Internal structure of the Earth (core, mantle, crust). Bowels of the earth. Internal structure of the Earth

Internal structure of the Earth

Recently, the American geophysicist M. Herndon hypothesized that in the center of the Earth there is a natural “nuclear reactor” of uranium and plutonium (or thorium) with a diameter of only 8 km. This hypothesis can explain the reversal of the Earth's magnetic field that occurs every 200,000 years. If this assumption is confirmed, then life on Earth may end 2 billion years earlier than expected, since both uranium and plutonium burn up very quickly. Their depletion will lead to the disappearance of the magnetic field that protects the earth from short-wave solar radiation and, as a consequence, to the disappearance of all forms of biological life. This theory was commented on by Corresponding Member of the Russian Academy of Sciences V.P. Trubitsyn: “Both uranium and thorium are very heavy elements, which, in the process of differentiation of the primary substance of the planet, can sink to the center of the Earth. But at the atomic level they are carried away with light elements, which are carried into the earth’s crust, which is why all uranium deposits are located in the very top layer of the crust. That is, if these elements were concentrated in the form of clusters, they could sink into the core, but, according to prevailing ideas, there should be a small number of them. Thus, in order to make statements about the Earth's uranium core, it is necessary to provide a more reasonable estimate of the amount of uranium that went into the iron core. The structure of the earth should also be

In the fall of 2002, Harvard University professor A. Dziewonski and his student M. Ishii, based on an analysis of data from more than 300,000 seismic events collected over 30 years, proposed a new model according to which the so-called “innermost” core lies within the inner core , having about 600 km across: Its presence may be evidence of the existence of two stages in the development of the inner core. To confirm such a hypothesis, it is necessary to place an even larger number of seismographs around the globe in order to carry out a more detailed identification of anisotropy (the dependence of the physical properties of a substance on the direction within it) that characterizes the very center of the Earth.

The individual face of the planet, like the appearance of a living being, is largely determined by internal factors that arise in its deep bowels. It is very difficult to study these subsoils, since the materials that make up the Earth are opaque and dense, so the amount of direct data on the substance of the deep zones is very limited. These include: the so-called mineral aggregate (large components of the rock) from natural ultra-deep well - kimberlite pipe to Lesotho ( South Africa), which is considered to be a representative of rocks located at a depth of about 250 km, as well as a core (a cylindrical column of rock) recovered from the world's deepest well (12,262 m) on the Kola Peninsula. The study of the planet's super depths is not limited to this. In the 70s of the twentieth century, scientific continental drilling was carried out on the territory of Azerbaijan - the Saablinskaya well (8,324 m). And in Bavaria, in the early 90s of the last century, an ultra-deep well KTB-Oberpfalz with a size of more than 9,000 m was laid.

There are many ingenious and interesting methods for studying our planet, but the main information about its internal structure is obtained from studies of seismic waves generated by earthquakes and powerful explosions. Every hour, about 10 vibrations of the earth's surface are recorded at various points on the Earth. In this case, seismic waves of two types arise: longitudinal and transverse. Both types of waves can propagate in a solid, but only longitudinal ones can propagate in liquids. Displacements of the earth's surface are recorded by seismographs installed throughout the globe. Observations of the speed at which waves travel through the earth allow geophysicists to determine the density and hardness of rocks at depths inaccessible to direct research. A comparison of densities known from seismic data and obtained during laboratory experiments with rocks (where temperature and pressure corresponding to a certain depth of the earth are simulated) allows us to draw a conclusion about the material composition of the earth's interior. The latest geophysics data and experiments related to the study of structural transformations of minerals have made it possible to model many features of the structure, composition and processes occurring in the depths of the Earth.

Back in the 17th century, the amazing coincidence of the outlines of the coastlines of the west coast of Africa and the east coast South America led some scientists to believe that the continents were “walking” around the planet. But it wasn't until three centuries later, in 1912, that the German meteorologist Alfred Lothar Wegener detailed his continental drift hypothesis, which posited that the relative positions of the continents had changed throughout Earth's history. At the same time, he put forward many arguments in favor of the fact that in the distant past the continents were brought together. In addition to the similarity of coastlines, they discovered the correspondence of geological structures, the continuity of relict mountain ranges and the identity of fossil remains on different continents. Professor Wegener actively defended the idea of ​​the existence in the past of a single supercontinent Pangea, its split and the subsequent drift of the resulting continents into different sides. But this unusual theory was not taken seriously, because from the point of view of that time it seemed completely inconceivable that giant continents could independently move around the planet. Moreover, Wegener himself was unable to provide a suitable “mechanism” capable of moving continents.

The revival of the ideas of this scientist occurred as a result of research on the ocean floor. The fact is that the outer relief of the continental crust is well known, but the ocean floor, for many centuries reliably covered with many kilometers of water, remained inaccessible to study and served as an inexhaustible source of all kinds of legends and myths. An important step advance in the study of its relief was the invention of a precision echo sounder, with the help of which it became possible to continuously measure and record the depth of the bottom along the line of movement of the vessel. One of the striking results of intensive research on the ocean floor has been new data on its topography. Today, the topography of the ocean floor is easier to map thanks to satellites that measure the “height” of the sea surface very precisely: it is accurately represented by differences in sea level from place to place. Instead of a flat bottom, devoid of any special features, covered with silt, deep ditches and steep cliffs, giant mountain ranges and largest volcanoes were discovered. The Mid-Atlantic mountain range, which cuts the Atlantic Ocean right down the middle, stands out especially clearly on the maps.

It turned out that the ocean floor ages as it moves away from the mid-ocean ridge, “spreading” from its central zone at a speed of several centimeters per year. The action of this process can explain the similarity of the outlines of the continental margins, if we assume that a new oceanic ridge is formed between the parts of the split continent, and the ocean floor, growing symmetrically on both sides, forms a new ocean. The Atlantic Ocean, in the middle of which lies the Mid-Atlantic Ridge, probably arose in this way. But if the seafloor area increases and the Earth does not expand, then something in the global crust must collapse to compensate for this process. This is exactly what is happening on the margins of much of the Pacific Ocean. Here the lithospheric plates come closer together, and one of the colliding plates plunges under the other and goes deep into the Earth. Such collision sites are marked by active volcanoes that stretch along the coast of the Pacific Ocean, forming the so-called “ring of fire.”

Direct drilling of the seabed and determination of the age of the uplifted rocks confirmed the results of paleomagnetic studies. These facts formed the basis of the theory of new global tectonics, or lithospheric plate tectonics, which made a real revolution in the sciences of the earth and brought a new understanding of the outer shells of the planet. The main idea of ​​this theory is the horizontal movements of plates.

How the earth was born

According to modern cosmological concepts, the earth was formed along with other planets about 4.5 billion years ago from pieces and debris revolving around the young Sun. It grew, taking over the surrounding matter, until it reached its current size. At first, the growth process took place very rapidly, and the continuous rain of falling bodies should have led to its significant heating, since the kinetic energy of the particles was converted into heat. During impacts, craters appeared, and the substance ejected from them could no longer overcome the force of gravity and fell back, and the larger the falling bodies, the more they heated the Earth. The energy of the falling bodies was no longer released on the surface, but in the depths of the planet, without having time to radiate into space. Although the initial mixture of substances could be homogeneous on a large scale, the heating of the earth's mass due to gravitational compression and bombardment of its debris led to the melting of the mixture and the resulting liquids were separated from the remaining solid parts under the influence of gravity. The gradual redistribution of the substance in depth in accordance with the density should have led to its separation into separate shells. Lighter substances, rich in silicon, separated from denser substances containing iron and nickel, and formed the first earth's crust. About a billion years later, as the Earth cooled significantly, the Earth's crust hardened into the planet's tough outer shell. As the earth cooled down, it ejected many different gases from its core (this usually happened during volcanic eruptions) - light ones such as hydrogen and helium, for the most part evaporated into outer space, but since the gravitational force of the earth was already quite strong, it retained the heavier ones at its surface. They formed the basis of the earth's atmosphere. Some of the water vapor from the atmosphere condensed, and oceans appeared on the earth.

What now?

Earth is not the largest, but not the smallest planet among its neighbors. Its equatorial radius, equal to 6378 km, is 21 km greater than the polar one due to the centrifugal force created by the daily rotation. The pressure in the center of the Earth is 3 million atm, and the density of matter is about 12 g/cm3. The mass of our planet, found by experimental measurements of the physical constant of gravity and acceleration of gravity at the equator, is 6*1024 kg, which corresponds to an average density of matter of 5.5 g/cm3. The density of minerals on the surface is approximately half the average density, which means that the density of matter in the central regions of the planet should be higher than the average value. The Earth's moment of inertia, which depends on the distribution of the density of matter along the radius, also indicates a significant increase in the density of matter from the surface to the center. A heat flow is constantly released from the depths of the Earth, and since heat can only be transferred from hot to cold, the temperature in the depths of the planet should be higher than on its surface. Deep drilling has shown that temperature increases with depth by about 20°C for every kilometer and varies from place to place. If the increase in temperature continued continuously, then in the very center of the Earth it would reach tens of thousands of degrees, but geophysical studies show that in reality the temperature here should be several thousand degrees.

The thickness of the Earth's crust (outer shell) varies from several kilometers (in oceanic regions) to several tens of kilometers (in mountainous regions of continents). The sphere of the earth's crust is very small, accounting for only about 0.5% of the total mass of the planet. The main composition of the bark is oxides of silicon, aluminum, iron and alkali metals. The continental crust, which contains an upper (granite) and lower (basaltic) sedimentary layer, contains the most ancient rocks of the Earth, the age of which is estimated at more than 3 billion years. The oceanic crust under the sedimentary layer contains mainly one layer, similar in composition to basalt. The age of the sedimentary cover does not exceed 100-150 million years.

The earth's crust is separated from the underlying mantle by the still mysterious Moho Layer (named after the Serbian seismologist Mohorovicic, who discovered it in 1909), in which the speed of propagation of seismic waves increases abruptly.

The Mantle accounts for about 67% of the planet's total mass. The solid layer of the upper mantle, extending to various depths under the oceans and continents, together with the earth's crust is called the lithosphere - the hardest shell of the Earth. Below it there is a layer where there is a slight decrease in the speed of propagation of seismic waves, which indicates a peculiar state of the substance. This layer, less viscous and more plastic in relation to the layers above and below, is called the asthenosphere. It is believed that the substance of the mantle is in continuous motion, and it is suggested that in the relatively deep layers of the mantle, with increasing temperature and pressure, the transition of the substance into denser modifications occurs. This transition is confirmed by experimental studies.

In the lower mantle at a depth of 2900 km there is sudden jump not only in the speed of longitudinal waves, but also in density, and transverse waves here disappear completely, which indicates a change in the material composition of the rocks. This is the outer boundary of the Earth's core.

The Earth's core was discovered in 1936. It was extremely difficult to image it due to the small number of seismic waves that reached it and returned to the surface. Additionally, the core's extreme temperatures and pressures have long been difficult to reproduce in the laboratory. The earth's core is divided into 2 separate regions: liquid (OUTER CORE) and solid (BHUTPEHHE), the transition between them lies at a depth of 5156 km. Iron is an element that corresponds to the seismic properties of the core and is abundant in the Universe to represent approximately 35% of its mass in the planet's core. According to modern data, the outer core is a rotating stream of molten iron and nickel that conducts electricity well. It is with it that the origin of the earth’s magnetic field is associated, believing that, electric currents, flowing in the liquid core, create a global magnetic field. The layer of the mantle in contact with the outer core is influenced by it, since temperatures in the core are higher than in the mantle. In some places, this layer generates huge heat and mass flows directed towards the Earth's surface - plumes.

The INNER SOLID CORE is not connected to the mantle. It is believed that its solid state, despite the high temperature, is ensured by the gigantic pressure in the center of the Earth. It has been suggested that in addition to iron-nickel alloys, the core should also contain lighter elements, such as silicon and sulfur, and possibly silicon and oxygen. The question of the state of the earth's core is still debatable. As you move away from the surface, the compression to which the substance is subjected increases. Calculations show that in the earth's core the pressure can reach 3 million atm. In this case, many substances seem to be metallized - they pass into the metallic state. There was even a hypothesis that the Earth's core consists of metallic hydrogen.

To understand how geologists created a model of the structure of the Earth, you need to know the basic properties and their parameters that characterize all parts of the Earth. These properties (or characteristics) include:

1. Physical - density, elastic magnetic properties, pressure and temperature.

2. Chemical - chemical composition and chemical compounds, distribution chemical elements in the Earth.

Based on this, the choice of methods for studying the composition and structure of the Earth is determined. Let's look at them briefly.

First of all, we note that all methods are divided into:

· direct - based on the direct study of minerals and rocks and their placement in the strata of the Earth;

· indirect - based on the study of the physical and chemical parameters of minerals, rocks and strata using instruments.

By direct methods we can study only the upper part of the Earth, because... the deepest well (Kola) reached ~12 km. The deeper parts can be judged by volcanic eruptions.

The deep internal structure of the Earth is studied by indirect methods, mainly by a complex of geophysical methods. Let's look at the main ones.

1.Seismic method(Greek seismos - shaking) - is based on the phenomenon of the occurrence and propagation of elastic vibrations (or seismic waves) in various media. Elastic vibrations arise in the Earth during earthquakes, meteorite falls or explosions and begin to propagate at different speeds from the source of their occurrence (the source of the earthquake) to the surface of the Earth. There are two types of seismic waves:

1-longitudinal P-waves (the fastest), pass through all media - solid and liquid;

2-transverse S-waves, slower and travel only through solid media.

Seismic waves during earthquakes occur at depths from 10 km to 700 km. The speed of seismic waves depends on the elastic properties and density of the rocks they cross. Reaching the surface of the Earth, they seem to illuminate it and give an idea of ​​the environment they crossed. The change in speeds gives an idea of ​​the heterogeneity and stratification of the Earth. In addition to changes in speed, seismic waves experience refraction when passing through inhomogeneous layers or reflection from the surface separating the layers.

2.Gravimetric method is based on the study of the acceleration of gravity Dg, which depends not only on geographical latitude, but also on the density of the Earth’s matter. Based on the study of this parameter, heterogeneity in the distribution of density in different parts of the Earth was established.

3.Magnetometric method- based on the study of the magnetic properties of the Earth's substance. Numerous measurements have shown that different rocks differ from each other in magnetic properties. This leads to the formation of areas with inhomogeneous magnetic properties, which make it possible to judge the structure of the Earth.

By comparing all the characteristics, scientists have created a model of the structure of the Earth, in which three main regions (or geospheres) are distinguished:

1-Earth's crust, 2-Earth's mantle, 3-Earth's core.

Each of them, in turn, is divided into zones or layers. Let's consider them and summarize the main parameters in the table.

1.Earth's crust(layer A) is the upper shell of the Earth, its thickness ranges from 6-7 km to 75 km.

2.Earth's mantle is divided into upper (with layers: B and C) and lower (layer D).

3. Core - divided into outer (layer E) and inner (layer G), between which there is a transition zone - layer F.

The border between earth's crust and mantle is the Mohorovicic section, between mantle and core also a sharp boundary - the Gutenberg division.

The table shows that the speed of longitudinal and transverse waves increases from the surface to the deeper spheres of the Earth.

A feature of the upper mantle is the presence of a zone in which the speed of shear waves sharply drops to 0.2-0.3 km/sec. This is explained by the fact that, along with the solid state, the mantle is partially represented by melt. This layer of reduced velocities is called asthenosphere. Its thickness is 200-300 km, depth 100-200 km.

At the boundary of the mantle and core there is a sharp decrease in the speed of longitudinal waves and attenuation of the speed of transverse waves. Based on this, it was assumed that the outer core is in a state of melt.

Average density values ​​for geospheres show its increase towards the core.

The following gives an idea of ​​the chemical composition of the Earth and its geospheres:

1- chemical composition of the earth’s crust,

2 - chemical composition of meteorites.

The chemical composition of the earth's crust has been studied in sufficient detail - its bulk chemical composition and the role of chemical elements in mineral and rock formation are known. The situation is more difficult with the study of the chemical composition of the mantle and core. We cannot do this using direct methods yet. Therefore, a comparative approach is used. The starting point is the assumption of protoplanetary similarity between the composition of meteorites that fell to the earth and the internal geospheres of the Earth.

All meteorites that hit the Earth are divided into types according to their composition:

1-iron, consist of Ni and 90% Fe;

2-iron stones (siderolites) consist of Fe and silicates,

3-stone, consisting of Fe-Mg silicates and nickel iron inclusions.

Based on the analysis of meteorites, experimental studies and theoretical calculations, scientists assume (according to the table) that the chemical composition of the core is nickel iron. True, in last years the point of view is expressed that in addition to Fe-Ni, the core may contain impurities of S, Si or O. For the mantle, the chemical spectrum is determined by Fe-Mg silicates, i.e. a kind of olivine-pyroxene pyrolite makes up the lower mantle, and the upper - rocks of ultrabasic composition.

The chemical composition of the earth's crust includes the maximum range of chemical elements, which is revealed in the variety of mineral species known to date. The quantitative ratio between chemical elements is quite large. A comparison of the most common elements in the earth's crust and mantle shows that the leading role is played by Si, Al and O 2.

Thus, having examined the main physical and chemical characteristics of the Earth, we see that their values ​​are not the same and are distributed zonally. Thus, giving an idea of ​​the heterogeneous structure of the Earth.

Structure of the Earth's crust

The types of rocks we considered earlier - igneous, sedimentary and metamorphic - participate in the structure of the earth's crust. According to their physicochemical parameters, all rocks of the earth’s crust are grouped into three large layers. From bottom to top it is: 1-basalt, 2-granite-gneiss, 3-sedimentary. These layers in the earth's crust are distributed unevenly. First of all, this is expressed in fluctuations in the power of each layer. In addition, not all parts exhibit a complete set of layers. Therefore, a more detailed study made it possible to distinguish four types of the earth’s crust based on composition, structure and thickness: 1-continental, 2-oceanic, 3-subcontinental, 4-suboceanic.

1. Continental type- has a thickness of 35-40 km to 55-75 km in mountain structures, contains all three layers. The basalt layer consists of gabbro-type rocks and metamorphic rocks of amphibolite and granulite facies. It is called that because its physical parameters are close to basalts. The composition of the granite layer is gneisses and granite-gneisses.

2.Ocean type- differs sharply from the continental one in thickness (5-20 km, average 6-7 km) and the absence of a granite-gneiss layer. Its structure involves two layers: the first layer is sedimentary, thin (up to 1 km), the second layer is basalt. Some scientists identify a third layer, which is a continuation of the second, i.e. has a basaltic composition, but is composed of ultrabasic mantle rocks that have undergone serpentinization.

3.Subcontinental type- includes all three layers and is thus close to continental. But it is distinguished by a lower thickness and composition of the granite layer (fewer gneisses and more acidic volcanic rocks). This type is found at the border of continents and oceans with intense volcanism.

4. Suboceanic type- located in deep troughs of the earth's crust (inland seas such as the Black and Mediterranean). It differs from the ocean type in the greater thickness of the sedimentary layer up to 20-25 km.

The problem of the formation of the earth's crust.

According to Vinogradov, the process of formation of the earth’s crust occurred according to the principle zone melting. The essence of the process: the substance of the Proto-Earth, close to meteorite, melted as a result of radioactive heating and the lighter silicate part rose to the surface, and Fe-Ni concentrated in the core. Thus, the formation of geospheres took place.

It should be noted that the earth's crust and the solid part of the upper mantle are combined into lithosphere, below which is located asthenosphere.

Tectonosphere- this is the lithosphere and part of the upper mantle to depths of 700 km (i.e., to the depth of the deepest earthquake foci). It is named so because the main tectonic processes that determine the restructuring of this geosphere take place here.

The main object of study of geology is the earth's crust, the outer hard shell of the Earth, which is of utmost importance for human life and activity. When studying the composition, structure and history of the development of the Earth and the earth's crust, in particular, geologists use: observations; experience or experiment, including various ones, both their own and those used in others natural sciences research methods, for example, physicochemical, biological, etc.; modeling; method of analogies; theoretical analysis; logical constructions (hypotheses), etc.

IN this section the question of the origin of the Earth, its shape and structure, composition, history of the development of the earth's crust (geochronology) is considered; tectonic movements of the earth's crust, surface shapes (relief).

ORIGIN, FORM AND STRUCTURE OF THE EARTH ORIGIN OF THE EARTH

The solar system consists of celestial bodies. It includes: Sun, nine major planets, including the Earth, and tens of thousands of small planets, comets and many meteoroids. The solar system is a complex and diverse world, far from being explored.

The question of the origin of the Earth is the most important question in natural science. For more than 100 years, the Kant-Laplace hypothesis was recognized, according to which the Solar system was formed from a huge hot gas-like nebula, rotating

axis around an axis, and the Earth was first in a liquid state, and then became a solid body.

Further development of science showed the inconsistency of this hypothesis. In the 40s of the XX century. acad. O.Yu. Schmidt put forward a new hypothesis for the origin of the planets of the Solar System, including the Earth, according to which the Sun on its way crossed and captured one of the dust accumulations of the Galaxy, so the planets were formed not from hot gases, but from dust particles revolving around the Sun. In this cluster, over time, compacted clumps of matter arose, giving rise to planets.

Land, according to O.Yu. Schmidt, was initially cold. The heating of its depths began when it reached large sizes. This happened due to the release of heat as a result of the decay of the radioactive substances present in it. The interior of the Earth acquired a plastic state, denser substances concentrated closer to the center of the planet, lighter ones at its periphery. The Earth separated into separate shells. According to the hypothesis of O.Yu. Schmidt, the separation continues to the present day. According to a number of scientists, this is precisely the main cause of movements in the earth’s crust, that is, the cause of tectonic processes.

The hypothesis of V.G. deserves attention. Fesenkov, who believes that nuclear processes occur in the depths of stars, including the Sun. During one period, this led to rapid compression and an increase in the speed of rotation of the Sun. In this case, a long protrusion was formed, which then broke off and disintegrated into separate planets. A review of hypotheses about the origin of the Earth and the most probable scheme of its origin are discussed in detail in the book by I.I. Potapov “Geology and ecology today” (1999).

A BRIEF SKETCH OF THE GLOBAL EVOLUTION OF THE EARTH

The origin of the planets of the solar system and their evolution were actively studied in the 20th century. in the fundamental works of O.Yu. Schmidt, V.S. Safronov, X. Alven and G. Arrhenius, A.V. Vityazev, A. Gingwood, V.E. Khaina, O.G. Sorokhtina, S.A. Umanova, L.M. Naimark, V. Elsasser, N.A. Bozhko, A. Smith, J. Jurajden and others. According to modern cosmological concepts laid down by O.Yu. Schmidt, the Earth and the Moon, as well as other planets of the Solar System, were formed due to the accretion (sticking together and further growth) of solid particles of a gas-dust protoplanetary cloud. At the first stage, the growth of the Earth proceeded in an accelerating accretion mode, but as the reserves of solid matter in the near-Earth swarm of planetesimals in the protoplanetary cloud were exhausted, this growth gradually slowed down. The process of Earth's accretion was accompanied by the release of a colossal amount of gravitational energy, approximately 23.3 10 ergs. Such an amount of energy was capable of not only melting the substance, but even dissolving it, but most of this energy was released in the near-surface part of the Proto-Earth and was lost in the form of thermal radiation. It took 100 million years for the Earth to form to 99% of its present mass.

At the first stage, the young Earth, immediately after its formation, was a relatively cold body, and the temperature of its interior did not exceed the melting point of the earth’s substance, due to the fact that during the formation of the planet there was not only heating due to falling planetesimals, but also cooling due to heat loss in the surrounding space, in addition, the Earth had a homogeneous composition. The further evolution of the Earth is determined by its composition, heat reserves and history of interaction with the Moon. The influence of composition is felt primarily through the decay energy of radioactive elements and the gravitational differentiation of earthly matter.

Before the formation of the planetary system, the Sun was an almost classic red giant. Stars of this type, as a result of internal nuclear reactions of hydrogen combustion, form heavier chemical elements with the release of huge amounts of energy and the emergence of strong light pressure from the surface to the gaseous atmosphere. As a result of the combined effects of this pressure and enormous gravity, the star's atmosphere experienced alternate compression and expansion. This process, under conditions of a dynamic increase in the mass of the gaseous shell, continued until, as a result of resonance, the outer gaseous shell, detached from the Sun, turned into a planetary nebula.

Under the influence of the star's force magnetic field, the ionized matter of the planetary nebula underwent electromagnetic separation of the chemical elements composing it. The gradual loss of thermal energy and electrical charges of the gases led them to stick together. At the same time, under the influence of the magnetic field of the star, the effective transfer of rotational torque was ensured to the planetesimals formed as a result of accretion, which served as the beginning of the formation of all the planets of the Solar system. When ionized chemical elements lost charge, they turned into molecules that reacted with each other, forming the simplest chemical compounds: hydrides, carbides, oxides, cyanides, iron sulfides and chlorides, etc.

The process of gradual compaction, heating and further differentiation of matter in the formed planets occurred with the capture of particles from the surrounding space. In the center of the forming protoplanet, metals were concentrated due to the gravitational separation of matter. Iron and nickel carbides, iron sulfide and iron oxides collected around this zone. Thus, an outer liquid core was formed, which in its shell contained hydrides and oxides of silicon and aluminum, water, methane, hydrogen, oxides of magnesium, potassium, sodium, calcium and other compounds. In this case, zone melting of the resulting shell occurred and the surface contracted and volume of the planet decreased. The next stages were the formation of the mantle, protocrust and melting of the asthenosphere. The protocrust was fragmented due to the above-mentioned reduction in volume and surface. Due to this, basalts were poured onto the surface, which, after cooling, again sank into the deep part of the mantle and were subjected to further melting; then part of the basaltic crust gradually transformed into granite.

The surface layers of the Earth at the stage of formation consisted of finely porous regolith, which actively bound the released water and carbon dioxide due to its ultrabasic composition. The total heat reserve of the Earth and the distribution of temperature in its interior were determined by the rate of growth of the planet. In general, unlike the Moon, the Earth never completely melted, and the process of formation of the Earth's core lasted approximately 4 billion years.

The state of the cold and tectonically passive Earth continued for approximately 600 million years. At this time, the interior of the planet slowly warmed up and about 4 billion years ago, active granitization appeared on Earth and the asthenosphere formed. At the same time, the Moon, as the most massive satellite, “cleared” from the near-Earth space all the smaller satellites and micromoons that were there,

and on the Moon itself there was an outbreak of basaltic magmatism, which coincided with the beginning of tectonic activity on Earth (the period lasted from 4.0 to 3.6 billion years ago). At the same moment, in the bowels of the Earth, the process of gravitational differentiation of the earth's matter is initiated - the main process that supported the tectonic activity of the Earth in all subsequent geological eras and led to the release and growth of the dense oxide-iron core of the earth.

Since in the cryptotectonic era (catarchaean) the earth's matter never melted, the processes of degassing of the Earth could not develop, therefore, for the first 600 million years of the Earth's existence, the hydrosphere was completely absent on its surface, and the atmosphere was extremely rarefied and consisted of noble gases. At this time, the Earth's relief was smoothed, consisting of dark gray regolith. Everything was illuminated by the yellow, weakly warming Sun (the luminosity was 30% less than the modern one) and the enormously large, spotless disk of the Moon (it was approximately 300-350 times larger than the modern visible area of ​​the Moon’s disk). The Moon was still a hot planet and could heat the Earth. The movement of the Sun was rapid - in just 3 hours it crossed the sky, only to rise again from the east after 3 hours. The Moon moved much more slowly, since it quickly rotated around the Earth in the same direction, so that the phases of the Moon went through all stages in 8-10 hours. The Moon revolved around the Earth in an orbit with a radius of 14-25 thousand km (now the radius is 384, 4 thousand km). Intense tidal deformations of the Earth caused a continuous (every 18-20 hours) series of earthquakes following the movement of the Moon. The amplitude of lunar tides was 1.5 km.

Gradually, about a million years after formation, due to the repulsion that took place, the lunar tides decreased to 130 m, after another 10 million years to 25 m, and after 100 million years - to 15 m, by the end of the Catarchean - to 7 m, and now at the sublunar point, modern tides of the solid Earth are 45 cm. Tidal earthquakes at that time were exclusively exogenous in nature, since there was no tectonic activity yet. In the Archean, at the very beginning, the differentiation of earthly matter occurred by smelting metallic iron from it at the level of the upper mantle. Due to the exceptionally high viscosity of the cold core of the young Earth, the resulting gravitational instability could be compensated by squeezing this core towards the Earth's surface and the flow of previously released heavy melts into its place, i.e. by forming a dense core near the Earth. This process was completed by the end of the Archean about 2.7-2.6 billion years ago; At this time, all the previously separated continental masses rapidly began to move towards one of the poles and united into the first supercontinent on the planet, Monogea. The landscapes of the Earth changed, the contrast of the relief did not exceed 1-2 km, all depressions in the relief were gradually filled with water, and in the Late Archean a shallow (up to 1 km) single World Ocean was formed.

At the beginning of the Archean, the Moon moved 160 thousand km away from the Earth. The Earth rotated around its axis at high speed (there were 890 days in a year, and a day lasted 9.9 hours). Lunar tides with an amplitude of up to 360 cm deformed the Earth's surface every 5.2 hours; By the end of the Archean, the rotation of the Earth had slowed down significantly (there were 490 days of 19 hours in a year), and the Moon ceased to influence the tectonic activity of the Earth. The atmosphere in the Archean was replenished with nitrogen, carbon dioxide and water vapor, but oxygen was absent, since it was instantly bound by the free (metallic) iron of the mantle material, which constantly rose through rift zones to the surface of the Earth.

In the Proterozoic, due to the redistribution of convective movements under the supercontinent Monogea, an upward flow led to its collapse (approximately 2.4-3.3 billion years ago). The subsequent formation and fragmentation of the supercontinents Megagaea, Mesogea and Pangea took place with the formation of the most complex tectonic structures and continued until the Cambrian and Ordovician (already in the Paleozoic). By this time, the mass of water on the Earth's surface had become so

large, which has already manifested itself in the formation of a deeper ocean. The ocean crust underwent hydration and this process was accompanied by increased absorption of carbon dioxide with the formation of carbonates. The atmosphere continued to be depleted of oxygen due to the continued binding of it by released iron. This process was completed only at the beginning of the Phanerozoic, and from that time the earth’s atmosphere began to be actively saturated with oxygen, gradually approaching its modern composition.

In this new situation, there was a sharp activation of life forms whose metabolism was based on reverse oxidation reactions organic matter, synthesized by plants. This is how organisms of the animal kingdom appeared, but this was already towards the end of the Cambrian period, in the Phanerozoic, and this led to the emergence of all types of skeletal and non-skeletal animals, which affected many geological processes in the surface zone of the Earth in subsequent geological eras. The geological evolution of the Phanerozoic has been studied in much more detail than other eras, and can be briefly described as follows. At this time closest to us, as it was revealed, transgressions and regressions of the ocean, global climate changes, in particular, alternation of glacial and practically ice-free periods occurred; by the way, the first, as it is assumed, on Earth was the Huronian glaciation in the Proterozoic.

The processes of transgressions and regressions of the ocean with the powerful development of life forms, the active eroding activity of glaciers and the erosive activity of glacial waters led to significant processing of the rocks that made up the surface zone of the earth's crust, the accumulation of terrigenous material on the ocean floor, sedimentation processes of the accumulation of organogenic and chemogenic material in water bodies. swimming pools.

The spatial arrangement of the continents and oceans gradually changed and was very different relative to the equator: alternately, then northern, then Southern Hemisphere was continental or oceanic. The climate also changed several times, being in close connection with glacial and interglacial periods. From the Paleozoic to the Cenozoic (and in it), there were active changes in the depths, temperature and composition of the waters of the World Ocean; the development of life forms led to their exit from the aquatic environment and the gradual development of land, as well as the evolution of life forms up to the known ones. Based on the analysis of the geological history of the Phanerozoic, it follows that all the main boundaries (division of the geochronological scale into eras, periods and epochs) are largely due to collisions and splits of continents in the process of global movement of the “ensemble” of lithospheric plates.

SHAPE OF THE EARTH

The shape of the Earth is commonly referred to as a globe. It has been established that the mass of the Earth is 5976 10 21 kg, the volume is 1.083 10 12 km 3. The average radius is 6371.2 km, the average density is 5.518 kg/m 3, the average acceleration due to gravity is 9.81 m/s 2. The shape of the Earth is close to a triaxial ellipsoid of rotation with polar compression: the modern Earth has a polar radius of 6356.78 km and an equatorial radius of 6378.16 km. The length of the earth's meridian is 40008.548 km, the length of the equator is 40075.704 km. Polar compression (or "oblateness") is caused by the rotation of the Earth around the polar axis and the magnitude of this compression is related to the speed of the Earth's rotation. Sometimes the shape of the Earth is called a spheroid, but for the Earth there is also

the proper name of the shape, namely geoid. The fact is that the earth's surface is variable and significant in height; there are the highest mountain systems of more than 8000 m (for example, Mount Everest - 8842 m) and deep ocean trenches of more than

11,000 m (Mariana Trench - 11,022 m). The geoid outside the continents coincides with the undisturbed surface of the World Ocean; on the continents, the geoid surface is calculated from gravimetric studies and using observations from space.

The earth has a complex magnetic field, which can be described as a field created by a magnetized ball or magnetic dipole.

The surface of the globe is 70.8% (361.1 million km 2) occupied by surface waters (oceans, seas, lakes, reservoirs, rivers, etc.). Land makes up 29.2% (148.9 million km2).

STRUCTURE OF THE EARTH

In general, as established by modern geophysical research based, in particular, on estimates of the speed of propagation of seismic waves, studies of the density of the earth's matter, the mass of the Earth, the results of space experiments to determine the distribution of air and water spaces and other data, the Earth is composed of several concentric shells : external - atmosphere (gas shell), hydrosphere (water shell), biosphere (area of ​​distribution of living matter, according to V.I. Vernadsky) and internal, which are called the geospheres proper (core, mantle and lithosphere) (Fig. 1).

The atmosphere, hydrosphere, biosphere and the uppermost part of the earth's crust are accessible to direct observation. With the help of boreholes, humans are able to study depths generally up to 8 km. Drilling of ultra-deep wells is carried out for scientific purposes in our country, the USA and Canada (in Russia, a depth of more than

12 km, which made it possible to select rock samples for immediate direct study). The main goal of ultra-deep drilling is to reach the deep layers of the earth's crust - the boundaries of the “granite” and “basalt” layers or the upper boundaries of the mantle. The structure of the deeper interior of the Earth is studied using geophysical methods, of which highest value have seismic and gravimetric. The study of matter raised from the boundaries of the mantle should clarify the problem of the structure of the Earth. The mantle is of particular interest, since

Rice. 1. Schematic representation of the structure of the Earth (A) and the earth's crust (b):

L- core; B y C - mantle; ABOUT - Earth's crust; E - atmosphere (according to M. Vasic); 1 - cover deposits; 2 - granite-like layer; 3 - basalt layer; 4-upper mantle; 5-mantle

The earth's crust with all its minerals was ultimately formed from its substance.

Atmosphere According to the temperature distributed in it, from bottom to top it is divided into the troposphere, stratosphere, mesosphere, thermosphere and exosphere. Troposphere makes up about 80% of the total mass of the atmosphere and reaches a height of 16-18 km in the equatorial part and

8-10 km in polar regions. The stratosphere extends to an altitude of 55 km and has upper limit ozone layer. Next comes the mesosphere up to an altitude of 80 km, the thermosphere up to 800-1000 km and above is the exosphere (sphere of dispersion), constituting no more than 0.5% of the mass of the earth’s atmosphere. IN The composition of the atmosphere includes nitrogen (78.1%), oxygen (21.3%), argon (1.28%), carbon dioxide (0.04%) and other gases and almost all water vapor. The ozone content (0 3) is 3.1 10 15 g, and the oxygen content (0 2) is 1.192 10 2! d. With distance from the Earth's surface, the temperature of the atmosphere drops sharply and at an altitude of 10-12 km it is already about -50 ° C. IN In the troposphere, clouds form and thermal air movements are concentrated. At the Earth's surface, the highest temperature was recorded in Libya (+58 ° C in the shade), in the territory former USSR in the area of ​​Termez (+50 °C in the shade).

Most low temperature recorded in Antarctica (-87 °C), and in Russia - in Yakutia (-71 °C).

Stratosphere - the next layer above the troposphere. The presence of ozone in this atmospheric layer causes the temperature in it to increase to +50 °C, but at an altitude of 8-90 km the temperature drops again to -60...-90 °C.

The average air pressure at sea level is 1.0132 bar (760 mm Hg), and the density is 1.3 10 3 g/cm. IN The atmosphere and its cloud cover absorb 18% of the sun's radiation. As a result of the radiation balance of the Earth-atmosphere system, the average temperature on the Earth's surface is positive (+15 °C), although its fluctuations in different climatic zones can reach 150 °C.

Hydrosphere- a water shell that plays a large role in the geological processes of the Earth. IN its composition includes all the waters of the Earth (oceans, seas, rivers, lakes, continental ice, etc.). The hydrosphere does not form a continuous layer and covers 70.8% of the earth's surface. Its average thickness is about 3.8 km, the greatest - over 11 km (11,022 m - Mariana Trench in Pacific Ocean).

The Earth's hydrosphere is much younger than the planet itself. In the first stages of its existence, the Earth's surface was completely anhydrous, and there was practically no water vapor in the atmosphere. The formation of the hydrosphere is due to the processes of separation of water from the mantle. The hydrosphere currently forms an inextricable unity with the lithosphere, atmosphere and biosphere. It is for the latter - the biosphere - that the unique properties of water as a chemical compound are very important, for example, changes in volume during the transition of water from one phase state to another (during freezing,

during evaporation); high dissolving ability in relation to almost all compounds on Earth.

It is the presence of water that inherently ensures the existence of life on Earth in the form we know. From the water, like simple connection, and carbon dioxide, plants are capable, under the influence of solar energy and in the presence of chlorophyll, of forming complex organic compounds, which is actually the process of photosynthesis. Water on Earth is unevenly distributed, most of it concentrated on the surface. In relation to the volume of the globe, the total volume of the hydrosphere does not exceed 0.13%. The main part of the hydrosphere is the World Ocean (94%), whose area is 361059 km 2, and its total volume is 1370 million km 3. In the continental crust there is 4.42 10 23 g of water, in the oceanic crust -3.61 10 23 g. In table. Figure 1 shows the distribution of water on Earth.

Table 1

Volume of the hydrosphere and intensity of water exchange

^Only 4,000 thousand km 3 of groundwater located at shallow depths can be subject to active water exchange and use.

The temperature of water in the ocean changes not only depending on the latitude of the area (proximity to the poles or the equator), but also on the depth of the ocean. The greatest temperature variability is observed in the surface layer down to a depth of 150 m. The highest water temperature in the upper layer was noted in the Persian Gulf (+35.6 °C), and the lowest in the Northern Gulf Arctic Ocean(-2.8 °C).

The chemical composition of the hydrosphere is very diverse: from very fresh to very salty waters, such as brines.

More than 98% of all water resources on Earth are salty waters of oceans, seas and some lakes, ^gtateke minera pussy yang-

new groundwater. Overall volume fresh water on Earth is equal to 28.25 million km 3, which is only about 2% of the total volume of the hydrosphere, while the largest part of fresh water is concentrated in the continental ice of Antarctica, Greenland, polar islands and high mountain regions. This water is currently inaccessible for practical human use.

The World Ocean contains 1.4-10 2 carbon dioxide (C0 2), which is almost 60 times more than in the atmosphere; There are 8 10 18 g of oxygen dissolved in the ocean, or almost 150 times less than in the atmosphere. Every year, rivers carry about 2.53 10 16 g of terrigenous material from land into the oceans, of which almost 2.25 10 16 g is suspended, the rest is soluble and organic matter.

Salinity (medium) sea ​​water equal to 3.5% (35 g/l). In addition to chlorides, sulfates and carbonates, sea water also contains iodine, fluorine, phosphorus, rubidium, cesium, gold and other elements. 0.48 10 23 g of salts are dissolved in water.

Deep-sea research carried out in recent years has made it possible to establish the presence of horizontal and vertical currents and the existence of life forms throughout the entire water column. The organic world of the sea is divided into benthos, plankton, nekton, etc. benthos These include organisms that live on the ground and in the soil of marine and continental water bodies. Plankton- a set of organisms inhabiting the water column that are unable to resist transport by currents. Nekton- actively swimming, such as fish and other marine animals.

Currently, the issue of fresh water shortage is becoming serious, which is one of the components of the developing global environmental crisis. The fact is that fresh water is necessary not only for human utilitarian needs (drinking, cooking, washing, etc.), but also for most industrial processes, not to mention the fact that only fresh water is suitable for agricultural production - agricultural technology and livestock farming, since the vast majority of plants and animals are concentrated on land and they use exclusively fresh water to carry out their life activities. The growth of the Earth's population (there are already more than 6 billion people on the planet) and the associated active development of industry and agricultural production have led to the fact that every year people consume 3.5 thousand km 3 of fresh water, with irreversible losses amounting to 150 km 3. The part of the hydrosphere that is suitable for water supply is 4.2 km 3, which is only 0.3% of the volume of the hydrosphere. Russia has quite large reserves of fresh water (about 150 thousand rivers, 200 thousand lakes, many reservoirs and ponds,

significant volumes of groundwater), but the distribution of these reserves throughout the country is far from uniform.

The hydrosphere plays an important role in the manifestation of many geological processes, especially in the surface zone of the earth's crust. On the one hand, under the influence of the hydrosphere, intensive destruction of rocks and their movement and redeposition occurs; on the other hand, the hydrosphere acts as a powerful creative factor, essentially being a basin for the accumulation within its limits of significant thicknesses of sediments of different compositions.

Biosphere is in constant interaction with the lithosphere, hydrosphere and atmosphere, which significantly affects the composition and structure of the lithosphere.

In general, the biosphere is currently understood as the area of ​​distribution of living matter (living organisms of forms known to science); it is a complexly organized shell connected by biochemical (and geochemical) cycles of migration of matter, energy and information. Academician V.I. Vernadsky in the concept of the biosphere includes all structures of the Earth that are genetically related to living matter; past or present activities of living organisms. Most of the geological history of the Earth is associated with the activity of living organisms, especially in the surface part of the earth's crust, for example, these are very thick sedimentary strata of organogenic rocks - limestones, diatomites, etc. The area of ​​distribution of the biosphere is limited in the atmosphere by the ozone layer (approximately 18-50 km above surface of the planet), above which the forms of life known on Earth are impossible without special means of protection, as is carried out during space flights beyond the atmosphere and to other planets. Until recently, the biosphere extended into the depths of the Earth to a depth of 11,022 m in the Mariana Trench, but when drilling the Kola superdeep well, a depth of more than 12 km was reached, which means that living matter penetrated to this depth.

The internal structure of the Earth, according to modern concepts, consists of a core, mantle and lithosphere. The boundaries between them are quite arbitrary, due to the interpenetration both in area and in depth (see Fig. 1).

Earth's core consists of an outer (liquid) and an inner (solid) core. The radius of the inner core (the so-called layer B) is approximately 1200-1250 km, the transition layer (B) between the inner and outer core has a thickness of about 300-400 km, and the radius of the outer core is 3450-3500 km (respectively, the depth is 2870-2920 km ). The density of matter in the outer core increases with depth from 9.5 to 12.3 g/cm 3 . In the central part

In the inner core, the density of the substance reaches almost 14 g/cm 3 . All this shows that the mass of the earth's core constitutes up to 32% of the total mass of the Earth, while the volume is approximately 16% of the volume of the Earth. Modern specialists It is believed that the earth's core is almost 90% iron with an admixture of oxygen, sulfur, carbon and hydrogen, and the inner core has, according to modern ideas, an iron-nickel composition, which fully corresponds to the composition of a number of studied meteorites.

Earth's mantle It is a silicate shell between the core and the base of the lithosphere. The mass of the mantle makes up 67.8% of the total mass of the Earth (O.G. Sorokhtin, 1994). Geophysical studies have established that the mantle, in turn, can be divided (see Fig. 1) into upper mantle(layer D to a depth of 400 km), Golitsyn transition layer(layer C at a depth of 400 to 1000 km) and lower mantle(layer IN with a base at a depth of approximately 2900 km). Under the oceans in the upper mantle there is a layer in which the mantle material is in a partially molten state. A very important element in the structure of the mantle is the zone underlying the base of the lithosphere. Physically, it represents a surface of transition from top to bottom from cooled hard rocks to partially molten mantle matter, which is in a plastic state and makes up the asthenosphere.

According to modern concepts, the mantle has an ultramafic composition (pyrolyte, a mixture of 75% peridotite and 25% tolerite basalt or lherzolite), and therefore it is often called a peridotite, or “stone” shell. The content of radioactive elements in the mantle is very low. So, on average 10 -8% 13; 10~ 7% TH, 10" 6% 40 K. The mantle is currently assessed as a source of seismic and volcanic phenomena, mountain-building processes, as well as a zone of magmatism.

Earth's crust represents the upper layer of the Earth, which has a lower boundary, or base, according to seismic data, according to the Mohorovicic layer, where an abrupt increase in the speed of propagation of elastic (seismic) waves up to 8.2 km/s is noted.

For a geological engineer, the earth's crust is the main object research, it is on its surface and in its depths that engineering structures are erected, that is, construction activities are carried out. In particular, to solve many practical problems, it is important to clarify the processes of formation of the surface of the earth's crust and the history of this formation.

In general, the surface of the earth’s crust is formed under the influence of processes directed opposite to each other:

• endogenous, including tectonic and magmatic processes that lead to vertical movements in the earth’s crust - uplifts and subsidences, i.e. create “irregularities” in the relief;
• exogenous, causing denudation (flattening, leveling) of the relief due to weathering, erosion of various types and gravitational forces;
• sedimentation (sedimentation), as “filling” with sediments all the irregularities created during endogenesis.

Currently, there are two types of earth's crust: “basaltic” oceanic and “granite” continental.

Oceanic crust It is quite simple in composition and represents a kind of three-layer formation. The upper layer, the thickness of which varies from 0.5 km in the middle part of the ocean to 15 km near deep-sea river deltas and continental slopes, where almost all terrigenous material accumulates, while in other zones of the ocean the sedimentary material is represented by carbonate sediments and non-carbonate red deep-sea clays. The second layer is composed of pillow lavas of oceanic type basalts, underlain by dolerite dikes of the same composition; the total thickness of this layer is 1.5-2 km. The third layer in the upper part of the section is represented by a layer of gabbro, which is underlain by serpentinites near the mid-ocean ridges; the total thickness of the third layer ranges from 4.7 to 5 km.

The average density of the oceanic crust (without precipitation) is 2.9 g/cm 3, its mass is 6.4 10 24 g, and the volume of sediment is 323 million km 3. The oceanic crust is formed in the rift zones of mid-ocean ridges due to the release of basaltic melts from the asthenosphere layer of the Earth and the outpouring of tolerite basalts onto the ocean floor. It has been established that 12 km 3 of basalts come from the asthenosphere annually. All these grandiose tectono-magmatic processes are accompanied by increased seismicity and have no equal on the continents.

Continental crust differs sharply from the oceanic in thickness, structure and composition. Its thickness varies from 20-25 km under island arcs and areas with a transitional type of crust to 80 km under the young folded belts of the Earth, for example, under the Andes or the Alpine-Himalayan belt. The thickness of the continental crust under the ancient platforms averages 40 km. The continental crust is composed of three layers, the upper of which is sedimentary, and the lower two are represented by crystalline rocks. The sedimentary layer is composed of clayey sediments and carbonates of shallow marine basins.

seins and has a very different thickness from 0 on ancient shields to 15 km in the marginal troughs of the platforms. Beneath the sedimentary layer lie Precambrian “granite” rocks, often transformed by processes of regional metamorphism. Next lies the basalt layer. The difference between the oceanic crust and the continental crust is the presence of a granite layer in the latter. Further, the oceanic and continental crust is underlain by rocks of the upper mantle.

The earth's crust has an aluminosilicate composition, represented mainly by fusible compounds. The predominant chemical elements are oxygen (43.13%), silicon (26%) and aluminum (7.45%) in the form of silicates and oxides (Table 2).

table 2

Average chemical composition of the earth's crust

The chemical composition of the earth's crust,%, is as follows: acidic

gender - 46.8; silicon - 27.3; aluminum - 8.7; iron -5.1; calcium - 3.6; sodium - 2.6; potassium - 2.6; magnesium - 2.1; others - 1.2.

As recent data show, the composition of the oceanic crust is so constant that it can be considered one of the global constants, just like the composition of atmospheric air or the average salinity of sea water. This is evidence of the unity of the mechanism of its formation.

An important circumstance that distinguishes the earth's crust from other internal geospheres is the presence in it of an increased content of long-lived radioactive isotopes of uranium 232 and thorium 237 T, potassium 40 K, and their highest concentration is noted for the “granite” layer of the continental crust, while in the oceanic crust there are radioactive the elements are negligible.

Rice. 3. Block diagram of an oceanic transform fault

lithosphere

Volcanoes

Crumpled

Continental

lithosphere

Igneous intrusions

Melting

Rice. 2. Schematic section of the zone of underthrust of the oceanic lithosphere

under the continental

Lithosphere- this is the shell of the Earth, combining the earth's crust and part of the upper mantle. A characteristic feature of the lithosphere is that it contains rocks in a solid crystalline state and is rigid and durable. Down the section from the Earth's surface, an increase in temperature is observed. The plastic shell of the mantle located under the lithosphere is the asthenosphere, in which at high temperatures the substance is partially melted, and as a result, unlike the lithosphere, the asthenosphere does not have strength and can be plastically deformed, up to the ability to flow even under the influence of very low excess pressures (Fig. 2, 3). In the light of modern ideas, according to the theory of lithospheric plate tectonics, it has been established that the lithospheric plates that make up the outer shell of the Earth are formed due to the cooling and complete crystallization of the partially molten substance of the asthenosphere, similar to what happens, for example, on a river when water freezes and ice formation on a frosty day.

It should be noted that the lherzolite that composes the upper mantle has a complex composition, and therefore the substance of the asthenosphere, being in a solid state, is mechanically

weakened so much that it is capable of creeping. This shows that the asthenosphere behaves like a viscous fluid on geological time scales. Thus, the lithosphere is capable of movement relative to the lower mantle due to the weakening of the asthenosphere. An important fact confirming the possibility of movement of lithospheric plates is that the asthenosphere is expressed globally, although its depth, thickness and physical properties vary widely. The thickness of the lithosphere varies from several kilometers under the rift valleys of mid-ocean ridges to 100 km under the periphery of the oceans, and under ancient shields the thickness of the lithosphere reaches 300-350 km.

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

Inner Spheres of the Earth: earth's crust, mantle and core.

Earth's crust most heterogeneous. In terms of depth, there are 3 layers (from top to bottom): sedimentary, granite and basalt.

Sedimentary layer formed by soft and sometimes loose rocks that arose by deposition of matter in a water or air environment on the surface of the Earth. Sedimentary rocks are usually arranged in strata bounded by parallel planes. The thickness of the layer varies from several 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 SiO 2 content in them is more than 60%, so they are classified as acidic rocks. The density of the rocks in the layer is 2.65-2.80 g/cm3. Thickness 20-40 km. As part of the oceanic crust (for example, at the bottom of the Pacific Ocean), there is no granite layer, 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 both the continental and oceanic crust. It is separated from the granite surface by the Conrad surface (K), on which the speed of seismic waves changes from 6 to 6.5 km/sec. The substance composing the basalt layer is close 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 speed of passage of longitudinal seismic waves increases from 6.5 to 7 km/sec at the lower boundary, where the speed jumps again and reaches 8-8.2 km/sec. This lower boundary of the earth's crust can be traced everywhere and is called the Mohorovicic boundary (Yugoslav scientist) or the M boundary.

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, increasing with depth and reaching 2300 o C at the lower boundary. However, the substance is there in a solid state due to pressure, which at great depths amounts to hundreds of thousands and millions of atmospheres. At the border with the core (2900 km), refraction and partial reflection of longitudinal seismic waves are observed, but transverse waves do not pass this boundary (“seismic shadow” ranges from 103° to 143° 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 decompressed rocks - asthenosphere, lying at a depth of 70-150 km (deeper under the oceans), in which a drop in elastic wave velocities of approximately 3% is recorded.

Core in physical properties it differs sharply from the mantle that envelops it. The speed of passage of longitudinal seismic waves is 8.2-11.3 km/sec. The fact is that at the boundary of the mantle and core there is a sharp drop in the speed of longitudinal waves from 13.6 to 8.1 km/sec. Scientists have long come to the conclusion 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 an iron-nickel core. The core 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 inner core pressure reaches 3.5 million atm., density 17.3-17.9 g/cm 3, longitudinal wave speed 11.2-11.3 km/sec. Calculations show that the temperature there should reach several thousand degrees (up to 4000 o). The substance there is in a solid state due to high pressure.

Outer spheres of the Earth: 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 understanding, the hydrosphere is a continuous shell of the Earth. Our course examines, first of all, that part of the hydrosphere that forms an independent water layer - oceanosphere.

From total area The land area is 510 million km2, 361 million km2 (71%) is covered with water. Schematically, the relief of the bottom of the World Ocean is depicted as hypsographic curve. It shows the distribution of land heights and ocean depths; 2 levels of the seabed are clearly visible 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 this a continental shelf or shelf. From the sea, the shelf is limited by a steep underwater ledge - continental slope(up to 3000 m). At depths of 3-3.5 km there is continental foot. Starts below 3500 m oceanic bed (ocean bed), the depth of which is up to 6000 m. The continental foot and the ocean floor constitute the second clearly defined level of the seabed, composed of typically oceanic crust (without a granite layer). Among the ocean floor, mainly in the peripheral parts of the Pacific Ocean, are located deep-sea depressions (trenches)- from 6000 to 11000 m. This is approximately what 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 raised above the ocean floor by 2 kilometers or more and occupying up to 1/3 of the area of ​​the ocean floor. The geological significance of this discovery will be discussed later.

Almost all known chemical elements are present in ocean water, but only 4 predominate: 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 (there are 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 boundary is not distinct, since the density of the atmosphere decreases with height and gradually passes into airless space. The lower boundary is the surface of the Earth. This boundary is also arbitrary, since air penetrates to a certain depth into the stone shell and is contained in a dissolved form in the water column. There are 5 main spheres in the atmosphere (from bottom to top): troposphere, stratosphere, mesosphere, ionosphere And exosphere. The troposphere is important for geology, since it is in direct contact with the earth’s crust and has a significant influence on it.

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

Biosphere- a kind of shell (isolated 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 a large 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, there are several types of water in the seas and oceans. bionomic zones(Greek “bios” - life, “nomos” - law). These zones differ in the conditions for the existence of organisms and their composition. In the shelf area there are 2 zones: littoral And neritic. The littoral zone is a relatively narrow strip of shallow water, drained twice a day during low tide. Due to its specific nature, the littoral zone is inhabited by organisms that can tolerate temporary drying (sea worms, some mollusks, sea urchins, stars). Deeper than the tidal zone within the shelf is the neritic zone, which is most richly populated by a variety of marine organisms. All types of fauna are widely represented here. According to lifestyle they distinguish benthic animals (bottom inhabitants): sessile benthos (corals, sponges, bryozoans, etc.), wandering benthos (crawling ones - hedgehogs, stars, crayfish). Nekton animals are able to move independently (fish, cephalopods); planktonic (plankton) - suspended in water (foraminifera, radiolaria, jellyfish). Corresponds to the continental slope bathyal zone, continental foot and oceanic bed - abyssal zone. The living conditions in them are not very favorable - complete darkness, high pressure, lack of algae. However, even there they 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 enriched it with oxygen, carbon dioxide, and nitrogen. The role of organisms in the formation of marine sediments is extremely important, many of which are minerals (caustobiolites, jaspilites, etc.).

Self-test questions.

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

What is the shape and size of the Earth?

What solid shells does the Earth consist of?

How does continental crust differ from oceanic crust?

What causes the Earth's magnetic field?

What is a hypsographic curve and its type?

What is benthos?

What is the biosphere and its boundaries?

Introduction

For many centuries, the question of the origin of the Earth remained the monopoly of philosophers, since factual material in this area was almost completely absent. The first scientific hypotheses regarding the origin of the Earth and the solar system, based on astronomical observations, were put forward only in the 18th century. Since then, more and more new theories have not ceased to appear, corresponding to the growth of our cosmogonic ideas.

The first in this series was the famous theory formulated in 1755 by the German philosopher Emmanuel Kant. Kant believed that the solar system arose from some primordial matter that was previously freely scattered in space. Particles of this matter moved in different directions and, colliding with each other, lost speed. The heaviest and densest of them, under the influence of gravity, connected with each other, forming a central clot - the Sun, which, in turn, attracted more distant, small and light particles.

Thus, a certain number of rotating bodies arose, the trajectories of which intersected each other. Some of these bodies, initially moving in opposite directions, were eventually drawn into a single flow and formed rings of gaseous matter, located approximately in the same plane and rotating around the Sun in the same direction, without interfering with each other. More dense nuclei formed in individual rings, to which lighter particles were gradually attracted, forming spherical accumulations of matter; This is how the planets formed, which continued to circle around the Sun in the same plane as the original rings of gaseous matter.

1. History of the earth

Earth is the third planet from the Sun in the solar system. It revolves around the star in an elliptical orbit (very close to circular) with an average speed of 29.765 km/s at an average distance of 149.6 million km over a period of 365.24 days. The Earth has a satellite, the Moon, orbiting the Sun at an average distance of 384,400 km. The inclination of the earth's axis to the ecliptic plane is 66033`22``. The period of rotation of the planet around its axis is 23 hours 56 minutes 4.1 seconds. Rotation around its axis causes the change of day and night, and the tilt of the axis and revolution around the Sun causes the change of seasons. The shape of the Earth is a geoid, approximately a triaxial ellipsoid, a spheroid. The average radius of the Earth is 6371.032 km, equatorial - 6378.16 km, polar - 6356.777 km. The surface area of ​​the globe is 510 million km2, volume - 1.083 * 1012 km2, average density 5518 kg/m3. The mass of the Earth is 5976 * 1021 kg. The earth has a magnetic field and a closely related electric field. The Earth's gravitational field determines its spherical shape and the existence of an atmosphere.

According to modern cosmogonic concepts, the Earth was formed approximately 4.7 billion years ago from gaseous matter scattered in the protosolar system. As a result of the differentiation of matter, the Earth, under the influence of its gravitational field, in conditions of heating the earth's interior, arose and developed shells of different chemical composition, state of aggregation and physical properties - the geosphere: the core (in the center), the mantle, the earth's crust, the hydrosphere, the atmosphere, magnetosphere. The composition of the Earth is dominated by iron (34.6%), oxygen (29.5%), silicon (15.2%), magnesium (12.7%). The Earth's crust, mantle and inner core are solid (the outer part of the core is considered liquid). From the surface of the Earth towards the center, pressure, density and temperature increase. The pressure in the center of the planet is 3.6 * 1011 Pa, the density is about 12.5 * 103 kg/m3, the temperature ranges from 50,000 to

60000 C. The main types of the earth's crust are continental and oceanic; in the transition zone from the continent to the ocean, a crust of intermediate structure is developed.

Most of the Earth is occupied by the World Ocean (361.1 million km2; 70.8%), land is 149.1 million km2 (29.2%), and forms six continents and islands. It rises above the level of the world's oceans by an average of 875 m (the highest height is 8848 m - Mount Chomolungma), mountains occupy more than 1/3 of the land surface. Deserts cover approximately 20% of the land surface, forests - about 30%, glaciers - over 10%. The average depth of the world's oceans is about 3800 m (the greatest depth is 11020 m - the Mariana Trench (trench) in the Pacific Ocean). The volume of water on the planet is 1370 million km3, the average salinity is 35 g/l.

The Earth's atmosphere, the total mass of which is 5.15 * 1015 tons, consists of air - a mixture mainly of nitrogen (78.08%) and oxygen (20.95%), the rest is water vapor, carbon dioxide, as well as inert and other gases. The maximum temperature of the land surface is 570-580 C (in the tropical deserts of Africa and North America), the minimum is about -900 C (in the central regions of Antarctica).

The formation of the Earth and the initial stage of its development belong to pre-geological history. The absolute age of the most ancient rocks is over 3.5 billion years. The geological history of the Earth is divided into two unequal stages: the Precambrian, which occupies approximately 5/6 of the entire geological chronology (about 3 billion years), and the Phanerozoic, covering the last 570 million years. About 3-3.5 billion years ago, as a result of the natural evolution of matter, life arose on Earth and the development of the biosphere began. The totality of all living organisms inhabiting it, the so-called living matter of the Earth, had a significant impact on the development of the atmosphere, hydrosphere and sedimentary shell. New

a factor that has a powerful influence on the biosphere is the production activity of man, who appeared on Earth less than 3 million years ago. The high growth rate of the Earth's population (275 million people in 1000, 1.6 billion people in 1900 and approximately 6.3 billion people in 1995) and the increasing influence of human society on the natural environment have raised problems of rational use of all natural resources and nature conservation.

2. Seismic model of the Earth's structure

A widely known model of the internal structure of the Earth (dividing it into the core, mantle and crust) was developed by seismologists G. Jeffries and B. Gutenberg in the first half of the 20th century. The decisive factor in this case was the discovery of a sharp decrease in the speed of passage of seismic waves inside the globe at a depth of 2900 km with a planetary radius of 6371 km. The speed of passage of longitudinal seismic waves directly above the indicated boundary is 13.6 km/s, and below it is 8.1 km/s. This is the boundary between the mantle and the core.

Accordingly, the radius of the core is 3471 km. The upper boundary of the mantle is the Mohorovicic seismic section, identified by the Yugoslav seismologist A. Mohorovicic (1857-1936) back in 1909. It separates the earth's crust from the mantle. At this point, the speeds of longitudinal waves passing through the earth's crust increase abruptly from 6.7-7.6 to 7.9-8.2 km/s, but this happens at different depth levels. Under continents, the depth of section M (that is, the base of the earth's crust) is a few tens of kilometers, and under some mountain structures (Pamir, Andes) it can reach 60 km, while under ocean basins, including the water column, the depth is only 10-12 km . In general, the earth's crust in this scheme appears as a thin shell, while the mantle extends in depth to 45% of the earth's radius.

But in the middle of the 20th century, ideas about the more detailed deep structure of the Earth entered science. Based on new seismological data, it turned out to be possible to divide the core into inner and outer, and the mantle into lower and upper (Fig. 1). This model, which has become widespread, is still used today. It was started by the Australian seismologist K.E. Bullen, who in the early 40s proposed a scheme for dividing the Earth into zones, which he designated with letters: A - the earth’s crust, B - zone in the depth range of 33-413 km, C - zone 413-984 km, D - zone 984-2898 km , D - 2898-4982 km, F - 4982-5121 km, G - 5121-6371 km (center of the Earth). These zones differ in seismic characteristics. Later, he divided zone D into zones D" (984-2700 km) and D" (2700-2900 km). Currently, this scheme has been significantly modified and only layer D" is widely used in the literature. Its main characteristic- reduction of seismic velocity gradients compared to the overlying mantle region.

The inner core, which has a radius of 1225 km, is solid and has a high density of 12.5 g/cm3. The outer core is liquid, its density is 10 g/cm3. At the core-mantle boundary, there is a sharp jump not only in the velocity of longitudinal waves, but also in density. In the mantle it decreases to 5.5 g/cm3. Layer D, which is in direct contact with the outer core, is influenced by it, since the temperatures in the core significantly exceed the temperatures of the mantle. In places, this layer generates huge heat and mass flows directed towards the Earth’s surface through the mantle, called plumes. They can manifest themselves on the planet in the form of large volcanic areas, such as in the Hawaiian Islands, Iceland and other regions.

The upper boundary of the D" layer is uncertain; its level from the surface of the core can vary from 200 to 500 km or more. Thus, it is possible

conclude that this layer reflects the uneven and different intensity supply of core energy to the mantle region.

The boundary of the lower and upper mantle in the scheme under consideration is the seismic section lying at a depth of 670 km. It has a global distribution and is justified by a jump in seismic velocities in the direction of their increase, as well as an increase in the density of matter in the lower mantle. This section is also the boundary of changes in the mineral composition of rocks in the mantle.

Thus, the lower mantle, contained between depths of 670 and 2900 km, extends along the radius of the Earth for 2230 km. The upper mantle has a well-documented internal seismic section, passing at a depth of 410 km. When crossing this boundary from top to bottom, seismic velocities increase sharply. Here, as at the lower boundary of the upper mantle, significant mineral transformations occur.

The upper part of the upper mantle and the earth's crust are collectively distinguished as the lithosphere, which is the upper solid shell of the Earth, as opposed to the hydro- and atmosphere. Thanks to the theory of lithospheric plate tectonics, the term “lithosphere” has become widespread. The theory assumes the movement of plates through the asthenosphere - a softened, partly, perhaps, liquid deep layer of low viscosity. However, seismology does not show a spatially consistent asthenosphere. For many areas, several asthenospheric layers located vertically, as well as their horizontal discontinuity, have been identified. Their alternation is especially clearly recorded within continents, where the depth of asthenospheric layers (lenses) varies from 100 km to many hundreds.

Under the ocean abyssal depressions, the asthenospheric layer lies at depths of 70-80 km or less. Accordingly, the lower boundary of the lithosphere is actually uncertain, and this creates great difficulties for the theory of kinematics of lithospheric plates, as noted by many researchers. These are the basic ideas about the structure of the Earth that have developed to date. Next, we turn to the latest data regarding deep seismic boundaries, which provide the most important information about the internal structure of the planet.

3. Geological structure of the Earth

The history of the geological structure of the Earth is usually depicted in the form of successively appearing stages or phases. Geological time is counted from the beginning of the formation of the Earth.

Phase 1(4.7 – 4 billion years). The earth is formed from gas, dust and planetesimals. As a result of the energy released during the decay of radioactive elements and the collision of planetesimals, the Earth is gradually warming up. The fall of a giant meteorite to Earth results in the ejection of material from which the Moon is formed.

According to another concept, the Proto-Moon, located in one of the heliocentric orbits, was captured by the Proto-Earth, resulting in the formation of the Earth-Moon binary system.

Degassing of the Earth leads to the beginning of the formation of an atmosphere consisting mainly of carbon dioxide, methane and ammonia. At the end of the phase under consideration, due to the condensation of water vapor, the formation of the hydrosphere begins.

Phase 2(4 – 3.5 billion years). The first islands, protocontinents, composed of rocks containing mainly silicon and aluminum appear. Protcontinents rise slightly above the still very shallow oceans.

Phase 3(3.5 – 2.7 billion years). Iron collects in the center of the Earth and forms its liquid core, which gives rise to the magnetosphere. The prerequisites are created for the appearance of the first organisms, bacteria. The formation of the continental crust continues.

Phase 4(2.7 – 2.3 billion years). A single supercontinent is formed. Pangea, which is opposed by the superocean Panthalassa.

Phase 5(2.3 – 1.5 billion years). Cooling of the crust and lithosphere leads to the disintegration of the supercontinent into microplate blocks, the spaces between which are filled with sediments and volcanoes. As a result, folded-surface systems arise and a new supercontinent is formed - Pangea I. The organic world is represented by blue-green algae, the photosynthetic activity of which contributes to the enrichment of the atmosphere with oxygen, which leads to the further development of the organic world.

Phase 6(1700 – 650 million years). The destruction of Pangea I occurs, the formation of basins with ocean-type crust. Two supercontinents are formed: Gondavana, which includes South America, Africa, Madagascar, India, Australia, Antarctica, and Laurasia, which includes North America, Greenland, Europe and Asia (except India). Gondwana and Laurasia are separated by the Tits Sea. The first ice ages begin. The organic world is rapidly becoming saturated with multicellular, non-skeletal organisms. The first skeletal organisms appear (trilobites, mollusks, etc.). oil formation occurs.

Phase 7(650 – 280 million years). The Appalachian mountain belt in America connects Gondwana with Laurasia - Pangea II is formed. Contours are indicated

Paleozoic oceans - Paleoatlantic, Paleo-Tethys, Paleo-Asian. Gondwana was covered by glaciation twice. Fish appear, and later amphibians. Plants and animals come to land. Intensive coal formation begins.

Phase 8(280 – 130 million years). Pangea II is penetrated by an increasingly dense network of continental reefs, slit-like, ditch-like stretches of the earth's crust. The splitting of the supercontinent begins. Africa is separated from South America and Hindustan, and the latter from Australia and Antarctica. Australia finally separates from Antarctica. Angiosperms colonize large areas of land. The animal world is dominated by reptiles and amphibians, birds and primitive mammals appear. At the end of the period, many groups of animals died, including huge dinosaurs. The causes of these phenomena are usually seen either in the collision of the Earth with a large asteroid, or in a sharp increase in volcanic activity. Both could lead to global changes (an increase in carbon dioxide content in the atmosphere, the occurrence of large fires, ashification), incompatible with the existence of many species of animals.

Phase 9(130 million years – 600 thousand years). The general configuration of continents and oceans is undergoing major changes; in particular, Eurasia is separated from North America, Antarctica - from South America. The distribution of continents and oceans has become very close to modern ones. At the beginning of the period under review, the climate throughout the Earth is warm and humid. The end of the period is characterized by sharp climatic contrasts. Following the glaciation of Antarctica, the glaciation of the Arctic occurs. A fauna and flora close to modern ones is emerging. The first ancestors of modern humans appear.

Phase 10(modernity). Between the lithosphere and the earth's core, magma flows rise and fall, breaking through cracks in the crust to the top. Fragments of oceanic crust sink all the way to the core, and then float up and possibly form new islands. Lithospheric plates collide with each other and are constantly influenced by magma flows. Where the plates move apart, new segments of the lithosphere are formed. There is a constant process of differentiation of the earth's matter, which transforms the state of all geological shells of the Earth, including the core.

Conclusion

The Earth is singled out by nature itself: in the Solar system, only on this planet do developed forms of life exist, only on this planet the local ordering of matter has reached an unusually high level, continuing the general line of development of matter. It was on Earth that the most difficult stage of self-organization was passed, marking a deep qualitative leap towards higher forms orderliness.

Earth is the largest planet in its group. But, as estimates show, even such dimensions and mass turn out to be the minimum at which the planet is able to maintain its gas atmosphere. The Earth is intensively losing hydrogen and some other light gases, which is confirmed by observations of the so-called Earth plume.

The Earth's atmosphere is fundamentally different from the atmospheres of other planets: in it low content carbon dioxide, high molecular oxygen content and relatively high water vapor content. Two reasons create the isolation of the Earth’s atmosphere: the water of the oceans and seas absorbs carbon dioxide well, and the biosphere saturates the atmosphere with molecular oxygen formed during the process of plant photosynthesis. Calculations show that if we freed all the carbon dioxide absorbed and bound in the oceans, simultaneously removing from the atmosphere all the oxygen accumulated as a result of the life of plants, then the composition of the earth’s atmosphere in its main features would become similar to the composition of the atmospheres of Venus and Mars.

In the Earth's atmosphere, saturated water vapor creates a cloud layer covering a significant part of the planet. The Earth's clouds are an important element in the water cycle occurring on our planet in the hydrosphere - atmosphere - land system.

Tectonic processes are actively occurring on Earth today; its geological history is far from complete. From time to time, the echoes of planetary activity manifest themselves with such force that they cause local catastrophic shocks that affect nature and human civilization. Paleontologists claim that in the early youth of the Earth, its tectonic activity was even higher. The modern topography of the planet has developed and continues to change under the influence of the combined action of tectonic, hydrosphere, atmospheric and biological processes on its surface.

Bibliography

V.F. Tulinov “Concepts of modern natural science”: Textbook for universities. - M.: UNITY-DANA, 2004.

A.V. Byalko “Our planet - Earth” - M. Nauka, 1989

G.V. Voitkevich “Fundamentals of the theory of the origin of the Earth” - M Nedra, 1988.

Physical encyclopedia. Tt. 1-5. – M. Great Russian Encyclopedia, 1988-1998.

Introduction………………………………………………………………………………..3

History of the Earth……………………………………………………..………………4

Seismic model of the Earth’s structure………………………………...6

Geological structure of the Earth………………………………………………………...9

Conclusion……………………………………………………………………………….13

References……………………………………………………………15

INSTITUTE OF ECONOMICS AND ENTREPRENEURSHIP

Extramural

ABSTRACT

On the subject "Concepts of modern natural science" Earth The Earth and the Sun are the main factor of life on EarthAbstract >> Biology

1. Earth and its place in the Universe Earth. Shape, size and relief. Internal structure. Moon. Earth, third... 384400 km. Internally structure The main role in the study of internal buildings Earth seismic methods play...

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

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Shape and size of planet Earth

Contrary to general misconception our planet is not round. Its shape is called a 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 earthly day.

The planet is encircled in the middle - an imaginary circle dividing the geoid into the Northern and Southern Hemispheres.

Besides 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 the reference point for geographic longitude and time zones.

The main characteristics of the globe include:

• diameter (km): equatorial – 12,756, polar (at 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, half the values ​​of its diameter at the poles and the equator are used.

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

Earth shells

Basic shells of the earth allocated depending on their contents. Since our planet is spherical in shape, its shells, held by gravity, are called spheres. If you look at tripling of the earth in cross-section, then three spheres can be seen:

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

1. Lithosphere - the hard shell of the planet, including minerals layers of the earth.
2. Hydrosphere - contains water resources - rivers, lakes, seas and oceans.
3. Atmosphere – is a shell of air surrounding the planet.

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

Important! Many scientists classify the planet's population as belonging to a separate vast shell called the anthroposphere.

The earth's shells - lithosphere, hydrosphere and atmosphere - are identified 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 shell, in its composition includes: nitrogen, carbon dioxide, gas, dust.

1. The troposphere is 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 from the upper boundary of the troposphere and ends at an altitude of about 50 km.
3. The mesosphere is a layer of the atmosphere extending 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 the increase in temperature as altitude increases.
5. Exosphere - begins from the upper boundary, lying below the thermosphere, and gradually moves into open space, it is characterized by low air content and 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 die very soon.

Atmosphere - earth's shell, without which life on the planet would be impossible.

It contains the air necessary for living organisms to breathe, determines suitable weather conditions, and protects the planet from negative influence solar radiation.

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

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

Hydrosphere

The hydrosphere is all the liquids on the planet.

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

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

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

The hydrosphere is, first of all,, fresh source drinking water, one of the main climate-forming factors. Water resources are used as communication routes and tourism and recreation (leisure) facilities.

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 mantle.

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

The lithosphere plates mainly consist of basalt, sand and clay, stone, and a soil layer.

Earth structure diagram together with the lithosphere, it is represented by the following layers:

• Earth's crust - upper, consisting of sedimentary, basaltic, metamorphic rocks and fertile soil. Depending on the location, continental and oceanic crust are distinguished;
• mantle - located under the earth's crust. Weighs about 67% of the total mass of the planet. The thickness of this layer is about 3000 km. The upper layer of the mantle is viscous and 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 mantle contains heavy iron and nickel materials. Processes occurring in the mantle are responsible for many phenomena on the surface of the planet (seismic processes, volcanic eruptions, formation of deposits);
• The central part of the earth is occupied core consisting of an inner solid and an outer liquid part. The thickness of the outer part is about 2200 km, the inner part 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 nucleus 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 in the center of the planet there is an inner star, surrounded on all sides by an impressive layer of water. This theory, apart from a small circle of adherents in the scientific community, has found widespread use in science fiction literature. An example is the novel by V.A. Obruchev's "Plutonia", which tells about the expedition of Russian scientists to the cavity inside the planet with its own small star and a world of animals and plants extinct on the surface.

Such a generally accepted diagram of the structure of the earth, including the earth's crust, mantle and core, is becoming more and more improved and refined every year.

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

So, for example, in order to find out exactly how many kilometers to the outer part of the core, more years of scientific research will be needed.

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

Layer-by-layer 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. Studying its structure in the future will help humanity understand the mysteries of natural phenomena and will make it possible to more accurately predict destructive natural disasters, discover new, not yet developed mineral deposits.