Structure of the Earth or Interior of the Earth

Structure of the Earth

Topic Cover:

Interior of the Earth:
  • Crust
  • Mental, and
  • Core.
Discontinuity Between Different Layers.

Interior of the Earth/Structure of the Earth:


πŸ’  Our knowledge of the earth is mostly limited to its surface. But the earth has a complicated interior.

πŸ’  The earth is made up of several concentric layers –
Lithosphere: Outer layer of earth’s crust,
Mental (Mesosphere): Immediately beneath the Lithosphere &
Core (Barysphere): Centre of the Earth.

πŸ’  The interior of the earth is composed of many minerals both in the solid and liquid state.
πŸ’  The temperature in general increases at the rate of 1° C for every 32 metres towards the earth’s interior.
 
Earth’s interior can be divided into the crust, upper mantle, lower mantle, outer core, and inner core.

The Crust:

The crust has two parts-

Upper Crust (Continental Crust):

  • It composed of silica and aluminum (sial).
  • Continental crust is thicker when compared to the oceanic crust.
  • The continental crust 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.
  • The density of the crust is less than 2.7 g/cm3.
 

Lower Crust (Oceanic Crust):

  • It is made up of silica and magnesium (sima).
  • Oceanic crust is thinner when compared to the continental crust.
  • The mean thickness of oceanic crust is 5 km.
  • The density of the crust is more than 2.7 g/cm3 (average 3.0 g/cm3).
 

Conorod Discontinuity/Boundary:

The boundary between the upper crust and the lower crust is termed as ‘Conorod boundary’.
 

The Mantle (Mesosphere):

  • The mantle is composed of silica, magnesium and iron.
  • It lies between the lower crust and the outer core.
  • It extends for about 2,900 km.
  • The mantle accounts for 83%  of the earth volume and 68% of the earth mass.
  • The density of the mantle is 3.9 g/cm3.
  • It is divided into upper mantle and lower mantle. The mantle generally is in a solid state.
  • The upper part of the mantle is called asthenosphere.
 

The Asthenosphere:

  • The word Asthen in Greek means weak (Semi-liquid state).  
  • The upper part of the asthenosphere is in the form of hot plastic like state.
  • It extends up to 400 km and it is the main source of magma.
 
Layers of the Earth


The Mohorovicic Discontinuity:

It is the boundary which divides the lower crust and the upper mantle.
 

The Core (Barysphere):

  • The core forms the centre of the earth.
  • The core is composed of Nickel and Ferrous (Iron) which is called NiFe (Barysphere).
  • Its density is 13.0 g/cm3.
  • Its temperature is about 5500° C to 6000° C.
  • The core is extended from 2,900 km to 6,370 km from the surface of the earth.
  • The core as whole accounts for either 16% or 16.5% volume and 32% mass of the earth.
  • The core has two parts namely the outer core and the inner core.
  • The outer core is in the liquid state while the inner core is in the solid state.
 
 

The Guttenberg Discontinuity:

The boundary between the lower mantle and the outer core is called Guttenberg margin.
 

The Lehmann Discontinuity:

The outer core and inner core are separated by Lehmann boundary.

 
The interior of the earth can be understood by direct and indirect evidences.

Reference: NCERT



Mains Based Questions on Interior of the Earth:

Que. Discuss the differentiation of layers of earth.
Que. How is the interior of the earth classified?
Que. What is interior of the earth?  





MCQ on Earth's Layer/Structure of the Earth (Prelims Based): 

Practice questions on Interior of the earth....Answer Key given Below in a box.... 

Que 1. How many layers of the earth are there?
a) 3
b) 5
c) 6
d) 7

Que 2. What is the upper crust of the Earth made of?
a) Silica and Magnesium
b) Silica and Aluminium
c) Silica and Nickel
d) Silica and Iron

Que 3. What is the lower crust of the Earth made of?
a) Silica and Magnesium
b) Silica and Aluminium
c) Silica and Nickel
d) Silica and Iron

Que 4. What is the mantle layer of the Earth made of?
a) Silica and Magnesium
b) Silica and Aluminium
c) Iron and Nickel
d) Silica, Iron, Nickel, and Magnesium

Que 5. What is the core (barysphere) of the Earth made of?
a) Silica and Magnesium
b) Silica and Aluminium
c) Nickel and Iron
d) Magnesium and Iron

Que 6. What is density of the earth crust?
a) 2.7 g/cm3
b) 3.7 g/cm3
c) 4.0 g/cm3
d) 5.0 g/cm3

Que 7. What is density of the mantle?
a) 2.9 g/cm3
b) 3.9 g/cm3
c) 4.0 g/cm3
d) 5.0 g/cm3

Que 8. What is density of the earth core?
a) 2.9 g/cm3
b) 3.9 g/cm3
c) 13.0 g/cm3
d) 11.0 g/cm3

Que 9. The Earth's inner core is in which state?
a) Solid
b) Liquid
c) Semi-liquid
d) Solid, Liquid and Gas

Que 10. The Earth's outer core is in which state?
a) Solid
b) Liquid
c) Semi-liquid
d) Solid, Liquid and Gas

Que 11. Which discontinuity separates the mantle from the crust?
a) Conorod Discontinuity
b) Lehmann Discontinuity
c) Guttenberg Discontinuity
d) Mohorovicic Discontinuity

Que 12. Which discontinuity separates the mantle from the core?
a) Conorod Discontinuity
b) Lehmann Discontinuity
c) Guttenberg Discontinuity
d) Mohorovicic Discontinuity

Que 13. Which discontinuity separates the outer core from the inner core?
a) Conorod Discontinuity
b) Lehmann Discontinuity
c) Guttenberg Discontinuity
d) Mohorovicic Discontinuity

Que 14. What happen to temperature and pressure towards earth interior?
a) Increases
b) Decreases
c) Constant
d) None

Que 15. Which layer of earth has the greatest volume and mass?
a) Mantle
b) Crust
c) Core
d) None

 

Answer of the MCQ on Earth's Layer/Structure of the Earth: 

1. (a),       2. (b),     3. (a),    4. (d),     5. (c),     6. (a),      7. (b),     8. (c),

9. (a),      10. (b),   11. (d),   12. (c),   13. (b),    14. (a),    15. (a)    




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