Au Revoir Atlantic, Hello Aurica
The study “The future of Earth’s oceans: consequences of subduction initiation in the Atlantic and implications for supercontinent formation” by João Duarte et al., recently published in Geological Magazine, presents their dramatic prediction for how the Earth may look in 250 million years from now as Supercontinent Aurica.
The formation of a supercontinent—when most continental land masses are joined together as a continuous land mass—is not an entirely new prospect in terms of Earth history. Perhaps most famously, Alfred Wegener, the “father of continental drift”, first articulated the concept of a supercontinent in 1915. This was Pangaea, the Paleozoic result of the slow but inevitable collision of Gondwana and Laurasia some 330 million years ago. But Pangaea was neither the first nor last supercontinent assembled and later torn apart on our planet. Several earlier supercontinents periodically dominated after 1.2 billion years ago and even as far back as 2 billion years ago, fundamentally altering our planet’s climatic belts, oceanographic circulation, and biological evolution for often hundreds of millions of years.
Supercontinents are built from the destruction of ocean basins. In the case of the Atlantic Ocean that is flanked by relatively stable passive margins, initiating subduction along these margins can be a tricky thing. Without a strong external “push” like a mantle plume, old, strong, stiff, and still buoyant lithosphere found at passive margins does not easily allow ‘spontaneous’ subduction initiation. Instead, the authors suggest “subduction zones may actually be more likely to nucleate in juvenile to middle aged lithosphere…rather than in locations with very old oceanic lithosphere”.
The key perturbation leading to the ‘irreversible’ demise of the Atlantic is argued to be the lateral invasion of Atlantic passive margins by active trenches already flanking the basin. The Lesser Antilles arc, Gibraltar arc, and Scotia arc are these key trenches ready to swallow up Atlantic oceanic lithosphere, with some already showing signs of invasion during the Cenozoic. “Together, these three arcs, are likely the precursor of a large-scale Atlantic subduction system that may ultimately lead to its closing…and to the formation of a new supercontinent.”
Yet Duarte et al. assert that not only must we say goodbye to the Atlantic Ocean but the Pacific Ocean is not long for this world—well, geologically speaking, that is—either. One of the authors’ model predicts that present-day Eurasia will split apart, rifting and opening up through the Himalaya and Tibetan Plateau. This inevitably allows one half of rifted Eurasia to nestle into eastern North America and close the Atlantic Ocean. The remaining other half docks to Australia and, with the last gasp of the Pacific Ocean, together collide with the Americas—creating Supercontinent Aurica.
This article continues the authors’ research on Atlantic subduction initiation that appeared in Geology in 2013. Senior author Duarte presented these latest results at the 2017 European Geosciences Union spring meeting that were also recently featured in an article by New Scientists.
The full article “The future of Earth’s oceans: consequences of subduction initiation in the Atlantic and implications for supercontinent formation” by João Duarte, Wouter Schellart, and Filipe Rosas is available to download free of charge for a limited time here.