Relative dating method of evaluating geologic time
They saw that the fossils in older rocks are different from the fossils in younger rocks.
As a result, many of the names they used came from towns or other local places where they studied in Europe.
For example, one chunk of time when many dinosaurs lived is called the Jurassic.
We find fossils of Earth's first green plants from the chunk of time named the Ordovician.
Imagine if you needed to think about one million, 100 million, or even several billion years. Have places like the Grand Canyon and the Mississippi River been around for all of those years, or were they formed more recently?
These exceptional lengths of time seem unbelievable, but they are exactly the spans of times that scientists use to describe the Earth. When did the giant Rocky Mountains form and when did dinosaurs walk the Earth?