Sinkhole risk in Carroll County, AR: Sinkhole country

Sinkhole country

Soluble rock at or near the surface across much of the county.

On soluble rock: 81%
At or near the surface: 81%
Buried under cover: 0%

What to do about a house in Carroll County

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

That works out to roughly 509 of Carroll County's 630 square miles on soluble rock, 509 of them with the rock at or near the surface. With about 28,968 residents (46 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 302 map points about 1.4 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Carroll County

The closest county with no soluble rock mapped is Johnson County, AR, about 53 miles south. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Madison County, AR 25 mi southwest · 27% at surface
Boone County, AR 26 mi east · 83% at surface
Stone County, MO 29 mi north · 100% at surface
Barry County, MO 30 mi northwest · 99% at surface
Newton County, AR 35 mi southeast · 24% at surface
Taney County, MO 35 mi northeast · 100% 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 37% of the county. Next is the Cotter and Jefferson City Dolomites at 30%.

Against the rest of Arkansas

Carroll County ranks 8 of 75 in Arkansas for soluble rock at the surface, and sits above 95% of US counties on that measure.