Sinkhole risk in Grady County, OK: Sinkhole country
Sinkhole country
Fast-dissolving gypsum or salt beds under a large part of the county.
- On soluble rock
- 42%
- At or near the surface
- 42%
- Buried under cover
- 0%
The next step for one property
Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.
That works out to roughly 462 of Grady County's 1,101 square miles on soluble rock, 462 of them with the rock at or near the surface. With about 58,353 residents (53 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 388 map points about 1.7 miles apart, so a pocket smaller than that can be missed or overstated.
Read next: why gypsum and salt move faster than limestone, and the signs to look for and how an inspection works.
Counties around Grady County
The closest county with no soluble rock mapped is McClain County, OK, about 25 miles east. 2 of the 6 closest counties land in the same band; the ground changes quickly around here.
- McClain County, OK 25 mi east · 0% at surface
- Caddo County, OK 30 mi west · 79% at surface
- Cleveland County, OK 34 mi east · 3% at surface
- Canadian County, OK 36 mi north · 40% at surface
- Stephens County, OK 37 mi south · 9% at surface
- Garvin County, OK 39 mi southeast · 0% at surface
What Grady County is built on
The largest mapped soluble unit here is the Dog Creek Shale (shale), Early Permian in age, covering about 15% of the county. Next is the Rush Springs Formation at 13%.
42% of the county sits on gypsum or salt, which dissolves in years rather than millennia. That share matters more than its size suggests.
Against the rest of Oklahoma
Grady County ranks 15 of 77 in Oklahoma for soluble rock at the surface, and sits above 85% of US counties on that measure.
- Delaware County 94%
- Adair County 79%
- Caddo County 79%
- Harmon County 77%
- Cherokee County 66%