EARTH'S CRUST, the upper solid shell of the Earth, bounded below by the Mohorovicic boundary. The term “earth’s crust” appeared in the 18th century in the works of M. V. Lomonosov and in the 19th century in the works of Charles Lyell; with the development of the contraction hypothesis in the 19th century, it received a certain meaning in accordance with the idea of ​​​​cooling the Earth until the crust formed (J. Dana). The basis for ideas about the composition, structure and physical properties of the earth's crust are geophysical data on the velocities of propagation of seismic waves (mainly longitudinal, V p), which at the Mohorovicic boundary, when moving to the rocks of the Earth's mantle, increase abruptly from 7.5-7.8 km /s to 8.1-8.2 km/s. The nature of the lower boundary of the earth's crust is apparently due to changes in the chemical composition of rocks (basic rocks - ultrabasic) or phase transitions (in the gabbro - eclogite system).

The earth's crust is characterized by horizontal heterogeneity (anisotropy), expressed in differences in the composition, structure, thickness and other characteristics of the crust within its individual structural elements: continents and oceans, platforms and folded belts, depressions and uplifts, etc. There are two main types of the earth's crust - continental and oceanic.

The continental crust, distributed within continents and microcontinents in the oceans, has an average thickness of 35-40 km, which decreases to 25-30 km on continental margins (on the shelf) and in areas of rifting and increases to 45-75 km in areas of mountain building. In the continental crust, sedimentary (V p up to 4.5 km/s), “granite” (V p 5.1-6.4 km/s) and “basaltic” (V p 6.1-7.5 km/s) are distinguished. c) layers. The sedimentary layer is absent on the shields and smaller uplifts of the foundation of ancient platforms, as well as in the axial zones of folded structures. In the depressions of young and ancient platforms, forward and intermountain troughs of folded structures, the thickness of the sedimentary layer reaches 10 km (rarely 20-25 km). It is composed mainly of continental and shallow-water sedimentary rocks, which are less than 1.7 billion years old, as well as plateau basalts (traps), sills of basic igneous rocks, and tuffs. The names of “granite” and “basalt” layers are arbitrary and are historically associated with the identification of the Conrad boundary (V p 6.2 km/s), separating the layers in which the velocities of longitudinal seismic waves correspond to the velocities in granite and basalt. Subsequent studies (including ultra-deep drilling) cast doubt on the existence of a clear seismic boundary, so both of these layers are combined into a consolidated crust. The “granite” layer protrudes to the surface within shields and arrays of platforms and in the axial zones of folded structures; it was also penetrated by ultra-deep drilling wells (including the Kola ultra-deep well to a depth of over 12 km). Its thickness on platforms is 15-20 km, in folded structures 25-30 km. Within the shields of ancient platforms, this layer includes gneisses, various crystalline schists, amphibolites, marbles, quartzites and granitoids, therefore it is often called granite-gneiss (V p 6-6.4 km/s). In the basement of young platforms and within young folded structures, the upper layer of the consolidated crust is composed of less metamorphosed rocks and contains less granites, and therefore it is also called granitic metamorphic (V p 5.1-6 km/s). Direct study of the “basalt” layer of the continental crust is impossible. The values ​​of seismic wave velocities by which it is distinguished can be satisfied by both igneous rocks of basic composition (mafic rocks) and rocks that have experienced a high degree of metamorphism (granulites), therefore the lower layer of the consolidated crust is sometimes called granulite-mafic. The assignment of rocks with longitudinal seismic wave velocities of more than 7 km/s to the earth's crust or upper mantle is controversial. The age of the oldest rocks of the consolidated crust reaches 4 billion years.

The main differences between the oceanic crust and the continental one are the absence of a “granite” layer, significantly lower thickness (on average 5-7 km), younger age (Jurassic, Cretaceous, Cenozoic; less than 170 million years), greater lateral homogeneity. The oceanic crust, the structure of which has been studied by deep-sea drilling, dredging, and observation from underwater vehicles in the walls of faults, consists of three layers. The first layer, or sedimentary, consists of pelagic siliceous, carbonate and clayey sediments (V p 1.6-5.4 km/s). In the direction of the continental foothills its thickness increases to 10-15 km. Sedimentary layer may be absent in the axial zones of mid-ocean ridges. In deep-sea basins of back-arc basins, some of which are underlain by oceanic crust, the thickness of the sedimentary layer, usually including turbidites, can reach 15-20 km. The second layer (V p 4.5-5.5 km/s) in the upper part is composed of basalts (often with pillow separateness - pillow basalts) with rare interlayers of pelagic sediments; in the lower part of the layer there is a complex of parallel dolerite dikes (total thickness 1.2-2 km). The third layer (V p 6-7.5 km/s) in the upper part consists of massive gabbros, in the lower part - of a layered complex in which gabbros alternate with ultrabasic rocks (total thickness 2-5 km). Within the internal rises of the oceans, the earth's crust is thickened to 25-30 km due to an increase in the thickness of the second and third layers. The ancient analogue of oceanic crust on continents is ophiolites.

Oceanic crust is formed at the divergent boundaries of lithospheric plates (stretching along the axial parts of mid-ocean ridges), on which basaltic magma rises to the surface and solidifies. Continental crust is formed during the reworking of oceanic crust on active continental margins.

In addition to the two main types of the earth's crust, transitional types are distinguished. The suboceanic crust is a continental crust thinned as a result of rifting up to 15-20 km, penetrated by dikes and sills of basic igneous rocks; developed along the continental slopes and foothills, and also underlies the deep-sea depressions of some back-arc basins. Subcontinental crust (poorly consolidated, less than 25 km thick) is observed in volcanic island arcs, where oceanic crust turns into continental crust.

The earth's crust experiences horizontal and vertical tectonic movements. It contains the foci of earthquakes, magma chambers are formed, and rocks locally or over large areas undergo metamorphism. Tectonic movements of the earth's crust and endogenous processes occurring in it are caused by the existence of a partially molten asthenosphere in the bowels of the Earth. Under the influence of tectonic movements and deformations, magmatic activity, metamorphism, exogenous processes (glacial movement, landslides, karst, river erosion, etc.), rocks of the earth's crust are involved in folded and fault tectonic dislocations. The impact of the atmosphere, hydro and biosphere on the rocks of the earth's crust leads to their weathering.

For information on the evolution of the earth's crust throughout geological history, see the article Earth.

Lit.: Khain V. E., Lomise M. G. Geotectonics with the basics of geodynamics. 2nd ed. M., 2005; Khain V. E., Koronovsky N. V. Planet Earth from the core to the ionosphere. M., 2007.


Plan:

Introduction 2

1. General information about the structure of the Earth and the composition of the earth’s crust 3

2. Types of rocks that make up the earth's crust 4

2.1. Sedimentary rocks 4

2.2. Igneous rocks 5

2.3. Metamorphic rocks 6

3. Structure of the earth's crust 6

4. Geological processes occurring in the earth’s crust 9

4.1. Exogenous processes 10

4.2. Endogenous processes 10

Conclusion 12

References 13

Introduction

All knowledge about the structure and history of the development of the earth's crust constitutes a subject called geology. The Earth's crust is the upper (rocky) shell of the Earth, also called the lithosphere (in Greek, “cast” means stone).

Geology as a science is divided into a number of independent departments that study certain issues of the structure, development and history of the earth's crust. These include: general geology, structural geology, geological mapping, tectonics, mineralogy, crystallography, geomorphology, paleontology, petrography, lithology, as well as mineral geology, including oil and gas geology.

The basic principles of general and structural geology are the foundation for understanding issues in the geology of oil and gas. In turn, the basic theoretical principles on the origin of oil and gas, the migration of hydrocarbons and the formation of their accumulations underlie the search for oil and gas. In the geology of oil and gas, the patterns of location of various types of hydrocarbon accumulations in the earth's crust are also considered, which serve as the basis for predicting the oil and gas content of the studied areas and areas and are used in prospecting and exploration for oil and gas.

This work will consider issues related to the earth's crust: its composition, structure, processes occurring in it.

1. General information about the structure of the Earth and the composition of the earth’s crust

In general, planet Earth has the shape of a geoid, or an ellipsoid flattened at the poles and equator, and consists of three shells.

In the center is core(radius 3400 km), around which is located mantle in the depth range from 50 to 2900 km. The inner part of the core is assumed to be solid, iron-nickel composition. The mantle is in a molten state, in the upper part of which there are magma chambers.

At a depth of 120 - 250 km under the continents and 60 - 400 km under the oceans lies a layer of mantle called asthenosphere. Here the substance is in a state close to melting, its viscosity is greatly reduced. All lithospheric plates seem to float in a semi-liquid asthenosphere, like ice floes in water.

Above the mantle is earth's crust, the power of which varies sharply on continents and oceans. The base of the crust (Mohorovicic surface) under the continents is at an average depth of 40 km, and under the oceans at a depth of 11 - 12 km. Therefore, the average thickness of the crust under the oceans (minus the water column) is about 7 km.

The earth's crust is composed mountain porosyes, i.e. communities of minerals (polymineral aggregates) that arose in the earth’s crust as a result of geological processes. Minerals- natural chemical compounds or native elements that have certain chemical and physical properties and arise in the earth as a result of chemical and physical processes. Minerals are divided into several classes, each of which includes tens and hundreds of minerals. For example, sulfur compounds of metals form the class of sulfides (200 minerals), salts of sulfuric acid form 260 minerals of the sulfate class. There are classes of minerals: carbonates, phosphates, silicates, the latter of which are the most widespread in the earth's crust and form more than 800 minerals.

2. Types of rocks that make up the earth's crust

So, rocks are natural aggregates of minerals of a more or less constant mineralogical and chemical composition, forming independent geological bodies that make up the earth’s crust. The shape, size and relative position of mineral grains determine the structure and texture of rocks.

According to education conditions (genesis) distinguish: sedimentary,igneous and metamorphic rocks.

2.1. Sedimentary rocks

Genesis sedimentary rocks- either the result of destruction and redeposition of pre-existing rocks, or precipitation from aqueous solutions (various salts), or - the result of the vital activity of organisms and plants. A characteristic feature of sedimentary rocks is their layering, reflecting the changing conditions of deposition of geological sediments. They make up about 10% of the mass of the earth's crust and cover 75% of the Earth's surface. Associated with sedimentary rocks is St. 3/4 mineral resources (coal, oil, gas, salts, iron ores, manganese, aluminum, placer gold, platinum, diamonds, phosphorites, building materials). Depending on the source material, sedimentary rocks are divided into clastic (terrigenetic), chemogenic, organogenic (biogenic) and mixed.

Clastic rocks are formed due to the accumulation of fragments of destroyed rocks, i.e. These are rocks made up of fragments of older rocks and minerals. Based on the size of the fragments, they are classified into coarse clastic (blocks, crushed stones, gravel, pebbles), sandy (sandstones), silty (siltstones, siltstones) and clayey rocks. The most widespread clastic rocks in the earth's crust are sands, sandstones, siltstones, and clays.

Chemogenic rocks are chemical compounds that are formed as a result of precipitation from aqueous solutions. These include: limestones, dolomites, rock salts, gypsum, anhydrite, iron and manganese ores, phosphorites, etc.

Organogenic rocks accumulate as a result of the death and burial of animals and plants, i.e. organogenic rocks (from organ and Greek genes - giving birth, born) (biogenic rocks) - sedimentary rocks consisting of the remains of animal and plant organisms or their metabolic products (limestone-shell rock, chalk, fossil coals, oil shale, etc.) .

Breeds mixed origin, as a rule, are formed due to various combinations of all the factors discussed above. Among these rocks are sandy and clayey limestones, marls (highly calcareous clays), etc.

2.2. Igneous rocks

Genesis igneous rocks- the result of solidification of magma at depth or on the surface. Magma, being molten and saturated with gaseous components, pours out from the upper part of the mantle.

The composition of magma mainly includes the following elements: oxygen, silicon, aluminum, iron, calcium, magnesium, sodium, potassium, hydrogen. The following elements are present in magma in small quantities: carbon, titanium, phosphorus, chlorine and other elements.

Magma, penetrating into the earth's crust, can solidify at various depths or pour out to the surface. In the first case, they are formed intrusive rocks, in the second - effusive. During the cooling of hot magma in the layers of the earth's crust, the formation of minerals of various structures (crystalline, amorphous, etc.) occurs. These minerals form rocks. For example, at great depths, when magma solidifies, granites are formed, at relatively shallow depths - quartz porphyries, etc.

Extrusive rocks are formed when magma quickly solidifies on the Earth's surface or on the seabed. Examples include tuffs and volcanic glass.

Intrusive rocks- igneous rocks formed as a result of the solidification of magma in the thickness of the earth's crust.

Igneous rocks according to the content of SiO 2 (quartz and other compounds) are divided into: acidic (SiO 2 more than 65%), medium - 65-52%, basic (52-40%) and ultrabasic (less than 40% SiO 2). The color of the rocks changes depending on the quartz content in the rocks. Acidic ones are usually light in color, while basic and ultrabasic ones are dark to black. Acid rocks include: granites, quartz porphyries; to the middle ones: syenites, diorites, nepheline syenites; the main ones: gabbro, diabase, basalts; to ultrabasic: pyroxenes, peridotites and dunites.

2.3. Metamorphic rocks

Metamorphic rocks are formed as a result of the influence of high temperatures and pressures on rocks of another primary genesis (sedimentary or igneous), i.e. due to chemical transformations under the influence of metamorphism. Metamorphic rocks include: gneisses, crystalline schists, marble. For example, marble is formed due to the metamorphism of primary sedimentary rock - limestone.

3. Structure of the earth's crust

The earth's crust is conventionally divided into three layers: sedimentary, granite and basalt. The structure of the earth's crust is shown in Fig. 1.

1 – water, 2 – sedimentary layer, 3 – granite layer, 4 – basalt layer, 5 – deep faults, igneous rocks, 6 – mantle, M – Mohorovicic surface (Moho), K – Conrad surface, OD – island arc, SH – mid-ocean ridge

Rice. 1. Scheme of the structure of the earth’s crust (according to M.V. Muratov)

Each of the layers is heterogeneous in composition, however, the name of the layer corresponds to the predominant type of rocks, characterized by the corresponding velocities of seismic waves.

The top layer is represented sedimentary rocks, where the speed of passage of longitudinal seismic waves is less than 4.5 km/s. The middle granite layer is characterized by wave speeds of the order of 5.5-6.5 km/s, which experimentally corresponds to granites.

The sedimentary layer is thin in the oceans, but has a significant thickness on the continents (in the Caspian region, for example, according to geophysical data, it is assumed to be 20-22 km).

granite layer absent in the oceans, where the sedimentary layer directly overlies basalt. The basalt layer is the lower layer of the earth's crust located between the Conrad surface and the Mohorovicic surface. It is characterized by the speed of propagation of longitudinal waves from 6.5 to 7.0 km/s.

On continents and oceans, the earth's crust varies in composition and thickness. The continental crust under mountain structures reaches 70 km, on the plains - 25-35 km. In this case, the upper layer (sedimentary) is usually 10-15 km, with the exception of the Caspian region, etc. Below is a granite layer up to 40 km thick, and at the base of the crust there is a basalt layer also up to 40 km thick.

The boundary between the crust and mantle is called Mohorovicic surface. In it, the speed of propagation of seismic waves increases abruptly. In general terms, the shape of the Mohorovicic surface is a mirror image of the relief of the outer surface of the lithosphere: under the oceans it is higher, under the continental plains it is lower.

Conrad surface(named after the Austrian geophysicist W. Conrad, 1876-1962) - the interface between the “granite” and “basalt” layers of the continental crust. The speed of longitudinal seismic waves when passing through the Conrad surface increases abruptly from approximately 6 to 6.5 km/sec. In a number of places, the Conrad surface is absent and the velocities of seismic waves gradually increase with depth. Sometimes, on the contrary, several surfaces of abrupt increase in speeds are observed.

The oceanic crust is thinner than the continental crust and has a two-layer structure (sedimentary and basaltic layers). The sedimentary layer is usually loose, several hundred meters thick, basaltic - from 4 to 10 km.

In transitional areas, where marginal seas are located and there are island arcs, the so-called transitionbark type. In such areas, the continental crust transforms into oceanic crust and is characterized by average layer thicknesses. At the same time, under the marginal sea, as a rule, there is no granite layer, but under the island arc it can be traced.

Island arc- an underwater mountain range, the peaks of which rise above the water in the form of an arched archipelago. Island arcs are part of the transition zone from continent to ocean; characterized by seismic activity and vertical movements of the earth's crust.

Mid-ocean ridges- the largest forms of relief of the bottom of the world's oceans, forming a single system of mountain structures with a length of over 60 thousand km, with relative heights of 2-3 thousand m and a width of 250-450 km (in some areas up to 1000 km). They are uplifts of the earth's crust, with highly dissected ridges and slopes; in the Pacific and Arctic oceans, mid-ocean ridges are located in the marginal parts of the oceans, in the Atlantic - in the middle.

4. Geological processes occurring in the earth’s crust

Throughout geological history, various geological processes have occurred and are occurring on the earth’s surface and inside the earth’s crust, which influence the formation of mineral deposits.

Sedimentary strata and minerals such as coal, oil, gas, oil shale, phosphorites and others are the result of the activity of living organisms, water, wind, sunlight and everything else associated with them.

In order for oil to form, for example, it is necessary first of all to accumulate a huge amount of fossil remains in sedimentary strata, plunging to a considerable depth, where, under the influence of high temperatures and pressures, this biomass is converted into oil or natural gas.

All geological processes are divided into exogenous (surface) and endogenous (internal).

4.1. Exogenous processes

Exogenous processes- this is the destruction of rocks on the surface of the Earth, the transfer of their fragments and accumulation in the seas, lakes, and rivers. Elevated areas of the terrain (mountains, hills) are subject to greater destruction, and the accumulation of fragments of destroyed rocks occurs, on the contrary, in lower areas (depressions, reservoirs).

Exogenous processes occur under the influence of atmospheric phenomena (precipitation, wind, melting glaciers, the life of animals and plants, the movement of rivers and other water flows, etc.).

Surface processes associated with the destruction of rocks are also called weathering or denudation. Under the influence of weathering, the relief appears to be leveled, as a result of which exogenous processes are weakened, and in some places (on the plains) they practically die out.

4.2. Endogenous processes

Also important in oil formation are endogenous processes, which include various movements of sections of the earth's crust (horizontal and vertical tectonic movements), earthquakes, volcanic eruptions and outpourings of magma (liquid fiery lava) on the surface of the Earth, on the bottom of seas and oceans, as well as deep faults in the earth's crust, tectonic disturbances, folding and etc. That is Endogenous processes include processes occurring inside the Earth.

During geological history, the earth's crust has been subject to both vertical oscillatory movements and horizontal movements of lithospheric plates. These global changes in the rocky shell of the Earth undoubtedly influenced the processes of formation of oil and gas accumulations.

Due to vertical movements, large depressions and troughs were formed, where thick layers of sediment accumulated.

The latter, in turn, could produce hydrocarbons (oil and gas). In other areas, on the contrary, large uplifts arose, which are also of interest in oil and gas terms, since they could accumulate hydrocarbons.

With horizontal movements of lithospheric plates, some continents merged and others split, which also affected the processes of formation and accumulation of oil and gas. At the same time, in certain areas of the earth's crust, favorable conditions arose for the accumulation of significant concentrations of hydrocarbons.

Endogenous processes also include metamorphism, i.e. recrystallization of rocks under the influence of high temperatures and pressures. Metamorphism is divided into three types.

Regional metamorphism- this is a change in the composition of rocks that are immersed to great depths and exposed to high temperature and pressure.

Another view - dynamometamorphism occurs when tectonic lateral pressure acts on rocks, which are crushed, split into tiles and acquire a slate-like appearance.

During the process of intrusion of magma into rocks, contact metamorphism, as a result of which partial remelting and recrystallization of the latter occurs near the contact zone of magmatic melts with host rocks.

Conclusion

Forecasting oil and gas potential, prospecting and exploration for oil and gas are based on knowledge of the geology of oil and gas, which, in turn, rests on a strong foundation - general and structural geology.

Issues of general geology include the study of the geological age of the layers of the earth's crust, the composition of the rocks that make up the crust, the geological history of the Earth and the geological processes occurring in the interior and on the surface of the planet.

Structural geology studies the structure, movement and development of the earth's crust, the occurrence of rocks, the reasons for their occurrence and development.

It is necessary to know the conditions of rock occurrence in order to correctly approach the identification of mineral deposits, including the discovery of deposits and accumulations of oil and gas. It is known that most oil and gas accumulations are located in anticlines, which are hydrocarbon traps. Therefore, searches for structural oil and gas traps are carried out on the basis of studying the structural features of the earth's crust in the study areas.

List of used literature:

    Mstislavskaya L.P., Pavlinich M.F., Filippov V.P., “Fundamentals of oil and gas production”, Publishing House “Oil and Gas”, Moscow, 2003

    Mikhailov A.E., “Structural geology and geological mapping”, Moscow, “Nedra”, 1984

    BUILDING Earth...

  1. Internal structure Lands (4)

    Abstract >> Geology

    Mantle. She, like earthly bark, has a complex structure.Back in the 19th century there became... external and internal forces of the Earth. Structure terrestrial bark heterogeneous (Fig. 19). Upper... waves are small. Rice. 19. Structure terrestrial bark Below, under the continents, there is a granite...

Studying the internal structure of planets, including our Earth, is an extremely difficult task. We cannot physically “drill” into the earth’s crust right down to the core of the planet, so all the knowledge we have acquired at the moment is knowledge obtained “by touch,” and in the most literal way.

How seismic exploration works using the example of oil field exploration. We “call” the earth and “listen” to what the reflected signal will bring us

The fact is that the simplest and most reliable way to find out what is under the surface of the planet and is part of its crust is to study the speed of propagation seismic waves in the depths of the planet.

It is known that the speed of longitudinal seismic waves increases in denser media and, on the contrary, decreases in loose soils. Accordingly, knowing the parameters of different types of rock and having calculated data on pressure, etc., “listening” to the response received, you can understand through which layers of the earth’s crust the seismic signal passed and how deep they are under the surface.

Studying the structure of the earth's crust using seismic waves

Seismic vibrations can be caused by two types of sources: natural And artificial. Natural sources of vibrations are earthquakes, the waves of which carry the necessary information about the density of the rocks through which they penetrate.

The arsenal of artificial sources of vibrations is more extensive, but first of all, artificial vibrations are caused by an ordinary explosion, but there are also more “subtle” ways of working - generators of directed pulses, seismic vibrators, etc.

Conducting blasting operations and studying seismic wave velocities seismic survey- one of the most important branches of modern geophysics.

What did the study of seismic waves inside the Earth give? Analysis of their distribution revealed several jumps in the change in speed when passing through the bowels of the planet.

Earth's crust

The first jump, in which speeds increase from 6.7 to 8.1 km/s, according to geologists, is recorded base of the earth's crust. This surface is located in different places on the planet at different levels, from 5 to 75 km. The boundary between the earth's crust and the underlying shell - the mantle - is called "Mohorovicic surfaces", named after the Yugoslav scientist A. Mohorovicic who first established it.

Mantle

Mantle lies at depths of up to 2,900 km and is divided into two parts: upper and lower. The boundary between the upper and lower mantle is also recorded by a jump in the speed of propagation of longitudinal seismic waves (11.5 km/s) and is located at depths from 400 to 900 km.

The upper mantle has a complex structure. In its upper part there is a layer located at depths of 100-200 km, where transverse seismic waves attenuate by 0.2-0.3 km/s, and the velocities of longitudinal waves essentially do not change. This layer is named waveguide. Its thickness is usually 200-300 km.

The part of the upper mantle and crust that lies above the waveguide is called lithosphere, and the layer of reduced velocities itself - asthenosphere.

Thus, the lithosphere is a rigid, solid shell underlain by a plastic asthenosphere. It is assumed that processes occur in the asthenosphere that cause movement of the lithosphere.

The internal structure of our planet

Earth's core

At the base of the mantle there is a sharp decrease in the speed of propagation of longitudinal waves from 13.9 to 7.6 km/s. At this level lies the boundary between the mantle and Earth's core, deeper than which transverse seismic waves no longer propagate.

The radius of the core reaches 3500 km, its volume: 16% of the volume of the planet, and mass: 31% of the mass of the Earth.

Many scientists believe that the core is in a molten state. Its outer part is characterized by sharply reduced values ​​of the velocities of longitudinal waves; in the inner part (with a radius of 1200 km) the velocities of seismic waves increase again to 11 km/s. The density of the core rocks is 11 g/cm 3, and it is determined by the presence of heavy elements. Such a heavy element could be iron. Most likely, iron is an integral part of the core, since a core of pure iron or iron-nickel composition should have a density 8-15% higher than the existing density of the core. Therefore, oxygen, sulfur, carbon and hydrogen appear to be attached to the iron in the core.

Geochemical method for studying the structure of planets

There is another way to study the deep structure of planets - geochemical method. The identification of different shells of the Earth and other terrestrial planets according to physical parameters finds quite clear geochemical confirmation based on the theory of heterogeneous accretion, according to which the composition of the cores of planets and their outer shells is, for the most part, initially different and depends on the earliest stage of their development.

As a result of this process, the heaviest ones were concentrated in the core ( iron-nickel) components, and in the outer shells - lighter silicate ( chondritic), enriched in the upper mantle with volatile substances and water.

The most important feature of the terrestrial planets (Earth) is that their outer shell, the so-called bark, consists of two types of substance: " mainland" - feldspathic and " oceanic" - basalt.

Continental crust of the Earth

The continental (continental) crust of the Earth is composed of granites or rocks similar to them in composition, that is, rocks with a large amount of feldspars. The formation of the “granite” layer of the Earth is due to the transformation of older sediments in the process of granitization.

The granite layer should be considered as specific the shell of the Earth's crust - the only planet on which the processes of differentiation of matter with the participation of water and having a hydrosphere, an oxygen atmosphere and a biosphere have been widely developed. On the Moon and, probably, on the terrestrial planets, the continental crust is composed of gabbro-anorthosites - rocks consisting of a large amount of feldspar, although of a slightly different composition than in granites.

The oldest (4.0-4.5 billion years) surfaces of the planets are composed of these rocks.

Oceanic (basaltic) crust of the Earth

Oceanic (basaltic) crust The earth was formed as a result of stretching and is associated with zones of deep faults, which led to the penetration of the basalt centers of the upper mantle. Basaltic volcanism is superimposed on previously formed continental crust and is a relatively younger geological formation.

Manifestations of basaltic volcanism on all terrestrial planets are apparently similar. The widespread development of basalt “seas” on the Moon, Mars, and Mercury is obviously associated with stretching and the formation, as a result of this process, of permeability zones along which basaltic melts of the mantle rushed to the surface. This mechanism of manifestation of basaltic volcanism is more or less similar for all terrestrial planets.

The Earth's satellite, the Moon, also has a shell structure that generally replicates that of the Earth, although it has a striking difference in composition.

Heat flow of the Earth. It is hottest in the areas of faults in the earth's crust, and coldest in areas of ancient continental plates

Method for measuring heat flow to study the structure of planets

Another way to study the deep structure of the Earth is to study its heat flow. It is known that the Earth, hot from the inside, gives up its heat. The heating of deep horizons is evidenced by volcanic eruptions, geysers, and hot springs. Heat is the main energy source of the Earth.

The increase in temperature with depth from the Earth's surface averages about 15° C per 1 km. This means that at the boundary of the lithosphere and asthenosphere, located at approximately a depth of 100 km, the temperature should be close to 1500 ° C. It has been established that at this temperature the melting of basalts occurs. This means that the asthenospheric shell can serve as a source of magma of basaltic composition.

With depth, the temperature changes according to a more complex law and depends on the change in pressure. According to calculated data, at a depth of 400 km the temperature does not exceed 1600 ° C and at the boundary of the core and mantle is estimated at 2500-5000 ° C.

It has been established that heat release occurs constantly over the entire surface of the planet. Heat is the most important physical parameter. Some of their properties depend on the degree of heating of rocks: viscosity, electrical conductivity, magnetism, phase state. Therefore, by the thermal state one can judge the deep structure of the Earth.

Measuring the temperature of our planet at great depths is a technically difficult task, since only the first kilometers of the earth’s crust are available for measurements. However, the Earth's internal temperature can be studied indirectly through heat flow measurements.

Despite the fact that the main source of heat on Earth is the Sun, the total power of the heat flow of our planet is 30 times greater than the power of all power plants on Earth.

Measurements have shown that the average heat flow on continents and oceans is the same. This result is explained by the fact that in the oceans most of the heat (up to 90%) comes from the mantle, where the process of transfer of matter by moving flows is more intense - convection.

Convection is a process in which heated fluid expands, becoming lighter, and rises, while cooler layers sink. Since mantle matter is closer in its state to a solid body, convection in it occurs under special conditions, at low flow rates of the material.

What is the thermal history of our planet? Its initial heating is probably associated with the heat generated by the collision of particles and their compaction in their own gravity field. The heat then resulted from radioactive decay. Under the influence of heat, a layered structure of the Earth and the terrestrial planets arose.

Radioactive heat is still being released in the Earth. There is a hypothesis according to which, at the border of the Earth’s molten core, the processes of splitting matter continue to this day with the release of a huge amount of thermal energy, heating the mantle.

The earth's crust in the scientific sense is the uppermost and hardest geological part of the shell of our planet.

Scientific research allows us to study it thoroughly. This is facilitated by repeated drilling of wells both on continents and on the ocean floor. Structure of the earth and the earth's crust in different parts of the planet differ both in composition and characteristics. The upper boundary of the earth's crust is the visible relief, and the lower boundary is the zone of separation of the two environments, which is also known as the Mohorovicic surface. It is often referred to simply as the “M boundary.” It received this name thanks to the Croatian seismologist Mohorovicic A. For many years he observed the speed of seismic movements depending on the depth level. In 1909, he established the existence of a difference between the earth's crust and hot the Earth's mantle. The M boundary lies at the level where the speed of seismic waves increases from 7.4 to 8.0 km/s.

Chemical composition of the Earth

Studying the shells of our planet, scientists have made interesting and even stunning conclusions. The structural features of the earth's crust make it similar to the same areas on Mars and Venus. More than 90% of its constituent elements are represented by oxygen, silicon, iron, aluminum, calcium, potassium, magnesium, and sodium. Combining with each other in various combinations, they form homogeneous physical bodies - minerals. They can be included in rocks in different concentrations. The structure of the earth's crust is very heterogeneous. Thus, rocks in a generalized form are aggregates of more or less constant chemical composition. These are independent geological bodies. They mean a clearly defined area of ​​the earth's crust, which has the same origin and age within its boundaries.

Rocks by group

1. Igneous. The name speaks for itself. They arise from cooled magma flowing from the mouths of ancient volcanoes. The structure of these rocks directly depends on the rate of lava solidification. The larger it is, the smaller the crystals of the substance. Granite, for example, was formed in the thickness of the earth's crust, and basalt appeared as a result of the gradual outpouring of magma onto its surface. The variety of such breeds is quite large. Looking at the structure of the earth's crust, we see that it consists of 60% igneous minerals.

2. Sedimentary. These are rocks that were the result of gradual deposition on land and ocean floor fragments of certain minerals. These can be either loose components (sand, pebbles), cemented components (sandstone), remains of microorganisms (coal, limestone), products chemical reactions(potassium salt). They make up up to 75% of the entire earth's crust on the continents.
According to the physiological method of formation, sedimentary rocks are divided into:

  • Clastic. These are the remains of various rocks. They were destroyed under the influence of natural factors (earthquake, typhoon, tsunami). These include sand, pebbles, gravel, crushed stone, clay.
  • Chemical. They are gradually formed from aqueous solutions of certain mineral substances (salt).
  • Organic or biogenic. Consist of the remains of animals or plants. This oil shale, gas, oil, coal, limestone, phosphorites, chalk.

3. Metamorphic rocks. Other components can be converted into them. This occurs under the influence of changing temperature, high pressure, solutions or gases. For example, you can get marble from limestone, gneiss from granite, and quartzite from sand.

Minerals and rocks that humanity actively uses in its life are called minerals. What are they?

These are natural mineral formations that affect the structure of the earth and the earth's crust. They can be used in agriculture and industry, both in their natural form and through processing.

Types of useful minerals. Their classification

Depending on their physical state and aggregation, minerals can be divided into categories:

  1. Solid (ore, marble, coal).
  2. Liquid (mineral water, oil).
  3. Gaseous (methane).

Characteristics of individual types of minerals

According to the composition and features of application, they are distinguished:

  1. Combustibles (coal, oil, gas).
  2. Ore. They include radioactive (radium, uranium) and noble metals (silver, gold, platinum). There are ores of ferrous (iron, manganese, chromium) and non-ferrous metals (copper, tin, zinc, aluminum).
  3. Non-metallic minerals play a significant role in such a concept as the structure of the earth's crust. Their geography is vast. These are non-metallic and non-combustible rocks. These are building materials (sand, gravel, clay) and chemicals (sulfur, phosphates, potassium salts). A separate section is devoted to precious and ornamental stones.

The distribution of minerals on our planet directly depends on external factors and geological patterns.

Thus, fuel minerals are primarily mined in oil, gas and coal basins. They are of sedimentary origin and form on the sedimentary covers of platforms. Oil and coal rarely occur together.

Ore minerals most often correspond to the basement, overhangs, and folded areas of platform plates. In such places they can create huge belts.

Core


The earth's shell, as is known, is multi-layered. The core is located in the very center, and its radius is approximately 3,500 km. Its temperature is much higher than that of the Sun and is about 10,000 K. Accurate data on the chemical composition of the core has not been obtained, but it presumably consists of nickel and iron.

The outer core is in a molten state and has even greater power than the inner one. The latter is subject to enormous pressure. The substances of which it consists are in a permanent solid state.

Mantle

The Earth's geosphere surrounds the core and makes up about 83 percent of the entire surface of our planet. The lower boundary of the mantle is located at a huge depth of almost 3000 km. This shell is conventionally divided into a less plastic and dense upper part (it is from this that magma is formed) and a lower crystalline one, the width of which is 2000 kilometers.

Composition and structure of the earth's crust

In order to talk about what elements make up the lithosphere, we need to give some concepts.

The earth's crust is the outermost shell of the lithosphere. Its density is less than half the average density of the planet.

The earth's crust is separated from the mantle by the boundary M, which was already mentioned above. Since the processes occurring in both areas mutually influence each other, their symbiosis is usually called the lithosphere. It means "stone shell". Its power ranges from 50-200 kilometers.

Below the lithosphere is the asthenosphere, which has a less dense and viscous consistency. Its temperature is about 1200 degrees. A unique feature of the asthenosphere is the ability to violate its boundaries and penetrate the lithosphere. It is the source of volcanism. Here there are molten pockets of magma, which penetrates the earth's crust and pours out to the surface. By studying these processes, scientists were able to make many amazing discoveries. This is how the structure of the earth's crust was studied. The lithosphere was formed many thousands of years ago, but even now active processes are taking place in it.

Structural elements of the earth's crust

Compared to the mantle and core, the lithosphere is a hard, thin and very fragile layer. It is made up of a combination of substances, in which more than 90 chemical elements have been discovered to date. They are distributed heterogeneously. 98 percent of the mass of the earth's crust is made up of seven components. These are oxygen, iron, calcium, aluminum, potassium, sodium and magnesium. The oldest rocks and minerals are over 4.5 billion years old.

By studying the internal structure of the earth's crust, various minerals can be identified.
A mineral is a relatively homogeneous substance that can be found both inside and on the surface of the lithosphere. These are quartz, gypsum, talc, etc. Rocks are made up of one or more minerals.

Processes that form the earth's crust

The structure of the oceanic crust

This part of the lithosphere mainly consists of basaltic rocks. The structure of the oceanic crust has not been studied as thoroughly as the continental one. Plate tectonic theory explains that the oceanic crust is relatively young, and the most recent parts of it can be dated to the Late Jurassic.
Its thickness practically does not change over time, since it is determined by the amount of melts released from the mantle in the zone of mid-ocean ridges. It is significantly influenced by the depth of sedimentary layers on the ocean floor. In the most voluminous areas it ranges from 5 to 10 kilometers. This type of earth's shell belongs to the oceanic lithosphere.

Continental crust

The lithosphere interacts with the atmosphere, hydrosphere and biosphere. In the process of synthesis, they form the most complex and reactive shell of the Earth. It is in the tectonosphere that processes occur that change the composition and structure of these shells.
The lithosphere on the earth's surface is not homogeneous. It has several layers.

  1. Sedimentary. It is mainly formed by rocks. Clays and shales predominate here, and carbonate, volcanic and sandy rocks are also widespread. In sedimentary layers you can find minerals such as gas, oil and coal. All of them are of organic origin.
  2. Granite layer. It consists of igneous and metamorphic rocks that are closest in nature to granite. This layer is not found everywhere; it is most pronounced on the continents. Here its depth can be tens of kilometers.
  3. The basalt layer is formed by rocks close to the mineral of the same name. It is denser than granite.

Depth and temperature changes in the earth's crust

The surface layer is heated by solar heat. This is the heliometric shell. It experiences seasonal temperature fluctuations. The average thickness of the layer is about 30 m.

Below is a layer that is even thinner and more fragile. Its temperature is constant and approximately equal to the average annual temperature characteristic of this region of the planet. Depending on the continental climate, the depth of this layer increases.
Even deeper in the earth's crust is another level. This is a geothermal layer. The structure of the earth's crust allows for its presence, and its temperature is determined by the internal heat of the Earth and increases with depth.

The temperature rise occurs due to the decay of radioactive substances that are part of rocks. First of all, these are radium and uranium.

Geometric gradient - the magnitude of the temperature increase depending on the degree of increase in the depth of the layers. This parameter depends on various factors. The structure and types of the earth's crust influence it, as well as the composition of rocks, the level and conditions of their occurrence.

The heat of the earth's crust is an important energy source. Its study is very relevant today.