Archean Period
4.0-2.5 billion years ago
About this Period
First simple life forms appeared
The Archean eon witnessed the most important event in Earth's history—the emergence of life itself, forever changing the trajectory of our planet.
This period saw the appearance of the first prokaryotic cells and the development of photosynthetic bacteria known as cyanobacteria. These pioneering organisms began producing oxygen as a byproduct, gradually transforming Earth's atmosphere and setting the stage for more complex life.
The Archean was also marked by the formation of the first continents and intense volcanic activity that shaped the landscape. The oldest known fossils—stromatolites—date from this time, representing layered rock structures built by ancient microbial communities.
Life's humble beginnings in the Archean would eventually transform every aspect of our planet.
