A cool early Earth
- 1Department of Geology and Geophysics, University of Wisconsin, Madison, Wisconsin 53706, USA
- 2School of Applied Geology, Curtin University of Technology, GPO Box U1987, Perth, Australia
Abstract
No known rocks have survived from the first 500 m.y. of Earth history, but studies of single zircons suggest that some continental crust formed as early as 4.4 Ga, 160 m.y. after accretion of the Earth, and that surface temperatures were low enough for liquid water. Surface temperatures are inferred from high δ18O values of zircons. The range of δ18O values is constant throughout the Archean (4.4–2.6 Ga), suggesting uniformity of processes and conditions. The hypothesis of a cool early Earth suggests long intervals of relatively temperate surface conditions from 4.4 to 4.0 Ga that were conducive to liquid- water oceans and possibly life. Meteorite impacts during this period may have been less frequent than previously thought.
Footnotes
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↵GSA Data Repository item 2002034, Table DR1, Values of δ18O and U-Pb ages of zircons from Archean igneous rocks, is available from Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301-9140, editing@geosociety.org, or at www.geosociety.org/pubs/ft2002.htm.
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↵*Valley-valley{at}geology.wisc.edu. Present addresses: Peck-Department of Geology, Colgate University, Hamilton, New York 13346, USA; King-Department of Geography-Geology, Illinois State University, Normal, Illinois 61790, USA.
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- Accepted December 19, 2001.
- Received July 31, 2001.
- Revision received December 12, 2001.
- Geological Society of America
