The structure of the globe (continued). Characteristics of the earth's shells

It is called the crust and is part of the lithosphere, which is translated from Greek language literally means "rocky" or "hard ball". It also includes part of the upper mantle. All this is located directly above the asthenosphere (“powerless ball”) - above a more viscous or plastic layer, as if underlying the lithosphere.

Internal structure of the Earth

Our planet has the shape of an ellipsoid, or more precisely, a geoid, which is a three-dimensional geometric body of a closed shape. This most important geodetic concept is literally translated as “earth-like.” This is what our planet looks like from the outside. Internally, it is structured as follows - the Earth consists of layers separated by boundaries, which have their own specific names (the clearest of them is the Mohorovicic boundary, or Moho, which separates the crust and mantle). The core, which is the center of our planet, the shell (or mantle) and the crust - the upper solid shell of the Earth - these are the main layers, two of which - the core and the mantle, in turn, are divided into 2 sublayers - internal and external, or lower and upper. Thus, the core, the radius of which is 3.5 thousand kilometers, consists of a solid inner core (radius 1.3) and a liquid outer one. And the mantle, or silicate shell, is divided into lower and upper parts, which together account for 67% of the total mass of our planet.

The thinnest layer of the planet

The soils themselves arose simultaneously with life on Earth and are a product of the influence of the environment - water, air, living organisms and plants. Depending on various conditions (geological, geographical and climatic), this most important natural resource has a thickness of 15 cm to 3 m. The value of some types of soil is very high. For example, during the occupation, the Germans exported Ukrainian black soil in rolls to Germany. Speaking about the earth's crust, we cannot help but mention large solid areas that slide along the more liquid layers of the mantle and move relative to each other. Their approach and “attacks” threaten tectonic shifts, which can cause disasters on Earth.

Atmospheric air consists of nitrogen (77.99%), oxygen (21%), inert gases (1%) and carbon dioxide (0.01%). The share of carbon dioxide increases over time due to the fact that fuel combustion products are released into the atmosphere, and, in addition, the area of ​​forests that absorb carbon dioxide and release oxygen decreases.

The atmosphere also contains a small amount of ozone, which is concentrated at an altitude of about 25-30 km and forms the so-called ozone layer. This layer creates a barrier to solar ultraviolet radiation, which is dangerous to living organisms on Earth.

In addition, the atmosphere contains water vapor and various impurities - dust particles, volcanic ash, soot, etc. The concentration of impurities is higher near the surface of the earth and in certain areas: above large cities, deserts.

Troposphere- lower, it contains most of the air and. The height of this layer varies: from 8-10 km near the tropics to 16-18 near the equator. in the troposphere it decreases with rise: by 6°C for every kilometer. The weather is formed in the troposphere, winds, precipitation, clouds, cyclones and anticyclones are formed.

The next layer of the atmosphere is stratosphere. The air in it is much more rarefied, and there is much less water vapor in it. The temperature in the lower part of the stratosphere is -60 - -80°C and falls with increasing altitude. It is in the stratosphere that the ozone layer is located. The stratosphere is characterized by high wind speeds (up to 80-100 m/sec).

Mesosphere- the middle layer of the atmosphere, lying above the stratosphere at altitudes from 50 to S0-S5 km. The mesosphere is characterized by a decrease in average temperature with height from 0°C at the lower boundary to -90°C at the upper boundary. Near the upper boundary of the mesosphere, noctilucent clouds are observed, illuminated by the sun at night. The air pressure at the upper boundary of the mesosphere is 200 times less than at the earth's surface.

Thermosphere- located above the mesosphere, at altitudes from SO to 400-500 km, in it the temperature first slowly and then quickly begins to rise again. The reason is the absorption of ultraviolet radiation from the Sun at altitudes of 150-300 km. In the thermosphere, the temperature continuously increases to an altitude of about 400 km, where it reaches 700 - 1500 ° C (depending on solar activity). Under the influence of ultraviolet, X-ray and cosmic radiation, ionization of the air (“auroras”) also occurs. The main regions of the ionosphere lie within the thermosphere.

Exosphere- the outer, most rarefied layer of the atmosphere, it begins at altitudes of 450-000 km, and its upper boundary is located at a distance of several thousand km from the earth’s surface, where the concentration of particles becomes the same as in interplanetary space. The exosphere consists of ionized gas (plasma); the lower and middle parts of the exosphere mainly consist of oxygen and nitrogen; With increasing altitude, the relative concentration of light gases, especially ionized hydrogen, rapidly increases. The temperature in the exosphere is 1300-3000° C; it grows weakly with height. The Earth's radiation belts are mainly located in the exosphere.

Ideas about the internal heterogeneity of the Earth's structure and its concentric-zonal structure are based on the results of comprehensive geophysical research. Direct evidence of the deep structure of the earth's interior refers to shallow depths. They were obtained in the process of studying natural sections ( outcrops) rocks, sections of quarries, mines and boreholes. The world's deepest well on the Kola Peninsula has gone 12 kilometers into the depths. This is only 0.2% of the radius of the Earth (the radius of the Earth is about 6 thousand km) (Fig. 3.5.). Products of volcanic eruptions make it possible to judge the temperatures and composition of matter at depths of 50-100 km.

Rice. 3.5. Inner shells of the earth

Seismic waves. The main method of subsurface exploration is the seismic method. It is based on measuring the speed of passage of mechanical vibrations of various types through the Earth's substance. This process is accompanied by the release of a large amount of energy and the occurrence of mechanical vibrations, which propagate in the form of seismic waves in all directions from the point of origin. The speed of propagation of seismic waves is very high and in dense bodies, for example in stone (rocks) reaches several kilometers per second. There are two groups of seismic waves - volumetric And superficial(Fig. 3.6. and 3.7.). The rocks that make up the Earth are elastic and therefore can be deformed and experience vibrations under sudden application of pressure (loads). Body waves propagate inside the rock volume. They are divided into two types: longitudinal (P) and transverse (S) . Longitudinal waves in the body of the Earth (as in any other physical bodies) arise as a reaction to changes in volume. Like sound waves in the air, they alternately compress and stretch rock matter in the direction of their movement. Waves of another type - transverse - arise as a reaction to a change in the shape of a body. They vibrate the medium through which they pass across the path of their movement.

At the boundary of two media with different physical properties, seismic waves experience refraction or reflection (P, S, PcP, PkP, etc.). Geophysical research was supplemented by thermodynamic calculations and the results of physical modeling and data from the study of meteorites.

The data obtained indicate the presence of numerous subhorizontal interfaces in the Earth's interior. At these boundaries, there is a change in the speeds and directions of propagation of physical waves (seismic, electromagnetic, etc.) as they propagate deep into the planet.

Rice. 3.6. Propagation of seismic waves (O – earthquake source).

These boundaries separate from each other separate shells - “geospheres”, which differ from each other in chemical composition and according to the state of aggregation of the substance in them. These boundaries are by no means the usual geometrically regular infinitely thin planes. Any of these boundaries is a certain volume of the subsoil, relatively small compared to the volume of the shared geospheres. Within each such volume, a rapid but gradual change in the chemical composition and state of aggregation of the substance occurs.

The bowels of the Earth. According to existing ideas, the globe is divided into a number of concentric shells (geospheres), as if nested within each other (Fig. 3.7., Table 3.5.). The "outer" shells and the "inner" shells (sometimes the latter are simply called "interiors") are separated from each other by the surface of the earth. The inner shells are represented by the core, mantle and crust, respectively. Each of these geospheres, in turn, has a complex structure. The Gutenberg-Bullen model uses geosphere indexing, which is still popular today. The authors highlight: earth's crust(layer A) - granites, metamorphic rocks, gabbro; upper mantle(layer B); transition zone(layer C); lower mantle(layer D), consisting of oxygen, silica, magnesium and iron. At a depth of 2900 km, the boundary between the mantle and core is drawn. Below is outer core(layer E), and from a depth of 5120 m - inner core(layer G), folded with iron:

- earth's crust – the thin outer rocky shell of the Earth. It is distributed from the surface of the Earth down to 35-75 km, layer A: Avg. thickness 6-7 km - under the oceans; 35-49 km – under the flat platform territories of the continents; 50-75 km - under young mountain structures. This is the outermost of the Earth's inner layers.

mantle - intermediate shell (35-75 km to 2900 km) (layers B, C, D) (Greek “mantion” - cover): layers B (75-400 km) and C (400-1000 km) correspond to the upper mantle ; transition layer D (1000-2900 km) - lower mantle.

-core – (2900 km – 6371 km) layers E, F, G where: E (2900-4980 km) – outer core; F (4980-5120 km) – transition shell; G (5120-6371 km) – inner core.

Earth's core . The core makes up 16.2% of its volume and 1/3 of its mass. It is apparently compressed at the poles by 10 km. At the boundary of the mantle and core (2900 km), there is an abrupt decrease in the velocity of longitudinal waves from 13.6 to 8.1 km/s. Shear waves below this interface do not penetrate. The core does not allow them to pass through itself. This gave rise to the conclusion that in the outer part of the core the substance is in a liquid (molten) state. Below the boundary of the mantle and core, the speed of longitudinal waves increases again - up to 10.4 km/s. At the boundary of the outer and inner core (5120 km), the speed of longitudinal waves reaches 11.1 km/s. And then to the center of the Earth it remains almost unchanged. On this basis, it is assumed that from a depth of 5080 km the core material again acquires the properties of a very dense body, and a solid internal " nucleolus"with a radius of 1290 km. According to some scientists, the earth's core consists of nickel iron. Others argue that iron, in addition to nickel, contains an admixture of light elements - silicon, oxygen, possibly sulfur, etc. In any case, iron, as a good conductor of electricity, can serve as a source of dynamo effect and formation magnetic field Earth.

Indeed, from the point of view of physics, the Earth, to some approximation, is a magnetic dipole, i.e. a kind of magnet with two poles: south and north.

Japanese scientists prove that the Earth's core is gradually increasing due to the differentiation of mantle matter 12 . makes up 82.3% of the Earth's volume. Only hypothetical assumptions can be made about its structure and material composition. They are based on seismological data and materials from experimental modeling of physical and chemical processes occurring in the subsurface at high pressures and temperatures. The speed of longitudinal seismic waves in the mantle increases to 13.6 km/s, transverse - to 7.2-7.3 km/s.

Earth's mantle (top And lower). Below the Mohorovicic division between the Earth's crust and the Earth's core is mantle(to a depth of about 2900 km). This is the most massive of the Earth's shells - it makes up 83% of the Earth's volume and about 67% of its mass. The Earth's mantle is divided into three layers according to its structure, composition and properties: Guttenberg layer - B to a depth of 200–400 km, Galicin layer - C up to 700-900 km and layer D up to 2900 km. As a first approximation, layers B and C are usually combined into the upper mantle, and layer D considered as the lower mantle. In general, within the mantle, the density of matter and the speed of seismic waves increase rapidly.

Upper mantle. The upper mantle is thought to be composed of igneous rocks highly depleted in silica but enriched in iron and magnesium (called ultramafic rocks), mainly peridotite. Peridotite consists of 80% of the mineral olivine (Mg,Fe) 2 and 20% of pyroxene (Mg,Fe) 2.

Earth's crust differs from the underlying shells in its structure and chemical composition. The base of the earth's crust is outlined by the Mohorovicic seismic boundary, at which the speed of propagation of seismic waves increases sharply and reaches 8 - 8.2 km/s.

Table 3.5. Occurrence of rocks in the earth's crust

(according to A.B. Ronov, A.A. Yaroshevsky, 1976. and V.V. Dobrovolsky, 2001)

	Breed groups	Abundance, % volume of the earth's crust	Weight, 10 18 t
	Sands and sand rocks
	Clays, shales, siliceous rocks
	Carbonates
	Salt-bearing sediments (sulfate and halide rocks)
	Granitoids, granite gneisses, acid volcanic rocks and their metamorphic equivalents
	Gabbro, basalts and their metamorphic equivalents
	Dunites, peridotites, serpentinites
	Metasandstones
	Paragneisses and crystalline schists
	Metamorphosed carbonate rocks
	Ferrous rocks

The earth's surface and approximately 25 km of the earth's crust are formed under the influence of:

1)endogenous processes(tectonic or mechanical and magmatic processes), due to which the relief of the earth’s surface is created and strata of igneous and metamorphic rocks are formed;

2) exogenous processes, causing denudation (destruction) and leveling of the relief, weathering and transfer of rock fragments and their redeposition in lower parts of the relief. As a result of the occurrence of very diverse exogenous processes, sedimentary rocks are formed, which make up the uppermost layer of the earth's crust.

There are two main types of earth's crust: continental(granite-gneiss) and ocean(basaltic) with discontinuous sedimentary layer. The transition from continental-type crust to oceanic-type crust is shown in Fig. 3.8.

The continental crust has three layers: upper- sedimentary and two lower composed of crystalline rocks. The thickness of the upper sedimentary layer varies widely: from almost complete absence on ancient shields to 10 - 15 km on the shelves of passive continental margins and in the marginal troughs of platforms. The average thickness of precipitation on stable platforms is about 3 km.

Under the sedimentary layer there are strata with a predominance of igneous and metamorphic rocks of the granitoid series, relatively rich in silica. In some places, in the areas where ancient shields are located, they come out onto the earth’s surface (Canadian, Baltic, Aldan, Brazilian, African, etc.). The rocks of the “granite” layer are usually transformed by processes of regional metamorphism and are very ancient in age (80% of the continental crust is older than 2.5 billion years).

P Below the “granite” layer is a “basalt” layer. Its material composition has not been studied, but judging by geophysical research data, it is assumed that it is close to the rocks of the ocean crust.

Both continental and oceanic crust are underlain by rocks of the upper mantle, from which they are separated by the Mohorovicic boundary (Moho boundary).

In general, the Earth's crust consists predominantly of silicates and aluminosilicates. It is dominated by oxygen (43.13%), silicon (26%) and aluminum (7.45%), mainly presented in the form of oxides, silicates and aluminosilicates. The average chemical composition of the earth's crust is given in table. 3.6.

In the continental crust there is a relatively high content of long-lived radioactive isotopes of uranium 238 U, thorium 232 Th and potassium 40 K. Their highest concentration is characteristic of the “granite” layer.

Table 3.6. Average chemical composition of continental and oceanic crust
Oxides and dioxides
	continental	oceanic

The oceanic crust differs from the continental crust in chemical composition and structure, but also has a three-layer structure

The uppermost layer - sedimentary - is represented by sandy-clayey and carbonate sediments deposited at shallow depths. At great depths, siliceous silts and deep-sea red clays are deposited.

The average thickness of ocean sediments does not exceed 500 m and only at the foot of the continental slopes, especially in areas of large river deltas, does it increase to 12-15 km. This is caused by a kind of fast-flowing “avalanche” sedimentation, when almost all the terrigenous material carried by river systems from the continent is deposited in the coastal parts of the oceans, on the continental slope and at its foot.

The second layer of oceanic crust in the upper part is composed of pillow basalt lavas. Below are dolerite dikes of the same composition. The total thickness of the second layer of ocean crust is 1.5 km and rarely reaches 2 km. Under the dike complex there are gabbros and serpentenites, which represent the upper part of the third layer. The thickness of the gabbro-serpentinite layer reaches 5 km. Thus, the total thickness of the oceanic crust without sedimentary cover is 6.5 - 7 km. Under the axial part of the mid-ocean ridges, the thickness of the ocean crust is reduced to 3-4, and sometimes to 2-2.5 km.

Beneath the crests of the mid-ocean ridges, the oceanic crust overlies pockets of basaltic melts released from the asthenosphere. The average density of the ocean crust without sedimentary layer is 2.9 g/cm 3 . Based on this, the total mass of the ocean crust is 6.4 10 24 g. The ocean crust is formed in the rift areas of the mid-ocean ridges due to the influx of basaltic melts from the asthenospheric layer of the Earth and the outpouring of tholeiitic basalts onto the ocean floor.

Lithosphere. The solid, dense shell lying above the asthenosphere (including the earth's crust) is called the lithosphere (Greek "lithos" - stone). A characteristic feature lithosphere is its rigidity and fragility. It is fragility that explains the observed block structure of the lithosphere. It is broken by large cracks - deep faults into large blocks - lithospheric plates.

Thanks to the global system of mechanical stresses, whose occurrence is associated with the rotation of the Earth, the lithosphere is split into fragments - blocks by faults in the submeridial, sublatitudinal and diagonal directions. These faults ensure the relative independence of the movement of lithospheric blocks relative to each other, which explains the difference in the structure and geological history of individual lithospheric blocks and their associations. The faults separating the blocks are weakened zones through which magmatic melts and flows of vapors and gases rise.

Unlike the lithosphere, the substance of the asthenosphere does not have a tensile strength and can deform (flow) under the action of even very small loads.

Chemical composition of the earth's crust . The abundance of elements in the earth's crust is characterized by a large contrast, reaching 10 10. The most common chemical elements (Fig. 3.10) throughout the Earth are:

oxygen(O 2) – makes up 47 mass% of the earth’s crust. It is part of about 2 thousand minerals;

silicon(Si) – makes up 29.5% and is included in more than a thousand minerals;

aluminum(Al) – 8.05%;

iron(Fe), calcium(Sa), potassium(TO), sodium(Na), titanium(Ti), magnesium (Mg) – make up the first% of the mass of the earth’s crust;

The remaining elements account for about 1%.

A.E. Fersman proposed expressing the Clarke numbers not in weight, but in atomic percentages, which better reflects the ratio of the numbers of atoms, rather than their masses, and formulated three main principles:

1. The abundance of elements in the earth’s crust is characterized by a large contrast, reaching 10 10 .

2. Only nine elements O, Si, Al, Fe, Ca, Na, K, Mg, H are the main builders of the lithosphere, accounting for 99.18% of its weight. Of these, the first three account for 84.55%. The remaining 83 account for less than 1% (Fig. 3.9.).

3. The leading element is oxygen. Its mass clarke is estimated in the range of 44.6 – 49%, atomic – 53.3 (according to A.E. Fersman), and volumetric (according to V.M. Goldschmidt) – 92%.

Thus, the earth's crust, both in volume and mass, consists mainly of oxygen.

If the average contents of elements in the crust, to a first approximation, can be considered unchanged throughout its history, then in its individual sections there are periodic changes. Although the earth's crust is not a closed system, its exchange of masses of matter with space and the deeper zones of the planet cannot yet be taken into account quantitatively, goes beyond the accuracy of our measurements and clearly will not affect the clarke numbers.

TO lark . In 1889, American geochemist Frank Clark first determined the average contents of chemical elements in the earth's crust. In honor of him, Russian academician A.E. Fersman proposed to name " Clarks" - the average content of chemical elements in any natural system - in the earth's crust, in a rock, in a mineral 13. The higher the natural clarke of a chemical element, the more minerals that contain this element. Thus, oxygen is found in almost half of all known minerals. Any area that contains more than a clarke of a given substance is potentially interesting, since there may be industrial reserves of this substance. Such areas are explored by geologists in order to identify mineral deposits.

Some chemical elements (such as radioactive elements) change over time. Thus, uranium and thorium, decaying, turn into stable elements - lead and helium. This gives reason to assume that in past geological epochs the clarks of uranium and thorium were obviously much higher, and the clarks of lead were lower than now. Apparently, this also applies to all other elements subject to radioactive transformations. The isotopic composition of some chemical elements changes over time (for example, the uranium isotope 238 U). It is believed that two billion years ago there were almost six times more atoms of the 235 U isotope on Earth than there are now.

The anthropogenic impact on nature is currently penetrating into all spheres, so it is necessary to briefly consider the characteristics of individual shells of the Earth.

The Earth consists of the core, mantle, crust, lithosphere, hydrosphere and. Due to the influence of living matter and human activity, two more shells arose - the biosphere and the noosphere, which includes the technosphere. Human activity extends to the hydrosphere, lithosphere, biosphere and noosphere. Let us briefly consider these shells and the nature of the impact of human activity on them.

General characteristics of the atmosphere

The outer gaseous shell of the Earth. The lower part is in contact with the lithosphere or, and the upper part is in contact with interplanetary space. consists of three parts:

1. The troposphere (lower part) and its height above the surface is 15 km. The troposphere consists of, the density of which decreases with height. The upper part of the troposphere is in contact with the ozone screen - a layer of ozone 7-8 km thick.

The ozone screen prevents hard ultraviolet radiation or high-energy cosmic radiation from reaching the Earth's surface (lithosphere, hydrosphere), which are harmful to all living things. The lower layers of the troposphere - up to 5 km above sea level - are an air habitat, while the lowest layers are most densely populated - up to 100 m from the land surface or. The greatest impact from human activity, which has the greatest ecological significance, is experienced by the troposphere and especially its lower layers.

2. Stratosphere - middle layer, the limit of which is an altitude of 100 km above sea level. The stratosphere is filled with rarefied gas (nitrogen, hydrogen, helium, etc.). It goes into the ionosphere.

3. Ionosphere - the upper layer that passes into interplanetary space. The ionosphere is filled with particles that arise from the decay of molecules - ions, electrons, etc. The “northern lights” appear in the lower part of the ionosphere, which is observed in areas above the Arctic Circle.

Environmentally highest value has a troposphere.

Brief characteristics of the lithosphere and hydrosphere

The surface of the Earth, located under the troposphere, is heterogeneous - part of it is occupied by water, which forms the hydrosphere, and part is land, forming the lithosphere.

Lithosphere - outer solid shell globe, formed by rocks (hence the name - “cast” - stone). It consists of two layers - the upper one, formed by sedimentary rocks with granite, and the lower one, formed by hard basaltic rocks. Part of the lithosphere is occupied by water (), and part is land, making up about 30% of the earth's surface. The topmost layer of land (for the most part) is covered with a thin layer of fertile surface - soil. Soil is one of the living environments, and the lithosphere is the substrate on which various organisms live.

The hydrosphere is the water shell of the earth's surface, formed by the totality of all bodies of water present on Earth. The thickness of the hydrosphere varies in different areas, but the average depth of the ocean is 3.8 km, and in some depressions it is up to 11 km. The hydrosphere is the source of water for all organisms living on Earth, it is a powerful geological force that circulates water and other substances, the “cradle of life” and habitat aquatic organisms. The anthropogenic impact on the hydrosphere is also great and will be discussed below.

General characteristics of the biosphere and noosphere

Since the appearance of life on Earth, a new, specific shell has emerged - the biosphere. The term “biosphere” was introduced by E. Suess (1875).

The biosphere (sphere of life) is that part of the Earth’s shells in which various organisms live. The biosphere occupies part (the lower part of the troposphere) of the lithosphere (the upper part, including the soil) and permeates the entire hydrosphere and the upper part of the bottom surface.

The biosphere can also be defined as a geological shell inhabited by living organisms.

The boundaries of the biosphere are determined by the presence of conditions necessary for the normal functioning of organisms. The upper part of the biosphere is limited by the intensity of ultraviolet radiation, and the lower part by high temperature (up to 100°C). Bacterial spores are found at an altitude of 20 km above sea level, and anaerobic bacteria are found at a depth of up to 3 km from the earth's surface.

It is known that they are formed by living matter. The concentration of living matter characterizes the density of the biosphere. It has been established that the highest density of the biosphere is characteristic of the surface of land and ocean at the border of contact of the lithosphere and hydrosphere with the atmosphere. The density of life in the soil is very high.

The mass of living matter is small compared to the mass of the earth's crust and hydrosphere, but plays a huge role in the processes of change in the earth's crust.

The biosphere is the totality of all biogeocenoses present on Earth, therefore it is considered the highest ecosystem of the Earth. In the biosphere, everything is interconnected and interdependent. The gene pool of all organisms on Earth ensures the relative stability and renewability of the planet's biological resources, unless there is a sharp intervention in natural ecological processes by various forces of a geological or interplanetary nature. At present, as mentioned above, anthropogenic factors influencing the biosphere have taken on the character of a geological force, which must be taken into account by humanity if it wants to survive on Earth.

Since the appearance of man on Earth, anthropogenic factors arose in nature, the effect of which intensifies with the development of civilization, and a new specific shell of the Earth arose - the noosphere (sphere of intelligent life). The term “noosphere” was first introduced by E. Leroy and T. Y. de Chardin (1927), and in Russia for the first time in his works was used by V. I. Vernadsky (30-40s of the 20th century). In the interpretation of the term “noosphere”, two approaches are distinguished:

1. “The noosphere is that part of the biosphere where human economic activity is realized.” The author of this concept is L. N. Gumilyov (son of the poetess A. Akhmatova and poet N. Gumilyov). This point of view is valid if it is necessary to highlight human activity in the biosphere and show its difference from the activities of other organisms. This concept characterizes the “narrow sense” of the essence of the noosphere as the shell of the Earth.

2. “The noosphere is the biosphere, the development of which is directed by the human mind.” This concept is widely represented in and is a concept in the broad understanding of the essence of the noosphere, since the influence human mind impact on the biosphere can be both positive and negative, with the latter very often prevailing. The noosphere includes the technosphere - the part of the noosphere associated with production activities person.

At the present stage of development of civilization and population, it is necessary to “reasonably” influence Nature, to optimally influence it in order to cause minimal harm to natural ecological processes, restore destroyed or disturbed biogeocenoses, and even human life as an integral part of the biosphere. Human activity inevitably makes changes to the world around us, but, taking into account the possible consequences, anticipating possible negative impacts, it is necessary to ensure that these consequences are the least destructive.

Brief description of emergency situations arising on the surface of the Earth and their classification

An important role in natural ecological processes is played by emergency situations that constantly arise on the surface of the Earth. They destroy local biogeocenoses, and if they are repeated cyclically, in some cases they are environmental factors, facilitating the course of evolutionary processes.

Situations in which the normal functioning of a large number of people or the biogeocenosis as a whole becomes difficult or impossible are called emergencies.

The concept of "emergency situations" in to a greater extent applies to human activities, but it also applies to natural communities.

By origin, emergency situations are divided into natural and anthropogenic (technogenic).

Natural emergencies arise as a result of natural phenomena. These include floods, earthquakes, landslides, mudflows, hurricanes, eruptions, etc. Let's consider some phenomena that cause natural emergencies.

This is a sudden release of potential energy from the earth's interior, taking the form of shock waves and elastic vibrations (seismic waves).

Earthquakes occur mainly due to underground volcanic phenomena, displacement of layers relative to each other, but they can also be technogenic in nature and occur due to the collapse of mineral deposits. During earthquakes, displacements, vibrations and vibrations of rocks occur from seismic waves and tectonic movements of the earth's crust, which leads to destruction of the surface - the appearance of cracks, faults, etc., as well as to the occurrence of fires and the destruction of buildings.

Landslides are the sliding movement of rocks down a slope from inclined surfaces (mountains, hills, sea terraces, etc.) under the influence of gravity.

During landslides, the surface is disturbed, biocenoses die, populated areas are destroyed, etc. The greatest damage is caused by very deep landslides, the depth of which exceeds 20 meters.

Volcanism (volcanic eruptions) is a set of phenomena associated with the movement of magma (molten mass of rock), hot gases and water vapor rising through channels or cracks in the earth's crust.

Volcanism is a typical natural phenomenon that causes great destruction of natural biogeocenoses, causing enormous damage to human economic activity, and heavily polluting the region adjacent to volcanoes. Volcanic eruptions are accompanied by other catastrophic natural phenomena - fires, landslides, floods, etc.

Mudflows are short-term stormy floods carrying a large amount of sand, pebbles, large rubble and stones, having the character of mud-stone flows.

Mudflows are typical for mountainous areas and can cause significant damage to human economic activity, cause the death of various animals and cause the destruction of local plant communities.

Snow avalanches are snow falls that carry with them more and more masses of snow and other bulk materials. Avalanches are of both natural and anthropogenic origin. They cause great damage to human economic activity, destroying roads, power lines, causing the death of people, animals and plant communities.

The above phenomena, which cause emergency situations, are closely related to the lithosphere. Natural phenomena that create emergency situations are also possible in the hydrosphere. These include floods and tsunamis.

Floods are the flooding of areas within river valleys, lake shores, seas and oceans.

If floods are strictly periodic (high and low tides), then in this case natural biogeocenoses are adapted to them as a habitat under certain conditions. But often floods are unexpected and associated with individual non-periodic phenomena (excessive snowfall in winter creates conditions for extensive floods, causing flooding of a large area, etc.). During floods, soil covers are disturbed, the area can be contaminated with various wastes due to the erosion of their storage facilities, the death of animals, plants and people, the destruction of populated areas, etc.

Gravitational waves of great strength arising on the surface of seas and oceans.

Tsunamis have natural and man-made causes. Natural causes include earthquakes, seaquakes and underwater volcanic eruptions, while man-made causes include underwater nuclear explosions.

Tsunamis cause the death of ships and accidents on them, which in turn leads to pollution of the natural environment, for example, the destruction of a tanker transporting oil will lead to the contamination of a huge water surface with an oil film that is poisonous to plankton and pelargic forms of animals (plankton are suspended small organisms living in the surface layer of water of an ocean or other body of water; pelargic forms of animals - animals that move freely in the water column due to active movement, for example, sharks, whales, cephalopods; benthic forms of organisms - organisms leading a benthic lifestyle, for example flounder, hermit crabs. , echinoderms, algae attached to the bottom, etc.). Tsunamis cause strong mixing of waters, transfer of organisms to an unusual habitat and death.

Phenomena causing emergencies also occur. These include hurricanes, tornadoes, various types storms

Hurricanes are tropical and extratropical cyclones, in which the pressure in the center is greatly reduced, and are accompanied by the emergence of winds that have high speed and destructive power.

There are weak, strong and extreme hurricanes, which cause heavy rains, sea waves and destruction of ground objects, the death of various organisms.

Vortex storms (squalls) are atmospheric phenomena associated with the occurrence strong winds, possessing great destructive power and a significant area of ​​distribution. There are snow, dust and dustless storms. Squalls cause the transfer of upper layers of soil, their destruction, death of plants and animals, and destruction of structures.

Tornadoes (tornadoes) are a vortex-like form of movement of air masses, accompanied by the appearance of air funnels.

The power of tornadoes is great; in the area of ​​their movement, complete destruction of the soil is observed, animals die, buildings are destroyed, objects are transferred from one place to another, causing damage to objects located there.

In addition to the natural phenomena described above that lead to emergency situations, there are other phenomena that cause them, the cause of which is human activity. To anthropogenic emergency situations include:

1. Transport accidents. When traffic rules are violated on various highways (roads, railways, rivers, seas), death occurs vehicles, people, animals, etc. Various substances enter the natural environment, including those that lead to the death of organisms of all kingdoms (for example, pesticides, etc.). As a result of transport accidents, fires and gases (hydrogen chloride, ammonia, fire and explosive substances) may occur.

2. Accidents at large enterprises. Violation technological processes, non-compliance with equipment operating rules, imperfect technology can cause releases into environment harmful compounds that cause various diseases in humans and animals, contribute to the appearance of mutations in the bodies of plants and animals, and also lead to the destruction of buildings and the occurrence of fires. The most dangerous accidents occur at enterprises using . Accidents at nuclear power plants (NPPs) cause great harm, since in addition to the usual damaging factors (mechanical destruction, release of harmful substances of a single action, fires), accidents at nuclear power plants are characterized by damage to the area by radionuclides, penetrating radiation, and the radius of damage in this case significantly exceeds the probability of occurrence accidents at other enterprises.

3. Fires covering large areas of forests or peatlands. As a rule, such fires are anthropogenic in nature due to violation of the rules for handling fire, but they can also be natural in nature, for example due to thunderstorm discharges (lightning). Such fires can also be caused by faults in power lines. Fires destroy natural communities of organisms over large areas and cause great economic damage to human economic activity.

All characterized phenomena that disrupt natural biogeocenoses and cause great damage to human economic activity require the development and adoption of measures to reduce their negative impact, which is implemented in the implementation of environmental actions and combating the consequences of emergency situations.

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.

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 the 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.

The atmosphere is the 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, protects the planet from negative influence of 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! Huge number fresh water is currently in the form of ice - today in permafrost zones in the form of glaciers, huge icebergs, permanent non-melting snow, there are about 34 million km3 of fresh water reserves.

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

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, as well as the 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.

On at the moment The deepest mine in the earth's crust dug by man is about 8 kilometers, so studying the mantle, and even more so 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, make it possible to more accurately predict destructive natural disasters, and discover new, not yet developed mineral deposits.