The science of sinkholes: should you be worried?
A car fell into a huge sinkhole in Duluth, Minn. on Wednesday, June 20, 2012. (AP / The Duluth News-Tribune, Bob King)
Christina Commisso-Georgee, CTVNews.ca
Published Saturday, March 2, 2013 2:25PM EST
Last Updated Saturday, March 2, 2013 3:03PM EST
A Florida man is presumed dead after the earth suddenly opened up beneath his home, swallowing his bedroom and leaving a suburban Tampa neighbourhood shaken. How common is this phenomenon?
While frightening, experts say sinkholes are nothing out of the ordinary in the Sunshine State. In fact, Florida’s Department of Environment Protection described sinkholes as a “common feature in Florida’s landscape.”
Where do sinkholes occur?
Sinkholes are common where the rock below the land surface is limestone, carbonate rock, salt beds, or rocks that can naturally be dissolved by the ground water circulating through them, according to the U.S. Geological Survey.
Sinkholes are a fact of life in Florida, as the entire state is underlain by limestone. An organic, sedimentary rock, limestone is weathered and dissolved by the weak natural acids found in rain.
A large sinkhole endangers the home of Cory Greenway in Frostproof, Fla. on Monday, Jan. 11, 2010. (AP / The Ledger, Pierre DuCharme)
Central Florida, including the Tampa area, is particularly known for sinkholes. In Hillsborough County, where Thursday's collapse occurred, the area is known as part of Florida's so-called “Sinkhole Alley”, where two-thirds of insurance claims for sinkhole damage occur.
How do sinkholes develop?
As the rock dissolves, spaces and caverns develop underground. Sinkholes tend to be dramatic because the land typically remains intact for prolonged periods of time until the underground spaces become too large. If there is not enough support for the land above the spaces, a sudden collapse of the land surface can occur.
These collapses can be small and uneventful, or they can be huge and deadly.
Sinkholes swallow buildings, cars and people
Like something out of a sci-fi movie, a gaping, perfectly round sinkhole swallowed a three-story building in Guatemala in 2010.
In this photo released by Guatemala's Presidency on Monday May 31, 2010, a sinkhole covers a street intersection in downtown Guatemala City, Monday May 31, 2010. (AP / Guatemala's Presidency, Luis Echeverria)
At 60-feet wide and about 30-storeys deep, scientists said the sinkhole had likely been weeks, even years, in the making. Experts said floodwaters from tropical storm Agatha caused the sinkhole to finally collapse.
A giant sinkhole formed suddenly in Texas in 2008. The hole expanded rapidly, swallowing vehicles, telephone poles and oil drilling equipment. Upon reached 600-feet wide, the crater stopped growing. Scientists were stumped as to what caused the formation, and suggested that it may have been caused by oil drilling in the area.
A massive sinkhole near Daisetta, Texas is seen Wednesday afternoon, May 7, 2008. (AP / Houston Chronicle, James Nielsen)
In Belize, the “Great Blue Hole” is a large submarine sinkhole off the country’s coast. Measuring 1,000 feet across and 400feet deep, the sinkhole has developed into a mecca for scuba divers.
The Great Blue Hole is seen off the coast of Belize. (Wikipedia)
Should you be worried?
Geologists say sinkholes are a worldwide phenomenon, as 10 per cent of the Earth’s surface is shaped by dissolving bedrock that’s prone to the holes.
While thousands develop each year, deaths and injuries from sinkholes are rare but not unheard of.
A sinkhole created by tropical storm Agatha covers a street intersection in downtown of Guatemala City on Sunday, May 30, 2010. (AP / STR)
A former University of Florida professor and contractor who has spent his career studying sinkholes told USA Today that he recalled only two other people in 40 years who have died because of sinkholes.
Anthony Randazzo said both of those cases were in Florida, and both times the individuals were drilling waters wells, which trigger the sinkholes to open underneath them.