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The geologic time scale is divided into chronostratigraphic units and their corresponding geochronologic units. An eon is the largest geochronologic time unit and is equivalent to a chronostratigraphic eonothem. [13] There are four formally defined eons: the Hadean, Archean, Proterozoic and Phanerozoic. [2]
A unit of time is any particular time interval, used as a standard way of measuring or expressing duration. The base unit of time in the International System of Units (SI), and by extension most of the Western world , is the second , defined as about 9 billion oscillations of the caesium atom.
According to Christian universalism, the Greek New Testament scriptures use the word aión (αἰών) to mean a long period and the word aiṓnion (αἰώνιον) to mean "during a long period"; thus, there was a time before the aeons, and the aeonian period is finite. After each person's mortal life ends, they are judged worthy of aeonian ...
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 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.
Units in geochronology and stratigraphy [1] Segments of rock in chronostratigraphy Time spans in geochronology Notes to geochronological units Eonothem: Eon: 4 total, half a billion years or more Erathem: Era: 10 defined, several hundred million years System: Period: 22 defined, tens to ~one hundred million years Series: Epoch
Units in geochronology and stratigraphy [3] Segments of rock in chronostratigraphy Time spans in geochronology Notes to geochronological units Eonothem: Eon: 4 total, half a billion years or more Erathem: Era: 10 defined, several hundred million years System: Period: 22 defined, tens to ~one hundred million years Series: Epoch
Units in geochronology and stratigraphy [1] Segments of rock in chronostratigraphy Time spans in geochronology Notes to geochronological units Eonothem: Eon: 4 total, half a billion years or more Erathem: Era: 10 defined, several hundred million years System: Period: 22 defined, tens to ~one hundred million years Series: Epoch