Scientists believe this type of quicksand forms when very fine sand forms a sedimentation layer over more granular sand. Dry quicksand was considered a potential danger during the Apollo missions. It may exist on the Moon and Mars. Quicksand also accompanies earthquakes. The vibration and resulting solid flow have been known to engulf people, cars, and buildings.
Technically speaking, quicksand is a non-Newtonian fluid. What this means it can change its ability to flow viscosity in response to stress. Undisturbed quicksand appears solid, but it's really a gel. Stepping on it initially lowers the viscosity, so you sink. If you stop after the first step, the sand particles beneath you get compressed by your weight. The sand around you also settles into place. Continued movement like thrashing around from panic keeps the mixture more like a liquid , so you sink further.
However, the average human has a density of about 1 gram per milliliter, while the average quicksand density is about 2 grams per milliliter. You'll only sink halfway, no matter how badly you freak out. Disturbing quicksand makes it flow like a liquid, but gravity acts against you.
The trick to escaping the trap is to move slowly and try to float. Strong forces stiffen quicksand, making it more like a solid than a liquid, so pulling and jerking only make a bad situation worse. A quick Google search reveals most writers don't have personal experience with quicksand or consult water rescue experts.
Quicksand can kill! It's true you don't sink in quicksand until you're submerged. Humans and animals typically float in water, so if you are standing upright, the furthest you'll sink in the quicksand is waist-deep. If the quicksand is near a river or coastal area, you can still drown the old-fashioned way when the tide comes in, but you won't suffocate with a mouthful of sand or mud. Dry quicksand presents its own special risks.
Buried in watery quicksand, a body must use a lot of force to loosen the mix enough to escape, according to the Nature article. Spreading limbs out helps the body float to the surface. And if stuck solid, the authors advise a quicksand victim to "take solace" in the knowledge that they can't sink in over their head. Live Science. At first they sunk a little, but as the sand gradually began to mix with water again, the buoyancy of the mixture increases and they floated back up to the top.
Bonn and his team tried placing all sorts of objects on his lab-made quicksand. If they were of density equivalent to a human they did sink, but never completely, only half way. This is really when quicksand can be dangerous.
The quicksand effect means that falling into a silo full of grain can often be fatal Credit: Getty Images. They tested samples from the shores of a lagoon in north eastern Brazil. They found that bacteria formed a crust on the top of the soil, giving the impression of a stable surface, but when stepped on the surface collapsed.
Dry quicksand, however, is another matter entirely. The quicksand effect means that falling into a silo full of grain can often be fatal. In a case report was published telling the tale of a man who fell into a grain store late one evening on a farm in Germany.
By the time the firefighters were able to establish which of eight tanks he was in, the grain was up to his armpits and acting according to the classic idea of quicksand, was dragging him down. The sand collapses, or becomes 'quick,' when additional force from loading, vibration or the upward migration of water overcomes the friction holding the grains together.
Most quicksand occurs in settings where there are natural springs, either at the base of alluvial fans cone-shaped bodies of sand and gravel formed by rivers flowing from mountains , along riverbanks or on beaches at low tide. In such cases, the loose packing is maintained by the upward movement of water. Quicksand does occur in deserts, but only very rarely: where loosely packed sands occur, such as on the down-wind sides of dunes, the amount of sinking is limited to a few centimeters, because once the air in the voids is expelled the grains are too densely packed to allow further compaction.
Answer originally published on October 7, Sign up for our email newsletter.
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