The Ground is Falling! The Ground is Falling! Why Florida is Sinking

Photo credit: Indiana DNR

Karst topography is the geological name given to an area of limestone bedrock featuring caves, sinkholes, and underground streams. In laymen terms, karst topography is anywhere the lower levels of the soil horizon has been dissolved by the physical or chemical weathering of the bedrock. These environments are comprised of carbonate rocks, such as dolomite and limestone, or having high amounts of evaporites, for example, salt and gypsum, as these materials tend to be highly soluble in water. Having these conditions within humid climate like Florida invites faster weathering. Another erosion accelerator is groundwater mixed with vegetation creates a weak acid that dissolves the limestone. (think baking soda mixing with vinegar) Over time, cracks become caves, and when caves collapse they form exposed openings known as karst windows.

karst map

Here’s the link to the .pdf poster above that explains the regions.

The area in which Spring Mill State Park is located has one of the highest concentrations of sinkholes in the United States, with an average of 100 per square mile. Just south on Indiana 37 near Orleans, an amazing 1,022 sinkholes were counted in one square mile. The funnel-shaped sinkholes vary in size but play an integral role in the development of cave systems.

Limestone cave at Mammoth Onyx Cave in Kentucky

Limestone cave at Mammoth Onyx Cave in Kentucky

The Lost River System in Indiana is notable because it has all of the significant features of karst terrain in a small watershed of only about 150 square miles. Indiana’s Lost River is one of the most complex hydrological systems in the world as 23 miles of the total 87 are underground. Visit the river after a week of rain, however, and you will see an entirely different watercourse. The river flows past the point where it once vanished underground, and flows on the surface, only to be gulped downstream by a ‘swallow holes’. The more rain that falls, the farther down the surface riverbed the water will flow, and the more violent the maelstroms/whirlpools over the swallow holes become. The huge piles of intertwined tree trunks lying over the larger downstream swallow holes in dry weather are testimony to the hydraulic power of the system when in full flood. The water flowing through all these underground channels creates caves. One cave system is known to extend for 18 miles, with still uncharted tunnels yet to explore.whirl-pool

Almost all of Florida is krast topography. This explains the constant news coverage of homes disappearing into the earth and sometimes causing fatalities.

 

There are four types of sinkholes in Florida:

Dissolution Sinkholes: Slow forming – generally forming small water bodies and/or wetlands.

sink 1

Cover-Subsidence Sinkholes: Slow forming holes where top layers are sand, which tend to pour into the hole like an hourglass.

sink 2

Cover-Collapse Sinkholes: Extremely fast occurring holes that form because of a thicker top layer that supports the cavity for awhile, but catastrophically caves in when it can no longer support the earth above. These are the ‘house eaters’.

sink 3

Man-Made Sinkholes: There are many. One kind is created in urban areas where sewer pipes are installed. Many times sewer pipes might develop a breach and they suck nearby material into the breach, which forms a sinkhole. Sinkholes can also form due to mining. The disaster below involved salt mining.

© Ilex Farrell ~ Midwestern Plant Girl

12 thoughts on “The Ground is Falling! The Ground is Falling! Why Florida is Sinking

    • Nope, not on my bucket list either!
      I joked w/my hubby recently… I’ve experienced many a disaster: tornado, earthquake, heat/cold wave, tsunami, volcano, hurricane, flood, blizzard, wildfire… I still need an avalanche or landslide to round out my list =-) Ha!

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  1. That was really interesting! My family lives in Florida, so when I fly in to visit, it’s usually through Orlando. One time I asked about all the little round lakes that you can see from the air coming in, and I was told they were sinkholes. I found that kind of alarming, since there were so many of them! Also I was told that the alligators love them and use them as sort of a highway, migrating from sinkhole to sinkhole at night.

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    • Thanks! I love geology, I’m learning more about it and this was a subject I was studying recently. Those holes are indeed sinkholes.
      The gators can become an issue at times.. ‘Alligator Lake’ was just 2 blocks from my home. Many little pets met their demise while running unleashed along the shore. (BAD pet owner, bad!!) I learned 2 things ASAP upon my arrival in FL. #1 Alligators can run fast in a straight line, if you’re being chased, serpentine! (Run zig-zag) #2 Learn all of the poisonous snakes by going to Busch Gardens. But, as far as I’m concerned ALL snakes are dangerous!! =-)

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