SinkholeOdds

Sinkhole risk in Warren 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
6%
At or near the surface
0%
Buried under cover
6%

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 35 of Warren County's 570 square miles on soluble rock. With about 56,343 residents (99 per square mile), homes are spread across towns and farmland, and a mapped unit may or may not reach the developed parts. The figures come from 389 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Read next: why gypsum and salt move faster than limestone, and why the 6% under cover still counts.

Counties around Warren County

The nearest county rated sinkhole country is Clayton County, IA, about 155 miles northeast. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

What Warren County is built on

The largest mapped soluble unit here is the Kansas City Group (limestone), Late Pennsylvanian-Missouri Series in age, covering about 3% of the county. Next is the Marmaton Group at 3%.

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

Warren County ranks 92 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.