Earth Science

Human Impacts on the Earth Environment

Ozone Depletion

Study Tip
After learning how the ozone layer protects us on Earth, can you predict what would happen when ozone levels go down?

How the Ozone is Destroyed

  • Chlorofluorocarbons (CFCs), produced from pollution, float up to the stratosphere. They freeze into polar stratospheric clouds (PSC), which are broken down when the weather gets warm.
  • The broken down chlorine atom attaches to one oxygen molecule, leaving only O₂ behind.
Study Tip
After learning how the ozone layer protects us on Earth, can you predict what would happen when ozone levels go down?

The Ozone Hole

  • The ozone hole —a layer where the ozone is dangerously thin— is centered at the South Pole, and forms during springtime.
  • It was measured at 2 million square km in 1981, and had grown to 28 million square km in 2006. The size of the hole changes each year, depending on levels of PSCs.
  • The North Pole also has ozone depletion, but it is not enough to be considered a hole.
Polar stratospheric clouds
Polar stratospheric clouds

Effects of Ozone Loss

  • Ozone loss increases sunburns, cataracts (clouded lens), skin cancer, and vulnerability of the human immune system.
  • It also decreases crop yield and the productivity of phytoplankton.
Concept Check
  • Where is the ozone hole?
  • What are the effects of ozone loss?
  • How is the ozone destroyed?