Different rock types, like sandstones, shales, and coal seams, have different physical characteristics that
impact the likelihood of the ability of fractures to grow upward toward the surface from various depths. When
they are sought after for fossil fuel extraction, the depth of the rock unit below the surface, the stiffness of the
rock unit being targeted and of the surrounding lithologies, the regional
stresses on the rocks, the depth of potable water, and many other considerations are used to predict the impact
hydraulic fracturing will have on a particular lithology