SinkholeOdds

Sinkhole risk in Armstrong County, TX: Pockets of it

Pockets of it

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

On soluble rock
27%
At or near the surface
27%
Buried under cover
0%

What to do about a house in Armstrong 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 248 of Armstrong County's 909 square miles on soluble rock, 248 of them with the rock at or near the surface. With about 1,809 residents (2 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 396 map points about 1.5 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 Armstrong County

The nearest county rated sinkhole country is Donley County, TX, about 31 miles east, close enough that the same rock may run under the county line. None of the 6 closest counties land in the same band, so Armstrong County stands out from its surroundings.

Which formation it is

The largest mapped soluble unit here is the Quartermaster Formation (shale), Permian; Guadalupe Series in age, covering about 18% of the county. Next is the Dockum Group, undivided at 5%.

23% of the county sits on gypsum or salt, which dissolves in years rather than millennia. That share matters more than its size suggests.

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 Texas

Armstrong County ranks 87 of 254 in Texas for soluble rock at the surface, and sits above 78% of US counties on that measure.