Geologic time scale

Geologic time scale (W)

This clock representation shows some of the major units of geological time and definitive events of Earth history. The Hadean eon represents the time before fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga (billion years ago).[1] Other subdivisions reflect the evolution of life; the Archean and Proterozoic are both eons, the Palaeozoic, Mesozoic and Cenozoic are eras of the Phanerozoic eon. The three million year Quaternary period, the time of recognizable humans, is too small to be visible at this scale.

In this timeline, Ma (for megaannum) means "million years ago," ka (for kiloannum) means "thousand years ago," and ya means "years ago."

Evidence from radiometric dating indicates that Earth is about 4.54 billion years old.

The primary defined divisions of tim are eons, in sequence the Hadean, the Archean, the Proterozoic and the Phanerozoic. The first three of these can be referred to collectively as the Precambrian supereon. Eons are divided into eras, which are in turn divided into periods, epochs and ages.

The following four timelines show the geologic time scale. The first shows the entire time from the formation of the Earth to the present, but this gives little space for the most recent eon. Therefore, the second timeline shows an expanded view of the most recent eon. In a similar way, the most recent era is expanded in the third timeline, and the most recent period is expanded in the fourth timeline

(LINK)

Millions of Years

Corresponding to eons, eras, periods, epochs and ages, the terms "eonothem", "erathem", "system", "series", "stage" are used to refer to the layers of rock that belong to these stretches of geologic time in Earth's history.

Geologists qualify these units as "early", "mid", and "late" when referring to time, and "lower", "middle", and "upper" when referring to the corresponding rocks. For example, the lower Jurassic Series in chronostratigraphy corresponds to the early Jurassic Epoch in geochronology.[2] The adjectives are capitalized when the subdivision is formally recognized, and lower case when not; thus "early Miocene" but "Early Jurassic."

Table of geologic time (LINK)

The following table summarizes the major events and characteristics of the periods of time making up the geologic time scale. This table is arranged with the most recent geologic periods at the top, and the most ancient at the bottom. The height of each table entry does not correspond to the duration of each subdivision of time.

The content of the table is based on the current official geologic time scale of the International Commission on Stratigraphy,[1] with the epoch names altered to the early/late format from lower/upper as recommended by the ICS when dealing with chronostratigraphy.[2]

Supereon	Eon	Era	Period^[b]	Epoch	Age^[c]	Major events	Start, million years ago^[c]
n/a^[d]	Phanerozoic	Cenozoic^[e]	Quaternary	Holocene	Meghalayan · Northgrippian · Greenlandian	Quaternary Ice Age recedes, and the current interglacial begins. Sahara forms from savannah. Rise of human civilization, beginning of agriculture. Stone Age cultures give way to Bronze Age (3300 BC) and Iron Age (1200 BC), giving rise to many pre-historic cultures throughout the world. Little Ice Age (stadial) causes brief cooling in Northern Hemisphere from 1400 to 1850. Following the Industrial Revolution, atmospheric CO₂ levels rise from around 280 parts per million volume (ppmv) to the current level of 400^[29] ppmv.^[30]^[f]	0.0117^[g]
				Pleistocene	Late (locally Tarantian · Tyrrhenian · Eemian · Sangamonian)	Flourishing and then extinction of Pleistocene megafauna. Evolution of anatomically modern humans. Quaternary Ice Age continues with glaciations and interstadials (and the accompanying fluctuations from 100 to 300 ppmv in atmospheric CO₂ levels^[30]^[f]), further intensification of Icehouse Earth conditions, roughly 1.6 Ma. Last glacial maximum (30000 years ago), last glacial period (18000–15000 years ago). Dawn of human stone-age cultures, with increasing technical complexity relative to previous ice age cultures, such as engravings and clay statues (e.g. Venus of Lespugue), particularly in the Mediterranean and Europe. Lake Toba supervolcano erupts 75000 years before present, causing a volcanic winter that possibly pushes humanity to the brink of extinction. Pleistocene ends with Oldest Dryas, Older Dryas/Allerød and Younger Dryas climate events, with Younger Dryas forming the boundary with the Holocene.	0.126
					Middle (formerly Ionian^{[citation needed]})		0.781
					Calabrian		1.8^*
					Gelasian		2.58^*
			Neogene	Pliocene	Piacenzian	Intensification of present Icehouse conditions, present (Quaternary) ice age begins roughly 2.58 Ma; cool and dry climate. Australopithecines, many of the existing genera of mammals, and recent mollusks appear. Homo habilis appears.	3.6^*
				Pliocene	Zanclean		5.333^*
				Miocene	Messinian	Moderate Icehouse climate, punctuated by ice ages; Orogeny in Northern Hemisphere. Modern mammal and bird families become recognizable. Horses and mastodons diverse. Grasses become ubiquitous. First apes appear (for reference see the article: "Sahelanthropus tchadensis"). Kaikoura Orogeny forms Southern Alps in New Zealand, continues today. Orogeny of the Alps in Europe slows, but continues to this day. Carpathian orogeny forms Carpathian Mountains in Central and Eastern Europe. Hellenic orogeny in Greece and Aegean Sea slows, but continues to this day. Middle Miocene Disruption occurs. Widespread forests slowly draw in massive amounts of CO₂, gradually lowering the level of atmospheric CO₂ from 650 ppmv down to around 100 ppmv.^[30]^[f]	7.246^*
					Tortonian		11.63^*
					Serravallian		13.82^*
					Langhian		15.97
					Burdigalian		20.44
					Aquitanian		23.03^*
			Paleogene	Oligocene	Chattian	Warm but cooling climate, moving towards Icehouse; Rapid evolution and diversification of fauna, especially mammals. Major evolution and dispersal of modern types of flowering plants	28.1
				Oligocene	Rupelian		33.9^*
				Eocene	Priabonian	Moderate, cooling climate. Archaic mammals (e.g. Creodonts, Condylarths, Uintatheres, etc.) flourish and continue to develop during the epoch. Appearance of several "modern" mammal families. Primitive whales diversify. First grasses. Reglaciation of Antarctica and formation of its ice cap; Azolla event triggers ice age, and the Icehouse Earth climate that would follow it to this day, from the settlement and decay of seafloor algae drawing in massive amounts of atmospheric carbon dioxide,^[30]^[f] lowering it from 3800 ppmv down to 650 ppmv. End of Laramide and Sevier Orogenies of the Rocky Mountains in North America. Orogeny of the Alps in Europe begins. Hellenic Orogeny begins in Greece and Aegean Sea.	37.8
					Bartonian		41.2
					Lutetian		47.8^*
					Ypresian		56^*
				Paleocene	Thanetian	Climate tropical. Modern plants appear; Mammals diversify into a number of primitive lineages following the extinction of the non-avian dinosaurs. First large mammals (up to bear or small hippo size). Alpine orogeny in Europe and Asia begins. Indian Subcontinent collides with Asia 55 Ma, Himalayan Orogeny starts between 52 and 48 Ma.	59.2^*
					Selandian		61.6^*
					Danian		66^*
		Mesozoic	Cretaceous	Late	Maastrichtian	Flowering plants proliferate, along with new types of insects. More modern teleost fish begin to appear. Ammonoidea, belemnites, rudist bivalves, echinoids and sponges all common. Many new types of dinosaurs (e.g. Tyrannosaurs, Titanosaurs, duck bills, and horned dinosaurs) evolve on land, as do Eusuchia (modern crocodilians); and mosasaurs and modern sharks appear in the sea. Primitive birds gradually replace pterosaurs. Monotremes, marsupials and placental mammals appear. Break up of Gondwana. Beginning of Laramide and Sevier Orogenies of the Rocky Mountains. atmospheric CO₂ close to present-day levels.	72.1 ± 0.2^*
					Campanian		83.6 ± 0.2
					Santonian		86.3 ± 0.5^*
					Coniacian		89.8 ± 0.3
					Turonian		93.9^*
					Cenomanian		100.5^*
				Early	Albian		~113
					Aptian		~125
					Barremian		~129.4
					Hauterivian		~132.9
					Valanginian		~139.8
					Berriasian		~145
			Jurassic	Late	Tithonian	Gymnosperms (especially conifers, Bennettitales and cycads) and ferns common. Many types of dinosaurs, such as sauropods, carnosaurs, and stegosaurs. Mammals common but small. First birds and lizards. Ichthyosaurs and plesiosaurs diverse. Bivalves, Ammonites and belemnites abundant. Sea urchins very common, along with crinoids, starfish, sponges, and terebratulid and rhynchonellid brachiopods. Breakup of Pangaea into Gondwana and Laurasia. Nevadan orogeny in North America. Rangitata and Cimmerian orogenies taper off. Atmospheric CO₂ levels 3–4 times the present day levels (1200–1500 ppmv, compared to today's 400 ppmv^[30]^[f]).	152.1 ± 0.9
					Kimmeridgian		157.3 ± 1.0
					Oxfordian		163.5 ± 1.0
				Middle	Callovian		166.1 ± 1.2
					Bathonian		168.3 ± 1.3^*
					Bajocian		170.3 ± 1.4^*
					Aalenian		174.1 ± 1.0^*
				Early	Toarcian		182.7 ± 0.7^*
					Pliensbachian		190.8 ± 1.0^*
					Sinemurian		199.3 ± 0.3^*
					Hettangian		201.3 ± 0.2^*
			Triassic	Late	Rhaetian	Archosaurs dominant on land as dinosaurs, in the oceans as Ichthyosaurs and nothosaurs, and in the air as pterosaurs. Cynodonts become smaller and more mammal-like, while first mammals and crocodilia appear. Dicroidiumflora common on land. Many large aquatic temnospondyl amphibians. Ceratitic ammonoids extremely common. Modern corals and teleost fish appear, as do many modern insect clades. Andean Orogeny in South America. Cimmerian Orogeny in Asia. Rangitata Orogeny begins in New Zealand. Hunter-Bowen Orogeny in Northern Australia, Queensland and New South Wales ends, (c. 260–225 Ma)	~208.5
					Norian		~227
					Carnian		~237^*
				Middle	Ladinian		~242^*
				Middle	Anisian		247.2
				Early	Olenekian		251.2
				Early	Induan		251.902 ± 0.06^*
		Paleozoic	Permian	Lopingian	Changhsingian	Landmasses unite into supercontinent Pangaea, creating the Appalachians. End of Permo-Carboniferous glaciation. Synapsid reptiles (pelycosaurs and therapsids) become plentiful, while parareptiles and temnospondyl amphibians remain common. In the mid-Permian, coal-age flora are replaced by cone-bearing gymnosperms (the first true seed plants) and by the first true mosses. Beetles and flies evolve. Marine life flourishes in warm shallow reefs; productid and spiriferid brachiopods, bivalves, forams, and ammonoids all abundant. Permian-Triassic extinction event occurs 251 Ma: 95% of life on Earth becomes extinct, including all trilobites, graptolites, and blastoids. Ouachita and Innuitian orogenies in North America. Uralian orogeny in Europe/Asia tapers off. Altaid orogeny in Asia. Hunter-Bowen Orogeny on Australian continent begins (c. 260–225 Ma), forming the MacDonnell Ranges.	254.14 ± 0.07^*
				Lopingian	Wuchiapingian		259.1 ± 0.4^*
				Guadalupian	Capitanian		265.1 ± 0.4^*
					Wordian		268.8 ± 0.5^*
					Roadian		272.95 ± 0.5^*
				Cisuralian	Kungurian		283.5 ± 0.6
					Artinskian		290.1 ± 0.26
					Sakmarian		295 ± 0.18
					Asselian		298.9 ± 0.15^*
			Carbon- iferous^[h]	Pennsylvanian	Gzhelian	Winged insects radiate suddenly; some (esp. Protodonata and Palaeodictyoptera) are quite large. Amphibians common and diverse. First reptiles and coal forests (scale trees, ferns, club trees, giant horsetails, Cordaites, etc.). Highest-ever atmospheric oxygen levels. Goniatites, brachiopods, bryozoa, bivalves, and corals plentiful in the seas and oceans. Testate forams proliferate. Uralian orogeny in Europe and Asia. Variscan orogeny occurs towards middle and late Mississippian Periods.	303.7 ± 0.1
					Kasimovian		307 ± 0.1
					Moscovian		315.2 ± 0.2
Bashkirian	323.2 ± 0.4^*
Mississippian	Serpukhovian			Large primitive trees, first land vertebrates, and amphibious sea-scorpions live amid coal-forming coastal swamps. Lobe-finned rhizodonts are dominant big fresh-water predators. In the oceans, early sharks are common and quite diverse; echinoderms (especially crinoids and blastoids) abundant. Corals, bryozoa, goniatites and brachiopods (Productida, Spiriferida, etc.) very common, but trilobites and nautiloids decline. Glaciation in East Gondwana. Tuhua Orogeny in New Zealand tapers off.	330.9 ± 0.2
	Viséan				346.7 ± 0.4^*
	Tournaisian				358.9 ± 0.4^*
Devonian	Late		Famennian	First clubmosses, horsetails and ferns appear, as do the first seed-bearing plants (progymnosperms), first trees (the progymnosperm Archaeopteris), and first (wingless) insects. Strophomenid and atrypid brachiopods, rugose and tabulate corals, and crinoids are all abundant in the oceans. Goniatite ammonoids are plentiful, while squid-like coleoids arise. Trilobites and armoured agnaths decline, while jawed fishes (placoderms, lobe-finned and ray-finned fish, and early sharks) rule the seas. First amphibians still aquatic. "Old Red Continent" of Euramerica. Beginning of Acadian Orogeny for Anti-Atlas Mountains of North Africa, and Appalachian Mountains of North America, also the Antler, Variscan, and Tuhua Orogeny in New Zealand.	372.2 ± 1.6^*
	Late		Frasnian		382.7 ± 1.6^*
	Middle		Givetian		387.7 ± 0.8^*
	Middle		Eifelian		393.3 ± 1.2^*
	Early		Emsian		407.6 ± 2.6^*
			Pragian		410.8 ± 2.8^*
			Lochkovian		419.2 ± 3.2^*
Silurian	Pridoli		First vascular plants (the rhyniophytes and their relatives), first millipedes and arthropleurids on land. First jawed fishes, as well as many armoured jawless fish, populate the seas. Sea-scorpions reach large size. Tabulate and rugose corals, brachiopods (Pentamerida, Rhynchonellida, etc.), and crinoids all abundant. Trilobites and mollusks diverse; graptolites not as varied. Beginning of Caledonian Orogeny for hills in England, Ireland, Wales, Scotland, and the Scandinavian Mountains. Also continued into Devonian period as the Acadian Orogeny, above. Taconic Orogeny tapers off. Lachlan Orogeny on Australian continent tapers off.	423 ± 2.3^*
	Ludlow			Ludfordian	425.6 ± 0.9^*
	Ludlow			Gorstian	427.4 ± 0.5^*
	Wenlock			Homerian	430.5 ± 0.7^*
	Wenlock			Sheinwoodian	433.4 ± 0.8^*
	Llandovery			Telychian	438.5 ± 1.1^*
				Aeronian	440.8 ± 1.2^*
				Rhuddanian	443.8 ± 1.5^*
Ordovician	Late		Hirnantian	Invertebrates diversify into many new types (e.g., long straight-shelled cephalopods). Early corals, articulate brachiopods (Orthida, Strophomenida, etc.), bivalves, nautiloids, trilobites, ostracods, bryozoa, many types of echinoderms (crinoids, cystoids, starfish, etc.), branched graptolites, and other taxa all common. Conodonts (early planktonic vertebrates) appear. First green plants and fungi on land. Ice age at end of period.	445.2 ± 1.4^*
			Katian		453 ± 0.7^*
			Sandbian		458.4 ± 0.9^*
	Middle		Darriwilian		467.3 ± 1.1^*
	Middle		Dapingian		470 ± 1.4^*
	Early		Floian (formerly Arenig)		477.7 ± 1.4^*
	Early		Tremadocian		485.4 ± 1.9^*
Cambrian	Furongian		Stage 10	Major diversification of life in the Cambrian Explosion. Numerous fossils; most modern animal phyla appear. First chordates appear, along with a number of extinct, problematic phyla. Reef-building Archaeocyatha abundant; then vanish. Trilobites, priapulid worms, sponges, inarticulate brachiopods (unhinged lampshells), and numerous other animals. Anomalocarids are giant predators, while many Ediacaran fauna die out. Prokaryotes, protists (e.g., forams), fungi and algae continue to present day. Gondwana emerges. Petermann Orogeny on the Australian continent tapers off (550–535 Ma). Ross Orogeny in Antarctica. Adelaide Geosyncline (Delamerian Orogeny), majority of orogenic activity from 514–500 Ma. Lachlan Orogeny on Australian continent, c. 540–440 Ma. Atmospheric CO₂ content roughly 15 times present-day (Holocene) levels (6000 ppmv compared to today's 400 ppmv)^[30]^[f]	~489.5
			Jiangshanian		~494^*
			Paibian		~497^*
	Miaolingian		Guzhangian		~500.5^*
			Drumian		~504.5^*
			Wuliuan		~509
	Series 2		Stage 4		~514
	Series 2		Stage 3		~521
	Terreneuvian		Stage 2		~529
	Terreneuvian		Fortunian		~541 ± 1.0^*
Precambrian^[i]	Proterozoic^[j]		Neoproterozoic^[j]	Ediacaran	Good fossils of the first multi-celled animals. Ediacaran biota flourish worldwide in seas. Simple trace fossils of possible worm-like Trichophycus, etc. First sponges and trilobitomorphs. Enigmatic forms include many soft-jellied creatures shaped like bags, disks, or quilts (like Dickinsonia). Taconic Orogeny in North America. Aravalli Range orogeny in Indian Subcontinent. Beginning of Petermann Orogeny on Australian continent. Beardmore Orogeny in Antarctica, 633–620 Ma.			~635^*
		Cryogenian		Possible "Snowball Earth" period. Fossils still rare. Rodinia landmass begins to break up. Late Ruker / Nimrod Orogeny in Antarctica tapers off.			~720^[k]
		Tonian		Rodinia supercontinent persists. Sveconorwegian orogeny ends. Trace fossils of simple multi-celled eukaryotes. First radiation of dinoflagellate-like acritarchs. Grenville Orogeny tapers off in North America. Pan-African orogeny in Africa. Lake Ruker / Nimrod Orogeny in Antarctica, 1,000 ± 150 Ma. Edmundian Orogeny (c. 920 – 850 Ma), Gascoyne Complex, Western Australia. Adelaide Geosyncline laid down on Australian continent, beginning of Adelaide Geosyncline (Delamerian Orogeny) in Australia.			1000^[k]
		Mesoproterozoic^[j]	Stenian	Narrow highly metamorphic belts due to orogeny as Rodinia forms. Sveconorwegian orogeny starts. Late Ruker / Nimrod Orogeny in Antarctica possibly begins. Musgrave Orogeny (c. 1,080 Ma), Musgrave Block, Central Australia.			1200^[k]
			Ectasian	Platform covers continue to expand. Green algae colonies in the seas. Grenville Orogeny in North America.			1400^[k]
			Calymmian	Platform covers expand. Barramundi Orogeny, McArthur Basin, Northern Australia, and Isan Orogeny, c.1,600 Ma, Mount Isa Block, Queensland			1600^[k]
		Paleoproterozoic^[j]	Statherian	First complex single-celled life: protists with nuclei. Columbia is the primordial supercontinent. Kimban Orogeny in Australian continent ends. Yapungku Orogeny on Yilgarn craton, in Western Australia. Mangaroon Orogeny, 1,680–1,620 Ma, on the Gascoyne Complex in Western Australia. Kararan Orogeny (1,650 Ma), Gawler Craton, South Australia.			1800^[k]
			Orosirian	The atmosphere becomes oxygenic. Vredefort and Sudbury Basin asteroid impacts. Much orogeny. Penokean and Trans-Hudsonian Orogenies in North America. Early Ruker Orogeny in Antarctica, 2,000–1,700 Ma. Glenburgh Orogeny, Glenburgh Terrane, Australian continent c. 2,005–1,920 Ma. Kimban Orogeny, Gawler craton in Australian continent begins.			2050^[k]
			Rhyacian	Bushveld Igneous Complex forms. Huronian glaciation.			2300^[k]
			Siderian	Oxygen catastrophe: banded iron formations forms. Sleaford Orogeny on Australian continent, Gawler Craton 2,440–2,420 Ma.			2500^[k]
	Archean^[j]	Neoarchean^[j]	Stabilization of most modern cratons; possible mantle overturn event. Insell Orogeny, 2,650 ± 150 Ma. Abitibi greenstone belt in present-day Ontario and Quebec begins to form, stabilizes by 2,600 Ma.				2800^[k]
		Mesoarchean^[j]	First stromatolites (probably colonial cyanobacteria). Oldest macrofossils. Humboldt Orogeny in Antarctica. Blake River Megacaldera Complex begins to form in present-day Ontario and Quebec, ends by roughly 2,696 Ma.				3200^[k]
		Paleoarchean^[j]	First known oxygen-producing bacteria. Oldest definitive microfossils. Oldest cratons on Earth (such as the Canadian Shield and the Pilbara Craton) may have formed during this period.^[l] Rayner Orogeny in Antarctica.				3600^[k]
		Eoarchean^[j]	Simple single-celled life (probably bacteria and archaea). Oldest probable microfossils. The first life forms and self-replicating RNA molecules evolve around 4,000 Ma, after the Late Heavy Bombardment ends on Earth. Napier Orogeny in Antarctica, 4,000 ± 200 Ma.				~4000
	Hadean^[j]^[m]	Early Imbrian (Neohadean) (unofficial)^[j]^[n]	Indirect photosynthetic evidence (e.g., kerogen) of primordial life. This era overlaps the beginning of the Late Heavy Bombardment of the Inner Solar System, produced possibly by the planetary migration of Neptune into the Kuiper belt as a result of orbital resonances between Jupiter and Saturn. Oldest known rock (4,031 to 3,580 Ma).^[32]				4130^[33]
		Nectarian (Mesohadean) (unofficial)^[j]^[n]	Possible first appearance of plate tectonics. This unit gets its name from the lunar geologic timescale when the Nectaris Basin and other greater lunar basins form by big impact events. Earliest evidence for life based on unusually high amounts of light isotopes of carbon, a common sign of life.				4280^[33]
		Basin Groups (Paleohadean) (unofficial)^[j]^[n]	End of the Early Bombardment Phase. Oldest known mineral (Zircon, 4,404 ± 8 Ma). Asteroids and comets bring water to Earth.^[34]				4533^[33]
		Cryptic (Eohadean) (unofficial)^[j]^[n]	Formation of Moon (4,533 to 4,527 Ma), probably from giant impact, since the end of this era. Formation of Earth (4,570 to 4,567.17 Ma), Early Bombardment Phase begins. Formation of Sun (4,680 to 4,630 Ma) .				4600