SinkholeOdds

Sinkhole risk in Jackson County, OK: Sinkhole country

Sinkhole country

Fast-dissolving gypsum or salt beds under a large part of the county.

On soluble rock
34%
At or near the surface
34%
Buried under cover
0%

What to do about a house in Jackson County

Get a sinkhole or geotechnical inspection before buying, building or adding weight to a foundation.

That works out to roughly 276 of Jackson County's 803 square miles on soluble rock, 276 of them with the rock at or near the surface. With about 24,541 residents (31 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 511 map points about 1.3 miles apart, so a pocket smaller than that can be missed or overstated.

Two things to read before deciding: why gypsum and salt move faster than limestone, and the signs to look for and how an inspection works.

Counties around Jackson County

The closest county with no soluble rock mapped is Tillman County, OK, about 31 miles southeast. 4 of the 6 closest counties land in the same band, so this is a regional pattern rather than a local quirk.

The rock underneath

The largest mapped soluble unit here is the Van Vacter Member of Blaine Formation (dolostone (dolomite)), Early Permian in age, covering about 16% of the county. Next is the Elm Fork Member of Blaine Formation at 8%.

34% of the county sits on gypsum or salt, which dissolves in years rather than millennia. That share matters more than its size suggests.

The county also lies over the Permian Basin, Anadarko Basin,Dalhart Basin, Palo Duro Basin, a deep salt or gypsum basin. Deep beds rarely cause surface collapse on their own, but wells and mining into them have.

Against the rest of Oklahoma

Jackson County ranks 22 of 77 in Oklahoma for soluble rock at the surface, and sits above 81% of US counties on that measure.