Sinkhole risk in Lycoming 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: 15%
At or near the surface: 6%
Buried under cover: 8%

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 178 of Lycoming County's 1,229 square miles on soluble rock, 79 of them with the rock at or near the surface. With about 113,236 residents (92 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 593 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why gypsum and salt move faster than limestone, and why the 8% under cover still counts.

Counties around Lycoming County

The nearest county rated sinkhole country is Union County, PA, about 26 miles south, close enough that the same rock may run under the county line. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Union County, PA 26 mi south · 53% at surface
Sullivan County, PA 29 mi east · 0% at surface
Montour County, PA 30 mi southeast · 40% at surface
Clinton County, PA 31 mi west · 21% at surface
Tioga County, PA 31 mi north · 0% at surface
Northumberland County, PA 38 mi southeast · 26% at surface

Which formation it is

The largest mapped soluble unit here is the Hamilton Group (shale), Devonian in age, covering about 4% of the county. Next is the Mauch Chunk Formation at 3%.

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

Lycoming County ranks 35 of 67 in Pennsylvania for soluble rock at the surface, and sits above 64% of US counties on that measure.