Composition & Structure of Earth's Atmosphere
What is Atmosphere?
- Atmosphere is the layer of gas that surrounds a planet.
- It is made up of different layers such as Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.
- It also consists of gases like nitrogen, oxygen, carbon-dioxide, argon, etc.
- The composition of the gases present in the atmosphere is Nitrogen which is 78%, Oxygen is 21%, Argon is 0.93%, Carbon-dioxide is 0.04%, and other gases are present in very small amounts.
- The Atmosphere protects us form harmful UV radiations emitted by the Sun.
- Atmosphere scatters sunlight entering the Earth's Surface, helping in regulation of various processes such as water-cycle, regulation of temperature and other natural processes.
- Atmosphere protects living beings from harmful green-house gases by maintaining the optimal temperature of Earth's Surface.
Composition of the Atmosphere:
There are several gases present in atmosphere such as:
a) Nitrogen: It is the most abundant gas of the atmosphere and is about 78% of the total gases present in the atmosphere. It is the component of many primary acids such as nitric acids, ammonia, etc. Nitrogen is used as fertilizers which are helpful in growth of plants.
c) Argon: Atmosphere is composed of 0.93% Argon. Argon is used as filler in light bulbs to prevent the oxidation of the filament. Argon is used in the process of welding.
d) Carbon Dioxide: The atmosphere contains 0.03% of Carbon Dioxide. It is used by plants to make oxygen. It is also one of the gases responsible for greenhouse effect.
Structure of the Atmosphere:
- Troposphere is the lowermost layer of Earth's Atmosphere.
- The average height of troposphere is 12 km, whereas, the height is 8 km near the poles and about 18 km near the Equator.
- At the equatorial region its thickness is greatest because heat is transported to great heights by strong convection currents.
- All the climatic and weather changes takes place in this layer of atmosphere.
- The temperature decreases with increase in height, for every 165 m of height, the temperature decreases by 1℃.
- Tropopause is the zone that separates the troposphere from the stratosphere.
- The temperature in this zone is nearly constant( -80℃ over equator and about -45℃ over the poles )and hence, it is called the tropopause.
2] Stratosphere:
- It is the second layer of the atmosphere, just above the troposphere and extends up to a height of 50 km.
- This layer of atmosphere contains the Ozone layer, which absorbs Ultraviolet Radiations from the Sun and protect life forms from harmful UV rays.
- The UV radiations absorbed by the ozone layer gets converted into heat, that is why the stratosphere gets warmer with increasing altitude.
- Weather- related phenomena are absent in this layer of atmosphere, due to which Aeroplanes fly in Stratosphere for smooth ride.
- Stratopause separates the stratosphere and the mesosphere.
- Mesosphere is the third layer of Atmosphere which extends up to a height of 80 km.
- In this layer, the temperature decreases with increasing altitude and drops down to (-100℃) at a height of 80 km.
- Meteorites burn in this layer on entering the atmosphere form outer space.
- It's upper limit is known as Mesopause which separates mesosphere and thermosphere.
4] Thermosphere:
- The ionosphere lies within the atmosphere.
- It is located between 80 km and 400 km above the mesosphere and contains electrically charged particles called ions, hence the name ionosphere.
- In this layer of atmosphere, temperature increases with increase in height.
- Radio Waves transmitting from Earth are reflected back to the Earth by this layer.
- Satellites orbit in the upper part of thermosphere.
5] Exosphere:
- Exosphere is the outermost layer of atmosphere.
- There is no upper boundary of this layer as it merges out in space.
- This layer is about 10,000 km thick.
- It is also known as the first layer that acts as a shield of Earth from meteors, asteroids and cosmic rays.