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Interior of the Earth

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The interior of the earth is divided into three layers- Crust, Mantle, and Core. Crust refers to the outermost layer of the earth, the mantle is the portion of the interior beyond the crust and Core refers to the innermost layer of the earth.


Interior of Earth

Interior of the Earth

The inside of the earth has 3 unique layers- Crust, Mantle, and Core. The peripheral layer of the earth is the Crust. The mantle is the following second layer and the centre is the deepest layer of our Earth.


The outermost layer of the earth is the Crust. It is fragile (weak). The thickness of the crust fluctuates under the maritime (5 km) and continental regions (35 km).

The oceanic crust is more slender when contrasted with the continental crust. The continental crust is thicker in the space of significant mountain frameworks. The crust is made of heavier rocks having a density of 5g/cm3. The rocks seen in the oceanic crust are basalt and the mean density is 2.7g/cm3. The discontinuity between the hydrosphere and crust is called Conrad Discontinuity.

Major constituent minerals are Silica (Si) and Aluminum The crust itself is partitioned into two sub-layers as oceanic crust and continental crust. The continental crust is a lot thicker than the oceanic crust. 

Oceanic Crust 

The crustal mass existing under the seas is around 10 km thick. It is by and large comprised of rocks wealthy in iron and magnesium.  The explanation is that this layer is overwhelmed by generally weighty, dull, thick shakes of “mafic” arrangement. The greater part of these mafic rocks are volcanic in beginning and are designated “basalts.”

Continental Crust

This crustal mass makes up the continental layer. The continental crust is around 30 to 50 km in thickness. It is comprised of igneous, metamorphic, and sedimentary rocks. The oceanic crust is thicker than the continental crust. The continental crust is comprised of lightly shaded rocks. These stones are essentially made out of silicates, improved in lighter components, like aluminum, potassium, and sodium. Consequently, this layer is called “SiAl”.


It is the earth’s rigid outer layer, with a thickness that ranges from 10 to 200 km. It consists of both the crust and the upper part of the mantle. Lithosphere is divided into tectonic plates, which move and create large-scale changes to the geological structure of the earth.


This lies below the lithosphere extending up to 80-200 km and rigid lithosphere can easily move over because the asthenosphere is soft. Its vicious, brittle, and ductile and density is higher than the crust. It is a primary source of magma that rises to the surface during eruptions of volcanos.


The portion of the interior of the earth beyond the crust is called the mantle. It is a solid state. It is nearly multiple times thicker than the external cover. The thickness ranges from 10-200km and the mantle extends from Moho’s discontinuity to a depth of 2,900 km.

As we dive deep, it abandons a strong to semi-fluid state. The asthenosphere is the upper piece of the Mantle. The central wellspring of magma tracks down its direction to the surface during volcanic emissions.  The discontinuity between the upper mantle and lower mantle is called Repetti Discontinuity.

The thickness of the mantle is higher than the crust. The highest piece of the mantle and outside layer shapes the lithosphere. It is very nearly 2900 kilometers in thickness. It is contained around 83% of the Earth’s complete volume. It is additionally partitioned into two particular layers upper mantle and lower mantle.

Upper Mantle

The upper mantle is around 670 kilometers from start to finish. It is a delicate and less thick mass. It is comprised of peridot sites. These rocks involved minerals like olivine and pyroxene stones in the upper mantle are more unyielding and delicate considering cooler temperatures and lower pressures. rocks are significantly improved with iron and magnesium, and they are called “ultramafic” rocks. These stones are dull in assortment on account of the presence of iron and magnesium.

Lower Mantle

The Lower Mantle is a lot thicker and denser. It is 670 to 2900 kilometers beneath the Earth’s surface. This layer is hot and plastic. It is delicate and in an almost fluid condition close to its inward limit.


The deepest layer is the core with a range of 3,500 km. The inner core is in a solid state whereas the outer core is in a liquid state. The core is made up of heavy material mostly constituted of nickel and iron; because of this, it is also called the ‘nife” layer.

The focal center has an exceptionally high temperature and tension. The core is separated from the mantle by Guttenberg’s Discontinuity. Core constitutes 15 percent of the earth’s volume and 32.5% of the earth’s mass. The core is the densest layer of the earth with a density of 9.4-14.5g/cm3.

The Earth’s central Core contains two distinct layers Outer Core and Inner Core.

Outer Core

The Outer Core is a hot fluid layer and the Inner Core is a hot and strong layer. The outer center is around 2250 km thick.
The outer center is known to exist in a fluid state due to the way of behaving of seismic tremor waves, especially shear body waves or auxiliary waves. The temperature in the external center is around 4000-50000C.

Inner Core

The inward center is 5150-6370 km underneath the world’s surface. It mostly comprises iron, nickel, and a few lighter components, likely sulfur, carbon, oxygen, silicon, and potassium. The temperature in the inward center is around 5000-60000C. Due to the high strain, the internal center is strong. The strength of the internal center is because of the presence of iron and nickel. The center is amazingly hot in the middle and the strain is incredible to such an extent that the liquefying point of iron and nickel is raised a long way past those high temperatures (6,500 K), leaving the nickel-iron as strong. 

Sources about Interior of the Earth

Direct Sources

This includes the rocks from the mining areas and the volcanic eruption.

Indirect Sources

Analyzing the rate of change of temperature and pressure from the surface to the interior.

  1. Meteors
  2. Gravitation
  3. Gravity Anomaly
  4. Magnetic sources
  5. Seismic Waves

Temperature, Pressure, and Density of the Interior of Earth


The rise of temperature is often found in mines and deep wells. Along with this, the molten lava supports the fact that temperature increases towards the center of the earth. The rate of increase in temperature is not always uniform. It is mostly faster in some places and not so in others. Thus, it is mostly assumed that the rate of increase of temperature beneath surface is decreasing towards the center. The temperature of the center is 3000°C to 5000°C, Mostly due to chemical reactions under high-pressure situations.


Pressure, as same as the temperature is increasing towards the center of the earth. This is mostly due to the weight of the overlying materials.


Due to the increase in pressure and the presence of heavier materials towards the center, the density of the earth also increases towards the center.

Layers of Earth- Seismic Discontinuities

Discontinuity refers to the boundary sharply present between layers in the earth’s internal structure and within these boundaries, waves undergo changes in terms of direction and speed. Types of discontinuities are:

  1. Conorod Discontinuity
  2. Mohorovicic Discontinuity
  3. Repiti Discontinuity
  4. Gutenberg Discontinuity
  5. Lehman Discontinuity

Earth’s Chemical Composition

It is composed mostly of the following:

  • Iron
  • Oxygen
  • Silicon
  • Magnesium
  • Sulfur
  • Nickel
  • Calcium 
  • Aluminium

FAQs on Interior of Earth

What are the 4 layers of the earth?

The 4 layers of earth include inner core, outer core, mantle and the crust.

What is earth’s interior called?

The earth’s interior is called the mantle.

What are the 3 major parts of earth interior?

The 3 major parts of earth interior are the crust, the mantle and the core.

Why is Earth’s interior important?

Earth’s interior important as it helps to learn about the processes which has helped in creation of earth and the driven plate tectonics.

Why interior of the earth is hot?

The interior of the earth is hot because of the heat from when planet was formed and heat from decay of radio active material.

Which is the hottest layer of the earth?

Inner core.

What is the thickest layer of the earth?

The mantle.

Last Updated : 22 Nov, 2023
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