The interior of the earth is composed of three layers.
1. Crust which is divided into upper and lower by the Conard Discontinuity.
2. Mantle which is divided into upper and lower by the Reptite Discontinuity.
3. Core which is divided into upper and lower by the Transition or Lehman Discontinuity.
4. Crust and mantle is separated by the Moho discontinuit.
5. Mantle and core is separated by the Gutenberg discontinuity.
Evidences:
Density:
The density of the crust varies between 2.7 to 3.5 g/cms. The average density of the whole earth is 5.5. So we can assume that the interior core of the earth should be greater than 5.5. So the general trend is the density increases with increasing depth.
Pressure:
It is believed that the high density of the core is due to the high pressure created by the super incumbent load of the rocks. This is proved wrong because the density will not increase due to ressure after a certain limit. So the core should be made up of heavy metallic minerals. Research has shown that core is made up Nickel and Iron.
Temperature:
Temperature increases from the surface of the earth downward at the rate of 2 to 3 degree Celsius. Using geothermal maps it is identified that the temperature is 1000C at 43 km depth in tectonically active area while it is 500 C in tectonically stable areas.
At a depth of 100 km temperature is about 1200 C the rocks are in a molten semi solid state and this region is called the Aesthenosphere. But at this rate the temperature would be 25000 C at which the earth will not exist. So the high temperature at asthenosphere is due to the disintegration of radioactive materials found in that region.
Inferences:
1.The average temperature id around 1100 C at the aesthenosphere.
2.At depths of 400 and 700 km it is 1500 C and 1900 C respectively.
3.At 2900 km it is 3700 C.
4.At 5100 km it is 4300 C.
Vulcanicity:
During volcanic eruptions molten rock lava is thrown out. So there must be a molten magma chanber in the interior of the earth. However with increasing pressure the melting point of the rocks increase So the inner core cannot be a liquid due to high pressure.
Seismic waves:
Seismology is the study of earth quakes and the different tremors and waves generated during an earthquake are called seismic waves which is broadly classified into primary (P) waves, secondary (S)waves and Surface waves.
Shadow regions:
The P waves are not observed in the regions at an angle of ~105 to ~140 degrees.
The S waves are not observed in the regions after an angle of 105 degrees.
The regions where the waves are not observed are called shadow regions.
The velocity of the P and S waves very with depth and research shows that there are three set of velocities implying three layers.
Based on the above inferences we can identify that
Crust is solid
Mantle is plastic (a solid that flows)
Outer Core is liquid
Inner Core is solid.
1. Crust which is divided into upper and lower by the Conard Discontinuity.
2. Mantle which is divided into upper and lower by the Reptite Discontinuity.
3. Core which is divided into upper and lower by the Transition or Lehman Discontinuity.
4. Crust and mantle is separated by the Moho discontinuit.
5. Mantle and core is separated by the Gutenberg discontinuity.
Evidences:
- Artificial Sources
- Density
- Pressure
- Temperature
- Natural Sources
- Vulcanicity
- Seismic Waves
Density:
The density of the crust varies between 2.7 to 3.5 g/cms. The average density of the whole earth is 5.5. So we can assume that the interior core of the earth should be greater than 5.5. So the general trend is the density increases with increasing depth.
Pressure:
It is believed that the high density of the core is due to the high pressure created by the super incumbent load of the rocks. This is proved wrong because the density will not increase due to ressure after a certain limit. So the core should be made up of heavy metallic minerals. Research has shown that core is made up Nickel and Iron.
Temperature:
Temperature increases from the surface of the earth downward at the rate of 2 to 3 degree Celsius. Using geothermal maps it is identified that the temperature is 1000C at 43 km depth in tectonically active area while it is 500 C in tectonically stable areas.
At a depth of 100 km temperature is about 1200 C the rocks are in a molten semi solid state and this region is called the Aesthenosphere. But at this rate the temperature would be 25000 C at which the earth will not exist. So the high temperature at asthenosphere is due to the disintegration of radioactive materials found in that region.
Inferences:
1.The average temperature id around 1100 C at the aesthenosphere.
2.At depths of 400 and 700 km it is 1500 C and 1900 C respectively.
3.At 2900 km it is 3700 C.
4.At 5100 km it is 4300 C.
Vulcanicity:
During volcanic eruptions molten rock lava is thrown out. So there must be a molten magma chanber in the interior of the earth. However with increasing pressure the melting point of the rocks increase So the inner core cannot be a liquid due to high pressure.
Seismic waves:
Seismology is the study of earth quakes and the different tremors and waves generated during an earthquake are called seismic waves which is broadly classified into primary (P) waves, secondary (S)waves and Surface waves.
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P Waves
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Can pass through all mediums solid liquid and Gas
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S Waves
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Cannot pass through Liquid.
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Surface Waves
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Low energy waves generated at the surface of the earth which causes
the maximum destruction.
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Shadow regions:
The P waves are not observed in the regions at an angle of ~105 to ~140 degrees.
The S waves are not observed in the regions after an angle of 105 degrees.
The regions where the waves are not observed are called shadow regions.
The velocity of the P and S waves very with depth and research shows that there are three set of velocities implying three layers.
Crust is solid
Mantle is plastic (a solid that flows)
Outer Core is liquid
Inner Core is solid.
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