Sinkhole risk in Worth 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 Worth 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 400 of Worth County's 400 square miles on soluble rock. With about 7,307 residents (18 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 392 map points about 1.0 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 Worth County

The nearest county rated sinkhole country is Clayton County, IA, about 104 miles east. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Cerro Gordo County, IA 21 mi south · 0% at surface
Freeborn County, MN 21 mi north · 0% at surface
Mitchell County, IA 23 mi east · 0% at surface
Winnebago County, IA 25 mi west · 0% at surface
Mower County, MN 32 mi northeast · 0% at surface
Floyd County, IA 32 mi southeast · 0% at surface

What Worth County is built on

The largest mapped soluble unit here is the Cedar Valley Limestone (limestone), Middle Dovonian in age, covering about 88% of the county. Next is the Shell Rock Formation at 12%.

Against the rest of Iowa

Worth County ranks 98 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.