Layers of the atmosphere


      To identify the five main layers of the Earth's atmosphere

What is the atmosphere ?

      An atmosphere is the layers of gases surrounding a planet. Earth's atmosphere is composed of about 78% nitrogen, 21% oxygen and one percent other gases. The Earth's atmosphere extends up to a height of about 1,600 kilometers.

Structure of Earth's atmosphere

     The Earth's atmosphere is divided into five layers starting from the earth’s surface based on composition, temperature and other properties. These are Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere. See Figure 1. 


                                                                         Figure 1: Layers of the atmosphere


     This layer is the most important layer of the Earth's atmosphere. Its average height is 13 kilometers. The air we breathe exists here. Almost all the weather phenomena, like rainfall, fog, and hailstorm, occur in this layer.


     Above the troposphere lies the stratosphere. It extends up to a height of 50 km. T his layer is almost free from clouds and associated weather phenomena, making conditions most ideal for flying aeroplanes. One important feature of the stratosphere is that it contains a layer of ozone gas. We have just learned how it protects us from the harmful effects of the sun's rays.


     This is the third layer of the atmosphere. It lies above the stratosphere. It extends up to a height of 80 kilometers. Meteorites burn up in this layer upon entering from space.


     In the thermosphere, temperature rises very rapidly with increasing height. The ionosphere is a part of this layer. It extends between 80-400 km. This layer helps with radio transmission. In fact, radio waves transmitted from the earth are reflected back to the earth by this layer.


    The uppermost layer of the Earth's atmosphere is known as the exosphere. This layer has very thin air. Light gases like helium and hydrogen float into space from here.