FRACKING is destructive to both people and the earth. The benefits are ephemeral and the damage is eternal. The primary dangers are increased earthquakes, the destruction of water supplies and the destruction of surface areas with drilling muds and subsurface tailings not to mention destruction of water supplies. Fracking is the shortcut name for "hydraulic fracturing," which comes from the pressurized water that splits or fractures the deep rock.
Basically a well driller drills a hole say 1-2 thousand feet deep and if appropriate directs the pipe in a horizontal direction. The earth, rock and water removed from the hole are deposited onto the surface into pits. A liquefied drilling "mud" is pressurized to say 2000 pounds per square inch and it is pumped down the hole. The composition of the drilling muds have been carefully classified as secrets by the various drilling companies. I don't know what the composition of the muds is but I believe that they are basically water, with the addition of a cheap acid such as Muriatic (Hydrochloric) Acid, to dissolve any limestone, fine silica to keep open any pores that are made by the drilling and pressurization process and possibly some detergent to insure that any oil or paraffin will be dissolved so as not to block any opened micro passages.
Water is essentially incompressible, so under pressure it will maintain its volume. As the fracking fluid pressure is increased the surrounding rock and soil are deformed, stress/strain, and the crystalline bonds in the subsurface rock are broken. The rock becomes more "liquid like" in that the rock's crystalline structure has been fractured/broken and later when the pressure is reduced any methane in the rock will be free to be released. This change in the deep rock is irreversible. For all time -- the deep rock will retain its more liquid character with a reduced structural integrity and earthquakes in the area will be more extreme due to the earth's diminished ability to resist any strain. The earth will shake and shear more readily as earthquakes relieve.stress in the earth.
The drilled hole has transcended any aquifer in the earth's surface. Now there is a connection from the deep-surface fracking area including any drilling fluid to the near-surface aquifer. If there is a leak in the casing or around the casing then drilling fluid or methane gas can seep into the aquifer. This explains why there have been water supplies that can catch on "fire" due to entrained Methane gas. This also explains how the drilling fluid which contains toxins can seep into the aquifer. It only takes 10-15 ppm of toxins in an aquifer to poison it and make it unfit for drinking for both people and livestock. Once an aquifer is poisoned it could take decades if not hundreds of years for the toxins in the water to be purged and the aquifer to become potable again.
In addition to gas and oil, millions of gallons of a fluid called flowback liquid are also pushed to the surface. Flowback liquid contains the injected fracking fluid as well as brines, ores, radioactive material, and hydrocarbons. The flowback liquid is stored on the fracking site in pits or tanks before being treated, recycled or disposed. Treating flowback water is expensive and beyond what most local treatment plants can handle. As a result, much of the flow back water is injected into deep underground wells for disposal. The deep injection wells can have the same problem with leaking casings etc. and can contaminate aquifers.
Economics - Generally fracking costs about $50 per recovered barrel or equivalent of petroleum fluids. This is expensive as far a drilling goes. In 2105-2016 with the price of crude oil being in the $30-40 range, new fracking drilling simply is uneconomical and has been discontinued.