This lake periodically fills up and then drains as the glacier moves, leaving icebergs stranded in the sand.

As a glacier moves, it picks up more ice and gets bigger and bigger.

And so rarely get to see a glacier move, or a cave of crystals?

"The crevasses change direction as the glacier moves, " he said, "and turn into thousands of Y chromosomes."

If two rigid sections of a glacier move at different speeds and directions, shear forces cause them to break apart, opening a crevasse.