Oxygen catastrophe: when air became poison 2.4 billion years ago
2.4 billion years ago cyanobacteria waste oxygen rusted oceans and poisoned most early life on Earth.
Bacteria that polluted the planet
About 2.4 billion years ago tiny cyanobacteria in shallow seas invented oxygen photosynthesis, dumping oxygen as waste gas. For 300 million years oxygen sinks absorbed it, then free gas flooded air from near zero to about one percent, a lethal shock.
Dissolved iron in oceans rusted out, settling as banded iron formations up to 3000 metres thick in Australia and Brazil. Anaerobic microbes that ruled for one billion years died across vast regions, while methane greenhouse collapsed and glaciers spread toward the equator.
Death that made us possible
Oxygen killed its makers kin but later built the ozone shield that blocks deadly ultraviolet light within 500 million years. Falling methane likely triggered the Huronian glaciation 2.3 billion years ago, burying continents under ice for 100 million years.
Survivors learned to breathe oxygen, gaining 16 times more energy per sugar molecule and enabling complex cells with mitochondria. Every breath you take, every forest and animal, descends from microbes that adapted to ancient bacterial pollution instead of dying.
- When: 2.4 billion years ago, Great Oxidation
- Who: cyanobacteria made oxygen waste
- Proof: banded iron, 3000 metres thick
- Victims: anaerobic microbes, methane world
- Gift: ozone shield, oxygen breathing