Sinkhole risk in Furnas 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: 32%
At or near the surface: 32%
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 229 of Furnas County's 719 square miles on soluble rock, 229 of them with the rock at or near the surface. With about 4,468 residents (6 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 403 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why gypsum and salt move faster than limestone, and the signs to look for and how an inspection works.

Counties around Furnas County

The nearest county rated sinkhole country is Harlan County, NE, about 27 miles east, close enough that the same rock may run under the county line. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Gosper County, NE 22 mi north · under 1% at surface
Harlan County, NE 27 mi east · 37% at surface
Norton County, KS 28 mi south · 22% at surface
Red Willow County, NE 30 mi west · 16% at surface
Phelps County, NE 35 mi northeast · 0% at surface
Frontier County, NE 35 mi northwest · under 1% at surface

The rock underneath

The largest mapped soluble unit here is the Niobrara Formation (limestone), Late Cretaceous in age, covering about 21% of the county. Next is the Pierre Shale at 11%.

11% 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

Furnas County ranks 13 of 93 in Nebraska for soluble rock at the surface, and sits above 80% of US counties on that measure.