In the twentieth century, through numerous studies, mankind revealed the secret of the earth's interior, the structure of the earth in the context became known to every schoolchild. For those who do not yet know what the earth consists of, what are its main layers, their composition, what is the name of the thinnest part of the planet, we will list a number of significant facts.

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The shape and size of the planet Earth

Contrary to popular misconception our planet is not round. Its shape is called the geoid and is a slightly flattened ball. The places where the globe is compressed are called poles. The axis of the earth's rotation passes through the poles, our planet makes one revolution around it in 24 hours - an earth day.

In the middle, the planet is surrounded by an imaginary circle dividing the geoid into the Northern and Southern hemispheres.

Apart from the equator there are meridians - circles perpendicular to the equator and passing through both poles. One of them, passing through the Greenwich Observatory, is called zero - it serves as a reference point for geographic longitude and time zones.

Back to main features the globe can be attributed:

• diameter (km.): equatorial - 12 756, polar (near the poles) - 12 713;
• length (km.) of the equator - 40,057, meridian - 40,008.

So, our planet is a kind of ellipse - a geoid, rotating around its axis passing through two poles - North and South.

The central part of the geoid is surrounded by the equator - a circle dividing our planet into two hemispheres. In order to determine what the radius of the earth is, use half the values ​​of its diameter at the poles and the equator.

And now about that what is the earth made of what shells it is covered with and what sectional structure of the earth.

Earth shells

Basic shells of the earth distinguished according to their content. Since our planet is spherical, its shells held together by gravity are called spheres. If you look at s trinity of the earth in a section, then three areas can be seen:

In order(starting from the surface of the planet) they are located as follows:

1. The lithosphere is a solid shell of the planet, including mineral layers of the earth.
2. Hydrosphere - contains water resources - rivers, lakes, seas and oceans.
3. Atmosphere - is a shell of air that surrounds the planet.

In addition, the biosphere is also distinguished, which includes all living organisms that inhabit other shells.

Important! Many scientists refer the population of the planet to a separate vast shell called the anthroposphere.

The earth's shells - the lithosphere, hydrosphere and atmosphere - are distinguished according to the principle of combining a homogeneous component. In the lithosphere - these are solid rocks, soil, the internal contents of the planet, in the hydrosphere - all of it, in the atmosphere - all the air and other gases.

Atmosphere

The atmosphere is a gaseous envelope its composition includes: , nitrogen, carbon dioxide, gas, dust.

1. Troposphere - the upper layer of the earth, containing most of the earth's air and extending from the surface to a height of 8-10 (at the poles) to 16-18 km (at the equator). Clouds and various air masses form in the troposphere.
2. The stratosphere is a layer in which the air content is much lower than in the troposphere. His average thickness is 39-40 km. This layer begins at the upper boundary of the troposphere and ends at an altitude of about 50 km.
3. The mesosphere is a layer of the atmosphere that extends from 50-60 to 80-90 km above the earth's surface. Characterized by a steady decrease in temperature.
4. Thermosphere - located 200-300 km from the surface of the planet, differs from the mesosphere by an increase in temperature as altitude increases.
5. Exosphere - begins with the upper boundary lying below the thermosphere, and gradually passes into outer space, it is characterized by low air content, high solar radiation.

Attention! In the stratosphere at an altitude of about 20-25 km there is a thin layer of ozone that protects all life on the planet from harmful ultraviolet rays. Without it, all living things would have perished very soon.

The atmosphere is the earth's shell, without which life on the planet would be impossible.

It contains the air necessary for the breathing of living organisms, determines suitable weather conditions, protects the planet from the negative impact of solar radiation.

The atmosphere consists of air, in turn, air is approximately 70% nitrogen, 21% oxygen, 0.4% carbon dioxide and other rare gases.

In addition, there is an important ozone layer in the atmosphere, at about 50 km altitude.

Hydrosphere

The hydrosphere is all the liquids on the planet.

This shell by location water resources and their degree of salinity includes:

• the world ocean is a huge space occupied by salt water and includes four and 63 seas;
• the surface waters of the continents are freshwater, as well as occasionally brackish water bodies. They are subdivided according to the degree of fluidity into reservoirs with a course - rivers on and reservoirs with stagnant water - lakes, ponds, swamps;
• groundwater - fresh water below the earth's surface. Depth their occurrence varies from 1-2 to 100-200 and more meters.

Important! A huge amount of fresh water is currently in the form of ice - today in zones permafrost in the form of glaciers, huge icebergs, permanent non-melting snow, there are about 34 million km3 of fresh water reserves.

The hydrosphere is primarily, source of fresh drinking water, one of the main climate-forming factors. Water resources are used as means of communication and objects of tourism and recreation (recreation).

Lithosphere

The lithosphere is solid ( mineral) layers of the earth. The thickness of this shell ranges from 100 (under the seas) to 200 km (under the continents). The lithosphere includes the earth's crust and upper part mantle.

What is located below the lithosphere is directly the internal structure of our planet.

The slabs of the lithosphere mainly consist of basalt, sand and clay, stone, and also the soil layer.

The scheme of the structure of the earth together with the lithosphere is represented by the following layers:

• Earth's crust - upper, consisting of sedimentary, basalt, metamorphic rocks and fertile soil. Depending on the location, there are continental and oceanic crust;
• mantle - located under the earth's crust. Weighs about 67% of total mass planets. The thickness of this layer is about 3000 km. The upper layer of the mantle is viscous, lies at a depth of 50-80 km (under the oceans) and 200-300 km (under the continents). The lower layers are harder and denser. The composition of the mantle includes heavy iron and nickel materials. The processes occurring in the mantle determine many phenomena on the planet's surface (seismic processes, volcanic eruptions, formation of deposits);
• The central part of the earth is the core, consisting of an inner solid and an outer liquid part. The thickness of the outer part is about 2200 km, the inner one is 1300 km. Distance from surface d about the core of the earth is about 3000-6000 km. The temperature in the center of the planet is about 5000 Cº. According to many scientists, the core land by composition is a heavy iron-nickel melt with an admixture of other elements similar in properties to iron.

Important! Among a narrow circle of scientists, in addition to the classical model with a semi-molten heavy core, there is also a theory that an inner luminary is located in the center of the planet, surrounded on all sides by an impressive layer of water. This theory, in addition to a small circle of adherents in the scientific community, has found wide circulation in science fiction literature. An example is the novel by V.A. Obruchev "Plutonia", which tells about the expedition of Russian scientists to the cavity inside the planet with its own small luminary and the world of animals and plants extinct on the surface.

Such a common earth structure map, including the earth's crust, mantle and core, every year more and more improved and refined.

Many parameters of the model with the improvement of research methods and the advent of new equipment will be updated more than once.

For example, in order to know exactly how many kilometers to outer part of the nucleus, it will take more years of scientific research.

At the moment, the deepest mine in the earth's crust, dug by man, is about 8 kilometers, so the study of the mantle, and even more so the core of the planet, is possible only in a theoretical context.

Layered structure of the Earth

We study what layers the Earth consists of inside

Conclusion

Having considered sectional structure of the earth we have seen how interesting and complex our planet is. The study of its structure in the future will help humanity to understand the mysteries natural phenomena, will make it possible to more accurately predict devastating natural disasters, to discover new, yet undeveloped mineral deposits.

Astronomers study space, receive information about the planets and stars, despite their great remoteness. At the same time, there are no less mysteries on the Earth itself than in the Universe. And today scientists do not know what is inside our planet. Watching how lava pours out during a volcanic eruption, one might think that the Earth is also molten inside. But it's not.

Core. The central part of the globe is called the core (Fig. 83). Its radius is about 3,500 km. Scientists believe that outer part the core is in a molten-liquid state, and the inner one is in a solid state. The temperature in it reaches +5,000 °C. From the core to the surface of the Earth, temperature and pressure gradually decrease.

Mantle. The Earth's core is covered by a mantle. Its thickness is approximately 2,900 km. The mantle, like the core, has never been seen. But it is assumed that the closer to the center of the Earth, the higher the pressure in it, and the temperature - from several hundred to -2,500 ° C. It is believed that the mantle is solid, but at the same time red-hot.

Earth's crust. Above the mantle, our planet is covered with crust. This is the top solid layer of the Earth. Compared to the core and mantle, the earth's crust is very thin. Its thickness is only 10-70 km. But this is the earthly firmament on which we walk, rivers flow, cities are built on it.

The earth's crust is formed by various substances. It is made up of minerals and rocks. Some of them you already know (granite, sand, clay, peat, etc.). Minerals and rocks differ in color, hardness, structure, melting point, solubility in water and other properties. Many of them are widely used by man, for example, as fuel, in construction, for the production of metals. material from the site

Granite

Sand

Peat

The upper layer of the earth's crust is visible in deposits on the slopes of mountains, steep river banks, and quarries (Fig. 84). And mines and boreholes, which are used to extract minerals, such as oil and gas, help to look into the depths of the crust.

The position of the earth's crust between the mantle and the outer shells - the atmosphere, hydrosphere and biosphere - determines the impact on it of the external and internal forces of the Earth.

The structure of the earth's crust is heterogeneous (Fig. 19). The upper layer, whose thickness varies from 0 to 20 km, is complex sedimentary rocks- sand, clay, limestone, etc. This is confirmed by the data obtained from the study of outcrops and cores of boreholes, as well as the results of seismic studies: these rocks are loose, the speed of seismic waves is low.

Rice. nineteen. The structure of the earth's crust

Below, under the continents, is located granite layer, composed of rocks, the density of which corresponds to the density of granite. The velocity of seismic waves in this layer, as in granites, is 5.5–6 km/s.

Under the oceans, the granite layer is absent, and on the continents in some places it comes to the surface.

Even lower is the layer in which seismic waves propagate at a speed of 6.5 km/s. This speed is typical for basalts, therefore, despite the fact that the layer is composed of different rocks, it is called basalt.

The boundary between the granite and basalt layers is called Conrad surface. This section corresponds to a seismic wave velocity jump from 6 to 6.5 km/s.

Depending on the structure and thickness, two types of bark are distinguished - mainland and oceanic. Under the continents, the crust contains all three layers - sedimentary, granite and basalt. Its thickness on the plains reaches 15 km, and in the mountains it increases to 80 km, forming the "roots of the mountains". Beneath the oceans, the granitic layer in many places is completely absent, and the basalts are covered with a thin cover of sedimentary rocks. In the deep parts of the ocean, the thickness of the crust does not exceed 3–5 km, and the upper mantle lies below.

Mantle. This is an intermediate shell located between the lithosphere and the Earth's core. Its lower boundary passes presumably at a depth of 2900 km. The mantle accounts for more than half of the Earth's volume. The substance of the mantle is in an overheated state and is under enormous pressure from the overlying lithosphere. The mantle has a great influence on the processes occurring on the Earth. In the upper mantle, magma chambers arise, ores, diamonds and other fossils are formed. From here, internal heat comes to the surface of the Earth. The substance of the upper mantle is constantly and actively moving, causing the movement of the lithosphere and the earth's crust.

Core. Two parts are distinguished in the core: the outer, to a depth of 5 thousand km, and the inner, to the center of the Earth. The outer core is liquid, as no oxygen passes through it. transverse waves, internal - solid. The substance of the core, especially the inner one, is highly compacted and corresponds in density to metals, which is why it is called metallic.

To physical properties The lands are attributed temperature regime(internal heat), density and pressure.

Internal heat of the Earth. According to modern concepts, the Earth after its formation was a cold body. Then the decay of radioactive elements gradually warmed it up. However, as a result of heat radiation from the surface to near-Earth space, it cooled. A relatively cold lithosphere and the earth's crust formed. At great depths and today high temperatures. An increase in temperature with depth can be observed directly in deep mines and boreholes, during volcanic eruptions. Thus, erupting volcanic lava has a temperature of 1200–1300 °C.

On the surface of the Earth, the temperature is constantly changing and depends on the influx solar heat. Daily temperature fluctuations extend to a depth of 1–1.5 m, seasonal fluctuations - up to 30 m. Below this layer lies a zone of constant temperatures, where they always remain unchanged and correspond to the average annual temperatures of a given area on the Earth's surface.

The depth of the zone of constant temperatures in different places is not the same and depends on the climate and the thermal conductivity of the rocks. Below this zone, temperatures begin to rise, on average by 30 ° C every 100 m. However, this value is not constant and depends on the composition of rocks, the presence of volcanoes, and the activity of thermal radiation from the bowels of the Earth. So, in Russia it ranges from 1.4 m in Pyatigorsk to 180 m on the Kola Peninsula.

Knowing the radius of the Earth, we can calculate that in the center of its temperature should reach 200,000 ° C. However, at this temperature, the Earth would turn into a hot gas. It is generally accepted that a gradual increase in temperature occurs only in the lithosphere, and the upper mantle serves as the source of the Earth's internal heat. Below, the rise in temperature slows down, and in the center of the Earth it does not exceed 50,000 °C.

Density of the Earth. The denser the body, the greater the mass per unit volume. The density standard is considered to be water, 1 cm 3 of which weighs 1 g, i.e. the density of water is 1 g / s 3. The density of other bodies is determined by the ratio of their mass to the mass of water of the same volume. From this it is clear that all bodies with a density greater than 1 sink, less - float.

The density of the Earth varies from place to place. Sedimentary rocks have a density of 1.5–2 g/cm3, while basalts have a density of more than 2 g/cm3. The average density of the Earth is 5.52 g / cm 3 - this is more than 2 times the density of granite. In the center of the Earth, the density of its constituent rocks increases and amounts to 15–17 g/cm 3 .

pressure inside the earth. Rocks located in the center of the Earth experience tremendous pressure from the overlying layers. It is calculated that at a depth of only 1 km the pressure is 10 4 hPa, while in the upper mantle it exceeds 6 * 10 4 hPa. Laboratory experiments show that under such pressure, solids, such as marble, bend and can even flow, that is, they acquire properties intermediate between a solid and a liquid. This state of matter is called plastic. This experiment allows us to state that in the deep bowels of the Earth, matter is in a plastic state.

The chemical composition of the Earth. In the Earth you can find all the chemical elements of the table of D. I. Mendeleev. However, their number is not the same, they are distributed extremely unevenly. For example, in the earth's crust, oxygen (O) is more than 50%, iron (Fe) is less than 5% of its mass. It is estimated that the basalt and granite layers consist mainly of oxygen, silicon and aluminum, while the proportion of silicon, magnesium and iron increases in the mantle. In general, it is considered that 8 elements (oxygen, silicon, aluminum, iron, calcium, magnesium, sodium, hydrogen) account for 99.5% of the composition of the earth's crust, and all the rest - 0.5%. The data on the composition of the mantle and the core are speculative.

The earth's crust only seems to be motionless, absolutely stable. In fact, it performs continuous and varied movements. Some of them occur very slowly and are not perceived by the human senses, others, such as earthquakes, are landslide, destructive. What titanic forces move the earth's crust?

The internal forces of the Earth, the source of their origin. It is known that at the boundary between the mantle and the lithosphere, the temperature exceeds 1500 °C. At this temperature, matter must either melt or turn into a gas. When solids pass into a liquid or gaseous state, their volume should increase. However, this does not happen, since the overheated rocks are under pressure from the overlying layers of the lithosphere. There is a "steam boiler" effect, when matter tending to expand puts pressure on the lithosphere, setting it in motion together with the earth's crust. Moreover, the higher the temperature, the stronger the pressure and the more actively the lithosphere moves. Particularly strong pressure centers arise in those places of the upper mantle where radioactive elements are concentrated, the decay of which heats the constituent rocks to even more high temperatures. The movements of the earth's crust under the influence of the internal forces of the Earth are called tectonic. These movements are divided into oscillatory, folding and discontinuous.

oscillatory movements. These movements occur very slowly, imperceptibly to humans, which is why they are also called century old or epeirogenic. In some places the earth's crust is rising, in others it is falling. In this case, the uplift is often replaced by a lowering, and vice versa. You can follow these movements only by those "traces" that remain after them on earth's surface. For example, on the Mediterranean coast, near Naples, there are the ruins of the temple of Serapis, the columns of which are excavated by sea mollusks at a height of up to 5.5 m above the level of the modern sea. This serves as unconditional proof that the temple, built in the 4th century, was at the bottom of the sea, and then it was raised. Now this piece of land is sinking again. Often on the coasts of the seas above their modern level there are steps - sea terraces, once created by the sea surf. On the platforms of these steps, you can find the remains of marine organisms. This indicates that the platforms of the terraces were once the bottom of the sea, and then the coast rose and the sea receded.

The lowering of the earth's crust below 0 m above sea level is accompanied by the onset of the sea - transgression and the rise - its retreat - regression. At present, in Europe, uplifts occur in Iceland, Greenland, and the Scandinavian Peninsula. Observations have established that the region of the Gulf of Bothnia is rising at a rate of 2 cm per year, i.e., 2 m per century. At the same time, the territory of Holland, southern England, northern Italy, the Black Sea lowland, and the coast of the Kara Sea are sinking. A sign of the lowering of the sea coasts is the formation of sea bays in the mouth sections of rivers - estuaries (lips) and estuaries.

With the rise of the earth's crust and the retreat of the sea, the seabed, composed of sedimentary rocks, turns out to be land. Thus, extensive marine (primary) plains: for example, West Siberian, Turan, North Siberian, Amazonian (Fig. 20).

Rice. 20. The structure of primary, or marine, stratal plains

Folding movements. In cases where rock layers are sufficiently plastic, under the action of internal forces, they are crushed into folds. When the pressure is directed vertically, the rocks are displaced, and if in a horizontal plane, they are compressed into folds. The shape of the folds is the most diverse. When the bend of the fold is directed downward, it is called a syncline, upward - an anticline (Fig. 21). Folds are formed at great depths, that is, at high temperatures and high pressure, and then, under the action of internal forces, they can be raised. This is how folded mountains Caucasian, Alps, Himalayas, Andes, etc. (Fig. 22). In such mountains, folds are easy to observe where they are exposed and come to the surface.

Rice. 21. Synclinal (1) and anticlinal (2) folds

Rice. 22. Fold mountains

Breaking movements. If the rocks are not strong enough to withstand the action of internal forces, cracks form in the earth's crust - faults and a vertical displacement of the rocks occurs. The sunken areas are called grabens, and those who have risen handfuls(Fig. 23). The alternation of horsts and grabens creates blocky (resurrected) mountains. Examples of such mountains are: Altai, Sayan, Verkhoyansk Range, Appalachians in North America and many others. The revived mountains differ from the folded ones both in their internal structure and in their appearance - morphology. The slopes of these mountains are often steep, the valleys, like the watersheds, are wide and flat. Rock layers are always displaced relative to each other.

Rice. 23. Restored fold-block mountains

The sunken areas in these mountains, the grabens, are sometimes filled with water, and then deep lakes are formed: for example, Baikal and Teletskoye in Russia, Tanganyika and Nyasa in Africa.

With a further increase in temperature in the bowels of the Earth, rocks, despite high pressure, melt, forming magma. This releases a lot of gases. This further increases both the volume of the melt and its pressure on the surrounding rocks. As a result, very dense, gas-rich magma tends to where the pressure is less. It fills cracks in the earth's crust, breaks and lifts the layers of its constituent rocks. Part of the magma, not reaching the earth's surface, solidifies in the thickness of the earth's crust, forming magmatic veins and laccoliths. Sometimes magma breaks out to the surface, and it erupts in the form of lava, gases, volcanic ash, rock fragments and hardened lava clots.

Volcanoes. Each volcano has a channel through which lava erupts (Fig. 24). This is vent, which always ends in a funnel-shaped expansion - crater. The diameter of the craters ranges from several hundred meters to many kilometers. For example, the diameter of the Vesuvius crater is 568 m. Very large craters are called calderas. For example, the caldera of the Uzona volcano in Kamchatka, which is filled by Lake Kronotskoye, reaches 30 km in diameter.

The shape and height of volcanoes depend on the viscosity of the lava. Liquid lava spreads quickly and easily and does not form cone-shaped mountains. An example is the Kilauza volcano in the Hawaiian Islands. The crater of this volcano is a rounded lake with a diameter of about 1 km, filled with bubbling liquid lava. The level of lava, like water in a spring bowl, then falls, then rises, splashing over the edge of the crater.

Rice. 24. Sectional volcanic cone

Volcanoes with viscous lava are more widespread, which, when cooled, form a volcanic cone. The cone always has a layered structure, which indicates that the outpourings occurred repeatedly, and the volcano grew gradually, from eruption to eruption.

The height of volcanic cones varies from several tens of meters to several kilometers. For example, the Aconcagua volcano in the Andes has a height of 6960 m.

There are about 1500 active and extinct mountain volcanoes. Among them are such giants as Elbrus in the Caucasus, Klyuchevskaya Sopka in Kamchatka, Fujiyama in Japan, Kilimanjaro in Africa and many others.

Most of the active volcanoes are located around Pacific Ocean, forming the Pacific "ring of fire", and in the Mediterranean-Indonesian belt. There are 28 active volcanoes in Kamchatka alone, and there are more than 600 of them in total. active volcanoes naturally - all of them are confined to the mobile zones of the earth's crust (Fig. 25).

Rice. 25. Zones of volcanism and earthquakes

In the geological past of the Earth, volcanism was more active than it is now. In addition to the usual (central) eruptions, fissure eruptions occurred. From giant cracks (faults) in the earth's crust, stretching for tens and hundreds of kilometers, lava erupted onto the earth's surface. Solid or patchy lava covers were created, leveling the terrain. The lava thickness reached 1.5–2 km. This is how lava plains. An example of such plains are separate sections Central Siberian Plateau, the central part of the Deccan Plateau in India, the Armenian Highlands, the Columbia Plateau.

Earthquakes. The causes of earthquakes are different: volcanic eruption, landslides in the mountains. But the strongest of them arise as a result of movements of the earth's crust. Such earthquakes are called tectonic. They usually originate at great depths, at the boundary between the mantle and the lithosphere. The origin of an earthquake is called hypocenter or hearth. On the Earth's surface, above the hypocenter, is epicenter earthquakes (Fig. 26). Here, the strength of the earthquake is greatest, and with distance from the epicenter, it weakens.

Rice. 26. Hypocenter and epicenter of an earthquake

The earth's crust is constantly shaking. Over 10,000 earthquakes are observed during the year, but most of them are so weak that they are not felt by humans and are recorded only by instruments.

The strength of earthquakes is measured in points - from 1 to 12. Powerful 12-point earthquakes are rare and are catastrophic. During such earthquakes, deformations occur in the earth's crust, cracks, shifts, faults, landslides in the mountains and dips in the plains are formed. If they occur in densely populated areas, then there is great destruction and numerous human casualties. The largest earthquakes in history are the Messinian (1908), Tokyo (1923), Tashkent (1966), Chilean (1976) and Spitak (1988). In each of these earthquakes, dozens, hundreds and thousands of people died, and cities were destroyed almost to the ground.

Often the hypocenter is under the ocean. Then a destructive ocean wave arises - tsunami.

Simultaneously with internal, tectonic processes, external processes operate on the Earth. Unlike internal ones, covering the entire thickness of the lithosphere, they act only on the surface of the Earth. The depth of their penetration into the earth's crust does not exceed a few meters, and only in caves - up to several hundred meters. The source of the origin of the forces that cause external processes, serves as thermal solar energy.

External processes are very diverse. These include the weathering of rocks, the work of wind, water and glaciers.

Weathering. It is divided into physical, chemical and organic.

physical weathering- this is mechanical crushing, grinding of rocks.

It occurs when there is a sudden change in temperature. When heated, the rock expands; when cooled, it contracts. Since the coefficient of expansion of different minerals included in the rock is not the same, the process of its destruction is enhanced. At first, the rock breaks up into large blocks, which are crushed over time. The accelerated destruction of the rock is facilitated by water, which, penetrating into the cracks, freezes in them, expands and breaks the rock into separate parts. Physical weathering is most active where there is a sharp change in temperature, and solid igneous rocks come to the surface - granite, basalt, syenites, etc.

chemical weathering- this is a chemical effect on rocks of various aqueous solutions.

In this case, unlike physical weathering, various chemical reactions occur, and as a result, a change in the chemical composition and, possibly, the formation of new rocks. Chemical weathering operates everywhere, but it proceeds especially intensively in easily soluble rocks - limestones, gypsum, dolomites.

organic weathering is the process of destruction of rocks by living organisms - plants, animals and bacteria.

Lichens, for example, settling on rocks, wear away their surface with the released acid. Plant roots also secrete acid, and in addition, root system acts mechanically, as if tearing the rock. earthworms, passing inorganic substances through themselves, transform the rock and improve the access of water and air to it.

weathering and climate. All types of weathering occur simultaneously, but act with different intensity. It depends not only on the constituent rocks, but also mainly on the climate.

In polar countries, frosty weathering is most actively manifested, in temperate countries - chemical, in tropical deserts - mechanical, in the humid tropics - chemical.

Wind work. The wind is capable of destroying rocks, carrying and depositing their solid particles. The stronger the wind and the more often it blows, the more work it can do. Where rocky outcrops come to the surface of the Earth, the wind bombards them with grains of sand, gradually erasing and destroying even the hardest rocks. Less resistant rocks are destroyed faster, specific, eolian landforms- stone lace, aeolian mushrooms, pillars, towers.

In sandy deserts and along the shores of seas and large lakes, the wind creates specific landforms - dunes and dunes.

dunes- These are mobile sandy hills of crescent shape. Their windward slope is always gentle (5-10°), and the leeward slope is steep - up to 35–40° (Fig. 27). The formation of dunes is associated with the deceleration of the wind flow carrying sand, which occurs due to any obstacles - surface irregularities, stones, bushes, etc. The wind strength weakens, and sand deposition begins. The more constant the winds and the more sand, the faster the dune grows. The highest dunes - up to 120 m - were found in the deserts of the Arabian Peninsula.

Rice. 27. The structure of the dune (the arrow shows the direction of the wind)

The dunes move in the direction of the wind. The wind drives the grains of sand down a gentle slope. Having reached the ridge, the wind flow swirls, its speed decreases, the grains of sand fall out and roll down the steep leeward slope. This causes the movement of the entire dune at a speed of up to 50–60 m per year. Moving, dunes can fill up oases and even entire villages.

On sandy beaches, the waving sands form dunes. They stretch along the coast in the form of huge sandy ridges or hills up to 100 m or more high. Unlike dunes, they do not have a permanent shape, but can also move inland from the beach. In order to stop the movement of the dunes, trees and shrubs are planted, primarily pines.

The work of snow and ice. Snow, especially in the mountains, does a lot of work. Huge masses of snow accumulate on the slopes of the mountains. From time to time they break down from the slopes, forming snow avalanches. Such avalanches, moving at great speed, capture fragments of rocks and carry them down, sweeping away everything in their path. For the formidable danger posed by snow avalanches, they are called "white death".

The solid material that remains after the snow melts forms huge rocky mounds that block and fill intermountain depressions.

Doing even more work glaciers. They occupy vast areas on Earth - more than 16 million km 2, which is 11% of the land area.

There are continental, or integumentary, and mountain glaciers. continental ice occupy vast areas in Antarctica, Greenland, and on many polar islands. The ice thickness of continental glaciers is not the same. For example, in Antarctica it reaches 4000 m. Under the influence of enormous gravity, the ice slides into the sea, breaks off, and forms icebergs- ice floating mountains.

At mountain glaciers two parts are distinguished - areas of nutrition or accumulation of snow and melting. Snow is accumulating in the mountains above snow line. The height of this line is not the same in different latitudes: the closer to the equator, the higher the snow line. In Greenland, for example, it lies at an altitude of 500-600 m, and on the slopes of the Chimborazo volcano in the Andes - 4800 m.

Above the snow line, snow accumulates, compacts and gradually turns into ice. Ice has plastic properties and under the pressure of the overlying masses begins to slide down the slope. Depending on the mass of the glacier, its saturation with water and the steepness of the slope, the speed of movement varies from 0.1 to 8 m per day.

Moving along the slopes of the mountains, glaciers plow out potholes, smooth out rock ledges, and widen and deepen valleys. The clastic material that the glacier captures during its movement, during the melting (retreat) of the glacier, remains in place, forming a glacial moraine. Moraine- these are piles of fragments of rocks, boulders, sand, clay left by the glacier. There are bottom, lateral, surface, middle and terminal moraines.

Mountain valleys, through which a glacier has ever passed, are easy to distinguish: in these valleys, the remains of moraines are always found, and their shape resembles a trough. Such valleys are called touches.

Work of flowing waters. Flowing waters include temporary rainfall and snowmelt, streams, rivers and groundwater. The work of flowing waters, taking into account the time factor, is grandiose. It can be said that the entire appearance of the earth's surface is to some extent created by flowing water. All flowing waters are united by the fact that they produce three types of work:

– destruction (erosion);

– transfer of products (transit);

– attitude (accumulation).

As a result, various irregularities are formed on the surface of the Earth - ravines, furrows on slopes, cliffs, river valleys, sandy and pebble islands, etc., as well as voids in the thickness of rocks - caves.

The action of gravity. All bodies - liquid, solid, gaseous, located on the Earth - are attracted to it.

The force with which a body is attracted to the earth is called gravity.

Under the influence of this force, all bodies tend to take the lowest position on the earth's surface. As a result, water flows in rivers, rain water seep into the thickness of the earth's crust, snow avalanches fall, glaciers move, fragments of rocks move down the slopes. Gravity is a necessary condition for the action of external processes. Otherwise, the weathering products would have remained at the site of their formation, covering the underlying rocks like a cloak.

As you already know, the Earth consists of many chemical elements - oxygen, nitrogen, silicon, iron, etc. When combined, the chemical elements form minerals.

Minerals. Most minerals are made up of two or more chemical elements. You can find out how many elements are contained in a mineral by its chemical formula. For example, halite (table salt) is composed of sodium and chlorine and has the formula NCl; magnetite (magnetic iron ore) - from three molecules of iron and two oxygen (F 3 O 2), etc. Some minerals are formed by one chemical element, for example: sulfur, gold, platinum, diamond, etc. Such minerals are called native. In nature, about 40 native elements are known, which account for 0.1% of the mass of the earth's crust.

Minerals can be not only solid, but also liquid (water, mercury, oil), and gaseous (hydrogen sulfide, carbon dioxide).

Most minerals have a crystalline structure. The shape of the crystal for a given mineral is always constant. For example, quartz crystals have the shape of a prism, halite has the shape of a cube, etc. If table salt is dissolved in water and then crystallized, the newly formed minerals will take on a cubic shape. Many minerals have the ability to grow. Their sizes range from microscopic to gigantic. For example, a beryl crystal 8 m long and 3 m in diameter was found on the island of Madagascar. Its weight is almost 400 tons.

By education, all minerals are divided into several groups. Some of them (feldspar, quartz, mica) are released from magma during its slow cooling at great depths; others (sulphur) - during the rapid cooling of lava; others (garnet, jasper, diamond) - at high temperatures and pressure at great depths; the fourth (garnets, rubies, amethysts) stand out from hot aqueous solutions in underground veins; the fifth (gypsum, salts, brown iron ore) are formed during chemical weathering.

In total, there are more than 2500 minerals in nature. For their definition and study great importance have physical properties, which include brilliance, color, color of the line, i.e., a trace left by a mineral, transparency, hardness, cleavage, fracture, specific gravity. For example, quartz has a prismatic crystal shape, glassy luster, no cleavage, conchoidal fracture, hardness 7, specific gravity 2.65 g / cm 3, has no features; halite has a cubic crystal shape, hardness 2.2, specific gravity 2.1 g / cm 3, glass luster, white color, perfect cleavage, salty taste, etc.

Of the minerals, 40-50 are the most known and widespread, which are called rock-forming (feldspar, quartz, halite, etc.).

Rocks. These rocks are an accumulation of one or more minerals. Marble, limestone, gypsum consist of one mineral, and granite, basalt - from several. In total, there are about 1000 rocks in nature. Depending on the origin - genesis - rocks are divided into three main groups: igneous, sedimentary and metamorphic.

igneous rocks. Formed when magma cools; crystalline structure, do not have layering; do not contain the remains of animals and plants. Among the igneous rocks, deep and erupted are distinguished. deep rocks formed in the depths of the earth's crust, where magma is under high pressure and its cooling is very slow. An example of a deep rock is granite, the most common crystalline rock, consisting mainly of three minerals: quartz, feldspar and mica. The color of granites depends on the color of feldspar. Most often they are gray or pink.

When magma erupts onto the surface, spilled rocks. They represent either a sintered mass resembling slag, or vitreous, then they are called volcanic glass. AT individual cases a fine-grained rock of the basalt type is formed.

Sedimentary rocks. They cover about 80% of the entire surface of the Earth. They are characterized by layering and porosity. As a rule, sedimentary rocks are the result of the accumulation in the seas and oceans of the remains of dead organisms or particles of destroyed hard rock. The accumulation process occurs unevenly, so layers of different thicknesses are formed. Fossils or imprints of animals and plants are found in many sedimentary rocks.

Depending on the place of formation, sedimentary rocks are divided into continental and marine. To continental rocks include, for example, clay. Clays are a crushed product of the destruction of hard rocks. They consist of the smallest scaly particles, have the ability to absorb water. Clays are plastic, waterproof. Their color is different - from white to blue and even black. White clays are used to make porcelain.

Continental origin and widespread rock - loess. It is a fine-grained, non-laminated yellowish rock, consisting of a mixture of quartz, clay particles, lime carbonate and iron oxide hydrates. Easily passes water.

Marine rocks usually formed at the bottom of the oceans. These include some clays, sands, gravel.

Large group of sedimentary biogenic rocks formed from the remains of dead animals and plants. These include limestone, dolomite and some combustible minerals (peat, coal, oil shale).

Especially widespread in the earth's crust is limestone, consisting of calcium carbonate. In its fragments one can easily notice accumulations of small shells and even skeletons of small animals. The color of limestones is different, mostly gray.

Chalk is also formed from the smallest shells - the inhabitants of the sea. Huge reserves of this rock are located in the Belgorod region, where along the steep banks of the rivers you can see outcrops of powerful layers of chalk, which stands out for its whiteness.

Limestones, in which there is an admixture of magnesium carbonate, are called dolomites. Limestones are widely used in construction. They are used to produce lime for plastering and cement. The best cement is made from marl.

In those seas where animals with flint shells used to live, and algae containing flint grew, a rock of tripoli was formed. This is a light, dense, usually yellowish or light gray rock, which is a building material.

Sedimentary rocks also include rocks formed by precipitation from aqueous solutions(gypsum, rock salt, potash salt, brown iron ore, etc.).

metamorphic rocks. This group of rocks was formed from sedimentary and igneous rocks under the influence of high temperatures, pressure, and chemical changes. So, under the action of temperature and pressure on clay, clay shales are formed, on sand - dense sandstones, and on limestones - marble. Changes, i.e., metamorphoses, occur not only with sedimentary rocks, but also with igneous ones. Under the influence of high temperatures and pressure, granite acquires a layered structure and a new rock is formed - gneiss.

High temperature and pressure promote recrystallization of rocks. A very strong crystalline rock, quartzite, is formed from sandstones.

Science has established that more than 2.5 billion years ago, the planet Earth was completely covered by the ocean. Then, under the action of internal forces, the uplift of individual sections of the earth's crust began. The process of uplift was accompanied by violent volcanism, earthquakes, and mountain building. This is how the first land areas appeared - the ancient cores of modern continents. Academician V. A. Obruchev called them "the ancient crown of the Earth."

As soon as the land rose above the ocean, external processes began to operate on its surface. Rocks were destroyed, the destruction products were carried into the ocean and accumulated along its margins in the form of sedimentary rocks. The sediment thickness reached several kilometers, and under its pressure, the ocean floor began to sag. Such giant troughs of the earth's crust under the oceans are called geosynclines. The formation of geosynclines in the history of the Earth has been continuous from ancient times to the present. There are several stages in the life of geosynclines:

– embryonic- deflection of the earth's crust and accumulation of sediments (Fig. 28, A);

– maturation– filling of the trough with sediments when their thickness reaches 15–18 km and radial and lateral pressure arises;

– folding- the formation of folded mountains under the pressure of the internal forces of the Earth (this process is accompanied by violent volcanism and earthquakes) (Fig. 28, B);

– attenuation- destruction of the mountains that have arisen by external processes and the formation of a residual hilly plain in their place (Fig. 28).

Rice. 28. Scheme of the structure of the plain formed as a result of the destruction of the mountains (the dotted line shows the reconstruction of the former mountainous country)

Since sedimentary rocks in the geosyncline are plastic, as a result of the pressure that has arisen, they are crushed into folds. Folded mountains are formed, such as the Alps, the Caucasus, the Himalayas, the Andes, etc.

The periods when folded mountains are actively formed in geosynclines are called periods of folding. Several such epochs are known in the history of the Earth: Baikal, Caledonian, Hercynian, Mesozoic and Alpine.

The process of mountain building in the geosyncline can also cover the extra-geosynclinal areas - the areas of former, now destroyed mountains. Since the rocks here are rigid, devoid of plasticity, they do not crumple into folds, but are broken by faults. Some areas rise, others fall - there are revived blocky and folded-blocky mountains. For example, in the Alpine era of folding, the folded Pamir mountains were formed and the Altai and Sayan mountains were revived. Therefore, the age of mountains is determined not by the time of their formation, but by the age of the folded base, which is always indicated on tectonic maps.

Geosynclines at different stages of development still exist today. So, along the Asian coast of the Pacific Ocean, in the Mediterranean Sea, there is a modern geosyncline, which is undergoing a stage of maturation, and in the Caucasus, in the Andes and other folded mountains, the process of mountain building is being completed; The Kazakh upland is a peneplain, a hilly plain formed on the site of the destroyed mountains of the Caledonian and Hercynian folding. The base of ancient mountains comes to the surface here - small hills - "witness mountains", composed of strong igneous and metamorphic rocks.

Vast areas of the earth's crust, with relatively low mobility and flat terrain, are called platforms. At the base of the platforms, in their foundation, there are strong igneous and metamorphic rocks, which testify to mountain building processes that once took place here. Usually the foundation is covered with a layer of sedimentary rocks. Sometimes the basement rocks come to the surface, forming shields. The age of the platform corresponds to the age of the foundation. The ancient (Precambrian) platforms include the East European, Siberian, Brazilian, etc.

Platforms are mostly plains. They experience predominantly oscillatory movements. However, in some cases, the formation of revived blocky mountains is also possible on them. Thus, as a result of the emergence of the Great African Rifts, the rise and fall of individual sections of the ancient African platform and formed blocky mountains and highlands East Africa, mountains-volcanoes Kenya and Kilimanjaro.

Lithospheric plates and their movement. The doctrine of geosynclines and platforms has received a name in science "fixism" because according to this theory, large blocks of the crust are fixed in one place. In the second half of the XX century. many scholars supported theory of mobilism which is based on the concept of horizontal movements of the lithosphere. According to this theory, the entire lithosphere is divided by deep faults reaching the upper mantle into giant blocks - lithospheric plates. The boundaries between plates can pass both on land and on the bottom of the oceans. In the oceans, these boundaries are usually mid-ocean ridges. In these areas, a large number of faults have been recorded - rifts, along which the substance of the upper mantle pours out to the ocean floor, spreading over it. In those areas where the boundaries between the plates pass, mountain building processes are often activated - in the Himalayas, Andes, Cordillera, Alps, etc. The base of the plates is in the asthenosphere, and along its plastic substrate, lithospheric plates, like giant icebergs, slowly move in different directions (Fig. 29). The movement of the plates is fixed by the most accurate measurements from space. Thus, the African and Arabian coasts of the Red Sea are slowly moving away from each other, which allowed some scientists to call this sea the "embryo" of the future ocean. Space images also make it possible to trace the direction of deep faults in the earth's crust.

Rice. 29. Motion lithospheric plates

The theory of mobilism convincingly explains the formation of mountains, since their formation requires not only radial, but also lateral pressure. Where two plates collide, one of them sinks under the other, and “hummocks”, i.e. mountains, form along the collision boundary. This process is accompanied by earthquakes and volcanism.

Relief- this is a set of irregularities of the earth's surface, differing in height above sea level, origin, etc.

These irregularities give a unique appearance to our planet. The formation of the relief is influenced by both internal, tectonic, and external forces. Due to tectonic processes, mainly large surface irregularities arise - mountains, highlands, etc., and external forces are aimed at their destruction and the creation of smaller relief forms - river valleys, ravines, dunes, etc.

All forms of relief are divided into concave (hollows, river valleys, ravines, beams, etc.), convex (hills, mountain ranges, volcanic cones, etc.), simply horizontal and inclined surfaces. Their size can be very diverse - from a few tens of centimeters to many hundreds and even thousands of kilometers.

Depending on the scale, planetary, macro-, meso- and micro-forms of relief are distinguished.

The planetary ones include the protrusions of the continents and the depressions of the oceans. Continents and oceans are often antipodes. So, Antarctica lies against the Arctic Ocean, North America- against the Indian, Australia - against the Atlantic and only South America - against Southeast Asia.

The depths of oceanic trenches fluctuate widely. The average depth is 3800 m, and the maximum, noted in the Mariana Trench of the Pacific Ocean, is 11,022 m. The highest land point, Mount Everest (Chomolungma), reaches 8848 m. Thus, the height amplitude reaches almost 20 km.

The prevailing depths in the ocean are from 3000 to 6000 m, and the heights on land are less than 1000 m. High mountains and deep-sea depressions cover only fractions of a percent of the Earth's surface.

The average height of the continents and their parts above sea level is also not the same: North America - 700 m, Africa - 640, South America - 580, Australia - 350, Antarctica - 2300, Eurasia - 635 m, and the height of Asia is 950 m, and Europe is only 320 m. Average land height 875 m.

Relief of the ocean floor. At the bottom of the ocean, as well as on land, there are various landforms - mountains, plains, depressions, trenches, etc. They usually have softer outlines than similar landforms, since external processes proceed more calmly here.

In the relief of the ocean floor, there are:

– continental shelf, or shelf (shelf), - a shallow part up to a depth of 200 m, the width of which in some cases reaches many hundreds of kilometers;

– continental slope– rather steep ledge up to a depth of 2500 m;

– ocean bed, which occupies most of the bottom with depths up to 6000 m.

The greatest depths are noted in gutters, or ocean trenches, where they exceed the mark of 6000 m. The trenches usually stretch along the continents along the outskirts of the ocean.

In the central parts of the oceans, there are mid-ocean ridges (rifts): South Atlantic, Australian, Antarctic, etc.

Sushi relief. The main elements of land relief are mountains and plains. They form the macrorelief of the Earth.

mountain they call a hill that has a peak point, slopes, sole line, rising above the terrain above 200 m; an elevation up to 200 m high is called hill. Linearly elongated landforms with a ridge and slopes are mountain ranges. The ridges are separated by located between them mountain valleys. Connecting with each other, mountain ranges form mountain ranges. The collection of ridges, chains and valleys is called mountain node, or mountain country, and in everyday life mountains. For example, the Altai Mountains, the Ural Mountains, etc.

Extensive areas of the earth's surface, consisting of mountain ranges, valleys and high plains, are called highlands. For example, the Iranian Highlands, the Armenian Highlands, etc.

By origin, mountains are tectonic, volcanic and erosional.

tectonic mountains formed as a result of movements of the earth's crust, they consist of one or many folds raised to a considerable height. All the highest mountains in the world - the Himalayas, the Hindu Kush, the Pamirs, the Cordillera, etc. - are folded. They are characterized by pointed peaks, narrow valleys (gorges), elongated ridges.

blocky and fold-block mountains are formed as a result of raising and lowering blocks (blocks) of the earth's crust along the fault planes. The relief of these mountains is characterized by flat tops and watersheds, wide, flat-bottomed valleys. These are, for example, the Ural Mountains, Appalachians, Altai, etc.

volcanic mountains formed as a result of the accumulation of products of volcanic activity.

Widespread on the surface of the earth erosion mountains, which are formed as a result of the dismemberment of high plains by external forces, primarily flowing waters.

According to the height, the mountains are divided into low (up to 1000 m), medium-high (from 1000 to 2000 m), high (from 2000 to 5000 m) and highest (above 5 km).

The height of the mountains is easy to determine by physical map. It can also be used to determine that most of the mountains are medium-high and high. Few peaks rise above 7000 m, and they are all in Asia. Only 12 mountain peaks located in the Karakorum mountains and the Himalayas have a height of more than 8000 m. The highest point of the planet is the mountain, or, more precisely, the mountain junction, Everest (Chomolungma) - 8848 m.

Most of the land surface is occupied by flat spaces. Plains- These are areas of the earth's surface that have a flat or slightly hilly relief. Most often, the plains are slightly sloping.

According to the nature of the surface, the plains are divided into flat, wavy and hilly, but on vast plains, such as Turan or West Siberian, one can meet areas with various forms of surface topography.

Depending on the height above sea level, the plains are divided into base(up to 200 m), sublime(up to 500 m) and high (plateaus)(over 500 m). Elevated and high plains are always strongly dissected by water flows and have a hilly relief, while lowlands are often flat. Some plains are located below sea level. So, the Caspian lowland has a height of 28 m. Quite often on the plains there are closed basins of great depth. For example, the Karagis depression has a mark of 132 m, and the Dead Sea depression - 400 m.

Elevated plains bounded by steep ledges separating them from the surrounding area are called plateau. Such are the Ustyurt, Putorana and other plateaus.

Plateau- flat-topped areas of the earth's surface, can have a significant height. So, for example, the Tibet plateau rises above 5000 m.

By origin, several types of plains are distinguished. Significant areas of land are occupied marine (primary) plains, formed as a result of marine regressions. These are, for example, the Turan, West Siberian, Great Chinese and a number of other plains. Almost all of them belong to the great plains of the planet. Most of them are lowlands, the relief is flat or slightly hilly.

Reservoir plains- These are flat sections of ancient platforms with almost horizontal occurrence of sedimentary rock layers. Such plains include, for example, East European. These plains are mostly hilly.

Small spaces in river valleys are occupied alluvial (alluvial) plains, formed as a result of leveling the surface with river sediments - alluvium. This type includes the Indo-Gangetic, Mesopotamian, and Labrador plains. These plains are low, flat, and very fertile.

Plains are raised high above sea level - lava sheets(Central Siberian Plateau, Ethiopian and Iranian Highlands, Deccan Plateau). Some plains, such as the Kazakh uplands, were formed as a result of the destruction of mountains. They are called erosional. These plains are always elevated and hilly. These hills are composed of solid crystalline rocks and represent the remains of the mountains that once were here, their "roots".

The soil- this is the upper fertile layer of the lithosphere, which has a number of properties inherent in living and inanimate nature.

The formation and existence of this natural body cannot be imagined without living beings. The surface layers of the rock are only the initial substrate, from which, under the influence of plants, microorganisms and animals, different kinds soils.

The founder of soil science, the Russian scientist V.V. Dokuchaev, showed that

the soil- this is an independent natural body formed on the surface of rocks under the influence of living organisms, climate, water, relief, as well as man.

This natural formation has been created for thousands of years. The process of soil formation begins with a settlement on bare rocks, stones of microorganisms. Feeding on carbon dioxide, nitrogen and water vapor from the atmosphere, using the mineral salts of the rock, microorganisms release organic acids as a result of their vital activity. These substances gradually change the chemical composition of rocks, make them less durable and eventually loosen the surface layer. Then lichens settle on such a rock. Unpretentious to water and nutrients, they continue the process of destruction, while enriching the rock with organic matter. As a result of the activity of microorganisms and lichens, the rock gradually turns into a substrate suitable for colonization by plants and animals. The final transformation of the original rock into soil occurs due to the vital activity of these organisms.

Plants absorb carbon dioxide from the atmosphere and water and minerals, create organic compounds. When dying, plants enrich the soil with these compounds. Animals feed on plants and their remains. Their waste products are excrement, and after death, their corpses also fall into the soil. The entire mass of dead organic matter accumulated as a result of the vital activity of plants and animals serves as a food base and habitat for microorganisms and fungi. They destruct organic substances, mineralize them. As a result of the activity of microorganisms, complex organic substances are formed that make up the humus of the soil.

soil humus is a mixture of stable organic compounds formed during the decomposition of plant and animal residues and their metabolic products with the participation of microorganisms.

The breakdown of primary minerals and the formation of clay secondary minerals occur in the soil. Thus, the circulation of substances takes place in the soil.

moisture capacity is the ability of the soil to hold water.

Soil with a lot of sand does not retain water well and has a low water capacity. clay soil, on the contrary, retains a lot of water and has a high moisture capacity. In the case of heavy rainfall, water fills all the pores in such soil, preventing the passage of air deep into. Loose, cloddy soils retain moisture better than dense ones.

moisture permeability is the ability of the soil to pass water.

The soil is permeated with tiny pores - capillaries. Through the capillaries, water can move not only down, but also in all directions, including from bottom to top. The higher the capillarity of the soil, the higher its moisture permeability, the faster water penetrates into the soil and rises from the deeper layers upwards. Water "sticks" to the walls of the capillaries and, as it were, creeps up. The thinner the capillaries, the higher the water rises through them. When the capillaries come to the surface, the water evaporates. Sandy soils are highly permeable, while clay soils are low. If a crust (with many capillaries) has formed on the surface of the soil after rain or watering, the water evaporates very quickly. When loosening the soil, the capillaries are destroyed, which reduces the evaporation of water. No wonder loosening the soil is called dry irrigation.

Soils can have a different structure, i.e., consist of lumps of various shapes and sizes, into which soil particles are glued. At the best soils, for example, chernozems, the structure is finely lumpy or granular. According to the chemical composition of the soil can be rich or poor in nutrients. An indicator of soil fertility is the amount of humus, since it contains all the main plant nutrients. For example, chernozem soils contain up to 30% humus. Soils can be acidic, neutral or alkaline. Neutral soils are the most favorable for plants. To reduce acidity, they are limed, and gypsum is added to the soil to reduce alkalinity.

Mechanical composition of soils. According to the mechanical composition of the soil are divided into clay, sandy, loamy and sandy loamy.

Clay soils have a high moisture capacity and are best provided with batteries.

sandy soils low moisture capacity, well moisture permeable, but poor in humus.

loamy- the most favorable in terms of their physical properties for agriculture, with an average moisture capacity and moisture permeability, well provided with humus.

sandy loam– structureless soils, poor in humus, well water- and air-permeable. To use such soils, it is necessary to improve their composition, to apply fertilizers.

Soil types. In our country, the following types of soils are most common: tundra, podzolic, sod-podzolic, chernozem, chestnut, gray earth, red earth and yellow earth.

tundra soils are located in the Far North in the permafrost zone. They are waterlogged and extremely poor in humus.

Podzolic soils common in the taiga under conifers, and sod-podzolic- under coniferous-deciduous forests. Broad-leaved forests grow on gray forest soils. All these soils contain enough humus and are well structured.

In the forest-steppe and steppe zones are located black earth soils. They were formed under the steppe and herbaceous vegetation, rich in humus. The humus gives the soil a black color. They have a strong structure and have high fertility.

chestnut soils located further south, they form in drier conditions. They are characterized by a lack of moisture.

Serozem soils characteristic of deserts and semi-deserts. They are rich in nutrients, but poor in nitrogen, and there is not enough water here.

Krasnozems and zheltozems are formed in the subtropics in a humid and warm climate. They are well structured, quite water-intensive, but have a lower humus content, so fertilizers are applied to these soils to increase fertility.

To improve soil fertility, it is necessary to regulate not only the content nutrients but also the presence of moisture and aeration. The arable layer of the soil should always be loose to ensure air access to the roots of plants.

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A characteristic property of the globe is its heterogeneity. It is subdivided into a number of layers or spheres, which are divided into internal and external.

Earth's inner spheres: the earth's crust, mantle and core.

Earth's crust the most heterogeneous. In depth, 3 layers are distinguished in it (from top to bottom): sedimentary, granite and basalt.

Sedimentary layer formed by soft, and sometimes loose rocks that arose by the deposition of a substance in water or air environment on the surface of the earth. Sedimentary rocks are usually arranged in layers bounded by parallel planes. The thickness of the layer ranges from a few meters to 10-15 km. There are areas where the sedimentary layer is almost completely absent.

granite layer composed mainly of igneous and metamorphic rocks rich in Al and Si. The average content of SiO 2 in them is more than 60%, so they are classified as acidic rocks. The density of the rocks of the layer is 2.65-2.80 g/cm 3 . Power 20-40 km. In the composition of the oceanic crust (for example, at the bottom of the Pacific Ocean), the granite layer is absent, thus being an integral part of the continental crust.

Basalt layer lies at the base of the earth's crust and is continuous, that is, unlike the granite layer, it is present in the composition of both continental and oceanic crust. It is separated from the granite by the Konrad surface (K), on which the speed of seismic waves changes from 6 to 6.5 km/sec. The substance composing the basalt layer is similar in chemical composition and physical properties to basalts (less rich in SiO 2 than granites). The density of the substance reaches 3.32 g/cm 3 . The velocity of propagation of longitudinal seismic waves increases from 6.5 to 7 km/s at the lower boundary, where again there is a jump in velocity and it reaches 8-8.2 km/s. This lower boundary of the earth's crust can be traced everywhere and is called the Mohorovichic boundary (Yugoslav scientist) or the M.

Mantle located under the earth's crust in the depth range from 8-80 to 2900 km. The temperature in the upper layers (up to 100 km) is 1000-1300 o C, it rises with depth and reaches 2300 o C at the lower boundary. However, the substance is there in a solid state due to pressure, which at great depths is hundreds of thousands and millions of atmospheres. At the boundary with the core (2900 km), refraction and partial reflection of longitudinal seismic waves are observed, while transverse waves do not pass this boundary ("seismic shadow" ranges from 103 o to 143 o of arc). The speed of wave propagation in the lower part of the mantle is 13.6 km/sec.

Relatively recently, it became known that in the upper part of the mantle there is a layer of decompacted rocks - asthenosphere, lying at a depth of 70-150 km (deeper under the oceans), in which a decrease in the velocities of elastic waves by approximately 3% is recorded.

Core in physical properties it differs sharply from the mantle that envelops it. The velocity of longitudinal seismic waves is 8.2-11.3 km/sec. The fact is that at the boundary of the mantle and the core, there is a sharp drop in the velocity of longitudinal waves from 13.6 to 8.1 km/sec. Scientists have long concluded that the density of the core is much higher than the density of the surface shells. It must correspond to the density of iron under appropriate barometric conditions. Therefore, it is widely believed that the core consists of Fe and Ni and has magnetic properties. The presence of these metals in the nucleus is associated with the primary differentiation of the substance by specific gravity. Meteorites also speak in favor of the iron-nickel core. The nucleus is divided into external and internal. In the outer part of the core, the pressure is 1.5 million atm.; density 12 g/cm 3 . Longitudinal seismic waves propagate here at a speed of 8.2-10.4 km/sec. The inner core is in a liquid state, and convective currents in it induce the Earth's magnetic field. In the inner core, the pressure reaches 3.5 million atm., density 17.3-17.9 g/cm 3 , longitudinal wave velocity 11.2-11.3 km/sec. Calculations show that the temperature should reach several thousand degrees there (up to 4000 o). The substance there is in a solid state due to high pressure.

Earth's outer spheres: hydrosphere, atmosphere and biosphere.

Hydrosphere unites the entire set of manifestations of water forms in nature, starting from a continuous water cover that occupies 2/3 of the Earth's surface (seas and oceans) and ending with water that is part of rocks and minerals. in this sense, the hydrosphere is a continuous shell of the Earth. Our course deals primarily with that part of the hydrosphere that forms an independent water layer - oceanosphere.

Of the total area of ​​the Earth of 510 million km 2, 361 million km 2 (71%) is covered with water. Schematically, the topography of the bottom of the World Ocean is depicted as hypsographic curve. It shows the distribution of land height and ocean depth; 2 levels of the seabed are clearly defined with depths of 0-200 m and 3-6 km. The first of them is an area of ​​relative shallow water, encircling the coasts of all continents in the form of an underwater platform. Is it a continental shelf or shelf. From the sea side, the shelf is limited by a steep underwater ledge - continental slope(up to 3000 m). At depths of 3-3.5 km is located continental foot. Below 3500 m begins ocean bed (bed of the ocean), the depth of which is up to 6000 m. The continental foot and the ocean floor constitute the second clearly expressed level of the seabed, composed of a typical oceanic crust (without a granite layer). Among the oceanic bed, mainly in the peripheral parts of the Pacific Ocean, are located deep water trenches (troughs)- from 6000 to 11000 m. This is how the hypsographic curve looked like 20 years ago. One of the most important geological discoveries of recent times was the discovery mid-ocean ridges a global system of seamounts, elevated above the ocean floor by 2 or more kilometers and occupying up to 1/3 of the ocean floor. The geological significance of this discovery will be discussed later.

Almost all known chemical elements are present in the water of the oceans, however, only 4 prevail: O 2, H 2, Na, Cl. The content of chemical compounds dissolved in sea water (salinity) is determined in weight percent or ppm(1 ppm = 0.1%). The average salinity of ocean water is 35 ppm (35 g of salts in 1 liter of water). Salinity varies widely. So, in the Red Sea it reaches 52 ppm, in the Black Sea up to 18 ppm.

Atmosphere represents the uppermost air shell of the Earth, which envelops it with a continuous cover. The upper limit is not clear, since the density of the atmosphere decreases with height and gradually passes into the airless space. The lower boundary is the surface of the Earth. This boundary is also conditional, since air penetrates to a certain depth into the stone shell and is contained in dissolved form in the water column. There are 5 main spheres in the atmosphere (from bottom to top): troposphere, stratosphere, mesosphere, ionosphere and exosphere. For geology, the troposphere is important, since it is in direct contact with the earth's crust and has a significant impact on it.

The troposphere is distinguished by its high density, the constant presence of water vapor, carbon dioxide and dust; gradual decrease in temperature with height and the existence of vertical and horizontal air circulation in it. AT chemical composition in addition to the main elements - O 2 and N 2 - CO 2, water vapor, some inert gases (Ar), H 2, sulfur dioxide and dust are always present. Air circulation in the troposphere is very complex.

Biosphere- a kind of shell (identified and named by Academician V.I. Vernadsky), unites those shells in which life is present. It does not occupy a separate space, but penetrates into the earth's crust, atmosphere and hydrosphere. The biosphere plays an important role in geological processes, participating both in the creation of rocks and in their destruction.

Living organisms penetrate most deeply into the hydrosphere, which is often called the "cradle of life". Life is especially rich in the oceanosphere, in its surface layers. Depending on the physical and geographical situation, primarily on the depths, several bionomic zones(Greek "bios" - life, "nomos" - law). These zones differ in the conditions of existence of organisms and their composition. There are 2 zones in the shelf area: littoral and neritic. The littoral is a relatively narrow strip of shallow water, drained twice a day at low tide. Due to its specificity, the littoral is inhabited by organisms that can tolerate temporary drying (marine worms, some molluscs, sea urchins, and stars). Deeper than the tidal zone within the shelf is the nerite zone, which is most richly populated by a variety of marine organisms. All types of the animal world are widely represented here. Distinguished by way of life benthic animals (bottom dwellers): sedentary benthos (corals, sponges, bryozoans, etc.), wandering benthos (crawling - hedgehogs, stars, crayfish). Nektonic animals are able to move independently (fish, cephalopods); planktonic (plankton) - hovering in water in suspension (foraminifera, radiolarians, jellyfish). corresponds to the continental slope bathyal zone, continental foot and oceanic bed - abyssal zone. Living conditions in them are not very favorable - complete darkness, high pressure, lack of algae. However, there have recently been discovered abyssal oases of life, confined to underwater volcanoes and zones of hydrothermal outflow. The biota here is based on giant anaerobic bacteria, vestimentifera and other peculiar organisms.

The depth of penetration of living organisms into the Earth is mainly limited by temperature conditions. Theoretically, for the most resistant prokaryotes, it is 2.5-3 km. Living matter actively influences the composition of the atmosphere, which in its modern form is the result of the vital activity of organisms that have enriched it with oxygen, carbon dioxide, and nitrogen. The role of organisms in the formation of marine sediments is extremely great, many of which are minerals (caustobiolites, jaspilites, etc.).

Questions for self-examination.

How were views on the origin of the solar system formed?

What is the shape and size of the earth?

What hard shells does the Earth consist of?

How is continental crust different from oceanic?

What causes the earth's magnetic field?

What is a hypsographic curve, its type?

What is benthos?

What is the biosphere, its boundaries?

The result of the geological development of the Earth was the formation of the uppermost shells - the atmosphere, hydrosphere and lithosphere. This happened as a result of the cooling of the Earth's surface and led to the formation of primary basaltic or close to it in the composition of the Earth's crust. Almost simultaneously, due to the condensation of water vapor, the planet's water shell, the hydrosphere, was formed.

Formation and structure of the lithosphere. The earth's crust is formed by rocks that have various forms of occurrence. The rocks lie in horizontal layers or are disturbed by faults and crumpled by folds. The occurrence of rocks is most often due to internal (endogenous) forces. The structure of the earth's crust, created by endogenous processes, is called a tectonic structure, or tectonics.

The modern topography of the planet has evolved over many hundreds of millions of years and continues to change under the influence of the combined action of tectonic, hydrospheric, atmospheric and biological processes on its surface. This began about 3.5 billion years ago, when volcanic arcs began to form. The formation of volcanic arcs took place on the primary residual or secondary crust, formed during the stretching of the oceanic crust above the zones of subsidence (collisions of lithospheric plates and their crawling under each other with the formation of a volcanic arc). As a result, approximately 2.7-2.5 billion years ago, significant areas of the continental crust arose, which, apparently, merged into a single supercontinent - the first Pangea in the history of the Earth. The thickness of this crust has already reached the modern thickness of 35-40 km. Her lower part is under the influence high pressures and temperatures experienced significant transformations, and at medium levels there was a melting of large masses of granite.

The next important moment in the development of the Earth took place approximately 2.5 billion years ago. The supercontinent that arose at the previous stage - the first Pangea - underwent significant changes and 2.2 billion years ago broke up into separate, relatively small continents, separated by basins with newly formed oceanic crust. Separate traces of these stages of plate tectonics can be found even now. The first stage (before the emergence of Pangea) is commonly called embryonic plate tectonics, and the second - small plate tectonics. By the end of the second period, about 1.7 billion years ago, the continents again merged into a single supercontinent. Pangea-N was formed. Its disintegration began about 1 billion years ago, although partial separations and reunions could have taken place even before that.

In the interval of 1-0.6 billion years ago, the structural plan of the Earth underwent radical changes and significantly approached the modern one. From that moment began full-scale plate tectonics. It is due to the fact that the Earth's lithosphere is divided into a limited number of large (5 thousand km) and medium (1 thousand km) rigid and monolithic plates in diameter, which are located on a more plastic and viscous shell - the asthenosphere. Lithospheric plates began to move along the asthenosphere in a horizontal direction, forming extensions and crawlings, which, on average, compensate each other on a planetary scale. Thus, in the history of the Earth as a planet, the process of formation and disintegration of Pangea has repeatedly occurred. The duration of such cycles is 500-600 million years. This large-scale periodicity is superimposed by smaller-scale periodicity associated with stretching and compression of the earth's crust.

As a result of tectonic activity, the relief of the earth's surface today is characterized by a global asymmetry of two hemispheres (Northern and Southern): one of them is a giant space filled with water. These are oceans, occupying more than 70% of the entire surface. In the other hemisphere, crustal uplifts are concentrated, forming continents. The global asymmetry in the structure of the surface of our planet was noticed long ago, which made it possible to divide the planetary relief into two main areas - oceanic and continental. The bottom of the oceans and continents differ from each other in the structure of the earth's crust, chemical and petrographic composition, as well as the history of geological development. The crust has an increased thickness in the area of ​​the continents and a reduced one in the areas of the ocean floor.

The average thickness of the continental crust is 35 km. Its upper layer is rich in granitic rocks, the lower layer is rich in basalt magmas. There is no granite layer at the bottom of the oceans, and the earth's crust consists only of a basalt layer. Its thickness is 5-10 km. In addition, continental crust contains more heat-generating radioactive elements than thin oceanic crust.

The earth's crust, which forms the upper part of the lithosphere, is mainly composed of eight chemical elements: oxygen, silicon, aluminum, iron, calcium, magnesium, sodium, and potassium. Half of the total mass of the crust is oxygen, which is contained in it in a bound state, mainly in the form of metal oxides.

The earth's crust is composed of rocks of various types and various origins. More than 70% are igneous rocks, 20% are metamorphic, 9% are sedimentary rocks.

We should not forget that the surface of the Earth is composed of lithospheric plates, the number and position of which changed from epoch to epoch. The plate is the entire mass of the earth's crust and the underlying mantle, which move as a whole along the surface of the earth. Today, 8-9 large plates and more than 10 small ones are distinguished. Plates slowly move horizontally (global plate tectonics). In areas of rift valleys, where the mantle material is carried outward, the plates diverge, and in places where the horizontal displacements of neighboring plates turn out to be opposite, they push each other. Along the boundaries of the lithospheric plates there are zones of increased tectonic activity.

When the plates move, their edges are crushed, forming mountain ranges or entire mountainous regions. Oceanic plates, originating in rift faults, increase in thickness as they approach the continents. They go under the island arcs or the continental plate, dragging the accumulated sedimentary rocks with them. The substance of the subducting plate reaches depths of up to 500-700 km in the mantle, where it begins to melt.