Archean Period
4.0-2.5 billion years ago
About this Period
First simple life forms appeared
Detailed Overview
The Archean eon saw the emergence of life on Earth, with the first prokaryotic cells appearing. This period was marked by the formation of the first continents, intense volcanic activity, and the development of photosynthetic bacteria (cyanobacteria). These bacteria began producing oxygen as a byproduct, gradually changing Earth's atmosphere. The oldest known fossils, stromatolites, date from this time.
