1. Book I, Chapter 1 “The Atmosphere”
Section 1, pages 4-9
“Characteristics of the Atmosphere”

2. Atmosphere – A mixture of gases that surrounds the Earth.
Composition of the Atmosphere:
Gases:
78% Nitrogen
21% Oxygen
1% Argon, CO2,
Water Vapor &
other Gases
Small amts. of Solids
& Liquids (ex. dust)

3. Air Pressure – A measure of the force with which the molecules push on a surface.
What causes air pressure?
Air pressure is caused as gravity pulls molecules in the atmosphere toward the Earth.

4. Example of Air Pressure
Popping of your ears. As an airplane goes up and down at different elevations the air pressure outside your ears changes, but the pressure inside your ears stays the same.

5. Altitude – The height of an object above the Earth’s surface.
Gravity pulls the molecules toward the Earth’s surface.
The farther away from the Earth’s surface, the pressure decreases.
Altitude = Pressure
Up Down

6. Layers of the Atmosphere – 4 layers based on temperature.
1. Troposphere (tropo means “change”)
Lowest layer of atmosphere (closest to Earth)
Weather take place here
Begins at surface of Earth & extends out 4-10 miles
Layer where we live also known as lower atmosphere
Temperature decreases with height

7. 2. Stratosphere (strato means “layer”)
Above the troposphere
Air very thin w/ little moisture
Extends miles above Earth’s surface
Temperature rises w/ increasing altitude, but still
well below freezing
Ozone layer located here
Ozone – made of 3 oxygen atoms & absorbs solar energy in form of UV rays in the ozone layer. This warms the air & protects life on the Earth’s surface.

8. 3. Mesosphere – (meso means “middle”)
Above the stratosphere
About miles above surface of the Earth
Coldest layer w/ temps as low as -93º C
Air is thin and molecules are very far apart
Strong wind storms
4. Thermosphere – (thermo means “heat”)
The uppermost layer
From miles above surface of the Earth
Temp increases w/ height as high as 1,700º C
Doesn’t feel hot b/c air particles are too far apart for energy to be transferred

9. Air Temperature & Altitude
Air temperatures change as altitude increases.
Temperature changes mainly from the way solar energy is absorbed as it moves downward through the atmosphere.
Some gases in the atmosphere absorb solar energy more than others, and warm the atmosphere.

10. What does air pressure, temperature, and layers of the atmosphere have to do with weather?
1. Areas of high pressure usually have clear skies, and areas of low pressure usually have clouds. 2. Our weather takes place in the lower layer of the atmosphere called the troposphere. 3. The movement of air tends to blow from high pressure to low pressure areas. 4. Changes in temperature lead to changes in air pressure, bringing different kinds of weather.

11. Made by Mrs. Villone Austintown Middle School Credits given to Holt, Rhinehart and Winston Science Textbook Company