Sinkhole risk in Madison County, ID: Mostly deep or small

Mostly deep or small

Some soluble rock, mostly deeply buried or in a small share of the county.

On soluble rock: 5%
At or near the surface: 5%
Buried under cover: 0%

What this means before you buy

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 22 of Madison County's 469 square miles on soluble rock, 22 of them with the rock at or near the surface. With about 55,549 residents (118 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 319 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Madison County

The nearest county rated sinkhole country is Emery County, UT, about 334 miles south. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Teton County, ID 22 mi east · 7% at surface
Bonneville County, ID 27 mi south · 17% at surface
Fremont County, ID 31 mi north · 9% at surface
Jefferson County, ID 33 mi west · 0% at surface
Clark County, ID 49 mi northwest · 14% at surface
Bingham County, ID 54 mi southwest · 8% 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 2% of the county. Next is the Coralline Limestone, sandstone, siltstone, shale, chert, and phosphorite; Mississippianshallow marine inner continental-shelf deposits; east-central Idaho, central Idaho at 2%.

Against the rest of Idaho

Madison County ranks 17 of 44 in Idaho for soluble rock at the surface, and sits above 62% of US counties on that measure.