Question

Describe the structure of the atmosphere.

Write a paragraph about the structure of the atmosphere.

Answer 1

In the atmosphere, there are concentric layers of air. Each layer has a different density. The upper layers press down the lower one. So, the air of the lower layer is always heavier or denser, while the upper layers are thinner or less dense. In this way, about 90 percent of the mass of air lies within a height of about 20 km from the surface of the earth. On the basis of the characteristics of temperature and air pressure there exist four thermal layers of the atmosphere. They are Troposphere, Stratosphere, Mesosphere, and Thermosphere. The Thermosphere is divided into Ionosphere and Exosphere.

Answer 2

• Atmosphereric layers:

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

• Troposphere:

1. The lowest layer of the atmosphere is the troposphere.
2. This layer extends upto 8 kms at the poles and upto 18 kms at the equator.
3. The temperature decreases with increasing height.
4. It is called weather making layer.

•  Stratosphere:

1. Stratosphere lies above the troposphere.
2. It extends to a height of about 50 km above earth surface.
3. Since this layer is a concentration of ozone molecules, it is also referred as ozonosphere.
4. Large jet planes normally fly here.

• Mesosphere:

1. Mesosphere extends between 50 km and 80 km.
2. The temperature increases with increasing height.
3. Radial waves transmitted from earth are reflected back to earth from this layer
4. Most of the meteors nearing the earth, get burned here.

• Thermosphere:

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

• Exosphere:

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