North America May Be Dripping Away Deep under the Midwest
Something very unusual seems to be unfolding deep beneath the Midwest and Ohio Valley in North America. Scientists have uncovered evidence that a long-lost slab of Earth’s crust may be slowly eroding the bottom of the continent’s oldest geological core, known as the North American craton.
Cratons are large, stable blocks of continental rock that have remained relatively unchanged for billions of years, resisting the forces of plate tectonics. However, recent research published in Nature Geoscience suggests that a hidden geological plate may be siphoning rock from the base of the North American craton, causing it to deteriorate from below.
While the idea of a craton eroding is not entirely unprecedented, it is certainly unexpected. According to Claire Currie, a geophysicist at the University of Alberta, cratons are considered to be the oldest parts of continents and have remained near the Earth’s surface for billions of years, making this discovery quite unusual.
The study, led by Junlin Hua, a geophysicist at the University of Science and Technology of China, utilized data from over 6,000 seismometers across North America to create detailed images of the continent’s subsurface. By analyzing seismic waves produced by more than 200 earthquakes, the researchers were able to map the structure of Earth’s interior with unprecedented precision.
What they found beneath the Midwest and Ohio Valley was unexpected. A patchy pattern of high-seismic-velocity material was observed sagging nearly 600 kilometers deep, close to the lower mantle. This anomaly suggested that the North American craton was dripping downward into the mantle, a phenomenon that the researchers struggled to explain.
Further investigation revealed that remnants of the Farallon plate, an ancient oceanic plate that existed around 100 million years ago, were influencing the erosion of the craton. Computer models showed that the Farallon slab acted as a sinker, pulling material off the craton and dragging it down into the Earth’s depths.
While this hypothesis is still speculative, scientists like Currie are intrigued by the findings. They are eager to explore additional evidence of the cratonic drip and investigate how the dense material of the mantle is able to pull down the lighter cratonic rock.
Overall, this research provides a fascinating insight into the dynamic nature of Earth’s continents. Despite being considered stable and unchanging, the continent is now revealing signs of ongoing transformation beneath its surface. As Hua notes, “The continent is not something static; it has a dynamic component.”
