Did you know that there are three types of ‘fracking’ or ‘hydraulic fracturing’? Natural, traditional and ‘super fracking’. While natural hydraulic fracturing already goes on for hundreds of millions years deep in the Earth’s crust, traditional fracking has only been in use in the conventional gas and oil production for more than 50 years. ‘Super fracting’, on the other hand, only became economically viable some 20 years ago. Its recent development results, though, in a lack of sufficient scientific knowledge of the poorly understood geophysical processes involved, to base any further technological development and to properly assess the environmental concerns associated with ‘super fracking’.
If you want to know more about this subject, I can only recommend this recently published instructive, balanced and comprehensive introductory article on ‘super fracking’:
Turcotte, D.L., Moores, E.M. & Rundle, J.B. Super fracking. Physics Today 67(8), August 2014, 34-39. doi: http://dx.doi.org/10.1063/PT.3.2480.