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STRUCTURE OF THE ATMOSPHERE, , Our atmosphere is divided into five layers starting from, the earth’s surface. These are Troposphere,, Stratosphere, Mesosphere, Thermosphere and, Exosphere (Fig. 4.2)., , Troposphere: This layer is the most important layer of, the atmosphere. Its average height is 13 km. The air, we breathe exists here., Almost all the weather, phenomena like rainfall,, fog and hailstorm occur in, this layer., , Stratosphere: Above the, troposphere lies the, stratosphere. It extends up, to a height of 50 km. This, layer is almost free from, clouds and associated, weather phenomenon,, making conditions most, ideal for flying aeroplanes., One important feature of, stratosphere is that it, contains a layer of ozone, gas. We have just learnt, how it protects us from, the harmful effect of the, sun rays., , pea, , Mesosphere: This is the, third layer of the, atmosphere. It lies above, the stratosphere. It extends, up to the height of 80 km., Meteorites burn up in, this layer on entering from, the space., , Thermosphere: In, thermosphere temperature, rises very rapidly with, increasing height., Ionosphere is a part of this, Fig. 4.2: Layers of the Atmosphere layer. It extends between, , uk ENVIRONMENT