SinkholeOdds

Sinkhole risk in Marion 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
46%
Buried under cover
54%

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 1,588 of Marion County's 1,588 square miles on soluble rock, 726 of them with the rock at or near the surface. With about 428,905 residents (270 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 315 map points about 2.2 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 Marion County

The nearest county rated sinkhole country is Sumter County, FL, about 34 miles south, close enough that the same rock may run under the county line. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

The rock underneath

The largest mapped soluble unit here is the Ocala Limestone (limestone), Eocene in age, covering about 66% of the county. Next is the Hawthorn Group, Coosawhatchie Formation at 17%.

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

Marion County ranks 30 of 67 in Florida for soluble rock at the surface, and sits above 86% of US counties on that measure.