1. The Ozone Shield
13.2

2. The Ozone Shield
Ozone is a layer of the stratosphere that absorbs UV light from the sun (like sunscreen).

4. Chemicals That Cause Ozone Depletion
CFC’s = chlorofluorocarbons
When these break apart in the ozone, they destroy parts of it.

6. thinning of ozone during spring over the north and south poles
caused by cold temperatures and CFC’s

7. The Ozone Hole
(credit: NASA)
2005 Ozone Layer Hole

9. How Does the Ozone Hole Form?

10. How Does the Ozone Hole Form?
During the dark polar winter, strong circulating winds over Antarctica, called the polar vortex, isolate cold air from surrounding warmer air.
Air within the vortex is extremely cold.

11. Polar stratospheric clouds form at high altitudes.
composed of water vapor and nitric acid

12. On the surfaces of polar stratospheric clouds, the products of CFCs are converted to molecular chlorine.

13. When sunlight returns to the South Pole in the spring, molecular chlorine is split into two chlorine atoms by UV radiation.
The chlorine atoms rapidly destroy ozone.

14. Ozone from pollution may stay in the troposphere and react with other chemicals.

15. Effects of Ozone Thinning on Humans
UV light damages DNA
Effects of Ozone Thinning on Humans

16. Causes: increase in skin cancer

18. Premature aging of skin

19. Cataracts – clouding of the lens

20. Effects of Ozone Thinning of Animals and Plants

21. Kills phytoplankton and disrupts food chain

22. Kills amphibian eggs

23. Interferes with photosynthesis in plants

24. Protecting the Ozone Layer
1987 – Montreal Protocol
Limits the use of CFCs

26. Review – The Ozone Shield
What is the ozone layer and what is its function?
What is ozone made up of?
What are CFC’s?
How do CFCs affect ozone?
What is the ozone hole?
What is a polar vortex?
Explain how does the ozone form?
Name 3 ways ozone thinning affects humans.
Name 3 ways ozone thinning affects plants and animals.
How are we protecting the ozone today?

27. Chemicals That Cause Ozone Depletion
CFC’s  chlorofluorocarbons
When these break apart in the ozone they destroy parts of it.
Ozone Hole: thinning of ozone during spring over the north and south poles.
(caused by cold temperatures + CFC’s)
4. Problems: damage to plant & animal life

28. How Does the Ozone Hole Form?
You may be thinking, “If ozone is also being produced as air pollution, why does this ozone not repair the ozone hole in the stratosphere?”
The answer is that ozone is very chemically reactive.
Ozone produced by pollution breaks down or combines with other substances in the troposphere long before it can reach the stratosphere to replace ozone that is being destroyed.

29. How Does the Ozone Hole Form?
When sunlight returns to the South Pole in the spring, molecular chlorine is split into two chlorine atoms by UV radiation.
The chlorine atoms rapidly destroy ozone.
The destruction of ozone causes a thin spot, or ozone hole, which lasts for several months.