Interior of the Earth: Core, Mantle and Crust-Geography UPSC

Hey Dosto, 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 interior of the earth?, what are the benefits of understanding the basic structure of the earth?

Don’t worry guys, Here is the answer-

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

Now we are going to discuss that the sources which provides knowledge about the interior of the earth and also the earth’s interior.

Sources to study earth’s interior

The sources which provides 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

Crust

  • Crust is the outermost solid part and 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 per centof 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 outer and lower crust is 2.8 and 3.0 respectively.
  • The continents are composed of lighter silicates silica + aluminium (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

Mantle

  • 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 mantle is called  asthenosphere.
  • The crust and the uppermost part of the mantle are called lithosphere. Its thickness ranges from 10-200 km.
  • The lower mantle extends beyond the asthenosphere. It is in solid state.
  • Density of mantle is higher than 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.
  • Mantle have been formed largely of silicate minerals rich in iron and magnesium.

Asthenosphere

  • The upper portion of the mantle is called 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’s.

Interior of the Earth

Core

  • The core-mantle boundry 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.
  • Density of core is higher than 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 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

earth's interior temperature
earth’s interior temperature

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