Ozone is a gas hevier than air. Wy does ozone layer not settle down near the earth ?

Explanation

In stratosphere, the formation of `O_(3)` goes ono continuously but `O_(3)` is also decomposed by UV-radiation `240` nm to `360 mm`
The `O`-atom reacts with sand `O_(3)` molecules
`O_(3) + O rarr 2O_(2)`
Net reaction , `2O_(3) rarr 3O_(2)`
Thus, the reaction form a delicate balance in which the rate of `O_(3)` decomposition match the rate of `O_(3)` formation is a dynamic equiilibrium exists and maintains a constant concentration of `O_(3)`.