Sinkhole risk in Merrick 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: 89%
At or near the surface: 79%
Buried under cover: 10%

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 436 of Merrick County's 488 square miles on soluble rock, 385 of them with the rock at or near the surface. With about 7,837 residents (16 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 394 map points about 1.1 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 why the 10% under cover still counts.

Counties around Merrick County

The nearest county rated sinkhole country is Kearney County, NE, about 66 miles southwest. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Nance County, NE 16 mi north · 31% at surface
Hamilton County, NE 21 mi south · 80% at surface
Polk County, NE 24 mi east · 2% at surface
Howard County, NE 25 mi west · 11% at surface
York County, NE 31 mi southeast · 0% at surface
Hall County, NE 32 mi southwest · 33% at surface

The rock underneath

The largest mapped soluble unit here is the Niobrara Formation (limestone), Late Cretaceous in age, covering about 81% of the county. Next is the Pierre Shale at 8%.

8% 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

Merrick County ranks 3 of 93 in Nebraska for soluble rock at the surface, and sits above 94% of US counties on that measure.