[(enigma)]

Originally Posted by Cat_Orange

Oxygen and Ozone
Initially: No oxygen = no ozone
BUT
- 3500 million years ago cyanobacteria began producing oxygen
- Initially oxygen produced precipitated sediments (eg BIF) and this continued til 1700 million years ago
THEN
- 2000 million years ago oxygen began accumulating in the atmosphere
THEREFORE
- So did ozone
SO
- By 1800 million years ago, there were high enough concentrated oxygen levels to produce enough concentrated ozone to protect life on earth

you should also know how ozone forms:
uv radiation reacts with oxygen molecules (O2) and splits them into two oxygen atoms (O). each one of those oxygen atoms then joins with another oxygen molecule when they collide together to form ozone (which is O3).

was that simple enough to understand? soz, i feel the need to make it more detailed as i do chem.