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The geologic time scale (GTS) is a system of
chronological datingChronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such object or event to be located in a previously established chronology. This usually requires what is commonly known as a "dat ...
that classifies
geological Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the processes by which th ...

geological
strata (
stratigraphy through Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic period million years ago (Year, Mya) to the beginning of the Cretaceous period ap ...

stratigraphy
) in time. It is used by
geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes the Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, although backgrounds in physics, ...

geologist
s,
paleontologists Paleontology, also spelled palaeontology or palæontology (), is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene The Holocene ( ) is the current geological epoch. It began approximate ...
, and other Earth scientists to describe the timing and relationships of events in geologic history. The time scale was developed through the study and observation of layers of rock and relationships as well as the times when different organisms appeared, evolved and became extinct through the study of fossilized remains and imprints. The table of geologic time spans, presented here, agrees with the
nomenclature Nomenclature (, ) is a system of names or terms, or the rules for forming these terms in a particular field of arts or sciences. The principles of naming vary from the relatively informal naming conventions, conventions of everyday speech to the in ...
, dates and standard color codes set forth by the
International Commission on Stratigraphy The International Commission on Stratigraphy (ICS), sometimes referred to unofficially as the "International Stratigraphic Commission", is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigrap ...
(ICS).


Terminology

The largest catalogued divisions of time are intervals called ''eons''. The first eon was the
Hadean The Hadean ( ) is a geologic eon of Earth history preceding the Archean. It began with the formation of the Earth about 4.6 billion years ago and ended, as defined by the International Commission on Stratigraphy The International Commissio ...

Hadean
, starting with the formation of the Earth and lasting about 540 million years until the
Archean The Archean Eon ( , also spelled Archaean or Archæan) is one of the four geologic Geology (from the Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient w ...

Archean
eon, which is when the Earth had cooled enough for continents and the earliest known life to emerge. After about 2.5 billion years, oxygen generated by photosynthesizing single-celled organisms began to appear in the atmosphere marking the beginning of the
Proterozoic The Proterozoic () is a geological eon spanning the time from the appearance of oxygen in Earth's atmosphere to just before the proliferation of complex life (such as trilobites or corals) on the Earth. The name Proterozoic combines the two form ...
. Finally, the
Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontolo ...
eon encompasses 541 million years of diverse abundance of multicellular life starting with the appearance of hard animal shells in the fossil record and continuing to the present. The first three eons (i.e. every eon but the Phanerozoic) can be referred to collectively as the
Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale The geologic ...

Precambrian
supereon. This is because of the significance of the Cambrian Explosion, a massive diversification of multi-cellular life forms that took place in the
Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million yea ...
period at the start of the Phanerozoic. Eons are divided into eras, which are in turn divided into periods, epochs and ages. A
polarity chronMagnetostratigraphy is a Geophysics, geophysical correlation technique used to date sedimentary and volcanic sequences. The method works by collecting oriented samples at measured intervals throughout the section. The samples are analyzed to determin ...
or just "chron" can be used as a subdivision of an age, though this is not included in the ICS system. Corresponding to eons, eras, periods, epochs and ages, the terms "
eonothem near Drumheller, Alberta ("Strong and free") , image_map = Alberta in Canada 2.svg , Label_map = yes , coordinates = , official_lang = English , capital = Edmonton , large ...
", "
erathem __NOTOC__ In stratigraphy through Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic period million years ago (Year, Mya) to the beginning o ...
", "
system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpo ...
", "
series Series may refer to: People with the name * Caroline Series (born 1951), English mathematician, daughter of George Series * George Series (1920–1995), English physicist Arts, entertainment, and media Music * Series, the ordered sets used i ...
", "
stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Stag ...
" are used to refer to the layers of rock that belong to these stretches of geologic time in Earth's history. Geologists qualify these units as "early", "mid", and "late" when referring to time, and "lower", "middle", and "upper" when referring to the corresponding rocks. For example, the Lower Jurassic Series in
chronostratigraphyChronostratigraphy is the branch of stratigraphy that studies the ages of rock stratum, strata in relation to time. The ultimate aim of chronostratigraphy is to arrange the sequence of Deposition (geology), deposition and the time of deposition of a ...
corresponds to the Early Jurassic Epoch in
geochronology 300px, An artistic depiction of the major events in the history of Earth Geochronology is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (gen ...
. The adjectives are capitalized when the subdivision is formally recognized, and lower case when not; thus "early Miocene" but "Early Jurassic."


Era definitions

The
Phanerozoic Eon The Phanerozoic Eon is the current geologic eon in the geologic time scale The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontolo ...
is divided into three eras: the
Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek ''palaiós'' (), "old" and ''zōḗ'' (), "life", meaning "ancient life") is the earliest of three geologic eras of the Phanerozoic Eon. It is the longest of the Phanerozoic eras, lasting fr ...
,
Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles and the Age of Conifers, is the second-to-last era of Earth's geological history, lasting from about and comprising the Triassic The Triassic ( ) is a geologic period and system A system ...
, and
Cenozoic The Cenozoic Era ( ) meaning "new life" is the current and most recent of the three geological eras of the Phanerozoic Eon. The Cretaceous–Paleogene extinction event near Drumheller, Alberta, where erosion has exposed the K–Pg boundary ...
(meaning "old life", "middle life" and "recent life") that represent the major stages in the macroscopic
fossil record A fossil (from Classical Latin: , literally "obtained by digging") is any preserved remains, impression, or trace of any once-Life, living thing from a past geological age. Examples include Bone, bones, Seashell, shells, exoskeletons, stone i ...
. These eras are separated by catastrophic
extinction Extinction is the termination of a kind of organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by ...

extinction
boundaries: the P-T boundary between the Paleozoic and the Mesozoic, and the K-Pg boundary between the Mesozoic and the Cenozoic. There is evidence that the P-T boundary was caused by the eruption of the
Siberian Traps The Siberian Traps (russian: Сибирские траппы, ) is a large region of volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a Rock (geology), rock formed from lava erupted from a volcano. In other ...
, and the K-Pg boundary was caused by the
meteorite impact
meteorite impact
that created the
Chicxulub crater The Chicxulub crater (; ) is an impact crater buried underneath the Yucatán Peninsula in Mexico Mexico ( es, México ; Nahuan languages: ), officially the United Mexican States (; EUM ), is a List of sovereign states, country in the s ...
. The
Hadean The Hadean ( ) is a geologic eon of Earth history preceding the Archean. It began with the formation of the Earth about 4.6 billion years ago and ended, as defined by the International Commission on Stratigraphy The International Commissio ...

Hadean
,
Archean The Archean Eon ( , also spelled Archaean or Archæan) is one of the four geologic Geology (from the Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient w ...

Archean
and
Proterozoic The Proterozoic () is a geological eon spanning the time from the appearance of oxygen in Earth's atmosphere to just before the proliferation of complex life (such as trilobites or corals) on the Earth. The name Proterozoic combines the two form ...
eons were as a whole formerly called the
Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale The geologic ...

Precambrian
. This covered the four billion years of Earth history prior to the appearance of hard-shelled animals. More recently, however, the Archean and Proterozoic eons have been subdivided into eras of their own.


Period definitions

The twelve currently recognised periods of the present eon – the
Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontolo ...
– are defined by the
International Commission on Stratigraphy The International Commission on Stratigraphy (ICS), sometimes referred to unofficially as the "International Stratigraphic Commission", is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigrap ...
(ICS) by reference to the
stratigraphy through Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic period million years ago (Year, Mya) to the beginning of the Cretaceous period ap ...

stratigraphy
at particular locations around the world. In 2004 the
Ediacaran The Ediacaran Period ( ) is a geological period that spans 94 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 541 Mya. It marks the end of the Proterozoic Eon, and the ...
Period of the latest
Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale The geologic ...

Precambrian
was defined in similar fashion, and was the first such newly designated period in 130 years. A consequence of this approach to the Phanerozoic periods is that the ages of their beginnings and ends can change from time to time as the absolute age of the chosen rock sequences, which define them, is more precisely determined. The set of rocks (
sedimentary Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at the Earth's surface, followed by cementation. Sedimentation Sedimentation is the tendency for particle (ecology), parti ...

sedimentary
,
igneous Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the p ...
or
metamorphic
metamorphic
) formed during a period belong to a chronostratigraphic unit called a
system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpo ...
. For example, the "Jurassic System" of rocks was formed during the "Jurassic Period" (between 201 and 145 million years ago).


Principles

Evidence from
radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the ...
indicates that Earth is about 4.54 billion years old. The geology or ''
deep time Deep time is a term introduced and applied by John McPhee to the concept of geologic time in his ''Basin and Range'' (1981), parts of which originally appeared in the '' New Yorker'' magazine. The philosophical concept of geological time was de ...
'' of Earth's past has been organized into various units according to events that are thought to have taken place. Different spans of time on the GTS are usually marked by corresponding
changes in the composition of strata
changes in the composition of strata
which indicate major geological or
paleontological Paleontology, also spelled palaeontology or palæontology (), is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene The Holocene ( ) is the current geological epoch. It began approximate ...
events, such as
mass extinction An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms. It o ...
s. For example, the boundary between the
Cretaceous The Cretaceous ( ) is a geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisions ...
period and the
Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago ( Mya) to the beginning o ...
period is defined by the
Cretaceous–Paleogene extinction event near Drumheller, Alberta, where erosion has exposed the K–Pg boundary File:Cretaceous Paleogene clay at Geulhemmergroeve.jpg, alt=Cretaceous Paleogene clay layer with finger pointing to boundary, Complex Cretaceous–Paleogene clay layer (gra ...
, which marked the demise of the non-avian
dinosaur Dinosaurs are a diverse group of reptiles of the clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a ...
s as well as many other groups of life. Older time spans, which predate the reliable fossil record (before the
Proterozoic eon The Proterozoic () is a geological eon spanning the time from the appearance of oxygen in Earth's atmosphere to just before the proliferation of complex life Life is a characteristic that distinguishes physical entities that have biologi ...
), are defined by their absolute age. Geologic units from the same time but different parts of the world often are not similar and contain different fossils, so the same time-span was historically given different names in different locales. For example, in North America, the Lower
Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million yea ...
is called the Waucoban series that is then subdivided into zones based on the succession of
trilobites Trilobites (; meaning "three lobes") are a group of extinction, extinct marine artiopodan arthropods that form the class (biology), class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobit ...

trilobites
. In
East Asia East Asia is the eastern region of Asia Asia () is Earth's largest and most populous continent, located primarily in the Eastern Hemisphere, Eastern and Northern Hemisphere, Northern Hemisphere of the Earth, Hemispheres. It shares the ...
and
Siberia Siberia (; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region spanning much of Northern Asia. Siberia has been Russian conquest of Siberia, part of modern Russia since the latter half of th ...

Siberia
, the same unit is split into Alexian,
Atdabanian Cambrian Stage 3 is the still unnamed third stage of the Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 55.6 million ye ...
, and
Botomian Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commission ...
stages. A key aspect of the work of the International Commission on Stratigraphy is to reconcile this conflicting terminology and define universal
horizons The horizon The horizon is the apparent line that separates earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. About 29% of Earth's surface is land consisting of continent A co ...
that can be used around the world. Some other
planets A planet is an astronomical body orbit In physics, an orbit is the gravitationally curved trajectory of an physical body, object, such as the trajectory of a planet around a star or a natural satellite around a planet. Normally, orbit r ...

planets
and
moons A natural satellite, or moon, is, in the most common usage, an astronomical body that orbit In physics, an orbit is the gravitationally curved trajectory of an physical body, object, such as the trajectory of a planet around a star or ...

moons
in the Solar System have sufficiently rigid structures to have preserved records of their own histories, for example,
Venus Venus is the second planet from the Sun. It is named after the Venus (mythology), Roman goddess of love and beauty. As List of brightest natural objects in the sky, the brightest natural object in Earth's night sky after the Moon, Venus can c ...
,
Mars Mars is the fourth planet A planet is an astronomical body orbiting a star or Stellar evolution#Stellar remnants, stellar remnant that is massive enough to be Hydrostatic equilibrium, rounded by its own gravity, is not massive enough to ...
and the
Earth's Moon The Moon is Earth's only Claimed moons of Earth, proper natural satellite. At one-quarter the diameter of Earth (comparable to the width of Australia), it is the largest natural satellite in the Solar System relative to the size of its plane ...
. Dominantly fluid planets, such as the
gas giant A gas giant is a giant planet composed mainly of hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. With a standard atomic weight of , hydrogen is the lightest element in the periodic t ...
s, do not comparably preserve their history. Apart from the
Late Heavy Bombardment The Late Heavy Bombardment (LHB), or lunar cataclysm, is a hypothesized event thought to have occurred approximately 4.1 to 3.8 billion year A year is the orbital period of a planetary body, for example, the Earth, moving in Earth's orbit, ...
, 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.


History and nomenclature of the time scale


Early history

In
Ancient Greece Ancient Greece ( el, Ἑλλάς, Hellás) was a civilization belonging to a period of History of Greece, Greek history from the Greek Dark Ages of the 12th–9th centuries BC to the end of Classical Antiquity, antiquity ( AD 600). This era was ...
,
Aristotle Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλόσοφος, , translit ...

Aristotle
(384–322 BCE) observed that
fossil A fossil (from Classical Latin Classical Latin is the form of Latin language Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the a ...

fossil
s of seashells in rocks resembled those found on beaches – he inferred that the fossils in rocks were formed by organisms, and he reasoned that the positions of land and sea had changed over long periods of time.
Leonardo da Vinci Leonardo di ser Piero da Vinci (15 April 14522 May 1519) was an Italian polymath of the High Renaissance who was active as a painter, Drawing, draughtsman, engineer, scientist, theorist, sculptor and architect. While his fame initially rest ...

Leonardo da Vinci
(1452–1519) concurred with Aristotle's interpretation that fossils represented the remains of ancient life. The 11th-century Persian polymath
Avicenna Ibn Sina ( fa, ابن سینا), also known as Abu Ali Sina (), Pur Sina (), and often known in the West as Avicenna (;  – June 1037), was a Persian polymath who is regarded as one of the most significant physicians, astronomers, t ...

Avicenna
(Ibn Sina, died 1037) and the 13th-century
Dominican Dominican may refer to: * Someone or something from or related to the Dominican Republic The Dominican Republic ( ; es, República Dominicana, ) is a country located on the island of Hispaniola in the Greater Antilles archipelago of the C ...
bishop A bishop is an ordained, consecrated, or appointed member of the Clergy#Christianity, Christian clergy who is generally entrusted with a position of authority and oversight. Within the Catholic, Eastern Orthodox, Oriental Orthodox, Moravian Chur ...
Albertus Magnus Albertus Magnus (c. 1200 – November 15, 1280), also known as Saint Albert the Great or Albert of Cologne, was a German Catholic The Catholic Church, often referred to as the Roman Catholic Church, is the List of Christian denominat ...
(died 1280) extended Aristotle's explanation into a theory of a petrifying fluid. Avicenna also first proposed one of the principles underlying geologic time scales, the
law of superposition#REDIRECT Law of superposition 250px, Layer upon layer of rocks on north shore of Isfjord (Svalbard), Isfjord, Svalbard, Norway. Since there is no overturning, the rock at the bottom is older than the rock on the top by the Law of Superposition. ...

law of superposition
of strata, while discussing the origins of mountains in ''
The Book of Healing ''The Book of Healing'' (; ; also known as ) is a scientific Science (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken i ...
'' (1027). The Chinese naturalist
Shen Kuo Shen Kuo (; 1031–1095) or Shen Gua, courtesy name A courtesy name (), also known as a style name, is a name bestowed upon one at adulthood in addition to one's given name. This practice is a tradition in the Sinosphere, including China, Jap ...
(1031–1095) also recognized the concept of "
deep time Deep time is a term introduced and applied by John McPhee to the concept of geologic time in his ''Basin and Range'' (1981), parts of which originally appeared in the '' New Yorker'' magazine. The philosophical concept of geological time was de ...
".


Establishment of primary principles

In the late 17th century
Nicholas Steno Nicolas Steno ( da, Niels Steensen; Latinized to ''Nicolaus Steno'' or ''Nicolaus Stenonius''; 1 January 1638 – 25 November 1686
(1638–1686) pronounced the principles underlying geologic (geological) time scales. Steno argued that rock layers (or strata) were laid down in succession and that each represents a "slice" of time. He also formulated the law of superposition, which states that any given stratum is probably older than those above it and younger than those below it. While Steno's principles were simple, applying them proved challenging. Steno's ideas also lead to other important concepts geologists use today, such as
relative dating Relative dating is the science of determining the relative order of past events (i.e., the age of an object in comparison to another), without necessarily determining their absolute age (i.e. estimated age). In geology, rock or superficial depo ...
. Over the course of the 18th-century geologists realized 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
Neptunist 200px, Abraham Gottlob Werner (1749–1817), the founder of neptunism Neptunism is a Superseded scientific theories, superseded scientific theory of geology proposed by Abraham Gottlob Werner (1749–1817) in the late 18th century, proposing that ...
theories popular at this time (expounded by
Abraham Werner
Abraham Werner
(1749–1817) in the late 18th century) proposed that all rocks had precipitated out of a single enormous flood. A major shift in thinking came when
James Hutton James Hutton (; 3 June 172614 June 1726 New Style. – 26 March 1797) was a Scottish geologist, Agricultural science, agriculturalist, chemist, chemical manufacturer, Natural history, naturalist and physician. Often referred to as the ‘fat ...

James Hutton
presented his ''Theory of the Earth; or, an Investigation of the Laws Observable in the Composition, Dissolution, and Restoration of Land Upon the Globe'' before the
Royal Society of Edinburgh The Royal Society of Edinburgh is Scotland's national academy of science and letters. It is a registered charity, operating on a wholly independent and non-party-political basis and providing public benefit throughout Scotland. It was establishe ...
in March and April 1785.
John McPhee John Angus McPhee (born March 8, 1931) is an American writer. He is considered one of the pioneers of creative nonfiction. He is a four-time finalist for the Pulitzer Prize in the category General Nonfiction, and he won that award on the fourth ...

John McPhee
asserts that "as things appear from the perspective of the 20th century, James Hutton in those readings became the founder of modern geology". Hutton proposed that the interior of Earth was hot and that this heat was the engine which drove the creation of new rock: land was eroded by air and water and deposited as layers in the sea; heat then consolidated the sediment into stone and uplifted it into new lands. This theory, known as "
Plutonism Plutonism (or volcanism) is the geologic theory A theory is a reason, rational type of abstraction, abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with ...
", stood in contrast to the "Neptunist" flood-oriented theory.


Formulation of geologic time scale

The first serious attempts to formulate a geologic time scale that could be applied anywhere on Earth were made in the late 18th century. The most influential of those early attempts (championed by
Werner
Werner
, among others) divided the rocks of Earth's crust into four types: Primary, Secondary, Tertiary, and Quaternary. Each type of rock, according to the theory, formed during a specific period in Earth history. It was thus possible to speak of a "Tertiary Period" as well as of "Tertiary Rocks." Indeed, "Tertiary" (now Paleogene and Neogene) remained in use as the name of a geological period well into the 20th century and "Quaternary" remains in formal use as the name of the current period. The identification of strata by the fossils they contained, pioneered by
William Smith
William Smith
,
Georges Cuvier Jean Léopold Nicolas Frédéric, Baron Cuvier (; 23 August 1769 – 13 May 1832), known as Georges Cuvier, was a French naturalist Natural history is a domain of inquiry involving organisms, including animals, fungus, fungi, and plants, in ...

Georges Cuvier
, Jean d'Omalius d'Halloy, and
Alexandre Brongniart Alexandre Brongniart (5 February 17707 October 1847) was a French chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a scientist A scientist is a person who conducts Scientific m ...

Alexandre Brongniart
in the early 19th century, enabled geologists to divide Earth history more precisely. It also enabled them to correlate strata across national (or even continental) boundaries. If two strata (however distant in space or different in composition) contained the same fossils, chances were good that they had been laid down at the same time. Detailed studies between 1820 and 1850 of the strata and fossils of Europe produced the sequence of geologic periods still used today.


Naming of geologic periods, eras and epochs

Early work on developing the geologic time scale was dominated by British geologists, and the names of the geologic periods reflect that dominance. The "Cambrian", (the classical name for
Wales Wales ( cy, Cymru ) is a country that is Countries of the United Kingdom, part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, and the Bristol Channel to the south. It ...

Wales
) and the "Ordovician" and "Silurian", named after ancient Welsh tribes, were periods defined using stratigraphic sequences from Wales. The "Devonian" was named for the English county of
Devon Devon (, archaically known as Devonshire) is a Counties of England, county in South West England, reaching from the Bristol Channel in the north to the English Channel in the south. It is bounded by Cornwall to the west, Somerset to the north- ...
, and the name "Carboniferous" was an adaptation of "the Coal Measures", the old British geologists' term for the same set of strata. The "Permian" was named after the region of Perm in Russia, because it was defined using strata in that region by Scottish geologist
Roderick Murchison Sir Roderick Impey Murchison, 1st Baronet, (22 February 1792 – 22 October 1871) was a British geologist who first described and investigated the Silurian system. Early life and work Murchison was born at Tarradale Castle, Tarradale House, M ...

Roderick Murchison
. However, some periods were defined by geologists from other countries. The "Triassic" was named in 1834 by a German geologist Friedrich Von Alberti from the three distinct layers (Latin meaning triad)
red bed Red is the color at the long wavelength end of the visible spectrum of light, next to Orange (colour), orange and opposite Violet (color), violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the ...
s, capped by
chalk Chalk is a soft, white, permeability (Earth sciences), porous, sedimentary rock, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic pla ...
, followed by black
shale Shale is a fine-grained, clastic sedimentary rock Sedimentary rocks are types of Rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at the Earth's surface, followed by Cementa ...

shale
sthat are found throughout Germany and Northwest Europe, called the ‘Trias’. The "Jurassic" was named by a French geologist
Alexandre Brongniart Alexandre Brongniart (5 February 17707 October 1847) was a French chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a scientist A scientist is a person who conducts Scientific m ...

Alexandre Brongniart
for the extensive marine
limestone Limestone is a common type of carbonate rock, carbonate sedimentary rock. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science), crystal forms of calcium carbonate (). Limestone forms ...

limestone
exposures of the
Jura Mountains The Jura Mountains ( , , , ; french: Massif du Jura; german: Juragebirge; it, Massiccio del Giura, rm, Montagnas da Jura) are a sub-alpine mountain range a short distance north of the Western Alps and mainly demarcate a long part of the ...

Jura Mountains
. The "Cretaceous" (from Latin ''creta'' meaning ‘
chalk Chalk is a soft, white, permeability (Earth sciences), porous, sedimentary rock, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic pla ...
’) as a separate period was first defined by Belgian geologist Jean d'Omalius d'Halloy in 1822, using strata in the
Paris basin The Paris Basin is one of the major geological regions of France France (), officially the French Republic (french: link=no, République française), is a country primarily located in Western Europe, consisting of metropolitan France and Ov ...
and named for the extensive beds of chalk (
calcium carbonate Calcium carbonate is a chemical compound with the formula Ca CO3. It is a common substance found in rocks as the minerals calcite and aragonite (most notably as limestone Limestone is a common type of carbonate rock, carbonate sediment ...

calcium carbonate
deposited by the shells of marine
invertebrate Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This includes all animals apart from the subphylum vertebrate, Vertebrata. Familiar example ...
s) found in Western Europe. British geologists were also responsible for the grouping of periods into eras and the subdivision of the Tertiary and Quaternary periods into epochs. In 1841 published the first global geologic time scale based on the types of fossils found in each era. Phillips' scale helped standardize the use of terms like ''
Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek ''palaiós'' (), "old" and ''zōḗ'' (), "life", meaning "ancient life") is the earliest of three geologic eras of the Phanerozoic Eon. It is the longest of the Phanerozoic eras, lasting fr ...
'' ("old life"), which he extended to cover a larger period than it had in previous usage, and ''
Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles and the Age of Conifers, is the second-to-last era of Earth's geological history, lasting from about and comprising the Triassic The Triassic ( ) is a geologic period and system A system ...
'' ("middle life"), which he invented.


Dating of time scales

When William Smith and Sir Charles Lyell first recognized that rock strata represented successive time periods, time scales could be estimated only very imprecisely since estimates of rates of change were uncertain. While
creationists Creationism is the religious belief that nature, and aspects such as the universe, Earth, life, and humans, originated with supernatural acts of Creation myth, divine creation.#Gunn 2004, Gunn 2004, p. 9, "The ''Concise Oxford Dictionary'' says ...
had been proposing dates of around six or seven thousand years for the age of Earth based on the
Bible The Bible (from Koine Greek Koine Greek (, , Greek approximately ;. , , , lit. "Common Greek"), also known as Alexandrian dialect, common Attic, Hellenistic or Biblical Greek, was the koiné language, common supra-regional form of Greek ...
, early geologists were suggesting millions of years for geologic periods, and some were even suggesting a virtually infinite age for Earth. Geologists and paleontologists constructed the geologic table based on the relative positions of different strata and fossils, and estimated the time scales based on studying rates of various kinds of
weathering Weathering is the deterioration of rocks A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition and the way in wh ...
,
erosion In earth science, erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust, and then sedime ...

erosion
,
sedimentation Sedimentation is the tendency for particle (ecology), particles in Suspension (chemistry), suspension to settle out of the fluid in which they are Entrainment (engineering), entrained and come to rest against a barrier. This is due to their motio ...
, and
lithification Lithification (from the Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following per ...
. Until the discovery of in 1896 and the development of its geological applications through
radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the ...
during the first half of the 20th century, the ages of various rock strata and the age of Earth were the subject of considerable debate. The first geologic time scale that included absolute dates was published in 1913 by the British geologist
Arthur Holmes Arthur Holmes (14 January 1890 – 20 September 1965) was a British geologist who made two major contributions to the understanding of geology. He pioneered the use of radiometric dating of minerals and was the first earth scientist to grasp th ...
. He greatly furthered the newly created discipline of
geochronology 300px, An artistic depiction of the major events in the history of Earth Geochronology is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (gen ...
and published the world-renowned book ''The Age of the Earth'' in which he estimated Earth's age to be at least 1.6 billion years. In a steady effort ongoing since 1974, the
International Commission on Stratigraphy The International Commission on Stratigraphy (ICS), sometimes referred to unofficially as the "International Stratigraphic Commission", is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigrap ...
has been working to correlate the world's local into one uniform planet-wide benchmarked system. In 1977, the ''Global Commission on Stratigraphy'' (now the
International Commission on Stratigraphy The International Commission on Stratigraphy (ICS), sometimes referred to unofficially as the "International Stratigraphic Commission", is a daughter or major subcommittee grade scientific daughter organization that concerns itself with stratigrap ...
) began to define global references known as GSSP ( Global Boundary Stratotype Sections and Points) for geologic periods and faunal stages. The commission's work is described in the 2012 geologic time scale of Gradstein et al. A
UML UML may refer to: * Unified Modeling Language, a software modeling language * University of Massachusetts Lowell, a research university * User-mode Linux, virtual machine software See also

* Unified Medical Language System (UMLS), a medical in ...
model for how the timescale is structured, relating it to the GSSP, is also available.


Correlation issues

American geologists have long considered the Mississippian and Pennsylvanian to be periods in their own right though the ICS now recognises them both as "subperiods" of the
Carboniferous The Carboniferous ( ) is a geologic period and system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environme ...
Period recognised by European geologists. Cases like this in China, Russia and even New Zealand with other geological eras has slowed the uniform organization of the stratigraphic record.


The Anthropocene

Popular culture and a growing number of scientists use the term "
Anthropocene The Anthropocene ( ) is a proposed geological epoch dating from the commencement of significant human Humans (''Homo sapiens'') are the most populous and widespread species of primates, characterized by bipedality, opposable thumbs, hairl ...
" informally to label the current epoch in which we are living. The term was coined by
Paul Crutzen Paul Jozef Crutzen (; 3 December 1933 – 28 January 2021) was a Dutch meteorologist Meteorologists are scientists who study and work in the field of meteorology Meteorology is a branch of the atmospheric sciences which includes atmospheric ...
and Eugene Stoermer in 2000 to describe the current time in which humans have had an enormous impact on the environment. It has evolved to describe an "epoch" starting some time in the past and on the whole defined by anthropogenic carbon emissions and production and consumption of plastic goods that are left in the ground. Critics of this term say that the term should not be used because it is difficult, if not nearly impossible, to define a specific time when humans started influencing the rock stratadefining the start of an epoch. The ICS has not officially approved the term . The Anthropocene Working Group met in Oslo in April 2016 to consolidate evidence supporting the argument for the Anthropocene as a true geologic epoch. Evidence was evaluated and the group voted to recommend "Anthropocene" as the new geological age in August 2016. Should the International Commission on Stratigraphy approve the recommendation, the proposal to adopt the term will have to be ratified by the International Union of Geological Sciences before its formal adoption as part of the geologic time scale.


Notable period changes

* Changes in recent years have included the abandonment of the former
Tertiary Tertiary ( ) is a widely used but obsolete term for the Period (geology), geologic period from 66 million to 2.6 million years ago. The period began with the demise of the non-bird, avian dinosaurs in the Cretaceous–Paleogene extincti ...

Tertiary
Period in favour of the
Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago ( Mya) to the beginning o ...
and succeeding
Neogene The Neogene ( ) (informally Upper Tertiary or Late Tertiary) is a geologic period and system that spans 20.45 million years from the end of the Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or E ...

Neogene
periods. This remains controversial. * The abandonment of the
Quaternary Quaternary ( ) is the current and most recent of the three Period (geology), periods of the Cenozoic Era (geology), Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from ...
period was also considered but it has been retained for continuity reasons. * Even earlier in the history of the science, the Tertiary was considered to be an "era" and its subdivisions (
Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era ...
,
Eocene The Eocene ( ) Epoch is a geological epoch In chronology 222px, Joseph Scaliger's ''De emendatione temporum'' (1583) began the modern science of chronology Chronology (from Latin Latin (, or , ) is a classical language belonging to the ...
,
Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define ...
,
Miocene The Miocene ( ) is the first Epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish author Charles Lyell; its name comes from the Greek words (', "less") and (', "new") and means "le ...
and
Pliocene The Pliocene ( ; also Pleiocene) epoch (geology), Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or Early Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago ( Mya) to the beginning o ...
and
Neogene The Neogene ( ) (informally Upper Tertiary or Late Tertiary) is a geologic period and system that spans 20.45 million years from the end of the Paleogene The Paleogene ( ; also spelled Palaeogene or Palæogene; informally Lower Tertiary or E ...

Neogene
periods.


Table of geologic time

The following table summarizes the major events and characteristics of the periods of time making up the geologic time scale. This table is arranged with the most recent geologic periods at the top, and the oldest at the bottom. The height of each table entry does not correspond to the duration of each subdivision of time. The content of the table is based on the current official geologic time scale of the International Commission on Stratigraphy (ICS), with the epoch names altered to the early/late format from lower/upper as recommended by the ICS when dealing with
chronostratigraphyChronostratigraphy is the branch of stratigraphy that studies the ages of rock stratum, strata in relation to time. The ultimate aim of chronostratigraphy is to arrange the sequence of Deposition (geology), deposition and the time of deposition of a ...
. The ICS provides an online interactive version of this chart
ics-chart
based on a service delivering a machine-readable
Resource Description Framework The Resource Description Framework (RDF) is a family of World Wide Web Consortium (W3C) specifications originally designed as a metadata data model. It has come to be used as a general method for conceptual description or modeling of information t ...
/
Web Ontology Language The Web Ontology Language (OWL) is a family of Knowledge representation and reasoning, knowledge representation languages for authoring Ontology (information science), ontologies. Ontologies are a formal way to describe taxonomies and classificatio ...
representation of the timescale, which is available through the
Commission for the Management and Application of Geoscience Information The Commission for the Management and Application of Geoscience Information (CGI), usually referred to by the unofficial "Commission for Geoscience Information" is subcommittee grade scientific organization that concerns itself with geology, geologi ...
GeoSciML project as a service and at a
SPARQL SPARQL (pronounced " sparkle" , a recursive acronym A recursive acronym is an acronym An acronym is a word or name formed from the initial components of a longer name or phrase, usually using individual initial letters, as in NATO (North A ...
end-point. This is not to scale, and even though the
Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontolo ...
eon looks longer than the rest, it merely spans 500 million years, whilst the previous three eons (or the
Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale The geologic ...

Precambrian
supereon) collectively span over 3.5 billion years. This bias toward the most recent eon is due to the relative lack of information about events that occurred during the first three eons (or supereon) compared to the current eon (the Phanerozoic). The proposed
Anthropocene The Anthropocene ( ) is a proposed geological epoch dating from the commencement of significant human Humans (''Homo sapiens'') are the most populous and widespread species of primates, characterized by bipedality, opposable thumbs, hairl ...
epoch is not included.


Proposed Precambrian timeline

The ICS's ''Geologic Time Scale 2012'' book which includes the new approved time scale also displays a proposal to substantially revise the Precambrian time scale to reflect important events such as the
formation of the Earth Earth is the third planet A planet is an astronomical body orbiting a star or Stellar evolution#Stellar remnants, stellar remnant that is massive enough to be Hydrostatic equilibrium, rounded by its own gravity, is not massive enough to c ...
or the
Great Oxidation Event upright=2, O2 build-up in the Earth's atmosphere. Red and green lines represent the range of the estimates while time is measured in billions of years ago (Ga). The Great Oxidation Event (GOE), also called the Great Oxygenation Event, the Oxyge ...
, among others, while at the same time maintaining most of the previous chronostratigraphic nomenclature for the pertinent time span. (See also .) *
Hadean The Hadean ( ) is a geologic eon of Earth history preceding the Archean. It began with the formation of the Earth about 4.6 billion years ago and ended, as defined by the International Commission on Stratigraphy The International Commissio ...

Hadean
Eon – 4568–4030 Ma ** Chaotian Era – 4568–4404 Ma – the name alluding both to the mythological Chaos and the
chaotic Chaotic was originally a Denmark, Danish trading card game. It expanded to an online game in United States, America which then became a television program based on the game. The program was able to be seen on 4Kids TV (Fox affiliates, nationwide), ...
phase of
planet formation The nebular hypothesis is the most widely accepted model in the field of cosmogony Cosmogony is any model concerning the origin of either the cosmos or the universe. Overview Scientific theories In astronomy, cosmogony refers to the st ...

planet formation
**Jack Hillsian or Zirconian Era – 4404–4030 Ma – both names allude to the Jack Hills Greenstone Belt which provided the oldest mineral grains on Earth,
zircons Zircon ( or ) is a mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which ...
*
Archean The Archean Eon ( , also spelled Archaean or Archæan) is one of the four geologic Geology (from the Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient w ...

Archean
Eon – 4031–2420 Ma **
Paleoarchean The Paleoarchean (), also spelled Palaeoarchaean (formerly known as early Archean), is a geologic era within the Archaean eon. It spans the period of time —the era is defined chronometrically and is not referenced to a specific level of a ...
Era – 4031–3490 Ma *** Acastan Period – 4031–3810 Ma – named after the
Acasta Gneiss The Acasta Gneiss is a tonalite Tonalite is an igneous, plutonic ( intrusive) rock, of felsic In geology, felsic is an adjective describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 200 ...

Acasta Gneiss
*** Isuan Period – 3810–3490 Ma – named after the Isua Greenstone Belt **
Mesoarchean The Mesoarchean (, also spelled Mesoarchaean) is a geologic era within the Archean Eon, spanning . The era is defined chronometrically and is not referenced to a specific level in a rock section on Earth. The Pongola glaciation occurred arou ...
Era – 3490–2780 Ma ***
Vaalbaran The geologic time scale (GTS) is a system of chronological datingChronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such object or event to be located in a previously establish ...
Period – 3490–3020 Ma – based on the names of the Kapvaal (Southern Africa) and
Pilbara The Pilbara () is a large, dry, thinly populated regions of Western Australia, region in the north of Western Australia. It is known for its Indigenous Australians, Aboriginal peoples; its ancient landscapes; the red earth; and its vast miner ...
(Western Australia)
craton A craton (, , or ; from el, κράτος ''kratos'' "strength") is an old and stable part of the continental lithosphere A lithosphere ( grc, wikt:λίθος#Ancient Greek, λίθος [] for "rocky", and [] for "sphere") is the rigid, outerm ...
s ***Pongolan Period – 3020–2780 Ma – named after the Pongola Supergroup **
Neoarchean The Neoarchean (; also spelled Neoarchaean) is a geologic era within the Archaean Eon. The Neoarchean spans the period from — the period being defined chronometrically and not referenced to a specific level in a rock section on Earth ...
Era – 2780–2420 Ma *** Methanian Period – 2780–2630 Ma – named for the inferred predominance of methanotrophic
prokaryotes A prokaryote () is a single-celled organism A unicellular organism, also known as a single-celled organism, is an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contig ...

prokaryotes
***
Siderian The Siderian Period (; el, σίδηρος, translit=sídēros, meaning "iron") is the first geologic period in the Paleoproterozoic Era and lasted from Ma to Ma (million years ago). Instead of being based on stratigraphy through Jurassic ...
Period – 2630–2420 Ma – named for the voluminous banded iron formations formed within its duration *
Proterozoic The Proterozoic () is a geological eon spanning the time from the appearance of oxygen in Earth's atmosphere to just before the proliferation of complex life (such as trilobites or corals) on the Earth. The name Proterozoic combines the two form ...
Eon – 2420–541 Ma **
Paleoproterozoic The Paleoproterozoic Era (;, also spelled Palaeoproterozoic), spanning the time period from (2.5–1.6  Ga), is the first of the three sub-divisions ( eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth ...
Era – 2420–1780 Ma ***
Oxygenian The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth sciences, Earth scientists to describe t ...
Period – 2420–2250 Ma – named for displaying the first evidence for a global oxidizing atmosphere ***Rhyacian, Jatulian or Eukaryian Period – 2250–2060 Ma – names are respectively for the Lomagundi–Jatuli δ13C isotopic excursion event spanning its duration, and for the (proposed) first fossil appearance of Eukaryota, eukaryotes ***Columbian Period – 2060–1780 Ma – named after the supercontinent Columbia (supercontinent), Columbia **Mesoproterozoic Era – 1780–850 Ma ***Rodinian Period – 1780–850 Ma – named after the supercontinent Rodinia, stable environment **Neoproterozoic Era – 850–541 Ma ***Cryogenian Period – 850–630 Ma – named for the occurrence of several glaciations ***
Ediacaran The Ediacaran Period ( ) is a geological period that spans 94 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 541 Mya. It marks the end of the Proterozoic Eon, and the ...
Period – 630–541 Ma Shown to scale: ImageSize = width:1100 height:120 PlotArea = left:65 right:15 bottom:20 top:5 AlignBars = justify Colors = id:precambrian value:rgb(0.968,0.262,0.439) id:proterozoic value:rgb(0.968,0.207,0.388) id:neoproterozoic value:rgb(0.996,0.701,0.258) id:ediacaran value:rgb(0.996,0.85,0.415) id:cryogenian value:rgb(0.996,0.8,0.36) id:tonian value:rgb(0.996,0.75,0.305) id:mesoproterozoic value:rgb(0.996,0.705,0.384) id:rodinian value:rgb(0.996,0.75,0.478) id:paleoproterozoic value:rgb(0.968,0.263,0.44) id:columbian value:rgb(0.968,0.459,0.655) id:eukaryian value:rgb(0.968,0.408,0.596) id:oxygenian value:rgb(0.968,0.357,0.537) id:archean value:rgb(0.996,0.157,0.498) id:neoarchean value:rgb(0.976,0.608,0.757) id:siderian value:rgb(0.976,0.7,0.85) id:methanian value:rgb(0.976,0.65,0.8) id:mesoarchean value:rgb(0.968,0.408,0.662) id:pongolan value:rgb(0.968,0.5,0.75) id:vaalbaran value:rgb(0.968,0.45,0.7) id:paleoarchean value:rgb(0.96,0.266,0.624) id:isuan value:rgb(0.96,0.35,0.65) id:acastan value:rgb(0.96,0.3,0.6) id:hadean value:rgb(0.717,0,0.494) id:zirconian value:rgb(0.902,0.114,0.549) id:chaotian value:rgb(0.8,0.05,0.5) id:black value:black id:white value:white Period = from:-4600 till:-541 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:500 start:-4500 ScaleMinor = unit:year increment:100 start:-4500 Define $markred = text:"*" textcolor:red shift:(0,3) fontsize:10 PlotData= align:center textcolor:black fontsize:8 mark:(line,black) width:25 shift:(0,-5) bar:supereon from: start till: -541 text:
Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale The geologic ...

Precambrian
color:precambrian bar:eon from: -2420 till: -541 text:
Proterozoic The Proterozoic () is a geological eon spanning the time from the appearance of oxygen in Earth's atmosphere to just before the proliferation of complex life (such as trilobites or corals) on the Earth. The name Proterozoic combines the two form ...
color:proterozoic from: -4031 till: -2420 text:
Archean The Archean Eon ( , also spelled Archaean or Archæan) is one of the four geologic Geology (from the Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient w ...

Archean
color:archean from: start till: -4031 text:
Hadean The Hadean ( ) is a geologic eon of Earth history preceding the Archean. It began with the formation of the Earth about 4.6 billion years ago and ended, as defined by the International Commission on Stratigraphy The International Commissio ...

Hadean
color:hadean bar:era from: -850 till: -541 text:Neoproterozoic color:neoproterozoic from: -1780 till: -850 text:Mesoproterozoic color:mesoproterozoic from: -2420 till: -1780 text:
Paleoproterozoic The Paleoproterozoic Era (;, also spelled Palaeoproterozoic), spanning the time period from (2.5–1.6  Ga), is the first of the three sub-divisions ( eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth ...
color:paleoproterozoic from: -2780 till: -2420 text:
Neoarchean The Neoarchean (; also spelled Neoarchaean) is a geologic era within the Archaean Eon. The Neoarchean spans the period from — the period being defined chronometrically and not referenced to a specific level in a rock section on Earth ...
color:neoarchean from: -3490 till: -2780 text:
Mesoarchean The Mesoarchean (, also spelled Mesoarchaean) is a geologic era within the Archean Eon, spanning . The era is defined chronometrically and is not referenced to a specific level in a rock section on Earth. The Pongola glaciation occurred arou ...
color:mesoarchean from: -4031 till: -3490 text:
Paleoarchean The Paleoarchean (), also spelled Palaeoarchaean (formerly known as early Archean), is a geologic era within the Archaean eon. It spans the period of time —the era is defined chronometrically and is not referenced to a specific level of a ...
color:paleoarchean from: -4404 till: -4031 text:Zirconian color:zirconian from: start till: -4404 text:Chaotian color:chaotian bar:period fontsize:6 from: -630 till: -541 text:Ediacaran, Ed. color:ediacaran from: -850 till: -630 text:Cryogenian color:cryogenian from: -1780 till: -850 text:Rodinian color:rodinian from: -2060 till: -1780 text:Columbian color:columbian from: -2250 till: -2060 text:Eukaryian color:eukaryian from: -2420 till: -2250 text:
Oxygenian The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth sciences, Earth scientists to describe t ...
color:oxygenian from: -2630 till: -2420 text:
Siderian The Siderian Period (; el, σίδηρος, translit=sídēros, meaning "iron") is the first geologic period in the Paleoproterozoic Era and lasted from Ma to Ma (million years ago). Instead of being based on stratigraphy through Jurassic ...
color:siderian from: -2780 till: -2630 text: Methanian color:methanian from: -3020 till: -2780 text:Pongolan color:pongolan from: -3490 till: -3020 text:
Vaalbaran The geologic time scale (GTS) is a system of chronological datingChronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such object or event to be located in a previously establish ...
color:vaalbaran from: -3810 till: -3490 text: Isuan color:isuan from: -4031 till: -3810 text: Acastan color:acastan from: start till: -4031 color:white
Compare with the current official timeline, not shown to scale: ImageSize = width:1100 height:120 PlotArea = left:65 right:15 bottom:20 top:5 AlignBars = justify Colors = id:precambrian value:rgb(0.968,0.262,0.439) id:proterozoic value:rgb(0.968,0.207,0.388) id:neoproterozoic value:rgb(0.996,0.701,0.258) id:ediacaran value:rgb(0.996,0.85,0.415) id:cryogenian value:rgb(0.996,0.8,0.36) id:tonian value:rgb(0.996,0.75,0.305) id:mesoproterozoic value:rgb(0.996,0.705,0.384) id:stenian value:rgb(0.996,0.85,0.604) id:ectasian value:rgb(0.996,0.8,0.541) id:calymmian value:rgb(0.996,0.75,0.478) id:paleoproterozoic value:rgb(0.968,0.263,0.44) id:statherian value:rgb(0.968,0.459,0.655) id:orosirian value:rgb(0.968,0.408,0.596) id:rhyacian value:rgb(0.968,0.357,0.537) id:siderian value:rgb(0.968,0.306,0.478) id:archean value:rgb(0.996,0.157,0.498) id:neoarchean value:rgb(0.976,0.608,0.757) id:mesoarchean value:rgb(0.968,0.408,0.662) id:paleoarchean value:rgb(0.96,0.266,0.624) id:eoarchean value:rgb(0.902,0.114,0.549) id:hadean value:rgb(0.717,0,0.494) id:black value:black id:white value:white Period = from:-4600 till:-541 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:500 start:-4500 ScaleMinor = unit:year increment:100 start:-4500 Define $markred = text:"*" textcolor:red shift:(0,3) fontsize:10 PlotData= align:center textcolor:black fontsize:8 mark:(line,black) width:25 shift:(0,-5) bar:supereon from: start till: -541 text:
Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale The geologic ...

Precambrian
color:precambrian bar:eon from: -2500 till: -541 text:
Proterozoic The Proterozoic () is a geological eon spanning the time from the appearance of oxygen in Earth's atmosphere to just before the proliferation of complex life (such as trilobites or corals) on the Earth. The name Proterozoic combines the two form ...
color:proterozoic from: -4031 till: -2500 text:
Archean The Archean Eon ( , also spelled Archaean or Archæan) is one of the four geologic Geology (from the Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient w ...

Archean
color:archean from: start till: -4031 text:
Hadean The Hadean ( ) is a geologic eon of Earth history preceding the Archean. It began with the formation of the Earth about 4.6 billion years ago and ended, as defined by the International Commission on Stratigraphy The International Commissio ...

Hadean
color:hadean bar:era from: -1000 till: -541 text:Neoproterozoic color:neoproterozoic from: -1600 till: -1000 text:Mesoproterozoic color:mesoproterozoic from: -2500 till: -1600 text:
Paleoproterozoic The Paleoproterozoic Era (;, also spelled Palaeoproterozoic), spanning the time period from (2.5–1.6  Ga), is the first of the three sub-divisions ( eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth ...
color:paleoproterozoic from: -2800 till: -2500 text:
Neoarchean The Neoarchean (; also spelled Neoarchaean) is a geologic era within the Archaean Eon. The Neoarchean spans the period from — the period being defined chronometrically and not referenced to a specific level in a rock section on Earth ...
color:neoarchean from: -3200 till: -2800 text:
Mesoarchean The Mesoarchean (, also spelled Mesoarchaean) is a geologic era within the Archean Eon, spanning . The era is defined chronometrically and is not referenced to a specific level in a rock section on Earth. The Pongola glaciation occurred arou ...
color:mesoarchean from: -3600 till: -3200 text:
Paleoarchean The Paleoarchean (), also spelled Palaeoarchaean (formerly known as early Archean), is a geologic era within the Archaean eon. It spans the period of time —the era is defined chronometrically and is not referenced to a specific level of a ...
color:paleoarchean from: -4031 till: -3600 text:Eoarchean color:eoarchean from: start till: -4031 color:white bar:period fontsize:6 from: -635 till: -541 text:Ediacaran, Ed. color:ediacaran from: -720 till: -635 text:Cryogenian, Cr. color:cryogenian from: -1000 till: -720 text:Tonian color:tonian from: -1200 till: -1000 text:Stenian color:stenian from: -1400 till: -1200 text:Ectasian color:ectasian from: -1600 till: -1400 text:Calymmian color:calymmian from: -1800 till: -1600 text:Statherian color:statherian from: -2050 till: -1800 text:Orosirian color:orosirian from: -2300 till: -2050 text:Rhyacian color:rhyacian from: -2500 till: -2300 text:
Siderian The Siderian Period (; el, σίδηρος, translit=sídēros, meaning "iron") is the first geologic period in the Paleoproterozoic Era and lasted from Ma to Ma (million years ago). Instead of being based on stratigraphy through Jurassic ...
color:siderian from: start till: -2500 color:white


See also

* Age of the Earth * Bubnoff unit * Cosmic calendar * Deep time * Evolutionary history of life * Geological history of Earth * Geology of Mars/areology * Geon (geology), Geon * Graphical timeline of the universe * History of the Earth * History of geology * History of paleontology * List of fossil sites * List of geochronologic names * Logarithmic timeline * Lunar geologic timescale * Martian geologic timescale * Natural history * New Zealand geologic time scale * Prehistoric life * Timeline of the Big Bang * Timeline of evolution * Timeline of the geologic history of the United States * Timeline of human evolution * Timeline of natural history * Timeline of paleontology


Notes


References


Further reading

* * * * * * * * *


External links


International Chronostratigraphic Chart (interactive)

International Chronostratigraphic Chart (v 2020/03)

Global Boundary Stratotype Section and Points



GSA: Geologic Time Scale



GeoWhen Database



SeeGrid: Geological Time Systems
Information model for the geologic time scale
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) * Lane, Alfred C, and Marble, John Putman 1937
Report of the Committee on the measurement of geologic time



Deep Time – A History of the Earth : Interactive InfographicGeology Buzz: Geologic Time Scale
{{Authority control Geologic time scales, Geology timelines, + Geochronology Geology-related lists, Timescale Articles which contain graphical timelines International Commission on Stratigraphy geologic time scale of Earth