How does quicksand form?« Back to Questions List

Films have made quicksand the scariest disaster one can face in life. People who wander in wild areas are also warned about quicksand being a deadly trap. But actually it is not as bad as they have been portrayed, but yes they can be dangerous occasionally. During World War II, an entire US army truck was engulfed by quicksand in Germany. It is a natural phenomenon that occurs at places closer to water sources.  They are most often found on banks of river, lakes, coastal areas and in marsh lands.

Quicksand is a pocket of ordinary sand that has been saturated by water moving in from an underground source. It is a colloid hydrogel.  It may consist of granular particles of clay, sand or slit along with water.    For instance water from a nearby river may seep upward through the sand. This force the sand grains apart, forming a soup like mixture in which heavy objects sink. It gets created when water trapped in the material finds it difficult to escape. The resultant liquefied soil will not have sufficient strength to support the weight of anything that falls in it and hence gets sink.   

Liquefaction of is special feature of quicksand. The formation may look quite solid but a change in pressure on top of the formation causes liquefaction.  A minor change in the pressure is sufficient to change its viscosity.  The presence of water creates a fluid like situation causing the object to sink.  Once the weight of object equals the weight of displaced fluid, it starts floating due to buoyancy. 

An animal or man is unlikely to sink entirely into the quick sand, thanks to the high density of the fluid. Human body has an approximate density of 1 gram per milliliter whereas a normal quicksand has higher density of about 2 grams per milliliter. Sometimes, even materials with higher density float on quicksand unless it attempts to move. When caught in quicksand one must not panic. Any extra weight like backpacks should be discarded because extra weights could pull us deep inside. Lying on our back with arms and legs spread out one must try to move lightly to the safety of solid ground. Wilder the movements one makes, deeper he might sink. 
 

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