Sinkhole risk in Marion County, SC: Pockets of it

Pockets of it

Soluble rock at the surface or under thin cover in part of the county.

On soluble rock: 53%
At or near the surface: 33%
Buried under cover: 20%

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 258 of Marion County's 489 square miles on soluble rock, 163 of them with the rock at or near the surface. With about 28,368 residents (58 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 478 map points about 1.0 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why the 20% under cover still counts, and the signs to look for and how an inspection works.

Counties around Marion County

The nearest county rated sinkhole country is Florence County, SC, about 21 miles west, 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.

Florence County, SC 21 mi west · 77% at surface
Dillon County, SC 21 mi north · 79% at surface
Horry County, SC 25 mi southeast · 29% at surface
Williamsburg County, SC 38 mi southwest · 31% at surface
Darlington County, SC 39 mi northwest · 87% at surface
Marlboro County, SC 40 mi northwest · 64% at surface

What Marion County is built on

The largest mapped soluble unit here is the Bear Bluff Formation (sand), Pliocene in age, covering about 26% of the county.

Against the rest of South Carolina

Marion County ranks 20 of 46 in South Carolina for soluble rock at the surface, and sits above 81% of US counties on that measure.