SinkholeOdds

Sinkhole risk in Polk 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
3%
Buried under cover
97%

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 1,798 of Polk County's 1,798 square miles on soluble rock, 58 of them with the rock at or near the surface. With about 852,878 residents (474 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 281 map points about 2.5 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: what Florida insurers have to cover, and why gypsum and salt move faster than limestone.

Counties around Polk County

The nearest county rated sinkhole country is DeSoto County, FL, about 53 miles south. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Which formation it is

The largest mapped soluble unit here is the Hawthorn Group, Coosawhatchie Formation (limestone), Eocene in age, covering about 26% of the county. Next is the Hawthorn Group, Peace River Formation at 26%.

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

Polk County ranks 61 of 67 in Florida for soluble rock at the surface, and sits above 60% of US counties on that measure.