Massive Florida sinkhole reopens. Why does Sunshine State have so many?

Florida is no stranger to sinkholes. Some 6,500 Floridians file sinkhole-related insurance claims each year.

Ron Spiller, director of code enforcement for Hillsborough County, center, behind microphones, addresses the media in front of where a sinkhole reopened on Wednesday, in Seffner, Fla.

Chris O'Meara/AP

August 19, 2015

A sinkhole opened Wednesday in the exact location where in 2013 a man was swallowed by one, according to Florida emergency responders.

The 20-feet hole opened in Seffner, east of Tampa, in a vacant lot.

There have been no reports of injuries or and no nearby homes have been evacuated, according to Ronnie Rivera of Hillsborough County Fire Rescue.

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In February 2013, at the same location, Jeffrey Bush was asleep in his bedroom when the floor collapsed and he was engulfed by a sinkhole.

Mr. Bush’s brother, Jeremy Bush, who was in the house, tried to rescue him by jumping into the hole. Jeremy had to be rescued by authorities as the ground crumbled around him. His brother’s body was never recovered.

And few months after that, in August, a 60-foot-wide sinkhole formed under a resort near Disney World in Orlando.

Florida is familiar with sinkholes. More than 6,500 sinkhole insurance claims are reported each year in the Sunshine State, BBC reported in 2014. But sinkhole-related deaths are rare in the state. Mr. Bush's death was the state’s first fatal collapse in decades.

Sinkholes are common where the rock below the land surface is limestone, carbonate rock, salt beds, or rocks that can naturally be dissolved by groundwater circulating through them, according to United States Geological Survey. The most damage from sinkholes tends to occur in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania.

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In Florida there are caverns below ground of limestone, so when it rains, much of the water collects underground, where it drains into the subsurface and dissolves the limestone.

Often when limestones dissolve, cavities are created in the subsurface and sand and mud gets washed into these cavities, according to BBC.

But not always. What is usually troublesome are “cover-collapse” sinkholes which, according to USGS, may develop abruptly and cause catastrophic damages.

“Cover-collapse” sinkholes occur where the covering sediments contain a significant amount of clay. Over time, the cavity breaches the ground surface and causes a sudden collapse.

This report includes material from the Associated Press.