The main features of the northeastern Crimea. North-eastern Crimea

The structure of the lithosphere

The lithosphere of the Earth consists of two layers: the earth's crust and part of the upper mantle. The border between them is the so-called. the Mohorovichich boundary, distinguished on the basis of an increase in the velocity of propagation of longitudinal seismic waves and the density of matter.

The Earth's crust is the upper solid shell of the Earth. The crust is not a unique formation inherent only to the Earth, because is found on most of the terrestrial planets, the satellite of the Earth - the Moon and satellites of the giant planets: Jupiter, Saturn, Uranus and Neptune. However, only on Earth there are two types of crust: oceanic and continental. In the border areas, the earth's crust is of an intermediate type - subcontinental or suboceanic, forming, for example, in the zones of island arcs. In the zones of mid-oceanic ridges, a rift-type crust can be distinguished, due to the absence of a gabbro-serpentinite layer in these zones and the close position of the asthenosphere.

The oceanic earth's crust consists of three layers: upper sedimentary, intermediate basaltic and lower gabbro-serpentinite, which until recently was included in the composition of basaltic.

Its thickness ranges from 2 km in zones of mid-oceanic ridges to 130 km in subduction zones, where the oceanic crust sinks into the mantle. This difference is associated with the fact that in the zones of mid-oceanic ridges, the oceanic crust is formed, with distance from the ridges, its thickness increases, rarely exceeding the value of 7 km, reaching a maximum in the zones of crust immersion in the upper mantle. The largest number of subduction zones falls on Pacific Ocean; they are associated with powerful seaquakes.

The sedimentary layer covering the melt is small: its thickness rarely exceeds 0.5 km, only near deltas large rivers reaching a thickness of 10-12 km. It consists of a sedimentary layer of sand, animal residues and precipitated minerals. Its base is often overlain by thin metal-bearing sediments, not sustained along strike, with a predominance of iron oxides. The lower part of the layer is composed of carbonate rocks, which are not found at great depths, due to the dissolution of foraminifera and coccolithophorids, which compose carbonate rocks, at high pressure. At depths exceeding 4.5 km, carbonate rocks are replaced by deep red clays and siliceous silts.

The basalt layer in the upper part is composed of tholeiitic basalt lavas, which are also called pillow lavas because of their characteristic shape. Below is a dike complex formed by dolerite dikes. Dikes are channels through which basaltic lava was poured to the surface. For this reason, the basalt layer is exposed in many places adjacent to the mid-ocean ridges.

In subduction zones, the basalt layer turns into ecgolites, which, having a density greater than the surrounding peridotites (the most common mantle rocks), sink into the depths. The mass of ecgolites is currently about 7% of the mass of the entire mantle of the Earth.

The gabbro-serpentinite layer lies directly above the upper mantle. It contains gabbroids and serpentinized peridotite, which are formed, respectively, during the slow crystallization of basaltic melts in the magma chamber and during the hydration of the basic mantle rocks along the cracks of the lithosphere. The layer thickness is 3-6 km; it can be found in all oceans. The velocities of longitudinal seismic waves within the layer are 6.5-7 km / sec.

The age of the oceanic crust is on average 100 million years. The oldest parts of the oceanic crust are 156 million years old (Late Jurassic) and are located in the Pijafet Basin in the Pacific Ocean.

Such a young age is due to the constant formation and absorption of oceanic crust. Every year in the rift zones of mid-oceanic ridges as a result of the separation of basaltic lava under them and its outpouring onto the surface of the ocean floor, 24 km 3 of igneous rocks weighing 70 billion tons are formed. If we take into account that the total mass of the oceanic crust, according to calculations, is 5.9 × 10 18 tons, it turns out that the entire oceanic crust is renewed in 100 million years, which is taken as its average age... The thickness of the oceanic crust practically does not change over time, due to its construction from the released melt.

The oceanic crust is concentrated not only within the seabed of the World Ocean. Small ancient parts of it are known in closed basins, an example of which is the northern depression of the Caspian Sea. The total area of ​​the oceanic crust is 306 million km 2.

The continental crust, as the name implies, lies beneath the Earth's continents and large islands. In contrast to the oceanic continental crust, it consists of three layers: upper sedimentary, middle granite and lower basaltic. The thickness of this type of earth's crust under young mountains reaches 75 km, under the plains it is from 35 to 45 km, and under the island arcs it is reduced to 20-25 km.

The sedimentary layer of the continental crust is formed by: clayey deposits and carbonates of shallow sea basins within the Proterozoic platforms; coarse clastic facies, replaced higher in the section by sandy-argillaceous deposits and carbonates of coastal facies in the foredeeps and on the passive margins of Atlantic continents.

The granite layer of the earth's crust is formed as a result of the intrusion of magma into cracks in the earth's crust. Consists of silica, aluminum and other minerals. The thickness of the granite layer reaches 25 km. The velocity of longitudinal seismic waves ranges from 5.5 to 6.3 km / sec. The layer is very ancient: its average age is about 3 billion years.

At depths of 15-20 km, the Konrad boundary is often traced, along which the propagation velocity of longitudinal seismic waves increases by 0.5 km / sec. The boundary separates the granite and basalt layers.

The basalt layer is formed when the main (basaltic) lavas erupt onto the land surface in zones of intraplate magmatism. Basalt is heavier than granite and contains more iron, magnesium and calcium. The velocity of longitudinal seismic waves within the layer is from 6.5 to 7.3 km / sec.

The border between the granite and basalt layers in a number of places runs along the so-called. Conrad surface, within which there is an abrupt increase in the velocity of longitudinal seismic waves from 6 to 6.5 km / s. In other places, the velocity of compressional seismic waves increases gradually and the boundary between the layers is blurred. And, finally, there are areas where several surfaces are observed at once, within which seismic waves increase.

The total mass of the earth's crust is estimated at 2.8 × 10 19 tons, which is only 0.473% of the mass of the entire planet Earth.

Below the earth's crust is separated from the upper mantle by the boundary of Mohorovicic or Moho, established in 1909 by the Croatian geophysicist and seismologist Andrei Mohorovich. At the boundary, there is a sharp increase in the velocities of longitudinal and transverse seismic waves. The density of the substance also increases. The Moho boundary may not coincide with the boundaries of the earth's crust, apparently dividing regions of different chemical composition: light acidic earth crust and dense ultrabasic mantle.

Layer underneath crust called the mantle. The mantle is divided by the Golitsyn layer into upper and lower ones, the boundary between which runs at a depth of about 670 km.

Within the upper mantle, the asthenosphere is distinguished - a lamellar layer, within which the velocities of seismic waves decrease.

The lithosphere is the upper hard shell of the Earth, consisting of the earth's crust and a layer of the upper mantle underlying the earth's crust. The lower boundary of the lithosphere is drawn at depths of about 100 km under the continents and about 50 km under the ocean floor. The upper part of the lithosphere (the one where life exists) - component biosphere.

The earth's crust is composed of igneous and sedimentary rocks, as well as metamorphic rocks formed at the expense of both.

Rocks are natural mineral aggregates of a certain composition and structure, formed as a result of geological processes and occurring in the earth's crust in the form of independent bodies. The composition, structure and conditions of bedding of rocks are due to the peculiarities of the geological processes that form them, which occur in a certain environment inside the earth's crust or on the earth's surface. Depending on the nature of the main geological processes, three genetic classes of rocks are distinguished: sedimentary, magmatic and metamorphic.

Igneous Rocks are natural mineral aggregates that arise during the crystallization of magmas (silicate and sometimes non-silicate melts) in the interior of the Earth or on its surface. According to the silica content, igneous rocks are divided into acidic (SiO 2 - 70-90%), medium (SiO 2> about 60%), basic ( SiO 2 about 50%) and ultrabasic (SiO 2 less than 40%). Examples of igneous rocks are volcanic base rock and granite.

Sedimentary Rocks are those rocks that exist in thermodynamic conditions characteristic of the surface part of the earth's crust, and are formed as a result of redeposition of weathering products and destruction of various rocks, chemical and mechanical precipitation from water, the vital activity of organisms, or all three processes at the same time. Many sedimentary rocks are essential minerals. Examples of sedimentary rocks are sandstones, which can be considered as accumulations of quartz and, therefore, concentrators of silica (SiO 2), and limestones - concentrators of CaO. The most common minerals of sedimentary rocks include quartz (SiO 2), orthoclase (KalSi 3 O 8) kaolinite (A1 4 Si 4 O 10 (OH) 8), calcite (CaCO 3), dolomite CaMg (CO 3) 2, etc. ...

Metamorphic call breeds, the main features of which ( mineral composition, structure, texture) are caused by the processes of metamorphism, while the signs of primary magmatic origin are partially or completely lost. Metamorphic rocks - schists, granulites, eclogites, etc. Typical minerals for them are mica, feldspar and garnet, respectively.

The substance of the earth's crust is composed mainly of light elements (up to Fe inclusive), and the elements that follow iron in the Periodic Table add up to only fractions of a percent. It is also noted that elements with an even value of atomic mass predominate significantly: they form 86% of the total mass of the earth's crust. It should be noted that in meteorites this deviation is even higher and amounts to 92% in metal meteorites and 98% in stone ones.

The average chemical composition of the earth's crust, according to different authors, is given in table. 25:

Table 25

Chemical composition of the earth's crust, wt. % (Gusakova, 2004)

Elements and oxides	Clark, 1924	Fugt, 1931	Goldschmidt, 1954	Half-dervaatr, 1955	Yaroshevsky, 1971
SiO 2	59,12	64,88	59,19	55,20	57,60
TiO 2	1,05	0,57	0,79	1,6	0,84
Al 2 O 3	15,34	15,56	15,82	15,30	15,30
Fe 2 O 3	3,08	2,15	6,99	2,80	2,53
FeO	3,80	2,48	6,99	5,80	4,27
MnO	0,12	-	-	0,20	0,16
MgO	3,49	2,45	3,30	5,20	3,88
CaO	5,08	4,31	3,07	8,80	6,99
Na 2 O	3,84	3,47	2,05	2,90	2,88
K 2 O	3,13	3,65	3,93	1,90	2,34
P 2 O 5	0,30	0,17	0,22	0,30	0,22
H 2 O	1,15	-	3,02	-	1,37
CO 2	0,10	-	-	-	1,40
S	0,05	-	-	-	0,04
Cl	-	-	-	-	0,05
C	-	-	-	-	0,14

Its analysis allows us to draw the following important conclusions:

1) the earth's crust is composed mainly of eight elements: O, Si, A1, Fe, Ca, Mg, Na, K; 2) the remaining 84 elements account for less than one percent of the mass of the crust; 3) Oxygen plays a special role among the most abundant elements in the earth's crust.

The special role of oxygen is that its atoms make up 47% of the mass of the crust and 90% of the volume of the most important rock-forming minerals.

There are a number of geochemical classifications of elements. At present, a geochemical classification is spreading, according to which all elements of the earth's crust are divided into five groups (Table 26).

Table 26

A variant of the geochemical classification of elements (Gusakova, 2004)

Lithophilic - these are elements of rocks. There are 2 or 8 electrons on the outer shell of their ions. Lithophilic elements are difficult to recover to an elementary state. They are usually associated with oxygen and constitute the bulk of silicates and aluminosilicates. They are also found in the form of sulfates, phosphates, borates, carbonates and gadogenides.

Chalcophilic elements are elements of sulfide ores. On the outer shell of their ions there are 8 (S, Se, Te) or 18 (for the rest) electrons. In nature, they are found in the form of sulfides, selenides, tellurides, as well as in the native state (Cu, Hg, Ag, Pb, Zn, As, Sb, Bi, S, Se, Te, Sn).

Siderophilic elements are elements with completed electronic d- and f-shells. They show a specific affinity for arsenic and sulfur (PtAs 2, FeAs 2, NiAs 2 , FeS , NiS , Mos 2, etc.), as well as to phosphorus, carbon, nitrogen. Almost all siderophilic elements are also found in a native state.

Atmophilic elements are elements of the atmosphere. Most of them have atoms with filled electron shells (inert gases). Nitrogen and hydrogen are also classified as atmospheric. Due to the high ionization potentials, atmospheric elements hardly enter into compounds with other elements and therefore are found in nature (except for H) mainly in an elementary (native) state.

Biophilic elements are elements that make up the organic components of the biosphere (C, H, N, O, P, S). From these (mainly) and other elements, complex molecules of carbohydrates, proteins, fats and nucleic acids... The average chemical composition of proteins, fats and carbohydrates is given in table. 27.

Table 27

Average chemical composition of proteins, fats and carbohydrates, wt. % (Gusakova, 2004)

Currently, more than 60 elements have been identified in various organisms. Elements and their compounds, required by organisms in relatively large quantities, are often called macrobiogenic elements. Elements and their compounds, which, although necessary for the life of biosystems, are required in extremely small quantities, are called microbiogenic elements. For plants, for example, 10 microelements are important: Fe, Mn, Cu, Zn, B, Si, Mo, C1, W, Co .

All these elements, except for boron, are required by animals. In addition, animals may require selenium, chromium, nickel, fluorine, iodine, and tin. It is impossible to draw a clear and identical boundary for all groups of organisms between macro- and microelements.

Weathering processes

The surface of the earth's crust is exposed to the atmosphere, which makes it susceptible to physical and chemical processes. Physical weathering is an mechanical process, as a result of which the rock is crushed to smaller particles without significant changes in chemical composition... When the restraining crustal pressure is removed by uplift and erosion, internal stresses within the underlying rock are also eliminated, allowing the expanded fractures to open. These cracks can then move apart due to thermal expansion (caused by daily temperature fluctuations), expansion of water during freezing, and exposure to plant roots. Other physical processes, such as glacial activity, landslides and sand abrasion, further weaken and break down the solid rock. These processes are important because they significantly increase the surface areas of the rock exposed to chemical weathering agents such as air and water.

Chemical weathering Caused by water - especially acidic water - and gases such as oxygen, which breaks down minerals. Some of the ions and compounds of the original mineral are removed with a solution that seeps through the debris and feeds groundwater and rivers. Fine-grained solids can be washed out of a weathered area, leaving chemically altered residues that form the basis of soils. Various mechanisms of chemical weathering are known:

1. Dissolution. The simplest weathering reaction is the dissolution of minerals. The water molecule is effective in breaking ionic bonds, such as those that bind sodium (Na +) and chlorine (Cl -) ions in halite (rock salt). We can express the dissolution of halite in a simplified manner, i.e.

NaCl (s) Na + (aq) + Cl - (aq)

2. Oxidation. Free oxygen plays an important role in the decomposition of substances in reduced form. For example, the oxidation of reduced iron (Fe 2+) and sulfur (S) in common sulfide, pyrite (FeS 2) leads to the formation of strong sulfuric acid (H 2 SO 4):

2FeS 2 (s) + 7.5 O 2 (g) + 7H 2 O (l) 2Fe (OH) 3 (s) + H 2 SO 4 (aq).

Sulfides are often found in silty-glium rocks, ore veins and coal deposits. During the development of ore and coal deposits, sulphide remains in the waste rock, which accumulates in dumps. These waste rock dumps have large surfaces exposed to the atmosphere where sulfide oxidation occurs rapidly and on a large scale. In addition, abandoned ore mines are quickly flooded with groundwater. The formation of sulfuric acid makes drainage water from abandoned mines highly acidic (pH up to 1 or 2). This acidity can increase the solubility of aluminum and cause toxicity to aquatic ecosystems. Microorganisms are involved in the oxidation of sulfides, which can be modeled by a number of reactions:

2FeS 2 (s) + 7О 2 (g) + 2Н 2 О (l) 2Fe 2+ + 4Н + (aq) + 4SO 4 2- (aq) (pyrite oxidation), then iron oxidation into:

2Fe 2+ + О 2 (g) + 10Н 2 О (l) 4Fe (OH) 3 (s) + 8Н + (aq)

Oxidation - occurs very slowly at low pH values ​​of acidic mine waters. However, below pH 4.5, iron oxidation is catalyzed by Thiobacillus ferrooxidans and Leptospirillum. Iron oxide can further interact with pyrite:

FeS 2 (aq) + 14 Fe 3+ (aq) + 8H 2 O (l) 15 Fe 2+ (aq) + 2SO 4 2- (aq) + 16H + (aq)

At pH values ​​much higher than 3, iron (III) precipitates as ordinary iron (III) oxide, goethite (FeOOH):

Fe 3+ (aq) + 2H 2 O (l) FeOOH + 3H + (aq)

Precipitated goethite covers the streams and masonry with a characteristic yellow-orange bloom.

Reduced iron silicates, such as some olivines, pyroxenes and amphiboles, can also undergo oxidation:

Fe 2 SiO 4 (s) + 1 / 2O 2 (g) + 5H 2 O (l) 2Fe (OH) 3 (s) + H 4 SiO 4 (aq)

The products are silicic acid (H 4 SiO 4) and colloidal iron hydroxide, a weak base that, upon dehydration, gives a number of iron oxides, for example Fe 2 O 3 (hematite is dark red), FeOOH (goethite and lepidocrocite are yellow or rust). The frequent occurrence of these iron oxides indicates their insolubility under the oxidizing conditions of the earth's surface.

The presence of water accelerates oxidative reactions, as evidenced by the daily observed oxidation phenomenon of metallic iron (rust). Water acts as a catalyst, the oxidation-potential depends on the partial pressure of the oxygen gas and the acidity of the solution. At pH 7, water in contact with air has an Eh of about 810 mV - an oxidation potential much higher than that required for the oxidation of ferrous iron.

Oxidation of organic matter. Oxidation of reduced organic matter in soils is catalyzed by microorganisms. Bacteria-mediated oxidation of dead organic matter to CO 2 is important in terms of acidity formation. In biologically active soils, the concentration of CO 2 can be 10-100 times higher than expected in equilibrium with atmospheric CO 2, leading to the formation of carbonic acid (H 2 CO 3) and H + during its dissociation. To simplify the equations, organic matter is represented by the generalized formula for carbohydrate, CH 2 O:

CH 2 O (s) + O 2 (g) CO 2 (g) + H 2 O (g)

CO 2 (g) + H 2 O (l) H 2 CO 3 (aq)

H 2 CO 3 (aq) H + (aq) + HCO 3 - (aq)

These reactions can lower the water pH of soils from 5.6 (the value that is established in equilibrium with atmospheric CO2) to 4-5. This is a simplification, since soil organic matter (humus) does not always completely decompose to CO2. However, the products of partial destruction have carboxyl (COOH) and phenolic groups, which, upon dissociation, give H + ions:

RCOOH (aq) RCOO - (aq) + H + (aq)

where R means a large organic structural unit. The acidity accumulated during the decomposition of organic matter is used in the destruction of most silicates in the process of acid hydrolysis.

3. Acid hydrolysis. Natural waters contain soluble substances that give them acidity - this is the dissociation of atmospheric CO 2 in rainwater, and partially the dissociation of soil CO 2 with the formation of H 2 CO 3, the dissociation of natural and anthropogenic sulfur dioxide (SO 2) with the formation of H 2 SO 3 and H 2 SO 4. The reaction between a mineral and acidic weathering agents is commonly referred to as acid hydrolysis. Weathering of CaCO 3 is demonstrated by the following reaction:

CaCO 3 (s) + H 2 CO 3 (aq) Ca 2+ (aq) + 2HCO 3 - (aq)

Acid hydrolysis of a simple silicate, such as magnesium-rich olivine, forsterite, can be summarized as follows:

Mg 2 SiO 4 (s) + 4H 2 CO 3 (aq) 2Mg 2+ (aq) + 4HCO 3 - (aq) + H 4 SiO 4 (aq)

Note that the dissociation of Н 2 СО 3 results in the formation of ionized НСО 3 -, slightly more strong acid than the neutral molecule (H 4 SiO 4), formed during the decomposition of silicate.

4. Weathering of complex silicates. So far, we have considered the weathering of monomeric silicates (for example, olivine), which dissolve completely (congruent dissolution). It made it easier chemical reactions... However, the presence of altered mineral residues during weathering suggests that incomplete dissolution is more common. Simplified weathering reaction using the example of calcium-rich anorthite:

CaAl 2 Si 2 O 8 (s) + 2H 2 CO 3 (aq) + H 2 O (l) Ca 2+ (aq) + 2HCO 3 - (aq) + Al 2 Si 2 O 5 (OH) 4 (s )

The solid product of the reaction is kaolinite Al 2 Si 2 O 5 (OH) 4, an important representative of clay minerals.

The lithosphere is called the hard shell of the planet, the name of which comes from the Greek word "lithos", meaning stone. The term was proposed by J. Burrell in 1916 and was used at first by him as a synonym for the earth's crust. Only a few years later it was proved that the structure of the Earth's lithosphere is more complex. It includes the following:

• Earth's crust;
• Robe (top layer).

Basic layers

The earth's crust is a constituent part of the lithosphere, which has a depth of 35–70 km under the continental part of the land and 5–15 km under ocean floor... It also consists of layers:

• Continental crust: sedimentary, granite, basalt layer;
• Oceanic: layer of marine sediments (may be absent in some cases at all), middle layer of basalt and serpentine, bottom layer of gabbro.

In the composition of the earth's crust, you can find almost the entire periodic table, only in different parts. Most of all, it contains oxygen, iron, silicon, aluminum, sodium, magnesium, calcium and potassium. The earth's crust accounts for about 1% of the total mass of the entire planet.

The mantle is the lower part of the lithosphere, the depth of which reaches 2900 km. It consists mainly of silicon, oxygen, iron, magnesium, nickel. Inside it, a special layer is distinguished - the asthenosphere, created from a special substance. The composition of the earth's hard shell includes that part of the mantle that is located before the asthenosphere. This is the lower boundary of the shell, while the upper one is located next to the atmosphere and hydrosphere, with which the lithosphere interacts, partially penetrating into them.

It is a mistake to classify the core, a separate layer of the globe, which is located at a depth of 2900–6371 km and consists of hot iron and nickel, as part of the lithosphere.

Shell features

Based on the structure of the Earth's lithosphere, it can be argued that it is a relatively fragile shell, since it is not monolithic. It is divided by deep faults into separate blocks (or plates), which move very slowly horizontally along the asthenosphere. Therefore, a distinction is made between relatively stable platforms and mobile areas (folded belts).

The structure of the Earth's lithosphere today is the division of the planet's surface into seven large and several small plates. The boundaries between them are marked by zones of the highest volcanic and seismic activity. In diameter, these elements of the lithosphere are 1–10 thousand km.

Isostasy

Separately, I would like to dwell on isostasy, a phenomenon that scientists discovered during the study of mountain ranges and the force of gravity at their foot (mountains are formed at the junction of lithospheric plates). Previously, it was believed that large irregularities in the relief increase the force of gravity in the region. However, it turned out that the force of gravity is the same on the entire earth's surface. Massive structures are balanced somewhere in the depths of the Earth, in the upper mantle: the larger the mountain, the deeper it is immersed in the lithosphere. For a while, the earth's crust can go out of balance under the influence of tectonic forces, but then it still returns to it.

The lithosphere is the solid shell of the planet Earth. It covers it completely, protecting the surface from the highest temperatures of the planet's core. Let's study what structure the lithosphere has and how it differs from other planets.

general characteristics

The lithosphere is bordered by the hydrosphere and atmosphere at the top, and the asthenosphere at the bottom. The thickness of this shell varies considerably and ranges from 10 to 200 km. in different parts of the planet. The lithosphere is thicker on the continents than in the oceans. The lithosphere is not a single whole - it is formed by separate plates that lie on the asthenosphere and gradually move along it. There are seven large lithospheric plates and several small ones. The boundaries between them are zones of seismic activity. On the territory of Russia, two such plates are connected - the Eurasian and the North American. The structure of the Earth's lithosphere is represented by three layers:

• Earth's crust;
• boundary layer;
• upper mantle.

Let's take a closer look at each layer.

Rice. 1. Layers of the lithosphere

Earth's crust

This is the upper and thinnest layer of the lithosphere. Its mass is only 1% of the mass of the Earth. The thickness of the earth's crust varies from 30 to 80 km. Smaller thickness is observed in flat areas, greater - in mountainous areas. There are two types of the earth's crust - continental and oceanic.

The division of the crust into two types exists only on the Earth, on the other planets the crust is of the same type.

The mainland crust consists of three layers:

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• sedimentary- formed by sedimentary and volcanic rocks;
• granite- formed by metamorphic rocks (quartz, feldspar);
• basaltic- represented by igneous rocks.

The oceanic crust contains only sedimentary and basalt layers.

Rice. 2. Layers of oceanic and continental crust

The earth's crust contains all known minerals, metals and chemicals in different quantities... The most common elements are:

• oxygen;
• iron;
• silicon;
• magnesium;
• sodium;
• calcium;
• potassium.

The complete renewal of the earth's crust occurs in 100 million years.

Boundary layer

It is called the Mohorovicic surface. In this zone, there is a sharp increase in the speed of seismic waves. Also here the density of the lithosphere substance changes, it becomes more elastic. The surface of Mokhorovichich lies at a depth of 5 to 70 km, completely repeating the relief of the earth's crust.

Rice. 3. Scheme of the Mohorovichich surface

Mantle

Only the upper layer of the mantle belongs to the lithosphere. It has a thickness of 70 to 300 km. What phenomena occur in this layer? Here, the centers of seismic activity arise - earthquakes. This is due to an increase in the speed of seismic waves here. What is the structure of this layer? It is formed mainly by iron, magnesium, calcium, oxygen.

What have we learned?

The Earth's lithosphere has a layer-by-layer structure. It is formed by the earth's crust and the upper layer of the mantle. Between these layers there is a boundary called the Mohorovicic surface. The total thickness of the lithosphere reaches 200 km. It contains almost all metals and trace elements.

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