Scientists Uncover Surprising Discovery: Earth’s Crust Dripping Beneath the Midwest U.S.

Underneath the American Midwest, something unusual is happening. The Earth’s crust is slowly leaking molten rock into the mantle below. Seismic studies have shown a thinning of the lithosphere, which is the outer layer of the Earth, in this area.

But don’t worry; this isn’t a cause for concern. It’s a natural process that has also been detected in various other regions around the world. This new discovery sheds light on the dynamic nature of our planet.

"Understanding these processes helps map out the evolution of Earth," says geophysicist Thorsten Becker from the University of Texas at Austin. He emphasizes that it provides insights into how continents form, change, and eventually recycle.

The lithosphere here can be classified as a craton, which is a stable, old part of the Earth’s crust. Cratons play a significant role in continental formation. Currently, about 35 cratons are known to exist under North America.

Lithospheric dripping occurs when the crust heats up enough to melt. Droplets of molten rock eventually become heavy and sink deeper into the Earth. This phenomenon is somewhat like the pitch drop experiment, where thick fluid drips slowly over time.

In other places, like the Andes or Türkiye’s Anatolian Plateau, similar processes might create visible surface deformations. However, in this study, seismologist Junlin Hua and his team used seismic data to explore what’s happening beneath the American Midwest.

They constructed a detailed map of the crust using seismic data from the EarthScope Consortium, providing a clearer understanding of the crust’s thickness and density variations.

Becker mentions, “Using full-waveform methods gives us a better understanding of what’s happening between the deep mantle and the shallow lithosphere.” Their findings indicate that the craton under the northern US is thinning, with the most significant change occurring under the Midwest, likely due to the lithospheric dripping.

Intriguingly, about 600 kilometers (about 373 miles) away, the ancient Farallon tectonic plate is being pushed under the North American plate in a process known as subduction. This subduction has been ongoing for millions of years, and much of the Farallon plate now resides in the lower mantle.

Scientific data suggests that this ancient plate’s presence affects large-scale movements in the mantle, which in turn weakens the craton. This could lead to an accelerated dripping process as well, possibly due to volcanic gases released from the subducting Farallon slab.

The combination of various geological activities could be softening the lithosphere, allowing for this dripping to occur, thus thinning the craton that supports the continent.

While the main activity is focused under the Midwest, the effects extend across the broader craton area. However, these geological changes happen over millions to billions of years, so they won’t pose a threat to anyone living in North America anytime soon.

For further insights on geological processes like lithospheric dripping, you can explore this detailed study published in Nature Geoscience.

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