SinkholeOdds

Sinkhole risk in Gila County, AZ: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock
35%
At or near the surface
35%
Buried under cover
0%

The next step for one property

Check the parcel against your state survey sinkhole map, and ask for an inspection if cracks, depressions or sticking doors show up.

That works out to roughly 1,665 of Gila County's 4,758 square miles on soluble rock, 1,665 of them with the rock at or near the surface. With about 54,073 residents (11 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 477 map points about 3.2 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 the signs to look for and how an inspection works.

Counties around Gila County

The nearest county rated sinkhole country is Emery County, UT, about 361 miles north. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

The rock underneath

The largest mapped soluble unit here is the Middle Proterozoic sedimentary rocks (sandstone), Middle Proterozoic in age, covering about 17% of the county. Next is the Permian to Pennsylvanian sedimentary rocks at 11%.

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 Tonto 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

Gila County ranks 2 of 15 in Arizona for soluble rock at the surface, and sits above 82% of US counties on that measure.