Sinkhole risk in Perry 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: 34%
At or near the surface: 34%
Buried under cover: 0%

What to do about a house in Perry County

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 190 of Perry County's 551 square miles on soluble rock, 190 of them with the rock at or near the surface. With about 46,816 residents (85 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 483 map points about 1.1 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Perry County

The nearest county rated sinkhole country is Union County, PA, about 41 miles north. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Juniata County, PA 12 mi northwest · 45% at surface
Cumberland County, PA 16 mi south · 48% at surface
Mifflin County, PA 25 mi northwest · 45% at surface
Dauphin County, PA 25 mi east · 8% at surface
Snyder County, PA 27 mi north · 38% at surface
Adams County, PA 37 mi south · 6% at surface

What Perry County is built on

The largest mapped soluble unit here is the Clinton Group (shale), Silurian in age, covering about 13% of the county. Next is the Hamilton Group at 10%.

Against the rest of Pennsylvania

Perry County ranks 15 of 67 in Pennsylvania for soluble rock at the surface, and sits above 81% of US counties on that measure.