Indian Ocean- 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 located in the Sunda Trench (7729 m).
- Area: 76,170 thousand km²
- Volume: 282,650 thousand km³
- Greatest 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. Border with Atlantic Ocean passes along the 20° meridian of eastern longitude; from Quiet - along 146°55’ meridian of eastern longitude. The northernmost point of the Indian Ocean is located at approximately 30°N 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 called the western part of the ocean known to them with the adjacent seas and bays the Erythraean 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 was named after India, the country most famous at that time for its wealth on the ocean shores. So Alexander the Great in the 4th 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: al-muhit al-hindiy) - “Indian Ocean”. Since the 16th century, the name Oceanus Indicus (Latin Oceanus Indicus) - Indian Ocean, introduced by the Roman scientist Pliny the Elder back in the 1st century, has been established.
Physiographic 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 (Donning Maud Land)). Border with Pacific Ocean passes: 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 the island of Sumatra, the Sunda Strait, the southern coast of the island 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 the northern border from 35° south. w. (based on the circulation of water and atmosphere) up to 60° south. w. (by the nature of the bottom topography) are classified as 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 ocean coast (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), Great Australian Gulf, Mawson Sea, Davis Sea, Commonwealth Sea, Cosmonaut Sea (the last four are sometimes referred to as the Southern Ocean). 
Some islands - for example, Madagascar, Socotra, the Maldives - are fragments of ancient continents, others - Andaman, Nicobar or Christmas Island - are of volcanic origin. The largest island of 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, Groot Island, Comoros, Tiwi Islands (Bathurst ), Zanzibar, Simelue, Furneaux Islands (Flinders), Nicobar Islands, Qeshm, King, Bahrain Islands, Seychelles, Maldives, Chagos Archipelago. 
History of the formation of the Indian Ocean
In Early Jurassic times, 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 the 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 the reduction in the area of the Pacific and Tethys oceans. In the Late Cretaceous, the split of the single 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 expansion of the Indian Ocean towards the Pacific stopped, but continued towards the Tethys Sea. At the end of the Eocene - beginning of the Oligocene, a collision of Hindustan with the Asian continent occurred. 
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 Australasian-Antarctic Rise. The Australian plate continues to move north at a speed 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 speed of 1-3 cm per year. The Somali Plate continues to break away from the African Plate along the East African Plate rift zone, which moves at a speed of 1-2 cm per year in a northeast direction. On December 26, 2004, the largest earthquake in the history of observations, with a magnitude of up to 9.3, occurred in the Indian Ocean off the island of Simeulue, located off the northwestern coast of the island of Sumatra (Indonesia). The reason was a shift of about 1200 km (according to some estimates - 1600 km) earth's crust 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 bottom topography of the Indian Ocean
Mid-ocean ridges
Mid-ocean ridges divide the floor 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 and Australian-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 the rift structure of the axial zone; it is cut by several oceanic faults of submeridional strike. In the area of Rodriguez Island (Mascarene archipelago) there is a so-called triple junction, where the ridge system 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 ultramafic rocks; a number of transecting faults of submeridial strike have been identified, with which very deep depressions (ocean 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 section of the ridge experienced a displacement of 250 km to the north. Further west the rift zone continues in the Gulf of Aden and to the north-northwest in the Red Sea. Here the rift zone is composed of carbonate sediments with volcanic ash. In the rift zone of the Red Sea, strata of evaporites and metal-bearing silts were discovered, associated with powerful hot (up to 70 °C) and very saline (up to 350 ‰) juvenile waters. 
In the southwest direction from the triple junction extends the Central Indian Ridge, which has a well-defined rift and flank zones, ending in the south with the volcanic Amsterdam plateau with the volcanic islands of Saint-Paul and Amsterdam. From this plateau, the Australian-Antarctic Rise extends to the east-southeast, looking 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 segment of the ocean
The underwater margin of Africa has a narrow shelf and a clearly defined continental slope with marginal plateaus and a continental foot. On South African continent forms protrusions extended to the south: the Agulhas Bank, Mozambique and Madagascar ridges, composed of continental-type earth crust. The continental foot forms a sloping plain that expands to the south along the coasts of Somalia and Kenya, which continues into the Mozambique Channel and borders Madagascar on the east. The Mascarene Range runs along the east of the sector, in the northern part of which are the Seychelles Islands.
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 uplifts there are basins of the ocean floor with hilly and mountainous terrain: Agulhas, Mozambique, Madagascar, Mascarene and Somali. In the Somali and Mascarene basins, extensive flat abyssal plains are formed, which receive a significant amount of terrigenous and biogenic sedimentary material. In the Mozambique Basin there is an underwater valley of the Zambezi River with a system of alluvial fans.
Indo-Australian ocean segment
The Indo-Australian segment occupies half the area of the Indian Ocean. In the west, in the meridional direction, the Maldives ridge runs, on the summit surface of which the islands of Laccadive, Maldives and Chagos are located. The ridge is composed of bark continental type. Along the coasts of Arabia and Hindustan stretch a very narrow shelf, a narrow and steep continental slope and a very wide continental foot, mainly formed by two giant fans of turbidity flows of the Indus and Ganges rivers. These two rivers each carry 400 million tons of debris into the ocean. The Indus Cone extends far into the Arabian Basin. But only South part This basin is occupied by a flat asbyssal plain with individual seamounts.
Almost exactly 90°E. The blocky oceanic East Indian Ridge stretches for 4000 km from north to south. Between the Maldives and East Indian ridges is the Central Basin, the largest basin in the Indian Ocean. Its northern part is occupied by the Bengal fan (from the Ganges River), the southern border of which is adjacent to the abyssal plain. In the central part of the basin there is a small ridge called Lanka and the Afanasy Nikitin underwater mountain. To the east of the East Indian Ridge are the Cocos and Western Australian basins, separated by the blocky sublatitudinal oriented Cocos uplift with the Cocos and Christmas islands. In the northern part of the Cocos Basin there is a flat abyssal plain. From the south it is bounded by the Western Australian Uplift, which abruptly breaks off to the south and gently plunges under the bottom of the basin to the north. From the south, the Western Australian Rise is limited by a steep scarp associated with the Diamantina fault zone. The ralom zone combines deep and narrow grabens (the most significant are Ob and Diamatina) and numerous narrow horsts. 
The transitional region of the Indian Ocean is represented by the Andaman Trench and the deep-sea Sunda Trench, to which it is confined maximum depth Indian Ocean (7209 m). The outer ridge of the Sunda island arc is the underwater Mentawai Ridge and its extension in the form of the Andaman and Nicobar Islands.
The underwater edge of the Australian mainland
Northern part Australian continent 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 Naturalist plateaus). In the western part of the Western Australian Basin there are the Zenith, Cuvier and other rises, which are pieces of the continental structure. Between the southern underwater 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 has been deepened. The wide continental slope is cut through by large and wide canyons, through which supercooled waters flow 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 sediments.
The largest protrusion of the Antarctic continent is the Kerguelen Plateau, as well as the volcanic rise of 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, has a coarsely hilly bottom topography. The Australian-Antarctic Basin, which lies 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-coccolithic deposits, occupying more than half of the bottom area. The widespread development of biogenic (including coral) calcareous deposits is explained by the location of a large part of the Indian Ocean within the tropical and equatorial belts, as well as the relatively shallow depth of the oceanic basins. Numerous mountain uplifts are also favorable for the formation of calcareous sediments. In the deep-sea parts of some basins (for example, Central, Western Australian) deep-sea red clays occur. The equatorial belt is characterized by radiolarian oozes. In the cold southern part of the ocean, where conditions for the development of diatom flora are especially favorable, siliceous diatom deposits are present. Iceberg sediments are deposited off the Antarctic coast. At the bottom of the Indian Ocean, ferromanganese nodules have become widespread, confined mainly to areas of deposition of red clays and radiolarian oozes.
Climate
In this region there are four climatic zones, stretched along parallels. Under the influence of the Asian continent, a monsoon climate with frequent cyclones moving towards the coasts is established in the northern part of the Indian Ocean. High atmospheric 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, winds of more than force 7 (with a frequency of 40%) often occur. 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 winter time does not extend north of 10°N. Average annual temperature reaches 25 °C. In the zone 40-45°S. Throughout the year, westerly transport of air masses is characteristic, especially strong in temperate latitudes, where the frequency 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 areas of Madagascar and the Mascarene Islands. In subtropical and temperate latitudes in summer the temperature reaches 10-22 °C, and in winter - 6-17 °C. Strong winds are typical 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 here (more than 5 points). The lowest 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 most of the year in the Arabian Sea. 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 the monsoon circulation. In winter, the South-West Monsoon Current is established, starting in the Bay of Bengal. South of 10° N. w. this current turns into the Western Current, crossing the ocean from the Nicobar Islands to the coast East Africa. Then it branches: one branch goes north to the Red Sea, the other goes south to 10° S. w. and, turning 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 that the entire mass of surface water moves eastward, and the Equatorial Countercurrent disappears. The summer monsoon current begins off the coast of Africa with the powerful Somali Current, which is joined by a current from the Red Sea in the Gulf of Aden area. In the Bay of Bengal, the summer monsoon current is divided into northern and southern, which flows into the South trade wind current.
In the southern hemisphere, currents are constant, without seasonal fluctuations. Driven by trade winds, the Southern Trade Wind Current crosses the ocean from east to west towards Madagascar. It intensifies in winter (for the southern hemisphere) due to additional supply from the Pacific Ocean waters flowing along the northern coast of Australia. Near Madagascar, the Southern Trade Wind Current branches, giving rise to the Equatorial Countercurrent, the 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 into 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 Bay of Bengal and the Great Australian Bay, and in the Antarctic waters.
The northern part of the Indian Ocean is characterized by a predominance of semi-diurnal tides. Tide amplitudes in the open ocean are small and average 1 m. In the Antarctic and subantarctic zones, the tidal amplitude decreases from east to west from 1.6 m to 0.5 m, and near the coast they increase to 2-4 m. Maximum amplitudes are observed between islands, in shallow bays. In the Bay of Bengal, the tidal range 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 tidal range is about 1-3 m.
Temperature, water salinity
In the equatorial zone of the Indian Ocean, the surface water temperature is about 28 °C all 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 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 observed south of 60°S. w. Ice formation in these areas begins in April and the thickness of 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. Icebergs are common in the southern Indian Ocean, sometimes reaching north of 40° S. w.
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 with the Brahmaputra and Irrawaddy, salinity is reduced to 30-34 ‰. Increased salinity correlates with zones of maximum evaporation and the least amount of precipitation. Low salinity (less than 34 ‰) is typical for Arctic waters, where the strong desalinating 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 transported by the monsoon current, forming a tongue of low salinity along 5° N. w. In summer this language disappears. In Arctic waters in winter, salinity increases slightly due to salinization of waters during the process of ice formation. From the surface to the bottom of the ocean, salinity decreases. 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. w. distinguish central and equatorial surface and subsurface water masses and underlying deep water masses (deeper than 1000 m). North to 15-20° S. w. The central water mass spreads. The temperature varies with depth from 20-25 °C to 7-8 °C, salinity 34.6-35.5 ‰. Surface layers north of 10-15° S. w. constitute an 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 waters, formed by the descent of Arctic water masses and the influx of circulation waters from the Atlantic Ocean; South Indian, formed as a result of the subsidence of subarctic surface waters; North Indian, formed by dense waters flowing from the Red Sea and the Gulf of Oman. Below 3.5-4 thousand m, bottom water masses are common, 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 are incredibly diverse. The tropical region is distinguished by the richness of plankton. The unicellular alga Trichodesmium (cyanobacteria) is especially abundant, due to which the surface layer of water becomes very cloudy and changes its color. Indian Ocean plankton features big number organisms that glow at night: peridines, some types of jellyfish, ctenophores, tunicates. Brightly colored siphonophores are abundant, including poisonous physalia. In temperate and arctic waters, the main representatives of plankton are copepods, euphausids and diatoms. The most numerous fish of the Indian Ocean are coryphens, tunas, nototheniids and various sharks. Among reptiles there are several species of giant sea turtles, sea snakes, and among mammals there are cetaceans (toothless and blue whales, sperm whales, dolphins), seals, and elephant seals. Most cetaceans live in temperate and subpolar regions, where, due to intense mixing of waters, favorable conditions for the development of planktonic organisms. Birds include albatross and frigatebirds, as well as several species of penguins that inhabit the coasts South Africa, Antarctica and the islands lying in temperate zone ocean. 
The flora of the Indian Ocean is represented by brown plants (sargassum, turbinaria) and green algae(caulerpa). The calcareous algae lithothamnia and halimeda also develop luxuriantly, which 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 the phytocenosis formed by mangroves. Such thickets are especially characteristic of river mouths and occupy significant areas in Southeast Africa, western Madagascar, Southeast Asia and other areas. For temperate and Antarctic waters, the most characteristic are red and brown algae, mainly from the fucus and kelp groups, porphyry, and gelidium. Giant macrocystis are found in the polar regions of the southern hemisphere. 
Zoobenthos is represented by a variety of mollusks, calcareous and flint sponges, echinoderms ( sea urchins, starfish, brittle stars, sea cucumbers), numerous crustaceans, hydroids, and bryozoans. Coral polyps are widespread in the tropical zone.
Ecological problems
Human activities in the Indian Ocean have led to the pollution of its waters and a reduction in 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 numbers were greatly reduced. Since the 1985-1986 season International Commission The whale industry 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 for the first time formed the idea that they could cause the extinction of other animals. 
A great danger in the ocean is water pollution with oil and oil products (the main pollutants), some heavy metals and nuclear industry waste. The routes of oil tankers transporting oil from the Persian Gulf countries lie across the ocean. Any major accident can lead to environmental disaster and the death of many animals, birds and plants.
Indian Ocean states
States along the Indian Ocean borders (clockwise):
- South African Republic,
- Mozambique,
- Tanzania,
- Kenya,
- Somalia,
- Djibouti,
- Eritrea,
- Sudan,
- Egypt,
- Israel,
- Jordan,
- Saudi Arabia,
- Yemen,
- Oman,
- United United Arab Emirates,
- Qatar,
- Kuwait,
- Iraq,
- Iran,
- Pakistan,
- India,
- Bangladesh,
- Myanmar,
- Thailand,
- Malaysia,
- Indonesia,
- East Timor,
- Australia.
Located in the Indian Ocean 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.
History of the study
The shores of the Indian Ocean are one of the areas where ancient peoples settled and the first river civilizations emerged. In ancient times, vessels such as junks and catamarans were used by people to sail under the monsoons from India to East Africa and back. The Egyptians, 3500 BC, conducted brisk maritime trade with the countries of the Arabian Peninsula, India and East Africa. The Mesopotamian countries made sea voyages to Arabia and India 3000 BC. From the 6th century BC, the Phoenicians, according to the Greek historian Herodotus, carried out sea voyages from the Red Sea across the Indian Ocean to India and around Africa. IN VI-V 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 difficult storm conditions, made a months-long voyage between the mouths of the Indus and Euphrates rivers. Byzantine merchants in the 4th-6th centuries penetrated into India in the east, and into Ethiopia and Arabia in the south. Beginning in the 7th century, Arab sailors began intensive exploration of the Indian Ocean. They perfectly studied the coast of East Africa, Western and Eastern India, the islands of Socotra, Java and Ceylon, visited the Laccadive and Maldives, the islands of Sulawesi, Timor and others. 
IN end of XIII century, the Venetian traveler Marco Polo, on his way back from China, passed through the Indian Ocean from the Strait of 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 influence on sailors, 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 shores of Africa (for example, the seven voyages of Zheng He in 1405-1433). An expedition led by the Portuguese navigator Vasco da Gama, circumnavigating 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, it was explored central part Indian Ocean and it has been proven that Australia is a continent. In 1772, a British expedition under the command of James Cook penetrated the southern Indian Ocean to 71° S. sh., and extensive scientific material on hydrometeorology and oceanography was obtained.
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, bottom topography and soils, the first map of ocean depths was compiled and the first collection was collected deep sea animals. Around the World Expedition on the Russian sailing-screw corvette "Vityaz" of 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 on the German ships Valkyrie (1898-1899) and Gauss (1901-1903), on the English ship Discovery II (1930-1951), and the Soviet expedition 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. It was the largest expedition ever to operate in the Indian Ocean. The oceanographic work program 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 the hydrology, hydrochemistry, meteorology, geology, geophysics and biology of the Indian Ocean. Since 1972, regular deep-sea drilling, work to study the movement of water masses at great depths, and biological research have been carried out on the American vessel Glomar Challenger.
In recent decades, numerous measurements of the ocean have been carried out using space satellites. The result was released in 1994 by American National Center geophysical data bathymetric atlas of the oceans with a map resolution of 3-4 km and depth accuracy of ±100 m.
Economic significance
Fisheries and marine industries
The importance of the Indian Ocean for global fisheries is small: catches here account for only 5% of the total. The main commercial fish in the local waters are tuna, sardines, anchovies, several species of sharks, barracudas and stingrays; Shrimp, lobster and lobster are also caught here. Until recently, whaling, which was intense in the southern regions of the ocean, is quickly curtailed due to the almost complete extermination of some species of whales. Pearls and mother-of-pearl are mined on the northwestern coast of Australia, Sri Lanka and the Bahrain Islands. 
Transport routes
The most important transport routes in 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 are: Mozambique, Bab el-Mandeb, Hormuz, Sunda. The Indian Ocean is connected by the artificial Suez Canal to the Mediterranean Sea of the Atlantic Ocean. All the major cargo flows of the Indian Ocean converge and diverge in the Suez Canal and the Red Sea. Major ports: Durban, Maputo (export: ore, coal, cotton, minerals, oil, asbestos, tea, raw sugar, cashew nuts, import: machinery and equipment, industrial goods, food), Dar es Salaam (export : cotton, coffee, sisal, diamonds, gold, petroleum 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, shoes, carpets, rice, fish, import: coal, coke, petroleum products , mineral fertilizers, equipment, metals, grain, food, paper, jute, tea, sugar), Mumbai (export: manganese and iron ores, petroleum products, sugar, wool, leather, cotton, fabrics, import: oil, coal, cast iron, equipment, grain, chemicals, industrial goods), Colombo, Chennai (iron ore, coal, granite, fertilizers, petroleum products, containers, cars), Kolkata (export: coal, iron and copper ores, tea, import: industrial 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, machinery, food, textiles), Perth-Fremantle (export: ores, alumina, coal, coke, caustic soda , phosphorus raw materials, import: oil, equipment). 
Minerals
The most important mineral resources of 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, and 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. There are deposits of barite and phosphorite off the coast of India and Australia, and deposits of cassiterite and ilmenite are exploited on an industrial scale in the offshore zones of Indonesia, Thailand and Malaysia. 
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 coastal urban agglomerations of India, the east coast of the island of Madagascar, the Seychelles and the Maldives. Among the Indian Ocean countries with the largest flow of tourists (according to 2010 data from the World Tourism Organization) are: 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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Less extensive than Quiet and. Its area is 76 million km2. This ocean is widest in the Southern Hemisphere, and in the Northern Hemisphere it looks like a large sea cutting deeply into the land. It was the large sea that people imagined the Indian Ocean from ancient times right up to.
The shores of the Indian Ocean are one of the areas of ancient civilizations. Scientists believe that navigation in it began earlier than in other oceans, approximately 6 thousand years ago. The Arabs were the first to describe ocean routes. The accumulation of information about the Indian Ocean began from the time of voyage (1497-1499). IN late XVIII century, the first soundings of its depths were carried out by an English navigator. Comprehensive study of the ocean began at the end of the 19th century. The largest studies were carried out by the British expedition on the Challenger ship. Nowadays, dozens of expeditions from different countries are studying the nature of the ocean and revealing its riches.
The average ocean depth is about 3,700 meters, and the maximum reaches 7,729 meters in the Java Trench. In the western part of the ocean there is an underwater ridge, connecting to the south with the Mid-Atlantic Ridge. Deep faults and areas on the ocean floor are confined to the center of the ridge in the Indian Ocean. These faults continue in and out onto land. The ocean floor is crossed by numerous rises.
Location: The Indian Ocean is bounded from the north by Eurasia, from the west by the eastern coast of Africa, from the east by the western coast of Oceania and from the south by the waters of the South Sea, the border of the Atlantic and Indian Oceans runs along the 20° meridian. d., between the Indian and Pacific Oceans - along the 147° meridian east. d.
Square: 74.7 million km2
Average depth: 3,967 m.
Greatest depth: 7729 m (Sonda, or Java, trench).
: from 30 ‰ to 37 ‰.
Additional Information: in the Indian Ocean there are the islands of Sri Lanka, Socotra, Laccadive, Maldives, Andaman and Nicobar, Comoros, and some others.
From the tropics to the ice of Antarctica
The Indian Ocean is located between four continents - Eurasia (the Asian part of the continent) in the north, Antarctica in the south, Africa in the west and in the east with Australia and a group of islands and archipelagos located between the Indochina Peninsula and Australia.
Most of the Indian Ocean is located in the southern hemisphere. The border with the Atlantic Ocean is determined by a conventional line from Cape Agulhas (the southern point of Africa) along the 20th meridian to Antarctica. The border with the Pacific Ocean runs from the Malacca Peninsula (Indochina) to the northern point of Sumatra Island, then along the line. connecting the islands of Sumatra, Java, Bali, Sumba, Timor and New Guinea. The border between New Guinea and Australia runs through the Torres Strait, to the south of Australia - from Cape Howe to the island of Tasmania and along its western coast, and from Cape Yuzhny (the southernmost point of the island of Tasmania) strictly along the meridian to Antarctica. The Indian Ocean does not border the Arctic Ocean.
You can see a complete map of the Indian Ocean.
The area occupied by the Indian Ocean is 74,917 thousand sq. km - it is the third largest ocean. The ocean coastline is slightly indented, so there are few marginal seas on its territory. In its composition, one can distinguish only such seas as the Red Sea, the Persian and Bengal Bays (in fact, these are huge marginal seas), Arabian Sea, Andaman Sea, Timor and Arafura Seas. The Red Sea is the internal sea of the basin, the rest are marginal.
The central part of the Indian Ocean consists of several deep-sea basins, among which the largest are the Arabian, Western Australian, and African-Antarctic. These basins are separated by extensive underwater ridges and uplifts. Deepest point Indian Ocean - 7130 m located in the Sunda Trench (along the Sunda island arc). The average depth of the ocean is 3897 m.
The bottom topography is quite monotonous, East End smoother than the western one. There are many shoals and banks in the area of Australia and Oceania. The bottom soil is similar to the soil of other oceans and consists of the following types: coastal sediments, organic silt (radiolar, diatomaceous earth) and clay at great depths (the so-called “red clay”). Coastal sediments are sand located in the shallows to a depth of 200-300 m. Silty sediments can be green, blue (near rocky coasts), brown (volcanic areas), lighter (due to the presence of lime) in areas of coral structures. Red clay occurs at depths greater than 4500 m. It has a red, brown, or chocolate color.
In terms of the number of islands, the Indian Ocean is inferior to all other oceans. The largest islands: Madagascar, Ceylon, Mauritius, Socotra and Sri Lanka are fragments of ancient continents. In the central part of the ocean there are groups of small islands of volcanic origin, and in tropical latitudes there are groups of coral islands. The most famous groups of islands: Amirante, Seychelles, Comorne, Reunion, Maldives, Cocos.
Water temperature In the ocean, climate zones determine currents. The cold Somali Current lies off the coast of Africa, here the average water temperature is +22-+23 degrees C, in the northern part of the ocean the temperature of the surface layers can rise to +29 degrees C, at the equator - +26-+28 degrees C, according to As you move south, it drops to -1 degrees C off the coast of Antarctica.
The flora and fauna of the Indian Ocean are rich and diverse. Many tropical coasts are mangroves, where special communities of plants and animals have formed, adapted to regular flooding and drying. Among these animals one can note numerous crabs and interesting fish- a mudskipper that inhabits almost all the mangroves of the ocean. Shallow tropical waters are favored by coral polyps, including many reef-building corals, fish and invertebrates. In temperate latitudes, in shallow waters, red and brown algae grow in abundance, among which the most numerous are kelp, fucus and giant macrocysts. Phytoplankton is represented by peridinians in tropical waters and diatoms in temperate latitudes, as well as blue-green algae, which form dense seasonal aggregations in some places.
Among the animals living in the Indian Ocean, the largest number of crustaceans are rootworms, of which there are over 100 species. If you weigh all the rootpods in the waters of the ocean, their total mass will exceed the mass of all its other inhabitants.
Invertebrate animals are represented by various mollusks (pteropods, cephalopods, valves, etc.). There are a lot of jellyfish and siphonophores. In the waters open ocean, as in the Pacific Ocean, there are numerous flying fish, tuna, coryphaenas, sailfish and luminous anchovies. There are many sea snakes, including poisonous ones, and there is even a saltwater crocodile, which is prone to attacking people.
Mammals presented big amount and variety. There are whales of different species, dolphins, killer whales, and sperm whales. Many pinnipeds (fur seals, seals, dugongs). Cetaceans are especially numerous in the cold southern waters of the ocean, where krill feeding grounds are located.
Among those living here sea birds frigates and albatrosses can be noted, and in cold and temperate waters - penguins.
Despite the richness of the animal world of the Indian Ocean, fishing and fishing in this region are poorly developed. The total catch of fish and seafood in the Indian Ocean does not exceed 5% of the world catch. Fisheries are represented only by tuna fishing in the central part of the ocean and by small fishing cooperatives and individual fishermen of the coasts and island regions.
In some places (off the coast of Australia, Sri Lanka, etc.) pearl mining is developed.
There is also life in the depths and bottom layer of the central part of the ocean. In contrast to the upper layers, which are more suitable for the development of flora and fauna, the deep-sea areas of the ocean are represented by a smaller number of fauna, but in species-wise exceeds the surface. Life in the depths of the Indian Ocean has been studied very little, as well as the depths of the entire World Ocean. Only the contents of deep-sea trawls, and rare dives of bathyscaphes and similar vehicles into multi-kilometer abysses, can approximately tell about the local life forms. Many forms of animals living here have body shapes and organs that are unusual to our eyes. Huge eyes, a toothy head larger than the rest of the body, bizarre fins and outgrowths on the body - all this is the result of animals adapting to life in conditions of pitch darkness and monstrous pressures in the depths of the ocean.
Many animals use luminous organs or light emitted by certain benthic microorganisms (benthos) to attract prey and protect themselves from enemies. Thus, the small (up to 18 cm) Platytroct fish, found in the deep-sea zones of the Indian Ocean, uses glow for protection. In moments of danger, she can blind the enemy with a cloud of glowing mucus and escape safely. Many living creatures that live in the dark abysses of the deep oceans and seas have similar weapons. The great white shark. There are many shark-hazardous places in the Indian Ocean. Off the coast of Australia, Africa, the Seychelles, the Red Sea, and Oceania, shark attacks on people are not uncommon.
There are many other animals dangerous to humans in the Indian Ocean. Poisonous jellyfish, blue-ringed octopus, cone clams, tridacnas, poisonous snakes, etc. can cause serious trouble for a person when communicating.
The following pages will tell you about the seas that make up the Indian Ocean, about the flora and fauna of these seas, and, of course, about the sharks that live in them.
Let's start with the Red Sea - a unique inland body of water in the Indian Ocean basin
Indian Ocean ranks third in area and volume of water. It occupies 1/5 of the area of the World Ocean and 1/7 of the surface of the planet (Fig. 1).
Rice. 1. Indian Ocean on the map.
Square Indian Ocean - 76.17 million km 2. Unlike the Pacific and Atlantic Oceans, it has a small number of seas, only 5. Temperature The surface layer of water is +17 °C, and the salinity is 36.5 ‰. The saltiest part of the Indian Ocean is the Red Sea, with a salinity of 41‰. Relief The Indian Ocean is unique: on the ocean floor there are 10 main basins, 11 underwater ridges and 1 trench more than 6 thousand meters deep.
Average depth The Indian Ocean is 3711 m, and the maximum is 7729 m. The coastline of the Indian Ocean is very slightly indented. Remember the location of the Indian Ocean objects: the Red Sea (Fig. 3), the Gulf of Aden, the Persian Gulf (Fig. 2), the Arabian Sea, the Bay of Bengal, the Greater Sunda Islands archipelago and the Mozambique Strait.
The most characteristic geographical feature of the Indian Ocean is that 84% of its area is located in the Southern Hemisphere, and there is no direct connection with the Arctic Ocean.
Rice. 2. Persian Gulf
Rice. 3. Red Sea
According to modern data, the western border of the Indian Ocean is the meridian of 20° east. on the stretch between Antarctica and Cape Agulhas in southern Africa. In the northeast, its border runs along the shores of Asia to the Strait of Malacca along the islands of Sumatra, Java, Timor, and New Guinea. Further east through the Torres Strait along the west coast of Australia and the island of Tasmania. Further along 147° E. to Antarctica. Southern border ocean is the coast of Antarctica from 20° east. d. to 147° east. d. Northern border - the southern coast of Eurasia.
History of ocean exploration
The shores of the Indian Ocean are one of the areas of ancient civilizations. The exploration of the ocean began from the north by Indian, Egyptian and Phoenician sailors, who 3 thousand years BC. e. sailed in the Arabian and Red Seas and the Persian Gulf. The first descriptions of the routes of voyages in the Indian Ocean were made by the Arabs. For European geographical science information about the ocean began to accumulate since the voyages Vasco da Gama(1497–1499) (Fig. 4), who, having rounded Africa, reached India.
In 1642–1643 Abel Tasman(Fig. 5) first passed from the Indian Ocean to the Pacific along southern shores Australia.
At the end of the 18th century, the first depth measurements were carried out here James Cook(Fig. 6).
A comprehensive and systematic study of the ocean began at the end of the 19th century with the circumnavigation of the English expedition on the Challenger ship (Fig. 7).
However, by the middle of the 20th century, the Indian Ocean was very poorly studied. In the 50s The Soviet expedition began work on the Ob ship (Fig. 8).
Today, the Indian Ocean is being studied by dozens of expeditions from different countries.
Lithospheric plates
At the bottom of the Indian Ocean there is a boundary of three lithospheric plates: African, Indo-Australian and Antarctic (Fig. 9). In the depression of the earth's crust, occupied by the waters of the Indian Ocean, all the large structural reliefs of the ocean floor are clearly expressed: shelf (accounting for more than 4% of the total ocean area), continental slope, ocean floor (ocean plains and basins, 56% of the total area ocean), mid-ocean ridges (17%), mountain ranges and underwater plateaus, deep-sea trench.
Rice. 9. Lithospheric plates on the map
Mid-ocean ridges divide the ocean floor into three large parts. The transition from the ocean floors to the continents is smooth, only in the northeastern part does the Sunda Islands arc form, under which the Indo-Australian lithospheric plate subducts. In this place, a deep-sea trench 4 thousand km long is formed. The deep Sunda Trench, like the underwater ridges, is a zone of active underwater volcanism and earthquakes.
Geological history of the ocean
Depression Indian Ocean is very young. It was formed about 150 million years ago as a result of the collapse of Gondwana and the moving apart of Africa, Australia, Antarctica and Hindustan. The Indian Ocean acquired its contours close to modern ones about 25 million years ago. Now the ocean is located within three lithospheric plates: African, Indo-Australian and Antarctic.
Climate
The Indian Ocean is located in the tropical and subequatorial zones of the Northern Hemisphere, as well as in all climatic zones of the Southern Hemisphere. Based on surface water temperatures, this is the warmest ocean. Temperature The Indian Ocean depends on latitude: the northern part of the ocean is warmer than the southern part. Monsoons also form in the northern Indian Ocean. The Indian Ocean washes the shores of big continent– Eurasia. Their interaction determines the features surface currents and atmospheric circulation over the northern part of the ocean and the southern coast of Asia. In winter, an area of high atmospheric pressure, and above the ocean there is an area of low pressure. Thus, a wind is formed - the northeast monsoon. In summer, on the contrary, the southwest monsoon forms.
Sailors have long known the changing nature of the winds and currents of the northern part of the Indian Ocean and skillfully used it while sailing on sailing ships. In Arabic, “monsoon” means “season”, and “breeze” in French means “light wind”. Small sailing ships in the northern Indian Ocean are still in use today.
Tsunami
Underwater earthquake in the Indian Ocean that occurred December 26, 2004, caused a tsunami that was considered the deadliest natural disaster in modern history. The magnitude of the earthquake, according to various sources, ranged from 9.1 to 9.3. This is the second or third strongest earthquake on record. The epicenter of the earthquake was in the Indian Ocean north of the island of Simeulue, located off the northwestern coast of the island of Sumatra (Indonesia). The tsunami reached the shores of Indonesia, Sri Lanka, southern India, Thailand and other countries. The height of the waves exceeded 15 meters. The tsunami led to huge destruction and a huge number of dead people even in Port Elizabeth, South Africa, 6 thousand 900 km from the epicenter (Fig. 10).
Rice. 10. After the earthquake, December 2004
According to various estimates, from 225 to 300 thousand people died. True number the deaths are unlikely to ever be known, as many people were swept out to sea.
Flora and fauna
Flora and fauna The Indian Ocean is quite rich. In shallow waters tropical zone corals grow, which create islands with red and green algae. Among the coral islands, the most famous are Maldives(Fig. 11). These robust coral structures are home to many species of invertebrates such as crabs, sea urchins, sponges, and coral fish. There are huge areas of dense thicket here. brown algae. The open ocean is mostly inhabited by planktonic algae, while the Arabian Sea is characterized by blue-green algae, which constantly cause water blooms.
Rice. 11. Maldives
The fauna of the ocean is also rich. For example, among the animal waters of the Indian Ocean, the most common crustaceans are copepods, and siphonophores And jellyfish. The ocean is inhabited by squid, some species of flying fish, white shark, sailfish, poisonous sea snake, whales, turtles, and seals (Fig. 12). The most common birds are frigates and albatrosses.
Rice. 12. Undersea world Indian Ocean
The flora and fauna of the Indian Ocean is very diverse and interesting, as animals and plants live in a place favorable for development. This is a flower garden for nature lovers, environmentalists and tourists. Oil and natural gas are produced on the Indian Ocean shelf. The most famous place in the world for oil production is the Persian Gulf. The Indian Ocean is considered to be the most polluted by oil compared to other oceans. There are also many shipping routes in the Indian Ocean; there are large port cities and various places of recreation and tourism: Karachi, Dar es Salaam, Maputo, Mumbai, etc.
Bibliography
1. Geography. Land and people. 7th grade: Textbook for general education. uch. / A.P. Kuznetsov, L.E. Savelyeva, V.P. Dronov, series “Spheres”. – M.: Education, 2011.
2. Geography. Land and people. 7th grade: atlas, “Spheres” series.
1. Internet portal "Complete Encyclopedia" ()
2. Internet portal "Geography" ()
3. Internet portal "All about sharks" ()
Introduction
1.History of the formation and exploration of the Indian Ocean
2.General information about the Indian Ocean
Bottom relief.
.Characteristics of the waters of the Indian Ocean.
.Bottom sediments of the Indian Ocean and its structure
.Minerals
.Indian Ocean climate
.Flora and fauna
.Fisheries and marine activities
Introduction
Indian Ocean- the youngest and warmest among the world's oceans. Most of it is located in the southern hemisphere, and in the north it extends far into the mainland, which is why ancient people considered it just a big sea. It was here, in the Indian Ocean, that man began his first sea voyages.
The largest rivers in Asia belong to the Indian Ocean basin: the Salween, the Irrawaddy and the Ganges with the Brahmaputra, which flow into the Bay of Bengal; Indus, flowing into the Arabian Sea; The Tigris and Euphrates merge slightly above their confluence with the Persian Gulf. From large rivers Africa, which also flows into the Indian Ocean, should be called the Zambezi and Limpopo. Because of them, the water off the ocean coast is cloudy, with a high content of sedimentary rocks - sand, silt and clay. But open waters the oceans are amazingly clean. The tropical islands of the Indian Ocean are famous for their cleanliness. A variety of animals have found their home on coral reefs. The Indian Ocean is home to the famous sea devils, rare whale sharks, largemouths, sea cows, sea snakes, etc.
1. History of formation and research
Indian Oceanformed at the junction of the Jurassic and Cretaceous periods as a result of the collapse of Gondwana (130-150 million years ago). Then there was a separation of Africa and the Deccan from Australia with Antarctica, and later - of Australia from Antarctica (in the Paleogene, about 50 million years ago).
The Indian Ocean and its shores remain poorly studied. The name of the Indian Ocean appears already at the beginning of the 16th century. by Schöner under the name Oceanus orientalis indicus, in contrast to the Atlantic Ocean, then known as Oceanus occidentalis. Subsequent geographers called the Indian Ocean mostly the Sea of India, some (Varenius) the Australian Ocean, and Fleuriet recommended (in the 18th century) even calling it the Great Indian Gulf, considering it as part of the Pacific Ocean.
In ancient times (3000-1000 BC), sailors from India, Egypt and Phenicia traveled through the northern part of the Indian Ocean. First navigation maps were compiled by the ancient Arabs. At the end of the 15th century, the first European, the famous Portuguese Vasco da Gama, circumnavigated Africa from the south and entered the waters of the Indian Ocean. By the 16th-17th centuries, Europeans (the Portuguese, and later the Dutch, French and English) increasingly appeared in the Indian Ocean basin, and by the middle of the 19th century, most of its shores and islands were already the property of Great Britain.
History of discoverycan be divided into 3 periods: from ancient voyages to 1772; from 1772 to 1873 and from 1873 to the present. The first period is characterized by the study of the distribution of ocean and land waters in this part globe. It began with the first voyages of Indian, Egyptian and Phoenician sailors, who 3000-1000 BC. traveled through the northern part of the Indian Ocean, and ended with the voyage of J. Cook, who in 1772-75 penetrated the South to 71° S. w.
The second period was marked by the beginning of deep-sea exploration, first carried out by Cook in 1772 and continued by Russian and foreign expeditions. The main Russian expeditions were O. Kotzebue on the Rurik (1818) and Pallena on the Cyclone (1858-59).
The third period is characterized by complex oceanographic research. Until 1960 they were carried out on separate ships. The largest works were carried out by expeditions on the ships "Challenger" (English) in 1873-74, "Vityaz" (Russian) in 1886, "Valdivia" (German) in 1898-99 and "Gauss" (German) in 1901-03, Discovery II (English) in 1930-51, the Soviet expedition to the Ob in 1956-58, etc. In 1960-65, the Intergovernmental Oceanographic Expedition under UNESCO carried out an international Indian Ocean expedition, which collected new valuable data on hydrology, hydrochemistry, meteorology , geology, geophysics and biology of the Indian Ocean.
. General information
Indian Ocean- the third largest ocean on Earth (after the Pacific and Atlantic), covering about 20% of its water surface. Almost all of it is located in the southern hemisphere. Its area is 74917 thousand km ² ; average volume of water - 291945 thousand km ³. In the north it is limited by Asia, in the west by the Arabian Peninsula and Africa, in the east by Indochina, the Sunda Islands and Australia, in the south by Southern Ocean. The border between the Indian and Atlantic Oceans runs along the 20° meridian of eastern longitude (Meridian of Cape Agulhas), between the Indian and Pacific Oceans runs along the 147° meridian of east longitude (meridian southern cape islands of Tasmania). The northernmost point of the Indian Ocean is located at approximately 30°N latitude in the Persian Gulf. The Indian Ocean is approximately 10,000 km wide between the southern points of Australia and Africa.
The greatest depth of the Indian Ocean is the Sunda or Java Trench (7729 m), the average depth is 3700 m.
The Indian Ocean washes three continents at once: Africa from the east, Asia from the south, Australia from the north and northwest.
The Indian Ocean has least amount seas compared to other oceans. In the northern part there are the largest seas: the Mediterranean - the Red Sea and the Persian Gulf, the semi-enclosed Andaman Sea and the marginal Arabian Sea; in the eastern part - the Arafura and Timor Seas.
In the Indian Ocean are the island states of Madagascar (the fourth largest island in the world), Sri Lanka, Maldives, Mauritius, Comoros, and Seychelles. The ocean washes the following states in the east: Australia, Indonesia; in the northeast: Malaysia, Thailand, Myanmar; in the north: Bangladesh, India, Pakistan; in the west: Oman, Somalia, Kenya, Tanzania, Mozambique, South Africa. In the south it borders with Antarctica. There are relatively few islands. In the open part of the ocean there are volcanic islands - Mascarene, Crozet, Prince Edward, etc. In tropical latitudes, coral islands rise on volcanic cones - the Maldives, Laccadives, Chagos, Cocos, most Andaman, etc.
. Bottom relief
The ocean floor is a system of mid-ocean ridges and basins. In the area of Rodriguez Island (Mascarene archipelago) there is a so-called triple junction, where the Central Indian and West Indian ridges, as well as the Australian-Antarctic Rise, converge. The ridges consist of steep mountain ranges, cut by faults perpendicular or oblique to the axes of the chains and divide the basalt ocean floor into 3 segments, and their peaks are, as a rule, extinct volcanoes. The bottom of the Indian Ocean is covered with sediments of the Cretaceous and later periods, the thickness of which varies from several hundred meters to 2-3 km. The deepest of the ocean's many trenches is the Java Trench (4,500 km long and 29 km wide). Rivers flowing into the Indian Ocean carry with them huge quantities of sediment, especially from India, creating high sediment thresholds.
The Indian Ocean coast is replete with cliffs, deltas, atolls, coastal coral reefs and salt marshes covered with mangroves. Some islands - for example, Madagascar, Socotra, the Maldives - are fragments of ancient continents. Numerous islands and archipelagos of volcanic origin are scattered in the open part of the Indian Ocean. In the northern part of the ocean, many of them are topped with coral structures. Andaman, Nicobar or Christmas Island - are of volcanic origin. The Kerguelen Plateau, located in the southern part of the ocean, is also of volcanic origin.
An undersea earthquake in the Indian Ocean on December 26, 2004 caused a tsunami that was considered the deadliest natural disaster in modern history. The magnitude of the earthquake was, according to various estimates, from 9.1 to 9.3. This is the second or third strongest earthquake on record.
The epicenter of the earthquake was in the Indian Ocean, north of the island of Simeulue, located off the northwestern coast of the island of Sumatra (Indonesia). The tsunami reached the shores of Indonesia, Sri Lanka, southern India, Thailand and other countries. The height of the waves exceeded 15 meters. The tsunami caused enormous destruction and a huge number of deaths, even in Port Elizabeth, South Africa, 6900 km from the epicenter. According to various estimates, from 225 thousand to 300 thousand people died. The true death toll is unlikely to ever be known, as many people were swept out to sea.
As for the properties of the bottom soil, then, like in other oceans, sediments on the bottom of the Indian Ocean can be divided into three classes: coastal sediments, organic silt (globigerine, radiolar or diatom) and special clay of great depths, the so-called red clay. Coastal sediments are sand, located mostly on coastal shallows to a depth of 200 meters, green or blue silt near rocky shores, with a brown color in volcanic areas, but lighter and sometimes pinkish or yellowish near coral coasts due to the predominant lime. Globigerine mud, composed of microscopic foraminifera, covers the deeper parts of the ocean floor to a depth of almost 4500 m; south of the parallel 50° S. w. calcareous foraminiferal deposits disappear and are replaced by microscopic siliceous, from the group of algae, diatoms. In terms of the accumulation of diatom remains on the bottom, the southern Indian Ocean is particularly different from other oceans, where diatoms are found only locally. Red clay occurs at depths greater than 4500 m; it is red, or brown, or chocolate in color.
Indian Ocean climate fossil fishery
4. Water characteristics
Surface water circulationin the northern part of the Indian Ocean has a monsoon character: in summer - northeastern and eastern current, in winter - southwestern and western currents. In the winter months between 3° and 8° S. w. The inter-trade wind (equatorial) countercurrent develops. In the southern part of the Indian Ocean, water circulation forms an anticyclonic gyre, which is formed from warm currents- Southern Trade Wind in the North, Madagascar and Agulhas in the West and cold - currents of the Western Winds in the South and Western Australian in the East South of 55° S. w. Several weak cyclonic water circulations develop, closing off the coast of Antarctica with an eastern current.
Indian Ocean water beltbetween 10 ° With. w. and 10 ° Yu. w. called the thermal equator, where the surface water temperature is 28-29°C. To the south of this zone the temperature drops, reaching about 1°C off the coast of Antarctica. In January and February, the ice along the coast of this continent melts, huge blocks of ice break off from the Antarctic ice sheet and drift towards the open ocean. To the north, the temperature characteristics of the waters are determined by the monsoon air circulation. In summer, temperature anomalies are observed here, when the Somali Current cools the surface waters to a temperature of 21-23°C. In the eastern part of the ocean on the same geographic latitude The water temperature is 28°C, and the highest temperature - about 30°C - was recorded in the Persian Gulf and the Red Sea. Average salinity ocean waters is 34.8‰ The most saline waters are the Persian Gulf, Red and Arabian Seas: this is explained by intense evaporation with a small amount of fresh water brought into the seas by rivers.
Tides in the Indian Ocean, as a rule, are small (off the coast of the open ocean and on the islands from 0.5 to 1.6 m), only at the tops of some bays they reach 5-7 m; in the Gulf of Cambay 11.9 m. The tides are predominantly semidiurnal.
Ice forms in high latitudes and is carried by winds and currents along with icebergs in a northerly direction (up to 55° S in August and up to 65-68 S in February).
. Bottom sediments of the Indian Ocean and its structure
Bottom sedimentsIndian Ocean have the greatest thickness (up to 3-4 km) at the foot of the continental slopes; in the middle of the ocean - small (about 100 m) thickness and in places where dissected relief is distributed - intermittent distribution. The most widely represented are foraminifera (on continental slopes, ridges and on the bottom of most basins at depths of up to 4700 m), diatoms (south of 50° S), radiolarians (near the equator) and coral sediments. Polygenic sediments - red deep-sea clays - are common south of the equator at a depth of 4.5-6 km or more. Terrigenous sediments - off the coast of continents. Chemogenic sediments are represented mainly by ferromanganese nodules, and riftogenic sediments are represented by products of destruction of deep rocks. Bedrock outcrops are most common on continental slopes (sedimentary and metamorphic rocks), mountains (basalts) and mid-ocean ridges, where, in addition to basalts, serpentinites and peridotites, representing the slightly altered material of the Earth’s upper mantle, were discovered.
The Indian Ocean is characterized by the predominance of stable tectonic structures both on the bed (thalassocratons) and along the periphery (continental platforms); active developing structures - modern geosynclines (Sunda arc) and georiftogenals (mid-ocean ridge) - occupy smaller areas and are continued in the corresponding structures of Indochina and the rifts of East Africa. These main macrostructures, sharply different in morphology, structure of the earth’s crust, seismic activity, volcanism, are divided into smaller structures: plates, usually corresponding to the bottom of oceanic basins, block ridges, volcanic ridges, in places topped coral islands and banks (Chagos, Maldives, etc.), fault trenches (Chagos, Obi, etc.), often confined to the foot of block ridges (East Indian, Western Australian, Maldives, etc.), fault zones, tectonic ledges. Among the structures of the Indian Ocean floor special place(by the presence of continental rocks - granites of the Seychelles and the continental type of the earth's crust) occupies the northern part of the Mascarene Range - a structure that is apparently part of the ancient continent of Gondwana.
. Minerals
The most important mineral resources of 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, and on the shelf of the Hindustan Peninsula. The Indian Ocean ranks first in the world in terms of reserves and production of these minerals. Ilmenite, monazite, rutile, titanite and zirconium are exploited on the coasts of Mozambique, Madagascar and Ceylon. There are deposits of barite and phosphorite off the coast of India and Australia, and deposits of cassiterite and ilmenite are exploited on an industrial scale in the offshore zones of Indonesia, Thailand and Malaysia. On the shelves - oil and gas (especially the Persian Gulf), monazite sands (coastal region of South-West India), etc.; in reef zones - ores of chromium, iron, manganese, copper, etc.; on the bed there are huge accumulations of ferromanganese nodules.
. ClimateIndian Ocean
Most of the Indian Ocean is located in warm climate zones - equatorial, subequatorial and tropical. Only its southern regions, located at high latitudes, are strongly influenced by Antarctica. Equatorial zone The climate of the Indian Ocean is characterized by a constant predominance of moist, warm equatorial air. Average monthly temperatures here range from 27° to 29°. The water temperature is slightly higher than the air temperature, which creates favorable conditions for convection and precipitation. Their annual amount is large - up to 3000 mm or more.
. Flora and fauna
The Indian Ocean is home to the most dangerous mollusks in the world - cone snails. Inside the snail there is a rod-like container with poison, which it injects into its prey (fish, worms); its poison is also dangerous for humans.
The entire Indian Ocean lies within the tropical and southern temperate zones. The shallow waters of the tropical zone are characterized by numerous 6- and 8-rayed corals and hydrocorals, which, together with calcareous red algae, can create islands and atolls. Among the powerful coral structures lives a rich fauna of various invertebrates (sponges, worms, crabs, mollusks, sea urchins, brittle stars and starfish), small but brightly colored coral fish. Most of the coasts are occupied by mangroves, in which the mudskipper, a fish capable of long time exist in the air. The fauna and flora of beaches and rocks that dry out at low tide are quantitatively depleted as a result of the depressing effect of sunlight. In the temperate zone, life on such sections of the coast is much richer; Dense thickets of red and brown algae (kelp, fucus, reaching enormous sizes of microcystis) develop here, and a variety of invertebrates are abundant. The open spaces of the Indian Ocean, especially the surface layer of the water column (up to 100 m), are also characterized by a rich flora. Among unicellular planktonic algae, several species of peredinian and diatom algae predominate, and in the Arabian Sea - blue-green algae, which often cause mass development so-called water bloom.
The bulk of ocean animals are crustaceans - copepods (more than 100 species), followed by pteropods, jellyfish, siphonophores and other invertebrate animals. The most common unicellular organisms are radiolarians; Squids are numerous. Of the fish, the most abundant are several species of flying fish, luminous anchovies - myctophids, coryphaenas, large and small tuna, sailfish and various sharks, poisonous sea snakes. Sea turtles and large marine mammals (dugongs, toothed and toothless whales, pinnipeds) are common. Among the birds, the most typical are albatrosses and frigatebirds, 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.
At night, the surface of the Indian Ocean shimmers with lights. Light is produced by small marine plants called dinoflagellates. The glowing areas sometimes have the shape of a wheel with a diameter of 1.5 m.
. Fisheries and marine activities
Fishing is poorly developed (the catch does not exceed 5% of the world catch) and is limited to the local coastal zone. There is tuna fishing near the equator (Japan), and whale fishing in Antarctic waters. Pearls and mother-of-pearl are mined in Sri Lanka, the Bahrain Islands and the northwestern coast of Australia.
The countries of the Indian Ocean also have significant resources of other valuable types of mineral raw materials (tin, iron and manganese ores, natural gas, diamonds, phosphorites, etc.).
Bibliography:
1.Encyclopedia "Science" Dorling Kindersley.
.“I'm exploring the world. Geography" V.A. Markin
3.slovari.yandex.ru ~ TSB books / Indian Ocean /
4.Large encyclopedic dictionary of Brockhaus F.A., Efron I.A.
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