Sinkhole risk in Johnson County, TN: Pockets of it

Pockets of it

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

On soluble rock: 21%
At or near the surface: 21%
Buried under cover: 0%

What this means before you buy

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 64 of Johnson County's 298 square miles on soluble rock, 64 of them with the rock at or near the surface. With about 18,506 residents (62 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 583 map points about 0.7 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 Johnson County

The nearest county rated sinkhole country is Bristol city, VA, about 20 miles northwest, close enough that the same rock may run under the county line. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Watauga County, NC 17 mi southeast · 5% at surface
Carter County, TN 19 mi southwest · 25% at surface
Bristol city, VA 20 mi northwest · 89% at surface
Ashe County, NC 20 mi east · 0% at surface
Washington County, VA 21 mi north · 62% at surface
Sullivan County, TN 25 mi west · 92% at surface

Which formation it is

The largest mapped soluble unit here is the Shady Dolomite (dolostone (dolomite)), Cambrian in age, covering about 21% of the county.

Against the rest of Tennessee

Johnson County ranks 65 of 95 in Tennessee for soluble rock at the surface, and sits above 75% of US counties on that measure.