Sinkhole risk in Beaverhead 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: 10%
At or near the surface: 10%
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 549 of Beaverhead County's 5,543 square miles on soluble rock, 549 of them with the rock at or near the surface. With about 10,006 residents (2 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 433 map points about 3.6 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Beaverhead County

The nearest county rated sinkhole country is Emery County, UT, about 438 miles south. 6 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Madison County, MT 49 mi east · 9% at surface
Lemhi County, ID 51 mi west · 12% at surface
Silver Bow County, MT 54 mi north · 10% at surface
Clark County, ID 64 mi southeast · 14% at surface
Deer Lodge County, MT 67 mi north · 10% at surface
Jefferson County, MT 79 mi northeast · 6% at surface

Which formation it is

The largest mapped soluble unit here is the Mississippian, undifferentiated (carbonate), Mississippian in age, covering about 4% of the county. Next is the Piegan group at 3%.

Against the rest of Montana

Beaverhead County ranks 18 of 56 in Montana for soluble rock at the surface, and sits above 68% of US counties on that measure.