September 28, 2005
How to Overcome that Sinking Feeling in Quicksand
LONDON -- Quicksand is not the bottomless pit portrayed in Hollywood films that sucks in unsuspecting victims and swallows them whole.
It is true the more people struggle, the deeper they will sink into the soupy mixture but its buoyancy makes it impossible to be completely submerged, scientists said on Wednesday.
"Everybody thinks, thanks to Hollywood, that you can drown in quicksand. Basically if you do a simple buoyancy calculation, the Archimedes force, it is immediately evident that you can't drown completely," said Daniel Bonn, of the Van der Waals-Zeeman Institute at the University of Amsterdam in the Netherlands.
Quicksand consists of salt, water, sand and clay. It is the water content that makes quicksand, which is found near estuaries, beaches and rivers, so dangerous.
"If you tread on quicksand, or liquefy it by moving, it goes from something that is almost completely solid to something that is almost completely liquid," Bonn told Reuters.
He and his colleagues showed that Hollywood had got it wrong by measuring the viscosity, the resistance to flow, of quicksand and its sinking ability.
They also calculated the amount of force necessary to get a trapped foot out -- and found it was the equivalent needed to lift a medium-sized car. Their findings are reported in the science journal Nature.
If someone falls into quicksand they begin to sink and the sand packs densely around the feet, forming a type of trap. In films people sinking in quicksand usually grab on to an overhanging tree branch or are pulled out just as they are about to disappear under the mucky surface.
But Bonn and his team said in real life the victim would sink halfway into the quicksand but would not disappear.
The scientists advised people trapped in quicksand not to panic and to wiggle.
"All you have to do to get your foot out is to introduce water into the sand and if you can do that along your leg by wiggling your leg around, that is the best way to get out," Bonn said.