Final answer:
Geologists use the principles of superposition and cross-cutting relationships to determine the relative age of sedimentary rock layers and the fossils contained within them.
Step-by-step explanation:
The two different types of information geologists use to determine the relative age of rock layers and the fossils contained within them are superposition and cross-cutting relationships.
Superposition refers to the principle that in undisturbed layers of sedimentary rocks, the oldest layers are at the bottom with progressively younger layers above. Cross-cutting relationships state that if a geological feature cuts across another, the feature that has been cut is older.
These principles help geologists to establish a sequence of events and the relative ages of rocks and fossils without knowing the exact number of years they have been formed.
To give an example, if a geologist observes a sedimentary rock layer that is intersected by a fault line, they can conclude that the rock layer was formed before the fault occurred, indicating that the rock's formation is relatively older than the fault.
Through the law of superposition, if another sedimentary layer lies on top of the first layer, it is considered younger than the first.