SinkholeOdds

Sinkhole risk in Twin Falls County, ID: Not karst, but voids possible

Not karst, but voids possible

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

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

What to do about a house in Twin Falls County

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

That works out to roughly 13 of Twin Falls County's 1,922 square miles on soluble rock, 13 of them with the rock at or near the surface. With about 96,509 residents (50 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 588 map points about 1.8 miles apart, so a pocket smaller than that can be missed or overstated.

Read next: how ground with no limestone still opens up, and how these percentages are measured.

Counties around Twin Falls County

The nearest county rated sinkhole country is Emery County, UT, about 310 miles southeast. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Which formation it is

The largest mapped soluble unit here is the Limestone, sandstone, dolostone, and chert; Permian to Pennsylvanian marine epicontinental-basin deposits; southeastern Idaho; (limestone), Early Permian to Early Pennsylvanian in age, covering about under 1% of the county. Next is the Limestone, arenite, dolostone, chert, siltstone, shale; Upper Paleozoic marine continental-shelf deposits; southeastern Idaho at under 1%.

Against the rest of Idaho

Twin Falls County ranks 23 of 44 in Idaho for soluble rock at the surface, and sits above 54% of US counties on that measure.