SinkholeOdds

Sinkhole risk in Oakland County, MI: 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
6%
At or near the surface
0%
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 53 of Oakland County's 867 square miles on soluble rock. With about 1,296,888 residents (1,495 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 375 map points about 1.5 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 6% under cover still counts.

Counties around Oakland County

The nearest county rated sinkhole country is Genesee County, MI, about 30 miles northwest, close enough that the same rock may run under the county line. 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 Bedford Shale (shale), Upper Devonian in age, covering about 6% of the county. Next is the Michigan Formation at under 1%.

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 Michigan

Oakland County ranks 66 of 83 in Michigan for soluble rock at the surface, and sits above 0% of US counties on that measure.