SinkholeOdds

Sinkhole risk in Onondaga 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
42%
At or near the surface
0%
Buried under cover
42%

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 326 of Onondaga County's 778 square miles on soluble rock. With about 469,812 residents (604 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 315 map points about 1.6 miles apart, so a pocket smaller than that can be missed or overstated.

Read next: why gypsum and salt move faster than limestone, and why the 42% under cover still counts.

Counties around Onondaga County

The nearest county rated sinkhole country is Union County, PA, about 148 miles south. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

What Onondaga County is built on

The largest mapped soluble unit here is the Vernon Formation (shale), Upper Silurian in age, covering about 23% of the county. Next is the Helderberg Group at 9%.

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 New York

Onondaga County ranks 36 of 62 in New York for soluble rock at the surface, and sits above 0% of US counties on that measure.