Sinkhole risk in Aurora 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: 29%
At or near the surface: 0%
Buried under cover: 29%

What to do about a house in Aurora County

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

That works out to roughly 204 of Aurora County's 708 square miles on soluble rock. With about 2,752 residents (4 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 389 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Aurora County

The nearest county rated sinkhole country is Boyd County, NE, about 58 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 21 mi east · 0% at surface
Jerauld County, SD 24 mi north · 0% at surface
Douglas County, SD 26 mi southeast · 0% at surface
Brule County, SD 26 mi west · under 1% at surface
Sanborn County, SD 32 mi northeast · 0% at surface
Charles Mix County, SD 36 mi south · 3% at surface

Which formation it is

The largest mapped soluble unit here is the Niobrara Formation (limestone), Late Cretaceous in age, covering about 29% of the county.

Against the rest of South Dakota

Aurora County ranks 14 of 66 in South Dakota for soluble rock at the surface, and sits above 0% of US counties on that measure.