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

The interior of the earth can be divided into 3 different layers – crust, mantle, and core. The crust is the outermost layer of the earth, and the core is the innermost layer of the earth, located at a depth of 2900 Km. This article briefly throws light on these 3 different interior layers of the earth.

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

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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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