Sinkhole risk in Madison 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: 27%
At or near the surface: 27%
Buried under cover: 0%

The next step for one property

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 224 of Madison County's 834 square miles on soluble rock, 224 of them with the rock at or near the surface. With about 17,865 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 313 map points about 1.6 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Madison County

The nearest county rated sinkhole country is Carroll County, AR, about 25 miles northeast, close enough that the same rock may run under the county line. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Carroll County, AR 25 mi northeast · 81% at surface
Washington County, AR 28 mi west · 29% at surface
Newton County, AR 29 mi east · 24% at surface
Johnson County, AR 34 mi southeast · 0% at surface
Franklin County, AR 36 mi south · 0% at surface
Benton County, AR 37 mi northwest · 93% at surface

Which formation it is

The largest mapped soluble unit here is the Boone Formation (limestone), Early Mississippian- Meramecian to Osagean in age, covering about 25% of the county. Next is the Powell Dolomite at 1%.

Against the rest of Arkansas

Madison County ranks 18 of 75 in Arkansas for soluble rock at the surface, and sits above 78% of US counties on that measure.