(Chicago, IL) - People are being warned not to venture on the shelf ice on Lake Michigan.  This comes after a man videotaped himself falling through shelf ice in Chicago.  Fortunately, the man was able to get out quickly.  However, experts said he was lucky because shelf ice often has air pockets.  The air pockets make the ice brittle and climbing out sometimes results in crashing back through the ice over and over again until exhaustion sets in and possibly death.

Shelf ice is created when water from waves crashing to the shoreline freezes.