Sinkhole risk in Howard County, AR: Pockets of it

Pockets of it

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

On soluble rock: 23%
At or near the surface: 23%
Buried under cover: 0%

What to do about a house in Howard 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 134 of Howard County's 587 square miles on soluble rock, 134 of them with the rock at or near the surface. With about 12,387 residents (21 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 241 map points about 1.6 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 Howard County

The nearest county rated sinkhole country is Adair County, OK, about 131 miles north. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Sevier County, AR 16 mi southwest · 26% at surface
Pike County, AR 20 mi east · 15% at surface
Little River County, AR 30 mi southwest · 4% at surface
Hempstead County, AR 30 mi southeast · 43% at surface
Polk County, AR 31 mi northwest · under 1% at surface
Montgomery County, AR 37 mi northeast · 14% at surface

What Howard County is built on

The largest mapped soluble unit here is the Trinity Group (sand), Early Cretaceous in age, covering about 12% of the county. Next is the Brownstown Marl at 3%.

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 Gulf Coast salt domes, 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 Arkansas

Howard County ranks 22 of 75 in Arkansas for soluble rock at the surface, and sits above 76% of US counties on that measure.