Which resembles the structure of the earth. Structure of the Earth

A characteristic feature of the evolution of the Earth is the differentiation of matter, the expression of which is the shell structure of our planet. The lithosphere, hydrosphere, atmosphere, biosphere form the main shells of the Earth, differing in chemical composition, thickness and state of matter.

Internal structure of the Earth

Chemical composition Earth(Fig. 1) similar to the composition of other planets terrestrial group, such as Venus or Mars.

In general, elements such as iron, oxygen, silicon, magnesium, and nickel predominate. The content of light elements is low. Average density Earth substances 5.5 g/cm 3.

There is very little reliable data on the internal structure of the Earth. Let's look at Fig. 2. It depicts the internal structure of the Earth. The earth is made up of earth's crust, mantle and core.

Rice. 1. Chemical composition of the Earth

Rice. 2. Internal structure of the Earth

Core

Core(Fig. 3) is located in the center of the Earth, its radius is about 3.5 thousand km. The temperature of the core reaches 10,000 K, i.e. it is higher than the temperature of the outer layers of the Sun, and its density is 13 g/cm 3 (compare: water - 1 g/cm 3). The core is believed to be composed of iron and nickel alloys.

The outer core of the Earth has a greater thickness than the inner core (radius 2200 km) and is in a liquid (molten) state. The inner core is subject to enormous pressure. The substances that compose it are in a solid state.

Mantle

Mantle- the Earth’s geosphere, which surrounds the core and makes up 83% of the volume of our planet (see Fig. 3). Its lower boundary is located at a depth of 2900 km. The mantle is divided into a less dense and plastic upper part (800-900 km), from which it is formed magma(translated from Greek means “thick ointment”; it is a molten substance earth's bowels- mixture chemical compounds and elements, including gases, in a special floor liquid state); and the crystalline lower one, about 2000 km thick.

Rice. 3. Structure of the Earth: core, mantle and crust

Earth's crust

Earth's crust - the outer shell of the lithosphere (see Fig. 3). Its density is approximately two times less than the average density of the Earth - 3 g/cm 3 .

Separates the earth's crust from the mantle Mohorovicic border(often called the Moho boundary), characterized by a sharp increase in speeds seismic waves. It was installed in 1909 by a Croatian scientist Andrei Mohorovicic (1857- 1936).

Since the processes occurring in the uppermost part of the mantle affect the movements of matter in the earth's crust, they are combined under common namelithosphere(stone shell). The thickness of the lithosphere ranges from 50 to 200 km.

Below the lithosphere is located asthenosphere- less hard and less viscous, but more plastic shell with a temperature of 1200 ° C. It can cross the Moho boundary, penetrating into the earth's crust. The asthenosphere is the source of volcanism. It contains pockets of molten magma, which penetrates into the earth's crust or pours out onto the earth's surface.

Composition and structure of the earth's crust

Compared to the mantle and core, the earth's crust is a very thin, hard and brittle layer. She is built more light substance, which currently contains about 90 natural chemical elements. These elements are not equally represented in the earth's crust. Seven elements - oxygen, aluminum, iron, calcium, sodium, potassium and magnesium - account for 98% of the mass of the earth's crust (see Fig. 5).

Peculiar combinations of chemical elements form various rocks and minerals. The oldest of them are at least 4.5 billion years old.

Rice. 4. Structure of the earth's crust

Rice. 5. Composition of the earth's crust

Mineral is a relatively homogeneous natural body in its composition and properties, formed both in the depths and on the surface of the lithosphere. Examples of minerals are diamond, quartz, gypsum, talc, etc. (Characteristics physical properties various minerals can be found in Appendix 2.) The composition of the Earth's minerals is shown in Fig. 6.

Rice. 6. General mineral composition Earth

Rocks consist of minerals. They can be composed of one or several minerals.

Sedimentary rocks - clay, limestone, chalk, sandstone, etc. - formed by sedimentation of substances in aquatic environment and on land. They lie in layers. Geologists call them pages of the history of the Earth, because they can learn about natural conditions that existed on our planet in ancient times.

Among sedimentary rocks distinguish organogenic and inorganogenic (clastic and chemogenic).

Organogenic Rocks are formed as a result of the accumulation of animal and plant remains.

Clastic rocks are formed as a result of weathering, destruction by water, ice or wind of the products of destruction of previously formed rocks (Table 1).

Table 1. Clastic rocks depending on the size of the fragments

Chemogenic Rocks are formed as a result of the precipitation of substances dissolved in them from the waters of seas and lakes.

In the thickness of the earth's crust, magma forms igneous rocks(Fig. 7), for example granite and basalt.

Sedimentary and igneous rocks, when immersed to great depths under the influence of pressure and high temperatures, undergo significant changes, turning into metamorphic rocks. For example, limestone turns into marble, quartz sandstone into quartzite.

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

Sedimentary layer(see Fig. 8) is formed mainly by sedimentary rocks. Clays and shales predominate here, and sandy, carbonate and volcanic rocks are widely represented. In the sedimentary layer there are deposits of such mineral, How coal, gas, oil. All of them are of organic origin. For example, coal is a product of the transformation of plants of ancient times. The thickness of the sedimentary layer varies widely - from complete absence in some areas of land up to 20-25 km in deep depressions.

Rice. 7. Classification of rocks by origin

"Granite" layer consists of metamorphic and igneous rocks, similar in their properties to granite. The most common here are gneisses, granites, crystalline schists, etc. The granite layer is not found everywhere, but on continents where it is well expressed, its maximum thickness can reach several tens of kilometers.

"Basalt" layer formed by rocks close to basalts. These are metamorphosed igneous rocks, denser than the rocks of the “granite” layer.

The thickness and vertical structure of the earth's crust are different. There are several types of the earth's crust (Fig. 8). According to the simplest classification, a distinction is made between oceanic and continental crust.

Continental and oceanic crust vary in thickness. Thus, the maximum thickness of the earth's crust is observed under mountain systems. It is about 70 km. Under the plains the thickness of the earth's crust is 30-40 km, and under the oceans it is thinnest - only 5-10 km.

Rice. 8. Types of the earth's crust: 1 - water; 2- sedimentary layer; 3—interlayering of sedimentary rocks and basalts; 4 - basalts and crystalline ultrabasic rocks; 5 – granite-metamorphic layer; 6 – granulite-mafic layer; 7 - normal mantle; 8 - decompressed mantle

The difference between the continental and oceanic crust in the composition of rocks is manifested in the fact that there is no granite layer in the oceanic crust. Yes, and a basalt layer oceanic crust very peculiar. In terms of rock composition, it differs from a similar layer of continental crust.

The boundary between land and ocean (zero mark) does not record the transition of the continental crust to the oceanic one. The replacement of continental crust by oceanic crust occurs in the ocean at a depth of approximately 2450 m.

Rice. 9. Structure of the continental and oceanic crust

There are also transitional types of the earth's crust - suboceanic and subcontinental.

Suboceanic crust located along continental slopes and foothills, can be found in marginal and Mediterranean seas. It represents continental crust with a thickness of up to 15-20 km.

Subcontinental crust located, for example, on volcanic island arcs.

Based on materials seismic sounding - speed of seismic waves - we receive data on deep structure earth's crust. Yes, Kola ultra-deep well, which for the first time made it possible to see rock samples from a depth of more than 12 km, brought many unexpected things. It was assumed that at a depth of 7 km a “basalt” layer should begin. In reality, it was not discovered, and gneisses predominated among the rocks.

Change in temperature of the earth's crust with depth. The surface layer of the earth's crust has a temperature determined by solar heat. This heliometric layer(from the Greek helio - Sun), experiencing seasonal temperature fluctuations. Its average thickness is about 30 m.

Below is even more thin layer, characteristic feature which is a constant temperature corresponding to the average annual temperature of the observation site. The depth of this layer increases in continental climates.

Even deeper in the earth's crust there is a geothermal layer, the temperature of which is determined by the internal heat of the Earth and increases with depth.

The increase in temperature occurs mainly due to the decomposition radioactive elements, which are part of rocks, primarily radium and uranium.

The amount of temperature increase in rocks with depth is called geothermal gradient. It fluctuates within a fairly wide range - from 0.1 to 0.01 °C/m - and depends on the composition of rocks, the conditions of their occurrence and a number of other factors. Under the oceans, temperature increases faster with depth than on continents. On average, with every 100 m of depth it becomes warmer by 3 °C.

The reciprocal of the geothermal gradient is called geothermal stage. It is measured in m/°C.

The heat of the earth's crust is an important energy source.

Part of the earth's crust extending to depths accessible to geological study, forms bowels of the earth. The Earth's interior requires special protection and wise use.

The Earth is part of a system where the center is the Sun, which contains 99.87% of the mass of the entire system. Characteristic feature All planets of the Solar system is their shell structure: each planet consists of a number of concentric spheres, differing in composition and state of matter.

The earth is surrounded by a thick gaseous shell - the atmosphere. It is a kind of regulator of metabolic processes between the Earth and Space. The gas shell contains several spheres that differ in composition and physical properties. The bulk gaseous substance enclosed in the troposphere, the upper boundary of which, located at an altitude of about 17 km at the equator, decreases towards the poles to 8-10 km. Higher up, throughout the stratosphere and mesosphere, the rarefaction of gases increases, and thermal conditions change complexly.

Fig.1. Comparison of the structure of the Earth and other terrestrial planets

At an altitude of 80 to 800 km there is the ionosphere - a region of highly rarefied gas, among the particles of which electrically charged ones predominate. The outermost part of the gas shell is formed by the exosphere, extending to an altitude of 1800 km. From this sphere the lightest atoms - hydrogen and helium - dissipate. The planet itself is even more complexly stratified. The mass of the Earth is estimated at 5.98 * 1027 g, and its volume is 1.083 * 1027 cm 3. Therefore, the average density of the planet is about 5.5 g/cm 3 . But the density of the rocks available to us is 2.7-3.0 g/cm 3 . It follows from this that the density of the Earth’s matter is heterogeneous.

The main methods of studying internal parts of our planet are geophysical, primarily observations of the speed of propagation of seismic waves generated from explosions or earthquakes. Just like a stone thrown into water different sides waves diverge along the surface of the water, so in a solid substance elastic waves propagate from the source of the explosion. Among them, waves of longitudinal and transverse vibrations are distinguished. Longitudinal vibrations are alternating compression and stretching of a substance in the direction of wave propagation. Lateral vibrations can be represented as alternating shifts in a direction perpendicular to the propagation of the wave.

Longitudinal vibration waves, or, as they say, longitudinal waves, propagate in a solid at a higher speed than transverse waves. Longitudinal waves propagate in both solid and liquid matter, transverse waves propagate only in solid matter. Consequently, if, when seismic waves pass through a body, it is found that it does not transmit transverse waves, then we can assume that this substance is in a liquid state. If both types of seismic waves pass through a body, then this is evidence of the solid state of the substance.

The speed of waves increases with increasing density of matter. With a sharp change in the density of the substance, the speed of the waves will change abruptly. As a result of studying the propagation of seismic waves through the Earth, it was discovered that there are several defined boundaries for the abrupt change in wave velocities. Therefore, it is assumed that the Earth consists of several concentric shells (geospheres).

Based on the established three main interfaces, three main geospheres are distinguished: the earth's crust, mantle and core. The first interface is characterized by an abrupt increase in the velocities of longitudinal seismic waves from 6.7 to 8.1 km/s. This boundary is called the Mohorovicic section (in honor of the Serbian scientist A. Mohorovicic, who discovered it), or simply the M boundary. It separates the earth's crust from the mantle. The density of the earth's crust, as indicated above, does not exceed 2.7-3.0 g/cm 3 . The M boundary is located under the continents at a depth of 30 to 80 km, and under the ocean floor - from 4 to 10 km. Considering that the radius of the Earth is 6371 km, the Earth's crust is a thin film on the surface of the planet, constituting less than 1% of its total mass and approximately 1.5% of its volume.

Shape of the Earth

The shape of the Earth (geoid) is close to an oblate ellipsoid. The discrepancy between the geoid and the ellipsoid that approximates it reaches 100 meters. The average diameter of the planet is approximately 12,742 km, and the circumference is 40,000 km, since the meter in the past was defined as 1/10,000,000 of the distance from the equator to the north pole via Paris (due to incorrect accounting of the polar compression of the Earth, the meter standard of 1795 was shorter approximately 0.2 mm, hence the inaccuracy). The rotation of the Earth creates an equatorial bulge, so the equatorial diameter is 43 km larger than the polar one. The highest point on the Earth's surface is Mount Everest (8,848 m above sea level), and the deepest is the Mariana Trench (10,994 m below sea level). Due to the convexity of the equator, the most remote points surfaces from the center of the Earth are the summit of the Chimborazo volcano in Ecuador and Mount Huascaran in Peru.

The Earth, like other terrestrial planets, has a layered internal structure. It consists of hard silicate shells (crust, extremely viscous mantle), and a metallic core. The outer part of the core is liquid (much less viscous than the mantle), and the inner part is solid.

Structure of the earth's crust

The earth's crust is a term that, although it came into use in natural sciences during the Renaissance, long time was interpreted very loosely due to the fact that it was impossible to directly determine the thickness of the crust and study its deep parts. The discovery of seismic vibrations and the creation of a method for determining the speed of propagation of their waves in media of different densities gave a powerful impetus to the study of the earth's interior. With the help of seismographic studies at the beginning of the 20th century. a fundamental difference in the speed of passage of seismic waves through the rocks that make up the earth's crust and the mantle was discovered, and the boundary between them was objectively established (the Mohorovicic boundary). Thus, the concept of “earth’s crust” received a specific scientific justification.

Fig.2. Internal structure of the Earth

Experimental study of the speed of distribution of shock elastic vibrations in rocks with different densities, on the one hand, and on the other, the “transmission” of the earth’s crust by seismic waves at many points on the earth’s surface, made it possible to discover that the earth’s crust consists of the following three layers, composed of rocks of different densities:

1) The outer layer, consisting of sedimentary rocks, in which waves of seismic vibrations propagate at a speed of 1-3 km/sec, which corresponds to a density of about 2.7 g/cm 3 . Some scientists call this layer the sedimentary shell of the Earth.

2) A layer of dense crystalline rocks that make up the upper part of the continents under the sedimentary strata, in which seismic waves propagate at a speed of 5.5 to 6.5 km/sec. Due to the fact that longitudinal seismic waves propagate at a specified speed in granites and rocks similar to them in composition, this thickness is conventionally called a granite layer, although it contains a wide variety of igneous and metamorphic rocks. Granitoids, gneisses, and crystalline schists predominate; crystalline rocks of intermediate and even basic composition (diorites, gabbros, amphibolites) are found.

3) A layer of denser crystalline rocks that forms the lower part of the continents and makes up the ocean floor. In the rocks of this layer, the propagation speed of longitudinal seismic waves is 6.5-7.2 km/sec, which corresponds to a density of about 3.0 g/cm 3 . Such speeds and density are characteristic of basalts, which is why this layer was called basaltic, although basalts do not completely compose this layer everywhere.

The concepts of “granite layer” and “basalt layer” are arbitrary and are used to designate the second and third horizons of the earth’s crust, characterized by the propagation speeds of longitudinal seismic waves of 5.5-6.5 and 6.5-7.2 km/sec, respectively.

The lower boundary of the basalt layer is the Mohorovic surface. Below are rocks belonging to the material of the upper mantle. They have a density of 3.2-3.3 g/m 3 or more, the speed of propagation of longitudinal seismic waves in them is 8.1 m/sec. Their composition corresponds to ultramafic rocks (peridotites, dunites).

It should be noted that the terms “earth’s crust” and “lithosphere” (rock shell) are not synonymous and have different meanings. Lithosphere - outer shell globe, composed of hard rocks, including rocks of the upper mantle of ultrabasic composition. The earth's crust is the part of the lithosphere that lies above the Mohorovicic boundary. Within these boundaries, the total volume of the earth’s crust is more than 10 billion km 3, and its mass is over 1018 tons.

Earth's mantle

The mantle is the silicate shell of the Earth, located between the earth's crust and the Earth's core. The mantle makes up 67% of the Earth's mass and about 83% of its volume (excluding the atmosphere). It extends from the boundary with the earth's crust (at a depth of 5-70 kilometers) to the boundary with the core at a depth of about 2900 km. It is separated from the earth's crust by the Mohorovicic surface, where the speed of seismic waves during the transition from the crust to the mantle quickly increases from 6.7-7.6 to 7.9-8.2 km/s. The mantle occupies a huge range of depths, and with increasing pressure in the substance, phase transitions occur, during which minerals acquire an increasingly dense structure. The Earth's mantle is divided into an upper mantle and a lower mantle. Upper layer, in turn, is divided into the substrate, the Gutenberg layer and the Golitsyn layer (middle mantle).

According to modern scientific ideas, the composition of the earth's mantle is considered to be similar to the composition stony meteorites, in particular chondrites. The composition of the mantle mainly includes chemical elements, who were in solid state or in solid chemical compounds during the formation of the Earth: silicon, iron, oxygen, magnesium, etc. These elements form silicates with silicon dioxide. In the upper mantle (substrate), most likely, there is more forsterite MgSiO 4; deeper, the content of fayalite Fe 2 SiO 4 increases slightly.

In the lower mantle under the influence of very high pressure these minerals decomposed into oxides (SiO 2, MgO, FeO). The aggregate state of the mantle is determined by the influence of temperatures and ultra-high pressure. Due to pressure, the substance of almost the entire mantle is solid. crystalline state despite the high temperature. The only exception is the asthenosphere, where the effect of pressure is weaker than temperatures close to the melting point of the substance. Because of this effect, it appears that the substance here is either in amorphous state, or semi-molten.

Earth's core

The core is the central, deepest part of the Earth, the geosphere, located under the mantle and, presumably, consisting of an iron-nickel alloy with an admixture of other siderophile elements. Depth of occurrence - 2900 km. The average radius of the sphere is 3485 km. It is divided into a solid inner core with a radius of about 1300 km and a liquid outer core with a radius of about 2200 km, between which a transition zone is sometimes distinguished. The temperature in the center of the Earth's core reaches 6000 °C, the density is about 12.5 t/m 3, the pressure is up to 360 GPa (3.55 million atmospheres). Core mass - 1.9354·1024 kg.

A characteristic property of the globe is its heterogeneity. It is divided into a number of layers or spheres, which are divided into internal and external.

Inner Spheres of the Earth: earth's crust, mantle and core.

Earth's crust most heterogeneous. In terms of depth, there are 3 layers (from top to bottom): sedimentary, granite and basalt.

Sedimentary layer formed by soft and sometimes loose rocks that arose by sedimentation of matter in water or air environment on the surface of the Earth. Sedimentary rocks are usually arranged in strata bounded by parallel planes. The thickness of the layer varies from several meters to 10-15 km. There are areas where the sedimentary layer is almost completely absent.

granite layer composed mainly of igneous and metamorphic rocks rich in Al and Si. The average SiO 2 content in them is more than 60%, so they are classified as acidic rocks. The density of the rocks in the layer is 2.65-2.80 g/cm3. Thickness 20-40 km. As part of the oceanic crust (for example, at the bottom Pacific Ocean) the granite layer is absent, thus being an integral part of the continental crust.

Basalt layer lies at the base of the earth's crust and is continuous, that is, unlike the granite layer, it is present in both the continental and oceanic crust. It is separated from the granite surface by the Conrad surface (K), on which the speed of seismic waves changes from 6 to 6.5 km/sec. The substance composing the basalt layer is close in chemical composition and physical properties to basalts (less rich in SiO 2 than granites). The density of the substance reaches 3.32 g/cm 3 . The speed of passage of longitudinal seismic waves increases from 6.5 to 7 km/sec at the lower boundary, where the speed jumps again and reaches 8-8.2 km/sec. This lower boundary of the earth's crust can be traced everywhere and is called the Mohorovicic boundary (Yugoslav scientist) or the M boundary.

Mantle located under the earth's crust in the depth range from 8-80 to 2900 km. The temperature in the upper layers (up to 100 km) is 1000-1300 o C, increasing with depth and reaching 2300 o C at the lower boundary. However, the substance is there in a solid state due to pressure, which at great depths amounts to hundreds of thousands and millions of atmospheres. At the border with the core (2900 km), refraction and partial reflection of longitudinal seismic waves are observed, and transverse waves they do not pass this boundary (the “seismic shadow” ranges from 103° to 143° arc). The speed of wave propagation in the lower part of the mantle is 13.6 km/sec.

Relatively recently, it became known that in the upper part of the mantle there is a layer of decompressed rocks - asthenosphere, lying at a depth of 70-150 km (deeper under the oceans), in which a drop in elastic wave velocities of approximately 3% is recorded.

Core in physical properties it differs sharply from the mantle that envelops it. The speed of passage of longitudinal seismic waves is 8.2-11.3 km/sec. The fact is that at the boundary of the mantle and core there is a sharp drop in the speed of longitudinal waves from 13.6 to 8.1 km/sec. Scientists have long come to the conclusion that the density of the core is much higher than the density of the surface shells. It must correspond to the density of iron under appropriate barometric conditions. Therefore, it is widely believed that the core consists of Fe and Ni and has magnetic properties. The presence of these metals in the nucleus is associated with the primary differentiation of the substance by specific gravity. Meteorites also speak in favor of an iron-nickel core. The core is divided into external and internal. In the outer part of the core, the pressure is 1.5 million atm; density 12 g/cm 3 . Longitudinal seismic waves propagate here at a speed of 8.2-10.4 km/sec. The inner core is in a liquid state, and convective currents in it induce the Earth's magnetic field. In the inner core, the pressure reaches 3.5 million atm, the density is 17.3-17.9 g/cm 3, the speed of longitudinal waves is 11.2-11.3 km/sec. Calculations show that the temperature there should reach several thousand degrees (up to 4000 o). The substance there is in a solid state due to high pressure.

Outer spheres of the Earth: hydrosphere, atmosphere and biosphere.

Hydrosphere unites the entire set of manifestations of water forms in nature, starting from a continuous water cover that occupies 2/3 of the Earth’s surface (seas and oceans) and ending with water that is part of rocks and minerals. in this understanding, the hydrosphere is a continuous shell of the Earth. Our course examines, first of all, that part of the hydrosphere that forms an independent water layer - oceanosphere.

From total area The land area is 510 million km2, 361 million km2 (71%) is covered with water. Schematically, the relief of the bottom of the World Ocean is depicted as hypsographic curve. It shows the distribution of land heights and ocean depths; 2 levels of the seabed are clearly visible with depths of 0-200 m and 3-6 km. The first of them is an area of ​​​​relative shallow water, encircling the coasts of all continents in the form of an underwater platform. Is this a continental shelf or shelf. From the sea, the shelf is limited by a steep underwater ledge - continental slope(up to 3000 m). At depths of 3-3.5 km there is continental foot. Starts below 3500 m oceanic bed (ocean bed), the depth of which is up to 6000 m. The continental foot and ocean floor constitute the second clearly defined level of the seabed, composed of typically oceanic crust (without a granite layer). Among the ocean floor, mainly in the peripheral parts of the Pacific Ocean, are located deep-sea depressions (trenches)- from 6000 to 11000 m. This is approximately what the hypsographic curve looked like 20 years ago. One of the most important geological discoveries of recent times was the discovery mid-ocean ridges - a global system of seamounts raised above the ocean floor by 2 kilometers or more and occupying up to 1/3 of the area of ​​the ocean floor. ABOUT geological significance this discovery will be discussed later.

Almost all known chemical elements are present in ocean water, but only 4 predominate: O 2, H 2, Na, Cl. The content of chemical compounds dissolved in sea water (salinity) is determined in weight percent or ppm(1 ppm = 0.1%). The average salinity of ocean water is 35 ppm (there are 35 g of salts in 1 liter of water). Salinity varies widely. So, in the Red Sea it reaches 52 ppm, in the Black Sea up to 18 ppm.

Atmosphere represents the uppermost air shell of the Earth, which envelops it with a continuous cover. Upper limit not distinct, since the density of the atmosphere decreases with height and gradually passes into airless space. The lower boundary is the surface of the Earth. This boundary is also arbitrary, since air penetrates to a certain depth into the stone shell and is contained in a dissolved form in the water column. There are 5 main spheres in the atmosphere (from bottom to top): troposphere, stratosphere, mesosphere, ionosphere And exosphere. The troposphere is important for geology, since it is in direct contact with the earth’s crust and has a significant influence on it.

The troposphere is characterized by high density, constant presence of water vapor, carbon dioxide and dust; a gradual decrease in temperature with height and the existence of vertical and horizontal air circulation in it. In addition to the main elements - O 2 and N 2 - the chemical composition always contains CO 2, water vapor, some inert gases (Ar), H 2, sulfur dioxide and dust. Air circulation in the troposphere is very complex.

Biosphere- a kind of shell (isolated and named by Academician V.I. Vernadsky), unites those shells in which life is present. It does not occupy a separate space, but penetrates into the earth's crust, atmosphere and hydrosphere. The biosphere plays a large role in geological processes, participating both in the creation of rocks and in their destruction.

Living organisms penetrate most deeply into the hydrosphere, which is often called the “cradle of life.” Life is especially rich in the oceanosphere, in its surface layers. Depending on the physical and geographical situation, primarily on the depths, there are several types of water in the seas and oceans. bionomic zones(Greek “bios” - life, “nomos” - law). These zones differ in the conditions for the existence of organisms and their composition. In the shelf area there are 2 zones: littoral And neritic. The littoral zone is a relatively narrow strip of shallow water, drained twice a day during low tide. Due to its specific nature, the littoral zone is inhabited by organisms that can tolerate temporary drying (sea worms, some mollusks, sea urchins, stars). Deeper than the tidal zone within the shelf is the neritic zone, which is most richly populated by a variety of marine organisms. All types of fauna are widely represented here. According to lifestyle they distinguish benthic animals (bottom inhabitants): sessile benthos (corals, sponges, bryozoans, etc.), wandering benthos (crawling ones - hedgehogs, stars, crayfish). Nekton animals are able to move independently (fish, cephalopods); planktonic (plankton) - suspended in water (foraminifera, radiolaria, jellyfish). Corresponds to the continental slope bathyal zone, continental foothills and oceanic bed - abyssal zone. The living conditions in them are not very favorable - complete darkness, high pressure, lack of algae. However, even there Lately discovered abyssal oases of life, confined to underwater volcanoes and zones of hydrothermal outflow. The biota here is based on giant anaerobic bacteria, vestimentifera and other peculiar organisms.

The depth of penetration of living organisms into the Earth is mainly limited by temperature conditions. Theoretically, for the most resistant prokaryotes it is 2.5-3 km. Living matter actively influences the composition of the atmosphere, which in its modern form is the result of the vital activity of organisms that enriched it with oxygen, carbon dioxide, and nitrogen. The role of organisms in the formation of marine sediments is extremely important, many of which are minerals (caustobiolites, jaspilites, etc.).

Self-test questions.

How were views on the origin of the solar system formed?

What is the shape and size of the Earth?

From which hard shells what does the earth consist of?

How does continental crust differ from oceanic crust?

What causes the Earth's magnetic field?

What is a hypsographic curve and its type?

What is benthos?

What is the biosphere and its boundaries?

Internal structure of the Earth established based on geophysical research materials (the nature of the passage of seismic waves). There are three main shells.

1. Earth's crust - greatest thickness up to 70 km.
2. Mantle - from the lower boundary of the earth’s crust to a depth of 2900 km.
3. Core - extends to the center of the Earth (to a depth of 6,371 km).

The boundary between the earth's crust and mantle is called border Mohorovicic (Moho), between the mantle and the core - border Gutenberg.
Earth's core is divided into two layers. External core (at a depth of 5,120 km to 2,900 km), the substance is liquid, since transverse waves do not penetrate into it, and the speed of longitudinal waves drops to 8 km/s (see “Earthquakes”). Internal core (from a depth of 6,371 km to 5,120 km), the matter here is in a solid state (the speed of longitudinal waves increases to 11 km/s or more). The composition of the core is dominated by iron-nickel melt with an admixture of silicon and sulfur. The density of the substance in the core reaches 13 g/cc.

Mantle is divided into two parts: upper and lower.

Upper mantle consists of three layers, dives to a depth of 800 - 900 km. Verkhni th a layer up to 50 km thick consists of a hard and brittle crystalline substance (longitudinal wave speeds up to 8.5 km/s or more). Together with the earth's crust it forms lithosphere- the rocky shell of the Earth.

Middle layer - asthenosphere(yielding shell) is characterized by an amorphous glassy state of the substance, and partly (by 10%) has a molten viscoplastic state (this is evidenced by a sharp drop in the speed of seismic waves). The thickness of the middle layer is about 100 km. The asthenosphere lies on different depths. Beneath mid-ocean ridges, where the thickness of the lithosphere is minimal, the asthenosphere lies at a depth of several kilometers. On the margins of the oceans, as the thickness of the lithosphere increases, the asthenosphere sinks to 60–80 km. Under the continents it lies at depths of about 200 km, and under continental rifts it rises again to a depth of 10–25 km. Lower layer of the upper mantle (Golitsin layer) is sometimes isolated as a transition layer or as independent part- middle mantle. It descends to a depth of 800 - 900 km, the substance here is crystalline solid (longitudinal wave speed is up to 9 km/s).

Lower mantle extends up to 2,900 km, composed of solid crystalline substance(the speed of longitudinal waves increases to 13.5 km/s). The composition of the mantle is dominated by olivine and pyroxene, its density in the lower part reaches 5.8 g/cm3.

Earth's crust is divided into two main types (continental and oceanic) and two transitional types (subcontinental and suboceanic). The types of bark differ in structure and thickness.

Continental The crust, distributed within the continents and shelf zones, has a thickness of 30 - 40 km in platform areas and up to 70 km in the highlands. Its lower layer is basaltic (mafic- enriched with magnesium and iron), consists of heavy rocks, its thickness is from 15 to 40 km. Above lies composed of lighter rocks granite-gneiss layer ( sialic- enriched with silicon and aluminum), with a thickness of 10 to 30 km. These layers may overlap at the top sedimentary layer, thickness from 0 to 15 km. The boundary between basalt and granite gneiss layers identified from seismic data ( border Conrad) is not always clearly visible.

Oceanic the crust, up to 6 - 8 km thick, also has a three-layer structure. The bottom layer is heavy basaltic, up to 4 - 6 km thick. The middle layer, about 1 km thick, is composed of interlayered layers dense sedimentary breeds and basalt Lav. The top layer consists of loose sedimentary rocks up to 0.7 km thick.

Subcontinental the crust, which has a structure close to the continental crust, is presented on the periphery of marginal and internal seas (in the zones of the continental slope and foot) and under island arcs, and is characterized by a sharply reduced thickness (up to 0 m) of the sedimentary layer. The reason for this decrease in the thickness of the sedimentary layer is the large slope of the surface, which facilitates the sliding of accumulated sediments. The thickness of this type of crust is up to 25 km, including the basalt layer up to 15 km, granite gneiss up to 10 km; Conrad's border is poorly defined.
Suboceanic crust, close in structure to oceanic, is developed within the deep-sea parts of the internal and marginal seas and in deep ocean trenches. It is distinguished by a sharp increase in the thickness of the sedimentary layer and the absence of a granite-gneiss layer. The extremely high thickness of the sedimentary layer is due to the very low hypsometric level of the surface - under the influence of gravity, gigantic strata of sedimentary rocks accumulate here. The total thickness of the suboceanic crust also reaches 25 km, including the basalt layer up to 10 km and the sedimentary layer up to 15 km. In this case, the thickness of the layer of dense sedimentary and basaltic rocks can be 5 km.

Density and pressure Lands also change with depth. The average density of the Earth is 5.52 g/cubic. cm. The density of rocks in the earth's crust varies from 2.4 to 3.0 g/cubic. cm (on average - 2.8 g/cc). The density of the upper mantle below the Moho boundary approaches 3.4 g/m3. cm, at a depth of 2,900 km it reaches 5.8 g/cubic. cm, and in the inner core up to 13 g/cubic. see According to the given data pressure at a depth of 40 km it is equal to 10 3 MPa, at the Gutenberg boundary 137 * 10 3 MPa, at the center of the Earth 361 * 10 3 MPa. The acceleration of gravity on the surface of the planet is 982 cm/s2, reaches a maximum of 1037 cm/s2 at a depth of 2900 km and is minimal (zero) at the center of the Earth.

A magnetic field The Earth is presumably caused by the convective movements of the liquid substance of the outer core that arise during the daily rotation of the planet. Studying magnetic anomalies(tension variations magnetic field) is widely used in the search for iron ore deposits.
Thermal properties Earths are forming solar radiation and heat flow spreading from the bowels of the planet. The influence of solar heat does not extend deeper than 30 m. Within these limits, at a certain depth, there lies a belt constant temperature, equal to the average annual air temperature of the given area. Deeper than this belt, the temperature gradually increases under the influence of heat flow the Earth itself. The intensity of heat flow depends on the structure of the earth's crust and the degree of activity endogenous processes. The average planetary value of heat flow is 1.5 μcal/cm2 * s, on shields it is about 0.6 - 1.0 μcal/cm2 * s, in the mountains up to 4.0 μcal/cm2 * s, and in the mid-ocean rifts up to 8.0 µcal/cm 2 * s. Among the sources that form the internal heat of the Earth, the following are assumed: the decay energy of radioactive elements, chemical transformations matter, gravitational redistribution of matter in the mantle and core. Geothermal gradient is the amount of temperature increase per unit depth. Geothermal stage is the depth at which the temperature increases by 1° C. These indicators vary greatly in different places on the planet. The maximum gradient values ​​are observed in mobile zones of the lithosphere, and the minimum values ​​are observed on ancient continental massifs. On average, the geothermal gradient of the upper part of the earth's crust is about 30 ° C per 1 km, and the geothermal step is about 33 m. It is assumed that with increasing depth the geothermal gradient decreases and the geothermal step increases. Based on the hypothesis about the predominance of iron in the composition of the core, its melting temperatures were calculated at different depths (taking into account the natural increase in pressure): 3700° C at the boundary of the mantle and the core, 4300° C at the boundary of the inner and outer core.

Chemical composition Earth is considered similar to the average chemical composition of studied meteorites. Meteorites have the following composition:
– iron(nickel iron with an admixture of cobalt and phosphorus) make up 5.6% of those found;
– ironstone (siderolites- a mixture of iron and silicates) are the least common - they make up only 1.3% of the known ones;
– stone (aerolites- silicates enriched with iron and magnesium with an admixture of nickel iron) are the most common - 92.7%.

Thus, the average chemical composition of the Earth is dominated by four elements. Oxygen and iron contain approximately 30% each, magnesium and silicon – 15% each. Sulfur accounts for about 2 - 4%; nickel, calcium and aluminum – 2% each.

The upper layer of the Earth, which gives life to the inhabitants of the planet, is just a thin shell covering many kilometers of internal layers. Little more is known about the hidden structure of the planet than outer space. The deepest Kola well, drilled into the earth's crust to study its layers, has a depth of 11 thousand meters, but this is only four hundredth of the distance to the center of the globe. Only seismic analysis can get an idea of ​​the processes occurring inside and create a model of the Earth’s structure.

Inner and outer layers of the Earth

The structure of planet Earth is made up of heterogeneous layers of internal and external shells, which differ in composition and role, but are closely related to each other. Inside the globe there are the following concentric zones:

• The core has a radius of 3500 km.
• Mantle - approximately 2900 km.
• The earth's crust is on average 50 km.

The outer layers of the earth make up a gaseous envelope called the atmosphere.

Center of the planet

The central geosphere of the Earth is its core. If you ask the question of which layer of the Earth has been studied practically the least of all, then the answer will be - the core. It is not possible to obtain accurate data on its composition, structure and temperature. All information published in scientific works, achieved through geophysical, geochemical methods and mathematical calculations and presented to the general public with the clause “supposedly”. As the results of seismic wave analysis show, the earth's core consists of two parts: internal and external. The inner core is the most unexplored part of the Earth, since seismic waves do not reach its limits. The outer core is a mass of hot iron and nickel, with a temperature of about 5 thousand degrees, which is constantly in motion and is a conductor of electricity. It is with these properties that the origin of the Earth’s magnetic field is associated. Compound inner core, according to scientists, is more diverse and is also supplemented with lighter elements - sulfur, silicon, and possibly oxygen.

Mantle

The planet's geosphere, which connects the central and upper layers of the Earth, is called the mantle. It is this layer that makes up about 70% of the mass of the globe. The lower part of the magma is the shell of the core, its outer boundary. Seismic analysis shows here a sharp jump in the density and velocity of longitudinal waves, which indicates a significant change in the composition of the rock. Composition of magma - mixture heavy metals, in which magnesium and iron predominate. Top part layer, or asthenosphere, is a mobile, plastic, soft mass with high temperature. It is this substance that breaks through the earth's crust and splashes out to the surface during volcanic eruptions.

The thickness of the magma layer in the mantle is from 200 to 250 kilometers, the temperature is about 2000 o C. The mantle is separated from the lower globe of the earth's crust by the Moho layer, or the Mohorovicic boundary, a Serbian scientist who determined sudden change the speed of seismic waves in this part of the mantle.

Hard shell

What is the name of the layer of the Earth that is the hardest? This is the lithosphere, the shell that connects the mantle and the earth's crust, it is located above the asthenosphere, and cleanses the surface layer from its hot influence. The main part of the lithosphere is part of the mantle: of the total thickness from 79 to 250 km, the earth's crust accounts for 5-70 km, depending on the location. The lithosphere is heterogeneous; it is divided into lithospheric plates, which are in constant slow motion, sometimes diverging, sometimes approaching each other. Such fluctuations lithospheric plates called tectonic movement, it is their rapid shocks that cause earthquakes, splits in the earth's crust, and the splashing of magma to the surface. The movement of lithospheric plates leads to the formation of trenches or hills; solidified magma forms mountain ranges. The plates have no permanent boundaries; they connect and separate. Areas of the Earth's surface above faults tectonic plates- these are places of increased seismic activity, where earthquakes, volcanic eruptions occur more often than others, and minerals are formed. On given time 13 lithospheric plates have been recorded, the largest of which are: American, African, Antarctic, Pacific, Indo-Australian and Eurasian.

Earth's crust

Compared to other layers, the earth's crust is the thinnest and most fragile layer of all. earth's surface. The layer in which organisms live, which is most saturated chemicals and trace elements, makes up only 5% of the total mass of the planet. The earth's crust on planet Earth has two types: continental or continental and oceanic. Continental crust harder, consists of three layers: basalt, granite and sedimentary. ocean floor make up basalt (main) and sedimentary layers.

• Basalt rocks- These are igneous fossils, the densest of the layers of the earth's surface.
• granite layer- absent under the oceans, on land it can approach the thickness of several tens of kilometers of granite, crystalline and other similar rocks.
• sedimentary layer formed during the destruction of rocks. In some places it contains mineral deposits of organic origin: coal, salt, gas, oil, limestone, chalk, potassium salts and others.

Hydrosphere

When characterizing the layers of the Earth's surface, one cannot fail to mention the planet's vital water shell, or hydrosphere. Water balance support on the planet ocean waters(main water mass), The groundwater, glaciers, continental waters of rivers, lakes and other bodies of water. 97% of the entire hydrosphere falls on salt water seas and oceans, and only 3% is fresh drinking water, of which the bulk is found in glaciers. Scientists assume that the amount of water on the surface will increase over time due to deep spheres. Hydrospheric masses are in constant circulation, pass from one state to another and closely interact with the lithosphere and atmosphere. The hydrosphere has big influence for all earth processes, development and vital activity of the biosphere. It was the water shell that became the environment for the emergence of life on the planet.

The soil

The thinnest fertile layer The earth called soil, or ground, together with the water shell, is of greatest importance for the existence of plants, animals and humans. This ball appeared on the surface as a result of erosion of rocks, under the influence organic processes decomposition. By processing the remains of vital activity, millions of microorganisms created a layer of humus - the most favorable for crops of all kinds land plants. One of the important indicators of high soil quality is fertility. The most fertile soils are those with an equal content of sand, clay and humus, or loam. Clayey, rocky and sandy soils are among the least suitable for farming.

Troposphere

The air shell of the Earth rotates along with the planet and is inextricably linked with all the processes occurring in the earth's layers. The lower part of the atmosphere penetrates deep into the body of the earth's crust through pores, while the upper part gradually connects with space.

The layers of the Earth's atmosphere are heterogeneous in their composition, density and temperature.

The troposphere extends at a distance of 10 - 18 km from the earth's crust. This part of the atmosphere is heated by the earth's crust and water, so it gets colder with height. The temperature in the troposphere decreases by approximately half a degree every 100 meters, and in highest points reaches from -55 to -70 degrees. This part of the airspace occupies the most significant share - up to 80%. It is here that the weather is formed, storms and clouds gather, precipitation and winds form.

High Layers

• Stratosphere - ozone layer planet that consumes ultraviolet radiation The sun, preventing it from destroying all living things. The air in the stratosphere is thin. Ozone maintains a stable temperature in this part of the atmosphere from - 50 to 55 o C. There is an insignificant amount of moisture in the stratosphere, so clouds and precipitation are not typical for it, in contrast to air currents of significant speed.
• Mesosphere, thermosphere, ionosphere- air layers of the Earth above the stratosphere, in which a decrease in the density and temperature of the atmosphere is observed. The ionospheric layer is where the glow of charged gas particles, called the aurora, occurs.
• Exosphere- sphere of dispersion of gas particles, blurred border with space.