Geologists generally know the age of a rock by determining the age of the group of rocks, or formation, that it is found in. The age of formations is marked on a geologic calendar known as the geologic time scale. Development of the...

[Free Registration/Login may be required to access all resource tools.] Looks at how stratigraphy can be used to determine the relative ages of rocks, how unconformities occur, ways to match rock layers in different areas, and how...