Within this layer of air, at an altitude of about 20 to 30 km from the ground, there is an area that contains a large amount of a gas called ozone. This area is called the ozone layer.
Sunlight contains invisible rays called ultraviolet rays, which are very dangerous to living organisms. The ozone layer absorbs these ultraviolet rays.
Recently, however, it has been discovered that the CFC gases used by humans are reaching the skies above us and beginning to destroy the ozone layer. And, areas with very little ozone, such as those above the Antarctic and Arctic Circles, have begun to appear. These areas are called "ozone holes.
The word "hole" means "hole," so it is called an "ozone hole. As the ozone hole gets bigger and bigger, the amount of ultraviolet rays falling to the ground will increase, which will be very dangerous to life on the earth. This is why efforts are being made around the world to ban the use of chlorofluorocarbon gases.