Sinkhole causes resort villa to partially collapse (Fla.)

[Igel]

3. Much of the area is screwed, long term.

See the nice picture from China at http://www.geotimes.org/apr07/article.html?id=Travels0407.html or just google "china karst" and look at the images.

The tops of those very steep-sided hills were near the surface. The underlying rock was limestone. All rainwater contains a bit of carbonic acid (it's ultimately what makes soda acid and accounts for the fizz). Acid dissolves limestone, gradually, and washes it to the sea. At first you get cracks that widen. Then you start having channels. Caves. Then the caves start to collapse. Over time, what was a flat surface becomes a flat surface with deep holes in it, and at some point the perspective shifts so that the "surface" is now dozens or hundreds of yards lower with things sticking up out of it.

Now, in much of Florida, you have a surface and the underlying rock is limestone. All rainwater contains ...

Karst was first named in S. Austria and Slovenia. A lot of the world's surface is karst.


Yes, they can check these days for what's underground. Not always cheap, but it's not hard to do. Karst can be dissolved, so what was stable a hundred years ago may not be today. It's also porous. When it's saturated with water it's a bit more stable--for a while--than when the water's drained out of it. Droughts are hard on buildings sitting on karst.