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Encyclopedia > Eon (geology)

In general usage, an eon (sometimes spelled æon) is an arbitrarily designated period of time. Geologists refer to an eon as the largest subdivision of time on the geologic time scale. For example, the Phanerozoic Eon, which is about 550 million years long, covers the period of time during which animals with hard shells that fossilize would have been abundant. The Geologist by Carl Spitzweg A geologist is a contributor to the science of geology, studying the physical structure and processes of the Earth and planets of the solar system (see planetary geology). ... Diagram of geological time scale. ... During the Phanerozoic the biodiversity shows a steady but not monotonic increase from near zero to several thousands of genera. ... For other uses, see Animal (disambiguation). ... For other uses, see Fossil (disambiguation). ...


An eon is composed of several geologic eras, which in turn are composed of geologic periods, which are composed of geologic epochs. We are currently in the Phanerozoic Eon, the Cenozoic Era, the Quaternary Period, and the Holocene epoch. Formerly, only one eon existed besides the Phanerozoic: the Precambrian. More recently, the Hadean, Archean, and Proterozoic "eras" of Precambrian time have been considered eons. The geologic timescale in terms of eons, eras, and periods looks like this: A geologic era is a subdivision of geologic time that is a separate classification that divides the Phanerozoic Eon into three parts timeframes. ... A geologic period is a subdivision of geologic time that divides an era into smaller timeframes. ... A division of geologic time less than a period and greater than an age. ... During the Phanerozoic the biodiversity shows a steady but not monotonic increase from near zero to several thousands of genera. ... Mammals are the dominant creatures of Cenozoic. ... The Quaternary Period is the geologic time period from the end of the Pliocene Epoch roughly 1. ... The Holocene epoch is a geological period, which began approximately 11,550 calendar years BP (about 9600 BC) and continues to the present. ... The Precambrian (Pre-Cambrian) is an informal name for the supereon comprising the eons of the geologic timescale that came before the current Phanerozoic eon. ... The name Hadean refers to the geologic period before 3800 million years ago (mya). ... The Archean is a geologic eon; it is a somewhat antiquated term for the time span between 2500 million years before the present and 3800 million years before the present. ... The Proterozoic (IPA: ) is a geological eon representing a period before the first abundant complex life on Earth. ...



Greek root

The English word eon is derived from the Koine Greek word aion. Koine redirects here. ...


Although a proposal was made in 1957 to define an aeon to be a unit of time equal to one billion years (1 Ga), the idea was not approved as a unit of scientific measure and is seldom used for a specific period of time. Its more common usage is for any lengthy or indefinite period of time. The origin is from the Greek root "aion" for "age" or "life force." A similar Latin word "aevum" for age is still present in words such as longevity and medieval. [1] For the geologic time, see eon (geology). ...


See also

Diagram of geological time scale. ...

References

Before the advent of absolute dating in the 20th century, archaeologists and geologists were largely limited to the use of Relative Dating techniques. ... In archaeology, seriation is a method in relative dating in which artifacts of numerous sites, in the same culture, are placed in chronological order. ... In archaeology, especially in the course of excavation, stratification is of major interest and significance. ... Amino acid dating is a technique used to estimate age in a wide variety of situations. ... The molecular clock (based on the molecular clock hypothesis (MCH)) is a technique in genetics, which researchers use to date when two species diverged. ... Generally a chronicle (Latin chronica, from Greek Χρόνος) is historical account of facts and events in chronological order. ... The New Chronology of Anatoly Timofeevich Fomenko is an attempt to rewrite world chronology, based on his conclusion that world chronology as we know it today is fundamentally flawed. ... Periodization is the attempt to categorize or divide time into discrete named blocks. ... A Synchronoptic view is a graphic display of a number of entities as they proceed through time. ... Look up timeline in Wiktionary, the free dictionary. ... For the political notion, see Year Zero (political notion). ... Look up Circa on Wiktionary, the free dictionary The Latin word circa, literally meaning about, is often used to describe various dates (often birth and death dates) that are uncertain. ... Floruit (or fl. ...

 
 

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