1. A mixture of gases surrounding the Earth.
Atmosphere
A mixture of gases surrounding the Earth.

2. Atmosphere Composition
Composition of Earth’s Atmosphere:
78% Nitrogen
21% Oxygen
1% Other

3. Air Pressure All the molecules in the air have mass.
Air molecules are pulled to the Earth’s surface by gravity.
Since air molecules are pulled to the Earth’s surface, sea level is where air is most dense.

4. Air Pressure
Since air molecules sink to the Earth’s surface, that is where air pressure is the highest.

5. Layers of the Atmosphere
Troposphere
Lowest layer of the atmosphere
Most dense layer of atmosphere
Where weather happens
Temperature decreases as altitude increases

6. Layers of the Atmosphere
Stratosphere:
Layer above the troposphere
Temperature increases as altitude increases. This occurs because the ozone layer, found at the top of the stratosphere, absorbs ultraviolet radiation from the sun, which warms the air.

7. Layers of the Atmosphere
Mesosphere:
The layer between the stratosphere and the thermosphere.
Temperature decreases as altitude increases.
The Mesosphere is the coldest layer of the atmosphere.

8. Layers of the Atmosphere
Thermosphere:
The uppermost layer of the atmosphere.
Temperature increases as altitude increases. Atoms of nitrogen and oxygen absorb high-energy solar radiation and release thermal energy.
Show Visual Concepts

9. Atmospheric Heating