| A | B |
|---|
| Age, in years, of a rock or other object; can be determined by using properties of the atoms that make up materials | Absolute age |
| Thin film of carbon residue preserved as a fossil | Carbon film |
| A type of body fossil that forms when crystals fill a mold or sediments wash into a mold and harden into rock | Cast |
| The remains, imprints,or traces of prehistoric organisms that can tell when and where organisms once lived and how they lived | Fossils |
| Time it takes for half the atoms of an isotope to decay | Half-life |
| Remains of species that existed on Earth for a relatively short period of time, were abundant and widespread geographically, and can be used by geologists to assign the ages of rock layers | Index fossil |
| A type of body fossil that forms in rock when an organism with hard parts is buried, decays or dissolves, and leaves a cavity in the rock | Mold |
| Fossils in which the spaces inside are filled with minerals from groundwater | Permineralized remains |
| States that in undisturbed rock layers, the oldest rocks are on the bottom and the rocks become progressively younger toward the top | Principle of Superposition |
| Process in which some isotopes break down into other isotopes and particles | Radioactive decay |
| Process used to calculate the absolute age of rock by measuring the ratio of parent isotope to daughter product in a mineral and knowing the half-life of the parent | Radiometric dating |
| The age of something compared with other things | Relative age |
| Gap in the rock layer that is due to erosion or periods without any deposition | Unconformity |
| Principle stating that Earth processes occurring today are similar to those that occurred in the past | Uniformitarianism |
