TheEoarchaean (Eoarchean) is the firstgeologicalera in theArchaeaneon that began 4billion years ago, and ended 3.6 billion years ago.[1] Before it was theHadean It is followed by thePalaeoarchaean.
The Eoarchaean is the earliestperiod of geology after the solidification ofEarth'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 fromc. 100 to 10 bar.[2][3][4]
It was formerly officially unnamed and usually referred to as the first part of theEarly Archaean (now an obsolete name) together with the laterPalaeoarchaean Era. It is the first part of theArchaean Eon, preceded by theHadean Eon.
The Eoarchaean was followed by the Palaeoarchaean Era.
The name comes from twoGreek words:eos (dawn) andarchaios (ancient). The 1st supercontinentVaalbara appeared around the end of this period around 3.6 billion years ago.
A characteristic of the Eoarchean is that Earth possessed a firmcrust 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: theLate Heavy Bombardment. The Eoarchaean is the first phase of our planet from which solid rock formations survived. The largest is theIsua greenstone belt at the southwest coast of Greenland. It appeared during the Eoarchaean around 3.8 billion years ago. TheAcasta Gneiss within theCanadian 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 theNuvvuagittuq greenstone belt in northernQuébec in Canada which has been dated to be 4.28 Ga.[5] These formations are presently under intense investigation.[6]
Earth's oceans formed 3.8 billion years ago.[7]
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