Florida is known as the Sunshine State, but living there has a dark side, as the family of Jeff Bush discovered when the 36-year-old man was killed after a sinkhole opened beneath his house last week.

Authorities are now reporting the development of a second sinkhole in Seffner, Fla., just 2 miles (3 kilometers) from the sinkhole that destroyed the Bush home, according to NBC News.

Sinkholes are an increasingly deadly risk in Florida, due primarily to the region’s geology. The state is largely underlain by porous limestone, which can hold immense amounts of water in underground aquifers. As groundwater slowly flows through the limestone, it forms a landscape called karst, known for features like caves, springs and sinkholes.

The water in aquifers also exerts pressure on the limestone and helps to stabilize the overlying surface layer, usually clay, silt and sand in Florida. Sinkholes form when that layer of surface material caves in.

The collapse can be triggered by a heavy overload, often caused by a downpour or flooding, or when water gets pumped out of the ground. When water leaves the cavities within the limestone, the pressure that supported the surface material also goes. Depending on various factors, that overlying layer can give way abruptly, as it recently did in Florida, or gradually, said Ann Tihansky, a hydrologist with the U.S. Geological Survey (USGS) in Florida. [See Amazing Photos of Sinkholes]

And Florida’s groundwater has been disappearing rapidly as the state’s population grows at breakneck speed: By 2015, Florida is expected to hit 20 million residents, making it the third-largest U.S. state, according to BusinessWeek.