Over the past several weeks, the phenomenon of sinkholes has become quite a popular topic.
After a large sinkhole in Seffner, Fla., "swallowed" a man and parts of his home in February, so-called "sinkhole sightings" are popping up all over the world– from Portugal to Chicago.
But is this an end-of-times scenario that we should be increasingly vigilant about?
One local expert says this is business as usual from a geological perspective.
"It's pretty typical," said Dr. Neil Anderson, a professor at Missouri S&T. "Sinkholes occur all over Missouri and in other different places...This type of activity is ongoing – 24/7."
In fact, a sinkhole at a Waterloo golf course near St. Louis "swallowed" a golfer on the fairway at the 14th hole on March 8, according to a report from the St. Louis Post-Dispatch.
According to the article, the "enclosure" was "up to 18 feet deep and 10 feet wide." The golfer was recovered from the sinkhole.
This was a far cry from the sinkhole in Florida, which claimed the life of 36-year-old Jeff Bush and devoured parts of his home. This particular sinkhole was approximately 60 feet deep and 30 feet wide on the surface, but below the surface it was about "100 feet across," according to a March report from USA Today.
According to the U.S Geological Survey, sinkholes occur most commonly "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."
The worst sinkhole damage is reported in states such as Florida, Texas, Alabama, Kentucky, Tennessee, Pennsylvania, and – you guessed it, Missouri.
"They've been forming for literally tens of millions of years," Anderson said. "As the limestone is dissolved, it isn't filled by soil, but rather an air pocket forms.
"As the limestone is dissolved, the air fill void becomes larger and larger, and eventually it becomes so large that the overlying soil basically has a little bit of a bridge over the void.
"Occasionally what happens is the ground surface will collapse catastrophically,
like in St. louis and in Florida."
Anderson was involved with a study of a sinkhole in Nixa, Missouri back in 2006.
According to his report, "the kitchen and attached garage of the single-family home... collapsed into a catastrophic sinkhole."
The sinkhole was approximately 75 feet deep and 50 feet in surface diameter, but the homeowner's vehicle and freezer were buried well beneath 75 feet.
"They estimated that it had been 90 feet deep to have completely swallowed the man's car," Anderson said.
Anderson says weather conditions can exacerbate occurrences of sinkholes, specifically heavy rain or the opposite, long periods of drought.
"It's like a soil bridge," he said. "If it gets really dry, the soil shrinks and cracks and you can have a catastrophic collapse."
Page 2 of 2 - But there's always the human factor, such as urbanization, causing an unusually heavy amount of storm water runoff.
Anderson maintains that sinkholes, even the large ones, are a common phenomenon.
"I think this is a little bit of the press picking up on something that has caught people's attention," Anderson said. "There are a lot of big sinkholes in Missouri that open up in a farmer's field and nobody cares. The one in Nixa was 75 feet deep but it didn't get much attention."