Atmosphere & their Structure

Physical Science

Atmosphere & their Structure


  •  It is a colourless, tasteless and odourless mixture of gases that
    surround the earth.
  •  It extends up to a height of about 1600 km.
  • However 99 per cent of total mass of the atmosphere is within
    40 km from the earth.
  • Structure of atmosphere: Based on vertical temperature differences
I. Troposphere:
  • It is the lower layer of atmosphere
  •  Extending up to a height of 8 to 18 km from the earth surface. (RPSC, AA0-09).
  • Temperature decreases with increase in altitude at the rate of 6 ‘V /km.
  • It influences earth climate.
  • It is dense part of atmosphere, contains 85 per cent of the atmosphere’s mass.
  •  All weather phenomena like clouds, rain, mist, fog, dew etc. occur in troposphere. (JRF, Ph. D -09)
2. Stratosphere:
  •  It lies beyond the height of 8 to 18 km extending up to 50 km.
  •  Warmest layer, Uniform temperature with altitude.
  • It is the actual seat of most of the photochemical reactions in air.
  • Presence of Ozone layer, hence also called ozonosphere
3. Mesosphere:
  •  It lies above the stratosphere; a height of 50 km extending up to 80 km from the earth surface.
  •  Cold region.
  • Strong decrease in temperature with increase in altitude.
4. Thermosphere:
  •  It is the outermost layer called exosphere.
  •  From earth surface extending a height of 80 km up to 1600 km.
  •  The lower layer of thermosphere is called ionosphere.
  •  Long distance radio communication is made possible through this ionized layer.
  •  Temperature increase with altitude.
Composition of atmospheric air:  (Gases Volume  in %)
  • Nitrogen -78.08%
  • Oxygen -20.95%
  • Argon – 0.93% (RPSC,AA 0-09)
  • Carbon dioxide – 0.03%
 Composition of soil air :
  •  Nitrogen percentage is more or less same as in atmosphere.
  •  Oxygen levels decrease as compared to atmosphere.
  •  CO2 levels will be nearly 8-10 times more (0.25%) as compare to atmosphere.

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