Relative Age Dating: Within a single locality, geologist are able to
1. Principle of Superposition: In a sequence of undeformed sedimentary rock layers, the rocks get older from top to bottom.
2. Principle of Original Horizontality: when sedimentary rock layers are being deposited, gravity forces them to be deposited as flat, horizontal layers.
3. Principle of faunal succession: groups, or assemblages, of plant and animal fossils appear in the geologic record in a specific order.
4. Principle of crosscutting relations: an igneous rock unit or fault that cuts across another rock unit must be younger that the unit it cuts across.
5. Principle of Inclusion: A rock unit that contains of preexisting rocks must be younger
6. Metamorphie Rocks: a metamorphic rock is always older then the non metamorphosed rocks around it.