Sinkhole risk in Hanson 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: 30%
At or near the surface: 0%
Buried under cover: 30%

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 132 of Hanson County's 435 square miles on soluble rock. With about 3,477 residents (8 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 400 map points about 1.0 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 30% under cover still counts, and how these percentages are measured.

Counties around Hanson County

The nearest county rated sinkhole country is Knox County, NE, about 72 miles south. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Davison County, SD 18 mi west · 0% at surface
McCook County, SD 22 mi east · 0% at surface
Hutchinson County, SD 24 mi south · 0% at surface
Miner County, SD 25 mi north · 0% at surface
Sanborn County, SD 28 mi northwest · 0% at surface
Douglas County, SD 35 mi southwest · 0% at surface

The rock underneath

The largest mapped soluble unit here is the Niobrara Formation (limestone), Late Cretaceous in age, covering about 30% of the county.

Against the rest of South Dakota

Hanson County ranks 35 of 66 in South Dakota for soluble rock at the surface, and sits above 0% of US counties on that measure.