The hot 'blob' moving toward New York has revealed a mysterious discovery deep within the Earth
Deep beneath the northeastern United States, a massive geological mystery has been hiding for millions of years. Scientists call it the "Northern Appalachian Anomaly" - a region hundreds of kilometers wide where rocks in the Earth's mantle are abnormally hot. A 2025 study even suggested that this mass is slowly moving southwest, and if the model is correct, its center could pass under the New York area in about 15 million years. Now, in an attempt to better understand what exactly is happening down there, a team of researchers from Yale and the University of Minnesota has created the most detailed 3D map of the region to date.
Deep beneath the northeastern United States, a massive geological mystery has been hiding for millions of years. Scientists call it the "Northern Appalachian Anomaly" - a region hundreds of kilometers wide where rocks in the Earth's mantle are abnormally hot. A 2025 study even suggested that this mass is slowly moving southwest, and if the model is correct, its center could pass under the New York area in about 15 million years.
Now, in an attempt to better understand what exactly is happening down there, a team of researchers from Yale and the University of Minnesota has created the most detailed 3D map of the region to date. However, instead of just solving the known mystery, the scan revealed a new one: beneath Connecticut lies a narrow and almost vertical structure that descends hundreds of kilometers deeper than the hot "blob" next to it.
And the really interesting part is that the two behave in completely opposite ways.
Like a CT scan - only for the Earth
The new study, published in the journal Journal of Geophysical Research: Solid Earth, used seismic tomography - a method that works somewhat like a medical CT scan.
Instead of X-rays passing through the human body, researchers measure seismic waves generated by distant earthquakes that pass through the Earth's interior. The speed of the waves varies depending on the temperature, density, and composition of the rocks they encounter, so they can be used to build a kind of 3D image of what is hidden hundreds of kilometers beneath our feet.
Researchers combined data from permanent monitoring systems in the United States and Canada with three temporary, dense networks of seismic stations placed in New England. In some places, the distance between stations was only 5 to 25 kilometers, which allowed for seeing details much smaller than those seen in previous mappings.
The result greatly sharpened the boundaries of the known anomaly. According to the new model, it extends from a depth of about 60 kilometers to about 200 kilometers below the surface and remains within the upper mantle.
P-waves, the fastest seismic waves generated by earthquakes, moved in parts of it at a speed about 4% lower than expected. Such a low speed usually corresponds to hotter rock or rock that has undergone a change in its composition.
But it is important to clarify: despite the picturesque nickname "hot blob," this is not a giant ball of lava or an underground magma lake. It is a huge volume of solid rock in the mantle whose characteristics are different from those of the rocks around it.
And then they discovered something completely different
Alongside the hot anomaly, beneath Connecticut, a small and narrow structure appeared in the scans that almost looks like a column descending vertically into the Earth.
Unlike the "blob," which causes seismic waves to slow down, inside this column they actually move faster. The possible meaning is that the rock there is colder and denser than the surroundings.
The structure passes through the upper mantle and continues to the bottom of the mantle transition zone - a depth that can reach about 660 kilometers below the Earth's surface.
Here, too, it is not a hollow "column" or an underground tunnel. It is a 3D volume of rock that researchers are able to identify only because seismic waves pass through it at a different speed.
Researchers even conducted tests to ensure that the structure is not an artificial result of gaps in the data or limitations of the mapping method. It remained visible in these tests as well, but what exactly it is and how it got there is still unknown.
Could a piece of America have simply broken off and sunk?
One of the main explanations offered by the researchers sounds almost like a scenario from a disaster movie - but it happens at an excruciatingly slow geological pace.
It is possible that the column is actually part of the continental lithosphere - the rigid layer that includes the Earth's crust and the uppermost part of the mantle - that detached beneath North America and began to sink due to its weight.
This process is called "lithospheric delamination." When a cold and dense part detaches and sinks, hotter and lighter material from the mantle below can rise and take its place.
If this is what happened in New England, it is possible that the cold column and the hot "blob" are actually two parts of the same story: a dense piece of rock sank down, and in its place rose hotter material that created the huge anomaly seen today.
But the researchers emphasize that the study does not yet prove that this is indeed the scenario.
Another possibility is that the two structures are two sides of a huge and slow current in the mantle. In such a scenario, hot material rises on one side, while cold and dense material descends on the other - a kind of underground conveyor belt that has been operating for millions of years.
And what is a hot "blob" doing under a quiet area anyway?
This is the question that has been bothering geologists for years. Areas of abnormally hot mantle are usually found near volcanoes or active boundaries between tectonic plates. New England does not fit any of these descriptions. The region is far from an active plate boundary, and the east coast of North America has been considered tectonically quiet for about 180 million years.
A separate study published in 2025 offered a surprising solution to the mystery: it is possible that the origin of the anomaly is actually 1,800 kilometers from where it is today.
According to the model proposed by researchers from the University of Southampton and the German GFZ Centre for Geosciences, the story began about 80 to 90 million years ago, when Greenland and Canada began to separate and the Labrador Sea opened between them.
This breakup, they claim, destabilized the lower part of the continental plate. Dense pieces of rock began to sink into the mantle, and in their place rose hotter material.
Researchers compared the process to drops rising and falling in a lava lamp, except that in this case, each movement takes millions of years.
According to the model, the anomaly is migrating southwest at a rate of about 20 kilometers every million years. If this rate continues, its center could reach under the New York area in about 15 million years.
New Yorkers can relax
Despite the inevitable headline about a "hot blob moving toward New York," there is no reason to start packing.
The anomaly is not expected to reach the city in a future that can be measured on a human scale, and the studies do not point to an immediate threat of a volcanic eruption, an unusual earthquake, or any other disaster in Connecticut, New York, or the surrounding states.
In fact, the movement attributed to it is so slow that throughout all of recorded human history, it would have barely moved in a noticeable way.
But from a geological perspective, the discovery could be very significant. Researchers believe that such processes could even explain why the Appalachian Mountains have remained relatively high despite hundreds of millions of years of erosion.
When hot material rises beneath a continent and some of its dense root disappears, the ground above can become lighter and more buoyant and rise. Thus, it is possible that processes occurring hundreds of kilometers below the surface continue to shape even today a mountain range that was formed hundreds of millions of years ago.
And the mysterious column discovered now beneath Connecticut might be the piece that was missing from this puzzle. Or, as the researchers themselves carefully clarify, it might turn out to be a completely different phenomenon. At this stage, they know it is there - but they still do not know exactly why.
