Geography of the oceans. What is included in the world's oceans The world's oceans and its waters

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 - 81%. The concept of the World Ocean was introduced into Russian science by Yu. M. Shokalsky. In terms of its physical, chemical, biological characteristics, the World Ocean is a single whole, but it is diverse in many characteristics - climatic, dynamic, optical, elements of the water regime, etc.

Parts of the oceans

According to the totality of all signs, the water shell of the Earth is subdivided into several oceans. These are large parts of the World Ocean, limited by the coastline of the 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 - the Southern Ocean, washing the shores of Antarctica. According to more ancient traditions, 7 oceans are also distinguished, dividing the Pacific and Atlantic oceans into the North and South 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 rather arbitrary. In a number of cases, borders are also conditional, 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, pattern of the coastline of continents and islands.

Despite the commonality of geostructures (the presence of the underwater margin of the continents, the transition zone, mid-ocean ridges and bed), they occupy different areas, and the bottom topography of each is individual. The oceans have their own structure of distribution of temperatures, salinity, transparency of waters, 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 have a significant impact on the formation of natural processes on the continents. Visual observations of astronauts over the oceans confirmed the individuality of each of the oceans, for example, each of them has a specific color. The Atlantic Ocean is seen from space blue, the Indian Ocean is turquoise, especially off the coast of Asia, and the Arctic Ocean is white.

A number of experts acknowledge the existence of the fifth ocean - the South Arctic. It was first isolated in 1650 by the Dutch scientist B. Varenius, who proposed the division of the World Ocean into five separate parts - the 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 allocated by the International Hydrographic Bureau until 1937. In Russian literature, it was shown as an independent one in 1966 in the Atlas of Antarctica. The southern boundary of this ocean is the coastline of Antarctica.

The special very harsh climatic and hydrological conditions in this region, increased ice cover, common circulation of the surface layer of waters, etc., serve as the basis for distinguishing the Southern Arctic Ocean. Some researchers draw the boundary of the Southern Ocean along the southern periphery of the Antarctic convergence, located on average at 55 ° S. sh. Within the specified northern boundary, the ocean area is 36 million km 2, that is, it is more than twice the size of the Arctic Ocean.

The climatic and hydrological conditions of the ocean differ in 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 geographic location, structural features of the basin, and morphometric characteristics.

On Earth, more than two-thirds of the surface is covered. The climate of the planet largely depends on the world's oceans, life originated in it (see the 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 is found in the Southern Hemisphere.

There are five main oceans

• The largest of them is, covering 32% of the earth's surface. It covers an area of ​​more than 160 million km 2 - more than the entire land. It is also the deepest ocean; its average depth is 4200 m, and the Mariana Trench is over 11 km deep.
• half the size of the Quiet: it covers 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,
• is located in the Southern Hemisphere and covers an area of ​​73.5 million km 2.
• The small one is almost completely surrounded by land and is usually covered with 3-4 m thick ice.
• Antarctic waters, sometimes called the Antarctic or Southern Ocean, are much larger and surround the mainland. Two thirds of these waters freeze in winter.

The seas are much 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 ocean planet. From space, the Earth appears blue because the oceans cover 930 million km 2. or 71% of its surface.

Marine jungle

Coral reefs grow in the warm coastal tropical waters of the world's oceans. Reefs can be called marine jungles because of the amazing variety 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 their fat, which led to a decrease in their numbers. The head of the sperm whale is about a third of the entire body length of the animal. Sperm whales have the largest brains of all mammals.

The first sailors

Floating ice

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

Oil leak

Man admires the world's oceans, is afraid of it, gets food in it, but at the same time pollutes and harms it. such as that occurred on the Exxon Waldez in March 1989 is just one of many examples of the destructive human impact on the oceans. Fortunately, work is currently underway on.

Mountain ranges at the bottom of the seas

Ridges prevail at the bottom of the seas. The Mid-Atlantic Ridge stretches from north to south, with abyssal (deep) plains located on either side of it. The underwater ridges of the Pacific and Indian Oceans are more complex in shape.

Features of the World Ocean

The term "World Ocean" was introduced into the practice of scientific research by the French hydrographic scientist Clare de Florie at the end of the 18th century. This concept means a set of oceans - the Arctic, Atlantic, Pacific and Indian (some researchers also distinguish the Southern Ocean, washing the shores of Antarctica, but its northern boundaries are quite vague), as well as marginal and inland seas. The oceans occupy 361 million km 2, or 70.8% of the world's area.

The oceans are not only water, but also aquatic animals and plants, its bottom and shores. At the same time, the World Ocean is understood as an independent integral formation, an object of a planetary scale, as an open dynamic system that exchanges matter and energy with the media in contact with it. This exchange takes place in the form of planetary gyres, in which heat, moisture, salts and gases that are part of the oceans and continents participate.

Salinity of the World Ocean

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

On average, the salinity of the World Ocean is 35% o, but fluctuates over a fairly wide range depending on the level of evaporation and the volume of river runoff. In the case when the river runoff in the seas prevails, the salinity falls below the average value. For example, in the Baltic Sea it is 6-11% o. If evaporation predominates, the 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 salty and bitter-saline lakes (Elton, Baskunchak, etc.) have the highest salinity.

Gases are dissolved in the ocean water: N 2, O 2, CO 2, H 2 S, etc. Due to the high horizontal and vertical hydrodynamics, due to the difference in temperature, density and salinity, atmospheric gases are mixed. The change in their content is 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.

For some semi-enclosed parts of the World Ocean - the Black Sea or the Gulf of Oman - hydrogen sulfide contamination is characteristic, which spreads from a depth of 200 m. bacteria.

Of great importance for the life of marine organisms is the transparency of the water, that is, the depth of penetration of sunlight to depth. Transparency depends on the mineral particles suspended in the water and the volume of microplankton. For the conditional transparency of ocean water, the depth is taken at which a white disk, the so-called Secchi disk, with a diameter of 30 cm becomes invisible. The conditional transparency (m) of the 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 established in the Persian Gulf, and the minimum temperature is -1.6; -1 ° С are typical for the polar regions.

At different depths of ocean waters, a quasi-homogeneous layer is located, which is characterized by almost the same temperatures. Below it is the seasonal thermocline. The temperature difference in it during the period of maximum heating reaches 10-15 ° C. The main thermocline lies under the seasonal thermocline, covering the main oceanic water column 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 the temperature conditions in the near-surface part, but also on the hydrodynamics and salinity of the World Ocean waters.

The bottom boundary layer adjoins the ocean floor, in which low temperatures are recorded, varying depending on the geographic location from 0.3 to -2 ° C.

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

World ocean currents

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

Drift currents are formed under the influence of the wind as a result of the friction of the air flow against 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 the Coriolis forces. A characteristic feature of drift currents is a gradual attenuation of their intensity with a change in depth.

Gradient currents result from the formation of an inclination of 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 that leads to the appearance of a surge or surge current. Gradient currents capture the entire water column, down to the bottom.

In the World Ocean, there are baro-gradient and convection currents. Baro-gradient arises 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 the difference in the density of seawater at the same depth, creating a horizontal pressure gradient.

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

In certain areas of the World Ocean, unsteady vortex-like water disturbances with a diameter of up to 400 km have been detected. They often cover the entire water column and reach the bottom. Their speed is several centimeters per second. Among them, there are frontal eddies that arise when cutting off bends and eddies from the main flow, and eddies of the open ocean.

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

Seiches are standing waves of closed bodies of water, typical only for inland seas. The water in them fluctuates with an amplitude of up to 60 m. The reasons for seiches are tidal phenomena or strong winds leading to surges and surges, as well as abrupt 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 these, about 0.27 * 10 9 tons are contained on the shelf, 1.2 * 10 9 tons in the thickets of coral reefs and algae, and 1 in estuaries, 4 * 10 9 tons, and in the open ocean - 1 * 10 9 tons. The World Ocean contains about 6 million tons of plant matter, mainly in the form of phytoplankton, and about 6 million tons of zooplankton. Shallow waters and submarine deltas located in tropical areas have the maximum bioproductivity. Significant biological productivity is observed in the places where underwater currents emerge on the surface of the oceans, carrying out water enriched with phosphates, nitrates and other salts from depths of more than 200 m. These areas are called upwelling zones. Zooplankton develops rapidly in places where currents emerge, such as, for example, in the Bay of Benguela, along the coasts of Peru, Chile and Antarctica.

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 organisms inhabiting it.

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 oceans provide life for the organisms inhabiting 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 a direct impact on the life of marine biota is the temperature factor. In many marine organisms, the breeding time 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. Depth. In the inhabitants of great depths, the variegation of color disappears, they become monotonous, 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 strongly influence the life and distribution of marine biota.

The dynamics of the waters of the World Ocean is one of the constituent parts of the ecological function of the World Ocean. The activity of surface and deep currents is associated with different temperature regimes and with the nature of the distribution of surface and bottom temperatures, features of salinity, density and hydrostatic pressure. Earthquakes, 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 bottom topography of the World Ocean.

The resource role of the World Ocean is great. By itself, sea water, regardless of the degree of its salinity, is a natural raw material that is used by mankind in various forms. The oceans are a kind of accumulator of heat. Slowly heating up, it slowly gives off heat and thus is the most important component of the climate-forming system, which, as you know, 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, vertical movements of waters (upwellings). They constitute energy resources, and, therefore, the World Ocean is an energy base that is gradually being mastered by mankind. The use of the energy of tides has been started and an attempt has been 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 the desalination of seawater. Existing desalination plants are energy-intensive and therefore receive electricity for their operation at nuclear power plants. The technologies for desalination of sea waters are quite expensive.

The oceans are a global habitat. Marine aquatic organisms live from the surface to the deepest 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 mankind. The biological resources of the oceans are just a 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 minerals. The mineral resources of the World Ocean include solid, liquid and gaseous minerals that lie in the coastal strip of land, at the bottom and in the bowels 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, and ferromanganese nodules.

The interaction of the surface of the World Ocean with such a moving shell, which is the atmosphere, leads to the occurrence of weather phenomena. Cyclones are born over the oceans that carry 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 oceans play a recreational role due to their physical and geographical features, mineral composition of waters and uniform distribution of temperatures and air moisture. 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 a great therapeutic role. Due to the balneological and micromineral qualities, the sea areas are 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 coast, carry and deposit debris. Abrasion of rocky and loose rocks that make up the coastline is associated with drift and tidal currents. Waves continuously erode and erode coastal cliffs. During storms, colossal masses of water fall on the coast, 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 for a certain distance shore protection structures (breakwaters, breakwaters, concrete blocks) weighing hundreds of tons. The force of the impact 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 because of its duration, but the daily wave splash has a strong impact on the shore. As a result of the almost continuous action of waves at the base of the coastal slope, a wave-breaker niche is formed, the deepening of which leads to a collapse of the cornice rocks.

At first, the blocks of the destroyed cornice slowly slide to the sea, and then disintegrate into separate fragments. Large blocks remain at the foot for some time, and the incoming waves crush and transform them. As a result of prolonged exposure to waves, an area is formed near the coast, covered with rounded debris - pebbles. A coastal (wave-breaking) scarp, or cliff, appears, and the coast itself, as a result of erosion, recedes into the interior of the land. As a result of the action of the waves, wave-breaking grottoes, stone bridges or arches and deep crevasses are formed.

Massifs of solid rocks, cut off from the land as a result of erosion, large fragments of the sea coast turn into sea cliffs or pillar rocks. As erosion moves inland to erode and remove rock from the coast, the coastal escarpment, along which the waves roll, expands and turns into a flat surface called a wave-breaking terrace. At low tide, it is exposed, and numerous irregularities are visible on it - pits, ditches, hills, rocky reefs.

Boulders, pebbles and sand, which owe their origin to the action of waves and serve as the cause of wave erosion, are themselves subject to erosion 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 rate of erosion and movement of the coast is different. For example, on the western coast of France (Medoc Peninsula), the coast moves away from the sea at a speed of 15-35 m / year, in the Sochi region - 4 m / year. A prime example of the impact of the sea on land is the island of Helgoland 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 rate of retreat was 0.9 km 2 ).

Coastal destruction occurs when waves are perpendicular to the coast. The smaller the angle or the greater the roughness of the coast, the less marine abrasion, which gives way to the accumulation of debris. Pebbles and sand accumulate on headlands, limiting the entrances to bays and bays, and in places where the action of waves is significantly reduced. Spits begin to form, gradually blocking the entrance to the bay. Then they turn into a mound, which separates the bay from the open sea. Lagoons appear. Examples are the Arabat Spit separating the 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 breakwater terraces.

Controlling coastal erosion and sedimentation in the coastal zone is one of the urgent 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 being erected to restrain the activity of waves and coastal currents. Although protective walls, bulkheads, lining, breakwaters, dams limit the impact of storm waves, sometimes they themselves violate the existing hydrological regime. At the same time, in some places the shores are suddenly eroded, and in others, debris begins to accumulate, which sharply reduces navigability. In a number of places, beaches are artificially replenished with sand. Special structures erected in the migration zone of beaches perpendicular to the coast are successfully used to build up a 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 saved from erosion at one time. Fragments of rocks for artificial washing up of the coast were dumped into the sea at certain points, and then by the waves themselves were transported along the coast, accumulating and gradually turning into pebbles and sand.

With all its positive impact, artificial bank alluviality is fraught with negative aspects. The dumped sand and pebbles, as a rule, are mined in the immediate vicinity of the coast, which ultimately negatively affects the ecological state of the region. Extraction in the 70s of the XX century. pebbles and sand for construction purposes led to the partial destruction of the Arabat Spit, which led to an increase in the salinity of the Azov Sea and, as a result, caused a reduction and even the disappearance of certain representatives of the marine fauna.

At one time, much attention was paid to the problem of the Kara-Bogaz-Gol Gulf. 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 formation processes of unique deposits of self-precipitated salts, led to deflation of the dried salt surface and the spread of salts over great distances. Salt was found even on the surface of the Tien Shan and Pamir glaciers, which caused their increased melting. Due to the wide spreading of salts and excessive irrigation, the irrigated lands began to become additionally saline.

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 landslides, underwater earthquakes and volcanic eruptions in the open ocean, peculiar waves - tsunamis - appear at the epicenter of earthquakes and places of eruptions or underwater landslides. Tsunamis travel from the place of their origin at a speed of up to 300 m / s. In the open ocean, such a wave, having a great length, can be completely invisible. However, when approaching the coast with decreasing depth, the height and speed of the tsunami increase. The height of the waves hitting the coast reaches 30-45 m, and the speed is almost 1000 km / h. With such parameters, tsunamis destroy coastal structures and lead to large human casualties. The coast of Japan, the western coast of the Pacific and Atlantic oceans are especially often affected by tsunamis. The famous Lisbon earthquake in 1775 was a typical example of the devastating impact of a tsunami. Its epicenter was under the bottom of the Bay of Biscay near Lisbon. At the beginning of the earthquake, the sea retreated, but then a huge wave 26 m high hit the coast and flooded the coast 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. At Cadiz, their height reached 20 m, but off the coast of Africa (Tangier and Morocco) - 6 m. After a while, similar waves reached the shores of America.

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

Short-period sea level fluctuations are mainly due to the dynamics of waves - wave movements, gradient, drift and tidal movements. Surge floods are the most negative from the ecological point of view. 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 (above the zero mark on the water meter, showing the average long-term water level) occurs quite often. One of the most significant water rises occurred in November 1824. At this time, the water level rose 410 cm above the ordinary.

In order to halt the negative impact of the surge flood, the construction of a protective dam was started, which blocked off the Neva Bay. However, long before the end of the construction, its negative aspects were revealed, which led to changes in the hydrological regime and the accumulation of pollutants in the 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 ice sheets, as well as changes in the volume of the World Ocean bowl as a result of tectonic movements. Different-scale and different-age changes in the level of the World Ocean were established as a result of paleogeographic reconstructions. On the basis of geological material, global transgressions (advance) and regressions (retreat) of the seas and oceans are revealed. Their ecological 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, a huge volume of sea water was withdrawn from the Arctic Ocean. At the same time, the shelves of the northern seas that protruded onto the earth's surface were covered with an ice shell. After the holo-price warming and melting of the ice sheet, the shelves of the northern seas were again filled, and the White and Baltic Seas arose in the relief depressions.

Large environmental impacts as a result of sea level fluctuations are noticeable on the coasts of the Black, Azov and Caspian Seas. In the Sukhum Bay, the buildings of the Greek colony of Dioscuria are flooded, Greek amphorae are found at the bottom off the coast of the Taman Peninsula in the Crimea, and flooded Scythian burial mounds were found off the northern coast of the Sea of ​​Azov. Signs of coastal sinking are expressed on the western coast of the Black Sea. Here, under water, Roman buildings were discovered, built about 3 thousand years BC. e., as well as the site of the early Neolithic man. All of these dives are associated with a post-glacial rise in sea level as a result of the vigorous melting of ice sheets.

The rise and fall of the sea level is especially well documented when studying the terraces of the Mediterranean.

A relative rise in the water level 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 leads to waterlogging, salinization and waterlogging of soils. This process 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 beginning of the flooding of Venice in the 70-80s of the XX century. The waters of the Adriatic Sea are considered to be subsidence of the seabed caused by subsidence due to pumping of fresh groundwater.

Global and regional environmental impacts in the oceans as a result of anthropogenic activities

The active economic activity of man has also touched the World Ocean. Firstly, mankind began to use the waters of the inland and marginal seas and ocean expanses as transport routes, secondly, as a source of food and mineral resources, and thirdly, as a repository for solid and liquid chemical and radioactive waste. All of the above actions gave rise to many environmental problems, and some of them proved to be intractable. In addition, the World Ocean, as a global natural complex with a more closed system than land, has become a kind of settler for various suspended matter and dissolved compounds carried out from the continents. Wastes and substances produced on the continents as a result of economic activities are carried by surface waters and winds into the inland seas and oceans.

According to international practice, the part of the World Ocean adjacent to the land is divided into territories with different state jurisdictions. From the outer border of the internal waters, a zone of territorial waters with a length of 12 miles is distinguished. From it extends a 12-mile contiguous zone, which, together with territorial waters, is 24 miles wide. A 200-mile economic zone stretches from inland waters towards the open sea, which is the territory of the sovereign right of the coastal state to explore, develop, preserve and reproduce biological and mineral resources. The state has the right to lease its economic zone.

At present, 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 persistent pollution is the Mediterranean Sea, which washes the land of 15 countries with different levels of industrial development. It has turned into a huge repository of industrial and domestic waste and sewage. Taking into account the fact 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 is rivers, which, together with suspended particles formed from erosion of land rocks, introduce a large volume of pollutants. The Rhine alone annually carries 35 thousand m 3 of solid waste, 10 thousand tons of chemicals (salts, phosphates and toxic substances) into the territorial waters of Holland.

In the World Ocean, a gigantic-scale process of bio-extraction, bio-accumulation and bio-sedimentation of pollutants is taking place. Its hydrological and biogenic systems are continuously working, 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 impact. Its ability to return to its initial state (homeostasis) after a stressful situation is the result of many adaptive processes, including mutational ones. Due to homeostasis, the processes of destruction of ecosystems at the first stage are unnoticed. However, homeostasis is unable to prevent long-term evolutionary changes or to resist powerful anthropogenic impact. Only long-term observations of physical, geochemical and hydrobiological processes make it possible to assess in which direction and at what speed the destruction of marine ecosystems is taking place.

Recreational zones, which include both natural and artificially created territories, traditionally used for recreation, treatment and entertainment, 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.

The greatest danger to aquatic organisms is represented by oil and oil products. More than 6 million tons of oil are supplied to the World Ocean annually by different routes. Over time, oil penetrates the water column, accumulates in bottom sediments and affects all groups of organisms. More than 75% of oil pollution occurs due to imperfect production, transportation and processing of oil. However, the greatest harm is caused by accidental oil spills. Particularly dangerous are accidents at stationary and floating drilling rigs developing offshore oil and gas fields, as well as accidents of tankers carrying oil products. One ton of oil is capable of covering a water area of ​​12 km 2 with a thin layer. The oil film blocks the sun's rays and interferes with photosynthesis. Animals trapped in a film of oil are not able to get rid of it. Fauna is especially often killed in coastal waters.

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, and others - 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, massive development of a few species, structural and functional rearrangements 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 oceans. Having a high solubility in fats, this drug and its metabolic products are able to accumulate in the tissues of organisms and maintain a toxic effect for many years.

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

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

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

Pollutants also penetrate into the oceans from air currents or from atmospheric precipitation in the form of acid rain.

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

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

Looking at the physical map of the hemispheres, you can see the uneven distribution of land and water on the planet's surface. Huge continents are scattered in the vastness of the oceans like islands. In the Southern Hemisphere, land accounts for less than 20%, in the Northern - about 40%. What is called the World Ocean in geography, ecology and other earth sciences? This is the most significant part of the hydrosphere - the watery shell of our planet. How many oceans are there on Earth, which one is the largest in area and the warmest? These and many other questions are answered in this article.

What is called the World Ocean (MO)?

All water on Earth forms a single shell, parts of which are linked by the circulation of H2O molecules and other substances. MO is a continuous part of the hydrosphere, which accounts for over 94% of the entire water area on the planet (oceans, seas, bays, straits, rivers, lakes and ponds). Usually Russian geographers distinguish 4 main parts of the World Ocean. Let us list them in order of decreasing surface area (million km 2): Quiet (179), Atlantic (92), Indian (76), Arctic (15).

How did people know about the relationship between the oceans?

Since ancient times, a person has been attracted by the vast expanses of the sea. Already in ancient times, fishermen set off on dangerous water voyages on fragile boats, rafts and catamarans. The history of the World Ocean mentions ancient descriptions, legends, legends about overcoming huge distances on rafts, oars and sailing ships. It is believed that the settlement of continents and islands in ancient times was due to the ability of people to overcome the oceans and seas.

The first known round the world trip was made by a Spanish squadron led by Fernand Magellan in 1519-1522. Moving from the Iberian Peninsula to the west, the ships crossed the Atlantic Ocean, circled South America, entered unknown waters. The weather was calm, so Magellan called the ocean Pacific. In a skirmish with the natives in the Philippine Islands, many Spanish sailors, along with the head of the expedition, died. Magellan's companions continued their journey west in search of spices, gold, and jewelry for the Spanish crown.

One of the ships, led by Captain Juan Elcano, crossed the central Indian Ocean, circled Africa from the south and returned to Europe. Thus, the sphericity of the Earth was proved, the existence of another part of the World Ocean was established. The voyage around the world and other travels marked the beginning of large-scale exploration of water bodies for the benefit of trade, science, industry and fisheries.

MO - the main part of the hydrosphere

When studying the topic "World Ocean" (grade 7), it is necessary to recall the previously studied material of grade 6 ("Hydrosphere"). The single one consists of two parts of unequal size - MO and land water. They are interconnected by the circulation of substances and energy, moisture transfer, surface and underground runoff. What is called the World Ocean in modern science? The term itself has been used in relation to large bodies of water since the 17th century, thanks to the work of the German-Dutch explorer Bernhard Varenius.

At the beginning of the 20th century, the Russian scientist Yu. M. Shokalsky introduced the term "World Ocean" into scientific use and identified 4 main parts of the MO. These are huge oceanic natural complexes separated from each other by continents and archipelagos (chains of islands). Minor branches of the Moscow region - bays, straits, seas (marginal and internal).

Traditional division of medical equipment into parts

Borders are often conditional, since there is a single body of water - the World Ocean. The MO map gives an idea of ​​the variety of dividing lines. For example, the Pacific Ocean and the Arctic Ocean are separated from each other by peninsulas (Chukchi and Alaska), connected by a narrow border between the Atlantic and Indian oceans south of Africa is drawn at 20 ° E. etc.

In a number of countries, it is customary to divide the main body of the hydrosphere into 5 or even 7 separate regions. In these cases, the Southern Ocean and two parts of the Atlantic are added. Depending on the country of residence, the answer to the usual question for the school curriculum "What is called the World Ocean?" differs in the number of parts allocated in its composition (oceans of the Earth).

Science about the oceans and its parts

The study of the bottom topography, temperature, salinity of waters, currents and other features of large bodies of water is engaged in oceanology (section of geography). Different parts of MC differ in the content of dissolved substances, density, which are measured with modern instruments at tens of thousands of points.

Determination of depths using echolocation made it possible to calculate the total amount of seawater on Earth and the compounds dissolved in it (chlorides, sulfates, iodides, which are of practical importance). The waters of the World Ocean have an average density of 1.024 g / cm 3. Such a liquid does not freeze at 0 ° C, but at -1 ... -3 ° C. The deeper, the less temperature readings depend on geographical latitude.

The depth of the oceans

How to find out the largest and smallest distances to the bottom surface? What are the depths at which the World Ocean will differ? The MO map contains information about the average and maximum depth. Sea areas are marked with different shades of blue. The dark color on the maps corresponds to the deepest places.

Light blue is used to represent shallows, mid-ocean ridges. The Pacific Ocean is considered the deepest; in its northwestern part it is over 11 km deep. The Peruvian Trench runs along the western coast of Chile (about 7 km). And the average depth of the Moscow region is 3.7 km.

Bottom relief

The continuation of the surface of the continents under water is a continental shelf, its depth in some places reaches 1 km. The world's oceans have one more transition zone along the entire perimeter - the continental slope. Within the continental shelf, plains of various origins stand out; there are deeply lowered areas in the Okhotsk, Barents and Japanese Seas. The ocean floor covers the central parts of the bottom and represents hollows and hills of different shapes and sizes. Deep-sea trenches have arisen in areas of collision of oceanic lithospheric plates with continental ones.

Among the mountain structures of the seabed, mid-oceanic ridges and ridges predominate, which are combined into a single continuous chain over 40 thousand km long. In addition, blocky and volcanic ridges, massifs and single underwater peaks are distinguished on the ocean floor. Other bottoms are plateaus and hills.

Movement of water in MO

Various causes and natural phenomena cause the movement of water masses in the oceans:

On the maps of the Moscow region in the atlases, the currents are indicated by arrows of red and blue color. Color conveys a feature such as a higher or lower temperature in the current compared to the ocean environment. The largest warm watercourses: the Gulf Stream in the northwestern part of the Atlantic, the Kuroshio near the Japanese islands, the North Atlantic Current. Cold water flows in the Moscow region: current of the Western winds, Peruvian, Benguela.

Water temperature in MO

The polar and subpolar parts of the Moscow Region are the coldest. A significant area of ​​the surface of the Arctic Ocean is covered with thick perennial ice. In the Arctic and Antarctic, there are ice fields and blocks in the water - icebergs. The coldest ocean is the Arctic, a significant part of which is frozen all year round. As you move from the Arctic Circle to the temperate zones, the Northern and Southern tropics, the water is heated more by the Sun. The Pacific Ocean is considered the warmest, the widest in the hot zone of illumination.

Surface water temperature changes faster. As a rule, the main flow of solar energy does not penetrate to depth. Therefore, in summer in temperate and tropical latitudes, the surface water temperature is higher than in winter. At great depths, seasonal differences are almost not felt. When moving from the surface for the first hundreds of meters, a strong decrease in temperature is noticeable. Above 1,000 meters, the changes are less pronounced, and below 3 thousand meters, the temperature is constantly in the range of + 2 ° ... 0 ° С.

Influence of the Moscow region on the climate of the continents

The oceans are important for the formation of climate and weather on land. the water surface of the MO is 17.4 ° С, while at the surface of the Earth this indicator is 14.4 ° С. The oceans can have a significant impact on the exchange of heat and moisture between the atmosphere and land. Water heats up and cools more slowly than continents and islands due to its high specific heat capacity.

Currents move cold ones to warmer regions, and vice versa. These processes have a great impact on the distribution of air pressure and temperature. In winter, MO is a kind of "stove" for heating continents, and in summer - a "refrigerator". The existing problems of the World Ocean - melting ice, rising water levels - threaten with changes in climatic conditions and vegetation on the continents, natural disasters.

Salinity

Almost all elements of the periodic table are present in seawater in varying amounts. The average content of various salts is 3.5%. A special unit of measurement is used - ppm - showing the amount of dissolved substances in grams in 1 liter of seawater (0/00). The average salinity of MO is 35 0/00. A connection is traced between the geographical location, distribution of surface currents, evaporation, salinity and other properties by which the World Ocean differs. The water resources of the Moscow Region far exceed those on land. To extract useful compounds, evaporation is used, to obtain drinking water - special desalination plants on sea vessels and in the coastal regions of many countries.

A significant amount of salt accumulates in ocean waters, which are located between 45 ° C. sh. and 10 ° S. sh. The content of substances in seawater depends on the surface runoff from the mainland, the thickness of the ice and its melting. The saltiest parts of the Moscow region are confined to tropical latitudes. This is the northwestern part of the Indian Ocean - the Red Sea and the Bab el-Mandeb Strait (41 and 42 ‰, respectively). is 39 ‰.

Natural resources of MO

A pantry of valuable chemicals, fuels, a source of energy, fresh water, food, a home for many living organisms - all this is the World Ocean. The geography of mineral reserves has not yet been sufficiently studied at great depths, and offshore development has been going on for many decades. The following natural resources of the MO are of great value:

• fuel (oil, gas, coal mining);
• metallic and non-metallic minerals (table salt, iron, manganese, bromine, calcium, gold, diamonds, amber, titanium, tin);
• energy (tides, waves, hot springs);
• building materials (sand, gravel);
• water supplies for desalination;
• fish, marine mammals, crustaceans, molluscs, sponges;
• vegetable;
• recreational.

For a long time, coastal zones have been used for shipping, sea fishing, cruise and beach recreation, and restoration of public health. Popular beaches are located on the warm sandy coasts of the Mediterranean, Red and Black Seas, Atlantic, Indian, Pacific oceans in subtropical and tropical climatic zones.

Environmental are largely associated with the growth of mining. When oil and oil products spill, an airtight film forms on the surface of the water. The exchange of oxygen and carbon dioxide between the atmosphere and the ocean is disrupted, aquatic animals and plants die.

"Fish latitudes" of the World Ocean

The oceans and seas are areas of intense fishing, coral and pearl mining. The marine industry accounts for about 10% of food raw materials. Commercial fish of the World Ocean are sardines, anchovies, herring, tuna, salmon, hake, capelin, mackerel, notothenia, pollock, cod, halibut, sprat, flounder.

In those latitudes where there are conditions for the development of plankton, there is an abundance of fish. For the reproduction of small organisms suspended in water, it is necessary that the so-called biogenic elements (nitrogen, silicon, phosphorus, calcium and others) rise from the bottom. Nature has created similar conditions in many regions of the Moscow region:

• off the Pacific coast of South America south of the equator;
• in the region of the Labrador Peninsula, off East Greenland in the north;
• near the coasts of Europe and North America in the Atlantic Ocean, near 40 ° N. w .;
• from the coast of Morocco in West Africa to the extreme point in the south of the hot continent;
• off the coast of Burma in the Indian Ocean, in the area of ​​the islands of Indonesia.

The oceans, as the most significant part of the continuous water shell of the Earth, play a huge role on the planet, and its riches have been used by man since time immemorial. According to individual characteristics, parts of the MO differ, but this is an integral natural complex of a planetary scale, which must be preserved for the well-being of the present and future generations.

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

The size 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 the oceans, as well as the boundaries of the seas within the oceans, are drawn rather conditionally. They are determined by the land areas that delimit the body of water, internal currents, differences in temperature and salinity.

The seas are distinguished by internal and marginal ones. The inland seas go deep enough into the land (for example,), and the marginal seas adjoin the land with one edge (for example, the North, Japanese).

Pacific Ocean

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

Since the Pacific Ocean captures almost everything but the coldest,

it is distinguished by a variety of climates. over the ocean ranges from + 30 °

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

The average salinity of the Atlantic Ocean is 35% o.

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

Indian Ocean

Most of the Indian Ocean is located in warm latitudes, wet monsoons dominate here, which determine the climate of the 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 Monsoon, Passat and.

The Indian Ocean is diverse, there are several ridges, between which there are relatively deep basins. The deepest point of the Indian Ocean is the Yavan depression, 7 km 709 m.

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

The average salinity of the Indian Ocean is 35% o.

Arctic Ocean

Most of the Arctic Ocean is covered with ice - almost 90% of the ocean's surface in winter. Only near the coast does the ice freeze to land, while most of the ice drifts. Drifting ice is called "pack".

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

A number of large currents are observed in the Arctic Ocean: a transarctic current passes along the north of Russia, as a result of interaction with the warmer waters of the Atlantic Ocean, a current is born.

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

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

Sea transport is an essential element of international trade. Countries such as others, cut off from the continents and not having enough of their own resources, are entirely dependent on. This is associated with a potential environmental hazard: the wreck of a ship carrying oil, fuel oil, coal and others causes serious damage.

Three-quarters of our planet's surface is covered by oceans and seas, the rest is land. The world's oceans, by definition, include all the oceans, seas of our planet and other bodies of water that communicate with them. The oceans and land are different in their qualities, but they are not isolated from each other: there is a constant exchange of energy and substances between them.

The oceans have an area of ​​361 million km2.

Oceans

The oceans are divided into four main parts:

• Quiet (or Great)
  • Area - 179 million km 2;
  • Average depth - 4,000 m;
  • The maximum depth is 11,000 m.
  • Located between the continents of Eurasia and in the West, North and South America in the East, Antarctica in the South.
• Atlantic
  • Area - 92 million km 2;
  • Average depth - 3600 m;
  • The maximum depth is 8,700 m.
  • Located mostly in the West. hemisphere stretched from North to South for 16000 km. Washes and, Antarctica, Europe. Connected with all oceans.
• Indian
  • Area - 76 million km 2;
  • Average depth - 3,700 m;
  • The maximum depth is 7,700 m.
  • Located mainly in the Southern Hemisphere, between the shores of Asia, Australia and Antarctica. The western border between the Atlantic Ocean and the Indian Ocean runs at 20 ° E. d., eastern - in the South of the southern tip of the island. Tasmania to Antarctica at 147 ° E d., north of Australia - 127 ° 30 ′ east. d. between the mainland and about. Timor and further west and northwest along the Lesser Sunda Islands, Java, Sumatra and the Malay Peninsula.
• Arctic
  • Area - 15 million km 2;
  • Average depth - 1200 m;
  • The maximum depth is 5,500 m.
  • Located between Eurasia and North America. Many islands: Greenland, Canadian Arctic arch., Spitsbergen, New. Land, North. Land, etc. with a total area of ​​4 million km 2. Large rivers flow into the Arctic Ocean - North. Dvina, Pechora, Khatanga, Indigirka, Kolyma, Makenzie.

The exchange of water masses between the oceans is ongoing. The division of the World Ocean into parts is largely conditional and the boundaries in history have changed more than once. The oceans, in turn, are also divided into parts. In the oceans, seas, bays, straits are distinguished. Parts of the ocean that protrude into the land and are separated from it by islands, peninsulas, as well as elevations of the underwater relief, are called seas.

Seas

The surface of the sea is called the water area. The part of the sea water area stretching along the territory of any state is called territorial waters. These very territorial waters have a certain width and are part of this state.

International law stipulates that the width of a strip of territorial waters stretching along the coast should not exceed 12 nautical miles. This value was recognized by about 100 states, including Russia, but 22 countries arbitrarily established wider territorial waters.

The part of the sea located outside the territorial waters is called the open sea. It is in common use by all states.

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The part of the sea or ocean that deeply flows into the land, but freely communicates with it, is called by the bay... According to the properties of currents, waters, organisms living in them, bays usually differ little from seas and oceans.

Parts of the oceans are called seas or bays in some cases incorrectly: for example, the Persian, Mexican, Hudson, Californian bays, according to their hydrological regimes, should be referred to as seas, while the Beaufort Sea (North America) should be called a bay.

What are the bays

There is another story about the bays.

Depending on the causes of occurrence, configuration, size, degree of connection with the main body of water, the following are distinguished among the bays:

bays- small water areas with more or less marked coastlines, bounded by capes or islands and usually convenient for ships to enter;

estuaries- funnel-shaped bays formed at river mouths under the influence of sea currents and high tides (lat.estuanum - flooded river mouths). Estuaries are formed at the confluence of the seas, the Thames and the St. Lawrence River;

fjords(Norwegian fjord) - narrow and deep bays with rocky and high shores. Fjords cut into the land to a great depth (up to 200 km), the depth is 1000 meters or more. Fjords were formed as a result of flooding of tectonic faults and river valleys, along which glaciers passed. For the fjords, the phenomenon is widespread, although it actually exists on the Kola Peninsula, Novaya Zemlya, Chukotka. Fjords are widespread along the shores of the Scandinavian Peninsula, Greenland, Alaska, New Zealand.

lagoons(lat, lacus - lake) - shallow bays, separated from the sea by narrow sandy spits. Exchange of water masses through straits, often shallow. In low latitudes in lagoons, the water is saltier than in the sea, and in high latitudes and at the confluence of large rivers, on the contrary, their salinity is lower than sea.

estuaries(Greek limen - harbor, bay). These bays are similar to lagoons and are formed when the widened estuaries of lowland rivers are inundated by the sea. The formation of the estuary is also associated with the sinking of the coastal strip. Just like in the lagoon, the water in the estuary has a significant salinity, but, in addition, it contains medicinal mud.

These bays are well expressed along the shores of the Black and Azov Seas. Estuaries in the Baltic Sea and in the Southern Hemisphere are called gafs (German haff - bay). Gafs are formed as a result of action along coastal currents and surf.

lip- sea bay at the mouth of the river. This is the Pomor name for large and small bays into which rivers flow. These are shallow bays, the water in them is strongly desalinated and sharply differs in color from the sea, the bottom in the bays is covered with river sediments carried out by the river. Onega Bay, Dvinskaya Bay, Obskaya Bay, Czech Bay, etc. are located in the north of Russia.

Straits

Parts of the World Ocean (seas, oceans, bays) are interconnected straits... The strait is a relatively wide body of water bounded on both sides by the shores of continents, islands or peninsulas.

The straits come in very different widths. The Drake Passage, which connects the Pacific and Atlantic oceans, is about 1000 km wide, and the Strait of Gibraltar, which connects the Mediterranean Sea with the Atlantic Ocean, at its narrowest point is not wider than 14 km.

From space, Earth has been described as "blue marble". Do you know why? Because most of our planet is covered by the oceans. In fact, almost three quarters (71%, or 362 million km²) of the Earth is ocean. Hence, healthy oceans are vital to our planet.

The ocean is unevenly distributed between the Northern and Southern Hemispheres. contains about 39% of the land, and in the Southern Hemisphere, the earth occupies about 19%.

When did the ocean appear?

Of course, the ocean originated long before the appearance of humanity, so no one knows exactly how this happened, however, it is believed that it was formed thanks to the water vapor present on Earth. When the Earth cooled down, this water vapor eventually evaporated, formed clouds, and fell out as rain. Over time, rain flooded the lowlands, creating the first oceans. When the water drained off the land, it trapped minerals, including salts, which formed salt water.

The meaning of the ocean

The ocean is extremely important to humanity and the entire Earth, with some things being more obvious than others:

• Provides food.
• Provides oxygen through tiny organisms called phytoplankton. These organisms produce approximately 50-85% of the oxygen we breathe and also store excess carbon.
• Regulates the climate.
• It is the source of important foods we use in cooking, including thickeners and stabilizers.
• Provides opportunities for relaxation.
• Contains such as natural gas and oil.
• Provides a “road” for international trade. More than 98% of US foreign trade takes place across the ocean.

How many oceans are there on planet Earth?

Map of all the oceans and continents of the Earth

The main part of the hydrosphere of our planet is the World Ocean, which connects all the oceans. There are currents, winds, tides and waves that constantly circulate around this ocean. But to simplify, the oceans have been divided into parts. Below are the names of the oceans with a short description and characteristics, from largest to smallest:

• Pacific Ocean: is the largest ocean and is considered the largest geographic feature on our planet. It is the west coast of America and the east coast of Asia and Australia. The ocean stretches from the Arctic Ocean (in the north) to the Southern Ocean surrounding Antarctica (in the south).
• Atlantic Ocean: is smaller than the Pacific Ocean. It is also shallower than the previous one and America in the west, Europe and Africa in the east, borders the Arctic Ocean in the north, and connects with the Southern Ocean in the south.
• Indian Ocean: is the third largest ocean. It is Africa in the west, Asia in the north and Australia in the east, and borders the Southern Ocean in the south.
• Southern or Antarctic Ocean: was allocated to a separate ocean by the International Hydrographic Organization in 2000. This ocean includes the waters of the Atlantic, Pacific and Indian Oceans, and it surrounds Antarctica. In the north, it does not have clear outlines of islands and continents.
• Arctic Ocean: it is the smallest ocean. It is on the northern coasts of Eurasia and North America.

What is seawater made of?

The salinity (salt content) of water varies in different parts of the ocean, but averages around 3.5%. To recreate seawater at home, you need to dilute a teaspoon of table salt in a glass of water.

However, the salt in sea water is different from table salt. Our edible salt is composed of the elements sodium and chlorine, and the salt in seawater contains over 100 elements, including magnesium, potassium and calcium.

Ocean water temperatures can vary greatly and range from -2 to + 30 ° C.

Oceans zones

By studying marine life and habitats, you will learn that different marine organisms can live in different zones, however, the two main ones are:

• Pelagic zone (pelagil), considered to be the "open ocean".
• The benthic zone (benthal), which is the bottom of the ocean.

The ocean is also divided into zones based on how much sunlight each zone receives. There is one that receives enough light to support the process of photosynthesis. In the dysphotic zone there is only a small amount of light, and in the aphotic zone there is no sunlight at all.

Some animals, such as whales, sea turtles, and fish, may occupy multiple zones throughout their life or in different seasons. Other animals, such as barnacles, are able to stay in the same zone for almost their entire life.

Oceanic habitats

Ocean habitats range from warm, shallow, light-filled waters to deep, dark, cold areas. The main habitats are:

• Littoral zone (littoral): it is a coastal area that is flooded with water at high tides and dried at low tides. Marine life here faces serious challenges, so living organisms must adapt to changes in temperature, salinity and moisture.
• : another habitat for organisms along the coast. These areas are covered with salt tolerant mangroves and are important habitats for some marine species.
• Sea herbs: They are flowering plants that grow in marine, completely saline environments. These unusual marine plants have roots that attach to the bottom and often form "meadows". The seagrass ecosystem is capable of supporting hundreds of species of organisms, including fish, shellfish, worms and many more. Grasslands store more than 10% of the total carbon in the oceans and also generate oxygen and protect coastal areas from erosion.
• : coral reefs are often referred to as the "marine forest" because of their great biodiversity. Most coral reefs are found in warm tropical and subtropical regions, although deep sea corals exist in some colder habitats. One of the most famous coral reefs is.
• Deep sea: While these cold, deep, and dark areas of the ocean may seem inhospitable, scientists have proven that they support a wide range of marine life. These are also important areas for scientific research, as about 80% of the ocean is over 1000 meters deep.
• Hydrothermal vents: they provide a unique, mineral-rich habitat, home to hundreds of species, including organisms called (which carry out the chemosynthesis process) and other animals such as rifthia, molluscs, mussels, crabs and shrimp.
• Algae forests: they are found in cold, fertile and relatively shallow waters. These underwater forests include an abundance of brown algae. Giant plants provide food and shelter for a huge number of marine species.
• Polar Regions: located near the polar circles of the Earth, north of the Arctic and south of Antarctica. These areas are cold, windy and have wide fluctuations in daylight throughout the year. Although these areas appear to be unsuitable for human life, they are rich in marine life, and many migratory animals travel to these areas to feed on krill and other prey. The polar regions are also home to iconic animals such as polar bears (in the Arctic) and penguins (in the Antarctic). The polar regions are under increasing scrutiny due to concerns about - as it is in these areas that the temperature rise is likely to be most noticeable and significant.

Oceans Facts

Scientists have studied the surfaces of the Moon, Mars and Venus better than the ocean floor of the Earth. However, the reason for this is not at all indifference to oceanography. In fact, it is more difficult to study the surface of the ocean floor, with the measurement of gravitational anomalies and using sonar at close ranges, than the surface of a nearby moon or planet, which can be done using a satellite.

Needless to say, Earth's ocean has not been explored. This complicates the work of scientists and, in turn, does not allow the inhabitants of our planet to fully realize how powerful and important resource it is. People need to understand their influence on the ocean and the influence of the ocean on them - humanity needs ocean literacy.

• The Earth has seven continents and five oceans, united into one World Ocean.
• The ocean is a very complex object: it hides mountain ranges with more volcanoes than on land.
• The fresh water used by mankind directly depends on the sea, through.
• Throughout geological time, the ocean has dominated land. Most of the rocks found on land were laid underwater when ocean levels were higher than they are today. Limestone and siliceous shale are biological products that have formed from the bodies of microscopic marine life.
• The ocean forms the coast of continents and islands. This happens not only during hurricanes but also with constant erosion, as well as with the help of waves and tides.
• The ocean dominates the global climate, driving three global cycles: water, carbon and energy. Rain comes from evaporated sea water, which carries not only water, but also solar energy, which took it out of the sea. The plants of the oceans produce most of the world's oxygen, and currents carry heat from the tropics to the poles.
• Life in the oceans has allowed the atmosphere to receive oxygen since the Proterozoic eon, billions of years ago. The first life arose in the ocean, and thanks to it, the Earth retained its precious supply of hydrogen, trapped in the form of water, and not lost in outer space, as it would have been otherwise.
• The diversity of habitats in the ocean is much greater than on land. Likewise, there are larger groups of living organisms in the ocean than on land.
• Most of the ocean is desert, with estuaries and reefs supporting the world's largest number of living organisms.
• The ocean and man are inextricably linked. It provides us with natural resources, and at the same time can be extremely dangerous. From it we extract food, medicine and minerals; trade also depends on sea routes. Most of the population lives near the ocean and this is the main recreational attraction. Conversely, storms, tsunamis and changes in water levels threaten coastal residents. But, in turn, humanity negatively affects the ocean, because we continuously use it, change it, pollute it, etc. These are questions that concern all countries and all inhabitants of our planet.
• Only 0.05% to 15% of our ocean has been studied in detail. Since the ocean makes up approximately 71% of the entire surface of the Earth, this means that there is still no information about most of our planet. As our dependence on the ocean continues to grow, marine science will become increasingly important in maintaining the health and value of the ocean, not just satisfying our curiosity and needs.