What if the Atlantic and the Pacific would close together to form a new supercontinent?
This is a new hypothesis published this month in the journal Geological Magazine by researchers from Instituto Dom Luiz-FCUL, VU-Amsterdam and Monash University.
To understand the implications of this new idea we have to go back to a time when the dinosaurs where ruling the planet. Two hundred million years ago all continents were gathered in one colossal supercontinent known as Pangaea. But Pangaea was not the only supercontinent that existed on Earth. During the planet’s history the continents seem to have gathered together and split in a recurring cycle known as the supercontinental cycle, with each cycle lasting about half a billion years.
And in the future, how will the next supercontinent form? Which of the major oceans will be the next to close?
Some scientists think that the Atlantic will soon start to close to reunite Pangaea in approximately 200 million years. This scenario is known as introversion. Other researchers have suggested that the continents once gathered around Pangaea will travel all the way across the globe and collide at the Pangaea’s antipode, therefore closing the Pacific Ocean. This scenario is called extroversion and would result in the Atlantic being the major ocean of the future. There is still a third scenario that proposes that the continents will gather at the North Pole, preserving both the Atlantic and the Pacific. This scenario is called orthoversion.
All this scenarios have a problem. They leave behind oceanic crust with far more than 500 millions years, and scientists know today that oceanic plates with this age may be unstable. This is because as oceanic plates age they become very dense and want to sink into the Earth’s mantle. This contradiction is also supported by the observation that oceanic plates older than 200 million years are practically inexistent on Earth, suggesting that oceans must start to close soon after 100 to 200 million years after their birth.
This reasoning leads us to an apparent paradox. The Pacific is already closing. But the Atlantic should start closing soon! So which of these major oceans will win? The Atlantic? The Pacific? Is there another alternative scenario that does not lead us to a paradox? “Yes, there is!” This is exactly what this group of researchers say! In this work totally new scenario is presented in which the Atlantic and the Pacific close simultaneously to form a new supercontinent that the researchers named Aurica.
This hypothesis is supported by the evidence that new subduction zones are propagating across the Atlantic, a requirement for oceans to close. There are already two fully developed subduction zones in the Atlantic: in the Scotia arc and in the Lesser Antilles arc; and another totally new subduction system may just be forming offshore SW Iberia. Giant quakes such as the 1755 Great Lisbon Earthquake may be the signal that major tectonic activity is ongoing in the area. This new hypothesis allows reconciling some of the long-lasting conundrums of plate tectonics, in particular why there seems to be an upper limit for the age of the oceanic crust. These news results have also the potential to be tested using the new generation of computational geodynamic models.
Link to the article here.