| A | B |
|---|
| relative dating | how old a rock is as compared to surrounding rocks |
| absolute dating | actual number of years since a rock was formed |
| igneous rock | formed by magma |
| sedimentary rock | formed by the erosion of existing rocks by wind, water, or ice |
| metamorphic rock | formed when existing rocks are subjected to intense heat and pressure |
| uniformitarianism | states that physical, chemical and biological laws operating today were also operating in the geological past |
| Principle of Original Horizontality | states that layers of sediment are generally deposited in a horizontal position |
| Law of Superposition | states that in an undisturbed sequency of sediment, the older layers are on the bottom |
| uncomformity | surface between 2 layers that were NOT laid down in an unbroken sequence (ex: weathering) |
| disconformity | occurs where 2 sedimentary layers are separated by an erosional surface |
| nonconformity | occurs where a sedimentary layer is on top of igneous or metamorphic rock |
| angular uncomformity | occurs where a sedimentary layer of rock is on top of sedimentary layers that have been tilted, folded or distorted |
| fault | area of rock cut by plate tectonics |
| Principle of cross-cutting | states that a fault is younger than the rocks it cuts |
| Principle of fossil succession | states that organisms succeed one another in a definite and determinate order |
| paleontology | the study of past life using fossils |
| index fossil | fossils that are widespread, abundant and limited to a short time span |
| ecological indicator | fossil from an organism that must live in a specific environment to survive |
| dendrochonology | dating method based on tree rings |
| fossil | preserved or petrified remains, molds, casts, carbon film, or impression of organisms from the geological past |
