The top layer of the lithosphere is called. Geographic shells of the Earth: types and characteristics

LITHOSPHERE

Structure and composition of the lithosphere. The neomobilism hypothesis. Formation of continental blocks and oceanic depressions. Movement of the lithosphere. Epeirogenesis. Orogenesis. The main morphostructures of the Earth: geosynclines, platforms. Age of the Earth. Geochronology. Epochs of mountain building. Geographical distribution mountain systems of different ages.

Structure and composition of the lithosphere.

The term “lithosphere” has been used in science for a long time – probably since the mid-19th century. But it acquired its modern significance less than half a century ago. Even in the 1955 edition of the geological dictionary it is said: lithosphere- the same as the earth's crust. In the dictionary of the 1973 edition and subsequent ones: lithosphere... in the modern sense, includes the earth's crust ... and hard upper part of the upper mantle Earth. Upper mantle is a geological term for a very large layer; the upper mantle has a thickness of up to 500, according to some classifications - over 900 km, and the lithosphere includes only the upper few tens to two hundred kilometers.

The lithosphere is the outer shell of the “solid” Earth, located below the atmosphere and the hydrosphere above the asthenosphere. The thickness of the lithosphere varies from 50 km (under the oceans) to 100 km (under the continents). It consists of the earth's crust and the substrate that is part of the upper mantle. The boundary between the earth's crust and the substrate is the Mohorovicic surface, when crossing it from top to bottom, the speed of longitudinal waves increases abruptly. seismic waves. The spatial (horizontal) structure of the lithosphere is represented by its large blocks - the so-called. lithospheric plates separated from each other by deep tectonic faults. Lithospheric plates move in a horizontal direction with average speed 5-10 cm per year.

Structure and power earth's crust are not the same: that part of it that can be called continental has three layers (sedimentary, granite and basalt) and an average thickness of about 35 km. Under the oceans, its structure is simpler (two layers: sedimentary and basaltic), the average thickness is about 8 km. Transitional types of the earth's crust are also distinguished (Lecture 3).

Science has firmly established the opinion that the earth's crust in the form in which it exists is a derivative of the mantle. Throughout geological history there was a directed irreversible process of enrichment of the Earth's surface with matter from earth's bowels. Three main types of rocks take part in the structure of the earth’s crust: igneous, sedimentary and metamorphic.

Igneous rocks are formed in the bowels of the Earth under conditions of high temperatures and pressures as a result of the crystallization of magma. They make up 95% of the mass of matter that makes up the earth's crust. Depending on the conditions under which the magma solidified, intrusive (formed at depth) and effusive (poured to the surface) rocks are formed. Intrusive materials include: granite, gabbro; igneous materials include basalt, liparite, volcanic tuff, etc.

Sedimentary rocks are formed on earth's surface in various ways: some of them are formed from the products of destruction of rocks formed earlier (clastic: sands, gels), some due to the vital activity of organisms (organogenic: limestone, chalk, shell rock; siliceous rocks, hard and brown coal, some ores), clayey ( clays), chemicals (rock salt, gypsum).

Metamorphic rocks are formed as a result of the transformation of rocks of a different origin (igneous, sedimentary) under the influence of various factors: high temperature and pressure in the depths, contact with rocks of a different chemical composition, etc. (gneisses, crystalline schists, marble, etc.).

Most of the volume of the earth's crust is occupied by crystalline rocks of igneous and metamorphic origin (about 90%). However, for the geographic envelope, the role of a thin and discontinuous sedimentary layer, which on most of the earth’s surface is in direct contact with water and air, is more significant, and takes an active part in geographical processes(thickness - 2.2 km: from 12 km in troughs, to 400 - 500 m in the ocean floor). The most common are clays and shales, sands and sandstones, and carbonate rocks. An important role in the geographic envelope is played by loess and loess-like loams, which make up the surface of the earth's crust in non-glacial regions of the northern hemisphere.

In the earth's crust - the upper part of the lithosphere - 90 chemical elements have been discovered, but only 8 of them are widespread and account for 97.2%. According to A.E. Fersman, they are distributed as follows: oxygen - 49%, silicon - 26, aluminum - 7.5, iron - 4.2, calcium - 3.3, sodium - 2.4, potassium - 2.4, magnesium - 2, 4%.

The earth's crust is divided into separate geologically different-aged, more or less active (dynamically and seismically) blocks, which are subject to constant movements, both vertical and horizontal. Large (several thousand kilometers in diameter), relatively stable blocks of the earth's crust with low seismicity and poorly dissected relief are called platforms ( plat– flat, form– form (French)). They have a crystalline folded foundation and a sedimentary cover of different ages. Depending on age, platforms are divided into ancient (Precambrian in age) and young (Paleozoic and Mesozoic). Ancient platforms are the cores of modern continents, the general uplift of which was accompanied by a more rapid rise or fall of their individual structures (shields and plates).

The upper mantle substrate, located on the asthenosphere, is a kind of rigid platform on which the earth’s crust was formed during the geological development of the Earth. The substance of the asthenosphere appears to be characterized by reduced viscosity and experiences slow movements (currents), which are presumably the cause of vertical and horizontal movements of lithospheric blocks. They are in a position of isostasy, which implies their mutual balancing: the rise of some areas causes the fall of others.

Theory lithospheric plates first expressed by E. Bykhanov (1877) and finally developed by the German geophysicist Alfred Wegener (1912). According to this hypothesis, before the Upper Paleozoic, the earth's crust was collected into the continent of Pangea, surrounded by the waters of the Pantallassa Ocean (the Tethys Sea was part of this ocean). In the Mesozoic, splits and drift (swimming) of its individual blocks (continents) began. Continents folded relatively light substance, which Wegener called sial (silicium-aluminium), floated on the surface of a heavier substance - sima (silicium-magnesium). South America was the first to separate and move to the west, then Africa, and later Antarctica, Australia and North America. The later developed version of the mobilism hypothesis allows for the existence in the past of two giant ancestral continents - Laurasia and Gondwana. From the first, North America and Asia were formed, from the second - South America, Africa, Antarctica and Australia, Arabia and Hindustan.

At first, this hypothesis (the theory of mobilism) captivated everyone, it was accepted with enthusiasm, but after 2-3 decades it turned out that the physical properties of the rocks did not allow such navigation and the theory of continental drift was put to death until the 1960s. the dominant system of views on the dynamics and development of the earth's crust was the so-called. fixism theory ( fixus- solid; unaltered; fixed (lat.), which asserted the unchangeable (fixed) position of the continents on the surface of the Earth and the leading role of vertical movements in the development of the earth's crust.

Only by the 60s, when the global system of mid-ocean ridges had already been discovered, was a practically new theory constructed, in which all that remained of Wegener’s hypothesis was a change in the relative positions of the continents, in particular, an explanation of the similarity of the outlines of the continents on both sides of the Atlantic.

The most important difference between modern plate tectonics (new global tectonics) and Wegener’s hypothesis is that for Wegener, the continents moved along the material that made up the ocean floor, while in the modern theory, the movement involves plates, which include areas of both land and the ocean floor; The boundaries between plates can run along the ocean floor, on land, and along the boundaries of continents and oceans.

The movement of lithospheric plates (the largest: Eurasian, Indo-Australian, Pacific, African, American, Antarctic) occurs along the asthenosphere - a layer of the upper mantle that underlies the lithosphere and has viscosity and plasticity. In places of mid-ocean ridges, lithospheric plates grow due to matter rising from the depths and move apart along the axis of faults or rifts to the sides - spreading (English spreading - expansion, distribution). But the surface globe cannot increase. The emergence of new sections of the earth's crust on the sides of the mid-ocean ridges must be compensated somewhere by its disappearance. If we believe that lithospheric plates are sufficiently stable, it is natural to assume that the disappearance of the crust, like the formation of a new one, should occur at the boundaries of approaching plates. There may be three different cases:

Two areas are approaching oceanic crust;

A section of continental crust is moving closer to a section of oceanic crust;

Two sections of the continental crust are moving closer together.

The process that occurs when sections of the oceanic crust approach each other can be schematically described as follows: the edge of one plate rises slightly, forming an island arc; the other goes under it, here the level of the upper surface of the lithosphere decreases, and a deep-sea oceanic trench is formed. These are the Aleutian Islands and the Aleutian Trench that frames them, the Kuril Islands and the Kuril-Kamchatka Trench, the Japanese Islands and the Japanese Trench, the Mariana Islands and the Mariana Trench, etc.; all this in the Pacific Ocean. In the Atlantic - Antilles and the Puerto Rico Trench, South Sandwich Islands, and South Sandwich Trench. The movement of the plates relative to each other is accompanied by significant mechanical stresses, so in all these places high seismicity and intense volcanic activity are observed. The sources of earthquakes are located mainly on the surface of contact of two plates and can be at great depths. The edge of the plate, which goes deeper, sinks into the mantle, where it gradually turns into mantle matter. The subducting plate is heated, magma is melted from it, which flows into the volcanoes of island arcs.

The process of one plate plunging under another is called subduction (literally, pushing). When sections of the continental and oceanic crust move towards each other, the process proceeds approximately the same as in the case of the meeting of two sections of oceanic crust, only instead of an island arc, a powerful chain of mountains is formed along the coast of the continent. The oceanic crust also sinks under the continental edge of the plate, forming deep-sea trenches, and volcanic and seismic processes are just as intense. A typical example is the Cordillera Central and South America and a system of trenches running along the coast - Central American, Peruvian and Chilean.

When two sections of the continental crust come together, the edge of each of them experiences folding. Rifts form, mountains form. Seismic processes are intense. Volcanism is also observed, but less than in the first two cases, because The earth's crust in such places is very thick. This is how the Alpine-Himalayan mountain belt was formed, stretching from North Africa and the western tip of Europe through all of Eurasia to Indochina; it includes the most high mountains on Earth, high seismicity is observed throughout its entire length; in the west of the belt there are active volcanoes.

According to the forecast, while maintaining the general direction of movement of the lithospheric plates, the Atlantic Ocean, the East African Rifts (they will be filled with MC waters) and the Red Sea, which will directly connect the Mediterranean Sea with the Indian Ocean, will significantly expand.

Rethinking the ideas of A. Wegener led to the fact that, instead of continental drift, the entire lithosphere began to be considered as the moving solid ground of the Earth, and this theory ultimately came down to the so-called “lithospheric plate tectonics” (today – “new global tectonics” ").

The main provisions of the new global tectonics are as follows:

1. The Earth's lithosphere, including the crust and the uppermost part of the mantle, is underlain by a more plastic, less viscous shell - the asthenosphere.

2. The lithosphere is divided into a limited number of large, several thousand kilometers in diameter, and medium-sized (about 1000 km) relatively rigid and monolithic plates.

3. Lithospheric plates move relative to each other in the horizontal direction; the nature of these movements can be threefold:

a) spreading (spreading) with filling of the resulting gap with new crust oceanic type;

b) subduction (subduction) of the oceanic plate under the continental or oceanic plate with the emergence of a volcanic arc or a continental-margin volcano-plutonic belt above the subduction zone;

c) sliding of one plate relative to another along a vertical plane, so-called. transform faults transverse to the axes of the median ridges.

4. The movement of lithospheric plates along the surface of the asthenosphere is subject to Euler’s theorem, which states that the movement of conjugate points on a sphere occurs along circles drawn relative to an axis passing through the center of the Earth; The places where the axis emerges from the surface are called poles of rotation, or opening.

5. On the scale of the planet as a whole, spreading is automatically compensated by subduction, i.e., as much as new oceanic crust is born over a given period of time, the same amount of older oceanic crust is absorbed in subduction zones, due to which the volume of the Earth remains unchanged.

6. The movement of lithospheric plates occurs under the influence of convective currents in the mantle, including the asthenosphere. Under the spreading axes of the median ridges, ascending currents are formed; they become horizontal at the periphery of ridges and descending in subduction zones on the margins of the oceans. Convection itself is caused by the accumulation of heat in the bowels of the Earth due to its release during the decay of naturally radioactive elements and isotopes.

New geological materials about the presence of vertical currents (jets) of molten matter rising from the boundaries of the core and mantle itself to the earth's surface formed the basis for the construction of a new, so-called. “plume” tectonics, or plume hypothesis. It is based on ideas about internal (endogenous) energy concentrated in the lower horizons of the mantle and in the outer liquid core of the planet, the reserves of which are practically inexhaustible. High-energy jets (plumes) penetrate the mantle and rush in the form of streams into the earth's crust, thereby determining all the features of tectono-magmatic activity. Some adherents of the plume hypothesis are even inclined to believe that it is this energy exchange that underlies all physicochemical transformations and geological processes in the body of the planet.

IN lately Many researchers have become increasingly inclined to believe that the uneven distribution of the Earth’s endogenous energy, as well as the periodization of some exogenous processes, is controlled by (cosmic) factors external to the planet. Of these, the most effective force, which directly influences the geodynamic development and transformation of the Earth’s matter, apparently, is the effect of the gravitational influence of the Sun, Moon and other planets, taking into account the inertial forces of the Earth’s rotation around its axis and its movement in orbit. Based on this postulate concept of centrifugal planetary mills allows, firstly, to give a logical explanation of the mechanism of continental drift, and secondly, to determine the main directions of sublithospheric flows.

Movement of the lithosphere. Epeirogenesis. Orogenesis.

The interaction of the earth's crust with the upper mantle is the cause of deep tectonic movements excited by the rotation of the planet, thermal convection or gravitational differentiation of the mantle substance (the slow descent of heavier elements into the depths and the rise of lighter ones upward); the zone of their appearance to a depth of about 700 km is called the tectonosphere.

There are several classifications of tectonic movements, each of which reflects one of the sides - direction (vertical, horizontal), place of manifestation (surface, deep), etc.

From a geographical point of view, it seems successful to divide tectonic movements into oscillatory (epeirogenic) and fold-forming (orogenic).

The essence of epeirogenic movements boils down to the fact that huge areas of the lithosphere experience slow uplifts or subsidences, are essentially vertical, deep, and their manifestation is not accompanied by a sharp change in the original occurrence of rocks. Epeirogenic movements have been everywhere and at all times of geological history. The origin of oscillatory movements is satisfactorily explained by the gravitational differentiation of matter in the Earth: upward currents of matter correspond to uplifts of the earth's crust, downward flows correspond to subsidence. The speed and sign (raising - lowering) of oscillatory movements change both in space and time. Their sequence exhibits cyclicity with intervals ranging from many millions of years to several thousand centuries.

For the formation of modern landscapes, the oscillatory movements of the recent geological past - the Neogene and Quaternary periods - were of great importance. They got the name recent or neotectonic. The scope of neotectonic movements is very significant. In the Tien Shan mountains, for example, their amplitude reaches 12-15 km and without neotectonic movements, in the place of this high mountainous country there would be a peneplain - almost a plain that arose on the site of destroyed mountains. On the plains, the amplitude of neotectonic movements is much smaller, but even here many forms of relief - hills and lowlands, the position of watersheds and river valleys - are associated with neotectonics.

The newest tectonics is still evident today. The speed of modern tectonic movements is measured in millimeters, less often in measured centimeters (in the mountains). On the Russian Plain maximum speeds uplifts of up to 10 mm per year are established for the Donbass and the northeast of the Dnieper Upland, maximum subsidence, up to 11.8 mm per year, in the Pechora Lowland.

The consequences of epeirogenic movements are:

1. Redistribution of the ratio between land and sea areas (regression, transgression). It is best to study oscillatory movements by observing the behavior coastline, because when oscillatory movements the boundary between land and sea shifts due to the expansion of the sea area due to a reduction in land area or the reduction of the sea area due to an increase in land area. If the land rises and the sea level remains unchanged, then the sections of the seabed closest to the coastline protrude onto the day surface - what happens is regression, i.e. retreat of the sea. A sinking of land with a constant sea level, or a rise in sea level with a stable land position entails transgression(advance) of the sea and the flooding of more or less significant areas of land. Thus, the main cause of transgressions and regressions is the uplift and subsidence of the solid earth's crust.

A significant increase in the area of land or sea cannot but affect the nature of the climate, which becomes more maritime or more continental, which over time should affect the nature of the organic world and soil cover, and the configuration of the seas and continents will change. In the event of sea regression, some continents and islands may unite if the straits separating them were shallow. During transgression, on the contrary, the separation of land masses into separate continents or the separation of new islands from the mainland occurs. The presence of oscillatory movements largely explains the effect of the destructive activity of the sea. The slow transgression of the sea onto steep coastlines is accompanied by the development abrasive(abrasion - cutting off the coast by the sea) of the surface and the abrasion ledge limiting it on the land side.

2. Due to the fact that vibrations of the earth’s crust occur in different points either with a different sign, or with different intensity - the very appearance of the earth's surface changes. Most often, uplifts or subsidences that cover vast areas create large waves on it: during uplifts - domes of enormous size, during downturns - bowls and huge depressions

During oscillatory movements, it can happen that when one section rises and the one next to it falls, then at the boundary between such differently moving sections (as well as within each of them) ruptures occur, due to which individual blocks of the earth’s crust acquire independent movement. Such a fracture, in which rocks move up or down relative to each other along a vertical or nearly vertical crack, is called reset. The formation of fault cracks is a consequence of stretching of the earth's crust, and stretching is almost always associated with areas of uplift where the lithosphere swells, i.e. its profile is made convex.

Folding movements are movements of the earth's crust, as a result of which folds are formed, i.e. of varying complexity wave-like bending of layers. They differ from oscillatory (epeirogenic) ones in a number of significant features: they are episodic in time, in contrast to oscillatory ones, which never stop; they are not ubiquitous and are each time confined to relatively limited areas of the earth’s crust; Covering very long periods of time, folding movements nevertheless proceed faster than oscillatory movements and are accompanied by high magmatic activity. In folding processes, the movement of the earth’s crust matter always occurs in two directions: horizontal and vertical, i.e. tangentially and radially. The consequence of tangential movement is the formation of folds, thrusts, etc. The vertical movement leads to the raising of the section of the lithosphere that is crushed into folds and to its geomorphological design in the form of a high shaft - a mountain range. Folding movements are characteristic of geosynclinal areas and are poorly represented or completely absent on platforms.

Oscillatory and folding movements are two extreme forms of a single process of movement of the earth's crust. Oscillatory movements are primary, universal, and at times, under certain conditions and in certain territories, they develop into orogenic movements: folding occurs in rising areas.

The most characteristic outward expression complex processes of the movement of the earth's crust is the formation of mountains, mountain ranges and mountainous countries. At the same time, in areas of different “hardness” it proceeds differently. In areas of development of thick strata of sediments that have not yet undergone folding and, therefore, have not lost the ability to plastic deformations, first the formation of folds occurs, and then the uplifting of the entire complex folded complex. A huge bulge of an anticlinal type appears, which subsequently, being dissected by the activity of rivers, turns into a mountainous country.

In areas that have already undergone folding in past periods of their history, the uplift of the earth's crust and the formation of mountains occurs without new folding, with the dominant development of fault dislocations. These two cases are the most typical and correspond to two main types mountainous countries: type of folded mountains (Alps, Caucasus, Cordillera, Andes) and type of block mountains (Tien Shan, Altai).

Just as mountains on Earth indicate uplift of the earth's crust, plains indicate subsidence. The alternation of bulges and depressions is also observed on the ocean floor, therefore, it is also affected by oscillatory movements (underwater plateaus and basins indicate submerged platform structures, underwater ridges indicate flooded mountainous countries).

Geosynclinal areas and platforms form the main structural blocks of the earth's crust, which are clearly expressed in modern relief.

The youngest structural elements of the continental crust are geosynclines. A geosyncline is a highly mobile, linearly elongated and highly dissected section of the earth's crust, characterized by multidirectional tectonic movements of high intensity, energetic phenomena of magmatism, including volcanism, frequent and strong earthquakes. The geological structure that arose where movements are geosynclinal in nature is called folded zone. Thus, it is obvious that folding is characteristic primarily of geosynclines; here it manifests itself in its most complete and vivid form. The process of geosynclinal development is complex and in many ways not yet sufficiently studied.

In its development, the geosyncline goes through several stages. At an early stage development in them there is a general subsidence and accumulation of thick strata of marine sedimentary and volcanogenic rocks. Of sedimentary rocks, this stage is characterized by flysch (a regular thin alternation of sandstones, clay and marls), and of volcanic rocks - lavas of basic composition. In the middle stage, when a thickness of sedimentary-volcanic rocks with a thickness of 8-15 km accumulates in geosynclines. The processes of subsidence are replaced by gradual uplift, sedimentary rocks undergo folding, and at great depths - metamorphism; acidic magma penetrates and hardens along the cracks and breaks that penetrate them. In the late stage development in place of the geosyncline, under the influence of the general uplift of the surface, high folded mountains arise, crowned active volcanoes with the outpouring of lavas of intermediate and basic composition; the depressions are filled with continental sediments, the thickness of which can reach 10 km or more. With the cessation of uplifting processes, high mountains are slowly but steadily destroyed until in their place a hilly plain - a peneplain - is formed with the emergence of “geosynclinal lows” in the form of deeply metamorphosed crystalline rocks. Having gone through a geosynclinal development cycle, the earth's crust thickens, becomes stable and rigid, incapable of new folding. The geosyncline transforms into a different qualitative block of the earth’s crust - platform.

Modern geosynclines on Earth are areas occupied by deep seas, classified as internal, semi-enclosed and interisland seas.

Throughout the geological history of the Earth, a number of epochs of intense folding mountain building were observed, followed by a change from the geosynclinal regime to the platform one. The most ancient folding epochs date back to Precambrian time, followed by Baikal(end of the Proterozoic – beginning of the Cambrian), Caledonian or Lower Paleozoic(Cambrian, Ordovician, Silurian, beginning of Devonian), Hercynian or Upper Paleozoic(end of Devonian, Carboniferous, Permian, Triassic), Mesozoic (Pacific), Alpine(end of Mesozoic - Cenozoic).

The lithosphere is the rocky shell of the Earth. From the Greek “lithos” - stone and “sphere” - ball

Lithosphere - external hard shell The Earth, which includes the entire crust of the Earth with part of the Earth's upper mantle and consists of sedimentary, igneous and metamorphic rocks. The lower boundary of the lithosphere is unclear and is determined by a sharp decrease in the viscosity of rocks, a change in the speed of propagation of seismic waves and an increase in the electrical conductivity of rocks. The thickness of the lithosphere on continents and under oceans varies and averages 25 - 200 and 5 - 100 km, respectively.

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

The Earth's crust is the thin upper shell of the Earth, which is 40-80 km thick on the continents, 5-10 km under the oceans and makes up only about 1% of the Earth's mass. Eight elements - oxygen, silicon, hydrogen, aluminum, iron, magnesium, calcium, sodium - form 99.5% of the earth's crust.

According to scientific research, scientists were able to establish that the lithosphere consists of:

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

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

Greatest thickness the earth's crust is in mountainous regions(under the Himalayas - over 75 km), the average - in the areas of the platforms (under the West Siberian Lowland - 35-40, within the borders of the Russian Platform - 30-35), and the smallest - in central regions oceans (5-7 km). The predominant part of the earth's surface is the plains of the continents and ocean floor.

The continents are surrounded by a shelf - a shallow strip with a depth of up to 200 g and an average width of about 80 km, which, after a sharp steep bend of the bottom, turns into a continental slope (the slope varies from 15-17 to 20-30°). The slopes gradually level out and turn into abyssal plains (depths 3.7-6.0 km). Greatest depths(9-11 km) have oceanic trenches, the vast majority of which are located on the northern and western edges Pacific Ocean.

The main part of the lithosphere consists of igneous igneous rocks (95%), among which granites and granitoids predominate on the continents, and basalts in the oceans.

Blocks of the lithosphere - lithospheric plates - move along a relatively plastic asthenosphere. The section of geology on plate tectonics is devoted to the study and description of these movements.

To designate the outer shell of the lithosphere, the now obsolete term sial was used, derived from the name of the main rock elements Si (Latin: Silicium - silicon) and Al (Latin: Aluminum - aluminum).

Lithospheric plates

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

Pacific– the most large stove planets along whose borders there are constant collisions tectonic plates and faults form - this is the reason for its constant decrease;
Eurasian– covers almost the entire territory of Eurasia (except Hindustan and Arabian Peninsula) and contains the most most of continental crust;
Indo-Australian– it includes the Australian continent and the Indian subcontinent. Due to constant collisions with the Eurasian plate, it is in the process of breaking;
South American– consists of South American continent and parts of the Atlantic Ocean;
North American– consists of the North American continent, part northeastern Siberia, northwestern Atlantic and half of the Arctic oceans;
African– consists of the African continent and the oceanic crust of the Atlantic and Indian Oceans. Interestingly, the plates adjacent to it move in the opposite direction from it, so the largest fault on our planet is located here;
Antarctic plate– consists of the continent of Antarctica and the nearby oceanic crust. Due to the fact that the plate is surrounded by mid-ocean ridges, the remaining continents are constantly moving away from it.

Movement of tectonic plates in the lithosphere

Lithospheric plates, connecting and separating, constantly change their outlines. This allows scientists to put forward the theory that about 200 million years ago the lithosphere had only Pangea - a single continent, which subsequently split into parts, which began to gradually move away from each other at a very low speed (on average about seven centimeters per year ).

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

When the oceanic and continental plates collide, the edge of the oceanic crust is subducted under the continental crust, while on the other side of the oceanic plate its boundary diverges from the adjacent plate. The boundary along which the movement of lithospheres occurs is called the subduction zone, where the upper and subducting edges of the plate are distinguished. It is interesting that the plate, plunging into the mantle, begins to melt when the upper part of the earth’s crust is compressed, as a result of which mountains are formed, and if magma also erupts, then volcanoes.

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

Lithosphere problems

The intensive development of industry has led to the fact that man and the lithosphere have recently begun to get along extremely poorly with each other: the pollution of the lithosphere is acquiring catastrophic proportions. This happened due to the increase in industrial waste combined with household waste and used in agriculture fertilizers and pesticides, which negatively affects chemical composition soil and living organisms. Scientists have calculated that about one ton of garbage is generated per person per year, including 50 kg of hard-to-degrade waste.

Today, lithosphere pollution has become actual problem, since nature is not able to cope with it on its own: the self-cleaning of the earth’s crust occurs very slowly, and therefore harmful substances gradually accumulate and over time have a negative impact on the main culprit of the problem - the person.

It is carried out by reducing the viscosity of rocks, increasing their electrical conductivity, and also due to the speed with which seismic waves propagate. The lithosphere has different thicknesses on land and under the oceans. Its average value is 25-200 km for land and 5-100 km for.

95% of the lithosphere consists of igneous magma rocks. Granites and granitoids are the predominant rocks on the continents, while basalts are such rocks.

The lithosphere is the environment for all known mineral resources, it is also an object human activity. Changes in the lithosphere have an impact on the environment.

Soils are one of the components upper parts earth's crust. For a person they have great importance. They are an organo-mineral product that is the result of thousands of years of activity various organisms, as well as such factors as air, water, solar light and warmth. The thickness of the soil, especially in comparison with the thickness of the lithosphere itself, is relatively small. IN different regions it ranges from 15-20 cm to 2-3 m.

Soils appeared along with the emergence of living matter. Further they developed, they were influenced by the activity of microorganisms, plants and animals. The bulk of all microorganisms and organisms existing in the lithosphere are concentrated in the soil at a depth of several meters.

The lithosphere is the outer shell of the Earth, made up of relatively hard material: This is the earth's crust and the upper layer of the mantle. The term “” was coined by the American scientist Burrell in 1916, but at that time this concept meant only the solid rocks that make up the earth’s crust - the mantle was no longer considered part of this shell. Later, the upper sections of this layer of the planet (up to several tens of kilometers wide) were included: they border on the so-called asthenosphere, which is characterized by low viscosity, high temperature, at which substances already begin to melt.

Thickness varies in different parts Earth: its layer can be from five kilometers thick - under the deepest places, and near the coast it already rises to 100 kilometers. Beneath the continents, the lithosphere extends up to two hundred kilometers deep.

In the past, it was believed that the lithosphere had a monolithic structure and did not break into parts. But this assumption has long been refuted - this one consists of several plates that move along the plastic mantle and interact with each other.

Hydrosphere

As the name suggests, the hydrosphere is the shell of the Earth consisting of water, or rather, all the water on the surface of our planet and under the Earth: oceans, seas, rivers and lakes, as well as groundwater. Ice and water in gaseous state or steam is also part water shell. The hydrosphere consists of more than one and a half billion cubic kilometers of water.

Water covers 70% of the Earth's surface, most of it in the World Ocean - almost 98%. Only one and a half percent is allocated to ice at the poles, and the rest is rivers, lakes, reservoirs, and groundwater. Fresh water it makes up only 0.3% of the entire hydrosphere.

The hydrosphere owes its appearance to

The state of rest is unknown to our planet. This applies not only to external ones, but also internal processes that occur in the bowels of the Earth: its lithospheric plates are constantly moving. True, some parts of the lithosphere are quite stable, while others, especially those located at the junctions of tectonic plates, are extremely mobile and constantly shake.

Naturally, people could not ignore such a phenomenon, and therefore throughout their history they studied and explained it. For example, in Myanmar there is still a legend that our planet is entwined with a huge ring of snakes, and when they begin to move, the earth begins to shake. Such stories could not satisfy inquisitive human minds for long, and in order to find out the truth, the most curious drilled into the ground, drew maps, built hypotheses and made assumptions.

The concept of lithosphere contains the hard shell of the Earth, consisting of the earth's crust and a layer of softened rocks that make up the upper mantle, the asthenosphere (its plastic composition allows the plates that make up the earth's crust to move along it at a speed of 2 to 16 cm per year). It is interesting that the upper layer of the lithosphere is elastic, and the lower layer is plastic, which allows the plates to maintain balance when moving, despite constant shaking.

During numerous studies, scientists came to the conclusion that the lithosphere has a heterogeneous thickness, and largely depends on the terrain under which it is located. So, on land its thickness ranges from 25 to 200 km (the older the platform, the larger it is, and the thinnest is located under young mountain ranges).

But the thinnest layer of the earth’s crust is under the oceans: its average thickness ranges from 7 to 10 km, and in some regions of the Pacific Ocean it even reaches five. The thickest layer of crust is located at the edges of the oceans, the thinnest is located under the mid-ocean ridges. Interestingly, the lithosphere has not yet fully formed, and this process continues to this day (mainly under the ocean floor).

What is the earth's crust made of?

The structure of the lithosphere under the oceans and continents is different in that there is no granite layer under the ocean floor, since the oceanic crust was subjected to melting processes many times during its formation. Common to the oceanic and continental crust are such layers of the lithosphere as basalt and sedimentary.

Thus, the earth's crust consists mainly of rocks that are formed during the cooling and crystallization of magma, which penetrates into the lithosphere along cracks. If the magma was not able to seep to the surface, then it formed coarse-crystalline rocks such as granite, gabbro, diorite, due to its slow cooling and crystallization.

But the magma, which managed to get out due to rapid cooling, formed small crystals - basalt, liparite, andesite.

As for sedimentary rocks, they were formed in the Earth’s lithosphere in different ways: clastic rocks appeared as a result of the destruction of sand, sandstones and clay, chemical rocks were formed due to various chemical reactions in aqueous solutions - these are gypsum, salt, phosphorites. Organic ones were formed by plant and calcareous residues - chalk, peat, limestone, coal.

Interestingly, some rocks appeared due to a complete or partial change in their composition: granite was transformed into gneiss, sandstone into quartzite, limestone into marble. According to scientific research, scientists have been able to establish that the lithosphere consists of:

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

As for the structure of the lithosphere, there are stable and mobile zones (in other words, platforms and folded belts). On tectonic maps you can always see the marked boundaries of both stable and dangerous territories. First of all, this is the Pacific fire ring(located along the edges of the Pacific Ocean), as well as part of the Alpine-Himalayan seismic belt (Southern Europe and the Caucasus).

Description of platforms

A platform is an almost motionless part of the earth's crust that has gone through a very long stage of geological formation. Their age is determined by the stage of formation of the crystalline foundation (granite and basalt layers). Ancient or Precambrian platforms on the map are always located in the center of the continent, young ones are either at the edge of the continent or between Precambrian platforms.

Mountain fold region

The folded mountain area was formed during the collision of tectonic plates located on the mainland. If mountain ranges were formed recently, increased seismic activity is recorded near them and they are all located along the edges of lithospheric plates (younger massifs belong to the Alpine and Cimmerian stages of formation). Older areas related to ancient, Paleozoic folding can be located either on the edge of the continent, for example, in North America and Australia, and in the center - in Eurasia.

It is interesting that scientists determine the age of folded mountain areas based on the youngest folds. Since mountain building occurs continuously, this makes it possible to determine only the time frame of the stages of development of our Earth. For example, the presence of a mountain range in the middle of a tectonic plate indicates that a boundary once passed there.

Lithospheric plates

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

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

The Pacific is the largest plate on the planet, along the boundaries of which constant collisions of tectonic plates occur and faults form - this is the reason for its constant decrease;
Eurasian - covers almost the entire territory of Eurasia (except for Hindustan and the Arabian Peninsula) and contains the largest part of the continental crust;
Indo-Australian - it includes the Australian continent and the Indian subcontinent. Due to constant collisions with the Eurasian plate, it is in the process of breaking;
South American - consists of the South American continent and part of the Atlantic Ocean;
North American - consists of the North American continent, part of northeastern Siberia, the northwestern part of the Atlantic and half of the Arctic oceans;
African - consists of the African continent and the oceanic crust of the Atlantic and Indian oceans. Interestingly, the plates adjacent to it move in the opposite direction from it, so the largest fault on our planet is located here;
Antarctic plate – consists of the continent of Antarctica and nearby oceanic crust. Due to the fact that the plate is surrounded by mid-ocean ridges, the remaining continents are constantly moving away from it.

Movement of tectonic plates

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

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

Relief

It is not surprising that the movement of lithospheres directly affects appearance of our planet, and the diversity of the Earth’s relief is amazing (relief is a set of irregularities on the earth’s surface, which are located above sea level at different heights, and therefore the main forms of the Earth’s relief are conventionally divided into convex (continents, mountains) and concave - oceans, river valleys, gorges).

It is worth noting that land occupies only 29% of our planet (149 million km2), and the lithosphere and topography of the Earth consists mainly of plains, mountains and lowlands. As for the ocean, it average depth amounts to a little less than four kilometers, and the lithosphere and relief of the Earth in the ocean consist of continental shallows, coastal slope, ocean bed and abyssal or deep-sea trenches. Most of the ocean has a complex and varied topography: there are plains, basins, plateaus, hills, and ridges up to 2 km high.

Lithosphere problems

The intensive development of industry has led to the fact that man and the lithosphere have recently begun to get along extremely poorly with each other: the pollution of the lithosphere is acquiring catastrophic proportions. This happened due to the increase in industrial waste in combination with household waste and fertilizers and pesticides used in agriculture, which negatively affects the chemical composition of the soil and living organisms. Scientists have calculated that about one ton of garbage is generated per person per year, including 50 kg of hard-to-degrade waste.

Today, pollution of the lithosphere has become an urgent problem, since nature is not able to cope with it on its own: the self-cleaning of the earth’s crust occurs very slowly, and therefore harmful substances gradually accumulate and, over time, negatively affect the main culprit of the problem - humans.

The lithosphere of planet Earth is the solid shell of the globe, which includes multi-layered blocks called lithospheric plates. As Wikipedia points out, translated from Greek language This " stone ball" It has a heterogeneous structure depending on the landscape and the plasticity of the rocks located in upper layers soil.

The boundaries of the lithosphere and the location of its plates are not fully understood. Modern geology has only limited quantity data about internal structure globe. It is known that lithospheric blocks have boundaries with the hydrosphere and atmospheric space of the planet. They are in close relationship with each other and touch each other. The structure itself consists of the following elements:

Asthenosphere. A layer with reduced hardness, which is located in the upper part of the planet relative to the atmosphere. In places it has very low strength and is prone to fractures and ductility, especially if groundwater flows within the asthenosphere.
Mantle. This is the part of the Earth called the geosphere, located between the asthenosphere and inner core planets. It has a semi-liquid structure, and its boundaries begin at a depth of 70–90 km. It is characterized by high seismic velocities, and its movement directly affects the thickness of the lithosphere and the activity of its plates.
Core. The center of the globe, which has a liquid etiology, and from the movement of its mineral components and molecular structure molten metals depend on the preservation of the planet's magnetic polarity and its rotation around its axis. The main component of the earth's core is an alloy of iron and nickel.

What is the lithosphere? In fact, it is the solid shell of the Earth, which acts as an intermediate layer between fertile soil, mineral deposits, ores and the mantle. On the plain, the thickness of the lithosphere is 35–40 km.

Important! In mountainous areas this figure can reach 70 km. In the area of such geological heights like Himalayan or Caucasus Mountains, the depth of this layer reaches 90 km.

Structure of the Earth

Layers of the lithosphere

If we consider the structure of lithospheric plates in more detail, they are classified into several layers, which form geological features one or another region of the Earth. They form the basic properties of the lithosphere. Based on this, the following layers of the hard shell of the globe are distinguished:

Sedimentary. Covers most of the top layer of all earth blocks. It mainly consists of volcanic rocks, as well as remains organic matter, which over many millennia have decomposed into humus. Fertile soils are also part of the sedimentary layer.
Granite. These are lithospheric plates located in constant movement. They are predominantly composed of super-strong granite and gneiss. The last component is a metamorphic rock, the vast majority of which is filled with minerals such as potassium spar, quartz and plagioclase. Seismic activity of this layer of solid shell is at the level of 6.4 km/sec.
Basaltic. It is predominantly composed of basalt deposits. This part of the Earth's solid shell was formed under the influence volcanic activity back in ancient times, when the formation of the planet took place and the first conditions for the development of life arose.

What is the lithosphere and its multilayer structure? Based on the above, we can conclude that this hard part globe, which has a heterogeneous composition. Its formation took place over several millennia, and high-quality composition depends on what metaphysical and geological processes took place in a particular region of the planet. The influence of these factors is reflected in the thickness of lithospheric plates and their seismic activity in relation to the structure of the Earth.

Layers of the lithosphere

Oceanic lithosphere

This variety earth's shell differs significantly from its mainland. This is due to the fact that the boundaries of lithospheric blocks and the hydrosphere are closely intertwined, and in some parts of it the water space is distributed beyond the surface layer of the lithospheric plates. This applies to bottom faults, depressions, cavernous formations of various etiologies.

Oceanic crust

That is why oceanic plates have their own structure and consist of the following layers:

marine sediments that have a total thickness of at least 1 km (in the deep ocean, they may be completely absent);
secondary layer (responsible for the distribution of medium and longitudinal waves moving at speeds of up to 6 km/sec., takes an active part in the movement of plates, thereby provoking earthquakes of varying power);
the lower layer of the hard shell of the globe in the area where the ocean floor is located, which is mainly composed of gabbro and borders the mantle ( average activity seismic waves range from 6 to 7 km/sec.).

A transitional type of lithosphere is also distinguished, located in the area of oceanic soil. It is characteristic of island zones formed in an arc. In most cases, their appearance is associated with geological process movements of lithospheric plates that were layered on top of each other, forming this kind of irregularities.

Important! A similar structure of the lithosphere can be found on the outskirts of the Pacific Ocean, as well as in some parts of the Black Sea.

Useful video: lithospheric plates and modern relief

Chemical composition

The lithosphere is not diverse in terms of its content of organic and mineral compounds and is mainly presented in the form of 8 elements.

Most of these are rocks that were formed during a period of active eruption of volcanic magma and plate movement. The chemical composition of the lithosphere is as follows:

Oxygen. Occupies at least 50% of the entire structure of the solid shell, filling its faults, depressions and cavities formed during the movement of plates. Plays a key role in the balance of compression pressure during geological processes.
Magnesium. This is 2.35% of the Earth's solid shell. Its appearance in the lithosphere is associated with magmatic activity in early periods formation of the planet. It is found throughout the continental, marine and oceanic parts of the planet.
Iron. Rock, which is the main mineral of lithospheric plates (4.20%). Its main concentration is in the mountainous regions of the globe. It is in this part of the planet highest density given chemical element. It is not presented in pure form, but is found in lithospheric plates mixed together with other mineral deposits.

Useful video: lithosphere and lithospheric plates

Conclusion

The rest chemical compounds, filling lithospheric blocks are carbon, potassium, aluminum, titanium, sodium and silicon. In some regions of the planet their concentration is greater, while in other parts of the Earth's solid shell they are present in minimal quantities.