Researchers Stephan V. Sobolev of the German Research Centre for Geosciences GFZ and the University of Potsdam, and Michael Brown of the University of Maryland have found that natural lubrication caused by surface-erosion debris was responsible for kicking off and maintaining plate tectonics, a natural process that shifted the continents.
Since the 1960s, scientists have understood that plate tectonics is driven by deep-mantle convection, a thermodynamic process that stirs hot and cold matter within the Earth. Therefore, it was believed that plate tectonics was only dependent on deep-Earth processes, such as the cooling of Earth’s mantle. But Sobolev and Brown suggest that surface erosion also played a vital role in plate tectonic evolution.
“Our hypothesis is counter-intuitive,” Sobolev said. “That was the main problem for us and we expect will be the main problem for the community to accept our ideas.”
Using already-available geological and geochemical data, which showed evidence of plate tectonic movement starting about 2.5 to 3 billion years ago — the same time Earth’s continents rose above sea level, Sobolev and Brown hypothesized that the evolution of plate tectonics was controlled by the continents’ shift above sea level and the major surface erosion events that followed
These erosion processes, such as the one that followed the global “Snowball Earth” glaciations that occurred 700 to 600 million years ago, produced continental sediments that worked as lubricant for subduction, a crucial process of plate tectonics, that reduced friction between the subducting plate and overriding plate.
“We suggested our hypothesis based on global geodynamic models of plate tectonics and regional models of subduction in the South American Andes,” Sobolev explained. “Then we used published geological and geochemical data to verify the hypothesis. Only the synergetic combination of all these disciplines made this study possible.”
More geochemical data is required to effectively test their hypothesis, Sobolev and Brown note.
“It must be fully quantified, which in turn will require coupled modelling of deep mantle convection and plate tectonics, surface processes and even climate, which is an important factor controlling surface erosion. That is an exciting challenge for the Earth system modeling community,” Sobolev said. “This will require building new types of models tightly linking deep Earth and surface processes.”
The new theory is published in Nature.
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