SinkholeOdds

Sinkhole risk in Spink 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
15%
At or near the surface
0%
Buried under cover
15%

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 224 of Spink County's 1,503 square miles on soluble rock. With about 6,108 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 396 map points about 1.9 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why the 15% under cover still counts, and how these percentages are measured.

Counties around Spink County

The nearest county rated sinkhole country is Boyd County, NE, about 142 miles south. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

The rock underneath

The largest mapped soluble unit here is the Niobrara Formation (limestone), Late Cretaceous in age, covering about 15% of the county.

Against the rest of South Dakota

Spink County ranks 58 of 66 in South Dakota for soluble rock at the surface, and sits above 0% of US counties on that measure.