Scientists solve mystery of some of Earth’s most dramatic landscapes

Results showed that when continents split, the stretching of the continental crust causes stirring in the Earth’s mantle

Asatellite image of the Great Escarpment in southern Africa from the Sentinel Hub Earth Observation Browser (Prof Tom Gernon/University of Southampton/PA Wire)

Scientists have solved one of Earth’s mysteries of how continents rose more than 1km and created some of the world’s most dramatic landscapes.

Experts have found that powerful waves deep within the Earth triggered when tectonic plates broke apart have caused continents to force the land up, creating giant plateaus.

The team, led by the researchers at the University of Southampton, say their findings have solved the “long-standing mystery” of how some of the most dramatic landforms came into being.

Tom Gernon, professor of earth science at the University of Southampton and lead author of the study, said: “Scientists have long suspected that steep kilometre-high topographic features called great escarpments — like the classic example encircling South Africa — are formed when continents rift and eventually split apart.

“However, explaining why the inner parts of continents, far from such escarpments, rise and become eroded has proven much more challenging.”

Asatellite image of the Great Escarpment in southern Africa from the Sentinel Hub Earth Observation Browser (Prof Tom Gernon/University of Southampton/PA Wire)

The team, which includes scientists from the Helmholtz Centre Potsdam – GFZ German Research Centre for Geosciences and the University of Birmingham say their results help explain why parts of continents previously thought of as “stable” experienced substantial uplift and erosion.

They say it also explains how such processes can migrate hundreds or even thousands of kilometres inland, forming sweeping elevated regions known as plateaus, like the Central Plateau of South Africa.

Their results showed that when continents split apart, the stretching of the continental crust causes stirring movements in the Earth’s mantle – the layer between the crust and the core.

Professor Sascha Brune, who leads the geodynamic modelling section at GFZ Potsdam, said: “This process can be compared to a sweeping motion that moves towards the continents and disturbs their deep foundations.”

The Lesotho Highlands in southern Africa, on the Central Plateau of the Great Escarpment. (Prof Tom Gernon/University of Southampton/PA Wire)

A University of Southampton spokesman said: “The scientists pieced together evidence to propose that the Great Escarpments originate at the edges of ancient rift valleys, much like the steep walls seen at the margins of the East African Rift today.

“Meanwhile, the rifting event also sets about a ‘deep mantle wave’ that travels along the continent’s base at about 15-20 kilometres per million years.”

Dr Steve Jones, associate professor in earth systems at the University of Birmingham, added: “What we have here is a compelling argument that rifting can, in certain circumstances, directly generate long-lived continental scale upper mantle convection cells, and these rift-initiated convective systems have a profound effect on Earth’s surface topography, erosion, sedimentation and the distribution of natural resources.”

In the study, published in the journal Nature, the team suggest that the disturbance of the continents would also have affected the climate.

Prof Gernon said: “Destabilising the cores of the continents must have impacted ancient climates too.”