Sinkhole risk in Warren County, NJ: 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: 45%
At or near the surface: 10%
Buried under cover: 35%

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 159 of Warren County's 357 square miles on soluble rock, 35 of them with the rock at or near the surface. With about 112,031 residents (314 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 490 map points about 0.9 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 35% under cover still counts, and how these percentages are measured.

Counties around Warren County

The nearest county rated sinkhole country is Union County, PA, about 107 miles west. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Northampton County, PA 17 mi southwest · 33% at surface
Hunterdon County, NJ 21 mi south · 5% at surface
Monroe County, PA 22 mi northwest · under 1% at surface
Morris County, NJ 24 mi east · 1% at surface
Sussex County, NJ 26 mi northeast · 0% at surface
Somerset County, NJ 28 mi southeast · under 1% at surface

The rock underneath

The largest mapped soluble unit here is the Allentown Dolomite (dolostone (dolomite)), Lower Ordovician and Upper Cambrian in age, covering about 21% of the county. Next is the Beekmantown Group, Lower Part at 9%.

Against the rest of New Jersey

Warren County ranks 3 of 21 in New Jersey for soluble rock at the surface, and sits above 68% of US counties on that measure.