A thinning shield

The idea

The ozone layer shields life by absorbing harmful UV radiation; when ozone is destroyed faster than it forms, as by human-made chlorofluorocarbons (CFCs), the layer thins, forming an ozone hole.

A shield with a hole

The ozone layer is like a shield for living things. Over the Antarctic, scientists found a place where this shield became very thin.

What might make a shield like this thin out?

• It is destroyed faster than it forms
• It is made of ice
• It runs out of Sun

The ozone story

Press Next step.

When the shield thins

The ozone layer works as a shield while enough ozone is there. CFCs destroyed ozone faster than it could form. A global agreement, the Montreal Protocol, reduced the use of CFCs, and the ozone layer is now slowly recovering.

The ozone layer shields life by absorbing harmful UV. When ozone is destroyed faster than it forms, as by human-made CFCs, the layer thins, forming an ozone hole.

Notes

The ozone layer absorbs harmful UV. If ozone is destroyed faster than it forms, as by CFCs, the layer thins and an ozone hole forms.

Check yourself

What does the ozone layer do for life on the Earth?

When does the ozone layer become thinner?

Which human-made chemicals caused severe ozone loss over Antarctica?

What happened after the Montreal Protocol reduced the use of CFCs?

• It traps heat leaving the surface. Trapping heat is done by greenhouse gases.
• It supplies oxygen for breathing. The ozone layer acts as a protective shield. It absorbs harmful UV.
• It absorbs harmful UV radiation from the Sun — correct. Yes!
• When ozone is destroyed faster than it is formed — correct. Yes!
• When ozone is formed faster than it is destroyed. Then the layer would not get thinner. It thins when ozone is destroyed faster than it forms.
• When it absorbs UV in the normal way. Absorbing UV is its normal job. It thins when ozone is destroyed faster than it forms.
• Carbon dioxide and methane. The chapter names chlorofluorocarbons (CFCs), used in refrigerators and aerosols, as the cause of the severe ozone loss.
• Chlorofluorocarbons (CFCs) — correct. Yes!
• Nitrogen and oxygen. These are the main gases of the atmosphere. CFCs caused the severe ozone loss.
• The ozone hole became larger. The chapter says the ozone layer is now slowly recovering.
• The ozone layer disappeared. The chapter says the ozone layer is now slowly recovering.
• The ozone layer is slowly recovering — correct. Yes!