Uh, Looks Like North America is ‘Dripping' Into Earth's Mantle
Cratons are the most ancient, stable pieces of tectonic plates, but even these geological formations can change over time.
A new study details how the North American plate is 'dripping' into the mantle due to the continued influence of the Farallon Plate, which has been subducting under the continent for 200 million years.
While this 'dripping' is located beneath the U.S., it doesn't hold any consequences for us surface-dwellers. But it does provide a unique opportunity for scientists to study the formation—and disintegration—of continents.
While there's often much to-do about tectonic plates, especially when their various subductions and transform sliding creates widespread devastation, cratons rarely nab the limelight. That's not because they're not unimportant—after all, they form the geologic core of all tectonic plates around the world. But as a result of being the most ancient pieces of Earth's lithosphere (containing the crust and uppermost mantle), they aren't subjected to nearly as much geologic dynamism as is found throughout the rest any particular plate. They're just kind of… there.
However, recent research has shown that even these geologic stalwarts face incredible change over time. A study by Chinese scientists in October of last year detailed how one of the oldest pieces of continental crust—the North China Craton (NCC)—had slowly been disintegrating in a process known as 'decratonization' over the course of 200 million years. At the time, the author noted that the North American craton could experience similar deformations. Now, a new study published in the journal Nature Geoscience shows the deformation currently impacting the North American craton.
Primarily located under the Midwest in the U.S., this craton appears to be 'dripping' into the mantle due to a subducting oceanic slab known as the Farallon Plate, according to researchers at the University of Texas at Austin (UT). What's fascinating about the North American craton's 'dripping' process—as opposed to the decratonization of the NCC, for example—is that this process is happening as we speak, which gives scientists an unprecedented opportunity to learn more about the geology of these lithospheric cores.
'We made the observation that there could be something beneath the craton,' Junlin Hua, the lead author of the study who is now a professor at University of Science and Technology of China, said in a press statement. 'Luckily, we also got the new idea about what drives this thinning.'
By creating a full-waveform tomographic model of the North American plate using seismic data gathered from the EarthScope project, Hua and his team were able to spot this 'dripping' behavior far beneath the Earth's surface. The main engine behind the dripping (shown in the image above) is the Farallon Plate—an oceanic plates that's been subducting under the North American Plate for 200 million years, and has played a starring role in shaping the continent. The researchers theorize that this plate is impacting the craton by redirecting mantle flow, while also releasing volatile compounds that wear away the base of the plate.
Of course, this doesn't mean that the Midwest will suddenly sink into an abyss. In fact, the researchers estimate that this 'dripping' will eventually end as the Farallon Plate continues to sink into the mantle and its influence on the craton wanes.
'This sort of thing is important if we want to understand how a planet has evolved over a long time,' Thorsten Becker, a co-author of the study from UT, said in a press statement. 'It helps us understand how do you make continents, how do you break them, and how do you recycle them [into the Earth.]'
Who says cratons can't be exciting?
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