Deep within our planet’s continents rise plateaus that defy simple explanation. No volcano, no continental collision, no plume of molten rock can clearly explain their location and dramatic features.

Researchers from the UK and Germany have proposed a radical new idea, using statistical analysis and simulations based on geological studies, arguing that slow-moving instabilities caused by faults in the Earth’s ruptured crust are behind the strange anomalies.

From the highlands of Brazil to the Great Rockies of South Africa and the Western Ghats of India, our planet is dotted with vast plateaus surrounded by steep walls that dominate the landscape.

These formidable plateaus lie hundreds of miles from the nearest fault, on areas of crust considered geologically stable, formed tens of millions of years after the forces pushing on the nearest continental veins had subsided, making it difficult to pin the blame squarely on Earth’s tectonic movements.

“Scientists have long suspected that the steep, kilometre-long topographic features called Great Rifts, of which the classic example is the one surrounding South Africa, were formed by continents pulling apart and eventually breaking apart,” says geologist Tom Gernon of the University of Southampton.

“But it turned out to be much harder to explain why the interiors of the continents, away from such prominences, were uplifted and eroded. Is this process linked to the formation of these raised prominences? Simply put, we didn’t know.”

Although there is a complex combination of geological forces that link the growth of these cliffs to the rupture of the Earth’s mantle, no theory can accurately explain all of their features.

Some suggest that weathering of rocks far below freed the Earth’s crust of mass, allowing it to form into the desired shape. Others suggest that sudden temperature changes caused convection in the mantle, pushing rocks upward, or that instead erosion and weathering further eroded the coastal landscape.

This new hypothesis connects the processes with the slow mixing of the mantle beneath the crust, which rotates at only 15-20 kilometers (about 9-12 miles) every million years.

Building on previous research into the processes that bring diamonds to the planet’s surface, the team found that stretching the crust as the plates move apart creates instability in the mantle, which vibrates beneath the solid lithosphere.

The team’s modelling showed that the speed of the waves following the break-up of Gondwana mirrored the timing of erosion around the Great Southern African Escarpment. It is believed that this slow echo of molten rock could have eroded the ancient roots of the continents, known as cratons.

“Just as a balloon loses weight to rise higher, this loss of continental material causes the continents to rise, a process called isostasy,” Bruen says.

Loss of material from the craton below and erosion of weathered rocks at the surface can together explain the sharp rise of the flattened terrain, and the team’s models accurately describe the combination of plateaus and steep slopes found across the globe.

Understanding the dynamics of processes hidden far below the surface can not only help us accurately map changes in the landscape responsible for the formation of minerals and valuable resources, but can also help us better interpret historical climate changes associated with the rise and fall of continents.

“The destabilization of the continental core must have also affected the ancient climate,” Gernon concludes. This research was published in the journal Nature.