Sinkhole risk in Mackinac County, MI: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 76%
At or near the surface: under 1%
Buried under cover: 76%

The next step for one property

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 780 of Mackinac County's 1,022 square miles on soluble rock, 5 of them with the rock at or near the surface. With about 11,144 residents (11 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 380 map points about 1.6 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 76% under cover still counts, and the signs to look for and how an inspection works.

Counties around Mackinac County

The nearest county rated sinkhole country is Emmet County, MI, about 43 miles south. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Luce County, MI 26 mi northwest · under 1% at surface
Chippewa County, MI 39 mi east · 0% at surface
Charlevoix County, MI 40 mi south · 11% at surface
Emmet County, MI 43 mi south · 0% at surface
Schoolcraft County, MI 44 mi west · 1% at surface
Cheboygan County, MI 62 mi southeast · 1% at surface

The rock underneath

The largest mapped soluble unit here is the Engadine Dolomite (dolostone (dolomite)), Lower Silurian in age, covering about 41% of the county. Next is the Burnt Bluff Formation at 17%.

Against the rest of Michigan

Mackinac County ranks 7 of 83 in Michigan for soluble rock at the surface, and sits above 53% of US counties on that measure.