What’s quicksand and can I drown in it?

What’s quicksand and can I drown in it?

Mona Chiang

You may have enjoyed watching many bad guys in Westerns getting sucked into a bottomless pit of desert quicksand. Sorry to disappoint you but, “I don’t see how that’s possible,” says Charles Byers, a geologist (earth scientist) at the University of Wisconsin. Finding quicksand in your backyard may be more likely, because the desert lacks the one ingredient that makes sand “quick”: WATER!

Quicksand is usually found near flowing water like a beach or riverbank. When sand is completely saturated (soaked) by water and can’t drain, water acts as a bubble around individual grains. This lessens the friction (rubbing of surfaces) between sand grains. “When you step on wet sand, the grains just slide past one another,” Byers explains. The sand can’t support a person’s weight, and what occurs is called thixotropy [THIX-O-tro-pee]–a solid substance that liquefies under force.

Can you drown in quicksand? “Not likely,” says Byers. A solid will sink in liquid only if its density (mass per unit volume) is greater than the liquid. The human body is less dense than a sand-and-water mixture (quicksand is even denser than water!). But if you do fall into a deep watery sandpit, don’t struggle. Struggling (as in an ocean undertow) only makes you lose footing, slide in deeper, and go under. Instead, slowly bring your legs up, lie in a horizontal position, and float on your back. “By spreading yourself over a larger surface area you don’t put as much force on one spot,” says Byers. “This holds you up better.”

So the next time you watch a movie and see quicksand in the middle of a desert, start laughing!

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