Fracturing shale rock to release the natural gas inside, called “fracking,” is either a great method for extracting new energy from existing resources or an ecological disaster that endangers our drinking water. Or both.

Extracting natural gas from shale formations has been going on for some time, but mostly through vertical wells that make extraction simple.
Remaining deposits are largely in horizontal wells, which need external stimulation to release the gas.
The most common technique is fracking—blasting millions of gallons of water mixed with sand and chemicals into the well to break up the shale and release the gas.
The Potential Gas Committee released a study in 2009 indicating that the United States has a resource base of 1,836 trillion cubic feet of natural gas—enough to supply our needs for the next hundred years.
Most of it is in geologic formations like the Marcellus Shale, which extends from Tennessee to New York. The gas is difficult to retrieve, though, without techniques like fracking.
The problem, environmentalists say, is the side effects of pumping millions of gallons of toxic—even carcinogenic—chemicals into the ground and then disposing of it. The Associated Press reports that
The “fracking liquid gushes back with natural underground brine, a brew now intensely salty and containing barium, strontium and radium from the earth.”
Oil and gas lobbyists have managed to have their formulas declared trade secrets so they're not required to disclose the chemicals they're using, but Pennsylvania's Department of Environmental Protection reports that public water utilities are struggling with dangerous levels of cancer-causing chemicals downstream from the wastewater release sites. A quick search on YouTube shows frightening videos of people setting their tap water on fire near fracking sites as far apart as West Virginia and Colorado, home of the Denver-Julesberg and Piceance Basins of geologic shale.
People the entire length of the Marcellus Shale have organized protests, and created marcellusprotest.org to keep residents informed of the concerns and ways to fight fracking. Director Josh Fox created the documentary Gasland as an exposé on fracking.
The problem is that there are no clear studies indicating actual harm caused by the process. BusinessWeek points to a New York Times discovery that EPA documents reveal radioactive wastewater being discharged into river basins.
Yet the government specifically exempted fracking from the Safe Water Drinking Act as part of the 2005 Energy bill.
The Colorado Oil & Gas Conservation Commission assured residents that the methane present in their tap water came from naturally occurring processes rather than as a byproduct of fracking, though it's unclear how that was expected to reassure them about flaming tap water.
The only things we know for sure are that fracking uses toxic chemicals, the government is not studying—or at least not releasing information about—the potential dangers, and people are drinking flammable water.
(Source: Contributor Network