| A | B |
|---|
| fossil | Preserved remains or traces of an organism |
| paleotologist | scientist who studies fossils |
| evolution | change in living things over time |
| extinction | when a species no longer exists and no longer will |
| relative age | age compared to something else |
| absolute age | number of year that have passed since something was made |
| law of superposition | in undisturbed horizontal layers of sedimentary rock, bottom layers are oldest |
| extrusion | lave that hardens on top of sedimentary rock |
| intrusion | magma that hardens between layers of sedimentary rock |
| index fossil | widely distributed fossil that lived a short time |
| radioactive decay | process by which radioactive material breaks down |
| half life | time it takes half of radioactive atoms in an object to break down |
| radioactive dating | using radioactive decay to determine absolute age of rocks |
| carbon-14 | material used to date remains of living things |
| unifomitarianism | geologic processes that operate today also operated in past |
| era | subdivision of geologic time |
| geologic time scale | record of geologic events/evolution |
