The facts behind the frack

To call it a fractious debate is an understatement.

Hydraulic fracturing, or fracking, wrenches open rock deep beneath the Earth's surface, freeing the natural gas that's trapped inside. Proponents argue that fracking-related gas recovery is a game changer, a bridge to the renewable energy landscape of the future. The gas, primarily methane, is cheap and relatively clean. Because America is brimful of the stuff, harvesting the fuel via fracking could provide the country jobs and reduce its dependence on foreign sources of energy.

But along with these promises have come alarming local incidents and national reports of blowouts, contamination and earthquakes. Fracking opponents contend that the process poisons air and drinking water and may make people sick. What's more, they argue, fracking leaks methane, a potent greenhouse gas that can blow up homes, worries highlighted in the controversial 2010 documentary Gasland.