external topography of the Earth is closely related to its internal structure. Although the study of the internal structure of the Earth is primarily a matter of geology, it is also studied in geography for the analysis of terrestrial topography. Since the interior is not visible to humans, information about it is usually from an indirect source. Scientists have made the following sources the basis for information about the internal structure of the Earth.
The source by which information can be obtained about the internal structure of the Earth are as follows.
1) Artificial Sources -
(i) Density (ii) Pressure, (iii) Temperature
(2) Evidences from the Theories of the Origin of the Earth
(3) ) Natural Sources:
(i)Volcanic Evidences (ii) Seismological Evidences.
Artificial Sources
1. Density -The average density of the Earth is 5.5 while the density of Crust is about 3.0. On this basis, it is concluded that the average density of the earth's core (innermost) Will be greater than 5.5. Generally, this density is assumed to be 11, which is 7 to 8 times heavier than water. It is clear that there will be an excess of density in the internal parts. Various density proofs show that the core density of the Earth is the highest.
2. Pressure
In relation to the high density of the core, the load and pressure of the rocks can be referenced. Although pressure increases
The density increases, but each rock has its own limit beyond which its density cannot exceed, no matter how high the pressure. This means that the interior rocks are made of high-density heavy metals.
3.Temperature
Normally the temperature increases by 1 ° C at every 32 m depth, but with increasing depth, the rate of increase of temperature also declines. First 100 km Each km in depth. But there is an increase of 12 ° C. 300 km after that Each km in depth. At 2 ° C and every km thereafter. There is an increase of 1 ° C at a depth of. Temperature is found to be relatively high in tectonically active regions. Heat flows from the interior of the Earth outward, in the form of thermal convection waves. This is made even more clear by the theory of plate tectonics.
Natural sources
(1) Evidence of Volcanic eruption
At the time of volcanic eruption, hot and liquid lava flows from the inner part of the earth to the surface which is located there in the form of a huge magma chamber and it is easy to conclude from this That some part inside the earth must be in a fluid state. But it is also necessary to clarify that the heavy pressure of the earth will not allow the rocks of the inner part to settle down. Therefore, the internal language of the earth must be solid because due to excessive pressure, the melting point of the rocks also falls down.Therefore, it is not easy to get information about the internal structure of the Earth based on the evidence of volcanic action.
(2) Evidence of seismology -, seismic waves that rise in the earth's crust are studied by marking them by seismograph. Some information about the internal structure of the earth has also been obtained from this study because different types of seismic waves have different properties and they travel across geological parts according to their nature before studying seismic waves. It is necessary to know that the place where the earthquake starts is the focus and the place where the earthquake is first experienced is called Epicenter. The epicenter is located on a vertical plane just above the origin of the earthquake. The waves generated during an earthquake are placed in three major categories, which are the following -
(i) Primary (P) or longitudinal waves. These waves, which move at the most rapid speed, move in a straight line like sound waves. In these, particles of matter move in the direction of motion. These waves flow at very high speeds in solid parts.
(ii) Secondary (S) or Transverse or Distortional Waves
Their nature is similar to that of light waves and the motion of the particle cuts at right angles to the direction of the wave. Their most salient feature is that they usually disappear in the liquid part.
(iii) Surface Waves - These are the most influential waves affecting the upper part of the Earth, which also cover the longest path than other waves. They have the lowest speed and are also called 'Long period or' L 'Waves'. The first tremor experienced at the epicenter of an earthquake is a small or weak tremor, which is known as Primary Tremor. After this, the second and more powerful one then goes to the main vibration.
According to these research the earth as a whole has been divided into three broad zones :-
The source by which information can be obtained about the internal structure of the Earth are as follows.
1) Artificial Sources -
(i) Density (ii) Pressure, (iii) Temperature
(2) Evidences from the Theories of the Origin of the Earth
(3) ) Natural Sources:
(i)Volcanic Evidences (ii) Seismological Evidences.
Artificial Sources
1. Density -The average density of the Earth is 5.5 while the density of Crust is about 3.0. On this basis, it is concluded that the average density of the earth's core (innermost) Will be greater than 5.5. Generally, this density is assumed to be 11, which is 7 to 8 times heavier than water. It is clear that there will be an excess of density in the internal parts. Various density proofs show that the core density of the Earth is the highest.
2. Pressure
In relation to the high density of the core, the load and pressure of the rocks can be referenced. Although pressure increases
The density increases, but each rock has its own limit beyond which its density cannot exceed, no matter how high the pressure. This means that the interior rocks are made of high-density heavy metals.
3.Temperature
Normally the temperature increases by 1 ° C at every 32 m depth, but with increasing depth, the rate of increase of temperature also declines. First 100 km Each km in depth. But there is an increase of 12 ° C. 300 km after that Each km in depth. At 2 ° C and every km thereafter. There is an increase of 1 ° C at a depth of. Temperature is found to be relatively high in tectonically active regions. Heat flows from the interior of the Earth outward, in the form of thermal convection waves. This is made even more clear by the theory of plate tectonics.
Natural sources
(1) Evidence of Volcanic eruption
At the time of volcanic eruption, hot and liquid lava flows from the inner part of the earth to the surface which is located there in the form of a huge magma chamber and it is easy to conclude from this That some part inside the earth must be in a fluid state. But it is also necessary to clarify that the heavy pressure of the earth will not allow the rocks of the inner part to settle down. Therefore, the internal language of the earth must be solid because due to excessive pressure, the melting point of the rocks also falls down.Therefore, it is not easy to get information about the internal structure of the Earth based on the evidence of volcanic action.
(2) Evidence of seismology -, seismic waves that rise in the earth's crust are studied by marking them by seismograph. Some information about the internal structure of the earth has also been obtained from this study because different types of seismic waves have different properties and they travel across geological parts according to their nature before studying seismic waves. It is necessary to know that the place where the earthquake starts is the focus and the place where the earthquake is first experienced is called Epicenter. The epicenter is located on a vertical plane just above the origin of the earthquake. The waves generated during an earthquake are placed in three major categories, which are the following -
(i) Primary (P) or longitudinal waves. These waves, which move at the most rapid speed, move in a straight line like sound waves. In these, particles of matter move in the direction of motion. These waves flow at very high speeds in solid parts.
(ii) Secondary (S) or Transverse or Distortional Waves
Their nature is similar to that of light waves and the motion of the particle cuts at right angles to the direction of the wave. Their most salient feature is that they usually disappear in the liquid part.
(iii) Surface Waves - These are the most influential waves affecting the upper part of the Earth, which also cover the longest path than other waves. They have the lowest speed and are also called 'Long period or' L 'Waves'. The first tremor experienced at the epicenter of an earthquake is a small or weak tremor, which is known as Primary Tremor. After this, the second and more powerful one then goes to the main vibration.
According to these research the earth as a whole has been divided into three broad zones :-
1 Crust
2 ,Mantle
3 Core
1. Crust - Even today, there is no consensus among scholars regarding the thickness of the crust. Its following thicknesses have been stated in various scholars and conferences (a) According to M. J. Bradshaw, A. J. Abbott, and A. P. G. Glastrop, 50 km below the continents and 5 km below the oceans. (B) 30 km according to the International Union of Geodesy and Geophysics. (C) 100 km according to other sources. It is again classified into two parts based on the difference in the speed of seismic waves -
2. Mantle - Below the lower crust. A sudden increase in the speed of seismic waves reflects the presence of this different layer, because while the P waves in the lower crust have a velocity of 6.9 km per second, in the mantle it increases from 7.9 km to 8.1 km per second. It has two parts -
(1) the depth of the upper mantle is 700 km from below the Moho disambiguation and
(2) Lower mantle depth is found from 700 km to 2,900 km
Densities ranging from 4.5 to 5.5 comprise 83% of the total volume of the Earth and 68% of the mass.
Moho Discontinuity - Based on the absolute increase in the speed of seismic waves in lower crust and upper mantle.( A. [Mohorovicic) first discovered in 1909 that an asymmetry existed between the two. It is called Moho discontinuity in his name. Actually the mantle starts below it. This discontinuity is in the form of a belt about 1 km thick.
1. Crust - Even today, there is no consensus among scholars regarding the thickness of the crust. Its following thicknesses have been stated in various scholars and conferences (a) According to M. J. Bradshaw, A. J. Abbott, and A. P. G. Glastrop, 50 km below the continents and 5 km below the oceans. (B) 30 km according to the International Union of Geodesy and Geophysics. (C) 100 km according to other sources. It is again classified into two parts based on the difference in the speed of seismic waves -
1. Upper crust and
2. Lower crust.
2. Lower crust.
The density of the upper crust is 2.8 and the density of the lower crust is 3.0. Both crusts are of similar structure and due to pressure there is a difference in their density. In upper crust, where the speed of P waves is 6.1 km per second, in the lower crust it increases to 6.9 km per second.
2. Mantle - Below the lower crust. A sudden increase in the speed of seismic waves reflects the presence of this different layer, because while the P waves in the lower crust have a velocity of 6.9 km per second, in the mantle it increases from 7.9 km to 8.1 km per second. It has two parts -
(1) the depth of the upper mantle is 700 km from below the Moho disambiguation and
(2) Lower mantle depth is found from 700 km to 2,900 km
Densities ranging from 4.5 to 5.5 comprise 83% of the total volume of the Earth and 68% of the mass.
Moho Discontinuity - Based on the absolute increase in the speed of seismic waves in lower crust and upper mantle.( A. [Mohorovicic) first discovered in 1909 that an asymmetry existed between the two. It is called Moho discontinuity in his name. Actually the mantle starts below it. This discontinuity is in the form of a belt about 1 km thick.
Zone of Low Velocity - The speed of seismic waves in the upper mantle is less than that of a sudden Moho-discontinuity due to which the thickness of 100 to 200 km of the upper mantle is called 'zone of low velocity. where the movement of P waves in Moho-discontinuity is up to 8.1 km per second while in this circle it turns out to be 7.8 km per second. This circle is also called the Asthenosphere.
Asthenosphere - The asthenosphere is a part of the mantle that exists in the form of a molten form at a depth of 100 to 250 km at its top, with no special layer in the Earth's internal structure. In this important part rocks also have some extent of movement because according to the plate tectonic theory, when two plates collide, a relatively light plate is bent and moves to the asthenosphere and as a result of it volcano or earthquake. Events like this happen.
Core - This is the innermost part of the earth which is found below the mantle to the center of the earth. Its depth ranges from 2900 km to 6371 km. Although its density is twice as high as the mantle, it contains only 16% of the Earth's volume and 32% of its mass. It has two subdivisions (a) Outer Core - It extends from 2,900 km to 5,150 km. Secondary earthquake waves or S Waves cannot enter it. This proves that this part is in liquid state. (B) Inner Core - This depth is from 5,150 km to 6,371 km (center of earth). Its density is 13.6 maximum. In this the speed of P waves of earthquake becomes 11.23 km per second.Nickel in the structure of the absolute innermost of the Earth and
there is an excess of ferium, with 80% ferium or iron20% silica is found. )
Asthenosphere - The asthenosphere is a part of the mantle that exists in the form of a molten form at a depth of 100 to 250 km at its top, with no special layer in the Earth's internal structure. In this important part rocks also have some extent of movement because according to the plate tectonic theory, when two plates collide, a relatively light plate is bent and moves to the asthenosphere and as a result of it volcano or earthquake. Events like this happen.
Core - This is the innermost part of the earth which is found below the mantle to the center of the earth. Its depth ranges from 2900 km to 6371 km. Although its density is twice as high as the mantle, it contains only 16% of the Earth's volume and 32% of its mass. It has two subdivisions (a) Outer Core - It extends from 2,900 km to 5,150 km. Secondary earthquake waves or S Waves cannot enter it. This proves that this part is in liquid state. (B) Inner Core - This depth is from 5,150 km to 6,371 km (center of earth). Its density is 13.6 maximum. In this the speed of P waves of earthquake becomes 11.23 km per second.Nickel in the structure of the absolute innermost of the Earth and
there is an excess of ferium, with 80% ferium or iron20% silica is found. )
Guttenberge Wiechert Discontinuity - A sudden change in density occurs at a depth of 2,900 km between the mantle and the innermost part of the Earth's interior. In the mantle located at the top of it, where the density is 5.5, at the bottom, it increases to 10.0. The speed of P waves in this section also suddenly increases to 13.6 km per second. This unmodified part is known as 'Gutenberg Vysart Discontinuity
Discontinuity refers to a surface where the speed of seismic waves changes abruptly, the reason for this change is the change in the physico-chemical structure of the Earth. Some of the major seismic correlations are:
Conard discontinuity - between external crust and internal crust
Moho discontinuity - discontinuity between internal crust and outer mantle
Repiti discontinuity
between external mantle and internal mantle
Guttenberg discontinuity between internal mantle and outer core -
Lehmann discontinuity between outer core and inner core.
Discontinuity refers to a surface where the speed of seismic waves changes abruptly, the reason for this change is the change in the physico-chemical structure of the Earth. Some of the major seismic correlations are:
Conard discontinuity - between external crust and internal crust
Moho discontinuity - discontinuity between internal crust and outer mantle
Repiti discontinuity
between external mantle and internal mantle
Guttenberg discontinuity between internal mantle and outer core -
Lehmann discontinuity between outer core and inner core.
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