Because it is plastic is why it flows, and why it becomes distorted. The bottom flows as well as the top. That is what your reference points out. It is what I was telling you. If ice was rigid (like granite), it would not flow at all. (The pressure at the bottom of a column of ice transforms the ice into crystalline structures that are not present at normal pressures. Consult a phase diagram for water to see how many numbered kinds of ice there can be. https://en.wikipedia.org/wiki/Phases_of_ice) (Yes, I know that even granite or basalt will move in the presence of fault lines, but that is over geological time, not human civilization time.)

So, you admit that glacier ice flows. Then you have to realize that trying to bore tunnels into that kind of substance is a losing game. There was too much movement during the tenure of Camp Century, which is WHY they had to abandon it.