Era (geology)

A geologic era is a subdivision of geologic time that divides an eon into smaller units of time. The Phanerozoic Eon is divided into three such time frames: the Paleozoic, Mesozoic, and Cenozoic represent the major stages in the macroscopic fossil record. These eras are separated by catastrophic extinction boundaries, the P-T boundary between the Paleozoic and the Mesozoic and the K-T boundary between the Mesozoic and the Cenozoic. There is evidence that catastrophic meteorite impacts played a role in demarcating the differences between the eras.

The Hadean, Archean and Proterozoic eons were as a whole formerly called the Precambrian. This covered the four billion years of Earth history prior to the appearance of hard-shelled animals. More recently, however, those eons have been subdivided into eras of their own.

List of geological eras in Earth's evolutionary history

Era Time frame (Ma = million years ago)
Cenozoic Expression error: Unexpected round operator Expression error: Unexpected < operator million years ago to present day
Mesozoic Expression error: Unexpected round operator Expression error: Unexpected < operator Cenozoic
Paleozoic Expression error: Unexpected round operator Expression error: Unexpected < operator Mesozoic
Neoproterozoic Expression error: Unexpected round operator Expression error: Unexpected < operator Paleozoic
Mesoproterozoic Expression error: Unexpected round operator Expression error: Unexpected < operator Neoproterozoic
Paleoproterozoic Expression error: Unexpected round operator Expression error: Unexpected < operator Mesoproterozoic
Neoarchean Expression error: Unexpected round operator Expression error: Unexpected < operator Paleoproterozoic
Mesoarchean Expression error: Unexpected round operator Expression error: Unexpected < operator Neoarchean
Paleoarchean Expression error: Unexpected round operator Expression error: Unexpected < operator Mesoarchean
Eoarchean Expression error: Unexpected round operator Expression error: Unexpected < operator Paleoarchean
Hadean Eon
not officially divided into eras		 Formation of Earth to Expression error: Unexpected round operator Expression error: Unexpected < operator million years ago

See also

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