SinkholeOdds

Sinkhole risk in Clarke 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
50%
At or near the surface
0%
Buried under cover
50%

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 213 of Clarke County's 431 square miles on soluble rock. With about 9,524 residents (22 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.

Two things to read before deciding: why gypsum and salt move faster than limestone, and why the 50% under cover still counts.

Counties around Clarke County

The nearest county rated sinkhole country is Jackson County, MO, about 143 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 Clarke County is built on

The largest mapped soluble unit here is the Kansas City Group (limestone), Late Pennsylvanian-Missouri Series in age, covering about 50% of the county.

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

Clarke County ranks 32 of 99 in Iowa for soluble rock at the surface, and sits above 0% of US counties on that measure.