Giant waves in Earth's mantle may cause continents to rise: study finds

A new study indicates that large waves in Earth's mantle may be causing continents to rise. Scientists say high plateaus rise in the interior of continents due to drilling deep inside the planet hundreds of miles from where they originate.

When continents break up, massive walls of rock can rise at the boundaries where the crust breaks apart. The study confirmed that this breakup causes a wave in Earth's mantle that slowly rolls inward over tens of millions of years, fueling plateau rise, LiveScience writes.

The study's lead author, Thomas Gernon, a scientist at the University of Southampton in the United Kingdom, said scientists have long known that continental cracks entail the growth of massive scarps, such as the walls of rock that, for example, separate the East African Rift Valley from the Ethiopian Plateau. And these steep cliffs sometimes wrap around inner plateaus rising from the powerful, stable cores of continents known as cratons.

But because these two landscape features typically form tens of millions to a hundred million years apart, many scientists thought the different formations were caused by different processes.

In the new study, however, Thomas Gernon and his colleagues examined three iconic coastal escarpments that formed during the breakup of Gondwana, Earth's last supercontinent. One, along the coast of India, wraps around the Western Ghats for about 2,000 kilometers. The second, in Brazil, encircles the Highland Plateau for about 3,000 kilometers. And the third, the great gradient of South Africa surrounds the Central Plateau and covers 6,000 kilometers. The researchers emphasized that the inner plateaus in these regions can rise by a kilometer or more.

The team used topographic maps to show scarps aligned with continental margins, indicating that a rift created them. Computer modeling showed that continental rifts disrupt the mantle, causing deep waves to roll inward toward the heart of the continent.

The scientists then analyzed the available mineral data to show that plateau uplift and erosion migrated inland at about the same time and at the same rate as the mantle wave that rolled many kilometers below. This showed that these two landscape features were likely caused by the same process of continental breakup.

In the case of the three scarps considered in this study, the landslide was very slow, advancing only 15-20 kilometers every million years. However, this non-fast mantle wave dramatically changed the landscape. Moving inward, it gradually peeled away the strong roots anchoring the continents at the crust-mantle boundary. Without these anchors, the cratons became more buoyant and therefore rose.

According to Thomas Gernon, this supercontinent breakup and mantle wave is the catalyst for other geological processes, such as the eruption of diamonds from the center of the Earth.

"The notion that the diamond you wear on your engagement ring may be just one result of the same geological processes that form some of the most dramatic landforms on Earth is striking," Gernon added.

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