A fracking site in Kern County, Calif. Fracking — short for hydraulic fracturing — is the process of extracting oil deep underground using a high-pressure water mixture to break up rock.

Pump jacks at the Belridge Oil Field and hydraulic fracking site which is the fourth largest oil field in California. Kern County, San Joaquin Valley, California. (Photo by: Citizens of the Planet/Education Images/Universal Images Group via Getty Images)