1. The Atmosphere Envelope of gases that surrounds the Earth.
Dense part of atmosphere (97% of mass) lies within 30 km of the Earth.

2. Composition of Earth’s Atmosphere
1 %
0.03%
21%
78%

3. Atmospheric layers

4. The Troposphere The lowest layer. The densest layer.
Extends up to 8-15 kilometers.
Contains up to 75% of the mass of the atmosphere.

5. The Troposphere Composed of nitrogen (78%) and oxygen (21%).
Unstable due to convection
Weather occurs in this layer.
Temperature decreases with
altitude.

6. The Stratosphere The second layer. Occurs at 50 km. Ozone is present.
Very Stable.
Temperature increases as the altitude increases.
Air is thinner at the top of the stratosphere than it is at the sea level.
Only few clouds form in this layer.

7. The Mesosphere
Temperatures drop with increasing altitude to about -100°C.
The coldest of the atmospheric layer.