A new study reveals that beneath the American Midwest, a unique geological process known as lithospheric dripping is occurring, shedding light on the continent’s evolution. This slow, gradual mechanism involves blobs of molten rock coalescing in the upper mantle and eventually leading to thinning of the lithosphere.
Geophysicist Thorsten Becker explains that this process helps scientists understand how continents form, break apart, and recycle. The region under study has a large, stable craton, which is thought to be the nucleus around which continents are formed. There are approximately 35 such cratons worldwide.
Lithospheric dripping occurs when the underside of Earth’s rocky crust is heated, causing it to melt and form a drop that eventually breaks off into the planet’s interior. This process can create surface wrinkles, like in the Andes and Anatolian Plateau. In this case, researchers used seismic data to reconstruct the activity beneath the craton.
Their computer model created a tomographic map of Earth’s crust, revealing where it is thickest and thinnest. The team found that the craton under most of North America is thinning, with the focal point beneath the Midwest US. The probable cause is lithospheric dripping caused by subduction of the ancient Farallon tectonic plate.
Subduction has been occurring for hundreds of millions of years, weakening the underside of the craton and facilitating lithospheric dripping. This process could soften the lithosphere, making it more susceptible to further thinning. The researchers conclude that while this process is slow and unlikely to affect living generations, it provides valuable insights into the Earth’s unique geological processes.
The study, published in Nature Geoscience, offers a new window into the dynamic evolution of our planet.
Source: https://www.sciencealert.com/earths-crust-is-dripping-under-midwest-us-scientists-discover