A Brief History of the Discovery of the Indian Ocean. History of Indian Ocean exploration

Most experts agree that the center of the origin and development of navigation was the Mediterranean. However, some scientists give the palm to the northern part of the Indian Ocean (for the first time its name was given by Sebastian Munster in his Cosmography (1555)).

The achievements of ancient navigators are often associated with Mesopotamia. It was here that one of the oldest world civilizations, Sumer, developed. It got its name from the name of the people who settled in the lower reaches of the Euphrates River, not far from its confluence with the Persian Gulf.

The “Royal List” has survived to this day, which is a sequential list of Sumerian dynasties that ruled from “antediluvian times”. Among the first semi-mythical rulers there are the names of Enmesharr, Lugalbanda and Gilgamesh. The epic poem about Gilgamesh (3 thousand BC) tells about the hero's wanderings, went to Syria to Mount Lebanon for cedars, visited the kingdom of Ziusudra, got the ocean.

Experts believe that reed shipbuilding developed in Mesopotamia back in those days when the southern lands of modern Iraq did not exist - instead of them, the waves of the Persian Gulf lapped. The Tigris and the Euphrates then rushed into it separately, NOT merging, as they do today, into the full-flowing stream of the Shatt al-Arab. The absence of stone and wood in Mesopotamia gave impetus to trade with lands rich in these natural resources.

The high reputation of seafarers Mesopotamia is directly related to the difficult navigational conditions of the Persian Gulf. It is a relatively narrow strip of water that separates the Arabian and Iranian deserts. The wind regime of the Persian Gulf is largely determined by the atmospheric processes of highlands and deserts. The most typical steady east wind - "Shamal" - blows only nine months of the year. It was a fair wind for the Sumerian sailing ships that left their harbors on the route Sumer - the island of Bahrain. "Shamal", like the trade winds of the World Ocean, is a kind of trade wind, its area of ​​\u200b\u200baction is limited to the Persian Gulf.

The antipode of "Shamala" is the sharp northern "Sharki". It is not as reliable as Shamal: its period of action is insignificant, and most importantly, it easily turns into a storm. The setting of two-way navigation in the Persian Gulf indicates that the ancient navigators had the secret to control their boats and could sail against the wind. And if we remember that the shallow Persian Gulf is rich in shoals and reefs, and its water area is characterized by a small but very steep wave, then the ability of ancient navigators to maneuver and avoid dangers becomes obvious.

The navigation of the Sumerians was not limited to the waters of the Persian Gulf. In ancient texts, there is evidence of ships that arrived from the country of Meluhha (this was probably the name of Ancient India) and delivered precious stones, timber, rice, cotton, ivory and golden sand to Sumer. In turn, in the valley of the Indus River, archaeologists found Sumerian trade seals. All these facts testify in favor of constant trade contacts between Sumer and India.

The transshipment point on the way between these ancient states, perhaps, was the Bahrain archipelago, where both Indian and Sumerian seals were found. Here was the Land of the Blessed (Dilmun), which the Sumerians considered the birthplace of mankind and the cradle of their culture.

Dilmun is mentioned in Sumerian trade records of the 3rd millennium BC. e. Subsequently, he played the role of a major trading center for a long time. This is evidenced by the records of the founder of the great Akkadian state - Sargon the Ancient. They say that Dilmun received ships from Meluhh and Magan.

Another, later document tells about the campaign of the Assyrians against the Babylonian ruler. They managed to conquer a significant territory on the coast of the "Bitter Sea" to the borders of Dil-na. King Dilmun, "whose abode is located like a fish, for thirty double hours in the middle of the sea of ​​​​the rising sun," sent his gifts to the Assyrians.

Bahrain played such an important role on the ancient trade routes because of the fresh water that caravans could stock up on. Throughout the Arabian Gulf, only here and on the mainland were its sources.

It is possible that the Persian Gulf was the cradle of world navigation. This is evidenced by the ancient ruins of Bahrain, which date back to W millennium BC. e. Some experts believe that about V! thousand years ago, stone blocks were delivered to the archipelago by sea.

The expanses of the Indian Ocean were also mastered by the Egyptians. So, their ships sailed the Red Sea. It should be said that this is a difficult area for sailors. For many months there is unbearable heat here, and there are few harbors with fresh water. Along the coast, navigation is hampered by coral reefs and strong winds. To get to the country of Punt, which, due to its remoteness and obscurity, was considered a magical "country of spirits", sufficiently fast and reliable sea vessels were needed. They brought incense and resins, exotic animals and rare tree species. Judging by how rarely the texts described the difficulties of navigation, such transportation was quite regular, but was considered distant and risky. The most famous military expedition to Punt was the time of the Egyptian Queen Hatshepsut (the First of the Worthy). Around 1481 B.C. e. from this country, located in East Africa, a rich tribute was received. On the wall of the temple in Der el-Bahari, inscriptions and images telling about this expedition were minted. One of the inscriptions says that the ships were loaded with precious wood, heaps of fragrant resins, fresh fragrant wood, ebony, ivory items sent from the country of Amu, Hezite wood and Achem incense, sacred resin, eye paint, dog-like monkeys, long-tailed monkeys, greyhounds, leopard skins and natives with their children.

Thanks to travel along the shores of the Red Sea, the Egyptians learned that sailing to the country of Punt should begin in June, when fair north-west winds blow, and return in the autumn, along south-east winds.

Approximately from the VIII-VII centuries. BC e. Indian sailors became active participants in the development of routes connecting the ancient centers of civilization in Egypt, Arabia and Mesopotamia with the Asian South East - Burma, Cambodia, Vietnam, Sumatra and Java.

The Russian historian Ya. M. Svet called this ancient trade route "the great South Asian monsoon road." Luxurious and everyday items found during excavations in India clearly testify to the close ties of the peoples inhabiting the subcontinent with the Eastern Mediterranean for almost the entire 1st millennium BC. e. Through the Persian Gulf, Indian goods entered the harbors of southern Mesopotamia.

In the VI-IV centuries. BC AD, when the kings of the Persian state of the Achaemenids owned the entire Middle East and Egypt, Indian merchants regularly sailed to Babylon. It is about these swimming that is told in the Buddhist legend "Babylon Jataka", which describes how Indian merchants brought peacocks to Babylon (Bauer).

In the old days, long-distance voyages of Indian ships began in an easterly direction. In ancient Chinese chronicles, a short message was found about a visit in the 7th century. BC e. Chinese port by foreign merchant ships. Historians of geographical discoveries I.P. Magidovich and V.I. Magidovich believe that the chronicle explicitly lists Indian goods. They claim to be most likely mentioned in the chronicles of a ship from India.

The ancient Indians discovered and settled the Laccadive and Maldives Islands - two groups of coral atolls, stretched almost along the 73 ° E meridian. for 1500 km. Discovery of the Andaman and Nicobar Islands, stretching for 900 km near 93 ° N. was a rather lengthy process. It probably started not earlier than the 4th century. BC e. sailors or merchants who traded with the country of Plaksa-dvipa (“Silver Island” - the region of the lower reaches of the Irrawaddy, where silver was delivered from the mines located on its tributary Chinduin). The seasonal current may have carried them southwest to the land subsequently named Anga-dvipa (Andaman Islands). It is possible that, moving from island to island, they themselves or their followers discovered the Nicobar Islands.

The development of navigation at the end of the 1st millennium BC. e. contributed to the changes in Indian society. At that time, Buddhism became the predominant religion in the Mauryan Empire, the characteristic features of which were objections to the division of people into castes, encouraging contact with other peoples and religious tolerance. These factors contributed to the search for new trading partners and the voyage of Indian merchants in the 4th-3rd centuries. BC e. along the entire coast of Indochina, including to the south, to the Malay Peninsula. Indian merchants penetrated Sumatra and explored it to the southern edge. Then they appeared on the island of Java and sailed the Java Sea. Subsequently, they discovered Camphor Island (Kalimantan), traced its northern coast for about 1000 km.

The Greeks also made a contribution to the study of the Indian Ocean. In 325 BC. e. Alexander the Great, being with his army on the Indus River, ordered his associate Nearchus to open the sea route from this river to the Euphrates.

Nearchus sailed in September. As he passed the harbor of Karachi, the monsoon began to change its direction, and the sailors had to wait twenty-four days for a favorable wind. Five days after the resumption of navigation, a storm broke out, during which three ships were lost (there were a total of 150 ships and about 5 thousand sailors). Throughout the voyage, the expedition was starving almost all the time.

Moving slowly along the coast, the Greeks reached Judd Point (65°E) in early November. Soon they entered the Strait of Hormuz and in the distance they saw the Musandam Peninsula, part of Arabia.

After Nearchus met with Alexander the Great and reported to him about the safe arrival in the Persian Gulf, he was ordered to continue sailing. At the beginning of December, Nearchus bypassed the island of Qeshm from the south and passed a series of islets near the northern shore of the bay to the mouth of the Euphrates River, which he reached at the end of January 324 BC. e. The fleet entered Pasitigris and, rising to Susa, joined the army of Alexander there. Nearchus' expedition lasted over six months.

Planning to capture Arabia, Alexander decided to explore its shores. This was successfully done by two of his captains - Androsthenes and Hieron, who explored most of the eastern coast of Arabia. From the Gulf of Suez towards Androsthenes and Hieronymus, on the orders of Alexander, several ships set off, the teams of which explored the western coast of Arabia from the Gulf of Aqaba to the Bab el-Mandeb Strait.

As a result of these voyages, the Greeks had a correct idea of ​​​​Arabia as a huge peninsula.

In the 1st century BC e. The Alexandrian navigator Hippalus discovered the existence of monsoons and the method of using them for sailing to India and back. By this, he facilitated and accelerated the establishment of relations between Europeans and the East.

In the Middle Ages, some countries of Southeast Asia achieved success in sea voyages. On the territory of the Sunda Archipelago, the state of Nusantara ("Island Country") was located. For all the peoples inhabiting its territory, the sea has long been a native element. On their light boats, the islanders sailed the Indian Ocean, gradually moving along the southern coast of Asia.

The historical development on the individual islands of the archipelago had its own characteristics. In the river deltas of Sumatra lived sedentary Malay tribes, related to the indigenous inhabitants of the deep parts of the island. Every patch of land they had to wrest from the virgin forest, and every step in its hot, jaded, humid atmosphere often cost incredible effort. Unsteady land, abundantly nourished the equatorial forest with its juices, opposed the Malays, so the sea became their friend. Coastal villages were combined with each other not by land, but by the “Big Salt Water”. Malay navigators used it to travel to distant lands. Even at the beginning of our era, they managed to cross the entire Indian Ocean from east to west and reach the islands of Madagascar. On the opposite side - in the east - invisible threads connected the Malays with the inhabitants of the Polynesian islands located in the Pacific Ocean.

Especially hectic life was in full swing on the shores of the Strait of Malacca (connects the Andaman and South China Seas). Cargoes from China to India and back went through it. Valuable commodities were silk, precious stones, gold and silver items. The “spice road” leading from the Moluccas, Timor and Celebes (Sulawesi) to Srivijaya (a medieval state in Southeast Asia) connected with this path. The rulers of Srivijaya managed to spread their influence over the entire island of Sumatra and the Malay Peninsula, established control over the Strait of Malacca.

Around the 8th century on about. Java formed another strong state - the kingdom of Mataram. These and other countries of the "southern seas" were described by Chinese merchants and pilgrims (wandering pilgrims), and later by Arab travelers, scientists and merchants. Their half-forgotten works tell of ships with teams of hundreds of people, led by experienced captains, of wonderful Buddhist palaces and temples, of rich rice fields and wide roads cut through the forests. It is also known that the maps compiled by the Malays were highly valued in the ports of Asia for the accuracy of the information contained in them.

An important record of sailing the Indian Ocean belongs to the Venetian Marco Polo. More is known about his journey to China and the seventeen-year stay at the court of Kublai Khan in Beijing. But it is worth dwelling on the maritime part of the travels of the European, information about which was dictated in the Genoese prison of the Pisans Rustici-Chano. The book of Marco Polo is very interesting, and although it contains many exaggerations and inaccuracies, it contains very important information.

Late 1291 Kublai Khan married his daughter to the Persian ruler and instructed the thirty-eight-year-old Marco Polo to organize her escort and protection. The Venetian offered to go by sea, and the khan agreed with him. A fleet of fourteen ships sailed in 1292 from Zaitong (Quanzhou), between Ama (Xiamen) and Fuch-zhou. Polo speaks of a nave and a barge, but from his description one can understand that we are talking about short, almost square junks (four masts, nine sails), equipped with stern oars. Behind each oar were four rowers. Polo claims that the largest ships of the expedition had "from fifty to sixty cabins, where the merchants were accommodated with all comforts, and could carry six hundred people", which, of course, is an exaggeration. In total, 2,000 people arrived from Zayton to Hormuz (Persian Gulf).

In the 7th century a new conquering people appeared - the Arabs. In one century, they created an empire that stretched from India to the Atlantic Ocean. Moving along the east coast of Africa, the Arabs first advanced from Cape Guardafui to 8°S. sh.

From the island of Zanzibar, which was colonized in the middle of the 8th century, they launched an offensive to the south, which lasted about three centuries. The Arabs discovered two of the six volcanic Comoros, the Seychelles, and no later than the 9th century. discovered the northwestern coast of the island of Madagascar. By the middle of the XII century. they established that Madagascar is an island.

In terms of depth and area, the third place belongs to the Indian Ocean, and it occupies about 20% of the entire water surface of our planet. Scientists suggest that the ocean began to form in the early Jurassic period after the breakup of the supercontinent. Africa, Arabia and Hindustan were formed, and a depression appeared, which increased in size during the Cretaceous period. Later, Australia appeared, and the Red Sea was formed due to the movement of the Arabian Plate. In the Cenozoic era, the boundaries of the ocean were relatively formed. Rift zones continue to move to this day, as does the Australian Plate.

The result of the movement of tectonic plates are frequent earthquakes that occur on the coast of the Indian Ocean, causing a tsunami. The largest was the earthquake on December 26, 2004 with a recorded magnitude of 9.3 points. Approximately 300,000 people died as a result of the disaster.

History of Indian Ocean exploration

The study of the Indian Ocean originated in the mists of time. Important trade routes ran through it, scientific research and sea fishing were carried out. Despite this, the ocean has not been studied enough; until recently, not so much information was collected. Navigators from ancient India and Egypt began to master it, and in the Middle Ages the Arabs mastered it, who made records about the ocean and its coast.

Written information about the water area was left by such researchers and sailors:

• Ibn Battut;
• B. Dias;
• Vasco da Gamma;
• A. Tasman.

Thanks to them, the first maps appeared with the outlines of the coastline and islands drawn. In modern times, the Indian Ocean was studied with their expeditions by J. Cook and O. Kotzebah. They recorded geographic indicators, made fixation of islands, archipelagos, monitored changes in depth, water temperature and salinity.

Comprehensive oceanographic studies of the Indian Ocean were carried out at the end of the nineteenth and in the first half of the twentieth century. A map of the ocean floor and changes in relief has already appeared, some species of flora and fauna, and the regime of the water area have been studied.

Modern studies of the ocean are complex and allow deeper exploration of the water area. Thanks to this, the discovery was made that all faults and ridges in the World Ocean are a single global system. As a result, the development of the Indian Ocean is of great importance for the life of not only local residents, but also of global importance, since the water area is the largest ecosystem on our planet.

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

Physical-geographical sketch

General information

Border I. o. in the west (with the Atlantic Ocean south of Africa) they are drawn along the meridian of Cape Agulhas (20 ° E) to the coast of Antarctica (Queen Maud Land), in the east (with the Pacific Ocean south of Australia) - along the eastern border of the Bass Strait to the island of Tasmania, and further along the meridian 146 ° 55 "" in. to Antarctica, in the northeast (with the Pacific Ocean) - between the Andaman Sea and the Strait of Malacca, then along the southwestern shores of the island of Sumatra, the Sunda Strait, the southern coast of 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. Southern high-latitude part of I. o. sometimes referred to as the Southern Ocean, which combines the Antarctic sectors of the Atlantic, Indian and Pacific Oceans. However, such a geographical nomenclature is not universally recognized, and, as a rule, I. o. viewed within its usual boundaries. And about. - the only one of the oceans, which is located b. hours in the Southern Hemisphere and is limited in the north by a powerful land mass. Unlike other oceans, its mid-ocean ridges form three branches, diverging in different directions from the central part of the ocean.

Area I. o. with seas, bays and straits 76.17 million km 2, water volume 282.65 million km 3, average depth 3711 m (2nd place after the Pacific Ocean); without them - 64.49 million km 2, 255.81 million km 3, 3967 m. The greatest depth in the deep Sunda Trench– 7729 m at 11°10"" S. sh. and 114°57"" E. The shelf zone of the ocean (conditionally up to 200 m depth) occupies 6.1% of its area, the continental slope (from 200 to 3000 m) 17.1%, the bed (over 3000 m) 76.8%. See map.

Seas

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

Islands

Unlike other oceans, the islands are few in number. The total area is about 2 million km2. The largest islands of mainland origin are Socotra, Sri Lanka, Madagascar, Tasmania, Sumatra, Java, Timor. Volcanic islands: Reunion, Mauritius, Prince Edward, Crozet, Kerguelen and others; coral - Laccadive, Maldivian, Amirant, Chagos, Nicobar, b. h. Andaman, Seychelles; coral Comoros, Cocos and other islands rise on volcanic cones.

coast

And about. is distinguished by a relatively small indentation of the coastline, with the exception of the northern and northeastern parts, where b. including the seas and the main large bays; there are few convenient bays. The coasts of Africa in the western part of the ocean are alluvial, poorly dissected, often surrounded by coral reefs; in the northwestern part - indigenous. In the north, low, slightly dissected coasts with lagoons and sand bars, places with mangroves, bordered by coastal lowlands (Malabar coast, Coromandel coast) prevail, abrasion-accumulative (Konkan coast) and deltaic coasts are also common. In the east, the shores are indigenous, in Antarctica they are covered with glaciers descending to the sea, ending in ice cliffs several tens of meters high.

Bottom relief

In the relief of the bottom I. o. four main elements of geotecture are distinguished: the underwater margins of the continents (including the shelf and the continental slope), transitional zones, or zones of island arcs, the ocean floor, and mid-ocean ridges. The area of ​​the underwater margins of the continents in the I. o. is 17,660 thousand km 2. The underwater margin of Africa is distinguished by a narrow shelf (from 2 to 40 km), its edge is located at a depth of 200–300 m. Only near the southern tip of the continent, the shelf expands significantly and extends up to 250 km from the coast in the region of the Agulhas Plateau. Significant areas of the shelf are occupied by coral structures. The transition from the shelf to the continental slope is expressed by a clear inflection of the bottom surface and a rapid increase in its slope up to 10–15°. The underwater margin of Asia off the coast of the Arabian Peninsula also has a narrow shelf, gradually expanding on the Malabar coast of Hindustan and off the coast of the Bay of Bengal, while the depth at its outer border increases from 100 to 500 m. 4200 m, Sri Lanka). The shelf and continental slope in some areas are cut by several narrow and deep canyons, the most pronounced canyons, which are underwater continuations of the channels of the Ganges rivers (together with the Brahmaputra River, it annually carries out into the ocean about 1200 million tons of suspended and entrained sediments that formed a layer of sediments over 3500 m thick). The Indian Ocean submarine margin of Australia is distinguished by an extensive shelf, especially in the northern and northwestern parts; in the Gulf of Carpentaria and the Arafura Sea up to 900 km wide; the greatest depth is 500 m. The continental slope to the west of Australia is complicated by underwater ledges and separate underwater plateaus. On the underwater margin of Antarctica, everywhere there are traces of the influence of the ice load of a huge glacier covering the mainland. The shelf here belongs to a special glacial type. Its outer boundary almost coincides with the 500 m isobath. The width of the shelf is from 35 to 250 km. The continental slope is complicated by longitudinal and transverse ridges, separate ridges, valleys and deep trenches. At the foot of the continental slope, almost everywhere there is an accumulative plume composed of terrigenous material brought by glaciers. The largest slopes of the bottom are noted in the upper part; with increasing depth, the slope gradually flattens out.

Transitional zone at the bottom I. o. stands out only in the area adjacent to the arc of the Sunda Islands, and represents the southeastern part of the Indonesian transitional region. It includes: the basin of the Andaman Sea, the island arc of the Sunda Islands and deep-sea trenches. The most morphologically expressed in this zone is the deep-water Sunda Trench with slopes of 30° or more. Relatively small deep-sea trenches stand out southeast of Timor Island and east of the Kai Islands, but due to the thick sedimentary layer, their maximum depths are relatively small - 3310 m (Timor Trench) and 3680 m (Kai Trench). The transition zone is extremely seismically active.

Mid-ocean ridges form three underwater mountain ranges, diverging from the area with coordinates 22 ° S. sh. and 68° E. to the northwest, southwest and southeast. Each of the three branches is divided according to morphological features into two independent ranges: the northwestern one - into the Middle Aden Range and Arabian Indian Range, southwestern - on West Indian Range and the African-Antarctic Ridge, southeast - on Central Indian Range and Australo-Antarctic Rise. That. the median ridges divide the bed of the I. o. into three major sectors. The median ridges are vast uplifts fragmented by transform faults into separate blocks with a total length of over 16 thousand km, the foot of which are located at depths of about 5000–3500 m. m.

In each of the three sectors of the ocean floor, I. o. characteristic forms of relief are distinguished: basins, individual ridges, plateaus, mountains, trenches, canyons, etc. 6000 m), Madagascar Basin(4500–6400 m), Agulhas(4000–5000 m); submarine ridges: Mascarene Ridge, Madagascar; plateau: Agulhas, Mozambique; separate mountains: Equator, Africana, Vernadsky, Hall, Bardin, Kurchatov; Amirant Trench, Mauritius Trench; canyons: Zambezi, Tanganyika and Tagela. The following basins are distinguished in the northeastern sector: Arabian (4000–5000 m), Central (5000–6000 m), Cocos (5000–6000 m), North Australian (Argo Plain; 5000–5500 m), West Australian Basin(5000–6500 m), Naturalista (5000–6000 m) and South Australian Basin(5000–5500 m); submarine ridges: maldives range, East Indian Range, Western Australian (Broken Plateau); Cuvier mountain range; Exmouth Plateau; upland Mill; separate mountains: Moscow State University, Shcherbakov and Afanasy Nikitin; East Indian Trench; canyons: rivers Indus, Ganges, Seatown and Murray. In the Antarctic sector, there are basins: Crozet (4500–5000 m), African-Antarctic basin (4000–5000 m) and Australo-Antarctic Basin(4000–5000 m, maximum - 6089 m); plateau: Kerguelen, Crozetand Amsterdam; separate mountains: Lena and Ob. The shapes and sizes of the basins are different: from round ones with a diameter of about 400 km (Komorskaya) to oblong giants 5500 km long (Central), the degree of their isolation and the bottom topography are different: from flat or gently undulating to hilly and even mountainous.

Geological structure

Feature I. about. is that its formation occurred both as a result of the splitting and subsidence of continental masses, and as a result of the expansion of the bottom and the neoformation of the oceanic crust within the mid-ocean (spreading) ridges, the system of which was repeatedly rebuilt. The modern system of mid-ocean ridges consists of three branches, converging at the point of the triple junction of Rodriguez. In the northern branch, the Arabian-Indian Ridge continues to the northwest of the Owen transform fault zone with the Gulf of Aden and Red Sea rift systems and connects with the East African intracontinental rift systems. In the southeastern branch, the Central Indian Ridge and the Australo-Antarctic Rise are separated by the Amsterdam Fault Zone, with which the plateau of the same name is connected with the volcanic islands of Amsterdam and St. Paul. The Arabian-Indian and Central Indian ridges are slow-spreading (the spreading rate is 2–2.5 cm/year), have a well-defined rift valley, and are crossed by numerous transform faults. The wide Australo-Antarctic Rise does not have a pronounced rift valley; speed spreading it is higher than in other ranges (3.7–7.6 cm/year). South of Australia, the uplift is broken by the Australo-Antarctic fault zone, where the number of transform faults increases and the spreading axis shifts along the faults to the south. The ridges of the southwestern branch are narrow, with a deep rift valley, and are densely crossed by transform faults oriented at an angle to the strike of the ridge. They are characterized by a very low spreading rate (about 1.5 cm/year). The West Indian Ridge is separated from the African-Antarctic Ridge by the Prince Edward, Du Toit, Andrew Bain and Marion faults, which shift the axis of the ridge almost 1000 km to the south. The age of the oceanic crust within the spreading ridges is predominantly Oligocene-Quaternary. The West Indian Ridge, which intrudes into the structures of the Central Indian Ridge as a narrow wedge, is considered the youngest.

The spreading ridges divide the ocean floor into three sectors - the African in the west, the Asian-Australian in the northeast and the Antarctic in the south. Within the sectors there are intra-oceanic uplifts of various nature, represented by "aseismic" ridges, plateaus and islands. Tectonic (blocky) uplifts have a block structure with different thicknesses of the crust; often include continental remnants. Volcanic uplifts are mainly associated with fault zones. Uplifts are the natural boundaries of deep-sea basins. African sector characterized by the predominance of fragments of continental structures (including microcontinents), within which the thickness of the earth's crust reaches 17–40 km (Agulyas and Mozambique plateaus, the Madagascar ridge with the island of Madagascar, individual blocks of the Mascarene ridge with the bank of the Seychelles and the bank of Saya de -Malya). Volcanic uplifts and structures include the Comoros underwater ridge crowned with archipelagos of coral and volcanic islands, the Amirantsky ridge, the Reunion Islands, Mauritius, Tromelin, the Farquhar massif. In the western part of the African sector, I. o. (western part of the Somali Basin, northern part of the Mozambique Basin), adjacent to the eastern submarine margin of Africa, the age of the earth's crust is predominantly Late Jurassic-Early Cretaceous; in the central part of the sector (Mascarenskaya and Madagascar basins) - Late Cretaceous; in the northeastern part of the sector (eastern part of the Somali Basin) - Paleocene-Eocene. Ancient spreading axes and transform faults crossing them have been identified in the Somali and Mascarene basins.

For the northwestern (Asian) part Asian-Australian sector typical meridional "aseismic" ridges of block structure with increased thickness of the oceanic crust, the formation of which is associated with a system of ancient transform faults. These include the Maldives Ridge, crowned with archipelagos of coral islands - Laccadive, Maldives and Chagos; so-called. 79° ridge, Lanka ridge with Mount Athanasius Nikitin, East Indian (so-called 90° ridge), Investigator, and others. the ridges extending in this direction, as well as the structures of the transition zone from the Indian Ocean to the southeastern margin of Asia, partially overlap. The Murri Range in the northern part of the Arabian Basin, which limits the Oman Basin from the south, is a continuation of the folded land structures; enters the Owen Fault Zone. To the south of the equator, a sublatitudinal zone of intraplate deformations up to 1000 km wide was revealed, which is characterized by high seismicity. It stretches in the Central and Coconut basins from the Maldives Range to the Sunda Trench. The Arabian Basin is underlain by the crust of the Paleocene-Eocene age, the Central Basin - by the crust of the Late Cretaceous - Eocene age; the bark is the youngest in the southern part of the basins. In the Coconut Basin, the age of the crust varies from Late Cretaceous in the south to Eocene in the north; an ancient spreading axis was established in its northwestern part, separating the Indian and Australian lithospheric plates until the middle Eocene. The coconut swell is a latitudinal uplift with numerous seamounts and islands towering above it (including the Cocos Islands) and the Ru uplift adjacent to the Sunda Trench separate the southeastern (Australian) part of the Asian-Australian sector. The West Australian Basin (Wharton) in the central part of the Asian-Australian sector of the I. o. underlain in the northwest by Late Cretaceous crust, in the east by Late Jurassic. Submerged continental blocks (marginal plateaus of Exmouth, Cuvier, Zenith, Naturalist) divide the eastern part of the basin into separate depressions - Cuvier (north of the Cuvier plateau), Perth (north of the Naturalist plateau). The crust of the North Australian Basin (Argo) is the most ancient in the south (Late Jurassic); becomes younger in a northerly direction (to the early Cretaceous). The age of the crust of the South Australian Basin is Late Cretaceous – Eocene. The Broken Plateau (West Australian Ridge) is an intra-oceanic uplift with an increased (from 12 to 20 km, according to various sources) crustal thickness.

AT Antarctic sector And about. mainly volcanic intraoceanic uplifts with an increased thickness of the earth's crust are located: the Kerguelen Plateau, Crozet (Del Cano) and Conrad. Within the limits of the largest plateau Kerguelen, supposedly laid down on an ancient transform fault, the thickness of the earth's crust (according to some data, the Early Cretaceous age) reaches 23 km. Towering above the plateau, the Kerguelen Islands are a multiphase volcanoplutonic structure (composed of alkaline basalts and syenites of the Neogene age). Heard Island has Neogene-Quaternary alkaline volcanic rocks. In the western part of the sector, there are the Konrad plateau with the Ob and Lena volcanic mountains, as well as the Crozet plateau with a group of volcanic islands Marion, Prince Edward, Crozet, composed of Quaternary basalts and intrusive massifs of syenites and monzonites. The age of the earth's crust within the African-Antarctic, Australo-Antarctic basins and the Crozet basin is Late Cretaceous - Eocene.

For I. about. in general, the predominance of passive margins (the continental margins of Africa, the Arabian and Hindustan peninsulas, Australia, and Antarctica) is characteristic. The active margin is observed in the northeastern part of the ocean (the Sunda Indian Ocean–Southeast Asia transition zone), where subduction(thrust) of the ocean lithosphere under the Sunda island arc. A subduction zone limited in length, the Makranskaya, has been identified in the northwestern part of I. O. Along the plateau Agulhas I. o. borders the African continent along the transform fault.

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

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

Bottom sediments

The rate of sedimentation in the I. o. generally lower than in the Atlantic and Pacific oceans. The thickness of modern bottom sediments varies from a discontinuous distribution on mid-ocean ridges to several hundred meters in deep-water basins and 5000–8000 m at the foot of continental slopes. The most widespread are calcareous (mainly foraminifero-coccolithic) oozes, covering over 50% of the ocean floor area (on continental slopes, ridges, and the bottom of basins at depths up to 4700 m) in warm oceanic regions from 20° N. sh. up to 40°S sh. with high biological productivity of waters. Polygenic sediments - red deep ocean clays- occupy 25% of the bottom area at depths of more than 4700 m in the eastern and southeastern parts of the ocean from 10 ° N. sh. up to 40°S sh. and on bottom areas remote from islands and continents; in the tropics, red clays alternate with siliceous radiolarian silts that cover the bottom of deep-water basins of the equatorial belt. In deep-sea deposits in the form of inclusions there are ferromanganese nodules. Siliceous, predominantly diatomaceous, oozes occupy about 20% of the bottom of the I. o.; distributed at great depths south of 50 ° S. sh. The accumulation of terrigenous sediments (pebbles, gravel, sands, silts, clays) occurs mainly along the coasts of the continents and within their underwater margins in the areas of river and iceberg runoff, significant wind removal of material. Sediments covering the African shelf are mainly of shell and coral origin; phosphorite concretions are widely developed in the southern part. Along the northwestern periphery of the I. O., as well as in the Andaman Basin and in the Sunda Trench, bottom sediments are mainly represented by sediments of turbid (turbid) flows - turbidites with the participation of products of volcanic activity, underwater landslides, landslides, and others. Sediments of coral reefs are widespread in the western part of the I. o. from 20°S sh. up to 15° s. sh., and in the Red Sea - up to 30 ° N. sh. Exits discovered in the Rift Valley of the Red Sea metal-bearing brines with temperatures up to 70 °C and salinity up to 300‰. AT metaliferous sediments formed from these brines, a high content of non-ferrous and rare metals. On continental slopes, seamounts, mid-ocean ridges, outcrops of bedrocks (basalts, serpentinites, peridotites) are noted. Bottom sediments around Antarctica stand out as a special type of iceberg deposits. They are characterized by the predominance of various clastic material, ranging from large boulders to silts and fine silts.

Climate

Unlike the Atlantic and Pacific Oceans, which have a meridional strike from the coast of Antarctica to the Arctic Circle and communicate with the Arctic Ocean, I. o. in the northern tropical region, it is bordered by a land mass, which largely determines the characteristics of its climate. The uneven heating of the land and ocean leads to a seasonal change in extensive minima and maxima of atmospheric pressure and to seasonal displacements of the tropical atmospheric front, which retreats southward to almost 10 ° S in the Northern Hemisphere in winter. sh., and in summer it is located in the foothills of southern Asia. As a result, over the northern part of I. o. monsoon climate dominates, which is primarily characterized by a change in wind direction during the year. The winter monsoon with relatively weak (3–4 m/s) and stable northeasterly winds operates from November to March. During this period, north of 10 ° S. sh. often calm. The summer monsoon with southwesterly winds is observed from May to September. In the northern tropical region and in the equatorial zone of the ocean, the average wind speed reaches 8–9 m/s, often reaching storm strength. In April and October, the baric field is usually restructured, and in these months the wind situation is unstable. Against the background of the prevailing monsoonal atmospheric circulation over the northern part of I. o. individual manifestations of cyclonic activity are possible. During the winter monsoon, there are cases of cyclones developing over the Arabian Sea, during the summer monsoon - over the waters of the Arabian Sea and the Bay of Bengal. Strong cyclones in these areas are sometimes formed during the periods of monsoon change.

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

South of 40°S sh. Atmospheric pressure in all seasons decreases uniformly from 1018–1016 hPa at the southern periphery of the South Indian High to 988 hPa at 60°S. sh. Under the influence of the meridional pressure gradient in the lower layer of the atmosphere, a stable reserve is maintained. air transfer. The highest average wind speed (up to 15 m/s) is observed in the middle of winter in the Southern Hemisphere. For higher southern latitudes, I. o. Throughout almost the entire year, storm conditions are typical, under which winds with speeds of more than 15 m/s, causing waves with a height of more than 5 m, have a frequency of 30%. South of 60°S sh. East winds and two or three cyclones per year are usually observed along the coast of Antarctica, most often in July - August.

In July, the highest values ​​of air temperature in the near layer of the atmosphere are observed at the top of the Persian Gulf (up to 34°C), the lowest are off the coast of Antarctica (–20°C), over the Arabian Sea and the Bay of Bengal, on average 26–28°C. Over the water area I. o. The air temperature almost everywhere varies according to the geographic latitude. In the southern part of I. o. it gradually decreases from north to south by about 1 °C for every 150 km. In January, the highest air temperatures (26–28 °C) are observed in the equatorial zone, near the northern coasts of the Arabian Sea and the Bay of Bengal - about 20 °C. In the southern part of the ocean, temperatures drop evenly from 26°C at the Tropic of the South to 0°C and slightly lower at the latitude of the Antarctic Circle. The amplitude of annual fluctuations in air temperature over b. hours of water area I. o. on average less than 10 °C and only off the coast of Antarctica increases to 16 °C.

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

Northeastern regions located in seismically active areas. The eastern coast of Africa and the islands of Madagascar, the shores of the Arabian Peninsula and the Hindustan Peninsula, almost all island archipelagos of volcanic origin, the western coasts of Australia, especially the arc of the Sunda Islands, in the past were repeatedly exposed to tsunami waves of various strengths, up to catastrophic ones. In 1883, after the explosion of the Krakatoa volcano, a tsunami with a wave height of over 30 m was recorded in the Jakarta region, in 2004 a tsunami caused by an earthquake in the region of the island of Sumatra had catastrophic consequences.

Hydrological regime

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

Water temperature. In the winter of the Northern Hemisphere, the highest water temperatures in the surface layer are observed in the equatorial zone - from 27 ° C off the coast of Africa to 29 ° C or more east of the Maldives. In the northern regions of the Arabian Sea and the Bay of Bengal, the water temperature is about 25 °C. In the southern part of I. o. Everywhere, a zonal distribution of temperature is characteristic, which gradually decreases from 27–28 ° C to 20 ° S. sh. to negative values ​​near the edge of drifting ice, located approximately at 65–67° S. sh. In the summer season, the highest water temperatures in the surface layer are observed in the Persian Gulf (up to 34 °C), in the northwest of the Arabian Sea (up to 30 °C), in the eastern part of the equatorial zone (up to 29 °C). In the coastal regions of the Somali and Arabian peninsulas, abnormally low values ​​\u200b\u200bare observed at this time of the year (sometimes less than 20 ° C), which is the result of the rise to the surface of cooled deep waters in the Somali Current system. In the southern part of I. o. The distribution of water temperature throughout the year retains a zonal character, with the difference that its negative values ​​in the winter of the Southern Hemisphere occur much further north, already at about 58–60 ° S. sh. The amplitude of annual fluctuations in water temperature in the surface layer is small and averages 2–5 °C, exceeding 7 °C only in the region of the Somali coast and in the Gulf of Oman of the Arabian Sea. The water temperature rapidly decreases vertically: at a depth of 250 m, it drops below 15 °C almost everywhere, and below 5 °C below 1000 m. At a depth of 2000 m, temperatures above 3 °C are observed only in the northern part of the Arabian Sea, in the central regions - about 2.5 °C, in the southern part it decreases from 2 °C to 50 ° S. sh. to 0 °C off the coast of Antarctica. Temperatures in the deepest (over 5000 m) basins range from 1.25 °C to 0 °C.

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

Density The highest density of water in I. o. noted in the Suez and Persian Gulfs (up to 1030 kg / m 3) and in cold Antarctic waters (1027 kg / m 3), the average - in the warmest and most saline waters in the northwest (1024–1024.5 kg / m 3) , the smallest is near the most freshened waters in the northeastern part of the ocean and in the Bay of Bengal (1018–1022 kg/m3). With depth, mainly due to a decrease in water temperature, its density increases, sharply increasing in the so-called. shock layer, which is most pronounced in the equatorial zone of the ocean.

Ice regime. Severity of climate in the southern part of the I. o. is such that the process of sea ice formation (when the air temperature is below –7 °C) can occur almost all year round. The ice cover reaches its maximum development in September-October, when the width of the drifting ice belt reaches 550 km, and the smallest - in January-February. The ice cover is characterized by high seasonal variability and its formation is very fast. The ice edge moves to the north at a speed of 5–7 km/day, and retreats to the south just as quickly (up to 9 km/day) during the melting period. The fast ice is established annually, reaches an average width of 25–40 km, and melts almost completely by February. Drifting ice near the coasts of the mainland moves under the influence of katabatic winds in the general direction to the west and northwest. Near the northern edge, the ice drifts eastward. A characteristic feature of the Antarctic ice cover is a large number of icebergs breaking off from the outlet and ice shelves of Antarctica. Especially large are table-shaped icebergs, which can reach a gigantic length of several tens of meters, towering 40-50 meters above the water. Their number rapidly decreases with distance from the coast of the mainland. The duration of the existence of large icebergs is on average 6 years.

I flow. The circulation of surface waters in the northern part of the I. o. It is formed under the influence of monsoon winds and therefore changes significantly from summer to winter. In February, from 8 ° N. sh. off the Nicobar Islands to 2° N. sh. off the coast of Africa there is a surface winter monsoon current with speeds of 50–80 cm/s; with a shaft running approximately 18°S. sh., in the same direction spreads the South Equatorial Current, which has an average speed on the surface of about 30 cm / s. Connecting off the coast of Africa, the waters of these two streams give rise to the Inter-trade countercurrent, which carries its waters to the east with velocities in the core of about 25 cm/s. Along the North African coast with a general direction to the south, the waters of the Somali Current move, partially passing into the Intertrade countercurrent, and to the south, the Mozambique and Cape of the Needle Current, going south at speeds of about 50 cm/s. Part of the South Equatorial Current off the east coast of the island of Madagascar turns south along it (the Madagascar Current). South of 40°S sh. the entire water area of ​​the ocean is crossed from west to east by the flow of the longest and most powerful in the oceans West wind currents(Antarctic Circumpolar Current). The velocities in its rods reach 50 cm/s, and the flow rate is about 150 million m 3 /s. At 100–110° E e. a stream branches off from it, heading north and giving rise to the West Australian Current. In August, the Somali current follows in a general direction to the northeast and, at a speed of up to 150 cm / s, draws water into the northern part of the Arabian Sea, from where the Monsoon current, skirting the western and southern shores of the Hindustan peninsula and the island of Sri Lanka, carries water to the shores of the island Sumatra, turns south and merges with the waters of the South Trade Wind. Thus, in the northern part of I. o. an extensive circulation is created, directed clockwise, consisting of the Monsoon, South Equatorial and Somali currents. In the southern part of the ocean, from February to August, the pattern of currents changes little. Off the coast of Antarctica in a narrow coastal strip, a current is observed all year round, caused by katabatic winds and directed from east to west.

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

Tides and waves e. The greatest distribution on the banks of I. o. have semidiurnal and irregular semidiurnal tides. Semi-diurnal tides are observed on the African coast south of the equator, in the Red Sea, off the northwestern shores of the Persian Gulf, in the Bay of Bengal, off the northwestern coast of Australia. Irregular semidiurnal tides - off the Somali Peninsula, in the Gulf of Aden, off the coast of the Arabian Sea, in the Persian Gulf, off the southwestern coast of the Sunda Island Arc. Diurnal and irregular daily tides are observed off the western and southern coasts of Australia. The highest tides are off the northwestern coast of Australia (up to 11.4 m), in the mouth zone of the Indus (8.4 m), in the mouth zone of the Ganges (5.9 m), off the coast of the Mozambique Channel (5.2 m) ; in the open ocean, the magnitude of the tides varies from 0.4 m near the Maldives to 2.0 m in the southeastern part of India. The excitement reaches its greatest strength in temperate latitudes in the zone of action of westerly winds, where the frequency of waves with a height of over 6 m is 17% per year. Near Kerguelen Island, waves 15 m high and 250 m long were recorded, off the coast of Australia, 11 m and 400 m, respectively.

Flora and fauna

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

The coastal zone of the ocean is characterized by the greatest species diversity. The shallow waters of the tropical zone are characterized by numerous 6- and 8-ray stony corals, hydrocorals, which, together with red algae, can create underwater reefs and atolls. The richest fauna of various invertebrates (sponges, worms, crabs, mollusks, sea urchins, brittle stars and starfish), small but brightly colored fish of coral reefs live among the powerful coral structures. Most of the coasts are occupied by mangroves. At the same time, the fauna and flora of the beaches and rocks that dry out at low tide are quantitatively depleted due to the depressing effect of the sun's rays. In the temperate zone, life on such stretches of coasts is much richer; dense thickets of red and brown algae (kelp, fucus, macrocystis) develop here, various invertebrates are abundant. According to L.A. Zenkevich(1965), St. 99% of all species of bottom and bottom animals living in the ocean live in the littoral and subtidal zones.

Rich flora is also characteristic of open spaces of the I. lake, especially for the surface layer. The food chain in the ocean begins with microscopic unicellular plant organisms - phytoplankton, which inhabits mainly the uppermost (about 100-meter) layer of ocean waters. Among them, several species of peridinium and diatom algae predominate, and in the Arabian Sea - cyanobacteria (blue-green algae), which often cause the so-called mass development of the so-called. water bloom. In the northern part of I. o. There are three areas of the highest phytoplankton production: the Arabian Sea, the Bay of Bengal and the Andaman Sea. The highest production is observed off the coast of the Arabian Peninsula, where the number of phytoplankton sometimes exceeds 1 million cells/l (cells per liter). Its high concentrations are also observed in the subantarctic and antarctic zones, where there are up to 300,000 cells/l during the spring flowering period. The smallest production of phytoplankton (less than 100 cells/l) is observed in the central part of the ocean between parallels 18 and 38°S. sh.

Zooplankton inhabits almost the entire thickness of oceanic waters, but its number rapidly decreases with increasing depth and decreases by 2–3 orders of magnitude towards the bottom layers. Food for b. phytoplankton serves as part of the zooplankton, especially those living in the upper layers, so the patterns of the spatial distribution of phyto- and zooplankton are largely similar. The highest rates of zooplankton biomass (from 100 to 200 mg/m 3) are observed in the Arabian and Andaman Seas, the Bengal, Aden and Persian Gulfs. Copepods (more than 100 species) make up the main biomass of the ocean's animals, with somewhat fewer pteropods, jellyfish, siphonophores, and other invertebrates. Of the unicellular, radiolarians are typical. In the Antarctic region, I. o. characterized by a huge number of euphausian crustaceans of several species, united under the name "krill". Euphausiids form the main food base for the largest animals on Earth - baleen whales. In addition, fish, seals, cephalopods, penguins and other bird species feed on krill.

Organisms that move freely in the marine environment (nekton) are represented in the I. o. mainly fish, cephalopods, cetaceans. From cephalopods to I. o. cuttlefish, numerous squids and octopuses are common. Of the fish, the most abundant are several species of flying fish, luminous anchovies (dollfish), sardinella, sardine, mackerel pike, notothenia, sea bass, several types of tuna, blue marlin, grenadier, sharks, rays. Sea turtles and poisonous sea snakes live in warm waters. The fauna of aquatic mammals is represented by various cetaceans. Of the baleen whales, the following are common: blue, sei whale, fin whale, humpback whale, Australian (Cape) whale. Toothed whales are represented by sperm whales, several species of dolphins (including killer whales). In the coastal waters of the southern part of the ocean, pinnipeds are widespread: Weddell seal, crabeater seal, seals - Australian, Tasmanian, Kerguelen and South African, Australian sea lion, sea leopard, etc. Among the birds, the most characteristic are the wandering albatross, petrels, large frigate, phaetons , cormorants, gannets, skuas, terns, gulls. South of 35°S sh., on the coasts of South Africa, Antarctica and the islands - numerous. colonies of several species of penguins.

In 1938, in I. o. a unique biological phenomenon was discovered - a living lobe-finned fish Latimeria chalumnae, considered extinct tens of millions of years ago. "Fossil" coelacanth lives at a depth of more than 200 m in two places - near the Comoros and in the waters of the Indonesian archipelago.

Research History

The northern coastal regions, especially the Red Sea and deeply incised bays, began to be used by man for navigation and fishing already in the era of ancient civilizations, several thousand years BC. e. For 600 years BC. e. Phoenician navigators, who were in the service of the Egyptian pharaoh Necho II, sailed around Africa. In 325-324 BC. e. comrade-in-arms of Alexander the Great Nearchus, commanding the fleet, sailed from India to Mesopotamia and compiled the first descriptions of the coast from the mouth of the Indus River to the top of the Persian Gulf. In the 8th–9th centuries The Arabian Sea was intensively mastered by Arab navigators, who created the first sailing directions and navigational guides for this area. In the 1st floor. 15th c. Chinese navigators led by Admiral Zheng He made a series of voyages along the Asian coast to the west, reaching the coast of Africa. In 1497–99 the Portuguese Vasco da Gama paved the sea route for Europeans to India and to the countries of Southeast Asia. A few years later, the Portuguese discovered the islands of Madagascar, the Amirante, Comoros, Mascarene and Seychelles. Following the Portuguese in I. o. infiltrated by the Dutch, French, Spanish and British. The name "Indian Ocean" first appeared on European maps in 1555. In 1772–75 J. cook got into I. about. to 71 ° 10 "S and carried out the first deep-sea measurements. The beginning of oceanographic research of the Acting Ocean was laid by systematic measurements of water temperature during the round-the-world voyages of the Russian ships Rurik (1815–18) and Enterprise (1823–26) In 1831–36, an English expedition took place on the ship Beagle, on which Charles Darwin carried out geological and biological work. in the northern part of the oceanographic survey was carried out by S. O. Makarov aboard the ship Vityaz in 1886. In the first half of the 20th century, oceanographic observations began to be carried out regularly, and by the 1950s they were carried out on almost 1,500 deep-sea oceanographic P. G. Schott’s monograph Geography of the Indian and Pacific Oceans, the first major publication summarizing the results of all previous studies in this region, was published in 1935. In 1959, Russian oceanographer A. M. Muromtsev published fun damental work - "The main features of the hydrology of the Indian Ocean." In 1960–65, the Scientific Committee on Oceanography of UNESCO conducted the International Indian Ocean Expedition (IIOE), the largest expedition that had previously worked in the Indian Ocean. Scientists from more than 20 countries of the world (USSR, Australia, Great Britain, India, Indonesia, Pakistan, Portugal, USA, France, Germany, Japan, etc.) took part in the MIOE program. During the MIOE, major geographical discoveries were made: the underwater West Indian and East Indian ridges were discovered; etc., deep trenches - the Ob, Chagos, Vima, Vityaz, etc. In the history of the study of I. o. the results of studies carried out in 1959–77 AD are especially highlighted. vessel "Vityaz" (10 voyages) and dozens of other Soviet expeditions on the ships of the Hydrometeorological Service and the State Committee for Fisheries. From the beginning 1980s ocean research was carried out within the framework of 20 international projects. Researches And. about. during the International Ocean Circulation Experiment (WOCE). After its successful completion in con. 1990s the volume of modern oceanographic information according to I. o. doubled.

Modern researches I. about. are carried out within the framework of international programs and projects, such as the International Geosphere-Biosphere Program (since 1986, 77 countries participate), including the projects Dynamics of Global Ocean Ecosystems (GLOBES, 1995–2010), Global Flows of Matter in the Ocean ( JGOFS, 1988–2003), Land–Ocean Interaction in the Coastal Zone (LOICZ), Integral Marine Biogeochemistry and Ecosystem Research (IMBER), Land–Ocean Interaction in the Coastal Zone (LOICZ, 1993–2015), Ocean Surface Interaction with lower atmosphere (SOLAS, 2004–15, ongoing); "World Climate Research Program" (WCRP, since 1980, 50 countries participate), the main marine part of which is the program "Climate and Ocean: Unsteadiness, Predictability and Variability" (CLIVAR, since 1995), based on the results of TOGA and WOCE; International Study of Biogeochemical Cycles and Large Scale Distribution of Trace Elements and Their Isotopes in the Marine Environment (GEOTRACES, 2006–15, ongoing) and more. etc. The Global Ocean Observing System (GOOS) is being developed. Since 2005, the international ARGO program has been operating, in which observations are carried out by autonomous sounding instruments throughout the World Ocean (including IO), and the results are transmitted via artificial Earth satellites to data centers. From con. 2015 begins the 2nd International Indian Ocean Expedition, designed for 5 years of research with the participation of many countries.

Economic use

Coastal zone I. o. has an exceptionally high population density. More than 35 states are located on the coasts and islands, in which about 2.5 billion people live. (over 30% of the world's population). The bulk of the coastal population is concentrated in South Asia (more than 10 cities with a population of over 1 million people). In most countries of the region, the problems of finding living space, creating jobs, providing food, clothing and housing, and medical care are acute.

The use of the sea, as well as other seas and oceans, is carried out in several main areas: transport, fishing, extraction of mineral resources, and recreation.

Transport

Role I. o. in maritime transportation increased significantly with the creation of the Suez Canal (1869), which opened a short sea route of communication with the states washed by the waters of the Atlantic Ocean. is an area of ​​transit and export of all kinds of raw materials, in which almost all major seaports are of international importance. In the northeastern part of the ocean (in the Straits of Malacca and Sunda) there are routes for ships going to the Pacific Ocean and back. The main export item to the US, Japan and Western Europe is crude oil from the Persian Gulf region. In addition, agricultural products are exported - natural rubber, cotton, coffee, tea, tobacco, fruits, nuts, rice, wool; wood; miner. raw materials - coal, iron ore, nickel, manganese, antimony, bauxite, etc.; machinery, equipment, tools and hardware, chemicals and pharmaceuticals, textiles, cut gems and jewellery. To the share of I. o. accounts for about 10% of the world shipping turnover, in con. 20th century about 0.5 billion tons of cargo per year was transported through its waters (according to IOC data). According to these indicators, it ranks third after the Atlantic and Pacific Oceans, yielding to them in terms of the intensity of shipping and total volumes of cargo transportation, but surpassing all other sea transport communications in terms of oil transportation. The main transport routes along the I. O. are directed to the Suez Canal, the Strait of Malacca, the southern extremities of Africa and Australia, and along the northern coast. Shipping is most intensive in the northern regions, although it is limited by storm conditions during the summer monsoon, less intensive in the central and southern regions. The growth in oil production in the countries of the Persian Gulf, in Australia, Indonesia, and other places contributed to the construction and modernization of oil loading ports and the appearance in the waters of the I. O. giant tankers. The most developed transport routes for the transportation of oil, gas and oil products: the Persian Gulf - the Red Sea - the Suez Canal - the Atlantic Ocean; Persian Gulf - Strait of Malacca - Pacific Ocean; the Persian Gulf - the southern tip of Africa - the Atlantic Ocean (especially before the reconstruction of the Suez Canal, 1981); The Persian Gulf - the coast of Australia (the port of Fremantle). Mineral and agricultural raw materials, textiles, precious stones, jewelry, equipment, computer equipment are transported from India, Indonesia, and Thailand. Australia transports coal, gold, aluminium, alumina, iron ore, diamonds, uranium ores and concentrates, manganese, lead, zinc; wool, wheat, meat products, as well as internal combustion engines, cars, electrical products, river boats, glass products, rolled steel, etc. Industrial goods, automobiles, electronic equipment, and others predominate in oncoming flows. engaged in the transport of passengers.

Fishing

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

Mineral resources

Practically throughout the entire shelf region of I. o. deposits of oil and natural combustible gas or oil and gas shows have been identified. Actively developed oil and gas fields in the Persian Gulf ( Persian Gulf oil and gas basin), Suez (Gulf of Suez oil and gas basin), Cambay ( Cambay oil and gas basin), Bengali ( Bengal oil and gas basin); off the northern coast of the island of Sumatra (North Sumatra oil and gas basin), in the Timor Sea, off the northwestern coast of Australia (gas-bearing Carnarvon basin), in the Bass Strait (gas-bearing Gippsland basin). Gas deposits have been explored in the Andaman Sea, oil and gas bearing areas - in the Red Sea, the Gulf of Aden, along the coast of Africa. Coastal-marine placers of heavy sands are mined off the coast of the island of Mozambique, along the southwestern and northeastern coasts of India, off the northeastern coast of the island of Sri Lanka, along the southwestern coast of Australia (mining of ilmenite, rutile, monazite and zircon); in the coastal regions of Indonesia, Malaysia, Thailand (cassiterite mining). On the shelves I. o. found industrial accumulations of phosphorites. Large fields of ferromanganese nodules, a promising source of Mn, Ni, Cu, and Co, have been established on the ocean floor. In the Red Sea, metal-bearing brines and sediments have been identified as potential sources for the extraction of iron, manganese, copper, zinc, nickel, etc.; there are deposits of rock salt. In the coastal zone I. o. sand is mined for construction and glass production, gravel, limestone.

Recreational resources

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

Port cities

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

As you know, the territory of our planet is washed by four oceans. The Atlantic and Indian Oceans rank second and third in terms of water volume, respectively.

These oceans are home to unique species of aquatic animals and vegetation.

History of the discovery of the Atlantic Ocean

The development of the Atlantic Ocean began in the era of early Antiquity. It was then that the ancient Phoenician navigators began to make the first trips to the Mediterranean Sea and the eastern coast of the Atlantic Ocean.

However, only European northern peoples managed to cross the Atlantic Ocean in the 9th century. The "golden era" of the exploration of the Atlantic was laid by the famous navigator Christopher Columbus.

During his expeditions, many seas and bays of the Atlantic Ocean were discovered. Modern scientists - oceanologists continue to study the Atlantic Ocean, in particular the relief structures of its bottom.

History of the discovery of the Indian Ocean

The history of the discovery of the Indian Ocean is rooted in the days of ancient civilizations. The ocean served as the main trade route for the Persians, Indians, Egyptians, and Phoenicians.

The Chinese were the first to explore the Indian Ocean. It is to the Chinese navigator Ho's wife managed for the first time during his expedition to explore the shores of Sri Lanka, the Arabian Peninsula, Persia and Africa.

The large-scale development of the Indian Ocean began with the first expeditions of the Portuguese Vasco de Gama, who managed not only to reach the coast of India, completely rounding the African coast, but also to discover many islands in the Indian Ocean.

Atlantic Ocean: general information

The Atlantic Ocean is the second largest ocean in the world in terms of its size. Its waters cover an area of ​​80 million square meters. km.

The formation of the Atlantic Ocean began more than 150 million years ago, at a time when the modern American continent began to separate from Eurasia. The Atlantic Ocean is considered the youngest among all existing oceans.

The maximum depth reaches 9 km(trough, which is located off the coast of Puerto Rico). The Atlantic Ocean washes the shores of such continents: Eurasia, Africa, South and North America, as well as Antarctica.

Indian Ocean: general information

Indian Ocean, with an area of ​​about 70 million km. sq., ranks third in size among other oceans. The deepest place in the Indian Ocean is a depression near Java islands(Indonesia), the depth of which reaches 7 km.

The waters of the Indian Ocean are characterized by frequent changes in the direction of the current. The Indian Ocean washes Eurasia, Africa, Australia, Antarctica.

The Indian Ocean is 20% of the world's oceans by volume. It is bounded by Asia to the north, Africa to the west, and Australia to the east.

In the zone of 35 ° S passes the conditional border with the Southern Ocean.

Description and characteristics

The waters of the Indian Ocean are famous for their transparency and azure color. The fact is that few freshwater rivers, these "troublemakers," flow into this ocean. Therefore, by the way, the water here is much saltier than in others. The Red Sea, the saltiest sea in the world, is located in the Indian Ocean.

And the ocean is rich in minerals. The region near Sri Lanka has been famous for its pearls, diamonds and emeralds since ancient times. And the Persian Gulf is rich in oil and gas.
Area: 76.170 thousand sq. km

Volume: 282.650 thousand cubic km

Average depth: 3711 m, the greatest depth is the Sunda Trench (7729 m).

Average temperature: 17°C, but in the north the waters warm up to 28°C.

Currents: two cycles are conditionally distinguished - northern and southern. Both move clockwise and are separated by the Equatorial Countercurrent.

Major currents of the Indian Ocean

Warm:

Northern Tradewind- originates in Oceania, crosses the ocean from east to west. Beyond the peninsula, Hindustan is divided into two branches. Part flows to the north and gives rise to the Somali current. And the second part of the flow goes south, where it merges with the equatorial countercurrent.

South Passatnoye- begins at the islands of Oceania and moves from east to west up to the island of Madagascar.

Madagascar- branches off from the South Tradewind and flows parallel to the Mozambique from north to south, but slightly east of the Madagascar coast. Average temperature: 26°C.

mozambican is another branch of the South Tradewind Current. It washes the coast of Africa and merges with the Agulhas in the south. The average temperature is 25°C, the speed is 2.8 km/h.

Agulhas, or the course of Cape Agulhas- a narrow and fast current that runs along the east coast of Africa from north to south.

Cold:

Somali- a current off the coast of the Somali peninsula, which changes its direction depending on the monsoon season.

The course of the West winds encircles the globe in southern latitudes. In the Indian Ocean, from it is the South Indian Ocean, which, near the coast of Australia, passes into the West Australian.

Western Australian- moves from south to north along the western coast of Australia. As you get closer to the equator, the water temperature rises from 15°C to 26°C. Speed: 0.9-0.7 km/h.

Underwater world of the Indian Ocean

Most of the ocean is located in the subtropical and tropical zones, and therefore is rich and diverse in terms of species.

The coast of the tropics is represented by vast thickets of mangroves, home to numerous colonies of crabs and amazing fish - mudskippers. Shallow waters are a great habitat for corals. And in temperate waters, brown, calcareous and red algae (kelp, macrocysts, fucuses) grow.

Invertebrates: numerous mollusks, a huge number of species of crustaceans, jellyfish. Lots of sea snakes, especially venomous ones.

Sharks of the Indian Ocean are a special pride of the water area. The largest number of shark species live here: blue, gray, tiger, great white, mako, etc.

Of the mammals, dolphins and killer whales are the most common. And the southern part of the ocean is the natural habitat of many species of whales and pinnipeds: dugongs, seals, seals. Most of the birds are penguins and albatrosses.

Despite the richness of the Indian Ocean, the seafood industry is poorly developed here. The catch is only 5% of the world. They harvest tuna, sardines, rays, lobsters, lobsters and shrimp.

Indian Ocean exploration

The coastal countries of the Indian Ocean are the centers of the most ancient civilizations. That is why the development of the water area began much earlier than, for example, the Atlantic or the Pacific Ocean. Approximately 6 thousand years BC. the waters of the ocean were already plowed by shuttles and boats of ancient people. The inhabitants of Mesopotamia sailed to the shores of India and Arabia, the Egyptians carried on a lively maritime trade with the countries of East Africa and the Arabian Peninsula.

Key dates in the history of ocean exploration:

7th century AD - Arab sailors draw up detailed navigational charts of the coastal zones of the Indian Ocean, explore the water area near the eastern coast of Africa, India, the islands of Java, Ceylon, Timor, and the Maldives.

1405-1433 - Zheng He's seven sea voyages and exploration of trade routes in the northern and eastern parts of the ocean.

1497 - Vasco de Gama sails and explores the east coast of Africa.

(Expedition of Vasco de Gama in 1497)

1642 - two raids by A. Tasman, exploration of the central part of the ocean and the discovery of Australia.

1872-1876 - the first scientific expedition of the English corvette "Challenger", the study of the biology of the ocean, relief, currents.

1886-1889 - expedition of Russian explorers led by S. Makarov.

1960-1965 - International Indian Ocean Expedition, established under the auspices of UNESCO. The study of hydrology, hydrochemistry, geology and biology of the ocean.

1990s - present: studying the ocean with the help of satellites, compiling a detailed bathymetric atlas.

2014 - after the crash of the Malaysian Boeing, detailed mapping of the southern part of the ocean was carried out, new underwater ridges and volcanoes were discovered.

The ancient name of the ocean is Eastern.

Many species of wildlife in the Indian Ocean have an unusual property - they glow. In particular, this explains the appearance of luminous circles in the ocean.

In the Indian Ocean, ships are periodically found in good condition, however, where the entire crew disappears remains a mystery. Over the past century, this has happened to three ships at once: the ship "Cabin Cruiser", the tankers "Houston Market" and "Tarbon".