A controversial method for extracting oil and natural gas from rock is prompting environmental organizations to action. But oil and gas experts say the fracking is safe and necessary to provide clean energy. The Marcellus Shale is a rock formation deep under Pennsylvania, New York, Ohio and West Virginia. It's believed to hold 1.9 trillion cubic feet of natural gas. Oil and gas company's use a method called hydraulic fracking to extract it. The process involves drilling a hole and pumping in water to fracture the rock to release the gas. "The fracking fluid itself is 99.5 percent sand and...