Sinkhole risk in DeKalb 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: 63%
At or near the surface: 0%
Buried under cover: 63%

What to do about a house in DeKalb County

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

That works out to roughly 396 of DeKalb County's 631 square miles on soluble rock. With about 101,335 residents (161 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 384 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around DeKalb County

The nearest county rated sinkhole country is Jo Daviess County, IL, about 81 miles northwest. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Kane County, IL 18 mi east · 0% at surface
Kendall County, IL 27 mi southeast · 2% at surface
Lee County, IL 29 mi west · under 1% at surface
Boone County, IL 29 mi north · 0% at surface
Ogle County, IL 30 mi west · 7% at surface
McHenry County, IL 34 mi northeast · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Galena-Platteville Groups (limestone), Ordovician in age, covering about 51% of the county. Next is the Prairie du Chien Group at 12%.

Against the rest of Illinois

DeKalb County ranks 41 of 102 in Illinois for soluble rock at the surface, and sits above 0% of US counties on that measure.