OzOnE LaYeR

Perhaps it is in the ozonosphere...or...perhaps it is in the encyclopedia...

The Stratosphere ... the zone from approximately 6 to 30 miles (10 to 50 kilometers) above the earth's surface ... comprises over 90% by volume but only about 10% by mass of the earth's atmosphere. Within the stratosphere, the hugely preponderant form of oxygen is the ozone molecule, which has 3 oxygen atoms as opposed to the 2 oxygen atoms which make up the breathable form of the gas. Ozone, O³, is produced by the destructive action of high energy electromagnetic radiation on the more comon 0² form of oxygen. Off the top of my head, that's about it. If you'd like more, it'd be easy enough to google for it.