What are the parts of the mantle and core? What is the earth made of? Seismic model of the structure of the earth

The Earth's mantle is the part of the geosphere located between the crust and the core. It contains a large proportion of the entire substance of the planet. The study of the mantle is important not only from the point of view of understanding the inner mantle. It can shed light on the formation of the planet, give access to rare compounds and rocks, help understand the mechanism of earthquakes, etc. However, obtaining information about the composition and features of the mantle is not easy. People do not yet know how to drill wells so deep. The Earth's mantle is now mainly studied using seismic waves. And also by modeling in the laboratory.

Structure of the Earth: mantle, core and crust

According to modern concepts, the internal structure of our planet is divided into several layers. The upper layer is the crust, followed by the mantle and core of the Earth. The crust is a hard shell divided into oceanic and continental. The Earth's mantle is separated from it by the so-called Mohorovicic boundary (named after the Croatian seismologist who established its location), which is characterized by an abrupt increase in the velocities of longitudinal seismic waves.

The mantle makes up about 67% of the planet's mass. According to modern data, it can be divided into two layers: upper and lower. In the first, the Golitsyn layer or the middle mantle is also distinguished, which is a transition zone from the upper to the lower. In general, the mantle extends at a depth of 30 to 2900 km.

The core of the planet, according to modern scientists, consists mainly of iron-nickel alloys. It is also divided into two parts. The inner core is solid, its radius is estimated at 1300 km. External - liquid, has a radius of 2200 km. Between these parts, a transition zone is distinguished.

Lithosphere

The crust and upper mantle of the Earth are united by the concept of "lithosphere". It is a hard shell with stable and mobile areas. The solid shell of the planet consists of which, as expected, move through the asthenosphere - a rather plastic layer, probably a viscous and highly heated liquid. It is part of the upper mantle. It should be noted that the existence of the asthenosphere as a continuous viscous shell is not confirmed by seismological studies. The study of the structure of the planet allows us to identify several similar layers located vertically. In the horizontal direction, the asthenosphere, apparently, is constantly interrupted.

Ways to study the mantle

The layers lying below the crust are inaccessible for study. The enormous depth, the constant increase in temperature and the increase in density are a serious problem for obtaining information about the composition of the mantle and core. However, it is still possible to imagine the structure of the planet. When studying the mantle, geophysical data become the main sources of information. The speed of seismic waves, the features of electrical conductivity and gravity allow scientists to make assumptions about the composition and other features of the underlying layers.

In addition, some information can be obtained from fragments of mantle rocks. The latter include diamonds, which can tell a lot even about the lower mantle. Mantle rocks are also found in the earth's crust. Their study helps to understand the composition of the mantle. However, they will not replace samples obtained directly from deep layers, since as a result of various processes occurring in the crust, their composition differs from that of the mantle.

Earth's mantle: composition

Another source of information about what the mantle is like is meteorites. According to modern concepts, chondrites (the most common group of meteorites on the planet) are close in composition to the earth's mantle.

It is assumed that it contains elements that were in a solid state or entered into a solid compound during the formation of the planet. These include silicon, iron, magnesium, oxygen and some others. In the mantle, they combine with form silicates. Magnesium silicates are located in the upper layer, the amount of iron silicate increases with depth. In the lower mantle, these compounds decompose into oxides (SiO 2 , MgO, FeO).

Of particular interest to scientists are rocks that are not found in the earth's crust. It is assumed that there are many such compounds (grospidites, carbonatites, and so on) in the mantle.

Layers

Let us dwell in more detail on the extent of the layers of the mantle. According to scientists, the upper of them occupies a range of about 30 to 400 km from there. Then there is a transition zone, which goes deeper into another 250 km. The next layer is the bottom. Its boundary is located at a depth of about 2900 km and is in contact with the outer core of the planet.

pressure and temperature

As you move deeper into the planet, the temperature rises. The Earth's mantle is under extremely high pressure. In the asthenosphere zone, the effect of temperature outweighs, so here the substance is in the so-called amorphous or semi-molten state. Deeper under pressure, it becomes solid.

Studies of the mantle and the Mohorovicic boundary

The Earth's mantle haunts scientists for quite a long time. In laboratories, experiments are being carried out on rocks that are presumably part of the upper and lower layers, allowing us to understand the composition and features of the mantle. Thus, Japanese scientists found that the lower layer contains a large amount of silicon. The upper mantle contains water reserves. It comes from the earth's crust, and also penetrates from here to the surface.

Of particular interest is the Mohorovichic surface, the nature of which is not fully understood. Seismological studies suggest that at a level of 410 km below the surface, a metamorphic change of rocks occurs (they become denser), which manifests itself in a sharp increase in the speed of waves. It is assumed that the basalt rocks in the area are transformed into eclogite. In this case, the density of the mantle increases by about 30%. There is another version, according to which, the reason for the change in the speed of seismic waves lies in the change in the composition of the rocks.

Chikyu Hakken

In 2005, a specially equipped ship Chikyu was built in Japan. His mission is to make a record deep well at the bottom of the Pacific Ocean. Scientists propose to take samples of the rocks of the upper mantle and the Mohorovichic boundary in order to get answers to many questions related to the structure of the planet. The implementation of the project is scheduled for 2020.

It should be noted that scientists have not just turned their attention to the oceanic bowels. According to studies, the thickness of the crust at the bottom of the seas is much less than on the continents. The difference is significant: under the water column in the ocean, it is necessary to overcome only 5 km to magma in some areas, while on land this figure increases to 30 km.

Now the ship is already working: samples of deep coal seams have been obtained. The implementation of the main goal of the project will make it possible to understand how the Earth's mantle is arranged, what substances and elements make up its transition zone, and also to find out the lower limit of the spread of life on the planet.

Our understanding of the structure of the Earth is still far from complete. The reason for this is the difficulty of penetrating into the bowels. However, technological progress does not stand still. Advances in science suggest that in the near future we will know much more about the characteristics of the mantle.

The mantle of the Earth is the most important part of our planet, since it is here that most of the substances are concentrated. It is much thicker than the rest of the components and, in fact, takes up most of the space - about 80%. Scientists have devoted most of their time to studying this particular part of the planet.

Structure

Scientists can only speculate about the structure of the mantle, since there are no methods that would unambiguously answer this question. But, the conducted studies made it possible to assume that this part of our planet consists of the following layers:

• the first, the outer one, occupies from 30 to 400 kilometers of the earth's surface;
• the transition zone, which is located immediately behind the outer layer - according to scientists, it goes deep into about 250 kilometers;
• the lower layer - its length is the largest, about 2900 kilometers. It starts right after the transition zone and goes straight to the core.

It should be noted that in the mantle of the planet there are such rocks that are not in the earth's crust.

Compound

It goes without saying that it is impossible to establish exactly what the mantle of our planet consists of, since it is impossible to get there. Therefore, everything that scientists manage to study happens with the help of fragments of this area, which periodically appear on the surface.

So, after a series of studies, it was possible to find out that this part of the Earth is black and green. The main composition is rocks, which consist of the following chemical elements:

• silicon;
• calcium;
• magnesium;
• iron;
• oxygen.

In appearance, and in some ways even in composition, it is very similar to stone meteorites, which also periodically fall on our planet.

The substances that are in the mantle itself are liquid, viscous, since the temperature in this area exceeds thousands of degrees. Closer to the Earth's crust, the temperature decreases. Thus, a certain circulation occurs - those masses that have already cooled down go down, and those heated to the limit go up, so the process of "mixing" never stops.

Periodically, such heated streams fall into the very crust of the planet, in which they are assisted by active volcanoes.

Ways to study

It goes without saying that layers that are at great depths are quite difficult to study, and not only because there is no such technique. The process is also complicated by the fact that the temperature rises almost constantly, and at the same time, the density also increases. Therefore, we can say that the depth of the layer is the least problem in this case.

However, scientists still managed to advance in the study of this issue. To study this part of our planet, geophysical indicators were chosen as the main source of information. In addition, during the study, scientists use the following data:

• seismic wave speed;
• gravity;
• characteristics and indicators of electrical conductivity;
• the study of igneous rocks and fragments of the mantle, which are rare, but still manage to be found on the surface of the Earth.

As for the latter, here it is diamonds that deserve special attention of scientists - in their opinion, by studying the composition and structure of this stone, one can find out a lot of interesting things even about the lower layers of the mantle.

Occasionally, but there are mantle rocks. Their study also allows you to get valuable information, but to one degree or another there will still be distortions. This is due to the fact that various processes occur in the crust, which are somewhat different from those that occur in the depths of our planet.

Separately, we should talk about the technique with which scientists are trying to get the original rocks of the mantle. So, in 2005, a special vessel was built in Japan, which, according to the developers of the project, will be able to make a record deep well. At the moment, work is still underway, and the start of the project is scheduled for 2020 - there is not so much to wait.

Now, all studies of the structure of the mantle are carried out within the framework of the laboratory. Scientists have already precisely established that the lower layer of this part of the planet, almost all consists of silicon.

pressure and temperature

The distribution of pressure within the mantle is ambiguous, in fact, as well as the temperature regime, but first things first. The mantle accounts for more than half of the planet's weight, or more precisely, 67%. In areas under the earth's crust, the pressure is about 1.3-1.4 million atm, while it should be noted that in places where the oceans are located, the pressure level drops significantly.

As for the temperature regime, the data here are completely ambiguous and are based only on theoretical assumptions. So, at the sole of the mantle, a temperature of 1500-10,000 degrees Celsius is assumed. In general, scientists have suggested that the temperature level in this part of the planet is closer to the melting point.

It has a special composition, differing from the composition of the earth's crust covering it. Data on the chemical composition of the mantle were obtained on the basis of analyzes of the deepest igneous rocks that entered the upper horizons of the Earth as a result of powerful tectonic uplifts with the removal of mantle material. These rocks include ultrabasic rocks - dunites, peridotites occurring in mountain systems. The rocks of the St. Paul Islands in the middle part of the Atlantic Ocean, according to all geological data, belong to the mantle material. The mantle material also includes rock fragments collected by Soviet oceanographic expeditions from the bottom of the Indian Ocean in the area of ​​the Indian Ocean Ridge. As regards the mineralogical composition of the mantle, significant changes can be expected here, starting from the upper horizons and ending with the base of the mantle, due to an increase in pressure. The upper mantle is composed mainly of silicates (olivines, pyroxenes, garnets), which are stable and within relatively low pressures. The lower mantle is composed of high-density minerals.

The most common component of the mantle is silicon oxide in the composition of silicates. But at high pressures, silica can go into a denser polymorphic modification - stishovite. This mineral was obtained by the Soviet researcher Stishov and named after him. If ordinary quartz has a density of 2.533 r/cm 3 , then stishovite, formed from quartz at a pressure of 150,000 bar, has a density of 4.25 g/cm 3 .

In addition, denser mineral modifications of other compounds are also probable in the lower mantle. Based on the foregoing, it can be reasonably assumed that with increasing pressure, the usual iron-magnesian silicates of olivines and pyroxenes decompose into oxides, which individually have a higher density than silicates, which are stable in the upper mantle.

The upper mantle consists mainly of ferruginous-magnesian silicates (olivines, pyroxenes). Some aluminosilicates can transform here into denser minerals such as garnets. Beneath the continents and oceans, the upper mantle has different properties and probably a different composition. One can only assume that in the area of ​​continents the mantle is more differentiated and has less SiO 2 due to the concentration of this component in the aluminosilicate crust. Beneath the oceans, the mantle is less differentiated. In the upper mantle, denser polymorphic modifications of olivine with a spinel structure, etc., can occur.

The transitional layer of the mantle is characterized by a constant increase in seismic wave velocities with depth, which indicates the appearance of denser polymorphic modifications of matter. Here, obviously, FeO, MgO, GaO, SiO 2 oxides appear in the form of wustite, periclase, lime, and stishovite. Their number increases with depth, while the amount of ordinary silicates decreases, and below 1000 km they make up an insignificant fraction.

The lower mantle within the depths of 1000-2900 km almost completely consists of dense varieties of minerals - oxides, as evidenced by its high density in the range of 4.08-5.7 g/cm 3 . Under the influence of increased pressure, dense oxides are compressed, further increasing their density. The content of iron also probably increases in the lower mantle.

Earth's core. The question of the composition and physical nature of the core of our planet is one of the most exciting and mysterious problems of geophysics and geochemistry. Only recently there has been a little enlightenment in solving this problem.

The vast central core of the Earth, which occupies the inner region deeper than 2900 km, consists of a large outer core and a small inner one. According to seismic data, the outer core has the properties of a liquid. It does not transmit transverse seismic waves. The absence of cohesive forces between the core and the lower mantle, the nature of the tides in the mantle and crust, the features of the movement of the Earth's rotation axis in space, the nature of the passage of seismic waves deeper than 2900 km indicate that the outer core of the Earth is liquid.

Some authors assumed that the composition of the core for a chemically homogeneous model of the Earth was silicate, and under the influence of high pressure, the silicates passed into a “metallized” state, acquiring an atomic structure in which the outer electrons are common. However, the geophysical data listed above contradict the assumption of a "metallized" state of the silicate material in the Earth's core. In particular, the absence of cohesion between the core and the mantle cannot be compatible with a "metallized" solid core, which was assumed in the Lodochnikov-Ramsay hypothesis. Very important indirect data on the core of the Earth were obtained during experiments with silicates under high pressure. In this case, the pressure reached 5 million atm. Meanwhile, in the center of the Earth, the pressure is 3 million atm., and at the boundary of the core - approximately 1 million atm. Thus, experimentally, it was possible to block the pressures that exist in the very depths of the Earth. In this case, for silicates, only linear compression was observed without a jump and transition to a “metallized” state. In addition, at high pressures and within the depths of 2900-6370 km, silicates cannot be in a liquid state, like oxides. Their melting point increases with increasing pressure.

Very interesting results have been obtained in recent years on the effect of very high pressures on the melting point of metals. It turned out that a number of metals at high pressures (300,000 atm. and above) go into a liquid state at relatively low temperatures. According to some calculations, an alloy of iron with an admixture of nickel and silicon (76% Fe, 10% Ni, 14% Si) at a depth of 2900 km under the influence of high pressure should be in a liquid state already at a temperature of 1000 ° C. But the temperature at these depths, according to the most conservative estimates of geophysicists, it should be much higher.

Therefore, in the light of modern data of geophysics and high-pressure physics, as well as cosmochemistry data indicating the leading role of iron as the most abundant metal in space, it should be assumed that the Earth's core is mainly composed of liquid iron with an admixture of nickel. However, the calculations of the American geophysicist F. Birch showed that the density of the earth's core is 10% lower than that of an iron-nickel alloy at temperatures and pressures prevailing in the core. It follows that the metallic core of the Earth must contain a significant amount (10-20%) of some kind of lung. Of all the lightest and most common elements, silicon (Si) and sulfur (S) are the most probable | The presence of one or the other can explain the observed physical properties of the earth's core. Therefore, the question of what is an admixture of the earth's core - silicon or sulfur, turns out to be debatable and is connected with the way our planet is formed in practice.

A. Ridgwood in 1958 assumed that the earth's core contains silicon as a light element, arguing this assumption by the fact that elemental silicon in an amount of several weight percent is found in the metal phase of some reduced chondrite meteorites (enstatite). However, there are no other arguments in favor of the presence of silicon in the earth's core.

The assumption that there is sulfur in the Earth's core follows from a comparison of its distribution in the chondrite material of meteorites and the Earth's mantle. Thus, a comparison of the elementary atomic ratios of some volatile elements in a mixture of the crust and mantle and in chondrites shows a sharp lack of sulfur. In the material of the mantle and crust, the concentration of sulfur is three orders of magnitude lower than in the average material of the solar system, which is taken as chondrites.

The possibility of loss of sulfur at the high temperatures of the primitive Earth is eliminated, since other more volatile elements than sulfur (for example, H2 in the form of H2O), found to be much less deficient, would be lost to a much greater extent. In addition, when solar gas cools, sulfur chemically bonds with iron and ceases to be a volatile element.

In this regard, it is quite possible that large amounts of sulfur enter the earth's core. It should be noted that, other things being equal, the melting point of the Fe-FeS system is much lower than the melting point of iron or mantle silicate. So, at a pressure of 60 kbar, the melting temperature of the system (eutectic) Fe-FeS will be 990 ° C, while pure iron - 1610 °, and mantle pyrolite - 1310. Therefore, with an increase in temperature in the bowels of the initially homogeneous Earth, an iron melt enriched with sulfur , will form first and, due to its low viscosity and high density, will easily drain into the central parts of the planet, forming a ferruginous-sulphurous core. Thus, the presence of sulfur in the nickel-iron environment acts as a flux, lowering its melting point as a whole. The hypothesis of the presence of significant amounts of sulfur in the earth's core is very attractive and does not contradict all the known data of geochemistry and cosmochemistry.

Thus, modern ideas about the nature of the interior of our planet correspond to a chemically differentiated globe, which turned out to be divided into two different parts: a powerful solid silicate-oxide mantle and a liquid, mostly metallic core. The earth's crust is the lightest upper solid shell, consisting of aluminosilicates and having the most complex structure.

Summarizing the above, we can draw the following conclusions.

1. The earth has a layered zonal structure. It consists of two-thirds of a solid silicate-oxide shell - the mantle and one-third of a metallic liquid core.
2. The main properties of the Earth indicate that the core is in a liquid state and only iron from the most common metals with an admixture of some light elements (most likely sulfur) is able to provide these properties.
3. In its upper horizons, the Earth has an asymmetric structure, covering the crust and upper mantle. The oceanic hemisphere within the upper mantle is less differentiated than the opposite continental hemisphere.

The task of any cosmogonic theory of the origin of the Earth is to explain these basic features of its internal nature and composition.

The earth's mantle is the geosphere located between the earth's crust and core. The mantle makes up 83% of the volume and 67% of the total mass of the Earth. It has several layers - the upper and lower mantles. There is no clear boundary between them. In addition, the upper mantle is further subdivided into several geospheres. The mantle occupies a huge range of depths, and with increasing pressure in the substance, phase transitions occur, in which minerals acquire an increasingly dense structure.

According to modern scientific concepts, the composition of the earth's mantle is considered to be similar to that of stony meteorites. The composition of the mantle mainly includes chemical elements that were in a solid state or in solid chemical compounds during the formation of the Earth: silicon, iron, oxygen, magnesium, etc.

The upper mantle is the geosphere located between the earth's crust and the lower mantle of the earth. From above, it is separated from the crust by the Mohorovichic surface. The lower boundary of the upper mantle is indistinct, located at a depth of about 900 km. The upper mantle plays an important role in tectonic, magmatic and metamorphic processes occurring in the earth's crust, in the formation of minerals, etc.

substrate. Substrate - a layer of the upper mantle, located on the asthenosphere. Together with the earth's crust, it forms the lithosphere. It is a rigid platform on which, in the process of geological development, the earth's crust arose. It is assumed that this geosphere has a reduced viscosity, and therefore, experiences slow movements (currents) under the influence of underlying structures. It is with this that the reason for the movement of lithospheric plates is associated. In addition, the entire substrate is in a state of isostasy, which determines the mutual balancing of the plates: when some of them sink, others rise.

Asthenosphere. Seismic wave velocities in the mantle increase with depth. But starting from a depth of 80–100 km under the continents and about 50 km under the oceans, they decrease for about 100 km, then they begin to rise and at a depth of about 400 km they return to normal values, corresponding to the general course of the curves on the velocity graph in this part. mantle. The decrease in the velocity of transverse waves is especially noticeable. This zone of low seismic wave velocities is called the asthenosphere or the Gutenberg layer.

Due to the high temperature and pressure, the substance does not melt, but passes into an amorphous state. There is another assumption: only the most fusible crystals melted in the Gutenberg layer, so that individual drops of liquid are interspersed in the solid in the common substance. From both assumptions it follows that the asthenosphere is characterized by a reduced viscosity, and this is very important for explaining many processes occurring on the Earth.

The fact is that rocks under high pressure and temperature can slowly flow, remaining solid, like a glacier flows from a mountain. It is obvious that the flow of material under non-uniform pressure just occurs in the asthenosphere. It is believed that isostasy occurs due to the flow of material in the Gutenberg layer.

When measuring the propagation velocity of seismic waves, it is observed that transverse elastic waves freely pass through the crust and the entire mantle, but it is known that they do not pass through the liquid. This indicates that neither the crust nor the mantle has a continuous liquid layer. The hardness of the upper mantle is also confirmed by the fact that earthquake centers are observed in it (as well as in the crust) - in some areas up to a depth of 700 km. There are no deeper earthquakes.

Golitsyn layer. The rest of the upper mantle under the asthenosphere is called the Golitsyn layer. In the Golitsyn layer, the seismic wave velocities increase especially rapidly with depth. This is explained by the fact that under the influence of very high pressure, silicates acquire a different form of crystals, with a denser packing of atoms. This leads to a strong increase in the velocities of seismic waves. At the same time, the density should also increase; therefore, in the Golitsyn layer, a rapid increase in density with depth is assumed.

The Golitsyn layer serves as the interface between the upper and lower mantle and is located at a depth of about 670 km.

The lower mantle is the part of the mantle located under the asthenosphere and occurring at depths of 670-2900 km. In the lower mantle, seismic wave velocities increase with depth just as they should increase due to pressure. The increase in density occurs only due to elastic compression under pressure. The lower mantle accounts for 47% of the Earth's volume and 41% of its mass. According to seismic data, layers D" and D" are distinguished in it.

Mantle layer D". It is characterized by a further increase in the velocities of seismic oscillations (the speed of transverse elastic waves reaches 10.75-13.68 km / s). At the turn of 660 km, the speed of seismic waves is anomalously low and has horizontal and vertical inhomogeneities. This is associated with a change in composition mantle (the transition of the minerals ringwoodtite and majorite to perovskite, magnesiowustite and oxide phases).Most researchers accept that the lower mantle is 70% composed of perovskite.

The increase in density with depth, starting from 670 km, is sometimes associated with an increase in the iron content, i.e. a change in the chemical composition of the mantle is allowed. Is the maximum viscosity (strength, quality factor) of the mantle substance noted at depth? 2000 km.

Section boundary. The very boundary between layers D" and D" is expressed with different clarity. In some areas the transition is gradual, in others it is abrupt; in some areas below this boundary, seismic velocities increase, in others they decrease.

Mantle layer D". A distinctive feature of this layer is a pronounced anisotropy. It is manifested by the unevenness of the roof, correspondingly variable thickness, significant variations in seismic velocities in the vertical and horizontal directions, and the presence of an ultra-low velocity zone at the base of the layer.

Of great importance is the discovery at the base of the layer of a zone of low seismic velocities, which has a thickness of 20-30 km. It is assumed that the matter here is in a state of significant partial melting, which determines the possibility of intense mass and heat transfer between the mantle and the Earth's core. Molten iron from the mantle flows into the core, while a huge amount of thermal energy is released and the mantle decompresses. The mantle layer D" is 75% composed of post-perovskite, which is stable over a wide range of thermodynamic conditions and well explains the properties of layer D"

Heat and mass transfer is carried out not only directly along the mantle-core boundary (2900 km), but also in the entire volume of the D layer, which, on the one hand, is the place of origin of large-scale ascending flows of heated, decompressed mantle matter, and, on the other hand, is the burial place of submerging slabs of the oceanic lithosphere.

> What is the Earth made of?

Internal structure of the earth. Study the structure of the planet: crust, core, mantle, what chemical elements the Earth consists of, the history of research, geology.

The earth is more than we can see from our vantage point. If it were possible to cut it in half, then you would be very surprised. We rush in search of new worlds, but we still do not know much about ours.

But seismology has managed to open the structure of the Earth and show the layers. Each is endowed with its own properties, characteristics and composition. And all this affects the earth processes. What is the earth made of?

Modern theory

The inner space of the planet is differentiated. That is, the structure (like the rest of the planets) is represented by layers. Remove one and you'll be taken to the next. And each will have its own temperature and chemical composition.

Our understanding of the layers of the planet is based on the results of seismological monitoring. It contains an examination of the sound waves created by an earthquake, as well as an analysis of how passing through different layers slows down their pace. Changes in seismic velocity lead to refraction.

They are used in conjunction with transformations in gravitational and magnetic fields and experiments with crystalline solids that simulate pressure and temperature in the interior of the planet.

Research

Even in ancient times, mankind tried to figure out the composition of the Earth. The first attempts were not even related to science. These were rather legends and myths associated with divine intervention. However, several theories have circulated among the population.

You may have heard of the flat earth. This opinion was common in Mesopotamian culture. The planet was depicted as a flat disk plowing the ocean. The Maya also considered it flat, but at the corners there were four jaguars that held the sky. The Persians saw the cosmic mountain, while the Chinese saw it as a four-sided cube.

In the 6th century BC e. the Greeks tended towards a rounded shape, and in the 3rd century BC. e. the idea of ​​a spherical Earth was gaining ground underfoot and the first evidence base. At the same moment, scientists begin to come into contact with geological research, and philosophers begin to consider minerals and metals.

But the real shift took place only in the 16th and 17th centuries. Edmund Halley proposed the "Void Earth" theory in 1692. He believed that there is a cavity inside, that is, a certain core, whose thickness is 800 km.

Between these spheres there is an air gap. In order to avoid the effect of friction, the inner sphere must be held in place by gravity. The model displayed two concentric shells around the nucleus. The diameter corresponded to Mercury, Venus and Mars.

Halley was based on the densities of the Moon and Earth put forward by Isaac Newton in 1687. Next, scientists decided to consider the reliability of the Bible. It was important for researchers to calculate the real age of the planet and find evidence of a flood. Here they began to consider fossils and develop a system for classifying the dating of layers.

In 1774, Abraham Werner presented in his writings a detailed system for identifying certain minerals based on their external characteristics.

In 1741, the first position in geology appeared at the National Museum of Natural History of France. After 10 years, the term "geology" came into use.

In the 1770s chemical analyzes come to the fore in research. One of the important tasks was to study places for the presence of liquid flooding in the past (flood). In the 1780s there were those who believed that the layers were created not because of water, but due to fire. The followers were called plutonists. They believed that the planet was formed due to the solidification of molten masses. And all this happened very slowly. This implied that the planet was much older than the Bible said.

In the 19th century, geology was greatly influenced by the industrial revolution, as well as the concept of the stratigraphic column - rock formations are arranged in the order of their appearance in time. Scientists began to realize that the age of fossils can be calculated geologically (the deeper they are found, the older).

The researchers got the opportunity to go on voyages to broaden their horizons and compare finds in different places. Among these lucky ones was Charles Darwin, recruited by the captain of the Beagle ship.

The giant fossils he found made him a geologist, and his theories about the causes of extinction led to the most important work, On the Origin of Species, written in 1859.

Scientists increased their knowledge and created geological maps of the Earth. They already calculated the earth's age in terms of millions, not thousandths. But the development of technology has helped to shift the remnants of dogmatic ideas.

In the 20th century, radiometric dating appeared. Then they thought that the planetary age reaches 2 billion years. In 1912, Alfred Wegener proposed the theory of continental drift. That is, once all the continents were one. This was later confirmed by geological analysis of the samples.

The theory of plate tectonics originated from the study of the ocean floor. Geophysical data show the lateral movement of the continents, and the oceanic crust is younger than the continental one.

In the 20th century, seismology, the study of earthquakes and the passage of waves through the Earth, was actively developed. This is what helped to understand the composition and get to the core.

In 1926, Harold Jeffis stated that the earth's core was liquid, and in 1937, Inge Lehmann expanded on this theory by adding that there was a solid solid inside the liquid core.

Earth layers

Earth can be divided mechanically or chemically. The first method studies liquid states. Here appears the lithosphere, asthenosphere and mesosphere, the outer and inner core. But the chemical method, which discovered the crust, mantle and core, gained great popularity.

The inner core is solid and the outer is liquid. The lower mantle is under strong pressure, and therefore has a lower viscosity than the upper one. All differences are caused by the processes accompanying the planetary development during 4.5 billion years. Let's take a closer look at the internal structure of the Earth.

Bark

This is the outer, cooled and frozen layer. It extends for 570 km and represents only 1% of the planetary volume.

The narrower parts are the oceanic crust underlying the ocean basins (5-10 km), and the denser part is the continental crust. The upper part of the mantle and the earth's crust is the lithosphere, covering 200 km. Most of the rocks were formed 100 million years ago.

Upper mantle

It occupies 84% ​​of the volume and appears mostly solid, but sometimes behaves like a viscous liquid. It starts from the "Mohorovicic Surface" - 7-35 km and deepens to 410 km.

Movement in the mantle is reflected in the movement of tectonic plates. The process is driven by heat from the depths. This is what leads to earthquakes and the formation of mountain ranges.

The temperature rises by 500-900°C. The layer at a depth of 410-660 km is considered a transition zone.

lower mantle

The temperature at a depth of 660-2891 km can reach 4000°C. But the pressure here is too strong, so the viscosity and melting are limited. Little is known about this layer, but it is believed to be seismically homogeneous.

outer core

This is a liquid shell with a thickness of 2300 km, and in a radius it covers 3400 km. Here the density is much higher - 9900-12200 kg / m 3. It is believed that the core is represented by 80% iron, as well as nickel and other light elements. There is no strong pressure, so it does not harden, although the composition resembles the inner core. Temperature - 4030 ° С.

In the liquid core, due to temperature and turbulence, a dynamo is created that affects the magnetic field.

inner core

What elements make up the Earth's core? It is represented by iron and nickel, and in a radius it covers 1220 km. Density - 12600-13000 kg / m 3, which hints at the presence of heavy elements (platinum, gold, palladium, tungsten and silver).

The temperature here rises to 5400°C. Why do solid metals remain liquid? Because the melting point is extremely high, as is the pressure. Internally, it is not strongly connected to the solid mantle, so it is believed that it rotates faster than the planet itself.

There is also an opinion that the inner core also has layers separated by a transition zone with a thickness of 250-400 km. The lowest layer is capable of extending 1180 km in diameter. Scientists testify to the dynamics, due to which the core expands by 1 mm per year.

As you can see, our planet is an amazing and full of mysteries place. It still lurks the heat accumulated billions of years ago. And this is not a dead body, but a dynamic object that is constantly changing.