Sinkhole risk in Polk 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: 20%
At or near the surface: 20%
Buried under cover: 0%

What to do about a house in Polk County

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 88 of Polk County's 435 square miles on soluble rock, 88 of them with the rock at or near the surface. With about 18,338 residents (42 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 316 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Counties around Polk County

The nearest county rated sinkhole country is Bradley County, TN, about 18 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.

Bradley County, TN 18 mi west · 89% at surface
Fannin County, GA 21 mi southeast · 0% at surface
McMinn County, TN 22 mi north · 86% at surface
Murray County, GA 24 mi southwest · 30% at surface
Cherokee County, NC 27 mi east · 4% at surface
Monroe County, TN 29 mi northeast · 37% at surface

The rock underneath

The largest mapped soluble unit here is the Knox Group, including Newala Formation, Mascot Dolomite, Kingsport Formation, Longview Dolomite, Chepultepec Dolomite, and Copper Ridge Dolomite (dolostone (dolomite)), Ordovician to Cambrian in age, covering about 13% of the county. Next is the Nolichucky Shale, and Maryville, Rogersville, and Rutledge Formations, and Pumpkin Valley Shale at 4%.

Against the rest of Tennessee

Polk County ranks 69 of 95 in Tennessee for soluble rock at the surface, and sits above 74% of US counties on that measure.