Sinkhole risk in Rock 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: 97%
At or near the surface: 0%
Buried under cover: 97%

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 696 of Rock County's 718 square miles on soluble rock. With about 165,461 residents (230 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 390 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Rock County

The nearest county rated sinkhole country is Lafayette County, WI, about 54 miles west. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Winnebago County, IL 23 mi south · 5% at surface
Green County, WI 27 mi west · 38% at surface
Walworth County, WI 27 mi east · 0% at surface
Boone County, IL 27 mi southeast · 0% at surface
Jefferson County, WI 28 mi northeast · 3% at surface
Dane County, WI 32 mi northwest · 19% at surface

What Rock County is built on

The largest mapped soluble unit here is the Sinnipee Group (dolostone (dolomite)), Ordovician in age, covering about 51% of the county. Next is the Ancell Group at 36%.

Against the rest of Wisconsin

Rock County ranks 59 of 72 in Wisconsin for soluble rock at the surface, and sits above 0% of US counties on that measure.