Drowning in quicksand is impossible, according to a new study,
relegating this popular plot device in adventure stories to the
category of pure folklore.
Consisting of a mixture of sand, salt
water, and clay, quicksand captured the attention of University of
Amsterdam physicist Daniel Bonn when he went on a family trip to
Iran, the birthplace of his wife. Collecting a sample of quicksand
near a body of water in Iran, and bringing it to his laboratory for
study, Bonn and his colleagues showed that shaking aluminum beads
designed to have the same density as human beings, would partially,
but never fully, submerge them.
Since quicksand is twice as dense
as water, the beads (and humans) only sink about halfway. Shaking
or otherwise disturbing the quicksand liquefies it, increasing the
downward flow of the beads by a factor of a million. This is how
humans can get stuck in it. Since quicksand is often located near
bodies of water, Bonn speculates that high tidal floods passing over
individuals stuck in quicksand may have caused casualties
incorrectly ascribed to sinking fully in it.
Bonn says his
conclusions apply to all kinds of quicksand. Nonetheless, the force
required to lift a foot out of quicksand can be equal to that
required to raise a car. His solution: wiggling the stuck foot will
cause water to trickle down, allowing the hapless adventurer to get
out of it.
Khaldoun et al.,
September 29, 2005