America's hidden sinkhole: Scientists uncover a geological shift
Beneath the surface of the United States, the Earth's crust is slowly sinking, creating a new geological phenomenon. Scientists from the U.S. and China have discovered that this may be due to a tectonic plate submerging into the Earth's mantle. They published their findings in the journal "Nature Geoscience."
The Earth's crust under the Midwest United States is gradually descending. In the Earth's upper mantle, clusters of molten rock form, which eventually gain mass and sink deeper. This process, revealed through seismic monitoring, shows how thin the lithosphere in this region is. Researchers from the University of Texas at Austin have discovered that the bottom of the North American continent may be sinking due to a tectonic plate submerging into the Earth's mantle. This phenomenon has been described in the journal "Nature Geoscience."
The subsidence of the lithosphere indicates that something is happening inside the planet
The lithosphere in this region is a craton—a large, stable part of the Earth's crust that remains unchanged for a long time. Cratons are considered nuclei around which continents form. About 35 such structures are known worldwide. This phenomenon, known as lithosphere dripping, also occurs in other parts of the world, but its discovery opens new possibilities for understanding Earth's dynamic geological processes. "We made the observation that there could be something beneath the craton," said Junlin Hua, the study's lead author.
Geophysicist Thorsten Becker from the University of Texas at Austin, co-author of the study, emphasizes in a university release that this is a significant discovery: "This sort of thing is important if we want to understand how a planet has evolved over a long time. It helps us understand how do you make continents, how do you break them, and how do you recycle them [into the Earth.]."
Lithosphere dripping occurs when the lower part of the Earth's crust heats to a specific temperature. As the rock melts, a drop forms, which over time becomes heavy enough to detach and sink deeper into the planet. Scientists believe this phenomenon resembles an extreme version of a pitch drop experiment.
In some places, like the Andes or the Anatolian Plateau in Turkey, this process can cause rifts on the planet's surface, revealing the activity occurring below. In this case, the team led by seismologist Junlin Hua from the University of Science and Technology of China used seismic data to reconstruct activity at the bottom of the Earth's crust.
What are the consequences of this discovery?
The discovery of craton "dripping" is special because it is happening now, allowing scientists to observe the process in real-time. Scientists reassure that there is no need to fear that the continent will hollow out or that the sinking of the continent will change the landscape in the near future. The processes in the Earth's mantle driving this phenomenon are very slow.
This study is part of a larger project that created a new seismic model for North America. This model, developed by Stephen Grand and his team, has revealed new details about the geological processes occurring in the crust and mantle beneath North America. "Because of the use of this full-waveform method, we have a better representation of that important zone between the deep mantle and the shallower lithosphere where we would expect to get clues on what’s happening with the lithosphere," said Becker.
This model helped scientists infer that the Farallon Plate, an oceanic tectonic plate that subducted beneath North America for the last 200 million years, may be driving this process. This plate, although separated from the craton by about 373 miles, influences the continent by directing mantle material flow in a way that shears the base of the craton and releases volatile compounds that weaken its base.
