Engineers are expected to carry out more tests Saturday on the ground around a sinkhole that buried a 37-year-old man under a Florida home Thursday night but they believe this occurred from one of the rarest kinds of sinkholes.
The Tampa Bay Times reported a cover collapse sinkhole, known for its suddenness and often the most catastrophic, likely collapsed the bedroom of the Seffner home, about 15 miles east of Tampa, sending Jeffrey Bush into a hole an estimated 30 feet wide and 20 feet deep.
Bush has not been heard from since the hole appeared at about 11 p.m. ET Thursday and is presumed dead.
Cover collapse sinkholes usually occur in areas where a layer of clay sits atop the Swiss cheese of limestone that lies beneath the ground in this part of the state, said University of South Florida geology professor Mark Stewart.
The limestone is pocked with caverns. Something triggers the clay atop a cavern to begin trickling into the hole, more and more of it drops away until all that's left is a slender land bridge. Then the bridge falls.
The bang is the last bit of sediment falling into the bottom of the cavern, Stewart said.
Deputy Douglas Duvall, the first person on the scene and inside the house, said he saw a hole in the ground that had swallowed an entire bedroom, and was still growing.
"Everything was sinking," Duvall said.
Larry Madrid, another engineer at the scene, said there appeared to be essentially two collapses of the earth under the home, which makes this an extremely dangerous sinkhole that will likely continue to grow.
Madrid said with the side of the sinkhole still very steep and the soil around the hole soft, the sides could continue to collapse into a diagonal angle before it would be done growing.
Sinkholes can occur naturally. They can also be caused by humans building homes, stores or retention ponds atop fragile land, or pumping too much water out of the aquifer.
Sinkholes are a common feature of Florida's landscape. They are only one of many kinds of karst landforms, which include caves, disappearing streams, springs and underground drainage systems, all of which occur in the state.