Sinkhole risk in Pike County, AR: 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: 15%
At or near the surface: 15%
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 87 of Pike County's 600 square miles on soluble rock, 87 of them with the rock at or near the surface. With about 10,027 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 275 map points about 1.5 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: why gypsum and salt move faster than limestone, and how these percentages are measured.

Counties around Pike County

The nearest county rated sinkhole country is Adair County, OK, about 133 miles northwest. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Howard County, AR 20 mi west · 23% at surface
Montgomery County, AR 27 mi north · 14% at surface
Clark County, AR 29 mi east · 21% at surface
Hempstead County, AR 29 mi south · 43% at surface
Sevier County, AR 35 mi west · 26% at surface
Nevada County, AR 40 mi southeast · 7% at surface

What Pike County is built on

The largest mapped soluble unit here is the Trinity Group (sand), Early Cretaceous in age, covering about 8% of the county. Next is the Brownstown Marl at 4%.

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 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

Pike County ranks 26 of 75 in Arkansas for soluble rock at the surface, and sits above 71% of US counties on that measure.