Earth’s third eon: the Proterozoic. At the beginning of the Proterozoic, in the Siderian period, the Oxygen Catastrophe occurs: some microorganisms invent photosynthesis and begin to poison the air with oxygen, lethal to almost all other organisms. This causes a gigantic mass extinction and a huge diversification of rocks, which begin to oxidize. It is the greatest extermination of living things of all time.
