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Tuesday, March 11, 2014

The ocean that might have been

You’re familiar with the Atlantic Ocean, but have you ever heard of the Saharan Atlantic Ocean? No? That’s because there is no Saharan Atlantic Ocean. But there might have been.

From 510 to 180 million years ago, South America and Africa were fused together in a supercontinent called Gondwana.

After that time, rifts in the Earth’s crust broke Gondwana apart, separating the Americas from Africa and resulting in the formation of the Atlantic Ocean. However, Christian Heine and Sascha Brune of the University of Sydney and the German Research Centre for Geosciences found that such an eventuality was far from certain. Instead, Africa itself could have split apart with the western half remaining attached to South America. You can see a model of what that might have looked like below.

A hypothetical model of the circum-Atlantic region at present-day, if Africa had split into two parts along the West African Rift system. Here, the north-west part of present day Africa would have moved with the South American continent, forming a "Saharan Atlantic ocean".
Credit: Sascha Brune/Christian Heine

For a while (some 20 million years), it looked like either scenario could have played out. Gondwana could have been split between Africa and South America or between Eastern and Western Africa.

Obviously, the former rift proved more powerful and the African rift was eventually abandoned. Thus we ended up with the Earth we have today.

Heine, C., & Brune, S. (2014). Oblique rifting of the Equatorial Atlantic: Why there is no Saharan Atlantic Ocean Geology, 42 (3), 211-214 DOI: 10.1130/G35082.1.