SinkholeOdds

Sinkhole risk in Smith County, KS: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock
40%
At or near the surface
40%
Buried under cover
0%

The next step for one property

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 357 of Smith County's 895 square miles on soluble rock, 357 of them with the rock at or near the surface. With about 3,541 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 414 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why gypsum and salt move faster than limestone, and the signs to look for and how an inspection works.

Counties around Smith County

The nearest county rated sinkhole country is Franklin County, NE, about 29 miles north, close enough that the same rock may run under the county line. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

What Smith County is built on

The largest mapped soluble unit here is the Niobrara Chalk (shale), Late Cretaceous in age, covering about 35% of the county. Next is the Ogallala Formation at 4%.

The county also lies over the Permian Basin, Anadarko Basin,Dalhart Basin, Palo Duro 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

Smith County ranks 32 of 105 in Kansas for soluble rock at the surface, and sits above 84% of US counties on that measure.