Sinkhole risk in Polk 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: 11%
At or near the surface: 0%
Buried under cover: 11%

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 99 of Polk County's 914 square miles on soluble rock. With about 45,831 residents (50 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 306 map points about 1.7 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Polk County

The nearest county rated sinkhole country is Vernon County, WI, about 152 miles southeast. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Chisago County, MN 22 mi west · 0% at surface
Burnett County, WI 28 mi north · 0% at surface
Barron County, WI 29 mi east · 0% at surface
St. Croix County, WI 30 mi south · 1% at surface
Washington County, MN 36 mi southwest · 0% at surface
Anoka County, MN 41 mi west · 0% at surface

The rock underneath

The largest mapped soluble unit here is the Prairie du Chien Group (shale), Lower Ordovician in age, covering about 11% of the county.

Against the rest of Wisconsin

Polk County ranks 55 of 72 in Wisconsin for soluble rock at the surface, and sits above 0% of US counties on that measure.