The continental crust is made up of 3 layers. Earth's crust

10.04.2020

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

Oceanic crust: properties, layers, thickness

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

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

It consists of three main layers:

sedimentary;
basalt;
gabbro-serpentinite.

Continental crust: properties, layers, thickness

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

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

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

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

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

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

The earth's crust is of great importance for our life, for the exploration of our planet.

This concept is closely related to others that characterize the processes occurring inside and on the surface of the Earth.

What is the earth's crust and where is it located

The earth has an integral and continuous shell, which includes: the earth's crust, troposphere and stratosphere, which are the lower part of the atmosphere, hydrosphere, biosphere and anthroposphere.

They closely interact, penetrating each other and constantly exchanging energy and matter. It is customary to call the earth's crust the outer part of the lithosphere - the solid shell of the planet. Most of its outer side is covered by the hydrosphere. The rest, a smaller part, is affected by the atmosphere.

Under the Earth's crust is a denser and more refractory mantle. They are separated by a conditional border, named after the Croatian scientist Mohorovich. Its feature is a sharp increase in the speed of seismic vibrations.

Various scientific methods are used to gain insight into the earth's crust. However, obtaining specific information is possible only by means of drilling to a greater depth.

One of the objectives of such a study was to establish the nature of the boundary between the upper and lower continental crust. The possibilities of penetration into the upper mantle with the help of self-heating capsules made of refractory metals were discussed.

The structure of the earth's crust

Under the continents, its sedimentary, granite and basalt layers are distinguished, the thickness of which in the aggregate is up to 80 km. Rocks, called sedimentary rocks, were formed as a result of the deposition of substances on land and in water. They are predominantly in layers.

clay
shales
sandstones
carbonate rocks
rocks of volcanic origin
coal and other rocks.

The sedimentary layer helps to learn more about the natural conditions on earth that were on the planet in time immemorial. Such a layer may have a different thickness. In some places it may not exist at all, in others, mainly in large depressions, it may be 20-25 km.

The temperature of the earth's crust

An important energy source for the inhabitants of the Earth is the heat of its crust. The temperature increases as you go deeper into it. The 30-meter layer closest to the surface, called the heliometric layer, is associated with the heat of the sun and fluctuates depending on the season.

In the next, thinner layer, which increases in continental climates, the temperature is constant and corresponds to the indicators of a particular measurement site. In the geothermal layer of the crust, the temperature is related to the internal heat of the planet and increases as you go deeper into it. It is different in different places and depends on the composition of the elements, the depth and conditions of their location.

It is believed that the temperature rises on average by three degrees as it deepens for every 100 meters. Unlike the continental part, the temperature under the oceans is rising faster. After the lithosphere, there is a plastic high-temperature shell, the temperature of which is 1200 degrees. It is called the asthenosphere. It has places with molten magma.

Penetrating into the earth's crust, the asthenosphere can pour out molten magma, causing volcanic phenomena.

Characteristics of the Earth's crust

The Earth's crust has a mass of less than half a percent of the total mass of the planet. It is the outer shell of the stone layer in which the movement of matter occurs. This layer, which has a density half that of the Earth. Its thickness varies within 50-200 km.

The uniqueness of the earth's crust is that it can be of continental and oceanic types. The continental crust has three layers, the upper of which is formed by sedimentary rocks. The oceanic crust is relatively young and its thickness varies little. It is formed due to the substances of the mantle from oceanic ridges.

earth's crust characteristic photo

The thickness of the crust under the oceans is 5-10 km. Its peculiarity is in constant horizontal and oscillatory movements. Most of the crust is basalt.

The outer part of the earth's crust is the hard shell of the planet. Its structure is distinguished by the presence of mobile areas and relatively stable platforms. Lithospheric plates move relative to each other. The movement of these plates can cause earthquakes and other cataclysms. The regularities of such movements are studied by tectonic science.

Functions of the earth's crust

The main functions of the earth's crust are:

resource;
geophysical;
geochemical.

The first of them indicates the presence of the resource potential of the Earth. It is primarily a set of mineral reserves located in the lithosphere. In addition, the resource function includes a number of environmental factors that ensure the life of humans and other biological objects. One of them is the tendency to form a hard surface deficit.

you can't do that. save our earth photo

Thermal, noise and radiation effects realize the geophysical function. For example, there is a problem of natural background radiation, which is earth's surface basically safe. However, in countries such as Brazil and India, it can be hundreds of times higher than the allowable one. It is believed that its source is radon and its decay products, as well as some types of human activity.

The geochemical function is associated with problems of chemical pollution harmful to humans and other representatives of the animal world. enter the lithosphere various substances possessing toxic, carcinogenic and mutagenic properties.

They are safe when they are in the bowels of the planet. Zinc, lead, mercury, cadmium and other heavy metals extracted from them can be very dangerous. In processed solid, liquid and gaseous form, they enter the environment.

What is the Earth's crust made of?

Compared to the mantle and core, the Earth's crust is fragile, tough, and thin. It consists of a relatively light substance, which includes about 90 natural elements in its composition. They are found in different places of the lithosphere and with varying degrees of concentration.

The main ones are: oxygen silicon aluminum, iron, potassium, calcium, sodium magnesium. 98 percent of the earth's crust is made up of them. Including about half is oxygen, more than a quarter - silicon. Due to their combinations, minerals such as diamond, gypsum, quartz, etc. are formed. Several minerals can form a rock.

An ultra-deep well on the Kola Peninsula made it possible to get acquainted with mineral samples from a depth of 12 km, where rocks similar to granites and shale were found.
The greatest thickness of the crust (about 70 km) was revealed under the mountain systems. Under the flat areas it is 30-40 km, and under the oceans - only 5-10 km.
A significant part of the crust forms an ancient low-density upper layer, consisting mainly of granites and shales.
The structure of the earth's crust resembles the crust of many planets, including those on the Moon and their satellites.

- limited to the surface of the land or the bottom of the oceans. It also has a geophysical boundary, which is the section Moho. The boundary is characterized by the fact that seismic wave velocities sharply increase here. It was installed in $1909 by a Croatian scientist A. Mohorovic ($1857$-$1936$).

The earth's crust is made up sedimentary, igneous and metamorphic rocks, and in terms of composition it stands out three layers. Rocks of sedimentary origin, the destroyed material of which was redeposited in the lower layers and formed sedimentary layer the earth's crust, covers the entire surface of the planet. In some places it is very thin and may be interrupted. In other places, it reaches a thickness of several kilometers. Sedimentary are clay, limestone, chalk, sandstone, etc. They are formed by sedimentation of substances in water and on land, they usually lie in layers. From sedimentary rocks, you can learn about the natural conditions that existed on the planet, so geologists call them pages of the history of the Earth. Sedimentary rocks are subdivided into organogenic, which are formed by the accumulation of the remains of animals and plants and non-organogenic, which are further subdivided into clastic and chemogenic.

Ready-made works on a similar topic

Course work The structure of the earth's crust 400 rub.
abstract The structure of the earth's crust 230 rub.
Test The structure of the earth's crust 190 rub.

clastic rocks are the product of weathering, and chemogenic- the result of the precipitation of substances dissolved in the water of the seas and lakes.

Igneous rocks make up granite layer of the earth's crust. These rocks were formed as a result of solidification of molten magma. On the continents, the thickness of this layer is $15$-$20$ km, it is completely absent or very much reduced under the oceans.

Igneous matter, but poor in silica composes basaltic layer with a high specific gravity. This layer is well developed at the base of the earth's crust of all regions of the planet.

The vertical structure and thickness of the earth's crust are different, therefore, several types of it are distinguished. According to a simple classification, there is oceanic and continental Earth's crust.

continental crust

Continental or continental crust is different from oceanic crust thickness and device. The continental crust is located under the continents, but its edge does not coincide with the coastline. From the point of view of geology, the real continent is the entire area of the continuous continental crust. Then it turns out that the geological continents are larger geographical continents. Coastal areas of the continents, called shelf- these are parts of the continents temporarily flooded by the sea. Such seas as the White, East Siberian, Azov Seas are located on the continental shelf.

There are three layers in the continental crust:

The upper layer is sedimentary;
The middle layer is granite;
The bottom layer is basalt.

Under young mountains this type of crust has a thickness of $75$ km, under plains up to $45$ km, and under island arcs up to $25$ km. The upper sedimentary layer of the continental crust is formed by clay deposits and carbonates of shallow marine basins and coarse clastic facies in foredeeps, as well as on the passive margins of Atlantic-type continents.

Magma invading the cracks in the earth's crust formed granite layer which contains silica, aluminum and other minerals. The thickness of the granite layer can be up to $25$ km. This layer is very ancient and has a solid age of $3 billion years. Between the granite and basalt layers, at a depth of up to $20$ km, there is a boundary Conrad. It is characterized by the fact that the propagation velocity of longitudinal seismic waves here increases by $0.5$ km/sec.

Formation basalt layer occurred as a result of outpouring of basalt lavas onto the land surface in zones of intraplate magmatism. Basalts contain more iron, magnesium and calcium, so they are heavier than granite. Within this layer, the propagation velocity of longitudinal seismic waves is from $6.5$-$7.3$ km/sec. Where the boundary becomes blurred, the velocity of longitudinal seismic waves increases gradually.

Remark 2

The total mass of the earth's crust of the mass of the entire planet is only $0.473$%.

One of the first tasks associated with determining the composition upper continental bark, young science undertook to solve geochemistry. Since the bark is made up of a wide variety of rocks, this task was very difficult. Even in one geological body, the composition of rocks can vary greatly, and different types of rocks can be common in different areas. Based on this, the task was to determine the general, average composition that part of the earth's crust that comes to the surface on the continents. This first estimate of the composition of the upper crust was made by Clark. He worked as an employee of the US Geological Survey and was engaged in the chemical analysis of rocks. In the course of many years of analytical work, he managed to summarize the results and calculate the average composition of the rocks, which was close to to granite. Work Clark was subjected to harsh criticism and had opponents.

The second attempt to determine the average composition of the earth's crust was made by W. Goldschmidt. He suggested that moving along the continental crust glacier, can scrape and mix exposed rocks that would be deposited during glacial erosion. They will then reflect the composition of the middle continental crust. Having analyzed the composition of banded clays, which were deposited during the last glaciation in Baltic Sea, he got a result close to the result Clark. Different methods gave the same scores. Geochemical methods were confirmed. These issues have been addressed, and the assessments received wide recognition. Vinogradov, Yaroshevsky, Ronov and others.

oceanic crust

oceanic crust located where the depth of the sea is more than $ 4 $ km, which means that it does not occupy the entire space of the oceans. The rest of the area is covered with bark intermediate type. The oceanic-type crust is not organized in the same way as the continental crust, although it is also divided into layers. It has almost no granite layer, while the sedimentary one is very thin and has a thickness of less than $1$ km. The second layer is still unknown, so it is simply called second layer. Bottom third layer basaltic. The basalt layers of the continental and oceanic crust are similar in seismic wave velocities. The basalt layer in the oceanic crust prevails. According to the theory of plate tectonics, the oceanic crust is constantly formed in the mid-ocean ridges, then it moves away from them and in areas subduction absorbed into the mantle. This indicates that the oceanic crust is relatively young. The largest number of subduction zones is typical for Pacific Ocean where powerful seaquakes are associated with them.

Definition 1

Subduction- this is the lowering of rock from the edge of one tectonic plate into a semi-molten asthenosphere

In the case when the upper plate is a continental plate, and the lower one is an oceanic one, ocean trenches.
Its thickness in different geographical areas varies from $5$-$7$ km. Over time, the thickness of the oceanic crust practically does not change. This is due to the amount of melt released from the mantle in the mid-ocean ridges and the thickness of the sedimentary layer at the bottom of the oceans and seas.

Sedimentary layer oceanic crust is small and rarely exceeds a thickness of $0.5$ km. It consists of sand, deposits of animal remains and precipitated minerals. Carbonate rocks of the lower part are not found at great depths, and at a depth of more than $4.5$ km, carbonate rocks are replaced by red deep-water clays and siliceous silts.

Basalt lavas of tholeiite composition formed in the upper part basalt layer, and below lies dike complex.

Definition 2

dikes- these are channels through which basalt lava flows to the surface

Basalt layer in zones subduction turns into ecgoliths, which submerge in depth because they have a high density of surrounding mantle rocks. Their mass is about $7$% of the mass of the entire Earth's mantle. Within the basalt layer, the velocity of longitudinal seismic waves is $6.5$-$7$ km/sec.

The average age of the oceanic crust is $100$ million years, while its oldest sections are $156$ million years old and are located in the basin Pijafeta in the Pacific Ocean. The oceanic crust is concentrated not only within the bed of the World Ocean, it can also be in closed basins, for example, the northern basin of the Caspian Sea. Oceanic the earth's crust has a total area of $306$ million sq. km.

Ready-made works on a similar topic

Course work The structure of the earth's crust 490 rub.
abstract The structure of the earth's crust 240 rub.
Test The structure of the earth's crust 230 rub.

clastic rocks are the product of weathering, and chemogenic- the result of the precipitation of substances dissolved in the water of the seas and lakes.

Igneous matter, but poor in silica composes basaltic layer with a high specific gravity. This layer is well developed at the base of the earth's crust of all regions of the planet.

continental crust

Continental or continental crust is different from oceanic crust thickness and device. The continental crust is located under the continents, but its edge does not coincide with the coastline. From the point of view of geology, the real continent is the entire area of the continuous continental crust. Then it turns out that the geological continents are larger than the geographical continents. Coastal areas of the continents, called shelf- these are parts of the continents temporarily flooded by the sea. Such seas as the White, East Siberian, Azov Seas are located on the continental shelf.

There are three layers in the continental crust:

The upper layer is sedimentary;
The middle layer is granite;
The bottom layer is basalt.

Remark 2

The total mass of the earth's crust of the mass of the entire planet is only $0.473$%.

oceanic crust

Definition 1

Subduction- this is the lowering of rock from the edge of one tectonic plate into a semi-molten asthenosphere

Basalt lavas of tholeiite composition formed in the upper part basalt layer, and below lies dike complex.

Definition 2

dikes- these are channels through which basalt lava flows to the surface

Line UMK "Classical geography" (5-9)

Geography

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

We often look at the sky and think about how the cosmos works. We read about astronauts and satellites. And it seems that all the mysteries unsolved by man are there - outside the globe. In fact, we live on a planet full of amazing mysteries. And we dream about space, without thinking about how complex and interesting our Earth is.

The internal structure of the Earth

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

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

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

Earth's crust

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

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

There are three layers of the continental crust:

sedimentary (10-15 km mostly sedimentary rocks);

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

basaltic (10-35 km of igneous rocks).

Mantle

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

Core

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

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

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

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