Interior of Earth: Crust, Core and Mantle

Earth’s interior consists of crust, mantle and core. Out of the three components, the mantle forms the major portion of the earth’s interior. The continental plates and the oceanic plates float over the aesthenosphere, which is a part of the mantle. The crust occupies the least volume of the earth, just around 1%. Phenomena such as earthquakes, volcanoes and tornadoes are connected to the interior of the earth. It is through studies of seismic waves scientists learn about the interior of the earth.

Also Read: Mineral and Energy Resources

Key Terms: Earth, Crust, Mantle, Core, Earthquake, Volcano, Waves, Lithosphere, Temperature, Pressure, Hydrosphere, Lava

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What is Interior of Earth?

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The interior of the earth has many layers and is majorly divided into three layers. 

• Crust
• Mantle
• Core

Asthenosphere is considered a part of the mantle. It is in the asthenosphere that the crust floats as the asthenosphere is basically molten lava. The core and the mantle are almost equal in thickness but the core occupies only 15% of the earth’s volume while the mantle has 84%.

Layers of Earth’s Interior

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Crust

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Crust forms the uppermost layer of the earth’s interior. A few properties of the crust are listed below.

• It is solid and is around 8-40 km thick.
• It is brittle in nature and forms nearly 1% of the earth’s volume.
• The continental crust is thicker than the oceanic crust.
• Majorly, it is composed of Silica(Si) and Aluminium(Al) and thus often termed SIAL.
• The discontinuity between the hydrosphere and the crust is known as Conrad discontinuity.

Also Read: Biogeochemical Cycle

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Mantle

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The mantle forms the middle layer of the earth’s interior. It is below the crust.

• The uppermost solid mantle and the crust together are known as the lithosphere.
• It is about 2900 km thick and occupies about 84% of the earth’s volume.
• Majorly, its constituents are Silica(Si) and Magnesium(Mg) and thus also called SIMA.
• The discontinuity between the crust and the mantle is called Mohorovich or Moho discontinuity.
• The asthenosphere, between 80-200 km, is the main source of magma. The lithosphere or the continental plates floats over the asthenosphere.
• The lower mantle is separated from the upper mantle by the Repetti discontinuity.

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Core

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The core forms the innermost layer of the earth’s interior, surrounding the centre of the earth. 

• The core forms nearly 15% of the earth’s volume.
• It is divided into two sub-layers namely, the inner core and the outer core.
• The inner core is solid while the outer core is liquid or semi-liquid.
• Majorly, the core is made up of Nickel(Ni) and Iron(Fe) and is thus also called NIFE.
• The outer core is separated from the mantle by Guttenberg’s discontinuity.
• The discontinuity between the inner core and the outer core is called Lehmann discontinuity.
• The core sometimes is termed as Barysphere.

Also Read: Weathering

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Characteristics of Earth’s Interior

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The earth’s interior has been observed through drilling and mining activities so to know more about it. The characteristics based on research so far are listed below.

• As one moves to the centre of the earth, there is a rise in the temperature.
• The temperature at the centre of the Earth is estimated to be around 3000 C to 5000 C, maybe even higher.
• The materials at the centre of the earth are in a solid state even after such high temperatures because of the immense pressure present there. 
• The pressure also increases as one moves towards the centre of the earth.
• The pressure is estimated to be around 3 to 4 million times the atmospheric pressure in the deeper portions of the earth.
• Due to high pressure and temperature and heavier metals such as iron, the density of the earth’s layers also increases towards the centre.

Also Read: Natural Resources

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Things to Remember

• The interior of the earth comprises of crust, mantle and core.
• The mantle and the core have almost the same thickness.
• The mantle occupies the majority of the earth’s volume, approximately 84%.
• The lithosphere/continental plates float on the mantle.
• As one moves down the centre of the earth, the temperature and the pressure increase.