The Geologic Time Scale (inside front cover of your book)

With geologic time, we use eons, eras, periods, and epochs. The largest unit of geologic time is an . eon. The four eons are the Hadean, Archean, Proterozoic, and the Phanerozoic. The first three eons are grouped together as . Precambrian Time. While the Precambrian spans . four. billion years, very few . ................
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