ARCHEAN EON (4.000-2.500 Ma)
From Greek arkhaîos (archaic).

EOARCHEAN ERA (4.000-3.600 Ma)
From Greek ēốs (dawn) arkhaîos (archaic).

Main events: beginning of plate tectonics.

Lifeforms: small single-celled organisms.

Paleoenvironment: the Earth had a solid crust with some volcanic islands and large oceans. The atmosphere was toxic and oxygen-free.