Eras

Proterozoic

proh-tur-uh-ZOH-ik

Citation Formats

General Reference

Earth and Environment Atlas. "Proterozoic." Accessed August 30, 2026. https://earth.interactiveatlas.org/eras/proterozoic.

APA Style

Earth and Environment Atlas. (n.d.). Proterozoic. Retrieved August 30, 2026, from https://earth.interactiveatlas.org/eras/proterozoic

BibTeX

@misc{earthandenvironmentatlas-proterozoic,
  author = {Earth and Environment Atlas},
  title = {Proterozoic},
  year = {2026},
  url = {https://earth.interactiveatlas.org/eras/proterozoic},
  note = {Accessed August 30, 2026}
}

The longest eon, spanning almost two billion years, in which Earth's atmosphere gained free oxygen and life grew from single cells into the first multicellular organisms.

Facts

Rank

Eon 1

Start (Million Years Ago)

2500 1

End (Million Years Ago)

538.8 1

Key Event

The Great Oxidation Event, when photosynthesis raised atmospheric oxygen for the first time, and the later evolution of the first complex, multicellular life. 1

Cross-Tradition Connections

Encompasses

Ediacaran

In Discipline

Geochronology

Source Geologic Time Scale (Wikipedia)

Sources

1. Geologic Time Scale (Wikipedia)

Wikimedia FoundationView the Source

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