World Geography Part 3 – Earth’s Interior

In this article, we will understand about the earth’s interior and about sources for knowing about earth’s interior


  • The earth is the only known planet where life is possible
  • Earth is spherical in shape, hot water and molten lava eject out from earth’s interior
  • World’s deepest mining is limited only to the depth of less than 5 km as the temperature below the earth is very high.
  • The interior of the earth –
  • Because of the huge size and changing nature of its internal composition, it’s not possible to make the direct observation.
  • We have limited information of earth’s interior, through mining and drilling operation, it’s so hot that it can even melt any tool for drilling.

Structure of the earth

  • The innermost layer surrounding the earth surface is called core.
  • The core is the densest layer of the earth with its density more than 11.0.
  • It is composed mainly of iron and nickel thus known as Nife.
  • Core consist of two sublayers, the inner one is solid (C2) and the outer one is semi-liquid (C1)
  • The layer surrounding the core is the mantle, is composed of basic silicates.
  • The major constituent of the mantle are magnesium and silicon, hence it’s also known as Sima (Silica+Magnesium).
  • Its density varies from 3.1 to 5.1 and surrounded by the outermost layer of the earth, known as lithosphere and its density varies from 2.75 to 2.90.
  • Major constituent elements of the lithosphere are silica (Si) and aluminium (Al), it is also known as Sial.
  • The outermost part of the lithosphere is known as the crust.



Sources for knowing about earth’s interior

The sources which provide knowledge about the interior of the earth may be classified into

  1. Artificial sources
  2. Natural sources
  3. Evidence from the theories of the origin of the earth

Artificial sources to understand the Interior of the earth

We can know about the interior of the earth with the help of following sources

  • Temperature
  • Pressure
  • Density


  1. It increases with the depth, as observed in the mines and deep wells
  2. The molten lava erupted from the earth’s interior also support this fact.
  3. It’s not uniform from the surface towards the earth’s centre, in beginning its increases at an average rate of 1 degree Celsius for every 32 meters increase in depth.
  4. With such a speed it will be 300 degree celcius at a depth of 10 km, and 1200 degree celcius at 40 km.
  5. But its interior is not in the molten state, because rocks buried under the pressure of several km thicknesses of overlying rocks melt at the higher temperature
  6. Than similar rock on the surface, a basaltic lava rock which will melt at 1250 degree celcius at the surface, will take 1400 degree celcius at 32 km of depth.

So from where we get extra heat –

It is being produced by radioactivity, as the result of the breakdown of atomic nuclei of minerals emitting radiant energy from in the form of heat from the rocks.

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