Our Earth Is Old!

We know that the Earth is very old. It is more than four billion years old. Scientists figured out the Earthís age by studying rocks. The rocks that you find near your house, in a park, or at school are all different ages. Some are quite young, made in the past few million years. Others are quite old Ė many millions or even billions of years old.

There is a special sort of calendar that shows geologic time. Itís called the geologic time scale. The geologic time scale shows the 4.6 billion years of geologic time along a timeline that is divided into sections. Broad sections of time are called Eras and smaller sections of time are called Periods. Having names for the different sections of time helps people talk about when events happened long ago such as when a dinosaur lived, when a volcano erupted, or when an asteroid hit.

Last modified August 20, 2004 by Lisa Gardiner.

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