Relative dating of fossils activity
Now, when we use fossils to date rocks, we have to be careful. Remember that some species of animals and plants lived for a very long time, while others existed only for a short period of time.
We don't want to use fossils belonging to species that lived for too long; these fossils would show up in more than one rock layer.
Stegosaurus and Triceratops were not part of the same assemblage because they lived at different times.
Obviously, the fossil assemblages change from period to period.
In previous lessons, we talked about the Geologic Time Scale and how scientists use it to piece together the history of the earth.
We want fossils of plants and animals that lived for a relatively short amount of time, like a few hundred thousand years or so.
I know that doesn't seem like a very short time span, but it is when we're talking about geologic time.
He began to identify rock layers by the fossils they contained, and he even noticed that the general order of strata was identical over many different parts of the country.
Smith was the first person to understand the principle of fossil succession.