The ozone layer filters much of the Sun's harmful ultraviolet radiation before it reaches Earth's surface. It is a region of elevated ozone concentration located mainly in the stratosphere, rather than a sharply bounded atmospheric layer.
Ozone is made of three oxygen atoms. High-energy ultraviolet light splits ordinary oxygen molecules into individual oxygen atoms, which can then combine with other oxygen molecules to form ozone. Ozone also absorbs UV radiation and breaks apart, creating a natural cycle that removes much of the incoming energy.
This protection is especially important because UV-B and UV-C radiation can damage DNA, cause skin cancer and cataracts, and harm plants and marine organisms. The ozone layer does not block all solar radiation, however; visible light and much infrared radiation pass through it.
A common mix-up is confusing the ozone layer with the stratosphere. The ozone layer is found within the stratosphere, which extends roughly from ин над 10 to 50 kilometers above Earth. Human-made chlorofluorocarbons damaged ozone, leading to international controls under the Montreal Protocol.