Sinkhole risk in Martin County, TX: Mostly deep or small

Mostly deep or small

Some soluble rock, mostly deeply buried or in a small share of the county.

On soluble rock: 3%
At or near the surface: 3%
Buried under cover: 0%

The next step for one property

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 26 of Martin County's 915 square miles on soluble rock, 26 of them with the rock at or near the surface. With about 5,179 residents (6 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.

Two things to read before deciding: why gypsum and salt move faster than limestone, and how these percentages are measured.

Counties around Martin County

The nearest county rated sinkhole country is Ector County, TX, about 46 miles southwest. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Dawson County, TX 30 mi north · 3% at surface
Howard County, TX 31 mi east · 25% at surface
Midland County, TX 34 mi south · 16% at surface
Andrews County, TX 40 mi west · under 1% at surface
Glasscock County, TX 40 mi southeast · 24% at surface
Borden County, TX 42 mi northeast · 57% at surface

What Martin County is built on

The largest mapped soluble unit here is the Dockum Group, undivided (fine-grained mixed clastic), Late Triassic in age, covering about 2% of the county. Next is the caliche deposits at 1%.

1% 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

Martin County ranks 132 of 254 in Texas for soluble rock at the surface, and sits above 59% of US counties on that measure.