High plateaus rise in the interior of continents thanks to flooding deep within the Earth hundreds of miles from where they eventually emerge, a new study suggests.
As continents break apart, massive walls of rock can rise near the boundaries where the crust is breaking apart. This separation causes a wave within The middle layer of the Earthmantle, slowly rolling inward over tens of millions of years, driving uplift of the plateaus, the new study found.
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Scientists have long known that continental rifting caused the rise of massive escarpments, like walls of rock that separate Rift Valley of East Africa from the Ethiopian plateau, the lead author said Thomas Gernona geoscientist at the University of Southampton in the UK And these craggy rocks sometimes wrap the interior plateaus that rise from the hard, stable cores of the continents, known as cratons.
But because these two landscape features typically form tens of millions to 100 million years apart, many scientists thought the different formations were driven by different processes, Gernon told Live Science in an email.
In the new study, published August 7 in the journal NatureGernon and colleagues studied three iconic coastal escarpments that formed during Earth’s last breakup supercontinent, Gondwana. One, along the coast of India, traverses the Western Ghats for about 1,200 miles (2,000 kilometers); another, in Brazil, encircles the Highland plateau for about 1,900 miles (3,000 km); and South Africa’s Great Escarpment surrounds the Central Plateau and spans a 3,700-mile (6,000 km), according to the study. Interior plateaus in these regions can rise a kilometer or more, Gernon said.
The team used topographic maps to show the escarpments aligned with continental margins, suggesting that the rift created them. Computer simulations showed that continental rifts disturb the mantle, causing deep waves that roll inward toward the heart of the continent.
Next, they analyzed existing mineral records to show that uplift and erosion on the plateau migrated inland at roughly the same time and speed as the mantle wave erupted miles below. This indicated that the two landscape features were caused by the same continental breakup process.
In the case of the three landslides in the current study, the flooding was very slow, advancing at only 9 to 12 miles (15 to 20 km) every million years, the study found. However, this slow-moving mantle wave dramatically reshaped the landscape. As it marched inland, it gradually developed the strong roots that anchor the continents at the crust-mantle boundary. Without these anchors, the cratons became more buoyant and therefore uplifted.
Wind and rain over the ages then reduced them further, making them lighter and more vivid. This process culminated in the stable, high plateaus we see today.
In theory, the same process could explain other escarpment/plateau regions, such as one in North and South Carolina or one in southern Cameroon, Gernon said. The cliffs and plateaus in the Carolinas are less dramatic than the three studied in the paper, likely because they formed up to 100 million years earlier than the three Gernon’s team examined. This gave erosion tens of millions of years to erase the traces of mantle flow and uplift.
“Gases from much earlier fission events are unlikely to be preserved in the geologic record,” Gernon said.
The same supercontinent breakup and mantle surge is a catalyst for other geological processes, including the explosion of diamonds from the center of the EarthGernon’s team previously found.
“It’s fascinating to think that a diamond worn in an engagement ring could be just one of the results of the same geologic processes that form some of the most dramatic landforms on Earth,” Gernon said.