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Are Sinkholes Occurring More Often Than They Once Were?

In 2013 alone, numerous massive sinkholes have made headlining news, swallowing people, cars, homes and even a resort.

In August, a 60-foot-wide sinkhole formed under the Summer Bay Resort in Clermont, Fla., near Disney World, forcing the evacuation of all guests.

In March, a house in a Tampa, Fla., suburb collapsed into a massive hole overnight while a man was asleep in his bedroom. The man awoke and screamed for help but was unable to be rescued.

Though the elusive, suddenly-forming holes have received significant publicity in recent months, it cannot be confirmed that they are occurring more frequently than they used to, experts say.

"Increased reporting of sinkholes (as the public becomes more aware of them), combined with urban sprawl, may lead to the impression that they are occurring more frequently now than in the past," according to Rick Green, geologist for the Florida Geological Survey.

Human influence has increased, however, Director of the Eastern Geology and Paleoclimate Science Center for the U.S. Geological Survey Randall Orndorff said.

"We have no hard evidence to say for sure that sinkholes are occurring more than they have in the past; however, since human influences such as paving and building in sinkhole-prone areas has increased, it probably follows that we are seeing them more often," Orndorff said.

Sinkholes form in karst terrain, land where the rock beneath the surface is made of limestone, carbonate rock, salt beds or rocks that can naturally be dissolved by groundwater circulating through them.

When this rock dissolves, gaps form underground and can eventually give way. This causes the surface to collapse and, often, consume whatever lies on top of it.

Heavy rainfall can promote this dissolution, as can extreme drought.

In April of 2013, a massive hole opened on a residential street in Chicago's South Side after more than 5 inches of rain fell in only 24 hours. The hole spanned the width of the road and consumed three cars.

Additionally, manmade changes to the ground, such as significant development, can result in their formation.

Many have blamed the recent massive hole formations to fracking and drilling, though scientists say a link has not been found.

"As for fracking, I am not aware of any link between this and sinkholes. Most sinkholes occur in the upper 100 meters or less of the surface, whereas fracking is typically thousands of meters deep," Green said.

Generally, tracking does not affect the surface of the ground, Orndorff agreed.

"If there are surface activities occurring in karst areas, there could be a direct impact, but we have not seen this," he said.