The surface of the oceans and seas covers about 70% of the surface of our planet. This is a whole world about which we know even less than about the world called land. We will touch on it with only a few words, because, having said the word "water", it is simply impossible not to say the word "sea".

Sea water is very complex in composition and contains almost all the elements of D.I. Mendeleev. For example, there are about three billion tons of gold alone in it, that is, as much by weight as all the fish in the seas and oceans. However, it is a very stable environment. In the open parts of the Ocean, sea water contains on average 35 g / kg of salts, in the Mediterranean - 38 g / kg, in the Baltic - 7 g / kg, in the Dead Sea - 278 g / kg. Salts in sea water are mainly in the form of compounds, the main of which are chlorides (88% of the weight of all dissolved solids), followed by sulfates (10.8%) and carbonates (0.3%), the rest (0.2%) include compounds of silicon, nitrogen, phosphorus, and organic substances.

The salty taste of water depends on the content of sodium chloride in it, otherwise table salt, the bitter taste is formed by magnesium chloride, sodium and magnesium sulfates. The slightly alkaline reaction of sea water, the pH of which is 8.38-8.40, depends on the predominant amount of alkaline elements: sodium, calcium, magnesium, potassium.

In its composition, sea water is very similar to the salt composition of human blood. During the Great Patriotic War, when there was a shortage of donor blood, Soviet doctors administered sea water intravenously as a blood substitute.

The ocean is the accumulator of life on our planet. The main feature of the ocean, if we consider it as a living space, is that the water column is inhabited in all three dimensions from the surface to the bottom sediments. The basis of life in the ocean is plankton.

R The distribution of salinity in the oceans depends mainly on climatic conditions, although salinity is partly influenced by several other factors, especially the nature and direction of currents. Outside the direct influence of land, the salinity of surface waters in the oceans ranges from 32 to 37.9 ppm.

The distribution of salinity over the surface of the ocean, outside the direct influence of runoff from land, is determined primarily by the balance of fresh water inflow and outflow. If the inflow of fresh water (precipitation + condensation) is greater than its outflow (evaporation), i.e., the inflow-output balance of fresh water is positive, the salinity of surface waters will be below normal (35 ppm). If the inflow of fresh water is less than the flow, i.e., the income-expenditure balance is negative, the salinity will be higher than 35 ppm.

A decrease in salinity is observed near the equator, in a calm zone. Salinity here is 34-35 ppm, since here a large number of atmospheric precipitation exceeds evaporation.

To the north and south of here, salinity first rises. The region of greatest salinity is found in the trade winds (between approximately 20 and 30° north and south latitude). We see on the map that these bands are especially pronounced in the Pacific Ocean. In the Atlantic Ocean, salinity is generally greater than in other oceans, and the maxima are located just at the tropics of Cancer and Capricorn. In the Indian Ocean, the maximum is at about 35°S. sh.

To the north and south of its maximum, salinity decreases, and in the middle latitudes of the temperate zone it is below normal; it is even less in the Arctic Ocean. The same decrease in salinity is seen in the southern circumpolar basin; there it reaches 32 ppm and even lower.

This uneven distribution of salinity depends on the distribution of barometric pressure, winds and precipitation. In the equatorial zone, the winds are not strong, evaporation is not great (although it is hot, the sky is covered with clouds); the air is humid, contains a lot of vapor, and there is a lot of precipitation. Due to the relatively small evaporation and dilution of salt water with precipitation, salinity becomes somewhat lower than normal. To the north and south of the equator, up to 30 ° N. sh. and yu. sh., - an area of ​​\u200b\u200bhigh barometric pressure, the air pulls towards the equator: the trade winds blow (constant northeast and southeast winds).

The descending currents of air, characteristic of areas of high pressure, descending to the surface of the ocean, heat up and move away from the state of saturation; cloudiness is small, there is little precipitation, fresh winds contribute to evaporation. Due to the large evaporation, the balance of fresh water inflow and outflow is negative, salinity is higher than normal.

Farther to the north and south, rather strong winds blow, mainly from the southwest and northwest. The humidity here is much higher, the sky is covered with clouds, there is a lot of precipitation, the balance of fresh water inflow and outflow is positive, the salinity is less than 35 ppm. In the circumpolar regions, the melting of the ice that is carried out also increases the supply of fresh water.

The decrease in salinity in the polar countries is explained by the low temperature in these areas, insignificant evaporation, and large clouds. In addition, vast expanses of land with large full-flowing rivers adjoin the northern polar seas; a large influx of fresh water greatly reduces salinity.

.The concept of water balance. World water balance.

Quantitatively, the water cycle is characterized by water balance. All components of the balance water can be divided into two parts: incoming and outgoing. In general, for the globe, the incoming part of the water balance is only atmospheric precipitation. The influx of water vapor from the deep layers of the earth and their condensation play an insignificant role. The expenditure part for the globe as a whole consists only of evaporation.

Every year, 577 thousand km3 of water evaporates from the surface of the globe.

During the year, only 0.037% of the total mass of the hydrosphere takes part in the World moisture cycle. Since the rate of transfer of individual types of water is not the same, the time of their consumption and renewal is also different (Table 2). The most rapidly renewed biological waters that are part of plants and living organisms. The change of atmospheric moisture and water reserves in the riverbeds is carried out in a few days. Water reserves in lakes are renewed within 17 years, in large lakes this process can last several hundred years. Thus, in Lake Baikal, the complete renewal of water reserves occurs within 380 years. The longest recovery period is for water reserves in the ground ice of the permafrost zone - 10,000 years. Complete renewal of ocean waters occurs after 2500 years. However, due to internal water exchange (sea currents), the waters of the World Ocean, on average, make a complete revolution within 63 years.

5. Thermal and ice regime of oceans and seas.

Self high temp. on the surface of the Red Sea + 32C. On the surface.

In black.m (in summer - + 26С, in winter - ice forms)

In the Azov m. (in summer - + 24С, in winter - 0С)

In the Baltic.m. (in summer - + 17С)

In the Baltic Sea (+10-+12C in summer, freezes in winter)

In Bel.m. (in summer - + 14C, in winter it freezes)

The temperature of the layers can be affected by the internal temperature of the earth (+72C)

The main source of heat received by the Mir.ok. surface is total solar radiation. Its share in the equatorial-tropical latitudes is 90%. The main expense item is the heat consumption for evaporation, which reaches 80% in the same latitudes. ADDITIONAL SOURCE of redistribution of heat - river waters, continents, prevailing winds, sea currents.

Water is the most heat-intensive body, and World.ok. makes up 71% of the surface of the globe, acts as a battery and acts as a temperature regulator of the planet. Average water surface temperature = +17.4 3 more than average annual air temperature.

Due to the low thermal conductivity of water, heat is poorly transferred to depth. Therefore, in general, the world. OK. is a cold sphere and has a medium temp. about +4.

In the distribution of the temperature of the surface waters of the Ocean, zoning is observed (it decreases from the equator to the pole).

In tropical and especially temperate latitudes, the zonal pattern of water temperature is disturbed by currents, which leads to regionality (provinciality)

In tropical zones in the west of the oceans, water is 5-7C due to warm currents warmer than in the east, where there are cold currents.

In the temperate latitudes of the southern hemisphere, where the sea expanses dominate, the water temperature gradually decreases towards the poles. In the northern hemisphere, this pattern is violated by currents.

In all oceans, except for high latitudes, 2 main layers are distinguished vertically: warm surface and powerful cold, extending to the bottom. Between them lies the transition layer of the temperature jump, or the main thermocline, within which the temp. It drops sharply by 10-12C. The equalization of temperatures in the surface layer is facilitated by convection due to seasonal changes in the temperature of the active surface and salinity, as well as waves and currents.

In polar and subpolar latitudes, the distribution of temp. The vertical is different: on top is a thin cold desalinated layer, formed due to the melting of continental and river ice. Further, the temperature rises by 2C as a result of the influx of cold and dense tributaries.

Brackish water, like fresh water, freezes when it reaches its freezing point, and salty water freezes at its highest density temperature.

Freezing of the polar seas is prevented by wind waves, and rivers and rains contribute to reducing the salinity of the water, as well as snow and icebergs, which not only desalinate the water, but also lower its rate. And relieve anxiety.

SEA WATER BEGINS TO FREEZE at -2C.

ICE IN THE OCEAN are seasonal and exist for more than one year. The process of ice formation goes through several stages.

The initial form is (needle-crystals), after the spot-discs (ice fat), snow (a mushy mass of snow soaked in water) and sludge (accumulation of ice in the form of stripes) simultaneously appear. At the same time, ice banks (bands of ice frozen to land) form off the coast in shallow waters .. after that they turn into fast ice, with a further decrease in temp. Ice disks (pancake ice) are formed. In calm weather, a continuous thin ice crust is formed (in desalinated water - a bottle, and in salty - nalasom). Young ice up to 10 cm thick is called young ice. As it thickens, it becomes adult ice.

In the Arctic and Antarctica, in addition to seasonal ice, there are annual ice (up to 1 m thick), biennial (up to 2 m thick), and perennial ice (a polar pack that has existed for more than 2 years, 5-7 m thick, blue).

Ice classification.

By origin, ice in the OCEAN is divided into sea (slightly saline, occupy the bulk of the ice area in the world app.), River (distributed only in the northern hemisphere.) And continental (also fresh).

By mobility, ice in the seas is divided into fixed (the main form is fast ice, several tens and even hundreds of kilometers wide. Such ice also includes stamukha ice that has come to the bottom in shallow waters) and drifting (moving under the influence of wind and current. icebergs or ice mountains, ice islands).

The destruction of ice occurs under the influence of solar radiation and warm air masses.

6. Dynamics of the waters of the World Ocean. Waves. Ocean water levels. Ebb and flow. Seaquakes and tsunamis.

Dynamics of the waters of the World Ocean

The waters of the oceans are never at rest. Movements occur not only in the surface water masses, but also in the depths, down to the bottom layers. Water particles perform both oscillatory and translational movements, usually combined, but with a noticeable predominance of one of them.

Wave movements (or excitement) are predominantly oscillatory movements. They represent oscillations of the water surface up and down from the average level; in the horizontal direction, the water masses do not move during waves. This can be seen by observing the float swaying on the waves.

Waves are characterized by the following elements:

The bottom of the wave is its lowest part;

The crest of a wave is its highest part;

The steepness of the slope of the wave - the angle between its slope and the horizontal surface;

Wave height - the vertical distance between the bottom and the crest. It can reach 14-25 meters;

Wavelength is the distance between two soles or two crests. The greatest length reaches 250 m, but waves up to 500 m are rare;

The speed of a wave is the distance traveled by the crest in one second. Wave speed characterizes the speed of its advancement.

By origin, the following types of waves are distinguished: friction waves (wind and deep), anemobaric, seismic, seiches, tidal waves.

The main reason for the formation of waves is the wind. At low speeds, ripples appear - a system of small uniform waves. They appear with every gust of wind and fade instantly. The crests of the wind waves are thrown back in the direction where the wind blows; when the wind subsides, the surface of the water continues to oscillate due to inertia - this is a swell. A large swell with a small steepness and a wavelength of up to 400 m in the absence of wind is called a wind swell. With a very strong wind turning into a storm, the leeward slope turns out to be steeper than the windward one, and with a very strong wind, the ridges break down and form white foam - “lambs”.

The excitement caused by the wind fades with depth. Deeper than 200 m, even strong excitement is imperceptible. When approaching a gently sloping coast, the lower part of the oncoming wave slows down on the ground; length decreases and height increases. The upper part of the wave moves faster than the lower part, the wave overturns, and its crest, falling, crumbles into small, air-saturated, foamy splashes. Waves breaking near the shore form surf. It is always parallel to the shore. The water splashed by the wave on the shore slowly flows back. When approaching a steep shore, the wave hits the rocks with all its might. The impact force sometimes reaches 30 tons per 1 m2. In this case, the main role is played not by the mechanical impacts of water masses on the rocks, but by the resulting water bubbles. They also destroy the rocks that make up the rocks (see "Coastal zone"). Breakwaters are built to protect port facilities, offshore berths, shores of stone or concrete blocks from waves.

The shape of the wave changes all the time, giving the impression of running. This is due to the fact that each water particle describes circles around the equilibrium level with uniform motion. All these particles move in the same direction. At each moment, the particles are at different points of the circle, this is the system of waves.

The largest wind waves are observed in the Southern Hemisphere, since most of it is occupied by the ocean and westerly winds are the most constant and strong. Here the waves can reach 25 meters in height and 400 meters in length. Their speed of movement is about 20 m / s. In the seas, the waves are smaller: for example, in the large Mediterranean Sea, they reach only 5 m.

The 9-point Beaufort scale is used to assess the degree of sea roughness.

As a result of underwater earthquakes and volcanoes, seismic waves arise - tsunamis (Japanese). These are gigantic waves with destructive power. Underwater earthquakes or volcanic eruptions are usually accompanied by a strong tremor transmitted by water to the surface, which is not safe for ships in the area. The subsequent waves caused by the impact are almost impossible to notice in the open sea, since they are gentle here. Approaching the shore, they become steeper and higher, acquiring terrible destructive power. As a result, giant waves can crash on the coast; their height is up to 50 m and more, and the propagation speed is from 50 to 1000 km/h.

Most often, tsunamis hit the Pacific coast, which is associated with high seismic activity in this area. Over the past millennium, the Pacific coast has been hit by tsunamis about 1,000 times, while in other oceans (except the Arctic), these giant waves have occurred only dozens of times.

Usually, before the arrival of a tsunami, within a few minutes, the water recedes from the coast by several meters, and sometimes by kilometers; the further the water recedes, the greater the height of the tsunami should be expected. There is a special warning service that warns residents of the coast in advance of possible danger. Thanks to her, the number of victims is decreasing.

The damage caused by a tsunami is many times greater than the consequences caused by the earthquake itself or a volcanic eruption. Great damage was caused by the Kuril tsunami (1952), Chile (1960), Alaska (1964).

Tsunamis can spread over very long distances. For example, the shores of Japan were significantly damaged by the waves that arose during the earthquake in Chile, and the tsunami caused by the eruption of the Krakatoa volcano in Indonesia (1912) bypassed the entire World Ocean and was recorded in Le Havre (France) 32 hours 35 minutes after the last explosion , covering a distance equal to half the circumference of the globe. The damage caused by this giant wave is even difficult to assess: the shores of all nearby islands were flooded, not only the inhabitants, but also all the soil, were washed away from them, in the port of about. Java large ships were torn off the anchors, and they were thrown 9 meters high, 3 km inland; buildings were actually wiped off the face of the Earth.

The tsunami is associated not only with severe destruction, but also with significant loss of life. The tsunami caused by the eruption of the Krakatau volcano in 1883 claimed the lives of 40,000 people, and during the tsunami in 1703 in Japan, about 100,000 people died.

Under the influence of the force of attraction of the Moon and the Sun, periodic fluctuations in the level of the ocean occur - tidal movements of ocean waters. These movements occur approximately twice a day. At high tide, the ocean level gradually rises and reaches its highest position. At low tide, the level gradually drops to the lowest. At high tide, water flows towards the shores; at low tide, it flows away from the shores. Ebb and flow are standing waves.

According to the laws of interaction of cosmic bodies, the Earth and the Moon attract each other. This attraction contributes to the “bending” of the surface of the oceans towards the lunar attraction. The moon moves around the Earth, and a tidal wave “runs” across the ocean behind it, it will reach the shore - the tide. A little time will pass, the water, following the Moon, will move away from the shore - ebb. According to the same cosmic laws, ebbs and flows are also formed from the attraction of the Sun. It pulls the Earth much more strongly than the Moon, but the Moon is much closer to the Earth, so the lunar tides are twice as strong as the sun's. If there were no Moon, then the tides on Earth would be 2.17 times less. The explanation of tide-forming forces was first given by I. Newton.

The highest level of water at high tide is called high water, the lowest level at low tide is called low water. The most common are semidiurnal tides, in which there are 2 full and 2 low waters per lunar day (24 hours 50 minutes). Depending on the position of the Moon relative to the Earth and on the configuration of the coastline, there are deviations from this regular alternation. Sometimes there is 1 full and 1 low water per day. Such a phenomenon can be observed on island arcs and coasts of East Asia and Central America.

The height of the tides is varied. Theoretically, one high water at lunar tide is 0.53 m and 0.24 m at solar tide. Thus, the highest tide should have a height of 0.77 m. In the open ocean and near the islands, the tide is close to theoretical: in the Hawaiian Islands - 1 m; on the Fiji Islands - 1.7 m, on the island of St. Helena - 1.1 m. At the mainlands, at the entrance to narrowing bays, the tide is much larger: in the Mezen Bay of the White Sea - 10 m; in Bristol Bay in England - 12m.

The largest recorded in the oceans are the following tides:

in the Atlantic Ocean in the Bay of Fundy - 16-17 m. This is the largest tide on the entire globe.

in the Sea of ​​Okhotsk in the Penzhina Bay - 12-14 m. This is the largest tide off the coast of Russia.

The significance of the tides is enormous: each tidal wave carries a huge supply of energy, and tidal power plants are now being built in a number of countries. In addition, the importance of the tides is great for maritime navigation.

The forward movement of water masses in the oceans and seas, caused by various forces, is called sea or ocean currents. These are "rivers in the ocean". They move at speeds up to 9 km / h. The causes of currents are the heating and cooling of the water surface, precipitation and evaporation, differences in water density, but the most significant cause of ocean currents is the wind.

Currents in the direction prevailing in them are divided into zonal (currents of westerly winds), going to the west, to the east, and meridional - carrying their waters to the north or south (Gulf Stream). In separate groups, countercurrents and monsoon currents can be distinguished. Countercurrents are currents that go towards neighboring, more powerful and extended ones. Currents that change their strength from season to season depending on the direction of coastal winds are called monsoons.

The most powerful in the oceans is the current of the Western winds. It is located in the Southern Hemisphere at latitudes off the coast of Antarctica, where there are no significant land masses. Strong and stable westerly winds prevail over this space, contributing to the intensive transfer of ocean water in an easterly direction. The course of the Western winds connects the waters of the three oceans in its circular flow and carries up to 200 million tons of water every second. The width of the current of the Western winds is 1300 km, but its speed is low: to bypass Antarctica once, the waters of the current need 16 years.

Another powerful current is the Gulf Stream. It carries 75 million tons every second, which is 3 times less than the current of the Western winds. The role of the Gulf Stream is very great: it carries the tropical waters of the Atlantic Ocean to temperate latitudes, thanks to which the climate of Europe is mild and warm. Approaching Europe, the Gulf Stream is no longer the same stream that breaks out of the Gulf of Mexico, so the northern continuation of this current is called the North Atlantic Current.

Ocean currents differ not only in directions, but also, depending on temperature, are divided into warm, cold and neutral. Currents moving away from the equator are warm, while those moving towards the equator are cold. They are usually less saline than warm, as they flow from areas where there is a lot of precipitation, or from areas where ice melt has a desalinating effect. The cold currents of tropical latitudes are formed due to the rise of cold deep waters. Examples of warm currents are the Gulf Stream, Kuroshio, North Atlantic, North Pacific, North trade winds, South trade winds, Brazil, etc. Examples of cold currents are the West Winds (or Antarctic), Peru, California, Canary, Bengal and others.

The direction of ocean currents is greatly influenced by the Coriolis acceleration, and the direction of the wind does not coincide with the direction of the currents. The current deviates to the right in the Northern Hemisphere and to the left in the Southern Hemisphere from the direction of the wind by an angle of up to 45°.

Numerous measurements have shown that currents end at a depth not exceeding 300 m, but sometimes currents are found in deep layers. The reason for this is the different density of water. It can be caused by the pressure of a mass of water from above (for example, in places of a surge or its wind sweep), changes in water temperature and salinity. Density changes are the cause of constant vertical movements of water: lowering cold (or more salty) and rising warm (less salty).

In addition to wind currents, tidal currents are also widespread, changing direction 4 or 2 times a day; in narrow straits, the speed of these currents can reach 6 m/s (22 km/h).

The significance of ocean currents lies primarily in the redistribution of solar heat on Earth: warm currents contribute to an increase in temperature, while cold ones lower it. Currents have a huge impact on the distribution of precipitation on land. Territories washed by warm waters always have a humid climate, and cold - dry; in last case rains do not fall, only mists have a moisturizing effect. Living organisms are carried along with currents. This primarily applies to plankton, followed by large animals. When warm currents meet cold currents, ascending currents of water are formed, which raise deep water rich in nutrient salts. It favors the development of plankton, fish and marine animals, so these places are important fishing grounds.

So, the currents in the ocean are caused by the wind (wind ocean currents); arise due to different heights of the water level (runoff currents) and its different density (density currents). In all cases, the direction of the current is affected by the rotation of the Earth. Wind ocean currents can be classified by direction and temperature.

7. Zoning of the waters of the World Ocean (latitudinal zonality).

Latitudinal zonality is a regular change in physical and geographical processes, components and complexes of geosystems from the equator to the poles.

The primary reason for zoning is the uneven distribution of solar energy over latitude due to the spherical shape of the Earth and the change in the angle of incidence of the sun's rays on the earth's surface. In addition, latitudinal zonality also depends on the distance to the Sun, and the mass of the Earth affects the ability to hold the atmosphere, which serves as a transformer and redistributor of energy.

Of great importance is the inclination of the axis to the plane of the ecliptic, this determines the irregularity of the supply of solar heat by season, and the daily rotation of the planet causes the deviation of air masses. The result of the difference in the distribution of the radiant energy of the Sun is the zonal radiation balance of the earth's surface. Uneven heat input affects the location of air masses, moisture circulation and atmospheric circulation.

Zoning is expressed not only in the average annual amount of heat and moisture, but also in intra-annual changes. Climatic zoning is reflected in the runoff and hydrological regime, the formation of a weathering crust, and waterlogging. A great influence is exerted on the organic world, specific landforms. Homogeneous composition and high air mobility smooth out zonal differences with height.

In each hemisphere, 7 circulation zones are distinguished.

8. CURRENTS and macrocirculation of the World Ocean. Global Ocean Conveyor.

There are 11 major circulations (systems)

5 tropical

1. Sev-atlant

2. North Pacific

3. south atlan.

4.south pacific

5.south indian

6.equatorial-counterflow

7.atlantic and icelandic

8. Pacific Ocean (Aleudian)

9.Indian-monsoon system

10. polar (antarctic)

11.arctic

Ocean, or sea, currents are the forward movement of water masses in the oceans and seas, caused by various forces. Although the most significant cause of the currents is the wind, they can also form due to the unequal salinity of individual parts of the ocean or sea, the difference in water levels, and the uneven heating of different parts of the water areas. In the ocean there are eddies created by uneven bottoms, their size often reaches 100-300 km in diameter, they capture layers of water hundreds of meters thick.

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

Monsoon currents change their direction from season to season, depending on how the coastal monsoon winds blow. Countercurrents are moving towards the neighboring, more powerful and extended currents in the ocean.

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

In the World Ocean, there are constantly thousands of large and small currents that go around the continents and merge into five giant rings. The system of currents of the World Ocean is called circulation and is connected, first of all, with the general circulation of the atmosphere.

Ocean currents redistribute solar heat absorbed by masses of water. Warm water, heated by the sun's rays at the equator, they carry to high latitudes, and cold water from the polar regions, due to currents, gets to the south. Warm currents increase air temperature, while cold currents, on the contrary, decrease it. Territories washed by warm currents are characterized by a warm and humid climate, and those near which cold currents pass are cold and dry.

The most powerful current of the World Ocean is the cold current of the West Winds, also called the Antarctic circumpolar (from lat. cirkum - around). The reason for its formation are strong and stable westerly winds blowing from west to east over vast expanses of the Southern Hemisphere from temperate latitudes to the coast of Antarctica. This current covers a zone with a width of 2500 km, extends to a depth of more than 1 km and carries up to 200 million tons of water every second. There are no large land masses on the path of the Western Winds, and it connects in its circular flow the waters of three oceans - the Pacific, Atlantic and Indian.

The Gulf Stream is one of the largest warm currents in the Northern Hemisphere. It passes through the Gulf of Mexico (eng. Gulf Stream - the Gulf) and carries the warm tropical waters of the Atlantic Ocean to high latitudes. This giant stream of warm water largely determines the climate of Europe, making it soft and warm. Every second, the Gulf Stream carries 75 million tons of water (for comparison: the Amazon, the most full-flowing river in the world, is 220 thousand tons of water). At a depth of about 1 km under the Gulf Stream, a countercurrent is observed.

General scheme of circulation of surface waters of the Ocean

Consistent zonal change of macrocirculation systems (large-scale movement system) is a general pattern of planetary water circulation.

In accordance with the zonal distribution of solar energy over the surface of the planet, the same type and genetically related circulation systems are created both in the ocean and in the atmosphere. The movement of water and air masses is determined by a pattern common to the atmosphere and hydrosphere: uneven heating and cooling of the Earth's surface. From this, macrocirculatory systems are more or less symmetrically located on both sides of the equator.

From it, in low latitudes, ascending currents (cyclonic eddies) and a decrease in masses arise, in other high latitudes, descending currents develop, an increase in masses (water, air) occurs, which is typical for anticyclonic vortex systems. The interaction of these systems is the circulation, the movement of the atmosphere and hydrosphere.

In tropical areas, the nature of the movements is anticyclonic, that is, the currents move clockwise, and in temperate and subpolar latitudes, the currents form a circulation directed counterclockwise, that is, they have a cyclonic character. Both cyclonic and anticyclonic eddies in the ocean correspond to climatic minima and atmospheric pressure maxima.

Anticyclonic and cyclonic gyres in each hemisphere are interconnected in such a way that the same flows (currents) are simultaneously the peripheral part of two gyres. For example, the North Atlantic Current is the northern branch of the tropical circulation and, at the same time, the southern branch of the cyclonic circulation of temperate and subpolar latitudes. Due to this, the cycles interact with each other. Therefore, water and the various substances they carry (salts, suspensions, etc.) are capable of moving from system to system throughout the entire length of the ocean. The transfer of masses, the exchange of energy and matter in the near-surface layer of the ocean occurs mainly in the latitudinal direction. Interlatitudinal exchange is carried out due to meridional exchange at the periphery of quasi-stationary water cycles. In low latitudes along the western coasts of the ocean, light tropical waters are carried out into the temperate zone. In temperate and subpolar latitudes, on the contrary, denser waters are transported along the western coasts, and less dense waters of the temperate and tropical zones are carried along the eastern coasts to the high latitudes of the World Ocean. The difference in water densities created in this way in the meridional direction increases the intensity of boundary currents in the coastal parts of anticyclonic and cyclonic systems.

The same macrocirculatory systems persist throughout the year. The seasonal variability of water circulation is characterized by a slight shift in the meridional direction in the cold season (in the winter of the northern hemisphere - to the north, in the summer of the northern hemisphere - to the south), as well as an increase in the intensity of circulation as a result of an increase in thermal contrasts between tropical and polar latitudes.

It has been established that the direct impact of the wind is limited to the upper layer with a thickness of about 30-50 m. Already in the subsurface layer between 50-100 and 200-300 m, the density (vertical) circulation plays a decisive role.

In the ocean, the speed of vertical motions is less than horizontal motions by about three to five orders of magnitude, and in the atmosphere, by about two to three orders of magnitude. But their significance is great, because thanks to them, the exchange of surface and deep waters with energy, salts and nutrients takes place.

The most intensive vertical exchange takes place in the zones of convergence (convergence) and divergence (divergence) of water mass flows. In convergence zones, there is a sinking of water masses, in divergence zones - their rise to the surface, called upwelling. Divergence zones are formed in the areas of cyclonic gyres, where centrifugal forces carry water from the periphery to the center and water rises in the central part of the gyre. Divergence occurs near the coast and where the wind from the land prevails (surface water surge). In anticyclone systems and in those coastal zones where the wind from the ocean dominates, water sinks.

The distribution of convergence and divergence zones is the same in different oceans. Slightly north of the equator is the equatorial convergence. On both sides of it, tropical divergences stretch along the troughs of tropical cyclonic systems, then subtropical convergences stretch along the axes of subtropical anticyclonic systems. High-latitude cyclonic systems correspond to polar divergences; the crest of the Arctic water cycle corresponds to Arctic convergence.

This is an ideal (averaged) scheme of surface ocean currents. The real, concrete situation is much more complicated, since the currents change speed, intensity, and sometimes direction. Some of them disappear from time to time. Ocean currents have a complex structure. Like rivers, they meander, forming smaller eddies (300-400 km in diameter).

The structure of surface ocean currents, which capture the upper hundreds of meters, basically coincides with the structure of atmospheric circulation. The exception is the westerly currents that close the gyres and do not necessarily go with the wind, plus intertrade countercurrents. Consequently, in nature there is a more complex than simple connection between wind and ocean currents. Real countercurrents. The total amount of solar energy absorbed by the World Ocean is determined to be 29.7∙1019 kcal/year, which is almost 80% of all radiation reaching the surface of the planet (36.5∙1019 kcal). In addition, the Ocean is the main accumulator of solar heat; it contains almost 21 times more than the amount of heat (76∙1022 kcal) that annually comes from the Sun to the Earth's surface. In a ten-meter layer of oceanic waters, there is 4 times more heat than in the entire atmosphere.

About 80% of the solar energy absorbed by the World Ocean is spent on evaporation - 26.8∙1019 kcal/year, which is only 3% of the heat accumulated by the World Ocean. Turbulent heat exchange with the atmosphere takes the rest of the absorbed solar radiation - 2.7∙1019 kcal/year. This is only 0.4% of the total heat content of the Ocean. Comparing the amount of incoming and outgoing amounts of heat exchange through the surface of the World Ocean with its heat content, we come to the conclusion that annually a surface layer about 50 m thick is involved in such an exchange with the atmosphere. Heat exchange of the most active 200-meter water column occurs in 3-4 years. That is, the distribution of energy largely depends on the structure of ocean currents (the Gulf Stream carries 22 times more heat than all the rivers of the globe).

Atmospheric movements are forced to adapt to the structure of oceanic movements, therefore oceanic and air currents form a single system that arises as a result of their adaptation to each other.

9. Water masses and hydrological fronts.

Water masses - These are large volumes of water that form in certain parts of the ocean and differ from each other in temperature, salinity, density, transparency, amount of oxygen and other properties. Unlike air masses, they great importance has vertical zonality. Depending on the depth, there are:

Surface water masses. They are formed under the influence of atmospheric processes and the influx of fresh water from the mainland to a depth of 200-250 m. Water temperature and salinity often change here, waves form, and their horizontal transport in the form of ocean currents is much stronger than the deep one. Surface waters have the highest content of plankton and fish;

Intermediate water masses. They have a lower limit within 500-1000 m. In tropical latitudes, intermediate water masses are formed under conditions of increased evaporation and a constant increase in salinity. This explains the fact that intermediate waters occur between 20° and 60° in the northern and southern hemispheres;

Deep water masses. They are formed as a result of mixing of surface and intermediate, polar and tropical water masses. Their lower limit is 1200-5000 m. Vertically, these water masses move extremely slowly, and horizontally they move at a speed of 0.2-0.8 cm / s (28 m / h);

Bottom water masses. They occupy the zone of the World Ocean below 5000 m and have a constant salinity, a very high density, and their horizontal movement is slower than vertical.

Depending on the origin, the following types of water masses are distinguished:

equatorial. Throughout the year, the water is strongly heated by the sun. Its temperature is 27-28°C. Seasonally, it changes by no more than 2°. These water masses have a salinity lower than in tropical latitudes, since they are desalinated by numerous rivers flowing into the ocean at equatorial latitudes, and by abundant atmospheric precipitation;

Tropical. They form in tropical latitudes. The water temperature here is 20-25°. The temperature of tropical water masses is greatly influenced by ocean currents. Warmer are the western parts of the oceans, where warm currents (see Ocean currents) come from the equator. The eastern parts of the oceans are colder, as cold currents come here. Seasonally, the temperature of tropical water masses varies by 4 °. The salinity of these water masses is much greater than that of the equatorial ones, since, as a result of descending air currents, an area of ​​high pressure is established here and little precipitation falls;

Moderate water masses. In the temperate latitudes of the Northern Hemisphere, the western parts of the oceans are cold, where cold currents pass. The eastern regions of the oceans are warmed by warm currents. Even in the winter months, the water in them has a temperature of 10°C to 0°C. In summer it varies from 10°С to 20°С. Thus, seasonally the temperature of moderate water masses varies by 10°C. They already have a change of seasons. But it comes later than on land, and is not so pronounced. The salinity of moderate water masses is lower than that of tropical ones, since not only rivers and atmospheric precipitation that fall here, but also icebergs entering these latitudes, have a desalination effect;

Polar water masses. Formed in the Arctic and off the coast of Antarctica. These water masses can be carried by currents to temperate and even tropical latitudes. In the polar regions of both hemispheres, water cools down to -2°C, but still remains liquid. A further decrease in temperature leads to the formation of ice. The polar water masses are characterized by an abundance of floating ice, as well as ice that forms huge ice expanses. In the Arctic Ocean, ice lasts all year and is in constant drift. In the Southern Hemisphere, in areas of polar water masses, sea ice enters temperate latitudes much further than in the Northern Hemisphere. The salinity of the polar water masses is low, since ice has a strong desalination effect. There are no clear boundaries between the listed water masses, but there are transition zones - zones of mutual influence of neighboring water masses. They are most clearly expressed in places where warm and cold currents meet. Each water mass is more or less homogeneous in its properties, but in transitional zones these characteristics can change dramatically.

Water masses actively interact with the atmosphere: they give it heat and moisture, absorb carbon dioxide from it, and release oxygen.

When water masses with different properties meet, oceanographic fronts (convergence zones) are formed at the junction of warm and cold surface currents and are characterized by the sinking of water masses. There are several frontal zones in the world ocean, but there are 4 main ones.

There are also zones of divergence in the ocean - zones of divergence of surface currents and the rise of deep waters: off the west coast of the continents died. Latitudes and over the thermal equator near the eastern continents. Such zones are rich in phytoplankton and zooplankton, fishing is good.

Every year my parents took me to the sea during the summer holidays, and I was always surprised by this unusual bitter-salty taste of sea water, which, of course, I swallowed during the incessant surface and underwater swims. Later, in chemistry classes, I learned that not only kitchen sodium chloride determines the taste of the sea, but also magnesium and potassium, and it can also be in the form of sulfate or carbonate.

Salt water occupies most of the waters of planet Earth. The first living organisms appeared in the ocean. So what is this water?

Salinity of the oceans

On average, the salinity of water is 35 ppm with a deviation from this value by 2-4%.

Lines of constant salinity (isohalines) are mainly located parallel to the equator, along which waters with not the highest concentration of salts are located. This is due to the abundance of precipitation, exceeding the volume of water evaporating from the surface.

At a distance from the equator to the subtropical climate zones up to 20-30 degrees latitude, areas with increased salinity are observed in the Southern and Northern hemispheres. Moreover, in the Atlantic Ocean, areas with the maximum concentration of salt have been identified.

Toward the poles, salinity decreases, and around 40 degrees there is an equilibrium between precipitation and evaporation.

The poles have the lowest salinity due to the melting of fresh ice, and in the Arctic Ocean, the runoff of large rivers has a great influence.

The most salty sea

The Red Sea is saltier than the rest of the planet's waters by more than 4% due to:

• low rainfall;
• strong evaporation;
• lack of rivers bringing fresh water;
• limited connection with the World Ocean, in particular, with the Indian.

One of the most beautiful seas with coral reefs that attract with their bright colors a large variety of fish, sea turtles, dolphins, and diving enthusiasts.

The freshest salty sea

The Baltic Sea contains 2-8 g of salts per liter of water. It was formed on the site of a glacial lake with large quantity rivers (more than 250), reducing salinity, and weak contact with ocean waters.

The average annual salinity of the waters of the World Ocean (in ppm). Data from the World Ocean Atlas, 2001

Sea water is a solution containing more than 40 chemical elements. The sources of salts are river runoff and salts coming in the process of volcanism and hydrothermal activity, as well as during underwater weathering of rocks - halmyrolysis. The total mass of salts is about 49.2 * 10 15 tons, this mass is enough for the evaporation of all ocean waters to cover the surface of the planet with a layer of layers 150 m thick. The most common anions and cations in waters are the following (in descending order): among the anions Cl -, SO 4 2-, HCO 3 -, among the anions Na +, Mg 2+, Ca 2+. Accordingly, in terms of layers, the largest amount falls on NaCl (about 78%), MgCl 2 , MgSO 4 , CaSO 4 . The salt composition of sea water is dominated by chlorides (while there are more carbonates in river water). It is noteworthy that the chemical composition of sea water is very similar to the salt composition of human blood. The salty taste of water depends on the content of sodium chloride in it, the bitter taste is determined by magnesium chloride, sodium and magnesium sulfates. The slightly alkaline reaction of sea water (pH 8.38-8.40) is determined by the predominant role of alkaline and alkaline earth elements - sodium, calcium, magnesium, potassium.

A significant amount of gases is also dissolved in the waters of the seas and oceans. Mostly it is nitrogen, oxygen and CO 2 . At the same time, the gas composition of sea waters is somewhat different from the atmospheric one - sea water, for example, contains hydrogen sulfide and methane.

Most of all, nitrogen is dissolved in sea water (10-15 ml / l), which, due to its chemical inertness, does not participate and does not significantly affect sedimentation and biological processes. It is assimilated only by nitrogen-fixing bacteria capable of converting free nitrogen into its compounds. Therefore, compared with other gases, the content of dissolved nitrogen (as well as argon, neon and helium) changes little with depth and is always close to saturation.

Oxygen entering the water in the process of gas exchange with the atmosphere and during photosynthesis. It is a very mobile and chemically active component of sea waters, therefore its content is very different - from significant to negligible; in the surface layers of the ocean, its concentration usually ranges from 5 to 9 ml/l. The supply of oxygen to the deep ocean layers depends on the rate of its consumption (oxidation of organic components, respiration, etc.), on the mixing of waters and their transfer by currents. The solubility of oxygen in water depends on temperature and salinity; in general, it decreases with increasing temperature, which explains its low content in the equatorial zone and higher in cold waters of high latitudes. With increasing depth, the oxygen content decreases, reaching values ​​of 3.0-0.5 ml/l in the oxygen minimum layer.

Carbon dioxide is contained in sea water in insignificant concentrations (no more than 0.5 ml/l), but the total content of carbon dioxide is approximately 60 times greater than its amount in the atmosphere. At the same time, it plays an important role in biological processes (being a source of carbon in the construction of a living cell), affects global climatic processes (participating in gas exchange with the atmosphere), and determines the features of carbonate sedimentation. In sea water, carbon oxides are distributed in free form (CO 2), in the form of carbonic acid and in the form of the HCO 3– anion. In general, the content of CO 2, as well as oxygen, decreases with increasing temperature; therefore, its maximum content is observed in cold waters of high latitudes and in deep zones of the water column. With depth, the concentration of CO 2 increases, since its consumption decreases in the absence of photosynthesis and the supply of carbon monoxide increases during the decomposition of organic residues, especially in the layer of the oxygen minimum.

Hydrogen sulfide in sea water is found in significant quantities in water bodies with difficult water exchange (the Black Sea is a well-known example of "hydrogen sulfide contamination"). The sources of hydrogen sulfide can be hydrothermal waters coming from the depths to the ocean floor, the reduction of sulfates by sulfate-reducing bacteria during the decomposition of dead organic matter, and the release of sulfur-containing organic residues during decay. Oxygen reacts rather quickly with hydrogen sulfide and sulfides, eventually oxidizing them to sulfates.

Important for the processes of oceanic sedimentation is the solubility of carbonates in sea water. Calcium in sea water contains an average of 400 mg / l, but a huge amount of it is bound in the skeletons of marine organisms, which dissolve when the latter die. Surface waters tend to be saturated with respect to calcium carbonate, so it does not dissolve in the upper water column immediately after the organisms die. With depth, the water becomes more and more undersaturated with calcium carbonate, and as a result, the rate at some depth of the dissolution rate of the carbonate substance is equal to the rate of its supply. This level is called depth of carbonate compensation. The depth of carbonate compensation varies depending on the chemical composition and temperature of sea water, averaging 4500 m. Below this level, carbonates cannot accumulate, which determines the replacement of essentially carbonate sediments by non-carbonate ones. The depth where the concentration of carbonates is equal to 10% of the dry matter of the sediment is called the critical depth of carbonate accumulation ( carbonate compensation depth).

Features of the relief of the ocean floor

Shelf(or continental shelf) - a slightly inclined, leveled part of the underwater margin of the continents, adjacent to the coast of the land and characterized by a common geological structure with it. Shelf depth is usually up to 100-200 m; shelf width ranges from 1-3 km to 1500 km (Barents Sea shelf). The outer boundary of the shelf is delineated by an inflection of the bottom topography - the edge of the shelf.

Modern shelves are mainly formed as a result of the flooding of the margins of the continents during the rise in the level of the World Ocean due to the melting of glaciers, as well as due to the subsidence of parts of the earth's surface associated with the latest tectonic movements. The shelf existed in all geological periods, in some of them growing sharply in size (for example, in the Jurassic and Cretaceous), in others, occupying small areas (Permian). The modern geological epoch is characterized by moderate development of shelf seas.

continental slope is the next of the main elements of the underwater margin of the continents; it is located between the shelf and the continental foot. It is characterized by steeper slopes of the surface compared to the shelf and ocean floor (on average 3-5 0, sometimes up to 40 0) and a significant dissection of the relief. Typical landforms are steps parallel to the crest and base of the slope, as well as submarine canyons, usually originating on the shelf and stretching to the continental foot. Seismic studies, dredging and deep-water drilling have established that, in terms of geological structure, the continental slope, like the shelf, is a direct continuation of the structures developed in the adjacent areas of the continents.

mainland foot is a plume of accumulative deposits that arose at the foot of the continental slope due to the movement of material down the slope (through turbidity flows, underwater landslides and landslides) and sedimentation of suspension. The depth of the continental foot reaches 3.5 km or more. Geomorphologically, it is a sloping hilly plain. Accumulative deposits that form the continental foot are usually superimposed on the ocean floor, represented by oceanic-type crust, or are located partly on the continental, partly on the oceanic crust.

Next are the structures formed on the crust of the oceanic type. The largest elements of the relief of the oceans (and the Earth as a whole) are the ocean floor and mid-ocean ridges. The bed of the ocean is divided by ridges, ramparts and hills into basins, the bottom of which is occupied by abyssal plains. These areas are characterized by a stable tectonic regime, low seismic activity and flat terrain, which allows them to be considered as oceanic plates - thalassocratons. Geomorphologically, these areas are represented by abyssal (deep water) accumulative and hilly plains. Accumulative plains have a leveled surface, a slightly inclined surface and are developed mainly along the periphery of the oceans in areas of significant inflow of sedimentary material from the continents. Their formation is associated with the supply and accumulation of material by suspension flows, which determines their inherent features: surface depression from the continental foot towards the ocean, the presence of submarine valleys, gradation layering of sediments, and leveled relief. The latter feature is determined by the fact that, moving deep into the ocean basins, sediments bury the primary dissected tectonic and volcanic relief. The hilly abyssal plains are characterized by a dissected relief and a small thickness of sediments. These plains are typical of the inner parts of the basins, remote from the coast. An important element of the relief of these plains are volcanic uplifts and individual volcanic structures.

Another element of the mega-relief is mid-ocean ridges, which are a powerful mountain system stretching across all the oceans. The total length of the mid-ocean ridges (MOR) is more than 60,000 km, the width is 200-1200 km, and the height is 1-3 km. In some areas, the peaks of the MOR form volcanic islands (Iceland). The relief is dissected, the relief forms are oriented mainly parallel to the length of the ridge. The sedimentary cover is thin, represented by carbonate biogenic silts and volcanogenic formations. The age of sedimentary strata becomes older with distance from the axial parts of the ridge; in the axial zones, the sedimentary cover is absent or is represented by modern deposits. MOR regions are characterized by intense manifestation of endogenous activity: seismicity, volcanism, high heat flux.

MOR zones are confined to the boundaries of the lithospheric plates moving apart, here the process of formation of a new oceanic crust takes place due to incoming mantle melts.

Particularly noteworthy are the transition zones from continental to oceanic crust - the margins of the continents. There are two types of continental margins: tectonically active and tectonically passive.

Passive Outskirts represent a direct continuation of the continental blocks, flooded by the waters of the seas and oceans. They include the shelf, the continental slope and the continental foot and are characterized by the absence of manifestations of endogenous activity. active ocarinas are confined to the boundaries of lithospheric plates, along which the subduction of oceanic plates under the continental ones takes place. These ocarinas are characterized by active endogenous activity; areas of seismic activity and modern volcanism are confined to them. Among the active ocarinas, two main types are distinguished by structure: the western Pacific (island-arc) and the eastern Pacific (Andean). The main elements of the margins of the Western Pacific type are deep-water trenches, volcanic island arcs, and marginal (or interarc) marine basins. The area of ​​the deep-water trench corresponds to the boundary where the plate with the oceanic-type crust is being subducted. The melting of a part of the subducting plate and the rocks of the lithosphere located above (associated with the influx of water in the subducting plate, which sharply lowers the melting temperature of the rocks) leads to the formation of magma chambers, from which melts enter the surface. Due to active volcanism, volcanic islands are formed, stretching parallel to the boundary of the subsidence of the plate. The margins of the East Pacific type are distinguished by the absence of volcanic arcs (volcanism is manifested directly on the margin of the land) and marginal basins. The deep-water trench is replaced by a steep continental slope and a narrow shelf.

Destructive and accumulative activity of the sea

Abrasion (from lat. "abrasion" - scraping, shaving) is the process of destruction of rocks by waves and currents. Abrasion occurs most intensively near the coast under the action of the surf.

The destruction of coastal rocks is composed of the following factors:

wave impact (the strength of which reaches 30-40 t / m 2 during storms);

· abrasive action of clastic material brought by the wave;

dissolution of rocks;

· compression of air in the pores and cavities of the rock during the impact of waves, which leads to cracking of rocks under the influence of high pressure;

· thermal abrasion, which manifests itself in the thawing of frozen rocks and ice shores, and other types of impact on the coast.

The impact of the abrasion process is manifested to a depth of several tens of meters, and in the oceans up to 100 m or more.

The impact of abrasion on the coast leads to the formation of clastic deposits and certain landforms. The abrasion process proceeds as follows. Hitting the shore, the wave gradually develops a depression at its base - wave-cutting niche, over which hangs a cornice. As the wave-cut niche deepens, under the action of gravity, the cornice collapses, the fragments are at the foot of the coast and, under the influence of waves, turn into sand and pebbles.

The cliff or steep ledge formed as a result of abrasion is called cliff. At the site of the retreating cliff, a abrasion terrace, or bench (English "bench"), which is composed of bedrock. The cliff may border directly on the bench or be separated from the latter by a beach. The transverse profile of the abrasion terrace has the form of a convex curve with small slopes near the shore and large slopes at the base of the terrace. The resulting clastic material is carried away from the shore, forming underwater accumulative terraces.

As the abrasion and accumulative terraces develop, the waves find themselves in shallow water, turn up and lose energy before reaching the root bank, because of this, the abrasion process stops.

Depending on the nature of the ongoing processes, the coast can be divided into abrasion and accumulative.

A, B, C - different stages of retreat of the coastal cliff, destroyed by abrasion; A 1 , B 2 , C 3 - different stages of development of the underwater accumulative terrace.

Waves carry out not only destructive work, but also the work of moving and accumulating detrital material. The oncoming wave carries pebbles and sand, which remain on the shore when the wave retreats, this is how beaches are formed. By the beach(from the French "plage" - sloping seashore) is called a strip of sediment on the sea coast in the zone of action of a surf stream. Morphologically, there are beaches of a full profile, which look like a gentle swell, and beaches of an incomplete profile, which are an accumulation of sediment inclined towards the sea, adjoining the foot of the coastal cliff with its back side. Beaches of a full profile are typical for accumulative shores, incomplete - mainly for abrasion shores.

When waves are burrowing at depths of a few meters, the material deposited under water (sand, gravel or shell) forms an underwater sand bank. Sometimes the underwater accumulative shaft, growing, protrudes above the surface of the water, stretching parallel to the shore. Such shafts are called bars(from the French "barre" - barrier, shoal).

The formation of a bar can lead to the separation of the coastal part of the sea basin from the main water area - lagoons are formed. Lagoon (from lat. lacus - lake) is a shallow natural water basin, separated from the sea by a bar or connected to the sea by a narrow strait (or straits). The main feature of the lagoons is the difference between the salinity of the waters and biological communities.

Sedimentation in the seas and oceans

Various precipitation accumulates in the seas and oceans, which can be divided into the following groups by origin:

· terrigenous, formed due to the accumulation of products of mechanical destruction of rocks;

biogenic, formed due to the vital activity and death of organisms;

chemogenic, associated with precipitation from sea water;

· volcanic, accumulating as a result of underwater eruptions and due to products of eruption brought from land;

polygenic, i.e. mixed sediments formed due to material of different origin.

In general, the material composition of bottom sediments is determined by the following factors:

· depth of sedimentation area and bottom topography;

hydrodynamic conditions (the presence of currents, the influence of wave activity);

· the nature of the supplied sedimentary material (determined by climatic zonality and distance from the continents);

biological productivity (marine organisms extract minerals from the water and deliver them to the bottom after death (in the form of shells, coral structures, etc.));

volcanism and hydrothermal activity.

One of the determining factors is the depth, which makes it possible to distinguish several zones that differ in the features of sedimentation. Littoral(from lat. "littoralis"- coastal) - the border strip between land and sea, regularly flooded at high tide and drained at low tide. The littoral is the zone of the seabed located between the levels of the highest tide and the lowest tide. nerite zone corresponds to the depths of the shelf (from the Greek. "erites"- sea mollusk). Bathyal zone(from the Greek "deep") roughly corresponds to the area of ​​the continental slope and foot and depths of 200 - 2500 m. This zone is characterized by the following environmental conditions: significant pressure, almost complete absence of light, slight seasonal fluctuations in temperature and water density; representatives of zoobenthos and fish predominate in the organic world, the plant world is very poor due to the lack of light. abyssal zone(from the Greek "bottomless") corresponds to sea depths of more than 2500 m, which corresponds to deep-water basins. The waters of this zone are characterized by relatively low mobility, constantly low temperature (1-2 0 C, in the polar regions below 0 0 C), constant salinity; there is no sunlight at all and enormous pressures are achieved, which determine the originality and poverty of the organic world. Areas deeper than 6000 m are usually distinguished as ultra-abyssal zones corresponding to the deepest parts of the basins and deep-water trenches.

The main feature that distinguishes water oceans from the waters of the land, is their high salinity. The number of grams of substances dissolved in 1 liter of water is called salinity.

Sea water is a solution of 44 chemical elements, but salts play a primary role in it. Table salt gives water a salty taste, while magnesium salt gives it a bitter taste. Salinity is expressed in ppm (%o). This is a thousandth of a number. In a liter of ocean water, an average of 35 grams of various substances are dissolved, which means that the salinity will be 35% o.

The amount of salts dissolved in will be approximately 49.2 10 tons. In order to visualize how large this mass is, we can make the following comparison. If all sea salt in dry form is distributed over the surface of the entire land, then it will be covered with a layer 150 m thick.

The salinity of the ocean waters is not the same everywhere. Salinity is influenced by the following processes:

• evaporation of water. In this process, salts with water do not evaporate;
• ice formation;
• fallout, lowering salinity;
• . The salinity of the ocean waters near the continents is much less than in the center of the ocean, since the waters desalinate it;
• melting ice.

Processes such as evaporation and ice formation contribute to an increase in salinity, while precipitation, river runoff, and melting ice lower it. Evaporation and precipitation play the main role in changing salinity. Therefore, the salinity of the surface layers of the ocean, as well as temperature, depends on latitude-related.

Seventy percent of the surface of our planet is covered with water - most of it falls on the oceans. The waters of the World Ocean are heterogeneous in composition and have a bitter-salty taste. Not every parent can answer the child's question: "Why does sea water taste so good?" What determines the amount of salt? There are different points of view on this matter.

What determines the salinity of water

At different times of the year in different parts of the hydrosphere, salinity is not the same. Several factors influence its change:

• ice formation;
• evaporation;
• precipitation;
• currents;
• river flow;
• melting ice.

While the water from the surface of the ocean evaporates, the salt does not erode and remains. Her concentration is increasing. The freezing process has a similar effect. Glaciers contain the largest supply of fresh water on the planet. The salinity of the oceans during their formation increases.

The opposite effect is characterized by the melting of glaciers, in which the salt content decreases. Salt also comes from rivers flowing into the ocean and precipitation. The closer to the bottom, the less salinity. Cold currents reduce salinity, warm currents increase it.

Location

According to experts, The concentration of salt in the seas depends on their location. Closer to the northern regions, the concentration increases, to the south it decreases. However, the concentration of salt in the oceans is always greater than in the seas, and location does not have any effect on this. This fact is not explained.

Salinity is due to the presence of magnesium and sodium. One of the options for explaining the different concentrations is the presence of certain land areas enriched in deposits of such components. However, such an explanation is not very plausible, if we take into account the sea currents. Thanks to them, over time, the salt level should stabilize throughout the volume.

World Ocean

The salinity of the ocean depends on the geographical latitude, the proximity of rivers, the climatic features of objects etc. Its average value according to the measurement is 35 ppm.

Near the Antarctic and the Arctic in cold areas, the concentration is less, but in winter, during the formation of ice, the amount of salt increases. Therefore, the water in the Arctic Ocean is the least salty, and in the Indian Ocean, the concentration of salt is the highest.

In the Atlantic and Pacific oceans, the concentration of salt is approximately the same, which decreases in the equatorial zone and, conversely, increases in tropical and subtropical regions. Some cold and warm currents balance each other. For example, the salty Labrador Current and the unsalted Gulf Stream.

Interesting to know: How many exist on Earth?

Why are the oceans salty

There are different points of view that reveal the essence of the presence of salt in the ocean. Scientists believe that the reason is the ability of water masses to destroy the rock, leaching easily soluble elements from it. This process is ongoing. Salt saturates the seas and gives a bitter taste.

However, there are diametrically opposed opinions on this issue:

Volcanic activity decreased over time, and the atmosphere cleared of vapor. Acid rain fell less and less, and about 500 years ago, the composition of the ocean water surface stabilized and became what we know it today. Carbonates, which enter the ocean with river water, are an excellent building material for marine organisms.