Sinkhole risk in Sullivan 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: 6%
At or near the surface: 0%
Buried under cover: 6%

The next step for one property

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

That works out to roughly 27 of Sullivan County's 450 square miles on soluble rock. With about 5,927 residents (13 per square mile), much of the land is open, and the mapped rock may sit far from where people actually live. The figures come from 271 map points about 1.3 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 6% under cover still counts.

Counties around Sullivan County

The nearest county rated sinkhole country is Union County, PA, about 43 miles southwest. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Bradford County, PA 24 mi north · 0% at surface
Wyoming County, PA 27 mi east · 0% at surface
Columbia County, PA 28 mi south · 4% at surface
Lycoming County, PA 29 mi west · 6% at surface
Montour County, PA 29 mi south · 40% at surface
Luzerne County, PA 33 mi southeast · 0% at surface

What Sullivan County is built on

The largest mapped soluble unit here is the Mauch Chunk Formation (shale), Mississippian in age, covering about 6% 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

Sullivan County ranks 62 of 67 in Pennsylvania for soluble rock at the surface, and sits above 0% of US counties on that measure.