Sinkhole risk in King County, TX: Sinkhole country

Sinkhole country

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

On soluble rock: 97%
At or near the surface: 97%
Buried under cover: 0%

What to do about a house in King County

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

That works out to roughly 885 of King County's 911 square miles on soluble rock, 885 of them with the rock at or near the surface. With about 215 residents (0 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 396 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around King County

The closest county with no soluble rock mapped is Archer County, TX, about 90 miles east. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Knox County, TX 30 mi east · 55% at surface
Stonewall County, TX 30 mi south · 82% at surface
Dickens County, TX 31 mi west · 63% at surface
Cottle County, TX 33 mi north · 79% at surface
Foard County, TX 34 mi northeast · 72% at surface
Kent County, TX 42 mi southwest · 72% at surface

What King County is built on

The largest mapped soluble unit here is the Blaine Formation (mudstone), Permian; Guadalupe Series in age, covering about 64% of the county. Next is the Whitehorse Group, undivided at 31%.

97% 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

King County ranks 5 of 254 in Texas for soluble rock at the surface, and sits above 98% of US counties on that measure.