Where is the lithosphere located. What is the Earth's lithosphere? Geological structure of the globe

The lithosphere is the stone shell of the Earth. From the Greek "lithos" - a stone and "sphere" - a ball

The lithosphere is the outer solid shell of the Earth, which includes the entire earth's crust with part of the Earth's upper mantle and consists of sedimentary, igneous and metamorphic rocks. The lower boundary of the lithosphere is fuzzy and is determined by a sharp decrease in rock viscosity, a change in the propagation velocity of seismic waves, and an increase in the electrical conductivity of rocks. The thickness of the lithosphere on the continents and under the oceans varies and averages 25 - 200 and 5 - 100 km, respectively.

Consider in general terms the geological structure of the Earth. The third planet farthest from the Sun - the Earth has a radius of 6370 km, an average density of 5.5 g / cm3 and consists of three shells - bark, robes and i. The mantle and core are divided into inner and outer parts.

The Earth's crust is a thin upper shell of the Earth, which has a thickness of 40-80 km on the continents, 5-10 km under the oceans and makes up only about 1% of the Earth's mass. Eight elements - oxygen, silicon, hydrogen, aluminum, iron, magnesium, calcium, sodium - form 99.5% of the earth's crust.

According to scientific research, scientists were able to establish that the lithosphere consists of:

Oxygen - 49%;
Silicon - 26%;
Aluminum - 7%;
Iron - 5%;
Calcium - 4%
The composition of the lithosphere includes many minerals, the most common are feldspar and quartz.

On the continents, the crust is three-layered: sedimentary rocks cover granitic rocks, and granitic rocks lie on basalt rocks. Under the oceans, the crust is "oceanic", two-layered; sedimentary rocks lie simply on basalts, there is no granite layer. There is also a transitional type of the earth's crust (island-arc zones on the outskirts of the oceans and some areas on the continents, such as the Black Sea).

The earth's crust is thickest in mountainous regions.(under the Himalayas - over 75 km), the middle one - in the areas of the platforms (under the West Siberian lowland - 35-40, within the boundaries of the Russian platform - 30-35), and the smallest - in the central regions of the oceans (5-7 km). The predominant part of the earth's surface is the plains of the continents and the ocean floor.

The continents are surrounded by a shelf - a shallow-water strip up to 200 g deep and an average width of about 80 km, which, after a sharp steep bend of the bottom, passes into the continental slope (the slope varies from 15-17 to 20-30 °). The slopes gradually level off and turn into abyssal plains (depths 3.7-6.0 km). The greatest depths (9-11 km) have oceanic trenches, the vast majority of which are located on the northern and western margins of the Pacific Ocean.

The main part of the lithosphere consists of igneous igneous rocks (95%), among which granites and granitoids predominate on the continents, and basalts in the oceans.

Blocks of the lithosphere - lithospheric plates - move along the relatively plastic asthenosphere. The section of geology on plate tectonics is devoted to the study and description of these movements.

To designate the outer shell of the lithosphere, the now obsolete term sial was used, which comes from the name of the main elements of rocks Si (lat. Silicium - silicon) and Al (lat. Aluminum - aluminum).

Lithospheric plates

It is worth noting that the largest tectonic plates are very clearly visible on the map and they are:

Pacific- the largest plate of the planet, along the boundaries of which constant collisions of tectonic plates occur and faults form - this is the reason for its constant decrease;
Eurasian- covers almost the entire territory of Eurasia (except Hindustan and the Arabian Peninsula) and contains the largest part of the continental crust;
Indo-Australian- It includes the Australian continent and the Indian subcontinent. Due to constant collisions with the Eurasian plate, it is in the process of breaking;
South American- consists of the South American mainland and part of the Atlantic Ocean;
North American- consists of the North American continent, part of northeastern Siberia, the northwestern part of the Atlantic and half of the Arctic Oceans;
African- consists of the African continent and the oceanic crust of the Atlantic and Indian oceans. It is interesting that the plates adjacent to it move in the opposite direction from it, therefore the largest fault of our planet is located here;
Antarctic Plate- consists of the mainland Antarctica and the nearby oceanic crust. Due to the fact that the plate is surrounded by mid-ocean ridges, the rest of the continents are constantly moving away from it.

Movement of tectonic plates in the lithosphere

Lithospheric plates, connecting and separating, change their outlines all the time. This allows scientists to put forward the theory that about 200 million years ago the lithosphere had only Pangea - a single continent, which subsequently split into parts, which began to gradually move away from each other at a very low speed (an average of about seven centimeters per year ).

It is interesting! There is an assumption that due to the movement of the lithosphere, in 250 million years a new continent will form on our planet due to the union of moving continents.

When the oceanic and continental plates collide, the edge of the oceanic crust sinks under the continental one, while on the other side of the oceanic plate its boundary diverges from the plate adjacent to it. The boundary along which the movement of the lithospheres occurs is called the subduction zone, where the upper and plunging edges of the plate are distinguished. It is interesting that the plate, plunging into the mantle, begins to melt when the upper part of the earth's crust is squeezed, as a result of which mountains are formed, and if magma also breaks out, then volcanoes.

In places where tectonic plates come into contact with each other, there are zones of maximum volcanic and seismic activity: during the movement and collision of the lithosphere, the earth's crust collapses, and when they diverge, faults and depressions form (the lithosphere and the Earth's relief are connected to each other). This is the reason that the largest landforms of the Earth are located along the edges of the tectonic plates - mountain ranges with active volcanoes and deep-sea trenches.

Problems of the lithosphere

The intensive development of industry has led to the fact that man and the lithosphere have recently become extremely difficult to get along with each other: pollution of the lithosphere is acquiring catastrophic proportions. This happened due to the increase in industrial waste in combination with household waste and fertilizers and pesticides used in agriculture, which negatively affects the chemical composition of the soil and living organisms. Scientists have calculated that about one ton of garbage falls per person per year, including 50 kg of hardly decomposable waste.

Today, pollution of the lithosphere has become an urgent problem, since nature is not able to cope with it on its own: the self-purification of the earth's crust is very slow, and therefore harmful substances gradually accumulate and eventually negatively affect the main culprit of the problem - man.

The lithosphere is the hard shell of the planet Earth. It covers it completely, protecting the surface from the highest temperatures of the planet's core. We will study what structure the lithosphere has and how it differs from other planets.

general characteristics

The lithosphere borders the hydrosphere and atmosphere above, and the asthenosphere below. The thickness of this shell varies considerably and ranges from 10 to 200 km. in different parts of the planet. On the continents, the lithosphere is thicker than in the oceans. The lithosphere is not a single whole - it is formed by separate plates that lie on the asthenosphere and gradually move along it. There are seven large lithospheric plates and several small ones. The boundaries between them are zones of seismic activity. On the territory of Russia, two such plates are connected - the Eurasian and North American. The structure of the Earth's lithosphere is represented by three layers:

Earth's crust;
boundary layer;
upper mantle.

Let's consider each layer in more detail.

Rice. 1. Layers of the lithosphere

Earth's crust

This is the upper and thinnest layer of the lithosphere. Its mass is only 1% of the mass of the Earth. The thickness of the earth's crust varies from 30 to 80 km. A smaller thickness is observed in the flat areas, a large one - in the mountains. There are two types of the earth's crust - continental and oceanic.

The division of the crust into two types is available only on Earth, on the other planets the crust is of the same type.

The continental crust consists of three layers:

boundary layer

It is called the Mohorovichic surface. In this zone, there is a sharp increase in the speed of seismic waves. Also here the density of the lithosphere substance changes, it becomes more elastic. The surface of Mohorovichich lies at a depth of 5 to 70 km, completely repeating the relief of the earth's crust.

Rice. 3. Scheme of the Mohorovichic surface

Mantle

Only the upper layer of the mantle belongs to the lithosphere. It has a thickness of 70 to 300 km. What phenomena occur in this layer? Seismic activity originates here - earthquakes. This is due to the increase in the speed of seismic waves here. What is the structure of this layer? It is formed mainly by iron, magnesium, calcium, oxygen.

What have we learned?

The Earth's lithosphere has a layered structure. It is formed by the earth's crust and the upper layer of the mantle. Between these layers there is a boundary called the Mohorovichic surface. The total thickness of the lithosphere reaches 200 km. It contains almost all metals and trace elements.

Topic quiz

Report Evaluation

Average rating: 4.3. Total ratings received: 355.

And any negative lithospheric changes can exacerbate the global crisis. From this article you will learn about what the lithosphere and lithospheric plates are.

Concept definition

The lithosphere is the outer hard shell of the globe, which consists of the earth's crust, part of the upper mantle, sedimentary and igneous rocks. It is rather difficult to determine its lower boundary, but it is generally accepted that the lithosphere ends with a sharp decrease in the viscosity of rocks. The lithosphere occupies the entire surface of the planet. The thickness of its layer is not the same everywhere, it depends on the terrain: on the continents - 20-200 kilometers, and under the oceans - 10-100 km.

The Earth's lithosphere mostly consists of igneous igneous rocks (about 95%). These rocks are dominated by granitoids (on the continents) and basalts (under the oceans).

Some people think that the concepts "hydrosphere" / "lithosphere" mean the same thing. But this is far from true. The hydrosphere is a kind of water shell of the globe, and the lithosphere is solid.

Geological structure of the globe

The lithosphere as a concept also includes the geological structure of our planet, therefore, in order to understand what the lithosphere is, it should be considered in detail. The upper part of the geological layer is called the earth's crust, its thickness varies from 25 to 60 kilometers on the continents, and from 5 to 15 kilometers in the oceans. The lower layer is called the mantle, separated from the earth's crust by the Mohorovichich section (where the density of matter changes dramatically).

The globe is made up of the earth's crust, mantle and core. The earth's crust is a solid, but its density changes dramatically at the boundary with the mantle, that is, at the Mohorovichic line. Therefore, the density of the earth's crust is an unstable value, but the average density of a given layer of the lithosphere can be calculated, it equals 5.5223 grams / cm 3.

The globe is a dipole, that is, a magnet. Earth's magnetic poles are located in the southern and northern hemispheres.

Layers of the Earth's lithosphere

The lithosphere on the continents consists of three layers. And the answer to the question of what the lithosphere is will not be complete without considering them.

The upper layer is built from a wide variety of sedimentary rocks. The middle one is conditionally called granite, but it consists not only of granites. For example, under the oceans, the granite layer of the lithosphere is completely absent. The approximate density of the middle layer is 2.5-2.7 grams/cm 3 .

The lower layer is also conditionally called basalt. It consists of heavier rocks, its density, respectively, is greater - 3.1-3.3 grams / cm 3. The lower basalt layer is located under the oceans and continents.

The earth's crust is also classified. There are continental, oceanic and intermediate (transitional) types of the earth's crust.

The structure of lithospheric plates

The lithosphere itself is not homogeneous, it consists of peculiar blocks, which are called lithospheric plates. They include both oceanic and continental crust. Although there is a case that can be considered an exception. The Pacific lithospheric plate consists only of oceanic crust. The lithospheric blocks consist of folded metamorphic and igneous rocks.

Each continent has at its base an ancient platform, the boundaries of which are defined by mountain ranges. Plains and only individual mountain ranges are located directly on the platform area.

Seismic and volcanic activity is quite often observed at the boundaries of lithospheric plates. There are three types of lithospheric boundaries: transform, convergent, and divergent. The outlines and boundaries of lithospheric plates change quite often. Small lithospheric plates are connected to each other, while large ones, on the contrary, break apart.

List of lithospheric plates

It is customary to distinguish 13 main lithospheric plates:

Philippine plate.
Australian.
Eurasian.
Somali.
South American.
Hindustan.
African.
Antarctic Plate.
Nazca plate.
Pacific;
North American.
Scotia plate.
Arabian plate.
Cooker Coconut.

So, we gave a definition of the concept of "lithosphere", considered the geological structure of the Earth and lithospheric plates. With the help of this information, it is now possible to answer with certainty the question of what the lithosphere is.

LITHOSPHERE- the outer sphere of the "solid" Earth, including the earth's crust and part of the upper mantle (Fig. 1).

The thickness of the crust under the continents is, on average, 35–40 km. Where young high mountains are located on land, it often exceeds 50 km (for example, under the Himalayas it reaches 90 km). Under the oceans, the crust is thinner - on average about 7-10 km, and in some areas of the Pacific Ocean - only 5 km.

The boundaries of the earth's crust are determined by the speed of propagation of seismic waves. Seismic waves also provide information about the properties of the mantle. It has been established that the upper mantle consists mainly of silicates of magnesium and iron. The composition of the lower mantle remains a mystery, but it has been suggested that it contains oxides of magnesium and silicon. Conclusions about the composition of the earth's core were made on the basis of not only the analysis of seismic waves, but also density calculations and the study of the composition of meteorites. The inner core is thought to be a hard alloy of iron and nickel. The outer core appears to be liquid and somewhat less dense. Some experts believe that it contains up to 14% sulfur.

The Earth's crust, hydrosphere and atmosphere were formed mainly as a result of the release of substances from the upper mantle of the young Earth. Now, in the mid-ridges at the bottom of the oceans, the formation of oceanic crust continues, accompanied by the release of gases and small amounts of water. Apparently, the formation of the crust on the young Earth was the result of similar processes, as a result of which a thin shell was formed, constituting less than 0.0001% of the volume of the entire planet. The composition of this shell, which forms the continental and oceanic crust, changed over time, primarily due to the transfer of elements from the mantle due to partial melting at a depth of about 100 km. The average chemical composition of the modern Earth's crust is characterized by a high content of oxygen, followed by silicon and aluminum (Fig. 2).

According to the suggestion of the Soviet geochemist A.E. Fersman (1883–1945), the average values of the relative content of chemical elements in the upper layer of the earth’s crust are called clarks of elements in honor of the American scientist Frank Wilgsworth Clark (1847–1931), who developed methods for quantifying the abundance of chemical elements.

An analysis of the clarke values makes it possible to understand many regularities in the distribution of chemical elements. The clarks of the chemical elements of the earth's crust differ by more than ten orders of magnitude. So, if aluminum in the earth's crust contains more than eight percent by weight, then, for example, gold is 4.3 10 -7%, copper - 5 10 -3%, uranium - 3 10 -4%, and such a rare metal , like rhenium - only 7 10 -8%. Elements contained in a relatively large amount form numerous independent chemical compounds in nature, and elements with small clarks are scattered mainly among chemical compounds of other elements. Elements whose clarks are less than 0.01% are called rare.

The main compounds that form the lithosphere are silicon dioxide, silicates and aluminosilicates. Most of the lithosphere is made up of crystalline substances formed during the cooling of magma - molten matter in the depths of the Earth. When the magma cooled, hot solutions were also formed. Passing through the cracks in the surrounding rocks, they cooled and released the substances contained in them.

Because some minerals are only stable under certain conditions, they break apart as temperatures and pressures change. For example, a number of silicates formed deep in the crust at high temperature and pressure become unstable when they hit the Earth's surface. On the other hand, at great depths, under the influence of the internal heat of the Earth and increased pressure, many rocks change their appearance, forming new crystalline forms.

The surface of the continental crust is exposed to the action of the atmosphere and hydrosphere, which is expressed in weathering processes. Physical weathering is a mechanical process that breaks down rock into smaller particles without significant changes in chemical composition. Chemical weathering leads to the formation of new substances, it occurs under the action of moisture, especially acidified, and certain gases (for example, oxygen) that destroy minerals.

The simplest weathering process is the dissolution of minerals. Water causes the breaking of ionic bonds connecting, for example, sodium cations and chloride ions in NaCl halite. Hydrogen cations are not involved in this process, so it does not depend on pH.

In the destruction of substances containing elements in low oxidation states, for example, sulfides, oxygen plays an important role. Microorganisms are often involved in these processes. Thus, the oxidation of pyrite FeS 2 can be modeled by the following series of reactions. Sulfur (–I) is oxidized first:

2FeS 2 + 2H 2 O + 7O 2 = 4H + + 4SO 4 2– + 2Fe 2+

This is followed by the oxidation of iron(II), catalyzed by iron-oxidizing bacteria:

4Fe 2+ + O 2 + 6H 2 O \u003d 4FeO (OH) + 8H +

The formed goethite FeO(OH) covers the bottom of the streams in the form of a characteristic yellow-orange coating.

Iron-oxidizing bacteria extract energy from the oxidation of inorganic substances, so they develop where there are no organic compounds, using CO 2 as a carbon source. However, iron oxidation is not a very efficient way of generating energy: approximately 220 g of iron(II) must be oxidized to produce 1 g of cellular carbon. As a result, where iron-oxidizing bacteria live, large deposits of iron(III) compounds form.

Weathering of carbonate minerals, such as CaCO 3 , occurs when interacting with acids contained in water due to the absorption of carbon dioxide, as well as anthropogenic sulfur dioxide. At the same time, surface waters are neutralized and enriched with hydrocarbonate ions:

CaCO 3 + H 2 CO 3 \u003d Ca 2+ + 2HCO 3 -

The destruction of silicates, for example Mg 2 SiO 4 (forsterite) can be described by the following equation:

Mg 2 SiO 4 + 4H 2 CO 3 \u003d 2Mg 2+ + 4HCO 3 - + H 4 SiO 4

The reaction proceeds due to the formation of an extremely weak orthosilicic acid, while the mineral completely dissolves over time. However, during the weathering of more complex silicates, not all products are soluble. In the general case, as a result of weathering, mainly quartz and clay minerals are formed - water-containing layered aluminosilicates. For example, during the weathering of CaAl 2 Si 2 O 8 (anorthite), the clay mineral kaolinite is a solid reaction product:

CaAl 2 Si 2 O 8 + 2H 2 CO 3 + H 2 O \u003d Ca 2+ + 2HCO 3 - + Al 2 Si 2 O 5 (OH) 4

The rate of weathering is influenced by the biosphere (where carbon dioxide is created), as well as land topography and climate, water composition, type of parent rock, and the kinetics of reactions involving individual minerals. So, in the humid tropics, weathering occurs faster. This is due to the fact that high temperatures accelerate reactions, and constant showers make it possible to quickly wash out and carry even practically insoluble compounds into the seas and oceans, for example, oxides of aluminum and iron.

Weathering products form loose continental deposits, the thickness of which varies from 10–20 cm on steep slopes to tens of meters on plains and hundreds of meters in depressions. The average mineralogical composition of the loose land cover differs markedly from the composition of the earth's crust of the continents (Fig. 3).

Soils have formed on loose cover deposits, which play an important role in the interaction of living organisms with the earth's crust. In soils, a significant amount of organic matter synthesized by higher plants is systematically conserved. Oxidation of organic matter in soils is catalyzed by enzymes of microorganisms, and carbon dioxide is formed, which, when interacting with water, gives weak carbonic acid. This can lower soil pH to 4–5, which has a significant effect on weathering processes. The soil is involved in the cycle of nitrogen, sulfur and phosphorus, as well as many metals. Therefore, the problem of soil protection is of great importance.

In the early stages of human history, human activity almost did not affect the depths of the Earth. However, with the beginning of the rapid development of industry, human needs for minerals increased sharply. Their extraction and processing began to have a harmful effect on nature. During the development of open mine workings, a lot of dust is generated that pollutes the surroundings. Huge areas are occupied by dumps of "waste" rock, formed during the extraction of solid minerals. Pumping water from mine workings leads to the formation of underground voids. Many mining enterprises discharge insufficiently treated wastewater into rivers, which leads to pollution of natural waters. Harmful substances from the dumps of these enterprises enter the environment. Many hazardous substances are dispersed during the transportation of ores and products of their processing.

Environmental pollution from the extraction and processing of minerals can be reduced if the achievements of science and better technologies are used.

Elena Savinkina

The lithosphere is the outer solid shell of the Earth, including the earth's crust and the upper part of the mantle. The lithosphere includes sedimentary, igneous and metamorphic rocks.

The lower boundary of the lithosphere is fuzzy and is determined by a decrease in the viscosity of the medium, the speed of seismic waves, and an increase in thermal conductivity. The lithosphere covers the earth's crust and the upper part of the mantle several tens of kilometers thick to the asthenosphere, in which the plasticity of rocks changes. The main methods for determining the boundary between the upper boundary of the lithosphere and the asthenosphere are magnetotelluric and seismological.

The thickness of the lithosphere under the oceans ranges from 5 to 100 km (the maximum value is at the periphery of the oceans, the minimum is under the Mid-Ocean Ridges), under the continents - 25-200 km (the maximum is under ancient platforms, the minimum is under relatively young mountain ranges, volcanic arcs ). The structure of the lithosphere under the oceans and continents has significant differences. Under the continents in the structure of the earth's crust of the lithosphere, sedimentary, granite and basalt layers are distinguished, the thickness of which as a whole reaches 80 km. Beneath the oceans, the Earth's crust has repeatedly undergone partial melting processes during the formation of the oceanic crust. Therefore, it is depleted in fusible rare compounds, devoid of a granite layer, and its thickness is much less than that of the continental part of the earth's crust. The thickness of the asthenosphere (a layer of softened, pasty rocks) is about 100-150 km.

Formation of the atmosphere, hydrosphere and earth's crust

The formation occurred during the release of substances from the upper layer of the mantle of the young Earth. Currently, on the ocean floor in the middle ridges, the process of formation of the earth's crust continues, which is accompanied by the release of gases and small volumes of water. Oxygen is present in high concentrations in the composition of the modern earth's crust, followed by silicon and aluminum in percentage. Basically, the lithosphere is formed by compounds such as silicon dioxide, silicates, aluminosilicates. Crystalline substances of igneous origin took part in the formation of most of the lithosphere. They were formed during the cooling of magma that came to the surface of the Earth, which is in the bowels of the planet in a molten state.

In cold regions, the thickness of the lithosphere is the greatest, and in warm regions it is the smallest. The thickness of the lithosphere can increase with a general decrease in the heat flux density. The upper layer of the lithosphere is elastic, and the lower layer is plastic in terms of the nature of the reaction to constantly acting loads. In tectonically active areas of the lithosphere, horizons of reduced viscosity are distinguished, where seismic waves travel at a lower speed. According to scientists, according to these horizons, some layers “slip” in relation to others. This phenomenon is called stratification of the lithosphere. In the structure of the lithosphere, mobile areas (folded belts) and relatively stable areas (platforms) are distinguished. Blocks of the lithosphere (lithospheric plates) move along the relatively plastic asthenosphere, reaching sizes from 1 to 10 thousand kilometers in diameter. At present, the lithosphere is divided into seven main and a number of small plates. The boundaries separating the plates from each other are the zones of maximum volcanic and seismic activity.