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You had to be a good swimmer on Earth 2.5 billion years ago
William Atkins
Wednesday, 21 January 2009 21:30
Page 1 of 3
According to a mathematical model developed by French and Australian scientists, the Earth was almost completely covered with water about 2.5 billion years ago, with only about two to three percent of land sticking above the oceans. Talk about your pricey ocean-front property!Their paper “A case for late-Archaean continental emergence from thermal evolution models and hypsometry” was published on October 10, 2008, in the journal Earth and Planetary Science Letters (DOI: 10.1016/j.epsl.2008.08.029).
The French-Australian authors include Nicolas Flament and Nicolas Coltice, of the Université de Lyon, Laboratoire de Sciences de la Terre, France, and Patrice F. Rey (and Flament), of the EarthByte Group, School of Geosciences, The University of Sydney, Sydney, NSW, Australia.
The modern surface of the Earth is composed of about 28% water and 72% land. However, approximately 2.5 billion years ago, those percentages were far different.
Scientists are not sure of the exact evolution of the Earth from then and to now, but they do know that the amount of land (continental crust) increased quite drastically as the waters subsided.
They state in the abstract to their paper, “The secular cooling of the Earth's mantle and the growth of the continental crust together imply changes in the isostatic balance between continents and oceans, in the oceanic bathymetry and in the area of emerged continental crust. The evolution of these variables is of fundamental importance to the geochemical coupling of mantle, continental crust, atmosphere and ocean.”
To determine the amount of water and land on Earth several billion years ago, the team decided to develop a model that calculates the area of emerged continental crust based on the temperature of the Earth’s mantle, along with continental area and hypsometry (the study of land elevation with respect to sea level).
Page two describes their mathematical model, along with comments from the scientists.
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