How many lithospheric plates are there on earth? According to scientific research, scientists were able to establish that the lithosphere consists of

Together with part of the upper mantle, it consists of several very large blocks called lithospheric plates. Their thickness varies - from 60 to 100 km. Most plates include both continental and oceanic crust. There are 13 main plates, of which 7 are the largest: American, African, Indo-, Amur.

The plates lie on a plastic layer of the upper mantle (asthenosphere) and slowly move relative to each other at a speed of 1-6 cm per year. This fact was established by comparing photographs taken with artificial satellites Earth. They suggest that the configuration in the future may be completely different from the present one, since it is known that the American lithospheric plate is moving towards the Pacific, and the Eurasian plate is moving closer to the African, Indo-Australian, and also the Pacific. American and African lithospheric plates slowly disperse.

The forces that cause the divergence of lithospheric plates arise when the material of the mantle moves. Powerful upward flows of this substance push the plates apart, tearing apart the earth's crust, forming deep faults in it. Due to underwater outpourings of lavas, strata are formed along faults. By freezing, they seem to heal wounds - cracks. However, the stretching increases again, and ruptures occur again. So, gradually increasing, lithospheric plates diverge in different directions.

There are fault zones on land, but most of them are in the ocean ridges, where the earth's crust is thinner. The largest fault on land is located in the east. It stretches for 4000 km. The width of this fault is 80-120 km. Its outskirts are dotted with extinct and active ones.

Along other plate boundaries, plate collisions are observed. It happens in different ways. If plates, one of which has oceanic crust and the other continental, come closer together, then the lithospheric plate, covered by the sea, sinks under the continental one. In this case, arcs () or mountain ranges () appear. If two plates that have continental crust collide, the edges of these plates are crushed into folds of rock, and mountainous regions are formed. This is how they arose, for example, on the border of the Eurasian and Indo-Australian plates. The presence of mountainous areas in internal parts lithospheric plate indicates that once there was a boundary of two plates that were firmly welded together and turned into a single, larger lithospheric plate. Thus, we can draw a general conclusion: the boundaries of lithospheric plates are moving areas to which volcanoes are confined , zones, mountainous regions, mid-ocean ridges, deep-sea depressions and trenches. It is at the border of lithospheric plates that they are formed, the origin of which is associated with magmatism.

What do we know about the lithosphere?

Tectonic plates are large, stable sections of the Earth's crust that are components lithosphere. If we turn to tectonics, the science that studies lithospheric platforms, we learn that large areas earth's crust are limited on all sides by specific zones: volcanic, tectonic and seismic activity. It is at the junctions of neighboring plates that phenomena occur that, as a rule, have catastrophic consequences. These include both volcanic eruptions and earthquakes that are strong on the scale of seismic activity. In the process of studying the planet, plate tectonics played a very important role important role. Its significance can be compared to the discovery of DNA or the heliocentric concept in astronomy.

If we recall geometry, we can imagine that one point can be the point of contact between the boundaries of three or more plates. Studies of the tectonic structure of the earth's crust show that the most dangerous and rapidly collapsing are the junctions of four or more platforms. This formation is the most unstable.

The lithosphere is divided into two types of plates, different in their characteristics: continental and oceanic. It is worth highlighting the Pacific platform, composed of oceanic crust. Most others consist of what is called a block, where a continental plate is welded into an oceanic one.

The arrangement of the platforms shows that about 90% of the surface of our planet consists of 13 large, stable sections of the earth's crust. The remaining 10% falls on small formations.

Scientists have compiled a map of the largest tectonic plates:

• Australian;
• Arabian subcontinent;
• Antarctic;
• African;
• Hindustan;
• Eurasian;
• Nazca Plate;
• Plate Coconut;
• Pacific;
• North and South American platforms;
• Scotia Plate;
• Philippine plate.

From theory we know that the solid shell of the earth (lithosphere) consists not only of plates that form the relief of the planet’s surface, but also of the deep part - the mantle. Continental platforms have a thickness from 35 km (in flat areas) to 70 km (in mountain ranges). Scientists have proven that the slab is thickest in the Himalaya zone. Here the thickness of the platform reaches 90 km. The thinnest lithosphere is found in the ocean zone. Its thickness does not exceed 10 km, and in some areas this figure is 5 km. Based on information about the depth at which the earthquake epicenter is located and the speed of propagation of seismic waves, the thickness of sections of the earth's crust is calculated.

The process of formation of lithospheric plates

The lithosphere consists predominantly of crystalline substances formed as a result of the cooling of magma as it reaches the surface. The description of the platform structure indicates their heterogeneity. The process of formation of the earth's crust took place over a long period, and continues to this day. Through microcracks in the rock, molten liquid magma came to the surface, creating new fancy shapes. Its properties changed depending on the change in temperature, and new substances were formed. For this reason, minerals that are located at different depths differ in their characteristics.

The surface of the earth's crust depends on the influence of the hydrosphere and atmosphere. Weathering occurs constantly. Under the influence of this process, forms change, and minerals are crushed, changing their characteristics while maintaining the same chemical composition. As a result of weathering, the surface became looser, cracks and microdepressions appeared. In these places deposits appeared, which we know as soil.

Tectonic plate map

At first glance, the lithosphere appears to be stable. Its upper part is such, but the lower part, which is distinguished by viscosity and fluidity, is movable. The lithosphere is divided into certain number parts of the so-called tectonic plates. Scientists cannot say how many parts the earth's crust consists of, since in addition to large platforms, there are also smaller formations. The names of the largest slabs were given above. The process of formation of the earth's crust occurs constantly. We do not notice this, since these actions occur very slowly, but by comparing the results of observations for different periods, we can see how many centimeters per year the boundaries of the formations shift. For this reason, the tectonic map of the world is constantly updated.

Coconut tectonic plate

The Cocos platform is a typical representative of the oceanic parts of the earth's crust. It is located in the Pacific region. In the west, its border runs along the ridge of the East Pacific Rise, and in the east its border can be defined by a conventional line along the coast North America from California to the Isthmus of Panama. This plate is being pushed under the neighboring Caribbean Plate. This zone is characterized by high seismic activity.

Mexico suffers the most from earthquakes in this region. Among all the countries of America, it is on its territory that the most extinct and active volcanoes. The country postponed a large number of earthquakes with a magnitude greater than 8. The region is quite densely populated, so in addition to destruction, seismic activity also leads to a large number victims. Unlike Cocos, located in another part of the planet, the Australian and West Siberian platforms are stable.

Movement of tectonic plates

For a long time, scientists have been trying to figure out why one region of the planet has mountainous terrain and another is flat, and why earthquakes and volcanic eruptions occur. Various hypotheses were based primarily on the knowledge that was available. Only after the 50s of the twentieth century was it possible to study the earth's crust in more detail. We studied mountains formed at places where plates broke, chemical composition these plates, and also created maps of regions with tectonic activity.

In the study of tectonics, the hypothesis of the movements of lithospheric plates has occupied a special place. Back at the beginning of the twentieth century, German geophysicist A. Wegener put forward a bold theory about why they move. He carefully examined the outline of the western coast of Africa and east coast South America. Starting point in his research it was precisely the similarity of the outlines of these continents. He suggested that perhaps these continents were previously a single whole, and then a break occurred and parts of the Earth’s crust began to shift.

His research affected the processes of volcanism, stretching of the surface of the ocean floor, and the viscous-liquid structure of the globe. It was the works of A. Wegener that served as the basis for research conducted in the 60s of the last century. They became the foundation for the emergence of the theory of “lithospheric plate tectonics.”

This hypothesis described the Earth model as follows: tectonic platforms with a rigid structure and different weights, were placed on the plastic substance of the asthenosphere. They were in a very unstable state and were constantly moving. For a simpler understanding, we can draw an analogy with icebergs that constantly drift in ocean waters. Yes and tectonic structures, being on a plastic substance, constantly move. During displacements, the plates constantly collided, overlapped one another, and joints and zones of moving apart plates appeared. This process occurred due to differences in mass. In places of collisions, areas with increased tectonic activity were formed, mountains arose, earthquakes and volcanic eruptions occurred.

The rate of displacement was no more than 18 cm per year. Faults formed, into which magma entered from the deep layers of the lithosphere. For this reason, the rocks that make up oceanic platforms have different ages. But scientists have put forward an even more incredible theory. According to some representatives of the scientific world, magma came to the surface and gradually cooled, creating a new structure of the bottom, while the “excesses” of the earth’s crust, under the influence of plate drift, sank into the bowels of the earth and again turned into liquid magma. Be that as it may, continental movements continue to occur in our time, and for this reason new maps are being created to further study the process of drift of tectonic structures.

Lithospheric plates– large rigid blocks of the Earth’s lithosphere, bounded by seismically and tectonically active fault zones.

The plates, as a rule, are separated by deep faults and move through the viscous layer of the mantle relative to each other at a speed of 2-3 cm per year. Where continental plates converge, they collide and form mountain belts . When the continental and oceanic plates interact, the plate with the oceanic crust is pushed under the plate with the continental crust, resulting in the formation of deep-sea trenches and island arcs.

The movement of lithospheric plates is associated with the movement of matter in the mantle. In certain parts of the mantle there are powerful flows of heat and matter rising from its depths to the surface of the planet.

More than 90% of the Earth's surface is covered 13 -th largest lithospheric plates.

Rift– a huge fracture in the earth's crust, formed during its horizontal stretching (i.e., where the flows of heat and matter diverge). In rifts, magma outflows, new faults, horsts, and grabens arise. Mid-ocean ridges form.

First continental drift hypothesis (i.e. horizontal movement of the earth's crust) put forward at the beginning of the twentieth century A. Wegener. Created on its basis lithospheric theory t. According to this theory, the lithosphere is not a monolith, but consists of large and small 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 (platforms) and mobile areas (folded areas - geosynclines).

- powerful underwater mountain structures within the ocean floor, most often occupying a middle position. Near mid-ocean ridges, lithospheric plates move apart and young basaltic oceanic crust appears. The process is accompanied by intense volcanism and high seismicity.

Continental rift zones are, for example, the East African Rift System, the Baikal Rift System. Rifts, like mid-ocean ridges, are characterized by seismic activity and volcanism.

Plate tectonics– a hypothesis suggesting that the lithosphere is divided into large slabs, which move horizontally through the mantle. Near mid-ocean ridges, lithospheric plates move apart and grow due to material rising from the bowels of the Earth; in deep-sea trenches, one plate moves under another and is absorbed by the mantle. Fold structures are formed where plates collide.

Consists of many layers piled on top of each other. However, what we know best is the earth's crust and lithosphere. This is not surprising - after all, we not only live on them, but also draw from the depths most of the resources available to us. natural resources. But the upper shells of the Earth still preserve millions of years of history of our planet and the entire solar system.

These two concepts appear so often in the press and literature that they have entered the everyday vocabulary modern man. Both words are used to refer to the surface of the Earth or another planet - however, there is a difference between the concepts, based on two fundamental approaches: chemical and mechanical.

Chemical aspect - earth's crust

If you divide the Earth into layers based on differences in chemical composition, top layer the planet will have the earth's crust. This is a relatively thin shell, ending at a depth of 5 to 130 kilometers below sea level - the oceanic crust is thinner, and the continental crust, in mountainous areas, is thickest. Although 75% of the crust's mass is composed only of silicon and oxygen (not pure, bound in different substances), it has the greatest chemical diversity of all layers of the Earth.

The wealth of minerals also plays a role - various substances and mixtures created over billions of years of the planet’s history. The Earth's crust contains not only "native" minerals that were created by geological processes, but also massive organic heritage, such as oil and coal, as well as alien inclusions.

Physical aspect - lithosphere

Relying on physical characteristics Earth, such as hardness or elasticity, we will get a slightly different picture - the interior of the planet will be wrapped in a lithosphere (from the other Greek lithos, “rocky, hard” and “sphaira” sphere). It is much thicker than the earth's crust: the lithosphere extends up to 280 kilometers deep and even covers the upper solid part of the mantle!

The characteristics of this shell fully correspond to the name - it is the only solid layer of the Earth, besides the inner core. Strength, however, is relative - the Earth’s lithosphere is one of the most mobile in solar system, because of which the planet has already changed its appearance. But significant compression, curvature and other elastic changes require thousands of years, if not more.

• An interesting fact is that the planet may not have a surface crust. So, the surface is its hardened mantle; The planet closest to the Sun lost its crust a long time ago as a result of numerous collisions.

To summarize, the Earth's crust is the upper, chemically diverse part of the lithosphere, the hard shell of the Earth. Initially they had almost the same composition. But when the depths were affected only by the underlying asthenosphere and high temperatures, the hydrosphere, atmosphere, meteorite remains and living organisms actively participated in the formation of minerals on the surface.

Lithospheric plates

Another feature that distinguishes the Earth from other planets is the diversity of different types of landscapes on it. Of course, water also played an incredibly important role, which we will talk about a little later. But even the basic forms of the planetary landscape of our planet differ from the same Moon. The seas and mountains of our satellite are pits from bombardment by meteorites. And on Earth they were formed as a result of hundreds and thousands of millions of years of movement of lithospheric plates.

You've probably already heard about plates - these are huge stable fragments of the lithosphere that drift along the fluid asthenosphere, like broken ice on a river. However, there are two main differences between the lithosphere and ice:

• The gaps between the plates are small and are quickly closed due to the molten substance erupting from them, and the plates themselves are not destroyed by collisions.
• Unlike water, there is no constant flow, which could set a constant direction of movement for the continents.

So, driving force The drift of lithospheric plates is the convection of the asthenosphere, the main part of the mantle - hotter flows from the earth's core rise to the surface when cold ones fall back down. Considering that the continents differ in size, and the topography of their lower side mirrors the irregularities of the upper side, they also move unevenly and inconsistently.

Main plates

Over billions of years of movement of lithospheric plates, they repeatedly merged into supercontinents, after which they separated again. In the near future, in 200–300 million years, the formation of a supercontinent called Pangea Ultima is also expected. We recommend watching the video at the end of the article - it clearly shows how lithospheric plates have migrated over the past several hundred million years. In addition, the strength and activity of continental movement is determined by the internal heating of the Earth - the higher it is, the more the planet expands, and the faster and freer the lithospheric plates move. However, since the beginning of the Earth's history, its temperature and radius have been gradually decreasing.

• An interesting fact is that plate drift and geological activity do not necessarily have to be powered by the internal self-heating of the planet. For example, the satellite of Jupiter has many active volcanoes. But the energy for this is not provided by the satellite’s core, but by gravitational friction c, due to which Io’s interior heats up.

The boundaries of lithospheric plates are very arbitrary - some parts of the lithosphere sink under others, and some, like the Pacific plate, are completely hidden under water. Geologists today count 8 main plates that cover 90 percent of the entire Earth's area:

• Australian
• Antarctic
• African
• Eurasian
• Hindustan
• Pacific
• North American
• South American

Such a division appeared recently - for example, the Eurasian plate, 350 million years ago, consisted of separate parts, during the merger of which the Ural Mountains, one of the oldest on Earth, were formed. Scientists to this day continue to study faults and the ocean floor, discovering new plates and clarifying the boundaries of old ones.

Geological activity

Lithospheric plates move very slowly - they creep over each other at a speed of 1–6 cm/year, and move away by 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.

• An interesting fact is that 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 on Mars, the highest point on the planet - its height reaches 27 kilometers!

Oceanic and continental crust of the Earth

The interaction of plates also leads to the formation of two various types earth's crust - oceanic and continental. Since the oceans, as a rule, are the junctions of different lithospheric plates, their crust is constantly changing - being broken or absorbed by other plates. At the site of faults, direct contact occurs with the mantle, from where hot magma rises. Cooling under the influence of water, it creates thin layer from basalts - the main volcanic rock. Thus, the oceanic crust is completely renewed every 100 million years - the oldest areas that are in Pacific Ocean, reach a maximum age of 156–160 million years.

Important! The oceanic crust is not all of the earth’s crust that is under water, but only its young sections at the junction of continents. Part of the continental crust is under water, in the zone of stable lithospheric plates.

Age of oceanic crust (red corresponds to young crust, blue to old crust).

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's consider in general view geological structure Earth. The third planet beyond the distance from the Sun, Earth, has a radius of 6370 km, average density- 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 were 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 along the edges of tectonic plates the most large forms Earth's topography - mountain ranges with active volcanoes and deep-sea trenches.

Lithosphere problems

The intensive development of industry has led to the fact that man and the lithosphere in Lately began to get along extremely poorly with each other: the pollution of the lithosphere is acquiring catastrophic proportions. This happened due to an increase industrial waste in conjunction with household waste and used in agriculture fertilizers and pesticides, 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 have a negative impact on the main culprit of the problem - the person.