![]() ![]() ![]() When they shook it only a little, the bead stayed floating on top. At rest, the bead remained on the surface, despite aluminum's higher density.īut then scientists started shaking the container. But a piece of aluminum will float on top of quicksand until motion causes the sand to liquefy.ĭuring their study, researchers placed an aluminum bead on top of a container of laboratory-created quicksand. Aluminum, for example, has a density of about 2.7 grams per milliliter. You would descend about up to your waist, but you'd go no further.Įven objects with a higher density than quicksand will float on it-until they move. At that level of density, sinking in quicksand is impossible. But human density is only about 1 gram per milliliter. ![]() Quicksand has a density of about 2 grams per milliliter. The reason is that humans just aren't dense enough. This causes a trapped body to sink when it starts to move.īut a person moving around in quicksand will never go all the way under. At rest, quicksand thickens with time, but it remains very sensitive to small variations in stress.Īt higher stresses, quicksand liquefies very quickly, and the higher the stress the more fluid it becomes. Researchers in the Netherlands and France studied quicksand, a combination of fine sand, clay, and salt water. Real quicksand is certainly hard to get out of, but it doesn't suck people under the way it always seems to in the movies.Īccording to a study published in the current issue of the journal Nature, it is impossible for a person immersed in quicksand to be drawn completely under. You won't sink in-at least not all the way. 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.Īnswer originally published on October 7, 2002.If stumbling into quicksand ranks on your list of worries, don't panic. In such cases, the loose packing is maintained by the upward movement of water. 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. 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. This arrangement is similar to a house of cards in that the space between the cards is significantly greater than the space occupied by the cards. Because many sand grains are elongate rather than spherical, loose packing of the grains can produce sand in which voids make up 30 to 70 percent of the mass. In normal sand, grains are packed tightly together to form a rigid mass, with about 25 to 30 percent of the space (voids) between the grains filled with air or water. ![]() Quicksand is a mixture of sand and water, or sand and air, that looks solid, but becomes unstable when disturbed by any additional stress. Long, a sedimentologist at the department of earth sciences at Laurentian University in Sudbury, Ontario, explains. ![]()
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