Notes
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Topics to be learn :
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The Composition of The Earth’s Interior:
- The earth was formed out of solar system itself.
- Initially, the earth was very hot and gaseous. While rotating around itself, the earth cooled down.
- The process of the cooling down of the earth began from the outer surface towards the earth’s centre. As its effect, the outer surface (crust) of the earth is found to be solid and cooler.
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- Crust, mantle and core are the three layers of the interior of the earth. On the basis of the magma, gases and steam coming out of volcanic eruptions, it is inferred that the earth’s interior is hot.
- To know more about the interior of the earth, the man has also dug deep bore holes.
- There is a difference between the elements, temperatures and the pressure found in the three parts of the interior of the earth, viz. crust, mantle and core.
In the interiors of the earth, the transitional areas are found between :
- continental crust and oceanic crust
- crust and mantle
- upper mantle and lower mantle
- mantle and core and
- outer core and inner core.
Therefore, there are discontinuities in the interior of the earth.
Crust :
The uppermost layer of the interior of the earth is called the crust. It is solid in state.
Continental crust and the oceanic crust are the two parts of the crust.
Continental crust :
Oceanic crust :
Mantle :
- The mantle is located below the crust of the earth. The mantle is divided into the upper mantle and the lower mantle.
- The average thickness of mantle is approximately 2870 km.
- Its average density is approximately 4.5 gm/ cm3.
- The rocks in the upper 100 to 200 km of the mantle melt due to the heat and magma is created. Magma chambers are found in this layer of the earth. Due to the heat and pressure, the energy waves are created in mantle. These energy waves move in vertical direction and magma comes out on the surface of the earth by volcanic eruptions.
- These endogenitic movements continuously occur in the upper layer of the mantle. Therefore, the upper layer of the mantle is known as the asthenosphere. It is more liquid in state. Magma chambers are found in this layer. Epicenters of earthquakes are found here. Endogenetic movements occurring in this layer leads to volcanic eruptions, earthquakes and the formation of mountains and rifts.
- The primary as well as secondary waves of earthquake travel through mantle.
- The temperature at the depth of 2400 to 2900 km is around 2200° to 2500° C. The density of the lower mantle is approximately 5.7 gm/ cm3.
| Know this :
The mixture of molten rocks, volatiles, etc. erupted from volcano or fissure on the surface of the earth is called lava. |
Core :
Only the primary waves of earthquake travel through core. The information about parts of core is as follows :
Outer core :
Inner Core :
The Magnetosphere :
- The average temperature of the outer core of the earth is around 5000° C. The average temperature of the inner core of the earth is around 6000° C.
- This difference between the temperature results in formation of vertical currents.
- The rotation of the earth gives eddy (circular) motion to these currents leading to generation of the magnetic field of the earth. This magnetic field is called magnetosphere.
- Magnetosphere protects the earth from solar winds.
| Know this :
Earth was formed approximately 4.6 billion years ago. Initially, the earth was in a gaseous state. It started cooling through the process of radiation. The earth then liquefied. With time, the outermost part of the earth cooled first and became solid. This outermost layer of the earth is called the crust. Even today outer planets of the solar system are in a gaseous state. |