The Hadean is a geologic eon of the Earth predating 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.[1] The geologist Preston Cloud coined the term in 1972, originally to label the period before the earliest-known rocks on Earth.

In the last decades of the 20th century geologists identified a few Hadean rocks from Western Greenland, Northwestern Canada, and Western Australia. In 2015, traces of carbon minerals interpreted as "remains of biotic life" were found in 4.1-billion-year-old rocks in Western Australia.[2][3]

The oldest dated zircon crystals, enclosed in a metamorphosed sandstone conglomerate in the Jack Hills of the Narryer Gneiss Terrane of Western Australia, date to 4.404 ± 0.008 Ga.[4] This zircon is a slight outlier, with the oldest consistently-dated zircon falling closer to 4.35 Ga[4]—around 200 million years after the hypothesized time of the Earth's formation.


  1. "International Chronostratigraphic Chart 2015". ICS. http://www.stratigraphy.org/ICSchart/ChronostratChart2015-01.pdf. Retrieved 23 January 2016. 
  2. Borenstein, Seth (19 October 2015). "Hints of life on what was thought to be desolate early Earth". Excite. Associated Press (Yonkers, NY: Mindspark Interactive Network). http://apnews.excite.com/article/20151019/us-sci--earliest_life-a400435d0d.html. Retrieved 2015-10-20. 
  3. (19 October 2015) "Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon" (PDF). Proc. Natl. Acad. Sci. U.S.A. 112: 14518–21. DOI:10.1073/pnas.1517557112. ISSN 1091-6490. PMID 26483481. Retrieved on 2015-10-20.  Early edition, published online before print.
  4. 4.0 4.1 (2001) "Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago". Nature 409 (6817): 175–178. DOI:10.1038/35051550.