The upper solid layer of the lithosphere. What is the lithosphere

LITHOSPHERE

Structure and composition of the lithosphere. The neomobility hypothesis. Formation of continental blocks and oceanic depressions. Movement of the lithosphere. Epeirogenesis. Orogeny. The main morphostructures of the Earth: geosynclines, platforms. Age of the Earth. Geochronology. Ages of mountain building. Geographic distribution of mountain systems of different ages.

Structure and composition of the lithosphere.

The term "lithosphere" has been used in science for a long time - probably from the middle of the 19th century. But it acquired its modern significance less than half a century ago. Even in the geological dictionary of the 1955 edition it is said: lithosphere- the same as the earth's crust. In the dictionary edition of 1973 and later: lithosphere... in the modern sense, includes the earth's crust ... and rigid the 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 ones from several 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, which is part of the upper mantle. The boundary between the earth's crust and the substratum is the Mohorovic surface, when crossing it from top to bottom, the velocity of longitudinal seismic waves increases abruptly. 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 at an average speed of 5-10 cm per year.

The structure and thickness of the earth's crust are not the same: that part of it, which can be called the mainland, 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 basalt), the average thickness is about 8 km. Transitional types of the earth's crust are also distinguished (lecture 3).

In science, the opinion has firmly entrenched that the earth's crust in the form in which it exists is a derivative of the mantle. Throughout geological history, a directed irreversible process of enrichment of the Earth's surface with matter from the Earth's interior has taken place. 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 magma crystallization. They make up 95% of the mass of the matter that makes up the earth's crust. Depending on the conditions under which the process of magma solidification took place, intrusive (formed at a depth) and effusive (poured to the surface) rocks are formed. Intrusive ones include: granite, gabbro, igneous ones - basalt, liparite, volcanic tuff, etc.

Sedimentary rocks are formed on the earth's surface in various ways: some of them are formed from the products of the destruction of rocks that formed earlier (detrital: sands, gelatins), some due to the vital activity of organisms (organogenic: limestones, chalk, shell rock; siliceous rocks, hard and brown coal, some ores), clay (clays), chemical (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 bowels, 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 shell, the role of a thin and discontinuous sedimentary layer is more significant, which on most of the earth's surface is in direct contact with water, air, takes an active part in geographical processes (thickness - 2.2 km: from 12 km in troughs, up to 400 - 500 m in the ocean bed). The most common are clays and shale, sands and sandstones, carbonate rocks. An important role in the geographic envelope is played by loess and loess-like loams, which form the surface of the earth's crust in the non-glacial regions of the northern hemisphere.

In the earth's crust - the upper part of the lithosphere - 90 chemical elements were found, 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, four%.

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

The substrate of the upper mantle, located on the asthenosphere, is a kind of rigid platform on which the earth's crust was formed in the course of the geological development of the Earth. The substance of the asthenosphere, apparently, is characterized by low viscosity and experiences slow displacements (currents), which, presumably, are 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 lowering of others.

The theory of lithospheric plates was 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 mainland Pangea, surrounded by the waters of the Pantallass Ocean (the Tethys Sea was part of this ocean). In the Mesozoic, splits and drift (floating) of its individual blocks (continents) began. The continents, composed of a relatively light substance, which Wegener called sial (silicium-aluminum), 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 moved away, later Antarctica, Australia and North America. A version of the mobilism hypothesis developed later allows the existence in the past of two giant pro-continents - Laurasia and Gondwana. From the first, S. 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 a bold cross was put on the theory of continental drift and up to 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.), asserting the invariable (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 built, in which only a change in the relative position of the continents remained from Wegener's hypothesis, 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, according to Wegener, the continents moved along the substance that made up the ocean floor, while in the modern theory, plates, which include areas of land and the ocean floor, participate in the movement; The boundaries between plates can run along the bottom of the ocean, and 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 - the layer of the upper mantle that underlies the lithosphere and has viscosity and plasticity. In places of the mid-ocean ridges, lithospheric plates are built up due to the substance rising from the bowels, and move apart along the fault axis or rifts to the sides - spreading (English spreading - expansion, distribution). But the surface of the globe cannot increase. The emergence of new sections of the earth's crust on the sides of the mid-ocean ridges must be compensated for by its disappearance somewhere. If we believe that lithospheric plates are sufficiently stable, it is natural to assume that the disappearance of the crust, as well as the formation of a new one, should occur at the boundaries of approaching plates. In this case, there can be three different cases:

Two sections of the oceanic crust are approaching;

A section of the continental crust approaches a section of the oceanic;

Two sections of the continental crust are approaching.

The process that occurs when parts of the oceanic crust approach each other can be schematically described as follows: the edge of one plate rises somewhat, forming an island arc; the other goes under it, here the level of the upper surface of the lithosphere decreases, and a deep-water oceanic trench is formed. These are the Aleutian Islands and the Aleutian Trench framing 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 - the Antilles and the Puerto Rico Trench, the South Sandwich Islands and the South Sandwich Trench. The movement of plates relative to each other is accompanied by significant mechanical stresses, therefore, in all these places, high seismicity and intense volcanic activity are observed. The sources of earthquakes are located mainly on the surface of contact between two plates and can be at great depths. The edge of the plate, which has gone deep, plunges into the mantle, where it gradually turns into mantle matter. The submerging plate is heated, magma is melted out of it, which pours out in the volcanoes of the island arcs.

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

When two sections of the continental crust approach each other, the edge of each of them experiences folding. Faults, mountains are formed. 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 powerful. 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 highest mountains on Earth, high seismicity is observed along its entire length, and there are active volcanoes in the west of the belt.

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

The rethinking of the ideas of A. Wegener led to the fact that, instead of the drift of the continents, the entire lithosphere began to be considered as the moving firmament of the Earth, and this theory ultimately came down to the so-called "tectonics of lithospheric plates" (today - "new global tectonics ").

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

1. The lithosphere of the Earth, 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 across, and medium-sized (about 1000 km) relatively rigid and monolithic plates.

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

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

b) underthrust (subduction) of an oceanic plate under a continental or oceanic one with the appearance of a volcanic arc or a marginal-continental volcanic-plutonic belt above the subduction zone;

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

4. The movement of lithospheric plates on the surface of the asthenosphere obeys the Euler theorem, which states that the movement of conjugated points on the sphere occurs along circles drawn relative to the axis passing through the center of the Earth; the points of exit of the axis to the surface are called the poles of rotation, or disclosure.

5. On the scale of the planet as a whole, spreading is automatically compensated by subduction, i.e. how much new oceanic crust is born in 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 axes of the separation of the median ridges, ascending currents are formed; they become horizontal at the periphery of the ridges and descend in subduction zones at the margins of the oceans. The 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 on 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 hypotheses. It is based on the concept of 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.

Recently, many researchers have increasingly begun to lean towards the idea that the uneven distribution of the Earth's endogenous energy, as well as the periodization of some exogenous processes, is controlled by external (cosmic) factors in relation to the planet. Of these, the most effective force directly affecting the geodynamic development and transformation of the Earth's matter, apparently, is the effect of the gravitational influence of the Sun, the Moon and other planets, taking into account the inertial forces of the Earth's rotation around its axis and its orbital movement. 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. Orogeny.

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 (slow sinking of heavier elements deep into and raising of lighter ones upwards), the zone of their appearance to a depth of about 700 km was called the tectonosphere.

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

From a geographical point of view, the division of tectonic movements into oscillatory (epeirogenic) and folding (orogenic) seems to be successful.

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

For the formation of modern landscapes, oscillatory movements of the recent geological past - the Neogene and the Quaternary period - were of great importance. They got the name recent or neotectonic. The range of neotectonic movements is very significant. In the Tien Shan mountains, for example, their amplitude reaches 12-15 km, and without neotectonic movements, a peneplain would exist in the place of this high mountainous country - almost a plain that arose on the site of the destroyed mountains. 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, less often in several centimeters (in the mountains). On the Russian Plain, the maximum uplift rates of up to 10 mm per year are established for the Donbass and the northeast of the Dnieper Upland, the maximum lowering rates, up to 11.8 mm per year, are in the Pechora Lowland.

The consequences of epeirogenic movements are:

1. Redistribution of the ratio between land and sea areas (regression, transgression). The best way to study oscillatory motions is by looking at the behavior of the coastline, because in oscillatory motions the boundary between land and sea shifts due to the expansion of the sea area due to the reduction of the land area or the reduction of the sea area due to the 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 - occurs regression, i.e. retreat of the sea. The sinking of the land at a constant sea level, or the rise of the sea level at a stable position of the land 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 be reflected in the nature of the organic world and soil cover, the configuration of the seas and continents will change. In the event of a regression of the sea, some continents and islands may unite if the straits separating them were shallow. In transgression, on the contrary, the land masses are separated into separate continents or new islands are separated from the mainland. The presence of oscillatory movements largely explains the effect of the destructive activity of the sea. The slow transgression of the sea to the steep coasts is accompanied by the development abrasive(abrasion - cutting off the coast by the sea) of the surface and the abrasion ledge limiting it from the land side.

2. Due to the fact that the fluctuations of the earth's crust occur at 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, covering vast areas, create large waves on it: during uplifts, huge domes; during subsidence, bowls and huge depressions.

During oscillatory movements, it can happen that when one section rises and the adjacent one descends, then breaks occur at the boundary between such differently moving sections (and also within each of them), 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 almost vertical crack, is called reset. The formation of normal faults is a consequence of crustal extension, and extension is almost always associated with uplift regions where the lithosphere swells, i.e. its profile becomes convex.

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

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

The most characteristic external expression of the complex processes of the movement of the earth's crust is the formation of mountains, mountain ranges and mountainous countries. However, in areas of different "rigidity" it proceeds differently. In areas of development of thick strata of sediments that have not yet undergone folding and, therefore, have not lost their ability to plastic deformation, folds first form, and then the entire complex folded complex is uplifted. A huge bulge of the anticlinal type arises, which subsequently, being dissected by the activity of the 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 occur without new folding, with the development of fault dislocations dominating. These two cases are the most characteristic and correspond to the two main types of mountainous countries: the type of folded mountains (Alps, Caucasus, Cordillera, Andes) and the type of blocky mountains (Tien Shan, Altai).

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

Geosynclinal regions and platforms form the main structural blocks of the earth's crust, which are clearly expressed in the 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, and frequent and strong earthquakes. The geological structure that has arisen where the movements are geosynclinal in nature is called folded zone. Thus, it is obvious that folding is primarily characteristic of geosynclines, here it manifests itself in its most complete and vivid form. The process of geosynclinal development is complex and in many respects has not yet been 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 volcanic rocks. Sedimentary rocks of this stage are characterized by flyschs (a regular thin alternation of sandstones, clays, and marls), and volcanic rocks are lavas of basic composition. At 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 - metamorphization, along the cracks and ruptures penetrating them, acid magma is introduced and solidifies. Late stage development at the site of the geosyncline under the influence of the general uplift of the surface, high folded mountains appear, crowned with active volcanoes with an outpouring of lavas of medium and basic composition; depressions are filled with continental deposits, the thickness of which can reach 10 km or more. With the cessation of uplift processes, high mountains are slowly but steadily destroyed until a hilly plain is formed in their place - peneplain - with access to the surface of "geosynclinal bottoms" in the form of deeply metamorphosed crystalline rocks. 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 - platform.

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

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

Since childhood, I was drawn to new knowledge like a magnet. While all my friends at the first opportunity ran into the yard to ride a bike and kick a ball, I spent hours reading children's encyclopedias. In one of them I met the answer to the question, what is lithosphere. I will tell you about this now.

How the planet works and what is the lithosphere

Imagine a bouncing rubber ball. It is completely made of one substance - that is, it has a homogeneous structure.

Our planet inside is not at all homogeneous.

• In the very center of the earth there is a dense red-hot nucleus.
• It is followed by mantle.
• On a surface the planet, like a blanket, covers Earth's crust.

Part of the mantle layer together with the earth's crust form the lithosphere - the shell of our planet. We live on it, we walk and drive on it, we build houses and plant plants.

What are lithospheric plates

Lithosphere It's not a complete shell. Imagine now a rubber ball that has been cut and glued back together. Each large piece such a ball this is a lithospheric plate.

Plate boundaries are very arbitrary because they are constantly changing are shifting collide - in general, live an active and eventful life. Of course, by our standards, they do not move too fast - a couple of centimeters a year, well, a maximum of six. But on a global scale, it still leads to big changes.

Past of the lithosphere

Geologists are extremely interested in how the planet developed. They found out a funny pattern: with a certain frequency, everything continents come together merging into one after which they part again. Like a group of friends who met, sat down and ran away again on business.

Now the planet is in the stage of separation, which occurred after the single continent of Pangea was divided into pieces.

It is believed that they are all will gather into a single whole - Pangea Ultima- in 200 million years. Those who are afraid to fly on airplanes will be very happy about this - there will be no need to cross the oceans.

True, you have to prepare for the strong climate change. The British will have to store warm clothes - they will be thrown to the North Pole. The inhabitants of Siberia, on the other hand, can rejoice - life in the subtropics shines on them.

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For the first time about structure of our planet I, like everyone else, learned in the classroom geography However, I didn't have any interest in it. Indeed, the lesson is boring, and pulls outside to play football and all that. Things were quite different when I started reading Jules Verne's novel. "Journey to the Center of the Earth". I still remember my impressions of what I read.

Earth structure

infiltrate deep into Earth it is quite problematic for a person, so the study of the depths is carried out using seismic equipment. Like a number of planets included in earth group, The earth has a layered structure. Under bark located mantle, and the central part is nucleus, consisting of iron-nickel alloy. Each of the layers is significantly different in its structure and composition. During the existence of our planet, heavier rocks and substances went deeper under the influence of gravity, and lighter stayed on the surface. Radius- the distance from the surface to the center, is more than 6 thousand kilometers.

What is the lithosphere

This term was first applied in 1916 coda, and until the middle of the last century was synonym notion "Earth's crust". Later it was proved that lithosphere captures the upper layers robes to a depth of several tens of kilometers. In the building, they are distinguished as stable (fixed) areas, as well as movable (folded belts). The thickness of this layer is from 5 to 250 kilometers. Beneath the surface of the oceans lithosphere has minimal thickness, and the maximum is observed in mountainous areas. This layer is the only one accessible to humans. Depending on the location, under the continent or the ocean, the structure of the crust may vary. The largest area is the oceanic crust, while the continental crust is 40%, but has a more complex structure. Science distinguishes three layers:

• sedimentary;
• granite;
• basaltic.

These layers contain the most ancient rocks, some of which are up to 2 billion years.

Lava lake in Erta Ale crater

The thickness of the crust under the oceans is from 5 to 10 kilometers. The thinnest crust is observed in the central oceanic regions. In the oceanic crust, like the continental, there are 3 layers:

• marine sediments;
• average;
• oceanic.

Nishinoshima Island. Formed in the Pacific Ocean after the eruption of an underwater volcano in 2013

mentioning oceanic crust, it is worth noting the deepest place in the world ocean - Mariana Trench located in the western part Pacific Ocean. Depth of depression over 11 kilometers. highest point lithosphere can be considered the highest mountain - Everest, whose height is 8848 meters above sea level. The most deep well, drilled in the thickness of the earth's crust, goes deep into 12262 meters. It is located on Kola Peninsula 10 kilometers west of the city Polar, what in Murmansk region.

Chomolungma, Everest, Sagarmatha - the highest peak of the Earth

As long as humanity has existed, so many disputes have been going on about what is the structure of the earth. Sometimes advanced completely crazy theories. Among the most striking is the theory of hollow earth, the theory about cellular cosmogony and the theory that icebergs emerge from the bowels of the earth which is completely unimaginable. In continuation of the theory of the hollow earth, there is an assumption about populated center, supposedly there people live :)

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I have always loved studying geography. As a child, I was interested in learning more about the Earth we walk on every day. Of course, when I realized that there is a nuclear reactor inside our planet, this did not please me much. However, the structure of the globe is already very exciting. For example, the upper solid part of the earth's surface.

What is the lithosphere

The lithosphere (from Greek - "stone ball") is called the shell of the earth's surface, or rather its solid part. That is, the oceans, seas, and other bodies of water are not the lithosphere. However, the bottom of any water resource is also considered to be a hard shell. Because of this, the thickness of the hard crust fluctuates. In the seas and oceans, it is thinner. On land, especially where mountains rise, it is thicker.

What is the thickness of the solid part of the Earth

But the lithosphere has a limit, if you dig into the depths, then the next ball after the lithosphere is the mantle. In addition to the earth's crust, the upper and hard cover of the mantle also enters the lower part of the lithosphere. But deeper in the bowels of the globe, the second layer softens, becomes more plastic. These areas are the limit of the solid shell of the earth. The thickness ranges from 5 to 120 kilometers.

Time divided the lithosphere into parts

There is such a thing as a lithospheric plate. The entire solid shell of the Earth split into several dozen plates. They tend to move slowly due to the compliance of the soft part of the mantle. It is interesting that, as a rule, volcanic and seismic activity is formed at the junctions of these plates. These are the largest lithospheric plates of this size.

• Pacific Plate - 103,000,000 km².
• North American Plate - 75,900,000 km².
• Eurasian plate - 67,800,000 km².
• African Plate - 61,300,000 km².

Plates can be continental or oceanic. They differ in thickness, oceanic ones are much thinner.

This is what the part of the globe is where we walk, drive, sleep and exist. The more I learn about the structure of our planet, the more I am surprised and delighted by how everything is globally thought out and arranged.

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After leaving school, I considered surveying as one of the options for further education. In order to enter the engineering specialty, in addition to mathematics, geography was required, so I diligently prepared for the entrance exams. One of the topics that I remember well then was the structure of the Earth - this is a very interesting section that tells about the structure of our planet.

Earth's crust or lithosphere

Imagine an ordinary chicken egg. It, like the Earth, has a hard shell (shell) on the outside, a liquid protein inside and in the very center - the yolk. It reminds me a little of the simplified structure of the Earth. But back to the lithosphere.

The hard shell of the planet is similar to an eggshell in that it is very thin and light. The Earth's crust is only 1% of the entire mass of the Earth and, unlike the shell, the lithosphere does not have an integral structure: the Earth's crust consists of plates drifting along the molten magma layer.

In one calendar year, the continents move by 7 cm.

This explains the frequent earthquakes and volcanic eruptions that affect territories located near the junctions of lithospheric plates.

The reason for the thinness of the lithosphere

To understand why the lithosphere took the form in which we know it, we need to turn to the history of the Earth.

4 billion years ago, an asteroid made of ice served as the basis for our planet. It revolved around the Sun in a giant cloud of space debris that stuck to it.

Soon the Earth became massive and all of its weight began to press on the inner layers so hard that they melted.

Melting led to the following consequences:

• water vapor rose to the surface;
• gases came out of the bowels;
• atmosphere has been formed.

Because of the Earth's gravity, steam and gases could not escape into space.

An incredible amount of water vapor appeared in the atmosphere, which collapsed from the clouds onto the boiling magma. Under the influence of precipitation, the magma cooled and petrified.

Newly minted pieces of the earth's crust collided with each other and were crushed - continents appeared, and water accumulated in places of depressions, which formed the World Ocean.

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In my understanding, the lithosphere is our habitat, our home, thanks to which the existence of all life is ensured. I think that The lithosphere is the most important resource potential of the Earth. Just imagine how many reserves of various minerals it contains!

What is the lithosphere from a scientific point of view

The lithosphere is a hard, but at the same time very fragile shell of our planet. Its outer part borders on the hydrosphere and atmosphere. It consists of the earth's crust and the upper part of the mantle.

The crust is divided into two types - oceanic and continental. Oceanic - young, it is relatively small in thickness. It oscillates constantly in the horizontal direction. The continental or, as it is also called, the continental layer is much thicker.

The structure of the earth's crust

Exists two major type plots bark: relatively fixed platforms and movable areas. Earthquakes and tsunamis are caused by plate movement. and other dangerous natural phenomena. The section of science studies these processes - tectonics. Due to the fact that I live in the relatively immobile central part of the European Plain, I was lucky not once in my life to see the destructive power of earthquakes with my own eyes.

Let's now go directly to the structure.

The continental crust consists of three main layers arranged in layers:

• Sedimentary. The surface layer on which we walk. Its thickness reaches up to 20 km.
• Granite. It is formed by igneous rocks. Its thickness is 10-40 km.
• Basaltic. Massive layer of igneous origin 15-35 km thick.

What is the earth's crust made of

Surprisingly, the earth's crust, which seems to us so powerful and thick, consists of relatively light-weight substances. It includes about 90 different elements.

The composition of the sedimentary layer includes:

• clay;
• shales;
• sandstones;
• carbonates;
• volcanic rocks;
• coal.

Other elements:

• oxygen (50% of the entire bark);
• silicon (25%);
• iron;
• potassium;
• calcium, etc.

As we can see, the lithosphere is a very complex structure. Not surprisingly, it has not yet been fully explored.

I've always been interested in getting to the bottom of things. Therefore, in childhood, I absolutely could not understand how the ancient "literates" claimed that the earth stands on elephants, turtles and other living creatures, without verifying this fact. And after I saw pictures with seas flowing down from the edge of the earth, I decided to thoroughly understand the issue of the structure of my native planet.

What is the lithosphere

This is the same “land” that was like a pancake located on the backs of three whales (in the view of the ancient “scientists”), that is solid shell of the planet. On it we build houses and grow crops, on its surface the oceans rage, mountains rise, and it shakes when an earthquake occurs. And although the word "shell" seems to be something solid and monolithic, but, nevertheless, The lithosphere consists of separate pieces - lithospheric plates, slowly drifting along the red-hot mantle.

Lithospheric plates

Like ice floes in a river lithospheric plates float, constantly colliding with each other or, on the contrary, moving in different directions. And it should be noted that the tiles are nothing like that, large ( 90% of the Earth's surface is made up of just 13 of these plates.).

The largest of them:

• Pacific Plate - 103300000 square km;
• North American - 75900000;
• Eurasian - 67800000;
• African - 61300000;
• Antarctic - 60900000.

Naturally, when such colossus collide, it cannot but end in something grandiose. True, this will happen very, very slowly, since the speed of movement of lithospheric plates is from 1 to 6 cm/year.

If one plate rests against another and begins to slowly crawl onto it, or both do not want to yield,mountains are formed(sometimes very high). And in the place where one "crust" of the earth has gone down, a deep gutter can appear.

If the plates, on the contrary, quarreled and move away from each other - magma begins to flow into the gap formed, forming small ridges.

And it also happens that the plates do not collide and do not scatter, but simply rub against each other, like a cat on the leg.

Then a very deep long crack appears in the earth, and unfortunately strong earthquakes can occur, which is clearly demonstrated by the San Andreas fault in seismically unstable California.

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And any negative lithospheric changes can exacerbate the global crisis. From this article you will learn about what the lithosphere and lithospheric plates are.

Concept definition

The lithosphere is the outer hard shell of the globe, which consists of the earth's crust, part of the upper mantle, sedimentary and igneous rocks. It is rather difficult to determine its lower boundary, but it is generally accepted that the lithosphere ends with a sharp decrease in the viscosity of rocks. The lithosphere occupies the entire surface of the planet. The thickness of its layer is not the same everywhere, it depends on the terrain: on the continents - 20-200 kilometers, and under the oceans - 10-100 km.

The Earth's lithosphere mostly consists of igneous igneous rocks (about 95%). These rocks are dominated by granitoids (on the continents) and basalts (under the oceans).

Some people think that the concepts "hydrosphere" / "lithosphere" mean the same thing. But this is far from true. The hydrosphere is a kind of water shell of the globe, and the lithosphere is solid.

Geological structure of the globe

The lithosphere as a concept also includes the geological structure of our planet, therefore, in order to understand what the lithosphere is, it should be considered in detail. The upper part of the geological layer is called the earth's crust, its thickness varies from 25 to 60 kilometers on the continents, and from 5 to 15 kilometers in the oceans. The lower layer is called the mantle, separated from the earth's crust by the Mohorovichich section (where the density of matter changes dramatically).

The globe is made up of the earth's crust, mantle and core. The earth's crust is a solid, but its density changes dramatically at the boundary with the mantle, that is, at the Mohorovichic line. Therefore, the density of the earth's crust is an unstable value, but the average density of a given layer of the lithosphere can be calculated, it equals 5.5223 grams / cm 3.

The globe is a dipole, that is, a magnet. Earth's magnetic poles are located in the southern and northern hemispheres.

Layers of the Earth's lithosphere

The lithosphere on the continents consists of three layers. And the answer to the question of what the lithosphere is will not be complete without considering them.

The upper layer is built from a wide variety of sedimentary rocks. The middle one is conditionally called granite, but it consists not only of granites. For example, under the oceans, the granite layer of the lithosphere is completely absent. The approximate density of the middle layer is 2.5-2.7 grams/cm 3 .

The lower layer is also conditionally called basalt. It consists of heavier rocks, its density, respectively, is greater - 3.1-3.3 grams / cm 3. The lower basalt layer is located under the oceans and continents.

The earth's crust is also classified. There are continental, oceanic and intermediate (transitional) types of the earth's crust.

The structure of lithospheric plates

The lithosphere itself is not homogeneous, it consists of peculiar blocks, which are called lithospheric plates. They include both oceanic and continental crust. Although there is a case that can be considered an exception. The Pacific lithospheric plate consists only of oceanic crust. The lithospheric blocks consist of folded metamorphic and igneous rocks.

Each continent has at its base an ancient platform, the boundaries of which are defined by mountain ranges. Plains and only individual mountain ranges are located directly on the platform area.

Seismic and volcanic activity is quite often observed at the boundaries of lithospheric plates. There are three types of lithospheric boundaries: transform, convergent, and divergent. The outlines and boundaries of lithospheric plates change quite often. Small lithospheric plates are connected to each other, while large ones, on the contrary, break apart.

List of lithospheric plates

It is customary to distinguish 13 main lithospheric plates:

• Philippine plate.
• Australian.
• Eurasian.
• Somali.
• South American.
• Hindustan.
• African.
• Antarctic Plate.
• Nazca plate.
• Pacific;
• North American.
• Scotia plate.
• Arabian plate.
• Cooker Coconut.

So, we gave a definition of the concept of "lithosphere", considered the geological structure of the Earth and lithospheric plates. With the help of this information, it is now possible to answer with certainty the question of what the lithosphere is.

The lithosphere is the outer solid shell of the Earth, including the earth's crust and the upper part of the mantle. The lithosphere includes sedimentary, igneous and metamorphic rocks.

The lower boundary of the lithosphere is fuzzy and is determined by a decrease in the viscosity of the medium, the speed of seismic waves, and an increase in thermal conductivity. The lithosphere covers the earth's crust and the upper part of the mantle several tens of kilometers thick to the asthenosphere, in which the plasticity of rocks changes. The main methods for determining the boundary between the upper boundary of the lithosphere and the asthenosphere are magnetotelluric and seismological.

The thickness of the lithosphere under the oceans ranges from 5 to 100 km (the maximum value is at the periphery of the oceans, the minimum is under the Mid-Ocean Ridges), under the continents - 25-200 km (the maximum is under ancient platforms, the minimum is under relatively young mountain ranges, volcanic arcs ). The structure of the lithosphere under the oceans and continents has significant differences. Under the continents in the structure of the earth's crust of the lithosphere, sedimentary, granite and basalt layers are distinguished, the thickness of which as a whole reaches 80 km. Beneath the oceans, the Earth's crust has repeatedly undergone partial melting processes during the formation of the oceanic crust. Therefore, it is depleted in fusible rare compounds, lacks a granite layer, and its thickness is much less than that of the continental part of the earth's crust. The thickness of the asthenosphere (a layer of softened, pasty rocks) is about 100-150 km.

Formation of the atmosphere, hydrosphere and earth's crust

The formation occurred during the release of substances from the upper layer of the mantle of the young Earth. Currently, on the ocean floor in the middle ridges, the process of formation of the earth's crust continues, which is accompanied by the release of gases and small volumes of water. Oxygen is present in high concentrations in the composition of the modern earth's crust, followed by silicon and aluminum in percentage. Basically, the lithosphere is formed by compounds such as silicon dioxide, silicates, aluminosilicates. Crystalline substances of igneous origin took part in the formation of most of the lithosphere. They were formed during the cooling of magma that came to the surface of the Earth, which is in the bowels of the planet in a molten state.

In cold regions, the thickness of the lithosphere is the greatest, and in warm regions it is the smallest. The thickness of the lithosphere can increase with a general decrease in the heat flux density. The upper layer of the lithosphere is elastic, and the lower layer is plastic in terms of the nature of the reaction to constantly acting loads. In tectonically active areas of the lithosphere, horizons of reduced viscosity are distinguished, where seismic waves travel at a lower speed. According to scientists, according to these horizons, some layers “slip” in relation to others. This phenomenon is called stratification of the lithosphere. In the structure of the lithosphere, mobile areas (folded belts) and relatively stable areas (platforms) are distinguished. Blocks of the lithosphere (lithospheric plates) move along the relatively plastic asthenosphere, reaching sizes from 1 to 10 thousand kilometers in diameter. At present, the lithosphere is divided into seven main and a number of small plates. The boundaries separating the plates from each other are the zones of maximum volcanic and seismic activity.