Earth’s changing atmosphere

Essential Question How does the atmosphere make life possible?

Earth's atmosphere

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

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

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

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

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