Editing Geologic time scale (section)

{{Short description|System that relates geologic strata to time}}
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{{Use British English|date=October 2023}}
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[[File:Geologic time scale - spiral - ICS colours (light) - path text.svg|upright=1.35|alt=Geologic time scale proportionally represented as a log-spiral. The image also shows some notable events in Earth's history and the general evolution of life.|thumb|The geologic time scale, proportionally represented as a [[Logarithmic spiral|log-spiral]] with some major events in Earth's history. A [[megaannus]] (Ma) represents one million (10<sup>6</sup>) years.]]

The '''geologic time scale''' or '''geological time scale''' ('''GTS''') is a representation of [[time]] based on the [[geologic record|rock record]] of [[Earth]]. It is a system of [[chronological dating]] that uses [[chronostratigraphy]] (the process of relating [[stratum|strata]] to time) and [[geochronology]] (a scientific branch of [[geology]] that aims to determine the age of rocks). It is used primarily by [[Earth science|Earth scientists]] (including [[geologist]]s, [[paleontology|paleontologists]], [[geophysics|geophysicists]], [[geochemistry|geochemists]], and [[paleoclimatology|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 [[lithology|lithologies]], [[paleomagnetism|paleomagnetic]] properties, and [[fossil]]s. The definition of standardised international units of geological time is the responsibility of the [[International Commission on Stratigraphy]] (ICS), a constituent body of the [[International Union of Geological Sciences]] (IUGS), whose primary objective<ref name="ICS_statutes">{{Cite web |title=Statues & Guidelines |url=https://stratigraphy.org/statutes |access-date=2022-04-05 |website= |publisher=International Commission on Stratigraphy}}</ref> is to precisely define global chronostratigraphic units of the International Chronostratigraphic Chart (ICC)<ref name="ICC_Cohen_2013">{{Cite journal |last1=Cohen |first1=K.M. |last2=Finney |first2=S.C. |last3=Gibbard |first3=P.L. |last4=Fan |first4=J.-X. |date=2013-09-01 |title=The ICS International Chronostratigraphic Chart |journal=Episodes |language=en |edition=updated |volume=36 |issue=3 |pages=199–204 |doi=10.18814/epiiugs/2013/v36i3/002 |s2cid=51819600 |issn=0705-3797|doi-access=free }}</ref> that are used to define divisions of geological time. The chronostratigraphic divisions are in turn used to define geochronologic units.<ref name="ICC_Cohen_2013" />