Question

(A) What are the two parts of the crust?
What is the basis of classification?
(B) Why is the upper mantle called the
asthenosphere?
(C) Magnetosphere of the earth is a result
of rotation. Explain.​

Answer 1

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A: The uppermost layer of the earth’s surface is in solid state and is called the crust. The two parts of the crust are Oceanic Crust and Continental Crust. Oceanic Crust is the second layer of the crust. It is made up of silica and magnesium. It was earlier called Sima. Continental Crust continents are mainly composed of Silica and Aluminum. Because of their high proportion in this layer, the layer was earlier known as Sial.

B: The upper layer of the Mantle is more in liquid state. Here, one finds magma chambers. It is through these chambers that magma comes out on the earth’s surface during volcanic eruptions. This layer is also known as asthenosphere. Epicenters of deep-seated earthquakes are usually found here.

C: The difference between the temperatures of the outer and inner core gives rise to vertical currents. The earth’s rotation gives them circular motion. Electric currents develop in these spiral eddies of liquid iron and thus magnetic field is generated. It is sometimes called the geo-dynamo. This magnetic field of the earth is functional even outside the earth’s surface for quite a distance. As a result, a cover develops around the earth because of the magnetic field. The earth’s atmosphere is protected from solar winds coming from the sun. The magnetic field thus developed around the earth is called the magnetosphere.

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