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What
is quicksand?
Let’s
see what exactly quicksand is. Quicksand is basically a blend of
sand particles, some light gritty mud and water. So quicksand is not
a type of sand but a condition which occurs within sand or any type
of soil. However the
condition is more commonly found in sand. What happens is that the
grains of sand and soil become saturated through water, which flows
upward. This causes the grains of sand to move away from one another
and in effect behave as a liquid would. Now can a liquid sustain and
carry weight? No. Similarly nether can quicksand, which takes on the
behavior of a liquid. Hence a person who steps into it finds
himself going down, as quicksand is unable to sustain his weight.
However, as mentioned earlier, an absence of movement or minimal
movement will cause floating rather than sinking due to the natural
qualities of buoyancy as with water.
Why
then do people sink?
You
might then wonder why people do sink in both water and in quicksand.
Well, the reason for this is a difference in density. Any solid
sinks in liquid if its density is greater than that of the liquid.
The human body has a density lower than that of water, so we float
when we lie in a horizontal position in water. But the difference in
density is not much.
Floating
continues as long as this difference is maintained. It is struggling
that leads to a loss of balance and consequently drowning. Remember
excess movements in the form of struggling are causing the sand in
quicksand to liquefy more. So anybody caught in quicksand should
have the presence of mind to stay as motionless as possible and try
to float till helped out.
Where
is quicksand generally found?
The
usual places where quicksand forms is in hollows at the mouths of
rivers, along flat stretches of streams or beaches and in swamps
where mixtures of sand, mud and vegetation take on the
characteristics of quicksand. Some
sands have a naturally loose state of occurrence. Such sand may form
into quicksand due to minor disturbances. The surface in such places
will appear quite solid till the disturbance occurs and once it
does, the apparently solid surface of sand turns into quicksand.
Quicksand generally has an underlying surface of stiff clay, which
prevents water drainage.
This
property of turning into a liquid on disturbance is called
thixotropy. Not only quicksand, but many other substances too
exhibit this property. An example of this is water saturated
landfills, which become liquid due to the disturbance caused by
earthquakes. Some liquids have the property to become firm when
agitated, this property is called isotropy.
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