Sinkhole risk in Scott 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: 91%
At or near the surface: under 1%
Buried under cover: 91%

What to do about a house in Scott County

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

That works out to roughly 418 of Scott County's 458 square miles on soluble rock, 2 of them with the rock at or near the surface. With about 175,601 residents (383 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 285 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 91% under cover still counts, and how these percentages are measured.

Counties around Scott County

The nearest county rated sinkhole country is Jo Daviess County, IL, about 54 miles northeast. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Rock Island County, IL 12 mi south · 0% at surface
Clinton County, IA 18 mi north · 1% at surface
Cedar County, IA 28 mi west · 0% at surface
Muscatine County, IA 28 mi southwest · 0% at surface
Mercer County, IL 31 mi south · 0% at surface
Henry County, IL 32 mi southeast · 0% at surface

Which formation it is

The largest mapped soluble unit here is the Niagaran Series (dolostone (dolomite)), Middle Silurian in age, covering about 78% of the county. Next is the Wapsipinicon Formation at 8%.

Against the rest of Iowa

Scott County ranks 13 of 99 in Iowa for soluble rock at the surface, and sits above 52% of US counties on that measure.