Sinkhole risk in Ogle County, IL: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 74%
At or near the surface: 7%
Buried under cover: 67%

The next step for one property

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 562 of Ogle County's 759 square miles on soluble rock, 51 of them with the rock at or near the surface. With about 51,345 residents (68 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 371 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 67% under cover still counts, and the signs to look for and how an inspection works.

Counties around Ogle County

The nearest county rated sinkhole country is Jo Daviess County, IL, about 51 miles northwest. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Lee County, IL 20 mi south · under 1% at surface
Winnebago County, IL 22 mi north · 5% at surface
Stephenson County, IL 28 mi northwest · 3% at surface
DeKalb County, IL 30 mi east · 0% at surface
Carroll County, IL 31 mi west · 11% at surface
Boone County, IL 32 mi northeast · 0% at surface

The rock underneath

The largest mapped soluble unit here is the Galena-Platteville Groups (limestone), Ordovician in age, covering about 69% of the county. Next is the Prairie du Chien Group at 3%.

Against the rest of Illinois

Ogle County ranks 12 of 102 in Illinois for soluble rock at the surface, and sits above 65% of US counties on that measure.