Global warming, holes in the ozone layer, and lush golf courses in the desert all reveal mankind’s ability to mess with the planet. But the Earth’s core, protected by an outer core consisting of some 1,000 miles of 8,000˚F liquid metal, appears safe from our meddling.
Geothermal energy systems don’t drain heat directly from the core. Instead, they pull radiant heat from the crust—the rocky upper 20 or so miles of the planet’s surface—either by sucking up pockets of heated water or by circulating water through the hot rock. Power plants then use steam from the hot water to spin turbines to make electricity. Geothermal energy generates 7 to 10 billion watts worldwide, barely enough to account for 0.05 percent of global energy consumption and far less than the estimated 44 trillion watts the planet produces.
But drawing energy from the crust won’t send it into a deep freeze: Its heat is constantly renewed by the virtually continuous decay of radioactive elements sprinkled throughout it. “Cooling the Earth’s core by drawing geothermal energy from the crust is like trying to cool the western end of Lake Superior with a few ice cubes,” says Paul Richards, a professor of natural science at Columbia University.
It’s a good thing that we can’t cool the core. The spinning metal there generates Earth’s magnetic field, which protects us from deadly cosmic radiation. If the outer core cooled, the liquid would solidify, and both it and the solid inner core would grind to a halt, the magnetic field would dissipate, and high-energy cosmic radiation would bombard the planet, essentially turning Earth into a giant microwave and ending life on the surface.