Geographic description of the Indian Ocean.  Indian Ocean description, interesting facts

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The Indian Ocean is the third largest ocean on Earth, covering about 20% of its water surface. Its area is 76.17 million km², volume - 282.65 million km³. The deepest point of the ocean is in the Sunda Trench (7729 m).

  • Area: 76,170 thousand km²
  • Volume: 282,650 thousand km³
  • Maximum depth: 7729 m
  • Average depth: 3711 m

In the north it washes Asia, in the west - Africa, in the east - Australia; in the south it borders on Antarctica. The border with the Atlantic Ocean runs along the 20 ° meridian of east longitude; from the Pacific - along the 146 ° 55 'meridian of eastern longitude. 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.

Etymology

The ancient Greeks called the western part of the ocean known to them with adjacent seas and bays the Erythrean Sea (ancient Greek Ἐρυθρά θάλασσα - Red Sea, and in old Russian sources the Red Sea). Gradually, this name began to be attributed only to the nearest sea, and the ocean gets its name from India, the country most famous at that time for its wealth on the shores of the ocean. So Alexander the Great in the IV century BC. e. calls it Indicon Pelagos (ancient Greek Ἰνδικόν πέλαγος) - "Indian Sea". Among the Arabs, it is known as Bar-el-Hind (modern Arabic المحيط الهندي‎‎ - al-mụkhіt al-hindi) - "Indian Ocean". Since the 16th century, the name Oceanus Indicus (lat. Oceanus Indicus) introduced by the Roman scientist Pliny the Elder back in the 1st century was established - the Indian Ocean.

Physical and geographical characteristics

General information

The Indian Ocean is mainly located south of the Tropic of Cancer between Eurasia to the north, Africa to the west, Australia to the east and Antarctica to the south. The border with the Atlantic Ocean runs along the meridian of Cape Agulhas (20 ° E to the coast of Antarctica (Queen Maud Land)). The border with the Pacific Ocean runs: south of Australia - along the eastern border of the Bass Strait to the island of Tasmania, then along the meridian 146 ° 55 'E. to Antarctica; north of Australia - between the Andaman Sea and the Strait of Malacca, further along the southwestern coast of Sumatra, the Sunda Strait, the southern coast of Java, the southern borders of the Bali and Savu seas, the northern border of the Arafura Sea, the southwestern coast of New Guinea and the western border of the Torres Strait . Sometimes the southern part of the ocean, with a northern boundary of 35 ° S. sh. (on the basis of the circulation of water and the atmosphere) up to 60 ° S. sh. (according to the nature of the bottom topography), they are attributed to the Southern Ocean, which is not officially distinguished.

Seas, bays, islands

The area of ​​the seas, bays and straits of the Indian Ocean is 11.68 million km² (15% of the total ocean area), the volume is 26.84 million km³ (9.5%). The seas and main bays located along the coast of the ocean (clockwise): Red Sea, Arabian Sea (Gulf of Aden, Gulf of Oman, Persian Gulf), Laccadive Sea, Bay of Bengal, Andaman Sea, Timor Sea, Arafura Sea (Gulf of Carpentaria), Large Australian Gulf, Mawson Sea, Davis Sea, Commonwealth Sea, Astronaut Sea (the last four are sometimes referred to as the Southern Ocean).

Some islands - for example, Madagascar, Socotra, Maldives - are fragments of ancient continents, others - Andaman, Nicobar or Christmas Island - are of volcanic origin. The largest island in the Indian Ocean is Madagascar (590 thousand km²). Largest islands and archipelagos: Tasmania, Sri Lanka, Kerguelen Archipelago, Andaman Islands, Melville, Mascarene Islands (Reunion, Mauritius), Kangaroo, Nias, Mentawai Islands (Siberut), Socotra, Groote Island, Comoros, Tiwi Islands (Bathurst ), Zanzibar, Simeulue, Furno (Flinders) Islands, Nicobar Islands, Qeshm, King, Bahrain Islands, Seychelles, Maldives, Chagos Archipelago.

The history of the formation of the Indian Ocean

During the early Jurassic, the ancient supercontinent Gondwana began to break apart. As a result, Africa with Arabia, Hindustan and Antarctica with Australia were formed. The process ended at the turn of the Jurassic and Cretaceous periods (140-130 million years ago), and a young basin of the modern Indian Ocean began to form. In the Cretaceous period, the ocean floor grew due to the movement of Hindustan to the north and the reduction in the area of ​​the Pacific and Tethys oceans. In the Late Cretaceous, the split of the single Australo-Antarctic continent began. At the same time, as a result of the formation of a new rift zone, the Arabian plate broke away from the African plate, and the Red Sea and the Gulf of Aden were formed. At the beginning of the Cenozoic era, the growth of the Indian Ocean stopped towards the Pacific, but continued towards the Tethys Sea. At the end of the Eocene - the beginning of the Oligocene, Hindustan collided with the Asian continent.

Today, the movement of tectonic plates continues. The axis of this movement is the mid-ocean rift zones of the African-Antarctic Ridge, the Central Indian Ridge, and the Australo-Antarctic Rise. The Australian plate continues to move north at a rate of 5-7 cm per year. The Indian plate continues to move in the same direction at a speed of 3-6 cm per year. The Arabian Plate is moving northeast at a rate of 1-3 cm per year. The Somali Plate continues to break away from the African Plate along the East African Rift Zone, which moves at a speed of 1-2 cm per year in a northeasterly direction. December 26, 2004 in the Indian Ocean near the island of Simeulue, located off the northwestern coast of the island of Sumatra (Indonesia), there was the largest earthquake in the history of observations with a magnitude of up to 9.3. The reason was a shift of about 1200 km (according to some estimates - 1600 km) of the earth's crust at a distance of 15 m along the subduction zone, as a result of which the Hindustan plate moved under the Burma plate. The earthquake caused a tsunami, which brought enormous destruction and a huge number of deaths (up to 300 thousand people).

Geological structure and topography of the bottom of the Indian Ocean

mid-ocean ridges

Mid-ocean ridges divide the bottom of the Indian Ocean into three sectors: African, Indo-Australian and Antarctic. There are four mid-ocean ridges: the West Indian, Arabian-Indian, Central Indian ridges and the Australo-Antarctic Rise. The West Indian Ridge is located in the southwestern part of the ocean. It is characterized by underwater volcanism, seismicity, rift-type crust and rift structure of the axial zone; it is crossed by several oceanic faults of submeridional strike. In the region of the island of Rodrigues (Mascarene archipelago), there is a so-called triple connection, where the system of ridges is divided to the north into the Arabian-Indian ridge and to the south-west into the Central Indian ridge. The Arabian-Indian ridge is composed of ultramafic rocks, a number of secant faults of submeridial strike were revealed, with which very deep depressions (oceanic troughs) with depths of up to 6.4 km are associated. The northern part of the ridge is crossed by the most powerful Owen Fault, along which the northern segment of the ridge experienced a displacement of 250 km to the north. Further west, the rift zone continues into the Gulf of Aden and north-northwest into the Red Sea. Here the rift zone is composed of carbonate deposits with volcanic ash. In the rift zone of the Red Sea, strata of evaporites and metal-bearing silts associated with powerful hot (up to 70 °C) and very saline (up to 350 ‰) juvenile waters have been found.

In the southwest direction from the triple junction extends the Central Indian Range, which has a well-defined rift and flank zones, ending in the south with the Amsterdam volcanic plateau with the volcanic islands of Saint-Paul and Amsterdam. From this plateau, the Australo-Antarctic Rise extends to the east-southeast, having the form of a wide, slightly dissected arch. In the eastern part, the uplift is dissected by a series of meridional faults into a number of segments displaced relative to each other in the meridional direction.

African segment of the ocean

The underwater margin of Africa has a narrow shelf and a distinct continental slope with marginal plateaus and continental foot. In the south, the African continent forms protrusions pushed to the south: the Agulhas bank, the Mozambique and Madagascar ridges, composed of continental-type earth's crust. The mainland foot forms a sloping plain extending south along the coast of Somalia and Kenya, which continues in the Mozambique Channel and borders Madagascar from the east. The Mascarene Range runs along the east of the sector, in the northern part of which the Seychelles are located.

The surface of the ocean floor in the sector, especially along the mid-ocean ridges, is dissected by numerous ridges and troughs associated with submeridional fault zones. There are many underwater volcanic mountains, most of which are built on coral superstructures in the form of atolls and underwater coral reefs. Between the mountain rises there are basins of the ocean floor with a hilly and mountainous relief: Agulhas, Mozambique, Madagascar, Mascarene and Somali. In the Somali and Mascarene basins, vast flat abyssal plains are formed, where a significant amount of terrigenous and biogenic sedimentary material enters. In the Mozambique Basin, there is an underwater valley of the Zambezi River with a system of alluvial fans.

Indo-Australian segment of the ocean

The Indo-Australian segment occupies half the area of ​​the Indian Ocean. In the west, in the meridional direction, the Maldives Range passes, on the top surface of which the islands of Laccadive, Maldives and Chagos are located. The ridge is composed of continental-type crust. A very narrow shelf, a narrow and steep continental slope, and a very wide continental foot stretched along the coast of Arabia and Hindustan, mainly formed by two giant fans of turbid streams of the Indus and Ganges rivers. These two rivers carry 400 million tons of debris into the ocean. The Indus cone extends far into the Arabian Basin. And only the southern part of this basin is occupied by a flat asbyssal plain with separate seamounts.

Almost exactly 90° E. The blocky oceanic East Indian Ridge stretches for 4,000 km from north to south. Between the Maldives and the East Indian Ranges is the Central Basin - the largest basin of the Indian Ocean. Its northern part is occupied by the Bengal alluvial fan (from the Ganges River), to southern border which adjoins the abyssal plain. In the central part of the basin there is a small Lanka ridge and the Afanasy Nikitin seamount. To the east of the East Indian Ridge are the Cocos and Western Australian Basins, separated by a blocky sublatitudinally oriented Cocos Rise with the Cocos and Christmas Islands. In the northern part of the Coconut Basin there is a flat abyssal plain. From the south, it is bounded by the West Australian Rise, which drops steeply to the south and gently plunges under the bottom of the basin to the north. From the south, the West Australian Rise is bounded by a steep ledge associated with the Diamantina Fault Zone. The ralome zone combines deep and narrow grabens (the most significant are the Ob and Diamatina) and numerous narrow horsts.

The transitional region of the Indian Ocean is represented by the Andaman Trench and the deep-water Sunda Trench, which is associated with the maximum depth of the Indian Ocean (7209 m). The outer ridge of the Sunda island arc is the underwater Mentawai Range and its continuation in the form of the Andaman and Nicobar Islands.

Underwater margin of the Australian mainland

The northern part of the Australian continent is bordered by a wide Sahul shelf with many coral structures. To the south, this shelf narrows and widens again off the coast of southern Australia. The continental slope is composed of marginal plateaus (the largest of them are the Exmouth and Naturalists plateaus). In the western part of the Western Australian Basin, the Zenith, Cuvier and other rises are located, which are pieces of the continental structure. Between the southern underwater margin of Australia and the Australo-Antarctic Rise, there is a small South Australian Basin, which is a flat abyssal plain.

Antarctic segment of the ocean

The Antarctic segment is bounded by the West Indian and Central Indian ridges, and from the south by the coast of Antarctica. Under the influence of tectonic and glaciological factors, the shelf of Antarctica is overdeepened. A wide continental slope is cut by large and wide canyons, through which supercooled water flows from the shelf into the abyssal depressions. The continental foot of Antarctica is distinguished by a wide and significant (up to 1.5 km) thickness of loose deposits.

The largest protrusion of the Antarctic continent is the Kerguelen Plateau, as well as the volcanic uplift of the Prince Edward and Crozet Islands, which divide the Antarctic sector into three basins. To the west is the African-Antarctic Basin, which is half located in the Atlantic Ocean. Most of its bottom is a flat abyssal plain. The Crozet Basin, located to the north, is characterized by a large-hilly bottom topography. The Australo-Antarctic Basin, lying to the east of Kerguelen, is occupied in the southern part by a flat plain, and in the northern part by Abyssotian hills.

Bottom sediments

The Indian Ocean is dominated by calcareous foraminiferal-coccolithic deposits, which occupy more than half of the bottom area. The wide development of biogenic (including coral) calcareous deposits is explained by the position of a large part of the Indian Ocean within the tropical and equatorial belts, as well as by the relatively shallow depth of oceanic basins. Numerous mountain uplifts are also favorable for the formation of lime deposits. In the deep parts of some basins (for example, the Central, Western Australian), deep-sea red clays occur. AT equatorial belt radiolarian muds are characteristic. In the southern cold part of the ocean, where the conditions for the development of diatom flora are especially favorable, siliceous diatom deposits are represented. Iceberg sediments are deposited off the Antarctic coast. At the bottom of the Indian Ocean, ferromanganese nodules are widely distributed, confined mainly to areas of deposition of red clays and radiolarian oozes.

Climate

In this region, four climatic zones are distinguished, stretched along the parallels. Under the influence of the Asian continent, a monsoonal climate is established in the northern part of the Indian Ocean with frequent cyclones moving towards the coasts. High Atmosphere pressure over Asia in winter causes the formation of the northeast monsoon. In summer, it is replaced by a humid southwest monsoon, carrying air from the southern regions of the ocean. During the summer monsoon, there is often a wind force of more than 7 points (with a frequency of 40%). In summer, the temperature over the ocean is 28-32 °C, in winter it drops to 18-22 °C.

In the southern tropics, the southeast trade wind dominates, which in winter time does not extend north of 10°N. The average annual temperature reaches 25 °C. In the zone 40-45°S. Throughout the year, the western transfer of air masses is characteristic, it is especially strong in temperate latitudes, where the frequency of storm weather is 30-40%. In the mid-ocean, stormy weather is associated with tropical hurricanes. In winter, they can also occur in the southern tropical zone. Most often, hurricanes occur in the western part of the ocean (up to 8 times a year), in the areas of Madagascar and the Mascarene Islands. In subtropical and temperate latitudes, the temperature reaches 10-22 °C in summer and 6-17 °C in winter. Strong winds are characteristic from 45 degrees and south. In winter, the temperature here ranges from -16 °C to 6 °C, and in summer - from -4 °C to 10 °C.

The maximum amount of precipitation (2.5 thousand mm) is confined to the eastern region of the equatorial zone. There is also increased cloudiness (more than 5 points). The least amount of precipitation is observed in the tropical regions of the southern hemisphere, especially in the eastern part. In the northern hemisphere most of the year clear weather characteristic of the Arabian Sea. The maximum cloudiness is observed in Antarctic waters.

Hydrological regime of the Indian Ocean

Surface water circulation

In the northern part of the ocean, there is a seasonal change in currents caused by monsoon circulation. In winter, the Southwest Monsoon Current sets in, starting in the Bay of Bengal. South of 10° N. sh. this current passes into the Western Current, crossing the ocean from the Nicobar Islands to the coast of East Africa. Further, it branches: one branch goes north to the Red Sea, the other - south to 10 ° S. sh. and, turning to the east, gives rise to the Equatorial countercurrent. The latter crosses the ocean and, off the coast of Sumatra, is again divided into a part that goes into the Andaman Sea and the main branch, which between the Lesser Sunda Islands and Australia goes to the Pacific Ocean. In summer, the southeast monsoon ensures the movement of the entire mass of surface water to the east, and the Equatorial countercurrent disappears. The summer monsoon current begins off the coast of Africa with the powerful Somali current, which is joined by the current from the Red Sea in the Gulf of Aden. In the Bay of Bengal, the summer monsoon current divides into north and south, which flows into the South Equatorial Current.

In the southern hemisphere, currents are constant, without seasonal fluctuations. Driven by the trade winds, the South Trade Wind Current crosses the ocean from east to west towards Madagascar. It intensifies in winter (for the southern hemisphere) due to additional feeding by the waters of the Pacific Ocean coming along the northern coast of Australia. At Madagascar, the South Equatorial Current forks, giving rise to the Equatorial Countercurrent, Mozambique and Madagascar currents. Merging southwest of Madagascar, they form warm current Agulhas. southern part of this current goes into the Atlantic Ocean, and part of it flows into the westerly winds. On the approach to Australia, the cold West Australian Current departs from the latter to the north. Local gyres operate in the Arabian Sea, the Bengal and Great Australian Bays, and in Antarctic waters.

The northern part of the Indian Ocean is characterized by the predominance of a semidiurnal tide. The amplitudes of the tide in the open ocean are small and average 1 m. In the Antarctic and subantarctic zones, the amplitude of the tides decreases from east to west from 1.6 m to 0.5 m, and near the coast they increase to 2-4 m. The maximum amplitudes are noted between islands, in shallow bays. In the Bay of Bengal, the tide is 4.2-5.2 m, near Mumbai - 5.7 m, near Yangon - 7 m, near northwestern Australia - 6 m, and in the port of Darwin - 8 m. In other areas, the amplitude of the tides about 1-3 m.

temperature, salinity

In the equatorial zone of the Indian Ocean all year round surface water temperature is about 28 °C in both the western and eastern parts of the ocean. In the Red and Arabian Seas, winter temperatures drop to 20-25 °C, but in summer the maximum temperatures for the entire Indian Ocean are set in the Red Sea - up to 30-31 °C. High winter water temperatures (up to 29 ° C) are typical for the coasts of northwestern Australia. In the southern hemisphere, at the same latitudes in the eastern part of the ocean, the water temperature in winter and summer is 1-2° lower than in the western part. Water temperatures below 0°C in summer are found south of 60°S. sh. Ice formation in these areas begins in April and the thickness of the fast ice reaches 1-1.5 m by the end of winter. Melting begins in December-January, and by March the waters are completely cleared of fast ice. In the southern part of the Indian Ocean, icebergs are common, sometimes setting north of 40 ° S. sh.

The maximum salinity of surface waters is observed in the Persian Gulf and the Red Sea, where it reaches 40-41 ‰. High salinity (more than 36 ‰) is also observed in the southern tropical zone, especially in the eastern regions, and in the northern hemisphere also in the Arabian Sea. In the neighboring Bay of Bengal, due to the desalination effect of the Ganges runoff from the Brahmaputra and the Irrawaddy, the salinity is reduced to 30-34 ‰. Increased salinity correlates with areas of maximum evaporation and the least amount of precipitation. Reduced salinity (less than 34 ‰) is characteristic of subarctic waters, where the strong freshening effect of melted glacial waters is felt. The seasonal difference in salinity is significant only in the Antarctic and equatorial zones. In winter, desalinated waters from the northeastern part of the ocean are carried by the monsoon current, forming a tongue of low salinity along 5°N. sh. In summer, this language disappears. In the Arctic waters in winter, salinity slightly increases due to the salinization of waters in the process of ice formation. Salinity decreases from the surface to the bottom of the ocean. Bottom waters from the equator to the arctic latitudes have a salinity of 34.7-34.8 ‰.

water masses

The waters of the Indian Ocean are divided into several water masses. In the part of the ocean north of 40 ° S. sh. distinguish between central and equatorial surface and subsurface water masses and underlying them (deeper than 1000 m) deep. To the north to 15-20 ° S. sh. the central water mass spreads. The temperature varies with depth from 20-25 °C to 7-8 °C, salinity is 34.6-35.5 ‰. Surface layers north of 10-15°S sh. make up the equatorial water mass with a temperature of 4-18 ° C and a salinity of 34.9-35.3 ‰. This water mass is characterized by significant speeds of horizontal and vertical movement. In the southern part of the ocean, subantarctic (temperature 5-15 ° C, salinity up to 34 ‰) and Antarctic (temperature from 0 to -1 ° C, salinity due to melting ice drops to 32 ‰) are distinguished. Deep water masses are divided into: very cold circulation, formed by lowering the Arctic water masses and the inflow of circulation water from the Atlantic Ocean; South Indian, formed as a result of lowering subarctic surface waters; North Indian, formed by dense waters flowing from the Red Sea and the Gulf of Oman. Deeper than 3.5-4 thousand m, bottom water masses are common, formed from the Antarctic supercooled and dense salt waters of the Red Sea and the Persian Gulf.

Flora and fauna

The flora and fauna of the Indian Ocean is extremely diverse. The tropical region stands out for its abundance of plankton. The single-celled alga Trichodesmium (cyanobacteria) is especially abundant, due to which the surface layer of water becomes very cloudy and changes its color. The plankton of the Indian Ocean is distinguished by a large number of night-luminous organisms: peridine, some species of jellyfish, ctenophores, and tunicates. Brightly colored siphonophores, including poisonous physalia, are abundant. In temperate and arctic waters, the main representatives of plankton are copepods, euphausids and diatoms. The most numerous fish of the Indian Ocean are dolphins, tuna, notothenia and various sharks. From reptiles there are several species of giant sea turtles, sea snakes, from mammals - cetaceans (toothless and blue whales, sperm whales, dolphins), seals, sea elephants. Most cetaceans live in temperate and polar regions, where, due to the intensive mixing of waters, favorable conditions arise for the development of planktonic organisms. Birds are represented by albatrosses and frigatebirds, as well as several species of penguins that inhabit the coasts of South Africa, Antarctica and islands in the temperate ocean.

The flora of the Indian Ocean is represented by brown algae (Sargasso, Turbinarium) and green algae (Caulerpa). The calcareous algae lithotamnia and chalimeda also flourish and participate together with corals in the construction of reef structures. In the process of activity of reef-forming organisms, coral platforms are created, sometimes reaching a width of several kilometers. Typical for the coastal zone of the Indian Ocean is a phytocenosis formed by mangroves. Such thickets are especially characteristic of river mouths and occupy large areas in Southeast Africa, western Madagascar, Southeast Asia and other regions. For temperate and Antarctic waters, red and brown algae, mainly from the groups of fucus and kelp, porphyry, helidium. In the subpolar regions of the southern hemisphere, giant macrocystis are found.

Zoobenthos is represented by a variety of mollusks, calcareous and flint sponges, echinoderms ( sea ​​urchins, starfish, brittle stars, holothurians), numerous crustaceans, hydroids, bryozoans. Coral polyps are widespread in the tropical zone.

Environmental problems

Human economic activity in the Indian Ocean has led to the pollution of its waters and to the reduction of biodiversity. At the beginning of the 20th century, some species of whales were almost completely exterminated, others - sperm whales and sei whales - still survived, but their number was greatly reduced. Since the 1985-1986 season, the International Whaling Commission has introduced a complete moratorium on commercial whaling of any kind. In June 2010, at the 62nd meeting of the International Whaling Commission, under pressure from Japan, Iceland and Denmark, the moratorium was suspended. The Mauritius dodo, destroyed by 1651 on the island of Mauritius, became a symbol of extinction and extinction of species. After it became extinct, people first formed the opinion that they could cause the extinction of other animals.

A great danger in the ocean is the pollution of waters with oil and oil products (the main pollutants), some heavy metals, and waste from the nuclear industry. The routes of oil tankers transporting oil from the countries of the Persian Gulf run across the ocean. Any major accident can lead to an ecological disaster and the death of many animals, birds and plants.

States of the Indian Ocean

States along the borders of the Indian Ocean (clockwise):

  • Republic Of South Africa,
  • Mozambique,
  • Tanzania,
  • Kenya,
  • Somalia,
  • Djibouti,
  • Eritrea,
  • Sudan,
  • Egypt,
  • Israel,
  • Jordan,
  • Saudi Arabia,
  • Yemen,
  • Oman,
  • United Arab Emirates,
  • Qatar,
  • Kuwait,
  • Iraq,
  • Iran,
  • Pakistan,
  • India,
  • Bangladesh,
  • Myanmar,
  • Thailand,
  • Malaysia,
  • Indonesia,
  • East Timor,
  • Australia.

In the Indian Ocean there are island states and possessions of states outside the region:

  • Bahrain,
  • British Indian Ocean Territory (UK),
  • Comoros,
  • Mauritius,
  • Madagascar,
  • Mayotte (France),
  • Maldives,
  • Reunion (France),
  • Seychelles,
  • French Southern and Antarctic Territories (France),
  • Sri Lanka.

Research History

The shores of the Indian Ocean - one of the areas of settlement ancient peoples and the emergence of the first river civilizations. In ancient times, ships such as junks and catamarans were used by people for sailing, with favorable monsoons from India to East Africa and back. The Egyptians in 3500 BC conducted a brisk maritime trade with the countries of the Arabian Peninsula, India and East Africa. The countries of Mesopotamia for 3000 years BC made sea trips to Arabia and India. From the 6th century BC, the Phoenicians, according to the Greek historian Herodotus, made sea voyages from the Red Sea across the Indian Ocean to India and around Africa. In the 6th-5th centuries BC, Persian merchants conducted maritime trade from the mouth of the Indus River along the east coast of Africa. At the end of the Indian campaign of Alexander the Great in 325 BC, the Greeks with a huge fleet with a crew of five thousand in severe storm conditions made a many-month voyage between the mouths of the Indus and Euphrates rivers. Byzantine merchants in the 4th-6th centuries penetrated in the east to India, and in the south - to Ethiopia and Arabia. Starting from the 7th century, Arab sailors began intensive exploration of the Indian Ocean. They perfectly studied the coast of East Africa, West and East India, the islands of Socotra, Java and Ceylon, visited the Laccadives and Maldives, the islands of Sulawesi, Timor and others.

At the end of the 13th century, the Venetian traveler Marco Polo, on his way back from China, passed through the Indian Ocean from Malacca to the Strait of Hormuz, visiting Sumatra, India, and Ceylon. The journey was described in the Book of the Diversity of the World, which had a significant impact on navigators, cartographers, and writers of the Middle Ages in Europe. Chinese junks made trips along the Asian shores of the Indian Ocean and reached the Eastern coast of Africa (for example, Zheng He's seven voyages in 1405-1433). The expedition, led by the Portuguese navigator Vasco da Gama, rounded Africa from the south, passing along the eastern coast of the continent in 1498, reached India. In 1642, the Dutch trading East India Company organized an expedition of two ships under the command of Captain Tasman. As a result of this expedition, the central part of the Indian Ocean was explored and it was proved that Australia is the mainland. In 1772, a British expedition under the command of James Cook penetrated the southern Indian Ocean to 71°S. sh., while extensive scientific material on hydrometeorology and oceanography was obtained.

From 1872 to 1876, the first scientific ocean expedition took place on the English sailing-steam corvette Challenger, new data were obtained on the composition of the ocean waters, on the flora and fauna, on the bottom topography and soils, the first map of the depths of the ocean was compiled and the first collection was collected. deep sea animals. The round-the-world expedition on the Russian propeller-sailing corvette "Vityaz" of 1886-1889 under the leadership of the scientist-oceanographer S. O. Makarov conducted a large-scale research work in the Indian Ocean. A great contribution to the study of the Indian Ocean was made by oceanographic expeditions on the German ships Valkyrie (1898-1899) and Gauss (1901-1903), on the English ship Discovery II (1930-1951), the Soviet expeditionary ship Ob ( 1956-1958) and others. In 1960-1965, under the auspices of the Intergovernmental Oceanographic Expedition under UNESCO, an international Indian Ocean Expedition was carried out. She was the largest of all the expeditions ever to work in the Indian Ocean. The program of oceanographic work covered almost the entire ocean with observations, which was facilitated by the participation of scientists from about 20 countries in the research. Among them: Soviet and foreign scientists on the research ships Vityaz, A. I. Voeikov”, “Yu. M. Shokalsky, non-magnetic schooner Zarya (USSR), Natal (South Africa), Diamantina (Australia), Kistna and Varuna (India), Zulfikvar (Pakistan). As a result, valuable new data were collected on hydrology, hydrochemistry, meteorology, geology, geophysics and biology of the Indian Ocean. Since 1972, the American ship Glomar Challenger has carried out regular deep-sea drilling, work on the study of the movement of water masses at great depths, and biological research.

In recent decades, numerous measurements of the ocean have been carried out using space satellites. The result was a bathymetric atlas of the oceans released in 1994 by the US National Geophysical Data Center with a map resolution of 3-4 km and a depth accuracy of ±100 m.

Economic importance

Fishing and marine industries

The importance of the Indian Ocean for the world fishing industry is small: the catches here are only 5% of the total. The main commercial fish of the local waters are tuna, sardine, anchovy, several species of sharks, barracudas and rays; Shrimps, lobsters and lobsters are also caught here. More recently, intense southern regions Ocean whaling is rapidly curtailing, due to the almost complete extermination of some species of whales. On the northwestern coast of Australia, in Sri Lanka and the Bahrain Islands, pearls and mother-of-pearl are mined.

Transport routes

The most important transport routes of the Indian Ocean are routes from the Persian Gulf to Europe, North America, Japan and China, as well as from the Gulf of Aden to India, Indonesia, Australia, Japan and China. The main navigable straits of the Indian Strait: Mozambique, Bab-el-Mandeb, Hormuz, Sunda. The Indian Ocean is connected by the artificial Suez Canal to the Mediterranean Sea of ​​the Atlantic Ocean. In the Suez Canal and the Red Sea, all the main cargo flows of the Indian Ocean converge and diverge. Major ports: Durban, Maputo (export: ore, coal, cotton, minerals, oil, asbestos, tea, raw sugar, cashew nuts, import: machinery and equipment, manufactured goods, food), Dar es Salaam (export : cotton, coffee, sisal, diamonds, gold, oil products, cashew nuts, cloves, tea, meat, leather, import: manufactured goods, food, chemicals), Jeddah, Salalah, Dubai, Bandar Abbas, Basra (export: oil, grain, salt, dates, cotton, leather, import: cars, timber, textiles, sugar, tea), Karachi (export: cotton, fabrics, wool, leather, shoes, carpets, rice, fish, import: coal, coke, oil products , mineral fertilizers, equipment, metals, grain, food, paper, jute, tea, sugar), Mumbai (export: manganese and iron ores, oil products, sugar, wool, leather, cotton, fabrics, import: oil, coal, cast iron, machinery, grains, chemicals, manufactured goods), Colombo, Chennai ( iron ore, coal, granite, fertilizers, oil products, containers, cars), Kolkata (export: coal, iron and copper ores, tea, import: manufactured goods, grain, food, equipment), Chittagong (clothing, jute, leather, tea, chemical substances), Yangon (export: rice, hardwood, non-ferrous metals, cake, legumes, rubber, precious stones, import: coal, cars, food, textiles), Perth Fremantle (export: ores, alumina, coal, coke, caustic soda, phosphate raw materials, import: oil, equipment).

Minerals

The most important mineral resources 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. On the coasts of India, Mozambique, Tanzania, South Africa, the islands of Madagascar and Sri Lanka, ilmenite, monazite, rutile, titanite and zirconium are exploited. Off the coast of India and Australia there are deposits of barite and phosphorite, and in the shelf zones of Indonesia, Thailand and Malaysia, deposits of cassiterite and ilmenite are exploited on an industrial scale.

Recreational resources

The main recreational areas of the Indian Ocean: the Red Sea, the western coast of Thailand, the islands of Malaysia and Indonesia, the island of Sri Lanka, the area of ​​coastal urban agglomerations of India, the eastern coast of Madagascar, the Seychelles and Maldives. Among the countries of the Indian Ocean with the largest flow of tourists (according to 2010 data from the World tourism organization) stand out: Malaysia (25 million visits per year), Thailand (16 million), Egypt (14 million), Saudi Arabia (11 million), South Africa (8 million), United Arab Emirates (7 million), Indonesia (7 million) , Australia (6 million), India (6 million), Qatar (1.6 million), Oman (1.5 million).

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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;
The largest islands are 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. The coastline of 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 the 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, the warm waters and picturesque coral islands of the Indian Ocean, which attract the attention of tourists from around the world, are carefully studied by numerous scientific expeditions from all over the world.

Indian Ocean is the warmest ocean on our planet. Occupying a fifth of the Earth's surface, the Indian Ocean is not the largest ocean, but it has rich flora and fauna, as well as a host of other advantages.

Indian Ocean

Indian Ocean occupies 20% of the world. This ocean is characterized by a rich and varied natural life.
shows vast territories and a large number of interesting islands for researchers and tourists. If you still don't know where Indian Ocean, map will prompt you.

Map of the currents of the Indian Ocean


Underwater world of the Indian Ocean

Rich and varied underwater world of the indian ocean. In it you can meet both very small aquatic inhabitants, and large and dangerous representatives of the aquatic world.

Since ancient times, man has been trying to subjugate the ocean and its inhabitants. Throughout the ages, the inhabitants of the underwater world of the Indian Ocean have been hunted.

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There are even those that can cause trouble to a person. For example, these are anemones that live in almost all the seas and oceans of our planet. Sea anemones can be found not only in the depths, but also in the shallow waters of the Indian Ocean. They almost always feel hungry, so they sit lurking with widely spaced tentacles. Predatory representatives of this species are poisonous. Their shot can hit small organisms, as well as cause burns to people. Sea urchins, seals, the most exotic species of fish live in the waters of the Indian Ocean. The flora is diverse, which makes diving truly exciting.

Fish in the Indian Ocean


The school course of the program in geography includes the study of the largest water areas - the oceans. This topic is quite interesting. Students are happy to prepare reports and abstracts on it. This article will provide information that contains a description of the geographical position of the Indian Ocean, its characteristics and features. So let's get started.

Brief description of the Indian Ocean

In terms of the scale and quantity of water reserves, the Indian Ocean is comfortably located in third place, behind the Pacific and Atlantic. A significant part of it is located on the territory of the Southern Hemisphere of our planet, and its natural aisles are:

  • Southern part of Eurasia in the north.
  • East coast of Africa in the west.
  • Northern and northwestern coasts of Australia in the east.
  • Northern part of Antarctica in the south.

In order to indicate the exact geographical position of the Indian Ocean, you need a map. It can also be used during a presentation. So, on the world map, the water area has the following coordinates: 14°05′33.68″ south latitude and 76°18′38.01″ east longitude.

According to one version, the ocean in question was first called Indian in the work of the Portuguese scientist S. Munster called "Cosmography", which was published in 1555.

Characteristic

The total, taking into account all the seas included in its composition, is 76.174 million square meters. km, the depth (average) is more than 3.7 thousand meters, and the maximum was recorded at over 7.7 thousand meters.

The geographical position of the Indian Ocean has its own characteristics. Due to its large size, it is found in several climatic zones. It is also worth paying attention to the size of the water area. For example, the maximum width is between Linde Bay and the Toros Strait. The length from west to east is almost 12 thousand km. And if we consider the ocean from north to south, then the largest indicator will be from Cape Ras Jaddi to Antarctica. This distance is 10.2 thousand km.

Features of the water area

Studying the features of the geographical position of the Indian Ocean, it is necessary to consider its boundaries. First, note that the entire water area is located in the Eastern Hemisphere. On the southwest side, it borders the Atlantic Ocean. In order to see this place on the map, you need to find 20 ° along the meridian in. e. The border with the Pacific Ocean is in the southeast. It runs along the 147° meridian east. e. The Indian Ocean is not connected with the Arctic Ocean. Its border in the north is the largest continent - Eurasia.

Structure coastline has a weak division. There are several large bays and 8 seas. There are relatively few islands. The largest are Sri Lanka, Seychelles, Curia-Muria, Madagascar, etc.

Bottom relief

The characterization will not be complete if you do not consider the features of the relief.

The Central Indian Ridge is an underwater formation located in the central part of the water area. Its length is about 2.3 thousand km. The width of the relief formation is within 800 km. The height of the ridge is more than 1 thousand meters. Some peaks protrude from the water, forming volcanic islands.

The West Indian Ridge is located in the southwestern part of the ocean. There is a lot of seismic activity here. The length of the ridge is about 4 thousand km. But in width it is less than the previous one by about half.

The Arabian-Indian Range is an underwater relief formation. It is located in the northwestern part of the water area. Its length is slightly less than 4 thousand km, and its width is about 650 km. At the end point (Rodriguez Island) it passes into the Central Indian Range.

The bottom of the Indian Ocean consists of sediments from the Cretaceous period. In some places, their thickness reaches 3 km. has a length of about 4500 km in length, and its width varies from 10 to 50 km. It's called Javanese. The depth of the depression is 7729 m (the largest in the Indian Ocean).

Climatic features

One of the most important circumstances in the formation of climate is the geographical position of the Indian Ocean relative to the equator. It divides the water area into two parts (the largest is in the south). Naturally, this arrangement affects temperature fluctuations and rainfall. The highest temperatures were recorded in the waters of the Red Sea and the Persian Gulf. Here, the average is a mark of +35 ° С. And in the southern point, the temperature can drop to -16 ° C in winter and up to -4 degrees in summer.

The northern part of the ocean is hot climate zone, thanks to which its waters are among the warmest in the oceans. Here it is mainly influenced by the Asian continent. Due to the current situation in the northern part, there are only two seasons - a hot rainy summer and a non-cold cloudless winter. As for the climate in this part of the water area, it practically does not change throughout the year.

Given the geographical position of the Indian Ocean, it is worth noting that its largest part is under the influence of air currents. From this we can conclude that the climate is mainly formed due to the monsoons. During the summer period, areas with low pressure are established over land, and areas with high pressure over the ocean. During this season, the wet monsoon runs from west to east. In winter, the situation changes, and then the dry monsoon begins to dominate, which comes from the east and moves to the west.

In the southern part of the water area, the climate is more severe, since it lies in the subarctic zone. Here, the ocean is influenced by proximity to Antarctica. Off the coast of this continent, the average temperature is fixed at around -1.5 ° C, and the buoyancy limit of ice reaches 60 ° parallel.

Summing up

The geographical position of the Indian Ocean is a very important issue that deserves special attention. Due enough large sizes This area has many features. Along the coastline there are a huge number of cliffs, estuaries, atolls, coral reefs. It is also worth noting such islands as Madagascar, Socotra, Maldives. They represent sections A Andaman, Nicobar descended from volcanoes that rose to the surface.

Having studied the proposed material, each student will be able to present an informative and interesting presentation.

One of the areas of ancient civilizations - the Indian Ocean - began to be developed by the peoples who inhabited its shores, as early as 5-4 millennia BC. In the Middle Ages, navigation also spread to the open areas of the ocean. However, until the middle of the XX century. it remained poorly explored, and its natural resources were used to a much lesser extent than other oceans. For many centuries, the Indian Ocean was mainly a sea route to the colonial possessions of Western European states. Its exploration and development of resources began relatively recently, when the colonial system collapsed and many countries in Asia and Africa gained independence.

In the conditions of modern life, the role of the Indian Ocean in the international arena has noticeably grown, which is largely due to its rich natural and human resources, its position in relation to other oceans and continents of the globe.

The Indian Ocean is located almost entirely south of the northern tropic. All the continents surrounding it take part in the formation of the nature of the ocean, but its proximity in the north to the huge Eurasian continent is of the greatest importance. In its southern part, the ocean has a wide connection with the Pacific Ocean. The boundaries between them are conditional.

In the southwest, the border with the Atlantic runs from Africa to Antarctica along the meridian of Cape Agulhas (20° E). In the southeast, the border with the Pacific Ocean is usually drawn from Australia to Antarctica along the meridian of Cape South on Tasmania (147 ° E). The most difficult border with the Pacific Ocean is in the northeast, where it goes from the Malay Peninsula to the northern tip of about. Sumatra (between the Andaman Sea and the Strait of Malacca), further along the southwestern and southern shores of about. Sumatra and about. Java, along the southern and eastern shores of the Lesser Sunda Islands, the southwestern coast of about. New Guinea and Torres Strait. However, sometimes the Sunda Islands and some seas of the archipelago are referred to the Indian Ocean. border with Southern Ocean in the east it rises north to 37°S. sh., and in the west it drops south to 43 ° S. sh.

In terms of area (76.2 million km 2), the Indian Ocean ranks third among the oceans.

The coastline is slightly indented, with the exception of the northern and northeastern regions, where most of the seas and large bays of the ocean are located.

In the southeast, off the coast of Australia, there is the Great Australian Gulf, in the south, off the coast of Antarctica, there are small marginal seas. There are relatively few islands in the Indian Ocean. The largest of them (mainland origin) are located near the continents - Madagascar, Sri Lanka, Socotra, Tasmania. In the open part of the ocean there are volcanic islands: Mascarene, Comoros, Andaman, Nicobar, Kerguelen, Crozet, etc. In tropical latitudes, coral islands rise on volcanic cones: Maldives, Laccadive, Chagos, Cocos, Amirante, etc. Many volcanic islands are bordered by coral reefs . A special place is occupied by the Seychelles, which lie within the ocean floor, but the largest of them are formed by the earth's crust of the continental type.

Unlike the Pacific Ocean, the Indian Ocean is framed along almost the entire perimeter by blocks of ancient continental platforms - the wreckage of Gondwana. At the junction of the oceanic and continental crust, there are passive oceanic margins here.

Despite the fact that the ocean goes to Antarctica in a wide front, its waters are quite warm, with the exception of the southernmost part. The southern tropic runs almost in the middle of the Indian Ocean, and the equatorial-tropical space is widely represented here. In the north, monsoon circulation and waters are exceptionally actively developed. In the Indian Ocean, the entire spectrum of physical and geographical belts of the Southern Hemisphere is observed, in the Northern Hemisphere, only one tropical and common equatorial belt is distinguished for both hemispheres.

Features of the economic and geographical position

The Indian Ocean, inferior in size to the Atlantic and Pacific, differs from them in its peculiar location on the planet. First, most of its water area is located in the southern hemisphere. Secondly, in the north it is limited by Eurasia and does not communicate directly with the Arctic Ocean. Other boundaries of the Indian Ocean are natural boundaries and conditional lines: in the west - the coast of Africa; in the southwest - along the meridian 20 ° E. e. from the Cape of Good Hope (Agulyas) to Antarctica; in the east - along the northern part of the Strait of Malacca, the southwestern and southern shores of the Greater and Lesser Sunda Islands, the southwestern coast of New Guinea, the Torres Strait, the western coast of Australia; in the southeast - along the meridian 147 ° E. d. from the southern tip of the island of Tasmania to the Northeast Cape in. Within these limits, the ocean area is 74.9 million km 2.

It is characterized by a relatively weak indentation of the coastline and a small number of seas. The most significant of them are the Red, Arabian, Andaman Seas and the Commonwealth Sea in the north of Antarctica. Two large bays protrude into the land - Persian and Bengal.

The relief of the bottom of the Indian Ocean is complex and varied, which is hidden by shallows, fault zones, mountain structures, depressions and trenches. Compared to the Atlantic and Pacific Oceans, it has a relatively poorly developed shelf zone, which occupies approximately 4.2% of its entire area. The shelves are significantly developed, mainly near the northern coasts of the ocean. The Persian Gulf lies within the shelf, reaching its greatest width off the western coast of Hindustan, at the top of the Bay of Bengal, in the Andaman Sea, in the northern part of the Strait of Malacca. In addition, a rather extensive shelf zone adjoins the northwestern coast of Australia, the area of ​​Cape Agulhas, and southeast Africa. The relief of the continental slope is varied, which in different regions has a different steepness.

The bed of the ocean occupies the largest part of its bottom. It is crossed by numerous uplifts, separated from each other by vast water basins. Among the highlands, the system of the Mid-Indian Ocean ridges stands out, three branches of which diverge from the region of Rodrigues Island. The Arabian-Indian Ridge departs to the northwest, the West Indian Ridge to the southwest, passing further into the African-Antarctic Ridge, and the Central Ridge to the southeast, which then continues with the Australo-Antarctic Rise. In the eastern part of the ocean, the East Indian Ridge stretches almost along the meridian. To the south of Kerguelen Island, the Kerguelen Ridge approaches Antarctica. In different parts of the ocean, many small uplifts can be traced. Large and less significant underwater elevations divide the oceanic bed into basins of various sizes and depths. These include: Omani, Arabian, Somali, Comorian, Mascarene, Madagascar, Crozet, Western and South Australian, etc. The maximum depth of the Indian Ocean (7130 m) is confined to the marginal deep-water Sunda Trench. The main features of the ocean floor topography have been revealed mainly in the last 10-15 years.

The Indian Ocean is elongated along the meridian. In the north, it almost does not go beyond the Northern Tropic, so its northern part lies in the equatorial and subequatorial belts, while the southern part covers higher latitudes up to the subantarctic. Therefore, the thermal equator in the Indian Ocean shifts to the southern hemisphere in winter. In addition, the northern part of the ocean, closed by land masses, is subject to significant continental influence, which results in pronounced monsoons here. This is the most feature climate of the Indian Ocean. In the south, it is wide open towards the Antarctic and therefore experiences its cooling effect. The most severe regions of the ocean are located here, and its northern part is the warmest.

The southern position of the Indian Ocean, the absence of a direct connection with the northern polar waters, and the monsoon circulation in its northern regions largely predetermine the complexity and diversity of hydrological conditions. The northern part of the ocean, the most heated and devoid of cold water inflow, is characterized by high values ​​(27-28 °) of surface water temperature. They exceed similar values ​​at the same latitudes in all other oceans. The average temperature on the surface of the water in the Indian Ocean as a whole is 17°, which is explained by the strong cooling effect of the Antarctic waters, given its relatively small size. In many areas of this ocean, the salinity of water on the surface is higher than the average salinity of the World Ocean, and in the Red Sea it reaches 40% o. Only in the Antarctic regions and in the Bay of Bengal does the salinity drop to 34% o and below.

The vertical distribution of water is characterized, in general, by its lowering to the bottom. It is especially pronounced in the upper 200 m layer. The course of salinity values ​​with depth is more complicated. A subsurface maximum is traced in it, and at lower (500-1000 m) horizons - a deep minimum of salinity.

Surface currents of the Indian Ocean component general circulation of its waters have their own characteristics. The main one is significant seasonal changes in currents in the area north of 10°S, under the influence of monsoons. To the south of this parallel, the seasonality of the currents is much less pronounced or does not appear at all.

In winter, during the greatest intensity of the northeast monsoon, the corresponding surface currents in the northern part of the ocean are very distinct. They form an almost closed cyclonic circulation in the Arabian Sea and an anticyclonic circulation in the Bay of Bengal. These currents here are not very stable. To the south, from about 10 ° N.S. before the equator, the drift currents are westward and unite under the name of the Monsoon, or North Equatorial, Current. Further south, the Equatorial Countercurrent moves from east to west. This is a compensatory current that replenishes the outflow of water from the eastern shores of the ocean. Outside the zone of monsoon circulation is the Trade Wind, or South Equatorial Current, the occurrence of which is associated with the system of south trade winds. It is directed from east to west and forms large-scale quasi-stationary eddies at the latitudinal boundaries. At the boundaries of the Antarctic zone of the ocean, a branch separates from the Antarctic Circular Current, which enters the ocean south of Madagascar and moves to the northeast under the name of the South Indian Ocean Current.

In summer, when the southwest monsoon develops, the current field in the northern part of the Indian Ocean is rebuilt in a few weeks. This season, the monsoon current changes its direction and moves from west to east, merging with the winter Equatorial Countercurrent. Off the northeastern coast of Africa, a powerful Somali current arises as a continuation of the Trade Wind. In the Arabian Sea and the Bay of Bengal, local circulations formed by the winter monsoon disappear. The summer field of surface currents in the zone of influence of the monsoon is thus represented by a large-scale circulation composed of the Monsoon and Tradewind currents. To the south, outside the monsoon region, the macroscale surface water cycle is formed by the Trade Wind, Madagascar, Agulhas, Antarctic Circular and West Australian currents. In some areas, small and unstable local circulations are created.

Vertical water movements are created in frontal zones, areas of deep water rising to the surface (for example, off the eastern coast of Somalia), in the northwestern part of the ocean, where convective currents are excited due to significant salinization of the upper layer as a result of evaporation. Thermodynamic processes make a vertical exchange of waters in the ocean and its seas.

The natural features of the Indian Ocean largely determine the direction of economic activity in its waters. However, at the same time, it largely depends on the socio-economic and political factors that are traced in the EGP of the ocean.

In relation to the surrounding land, the EGP of the Indian Ocean has its own characteristics. Its waters border on three continents, on which about 40 states are located, where more than 1 billion people live - a significant part of the world's population.

The most important feature of the countries of the Indian Ocean basin is their centuries-old colonial past, which has markedly affected the economic development of most of these countries. After the Second World War, the collapse of the colonial system began. The national liberation movement intensified sharply in Asian and African countries, most of which achieved political independence.

The coastal part and the areas of land framing the ocean remote from it are very rich in a variety of natural resources. Among them are gas, ferrous and non-ferrous ores, diamonds and other precious stones, forests with valuable breeds trees, tropical fruits and more. Almost everywhere they are intensively developed, but they are processed and, moreover, consumed on a small scale. The main thing here is the extraction of raw materials for export. Only in Australia and, to a lesser extent, in India, ore beneficiation is carried out as the primary form of processing. Thus, the Indian Ocean is conveniently located in relation to the main centers of production. natural resources, as certain types of them are found along the entire coast. However, the largest production centers are located on the northern shores of the ocean. This is another important distinguishing feature of his EGP.

In the northern part of the Indian Ocean, where the main exporting countries of raw materials are located, the shortest (the Suez Canal and narrow straits separating the islands) lie, but sea routes limited for modern large-capacity ships to the Atlantic and. In the southern regions remote from the coasts, all three oceans are widely and freely communicated, however, long distances reduce the efficiency of the transport use of these waters. Thus, in relation to the main routes of world shipping, only the northern part of the Indian Ocean is favorably located. This is another salient feature his EGP.

The history of the formation and development of the basin

The basin of the Indian Ocean, in contrast to the Pacific, is a relatively young geological formation that arose in the Mesozoic as a result of the collapse of Gondwana, the pushing apart of the continental plates of the Southern continents and the destruction of the ancient oceanic crust of the Pacific and Tethys oceans. The split of Gondwana into several independent continental blocks (South America, Africa with Arabia, Madagascar, Hindustan and Antarctica with Australia) occurred at the turn of the Jurassic and Cretaceous periods (140-130 million years ago).

At the beginning of the Cretaceous period, the relatively rapid removal of Hindustan from Africa and the single continent of Australo-Antarctica began. From the end of the Cretaceous - the beginning of the Cenozoic (70-65 million years ago), the main direction of the growth of the crust of the Indian Ocean was determined by the divergent boundary, which was formed as a result of the separation at the beginning of Hindustan, and then the separation of Australia and Antarctica.

The invasion of the rift zone of the northwestern branch of the Middle Indian Ridge to the African continent led in the Paleocene - Eocene to the formation of the Gulf of Aden and the Red Sea.

In the northeast of the ocean, a system of island arcs and seas of the Indonesian region began to form as early as the Cretaceous. The connection of the Indian Ocean in its northeastern part with the Pacific has been significantly reduced. At the same time, in the southeastern part, the Indian Ocean received a wide passage to the Pacific Ocean between Australia and Antarctica. By the beginning of the Oligocene, the continental bridge between South America and Antarctica was also destroyed. All this led to the formation of a circumpolar ocean current.

Thus, at the turn of the Paleogene and Neogene, the outlines of the Indian Ocean and the position of the spreading axes on its bed were already close to modern ones.

The main features of the bottom topography

The history of the development of the Indian Ocean basin largely determines the features of its bottom topography.

The underwater margins of the continents occupy about 30% of the area of ​​the ocean floor. The shelf is relatively poorly developed (about 4% of the bottom area) and in most areas stretches in a narrow strip along the coast. Despite the small width of the shelf (from several kilometers to 80-100 km), the zone of the underwater margins of the continents as a whole occupies a prominent place in the Indian Ocean due to the spread of marginal plateaus and the developed continental foot.

The underwater margin of Africa, with a very narrow shelf in the south, is expanding significantly due to underwater elevations with continental-type crust - the Agulhas Bank, the Mozambique and Madagascar ridges.

The Madagascar marginal plateau (together with the island of the same name) can be considered as a kind of microcontinent with a clearly defined shallow, slope and foot. For a long distance from the mouth of the river. From the Zambezi to the Somali peninsula, the relief of the shallow waters of the continental margin is complicated by coral structures.

The shelf off the coast of Eurasia is somewhat wider. In the Bay of Bengal and the Persian Gulf, it is composed of fluvial sediments supplied with the runoff of suspended sediments from the rivers (Ganges, Brahmaputra and Shatt al-Arab).

An extensive continental shelf (Sahul shelf) is located off the northern outskirts of Australia. It includes the bottom of the Timor and Arafura seas and the Gulf of Carpentaria.

The maximum shelf width exceeds 1000 km. At the western coast of the mainland, it narrows, but still its width reaches 100 km. The shelf of the Great Australian Bight has a width of 80 to 200 km.

The continental shelf of Antarctica, up to 300 km wide, partially covered by ice shelves, is characterized by a general overdeepening (up to 200 m and often more than 500 m). This is attributed to the sinking of the earth's crust under the weight of the ice sheet of Antarctica.

The continental slope along the African and Asian coasts is almost universally narrow and steep, dissected by submarine canyons, which are especially numerous off the coast of Somalia and Kenya.

Submarine canyons are routes of turbidity flows. Along the northwestern and western coasts of Australia, the continental slope has a complex structure, forming in a number of places large steps and massive ledges, of which the marginal plateaus of Exmouth and Naturalists are the most significant. Along the underwater margin of Antarctica, the continental slope is wide, strongly dissected by underwater canyons, the formation of which is explained not only by the activity of turbidity flows, but also by the erosive work of density bottom currents that occur when supercooled waters flow from the continental shallows into abyssal basins. The slope here has a stepped relief, is complicated by uplifts in the form of horsts and resembles a borderland. The underwater Kerguelen ridge with many (some are visible above the ocean surface - Kerguelen Island, Heard Island, etc.) is a large ledge of the continent. The continental foot of Antarctica is characterized by a significant width and thickness of bottom sediments.

The canyons of the Indus and the Ganges, dismembering the continental slopes, stand out in particular.

The top of the Indian Canyon is only 4 km from the mouth of the river. It has a wide (3-6 km) flat bottom and steep (up to 20°) slopes complicated by landslide formations. The absolute depth exceeds 1 km. When entering the zone of the continental foot, the canyon takes the form of a wide valley with a giant fan of turbidity flows extended far into the ocean floor. The thickness of the sediments composing this formation is 5-8 km. The largest alluvial fan in the world - Bengal occupies almost the entire bottom of the bay of the same name and extends far beyond its limits to the northern part of the Central Basin. It is confined to the underwater canyon of the Ganges - Bengal. The Ganges with the Brahmaputra annually carry out into the ocean more than 2 billion tons of sedimentary material (Indus - about 500 million tons), which forms this giant alluvial fan.

The transition zone in the Indian Ocean is developed only in its northeastern part and occupies a little more than 2% of the total area. This is only a small part of the complex Indonesian transitional region, located mainly in the Pacific Ocean.

It includes the Andaman Sea depression, the Sunda island arc, and the Sunda, Timor, and Kai deep-sea trenches. The arc of the Sunda Islands, starting in the Andaman Sea in the form of small anticline ridges, continues with a large megaanticlinorium about. Sumatra, about. Java and the Lesser Sunda Islands. There are more than 300 volcanoes here, of which more than 100 are active (including the well-known Krakatoa). The arc is accompanied by the Sunda Deep Trench. This is one of the largest morphostructures of this kind: the length is about 4000 km, the maximum depth in the eastern part (Yavan Trench) is 7729 m (the greatest depth of the entire Indian Ocean). The Timorsky and Kay trenches differ from the Sonda trenches in their relatively shallow depth (less than 4000 m), but they have all the main features of deep water.

Mid-ocean ridges occupy about 17% of the Indian Ocean. A feature of the system is their triple articulation. In the southwestern part of the ocean, the West Indian Ridge is located - this is a continuation of the African-Antarctic Rise, stretching from the Atlantic to the Indian Ocean, which extends from the southwest to the northeast and articulates with two other branches of the intraocean spreading zone in the southern tropic: the Arabian-Indian Range departs to the north, and the Central Indian Range to the southeast. Structural continuation of the Arabian-Indian ridge is the zone of uplifts of the oceanic crust in the Gulf of Aden and the rift of the Red Sea. The Central Indian Ridge in the region of the Amsterdam and St. Paul Islands passes into the Australo-Antarctic Rise.

The West Indian Ridge (length - more than 2000 km and width - 300-600 km) and the Arabian-Indian (length - 3700 km, width - 300-650 km) are characterized by all signs of mid-ocean uplifts. They have a pronounced rift structure of the axial zone, significant seismicity, outcrops of ultramafic rocks, etc. The Arabian-Indian ridge is cut by transverse faults (Owen, Vityaz, etc.)

The Central Indian Range has a length of more than 2000 km, a width of up to 500 km. In the south, it is separated by a fault from the Australo-Antarctic Rise, which, unlike other median ridges of the Indian Ocean, has much in common with the Pacific Ocean uplifts in its structure: it is a flat wide (up to 1200 km) shaft with a relative height of 1-1.2 km . The rift zone is absent in most of it. Numerous meridional transverse transform faults are very characteristic.

The Arabian-Indian ridge continues in the form of a complexly dissected bottom of the Gulf of Aden and the emerging rift of the Red Sea, which is a transitional structure between the inland East African rifts and the middle ridges of the Indian Ocean. In the course of deep-water drilling in the Red Sea, powerful outcrops of hot (up to 70°C) and extremely saline (up to 350% o) juvenile waters were revealed. The discovered strata of salt-bearing and metal-bearing sediments are associated with them.

Ocean bed

The bed of the Indian Ocean is divided by mid-ocean ridges into three segments: African, Asian-Australian and Antarctic.

The African segment is the most complex part of the lodge. Numerous bottom uplifts are located here.

There is a large Mascarene Range (about 2000 km long) with the Reunion, Mauritius, Cargados-Carahos, etc. islands and the Seychelles Plateau, which is a real microcontinent composed of limestones deposited on a granite base. Hills and ridges limit several large basins of the bed: Agulhas (6150 m) - common with the Atlantic, Mozambique (6046 m), Madagascar (6400 m), Mascarene (5349 m) and Somali (5185 m) with a hilly, and often mountainous terrain (there are guyots).

In the Asian-Australian segment, the bed of the Indian Ocean occupies the most prominent place among the bottom uplifts.

The East Indian Range is the largest mountain structure in the Indian Ocean bed.

The ridge is a kind of narrow (up to 450 km) and long (more than 5000 km) rectilinearly elongated horst almost along the meridian with a flat or slightly convex top surface. A narrow graben with a maximum depth of 6335 m extends along the eastern foot of the southern half of the ridge. In the south, the East Indian Ridge is adjacent to the same blocky West Australian Ridge, but of sublatitudinal strike. The largest basins of the Asian-Australian sector of the bed of the Indian Ocean are Arabian (4850 m), Central (6090 m), Cocos (5490 m), Western Australian (6429 m), Naturalists (6035 m) and South Australian (5853 m). The relief of the bottom of the basins is mainly undulating and hilly abyssal plains.

The Antarctic segment of the Indian Ocean floor is characterized by a relatively simple structure.

The Kerguelen Rise, as well as the volcanic massif of the Prince Edward and Crozet Islands, divide the ocean floor into three basins: African-Antarctic (6972 m), Crozet (5625 m) and Australo-Antarctic (6089 m). The bottom of the Antarctic basins is mainly flat abyssal plains, since the tectonic irregularities here are covered by a layer of terrigenous sediments.

Bottom sediments

Among the bottom sediments, in contrast to the Pacific Ocean, in the Indian Ocean, foraminiferal silts predominate, occupying more than half of its bottom area. This is due both to the position of most of the ocean within the equatorial-tropical and subtropical latitudes, and to the shallower depth of the oceanic basins (most of the area of ​​the bottom of the basins lies at depths of less than 5 thousand m) and the wide distribution of various bottom uplifts. In the deep parts of the basins, red deep-sea clays are common, and in the equatorial belt - radiolarian silts. In the western part of the ocean there are significant fields of coral deposits. In the southern Antarctic sector, there is a wide belt of siliceous diatom deposits, and in the immediate vicinity of Antarctica - iceberg sediments.

Mineral resources of the bottom

Among the mineral resources of the bottom of the Indian Ocean, a special place, as in the Pacific Ocean, is occupied by ferromanganese nodules. They are widespread in all oceanic basins, but their main fields are in the Central Basin and in the depressions of the eastern part of the ocean. Large accumulations of phosphorite nodules have also been found (near the southern part of Africa, in the region of the Arabian Peninsula, etc.). In the shelf zone, sands containing ilmenite, rutile, zircon, monazite and magnetite are being developed (Hindostan, Sri Lanka, southeast Africa, southwest Australia). Cassiterite placers are developed in the countries of Southeast Asia (Indonesia, Malaysia, Burma, Thailand). Among non-metallic raw materials, building materials (limestone-shell rock, gravel, sand, etc.), glauconite, dolomite, sulfur, etc. are of great value. Metal-bearing silts enriched in iron, manganese, zinc , lead, copper, silver and other elements. But the main mineral resources of the bottom of the Indian Ocean are currently oil and natural gas. More than half of the world's oil reserves are concentrated in the Middle East region. The Persian Gulf with the land adjacent to it stands out in particular. By 1980, the states of the Persian Gulf came out on top in the world in offshore oil production. Oil and gas shows have also been identified near the western coast of Hindustan and Australia.



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