Sinkhole risk in Sumter 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: 46%
At or near the surface: 46%
Buried under cover: 0%

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 413 of Sumter County's 904 square miles on soluble rock, 413 of them with the rock at or near the surface. With about 11,607 residents (13 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 586 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Sumter County

The nearest county rated sinkhole country is Noxubee County, MS, about 41 miles northwest. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Greene County, AL 22 mi northeast · 18% at surface
Kemper County, MS 27 mi northwest · 36% at surface
Lauderdale County, MS 30 mi southwest · 0% at surface
Marengo County, AL 34 mi southeast · 33% at surface
Hale County, AL 35 mi east · 20% at surface
Noxubee County, MS 41 mi northwest · 88% at surface

What Sumter County is built on

The largest mapped soluble unit here is the Midway Group; Porters Creek Formation (clay or mud), Paleocene in age, covering about 20% of the county. Next is the Selma Group; Demopolis Chalk at 19%.

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

Sumter County ranks 15 of 67 in Alabama for soluble rock at the surface, and sits above 86% of US counties on that measure.