Underneath a Glacier

Here's a quick clip from the PBS series NOVA showing a French scientist who studies glacial activity on Mont Blanc. Descending into a cave beneath the glacier, braving underground torrents of meltwater, he gets to see this:

http://www.youtube.com/watch?v=njTjfJcAsBg

350 feet of ice above him! That's quite a river, even at such a slow speed.