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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 the age of rocks).
The Precambrian includes approximately 90% of geologic time. It extends from 4.6 billion years ago to the beginning of the Cambrian Period (about 539 Ma).It includes the first three of the four eons of Earth's prehistory (the Hadean, Archean, and Proterozoic) and precedes the Phanerozoic eon.
31.6 Ps (1000 Ma, 1 Ga): One giga-annum (Ga), one billion years, the largest fixed time unit used in the standard geological time scale, approximately the order of magnitude of an eon, the largest division of geological time. +1 Ga: The estimated remaining habitable lifetime of Earth, according to some models.
The following five timelines show the geologic time scale to scale. ... 483–487 As the division of labor was completed in the different ... For a long time, the ...
The Proterozoic (IPA: / ˌ p r oʊ t ər ə ˈ z oʊ ɪ k, ˌ p r ɒ t-,-ər oʊ-,-t r ə-,-t r oʊ-/ PROH-tər-ə-ZOH-ik, PROT-, -ər-oh-, -trə-, -troh-) [3] [4] [5] is the third of the four geologic eons of Earth's history, spanning the time interval from 2500 to 538.8 Mya, [6] and is the longest eon of Earth's geologic time scale.
The term geon (for geological eon) refers to large, geologic units of time. Geologists traditionally subdivide Earth history into a hierarchy of named intervals: eons, eras, periods, etc. (e.g., the Jurassic Period of the Mesozoic Era). Historians subdivide the history of human activity into intervals that are comparatively much shorter.
The Paleoproterozoic Era [4] (also spelled Palaeoproterozoic) is the first of the three sub-divisions of the Proterozoic eon, and also the longest era of the Earth's geological history, spanning from (2.5–1.6 Ga).
Tertiary (/ ˈ t ɜːr. ʃ ə. r i, ˈ t ɜː r. ʃ i ˌ ɛr. i / TUR-shə-ree, TUR-shee-err-ee) [1] is an obsolete term for the geologic period from 66 million to 2.6 million years ago. The period began with the extinction of the non-avian dinosaurs in the Cretaceous–Paleogene extinction event, at the start of the Cenozoic Era, and extended to the beginning of the Quaternary glaciation at ...