Interior of the Earth: Complete Study Notes

Interior of the Earth: Complete Study Notes

GA Study Notes On Inside our Earth: SSC CGL Tier-1 2018. Learn different layers of the Earth – Crust, Core and Mantle very important for SSC CGL, SSC CHSL, CDS, NDA, BANK PO, BANK CLERK, RAILWAYS, LIC etc.

Important points about the Interior Structure of the Earth:

❖ Earth is made up of several different layers, each with unique properties.

❖ The interior structure of the Earth is layered in spherical shells, like an onion.

❖ These layers can be defined by their chemical and their rheological properties.

❖ Earth has an outer silicate solid crust, a highly viscous mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core.

❖ The planet Earth is made up of three main shells: the very thin, brittle crust, the mantle, and the core; the mantle and core.


  • The uppermost layer over the earth’s surface is called the crust.
  • It is the thinnest of all the layers.
  • It is about 35 km on the continental masses and only 5 km on the ocean floors.
  • The main mineral constituents of the continental mass are silica and alumina. It is thus called sial (Silica – Alumina).
  • The oceanic crust mainly consists of silica and magnesium; it is therefore called sima (Silica – Magnesium).
  • The discontinuity between the hydrosphere and crust is termed as the Conrad Discontinuity.


  • The mantle is a layer between the crust and the outer core.
  • The discontinuity between the crust and mantle is called as the Mohorovich Discontinuity or Moho discontinuity.
  • The mantle is about 2900kms in thickness.
  • Nearly 84% of the earth’s volume and 67% of the earth’s mass is occupied by the mantle.
  • The major constituent elements of the mantle are Silicon and Magnesium and hence it is also termed as SIMA.
  • The density of the layer is higher than the crust and varies from 3.3 – 5.4g/cm3.
  • The uppermost solid part of the mantle and the entire crust constitute the Lithosphere.
  • The asthenosphere is a highly viscous, mechanically weak and ductile,  deforming region of the upper mantle which lies just below the lithosphere.
  • The asthenosphere is the main source of magma and it is the layer over which the lithospheric plates/ continental plates move.
  • The discontinuity between the upper mantle and the lower mantle is known as Repetti Discontinuity.
  • The portion of the mantle which is just below the lithosphere and asthenosphere, but above the core is called as Mesosphere.


  • The innermost layer is the core with a radius of about 3500 km.
  • It is mainly made up of nickel and iron and is called nife (Nickel and Ferrous).
  • The central core has very high temperature and pressure.
  • The core is separated from the mantle by Guttenberg’s Discontinuity.
  • The core is the densest layer of the earth.
  • The discontinuity between the upper core and the lower core is called as Lehmann Discontinuity.
  • Barysphere is sometimes used to refer the core of the earth or sometimes the whole interior.

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  1. September 12, 2018

    […] Interior of the Earth: Complete Study Notes […]

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