SinkholeOdds

Sinkhole risk in Decatur 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
47%
At or near the surface
0%
Buried under cover
47%

What this means before you buy

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

That works out to roughly 248 of Decatur County's 532 square miles on soluble rock. With about 7,656 residents (14 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 408 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 gypsum and salt move faster than limestone, and why the 47% under cover still counts.

Counties around Decatur County

The nearest county rated sinkhole country is Jackson County, MO, about 123 miles south. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

What Decatur County is built on

The largest mapped soluble unit here is the Kansas City Group (limestone), Late Pennsylvanian-Missouri Series in age, covering about 39% of the county. Next is the Marmaton Group at 7%.

The county also lies over the Forest City Basin, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Iowa

Decatur County ranks 37 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.