Actually the some of the main FE's come unto cadmium's conclusion as well, the ice wall is 150ish feet high, what is below that is most likely rock, very dense and solid rock.
This would not only be important for the point youre bringing up right now, but the fact that ice floats, so there is a rock wall under this.
And to stop any whiny posts, I did not make this up right now, it was discussed at legnth in a thread