Sinkhole risk in Indiana County, PA: Pockets of it

Pockets of it

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

On soluble rock: 16%
At or near the surface: 16%
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 133 of Indiana County's 827 square miles on soluble rock, 133 of them with the rock at or near the surface. With about 82,953 residents (100 per square mile), homes are spread across towns and farmland, and a mapped unit may or may not reach the developed parts. The figures come from 267 map points about 1.8 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 Indiana County

The nearest county rated sinkhole country is Washington County, MD, about 99 miles southeast. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Cambria County, PA 22 mi southeast · 2% at surface
Armstrong County, PA 23 mi northwest · 37% at surface
Westmoreland County, PA 31 mi southwest · 26% at surface
Jefferson County, PA 34 mi north · 24% at surface
Clearfield County, PA 40 mi northeast · under 1% at surface
Clarion County, PA 42 mi northwest · 36% at surface

The rock underneath

The largest mapped soluble unit here is the Allegheny Formation (sandstone), Pennsylvanian in age, covering about 15% of the county. Next is the Monongahela Group at 2%.

The county also lies over the Michigan Basin; Ohio Basin; Appalachian 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 Pennsylvania

Indiana County ranks 29 of 67 in Pennsylvania for soluble rock at the surface, and sits above 72% of US counties on that measure.