Geologic History:
The Geologic Time Scale
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Geological time or "deep time" dates Earth at about 4.57 bya. Earth's past has been organized into various units according to major geologic and life based events which took place. For example, the break up of a super continent or the formation of a new mountain range would be a geologic reason to begin or end an eon, period, or epoch. |
A new life form evolving or a mass extinction would be examples of life based reasons.
For example, the boundary between the Cretaceous period and the Paleogene period is defined by the mass extinction event, which marked the end of the dinosaurs and of many marine species.
For example, the boundary between the Cretaceous period and the Paleogene period is defined by the mass extinction event, which marked the end of the dinosaurs and of many marine species.
Click the image below to open the Interactive Geologic Time Scale
Determining the Age of Rocks and Geologic Structures
Relative Age:
Reconstruction
Absolute Age:
Is the determination of the actual date a rock formed by using radiometric dating.
Periods of time that are so old that they predate the reliable fossil record are defined by absolute age.
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Virtual Labs: Absolute Age 
Click the image above to be directed to the
"Clocks in Rocks" Virtual Lab |
Click the image above to be directed to the
"Radiocarbon Dating" Virtual Lab |
Review Games:
Relative and Absolute Age:
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Absolute Age:
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