| A | B |
|---|
| uniformitarianism | Earth changes due to slow processes such as WED |
| catastrophism | Earth changes occur suddenly |
| paleontology | study of past life |
| relative dating | finding the age by comparing |
| superposition | younger rocks lie above older rocks |
| geologic column | ideal arrangement of rocks with oldest on bottom |
| unconformity | break in the geologic record |
| disconformities | part of sequence of rock layers is missing |
| nonconformity | sedimentary rock filling in where older rock is eroded |
| fault | break in Earth's crust |
| tilting | slanting rock layers |
| folding | bending rock layers |
| absolute dating | measuring the age of rock in years |
| isotope | atom with the same number of protons but different neutrons |
| radioactive decay | unstable isotope breaks down |
| radiometric dating | finding the age by studying decay |
| half-life | time needed for half of a unstable sample to decay |
