As its name implies, this includes all of geological time prior to the Cambrian period. Hadean Era (4,550-3,850 mya) The Precambrian's oldest era, the Hadean, predates most of the geologic record.

The geological time scale (GTS), as defined by international convention ... Over time, the Earth cooled, causing the formation of a solid crust, and allowing liquid water on the surface. The Hadean ...