Today In this article of Geomorphology we are going to know more about Interior Of The Earth.

So first of all this question arises in mind that why we are studying the interior of the earth? what are the benefits of understanding the basic structure of the earth?

Here is the answer-

  • Understanding the earth’s interior is essential to understand the nature of changes that take place over and below the earth’s surface.
  • To understand a geophysical phenomenon like volcanism, earthquakes, etc..
  • To understand the internal structure of various solar system objects.
  • To understand the evolution and present composition of the atmosphere.
  • Future deep-sea mineral exploration etc.

Now Let’s discuss the sources which provide knowledge about the interior of the earth and also the earth’s interior.

Sources to study the earth’s interior

The sources which provide knowledge about the interior of the earth may be classified into 2 sources-

  1. Direct sources
  2. Indirect sources

Direct sources

  • Mining and drilling
  • Volcanic eruption

Indirect sources

  • Temperature and pressure variation
  • Meteors
  • Seismicity

Structure of the earth’s interior

The structure of the earth’s interior is made up of several concentric layers. Structure of Interior Of The Earth is divided into three layers-

  • Crust
  • Mantle
  • Core
Interior of the Earth


  • The crust is the outermost solid part and a thin layer of the earth with a total thickness normally between30-50 km.
  • The thickness of the crust varies under the oceanic and continental areas.
  • Oceanic crust is thinner (5-30 km thick) as compared to the continental crust(50-70 km thick).
  • The continental crust is thicker in the areas of major mountain systems.
  • It is as much as 70 -100 km thick in the Himalayan region.
  • It forms 0.5-1.0 percent of the earth’s volume.
  • The outer covering of the crust is of sedimentary material(granitic rocks) and below that lie crystalline, igneous and metamorphic rocks which are acidic in nature.
  • The lower layer of the crust consists of basaltic and ultra-basic rocks.
  • The average density of the outer and lower crusts is 2.8 and 3.0 respectively.
  • The continents are composed of lighter silicates silica + aluminum (also called ‘sial’) while the oceans have the heavier silicates—silica + magnesium (also called ‘sima’).
  • Mohorovicic (Moho) discontinuity forms between lower crust and upper mantle.
earth interior


  • The portion of the interior beyond the crust is called the mantle.
  • The mantle extends from Moho’s discontinuity(35 km) to a depth of 2,900 km.
  • The upper portion of the mantle is called the asthenosphere.
  • 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 a solid-state.
  • The density of mantle is higher than the crust and varies from 3.3 to 5.5.
  • It contains 83 percent of the total volume and 68 percent of the total mass of the earth.
  • The mantle has been formed largely of silicate minerals rich in iron and magnesium.


  • The upper portion of the mantle is called the asthenosphere.
  • It is considered to be extending up to 400 km.
  • 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.
Interior of the Earth


  • The core-mantle boundary is located at the depth of 2900 km.
  • Core lies between 2900 km and 6400 km below the earth’s surface.
  • The outer core is liquid while the inner core is solid.
  • The density of the core is higher than the mantle and varies from 5.5 to 13.6 g/cm3
  • The core is made up of heavy material mostly constituted by nickel and iron [nife].
  • Volume and mass of core are 16% and 32% of the total volume and mass of the earth respectively.

Earth’s Layers- Seismic Discontinuities

  • Conorod Discontinuity– between upper and lower crust
  • Mohorovicic Discontinuity (Moho) – separates the crust from the mantle, its average depth being about 35 km.
  • Repiti Discontinuity – between the upper and lower mantle
  • Gutenberg Discontinuity – lies between the mantle and the outer core. Below 2900 km from earth’s surface.
  • Lehman Discontinuity- between inner and outer core.
earth interior

Earth’s Chemical Composition

Earth’s Chemical Composition

The Major Elements of the Earth’s Crust:

Elements                   By Weight(%)

  1. Oxygen                            46.60
  2. Silicon                              27.72
  3. Aluminum                            8.13
  4. Iron                                  5.00
  5. Calcium                                3.63
  6. Sodium                              2.83
  7. Potassium                        2.59
  8. Magnesium                         2.09
  9. Others                               1.41


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Pintu Saikia

Very helpful for aspirants. Thank you sir…🙏

Arjun Arya

Sir is this sufficient for GS 1 for geography part