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

• 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

• 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

• 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.

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

• 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).

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