GK - Structure of Atmosphere


  • The structure of the atmosphere is classified into the following layers −

    • Troposphere: 0 to 12 km

    • Stratosphere: 12 to 50 km

    • Mesosphere: 50 to 80 km

    • Thermosphere: 80 to 700 km

    • Exosphere: 700 to 10,000 km


  • Troposphere is the closest to the Earth’s surface and contains water vapor (clouds), moisture, dust, etc.

  • Most of the weather phenomena take place in Troposphere.

  • Height of the Troposphere varies i.e. at the equator, it is measured about 18 km and at the poles, it is 12 km.

  • Tropopause is the transitional zone that separates Troposphere and Stratosphere.


  • Stratosphere is the second-lowest layer of the Earth’s Atmosphere that goes up to 50 km.

  • Stratosphere contains Ozone (O3) Layer that absorbs the ultraviolet rays (coming through the Sun rays) and protects life on the Earth.

  • As the ultraviolet radiation absorbs in Stratosphere, therefore the temperature rises with increasing altitude.

  • The Stratopause is the transitional zone that separates Stratosphere and Mesosphere.


  • Mesosphere, present above the Stratosphere, extends up to (from 50 km to) 80 km.

  • Temperature in the Mesosphere decreases with increasing altitude.

  • Mesopause is the transitional zone that separates Mesosphere and Thermosphere.


  • Above the Mesosphere, Thermosphere is the second-highest layer that starts at the altitude of 80 km and extends up to (roughly) 700 km (however, it varies between 500 and 1000 km).

  • The lower part of the Thermosphere (roughly between 80 km and 550 km) contains ions and known as Ionosphere.

  • The temperature of the Thermosphere rises with increasing altitude.

  • Thermopause is the transitional zone that separates Thermosphere and Exosphere.


  • Exosphere is the highest or outermost layer of the Earth’s atmosphere that extends (starting from 700 km altitude) up to 10,000 km where it ultimately merges into the solar wind.

  • Major constituents of the Exosphere are helium, hydrogen, nitrogen, oxygen, and carbon dioxide.

  • The phenomena of Aurora Borealis and Aurora Australis can be seen in the lower part of the Exosphere (merged with upper part of the Thermosphere).

Structure of Atmosphere
  • The Satellite (orbiting the Earth) is normally placed in the Exosphere (as shown in the image given above).