Sinkhole risk in Yellowstone 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 Yellowstone 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 5 of Yellowstone County's 2,633 square miles on soluble rock, 5 of them with the rock at or near the surface. With about 171,583 residents (65 per square mile), homes are spread across towns and farmland, and a mapped unit may or may not reach the developed parts. The figures come from 537 map points about 2.2 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: how these percentages are measured, and the warning signs that apply anywhere.

Counties around Yellowstone County

The nearest county rated sinkhole country is Fall River County, SD, about 300 miles southeast. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Musselshell County, MT 40 mi north · 0% at surface
Big Horn County, MT 52 mi southeast · 11% at surface
Treasure County, MT 52 mi northeast · 0% at surface
Golden Valley County, MT 53 mi northwest · 4% at surface
Stillwater County, MT 57 mi west · under 1% at surface
Carbon County, MT 61 mi southwest · 12% at surface

The rock underneath

The largest mapped soluble unit here is the Jurassic, undifferentiated (fine-grained mixed clastic), Jurassic in age, covering about under 1% of the county.

Against the rest of Montana

Yellowstone County ranks 36 of 56 in Montana for soluble rock at the surface, and sits above 50% of US counties on that measure.