September 16, 2013
New Research Into How Continents Formed
Lee Rannals for redOrbit.com – Your Universe Online
Scientists writing in the journal Nature Geoscience say they've unveiled more clues about how continents formed early in the Earth's history.
The latest research provides strong evidence against continent formation above a hot mantle plume. Instead, the analysis indicates that the nuclei of Earth's continents formed as a byproduct of the mountain-building processes, by stacking up slabs of relatively cold oceanic crust.
Researchers performed computer simulations that showed the slow, diffusive cooling of Earth's mantle over a time span of billions of years. The results showed a process that created thick "keels" in the Earth's mantle that supported the overlying crust and enabled continents to form.
"For the first time, we are able to quantify the thermal evolution of a realistic 3D Earth model spanning billions of years from the time continents were formed," Claire Perry, an assistant professor from the Universite du Quebec a Montreal, said in a statement.
Mantle plumes consist of an upwelling of hot material within Earth's mantle, similar to what is witnessed around the Hawaiian Islands. Diamonds have provided a wealth of information on how the host mantle region may have formed because they are generally limited to the deepest and oldest parts of the continental mantle. Scientists say that impurities in diamonds can be the perfect time capsules to look back at the time when continents began drifting apart.
"Ancient mantle keels are relatively strong, cold and sometimes diamond-bearing material. They are known to extend to depths of 200 kilometers (124 miles) or more beneath the ancient core regions of continents," David Eaton, professor in the University of Calgary's Department of Geoscience, said in a statement. "These mantle keels resisted tectonic recycling into the deep mantle, allowing the preservation of continents over geological time and providing suitable environments for the development of the terrestrial biosphere."
The researchers' method looks at important factors like dwindling contribution of natural radioactivity to the heat budget. It also allows for the calculation of other properties that influence mantle evolution, such as bulk density and mechanical strength.
"Our computer model emerged from a multi-disciplinary approach combining classical physics, mathematics and computer science," explains Eaton. "By combining those disciplines, we were able to tackle a fundamental geoscientific problem, which may open new doors for future research."