Ozone

Relationship between changes in oxygen concentration and the development of the ozone layer 3500mya Cyanobacteria (photosynthetic) began producing molecular oxygen. Cyanobacteria = Oxygen

Up until about 2000mya the oxygen was used up in precipitating sediment. Evidence for this are Banded Iron Formations (BIF). This process stopped around 1700mya

From about 2000mya oxygen began to accumulate in the atmosphere From about 2000mya oxygen began to accumulate in the atmosphere. It was only when oxygen levels reached high enough levels that ozone could start to be produced

The amount of ozone built up over time to form a thin layer that protected the Earths surface from harmful UV radiation from the sun. Ozone absorbs UV light of certain frequency.

This shield allowed for the emergence of aerobic life forms during the Proterozoic and the production of an ozone layer allowed for the emergence of life forms onto land at the end of the Phanerozoic