The earth's crust is the hard surface layer of our planet. It was formed billions of years ago and is constantly changing its appearance under the influence of external and internal forces. Part of it is hidden under water, the other part forms land. The earth's crust is made up of various chemical substances. Let's find out which ones.

planet surface

Hundreds of millions of years after the formation of the Earth, its outer layer of boiling molten rocks began to cool and formed the earth's crust. The surface changed from year to year. Cracks, mountains, volcanoes appeared on it. The wind smoothed them out so that after a while they reappeared, but in other places.

Due to the external and internal solid layer of the planet is heterogeneous. From a structural point of view, the following elements can be distinguished earth's crust:

• geosynclines or folded areas;
• platforms;
• marginal faults and deflections.

Platforms are vast, sedentary areas. Their upper layer (up to a depth of 3-4 km) is covered with sedimentary rocks that occur in horizontal layers. The lower level (foundation) is strongly crumpled. It is composed of metamorphic rocks and may contain igneous inclusions.

Geosynclines are tectonically active areas where mountain building processes take place. They arise at the junction of the ocean floor and the continental platform, or in the trough of the ocean floor between the continents.

If mountains form close to the platform boundary, marginal faults and troughs may occur. They reach up to 17 kilometers in depth and stretch along the mountain formation. Over time, sedimentary rocks accumulate here and deposits are formed. mineral(oil, rock and potash salts, etc.).

Bark composition

The mass of the bark is 2.8 1019 tons. This is only 0.473% of the mass of the entire planet. The content of substances in it is not as diverse as in the mantle. It is formed by basalts, granites and sedimentary rocks.

99.8% of the earth's crust consists of eighteen elements. The rest account for only 0.2%. The most common are oxygen and silicon, which make up the bulk of the mass. In addition to them, the bark is rich in aluminum, iron, potassium, calcium, sodium, carbon, hydrogen, phosphorus, chlorine, nitrogen, fluorine, etc. The content of these substances can be seen in the table:

Astatine is considered the rarest element - an extremely unstable and poisonous substance. Tellurium, indium, and thallium are also rare. Often they are scattered and do not contain large clusters in one place.

continental crust

The mainland or continental crust is what we commonly refer to as dry land. It is quite old and covers about 40% of the entire planet. Many of its sections reach an age of 2 to 4.4 billion years.

The continental crust consists of three layers. From above it is covered with a discontinuous sedimentary cover. The rocks in it lie in layers or layers, as they are formed due to the pressing and compaction of salt deposits or microbial residues.

The lower and older layer is represented by granites and gneisses. They are not always hidden under sedimentary rocks. In some places they come to the surface in the form of crystalline shields.

The lowest layer consists of metamorphic rocks like basalts and granulites. The basalt layer can reach 20-35 kilometers.

oceanic crust

The part of the earth's crust hidden under the waters of the oceans is called oceanic. It is thinner and younger than continental. By age, the crust does not even reach two hundred million years, and its thickness is approximately 7 kilometers.

The continental crust is composed of sedimentary rocks from deep-sea remnants. Below is a basalt layer 5-6 kilometers thick. Below it begins the mantle, represented here mainly by peridotites and dunites.

Every hundred million years the crust is renewed. It is absorbed in subduction zones and re-formed at mid-ocean ridges with the help of outward minerals.

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 planets terrestrial group like 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

Core

Core(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, aluminum, 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. (You will find a description of the physical properties of various minerals in Appendix 2.) The composition of the Earth's minerals 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, since they can learn about 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 destruction products 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

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, turning into 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 are of 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. This 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, the characteristic feature of 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.

According to modern concepts of geology, our planet consists of several layers - geospheres. They differ in physical properties, chemical composition and In the center of the Earth is the core, followed by the mantle, then - the earth's crust, hydrosphere and atmosphere.

In this article, we will consider the structure of the earth's crust, which is the upper part of the lithosphere. It is an outer hard shell whose thickness is so small (1.5%) that it can be compared with a thin film on a global scale. However, despite this, it is the upper layer of the earth's crust that is of great interest to mankind as a source of minerals.

The crust of the earth is conditionally divided into three layers, each of which is remarkable in its own way.

1. The top layer is sedimentary. It reaches a thickness of 0 to 20 km. Sedimentary rocks are formed as a result of the deposition of substances on land, or their settling at the bottom of the hydrosphere. They are part of the earth's crust, located in it in successive layers.
2. The middle layer is granite. Its thickness can vary from 10 to 40 km. This is an igneous rock that formed a solid layer as a result of eruptions and subsequent solidification of magma in the earth's thickness at high pressure and temperature.
3. The lower layer, which is part of the structure of the earth's crust - basalt, also has a magmatic origin. It contains more calcium, iron and magnesium, and its mass is greater than that of granite rock.

The structure of the earth's crust is not the same everywhere. Particularly striking differences are between the oceanic and continental crusts. Under the oceans, the earth's crust is thinner, and thicker under the continents. It has the greatest thickness in areas of mountain ranges.

The composition includes two layers - sedimentary and basalt. Beneath the basaltic layer is the Moho surface, and behind it is the upper mantle. The ocean floor has the most complex relief forms. Among all their diversity, a special place is occupied by huge mid-ocean ridges, in which young basaltic oceanic crust is born from the mantle. Magma has access to the surface through a deep fault - a rift that runs along the center of the ridge along the peaks. Outside, the magma spreads, thereby constantly pushing the walls of the gorge to the sides. This process is called "spreading".

The structure of the earth's crust is more complex on the continents than under the oceans. Continental crust occupies a much smaller area than oceanic - up to 40% earth's surface but has a lot more power. Under it reaches a thickness of 60-70 km. The continental crust has a three-layer structure - a sedimentary layer, granite and basalt. In areas called shields, the granite layer is on the surface. As an example - composed of granite rocks.

The underwater extreme part of the mainland - the shelf, also has a continental structure of the earth's crust. It includes the islands of Kalimantan, New Zealand, New Guinea, Sulawesi, Greenland, Madagascar, Sakhalin, etc. As well as inland and marginal seas: the Mediterranean, Azov, Black.

It is possible to draw a boundary between the granite layer and the basalt layer only conditionally, since they have a similar seismic wave propagation velocity, which determines the density of the earth's layers and their composition. The basalt layer is in contact with the Moho surface. The sedimentary layer can have a different thickness, which depends on the relief form located on it. In the mountains, for example, it is either completely absent or has a very small thickness, due to the fact that loose particles move down the slopes under the influence of external forces. But on the other hand, it is very powerful in the foothill regions, depressions and hollows. So, in it reaches 22 km.

I can’t say that the school was a place of incredible discoveries for me, but there were really memorable moments in the lessons. For example, once in a literature class I was leafing through a geography textbook (don't ask), and somewhere in the middle I found a chapter on the differences between oceanic and continental crust. This information really surprised me. That's what I remember.

Oceanic crust: properties, layers, thickness

It is distributed, obviously, under the oceans. Although under some seas lies not even oceanic, but continental crust. This applies to those seas that are located above continental shelf. Some underwater plateaus - microcontinents in the ocean are also composed of continental, and not oceanic crust.

But most of our planet is still covered by the oceanic crust. The average thickness of its layer is 6-8 km. Although there are places with a thickness of both 5 km and 15 km.

It consists of three main layers:

• sedimentary;
• basalt;
• gabbro-serpentinite.

Continental crust: properties, layers, thickness

It is also called continental. It occupies smaller areas than the oceanic one, but it is many times greater than it in thickness. On flat areas, the thickness varies from 25 to 45 km, and in the mountains it can reach 70 km!

It has from two to three layers (from bottom to top):

• lower ("basalt", also known as granulite-basite);
• upper (granite);
• "cover" from sedimentary rocks (not always happens).

Those parts of the crust where "sheath" rocks are absent are called shields.

The layered structure is somewhat reminiscent of the oceanic, but it is clear that their basis is completely different. The granite layer, which makes up most of the continental crust, is absent in the oceanic one as such.

It should be noted that the names of the layers are rather conditional. This is due to the difficulties of studying the composition of the earth's crust. The possibilities of drilling are limited, therefore, the deep layers were initially studied and are being studied not so much on the basis of "live" samples, but on the speed of seismic waves passing through them. Passing speed like granite? Let's call it granite. It is difficult to judge how "granite" the composition is.

Line UMK "Classical geography" (5-9)

Geography

The internal structure of the Earth. A world of amazing secrets in one article

The internal structure of the Earth

Planet Earth is made up of three main layers: earth's crust, robes And nuclei. You can compare the globe to an egg. Then the eggshell will be the earth's crust, the egg white will be the mantle, and the yolk will be the core.

The upper part of the earth is called lithosphere(translated from Greek "stone ball"). This is a hard shell of the globe, which includes the earth's crust and the upper part of the mantle.

Tutorial addressed to students of grade 6 and is included in the teaching materials "Classical geography". Modern design, a variety of questions and tasks, the possibility of parallel work with electronic form textbooks contribute to the effective assimilation educational material. The textbook complies with the Federal State educational standard basic general education.

Earth's crust

The earth's crust is a stone shell that covers the entire surface of our planet. Under the oceans, its thickness does not exceed 15 kilometers, and on the continents - 75. If we return to the egg analogy, then the earth's crust in relation to the entire planet is thinner than an eggshell. This layer of the Earth accounts for only 5% of the volume and less than 1% of the mass of the entire planet.

In the composition of the earth's crust, scientists have found oxides of silicon, alkali metals, aluminum and iron. The crust under the oceans consists of sedimentary and basalt layers, it is heavier than the continental (mainland). While the shell covering the continental part of the planet has a more complex structure.

There are three layers of the continental crust:

sedimentary (10-15 km mostly sedimentary rocks);

granite (5-15 km of metamorphic rocks, similar in properties to granite);

basaltic (10-35 km of igneous rocks).

Mantle

Under the earth's crust is the mantle ( "veil, cloak"). This layer is up to 2900 km thick. It accounts for 83% of the total volume of the planet and almost 70% of the mass. The mantle consists of heavy minerals rich in iron and magnesium. This layer has a temperature of over 2000°C. However, much of the material in the mantle retains its solid crystalline state due to the enormous pressure. At a depth of 50 to 200 km, there is a mobile upper layer of the mantle. It's called the asthenosphere "powerless sphere"). The asthenosphere is very plastic, it is because of it that volcanic eruptions and the formation of mineral deposits occur. The thickness of the asthenosphere reaches from 100 to 250 km. The substance that penetrates from the asthenosphere into the earth's crust and sometimes pours out to the surface is called magma. ("mush, thick ointment"). When magma solidifies on the Earth's surface, it turns into lava.

Core

Under the mantle, as if under a veil, is the earth's core. It is located 2900 km from the surface of the planet. The core has the shape of a ball with a radius of about 3500 km. Since people have not yet managed to get to the core of the Earth, scientists are guessing about its composition. Presumably, the core consists of iron with an admixture of other elements. This is the densest and heaviest part of the planet. It accounts for only 15% of the volume of the Earth and as much as 35% of the mass.

It is believed that the core consists of two layers - a solid inner core (with a radius of about 1300 km) and a liquid outer one (about 2200 km). The inner core seems to be floating in the outer liquid layer. Because of this smooth movement around the Earth, its magnetic field is formed (it is it that protects the planet from dangerous cosmic radiation, and the compass needle reacts to it). The core is the hottest part of our planet. For a long time it was believed that its temperature reaches, presumably, 4000-5000°C. However, in 2013, scientists conducted a laboratory experiment in which they determined the melting point of iron, which is likely part of the Earth's inner core. So it turned out that the temperature between the inner solid and outer liquid core is equal to the temperature of the surface of the Sun, that is, about 6000 ° C.

The structure of our planet is one of the many mysteries unsolved by mankind. Most of the information about it has been obtained by indirect methods; not a single scientist has yet been able to obtain samples of the earth's core. The study of the structure and composition of the Earth is still fraught with insurmountable difficulties, but researchers do not give up and are looking for new ways to get reliable information about the planet Earth.

When studying the topic “Internal structure of the Earth”, students may have difficulty remembering the names and order of the layers of the globe. Latin names will be much easier to remember if the children create their own model of the Earth. You can invite students to make a model of the globe from plasticine or talk about its structure using fruits as an example (peel - earth's crust, pulp - mantle, bone - core) and objects that have a similar structure. The textbook by O.A. Klimanova will help in conducting the lesson, where you will find colorful illustrations and detailed information on the topic.