Sinkhole risk in Dane County, WI: Pockets of it

Pockets of it

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

On soluble rock: 56%
At or near the surface: 19%
Buried under cover: 37%

What to do about a house in Dane County

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 665 of Dane County's 1,196 square miles on soluble rock, 225 of them with the rock at or near the surface. With about 588,347 residents (492 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 378 map points about 1.8 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Dane County

The nearest county rated sinkhole country is Iowa County, WI, about 36 miles west, close enough that the same rock may run under the county line. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Columbia County, WI 28 mi north · under 1% at surface
Green County, WI 29 mi south · 38% at surface
Rock County, WI 32 mi southeast · 0% at surface
Jefferson County, WI 33 mi east · 3% at surface
Sauk County, WI 36 mi northwest · 16% at surface
Iowa County, WI 36 mi west · 77% at surface

The rock underneath

The largest mapped soluble unit here is the Prairie du Chien Group (shale), Lower Ordovician in age, covering about 24% of the county. Next is the Ancell Group at 19%.

Against the rest of Wisconsin

Dane County ranks 12 of 72 in Wisconsin for soluble rock at the surface, and sits above 74% of US counties on that measure.