Sinkhole risk in Shelby 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: 72%
At or near the surface: 0%
Buried under cover: 72%

The next step for one property

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

That works out to roughly 428 of Shelby County's 591 square miles on soluble rock. With about 11,821 residents (20 per square mile), much of the land is open, and the mapped rock may sit far from where people actually live. The figures come from 369 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 72% under cover still counts, and how these percentages are measured.

Counties around Shelby County

The nearest county rated sinkhole country is Knox County, NE, about 148 miles northwest. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Audubon County, IA 21 mi east · 0% at surface
Crawford County, IA 25 mi north · 0% at surface
Pottawattamie County, IA 26 mi southwest · 0% at surface
Harrison County, IA 27 mi west · 0% at surface
Cass County, IA 31 mi southeast · 0% at surface
Carroll County, IA 34 mi northeast · 0% at surface

The rock underneath

The largest mapped soluble unit here is the Kansas City Group (limestone), Late Pennsylvanian-Missouri Series in age, covering about 40% of the county. Next is the Marmaton Group at 33%.

Against the rest of Iowa

Shelby County ranks 84 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.