Defining the World

Definitions and History

What is geologic time

Geologic time is a time scale that divides the history of the planet Earth into eras, periods, and epochs from the birth of the planet to the present. The oldest era is the Precambrian, which began 4.6 billion years ago and ended about 570 million years ago. Next came the Paleozoic Era, which lasted from 570 to 245 million years ago, followed by the Mesozoic Era, from 245 to 66 million years ago. We’re now living in the Cenozoic Era, which began 66 million years ago. The Paleozoic, Mesozoic, and Cenozoic eras are each divided into periods. Additionally, the Cenozoic Era is divided into even smaller units of time called epochs. The last ten thousand years (the time since the last significant Ice Age) is called the Holocene Epoch.


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