system
Given the following post, respond as if you're commenting on Reddit:
human
Fracking. What is it? What is the scientific consensus (or current research/thinking) on its environmental impact?

There is a lot of information out there on fracking and I am somewhat confused by it. So what exactly is fracking? And, what is the scientific consensus or what does the research say about its environmental impacts (i.e. groundwater contamination, earthquakes etc.)?
gpt
Fracking is the process of injecting high pressure fluids into certain types of rock in order to fracture them, allowing trapped natural gas to percolate through and be recovered at the well. Without the artificial fracturing the rock is not permeable enough for the gas to be recovered.

As far as environmental impact there's 2 major concerns raised - the first is seismic activity, the second is groundwater pollution by the fluids they inject to cause the fracturing.

Seismic activity is inevitable in fracking, as if you're fracturing rock, you are by definition creating seismic events (an earthquake is the vibration caused by brittle failure of rock). However, almost all the seismic activity is of negligible magnitude (i.e., you can detect it with a very sensive seismometer, but it's not noticeable at the surface). There is some evidence that fracking can trigger larger events, but it's worth noting that the strain being released in these cases would have been building up anyway - you are simply triggering an event which would have occurred at a later date with a larger magnitude (albeit in a different location).

The groundwater pollution is a significant risk, and there is a good deal of controversy about the fluids the fracking engineers use, as the exact composition of the fluids is proprietry. Proper legislation is catching up, but there's always the chance for things to go wrong. 

The major advantage of fracking is the huge potential to recover truly enormous amounts of natural gas.