The laws of superposition and the law of crosscutting relationships allow geologists to reconstruct the history of an area. The Law of Superposition says that younger rocks will generally overlie older rocks. The Law of Crosscutting Relationships says that something that cuts across another rock unit is the younger unit.

In the example shown using these laws, the following sequence can be discerned:

1. Deposition of Unit C
2. Deposition of Unit B
3. Deposition of Unit A
4. Intrusion by Unit D
5. Faulting at E
6. Finally recent erosion.