SinkholeOdds

Sinkhole risk in Monroe 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
5%
At or near the surface
0%
Buried under cover
5%

What to do about a house in Monroe County

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

That works out to roughly 23 of Monroe County's 434 square miles on soluble rock. With about 7,373 residents (17 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 390 map points about 1.1 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 5% under cover still counts.

Counties around Monroe County

The nearest county rated sinkhole country is Clayton County, IA, about 148 miles northeast. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

The rock underneath

The largest mapped soluble unit here is the Marmaton Group (shale), Middle Pennsylvanian-Des Moines Series in age, covering about 3% of the county. Next is the Meramec Series at 2%.

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

Monroe County ranks 70 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.