Sinkhole risk in Adams 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: 79%
At or near the surface: 79%
Buried under cover: 0%

What to do about a house in Adams County

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 445 of Adams County's 563 square miles on soluble rock, 445 of them with the rock at or near the surface. With about 31,196 residents (55 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 1.2 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 Adams County

The nearest county rated sinkhole country is Kearney County, NE, about 24 miles west, 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.

Webster County, NE 23 mi south · 78% at surface
Kearney County, NE 24 mi west · 47% at surface
Clay County, NE 24 mi east · 60% at surface
Hall County, NE 24 mi north · 33% at surface
Nuckolls County, NE 34 mi southeast · 52% at surface
Franklin County, NE 34 mi southwest · 78% at surface

Which formation it is

The largest mapped soluble unit here is the Niobrara Formation (limestone), Late Cretaceous in age, covering about 66% of the county. Next is the Pierre Shale at 13%.

13% 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

Adams County ranks 2 of 93 in Nebraska for soluble rock at the surface, and sits above 94% of US counties on that measure.