Our planet belongs to the terrestrial planets. Unlike planets like Jupiter, the Earth's surface is solid, not gas.
Earth is the largest terrestrial planet in the solar system and has the strongest magnetic field and surface gravity.
The shape and chemical composition of the Earth
The shape of our planet is a geoid (oblate ellipsoid). The equatorial bulge is created by the rotation of the Earth, which is why the equatorial diameter exceeds the diameter between the poles by 43 km.
Approximate indicators of the mass of the earth are 5.98 1024 kg. Our planet consists of iron (32%), silicon (15%), oxygen (390%), sulfur (3%), magnesium (14%), nickel, aluminum and calcium (1.3% each).
The internal structure of the Earth
Like all other terrestrial planets, the Earth has a layered internal structure. The main elements of the Earth's structure are the metal core and hard silicate shells (mantle and crust).
The earth's crust is the upper solid part of the earth. The thickness of the Earth's crust varies depending on the location of certain territories. So the thickness of the crust of the ocean floor becomes only 6 km, while the continental crust reaches 40-50 km.
The continental crust consists of three layers: granite, basalt and sedimentary cover. The sedimentary cover in the oceanic crust is primitive, sometimes completely absent.
The mantle is the silicate shell of the planet, which consists mainly of calcium, iron and magnesium silicates. The mantle occupies a huge volume of depth, its thickness becomes 2500 km.
The mantle makes up about 80% of the volume of our planet, and 68% of its total mass. The central and deepest part of the Earth is the core. The core is the geosphere under the mantle, presumably composed of an alloy of iron and nickel.
The depth of the core is approximately 3000 km. The average radius of the core is 3 thousand km2. The core consists of an outer and an inner layer. The center of the earth's core has a very high temperature - it reaches 5000 ° C.
Tectonic platforms
The outer part of the earth's crust (lithosphere) consists of tectonic plates. Tectonic plates can move, thus provoking changes in the earth's topography.
In geography, three types of movement of tectonic plates are distinguished: divergence, convergence and shear movements along faults. Mountain-forming processes, earthquakes, volcanic activity, and the formation of oceanic troughs often occur in places where tectonic plates break.
The largest tectonic plates include the Arabian, Caribbean, Hindustan plates, Scotia and Nazca plates.
Astronomers study space, get information about planets and stars, despite their great remoteness. Moreover, there are no less secrets on the Earth itself than in the Universe. And today scientists do not know what is inside our planet. Observing how lava pours out during a volcanic eruption, you might think that the Earth is also molten inside. But this is not the case.
Nucleus. The central part of the globe is called the core (Fig. 83). Its radius is about 3,500 km. Scientists believe that the outer part of the core is in a molten-liquid state, and the inner part is solid. The temperature in it reaches +5,000 ° С. Temperature and pressure gradually decrease from the core to the surface of the Earth.
Mantle. The Earth's core is covered with a mantle. Its thickness is approximately 2,900 km. The mantle, like the core, has never been seen. But it is assumed that the closer to the center of the Earth, the higher the pressure in it, and the higher the temperature - from several hundred to -2,500 ° C. It is believed that the mantle is solid, but at the same time red-hot.
Earth's crust.Our planet is covered with crust on top of the mantle. This is the top solid layer of the Earth. Compared to the core and mantle, the earth's crust is very thin. Its thickness is only 10-70 km. But this is the earthly firmament, on which we walk, those-kut rivers, cities are built on it.
The earth's crust is formed by various substances. It is composed of minerals and rocks. Some of them are already known to you (granite, sand, clay, peat, etc.). Minerals and rocks differ in color, hardness, structure, melting point, solubility in water and other properties. Many of them are widely used by humans, for example, as fuel, in construction, to obtain metals. Material from the site
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The upper layer of the earth's crust can be seen in deposits on mountain slopes, steep river banks, and quarries (Fig. 84). And to look deep into the crust, mines and boreholes, which are used for the extraction of minerals, for example, oil and gas, help.
Methods for studying the internal structure and composition of the EarthMethods 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 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 in the results obtained. At the same time, the possibilities of these methods when 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 shallower depths were achieved when drilling the ocean floor (about -1500 m, drilling from 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 the patterns of change with depth of various physical parameters (electrical conductivity, mechanical quality factor, etc.), measured in geophysical studies. The development of models of the Earth's internal structure is based primarily on the results of seismic studies, based on data on the patterns of propagation of seismic waves. In the foci of earthquakes and powerful explosions, seismic waves arise - elastic vibrations. These waves are divided into volume waves - propagating in the interior 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 - hundreds of kilometers.
Body waves, in turn, are divided into two types - longitudinal and transverse. P-waves, which have a high propagation velocity, are first recorded by geophones, they are called primary or P-waves ( from English primary - primary), the "slower" shear waves are called S-waves ( from English secondary - secondary). It is known that transverse waves have an important feature - they propagate only in a solid medium.
Refraction of waves occurs at the boundaries of media with different properties, and at the boundaries of abrupt changes in properties, in addition to refracted ones, reflected and converted waves appear. Shear waves can be displaced perpendicular to the plane of incidence (SH waves) or displaced in the plane of incidence (SV waves). When crossing the boundary of media with different properties, SH waves experience normal refraction, and SV waves, in addition to refracted and reflected SV waves, excite P waves. This is how a complex system of seismic waves "shines through" the interior of the planet.
Analyzing the patterns of wave propagation, it is possible to reveal inhomogeneities in the interior of the planet - if at a certain depth an abrupt change in the velocities of seismic waves propagation, their refraction and reflection is recorded, we can conclude that at this depth the boundary of the Earth's inner shells, differing in their physical properties, passes.
The study of the paths and speed of propagation of seismic waves in the interior of the Earth made it possible to develop a seismic model of its internal structure.
Seismic waves, propagating from the source of the earthquake deep into the Earth, experience the most significant jump-like changes in velocity, are refracted and reflected at the 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 interior 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 speed of both longitudinal and transverse waves increases abruptly. So the speed of transverse waves increases sharply from 6.7-7.6 km / s in the lower crust to 7.9-8.2 km / s in the mantle. This border was discovered in 1909 by the Yugoslav seismologist Mohorovich and was later named the border of Mohorovicic (often called the Moho boundary, or the M boundary). The average depth of the border is 33 km (it should be noted that this is a very approximate value due to the different thickness in different geological structures); at the same time, under the continents, the depth of the Mohorovichich division can reach 75-80 km (which is recorded under the young mountain structures - the Andes, the Pamirs), under the oceans it decreases, reaching a minimum thickness of 3-4 km.
An even sharper seismic boundary separating the mantle and the core is fixed at depth 2900 km... In this seismic section, the P-wave velocity abruptly drops from 13.6 km / s at the base of the mantle to 8.1 km / s at the core; S-waves - from 7.3 km / s to 0. The disappearance of shear 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 it is often called gutenberg borderalthough this name is not official.
Sharp changes in the speed and nature of wave propagation are recorded at depths of 670 km and 5150 km. Border 670 km separates the mantle into the upper mantle (33-670 km) and the lower mantle (670-2900 km). Border 5150 km separates the core into an outer liquid (2900-5150 km) and an inner solid (5150-6371 km).
Significant changes are noted in the seismic section. 410 kmdividing the upper mantle into two layers.
The obtained data on the global seismic boundaries provide a basis for considering the modern seismic model of the deep structure of the Earth.
The outer shell of the solid Earth is earth's crust, limited by the border of Mohorovichi. This relatively thin shell, the thickness of which ranges from 4-5 km under the oceans to 75-80 km under the continental mountain structures. The upper sedimentary layer, consisting of unmetamorphosed sedimentary rocks, among which volcanics may be present, and the bedding consolidated, or crystalline, barkformed 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 submarine margins, has a thickness of 35-45 km to 55-80 km, 3 layers are distinguished in its section. The upper layer is usually 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 speed of P-waves 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 to the chemical composition of granodiorite). The velocity of the 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 speed 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-basic layer) is distinguished by a higher wave velocity (6.7-7.5 km / s for P-waves), which is due to a change in the composition of rocks during the transition from the upper mantle. According to the most pleasant model, its composition corresponds to granulite.
In the formation of the continental crust, rocks of various geological ages take part, up to the most ancient ones, about 4 billion years old.
Ocean crust has a relatively low thickness, on average 6-7 km. In its most general form, 2 layers can be distinguished. The upper layer is sedimentary, characterized by low thickness (about 0.4 km on average) and low P-wave velocity (1.6-2.5 km / s). The lower layer - "basalt" - 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 age of the oldest rocks of the modern oceanic crust is about 160 million years.
Mantle represents the largest in volume and mass of the inner shell of the Earth, bounded from above by the Moho boundary, from below - by the Gutenberg boundary. It includes an upper mantle and a lower mantle, separated by a 670 km boundary.
The upper mania is divided into two layers according to geophysical features. Upper layer - subcrustal mantle - extends from the Moho border 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 velocity 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 a global interface of 410 km, a layer of reduced velocities is located. As the name suggests, the seismic wave velocities in it are lower than in the subcrustal mantle. Moreover, in some areas, lenses are revealed that do not transmit S-waves at all, which gives grounds to state that the mantle material 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 the English-language literature as LVZ - Low Velocity Zone... Thus, 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), revealed on the basis of a decrease in the speed of passage of seismic waves and has a reduced strength and viscosity. The surface of the asthenosphere is well established by a sharp decrease in resistivity (to values \u200b\u200bof about 100 Ohm . m).
The presence of a plastic asthenospheric layer, which differs in mechanical properties from the solid overlying layers, provides a basis for identifying lithosphere - the hard shell of the Earth, including the earth's crust and subcrustal mantle, located above the asthenosphere. The thickness of the lithosphere ranges from 50 to 300 km. It should be noted that the lithosphere is not a monolithic rocky shell of the planet, but is divided into separate plates constantly moving along the plastic asthenosphere. Centers of earthquakes and modern volcanism are confined to the boundaries of the lithospheric plates.
Deeper than the 410 km section in the upper mantle, both P- and S-waves are ubiquitous, and their velocity increases relatively monotonically with depth.
IN bottom mantleseparated by a sharp global boundary of 670 km, the speed of P- and S-waves monotonically, without abrupt changes, increases, respectively, to 13.6 and 7.3 km / s up to the Gutenberg section.
In the outer core, the speed of the P-waves drops sharply to 8 km / s, while the S-waves completely disappear. The disappearance of shear waves suggests that the outer core of the Earth is in a liquid state. Below the 5150 km section is the 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 above-described velocity model of the Earth is that our planet consists of a series of concentric shells representing the ferruginous core, silicate mantle and aluminosilicate crust.
Geophysical characteristics of the Earth
Mass distribution among the inner geospheres
The bulk of the Earth's mass (about 68%) falls on its relatively light, but large in volume mantle, while about 50% falls on the lower mantle and about 18% - on the upper one. 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 3.1-3.5g / cm 3. In the mantle, the density gradually increases due to the compression of silicate material and phase transitions (restructuring of the crystalline structure of the material in the course of "adaptation" to increasing pressure) from 3.3 g / cm 3 in the subcrustal part to 5.5 g / cm 3 at the bottom of the lower mantle ... At the Gutenberg border (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 are of a different nature: a change in the chemical composition of matter occurs at the mantle / core interface (transition from a silicate mantle to an iron core), and a jump at the 5150 km boundary 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 interior of the Earth is calculated based on its density model. The increase in pressure with distance from the surface is due to several reasons:
compression due to the weight of the overlying shells (lithostatic pressure);
phase transitions in shells homogeneous in chemical composition (in particular, in the mantle);
the difference in the chemical composition of the shells (crust and mantle, mantle and core).
At the bottom 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, at the Gutenberg boundary it reaches 135 GPa. In the outer core, the pressure growth gradient increases, while in the inner core, on the contrary, decreases. The calculated values \u200b\u200bof 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
Geological processes occurring on the surface and in the depths 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 interior of the planet, and exogenous (or external to the planet). The intensity of the flow of thermal energy from the subsurface to the surface is reflected in the magnitude of the geothermal gradient. Geothermal gradient - temperature increment with depth, expressed in 0 С / km. The "inverse" characteristic is geothermal stage - depth in meters, upon submersion to which the temperature will increase by 1 0 C. The average value of the geothermal gradient in the upper part of the crust is 30 0 C / km and ranges from 200 0 C / km in areas of modern active magmatism to 5 0 C / km in areas with a calm tectonic regime. With depth, the value of the geothermal gradient decreases significantly, amounting to about 10 0 C / km in the lithosphere, and less than 1 0 C / km in the mantle. The reason for this lies in the distribution of heat sources and the nature of heat transfer.
Sources of endogenous energy are as follows.
1. Energy of deep gravitational differentiation, i.e. heat release during the redistribution of matter by 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 heatarising from the decay of radioactive isotopes. According to some calculations, this source accounts for about 25% of the heat flux emitted by the Earth. However, it is necessary to take into account that increased concentrations of the main long-lived radioactive isotopes - uranium, thorium and potassium - are observed only in the upper part of the continental crust (zone of isotopic enrichment). 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 area of \u200b\u200bthe planet.
3. Residual heat, preserved in the bowels from the time of the formation of the planet.
4. Solid tidescaused by the attraction of the moon. The transition of kinetic tidal energy to heat occurs due to internal friction in the rock mass. The share of this source in the total heat balance is small - about 1-2%.
In the lithosphere, the conductive (molecular) mechanism of heat transfer prevails; in the sublithospheric mantle of the Earth, a transition to a predominantly convective mechanism of heat transfer occurs.
Calculations of temperatures in the interior 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 0 C, at the border 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 was taken into account - 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, exogenous source heat - solar radiation. Below the surface, the influence of solar heat is sharply reduced. Already at a shallow depth (up to 20-30 m) there is a belt of constant temperatures - a region of depths where the temperature remains constant and 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 located close to geographic ones, but do not coincide with them. Therefore, in the readings of the magnetic compass needle, a distinction is made between magnetic declination and magnetic inclination.
Magnetic declination Is the angle between the direction of the magnetic compass needle and the geographic meridian at this 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 move vertically.
It is assumed that the emergence of a magnetic field is due to the systems of electric currents that arise during the rotation of the Earth, in connection with convective movements in the liquid outer core. The total magnetic field consists of the values \u200b\u200bof the main field of the Earth and the field caused by ferromagnetic minerals in the rocks of the earth's crust. Magnetic properties are 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 on magnetic anomalies. These minerals are characterized by the phenomenon of remanent magnetization, which inherits the orientation of the Earth's magnetic field, which existed during the formation of these minerals. 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 were swapped. The process of changing the magnetic sign of the geomagnetic field lasts from several hundred to several thousand years and begins with an intense decrease in the strength of the main magnetic field of the Earth to almost zero, then a reverse polarity is established and after a while a rapid restoration of the strength follows, but already of the opposite sign. The North Pole took the place of the South Pole and, conversely, 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.
The Earth, like many other planets, has a layered internal structure. Our planet has three main layers. The inner layer is the core, the outer layer is the earth's crust, and the mantle is placed between them.
The core is the central part of the Earth and is located at a depth of 3000-6000 km. The radius of the core is 3500 km. According to scientists, the core consists of two parts: the outer - probably liquid, and the inner - solid. The core temperature is around 5000 degrees. Modern ideas about the core of our planet were obtained in the course of long-term research and analysis of the data obtained. Thus, it has been proven that the iron content in the planet's core reaches 35%, which determines its characteristic seismic properties. The outer part of the core is represented by rotating streams of nickel and iron, which conduct electric current well. The origin of the Earth's magnetic field is associated with this part of the core, since the global magnetic field is created by electric currents flowing in the liquid substance of the outer core. Due to the very high temperature, the outer core has a significant effect on the parts of the mantle in contact with it. In some places, there are huge heat and mass flows directed to the surface of the Earth. The inner core of the Earth is solid and also hot. Scientists believe that such a state of the inner part of the core is provided by a very high pressure at the center of the Earth, reaching 3 million atmospheres. As the distance from the Earth's surface increases, the compression of substances increases, and many of them pass into a metallic state.
The intermediate layer - the mantle - covers the core. The mantle occupies about 80% of the volume of our planet, this is the largest part of the Earth. The mantle is located upward from the core, but does not reach the surface of the Earth, outside it is in contact with the earth's crust. Basically, the material of the mantle is in a solid state, except for the upper viscous layer about 80 km thick. This is the asthenosphere, translated from Greek means "weak ball". According to scientists, the material of the mantle is constantly moving. With an increase in the distance from the earth's crust towards the core, a transition of mantle matter into a denser state occurs.
Outside, the mantle is covered by the earth's crust - an outer strong shell. Its thickness varies from several kilometers under the oceans to several tens of kilometers in mountain ranges. The earth's crust accounts for only 0.5% of the total mass of our planet. The bark contains oxides of silicon, iron, aluminum, alkali metals. The continental crust is divided into three layers: sedimentary, granite and basalt. The oceanic crust is composed of sedimentary and basalt layers.
The lithosphere of the Earth is formed by the earth's crust together with the upper layer of the mantle. The lithosphere is composed of tectonic lithospheric plates, which seem to "slide" along the asthenosphere at a speed of 20 to 75 mm per year. Lithospheric plates moving relative to each other are different in size, and the kinematics of movement is determined by plate tectonics.
Video presentation "The internal structure of the Earth":
Presentation "Geography as a Science"
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Our house
The planet we live on is used by us in absolutely all spheres of our life: we do not build our cities and dwellings on it; we eat the fruits of plants growing on it; use for our own purposes the natural resources extracted from its bowels. The earth is the source of all the benefits 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 has been written. Someone, having read it, will refresh the already existing knowledge. And someone, perhaps, will find out about which they had not the slightest idea. 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 planet Earth
The Earth is the third planet from the Sun (Venus is in front of it, Mars is behind it). Distance from the Sun - about 150 million km. Refers to a group of planets called "terrestrial group" (also includes Mercury, Venus and Mars). Its mass is 5.98 * 10 27, and its 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 Earth is approximately 4.5 billion years old. 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 the composition of the other planets from the terrestrial group - it is dominated by oxygen, iron, silicon, nickel and magnesium.
Structure of the earth
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 it that people actively use. And this layer has been studied best of all. 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 hard rocks, sediments of plant and animal remains, deposition of various substances on the bottom of the world's oceans. The next layer is granite. It is formed from solidified magma (molten material from the depths of the earth that fills cracks in the crust) under pressure and high temperatures. Also, this layer contains various minerals: aluminum, calcium, sodium, potassium. Typically, this layer is missing 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 humans use. The thickness of the earth's crust ranges from 5 km (under the oceans) to 75 km (under the continents). The crust of the Earth is about 1% of its total volume.
Mantle
It is located under the bark and surrounds the core. It makes up 83% of the total volume of the planet. The mantle is divided into an upper (at a depth of 800-900 km) and a lower (at a depth of 2900 km) parts. From the top, magma forms, which we mentioned above. The mantle consists of dense silicate rocks, which contain oxygen, magnesium and silicon. Also, based on seismological data, scientists have come to the conclusion that at the base of the mantle there is an alternating layer of giant continents. And they, in turn, could have formed as a result of mixing of rocks of the mantle itself with the material of the core. But another option is that these areas could represent the bottom of ancient oceans. Music is already a detail. Further, the geological structure of the Earth continues with the core.
Nucleus
The formation of the core is explained by the fact that in the early historical period of the Earth, the substances with the highest density (iron and nickel) settled in the center and formed the core. It is the densest part representing the structure of the Earth. It is divided into a molten outer core (about 2200 km thick) and a solid inner core (about 2500 km in diameter). It makes up 16% of the total volume of the Earth and 32% of its entire mass. Its radius is 3500 km. What happens inside the core is not very easy to imagine - here the temperature is over 3000 ° C and the colossal pressure.
Convection
The heat, which was accumulated during the formation of the Earth, is still 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 in motion the very matter of the mantle - first, the hot rocks rise up from the core, and then, 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 electric currents that generate the Earth's magnetic field. It spreads to cosmic distances and creates a magnetic shell around the Earth, which reflects the streams of the solar wind (charged particles emitted by the Sun) and protects living beings from deadly radiation.
Where does the data come from
All information is obtained using various geophysical methods. On the surface of the Earth, seismologists (scientists who study the Earth's vibrations) set up seismological stations, where any vibrations of the earth's crust are recorded. 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, similar to how an X-ray "shines through" the human body.
Finally
We just talked a little about what the structure of the Earth is. In fact, you can study this issue for a very long time, tk. it is full of nuances and peculiarities. For this purpose, there are seismologists. For the rest, it is enough to have general information about its structure. But in no case should we forget that planet Earth is our home, without which we would not exist. And you need to treat her with love, respect and care.