Sinkhole risk in Glacier 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: 5%
At or near the surface: 5%
Buried under cover: 0%

What to do about a house in Glacier County

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

That works out to roughly 141 of Glacier County's 2,995 square miles on soluble rock, 141 of them with the rock at or near the surface. With about 13,503 residents (5 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 3.2 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Glacier County

The nearest county rated sinkhole country is Fall River County, SD, about 592 miles southeast. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Pondera County, MT 48 mi southeast · 6% at surface
Flathead County, MT 56 mi southwest · 25% at surface
Toole County, MT 58 mi east · 0% at surface
Teton County, MT 69 mi southeast · 9% at surface
Lake County, MT 89 mi southwest · 15% at surface
Liberty County, MT 90 mi east · under 1% at surface

Which formation it is

The largest mapped soluble unit here is the Siyeh limestone (carbonate), Middle-Proterozoic in age, covering about 3% of the county. Next is the Altyn limestone at 1%.

Against the rest of Montana

Glacier County ranks 27 of 56 in Montana for soluble rock at the surface, and sits above 62% of US counties on that measure.