Had the ancient supercontinent Gondwana broken up differently, the shape of the African and South American continents would have been remarkably different, with a vast ocean cutting through today's Sahara desert, according to research from the University of Sydney and the GFZ German Research Centre for Geosciences.
Before Gondwana broke up about 130 million years ago, the enormous landmass comprised what is today Africa, South America, Antarctica and Australia.
Writing in the journal Geology, the team of researchers report that they used sophisticated plate tectonic and 3D numerical modeling to investigate the reasons why Gondwana broke-up the way it did.
The causes for the Gondwanan break-up are still debated, but there is consensus that the first phase of the split occurred along the East Africa coast, which split into two parts before the separation of South America from Africa took place.
The way the continental margins are shaped today provide insight into how South America and Africa were shaped by the break-up of the supercontinent.
The research team, which included geoscientists Christian Heine of University of Sydney and Sascha Brune of GFZ, investigated why the South Atlantic part of the giant rift system evolved into an ocean basin but the northern part along the West African rift became stuck.
"Extension along the so-called South Atlantic and West African rift systems was about to split the African-South American part of Gondwana North-South into nearly equal halves, generating a South Atlantic and a Saharan Atlantic Ocean," Brune said in a statement.
"In a dramatic plate tectonic twist, however, a competing rift along the present-day Equatorial Atlantic margins, won over the West African rift, causing it to become extinct, avoiding the break-up of the African continent and the formation of a Saharan Atlantic ocean," he said.
According to the researchers, the reason for this is all in the numbers.
"The larger the angle between rift trend and extensional direction, the more force is required to maintain a rift system. The West African rift featured a nearly orthogonal orientation with respect to westward extension which required distinctly more force than its ultimately successful Equatorial Atlantic opponent," they said in a statement.
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