Why ozone hole is devoloped in Antarctica?

Ozone is a simply a tri-oxygen molecule (O3) which exists as thin layer in the lower stratosphere region in the Earth's atmosphere, approximately 20-30 km above the Earth's surface. The O3 molecule is quite unstable and easily reacts with halogen elements like Chlorine, Bromine etc. This reaction breaks down the ozone molecules into oxygen molecules (O2) and this is the primary reason for the depletion of the ozone layer (or a ozone hole).This reaction occurs more readily in cooler temperatures, conditions that are prevalent in the polar regions (like Antarctica,Greenland etc.).

 So, this is why the depletion of ozone layer mainly noticed in cold region like Antarctic pole.