Eon (geology)

From Academic Kids

In general usage, an eon (also spelled Aeon) is a very long period of time. Geologists refer to an eon as the largest period of geologic time. For example, the Phanerozoic eon, which is about 550 million years long, covers the period of time during which animals with hard shells that fossilize well have been abundant.

An eon is composed of several eras, which in turn are composed of periods. We are currently in the Phanerozoic eon, the Cenozoic era and the Neogene period.

Eon Era Period (mya = million of years ago)
Phanerozoic Cenozoic 66 mya to present day
Mesozoic 245 mya - 66 mya
Paleozoic 570 mya - 245 mya
Proterozoic 2500 mya - 570 mya
Archaean 3800 mya - 2500 mya
Hadean 4550 mya - 3800 mya

The Hadean, Archaean and Proterozoic form what is informally called the Precambrian. This covers the four billion years of Earth history prior to the appearance of hardshelled animals.

Template:Geol-stub

References

da:on de:on (Geologie) fr:on pl:Eon sv:Eon

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