By Todd Bates - Rutgers University
Slowly but steadily, an enormous mass of warm rock is rising beneath part of New England. But don’t worry—a major volcanic eruption isn’t likely for millions of years.
“The upwelling we detected is like a hot air balloon, and we infer that something is rising up through the deeper part of our planet under New England,” says Vadim Levin, a geophysicist and professor of earth and planetary sciences at Rutgers University–New Brunswick and lead author of a new study in Geology.
“It is not Yellowstone (National Park)-like, but it’s a distant relative in the sense that something relatively small—no more than a couple hundred miles across—is happening.”
“Our study challenges the established notion of how the continents on which we live behave,” Levin says. “It challenges the textbook concepts taught in introductory geology classes.”
Researchers tapped seismic data through the National Science Foundation’s EarthScope program in which thousands of seismic measurement devices 46.6 miles apart covered the continental United States for two years.
The EarthScope program is designed to reveal the structure and evolution of the North American continent and the processes that cause earthquakes and volcanic eruptions.
Levin studies seismic waves, or the vibrations that pass the planet following earthquakes. Seismic waves provide a window into Earth’s interior by revealing the shapes of objects, changes in the state of materials, and clues about their texture.
The new study focused on New England, where scientists had previously documented an area of great warmth (hundreds of degrees Celsius warmer than neighboring areas) in the Earth’s upper mantle. The lithosphere, Earth’s solid outer shell, consists of the upper mantle and the crust that includes the surface.
“We’re interested in what happens at the interface between tectonic plates—thick, solid parts that cover our planet—and material in the upper mantle beneath the plates,” Levin says. “We want to see how North America is gliding over the deeper parts of our planet. It is a very large and relatively stable region, but we found an irregular pattern with rather abrupt changes in it.”
The upwelling pattern appears to be largely beneath central Vermont and western New Hampshire, but it’s also under western Massachusetts. It may be present elsewhere, but the study’s findings were based on available seismic observations.
“The Atlantic margin of North America did not experience intense geologic activity for nearly 200 million years. It is now a so-called ‘passive margin’—a region where slow loss of heat within the Earth and erosion by wind and water on the surface are the primary change agents. So we did not expect to find abrupt changes in physical properties beneath this region, and the likely explanation points to a much more dynamic regime underneath this old, geologically quiet area,” Levin says.
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