Have you ever wondered why the “stable” parts of continents gradually rise up to form some of the largest landforms on Earth, like the vast plateau of South Africa? This question has baffled geologists for decades, but a recent study published in the journal Nature has shed light on the answer. If you’re curious, you can find out more on Nature.
The research team led by Professor Thomas Gernon discovered that when tectonic plates break apart, they can trigger powerful waves deep inside the Earth, resulting in the uplift of the continental surface by more than a kilometre.
This process elucidates the formation of striking landforms such as the Great Escarpment, which are steep terrains that create long, dramatic cliff-like edges along continents, as well as vast plateaus that significantly impact climate and biodiversity.
“Scientists have long speculated that the Great Escarpment, including the towering cliffs found around South Africa, formed during the breakup and separation of continents,” explained Gernon.
“However, understanding why continental interiors, far from these cliffs, would rise and erode has been a challenge.” The team employed advanced computer models and statistical methods to analyze how the Earth’s surface responds to continental breakup that began hundreds of millions of years ago.
Prior to the breakup, Earth’s continents were united in a supercontinent known as Pangaea, which eventually split into Gondwana and Laurasia, subsequently breaking apart further to form the present-day continents.
The researchers revealed that when continents separate, the stretching of the continental crust induces vigorous movements in the Earth’s mantle, resulting in “sweeping movements” that disturb the continent’s deep basement.
“It’s like stretching toffee,” likened Gernon. “The deformation occurs in the center, where the crust thins, causing hot material to rise from below.”
This rising hot material collides with the cool continent, cools down, and descends back down, creating a convection cycle of swirling material.
The instabilities caused by these convective cycles lead to disturbances in adjacent material, initiating similar behaviors.
This disruption triggers a chain reaction that propels “deep mantle waves” to travel along the continent’s base at speeds of 15 to 20 kilometers per million years. Although seemingly slow, this movement peels away layers of rock from the continent’s base.
Consequently, continents rise through isostasy, akin to a hot air balloon ascending as it loses weight.
In addition, this uplift induces surface erosion through weathering over millions of years. This erosion progresses across the continent, removing substantial amounts of rock from the surface and further contributing to the rise of plateaus.
This phenomenon clarifies why seemingly stable parts of continents undergo substantial uplift and erosion.
Gernon elaborated: “And what’s truly captivating about this phenomenon is that these areas represent the ancestral heartlands of the continents, surviving for billions of years.”
“They have weathered significant events in Earth’s history, and for some reason, the continents parted ways, leading to this major disruption.”
Fascinatingly, the team’s findings link this process of continental reshaping to the formation of diamonds.
“Disturbing the source of a continent causes it to melt and release ancient material containing all the necessary elements for diamond formation,” stated Gernon.
However, this process of continent-building holds greater significance beyond the emergence of exquisite gems in the earth. “The importance of this process cannot be overstated,” emphasized Gernon.
While Africa serves as a model, similar processes have unfolded worldwide, from the Americas to regions in northern Europe, Antarctica, and Greenland. Whenever land rises by hundreds of meters, ecosystems undergo drastic transformations, compelling species to adapt and evolve in response.
About our experts
Thomas Gernon: Holds a BSc (Hons) in Geology from University College Dublin and a PhD in Volcanic Physics from the University of Bristol. He was a Geology lecturer at Trinity College Dublin (2008-2009) before joining the University of Southampton, where he serves as an Associate Professor in Earth Sciences. Gernon has authored or co-authored over 60 peer-reviewed articles in international scientific journals and delivered numerous presentations at conferences, workshops, seminars, and public lectures.
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Source: www.sciencefocus.com
