Secondary 2 Geography-Ozone Depletion


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Secondary 2 Geography-Ozone Depletion

  1. 1. Ozone Depletion
  2. 2. Introduction • Ozone molecules are natural substance in the upper atmosphere known as the stratosphere. It is in between 19 to 30 kilometer above the Earth surface. • The ozone layer helps shield harmful Ultraviolet Rays from the sun. • Ozone layer is measured in Dobson Unit. The normal thickness of the ozone layer should be 300 Dobson Unit • A slow and steady declination of the ozone layer is known as ozone depletion
  3. 3. Cause of Ozone Depletion • Doctor Molina and Rowland found out that chlorofluorocarbon is depleting the ozone layer in 1974. However, no one believe them until the ozone layer in Antarctic depletes in 1985 • Chlorofluorocarbon are man-made chemicals that contains chlorine which depletes the ozone layer. • Chlorofluorocarbon would be released to the atmosphere
  4. 4. • The chlorofluorocarbon would release chlorine when sunlight break them down • The chlorine would change the ozone layer into oxygen when the chlorine hit them • Ozone depletion would happen if the ozone layer is depleted faster than it can recover. There would be an ozone hole if the ozone layer falls below 200 DU • Chlorofluorocarbon can remain in the atmosphere for 20 to 100 years
  5. 5. • The ozone layer is depleting at a rate of 3% from 1979 to 1991 • Places like North America, Europe, Russia, Australia, New Zealand and South America is facing Ozone depletion • Global warming is predicted to let the hole in the ozone layer at Antarctic grow larger in the decades
  6. 6. Consequence of Ozone Depletion • The ozone layer help shield Ultraviolet Rays. Without it, there will be dangers including – Risk in human health – Disruption of ecosystem in marine – Disruption in plant growth
  7. 7. Risk in human health • Ultraviolet rays can cause skin cancers. It is predicted that more than 60000000 Americans will get skin cancer because of the Ultraviolet rays • Ultraviolet rays may also damage immune system. People are prone to have infectious diseases. It can even cause eyes disorder
  8. 8. Disruption of ecosystem in marine • In the ocean, plankton is the foundation of marine food webs. There are the main source of food in the ocean. • The Plankton don’t have protective outer layers, so they were highly sensitive to Ultraviolet rays. Marine life would be disrupted if the plankton were killed. • Marine animals will die when exposed to Ultraviolet radiation. Food web is disrupted as predators have no preys to prey on.
  9. 9. Disruption in plant growth • The Ultraviolet rays can kill plants which are the food producer. This would disrupt food web. Plants also help redeem oxygen. • Crops like rice would also die. This could cause shortage of food