The function of the ozone layer is to shield the Earth from the harmful ultraviolet rays of the sun and to keep the Earth warm. The ozone layer is composed of ozone, a molecule made up of three oxygen atoms bonded together.
Most of the ozone on Earth accumulates in the stratosphere, a layer of the atmosphere between 15 and 30 kilometers above the Earth's surface. The ozone layer prevents the heat energy reflected by the Earth's surface from being re-radiated into space. This process traps heat on the Earth and keeps it warm.
Ozone is formed, broken apart and reformed on a consistent basis in the stratosphere; however, the total amount of ozone at any given time remains stable. When UV rays hit ozone molecules, they split the molecules, and the UV rays become harmless. Ultraviolet rays, namely UVB rays, can cause skin cancer and cataracts in humans as well as damage crops.