Recent research conducted by the University of Southampton suggests that a substantial area of exceptionally hot rock beneath the Appalachian Mountains may be associated not with the recognised separation of North America from Northwest Africa 180 million years ago, but with a more recent continental rifting event.

The research suggests that the Northern Appalachian Anomaly (NAA) – a 350-kilometer-wide region of unusually heated rock situated around 200 km beneath New England — began far further north. Researchers currently assert that it originated near the Labrador Sea, when Greenland and North America commenced rifting approximately 90 to 80 million years ago.

Over the subsequent tens of millions of years, this profound thermal feature seems to have relocated approximately 1,800 km to its current position, advancing gradually into the Earth’s lithosphere at an estimated rate of 20 km per million years.

The study, published in the journal Geology, was conducted in partnership with the Helmholtz Centre for Geosciences (GFZ) in Germany and the University of Florence in Italy.

Professor Tom Gernon, the principal author from the University of Southampton, elucidated: “This thermal upwelling has long been a puzzling feature of North American geology. It lies beneath part of the continent that’s been tectonically quiet for 180 million years, so the idea it was just a leftover from when the landmass broke apart never quite stacked up. Our research suggests it’s part of a much larger, slow-moving process deep underground that could potentially help explain why mountain ranges like the Appalachians are still standing. Heat at the base of a continent can weaken and remove part of its dense root, making the continent lighter and more buoyant, like a hot air balloon rising after dropping its ballast. This would have caused the ancient mountains to be further uplifted over the past few million years.”

The researchers utilised its newly formulated ‘mantle wave’ theory, a finalist for Science magazine’s 2024 Breakthrough of the Year, to investigate the phenomena. The idea elucidates that, during continental rifting, thick material at the base of tectonic plates detaches in wave-like patterns, like to blobs in a lava lamp. These sluggish ‘waves’ traverse beneath continents for tens of millions of years, possibly elucidating atypical inland volcanism and heightened topography.

Utilising models, seismic tomography (analogous to ultrasound imaging of the Earth’s subsurface), and tectonic plate reconstructions, the researchers traced the genesis of the NAA to the separation of Greenland and Canada.

Professor Sascha Brune, a co-author from GFZ in Potsdam, expounded:

“These convective instabilities cause chunks of rock, several tens of kilometres thick, to slowly sink from the base of the Earth’s outer layer known as the lithosphere. As the lithosphere thins, hotter mantle material rises to take its place, creating a warm region known as a thermal anomaly. Our earlier research shows that these ‘drips’ of rock can form in series, like domino stones when they fall one after the other, and sequentially migrate over time. The feature we see beneath New England is very likely one of these drips, which originated far from where it now sits.”

If correct, the NAA has been progressively shifting southwest across the North American lithosphere for more than 80 million years. The present dimensions and depth—approximately 350 km in width and 200 km in depth—align with forecasts generated by geodynamic models. The researchers project that the anomaly’s centre will traverse beneath the New York region approximately 15 million years.

The research also suggests a mirror anomaly located beneath north-central Greenland, which may have developed concurrently with the NAA, originating from the opposite side of the Labrador Sea during the rift. This Greenlandic hot zone is thought to augment heat transfer beneath the extensive ice sheet, thereby affecting contemporary melting and ice dynamics.

As Professor Gernon noted: “Ancient heat anomalies continue to play a key role in shaping the dynamics of continental ice sheets from below.”

Co-author Dr. Derek Keir, tectonics expert from Southampton and the University of Florence, added:

“The idea that rifting of continents can cause drips and cells of circulating hot rock at depth that spread thousands of kilometres inland makes us rethink what we know about the edges of continents both today and in Earth’s deep past.”

The research highlights that deep Earth processes can last for tens of millions of years after surface tectonic activity has ceased, significantly influencing elevation, volcanism, and erosion in areas deemed geologically stable.

Professor Gernon concluded: “Even though the surface shows little sign of ongoing tectonics, deep below, the consequences of ancient rifting are still playing out. The legacy of continental breakup on other parts of the Earth system may well be far more pervasive and long-lived than we previously realised.”

Original Publication
Authors: Thomas M. Gernon, Sascha Brune, Thea K. Hincks and Derek Keir.
Journal: Geology
DOI: 10.1130/G53588.1
Article Title: A viable Labrador Sea rifting origin of the Northern Appalachian and related seismic anomalies
Article Publication Date: 30-Jul-2025