Sinkhole risk in Perry County, IN: Pockets of it

Pockets of it

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

On soluble rock: 57%
At or near the surface: 49%
Buried under cover: 9%

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 219 of Perry County's 382 square miles on soluble rock, 185 of them with the rock at or near the surface. With about 19,320 residents (51 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 1.2 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 9% under cover still counts.

Counties around Perry County

The nearest county rated sinkhole country is Crawford County, IN, about 18 miles northeast, close enough that the same rock may run under the county line. None of the 6 closest counties land in the same band, so Perry County stands out from its surroundings.

Crawford County, IN 18 mi northeast · 83% at surface
Hancock County, KY 19 mi southwest · 6% at surface
Spencer County, IN 21 mi west · under 1% at surface
Breckinridge County, KY 23 mi southeast · 89% at surface
Dubois County, IN 24 mi northwest · 5% at surface
Meade County, KY 24 mi east · 91% at surface

Which formation it is

The largest mapped soluble unit here is the Buffalo Wallow Group (shale), Mississippian in age, covering about 43% of the county. Next is the Stephensport Group at 10%.

The county also lies over the Illinois Basin, 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 Indiana

Perry County ranks 7 of 92 in Indiana for soluble rock at the surface, and sits above 87% of US counties on that measure.