SinkholeOdds

Sinkhole risk in Grand Traverse 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
1%
At or near the surface
0%
Buried under cover
1%

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 6 of Grand Traverse County's 464 square miles on soluble rock. With about 96,625 residents (208 per square mile), homes are spread across towns and farmland, and a mapped unit may or may not reach the developed parts. The figures come from 260 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Read next: why gypsum and salt move faster than limestone, and how these percentages are measured.

Counties around Grand Traverse County

The nearest county rated sinkhole country is Wexford County, MI, about 27 miles south, 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 Michigan Formation (black shale), Mississippian in age, covering about 1% of the county.

1% of the county sits on gypsum or salt, which dissolves in years rather than millennia. That share matters more than its size suggests.

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

Grand Traverse County ranks 36 of 83 in Michigan for soluble rock at the surface, and sits above 0% of US counties on that measure.