SinkholeOdds

Sinkhole risk in Montmorency 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
20%
At or near the surface
0%
Buried under cover
20%

What to do about a house in Montmorency County

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 107 of Montmorency County's 547 square miles on soluble rock. With about 9,828 residents (18 per square mile), much of the land is open, and the mapped rock may sit far from where people actually live. The figures come from 404 map points about 1.2 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 20% under cover still counts.

Counties around Montmorency County

The nearest county rated sinkhole country is Crawford County, MI, about 33 miles southwest, 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 Traverse Group (limestone), Middle Devonian in age, covering about 11% of the county. Next is the Bedford Shale 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 Michigan

Montmorency County ranks 63 of 83 in Michigan for soluble rock at the surface, and sits above 0% of US counties on that measure.