Composition of the Atmosphere - Facts for UPSC

The earth’s atmosphere is a life-supporting atmosphere. Questions can sometimes be asked in UPSC prelims regarding the composition of the earth’s atmosphere. Hence, IAS Exam aspirants should know about the relevant facts about the atmosphere’s composition.

Salient Facts about Earth’s Atmosphere

Atmosphere is described as the air that surrounds the earth.

  1. The thickness of the earth’s atmosphere is about 480 kms. 99 percent of the thickness lies upto the hieght of 32 kms from the earth.
  2. With increasing altitude, the air pressure decreases.
  3. The atmosphere has mixture of gases that sustains the life on earth.
  4. The earth gravity helps holding the atmosphere in place.
  5. The major role of the atmosphere is to contain the entry of ultraviolate rays.

As per the NASA, the composition of the earth’s atmosphere is as mentioned below:

  1. Nitrogen — 78 percent
  2. Oxygen — 21 percent
  3. Argon — 0.93 percent
  4. Carbon dioxide — 0.04 percent
  5. Trace amounts of neon, helium, methane, krypton and hydrogen, as well as water vapor

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 Composition of the atmosphere

  • The atmosphere is comprised of several gases, dust particles, and water vapour.
  • The presence of oxygen becomes insignificant at the height of 120 km from the surface of the earth with respect to the composition of the atmosphere.
  • Water vapour and Carbon dioxide occur only up to 90 km.

Composition of the atmosphere – Ozone gas

  • Present around 10-50 km above earth surface and acts as a sieve, absorbing UV (ultraviolet rays) from the sun.
  • Ozone averts the harmful rays from reaching the surface of the earth.

Composition of the atmosphere – Water Vapour

  • Water vapour is a variable gas, declines with altitude.
  • It also drops towards the poles from the equator.
  • It acts like a blanket letting the earth to neither to become too hot nor too cold.
  • It also contributes to the stability and instability in the air.

Composition of the atmosphere – Dust particles

  • Dust particles are in higher concentration in temperate and subtropical regions due to dry winds in contrast to the Polar Regions and equatorial regions.
  • They act as hygroscopic nuclei over which water vapour of atmosphere condenses to create clouds.

Composition of the atmosphere – Nitrogen

  • The atmosphere is composed of 78% nitrogen.
  • Nitrogen cannot be used directly from the air.
  • Biotic things need nitrogen to make proteins.
  • The Nitrogen Cycle is the way of supplying the required nitrogen for living things.

Composition of the atmosphere – Oxygen

  • The atmosphere is composed of 21% oxygen.
  • It is used by all living things and is essential for respiration.
  • It is obligatory for burning.

Composition of the atmosphere – Argon

  • The atmosphere is composed of 0.9% argon.
  • They are mainly used in light bulbs.

Composition of the atmosphere – Carbon Dioxide

  • The atmosphere is composed of 0.03% carbon dioxide.
  • Plants use it to make oxygen.
  • It is significant as it is opaque to outgoing terrestrial radiation and transparent to incoming solar radiation.
  • It is also blameable for the greenhouse effect.

Composition of the atmosphere (UPSC Notes):- Download PDF Here

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