SVR Murthy

Quicksand is a hydrocolloid gel consisting of fine granular matter (such as sand or slit), clay,and salt water.The origin of the name refers to "quick" in the older meaning of "alive" rather than "fast," and is thus similar to the origin of the term quick silver for mercury.

When undisturbed it often appears to be solid but a minor (less than 1%) change in the stress on the quicksand will cause a sudden decrease in its viscocity. After the initial perturbation—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 suddenly increase. In order to move within the quicksand, a person or object must apply sufficient pressure on the compacted sand to re-introduce enough water to liquifey it. The forces required to do this are quite large: to remove a foot from quicksand at a speed of one centimeter per second  would require the same amount of force as "that needed to lift a medium-sized car." 

It was commonly believed that the behavior of quicksand was due solely to saturated or supersaturated suspensions of granules in water. Pressure from underground sources of water would separate and suspend the granular particles, reducing the friction between them.

. As quicksand is rarely more than a few feet deep, there is usually little danger of sinking below the surface. Even when the quicksand is deep enough, deliberate effort is required to sink below the surface. Quicksand is typically denser  than the human body  meaning that a body is much more buyoant  in quicksand than in water. Thus, the body will float quite easily in quicksand.