Sinkhole risk in Northampton 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: 37%
At or near the surface: 33%
Buried under cover: 4%

What to do about a house in Northampton 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 138 of Northampton County's 370 square miles on soluble rock, 122 of them with the rock at or near the surface. With about 322,989 residents (873 per square mile), most of the county is built up, so a mapped unit is likely to sit under somebody's street. The figures come from 467 map points about 0.9 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 Northampton County

The nearest county rated sinkhole country is Union County, PA, about 92 miles west. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Warren County, NJ 17 mi northeast · 10% at surface
Lehigh County, PA 18 mi southwest · 29% at surface
Monroe County, PA 21 mi north · under 1% at surface
Carbon County, PA 24 mi northwest · under 1% at surface
Hunterdon County, NJ 24 mi southeast · 5% at surface
Bucks County, PA 31 mi south · 2% at surface

The rock underneath

The largest mapped soluble unit here is the Allentown Formation (dolostone (dolomite)), Cambrian in age, covering about 11% of the county. Next is the Epler Formation at 11%.

Against the rest of Pennsylvania

Northampton County ranks 16 of 67 in Pennsylvania for soluble rock at the surface, and sits above 81% of US counties on that measure.