| A | B |
|---|
| How old is the earth? | 4.6 billion years old |
| The name of the time from the earth's formation to the beginning of the Paleozoic? | Precambrian time |
| Age of Reptiles; First birds; Dinos dominated | Mesozoic Era |
| Age of Mammals; shortest of the 3 eras | Cenozoic Era |
| Means "ancient life"; simpler life forms such as invertebrates and fish | Paleozoic Era |
| Any method of measuring the age of an event or object in years | absolute dating |
| The process of unstable nuclei breaking apart | radioactive decay |
| the time it takes for half of a radioactive sample to decay | half-life |
| an atom that has the same number of protons but a different number of neutrons | isotope |
| Name of 3 eras in the Phanerozoic Eon | Paleozoic, Mesozoic, Cenozoic |
| Why can't radiometric dating be used on sedimentary rock? | Sediment in rock are weathered from so many different rocks of different ages |
| How go geologists get the age of sedimentary rock? | Relate it to datable masses of igneous/metamorphic rock above and below |
| Ratio of unstable to stable isotope in very old rocks | The older the sample, the more stable daughter product it contains. |
