Earth's crust might be thinning in real-time, a funnel is dragging crust into the mantle

In a groundbreaking discovery, scientists have revealed that a portion of North America's ancient continental crust, known as a craton, is slowly "dripping" into the Earth's deeper layers. This rare and complex geological process, observed through advanced seismic imaging technology, challenges long-held assumptions about the stability of the planet’s interior. Cratons, considered the oldest and most stable parts of Earth’s crust, were once thought to be immovable. However, this new evidence suggests otherwise, highlighting a far more dynamic and evolving mantle system beneath our feet.

Cratons are the oldest and most stable parts of Earth’s continents. Think of them as the tough "core" of continents, typically untouched for billions of years. But this new study, published in Nature Geoscience, reveals something surprising: parts of the North American craton are actively thinning, possibly due to forces pulling it down from deep within the planet.
Scientists have found a massive funnel-shaped region beneath the Midwest that is drawing rock from across North America toward it in a horizontal flow, before pulling it down into the Earth's mantle. This phenomenon is gradually stripping away material from the bottom of the continent's crust.
Using a high-resolution seismic technique called full-waveform tomography, researchers created a detailed map of what lies beneath the central United States. What they saw were large, drip-like structures extending from the base of the craton into the mantle transition zone, an area roughly 400 to 700 kilometres below Earth's surface.

The culprit seems to be the Farallon slab, an ancient piece of tectonic plate that sank deep into the Earth's mantle millions of years ago. Even though it is now far below the surface, this slab still influences mantle flow and pulls parts of the craton downward, like taffy being stretched.
The study also suggests that previous volcanic activity and fluid release from the sinking slab may have weakened the craton’s base, making it easier for bits to peel off and drip downward.
This discovery challenges long-held beliefs about the permanence of Earth’s oldest geological structures. It provides new insight into how continents evolve and shows that even the most stable parts of our planet are constantly changing.
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