And a core of molten iron. It occupies the bulk of the Earth, accounting for two-thirds of the planet's mass. The mantle begins at a depth of about 30 kilometers and reaches 2,900 kilometers.

Structure of the earth

The Earth has the same composition of elements as (excluding hydrogen and helium, which have escaped due to the Earth's gravity). Without taking into account the iron in the core, we can calculate that the mantle is a mixture of magnesium, silicon, iron and oxygen, which roughly corresponds to the composition of the minerals.

But the very fact that a mixture of minerals is present at a given depth is a complex issue that is not sufficiently substantiated. We can get samples from the mantle, chunks of rock raised by certain volcanic eruptions, from a depth of about 300 kilometers, and sometimes much deeper. They show that the uppermost part of the mantle is composed of peridotite and eclogite. The most interesting thing we get from the mantle is diamonds.

Activity in the mantle

The upper part of the mantle is slowly stirred by the movements of the plates passing over it. This is due to two activities. First, there is a downward movement of movable plates, which slide under each other. Second, there is an upward movement of mantle rock when two tectonic plates diverge and move apart. However, all these actions do not completely blend the upper mantle layer, and geochemists consider the upper mantle to be a stone version of a marble cake.

World models of volcanism reflect plate tectonics, with the exception of a few areas of the planet called hotspots. Hot spots may hold the key to the rise and fall of materials much deeper into the mantle, possibly from its very base. Today there is a vigorous scientific discussion about the hot spots of the planet.

Exploring the Mantle with Seismic Waves

Our most powerful method for studying the mantle is by monitoring seismic waves from earthquakes around the world. Two different kinds seismic waves: P waves (similar to sound waves) and S waves (like waves from a shaken rope) respond physical properties the breed they pass through. Seismic waves reflect some types of surfaces and refract (bend) other types of surfaces when struck. Scientists use these effects to determine the interior surfaces of the Earth.

Our instruments are good enough to view the Earth's mantle the way doctors take ultrasound images of their patients. After a century of collecting earthquake data, we can now make some impressive maps of the mantle.

Modeling the mantle in the laboratory

Minerals and rocks change under high pressure. For example, a common mantle mineral, olivine, transforms into various crystalline forms at depths of about 410 kilometers and again at 660 kilometers.

The study of the behavior of minerals in the mantle occurs in two ways: computer modeling based on equations of the physics of minerals and laboratory experiments. In this way, modern research mantles are carried out by seismologists, programmers and laboratory researchers who can now reproduce conditions anywhere in the mantle using high pressure laboratory equipment such as a diamond anvil cell.

Mantle layers and inner boundaries

A century of research has filled some of the gaps in knowledge about the mantle. It has three main layers. Upper mantle extends from the base of the crust (Mohorovichich) to a depth of 660 kilometers. The transition zone is located between 410 and 660 kilometers, where significant physical changes in minerals take place.

The lower mantle extends from 660 to about 2,700 kilometers. Here, seismic waves are strongly muted, and most researchers believe that the rocks beneath them are different in chemical composition, and not only in crystallography. And the last disputable layer at the bottom of the mantle is about 200 kilometers thick and is the boundary between the core and the mantle.

Why the mantle of the Earth is special

Since the mantle is an essential part of the Earth, its history is fundamental to. The mantle was formed during the birth of the Earth, like an ocean of liquid magma on an iron core. As it solidified, elements that did not fit into the basic minerals collected as scale at the top of the crust. Then, the mantle began a slow circulation that has continued for the past 4 billion years. The top of the mantle began to cool as it was mixed and hydrated by tectonic movements of the surface plates.

At the same time, we learned a lot about the structure of others (Mercury, Venus and Mars). Compared to them, the Earth has an active oiled mantle that is special because of the same element that distinguishes its surface: water.

UMK line "Classical Geography" (5-9)

Geography

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

The internal structure of the Earth

Planet Earth consists of three main layers: crust, mantle and kernels... You can compare the globe with an egg. Then the eggshell will be earth crust, the egg white is the mantle, and the yolk is the core.

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

Tutorial is addressed to 6th grade students and is included in the Classical Geography teaching and learning complex. Modern design, a variety of questions and tasks, the ability to work in parallel with the electronic form of the textbook contribute to effective assimilation teaching material... The textbook complies with the Federal State Educational Standard of Basic General Education.

Earth's crust

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

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

There are three layers of the continental crust:

sedimentary (10-15 km of mainly sedimentary rocks);

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

basaltic (10-35 km of igneous rocks).

Mantle

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

Core

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

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

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

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

> What is the Earth made of?

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

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

But seismology was able to reveal the structure of the Earth and show the layers. Each is endowed with its own properties, characteristics and composition. And all this affects earthly processes. What is the Earth made of?

Modern theory

The inner space of the planet is differentiated. That is, the structure (like other planets) is represented by layers. Remove one and go to the next. Moreover, 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 includes an investigation 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 result in refraction.

They are used together with transformations in gravitational and magnetic fields and experiments with crystal solids simulating 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 did not even relate to science. These were rather legends and myths associated with divine intervention. However, several theories have spread among the population.

You may have heard about flat earth... This opinion was prevalent in the Mesopotamian culture. The planet was portrayed as a flat disk plying the ocean. Maya also considered it flat, but at the corners there were four jaguars that held the sky. The Persians saw a space mountain, while the Chinese had 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 and the first evidence base. At the same moment, scientists begin to come into contact with geological research, and philosophers consider minerals and metals.

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

An air gap is located between these spheres. To avoid the effect of friction, the inner sphere must be held in place by gravity. The model displayed two concentric shells around the core. The diameter corresponded to Mercury, Venus and Mars.

Halley drew on the densities of the Moon and Earth, as put forward by Isaac Newton in 1687. Next, scholars decided to consider the reliability of the Bible. It was important for the researchers to calculate the real age of the planet and find evidence of the flood. It was here that 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 also 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 from the solidification of molten masses. And all this happened extremely slowly. From this it followed that the planet is much older than what the Bible said.

In the 19th century, geology was heavily influenced by the Industrial Revolution, as well as the concept of a 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).

Researchers were able 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.

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 have already calculated the earthly age in terms of millions, not thousandths. But advances in technology have helped to shift the remnants of dogmatic beliefs.

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

The theory of plate tectonics arose from the study of the ocean floor. Geophysical data show 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, were actively developing. This is what helped to understand the composition and get to the core.

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

Earth layers

The earth can be divided mechanically or chemically. The first way studies liquid states. Here appears the lithosphere, asthenosphere and mesosphere, the outer and inner core. But the chemical method became very popular, discovering the crust, mantle and core.

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

Bark

It is the outer, cooled and hardened layer. It stretches for 570 km and represents only 1% of the planetary volume.

The narrower parts are the oceanic crust underlying the oceanic basins (5-10 km), and the denser parts are the continental ones. 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 is mostly solid, but sometimes behaves like a viscous liquid. It starts from the "Mohorovichich Surface" - 7-35 km and goes deeper for 410 km.

Movement in the mantle is reflected in the movement of tectonic plates. The process is driven by heat from deep within. 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

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

Outer core

It 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 solidify, although in composition it resembles the inner core. Temperature - 4030 ° C.

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

Inner core

What are the elements of the Earth's core? It is represented by iron and nickel, and in a radius it covers 1220 km. The density is 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 associated with a solid mantle, therefore it is believed that it rotates faster than the planet itself.

It is also believed 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 nucleus expands by 1 mm per year.

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

Below the earth's crust is the next layer called the mantle. It surrounds the core of the planet and is almost three thousand kilometers thick. The structure of the Earth's mantle is very complex and therefore requires detailed study.

Mantle and its features

The name of this shell (geosphere) comes from the Greek word for a cloak or veil. In reality, the mantle envelops the core like a veil. It accounts for about 2/3 of the Earth's mass and about 83% of its volume.

It is generally accepted that the temperature of the shell does not exceed 2500 degrees Celsius. Its density in different layers differs significantly: in the upper part it is up to 3.5 t / m3, and in the lower - 6 t / m3. The mantle consists of solid crystalline substances (heavy minerals rich in iron and magnesium). The only exception is the asthenosphere, which is in a semi-molten state.

Shell structure

Now let's look at the structure of the earth's mantle. The geosphere consists of the following parts:

• upper mantle, 800-900 km thick;
• asthenosphere;
• the lower mantle, about 2000 km thick.

The upper mantle is the part of the shell that is located below the earth's crust and enters the lithosphere. In turn, it is divided into the asthenosphere and the Golitsin layer, which is characterized by an intense increase in the velocities of seismic waves. This part of the Earth's mantle influences processes such as tectonic plate movements, metamorphism and magmatism. It should be noted that its structure differs depending on which tectonic object it is located under.

Asthenosphere. The very name of the middle layer of the shell with Greek translates as "weak ball". The geosphere, which is referred to as the upper part of the mantle, and sometimes separated into a separate layer, is characterized by reduced hardness, strength, and toughness. The upper boundary of the asthenosphere is always below the extreme line of the earth's crust: under the continents - at a depth of 100 km, under the seabed - 50 km. Its lower line is located at a depth of 250-300 km. The asthenosphere is the main source of magma on the planet, and the movement of amorphous and plastic matter is considered to be the cause of tectonic movements in the horizontal and vertical planes, magmatism and metamorphism of the earth's crust.

Scientists know little about the lower part of the mantle. It is believed that a special layer D is located on the border with the core, resembling the asthenosphere. It is distinguished by a high temperature (due to the proximity of a hot core) and an inhomogeneous substance. The composition of the mass includes iron and nickel.

Composition of the Earth's mantle

In addition to the structure of the Earth's mantle, its composition is also interesting. The geosphere is formed by olivine and ultrabasic rocks (peridotites, perovskites, dunites), but basic rocks (eclogites) are also present. It was found that the envelope contains rare species that are not found in the earth's crust (grospidites, phlogopite peridotites, carbonatites).

If we talk about the chemical composition, then the mantle contains in different concentrations: oxygen, magnesium, silicon, iron, aluminum, calcium, sodium and potassium, as well as their oxides.

Mantle and its study - video

The mantle contains most of the Earth's material. The mantle is also on other planets. The Earth's mantle ranges from 30 to 2,900 km.

Within its limits, according to seismic data, the following are distinguished: the upper mantle layer V depth up to 400 km and WITH up to 800-1000 km (some researchers layer WITH called the middle mantle); lower mantle layer D before depth 2700 with transition layer D1 from 2700 to 2900 km.

The border between the crust and the mantle is the border of Mohorovichich or, for short, Moho. On it there is a sharp increase in seismic velocities - from 7 to 8-8.2 km / s. This border is located at a depth of 7 (under the oceans) to 70 kilometers (under folded belts). The Earth's mantle is subdivided into an upper mantle and a lower mantle. The boundary between these geospheres is the Golitsyn layer, located at a depth of about 670 km.

The structure of the Earth according to the views of various researchers

The difference in the composition of the earth's crust and mantle is a consequence of their origin: the initially homogeneous Earth, as a result of partial melting, was divided into a fusible and light part - a crust and a dense and refractory mantle.

Sources of information about the mantle

The Earth's mantle is inaccessible to direct research: it does not come out to the earth's surface and is not reached by deep drilling. Therefore, most of the information about the mantle has been obtained by geochemical and geophysical methods. The data on its geological structure are very limited.

The mantle is studied according to the following data:

• Geophysical data. First of all, data on seismic wave velocities, electrical conductivity and gravity.
• Mantle melts - basalts, komatiites, kimberlites, lamproites, carbonatites and some other igneous rocks are formed as a result of partial melting of the mantle. The composition of the melt is a consequence of the composition of the melted rocks, the inter-anism of melting, and the physicochemical parameters of the melting process. In general, the reconstruction of the source from the melt is a difficult task.
• Fragments of mantle rocks carried to the surface by mantle melts - kimberlites, alkaline basalts, etc. These are xenoliths, xenocrysts and diamonds. Diamonds occupy a special place among the sources of information about the mantle. It is in diamonds that the deepest minerals are found, which, possibly, originate even from the lower mantle. In this case, these diamonds represent the deepest fragments of the earth available for direct study.
• Mantle rocks in the earth's crust. Such complexes most closely correspond to the mantle, but also differ from it. The most important difference is in the very fact of their being in the composition of the earth's crust, from which it follows that they were formed as a result of not entirely ordinary processes and, perhaps, do not reflect a typical mantle. They are found in the following geodynamic settings:

1. Alpine-type hyperbasites are parts of the mantle embedded in the earth's crust as a result of mountain building. Most common in the Alps, from which the name originates.
2. Ophiolite hyperbasites - peredotites as part of ophiolite complexes - parts of the ancient oceanic crust.
3. Abyssal peridotites are protrusions of mantle rocks at the bottom of oceans or rifts.

These complexes have the advantage that geological relationships between different rocks can be observed in them.

It was recently announced that Japanese researchers are planning to attempt to drill oceanic crust up to the mantle. For this, the Chikyu ship was built. Drilling is planned to start in 2007.

The main drawback of the information obtained from these fragments is the impossibility of establishing geological relationships between different types of rocks. These are puzzle pieces. As the classic said, “determining the composition of the mantle by xenoliths resembles attempts to determine geological structure mountains on the pebbles, which the river carried out of them. "

Mantle composition

The mantle is composed mainly of ultrabasic rocks: peridotites (lherzolites, harzburgites, wehrlites, pyroxenites), dunites and, to a lesser extent, basic rocks - eclogites.

Also, among the mantle rocks, rare varieties of rocks are found that are not found in the earth's crust. These are various phlogopite peridotites, grospidites, carbonatites.

The structure of the mantle

The processes taking place in the mantle have the most direct effect on the earth's crust and surface of the earth, are the cause of the movement of continents, volcanism, earthquakes, mountain building and the formation of ore deposits. There is growing evidence that the mantle itself is actively influenced by the metal core of the planet.

Convection and plumes

Bibliography

• D.Yu. Pushcharovsky, Yu.M. Pushcharovsky Composition and structure of the Earth's mantle // Soros Educational Journal, 1998, No 11, p. 111-119.
• A.A. Kovtun Electrical conductivity of the Earth // Soros Educational Journal, 1997, No 10, p. 111-117

A source: Koronovskiy N.V., Yakushova A.F. "Fundamentals of Geology", M., 1991

Links

• Images of the Earth "s Crust & Upper Mantle // International Geological Correlation Program (IGCP), Project 474