Transcript
HlY8S57-27g • A Hidden Cause of Sinkholes Is Lurking Underground | NOVA | PBS
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Language: en
an active mine in Illinois suddenly
collapsed causing this 100t wide
sinkhole to swallow up part of a soccer
field lights and all sinkles can happen
just about anywhere on roads under homes
and sometimes in remote areas but in the
US they happen most often in Florida
Texas Alabama Missouri Kentucky
Tennessee and Pennsylvania anywhere the
Bedrock is vulnerable to erosion by
groundwater in many cases the main
trigger for sinkholes is water either
too much of it or not enough if
groundwater dries up like during a
drought it can take away support for the
ground above causing it to sink but if
there's too much water like during big
storms or water main breaks the sudden
influx of groundwater can also cause
instability the kind of sinkhole that
opened up on the Illinois Soccer field
is actually kind of unusual in that it
was spurred on by an active mine but
it's not
unprecedented near carsbad New Mexico
giant sink holes from mining activities
started to pop up in 2008
then officials discovered that one well
that was being mined near the city was
on the brink of collapse years of
extracting the salt created a wide
underground cavity a sinkhole seemed
imminent and if it collapsed it would
have taken part of the city with it what
happened next was a long and expensive
remediation effort and today that brine
well is filled sinkles can form either
really quickly or really slowly over a
long period of time and they don't
always come with warning signs l time
Stone mines like the one in Illinois are
usually carefully engineered to prevent
collapse pillars are often carved out to
hold up the ground above but when mines
do collapse and cause sinkholes here's
what's usually happening underground
underground mines are usually deep in
Bedrock and over time cracks can form in
the Bedrock roof over the mine and water
and sediments slowly trickle down into
the mine leaving behind a new cavity in
the rock or soil layer above eventually
when the top layer of soil can no longer
support weight it gives way forming a
dramatic hole in the ground a sinkhole
and sink holes are usually round because
the shape of a circle takes the least
amount of energy to create think about
how when you dig a hole in the sand at
the beach the surrounding sand uniformly
falls in around it making a circle
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