146-564: The Phanerozoic is the current and the latest of the four geologic eons in the Earth 's geologic time scale , covering the time period from 538.8 million years ago to the present. It is the eon during which abundant animal and plant life has proliferated , diversified and colonized various niches on the Earth's surface , beginning with the Cambrian period when animals first developed hard shells that can be clearly preserved in
292-649: A disaster fauna , a group of survivor animals with low diversity and cosmopolitanism (wide geographic ranges). Temnospondyli recovered first and evolved into large aquatic predators during the Triassic. Other reptiles also diversified rapidly, with aquatic reptiles such as ichthyosaurs and sauropterygians proliferating in the seas. On land, the first true archosaurs appeared, including pseudosuchians (crocodile relatives) and avemetatarsalians (bird/dinosaur relatives). The Middle Triassic spans from 247 million to 237 million years ago. The Middle Triassic featured
438-474: A negative feedback that arises from resource limitation, or both. The hyperbolic model implies a second-order positive feedback. The hyperbolic pattern of the human population growth arises from quadratic positive feedback, caused by the interaction of the population size and the rate of technological growth. The character of biodiversity growth in the Phanerozoic Eon can be similarly accounted for by
584-539: A body mass over 10 kilograms became extinct, and the Age of Dinosaurs came to an end. The Cenozoic featured the rise of mammals and birds as the dominant class of animals, as the end of the Age of Dinosaurs left significant open niches . There are three divisions of the Cenozoic: Paleogene, Neogene and Quaternary. The Paleogene spans from the extinction of the non-avian dinosaurs, some 66 million years ago, to
730-507: A cooling trend that would continue into the Cenozoic Era. Eventually, the tropical climate was restricted to the equator and areas beyond the tropic lines featured more seasonal climates. Dinosaurs still thrived as new species such as Tyrannosaurus , Ankylosaurus , Triceratops and hadrosaurs dominated the food web. Whether or not pterosaurs went into a decline as birds radiated is debated; however, many families survived until
876-475: A feedback between the diversity and community structure complexity. It has been suggested that the similarity between the curves of biodiversity and human population probably comes from the fact that both are derived from the superposition on the hyperbolic trend of cyclical and random dynamics. Across the Phanerozoic, the dominant driver of long-term climatic change was the concentration of carbon dioxide in
1022-597: A formal proposal to the ICS for the establishment of the Anthropocene Series/Epoch. Nevertheless, the definition of the Anthropocene as a geologic time period rather than a geologic event remains controversial and difficult. 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
1168-466: 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 the Ediacaran and Cambrian periods (geochronologic units) was revised from 541 Ma to 538.8 Ma but the rock definition of the boundary (GSSP) at
1314-691: A known geological context. The geological 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). Cenozoic The Cenozoic ( / ˌ s iː n ə ˈ z oʊ . ɪ k , ˌ s ɛ n -/ SEE -nə- ZOH -ik, SEN -ə- ; lit. ' new life ' )
1460-593: A lesser extent shelled cephalopods (such as orthocones ). Almost all phyla of marine animals evolved in this period. During this time, the super-continent Pannotia began to break up, most of which later recombined into the super-continent Gondwana . The Ordovician spans from 485 million to 444 million years ago. The Ordovician was a time in Earth's history in which many groups still prevalent today evolved or diversified, such as primitive nautiloids , vertebrates (then only jawless fish ) and corals . This process
1606-635: A machine-readable Resource Description Framework / Web Ontology Language representation of the time scale, which is available through the Commission for the Management and Application of Geoscience Information GeoSciML project as a service and at a SPARQL end-point. Some other planets and satellites in the Solar System have sufficiently rigid structures to have preserved records of their own histories, for example, Venus , Mars and
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#17327661555101752-607: A mass extinction that began roughly 10,000 years ago, though the species becoming extinct have only been recorded since the Industrial Revolution . This is sometimes referred to as the " Sixth Extinction ". It is often cited that over 322 recorded species have become extinct due to human activity since the Industrial Revolution, but the rate may be as high as 500 vertebrate species alone, the majority of which have occurred after 1900. Geologically ,
1898-471: A relative interval of geologic time. A chronostratigraphic 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. A geochronologic unit
2044-418: A result, the world was warm and partially tropical, though possibly with short colder intervals. Plesiosaurs , ichthyosaurs and ammonites dominated the seas, while dinosaurs, pterysaurs and other reptiles dominated the land, with species such as Dilophosaurus at the apex. Crocodylomorphs evolved into aquatic forms, pushing the remaining large amphibians to near extinction. True mammals were present during
2190-1025: A severe extinction of sauropods in northern continents, alongside many ichthyosaurs. However, the Jurassic-Cretaceous boundary did not strongly impact most forms of life. The Cretaceous is the Phanerozoic's longest period and the last period of the Mesozoic. It spans from 145 million to 66 million years ago, and is divided into two epochs: Early Cretaceous , and Late Cretaceous . The Early Cretaceous Epoch spans from 145 million to 100 million years ago. Dinosaurs continued to be abundant, with groups such as tyrannosauroids , avialans ( birds ), marginocephalians , and ornithopods seeing early glimpses of later success. Other tetrapods, such as stegosaurs and ichthyosaurs, declined significantly, and sauropods were restricted to southern continents. The Late Cretaceous Epoch spans from 100 million to 66 million years ago. The Late Cretaceous featured
2336-429: A specific and reliable order. This allows for a correlation of strata even when the horizon between them is not continuous. The geologic time scale is divided into chronostratigraphic units and their corresponding geochronologic units. The subdivisions Early and Late are used as the geochronologic equivalents of the chronostratigraphic Lower and Upper , e.g., Early Triassic Period (geochronologic unit)
2482-532: A supervolcano eruption in Sumatra 74,000 years ago caused a global population bottleneck of humans, a second wave of Homo sapiens migration successfully repopulated every continents except Antarctica. As the Pleistocene drew to a close, a major extinction wiped out much of the world's megafauna , including non- Homo sapiens human species such as Homo neanderthalensis and Homo floresiensis . All
2628-547: 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 its stratotype or type locality . The name of stages should also be derived from a geographic feature in the locality of its stratotype or type locality. Informally, the time before the Cambrian is often referred to as
2774-525: A trend of desiccation which resulted in the creation of the Sahara , Namib , and Kalahari deserts. Many animals evolved including mammoths , giant ground sloths , dire wolves , sabre-toothed cats, and Homo sapiens . 100,000 years ago marked the end of one of the worst droughts in Africa, and led to the expansion of primitive humans. As the Pleistocene drew to a close, a major extinction wiped out much of
2920-490: A trend of desiccation which resulted in the creation of the Sahara, Namib and Kalahari deserts. Mammoths , giant ground sloths , dire wolves , sabre-toothed cats and archaic humans such as Homo erectus were common and widespread during the Pleistocene. A more anatomically modern human , Homo sapiens , began migrating out of East Africa in at least two waves, the first being as early as 270,000 years ago. After
3066-459: A very important role in this era, shaping the evolution of the birds and mammals that fed on them. One group that diversified significantly in the Cenozoic as well were the snakes . Evolving in the Cenozoic, the variety of snakes increased tremendously, resulting in many colubrids , following the evolution of their current primary prey source, the rodents . In the earlier part of the Cenozoic,
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#17327661555103212-458: 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 on denudation rates and sedimentary thicknesses or ocean chemistry, and physicists determining ages for
3358-607: Is Earth's current geological era , representing the last 66 million years of Earth's history. It is characterized by the dominance of mammals , birds , conifers , and angiosperms (flowering plants). It is the latest of three geological eras of the Phanerozoic Eon , preceded by the Mesozoic and Paleozoic . The Cenozoic started with the Cretaceous–Paleogene extinction event , when many species, including
3504-500: Is a numeric-only, chronologic reference point used to define the base of geochronologic units prior to the Cryogenian. These points are arbitrarily defined. 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
3650-429: Is a period in which grass spread further across, effectively dominating a large portion of the world, diminishing forests in the process. Kelp forests evolved, leading to the evolution of new species such as sea otters . During this time, perissodactyls thrived, and evolved into many different varieties. Alongside them were the apes , which evolved into 30 species. Overall, arid and mountainous land dominated most of
3796-491: Is a period in which grasses spread further, dominating a large portion of the world, at the expense of forests. Kelp forests evolved, encouraging the evolution of new species, such as sea otters . During this time, perissodactyla thrived, and evolved into many different varieties. Apes evolved into 30 species. The Tethys Sea finally closed with the creation of the Arabian Peninsula , leaving only remnants as
3942-479: Is a subdivision of geologic time. It is a numeric representation of an intangible property (time). These units are arranged in a hierarchy: eon, era, period, epoch, subepoch, age, and subage. 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
4088-413: Is a way of representing deep time based on events that have occurred throughout Earth's history , a time span of about 4.54 ± 0.05 Ga (4.54 billion years). It chronologically organises strata, and subsequently time, by observing fundamental changes in stratigraphy that correspond to major geological or paleontological events. For example, the Cretaceous–Paleogene extinction event , marks
4234-538: Is debated. The Oligocene Epoch spans from 34 million to 23 million years ago. The Oligocene was an important transitional period between the tropical world of the Eocene and more modern ecosystems. This period featured a global expansion of grass which led to many new species taking advantage, including the first elephants , felines , canines , marsupials and many other species still prevalent today. Many other species of plants evolved during this epoch also, such as
4380-508: Is known as the Great Ordovician Biodiversification Event or GOBE. Trilobites began to be replaced by articulate brachiopods , and crinoids also became an increasingly important part of the fauna. The first arthropods crept ashore to colonise Gondwana , a continent empty of animal life. A group of freshwater green algae , the streptophytes , also survived being washed ashore and began to colonize
4526-548: Is mostly a transitional recovery period between the desolate aftermath of the Permian Extinction and the lush Jurassic Period. It has three major epochs: Early Triassic , Middle Triassic , and Late Triassic . The Early Triassic lasted between 252 million to 247 million years ago, and was a hot and arid epoch in the aftermath of the Permian Extinction. Many tetrapods during this epoch represented
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4672-401: Is the field of geochronology that numerically quantifies geologic time. A Global Boundary Stratotype Section and Point (GSSP) is an internationally agreed-upon reference point on a stratigraphic section that defines the lower boundaries of stages on the geologic time scale. (Recently this has been used to define the base of a system) A Global Standard Stratigraphic Age (GSSA)
4818-697: Is the responsibility of the International Commission on Stratigraphy (ICS), a constituent body of the International Union of Geological Sciences (IUGS), whose primary objective is to precisely define global chronostratigraphic units of the International Chronostratigraphic Chart (ICC) that are used to define divisions of geologic time. The chronostratigraphic divisions are in turn used to define geochronologic units. The geologic time scale
4964-594: 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 the Silurian System are the Silurian System and they were deposited during the Silurian Period. This definition means the numeric age of
5110-618: The Anthropocene 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. As of April 2022 the Anthropocene has not been ratified by the ICS; however, in May 2019 the Anthropocene Working Group voted in favour of submitting
5256-535: The Black , Red , Mediterranean and Caspian Seas . This increased aridity. Many new plants evolved: 95% of modern seed plants families were present by the end of the Miocene. The Pliocene Epoch lasted from 5.333 to 2.58 million years ago. The Pliocene featured dramatic climatic changes, which ultimately led to modern species of flora and fauna. The Mediterranean Sea dried up for several million years (because
5402-539: The Brothers of Purity , who wrote on the processes of stratification over the passage of time in their treatises . Their work likely inspired that of the 11th-century Persian polymath Avicenna (Ibn Sînâ, 980–1037) who wrote in The Book of Healing (1027) on the concept of stratification and superposition, pre-dating Nicolas Steno by more than six centuries. Avicenna also recognised fossils as "petrifications of
5548-472: The Ediacaran period ( Avalon explosion ) of the preceding Proterozoic eon have since been discovered, and the modern scientific consensus now agrees that complex life (in the form of placozoans and primitive sponges such as Otavia ) has existed at least since the Tonian period and the earliest known life forms (in the form of simple prokaryotic microbial mats ) started in the ocean floor during
5694-708: The Isthmus of Panama around 2.8 million years ago , the Arctic region cooled due to the strengthening of the Humboldt and Gulf Stream currents, eventually leading to the glaciations of the Quaternary ice age , the current interglacial of which is the Holocene Epoch. Recent analysis of the geomagnetic reversal frequency, oxygen isotope record, and tectonic plate subduction rate, which are indicators of
5840-796: The K-Pg event , the planet was dominated by relatively small fauna, including small mammals, birds, reptiles, and amphibians. From a geological perspective, it did not take long for mammals to greatly diversify in the absence of the dinosaurs that had dominated during the Mesozoic. Birds also diversified rapidly; some flightless birds grew larger than humans. These species are sometimes referred to as " terror birds ", and were formidable predators. Mammals came to occupy almost every available niche (both marine and terrestrial ), and some also grew very large, attaining sizes not seen in most of today's terrestrial mammals. The ranges of many Cenozoic bird clades were governed by latitude and temperature and have contracted over
5986-572: The K–Pg extinction event included the extinction of large herbivores , which permitted the spread of dense but usually species-poor forests. The Early Paleocene saw the recovery of Earth. The continents began to take their modern shape, but all the continents and the subcontinent of India were separated from each other. Afro-Eurasia was separated by the Tethys Sea , and the Americas were separated by
Phanerozoic - Misplaced Pages Continue
6132-520: The Messinian salinity crisis . Along with these major geological events, Africa saw the appearance of Australopithecus , the ancestor of Homo . The Isthmus of Panama formed, and animals migrated between North and South America, wreaking havoc on the local ecology. Climatic changes brought savannas that are still continuing to spread across the world, Indian monsoons , deserts in East Asia, and
6278-631: The Ordovician–Silurian extinction , during which 60% of marine invertebrates and 25% of families became extinct. Though one of the deadliest mass extinctions in earth's history, the O–S extinction did not cause profound ecological changes between the periods. The Silurian spans from 444 million to 419 million years ago, which saw a warming from an icehouse Earth. This period saw the mass diversification of fish , as jawless fish became more numerous, and early jawed fish and freshwater species appeared in
6424-536: The Precambrian or pre-Cambrian (Supereon). While a modern geological time scale was not formulated until 1911 by Arthur Holmes , the broader concept that rocks and time are related can be traced back to (at least) the philosophers of Ancient Greece . Xenophanes of Colophon (c. 570–487 BCE ) observed rock beds with fossils of shells located above the sea-level, viewed them as once living organisms, and used this to imply an unstable relationship in which
6570-589: The Quaternary glaciation dried and cooled Earth. Cenozoic derives from the Greek words kainós ( καινός 'new') and zōḗ ( ζωή 'life'). The name was proposed in 1840 by the British geologist John Phillips (1800–1874), who originally spelled it Kainozoic . The era is also known as the Cænozoic , Caenozoic , or Cainozoic ( / ˌ k aɪ . n ə ˈ z oʊ . ɪ k , ˌ k eɪ -/ ). In name,
6716-700: The Tethys Sea , and the Americas were separated by the Panamanic Seaway (as the Isthmus of Panama had not yet formed). This epoch featured a general warming trend that peaked at the Paleocene-Eocene Thermal Maximum , and the earliest modern jungles expanded, eventually reaching the poles. The oceans were dominated by sharks, as the large reptiles that had once ruled had become extinct. Mammals diversified rapidly, but most remained small. The largest tetrapod carnivores during
6862-597: The flood plains and riparian zones , giving rise to primitive land plants . By the end of the Ordovician, Gondwana had moved from the equator to the South Pole , and Laurentia had collided with Baltica , closing the Iapetus Ocean . The glaciation of Gondwana resulted in a major drop in sea level, killing off all life that had established along its coast. Glaciation caused an icehouse Earth , leading to
7008-530: The fossil record . The time before the Phanerozoic, collectively called the Precambrian , is now divided into the Hadean , Archaean and Proterozoic eons. The time span of the Phanerozoic starts with the sudden appearance of fossilised evidence of a number of animal phyla ; the evolution of those phyla into diverse forms; the evolution of plants ; the evolution of fish , arthropods and molluscs ;
7154-624: The ice ages reduced sea levels, disconnecting the Atlantic from the Mediterranean, and evaporation rates exceeded inflow from rivers). Australopithecus evolved in Africa , beginning the human branch. The isthmus of Panama formed, and animals migrated between North and South America during the great American interchange , wreaking havoc on local ecologies. Climatic changes brought: savannas that are still continuing to spread across
7300-763: The isthmus of Panama . India collided with Asia 55 to 45 million years ago creating the Himalayas; Arabia collided with Eurasia, closing the Tethys Ocean and creating the Zagros Mountains , around 35 million years ago . The break-up of Gondwana in Late Cretaceous and Cenozoic times led to a shift in the river courses of various large African rivers including the Congo , Niger , Nile , Orange , Limpopo and Zambezi . In
7446-426: The terrestrial colonization and evolution of insects , chelicerates , myriapods and tetrapods ; and the development of modern flora dominated by vascular plants . During this time span, tectonic forces which move the continents had collected them into a single landmass known as Pangaea (the most recent supercontinent ), which then separated into the current continental landmasses. The term "Phanerozoic"
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#17327661555107592-512: The "Age of the Fish", the Devonian features a huge diversification in fish such as the jawless conodonts and ostracoderms , as well as jawed fish such as the armored placoderms (e.g. Dunkleosteus ), the spiny acanthodians and early bony fish . The Devonian also saw the primitive appearance of modern fish groups such as chondricthyans ( cartilaginous fish ) and osteichthyans (bony fish),
7738-471: The Age of Reptiles, Age of Dinosaurs or Age of Conifers, the Mesozoic featured the first time the sauropsids ascended to ecological dominance over the synapsids, as well as the diversification of many modern ray-finned fish , insects , molluscs (particularly the coleoids ), tetrapods and plants. The Mesozoic is subdivided into three periods: the Triassic, Jurassic and Cretaceous. The Triassic ranges from 252 million to 201 million years ago. The Triassic
7884-500: The Carboniferous as semiaquatic amphibians such as the temnospondyls , and one lineage developed extraembryonic membranes that allowed their eggs to survive outside of the water. These tetrapods, the amniotes , included the first sauropsids (which evolved the reptiles , dinosaurs and birds ) and synapsids (the ancestors of mammal ). Throughout the Carboniferous, there was a cooling pattern, which eventually led to
8030-589: The Cenozoic ( lit. ' new life ' ) is comparable to the preceding Mesozoic ('middle life') and Paleozoic ('old life') Eras, as well as to the Proterozoic ('earlier life') Eon. The Cenozoic is divided into three periods: the Paleogene , Neogene , and Quaternary ; and seven epochs : the Paleocene , Eocene , Oligocene , Miocene , Pliocene , Pleistocene , and Holocene . The Quaternary Period
8176-494: The Cenozoic is the era when the continents moved into their current positions. Australia-New Guinea , having split from Pangea during the early Cretaceous , drifted north and, eventually, collided with Southeast Asia ; Antarctica moved into its current position over the South Pole ; the Atlantic Ocean widened and, later in the era (2.8 million years ago), South America became attached to North America with
8322-691: The Commission on Stratigraphy (applied in 1965) 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". Following on from Holmes, several A Geological Time Scale books were published in 1982, 1989, 2004, 2008, 2012, 2016, and 2020. However, since 2013,
8468-600: The Cretaceous, the climate was hot and humid with lush forests at the poles, there was no permanent ice and sea levels were around 300 metres higher than today. This continued for the first 10 million years of the Paleocene, culminating in the Paleocene–Eocene Thermal Maximum about 55.5 million years ago . Around 50 million years ago Earth entered a period of long term cooling. This
8614-483: The Early-Eocene, species living in dense forest were unable to evolve into larger forms, as in the Paleocene. Among them were early primates, whales and horses along with many other early forms of mammals. At the top of the food chains were huge birds, such as Paracrax . Carbon dioxide levels were approximately 1,400 ppm . The temperature was 30 degrees Celsius with little temperature gradient from pole to pole. In
8760-474: The Earth's Moon . Dominantly fluid planets, such as the giant planets , do not comparably preserve their history. Apart from the Late 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
8906-403: 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. The geologic history of Earth's Moon has been divided into a time scale based on geomorphological markers, namely impact cratering , volcanism , and erosion . This process of dividing the Moon's history in this manner means that
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#17327661555109052-513: The Earth, and the large amounts of trees sequestered much of the carbon that became coal deposits (hence the name Carboniferous and the term " coal forest "). About 90% of all coal beds were deposited in the Carboniferous and Permian periods, which represent just 2% of the Earth's geologic history. The high oxygen levels caused by these wetland rainforests allowed arthropods, normally limited in size by their respiratory systems , to proliferate and increase in size. Tetrapods also diversified during
9198-401: 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. Subsequent Geologic Time Scale books (2016 and 2020 ) are commercial publications with no oversight from
9344-404: 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 the Earth to
9490-415: The ICS. While some regional terms are still in use, the table of geologic time conforms to the nomenclature , ages, and colour codes set forth by the International Commission on Stratigraphy in the official International Chronostratigraphic Chart. The International Commission on Stratigraphy also provide an online interactive version of this chart. The interactive version is based on a service delivering
9636-526: 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 unit Ma (megaannum, for 'million years '). For example, 201.4 ± 0.2 Ma, the lower boundary of the Jurassic Period, is defined as 201,400,000 years old with an uncertainty of 200,000 years. Other SI prefix units commonly used by geologists are Ga (gigaannum, billion years), and ka (kiloannum, thousand years), with
9782-476: The Jurassic but remained small, with average body masses of less than 10 kilograms (22 lb) until the end of the Cretaceous. The Middle and Late Jurassic Epochs span from 174 million to 145 million years ago. Conifer savannahs made up a large portion of the world's forests. In the oceans, plesiosaurs were quite common, and ichthyosaurs were flourishing. The Late Jurassic Epoch spans from 163 million to 145 million years ago. The Late Jurassic featured
9928-418: The Late Triassic, and pterosaurs evolved a bit later. Other large reptilian competitors to the dinosaurs were wiped out by the Triassic–Jurassic extinction event , in which most archosaurs (excluding crocodylomorphs , pterosaurs and dinosaurs), most therapsids (except cynodonts ) and almost all large amphibians became extinct, as well as 34% of marine life in the fourth mass extinction event. The cause of
10074-411: The Mid-Eocene, the Antarctic Circumpolar Current between Australia and Antarctica formed. This disrupted ocean currents worldwide and as a result caused a global cooling effect, shrinking the jungles. This allowed mammals to grow to mammoth proportions, such as whales which, by that time, had become almost fully aquatic. Mammals like Andrewsarchus were at the top of the food-chain. The Late Eocene saw
10220-471: The Middle Devonian, shrub-like forests existed: lycophytes , horsetails and progymnosperm . This greening event also allowed the diversification of arthropods as they took advantage of the new habitat. Near the end of the Devonian, 70% of all species became extinct in a sequence of mass extinction events, collectively known as the Late Devonian extinction . The Carboniferous spans from 359 million to 299 million years ago. Tropical swamps dominated
10366-464: The Paleocene were reptiles, including crocodyliforms , choristoderans and snakes . Titanoboa , the largest known snake, lived in South America during the Paleocene. The Eocene Epoch ranged from 56 million to 34 million years ago. In the early Eocene, most land mammals were small and living in cramped jungles, much like the Paleocene. Among them were early primates , whales and horses along with many other early forms of mammals. The climate
10512-486: The Paleozoic Era and ran from 539 million to 485 million years ago. The Cambrian sparked a rapid expansion in the diversity of animals, in an event known as the Cambrian explosion , during which the greatest number of animal body plans evolved in a single period in the history of Earth. Complex algae evolved, and the fauna was dominated by armoured arthropods (such as trilobites and radiodontids ) and to
10658-401: The Phanerozoic correlate much better with the hyperbolic model (widely used in demography and macrosociology ) than with exponential and logistic models (traditionally used in population biology and extensively applied to fossil biodiversity as well). The latter models imply that changes in diversity are guided by a first-order positive feedback (more ancestors, more descendants) or
10804-411: The Phanerozoic were strongly associated with mass extinctions. Eon (geology) The geologic time scale or geological time scale ( GTS ) is a representation of time based on the rock record of Earth . It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (a scientific branch of geology that aims to determine
10950-445: The action of gravity. However, it is now known that not all sedimentary layers are deposited purely horizontally, but this principle is still a useful concept. The principle 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. Layers do not extend indefinitely; their limits are controlled by
11096-505: The age of rocks). It is used primarily by Earth scientists (including geologists , paleontologists , geophysicists , geochemists , and paleoclimatologists ) 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 as lithologies , paleomagnetic properties, and fossils . The definition of standardised international units of geologic time
11242-409: The amount and type of sediment in a sedimentary basin , and the geometry of that basin. The principle of cross-cutting relationships that states a rock that cuts across another rock must be younger than the rock it cuts across. The law 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
11388-810: The ancestors of modern mammals. The first conifers evolved during this period, then dominated the terrestrial landscape. The Permian ended with at least one mass extinction , an event sometimes known as " the Great Dying ", caused by large floods of lava (the Siberian Traps in Russia and the Emeishan Traps in China). This extinction was the largest in Earth's history and led to the loss of 95% of all species of life. The Mesozoic ranges from 252 million to 66 million years ago. Also referred to as
11534-454: The atmosphere, though some studies have suggested a decoupling of carbon dioxide and palaeotemperature, particularly during cold intervals of the Phanerozoic. Phanerozoic carbon dioxide concentrations have been governed partially by a 26 million year oceanic crustal cycle. Since the Devonian, large swings in carbon dioxide of 2,000 ppm or more were uncommon over short timescales. Variations in global temperature were limited by negative feedbacks in
11680-513: The base of the Cambrian, and thus the boundary between the Ediacaran and Cambrian systems (chronostratigraphic units) has not been changed; rather, the absolute age has merely been refined. Chronostratigraphy is the element of stratigraphy that deals with the relation between rock bodies and the relative measurement of geological time. It is the process where distinct strata between defined stratigraphic horizons are assigned to represent
11826-637: The beginnings of the Sahara Desert . The Earth's continents and seas moved into their present shapes. The world map has not changed much since, save for changes brought about by the Quaternary glaciation such as Lake Agassiz (precursor of the Great Lakes ). The Quaternary spans from 2.58 million years ago to present day, and is the shortest geological period in the Phanerozoic Eon . It features modern animals, and dramatic changes in
11972-824: The beginnings of the break-up of Pangaea as rifting commenced in north Pangaea. The northern part of the Tethys Ocean , the Paleotethys Ocean, had become a passive basin, but a spreading center was active in the southern part of the Tethys Ocean, the Neotethys Ocean. Phytoplankton , coral, crustaceans and many other marine invertebrates recovered from the Permian extinction by the end of the Middle Triassic. Meanwhile, on land, reptiles continued to diversify, conifer forests flourished, as well as
12118-529: The bodies of plants and animals", with the 13th-century Dominican bishop Albertus Magnus (c. 1200–1280) extending this into a theory of a petrifying fluid. These works appeared to have little influence on scholars in Medieval Europe who looked to the Bible to explain the origins of fossils and sea-level changes, often attributing these to the ' Deluge ', including Ristoro d'Arezzo in 1282. It
12264-552: The boundaries of the Holocene epoch. Human activity is blamed for an ongoing mass extinction that began roughly 10,000 years ago, though the species becoming extinct have only been recorded since the Industrial Revolution . This is sometimes referred to as the " Sixth Extinction " with hundreds of species gone extinct due to human activities such as overhunting , habitat destruction and introduction of invasive species . It has been demonstrated that changes in biodiversity through
12410-460: The changes in the heat flux at the core mantle boundary, climate and plate tectonic activity, shows that all these changes indicate similar rhythms on million years' timescale in the Cenozoic Era occurring with the common fundamental periodicity of ~13 Myr during most of the time. The levels of carbonate ions in the ocean fell over the course of the Cenozoic. Early in the Cenozoic, following
12556-564: The climate. It is divided into two epochs: the Pleistocene and the Holocene . The Pleistocene lasted from 2.58 million to 11,700 years ago. This epoch was marked by a series of glacial periods ( ice ages ) as a result of the cooling trend that started in the mid-Eocene. There were numerous separate glaciation periods marked by the advance of ice caps as far south as 40 degrees N latitude in mountainous areas. Meanwhile, Africa experienced
12702-469: The climate. It is divided into two epochs: the Pleistocene and the Holocene. The Pleistocene lasted from 2.58 million to 11,700 years ago. This epoch was marked by ice ages as a result of the cooling trend that started in the Mid-Eocene. There were at least four separate glaciation periods marked by the advance of ice caps as far south as 40° N in mountainous areas. Meanwhile, Africa experienced
12848-415: The continents were affected, but Africa was impacted to a lesser extent and retained many large animals such as elephants, rhinoceros and hippopotamus . The extent to which Homo sapiens were involved in this megafaunal extinction is debated. The Holocene began 11,700 years ago at the end of Younger Dryas and lasts until the present day. All recorded history and so-called " human history " lies within
12994-404: The cooling climate even as more archaic forms died out. By the end of the Eocene, whales such as Basilosaurus had become fully aquatic. The late Eocene Epoch saw the rebirth of seasons, which caused the expansion of savanna-like areas with the earliest substantial grasslands . At the transition between the Eocene and Oligocene epochs there was a significant extinction event , the cause of which
13140-569: The cooling of the Earth or the Sun using basic thermodynamics or orbital physics. These estimations varied from 15,000 million years to 0.075 million years depending on method and author, but the estimations of Lord Kelvin and Clarence 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 discovery of radioactive decay by Henri Becquerel , Marie Curie , and Pierre Curie laid
13286-420: The course of this era as the world cooled. During the Cenozoic, mammals proliferated from a few small, simple, generalised forms into a diverse collection of terrestrial , marine , and flying animals, giving this period its other name, the Age of Mammals. The Cenozoic is just as much the age of savannas , the age of co-dependent flowering plants and insects , and the age of birds. Grasses also played
13432-519: The dawn of the Neogene 23 million years ago. It features three epochs : Paleocene , Eocene and Oligocene . The Paleocene Epoch began with the K–Pg extinction event, and the early part of the Paleocene saw the recovery of the Earth from that event. The continents began to take their modern shapes, but most continents (and India) remained separated from each other: Africa and Eurasia were separated by
13578-457: The developments in mass spectrometry pioneered by Francis William Aston , Arthur Jeffrey Dempster , and Alfred O. C. Nier during the early to mid- 20th century would finally allow for the accurate determination of radiometric ages, with Holmes publishing several revisions to his geological time-scale with his final version in 1960. The establishment of the IUGS in 1961 and acceptance of
13724-404: 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
13870-494: The earlier Archean eon. The Proterozoic –Phanerozoic boundary is at 538.8 million years ago. In the 19th century, the boundary was set at time of appearance of the first abundant animal ( metazoan ) fossils , but trace fossils of several hundred groups ( taxa ) of complex soft-bodied metazoa from the preceding Ediacaran period of the Proterozoic eon, known as the Avalon Explosion , have been identified since
14016-427: The end of the Cretaceous, alongside new forms such as the gigantic Quetzalcoatlus . Mammals diversified despite their small sizes, with metatherians ( marsupials and kin) and eutherians ( placentals and kin) coming into their own. In the oceans, mosasaurs diversified to fill the role of the now-extinct ichthyosaurs, alongside huge plesiosaurs such as Elasmosaurus . Also, the first flowering plants evolved. At
14162-554: The end of the Cretaceous, the Deccan Traps and other volcanic eruptions were poisoning the atmosphere. As this was continued, it is thought that a large meteor smashed into Earth, creating the Chicxulub Crater and causing the event known as the K–Pg extinction , the fifth and most recent mass extinction event, during which 75% of life on Earth became extinct, including all non-avian dinosaurs. Every living thing with
14308-583: The evergreen trees. The long term cooling continued and seasonal rain patterns established. Mammals continued to grow larger. Paraceratherium , one of the largest land mammals to ever live, evolved during this epoch, along with many other perissodactyls . The Neogene spans from 23.03 million to 2.58 million years ago. It features two epochs: the Miocene and the Pliocene . The Miocene spans from 23.03 million to 5.333 million years ago and
14454-457: The extinction is debated, but likely resulted from eruptions of the CAMP large igneous province . The Jurassic ranges from 201 million to 145 million years ago, and features three major epochs: Early Jurassic , Middle Jurassic and Late Jurassic . The Early Jurassic epoch spans from 201 million to 174 million years ago. The climate was much more humid than during the Triassic, and as
14600-523: The first elephants, cats, dogs, marsupials and many other species still prevalent today. Many other species of plants evolved in this period too. A cooling period featuring seasonal rains was still in effect. Mammals still continued to grow larger and larger. The Neogene spans from 23.03 million to 2.58 million years ago. It features 2 epochs: the Miocene, and the Pliocene. The Miocene Epoch spans from 23.03 to 5.333 million years ago and
14746-608: The first flies. The Late Triassic spans from 237 million to 201 million years ago. Following the bloom of the Middle Triassic, the Late Triassic was initially warm and arid with a strong monsoon climate and with most precipitation limited to coastal regions and high latitudes. This changed late in the Carnian period with a 2 million years-long wet season which transformed the arid continental interior into lush alluvial forests . The first true dinosaurs appeared early in
14892-717: The fossil record. Arthropods remained abundant, and some groups, such as eurypterids , became apex predators in the ocean. Fully terrestrial life established itself on land, including early fungi , arachnids , hexapods and myriapods . The evolution of vascular plants (mainly spore -producing ferns such as Cooksonia ) allowed land plants to gain a foothold further inland as well. During this time, there were four continents: Gondwana (Africa, South America, Australia, Antarctica, India), Laurentia (North America with parts of Europe), Baltica (the rest of Europe), and Siberia (Northern Asia). The Devonian spans from 419 million to 359 million years ago. Also informally known as
15038-414: The foundational principles of determining the correlation of strata relative to geologic time. Over the course of the 18th-century geologists realised that: The apparent, earliest formal division of the geologic record with respect to time was introduced during the era of Biblical models by Thomas Burnet who applied a two-fold terminology to mountains by identifying " montes primarii " for rock formed at
15184-465: 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 the Phanerozoic Eon looks longer than
15330-608: The glaciation of Gondwana as much of it was situated around the South Pole . This event was known as the Permo-Carboniferous Glaciation and resulted in a major loss of coal forests, known as the Carboniferous rainforest collapse . The Permian spans from 299 million to 251 million years ago and was the last period of the Paleozoic era. At its beginning, all landmasses came together to form
15476-492: The ground work for radiometric dating, but the knowledge and tools required for accurate determination of radiometric ages would not be in place until the mid-1950s. Early attempts at determining ages of uranium minerals and rocks by Ernest Rutherford , Bertram Boltwood , Robert Strutt , and Arthur Holmes, would culminate in what are considered the first international geological time scales by Holmes in 1911 and 1913. The discovery of isotopes in 1913 by Frederick Soddy , and
15622-473: The last of which includes fish , amphibians and the fully terrestrial amniotes ( synapsids and sauropsids ). The Mesozoic features the evolution of crocodilians , turtles , dinosaurs (including birds ), lepidosaurs ( lizards and snakes ) and mammals . The Cenozoic begins with the extinction of all non-avian dinosaurs , pterosaurs and marine reptiles , and features the great diversification in birds and mammals. Humans appeared and evolved during
15768-536: The latter of which include two clades — the actinopterygians ( ray-finned fish ) and sarcopterygians ( lobe-finned fish ). One lineage of sarcopterygians, Rhipidistia , evolved the first four-limbed vertebrates , which would eventually become tetrapods . On land, plant groups diversified after the Silurian-Devonian Terrestrial Revolution ; the first woody ferns and the earliest seed plants evolved during this period. By
15914-866: 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. Phanerozoic Eonothem 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), and Cenozoic (new life). Names of systems are diverse in origin, with some indicating chronologic position (e.g., Paleogene), while others are named for lithology (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
16060-561: 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. 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 against Genesis were not readily accepted and dissent from religious doctrine
16206-537: 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 stratigraphic horizons 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
16352-629: The lower boundary of the Paleogene System/Period and thus the boundary between the Cretaceous and Paleogene systems/periods. For divisions prior to the Cryogenian , 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. Historically, regional geologic time scales were used due to
16498-404: The most recent part of the Cenozoic. The Paleozoic is a time in Earth's history when active complex life forms evolved, took their first foothold on dry land, and when the forerunners of all multicellular life on Earth began to diversify. There are six periods in the Paleozoic era: Cambrian , Ordovician , Silurian , Devonian , Carboniferous and Permian . The Cambrian is the first period of
16644-586: The non-avian dinosaurs , became extinct in an event attributed by most experts to the impact of a large asteroid or other celestial body, the Chicxulub impactor . The Cenozoic is also known as the Age of Mammals because the terrestrial animals that dominated both hemispheres were mammals – the eutherians (placentals) in the northern hemisphere and the metatherians (marsupials, now mainly restricted to Australia and to some extent South America ) in
16790-408: The pertinent time span. As of April 2022 these proposed changes have not been accepted by the ICS. The proposed changes (changes from the current scale [v2023/09]) are italicised: Proposed pre-Cambrian timeline (GTS2012), shown to scale: Current ICC pre-Cambrian timeline (v2023/09), shown to scale: The following table summarises the major events and characteristics of the divisions making up
16936-512: The phosphorus cycle, wherein increased phosphorus input into the ocean would increase surficial biological productivity that would in turn enhance iron redox cycling and thus remove phosphorus from seawater; this maintained a relatively stable rate of removal of carbon from the atmosphere and ocean via organic carbon burial. The climate also controlled the availability of phosphate through its regulation of rates of continental and seafloor weathering. Major global temperature variations of >7 °C during
17082-452: 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 (above timelines) / Thousands of years (below timeline) First suggested in 2000,
17228-489: 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 from Creation ). While Steno's principles were simple and attracted much attention, applying them proved challenging. These basic principles, albeit with improved and more nuanced interpretations, still form
17374-626: The rebirth of seasons, which caused the expansion of savanna-like areas, along with the evolution of grasses . The end of the Eocene was marked by the Eocene–Oligocene extinction event , the European face of which is known as the Grande Coupure . The Oligocene Epoch spans from 33.9 million to 23.03 million years ago. The Oligocene featured the expansion of grasslands which had led to many new species to evolve, including
17520-521: The relative relationships of rocks and thus their chronostratigraphic position. The law 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. In practice, this means a younger rock will lie on top of an older rock unless there is evidence to suggest otherwise. The principle of original horizontality that states layers of sediments will originally be deposited horizontally under
17666-432: The relatively young, well-preserved rocks associated with it. The Paleogene spans from the extinction of non-avian dinosaurs, 66 million years ago, to the dawn of the Neogene, 23.03 million years ago. It features three epochs : the Paleocene , Eocene and Oligocene . The Paleocene Epoch lasted from 66 million to 56 million years ago. Modern placental mammals originated during this time. The devastation of
17812-473: The rest, it merely spans ~539 million years (~12% of Earth's history), whilst the previous three eons 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). The use of subseries/subepochs has been ratified by
17958-504: The rhinoceros-like brontotheres , various bizarre groups of mammals from South America, such as the vaguely elephant-like pyrotheres and the dog-like marsupial relatives called borhyaenids and the monotremes and marsupials of Australia. Mammal evolution in the Cenozoic was predominantly shaped by climatic and geological processes. Cenozoic calcareous nannoplankton experienced rapid rates of speciation and reduced species longevity, while suffering prolonged declines in diversity during
18104-630: The rock record to bring it in line with the post-Tonian geologic time scale. This work assessed the geologic history of the currently defined eons and eras of the pre-Cambrian, and the proposals in the "Geological Time Scale" books 2004, 2012, and 2020. Their recommend revisions of the pre-Cryogenian geologic time scale were (changes from the current scale [v2023/09] are italicised): Proposed pre-Cambrian timeline (Shield et al. 2021, ICS working group on pre-Cryogenian chronostratigraphy), shown to scale: Current ICC pre-Cambrian timeline (v2023/09), shown to scale: The book, Geologic Time Scale 2012,
18250-474: The sea had at times transgressed over the land and at other times had regressed . This view was shared by a few of Xenophanes's contemporaries and those that followed, including Aristotle (384–322 BCE) who (with additional observations) reasoned that the positions of land and sea had changed over long periods of time. The concept of deep time was also recognised by Chinese naturalist Shen Kuo (1031–1095) and Islamic scientist -philosophers, notably
18396-544: The second rock was forming. The relationships of unconformities 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. Observing the type and relationships of unconformities in strata allows geologist to understand the relative timing the strata. The principle of faunal succession (where applicable) that states rock strata contain distinctive sets of fossils that succeed each other vertically in
18542-457: The southern hemisphere. The extinction of many groups allowed mammals and birds to greatly diversify so that large mammals and birds dominated life on Earth. The continents also moved into their current positions during this era. The climate during the early Cenozoic was warmer than today, particularly during the Paleocene–Eocene Thermal Maximum . However, the Eocene to Oligocene transition and
18688-442: The strait of Panama, as the isthmus had not yet formed. This epoch featured a general warming trend, with jungles eventually reaching the poles. The oceans were dominated by sharks as the large reptiles that had once predominated were extinct. Archaic mammals filled the world such as creodonts (extinct carnivores, unrelated to existing Carnivora ). The Eocene Epoch ranged from 56 million years to 33.9 million years ago. In
18834-424: The supercontinent Pangaea , surrounded by one expansive ocean called Panthalassa . The Earth was relatively dry compared to the Carboniferous, with harsh seasons , as the climate of the interior of Pangaea was not moderated by large bodies of water. Amniotes still flourished and diversified in the new dry climate, particularly synapsids such as Dimetrodon , Edaphosaurus and therapsids , which gave rise to
18980-505: The systematic study of those forms started in the 1950s. The transition from the largely sessile Precambrian biota to the active mobile Cambrian biota occurred early in the Phanerozoic. The Phanerozoic is divided into three eras : the Paleozoic , Mesozoic and Cenozoic , which are further subdivided into 12 periods . The Paleozoic features the evolution of the three most prominent animal phyla, arthropods , molluscs and chordates ,
19126-548: 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 early 19th century with a key driver for resolution of this debate being
19272-735: The time of the 'Deluge', and younger " monticulos secundarios" formed later from the debris of the " primarii" . Anton Moro (1687–1784) also used primary and secondary divisions for rock units but his mechanism was volcanic. In this early version of the Plutonism 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 by Giovanni Targioni Tozzetti (1712–1783) and Giovanni Arduino (1713–1795) to include tertiary and quaternary divisions. These divisions were used to describe both
19418-573: 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. The Moon is unique in the Solar System in that it is the only other body from which humans have rock samples with
19564-533: The work of James Hutton (1726–1797), in particular his Theory of the Earth , first presented before the Royal Society of Edinburgh in 1785. Hutton's theory would later become known as uniformitarianism , popularised by John Playfair (1748–1819) and later Charles Lyell (1797–1875) in his Principles of Geology . Their theories strongly contested the 6,000 year age of the Earth as suggested determined by James Ussher via Biblical chronology that
19710-581: The world was dominated by the gastornithid birds, terrestrial crocodylians like Pristichampsus , large sharks such as Otodus , and a handful of primitive large mammal groups like uintatheres , mesonychians , and pantodonts . But as the forests began to recede and the climate began to cool, other mammals took over. The Cenozoic is full of mammals both strange and familiar, including chalicotheres , creodonts , whales , primates , entelodonts , sabre-toothed cats , mastodons and mammoths , three-toed horses , giant rhinoceros like Paraceratherium ,
19856-516: The world's megafauna, including some of the hominid species, such as Neanderthals . All the continents were affected, but Africa to a lesser extent. It still retains many large animals, such as hippos. The Holocene began 11,700 years ago and lasts to the present day. All recorded history and "the Human history " lies within the boundaries of the Holocene Epoch. Human activity is blamed for
20002-535: The world, as did grazers. The Tethys Sea finally closed with the creation of the Arabian Peninsula and in its wake left the Black , Red , Mediterranean and Caspian seas. This only increased aridity. Many new plants evolved, and 95% of modern seed plants evolved in the mid-Miocene. The Pliocene lasted from 5.333 million to 2.58 million years ago. The Pliocene featured dramatic climatic changes, which ultimately led to modern species and plants. The Mediterranean Sea dried up for hundreds of thousand years in
20148-527: The world; Indian monsoons ; deserts in central Asia ; and the beginnings of the Sahara desert. The world map has not changed much since, save for changes brought about by the glaciations of the Quaternary, such as the Great Lakes , Hudson Bay , and the Baltic Sea . The Quaternary spans from 2.58 million years ago to present day, and is the shortest geological period in the Phanerozoic Eon . It features modern animals, and dramatic changes in
20294-429: 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 century William Smith , Georges Cuvier , Jean d'Omalius d'Halloy , and Alexandre 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
20440-546: Was coined in 1930 by the American geologist George Halcott Chadwick (1876–1953), deriving from the Ancient Greek words φανερός ( phanerós ), meaning "visible"; and ζωή ( zōḗ ), meaning "life". This is because it was once believed that life began in the Cambrian , the first period of this eon, due to the lack of Precambrian fossil record back then. However, trace fossils of booming complex life from
20586-415: Was in some places unwise, scholars such as Girolamo Fracastoro shared da Vinci's views, and found the attribution of fossils to the 'Deluge' absurd. Niels Stensen, more commonly known as Nicolas Steno (1638–1686), is credited with establishing four of the guiding principles of stratigraphy. In De solido intra solidum naturaliter contento dissertationis prodromus Steno states: Respectively, these are
20732-535: Was mainly due to the collision of India with Eurasia, which caused the rise of the Himalayas : the upraised rocks eroded and reacted with CO 2 in the air, causing a long-term reduction in the proportion of this greenhouse gas in the atmosphere. Around 35 million years ago permanent ice began to build up on Antarctica. The cooling trend continued in the Miocene , with relatively short warmer periods. When South America became attached to North America creating
20878-548: Was not until the Italian Renaissance when Leonardo da Vinci (1452–1519) would reinvigorate the relationships between stratification, relative sea-level change, and time, denouncing attribution of fossils to the 'Deluge': 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
21024-612: Was officially recognised by the International Commission on Stratigraphy in June 2009. In 2004, the Tertiary Period was officially replaced by the Paleogene and Neogene Periods. The common use of epochs during the Cenozoic helps palaeontologists better organise and group the many significant events that occurred during this comparatively short interval of time. Knowledge of this era is more detailed than any other era because of
21170-485: Was the last commercial publication of an international chronostratigraphic chart that was closely associated with the ICS. It included a proposal to substantially revise the pre-Cryogenian time scale to reflect important events such as the formation of the Solar System and the Great Oxidation Event , among others, while at the same time maintaining most of the previous chronostratigraphic nomenclature for
21316-635: Was warm and humid, with little temperature gradient from pole to pole. In the Middle Eocene Epoch, the Antarctic Circumpolar Current formed when South America and Australia both separated from Antarctica to open up the Drake Passage and Tasmanian Passage , disrupting ocean currents worldwide, resulting in global cooling and causing the jungles to shrink. More modern forms of mammals continued to diversify with
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