Sinkhole risk in Marlboro County, SC: Sinkhole country

Sinkhole country

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

On soluble rock: 64%
At or near the surface: 64%
Buried under cover: 0%

What this means before you buy

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

That works out to roughly 307 of Marlboro County's 480 square miles on soluble rock, 307 of them with the rock at or near the surface. With about 25,498 residents (53 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 520 map points about 1.0 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 Marlboro County

The closest county with no soluble rock mapped is Union County, NC, about 55 miles northwest. 5 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Scotland County, NC 20 mi northeast · 91% at surface
Dillon County, SC 23 mi southeast · 79% at surface
Darlington County, SC 25 mi southwest · 87% at surface
Chesterfield County, SC 27 mi west · 63% at surface
Richmond County, NC 28 mi north · 20% at surface
Robeson County, NC 33 mi east · 89% at surface

What Marlboro County is built on

The largest mapped soluble unit here is the Duplin Formation (sand), Pliocene in age, covering about 35% of the county. Next is the Bear Bluff Formation at 22%.

Against the rest of South Carolina

Marlboro County ranks 12 of 46 in South Carolina for soluble rock at the surface, and sits above 91% of US counties on that measure.