What are the three layers of Earth?

Earth’s interior is generally divided into three major layers: the crust, the mantle, and the core.

Crust:

  • It is the outermost solid part of the earth. It is brittle in nature. 
  • The thickness of the crust varies under the oceanic and continental areas. 
  • Oceanic crust is thinner as compared to the continental crust. The mean thickness of the oceanic crust is 5 km whereas that of the continental is around 30 km. 
  • The continental crust is thicker in the areas of major mountain systems. It is as much as 70 km thick in the Himalayan region. 
  • It is made up of heavier rocks having a density of 3 g/cm3. This type of rock found in the oceanic crust is basalt. The mean density of material in the oceanic crust is 2.7 g/cm3.

Mantle:

  • The portion of the interior beyond the crust is called the mantle. 
  • The mantle extends from Moho’s discontinuity to a depth of 2,900 km. 
  • The upper portion of the mantle is called the asthenosphere. It is the main source of magma that finds its way to the surface during volcanic eruptions. 
  • It has a density higher than the crust’s (3.4 g/cm3). The crust and the uppermost part of the mantle are called the lithosphere. Its thickness ranges from 10-200 km. 
  • The lower mantle extends beyond the asthenosphere. It is in solid state.

Core:

  • The core-mantle boundary is located at the depth of 2,900 km. 
  • The outer core is in a liquid state while the inner core is in solid state. 
  • The density of material at the mantle core boundary is around 5 g/cm3 and at the centre of the earth at 6,300 km, the density value is around 13g/cm3.
  •  The core is made up of very heavy material mostly constituted by nickel and iron. It is sometimes referred to as the nife layer.

Further Reading:

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