Sinkhole risk in Santa Cruz 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: 4%
At or near the surface: 4%
Buried under cover: 0%

What to do about a house in Santa Cruz County

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

That works out to roughly 49 of Santa Cruz County's 1,236 square miles on soluble rock, 49 of them with the rock at or near the surface. With about 50,508 residents (41 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 326 map points about 1.9 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Santa Cruz County

The nearest county rated sinkhole country is Eddy County, NM, about 388 miles east. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Cochise County, AZ 67 mi east · 6% at surface
Pima County, AZ 69 mi northwest · under 1% at surface
Pinal County, AZ 101 mi north · 3% at surface
Graham County, AZ 112 mi northeast · under 1% at surface
Hidalgo County, NM 126 mi east · 2% at surface
Greenlee County, AZ 151 mi northeast · 2% at surface

What Santa Cruz County is built on

The largest mapped soluble unit here is the Permian to Pennsylvanian sedimentary rocks (sandstone), Pennsylvanian to Permian in age, covering about 3% of the county. Next is the Paleozoic sedimentary rocks at under 1%.

3% 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 Tuscon 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

Santa Cruz County ranks 8 of 15 in Arizona for soluble rock at the surface, and sits above 61% of US counties on that measure.