Dating by Geology

Several different geologic methods are used to establish a fossil's age. In the field we look for clues in the rocks to figure out how old the fossils from the rocks are.

First, to establish whether one fossil is older or younger than another, we look at it's position in the sequence of rock layers.

Since rock layers are laid down one on top of the other, fossils that are lower in the sequence are older than ones that are higher.

But to estimate how many millions of years ago the fossils formed, we have tried to use two other methods.