1. Earth’s changing atmosphere

2. Essential Question
How does the atmosphere make life possible?

3. Earth's atmosphere

4. Supports & Protects Life
What is the atmosphere?
Layer of air the surrounds Earth to support and protect life
Absorbs harmful radiation
Maintains Earth’s temperatures
Provides elements essential for life

5. Characteristics of the Atmosphere
Chemical and physical properties
The density of the atmosphere decreases with altitude
Most of the mass of the atmosphere is close to Earth’s surface

6. Materials in the Atmosphere
Most of the materials are gases
Nitrogen—78%
Promotes plant growth
Oxygen– 21%
Needed to perform life processes
Argon, CO2 and other gases—1%
Carbon Dioxide—plants use it to make food
Other gases include—dust, sea salt, and water droplets

7. Cycles in the Atmosphere
These cycles affect the atmosphere in varying ways:
1. Carbon cycle—photosynthesis and respiration
2. Nitrogen cycle—nitrogen fixing bacteria convert nitrogen into solid forms and solutions (decaying organisms use this nitrogen and release it into the soil)
3. Water cycle—water is constantly circulated between Earth’s surface and atmosphere by evaporation, condensation and precipitation

11. Sudden Changes
Dramatic events cause changes in the atmosphere and it takes time before the atmosphere is able to restore balance
Volcanic eruptions
Forest fires
Dust storms