SinkholeOdds

Sinkhole risk in Iroquois County, IL: 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
52%
At or near the surface
0%
Buried under cover
52%

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 583 of Iroquois County's 1,117 square miles on soluble rock. With about 26,067 residents (23 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 383 map points about 1.7 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 52% under cover still counts.

Counties around Iroquois County

The nearest county rated sinkhole country is Monroe County, IN, about 130 miles southeast. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

What Iroquois County is built on

The largest mapped soluble unit here is the Silurian (dolostone (dolomite)), Silurian in age, covering about 34% of the county. Next is the Middle Devonian at 15%.

The county also lies over the Illinois 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 Illinois

Iroquois County ranks 59 of 102 in Illinois for soluble rock at the surface, and sits above 0% of US counties on that measure.