Photosynthesis

2500 million years
or 610 meters to today

Geolo­gi­cal era: Proterozoic/Siderian

Cells are deve­lo­ping the ability to produce energy from sunlight ever more effi­ci­ently. Over milli­ons of years, the oxygen produ­ced leads to the forma­tion of water inso­luble metal salts in the oceans. This results in the signi­fi­cant banding layers which are being mined today. The iron concen­tra­tion in the water decre­a­ses, so that free oxygen appears. This oxygen is toxic to life at this time and the first major extinc­tion (“Great oxygen cata­stro­phe”) affects most species. Orga­nisms that live in an oxygen-free envi­ron­ment remain unaf­fec­ted. New species that can tole­rate oxygen or even gain a lot of energy from it spread.

After the first oxygen enters the atmo­s­phere, its share incre­a­ses steadily. At the same time, the carbon dioxide content is decre­a­sing. The Earth is predo­mi­nantly cove­red by oceans. Only occa­sio­nally do volca­nic cones or eleva­ted clods of earth (cratons) tower above the water surface.

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