Unusual ‘blob’ of hot rock found under New England

A hot blob of rock seems to be rising in the direction of the surface under the North American tectonic plate under a part of New England. (Credit: iStock)


The continental rock underlying the eastern coast of North America is pretty boring, tectonically speaking. The recent and dramatic geological goings-on happened around 200 million years ago, and most of the change since then is of glacial, wind and water erosion.

But a project that helped the image of the layers of rock under the continent with an unprecedented brightness has helped, revealing a small, unusual feature that seems to be a relatively new “blob” of warm, rising rock under a part of the AMERICAN Northeast.

Exactly what caused this blob, and or other similar blob structures can lurk under other continents is not clear, says the study co-author Vadim Levin, Rutgers University geophysicist, but it brings many interesting questions. The work on the blob is published online Nov. 29 in the journal Geology and is presented Monday (Dec. 11) at the annual meeting of the American Geophysical Union in New Orleans. [Photos: Ocean Hidden Beneath the Earth’s Surface]

The unusual feature had been spotted, as scientists used the seismic waves that routinely ricochet through the interior of the Earth to reveal some of the structures hidden beneath our feet. These waves travel at different speeds and angles with different types of rock, including rocks of different temperatures and rock moving in different directions. The small function below, the Northeast, the area of the unusually high temperature, but the photos are pretty fuzzy.

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Enter the EarthScope project, a National Science Foundation-funded company which placed thousands of seismic detectors and other instruments in the United States to get a clearer picture of the different functions — such as the earthquake faults and the different layers of ancient rock that lurk under the surface. Levin compared the EarthScope data to go from the use of a small flashlight in a dusty room with an overhead light.

Or, to compare with other world-the ease of the project, “it is similar to the sending of the Hubble telescope,” he said, referring to the legendary space telescope.

With the help of the undergraduate students working on a thesis projects, Levin and his colleagues found that the telltale stretch marks left as the rock in the interior of the Earth moves, were the same area where the rock below the surface appeared warmer.

All in all, the evidence suggests that a blob of hot rock ‘ n 100 miles (160 kilometers) to down-welling upwards in the upper part of the Earth’s mantle (the layer of Earth just below the crust), the study authors said.

The exact source of this blob is not clear; it does not have the deep roots down in the mantle of the earth as seen in hotspots such as those that lie below the Yellowstone or the Hawaiian Islands, and the fuel of the former hot springs, and Hawaii volcanoes found at each place, Levin said.

Barbara Romanowicz, a geophysicist at the university of Berkeley, who was not involved in the research, said in an e-mail that this blob may be attached to a finger of the material deeper in the mantle that she and one of her graduate students describe in work currently under review for publication in a scientific journal. That finger slide horizontally along a hotspot track (or the track if the tectonic plates shifted over a volcanic hotspot) of the mid-Atlantic ridge, the seam that runs from the middle of the bottom of the sea and inland waterways and against the north, ” she said.

“There may be other functions, such as the document along the track to tapping into the deeper tubes. The data are just not there to see them,” Romanowicz said.

The blob is the small size and the warm temperature also suggest that it is a relatively young feature on the scale of tens of millions of years old — because it probably would have cooled down when they were younger, ” he said. Also, there are no surface features that can be connected to it, as it sits well below the lower edge of the tectonic plate, Levin added.

The mechanisms that cause the bubbles of the mantle material to form closer to the surface than would normally be the culprit for the blob, he said, but that would be more work to investigate.

Another big question is whether this is a attribute that happens more in general, under the Earth, the continents, or if it’s more of curiosity. To answer that, scientists would need to implement versions of EarthScope on other continents to have the same kind of precise images obtained for North America, Levin said.

“This is the kind of resolution we need everywhere, and I would say, not only under the continents, but also under the oceans. Perhaps even more under the oceans,” Romanowicz said. Cost and technical problems have hampered such efforts to date, but there is a renewed interest in the performance of such networks. “This will help you figure out the pipes in the Earth mantle, and much of the action is under the oceans,” she said.

Original article on Live Science.

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