Question: what is the o-zone layer

Leila Battison answered on 12 Mar 2012:

It is a layer in the atmosphere about 10km thick, 20km above sea level, where there is a high concentration of the molecule O3. Oxygen usually comes as O2, but up there, special chemical reactions make O3, which is very good at absorbing dangerous UV radiation from the sun.

O3 can be destroyed by extreme cold, or by chemicals made by people and emitted into the atmosphere, but laws have been passed to limit this. If the ozone layer were destroyed, the UV radiation would cause skin cancer and burn plants, spelling big problems for all life on earth.