Geological Time

Eon/time	Era	Period / comment	Epoch / comment
Hadean Eon : 4.6 - 3.8Ga
Archean Eon : 3.8 - 2.5 Ga
3.8-3.6 Ga	Eoarchean	Vaalbara Ur Kenorland	abiogenesis stromatolite reefs
3.6-3.2 Ga	Paleoarchean
3.2-2.8 Ga	Mesoarchean
2.8-2.5 Ga	Neoarchean
Proterozoic Eon : 2.5 Ga ~ 542 Ma
2.5-1.6 Ga	Paleoproterozoic Era	Siderian 2.5-2.3	evolution of oxygenic photosynthesis continents stabilized
		Rhyacian 2.3-2.05
		Orosinian 2.05-1.8
		Stratherian 1.8-1.6
1.6-1.0 Ga	Mesoproterozoic Era	Calymmian 1.6-1.4	Rodinia starts to assemble evolution of sexual reproduction
		Ectasian 1.4-1.2
		Stenian 1.2-1
1.0 Ga-542 Ma	Neoproterozoic Era	Tonian 1.0 Ga -850 Ma	glaciations dubbed "Snowball Earth" earliest multicelled fossils
		Cryogenian 850-635 Ma
		Vendian or Ediacaran, 635-542
Phanerozoic Eon : 542 Ma - present
542-251 Ma	Paleozoic Era	Cambrian 542-488.3	Cambrian "explosion" Gondwanaland
		Ordovician 488.3-443.7	began and ended (2nd largest) with extinction events: graptolites, first jawed fish, land plants Gondwana, Taconinc orogeny
		Silurian 443.7-416	Named for Wales. Euramerica and Caledonian orogeny graptolites, coral reefs, first bony fish, Myriapods were first terrestrial animals, first vascular plants; eurypterids; brachiopods, bryozoa, molluscs, and trilobites abundant in warm seas
		Devonian 416-359.2	"Age of Fishes", first sharks, first ammonites; land - first tetrapods, insects, spiders, and seed-bearing plants
		Carboniferous 359.2-299.0	Pangaea assembling, Hercynian and Alleghanian orogenies Mississippian and Pennsylvanian separated by an unconformity: cyclothemic coal deposits, widespread epicontinental seas and carbonate depostion. Insect and amphibian gigantism. Foraminifera prominent.
		Permian 299-251	Pangaea. Permian-Triassic extinction event (largest) with loss of 90% to 95% of marine species and 70% of all land organisms
251-65.5	Mesozoic Era	Triassic 251-199.6	starts and ends with extinction events, adaptive radiation after P-T extinction; angiosperms, pterosaurs
		Jurassic 199.6-145.4	Pangaea break-up "Age of Dinosaurs"
		Cretaceous 145.4-65.5	Named for chalk (coccolith) deposits of France and South England K-T boundary extinction event - Chicxulub impact crater
65.5-present	Cenozoic Era	Paleogene 65.5-23.03	Paleocene 65.5-55.8 (mammals)
			Eocene 55.8-33.9 : ends with Grande Coupure extinction event first modern mammals
			Oligocene 33.9-23.03 : climate cooling begins by end of epoch
		Neogene 23.03-present	Miocene 23.03-5.332 Horses, mastodons, first apes
			Pliocene 5.332-1.806 Australopithecus, Homo habilis
			Pleistocene 1.506-.005 glaciations, megafauna, anatomically modern humans
			.005- present end of recent glaciation, rise of civilization