The rise and fall of quicksand.

The state of the universe.
Aug. 23 2010 9:08 AM

Terra Infirma

The rise and fall of quicksand.

(Continued from Page 3)

Yet experience tells me that city kids are no less susceptible to the pull of quicksand. I have my own memories of playing out melodramatic movie scenarios just a few blocks from where I grew up, on the Upper West Side of Manhattan. My own personal Disneyland, if you want to call it that, was not an enormous pit of sand slurry out West but a modest sandbox in Riverside Park. The kids in my neighborhood had no trouble imagining jungle adventures in the playground. Sometimes we poured water in the sand to make the danger seem more real.

As it happens, there's another recent trend that's worth considering when it comes to quicksand—and one that bears on the games we played in city parks. In the 1970s, when I was born, roughly 800 sandboxes could be found in public playgrounds around New York City. By 1995, just 44 remained. (In Brooklyn, where I live now, the number dropped to four.) Over the course of my childhood, then, and through the concurrent decline of quicksand in the movies, the number of sandboxes in the nation's largest city dropped by 95 percent.

The sudden disappearance of sandboxes wasn't unique to the Big Apple, either. The playground accessory had been invented more than a century earlier by the German educator Friedrich Froebel. (One early mention comes from 1847, when an associate of Froebel's asked him in a letter, "Might not a plane of sand be made a useful and entertaining game? … A few drops of water mixed with it would enable the child to form mountains and valleys in it, and so on.") Sandboxes—or, as they were originally known, sandgartens—became increasingly popular in the United States starting in the 1880s. By the 1930s, 58 percent of well-off families had their own sandboxes. Fifty years later, the sandbox culture dissolved all at once.

In 1986, a geologist and medical doctor named Mark Germine published a letter in the New England Journal of Medicine describing an analysis he'd performed on several bags of commercial sand. The stuff that went into public playgrounds, he said, contained particles of tremolite, a substance similar to asbestos. That same year, the EPA declared for the first time that asbestos may cause cancer at any level of exposure. The nation's children were frolicking in carcinogens.

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Pretty soon, a watchdog group affiliated with Ralph Nader became embroiled in a long, public feud with the U.S. Consumer Product Safety Commission over the regulation of sandboxes. (The commission was skeptical: "In the minds of our scientific staff, that evidence doesn't exist," a spokesman said.) Leaving aside the asbestos controversy, many parents and city officials worried that other, macroscopic dangers might be finding their way into the playground—hypodermic needles, used condoms, and broken crack pipes. In New York, the burden of keeping sandboxes clean proved too costly for the Parks Department; by 1995, the city was "aggressively and systematically removing them."

Access to sand and water may have given kids like me something that has since disappeared—a venue for a certain kind of wilderness fantasy, or "a peril over which the child's imagination has complete control," as Jesse, the quicksand fan, describes it. The ubiquity of sandboxes once nurtured the playful idea of being swallowed whole, while the kids who dreamed of quicksand sustained the movie myth. But in the late 1980s, nervous parents started to take our sand away. When they looked at the sandbox, they saw danger, too.

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There's an episode of the show MythBusters in which Adam and Jamie, professional debunkers, take on the idea of "killer quicksand." Can people really get sucked into a mixture of sand and water like they do in the movies? To find out, they fill an enormous canister with 20,000 pounds of very fine sand, and then turn it into a squishy, sinking slurry by pumping water up through the bottom. Adam climbs in, wearing a pith helmet, and starts sinking—but only to his chest. "Alright, what's our final verdict on movie-style killer quicksand?" he says when the experiment is over.

"Surprised you even have to ask," says Jamie. "It's absolutely busted. No such thing."

More than one quicksand fan blames shows like this for squeezing his favorite gimmick from American movies and TV. The problem with quicksand, they argue, is that we know too much about it. "Viewers are more educated now than before," says Crypto. "They now know that quicksand that 'sucks you under' just doesn't exist in real life." The facts are too easily Googled or discovered on the Discovery Channel. The adventure gag has been drained of its magic. ("Hasn't science always been an efficient killjoy?" Jesse asks.)

Ironically, the debunking of quicksand is as much a cliché as quicksand itself. The MythBusters episode first aired in 2004; a year later, the myth of quicksand was busted all over again in the prestigious science journal Nature. For that study, physicist Daniel Bonn collected wild quicksand from a salt lake in Iran and brought it back to his laboratory in the Netherlands. Then he placed an aluminum bead on top and watched how far it sank. The conclusion? "Scientists Debunk Quicksand Myth," read the headline on MSNBC. A person trapped in quicksand would sink only to his armpits.

This point has, in fact, been made many, many times before—even in the pages of Nature itself. In 1910, the journal noted of quicksand, "a certain amount of unnecessary mystery seems to surround this matter." In another paper, from 1946, a researcher at DePauw University made quicksand in the lab and placed in it a wooden figurine with lead feet. It sank to the elbows. Indeed, the sheer impossibility of being sucked under quicksand had been inscribed in standard textbooks by the 1960s. Bonn jokes that his paper restated a discovery that was first made more than 2,000 years ago: According to Archimedes' principle, a floating object displaces its own weight and nothing more. Since people are less dense than quicksand, they'll never go completely under.

That's not to say quicksand can't kill you. Bonn calculates that the suction force created as your foot squeezes water from a quicksand matrix can be enormous: For his Iranian sample, it would take 100,000 newtons of force to get out—enough to lift a car. In most real-world situations, it's easy enough to wriggle free from sinking ooze, but people have gotten stuck and then drowned in the rising tide. Among the more famous and deadly sites are those around France's Mont St. Michel—where a yielding structure of mud and water hides beneath an elastic algal crust—and England's Morecambe Bay. The latter is so treacherous as to merit the appointment of the "Queen's Guide to the Sands." (That responsibility now falls to an elderly fisherman named Cedric Robinson, who leads tourists around the bay with a whistle and a long stick.) In the United States, several people have become ensconced in mud above the knee and then submerged in the waters of Alaska's Turnagain Arm.

YouTube video of a tourist trapped in quicksand near Mont St. Michel

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