Sinkhole risk in Mohave 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: 32%
At or near the surface: 32%
Buried under cover: 0%

What to do about a house in Mohave County

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 4,213 of Mohave County's 13,332 square miles on soluble rock, 4,213 of them with the rock at or near the surface. With about 226,479 residents (17 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 573 map points about 4.8 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Mohave County

The nearest county rated sinkhole country is Emery County, UT, about 282 miles northeast. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Clark County, NV 79 mi northwest · 29% at surface
Yavapai County, AZ 100 mi southeast · 12% at surface
Washington County, UT 108 mi north · 16% at surface
Coconino County, AZ 111 mi east · 56% at surface
La Paz County, AZ 138 mi south · 0% at surface
Lincoln County, NV 146 mi northwest · 17% at surface

What Mohave County is built on

The largest mapped soluble unit here is the Permian sedimentary rocks (limestone), Permian in age, covering about 13% of the county. Next is the Mississippian, Devonian, and Cambrian sedimentary rocks at 7%.

12% 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 Virgina Valley, 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

Mohave County ranks 3 of 15 in Arizona for soluble rock at the surface, and sits above 80% of US counties on that measure.