Life Lessons #2: How to Escape from Quicksand

recently, my brother (and some friends) went on a camping trip in the high wilderness of Jersey. among the many pictures he showed me, I noticed a few shots of quicksand.

aside from seeing quicksand in video games and movies, I knew very little about how it worked. thankfully, I was enlighted by bill nye, the science guy.



interestingly enough, Bill asserts that quicksand will not "suck you down and make you disappear," but that drowning is an impossibility "ya wouldn't drown!" his explanation is that quicksand is simply a heavily concentrated mixture of sand and water--sinking in quicksand is as natural as sinking is water. all one needs to do is lie on his/her back, and wait minutes, days, or years for the next guy to come and save you.

just to check up on Bill Nye's claims, I found a source which stated something similar. pretty interesting!

"One of the most common reactions once a person finds his or her foot stuck is to shift weight to the other foot. At this point, a sort of seesaw motion happens -- with the person alternating their weight back and forth, trying to get a foot out of the quicksand. This movement actually worsens the predicament. What you should do instead is fall forward and try to spread the weight of your body over a large area of ground. Continue to work at freeing your foot, using slow motions so that you don't work your foot in deeper. Once you've pulled your foot out, roll away from the area, jump up very quickly and sprint to solid ground.

There have been many cases where people have gotten their legs trapped in quicksand and haven't been able to escape on their own. The sand has to be at just the right moisture for this to happen and the person has to be at least thigh-deep with both legs. Extricating a person from this takes at least two passersby, if not a full-fledged rescue team."

wow. lots of physics here. first, by shifting weight from a foot already locked into the ground to a different foot, the only thing one accomplishes is pushing the "other" foot harder into the ground. clearly, that will not work!

next, the source suggests spreading the weight of your body over as much area as possible. This is good advice to not only individuals stuck in quicksand, but people learning how to swim. spreading one's body over the water increases the amount of the body which is submerged, resulting in a greater force downward into the water. however, according to archimedes's principle, an equal and opposite force in magnitude (buoyant force) will keep you afloat. thus, spreading out your body, not struggling with your feet, will help you survive a quicksand attack.

finally, your success in the encounter with quicksand depends largely on how "concentrated" the quicksand is--the ratio of sand:water. While quicksand is normally much more dense than water, some breeds of quicksand probably contain high concentrations of water. Meaning, it would be a lot harder to float, and a lot easier to drown. The same effect can be observed when swimming: extremely salty water is much easier to float in, as highly concentrated salt water is much denser than fresh water.

so, if you ever encounter quicksand on your date with life, think:
1st) fluid mechanics--first, archimedes' principle, second, density.
2nd) get your phone and all electronics out, NOW.
3rd) if all else fails, you need to wait for some random dude to come help you. don't worry, if I ever see you stuck in a puddle of quicksand, i'll call 911 for sure.


source: http://science.howstuffworks.com/quicksand-sinking1.htm