Sinkhole risk in Coal County, OK: Mostly deep or small

Mostly deep or small

Some soluble rock, mostly deeply buried or in a small share of the county.

On soluble rock: 4%
At or near the surface: 4%
Buried under cover: 0%

The next step for one property

Sinkholes are uncommon here; watch for new depressions after heavy rain or leaking pipes.

That works out to roughly 19 of Coal County's 517 square miles on soluble rock, 19 of them with the rock at or near the surface. With about 5,414 residents (10 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 357 map points about 1.2 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: how these percentages are measured, and the warning signs that apply anywhere.

Counties around Coal County

The nearest county rated sinkhole country is Grady County, OK, about 96 miles west. 1 of the 6 closest counties land in the same band; the ground changes quickly around here.

Atoka County, OK 19 mi southeast · 5% at surface
Pontotoc County, OK 25 mi northwest · 28% at surface
Johnston County, OK 28 mi southwest · 33% at surface
Hughes County, OK 33 mi north · 0% at surface
Pittsburg County, OK 39 mi northeast · under 1% at surface
Bryan County, OK 43 mi south · 18% at surface

Which formation it is

The largest mapped soluble unit here is the Sylvan Shale + Fernvale Limestone and Viola Limestone (limestone), Late Ordovician to Middle Ordovician in age, covering about 2% of the county. Next is the Hunton Group at 1%.

Against the rest of Oklahoma

Coal County ranks 56 of 77 in Oklahoma for soluble rock at the surface, and sits above 61% of US counties on that measure.