Sinkhole risk in Fremont 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: 9%
At or near the surface: 9%
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 171 of Fremont County's 1,864 square miles on soluble rock, 171 of them with the rock at or near the surface. With about 14,399 residents (8 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 586 map points about 1.8 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: how these percentages are measured, and the warning signs that apply anywhere.

Counties around Fremont County

The nearest county rated sinkhole country is Emery County, UT, about 362 miles south. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Madison County, ID 31 mi south · 5% at surface
Teton County, ID 34 mi southeast · 7% at surface
Clark County, ID 43 mi west · 14% at surface
Jefferson County, ID 51 mi southwest · 0% at surface
Teton County, WY 54 mi east · 14% at surface
Bonneville County, ID 57 mi south · 17% at surface

The rock underneath

The largest mapped soluble unit here is the Rhyolite flows and ignimbrites; Late Pleistocene felsic volcanics of subunit 3f; Yellowstone Plateau (rhyolite), Late Pleistocene in age, covering about 7% of the county. Next is the Mica schist, marble, quartzite, and amphibolite; Early Middle to Early Proterozoic metasedimentary rocks; southern Belt province at under 1%.

Against the rest of Idaho

Fremont County ranks 13 of 44 in Idaho for soluble rock at the surface, and sits above 67% of US counties on that measure.