North America Is Sinking Into the Earth’s Mantle

A study published in the journal Nature Geoscience has revealed a subtle yet significant phenomenon beneath the North American continent: its ancient bedrock is slowly sinking into the Earth’s mantle. This descent occurs in a drip-like fashion, forming a funnel-shaped structure concentrated in the Midwestern United States, which pulls the ancient rocks horizontally before they drop into deeper layers.

What Are Cratons — And Why Do They Matter?

The ancient rock in question is known as a craton—extremely old and stable blocks that form the foundation upon which continents rest. Around 35 major cratons are recognized worldwide. But stability doesn’t mean immutability.

Cratons can change due to the influence of mantle plumes—upwellings of hot material from deep within the Earth that can locally melt and deform the crust above. For example, the North China Craton experienced extensive disintegration over millions of years, losing its deepest root layers. Geologists had long suspected that something similar might be happening beneath North America.

Led by Junlin Hua, the team behind the new study created a full-waveform seismic tomographic model of North America using data from the EarthScope project. This model offered new insights into the geological processes at work beneath the continent’s crust and mantle.

Until now, craton thinning had only been studied retrospectively, looking at changes millions of years after they happened. What sets this study apart is that it shows the process is happening right now—giving researchers a rare opportunity to observe and study cratonic deformation in real time.

“We observed that something might be happening beneath the craton. Fortunately, we also developed a new idea about what’s driving this thinning,” said Hua.

Researchers believe the main force behind the thinning of the North American craton is the Farallon Plate, which has been subducting beneath North America for more than 200 million years. Though it once played a key role in shaping the continent, its ongoing subduction continues to supply magma and release volatile compounds that gradually weaken the craton’s base.

A Broader Impact Beyond the Dripping Zone

The Farallon Plate appears to affect the entire craton, spanning much of the U.S. and Canada, even though the dripping concentrates in just one area.

Still, researchers stress that there’s no reason for alarm—North America is not hollowing out or facing sudden surface collapse. More intriguingly, the dripping process may eventually stop as the plate sinks deeper into the mantle and its influence diminishes.

This kind of discovery is crucial if we want to understand how a planet evolves over long periods,” said geophysicist Thorsten Becker. It helps scientists explain how geological forces form continents, break them apart, and recycle them back into the Earth.

Read the original article on: New Atlas

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