Sinkhole risk in Marshall County, KS: 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: 40%
At or near the surface: 2%
Buried under cover: 38%

The next step for one property

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

That works out to roughly 364 of Marshall County's 900 square miles on soluble rock, 18 of them with the rock at or near the surface. With about 9,950 residents (11 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 401 map points about 1.5 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 why the 38% under cover still counts.

Counties around Marshall County

The nearest county rated sinkhole country is Dickinson County, KS, about 72 miles southwest. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Nemaha County, KS 27 mi east · 0% at surface
Pawnee County, NE 29 mi northeast · 0% at surface
Pottawatomie County, KS 29 mi south · 6% at surface
Washington County, KS 31 mi west · 15% at surface
Gage County, NE 34 mi north · 0% at surface
Riley County, KS 36 mi south · 73% at surface

What Marshall County is built on

The largest mapped soluble unit here is the Chase Group (shale), Early Permian - Gearyan in age, covering about 30% of the county. Next is the Council Grove Group at 6%.

The county also lies over the Northern Anadarko 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 Kansas

Marshall County ranks 87 of 105 in Kansas for soluble rock at the surface, and sits above 58% of US counties on that measure.