The lithosphere, its structure and composition. The structure and material composition of the lithosphere

Sections:

Necessary explanations.

In the 7th grade, the lessons on the topic “The lithosphere and its structure” somewhat duplicate a similar topic in the 6th grade. This material is complex, so its explanation is based on the knowledge gained in grades 5 and 6, but at a new level. Students are given not ready-made formulations, but the assimilation of knowledge by methods of analysis, analogies and search. Much is involved in explaining the material. intersubject communications: biology, chemistry, physics. There are elements of advanced learning. For example, the concept of "shield", the confinement of minerals to certain landforms, etc.

Lesson planning for topic 1 "The lithosphere and its structure"

Lesson 1 - The material composition and structure of the earth's crust
Lesson 2 - Continental drift and the evolution of the earth's crust.
Lesson 3 - The theory of lithospheric plates and its practical value. Relief of the Earth.

Generalizing repetition in the form of the game "Geographic Lotto".

Additional lesson (if possible) - "Gemstones" is given after 1 lesson or after 3 lessons together with a chemistry teacher and requires a mandatory colorful exhibition.

Lesson "Material composition and structure of the earth's crust"

The purpose of the lesson- to form an idea of ​​the evolution of the Earth's shells and the emergence of the earth's crust in the process of evolution various types and composition.

Equipment:

1. Collection of minerals and rocks.
2. Demonstration table or slide "Education solar system»
3. Demonstration drawings or slides "The structure of the continental and oceanic crust."
4. Demonstration table or slide "Classification of minerals."

During the classes.

1. Repetition of the past.

Knowledge about the structure of our planet and its shells cannot be obtained without correct ideas about the Universe. Our planet Earth is one of the planets of the solar system located in the universe. Recall the material from the natural history course of grade 5 and physical geography 6th grade.

What is the Universe?

(This is a huge and endless space that surrounds us)

What do we call the Galaxy?

(This is a star system, part of the universe)

What is the name of our galaxy?

(Milky Way)

Why did she get such a name?

(In the sky you can see a wide luminous band irregular shape, view which reminded ancient people of spilled milk)

How many stars are located in our Galaxy.

(100 million stars of different sizes and brightness)

Name the closest star to us.

(The sun)

What is called the solar system?

(Sun with planets revolving around it)

How are planets different from stars?

(shine with reflected light)

How can you describe the position of our planet in the solar system?

(This is the third planet from the Sun, located at a distance of 149 million 600 thousand kilometers.)

How many years has the earth existed cosmic body?

(Approximately 4.5 billion years)

How many years ago did the solid surface of the planet form?

(Approximately 2 billion years ago)

2. Explanation of new material.

• . There are many hypotheses about the origin of the planets. Modern views are. The solar system formed from a cold disk-shaped cloud of gas and dust. As the cloud rotated, its particles stuck together, condensed and turned into larger bodies. The cloud thickened. Instead of erratic movement, its contents began to slowly rotate. In the center of the cloud, its main mass formed into a rounded body, from which the Sun flared up, the Earth and other planets formed around. The planets formed about 5 billion years ago. Our Earth, initially cold, warmed up from the inside, where pressure and friction were stronger. With an increase in temperature in the depths of the Earth, a melt of its substance was formed.
  heavy substances the melt accumulated in the center, forming a core, and the lungs tended to the surface. This redistribution of matter caused the formation of the Earth's shells.
  As a result of long-term processes of changing the matter of the Earth, it passes from the stellar stage into the planetary one. It is the appearance of the earth's crust that means the beginning of a new stage in the development of the Earth - it is called the geological stage. At this stage, there are rocks and minerals. They, like everything that surrounds us, consist of smallest particles, the existence of which was guessed in ancient Greece.

• In order to imagine this well, we have to go back to what we went through in the 5th and 6th grades.

What are all the bodies and substances of nature made of?

(of atoms and molecules)

How is an atom arranged?

(An atom consists of a positively charged nucleus and rotating around the nucleus negatively charged electrons.)

How are atoms different from each other?

(by the mass of the nucleus and the number of electrons)

What is the name of certain kind atoms?

(Chemical element)

Why do atoms combine into molecules?

(For more stability)

What is the name of the connection of different chemical elements?

(mineral)

What are minerals?

(Amorphous and crystalline. There are very few amorphous or shapeless minerals.)

• Sometimes crystals in the earth's crust grow large and beautiful. We will have the opportunity to talk about these unique formations. More often, when looking at stones, we see in total mass individual small "grains" that differ in color, luster, roughness, etc. These are individual minerals that form rocks. So, the difference between minerals and rocks is that Minerals are parts of rocks that are homogeneous in composition and structure., a rocks - most often heterogeneous and consist of various minerals.

The rocks that make up the earth's crust are different age. The most ancient - 3.7 - 3.8 billion years - were discovered in Antarctica.
Primary Earth's crust was very thin. Magma poured out of the melts under the earth's crust, gases and water vapor escaped. The atmosphere was taking shape. When the temperature on the surface of the Earth dropped below 100 degrees, the first rains began to fall.

• Consider Chart 1 on page 9 "Rock Classification".

What do you think, the formation of what rocks took place at the beginning of the geological stage of the Earth's development?

(magmatic)

Indeed, the formation of the basalt layer of the earth's crust took place from the upper part of the mantle. Scheme No. 1 reminds you that igneous rocks are divided into deep and erupted.
What type of igneous rocks are basalts?

(poured out)

• Let's look at samples of basalt. They have dark color and uniform structure. The outflowing basalts solidified quickly. Gas and water vapor were released from them, iron and magnesium remained, so they are heavy. The basalt layer formed the base of the earth's crust, its first floor.
• If the magma broke through the formed earth's crust and cooled in the depths of the Earth, then the cooling occurred in a different way: through the redistribution of matter. Molecules had time to "settle" next to their own kind - minerals appeared in the form of crystals. The resulting rock in this case will no longer look homogeneous.
• Now I will show you one of the most common crystalline rocks.

Remember the name of the rock, the name of which translates as "granular".

(Granite)

What type of igneous rock is granite?

(deep)

Granites that rose from the depths could form uplifts in the form of domes. We will find one of these uplifts when studying Australia. This is very beautiful mountain- Ayers Rock. During the destruction of igneous rocks, sedimentary rocks were formed. When changing under the influence of temperature, pressure and hot solutions of magma, igneous and sedimentary rocks turned into metamorphic - changed.

• - Using scheme 1 on page 9, remember and name the groups of sedimentary rocks of the earth's crust.

(detrital, clayey, organic, chemical)

Name the metamorphic rocks that I will show you, and tell me what rocks they were formed from.

(Gneiss is from granite, marble is from limestone.)

• Already on early stage formation of the earth's crust, its difference in the continental and oceanic parts was outlined. The continental and oceanic crusts were formed from the same material of the mantle, and the differences between them were formed as a result due to the difference in their melting.

Water, formed as a result of the conversion of steam into a liquid, accumulated where the earth's crust formed depressions and was thinner. The most stable sections of the crust, consisting of igneous and metamorphic rocks, cemented by intruding magma, formed the cores of future continents.

• Consider Fig. 1 on page 10 and answer the questions of the geographical task set before us:

Determine the differences in the number of layers of the earth's crust of the continents and oceans.

(The earth's crust of the continents - basalt layer, granite layer, sedimentary layer. The earth's crust of the oceans - basalt layer, sedimentary layer).

How does the thickness of the earth's crust differ between continents and oceans?

(The earth's crust of the continents is thicker than the oceanic)

Name the thickness of the continental and oceanic crust, using the information on page 8 of the textbook.

(5-10 km in the oceans and 30 to 80 km on the continents)

Looking at figure 1 page 10, explain what is called the earth's crust and what is called the lithosphere.

(The Earth's crust is the outermost solid shell of the Earth. The lithosphere is the shell of the Earth, which includes the earth's crust and part of the upper mantle).

• The boundary between the earth's crust and the mantle is the Moho section. It is named after the Croatian scientist, seismologist Mohorović, who discovered it.

The upper part of the mantle is combined with the earth's crust, because it has the properties solid body. The division between the upper and lower mantle occurs along a layer called the asthenosphere. This is a partially molten and therefore less dense substance, on which the upper surface slides. solid. She is the main source of magma.
The asthenosphere is located at a depth of 100-250 km under the continents and 50-100 km under the oceans.
In the earth's crust of both types, the formation of minerals took place - formations that a person uses in economic activity. Minerals can be divided as rocks - by origin: igneous, sedimentary and metamorphic. You can divide them according to the principle of human use.

• Consider the classification in diagram 2, page 9.

Give examples of rocks of each group.

(Fuel - oil, gas, coal.
Construction - sand, clay, granite, basalt.
Ore - compounds of iron, aluminum, copper, etc. with non-metals
Chemical raw materials - salts, apatites, phosphorites).

Minerals include both certain rocks and minerals.
- What do you think, which of the following is more common in the bowels of the earth?

(Rocks)

Indeed, in nature, where the circulation of matter and energy, the interaction and interpenetration of molecules and atoms, minerals are more difficult to meet. Minerals that have formed large crystals are especially valued. Some crystals are very beautiful. There are also beautiful combinations of crystals in rocks that look like different lines and colors. Such rocks and minerals form a special group of minerals - ornamental and precious stones.

3. Consolidation of the past.

• Arrange listed processes in the correct sequence.

The formation of a gas cloud in the Universe, the heating of the interior as a result of the approach of particles and the increase in friction forces, the appearance of basalt rocks, the formation of the planet's core, the rotation and thickening of the gas cloud, the formation of clots of future planets and the Sun in the center of the cloud, the appearance of granites, the formation of the mantle and the primary thin Earth crust, the appearance of sedimentary rocks.

(Formation of a gas cloud in the Universe, rotation and condensation of a gas cloud, formation of clumps of future planets and the Sun in the center of the cloud, heating of the interior as a result of the approach of particles and an increase in friction forces, formation of the planet's core, formation of the mantle and primary thin earth's crust, the appearance of basalt rocks, the appearance of granites, the appearance of sedimentary rocks).

• Where and why should one look for sedimentary minerals - on the uplands or in the depressions? Explain your answer.

(Sedimentary rocks accumulated in depressions, therefore, in the place of ancient troughs one should look for sedimentary minerals)

• Is it true that igneous minerals can be found anywhere, but not everywhere they can be obtained? Explain your answer.

(Since there is a magmatic layer of the earth's crust anywhere, theoretically, there are igneous minerals everywhere. Only it is difficult to "get" to them through a multi-kilometer layer of sediments. We need to look for shallow places)

• Can the same mineral be both in the form of a mineral and in the composition of a rock?

(Of course. For example, quartz is part of both a rock - granite, so it can be in the form of minerals. Beautiful and transparent quartz crystals are called rock crystal).

• Can a mineral be artificial?

(If a mineral is a compound of different chemical elements, then such a compound can be created artificially. The first artificially created crystal was called cubic zirconia. Now they have learned how to grow different crystals. For example, most rubies in modern jewelry are artificially grown).

4. Homework:

1. Write out definitions in your notebook:

• mineral
• rock
• Earth's crust
• lithosphere
• geographical envelope

If desired, make explanatory drawings for the written definitions.

1. Find out the name of jewelry and ornamental stones that are stored at home with you or your friends. Ask them what they know about the properties of the stones they wear as jewelry.

5. Literature.

1. Gerasimova T. P. " General geography. Textbook for grade 10. S-Pb. "Specialist. Lit. 2001
2. Children's encyclopedia. Earth. M. "Pedagogy". 1971
3. Krylova O. V. “Continents and oceans. Textbook for grade 7. M. "Enlightenment". 2002.
4. Kondratiev B. A. Metreveli P. M. “Geography Lessons”. M. "Enlightenment" 1985
5. Muzafarov V. G. "Fundamentals of Geology". M. "Enlightenment". 1982
6. Sukhov P.V. “Geography. Textbook for grade 8 "M. "Enlightenment". 1991.
7. Ushakov S. A., Yasamanov N. A. "Continental drift and climates of the Earth". M. "Thought". 1984

One of important topics in the study of geography is considered the composition and structure of the lithosphere, which has a significant impact on people's lives.

The concept of the lithosphere

The lithosphere is the uppermost and hard shell, consisting of rocks similar in composition to granites. The exact thickness of the lithosphere has not yet been determined, many believe that the thickness is 60-30 km, many that it is 90-100 km.

The earth's crust also has a certain relation to the lithosphere, especially to its upper and solid part. Often, the lithosphere also includes ore, basalt and granite shells - thicker layers, their thickness can be about 1200 km.

Composition of the lithosphere: chemical elements

It is possible to study the lithosphere only in the land area, thanks to which geographers study the composition and structure of the earth's crust. On the this moment, it is possible to explore areas that belong to the surface of the earth's crust down to great depths. This is due to the natural outcrops that can be found along the shores of the seas, rivers and heavily destroyed mountains.

Therefore, the composition and structure of the earth's crust is known approximately to a depth of 16 km. And about those layers that are much deeper, we can only guess. Special gravimetric studies and the study of seismic phenomena allow us to speculate about this.

The earth's crust mainly consists of rocks of igneous origin - this is about 90%. Granites enjoy the most widespread, it is from them that the upper and solid part of the earth's crust is composed. But chemical composition granites differs significantly from igneous rocks, which are the results of modern eruptions.

The first group of breeds is called sialic- they contain a large number of silicon and aluminium. The second group is characterized by the content of a large amount of magnesium - this is simmatic breeds. The rocks from the first group have a lower specific gravity.

Thanks to numerous studies, it became clear that the surface part of the lithosphere - the part that is available for study by people, mainly consists of sialic rocks. And those layers that are much deeper are simatic rocks.

It should be remembered that most of the surface of the lithosphere is hidden from human eyes by oceans and seas. Therefore, the composition and structure of the lithosphere applies only to those areas that are on land.

Also, the rocks that make up the lithosphere can be divided into three main groups. Rocks that originated from molten magmatic masses belong to the first group. These are basalt, diorite and granite, their common name is igneous rocks.

The second group consists of sedimentary rocks, which were formed by the deposition of materials from water and air. These include sandstone, limestone and shale. The third group is the breeds that have experienced strong changes under influence high temperature and pressure. They are called metamorphic, the composition includes marble, gneiss and graphite. Both igneous and sedimentary rocks could also experience such changes.

Composed of minerals and rocks. Minerals are quite stable chemical compounds and native elements that have a strictly specific internal structure inherent only to them. Minerals are formed as a result of endogenous and exogenous processes, and can also be grown in laboratories, factories (gems) and marine farms (pearls).

In nature, there are solid (diamond, quartz), liquid (water, oil, mercury) and gaseous (all gases) minerals. Solid minerals can be crystalline (halite, quartz) and amorphous (opal, all resins). Crystals are made up of many structural elements, which are polyhedra-crystals, amorphous crystals Dont Have. The structure of minerals determines their properties. The same chemical element (or compound) can form different crystalline forms, i.e. different minerals. So, diamond and graphite are composed of carbon (C), pyrite and marcasite - of iron sulfide (FeS 2), calcite and aragonite - of calcium carbonate (CaCO 3), etc.

More than 2500 minerals are known, and if we take into account their varieties - about 4000, however, only a little more than 50 (up to 1%) of them are of rock-forming significance. Modern classification minerals is based on their composition and structure.

Rocks are mineral aggregates with a more or less constant mineral composition. They may be monomineral, i.e. consisting of one, such as rock salt(from halite), or from several minerals, such as granite (from feldspars, quartz, biotite, amphibole). Many monomineral rocks bear the same names as the minerals that compose them: oil, water, mica, clay, anhydrite, gypsum, etc. Loose, liquid and plastic rocks are often called geological formations.

According to the genesis (origin), rocks are classified into igneous, metamorphic and sedimentary. Of these, only igneous rocks are primary. Metamorphic and sedimentary rocks were formed due to the change and destruction of igneous rocks.

Igneous rocks. Igneous rocks, like the minerals that make them up, are formed from magmatic melt during solidification in the bowels (intrusive) and on the surface (effusive) of the Earth. Most igneous rocks are composed of silicate minerals and, according to the content of silicic acid (SiO 2 ), they are divided into acidic, medium, basic, and ultrabasic.

Intrusive igneous rocks are formed when magma solidifies at depth. This process is quite slow, and there is enough time for crystal growth, so intrusive rocks have crystal structure. Effusive igneous rocks are formed during the rapid cooling of magma (lava) that has escaped to the earth's surface, and crystals do not have time to form, so the rocks have a glassy (i.e., non-crystalline) structure. A special group of igneous formations are vein rocks, which are associated with deposits of iron, copper, zinc, tin, gold, silver, precious stones and many other minerals. Thus, intrusive rocks are distinguished from effusive ones by their internal structure, and acid, medium, basic and ultrabasic - by color, which reflects the content of SiO 2 in the rock, and for intrusive rocks - their mineral composition.

metamorphic rocks. Metamorphic rocks are formed as a result of complex transformations in the composition and structure of rocks due to the impact on them of high temperatures and pressures. Certain rocks are associated with each type of metamorphism (regional, dislocation, contact, and impact). The most extensive range of rocks is associated with the regional one, which is typical for vast platform areas. Closer to the surface (but at a sufficient depth!) rocks of the so-called greenstone facies are formed, containing a lot of the green mineral chlorite. The most typical for this zone are shales - rocks with a schistous structure and serpentinites. Deeper, i.e. at higher temperatures and , denser crystalline schists, gneisses, amphibolites and, as a result of partial remelting of amphibolites, migmatites are formed. At great depths, near the interface with the mantle, granulites and eclogites appear - peculiar dense crystalline rocks with a set of metamorphic minerals.

Dynamo-metamorphism (dislocation) is accompanied by the formation of material of destruction of the parent rock, in which there are metamorphic neoplasms (chlorite, talc, mica). These loose rocks are called mylonites. Compacting, mylonites acquire a slate structure. In this already strong rock, all mineral grains and their aggregates are flattened. Such rocks are called blastomylonites.

In the contact type of metamorphism, rocks that are in contact with the intruded intrusion undergo transformation. If the enclosing rock is limestone, and a large amount of hot mineralized and water vapor is released from the magma, a peculiar multi-crystalline rock called skarn is formed in the contact zone. Skarns are rocks that are a real natural pantry of industrial accumulations of iron, tungsten, tin, zinc and many precious stones. With simple roasting of rocks in the contact zone, hornfelses are formed.

The fall to the Earth causes the process of impact metamorphism. Of course, the degree of metamorphism in such zones () is maximum at the point of impact and decreases conically with depth. Breeds resulting from impact type metamorphism, merged common name- impactites. They are associated with deposits of diamonds and garnets.

Thus, metamorphic rocks are very, very diverse. Knowledge of the features of the structure and the set of typically metamorphic minerals can help distinguish them.

Sedimentary rocks. Sedimentary rocks are formed on the surface of the Earth or a little deeper from the products of the vital activity of organisms, through the chemical precipitation of salts from supersaturated solutions. A special group of rocks are combustible. Sedimentary rocks cover about 75% of the surface of the continents, and the vast majority of them were formed from marine rocks. On a genetic basis, they are divided into four classification groups: detrital; clay; chemical and organogenic; caustobioliths.

Clastic rocks are composed mainly of products of physical weathering and are subdivided according to the size of their constituent fragments into: coarse clastic (boulders, crushed stone, pebbles, gravel - loose, conglomerates and breccias - cemented); medium clastic (sands and sandstones); fine clastic (siltstones and siltstones). The lower limit of the size of particles that make up clastic materials is 0.01 mm.

Clay rocks consist mainly of chemical weathering products and are composed of particles 0.01-0.001 mm in size and smaller. In addition, clay rocks are composed of clay minerals with specific properties. Clay rocks make up about 50% of the mass of all sedimentary rocks. Fossilized clay is called mudstone.

In Quaternary deposits, especially of origin, there are sandy-argillaceous (more clay than sand) and clayey-sandy (more sand than clay), which, with a content of a smaller component of about 30%, are called loams and sandy loams, respectively.

Chemical and organogenic rocks by origin are either chemically precipitated or formed by skeletal fragments of organisms. Some rocks of this group can be of both chemical and organogenic genesis (carbonate, siliceous, phosphate). In specific marine environments, ferromanganese, phosphorite, barite nodules, aragonite needles and oolites and other mineral formations are formed. Deposits of chloride (stone and potash), sulfate (gypsum, anhydrite, barite), carbonate (limestone, dolomite) and other salts are formed in reservoirs of arid (dry) zones.

Combustible minerals (caustobiolites) form two genetic series: coal and oil. The range of coal includes peat, lignite, brown and anthracite. The oil series includes all hydrocarbon gases, oil, ozocerite (mountain wax), asphalt. However, anthracite, as well as oil shales belonging to this group of rocks, are essentially metamorphic rocks and are conventionally classified as sedimentary.

Subject:Structure and material composition of the lithosphere.

The purpose of the lesson:explain the features of the structure of the earth, the earth's crust;

Know the definitions: hydrosphere, biosphere, lithosphere, atmosphere;

Show the connection between the lithosphere and the mantle;

Teacher activity

Student activities

visibility

3 min.

I. Organizational moment. Greets students. Creates a psychological atmosphere in the classroom.

With the help of cut puzzles, the class is divided into groups.

Puzzles

10 minutes.

II. Preparing for the perception of a new topic. Use leading questions to lead to the topic of the lesson.

Name the extra object, divide the rest of the objects into groups.

What word did I encrypt with these pictures? (shutter opens)

How is the word "Earth" spelled? What does it mean? How can this word and our lesson be connected?

Demonstrate their knowledge and skills.

Cards

20 minutes.

III. Knowledge update

Setting the goal of the lesson. According to the "JIGSO" method, he masters new material.

Do you really know little about the Earth? Let's spend game "Tell me a word"

1 group- 1. Our Earth in a row is ... a planet in the solar system.

2. The earth rotates around its axis for ...

2 group- 1. The earth has a shape….

2. When the Earth rotates around its axis, ... occurs.

3 group- 1. Satellite of the Earth - ...

2. The Earth revolves around the Sun in….

4 group- 1. Only on our planet there is ...

2. When the Earth rotates around the Sun, ...

Groups prepare a description of their shell, read from the textbook.

Textbook

5 minutes.

IV. Consolidation of the lesson.Fix the lesson according to the method "Sinkwine".

Determine the shell of the Earth and its meaning

In the classroom, there are inscriptions denoting objects of the surrounding world. Groups, moving around the class, need to collect inscriptions that correspond to their shell (living organisms, mountains, river, air, man, lake, stones, sea).

Each group needs to find the "extra" word in the list of 4 words.)

Group 1 - biosphere, lithosphere,geography , atmosphere

Group 2 - core, mantle, earth's crust,The sun

3rd group -water , snake, student, flowers

4 group - astronomy,biosphere , ecology, geography

test work . Choose the letter of the correct answer:

1) The atmosphere is ... K. the shell of life L. water shell

M. air envelope

2) Earth's crust ... E. hard E. viscous J. soft

3) In the center of the Earth is ... A. mantle I. core O. earth's crust

4) All living organisms belong ... Z. to the biosphere

I. to the hydrosphere J. to the atmosphere

5) The hydrosphere is ... K. air shell L. water shell

M. shell of life

From the selected letters of the answers (M, E, Z, Z, L) solve the anagram (EARTH).

Front work

group work

Cards are attached to the board, the correctness of the work is discussed.

The representative of the group expresses the opinion of the group, argues the answer.

Pair work, frontal check

A4 paper

5 minutes.

V. Lesson summary Organizes the systematization and generalization of joint achievements. Organizes individual work by personal achievement. Conducts reflection.

Did you like the lesson?

What was difficult for you?

What did you like more?

Self-assessment by students of the results of their learning activities

Write down your opinion about the lesson on stickers.

Evaluation paper

Stickers

2 minutes.

VI. Homework. Explains homework.

write down homework in diaries.

Outcome of the lesson: _________________________________________________________________

Positive sides lesson:__________________________________________________

_____________________________________________________________________________

Negative aspects of the lesson: _________________________________________________

______________________________________________________________________

LITHOSPHERE

THEME 4

Term ʼʼlithosphereʼʼ has been used in science since the middle of the 19th century, but contemporary meaning he acquired less than half a century ago. Even in the geological dictionary edition of 1955 ᴦ. says: lithosphere- the same as the earth's crust. In the dictionary edition of 1973 ᴦ. and in subsequent ones: lithosphere… in modern understanding includes the earth's crust ... and rigid upper part upper mantle Earth. Upper mantle – ϶ᴛᴏ a geological term for a very large layer; the upper mantle has a thickness of up to 500, according to some classifications - over 900 km, and the lithosphere includes only the upper ones from several tens to two hundred kilometers.

Lithosphere - ϶ᴛᴏ outer shell of the "solid" Earth, located below the atmosphere and hydrosphere above the asthenosphere. The thickness of the lithosphere varies from 50 km (under the oceans) to 100 km (under the continents). It consists of the earth's crust and the substrate, which is part of the upper mantle. The boundary between the earth's crust and the substratum is the Mohorovichic surface, when crossing it from top to bottom, the velocity of longitudinal seismic waves increases abruptly. The spatial (horizontal) structure of the lithosphere is represented by its large blocks - the so-called. lithospheric plates separated from each other by deep tectonic faults. Lithospheric plates move horizontally average speed 5-10 cm per year.

The structure and thickness of the earth's crust are not the same: that part of it, which can be called the mainland, has three layers (sedimentary, granite and basalt) and an average thickness of about 35 km. Under the oceans, its structure is simpler (two layers: sedimentary and basalt), the average thickness is about 8 km. Transitional types of the earth's crust are also distinguished (see topic 3).

In science, the opinion has firmly entrenched that the earth's crust in the form in which it exists is a derivative of the mantle. During the entire geological history there was a directed irreversible process of enrichment of the Earth's surface with matter from earth's interior.
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Three are involved in the structure of the earth's crust. base type rocks: igneous, sedimentary and metamorphic.

Igneous rocks are formed in the bowels of the Earth under conditions of high temperatures and pressures as a result of magma crystallization. Οʜᴎ make up 95% of the mass of the substance that makes up the earth's crust. Considering the dependence on the conditions in which the process of magma solidification took place, intrusive (formed at depth) and effusive (poured to the surface) rocks are formed. Intrusive ones include: granite, gabbro, igneous ones - basalt, liparite, volcanic tuff, etc.

Sedimentary rocks are formed on earth's surface in various ways: some of them are formed from the products of the destruction of rocks that formed earlier (clastic: sands, gels), some due to the vital activity of organisms (organogenic: limestone, chalk, shell rock; siliceous rocks, coal and brown coal, some ores), clay (clays), chemical (rock salt, gypsum).

Metamorphic rocks are formed as a result of the transformation of rocks of a different origin (igneous, sedimentary) under the influence of various factors: high temperature and pressure in the bowels, contact with rocks of a different chemical composition, etc.
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(gneisses, crystalline schists, marble, etc.).

Most volume of the earth's crust is occupied by crystalline rocks of igneous and metamorphic origin (about 90%). At the same time, for the geographic envelope, the role of a thin and discontinuous sedimentary layer is more significant, which, on most of the earth's surface, is in direct contact with water, air, takes Active participation in geographical processes(thickness - 2.2 km: from 12 km in troughs, up to 400 - 500 m in the oceanic bed). The most common are clays and shale, sands and sandstones, carbonate rocks. Important role in geographical envelope play loess and loess-like loams that make up the surface of the earth's crust in the extraglacial regions of the northern hemisphere.

In the earth's crust - the upper part of the lithosphere - 90 chemical elements were found, but only 8 of them are widespread and account for 97.2%. According to A.E. Fersman, they are distributed as follows: oxygen - 49%, silicon - 26, aluminum - 7.5, iron - 4.2, calcium - 3.3, sodium - 2.4, potassium - 2.4, magnesium - 2.4%.

The earth's crust is divided into separate geologically uneven-aged, more or less active (dynamically and seismically) blocks that are subject to constant movements, both vertical and horizontal. Large (several thousand kilometers across), relatively stable blocks of the earth's crust with low seismicity and weakly dissected relief are called platforms ( plat- flat, form- form (fr.). Οʜᴎ have a crystalline folded basement and a sedimentary cover of different ages. Given the dependence on age, platforms are divided into ancient (Precambrian in age) and young (Paleozoic and Mesozoic). Ancient platforms are the cores of modern continents, the general uplift of which was accompanied by a faster rise or fall of them individual structures(shields and plates).

The substrate of the upper mantle, located on the asthenosphere, is a kind of rigid platform on which, in the process geological development The earth's crust was formed. The substance of the asthenosphere, apparently, is characterized by low viscosity and experiences slow movements (currents), which, presumably, are the cause of vertical and horizontal movements lithospheric blocks. Οʜᴎ are in a position of isostasy, suggesting their mutual balancing: the rise of some areas causes the lowering of others.