Sinkhole risk in Clarion 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: 36%
At or near the surface: 36%
Buried under cover: 0%

What to do about a house in Clarion 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 214 of Clarion County's 601 square miles on soluble rock, 214 of them with the rock at or near the surface. With about 36,855 residents (61 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 298 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Clarion County

The nearest county rated sinkhole country is Union County, PA, about 124 miles east. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Jefferson County, PA 22 mi east · 24% at surface
Venango County, PA 23 mi northwest · 5% at surface
Forest County, PA 24 mi north · 0% at surface
Armstrong County, PA 27 mi south · 37% at surface
Butler County, PA 33 mi southwest · 35% at surface
Indiana County, PA 42 mi southeast · 16% at surface

Which formation it is

The largest mapped soluble unit here is the Allegheny Formation (sandstone), Pennsylvanian in age, covering about 36% of the county.

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

Clarion County ranks 12 of 67 in Pennsylvania for soluble rock at the surface, and sits above 82% of US counties on that measure.