Sinkhole risk in Clarke County, AL: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 39%
At or near the surface: 15%
Buried under cover: 23%

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 477 of Clarke County's 1,238 square miles on soluble rock, 189 of them with the rock at or near the surface. With about 22,142 residents (18 per square mile), much of the land is open, and the mapped rock may sit far from where people actually live. The figures come from 589 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why gypsum and salt move faster than limestone, and why the 23% under cover still counts.

Counties around Clarke County

The nearest county rated sinkhole country is Noxubee County, MS, about 107 miles northwest. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Monroe County, AL 27 mi east · 12% at surface
Washington County, AL 30 mi southwest · 3% at surface
Choctaw County, AL 33 mi northwest · 5% at surface
Wilcox County, AL 37 mi northeast · 27% at surface
Marengo County, AL 39 mi north · 33% at surface
Wayne County, MS 51 mi west · 17% at surface

The rock underneath

The largest mapped soluble unit here is the Oligocene Series undifferentiated (limestone), Oligocene in age, covering about 22% of the county. Next is the Oligocene Series undifferentiated at 8%.

The county also lies over the Gulf Coast salt domes, 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 Alabama

Clarke County ranks 36 of 67 in Alabama for soluble rock at the surface, and sits above 72% of US counties on that measure.