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The Blue Marble—Earth as seen by Apollo 17 in 1972

WELCOME TO DEEP TIME

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What is Deep Time?

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Deep time is the concept of geologic time. The modern philosophical concept was developed in the 18th century by Scottish geologist James Hutton (1726–1797).[1][2] Modern scientists believe, after a long and complex history of developments, that the age of the Earth is around 4.55 billion years.[3]

Scientific concept of Deep Time

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Hutton based his view of deep time on a form of geochemistry that had been developed in Scotland and Scandinavia from the 1750s onward.[4] As mathematician John Playfair, one of Hutton's friends and colleagues in the Scottish Enlightenment, later remarked upon seeing the strata of the angular unconformity at Siccar Point with Hutton and James Hall in June 1788, "the mind seemed to grow giddy by looking so far into the abyss of time".[5]

Early geologists such as Nicolas Steno and Horace-Bénédict de Saussure developed ideas of geological strata forming from water through chemical processes, which Abraham Gottlob Werner (1749–1817) developed into a theory known as Neptunism, envisaging the slow crystallisation of minerals in the ancient oceans of the Earth to form rock. Hutton's innovative 1785 theory, based on Plutonism, visualised an endless cyclical process of rocks forming under the sea, being uplifted and tilted, then eroded to form new strata under the sea. In 1788 the sight of Hutton's Unconformity at Siccar Point convinced Playfair and Hall of this extremely slow cycle, and in that same year Hutton memorably wrote "we find no vestige of a beginning, no prospect of an end".[6][7]

Other scientists such as Georges Cuvier put forward ideas of past ages, and geologists such as Adam Sedgwick incorporated Werner's ideas into concepts of catastrophism; Sedgwick inspired his university student Charles Darwin to exclaim "What a capital hand is Sedgewick for drawing large cheques upon the Bank of Time!".[8] In a competing theory, Charles Lyell in his Principles of Geology (1830–1833) developed Hutton's comprehension of endless deep time as a crucial scientific concept into uniformitarianism. As a young naturalist and geological theorist, Darwin studied the successive volumes of Lyell's book exhaustively during the Beagle survey voyage in the 1830s, before beginning to theorise about evolution.

Physicist Gregory Benford addresses the concept in Deep Time: How Humanity Communicates Across Millennia (1999), as does paleontologist and Nature editor Henry Gee in In Search of Deep Time: Beyond the Fossil Record to a New History of Life (2001)[9][10] Stephen Jay Gould's Time's Arrow, Time's Cycle (1987) also deals in large part with the evolution of the concept.

John McPhee discussed "deep time" at length with the layman in mind in Basin and Range (1981), parts of which originally appeared in the The New Yorker magazine.[11] In Time's Arrow, Time's Cycle, Gould cited one of the metaphors McPhee used in explaining the concept of deep time:

Consider the Earth's history as the old measure of the English yard, the distance from the King's nose to the tip of his outstretched hand. One stroke of a nail file on his middle finger erases human history.[11]

Concepts similar to geologic time were recognized in the 11th century by the Persian geologist and polymath Avicenna (Ibn Sina, 973–1037),[12] and by the Chinese naturalist and polymath Shen Kuo (1031–1095).[13]

The Roman Catholic theologian Thomas Berry (1914–2009) explored the spiritual implications of the concept of Deep Time. Berry proposes that a deep understanding of the history and functioning of the evolving universe is a necessary inspiration and guide for our own effective functioning as individuals and as a species. This view has greatly influenced the development of deep ecology and ecophilosophy. The experiential nature of the experience of deep time has also greatly influenced the work of Joanna Macy and John Seed.

H.G. Wells and Julian Huxley regarded the difficulties of coping with the concept of deep time as exaggerated:

"The use of different scales is simply a matter of practice", they said in The Science of Life (1929). "We very soon get used to maps, though they are constructed on scales down to a hundred-millionth of natural size. . .  to grasp geological time all that is needed is to stick tight to some magnitude which shall be the unit on the new and magnified scale—a million years is probably the most convenient—to grasp its meaning once and for all by an effort of imagination, and then to think of all passage of geological time in terms of this unit."[14]

Geologic Time

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Image: The geologic clock with periods

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Geochronology and stratigraphy

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Units in geochronology and stratigraphy[15]
Segments of rock (strata) in chronostratigraphy Time spans in geochronology Notes to
geochronological units
Eonothem Eon 4 total, half a billion years or more
Erathem Era 10 defined, several hundred million years
System Period 22 defined, tens to ~one hundred million years
Series Epoch 34 defined, tens of millions of years
Stage Age 99 defined, millions of years
Chronozone Chron subdivision of an age, not used by the ICS timescale

Geologic time scale

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(The Precambrian supereon accounts for 88% of all geologic time.)

Table: Basic geologic time: Eons, Eras, Periods, Epochs and Ages
Eon Era Period Extent, Million
Yrs Ago 		Duration,
Millions of Yrs
Phanerozoic Cenozoic Quaternary
(Pleistocene/Holocene) 		2.588–0 2.588+
Neogene
(Miocene/Pliocene) 		23.03–2.588 20.4
Paleogene
(Paleocene/Eocene/Oligocene) 		66.0–23.03 42.9
Mesozoic Cretaceous 145.5–66.0 79.5
Jurassic 201.3–145.0 56.3
Triassic 252.17–201.3 50.9
Paleozoic Permian 298.9–252.17 46.7
Carboniferous
(Mississippian/Pennsylvanian) 		358.9–298.9 60
Devonian 419.2–358.9 60.3
Silurian 443.4–419.2 24.2
Ordovician 485.4–443.4 42
Cambrian 541.0–485.4 55.6
Proterozoic Neoproterozoic Ediacaran 635.0–541.0 94
Cryogenian 850–635 215
Tonian 1000–850 150
Mesoproterozoic Stenian 1200–1000 200
Ectasian 1400–1200 200
Calymmian 1600–1400 200
Paleoproterozoic Statherian 1800–1600 200
Orosirian 2050–1800 250
Rhyacian 2300–2050 250
Siderian 2500–2300 200
Archean Neoarchean 2800-2500 300
Mesoarchean 3200-2800 400
Paleoarchean 3600-3200 400
Eoarchean 4000-3600 400
Hadean (-)4600-4000 600+

The following table summarizes the major events and characteristics of the periods of time making up the geologic time scale. As with the time scales above, this time scale is based on the International Commission on Stratigraphy. (See lunar geologic timescale for a discussion of the geologic subdivisions of Earth's moon.) 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,[16] with the epoch names altered to the early/late format from lower/upper as recommended by the ICS when dealing with chronostratigraphy.[17]

Table: Detailed Geologic Time: Supereons, Eons, Eras, Periods, Epochs and Ages
Supereon Eon Era Period[18] Epoch Age[19] Major events Start, million years ago[19]
n/a[20] Phanerozoic Cenozoic[21] Quaternary Holocene

chrons: Subatlantic · Subboreal · Atlantic · Boreal · Preboreal

Quaternary Ice Age recedes, and the current interglacial begins; rise of human civilization. Sahara forms from savannah, and agriculture begins. 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[22] ppmv.[23][24] 0.0117[25]
Pleistocene Late (locally Tarantian · Tyrrhenian · Eemian · Sangamonian) Flourishing and then extinction of many large mammals (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[23][24]), 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 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. 0.129
Middle (formerly Ionian) 0.774
Calabrian 1.8*
Gelasian 2.58*
Neogene Pliocene Piacenzian/Blancan 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*
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.[23][24] 7.246*
Tortonian 11.63*
Serravallian 13.82*
Langhian 15.98
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 27.82
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,[23][24] 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. 37.71
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 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 ~121.4
Barremian ~125.77
Hauterivian ~132.6
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. Rantigata and Cimmerian Orogenies taper off. Atmospheric CO2 levels 4–5 times the present day levels (1200–1500 ppmv, compared to today's 385 ppmv[23][24]). 149.2 ± 0.9
Kimmeridgian 154.8 ± 1.0
Oxfordian 161.5 ± 1.0
Middle Callovian 165.3 ± 1.2
Bathonian 168.2 ± 1.3*
Bajocian 170.9 ± 1.4*
Aalenian 174.7 ± 1.0*
Early Toarcian 184.2 ± 0.7*
Pliensbachian 192.9 ± 1.0*
Sinemurian 199.5 ± 0.3*
Hettangian 201.4 ± 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*
Anisian 247.2
Early Olenekian 251.2
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*
Wuchiapingian 259.51 ± 0.4*
Guadalupian Capitanian 264.28 ± 0.4*
Wordian/Kazanian 266.9 ± 0.5*
Roadian/Ufimian 273.01 ± 0.5*
Cisuralian Kungurian 283.5 ± 0.6
Artinskian 290.1 ± 0.26
Sakmarian 293.52 ± 0.18
Asselian 298.9 ± 0.15*
Carbon-
iferous[26] 		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*
Frasnian 382.7 ± 1.6*
Middle Givetian 387.7 ± 0.8*
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/Cayugan Ludfordian 425.6 ± 0.9*
Gorstian 427.4 ± 0.5*
Wenlock Homerian/
Lockportian 		430.5 ± 0.7*
Sheinwoodian/
Tonawandan 		433.4 ± 0.8*
Llandovery/
Alexandrian 		Telychian/
Ontarian 		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*
Dapingian 470 ± 1.4*
Early Floian
(formerly Arenig) 		477.7 ± 1.4*
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 20–35 times present-day (Holocene) levels (6000 ppmv compared to today's 385 ppmv)[23][24] ~489.5
Jiangshanian ~494*
Paibian ~497*
Series 3 Guzhangian ~500.5*
Drumian ~504.5*
Stage 5 ~509
Series 2 Stage 4 ~514
Stage 3 ~521
Terreneuvian Stage 2 ~529
Fortunian 538.8 ± 1.0*
Precambrian[27] Proterozoic[28] Neoproterozoic[28] 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 (likeDickinsonia). 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[29]
Tonian Rodinia supercontinent persists. 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, 1000 ± 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 that continent. 1000[29]
Mesoproterozoic[28] Stenian Narrow highly metamorphic belts due to orogeny as Rodinia forms. Late Ruker / Nimrod Orogeny in Antarctica possibly begins. Musgrave Orogeny (c. 1080 Ma), Musgrave Block, Central Australia. 1200[29]
Ectasian Platform covers continue to expand. Green algae colonies in the seas. Grenville Orogeny in North America. 1400[29]
Calymmian Platform covers expand. Barramundi Orogeny, McArthur Basin, Northern Australia, and Isan Orogeny, c.1600 Ma, Mount Isa Block, Queensland 1600[29]
Paleoproterozoic[28] 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, 1680–1620 Ma, on the Gascoyne Complex in Western Australia. Kararan Orogeny (1650– Ma), Gawler Craton, South Australia. 1800[29]
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, 2000–1700 Ma. Glenburgh Orogeny, Glenburgh Terrane, Australian continent c. 2005–1920 Ma. Kimban Orogeny, Gawler craton in Australian continent begins. 2050[29]
Rhyacian Bushveld Igneous Complex forms. Huronian glaciation. 2300[29]
Siderian Oxygen catastrophe: banded iron formations forms. Sleaford Orogeny on Australian continent, Gawler Craton 2440–2420 Ma. 2500[29]
Archean[28] Neoarchean[28] Stabilization of most modern cratons; possible mantle overturn event. Insell Orogeny, 2650 ± 150 Ma. Abitibi greenstone belt in present-day Ontario and Quebec begins to form, stabilizes by 2600 Ma. 2800[29]
Mesoarchean[28] 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 2696 Ma. 3200[29]
Paleoarchean[28] 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.[30] Rayner Orogeny in Antarctica. 3600[29]
Eoarchean[28] Simple single-celled life (probably bacteria and archaea). Oldest probable microfossils. 4031
Hadean[28][31] Early Imbrian[28][32] Indirect photosynthetic evidence (e.g., kerogen) of primordial life. This era overlaps the end of the Late Heavy Bombardment of the Inner Solar System. ~4100
Nectarian[28][32] This unit gets its name from the lunar geologic timescale when the Nectaris Basin and other greater lunar basins form by big impact events. ~4300
Basin Groups[28][32] Oldest known rock (4030 Ma).[33] The first life forms and self-replicating RNA molecules evolve around 4000 Ma, after the Late Heavy Bombardment ends on Earth. Napier Orogeny in Antarctica, 4000 ± 200 Ma. ~4500
Cryptic[28][32] Oldest known mineral (Zircon, 4404 ± 8 Ma).[34] Formation of Moon (4533 Ma), probably from giant impact. Formation of Earth (4567.17 to 4570 Ma) ~4567

Condensed graphical timelines

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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 compresses the most recent eon. Therefore, the second scale shows the most recent eon with an expanded scale. The second scale compresses the most recent era, so the most recent era is expanded in the third scale. Since the Quaternary is a very short period with short epochs, it is further expanded in the fourth scale. The second, third, and fourth timelines are therefore each subsections of their preceding timeline as indicated by asterisks. The Holocene (the latest epoch) is too small to be shown clearly on the third timeline on the right, another reason for expanding the fourth scale. The Pleistocene (P) epoch. Q stands for the Quaternary period.

SiderianRhyacianOrosirianStatherianCalymmianEctasianStenianTonianCryogenianEdiacaranEoarcheanPaleoarcheanMesoarcheanNeoarcheanPaleoproterozoicMesoproterozoicNeoproterozoicPaleozoicMesozoicCenozoicHadeanArcheanProterozoicPhanerozoicPrecambrian


CambrianOrdovicianSilurianDevonianCarboniferousPermianTriassicJurassicCretaceousPaleogeneNeogeneQuaternaryPaleozoicMesozoicCenozoicPhanerozoic


PaleoceneEoceneOligoceneMiocenePliocenePleistoceneHolocenePaleogeneNeogeneQuaternaryCenozoic


GelasianCalabrian (stage)PleistocenePleistocenePleistoceneHoloceneQuaternary
Millions of Years


Recommended viewing and reading

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Television Series

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  1. Africa
  2. Australia
  3. The Americas
  4. Eurasia
  • BBC, Men of Rock, a 2010 TV series about pioneering geologists working in Scotland. It consists of three episodes presented by Professor Iain Stewart:
  1. Deep Time. The story of James Hutton, the founding father of geology.
  2. Moving Mountains. An examination of how geologist Edward Bailey discovered Scotland once had super volcanoes.
  3. The Big Freeze. The story of Louis Agassiz, who first proposed that the earth had experienced an ice age.
  • PBS Nova, Making North America (2015), the epic 3 billion-year story of how our continent came to be. From the palm trees that once flourished in Alaska to titanic eruptions that nearly tore the Midwest in two, discover how forces of almost unimaginable power gave birth to North America.
  1. Part 1: Origins.
  2. Part 2: Life
  3. Part 3: Humans
  • Channel4, UK, Catastrophe - This spectacular five-part documentary series, presented by Tony Robinson, investigates the history of natural disasters from the planet's beginnings to the present, putting a new perspective on our existence and suggesting that we are the product of catastrophe.
  1. Episode 1 - Birth of the Planet.
  2. Episode 2 - Snowball Earth.
  3. Episode 3 - Planet of Fire.
  4. Episode 4 - Asteroid Impact.
  5. Episode 5 - Survival Earth.
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  1. ^ Palmer & Zen.
  2. ^ Kubicek 2008.
  3. ^ Braterman, Paul S. "How Science Figured Out the Age of Earth". Scientific American. Retrieved 2016-04-17.
  4. ^ Eddy, Matthew Daniel (2008). The Language of Mineralogy: John Walker, Chemistry and the Edinburgh Medical School 1750-1800. London: Ashgate. p. Ch. 5.
  5. ^ Playfair 1805.
  6. ^ Montgomery 2003.
  7. ^ Rance 1999.
  8. ^ Darwin 1831.
  9. ^ Korthof 2000.
  10. ^ Campbell 2001.
  11. ^ a b McPhee 1998, p. 77.
  12. ^ Toulmin & Goodfield 1965, p. 64.
  13. ^ Sivin 1995, pp. iii, 23–24.
  14. ^ H.G. Wells, Julian S. Huxley, and G.P. Wells, The Science of Life (New York: The Literary Guild, 1934; orig. publ. 1929), p. 326.
  15. ^ Cohen, K.M.; Finney, S.; Gibbard, P.L. (2015), International Chronostratigraphic Chart (PDF), International Commission on Stratigraphy.
  16. ^ "International Stratigraphic Chart". International Commission on Stratigraphy.
  17. ^ Cite error: The named reference ICSchronostrat was invoked but never defined (see the help page).
  18. ^ Paleontologists often refer to faunal stages rather than geologic (geological) periods. The stage nomenclature is quite complex. For a time-ordered list of faunal stages, see "The Paleobiology Database". Retrieved 2006-03-19.
  19. ^ a b Dates are slightly uncertain with differences of a few percent between various sources being common. This is largely due to uncertainties in radiometric dating and the problem that deposits suitable for radiometric dating seldom occur exactly at the places in the geologic column where they would be most useful. The dates and errors quoted above are according to the International Commission on Stratigraphy 2015 time scale except the Hadean eon. Where errors are not quoted, errors are less than the precision of the age given.

    * indicates boundaries where a Global Boundary Stratotype Section and Point has been internationally agreed upon.
  20. ^ References to the "Post-Cambrian Supereon" are not universally accepted, and therefore must be considered unofficial.
  21. ^ Historically, the Cenozoic has been divided up into the Quaternary and Tertiary sub-eras, as well as the Neogene and Paleogene periods. The 2009 version of the ICS time chart recognizes a slightly extended Quaternary as well as the Paleogene and a truncated Neogene, the Tertiary having been demoted to informal status.
  22. ^ "NASA Scientists React to 400 ppm Carbon Milestone". Retrieved 2014-01-15 [1]
  23. ^ a b c d e f Royer, Dana L. (2006). "CO2-forced climate thresholds during the Phanerozoic" (PDF). Geochimica et Cosmochimica Acta. 70 (23): 5665–75. Bibcode:2006GeCoA..70.5665R. doi:10.1016/j.gca.2005.11.031.
  24. ^ a b c d e f For more information on this, see Atmosphere of Earth#Evolution of Earth's atmosphere, Carbon dioxide in the Earth's atmosphere, and Climate change. Specific graphs of reconstructed CO2 levels over the past ~550, 65, and 5 million years can be seen at File:Phanerozoic Carbon Dioxide.png, File:65 Myr Climate Change.png, File:Five Myr Climate Change.png, respectively.
  25. ^ The start time for the Holocene epoch is here given as 11,700 years ago. For further discussion of the dating of this epoch, see Holocene.
  26. ^ In North America, the Carboniferous is subdivided into Mississippian and Pennsylvanian Periods.
  27. ^ The Precambrian is also known as Cryptozoic.
  28. ^ a b c d e f g h i j k l m n The Proterozoic, Archean and Hadean are often collectively referred to as the Precambrian Time or sometimes, also the Cryptozoic.
  29. ^ a b c d e f g h i j k l Defined by absolute age (Global Standard Stratigraphic Age).
  30. ^ The age of the oldest measurable craton, or continental crust, is dated to 3600–3800 Ma
  31. ^ Though commonly used, the Hadean is not a formal eon and no lower bound for the Archean and Eoarchean have been agreed upon. The Hadean has also sometimes been called the Priscoan or the Azoic. Sometimes, the Hadean can be found to be subdivided according to the lunar geologic timescale. These eras include the Cryptic and Basin Groups (which are subdivisions of the Pre-Nectarian era), Nectarian, and Early Imbrian units.
  32. ^ a b c d These unit names were taken from the lunar geologic timescale and refer to geologic events that did not occur on Earth. Their use for Earth geology is unofficial. Note that their start times do not dovetail perfectly with the later, terrestrially defined boundaries.
  33. ^ Bowring, Samuel A.; Williams, Ian S. (1999). "Priscoan (4.00–4.03 Ga) orthogneisses from northwestern Canada". Contributions to Mineralogy and Petrology. 134 (1): 3. Bibcode:1999CoMP..134....3B. doi:10.1007/s004100050465. The oldest rock on Earth is the Acasta Gneiss, and it dates to 4.03 Ga, located in the Northwest Territories of Canada.
  34. ^ Geology.wisc.edu
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