Sinkhole risk in Polk County, AR: No soluble rock mapped

No soluble rock mapped

No soluble bedrock mapped.

On soluble rock: under 1%
At or near the surface: under 1%
Buried under cover: 0%

What to do about a house in Polk County

No soluble bedrock is mapped here, so natural sinkholes are unlikely. Collapses from broken pipes or old mines are a separate risk.

That works out to roughly 3 of Polk County's 857 square miles on soluble rock, 3 of them with the rock at or near the surface. With about 19,434 residents (23 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 311 map points about 1.7 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: how these percentages are measured, and the warning signs that apply anywhere.

Counties around Polk County

The nearest county rated sinkhole country is Adair County, OK, about 100 miles north. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Scott County, AR 27 mi north · 0% at surface
Howard County, AR 31 mi southeast · 23% at surface
Montgomery County, AR 32 mi east · 14% at surface
Sevier County, AR 34 mi south · 26% at surface
Le Flore County, OK 39 mi northwest · 0% at surface
Pike County, AR 40 mi southeast · 15% at surface

Which formation it is

The largest mapped soluble unit here is the Womble Shale (Middle Ordovician) (shale), Middle Ordovician in age, covering about under 1% of the county.

Against the rest of Arkansas

Polk County ranks 35 of 75 in Arkansas for soluble rock at the surface, and sits above 51% of US counties on that measure.