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A Timeline of Geologic and Evolutionary EventsA Quick Reference to Eons, Eras, Periods, Epochs and Ages
By Laura Klappenbach, About.com
The chart below provides brief information about the various eons, eras, periods, epochs, and ages that are used to describe the Earth's history. Origin of Universe • 13,730 MYA • The Origin of the Universe (approximately 13,730 MYA) is thought to have started with an event known as the Big Bang. At the time of the Big Bang, all matter and energy was condensed to a single point with infinite density. Following the Big Bang, the universe began expanding. Precambrian • 4500 to 543 MYA • The Precambrian is a period of time that begins with the formation of the Earth and culminates with the Cambrian Explosion. The Precambrian encompasses the Hadean Eon, the Archean Eon, and the Proterozoic Eon.
Hadean Eon • 4500 to 3800 MYA • During the Hadean Eon, the Solar System was still forming, the sun formed and the planets began forming. The early Earth consisted of molten rock. As Earth cooled, the molten rock solidified and the geological history of our planet began. The oldest known rocks on earth are 3800 million years old. The end of the Hadean Eon coincides with the formation of solid rock on our planet.
Archean Eon • 3800 to 2500 MYA • The Archean Eon was the time period in which the first lifeforms appeared on our planet. At that time, Earth was very different from what it is today. The atmosphere was composed of toxic gases such as methane and ammonia (the atmosphere of early Earth was known as a reducing atmosphere). As the Earth's crust cooled, rocks and continental plates formed. The lifeforms of the Archean were bacterial, including stromatolites.
Paleoarchean (Early Archean) Era • 3800 to 3300 BYA • The bacteria microfossils such as cyanobacteria that date back to 3500 MYA are the oldest known fossils on our planet.
Mesoarchean (Middle Archean) Era • 3300 to 2900 BYA •
Neoarchean (Late Archean) Era • 2900 to 2500 BYA •
Proterozoic Eon • 2500 to 543 MYA • Continents first formed and continued to accrete. First eukaryotic cells appeared.
Paleoproterozoic Era • 2500 to 1600 MYA • Development of oxygen atmosphere. Origin of eukaryotes (approximately 1800 MYA).
Mesoproterozoic Era • 1600 to 900 MYA • First supercontinent, Rodinia, formed. Sexual reproduction arises. Sea chemistry in flux, atmospheric oxygen levels started building up (about 1% of present day concentrations).
Calymmian Period • 1600 to 1400 MYA •
Ectasian Period • 1400 to 1200 MYA •
Stenian Period • 1200 to 900 MYA •
Tonian Period • 900 to 850 MYA •
Cryogenian Period • 850 to 650 MYA •
Ediacaran (or Ediacarian or Vendian or Verangian) Period • 650 to 543 MYA • Macroscopic fossils of soft-bodied organisms.
Paleozoic Era • 543 to 248 MYA •
Cambrian Period • 543 to 490 MYA • The fossil record indicates that it was during the Cambrian Period that most major groups of animals first appeared. A period of rapid diversification (in evolutionary terms) known as the Cambrian Explosion occurred during the Cambrian.
Early Cambrian Epoch • 543 to 510 MYA •
Manykaian (or Nemakit-Daldynian) Age • 544 to 530 MYA •
Tommotian Age • 530 to 527 MYA •
Atdbanian Age • 527 to 520 MYA •
Botomian (or Toyonian or Lenian) Age • 520 to 510 MYA •
Middle Cambrian Epoch • 510 to 500 MYA
Solvan (or Manevian) Age • 510 to 500 MYA
Late Cambrian Epoch • 500 to 490 MYA
Ordovician Period • 490 to 443 MYA
Early Ordovician Epoch • 490 to 478 MYA
Tremadocian Age • 490 to 485 MYA
Arenigian Age • 485 to 478 MYA
Middle Ordovician Epoch • 478 to 458 MYA
Llanvirnian Age • 478 to 468 MYA
Llandeilian Age • 468 to 458 MYA
Late Ordovician Epoch • 458 to 443 MYA
Caradocian Age • 458 to 448 MYA
Ashgillian Age • 448 to 443 MYA
Silurian Period • 443 to 417 MYA
Llandoverian Age • •
Wenlockian Age • •
Late Silurian Epoch • 421 to 410 MYA
Ludlovian Age • 421 to 414 MYA
Pridolian Age • 414 to 410 MYA
Devonian Period • 417 to 354 MYA
Early Devonian Epoch • 417 to 387 MYA
Eifelian Age • •
Givetian Age • •
Frasnian Age • •
Famennian Age • •
Carboniferous Period • 354 to 290 MYA •
Mississippian Epoch (Early or Lower Carboniferous) • 354 to 323 MYA •
Pennsylvanian Epoch (Middle & Late or Upper Carboniferous) • 323 to 290 MYA •
Permian Period • 290 to 248 MYA •
Triassic Period • 248 to 206 MYA •
Jurassic Period • 206 to 144 MYA •
Cretaceous Period • 144 to 65 MYA •
Berriasian Age • •
Valanginian Age • •
Hauterivian Age • •
Barremian Age • •
Aptian Age • •
Albian Age • •
Tertiary Period • 65 to 1.8 MYA •
Paleocene Epoch (First Epoch of the Paleogene) • 65 to 54.8 MYA •
Danian Age • •
Selandian Age • •
Eocene Epoch (Second Epoch of the Paleogene) • 54.8 to 33.7 MYA •
Oligocene Epoch (Last Epoch of the Paleogene) • 33.7 to 23.8 MYA •
Rupelian Age • •
Chattian Age • •
Miocene Epoch (First Epoch of the Neogene) • 23.8 to 5.3 MYA •
Aquitanian Age • •
Burdigalian Age • •
Langhian Age • •
Serravalian Age • •
Tortonian Age • •
Messinian Age • •
Pliocene Epoch (Last Epoch of the Neogene) • 5.3 to 1.8 MYA •
Zanclean Age • •
Piacenzian Age • •
Quaternary Period • 1.8 MYA to Present •
Pleistocene Epoch • 1.8 MYA to 10,000 Years Ago •
Calabrian Age • •
Holocene (Anthropogene) Epoch • 10,000 Years Ago to Present • Age of Man. Mass extinction of plant and animal species.
The following references were used to construct this timeline:
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