The science behind QUICKSAND


Science for youth

By Hiya Islam

As portrayed by cartoons quicksand is a gooey monster that feeds on anything that falls in it. A person who mistakenly steps in disappears rapidly underneath, pulling down whoever is trying to help him as well. It is like a death pit full of mystic force. Its origin is unknown and there are warning signs scattered near one. They are hard to spot by looking, as from above they look just like normal sand. It is only the application of force or weight that shows its real “sucky” nature.

A closer look by scientists has unraveled the mystery. Quicksand is composed of sand, water, clay, and often, salt. The sand is said to be saturated with water. The source of this water is underground reservoirs. The water travels up due to pressure and remains trapped between sand particles. This causes sand particles to lose friction as they are separated from one another and enables them to slide against one another. Unlike desert sand, this sand loses the ability to tolerate weight and any object, heavy enough, dropped on it will inevitably sink. Quicksand, in short, is a non-Newtonian fluid. Such fluids show weird characteristics. They change their phases from solid to liquid and vice versa under pressure. In other words, they become thicker or runnier. If the stress is removed, the material will go back to its original state eventually.

Quicksand can be found in beaches, riverbanks, marshes and shorelines. It needs excess water to form which is why one will never come across such terror in deserts. A common myth is that quicksand is bottomless. In fact, these are just a few feet deep. And more importantly, it cannot drown humans. The average density of humans is about 1 g/cm3 whereas that of quicksand is about 2 g/cm3. Therefore, humans being less dense can more easily float on quicksand than on water which is 1 g/cm3!

However, when stuck in quicksand getting out can be tricky. A person only sinks deeper as panic strikes and the movement increases. Agitation makes the sand runnier. But a person can only sink chest-deep at most. As already explained, given some time the quicksand will return to a thicker state. The key to your escape is to remain calm and slowly move your trapped parts to the surface. Try spreading your hands and legs or laying on your back to increase surface area and help you float. All this mess can be surely avoided if you carefully tread on land. Perhaps, get a stick to prod on the ground next time you are on an adventure.

Quicksand’s cousin, dry quicksand is something to watch out for. In place of water, air separates the sand particles. And it can potentially swallow anything wholly as the presence of air makes it less dense than water. These are formed by flowing air through fine grains of sand. Fortunately, dry quicksand has only been created in lab. There are no confirmed natural occurrences, phew!

Hiya Islam is a student of BRAC University.


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