It's not that it's "staying up there", it's that it never

has a chance to fall. Ozone is FORMED up there, and it

breaks apart again before it has a chance to fall.

Ozone is formed when UV radiation hits oxygen (O2),

splitting it apart. Oxygen atoms hate to be alone, so they

recombine with an O2 molecule to make O3, ozone. Before the

ozone has a chance to fall, IT gets hit with MORE uv

radiation, turning it back into oxygen. Ozone just keeps

getting made and destroyed before it has a chance to fall.