Sinkhole risk in Monona 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: 32%
At or near the surface: 0%
Buried under cover: 32%

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 220 of Monona County's 694 square miles on soluble rock. With about 8,429 residents (12 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 325 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 32% under cover still counts, and how these percentages are measured.

Counties around Monona County

The nearest county rated sinkhole country is Knox County, NE, about 107 miles northwest. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Burt County, NE 24 mi southwest · 0% at surface
Woodbury County, IA 24 mi north · 0% at surface
Harrison County, IA 26 mi south · 0% at surface
Crawford County, IA 29 mi east · 0% at surface
Thurston County, NE 30 mi west · 0% at surface
Ida County, IA 33 mi northeast · 0% at surface

What Monona County is built on

The largest mapped soluble unit here is the Kansas City Group (limestone), Late Pennsylvanian-Missouri Series in age, covering about 25% of the county. Next is the Marmaton Group at 7%.

Against the rest of Iowa

Monona County ranks 69 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.