A characteristic feature of the evolution of the Earth is the differentiation of matter, the expression of which is the shell structure of our planet. The lithosphere, hydrosphere, atmosphere, biosphere form the main shells of the Earth, differing in chemical composition, thickness and state of matter.

Internal structure of the Earth

Chemical composition of the Earth(Fig. 1) is similar to the composition of other terrestrial planets, such as Venus or Mars.

In general, elements such as iron, oxygen, silicon, magnesium, and nickel predominate. The content of light elements is low. The average density of the Earth's substance is 5.5 g/cm 3 .

There is very little reliable data on the internal structure of the Earth. Let's look at Fig. 2. It depicts the internal structure of the Earth. The Earth consists of the crust, mantle and core.

Rice. 1. Chemical composition of the Earth

Rice. 2. Internal structure of the Earth

Core

Core(Fig. 3) is located in the center of the Earth, its radius is about 3.5 thousand km. The temperature of the core reaches 10,000 K, i.e. it is higher than the temperature of the outer layers of the Sun, and its density is 13 g/cm 3 (compare: water - 1 g/cm 3). The core is believed to be composed of iron and nickel alloys.

The outer core of the Earth has a greater thickness than the inner core (radius 2200 km) and is in a liquid (molten) state. The inner core is subject to enormous pressure. The substances that compose it are in a solid state.

Mantle

Mantle- the Earth’s geosphere, which surrounds the core and makes up 83% of the volume of our planet (see Fig. 3). Its lower boundary is located at a depth of 2900 km. The mantle is divided into a less dense and plastic upper part (800-900 km), from which it is formed magma(translated from Greek means “thick ointment”; this is the molten substance of the earth’s interior - a mixture of chemical compounds and elements, including gases, in a special semi-liquid state); and the crystalline lower one, about 2000 km thick.

Rice. 3. Structure of the Earth: core, mantle and crust

Earth's crust

Earth's crust - the outer shell of the lithosphere (see Fig. 3). Its density is approximately two times less than the average density of the Earth - 3 g/cm 3 .

Separates the earth's crust from the mantle Mohorovicic border(often called the Moho boundary), characterized by a sharp increase in seismic wave velocities. It was installed in 1909 by a Croatian scientist Andrei Mohorovicic (1857- 1936).

Since the processes occurring in the uppermost part of the mantle affect the movements of matter in the earth's crust, they are combined under the general name lithosphere(stone shell). The thickness of the lithosphere ranges from 50 to 200 km.

Below the lithosphere is located asthenosphere- less hard and less viscous, but more plastic shell with a temperature of 1200 ° C. It can cross the Moho boundary, penetrating into the earth's crust. The asthenosphere is the source of volcanism. It contains pockets of molten magma, which penetrates into the earth's crust or pours out onto the earth's surface.

Composition and structure of the earth's crust

Compared to the mantle and core, the earth's crust is a very thin, hard and brittle layer. It is composed of a lighter substance, which currently contains about 90 natural chemical elements. These elements are not equally represented in the earth's crust. Seven elements - oxygen, aluminum, iron, calcium, sodium, potassium and magnesium - account for 98% of the mass of the earth's crust (see Fig. 5).

Peculiar combinations of chemical elements form various rocks and minerals. The oldest of them are at least 4.5 billion years old.

Rice. 4. Structure of the earth's crust

Rice. 5. Composition of the earth's crust

Mineral is a relatively homogeneous natural body in its composition and properties, formed both in the depths and on the surface of the lithosphere. Examples of minerals are diamond, quartz, gypsum, talc, etc. (You will find characteristics of the physical properties of various minerals in Appendix 2.) The composition of the Earth's minerals is shown in Fig. 6.

Rice. 6. General mineral composition of the Earth

Rocks consist of minerals. They can be composed of one or several minerals.

Sedimentary rocks - clay, limestone, chalk, sandstone, etc. - were formed by the precipitation of substances in the aquatic environment and on land. They lie in layers. Geologists call them pages of the history of the Earth, since they can learn about the natural conditions that existed on our planet in ancient times.

Among sedimentary rocks, organogenic and inorganogenic (clastic and chemogenic) are distinguished.

Organogenic Rocks are formed as a result of the accumulation of animal and plant remains.

Clastic rocks are formed as a result of weathering, destruction by water, ice or wind of the products of destruction of previously formed rocks (Table 1).

Table 1. Clastic rocks depending on the size of the fragments

Breed name	Size of bummer con (particles)
	More than 50 cm
	5 mm - 1 cm
	1 mm - 5 mm
Sand and sandstones	0.005 mm - 1 mm
	Less than 0.005mm

Chemogenic Rocks are formed as a result of the precipitation of substances dissolved in them from the waters of seas and lakes.

In the thickness of the earth's crust, magma forms igneous rocks(Fig. 7), for example granite and basalt.

Sedimentary and igneous rocks, when immersed to great depths under the influence of pressure and high temperatures, undergo significant changes, turning into metamorphic rocks. For example, limestone turns into marble, quartz sandstone into quartzite.

The structure of the earth's crust is divided into three layers: sedimentary, granite, and basalt.

Sedimentary layer(see Fig. 8) is formed mainly by sedimentary rocks. Clays and shales predominate here, and sandy, carbonate and volcanic rocks are widely represented. In the sedimentary layer there are deposits of such minerals, like coal, gas, oil. All of them are of organic origin. For example, coal is a product of the transformation of plants of ancient times. The thickness of the sedimentary layer varies widely - from complete absence in some land areas to 20-25 km in deep depressions.

Rice. 7. Classification of rocks by origin

"Granite" layer consists of metamorphic and igneous rocks, similar in their properties to granite. The most common here are gneisses, granites, crystalline schists, etc. The granite layer is not found everywhere, but on continents where it is well expressed, its maximum thickness can reach several tens of kilometers.

"Basalt" layer formed by rocks close to basalts. These are metamorphosed igneous rocks, denser than the rocks of the “granite” layer.

The thickness and vertical structure of the earth's crust are different. There are several types of the earth's crust (Fig. 8). According to the simplest classification, a distinction is made between oceanic and continental crust.

Continental and oceanic crust vary in thickness. Thus, the maximum thickness of the earth’s crust is observed under mountain systems. It is about 70 km. Under the plains the thickness of the earth's crust is 30-40 km, and under the oceans it is thinnest - only 5-10 km.

Rice. 8. Types of the earth's crust: 1 - water; 2- sedimentary layer; 3—interlayering of sedimentary rocks and basalts; 4 - basalts and crystalline ultrabasic rocks; 5 – granite-metamorphic layer; 6 – granulite-mafic layer; 7 - normal mantle; 8 - decompressed mantle

The difference between the continental and oceanic crust in the composition of rocks is manifested in the fact that there is no granite layer in the oceanic crust. And the basalt layer of the oceanic crust is very unique. In terms of rock composition, it differs from a similar layer of continental crust.

The boundary between land and ocean (zero mark) does not record the transition of the continental crust to the oceanic one. The replacement of continental crust by oceanic crust occurs in the ocean at a depth of approximately 2450 m.

Rice. 9. Structure of the continental and oceanic crust

There are also transitional types of the earth's crust - suboceanic and subcontinental.

Suboceanic crust located along continental slopes and foothills, can be found in marginal and Mediterranean seas. It represents continental crust with a thickness of up to 15-20 km.

Subcontinental crust located, for example, on volcanic island arcs.

Based on materials seismic sounding - the speed of passage of seismic waves - we obtain data on the deep structure of the earth’s crust. Thus, the Kola superdeep well, which for the first time made it possible to see rock samples from a depth of more than 12 km, brought a lot of unexpected things. It was assumed that at a depth of 7 km a “basalt” layer should begin. In reality, it was not discovered, and gneisses predominated among the rocks.

Change in temperature of the earth's crust with depth. The surface layer of the earth's crust has a temperature determined by solar heat. This heliometric layer(from the Greek helio - Sun), experiencing seasonal temperature fluctuations. Its average thickness is about 30 m.

Below is an even thinner layer, the characteristic feature of which is a constant temperature corresponding to the average annual temperature of the observation site. The depth of this layer increases in continental climates.

Even deeper in the earth's crust there is a geothermal layer, the temperature of which is determined by the internal heat of the Earth and increases with depth.

The increase in temperature occurs mainly due to the decay of radioactive elements that make up rocks, primarily radium and uranium.

The amount of temperature increase in rocks with depth is called geothermal gradient. It varies within a fairly wide range - from 0.1 to 0.01 °C/m - and depends on the composition of rocks, the conditions of their occurrence and a number of other factors. Under the oceans, temperature increases faster with depth than on continents. On average, with every 100 m of depth it becomes warmer by 3 °C.

The reciprocal of the geothermal gradient is called geothermal stage. It is measured in m/°C.

The heat of the earth's crust is an important energy source.

The part of the earth's crust that extends to depths accessible to geological study forms bowels of the Earth. The Earth's interior requires special protection and reasonable use.

According to modern concepts of geology, our planet consists of several layers - geospheres. They differ in physical properties, chemical composition and In the center of the Earth there is a core, followed by the mantle, then the earth's crust, hydrosphere and atmosphere.

In this article we will look at the structure of the earth's crust, which is the upper part of the lithosphere. It is an outer solid shell whose thickness is so small (1.5%) that it can be compared to a thin film on the scale of the entire planet. However, despite this, it is the upper layer of the earth’s crust that is of great interest to humanity as a source of minerals.

The earth's crust is conventionally divided into three layers, each of which is remarkable in its own way.

1. The top layer is sedimentary. It reaches a thickness of 0 to 20 km. Sedimentary rocks are formed due to the deposition of substances on land, or their settling at the bottom of the hydrosphere. They are part of the earth's crust, located in it in successive layers.
2. The middle layer is granite. Its thickness can vary from 10 to 40 km. This is an igneous rock that formed a solid layer as a result of eruptions and subsequent solidification of magma in the earth at high pressure and temperature.
3. The lower layer, which is part of the structure of the earth's crust, is basalt, also of magmatic origin. It contains higher amounts of calcium, iron and magnesium, and its mass is greater than that of granite rock.

The structure of the earth's crust is not the same everywhere. The oceanic crust and the continental crust have especially striking differences. Under the oceans the earth's crust is thinner, and under the continents it is thicker. It is thickest in mountainous areas.

The composition includes two layers - sedimentary and basalt. Below the basalt layer is the Moho surface, and behind it is the upper mantle. The ocean floor has complex relief forms. Among all their diversity, a special place is occupied by the huge mid-ocean ridges, in which young basaltic oceanic crust is born from the mantle. Magma has access to the surface through a deep fault - a rift, which runs along the center of the ridge along the peaks. Outside, magma spreads, thereby constantly pushing the walls of the gorge to the sides. This process is called “spreading”.

The structure of the earth's crust is more complex on continents than under the oceans. The continental crust occupies a much smaller area than the oceanic crust - up to 40% of the earth's surface, but has a much greater thickness. Below it reaches a thickness of 60-70 km. The continental crust has a three-layer structure - a sedimentary layer, granite and basalt. In areas called shields, a granite layer is on the surface. As an example, it is made of granite rocks.

The underwater extreme part of the continent - the shelf, also has a continental structure of the earth's crust. It also includes the islands of Kalimantan, New Zealand, New Guinea, Sulawesi, Greenland, Madagascar, Sakhalin, etc. As well as internal and marginal seas: Mediterranean, Azov, Black.

It is possible to draw a boundary between the granite layer and the basalt layer only conditionally, since they have a similar speed of passage of seismic waves, which is used to determine the density of the earth’s layers and their composition. The basalt layer is in contact with the Moho surface. The sedimentary layer can have different thicknesses, depending on the landform located on it. In the mountains, for example, it is either absent altogether or has a very small thickness, due to the fact that loose particles move down the slopes under the influence of external forces. But it is very powerful in foothill areas, depressions and basins. So, in it reaches 22 km.

Studying the internal structure of planets, including our Earth, is an extremely difficult task. We cannot physically “drill” the earth’s crust right down to the core of the planet, therefore all the knowledge we have acquired at the moment is knowledge obtained “by touch,” and in the most literal way.

How seismic exploration works using the example of oil field exploration. We “call” the earth and “listen” to what the reflected signal will bring us

The fact is that the simplest and most reliable way to find out what is under the surface of the planet and is part of its crust is to study the speed of propagation seismic waves in the depths of the planet.

It is known that the speed of longitudinal seismic waves increases in denser media and, on the contrary, decreases in loose soils. Accordingly, knowing the parameters of different types of rock and having calculated data on pressure, etc., “listening” to the response received, you can understand through which layers of the earth’s crust the seismic signal passed and how deep they are under the surface.

Studying the structure of the earth's crust using seismic waves

Seismic vibrations can be caused by two types of sources: natural And artificial. Natural sources of vibrations are earthquakes, the waves of which carry the necessary information about the density of the rocks through which they penetrate.

The arsenal of artificial sources of vibrations is more extensive, but first of all, artificial vibrations are caused by an ordinary explosion, but there are also more “subtle” ways of working - generators of directed pulses, seismic vibrators, etc.

Conducting blasting operations and studying seismic wave velocities seismic survey- one of the most important branches of modern geophysics.

What did the study of seismic waves inside the Earth give? An analysis of their distribution revealed several jumps in the change in speed when passing through the bowels of the planet.

Earth's crust

The first jump, in which speeds increase from 6.7 to 8.1 km/s, according to geologists, is recorded base of the earth's crust. This surface is located in different places on the planet at different levels, from 5 to 75 km. The boundary between the earth's crust and the underlying shell, the mantle, is called "Mohorovicic surfaces", named after the Yugoslav scientist A. Mohorovicic who first established it.

Mantle

Mantle lies at depths of up to 2,900 km and is divided into two parts: upper and lower. The boundary between the upper and lower mantle is also recorded by a jump in the speed of propagation of longitudinal seismic waves (11.5 km/s) and is located at depths from 400 to 900 km.

The upper mantle has a complex structure. In its upper part there is a layer located at depths of 100-200 km, where transverse seismic waves attenuate by 0.2-0.3 km/s, and the velocities of longitudinal waves essentially do not change. This layer is named waveguide. Its thickness is usually 200-300 km.

The part of the upper mantle and crust that lies above the waveguide is called lithosphere, and the layer of reduced velocities itself - asthenosphere.

Thus, the lithosphere is a rigid, solid shell underlain by a plastic asthenosphere. It is assumed that processes occur in the asthenosphere that cause movement of the lithosphere.

The internal structure of our planet

Earth's core

At the base of the mantle there is a sharp decrease in the speed of propagation of longitudinal waves from 13.9 to 7.6 km/s. At this level lies the boundary between the mantle and Earth's core, deeper than which transverse seismic waves no longer propagate.

The radius of the core reaches 3500 km, its volume: 16% of the volume of the planet, and mass: 31% of the mass of the Earth.

Many scientists believe that the core is in a molten state. Its outer part is characterized by sharply reduced values ​​of the velocities of longitudinal waves; in the inner part (with a radius of 1200 km) the velocities of seismic waves increase again to 11 km/s. The density of the core rocks is 11 g/cm 3, and it is determined by the presence of heavy elements. Such a heavy element could be iron. Most likely, iron is an integral part of the core, since a core of pure iron or iron-nickel composition should have a density 8-15% higher than the existing density of the core. Therefore, oxygen, sulfur, carbon and hydrogen appear to be attached to the iron in the core.

Geochemical method for studying the structure of planets

There is another way to study the deep structure of planets - geochemical method. The identification of different shells of the Earth and other terrestrial planets according to physical parameters finds quite clear geochemical confirmation based on the theory of heterogeneous accretion, according to which the composition of the cores of planets and their outer shells is, for the most part, initially different and depends on the earliest stage of their development.

As a result of this process, the heaviest ones were concentrated in the core ( iron-nickel) components, and in the outer shells - lighter silicate ( chondritic), enriched in the upper mantle with volatile substances and water.

The most important feature of the terrestrial planets (Earth) is that their outer shell, the so-called bark, consists of two types of substance: " mainland" - feldspathic and " oceanic" - basalt.

Continental crust of the Earth

The continental (continental) crust of the Earth is composed of granites or rocks similar to them in composition, that is, rocks with a large amount of feldspars. The formation of the “granite” layer of the Earth is due to the transformation of older sediments in the process of granitization.

The granite layer should be considered as specific the shell of the Earth's crust - the only planet on which the processes of differentiation of matter with the participation of water and having a hydrosphere, an oxygen atmosphere and a biosphere have been widely developed. On the Moon and, probably, on the terrestrial planets, the continental crust is composed of gabbro-anorthosites - rocks consisting of a large amount of feldspar, although of a slightly different composition than in granites.

The oldest (4.0-4.5 billion years) surfaces of the planets are composed of these rocks.

Oceanic (basaltic) crust of the Earth

Oceanic (basaltic) crust The earth was formed as a result of stretching and is associated with zones of deep faults, which led to the penetration of the basalt centers of the upper mantle. Basaltic volcanism is superimposed on previously formed continental crust and is a relatively younger geological formation.

Manifestations of basaltic volcanism on all terrestrial planets are apparently similar. The widespread development of basalt “seas” on the Moon, Mars, and Mercury is obviously associated with stretching and the formation, as a result of this process, of permeability zones along which basaltic melts of the mantle rushed to the surface. This mechanism of manifestation of basaltic volcanism is more or less similar for all terrestrial planets.

The Earth's satellite, the Moon, also has a shell structure that generally replicates that of the Earth, although it has a striking difference in composition.

Heat flow of the Earth. It is hottest in the areas of faults in the earth's crust, and coldest in areas of ancient continental plates

Method for measuring heat flow to study the structure of planets

Another way to study the deep structure of the Earth is to study its heat flow. It is known that the Earth, hot from the inside, gives up its heat. The heating of deep horizons is evidenced by volcanic eruptions, geysers, and hot springs. Heat is the main energy source of the Earth.

The increase in temperature with depth from the Earth's surface averages about 15° C per 1 km. This means that at the boundary of the lithosphere and asthenosphere, located at approximately a depth of 100 km, the temperature should be close to 1500 ° C. It has been established that at this temperature the melting of basalts occurs. This means that the asthenospheric shell can serve as a source of magma of basaltic composition.

With depth, the temperature changes according to a more complex law and depends on the change in pressure. According to calculated data, at a depth of 400 km the temperature does not exceed 1600 ° C and at the boundary of the core and mantle is estimated at 2500-5000 ° C.

It has been established that heat release occurs constantly over the entire surface of the planet. Heat is the most important physical parameter. Some of their properties depend on the degree of heating of rocks: viscosity, electrical conductivity, magnetism, phase state. Therefore, by the thermal state one can judge the deep structure of the Earth.

Measuring the temperature of our planet at great depths is a technically difficult task, since only the first kilometers of the earth’s crust are available for measurements. However, the Earth's internal temperature can be studied indirectly through heat flow measurements.

Despite the fact that the main source of heat on Earth is the Sun, the total power of the heat flow of our planet is 30 times greater than the power of all power plants on Earth.

Measurements have shown that the average heat flow on continents and oceans is the same. This result is explained by the fact that in the oceans most of the heat (up to 90%) comes from the mantle, where the process of transfer of matter by moving flows is more intense - convection.

Convection is a process in which heated fluid expands, becoming lighter, and rises, while cooler layers sink. Since mantle matter is closer in its state to a solid body, convection in it occurs under special conditions, at low flow rates of the material.

What is the thermal history of our planet? Its initial heating is probably associated with the heat generated by the collision of particles and their compaction in their own gravity field. The heat then resulted from radioactive decay. Under the influence of heat, a layered structure of the Earth and the terrestrial planets arose.

Radioactive heat is still being released in the Earth. There is a hypothesis according to which, at the border of the Earth’s molten core, the processes of splitting matter continue to this day with the release of a huge amount of thermal energy, heating the mantle.

A distinctive feature of the earth's lithosphere, associated with the phenomenon of global tectonics of our planet, is the presence of two types of crust: continental, which makes up the continental masses, and oceanic. They differ in composition, structure, thickness and the nature of the prevailing tectonic processes. The oceanic crust plays an important role in the functioning of the single dynamic system that is the Earth. To clarify this role, it is first necessary to consider its inherent features.

General characteristics

The oceanic type of crust forms the largest geological structure on the planet - the ocean floor. This crust has a small thickness - from 5 to 10 km (for comparison, the thickness of continental-type crust is on average 35-45 km and can reach 70 km). It occupies about 70% of the total surface area of ​​the Earth, but is almost four times smaller in mass than the continental crust. The average density of rocks is close to 2.9 g/cm3, that is, higher than that of the continents (2.6-2.7 g/cm3).

Unlike isolated blocks of continental crust, oceanic crust is a single planetary structure, which, however, is not monolithic. The Earth's lithosphere is divided into a number of moving plates formed by sections of the crust and the underlying upper mantle. The oceanic type of crust is present on all lithospheric plates; there are plates (for example, the Pacific or Nazca) that do not have continental masses.

Plate tectonics and crustal age

The oceanic plate includes large structural elements such as stable platforms - thalassocratons - and active mid-ocean ridges and deep-sea trenches. Ridges are areas of spreading, or the moving apart of plates and the formation of new crust, and trenches are zones of subduction, or the movement of one plate under the edge of another, where the crust is destroyed. Thus, its continuous renewal occurs, as a result of which the age of the oldest crust of this type does not exceed 160-170 million years, that is, it was formed in the Jurassic period.

On the other hand, it should be borne in mind that the oceanic type appeared on Earth earlier than the continental one (probably at the Catarchean-Archaean boundary, about 4 billion years ago), and is characterized by a much more primitive structure and composition.

What and how is the earth's crust composed under the oceans?

Currently, three main layers of oceanic crust are usually distinguished:

1. Sedimentary. It is formed mainly by carbonate rocks, partly by deep-sea clays. Near the slopes of continents, especially near deltas of large rivers, there are also terrigenous sediments entering the ocean from land. In these areas, the thickness of precipitation can be several kilometers, but on average it is small - about 0.5 km. Near mid-ocean ridges there is virtually no precipitation.
2. Basaltic. These are pillow-type lavas that erupt, as a rule, under water. In addition, this layer includes the complex complex of dikes located below - special intrusions - of dolerite (that is, also basaltic) composition. Its average thickness is 2-2.5 km.
3. Gabbro-serpentinite. It is composed of an intrusive analogue of basalt - gabbro, and in the lower part - serpentinites (metamorphosed ultrabasic rocks). The thickness of this layer, according to seismic data, reaches 5 km, and sometimes more. Its base is separated from the upper mantle underlying the crust by a special interface - the Mohorovicic boundary.

The structure of the oceanic crust indicates that, in fact, this formation can in some sense be considered as a differentiated upper layer of the earth's mantle, consisting of its crystallized rocks, which is covered on top by a thin layer of marine sediments.

"Conveyor" of the ocean floor

It is clear why this crust contains few sedimentary rocks: they simply do not have time to accumulate in significant quantities. Growing from spreading zones in the areas of mid-ocean ridges due to the supply of hot mantle material during the convection process, lithospheric plates seem to carry the oceanic crust further and further from the place of formation. They are carried away by the horizontal section of the same slow but powerful convective current. In the subduction zone, the plate (and the crust in its composition) sinks back into the mantle as the cold part of this flow. A significant part of the sediments is torn off, crushed and ultimately goes towards the growth of continental-type crust, that is, towards a reduction in the area of ​​the oceans.

The oceanic type of crust is characterized by such an interesting property as strip magnetic anomalies. These alternating areas of direct and reverse magnetization of basalt are parallel to the spreading zone and are located symmetrically on both sides of it. They arise during the crystallization of basaltic lava, when it acquires residual magnetization in accordance with the direction of the geomagnetic field in a particular era. Since it experienced reversals many times, the direction of magnetization was periodically reversed. This phenomenon is used in paleomagnetic geochronological dating, and half a century ago it served as one of the most compelling arguments in favor of the correctness of the theory of plate tectonics.

Oceanic type of crust in the cycle of matter and in the heat balance of the Earth

Participating in the processes of lithospheric plate tectonics, the oceanic crust is an important element of long-term geological cycles. This is, for example, the slow mantle-oceanic water cycle. The mantle contains a lot of water, and a considerable amount of it enters the ocean during the formation of the basalt layer of the young crust. But during its existence, the crust, in turn, is enriched due to the formation of the sedimentary layer with ocean water, a significant proportion of which, partly in a bound form, goes into the mantle during subduction. Similar cycles operate for other substances, for example, carbon.

Plate tectonics plays a key role in the Earth's energy balance, allowing for slow heat transfer from hot interior regions and heat loss from the surface. Moreover, it is known that throughout its geological history the planet has lost up to 90% of its heat through the thin crust under the oceans. If this mechanism did not work, the Earth would get rid of excess heat in a different way - perhaps, like Venus, where, as many scientists assume, global destruction of the crust occurred when superheated mantle material broke through to the surface. Thus, the importance of the oceanic crust for the functioning of our planet in a mode suitable for the existence of life is also extremely great.

Such a question as the structure of the Earth interests many scientists, researchers and even believers. With the rapid development of science and technology since the beginning of the 18th century, many worthy workers of science have spent a lot of effort in order to understand our planet. Daredevils descended to the bottom of the ocean, flew into the highest layers of the atmosphere, and drilled enormously deep wells to study soils.

Today there is a fairly complete picture of what the Earth is made of. True, the structure of the planet and all its regions is still not 100% known, but scientists are gradually expanding the boundaries of knowledge and are receiving more and more objective information on this matter.

Shape and size of planet Earth

The shape and geometric dimensions of the Earth are the basic concepts by which it is described as a celestial body. In the Middle Ages, it was believed that the planet was flat in shape, located at the center of the Universe, and the Sun and other planets revolved around it.

But such brave naturalists as Giordano Bruno, Nicolaus Copernicus, Isaac Newton refuted such judgments and mathematically proved that the Earth has the shape of a ball with flattened poles and rotates around the Sun, and not vice versa.

The structure of the planet is very diverse, despite the fact that its dimensions are quite small by the standards of even the solar system - the length of the equatorial radius is 6378 kilometers, the polar radius is 6356 km.

The length of one of the meridians is 40,008 km, and the equator extends for 40,007 km. This also shows that the planet is somewhat “flattened” between the poles, its weight is 5.9742 × 10 24 kg.

Earth shells

The earth consists of many shells that form unique layers. Each layer is centrally symmetrical with respect to the base center point. If you visually cut through the soil along its entire depth, layers with different composition, state of aggregation, density, etc. will be revealed.

All shells are divided into two large groups:

1. The internal structure is described, accordingly, by the internal shells. They are the earth's crust and mantle.
2. External shells, which include the hydrosphere and atmosphere.

The structure of each shell is the subject of study by separate sciences. Scientists still, in the age of rapid technological progress, have not fully clarified all the issues.

Earth's crust and its types

The Earth's crust is one of the planet's shells, occupying only about 0.473% of its mass. The depth of the crust is 5 - 12 kilometers.

It is interesting to note that scientists practically did not penetrate deeper, and if we draw an analogy, the bark is like the skin on an apple in relation to its entire volume. Further and more accurate study requires a completely different level of technological development.

If you look at the planet in cross-section, then depending on the depth of penetration into its structure, the following types of the earth’s crust can be distinguished in order:

1. Oceanic crust- consists mainly of basalts, located on the bottom of the oceans under huge layers of water.
2. Continental or continental crust- covers the land, consists of a very rich chemical composition, including 25% silicon, 50% oxygen, as well as 18% other basic elements of the periodic table. For the purpose of convenient study of this cortex, it is also divided into lower and upper. The most ancient ones belong to the lower part.

The temperature of the crust increases with depth.

Mantle

The bulk of our planet is the mantle. It occupies the entire space between the cortex and the core discussed above and consists of many layers. The minimum thickness to the mantle is about 5 - 7 km.

The current level of development of science and technology does not allow direct study of this part of the Earth, therefore indirect methods are used to obtain information about it.

Very often, the birth of a new earth's crust is accompanied by its contact with the mantle, which occurs especially actively in places under ocean waters.

Today it is believed that there is an upper and lower mantle, which are separated by the Mohorovicic boundary. The percentages of this distribution are calculated quite accurately, but require clarification in the future.

Outer core

The planet's core is also not homogeneous. Enormous temperatures and pressure force many chemical processes to take place here, and the distribution of masses and substances occurs. The core is divided into internal and external.

The outer core is about 3,000 kilometers thick. The chemical composition of this layer is iron and nickel in the liquid phase. The ambient temperature here ranges from 4400 to 6100 degrees Celsius as it approaches the center.

Inner core

The central part of the Earth, the radius of which is approximately 1200 kilometers. The lowest layer, which also consists of iron and nickel, as well as some impurities of light elements. The state of aggregation of this nucleus is similar to amorphous. The pressure here reaches an incredible 3.8 million bar.

Do you know how many kilometers to the core of the earth? The distance is approximately 6371 km, which is easily calculated if you know the diameter and other parameters of the ball.

Comparison of the thickness of the Earth's inner layers

The geological structure is sometimes assessed by such a parameter as the thickness of the internal layers. It is believed that the mantle is the most powerful, since it has the greatest thickness.

Outer spheres of the globe

Planet Earth differs from any other space object known to scientists in that it also has outer spheres, to which they belong:

• hydrosphere;
• atmosphere;
• biosphere.

The methods for studying these areas differ significantly, because they all vary greatly in their composition and object of study.

Hydrosphere

The hydrosphere refers to the entire water shell of the Earth, including both the huge oceans, occupying approximately 74% of the surface, and seas, rivers, lakes and even small streams and reservoirs.

The greatest thickness of the hydrosphere is about 11 km and is observed in the Mariana Trench area. It is water that is considered the source of life and what distinguishes our ball from all others in the Universe.

The hydrosphere occupies approximately 1.4 billion km 3 of volume. Life is in full swing here, and conditions for the functioning of the atmosphere are provided.

Atmosphere

The gaseous shell of our planet, reliably covering its interior from space objects (meteorites), cosmic cold and other phenomena incompatible with life.

The thickness of the atmosphere is, according to various estimates, about 1000 km. Near the ground surface the atmospheric density is 1.225 kg/m 3 .

The gas shell consists of 78% nitrogen, 21% oxygen, the rest consists of elements such as argon, carbon dioxide, helium, methane and others.

Biosphere

Regardless of how scientists study the issue under consideration, the biosphere is the most important part of the structure of the Earth - this is the shell that is inhabited by living beings, including people themselves.

The biosphere is not only inhabited by living beings, but is also constantly changing under their influence, especially under the influence of humans and their activities. A comprehensive teaching about this area was developed by the great scientist V.I. Vernadsky. This very definition was introduced by the Austrian geologist Suess.

Conclusion

The surface of the Earth, as well as all the shells of its external and internal structure, are a very interesting subject of study for entire generations of scientists.

Although at first glance it seems that the areas considered are quite disparate, in fact they are connected by unbreakable connections. For example, life and the entire biosphere are simply impossible without the hydrosphere and atmosphere, which, in turn, originate from the depths.