Dry Quicksand

chessie writes "Just in time for the holidays, new and improved quicksand! The new dry quicksand is a physical curiousity, made with air and sand instead of water with porewater pressure overcoming the density of sand . It is possible to vanish into a pile of completely dry sand as well. Worse, their sand looks the same as the normal, weight-supporting variety. Obviously, the US Army wants in on it."