SinkholeOdds

Sinkhole risk in Hamilton 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
88%
Buried under cover
12%

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 514 of Hamilton County's 514 square miles on soluble rock, 455 of them with the rock at or near the surface. With about 14,334 residents (28 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 258 map points about 1.4 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 Hamilton County

The closest county with no soluble rock mapped is Randolph County, GA, about 138 miles northwest. None of the 6 closest counties land in the same band, so Hamilton County stands out from its surroundings.

What Hamilton County is built on

The largest mapped soluble unit here is the Hawthorn Group, Statenville Formation (sandstone), Miocene in age, covering about 79% of the county. Next is the Suwannee Limestone at 12%.

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

Hamilton County ranks 6 of 67 in Florida for soluble rock at the surface, and sits above 96% of US counties on that measure.