A massive blob of hot rock underneath New England appears to be part of an ancient ‘wave’ that’s moving towards millions of Americans in New York.
Scientists said this nearly 250-mile blob called the Northern Appalachian Anomaly (NAA) is roughly 125 miles underground, stretching across Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont.
A team from the University of Southampton in the UK and the Helmholtz Center for Geosciences in Germany found it using seismic tomography, a method that’s like taking a CT scan of the Earth.
Unlike typical hot spots near volcanoes, this blob is far inland, hidden beneath the ancient Appalachian Mountains, and it’s still moving south, towards New York and New Jersey.
Until now, these kinds of mysterious underground formations have only been seen near volcanoes or around the border of tectonic plates. However, New England isn’t near either of these.
Researchers concluded that it’s part of a slow-moving ‘mantle wave,’ a chain of sinking and rising rock set in motion over 90 million years ago when North America split from Europe near the Labrador Sea, which sits between Canada and Greenland.
The NAA’s slow creep of roughly 12 miles every million years suggests it will reach New York City in about 15 million years.
However, the new study noted that this immense moving blob is not alone, and older blobs could be part of an ongoing ‘drip’ of heavy rock sinking like a glob of syrup in water under the US.
Scientists believe a nearly 250-mile blob called the Northern Appalachian Anomaly is still moving and shaping mountains in the US
Tom Gernon, lead author of the study and Professor of Earth Science at the University of Southampton, said: ‘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.’
This discovery has challenged the idea that the eastern US is a ‘geologically dead’ area, hinting that similar drips, like the Central Appalachian Anomaly (CAA) further south, may have shaped America’s mountains millions of years ago.
‘The ‘mantle wave’ refers to a newly-discovered chain reaction of convective instabilities in the mantle that begins when a continent starts to rift,’ said Gernon.
The study author and his team found that the NAA was likely formed by a Rayleigh-Taylor instability, a process where the mantle became unstable during an ancient breakup of the tectonic plates.
The breakup caused a ‘drip’ of denser material sinking into the mantle, pulling lighter, hotter rock upward to create these blobs, where earthquake waves move slower due to the hotter, less dense rock.
This may contribute to fewer earthquakes in the Northeast because the blob creates a softer, more flexible mantle that absorbs tectonic stress, reducing the chance of sudden crustal breaks.
However, geologists have noted that the region’s overall stability generally comes from its old, thick crust formed long ago.
The blob is moving about 12 miles every million years, putting it beneath New York City in about 15 million years
The team’s findings, published in the journal Geology, revealed the NAA is currently located near the boundary of a deep geological structure formed by the Laramide Orogeny, suggesting its position is influenced by an ancient tectonic breakup.
The Laramide Orogeny, active around 1.5 million years ago, was a period when the Earth’s crust was compressed and folded, creating major mountain ranges like the Rockies and leaving a thickened layer of crust beneath parts of the eastern US.
By linking the NAA’s current position to a tectonic feature from millions of years ago, the study revealed how past continental shifts guide today’s underground movements, baffling scientists who thought the eastern US was geologically stable.
‘These ‘drips’ migrate inland over time, away from the rift. We think this same process might explain unusual seismic patterns beneath the Appalachians. The timing lines up perfectly,’ Gernon explained to Newsweek.
The researchers also proposed that the drips are part of a chain reaction, where one sinking blob triggers another, moving inland over millions of years like a slow underground conveyor belt.
For example, the Central Appalachian Anomaly, found in parts of Pennsylvania, Virginia, and West Virginia, is likely an older drip from this same chain, formed around 135 million years ago.
‘It’s not a literal wave, but a progressive flow and deformation of mantle material that behaves like a wave in how it propagates,’ Gernon noted.
Study authors said this process might still be active, as the mantle continues to shift slowly, potentially creating new blobs in the future, though limited seismic data from areas like Newfoundland makes it hard to confirm if newer drips exist yet.
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