What is called the world ocean? World ocean: resources. World ocean: origin, age, evolution

instead of a preface.

In this section of the site, we set ourselves the task of bringing to our readers more detailed information about the World Ocean, as the main part of the Earth's biosphere. The section "The World Ocean" contains information about the origin and evolution of the World Ocean, about its size and components, about the composition and properties of sea water, about the structural features of the ocean floor, about ocean currents, about life in the ocean, about the use of ocean resources. The reader will be able to be convinced of the great importance of the ocean for mankind, as well as that the ocean, like a living being, needs protection.

1. General Provisions. Origin of the ocean.

Earth is the only planet in the solar system that has a hydrosphere. The main and main part of the hydrosphere is the World Ocean. It is the ocean that gives the Earth its unique beauty and originality. Of course, being on the surface of the Earth, a person cannot see the globe from the side and appreciate its beauty. But it is known what delight seizes astronauts when they admire our planet from near space. Even the first cosmonaut of the Earth, Yuri Alekseevich Gagarin, who had very little time in flight, managed to see from orbit and appreciate the stunning beauty of our planet.

And this beauty is created to a certain extent by the boundless World Ocean, turning the Earth into a blue planet.

The ocean is huge. The area of the entire surface of the Earth is estimated at 510 million km 2, of which about 361 million km 2 (70.8%) is covered with water. But if we take into account the glaciers that cover 11% of the land, it turns out that not 361, but 380 million km 2, that is, 75% of its surface, are covered with water on Earth.

It is estimated that the amount of water in the ocean is approximately 1370 million km 3 . Interestingly, the volume of land rising above sea level is about 111 million cubic kilometers, that is, ten and a half times less than the volume of water.

About 4% of all water on the planet falls on the share of lakes, swamps, rivers, underground (more precisely, intra-ground) water and the atmosphere, and the rest of the water fills a giant bowl called the World Ocean.

Where did such a huge amount of water come from on Earth? Scientists and thinkers have been looking for an answer to this question for centuries. It is now officially recognized in science Earth degassing hypothesis , according to which 4 billion years ago, after the cooling of the earth's crust, through cracks in the crust and the vents of volcanoes, the ejection of hot magma began with the simultaneous release of gases, water vapor and hot water to the surface. The beginning of the degassing process is considered the beginning of the geological history of the Earth and the beginning of the formation of its hydrosphere.

The time of the beginning of the process of degassing, which means the appearance of water on Earth, is indirectly confirmed, for example, by the fact that in the most ancient rocks of the earth's crust, whose age is determined at 3.8 billion years, imprints of unicellular organisms were found that could exist only if liquid water.

During the presumably first billion years of the planet's existence, the upper mantle was subjected to an active process of degassing, when water and acidic degassing products of mantle matter were carried to the Earth's surface. The volume of water coming from the bowels of the Earth increased from 0 to 1.3 km 3 per year. About 2.5 billion years ago, the average thickness of the water layer in the ocean probably did not exceed 2000 meters. Approximately 1.7 billion years ago, the chemical composition of oceanic waters and the earth's atmosphere became close to modern. The volume of water coming from the bowels of the Earth slowly decreased and is currently about 0.25 km 3 per year. This means that the process of degassing continues, which is confirmed by the still ongoing volcanic activity on Earth.

The hypothesis looks logical and quite scientific. In fact, it was not from outer space that water entered the ancient depressions of the earth's crust. And if later, with the advent of the atmosphere, water poured from the clouds, then it was still terrestrial in origin, since the clouds contained a condensate of water vapor coming out of the bowels of the Earth.

Some provisions of this hypothesis are questionable. For example, its authors (V.S. Safronov, O.G. Sorokhtin and others) believe that the heating of the interior of the young Earth occurred due to the fall of cosmic bodies onto its surface, and also partially due to the radioactive decay of the nuclei of heavy elements. It is difficult to argue about radioactive decay here, but what mass should the hypothetical cosmic bodies have in order for their impacts on the Earth's surface to heat up its bowels? On the other hand, why warm up the bowels if they were originally hot? But let's not get distracted by the specifics.

Oceanologists believe that The water cycle on Earth is not closed, since 0.25 km 3 of additional water annually flows from the bowels of the planet through rift cracks. Part of the water, rising in the form of vapor to the upper layers of the atmosphere, decomposes into hydrogen and oxygen under the influence of solar and cosmic radiation and goes into space.

The rift cracks just mentioned are fractures in the earth's crust that occur at the boundaries of the lithospheric plates in zones where the plates move away from each other. The process by which lithospheric plates move away from each other is called in geology spreading. A giant rift crack that appeared in the spreading zone, for example, crosses almost in the middle of the entire Atlantic Ocean in the meridian direction.

So, the ocean has existed throughout the earth's geological history . There are facts that prove this assertion. For example, in the south-west of Greenland in the 70s of the twentieth century, sedimentary brown ironstone was found, whose age is estimated at 3.76 billion years. This means that even then, in the epoch of the Catarchean, sedimentary rocks began to form as a result of the water cycle between the ocean, atmosphere and land.

Note: Catarchean is the geological epoch immediately following the pregeological era. The duration of the Katarchean is estimated at 800 million years (from 3500 to 2700 million years ago).

Russian volcanologists have calculated that during a volcanic eruption, the proportion of water vapor is about 3% of the mass of erupted substances. It turned out that this value almost exactly corresponds to the ratio between the masses of the modern hydrosphere (1.46 * 10 6) and the earth's crust (4.7 * 10 7). This is the second proof of the constant presence of the hydrosphere on the globe.

The third proof of the eternal and continuous existence of the ocean is the finds of the remains and imprints of the bodies of ancient living organisms. Thus, life on Earth has existed without interruption for a moment for three billion years, and its prosperity is provided by the ocean. Life originated in the ocean as a result of a long interaction of various substances dissolved in sea water. Now this hypothesis is almost universally accepted. Why almost? Because there must always be doubt. And when there is doubt, then there is a reason and a stimulus for further work of thought. But one thing is certain: the evolution of the organic world is directly related to the appearance and development of the water shell of the Earth. It should be noted that if life in the ocean originated three billion years ago, then it appeared on land only 600 million years ago.

The upper hundred-meter layer of ocean water contains a huge amount of photosynthetic single-celled algae. These tiny organisms, together with other plants living in the water, release oxygen and absorb carbon dioxide dissolved in sea water. There is a constant exchange of gases between water and the atmosphere. It means that The ocean plays a vital role in the balance of oxygen and life on the entire planet..

It hardly needs to be proven the critical importance of the ocean as a source of food resources for humans. At present, due to the constant growth of the world's population and the often unreasonable, predatory use by man of the biological resources of the ocean, marine fishing has essentially reached its limit. The time has come when it is necessary not only to procure animals and plants in the seas, but also to breed and cultivate many of their species exactly as man has been forced to do on land for thousands of years.

The ocean stores a huge amount of salts and other minerals needed by man.. Under the bottom of the shelf and the ocean floor there are deposits of coal, oil and gas, the development of which has long been carried out in many countries.

The ocean can be seen as colossal energy storage which is still little used. Not much time will pass, even on the scale of human life, and the natural reserves of oil, gas, coal and radioactive ores will run out. Then the ocean will become the main source of energy for industrial and domestic needs. True, extracting energy from the ocean will be much more difficult than simply burning gas, coal and oil products in furnaces.

If we talk about the meaning of the ocean as the main means of transport links between continents, it should be noted that no "road surfaces" or rails are required for laying sea lanes. All that is needed is reliable vehicles for the transport of people and goods and appropriate coastal infrastructure. And this is a certain economic advantage of sea routes over land routes. Another thing is that sea travel and cargo transportation are much more dangerous than land travel. But this forces scientists and designers to constantly improve the design and increase the reliability of ships not only for military, but also for national economic purposes.

Includes all the 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 ocean consists of four oceans: Pacific, Atlantic, Indian and Arctic.

The size of the Pacific oceans - 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 conventionally. They are determined by land areas that delimit the water space, internal currents, differences in temperature and salinity.

The seas are divided into internal and marginal. The inland seas protrude deep enough into the land (for example, the Mediterranean), while the marginal seas adjoin the land at one edge (for example, the North Sea, the Sea of Japan).

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 the North and, in the west - the coast and, in the south - Antarctica. He owns 20 seas and more than 10,000 islands.

Since the Pacific takes over almost all but the coldest,

it has a varied climate. over the ocean fluctuates from +30°

to -60 ° C. In the tropical zone, trade winds are formed, to the north, off the coast of Asia and Russia, monsoons are not uncommon.

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

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°С to +26°С, the average water temperature is +16°С.

The average salinity of the Atlantic Ocean is 35%.

The organic world of the Atlantic Ocean is rich in green plants and plankton.

Indian Ocean

Most of the Indian Ocean is located in warm latitudes, humid monsoons dominate here, which determine the climate of East Asian countries. The southern edge of the Indian Ocean is very cold.

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

The Indian Ocean has a diverse relief, 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°С off the coast of Antarctica to +30°С near the equator, the average water temperature is +18°С.

The average salinity of the Indian Ocean is 35%.

Arctic Ocean

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

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

A number of large currents are observed in the Arctic Ocean: the transarctic current passes along the north of Russia, 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.

Water under ice always has a negative temperature: -1.5 - -1°C. 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 is 31-34% o, in summer off the coast of Siberia it can be up to 20% o.

When studying our planet, it is very important to know what part of the Earth's surface is occupied by the oceans. Its area is truly impressive, because it occupies most of the surface of the globe. From space, it looks as if the Earth is a single body of water, on which the continents are located as separate islands.

Volume of the World Ocean

For the first time the concept of "World Ocean" was introduced at the beginning of the twentieth century by the famous Russian oceanologist Yu. M. Shokalsky. It denotes the totality of all the seas, oceans, bays and straits with which the planet is so rich. With the development of technology and in the course of numerous studies, it was found that the area of the World Ocean is 70% of the Earth's surface, that is, 361 million square meters. km.

It should be noted that the distribution of the waters of the World Ocean is uneven, and as a percentage it looks like this:

81% of ocean waters are distributed in the Southern Hemisphere;
61% - in the Northern Hemisphere.

Such unevenness is one of the most important factors in the formation of nature and climate on Earth.

Fig.1. Map of the World Ocean.

The volume of the Ocean is more than 1300 million cubic meters. km. But if you take into account the water that is concentrated in the silt of the ocean floor, then you can safely add 10% to this figure.

Square of four oceans

For a long time, scientists could not come to a consensus on how to divide the World Ocean into regions and how many oceans exist on the planet. Only in 1953, the International Hydrogeographic Bureau developed a common division of the waters of the World Ocean for all, which is still successfully applied in practice.

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The World Ocean consists of four oceans, each of which has a unique geological structure, features of the continental coastline, bottom topography, currents, natural resources, and many other indicators.

Pacific Ocean- the largest on the planet, its area occupies almost half of the waters of the oceans and is 179 mn. sq. km. Its deepest place is the famous Mariana Trench with a depth of 11 km.
Atlantic Ocean- the second largest, its area is almost 92 million square meters. km. The maximum depth is 8.7 km. in a trough called Puerto Rico.
Indian Ocean- a little less than the Atlantic - 76 million square meters. km. Its deepest point is the Yavan depression, whose depth reaches 7.7 km.
Arctic- completes the four world oceans, its area is slightly less than 15 million square meters. km. The greatest depth was recorded in the Nansen trench - 5.5 km.

Rice. 2. Arctic Ocean.

The relief of the ocean floor largely determines the depth of the oceans. A relatively shallow continental shoal or shelf, which extends for about 200 m, is followed by a continental slope, smoothly turning into a bed. Here, the average depth of the World Ocean is 4 km, but do not forget about the presence of depressions that can reach 11 km. in depth.

World Ocean

Ocean
World Ocean
a water shell that covers most of the earth's surface (four-fifths in the southern hemisphere and more than three-fifths in the northern hemisphere). Only in some places the earth's crust rises above the surface of the ocean, forming continents, islands, atolls, etc. Although the World Ocean is a single whole, for the convenience of research, its individual parts have been given different names: the Pacific, Atlantic, Indian and Arctic oceans.
The largest oceans are the Pacific, Atlantic and Indian. The Pacific Ocean (an area of approximately 178.62 million km 2) has a rounded shape in plan and occupies almost half of the water surface of the globe. The Atlantic Ocean (91.56 million km 2) has the shape of a wide letter S, and its western and eastern coasts are almost parallel. The Indian Ocean with an area of 76.17 million km 2 has the shape of a triangle.
The Arctic Ocean with an area of only 14.75 million km 2 is surrounded by land on almost all sides. Like Quiet, it has a rounded shape. Some geographers identify another ocean - the Antarctic, or the South - the body of water surrounding Antarctica.
Ocean and atmosphere. The oceans, the average depth of which is approx. 4 km, contains 1350 million km 3 of water. The atmosphere, enveloping the entire Earth in a layer several hundred kilometers thick, with a much larger base than the World Ocean, can be considered as a "shell". Both the ocean and the atmosphere are the fluids in which life exists; their properties determine the habitat of organisms. Circulation flows in the atmosphere affect the general circulation of water in the oceans, and the properties of ocean waters largely depend on the composition and temperature of the air. In turn, the ocean determines the main properties of the atmosphere and is a source of energy for many processes occurring in the atmosphere. The circulation of water in the ocean is affected by winds, the rotation of the Earth, and land barriers.
Ocean and climate. It is well known that the temperature regime and other climatic characteristics of the area at any latitude can change significantly in the direction from the ocean coast to the interior of the mainland. Compared to land, the ocean heats up more slowly in summer and cools more slowly in winter, smoothing out temperature fluctuations on adjacent land.
The atmosphere receives from the ocean a significant part of the heat coming to it and almost all of the water vapor. The vapor rises, condenses, and forms clouds that are carried by the winds and support life on the planet, falling as rain or snow. However, only surface waters participate in heat and moisture exchange; more than 95% of the water is in the depths, where its temperature remains virtually unchanged.
Composition of sea water. The ocean water is salty. The salty taste comes from the 3.5% dissolved minerals it contains—mainly sodium and chlorine compounds—the main ingredients in table salt. Magnesium is next in number, followed by sulfur; all common metals are also present. Of the non-metallic components, calcium and silicon are especially important, since they are involved in the structure of the skeletons and shells of many marine animals. Due to the fact that the water in the ocean is constantly mixed by waves and currents, its composition is almost the same in all oceans.
properties of sea water. The density of sea water (at a temperature of 20 ° C and a salinity of approx. 3.5%) is approximately 1.03, i.e. slightly higher than the density of fresh water (1.0). The density of water in the ocean varies with depth due to the pressure of the overlying layers, as well as depending on temperature and salinity. In the deepest parts of the ocean, the waters tend to be saltier and colder. The densest masses of water in the ocean can remain at depth and maintain a lower temperature for more than 1000 years.
Since sea water has a low viscosity and high surface tension, it offers relatively little resistance to the movement of a ship or swimmer and flows quickly from various surfaces. The predominant blue color of sea water is associated with the scattering of sunlight by small particles suspended in water.
Sea water is much less transparent to visible light than air, but more transparent than most other substances. The penetration of sunlight into the ocean to a depth of 700 m has been recorded. Radio waves penetrate the water column only to a shallow depth, but sound waves can propagate under water for thousands of kilometers. The speed of sound propagation in sea water fluctuates, averaging 1500 m per second.
The electrical conductivity of sea water is about 4000 times higher than that of fresh water. The high salt content prevents its use for irrigation and irrigation of agricultural crops. It is also unsuitable for drinking.
RESIDENTS OF THE SEA
Life in the ocean is extremely diverse - more than 200,000 species of organisms live there. Some of them, such as the lobe-finned coelacanth fish, are living fossils whose ancestors flourished here more than 300 million years ago; others have appeared more recently. Most marine organisms are found in shallow waters where sunlight penetrates to promote photosynthesis. Zones enriched with oxygen and nutrients, such as nitrates, are favorable for life. The phenomenon known as "upwelling" is widely known. . upwelling) - the rise to the surface of deep sea waters enriched with nutrients; it is with him that the richness of organic life is associated along some coasts. Life in the ocean is represented by a wide variety of organisms - from microscopic single-celled algae and tiny animals to whales exceeding 30 m in length and larger than any animal that has ever lived on land, including the largest dinosaurs. Oceanic biota is divided into the following main groups.
Plankton is a mass of microscopic plants and animals that are not capable of independent movement and live in the near-surface well-lit layers of water, where they form floating "foraging grounds" for larger animals. Plankton consists of phytoplankton (including plants such as diatoms) and zooplankton (jellyfish, krill, crab larvae, etc.).
Nekton consists of organisms freely floating in the water column, mostly predatory, and includes more than 20,000 species of fish, as well as squid, seals, sea lions, and whales.
Benthos consists of animals and plants that live on or near the ocean floor, both at great depths and in shallow water. Plants represented by various algae (for example, brown ones) are found in shallow water, where sunlight penetrates. Of the animals, sponges, sea lilies (at one time considered extinct), brachiopods, and others should be noted.
food chains. More than 90% of the organic substances that form the basis of life in the sea are synthesized under sunlight from minerals and other components by phytoplankton, which abundantly inhabit the upper layers of the water column in the ocean. Some organisms that make up zooplankton eat these plants and in turn are a food source for larger animals that live at greater depths. Those are eaten by larger animals that live even deeper, and this pattern can be traced to the very bottom of the ocean, where the largest invertebrates, such as glass sponges, receive the nutrients they need from the remains of dead organisms - organic detritus that sinks to the bottom from the overlying water column. However, it is known that many fish and other free-roaming animals have managed to adapt to the extreme conditions of high pressure, low temperature and constant darkness that are characteristic of great depths. see also marine biology.
WAVES, TIDES, CURRENTS
Like the entire universe, the ocean is never at rest. A variety of natural processes, including such catastrophic ones as underwater earthquakes or volcanic eruptions, cause the movement of ocean waters.
Waves. Ordinary waves are caused by wind blowing at varying speeds over the surface of the ocean. First, ripples appear, then the surface of the water begins to rise and fall rhythmically. Although the water surface rises and falls, individual water particles move along a trajectory that is almost a vicious circle, with little or no horizontal displacement. As the wind gets stronger, the waves get higher. In the open sea, the height of the crest of a wave can reach 30 m, and the distance between adjacent crests is 300 m.
Approaching the shore, the waves form breakers of two types - diving and sliding. Diving breakers are characteristic of waves that originated at a distance from the coast; they have a concave front, their crest overhangs and collapses like a waterfall. Sliding breakers do not form a concave front, and the wave declines gradually. In both cases, the wave rolls onto the shore and then rolls back.
catastrophic waves can occur as a result of a sharp change in the depth of the seabed during the formation of faults (tsunamis), during severe storms and hurricanes (storm surges), or during avalanches and landslides of coastal cliffs.
Tsunamis can propagate in the open ocean at speeds up to 700–800 km/h. When approaching the shore, the tsunami wave slows down, and its height simultaneously increases. As a result, a wave with a height of up to 30 m or more (relative to the mean ocean level) rolls onto the coast. Tsunamis have tremendous destructive power. Although areas near seismically active zones such as Alaska, Japan, Chile suffer the most from them, waves from distant sources can cause significant damage. Similar waves occur during explosive volcanic eruptions or the collapse of crater walls, as, for example, during the volcanic eruption on the island of Krakatau in Indonesia in 1883.
Even more destructive can be storm waves generated by hurricanes (tropical cyclones). Repeatedly similar waves crashed on the coast in the upper part of the Bay of Bengal; one of them in 1737 led to the death of about 300 thousand people. Now, thanks to a significantly improved early warning system, it is possible to warn the population of coastal cities in advance of approaching hurricanes.
Catastrophic waves caused by landslides and rock falls are relatively rare. They arise as a result of the fall of large blocks of rock into deep-sea bays; in this case, a huge mass of water is displaced, which falls on the shore. In 1796, a landslide came down on the island of Kyushu in Japan, which had tragic consequences: three huge waves generated by it claimed the lives of approx. 15 thousand people.
Tides. Tides roll on the shores of the ocean, as a result of which the water level rises to a height of 15 m or more. The main cause of tides on the surface of the Earth is the attraction of the Moon. There are two high tides and two low tides every 24 hours and 52 minutes. Although these level fluctuations are only noticeable near the coast and in the shallows, they are known to manifest themselves in the open sea as well. Many very strong currents in the coastal zone are caused by tides, therefore, for safe navigation, sailors need to use special tables of currents. In the straits connecting the Inland Sea of Japan with the open ocean, tidal currents reach a speed of 20 km / h, and in the Seymour-Narrows Strait off the coast of British Columbia (Vancouver Island) in Canada, a speed of approx. 30 km/h.
currents in the ocean can also be created by waves. Coastal waves approaching the shore at an angle cause relatively slow alongshore currents. Where the current deviates from the shore, its speed increases sharply - a discontinuous current is formed, which can be dangerous for swimmers. The rotation of the Earth causes major ocean currents to move clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. Some of the currents are associated with the richest fishing grounds, such as the Labrador Current off the eastern coast of North America and the Peruvian Current (or Humboldt) off the coast of Peru and Chile.
Turbid currents are among the strongest currents in the ocean. They are caused by the movement of a large volume of suspended sediment; these sediments can be carried by rivers, be the result of waves in shallow water, or be formed by a landslide on an underwater slope. Ideal conditions for the origin of such currents exist in the tops of submarine canyons located near the coast, especially at the confluence of rivers. Such currents develop speeds from 1.5 to 10 km / h and sometimes damage submarine cables. After the 1929 earthquake with its epicenter in the area of the Great Newfoundland Bank, many transatlantic cables connecting Northern Europe and the USA were damaged, probably due to strong turbidity currents.
COASTS AND COASTLINES
The maps clearly show an extraordinary variety of coastlines. Examples include indented coastlines with islands and winding straits (in Maine, southern Alaska, and Norway); shores of relatively simple outline, as on much of the west coast of the United States; deeply penetrating and branching bays (for example, Chesapeake) in the middle part of the Atlantic coast of the USA; protruding low-lying coast of Louisiana near the mouth of the Mississippi River. Similar examples can be given for any latitude and any geographic or climatic region.
Coastal evolution. First of all, let's look at how the sea level has changed over the past 18 thousand years. Just before that, most of the land at high latitudes was covered by huge glaciers. As these glaciers melted, melt water entered the ocean, as a result of which its level rose by about 100 m. At the same time, many river mouths were flooded - this is how estuaries were formed. Where glaciers have created valleys deepened below sea level, deep bays (fjords) have formed with numerous rocky islands, as, for example, in the coastal zone of Alaska and Norway. When attacking low-lying coasts, the sea also flooded the river valleys. On the sandy coasts, as a result of wave activity, low barrier islands were formed, stretched along the coast. Such forms are found off the southern and southeastern coasts of the United States. Sometimes barrier islands form accumulative coastal protrusions (for example, Cape Hatteras). At the mouths of rivers carrying a large amount of sediment, deltas appear. On tectonic block shores experiencing uplifts that compensated for sea level rise, rectilinear abrasion ledges (cliffs) can form. On the island of Hawaii, as a result of volcanic activity, lava flows flowed into the sea and lava deltas formed. In many places, the development of the coast proceeded in such a way that the bays formed during the flooding of the mouths of the rivers continued to exist - for example, the Chesapeake Bay or the bays on the northwestern coast of the Iberian Peninsula.
In the tropics, rising sea levels promoted more intensive growth of corals on the outer (marine) side of the reefs, so that lagoons formed on the inner side, separating the barrier reef from the coast. A similar process also took place where, against the background of a rise in sea level, the island was submerged. At the same time, the barrier reefs on the outer side were partially destroyed during storms, and coral fragments were piled up by storm waves above calm sea level. Reef rings around submerged volcanic islands have formed atolls. In the last 2000 years, there has been practically no rise in the level of the World Ocean.
Beaches have always been highly valued by man. They are composed mainly of sand, although there are also pebble and even small boulder beaches. Sometimes sand is a shell crushed by waves (the so-called shell sand). In the profile of the beach, sloping and almost horizontal parts stand out. The angle of inclination of the coastal part depends on the sand that composes it: on beaches composed of fine sand, the frontal zone is the most gentle; on coarse-grained sand beaches, the slopes are somewhat greater, and the steepest ledge is formed by pebble and boulder beaches. The rear zone of the beach is usually located above sea level, but sometimes huge storm waves flood it too.
There are several types of beaches. For the coasts of the United States, the most typical are long, relatively straight beaches, bordering the barrier islands from the outside. Such beaches are characterized by alongshore hollows, where currents dangerous for swimmers can develop. On the outer side of the hollows there are sand bars stretched along the coast, where the destruction of the waves occurs. With strong waves, discontinuous currents often occur here.
Irregularly shaped rocky shores usually form many small bays with small isolated stretches of beaches. These bays are often protected from the sea by rocks or underwater reefs protruding above the surface of the water.
On the beaches, formations created by waves are common - beach festoons, ripple marks, traces of wave splash, gullies formed during the runoff of water at low tide, as well as traces left by animals.
When beaches are washed out during winter storms, sand moves towards the open sea or along the coast. When the weather is calmer in summer, new masses of sand come to the beaches, brought by rivers or formed when coastal ledges are washed away by waves, and thus the beaches are restored. Unfortunately, this compensatory mechanism is often disrupted by human intervention. The construction of dams on rivers or the construction of bank protection walls prevents the flow of material to the beaches to replace the material washed away by winter storms.
In many places, sand is carried by waves along the coast, mainly in one direction (the so-called alongshore sediment flow). If coastal structures (dams, breakwaters, piers, groins, etc.) block this flow, then the beaches “upstream” (i.e., located on the side from which the sediment comes from) are either washed away by waves or expand beyond sediment input, while the "downstream" beaches are hardly fed by new sediments.
RELIEF OF THE BOTTOM OF THE OCEANES
At the bottom of the oceans are huge mountain ranges, deep crevices with steep walls, extended ridges and deep rift valleys. In fact, the seabed is no less rugged than the land surface.
Shelf, continental slope and continental foot. The platform that fringes the continents and is called the continental shelf, or shelf, is not as flat as it was once believed. Rock ledges are common on the outer part of the shelf; Bedrock often comes out on the part of the continental slope adjacent to the shelf.
The average depth of the outer edge (edge) of the shelf separating it from the continental slope is approx. 130 m. Near the shores subjected to glaciation, hollows (troughs) and depressions are often noted on the shelf. So, off the fjord coasts of Norway, Alaska, and southern Chile, deep-water areas are found near the modern coastline; deep water troughs exist off the coast of Maine and in the Gulf of St. Lawrence. Glacier-carved troughs often run across the entire shelf; in some places along them there are shallows exceptionally rich in fish, for example, the banks of Georges or the Great Newfoundland.
Shelves off the coast, where there was no glaciation, have a more uniform structure, however, even on them sandy or even rocky ridges are often found, rising above the general level. During the Ice Age, when the level of the ocean dropped due to the fact that huge masses of water accumulated on land in the form of ice sheets, river deltas were created in many places of the present shelf. In other places on the outskirts of the continents, at the then sea level marks, abrasion platforms were cut into the surface. However, the results of these processes, which took place under conditions of a low level of the World Ocean, were significantly transformed by tectonic movements and sedimentation in the subsequent post-glacial epoch.
The most surprising thing is that in many places on the outer shelf one can still find deposits that formed in the past, when the sea level was more than 100 m below the present. There are also found the bones of mammoths who lived in the Ice Age, and sometimes the tools of primitive man.
Speaking about the continental slope, the following features should be noted: firstly, it usually forms a clear and well-defined boundary with the shelf; secondly, it is almost always crossed by deep submarine canyons. The average angle of inclination on the continental slope is 4°, but there are also steeper, sometimes almost vertical sections. At the lower boundary of the slope in the Atlantic and Indian Oceans there is a gently sloping surface, called the "continental foot". Along the periphery of the Pacific Ocean, the continental foot is usually absent; it is often replaced by deep sea trenches, where tectonic movements (faults) generate earthquakes and where most tsunamis originate.
Submarine canyons. These canyons, cut into the seabed for 300 m or more, are usually characterized by steep sides, a narrow bottom, and sinuosity in plan; like their land-based counterparts, they receive numerous tributaries. The deepest known underwater canyon, the Grand Bahama Canyon, is incised for almost 5 km.
Despite the similarity to the formations of the same name on land, the majority of submarine canyons are not ancient river valleys submerged below sea level. Turbid currents are quite capable of both working out a valley at the bottom of the ocean, and deepening and transforming a flooded river valley or a depression along a fault line. Submarine valleys do not remain unchanged; sediment transport is carried out along them, as evidenced by the signs of ripples on the bottom, and their depth is constantly changing.
Deep sea trenches. Much has become known about the relief of the deep parts of the ocean floor as a result of large-scale research that unfolded after the Second World War. The greatest depths are confined to the deep-sea trenches of the Pacific Ocean. The deepest point - the so-called. "Challenger Deep" - is located within the Mariana Trench in the southwest Pacific Ocean. The following are the greatest depths of the oceans, with their names and locations:
Arctic- 5527 m in the Greenland Sea;
Atlantic- Puerto Rico trench (off the coast of Puerto Rico) - 8742 m;
Indian- Sunda (Yavansky) trench (to the west of the Sunda archipelago) - 7729 m;
Quiet- Mariana Trench (near the Mariana Islands) - 11,033 m; the Tonga trench (near New Zealand) - 10,882 m; Philippine Trench (near the Philippine Islands) - 10,497 m.
Mid-Atlantic Ridge. The existence of a large underwater ridge stretching from north to south across the central part of the Atlantic Ocean has long been known. Its length is almost 60 thousand km, one of its branches stretches into the Gulf of Aden to the Red Sea, and the other ends off the coast of the Gulf of California. The width of the ridge is hundreds of kilometers; its most striking feature is the rift valleys that can be traced along almost its entire length and resemble the East African rift zone.
An even more surprising discovery was that the main ridge is crossed at right angles to its axis by numerous ridges and hollows. These transverse ridges are traced in the ocean for thousands of kilometers. At the places where they intersect with the axial ridge, there are so-called. fault zones, which are associated with active tectonic movements and where the centers of large earthquakes are located.
A. Wegener's Continental Drift Hypothesis. Until about 1965, most geologists believed that the position and shape of the continents and ocean basins remained unchanged. There was a rather vague notion that the Earth was contracting, and that this contraction resulted in the formation of folded mountain ranges. When, in 1912, the German meteorologist Alfred Wegener proposed the idea that the continents were moving ("drifting") and that the Atlantic Ocean was formed in the process of widening a crack that split an ancient supercontinent, this idea was met with incredulity, despite a lot of evidence in its favor. (the similarity of the outlines of the eastern and western coasts of the Atlantic Ocean; the similarity of fossil remains in Africa and South America; traces of the great glaciations of the Carboniferous and Permian periods in the interval 350-230 million years ago in areas now located near the equator).
Growth (spreading) of the ocean floor. Gradually, Wegener's arguments were reinforced by the results of further research. It has been suggested that rift valleys within mid-ocean ridges originate as extensional fissures, which are then filled by rising magma from the depths. The continents and adjacent parts of the oceans form huge plates moving away from the underwater ridges. The frontal part of the American Plate is pushing against the Pacific Plate; the latter, in turn, moves under the mainland - a process called subduction occurs. There is a lot of other evidence in favor of this theory: for example, the confinement of earthquake centers, marginal deep-sea trenches, mountain ranges and volcanoes to these areas. This theory makes it possible to explain almost all major landforms of continents and ocean basins.
Magnetic anomalies. The most convincing argument in favor of the hypothesis of the expansion of the ocean floor is the alternation of bands of direct and reverse polarity (positive and negative magnetic anomalies), traced symmetrically on both sides of the mid-ocean ridges and running parallel to their axis. The study of these anomalies made it possible to establish that the spreading of the oceans occurs on average at a rate of several centimeters per year.
Plate tectonics. Another proof of the likelihood of this hypothesis was obtained with the help of deep-sea drilling. If, as follows from historical geology, the expansion of the oceans began in the Jurassic, no part of the Atlantic Ocean can be older than this time. Deep-sea boreholes have penetrated Jurassic deposits (formed 190–135 million years ago) in some places, but older ones have not been found anywhere. This circumstance can be considered weighty evidence; at the same time, it leads to the paradoxical conclusion that the ocean floor is younger than the ocean itself.
OCEAN RESEARCH
early research. The first attempts to explore the oceans were purely geographical in nature. Travelers of the past (Columbus, Magellan, Cook, etc.) made long tedious voyages across the seas and discovered islands and new continents. The first attempt to explore the ocean itself and its bottom was made by the British expedition on the Challenger (1872-1876). This voyage laid the foundations of modern oceanology. The echo sounding method, developed during the First World War, made it possible to compile new maps of the shelf and the continental slope. Special oceanological scientific institutions that appeared in the 1920s and 1930s extended their activities to deep-sea areas.
Modern stage. Real progress in research, however, begins only after the end of the Second World War, when the navies of various countries took part in the study of the ocean. At the same time, many oceanographic stations received support.
The leading role in these studies belonged to the USA and the USSR; on a smaller scale, similar work was carried out by Great Britain, France, Japan, West Germany and other countries. In about 20 years, it was possible to get a fairly complete picture of the topography of the ocean floor. On the published maps of the bottom relief, a picture of the distribution of depths emerged. The study of the ocean floor with the help of echo sounding, in which sound waves are reflected from the surface of bedrock buried under loose sediments, has also acquired great importance. Now more is known about these buried deposits than about the rocks of the continental crust.
Submersibles with a crew on board. A great step forward in ocean research was the development of deep-sea submersibles with portholes. In 1960, Jacques Picard and Donald Walsh, on the Trieste I submersible, dived in the deepest known area of the ocean, the Challenger Deep, 320 km southwest of Guam. The "diving saucer" by Jacques-Yves Cousteau turned out to be the most successful among devices of this type; with its help, it was possible to discover the amazing world of coral reefs and underwater canyons to a depth of 300 m. Another apparatus, Alvin, descended to a depth of 3650 m (with a design diving depth of up to 4580 m) and was actively used in scientific research.
Deep water drilling. Just as the concept of plate tectonics revolutionized geological theory, deep sea drilling revolutionized the understanding of geological history. An advanced drilling rig allows you to pass hundreds and even thousands of meters in igneous rocks. If it was necessary to replace the blunt bit of this installation, a casing string was left in the well, which could be easily detected by a sonar mounted on a new drill pipe bit, and thus continue drilling the same well. Cores from deep-sea wells have made it possible to fill in many gaps in the geological history of our planet and, in particular, have provided much evidence for the correctness of the ocean floor spreading hypothesis.
OCEAN RESOURCES
As the planet's resources increasingly struggle to meet the needs of a growing population, the ocean is becoming increasingly important as a source of food, energy, minerals and water.
Ocean food resources. Tens of millions of tons of fish, shellfish and crustaceans are caught in the oceans every year. In some parts of the oceans, modern factory ship fishing is very intensive. Some species of whales are almost completely exterminated. Continued intensive fishing can cause severe damage to such valuable commercial fish species as tuna, herring, cod, sea bass, sardine, hake.
Fish farming. Large areas of the shelf could be singled out for fish breeding. At the same time, you can fertilize the seabed to ensure the growth of marine plants that feed on fish.
Mineral resources of the oceans. All the minerals that are found on land are also present in sea water. Salts, magnesium, sulfur, calcium, potassium, bromine are most common there. Recently, oceanologists have discovered that in many places the ocean floor is literally covered with a scattering of ferromanganese nodules with a high content of manganese, nickel and cobalt. Phosphorite concretions found in shallow water can be used as a raw material for the production of fertilizers. Sea water also contains valuable metals such as titanium, silver and gold. Currently, only salt, magnesium and bromine are extracted from sea water in significant quantities.
Oil . A number of large oil fields are already being developed on the shelf, for example, off the coast of Texas and Louisiana, in the North Sea, the Persian Gulf and off the coast of China. Exploration is ongoing in many other areas, such as off the coast of West Africa, off the east coast of the United States and Mexico, off the coast of Arctic Canada and Alaska, Venezuela and Brazil.
The ocean is a source of energy. The ocean is an almost inexhaustible source of energy.
Tidal energy. It has long been known that tidal currents passing through narrow straits can be used for energy in the same way as waterfalls and dams on rivers. Thus, for example, a tidal hydroelectric power station has been successfully operating in Saint-Malo in France since 1966.
Wave energy can also be used to generate electricity.
Thermal Gradient Energy. Nearly three-quarters of the solar energy that hits Earth comes from the oceans, so the ocean is the perfect giant heat sink. Energy generation, based on the use of the temperature difference between the surface and deep layers of the ocean, could be carried out on large floating power plants. Currently, the development of such systems is in the experimental stage.
Other resources. Other resources include pearls, which are formed in the body of some molluscs; sponges; algae used as fertilizers, food products and food additives, as well as in medicine as a source of iodine, sodium and potassium; deposits of guano - bird droppings mined on some atolls in the Pacific Ocean and used as fertilizer. Finally, desalination makes it possible to obtain fresh water from sea water.
OCEAN AND MAN
Scientists believe that life originated in the ocean about 4 billion years ago. The special properties of water have had a huge impact on human evolution and still make life possible on our planet. Man used the seas as a way of trade and communication. Sailing the seas, he made discoveries. He turned to the sea in search of food, energy, material resources and inspiration.
Oceanography and Oceanology. Ocean research is often subdivided into physical oceanography, chemical oceanography, marine geology and geophysics, marine meteorology, ocean biology, and engineering oceanography. In most countries with access to the ocean, oceanographic research is being carried out.

The surface of the earth's crust and surrounds the areas of the earth's crust lying above the surface of the World Ocean, and also containing approximately the total content of the salt composition. From the point of view of the qualitative chemical composition of water in the ocean, physical and chemical properties, the World Ocean acts as an indivisible whole. If we consider the quantitative indicators of the hydrochemical and hydrological regimes, then there will be significant differences, which are very diverse. The largest land areas protruding above the surface of the ocean waters are called continents (continents), much smaller islands, atolls, rocks. Islands, in turn, can be located singly and in groups - archipelagos. The largest archipelago - the Canadian Arctic Archipelago, with 36,563 islands - an area of 1.3 million km 2 is located in northern Canada off the coast of North America. The largest island on the planet is the island of Greenland with an area of 2176 thousand km 2 in the northern part of the Atlantic Ocean off the northeastern coast of the mainland of North America. The level of the World Ocean is the boundary between the water and air spaces of the Earth, the so-called zero mark of depths and heights on Earth. From this mark, all measurements of depths and heights lying below and above the ocean level are made. The level of the ocean is considered to be the same at all points of the World Ocean, although in reality, although not significantly, it differs. Ocean level can be influenced by various factors, both internal and external. One of these factors is the Moon, which, by its attraction, can significantly change the height of the ocean level, which are called tides.

The waters of the World Ocean are included in the larger structure of the Earth - the hydrosphere. Being part of the Earth's hydrosphere, the waters of the ocean constantly interact with the earth's crust and atmosphere, imposing certain features and many of its significant features. The World Ocean is a grand accumulator of energy and heat supplied by our luminary. Thanks to the ocean, favorable conditions are created on Earth for the development of flora and fauna by smoothing out sudden temperature changes and moistening remote areas of land. The waters of the world ocean account for most of the entire hydrosphere of the Earth - 94%, and 70.8% of the entire surface of the Earth. The entire surface of the world's oceans is divided by continents into separate large water areas called oceans, as well as smaller seas, bays, and straits. All the oceans of the Earth have direct communication between themselves through the straits and between the island seas. The entire World Ocean consists of four oceans and the seas that are part of these oceans. The boundaries separating the oceans are taken conditionally. There are no clear boundaries between the oceans, since in principle this was never required, it was always enough to have a conditional definition. The area of the World Ocean is 361.06 million km 2, the volume is 1370 million km 3, the average depth is 3795 m, the greatest depth is 11022 meters located in the western part of the Pacific Ocean at the bottom of the Mariana Trench on the eastern edge of the Philippine Sea.

Also, sometimes a fifth ocean is distinguished in the World Ocean - the Southern Ocean. The Southern Ocean is the body of water around the southern continent of Antarctica.

Seas of the World Ocean according to the agreement of the Intergovernmental Oceanographic Commission of UNESCO of 1967, there are 62 seas. The area of the seas of the World Ocean is about 10% of the total area of the World Ocean, the volume of water in the seas is about 3%. Also, some large parts of the World Ocean, according to their natural characteristics and features related to the seas, are called bays such as the Hudson Bay, Mexican, Bengal, Persian.

The largest seas of the World Ocean:

Sargasso Sea - about 6000 km 2
Philippine Sea - 5726 km 2
Coral Sea - 4791 km 2
Arabian Sea - 3862 km 2
South China Sea - 3500 km 2
Fiji Sea - 3177 km 2
Weddell Sea - 2800 km 2
Caribbean Sea - 2754 km 2
Mediterranean Sea - 2500 km 2
Tasman Sea - 2330 km 2
Bering Sea - 2260 km 2

The largest bays of the World Ocean:

Bengal - area 2,172,000 km 2, average water volume 5,616,000 km 3, average depth 2586 m, maximum depth 5258 m.
* Mexican - area 1,543,000 km 2, volume 2,332,000 km 3, depth 1522 m, maximum 3822 m.
Guinean - area 1,533,000 km 2, maximum depth 6363 m.
Big Australian - area 1,335,000 km 2, depth up to 5670 m.
* Hudson Bay - area 1,230,000 km 2, 92,000 km 3, average depth 112 m, maximum 301 m.
Alaska - area 384,000 km 2, depth up to 5659 m.
* Persian - area 239,000 km 2, volume 9,100 km 3, most depths less than 50 m, maximum 102 m.
Biscay - area 194,000 km 2, average depth 1715 m, maximum 5120 m.
* Gulf of California - area 177,000 km 2, average depth 818 m, maximum depth 3292 m.

* - according to the hydrological regime, these marine areas are classified as seas, but nevertheless the name “Gulf” has been assigned to them.

The largest islands in the oceans:

Greenland - area 2,175,600 km2.
New Guinea - an area of 790,000 km 2.
Kalimantan (Borneo) - area 737,500 km 2.
Madagascar - area 587,041 km 2.
Baffin Island - area 507,451 km2.
Sumatra - an area of 425,000 km 2.
Great Britain - area 229,946 km 2.
Honshu - an area of 227,414 km 2.
Victoria - area 217,291 km 2.
Ellesmere - area 196,236 km2.

Map of the Earth's oceans and their location in the World Ocean

Distribution map of bottom sediments of the World Ocean

Waters of the World Ocean not evenly distributed over the earth's surface. So the northern hemisphere accounts for 61% of the surface of the globe, the southern hemisphere - 81%. Most of the ocean floor area (73.8%) is located at depths of 3,000 to 6,000 meters below sea level. The bottom of the World Ocean is the most leveled parts of the surface of the earth's crust, covered with water between the continents and islands. The relief of the bottom of the World Ocean in its structure is as diverse as the relief of the areas of the earth's surface located above the level of the ocean waters and has all the same relief elements. Grandiose geological formations are located at the bottom of the World Ocean, surpassing similar formations on the surface of the continents in scale. Thus, the largest mountain system on Earth, the longest underwater mountain range, the Mid-Atlantic Ridge, runs along the center of the bottom of the Atlantic Ocean. The Mid-Atlantic Ridge is larger than all known mountain systems on Earth. The Mid-Atlantic Ridge stretches over 18,000 kilometers from the borders of the Arctic Ocean to the coast of Antarctica. The Mid-Atlantic Ridge, in turn, is part of the system of mid-ocean ridges on the bottom of the World Ocean. Also at the bottom are the largest plains, basins, mountain peaks, depressions and gutters. The bottom of the World Ocean is subdivided in its structure into several parts - continental slopes, shelf areas, ocean beds, deep-sea trenches, mid-ocean ridges, submarine basins, oceanic plains and plateaus, seamounts and volcanoes. Along the bottom of the oceans are the boundaries of the contact of the tectonic plates of the earth's crust. In places where tectonic plates interact, underwater mountain ranges or deep-sea trenches arise. On the boundaries of tectonic plates, the highest volcanic and seismic activity. In places of active volcanic activity, underwater eruptions occur, leading to the formation of underwater volcanoes, which sometimes, as a result of ejection and accumulation of large volumes of volcanic rocks, eventually rise above ocean level, thereby forming volcanic islands. A striking example of such islands is the Hawaiian Islands located in the Pacific Ocean. The Hawaiian Islands are characterized by high volcanic activity. Also, as a result of the interaction of tectonic plates, strong underwater earthquakes occur, which in turn are the initiators of destructive, giant ocean waves - tsunamis.

Ocean water is a cocktail of salt solutions with an average concentration of about 35 G/l. Almost all the elements of the periodic table are found in sea water. In total, the waters of the oceans contain 5 10 22 G dissolved salts. Their composition is dominated by Na + , Mg 2+ , K + , Ca 2+ , Cl - ions, which make up 99% of the total salts. Many other elements are found in parts per million and parts per billion. The salinity of sea water in the ocean is on average about the same everywhere. The salinity of the water of the World Ocean in one place or another depends on the distance from the continents and islands, from the rivers flowing into the ocean, from the depth where the salinity is measured, the deeper, the more saturated the water is with dissolved salts.

The oceans are the richest depository of mineral resources. All mineral resources of the ocean are divided into chemical elements dissolved in sea water, mineral deposits on the surface and under the surface of the seabed. Until the 70s. In the 20th century, mainly significant amounts of table salt (about 8 million tons per year), sodium sulfate, magnesium chloride, potassium chloride, and bromine were extracted from sea water. With the development of scientific and technological progress, the list of extractable chemical elements is constantly increasing. More than 90% of the total cost of minerals obtained from the world's oceans come from oil and gas. The total oil and gas bearing area within the shelf is estimated at 13 million hectares. km 2 (about 1/2 of its area). According to tentative estimates, geological oil reserves (up to a depth of 305 m) are defined as 280 billion. t, gas in 140 trillion m 3 " , their potential reserves in terms of oil are estimated at 1410 billion tons. t. Until the beginning of the 70s. oil and gas production was limited to a depth of 100-110 m and a distance from the coast of about 150 km, with the development of technology, the extraction of mineral resources is moving to ever greater depths. In addition to obtaining mineral resources, the oceans are used to generate electricity, they build tidal power plants that use the power of the tides, as well as to obtain energy due to the difference in water temperature at different depths.

When considering the hydrological regime of the World Ocean, factors are taken into account: Heat balance, water balance, temperature, salinity, water circulation, waves, tides, mixing, level, ice, color and transparency of water, zonality. The surface level of the oceans is constantly fluctuating. From time to time there is a decrease or increase in the oceans. The decrease or increase in the level of the World Ocean mainly depends on the climatic conditions on Earth. So, during the period of the most severe cooling, during the so-called ice age, the general level in the ocean decreases due to freezing of water and accumulation in the form of extensive ice coverings on land, at such moments the previously flooded land areas are released. And vice versa, with warming, ice melts, at such times the level of the World Ocean rises, which causes flooding of the lowest coastal parts of the land. The waters of the World Ocean are in constant motion in all its parts. The movement of the oceans is due to its currents. Currents by their nature are divided into two main groups - cold currents and warm ones. Cold currents are predominantly deep, warm currents of the World Ocean are surface. The currents are of global importance for the formation of the climate of the World Ocean, as well as the climate throughout the Earth. The climate of the World Ocean throughout its area is diverse and depends on which part of the globe the ocean area is considered. In the equatorial part of the World Ocean, the climate is the warmest; closer to the poles of the planet, the climate becomes colder and more severe. The water temperature of the World Ocean also varies throughout its length. The temperature of the water on the surface of the ocean depends on the climatic conditions in which the area is located. In the polar regions, the temperature in the surface layers can drop significantly below zero degrees Celsius, which leads to the formation of extensive ice sheets. So the polar region of the Arctic Ocean in the region of the northern geographic pole of the Earth is under ice all year round. The water temperature also changes with depth. As the depth increases, the water temperature drops significantly. The surface layers are the warmest.

Flora and fauna of the oceans play an important role in the state of the ocean, in its chemical, biological, geological processes. Flora and fauna are actively involved in the circulation of substances in the ocean water column. Life in the water column of the World Ocean is found in all its sections at all depths. The greatest amount of vegetation and living beings is found at depths of up to 200 meters. In its diversity and richness, the flora and fauna of the deep sea far exceeds the flora and fauna that inhabit the land of the planet. Until now, when studying marine life, scientists are discovering new types of plants and living creatures. The biomass of the oceans also exceeds the biomass of land. The biological resources of the World Ocean are of great importance in the life of the planet's population. The biological resources of the ocean are significant, but not unlimited. Every year, due to the increase in the population of the planet, the need for biological resources of the oceans is increasing more and more. Uncontrolled, growing every year, the volume of catching fish and other marine organisms leads to the rapid depletion of the bioresources of the oceans.

For a more detailed description of the structure, biology, chemical composition and properties, physical properties, the definition of the "World Ocean" as part of the Earth's hydrosphere, see the article "Ocean" .

In the modern world, the economic role of the oceans is increasing more and more. The oceans are a major supplier of mineral and biological resources, as well as an important transport medium. Many countries have access to the oceans. For countries with access to the World Ocean, the use of both ocean resources and the use of the expanses of the World Ocean as a transport medium is of vital paramount importance. Every year, hundreds of millions of tons of cargo for various purposes are transported along sea routes, and passenger traffic is also growing along with cargo transportation. Telecommunication cables and pipelines are laid along the bottom of the oceans and seas for transporting gas and oil. Increasing activity in the use of the expanses and resources of the World Ocean inevitably leads to global environmental problems, primarily related to pollution of the expanses of the World Ocean. Recently, an increasing role has been assigned to the environmental safety of the oceans.

Ocean exploration is of paramount importance in people's lives. Research is necessary for knowledge of the physical laws by which the World Ocean exists. Knowledge of these laws will allow not only the rational use of all the resources of the World Ocean, but also to preserve the ocean in its original form with all its diversity of flora and fauna. Researches constantly brought every year reveal more and more mysteries of the World Ocean. All the secrets of the oceans have not yet been revealed. There are more white spots in the study of the expanses of the World Ocean than on the surface of the Earth. It is not for nothing that they say that people throughout their history have learned much more about the Moon and the entire solar system than about the ocean next to which they live. Many misunderstood and unsolved mysteries of the World Ocean give rise to many legends and legends.

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