Sinkhole risk in Blaine County, MT: No soluble rock mapped

No soluble rock mapped

No soluble bedrock mapped.

On soluble rock: under 1%
At or near the surface: under 1%
Buried under cover: 0%

What to do about a house in Blaine County

No soluble bedrock is mapped here, so natural sinkholes are unlikely. Collapses from broken pipes or old mines are a separate risk.

That works out to roughly 25 of Blaine County's 4,228 square miles on soluble rock, 25 of them with the rock at or near the surface. With about 6,903 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 325 map points about 3.6 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: how these percentages are measured, and the warning signs that apply anywhere.

Counties around Blaine County

The nearest county rated sinkhole country is Fall River County, SD, about 445 miles southeast. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Phillips County, MT 49 mi east · under 1% at surface
Hill County, MT 54 mi west · 0% at surface
Chouteau County, MT 77 mi southwest · 0% at surface
Fergus County, MT 84 mi south · 12% at surface
Liberty County, MT 95 mi west · under 1% at surface
Petroleum County, MT 95 mi south · 0% at surface

What Blaine County is built on

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

Against the rest of Montana

Blaine County ranks 33 of 56 in Montana for soluble rock at the surface, and sits above 53% of US counties on that measure.