The Great Oxidation Event
Oxygen floods the atmosphere, and almost everything alive is poisoned by it.
- When
- —
- Duration
- 100 million years
- Known to
- ± 30 million years
- Era
- Paleoproterozoic, Proterozoic
After hundreds of millions of years in which every molecule of oxygen was absorbed by dissolved iron and volcanic gases, the sinks finally saturate and free oxygen accumulates in the air. Isotope records place the transition between roughly 2.43 and 2.33 billion years ago. To the anaerobic organisms that then dominated the planet, oxygen was corrosive waste, and the event is often called the oxygen catastrophe — probably the largest extinction in Earth's history, though almost none of its victims left fossils. It also made every later form of complex life possible.