The Archean ( /ɑrˈkiːən/, also spelled Archaean; formerly Archaeozoic /ɑrkiəˈzoʊɨk/), also spelled Archeozoic or Archæozoic) is a geologic eon before the Proterozoic Eon, before 2.5 Ga (billion years, or 2,500 Ma) ago. Instead of being based on stratigraphy, this date is defined chronometrically. The lower boundary (starting point) has not been officially recognized by the International Commission on Stratigraphy, but it is usually set to 3.8 Ga, at the end of the Hadean Eon. In older literature, the Hadean is included as part of the Archean. The name comes from the ancient Greek "Αρχή" (Arkhē), meaning "beginning, origin".
The Videos..
No comments:
Post a Comment