Sinkhole risk in Park 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: 1%
At or near the surface: 1%
Buried under cover: 0%

What to do about a house in Park County

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

That works out to roughly 97 of Park County's 6,939 square miles on soluble rock, 97 of them with the rock at or near the surface. With about 31,082 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 279 map points about 5.0 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Park County

The nearest county rated sinkhole country is Fall River County, SD, about 315 miles east. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Teton County, WY 51 mi southwest · 14% at surface
Carbon County, MT 58 mi northeast · 12% at surface
Hot Springs County, WY 78 mi southeast · 18% at surface
Big Horn County, WY 79 mi east · 25% at surface
Stillwater County, MT 81 mi north · under 1% at surface
Park County, MT 81 mi northwest · 6% at surface

Which formation it is

The largest mapped soluble unit here is the Madison Limestone, Darby or Three Forks, Jefferson, and Beartooth Butte Formations, and Bighorn Dolomite (carbonate), Middle Ordovician-Upper Mississippian in age, covering about under 1% of the county. Next is the Gallatin Limestone, Gros Ventre Formation and equivalents, and Flathead Sandstone (N) or Cambrian Rocks (S) at under 1%.

The county also lies over the Bighorn 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

Park County ranks 18 of 23 in Wyoming for soluble rock at the surface, and sits above 56% of US counties on that measure.