Sinkhole risk in Fulton 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: 3%
At or near the surface: 0%
Buried under cover: 3%

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 22 of Fulton County's 866 square miles on soluble rock. With about 32,510 residents (38 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 319 map points about 1.6 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 how these percentages are measured.

Counties around Fulton County

The nearest county rated sinkhole country is Calhoun County, IL, about 93 miles south. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Mason County, IL 22 mi southeast · 0% at surface
McDonough County, IL 25 mi west · under 1% at surface
Schuyler County, IL 30 mi southwest · 0% at surface
Peoria County, IL 32 mi northeast · 0% at surface
Knox County, IL 32 mi north · 0% at surface
Cass County, IL 34 mi south · 0% at surface

What Fulton County is built on

The largest mapped soluble unit here is the Upper Valmeyeran (Aux Vases, Ste. Genevieve, St. Louis) Series (limestone), Mississippian in age, covering about 2% of the county. Next is the Middle Valmeyeran (Salem, Warsaw, Borden, Springville; includes thin Mvl and Mk in south and east) Series at under 1%.

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

Fulton County ranks 51 of 102 in Illinois for soluble rock at the surface, and sits above 0% of US counties on that measure.