Sinkhole risk in Wheatland County, MT: 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: 6%
At or near the surface: 6%
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 78 of Wheatland County's 1,422 square miles on soluble rock, 78 of them with the rock at or near the surface. With about 2,058 residents (1 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 365 map points about 2.0 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 how these percentages are measured.

Counties around Wheatland County

The nearest county rated sinkhole country is Fall River County, SD, about 384 miles southeast. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Golden Valley County, MT 34 mi east · 4% at surface
Judith Basin County, MT 43 mi northwest · 33% at surface
Sweet Grass County, MT 48 mi south · 3% at surface
Meagher County, MT 51 mi west · 49% at surface
Fergus County, MT 58 mi northeast · 12% at surface
Stillwater County, MT 62 mi south · under 1% at surface

Which formation it is

The largest mapped soluble unit here is the Mississippian, undifferentiated (carbonate), Mississippian in age, covering about 5% of the county. Next is the Devonian, undifferentiated at under 1%.

The county also lies over the Crazy Mountains 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 Montana

Wheatland County ranks 26 of 56 in Montana for soluble rock at the surface, and sits above 63% of US counties on that measure.