A vast pocket of unusually warm rock is making its way under the Appalachians toward New York, but it's not in a big hurry—the so-called Northern Appalachian Anomaly is moving at a pace of around 12 miles every million years. Scientists say this ancient "hot blob" may hold clues to why the mountains remain standing tall today despite millions of years of erosion. Geologists had previously pegged its origins to the ancient split between North America and Africa, but new research points the finger at a more recent continental shake-up—when Greenland and North America went their separate ways roughly 80 million years ago, Live Science reports.
According to Thomas Gernon of the University of Southampton, lead author of the study published in Geology, the idea that this anomaly was a leftover from the continent's earlier split "never quite stacked up," since the region's surface has been geologically quiet for the past 180 million years. Instead, the new study uses computer models and geological evidence to show that this hot blob formed as the Earth's mantle welled up to fill gaps left by the Greenland rift, then began drifting southwest beneath the continent.
Gernon says the blob could explain why the Appalachians—once part of the same ancient mountain range as the Scottish Highlands—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," he says, per Live Science. "This would have caused the ancient mountains to be further uplifted over the past million years."
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The anomaly, about 125 miles down and 220 miles wide, is expected to slide from New England under New York in the next 10 million to 15 million years. Once it moves on, the region's crust should eventually settle, and erosion will begin to take more of a toll on the mountains. Greenland has its own "twin" anomaly, which is currently influencing the movement and melting of its ice sheet. "Even though the surface shows little sign of ongoing tectonics, deep below, the consequences of ancient rifting are still playing out," Gernon says, per a release. "The legacy of continental breakup on other parts of the Earth system may well be far more pervasive and long-lived than we previously realized."
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