Massive And Slow-Moving Waves Within Earth’s Mantle Cause The Rise Of High Plateaus In The Interior Of Continents Over Tens Of Millions Of Years
Deep within the Earth, massive, slow-moving waves in the mantle have been discovered to cause the rise of high plateaus in the interior of continents.
The waves are triggered by continents breaking up. Over tens of millions of years, the waves roll inward slowly, which leads to the formation of new plateaus and tall cliff walls near the boundaries where the crust has pulled apart.
For a while, scientists have been aware that continental rifts cause the rise of steep slopes and cliffs, such as the cliff walls that divide the East African Rift Valley and the Ethiopian plateau, according to Thomas Gernon, the lead author of the study and a geoscientist at the University of Southampton in the U.K.
Sometimes, these cliffs surround plateaus, but since the two landscape features typically form millions of years apart, many experts thought that they were created by different processes. It turns out that cliff walls and plateaus are produced by the same underground activity.
In the new study, Gernon and colleagues examined three coastal escarpments that were formed during the separation of Gondwana, Earth’s last supercontinent. One of them runs along the Western Ghats on the coast of India for about 1,200 miles.
Another encircles the Highland Plateau in Brazil for approximately 1,900 miles, and the third is the Great Escarpment of South Africa, which borders the Central Plateau and spans 3,700 miles.
The team employed topographic maps to illustrate how the escarpments lined up with the continental boundaries, which suggests that they were created by rifting.
Computer simulations demonstrated that the continental rifts disturbed the Earth’s mantle, setting off deep, gigantic waves that rolled toward the heart of the continent.
Next, they analyzed mineral data to show that the elevation and erosion on the plateau moved inland around the same time and speed as the mantle waves that were occurring miles beneath the Earth. This indicates that steep cliffs and plateaus were likely created by the same continental splits.
dimazel – stock.adobe.com – illustrative purposes only
For the three escarpments in the study, the waves moved extremely slowly at just nine to 12 miles every million years.
Yet, they still reshaped the landscape in dramatic ways. As the waves inched inward, they stripped the continents of their anchors at the crust-mantle boundary.
Without the anchors, the land rose. Over time, wind and rain weathered the anchors down even more, resulting in the high, stable plateaus we see today.
The study suggests that similar processes might explain other geological features in regions around the world, such as the cliffs and plateaus in North and South Carolina.
They are less pronounced than the three that were evaluated in the paper, probably because they developed up to 100 million years earlier. So, erosion had plenty of time to erase all mantle activity.
The paper was published in the journal Nature.
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