What tectonic structures are plates made of? Tectonic plates are moving

Perhaps some readers have heard discussions about the identification of the planet Earth with some kind of living superorganism. In particular, it is usually argued that the Earth itself is capable of controlling the processes occurring on it and with it, in addition to being responsible for the existence of life. It's about the Gaia theory. Gaia, in turn, was the ancient Greek goddess of the Earth. By and large, it doesn’t matter at all whether life on the planet will be the result of the “conscious” activity of the planet itself as an organism, the confluence of a number of “random” circumstances, or the consequence of the existence of a universal law on zones favorable for life.

One way or another, life exists on the planet, and it is likely that in order for it to arise, many coincidences or assumptions of different nature were necessary. One of which, of course, is the geology of the planet.

Tectonic or lithospheric plates are responsible for geological activity on Earth.

Lithospheric plates of our planet

For a more visual representation, you can see the 3D model:

It is believed that the movement of plates can affect the existence of life on the planet. Thus, geological activity is characteristic not only of the Earth, but also of the celestial bodies of the solar system. However, the Earth is unique not in the presence of earthquakes, which are even on or Mars (which are called moonquakes and marsquakes, respectively), but rather in the presence of developed and strong tectonic activity.

seismometer on the moon

Also, the Earth is the only planet in the solar system, the outer crust of which is broken into plates. Tectonic plates reach tens of kilometers in thickness.

Power (thickness) of the Earth's layers

They tried to describe the reason for the movement of tectonic plates and continents by expanding the radius of the Earth. This is a very beautiful hypothesis, which is unlikely to have anything in common with reality.

Models by Christoph Hilgenberg showing an expanding Earth

In fact, the main reason for the active movement of lithospheric plates is thermal convection. When heated, the lower layers become lighter and float, while the upper ones cool down away from the heat source and, becoming heavier, sink down. Convection can be observed when the wind moves, when in some parts of the Earth the air heats up, while in others it cools at the point of contact and movement is created. And if we, in fact, cannot observe the wind and air currents (it is only possible to feel them), then we can look at the phenomenon of convection in a lava lamp.

Of course, the oil in a lava lamp is not igneous rocks in the mantle, but we should not forget about such a factor as time. Namely, the fact that on the scale of seconds (in which, in fact, an individual person lives and thinks), the substance of the Earth's mantle is solid, but on the scale of years and decades, this substance acquires liquid properties. Perhaps it also depends on the size of the object in question.

Comparison of convection in the Earth's mantle and in lava lamps

In part, this also indicates that the life and speed of perception of the surrounding space is most preferable precisely on the scale of seconds (or maximum minutes). Whereas global and cosmic processes must exist on a slower time scale. It turns out that in addition to the need for the existence of favorable zones for life, there is a need for a certain time window of a certain scale. But we will talk about this later.

It will be interesting to look at the phenomenon of convection in the mantle from the results of modern research by Schmelling, which display cold (blue) and hot (red) regions in the Earth's mantle.

Convective movement in the Earth's mantle, color represents temperature. The z-coordinate displays the depth to the boundary of the mantle with the core (Gutenberg gap), and the x-coordinate displays the part of the circumference of the core (or Gutenberg gap)

This image clearly shows the convective movement inside the mantle. The movement caused by convection leads to a number of processes, namely the movement of tectonic plates and its consequences.

Movement between two plates can obviously be either convergent and colliding, or divergent to form a fault. Convergence or convergence leads to subduction (one plate crawls under another) or collision (collapse of two plates with the formation of mountain ranges). The divergence or divergence leads to spreading (moving plates apart with the formation of ridges in the oceans) and rifting (with the formation of a break in the continental crust). There is also a third type of plate movement - transform, when the plates move along the fault. One way or another, it is worth talking about the nature of plate movement separately, especially given the large amount of terminology.

The speed of movement of the Earth's tectonic plates, and the types of movement of these plates at their boundaries

It is also worth mentioning the thickness of the plates, or their power. The earth's crust is continental and oceanic; the oceanic crust reaches 5–15 km, while the continental crust reaches 15–80 km. This suggests that, compared with the mantle, the earth's crust is extremely "thin". Therefore, the movement of plates and their stable state, even on a scale of seconds, is extremely difficult to imagine (if at all possible). And so the movement of tectonic plates in itself can cause extreme surprise with its impossibility of structure, complexity of implementation and seeming unreliability. One way or another, nothing better is given to us.

The result of plate movement, in addition to existing life (although this has not been proven), is earthquakes and volcanism. If volcanoes are distributed not only at the boundaries of plates, then the map of earthquakes over the past decades clearly outlines the boundaries of tectonic plates, and the dependence here is apparently direct. The ring of volcanoes around the Pacific Plate is called the Pacific Ring of Fire.

Map of recent earthquakes and active volcanoes

What will the movement of tectonic plates on Earth lead to in the future, and what will come of it, we will tell in subsequent materials.

Last week, the public was stirred by the news that the Crimean peninsula is moving towards Russia, not only thanks to the political will of the population, but also according to the laws of nature. What are lithospheric plates and on which of them is Russia territorially located? What makes them move and where? Which territories still want to "join" Russia, and which ones threaten to "escape" to the USA?

"And we're going somewhere"

Yes, we are all going somewhere. While you are reading these lines, you are slowly moving: if you are in Eurasia, then to the east at a speed of about 2-3 centimeters per year, if in North America, then at the same speed to the west, and if somewhere at the bottom of the Pacific Ocean (how did you get there?), then it takes you to the northwest by 10 centimeters a year.

If you sit back in your chair and wait about 250 million years, you will find yourself on a new supercontinent that will unite all the earth's land - on the mainland Pangea Ultima, named so in memory of the ancient supercontinent Pangea, which existed just 250 million years ago.

Therefore, the news that "Crimea is moving" can hardly be called news. Firstly, because Crimea, together with Russia, Ukraine, Siberia and the European Union, is part of the Eurasian lithospheric plate, and all of them have been moving together in one direction for the last hundred million years. However, Crimea is also part of the so-called Mediterranean mobile belt, it is located on the Scythian plate, and most of the European part of Russia (including the city of St. Petersburg) - on the East European platform.

And this is where confusion often arises. The fact is that in addition to huge sections of the lithosphere, such as the Eurasian or North American plates, there are completely different smaller "tiles". If very conditionally, then the earth's crust is composed of continental lithospheric plates. They themselves consist of ancient and very stable platforms.and mountain building zones (ancient and modern). And already the platforms themselves are divided into slabs - smaller sections of the crust, consisting of two "layers" - the foundation and the cover, and shields - "single-layer" outcrops.

The cover of these non-lithospheric plates consists of sedimentary rocks (for example, limestone, composed of many shells of marine animals that lived in the prehistoric ocean above the surface of Crimea) or igneous rocks (thrown from volcanoes and solidified lava masses). A fslab foundations and shields most often consist of very old rocks, mainly of metamorphic origin. This is the name given to igneous and sedimentary rocks that have sunk into the depths of the earth's crust, where, under the influence of high temperatures and enormous pressure, various changes occur with them.

In other words, most of Russia (with the exception of Chukotka and Transbaikalia) is located on the Eurasian lithospheric plate. However, its territory is "divided" between the West Siberian plate, the Aldan shield, the Siberian and East European platforms and the Scythian plate.

Probably, the director of the Institute of Applied Astronomy (IPA RAS), Doctor of Physical and Mathematical Sciences Alexander Ipatov, said about the movement of the last two plates. And later, in an interview with Indicator, he clarified: "We are engaged in observations that allow us to determine the direction of movement of the plates of the earth's crust. The plate on which the Simeiz station is located moves at a speed of 29 millimeters per year to the northeast, that is, to where Russia And the plate where Peter is located is moving, one might say, towards Iran, to the south-southwest."However, this is not such a discovery, because this movement has been around for several decades, and it itself began back in the Cenozoic era.

Wegener's theory was received with skepticism - mainly because he could not offer a satisfactory mechanism to explain the movement of the continents. He believed that the continents move, breaking through the earth's crust, like icebreakers through ice, due to the centrifugal force from the rotation of the Earth and tidal forces. His opponents said that the continents-"icebreakers" in the process of movement would change their appearance beyond recognition, and centrifugal and tidal forces are too weak to serve as a "motor" for them. One critic calculated that if the tidal force were strong enough to move the continents so fast (Wegener estimated their speed at 250 centimeters per year), it would stop the rotation of the Earth in less than a year.

By the end of the 1930s, the theory of continental drift was rejected as unscientific, but by the middle of the 20th century it had to be returned to: mid-ocean ridges were discovered and it turned out that new crust was continuously forming in the zone of these ridges, due to which the continents were "moving apart" . Geophysicists have studied the magnetization of rocks along the mid-ocean ridges and found "bands" with multidirectional magnetization.

It turned out that the new oceanic crust "records" the state of the Earth's magnetic field at the time of formation, and scientists have received an excellent "ruler" to measure the speed of this conveyor. So, in the 1960s, the theory of continental drift returned for the second time, for good. And this time, scientists were able to understand what moves the continents.

Ice floes in the boiling ocean

"Imagine an ocean where ice floes float, that is, there is water in it, there is ice, and, let's say, wooden rafts are also frozen into some ice floes. Ice is lithospheric plates, rafts are continents, and they float in the substance of the mantle," explains Corresponding Member of the Russian Academy of Sciences Valery Trubitsyn, chief researcher at the Institute of Physics of the Earth named after O.Yu. Schmidt.

Back in the 1960s, he put forward the theory of the structure of giant planets, and at the end of the 20th century he began to create a mathematically based theory of continental tectonics.

The intermediate layer between the lithosphere and the hot iron core in the center of the Earth - the mantle - consists of silicate rocks. The temperature in it varies from 500 degrees Celsius in the upper part to 4000 degrees Celsius at the border of the core. Therefore, from a depth of 100 kilometers, where the temperature is already more than 1300 degrees, the mantle substance behaves like a very thick resin and flows at a speed of 5-10 centimeters per year, says Trubitsyn.

As a result, in the mantle, as in a pot of boiling water, convective cells appear - areas where hot matter rises from one edge, and cooled down from the other.

"There are about eight of these large cells in the mantle and many more small ones," the scientist says. Mid-ocean ridges (for example, in the center of the Atlantic) are the place where the material of the mantle rises to the surface and where new crust is born. In addition, there are subduction zones, places where a plate begins to "creep" under the neighboring one and sinks down into the mantle. Subduction zones are, for example, the western coast of South America. This is where the most powerful earthquakes occur.

“In this way, the plates take part in the convective circulation of the mantle substance, which temporarily becomes solid while on the surface. Plunging into the mantle, the plate substance heats up and softens again,” explains the geophysicist.

In addition, separate jets of matter rise to the surface from the mantle - plumes, and these jets have every chance to destroy humanity. After all, it is mantle plumes that are the cause of the appearance of supervolcanoes (see). Such points are in no way connected with lithospheric plates and can remain in place even when the plates move. When the plume exits, a giant volcano arises. There are many such volcanoes, they are in Hawaii, in Iceland, a similar example is the Yellowstone caldera. Supervolcanoes can generate eruptions thousands of times more powerful than most ordinary volcanoes like Vesuvius or Etna.

"250 million years ago, such a volcano on the territory of modern Siberia killed almost all life, only the ancestors of dinosaurs survived," says Trubitsyn.

Agreed - dispersed

Lithospheric plates consist of relatively heavy and thin basaltic oceanic crust and lighter, but much thicker continents. A plate with a continent and oceanic crust "frozen" around it can move forward, while the heavy oceanic crust sinks under its neighbor. But when continents collide, they can no longer sink under each other.

For example, about 60 million years ago, the Indian plate broke away from what later became Africa and went north, and about 45 million years ago it met with the Eurasian plate, the Himalayas, the highest mountains on Earth, grew at the point of collision.

The movement of the plates will sooner or later bring all the continents into one, as leaves converge into one island in a whirlpool. In the history of the Earth, the continents have united and broken up approximately four to six times. The last supercontinent Pangea existed 250 million years ago, before it was the supercontinent Rodinia, 900 million years ago, before it - two more. "And already, it seems, the unification of the new continent will soon begin," the scientist clarifies.

He explains that the continents act as a thermal insulator, the mantle beneath them begins to heat up, updrafts occur, and therefore the supercontinents break apart again after a while.

America will "take away" Chukotka

Large lithospheric plates are drawn in textbooks, anyone can name them: Antarctic plate, Eurasian, North American, South American, Indian, Australian, Pacific. But at the boundaries between the plates there is a real chaos of many microplates.

For example, the boundary between the North American Plate and the Eurasian Plate does not run along the Bering Strait at all, but much to the west, along the Chersky Ridge. Chukotka thus turns out to be part of the North American Plate. At the same time, Kamchatka is partly located in the zone of the Okhotsk microplate, and partly in the zone of the Bering Sea microplate. And Primorye is located on the hypothetical Amur Plate, the western edge of which rests on Baikal.

Now the eastern edge of the Eurasian plate and the western edge of the North American plate are "spinning" like gears: America is turning counterclockwise, and Eurasia is turning clockwise. As a result, Chukotka may finally come off "along the seam", and in this case, a giant circular seam may appear on Earth, which will pass through the Atlantic, the Indian, Pacific and Arctic Oceans (where it is still closed). And Chukotka itself will continue to move "in the orbit" of North America.

Speedometer for the lithosphere

Wegener's theory has been resurrected, not least because scientists have the ability to accurately measure the displacement of the continents. Now satellite navigation systems are used for this, but there are other methods. All of them are needed to build a single international coordinate system - the International Terrestrial Reference Frame (ITRF).

One of these methods is very long baseline radio interferometry (VLBI). Its essence lies in simultaneous observations with the help of several radio telescopes in different parts of the Earth. The difference in signal acquisition time makes it possible to determine offsets with high accuracy. Two other ways to measure speed are laser ranging observations using satellites and Doppler measurements. All these observations, including with the help of GPS, are carried out at hundreds of stations, all these data are brought together, and as a result, we get a picture of continental drift.

For example, the Crimean Simeiz, where a laser sounding station is located, as well as a satellite station for determining coordinates, "travels" to the northeast (in azimuth about 65 degrees) at a speed of about 26.8 millimeters per year. Zvenigorod, near Moscow, is moving about a millimeter a year faster (27.8 millimeters a year) and keeps its course to the east - about 77 degrees. And, say, the Hawaiian volcano Mauna Loa is moving northwest twice as fast - 72.3 millimeters per year.

Lithospheric plates can also be deformed, and their parts can "live their own lives", especially at the boundaries. Although the scale of their independence is much more modest. For example, Crimea is still moving independently to the northeast at a speed of 0.9 millimeters per year (and at the same time growing by 1.8 millimeters), and Zvenigorod is moving somewhere to the southeast at the same speed (and down - by 0 .2 millimeters per year).

Trubitsyn says that this independence is partly explained by the "personal history" of different parts of the continents: the main parts of the continents, the platforms, may be fragments of ancient lithospheric plates that "merged" with their neighbors. For example, the Ural Range is one of the seams. Platforms are relatively rigid, but parts around them can deform and move at will.

tectonic fault lithospheric geomagnetic

Beginning with the Early Proterozoic, the rate of movement of lithospheric plates consistently decreased from 50 cm/yr to its current value of about 5 cm/yr.

The decrease in the average speed of plate movement will continue further, up to the moment when, due to an increase in the power of oceanic plates and their friction against each other, it will not stop at all. But this will happen, apparently, only after 1-1.5 billion years.

To determine the velocities of the movement of lithospheric plates, data on the location of banded magnetic anomalies on the ocean floor are usually used. These anomalies, as has now been established, appear in the rift zones of the oceans due to the magnetization of the basalt erupted on them by the magnetic field that existed on Earth at the time of the basalt outpouring.

But, as you know, the geomagnetic field from time to time changed direction to the exact opposite. This led to the fact that basalts that erupted during different periods of geomagnetic field reversals turned out to be magnetized in opposite directions.

But due to the expansion of the ocean floor in the rift zones of the mid-ocean ridges, the older basalts always turn out to be moved to greater distances from these zones, and together with the ocean floor, the ancient magnetic field of the Earth “frozen” into the basalts also moves away from them.

Rice.

The expansion of the oceanic crust together with differently magnetized basalts usually develops strictly symmetrically on both sides of the rift fault. Therefore, the magnetic anomalies associated with them are also located symmetrically along both slopes of the mid-ocean ridges and the abyssal basins surrounding them. Such anomalies can now be used to determine the age of the ocean floor and its expansion rate in rift zones. However, for this it is necessary to know the age of individual reversals of the Earth's magnetic field and compare these reversals with the magnetic anomalies observed on the ocean floor.

The age of magnetic reversals was determined from detailed paleomagnetic studies of well-dated sequences of basaltic sheets and sedimentary rocks of the continents and ocean floor basalts. As a result of comparing the geomagnetic time scale obtained in this way with magnetic anomalies on the ocean floor, it was possible to determine the age of the oceanic crust in most of the waters of the World Ocean. All oceanic plates that formed earlier than the Late Jurassic have already subsided into the mantle under modern or ancient zones of plate underthrust, and, consequently, no magnetic anomalies older than 150 million years have been preserved on the ocean floor.

The above conclusions of the theory make it possible to quantitatively calculate the motion parameters at the beginning of two adjacent plates, and then for the third, taken in tandem with one of the previous ones. In this way, one can gradually involve the main of the identified lithospheric plates in the calculation and determine the mutual displacements of all plates on the Earth's surface. Abroad, such calculations were performed by J. Minster and his colleagues, and in Russia by S.A. Ushakov and Yu.I. Galushkin. It turned out that the ocean floor is moving apart with maximum speed in the southeastern part of the Pacific Ocean (near Easter Island). In this place, up to 18 cm of new oceanic crust grows annually. In terms of geological scale, this is a lot, since only in 1 million years a strip of a young bottom up to 180 km wide is formed in this way, while approximately 360 km3 of basalt lavas are poured out at each kilometer of the rift zone in the same time! According to the same calculations, Australia is moving away from Antarctica at a rate of about 7 cm/year, and South America is moving away from Africa at a rate of about 4 cm/year. The pushing away of North America from Europe is slower - 2-2.3 cm/year. The Red Sea expands even more slowly - by 1.5 cm/year (correspondingly, there is less basalt outflow here - only 30 km3 per linear kilometer of the Red Sea rift in 1 million years). On the other hand, the rate of "collision" between India and Asia reaches 5 cm/year, which explains the intense neotectonic deformations developing before our eyes and the growth of the mountain systems of the Hindu Kush, the Pamirs and the Himalayas. These deformations create a high level of seismic activity in the entire region (the tectonic impact of the collision of India with Asia affects far beyond the plate collision zone itself, extending all the way to Lake Baikal and the regions of the Baikal-Amur Mainline). The deformations of the Greater and Lesser Caucasus are caused by the pressure of the Arabian Plate on this region of Eurasia, however, the rate of convergence of the plates here is much less - only 1.5-2 cm / year. Therefore, the seismic activity of the region is also less here.

Modern geodetic methods, including space geodesy, high-precision laser measurements and other methods, have established the speed of movement of lithospheric plates and it has been proved that oceanic plates move faster than those in the structure of which the continent is included, and the thicker the continental lithosphere, the lower the speed of the plate movement.

• 1)_The first hypothesis arose in the second half of the 18th century and was called the uplift hypothesis. It was proposed by M. V. Lomonosov, German scientists A. von Humboldt and L. von Buch, Scot J. Hutton. The essence of the hypothesis is as follows - mountain uplifts are caused by the rise of molten magma from the depths of the Earth, which on its way had a pushing effect on the surrounding layers, leading to the formation of folds, abysses of various sizes. Lomonosov was the first to distinguish two types of tectonic movements - slow and fast, causing earthquakes.
• 2) In the middle of the 19th century, this hypothesis was replaced by the contraction hypothesis of the French scientist Elie de Beaumont. It was based on the cosmogonic hypothesis of Kant and Laplace about the origin of the Earth as an initially hot body with subsequent gradual cooling. This process led to a decrease in the volume of the Earth, and as a result, the Earth's crust was compressed, and folded mountain structures arose similar to giant "wrinkles".
• 3) In the middle of the 19th century, the Englishman D. Airy and the priest from Calcutta D. Pratt discovered a pattern in the positions of gravity anomalies - high in the mountains, the anomalies turned out to be negative, i.e., a mass deficit was detected, and in the oceans the anomalies were positive. To explain this phenomenon, a hypothesis was proposed, according to which the earth's crust floats on a heavier and more viscous substrate and is in isostatic equilibrium, which is disturbed by the action of external radial forces.
• 4) The cosmogonic hypothesis of Kant-Laplace was replaced by the hypothesis of O. Yu. Schmidt about the initial solid, cold and homogeneous state of the Earth. There was a need for a different approach in explaining the formation of the earth's crust. Such a hypothesis was proposed by V. V. Belousov. It's called radio migration. The essence of this hypothesis:
• 1. The main energy factor is radioactivity. The heating of the Earth with subsequent compaction of matter occurred due to the heat of radioactive decay. Radioactive elements at the initial stages of the Earth's development were distributed evenly, and therefore the heating was strong and ubiquitous.
• 2. Heating of the primary substance and its compaction led to the separation of magma or its differentiation into basalt and granite. The latter concentrated radioactive elements. As a lighter granitic magma “floated up” to the upper part of the Earth, while the basalt magma sank down. At the same time, there was also a temperature difference.

Modern geotectonic hypotheses are developed using the ideas of mobilism. This idea is based on the concept of the predominance of horizontal movements in the tectonic movements of the earth's crust.

• 5) For the first time, to explain the mechanism and sequence of geotectonic processes, the German scientist A. Wegener proposed the hypothesis of horizontal continental drift.
• 1. The similarity of the outlines of the coasts of the Atlantic Ocean, especially in the southern hemisphere (near South America and Africa).
• 2. Similarity of the geological structure of the continents (coincidence of some regional tectonic strikes, similarity in composition and age of rocks, etc.).

hypothesis of lithospheric plate tectonics or new global tectonics. The main points of this hypothesis are:

• 1. The earth's crust with the upper part of the mantle forms the lithosphere, which is underlain by the plastic asthenosphere. The lithosphere is divided into large blocks (plates). The boundaries of the plates are rift zones, deep-water trenches, which are adjacent to faults that penetrate deep into the mantle - these are the Benioff-Zavaritsky zones, as well as zones of modern seismic activity.
• 2. Lithospheric plates move horizontally. This movement is determined by two main processes - pushing apart plates or spreading, submersion of one plate under another - subduction or thrusting of one plate onto another - obduction.
• 3. Basalts from the mantle periodically enter the pull apart zone. Evidence of the separation is provided by strip magnetic anomalies in basalts.
• 4. In the regions of island arcs, zones of accumulation of sources of deep-focus earthquakes are distinguished, which reflect zones of subsidence of a plate with basaltic oceanic crust under the continental crust, i.e., these zones reflect subduction zones. In these zones, due to crushing and melting, part of the material sinks, while the other part penetrates into the continent in the form of volcanoes and intrusions, and thereby the thickness of the continental crust increases.

Plate tectonics is a modern geological theory about the movement of the lithosphere. According to this theory, global tectonic processes are based on horizontal movement of relatively integral blocks of the lithosphere - lithospheric plates. Thus, plate tectonics considers the movements and interactions of lithospheric plates. Alfred Wegener first suggested horizontal movement of crustal blocks in the 1920s as part of the “continental drift” hypothesis, but this hypothesis did not receive support at that time. Only in the 1960s, studies of the ocean floor provided indisputable evidence of the horizontal movement of plates and the processes of expansion of the oceans due to the formation (spreading) of the oceanic crust. The revival of ideas about the predominant role of horizontal movements occurred within the framework of the "mobilistic" direction, the development of which led to the development of the modern theory of plate tectonics. The main provisions of plate tectonics were formulated in 1967-68 by a group of American geophysicists - W. J. Morgan, C. Le Pichon, J. Oliver, J. Isaacs, L. Sykes in the development of earlier (1961-62) ideas of American scientists G. Hess and R. Digts on the expansion (spreading) of the ocean floor. one). The upper stone part of the planet is divided into two shells, which differ significantly in rheological properties: a rigid and brittle lithosphere and an underlying plastic and mobile asthenosphere. 2). The lithosphere is divided into plates, constantly moving along the surface of the plastic asthenosphere. The lithosphere is divided into 8 large plates, dozens of medium plates and many small ones. Between the large and medium slabs there are belts composed of a mosaic of small crustal slabs. 3). There are three types of relative plate movements: divergence (divergence), convergence (convergence) and shear movements. 4). The volume of oceanic crust absorbed in subduction zones is equal to the volume of crust formed in spreading zones. This provision emphasizes the opinion about the constancy of the volume of the Earth. 5). The main cause of plate movement is mantle convection, caused by mantle heat and gravity currents.

The source of energy for these currents is the temperature difference between the central regions of the Earth and the temperature of its near-surface parts. At the same time, the main part of the endogenous heat is released at the boundary of the core and mantle during the process of deep differentiation, which determines the decay of the primary chondrite substance, during which the metal part rushes to the center, increasing the core of the planet, and the silicate part is concentrated in the mantle, where it further undergoes differentiation. 6). Plate movements obey the laws of spherical geometry and can be described on the basis of Euler's theorem. Euler's rotation theorem states that any rotation of three-dimensional space has an axis. Thus, rotation can be described by three parameters: the coordinates of the rotation axis (for example, its latitude and longitude) and the angle of rotation.

Geographical consequences of the movement of Lith plates (Seismic activity increases, faults form, ridges appear, and so on). In the theory of plate tectonics, the key position is occupied by the concept of the geodynamic setting - a characteristic geological structure with a certain ratio of plates. In the same geodynamic setting, the same type of tectonic, magmatic, seismic, and geochemical processes occur.

Lithospheric plates- large rigid blocks of the Earth's lithosphere, limited by seismically and tectonically active fault zones.

The plates, as a rule, are separated by deep faults and move along the viscous layer of the mantle relative to each other at a rate of 2-3 cm per year. Where continental plates collide, they form mountain belts . When the continental and oceanic plates interact, the plate with the oceanic crust moves 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 separate parts of the mantle, there are powerful flows of heat and matter rising from its depths to the surface of the planet.

Over 90% of the Earth's surface is covered 13 the 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 the rifts there is an outpouring of magma, new faults, horsts, grabens appear. Mid-ocean ridges are forming.

First continental drift hypothesis (i.e. the horizontal movement of the earth's crust) put forward at the beginning of the twentieth century A. Wegener. On its basis, created theory of lithospheric plates m. According to this theory, the lithosphere is not a monolith, but consists of large and small plates, "floating" on the asthenosphere. The boundary regions 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 sections (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 basalt 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 plates that move along the mantle in a horizontal direction. Near mid-ocean ridges, lithospheric plates move apart and build up due to matter rising from the bowels of the Earth; in deep-sea trenches, one plate moves under another and is absorbed by the mantle. In places where plates collide, folded structures are formed.