The ozone layer is part of the stratosphere, a layer of the Earth’s atmosphere that lies about 10 to 30 miles (16 to 48 kilometers) above the surface of the Earth. Ozone (O3) is like regular gaseous oxygen (O2) with an extra oxygen atom attached to it. It is created when short-wavelength ultraviolet radiation interacts with O2 molecules. The energy from the radiation breaks the molecules apart, which then recombine into ozone.

The ozone layer is important because it protects life on Earth from harmful ultraviolet radiation. While it does not absorb all of this radiation (otherwise, it would be impossible for you to get a tan!), it prevents about 80 percent of it from reaching life on Earth. As anyone who knows about melanoma can tell you, too much ultraviolet radiation can lead to cancer.