Sinkhole risk in Crawford County, IN: Sinkhole country

Sinkhole country

Soluble rock at or near the surface across much of the county.

On soluble rock: 85%
At or near the surface: 83%
Buried under cover: 2%

The next step for one property

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

That works out to roughly 260 of Crawford County's 306 square miles on soluble rock, 255 of them with the rock at or near the surface. With about 10,523 residents (34 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 240 map points about 1.1 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 the signs to look for and how an inspection works.

Counties around Crawford County

The closest county with no soluble rock mapped is Spencer County, IN, about 36 miles southwest. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Perry County, IN 18 mi southwest · 49% at surface
Orange County, IN 18 mi north · 90% at surface
Harrison County, IN 20 mi east · 94% at surface
Dubois County, IN 24 mi west · 5% at surface
Meade County, KY 26 mi southeast · 91% at surface
Washington County, IN 28 mi northeast · 62% at surface

The rock underneath

The largest mapped soluble unit here is the Stephensport Group (sandstone), Mississippian in age, covering about 32% of the county. Next is the West Baden Group at 20%.

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

Crawford County ranks 3 of 92 in Indiana for soluble rock at the surface, and sits above 95% of US counties on that measure.