Legend Of Korra: Will It Bend!

[thubby]

how do you come to that conclusion?
tunnel, no.. bending..
bending the ground is pretty much the definition of earthbending. even metalbending happens because of tiny particles of ground mixed with the metal. tunneling underground is precisely what badgermoles do

because not all ground can support itself. the mudd you find when you start digging near water, for example, simply won't hold its shape without substantial bracing if it can be done at all.
many areas with soft or brittle stone formations won't hold up if you try and bore through them.