SinkholeOdds

Sinkhole risk in Billings County, ND: Not karst, but voids possible

Not karst, but voids possible

No soluble bedrock; some pseudokarst (piping or lava-tube ground).

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

What this means before you buy

Not true karst, but soil piping or lava tubes can still open voids - mention it to an inspector.

Across 1,148 square miles, under one square mile of Billings County maps onto soluble rock. With about 1,063 residents (1 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 311 map points about 1.9 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why gypsum and salt move faster than limestone, and how ground with no limestone still opens up.

Counties around Billings County

The nearest county rated sinkhole country is Fall River County, SD, about 262 miles south. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Against the rest of North Dakota

Billings County ranks 9 of 53 in North Dakota for soluble rock at the surface, and sits above 0% of US counties on that measure.