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Names on the Staircase of Time
The odd names of the different time periods on the Staircase of Time were made up by geologists, who were the first people really interested in finding out the actual age of the Earth. Most of the names have to do with places where certain types of fossils were found.

Fossils! The word "fossil" means "things dug up," but now we usually use it to refer to any evidence of past life buried in the ground. It is by studying fossils that we first began to discover how much really happened on good old Mother Earth. Fossils are found in many places on the surface of Earth, but not all. Through careful study, we find that certain types of fossils always occur together, and that these different groups of fossils are always found in the same order where many layers of rocks were visible (like on a mountain side or in a deep mine). These groups of fossils show that different types of life forms have lived on Earth at different times in its history. When geologists first learned about the different fossil groups, they named the different time periods after the locations where the fossils were found. For example, the Devonian period was named for a group of fossils found in the shire of Devon in England.

Image of a map that shows Ireland, Northern Ireland, Scotland, England and an area called Devon in southern England where fossils have been found.  Please have someone assist you with this.

Of course, just like we divide up the year into months, weeks, and days, geologists divide the history of Earth into several different time periods. The longest time period geologists use is called an "eon." Eons are divided into shorter time periods called "eras," and eras are divided into even shorter times called "periods." There are even shorter periods of time called "epochs" and "ages," but we won't worry about them! On the Staircase of Time, the different colored sections of the staircase show the different eras and the Precambrian Eon. The steps within the Precambrian Eon represent different eras, while the remaining steps represent different periods.

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Geologic Time
Cenozoic Era
Mesozoic Era
Paleozoic Era
The Precambrian Eon
Image of a star. Names on the Staircase of Time
How Old is That Rock?
Geologic Time Activity
What is a Million?
Finding an Event in Time
 
             
     
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Geologic Time | Cenozoic Era | Mesozoic Era | Paleozoic Era | The Precambrian Eon | The Staircase of Time | How Old is That Rock? | Geologic Time Activity | What is a Million? | Finding a Place in Time

Diversity | Adaptation | Plate Tectonics | Cycles | Spheres | Biomes | Geologic Time

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April 28, 2005

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