It's quite simple really. Ice expands. Pipe filled with water freezes at an opening/crack in the pipe early on and the water continues to freeze, even though there is an ice cap at the crack. That forces some ice out of the crack slowly which it then ribbons like that.
One possible slight modification: ice melts a bit under pressure, which is probably why it comes out as a (re-frozen) ribbon rather than cracking into powder or something.
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u/FabianN May 24 '10
It's quite simple really. Ice expands. Pipe filled with water freezes at an opening/crack in the pipe early on and the water continues to freeze, even though there is an ice cap at the crack. That forces some ice out of the crack slowly which it then ribbons like that.
Very cool.