The Physics of Quicksand (2024)

I had heard that you should not move and flail around; keep calm and either someone comes by to help you or put a bullet through you. Unload the back pack and toss it, except for your water and a morsel of food that will not attract a viscious animal.

But, as the article indicates you will probably lose a shoe. If you are in those fishing boots (I guess rivers teaming with fish could be around quicksand but I don’t know) that may be a bigger problem. If you sink low enough for those to start filling, then you might be in trouble.

My failsafe: always carry a cell phone. I guess the only issue with that is “Can you hear me? Hello? HELLO?”

superfart said: “I was on a hot air balloon safari in sub-saharan Africa last June. I saw some hippos so I ordered the balloonist to land as I love hippos. I approached the hippo with a big stick with a dab of feces on it and rubbed it in his ear.”

Rofflesuace!

While working for the local zoo, I was sent to Africa with a video crew to film water fowl in their natural habitat. We spent weeks on site without any luck. My camera man and I decided that the problem was that we were too visible and were frightening the wild life. As we discussed the problem, a great idea came to mind, and the next day we came back in a hippo suit……………..

Sorry Alan, I couldn’t help myself.

MeasureMan said: “Sorry Alan, I couldn’t help myself.”

[shaking fist]Damn you, MeasureMan![/shaking fist]

Vishal said: “Very intresting, how about a few pointers on what to do when a quicksand is encountered? Or how to be prepared for one?”

Hurm…. From what I know, when you encounter a quicksand, you should lie back slowly. Try not to be too struggle and panicked. Relax and cool down. The best thing to do is to make slow movements and bring yourself to the surface, then just lie back. You’ll float to a safe level.
Try visit the how stuff works website for further information.

The link: http://science.howstuffworks.com/quicksand2.htm

gorgeousplanet said: “Dry quicksand… wasn’t that in the Fire Swamp? Next there will be an article about R.O.U.S.’s”

Lightningsand! Classic Morgenstern. My thought exactly!

ur2sensitive said: “One thing about dry quicksand we are leaving out completely…How about grain storage bins? You hear this story all the time about farm accidents involving some JimBo falling into the grain and disappearing in seconds. Certainly, the physix of the whole thing has a lot in common with the dry form of quicksand.”

That does happen regularly, but I don’t know that there is much similarity in the two situations. Corn kernels, soy beans, or wheat grain are much larger than your typical grain of sand, and have much smaller contact area from which a force chain can result. So a heavy weight placed at the top of a pile of grain can quickly displace the grain below and sink quickly. And those accidents seem to happen more often when the grain is being transferred out of a bin; usually an auger pulls the grain from the bottom of the bin as gravity keeps the grain flowing. Pockets can develop in the bin as grain is pulled out from the bottom; to break up the pockets and keep the grain flowing people will sometimes jump into the bin, and they can find themselves buried very quickly.

Growing up in farm country, I was always told if you fell into a wagon or bin of grain to not try to stand up; instead lie flat to distribute the weight over a greater area. Never had the chance to try that, nor saw it in action, but it seems like it’d be a better way to go about it.

@Vishal

See the movie “Blazing Saddles” were you can see actual footage of the rescue of a valueable machine from quicksand.

CanInternet said: “@Vishal

See the movie “Blazing Saddles” were you can see actual footage of the rescue of a valueable machine from quicksand.”

…it’s not exactly ground and it’s not exactly water…QUICKSAND! Then again, I get no kicks from Champagne.

I saw something on Discovery channel…there is a similar phenomena in water when excess air or other gasas are released from the sea floor. The density of water is reduced and therefore, once buoyant objects…sink. There was talk about this in the Bermuda Triangle too…but that wouldn’t explain why aircraft have disappeared in the same area.

This is somewhat like liquefaction (the process, not the result) where soil becomes so saturated with water and “stacked” like a house of cards, so one gentle shake could send it tumbling. The soil is beyond its saturation point, but because of the way it is stacked, it does not become a liquid. Given an earthquake, or such, however, it will, and it poses a pretty big threat. One such example, from Japan, I think:

http://www.ce.washington.edu/~liquefaction/selectpiclique/nigata64/tiltedbuilding.jpg

As I understand it, they got the buildings righted again afterward, and since all the oversaturated soil was gone, there was no longer a threat.

The movie Kekexili (about Tibet) has the coolest quicksand death scene that I’ve ever seen.

What do you think about it? It that likely to happen?

http://www.myspace.com/basicaustin

In France, around the “Mt Saint Michel”, quicksands are tragically famous. As said in the article there aren’t really deep, but still you can get stuck in it up to your knees.

So why are they deadly?

The bay of Mt Saint Michel is a beautiful place and it is really tempting to go for a walk when the tide is low. If you careless you can find yourself trap in the quicksand and this is when troubles start, because if, for sure, you are not about to sank in the sand and if nobody helps you to get out , it will be difficult to extract yourself of it. Then the tide is back and, as the people around say, it is coming “a la vitesse d’un cheval au gallop” (at the speed of a galloping horse) you will just drown.
Anyway you can visit the bay with a guide by feet or by horse and it is, somehow, a mystic experience due to presence of the Mont itself.

I’m going to get a little long winded here:

Beaches are not quicksand because the water migrates up into the sand after it has already been deposited by liquid force and consolidated due to wave action and the weight of the sand. If you have a water pocket in the depositional sequence it could theoretically become quicksand, but I have never seen anything like this.

Although, a mobile dune could migrate into tidal pools or such and probably create quicksand. This is much more likely than beach/river sands becoming quicksand for reasons I will get to later.

Quicksand forms is stream/river environments because there is large amounts of sand being transported by the water. Depending on the sands mineral composition, it can cause it to have some buoyancy. Most river sand is sub-angular mature quartz. It is mature, because most of the softer minerals have been eroded into silts and clays (feldspars in particularly). So anyway, quartz sand that gets deposited into a water “hole” can exhibit some buoyancy, causing it to become a loosely consolidated sludge. I suppose the current could probably undercut a bank or something and form quicksand at a deeper level also.

Note: some buoyancy, very minimal

In my opinion I don’t think that a saturated sand within a few feet of the surface could turn into quicksand. Most alluvial sands have a dry density of about 115 pcf within a few feet of the surface. Maximum dry density of alluvial sands by the Standard Proctor Method is usually around 120pcf. That tells you several things, mostly that the sand is relatively consolidated to begin with, and the pores between the sand grains are most likely in a state of positive pore pressure, not allowing water to migrate into the sediment package.

In the case of water loss, the sands are going to remain compacted, but they are going to exhibit negative pore pressure, allowing water to migrate back into the package when it becomes available. The overburden of the existing sediment will keep the sand compacted though, even against the buoyancy of the sand grains.

Ok, about the sand dunes. Wind deposited (aeolian) sand is typically very mature, has well sorted grain sizes, and is rounded. Wind is a much more efficient erosional force than water, something on the order of about 100 times. It also is very good at sorting sand, because wind can only transport the smaller particles, leaving the gravels behind. It also tends to pick up some silt as it is transported and deposited. (silt is the same thing as sand, just smaller particle sizes)

I will state that aeolian sands are not entirely consistent everywhere. They can be beach or river sands that have been moved by wind, but in some instances they are actually glacial sediments (glaciofluvial outwash). Essentially, these blew off the moraines from the last ice age. This is what the sandhills in Nebraska are.

I would think that wind deposited sand would have a much greater tendency to form quicksand than alluvial sands because these sands are typically in place at about 85-90pcf dry density, with a max of about 115pcf dry density, they don’t interlock well because of their rounded shape, and they have up to about a 15% silt content.

Note: dry densities are relative as is 15% silt content. Density would increase as depth increased due to consolidation of the sediment from overburden. The 15% is kind of an arbitrary number. It is what I’m used to seeing around here. The UCS would classify it as a cohesive soil instead of a sand at around 30%. The silt is an important factor here though because ambient moisture will cause it to form a sort of weak matrix with the sand grains in the first 5 or so feet of sediment. Increased contact with moisture or any type of overburden will cause the matrix to collapse, but it makes for larger pore sizes in said upper layer.

So aeolian sands have relatively more pore space than alluvial sands due to their small amount of consolidation. This would allow for more water to infiltrate the package, along with increased buoyancy due to smaller particle sizes. The same could be said about a sand dune migrating into a tidal pool or small water pocket along a river. As the sand was deposited in the water, it would not consolidate under it’s own weight, allowing a very loose suspension to form, giving us quicksand.

This also implies some things about Peorian Loess that I had not previously though of, but thats for a different time and place.

Anyway, this was my first post. If I’m not supposed to be posting in this old of an entry, sorry. I really do enjoy this site, I have slowly been working my way through every article and I’m gonna have to pick up the book.

Also, there is a pretty major error in the How It Works page for quicksand.

It states “A moderate amount of water works to increase the friction between sand particles. This is what allows you to build sand castles.”.

This is absolutely wrong. The effect that allows you to build sand castles is surface tension. As with most any soil/sand, a moderate amount of water acts as a lubricant allowing the particles to consolidate easier. This is the basis of the Proctor test, and describes the moisture/density relationship of a soil/sand with a parabolic curve indicating at what percent moisture maximum consolidation can be achieved.

I’ve had two personal experiences with quicksand. The first was in south Alabama near a small pool of water found in the woods. I stepped onto a sandy beach and quickly sank up to my waist. Apparently the pool was fed by a spring which flowed under the sand. I laid back and stayed still and didn’t sink any farther, and was lucky enough to have several friends with me. They pulled me out slowly with quite some effort, and I was barely able to keep my shoes on. I’m not sure how I would have gotten out had I been alone, but had the feeling that I could have laid flat and wiggled out given enough time.

The most recent was on a hike to the Keet Seel pueblo ruins in the Navajo National Monument in northern Arizona. The ruins are reputed to be the best preserved anywhere, probably because the site can only be accessed after a strenuous eight mile hike, most of which is along a sandy stream bed. The guides warn all visitors of the quicksand, which most often forms on the downstream side of boulders, since the surface water flows around the boulder but the subsurface water is pulled upwards and suspends the sand. The quicksand forms at other spots as well, particularly near the edge of the stream on the inside arcs, and we learned to anticipate it after a while. For the most part, the quicksand is no more than calf or knee deep, and is really just an annoyance.

In regards to dry quicksand, I remember my father telling me about a death at his chemical plant that often gave me nightmares as a child. An operator was filling a boxcar full of a very fine chemical powder, which my father likened to microbeads used for fiberglass repair. The powder was blown in through a large flexible hose, somewhat like an air conditioning duct. The boxcar was mostly full when the operator somehow fell in and sank to the bottom as if he were falling through air. The man apparently suffocated quickly, and was quite dead when they were finally able to fish him out.

It’s possible the dry quicksand phenomena is caused by soil or sand liquefaction following or during a seismic event. This is where the shaking caused by an earthquake causes the solid sand layers to behave more like a liquid. This is best seen by buildings partially sunk into the ground after an earthquake.

One of the phenomena accompanying this liquefaction is geysers of sand blowing upward as the surrounding sand settles, much like the graphic of an apple disappearing into the sand accompanying this article.

“Disappearing caravans” are possible under these conditions, I’d think. Dry quicksand would require an outflow of gas, such as methane (natural gas) to unsettle the sand particles enough to behave as a liquid – not just air. I can think of a condition or two where a large seismic event wouldn’t even be necessary – just a breach of a methane pocket.

Liked this article!

Similar to quicksand,sinkholes in bogs and marshes are much more deadly.Being born and bred in Newfoundland and Labrador,I`ve encountered sinkholes countless times,counting the fact that they are in most marshes and bogs on both Provinces.Traditionally,a bog or marsh of NL is a humongous body of murky mud water,ridden with clay,peat,sand,net-like roots,etc,and usually is covered in a network of plants and grass intertwined with each other,forming say a “`sponge“ with the exception of trees.These marshes are home to Bake Apples,and of course sinkholes,except these are no run of the mill sinkholes….more like “sink-pools“. Here is wiki`s definition of a sinkhole: http://en.wikipedia.org/wiki/Sinkhole .

Picture that you are on a dirt trail in a bog,and much like quicksand,the top of a sinkhole looks like normal solid ground(some are commonly noticeable).You then walk upon some ground,and suddenly you are submersed up to the groins.Unlike quicksand,a sinkhole will suck an object down almost instantaneously(depending on how solid the ground is. i.e if the ground looks solid,but in fact is water blended into the ground). Of course there are the instances where you can step on the ground without sinking,but with enough effort…you will…almost like playing in the mud.The big difference here is that in a marsh,the chances are solid ground vs soft is greatly overwhelmed do to a mass amount of water..Getting out is just as hard as quicksand and can be much more difficult considering that muck is much heavier than sand.If you don`t have anyone near by and are in a pool of muck.chances are you are screwed(unless the pool is made of up of more water than minerals). During the winter,traveling on a marsh is a brainless endeavour within itself. Although during the spring,summer,and fall seasons,it is safest to walk upon the spongy grass.

For example: Once upon a time while playing upon a marsh.A friend and I were traversing the marsh,during winter by the way.Although we knew the the dangers of a marsh,being kids we had a confidence of being impervious to such dangers.While running around on ice and snow,I so happened to walk upon a soft spot and all of a sudden I lost my footing. Within a second, my right leg was completely submersed in cold,thick muck. It just so happened that my left leg was on solid ground…so I fell to the side leaving myself halfway between safety and almost certain death.Lucky me,my friend was there to reach a hand and helped to pull out my leg. Of course I lost my boot and sock,but was relieved to be free from the clutches of the muck.

Brilliant! And just what I was looking for. The villain in my upcoming book was going to use a hidden pit of quicksand as his pulp-tastic method of disposing of the hero, but dry quicksand is so much more effective–and nefarious!

Thanks,
James Schannep