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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