Lithosphere and its structure. The structure of the lithosphere. Geological structure of the globe

Lithosphere is the hard shell of the Earth.

Introduction

The lithosphere is important for all living organisms that live on its territory.

First of all, people, animals, insects, birds, etc. live on or inside land.

Secondly, this shell of the earth’s surface has enormous resources that organisms need for food and life.

Thirdly, it promotes the functioning of all systems, the mobility of the bark, rocks and soil.

What is the lithosphere

The term lithosphere consists of two words - stone and ball or sphere, which is literally translated from Greek language means the hard shell of the earth's surface.

The lithosphere is not static, but is in constant motion, which is why plates, rocks, resources, minerals, and water provide everything organisms need.

Where is the lithosphere located?

The lithosphere is located on the very surface of the planet, goes inside the mantle, to the so-called asthenosphere - a plastic layer of the Earth, consisting of viscous rocks.

What does the lithosphere consist of?

The lithosphere has three interconnected elements, which include:

Crust (earth);
Mantle;
Core.

lithosphere structure photo

In turn, the crust and the uppermost part of the mantle - the asthenosphere - are solid, and the core consists of two parts - solid and liquid. The core has solid rock inside and the outside is surrounded by liquid substances. The crust consists of rocks that arose after the cooling and crystallization of magma.

Sedimentary rocks arise in various ways:

When sand or clay breaks down;
During the course chemical reactions in water;
Organic rocks arose from chalk, peat, coal;
Due to changes in the composition of rocks - completely or partially.

Scientists have found that the lithosphere consists of such important elements as oxygen, silicon, aluminum, iron, calcium, and minerals. According to its structure, the lithosphere is divided into mobile and stable, i.e. platforms and pleated belts.

A platform is usually understood as areas of the earth's crust that do not move as a result of the presence of a crystalline base. It can be either granite or basalt. In the middle of the continents there are usually ancient platforms, and at the edges there are those that arose later, in the so-called Precambrian period.

The folded belts arose after colliding with each other. As a result of such processes, mountains and mountain ranges arise. Most often they are located at the edges of the lithosphere. The most ancient ones can be seen in the center of the continent - this is Eurasia, or along the very edges, which is typical for America (North) and Australia.

Mountain formation occurs constantly. If a mountain range runs along a tectonic plate, this means that plates once collided here. There are 14 plates in the lithosphere, which makes up 90% of the entire shell. There are both large and small slabs.

tectonic plates photos

The largest tectonic plates are the Pacific, Eurasian, African, and Antarctic. The lithosphere under oceans and continents is different. In particular, under the former the shell consists of oceanic crust, where there is almost no granite. In the second case, the lithosphere consists of sedimentary rocks, basalt and granite.

Lithosphere boundaries

The features of the lithosphere have different outlines. The lower boundaries are blurred, which is associated with a viscous medium, high heat conductivity and the speed of seismic waves. The upper boundary is the crust and mantle, which is quite thick and can only change due to the plasticity of the rock.

Functions of the lithosphere

The solid shell of the earth's surface has geological and ecological functions, which determine the course of life on the planet. It involves underground waters, oil, gases, fields of geophysical significance, processes, and the participation of various communities.

Among the most important functions are:

Resource;
Geodynamic;
Geochemical;
Geophysical.

Functions are manifested under the influence of natural and man-made factors, which is associated with the development of the planet, human activities and the formation of various ecological systems.

The lithosphere arose in the process of gradually releasing substances from the Earth's mantle. Similar phenomena are still sometimes observed on the ocean floor, resulting in the appearance of gases and some water.
The thickness of the lithosphere varies depending on climate and natural conditions. So, in cold regions, it reaches maximum value, and in warm weather it remains at minimum levels. The uppermost layer of the lithosphere is elastic, while the lower layer is very plastic. The solid shell of the Earth is constantly under the influence of water and air, which causes weathering. It happens physically when the rock disintegrates, but its composition does not change; as well as chemical - new substances appear.
Due to the fact that the lithosphere is constantly moving, the appearance of the planet, its relief, the structure of plains, mountains, and lowlands change. Man constantly influences the lithosphere, and this participation is not always useful, resulting in serious contamination of the shell. First of all, this is due to the accumulation of garbage, the use of poisons and fertilizers, which changes the composition of soil, soil, and living beings.

The rocky shell of the Earth - the earth's crust - is firmly attached to the upper mantle and forms a single whole with it -. The study of the earth's crust and lithosphere allows scientists to explain the processes occurring on the Earth's surface and anticipate changes in the appearance of our planet in the future.

Structure of the earth's crust

The Earth's crust, consisting of igneous, metamorphic and sedimentary rocks, on and under the oceans has different thicknesses and structures.

It is customary to distinguish three layers in the continental crust. The upper layer is sedimentary, in which sedimentary rocks predominate. The two lower layers are conventionally called granite and basalt. The granite layer consists mainly of granite and metamorphic Basalt layer - of denser rocks, comparable in density to basalts. Oceanic crust has two layers. In it, the upper layer - sedimentary - has a small thickness, the lower layer - basalt - consists of basalt rocks, and there is no granite layer.

The thickness of the continental crust under is 30-50 kilometers, under the mountains - up to 75 kilometers. The oceanic crust is much thinner, its thickness is from 5 to 10 kilometers.

There is a crust on other terrestrial planets, on the Moon and on many satellites of the giant planets. But only the Earth has two types of crust: continental and oceanic. On other planets, in most cases it consists of basalts.

Lithosphere

The rocky shell of the Earth, including the upper part of the mantle, is called the lithosphere. Beneath it there is a heated plastic layer of the mantle. The lithosphere seems to float on this layer. The thickness of the lithosphere in different regions of the Earth varies from 20 to 200 kilometers or more. In general, it is thicker under continents than under oceans.

Scientists have found that the lithosphere is not monolithic, but consists of. They are separated from each other by deep faults. There are seven very large and several smaller lithospheric plates, which constantly but slowly move along the plastic layer of the mantle. average speed their movements are about 5 centimeters per year. Some plates are entirely oceanic, but most have different types earth's crust.

Lithospheric plates move relative to each other in different directions: either they move away, or, conversely, they come closer and collide. As part of the lithospheric plates, their upper “floor” - the earth’s crust - also moves. Due to the movement of lithospheric plates, the location on the Earth's surface changes. The continents either collide with each other or move thousands of kilometers away from each other.

Engineering geology, its tasks and place in the system of engineering disciplines.

Engineering geology studies the natural, geological situation of an area before construction begins, and also determines those changes that will occur during the operation and construction of structures. Currently, before designing any structure, it is necessary to carry out engineering-geological surveys, which determine the main design tasks: Selecting the location that is most geologically favorable for this structure. Identification of engineering-geological conditions in order to select the most rational foundations, as well as technological process execution construction work. Recommendations for necessary measures for engineering improvement of the selected area (these are: soil soaking, fastening, reclamation, etc.). At the present time, engineering geology is called upon to solve the most complex problems under any construction conditions. The need for engineering-geological study of our country in order to justify the regional location of national economic objects and the proper development of new territories is also complemented not only by the requirements of studying engineering-geological conditions, but also by the need to develop forecasts for the development of modern geological processes and phenomena in order to prevent natural disasters. Geology is the science of the Earth, its structure, composition, and history of development. It is a complex science consisting of various numerous disciplines: crystallography - the study of crystals and the crystalline structure of substances; mineralogy - the science of minerals; petrography - the science of rocks; dynamic geology - the science of processes occurring on the surface and inside the earth; historical geology - the science of the history of the development of the earth; hydrogeology - the science of groundwater; geomorphology is the science of the development of the relief of the earth's crust. Engineering geology is a science that studies the geological processes of the upper layers of the earth's crust and the physical and mechanical properties of rocks in connection with human engineering and construction activities. The main object of study of geology is the lithosphere and the earth's crust. The founders of geology are M.V. Lomonosov and V.M. Severgin. We will study the most significant section of geology for construction, “Engineering Geology.”

Structure of the Earth, geosphere.

The shape of the Earth is close to a sphere, but flattened at the poles. This shape is called a spheroid, but due to the fact that the earth's surface has depressions and mountains, it was called a geoid. Our planet has a concentric structure and consists of a core and shells. On the surface of the earth there is a shell of water - the hydrosphere and atmosphere. The earth's core (see Figure 1) is believed to have a silicate composition with a high iron content. The radius of the core is approximately 3500 km, the temperature of the core is 2000...25000. Intermediate shell - the boundary is a depth of 2900 km (see Figure 2). Consists mainly of silicon, iron, magnesium. Behind the intermediate shell lies peridotite, consisting of silicate rocks, with a predominance of silicon and magnesium. Its upper part contains molten masses. Seismic phenomena are born here. The outer part of the earth, up to 50...70 km deep, is called the lithosphere, it is a source of mineral raw materials.

Hydrosphere - the water shell covers up to 70% of the earth's surface. The greatest depth is 11521 meters (Mariana Trench). Water temperature depends on the latitude and depth of the area. The highest is +35.60 in the Persian Gulf, the lowest is -2.80 in the Arctic Ocean.

The biosphere is the living environment of organisms and is associated with the lithosphere, hydrosphere and atmosphere.

Atmosphere - surrounds the earth at an altitude of 3000 km. It consists of 3 shells: troposphere, stratosphere, ionosphere.

Troposphere - ground layer from 6 km to 18 km (at the equator). With distance from the surface, the temperature drops sharply and at an altitude of 10 - 12 km it is 50 degrees.

The stratosphere is the next layer with a height of 80 - 90 km.

The ionosphere is the upper part of the atmosphere, passing at an altitude of 3000 km into interplanetary space. It has low density and high ionization.

The structure of the lithosphere. Concept of tectonic plates.

The deep crust and the upper (solid) part of the mantle form the lithosphere. It is a “ball” of solid matter with a radius of about 6400 km. Earth's crust - outer shell lithosphere. Consists of sedimentary, granite and basalt layers. Distinguish between oceanic and continental crust. The first one lacks a granite layer. The maximum thickness of the earth's crust is about 70 km - under mountain systems, 30-40 km - under plains, the thinnest earth's crust is under the oceans, only 5-10 km.

We call the rest the inner lithosphere, which also includes the central part, called the core. We know almost nothing about the inner layers of the lithosphere, although they account for almost 99.5% of the total mass of the Earth. They can only be studied through seismic research.

The lithosphere is divided into blocks - lithospheric plates are large rigid blocks of the earth's crust that move along a relatively plastic asthenosphere. The lithosphere beneath oceans and continents varies considerably.

The lithosphere beneath the oceans has undergone many stages of partial melting as a result of the formation of the oceanic crust, it is highly depleted in fusible trace elements and mainly consists of dunites and harzburgites.

The lithosphere under the continents is much colder, thicker and, apparently, more diverse. It does not participate in the process of mantle convection, and has undergone fewer cycles of partial melting. In general, it is richer in incompatible rare elements. Lherzolites, wehrlites and other rocks rich in rare elements play a significant role in its composition.

The lithosphere is split into approximately 10 large plates, the largest being the Eurasian, African, Indo-Australian, American, Pacific, and Antarctic. Lithospheric plates move with the land rising on them. The theory of the movement of lithospheric plates is based on A. Wegener's hypothesis about continental drift.

Lithospheric plates constantly change their shape; they can split as a result of rifting and weld together, forming a single plate as a result of collision. On the other hand, the division of the earth's crust into plates is not unambiguous, and as geological knowledge accumulates, new plates are identified, and some plate boundaries are recognized as non-existent. The movement of lithospheric plates is caused by the movement of matter in the upper mantle. In rift zones, it tears the earth's crust and pushes plates apart. Most rifts are found on the ocean floor, where the Earth's crust is thinner. On land, the largest rifts are located in the African Great Lakes and Lake Baikal regions. The speed of movement of lithospheric plates is -1-6 cm per year.

When lithospheric plates collide at their boundaries, mountain systems are formed if in the collision zone both plates bear continental crust (Himalayas), and deep-sea trenches if one of the plates carries oceanic crust (Peruvian Trench). This theory is consistent with the assumption of the existence of ancient continents: the southern - Gondwana and the northern - Laurasia.

The boundaries of lithospheric plates are mobile areas where mountain formation occurs, areas of earthquakes and most active volcanoes (seismic belts) are concentrated. The most extensive seismic belts are the Pacific and Mediterranean - Trans-Asian.

At a depth of 120-150 km under the continents and 60-400 km under the oceans there is a layer of mantle called the asthenosphere. All lithospheric plates seem to float in a semi-liquid asthenosphere, like ice floes in water.

Currently, plate tectonics presents the following picture. The modern lithosphere is divided into many lithospheric plates, but 90% of the earth's surface is divided into eight main plates. The earth's surface is of two types: oceanic crust (younger, as it is constantly renewed) and continental crust (more ancient). Lithospheric plates can carry out Various types movements relative to each other, there are three main types of movement: first, divergence, that is, the discrepancy between the plates; secondly, convergence, that is, convergence, rapprochement between plates; thirdly, shear movements along transform geological faults. Scientists currently believe that plate tectonics does not play a decisive role in global changes climate, however, can have an auxiliary effect on these processes.

Lithosphere structure

The Earth's lithosphere consists of two layers: the earth's crust and part of the upper mantle. The border between them is the so-called. Mohorovicic boundary, identified on the basis of an increase in the speed of propagation of longitudinal seismic waves and the density of matter.

The Earth's crust is the upper solid shell of the Earth. The crust is not a unique formation unique to the Earth, because... found on most of the terrestrial planets, the Earth's satellite - the Moon and the satellites of the giant planets: Jupiter, Saturn, Uranus and Neptune. However, only on Earth there are two types of crust: oceanic and continental. In the border areas, an intermediate type of crust develops - subcontinental or suboceanic, forming, for example, in island arc zones. In the zones of mid-ocean ridges, a rift-type crust can be distinguished, due to the absence of a gabbro-serpentinite layer in these zones and the close position of the asthenosphere.

The oceanic crust consists of three layers: upper sedimentary, intermediate basaltic and lower gabbro-serpentinite, which until recently was included in the basaltic composition.

Its thickness ranges from 2 km in mid-ocean ridge zones to 130 km in subduction zones, where the oceanic crust sinks into the mantle. This difference is due to the fact that in the zones of mid-ocean ridges the oceanic crust is formed; as it moves away from the ridges, its thickness increases, rarely exceeding a value of 7 km, reaching a maximum in the zones of subsidence of the crust into the upper mantle. The largest number of subduction zones occur in Pacific Ocean; Powerful seaquakes are associated with them.

The sedimentary layer covering the melt is small: its thickness rarely exceeds 0.5 km, reaching a thickness of 10-12 km only near the deltas of large rivers. The sedimentary layer consists of sand, deposits of animal remains and precipitated minerals. At its base there are often thin metal-bearing sediments, which are not consistent along the strike, with a predominance of iron oxides. The lower part of the layer is composed of carbonate rocks, which are not found at great depths due to the dissolution of the shells of foraminifera and coccolithophores that make up the carbonate rocks under high pressure. At depths exceeding 4.5 km, carbonate rocks are replaced by red deep-sea clays and siliceous silts.

The basalt layer in the upper part is composed of basaltic lavas of tholeiitic composition, which are also called pillow lavas because of their characteristic shape. Below lies a dike complex formed by dolerite dikes. Dikes are channels through which basaltic lava flowed to the surface. For this reason, basalt layer is exposed in many places adjacent to mid-ocean ridges.

In subduction zones, the basalt layer turns into ecgoliths, which, having a density greater than the surrounding peridotites (the most common mantle rocks), sink into the depths. The mass of ecgoliths currently accounts for about 7% of the mass of the entire Earth's mantle.

The gabbro-serpentinite layer lies directly above the upper mantle. Its composition includes gabbroids and serpentinized peridotite, which are formed, respectively, during the slow crystallization of basaltic melts in a magma chamber and during the hydration of basic mantle rocks along lithosphere cracks. The thickness of the layer is 3-6 km; it can be traced in all oceans. The velocities of longitudinal seismic waves within the layer are 6.5-7 km/sec.

The age of the oceanic crust is on average 100 million years. The oldest sections of the oceanic crust are 156 million years old (Late Jurassic) and are located in the Pijafeta depression in the Pacific Ocean.

Such a young age is explained by the constant formation and absorption of oceanic crust. Every year, in the rift zones of mid-ocean ridges, as a result of the separation of basaltic lava occurring underneath them and its outpouring onto the surface of the ocean floor, 24 km 3 of igneous rocks weighing 70 billion tons are formed. If we take into account that the total mass of the oceanic crust, according to calculations, is 5.9 × 10 18 tons, it turns out that the entire oceanic crust is renewed in 100 million years, which is taken to be its average age. The thickness of the oceanic crust remains virtually unchanged over time, due to its construction from the released melt.

The oceanic crust is concentrated not only within the bed of the World Ocean. Small ancient sections of it are known in closed basins, an example of which is the northern depression of the Caspian Sea. The total area of the oceanic crust is 306 million km 2.

The continental crust, as the name suggests, lies beneath the Earth's continents and large islands. Unlike the oceanic crust, the continental crust consists of three layers: upper sedimentary, middle granitic and lower basaltic. The thickness of this type of crust under young mountains reaches 75 km, under plains it ranges from 35 to 45 km, under island arcs it is reduced to 20-25 km.

The sedimentary layer of the continental crust is formed by: clayey sediments and carbonates of shallow sea basins within Proterozoic platforms; coarse clastic facies, replaced higher up the section by sandy-clay deposits and carbonates of coastal facies in marginal troughs and on the passive margins of Atlantic-type continents.

The granite layer of the earth's crust is formed as a result of the intrusion of magma into cracks in the earth's crust. Consists of silica, aluminum and other minerals. The thickness of the granite layer reaches 25 km. The speed of longitudinal seismic waves ranges from 5.5 to 6.3 km/sec. The layer is very ancient: its average age is about 3 billion years.

At depths of 15-20 km, the Conrad boundary is often visible, along which the speed of propagation of longitudinal seismic waves increases by 0.5 km/sec. The boundary separates the granite and basalt layers.

The basalt layer is formed when basic (basaltic) lavas erupt onto the land surface in zones of intraplate magmatism. Basalt is heavier than granite and contains more iron, magnesium and calcium. The speed of longitudinal seismic waves within the layer is from 6.5 to 7.3 km/sec.

The boundary between granite and basalt layers in a number of places passes along the so-called. Conrad surface, within which there is an abrupt increase in the speed of longitudinal seismic waves from 6 to 6.5 km/sec. In other places, the speed of longitudinal seismic waves increases gradually and the boundary between the layers is blurred. And finally, there are areas where several surfaces are observed at once, within which seismic waves increase.

The total mass of the earth's crust is estimated at 2.8 × 10 19 tons, which is only 0.473% of the mass of the entire planet Earth.

Below, the Earth's crust is separated from the upper mantle by the Mohorovicic or Moho boundary, established in 1909 by Croatian geophysicist and seismologist Andrej Mohorovicic. At the boundary there is a sharp increase in the velocities of longitudinal and transverse seismic waves. The density of the substance also increases. The Moho boundary may not coincide with the boundaries of the earth's crust, apparently separating areas of different chemical composition: light acidic earth's crust and dense ultrabasic mantle.

The layer underlying the earth's crust is called the mantle. The mantle is divided by the Golitsyn layer into upper and lower, the boundary between which passes at a depth of about 670 km.

Within the upper mantle, the asthenosphere is distinguished - a plate layer, within which the velocities of seismic waves decrease.

Term "lithosphere" has been used in science since the mid-19th century, but modern meaning he acquired it 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 earth's crust is the outer shell of the lithosphere. Consists of sedimentary, granite and basalt layers. Distinguish between oceanic and continental crust. The first one lacks a granite layer. The maximum thickness of the earth's crust is about 70 km - under mountain systems, 30-40 km - under plains, the thinnest earth's crust is under the oceans, only 5-10 km.

The surface of the earth's crust is formed due to the multidirectional effects of tectonic movements that create uneven relief, denudation of this relief through the destruction and weathering of its constituent rocks, and due to sedimentation processes. As a result, the constantly forming and simultaneously smoothing surface of the earth's crust turns out to be quite complex. The maximum relief contrast is observed only in places of the greatest modern tectonic activity of the Earth, for example, on the active continental margin of South America, where the difference in relief levels between the Peruvian-Chilean deep-sea trench and the peaks of the Andes reaches 16-17 km. Significant altitude contrasts (up to 7-8 km) and great dissected relief are observed in modern continental collision zones, for example, in the Alpine-Himalayan fold belt.

In both of these cases, the maximum differences in relief heights are determined not only by the intensity of tectonic deformations of the earth's crust and the rate of its denudation, but also by the rheological properties of crustal rocks, which pass under the influence of excess and uncompensated stresses into a plastic state. Therefore, large changes in relief in the Earth's gravitational field lead to the appearance of excess stresses that exceed the plasticity limits of rocks and to the plastic spreading of too large relief irregularities.

The lithosphere is formed - 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 seismic waves increases abruptly. The spatial (horizontal) structure of the lithosphere is represented by its large blocks - the so-called. lithospheric plates.

Lithospheric plates are large, rigid blocks of the earth's crust that move along a relatively plastic asthenosphere. The lithosphere beneath oceans and continents varies considerably.

In the lithosphere, a mass of rocks is distinguished, earth's surface and soil. 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. The upper layer of the lithosphere is the earth's crust, the minerals of which consist mainly of silicon and aluminum oxides, iron oxides and alkali metals.

The bulk of organisms and microorganisms of the lithosphere are concentrated in the soil, at a depth of no more than a few meters. Soils are an organo-mineral product of long-term (hundreds and thousands of years) general activities living organisms, water, air, solar heat and light are some of the most important natural resources. Modern soils are a three-phase system (different-grained solid particles, water and gases dissolved in water and pores), which consists of a mixture of mineral particles (products of rock destruction), organic substances (products of the vital activity of the biota, its microorganisms and fungi). The uppermost, surface horizon of the lithosphere within the land is subject to the greatest transformation. Land occupies 29.2% of the surface of the globe and includes lands of various categories, of which fertile soil is of most importance.

The surface layer of the lithosphere, in which the interaction of living matter with mineral (inorganic) takes place, is soil. The remains of organisms after decomposition turn into humus (the fertile part of the soil). Components Soils contain minerals, organic matter, living organisms, water, and gases.

The predominant elements of the chemical composition of the lithosphere: O, Si, Al, Fe, Ca, Mg, Na, K.

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