TIME

Great Oxidation

≈ 2.4 billion years ago

Cliff face of red, purple, and gray banded iron formation rock with green plants growing along the ledges.

Earth & LifeGreat Oxidation

Oxygen fills the atmosphere.

Oxygen made by microorganisms began to build up in Earth’s atmosphere. It changed the planet’s chemistry and set the stage for later complex life.

The oxygen first reacted with dissolved iron, and the rust settled on the seafloor. The rise was slow.

2.4 billion years ago, placed on the scale of its era on a line leading toward now.

Era
Earth & Life
Period
≈ 2.4 billion years ago
Edition
1/1
Status
Not Released
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Background artwork

Cinematic background showing oxygen bubbling through an iron-rich sea. An illustration generated with an AI image tool for TIME. It is an artistic depiction, not a photograph or a record of the moment. The colours are a reconstruction from the rocks that record the change.