Geography
Answer
The atmosphere consists of concentric layers of air. On the basis of the characteristics of temperature and air pressure, it can be divided into four thermal layers — Troposphere, Stratosphere, Mesosphere and Thermosphere. The Thermosphere is divided into Ionosphere and Exosphere. The four layers are briefly described below:
- Troposphere — It is the lowermost and densest layer. Its height varies from 18 km at the Equator to 8 km at the Poles.
- Stratosphere — This layer lies above the Troposphere. It extends to a height of 50 km from sea level.
- Mesosphere — This layer lies above the Stratosphere. It extends to a height of 80 km from ground level.
- Thermosphere — It lies above Mesosphere and consists of two parts:
- Ionosphere — It extends up to a height of about 400 km.
- Exosphere — It is the uppermost layer of the atmosphere. It lies between 400 to 1500 km above the earth.