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Geologic Time

Geologic time is used by paleontologists and geologists to make sense of the vast expanse of time in the history of the earth. We are talking about 4.5 billion years! In order to put this all in perspective geologic time uses divisions and sub-divisions. The major divisions are called Eons. On the charts below there are 4 eons, The Hadean, Archaean, Proterozoic, and Phanerozoic. Each eon is divided into Eras, the eras are divided into Periods, and the Periods are divided into Epochs

Everyone of these time divisions has characteristics that are unique and identify a stage in the earth's long history. 

We have 2 charts below to help you visualize some if the relationships of geologic time. To read the charts remember that the oldest times are at the bottom of the charts. More recents times show up closer to the top. 

Learning the age of your fossils is part of the fun of being a collector. The age of fossils is given as a number of million years ago or as a Period in the history of the earth such as the Jurassic Period. A paleontologist tries to visualize an environment to help understand a fossil. You can learn a lot about the geography, climate, and other plants and animals that existed at the time a fossil was a living thing.

The first Geologic Time Chart below has 3 sections. In the center are the names of the eons, eras, and periods paleontologists and geologists use to talk about geologic history. The most recent times are near the top of the chart. As we go toward the bottom of the chart we are going back farther and farther into the earth's history.

The left side is a simplied look at the evolution of life. It follows the center section starting at the bottom and moving forward in time toward the top. The lines represent groups of related animals.  The right side of the chart lists some of the major events in earth's history, again starting at the bottom.

geologic time chart

Chart 2

In this chart the names of each Eon, Era or Period are linked to pages that contain information on the geology, biology, and climate of that particular time. Simply click on the name of the time division for more detailed information about it.

Note: At the upper right of the chart is a section labled Old Periods. Like all of the sciences our understanding changes as we learn more. The names and times of these divisions are modified as we learn more about the history of the earth. Not too long ago the names of the periods of the Cenozoic Era were changed as noted on the chart.

Super Eon
Old Periods


541 mya to Present
Cenozoic Era
66 mya to Present
.012 to present
2.58 to .012 mya
5.3 to 2.58 mya
23 to 5.3 mya
34 to 23 mya
56 to 34 mya
66 to 56 mya
Mesozoic Era

252 mya to 66 mya
Cretaceous Period 145 mya to 66 mya
Jurassic Period 201 to 145 mya
Triassic Period 252 to 201 mya
Paleozoic Era
541 to 252 mya
Permian Period 299 to 252 mya
Carboniferous Period 359 to 299 mya
Devonian Period 419 to 359 mya
Silurian Period 444 to 419 mya
Ordovician Period 485 to 444 mya
Cambrian Period 541 to 485 mya
Precambrian Time
4,600 to 541 mya
Ediacaran Period 635 to 541 mya
Proterozoic Eon 2,500 to 541 mya
Archaean Eon 4,000 to 2,500 mya
Hadean Eon 4,600 to 4,000 mya

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INTERESTED IN MORE INFORMATION? IF SO, YOU MAY WANT TO CHECK OUT OUR OTHER SITES: - An educational site about fossils and geologic time - An educational site about rocks, minerals, and geology.

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