NCERT Notes: Structure Of The Earth [Geography Notes For UPSC]

NCERT notes on important topics for the IAS aspirants. These notes will also be useful for other competitive exams like banking PO, SSC, state civil services exams, and so on. This article talks about the structure of Earth- The Crust, Mantle, and Core.

Structure of the Earth (UPSC Notes):- Download PDF Here

Structure of the Earth


  • The Crust
  • The Mantle
  • The Core

The Crust
  • The crust is the outermost solid part of the earth.
  • It is fragile.
  • The thickness of the crust varies under the oceanic and continental areas.
  • Oceanic crust is thinner as compared to the continental crust.
  • The continental crust is thicker in the areas of major mountain systems.
  • The crust is made up of heavier rocks having a density of 3 g/cm3.
  • The kind of rock seen in the oceanic crust is basalt.
  • The mean density of material in the oceanic crust is 2.7 g/cm3.
  • Silica (Si) and Aluminium (Al) are major constituent minerals. Hence it is often termed as SIAL. Also, sometimes SIAL is used to refer to the Lithosphere.

The Mantle
  • The portion of the interior beyond the crust is called the mantle.
  • It is in a solid-state.
  • It has a density higher than the crust portion.
  • The thickness ranges from 10-200 km.
  • The mantle extends from Moho’s discontinuity to a depth of 2,900 km.
  • The asthenosphere is the upper portion of Mantle.
  • It is the chief source of magma that finds its way to the surface during volcanic eruptions.
  • The crust and the uppermost part of the mantle are called the lithosphere.
  • The major constituent elements of the mantle are Silicon and Magnesium and hence it is also termed as SIMA

The Core
  • The core-mantle boundary is positioned at the depth of 2,900 km.
  • The inner core is in the solid-state whereas the outer core is in the liquid state.
  • The core is made up of very heavy material mostly constituted by nickel and iron. Hence it is also called the “nife” layer.

Structure of the Earth (UPSC Notes):- Download PDF Here

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