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CLASS: SS 1           



Outer Structure of the earth

(a) Major Spheres of the Earth:

  • The Atmosphere
  • The Lithosphere
  • The Hydrosphere
  • The Biosphere.

(b) Relationship between the three major spheres (atmosphere, lithosphere and hydrosphere) (c) Relevance to Human activities.

Inner Structure of the earth

  • The Crust – SIAL and SIMA, Mohorovisic-discontinuity
  • The Mantle
  • The Core.


The structure of the earth is grouped into the outer structure and the internal structure of the earth. The outer structures of the earth consist of four zones or layers. Three are made up of physical constituents, which consist of the three different states of matter; which are solid, liquid and gaseous substances. While the fourth which is made up of the Biological constituents, consist of living organisms.

These outer structures of the earth include: – i. The Atmosphere, ii. The Lithosphere, iii. The Hydrosphere and iv. The Biosphere.

The External and Internal Structure of the Earth

THE ATMOSPHERE: The atmosphere is the portion of the earth that consists of gases. These mixtures of various gases and other matter, forms and envelops round the earth. The atmosphere is loosely called “Air”, around us but in the real fact the atmosphere contain more than just air. The pure air in it, is made up of the following gases:

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Nitrogen ——– ———————–78%

Oxygen ——————————— 21%

Argon and Neon (rare gases——- 0.93%

Carbon dioxide ———————-0.03%

The atmosphere also contains water vapour and dust particles. The atmosphere also is made up of four layers which include:

  1. the troposphere,
  2. the stratosphere,
  3. the mesosphere and

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