What is another word for Precambrian eon?
Pronunciation: [pɹɪkˈambɹi͡ən ˈiːɒn] (IPA) 
The Precambrian eon refers to the earliest part of the Earth's history, which extends from the formation of the planet, about 4.6 billion years ago, to the emergence of complex life forms in the Cambrian period, about 540 million years ago. Several synonyms have been used to refer to this eon, including the "archean eon" and the "proterozoic eon." The Archean eon, which lasted from 4.0 to 2.5 billion years ago, covers most of the Precambrian eon and is characterized by the formation of the first continents and the emergence of primitive life forms. The Proterozoic eon, which lasted from 2.5 billion to 541 million years ago, is marked by the diversification of life forms and the evolution of complex organisms.
