Sinkhole risk in Sumter County, FL: Sinkhole country

Sinkhole country

Soluble rock at or near the surface across much of the county.

On soluble rock: 100%
At or near the surface: 59%
Buried under cover: 41%

The next step for one property

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

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 557 of Sumter County's 557 square miles on soluble rock, 330 of them with the rock at or near the surface. With about 154,693 residents (278 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 241 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: what Florida insurers have to cover, and why gypsum and salt move faster than limestone.

Counties around Sumter County

The closest county with no soluble rock mapped is Gulf County, FL, about 209 miles northwest. None of the 6 closest counties land in the same band, so Sumter County stands out from its surroundings.

Lake County, FL 22 mi east · under 1% at surface
Hernando County, FL 30 mi west · 39% at surface
Citrus County, FL 33 mi west · 48% at surface
Marion County, FL 34 mi north · 46% at surface
Pasco County, FL 39 mi southwest · 18% at surface
Orange County, FL 47 mi east · 7% at surface

The rock underneath

The largest mapped soluble unit here is the Ocala Limestone (limestone), Eocene in age, covering about 100% of the county.

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

Sumter County ranks 20 of 67 in Florida for soluble rock at the surface, and sits above 90% of US counties on that measure.