Sinkhole risk in McCook County, SD: 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: 43%
At or near the surface: 0%
Buried under cover: 43%

What to do about a house in McCook County

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

That works out to roughly 244 of McCook County's 574 square miles on soluble rock. With about 5,771 residents (10 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 391 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 43% under cover still counts, and how these percentages are measured.

Counties around McCook County

The nearest county rated sinkhole country is Knox County, NE, about 77 miles south. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Hanson County, SD 22 mi west · 0% at surface
Miner County, SD 27 mi northwest · 0% at surface
Lake County, SD 27 mi northeast · 0% at surface
Turner County, SD 28 mi south · 0% at surface
Minnehaha County, SD 28 mi east · 0% at surface
Hutchinson County, SD 31 mi southwest · 0% at surface

What McCook County is built on

The largest mapped soluble unit here is the Niobrara Formation (limestone), Late Cretaceous in age, covering about 43% of the county.

Against the rest of South Dakota

McCook County ranks 47 of 66 in South Dakota for soluble rock at the surface, and sits above 0% of US counties on that measure.