Salt Lake City – If it weren’t for the hot rocks down below Earth’s crust, most of North America would be below sea level, report researchers who say the significance of Earth’s internal heat has been overlooked.
Without it, mile-high Denver would be 727 feet below sea level, the scientists calculate, and New York City, more than a quarter-mile below. Los Angeles would be almost three-quarters of a mile beneath the Pacific.
In fact, most of the United States would disappear, except for some major Western mountain ranges, according to research at the University of Utah.
“Researchers have failed to appreciate how heat makes rock in the continental crust and upper mantle expand to become less dense and more buoyant,” said Derrick Hasterok, a graduate student in geology and geophysics.
Hasterok and his professor, David Chapman, published their findings in the June online issue of Journal of Geophysical Research-Solid Earth.
In what they said was the first calculation of its kind, the researchers said heat inside the planet accounts for half of the reason land rises above sea level or higher to form mountains.
Scientists previously gave other factors greater weight in explaining elevation differences, such as the density and makeup of rocks and tectonic forces.
The Utah team calculated how much of North America would sink if the engine of heat were taken away, leaving regions as relatively cold as the bottom of the vast Canadian shield – bedrock that hasn’t changed for billions of years.
They did it by estimating temperatures under the North American plate based on previous experiments that bounced seismic waves deep underground. The waves travel faster through colder, denser rock.
Their measurements showed that among coastal cities, New York would drop to 1,427 feet below the Atlantic Ocean, and Boston and Miami even deeper. Los Angeles would rest 3,756 feet below the surface of the Pacific Ocean.
New Orleans, still recovering from Hurricane Katrina’s 2005 storm surges, wouldn’t have a chance without planetary heat. No levee could protect the city, which would sit 2,426 feet deep in the Gulf of Mexico.
Hasterok said heat from Earth’s deep interior will stay around for a long time to come. Even if the planet’s interior cooled, it would take billions of years for continents to sink.
