Sinkhole risk in Butler 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: 100%
At or near the surface: 0%
Buried under cover: 100%

What to do about a house in Butler 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 580 of Butler County's 580 square miles on soluble rock. With about 14,156 residents (24 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 the signs to look for and how an inspection works.

Counties around Butler County

The nearest county rated sinkhole country is Clayton County, IA, about 74 miles east. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Floyd County, IA 22 mi north · 0% at surface
Grundy County, IA 23 mi south · 0% at surface
Bremer County, IA 23 mi east · 0% at surface
Franklin County, IA 25 mi west · 0% at surface
Black Hawk County, IA 30 mi southeast · 0% at surface
Chickasaw County, IA 32 mi northeast · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Cedar Valley Limestone (limestone), Middle Dovonian in age, covering about 67% of the county. Next is the Lime Creek Formation at 24%.

Against the rest of Iowa

Butler County ranks 24 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.