Geologic Time Scale

Phanerozoic

Eon extending 543 million years ago until the present. Includes Cenozoic, Mesozoic, and Paleozoic Eras. Characterized as the time of our life.

Precambrian

Eon extending from the creation of Earth until 543 million years ago. Divided into Proterozoic, Archean, and Hadean. Characterized as time before the emergence of complex life.

Archean

Eon extending from the end of the Hadean era until 2.5 billion years ago. Includes Early, Middle, and Late eras. Characterized by the emergence of prokaryotes.

Proterozoic

Eon from 2.5 billion - 543 million years ago. Early, Middle, and Late eras. Part of Phanerozoic Eon. Characterized by the emergence of eukaryotes.

Paleozoic

Era from 248 - 543 million years ago. Includes Permian, Carboniferous, Devonian, Silurian, Ordovician, and Cambrian Periods. Part of Phanerozoic Eon. Characterized by the emergence of complex life.

Mesozoic

Era from 65 - 248 million years ago. Includes Cretaceous, Jurassic, and Triassic Periods. Part of Phanerozoic Eon. Characterized as the time of the dinosaurs.

Cenozoic

Era from 65 million years ago until the present. Includes Tertiary (Paleogene and Neogene) and Quaternary Periods. Part of Phanerozoic Eon. Characterized by time following the dinosaurs' extinction.

Cambrian

Period from 490 - 543 million years ago. Includes A-D epochs. Part of Paleozoic Era. Characterized by the first abundant record of marine life. Trilobites dominant.

Ordovician

Period from 443 - 490 million years ago. Includes Early, Middle, and Late epochs. Part of Paleozoic Era. Characterized by the first fish. Invertebrates are dominant.

Hadean

Earliest eon. Before any life existed on Earth.

Silurian

Period from 417 - 443 million years ago. Includes Early and Late epochs. Part of Paleozoic Era. Characterized by the first terrestrial plants and animals.

Devonian

Period from 354 - 417 million years ago. Includes Early, Middle, and Late epochs. Part of Paleozoic Era. Characterized by the first amphibians.

Mississippian

Subdivision of Carboniferous Period from 323 - 354 million years ago. Part of Paleozoic Era. Characterized by abundant sharks and amphibians.

Pennsylvanian

Subdivision of Carboniferous Period from 290 - 323 million years ago. Part of Paleozoic Era. Characterized by the first reptiles.

Permian

Period from 248 - 290 million years ago. Includes Early and Late epochs. Part of Paleozoic Era. Characterized by the extinction of most kinds of marine life, including trilobites. Southern glaciation.

Triassic

Period from 206 - 248 million years ago. Includes Early, Middle, and Late epochs. Part of Mesozoic Era. Characterized by the first dinosaurs. Abundant cycads and conifers.

Jurassic

Period from 144 - 206 million years ago. Includes Early, Middle, and Late epochs. Part of Mesozoic Era. Characterized by the first birds and mammals. Abundant dinosaurs and ammonites.

Cretaceous

Period from 65 - 144 million years ago. Includes Early and Late epochs. Part of Mesozoic Era. Characterized by the first angiosperms. Climax of dinosaurs and ammonites.

Tertiary

Period from 1.8 - 65 million years ago. Divided into Paleogene and Neogene. Includes Paleocene, Eocene, Oligocene, Miocene, and Pliocene epochs. Part of Cenozoic Era. Characterized as following the mass extinction of the dinosaurs.

Paleogene

Subdivision of Tertiary Period including the Paleocene and Eocene epochs. Part of Cenozoic Era.

Neogene

Subdivision of Tertiary Period including the Oligocene, Miocene, and Pliocene epochs. Part of Cenozoic Era.

Quaternary

Period from 1.8 million years ago until the present. Includes Pleistocene and Holocene epochs. Part of Cenozoic Era. Characterized by the appearance of humans.

Paleocene

Epoch from 54.8 - 65 million years ago. Part of Tertiary Period. Characterized by the first placental animals.

Eocene

Epoch from 33.7 - 54.8 million years ago. Part of Tertiary Period. Characterized by many modern types of mammals.

Oligocene

Epoch from 23.7 - 33.7 million years ago. Part of Tertiary Period. Characterized by large running mammals.

Miocene

Epoch from 5.3 - 23.7 million years ago. Part of Tertiary Period. Characterized by first abundant grazing mammals.

Pliocene

Epoch from 1.8 - 5.3 million years ago. Part of Tertiary Period. Characterized by large carnivores.

Pleistocene

Epoch from 0.01 - 1.8 million years ago. Part of Quaternary Period. Characterized by early man and northern glaciation.

Holocene

Epoch from 0.01 million years ago until the present. Part of Quaternary Period. Characterized by modern man.

Carboniferous

Period from 290 - 354 million years ago. Includes Mississippian and Pennsylvanian subdivisions. Part of Paleozoic Era. Characterized by tons and tons and tons of trees.