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English: The Archean (also spelled Archaean, formerly called the Archaeozoic, also spelled Archeozoic) is a geologic eon before the Proterozoic, ending 2500 Ma (million years 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 3800 Ma at the end of the Hadean eon.
This category has the following 5 subcategories, out of 5 total.
Media in category "Archean"
The following 16 files are in this category, out of 16 total.
- Ancient rocks mix.jpg 715 KB