Sinkhole risk in Brooks County, GA: 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%

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.

That works out to roughly 493 of Brooks County's 493 square miles on soluble rock, 143 of them with the rock at or near the surface. With about 16,344 residents (33 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 277 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why gypsum and salt move faster than limestone, and why the 71% under cover still counts.

Counties around Brooks County

The nearest county rated sinkhole country is Hamilton County, FL, about 44 miles southeast. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Lowndes County, GA 19 mi east · 16% at surface
Thomas County, GA 20 mi west · 34% at surface
Cook County, GA 24 mi north · 16% at surface
Madison County, FL 27 mi south · 47% at surface
Colquitt County, GA 28 mi northwest · 21% at surface
Lanier County, GA 34 mi northeast · under 1% at surface

What Brooks County is built on

The largest mapped soluble unit here is the "Hawthorn Formation" (sand), Miocene in age, covering about 71% of the county. Next is the "Hawthorn 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 Georgia

Brooks County ranks 31 of 159 in Georgia for soluble rock at the surface, and sits above 79% of US counties on that measure.