NCERT Notes: Geography- Structure of Atmosphere

Subject: Geography 
Category: The Fundamentals of Physical Geography 
Topic: Structure of Atmosphere

NCERT notes on important topics for the UPSC civil services exam. These notes will also be useful for other competitive exams like banking PO, SSC, state civil services exams and so on. This article talks about the Structure of Atmosphere.

Structure of Atmosphere

There are five layers in the structure of atmosphere depending upon temperature. These layers are:

  • Troposphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • Ionosphere
  • Exosphere
Troposphere
  • It is considered as the lowest layer of Earth’s atmosphere.
  • The troposphere starts at surface of the earth and goes up to a height of 7 to 20 km.
  • All weather occurs within this layer.
  • This layer has water vapour and mature particles.
  • Temperature decreases at the rate of 1 degree Celsius for every 165 m of height.
  • Tropopause separates Troposphere and Stratosphere.
Stratosphere
  • It is the second layer of the atmosphere found above the troposphere.
  • It extends up to 50 km of height.
  • This layer is very dry as it contains little water vapour.
  • This layer provides some advantages for flight because it is above stormy weather and has steady, strong, horizontal winds.
  • The ozone layer is found in this layer.
  • The ozone layer absorbs UV rays and safeguards earth from harmful radiation.
  • Stratopause separates Stratosphere and Mesosphere.
Mesosphere
  • The Mesosphere is found above the stratosphere.
  • It is the coldest of the atmospheric layers.
  • The mesosphere starts at 50 km above the surface of Earth and goes up to 85 km.
  • The temperature drops with altitude in this layer.
  • By 80 km it reaches -100 degrees Celsius.
  • Meteors burn up in this layer.
  • The upper limit is called Mesopause which separate Mesosphere and Thermosphere.
Thermosphere
  • This layer is found above Mesopause from 80 to 400 km.
  • Radio waves which are transmitted from the earth are reflected back by this layer.
  • The temperature increases with height.
  • Aurora and satellites occur in this layer.
Ionosphere
  • The lower Thermosphere is called the Ionosphere.
  • Ionosphere consists of electrically charged particles known as ions.
  • This layer is defined as the layer of the atmosphere of Earth that is ionized by cosmic and solar radiation.
  • It is positioned between 80 and 400 km above the Mesopause.
Exosphere
  • It is the outermost layer of the atmosphere.
  • The zone where molecules and atoms escape into space is mentioned as the exosphere.
  • It extends from the top of the thermosphere up to 10,000 km.

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