The shape of the Earth (geoid) is close to an oblate ellipsoid. The average diameter of the planet is approximately 12,742 km.

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

The earth's crust is the top solid ground. It is separated from the mantle by a boundary with a sharp increase in velocities seismic waves- the border of Mohorovichich. There are two types of crust - continental and oceanic. The thickness of the crust varies from 6 km under the ocean to 30–50 km on the continents. Three geological layers are distinguished in the structure of the continental crust: sedimentary cover, granite and basalt. The oceanic crust is composed mainly of mafic rocks, plus a sedimentary cover. The earth's crust is divided into different sizes lithospheric plates moving relative to each other.

The mantle is a silicate shell of the Earth, composed mainly of peridotites - rocks consisting of silicates of magnesium, iron, calcium, etc. Partial melting of mantle rocks gives rise to basalt and similar melts that form the earth's crust when rising to the surface.

The mantle makes up 67% of the total mass of the Earth and about 83% of the total volume of the Earth. It extends from depths of 5-70 kilometers below the boundary with the earth's crust, to the boundary with the core at a depth of 2900 km. The mantle is located in a huge range of depths, and with increasing pressure in the substance, phase transitions occur, in which minerals acquire an increasingly dense structure. The most significant transformation occurs at a depth of 660 kilometers. The thermodynamics of this phase transition is such that mantle matter below this boundary cannot penetrate it, and vice versa. Above the border of 660 kilometers is the upper mantle, and below, respectively, the lower. These two parts of the mantle have a different composition and physical properties. Although information on the composition of the lower mantle is limited, and the number of direct data is very small, it can be confidently asserted that its composition has changed much less since the formation of the Earth than the upper mantle, which gave rise to the earth's crust.

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 - 2900 km. Medium radius spheres - 3.5 thousand 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 5000 C, the density is about 12.5 t/m3, and the pressure is up to 361 GPa. The mass of the core is 1.932×1024 kg.

The Earth's crust is the outer solid shell of the Earth (geosphere). The Moho boundary separates the crust and mantle. From the outside, most of the crust is covered by the hydrosphere, and the smaller part is under the influence of the atmosphere. The earth has two types of crust: continental and oceanic.

Weight earth's crust is estimated at 2.8×1019 tons (of which 21% is oceanic crust and 79% is continental). The bark is only 0.473% total weight Earth.

The oceanic crust consists mainly of basalts. the oceanic crust is relatively young, and its oldest sections date back to the Late Jurassic. The thickness of the oceanic crust practically does not change with time, since it is mainly determined by the amount of melt released from the mantle material in the zones of mid-ocean ridges. To some extent, the thickness of the sedimentary layer at the bottom of the oceans has an effect. in different geographical areas the thickness of the oceanic crust varies between 5-7 kilometers.

The standard oceanic crust has a thickness of 7 km, and a strictly regular structure. From top to bottom, it is composed of the following complexes:

sedimentary rocks represented by deep oceanic sediments.

basalt covers erupted under water.

The dike complex consists of nested basalt dikes.

layer of main layered intrusions

The mantle is represented by dunites and peridotites.

Dunites and peridotites usually occur at the base of the oceanic crust.

The continental crust has a three-layer structure. The upper layer is represented by a discontinuous cover of sedimentary rocks, which is widely developed, but rarely has a large thickness. Most of crust is folded under the upper crust - a layer consisting mainly of granites and gneisses, which has a low density and ancient history. Below is lower cortex, consisting of metamorphic rocks - granulites and the like.

Composition of the upper continental crust

The Earth's crust is made up of a relatively small number of elements. About half of the mass of the earth's crust is oxygen, more than 25% - silicon. A total of 18 elements: O, Si, Al, Fe, Ca, Na, K, Mg, H, Ti, C, Cl, P, S, N, Mn, F, Ba - make up 99.8% of the mass of the earth's crust. The earth's crust is made up of many rocks of various compositions. different areas can be completely distributed different types breeds.

Define real size The ancient Greeks tried the earth. But it was possible to do this with great accuracy only with the beginning of the space age. Although it must be said that the great scientists - Isaac Newton, Johannes Kepler, Tycho Brahe used the laws and formulas they derived to calculate the sizes of celestial bodies, and quite successfully. And although man has populated the entire planet, not everyone knows what the size of the Earth is.

The shape, movement and dimensions of the Earth

Most of all, the Earth resembles an ellipsoid, slightly flattened at both poles and somewhat stretched along the equator. What is the size of the Earth? Its average radius is 6371 kilometers.

The globe moves in a circular orbit around the sun, which is ideal for the existence of life. Our planet makes a complete revolution around its native star in 365.24 days. The unique inclination of the axis of the globe to the plane of the ecliptic and the speed of its revolution around the star have a decisive influence on the climate of the Earth - thanks to this, there are seasons. Rotation about an axis determines perfect ratio day and night. Over time, the movement of the planet around its axis slows down. Of course, relative to the duration of human life, it is insignificant, but by universal standards, this happens quite quickly - by 0.0015 seconds every century.

The size of the Earth is very large - its area is more than 510 million square kilometers. Almost 71 percent of the entire surface is covered by oceans. The average thickness of the water expanses is 3.8 km, and the most deep place- 11.022 kilometers. The land is divided into islands and six continents. highest height land - 8 kilometers 848 meters. Moreover, both of these extremes are in the Asia-Pacific region.

Mountainous terrain makes up more than a third of the entire land surface. Twenty percent is desert.

The emergence of the planet

According to modern ideas The earth was formed about 4.6-4.7 billion years ago. At first it was a protoplanetary cloud, which was captured by the solar attraction. The very first rocks "matured" for almost 200 million years. The modern size of the Earth was formed about 3.5 billion years ago. Around this time, the conditions for the origin of life had developed. Man like separate view appeared on Earth only 500 thousand years ago.

Satellite

Earth, unlike other planets in our system, has only one natural satellite. The size of the Earth allows the Moon to make full turn for 27.32166 days. Our satellite has a spherical shape. The tidal forces of the Earth over the past millennia have stopped its rotation around own axis. The size of the Moon and the Earth used to be considered the same, but now we know that our planet is almost 81 times larger than the Moon. The density of the satellite is also much less.

There are several theories about the origin of the satellite. One of them claims that the centrifugal forces of the nascent semi-liquid Earth threw out part of it. terrestrial matter, which, due to the influence of magnetic and gravitational fields, could not fly into space and remained rotating around the Earth, acquiring its shape over time.

Other scientists believe that the formation of the Moon occurred without any "intervention" of the Earth. It turned into a satellite much later, when it fell under the influence of planetary gravity.

The third theory says that the Moon and the Earth were born at the same time, from the same protoplanetary cloud. Completely none of existing theories cannot explain the existence of the moon. Each of them has contradictions and confirmations, but a clear answer to this moment does not exist.

Nevertheless, the most common version is that the Moon arose as a result of a collision of an incompletely formed Earth with a huge celestial body, no less than Mars in size.

Internal structure

In the study of the internal structure of the globe big role play seismic methods. These studies give grounds to divide the Earth into several zones: the core, the earth's crust and its mantle. On the outside there is a crust - its thickness reaches 35 kilometers. It is divided into two main types: oceanic and continental. An intermediate type of crust is formed at the boundary between land and ocean. Its thickness varies from 10 kilometers at the bottom of the seas to the mainland, the crust of which is ten times thicker.

A bunch of various elements that make up the earth are radioactive. When they break down, they release huge amount heat. In the center of the planet, the temperature reaches five thousand degrees Celsius. The highest temperature on the surface was recorded in areas of Africa - +60 o C. The minimum - minus 90 o - in Antarctica.

Modernity

The size of the planet Earth is practically the only indicator that cannot be influenced human activity. Man has a huge impact on the bio- and geosphere. Now the forces of scientists are aimed at solving the question of how to minimize the pressure of civilization on the natural course of things.

The increased growth rates of the human population have brought to the fore the problems of adequate nature management and nature protection.

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The lithosphere is the stone shell of the Earth. From the Greek "lithos" - a stone and "sphere" - a ball

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

Consider in general view geological structure Earth. The third planet farthest from the Sun - the Earth has a radius of 6370 km, an average density of 5.5 g / cm3 and consists of three shells - bark, robes and i. The mantle and core are divided into inner and outer parts.

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

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

• Oxygen - 49%;
• Silicon - 26%;
• Aluminum - 7%;
• Iron - 5%;
• Calcium - 4%
• The composition of the lithosphere includes many minerals, the most common are feldspar and quartz.

On the continents, the crust is three-layered: sedimentary rocks cover granitic rocks, and granitic rocks lie on basalt ones. Under the oceans, the crust is "oceanic", two-layered; sedimentary rocks lie simply on basalts, there is no granite layer. There is also a transitional type of the earth's crust (island-arc zones on the outskirts of the oceans and some areas on the continents, such as the Black Sea).

The Earth's crust is thickest in mountainous areas (under the Himalayas - over 75 km), the middle one - in the areas of the platforms (under the West Siberian lowland - 35-40, within the boundaries of the Russian platform - 30-35), and the smallest - in central regions oceans (5-7 km). Dominant part earth's surface- these are the plains of the continents and the ocean floor.

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

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

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

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

Lithospheric plates

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

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

Movement of tectonic plates in the lithosphere

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

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

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

In places where tectonic plates are in contact with each other, there are zones of maximum volcanic and seismic activity: during the movement and collision of the lithosphere, the earth's crust collapses, and when they diverge, faults and depressions form (the lithosphere and the Earth's relief are connected with each other). This is the reason that along the edges of tectonic plates are located the most large forms relief of the Earth - mountain ranges with active volcanoes and deep-sea trenches.

Problems of the lithosphere

The intensive development of industry has led to the fact that man and the lithosphere in recent times began to get along extremely badly with each other: pollution of the lithosphere is acquiring catastrophic proportions. This happened due to the increase in industrial waste in conjunction with household waste and used in agriculture fertilizers and pesticides, which negatively affects the chemical composition of the soil and living organisms. Scientists have calculated that about one ton of garbage falls per person per year, including 50 kg of hardly decomposable waste.

Today pollution of the lithosphere has become topical issue, since nature is not able to cope with it on its own: the self-purification of the earth's crust is very slow, and therefore harmful substances gradually accumulate and over time have a negative impact on the main culprit of the problem that has arisen - a person.

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The structure of the earth's crust
The concept of the earth's crust arose in the 18th century. At that time, scientists believed that the Earth was formed from a cloud of hot gases. Cooling, this cloud thickened to a fiery liquid, condensed and covered from the surface with a hard crust, under which, as was believed, still exists. uncooled liquid core. Now geophysicists unanimously consider almost the entire Earth to be solid. According to modern concepts, the earth's crust is the upper, solid, mostly crystalline, complexly built shell of the globe with a density of matter at its sole of 2.9-3.2 g/cm3. Below the crust lies a denser shell - the mantle.
The thickness of the earth's crust, the structure, composition of the rocks that make it up and their properties differ sharply in different parts continents and especially in the oceans. On the continents, the crust consists of three layers: sedimentary, granite-gneiss and basalt. Their names are arbitrary: they are rooted in geology because the propagation velocities of seismic waves in them are close to those observed when passing through sedimentary rocks, granites and basalts on the Earth's surface. At great depths, in conditions high pressures and temperatures known speeds may be in other breeds. There is no granite layer in the oceans, and the sediment layer is very thin - no more than 2 km. AT transition region from the continents to the oceans, the crust is of an intermediate type, with a more powerful granite layer. In the zone of volcanic arcs, as, for example, in the Kuril-Kamchatka or Japan, the granite-gneiss layer is more thickened, and in the mid-ocean ridges - the basalt layer.
AT mountainous countries the crust is almost twice as thick (up to 70-80 km) than in the plains, due to the thickening of the sedimentary and granite layers. The latter, together with the basalt layer, forms, as it were, the roots of young mountain-fold systems - such as the Caucasus, the Pamirs and the Himalayas. In the Black Sea and in the southern part of the Caspian, the crust resembles an oceanic one, but is covered with a layer of sediments up to 15-20 km thick. Relief range between maximum depths oceans (11022 m) and the top of the Himalayas (8848 M) is approximately 20 km, i.e., it is half the thickness of the crust of the continents. This indicates a greater mobility of the margins of the oceans, intermountain seas and mountains. Such moving areas are called geosynclines. Plains, on the contrary, are associated with stable, slow-moving crustal structures - rigid slabs, which are called platforms. The thickness of the crust here is 30-40 km. Volcanic island arcs are extended along deep fault zones separating the ocean with basalt crust 5-10 km thick from the continental marginal seas with an intermediate type of crust, and represent the embryos of the continental crust.
The structure of the Earth and the earth's crust. Shells of the globe: A - the earth's crust; B and C - upper mantle; D - lower mantle; E - outer part of the nucleus; F - transition zone between the inner and outer core; G - inner core; d - density; p - pressure. The numbers indicate the depths of the boundaries in km.
What explains such a division of the crust into heterogeneous layers? A comparison of the chemical composition of the Earth as a whole, the mantle and crust, as well as all three main layers of the crust, shows that the content of lighter elements increases from the core to the crust: oxygen, silicon, aluminum, potassium, and sodium. The same regularity is observed in the sedimentary shell compared to the granite layer, and in the granite layer - compared to the basalt layer. Such a distribution of substances in the Earth and the crust is obviously related to the law gravity and with its manifestation on Earth - gravity.
There are many methods for studying the earth's crust. Research begins with a description of the relief, the study of the composition and structure of rocks on the surface of the Earth. Geologists judge the deep structure of the earth's crust by the composition, structure, and conditions of occurrence of rocks observed on the ground, or by soil samples from the ocean floor, etc. Valuable information is provided by boreholes, the depth of which has already exceeded 8 km. Geophysicists determine pl

Earth's crust called the outer hard shell Earth, bounded from below by the surface of Mohorovichich, or Moho, which is distinguished by a sharp increase in speed elastic waves during their passage from the surface of the Earth to its depths.

Below the Mohorovichic surface is the following hard shell - upper mantle . The uppermost part of the mantle, together with the earth's crust, is a rigid and brittle solid shell of the Earth. - lithosphere (a rock). It is underlain by more plastic and pliable to deformation, less viscous layers of the mantle - asthenosphere (weak). In it, the temperature is close to the melting point of the mantle substance, but due to the high pressure, the substance does not melt, but is in an amorphous state and can flow, remaining solid, like a glacier in the mountains. It is the asthenosphere that is the plastic layer along which individual blocks of the lithosphere float.

The thickness of the earth's crust on the continents is about 30-40 km, under the mountain ranges it increases to 80 km (continental type of the earth's crust). Under the deep part of the oceans, the thickness of the earth's crust is 5-15 km (oceanic type of the earth's crust). On average, the sole of the earth's crust (the surface of Mohorovichich) lies under the continents at a depth of 35 km, and under the oceans at a depth of 7 km, i.e., the oceanic earth's crust is about five times thinner than the continental one.

In addition to differences in thickness, there are differences in the structure of the earth's crust of continental and oceanic types.

continental crust consists of three layers: upper - sedimentary, extending on average to a depth of 5 km; medium granite (the name is due to the fact that the speed of seismic waves in it is the same as in granite) with an average thickness of 10-15 km; the lower one is basalt, about 15 km thick.

oceanic crust also consists of three layers: the upper layer is sedimentary to a depth of 1 km; medium-sized with a little-known composition, occurring at depths from 1 to 2.5 km; the lower one is basaltic with a thickness of about 5 km.

A visual representation of the nature of the distribution of land heights and depths ocean floor gives hypsographic curve (Fig. 1). It reflects the ratio of the areas of the solid shell of the Earth with different heights on land and with different depths in the sea. Using the curve, the average values ​​of the land height (840 m) and the average sea depth (-3880 m) are calculated. If you do not take into account the mountainous regions and deep sea trenches, occupying a relatively small area, then two predominant levels are clearly distinguished on the hypsographic curve: the level of the continental platform with a height of about 1000 m and the level of the oceanic bed with elevations from -2000 to -6000 m. The transition zone connecting them is a relatively sharp ledge and is called the continental slope . Thus, the natural boundary separating the ocean and the continents is an invisible coastline, and the outer boundary of the slope.

Rice. Fig. 1. Hypsographic curve (A) and generalized profile of the ocean floor (B). (I - underwater margin of the continents, II - transition zone, III - ocean bed, IV - mid-ocean ridges).

Within the oceanic part of the hypsographic (batygraphic) The curve distinguishes four main stages of the bottom topography: the continental shallow or shelf (0-200 m), the continental slope (200-2000 m), the ocean floor (2000-6000 m) and deep-water depressions (6000-11000 m).

Shelf (mainland)- underwater continuation of the mainland. This is an area of ​​the continental crust, which is generally characterized flat relief with traces of flooded river valleys, Quaternary glaciation, ancient coastlines.

The outer boundary of the shelf is edge - a sharp inflection of the bottom, beyond which the continental slope begins. The average depth of the shelf crest is 130 m, however, in specific cases, its depth may vary.

The width of the shelf varies in a very wide range: from zero (in a number of areas of the African coast) to thousands of kilometers (off the northern coast of Asia). In general, the shelf occupies about 7% of the area of ​​the World Ocean.

continental slope- the area from the edge of the shelf to the continental foot, i.e., before the transition of the slope to a flatter ocean bed. The average angle of inclination of the continental slope is about 6°, but often the steepness of the slope can increase up to 20-30 0 , and in some cases almost sheer ledges are possible. The width of the continental slope due to the steep drop is usually small - about 100 km.

The relief of the continental slope is characterized by great complexity and diversity, but its most characteristic form is submarine canyons . This is narrow gutters, which have a large angle of incidence along longitudinal profile and steep slopes. The tops of underwater canyons often cut into the edge of the shelf, and their mouths reach the continental foot, where in such cases alluvial fans of loose sedimentary material are observed.

mainland foot- the third element of the topography of the ocean floor, located within the continental crust. The continental foot is a vast sloping plain formed by sedimentary rocks up to 3.5 km thick. The width of this slightly hilly plain can reach hundreds of kilometers, and the area is close to that of the shelf and continental slope.

Ocean bed- the deepest part of the ocean floor, occupying more than 2/3 of the entire area of ​​\u200b\u200bthe World Ocean. The prevailing depths of the ocean floor range from 4 to 6 km, and the bottom relief is the most calm. The main elements of the relief of the ocean floor are oceanic basins, mid-ocean ridges and oceanic uplifts.

oceanic basins- extensive depressions of the bottom of the World Ocean with depths of about 5 km. The leveled surface of the bottom of the basins is called abyssal (bottomless) plains, and it is due to the accumulation of sedimentary material brought from land. Abyssal plains in the World Ocean occupy about 8% of the ocean floor.

mid-ocean ridges- tectonically active zones in the ocean, in which the formation of the earth's crust occurs. They are composed of basalt rocks formed as a result of the entry of matter from the upper mantle from the bowels of the Earth. This led to the peculiarity of the earth's crust of the mid-ocean ridges and its allocation to the rift type.

ocean rises- large positive forms relief of the ocean floor, not associated with mid-ocean ridges. They are located within the oceanic type of the earth's crust and are distinguished by large horizontal and vertical dimensions.

Separate seamounts of volcanic origin have been discovered in the deep part of the ocean. seamounts with flat tops, located at a depth of more than 200 m, are called guyots.

Deep sea trenches (troughs)- zones of the greatest depths of the World Ocean, exceeding 6000 m.

The deepest depression is the Mariana Trench, discovered in 1954 by the Vityaz research vessel. Its depth is 11022 m.

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The internal structure of the Earth

There are three main shells in the structure of the Earth: the earth's crust, mantle and core.

Diagram of the internal structure of the Earth

The surface of the Earth is covered with a stone shell - Earth's crust. Its thickness under the oceans is only 3–15 km, and on the continents it reaches 75 km. It turns out that in relation to the entire planet, the earth's crust is thinner than the peel of a peach. The upper layer of the crust is formed by sedimentary rocks, under it there are "granite" and "basalt" layers, which are called so conventionally.

Located under the earth's crust mantle. The mantle is the inner shell that covers the Earth's core. With Greek"mantle" is translated as "veil". Scientists suggest that the upper part of the mantle consists of dense rocks, that is, it is solid. However, in it, at a depth of 50-250 km from the Earth's surface, a partially molten layer is located, which is called magma.

Earth's crust

It is relatively soft and plastic, able to flow slowly and thus move. The speed of movement of magma is small - a few centimeters per year. However, it plays a decisive role in the movements of the earth's crust. The temperature of the upper layer of magma is about +2000 °C, and in the lower layers the heat can reach +5000 °C. The earth's crust, together with the upper layer of the hot mantle, is called the lithosphere.

Under the mantle, at a depth of about 2900 km from the surface, hidden core of the earth. It has the shape of a ball with a radius of almost 3500 km. In the nucleus, the outer and inner part, which differ in composition, temperature and density. The inner core is the hottest and densest part of our planet and is believed to be made up mostly of iron and nickel. In the inner core, the pressure is so high that, despite the enormous temperature (+6000 ... +10,000 °С), it is solid. The outer core is in a liquid state, its temperature is 4300 °C.

The structure of the earth's crust

Most of the crust is covered on the outside by the hydrosphere, while the smaller part borders on the atmosphere. In accordance with this, the earth's crust is distinguished oceanic and mainland types and they have different structures.

The continental (continental) crust occupies a smaller area (about 40% of the entire surface of the Earth), but has more complex structure. Under high mountains its thickness reaches 60-70 km. Composed continental crust from 3 layers - basalt, granite and sedimentary. The oceanic crust is thinner - only 5-7 km. It consists of two layers: lower - basalt and upper - sedimentary.

The Earth's crust is best studied to a depth of 20 km. Based on the results of the analysis of numerous samples of rocks and minerals that come to the surface of the earth during mountain-building processes, as well as those taken from mine workings and deep boreholes, we calculated average composition chemical elements earth's crust.

The boundary layer separating the mantle and the Earth's crust is called the Mohorovicic boundary, or the Moho surface, in honor of the Croatian scientist A. Mohorovicic. In 1909, he was the first to point out the characteristic order of seismic waves when crossing the boundary, which can be traced throughout the globe at a depth of 5 to 70 km.

How is the mantle studied?

The mantle is deep under the Earth, and even the deepest boreholes do not reach it. But sometimes, when gases break through the earth's crust, so-called kimberlite pipes. Through them, mantle rocks and minerals come to the surface. The most famous of these is the diamond, the deepest fragment of our planet that we can study. Thanks to such tubes, we can judge the structure of the mantle.

The kimberlite pipe in Yakutia, where diamonds are mined, has long been developed. Huge quarries have been built in place of such pipes. Their very name comes from the city of Kimberley in South Africa.

Until recently, ideas about the thickness of the earth's crust under the ocean floor were based on rather rare profiles. seismic research deep structure.

Some data on the possible thickness of the crust under the bottom of the oceans were obtained by V. F. Bonchkovsky on the basis of a study surface waves earthquakes.

R. M. Demenitskaya, having developed new method determining the thickness of the earth's crust, based on known connections her with gravity anomalies (in the Bouguer reduction) and with the relief of the earth's surface, built schematic maps distribution of the thickness of the earth's crust of the continents and oceans. Judging by these maps, the thickness of the earth's crust in the oceans is as follows.

In the Atlantic Ocean, within the continental shelf, the thickness of the crust varies from 35 to 25 km. It does not differ from that in the adjacent parts of the mainland, since the continental structures directly continue on the shelf. In the area of ​​the continental slope, as the depth increases, the thickness of the crust decreases from 25-15 km in the upper part of the slope to 15-10 and even less than 10 km in its lower part. The bottom of the basins of the Atlantic Ocean is characterized by a crust of small thickness - from 2 to 7 km, but where it composes underwater ridges or plateaus, its thickness increases to 15-25 km (Bermuda submarine plateau, Telegraph plateau).

We see a similar picture in the Arctic basin of the Arctic Ocean with a crust thickness of 15 to 25 km; only in its central parts it is less than 10-5 km. In the Scandic basin, the crust thickness (from 15 to 25 km) differs from that typical for ocean basins. On the continental slope, the thickness of the crust varies in the same way as in the Atlantic Ocean. We see the same analogy in the crust of the continental shelf of the Arctic Ocean with a crust thickness of 25 to 35 km; it thickens in the Laptev Sea, as well as in the adjacent parts of the Kara and East Siberian Seas and further on the Lomonosov Ridge.

The internal structure of the Earth

It is possible that the increase in the thickness of the crust here is associated with the spread of young Mesozoic folded structures.

In the Indian Ocean, there is a relatively thick crust (more than 25 km) in the Mozambique Channel and partly east of Madagascar up to and including the Seychelles Range. median ridge indian ocean the thickness of the crust does not differ from the Mid-Atlantic Ridge. The southern part of the Arabian Sea and the Bay of Bengal are distinguished by relatively thin crust, despite their comparative youth.

Some features characterize the thickness of the earth's crust in the Pacific Ocean. In the Bering and Okhotsk seas, the thickness of the crust is more than 25 km. It has a smaller thickness only in the southern deep part of the Bering Sea. In the Sea of ​​Japan, the thickness sharply decreases (up to 10-15 km), in the seas of Indonesia it increases again (more than 25 km), remaining the same further south, up to the Arafura Sea inclusive. In the western part of the Pacific Ocean, directly adjacent to the belt of geosynclinal seas, thicknesses from 7 to 10 km prevail, but in individual depressions of the ocean floor they decrease to 5 km, while in areas of seamounts and islands they increase to 10–15 and often to 20– 25 km.

In the central part of the Pacific Ocean - the region of the deepest basins, as in other oceans, the thickness of the crust is the smallest - in the range from 2 to 7 km. In some depressions of the ocean floor, the crust is also thinner. In the most elevated parts of the ocean floor - on the median underwater ridges and the spaces adjacent to them, the thickness of the crust increases to 7-10 km. The same thicknesses of the crust are characteristic of the eastern and southeastern parts ocean along the strike of the South Pacific and East Pacific ridges, as well as the underwater Albatross plateau.

Maps of the thickness of the earth's crust, compiled by R. M. Demenitskaya, give an idea of ​​the total thickness of the crust. To elucidate the structure of the crust, it is necessary to turn to data obtained through seismic surveys.

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