| Prehistoric Scratchpad|
- Phanerozoic Eon (0.542-0.0 BYA) - The current geological eon, and the one where abundant animal life is present.
- Proterozoic Eon (2.50-0.541 BYA) - Eon where there was abundant microbial life in an oxygenated atmosphere.
- Archean Eon (4.0-2.5 BYA) - Eon where the first preserved solid rocks have been found and microbial life first formed, prior to the oxygenation of the atmosphere. It is not known if plate tectonics were active at this time.
- Hadean Eon (4.54 (or 4.4)-4.00 BYA) - Eon on Earth before solid land took form, essentially molton, before the earliest preserved rocks. A proposed beginning would be the impact that formed the Moon. It is believed there was no life during this time period, or, if there was, it would have lasted long and would have to reinvent itself.
- Chaotian Eon (4.68-4.5 BYA) - A proposed Eon marking the beginnings of Earth as a planet up until the collision that formed the Moon. A later 2012 proposal divided this Eon between the Hadean and Prechaotian Eons.
- Prenephelean Eon (44.5-4.68 BYA) - A proposed Eon representing the time before Earth formed. Starts with the Big Bang and ends with the formation of the Solar System. A proposal in 2012 suggested moving the time spanned by the Neochaotian Era to the Hadean and redubbed the Chaotian Era, which would leave the Eochaotian Era as part of the preceeding Eon, which could be dubbed the "Prechaotian".
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