Based on recent incidents, Florida seems to be collapsing in on itself fast – but sinkholes have always been part of the landscape
• Florida's most famous sinkhole
Every couple of weeks, Lisa Jaudon climbs into her car and takes the short five-mile drive to the tiny Florida town of Seffner, then sits for a while looking across the fenced-off plot of land where her home of 21 years used to be.
There's little to see there now. Just a giant void that once contained her family's house and those of two neighbours, friends whose lives were suddenly changed when a deadly sinkhole opened up in the ground on the night of 28 February.
The hole was smaller than the 100ft wide crater that appeared early Monday in Clermont and swallowed almost half of an apartment block belonging to the Summer Bay vacation resort near Disney World. But for Jaudon and her neighbours the incident was even more devastating.
Unlike the Clermont sinkhole, in which 105 guests were able to scramble to safety when loud cracks in the building alerted them to the imminent collapse, the Seffner families received no warning and one resident, 37-year-old Jeff Bush, was sucked to his death as his bedroom fell in. His body has never been recovered.
"It felt surreal, unreal," said Jaudon, whose house was next door. "A fireman knocked on the door and said a sinkhole had opened up and someone had fallen in, and that we had to evacuate. He couldn't tell us when or if we would be allowed to return."
As it turned out, Jaudon and her family were permitted to go back in for only 30 minutes the following day, to gather whatever they could of their family's most treasured belongings before turning their backs on the property forever.
Engineers determined that her house, which appeared undamaged from the original collapse next door, was at risk and could be swallowed up at any moment.
"The 30 minutes went by in the blink of an eye. We got photo albums, pictures off the walls, poetry that my late husband had written, the things that were meaningful and important to us, and very little else," she said.
"All the time a fireman was stood at the door, counting down the minutes and telling us that if he heard any strange sounds he'd blow his horn and we had to get out fast. It was eerie. Very scary."
Jaudon, whose 20-year-old daughter Jolie told her she would have been too terrified to sleep in the house again anyway, went to stay with friends. She returned to the site in May to watch it being demolished, along with another neighbour's house the other side of the property that suffered the original collapse, which had already been pulled down.
Seffner is in the heart of Florida's so-called Sinkhole Alley, the counties of Pasco, Hernando and Hillsborough in the west central area of the state, close to Tampa, which accounted for more than two-thirds of sinkhole claims reported to Office of Insurance Regulation between 2006 and 2010.
During that time, the number of annual claims per year statewide rose from 2,300 to 6,700 and cost the insurance industry more than $1.4bn.
Such statistics, and headline-grabbing incidents such as those in Clermont and Seffner, would appear to give the impression that Florida is collapsing in on itself at an ever-increasing rate. Experts, however, say that sinkholes have always been a feature of the landscape and that massive recent population growth means that sinkholes are opening up in built-up areas that once were rural.
"I've always said it's a given that when you move to Florida you get beaches, sunshine, hurricanes and sinkholes," said Clint Kromhout, a senior scientist with the Florida Geological Survey, which has just been awarded a $1.1m grant from the Federal Emergency Management Agency to conduct a three-year study of sinkhole vulnerability across the state.
"Sinkholes have been around for millions and millions of years. If you live in Florida they're just a fact of life."
Perched atop thousands of feet of porous limestone, Florida is particularly susceptible to "karst" landscape features such as sinkholes and underground caverns and springs, Kromhout said. Naturally acidic groundwater and rainwater dissolves the limestone, giving it the appearance of Swiss cheese.
Sinkholes occur when the surface layer above the formed voids gives way, which can often be caused by flooding from above or the draining of water from supporting underground aquifers below. This explains why sinkhole activity in Florida peaks in the colder months of January and February, when farmers pump underground water to keep crops from freezing, and again in the drier months of May and June, when aquifer water levels are low.
"It's too much water or it's too little water," said Tony Estevez, a sinkhole expert whose Pasco County-based company RAB Foundation Repair is busier than ever.
"Sinkholes can be man-made – they'll occur under roads where they run pipes and sewers that aren't properly backfilled. But the main problem is the soluble limestone of the west central Florida geology, where you get a lot of caverns and crevices forming."
Even so, he said, sudden collapses such as those in Clermont and Seffner are the exception. "Something like that is very rare, perhaps one in a thousand," Estevez said.
"It's much more common to have subsidence over time where migrating water causes moderate depressions. The first you'll know about it is when windows and doors won't close properly or you have tiles popping out."
But, he added, with sinkholes likely anywhere in the state, it is almost impossible to predict where one might occur, or to do anything to prevent it.
"It's the pick of the draw," he said. "You either get lucky or you don't."
