The Smile of the Cheshire Cat

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Science  27 Jul 2001:
Vol. 293, Issue 5530, pp. 619-620
DOI: 10.1126/science.1063288

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Little is known about geological processes on Earth during the Hadean, over 4000 million years ago. In his Perspective, Kramers discusses evidence for crust formation during this early period. The new calibration of the lutetium-176 decay constant reported by Scherer et al. necessitates a new interpretation of existing data. It appears that continental crust existed as long as 4400 million years ago but that it was rare.