SinkholeOdds

Sinkhole risk in La Plata County, CO: 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
2%
At or near the surface
2%
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 32 of La Plata County's 1,690 square miles on soluble rock, 32 of them with the rock at or near the surface. With about 56,823 residents (34 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 319 map points about 2.3 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why gypsum and salt move faster than limestone, and how these percentages are measured.

Counties around La Plata County

The nearest county rated sinkhole country is Emery County, UT, about 197 miles northwest. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Which formation it is

The largest mapped soluble unit here is the Leadville, Gilman, Dyer, Parting, and Sawatch Fms in west-central and south-central. Leadville Limestone, Ouray Limestone, Elbert Fm, and Ignacio Quartzite in far southwest (limestone), Mississipian-Cambrian in age, covering about 2% of the county. Next is the Leadville Limestone, Gilman Sandstone, Dyer Dolomite, and Parting Fm at under 1%.

The county also lies over the Paradox Basin, 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 Colorado

La Plata County ranks 26 of 64 in Colorado for soluble rock at the surface, and sits above 57% of US counties on that measure.