Earth shape (geoid) is close to a flattened ellipsoid. The average diameter of the planet is approximately 12,742 km.
The earth has a layered inner structure. It consists of solid silicate shells (bark, extremely viscous mantle), and metal kernel. The outer part of the kernel is liquid (significantly less viscous than mantle), and internal - solid.
The earth Cora is the upper part of the solid land. The mantle is separated by the boundary with a sharp increase in the rates of seismic waves - the boundary of Mochorovichich. There are two types of bark - continental and oceanic. The thickness of the cortex ranges from 6 km under the ocean, up to 30--50 km on continents. In the structure of the continental bark, three geological layers are distinguished: sedimentary case, granite and basalt. The oceanic bark is prepared mainly by the rocks of the main composition, plus a sedimentary case. The earth's crust is divided into various largest lithospheric plates moving relative to each other.
The mantle is a silicate Earth shell, composed mainly by peridotitis - rocks consisting of magnesium silicates, iron, calcium, etc. Partial melting of mantle rocks generates basalt and similar melts that form a terrestrial bark when approaching the surface.
The mantle is 67% of the entire mass of the Earth and about 83% of the total volume of land. It extends from the depths of 5--70 kilometers below the border with the earth's crust, to the border with the kernel 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 the mantle substance is below this border can not penetrate it, and vice versa. Above the boundaries of 660 kilometers are the upper mantle, and below, respectively, the bottom. These two parts of the mantle have a different composition and physical properties. Although the information on the composition of the lower mantle is limited, and the number of direct data is very small, it is possible to confidently assert that its composition has changed significantly less than the upper mantle that has breeding the globe.
The kernel is the central, the most profound part of the Earth, the geosphere under the mantle and, presumably consisting of iron-nickel alloy with an admixture of the e-siderophilic elements. Salmon depth - 2900 km. The average radius of the sphere is 3.5 thousand km. It is divided into a solid inner core with a radius of about 1300 km and the liquid external core with a radius of about 2,200 km, between which the transition zone sometimes is distinguished. The temperature in the center of the land core reaches 5000 s, a density of about 12.5 t / mі, pressure up to 361 GPa. The core mass is 1.932ch1024 kg.
Ground Coras - the outer solid sheath of the Earth (geosphere). Separates the bark and mantle border Moss. From the outside, most of the cortex is covered with hydrosphere, and the smaller is under the influence of the atmosphere. The land has a bark of two types: continental and oceanic.
The mass of the earth's crust is estimated at 2.8CH1019 tons (21% of them are the ocean bark and 79% continental). The bark is only 0.473% of the total mass of the Earth.
The ocean bark consists mainly of basalts. The ocean bark is relatively young, and the most ancient sections are dated late. The thickness of the oceanic cortex is practically not changed over time, since it is mainly determined by the amount of melt, highlighted from the material of the mantle in the zones of the mid-ocean ridges. To some extent, the effect of the sedimentary layer at the bottom of the oceans has a thickness. In different geographic areas, the thickness of the oceanic bark varies within 5-7 kilometers.
The standard Ocean Cora has a power of 7 km, and a strictly natural structure. It is folded from top to bottom with the following complexes:
sedimentary rocks represented by deep-sea oceanic precipitation.
basalt covers flying under water.
the dike complex consists of basalt ducks invested in each other.
layer of basic stratified intrusions
mantle, represented by Dunits and Peridotitis.
In the sole of the oceanic bark usually run dunites and peridotites
The continental bark has a three-layer structure. The upper layer is represented by intermittent cover of sedimentary rocks, which is developed widely, but rarely has a greater power. Most of the cortex is composed under the upper bark - a layer consisting mainly of granites and gneisses with low density and ancient history. Below is the lower bark, consisting of metamorphic breeds - granulites and the like.
The composition of the upper continental bark
The earth's boron makes up a relatively small number of elements. About half of the mass of the earth's crust falls on oxygen, more than 25% - on silicon. Total 18 elements: O, Si, Al, Fe, Ca, Na, K, Mg, H, Ti, C, Cl, P, S, N, Mn, F, Ba are 99.8% of the mass of the earth's crust. The earth's crust consists of a variety of breeds of a variety of composition in different areas, completely different types of breeds can be distributed.
Earth, with an average distance 149 597 890 km from the Sun, is the third and one of the most unique planets in the solar system. It formed about 4.5-4.6 billion years ago and is the only planet that is known to support life. This is associated with a number of factors, for example, atmospheric composition and physical properties, such as the presence of water, occupying about 70.8% of the surface of the planet, allow life to flourish.
The land is also unique in that it is the largest of the planets of the earth group (Mercury, Venus, Earth and Mars), consisting of a thin layer of rocks, in comparison with gas giants (Jupiter, Saturn, Neptune and Uranus). Taking into account the mass, density and diameter, the land is the fifth largest planet in the entire solar system.
Earth size: mass, volume, circle and diameter
Planets of the earth group (Mercury, Venus, Earth and Mars)
As the largest of the planets of the earth group, the Earth has an estimated mass of 5.9722 ± 0.0006 × 10 24 kg. Its volume is also the largest of these planets and is 1.08321 × 10¹² km³.
In addition, our planet is the most dense of the planets of the earth group, as it consists of bark, mantle and core. The Earth Cora is the most subtle of these layers, while the mantle is 84% \u200b\u200bof the volume of land and extends 2900 km below the surface. The core is the component that makes the ground is the tight. This is the only planet of the earth's group with a liquid outer core surrounding a solid, dense inner core.
The average density of the Earth is 5.514 × 10 g / cm³. Mars, the smallest of the land-like planets of the solar system, has only about 70% of the density of the Earth.
Earth is also classified as the largest of the planets of the earth group around the circle and diameter. Equatorial circle of Earth is 40,075.16 km. It is slightly smaller between the northern and southern poles - 40,008 km. The diameter of the land at the pole is 12,713.5 km, and at the equator - 12,756.1 km. For comparison, the largest planet in the solar system, Jupiter, has a diameter of 142,984 km.
Form of land
Projection Hammer-Aitova
The circle and the diameter of the Earth differ, because its form represents a flattened spheroid or ellipsoid instead of the true sphere. The planet's poles are slightly flattened, which leads to convexity at the equator and, therefore, to a greater circle and diameter.
Equatorial bulge of the Earth is 42.72 km and is caused by the rotation and gravity of the planet. The gravity itself causes the planets and other celestial bodies to shrink and form the sphere. This is due to the fact that it pulls the whole mass of the object as close as possible to the center of gravity (the earth's core in this case).
Since the planet rotates, the sphere is distorted by the centrifugal force. This is the force that causes objects to move from the center of gravity. When the Earth rotates, the highest centrifugal force at the equator, so it causes a small outer convexity, giving this region a large circle and diameter.
Local topography also plays a role in the form of Earth, but globally is minor. The greatest difference in local topography worldwide is Mount Everest, the highest point above sea level - 8,848 m and Mariana Wpadina, the lowest point below sea level - 10,994 ± 40 m. This difference is only about 19 km, which is very slightly in a planetary scale. If we consider the equatorial convexity, the highest point of the world and the place most distant from the center of the Earth is the top of the Chimbora's volcano in Ecuador, which is the highest peak near the equator. Its height is 6,677 m.
Geodesy
To properly study the size and shape of the Earth, geodesy is used, the science industry responsible for measuring the size and shape of the Earth through surveys and mathematical calculations.
Throughout history, geodesy was an important branch of science, as early scientists and philosophers tried to determine the form of the Earth. Aristotle is the first person who is attributed to an attempt to calculate the size of the Earth and, therefore, early geodesist. Then the Greek philosopher Eratosthenes followed, an estimated circle of Earth at 40 233 km, which is only a little more adopted in our day measurements.
To explore the Earth and use geodesy, the researchers often refer to the ellipsoid, geoid and reference ellipsoid. The ellipsoid is a theoretical mathematical model that shows a smooth, simplified view of the surface of the Earth. It is used to measure distances on the surface without taking into account factors such as changes in the height and form of relief. Taking into account the reality of the earth's surface, the geodesists use the geoid - the model of the planet, which is built using the global average sea level and, therefore, takes into account the height differences.
The basis of geodesy today is the data that act as guidelines for global geodesic works. Today, technologies such as satellites and global positioning systems (GPS) allow geodesists and other scientists to make extremely accurate measurements of the earth's surface. In fact, they are so accurate that they allow to obtain data on the surface of the earth with an accuracy of centimeters, providing the most accurate measurements of the size and shape of the Earth.
If you have found a mistake, please select the text fragment and click Ctrl + Enter..
Earth Kore They call the external solid shell of the Earth, limited to the bottom of the Mochorovichi surface, or MOCHO, which is distinguished by a sharp increase in the speed of elastic waves when they pass from the surface of the Earth to its depth.
Below the surface of Mochorovichich is the following solid sheath - Upper mantle . The upper part of the mantle together with the earth's crust is a rigid and fragile solid shell of the Earth - Lithospher (a rock). It is pretty more plastic and militant to deformation, less viscous layers of mantle - asthenosphere (weak). In it, the temperature is close to the melting point of the mantle substance, but due to a large pressure, the substance is not melted, but is in amorphous state and can flow, remaining solid, like a glacier in the mountains. It is an asthenosphere that is the plastic layer for which individual lithosphere blocks float.
The thickness of the earth's crust on the mainland is about 30-40 km, under the mountain ranges it increases to 80 km (mainland type of earthly crust). Under the deep-sea part of the oceans, the thickness of the earth's crust is 5-15 km (the oceanic type of earthly crust). On average, the sole of the earth's crust (Mochorovichi's surface) lies under the continents at a depth of 35 km, and under the oceans - at a depth of 7 km, i.e., the ocean earth bark is about five times thinner.
In addition to differences in thickness, there are differences in the structure of the earth's crust of the mainland and oceanic types.
Mainland earth bark 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; Nizhny - basalt, about 15 km thick.
Ocean globe It also consists of three layers: upper - sedimentary to depth 1 km; Middle with a little-known composition that lies at depths from 1 to 2.5 km; Nizhny - basalt with a thickness of about 5 km.
A visual idea of \u200b\u200bthe nature of the distribution of the heights of sushi and the depths of the ocean bottom gives gypsum curve (Fig. 1). It reflects the ratio of the area of \u200b\u200bthe Earth's solid shell with different heights on land and with different depths in the sea. Using the curve, the average sushi height values \u200b\u200b(840 m) and the middle depths of the sea (-3880 m) are calculated. If you do not take into account the mountainous areas and deep-water depressions, occupying a relatively small area, then two prevailing levels are distinguished on the plaster curve: the mainboard platform level is a height of about 1000 m and the level of oceanic beds with marks from -2000 to -6000 m. Connecting them The zone is a relatively sharp ledge and is called a mainland slope. Thus, the natural border separating the ocean and continents is not a visible coastline, but the outer boundary of the slope.
Fig. 1. Plaster curve (a) and a generalized profile of the ocean bottom (b). (I - Underwater outskirts of the mainland, II - transition zone, III - ocean bed, IV-middle-an oceanic ridges).
Within the oceanic part of the plaster (Batigraphic) The curve distinguishes four main levels of the bottom of the bottom: Material Oven or Shelf (0-200 m), mainland slope (200-2000 m), ocean bed (2000-6000 m) and deep-water depressions (6000-11000 m).
Shelf (mainland shallow) - Underwater continuation of the mainland. This is the region of the mainland crust for which the plain relief is generally characterized with traces of flooded river valleys, quaternary glaciation, ancient coastlines.
The outer boundary of the shelf is brocci - sharp running of the bottom, outside of which the mainland slope begins. The average depth of the shelf of the shelf is 130 m, however, in specific cases, its depth may vary.
The width of the shelf varies in a very large range: from zero (in a number of areas of the African coast) to a thousand kilometers (near the northern coast of Asia). In general, the shelf takes about 7% of the Ocean Square.
Mainland slope - region from the shelf's browch to the mainland foot, i.e., before the slope is moving to a more flat face of the ocean. The average angle of inclination of the mainland slope is about 6О, but often the slope can increase to 20-30 0, and in some cases there are almost one-time ledge. The width of the mainland slope due to the steep fall is usually small - about 100 km.
The relief of the mainland slope is characterized by great complexity and variety, but the most characteristic form is underwater canyons . It is a narrow gutter having a large angle of falling along the longitudinal profile and steep slopes. The vertices of the underwater canyons are often cut into the shelf's heating, and their mouths reaches the mainland foot, where in such cases there are cones of the carrying of loose sedimentary material.
Mainland fit - The third element of the bottom of the bottom of the ocean, located within the mainland crust. The mainland foot is an extensive inclined plain formed by sedimentary rocks with a thickness of up to 3.5 km. The width of this slightly chemmed plain can reach hundreds of kilometers, and the area is close to the squares of the shelf and the mainland slope.
Ocean bed - The most profound part of the bottom of the ocean, which occupies more than 2/3 of the entire World Ocean area. The prevailing depths of the ocean bed oscillate from 4 to 6 km, and the bottom relief is most calm. The main elements of the relief of the ocean bed are ocean basins, mid-oceanic ridges and oceanic raising.
Oceanic basins - Extensive decreases of the bottom of the World Ocean with depths of about 5 km. The aligned surface of the bottom Kotlovin is called absective (bottomless) plains, and it is due to the accumulation of sedimentary material, brought from sushi. Assual plains in the world ocean occupy about 8% of the ocean bed.
Mid-oceanic ridges - Tectonically active zones in the ocean, in which the neoplasm of the earth's crust occurs. They are stacked by basalt rocks formed as a result of the advent of the substance of the upper mantle from the depths of the Earth. This led to the peculiarity of the earth's crust of the mid-oceanic ridges and the allocation of it in the riftogenal type.
Ocean raising - major positive form of the relief of the Ocean Lodge, not related to the average and ocean ridges. They are located within the oceanic type of terrestrial crust and are distinguished by large horizontal and vertical dimensions.
Separate underwater mountains of volcanic origin were found in the deep sea part of the ocean. Underwater mountains with flat vertices located at a depth of more than 200 m, called gailets.
Deep-sea depressions (chute) - zones of the largest depths of the World Ocean, exceeding 6000 m.
The very deep cavity is the Mariany chute opened in 1954 by the Research Ship "Vityaz". Its depth is 11022 m.
⇐ Previous45678910111213Next ⇒
Publication date: 2014-10-14; Read: 1461 | Violation of copyright page
Studopedia.org - Studdia. Org - 2014-2018. (0.004 s) ...
The inner structure of the Earth
In the structure of the Earth, three main shells: earth bark, mantle and core.
The diagram of the internal structure of the Earth
The surface of the earth covers a stone shell - earth's crust. Its thickness under the oceans is only 3-15 km, and at the continent comes up to 75 km. It turns out that in relation to the entire planet, the earth's crust is thinner than peach skin. The top layer of the crust is formed by sedimentary rocks, under it are "granite" and "basalt" layers, which are so conseen.
Under the earth's crust is located mantle. Mantle is an inner shell covering the core of the Earth. From the Greek language "Mantle" translates as "bedspread". Scientists suggest that the upper part of the mantle consists of dense rocks, that is, it is solid. However, in her depth 50-250 km from the surface of the Earth, partially molten layer is located, which is called magma.
Earth's crust
It is relatively mild and plastic, capable of slowly flowing and thus move. Magma's speed is small - a few centimeters per year. However, this 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 top layer of the hot mantle, is called a lithosphere.
Under the mantle, at a depth of about 2900 km from the surface, hidden core of land. It has a ball shape with a radius of almost 3500 km. The nucleus is distinguished by an external and inner part, which differ in composition, temperature and density. The inner core is the hottest and dense part of our planet, consisting, as scientists believe, mainly of iron and nickel. In the inner core, the pressure is so great that it, despite the huge temperature (+ 6000 ... + 10 000 ° C), is a solid body. The external kernel is in a liquid state, its temperature is 4300 ° C.
The structure of the earth's crust
Most of the cortex outside is covered with hydrosphere, and the smaller borders with the atmosphere. In accordance with this distinguish between the Earth Corra oceanic and mainland Types, Moreover, they have a different structure.
The mainland (continental) earth bark occupies a smaller area (about 40% of the entire surface of the Earth), but has a more complex structure. Under the high mountains, its thickness reaches 60-70 km. Consists of a continental bark of 3 layers - basalt, granitis and sediment. Ocean earth bark is thinner - only 5-7 km. It consists of two layers: lower - basalt and upper - sedimentary.
The earth's crust is most studied at a depth of 20 km. According to the results of the analysis of numerous samples of rocks and minerals overlooking the surface of the Earth in the formation processes, as well as taken from mountain generations and deep drilling wells, the average composition of the chemical elements of the earth's crust was calculated.
The border layer, separating the mantle and the bark of the Earth, is called the limit of Mocho-Rovichich, or the Mocho surface, in honor of the Croatian scientist A. Mochorovichich. He was the first in 1909 to indicate the characteristic command of seismic waves during the transition of the border, which can be traced throughout the globe at a depth of 5 to 70 km.
How to study the mantle?
The mantle is deep underground, and even the deepest drilling wells do not reach it. But sometimes the so-called kimberlite tubes are formed in the breakthrough of gases through the globe. Through them, mantle breeds and minerals come to the surface. The most famous of them is a diamond, the most profound fragment of our planet, which we can learn. Thanks to such tubes, we can judge the structure of the mantle.
Kimberlite tube in Yakutia, where diamonds are produced, has long been developed. There are huge careers on the site of such tubes. The very name of them occurred from the city of Kimberly in South Africa
Until recently, the presentation of the thickness of the earth's crust under the bottom of the oceans was relied on fairly rare profiles of seismic studies of the 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 the study of surface waves of earthquakes.
R. M. Demenitskaya, developing a new method for determining the thickness of the earth's crust, based on the well-known links with the abnormalities of gravity (in the reduction of the BUGE) and with the relief of the earth's surface, built schematic cards of the distribution of the thickness of the ground cortex of continents and oceans. Judging by these cards, the thickness of the earth's crust in the oceans is such.
In the Atlantic Ocean, within the mainland, the thickness of the bark varies from 35 to 25 km. It does not differ from that in the adjacent parts of the mainland, since the mainland structures directly continue on the shelf. In the field of the mainland slope, as the depth is increasing depth, the thickness of the cortex decreases from 25-15 km at the top of the slope to 15-10 and even less than 10 km - in its lower part. The bottom of the Atlantic Ocean Kotlovin is characterized by a bark of a small thickness - from 2 to 7 km, but where it is losing underwater ridges or a plateau, its power increases to 15-25 km (Bermuda underwater plateau, telegraph plateau).
We see a similar picture in the Arctic Basin of the Northern Ocean Ocean with a thickness of a bark from 15 to 25 km; Only in its central parts it is less than 10-5 km. In the pool Scandik the thickness of the bark (from 15 to 25 km) differs from typical of ocean pools. On the mainland slope, the power of the cortex changes in the same way as in the Atlantic Ocean. We see the same analogy in the lard crust of the Northern Arctic Ocean with a thickness of a bark from 25 to 35 km; It thickens in the sea of \u200b\u200bLaptev, as well as in the adjacent parts of the Karis and East Siberian seas and further on the Lomonosov Ridge.
The inner structure of the Earth
It is possible that the increase in the thickness of the bark here is associated with the spread of young - mesozoic folded structures.
In the Indian Ocean, a relatively powerful bark (more than 25 km) in the Mozambician Strait and partly east of Madagascar to the Seychelian ridge inclusive. The middle ridge of the Indian Ocean in the thickness of the bark does not differ from the middle Atlantic ridge. A relatively small thickness of the crust is the southern part of the Arabian Sea and the Bengal Bay, despite their comparative youth.
Some features are characterized by the thickness of the earth's crust in the Pacific Ocean. In the Bering and Okhotsk seas, the thickness of the bark is more than 25 km. It has a smaller power only in the southern deep-water part of the Bering Sea. In the Japanese sea, the power is sharply reduced (up to 10-15 km), in the seas of Indonesia again increases (more than 25 km), remaining such and south - to the Arafur Sea inclusive. In the western part of the Pacific, directly adjacent to the geosynclinal seas, thickness predominate from 7 to 10 km, but in certain decreases of the oceanium, they decrease to 5 km, in the areas of the underwater mountains and the islands increase to 10-15 and often up to 20- 25 km.
In the central part of the Pacific Ocean - the area of \u200b\u200bthe most deep-water basins, as in other oceans, the low power of the cortex - ranging from 2 to 7 km. In some decrees of the oceanic bottom, the bark has a smaller thickness. In the most sublime parts of the oceanium - on the median underwater ridges and the spaces adjacent to them, the power of the cortex increases to 7-10 km. The same crust thicknesses are characteristic of the eastern and southeastern parts of the ocean on the strike of the South Pacific and East-Pacific, as well as the Albatross underwater plateau.
Maps of the thickness of the earth's crust, compiled by R. M. Demenitskoy, give an idea of \u200b\u200bthe total capacity of the crust. To clarify the structure of the cortex, you need to refer to the data obtained by seismic studies.
If you have found a mistake, please select the text fragment and click Ctrl + Enter..
In contact with
The globe has a few shells: - air sheath, - water shell, - a solid shell.
The third for the remoteness of the Sun. Planet Earth has a radius of 6370 km, an average density of 5.5 g / cm2. In the inner structure of the earth, it is customary to distinguish the following layers:
earth's crust - upper layer of land in which living organisms can exist. The thickness of the earth's crust can be from 5 to 75 km.
mantle - solid layer, which is below the earth's crust. Its temperature is high enough, but the substance is in a solid state. Mantle thickness of about 3,000 km.
core - Central part of the globe. Its radius is approximately 3,500 km. The temperature inside the nucleus is very high. It is believed that the core consists mainly of molten metal,
Presumably - iron.
Earth's crust
Two main types of terrestrial crust are distinguished - continental and oceanic, plus intermediate, subcontinental.
The earth Cort is thinned under the oceans (about 5 km) and thicker - under the mainland (up to 75 km.). It is heterogeneous, there are three layers: basalt (lies below everything), granite and sedimentary (upper). The continental bark consists of three layers, whereas there is no oceanic granite layer. The earth's crust was generated gradually: first the basalt layer was formed, then the granite, the sedimentary layer continues to be formed and at present.
- The substance from which the earth's crust is. Mountain breeds are divided into the following groups:
1. Magmatic rocks. They are formed during the solidification of the magma in the thickness of the earth's crust or on the surface.
2. Sedimentary rocks. They are formed on the surface, form from products of destruction or changes other breeds, biological organisms.
3. Metamorphic rocks. They are formed in the thickness of the earth's crust from other rocks under the action of certain factors: temperatures, pressure.
Until recently, the presentation of the thickness of the earth's crust under the bottom of the oceans was relied on fairly rare profiles of seismic studies of the 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 the study of surface waves of earthquakes.
R. M. Demenitskaya, developing a new method for determining the thickness of the earth's crust, based on the well-known links with the abnormalities of gravity (in the reduction of the BUGE) and with the relief of the earth's surface, built schematic cards of the distribution of the thickness of the ground cortex of continents and oceans. Judging by these cards, the thickness of the earth's crust in the oceans is such.
In the Atlantic Ocean, within the mainland, the thickness of the bark varies from 35 to 25 km. It does not differ from that in the adjacent parts of the mainland, since the mainland structures directly continue on the shelf. In the field of the mainland slope, as the depth is increasing depth, the thickness of the cortex decreases from 25-15 km at the top of the slope to 15-10 and even less than 10 km - in its lower part. The bottom of the Atlantic Ocean Kotlovin is characterized by a bark of a small thickness - from 2 to 7 km, but where it is losing underwater ridges or a plateau, its power increases to 15-25 km (Bermuda underwater plateau, telegraph plateau).
We see a similar picture in the Arctic Basin of the Northern Ocean Ocean with a thickness of a bark from 15 to 25 km; Only in its central parts it is less than 10-5 km. In the pool Scandik the thickness of the bark (from 15 to 25 km) differs from typical of ocean pools. On the mainland slope, the power of the cortex changes in the same way as in the Atlantic Ocean. We see the same analogy in the lard crust of the Northern Arctic Ocean with a thickness of a bark from 25 to 35 km; It thickens in the sea of \u200b\u200bLaptev, as well as in the adjacent parts of the Karis and East Siberian seas and further on the Lomonosov Ridge. It is possible that the increase in the thickness of the bark here is associated with the spread of young - mesozoic folded structures.
In the Indian Ocean, a relatively powerful bark (more than 25 km) in the Mozambician Strait and partly east of Madagascar to the Seychelian ridge inclusive. The middle ridge of the Indian Ocean in the thickness of the bark does not differ from the middle Atlantic ridge. A relatively small thickness of the crust is the southern part of the Arabian Sea and the Bengal Bay, despite their comparative youth.
Some features are characterized by the thickness of the earth's crust in the Pacific Ocean. In the Bering and Okhotsk seas, the thickness of the bark is more than 25 km. It has a smaller power only in the southern deep-water part of the Bering Sea. In the Japanese sea, the power is sharply reduced (up to 10-15 km), in the seas of Indonesia again increases (more than 25 km), remaining such and south - to the Arafur Sea inclusive. In the western part of the Pacific, directly adjacent to the geosynclinal seas, thickness predominate from 7 to 10 km, but in certain decreases of the oceanium, they decrease to 5 km, in the areas of the underwater mountains and the islands increase to 10-15 and often up to 20- 25 km.
In the central part of the Pacific Ocean - the area of \u200b\u200bthe most deep-water basins, as in other oceans, the low power of the cortex - ranging from 2 to 7 km. In some decrees of the oceanic bottom, the bark has a smaller thickness. In the most sublime parts of the oceanium - on the median underwater ridges and the spaces adjacent to them, the power of the cortex increases to 7-10 km. The same crust thicknesses are characteristic of the eastern and southeastern parts of the ocean on the strike of the South Pacific and East-Pacific, as well as the Albatross underwater plateau.
Maps of the thickness of the earth's crust, compiled by R. M. Demenitskoy, give an idea of \u200b\u200bthe total capacity of the crust. To clarify the structure of the cortex, you need to refer to the data obtained by seismic studies.