The Archean Eon, which is part of the Precambrian period along with the Proterozoic Eon.
Either
•Precambrian Time
•eras
•periods
•years
An Era
The Precambrian.
Eons are the largest divisions of geologic time.
Cenozoic Mesozoic Paleozoic Precambrian
Eon
period.
The Precambrian.
The geologic time scale that represents the longest time span is the eon. It is a unit of time that is equal to a billion years.
The Precambrian.
Eons are the largest divisions of geologic time.
Cenozoic Mesozoic Paleozoic Precambrian
Eon
The geological division of time is as follows (from largest to smallest): Eon, Era, Period, Epoch, Age. The "normal" divisions of time in use take the form: Year, Month, Week, Day, Hour, Minute, Second.
The longest in geological time is an Eon eg. Archeozoic Eon . Edit: there is also the supereon, which is usually composed of 2-3 eons.
Periods
Eon
period.
A large division of time can be called an era, epoch, or eon.