Hydraulic fracturing, or fracking, pumps millions of gallons of water mixed with fine sand and chemicals deep into oil and gas wells to crack gas-bearing rock.
Hydraulic fracturing pumps many thousands of gallons of mainly water and sand, with a few chemicals, at high pressure into tight gas-bearing shale deposits (hardened muds), creating cracks that allow gas to flow back up the well to the surface ( Shale Shock).