STANDARD GEOLOGIC TIME SCALE
| EON | ERA | PERIOD | EPOCH | AGE (M.y.) | IMPORTANT EVENTS |
| PHANEROZOIC | CENOZOIC | Quaternary | Holocene | 0.01 - present | Human civilization develops. |
| Pleistocene | 1.6 - 0.01 | Continental glaciation in the northern hemisphere | |||
| Tertiary | Pliocene | 5.3 - 1.6 | Humans appear for the first time. | ||
| Miocene | 23.7 - 5.3 | Antarctic Ice Sheet develops. | |||
| Oligocene | 36.6 - 23.7 | Himalaya Mountains begin to form. | |||
| Eocene | 57.8 - 36.6 | The Alps form in Europe. | |||
| Paleocene | 66.4 - 57.8 | Mammals become dominant land animals | |||
| MESOZOIC | Cretaceous | 144 - 66.4 | Dinosaurs become extinct; Rocky Mountains begin forming. | ||
| Jurassic | 208 - 144 | Atlantic Ocean begins to form between N. America & Africa. | |||
| Triassic | 245 - 208 | 1st dinosaurs; North America begins to separate from Africa. | |||
| PALEOZOIC | Permian | 286 - 245 | All land masses joined to form a single supercontinent called Pangea. | ||
| Pennsylvanian | 320 - 286 | Appalachian Mountains & Ouachita Mountains formed by continental collision with Africa. | |||
| Mississippian | 360 - 320 | Extensive deposits of coal developed worldwide. | |||
| Devonian | 408-360 | 1st fossils of amphibians (animals which could live on land). | |||
| Silurian | 438 - 408 | 1st fossils of land plants. | |||
| Ordovician | 505 - 438 | 1st fossil fish; evidence of continental glaciation in Africa. | |||
| Cambrian | 545 - 505 | Abundant fossils of marine organisms. | |||
| PROTEROZOIC | PRECAMBRIAN | 2500 - 545 | 1st evidence of oxygen in atmosphere = 2.0 billion years ago. | ||
| ARCHEAN | 4500 - 2500 | Earliest evidence of life = 3.8 billion years ago. Earth forms = 4.5 billion years ago. |
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