The geologic time scale, proportionally represented as alog-spiral with some major events in Earth's history. Amegaannus (Ma) represents one million (106) years.
Thegeologic time scale orgeological time scale (GTS) is a representation oftime based on therock record ofEarth. It is a system ofchronological dating that useschronostratigraphy (the process of relatingstrata to time) andgeochronology (a scientific branch ofgeology that aims to determine the age of rocks). It is used primarily byEarth scientists (includinggeologists,paleontologists,geophysicists,geochemists, andpaleoclimatologists) to describe the timing and relationships of events in geologic history. The time scale has been developed through the study of rock layers and the observation of their relationships and identifying features such aslithologies,paleomagnetic properties, andfossils. The definition of standardised international units of geological time is the responsibility of theInternational Commission on Stratigraphy (ICS), a constituent body of theInternational Union of Geological Sciences (IUGS), whose primary objective[1] is to precisely define global chronostratigraphic units of the International Chronostratigraphic Chart (ICC)[2] that are used to define divisions of geological time. The chronostratigraphic divisions are in turn used to define geochronologic units.[2]
The geologic time scale is a way of representingdeep time based on events that have occurred throughoutEarth's history, a time span of about4.54 ± 0.05 Ga (4.54 billion years).[3] It chronologically organises strata, and subsequently time, by observing fundamental changes in stratigraphy that correspond to major geological or paleontological events. For example, theCretaceous–Paleogene extinction event, marks the lower boundary of thePaleogene System/Period and thus the boundary between theCretaceous and Paleogene systems/periods. For divisions prior to theCryogenian, arbitrary numeric boundary definitions (Global Standard Stratigraphic Ages, GSSAs) are used to divide geologic time. Proposals have been made to better reconcile these divisions with the rock record.[4][5]
Historically, regional geologic time scales were used[5] due to the litho- and biostratigraphic differences around the world in time equivalent rocks. The ICS has long worked to reconcile conflicting terminology by standardising globally significant and identifiable stratigraphichorizons that can be used to define the lower boundaries of chronostratigraphic units. Defining chronostratigraphic units in such a manner allows for the use of global, standardised nomenclature. The International Chronostratigraphic Chart represents this ongoing effort.
Several key principles are used to determine the relative relationships of rocks and thus their chronostratigraphic position.[6][7]
Thelaw of superposition that states that in undeformed stratigraphic sequences the oldest strata will lie at the bottom of the sequence, while newer material stacks upon the surface.[8][9][10][7] In practice, this means a younger rock will lie on top of an older rock unless there is evidence to suggest otherwise.
Theprinciple of original horizontality that states layers of sediments will originally be deposited horizontally under the action of gravity.[8][10][7] However, it is now known that not all sedimentary layers are deposited purely horizontally,[7][11] but this principle is still a useful concept.
Theprinciple of lateral continuity that states layers of sediments extend laterally in all directions until either thinning out or being cut off by a different rock layer, i.e. they are laterally continuous.[8] Layers do not extend indefinitely; their limits are controlled by the amount and type of sediment in asedimentary basin, and the geometry of that basin.
Thelaw of included fragments that states small fragments of one type of rock that are embedded in a second type of rock must have formed first, and were included when the second rock was forming.[10][7]
The relationships ofunconformities which are geologic features representing a gap in the geologic record. Unconformities are formed during periods of erosion or non-deposition, indicating non-continuous sediment deposition.[7] Observing the type and relationships of unconformities in strata allows geologist to understand the relative timing the strata.
Theprinciple of faunal succession (where applicable) that states rock strata contain distinctive sets of fossils that succeed each other vertically in a specific and reliable order.[12][7] This allows for a correlation of strata even when the horizon between them is not continuous.
Aperiod is equivalent to a chronostratigraphicsystem.[14][13] There are 22 defined periods, with the current being theQuaternary period.[2] As an exception, two subperiods are used for theCarboniferous Period.[14]
Anepoch is the second smallest geochronologic unit. It is equivalent to a chronostratigraphicseries.[14][13] There are 37 defined epochs and one informal one. The current epoch is theHolocene. There are also 11 subepochs which are all within theNeogene and Quaternary.[2] The use of subepochs as formal units in international chronostratigraphy was ratified in 2022.[15]
Anage is the smallest hierarchical geochronologic unit. It is equivalent to a chronostratigraphicstage.[14][13] There are 96 formal and five informal ages.[2] The current age is theMeghalayan.
Achron is a non-hierarchical formal geochronology unit of unspecified rank and is equivalent to a chronostratigraphicchronozone.[14] These correlate withmagnetostratigraphic,lithostratigraphic, orbiostratigraphic units as they are based on previously defined stratigraphic units or geologic features.
Formal, hierarchical units of the geologic time scale (largest to smallest)
Several hundred million years to two billion years
Erathem
Era
Tens to hundreds of millions of years
System
Period
Millions of years to tens of millions of years
Series
Epoch
Hundreds of thousands of years to tens of millions of years
Subseries
Subepoch
Thousands of years to millions of years
Stage
Age
Thousands of years to millions of years
The subdivisionsEarly andLate are used as the geochronologic equivalents of the chronostratigraphicLower andUpper, e.g., EarlyTriassic Period (geochronologic unit) is used in place of Lower Triassic System (chronostratigraphic unit).
Rocks representing a given chronostratigraphic unit are that chronostratigraphic unit, and the time they were laid down in is the geochronologic unit, e.g., the rocks that represent theSilurian Systemare the Silurian System and they were depositedduring the Silurian Period. This definition means the numeric age of a geochronologic unit can be changed (and is more often subject to change) when refined by geochronometry while the equivalent chronostratigraphic unit (the revision of which is less frequent) remains unchanged. For example, in early 2022, the boundary between theEdiacaran andCambrianperiods (geochronologic units) was revised from 541 Ma to 538.8 Ma but the rock definition of the boundary (GSSP) at the base of the Cambrian, and thus the boundary between the Ediacaran and Cambriansystems (chronostratigraphic units) has not been changed; rather, the absolute age has merely been refined.
Chronostratigraphy is the element ofstratigraphy that deals with the relation between rock bodies and the relative measurement of geological time.[14] It is the process where distinct strata between defined stratigraphic horizons are assigned to represent a relative interval of geologic time.
Achronostratigraphic unit is a body of rock, layered or unlayered, that is defined between specified stratigraphic horizons which represent specified intervals of geologic time. They include all rocks representative of a specific interval of geologic time, and only this time span. Eonothem, erathem, system, series, subseries, stage, and substage are the hierarchical chronostratigraphic units.[14]
Ageochronologic unit is a subdivision of geologic time. It is a numeric representation of an intangible property (time).[16] These units are arranged in a hierarchy: eon, era, period, epoch, subepoch, age, and subage.[14]Geochronology is the scientific branch of geology that aims to determine the age of rocks, fossils, and sediments either through absolute (e.g.,radiometric dating) or relative means (e.g.,stratigraphic position,paleomagnetism,stable isotope ratios).Geochronometry is the field of geochronology that numerically quantifies geologic time.[16]
AGlobal Standard Stratigraphic Age (GSSA)[19] is a numeric-only, chronologic reference point used to define the base of geochronologic units prior to the Cryogenian. These points are arbitrarily defined.[14] They are used where GSSPs have not yet been established. Research is ongoing to define GSSPs for the base of all units that are currently defined by GSSAs.
The standard international units of the geologic time scale are published by the International Commission on Stratigraphy on the International Chronostratigraphic Chart; however, regional terms are still in use in some areas. The numeric values on the International Chronostratigrahpic Chart are represented by the unitMa (megaannum, for 'millionyears'). For example, 201.4 ± 0.2 Ma, the lower boundary of theJurassic Period, is defined as 201,400,000 years old with an uncertainty of 200,000 years. OtherSI prefix units commonly used by geologists areGa (gigaannum, billion years), andka (kiloannum, thousand years), with the latter often represented in calibrated units (before present).
The names of geologic time units are defined for chronostratigraphic units with the corresponding geochronologic unit sharing the same name with a change to the suffix (e.g. PhanerozoicEonothem becomes the Phanerozoic Eon). Names of erathems in the Phanerozoic were chosen to reflect major changes in the history of life on Earth:Paleozoic (old life),Mesozoic (middle life), andCenozoic (new life). Names of systems are diverse in origin, with some indicating chronologic position (e.g., Paleogene), while others are named forlithology (e.g., Cretaceous),geography (e.g.,Permian), or are tribal (e.g.,Ordovician) in origin. Most currently recognised series and subseries are named for their position within a system/series (early/middle/late); however, the International Commission on Stratigraphy advocates for all new series and subseries to be named for a geographic feature in the vicinity of itsstratotype ortype locality. The name of stages should also be derived from a geographic feature in the locality of its stratotype or type locality.[14]
Informally, the time before the Cambrian is often referred to as thePrecambrian or pre-Cambrian (Supereon).[4][note 2]
Time span andetymology of geologic eonothem/eon names
Coined byWilhelm Philippe Schimper in 1874 as a portmanteau of paleo- + Eocene, but on the surface from Greek παλαιός (palaios) 'old' and καινός (kainós) 'new'
Named for theGuadalupe Mountains of the American Southwest, ultimately from Arabic وَادِي ٱل (wādī al) 'valley of the' and Latinlupus 'wolf' via Spanish
The most modern geological time scale was not formulated until 1911[36] byArthur Holmes (1890 – 1965), who drew inspiration fromJames Hutton (1726–1797), a Scottish Geologist who presented the idea of uniformitarianism or the theory that changes to the Earth's crust resulted from continuous and uniform processes.[37] The broader concept of the relation between rocks and time can be traced back to (at least) thephilosophers ofAncient Greece from 1200 BC to 600 AD.Xenophanes of Colophon (c. 570–487 BCE) observed rock beds with fossils of seashells located above the sea-level, viewed them as once living organisms, and used this to imply an unstable relationship in which the sea had at timestransgressed over the land and at other times hadregressed.[38] This view was shared by a few of Xenophanes's scholars and those that followed, includingAristotle (384–322 BC) who (with additional observations) reasoned that the positions of land and sea had changed over long periods of time. The concept ofdeep time was also recognized byChinese naturalistShen Kuo[39] (1031–1095) andIslamicscientist-philosophers, notably theBrothers of Purity, who wrote on the processes of stratification over the passage of time in theirtreatises.[38] Their work likely inspired that of the 11th-centuryPersianpolymathAvicenna (Ibn Sînâ, 980–1037) who wrote inThe Book of Healing (1027) on the concept of stratification and superposition, pre-datingNicolas Steno by more than six centuries.[38] Avicenna also recognized fossils as "petrifications of the bodies of plants and animals",[40] with the 13th-centuryDominicanbishopAlbertus Magnus (c. 1200–1280), who drew fromAristotle's natural philosophy, extending this into a theory of a petrifying fluid.[41] These works appeared to have little influence onscholars inMedieval Europe who looked to theBible to explain the origins of fossils and sea-level changes, often attributing these to the 'Deluge', includingRistoro d'Arezzo in 1282.[38] It was not until theItalian Renaissance whenLeonardo da Vinci (1452–1519) would reinvigorate the relationships between stratification, relative sea-level change, and time, denouncing attribution of fossils to the 'Deluge':[42][38]
Of the stupidity and ignorance of those who imagine that these creatures were carried to such places distant from the sea by the Deluge...Why do we find so many fragments and whole shells between the different layers of stone unless they had been upon the shore and had been covered over by earth newly thrown up by the sea which then became petrified? And if the above-mentioned Deluge had carried them to these places from the sea, you would find the shells at the edge of one layer of rock only, not at the edge of many where may be counted the winters of the years during which the sea multiplied the layers of sand and mud brought down by the neighboring rivers and spread them over its shores. And if you wish to say that there must have been many deluges in order to produce these layers and the shells among them it would then become necessary for you to affirm that such a deluge took place every year.
Sketch of the Succession of Strata and their Relative Altitudes (William Smith)
These views of da Vinci remained unpublished, and thus lacked influence at the time; however, questions of fossils and their significance were pursued and, while views againstGenesis were not readily accepted and dissent fromreligious doctrine was in some places unwise, scholars such asGirolamo Fracastoro shared da Vinci's views, and found the attribution of fossils to the 'Deluge' absurd.[38] Although many theories surrounding philosophy and concepts of rocks were developed in earlier years, "the first serious attempts to formulate a geological time scale that could be applied anywhere on Earth were made in the late 18th century."[41] Later, in the 19th century, academics further developed theories on stratification.William Smith, often referred to as the "Father of Geology"[43] developed theories through observations rather than drawing from the scholars that came before him. Smith's work was primarily based on his detailed study of rock layers and fossils during his time and he created "the first map to depict so many rock formations over such a large area”.[43] After studying rock layers and the fossils they contained,Smith concluded that each layer of rock contained distinct material that could be used to identify and correlate rock layers across different regions of the world.[44] Smith developed the concept of faunal succession or the idea that fossils can serve as a marker for the age of the strata they are found in and published his ideas in his 1816 book, "Strata identified by organized fossils."[44]
Niels Stensen, more commonly known as Nicolas Steno (1638–1686), is credited with establishing four of the guiding principles of stratigraphy.[38] InDe solido intra solidum naturaliter contento dissertationis prodromus Steno states:[8][45]
When any given stratum was being formed, all the matter resting on it was fluid and, therefore, when the lowest stratum was being formed, none of the upper strata existed.
... strata which are either perpendicular to the horizon or inclined to it were at one time parallel to the horizon.
When any given stratum was being formed, it was either encompassed at its edges by another solid substance or it covered the whole globe of the earth. Hence, it follows that wherever bared edges of strata are seen, either a continuation of the same strata must be looked for or another solid substance must be found that kept the material of the strata from being dispersed.
If a body or discontinuity cuts across a stratum, it must have formed after that stratum.
Respectively, these are the principles of superposition, original horizontality, lateral continuity, and cross-cutting relationships. From this Steno reasoned that strata were laid down in succession and inferred relative time (in Steno's belief, time fromCreation). While Steno's principles were simple and attracted much attention, applying them proved challenging.[38] These basic principles, albeit with improved and more nuanced interpretations, still form the foundational principles of determining the correlation of strata relative to geologic time.
Over the course of the 18th-century geologists realised that:
Sequences of strata often become eroded, distorted, tilted, or even inverted after deposition
Strata laid down at the same time in different areas could have entirely different appearances
The strata of any given area represented only part of Earth's long history
The apparent, earliest formal division of the geologic record with respect to time was introduced during the era of Biblical models byThomas Burnet who applied a two-fold terminology to mountains by identifying "montes primarii" for rock formed at the time of the 'Deluge', and younger "monticulos secundarios" formed later from the debris of the "primarii".[46][38]Anton Moro (1687–1784) also used primary and secondary divisions for rock units but his mechanism was volcanic.[47][38] In this early version of thePlutonism theory, the interior of Earth was seen as hot, and this drove the creation of primary igneous and metamorphic rocks and secondary rocks formed contorted and fossiliferous sediments. These primary and secondary divisions were expanded on byGiovanni Targioni Tozzetti (1712–1783) andGiovanni Arduino (1713–1795) to include tertiary and quaternary divisions.[38] These divisions were used to describe both the time during which the rocks were laid down, and the collection of rocks themselves (i.e., it was correct to say Tertiary rocks, and Tertiary Period). Only the Quaternary division is retained in the modern geologic time scale, while the Tertiary division was in use until the early 21st century. The Neptunism and Plutonism theories would compete into the early19th century with a key driver for resolution of this debate being the work ofJames Hutton (1726–1797), in particular hisTheory of the Earth, first presented before theRoyal Society of Edinburgh in 1785.[48][9][49] Hutton's theory would later become known asuniformitarianism, popularised byJohn Playfair[50] (1748–1819) and laterCharles Lyell (1797–1875) in hisPrinciples of Geology.[10][51][52] Their theories strongly contested the 6,000 year age of the Earth as suggested determined byJames Ussher via Biblical chronology that was accepted at the time by western religion. Instead, using geological evidence, they contested Earth to be much older, cementing the concept of deep time.
During the early 19th centuryWilliam Smith,Georges Cuvier,Jean d'Omalius d'Halloy, andAlexandre Brongniart pioneered the systematic division of rocks by stratigraphy and fossil assemblages. These geologists began to use the local names given to rock units in a wider sense, correlating strata across national and continental boundaries based on their similarity to each other. Many of the names below erathem/era rank in use on the modern ICC/GTS were determined during the early to mid-19th century.
During the 19th century, the debate regarding Earth's age was renewed, with geologists estimating ages based ondenudation rates and sedimentary thicknesses or ocean chemistry, and physicists determining ages for the cooling of the Earth or the Sun using basicthermodynamics or orbital physics.[3] These estimations varied from 15,000 million years to 0.075 million years depending on method and author, but the estimations ofLord Kelvin andClarence King were held in high regard at the time due to their pre-eminence in physics and geology. All of these early geochronometric determinations would later prove to be incorrect.
The establishment of the IUGS in 1961[58] and acceptance of the Commission on Stratigraphy (applied in 1965)[59] to become a member commission of IUGS led to the founding of the ICS. One of the primary objectives of the ICS is "the establishment, publication and revision of the ICS International Chronostratigraphic Chart which is the standard, reference global Geological Time Scale to include the ratified Commission decisions".[1]
Following on from Holmes, severalA Geological Time Scale books were published in 1982,[60] 1989,[61] 2004,[62] 2008,[63] 2012,[64] 2016,[65] and 2020.[66] However, since 2013, the ICS has taken responsibility for producing and distributing the ICC citing the commercial nature, independent creation, and lack of oversight by the ICS on the prior published GTS versions (GTS books prior to 2013) although these versions were published in close association with the ICS.[2] SubsequentGeologic Time Scale books (2016[65] and 2020[66]) are commercial publications with no oversight from the ICS, and do not entirely conform to the chart produced by the ICS. The ICS produced GTS charts are versioned (year/month) beginning at v2013/01. At least one new version is published each year incorporating any changes ratified by the ICS since the prior version.
The following five timelines show the geologic time scale to scale. The first shows the entire time from the formation of Earth to the present, but this gives little space for the most recent eon. 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, the most recent period is expanded in the fourth timeline, and the most recent epoch is expanded in the fifth timeline.
(Horizontal scale is millions of years for the above timelines; thousands of years for the timeline below)
First suggested in 2000,[67] theAnthropocene is a proposed epoch/series for the most recent time in Earth's history. While still informal, it is a widely used term to denote the present geologic time interval, in which many conditions and processes on Earth are profoundly altered by human impact.[68] As of April 2022[update] the Anthropocene has not been ratified by the ICS; however, in May 2019 theAnthropocene Working Group voted in favour of submitting a formal proposal to the ICS for the establishment of the Anthropocene Series/Epoch.[69] Nevertheless, the definition of the Anthropocene as a geologic time period rather than a geologic event remains controversial and difficult.[70][71][72][73]
Proposals for revisions to pre-Cryogenian timeline
An international working group of the ICS on pre-Cryogenian chronostratigraphic subdivision have outlined a template to improve the pre-Cryogenian geologic time scale based on the rock record to bring it in line with the post-Tonian geologic time scale.[4] This work assessed the geologic history of the currently defined eons and eras of the pre-Cambrian,[note 2] and the proposals in the "Geological Time Scale" books2004,[74]2012,[5] and2020.[75] Their recommend revisions[4] of the pre-Cryogenian geologic time scale were (changes from the current scale [v2023/09] are italicised):
Three divisions of the Archean instead of four by dropping Eoarchean, and revisions to their geochronometric definition, along with the repositioning of the Siderian into the latest Neoarchean, and a potential Kratian division in the Neoarchean.
Archean (4000–2450 Ma)
Paleoarchean (4000–3500 Ma)
Mesoarchean (3500–3000 Ma)
Neoarchean (3000–2450 Ma)
Kratian (no fixed time given, prior to the Siderian) – from Greek κράτος (krátos) 'strength'.
Siderian (?–2450 Ma) – moved from Proterozoic to end of Archean, no start time given, base of Paleoproterozoic defines the end of the Siderian
Refinement of geochronometric divisions of the Proterozoic, Paleoproterozoic, repositioning of the Statherian into the Mesoproterozoic, new Skourian period/system in the Paleoproterozoic, new Kleisian or Syndian period/system in the Neoproterozoic.
Paleoproterozoic (2450–1800 Ma)
Skourian (2450–2300 Ma) – from Greek σκουριά (skouriá) 'rust'.
The book,Geologic Time Scale 2012, was the last commercial publication of an international chronostratigraphic chart that was closely associated with the ICS.[2] It included a proposal to substantially revise the pre-Cryogenian time scale to reflect important events such as theformation of the Solar System and theGreat Oxidation Event, among others, while at the same time maintaining most of the previous chronostratigraphic nomenclature for the pertinent time span.[76] As of April 2022[update] these proposed changes have not been accepted by the ICS. The proposed changes (changes from the current scale [v2023/09]) are italicised:
Jack Hillsian orZirconian Era/Erathem (4404–4030 Ma) – both names allude to the Jack Hills Greenstone Belt which provided the oldest mineral grains on Earth,zircons.[64][77]
Vaalbaran Period/System (3490–3020 Ma) – based on the names of theKaapvaal (Southern Africa) andPilbara (Western Australia)cratons, to reflect the growth of stable continental nuclei or proto-cratonic kernels.[64]
Pongolan Period/System (3020–2780 Ma) – named after the Pongola Supergroup, in reference to the well preserved evidence of terrestrial microbial communities in those rocks.[64]
Oxygenian Period/System (2420–2250 Ma) – named for displaying the first evidence for a global oxidising atmosphere.[64]
Jatulian orEukaryian Period/System (2250–2060 Ma) – names are respectively for the Lomagundi–Jatuli δ13C isotopic excursion event spanning its duration, and for the (proposed)[79][80] first fossil appearance ofeukaryotes.[64]
The following table summarises the major events and characteristics of the divisions making up the geologic time scale of Earth. This table is arranged with the most recent geologic periods at the top, and the oldest at the bottom. The height of each table entry does not correspond to the duration of each subdivision of time. As such, this table is not to scale and does not accurately represent the relative time-spans of each geochronologic unit. While thePhanerozoic Eon looks longer than the rest, it merely spans ~539 million years (~12% of Earth's history), whilst the previous three eons[note 2] collectively span ~3,461 million years (~76% of Earth's history). This bias toward the most recent eon is in part due to the relative lack of information about events that occurred during the first three eons compared to the current eon (the Phanerozoic).[4][81] The use of subseries/subepochs has been ratified by the ICS.[15]
While some regional terms are still in use,[5] the table of geologic time conforms to thenomenclature, ages, and colour codes set forth by the International Commission on Stratigraphy in the official International Chronostratigraphic Chart.[1][82] The International Commission on Stratigraphy also provide an online interactive version of this chart. The interactive version is based on a service delivering a machine-readableResource Description Framework/Web Ontology Language representation of the time scale, which is available through theCommission for the Management and Application of Geoscience InformationGeoSciML project as a service[83] and at aSPARQL end-point.[84][85]
Orogeny inNorthern Hemisphere. Start ofKaikoura Orogeny formingSouthern Alps in New Zealand. Widespread forests slowlydraw in massive amounts of CO2, gradually lowering the level of atmospheric CO2 from 650ppmv down to around 100 ppmv during the Miocene.[90][note 7] Modernbird and mammal families become recognizable. The last of the primitive whales go extinct.Grasses become ubiquitous. Ancestor ofapes, including humans.[91][92] Afro-Arabia collides with Eurasia, fully forming theAlpide Belt and closing the Tethys Ocean, while allowing a faunal interchange. At the same time, Afro-Arabia splits intoAfrica andWest Asia.
Starts withChicxulub impact and theK–Pg extinction event, wiping out all non-avian dinosaurs and pterosaurs, most marine reptiles, many other vertebrates (e.g. many Laurasian metatherians), most cephalopods (onlyNautilidae andColeoidea survived) and many other invertebrates.Climate tropical.Mammals andbirds (avians) diversify rapidly into a number of lineages following the extinction event (while the marine revolution stops). Multituberculates and the firstrodents widespread. First large birds (e.g.ratites andterror birds) and mammals (up to bear or small hippo size).Alpine orogeny in Europe and Asia begins. Firstproboscideans andplesiadapiformes (stem primates) appear.Some marsupials migrate to Australia.
First uncontroversialeukaryotes:protists with nuclei and endomembrane system.Columbia forms as the second undisputed earliest supercontinent. Kimban Orogeny in Australian continent ends. Yapungku Orogeny onYilgarn craton, in Western Australia. Mangaroon Orogeny, 1,680–1,620 Ma, on theGascoyne Complex in Western Australia. Kararan Orogeny (1,650 Ma), Gawler Craton,South Australia. Oxygen levels drop again.
Formation ofprotolith of the oldest known rock (Acasta Gneiss) c. 4,031 to 3,580 Ma.[100][101] Possible first appearance ofplate tectonics. First hypotheticallife forms. End of the Early Bombardment Phase. Oldest knownmineral (Zircon, 4,404 ± 8 Ma).[102] Asteroids and comets bring water to Earth, forming the first oceans. Formation ofMoon (4,510 Ma), probably from agiant impact. Formation of Earth (4,543 to 4,540 Ma)
Some otherplanets andsatellites in theSolar System have sufficiently rigid structures to have preserved records of their own histories, for example,Venus,Mars and the Earth'sMoon. Dominantly fluid planets, such as thegiant planets, do not comparably preserve their history. Apart from theLate Heavy Bombardment, events on other planets probably had little direct influence on the Earth, and events on Earth had correspondingly little effect on those planets. Construction of a time scale that links the planets is, therefore, of only limited relevance to the Earth's time scale, except in a Solar System context. The existence, timing, and terrestrial effects of the Late Heavy Bombardment are still a matter of debate.[note 12]
Thegeologic history of Earth's Moon has been divided into a time scale based ongeomorphological markers, namelyimpact cratering,volcanism, anderosion. This process of dividing the Moon's history in this manner means that the time scale boundaries do not imply fundamental changes in geological processes, unlike Earth's geologic time scale. Five geologic systems/periods (Pre-Nectarian,Nectarian,Imbrian,Eratosthenian,Copernican), with the Imbrian divided into two series/epochs (Early and Late) were defined in the latest Lunar geologic time scale.[103] The Moon is unique in the Solar System in that it is the only other body from which humans have rock samples with a known geological context.
Thegeological history of Mars has been divided into two alternate time scales. The first time scale for Mars was developed by studying the impact crater densities on the Martian surface. Through this method four periods have been defined, the Pre-Noachian (~4,500–4,100 Ma), Noachian (~4,100–3,700 Ma), Hesperian (~3,700–3,000 Ma), and Amazonian (~3,000 Ma to present).[104][105]
Martian time periods (millions of years ago)
Epochs:
A second time scale based on mineral alteration observed by the OMEGAspectrometer on board theMars Express. Using this method, three periods were defined, the Phyllocian (~4,500–4,000 Ma), Theiikian (~4,000–3,500 Ma), and Siderikian (~3,500 Ma to present).[106]
^Time spans of geologic time units vary broadly, and there is no numeric limitation on the time span they can represent. They are limited by the time span of the higher rank unit they belong to, and to the chronostratigraphic boundaries they are defined by.
^abcPrecambrian or pre-Cambrian is an informal geological term for time before the Cambrian period
^abThe Tertiary is a now obsolete geologic system/period spanning from 66 Ma to 2.6 Ma. It has no exact equivalent in the modern ICC, but is approximately equivalent to the merged Palaeogene and Neogene systems/periods.[20][21]
^abGeochronometric date for the Ediacaran has been adjusted to reflect ICC v2023/09 as the formal definition for the base of the Cambrian has not changed.
^Kratian time span is not given in the article. It lies within the Neoarchean, and prior to the Siderian. The position shown here is an arbitrary division.
^Desnoyers, J. (1829)."Observations sur un ensemble de dépôts marins plus récents que les terrains tertiaires du bassin de la Seine, et constituant une formation géologique distincte; précédées d'un aperçu de la nonsimultanéité des bassins tertiares" [Observations on a set of marine deposits [that are] more recent than the tertiary terrains of the Seine basin and [that] constitute a distinct geological formation; preceded by an outline of the non-simultaneity of tertiary basins].Annales des Sciences Naturelles (in French).16:171–214,402–491.From p. 193:"Ce que je désirerais ... dont il faut également les distinguer." (What I would desire to prove above all is that the series of tertiary deposits continued – and even began in the more recent basins – for a long time, perhaps after that of the Seine had been completely filled, and that these later formations –Quaternary (1), so to say – should not retain the name of alluvial deposits any more than the true and ancient tertiary deposits, from which they must also be distinguished.) However, on the very same page, Desnoyers abandoned the use of the term "Quaternary" because the distinction between Quaternary and Tertiary deposits wasn't clear. From p. 193:"La crainte de voir mal comprise ... que ceux du bassin de la Seine." (The fear of seeing my opinion in this regard be misunderstood or exaggerated, has made me abandon the word "quaternary", which at first I had wanted to apply to all deposits more recent than those of the Seine basin.)
^d'Halloy, d'O., J.-J. (1822)."Observations sur un essai de carte géologique de la France, des Pays-Bas, et des contrées voisines" [Observations on a trial geological map of France, the Low Countries, and neighboring countries].Annales des Mines.7:353–376.{{cite journal}}: CS1 maint: multiple names: authors list (link) From page 373: "La troisième, qui correspond à ce qu'on a déja appelé formation de la craie, sera désigné par le nom de terrain crétacé." (The third, which corresponds to what was already called the "chalk formation", will be designated by the name "chalky terrain".)
^Butcher, Andy (26 May 2004)."Re: Ediacaran".LISTSERV 16.0 - AUSTRALIAN-LINGUISTICS-L Archives. Archived fromthe original on 23 October 2007. Retrieved19 July 2011.
^Burnet, Thomas (1681).Telluris Theoria Sacra: orbis nostri originen et mutationes generales, quasi am subiit aut olim subiturus est, complectens. Libri duo priores de Diluvio & Paradiso (in Latin). London: G. Kettiby.
^Crutzen, Paul J.; Stoermer, Eugene F. (2021), Benner, Susanne; Lax, Gregor; Crutzen, Paul J.; Pöschl, Ulrich (eds.),"The 'Anthropocene' (2000)",Paul J. Crutzen and the Anthropocene: A New Epoch in Earth's History, The Anthropocene: Politik—Economics—Society—Science, vol. 1, Cham: Springer International Publishing, pp. 19–21,doi:10.1007/978-3-030-82202-6_2,ISBN978-3-030-82201-9,S2CID245639062, retrieved15 April 2022
^Van Kranendonk, Martin J. (2012). "A Chronostratigraphic Division of the Precambrian". In Felix M. Gradstein; James G. Ogg; Mark D. Schmitz; abi M. Ogg (eds.).The geologic time scale 2012 (1st ed.). Amsterdam: Elsevier. pp. 359–365.doi:10.1016/B978-0-444-59425-9.00016-0.ISBN978-0-44-459425-9.
^Cox, Simon J. D.; Richard, Stephen M. (2014). "A geologic timescale ontology and service".Earth Science Informatics.8:5–19.doi:10.1007/s12145-014-0170-6.S2CID42345393.
^Medlin, L. K.; Kooistra, W. H. C. F.; Gersonde, R.; Sims, P. A.; Wellbrock, U. (1997). "Is the origin of the diatoms related to the end-Permian mass extinction?".Nova Hedwigia.65 (1–4):1–11.doi:10.1127/nova.hedwigia/65/1997/1.hdl:10013/epic.12689.
Aubry, Marie-Pierre; Van Couvering, John A.; Christie-Blick, Nicholas; Landing, Ed; Pratt, Brian R.; Owen, Donald E.; Ferrusquia-Villafranca, Ismael (2009). "Terminology of geological time: Establishment of a community standard".Stratigraphy.6 (2):100–105.doi:10.7916/D8DR35JQ.
Exploring Time from Planck Time to the lifespan of the universe
Episodes, Gradstein, Felix M. et al. (2004)A new Geologic Time Scale, with special reference to Precambrian and Neogene, Episodes, Vol. 27, no. 2 June 2004 (pdf)
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