The next time you find yourself wandering through a wet, sandy, unfamiliar place, it might be wise to keep an eye out for that exotic menace known as quicksand. If you are not careful, you could lose your life. Or, far more realistically, a shoe.
Quicksand has long been a favorite hazard in low budget adventure movies and cartoons. It is usually shown as a hidden pool of sandy goo waiting to swallow anyone who steps into it. The victim sinks slowly, calls for help, and disappears beneath the surface unless a vine or a heroic friend comes to the rescue. Real quicksand is much less dramatic, but it does have a more dangerous cousin that would be genuinely frightening if it ever appeared in nature.
Traditional quicksand forms when water rises from below and saturates sand, silt, clay, or any other grainy soil. Dry sand can support a surprising amount of weight because friction between the grains creates a strong network that distributes pressure. When enough water seeps in, the grains begin to float within the water, reducing friction and weakening the structure. Because the water comes from below, the top layer often looks dry and harmless.
In most cases, quicksand is only a few feet deep, which makes it more of a messy inconvenience than a deadly trap. The biggest danger is exhaustion, since struggling to pull your legs free can take a tremendous amount of effort. Moving your limbs under the surface creates vacuum pressure that makes every motion harder. This same effect is why certain types of mud can yank your shoes right off your feet.
Even in the rare situation where quicksand is deep enough to submerge a person, sinking all the way under is unlikely. The human body is more buoyant in quicksand than in water, so a person tends to float on the surface like a cork.
That does not mean there are no risks. Carrying a heavy pack can reduce buoyancy enough to make sinking possible, so a quick release backpack is a smart idea in areas where quicksand is common. Flailing around can also make you sink deeper by increasing the suction effect. And while the quicksand itself may not be deadly, heat exhaustion, rising tides, wildlife, and other environmental hazards can turn the situation dangerous. Not to mention the near certainty that sand will end up in places you would rather it did not.
There is also a more sinister version known as dry quicksand, which is potentially far more dangerous, although it has never been confirmed in nature. Dry quicksand forms when grains of sand create an extremely loose structure that can barely support its own weight. In the lab, this is created by blowing air through the sand. In theory, it could also form naturally if very fine sand accumulates after being carried by the wind. When something heavy lands on this fragile structure, it collapses instantly, causing the object to sink rapidly while a plume of sand shoots into the air.
A deep, naturally occurring patch of dry quicksand would be a serious hazard, capable of burying a person almost instantly. Although no verified examples have ever been found, there are old stories of travelers, animals, and even entire caravans vanishing into the sand. These tales are usually dismissed as folklore, but the idea is not entirely impossible. During planning for the Apollo moon missions, scientists even added large plates to the Lunar Module’s legs in case the astronauts encountered dry quicksand on the moon. The precaution turned out to be unnecessary, but it shows that the concept was taken seriously.
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