The Hadean ( /ˈheɪdiən/) is a geologic eon of the Earth pre-dating the Archean. It began with the formation of the Earth about 4.6 billion years ago and ended, as defined by the ICS, 4 billion years ago. As of 2016[update], the ICS describes its status as "informal". Geologist Preston Cloud coined the term in 1972, originally to label the period before the earliest-known rocks on Earth. W. Brian Harland later coined an almost synonymous term, the "Priscoan period", from priscus, the Latin word for "ancient". Other, older texts refer to the eon as the Pre-Archean.
This table shows the example usage of word lists for keywords extraction from the text above.
|Word||Word Frequency||Number of Articles||Relevance|