Interior of the Earth: Structure and Composition

Based on the evidences of Earth, the scientist has formed a largely uniform opinion about interior of the earth which is as follows:

  • Earth’s interior has three major layers having different composition, density and state.
  • These layers are 1) Crust; 2) Mantle and 3) Core
Fig.1: Interior of the Earth

1. Crust

  • Crust extends to about 5-30 km in case of the oceanic crust and as 50-100 km in case of the continental crust. Averages around 30 kms.
  • GK: Mohorvich Discontinuity is the boundary between crust and mental.
  • Average density crust is about 2.7 g/cm3
  • The temperature of the crust increases with depth, reaching about 200 °C to 400 °C at the boundary with the underlying mantle.
  • Formed largely of Silica and Aluminum (SiAl).
  • GK: Oxygen is largest single component element of crust.

2. Mantle

  • Mantle extends from base of crust to about 2900 kms deep.
  • Density of Mantle is approx. 2.9 to 3.3 g/cm3.
  • Temperature ranges from 2000 °C to 4000 °C.
  • It is Formed largely of Silica and Magnesium (SiMa). About 45% of matter in mantle is formed of Oxygen.
  • Modern Views: Four sub-layers in Mantle i.e. upper mantle – lithospheric mantle (30-100 kms); asthenosphere (100—410 kms); transition zone (410-660 kms); lower mantle (660-2900 kms)
  • GK: The boundary between upper and lower mantle is called Repetti Discontinuity. The boundary between Mantle and Core is called Gutenberg Discontinuity.

3. Core

  • It extends from 2900 to the center of earth i.e. 6378 kms. Density of core is about 9.9 g/cm3to 14.2 g/cm3
  • GK: Guttenberg Discontinuity is the boundary between mantle and core.
  • Temperature reaches about 60000C at the centre of earth.
  • Formed Largely of Nickel and Ferrous (NiFe)
  • Consists of two Layer i.e. outer core (2900-5100 kms) and inner core (5100 to 6378 kms)
  • The outer core is in liquid state whereas the inner core is in solid state.
  • GK: The boundary between upper core and inner core is called Lehmann Discontinuity.

For Evidences of the Interior of the Earth, Click Here.

Modern Views on Core

  • Core of the earth works like a dynamo which produces magnetic field to protect earth from solar storms.
  • The swarm satellite constellation of ESA has observed that the outer core’s liquid material moves in wave like pattern towards the west similar to jet stream.
  • The KTH institute in Sweden also observed that the inner core is in a metallic crystalline state unlike the solid state of nickel and ferrous on surface.. The core manages to stay in solid state due to reshuffling of iron crystal. As soon as iron crystal is liquefied, it is slide away and is replaced by solid iron crystal just like shuffling of a deck of cards.