Chaotian (geology)

The Chaotian is an unofficial eon or era on the Geologic time scale, first proposed in 2010, and named after Chaos, the primeval void, in Greek mythology. This proposed geological time period was defined to begin at the point when the nebula from which the solar system formed became a closed system, and to end at the time of the hypothetical impact of Theia with the early Earth. [1] An alternative proposal treats it, instead, as the earliest era within the Hadean eon, in which case it is instead considered to end at the date of the oldest preserved rocks on Earth (approximately 4.4 Ga).[2]

Chaotian Eon/Era
4700–4600 million years ago
-4500 —
–
-4000 —
–
-3500 —
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-3000 —
–
-2500 —
–
-2000 —
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-1500 —
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-1000 —
–
-500 —
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0 —

Origins

This geological era designation was proposed by scientists at the Ames Research Center in 2010 to formalize terminology in the earliest stages of Earth's history.[1] This proposal divides the Chaotian into the Eochaotian (4.7–4.65 Gya) and Neochaotian (4,650–4,600 Mya) eras. The Eochaotian is proposed to be divided into the Nephelean (4.7–4.68 Gya) and Erebrean (4,680–4,650 Mya) periods, and the Neochaotian into the Hyperitian (4,650–4,620 Mya) and Titanomachean (4,620–4,600 Mya).[1] As of May 2017, this has not been adopted by the IUGS.

Age of the Earth

Zircon is the oldest conservation-capable mineral found, with the oldest from the Yilgarn Craton dating to 4,404 Mya (± 8 Mya).[3] This gives the oldest age possible for the Earth's solid crust.

However, the exact age of our solar system—and thus the age of the Earth—is still an ongoing question. Outgassing and differentiation of the earth in an iron-rich core and mantle may have been completed 4,450 Mya.[4] The giant impact hypothesis' proposed collision with Theia, leading to the formation of the Moon, is estimated to have occurred 4,527 Mya.[5] Calcium-aluminium-rich inclusions (CAI), the first condensate from the planetary orbit, were dated to 4,567.30 Mya (± 0.16 Mya) by the uranium-lead method.[6] In 1979, dating of the Mundrabilla iron meteorite of Western Australia using the argon method determined an age of 4,570 Mya (± 60 Mya).[7] Manganese-chromium dating of chondrules revealed an age of 4,571 Mya.[8]

Due to the uncertainty of the lower limit of Earth's age, 4,600 Mya is used as the estimated lowest limit of geological time.

References
  1. Goldblatt, C.; Zahnle, K.J.; Sleep, N.H.; Nisbet, E.G. (2 February 2010). "The Eons of Chaos and Hades". Solid Earth. 1 (1): 1–3. Bibcode:2010SolE....1....1G. doi:10.5194/se-1-1-2010.
  2. Gradstein, F.M.; Ogg, J.G.; Schmitz, Mark; Ogg, Gabi (2012). The Geologic Time Scale 2012. Oxford: Elsevier. pp. 360–364. ISBN 0444594485.
  3. Wilde, SA; Valley, John W.; Peck, William H.; Graham, Colin M. (11 January 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. Bibcode:2001Natur.409..175W. doi:10.1038/35051550. PMID 11196637.
  4. Allègre, Claude J.; Manhès, Gérard; Göpel, Christa (April 1995). "The age of the Earth". Geochimica et Cosmochimica Acta. 59 (8): 1445–1456. Bibcode:1995GeCoA..59.1445A. doi:10.1016/0016-7037(95)00054-4.
  5. Lee, Der-Chuen; Halliday, Alex N.; Snyder, Gregory A.; Taylor, Lawrence A. (1997). "Age and origin of the Moon". Science. 278 (5340): 1098–1103. doi:10.1126/science.278.5340.1098.
  6. Connelly, James N.; Bizzarro, Martin; Krot, Alexander N.; Nordlund, Åke; Wielandt, Daniel; Ivanova, Marina A. (2012). "The Absolute Chronology and thermal Processing of solids in the solar Protoplanetary Disk". Science. 338 (6107): 651–655. Bibcode:2012Sci...338..651C. doi:10.1126/science.1226919. PMID 23118187.
  7. Niemeyer, Sidney (1979). "40Ar–39Ar dating of inclusions from IAB iron meteorites". Geochimica et Cosmochimica Acta. 43: 1829–1840. doi:10.1016/0016-7037(79)90031-0.
  8. Shukolyukov, A.; Lugmair, G.W. (2002). "Chronology of Asteroid Accretion and Differentiation". In Bottke, W.; Cellino, A.; Paolicchi, P.; Binzel, R. (eds.). Asteroids III. University of Arizona Press. pp. 687–695. ISBN 0-8165-2281-2.
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