An informal name for hydraulic fracturing, which is a method used to release and recover oil and natural gas from rock in natural underground reservoirs by fracturing the rock using a pressurized fluid. By injecting a fluid such as water, oil, or gas at high pressures into channels within the reservoir rock, new channels are created by fracturing the rock thereby increasing the release and recovery of the fossil fuels. A proppant such as sand is also used, which is intended to fill the cracks and prevent collapse of cracks. There is some concern that fracking results in noticeable seismic activity and that drinking water supplies from underground aquifers may become contaminated with oil.