The term is shorthand for hydraulic fracturing, which is a process of extracting gas or oil deep underground using a high-pressure mixture of water, sand and chemicals to break up rock.
Pennsylvania is the second-largest producer of natural gas in the country.
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Both candidates claim they will not ban fracking.
Harris was asked about her 2019 presidential bid for president when she firmly stood for a ban.
"I will not ban fracking," Harris clarified during the debate. "My position is that we have got to invest in diverse sources of energy so we reduce our reliance on foreign oil."
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"Fracking. She's been against it for 12 years. She will never allow fracking in Pennsylvania. If she wins the election, it will end day one," Trump rebutted.
Federal energy statistics indicate U.S. natural gas production and crude oil production have hit record monthly highs in the past year.