Sinkhole risk in Sullivan County, TN: Sinkhole country

Sinkhole country

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

On soluble rock: 92%
At or near the surface: 92%
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 379 of Sullivan County's 414 square miles on soluble rock, 379 of them with the rock at or near the surface. With about 162,703 residents (393 per square mile), there is effectively nowhere in the county off the soluble rock, town or country. The figures come from 596 map points about 0.8 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 Sullivan County

The closest county with no soluble rock mapped is Mitchell County, NC, about 35 miles south. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

Bristol city, VA 11 mi northeast · 89% at surface
Washington County, TN 18 mi southwest · 88% at surface
Carter County, TN 18 mi southeast · 25% at surface
Scott County, VA 22 mi northwest · 72% at surface
Johnson County, TN 25 mi east · 21% at surface
Washington County, VA 25 mi northeast · 62% at surface

The rock underneath

The largest mapped soluble unit here is the Sevier Shale (shale), Ordovician in age, covering about 37% of the county. Next is the Knox Group at 35%.

Against the rest of Tennessee

Sullivan County ranks 11 of 95 in Tennessee for soluble rock at the surface, and sits above 97% of US counties on that measure.