Sinkhole risk in Marengo 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: 33%
At or near the surface: 33%
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 319 of Marengo County's 977 square miles on soluble rock, 319 of them with the rock at or near the surface. With about 18,512 residents (19 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 272 map points about 1.9 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Marengo County

The nearest county rated sinkhole country is Noxubee County, MS, about 75 miles northwest. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Choctaw County, AL 32 mi southwest · 5% at surface
Wilcox County, AL 34 mi southeast · 27% at surface
Sumter County, AL 34 mi northwest · 46% at surface
Hale County, AL 36 mi north · 20% at surface
Clarke County, AL 39 mi south · 15% at surface
Perry County, AL 40 mi northeast · 29% at surface

What Marengo County is built on

The largest mapped soluble unit here is the Selma Group; Demopolis Chalk (carbonate), Cretaceous in age, covering about 16% of the county. Next is the Midway Group; Porters Creek Formation at 15%.

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

Marengo County ranks 18 of 67 in Alabama for soluble rock at the surface, and sits above 81% of US counties on that measure.