1. Hadean; Hadean eonGeology, etc. term
Wikipedia definition
2. HadeanThe Hadean is the unofficial geologic eon that lies before the Archean. It began with the formation of the Earth about 4.5 Ga (billion years ago) and ended roughly 3.8 Ga, though the latter date varies according to different sources. The name "Hadean" derives from Hades, Greek for "Underworld", referring to the "hellish" conditions on Earth at the time. The geologist Preston Cloud coined the term in 1972, originally to label the period before the earliest-known rocks on Earth. W.
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