Chaotian (geology)

Chaotian Eon/Era
4700–4600 million years ago
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In the geologic record the Chaotian eon or era is unofficially proposed to denote the time preceding the solidification of the Earth's crust and the formation of Earth's moon, it is the earliest era within the eon of Hadean. It lasted 196 million years, at 4,600 million years ago to the beginning of the Zirconian era, 4,404 million years ago. It is named after Chaos, the primeval void in Greek mythology. The Chaotian sets in with the emergence of Earth at 4.6 billion years ago. Its upper limit and thus the transition to the Zirconian era is defined by the occurrence of the first conservation capable mineral. These are zircon, the oldest mineral in the Jack Hills of Narryer Gneiss Terrane in Western Australia (Yilgarn craton) found and were dated 4,404 ± 8 million years ago [1]

According to first proposal, it precedes the Hadean eon and is the earliest eon in Earth's history as a planet. The end of the Chaotian was marked by the hypothetical collision of the proto-Earth and a planet-sized body named Theia, leading to the formation of the Moon.[2][3]

Alternatively it is defined as the first era of the Hadean eon, before the formation of the first crust on the Earth. As of 2012, it is considered to be part of a proposed revision of the Precambrian time scale.[4][5]

Etymology

The term 'Chaotian' is derived from mythological chaos, reflecting the chaotic conditions thought to have existed at the start of the formation of the Earth.[6]

Meaning

Information about this earliest period can therefore only be obtained indirectly, for example by astrophysical considerations and geochemical survey of meteorite material and lunar rock.

Origins

This geological era designation was proposed by NASA scientists at the Ames Research Center in 2010 to formalize terminology in the earliest stages of Earth's history.[6]

The NASA proposal divides the Chaotian into the Eochaotian (4.7-4.65 Gya) and Neochaotian (4.65-4.6 Gya) eras, which are in turn proposed to be divided into the Nephelean (4.7-4.68 Gya) and Erebrean (4.68-4.65 Gya), and Hyperitian (4.65-4.62 Gya) and Titanomachean (4.62-4.6 Gya) periods, respectively.[6] As of May 2017, this has been adopted by the IUGS.

Timing of events

The exact date of the birth of our solar system (and the earth) is still controversial. Calcium-aluminium-rich inclusions (CAI), the first condensate from the planetary orbit, were dated to 4,567.30 ± 0.16 million years ago by the uranium-lead method.[7]

Manganese-chromium dating of chondrules revealed an age of 4.571 billion years ago.[8] In 1979 dating of the Mundrabilla iron meteorite of Western Australia using the argon method determined an age of 4,570 ± 60 million years ago.[9]

The proposed collision with Theia, leading to the formation of the Moon, is estimated to have occurred 4.527 billion years ago.[10]

Outgassing and differentiation of the earth in an iron-rich core and mantle may have been completed 4.45 billion years ago.[11]

References

  1. ↑ Wilde, SA; et al. (2001), "Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago", Nature, 409 (6817): 175–178
  2. ↑ Fox, Stuart (7 January 2010). "NASA Scientists Classify the Time Before Earth Existed: the Chaotian Era". Popular Science. Retrieved 30 July 2013.
  3. ↑ "Beyond Hades". The Economist. 7 January 2010. ISSN 0013-0613.
  4. ↑ Gradstein, F.M.; Ogg, J.G.; Schmitz, Mark; Ogg, Gabi (2012). The Geologic Time Scale 2012. Elsevier. pp. 360–364. ISBN 0444594485.
  5. ↑ Felix M. Gradstein among others (2012). "On the Geologic Time Scale". Newsletters on Stratigraphy. 45/2: 171–188.
  6. 1 2 3 Goldblatt, C.; Zahnle, K.J.; Sleep, N.H.; Nisbet, E.G. (2 February 2010). "The Eons of Chaos and Hades" (PDF). Solid Earth.
  7. ↑ Connelly, JN among others (2012), "The Absolute Chronology and thermal Processing of solids in the solar Protoplanetary Disk", Science, (6107) 338: 651–655, doi:10.1126/science.1226919
  8. ↑ Shukolyukov, A.; Lugmair, G.W. (2002). "Chronology of Asteroid Accretion and Differentiation" (PDF). In Bottke, W.; Cellino, A.; Paolicchi, P. and Binzel, R. (editors). Asteroids III. University of Arizona Press. pp. 687–695. ISBN 0-8165-2281-2.
  9. ↑ Niemeyer, p (1979), "40Ar39 Ar dating of inclusions from IAB iron meteorites", Geochimica et Cosmochimica Acta, 43: 1829–1840
  10. ↑ Lee, DC, among others (1997), "Age and origin of the Moon", Science, 278 (5340): 1098–103
  11. ↑ Allègre, Claude J. among others (1995), "The age of the Earth", Geochimica et Cosmochimica Acta, 59: 1445–1456, doi:10.1016/0016-7037(95)00054-4
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