The ozone layer is a layer in the stratosphere that contains high concentrations of ozone gas, which absorbs 97-99% of the sun's harmful ultraviolet radiation. It was discovered in 1984 by British scientists who found a recurring springtime ozone hole over Antarctica. The ozone layer is composed of ozone gas, which is formed when ultraviolet radiation from the sun breaks oxygen molecules into atoms, allowing them to recombine into ozone molecules. Ultraviolet radiation is a type of electromagnetic radiation that is present in sunlight and has wavelengths shorter than visible light but longer than x-rays.