The lithosphere is the rocky shell of the Earth. From the Greek “lithos” - stone and “sphere” - 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 unclear and is determined by a sharp decrease in the viscosity of rocks, a change in the speed of propagation of seismic waves and an increase in the electrical conductivity of rocks. The thickness of the lithosphere on continents and under oceans varies and averages 25 - 200 and 5 - 100 km, respectively.

Let us consider in general terms the geological structure of the Earth. The third planet beyond the distance from the Sun, Earth, has a radius of 6370 km, an average density of 5.5 g/cm3 and consists of three shells - bark, mantle and and. The mantle and core are divided into internal and external parts.

The Earth's crust is the thin upper shell of the Earth, which is 40-80 km thick 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 have been able to establish that the lithosphere consists of:

• Oxygen – 49%;
• Silicon – 26%;
• Aluminum – 7%;
• Iron – 5%;
• Calcium – 4%
• The lithosphere contains many minerals, the most common being spar and quartz.

On continents, the crust is three-layered: sedimentary rocks cover granite rocks, and granite rocks overlie basaltic rocks. Under the oceans the crust is “oceanic”, of a two-layer type; sedimentary rocks simply lie on basalts, there is no granite layer. There is also a transitional type of the earth's crust (island-arc zones on the margins of the oceans and some areas on continents, for example the Black Sea).

The earth's crust is thickest in mountainous regions(under the Himalayas - over 75 km), the average - in the areas of the platforms (under the West Siberian Lowland - 35-40, within the borders 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 strip with a depth of up to 200 g and an average width of about 80 km, which, after a sharp steep bend of the bottom, turns into a continental slope (the slope varies from 15-17 to 20-30°). The slopes gradually level out and turn into abyssal plains (depths 3.7-6.0 km). The oceanic trenches have the greatest depths (9-11 km), the vast majority of which are located on the northern and western edges 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 a 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, derived from the name of the main rock elements Si (Latin: Silicium - silicon) and Al (Latin: 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 on 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 for 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 continent 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. Interestingly, the plates adjacent to it move in the opposite direction from it, so the largest fault on our planet is located here;
• Antarctic plate– consists of the continent of Antarctica and the nearby oceanic crust. Due to the fact that the plate is surrounded by mid-ocean ridges, the remaining continents are constantly moving away from it.

Movement of tectonic plates in the lithosphere

Lithospheric plates, connecting and separating, constantly change their outlines. 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 (on average about seven centimeters per year ).

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

When the oceanic and continental plates collide, the edge of the oceanic crust subducts under the continental crust, while on the other side of the oceanic plate its boundary diverges from the adjacent plate. The boundary along which the movement of lithospheres occurs is called the subduction zone, where the upper and subducting 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 compressed, as a result of which mountains are formed, and if magma also erupts, then volcanoes.

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

Lithosphere problems

The intensive development of industry has led to the fact that man and the lithosphere have recently begun to get along extremely poorly with each other: the 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 is generated per person per year, including 50 kg of hard-to-degrade 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-cleaning of the earth’s crust occurs very slowly, and therefore harmful substances gradually accumulate and, over time, negatively affect the main culprit of the problem - humans.

Lithosphere. Earth's crust. 4.5 billion years ago, the Earth was a ball consisting of only gases. Gradually, heavy metals such as iron and nickel sank to the center and became denser. Light rocks and minerals floated to the surface, cooled and solidified.

Internal structure of the Earth.

It is customary to divide the body of the Earth into three main parts – lithosphere(earth's crust), mantle And core.

The core is the center of the Earth , the average radius of which is about 3500 km (16.2% of the Earth's volume). It is believed to consist of iron mixed with silicon and nickel. The outer part of the core is in a molten state (5000 ° C), the inner part is apparently solid (subcore). The movement of matter in the core creates a magnetic field on Earth that protects the planet from cosmic radiation.

The core is replaced mantle , which extends almost 3000 km (83% of the Earth's volume). It is believed to be hard, but at the same time plastic and hot. The mantle consists of three layers: Golitsyn layer, Guttenberg layer and substrate. The upper part of the mantle, called magma , contains a layer with reduced viscosity, density and hardness - the asthenosphere, on which sections of the earth's surface are balanced. The boundary between the mantle and core is called the Guttenberg layer.

Lithosphere

Lithosphere - the upper shell of the “solid” Earth, including the earth’s crust and the upper part of the underlying upper mantle of the Earth.

Earth's crust – the upper shell of the “solid” Earth. The thickness of the earth's crust ranges from 5 km (under the oceans) to 75 km (under the continents). The earth's crust is heterogeneous. It distinguishes 3 layers – sedimentary, granite, basalt. Granite and basalt layers are so named because they contain rocks similar in physical properties to granite and basalt.

Compound earth's crust: oxygen (49%), silicon (26%), aluminum (7%), iron (5%), calcium (4%); the most common minerals are feldspar and quartz. The boundary between the earth's crust and mantle is called Moho surface .

Distinguish continental And oceanic the earth's crust. Oceanic different from continental (mainland) absence of granite layer and significantly less powerful (from 5 to 10 km). Thickness continental crust on the plains is 35-45 km, in the mountains 70-80 km. At the border of continents and oceans, in the areas of islands, the thickness of the earth's crust is 15-30 km, the granite layer pinches out.

The position of layers in the continental crust indicates different times of its formation . The basalt layer is the oldest, younger than it is the granite layer, and the youngest is the upper, sedimentary layer, which is still developing today. Each layer of crust was formed over a long period of geological time.

Lithospheric plates

The earth's crust is in constant motion. The first hypothesis about continental drift(i.e. horizontal movement of the earth's crust) put forward at the beginning of the twentieth century A. Wegener. Created on its basis plate theory . According to this theory, the lithosphere is not a monolith, but consists of seven large and several smaller plates “floating” on the asthenosphere. The boundary areas between lithospheric plates are called seismic belts - these are the most “restless” areas of the planet.

The earth's crust is divided into stable and mobile areas.

Stable areas of the earth's crust - platforms- are formed on the site of geosynclines that have lost mobility. The platform consists of a crystalline basement and sedimentary cover. Depending on the age of the foundation, ancient (Precambrian) and young (Paleozoic, Mesozoic) platforms are distinguished. At the base of all continents lie ancient platforms.

Mobile, highly dissected areas of the earth's surface are called geosynclines ( folded areas ). In their development there are two stages : at the first stage, the earth’s crust experiences subsidence, sedimentary rocks accumulate and metamorphose. Then the earth's crust begins to rise, and the rocks are crushed into folds. There were several eras of intense mountain building on Earth: Baikal, Caledonian, Hercynian, Mesozoic, Cenozoic. In accordance with this, various folding areas are distinguished.

§ 13. The Earth's crust and lithosphere - the rocky shells of the Earth

Remember

• What inner shells of the Earth stand out? Which shell is the thinnest? Which shell is the largest? How are granite and basalt formed? What is their appearance?

The earth's crust and its structure. The Earth's crust is the outermost rocky shell of the Earth. It consists of igneous, metamorphic and sedimentary rocks. On continents and under oceans it is structured differently. Therefore, a distinction is made between the continental crust and the oceanic crust (Fig. 42).

They differ from each other in thickness and structure. The continental crust is thicker - 35-40 km, under high mountains - up to 75 km. It consists of three layers. The top layer is sedimentary. It is composed of sedimentary rocks. The second and third layers consist of a variety of igneous and metamorphic rocks. The second, middle layer is conventionally called “granite”, and the third, lower layer is called “basalt”.

Rice. 42. Structure of the continental and oceanic crust

The oceanic crust is much thinner - from 0.5 to 12 km - and consists of two layers. The upper, sedimentary layer is composed of sediments covering the bottom of modern seas and oceans. The bottom layer consists of solidified basaltic lavas and is called basalt.

Continental and oceanic crust on the surface of the Earth form giant steps of different heights. The higher levels are the continents rising above sea level, the lower ones are the bottom of the World Ocean.

Lithosphere. As you already know, under the earth's crust is the mantle. The rocks that make it up differ from the rocks of the earth's crust: they are denser and heavier. The earth's crust is firmly attached to the upper mantle, forming a single whole with it - the lithosphere (from the Greek "cast" - stone) (Fig. 43).

Rice. 43. Relationship between the lithosphere and the earth's crust

Consider the relationship between the earth's crust and lithosphere. Compare their thickness.

Remember why there is a layer of plastic material in the mantle. Determine from the drawing the depth at which it lies.

Find in the figure the boundaries of separation and the boundaries of collision of lithospheric plates.

Lithosphere is the solid shell of the Earth, consisting of the earth's crust and the upper part of the mantle.

Under the lithosphere there is a heated plastic layer of the mantle. The lithosphere seems to float on it. At the same time, it moves in different directions: it rises, falls and slides horizontally. Together with the lithosphere, the earth's crust - the outer part of the lithosphere - also moves.

Rice. 44. Main lithospheric plates

The lithosphere is not monolithic. It is divided by faults into separate blocks - lithospheric plates (Fig. 44). In total, there are seven very large lithospheric plates and several smaller ones on Earth. Lithospheric plates interact with each other in different ways. Moving along the plastic layer of the mantle, they move apart in some places and collide with each other in others.

Questions and tasks

1. What two types of earth's crust do you know?
2. How is the lithosphere different from the earth's crust?
3. What lithospheric plate do you live on?

The Earth's crust, along with the upper part of the mantle, are the main components of the lithosphere (the solid shell of the Earth). The earth's crust is characterized by large irregularities on land, and in some places its thickness can reach seventy kilometers. We are talking primarily about mountain ranges. Scientists calculate the thickness based on the speed of propagation of seismic waves.

The difference in the structure of the earth's crust had a direct impact on the formation of continents, their existence and relative location. Researchers are confident that several million years ago our planet looked completely different, and the movement of lithospheric plates gradually formed the current location of the continents. For the first time, the famous geographer from Germany Weneger Alfred was able to formulate a scientific theory about continental drift.

It is known that for quite a long time man could not accurately determine the content of chemical substances in the earth’s crust. However, with the development of science, it became known that the earth’s crust contains the most oxygen at a depth of up to sixteen kilometers.

Oxygen makes up about fifty percent of the total weight. Aluminum ranks second - about seven to eight percent. Potassium, calcium, magnesium, sodium in general make up just over ten percent of the total mass.

It turns out that in ancient times attempts were also made to study the geological structure of the earth's crust, although the methods were quite primitive when compared with today. For example, Diodorus Siculus wrote that “the workers were able to find very brilliant veins thanks to the properties of the earth.” It was about gold.

The movement of the earth's crust is of considerable interest. In particular, several million years ago India was part of the African continent. However, the movement of the earth’s crust led to the fact that it simply broke off and, after completing a small arc, “crashed” into Eurasia. The collision led to the formation of the Himalayas. By the way, some scientists are of the opinion that perhaps another piece will break off from Africa.

Continental crust

Its overall thickness varies greatly depending on elevation changes, bark structure and other factors. The continental crust is usually divided into several layers:

• The uppermost one is presented in the form of sedimentary rocks. It can reach fifteen kilometers;
• Just below there is a granite layer. It received its name due to the fact that the rocks composing it are similar in many of their qualities to granite. The average thickness of this layer varies from five to fifteen kilometers;
• The thickness of the basalt layer varies even more (it ranges from 10 to 35 kilometers).

That is, the average thickness of the continental (or mainland) crust can reach 30-70 kilometers.

Oceanic crust

The absence of a granite layer is the main difference between the oceanic crust. It is for this reason that its thickness is small and varies from six to fifteen kilometers. Another significant difference is the high basalt content. Scientists were able to prove that most of the rocks of the oceanic crust were formed a very long time ago - about three billion years ago.

Modern experts believe that it was the oceanic crust that appeared first. Then folds began to appear in it (modern mountain ranges). Their formation occurred under the influence of processes that were observed inside the earth. Thus, the thickness of the crust gradually increased, which led to the formation of the continental crust - this is how the first continents appeared.

The rocky shell of the Earth - the earth's crust - is firmly attached to the upper mantle and forms a single whole with it - the lithosphere. The study of the earth's crust and lithosphere allows scientists to explain the processes occurring on the Earth's surface and anticipate changes in the appearance of our planet in the future.

Structure of the earth's crust

The earth's crust, consisting of igneous, metamorphic and sedimentary rocks, on continents and under oceans has different thickness and structure. It is customary to distinguish three layers in the continental crust. The upper layer is sedimentary, in which sedimentary rocks predominate. The two lower layers are conventionally called granite and basalt. The granite layer consists primarily of granite and metamorphic rocks. The basalt layer is made of denser rocks, comparable in density to basalts. Oceanic crust has two layers. In it, the upper layer - sedimentary - has a small thickness, the lower layer - basalt - consists of basalt rocks, and the granite layer is absent.

The thickness of the continental crust under the plains is 30–50 kilometers, under the mountains – up to 75 kilometers. The oceanic crust is much thinner, its thickness is from 5 to 10 kilometers. There is a crust on other terrestrial planets, on the Moon and on many satellites of the giant planets of the Solar System. But only the Earth has two types of crust: continental and oceanic. On other planets, in most cases it consists of basalts.

Lithosphere

origin of name

The lithosphere is the solid shell of the Earth. It consists of the earth's crust, as well as the upper part of the mantle. The term “lithosphere” was proposed in 1916 by J. Burrell and until the 60s. twentieth century was synonymous with the earth's crust. Then it was proven that the lithosphere also includes the upper layers of the mantle up to several tens of kilometers thick. This concept itself comes from two Greek words, the first of which means “stone”, and the second - “ball” or “sphere”.

The lithosphere is the solid shell of the Earth, which includes the earth's crust and part of the upper mantle. The thickness of the lithosphere on land on average ranges from 35-40 km (in flat areas) to 70 km (in mountainous areas). Under the ancient mountains the thickness of the earth's crust is even greater: for example, under the Himalayas its thickness reaches 90 km. The Earth's crust under the oceans is also the lithosphere. Here it is the thinnest - on average about 7-10 km, and in some areas of the Pacific Ocean - up to 5 km.

General characteristics of the lithosphere

In the structure of the lithosphere, mobile regions (folded belts) and relatively stable platforms are distinguished.

The thickness of the lithosphere varies from 5 to 200 km. Under the continents, the thickness of the lithosphere varies from 25 km under young mountains, volcanic arcs and continental rift zones to 200 or more kilometers under the shields of ancient platforms. Under the oceans, the lithosphere is thinner and reaches a minimum of 5 km under the mid-ocean ridges; on the periphery of the ocean, gradually thickening, reaching a thickness of 100 km. The lithosphere reaches its greatest thickness in the least heated areas, and its least in the hottest ones.

Based on the response to long-term loads in the lithosphere, it is customary to distinguish the upper elastic and lower plastic layers. Also, at different levels in tectonically active areas of the lithosphere, horizons of relatively low viscosity can be traced, which are characterized by low velocities of seismic waves. Geologists do not exclude the possibility of some layers slipping relative to others along these horizons. This phenomenon is called lithospheric layering.

The largest elements of the lithosphere are lithospheric plates with dimensions of 1–10 thousand km in diameter. Currently, the lithosphere is divided into seven main and several minor plates. The boundaries between plates are drawn along the zones of greatest seismic and volcanic activity.

Lithosphere boundaries

The upper part of the lithosphere borders the atmosphere and hydrosphere. The atmosphere, hydrosphere and upper layer of the lithosphere are in a strong relationship and partially penetrate each other.

The lower boundary of the lithosphere is located above the asthenosphere - a layer of reduced hardness, strength and viscosity in the upper mantle of the Earth. The boundary between the lithosphere and asthenosphere is not sharp - the transition of the lithosphere into the asthenosphere is characterized by a decrease in viscosity, a change in the speed of seismic waves and an increase in electrical conductivity. All these changes occur due to an increase in temperature and partial melting of the substance. Hence the main methods for determining the lower boundary of the lithosphere - seismological and magnetotelluric.

Lithospheric plates

Despite the fact that ninety percent of the lithosphere consists of fourteen lithospheric plates, many disagree with this statement and draw their own tectonic maps, saying that there are seven large and about ten small ones. This division is quite arbitrary, since with the development of science, scientists either identify new plates, or recognize certain boundaries as non-existent, especially when it comes to small plates.

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

• The Pacific is the largest plate on 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 for 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 continent 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. Interestingly, the plates adjacent to it move in the opposite direction from it, so the largest fault on our planet is located here;
• Antarctic plate – consists of the continent of Antarctica and nearby oceanic crust. Due to the fact that the plate is surrounded by mid-ocean ridges, the remaining continents are constantly moving away from it.

Geological activity

Lithospheric plates move very slowly - they creep over each other at a speed of 1–6 cm/year, and move away at a maximum of 10–18 cm/year. But it is the interaction between the continents that creates the geological activity of the Earth, noticeable on the surface - volcanic eruptions, earthquakes and the formation of mountains always occur in the contact zones of lithospheric plates.

However, there are exceptions - so-called hot spots, which can also exist deep in lithospheric plates. In them, molten flows of asthenosphere matter break upward, melting the lithosphere, which leads to increased volcanic activity and regular earthquakes. Most often, this happens near those places where one lithospheric plate creeps onto another - the lower, depressed part of the plate sinks into the Earth’s mantle, thereby increasing the pressure of magma on the upper plate. However, now scientists are inclined to believe that the “drowned” parts of the lithosphere are melting, increasing pressure in the depths of the mantle and thereby creating upward flows. This can explain the anomalous distance of some hot spots from tectonic faults.

Interesting fact– shield volcanoes, characterized by their flat shape, often form in hot spots. They erupt many times, growing due to flowing lava. This is also a typical alien volcano format. The most famous of them is the Olympus volcano on Mars, the highest point on the planet - its height reaches 27 kilometers!

Lithosphere and crust of the Earth in astronomy

Studying the Earth rarely happens just like that - often the searches of scientists have a very clear practical goal. This is especially relevant in the study of the lithosphere: at the junctions of lithospheric plates, whole placers of ores and valuable minerals come out, for the extraction of which in another place it would be necessary to drill a many-kilometer well. Many data about the earth's crust were obtained thanks to the oil field - in the search for oil and gas deposits, scientists learned a lot about the internal mechanisms of our planet.

Therefore, it is not for nothing that astronomers strive for a detailed study of the crust of other planets - its outlines and appearance reveal the entire internal structure of a space object. For example, on Mars, volcanoes are very high and erupt repeatedly, while on Earth they constantly migrate, appearing periodically in new places. This indicates that on Mars there is no such active movement of lithospheric plates as on Earth. Together with the absence of a magnetic field, the stability of the lithosphere became the main evidence of the stopping of the red planet’s core and the gradual cooling of its interior.