Sinkhole risk in Hall County, NE: Pockets of it

Pockets of it

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

On soluble rock: 33%
At or near the surface: 33%
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 182 of Hall County's 547 square miles on soluble rock, 182 of them with the rock at or near the surface. With about 62,869 residents (115 per square mile), homes are spread across towns and farmland, and a mapped unit may or may not reach the developed parts. The figures come from 396 map points about 1.2 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 Hall County

The nearest county rated sinkhole country is Kearney County, NE, about 34 miles southwest, close enough that the same rock may run under the county line. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Adams County, NE 24 mi south · 79% at surface
Howard County, NE 24 mi north · 11% at surface
Hamilton County, NE 25 mi east · 80% at surface
Buffalo County, NE 30 mi west · 4% at surface
Merrick County, NE 32 mi northeast · 79% at surface
Clay County, NE 33 mi southeast · 60% at surface

What Hall County is built on

The largest mapped soluble unit here is the Pierre Shale (shale), Late Cretaceous in age, covering about 18% of the county. Next is the Niobrara Formation at 15%.

18% of the county sits on gypsum or salt, which dissolves in years rather than millennia. That share matters more than its size suggests.

Against the rest of Nebraska

Hall County ranks 11 of 93 in Nebraska for soluble rock at the surface, and sits above 81% of US counties on that measure.