Forming Fossils

Geologic Time

What is relative time in relationship to geologic time?

Relative time is a way to establish the relative age of rocks and fossils. It is based on the location of a rock layer in comparison to the location of other rock layers; that is, it is only relative, not absolute, time. In many cases, rock layers are laid down in order, the older layers being below the younger layers. For example, a fossil found in a higher rock layer is usually younger than a fossil found in a rock layer below it. During the nineteenth century, scientists used this method to date rock layers relative to each other and to establish and construct the first geologic time scale.


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