| A | B |
|---|
| fossil | A trace or the remains of a once living thing from long ago. |
| Sedimentary rock | type of rock that forms fossils. |
| Igneous rock | the type of rock the has radioactive elements for dating fossils |
| Original remains | A fossil that is the actual body parts of an organism. |
| Tar, Amber or Ice | The materials that can preserve original remains. |
| Half-life | The length of time it takes for half the atoms in an unstable element to decay. |
| Absolute Age | The actual age of a fossil determined by radioactive decay of elements. |
| Relative Age | The age of an event or object in relation to other events. |
| Uniformitarianism | The theory that the Earth is always changing and the processes that change the Earth now were at work in the past. |
| Cenozoic era | Began 65 mya: Age of Mammals |
| Paleozoic, Mesozoic and Cesozoic | The eras on the geological time scale. |
| Precambrian Time | 90% of Earth's history. |
| Mesozoic era | Around 200 mya: Dinosaurs live on Pangea. |
| Paleozoic era | Around 400 mya: All life was in the ocean. |
| Periods | The smaller division of the geological time scale. |
| Petrified Wood | A stone fossil of tree's where the water is replaced with minerals like silicon. |
| Molds and Casts, Trace Fossils and Carbon Films | Other, more typical types of fossils. |
| Eons | The largest division of the geological time scale. |
| Bones, teeth and shells | The hard parts of organisms that are able to form fossils. |
| 4.6 billion years | The age of the planet Earth |
