Patch sites in Brandon, Fla. have been following the ongoing case of a Florida man who was swallowed by a massive sinkhole while he slept. The news has the nation wondering how this could happen.

The U.S. Geological Survey (USGS) knows exactly how such things happen. The holes are "an area of ground that has no natural external surface drainage," according to the USGS website. "When it rains, all of the water stays inside the sinkhole and typically drains into the subsurface." 

When the rock surrounding the surface is saturated with water, it will "naturally be dissolved by ground water circulating through them," according to USGS.

But what does a massive sinkhole in Florida have to do with Pennsylvania? Along with the Sunshine State, Pennsylvania is listed in the top seven states in the nation to have such sizeable sinkholes.

"The most damage from sinkholes tends to occur in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania," said the USGS site.

Just this past spring, a sizeable hole caused a major mess for traffic in King of Prussia. When the intersection at Crooked and Manor lanes was replaced with a sinkhole, many went without water service. A Pennsylvania American Water line cracked in the creation of the sinkhole, taking hours to repair.

Another sinkhole was created in April 2012 in Forks Township in the Lehigh Valley, putting a nearby elementary school's staff on edge. 

Just today (Friday), Patch sites outside of Pittsburgh, Pa. reported that an underground cement box created a massive sinkhole in a parking lot.

According to the Department of Conservation and Natural Resources (DCNR) of Pennsylvania, the state is filled with developments on areas of rock that often have been known to cause sinkholes.

As you can see from the enclosed mapping created by DCNR of Montgomery County, there are many locations in which are built upon "non-carbonate rock." Those areas are designated in purple.

DCNR's website explains that sinkholes don't occur ONLY in the areas of purple, but do have a greater likelihood in those spots.

"Sinkholes can occur in areas where no karst features have been observed," said the DCNR-PA website. "The occurrence of sinkholes, therefore, is not restricted to the high-density areas delineated on the map."

In short, with the types of rock the state of Pennsylvania is built upon, it is very likely that sizeable sinkholes can (and clearly do) happen in the area.