North America Is Dripping From Below, Geoscientists Discover – ryan

North America is dripping—with sizable blobs of rock sinking from the underside of the continent, beneath the U.S. Midwest, into the Earth’s mantle below.

This is the conclusion of researchers from the U.S. and China, who found that the crust is thinning as a result of a piece of ancient ocean plate sinking beneath it.

The affected part of the North American continent is an example of a “craton”—ancient and stable parts of the crust that typically undergo very little deformation but, as the study highlights, are not completely immune to change.

Fortunately the changes are very slow—such, certainly, that the Midwest won’t experience any noticeable effects—and will eventually stop when the trigger plate sinks deeper into the mantle.

“This sort of thing is important if we want to understand how a planet has evolved over a long time,” said paper author and geophysicist professor Thorsten Becker of the University of Texas at Austin in a statement.

“It helps us understand—how do you make continents, how do you break them, and how do you recycle them.”

In their study, the researchers used a new technique to analyze seismic data and build up a computer model of the crust and mantle beneath the North American continent.

“Because of the use of this full-waveform method, we have a better representation of that important zone between the deep mantle and (overlying) shallow lithosphere where we would expect to get clues on what’s happening with the lithosphere,” said Becker.

Along with providing the first indications of the continental dripping beneath the U.S., the modeling also revealed the surprising cause—a sinking oceanic plate some 370 miles deeper into the mantle.

This body—the “Farallon Plate”—was once one of the three main plates of the vast Panthalassic Ocean that surrounded the supercontinent Pangaea, but has been subducting—or moving underneath a separate plate—under North America for the last 200 million years.

The team believe that the sinking remains of the Farallon Plate are both redirecting the flow of material in the mantle such that it is wearing away the bottom of the North American craton—alongside releasing volatile compounds that are weakening the base of the crust.

The team’s modeling showed that the craton dripped when the Farallon Plate was present in the mantle; when the plate was removed from the calculations, the dripping stopped.

According to the researchers, while the dripping is concentrated under the Midwest, the plate is interacting with material from across the whole craton, which underlies most of the U.S. and Canada.

“A very broad range is experiencing some thinning,” said paper author and geoscientist Justin Hua of the University of Science and Technology of China in a statement.

As Becker notes, models have their inherent limitations—but its resemblance to the real-world data is a good sign, he said.

“You look at a model and say, ‘Is it real, are we overinterpreting the data, or is it telling us something new about Earth?,” the geophysicist added.

“But it does look like in many places that these blobs come and go, that it’s a real thing.”

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Reference

Hua, J., Grand, S. P., Becker, T. W., Janiszewski, H. A., Liu, C., Trugman, D. T., & Zhu, H. (2025). Seismic full-waveform tomography of active cratonic thinning beneath North America consistent with slab-induced dripping. Nature Geoscience.