SinkholeOdds

Sinkhole risk in Lawrence County, PA: Mostly deep or small

Mostly deep or small

Some soluble rock, mostly deeply buried or in a small share of the county.

On soluble rock
55%
At or near the surface
6%
Buried under cover
50%

What this means before you buy

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 198 of Lawrence County's 357 square miles on soluble rock, 21 of them with the rock at or near the surface. With about 84,233 residents (236 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 347 map points about 1.0 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 why the 50% under cover still counts.

Counties around Lawrence County

The nearest county rated sinkhole country is Washington County, MD, about 164 miles southeast. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

The rock underneath

The largest mapped soluble unit here is the Allegheny Formation (sandstone), Pennsylvanian in age, covering about 55% 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

Lawrence County ranks 36 of 67 in Pennsylvania for soluble rock at the surface, and sits above 64% of US counties on that measure.