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Layers of the Earth:

The layers of the Earth is divided into the following sections - 1. Inner Core, 2. Outer Core, 3. Mantle and 4. Crust.

LayerDescription
CrustIt is the outermost layer of the Earth. It ranges from 5 - 100 km in depth. It is composed of igneous, metamorphic, and sedimentary rocks. The majority of the Crust is made of silicates. This is the layer where life exists both on land and ocean. The Crust is divided into huge plates. When these plates grind against each other earthquakes occurs.
The Crust and the Upper Mantle constitutes the Lithosphere.
MantleIt is a layer between Crust and Outer Core. Earths' Mantle extends to a depth of 3,000 km and is the thickest layer of the Earth crust. It is composed mostly of silicate rocks rich in magnesium and iron. Upper Mantle consists of two parts : The inner Asthenosphere composed of plastic flowing rock (200 km thick) and the lowermost part of the lithosphere composed of rigid rock (50 to 120 km thick). It has different temperatures at different depths. The temperature of the Mantle increases with depth.
Outer CoreThe Outer Core consists of super-heated liquid molten lava (2260 km thick), which is mostly iron and nickel. Its outer boundary lies 2,890 km beneath the surface of the Earth. Convection of molten lava in the outer core creates the Earth's magnetic field. The liquid Outer Core surrounds the Inner Core.
Inner CoreThe Inner Core extends 1440 km towards the center of the Earth. It is entirely composed of Iron and some Nickel. The solid Inner Core was discovered by Inge Lehmann in 1936.


Objective Questions on Layers of the Earth frequently asked in SSC, CDS, NDA, PSC, Railways and other competitive examinations-
1. Which of the following is the inner most layer of the Earth?
(a) Crust
(b) Mantle
(c) Inner Core
(d) Outer Core

2. Deepest layer of the Earth a person has ever gone to?
(a) Crust
(b) Inner Core
(c) Upper Mantle
(d) Mantle

3. Which of the following best describes the Mantle?
(a) Solid
(b) Liquid
(c) Gas
(d) Viscous

4. Which of the following is the thickest layer of the Earth?
(a) Crust
(b) Mantle
(c) Inner Core
(d) Outer Core

5. Core is made up of?
(a) Iron and Nickel
(b) Iron
(c) Aluminium
(d) Steel

6. Which of the following best describes the Outer Core?
(a) Solid
(b) Liquid
(c) Gas
(d) Viscous

7. What is caused due to shifting of tectonic plates?
(a) Volcanoes
(b) Earthquakes
(c) Thunder
(d) Tornadoes

8. Which two layers constitutes the Lithosphere?
(a) Upper Mantle and Crust
(b) Inner Core and Outer Core
(c) Mantle and Outer Core
(d) None of the above


Answers - 1(c), 2(a), 3(d), 4(b), 5(a), 6(b), 7(b) and 8(a).