Geologic time scale

This clock representation shows some of the major units of geological time and definitive events of Earth history. The Hadean eon represents the time before fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga (billion years ago).[1] Other subdivisions reflect the evolution of life; the Archean and Proterozoic are both eons, the Palaeozoic, Mesozoic and Cenozoic are eras of the Phanerozoic eon. The three million year Quaternary period, the time of recognizable humans, is too small to be visible at this scale.

The geologic time scale (GTS) is a system of chronological dating that relates geological strata (stratigraphy) to time. It is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth's history. The table of geologic time spans, presented here, agree with the nomenclature, dates and standard color codes set forth by the International Commission on Stratigraphy (ICS).


The primary defined divisions of time are eons, in sequence the Hadean, the Archean, the Proterozoic and the Phanerozoic. The first three of these can be referred to collectively as the Precambrian supereon. Eons are divided into eras, which are in turn divided into periods, epochs and ages.

The following four timelines show the geologic time scale. The first shows the entire time from the formation of the Earth to the present, but this gives little space for the most recent eon. Therefore, 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, and the most recent period is expanded in the fourth timeline.

GelasianCalabrian (stage)PleistocenePleistocenePleistoceneHoloceneQuaternary
Millions of Years

Corresponding to eons, eras, periods, epochs and ages, the terms "eonothem", "erathem", "system", "series", "stage" 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 chronostratigraphy corresponds to the early Jurassic Epoch in geochronology.[2] The adjectives are capitalized when the subdivision is formally recognized, and lower case when not; thus "early Miocene" but "Early Jurassic."

Other Languages
Basa Banyumasan: Kurun Wektu Geologis
čeština: Geologický čas
한국어: 지질 시대
Bahasa Indonesia: Skala waktu geologi
interlingua: Era geologic
Kreyòl ayisyen: Echèl tan jeyolojik
Lëtzebuergesch: Geologesch Zäitskala
Lingua Franca Nova: Scala de edas jeolojial
македонски: Геолошки период
Bahasa Melayu: Skala masa geologi
日本語: 地質時代
norsk nynorsk: Geologisk tidsskala
саха тыла: Геохронология
Simple English: Historical geology
српски / srpski: Геолошка доба
srpskohrvatski / српскохрватски: Geološka kronologija
vèneto: Era zeolosega
文言: 地質時標
吴语: 地质年代
粵語: 地質時代
中文: 地质年代