Presentation on theme: "Ozone – molecule made of 3 oxygen atoms."— Presentation transcript:
1Ozone – molecule made of 3 oxygen atoms. The Ozone ShieldThe 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.
2Ozone DepletionChlorofluorocarbons (CFCs) – human-made chemical once used as:Coolants in refrigeration & air conditioningGassy fizz for making plastic foamsPropellant in spray cansCFCs –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.
3The Ozone HoleThe ozone hole is a thinning of stratospheric ozone that occurs over the poles during the spring.
4Why 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.
5Negative Effects of Ozone Depletion Humans & Land AnimalsSkin cancersPremature aging of skinCataractsWeakened immune systemAmphibiansDeath of eggsGenetic mutationsReduced PopulationsMarine LifeDisruption of food chain (death of surface plankton & photosynthesizers)Land PlantsPhotosynthesis interferenceReduced crop yields
6Protecting the Ozone Layer Montreal Protocol – agreement among nations to limit the production of CFCs.Developed nations agreed to eliminate CFCs by 1995.Aerosol cans no longer use CFCs as propellantsAir conditioners and refrigerators are CFC-free