Sinkhole risk in Floyd County, IA: Pockets of it

Pockets of it

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

On soluble rock: 99%
At or near the surface: 0%
Buried under cover: 99%

The next step for one property

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 497 of Floyd County's 501 square miles on soluble rock. With about 15,008 residents (30 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 400 map points about 1.1 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why the 99% under cover still counts, and the signs to look for and how an inspection works.

Counties around Floyd County

The nearest county rated sinkhole country is Clayton County, IA, about 75 miles east. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Mitchell County, IA 20 mi north · 0% at surface
Butler County, IA 22 mi south · 0% at surface
Cerro Gordo County, IA 23 mi west · 0% at surface
Chickasaw County, IA 24 mi east · 0% at surface
Bremer County, IA 30 mi southeast · 0% at surface
Howard County, IA 32 mi northeast · 5% at surface

Which formation it is

The largest mapped soluble unit here is the Cedar Valley Limestone (limestone), Middle Dovonian in age, covering about 66% of the county. Next is the Shell Rock Formation at 26%.

Against the rest of Iowa

Floyd County ranks 40 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.