Modern tectonic movements

contemporary movements earth's crust, uplifts, subsidences, shifts of the earth's crust, occurring at the present time or occurring several hundred years ago. Identified by geodetic data (re-leveling, triangulation, trilateration), hydrographic (level gauge) and geological and geomorphological observations, by comparing old and new maps, aerial photographs different years, according to historical and archaeological materials. Methods of astronomical space geodesy and geophysical methods (seismological, tilt-measuring, etc.) are being developed. Some researchers refer to S. t. d. the movements that have taken place in the course of historical time. There are modern movements of different frequency ranges (from seismic waves to secular movements), vertical and horizontal solar waves, and so on. They arise as a result of endogenous causes, lunisolar tides in the “solid” Earth, periodic and non-periodic processes in the atmosphere and hydrosphere, and also as a result of human activity.

The velocities of the vertical component of S. t. d. within the plain-platform areas are usually measured 0.1-4 mm/year, but in the centers of the Pleistocene ice sheet (Fennoscandia, the northern part North America, the island of Svalbard) and on the periphery of modern glaciation (Greenland) reach 5-20 mm/year. In areas of active mountain building (the Cordillera, the Caucasus, the Carpathians, and the Tien Shan), the mountain ranges are sharply differentiated in accordance with the geological structures; speeds here reach 5-15 mm/year(for vertical components) and 10-30 mm/year(for horizontal). In seismic and volcanic regions, the velocities of S. t.d. during periods of activation increase by several orders of magnitude.

The study of structural engineering is necessary for large-scale industrial and civil construction (cities, ports, hydroelectric power stations, reservoirs), exploitation of deposits of coal, oil, gas, groundwater; data are used in the development of earthquake prediction methods, volcanic eruptions and etc.

The study of vertical struc- ture is being carried out in many countries (the USSR, Japan, Canada, the USA, and Finland), and a map of the vertical struc- tures of Eastern Europe has been published. On a global scale, cooperation is carried out by the International Commission for the Study of S. etc. See also Neotectonics.

A. A. Nikonov.

Big soviet encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what "Modern tectonic movements" are in other dictionaries:

- ... Wikipedia

Movements of the earth's crust caused by processes taking place in its interior (convective movements in the mantle, excited by the thermal energy of decay radioactive elements, and the gravitational differentiation of the mantle substance in combination with the action of a force ... ... Geographic Encyclopedia

tectonic movements- Movements of the outer solid shell of the Earth, occurring under the influence of endogenous forces (there are secular and modern movements of the earth's crust). Syn.: movements of the earth's crust ... Geography Dictionary

Mechanical movements of the earth's crust caused by forces that act in the earth's crust and mainly in the earth's mantle (see Earth's mantle), leading to deformation of the rocks that make up the crust. Etc., as a rule, are associated with a change in the chemical ... ...

Tectonic movements that occurred during the Neogene and Anthropogenic periods geological history Earth. As a result of these movements, the main features were formed modern relief. See also Oscillatory motions of the earth ... ... Great Soviet Encyclopedia

crustal movements- Movements of the outer solid shell of the Earth, occurring under the influence of endogenous forces (there are secular and modern movements of the earth's crust). Syn.: tectonic movements… Geography Dictionary

Manifested in historical time and manifested in modern era. They are expressed in the subsidence and uplift of sections of the earth's crust, in the formation of faults and displacements along them, as well as in the formation of folded structures. D. t. s. lend themselves to a number of ... ... Geological Encyclopedia

Tangential movements of the earth's crust, movements occurring in a direction parallel (tangential) earth's surface. They are opposed to vertical (radial) movements of the crust (see Oscillatory movements of the earth's crust). Manifestations ... ... Great Soviet Encyclopedia

Slow ups and downs of the earth's crust, occurring everywhere and continuously. Thanks to them, the earth's crust never remains at rest: it is always divided into sections, some of which rise, others sag. K. d. h. to.… … Great Soviet Encyclopedia

- (from Neo ... and Tectonics is the latest tectonics, a direction in geotectonics devoted to the study tectonic processes manifested in the Neogene Anthropogenic time. These processes led to a change in the structure of the earth's crust with the formation of new ... ... Great Soviet Encyclopedia

Books

• Modern microamplitude tectonic movements, remote methods of their study and significance for oil and gas geology, Trofimov Dmitry Mikhailovich. The work is devoted to the generalization of the first experience practical use new method of studying modern tectonic movements- radar interferometry in combination with…
• Modern microamplitude tectonic movements, remote methods of their study and significance, Trofimov D. M.. The work is devoted to the generalization of the first experience of the practical use of a new method for studying modern tectonic movements - radar interferometry in combination with…

During geological history, the earth's crust experiences complex movements in space. The rocks composing it are crumpled into folds, moving towards each other, torn apart. As a result, the relief of the earth's surface changes, mountains and depressions form. Thus, tectonic movements are understood as mechanical movement blocks of the lithosphere, which reflects the development of the structure of the earth's crust and the planet as a whole.

At present, there are a number of classifications that reflect the direction of tectonic movements, areas of their manifestation, and duration. So, in the direction of tectonic movements are divided into vertical and horizontal; by speed into slow and fast; according to the flow time into neotectonic (occurring in the Cenozoic) and proper tectonic (occurring at earlier stages of the Earth's development). In turn, among the neotectonic movements, modern ones stand out, which occur in modern historical time.

Slow tectonic movements otherwise called oscillatory, or epeirogenic (creating continents), which lead to a change in the spatial position of the layers rocks. Among the reasons causing slow tectonic movements are the processes of mountain building in adjacent areas, as well as the intrusion of huge intrusive bodies into the earth's crust. In addition, oscillatory tectonic movements can sometimes be due to purely exogenous processes. For example, the development of giant ice sheets leads to the sinking of land, and the melting of glaciers leads to its rise. Oscillatory tectonic movements associated with the emergence or disappearance additional load to the lithosphere are called isostatic or compensatory.

Vertical oscillatory movements lead to a long and slow subsidence or uplift of large areas of the lithosphere (with an area of ​​tens and hundreds of thousands of square kilometers). The rate of such movements is usually 1–2 mm/year, and almost never exceeds 1–2 cm/year. Due to the fact that the sign of the direction of motion does not change over thousands and millions of years, vertical oscillatory motions of motion are able to change absolute altitude area for several kilometers. As a result, there is a change in the physical and geographical conditions of the area and, as a result, a change in the nature of the exogenous processes occurring on it. Thus, the tectonic sinking of land leads to marine transgression, and hence to the accumulation of marine sediments, that is, to the formation of a sedimentary cover and leveling of the relief. Conversely, tectonic uplift causes marine regression and land uplift. Under these conditions, erosion processes are activated on land, the dissection of the relief increases, instead of the accumulation of sediments, they are destroyed and demolished, and in coastal zone marine terraces are formed.

Horizontal oscillatory movements are still different greater sustainability in time. Because of this, the amplitude of horizontal movements of lithospheric blocks can reach several thousand kilometers, incommensurably exceeding the amplitude vertical displacements. Horizontal movements are main reason formation of oceans and land masses. And even more than that, it can be argued that it is slow horizontal movements that underlie almost all other endogenous processes.

Tectonic movements lead not only to the uplift and subsidence of sections of the earth's crust, but also to the violation of the conditions for the occurrence of rocks. Most sedimentary rocks are formed on almost flat surface the bottom of the seas and oceans, so at first they lie horizontally or almost horizontally. Such a primary horizontal occurrence of rock layers is called undisturbed. As a result of the action of tectonic movements, the rock layers are deformed, the initial conditions of their occurrence are violated, and new secondary structural forms arise. Such a secondary occurrence of layers is called disturbed, and tectonic movements that cause disturbances in the conditions of the initial occurrence of rock layers are called fast tectonic movements , and the disturbances themselves are called dislocations.

Tectonic dislocations are divided into two types:

a) plicative (folded, plastic). With plicative dislocations, the integrity of rock layers is not violated, but only the form of their occurrence changes .;

b) disjunctive (discontinuous), as a result of which the integrity of rock layers is violated and ruptures occur.

Plicative dislocations can be divided into three types.

1. Monoclinals- vast territories, composed of layers obliquely falling in one direction.

2. Flexures- steep inflections of layers in places of a sharp change in the depth of their occurrence. At the same time, sections of different heights separated by flexure lie parallel or at a slight angle to each other.

Monoclinals and flexures are characteristic of the sedimentary cover of platforms, that is, they usually arise due to slow tectonic movements.

3. Folded dislocations are represented by wavy bends of the layers. They are characteristic of mountainous areas and rocks of the crystalline basement of platforms, therefore, they are formed as a result of fast ( orogenic, i.e. mountain building) movements. In the structure of each fold, the following elements are distinguished (Fig. 1):

- lock - the place of the inflection of the layers;

- wings - sections of the curved layer diverging from the castle;

- hinge - the line of inflection of the fold in the lock, smooth hinges are quite rare, as a rule, they bend in waves - the phenomenon undulation;

- the axis of the fold - the projection of the hinge on horizontal plane;

- axial plane - a plane drawn through the hinge and equidistant from both wings;

- core - inner part fold, relative to which the layers collapsed.

Rice. 1. Fold elements.

Folds are classified according to four criteria.

1. According to the ratio of the age of the core and wings folds are anticlinal and synclinal. AT anticlinal The core rock fold is older than the wing rock. AT synclinal the core rock fold is younger than the wing rock.

2. By the position of the axial plane(OP) folds are:

– straight– OP is vertical;

– oblique- wings fall under different angles and OP is inclined towards a flatter wing;

– overturned- both wings and OP fall in one direction;

– recumbent- OP lies horizontally;

- inverted– OP is inclined at a negative angle.

2. According to the ratio of the length and width of the fold:

– linear- their length is many times greater than their width (syncline - a fold that has a concave shape, in the axial part of which younger layers of rocks occur, and on the wings - older ones; anticline - a fold that has a convex shape, in the axial part of which older rocks occur, and on the wings - younger ones); such folds are characteristic of the central zones of folded areas, where parallel systems of linear folds can form synclinoria and anticlinoria;

– brachifolds (short folds) - their length is two to three times their width, they are called accordingly brachyanticlines or brachysynclines (molds); usually occur on the periphery of folded areas;

– equal folds- their length is approximately equal to their width, with the anticlinal nature of the occurrence of layers, domes, and with synclinal - bowls; such formations are represented within the platforms.

3. According to the shape of the castle and wings allocate a large number of types of folds, some of which are shown in Figure 2.

During folded deformations, rock layers are usually cut by a dense network of parallel cracks into thin plates or prisms. This phenomenon is called cleavage.

Rice. 2. Types of folds according to the shape of the castle and wings.

The set of folds inherent in certain structures of the earth's crust is called folding. It is complete, intermittent and intermediate. Complete folding is characterized by the fact that linear folds (anticlines and synclines), which are approximately the same size, are located parallel to each other over the entire area of ​​​​a given territory and do not leave areas with undisturbed occurrence of rock layers. Complete folding is characteristic of folded areas. Often large uplifts and troughs occur in folded areas, complicated by a large number of anticlinal and synclinal folds. The first of them are called anticlinoria, the second synclinoria.

Discontinuous folding is characterized by the alternation of individual isolated folds with areas of undisturbed occurrence of rock layers. In their form, these are predominantly dome-like folds, troughs, brachifolds and flexures. This type of folding is characteristic of platform areas.

Intermediate folding is characteristic of transitional zones between folded areas and platforms, deflections.

Already the ancient Greeks and Romans, who lived in a tectonically and seismically highly active region of the Mediterranean, knew that the earth's surface can experience uplifts and subsidence, although their guesses about the reasons for this were very naive. ic stayed that way for a long time. There was also no idea of ​​the scale and speed of these movements. For the first time, an attempt to determine the sign and speed of modern movements was made in the 18th century. the famous Swedish naturalist A. Celsius. Interested in level fluctuations Baltic Sea, he made notches on the granite rocks of the Swedish coast to observe
give for fluctuations in sea level relative to these serifs. Later, in the 19th century, famous explorer Siberia ID Chersky did the same on the shores of Lake Baikal. In the same 19th century, according to such serifs in Sweden and Finland, it was established that the northern part of the Baltic coasts is experiencing an uplift, and the southern part is sinking. Despite the evidence of the determining role in this of the movements of the earth's crust, in the geological literature there have long been disputes about what is the main cause of fluctuations in the level of the ocean and the seas associated with it - tectonic movements of the earth's crust of the continents or own, eustatic, fluctuations in the ocean level.
on, due to changes in the volume of basins or the masses of water enclosed in them. This contradiction was resolved only in the 20s of our century by the Finnish geologist V. Ramsay, who pointed out that in reality both factors interact - tectonics.
chesky and eustatic. The systematic study of modern movements began in
late XIX in.; thus, instrumental observations of these movements have been carried out for over a century. During this time, a number of special methods studying both vertical,
and horizontal movements, and, as we will see below, especially significant progress has been made in this area in the post-
the last one and a half to two decades. arose special section tectonic science, for which V. E. Khain proposed the name pctuotectonics.

4.1. Study Methods vertical movements

The oldest of the methods for studying vertical movements is the further development"the ideas of Celsius and Chersky. Since the 80s of the last century, water measuring instruments have been installed in many ports of the world - first rails, then tide gauges with a self-recording device for observing changes in the position of the sea level. These changes, as
i noted, are due to two reasons: 1) own, eustatic, fluctuations in the level of the World Ocean, due to a change in para. water mass or bottom topography; 2) under we take or summarize the results of observations "we will send to the ports of the world where they are installed
water meters, shows that in last century there is a systematic rise in ocean level at a rate of approximately 1.2 mm/year. It is most likely caused by the melting of the ice sheets of Antarctica and Greenland due to with warming of the earth's climate. Meanwhile, the recorded level changes have, as a rule, higher values ​​and different sign, which indicates the decisive importance of the second factor - coastal land movements. Obviously to get correct representation about the amplitude and speed of the latter, it is necessary to subtract (in the case of lowering) or add to the measured value the eustatic
component - 1.2 mm/year. Water meter observations are carried out not only on the shores of the oceans and seas, but also on large lakes and rivers, where the interpretation of their results does not differ from the above.

Releveling method. As the railways were built, there was a need for periodic high-precision leveling along their lines to ensure traffic safety. Re-leveling revealed a change in the marks of the benchmarks over time. It turned out that in most cases these changes cannot be explained by surface deformation due to exogenous phenomena (subsidence or buckling of the soil), which
they are systematic, that is, they occur at a given point with one sign, and that this sign usually coincides with the sign of the structure on which the benchmark is located. This led to the conclusion that "movements" of the earth's crust "are the main cause of benchmark displacement" and that, therefore, the results of releveling along railroad lines can be used to identify modern vertical land movements (Figure 4.1). In this case, it is necessary to link the measurements along different lines and link them to the ocean level in the ports where water-gauging observations are carried out. Such processing of re-leveling data made it possible to map the current movements of the European part of the USSR (1958, 1963), and then the whole of Eastern Europe (1971). These maps were compiled under the guidance of Yu. A. Meshcheryakov.

Modern vertical movements in Eastern Europe based on re-leveling results. From the map edited by Yu. A. Meshcheryakov (1971), simplified

Subsequently, repeated high-precision leveling was included in the complex of observations made at special geodynamic testing grounds, which were organized in the former USSR in a number of regions Results of the study of modern vertical movements
embrace the methods described above have shown that they occur
di i at a rate of fractions to several millimeters, rarely more than 10 mm/year. In most cases, as noted, the sign of the motions agrees with structural plan, indicating the inherited development of uplifts and troughs; for the Russian Plain, such a correspondence is observed in about 70% of cases. Nevertheless, in a number of regions the signs of movements and structures do not coincide; Thus, according to leveling data, the Caspian Basin is experiencing an uplift, and the Urals with adjacent areas are down (but a relative uplift compared to the immediate framing). It is paradoxical that in some places on the Russian Plain, for example, in
the central part of the Ukrainian shield, the rate of uplifts is no less than in the Caucasus - more than 10 mm/year. If we assume that the uplift here proceeded at such a speed, even during the entire last million years, it should have created (without
corrections for denudation) mountains 10 km high! In general, the rate of modern movements turns out to be at least one or two orders of magnitude higher than that measured by the power analysis method for movements of a more distant geological past, and an order of magnitude
higher than established by geomorphological methods for the latest movements. This “paradox of speeds” can have a twofold explanation: 1) the real acceleration of vertical movements in the latest and especially modern era, and 2) vertical movements have an oscillatory nature and a true representation
their speed can only be given by algebraic summation over a sufficiently long period of time. Modern era really different high pace vertical movements, but still this acceleration is not enough to explain the "pa-
speed radox. Obviously, the oscillatory nature of movements is of primary importance, which is confirmed by a number of facts: a change in the sign of movements in the ports of the Caspian Sea relative to one of them, taken as stationary, or benchmarks during the third round of leveling in the Baltic, etc.

4.2. Methods studying horizontal movements

Until recently, repeated triangulations served as the main method for studying horizontal movements, which at first were also not carried out in order to reveal tectonic displacements and only then began to be used in this direction. currently instead of triangulation are produced trilateration, at which the length of not one, but all sides of the triangle is measured. Particularly noticeable horizontal displacements, as well as
vertical, are found after large. The results of the study of horizontal movements show that their speed is not inferior to the speed of vertical movements, and often exceeds the latter. At the same time, horizontal movements are not oscillatory, but directional, which explains the fact that their total amplitude for a certain time interval is much higher than the amplitude of vertical movements.

However, it should be noted that during some major earthquakes, for example, Tokyo 1923, short-term reversals of the sign of the horizontal movements of the earth's surface were observed. Of particular interest is the identification of relative displacements lithospheric plates. Previous attempts to measure these displacements by redefining geographical coordinates for locations located on different continents, ordinary
astronomical method were found to be unreliable. Currently, two other, much more accurate methods are used to re-measure the distance between
distant points: _1) with the help of laser reflectors installed on the Moon or "1Ta ~ y artificial satellites of the Earth; 2) using the registration of radio signals from quasars (long-baseline radio interferometric method) ..

Shape of igneous bodies

Rocks igneous origin compose geological bodies of various morphologies. At the same time, the shapes of bodies formed during volcanic and plutonic processes are mostly different.

When solidification of magmatic melts on the surface are formed:

- lava flows- flattened tongue-shaped bodies formed by lava flowing down the slopes of volcanic structures;

- lava sheets different from streams larger area distribution; they are formed as a result of the spreading of lavas with very low viscosity over a wide area;

- domes are formed during extrusive eruptions, as a result of the solidification of very viscous lavas above the vent and in its immediate vicinity.

The products of explosive eruptions occur in the form layers like rocks of sedimentary origin.

When lava solidifies in the vent of a central type volcano, neck- a narrow cylindrical body of vertical orientation. And when it solidifies in a cracked channel - dike, a body in the form of a narrow plate, cutting through the surrounding rocks.

Magma, which has intruded into the surrounding rocks and solidified at a depth, composes intrusive bodies (or intrusions) of various shapes. The morphology of intrusive bodies depends on the conditions of intrusion, to the greatest extent on the nature geological structures formed by host rocks. When the melt penetrates into cracks, dikes are the same as in the roots of fissure-type volcanoes. Other most common forms of intrusions include the following:

- sills- bodies similar in shape to dikes. They are formed as a result of layer-by-layer injections of magma between layers of sedimentary rocks. The difference between a dike and a sill is that the sill lies in line with the host rocks (parallel to their bedding), while the dike cuts through the bedding of the host rocks at one angle or another.

An intrusion consisting of articulated dikes and possibly sills of various orientations is called frame.

- laccoliths- lenticular gently sloping bodies with a convex (dome-shaped) roof. Formed when a large portion of magma, during intrusion, lifts the overlying layers.

- lopolites- bent lenticular bodies, formed as a result of the introduction of the melt between the layers of a gently curved downward fold of host rocks.

- Rods- sub-vertical, isometric in terms of the body, going to great depths. Morphologically they are similar to necks, but differ in larger diameter and less geometric regularity of shape.

Intrusive bodies are very large sizes(occupying areas of many thousands of square kilometers) and irregularly shaped are often called batholiths. But now many experts prefer not to use this term. The reason is that initially "batholiths" were understood as bodies, vast in area, gradually expanding downwards and leaving their roots in the deepest horizons of the earth's crust or even in the mantle. According to modern data, intrusions of large areal dimensions have a sole ( bottom line) is found already at depths of a few kilometers, and thus they have the form of not very regular plates of great thickness.

If portions of the smelted magmatic melt do not move anywhere, but freeze at the place of their formation, numerous small irregularly shaped bodies are formed, called akmoliths.

Some igneous rocks of deep origin can be extruded up along fault zones in the earth's crust during tectonic movements. Bodies formed in this way are called protrusions . They are characterized by a lenticular or plate-like shape.

There are several classifications of tectonic movements. According to one of them, these movements can be divided into two types: vertical and horizontal. In the first type of movement, stresses are transmitted in a direction close to the radius of the Earth, in the second - along a tangent to the surface of the shells of the earth's crust. Very often these movements are interrelated, or one type of movement gives rise to another.

AT different periods of the development of the Earth, the direction of vertical movements can be different, but the resulting components of them are directed either downward or upward. Movements directed downwards and leading to the lowering of the earth's crust are called descending, or negative; movements directed upwards and leading to a rise are ascending, or positive. The sinking of the earth's crust entails the movement of the coastline towards land - transgression or the advance of the sea. When rising, when the sea recedes, they speak of it regression.

Based on the place of manifestation, tectonic movements are divided into surface, crustal and deep. There is also a division of tectonic movements into oscillatory and dislocation ones.

Oscillatory tectonic movements

Oscillatory, or epeirogenic, tectonic movements (from the Greek epeirogenesis - the birth of continents) are predominantly vertical, generally crustal or deep. Their manifestation is not accompanied abrupt change original occurrence of rocks. There are no areas on the surface of the Earth that would not experience this type of tectonic movement. Speed ​​and sign (raise-lower) oscillatory movements change both in space and in time. In their sequence, cyclicity is observed with intervals from many millions of years to several centuries.

The oscillatory movements of the Neogene and Quaternary period are called newest, or neotectonic. The amplitude of neotectonic movements can be quite large, for example, in the Tien Shan mountains it was 12-15 km. On the plains, the amplitude of neotectonic movements is much less, but here, too, many landforms - uplands and lowlands, the position of watersheds and river valleys - are associated with neotectonics.

The latest tectonics is also manifesting at the present time. The speed of modern tectonic movements is measured in millimeters and, less often, in the first centimeters (in the mountains). For example, on the Russian Plain maximum speeds uplifts - up to 10 mm per year - are established for the Donbass and the north-east of the Dnieper Upland, and maximum subsidence - up to 11.8 mm per year - for the Pechora Lowland.

Steady subsidence over historical time is characteristic of the territory of the Netherlands, where a person has been struggling with advancing waters for many centuries. North Sea by building dams. Almost half of this country is occupied polders- cultivated low-lying plains lying below the level of the North Sea, stopped by dams.

Dislocation tectonic movements

To dislocation movements(from lat. dislocation - displacement) include tectonic movements of various directions, mainly intracrustal, accompanied by tectonic disturbances (deformations), i.e., changes in the primary occurrence of rocks.

Allocate the following types tectonic deformations (Fig. 1):

• deformations of large deflections and uplifts (caused by radial movements and are expressed in gentle uplifts and deflections of the earth's crust, most often of a large radius);
• folded deformations (formed as a result of horizontal movements that do not break the continuity of the layers, but only bend them; they are expressed in the form of long or wide, sometimes short, rapidly fading folds);
• discontinuous deformations (characterized by the formation of ruptures in the earth's crust and the movement of individual sections along cracks).

Rice. 1. Types of tectonic deformations: a-c - rocks

Folds are formed in rocks with some plasticity.

The simplest type of folds is anticline- a convex fold, in the core of which lie the most ancient rocks - and syncline- concave fold with a young nucleus.

In the Earth's crust, anticlines always turn into synclines, and therefore these folds always have a common wing. In this wing, all layers are approximately equally inclined to the horizon. This is monoclinal end of folds.

A fracture of the earth's crust occurs if the rocks have lost their plasticity (acquired rigidity) and parts of the layers are mixed along the fault plane. When shifted down, it forms reset, up - uplift, when mixed at a very small angle of inclination to the horizon - feat and thrust. In rigid rocks that have lost plasticity, tectonic movements create discontinuous structures, the simplest of which are horsts and grabens.

Folded structures after the loss of plasticity by the rocks composing them can be torn apart by faults (reverse faults). As a result, anticlinal and synclinal broken structures.

Unlike vibrational motions, dislocation motions are not ubiquitous. They are characteristic of geosynclinal regions and are poorly represented or completely absent on the platforms.

Geosynclinal regions and platforms are the main tectonic structures, which are clearly expressed in modern relief.

Tectonic structures- forms of occurrence of rocks regularly repeating in the earth's crust.

Geosynclines- mobile linearly elongated areas of the earth's crust, characterized by multidirectional tectonic movements of high intensity, energetic phenomena of magmatism, including volcanism, frequent and strong earthquakes.

On the early stage development in them, a general subsidence and accumulation of thick rock strata are observed. On the middle stage, when a thickness of sedimentary-volcanic rocks with a thickness of 8-15 km accumulates in geosynclines, the subsidence processes are replaced by a gradual uplift, sedimentary rocks undergo folding, and at great depths - metamorphization, along the cracks and ruptures penetrating them, magma is introduced and solidifies. AT late stage development at the site of the geosyncline under the influence of a general uplift of the surface, high folded mountains appear, crowned with active volcanoes; depressions are filled with continental deposits, the thickness of which can reach 10 km or more.

Tectonic movements leading to the formation of mountains are called orogenic(mountain building), and the process of mountain building - orogeny. Throughout the geological history of the Earth, a number of epochs of intense folded orogeny have been observed (Tables 9, 10). They are called orogenic phases or epochs of mountain building. The most ancient of them belong to the Precambrian time, then follow Baikal(end of the Proterozoic - beginning of the Cambrian), Caledonian(Cambrian, Ordovician, Silurian, early Devonian), hercynian(Carboniferous, Permian, Triassic), Mesozoic, Alpine(late Mesozoic - Cenozoic).

Table 9. Distribution of geostructures of different ages across continents and parts of the world

Geostructures	Continents and parts with a pet
			North America	South America		Australia	Antarctica
Cenozoic
Mesozoic
Hercynian
Caledonian
Baikal
pre-Baikal

Table 10. Types of geostructures and their reflection in the relief

Types of geostructures		Landforms
Meganticlinoria, anticlinoria		High blocky-folded, sometimes with alpine landforms and volcanoes, less often medium folded-blocky mountains
Foothill and intermountain troughs	blank	low plains
	filled and raised	High plains, plateaus, plateaus
Median massifs	lowered	Low plains, hollows of inland seas
	raised	Plateaus, plateaus, uplands
Exits to the surface of the folded base		Low, rarely medium folded-blocky mountains with leveled peaks and often steep tectonic slopes
	raised parts	Ridges, plateaus, plateaus
	omitted parts	Low plains, lake basins, coastal parts of the seas
	with anteclises	Uplands, plateaus, low folded-block mountains
	with syneclises	Low plains, coastal parts of the seas

The most ancient mountain systems, which now exist on Earth, were formed in the Caledonian era of folding.

With the cessation of the lifting processes high mountains are slowly but steadily destroyed, until in their place is formed rolling plain. Gsosynclinal cycle is long enough. It does not fit even within the framework of one geological period.

Having passed the geosynclinal cycle of development, the earth's crust thickens, becomes stable and rigid, incapable of new folding. The geosyncline passes into another qualitative block of the earth's crust - a platform.

As a result of a long history of geological development on the territory of Russia, the main types of g e o t e c t u r- flat-platform areas and large orogenic mobile belts. However, within the same geotectures, completely different relief is often distributed (low basement plains of Karelia and the Aldan Highlands on the shields of ancient platforms; low Ural mountains and high-altitude Altai within the Ural-Mongolian belt, etc.); on the contrary, a similar relief can form within different geotectures (the high mountains of the Caucasus and Altai). This is due to the great influence on the modern relief of neotectonic movements that began in the Oligocene (Upper Paleogene) and continue to the present.

After a period of relative tectonic calm at the beginning of the Cenozoic, when low plains predominated and mountains were practically not preserved (only in the area of ​​​​Mesozoic folding, in some places, apparently, small hills and low mountains were preserved), vast areas Western Siberia and the south of the East European Plain were covered by the waters of shallow marine basins. In the Oligocene, a new period of tectonic activation began - a neotectonic stage, which led to a radical restructuring of the relief.

Recent tectonic movements and morphostructures. Neotectonics, or the latest tectonic movements, V.A. Obruchev defined as the movements of the earth's crust that created the modern relief. It is with the latest (Neogene-Quaternary) movements that the formation and distribution of morphostructures across the territory of Russia is connected - large forms relief, resulting from the interaction of endogenous and exogenous processes with the leading role of the former.

The latest tectonic movements are associated with the interaction of modern lithospheric plates (see Fig. 6), along the margins of which they manifested themselves most actively. The amplitude of Neogene-Quaternary movements in the marginal parts reached several kilometers (from 4-6 km in Transbaikalia and Kamchatka to 10-12 km in the Caucasus), and in the inner regions of the plates it was measured in tens, less often hundreds of meters. Sharply differentiated movements prevailed in the marginal parts: uplifts of large amplitude were replaced by equally grandiose subsidences of adjacent areas. In the central parts of the lithospheric plates, movements of the same sign occurred over large areas.

Mountains arose in the immediate contact zone of various lithospheric plates. All the mountains that currently exist on the territory of Russia are the product of the latest tectonic movements, that is, they all arose in the Neogene-Quaternary time and, therefore, are of the same age. But the morphostructures of these mountains are very different depending on the mode of their origin, and it is connected with the position of the mountains within the various tectonic structures.

Where mountains arose on the young oceanic or transitional crust of the marginal parts of the plates with a thick cover of sedimentary rocks crumpled into folds (areas of the Alpine and Pacific foldings), young folded mountains formed (the Greater Caucasus, the Sakhalin ridges) sometimes with areas of volcanic mountains (the ridges of Kamchatka ). The mountain ranges here are linearly extended along the margin of the plate. In those places where, at the boundaries of the lithospheric plate, there were territories that had already experienced folding movements and turned into plains on a folded base, with a rigid continental crust that could not be compressed into folds (areas of pre-Paleozoic and Paleozoic folding), the formation of mountains proceeded differently. Here, with lateral pressure arising from the approach of lithospheric plates, the rigid foundation was broken by deep faults into separate blocks (blocks), some of which were squeezed upwards during further movement, others - downwards. So mountains are reborn in place of the plains. These mountains are called revived blocky, or folded-blocky. All the mountains of the south of Siberia, the Urals, the Tien Shan are revived.

In the areas of Mesozoic folding, where by the time of the beginning of intensive movements the mountains could not be completely destroyed, where areas of low-mountain or small-hilly relief were preserved, the orographic pattern of the mountains could not change or change only partially, but the height of the mountains increased. Such mountains are called rejuvenated blocky-folded. They reveal the features of both folded and blocky mountains with a predominance of one or the other. The rejuvenated ones include the Sikhote-Alin, the mountains of the North-East and partly the Amur region. The inner parts of the Eurasian lithospheric plate belong to the areas of weak and very weak uplifts and predominantly weak and moderate subsidence. Only the Caspian lowland and southern part Scythian plate. Most of the territory of Western Siberia experienced weak subsidence (up to 100 m), and only in the north were subsidence moderate (up to 300 m or more). The southern and western outskirts of Western Siberia and the greater eastern part of the East European Plain were a weakly mobile plain. The greatest amplitudes of uplifts on the East European Plain are characteristic of the Central Russian, Volga and Bugulmino-Belebeevskaya Uplands (100-200 m). On the Central Siberian Plateau, the amplitude of uplifts was greater. The Yenisei part of the plateau is raised by 300-500 m, and the Putorana plateau even by 500-1000 m and higher.

The result of the latest movements was the morphostructure of the platform plains. On the shields, which had a constant tendency to rise, basement plains (Karelia, Kola Peninsula), plateaus (Anabar massif) and ridges (Timan, Yenisei, eastern spurs of Donetsk) were formed - hills that have an elongated shape and formed by dislocated rocks of a folded base. On the slabs, where the basement rocks are covered by a sedimentary cover, accumulative plains, stratal plains and plateaus have formed.

Accumulative plains are confined to areas of subsidence in recent times (see Figs. 6 and 7), as a result of which they have a fairly thick cover of Neogene-Quaternary deposits. The accumulative plains are the middle and northern parts of the West Siberian Plain, the Middle Amur Plain, the Caspian Lowland, and the north of the Pechora Lowland. Layered plains and plateaus are morphostructures of plate sections that have experienced predominant uplifts. With a monoclinal occurrence of rocks of the sedimentary cover, inclined layered plains predominate, with a subhorizontal layer - layered plains and plateaus. Layered plains are characteristic of most of the East European Plain, the southern and western margins of Western Siberia, and partly for Central Siberia. On the territory of Central Siberia, plateaus are widely represented, both sedimentary (structural - Angara-Lena, Lena-Aldan, etc.), and volcanic (Putorana, Central Tungusskoye, Syverma, etc.).

Volcanic plateaus are also characteristic of mountainous regions (the Eastern Sayan, the Vitim Plateau, the Eastern Range in Kamchatka, etc.). Shield morphostructures can also be found in the mountains, and accumulative and, to a lesser extent, stratified plains (Kuznetsk Basin) can be found in intermountain basins.

1) from the Gakkel Ridge in the Arctic Ocean through the Chersky Ridge, where the Chukchi-Alaska block of the North American Plate has broken off from the Eurasian Plate and is moving away at a rate of 1 cm/year;

2) in the region of the basin of Lake Baikal, the Amur Plate broke away from the Eurasian Plate, which rotates counterclockwise and moves away at a speed of 1-2 mm/year in the Baikal region. For 30 million years, a deep gap arose here, within which the lake is located;

3) in the Caucasus region, which falls into the seismic belt stretching along the southwestern margin of the Eurasian plate, where it approaches the African-Arabian plate at a rate of 2-4 cm/year.

Earthquakes testify to the existence of deep tectonic stresses in these areas, which are expressed from time to time in the form of powerful earthquakes and ground vibrations. The last catastrophic earthquake in Russia was the earthquake in the north of Sakhalin in 1995, when the city of Neftegorsk was wiped off the face of the earth.

In the Far East, there are also underwater earthquakes, accompanied by seaquakes and giant destructive tsunami waves.

Platform areas with their flat relief, with weak manifestations of neotectonic movements, do not experience significant earthquakes. Earthquakes are extremely rare here and manifest themselves in the form of weak vibrations. So, the earthquake of 1977 is still remembered by many Muscovites. Then the echo of the Carpathian earthquake reached Moscow. In Moscow, on the 6th-10th floors, chandeliers swayed and bunches of keys rang in the doors. The magnitude of this earthquake was 3-4 points.

Not only earthquakes, but also volcanic activity is evidence of the tectonic activity of the territory. Currently, volcanic phenomena in Russia are observed only in Kamchatka and the Kuril Islands.

The Kuril Islands are volcanic ranges, highlands and solitary volcanoes. In total, there are 160 volcanoes in the Kuril Islands, of which about 40 are currently active. The highest of them is Alaid volcano (2339) on Atlasov Island. In Kamchatka, volcanism gravitates toward the eastern coast of the peninsula, from Cape Lopatka to 56°N, where the northernmost Shiveluch volcano is located.