Sinkhole risk in Caribou County, ID: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 24%
At or near the surface: 24%
Buried under cover: 0%

What this means before you buy

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 429 of Caribou County's 1,764 square miles on soluble rock, 429 of them with the rock at or near the surface. With about 7,239 residents (4 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 313 map points about 2.4 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why gypsum and salt move faster than limestone, and the signs to look for and how an inspection works.

Counties around Caribou County

The nearest county rated sinkhole country is Emery County, UT, about 264 miles south. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Bannock County, ID 35 mi west · 29% at surface
Bear Lake County, ID 36 mi south · 45% at surface
Bonneville County, ID 42 mi north · 17% at surface
Franklin County, ID 45 mi south · 37% at surface
Bingham County, ID 52 mi northwest · 8% at surface
Lincoln County, WY 58 mi southeast · 27% at surface

The rock underneath

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 7% of the county. Next is the Limestone, arenite, shale, dolostone, and siltstone; Upper Proterozoic to Cambrian marine continental-shelf deposits; southeastern Idaho at 3%.

3% of the county sits on gypsum or salt, which dissolves in years rather than millennia. That share matters more than its size suggests.

The county also lies over the Wyoming Thrust belt, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Idaho

Caribou County ranks 5 of 44 in Idaho for soluble rock at the surface, and sits above 77% of US counties on that measure.