A bit of explanation on Florida sinkhole formation

Slashdot.org can lead us to more information than we may have thought we needed to know about sinkholes - much in the news from having killed one person in Florida.

Florida Sinkhole Highlights State's Geologic Instability183

Posted by Soulskillon Saturday March 02, @02:49PM
from the this-planet-will-not-hesitate-to-attack-you dept.

An anonymous reader writes "Last Thursday night, a sinkhole took the life of a man (TV news video, with ad) while he slept in his home in Seffner FL, near Tampa.  While human fatalies are rare, sinkholes are so common in Florida that the insurance industry successfully lobbied the state lawmakers to pass legislation in 2011 making it more difficult for homeowners to claim sinkhole damages.  The bedrock in Florida is limestone, a weakly soluble mineral formed from calcified deposits of sea creatures tens of millions of years ago.  Above the limestone is a clay layer called the Hawthorn Formation which shields the limestone from ground water; and above the clay is sand.  However, the protective clay layer is thin or nonexistent in some areas of Florida, particularly in the middle part of the state near the Gulf coast, where caves and sinkholes are common.  Geologists say that human activity, particularly construction and irrigation, can trigger sinkholes by destabilizing the landscape above caverns by drawing down water tables and massing structures above them."

FromThe Christian Science Monitor, I would add:

Changes in drainage due to construction or agricultural irrigation have been known to activate mass outbreaks of sinkholes, where dozens of sinkholes can suddenly appear next to drainage wells and farm fields. Drought followed by heavy rains can also instigate sinkholes as heavy, water-logged earth presses down on limestone caves suddenly devoid of buoyant water. The two previous deaths attributed to sinkholes both involved professional well drillers whose activities cracked the top of limestone caverns, causing collapse. "Humans can [destabilize karst landscapes] by drawing down water tables or irrigate too much, increasing the weight of the mass of materials that sits on top of the void," says Jonathan Martin, a geologist at the University of Florida, in Gainesville.

"It's not yet clear what caused the Seffner sinkhole, however, but geologists say the area, which is part of the heavily populated I-4 corridor that crosses Florida's midriff from Tampa to Daytona, is particularly prone to sinkhole collapses. Humans can modify the environment" enough to cause sinkholes.

 

Comments

[m.e.]

we have sinkholes here in DC, too. I'm watching the metro parking lot near me, which seems to be acquiring lots of new cracks from underground springs?

[Cop Car]

XE--Yes, sinkholes are not just indigenous to Florida. Worldwide, there's no shortage of them.

Underground springs can play havoc with parking lots and building foundations, as can voids of various types. They did a good job of laying drainage tiles around this house and, usually when it rains, just one of the drains (there are four) that goes into our sumphole flows - and it doesn't take much rain to start the flow. That flow comes from the tiling that services the foundation under the front of our house. I've been able to isolate the cause of the flow (through experimenting with garden hoses) as the area adjacent to just two of our rooms, but I don't know why that section has more/faster percolation than the sections adjacent to the rest of the house.

[Hattie]

The current New Yorker has a great article about Florida sinkholes.

[Cop Car]

Hattie--Thanks. My copy of the New Yorker has not yet been opened (it was in yesterday's or Monday's mail. Hunky Husband is religious about picking up our mail, but - probably because I'm an atheist - I'm not at all religious about looking at mine.)

[Joared]

I think there must be a point at which extraction or injection of various matters from or into underground can become a problem. There's interest here in California about possible fracking/earthquake relationships if the former is instituted here.

As I recall Ohio, around the Akron/Canton area, I think, experienced a small earthquake that was attributed to fracking in recent years. Kay D. might recall. Earthquake is quite atypical for that area. Coal mining and the mountain topping done in the southern part of Ohio has been terribly destructive as is more recent fracking.

[Cop Car]

Joared--US Geological Survey has tied fracking to the increase in numbers of small earthquakes in the mid-section of the Continental US, according to news reports. [One such report is carried by Bloomberg.]

We, here in south-central Kansas, experienced an earthquake in November 2011, the epicenter of which was in Oklahoma. It was pure speculation on my part that decades of pumping oil out of the ground may have been a contributing factor, if not a cause.

According to news reports, the magnitude was greater than had been previously attributed to fracking, and there was a fault along which the quake occurred. According to an article in Huff Post Green, "In the past, earthquakes have been linked to energy exploration and production, including from injections of enormous amounts of drilling wastewater or injections of water for geothermal power, experts said. They point to recent earthquakes in the magnitude 3 and 4 range – not big enough to cause much damage, but big enough to be felt – in Arkansas, Texas, California, England, Germany and Switzerland. And back in the 1960s, two Denver quakes in the 5.0 range were traced to deep injection of wastewater."

Logic dictates that, just as injecting our own effluents into the atmosphere has consequences, injecting our effluents into the underground has consequences. Recognition that pumping oil out of the underground had consequences (for instance: collapse into the void) is, after all, what first led to injecting water into the underground to replace the oil. I'll stop now. I see eyes glazing over. *smiling*
P.S. The Huff Post Green article has an embedded video that is interesting.