SinkholeOdds

Sinkhole risk in Rockland County, NY: 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
2%
At or near the surface
0%
Buried under cover
2%

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 4 of Rockland County's 174 square miles on soluble rock. With about 348,144 residents (2,004 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 502 map points about 0.6 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: how these percentages are measured, and the warning signs that apply anywhere.

Counties around Rockland County

The nearest county rated sinkhole country is Union County, PA, about 158 miles west. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Which formation it is

The largest mapped soluble unit here is the Rusty and gray biotite-quartz-feldspar gneiss (gneiss), Middle Proterozoic in age, covering about 2% of the county. Next is the Manhattan Formation (A Member) at under 1%.

Against the rest of New York

Rockland County ranks 46 of 62 in New York for soluble rock at the surface, and sits above 0% of US counties on that measure.