Archean

The Archean is a time of significant geological and biological development. The Earth’s lithosphere thickened, and the first cratons—stable portions of continental crust—formed, forming the foundation of modern continents. Substantial volcanic activity occurred during this era, as well as the movement of tectonic plates, though plate tectonics likely operated differently than they do today due to the hotter mantle temperatures. 

Life during the Archean was limited to simple, single-celled organisms, primarily bacteria and archaea. Fossil evidence of stromatolites—layered structures formed by the activity of cyanobacteria—suggests that microbial life was widespread by the end of the era. Although the atmosphere was still largely reducing, the activity of these microorganisms laid the groundwork for the eventual oxygenation of the planet.