SinkholeOdds

Sinkhole risk in Keokuk 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
82%
At or near the surface
0%
Buried under cover
82%

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 473 of Keokuk County's 579 square miles on soluble rock. With about 9,855 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 391 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why gypsum and salt move faster than limestone, and why the 82% under cover still counts.

Counties around Keokuk County

The nearest county rated sinkhole country is Clayton County, IA, about 113 miles north. 6 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 Meramec Series (limestone), Late Mississippian in age, covering about 40% of the county. Next is the Osage Series at 38%.

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

Keokuk County ranks 57 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.