Sinkhole risk in Park 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: 13%
At or near the surface: 13%
Buried under cover: 0%

What to do about a house in Park County

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

That works out to roughly 292 of Park County's 2,194 square miles on soluble rock, 292 of them with the rock at or near the surface. With about 18,316 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 315 map points about 2.6 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 Park County

The nearest county rated sinkhole country is Emery County, UT, about 268 miles west. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Teller County, CO 33 mi southeast · under 1% at surface
Lake County, CO 34 mi west · 5% at surface
Clear Creek County, CO 39 mi north · 0% at surface
Jefferson County, CO 41 mi northeast · 2% at surface
Chaffee County, CO 41 mi southwest · 4% at surface
Summit County, CO 41 mi northwest · 4% at surface

Which formation it is

The largest mapped soluble unit here is the Evaporitic facies of Minturn And Belden Fms in South Park and southward (siltstone), Pennsylvanian in age, covering about 4% of the county. Next is the Oligocene sedimentary rocks at 2%.

11% 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 Denver 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

Park County ranks 10 of 64 in Colorado for soluble rock at the surface, and sits above 70% of US counties on that measure.