What's that sound?
The pipes in your basement creak and groan.
The floor starts to tremble and shake.
Cracks start to form and crawl up your walls.
Is an earthquake happening?
You drop down on the ground
and crawl under a table.
All of a sudden, the ground
beneath you starts to slump and collapse.
Before you have time to react,
a giant sinkhole swallows everything in sight.
Sinkholes are craters in the ground
that form when water dissolves the rock layer
underneath the soil.
Sinkholes can create small ponds,
or cause the ground to dip.
In most cases, these sinkholes
aren't dangerous since they form slowly.
But you don't want to find yourself
standing above a cover-collapse sinkhole.
They happen when there's a layer of clay
between the surface and the bedrock.
Water seeps in and slowly wears away the clay,
creating a cavern.
When that layer caves in,
everything above it is swallowed into the Earth.
The best way to survive
falling into a sinkhole is not to fall in one.
Sinkholes tend to show plenty of
warning signs before they
start to become dangerous.
Watch out for cracks in building foundations,
walls, or sidewalks.
Take a look outside as well.
When a sinkhole forms,
water will start pooling on the ground.
Trees and fence posts will
start to tilt or fall over.
And vegetation might wilt and die
due to the sinkhole draining away water.
If you notice these signs,
find out if you live in an area
that's susceptible to sinkholes.
Ask a geologist or soil engineer
if your house is at risk.
If it is, a professional can inject grout
into the hole to reinforce the foundation.
But, what if you aren't able to see these signs
until it's too late?
By the time that cracks start rapidly appearing,
you may only have seconds to get out
before the ground collapses.
If you do get caught in the sinkhole,
brace for impact.
The size of a sinkhole ranges from 1 m (3 ft)
to hundreds of meters in diameter and depth.
Cover your head,
tuck your knees with your legs together,
and fall on your side, rolling backward.
This is called the parachute landing fall.
It evenly distributes the shock
of impact across your body.
The last thing you'd want to do is
land flat on your back or head.
Ouch.
Okay, you've survived the impact,
but now you're trapped deep in the sinkhole.
If you can, try to move towards
the middle of the hole,
but don't stretch out and relax.
Anything above you could still fall.
Stay low and small.
See if there's anything you can grab on to.
The ground around you is probably
unstable and could sink even further.
Wait until you're on steady ground,
and it's safe to move.
Then, you can start making your escape.
Take a look at your surroundings.
Is there any water filling the sinkhole?
Do you have your cell phone to call for help?
Is the hole small enough to climb out of?
If the hole is too deep,
you probably shouldn't try to climb out.
There's a good chance that
anything you climb onto is loose.
Not only that, but climbing
could cause more of the debris
to fall from above.
In this case, your best bet
is to call for help and wait.
Now, your entire house might be destroyed,
but luckily, you got out
of this mess in one piece.
Pay attention. Look for the signs of a sinkhole.
If you do happen to fall into one,
use the parachute landing fall, find a safe spot,
and call for help. Don't try to climb out.
Now, what if that trembling
turned out to be an earthquake?
Well, we'll show you what to do
on another episode