Natural Resources — Science STD 9 — Question

Atmosphere is divided into five distinct layers: Troposphere, stratosphere, mesosphere, thermosphere and exosphere.

1. Troposphere is the lowest region of atmosphere which contains air and is subject of differential heating. It extends from the surface of the earth upto 8-20kms. Many important climatic events such as cloud formation, lightning, thundering etc all takes place in the troposphere.
2. The Stratosphere extends from the top of the troposphere up to around 31 miles (50km) above the Earth's surface. In this region the temperature increases with height. Heat is produced due to the formation of ozone.
3. The mesosphere extends from the top of the stratosphere to about 53 miles (85km) above the earth. The gases, including the oxygen molecules, continue to become thinner and thinner with height.
4. Above the mesosphere the thermosphere extends up to near 375 miles (600km) above the earth. This layer is known as the upper atmosphere. As such, incoming high energy ultraviolet and x-ray radiation from the sun, absorbed by the molecules in this layer, causes a large temperature increase.
5. Exosphere exists above the thermosphere.