The document outlines the four main layers of Earth's atmosphere: 1) The troposphere extends from the surface to about 12 km high and contains over 80% of the atmosphere's mass. Temperature decreases with altitude in this layer. 2) The stratosphere is between 10-50 km high, contains most of the atmosphere's ozone layer, and temperatures increase with altitude. 3) The mesosphere ranges from 50-80 km and is the coldest layer, protecting Earth from meteoroids. 4) The thermosphere extends from 80-320+ km, where temperatures can reach over 2000 degrees Celsius due to ultraviolet radiation. It contains the ionosphere and exosphere.

1. STRUCTURE OF ATMOSPHERE.
• Outline:
• Four Layers of atmosphere
• Troposphere.
• Stratosphere.
• Mesosphere.
• Thermosphere.

2. Structure of Atmosphere:
• The formation of Earth’s atmosphere is divided into
layers according to major changes in temperature.
• Gravity pushes the layers of air down on the earth’s
surface. This push is called air pressure.
• The 99% of the total mass of the atmosphere is below
32 kilometers.

3. Troposphere:
• It is the layer just above the earth’s surface whose distance is
between 0 – 12 km
• The bottom layer where temperature decreases with an
increase in altitude, is the troposphere.
• The troposphere contains over 80% of the mass of the
atmosphere, along with nearly all of the water vapor.
• The temperature drops about 6.5 degrees Celsius for every
kilometer above the earth’s surface.
• Tropopause separates Troposphere and Stratosphere.
• The temperature remains fairly constant here. We find the jet
stream here.

4. Stratosphere:
• The layer above the troposphere at a distance between
10 – 50km above the earth’s surface.
• In the lower part of the stratosphere temperature
remains fairly constant. This heat warms the
atmosphere in the layer at about (20–45 km) and gives
the stratosphere its characteristic temperature increase
with height.
• The stratosphere contains most of the ozone found in
the earth’s atmosphere.
• Ozone layer protect the Earth from Ultraviolet radiation
of the Sun.

5. Mesosphere:
• The layer above stratosphere at a distance between 50 –
80km above the earth’s surface.
• The temperature drops in this layer to about -100 degrees
Celsius.
• This is the coldest region of the atmosphere.
• This layer protects the earth from meteoroids. They burn
up in this area.
• The upper limit is called Mesopause which separates
Mesosphere and Thermosphere.

6. Thermosphere:
• The layer above the mesosphere at a distance between 80 -
320km.The air is very thin in this layer.
• Thermosphere means “heat sphere”. The temperature is
very high in this layer because ultraviolet radiation is
turned into heat.
• Temperatures often reach 2000 degrees Celsius or more.
• Radio waves that are transmitted from the earth are
reflected by this layer.
• The temperature increases with height.
• Aurora and satellites occur in this layer.

7. This layer contains:
Ionosphere:
• This is the lower part of the thermosphere. It extends
from about 80 to 550 km.
• The ionosphere consists of electrically charged
particles known as ions.
• This layer is defined as the layer of the atmosphere
of Earth that is ionized by cosmic and solar
radiation.

8. Exosphere:
• The upper part of the thermosphere.
• It extends from about 550 km for thousands of
kilometers.
• Air is very thin here.
• The zone where molecules and atoms escape into
space is mentioned as the exosphere.
• This is the area where satellites orbit the earth.

9. LAYERS OF ATMOSPHERE