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Identify the  layers of the earth. Write the layer that correspond to the number in the space provided. What is Mohorovicic Discontinuity and what is it composed of.


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                                                          The Internal Process Questions


1.Inner Core


3.Oceanic Crust

4.Outer Core

5.Upper Mantle

6.Continental Crust

7.Lower Mantle

8.Mohorovicic Discontinuity

Mohorovicic discontinuity is the boundary between the Earth’s crust and the mantle. It is also termed as Moho and is named after the person discovered, Andrija Mohorovicic, a Croatian seismologist. On an average, Moho is 8 kms beneath the Ocean floor and 35 kms beaneath the typical continental crusts. The Moho is the place where the seismic P-waves experiences sudden increase in velocity because of the change in composition from lighter basalts in the crust to denser silicates ((peroidotite, dunite) in the mantle.

9. Lithosphere

Lithossphere is defined as the rigid, outermost shell of a rocky planet. The Lithosphere of Earth consists of the crust and the upper mantle. The two types of Earth’s lithosphere are Oceanic lithosphere and Continental lithosphere. The Oceanic lithosphere mainly comprises of mafic (which is rich in magnesium and iron) crust and ultramafic (over 90% mafic) mantle and is denser than continental lithosphere. The continental lithosphere mainly consists of granitic rock and it is the layer of igneous, sedimentary rock that forms the continents and the continental shelves.

10-11. Mantle

The mantle is the portion between the Earth’s crust and the outer core. The mantle is the largest layer of the Earth and makes up-to 84% of the Earth’s volume. It is predominantly solid and composed of silicates rich in magnesium and iron. The mantle is about 1800 miles deep out of which the inner mantle is 200 to 250 miles thick and the rest is inner mantle.

12-13. Alfred Wegener

Alfred Wegener was a German polar researcher, geophysicist and meteorologist. He was the one who proposed the theory of continental drift. In 1912, he proposed a hypothesis named “Continental drift theory” which states that the continents were once joined together as a single big land mass (termed as Pangea or super-continent) and started to drift slowly around the earth.


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