The Science Behind Florida’s Sinkhole Epidemic

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https://www.smithsonianmag.com/science-n...180969158/

EXCERPT: . . . That there’s such a thing as “sinkhole season,” just as there’s a “tornado season” and “hurricane season,” speaks to the many factors that contribute to the threat. Underlying all of them is the fact that Florida is built on a bedrock of carbonate, primarily limestone. That rock dissolves relatively easily in rainwater, which becomes acidic as it seeps through the soil. The resulting terrain, called “karst,” is honeycombed with cavities. When a cavity becomes too big to support its ceiling, it suddenly gives way, collapsing the clay and sand above to leave a cavernous hole at the surface.

The main trigger for sinkholes is water—too much of it, or too little. The normally moist soil of Florida has a stabilizing effect on karst. But during a drought, cavities that were supported by groundwater empty out and become unstable. During a heavy rainstorm, the weight of pooled water can strain the soil, and the sudden influx of groundwater can wash out cavities. Central Florida was in a severe drought at the beginning of 2017, followed by the intense rainfall of Hurricane Irma that hit The Villages in September—and a deluge after a drought is the optimal condition for a sinkhole outbreak.

But those major events from Mother Nature in 2017 don’t account for the spate of sinkholes this year already. The weather in Sumter County has been pretty typical. So what’s going on?

Man-made development, it turns out, is the most persistent factor for increased sinkholes. Earth-moving equipment scrapes away protective layers of soil; parking lots and paved roads divert rainwater to new infiltration points; the weight of new buildings presses down on weak spots; buried infrastructure can lead to leaking pipes; and, perhaps most of all, the pumping of groundwater disrupts the delicate water table that keeps the karst stable. “Our preliminary research indicates that the risk of sinkholes is 11 times greater in developed areas than undeveloped ones,” says George Veni, the executive director of the National Cave and Karst Research Institute who conducted a field study in Sinkhole Alley....

MORE: https://www.smithsonianmag.com/science-n...180969158/
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