Sinkhole risk in Butler 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: 25%
At or near the surface: 25%
Buried under cover: 0%

What this means before you buy

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 192 of Butler County's 777 square miles on soluble rock, 192 of them with the rock at or near the surface. With about 18,256 residents (24 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 369 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 the signs to look for and how an inspection works.

Counties around Butler County

The nearest county rated sinkhole country is Geneva County, AL, about 68 miles southeast. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Crenshaw County, AL 21 mi east · 30% at surface
Lowndes County, AL 27 mi north · 49% at surface
Conecuh County, AL 29 mi southwest · 16% at surface
Covington County, AL 38 mi south · 4% at surface
Wilcox County, AL 40 mi northwest · 27% at surface
Montgomery County, AL 42 mi northeast · 49% at surface

The rock underneath

The largest mapped soluble unit here is the Midway Group; Porters Creek Formation (clay or mud), Paleocene in age, covering about 18% of the county. Next is the Midway Group; Clayton Formation at 7%.

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

Butler County ranks 28 of 67 in Alabama for soluble rock at the surface, and sits above 77% of US counties on that measure.