this is a long shot, but i think it might be due to the fact that rain, being made of a liquid type stuff, and soil being porous, and as a result of these 2 combining during a passing cloud event, resulted in the surface structure of the soil softening to a point where it can no longer support the weight of anything without deforming. aircraft included.
Last edited by Ultralights; 2nd Oct 2009 at 22:23.