Mantle Blob Beneath New Hampshire Shapes Appalachians

A hot mantle anomaly beneath New Hampshire may help explain why the Appalachians stay tall and is slowly drifting toward New York.

Mantle Blob Beneath New Hampshire Shapes Appalachians

A large hot rock mass lies beneath New Hampshire, named the Northern Appalachian Anomaly (NAA). It sits about 124 miles (200 kilometers) beneath the Appalachian region and spans 217 to 249 miles (350–400 kilometers) in width in the asthenosphere. It is a thermal anomaly, hotter than its surroundings. New research links its origin to Greenland and North America separating about 80 million years ago, revising earlier ideas of a breakup 180 million years ago. The anomaly has migrated about 1,118.5 miles (1,800 kilometers) since its formation, at a rate of 12.4 miles (20 kilometers) per million years. Projections place its center passing beneath New York in roughly 15 million years. Scientists used seismic imaging, mantle-wave modeling, and plate reconstructions to trace the path. The mass may help explain why ancient mountains like the Appalachians have resisted erosion by warming the base of the continent, making the crust lighter and more buoyant. The movement is slow, but over millions of years it could influence surface geology and mountain height. The work adds to a growing view that deep mantle processes shape the surface far more than once thought.

The study relies on mantle-wave theory and edge-driven convection, where hot, dense rock detaches from plate edges and travels inland. This model paints the Appalachian region as a dynamic stage where deep currents silently reshape topography. It also raises questions about how often similar anomalies exist elsewhere and how they interact with surface tectonics.

Yet the conclusions rest on imaging and simulations with uncertainties, so researchers caution that multiple mechanisms may act together. If confirmed, the idea changes how we picture continental edges not as static borders but as evolving zones that influence mountains, earthquakes, and perhaps future landscapes.

Highlights

The planet keeps its deeper secrets ready for the next chapter