Video narration
If ozone is Earth's sunscreen, why does sunlight sometimes seem to destroy it? High-altitude ozone is a protective shield, absorbing much of the Sun's harmful ultraviolet, or UV, not a permanent hole in the sky. Here's the surprising part: UV splits oxygen molecules, O2, apart. Freed oxygen atoms join other oxygen molecules, forming ozone, O3. That ozone absorbs more harmful UV, helping protect life below. But human-made CFCs, chemicals once widely used in industry, are also broken apart by UV high above us. They release chlorine, which attacks ozone and turns it into ordinary oxygen. And chlorine keeps going: one chlorine atom can destroy many ozone molecules before leaving the cycle. So sunlight is not simply ozone's enemy. It helps build ozone-but CFCs let it drive destruction. The answer: ozone forms naturally from oxygen, but human-released CFCs shift the balance toward depletion.