The Indian Ocean is occupied. Template: Indian Ocean Currents (Image Map)

The Indian Ocean is the third largest ocean. Geologically, this is basically a relatively young ocean, although it should be noted, as for other oceans, that many aspects of its earliest geological history and origin have not yet been studied. Western border south of Africa: along the meridian of Cape Igolny (20 ° E) to Antarctica (Queen Maud Land). Eastern border south of Australia: along the western border of the Bass Strait from Cape Otway to King Island, then to Cape Grim (Northwest Tasmania) and from the southeastern tip of Tasmania along 147 ° E. to Antarctica (Fisher Bay, George V Coast). There were many discussions regarding the eastern border north of Australia, caused by the fact that some scientists attribute the Arafura Sea, and some even the Timor

sea ​​to the Pacific Ocean, although this is not entirely logical, since the Timor Sea, by the nature of the hydrological regime, is inextricably linked with the Indian Ocean, and the Sahul shelf, in geological terms, is clearly part of the Northwest Australian Shield, connecting the region of the once existing Gondwana with the Indian by the ocean Most geologists draw this boundary along the narrowest (western) part of the Torres Strait; as determined by the International Hydrographic Bureau, the western boundary of the strait runs from Cape York (11 ° 05 "S, 142 ° 03" E) to the mouth of the Bensbek River (New Guinea) (141 ° 01 "E), which coincides with the eastern border of the Arafura Sea.

The northeastern border of the Indian Ocean runs (from island to island) through the Lesser Sunda Islands to the islands of Java, Sumatra and then to the island of Singapore. About the marginal seas of the Indian Ocean, located along its northern border. The area south of the Cape Agolny - Cape Louin line (Western Australia) is sometimes considered the southern sector of the Indian Ocean.

Indian Ocean area within the boundaries excluding the Arafura Sea 74 917 thousand km2, with the Arafura Sea 75 940 thousand km. Average depth 3897 m; the maximum recorded depth is 7437 m3. Indian Ocean water volume 291,945 thousand km3.

Bottom relief

In terms of bathymetry, five morphological units can be distinguished in the Indian Ocean.

Continental outskirts

The shelves of the Indian Ocean are on average slightly narrower than the shelves of the Atlantic Ocean; their width ranges from several hundred meters around some oceanic islands to 200 km or more in the Bombay region. The kink, which forms the outer edge of the shelves of Africa, Asia and Australia, has an average depth of 140 m. The boundary of the continental platform is formed by a continental slope, steep marginal ledges and slopes of troughs.

The continental slope is cut by numerous underwater canyons. Particularly long underwater canyons lie on the continuation of the mouths of the Ganges and Indus rivers. The continental foot slopes from 1: 40 at the border with the continental slope to 1: 1000 at the border with the abyssal plains. The relief of the continental foot is characterized by sporadic seamounts, hills and canyons. The underwater canyons at the foot of the continental slope are usually narrow in diameter and difficult to spot, so few are well surveyed. The mouths of the Ganges and Indus rivers show large accumulations of sediment known as archipelagic fan assemblies.

The Javan Trench stretches along the Indonesian arc from Burma to Australia. On the side of the Indian Ocean, it is bordered by a gentle outer ridge.

Ocean bed

The most characteristic elements of the relief of the oceanic bed are the abyssal plains. Slopes here range from 1: 1000 to 1: 7000. With the exception of isolated peaks of buried hills and mid-oceanic canyons, the height of the relief of the oceanic bed does not exceed 1-2 m. The abyssal plains of the northern and southern parts of the Indian Ocean are very clearly expressed, but in Australia they are less pronounced. The seaward margins of the abyssal plains are usually characterized by abyssal hills; some areas are characterized by low, linearly elongated ridges.

Microcontinent

The most characteristic feature of the bottom topography of the Indian Ocean are micro-continents elongated from north to south. In the northern part of the Indian Ocean, in the direction from west to east, the following aseismic microcontinent can be indicated: Mozambique Ridge, Madagascar Ridge, Mascarenskoe Plateau, Chagos-Lakkadiv Plateau, Nintiist Ridge. In the southern part of the Indian Ocean, the Kerguelen Plateau and the asymmetric Broken Ridge, stretching from east to west, have a noticeable meridional linearity. Morphologically, microcontinents are easily distinguished from the mid-ocean ridge; they usually represent higher areas of the arrays with more flattened relief.

A well-defined microcontinent is the island of Madagascar. The presence of granites in the Seychelles also suggests that at least the northern part of the Mascarene plateau is of continental origin. The Chagos Islands are coral islands that rise above the Indian Ocean in the vast, slightly curved Chagos Laccadive Plateau. The Nintiist Ridge is arguably the longest and most straight ridge found in the oceans during the Indian Ocean International Expedition. This ridge was traced from 10 ° N. NS. up to 32 ° S.

In addition to the aforementioned micro-continents, there is a distinct Diamantine Fault Zone in the Indian Ocean 1,500 miles west of the southwestern tip of Australia. The Broken Ridge, which forms the northern boundary of this fault zone, at 30 ° S lat. NS. connects with the Nintiist Ridge, which runs at right angles to the Diamantin Fault Zone in a north-south direction.

Mid ocean ridge

The most prominent feature of the Indian Ocean floor is the Central Indian Ridge, part of the global mid-ocean ridge, which in the central part of the Indian Ocean has an inverted V-shape. A seismically active depression, or rift, stretches along the axis of this mid-ocean ridge. The entire ridge has a generally mountainous relief with stripes parallel to the axis of the ridge.

Fault zones

The Indian Ocean is dissected by several distinct fault zones that shift the axis of the mid-ocean ridge. To the east of the Arabian Peninsula and the Gulf of Aden lies the Owen Fault, displacing the axis of the mid-ocean ridge approximately 200 miles to the right. The recent formation of this displacement is indicated by the Wheatley Trench, a well-defined depression with depths more than 1000 m greater than the depths of the Indian Abyssal Plain.

Several small right lateral strike-slip faults displace the axis of the Carlsberg Ridge. In the Gulf of Aden, the axis of the mid-oceanic ridge is offset by several left lateral strike-slip faults running almost parallel to the Owen Fault. In the southwestern Indian Ocean, the mid-ocean ridge axis is offset by a series of left-sided fault zones that have roughly the same orientation as the Owen Fault Zone, the Malagasy Fault Zone, which lies east of Madagascar Ridge, is likely a southern extension of the Fault Zone Owen. In the area of ​​the islands of Saint-Paul and Amsterdam, the axis of the mid-oceanic ridge is displaced by the Amsterdam fault zone. These zones run parallel to the Nintiist Ridge and have approximately the same meridional orientation as the fault zones in the western Indian Ocean. Although the Indian Ocean is most characterized by meridional strikes, the Diamantina and Rodriguez fault zones stretch approximately from east to west.

The highly dissected tectonic relief of the mid-oceanic ridge in general presents a noticeable contrast with the highly leveled relief of the continental foot and the almost absolutely smoothed relief of the abyssal plains. In the Indian Ocean, there are areas of smooth undulating or undulating relief, apparently caused by a thick cover of pelagic sediments. The slopes of the mid-ocean ridge south of the polar front are flatter than north of the polar front. This may be due to the higher deposition rate of pelagic sediments due to the increased organic productivity of the Southern Ocean.

The Crozet plateau has an extremely smoothed relief. In this area, the narrow zone of the ridge of the mid-ocean ridge is usually highly dissected, while the oceanic bed in this area is extremely flat.

Indian Ocean climate

Air temperature. In January, the thermal equator for the Indian Ocean is slightly displaced south of the geographic, in the region between 10 s. NS. and 20 y. NS. the air temperature is above 27 ° C. In the northern hemisphere, the 20 ° C isotherm, which separates the tropical from the temperate zone, goes from the south of the Arabian Peninsula and the Gulf of Suez through the Persian Gulf to the northern part of the Bay of Bengal almost parallel to the Tropic of Cancer. In the southern hemisphere, the 10 ° C isotherm, which separates the temperate zone from the subpolar zone, runs almost along the parallel of 45 ° S. In the middle latitudes (southern hemisphere (between 10 and 30 ° S), 27-21 ° C isotherms are directed from WES to ENE, from South Africa across the Indian Ocean to Western Australia, indicating that the temperature of the western sector in some and at the same latitudes, 1–3 ° C higher than the temperature of the eastern sector.On the western coast of Australia, isotherms of 27–21 ° C descend to the south due to the influence of the strongly heated continent.

In May, the highest temperature (above 30 ° C) is observed in the interior regions of the southern part of the Arabian Peninsula, Northeast Africa, Burma and India. In India, it reaches more than 35 ° C. The thermal equator for the Indian Ocean lies at about 10 ° N. NS. Isotherms from 20 to 10 ° C run in the southern hemisphere between 30 and 45 ° S. NS. from ESE to WNW, indicating that the western sector is warmer here than the eastern one. In July, the zone of the highest temperatures on land moves north of the Tropic of Cancer.

Temperatures over the Arabian Sea and the Gulfs of Bengal have dropped slightly since May, and in addition, the air temperature in the Arabian Sea region is lower than over the Bay of Bengal. Near Somalia, the air temperature due to the rise of cold deep waters drops below 25 ° C. August. In the southern hemisphere, the region west of South Africa is somewhat warmer than the central part at the same latitudes. Temperatures are also much higher off the western coast of Australia than in the interior of the mainland.

In November, the thermal equator with a small temperature zone above 27.5 ° С almost coincides with the geographic equator. In addition, over the Indian Ocean region north of 20 ° S. NS. the temperature is almost uniform (25-27 C) with the exception of a small area over the central Indian Ocean.

Annual amplitudes of air temperature for the central part, between 10 ° C. NS. and 12 ° S. sh., less than 2.5 C, and for the area between 4 ° N. NS. and 7 ° S. NS. - less than 1 C. In the coastal areas of the Bay of Bengal and the Arabian Sea, as well as in the area between 10 and 40 ° S. NS. west of 100 ° W the annual amplitude exceeds 5 ° C.

Baric field and surface winds. In January, the meteorological equator (minimum atmospheric pressure 1009-1012 mbar, calm and variable winds), like the thermal equator, is located about 10 ° S. NS. it divides the northern and southern hemispheres with different meteorological conditions.

The prevailing wind north of the meteorological equator is the northeast trade wind, or more precisely the northeast monsoon, which changes direction north at the equator and northwest (northwest monsoon) and southern hemisphere. South of the meteorological equator, due to the heating of the continents in the summer of the southern hemisphere, the minimum pressure (less than 1009 mbar) is observed over Australia, Africa and the island of Madagascar. The high-pressure area of ​​the southern subtropical latitudes is located along 35 ° S latitude. the maximum pressure (above 1020 mbar) is observed over the central part of the Indian Ocean (near the islands of Saint-Paul and Amsterdam). The northern bulge of the 1014 mbar isobar in the central Indian Ocean is caused by the effect of lower air and surface water temperatures, in contrast to the South Pacific, where a similar bulge is observed in the eastern sector of South America. South of the high pressure area, there is a gradual decrease in pressure towards a subpolar depression at about 64.5 ° S. sh., where the pressure is below 990 mbar. This baric system creates two types of wind systems south of the meteorological equator. In the northern part, the southeastern trade winds cover the entire water area of ​​the Indian Ocean, with the exception of areas near Australia, where they change direction to the south or southwest. South of the trade winds (between 50 and 40 ° S lat.) Westerly winds occur from the Cape of Good Hope to Cape Horn, in an area called the Roaring Forties. The essential difference between westerly winds and trade winds is not only that the former have higher speeds, but also that the daily fluctuations in direction and speed are also much greater for the former than for the latter. In July, for a wind field from the north of 10 ° S. NS. the picture is opposite to that of January. An equatorial depression with pressures below 1005 mbar is located over the eastern part of the Asian continent.

To the south of this depression, the pressure gradually increases from 20 s. NS. to 30 ° S sh., ie, to the area of ​​the southern borders of the "horse" latitudes. The southern trade winds cross the equator and become very intense southwestern monsoons in the northern hemisphere, characterized by severe storms off the coast of Somalia in the Arabian Sea.

This area is a good example of the complete shear of winds with an annual cycle in the northern trade wind zone, which is a consequence of the strong heating and cooling effect of the Asian mainland. In the middle and high latitudes of the southern hemisphere, the softening effect of the Indian Ocean reduces the differences in pressure and wind fields in June and January.

However, at high latitudes, westerly winds increase significantly, and fluctuations in their direction and speed also increase. The distribution of the recurrence rate of storm winds (more than 7 points) showed that in the winter of the northern hemisphere over most of the Indian Ocean north of 15 ° S. NS. storm winds are practically not observed (their frequency is less than 1%). In the area of ​​10 ° S. sh., 85-95 ° E (northwest of Australia) from November to April, tropical cyclones sometimes form, moving southeast and southwest. South of 40 ° S NS. the recurrence of storm winds is more than 10% even in the summer of the southern hemisphere. In the summer of the northern hemisphere, from June to August, the southwestern monsoons in the western Arabian Sea (off the coast of Somalia) are always so strong that approximately 10-20% of the winds are 7 points. In this season, the calm zones (with the frequency of storm winds less than 1%) are shifted to the area between 1 ° S. NS. and 7 ° n. NS. and west of 78 ° E. d. In the region of 35-40 ° S. NS. the frequency of occurrence of storm winds in comparison with the winter season increases by 15–20%.
Cloud cover and precipitation. In the northern hemisphere, cloud cover has significant seasonal variations. During the northeastern monsoon (December-March), the cloud cover over the Arabian Sea and the Bay of Bengal is less than 2 points. However, in summer, the southwestern monsoons bring rainy weather to the Malay Archipelago and Burma, while the average cloudiness is already 6-7 points. The region south of the equator, the southeastern monsoon zone, is characterized by large cloud cover throughout the year - 5-6 points in the northern hemisphere in summer and 6-7 points in winter. Even in the southeastern monsoon zone, a relatively large cloud cover is observed, and it is extremely rare in it to find areas of a cloudless sky characteristic of the southeastern monsoon zone of the Pacific Ocean. Clouds in areas west of Australia exceed 6 points. However, it is pretty cloudless off the coast of Western Australia.

In summer, sea fog (20-40%) and very poor visibility are often observed off the coast of Somalia and the southern part of the Arabian Peninsula. The water temperature here is 1-2 ° C lower than the air temperature, which causes condensation, amplified by dust brought from the deserts on the continents. Area south of 40 ° S NS. also characterized by frequent sea fogs throughout the year.

The total annual rainfall for the Indian Ocean is high - over 3000 mm at the equator and over 1000 mm in the western zone of the southern hemisphere. Between 35 and 20 ° S NS. in the trade wind zone, precipitation is relatively rare; the area off the western coast of Australia is especially dry - the amount of precipitation is less than 500 mm. The northern boundary of this dry zone is parallels 12-15 ° S, that is, it does not reach the equator, as in the southern part of the Pacific Ocean. The northwest monsoon zone is generally the boundary region between the north and south wind systems. North of this area (between the equator and 10 ° S lat.) Is the equatorial rainy zone, which stretches from the Java Sea to the Seychelles. In addition, very high rainfall is observed in the eastern part of the Bay of Bengal, especially in the Malay Archipelago. The western Arabian Sea is very dry, and the rainfall in the Bay of Aden and the Red Sea is less than 100 mm. The maximum precipitation in rainy zones in December-February is between 10 and 25 ° S. NS. and in March-April between 5 s. NS. and 10th y. NS. in the western part of the Indian Ocean The highest values ​​in the summer of the northern hemisphere are observed in the Bay of Bengal. The heaviest rains are observed almost throughout the year to the west of Sumatra.

Surface water temperature, salinity and density

In February, the northern Indian Ocean experiences typical winter conditions. In the interior regions of the Persian Gulf and the Red Sea, the surface water temperature is 15 and 17.5 ° C, respectively, while in the Gulf of Aden it reaches 25 ° C. Isotherms 23-25 ​​° C run from the southwest to the northeast, and therefore , the surface waters of the western part of the Indian Ocean are warmer than the surface waters of the eastern part for the same latitudes (the same with respect to air temperature).

This difference is caused by the circulation of water. It is observed in all seasons of the year. In the southern hemisphere, where it is summer at this time, the zone of high surface layer temperatures (above 28 ° C) runs in the ENE direction from the eastern coast of Africa to the area west of the island of Sumatra and then south of Java and north of Australia, where the water temperature sometimes exceeds 29 ° C. Isotherms 25-27 ° C between 15 and 30 S. NS. directed from the WSW to ENE, from the coast of Africa to approximately 90-100 ° E. and then they turn to the southwest, as in the western part of the Bay of Bengal, in contrast to the South Pacific, where these isotherms are directed off the coast of South America towards the ENE. Between 40 and 50 ° S NS. there is a transition zone between water masses of middle latitudes and polar waters, which is characterized by thickening of isotherms; temperature difference of the order of 12 ° C.

In May, the surface waters of the northern Indian Ocean are heated to a maximum and have temperatures generally above 29 ° C. At this time, the northeastern monsoons are replaced by the southwestern ones, although rain and sea level rise have not yet been observed at this time. In August, only in the Red Sea and the Persian Gulf, the water temperature reaches a maximum (above 30 ° C), however, the surface waters of most of the northern sector of the Indian Ocean, including the Gulf of Aden, the Arabian Sea and most of the Bay of Bengal, with the exception of its western regions, have lower temperatures than in May. The zone of low temperatures of the surface layer (below 25 ° C) stretches from the coast of Somalia to the southeastern coast of the Arabian Peninsula. The decrease in temperature is caused by the intense rise of cold deep waters due to the southwestern monsoons. In addition, in August, there are three characteristic features of the temperature distribution south of 30 ° S. lat .: 20-25 ° C isotherms in the eastern and central parts of the Indian Ocean are directed from the WNW to the ENE, there is a thickening of isotherms between 40 and 48 ° S. sh., and isotherms west of Australia are directed to the south. In November, the surface water temperature is generally close to the annual average. The low temperature zone (below 25 ° C) between the Arabian Peninsula and Somalia and the high temperature zone in the western part of the Bay of Bengal are almost disappearing. In a huge area north of 10 ° S. NS. surface layer temperatures are kept between 27 and 27.7 ° C.

The salinity of the surface waters of the southern part of the Indian Ocean has the same distributional characteristics that are characteristic of the southern part of the Pacific Ocean. To the west of Australia, the maximum salinity is observed (above 36.0 ppm). The equatorial zone of low salinity, corresponding to the transition zone between the southeastern trade winds and monsoons, stretches up to 10 ° S. sh., but clearly expressed only in the eastern part of the Indian Ocean.
The minimum salinity values ​​in this zone are noted to the south of the islands of Sumatra and Java. The salinity of surface waters in the northern Indian Ocean varies not only regionally but also with the seasons. In the northern hemisphere summer, surface water salinity has the following characteristic features: it is extremely low in the Bay of Bengal, rather high in the Arabian Sea, and very high (above 40 ppm) in the Persian Gulf and Red Sea.

The density of surface waters in the southern part of the Indian Ocean in the summer of the southern hemisphere decreases uniformly northward from about 27.0 in the region of 53-54 ° S. NS. up to 23.0 at 17 ° S. NS.; in this case, the isopycnes run almost parallel to the isotherms. Between 20 ° S NS. and 0 ° there is a huge zone of low density waters (below 23.0); near the islands of Sumatra and Java, there is a zone with a density below 21.5, corresponding to the zone of minimum salinity in this area. In the northern Indian Ocean, salinity influences the density change. In summer, the density decreases from 22.0 in the southern part of the Bay of Bengal to 19.0 in its northwestern part, while for most of the Arabian Sea it is higher than 24.0, and near the Suez Canal and in the Persian Gulf reaches 28.0 and 25.0. In addition, seasonal changes in surface water density are mainly caused by changes in temperature. For example, the northern Indian Ocean is characterized by an increase in density by 1.0-2.0 from summer to winter.

Indian Ocean currents

The currents in the northern Indian Ocean, strongly influenced by monsoons and changing with seasons, are called southwest and northeast monsoon drifts for summer and winter, respectively. In the southern part of the Indian Ocean, the South Tradewind Current and the current of the West Winds pass. In addition to these currents, closely related to wind systems, there are currents of a local nature, caused mainly by the density structure of the Indian Ocean, such as the Mozambique Current, Cape Needle Current, Interpass (equatorial) countercurrent, Somali Current and West Australian Current.

There is a large anticyclonic circulation in the southern Indian Ocean, similar to that in the southern Pacific and Atlantic oceans, but here this circulation is subject to more significant annual changes. Its extreme southern part is the current of the Western Winds (between 38 and 50 ° S lat.), 200-240 miles wide, strengthening in an easterly direction. This current is bordered by the zones of subtropical and Antarctic convergence. The speed of the current depends on the strength of the wind and varies seasonally and regionally. The maximum speed (20-30 miles / day) is observed near Kerguelen Island. In the summer of the southern hemisphere, when approaching Australia, this current turns northward and joins the current flowing from the Pacific Ocean south of Australia.

In winter, the wind drift merges with the flow going south along the western shores of Australia and continues in the Pacific Ocean along the southern shores of Australia. The eastern part of the cyclonic circulation in the southern hemisphere is the West Australian Current, which has a steady northerly direction only in the summer of the southern hemisphere and reaches 10-15 miles / day north of 30 ° S. NS. This current becomes weak in winter and changes direction to the south.

The northern part of the anticyclonic gyre is the South Tradewind Current, which originates in the area where the West Australian Current exits to the Tropic of Capricorn under the influence of the southeastern trade winds. The maximum current speed (more than 1 knot) is observed in its eastern part in the winter of the southern hemisphere, when the western flow from the Pacific Ocean increases to the north of Australia. In the summer of the southern hemisphere, when this current becomes easterly, the northern border of the South Tradewind Current is between 100 and 80 ° E. d. is located about 9 ° S. sh., slightly shifting southeast of 80 ° E. etc .; its southern border passes at this time about 22 ° S. NS. in the eastern sector. In the winter of the southern hemisphere, the northern boundary of this current shifts northward by 5-6 °, following the northern shift of the southeastern trade wind. Before the island of Madagascar, the current splits into several branches.

One of them goes north around the island of Madagascar at a speed of 50-60 miles / day and then turns west. It splits into two branches again at Cape Delgado. One branch turns north (East African Coastal Current), the other turns south, following the Strait of Mozambique (Mozambique Current). The speed of this current varies from almost zero to 3-4 knots during the northeastern monsoon.

The Cape Agulhas Current is formed from the continuation of the Mozambique Current and the southern branch of the South Tradewind Current south of the island of Mauritius. This current, narrow and distinct, extends less than 100 km from the coast. As you know, the flow directed to the south in the Southern Hemisphere is characterized by a slope of the water surface to the left. At a distance of 110 km from Port Elizabeth, the inclination of the level towards the ocean increases by about 29 cm. Between Durban and 25 ° E. e. the speed of this current at the edge of the Agulhas Bank reaches 3-4.5 knots. South of Africa, the main part of the current turns sharply to the south, and then to the east, and thus merges with the current of the West Winds. However, small and at the same time continues to move into the Atlantic Ocean. Due to a change in direction and a ramified current along the coast of South Africa, numerous eddies and gyres develop, the position of which changes during the year.

North of 10 ° S NS. There is a strong variability in the surface currents of the Indian Ocean from winter to summer. During the northeastern monsoon, from November to March, the North Passat Current develops (the drift of the northeastern monsoon). The southern boundary of this current varies from 3-4 ° N. NS. in November up to 2-3 ° S. NS. in February. In March, the current turns north again and disappears with the appearance of the southwest monsoon drift. With the onset of the northeastern monsoon (from November), the inter-trade countercurrent begins to develop. It is formed under the combined influence of the current flowing southwest of the coast of Somalia and the East African coastal current flowing north of the cape. Delgado. The countercurrent is narrow and reaches almost to the island of Sumatra. Its northern border runs north of the equator in November, and shifts to 2-3 ° S in February. Later, the current rises again to the north and then disappears. The southern boundary of the current lies between 7 and 8 ° S. NS. Current speed is between 60 and 70 ° E. d. reaches 40 miles / day, but further to the east it decreases.

During the period of the southwest monsoon, from April to October, the North Passat Current (the drift of the northeast monsoon disappears and is replaced by the drift of the southwest monsoon, going east south of India. South of Sri Lanka, its speed is 1-2 knots, and sometimes reaches 3 knots The branches of this current create a clockwise circulation in the Arabian Sea following the contours of the coastline.The speed of the southeast current off the western coast of India reaches 10-42 miles / day. During this season, the Somali current along the coast of Somalia in the region of 10 ° S is directed to the north, and the waters of the South Passat Current cross the equator. Off the coast of Somalia, there is an intensive rise of waters, causing cooling of surface waters in a large area.

Subsurface currents in the Indian Ocean north of 10 ° S. NS. were measured at the horizons 15, 50, 100, 200, 300, 500 and 700 m during the 31st cruise of the Vityaz (January-April 1960), at approximately 140 deep-water stations.

It was found that at a depth of 15 m, the distribution of currents turned out to be almost similar to the surface winter of the northern hemisphere, except that, according to observational data, the inter-trade countercurrent originates at 60 ° E. and covers the area between 0 and 3 ° S latitude. those. its width is much smaller than on the surface. On the horizon 200 m of current south of 5 ° N. NS. have a direction opposite to the currents at a horizon of 15 m: they are directed to the east under the North and South trade winds and to the west under the inter-trade countercurrent east of 70 ° E. e. At a depth of 500 m, the current is between 5 ° N. NS. and 10 ° S. NS. generally have an easterly direction and form a small cyclonic gyre centered at 5 ° S. w., 60 ° E In addition, direct measurements of currents and data of dynamic calculations for the period November-December 1960, obtained during the 33rd cruise of the Vityaz, indicate that the observed system of currents does not yet correspond to the system of currents characteristic of the winter monsoon. , despite the fact that north-westerly winds are already beginning to prevail here. At a depth of 1500 m south of 18 ° S. NS. the current of the eastern direction was revealed at a speed of 2.5-4 5 cm / s. About 80 ° E This current is combined with the southern stream, which has a velocity of 4.5-5.5 cm / s, and its speed increases rapidly. About 95 ° E This current turns sharply to the north and then to the west, forming an anticyclonic gyre, the northern and southern parts of which have velocities of 15-18 and 54 cm / s, respectively.

About 20-25 ° S. w., 70-80 ° E e. the branch of this current in the southern direction has a velocity of less than 3.5 cm / s. On the horizon 2000 m between 15 and 23 ° S. NS. the same current has an easterly direction and a speed of less than 4 cm / s. About 68 ° E a branch departs from it, going north at a speed of 5 cm / s. Anticyclonic circulation between 80 and 100 ° E. d. on the horizon of 1500 m covers a large area between 70 and 100 ° E. e. A current flowing south from the Bay of Bengal meets another current at the equator, coming from the east, and turns north, and then north-west, to the Red Sea.

On the horizon 3000 m between 20 and 23 ° S. NS. the current is directed to the east with velocities in some places up to 9 cm / s. Cyclonic circulation at 25-35 ° S. lat., 58-75 ° E here becomes clearly pronounced at speeds up to 5 cm / s. Anticycloic circulation between the 80s and 100s. d., observed at a horizon of 1500 m, here breaks up into a series of small eddies.

Water masses

The Indian Ocean, in addition to the subantarctic water mass, is characterized by three main water masses: the central water mass of the Indian Ocean (subtropical subsurface), the equatorial water mass of the Indian Ocean, extending to medium depths, and the deep water of the Indian Ocean, below the 1000 m horizon. There are also intermediate water masses. These are the Antarctic intermediate waters, the waters of the Red Sea and others at medium depths.

The Indian Ocean is the third largest. The area of ​​the Indian Ocean is 76.17 million km 2, the average depth is 3711 m. The name of the ocean is associated with the name of the Indus River - "irrigator", "river".

Geographical position.

A characteristic feature of the geographical position of the Indian Ocean is its location almost entirely in the Southern Hemisphere and entirely in the Eastern. Its waters wash the shores of Africa, Eurasia, Australia and Antarctica. The Indian Ocean includes 8 seas, the largest is Arabian... One of the warmest (up to +32 ¨C) and salty (38-42 ‰) seas in the world is Red. It gets its name from the significant accumulation of algae that gives the water its red color.

Relief the bottom of the Indian Ocean is diverse. The shelf zone occupies a narrow strip and accounts for only 4% of the total bottom area. The continental slope is very gentle. The ocean floor is crossed by mid-ocean ridges with an average height of about 1500 m. They are characterized by rifts and transverse faults, areas of seismic activity. There are separate volcanic mountains, several large basins (Central, Western Australian, etc.). Maximum depth 7729 m ( Sunda Trench).

Climate determined by the location of the main part of the Indian Ocean in the equatorial, subequatorial and tropical climatic zones. The climate of the northern part of the ocean is greatly influenced by land. Seasonal winds monsoons in summer from the ocean carry a huge amount of moisture to land (in the Bay of Bengal up to 3000 mm per year), in winter they blow from land to the ocean. A southeastern trade wind blows from the high-pressure area to the equator. In temperate latitudes, westerly winds of great strength prevail, accompanied by cyclones. The proximity of Antarctica has a cooling effect on the southern outskirts of the ocean.

The Indian Ocean is called the "ocean of heated waters" for the high temperature of the water on the surface. Average temperature +17 ¨С. (Study surface water temperatures and precipitation from climate maps.) District Persian Gulf has the highest temperature (+34 ¨С in August). The smallest amount of precipitation (100 mm) falls off the coast of Arabia. The average salinity of the Indian Ocean is 34.7 ‰, the maximum is 42 ‰ (in the north of the Red Sea).

Due to high evaporation from the water surface, low amount of atmospheric precipitation and lack of river runoff, the highest salinity in the World Ocean is observed in the Red Sea.

The formation of currents is greatly influenced by monsoons. The Indian Ocean has a complex system of currents. In the equatorial part of the ocean, the system of currents is directed clockwise, in the Southern Hemisphere - against. (Show currents on a map.

Find cold currents.)

Natural resources and environmental problems.

The largest oil and gas fields are located in the Persian Gulf. The main areas of modern oil production are the countries of the Persian Gulf: Iran, Iraq, Kuwait, Saudi Arabia, etc. A large number of ferromanganese nodules were found at the bottom of the ocean basins, but their quality is lower than in the Pacific Ocean, and they lie at great depths (4000 m ).

Rice. 45. Coral structures in the Indian Ocean

The fauna of the warm waters of the Indian Ocean is diverse, especially in the northern tropical part: there are many sharks, sea snakes, and coral polyps (Fig. 45). Giant sea turtles are at the extinction stage. Oysters, shrimps, and crabs are found in the mangroves of the tropical coasts. In the open waters of tropical zones, tuna fishing is common. The Indian Ocean is famous for pearl mining. In temperate latitudes, toothless and blue whales, seals, and an elephant seal live. The species composition of fish is rich: sardinella, mackerel, anchovy, etc.

On the coast of the Indian Ocean there are dozens of states with a total population of about 2 billion people. These are mainly developing countries. Therefore, the development of the natural resources of the ocean is proceeding more slowly than in other oceans. In the development of shipping, the Indian Ocean is inferior to the Atlantic and Pacific. (Explain why.) The Indian Ocean is of great transport importance for the countries of South and Southeast Asia, Australia. Intensive transportation of oil and oil products from the Persian Gulf has led to a deterioration in water quality, a decrease in stocks of commercial fish and seafood. Whaling has practically ceased. Warm waters, coral islands, the beauty of the Indian Ocean attract many tourists here.

Bibliography

1. Geography grade 8. Textbook for grade 8 institutions of general secondary education with the Russian language of instruction / Edited by Professor P. S. Lopukh - Minsk "Narodnaya Asveta" 2014

In the Indian Ocean, surface currents can be divided into three divisions: monsoon currents, southern hemisphere currents, and sea currents. An overview map of currents for the summer and winter of the northern hemisphere, gives an overall picture of ocean currents: in addition, maps of the northern part of the ocean and the Needle Current supplement information about the currents of the Indian Ocean. Indian Ocean monsoon currents... Between 10 ° S NS. and the mainland of Asia over the Indian Ocean are dominated every year by periodic winds - monsoons, blowing from October to March from NE, and from April to September from SW in the northern hemisphere and from NW and SE in the corresponding months between the equator and 10 ° S. NS. It is the existence of periodic winds over this part of the ocean that determines the formation here of a system of periodic currents in the surface layers of the ocean, which once again confirms the great importance of winds as the cause of currents. The dependence of ocean currents on air currents is very noticeable, and moreover, not only in the area of ​​monsoon currents, but also in other areas of the ocean. Indian Ocean monsoon currents in the northern hemisphere winter . Monsoon currents in the northern hemisphere winter north of the equator generally go west (NE monsoon blows over the ocean). In October, the NE monsoon begins to set, while the surface currents at this time are irregular and begin to set only in November. In the Bay of Bengal, the currents in the northern part are incorrect, and in the southern part from the Molucca Strait to Ceylon and to the south of it, the currents go to W at a speed of 50-70 nautical miles. In the Arabian Sea, the current flows to W and WSW at an average speed of 10-20 nautical miles, and, approaching the coast of Africa (coast of Somalia), increases, reaching speeds of 50-70 nautical miles. This Somali current, crossing the equator, meets a branch of the Equatorial Current, coming from the south, and turns to E, forming the Equatorial Countercurrent. It crosses the ocean between 0 and 10 ° S. NS. and off the coast of Sumatra there is a fairly significant speed (40-60 nautical miles); here it partly goes to N, but mainly turns to S and connects with the Equatorial Current (see fig. 179, p. 406). The monsoon currents of the winter half of the year begin to weaken from March (the monsoon blows correctly only until the end of February), and in April the currents begin to change. Monsoon currents in the northern hemisphere summer . Since May, currents of approximately the opposite direction have been established in the Northern Hemisphere. Off the coast of Africa, the Equatorial current, meeting the mainland, splits, and one of its branches goes to N along the Somali coast. Having crossed the equator, it gains greater speed and stability under the influence of the fresh SW monsoon here, which constitutes the continuation of the SE monsoon and trade winds of the southern hemisphere. The speed of this part of the monsoon currents (along the coast of Africa) averages about 40 nautical miles, and the highest reaches 80-120 nautical miles. Between Africa and Ceylon, the current flows eastward at a speed of 25-50 nautical miles. South of Ceylon the speed increases again and happens to be 70-80 nautical miles; reaching the coast of Sumatra, the current turns to S and joins the Equatorial. In the Bay of Bengal, the currents are NE with a speed of 10-40 nautical miles. This character of the current persists all the time from May to September; in October, they begin to weaken and become less etching, primarily in the Arabian Sea and the Bay of Bengal, and in November, reverse currents begin to be established. All monsoon currents in the Indian Ocean belong to warm currents and are purely drift currents, excited exclusively by monsoon winds. The fact that monsoon currents require about 2.5-3 months for their establishment and achievement of the greatest strength is in full agreement with the conditions of the Ekman drift theory of currents. Modifications and deviations seen in monsoon currents owe their origin to the influence of the shape and location of the shores in the part of the Indian Ocean where these currents occur. Recent studies of the features of these currents (for example, the Somali current) have shown that, within the accuracy of the available material, they fully correspond to the conditions of the theory of Ekman drift currents, i.e., they confirm it. Currents of the southern hemisphere of the Indian Ocean ... The equatorial current exists in the Indian Ocean only in the southern hemisphere, and the northern boundary is about 10 ° S. NS. Thus, it is displaced significantly to the south in comparison with other oceans, which is a consequence of the existence north of 10 ° S. NS. highly developed monsoon area. In the Indian Ocean, the SE trade wind lies 10 ° farther south than in the other two oceans, where its area reaches the equator, and the Indian Ocean Equatorial Current also lies 10 ° south. The coincidence of the Equatorial Current with the SE area of ​​the trade wind once again convinces us that the Equatorial currents in general are drift currents excited by the trade winds. The equatorial warm current runs from Australia to Madagascar in the winter of the northern hemisphere at a slightly higher speed; its average speed is about 35 nautical miles, and the highest is 50-60 nautical miles. The southern boundary of the current is poorly defined. At Madagascar, the current is divided, one branch runs to the north of the island and against Cape Delgado (10 ° S) on the coast of Africa, it is divided in turn into two parts (both cases of division of the current into parts are a consequence of the influence of the shape of the coast). Part of the current, going north along the coast of Africa, in the winter of the northern hemisphere does not reach the equator, but. having met the mousse current passing from the northern to the southern hemisphere, together with it, it forms the Equatorial countercurrent, which has already been mentioned above. The second part of the northern branch of the Equatorial Current, extending from Cape Delgado (eastern coast of Africa, 10 ° S lat.) To the south, forms the Mozambique Current, which is distinguished by a greater speed, especially in the winter of the northern hemisphere; the average speed is about 40 nautical miles, and a large one in winter, up to 100 nautical miles (on the other side of the strait, closer to Madagascar, the currents are less regular, often go to N and have a compensatory character). The Mozambican current, continuing to go on the S along the coast of Africa, passes into the Cape of Igolny (starting from 30 ° S lat.) - one of the strongest and most stable currents in the oceans. The average speed of the current is about 50 nautical miles, and the highest reaches 100 nautical miles (in the summer of the northern hemisphere, because at this time of the year E and SE winds blow in the Mozambique current). The needle current on the meridian of the cape of the same name (approximately 20 ° E) turns into S and E _ and washes with its branches on all sides the bank of Agulhas, which lies somewhat southeast of the cape (still at 36 ° S lat.). the current goes to W, and already at 38 ° S lat. it goes to E). Here this warm current meets cold waters flowing from the Atlantic Ocean and southern latitudes, as a result of which the surface water temperatures at close distances here often differ by 4-8 ° (to the southwest of the Newfoundland Bank, temperature differences reach 15 °). which contributes to the frequent formation of fogs here, as in the Newfoundland Bank. Further to the east, the Needle Current waters mix with cold oxen from the Atlantic Ocean to form the cold Indian Ocean Transverse Current going eastward at a speed of 10-25 nautical miles. The warm Madagascar Current joins the Cross Current from the north, representing a branch of from it at 20 ° S. NS. due to the meeting of the shore about. Madagascar (example of the influence of coastal contours on currents). The speed of this current is low, about 10-25 nautical miles. With its warm waters, mixing with the cold waters of the Cross Current, it determines the variability of water temperature along the entire northern edge of the latter. Approaching Australia, part of the Cross Current goes further east to the south of it, and part turns to N under the name of the West Australian Current at speeds of 15-30 nautical miles, this current is not stable and differs in low water temperature, completely similar to the Benguela Current in Atlantic Ocean. Approaching the tropics, the Western Australian Current turns to W and gives rise to the Equatorial Current, closing the circulation of surface waters in the southern hemisphere in the Indian Ocean. In the part of the ocean lying between the southern edge of the Sunda Archipelago and Australia, as well as along the shores of the latter up to the Torres Strait, tidal currents dominate. Indian Ocean currents... The Indian Ocean is poor in seas, there are only two of them: the Red Sea and the Persian Gulf. In the Red Sea, the currents do not have the correct character, but arise under the influence of winds, sometimes reaching speeds of up to 30-40 nautical miles. There are two currents in the Bab-el-Mandeb Strait, just like in the Dardanelles or the Bosphorus. The strait has a depth of about 200 m and in it, from the surface to a depth of about 120 m, a current flows from the Gulf of Aden to the Red Sea at a speed of up to 2-2.5 nautical miles per hour. Below 120 m, there is a reverse current from the Red Sea of ​​approximately the same speed. Tidal currents also exist here, as in Gibraltar, and exert their influence on the strengthening and weakening of permanent currents. In the Persian Gulf, in summer, the current flows from the ocean, and in winter from the bay to the ocean. Ebb and flow currents are of great importance here too.

Currents:

Benguela current- cold Antarctic current.

It arises south of the Cape of Good Hope as a branch of the Western Wind and goes to the north. Reaches the Namibaw area of ​​Africa.

Western Australian Current- cold current in the southeastern part of the Indian Ocean. It flows off the western shores of Australia from south to north, represents the northern branch of the Western Winds. In the tropical zone of the Southern Hemisphere, part of the Western Australian Current passes into the South Tradewind Current, and part of it dissipates in the Timor Sea.

The current speed is 0.7-0.9 km per hour, salinity is 35.5-35.70 grams per liter. The water temperature along the course varies from 19 to 26 ° C in February and from 15 to 21 ° C in August.

Madagascar current- warm surface current of the Indian Ocean off the eastern and southern shores of Madagascar; branch of the South Tradewind Current.

Directed to the south and southwest at a speed of 2-3 km / h. The average water temperature at the surface per year is up to 26 ° C. The salinity of the water is more than 35 ‰. In the south-west, it partly connects with the warm current of Cape Igolny.

Mozambican current- warm surface currents in the Mozambique Channel, in the western part of the Indian Ocean; branch of the South Tradewind Current. Directed to the south, along the coast of Africa, where it passes into the Current of Cape Agulhas.

North trade wind- warm surface currents in the Mozambique Channel, in the western part of the Indian Ocean; branch of the South Tradewind Current. Directed to the south, along the coast of Africa, where it passes into the Current of Cape Agulhas.

Speed ​​up to 2.8 km / h (from November to April). The average water temperature at the surface per year is up to 25 ° C. Salinity is 35 ‰.

North equatorial current- warm sea current in the Quiet, Atlantic and Indian oceans.

In the Pacific Ocean, the North Equatorial (North Tradewind) Current arises as a result of the deflection of the California Current and flows between 10 ° and 20 ° N latitude in a westerly direction until, in front of the east coast of the Philippines, it deflects and passes into the warm Kuroshio Current.

In the Atlantic Ocean, it arises from the Canary Current and flows between 10 ° and 30 ° north latitude in the northwest direction, being one of the sources of the Gulf Stream.

In the Indian Ocean, the direction of the North Equatorial Current depends on the season. During the winter months, during which the rainy season falls from the northeast, it is a slight westerly current along the Equator. During the summer months, when it rains from the southwest, the Somali current intensifies, flowing in a northeast direction along the coast of Africa, turning east, bypassing India.

Somali current-current in the Indian Ocean of the Somali Peninsula. The fastest current in the open ocean, can reach speeds of 12.8 km / h

Changes its direction in seasons, caused by monsoon winds. During the summer monsoon (July - August), with a south-westerly wind, it reaches a width of about 150 km and a thickness of about 200 m in the stream. In summer, waters rise from the depths along the eastern coast of Somalia. The water temperature sometimes drops to 13 ° (at the surface). In winter, the northeast monsoon interrupts the Somali current and turns it southwest. The rise of water from the depth practically stops.

The current of Cape Igolny, or the course of Agulhas- the warm western boundary current in the Southwest Indian Ocean, which is part of the westward South Equatorial Current. Mainly runs along the western coast of Africa. The current is narrow and fast (on the surface the speed can reach 200 cm / s).

Equatorial countercurrent- powerful countercurrent in the interval between the North trade wind and the South trade wind, observed in the equatorial region around the entire globe in the Pacific, Atlantic and Indian oceans.

Surface countercurrents in the Atlantic, Pacific and Indian Oceans have been known since the 19th century. These currents are directed to the east against the prevailing winds and against the movement of the main surface currents. Inter-trade countercurrents are caused by the transverse unevenness of the prevailing winds (trade winds), therefore, their speed and flow rate fluctuate significantly, up to disappearance, depending on the strength and uniformity of the winds.

In the middle of the 20th century, subsurface and even deep countercurrents were discovered. Including the powerful equatorial subsurface countercurrents of the Cromwell Pacific current and the Lomonosov current in the Atlantic oceans. Subsurface equatorial currents are caused by pressure gradients and flow in a narrow flow eastward under the westward trade wind current.

During the period of weakening of the trade winds, subsurface countercurrents can "come out" to the ocean surface and be observed as surface currents.

South Tradewind Current- named after the prevailing winds in the region - the trade winds blowing from the east to the west - the warm current in the World Ocean, passing through the southern tropical latitudes.

In the Pacific Ocean, it starts off the coast of South America, approximately in the Galapagos Islands, and goes west to the shores of New Guinea and Australia.

The northern boundary of the current ranges from 1 degree north latitude in summer to 3 degrees south latitude in winter.

At the western coast of the Pacific Ocean, the current splits into branches - part of the current turns to the east, merging into the Equatorial Countercurrent. Another major branch of the current is the East Australian Current, which begins off the coast of Australia.

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 ° east longitude meridian; with Tikhim - along the 146 ° 55 'meridian of east longitude. The northernmost point of the Indian Ocean lies at about 30 ° north latitude in the Persian Gulf. The Indian Ocean is approximately 10,000 km wide between the southern points of Australia and Africa.

Etymology

The ancient Greeks known to them the western part of the ocean with adjacent seas and bays was called the Eritrean Sea (ancient Greek Ἐρυθρά θάλασσα - Red, and in old Russian sources the Red Sea). Gradually, this name began to be attributed only to the nearest sea, and the ocean received its name from India, the most famous country at that time for its riches on the shores of the ocean. So Alexander the Great in the 4th century BC. NS. 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-mụhӣ̣t al-hindiy) - "Indian Ocean". Since the 16th century, the name Oceanus Indicus, introduced by the Roman scientist Pliny the Elder back in the 1st century, has been established - the Indian Ocean.

Physical and geographical characteristics

General information

The Indian Ocean is mainly located south of the Tropic of Cancer, between Eurasia in the north, Africa in the west, Australia in the east, and Antarctica in 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 Sava 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 from 35 ° S. NS. (based on the circulation of water and atmosphere) up to 60 ° S. NS. (by the nature of the bottom topography), refer 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%). Seas and main bays 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), Big Australian Gulf, Mawson Sea, Davis Sea, Commonwealth Sea, Sea of ​​Astronauts (the latter 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). The largest islands and archipelagos: Tasmania, Sri Lanka, Kerguelen archipelago, Andaman Islands, Melville, Mascarene Islands (Reunion, Mauritius), Kangaroo, Nias, Mentawai Islands (Siberut), Socotra, Groot Island, Comoros, Bater Tiwi Islands ( ), Zanzibar, Simeulue, Furno Islands (Flinders), Nicobar Islands, Qeshm, King, Bahrain Islands, Seychelles, Maldives, Chagos archipelago.

The history of the formation of the Indian Ocean

In the early Jurassic times, the ancient supercontinent of Gondwana began to split. 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 depression of the modern Indian Ocean began to form. During the Cretaceous period, the ocean floor expanded due to the movement of Hindustan to the north and a reduction in the area of ​​the Pacific and Tethys oceans. In the Late Cretaceous, the split of the united Australian-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 towards the Pacific stopped, but continued towards the Tethys Sea. At the end of the Eocene - the beginning of the Oligocene, the Indian subcontinent collided with the Asian continent.

Today, the movement of tectonic plates continues. The axis of this movement is the mid-oceanic rift zones of the African-Antarctic Ridge, the Central Indian Ridge and the Australian-Antarctic Rise. The Australian plate continues to move northward 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 moves northeast at a speed of 1-3 cm per year. The Somali plate continues to split off the African plate along the East African rift zone, which moves at a speed of 1-2 cm per year in a northeasterly direction. On December 26, 2004, in the Indian Ocean off the island of Simeolue, located off the northwestern coast of the island of Sumatra (Indonesia), there was the largest earthquake on record, with a magnitude of up to 9.3. The reason was the 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 shifted under the Burma plate. The earthquake caused a tsunami, which brought tremendous 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 Indian Ocean floor into three sectors: African, Indo-Australian and Antarctic. There are four mid-oceanic ridges: the West Indian, Arabian-Indian, Central Indian ridges and the Australian-Antarctic uplift. The West Indian Ridge is located in the southwestern part of the ocean. It is characterized by underwater volcanism, seismicity, a riftogenic crust and a rift structure of the axial zone; it is cut by several oceanic faults of submeridional strike. In the area of ​​the island of Rodrigues (Mascarene archipelago) there is a so-called triple junction, where the system of ridges is divided to the north into the Arabian-Indian ridge and to the southwest into the Central Indian ridge. The Arabian-Indian Ridge is composed of ultrabasic rocks; a number of submeridial-striking intersecting faults have been identified, with which very deep depressions (oceanic troughs) are associated with depths of up to 6.4 km. The northern part of the ridge is crossed by the most powerful Owen fault, along which the northern part of the ridge experienced a displacement of 250 km to the north. Further west, the rift zone continues in the Gulf of Aden and north-northwest in 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 metalliferous silts were found, associated with powerful hot (up to 70 ° C) and very salty (up to 350 ‰) juvenile waters.

In the southwest direction from the triple junction, the Central Indian Ridge extends, which has a well-defined rift and flank zones, ending in the south with the volcanic plateau Amsterdam with the volcanic islands of Saint-Paul and Amsterdam. From this plateau to the east-southeast extends the Australian-Antarctic uplift, which looks like a wide, weakly 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 Ocean Segment

The submarine edge of Africa has a narrow shelf and a distinct continental slope with marginal plateaus and continental foot. In the south, the African continent forms projections extended to the south: the Agulhas Bank, the Mozambique and Madagascar ridges, folded by the earth's crust of the continental type. The continental foot forms a sloping plain extending south along the coast of Somalia and Kenya, which continues into the Mozambique Channel and borders Madagascar to the east. In the east of the sector is the Mascarene ridge, in the northern part of which are the Seychelles.

The surface of the ocean floor in the sector, especially along the mid-ocean ridges, is dissected by numerous ridges and hollows associated with submeridional fault zones. There are many volcanic seamounts, most of which are built with coral superstructures in the form of atolls and underwater coral reefs. Between the mountain rises there are the ocean floor hollows with 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 fan system.

Indo-Australian Ocean Segment

The Indo-Australian segment covers half the area of ​​the Indian Ocean. In the west, in the meridional direction, the Maldives ridge passes, on the summit surface of which the Lakkadiv, Maldives and Chagos islands are located. The ridge is composed of continental type crust. Along the coast of Arabia and Hindustan, there is a very narrow shelf, a narrow and steep continental slope and a very wide continental foot, mainly formed by two giant cones of removal of turbid flows of the Indus and Ganges rivers. These two rivers carry 400 million tons of debris into the ocean. The Indian cone is pushed 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 4000 km from north to south. The Central Basin, the largest basin in the Indian Ocean, is located between the Maldives and the East Indian Ridges. Its northern part is occupied by the Bengal fan (from the Ganges River), to the southern border of which the abyssal plain adjoins. In the central part of the basin there is a small ridge Lanka and the seamount Afanasy Nikitin. To the east of the East Indian Ridge, there are the Cocos and West 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. In the south, it is bounded by the Western Australian Rise, which drops abruptly to the south and gently plunges under the bottom of the basin to the north. In the south, the Western Australian Rise is bounded by a steep scarp associated with the Diamantine Fault Zone. The Ralom zone combines deep and narrow grabens (the most significant are the Ob and Diamatina) and numerous narrow horsts.

The transitional area of ​​the Indian Ocean is represented by the Andaman trench and the deep-water Sunda trench, to which the maximum depth of the Indian Ocean (7209 m) is confined. The outer ridge of the Sunda Island Arc is the underwater Mentawai Ridge and its continuation in the form of the Andaman and Nicobar Islands.

Underwater outskirts of the Australian mainland

The northern part of the Australian continent is bordered by the 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 plateau). In the western part of the Western Australian Basin, the Zenith, Cuvier and other uplifts are located, which are pieces of a continental structure. Between the southern submarine margin of Australia and the Australian-Antarctic Rise, there is a small South Australian Basin, which is a flat abyssal plain.

Antarctic Ocean Segment

The Antarctic segment is limited by the West Indian and Central Indian ridges, and from the south by the shores of Antarctica. Under the influence of tectonic and glaciological factors, the Antarctic shelf is deepened. Large and wide canyons cut through a wide continental slope, along which supercooled waters flow from the shelf into abyssal depressions. The continental foot of Antarctica is distinguished by a wide and significant (up to 1.5 km) thickness of loose sediments.

The largest bulge 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. In 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, has a large hilly bottom relief. The Australian-Antarctic Basin, lying to the east of Kerguelen, is occupied by a flat plain in the southern part, and abyssal hills in the northern part.

Bottom sediments

The Indian Ocean is dominated by calcareous foraminiferal-coccolith deposits, which occupy more than half of the bottom area. The widespread 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 zones, as well as the relatively shallow depth of oceanic basins. Numerous mountain rises are also favorable for the formation of limestone sediments. In the deep-water parts of some basins (for example, Central, Western Australian) deep-water red clays occur. The equatorial belt is characterized by radiolarian oozes. In the southern cold part of the ocean, where conditions for the development of diatom flora are especially favorable, siliceous diatom deposits are present. Iceberg sediments are deposited near the Antarctic coast. At the bottom of the Indian Ocean, ferromanganese nodules are widespread, mainly confined to areas of red clay and radiolarian ooze.

Climate

In this region, four climatic zones are distinguished, elongated along the parallels. Under the influence of the Asian continent, a monsoon climate is established in the northern part of the Indian Ocean with frequent cyclones moving towards the coasts. High atmospheric pressure over Asia in winter causes the formation of a northeast monsoon. In summer, it is replaced by a humid southwestern monsoon, carrying air from the southern regions of the ocean. During the summer monsoon, winds are often stronger than 7 (with a repeatability 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 southeastern trade wind dominates, which does not extend north of 10 ° N in winter. The average annual temperature reaches 25 ° C. In the zone 40-45 ° S lat. Throughout the year, the western transport of air masses is characteristic, it is especially strong in temperate latitudes, where the recurrence of stormy 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 regions 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 typical from 45 degrees and further 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 an increased cloudiness (more than 5 points). The least rainfall is observed in the tropical regions of the southern hemisphere, especially in the eastern part. In the northern hemisphere, clear weather is typical for the Arabian Sea for most of the year. The maximum cloud cover 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 is established, beginning in the Bay of Bengal. South of 10 ° N. NS. this current passes into the Western Current, crossing the ocean from the Nicobar Islands to the shores of East Africa. Further, it branches: one branch goes north into the Red Sea, the other - south to 10 ° S. NS. 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 southeastern monsoon provides 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 a powerful Somali current, to which the current from the Red Sea joins in the Gulf of Aden. In the Bay of Bengal, the summer monsoon current is divided into north and south, which flows into the South Tradewind Current.

In the southern hemisphere, the currents are constant, without seasonal fluctuations. Driven by the trade winds, the South Tradewind Current crosses the ocean from east to west to Madagascar. It intensifies in the winter (for the southern hemisphere), due to the additional feeding of the waters of the Pacific Ocean flowing along the northern coast of Australia. At Madagascar, the South Passat Current forks, giving rise to the Equatorial Countercurrent, Mozambique and Madagascar currents. Merging southwest of Madagascar, they form the warm Agulhas current. The southern part of this current goes into the Atlantic Ocean, and part of it flows in during the Western 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 the Great Australian Bays, and in Antarctic waters.

The northern part of the Indian Ocean is characterized by a predominance of semi-diurnal tide. The amplitudes of the tide in the open ocean are small and on average 1 m islands, in shallow bays. In the Bay of Bengal, the tide value is 4.2-5.2 m, near Mumbai - 5.7 m, near Yangon - 7 m, in 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 of water

In the equatorial Indian Ocean, surface water temperatures are around 28 ° C year-round 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 Red Sea sets maximum temperatures for the entire Indian Ocean - up to 30-31 ° C. High winter water temperatures (up to 29 ° C) are characteristic of the coast 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 one. Water temperatures below 0 ° C in summer are noted south of 60 ° S. NS. Ice formation in these areas begins in April and the fast ice thickness 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 widespread, sometimes setting north of 40 ° S. NS.

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 belt, especially in the eastern regions, and in the northern hemisphere also in the Arabian Sea. In the neighboring Bay of Bengal, due to the desalting effect of the Ganges runoff with Brahmaputra and Ayeyarwaddy, salinity is reduced to 30-34 ‰. Increased salinity correlates with the zones of maximum evaporation and the least amount of atmospheric precipitation. Decreased salinity (less than 34 ‰) is characteristic of the Arctic waters, where the strong desalination effect of melt glacial waters affects. 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. NS. This language disappears in the summer. In Arctic waters in winter, salinity slightly increases due to salinization of the waters in the process of ice formation. Salinity decreases from the surface to the bottom of the ocean. The 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. NS. distinguish the central and equatorial surface and subsurface water masses and their underlying (deeper than 1000 m) deep. To the north up to 15-20 ° S. NS. the central water mass is spreading. Temperature varies with depth from 20-25 ° C to 7-8 ° C, salinity 34.6-35.5 ‰. Surface layers north of 10-15 ° S. NS. 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 horizontal and vertical movement rates. In the southern part of the ocean, there are 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 ‰). Deep water masses are divided into: very cold circulating masses, formed by the sinking of the Arctic water masses and the influx of circulating waters from the Atlantic Ocean; South Indian, formed as a result of subsidence of 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 widespread, forming from the Antarctic supercooled and dense salty waters of the Red Sea and the Persian Gulf.

Flora and fauna

The flora and fauna of the Indian Ocean is unusually diverse. The tropical region stands out for the richness of plankton. The unicellular alga Trichodesmia (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 organisms glowing at night: peridinia, some species of jellyfish, ctenophores, tunicates. There are abundant brightly colored siphonophores, including poisonous physalia. In temperate and arctic waters, the main representatives of plankton are copepods, euphausids and diatoms. The most abundant fish in the Indian Ocean are coryphans, tuna, notothenium and a variety of sharks. From reptiles there are several species of giant sea turtles, sea snakes, from mammals - cetaceans (toothless and blue whales, sperm whales, dolphins), seals, elephant seals. Most cetaceans live in the temperate and circumpolar regions, where, due to the intensive mixing of waters, favorable conditions for the development of planktonic organisms arise. Birds are represented by albatrosses and frigates, as well as several species of penguins that inhabit the coasts of South Africa, Antarctica and islands lying in the temperate zone of the ocean.

The flora of the Indian Ocean is represented by brown (sargassum, turbinaria) and green algae (caulerpa). The limestone algae of lithothamnia and khalemeda also flourish and participate together with corals in the construction of reef buildings. In the course of the 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 mangrove thickets. Especially such thickets are characteristic of river mouths and occupy significant areas in Southeast Africa, western Madagascar, Southeast Asia and other regions. For temperate and Antarctic waters, red and brown algae are most characteristic, mainly from the groups of fucus and laminaria, porphyry, and gelidium. In the circumpolar regions of the southern hemisphere, giant macrocystis are found.

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

Ecological problems

Human economic activities in the Indian Ocean have 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 - were still preserved, but their number was greatly reduced. Since the 1985-1986 season, the International Whaling Commission has introduced a complete moratorium on all types of commercial whaling. 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 extinction and 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 wastes from the nuclear industry. The routes of oil tankers, transporting oil from the Persian Gulf countries, run across the ocean. Any major accident can lead to an environmental disaster and the death of many animals, birds and plants.

Indian Ocean States

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

• 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 not included in 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 are one of the areas of settlement of the most ancient peoples and the emergence of the first river civilizations. In ancient times, vessels such as junks and catamarans were used by people for sailing, with passing monsoons from India to East Africa and back. The Egyptians in 3500 BC carried on a brisk maritime trade with the countries of the Arabian Peninsula, India and East Africa. The countries of Mesopotamia 3000 years BC made sea voyages to Arabia and India. From the 6th century BC, the Phoenicians, according to the testimony of 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 carried out sea trade from the mouth of the Indus along the eastern coast of Africa. At the end of the Indian campaign of Alexander the Great in 325 BC, the Greeks sailed for many months between the mouths of the Indus and Euphrates rivers in a huge fleet with a five-thousand-strong team in severe storm conditions. Byzantine merchants in the IV-VI centuries penetrated in the east to India, and in the south to Ethiopia and Arabia. Beginning in the 7th century, Arab sailors began intensive exploration of the Indian Ocean. They perfectly explored the coast of East Africa, West and East India, Socotra, Java and Ceylon, visited the Laccadive and Maldives, Sulawesi, Timor and others.

At the end of the 13th century, the Venetian traveler Marco Polo on his way back from China crossed the Indian Ocean from the Strait of Malacca to the Strait of Hormuz, visiting Sumatra, India, Ceylon. The journey was described in the "Book on the diversity of the world", which had a significant impact on navigators, cartographers, writers of the Middle Ages in Europe. Chinese junks made treks along the Asian shores of the Indian Ocean and reached the Eastern shores of Africa (for example, the seven voyages of Zheng He in 1405-1433). The expedition led by the Portuguese navigator Vasco da Gama, circling Africa from the south, passing along the eastern coast of the continent in 1498, reached India. In 1642, the Dutch East India Trading Company organized a two-ship expedition 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 a mainland. In 1772, a British expedition led by James Cook penetrated the southern Indian Ocean to 71 ° S. sh., while obtaining extensive scientific material on hydrometeorology and oceanography.

From 1872 to 1876, the first scientific oceanic expedition took place on the English sailing-steam corvette Challenger, new data were obtained on the composition of ocean waters, flora and fauna, the bottom topography and soils, the first map of the ocean depths was compiled and the first collection was collected deep-sea animals. A round-the-world expedition on the Russian sailing-propeller corvette "Vityaz" in 1886-1889 under the leadership of the oceanographer S.O. Makarov carried out a large-scale research work in the Indian Ocean. A great contribution to the study of the Indian Ocean was made by oceanographic expeditions aboard the German ships Valkyrie (1898-1899) and Gauss (1901-1903), 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 at UNESCO, an international Indian Ocean expedition was carried out. She was the largest expedition ever to sail 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. 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 vessel "Glomar Challenger" has carried out regular deep-water 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 American National Geophysical Data Center, with a map resolution of 3-4 km and a depth accuracy of ± 100 m.

Economic significance

Fishing and marine industries

The importance of the Indian Ocean for the world fishing industry is small: catches here account for only 5% of the total volume. The main commercial fish of the local waters are tuna, sardine, anchovy, several species of sharks, barracuda and rays; shrimp, lobster and lobster are also caught here. Until recently, whaling, intensive in the southern regions of the ocean, is rapidly curtailing, due to the almost complete extermination of some species of whales. Pearls and mother-of-pearl are mined on the northwest coast of Australia, in Sri Lanka and the Bahrain Islands.

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 with 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, mineral raw materials, oil, asbestos, tea, raw sugar, cashew nuts, import: machinery and equipment, industrial goods, food), Dar es Salaam (export : cotton, coffee, sisal, diamonds, gold, oil products, cashew nuts, cloves, tea, meat, leather, import: industrial 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, footwear, carpets, rice, fish, import: coal, coke, oil products , mineral fertilizers, equipment, metals, grain, food, paper, jute, tea, sugar), Mumbai (export: manganese and iron ore, oil products, sugar, wool, leather, cotton, fabrics, import: oil, coal, cast iron, equipment, grain, chemicals, industrial goods), Colombo, Chennai (iron ore, coal, granite, fertilizers, oil products, containers, cars), Kolkata (export: coal, iron and copper ore, tea, import: industrial goods, grain, food, equipment), Chittagong (clothing, jute, leather, tea, chemicals), Yangon (export: rice, hardwood, non-ferrous metals, cake, legumes, rubber, precious stones, imports: coal, machinery, food, textiles), Perth Fremantle (exports: ore, alumina, coal, coke, caustic soda, phosphorus raw materials, imports: oil, equipment).

Minerals

The most important minerals in the Indian Ocean are oil and natural gas. Their deposits are located on the shelves of the Persian and Suez Gulfs, in the Bass Strait, on the shelf of the Indian subcontinent. Ilmenite, monazite, rutile, titanite and zirconium are exploited on the coasts of India, Mozambique, Tanzania, South Africa, the islands of Madagascar and Sri Lanka. 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 being exploited on an industrial scale.

Recreational resources

The main recreational areas of the Indian Ocean: the Red Sea, the west coast of Thailand, the islands of Malaysia and Indonesia, the island of Sri Lanka, the region of coastal urban agglomerations of India, the east coast of Madagascar, the Seychelles and Maldives. Among the countries of the Indian Ocean with the largest flow of tourists (as of 2010 by 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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