| A | B |
|---|
| relative dating | order by oldest to youngest |
| superposition | newer layer is placed on top of older |
| horizontal layers | how sedimentary rocks form |
| daughter atom | produced by radioactive decay |
| half-life | amount of time for 50% of sample to decay |
| 4.6 billion years | believed age of earth |
| absolute dating | determining actural age of item |
| 1/4 sample remains | 2 half-lives went by |
| 1/2 sample remains | 1 half-life went by |
| trace fossil | evidence of animal but not actual body |
| Pangea | all land or all earth |
| uniformitarianism | gradual changes happening now, happened in past same way |
| dependent variable | what is measured |
| independent variable | what is changed |
| control | compared to in experiment |
| constant | what doesn't change in an experiment |
| continental drift | land masses slowly move on earth |
| mold | imprint of an organism |
| cast | when imprint fills up and makes fossil |
| fossil | part of organism that has been preserved |
