The Eoarchaean (Eoarchean) is the first geological era in the Archaean eon that began 4 billion years ago, and ended 3.6 billion years ago. Before it was the Hadean It is followed by the Palaeoarchaean.
The Eoarchaean is the earliest period of geology after the solidification of Earth's crust. The abiotic origins of life (abiogenesis) have been dated to a time window from 4 to 3.6 billion years ago when atmospheric pressure values ranged from c. 100 to 10 bar.
Chronology[change | change source]
It was formerly officially unnamed and usually referred to as the first part of the Early Archaean (now an obsolete name) together with the later Palaeoarchaean Era. It is the first part of the Archaean Eon, preceded by the Hadean Eon.
The Eoarchaean was followed by the Palaeoarchaean Era.
Geology[change | change source]
A characteristic of the Eoarchean is that Earth possessed a firm crust for the first time. However, this crust may have been incomplete at many sites and areas of lava may have existed at the surface. The beginning of the Eoarchaean is characterized by heavy asteroid bombardment within the inner solar system: the Late Heavy Bombardment. The Eoarchaean is the first phase of our planet from which solid rock formations survived. The largest is the Isua greenstone belt at the southwest coast of Greenland. It appeared during the Eoarchaean around 3.8 billion years ago. The Acasta Gneiss within the Canadian Shield have been dated to be 4.03 Ga and are therefore the oldest preserved rock formations. In 2008 another rock formation was discovered in the Nuvvuagittuq greenstone belt in northern Québec in Canada which has been dated to be 4.28 Ga. These formations are presently under intense investigation.
Earth's oceans formed 3.8 billion years ago.
References[change | change source]
- Mulkidjanian, A. Y. (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.
- Mulkidjanian, A. Y. (2012). "Origin of first cells at terrestrial, anoxic geothermal fields". Proc. Natl. Acad. Sci. USA. Bibcode:2012PNAS..109E.821M. doi:10.1073/pnas.1117774109. Unknown parameter
- Mulkidjanian, A. Y. (2011). "Energetics of the First Life". In R. Egel, D.-H. Lankenau, and A. Y. Mulkidjanian (ed.), Origins of Life: The Primal Self-Organization. Springer Verlag, Heidelberg.(book): 3–33. Italic or bold markup not allowed in:
- O'Neil, J. "Neodymium-142 Evidence for Hadean Mafic Crust". Science. 321: 1828–1831. Bibcode:2008Sci...321.1828O. doi:10.1126/science.1161925. PMID 18818357. Text "2008" ignored (help); Unknown parameter
- Jean David, Laurent Godin, Ross Stevenson, Jonathan O'Neil and Don Francis: U-Pb ages (3.8–2.7 Ga) and Nd isotope data from the newly identified Eoarchean Nuvvuagittuq supracrustal belt, Superior Craton, Canada. GSA Bulletin, Bd. 121; No. 1-2; pp. 150-163; January 2009, doi:10.1130/B26369.1
- "Why do we have oceans?". National Oceanic and Atmospheric Service. June 25, 2018. Retrieved July 16, 2020. CS1 maint: discouraged parameter (link)