Fracking

Hydraulic fracturing, or fracking, is a method of extracting oil and gas from tight rock formations, such as shale. Operators drill a well vertically and then horizontally, and pump water, sand and chemicals at high pressure to crack the rock, so that hydrocarbons flow to the well. The sand holds the fractures open.

Combined with horizontal drilling, it was commercialized in the 2000s, first for natural gas in the Barnett Shale in Texas and then for oil in places such as North Dakota's Bakken and the Permian Basin. It led to a dramatic increase in U.S. production, transformed energy independence, lowered natural gas prices and helped cut power-sector carbon emissions as gas displaced coal.

Supporters argue that fracking brings economic benefits, jobs, lower energy costs and geopolitical advantages. Critics raise environmental concerns, including methane leaks, water use, wastewater disposal and its link to induced earthquakes in places such as Oklahoma, possible groundwater contamination and the emissions from burning fossil fuels; studies of risks to drinking water have found problems in specific cases. Several states, such as New York and Maryland, have banned it; the federal government has a limited regulatory role, with much oversight by states. Politicians' positions, for example on banning fracking, have been prominent in campaigns in Pennsylvania. See net zero.