When continents formed
Scientists have developed a new way to calculate the age of the Earth’s crust, in a new report published today (Friday 14 January 2011).
The research, by experts at the Universities of St Andrews and Bristol, suggests that the continental crust is up to 300 million years younger than previously thought.
The continental crust is the principal record of conditions on Earth over the last 4.4 billion years. It supports life, is responsible for the atmosphere, and absorbs CO2 through weathering and erosion. Despite its key role in the evolution of the Earth, the timing of its formation remains a topic of considerable debate. It is hoped that the new method, developed by St Andrews’ researcher Dr Bruno Dhuime, will help aid better understanding of the Earth’s evolution.
At the moment, radiogenic isotopes are used to calculate ‘model ages’ of crust formation, which represent the time a crustal sample was separated from its mantle source. Though commonly used in crustal evolution studies for the last three decades, the method can lead to incomplete interpretations.
In a paper published by Science, Dr Dhuime (who is partly based at Bristol’s School of Earth Sciences) and colleagues describe a new methodology for the calculation of model ages, based on the isotope composition of the average new continental crust.
Dr Dhuime explained, “The concept of ‘age’ is absolutely fundamental in Earth Sciences, and any age obtained from the analysis of any rock or mineral would be useless without a proper estimate over its accuracy. Ages calculated with this new method are significantly younger than model ages previously calculated from the isotope composition of the depleted mantle.”
The postdoctoral researcher works with Professors Christopher Hawkesworth and Peter Cawood at St Andrews. Professor Hawkesworth noted, “Our principal conclusion is that ages calculated by our method are up to 300 million years younger than those calculated by the previous method. These new ages obtained are more consistent with the geological record, which opens new perspectives in crustal evolution studies based on radiogenic isotopes.”
‘When Continents Formed’ by Bruno Dhuime, Chris Hawkesworth, Peter Cawood is published by Science.
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Ref: New continents 140111
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