The Ozone Shield Section 13.2

1. The Ozone ShieldSection 13.2 Objectives: Explain how the ozone layer shields the Earth from much of the sun’s harmful radiation. Describe the damaging effects of ultraviolet radiation. Explain why the threat to the ozone layer is still continuing today.

2. The Ozone Layer: • An area in the stratosphere where ozone is highly concentrated • Absorbs most of the UV light from the sun • Acts like a sunscreen for Earth’s inhabitants

3. Chlorofluorocarbons (CFC’s): • Are nonpoisonous, nonflammable, and non-corrosive • Were used as coolants in refrigerators and air conditioners • Also used as propellants in spray cans • Under ideal conditions, 1 chlorine atom can destroy 100,000 ozone molecules

4. The Ozone Hole: • A thinning of stratospheric ozone that occurs over the poles in the spring

5. Effects of Ozone Thinning

6. Protecting the Ozone Layer • 1987 – Montreal Protocol – nations agreed to limit production of CFC’s • 1992 – developed countries agreed to eliminate most CFC’s by 1995 • Ozone depletion continues because CFC’s remain active in the stratosphere for 60-120 years

7. Know for Test! • P.338 (3-5)