| A | B |
|---|
| Cambrian explosion | The ancestors of the most major animal groups diversited in what incacred |
| Era | The next largest division of me geologic time scale |
| Relative dating | A method used to determine the aged rocks by comparing them with those in other layers |
| Fossils | Any preserved evidence of an organism |
| Spontaneous Generation | Idea that life can arise from nonlife |
| Radiometric dating | The decay of radioactive isotopes to measure the age of a rock |
| Geologic Time Sale | A model that expresses the major geological and biological events |
| Palentologist | A scienist who studies fossils |
| Half Life | The amount of time it takes for half of the original isotopes to decay |
| Plate tectonics | Describes the movement of the changing of the continent's |
| K-T Boundary | Layer of iridium- rich material between rocks of the cretaccous period and rocks of paleogene period that provivde evindence of a meterite impact |
| Law of superposition | States that younger layers of rock are deposited on top of older layers. |
| Period | Subdivision of an era on the geologic time scale |
