Sinkhole risk in Knox County, TX: Sinkhole country

Sinkhole country

Fast-dissolving gypsum or salt beds under a large part of the county.

On soluble rock: 55%
At or near the surface: 55%
Buried under cover: 0%

The next step for one property

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

That works out to roughly 470 of Knox County's 851 square miles on soluble rock, 470 of them with the rock at or near the surface. With about 3,255 residents (4 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 377 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Knox County

The closest county with no soluble rock mapped is Archer County, TX, about 60 miles east. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Foard County, TX 25 mi north · 72% at surface
King County, TX 30 mi west · 97% at surface
Baylor County, TX 30 mi east · 50% at surface
Haskell County, TX 30 mi south · 50% at surface
Stonewall County, TX 42 mi southwest · 82% at surface
Throckmorton County, TX 43 mi southeast · 37% at surface

What Knox County is built on

The largest mapped soluble unit here is the Clear Fork Group (mudstone), Permian; Leonard Series in age, covering about 39% of the county. Next is the San Angelo Formation at 12%.

55% 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

Knox County ranks 41 of 254 in Texas for soluble rock at the surface, and sits above 89% of US counties on that measure.