Sinkhole risk in Morris 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: 8%
At or near the surface: 1%
Buried under cover: 6%

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 35 of Morris County's 461 square miles on soluble rock, 6 of them with the rock at or near the surface. With about 523,053 residents (1,135 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 506 map points about 1.0 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 6% under cover still counts, and how these percentages are measured.

Counties around Morris County

The nearest county rated sinkhole country is Union County, PA, about 131 miles west. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Essex County, NJ 16 mi east · 0% at surface
Passaic County, NJ 18 mi northeast · 0% at surface
Union County, NJ 19 mi southeast · 0% at surface
Somerset County, NJ 21 mi south · under 1% at surface
Sussex County, NJ 21 mi north · 0% at surface
Warren County, NJ 24 mi west · 10% at surface

The rock underneath

The largest mapped soluble unit here is the Leithsville Formation (dolostone (dolomite)), Middle and Lower Cambrian in age, covering about 5% of the county. Next is the Allentown Dolomite at 1%.

Against the rest of New Jersey

Morris County ranks 8 of 21 in New Jersey for soluble rock at the surface, and sits above 56% of US counties on that measure.