Quicksand - Properties

Properties

Quicksand is a non-Newtonian fluid: when undisturbed, it often appears to be solid ("gel" form), but a minor (less than 1%) change in the stress on the quicksand will cause a sudden decrease in its viscosity ("sol" form). After an initial disturbance — such as a person attempting to walk on it — the water and sand in the quicksand separate and dense regions of sand sediment form; it is because of the formation of these high volume fraction regions that the viscosity of the quicksand seems to increase suddenly. Someone stepping on it will start to sink. To move within the quicksand, a person or object must apply sufficient pressure on the compacted sand to re-introduce enough water to liquefy it. The forces required to do this are quite large: to remove a foot from quicksand at a speed of .01 m/s would require the same amount of force as "that needed to lift a medium-sized car."

Because of the higher density of the quicksand, it would be impossible for a human or animal to completely sink in the quicksand, though natural hazards present around the quicksand would lead people to believe that quicksand is dangerous. In actuality the quicksand is harmless on its own, but because it greatly impedes human locomotion, the quicksand would allow harsher elements like solar radiation, dehydration, hypothermia or tides to harm a trapped person.

The way to escape is to wiggle the legs as slowly as possible in order to reduce viscosity, to try spreading the arms and legs far apart and lying supine to increase the body's surface area, which should allow one to float.