|MadSci Network: Earth Sciences|
Quicksand is found in many parts of the US. Places that I am familiar with include New Jersey, the coast of North Carolina, and many areas in the Southeast (particularly Florida). In general, however, quicksand can occur anywhere where two conditions are satisfied: sand and a source of rising water. The sand can come from bedrock, alluvial (river) deposits, glacial deposits, or beaches. The water usually comes from springs or other types of groundwater flow. Basically, you need sufficient hydraulic pressure on the water to drive it up into the sandy deposit. Really flat areas tend not to have quicksand because there isn't sufficient pressure to force the water to form springs while steep areas tend to generate runoff that forms rivers. Quicksand can often be found in areas of rolling topography where the subsurface material can transmit water (limestone and dolostone do this well). As I'm sure you may have read or seen, quicksand can also form in swampy or wet areas, especially if that swamp is fed by springs. Another interesting way that quicksand or even "quicksoil" can form is during earthquakes. In the same way that rising water can agitate sand grains to cause the sand to lose it cohesion, vibrations in an earthquake can shake up wet sand or soil, causing it to become liquid. A particularly vivid example of this is thought to have occurred in Port Royal, Jamaica in 1692 (see the article by Kruszelnicki below). Buildings and people were sucked under the earth as the sandy spit where the town was located liquefied. If you want to know more about quicksand, I suggest you locate the following articles: "Quicksand" by Gerard Matthes in the June 1953 issue of Scientific American, page 97. "The Earth Did Swallow Them Up" by Karl Kruszelnicki in the December 21/28th issue of New Scientist pages 27-29.
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