by Julia Conley and John Light
Hydraulic fracturing or fracking — a method of extracting natural gas from underground shale formations — has become a contentious issue across America, especially in New York, Pennsylvania, West Virginia and Ohio, states that sit on top of the Marcellus Shale, the largest known deposit of shale gas in America. Some estimate that the shale formation could contain nearly 500 trillion cubic feet of gas — enough to power all American homes for 50 years. Oil and mining companies want to get the gas out, but environmentalist groups say the process is not safe. Here are the facts: