Archean



Archean Eon 4000–2500 million years ago

The Archean Eon ( /ɑːrˈkiːən/, also spelled Archaean or Archæan) is one of the four geologic eons of Earth history, occurring 4,000 to 2,500 million years ago (4 to 2.5 billion years ago). During the Archean, the Earth's crust had cooled enough to allow the formation of continents and life started to form.