Powerful waves triggered deep within Earth cause stable parts of continents rise and form expansive escarpments & plateaus
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A new study led by the University of Southampton has answered one of the most puzzling questions in plate tectonics: how and why ‘stable’ parts of continents gradually rise to form some of the planet’s greatest topographic features. The study, published in Nature, used advanced computer models and statistical methods to deduce that when tectonic plates break apart, powerful waves – triggered deep within the Earth – cause continental surfaces to rise by over a kilometre.
When continents split apart, the Earth’s continental crust stretches and causes stirring movements within the Earth’s mantle (the layer between the crust and core).
‘This process can be compared to a sweeping motion that moves towards the continents and disturbs their deep foundations,’ said leader of the Geodynamic Modelling Section at GFZ Potsdam, Professor Sascha Brune.
In simulations undertaken in the study, the speed of the mantle ‘waves’ underneath continents closely matched the speed of major erosion events that occurred in South Africa, following the splitting of the ancient supercontinent Gondwana. It is these waves that scientists believe convectively remove layers of rock from their continental roots.
‘Much like how a hot-air balloon sheds weight to rise higher, this loss of continental material causes the continents to rise – a process called isostasy,’ said Professor Brune.
The vertical motions of stable parts of continents – known as cratons – are one of the least understood aspects of plate tectonics, but with new research it is now understood why areas of continents – previously thought of as ‘stable’ – can erode and rise. Such processes can migrate thousands of kilometres inland, to form elevated regions known as plateaus – such as the Central Plateau of South Africa.
‘Our landscape evolution models show how a sequence of events linked to rifting can result in an escarpment as well as a stable, flat plateau, even though a layer of several thousands of meters of rocks has been eroded away,’ said Professor of Earth Surface Process Modelling at GFZ Potsdam, Jean Braun.
These mantle disturbances are also the same as those which trigger diamonds to rise rapidly from deep within the Earth’s interior, and can affect many factors from regional climates to human settlement patterns.
