Presentation on theme: "The Ozone Shield The ozone layer is an area in the stratosphere where ozone is highly concentrated. It absorbs most of the UV rays from the sun. Ozone."— Presentation transcript:
The Ozone Shield The ozone layer is an area in the stratosphere where ozone is highly concentrated. It absorbs most of the UV rays from the sun. Ozone – molecule made of 3 oxygen atoms.
Ozone Depletion Chlorofluorocarbons (CFCs) – human-made chemical once used as: – Coolants in refrigeration & air conditioning – Gassy fizz for making plastic foams – Propellant in spray cans CFCs –break down in the stratosphere and destroy ozone molecules. –A single CFC can destroy 100,000 ozone molecules. –Remain active in the stratosphere for up to 120 years.
The Ozone Hole The ozone hole is a thinning of stratospheric ozone that occurs over the poles during the spring.
Why is the ozone hole over the poles? It is so cold at the poles during winter that clouds are able to form in the stratosphere (polar stratospheric clouds). CFCs travel into the stratosphere on these clouds.
Negative Effects of Ozone Depletion Humans & Land Animals Skin cancers Premature aging of skin Cataracts Weakened immune system Amphibians Death of eggs Genetic mutations Reduced Populations Marine Life Disruption of food chain (death of surface plankton & photosynthesizers) Land Plants Photosynthesis interference Reduced crop yields
Protecting the Ozone Layer Montreal Protocol – agreement among nations to limit the production of CFCs. Developed nations agreed to eliminate CFCs by –Aerosol cans no longer use CFCs as propellants –Air conditioners and refrigerators are CFC-free