The atmosphere is thick near the earth surface and thins out until it eventually merges with space. The five atmospheric layers are:
Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere

TROPOSPHERE
The lowest layer of the atmosphere is the troposphere. The Greek word ‘tropos’ means ‘turn’ or change. The layer extends upto 8kms at the pole and upto 18kms at the Equator.

The temperature decreases with increasing height. Almost all weather phenomenon take place in this layer. Hence it is called weather making layer. The upper limit of the troposphere is called tropopause.

STRATOSPHERE
Stratosphere lies above the troposphere. It extends to a height of about 50km above Earth surface. Since this layer is a concentration of ozone molecules, it is also referred as ozonosphere.

The temperature increases with increase in height in this layer. Large jet planes normally fly here. The upper limit of the stratosphere is called as stratosphere.

MESOSPHERE
Mesosphere extends between 50km and 80km. The temperature decreases with increasing height.

Most of the meteors nearing the Earth, get burned here. The upper most limit of the mesosphere is the mesosphere.

THERMOSPHERE
Thermosphere exists above the mesosphere. It extends to about 600km. The composition of gases in the lower thermosphere is more or less uniform, hence it is called ‘Homosphere’. The upper portion of the thermosphere has uneven composition of gases and hence it is referred as ‘Heterosphere’.

Here the temperature increases with increasing height. Ionosphere is a layer of the thermosphere that contains Ions and free electrons. Radio waves transmitted from earth are reflected back to Earth from this layer.

EXOSPHERE
The uppermost layer of the atmosphere is called exosphere. This layer is extremely rarefied with gases and gradually merges with the outer space. This zone is characterized by aurora Australis and aurora borealis.