Every now and then certain stable parts of the continents on Earth begin to rise and develop into some stunning topographic features. The reason why this happens has now been revealed. Scientists at the University of Southampton studied plate tectonics to find out how did this happen. They say that tectonic plates often break apart, and this triggers powerful waves deep within the Earth. This event causes continental surfaces to rise, sometimes by over a kilometre.
Scientists have been trying to understand for years how these topographical features known as "escarpments" and "plateaus" come into existence. The findings published in the journal Nature are a reasult of studying the impact of global tectonic forces on landscape evolution over hundreds of millions of years.
"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," Tom Gernon, Professor of Earth Science at the University of Southampton and lead author of the study said.
The researchers from the University of Southampton - Dr Thea Hinkes, Dr Derek Keir, and Alice Cunningham - collaborated with colleagues from the Helmholtz Centre Potsdam—GFZ German Research Centre for Geosciences and the University of Birmingham. They tried to understand why stable parts of continents sometimes move vertically.
The study
They discovered that continental crust stretches when continents split apart, and this stretching causes stirring movemrnts in Earth's mantle. 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."
Professor Brune and Dr Anne Glerum then ran simulations and noted that the speed of the mantle "waves" moving under the continents was extremely close to the speed of major erosion events that happened in the landscape in Southern Africa following the breakup of the ancient supercontinent Gondwana. They added that the Great Escarpments originate at the edges of ancient rift valleys. This led them to conclude that a rifting event also sets in motion a "deep mantle wave". This wave travels along the continent's base at about 15–20 kilometres per million years.
"Much like how a hot-air ballons sheds weight to rise higher, this loss of continental material causes the continents to rise—a process called isostasy," said Professor Brune.
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