Beneath the quiet plains and bustling cities of the U.S. and Canada, an ancient process is slowly playing out. According to a new study published in Nature Geoscience, pieces of North America’s oldest and most stable rock are dripping into the Earth’s mantle. Yes, you read that right—North America is sinking.
This surprising shift involves what geologists call the craton, a billion-year-old bedrock core that serves as the foundation of our continent. Think of it as North America’s deep structural spine. It is hard, unyielding, and, until recently, assumed to be mostly unchanged over time.
But change is happening. Using seismic data from the EarthScope project, researchers created a detailed model of the continent’s subsurface. They found a funnel-shaped zone in the Midwest where the craton is thinning.
Rock from this ancient layer is being pulled downward into the Earth’s mantle. It’s almost like the craton is dripping through that funnel, causing North America to sink slowly in the process.
Researchers say the blame likely falls on the Farallon Plate, a long-subducted tectonic plate still interacting with North America from below. As remnants of the Farallon continue to dive deeper, they release heat and chemicals that soften the base of the craton. Over time, these effects have weakened parts of the craton enough that gravity is winning, and pieces are slowly dripping away.
The good news is that the sinking is happening over geological timescales, not human ones. So, this isn’t as big of a deal as the hundreds of cities sinking into the ocean around the world. Still, it could be concerning one day.
Studying why and how North America is sinking will provide us with a valuable window into how the continents of our world continue to evolve. It also helps explain how landmasses form, fracture, and eventually recycle back into the planet. Until now, such insights have come only from fossilized geology.
With this discovery, though, we can finally watch it happen in real-time. That kind of observation is a “game-changer,” the researchers say. And it will further help us reshape how we think about tectonic stability on Earth.
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