Sinkhole risk in Randolph County, AR: Sinkhole country

Sinkhole country

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

On soluble rock: 60%
At or near the surface: 60%
Buried under cover: 0%

What to do about a house in Randolph County

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

That works out to roughly 390 of Randolph County's 652 square miles on soluble rock, 390 of them with the rock at or near the surface. With about 19,040 residents (29 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 269 map points about 1.6 miles apart, so a pocket smaller than that can be missed or overstated.

Worth reading for this county: the signs to look for and how an inspection works, and how these percentages are measured.

Counties around Randolph County

The closest county with no soluble rock mapped is Greene County, AR, about 30 miles southeast. 3 of the 6 closest counties land in the same band; the ground changes quickly around here.

Lawrence County, AR 21 mi south · 37% at surface
Ripley County, MO 23 mi north · 95% at surface
Sharp County, AR 27 mi southwest · 100% at surface
Greene County, AR 30 mi southeast · 0% at surface
Oregon County, MO 32 mi northwest · 100% at surface
Clay County, AR 34 mi east · 0% at surface

What Randolph County is built on

The largest mapped soluble unit here is the Cotter and Jefferson City Dolomites (dolostone (dolomite)), Early Ordovician in age, covering about 58% of the county. Next is the Powell Dolomite at 2%.

Against the rest of Arkansas

Randolph County ranks 9 of 75 in Arkansas for soluble rock at the surface, and sits above 90% of US counties on that measure.