SinkholeOdds

Sinkhole risk in Seminole 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
29%
Buried under cover
71%

What to do about a house in Seminole County

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 309 of Seminole County's 309 square miles on soluble rock, 88 of them with the rock at or near the surface. With about 494,605 residents (1,599 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 262 map points about 1.1 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 Seminole County

The nearest county rated sinkhole country is Sumter County, FL, about 57 miles west. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

What Seminole County is built on

The largest mapped soluble unit here is the Shelly sediments of Plio-Pleistocene age (beach sand), Holocene in age, covering about 36% of the county. Next is the Hawthorn Group, Coosawhatchie Formation at 32%.

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

Seminole County ranks 45 of 67 in Florida for soluble rock at the surface, and sits above 79% of US counties on that measure.