Valley tagged posts

MAS March Monthly Meeting

Prof. John Valley

CANCELLED DUE TO COVID-19 PUBLIC HEALTH RECOMMENDATIONS

Analysis of terrestrial zircons yields radiometric ages nearly as old as the Earth, but these ages (4 – 4.4 billion years old) have been challenged. Questions around Uranium-Lead (U-Pb) radiometric dating geochronology have been in play for over 100 years, and were first resolved in 2014 for a 4.374 billion year old zircon. These new results based on oxygen isotopes show that most of the Hadean Eon (ca. 4 – 4.4 billion years ago) was not “hell-like” as commonly believed and implied by the name. The earliest Earth was indeed hot, violent and inhospitable, but by 4.3 billion years ago its surface had cooled and the steam atmosphere condensed to form habitable oceans...

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