The reason you are sitting where you are right now may be because Pangaea, the most recent supercontinent to gather together all the world鈥檚 landmasses together, ate itself nearly 300 million years ago.
Convection in the Earth鈥檚 mantle shifts the floating continental plates around, eventually driving them together into supercontinents every few hundred million years. We know supercontinents eventually break up again, but it is not clear how they do this.
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of the University of Salamanca in Spain and colleagues think they may be able to explain the most recent break up which split Pangaea into today鈥檚 continents. They have proposed a mechanism called 鈥溾��, which would explain several geological mysteries better than prior theories.
In standard subduction, one tectonic plate slips under another. The situation could have been slightly different 300 million years ago because Pangaea was shaped like a pie with one piece missing. This area was occupied by an ocean called Paleo-Tethys.
Who ate all the pies?
The new theory has it that, as Pangaea鈥檚 southern coast moved northward, the ocean began to close up. Eventually, the continent鈥檚 southern continental shelf was subducted beneath the northern coast.
鈥淚t鈥檚 like a cat trying to bite its own tail,鈥� says Fernando Corf煤, a geologist at the , and one of Guti茅rrez-Alonso鈥檚 collaborators.
The theory predicts that the land in Pangaea鈥檚 centre would have compressed, explaining the Iberian-Armorican Arc, a twisted mountain range that is known to have stretched from modern-day Turkey up to the UK and then down to Spain.
Meanwhile, the rest of the pie would have stretched to breaking point, allowing surrounding oceanic plates to move into the gaps. This explains why a number of ancient rifts, including ones that can be visited today in Norway and Madagascar, were once arranged radially like the spokes of a bicycle.
Journal reference: , DOI: 10.1038/ngeo250
