(c) Ultraviolet radiation from sunlight causes a reaction which produces Ozone. The Ozone layer or Ozone shield is a region of Earth’s stratosphere that absorbs most of the Sun’s ultraviolet radiation. It contains high concentrations of ozone (O3) in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere. The ozone layer contains less than 10 parts per million of ozone.