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Quicksand forms in saturated loose sand when the sand is suddenly agitated. When water in the sand cannot escape, it creates a liquefied soil that loses strength and cannot support weight. Quicksand can form in standing water or in upwards flowing water (as from an artesian spring). In the case of upwards flowing water, seepage forces oppose the force of gravity and suspend the soil particles.
The saturated sediment may appear quite solid until a sudden change in pressure or shock initiates liquefaction. This causes the sand to form a suspension and lose strength. The cushioning of water gives quicksand, and other liquefied sediments, a spongy, fluidlike texture. Objects in liquefied sand sink to the level at which the weight of the object is equal to the weight of the displaced soil/water mix and the submerged object floats due to its buoyancy.
Liquefaction is a special case of quicksand. In this case, sudden earthquake forces immediately increase the pore pressure of shallow groundwater. The saturated liquefied soil loses strength, causing buildings or other objects on that surface to sink or fall.
Quicksand is a shear thinning non-Newtonian fluid: when undisturbed, it often appears to be solid ("gel" form), but a minor (less than 1%) change in the stress on the quicksand will cause a sudden decrease in its viscosity ("sol" form). After an initial disturbance—such as a person attempting to walk on it—the water and sand in the quicksand separate and dense regions of sand sediment form; it is because of the formation of these high volume fraction regions that the viscosity of the quicksand seems to decrease suddenly. Someone stepping on it will start to sink. To move within the quicksand, a person or object must apply sufficient pressure on the compacted sand to re-introduce enough water to liquefy it. The forces required to do this are quite large: to remove a foot from quicksand at a speed of .01 m/s would require the same amount of force as "that needed to lift a medium-sized car."
Quicksand itself is harmless: a human or animal is unlikely to sink entirely into quicksand at all due to the higher density of the fluid (assuming the quicksand is on dry ground and not under water, but even if underwater, sinking is still impractical). Quicksand has a density of about 2 grams per milliliter, whereas the density of the human body is only about 1 gram per milliliter. At that level of density, sinking in quicksand is impossible. Descending about up to the waist is possible, but not any further. Even objects with a higher density than quicksand will float on it—until they move. Aluminum, for example, has a density of about 2.7 grams per milliliter. But a piece of aluminum will float on top of quicksand until motion causes the sand to liquefy. Continued or panicked movement may cause the victim to sink deeper, leading to belief that quicksand is dangerous. Because it increasingly impairs human locomotion, it allows harsher elements such as sunlight, dehydration, carnivores, omnivores, hypothermia or tides to harm a trapped person. Quicksand may be escaped by slow movement of the legs in order to increase viscosity of the fluid, and rotation of the body so as to float in the supine position. The putative and fictitious danger of quicksand should be contrasted with the genuine danger of becoming entrapped in flowing or standing mud, slurry, storm runoff, or commercial or agricultural products and becoming exhausted and/or suffocating.
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People falling into (and, unrealistically, being submerged in) quicksand or a similar substance is a trope of adventure fiction, notably in movies. According to Slate, this gimmick had its heyday in the 1960s, when almost 3% of all films showed someone sinking in mud, sand, or clay. For instance, T.E. Lawrence's servant boy Daud dies in quicksand in a scene in the 1962 movie, Lawrence of Arabia. Actor Al Mulock's character dies quite dramatically by falling into a quicksand pit after chasing Sean Connery through the jungle and being attacked by a leopard in the 1959 adventure Tarzan's Greatest Adventure. The proliferation of quicksand scenes in movies has given rise to an internet subculture scene dedicated to the topic.
Television programs of the 1950s–1960s likewise portrayed the perils of quicksand in dramatic fashion. In the Western television program, The Rifleman, for example, two teens are portrayed venturing into a swamp and sinking in quicksand up to their necks, frantically yelling for help until rescued by the title character, Lucas McCain, in the episode "Old Tony", which ended the series' final season in 1963 (episode #168).
One of the earliest popular fictional references to quicksand occurs in Les Miserables, wherein Victor Hugo dedicates two chapters to the subject. In Robert Louis Stevenson's The Pavilion in the Links quicksand plays an important role.
The Tamil language movie Mella Thirandhathu Kadhavu uses quicksand as a major plot point in the flashback parts of the protagonist's story. Quicksand also features heavily in the Bengali novel Chorabali (Bengali for "quicksand"), in the Byomkesh Bakshi detective series by Sharadindu Bandyopadhyay.
David Bowie has a song called "Quicksand" on his 1971 album "Hunky Dory". It was released as the b-side of his "Rock 'n' Roll Suicide" single three years later.
Pete Seeger's song "Waist Deep in the Big Muddy" mentions someone drowning after getting stuck in quicksand. The Charlie Daniels Band song "The Legend of Wooley Swamp" mentions three young men who drown in quicksand shortly after killing and robbing an elderly man and trying to get away with the money they stole.
"Another Day in Quicksand" is a song from the 2000 album "Clayman" by In Flames.
"Quicksand" is the lead track off of American rock band Incubus's sixth studio album, "Light Grenades".
American rock band Skid Row featured the song "Quicksand Jesus" on their 1991 album "Slave to the grind"
American singer Britney Spears recorded a song called "Quicksand", written by Lady Gaga, for her 2008 album Circus. The song tells the story about a girl who cannot seem to forget her ex-boyfriend and uses the analogy of quicksand to say she still loves him, as if they are still "sinking". In 2014 the indie rock band Bad Suns released a song titled "Dancing on Quicksand".
Caro Emerald released a Single called Quicksand in 2015. It is the part of her album of 2015.
La Roux released a song called quicksand in their Album La Roux.
- Khaldoun, A., E. Eiser, G. H. Wegdam, and Daniel Bonn. 2005. "Rheology: Liquefaction of quicksand under stress." Nature 437 (29 Sept.): 635. doi:10.1038/437635a
- Discovery Channel. MythBusters. Season 2. "Killer Quicksand." October 20, 2004.
- Bakalarfor, Nicholas (September 28, 2005). "Quicksand Science: Why It Traps, How to Escape". National Geographic News. Retrieved October 9, 2011.
- Engber, Daniel (23 August 2010). "Terra Infirma: The rise and fall of quicksand.". Slate. Retrieved 23 August 2010.
- Seeger, Pete. "HOW WAIST DEEP IN THE BIG MUDDY FINALLY GOT ON NETWORK TELEVISION IN 1968". Pete Seeger Appreciation. Jim Capaldi. Retrieved 2 August 2013.
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