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This work assessed the geologic history of the currently defined eons and eras of the pre-Cambrian, [note 2] and the proposals in the "Geological Time Scale" books 2004, [74] 2012, [5] and 2020. [75] Their recommend revisions [4] of the pre-Cryogenian geologic time scale were (changes from the current scale [v2023/09] are italicised):
Geologic Time – Period prior to humans. 4.6 billion to 3 million years ago. (See "prehistoric periods" for more detail into this.) Primatomorphid Era – Period prior to the existence of Primatomorpha; Simian Era – Period prior to the existence of Simiiformes; Hominoid Era – Period prior to the existence of Hominoidea
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.
The geological time scale (GTS), as defined by international convention, [3] depicts the large spans of time from the beginning of the Earth to the present, and its divisions chronicle some definitive events of Earth history. Earth formed around 4.54 billion years ago, approximately one-third the age of the universe, by accretion from the solar ...
Geologic time is the timescale used to calculate dates in the planet's geologic history from its origin (currently estimated to have been some 4,600 million years ago) to the present day. Radiometric dating measures the steady decay of radioactive elements in an object to determine its age. It is used to calculate dates for the older part of ...
The Proterozoic is subdivided into three geologic eras (from oldest to youngest): the Paleoproterozoic, Mesoproterozoic and Neoproterozoic. [7] It covers the time from the appearance of free oxygen in Earth's atmosphere to just before the proliferation of complex life on the Earth during the Cambrian Explosion.
The Phanerozoic [5] 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. [1]
1862 – Lord Kelvin attempts to find the age of the Earth by examining its cooling time and estimates that the Earth is between 20 and 400 million years old; 1884 – Marcel Alexandre Bertrand, Nappe and Thrust fault theory