eon
subdivision of geological time; short than a supereon and longer than an era
Proterozoic
third eon of the geological timescale, last eon of the Precambrian Supereon
Phanerozoic
fourth and current eonothem and eon of the geological timescale
Hadean
first eon of the geological timescale, beginning with the formation of the Earth about 4.567 billion years ago
Archean
second eon of the geologic timescale, spanning from around 4.031 to 2.5 billion years ago