Sinkholes: Why Do They Keep Happening?

Stories of sinkholes swallowing victims across the nation have been repeated throughout the news over the last two weeks, the deadliest of which took place in Florida on March 1 when a man's bedroom floor suddenly disappeared, taking the 37-year-old Jeff Bush with it.

His brother Jeremy jumped in after him, digging through the wreckage, telling the news he could hear his brother's screams. Jeremy only stopped when the police pulled him from the site because they feared the floors would continue to give way.

Less than two weeks later, a golfer disappeared down an 18-foot sinkhole on a fairway in Illinois.

Mike Mihal told the Associated Press the fall was quick and sudden.

"It didn't look unstable," he said. "And then I was gone. I was just freefalling. It felt like forever, but it was just a second or two, and I didn't know what I was going to hit. And all I saw was darkness."

Fortunately, Mihal only sprained his shoulder.

Then, a week after that, a California man reported that his pond had been swallowed by a sinkhole behind his house in Newcastle.

Such dangerous and seemingly unpredictable events beg the question, what exactly are sinkholes and what's causing them?

According to the U.S. Geological Survey, a sinkhole is an area where the ground cannot drain water externally, forcing the water to seep down beneath the earth. Over time the water erodes underground rock formations until one day they collapse suddenly, taking down everything above them.

 Some are a few feet and others hundreds of acres and can be anywhere from 1 to 100 feet deep. And while some occur naturally, others are the result of human activity.

For example, when industrial and runoff-storage ponds are created, the added weight puts pressure on the ground beneath it and is prone to collapse.

Areas most prone to sinkholes are Florida, Texas, Alabama, Missouri, Kentucky, Tennessee and Pennsylvania; however, the list will only grow as people continue to alter the landscape and build on unstable surfaces.