Dear wwh,

You wrote:

When it becomes over a hundred feet deep, the ice at the bottom cannot stay rigid any longer.

Why not? Is the mystery of glacial movement tied into this 100-foot depth? Avalanches make a lot more sense than this. I was about to give up on glaciers till I went back and read what you wrote above.

Sorry to be so thick here, but the glacier in my mind must not be at 100 feet yet and, therefore, not ready to slide on out.

Best regards,
DubDub
PS: To Helen: What a profusion of facts you have in your head! Astonishing!