Deep heat beneath US traced to ancient rift with Greenland

A large unusually hot rock region under the mountains of the Appalachians in the United States could be linked to Greenland and North America separating 80 million years ago, according to new research by the University of Southampton.

Scientists argue that it was not, as has long been believed, the result of plaque tectonic movements causing it from the North American continent in North Africa 180 million years ago.

The hot area in question is the anomaly of the Appalachians of the North (NAA), a region 350 kilometers wide from the hot rocky rock which is about 200 km under the mountains of the Appalachians in New England.

Research, published in the journal Geologysuggests that the NAA was actually developed about 1,800 km from the place where it is now, when the crust of the earth has started to separate near the sea from the Labrador between Canada and Greenland.

Over time, this hot and unstable rock area deeply under the surface of the earth has slowly moved where it is today – at a rate of about 20 km per million years.

Research was undertaken by the University of Southampton in the United Kingdom, the Helmholtz Center for Geosciences in Potsdam (GFZ), Germany and the University of Florence in Italy.

Tom Gernon, main author of the study and professor of earth sciences at the University of Southampton, said: “This thermal upwelling has long been a confusing characteristic of North American geology. It is under a part of the continent which has been tectonically silent for 180 million years, so the idea was just a respect for the death of the terminal mass for 180 million years, of the end of the land mass for 180 million years.

“Our research suggests that it is part of a slow and much larger depth process that could potentially help explain why mountain ranges like the Appalachians are still standing.

“The heat at the base of a continent can weaken and eliminate part of its dense root, which makes the continent lighter and more dynamic, like an increased hot air balloon after dropping its ballast.

Theory of “ coat vague ”

Scientists have turned to a new idea that they recently proposed called “Mantle Wave” theory, which was recognized as a finalist for Science The “breakthrough of the year” of the magazine magazine.

The theory describes how dense rock slowly gives way to the base of the tectonic plates – a bit like stains in a lava lamp – after the continents separate. These “waves” stand along the lower surfaces of continents on tens of millions of years and can help explain the rare volcanic eruptions which surface diamonds, and why certain interior regions are exceptionally high.

Using advanced geodynamic simulations, seismic tomography data (such as medical ultrasound, but using seismic waves for images inside the earth) and reconstructions of tectonic plates, the research team has traced the probable origin of NAA at the break of the Labrador Sea, which occurred between 90 and 80 million years when the Greenland is separated from Canada.

Professor Sascha Brune, co-author of the study which directs the geodynamic modeling section of GFZ in Potsdam, in Germany, declared: “These convective instabilities cause pieces of rock, several tens of thick kilometers, to slowly flow from the base of the exterior layer of the earth known under the name of coast.

“Our previous research shows that these rock” drops “can form in series, like Domino Stones, when they fall one after the other, and migrate sequentially over time. The characteristic that we see under New England is most likely one of these drops, which is from the place where it is now.”

If it is correct, the NAA has probably slowly migrated the South West through the North American lithosphere at a rate of approximately 20 kilometers per million years, which is largely coherent with independent geodynamic predictions. The current size of the NAA (approximately 350 km in diameter) and the depth are aligned closely with what the models predict such migratory instabilities.

Based on the team’s research, the hot anomaly should go under the New York region in the next 10 to 15 million years.

A naa mirror

The study also proposes that an abnormal hot zone similar under the North Center of Greenland can share the same origin, which actually makes it a twin mirror image of the NAA – having emerged from the opposite flank of the Labrador Sea while it was moving away.

Under Greenland, this thermal anomaly contributes to a high heat flow at the base of the ice cap of thickness of the kilometers, influencing the way the ice moves and melts today.

In this way, “anomalies of ancient heat continue to play a key role in the formation of the dynamics of continental glacial caps from below,” said Professor Gernon.

Dr. Derek Keir, co-author of the study and tectonic expert at the University of Southampton and at the University of Florence, said: “The idea that the rifting of the continents can cause in-depth hot rock drops and cells which distributes thousands of kilometers inside.”

The results of the team rely on research indicating that the deep earth processes can continue to take place for several tens of millions of years after the limits of the surface plate have ceased to be active.

These long -term instabilities can shape everything, from regional elevation to models of volcanism and erosion, even in certain parts of the continental interiors that were thought before geologically stable.

Professor Gernon added: “Even if the surface shows few signs of current tectonics, deep below, the consequences of the old rifting always take place. The inheritance of the continental rupture on other parts of the terrestrial system could well be much more omnipresent and long than we have done before.”