Sinkhole risk in Custer 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: 15%
At or near the surface: 15%
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 753 of Custer County's 4,922 square miles on soluble rock, 753 of them with the rock at or near the surface. With about 4,597 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 574 map points about 2.9 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Custer County

The nearest county rated sinkhole country is Emery County, UT, about 407 miles southeast. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Lemhi County, ID 49 mi north · 12% at surface
Camas County, ID 59 mi southwest · 2% at surface
Blaine County, ID 63 mi south · 16% at surface
Butte County, ID 67 mi southeast · 24% at surface
Boise County, ID 75 mi west · 0% at surface
Valley County, ID 78 mi northwest · 1% at surface

What Custer County is built on

The largest mapped soluble unit here is the Limestone, shale, siltstone, chert, and conglomerate; Mississippian western turbiditic flysch to eastern shallow-water carbonates; east-central Idaho (limestone), Mississippian in age, covering about 9% of the county. Next is the Sandstone, limestone, siltstone, shale, and conglomerate; Lower Permian to Middle Pennsylvanian deltaic turbidites; central Idaho; at 2%.

Against the rest of Idaho

Custer County ranks 10 of 44 in Idaho for soluble rock at the surface, and sits above 72% of US counties on that measure.