Archaean

• Archean
• Archæan (archaic)

From Ancient Greek ἀρχαῖα (arkhaîa, “ancient”), neuter plural of ἀρχαῖος (arkhaîos, “ancient”).

• (Received Pronunciation) IPA^(key): /ɑːˈkiːən/

• Audio (Southern England)

  (file)

• (General American) IPA^(key): /ɑɹˈkiːən/
• Rhymes: -iən

Archaean (not comparable)

1. (geology) Of, or relating to the geologic eon from about 3,800 to 2,500 million years ago; comprises the Eoarchean, Paleoarchean, Mesoarchean and Neoarchean eras; marked by an atmosphere with little oxygen, the formation of the first continents and oceans and the emergence of simple life.
   • 2006 March 25, NewScientist, page 12/1:

     The oldest vestiges of continental crust, which date from the Archaean aeon about 4 billion years ago, are in Acasta in north-west Canada.

Archaean

1. (geology) The eon from 2,500 Ma to 4,000 Ma.

• (eon 2,500–4,000 Ma): Precambrian

• (eon 2,500–4,000 Ma): Eoarchaean, Paleoarchaean, Mesoarchaean, Neoarchaean

• (eon 2,500–4,000 Ma): Hadean, Proterozoic - eons in Precambrian

• Appendix:Geologic timescale

• Archaean on Wikipedia.Wikipedia