The heat generated by the Earth's interior is partly responsible for keeping some big portions of the planet's crust, and hence most of us, above sea level.

That's the news out of the University of Utah where conventional thinking on the matter is being challenged.

"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.

What if this "heat engine" died? Only the tips of some of the tallest U.S mountain ranges would peek above the water. But there's no point in worrying about that for now.

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.

Better to worry about surface temps, it looks like.