Why fracking won't cause subsidence
There are drains, sewers and tunnels that have been built much nearer to the surface and directly under our homes, but that haven't caused subsidence - even though they're in present in the ground where it is much softer.
A shale gas well, right down at the bottom where the fracking takes place, has an internal diameter of just 6 cm and is found at depths of over a mile. There is no reason to believe that this sort of infrastructure would be any more likely to cause subsidence than those pipes and tunnels nearer the surface.
The fractures that are created from a horizontal well extend vertically too, and so even as they close over time because of the pressure of the surrounding rock, they are not going to cause the shale to slip.
Check out our comparison between the 6.2 metre diameter Crossrail tunnel, that runs under London at depths of up to just 40 metres, and the 6 cm shale gas borehole running under Lancashire at a depth of at least 1,300 metres. We've produced it to scale so you can really see the differences involved. Even if the horizontal or lateral wells are "laddered" or "multi-stacked" because of the thickness of the shale, the fact that the borehole diameter is so small, at depths of over 1,300 metres, and with all those different layers of rock above suggests that it's not a problem.
As far as we can tell, there is no credible risk of fracking causing landslip, heave or subsidence.