[Overtaxed]

Would be kind of interesting to know just how they did it --

I thought they did it by busting up rock...and other things....with their roots/feet and maybe by sonic attack Hroom Hom!

[LinnieBeth]

did it by busting up rock...

I think you're right, and perhaps using themselves as battering rams?

[Scott from the Left Coast]

Well, that's kind of what I wondered...I can come up with ways that I imagined they did it -- but I'm interested in the interpretation of others (including the moviemakers).

They can certainly move around heavy objects with alacrity -- given that they stopped up and redirected rivers (with no machinery!).