The earth's crust consists of lithospheric plates... Each lithospheric plate is characterized by uninterrupted movement. People do not notice such movements, because they are extremely slow.

Causes and consequences of the movement of the earth's crust

We all know that our planet consists of three parts: the earth's core, the earth's mantle, and the earth's crust. Many are concentrated in the core of our planet chemical substances which constantly enter into chemical reactions with each other.

As a result of such chemical, radioactive and thermal reactions, vibrations occur in the lithosphere. Due to this, the earth's crust can move vertically and horizontally.

The history of studying the movements of the earth's crust

Tectonic movements were studied by scientists of the Antiquity era. The ancient Greek geographer Strabo was the first to put forward the theory that certain areas of land are systematically rising. The famous Russian scientist Lomonosov called the movements of the earth's crust as long-term and insensitive earthquakes.

However, a more detailed study of the processes of movement of the earth's crust began at the end of the 19th century. The American geologist Gilbert classified the movements of the earth's crust into two main types: those that create mountains (orogenic) and those that create continents (epeirogenic). The study of the movement of the earth's crust was carried out by both foreign and domestic scientists, in particular: V. Belousov, Yu. Kosygin, M. Tetyaev, E. Haarman, G. Shtille.

Types of movement of the earth's crust

There are two types of tectonic movements: vertical and horizontal. Vertical movements are called radial. Such movements are expressed in the systematic raising (or lowering) of lithospheric plates. Often, radial movements of the earth's crust occur as a consequence of strong earthquakes.

Horizontal movements represent the displacement of lithospheric plates. According to many modern scientists, all existing continents were formed as a result of horizontal displacement of lithospheric plates.

The meaning of the movement of the earth's crust for humans

The movements of the earth's crust today threaten the lives of many people. A prime example is the Italian city of Venice. The city is located on an area of ​​the lithospheric plate, which is sinking at a high speed.

Every year, the city sinks under water - a transgression process takes place (long-term offensive sea ​​water on land). In history, there are cases when, due to the movement of the earth's crust, cities and towns went under water, and after a while they rose again (the process of regression).

The earth's crust only seems motionless, absolutely stable. In fact, it makes continuous and varied movements. Some of them occur very slowly and are not perceived by the human senses, others, for example earthquakes, are of a landslide, destructive nature. What titanic forces set in motion the earth's crust?

The inner forces of the Earth, the source of their origin. It is known that the temperature at the boundary of the mantle and lithosphere exceeds 1500 ° C. At this temperature, matter must either melt or turn into gas. During the transition solids in a liquid or gaseous state, their volume must increase. However, this does not happen, since the overheated rocks are under pressure from the overlying layers of the lithosphere. The effect of a "steam boiler" arises, when matter tending to expand presses on the lithosphere, setting it in motion together with the earth's crust. Moreover, the higher the temperature, the stronger the pressure and the more actively the lithosphere moves. Particularly strong centers of pressure arise in those places of the upper mantle where radioactive elements are concentrated, the decay of which heats the constituent rocks to even higher temperatures. The movements of the earth's crust under the influence of the internal forces of the Earth are called tectonic. These movements are subdivided into oscillatory, folding and breaking.

Oscillatory motion. These movements occur very slowly, imperceptibly for a person, therefore they are also called age-old or epeirogenic. In some places, the earth's crust rises, in others it falls. At the same time, raising is often replaced by lowering, and vice versa. It is possible to trace these movements only by those "traces" that remain after them on the earth's surface. For example, on the Mediterranean coast, near Naples, there are the ruins of the Temple of Serapis, the columns of which are eaten away by sea molluscs at an altitude of 5.5 m above modern sea level. This serves as unconditional proof that the temple, built in the 4th century, went to the bottom of the sea, and then it was raised. Now this piece of land is sinking again. Often on the coasts of the seas above their present level there are steps - sea terraces, once created by the sea surf. On the sites of these steps, you can find the remains of marine organisms... This indicates that the terraces were once the bottom of the sea, and then the coast rose and the sea retreated.

The sinking of the earth's crust below 0 m above sea level is accompanied by the onset of the sea - transgression, and raising - by his retreat - regression. Currently, in Europe, uplifts occur in Iceland, Greenland, on the Scandinavian Peninsula. Observations have established that the area of ​​the Gulf of Bothnia rises at a rate of 2 cm per year, that is, by 2 m per century. Simultaneously with this, the territory of Holland, southern England, northern Italy, the Black Sea lowland, and the coast of the Kara Sea subsided. The formation of sea bays in estuarine sections of rivers - estuaries (lips) and estuaries - serves as a sign of the sinking of the sea coasts.

With the uplifting of the earth's crust and the retreat of the sea, the seabed, composed of sedimentary rocks, turns out to be dry land. This is how extensive marine (primary) plains: for example, West Siberian, Turanian, North Siberian, Amazonian (Fig. 20).

Rice. twenty. The structure of primary, or marine, stratal plains

Folding movements. In those cases when rock layers are sufficiently plastic, under the action of internal forces, they are crushed into folds. When the pressure is directed vertically, the rocks are displaced, and if in the horizontal plane, they are compressed into folds. The shape of the folds is very diverse. When the bend of the fold is directed downward, it is called a syncline, upward - an anticline (Fig. 21). Folds are formed at great depths, that is, at high temperatures and high pressure, and then, under the action of internal forces, they can be lifted. This is how folded mountains Caucasian, Alps, Himalayas, Andes, etc. (Fig. 22). In such mountains, folds are easy to observe where they are exposed and emerge to the surface.

Rice. 21. Synclinal (1) and anticlinal (2) folds

Rice. 22. Folded mountains

Bursting movements. If the rocks are not strong enough to withstand the action of internal forces, cracks form in the earth's crust - faults and a vertical displacement of rocks occurs. The subsided areas are called grabens, and those who have risen - by handfuls(fig. 23). The alternation of horsts and grabens creates blocky (revived) mountains. Examples of such mountains are: Altai, Sayan, Verkhoyansk ridge, Appalachians in North America and many others. The revived mountains differ from folded ones both in their internal structure and in outward appearance- morphology. The slopes of these mountains are often steep, the valleys, like the watersheds, are wide and flat. Rock layers are always offset from each other.

Rice. 23. Revived folded-block mountains

The sunken areas in these mountains, grabens, are sometimes filled with water, and then deep lakes are formed: for example, Baikal and Teletskoye in Russia, Tanganyika and Nyasa in Africa.

Movement of the earth's crust associated with internal forces in the earth's crust and the Earth's mantle is called tectonic.Branch of geology, which studies these movements, as well as the modern structure and development of the structural elements of the earth's crust is called tectonics.

The largest structural elements of the earth's crust are platforms, geosynclines, and oceanic plates.

Platforms are huge, relatively immobile, stable sections of the earth's crust. The platforms are characterized by a two-tiered structure. The lower, more ancient stage (crystalline basement) is composed of sedimentary rocks, crumpled into folds, or igneous rocks that have undergone metamorphism. The upper layer (platform cover) consists almost entirely of horizontally deposited sedimentary rocks.

Classical examples of platform regions are the East European (Russian) platform, West Siberian, Turanian and Siberian, which occupy vast areas. The North African, Indian and other platforms are also known in the world.

The thickness of the upper tier of platforms reaches 1.5-2.0 km and more. An area of ​​the earth's crust where the upper layer is absent and the crystalline basement goes directly to the outer surface is called shields (Baltic, Voronezh, Ukrainian, etc.).

Within the platforms, tectonic movements are expressed in the form of slow vertical oscillatory movements of the earth's crust. Volcanism and seismic movements (earthquakes) are poorly developed or completely absent. The relief of the platforms is closely related to the deep structure of the earth's crust and is expressed mainly in the form of vast plains (lowlands).

Geosynclines are the most mobile, linearly elongated sections of the earth's crust, framing platforms. On early stages of their development, they are characterized by intense immersions, and on the final ones - by impulsive uplifts.

Geosynclinal areas are the Alps, Carpathians, Crimea, Caucasus, Pamir, Himalayas, the Pacific coast strip and other mountain-folded structures. All these areas are characterized by active tectonic movements, high seismicity and volcanism. In the same areas, powerful magmatic processes are actively developing with the formation of effusive lava sheets and flows and intrusive bodies (stocks, etc.). In Northern Eurasia, the Kuril-Kamchatka zone is the most mobile and seismically active region.

Oceanic plates are the largest tectonic structures of the earth's crust and form the basis of the ocean floor. In contrast to continents, oceanic plates have not been sufficiently studied, which is associated with significant difficulties in obtaining geological information about their structure and composition of matter.

There are the following main tectonic movements of the earth's crust:

- oscillatory;

- folded;

- discontinuous.

Oscillatory tectonic movements are manifested in the form of slow, uneven uplifts and subsidence of individual sections of the earth's crust. The oscillatory nature of their movement consists in a change in its sign: an uplift in some geological epochs is replaced by a sinking in others. Tectonic movements of this type occur continuously and everywhere. There are no tectonically immobile sections of the earth's crust on the earth's surface - some rise, others fall.

According to the time of their manifestation, oscillatory movements are subdivided into modern (last 5-7 thousand years), newest (Neogene and Quaternary) and movements of past geological periods.

Modern oscillatory movements are studied at special test sites with the help of repeated geodetic observations by the method of high-precision leveling. More ancient oscillatory movements are judged by the alternation of marine and continental deposits and a number of other signs.

The rate of raising or lowering of individual parts of the earth's crust varies widely and can reach 10-20 mm per year or more. For example, the southern coast of the North Sea in Holland sinks by 5-7 mm per year. Holland is saved from the invasion of the sea on land (transgression) by dams up to 15 m high, which are constantly being built up. At the same time, in closely located areas in northern Sweden in the coastal zone, there are modern uplifts of the earth's crust up to 10-12 mm per year. In these areas, part of the port facilities turned out to be remote from the sea due to its retreat from the coast (regression).

Geodetic observations carried out in the regions of the Black, Caspian and Azov Seas showed that the Caspian lowland, the eastern coast of the Akhzov Sea, the depressions in the mouths of the Terek and Kuban rivers, the northwestern coast of the Black Sea descend at a rate of 2-4 mm per year. As a result, there is a transgression in these areas, i.e. the advance of the sea on land. On the contrary, slow uplifts are experienced by land areas on the coast of the Baltic Sea, as well as, for example, Kursk regions, Altai mountain regions, Sayan, Novaya Zemlya, etc. Other areas continue to sink Moscow (3.7 mm / year), St. Petersburg (3 , 6 mm / year), etc.

The highest intensity of oscillatory movements of the earth's crust is noted in the geosynclinal regions, and the lowest in the platform regions.

The geological significance of oscillatory movements is enormous. They determine the conditions of sedimentation, the position of the boundaries between land and sea, shallowing or intensification of the erosion activity of rivers. Oscillatory movements occurring in recent times (Neogene-Quaternary period) have had a decisive influence on the formation of the modern relief of the Earth.

Oscillatory (modern) movements must be taken into account in the construction of hydraulic structures such as reservoirs, dams, shipping canals, cities by the sea, etc.

Folded tectonic movements. In geosynclinal areas, tectonic movements can significantly disrupt the original form of bedding of rocks. Violation of the forms of the primary bedding of rocks caused by the tectonic movement of the earth's crust are called dislocations. They are subdivided into folded and discontinuous.

Folded dislocations can be in the form of elongated linear folds or be expressed in a general inclination of the layers to one side.

The anticline is an elongated linear fold, convex upward. Older layers lie in the core (center) of the anticline, while folds on the wings are younger.

The syncline is a fold similar to the anticline, but convex downward. In the core of the syncline, there are younger layers than on the wings.

Monocline - is a stratum of rock layers, inclined to one side at the same angle.

Flexura is a knee-like fold with a stepped bend of the layers.

The orientation of the layers at monoclinal bedding is characterized by the strike line, the line of incidence and the angle of incidence.

Discontinuous tectonic movements. They lead to a violation of the continuity of rocks and their rupture along any surface. Breaks in rocks occur when stresses in the earth's crust exceed the ultimate strength of rocks.

Fault dislocations include faults, reverse faults, thrust faults, strike-slip faults, grabens, and horsts.

Reset- formed as a result of the subsidence of one part of the strata relative to the other.

Uplift - is formed when one part of the strata rises relative to another.

Thrust - displacement of rock blocks along the inclined surface of the fault.

Shear - displacement of rock blocks in the horizontal direction.

Graben is an area of ​​the earth's crust bounded by tectonic ruptures (faults) and lowered along them relative to adjacent areas.

An example of large grabens is the depression of Lake Baikal and the valley of the Rhine River.

Horst is an uplifted area of ​​the earth's crust, bounded by faults or uplifts.

Fracture tectonic movements are often accompanied by the formation of various tectonic cracks, which are characterized by the capture of thick rock strata, the consistency of orientation, the presence of traces of displacements, and other signs.

Deep faults that divide the earth's crust into separate large blocks are a special type of discontinuous tectonic faults. Deep faults are hundreds and thousands of kilometers long and more than 300 kilometers deep. The zones of their development are associated with modern intense earthquakes and active volcanic activity (for example, the faults of the Kuril-Kamchatka zone).

Tectonic movements that cause the formation of folds and breaks are called mountain building.

The importance of tectonic conditions for construction. The tectonic features of the area have a very significant impact on the choice of the location of various buildings and structures, their layout, conditions for the construction and operation of construction projects.

Areas with horizontal undisturbed layers are favorable for construction. The presence of dislocations and a developed system of tectonic fractures significantly impairs the engineering and geological conditions of the construction area. In particular, during the construction development of a territory with active tectonic activity, it is necessary to take into account the intense fracturing and fragmentation of rocks, which reduces their strength and stability, a sharp increase in seismic activity in places where rupture dislocations develop, and other features.

The intensity of vibrational movements of the earth's crust must be taken into account in the construction of protective dams, as well as linear structures of considerable length (canals, railways, etc.).

The movements of the earth's crust

The surface of our planet is constantly changing. Even during his life, a person notices how the surrounding nature is changing: the banks of rivers are crumbling, a meadow is overgrown, new forms of relief appear, often the person himself participates in their emergence. Then, if they were created by his hands, such relief forms are called anthropogenic. However, most of these changes are due to external, exogenous forces Earth. Observe the same internal, endogenous forces the planet is not communicated directly to everyone. It must be for the best - these internal forces capable of moving continents are very grandiose and at times destructive. And having escaped to the surface once, internal forces can awaken a dormant volcano, can immediately change the surrounding relief with a strong earthquake, these forces are much more powerful in their manifestations than wind, flowing water, moving glaciers. And at a time when the external forces of the Earth for years and centuries have been forming small and medium forms of relief, grinding stones, grinding mountains; the internal forces of the Earth, even over millions of years, these mountains erect and move individual blocks of the lithosphere thousands of kilometers away. So it's even good that most of these internal processes are hidden from us by the huge thickness of the earth's crust.

So the earth's crust is moving. It usually moves very slowly together with separate blocks of the lithosphere - lithospheric plates. The speed of this movement does not exceed a few centimeters per year. Sometimes, especially near the boundaries of the lithospheric plates, the earth's crust can move rapidly, resulting in an earthquake. Scientists believe that the reason for the movement of the earth's crust is the movement of the mantle. Recall that the bowels of the Earth are very hot, and the mantle is a special viscous substance. With depth, its temperature rises and already in the core it reaches several thousand degrees. With heating, the density of a substance decreases due to its expansion. It is fair to assume that in the interior of the planet, the hotter and less dense mantle slowly tends to rise up, and the upper, colder layers sink down until they are heated again. This process lasts for millions of years and will continue until the bowels of the Earth cool down. The circulation of the mantle carries with it a relatively thin one (by the standards of the planet).

Fast movements are chaotic, they do not have a specific direction, and we will talk about them in the topic "earthquakes".

The slow movements of the earth's crust can be divided into horizontal and vertical.

Horizontal movements- this is, first of all, the movements of lithospheric plates. When the plates collide, mountains are formed, at the place of their divergence, faults are formed in the earth's crust. Lakes Baikal, Nyasa and Tanganyika are striking examples of such faults. Mid-ocean ridges also form on the ocean floor at fault locations.

Vertical movement- these are the processes of raising and lowering areas of land or the bottom of the sea. Vertical movements are often the result of horizontal collisions of two lithospheric plates. This is how the highest mountains in the world, the Himalayas, grow by several millimeters a year. You can observe how the ancient ancient cities for thousands of years were raised above sea level, and their seaside structures were far from the coastline. Probably, the myth of Atlantis, too, may have its real preconditions; at least the monuments of ancient civilizations flooded by the Mediterranean Sea have been discovered by modern archaeologists. The reason for this is the subsidence and uplift of the earth's crust at the border of the Eurasian and African lithospheric plates in the Mediterranean region. Experiencing the uplifts and shores of Scandinavia. However, it is likely that the crust rises here due to the fact that several thousand years ago it was covered by a huge glacier. Now the ice age is long over, and the surface of the Earth, which experienced tremendous pressure in this place, is still slowly straightening back. What can not be said about the shores of neighboring Holland, which, on the contrary, has to struggle century after century with the advancing sea. Only a system of dams and special structures protects a significant part of the Netherlands from flooding. It is no coincidence that there is a saying that God created the sea, and the Dutch created the shores.

The peculiarity of the occurrence of rocks on the Earth helps to study the direction of movement of the earth's crust. The fact is that rocks usually occur in layers, so that the entire earth's crust resembles a kind of layer cake. And the higher the layer is, the later it should have formed. Geologists usually judge the time of formation of a layer by the fossilized remains of organisms that are found in it. But sometimes the layers are uneven, they can wrinkle into folds and even change their location. Such movements can be confusing, but they can also tell about the movements of the earth's crust that she experienced in this place.

If one of the fragments of the observed area seems to have moved or moved down relative to the other, then this phenomenon is called discharge... When there is an obvious uplift of one of the sections, then this uplift... Sometimes the uplift is so strong that the uplifted area seems to fall on the adjacent one, this will manifest itself in the repetition of identical layers, first in the lower, and then in the area that has advanced on it. This phenomenon is called thrust.
If one of the fragments was raised above the others, this is horst, and if he seemed to have fallen down - this graben.
Rocks, especially in the mountains, are often crumpled into folds. A fold that goes up is called anticline, and bent down - syncline.

The earth's crust only seems motionless, absolutely stable. In fact, it makes continuous and varied movements. Some of them occur very slowly and are not perceived by the human senses, others, for example earthquakes, are of a landslide, destructive nature. What titanic forces set in motion the earth's crust?

The inner forces of the Earth, the source of their origin. It is known that the temperature at the boundary of the mantle and lithosphere exceeds 1500 ° C. At this temperature, matter must either melt or turn into gas. During the transition of solids into a liquid or gaseous state, their volume should increase. However, this does not happen, since the overheated rocks are under pressure from the overlying layers of the lithosphere. The effect of a "steam boiler" arises, when matter tending to expand presses on the lithosphere, setting it in motion together with the earth's crust. Moreover, the higher the temperature, the stronger the pressure and the more actively the lithosphere moves. Particularly strong centers of pressure arise in those places of the upper mantle where radioactive elements are concentrated, the decay of which heats the constituent rocks to even higher temperatures. The movements of the earth's crust under the influence of the internal forces of the Earth are called tectonic. These movements are subdivided into oscillatory, folding and breaking.

Oscillatory motion. These movements occur very slowly, imperceptibly for a person, therefore they are also called age-old or epeirogenic. In some places, the earth's crust rises, in others it falls. At the same time, raising is often replaced by lowering, and vice versa. It is possible to trace these movements only by those "traces" that remain after them on the earth's surface. For example, on the Mediterranean coast, near Naples, there are the ruins of the Temple of Serapis, the columns of which are eaten away by sea molluscs at an altitude of 5.5 m above modern sea level. This serves as unconditional proof that the temple, built in the 4th century, went to the bottom of the sea, and then it was raised. Now this piece of land is sinking again. Often on the coasts of the seas above their present level there are steps - sea terraces, once created by the sea surf. Remains of marine organisms can be found on the sites of these steps. This indicates that the terraces were once the bottom of the sea, and then the coast rose and the sea retreated.

The sinking of the earth's crust below 0 m above sea level is accompanied by the onset of the sea - transgression, and raising - by his retreat - regression. Currently, in Europe, uplifts occur in Iceland, Greenland, on the Scandinavian Peninsula. Observations have established that the area of ​​the Gulf of Bothnia rises at a rate of 2 cm per year, that is, by 2 m per century. Simultaneously with this, the territory of Holland, southern England, northern Italy, the Black Sea lowland, and the coast of the Kara Sea subsided. The formation of sea bays in estuarine sections of rivers - estuaries (lips) and estuaries - serves as a sign of the sinking of the sea coasts.

With the uplifting of the earth's crust and the retreat of the sea, the seabed, composed of sedimentary rocks, turns out to be dry land. This is how extensive marine (primary) plains: for example, West Siberian, Turanian, North Siberian, Amazonian (Fig. 20).

Rice. twenty. The structure of primary, or marine, stratal plains

Folding movements. In those cases when rock layers are sufficiently plastic, under the action of internal forces, they are crushed into folds. When the pressure is directed vertically, the rocks are displaced, and if in the horizontal plane, they are compressed into folds. The shape of the folds is very diverse. When the bend of the fold is directed downward, it is called a syncline, upward - an anticline (Fig. 21). Folds are formed at great depths, that is, at high temperatures and high pressure, and then, under the action of internal forces, they can be lifted. This is how folded mountains Caucasian, Alps, Himalayas, Andes, etc. (Fig. 22). In such mountains, folds are easy to observe where they are exposed and emerge to the surface.

Rice. 21. Synclinal (1) and anticlinal (2) folds

Rice. 22. Folded mountains

Bursting movements. If the rocks are not strong enough to withstand the action of internal forces, cracks form in the earth's crust - faults and a vertical displacement of rocks occurs. The subsided areas are called grabens, and those who have risen - by handfuls(fig. 23). The alternation of horsts and grabens creates blocky (revived) mountains. Examples of such mountains are: Altai, Sayan, Verkhoyansk ridge, Appalachians in North America and many others. Revived mountains differ from folded ones both in internal structure and in appearance - morphology. The slopes of these mountains are often steep, the valleys, like the watersheds, are wide and flat. Rock layers are always offset from each other.