Sinkhole risk in Lapeer County, MI: Sinkhole country

Sinkhole country

Fast-dissolving gypsum or salt beds under a large part of the county.

On soluble rock: 35%
At or near the surface: 0%
Buried under cover: 35%

What this means before you buy

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

That works out to roughly 223 of Lapeer County's 647 square miles on soluble rock. With about 89,168 residents (138 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 354 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Lapeer County

The closest county with no soluble rock mapped is Saginaw County, MI, about 45 miles west. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Genesee County, MI 25 mi west · 0% at surface
Tuscola County, MI 30 mi north · 0% at surface
St. Clair County, MI 30 mi east · under 1% at surface
Oakland County, MI 31 mi south · 0% at surface
Macomb County, MI 33 mi southeast · 0% at surface
Sanilac County, MI 38 mi northeast · 0% at surface

What Lapeer County is built on

The largest mapped soluble unit here is the Michigan Formation (black shale), Mississippian in age, covering about 35% of the county.

35% 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

Lapeer County ranks 52 of 83 in Michigan for soluble rock at the surface, and sits above 0% of US counties on that measure.