The Earth's crust is the upper solid shell of the Earth. Atmosphere - the air envelope of the Earth

home 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.

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.

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 the 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. up 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 do not penetrate below this interface. 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. About its structure and material composition Only hypothetical assumptions can be made. 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 (upper volumetric 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)

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. Average power 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.

The topmost 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 out river systems from the continent, 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, the American geochemist Frank Clark first determined the average contents 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.

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 closed form. 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 impact environment- water, air, living organisms and plants. Depending on the 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.

External: The atmosphere is the air shell of the Earth.

Hydrosphere- water shell Earth.

The biosphere is the “sphere of life”; it is formed by living organisms and the environment in which they live.

These shells penetrate one another and are in constant interaction between themselves, the lithosphere and mantle of the Earth, expressed in the exchange of matter and energy. The interaction is associated not only with the difference in their physical properties, but also in composition.

A common property of the outer shells of the Earth is their high mobility, due to which any change in the composition of each of them very quickly spreads often to its entire mass. This explains the relative uniformity of the composition of the shells in each this moment, despite the fact that during geological development they experienced very significant changes.

Domestic: The Earth's crust is the hard, rocky shell of the Earth, consisting of minerals and rocks. Its thickness ranges from 5-10 km in the oceans to 70-80 km on the continents.

The lithosphere is the solid shell of the Earth, including the earth's crust and the upper part of the mantle. The thickness of the lithosphere averages 70 – 250 km

Mantle Mohorovicic surface observed in all areas globe, is conventionally considered the lower boundary of the earth's crust. Below it, to a depth of 2900 km, is the inner shell of the Earth, or mantle. . It is divided into two layers: the upper mantle and the lower mantle. Scientists believe that the upper mantle is close in chemical and mineralogical composition to rocks rich in magnesium and iron, which have significant density. The lower layer of the shell is homogeneous compared to the upper one.

Core Beneath the mantle is the earth's core. The outer part of the earth's core has the properties of a liquid: transverse waves do not pass through it. The radius of the earth's core is about 3470 km. During the transition from the shell (mantle) to the core, they change sharply physical properties substances. The core also contains an inner core Earth; its radius is about 1250 km.

Earth- third planet from the Sun solar system, the largest in diameter, mass and density among the terrestrial planets. Most often referred to as World, Blue Planet, Sometimes Terra(from lat. Terra). The only thing known to man at the moment, the body of the Solar system in particular and the Universe in general, inhabited by living beings.

Scientific evidence indicates that the Earth formed from the Solar Nebula about 4.54 billion years ago, and acquired its only natural satellite- The moon. Life appeared on Earth about 3.5 billion years ago. Since then, the Earth's biosphere has significantly changed the atmosphere and other abiotic factors, causing the quantitative growth of aerobic organisms, as well as the formation of the ozone layer, which, together with the Earth’s magnetic field, weakens harmful solar radiation, thereby maintaining conditions for life on Earth.

The Earth interacts (is pulled by gravitational forces) with other objects in space, including the Sun and Moon. The Earth orbits the Sun and makes a complete revolution around it in approximately 365.26 days. The Earth's rotation axis is tilted 23.4° relative to its orbital plane, causing seasonal changes on the surface of the planet with a period of one tropical year (365.24 solar days). The Moon began its orbit around the Earth approximately 4.53 billion years ago, which stabilized the planet's axial tilt and is responsible for the tides that slow the Earth's rotation.

5. Geological activity factors of the external dynamics of the Earth (exogenous factors).

Exogenous processes- these are processes of external dynamics. They occur on the surface of the Earth or at shallow depths in the earth's crust under the influence of forces caused by the energy of solar radiation, gravity, the vital activity of plant and animal organisms and human activity. These processes that transform the relief of continents include: weathering, various slope processes, the activity of flowing water, the activity of oceans and seas, lakes, ice and snow, permafrost processes, wind activity, groundwater, processes caused by human activity, biogenic processes.

All exogenous processes carry out geological work on the destruction, transfer (denudation) and accumulation (accumulation) of transported material.

6. Geological activity of factors of the internal dynamics of the Earth (endogenous factors).

Endogenous processes are processes of internal dynamics that manifest themselves when exposed to internal forces Earth onto a hard shell. These include: tectonic movements of the earth's crust, magmatism, metamorphism and earthquakes, which are a type of tectonic movements. Tectonic movements of the earth's crust create basic forms over a long period of time earth's surface- mountain or depression, i.e. play a decisive role in the formation of the modern topography of the earth's surface.

Products volcanic activity(these are also endogenous processes) can be liquid (lava), solid (volcanic bombs, sand, ash) and gaseous (fumaroles, sulfates). Many hot springs (therms) and their variety - geysers (periodically gushing) that bring to the surface are associated with the activity of volcanoes. a large number of minerals.

Igneous activity is the main reason for the formation of primary igneous (granite, basalt, marble, etc.) and metamorphic rocks that predominate in the lithosphere and the appearance of mountainous terrain.

7. Periodic law of geographic zoning and its geophysical essence.

Zoning- change natural ingredients and processes from the equator to the poles (depending on the spherical shape of the Earth, the angle of inclination of the Earth's axis to the ecliptic plane (orbital rotation), the size of the Earth, the distance of the Earth from the Sun).

The term was first introduced by Humboldt in the early 18th century. The founder of the doctrine of zonality Dokuchaev.

According to Dokuchaev, the manifestation of zonality in: the earth’s crust, water, air, vegetation, soil, fauna.

The periodic law of geographic zoning is the presence of similar landscape areas in different zones associated with the repetition of the same ratios of heat and moisture. This law was formed by A.A. Grigoriev and M.I. Budyko.

According to periodic law Geographical zoning is based on the division of the geographical envelope:

1) the amount of absorbed solar energy;

2) the amount of incoming moisture;

3) the ratio of heat and moisture.

Climatic conditions Geographic zones and zones can be assessed using indicators: humidification coefficient Vysotsky-Ivanov and radiation dryness index Budyko. The value of the indicators is determined by the nature of landscape moisture: arid (dry) and humid (wet).

Geographical zoning is inherent not only to the continents, but also to the World Ocean, within which different zones differ in the amount of incoming solar radiation, balances of evaporation and precipitation, water temperature, characteristics of surface and deep currents, and, consequently, the world of living organisms.

Azonality refers to the distribution of some object or phenomenon without connection with the zonal features of a given territory. There are two main forms of manifestation of azonality - sectorialization of geographical zones and altitudinal zone. The reason for azonality is the heterogeneity of the earth's surface: the presence of continents and oceans, mountains and plains, the uniqueness of local factors: the composition of rocks, relief, moisture conditions and other features.

Geographical zoning is most fully expressed in the very major continent Lands – in Eurasia – from Arctic to equatorial belt inclusive. The most pronounced longitudinal differentiation is presented in the temperate and subtropical zones Eurasia, where all three sectors are clearly expressed. IN tropical zone There are two sectors. The sectorality is weakly expressed in the equatorial and subpolar belts.

At low latitudes (from approximately 0° to 30°), the factor limiting the growth of vegetation is moisture. The following zones are observed here: wet equatorial forests, rainforests, deciduous forests, savannas, desert savannas, tropical desert. At high latitudes (from about 65° and above), the limiting factor is heat - pppa.ru. Forest-tundras, tundras, arctic deserts. Between high and low latitudes in subtropical and temperate zones, different combinations of heat and moisture are observed. Thus, deserts (subtropical and temperate zone) are located in areas where moisture is insufficient (to<1, r>1), and humid subtropical, broad-leaved, mixed forests and taiga formed in areas with good moisture (k and r are close to 1).

The next manifestation of azonality is altitudinal zonation - a natural change in natural components and natural complexes with an ascent to the mountains from their foot to the peaks. It is caused by climate change with altitude: a decrease in temperature and, up to a certain altitude (up to 2-3 km), an increase in precipitation.

Azonal formations include swamps, floodplains and terraces of river valleys and a number of other natural complexes.

Azonality– a specific form of manifestation of zonality. Therefore, any part of the earth's surface is simultaneously zonal and azonal.

Intrazonality- the distribution of any features or components of nature (soils, vegetation, landscapes) in the form of separate areas that form regular inclusions within one or more adjacent geographical zones. Intrazonal phenomena bear the imprint of the influences of the nature of the zones surrounding them. I. is a special case of azonality.

PERIODIC LAW OF GEOGRAPHIC ZONING - a law that establishes the repetition at different latitudes of geographical zones that have certain general properties. Formulated by A. A. Grigoriev and M. I. Budyko in 1956. P. z. g.z. develops the law of geographical zoning by V.V. Dokuchaev. According to P. z. g. z., the division of the geographical envelope is based on: 1) the amount of absorbed solar energy, increasing from the poles to the equator and characterized by annual values radiation balance of the earth's surface; 2) the amount of incoming moisture, which experiences a number of fluctuations against the background of general growth in the same direction and is characterized by annual precipitation amounts; 3) the ratio of heat and moisture, more precisely, the ratio of radiation. balance to the amount of heat required to evaporate the annual amount of precipitation. The last value, called the radiation dryness index, ranges from O to 5, passing through values ​​close to unity three times between the pole and the equator: in zones deciduous forests temperate zone, subtropical rain forests and equatorial forests, turning into light tropical forests. Three periods of radiation. dryness index have their differences. Due to the increase in the direction of the equator abs. radiation values balance and precipitation, each passage of the dryness index through unity occurs with an increasingly higher influx of heat and moisture. This results in an increase from high latitudes to low intensities natural processes and especially organic productivity. peace.

8. Basic characteristics of the Earth. The role of orbital motion around the Sun, daily rotation and cycles of solar activity in the rhythm of natural processes and phenomena.

Introduction

1. Basic shells of the earth

3. Geothermal regime of the earth

Conclusion

List of sources used

Introduction

Geology is the science of the structure and history of the development of the Earth. The main objects of research are rocks that contain the geological record of the Earth, as well as modern physical processes and mechanisms operating both on its surface and in its interior, the study of which allows us to understand how our planet developed in the past.

The earth is constantly changing. Some changes occur suddenly and very violently (for example, volcanic eruptions, earthquakes or large floods), but more often - slowly (a layer of sediment no more than 30 cm thick is removed or accumulated over a century). Such changes are not noticeable throughout the life of one person, but some information has been accumulated about changes over a long period of time, and with the help of regular accurate measurements, even minor movements of the earth’s crust are recorded.

The history of the Earth began simultaneously with the development of the solar system approximately 4.6 billion years ago. However, the geological record is characterized by fragmentation and incompleteness, because many ancient rocks were destroyed or covered by younger sediments. Gaps must be filled by correlation with events that have occurred elsewhere and for which more data are available, as well as by analogy and hypotheses. The relative age of rocks is determined on the basis of the complexes of fossil remains they contain, and sediments in which such remains are absent are determined by relative position both of them. In addition, the absolute age of almost all rocks can be determined by geochemical methods.

IN this work The main shells of the earth, its composition and physical structure are considered.

1. Basic shells of the earth

The Earth has 6 shells: atmosphere, hydrosphere, biosphere, lithosphere, pyrosphere and centrosphere.

Atmosphere - external gas envelope Earth. Its lower boundary runs along the lithosphere and hydrosphere, and its upper boundary is at an altitude of 1000 km. The atmosphere is divided into the troposphere (moving layer), stratosphere (layer above the troposphere) and ionosphere (upper layer).

Average height troposphere - 10 km. Its mass makes up 75% of the total mass of the atmosphere. The air in the troposphere moves in both horizontal and vertical directions.

The stratosphere rises 80 km above the troposphere. Its air, moving only in a horizontal direction, forms layers.

Even higher extends the ionosphere, which got its name due to the fact that its air is constantly ionized under the influence of ultraviolet and cosmic rays.

The hydrosphere occupies 71% of the Earth's surface. Its average salinity is 35 g/l. The temperature of the ocean surface is from 3 to 32°C, density is about 1. sunlight penetrates to a depth of 200 m, and ultra-violet rays- to a depth of up to 800 m.

The biosphere, or sphere of life, merges with the atmosphere, hydrosphere and lithosphere. Its upper boundary reaches the upper layers of the troposphere, the lower boundary runs along the bottom of the ocean basins. The biosphere is divided into the sphere of plants (over 500,000 species) and the sphere of animals (over 1,000,000 species).

The lithosphere - the rocky shell of the Earth - is from 40 to 100 km thick. It includes continents, islands and the bottom of the oceans. Average height of the continents above sea level: Antarctica - 2200 m, Asia - 960 m, Africa - 750 m, North America- 720 m, South America- 590 m, Europe - 340 m, Australia - 340 m.

Under the lithosphere is the pyrosphere - the fiery shell of the Earth. Its temperature increases by about 1°C for every 33 m of depth. Due to high temperatures and high pressure, rocks at significant depths are likely to be in a molten state.

The centosphere, or the core of the Earth, is located at a depth of 1800 km. According to most scientists, it consists of iron and nickel. The pressure here reaches 300000000000 Pa (3000000 atmospheres), the temperature is several thousand degrees. The state of the core is still unknown.

The fiery sphere of the Earth continues to cool. The hard shell thickens, the fiery shell thickens. At one time, this led to the formation of solid stone blocks - continents. However, the influence of the fiery sphere on the life of planet Earth is still very great. The outlines of continents and oceans, the climate, and the composition of the atmosphere changed repeatedly.

Exogenous and endogenous processes continuously change the solid surface of our planet, which, in turn, actively affects the Earth's biosphere.

2. Composition and physical structure of the earth

Geophysical data and the results of studying deep inclusions indicate that our planet consists of several shells with different physical properties, the change in which reflects both the change in the chemical composition of the substance with depth and the change in its state of aggregation as a function of pressure.

The uppermost shell of the Earth - the earth's crust - under the continents has an average thickness of about 40 km (25-70 km), and under the oceans - only 5-10 km (without the layer of water, which averages 4.5 km). The lower edge of the earth's crust is taken to be the Mohorovicic surface - a seismic section on which the speed of propagation of longitudinal elastic waves with a depth of 6.5-7.5 to 8-9 km/s increases abruptly, which corresponds to an increase in the density of matter from 2.8-3 .0 to 3.3 g/cm3.

From the surface of Mohorovicic to a depth of 2900 km, the Earth's mantle extends; the upper least dense zone, 400 km thick, is distinguished as the upper mantle. The interval from 2900 to 5150 km is occupied by the outer core, and from this level to the center of the Earth, i.e. from 5150 to 6371 km, the inner core is located.

The Earth's core has interested scientists since its discovery in 1936. It was extremely difficult to image because of the relatively small number of seismic waves that reached it and returned to the surface. Besides, extreme temperatures and core pressure for a long time difficult to reproduce in the laboratory. New research may provide a more detailed picture of the center of our planet. The earth's core is divided into 2 separate regions: liquid (outer core) and solid (inner core), the transition between which lies at a depth of 5,156 km.

Iron is the only element that closely matches the seismic properties of the Earth's core and is abundant enough in the Universe to represent approximately 35% of the planet's mass in the 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, like a giant generator, electric currents, current in liquid core, create a global magnetic field. The layer of the mantle that is in direct 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 controversial. 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. At the same time, 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.

The outer core is also metallic (essentially iron), but unlike the inner core, the metal is here in a liquid state and does not transmit transverse elastic waves. Convective currents in the metallic outer core cause the formation of the Earth's magnetic field.

The Earth's mantle consists of silicates: compounds of silicon and oxygen with Mg, Fe, Ca. The upper mantle is dominated by peridotites - rocks consisting mainly of two minerals: olivine (Fe,Mg) 2SiO4 and pyroxene (Ca, Na) (Fe,Mg,Al) (Si,Al) 2O6. These rocks contain relatively little (< 45 мас. %) кремнезема (SiO2) и обогащены магнием и железом. Поэтому их называют ультраосновными и ультрамафическими. Выше поверхности Мохоровичича в пределах континентальной земной коры преобладают силикатные магматические породы основного и кислого составов. Основные породы содержат 45-53 мас. % SiO2. Кроме оливина и пироксена в состав основных пород входит Ca-Na полевой шпат - плагиоклаз CaAl2Si2O8 - NaAlSi3O8. Кислые магматические породы предельно обогащены кремнеземом, содержание которого возрастает до 65-75 мас. %. Они состоят из кварца SiO2, плагиоклаза и K-Na полевого шпата (K,Na) AlSi3O8. Наиболее распространенной интрузивной породой основного состава является габбро, а вулканической породой - базальт. Среди кислых интрузивных пород чаще всего встречается гранит, a вулканическим аналогом гранита является риолит .

Thus, the upper mantle consists of ultrabasic and ultramafic rocks, and the earth’s crust is formed mainly by basic and acidic igneous rocks: gabbro, granites and their volcanic analogues, which, compared to the peridotites of the upper mantle, contain less magnesium and iron and at the same time are enriched in silica , aluminum and alkali metals.

Beneath the continents, mafic rocks are concentrated in the lower part of the crust, and felsic rocks are concentrated in the upper part. Beneath the oceans, the thin crust of the earth consists almost entirely of gabbro and basalt. It is firmly established that the basic rocks, which according to various estimates constitute from 75 to 25% of the mass of the continental crust and almost all of the oceanic crust, were smelted from the upper mantle during the process of magmatic activity. Felsic rocks are usually considered to be the product of repeated partial melting of mafic rocks within the continental crust. Peridotites from the uppermost part of the mantle are depleted in fusible components transported into the earth's crust during magmatic processes. The upper mantle beneath the continents, where the thickest crust arose, is especially “depleted.”

Finally, a very sharp jump occurs at a depth of 2900 km. The part of the globe enclosed between the base of the earth's crust, at a depth of 50-60 km, and a depth of 2900 km, is called the Earth's shell. The part of the globe contained within the interface at a depth of more than 2900 km is called the Earth's core, and the interface itself is called the core boundary.

The Earth's core consists of a substance that does not resist changing shape, i.e. it behaves in relation to seismic vibrations like a liquid or gaseous body.

The top cover of the globe, which makes up the continents and ocean floors, is divided into two main layers. The uppermost layer of the continental part of the earth's crust consists mainly of strata of so-called sedimentary rocks and rocks similar in composition to granites. Therefore, the top layer is usually called granite, although it must be remembered that this name is conditional, since there are other rocks in this layer, and its composition may vary somewhat from area to area.

Below lies the so-called basalt layer. The main role in its structure is played by rocks rich in magnesium and iron and poor in silicic acid. These are varieties of the basaltic group of rocks, and therefore the lower layer of the crust is called basaltic. This layer is separated from the underlying rocks of the subcrustal layer by a surface that is clearly distinguishable by seismic waves. This surface is called the S. Mohorovicic surface, named after the Yugoslav scientist who discovered it. The speed of seismic waves deeper than the interface immediately increases to 8 km/sec, which is due to an increase in the density of the Earth's substance.

The substance of the earth's crust is in a crystalline state. The thickness of the Earth's crust is less under the oceans than under the continents. It's possible that underneath Pacific Ocean There is no granite layer at all.

The uppermost part of the earth's crust largely consists of layered sedimentary rocks formed by the deposition of various fine particles in the seas and oceans. They contain the remains of animal organisms and plants that previously inhabited the globe. The total thickness of sedimentary rocks does not exceed 12-15 km. Their successive strata and the fossils of animals and plants they contain allow geologists to reconstruct the history of the development of life on Earth.

The upper part of the inner shell of the Earth is closest in chemical composition to the composition of rocks known as peridotites and pyroxenites, which are very rich in magnesium and iron and have a significant specific gravity.

We have some evidence of the real existence of this subcrustal shell. In the masses of rocks filling the vertical diamond-bearing “pipes” of the Kimberley in South Africa, as well as in the diamond mines of Yakutia, pieces of olivine and peridotite rocks brought from great depths are found in abundance. These are the deepest materials we know that make up the Earth. But using the methods of modern geophysics, we are cognizing the Earth further in depth, although only in relation to the distribution of material by density and elasticity, without yet knowing its other properties.

Thus, we can assume that the inner shell of the Earth extends to a depth of 2900 km. The shell substance is solid, but has plasticity, in the lower part it lacks a crystalline structure (amorphous). Its composition is apparently the same as in the uppermost (subcrustal) part. The change in the density of the Earth's shell is associated not so much with a change in composition, but with pressure, which reaches enormous values ​​here.

So, for example, the pressure per unit surface is equal to:

The earth's core has the properties of a liquid. The radius of the earth's core is 3471 km. When passing from the shell to the core, the physical properties of the substance change sharply. The reason for this change is probably a change in the atomic structure under the influence of high pressures, reaching about 3 million atmospheres. The temperature inside the Earth rises to 2000-3000°, while the temperature rises most quickly in the earth's crust, then much more slowly, and at great depths it remains constant.

The Earth's density increases from 2.6 at the surface to 6.8 at the boundary of the Earth's core. In the core itself the density increases to 10, and in its central parts it exceeds 12.

Until recently, it was believed that the core had an iron composition, similar to iron meteorites, and the shell had a silicate composition, corresponding to stony meteorites. However, according to modern scientific views, the reason for the sharp jump in densities and a sharp decrease in hardness at the boundary of the Earth’s core is not in the division of matter according to chemical composition, but in the physical and chemical process - the partial destruction of the electron shell of atoms at a critical pressure reaching 1.4 million atmospheres .

The separation of electrons from nuclei under the influence of enormous pressure and high temperature facilitates the sharp compaction of a substance and gives it new properties, similar in terms of hardness to the properties of liquid bodies (the ability of liquid bodies, while maintaining volume, to change their original shape), and in terms of electrical conductivity - with the properties of metals. Therefore, such a transformation is called the transition of a substance into the metallic phase.

Thus, the conditions for the existence of matter in the great depths of the globe are sharply different from the conditions on the earth's surface and those that we can so far create through experience.

Every year, data from geophysics and astrophysics allow us to better and better understand the structure of the globe, and this, in turn, gives us the opportunity to see the connection between a number of the most important geological processes occurring in the earth’s crust with processes occurring in the depths of the globe.

That is why it is so important and so interesting to study the structure of our planet.

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