SinkholeOdds

Sinkhole risk in Apache County, AZ: 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
10%
At or near the surface
10%
Buried under cover
0%

The next step for one property

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

That works out to roughly 1,131 of Apache County's 11,198 square miles on soluble rock, 1,131 of them with the rock at or near the surface. With about 64,800 residents (6 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 317 map points about 5.9 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why gypsum and salt move faster than limestone, and how these percentages are measured.

Counties around Apache County

The nearest county rated sinkhole country is Emery County, UT, about 259 miles north. 3 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 San Rafael Group (sandstone), Middle to Late Jurassic in age, covering about 4% of the county. Next is the Permian to Pennsylvanian sedimentary rocks at 3%.

8% 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 Holbrook 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 Arizona

Apache County ranks 6 of 15 in Arizona for soluble rock at the surface, and sits above 68% of US counties on that measure.