for cracks in glaciers. maybe something here:
http://wiki.openstreetmap.org/wiki/Proposed_features/Climbing
????
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RP:make something up, document it:
natural=crevasse sounds likely
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HB Aug 25 2012: natural=crevasse now exists,
http://wiki.openstreetmap.org/wiki/Proposed_features/crevasse
Fine with me, approving for the Antarctic.