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.
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