Sinkhole risk in Manitowoc County, WI: 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: 99%
At or near the surface: under 1%
Buried under cover: 99%

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 583 of Manitowoc County's 589 square miles on soluble rock, 2 of them with the rock at or near the surface. With about 81,513 residents (138 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 298 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 99% under cover still counts, and how these percentages are measured.

Counties around Manitowoc County

The nearest county rated sinkhole country is Oceana County, MI, about 67 miles southeast. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Sheboygan County, WI 30 mi south · 0% at surface
Brown County, WI 30 mi northwest · under 1% at surface
Kewaunee County, WI 32 mi north · 0% at surface
Calumet County, WI 32 mi west · 0% at surface
Ozaukee County, WI 47 mi south · 0% at surface
Outagamie County, WI 47 mi northwest · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Silurian, undivided (dolostone (dolomite)), Silurian in age, covering about 99% of the county.

Against the rest of Wisconsin

Manitowoc County ranks 23 of 72 in Wisconsin for soluble rock at the surface, and sits above 51% of US counties on that measure.