Sinkhole risk in Mifflin 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: 45%
At or near the surface: 45%
Buried under cover: 0%

What to do about a house in Mifflin 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 185 of Mifflin County's 411 square miles on soluble rock, 185 of them with the rock at or near the surface. With about 45,935 residents (112 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 394 map points about 1.0 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Mifflin County

The nearest county rated sinkhole country is Union County, PA, about 40 miles northeast, close enough that the same rock may run under the county line. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Juniata County, PA 14 mi east · 45% at surface
Huntingdon County, PA 21 mi southwest · 35% at surface
Centre County, PA 24 mi northwest · 40% at surface
Perry County, PA 25 mi southeast · 34% at surface
Snyder County, PA 32 mi east · 38% at surface
Blair County, PA 35 mi west · 36% at surface

What Mifflin County is built on

The largest mapped soluble unit here is the Clinton Group (shale), Silurian in age, covering about 11% of the county. Next is the Onondaga and Old Port Formations, undivided at 8%.

Against the rest of Pennsylvania

Mifflin County ranks 5 of 67 in Pennsylvania for soluble rock at the surface, and sits above 86% of US counties on that measure.