Sifting through the causes, concepts and misconceptions of quicksand

Despite growing up in tame suburban landscape of sidewalks and lawns, my kids are very concerned about how to deal with quicksand. I can only assume that repeated viewings of Wreck It Ralph and The Force Awakens (no Princess Bride yet) have helped build up the mystery of watery sand, particularly since fiction usually portrays it as something perilous that can capture a hero without warning. Of course, having seen DuckTales and G.I. Joe, I know that my kids’ concerns are unfounded, and that we’ll never run into quicksand near our home. Or so I thought.

Sources of soupy sand

Well, I was right about the general composition of quicksand. It’s any loose, grainy soil with a large concentration of water in it to turn it into a fluid. One of the most common places to run into quicksand is at the beach when water rushes into loose sand. Sand that’s only moist is likely to clump together, but with enough water flowing through the sand, each grain will separate and basically roll around independently of each other. The resulting soup can then look like solid ground from above, but has a consistency just a bit thicker than water when you step into it. While quicksand in nature is going to involve water, Mark Rober has a great demonstration of how sand can behave like a fluid using air as well.

Now, not every puddle turns into quicksand, obviously, mainly because the water needs to flow in a way that helps separate the grains of sand or soil. A great way to break up clumped soil turns out to be vibrations from earthquakes, and tremblors are a major cause of quicksand in all kinds of environments. Quake-produced quicksand is actually a significant safety hazard, not so much for people suddenly in need of conveniently placed vines, but for buildings that partially sink into the ground, stressing or warping their structural integrity. As such, researching the exact combinations of vibrations, soil composition and water flow has been the subject of research looking to predict which locations are most likely to suddenly turn to soup when the ground shakes.

Saving yourself from sinking

Aside from our next trip to the beach, the intersection of quakes and quicksand adds sudden legitimacy to my kids’ concerns about sinking into the soil. We don’t live especially close to a marsh or lake, but earthquakes aren’t uncommon in the Bay Area. Unless a water pipe bursts at just the right spot, it still seems unlikely that we’ll run into quicksand nearby, but there aren’t many conveniently placed vines to grab hold of if we did. Despite what cartoons and movies have taught us, that’s probably ok, since most quicksand isn’t likely to swallow you up in the first place.

While drowning in fluidized soil can happen, most instances of quicksand in nature aren’t that deep, so you aren’t likely to be fully submerged in order to drown. You might get stuck though, and trying to lift your legs straight up to take a step would be very difficult. Your best option is to try to lean back and spread your arms, letting buoyancy help lift you up. Small movements of your legs will help loosen them, but sharp vertical yanks aren’t going to be practical. This isn’t to say that people don’t die after getting stuck in quicksand, but some of those cases are due to other factors, like rising water levels, than the quicksand on its own.

Source: How Quicksand Works by Kevin Bonsor, How Stuff Works