era
subdivision of geological time; shorter than an eon and longer than a period
Mesozoic
second erathem and era of the Phanerozoic Eonothem and Eon
Cenozoic
third and current era of the Phanerozoic Eon
Cryptic era
Term for earliest geologic evolution of the Earth and Moon
Paleozoic
first erathem and era of the Phanerozoic eonothem and eon
Zirconian
proposed era of the Hadean eon