfish and other invertebrates are almost as numerous as species. Several species of flying fish, sharks, glowing anchovies, tuna, and sea snakes frolic in the waters of the ocean. Whales, pinnipeds, sea turtles, dugongs are no less common in these waters.

Feathered inhabitants are represented by albatrosses, frigates and several species of penguins.

Minerals

Oil deposits are being developed in the waters of the Indian Ocean. In addition, the ocean is also rich in phosphates, potash raw materials necessary for fertilizing agricultural land.

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.

Physical-geographical 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 (Queen Maud Land), in the east (with the Pacific Ocean south of Australia) - along the eastern border of the Bass Strait to the island of Tasmania , and then along the meridian of 146 ° 55' east longitude to Antarctica, in the northeast (with the Pacific basin) - between the Andaman Sea and the Strait of Malacca, then along the southwestern shores 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, this geographical nomenclature is not universally recognized, and, as a rule, the Indian Ocean is considered within its usual boundaries. The Indian Ocean is the only one of the oceans that is located mostly in the Southern Hemisphere and is limited in the north by a powerful landmass. Unlike other oceans, its mid-ocean ridges form three branches, diverging 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 km 2, the volume of water is 282.65 million km 3, 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-water Sunda Trench is 7729 m at 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 map.

Seas. Seas, bays and straits in the Indian Ocean are almost three times less than in the Atlantic or Pacific Ocean, 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 about 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 km2. Most major islands mainland origin - Socotra, Sri Lanka, Madagascar, Tasmania, Sumatra, Java, Timor. Volcanic islands: Reunion, Mauritius, Prince Edward, Crozet, Kerguelen and others; coral - Laccadive, Maldivian, Amirant, Chagos, Nicobar, most of the Andaman, Seychelles; coral Comoros, Mascarene, Cocos and other islands rise on volcanic cones.

coast. The Indian Ocean is distinguished by a relatively small indentation of the 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, poorly dissected, often surrounded by coral reefs; in the northwestern part - indigenous. In the north, low, slightly dissected coasts with lagoons and sand bars, places with mangroves, bordered by coastal lowlands (Malabar coast, Coromandel coast) prevail, abrasion-accumulative (Konkan coast) and deltaic coasts 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 topography of the bottom of the Indian Ocean, four main elements of geotecture are distinguished: the underwater margins of the continents (including the shelf and the continental slope), transitional zones, or zones of island arcs, the ocean floor, and mid-ocean ridges. The area of ​​the underwater margins of the continents in the Indian Ocean is 17660 thousand km2. 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 mainland, the shelf expands significantly and in the region 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 inflection of the bottom surface and a rapid increase in its slope up 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 at its outer border increases from 100 to 500 m. 4200 m, Sri Lanka). The shelf and the continental slope in some areas are cut by several narrow and deep canyons, the most pronounced canyons, which are underwater continuations of the channels of the Ganges rivers (together with the Brahmaputra River, it annually carries into the ocean about 1200 million tons of suspended and entrained sediments, which formed a layer of sediments over 3500 m thick ) and Ind. The underwater margin of Australia is distinguished 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; the greatest depth is 500 m. The continental slope to the west of Australia is complicated by underwater ledges and separate underwater plateaus (the greatest height is 3600 m, the Aru Islands). On the underwater margin of Antarctica, everywhere there are traces of the influence of the ice load of a huge glacier covering the mainland. The shelf here belongs to a special glacial type. Its outer boundary almost coincides with the 500 m isobath. The width of the shelf is from 35 to 250 km. The continental slope is complicated by longitudinal and transverse ridges, separate ridges, valleys and deep trenches. At the foot of the continental slope, almost everywhere there is an accumulative plume composed of terrigenous material brought by glaciers. The largest slopes of the bottom are noted in the upper part; with increasing depth, the slope gradually flattens out.

The transition zone at the bottom of the Indian Ocean is distinguished only in the area adjacent to the arc of the Sunda Islands, and represents the southeastern part of the Indonesian transition region. It includes: the basin of the Andaman Sea, the island arc of the Sunda Islands and deep-sea trenches. The most morphologically expressed in this zone is the deep-water Sunda Trench with slopes of 30° or more. Relatively small deep-sea trenches stand out southeast of the island of Timor and east of the Kai Islands, but due to their thick sedimentary layer maximum depths 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, diverging from the area with coordinates 22 ° south latitude and 68 ° east longitude to the northwest, southwest and southeast. Each of the three branches is divided according to morphological features into two independent ridges: the northwestern one - into the Middle Aden Ridge and the Arabian-Indian Ridge, the southwestern one - into the West Indian Ridge and the African-Antarctic Ridge, the southeastern one - into the Central the Indian Ridge and the Australo-Antarctic Rise. Thus, the median ridges divide the bed 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 foot of which are located at depths of about 5000-3500 m. The relative height of the ridges is 4700-2000 m, the width is 500-800 km, the depth of the rift valleys is 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, the largest basins are: Somali (with depths of 3000-5800 m), -5300 m), Mozambique (4000-6000 m), Madagascar Basin (4500-6400 m), Agulhas (4000-5000 m); underwater ridges: Mascarene Ridge, Madagascar, Mozambique; Plateau: Agulhas, Mozambique Plateau; separate mountains: Equator, Africana, Vernadsky, Hall, Bardin, Kurchatov; Amirant Trench, Mauritius Trench; canyons: Zambezi, Tanganyika and Tagela. The following basins are distinguished in the northeastern sector: Arabian (4000-5000 m), Central (5000-6000 m), Cocos (5000-6000 m), North Australian (5000-5500 m), West Australian Basin (5000-6500 m), Naturalista (5000-6000 m) and the South Australian Basin (5000-5500 m); underwater ranges: Maldives Ridge, East Indian Ridge, West Australian; Cuvier mountain range; Exmouth Plateau; upland Mill; separate mountains: Moscow State University, Shcherbakov and Afanasy Nikitin; East Indian Trench; canyons: rivers Indus, Ganges, Seatown and Murray. In the Antarctic sector - basins: Crozet (4500-5000 m), African-Antarctic basin (4000-5000 m) and Australo-Antarctic basin (4000-5000 m); plateau: Kerguelen, Crozet and Amsterdam; separate mountains: Lena and Ob. The shapes and sizes of the basins are different: from round ones with a diameter of about 400 km (Komorskaya) to oblong giants 5500 km long (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 splitting and subsidence of continental masses, and as a result of the spreading of the bottom and the neoformation of the oceanic crust within the mid-ocean (spreading) ridges, the system of which was repeatedly rebuilt. The modern system of mid-ocean ridges consists of three branches, converging at the point of the triple junction of Rodriguez. In the northern branch, the Arabian-Indian Ridge continues to the northwest of the Owen transform fault zone with the Gulf of Aden and Red Sea rift systems and connects with the East African intracontinental rift systems. In the southeastern branch, the Central Indian Ridge and the Australo-Antarctic Rise are separated by the Amsterdam Fault Zone, with which the plateau of the same name is connected with the volcanic islands of Amsterdam and St. Paul. The Arabian-Indian and Central Indian ridges are slow-spreading (the spreading rate is 2-2.5 cm/year), have a well-defined rift valley, and are crossed by numerous transform faults. The wide Australo-Antarctic Rise does not have a pronounced rift valley; spreading rate on it is higher than in other ridges (3.7-7.6 cm/year). South of Australia, the uplift is broken by the Australo-Antarctic fault zone, where the number of transform faults increases and the spreading axis shifts along the faults to the south. The ridges of the southwestern branch are narrow, with a deep rift valley, and are densely crossed by transform faults oriented at an angle to the strike of the ridge. They are characterized by a very low spreading rate (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 faults, which shift the axis of the ridge 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 intrudes into the structures of the Central Indian Ridge as a narrow wedge, is considered the youngest.

The spreading ridges divide the ocean floor into three sectors - the African in the west, the Asian-Australian in the northeast, and the Antarctic in the south. Within the sectors there are various types of intra-oceanic uplift, represented by "aseismic" ridges, plateaus and islands. Tectonic (blocky) uplifts have a block structure with different thicknesses of the crust; often include continental remnants. Volcanic uplifts are mainly associated with fault zones. 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 Mozambique plateaus, the Madagascar ridge with the island of Madagascar, individual blocks of the Mascarene plateau with the bank of the Seychelles and the bank of Saya de -Malya). Volcanic uplifts and structures include the Comoros underwater ridge crowned with archipelagos of coral and volcanic islands, the Amirantsky ridge, the Reunion Islands, Mauritius, Tromelin, the Farquhar massif. In the western part of the African sector of the Indian Ocean (the western part of the Somali Basin, the northern part of the Mozambique Basin), adjacent to the eastern submarine 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 crossing them have been identified in the Somali and Mascarene basins.

The northwestern (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 with archipelagos of coral islands - Laccadive, Maldives and Chagos; the so-called 79° ridge, Lanka ridge with Mount Athanasius Nikitin, East Indian (the so-called 90° ridge), Investigator, etc. Thick (8-10 km) sediments of the Indus, Ganges and Brahmaputra rivers in the northern Indian Ocean partially overlap the in this direction, the ridges, as well as the structures of the transition zone of the Indian Ocean - the southeastern outskirts of Asia. The Murri Range in the northern part of the Arabian Basin, which limits the Oman Basin from the south, is a continuation of the folded land structures; enters the Owen Fault Zone. To the south of the equator, a sublatitudinal zone of intraplate deformations up to 1000 km wide was revealed, which is characterized by high seismicity. It stretches in the Central and Coconut basins from the Maldives Range to the Sunda Trench. The Arabian Basin is underlain by the crust of the Paleocene-Eocene age, the Central Basin - by the crust of the Late Cretaceous - Eocene age; the bark is the youngest in the southern part of the basins. In the Coconut Basin, the age of the crust varies from Late Cretaceous in the south to Eocene in the north; an ancient spreading axis was established in its northwestern part, separating the Indian and Australian lithospheric plates until the middle Eocene. The Coconut Rise, a latitudinal uplift with numerous seamounts and islands (including the Cocos Islands) rising above it, and the Ru Rise adjacent to the Sunda Trench separate the southeastern (Australian) part of the Asian-Australian sector. The West Australian basin (Wharton) in the central part of the Asian-Australian sector of the Indian Ocean is underlain in the northwest by the Late Cretaceous crust, in the east by the Late Jurassic. Submerged continental blocks (marginal plateaus of Exmouth, Cuvier, Zenith, Naturalist) divide the eastern part of the basin into separate depressions - Cuvier (north of the Cuvier plateau), Perth (north of the Naturalist plateau). The crust of the North Australian Basin (Argo) is the most ancient in the south (Late Jurassic); becomes younger in a northerly direction (to the early Cretaceous). The age of the crust of the South Australian Basin is Late Cretaceous - Eocene. The Broken Plateau is an intra-oceanic uplift with an 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 uplifts with an increased thickness of the earth's crust: the Kerguelen Plateau, Crozet (Del Cano) and Conrad. Within the limits of the largest plateau Kerguelen, presumably laid down on an ancient transform fault, the thickness of the earth's crust (according to some data, the Early Cretaceous age) reaches 23 km. Towering above the plateau, the Kerguelen Islands are a multiphase volcanoplutonic structure (composed of alkaline basalts and syenites of the Neogene age). On Heard Island - Neogene-Quaternary alkaline volcanic rocks. In the western part of the sector, there are the Konrad plateau with the Ob and Lena volcanic mountains, 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, Australo-Antarctic basins and the Crozet basin is Late Cretaceous - Eocene.

The Indian Ocean is characterized by the predominance of passive margins (the continental margins of Africa, the Arabian and Hindustan peninsulas, Australia, and Antarctica). The active margin is observed in the northeastern part of the ocean (the Sunda zone of the Indian Ocean-Southeast Asia transition), where subduction (underthrust) of the ocean's lithosphere occurs under the Sunda island arc. A subduction zone limited in length - Makranskaya - was 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 middle of the Mesozoic during the breakup of the Gondwana part (see Gondwana) of the Patea supercontinent, which was preceded by continental rifting during the Late Triassic - Early Cretaceous. The formation of the first sections of the 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 bottom expansion and the new formation of the oceanic crust experienced the northern part of the Mozambique Basin (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 oceanic 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 to the north and west of Australia, off the coast of Antarctica and in the Mozambique Channel, died off. 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 Australo-Antarctic Rise. At the turn of the Cretaceous and Paleogene, Hindustan separated from the Mascarene-Seychelles block; the Arabian-Indian spreading ridge arose; spreading axes died off 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 a close to modern appearance at the beginning - middle of the Miocene. In the middle of the Miocene (about 15 million years ago), during the breakup of the Arabian and African plates, a new formation of oceanic crust began in the Gulf of Aden and the Red Sea.

Recent tectonic movements in the Indian Ocean have been noted in mid-ocean ridges (associated with shallow-focus earthquakes), as well as in individual transform faults. The area of ​​intense seismicity is the Sunda island arc, where deep-focus earthquakes are due to the presence of a seismofocal zone plunging in a northeasterly direction. During earthquakes on the northeastern margin of the Indian Ocean, the formation of a tsunami is possible.

Bottom sediments. The rate of sedimentation in the Indian Ocean is generally lower than in the Atlantic and Pacific oceans. The thickness of modern bottom sediments varies from a discontinuous distribution on mid-ocean ridges to several hundred meters in deep-water basins and 5000-8000 m at the foot of continental slopes. The most widespread are calcareous (mainly foraminiferal-coccolithic) muds covering over 50% of the ocean floor area (on continental slopes, ridges and the bottom of basins at depths up to 4700 m) in warm oceanic regions from 20° north latitude to 40° south latitude from high biological productivity of waters. Polygenic sediments - red deep-sea oceanic clays - occupy 25% of the bottom area at depths of more than 4700 m in the eastern and southeastern parts of the ocean from 10 ° north latitude to 40 ° south latitude and in bottom areas remote from islands and continents; in the tropics, red clays alternate with siliceous radiolarian silts that cover the bottom of deep-water basins of the equatorial belt. In deep-sea sediments, ferromanganese nodules are present as inclusions. Siliceous, mainly diatomaceous, oozes occupy about 20% of the bottom of the Indian Ocean; 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 the continents and within their underwater margins in the areas of river and iceberg runoff, significant wind removal of material. Sediments covering the African shelf are mainly of shell and coral origin; phosphorite concretions are widely developed in the southern part. Along the northwestern periphery of the Indian Ocean, as well as in the Andaman Basin and in the Sunda Trench, bottom sediments are mainly represented by deposits of turbidity (turbid) flows - turbidites with the participation of products of volcanic activity, underwater landslides, landslides, etc. Sediments of coral reefs are widespread in the 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 rift valley Outcrops of metal-bearing brines with temperatures up to 70°C and salinity up to 300‰ have been found in the Red Sea. In the metal-bearing sediments formed from these brines, the content of non-ferrous and rare metals is high. On continental slopes, seamounts, mid-ocean ridges, outcrops of bedrocks (basalts, serpentinites, peridotites) are noted. Bottom sediments around Antarctica stand out as a special type of iceberg deposits. They are characterized by the predominance of various detrital material, ranging from large boulders to silts and fine silts.

Climate. Unlike the Atlantic and Pacific Oceans, which have a meridional strike from the coast of Antarctica to the Arctic Circle and communicate with the North 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 the land and ocean leads to a seasonal change in extensive minima and maxima of atmospheric pressure and to seasonal displacements of the tropical atmospheric front, which retreats southward to almost 10 ° south latitude in the winter of the Northern Hemisphere, and is located in the foothill regions of southern Asia in summer. As a result, a monsoonal climate dominates over the northern part of the Indian Ocean, which is primarily characterized by a change in wind direction during the year. The winter monsoon with relatively weak (3-4 m/s) and stable northeasterly winds operates from November to March. During this period, north of 10 ° south latitude, calms are not uncommon. The summer monsoon with southwesterly winds is observed 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 strength. In April and October, the baric field is usually restructured, and in these months the wind situation is unstable. Against the background of the prevailing monsoonal atmospheric circulation over the northern part of the Indian Ocean, individual manifestations of cyclonic activity are possible. During the winter monsoon, there are cases of cyclones developing over the Arabian Sea, during the summer monsoon - over the waters of the Arabian Sea and the Bay of Bengal. Strong cyclones in these areas are sometimes formed during the periods of monsoon change.

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

South of 40° South latitude, atmospheric pressure in all seasons decreases uniformly 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 transport of air is maintained. The highest average wind speed (up to 15 m/s) is observed in the middle of winter in the Southern Hemisphere. For the higher southern latitudes of the Indian Ocean, storm conditions are typical throughout almost the entire year, under which winds with speeds of more than 15 m/s, causing waves with a height of more than 5 m, have a frequency of 30%. East winds and two or three cyclones per year are usually observed south of 60 ° south latitude along the coast of Antarctica, most often in July - August.

In July, the highest air temperatures in the near 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 water area of ​​the Indian Ocean, the air temperature changes almost everywhere in accordance with the geographical 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 zone, 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 drops evenly from 26°C in the Southern Tropic to 0°C and somewhat lower at the latitude of the Antarctic Circle. The amplitude of annual fluctuations in air temperature 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 eastern shores islands of Madagascar (more than 3500 mm). In the northern coastal part of the Arabian Sea, the least amount of precipitation falls (100-200 mm per year).

The northeastern regions of the Indian Ocean are located in seismically active areas. East coast of Africa and the island of Madagascar, the coast of the Arabian Peninsula and the Hindustan Peninsula, almost all island archipelagos of volcanic origin, the western shores of Australia, especially the arc of the Sunda Islands, in the past were repeatedly exposed to tsunami waves of various strengths, up to catastrophic ones. In 1883, after the explosion of the Krakatau volcano in the Jakarta region, a tsunami with a wave height of over 30 m was recorded, in 2004 a tsunami caused by an earthquake in the region 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 time of the southwest monsoon (May - September), the winter - the northeast monsoon (November - March). A feature of the seasonal variability of the hydrological regime is that the restructuring of the hydrological fields is somewhat late 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 the Bay of Bengal, the water temperature is about 25°C. In the southern part of the Indian Ocean, a zonal temperature distribution is characteristic everywhere, which gradually decreases from 27-28 ° C at 20 ° south latitude to negative values ​​\u200b\u200bat the edge of drifting ice, located approximately at 65-67 ° south latitude. In the summer season, the highest water temperatures in the surface layer are observed in the Persian Gulf (up to 34°С), in the northwest of the Arabian Sea (up to 30°С), in the eastern part of the equatorial zone (up to 29°С). In the coastal regions of the Somali and Arabian peninsulas, abnormally low values ​​\u200b\u200bare observed at this time of the year (sometimes less than 20 ° C), 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 retains a zonal character, with the difference that its negative values ​​\u200b\u200bin the winter of the Southern Hemisphere occur much further north, already at about 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 region of the Somali coast and in the Gulf of Oman of the Arabian Sea exceeds 7°C. The water temperature rapidly decreases vertically: at a depth of 250 m, it drops below 15°C almost everywhere, and below 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 central regions- about 2.5°С, in the southern part decreases from 2°С at 50° south latitude to 0°С off the coast of Antarctica. Temperatures in the deepest (over 5000 m) basins range from 1.25°С to 0°С.

The salinity of the surface waters of the Indian Ocean is determined by the balance between the amount of evaporation and the total amount of precipitation and river runoff for each area. The absolute maximum of salinity (over 40‰) is observed in the Red Sea and the Persian Gulf, in the Arabian Sea everywhere, except for 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 arc of the Sunda Islands, where fresh river flow is large and the greatest amount of precipitation falls. In the northern part of the Bay of Bengal in February, salinity is 30-31‰, in August - 20‰. An extensive tongue of waters with a salinity of 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 salinity during the formation sea ​​ice and corresponding desalination during the period of ice melting. Seasonal changes in salinity are noticeable only in the upper 250-meter layer. With increasing depth, not only seasonal fluctuations, but also the spatial variability of salinity fade, deeper than 1000 m it fluctuates between 35-34.5‰.

Density. The highest water density in the Indian Ocean is noted in the Suez and Persian Gulfs (up to 1030 kg / m 3) and in cold Antarctic waters (1027 kg / m 3), the average - in the warmest and salty waters in the northwest (1024-1024.5 kg / m 3), the smallest - in the most fresh waters in the northeastern part of the ocean and in the Bay of Bengal (1018-1022 kg / m 3). With depth, mainly due to a decrease in water temperature, its density increases, sharply increasing in the so-called jump layer, which is most pronounced in the equatorial zone of the ocean.

Ice regime. The severity of the climate in the southern part of the Indian Ocean is such that the process of formation of sea ice (at air temperatures below -7 ° C) can occur almost all year round. The maximum development of the ice cover reaches in September - October, when the width of the drifting ice belt reaches 550 km, the smallest - in January - February. The ice cover is characterized by high seasonal variability and its formation is very fast. The ice edge moves to the north at a speed of 5-7 km/day, just as quickly (up to 9 km/day) retreats 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 near the coasts of the mainland moves under the influence of katabatic winds in the general direction to the west and northwest. Near the northern edge, the ice drifts eastward. A characteristic feature of the Antarctic ice cover is a large number of icebergs breaking off from the outlet and ice shelves of Antarctica. Table-shaped icebergs are especially large, which can reach a gigantic length of several tens of meters, towering 40-50 meters above the water. Their number rapidly decreases with distance from the coast of the mainland. The duration of the existence of large icebergs is on average 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 changes significantly from summer to winter. 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 with speeds of 50-80 cm/s; with a rod passing approximately along 18 ° south latitude, the South Equatorial 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 Inter-trade 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 passing into the Intertrade countercurrent, and to the south, the Mozambique and Cape of Agulhas currents, going south at speeds of about 50 cm / s. Part of the South Equatorial Current east coast Islands Madagascar turns along it to the south (Madagascar current). South of 40 ° south latitude, the entire water area of ​​the ocean is crossed from west to east by the flow of the longest and most powerful West Wind Current in the World Ocean (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 West Australian Current. In August, the Somali current follows in a general direction to the northeast and, at a speed of up to 150 cm / s, draws 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. Thus, an extensive clockwise circulation is created in the northern part of the Indian Ocean, consisting of the Monsoon, South Equatorial and Somali currents. In the southern part of the ocean, from February to August, the pattern of currents changes little. Off the coast of Antarctica in a narrow coastal strip, a current is observed all year round, caused by katabatic winds and directed from east to west.

water masses. In the vertical structure of the water masses of the Indian Ocean, according to hydrological characteristics and depth of occurrence, surface, intermediate, deep and bottom waters are distinguished. Surface waters are distributed in a relatively thin surface layer and on average occupy the upper 200-300 m. From north to south, water masses stand out 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. So, in intermediate waters, the lower limit of which reaches 2000 m in temperate and low latitudes and up to 1000 m in high latitudes, Persian and Red Sea in the Arabian Sea, Bengal in the Bay of Bengal, Subantarctic and Antarctic intermediate water masses stand out. 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 water everywhere, except for the Bay of Bengal, is represented by one Antarctic bottom water mass, which fills all deep-water basins. The upper limit of bottom water is located on average at a horizon of 2500 m off the coast of Antarctica, where it forms, up to 4000 m in the central regions of the ocean and rises to almost 3000 m north of the equator.

Tides and excitement. Semidiurnal and irregular semidiurnal tides are most widespread on the shores of the Indian Ocean. Semi-diurnal tides are observed on the African coast south of the equator, in the Red Sea, off the northwestern shores of the Persian Gulf, in the Bay of Bengal, 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 daily tides are observed 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 Channel (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 its greatest strength in temperate latitudes in the zone of action of westerly winds, where the frequency of waves with a height of over 6 m is 17% per year. Near Kerguelen Island, waves 15 m high and 250 m long were recorded, off the coast of Australia, 11 m and 400 m, respectively.

Flora and fauna. The main part of the Indian Ocean is located within the tropical and southern temperate zones. The absence of the 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 hinders deep-sea convection, which negatively affects the renewal of deep waters in 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 depletion of the species composition and reduces the total zooplankton biomass in the intermediate layers. When oxygen-poor waters in the Arabian Sea reach the shelf, local kills occur (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 a powerful upwelling that brings waters rich in nutrient salts to the surface. The winter monsoon, although to a lesser extent, leads to seasonal upwelling with similar effects in west coast peninsulas of Hindustan.

The coastal zone of the ocean is characterized by the greatest species diversity. The shallow waters of the tropical zone are characterized by numerous 6- and 8-ray stony corals, hydrocorals, which, together with red algae, can create underwater reefs and atolls. The richest fauna of various invertebrates (sponges, worms, crabs, mollusks, sea urchins, brittle stars and starfish), small but brightly colored fish of coral reefs live among the powerful coral structures. Most of the coasts are occupied by mangroves. At the same time, the fauna and flora of the beaches and rocks that dry out at low tide are quantitatively depleted due to the depressing effect of the sun's rays. In the temperate zone, life on such stretches of coasts is much richer; dense thickets of red and brown algae (kelp, fucus, macrocystis) develop here, various invertebrates are abundant. According to L. A. Zenkevich (1965), over 99% of all species of bottom and bottom 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 rich flora. The food chain in the ocean begins with microscopic unicellular plant organisms - phytoplankton, which inhabits mainly the uppermost (about 100-meter) layer of ocean waters. Among them, several species of peridinium and diatom algae predominate, and in the Arabian Sea - cyanobacteria (blue-green algae), often causing the so-called water bloom during mass development. There are three areas of the highest phytoplankton production in the northern Indian Ocean: the Arabian Sea, the Bay of Bengal and the 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 spring flowering 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 number rapidly decreases with increasing depth and decreases by 2-3 orders of magnitude towards the bottom layers. The food for most of the 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 rates 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 is copepods (more than 100 species), somewhat less pteropods, jellyfish, siphonophores and other invertebrates. Of the unicellular, radiolarians are typical. In the Antarctic region of the Indian Ocean, a huge number of euphausian crustaceans of several species, united under the name "krill", is characteristic. Euphausiids form the main food base 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. Of the cephalopods in the Indian Ocean, cuttlefish, numerous squids and octopuses are common. Of the fish, the most abundant are several species of flying fish, luminous anchovies (dollfish), sardinella, sardine, mackerel pike, notothenia, sea bass, several types of tuna, blue marlin, grenadier, sharks, rays. Sea turtles and poisonous sea snakes live in warm waters. The fauna of aquatic mammals is represented by various cetaceans. Of the baleen whales, the following are common: blue, sei whale, fin whale, humpback whale, Australian (Cape) Chinese. Toothed whales are represented by sperm whales, several species of dolphins (including killer whales). In the coastal waters of the southern part of the ocean, pinnipeds are widespread: Weddell seal, crabeater seal, seals - Australian, Tasmanian, Kerguelen and South African, Australian sea lion, sea leopard, etc. Among the birds, the most characteristic are the wandering albatross, petrels, large frigate, 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 - the living lobe-finned fish Latimeria chalumnae, which was considered extinct tens of millions of years ago. The "fossil" coelacanth lives at a depth of more than 200 m in two places - near the Comoros and in the waters of the Indonesian archipelago.

Research History

The northern coastal regions, especially the Red Sea and deeply incised bays, began to be used by man for navigation and fishing already in the era of ancient civilizations, several thousand years before our era. For 600 years BC, the Phoenician navigators who were in the service of Egyptian pharaoh Necho II, sailed around Africa. In 325-324 BC, an ally of Alexander the Great, Nearchus, commanding a fleet, sailed from India to Mesopotamia and compiled the first descriptions of the coast 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 navigational guides for this area. In the first half of the 15th century, Chinese navigators led by 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) laid a sea route for Europeans to India and to the countries South-East Asia. A few years later, the Portuguese discovered the island of Madagascar, the 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. Start oceanographic research Indian Ocean is based on systematic measurements of water temperature during circumnavigations Russian ships "Rurik" (1815-18) and "Enterprise" (1823-26). In 1831-36, an English expedition took place on the Beagle ship, on which Charles Darwin carried out geological and biological work. Comprehensive oceanographic measurements in the Indian Ocean were carried out during the British expedition on board the Challenger 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 first half of the 20th century, oceanographic observations began to be carried out regularly, and by the 1950s they were carried out at almost 1500 deep-sea oceanographic stations. In 1935, the monograph "Geography of the Indian and Pacific Oceans" by P. G. Schott 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, the Scientific Committee on Oceanography of UNESCO 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 the MIOE, major geographical discoveries were made: the underwater West Indian and East Indian ridges were discovered; etc., deep-sea trenches - the Ob, Chagos, Vima, Vityaz, etc. In the history of the study of the Indian Ocean, the results of studies carried out in 1959-77 by the Vityaz research vessel (10 voyages) and dozens of other Soviet expeditions on ships of the Hydrometeorological Service stand out and the State Committee for Fisheries. Since the early 1980s, ocean research has been carried out within the framework of 20 international projects. The research of the Indian Ocean became especially active during the International World Ocean Circulation Experiment (WOCE). Since its successful completion in the late 1990s, the amount of modern oceanographic information for the Indian Ocean has doubled.

Economic use

The coastal zone of the Indian Ocean is characterized by an exceptionally high population density. Over 35 states are located on the coasts and islands of the ocean, in which about 2.5 billion people (over 30% of the world's population) live. 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 of the region, the problems of gaining living space, creating jobs, providing food, clothing and housing, and medical care are acute.

The use of the Indian Ocean, as well as other seas and oceans, is carried out in several main areas: transport, fishing, mining, and recreation.

Transport. The role of the Indian Ocean in maritime transportation increased significantly with the creation of the Suez Canal (1869), which opened a short sea route of communication with the states washed by the waters of the Atlantic Ocean. The Indian Ocean is an area of ​​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 Straits of Malacca and Sunda) there are routes for ships going to the Pacific Ocean and back. Main export to USA, Japan and countries Western Europe- 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, chemicals and pharmaceuticals, textiles, cut gems and jewellery. The Indian Ocean accounts for about 10% of the world's shipping traffic; at the end of the 20th century, about 0.5 billion tons of cargo per year was transported through its waters (according to IOC). According to these indicators, it ranks third after the Atlantic and Pacific Oceans, yielding to them in terms of the intensity of shipping and total volumes of cargo transportation, but surpassing all other sea transport communications in terms of oil transportation. The main transport routes across the Indian Ocean are directed to the Suez Canal, the Strait of Malacca, the southern tip of Africa and Australia, and along the northern coast. Shipping is most intensive in the northern regions, although it is limited by storm conditions during the summer monsoon, less intensive in the central and southern regions. The growth of oil production in the countries of the Persian Gulf, in Australia, Indonesia and other places contributed to the construction and modernization of oil ports and the emergence of giant tankers in the Indian Ocean.

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

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

Mineral resources. Deposits of oil and natural combustible gas or oil and gas shows have been discovered practically throughout the shelf area of ​​the Indian Ocean. Actively developed oil and gas fields are of the greatest industrial importance in the bays: Persian (Persian Gulf oil and gas basin), Suez (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 (gas-bearing Carnarvon basin), in the Bass Strait (gas-bearing Gippsland basin). Gas deposits have been explored in the Andaman Sea, oil and gas bearing areas - in the Red Sea, the Gulf of Aden, along the coast of Africa. Coastal-marine placers of heavy sands are mined 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 of ilmenite, rutile, monazite and zircon); in the coastal regions 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 have been identified as potential sources for the extraction of iron, manganese, copper, zinc, nickel, etc.; there are deposits of rock salt. In the coastal zone of the Indian Ocean, sand is mined for construction and glass production, gravel, limestone.

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 coast of the continents and on numerous tropical islands in the ocean. The most visited resorts are in Thailand (the island of Phuket, 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) , on the Maldives, in Sri Lanka, on Seychelles, on the islands of Mauritius, Madagascar, in South Africa, etc.

Sharm El Sheikh. Hotel "Concord".

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), El Kuwait (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 VF Relief of the bottom of the Indian Ocean. M., 1979; Indian Ocean. L., 1982; Udintsev GB 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. Nepronov. K., 1990; Neiman V. G., Burkov V. A., Shcherbinin A. D. Dynamics of the waters of the Indian Ocean. M., 1997; Pushcharovsky Yu. M. Tectonics of the Earth. Fav. works. M., 2005. Vol. 2: Tectonics of the oceans.

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

Ocean area - 76.2 million square kilometers;
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;
Most big islands- the island of Madagascar, Sri Lanka;
The strongest currents:
- warm - South Tradewind, Monsoon;
- cold - Western Winds, Somali.

The Indian Ocean is the third largest in terms of size. Most of it is 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. Coastline The Indian Ocean is slightly indented. On the north side, the Indian Ocean seems to be shrouded in land, as a result of which it is the only one of the oceans that is not connected to the Arctic Ocean.
The Indian Ocean was formed as a result of the split of the ancient mainland Gondwana into parts. It is located on the border of three lithospheric plates - Indo-Australian, African and Antarctic. The Arabian-Indian, West Indian, and Australo-Antarctic mid-ocean ridges are the boundaries between these plates. Underwater ridges and elevations divide the ocean floor into separate basins. The shelf zone of the ocean is very narrow. Most of the ocean is within the boundaries of the bed and has a significant 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 regions 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 oceans. The 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 saturated with life. In the warm waters of the Pacific Ocean there are giant sea turtles, sea snakes, many squids, cuttlefish, starfish. Closer to Antarctica there are whales and seals. In the Persian Gulf near the island of Sri Lanka, pearls are mined.
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 mediterranean sea.
The first information about the Indian Ocean was collected as far back as 3 thousand years BC by Indian, Egyptian and Phoenician navigators. The first sailing routes in the Indian Ocean were compiled by the Arabs.
Vasco da Gama, after the discovery of India in 1499, Europeans began to explore the Indian Ocean. English navigator James Cook during the expedition 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 19th 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.

Position of the Indian Ocean
Or where is the Indian Ocean

First of all, the Indian Ocean is the youngest on Earth. It is located mainly in the Southern Hemisphere. Four continents surround it. In the north - the Asian part of Eurasia, in the west Africa, in the east Australia and Antarctica in the south. Along the line from Cape Agulhas, the southernmost point of Africa, and along the twentieth meridian to Antarctica, its waves merge with the Atlantic. The Indian Ocean borders the Pacific Ocean in the north from the western coast of the Malay Peninsula to the northern point of the island of Sumatra and further along the islands of Sumatra, Java, Bali, Sumba, Timor and New Guinea. There was a lot of controversy among geographers about the eastern border. But now everyone seems to have agreed to count it from Cape York in Australia, through the Torres Strait, New Guinea and further northeast through the Lesser Sunda Islands to the islands of Java, Sumatra and the city of Singapore. Between the islands of New Guinea and Australia, its border runs along the Torres Strait. In the south, the ocean boundary runs from Australia to the western coast of Tasmania and further along the meridian to Antarctica. Thus, when viewed from space, The Indian Ocean is shaped like a triangle…

What is the area of ​​the Indian Ocean?

The Indian Ocean is the third largest after the Pacific and Atlantic (), its area is 74,917 thousand square kilometers.

Seas of the Indian Ocean

The shores of the bordering continents are slightly indented, therefore there are very few seas in it - in the north it is the Red Sea, the Persian Gulf, the Arabian Sea, the Bay of Bengal and the Andaman Sea, and in the east - the Timor and Arafura Seas.

Depth of the Indian Ocean

At the bottom of the Indian Ocean, in its central part, there are several deep-water basins separated by underwater ridges and underwater plateaus, and along the Sunda island arc there is deep water Sunda Trench. In it, oceanologists found the deepest hole on the ocean floor - 7130 meters from the surface of the water. The average depth of the ocean is 3897 meters. The largest islands in the Indian Ocean are Madagascar, Socotra and Sri Lanka. All of them are fragments of ancient continents. In the central part of the ocean there are groups of small volcanic islands, and in tropical latitudes there are quite a lot of coral islands.

Temperature of the Indian Ocean

The water in the Indian Ocean is warm. In June - August, closer to the equator, its temperature, as in a bath, is 27-28 ° C (and there are places where the thermometer shows 29 ° C). And only off the coast of Africa, where the cold Somali current passes, the water is colder - 22-23 ° С. But from the equator south to the Antarctic, the temperature of the water in the ocean changes to 26 and even 28 ° C. From the north, it is limited by the shores of the Eurasian continent. From the south - a conditional line connecting the tips of South Africa and Australia. West is Africa.

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But why is the Indian Ocean considered the youngest? On the geographical map it is clearly visible how its basin is surrounded by continental land areas. In the not so distant geological past of our planet, these areas were most likely connected into a single mainland Gondwana, which split, and its parts spread out in different directions, making room for water.

At the bottom of the Indian Ocean, scientists have discovered several underwater mountain ranges. And The Central Indian Range divides the ocean basin into two regions. with completely different types of earth's crust. Deep cracks adjoin the seamounts. Such proximity inevitably causes frequent earthquakes in these areas, or rather, seaquakes. As a result, tsunamis are born that bring innumerable troubles to island and coastal mainland residents.

Submarine volcanoes in these restless regions eject so much material from the bowels that new islands appear from time to time. Many coral reefs and atolls are found in the local warm waters. Driving ships in the Indian Ocean is not easy. During stormy periods, in some of its areas, huge waves as high as a five-story building were recorded! .. Giant catastrophic tsunami waves are not such a rare exotic for the inhabitants of the Indian Ocean basin.