Mantle blob may shape future Appalachians

A deep mantle anomaly beneath New Hampshire may have helped the Appalachians stay tall and is moving inland over millions of years.

Hot mantle under New Hampshire helps explain Appalachian resilience

Scientists identify a giant hot blob of rock beneath the Appalachians, called the Northern Appalachian Anomaly. It sits about 124 miles (200 kilometers) below the surface and spans roughly 217 to 249 miles (350 to 400 kilometers) across in the upper mantle. The feature is a thermal anomaly, meaning its temperature is higher than surrounding rock, and it could help explain why the mountains have remained relatively high despite long erosion. A study published in Geology on July 29 links the anomaly to the Greenland–North America separation about 80 million years ago. By tracing the path of mantle material, researchers say the blob has moved about 1,118.5 miles (1,800 kilometers) from its origin near the Labrador Sea, at a rate of about 12.4 miles per million years.

Using seismic imaging, geodynamic models, and plate reconstructions, the team argues that mantle waves and edge-driven convection moved the anomaly inland. When hot mantle material interacts with the edge of thinning continental lithosphere, it can create a series of deep drips that eventually influence surface topography. The authors say the process may have uplifted parts of the Appalachians during the last tens of millions of years, and the current movement toward New York will likely settle the crust again only after long timescales. The research also notes a possible sibling anomaly beneath north-central Greenland, hinting that the legacy of continental breakup shapes Earth far below the surface.

This study challenges the idea that Appalachian uplift is only a surface story. By pointing to a deep mantle engine, it reframes how geologists view mountain longevity and the long reach of tectonic events. The finding shows how internal heat can act like a slow, persistent force that reshapes the landscape over millions of years.

Yet the model invites questions about certainty. Mantle dynamics are complex and data remain sparse in some regions, so more seismic work and cross-checks are needed. The research reminds readers that our map of the Earth is an evolving story, not a final verdict. It also raises practical questions: how many other regions hide similar deep drivers that quietly sculpt continents long after surface motion seems to have slowed.

Highlights

As scientists push deeper, the surface story of our mountains continues to evolve.