1 what is the world ocean. General provisions. Origin of the ocean

The World Ocean is a continuous water shell of the Earth, which occupies 71% of its surface (361.1 million km 2). In the Northern Hemisphere, the ocean accounts for 61% of the surface, in the Southern Hemisphere - 81%. The concept of the World Ocean was introduced into Russian science by Yu. M. Shokalsky. In terms of its physical, chemical, and biological characteristics, the World Ocean represents a single whole, but is diverse in many characteristics - climatic, dynamic, optical, elements of the water regime, etc.

Parts of the World Ocean

Based on the totality of all the characteristics, the water shell of the Earth is divided into several oceans. These are large parts of the World Ocean, limited by the coastlines of continents. The existence of three oceans is canonically recognized: the Pacific, Atlantic and Indian. In our country and a number of foreign countries, for example in Great Britain, it is customary to distinguish the Arctic Ocean. In addition, many recognize the existence of another one - the Southern Ocean, washing the shores of Antarctica. According to more ancient traditions, 7 oceans are distinguished, dividing the Pacific and Atlantic oceans into the Northern and Southern parts. This is evidenced by the concept of the North Atlantic that has survived to this day.

The division of the World Ocean into separate parts is quite arbitrary. In some cases, the boundaries are also arbitrary, especially in the south (for example, between the Atlantic and Indian Oceans, the Indian and Pacific Oceans). Nevertheless, there are a number of signs and characteristics that are inherent in each of the four oceans separately. Each of the oceans has a certain configuration, size, and pattern of the coastline of continents and islands.

Despite the commonality of geostructures (the presence of underwater continental margins, transition zones, mid-ocean ridges and beds), they occupy different areas, and the bottom topography of each is individual. Oceans have their own structure of temperature distribution, salinity, water transparency, characteristic features of atmospheric and water circulation, their own system of currents, ebbs and flows, etc.

The individual characteristics of each ocean make it an independent giant biotope. Physical, chemical and dynamic properties create special conditions for the life of plants and animals.

The oceans significantly influence the formation of natural processes on the continents. Visual observations of the oceans by astronauts confirmed the individuality of each of the oceans, for example, each of them has a specific color. The Atlantic Ocean appears blue from space, the Indian Ocean appears turquoise, especially off the coast of Asia, and the Arctic Ocean appears white.

A number of experts recognize the existence of a fifth ocean - the Southern Arctic. It was first isolated in 1650 by the Dutch scientist B. Varenius, who proposed dividing the World Ocean into five separate parts - oceans. The Southern Arctic Ocean is the part of the World Ocean adjacent to Antarctica. In 1845 it was named Antarctic by the Royal Geographical Society of Great Britain, and under these two names it was distinguished by the International Hydrographic Office until 1937. In Russian literature, it was shown as an independent species in 1966 in the Atlas of the Antarctic. The southern border of this ocean is the coastline of Antarctica.

The basis for distinguishing the Southern Ocean are the special, very harsh climatic and hydrological conditions in this region, increased ice cover, common circulation of the surface layer of water, etc. Some researchers draw the boundary of the Southern Ocean along the southern periphery of the Antarctic convergence, located on average at 55° S. w. Within the indicated northern border, the ocean area is 36 million km 2, i.e. it is more than two times larger than the Arctic Ocean.

The climatic and hydrological conditions of the ocean have specific features, but are inextricably linked with the adjacent regions of the Pacific, Atlantic and Indian Oceans.

The spatial heterogeneity of the oceans is largely determined by their geographical location, structural features of the basin and morphometric characteristics.

On Earth, more than two-thirds of the surface is covered with water. The climate of the planet largely depends on the world ocean; life originated in it (see article ““), it provides us with food and many other necessary products. The total volume of the world's oceans is about 1400 million km 3, but it is unevenly distributed over the surface of the planet. Most of this water occurs in the Southern Hemisphere.

There are five main oceans

The largest of them is, covering 32% of the surface of the globe. It covers an area of more than 160 million km2 - more than the entire land mass. It is also the deepest ocean; its average depth is 4200 m, and the Mariana Trench has a depth of over 11 km.
half the size of the Quiet: it occupies an area of 80 million km 2. It is inferior to the Pacific Ocean in depth: it reaches its maximum depth (9558 m) in the Puerto Rico Trench,
located in the Southern Hemisphere and covers an area of 73.5 million km 2.
Little is almost completely surrounded by land and is usually covered with ice 3-4 m thick.
The Antarctic waters, sometimes called the Antarctic or Southern Ocean, are significantly larger and surround the mainland. Two thirds of these waters freeze in winter.

Seas are significantly smaller and shallower parts of the oceans and are partially surrounded by land. These include, for example, the Mediterranean, Baltic, Bering and Caribbean seas. - a real planet-ocean. From space, the Earth appears blue because the oceans cover 930 million km2. or 71% of its surface.

Sea jungle

Coral reefs grow in the warm coastal tropical waters of the world's oceans. Reefs can be called marine jungles due to the amazing diversity of plants and animals found around them.

Sperm whales

Sperm whales live in all oceans. This is the most numerous species, but for a long time they were intensively hunted for fat, which led to a reduction in their numbers. The sperm whale's head makes up about a third of the animal's total body length. Sperm whales have the largest brains of any mammal.

The first navigators

floating ice

Icebergs are huge floes that break off from glaciers or shelf (coastal) ice and float on ocean currents.

Oil leak

Man admires the world's oceans, is afraid of it, extracts food from it, but at the same time pollutes and harms it. , such as what happened on the Exxon Voldez tanker in March 1989, is just one of many examples of the destructive impact of humans on the oceans. Fortunately, work is currently underway on .

Mountain ranges at the bottom of the seas

The bottom of the seas is dominated by ridges. The Mid-Atlantic Ridge extends from north to south, with abyssal (deep) plains on either side of it. The underwater ridges of the Pacific and Indian Oceans have a more complex shape.

Features of the World Ocean

The term “World Ocean” was introduced into the practice of scientific research by the French hydrographer Claret de Florier at the end of the 18th century. This concept refers to the totality of the oceans - the Arctic, Atlantic, Pacific and Indian (some researchers also identify the Southern Ocean, which washes the shores of Antarctica, but its northern boundaries are quite uncertain), as well as marginal and inland seas. The world's oceans occupy 361 million km 2, or 70.8% of the globe's area.

The world's oceans are not only about water, but also about aquatic animals and plants, its bottom and shores. At the same time, the World Ocean is understood as an independent integral formation, an object on a planetary scale, as an open dynamic system that exchanges matter and energy with the media in contact with it. This exchange occurs in the form of planetary cycles, which involve heat, moisture, salts and gases that make up the oceans and continents.

Salinity of the World Ocean

By its structure, sea water is a completely ionized homogeneous solution. Its salinity is determined by the presence of halogens, sulfates, sodium carbonates, potassium, magnesium and calcium in the dissolved state (in % 0).

On average, the salinity of the World Ocean is 35% o, but varies within fairly wide limits depending on the level of evaporation and the volume of river flow. In the case when river flow in the seas predominates, salinity drops below the average value. For example, in the Baltic Sea it is 6-11% o. If evaporation predominates, salinity rises above average. In the Mediterranean Sea it ranges from 37 to 38% o, and in the Red Sea it is 41% o. The Dead Sea and some salt and bitter-salt lakes (Elton, Baskunchak, etc.) have the highest salinity.

Gases are dissolved in ocean water: N 2, O 2, CO 2, H 2 S, etc. Due to high horizontal and vertical hydrodynamics, caused by differences in temperature, density and salinity, mixing of atmospheric gases occurs. Changes in their content are associated with the vital activity of organisms, underwater volcanism, chemical reactions in the water column and at the bottom, as well as the intensity of the removal of suspended or dissolved matter from the continents.

Some semi-enclosed parts of the World Ocean - the Black Sea or the Gulf of Oman - are characterized by hydrogen sulfide contamination, which spreads from depths of 200 m. The cause of such contamination is not only juvenile gases, but also chemical reactions leading to the reduction of sulfates that occur in sediments with the participation of anaerobic bacteria.

Water transparency, i.e., the depth of penetration of sunlight into the depths, is of great importance for the life of marine organisms. Transparency depends on the mineral particles suspended in the water and the volume of microplankton. The conditional transparency of ocean water is taken to be the depth at which a white disk, the so-called Secchi disk, with a diameter of 30 cm, becomes invisible. The relative transparency (m) of parts of the World Ocean is different.

Temperature regime of the World Ocean

The temperature regime of the ocean is determined by the absorption of solar radiation and the evaporation of water vapor from its surface. The average of the World Ocean is 3.8°C, the maximum, 33°C, is set in the Persian Gulf, and the minimum temperature is -1.6; -1°С are typical for polar regions.

At different depths of ocean waters there is a quasi-homogeneous layer, which is characterized by almost identical temperatures. Below it is the seasonal thermocline. The temperature difference in it during the period of maximum heating reaches 10-15°C. Below the seasonal thermocline lies the main thermocline, which covers the main column of ocean waters with a temperature difference of several degrees. The depth of the thermocline in different parts of the same ocean is not the same. This depends not only on temperature conditions in the near-surface part, but also on the hydrodynamics and salinity of the waters of the World Ocean.

Adjacent to the ocean floor is a bottom boundary layer in which low temperatures are recorded, varying depending on the geographical location from 0.3 to -2 °C.

The density of ocean water changes depending on the temperature. Its average density in the surface areas is 1.02 g/cm 3 . With depth, as temperature decreases and pressure increases, density increases.

Currents of the World Ocean

As a result of the action of Coriolis forces, temperature differences, fluctuations in atmospheric pressure, and interaction with the moving atmosphere, currents arise, which are divided into drift, gradient and tidal. In addition to them, the ocean is characterized by synoptic eddies, seiches and tsunamis.

Drift currents are formed under the influence of wind as a result of friction of the air flow on the water surface. The direction of the current makes an angle of 45° with the direction of the wind, which is determined by the influence of Coriolis forces. A characteristic feature of drift currents is the gradual attenuation of their intensity with changes in depth.

Gradient currents arise as a result of the formation of a slope in the water level under the influence of wind blowing for a long time. The maximum slope is observed near the coast. It creates a pressure gradient, which leads to the appearance of a surge or surge current. Gradient currents capture the entire thickness of the water, right down to the bottom.

There are barogradient and convection currents in the World Ocean. Barogradient ones arise as a result of differences in atmospheric pressure in cyclones and anticyclones over different parts of the World Ocean. Convection currents are formed due to differences in the density of sea water at the same depth, creating a horizontal pressure gradient.

Tidal currents exist in marginal seas and within shallow seas. They arise as a result of the influence on the water column of the gravitational fields of the Earth, Moon and Sun, as well as the centrifugal force of the Earth’s rotation and Coriolis forces.

In certain areas of the World Ocean, non-stationary vortex-like disturbances of water with a diameter of up to 400 km have been discovered. They often cover the entire thickness of the water and reach the bottom. Their speed is several centimeters per second. Among them are frontal vortices, which arise when bends and eddies are cut off from the main flow, and open ocean vortices.

Waves caused by earthquakes on the sea or ocean floor. The wavelength ranges from several tens to hundreds of kilometers with a period of 2 to 200 minutes and a speed in the open ocean of up to 1000 km/h. In the open ocean, tsunami waves can be about a meter high and may not even be noticed. However, in shallow waters and off the coast, wave heights reach 40-50 m.

Seiches are standing waves of enclosed bodies of water, characteristic only of inland seas. The water in them fluctuates with an amplitude of up to 60 m. Seiches are caused by tidal phenomena or strong winds leading to surges and surges, as well as sudden changes in atmospheric pressure.

Bioproductivity of the World Ocean

Bioproductivity is determined by the biomass of animals, aquatic plants and microorganisms living in the water column. The total biomass in the World Ocean exceeds 3.9 * 10 9 tons. Of this, about 0.27 * 10 9 tons are found on the shelf, in thickets of coral reefs and algae - 1.2 * 10 9 tons, in estuaries - 1, 4 * 10 9 tons, and in the open ocean - 1 * 10 9 tons. In the World Ocean there are about 6 million tons of plant matter, mainly in the form of phytoplankton, and about 6 million tons of zooplankton. Shallow waters and underwater sea deltas located in tropical areas have maximum bioproductivity. The places where underwater currents reach the surface of the oceans, carrying water enriched with phosphates, nitrates and other salts from depths of more than 200 m, have significant biological productivity. These areas are called upwelling zones. In places where such currents emerge, such as in the Bay of Benguela, along the coasts of Peru, Chile and Antarctica, zooplankton develops rapidly.

Ecological functions of the World Ocean

The World Ocean performs very diverse and extensive ecological functions through the active interaction of the aquatic environment with the atmosphere, lithosphere, continental runoff and with the organisms inhabiting its expanses.

As a result of interaction with the atmosphere, energy and matter are exchanged, in particular oxygen and carbon dioxide. The most intense oxygen exchange in the ocean system occurs in temperate latitudes.

The world's oceans provide life to the organisms that inhabit it, giving them warmth and food. Each representative of these very extensive ecosystems (plankton, nekton and benthos) develops depending on temperature, hydrodynamic regimes and the availability of nutrients. A typical example of the direct impact on the life of marine biota is the temperature factor. In many marine organisms, the timing of reproduction is confined to certain temperature conditions. The life of marine animals is directly influenced not only by the presence of light, but also by hydrostatic pressure. In ocean waters it increases by one atmosphere for every 10 m of depth. In the inhabitants of great depths, the variegation of color disappears, they become monochromatic, the skeleton becomes thinner, and from certain depths (deeper than 4500 m) forms with a calcareous shell completely disappear, which are replaced by organisms with a silica or organic skeleton. Surface and deep currents greatly influence the life and distribution of marine biota.

The dynamics of the waters of the World Ocean is one of the components of the ecological function of the World Ocean. The activity of surface and deep currents is associated with different temperature regimes and the nature of the distribution of surface and bottom temperatures, characteristics of salinity, density and hydrostatic pressure. Earthquakes and tsunamis, together with storms and strong wave movements of water, are involved in widespread marine abrasion of coastal areas. Underwater gravitational processes, as well as underwater volcanic activity, together with underwater hydrodynamics, form the topography of the bottom of the World Ocean.

The resource role of the World Ocean is great. Sea water itself, regardless of its degree of salinity, is a natural raw material that is used by humanity in various forms. The world's oceans are a kind of heat accumulator. Slowly heating up, it slowly releases heat and thus is an important component of the climate-forming system, which, as is known, includes the atmosphere, biosphere, cryosphere and lithosphere.

Part of the kinetic and thermal energy of the World Ocean is fundamentally available for use in human economic activities. Kinematic energy is possessed by waves, ebbs and flows, sea currents, and vertical movements of water (upwellings). They constitute energy resources, and, therefore, the World Ocean is an energy base that is gradually being developed by humanity. The use of tidal energy began and an attempt was made to use waves and sea surf.

A number of coastal states, located in arid regions and experiencing a shortage of fresh water, have high hopes for desalination of sea water. Existing desalination plants are energy-intensive and therefore require electricity from nuclear power plants to operate them. Seawater desalination technologies are quite expensive.

The world's oceans are a global habitat. Marine aquatic organisms live from the surface to the greatest depths. Organisms inhabit not only the water column, but also the seas and oceans. All of them represent biological resources. However, only a small part of the organic world of the ocean is used by humanity. The biological resources of the World Ocean are only those few groups of marine life, the extraction of which is currently economically justified. These include fish, marine invertebrates (bivalves, cephalopods and gastropods, crustaceans and echinoderms), marine mammals (cetaceans and pinnipeds), and algae.

Many regions of the World Ocean, from the shelf zone to the abyssal depths, have a variety of mineral resources. The mineral resources of the World Ocean include solid, liquid and gaseous minerals located in the coastal strip of land, on the bottom and in the subsoil under the bottom of the World Ocean. They arose in different geodynamic and physical-geographical conditions. The main ones are coastal placers of titanium magnetite, zirconium, monazite, cassiterite, native gold, platinum, chromite, silver, diamonds, deposits of phosphorites, sulfur, oil and gas, ferromanganese nodules.

The interaction of the surface of the World Ocean with such a mobile shell as the atmosphere leads to the occurrence of weather phenomena. Cyclones are born over the oceans, which transport moisture to the continents. Depending on the place of their birth, cyclones are divided into cyclones of tropical and extratropical latitudes. The most mobile are tropical cyclones, which often become sources of severe natural disasters covering vast regions. These include typhoons and hurricanes.

The world ocean, due to its physical and geographical features, the mineral composition of waters and the uniform distribution of temperatures and air moisture, plays a recreational role. Due to the high content of certain ions, sea water and sea water, which in its chemical composition is close to the composition of blood plasma, play an important therapeutic role. Thanks to their balneological and micromineral qualities, sea waters serve as an excellent place for recreation and treatment of people.

Geological impacts and environmental consequences of natural processes in the World Ocean

Sea waves erode the shore and transport and deposit debris. Abrasion of rocky and loose rocks that make up the coasts is associated with drift and tidal currents. Waves continuously undermine and destroy coastal rocks. During storms, colossal masses of water fall onto the shore, forming splashes and breakers several tens of meters high. The force of the impact of the waves is such that they are capable of destroying and moving over a certain distance shore protection structures (breakwaters, breakwaters, concrete blocks) weighing hundreds of tons. The impact force of waves during a storm reaches several tons per square meter. Such waves not only destroy and crush rocks and concrete structures, but also move blocks of rocks weighing tens and hundreds of tons.

Less impressive due to its duration, but a strong impact on the shore is exerted by everyday wave splashes. As a result of the almost continuous action of waves, a wave-breaking niche is formed at the base of the coastal slope, the deepening of which leads to the collapse of the cornice rocks.

At first, the blocks of the destroyed cornice slowly slide towards the sea, and then break up into separate fragments. Large blocks remain at the foot for some time, and the oncoming waves crush and transform them. As a result of prolonged exposure to waves, a platform is formed near the shore, covered with rounded debris - pebbles. A coastal (wave-breaking) ledge or cliff appears, and the coast itself, as a result of erosion, retreats inland. As a result of the action of waves, wave-cut grottoes, stone bridges or arches and deep crevasses are formed.

Massifs of durable rocks separated from the land as a result of erosion, large fragments of sea coasts turn into sea cliffs or columnar rocks. As erosion moves inland, destroying and removing coastal rocks, the coastal slope along which the waves roll expands and turns into a flat surface called a wave terrace. At low tide it is exposed, and numerous irregularities are visible on it - holes, ditches, hills, rocky reefs.

Boulders, pebbles and sand, which originate from wave action and cause wave erosion, are themselves eroded over time. They rub against each other, acquiring a rounded shape and decreasing in size.

Depending on the duration and strength of the waves, the speed of erosion and movement of the coast is different. For example, on the western coast of France (Médoc Peninsula) the coast is moving away from the sea at a rate of 15-35 m/year, in the Sochi region - 4 m/year. A striking example of the influence of the sea on land is the island of Heligoland in the North Sea. As a result of wave erosion, its perimeter decreased from 200 km, which it was in 900, to 5 km in 1900. Thus, its area decreased by 885 km 2 over a thousand years (the annual retreat rate was 0.9 km 2 ).

Coastal destruction occurs when waves are directed perpendicular to the shore. The smaller the angle or the more rugged the coast, the less marine abrasion, which gives way to the accumulation of debris. Pebbles and sand accumulate on capes that limit the entrances to bays and bays, and in places where wave action is significantly reduced. Spit marks begin to form, gradually blocking the entrance to the bay. Then they turn into a bar, separating the bay from the open sea. Lagoons appear. Examples include the Arabat Spit, which separates Sivash from the Sea of Azov, the Curonian Spit at the entrance to the Gulf of Riga, etc.

Coastal sediments accumulate not only in the form of spits, but also in the form of beaches, bars, barrier reefs and wave terraces.

Control of coastal erosion and sedimentation in the coastal zone is one of the pressing problems of protecting sea coasts, especially those that have been developed by humans and are used both as resort areas and as port facilities. In order to prevent sea erosion and damage to port facilities, artificial structures are erected to restrain the activity of waves and coastal currents. Protective walls, lintels, lining, breakwaters, and dams, although they limit the impact of storm waves, sometimes themselves disrupt the existing hydrological regime. At the same time, in some places the shores suddenly erode, while in others debris material begins to accumulate, which sharply reduces navigability. In a number of places, beaches are artificially replenished with sand. Special structures built in the beach migration zone perpendicular to the shore are successfully used to build up the sandy beach. Knowledge of the hydrological regime made it possible to build wonderful sandy beaches in Gelendzhik and Gagra; the beach at Cape Pitsunda was once saved from erosion. Rock fragments for artificial reclamation of the coast were thrown into the sea at certain points, and then transported along the coast by the waves themselves, accumulating and gradually turning into pebbles and sand.

For all its positive effects, artificial bank reclamation also has negative aspects. Discarded sand and pebbles are usually mined in close proximity to the coast, which ultimately negatively affects the ecological state of the region. Production in the 70s of the XX century. pebbles and sand for construction needs led to the partial destruction of the Arabat Spit, which entailed an increase in the salinity of the Azov Sea and, as a consequence, caused a reduction and even the disappearance of individual representatives of the marine fauna.

At one time, much attention was paid to the problem of the Kara-Bogaz-Gol Bay. The decrease in the level of the Caspian Sea was directly related to the large volume of evaporation in this gulf. It was believed that only the construction of a dam, blocking the access of water to the bay, could save the Caspian Sea. However, the dam not only did not lead to an increase in the level of the Caspian Sea (the sea level began to rise for other reasons and long before the construction of the dam), but also upset the balance between the inflow and evaporation of sea water. This, in turn, caused the drainage of the bay, changed the processes of formation of unique deposits of self-sedimentary salts, led to deflation of the dried salt surface and the spread of salts over vast distances. Salt was even found on the surface of the Tien Shan and Pamir glaciers, which caused their increased melting. Due to the widespread distribution of salts and excessive watering, irrigated lands began to become increasingly salinized.

Endogenous geological processes occurring at the bottom of the World Ocean, expressed in the form of underwater eruptions, earthquakes and in the form of “black smokers”, are reflected on its surface and adjacent shores in the form of coastal floods and the formation of seamounts and hills. After grandiose underwater collapses, underwater earthquakes and volcanic eruptions in the open ocean, peculiar waves - tsunamis - arise at the epicenter of earthquakes and places of eruptions or underwater collapses. Tsunamis travel from their point of origin at speeds of up to 300 m/s. In the open ocean, such a wave, being long, can be completely invisible. However, when approaching the shore with decreasing depth, the height and speed of the tsunami increase. The height of the waves hitting the shores reaches 30-45 m, and the speed is almost 1000 km/h. With such parameters, a tsunami destroys coastal structures and leads to large casualties. The coast of Japan and the western coasts of the Pacific and Atlantic oceans are especially often affected by tsunamis. A typical example of the destructive impact of a tsunami was the famous Lisbon earthquake in 1775. Its epicenter was located under the bottom of the Bay of Biscay near the city of Lisbon. At the beginning of the earthquake, the sea retreated, but then a huge wave 26 m high hit the shore and flooded the coastline up to 15 km wide. More than 300 ships were sunk in Lisbon harbor alone.

The waves of the Lisbon earthquake passed through the entire Atlantic Ocean. Near Cadiz their height reached 20 m, but off the coast of Africa (Tangier and Morocco) - 6 m. After some time, similar waves reached the shores of America.

As you know, the sea constantly changes its level, and this is especially noticeable on the coastal ledges. There are short-period (minutes, hours and days) and long-period (tens of thousands to millions of years) fluctuations in the level of the World Ocean.

Short-period fluctuations in sea level are caused primarily by wave dynamics - wave movements, gradient, drift and tidal movements. The most negative environmental impacts are surge floods. The most famous among them are surge floods in St. Petersburg, which occur during strong westerly winds in the Gulf of Finland, which delay the flow of water from the Neva into the sea. The rise of water above the ordinary level (above the zero mark on the water gauge, showing the average long-term water level) occurs quite often. One of the most significant rises in water occurred in November 1824. At this time, the water level rose 410 cm above normal.

To stop the negative impact of surge flooding, the construction of a protective dam was started to block the Neva Bay. However, long before the completion of construction, its negative aspects were revealed, which led to changes in the hydrological regime and the accumulation of pollutants in silt sediments.

Long-term changes in sea level are associated with changes in the total amount of water in the World Ocean and are manifested in all its parts. Their causes are the emergence and subsequent melting of cover glaciers, as well as changes in the volume of the World Ocean as a consequence of tectonic movements. Different-scale and different-age changes in the level of the World Ocean have been established as a result of paleogeographic reconstructions. Geological material is used to reveal global transgressions (advance) and regressions (retreat) of seas and oceans. Their environmental consequences were negative, as the living conditions of organisms changed and food resources were reduced.

During the cooling period at the beginning of the Quaternary period, a huge volume of sea water was withdrawn from the Arctic Ocean. At the same time, the shelves of the northern seas protruding onto the earth's surface were covered with an glacial shell. After the Holocene warming and melting of the ice sheet, the shelves of the northern seas were filled again, and the White and Baltic seas arose in depressions of the relief.

Large environmental consequences as a result of sea level fluctuations are noticeable on the coasts of the Black, Azov and Caspian seas. The buildings of the Greek colony of Dioscuria were flooded in Sukhumi Bay, Greek amphorae were found at the bottom off the coast of the Taman Peninsula in Crimea, and submerged Scythian mounds were discovered off the northern coast of the Sea of Azov. Signs of coastal subsidence are evident on the western coast of the Black Sea. Roman buildings built around 3 thousand years BC were discovered underwater here. e., as well as sites of early Neolithic man. All of these dives are associated with post-glacial sea level rise as a result of vigorous melting of ice sheets.

The rise and fall of sea level has been especially well documented in the study of Mediterranean terraces.

A relative rise in water levels leads to flooding of coastal areas. This is due to the backwater and rise of groundwater. Flooding causes destruction of foundations and flooding of basements in cities, and in rural areas it leads to waterlogging, salinization and waterlogging of soils. This is exactly the process that is currently taking place on the coast of the Caspian Sea, the level of which is rising. In some cases, transgressions in limited areas are caused by human economic activity. One of the reasons for the flooding of Venice that began in the 70-80s of the XX century. The waters of the Adriatic Sea are considered to be the subsidence of the seabed caused by subsidence due to the pumping of fresh groundwater.

Global and regional environmental consequences in the World Ocean as a result of anthropogenic activities

Active human economic activity has also affected the World Ocean. Firstly, humanity began to use the waters of internal and marginal seas and ocean spaces as transport routes, secondly, as a source of food and mineral resources, and thirdly, as a storage facility for solid and liquid chemical and radioactive waste. All of the above actions have created many environmental problems, some of which have proven difficult to resolve. In addition, the World Ocean, as a global natural complex with a more closed system than land, has become a kind of settling tank for various suspended matter and dissolved compounds carried out from the continents. Wastewater and substances produced on the continents as a result of economic activities are carried by surface waters and winds into inland seas and oceans.

According to international practice, the part of the World Ocean adjacent to land is divided into territories with different state jurisdictions. A zone of territorial waters with a length of 12 miles is allocated from the outer boundary of internal waters. From it extends a 12-mile contiguous zone, which, together with territorial waters, has a width of 24 miles. A 200-mile economic zone extends from internal waters towards the open sea, which is the territory of the sovereign right of a coastal state to the exploration, development, conservation and reproduction of biological and mineral resources. The state has the right to lease its economic zone.

Currently, intensive development of the economic zone of the World Ocean is taking place. Its area is about 35% of the area of the entire World Ocean. It is this territory that experiences the maximum anthropogenic load from the coastal states.

A striking example of ongoing pollution is the Mediterranean Sea, which washes the land of 15 countries with varying levels of industrial development. It has turned into a huge storage facility for industrial and domestic waste and sewage. Considering that the water in the Mediterranean Sea is renewed every 50-80 years, at the current rate of wastewater discharge, its existence as a relatively clean and safe basin may completely cease in 30-40 years.

A large source of pollution are rivers, which, together with suspended particles formed from the erosion of land rocks, introduce a large volume of pollutants. The Rhine alone annually carries 35 thousand m 3 of solid waste and 10 thousand tons of chemicals (salts, phosphates and toxic substances) into the territorial waters of Holland.

In the World Ocean, a gigantic process of bioextraction, bioaccumulation and biosedimentation of pollutants takes place. Its hydrological and biogenic systems operate continuously, and thanks to this, the biological purification of the waters of the World Ocean is carried out. The marine ecosystem is dynamic and quite resistant to moderate anthropogenic impacts. Its ability to return to the initial state (homeostasis) after a stressful situation is the result of many adaptive processes, including mutation ones. Thanks to homeostasis, the processes of destruction of ecosystems at the first stage go unnoticed. However, homeostasis is not able to prevent long-term changes of an evolutionary nature or withstand powerful anthropogenic impacts. Only long-term observations of physical, geochemical and hydrobiological processes make it possible to assess in what direction and at what speed the destruction of marine ecosystems occurs.

Recreational areas, which include both natural and artificially created areas traditionally used for recreation, treatment and entertainment, also play a certain role in the pollution of territorial waters. The high anthropogenic load of these territories significantly changes the purity of the water and worsens the bacterial situation in coastal waters, which contributes to the spread of various diseases, including epidemic ones.

Oil and petroleum products pose the greatest danger to aquatic organisms. Every year, over 6 million tons of oil enter the World Ocean through different routes. Over time, oil penetrates into the water column, accumulates in bottom sediments and affects all groups of organisms. More than 75% of oil pollution occurs due to imperfections in oil production, transportation and refining. However, the greatest damage is caused by accidental oil spills. A particular danger is posed by accidents on stationary and floating drilling rigs developing offshore oil and gas fields, as well as accidents of tankers transporting petroleum products. One ton of oil can cover an area of 12 km2 of water with a thin layer. The oil film does not allow sunlight to pass through and prevents photosynthesis. Animals caught in a film of oil are unable to free themselves from it. Fauna in coastal waters especially often die.

Oil pollution has a pronounced regional character. The lowest concentration of oil pollution is observed in the Pacific Ocean (0.2-0.9 mg/l). The Indian Ocean has the highest level of pollution: in some areas the concentration reaches 300 mg/l. The average concentration of oil pollution in the Atlantic is 4-5 mg/l. Shallow marginal and inland seas - the North, Japan, etc. - are especially heavily polluted with oil.

Oil pollution is characterized by eutrophication of the water area and, as a consequence, a decrease in species diversity, destruction of trophic links, mass development of a few species, structural and functional restructuring of the biocenosis. After an oil spill, the number of hydrocarbon-oxidizing bacteria increases by 3-5 orders of magnitude.

Over the past quarter century, about 3.5 million tons of DDT have entered the World Ocean. Possessing high solubility in fats, this drug and its metabolic products can accumulate in the tissues of organisms and maintain a toxic effect for many years.

Until 1984, radioactive waste was buried in the oceans. In our country, it was carried out most intensively within the Barents and Kara seas, as well as in some places in the Far Eastern seas. Currently, according to international agreements, the practice of burying radioactive waste has been suspended due to the fact that the safety of the used containers in which radioactive waste is stored is limited to several decades.

However, the danger of radioactive contamination of the World Ocean remains due to ongoing accidents of nuclear submarines, emergencies on nuclear icebreakers, accidents of surface ships carrying nuclear weapons, accidents and losses of nuclear warheads on aircraft, as well as nuclear explosions carried out by France on Mororua Atoll.

The most dangerous radioactive isotopes for marine biocenoses and humans entering the World Ocean are 90 Sr and 137 Cs, which participate in the biological cycle.

Pollutants also penetrate into the World Ocean from air currents or with precipitation in the form of acid rain.

The spread of pollution in the World Ocean is facilitated not only by the interaction of its surface with the atmosphere, but also by the dynamics of water itself. Due to their mobility, waters relatively quickly spread pollutants throughout the oceans.

Ocean pollution is a global threat. Anthropogenic impacts change all existing interconnected systems of the World Ocean, causing damage to flora and fauna, including humans. Its pollution not only contributes to the spread of toxic substances, but also significantly affects the global distribution of oxygen. After all, one fourth of all oxygen production by plants comes from the World Ocean.

Instructions

The world ocean is a single and continuous body of water covering ¾ of the entire earth's surface. This gigantic water area is divided into several large parts - oceans. Of course, the nfrjt division is very conditional. The boundaries of the oceans are the coastlines of continents, islands, and archipelagos. Sometimes, in the absence of such, boundaries are drawn along parallels or meridians. The main characteristics by which the water space is divided into components are the properties inherent in one or another part of the World Ocean - climatic and hydrological features, salinity and transparency of water, independence of atmospheric circulation systems and ocean currents, etc.

Until recently, it was accepted to divide the world's waters into 4 oceans: the Pacific, Atlantic, Indian and Arctic, although some scientists believed that it would be correct to also separate the South Antarctic Ocean. The basis for this is the specific climatic and hydrological conditions of this part of the World Ocean. In fact, the Southern Ocean existed on geographical maps from the mid-17th to the first quarter of the 20th century. During the time of Varenius, the Dutch geographer who first proposed identifying the southern polar region as an independent part of the world's waters, Antarctica was considered an ocean. Its northern border was drawn along the latitude of the Antarctic Circle. For a long time, there was no consensus in the scientific world on the question of whether the Southern Ocean should be distinguished. However, in 2000, the international geographical organization, based on new oceanological data, announced its decision: the South Antarctic Ocean should again appear on world maps.

The constituent parts of the oceans are seas, bays and straits. The sea is a part of the ocean separated from its main water area by islands, peninsulas or features of the underwater relief. Seas have their own, different from oceanic, hydrological and meteorological conditions, and often their own flora and fauna. An exception to the general rule is the Sargasso Sea, which is not at all. In total, there are 54 seas in the World Ocean.

The biosphere is the living shell of the Earth. The boundaries of the biosphere are the area of distribution of living organisms.

Unlike other shells, the geographic one has a complex composition and the largest reserves of free energy. It is also distinguished by the presence of life. The existence and development of the geographical shell is subject to the following laws: integrity, rhythm, zonality.

Integrity is the interaction of components due to the continuous circulation of substances and energy. A change in one of the components leads to a change in the others.

Rhythm is the constant repetition of certain phenomena over time. For example, the annual rhythms that the Earth provides as it revolves around the Sun. The phenomenon of climate change can also be attributed to rhythm.

All forms of the water cycle constitute a single hydrological cycle, during which all types of water are renewed. The greatest period is during the renewal of glaciers and deep-lying groundwater. Atmospheric waters and biological waters, which are part of plants and animals, are most quickly renewed.

The hydrosphere is an open system. There is a close relationship between its waters, which determines the unity of the Earth’s water shell as a natural system and its interaction with other geospheres.

In addition, water is the cradle of life on our planet. After all, only at the beginning of the Paleozoic era did they reach land. Until this moment, they developed in an aquatic environment.

Modern is the result of the long evolution of the Earth and the differentiation of its substances.

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A country is a territory that has certain boundaries. It may have state independence (sovereignty) or be under the authority of another state. Today there are more than 250 states and territories around the world. All countries of the world have their own economic, political and social situation.

Countries of the world vary in territory size (large, medium, small), population, geographical location (peninsular, island, inland), natural resource potential, religious and historical characteristics. States have different forms of government (republic, monarchy), administrative-territorial structure (unitary, federal). Island countries include Great Britain, New Zealand, Cuba, and Ireland. To the peninsular ones - India, Norway, Portugal, Italy. Inland countries are the majority of countries in the world that do not have water borders. Based on territoriality, the seven largest countries are distinguished - Russia, Canada, China, USA, Brazil, Australia and India.

According to the level of socio-economic development, states are classified into developed countries with market economies, countries with transition economies and developing countries. The former include almost all countries of Western Europe, Canada, the USA, Japan, Israel, Australia and New Zealand, and South Africa. All these states have a high level of social and economic development. Countries with economies in transition are the states of Eastern Europe, Russia, Albania, China, Vietnam, former republics of the USSR, Mongolia. Developing countries include most countries in Asia, Africa, and Latin America. A special subgroup includes oil exporting countries. These are Algeria, Venezuela, Indonesia, Iraq, Iran, Kuwait, Qatar, Libya, Nigeria, Saudi Arabia, UAE, Brunei, Bahrain and others. An indicator of the level of socio-economic development is, first of all, the size of the country's gross domestic product (GDP). Its dimensions express the total value of final goods and services that are produced in the territory of one’s country. In addition, the level and quality of life, which are determined by a set of indicators - life expectancy, level of education, unemployment, consumption of goods and services, and the state of the natural environment, are of great importance.

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Countries of the world in 2019

Includes all the seas and oceans of the Earth. It occupies about 70% of the planet's surface and contains 96% of all water on the planet. The world ocean consists of four oceans: the Pacific, Atlantic, Indian and Arctic.

Sizes of the oceans: Pacific - 179 million km2, Atlantic - 91.6 million km2, Indian - 76.2 million km2, Arctic - 14.75 million km2

The boundaries between oceans, as well as the boundaries of seas within oceans, are drawn rather arbitrarily. They are determined by land areas delimiting the water space, internal currents, differences in temperature and salinity.

Seas are divided into internal and marginal. Inland seas protrude quite deeply into the land (for example, the Mediterranean), and marginal seas adjoin the land with one edge (for example, the Northern, Japanese).

Pacific Ocean

The Pacific is the largest of the oceans. It is located in both the northern and southern hemispheres. In the east, its border is the coast of North and, in the west - the coast of and, in the south - Antarctica. It owns 20 seas and more than 10,000 islands.

As the Pacific Ocean covers all but the coldest,

it has a diverse climate. over the ocean varies from +30°

to -60° C. Trade winds form in the tropical zone; monsoons are frequent to the north, off the coast of Asia and Russia.

The main currents of the Pacific Ocean are closed in circles. In the northern hemisphere, the circle is formed by the Northern Trade Wind, North Pacific and California Currents, which are directed clockwise. In the southern hemisphere, the circle of currents is directed counterclockwise and consists of the Southern Trade Wind, East Australian, Peruvian and Western Winds.

The Pacific Ocean is located on the Pacific Ocean. Its bottom is heterogeneous; there are underground plains, mountains and ridges. On the territory of the ocean is the Mariana Trench - the deepest point of the World Ocean, its depth is 11 km 22 m.

The water temperature in the Atlantic Ocean ranges from -1 °C to + 26 °C, the average water temperature is +16 °C.

The average salinity of the Atlantic Ocean is 35%.

The organic world of the Atlantic Ocean is distinguished by a wealth of green plants and plankton.

Indian Ocean

Most of the Indian Ocean is located in warm latitudes and is dominated by humid monsoons, which determine the climate of East Asian countries. The southern edge of the Indian Ocean is sharply cold.

Indian Ocean currents change direction depending on the direction of the monsoons. The most significant currents are the Monsoon, Trade Wind and.

The Indian Ocean has a varied topography; there are several ridges, between which there are relatively deep basins. The deepest point of the Indian Ocean is the Java Trench, 7 km 709 m.

The water temperature in the Indian Ocean ranges from -1°C off the coast of Antarctica to +30°C near the equator, the average water temperature is +18°C.

The average salinity of the Indian Ocean is 35%.

Arctic Ocean

Much of the Arctic Ocean is covered in thick ice—almost 90% of the ocean surface in winter. Only near the coast does the ice freeze to the land, while most of the ice drifts. Drifting ice is called "pack".

The ocean is located entirely in northern latitudes and has a cold climate.

A number of large currents are observed in the Arctic Ocean: the Trans-Arctic Current runs along the north of Russia, and as a result of interaction with the warmer waters of the Atlantic Ocean, the Norwegian Current is born.

The relief of the Arctic Ocean is characterized by a developed shelf, especially off the coast of Eurasia.

The water under the ice always has a negative temperature: -1.5 - -1°C. In summer, the water in the seas of the Arctic Ocean reaches +5 - +7 °C. The salinity of ocean water decreases significantly in summer due to the melting of ice and, this applies to the Eurasian part of the ocean, deep Siberian rivers. So in winter the salinity in different parts is 31-34% o, in summer off the coast of Siberia it can be up to 20% o.

If you open the atlas for grade 7, you can see that our planet is almost completely blue. These are the waters of the world's oceans, where life once originated.

Origin

There is a theory that many millions of years ago there was one continent on Earth, Pangea, washed by a single ocean called Panthalassa. But the earth’s crust does not stand still, and as a result of its movement, the ancient continent was divided into 4 parts, and a single body of water was divided into four oceans: Pacific, Atlantic, Indian and Arctic.

Rice. 1. Image of Pangea and the Panthalassa Ocean

World Ocean- this is part of the hydrosphere, or a single water area of the Earth, which includes all oceans, seas, straits and bays. It occupies 71% of the entire surface of the planet.

Strait is a narrow strip of water surrounded at two opposite ends by land. The widest is the Drake Passage, connecting the Pacific and Atlantic Oceans.

Bay- a part of the sea or ocean, surrounded on all sides by land, but having free water exchange with the world's waters. The largest is the Bay of Bengal.

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The southern hemisphere is covered by much more water than the northern hemisphere. In this regard, some scientists propose to identify another ocean - the Southern Ocean.

In geography, several properties of the waters of the World Ocean are distinguished:

Salinity. An indicator that determines how much salt is contained in one liter of water. Calculated in ppm. The average salinity of all sea water is 35‰.
Temperature. Depends on latitude and changes with depth. For example, in the deepest place - the Mariana Trench - no higher than 2°C. The average water temperature of the World Ocean is 17.5°C.

The Pacific Ocean is considered the warmest. An average of 19.4° is recorded on its surface. It is followed by Indian (17.3°) and Atlantic (16.5°). The coldest is the Arctic, where the average temperature is 1°C.

Rice. 2. Average water temperature of the world's oceans

Ice in the ocean. Sea water is characterized by long periods of non-freezing. The temperature at which crystallization begins is minus 2°C. In this case, it should be constantly cold, as in the Arctic and subarctic latitudes. Special blocks of ice - icebergs - pose a particular danger to ships. Most of them are hidden under water and cannot be seen.
Water masses. These are huge volumes of water, different from each other in certain parameters, namely: temperature, transparency, characteristic organic world. There are different types of water bodies: surface, intermediate, deep, bottom.
Movement of waters in the ocean occurs in the following directions: wave, vertical, horizontal (surface movement of currents).

Currents

Currents are the movements of a huge mass of water in a directional movement along a certain channel. This is why they are sometimes called “rivers of the oceans.” The speed of different currents is variable. Some move 1 km. per hour, others run up to 9 km. at one o'clock. Another feature is that the direction of flows differs in different parts of the world. In the Northern Hemisphere everyone moves clockwise, in the Southern Hemisphere everything moves counterclockwise.

Rice. 3. Ocean currents

Currents play a huge role. They are warm and cold and largely determine the climate of the continents. The warmest current is the Gulf Stream in the Atlantic Ocean.

What have we learned?

The world ocean is a huge area of water on planet Earth. Patterns in weather change and climatic conditions on land are formed under the influence of the World Ocean. Its main properties are: salinity, temperature, movement of water masses, ice formation. The world's waters include: the Pacific, Atlantic, Indian, Arctic oceans, all straits and bays. Currents are huge masses of water, the temperature of which may differ from the average value in the World Ocean. They influence the climate of the continents.

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The World Ocean is the main part of the hydrosphere, constituting 94.2% of its total area, a continuous but not continuous water shell of the Earth, surrounding continents and islands, and characterized by a common salt composition.

Continents and large archipelagos divide the world's oceans into four large parts (oceans):

Atlantic Ocean,
Indian Ocean,
Pacific Ocean,
Arctic Ocean.

Sometimes the Southern Ocean also stands out from them.

Large regions of the oceans are known as seas, bays, straits, etc. The study of the earth's oceans is called oceanology.

Origin of the World Ocean

The origin of the oceans has been the subject of debate for hundreds of years.

It is believed that in the Archean the ocean was hot. Due to the high partial pressure of carbon dioxide in the atmosphere, reaching 5 bar, its waters were saturated with carbonic acid H2CO3 and were characterized by an acidic reaction (pH ≈ 3−5). A large number of different metals were dissolved in this water, especially iron in the form of FeCl2 chloride.

The activity of photosynthetic bacteria led to the appearance of oxygen in the atmosphere. It was absorbed by the ocean and spent on the oxidation of iron dissolved in water.

There is a hypothesis that starting from the Silurian period of the Paleozoic and up to the Mesozoic, the supercontinent Pangea was surrounded by the ancient Panthalassa ocean, which covered about half of the globe.

History of the study

The first explorers of the ocean were sailors. During the Age of Discovery, the outlines of continents, oceans and islands were studied. The voyage of Ferdinand Magellan (1519-1522) and the subsequent expeditions of James Cook (1768-1780) allowed Europeans to gain an understanding of the vast expanses of water surrounding the continents of our planet, and to roughly determine the outlines of the continents. The first maps of the world were created. In the 17th and 18th centuries, the coastline was detailed and the world map took on its modern form. However, the depths of the ocean have been very poorly studied. In the middle of the 17th century, the Dutch geographer Bernhardus Varenius proposed using the term “World Ocean” in relation to the water spaces of the Earth.

On December 22, 1872, the sailing-steam corvette Challenger, specially equipped to participate in the first oceanographic expedition, left the English port of Portsmouth.

The modern concept of the World Ocean was compiled at the beginning of the 20th century by Russian and Soviet geographer, oceanographer and cartographer Yuliy Mikhailovich Shokalsky (1856 - 1940). He first introduced the concept of “World Ocean” into science, considering all oceans - Indian, Atlantic, Arctic, Pacific - as parts of the World Ocean.

In the second half of the 20th century, intensive study of the ocean depths began. Using the echolocation method, detailed maps of the ocean depths were compiled, and the main forms of relief of the ocean floor were discovered. These data, combined with the results of geophysical and geological research, led to the creation of the theory of plate tectonics in the late 1960s. Plate tectonics is a modern geological theory about the movement of the lithosphere. To study the structure of the oceanic crust, an international program was organized to drill the ocean floor. One of the main results of the program was the confirmation of the theory.

Research methods

Research of the World Ocean in the 20th century was actively carried out on research vessels. They made regular voyages to certain areas of the oceans. Research on such domestic ships as Vityaz, Akademik Kurchatov, and Akademik Mstislav Keldysh made a great contribution to science. Major international scientific experiments were carried out in the ocean Polygon-70, MODE-I, POLYMODE.
The study used deep-sea manned vehicles such as Paisis, Mir, and Trieste. In 1960, the research bathyscaphe Trieste made a record dive into the Mariana Trench. One of the most important scientific results of the dive was the discovery of highly organized life at such depths.
At the end of the 1970s. The first specialized oceanographic satellites were launched (SEASAT in the USA, Kosmos-1076 in the USSR).
On April 12, 2007, the Chinese satellite Haiyang-1B (Ocean 1B) was launched to study the color and temperature of the ocean.
In 2006, NASA's Jason-2 satellite began participating in the international oceanography project Ocean Surface Topography Mission (OSTM) to study ocean circulation and sea level fluctuations.
By July 2009, one of the largest scientific complexes for studying the World Ocean had been built in Canada.

Scientific organizations

AARI
VNII Oceangeology
Institute of Oceanology named after. P. P. Shirshov RAS
Pacific Oceanological Institute named after. V. I. Ilyichev FEB RAS.
California Scripps Institution of Oceanography.

Museums and aquariums

Museum of the World Ocean
Oceanographic Museum of Monaco
Oceanarium in Moscow

There are only 4 oceanariums in Russia so far: the St. Petersburg Oceanarium, Aquamir in Vladivostok, the oceanarium in Sochi and the oceanarium in Moscow on Dmitrovskoye Shosse (recently opened).

Division of the World Ocean

Basic morphological characteristics of the oceans

	Water surface area, million km²	Volume, million km³	Average depth, m	Greatest ocean depth, m
Atlantic				Puerto Rico Trench (8742)
Indian				Sunda Trench (7209)
Arctic				Greenland Sea (5527)
Quiet				Mariana Trench (11022)
World

Today, there are several views on the division of the World Ocean, taking into account hydrophysical and climatic features, water characteristics, biological factors, etc. Already in the 18th-19th centuries, there were several such versions. Malthe-Brön, Conrad Malthe-Brön and Fleurier, Charles de Fleurier identified two oceans. The division into three parts was proposed, in particular, by Philippe Buache and Heinrich Stenffens. The Italian geographer Adriano Balbi (1782-1848) identified four regions in the World Ocean: the Atlantic Ocean, the North and South Arctic Seas and the Great Ocean, of which the modern Indian Ocean became part (this division was a consequence of the impossibility of determining the exact boundary between the Indian and Pacific oceans and the similarity of zoogeographic conditions of these regions). Today people often talk about the Indo-Pacific region - a zoogeographic zone located in the tropical sphere, which includes the tropical parts of the Indian and Pacific Oceans, as well as the Red Sea. The region's border runs along the coast of Africa to Cape Agulhas, later from the Yellow Sea to the northern shores of New Zealand, and from Southern California to the Tropic of Capricorn.

In 1953, the International Hydrogeographical Bureau developed a new division of the World Ocean: it was then that the Arctic, Atlantic, Indian and Pacific oceans were finally identified.

Geography of the oceans

General physical and geographical information:

Average temperature: 5 °C;
Average pressure: 20 MPa;
Average density: 1.024 g/cm³;
Average depth: 3730 m;
Total weight: 1.4·1021 kg;
Total volume: 1370 million km³;
pH: 8.1±0.2.

The deepest point of the ocean is the Mariana Trench, located in the Pacific Ocean near the Northern Mariana Islands. Its maximum depth is 11,022 m. It was explored in 1951 by the British submarine Challenger II, in honor of which the deepest part of the depression was named Challenger Deep.

Waters of the World Ocean

The waters of the World Ocean make up the main part of the Earth's hydrosphere - the oceanosphere. Ocean waters account for more than 96% (1338 million cubic km) of the Earth's water. The volume of fresh water entering the ocean with river runoff and precipitation does not exceed 0.5 million cubic kilometers, which corresponds to a layer of water on the ocean surface about 1.25 m thick. This determines the constancy of the salt composition of ocean waters and minor changes in their density. The unity of the ocean as a water mass is ensured by its continuous movement in both horizontal and vertical directions. In the ocean, as in the atmosphere, there are no sharp natural boundaries; they are all more or less gradual. Here, a global mechanism of energy transformation and metabolism takes place, which is supported by uneven heating of surface waters and the atmosphere by solar radiation.

Bottom relief

Systematic study of the bottom of the world's oceans began with the advent of echo sounders. Most of the ocean floor is flat surfaces, the so-called abyssal plains. Their average depth is 5 km. In the central parts of all oceans there are linear rises of 1-2 km - mid-ocean ridges, which are connected into a single network. The ridges are divided by transform faults into segments that appear in the relief as low elevations perpendicular to the ridges.

On the abyssal plains there are many single mountains, some of which protrude above the surface of the water in the form of islands. Most of these mountains are extinct or active volcanoes. Under the weight of the mountain, the oceanic crust bends and the mountain slowly sinks into the water. A coral reef forms on it, which builds on the top, resulting in the formation of a ring-shaped coral island - an atoll.

If the continent's margin is passive, then between it and the ocean there is a shelf - the underwater part of the continent, and a continental slope, smoothly turning into an abyssal plain. In front of subduction zones, where the oceanic crust plunges beneath the continents, are deep-sea trenches - the deepest parts of the oceans.

Sea currents

Sea currents - the movement of large masses of ocean water - have a serious impact on the climate of many regions of the world.

Climate

The ocean plays a huge role in shaping the Earth's climate. Under the influence of solar radiation, water evaporates and is transported to continents, where it falls in the form of various precipitation. Ocean currents transport heated or cooled water to other latitudes and are largely responsible for the distribution of heat across the planet.

Water has a huge heat capacity, so ocean temperatures change much more slowly than air or land temperatures. Areas close to the ocean have smaller daily and seasonal temperature fluctuations.

If the factors causing currents are constant, then a constant current is formed, and if they are episodic in nature, then a short-term, random current is formed. According to the predominant direction, currents are divided into meridional, carrying their waters to the north or south, and zonal, spreading latitudinally. Currents in which the water temperature is higher than the average temperature for the same latitudes are called warm, lower ones are called cold, and currents that have the same temperature as the surrounding waters are called neutral.

The direction of currents in the World Ocean is influenced by the deflecting force caused by the rotation of the Earth - the Coriolis force. In the Northern Hemisphere, it deflects currents to the right, and in the Southern Hemisphere, to the left. The speed of currents on average does not exceed 10 m/s, and their depth extends to no more than 300 m.

Ecology, flora and fauna

The ocean is a habitat for many life forms; among them:

cetaceans such as whales and dolphins
cephalopods such as octopuses, squids
crustaceans such as lobsters, shrimp, krill
sea worms
plankton
corals
seaweed

A decrease in ozone concentration in the stratosphere over Antarctic waters leads to less absorption of carbon dioxide by the ocean, which threatens the calcium shells and exoskeletons of mollusks, crustaceans, etc.

Economic significance

The oceans are of enormous transport importance: huge amounts of cargo are transported by ships between the world's seaports. In terms of the cost of transporting a unit of cargo per unit of distance, sea transport is one of the cheapest, but far from the fastest. To reduce the length of sea routes, canals were built, the most important of which include Panama and Suez.

To heat the oceans to boiling point, the energy released from the decay of 6.8 billion tons of uranium is needed.
If you take all the ocean water (1.34 billion km3) and make a ball out of it, you will get a planet with a diameter of about 1400 km.
The World Ocean contains approximately 37 septillion (37*1024) drops.

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