| A | B |
|---|
| Geologic Time | the time of the physical formation and development of earth |
| half life | the time it takes for half the mass of a given amount of radioactive element to decay into its daughter elements |
| isotope | atoms of an element that have the same atomic number but different atomic mass numbers |
| Law of Superposition | principle that a sedimentary rock layer is odler than the layers above it an dyounger than the layers below it |
| radioactive decay | the process through which an atom loses protons or neutrons |
| radiometric dating | a method of determining the age of an object based on the amount of a particular isotope contained within it |
