Sinkhole risk in Teton 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: 9%
At or near the surface: 9%
Buried under cover: 0%

What to do about a house in Teton County

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

That works out to roughly 209 of Teton County's 2,272 square miles on soluble rock, 209 of them with the rock at or near the surface. With about 6,444 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 295 map points about 2.8 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Teton County

The nearest county rated sinkhole country is Fall River County, SD, about 530 miles southeast. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Pondera County, MT 28 mi north · 6% at surface
Lewis and Clark County, MT 48 mi south · 25% at surface
Cascade County, MT 56 mi southeast · 18% at surface
Toole County, MT 62 mi northeast · 0% at surface
Glacier County, MT 69 mi northwest · 5% at surface
Powell County, MT 74 mi southwest · 13% at surface

Which formation it is

The largest mapped soluble unit here is the Mississippian, undifferentiated (carbonate), Mississippian in age, covering about 6% of the county. Next is the Devonian, undifferentiated 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.

Against the rest of Montana

Teton County ranks 22 of 56 in Montana for soluble rock at the surface, and sits above 67% of US counties on that measure.