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What is geologic time?

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Welcome to CoreFacts, where we're always short on time and big on science. I'm Jessica Robertson. Today's question is...

What is geologic time?

Geologic time is the period of time extending from the formation of the earth to the present. Many international debates have occurred over names and boundaries of units, and various time scales have been used by the geoscience community. Since the mid-1990s, scientists from the USGS, State geological surveys, academia, and other organizations have sought a consistent time scale to be used in communicating ages of geologic units in the U.S. For consistency purposes, the USGS Geologic Names Committee and the Association of American State Geologists developed Divisions of Geologic Time.

For more information about the various eras and the Divisions of Geologic Time, visit

And now you know. Join us again every week for a new CoreFact. For other CoreFacts or for CoreCast, our in depth science podcast, go to If you'd like to have questions featured on our show, give us an email at or a phone call at 703-648-5600. Remember, long distance fees do apply.

CoreFacts is a product of the U.S. Geological Survey, Department of the Interior.

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Title: What is geologic time?

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Date Recorded: 11/12/2008

Usage: This audio file is public domain/of free use unless otherwise stated. Please refer to the USGS Copyright section for how to credit this audio.

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