| A | B |
|---|
| fossils | remains, imprints, or traces of prehistoric organisms |
| permineralized remains | fossils in which the spaces inside are filled with minerals from groundwater. |
| carbon film | thin film of carbon residue left, which from a silhouette (outline of the body) of the original organism. |
| mold | cavity left in a rock after an organism, part of an organism, or shell dissolves and leave behind a cavity (or hole) |
| cast | when mineral rich water or sediment enters the cavity (or hole) left after an organism, part of an organism, or shell dissolves and forms new rock forming a copy of the original object. |
| index fossils | remains of species that existed in earth for relatively short periods of time, they were abundant (means a lot of them), and were widespread geographically (means found all over the place) |
| principle of superposition | in undisturbed layers of rock, the oldest rocks are on the bottom and the newest rocks are on the top |
| unconformities | when layers of rock are missing |
| absolute age | is the age of rocks or other objects in years |
| radioactive decay | the process of breaking down |
| half-life | the time it takes for half the atoms in an isotope to decay |
| radiometric dating | the process of calculating the absolute age of a rock |
| principle of uniformitarianism | states that earth processes occurring today are similar to those that occurred in the past |
| relative age | the age of something in comparison to something else |
