Sinkhole risk in Clarke County, VA: Sinkhole country

Sinkhole country

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

On soluble rock: 74%
At or near the surface: 74%
Buried under cover: 0%

What to do about a house in Clarke County

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

That works out to roughly 130 of Clarke County's 176 square miles on soluble rock, 130 of them with the rock at or near the surface. With about 15,598 residents (89 per square mile), homes are spread across towns and farmland, and a mapped unit may or may not reach the developed parts. The figures come from 511 map points about 0.6 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 Clarke County

The closest county with no soluble rock mapped is Fauquier County, VA, about 27 miles south. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.

Winchester city, VA 11 mi west · 90% at surface
Jefferson County, WV 15 mi northeast · 84% at surface
Frederick County, VA 16 mi northwest · 30% at surface
Warren County, VA 18 mi southwest · 23% at surface
Loudoun County, VA 19 mi east · 7% at surface
Berkeley County, WV 23 mi north · 44% at surface

The rock underneath

The largest mapped soluble unit here is the Beekmantown Group (dolostone (dolomite)), Ordovician in age, covering about 27% of the county. Next is the Conococheague Formation at 18%.

Against the rest of Virginia

Clarke County ranks 10 of 133 in Virginia for soluble rock at the surface, and sits above 93% of US counties on that measure.