Composition and structure of the earth's crust. The internal structure of the earth

Earth's crust is of great importance for our life, for the exploration of our planet.

This concept is closely related to others that characterize the processes occurring inside and on the surface of the Earth.

What is the earth's crust and where is it located

The earth has an integral and continuous shell, which includes: the earth's crust, troposphere and stratosphere, which are the lower part of the atmosphere, hydrosphere, biosphere and anthroposphere.

They closely interact, penetrating each other and constantly exchanging energy and matter. It is customary to call the earth's crust the outer part of the lithosphere - the solid shell of the planet. Most its outer side is covered by the hydrosphere. The rest, a smaller part, is affected by the atmosphere.

Under the Earth's crust is a denser and more refractory mantle. They are separated by a conditional border, named after the Croatian scientist Mohorovich. Its feature is a sharp increase in the speed of seismic vibrations.

Various scientific methods are used to gain insight into the earth's crust. However, obtaining specific information is possible only by means of drilling to a greater depth.

One of the objectives of such a study was to establish the nature of the boundary between the upper and lower continental crust. The possibilities of penetration into the upper mantle with the help of self-heating capsules made of refractory metals were discussed.

The structure of the earth's crust

Under the continents, its sedimentary, granite and basalt layers are distinguished, the thickness of which in the aggregate is up to 80 km. Rocks, called sedimentary rocks, were formed as a result of the deposition of substances on land and in water. They are predominantly in layers.

• clay
• shales
• sandstones
• carbonate rocks
• rocks of volcanic origin
• coal and other rocks.

The sedimentary layer helps to learn more about natural conditions on earth, which were on the planet in time immemorial. Such a layer may have a different thickness. In some places it may not exist at all, in others, mainly in large depressions, it may be 20-25 km.

The temperature of the earth's crust

An important energy source for the inhabitants of the Earth is the heat of its crust. The temperature increases as you go deeper into it. The 30-meter layer closest to the surface, called the heliometric layer, is associated with the heat of the sun and fluctuates depending on the season.

In the next, thinner layer, which increases in continental climates, the temperature is constant and corresponds to the indicators of a particular measurement site. In the geothermal layer of the crust, the temperature is related to the internal heat of the planet and increases as you go deeper into it. It is different in different places and depends on the composition of the elements, the depth and conditions of their location.

It is believed that the temperature rises on average by three degrees as it deepens for every 100 meters. Unlike the continental part, the temperature under the oceans is rising faster. After the lithosphere, there is a plastic high-temperature shell, the temperature of which is 1200 degrees. It is called the asthenosphere. It has places with molten magma.

Penetrating into the earth's crust, the asthenosphere can pour out molten magma, causing volcanic phenomena.

Characteristics of the Earth's crust

The Earth's crust has a mass of less than half a percent of the total mass of the planet. It is the outer shell of the stone layer in which the movement of matter occurs. This layer, which has a density half that of the Earth. Its thickness varies within 50-200 km.

The uniqueness of the earth's crust is that it can be of continental and oceanic types. The continental crust has three layers, the upper of which is formed by sedimentary rocks. The oceanic crust is relatively young and its thickness varies little. It is formed due to the substances of the mantle from oceanic ridges.

earth's crust characteristic photo

The thickness of the crust under the oceans is 5-10 km. Its feature is in constant horizontal and oscillatory movements. Most of the crust is basalt.

The outer part of the earth's crust is the hard shell of the planet. Its structure is distinguished by the presence of mobile areas and relatively stable platforms. Lithospheric plates move relative to each other. The movement of these plates can cause earthquakes and other cataclysms. The patterns of such movements are studied by tectonic science.

Functions of the earth's crust

The main functions of the earth's crust are:

• resource;
• geophysical;
• geochemical.

The first of them indicates the presence of the resource potential of the Earth. It is primarily a collection mineral located in the lithosphere. In addition, the resource function includes a number of environmental factors that ensure the life of humans and other biological objects. One of them is the tendency to form a hard surface deficit.

you can't do that. save our earth photo

Thermal, noise and radiation effects realize the geophysical function. For example, there is a problem of natural radiation background, which is on earth's surface basically safe. However, in countries such as Brazil and India, it can be hundreds of times higher than the allowable one. It is believed that its source is radon and its decay products, as well as some types of human activity.

The geochemical function is associated with problems of chemical pollution harmful to humans and other representatives of the animal world. Various substances with toxic, carcinogenic and mutagenic properties enter the lithosphere.

They are safe when they are in the bowels of the planet. Zinc, lead, mercury, cadmium and other heavy metals extracted from them can be very dangerous. In processed solid, liquid and gaseous form, they enter the environment.

What is the Earth's crust made of?

Compared to the mantle and core, the Earth's crust is fragile, tough, and thin. It consists of a relatively light substance, which includes about 90 natural elements in its composition. They are found in different places of the lithosphere and with varying degrees of concentration.

The main ones are: oxygen silicon aluminum, iron, potassium, calcium, sodium magnesium. 98 percent of the earth's crust is made up of them. Including about half is oxygen, more than a quarter - silicon. Due to their combinations, minerals such as diamond, gypsum, quartz, etc. are formed. Several minerals can form a rock.

• An ultra-deep well on the Kola Peninsula made it possible to get acquainted with mineral samples from a depth of 12 km, where rocks similar to granites and shale were found.
• The greatest thickness of the crust (about 70 km) was revealed under the mountain systems. Under the flat areas it is 30-40 km, and under the oceans - only 5-10 km.
• A significant part of the crust forms an ancient low-density upper layer, consisting mainly of granites and shale.
• The structure of the earth's crust resembles the crust of many planets, including those on the Moon and their satellites.

A characteristic feature of the evolution of the Earth is the differentiation of matter, the expression of which is the shell structure of our planet. The lithosphere, hydrosphere, atmosphere, biosphere form the main shells of the Earth, differing in chemical composition, power and state of matter.

The internal structure of the Earth

The chemical composition of the Earth(Fig. 1) is similar to the composition of other terrestrial planets, such as Venus or Mars.

In general, elements such as iron, oxygen, silicon, magnesium, and nickel predominate. The content of light elements is low. The average density of the Earth's matter is 5.5 g/cm 3 .

There is very little reliable data on the internal structure of the Earth. Consider Fig. 2. It depicts the internal structure of the Earth. The earth consists of the earth's crust, mantle and core.

Rice. 1. The chemical composition of the Earth

Rice. 2. Internal structure Earth

Nucleus

Nucleus(Fig. 3) is located in the center of the Earth, its radius is about 3.5 thousand km. The core temperature reaches 10,000 K, i.e., it is higher than the temperature of the outer layers of the Sun, and its density is 13 g / cm 3 (compare: water - 1 g / cm 3). The core presumably consists of alloys of iron and nickel.

The outer core of the Earth has a greater power than the inner core (radius 2200 km) and is in a liquid (molten) state. The inner core is under enormous pressure. The substances that compose it are in a solid state.

Mantle

Mantle- the geosphere of the Earth, which surrounds the core and makes up 83% of the volume of our planet (see Fig. 3). Its lower boundary is located at a depth of 2900 km. The mantle is divided into a less dense and plastic upper part (800-900 km), from which magma(translated from Greek means "thick ointment"; this is the molten substance of the earth's interior - a mixture chemical compounds and elements, including gases, in a special semi-liquid state); and a crystalline lower one, about 2000 km thick.

Rice. 3. Structure of the Earth: core, mantle and earth's crust

Earth's crust

Earth's crust - the outer shell of the lithosphere (see Fig. 3). Its density is approximately two times less than the average density of the Earth - 3 g/cm 3 .

Separates the earth's crust from the mantle Mohorovicic border(it is often called the Moho boundary), characterized by a sharp increase in seismic wave velocities. It was installed in 1909 by a Croatian scientist Andrey Mohorovichich (1857- 1936).

Since the processes occurring in the uppermost part of the mantle affect the movement of matter in the earth's crust, they are combined under the general name lithosphere(stone shell). The thickness of the lithosphere varies from 50 to 200 km.

Below the lithosphere is asthenosphere- less hard and less viscous, but more plastic shell with a temperature of 1200 °C. It can cross the Moho boundary, penetrating into the earth's crust. The asthenosphere is the source of volcanism. It contains pockets of molten magma, which is introduced into the earth's crust or poured onto the earth's surface.

The composition and structure of the earth's crust

Compared to the mantle and core, the earth's crust is a very thin, hard, and brittle layer. It is composed of a lighter substance, which currently contains about 90 natural chemical elements. These elements are not equally represented in the earth's crust. Seven elements—oxygen, aluminium, iron, calcium, sodium, potassium, and magnesium—account for 98% of the mass of the earth's crust (see Figure 5).

Peculiar combinations of chemical elements form various rocks and minerals. The oldest of them are at least 4.5 billion years old.

Rice. 4. The structure of the earth's crust

Rice. 5. The composition of the earth's crust

Mineral is a relatively homogeneous in its composition and properties of a natural body, formed both in the depths and on the surface of the lithosphere. Examples of minerals are diamond, quartz, gypsum, talc, etc. (Characteristic physical properties various minerals you will find in Appendix 2.) The composition of the minerals of the Earth is shown in fig. 6.

Rice. 6. General mineral composition of the Earth

Rocks are made up of minerals. They can be composed of one or more minerals.

Sedimentary rocks - clay, limestone, chalk, sandstone, etc. - formed by the precipitation of substances in the aquatic environment and on land. They lie in layers. Geologists call them pages of the history of the Earth, because they can learn about the natural conditions that existed on our planet in ancient times.

Among sedimentary rocks, organogenic and inorganic (detrital and chemogenic) are distinguished.

Organogenic rocks are formed as a result of the accumulation of the remains of animals and plants.

Clastic rocks are formed as a result of weathering, the formation of products of destruction of previously formed rocks with the help of water, ice or wind (Table 1).

Table 1. Clastic rocks depending on the size of the fragments

Breed name	Size of bummer con (particles)
	Over 50 cm
	5 mm - 1 cm
	1 mm - 5 mm
Sand and sandstones	0.005 mm - 1 mm
	Less than 0.005mm

Chemogenic rocks are formed as a result of sedimentation from the waters of the seas and lakes of substances dissolved in them.

In the thickness of the earth's crust, magma forms igneous rocks(Fig. 7), such as granite and basalt.

Sedimentary and igneous rocks when immersed to great depths under the influence of pressure and high temperatures undergo significant changes, becoming metamorphic rocks. So, for example, limestone turns into marble, quartz sandstone into quartzite.

Three layers are distinguished in the structure of the earth's crust: sedimentary, "granite", "basalt".

Sedimentary layer(see Fig. 8) is formed mainly by sedimentary rocks. Clays and shales predominate here, sandy, carbonate and volcanic rocks are widely represented. In the sedimentary layer there are deposits of such mineral, like coal, gas, oil. All of them organic origin. For example, coal is a product of the transformation of plants of ancient times. The thickness of the sedimentary layer varies widely - from complete absence in some areas of land to 20-25 km in deep depressions.

Rice. 7. Classification of rocks by origin

"Granite" layer consists of metamorphic and igneous rocks similar in their properties to granite. The most common here are gneisses, granites, crystalline schists, etc. The granite layer is not found everywhere, but on the continents, where it is well expressed, its maximum thickness can reach several tens of kilometers.

"Basalt" layer formed by rocks close to basalts. These are metamorphosed igneous rocks, denser than the rocks of the "granite" layer.

The thickness and vertical structure of the earth's crust are different. There are several types of the earth's crust (Fig. 8). According to the simplest classification, oceanic and continental crust are distinguished.

Continental and oceanic crust are different in thickness. Thus, the maximum thickness of the earth's crust is observed under mountain systems. It is about 70 km. Under the plains, the thickness of the earth's crust is 30-40 km, and under the oceans it is the thinnest - only 5-10 km.

Rice. 8. Types of the earth's crust: 1 - water; 2 - sedimentary layer; 3 - interbedding of sedimentary rocks and basalts; 4, basalts and crystalline ultramafic rocks; 5, granite-metamorphic layer; 6 - granulite-mafic layer; 7 - normal mantle; 8 - decompressed mantle

The difference between the continental and oceanic crust in terms of rock composition is manifested in the absence of a granite layer in the oceanic crust. Yes, and the basalt layer of the oceanic crust is very peculiar. In terms of rock composition, it differs from the analogous layer of the continental crust.

The boundary of land and ocean (zero mark) does not fix the transition of the continental crust into the oceanic one. The replacement of the continental crust by oceanic occurs in the ocean approximately at a depth of 2450 m.

Rice. 9. The structure of the continental and oceanic crust

There are also transitional types of the earth's crust - suboceanic and subcontinental.

Suboceanic crust located along the continental slopes and foothills, can be found in the marginal and mediterranean seas. It is a continental crust up to 15-20 km thick.

subcontinental crust located, for example, on volcanic island arcs.

Based on materials seismic sounding - seismic wave velocity - we get data on the deep structure of the earth's crust. Thus, the Kola superdeep well, which for the first time made it possible to see rock samples from a depth of more than 12 km, brought a lot of unexpected things. It was assumed that at a depth of 7 km, a “basalt” layer should begin. In reality, however, it was not discovered, and gneisses predominated among the rocks.

Change in the temperature of the earth's crust with depth. The surface layer of the earth's crust has a temperature determined by solar heat. it heliometric layer(from the Greek Helio - the Sun), experiencing seasonal temperature fluctuations. Its average thickness is about 30 m.

Below is an even thinner layer, feature which is a constant temperature corresponding to the average annual temperature of the observation site. The depth of this layer increases in the continental climate.

Even deeper in the earth's crust, a geothermal layer is distinguished, the temperature of which is determined by the internal heat of the Earth and increases with depth.

The increase in temperature occurs mainly due to the decay of radioactive elements that make up the rocks, primarily radium and uranium.

The magnitude of the increase in temperature of rocks with depth is called geothermal gradient. It varies over a fairly wide range - from 0.1 to 0.01 ° C / m - and depends on the composition of the rocks, the conditions of their occurrence and a number of other factors. Under the oceans, the temperature rises faster with depth than on the continents. On average, with every 100 m of depth it becomes warmer by 3 °C.

The reciprocal of the geothermal gradient is called geothermal step. It is measured in m/°C.

The heat of the earth's crust is an important energy source.

The part of the earth's crust extending to the depths available for geological study forms bowels of the earth. The bowels of the Earth require special protection and reasonable use.

The earth's crust in the scientific sense is the uppermost and hardest geological part of the shell of our planet.

Scientific research allows you to study it thoroughly. This is facilitated by repeated drilling of wells both on the continents and on the ocean floor. The structure of the earth and the earth's crust in different parts of the planet differ both in composition and in characteristics. The upper boundary of the earth's crust is the visible relief, and the lower boundary is the zone of separation of the two media, which is also known as the Mohorovichic surface. It is often referred to simply as the "M boundary". She received this name thanks to the Croatian seismologist Mohorovichich A. He long years observed the speed of seismic movements depending on the level of depth. In 1909, he established the existence of a difference between the earth's crust and the red-hot mantle of the Earth. The M boundary lies at the level where the seismic wave velocity increases from 7.4 to 8.0 km/s.

The chemical composition of the Earth

Studying the shells of our planet, scientists made interesting and even amazing conclusions. The structural features of the earth's crust make it similar to the same areas on Mars and Venus. More than 90% of its constituent elements are represented by oxygen, silicon, iron, aluminum, calcium, potassium, magnesium, sodium. Combining with each other in various combinations, they form homogeneous physical bodies- minerals. They can enter the composition of rocks in different concentrations. The structure of the earth's crust is very heterogeneous. So, rocks in a generalized form are aggregates of a more or less constant chemical composition. These are independent geological bodies. They are understood as a clearly defined area of ​​the earth's crust, which has the same origin and age within its boundaries.

Rocks by groups

1. Magmatic. The name speaks for itself. They arise from cooled magma flowing from the vents of ancient volcanoes. The structure of these rocks directly depends on the rate of lava solidification. The larger it is, the smaller the crystals of the substance. Granite, for example, was formed in the thickness of the earth's crust, and basalt appeared as a result of a gradual outpouring of magma on its surface. The variety of such breeds is quite large. Considering the structure of the earth's crust, we see that it consists of magmatic minerals by 60%.

2. Sedimentary. These are rocks that were the result of the gradual deposition on land and the ocean floor of fragments of various minerals. These can be loose components (sand, pebbles), cemented (sandstone), microorganism residues (coal, limestone), chemical reaction products (potassium salt). They make up to 75% of the entire earth's crust on the continents.
According to the physiological method of formation, sedimentary rocks are divided into:

• Clastic. These are the remains of various rocks. They were destroyed under the influence of natural factors (earthquake, typhoon, tsunami). These include sand, pebbles, gravel, crushed stone, clay.
• Chemical. They are gradually formed from aqueous solutions of various mineral substances (salts).
• organic or biogenic. Consist of the remains of animals or plants. These are oil shale, gas, oil, coal, limestone, phosphorites, chalk.

3. Metamorphic rocks. Other components can turn into them. This happens under the influence of changing temperature, high pressure, solutions or gases. For example, marble can be obtained from limestone, gneiss from granite, and quartzite from sand.

Minerals and rocks that humanity actively uses in its life are called minerals. What are they?

These are natural mineral formations that affect the structure of the earth and the earth's crust. They can be used in agriculture and industry, both in its natural form and being processed.

Types of useful minerals. Their classification

Depending on the physical condition and aggregation, minerals can be divided into categories:

1. Solid (ore, marble, coal).
2. Liquid (mineral water, oil).
3. Gaseous (methane).

Characteristics of individual types of minerals

According to the composition and features of the application, there are:

1. Combustible (coal, oil, gas).
2. Ore. They include radioactive (radium, uranium) and noble metals(silver, gold, platinum). There are ores of ferrous (iron, manganese, chromium) and non-ferrous metals (copper, tin, zinc, aluminum).
3. Non-metallic minerals play a significant role in such a concept as the structure of the earth's crust. Their geography is extensive. These are non-metallic and non-combustible rocks. These are building materials (sand, gravel, clay) and chemicals (sulfur, phosphates, potassium salts). A separate section is devoted to precious and ornamental stones.

The distribution of minerals on our planet directly depends on external factors and geological patterns.

Thus, fuel minerals are primarily mined in oil and gas bearing and coal basins. They are of sedimentary origin and form on the sedimentary covers of platforms. Oil and coal rarely occur together.

Ore minerals most often correspond to the basement, ledges and folded areas of platform plates. In such places they can create huge belts.

Nucleus

The earth's shell, as you know, is multi-layered. The core is located in the very center, and its radius is approximately 3,500 km. Its temperature is much higher than that of the Sun and is about 10,000 K. Accurate data on the chemical composition of the core have not been obtained, but presumably it consists of nickel and iron.

The outer core is in a molten state and has even more power than the inner one. The latter is under enormous pressure. The substances of which it is composed are in a permanent solid state.

Mantle

The geosphere of the Earth surrounds the core and makes up about 83 percent of the entire shell of our planet. The lower boundary of the mantle is located at a great depth of almost 3000 km. This shell is conventionally divided into a less plastic and dense upper part (it is from it that magma is formed) and a lower crystalline one, the width of which is 2000 kilometers.

The composition and structure of the earth's crust

In order to talk about what elements make up the lithosphere, it is necessary to give some concepts.

The earth's crust is the outermost shell of the lithosphere. Its density is less than two times compared to the average density of the planet.

The earth's crust is separated from the mantle by the boundary M, which has already been mentioned above. Since the processes occurring in both areas mutually influence each other, their symbiosis is usually called the lithosphere. It means "stone shell". Its power ranges from 50-200 kilometers.

Below the lithosphere is the asthenosphere, which has a less dense and viscous consistency. Its temperature is about 1200 degrees. A unique feature of the asthenosphere is the ability to violate its boundaries and penetrate into the lithosphere. It is the source of volcanism. Here are molten pockets of magma, which is introduced into the earth's crust and pours out to the surface. By studying these processes, scientists have been able to make many amazing discoveries. This is how the structure of the earth's crust was studied. The lithosphere was formed many thousands of years ago, but even now active processes are taking place in it.

Structural elements of the earth's crust

Compared to the mantle and core, the lithosphere is a hard, thin, and very fragile layer. It is composed of a combination of substances, in which more than 90 chemical elements have been found to date. They are distributed unevenly. 98 percent of the mass of the earth's crust is accounted for by seven components. These are oxygen, iron, calcium, aluminum, potassium, sodium and magnesium. The oldest rocks and minerals are over 4.5 billion years old.

By studying the internal structure of the earth's crust, various minerals can be distinguished.
A mineral is a relatively homogeneous substance that can be located both inside and on the surface of the lithosphere. These are quartz, gypsum, talc, etc. Rocks are made up of one or more minerals.

Processes that form the earth's crust

The structure of the oceanic crust

This part of the lithosphere mainly consists of basalt rocks. The structure of the oceanic crust has not been studied as thoroughly as the continental one. The plate tectonic theory explains that the oceanic crust is relatively young, and its most recent sections can be dated to the Late Jurassic.
Its thickness practically does not change with time, since it is determined by the amount of melts released from the mantle in the zone of mid-ocean ridges. It is significantly affected by the depth of sedimentary layers on the ocean floor. In the most voluminous sections, it ranges from 5 to 10 kilometers. This type the earth's shell refers to the oceanic lithosphere.

continental crust

The lithosphere interacts with the atmosphere, hydrosphere and biosphere. In the process of synthesis, they form the most complex and reactive shell of the Earth. It is in the tectonosphere that processes occur that change the composition and structure of these shells.
The lithosphere on the earth's surface is not homogeneous. It has several layers.

1. Sedimentary. It is mainly formed by rocks. Clays and shales predominate here, as well as carbonate, volcanic and sandy rocks. In the sedimentary layers one can find such minerals as gas, oil and coal. All of them are of organic origin.
2. granite layer. It consists of igneous and metamorphic rocks, which are closest in nature to granite. This layer is not found everywhere, it is most pronounced on the continents. Here, its depth can be tens of kilometers.
3. The basalt layer is formed by rocks close to the mineral of the same name. It is denser than granite.

Depth and change in the temperature of the earth's crust

The surface layer is heated by solar heat. This is a heliometric shell. It experiences seasonal fluctuations in temperature. The average layer thickness is about 30 m.

Below is a layer that is even thinner and more fragile. Its temperature is constant and approximately equal to the average annual temperature characteristic of this region of the planet. Depending on the continental climate, the depth of this layer increases.
Even deeper in the earth's crust is another level. This is the geothermal layer. The structure of the earth's crust provides for its presence, and its temperature is determined by the internal heat of the Earth and increases with depth.

The increase in temperature occurs due to the decay of radioactive substances that are part of the rocks. First of all, it is radium and uranium.

Geometric gradient - the magnitude of the increase in temperature depending on the degree of increase in the depth of the layers. This setting depends on various factors. The structure and types of the earth's crust affect it, as well as the composition of rocks, the level and conditions of their occurrence.

The heat of the earth's crust is an important energy source. His study is very relevant today.