SinkholeOdds

Sinkhole risk in Weston County, WY: 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
14%
At or near the surface
14%
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 331 of Weston County's 2,398 square miles on soluble rock, 331 of them with the rock at or near the surface. With about 6,866 residents (3 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 384 map points about 2.5 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 Weston County

The nearest county rated sinkhole country is Fall River County, SD, about 68 miles southeast. None of the 6 closest counties land in the same band, so Weston County stands out from its surroundings.

Which formation it is

The largest mapped soluble unit here is the Greenhorn Formation and Belle Fourche and Mowry Shale (mixed clastic/carbonate), Lower Cretaceous in age, covering about 4% of the county. Next is the Sundance and Gypsum Spring Formations at 3%.

5% 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 Powder River 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 Wyoming

Weston County ranks 10 of 23 in Wyoming for soluble rock at the surface, and sits above 70% of US counties on that measure.