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 the relevant facts about the atmosphere’s composition.
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Salient Facts about Earth’s Atmosphere
The atmosphere is described as the air that surrounds the earth.
- The thickness of the earth’s atmosphere is about 480 km. 99 percent of the thickness lies up to the height of 32 km from the earth.
- With increasing altitude, the air pressure decreases.
- The atmosphere has a mixture of gases that sustains life on earth.
- The earth’s gravity helps hold the atmosphere in place.
- The major role of the atmosphere is to contain the entry of ultraviolet rays.
As per NASA, the composition of the earth’s atmosphere is as mentioned below:
- Nitrogen — 78 percent
- Oxygen — 21 percent
- Argon — 0.93 percent
- Carbon dioxide — 0.04 percent
- Trace amounts of neon, helium, methane, krypton and hydrogen, as well as water vapour
|Structure of Earth’s Atmosphere||Important Points about Atmosphere|
|Atmospheric Pressure||Heating and Cooling of the Atmosphere|
Composition of the Atmosphere
The atmosphere is a layer of gas or layers of gases that envelope a planet and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low.
- The atmosphere of earth is composed of nitrogen (78%), oxygen (21%), argon (0.9%), carbon dioxide (0.04%) and trace gases. A variable amount of water vapour is also present in the atmosphere (approx.1% at sea level) and it decreases with altitude.
- Carbon dioxide gas is largely responsible for the greenhouse effect. It is transparent to the incoming solar radiation but is opaque to the outgoing terrestrial radiation. It absorbs a part of terrestrial radiation and reflects back some of it towards the earth’s surface.
- Dust particles are also present in the atmosphere. They originate from different sources like fine soil, smoke-soot, pollen, dust and disintegrated particles of meteors. Dust and salt particles act as hygroscopic nuclei around which water vapour condenses to produce clouds.
Composition of the Atmosphere – Ozone Gas
- Present around 10-50 km above the earth’s surface and acts as a sieve, absorbing UV (ultraviolet rays) from the sun.
- Ozone averts 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 from becoming neither 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 concentrations in temperate and subtropical regions due to dry winds in contrast to the polar and equatorial regions.
- They act as hygroscopic nuclei over which water vapour of the 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.
Also read: Oxygen Cycle
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 one of the gases responsible for the greenhouse effect.
Structure of the Atmosphere
The atmosphere is divided into five different layers depending upon the temperature conditions – troposphere, stratosphere, mesosphere, thermosphere and exosphere.
Composition & structure of the atmosphere (UPSC Notes):- Download PDF Here