Nightly News | August 12, 2013
>>> good evening, i'm lester holt sitting in tonight for brian. what an incredibly close call in a resort near disney world when the ground literally opened up beneath them as many slept. what it looks like from above the scene now in clermont, florida , where a massive sink hole opened up overnight chancing much of the resort structure. more than 100 people were forced to evacuate. some under harrowing conditions, remarkably no one was killed. nbc's kerry sanders is there with late details. kerry, i assume you're on firm ground right now, but how big a danger area at risk is there?
>> reporter: well, good evening, lester. they've moved up three city blocks fearing the sinkhole would continue to grow. the problem actually begins about 20 to 100 feet down where there's limestone. rainwater goes through the earth and hit that limestone and it can cause it to dissolve. that is a recipe for disaster.
>> we need to know what room everybody was in.
>> reporter: shortly after 3:00 in the morning, maggie started her camera during the chaos. she says it came without warning while on vacation with family and friends from virginia, she heard a single window pop its frame, then another and another. at first she thought it was someone in a fight.
>> glass flying. people jumping out of windows. luggage flying out of windows, people trying to salvage what they could.
>> to me, it sounded like popcorn popping. porti pop, pop, pop.
>> reporter: in all evacuating 1 a 5 tourists here on vacation.
>> people were sleeping. i literally had to wake them up and tell them get out of the building.
>> reporter: why do sinkholes occur? in florida , sandy clay all supported on a layer of limestone. limestone is like a strainer. the water migrates down and hits florida 's underground river , but when there is too much rain or a drought it can create a void like a balloon with air. as that void gets bigger, the earth on top becomes too heavy, and the balloon pops, causing a catastrophic event . a sinkhole.
>> geologists say they know when conditions are ripe for a sinkhole, but like an earthquake, they cannot predict when or where one will open up.
>> the open sinkholes may open other sink holes .
>> reporter: trigger them?
>> yes, it's possible. because these are connected undergroun, again, by the same limestone cavity and cave structures.
>> reporter: 20% of the nation is susceptible. other likely locations for sinkholes, pennsylvania, tennessee and utah. in florida in march, a sinkhole 30 feet wide and 50 feet deep opened up swallowing 36-year-old jeff bush from his bedroom. his body was never recovered. here in clermont, florida , 15 hours later, survivors are still anxious.
>> i'm still in shock and just very, very thankful.
>> reporter: lester, the sinkhole right now is about 100 feet wide about 15 feet deep they guess as looking down there. the likelihood of something like this is being struck by lightning, which, as we know, can also happen.
>> we've seen them before, kery. sounds like a bit of a guessy game. what can home owners do or know ob going into a neighborhood that's at risk?
>> reporter: get a geological survey too look down there. a situation that's constantly changing depending on the rain situation. even the bubbles don't necessarily tell thru is going to be a catastrophic collapse. one thing everybody needs , sinkhole insurance.
>> kerry sanders , yes.