Layers of atmosphere

Earth has four Sphere

1. Lithosphere (land)
2. Hydrosphere (water)
3. Biosphere (living things)
4. Atmosphere (air)

Composition of Gases in the atmosphere

Elements	Formula	Percentage by Volume
Nitrogen	N2	78.08
Oxygen	O2	20.95
Argon	Ar	0.93
Carbon dioxide	CO2	0.036 or 0.04
Neon	Ne	0.002
Helium	He	0.0005
Krypto	Kr	0.001
Xenon	Xe	0.00009
Hydrogen	H2	0.00005
Ozone	O3	0.0006
Water Vapour		1% at sea level and 4% at the entire atmosphere

Layers of Atmosphere

1. Troposphere

2. Stratosphere

3. Mesosphere

4. Thermosphere or Ionosphere

5. Exosphere

Troposphere

1. This is the first layer that extends height up to 18 km and on pole 8 km.  
2. 165 m up decreases 1-degree celsius.
3. 1 km up – 6.5 decree centigrade less
4. Almost all the weather phenomena like rainfall, fog, and hailstorm occur in this layer.
5. The density of air decreases with height and so the heat absorbed is less.
6. Almost 90% of the gases were present in this sphere.
7. The height at which the temperature stops decreasing is called tropopause. Here temperature may be -58 degrees Celsius. 

Stratosphere

1. This is the second layer of the atmosphere
2. Extend from the tropopause to about 50 km.
3. First 20 km the temperature is constant then the temperature starts to increase due to the absorption of the ultraviolet radiation of the sun by the ozone present in this layer.
4. The temperature slowly increases to 4 degrees Celsius.
5. This layer is almost free from clouds and associated weather phenomena, making conditions most ideal for flying airplanes.

Mesosphere

1. The mesosphere extends from 50 km to 80 km.
2. Here, again temperature starts to decrease and falls as low – as 90.
3. It has the atmosphere’s lowest temperature. Meteorites burn up in this layer on entering from the space.

Thermosphere or Ionosphere

1. The thermosphere extends according to NASA extends to a height of about 513 km, According to NCERT – 400 km.
2. In this layer temperate rapidly increases and goes up to 2482.22 degrees Celsius.
3. D – Layer (Longwave), E- Layer (Kennely-Heavyside layer) short wave and medium wave. F – Layer (Appleton layer); G – Layer (long/medium/short wave).
4. This layer helps in radio transmission – radio waves transmitted from the earth are reflected back to the earth by this layer.

Exosphere

1. This is the outermost layer of our atmosphere.
2. Its extent is up to 960 km.
3. The temperature in this zone is about 300  to 1650    
4. This layer has very thin air.
5. Gases like helium and hydrogen float into space from here.