(File Photo)

    BEIJING, June 27 (Xinhuanet) -- Researchers said the significance of Earth's internal heat has been overlooked and if it weren't for the hot rocks down below Earth's crust, most of the United States would disappear, except for some major Western mountain ranges, media reported Wednesday.

    Without it, mile-high Denver would be hundreds of meters below sea level, New York City, more than a quarter-mile below and Los Angeles would be almost three-quarters of a mile beneath the Pacific, researchers calculated.

    "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 at the University of Utah, U.S.

    Researchers said heat inside the planet accounts for half 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.

    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 some 900 mters deep in the Gulf of Mexico.

    Hasterok said heat from Earth's deep interior and from radioactive decay of uranium, thorium and potassium in Earth's crust 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. Coastal areas face a more immediate threat from global warming, which could raise sea levels and flood cities, he said.

    (Agencies)