Based primarily on the temperature pattern, earth’s atmosphere can be roughly divided into four major zones or layers.

1. The troposphere:

The zone immediately above earth’s surface is known as the troposphere which extends up to a height of about 20 kms above the equator and about 8 kms over the poles. The temperature in this zone drops with height being as low as -60°C at its upper extremity.

2. The stratosphere:

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The layer next to troposphere is called the stratosphere. It is about 30 kms in thickness and is a very important zone of atmosphere as it contains the vital ozone layer. The temperature in this zone rises from -60°C to about 0°C in its upper layers. The rise in temperature is due to the formation of ozone under the influence of ultra-violet radiations.

3. The mesosphere:

It is a zone of about 40 kms in thickness which lies next to the stratosphere. This zone is characterised by gradual decline in temperatures to about -90°C.

4. The thermosphere:

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It is the zone next to mesosphere in which temperature increases with height. Most of the constituents of this zone are in ionized state.