Chapter 9 - Atmosphere & Mountains

Composition of Atmosphere

Gas	Percentage
Nitrogen	78.9
Oxygen	20.95
Argon	0.93
Carbon Dioxide	0.03

Structure Of Atmosphere

• Ozone is found between 10-50 Km
• CO2 & water vapour available upto 90 Km
• Water Vapour decreases from Equator to pole, act as a blanket & allow earth not to become too hot or too cold
• Dust Particles act as Hygroscopic Nuclie around which water vapour condence to produce cloud.

Earth's atmosphere can be divided into 4 major layers from bottom to top

1. Troposphere

• The troposphere is the lowest layer of Earth's atmosphere. It extends from Earth's surface to an average height of about 12 km, although this altitude actually varies from about 9 km at the poles to 17 km at the equator.
• The temperature usually declines with increasing altitude i.e. 1degree decrease after 165 m in the troposphere because the troposphere is mostly heated through energy transfer from the surface.
• All weather & climate activities occurs in this layer i.e. Lightning, thundering
• All water vapour & dust particles are present in this layer
• The troposphere is bounded above by the tropopause, a boundary marked by stable temperatures.

     2. Stratosphere

• It is the 2nd lowest layer of atmosphere which extends from 12 km to 50 km & terminates at Stratopause.
• It contains the Ozone layer, which protects us from harmful UV rays from Sun.
• It is this layer that provides a stable environment for Jet powered aircrafts to fly with out any turbulence.
• In this layer temperature rises with increasing altitude.

     3. Mesosphere

• It extends from 50 km to 80 km & terminates at Mesopause which is the coldest place having temperature of -100 degree Celsius.
• In this layer temperature decreases with the increasing altitude
• In this layer most of the Meteors burn up & mostly accessed by Sounding rockets

     4. Thermosphere

• It extends from 80 km to 400 km which contains Ionosphere that is usually used for transmission purpose.
• In this the Temperature rises with the increasing temperature.
• This layer terminates at Exosphere where we can find most of the satellites orbiting.

Mountain Types

1. Fold Mountains

• They were formed when the rock of the crust of earth folded under stress, mainly by forces of compression. On this basis they are further classified as 

i. Young Fold Mountains -: Himalayas, Alps, Rockies, Andes
ii. Old Fold Mountains -: Aravali (oldest), Appalachians (N America), Ural (Russia)

2. Block Mountains

• They were formed when great block of earth's crust are raised or lowered. The Land between two parallel faults either raises called Block Mountains or Horsts or depresses called Rift Valley or Graben

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• Examples -: Rhine Valley, Vosges Mountains (Europe)

3. Volcanic Mountains

• They were formed as a result of volcanic erruption & outflow of Lava therefore also known as Mountains of Accumulation
• Example -: Mt Kilimanjaro (Africa's Highest), Mt Fujiyama

4. Relict Mountain

• They were carved out as a result of Erosion of plateaus & high planes by various agents of erosion  
• Examples -: Highlands Scotland, Sierras of Spain, Catskill Mountain of New York, Nilgiri, Paraasnath, Girnar, Rajmahal