In Hollywood, few moments have you on the edge of your seat more than when a character gets trapped in quicksand. The stunt is sometimes used during a peak dramatic moment, like in Lawrence of Arabia, but it can also be used for comedic relief, like on Gilligan's Island.
Yet quicksand is more than a plot device — it's very real, and has been trapping people for centuries. The messy stuff exists just about everywhere on the planet, so if you do encounter it, be careful. Though it can't drag people under as you may have seen on screen, quicksand is still very dangerous. Check out these common questions about the stuff and let the answers sink in.
What Is Quicksand Made Of?
At first glance, quicksand looks like wet sand you typically see at the beach, which explains why people step in it without thinking twice. However, unlike slightly damp beach sand, quicksand is saturated with water. This saturation occurs when water isn't able to flow away, usually due to the presence of dense material, such as a bed of clay that stops drainage.
Quicksand often has salt and clay mixed in as well. The presence of salt results in clay particles clumping together instead of intermingling with the grains of sand, and adds to quicksand's instability.
But some quicksands form without the presence of salt. In Brazil, quicksand was found around a lagoon where bacteria created a crust that looked like the regular ground but turned into quicksand when stepped on.
Quicksand can form in any location where water and sand meet, such as near rivers, lakes, beaches, marshy areas, and natural springs. Quicksand can also be created when water escapes from an underground reservoir, perhaps due to a natural disaster.
Why Do People Sink In Quicksand?
The water saturation of quicksand cuts down the friction between sand particles. As a result, quicksand cannot support any weight. If someone steps on quicksand and adds weight, the pressure disturbs the quicksand's structure. Quicksand then turns into a viscous liquid, which people and animals sink into.
After someone or something has sunk into the liquified sand, quicksand becomes more viscous and starts to solidify once more. This makes it harder to move, increasing the difficulty of escape.
Quicksand's inability to support weight can have consequences beyond individuals sinking into it. If quicksand appears around a bridge or building, the structure can collapse.
How Dangerous Is Quicksand?
It's true that if you ever step into quicksand, you'll start sinking into its murky depths. Fortunately, despite what’s shown in movies and on television, you don't need to worry about being swallowed up and disappearing beneath the surface.
A human body is less dense than quicksand (one gram per milliliter for humans vs. two grams per milliliter for quicksand). If you go into quicksand feet first, buoyancy will keep you from sinking much more than waist-deep — though your legs are denser, your lungs offer enough upthrust to keep your head above the surface.
That doesn't mean quicksand isn't dangerous, though. For one thing, it takes time for anyone to get themselves out of it. A man hiking in Utah's Zion National Park in 2019 was sucked into quicksand and remained stuck for hours. He experienced hypothermia, exposure, and other injuries before he could be rescued.
In some situations, such as when water levels rise due to incoming tides, people can drown when they're trapped in place by quicksand. Such fatalities are rare, but they've happened even as recently as 2012 and 2015.
What Should You Do If You Step in Quicksand?
If you do stumble upon quicksand, here are a few tips about what to do next. First, though it may be hard advice to follow, try not to panic. You risk being dragged down further if you struggle.
Second, don't just ask someone who's nearby to pull you out of the quicksand. The amount of force required to lift a foot out of quicksand at a rate of one centimeter per second is 100,000 newtons. This is enough power to lift a midsize car, and it means that the amount of force needed to lift someone out of quicksand could backfire and cause more extreme injury.
Instead, take time to work your way out of the quicksand. One tactic is to slowly move your legs and feet. This allows water to get to the quicksand that's gripping you, which will lessen the strength of that hold. Spreading your weight over as much space as possible will also help.
Remember, your body's density is less than quicksand's density, so you have buoyancy on your side. With time, you’ll be able to get free.