Sinkhole risk in Cerro Gordo County, IA: 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: 100%
At or near the surface: 0%
Buried under cover: 100%

What to do about a house in Cerro Gordo County

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 568 of Cerro Gordo County's 568 square miles on soluble rock. With about 42,493 residents (75 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 391 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why the 100% under cover still counts, and how these percentages are measured.

Counties around Cerro Gordo County

The nearest county rated sinkhole country is Clayton County, IA, about 99 miles east. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Worth County, IA 21 mi north · 0% at surface
Franklin County, IA 23 mi south · 0% at surface
Floyd County, IA 23 mi east · 0% at surface
Hancock County, IA 25 mi west · 0% at surface
Mitchell County, IA 30 mi northeast · 0% at surface
Winnebago County, IA 32 mi northwest · 0% at surface

The rock underneath

The largest mapped soluble unit here is the Lime Creek Formation (limestone), Late Devonian in age, covering about 65% of the county. Next is the Shell Rock Formation at 15%.

Against the rest of Iowa

Cerro Gordo County ranks 29 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.