Eoarchean

Eoarchean
Eoarchean
Chronology
−4000 — – −3950 — – −3900 — – −3850 — – −3800 — – −3750 — – −3700 — – −3650 — – −3600 — –	Hadean A ; r ; c ; h ; e ; a ; n Eoarchean Paleoarchean
	Events of the Eoarchean. ; Axis scale: millions of years ago.;
Etymology
Name formality	Formal
Alternate spelling(s)	Eoarchaean
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Era
Stratigraphic unit	Erathem
Time span formality	Formal
Lower boundary definition	Defined Chronometrically
Lower GSSA ratified	1991[citation needed]
Upper boundary definition	Defined Chronometrically
Upper GSSA ratified	1991[citation needed]

The Eoarchean (IPA: /ˌiːoʊ.ɑːrˈkiːən/ EE-oh-ar-KEE-ən; also spelled Eoarchaean) is the first era of the Archean Eon of the geologic record. It spans 400 million years, from the end of the Hadean Eon 4 billion years ago (4000 Mya) to the start of the Paleoarchean Era 3600 Mya. The beginnings of life on Earth have been dated to this era and evidence of archaea and cyanobacteria date to 3500 Mya, comparatively shortly after the Eoarchean. At that time, the atmosphere was without oxygen and the pressure values ranged from 10 to 100 bar (around 10 to 100 times the atmospheric pressure today).^[1]^[2]^[3]

^ Mulkidjanian, Armen Y. (August 2009). "On the origin of life in the zinc world: 1. Photosynthesizing, porous edifices built of hydrothermally precipitated zinc sulfide as cradles of life on Earth". Biol. Direct. 4: 26–. doi:10.1186/1745-6150-4-26. PMC 3152778. PMID 19703272.
^ Mulkidjanian, A. Y.; Bychkov, A. Y.; Dibrova, D. V.; Galperin, M. Y.; Koonin, E. V. (2012). "Origin of first cells at terrestrial, anoxic geothermal fields". Proc. Natl. Acad. Sci. USA. 109 (14): E821–30. Bibcode:2012PNAS..109E.821M. doi:10.1073/pnas.1117774109. PMC 3325685. PMID 22331915.
^ Mulkidjanian, A. Y. (2011). "Energetics of the First Life". In Egel, R.; Lankenau, D.-H.; Mulkidjanian, A. Y. (eds.). Origins of Life: The Primal Self-Organization. Heidelberg: Springer Verlag. pp. 3–33. ISBN 978-3-642-21625-1.

[1] Mulkidjanian, Armen Y. (August 2009). "On the origin of life in the zinc world: 1. Photosynthesizing, porous edifices built of hydrothermally precipitated zinc sulfide as cradles of life on Earth". Biol. Direct. 4: 26–. doi:10.1186/1745-6150-4-26. PMC 3152778. PMID 19703272.

[2] Mulkidjanian, A. Y.; Bychkov, A. Y.; Dibrova, D. V.; Galperin, M. Y.; Koonin, E. V. (2012). "Origin of first cells at terrestrial, anoxic geothermal fields". Proc. Natl. Acad. Sci. USA. 109 (14): E821–30. Bibcode:2012PNAS..109E.821M. doi:10.1073/pnas.1117774109. PMC 3325685. PMID 22331915.

[3] Mulkidjanian, A. Y. (2011). "Energetics of the First Life". In Egel, R.; Lankenau, D.-H.; Mulkidjanian, A. Y. (eds.). Origins of Life: The Primal Self-Organization. Heidelberg: Springer Verlag. pp. 3–33. ISBN 978-3-642-21625-1.

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