The structure of the earth in a section with dimensions. What the Earth is made of - an explanation for children. Temperature. Sources of thermal energy

Our house

The planet on which we live is used by us in absolutely all spheres of our life: we build our cities and dwellings on it; we eat the fruits of plants growing on it; use for our purposes Natural resources mined from its depths. The earth is the source of all the blessings available to us, our home. But few people know what the structure of the Earth is, what are its features and why it is interesting. For people who are specifically interested in this issue, this article is written. Someone, having read it, will refresh the knowledge they already have in their memory. And someone, perhaps, will find out something that he had no idea about. But before moving on to talking about what characterizes the internal structure of the Earth, it is worth saying a little about the planet itself.

Briefly about the planet Earth

Earth is the third planet from the Sun (Venus is in front of it, Mars is behind it). The distance from the Sun is about 150 million km. It belongs to a group of planets called the "earth group" (also includes Mercury, Venus and Mars). Its mass is 5.98 * 10 27, and the volume is 1.083 * 10 27 cm³. The orbital speed is 29.77 km/s. The Earth makes a complete revolution around the Sun in 365.26 days, and a complete revolution around its own axis - in 23 hours 56 minutes. Based on scientific data, scientists have concluded that the age of the Earth is approximately 4.5 billion years. The planet has the shape of a ball, but its outlines sometimes change due to inevitable internal dynamic processes. The chemical composition is similar to that of the rest of the terrestrial planets - it is dominated by oxygen, iron, silicon, nickel and magnesium.

Earth structure

The earth consists of several components - this is the core, the mantle and the earth's crust. A little about everything.

Earth's crust

This is the top layer of the earth. It is he who is actively used by a person. And this layer is the best studied. It contains deposits of rocks and minerals. It consists of three layers. The first is sedimentary. It is represented by softer rocks formed as a result of the destruction of solid rocks, deposits of plant and animal remains, and sedimentation of various substances on the bottom of the world's oceans. The next layer is granite. It is formed from solidified magma (molten substance of the earth's depths that fills cracks in the crust) under conditions of pressure and high temperatures. Also, this layer contains various minerals: aluminum, calcium, sodium, potassium. As a rule, this layer is absent under the oceans. After the granite layer comes the basalt layer, consisting mainly of basalt (a rock of deep origin). This layer contains more calcium, magnesium and iron. These three layers contain all the minerals that a person uses. The thickness of the earth's crust ranges from 5 km (under the oceans) to 75 km (under the continents). The Earth's crust makes up about 1% of its total volume.

Mantle

It is located under the cortex and surrounds the nucleus. It makes up 83% of the total volume of the planet. The mantle is divided into upper (at a depth of 800-900 km) and lower (at a depth of 2900 km) parts. From the upper part, magma is formed, which we mentioned above. The mantle consists of dense silicate rocks, which contain oxygen, magnesium and silicon. Also based on seismological data, scientists have concluded that at the base of the mantle there is an alternately interrupted layer consisting of giant continents. And they, in turn, could have formed as a result of the mixing of the rocks of the mantle itself with the substance of the core. But another possibility is that these areas could represent the bottom of ancient oceans. Notes are details. Further geological structure The earth continues with the core.

Nucleus

The formation of the nucleus is explained by the fact that in the early historical period The lands of matter with the highest density (iron and nickel) settled to the center and formed the core. It is the most dense part, representing the structure of the Earth. It is divided into a molten outer core (approximately 2200 km thick) and a solid inner core (approximately 2500 km in diameter). It makes up 16% of the total volume of the Earth and 32% of its total mass. Its radius is 3500 km. What happens inside the core is hardly imaginable - here the temperature is over 3000 ° C and colossal pressure.

Convection

The heat that was accumulated during the formation of the Earth is still being released from its depths as the core cools and radioactive elements decay. It does not come to the surface only due to the fact that there is a mantle, the rocks of which have excellent thermal insulation. But this heat sets the very substance of the mantle in motion - first, hot rocks rise up from the core, and then, being cooled by it, return again. This process is called convection. It results in volcanic eruptions and earthquakes.

A magnetic field

The molten iron in the outer core has a circulation that creates electrical currents that generate the Earth's magnetic field. It spreads into space and creates a magnetic shell around the Earth, which reflects the flows of the solar wind (charged particles ejected by the Sun) and protects living beings from deadly radiation.

Where is the data from

All information is obtained using various geophysical methods. On the surface of the Earth, seismologists (scientists who study the vibrations of the Earth) set up seismological stations, where any vibrations of the earth's crust are recorded. By observing the activity of seismic waves in different parts of the Earth, the most powerful computers reproduce a picture of what is happening in the depths of the planet in the same way that X-rays “shine through” the human body.

Finally

We only talked a little about what the structure of the Earth is. In fact, this issue can be studied for a very long time, because. it is full of nuances and features. For this purpose, there are seismologists. The rest is enough to have general information about its structure. But in no case should we forget that the planet Earth is our home, without which we would not exist. And it should be treated with love, respect and care.

Methods for studying the internal structure and composition of the Earth can be divided into two main groups: geological methods and geophysical methods. Geological methods are based on the results of a direct study of rock strata in outcrops, mine workings (mines, adits, etc.) and boreholes. At the same time, researchers have at their disposal the entire arsenal of methods for studying the structure and composition, which determines the high degree of detail of the results obtained. At the same time, the possibilities of these methods in studying the depths of the planet are very limited - the deepest well in the world has a depth of only -12262 m (Kola superdeep in Russia), even smaller depths have been achieved when drilling the ocean floor (about -1500 m, drilling from the side of the American research vessel "Glomar Challenger"). Thus, depths not exceeding 0.19% of the planet's radius are available for direct study.

Information about the deep structure is based on the analysis of indirect data obtained geophysical methods, mainly patterns of change with depth of various physical parameters (electrical conductivity, mechanical figure of merit, etc.) measured during geophysical surveys. The development of models of the internal structure of the Earth is based primarily on the results of seismic studies based on data on the patterns of propagation of seismic waves. In the centers of earthquakes and powerful explosions, seismic waves arise - elastic vibrations. These waves are divided into volume waves - propagating in the bowels of the planet and "translucent" them like X-rays, and surface waves - propagating parallel to the surface and "probing" the upper layers of the planet to a depth of tens or hundreds of kilometers.
Body waves, in turn, are divided into two types - longitudinal and transverse. Longitudinal waves with a high propagation speed are the first to be recorded by seismic receivers, they are called primary or P-waves ( from English. primary - primary), the "slower" transverse waves are called S-waves ( from English. secondary - secondary). Transverse waves are known to have important feature– they spread only in a solid medium.

At the boundaries of media with different properties, waves are refracted, and at the boundaries of sharp changes in properties, in addition to refracted, reflected and converted waves arise. Shear waves can be offset perpendicular to the plane of incidence (SH waves) or offset in the plane of incidence (SV waves). When crossing the boundary of media with different properties, the SH waves experience ordinary refraction, and the SV waves, except for the refracted and reflected SV waves, excite P-waves. This is how a complex system of seismic waves arises, "seeing through" the bowels of the planet.

Analyzing the patterns of wave propagation, it is possible to identify inhomogeneities in the bowels of the planet - if at a certain depth an abrupt change in the propagation velocities of seismic waves, their refraction and reflection is recorded, we can conclude that at this depth there is a boundary of the Earth's inner shells, differing in their physical properties.

The study of the ways and speed of propagation of seismic waves in the bowels of the Earth made it possible to develop a seismic model of its internal structure.

Seismic waves, propagating from the earthquake source into the depths of the Earth, experience the most significant jumps in velocity, refract and reflect on seismic sections located at depths 33 km and 2900 km from the surface (see fig.). These sharp seismic boundaries make it possible to divide the bowels of the planet into 3 main internal geospheres - the earth's crust, mantle and core.

The earth's crust is separated from the mantle by a sharp seismic boundary, on which the velocity of both longitudinal and transverse waves increases abruptly. Thus, the velocity of transverse waves sharply increases from 6.7-7.6 km/s in the lower part of the crust to 7.9-8.2 km/s in the mantle. This boundary was discovered in 1909 by the Yugoslavian seismologist Mohorovičić and was subsequently named Mohorović border(often abbreviated as the Moho or M boundary). The average depth of the boundary is 33 km (it should be noted that this is a very approximate value due to different thicknesses in different geological structures); at the same time, under the continents, the depth of the Mohorovichich section can reach 75-80 km (which is fixed under young mountain structures - the Andes, Pamir), under the oceans it decreases, reaching a minimum thickness of 3-4 km.

An even sharper seismic boundary separating the mantle and core is fixed at depth 2900 km. On this seismic section P-wave speed drops abruptly from 13.6 km/s at the base of the mantle to 8.1 km/s in the core; S-waves - from 7.3 km / s to 0. The disappearance of transverse waves indicates that the outer part of the core has the properties of a liquid. The seismic boundary separating the core and mantle was discovered in 1914 by the German seismologist Gutenberg and is often referred to as Gutenberg border, although this name is not official.

Sharp changes in the speed and nature of the passage of waves are recorded at depths of 670 km and 5150 km. Border 670 km divides the mantle into upper mantle (33-670 km) and lower mantle (670-2900 km). Border 5150 km divides the core into an external liquid (2900-5150 km) and an internal solid (5150-6371 km).

Significant changes are also noted in the seismic section 410 km dividing the upper mantle into two layers.

The obtained data on global seismic boundaries provide a basis for considering a modern seismic model of the deep structure of the Earth.

The outer shell of the solid earth is Earth's crust bounded by the Mohorovichic boundary. This is a relatively thin shell, the thickness of which ranges from 4-5 km under the oceans to 75-80 km under continental mountain structures. The upper crust is distinctly distinguished in the composition of the sedimentary layer, consisting of non-metamorphosed sedimentary rocks, among which volcanics may be present, and underlying it consolidated, or crystalline,bark, formed by metamorphosed and igneous intrusive rocks. There are two main types of the earth's crust - continental and oceanic, fundamentally different in structure, composition, origin and age.

continental crust lies under the continents and their underwater margins, has a thickness of 35-45 km to 55-80 km, 3 layers are distinguished in its section. The upper layer, as a rule, is composed of sedimentary rocks, including a small amount of weakly metamorphosed and igneous rocks. This layer is called sedimentary. Geophysically, it is characterized by a low P-wave velocity in the range of 2-5 km/s. The average thickness of the sedimentary layer is about 2.5 km.
Below is the upper crust (granite-gneiss or "granite" layer), composed of igneous and metamorphic rocks rich in silica (on average, corresponding in chemical composition to granodiorite). The velocity of P-waves in this layer is 5.9-6.5 km/s. At the base of the upper crust, the Konrad seismic section is distinguished, reflecting an increase in the velocity of seismic waves during the transition to the lower crust. But this section is not fixed everywhere: in the continental crust, a gradual increase in wave velocities with depth is often recorded.
The lower crust (granulite-mafic layer) is distinguished by a higher wave speed (6.7-7.5 km/s for P-waves), which is due to a change in the rock composition during the transition from the upper mantle. According to the most accepted model, its composition corresponds to granulite.

Rocks of various geological ages take part in the formation of the continental crust, up to the most ancient ones, about 4 billion years old.

oceanic crust has a relatively small thickness, an average of 6-7 km. In its section in the very general view 2 layers can be distinguished. The upper layer is sedimentary, characterized by low thickness (about 0.4 km on average) and low P-wave speed (1.6-2.5 km/s). The lower layer - "basalt" - is composed of basic igneous rocks (above - basalts, below - basic and ultrabasic intrusive rocks). The velocity of longitudinal waves in the "basalt" layer increases from 3.4-6.2 km/s in basalts to 7-7.7 km/s in the lowest horizons of the crust.

The oldest rocks of modern oceanic crust are about 160 million years old.

Mantle It is the largest inner shell of the Earth in terms of volume and mass, bounded from above by the Moho boundary, from below by the Gutenberg boundary. In its composition stands out upper mantle and the lower mantle, separated by a boundary of 670 km.

The upper mania is divided into two layers according to geophysical features. Upper layer - subcrustal mantle- extends from the Moho boundary to depths of 50-80 km under the oceans and 200-300 km under the continents and is characterized by a smooth increase in the speed of both longitudinal and transverse seismic waves, which is explained by the compaction of rocks due to the lithostatic pressure of the overlying strata. Below the subcrustal mantle to the global interface of 410 km there is a layer of low velocities. As follows from the name of the layer, the seismic wave velocities in it are lower than in the subcrustal mantle. Moreover, lenses that do not transmit S-waves at all are revealed in some areas, which gives grounds to state that the mantle substance in these areas is in a partially molten state. This layer is called the asthenosphere ( from the Greek "asthenes" - weak and "sphair" - sphere); the term was introduced in 1914 by the American geologist J. Burrell, often referred to in English literature as LVZ - Low Velocity Zone. In this way, asthenosphere- this is a layer in the upper mantle (located at a depth of about 100 km under the oceans and about 200 km or more under the continents), identified on the basis of a decrease in the speed of passage of seismic waves and having a reduced strength and viscosity. The surface of the asthenosphere is well established by a sharp decrease in resistivity (to values ​​of about 100 Ohm . m).

The presence of a plastic asthenospheric layer, which differs in mechanical properties from the solid overlying layers, gives grounds for isolating lithosphere- the solid shell of the Earth, including the earth's crust and subcrustal mantle, located above the asthenosphere. The thickness of the lithosphere is from 50 to 300 km. It should be noted that the lithosphere is not a monolithic stone shell of the planet, but is divided into separate plates constantly moving along the plastic asthenosphere. The foci of earthquakes and modern volcanism are confined to the boundaries of lithospheric plates.

Deeper than 410 km in the upper mantle, both P- and S-waves propagate everywhere, and their speed increases relatively monotonously with depth.

AT lower mantle, separated by a sharp global boundary of 670 km, the speed of P- and S-waves increases monotonically, without abrupt changes, up to 13.6 and 7.3 km/s, respectively, up to the Gutenberg section.

In the outer core, the speed of P-waves sharply decreases to 8 km/s, while S-waves completely disappear. The disappearance of transverse waves suggests that the outer core of the Earth is in a liquid state. Below the 5150 km section, there is an inner core in which the speed of P-waves increases, and S-waves begin to propagate again, which indicates its solid state.

The fundamental conclusion from the velocity model of the Earth described above is that our planet consists of a series of concentric shells representing a ferruginous core, a silicate mantle, and an aluminosilicate crust.

Geophysical characteristics of the Earth

Distribution of mass between the inner geospheres

The bulk of the Earth's mass (about 68%) falls on its relatively light, but large mantle, with about 50% falling on the lower mantle and about 18% on the upper. The remaining 32% of the total mass of the Earth falls mainly on the core, and its liquid outer part (29% of the total mass of the Earth) is much heavier than the inner solid part (about 2%). Only less than 1% of the total mass of the planet remains on the crust.

Density

The density of the shells naturally increases towards the center of the Earth (see fig.). The average density of the bark is 2.67 g/cm 3 ; at the Moho border, it increases abruptly from 2.9-3.0 to 3.1-3.5 g/cm3. In the mantle, the density gradually increases due to the compression of the silicate substance and phase transitions (restructuring of the crystalline structure of the substance in the course of "adaptation" to increasing pressure) from 3.3 g/cm 3 in the subcrustal part to 5.5 g/cm 3 in the lower mantle . At the Gutenberg boundary (2900 km), the density almost doubles abruptly, up to 10 g/cm 3 in the outer core. Another jump in density - from 11.4 to 13.8 g / cm 3 - occurs at the border of the inner and outer core (5150 km). These two sharp density jumps have a different nature: at the mantle/core boundary, there is a change chemical composition matter (transition from a silicate mantle to an iron core), and the jump at the boundary of 5150 km is associated with a change in the state of aggregation (transition from a liquid outer core to a solid inner core). In the center of the Earth, the density of matter reaches 14.3 g/cm 3 .

Pressure

The pressure in the Earth's interior is calculated based on its density model. The increase in pressure as you move away from the surface is due to several reasons:

compression due to the weight of the overlying shells (lithostatic pressure);

phase transitions in chemically homogeneous shells (in particular, in the mantle);

the difference in the chemical composition of the shells (crust and mantle, mantle and core).

At the foot of the continental crust, the pressure is about 1 GPa (more precisely, 0.9 * 10 9 Pa). In the Earth's mantle, the pressure gradually increases, reaching 135 GPa at the Gutenberg boundary. In the outer core, the pressure growth gradient increases, while in the inner core, on the contrary, it decreases. The calculated values ​​of pressure at the boundary between the inner and outer cores and near the center of the Earth are 340 and 360 GPa, respectively.

Temperature. Sources of thermal energy

The geological processes occurring on the surface and in the bowels of the planet are primarily due to thermal energy. Energy sources are divided into two groups: endogenous (or internal sources), associated with the generation of heat in the bowels of the planet, and exogenous (or external in relation to the planet). The intensity of the flow of thermal energy from the depths to the surface is reflected in the magnitude of the geothermal gradient. geothermal gradient is the temperature increment with depth, expressed in 0 C/km. The "inverse" characteristic is geothermal stage- depth in meters, upon immersion to which the temperature will increase by 1 0 С. areas with a calm tectonic regime. With depth, the value of the geothermal gradient decreases significantly, amounting to an average of about 10 0 С/km in the lithosphere, and less than 1 0 С/km in the mantle. The reason for this lies in the distribution of thermal energy sources and the nature of heat transfer.

Sources of endogenous energy are the following.
1. Energy of deep gravitational differentiation, i.e. heat release during the redistribution of matter in density during its chemical and phase transformations. The main factor in such transformations is pressure. The core-mantle boundary is considered as the main level of this energy release.
2. Radiogenic heat produced by the decay of radioactive isotopes. According to some calculations, this source determines about 25% of the heat flux radiated by the Earth. However, it should be taken into account that elevated contents of the main long-lived radioactive isotopes - uranium, thorium and potassium are observed only in the upper part of the continental crust (isotopic enrichment zone). For example, the concentration of uranium in granites reaches 3.5 10 -4%, in sedimentary rocks - 3.2 10 -4%, while in the oceanic crust it is negligible: about 1.66 10 -7%. Thus, radiogenic heat is an additional source of heat in the upper part of the continental crust, which determines the high value of the geothermal gradient in this region of the planet.
3. Residual heat, preserved in the depths since the formation of the planet.
4. Solid tides, due to the attraction of the moon. The transition of kinetic tidal energy into heat occurs due to internal friction in the rock masses. Share of this source in total thermal balance small - about 1-2%.

In the lithosphere, the conductive (molecular) mechanism of heat transfer predominates; in the sublithospheric mantle of the Earth, a transition occurs to a predominantly convective mechanism of heat transfer.

Calculations of temperatures in the bowels of the planet give the following values: in the lithosphere at a depth of about 100 km, the temperature is about 1300 0 C, at a depth of 410 km - 1500 0 C, at a depth of 670 km - 1800 0C, at the boundary of the core and mantle - 2500 0 C, at a depth of 5150 km - 3300 0 С, in the center of the Earth - 3400 0 С. In this case, only the main (and most probable for deep zones) heat source is the energy of deep gravitational differentiation.

Endogenous heat determines the course of global geodynamic processes. including the movement of lithospheric plates

On the surface of the planet, the most important role is played by exogenous source heat is solar radiation. Below surface impact solar heat decreases sharply. Already at a shallow depth (up to 20-30 m) there is a zone of constant temperatures - a region of depths where the temperature remains constant and is equal to the average annual temperature of the region. Below the belt of constant temperatures, heat is associated with endogenous sources.

Earth magnetism

The earth is a giant magnet with a magnetic force field and magnetic poles that are close to geographic, but do not coincide with them. Therefore, in the readings of the magnetic needle of the compass, magnetic declination and magnetic inclination are distinguished.

Magnetic declination- this is the angle between the direction of the magnetic needle of the compass and the geographic meridian at a given point. This angle will be the largest at the poles (up to 90 0) and the smallest at the equator (7-8 0).

Magnetic inclination- the angle formed by the inclination of the magnetic needle to the horizon. When approaching the magnetic pole, the compass needle will take a vertical position.

It is assumed that the occurrence magnetic field due to systems of electric currents arising from the rotation of the Earth, in connection with convective movements in the liquid outer core. The total magnetic field consists of the values ​​of the main field of the Earth and the field due to ferromagnetic minerals in the rocks of the earth's crust. Magnetic properties characteristic of minerals - ferromagnets, such as magnetite (FeFe 2 O 4), hematite (Fe 2 O 3), ilmenite (FeTiO 2), pyrrhotite (Fe 1-2 S), etc., which are minerals and are established by magnetic anomalies. These minerals are characterized by the phenomenon of remanent magnetization, which inherits the orientation of the Earth's magnetic field that existed at the time of the formation of these minerals. The reconstruction of the location of the Earth's magnetic poles in different geological epochs indicates that the magnetic field periodically experienced inversion- a change in which the magnetic poles are reversed. The process of changing the magnetic sign of the geomagnetic field lasts from several hundred to several thousand years and begins with an intensive decrease in the intensity of the main magnetic field of the Earth to almost zero, then the reverse polarity is established, and after some time follows fast recovery tension, but of the opposite sign. The North Pole took the place of the South Pole and, vice versa, with an approximate frequency of 5 times in 1 million years. The current orientation of the magnetic field was established about 800 thousand years ago.

There are five main layers of the Earth: crust, upper mantle, lower mantle, liquid outer core, and solid inner core. The crust is the thinnest outer layer of the Earth, on which the continents are located. It is followed by the mantle - the thickest layer of our planet, which is divided into two layers. The core also separates into two layers - a liquid outer core and a solid spherical inner core. There are several ways to create a model of the Earth's layers. The simplest and most common options are a three-dimensional model of sculpted clay, plasticine or modeling dough, or a flat image on paper.

What will you need

Play dough model

• 2 cups of flour
• 1 cup coarse sea salt
• 4 teaspoons potassium tartrate
• 2 tablespoons vegetable oil
• 2 glasses of water
• Pot
• Wooden spoon
• Food coloring: yellow, orange, red, brown, green, and blue (if you don't have one, use what you have)
• Fishing line or dental floss

paper model

• 5 sheets of heavy paper or thin card stock (brown, orange, red, blue, and white)
• Compasses or stencil with circles of 5 different diameters
• Glue stick
• Scissors
• Large sheet of cardboard

foam model

• Large styrofoam ball (13-18 cm diameter)
• Pencil
• Ruler
• Long serrated knife
• Acrylic paints (green, blue, yellow, red, orange and brown)
• tassel
• 4 toothpicks
• Scotch
• Small strips of paper

Steps

Model from the test

To make a three-dimensional model, you will need to buy sculpting clay or plasticine, or prepare dough for modeling. In any case, seven colors are needed: two shades of yellow, orange, red, brown, green and blue. It is recommended to cook the dough with your own hands under the supervision of parents.

Prepare dough for modeling. If you bought sculpting clay or clay, skip this step. Mix all the ingredients (flour, salt, potassium tartrate, oil and water) until smooth, without lumps. Then transfer the mixture to a saucepan and heat over low heat, stirring constantly. The dough will thicken as it heats up. When the dough begins to pull away from the sides of the pan, remove the pan from the burner and let it cool to room temperature.

• The cooled dough must be kneaded for 1-2 minutes.
• This step is recommended to be performed under parental supervision.
• Large salt crystals will still be visible in the dough - this is normal.

1. Divide the dough into seven balls of different sizes and add the dyes. First, make two small golf ball sized balls. Next, make two medium-sized balls and three large balls. Use a few drops food coloring for each ball according to the following list. Knead each piece of dough to evenly distribute the color.

   • two small balls: green and red;
   • two medium balls: orange and brown;
   • three large balls: two shades of yellow and blue.

2. Wrap the red ball in the orange dough. You will be building the earth model from the inner layer to the outer layers. The red ball will represent the inner core. The orange dough is the outer core. Flatten the orange ball slightly to wrap the dough around the red ball.

   • The entire model must be spherical to resemble the shape of the Earth.

3. Wrap the resulting sphere in two yellow layers. The next layer is the mantle, which corresponds to the yellow dough. The mantle is the widest layer of planet Earth, so wrap the inner core in two thick layers of yellow dough in different shades.

   • Roll out the dough to the desired thickness and wrap around the ball, carefully connecting on all sides to get a single layer.

4. Next, roll out and wrap the brown layer around the model. The brown dough will represent the earth's crust, the thinnest layer of the planet. Roll out the brown dough to get a thin layer, and then wrap around the ball in the same way as the previous layers.

5. Add the world ocean and continents. wrap up Earth into a thin layer of blue dough. This is the last layer of our model. The ocean and continents are part of the crust, so they should not be considered as separate layers.

   • Finally, give the green dough the approximate shape of the continents. Press them against the ocean, positioning them like they are on a globe.

6. Cut the balloon in half with dental floss. Place the ball on the table and pull the thread over the center of the sphere. Imagine an imaginary equator on the model and hold the thread over this place. Cut the ball in half with the string.

   • On the two halves, a clear cross-section of the layers of the Earth will be visible.

7. Label each layer. Make small checkboxes for each layer. Wrap a strip of paper around a toothpick and secure with tape. Make five flags: crust, upper mantle, lower mantle, outer core, and inner core. Paste each checkbox into its respective layer.

   • Now you have two halves of the Earth, so you can use the half with flags to show the layers of the planet, and the other with the ocean and continents as a top view.

8. Gather Interesting Facts for each layer. Find information about the composition and thickness of each layer. Provide information on density and temperatures present. Make a short report or infographic to supplement the 3D model with the necessary explanations.

   paper model

   foam model

   1. Prepare the necessary materials. This model uses a Styrofoam sphere in the form of the Earth, the fourth part of which is cut out so that you can see the internal structure of the planet. The incision should be made under parental supervision.

      • All materials and supplies can be found at home or at an art supply store.

   2. Draw circles along the horizontal and vertical center of the Styrofoam ball. You need to cut about a quarter of the foam ball. The circles dividing the ball into horizontal and vertical halves will help you with this. Perfect accuracy isn't necessary, but try to stick to the center.

      • Hold the ruler in the center.
      • Hold the pencil in place above the ruler.
      • Have a friend rotate the ball horizontally while you hold the pencil and make sure the line is centered.
      • After drawing a full circle, repeat the procedure vertically.
      • As a result, you will get two lines that divide the ball into four equal parts.

   3. Cut out a quarter of the ball. Two intersecting lines will divide the ball into four parts. You need to cut out one quarter with a knife. We strongly recommend that you perform this action under the supervision of parents.

      • Position the ball so that one of the lines points straight up.
      • Place the knife over the line and gently cut back and forth until you reach the center of the ball (horizontal line).
      • Flip the ball over so that the horizontal line is now pointing up.
      • Cut carefully until you reach the center of the ball.
      • Gently wiggle the cut out quarter to separate it from the styrofoam ball.

The structure of our planet is heterogeneous. One consists of several levels, including solid and liquid shells. What are the layers of the earth called? How many? How do they differ from each other? Let's figure it out.

How were the layers of the earth formed?

Among the terrestrial planets (Mars, Venus, Mercury), the Earth has the largest mass, diameter and density. It formed about 4.5 billion years ago. According to one version, our planet, like others, was formed from small particles that arose after the Big Bang.

Debris, dust and gas began to combine under the influence of gravity and acquired a spherical shape. The proto-Earth was very hot and melted the minerals and metals that fell on it. The denser substances went down to the center of the planet, the less dense ones went up.

This is how the first layers of the Earth appeared - the core and the mantle. Together with them, a magnetic field arose. From above, the mantle gradually cooled and became covered with a film, which later became the crust. The processes of the formation of the planet did not end there, in principle, they continue to this day.

The gases and seething substances of the mantle constantly broke out through cracks in the crust. Their weathering formed the primary atmosphere. Then, along with hydrogen and helium, it contained a lot of carbon dioxide. Water, according to one version, appeared later from the condensation of ice, which was brought by asteroids and comets.

Nucleus

The layers of the Earth are represented by the core, mantle and crust. All of them differ in their properties. At the center of the planet is the core. It has been studied less than other shells, and all information about it is, although scientific, but still assumptions. The temperature inside the core reaches about 10,000 degrees, so it is not yet possible to reach it even with the best technology.

The core lies at a depth of 2900 kilometers. It is generally accepted that it has two layers - external and internal. Together they have an average radius of 3.5 thousand kilometers and are composed of iron and nickel. It is assumed that the core may contain sulfur, silicon, hydrogen, carbon, phosphorus.

Its inner layer is in a solid state due to the enormous pressure. The size of its radius is equal to 70% of the radius of the Moon, which is about 1200 kilometers. The outer core is in a liquid state. It consists not only of iron, but also of sulfur and oxygen.

The temperature of the outer core ranges from 4 to 6 thousand degrees. Its fluid is constantly moving and thus affects the Earth's magnetic field.

Mantle

The mantle envelops the core and represents the middle level in the structure of the planet. It is not available for direct study and is studied using geophysical and geochemical methods. It occupies about 83% of the planet's volume. Under the surface of the oceans, its upper boundary runs at a depth of several kilometers; under the continents, these figures increase to 70 kilometers.

It is divided into upper and lower parts, between which there is a layer of Golitsin. Like the lower layers, it has a high temperature - from 900 to 4000 degrees. It is viscous in consistency, while its density fluctuates depending on chemical changes and pressure.

The composition of the mantle is similar to stony meteorites. It contains silicates, silicon, magnesium, aluminum, iron, potassium, calcium, as well as grospidites and carbonatites, which are not found in the earth's crust. Under the influence of high temperatures in the lower level of the mantle, many minerals decompose into oxides.

outer layer of the earth

Above the mantle is the Mohorovichic surface, marking the boundary between shells of different chemical composition. In this part, the speed of seismic waves increases sharply. The top layer of the Earth is represented by the crust.

The outer part of the shell is in contact with the hydrosphere and atmosphere of the planet. Under the oceans, it is much thinner than on land. Approximately 3/4 of it is covered with water. The structure of the crust is similar to the crust of the planets of the terrestrial group and partly of the Moon. But only on our planet it is divided into continental and oceanic.

Relatively young. Most of it is represented by basalt rocks. The thickness of the layer in different parts of the ocean ranges from 5 to 12 kilometers.

The continental crust consists of three layers. Below are granulites and other similar metamorphic rocks. Above them is a layer of granites and gneisses. The upper level is represented by sedimentary rocks. The continental crust contains 18 elements, including hydrogen, oxygen, silicon, aluminum, iron, sodium and others.

Lithosphere

One of the spheres of our planet is the lithosphere. It unites such layers of the Earth as the upper mantle and crust. It is also defined as the solid shell of the planet. Its thickness ranges from 30 kilometers in the plains to 70 kilometers in the mountains.

The lithosphere is divided into stable platforms and mobile folded areas, in the areas of which mountains and volcanoes are located. The upper layer of the solid shell was formed by magma flows that broke through the earth's crust from the mantle. Due to this, the lithosphere consists of crystalline rocks.

It is subject to the Earth, such as weathering. The processes in the mantle do not subside and are manifested by volcanic and seismic activity, mountain building. This, in turn, also affects the structure of the lithosphere.

Definition 2

Hydrosphere- the water shell of the planet's surface, consisting of all the water bodies that exist on Earth.

The thickness of this water shell is different in different areas. The average depth is $3.8$ km, and the maximum depth is $11$ km. The hydrosphere is a powerful geological force that carries out the cycle of both water and other substances.

Another new shell appears with the advent of life on Earth - this biosphere. The term was introduced E. Suessom ($1875$).

Definition 3

Biosphere- this is that part of the shells of the Earth in which various organisms live.

The boundaries of this shell are associated with the presence of conditions necessary for normal life, so its upper part is limited intensity of ultraviolet radiation, and the lower one with temperatures up to $100$ degrees.

Remark 3

Biosphere considered the highest ecosystem of the Earth, because it is a combination of all biogeocenoses.

The appearance of man on Earth led to the emergence of anthropogenic factors, which, with the development of civilization, intensified and led to the emergence of a specific shell - noosphere. This term was first introduced E. Leroy($1870-1954$) and T.Ya. de Chardin ($1881-1955$).

The noosphere is the highest stage in the evolution of the biosphere, and is closely related to the development of human society. This is the sphere of interaction between society and nature. Within the boundaries of this interaction, intelligent human activity becomes the determining factor.

Remark 4

Noosphere is part of biosphere, the development of which is directed the mind of man.