
AsianScientist (Jul. 21, 2016) – Every now and then in Earth’s history, a pair of continents draws close enough to form one. But there comes a time when they must inevitably part ways.
Scientists at Australia’s EarthByte research group, in collaboration with researchers in Germany, have revealed the underlying mechanics of a continental breakup when this time arrives in a supercontinent’s life cycle. The findings are published in Nature.
With the help of seismic data and sophisticated computer simulations, the team from the University of Sydney in Australia and the University of Potsdam in Germany uncovered a distinct two-phase separation process: at first, continents gradually inch apart as a hot, jagged rift is etched into the landscape.
Then, after many millions of years of strained, relentless pulling of the Earth’s crust, the continents lurch away from each other, beginning their steady march towards separate sides of the globe as a new ocean forms between them.
Co-author Professor Dietmar Müller from the University of Sydney School of Geosciences said that because the plates sit on very viscous mantle, they tend shift around quite slowly. But there have been plenty of instances where plates have suddenly sped up during the breakup. This bizarre behavior has puzzled researchers for decades, as it does not quite fit into current understanding of what drives plate motion.
Müller compared the mechanism to pulling apart a thick piece of dough. At first, separating the dough requires a lot of effort as the dough resists your actions.
“If you’re persistent, you’ll eventually reach a point where the dough becomes thin enough to separate quite easily and quickly. The same principle applies to rifting continents once the connection between them has been thinned sufficiently,” Müller said.
Lead author Dr. Sascha Brune, from the University of Potsdam, said the split does not tend to end amicably.
“This breakup process leads to margin segmentation, where rapid subsidence, high heat flow, and enhanced volcanism characterize the outer margin,” said Brune.
The result is a full-margin rupture that sends the outer rims of the continents plunging into the sea.
“The Earth’s submerged continental shelves play an indelible role in biogeochemical cycles such as carbon burial and nutrient cycling,” added Brune.
“They are also favorable environments for cultivating and preserving the energy resources upon which our modern society still relies; for instance, natural gas.”
The article can be found at: Brune et al. (2016) Abrupt Plate Accelerations Shape Rifted Continental Margins.
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Source: University of Sydney; Photo: Sascha Brune.
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