1. OZONE LAYER.
The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone (O3).
This layer absorbs 97–99% of the Sun's high frequency ultraviolet light, which potentially damages the life forms on Earth.
It is mainly located in the lower portion of the stratosphere from approximately 20 to 30 kilometres above Earth.
Created by ultraviolet light striking oxygen atoms (O2), splitting them into individual oxygen atoms (atomic oxygen);
The atomic oxygen then combines with unbroken O2 to create ozone, O3

3. OZONE LAYER DEPLETION.
The ozone layer can be depleted by free radicals
hydroxyl (OH-),
chlorine (Cl-),
bromine (Br-).
chlorofluorocarbons (CFCs) and bromofluorocarbons

4. EFFECTS OF OZONE DEPLETION.
More ultraviolet light from the sun can reach the Earth.
UV increase can cause skin cancer, cataracts (snowblindness or photokeratitis), and suppression of the human immune system.
In addition to cancer, some research shows that a decreased ozone layer will increase rates of malaria and other infectious diseases.   
Oceans will be affected as well.  The most basic microscopic organisms such as plankton may not be able to survive. 
Climate changes. Melting of glaziers (rising sea levels)