SinkholeOdds

Sinkhole risk in Madison County, FL: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock
100%
At or near the surface
47%
Buried under cover
53%

The next step for one property

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

Standard Florida homeowners policies cover only catastrophic ground cover collapse; full sinkhole coverage is a separately priced option insurers must offer.

That works out to roughly 697 of Madison County's 697 square miles on soluble rock, 328 of them with the rock at or near the surface. With about 18,364 residents (26 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 263 map points about 1.6 miles apart, so a pocket smaller than that can be missed or overstated.

Read next: what Florida insurers have to cover, and why gypsum and salt move faster than limestone.

Counties around Madison County

The nearest county rated sinkhole country is Hamilton County, FL, about 31 miles east, close enough that the same rock may run under the county line. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

What Madison County is built on

The largest mapped soluble unit here is the Hawthorn Group, Torreya Formation (limestone), Miocene in age, covering about 47% of the county. Next is the Hawthorn Group, Torreya Formation at 27%.

The county also lies over the Floridan shelf, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Florida

Madison County ranks 28 of 67 in Florida for soluble rock at the surface, and sits above 86% of US counties on that measure.